Residual oil cracking process using dry gas as lift gas initially in riser reactor

Description

[0001] The invention relates to the catalytic cracking of hydrocarbon feedstocks, particularly residual portions of crude oils comprising substantial amounts of asphaltenes, asphalt and other carbon producing components and substantial amounts of heavy metal contaminants such as nickel and vanadium, and sulfur and nitrogen compounds. The catalytic cracking of crude oil fractions is well known in the art. In a typical cracking operation the hydrocarbon feedstock is contacted in a riser with an upflowing stream of catalyst particles, particularly a crystalline zeolite, following which the products are separated, the catalyst particles passed to a regeneration zone in which they are contacted with a hot-oxygen containing gas to burn off deposited carbon, following which the regenerated catalyst particles are recycled to the riser.

[0002] More particularly, the present invention relates to improving the product selectivity obtained and maintaining the desired equilibrium catalyst activity during the cracking of such heavy oil feeds.

[0003] Amongst prior art processes for the cracking of hydrocarbons there may be mentioned:

US-A-2,900,326 which discloses the processing of a gas oil in a fluidized catalytic cracking (FCC) unit and in which the hydrogen containing light gases produced are recycled in admixture with fresh feed in order to suppress C₁-C₄ formation.

US-A-2,904,504 discloses admixing C₁-C_S hydrocarbons with the hot regenerated catalyst particles recycled to the riser and prior to the oil feed injection. The light hydrocarbons are fed at a rate of about 35.6 to 89.0 cubic metres per cubic metre of feed (about 200 to 500 cubic feet per barrel of feed). (All references to "barrel" herein refer to barrels of feed unless otherwise expressly noted.)

US-A-3,849,932 discloses the introduction of light hydrocarbons to the bottom of the riser and the introduction of gas oil further up the riser, followed by hydrocarbon injection still further up. The suspended catalyst moves upwardly by these injection points and is lifted by vaporous hydrocarbons and the charged light hydrocarbons.

US-A-2,888,395 discloses contacting a heavy hydrocarbon with a catalyst in a riser in the presence of substantially pure hydrogen. The hydrogen is produced outside the cracking unit. The use of hydrogen with the oil feed is said to reduce coke deposits and to reduce the production of unsaturated products.

US-A-4,268,416 discloses contacting the catalyst with water saturated hydrogen prior to introduction of the catalyst into the riser in order to reduce catalyst contamination by nickel and vanadium.

US-A-4,280,895 and US-A-4,280,896 both disclose treatment of the regenerated catalyst with hydrogen, carbon monoxide or hydrogen-carbon monoxide mixture in a reduction zone prior to its recycle to the riser.

US-A-4,345,992 discloses the transfer of regenerated catalyst to a reduction zone where the catalyst is contacted with hydrogen following which the reduced catalyst and unconsumed hydrogen are transferred to the riser.

US-A-4,361,496 discloses the treatment of regenerated metal-contaminated catalyst with a gaseous hydrocarbon of three carbon atoms or less, or a mixture thereof, to achieve complete reduction of contaminant metals which are carbonized in the conduit located between the regenerator and the riser and which is used to convey catalyst from the regenerator to the riser.

US-A-4,364,848 contains a disclosure similar to US-A-4,361,496 above in that a reducing gas mixture of one, two, three carbon atoms is used to passivate the metals to the metallic state before the carbonization thereof.

US-A-2,937,988 discloses a riser reactor system for cracking an oil feed such as a heavy hydrocarbon residuum, vacuum or atmospheric crude bottom, pitch, asphalt or mixtures thereof wherein hot coke particles are initially dispersed in fluidizing gases such as steam, light hydrocarbons, an inert gas or mixtures thereof.

US-A-3,406,112 discloses utilizing C₆ or C₅ hydrocarbons in an amount sufficient to form a suspension with zeolite catalyst particles in a lower portion of a riser reaction zone before charging the oil feed thereto.

US-A-3,849,291 discloses the use of a dry or wet gas cracking product as a diluent material in the riser.

US-A-3,894,932 discloses the use of a C₃-C₄ hydrocarbon gas mixture in the bottom portion of the riser to form an upflowing suspension of zeolite catalyst particles prior to contact with the oil feed.

US-A-2,684,931 discloses a fluidized solids process where a gaseous cracking product is used comprising hydrogen, methane and other normally gaseous hydrocarbons both unsaturated and saturated.

US-A-4,431,515 discloses a carbometallic oil conversion process using hydrogen in the riser reactor and utilizing a high metals containing catalyst.

[0004] The addition of hydrogen to the riser reduces the formation of conjugated diolefins, and this, it is postulated, reduces coke deposition on the metals containing catalyst.

[0005] US-A-4,427,537 discloses a process in which an atomized oil-diluent feed mixture is formed externally of the riser in an atomizing gas comprising water, steam, CO₂ or normally gaseous hydrocarbons which is then introduced into an upwardly flowing stream of catalyst particles suspended in a lift gas likewise comprising C0₂, steam or normally gaseous hydrocarbons.

[0006] EP-A-0 074 501 discloses a specific zeolite catalyst which is used in combination with a lift gas comprising naphtha, steam and water for the cracking of reduced crudes high in metal contaminants and Conradson carbon producing components.

[0007] Finally, EP-A-0 154 676, published subsequently to the filing of the present application but claiming an earlier priority date (and designating only AT, DE, FR, GB, IT and NL in common herewith) discloses a fluid catalytic cracking (FCC) process for the conversion of relatively high boiling feedstocks to lighter hydrocarbons in which the regenerated catalyst is beneficially conditioned prior to contact with the feedstock in order to promote the catalyst feed interaction and maximise the yield of desired products. This is achieved by utilizing as the lift gas a hydrocarbon-containing gas which includes not more than 10 mole% of C₃ or heavier hydrocarbons, and which is contacted with the regenerated catalyst particles in the lower regions of the riser, and before contact with the feed, thereby selectively to carbonize reaction sites on the catalyst prior to contact with the feed whilst simultaneously accelerating the catalyst to a velocity sufficient to provide turbulent dilute flow at the point of contact with the feedstock. Gas velocities in the lower part of the riser range from 1.8 to 12.2 m/sec. with a catalyst residence time of from 0.5 to 15 seconds. The prior contact of the lift gas with the catalyst particles selectively carbonizes active contaminating metal sites and acid sites on the catalyst thereby respectively reducing hydrogen and coke production believed to result from the former, and providing greater product selectivity. In addition, the lift gas may also contain other species such as H₂, H₂S, N₂, CO and/or C0₂. The published application, however, does not focus on the cracking of reduced crude feedstocks high in metal contaminants and of high Ramsbottom carbon values, the metals content of the catalyst, and more particularly the desirability of maintaining finite but extremely short contact times between the regenerated catalyst particles and the lift gas sufficient to reduce the metal oxide contaminants to a lower oxidation state, or to the elemental metal, but without significant deposit of carbon on the catalyst prior to contact with the feedstock.

[0008] In contrast to the foregoing, the present invention employes a particular dry gas composition in combination with a cooling fluid as the lift gas to form an upflowing desired high temperature regenerated catalyst suspension which optimizes the product selectivity obtainable of a given hydrocarbon feed, particularly of reduced crudes high in metal contaminants, and high Ramsbottom carbon values.

[0009] In general, gasoline and other liquid hydrocarbon fuels boil in the range of 38°C to 343°C (100°F to 650°F); however, the crude oil from which these fuels are made is a diverse mixture of hydrocarbons and other compounds which vary widely in molecular weight and therefore boil over a wider range. For example, crude oils are known in which 30% to 60% or more of the total volume is composed of compounds boiling at temperatures above 343°C (650°F). Among these cudes are crudes in which from 10% to 30% or more of the total volume consists of compounds having boiling points above 552°C (1025°F) at atmospheric pressure.

[0010] Because these relatively abundant high boiling components of crude oil are unsuitable for inclusion in gasoline and other liquid hydrocarbon fuels, the Fluid Catalytic Cracking (FCC) process was developed for cracking or breaking the molecules of high molecular weight, high boiling compounds into smaller molecules which boil over an appropriate boiling range. Although the FCC process has reached a highly advanced state, and many modified forms and variations have been developed, their unifying factor is that a vaporized hydrocarbon feedstock which contains high molecular weight, high boiling components is caused to crack at an elevated temperature in contact with a cracking catalyst that is suspended in the feedstock vapors. Upon attainment of the desired molecular weight and boiling point reduction, the catalyst is separated from the desired products.

[0011] By contrast, the present invention is primarily concerned with using hydrocarbon feedstocks which have Ramsbottom carbon values which exhibit a substantially greater potential for coke formation than does the usual FCC feedstock. In conventional FCC practice, Ramsbottom carbon values of the order of about 0.1 to about 1.0 are regarded as indicative of acceptable feed. Conventional FCC practice has employed as feedstock those fractions of crude oil which boil in the range 343°C to 538°C (650°F to 1000°F), and which are relatively free of coke precursors and heavy metal contaminants. Such feedstocks known as "vacuum gas oil" (VGO) are generally prepared from crude oil by distilling off the fractions boiling below about 343°C (650°F) at atmospheric pressure and then separating, by further vacuum distillation from the heavier fractions, the cut boiling between 343°C and 538°C (650°F and 1000°F).

[0012] Since the various heavy metals in carbometallic oil are not of equal catalyst poisoning activity, it is convenient to express the poisoning activity of an oil containing a given poisoning metal or metals in terms of the amount of a single metal which is estimated to have equivalent poisoning activity. Thus, the heavy metals content of an oil can be expressed by the following formula (patterned after that of W.L. Nelson in Oil and Gas Journal, page 143, October 23, 1961) in which the content of each metal present is expressed in parts per million of such metal, as metal, on a weight basis, based on the weight of feed.

Nickel Equivalents =

[0013] The above formula can also be employed as a measure of the accumulation of heavy metals on the cracking catalyst, except that the quantity of metal employed in the formula is based on the weight of catalyst (moisture free basis) instead of the weight of feed.

[0014] The present invention is concerned with the processing of feedstocks containing heavy metals substantially in excess of that in conventional FCC processing, and which therefore have potential for accumulating on and poisoning the catalyst.

[0015] In particular the present invention is notable in providing a simple, relatively straightforward and highly productive approach to the conversion of oil feeds to various lighter products, such as gasoline, from crude oils and reduced crude oil fractions boiling above about 343°C (650°F) and having heavy metals content of at least 4, preferably at least 5, and, most preferably at least about 5.5 calculated as Nickel Equivalents and having carbon residues on pyrolysis of at least 1% and more preferably at least 2% by weight.

[0016] In particular, such feedstocks are cracked catalytically using a hydrogen rich dry lift gas of limited C₃ plus content and a regenerated catalyst in which the heavy metal content is maintained in a specific range of up to 20,000 ppm Ni + V.

[0017] In a more particular aspect, the present invention is concerned with using a dry gas stream as the lift gas for the hot regenerated catalyst particles, possibly in conjunction with one or more cooling fluids such as steam, water and combinations thereof to adjust the temperature thereof to a value suitable for effecting the catalytic cracking of the hydrocarbon feed, the lift gas stream comprising less than 10 vol.% of C₃ plus hydrocarbons (i.e. containing 3 or more carbon atoms) and hydrogen in an amount of at least 10 vol.%. Such a hydrogen containing dry gas stream is readily available, and may readily be recovered from one or more downstream operations of the refinery process.

[0018] The advantages obtained by using a dry gas stream, optionally with steam and/or water in place of naphtha, light hydrocarbon, a high purity hydrogen gas or a wet gas stream comprising substantial C₃ plus hydrocarbon components as the lift gas are unexpected and not predictable. In fact, there is some considerable published prior art which suggests that a metal contaminated cracking catalyst should comprise some considerable residual coke, thereon, to suppress the hydrogenating and dehydrogenating functions of the metal contaminants. However the present operating technique produces unexpected liquid product selectivity using a relative inexpensive dry gas product, and substantially reduced coke deposits.

CATALYST

[0019] The catalyst employed in the catalytic cracking operation of the present invention may be any crystalline zeolite cracking catalyst known in the prior art and comprising rare earth and/or hydrogen ions in the crystal structure of the zeolote. The zeolite is dispersed in a siliceous-clay matrix material which may or may not provide some cracking activity. Thus, the matrix may be selected from silica-alumina, silica-zirconium or silica-chromium promoted with one or more metal additives which are effective in passivating accumulated metal contaminants. Suitable additives which may be used include rare earth metals providing excess lanthanum, and compounds of antimony and titanium. The cracking catalyst employed in the invention may comprise the active crystalline zeolite component in an amount less than about 40 wt.% and more usually in an amount within the range of 5 to 20 wt.%

[0020] Suitable catalysts are disclosed in US-A-4,440,868 and US-A-4,435,515.

[0021] A particularly preferred class of catalysts includes those that are capable of activating hydrogen and that have pore structures into which molecules of feed may enter for adsorption and/or for contact with active catalytic sites within or adjacent the pores. Various types of catalysts are available within this classification, including for example the layered silicates, e.g. smectites.

[0022] The zeolite-containing catalysts used in the present invention may include any zeolite, whether natural, semi-synthetic or synthetic, alone or in admixture with other materials which do not significantly impair the suitability of the catalyst, provided the resultant catalyst has the activity and pore structure referred to below. For example, if the catalyst is a mixture, it may include the zeolite component associated with or dispersed in a porous refractory inorganic oxide carrier; in such case the catalyst may for example contain about 1% to about 60%, more preferably about 1 % to about 40%, and most typically about 5% to about 40% by weight of the zeolite dispersed in the carriers, based on the total weight of catalyst (water free basis) of the porous refractory inorganic oxide alone or in combination with any of the known adjuvants for promoting or supres- sing various desired and undesired reactions, some of which are discussed below.

[0023] For a general explanation of the genus of zeolite molecular sieve catalysts useful in the invention, attention is drawn to the disclosures of the articles entitled "Refinery Catalysts Are A Fluid Business" and "Making Cat Crackers Work on Varied Diet", appearing respectively in the July 26, 1978 and September 13, 1978 issues of Chemical Week magazine.

[0024] In general, it is preferred to employ catalysts having an overall particle size in the range 5 to 160 microns, more preferably 40 to 120 microns, and containing a proportionately major amount in the 40 to 80 microns range.

[0025] It is preferred to employ a catalyst initially having a relatively high level of cracking activity and selectivity, and providing high levels of conversion and productivity at low residence times. The conversion capabilities of the catalyst may be expressed in terms of the conversion produced during actual operation or by standard catalyst activity test. (See the classical Shankland and Schmitkons "Determination of Activity and Selectivity of Cracking Catalyst", Proc. API 27 (III), 1947, pp. 57-77). For example, it is preferred to employ catalysts which, in the course of extended operation in the process, are sufficiently active for sustaining a level of conversion of at least about 50% or more preferably at least about 60%. In this connection, conversion is expressed in liquid volume percent, based on fresh feed.

[0026] The preferred catalyst may also be defined as one which, in its virgin or equilibrium stated, exhibits a specified activity expressed as a volume percentage derived by the MAT (micro- activity test). For a discussion relating to performing MAT's, and their significance to the present invention, see US-A-4,299,687.

[0027] When characterized on the basis of MAT activity, the preferred catalysts may be described on the basis of their MAT activity "as introduced" into the process of the present invention, or on the basis of their "as withdrawn" or equilibrium MAT activity, or on both of these bases.

[0028] A preferred MAT activity for virgin and non-virgin catalyst "as introduced" in the process of the present invention is at least about 60%, but it will be appreciated that, particularly in the case of non-virgin catalysts supplied at high addition rates, lower MAT activity levels may be acceptable.

[0029] An acceptable equilibrium MAT activity level of catalyst which has been used in the process of the present invention is about 20%, preferably at least about 40%, or more preferably about 60% or more are preferred values.

CATALYST ADDITION

[0030] In general, the weight ratio of catalyst to fresh feed (feed which has not previously been exposed to cracking catalyst under cracking conditions) used in the present invention is in the range of about 3 to 18. Preferred ratios may be about 4 to 12, depending on the coke forming tendencies of the feed. Within the limitations of product quality requirements, controlling the catalyst to oil ratio at relatively low levels within the aforesaid ranges tends to reduce the coke yield of the oil, based on fresh feed.

[0031] Catalyst may be added continuously or periodically, such as, for example, to make up for normal losses of catalyst from the system. Moreover, catalyst addition may be conducted in conjunction with withdrawal of catalyst, such as, for example, to maintain or increase the average activity level of the catalyst in the unit or to maintain a constant amount of metal on catalyst.

[0032] For example, the rate at which virgin catalyst is added to the unit may be in the range of about 0.285 kilograms per m³ of feed (0.1 to about 3 Ib/ bbl) to about 8.55 kilograms per m³ of feed or more (about 0.03 to 1 wt.% of the feedstock, or more), depending on the metal content in the feed, and the level of metal allowed to reside on the equilibrium catalyst. If, on the other hand, equilibrium catalyst is employed, a replacement rate as high as about 14.25 kilograms per m³ of feed (about 5 pounds per barrel) or more can be practiced. Where circumstances are such that the conditions in the unit tend to promote more rapid deactivation, one may employ rates of addition greater than those stated above; but in the opposite circumstances, lower rates of addition may be employed.

METAL-ON-CATALYST

[0033] The invention may be practiced with catalyst bearing accumulations of heavy metals which heretofore would have been considered quite intolerable in conventional fluid catalytic cracking (FCC), vacuum gas oil (VGO) operations. Employing catalyst bearing heavy metals accumulations in the range 1000 to 20,000 ppm Ni + V is preferred, but the accumulation may be as high as 30,000 ppm or even 50,000 ppm. The foregoing ranges are based on parts per million of heavy metal, including nickel, vanadium, incremental iron (that additional iron accumulated while being used) and copper, in which the metals are expressed as metal, by weight, and based on regenerated equilibrium catalyst, i.e. previously used catalyst. In some cases there may be used equilibrium catalysts from another unit, for example, an FCC unit, which has been used in the cracking of vacuum gas oil, having a carbon residue on pryolysis of less than 1% and containing less than about 4 Nickel Equivalents of heavy metals.

CATALYST PROMOTERS

[0034] The catalyst composition may also include one or more combustion promoters which are useful in the subsequent step of regenerating the catalyst. In order to restore the activity of the catalyst, coke is burned off in a regeneration step, in which coke is converted to combustion gases including carbon monoxide and/or carbon dioxide. Various substances e.g. Pt, Pd, rare earths, are known which, when incorporated into a cracking catalyst in small quantities (or added with the feedstock), tend to promote conversion of coke to carbon monoxide and/or carbon dioxide. Promoters of combustion to carbon monoxide tend to lower the temperature at which a given degree of coke removal can be attained, thus diminishing the potential for thermal deactivation of the catalyst.

[0035] Such promoters, normally used in effective amounts ranging from a trace up to about 10% to 20% by weight of catalyst, may, for example, be of any type which generally promotes combustion of carbon under regenerating conditions.

ADDITIONAL MATERIALS

[0036] The amount of additional materials which may be present in the feed may be varied as desired; but said amount will preferably be sufficient to substantially heat balance the process. These materials may for example be introduced into the reaction zone in a weight ratio relative to feed of up to about 0.4, preferably in the range of about 0.02 to about 0.4, more preferably about 0.03 to about 0.3 and most preferably about 0.05 to about 0.25.

[0037] When liquid water, recycled from the regeneration step, is added to the reaction zone as an additional material, either already admixed with the feed or separately, a preferred embodiment is to have hydrogen silfide dissolved therein within the above ranges, based on the total amount of feed. Alternately, about 500 ppm to about 5,000 ppm of hydrogen sulfide should be dissolved in the recycled liquid water. Hydrogen sulfide gas, in the above weight ratio ranges, may also be added as the additional material instead of hydrogen sulfide dissolved in recycled liquid water.

[0038] The process of the present invention employs ballistic separation of catalyst and vapours at the downstream of a progressive flow type riser, such as is taught in US-A-4,066,533 and US-A-4,070,159 to which reference should be made for further details.

[0039] Depending upon whether there is slippage between the catalyst and hydrocarbon vapour in the riser, the catalyst riser residence time may or may not be the same as that of the vapour. Thus, the ratio of average catalyst reactor residence time versus vapour reactor residence time, i.e. slippage, may be in the range of about 1 to about 5, more preferably about 1 to about 4, and most preferably about 1.1 to about 3, with about 1.2 to about 2 being the preferred range.

[0040] It is considered advantageous if the vapour riser residence time and vapour-catalyst contact time in the riser are substantially the same for at least about 80% of the riser length.

CATALYST REGENERATION

[0041] Regeneration of catalyst may be performed at a temperature in the range 593°C to 871°C (1100°F to 1600°F), measured at the catalyst regenerator outlet. More usually this temperature will be in the range 649°C to 816°C (1200°F to 1500°F), more preferably in the range 677°C to 774°C (1250°F to 1425°F) and optimally from 704°C to 760°C (1300°F to 1400°F).

[0042] To minimize regeneration temperatures and demand for regeneration capacity, it is desirable to employ conditions of time, temperature and atmosphere in a stripper which are sufficient to reduce potentially volatile hydrocarbon material borne by the stripped catalyst to about 10% or less by weight carried to the regenerator. Such stripping may for example include reheating of the catalyst, extensive stripping with steam, the use of gases having a temperature considered higher than normal for FCCNGO operations, such as for instance flue gas from the regenerator, as well as other refinery stream gases such as hydrotreater off-gas (H₂S containing), hydrogen and others. The stripper may be operated at a temperature above about 482°C (900°F). Stripping operations in which the temperature of the spent catalyst is raised to higher temperatures is also within the scope of the present invention.

[0043] In order to maintain desired activity of the zeolite catalyst, it is desirable to regenerate the catalyst under conditions of time, temperature and atmosphere sufficient to reduce the percent by weight of carbon remaining on the catalyst to about 0.05% or less, whether the catalyst bears a large heavy metals accumulation or not. The term coke should be understood to include any residual unvapourized feed or hydrocarbonaceous material present on the catalyst after stripping thereof.

[0044] The substantial levels of conversion accomplished by the process of the present invention result in relatively large yields of coke, such as for example about 4% to about 17% by weight based on fresh feed, more commonly about 6% to about 14% and most frequently about 6 06% to about 12%.

[0045] At contemplated catalyst to oil ratios, the result ant coke laydown may be in excess of about 0.3%, more commonly in excess of about 0.5% and very frequently in excess of about 1% of coke by weight, based on the weight of moisture free virgin or regenerated catalyst. Such coke laydown may range as high as about 2%, or about 3%, or even higher, although coke in the range of 0.5 to about 1.5% is more commonly experienced.

[0046] According to a preferred embodiment of the present invention, the sub-process of regeneration, as a whole, may be carried out to the abovementioned low levels of coke on regenerated catalyst with oxygen supplied to the one or more stages of regeneration in the stoichiometric amount required to burn all hydrogen in the coke ot H₂0 and to burn all carbon in the coke to CO and/or C₂ and to burn all sulfur in the coke to S0₂. If the coke includes other combustibles, the aforementioned stoichiometric amount can be adjusted to include the amount of oxygen required to burn them.

[0047] Multi-stage regeneration offers the technique of combining oxygen deficient regeneration with control of the CO:CO₂ molar ratio and still provide means by which coke on catalyst is reduced preferably to 0.05% or lower. Thus, about 65% to about 80% by weight of the coke on the catalyst is removed in a first stage of regeneration in which the molar ratio of CO:C0₂ is controlled.

[0048] In combination with the foregoing, the last weight percent of the coke originally present, up to the entire amount of coke remaining after the preceding stage can be removed in a subsequent stage of regeneration in which more oxygen is present.

[0049] A particularly preferred embodiment of the present invention is two stage catalyst regeneration at a maximum temperature of about 816°C (1500°F) but preferably not above 760°C (1400°F). The second stage temperature is the same or lower than the first stage, with reduction of carbon on catalyst to about 0.05% or less or even about 0.025% or less by weight in the second zone. In fact, catalyst can readily be regenerated to carbon levels as low as 0.01% by this technique, even though the carbon on catalyst prior to regeneration is as much as about 1% or greater.

[0050] Still another particularly preferred technique for controlling or restricting the regeneration heat imparted to fresh feed via recycled catalyst involves the diversion of a portion of the heat borne by recycled catalyst to additional material, discussed herein. The catalyst discharged from the regenerator is stripped with appropriate stripping gases to remove oxygen containing gases. Such stripping may for instance be conducted at relatively high temperatures, using steam nitrogen or inert gas(es) as the stripping gas. The use of nitrogen or other inert gases is beneficial from the standpoint of avoiding a tendency toward hydrothermal catalyst deactivation which may result from the use of steam.

FEEDSTOCK

[0051] Although the present invention is primarily applicable to the catalytic conversion of heavy residual oil feeds, including vacuum bottoms and portions thereof which have been subjected to a previous partial hydrogenation operation to remove sulfur and nitrogen compounds, and which contain heavy metal contamination and high Ramsbottom carbon values, the invention may also be applied to lighter gas oil feeds and heavy crude oil feeds which have been partially decarbonized and demetallized by contact with a sorbent material under thermal visbreaking conditions in the presence of a diluent with or without the presence of hydrogen. The sorbent material employed in the visbreaking operation may be relatively inert or of such low catalytic activity that it is no longer suitable for use in a catalytic cracking operation. Thus, the process of the present invention will be applicable to operation of the type disclosed in US-A-4,434,044 to which reference should be made.

[0052] The conditions employed in the catalytic cracking operation of this invention, i.e. in the riser, will vary depending upon the composition and boiling range of the oil feed charged. Generally, the regenerated catalyst charged to the riser will be at a temperature in the range 649°C to 816°C (1200°F to 1500°F) and more usually in the range 704°C to 760°C (1300°F to 1400°F). The catalyst to oil ratio and hydrocarbon feed partial pressure will vary with the feed boiling range and volume of gaseous diluent used so that vapourous hydrocarbon conversion products comprising suspended cracking catalyst, lift gas and feed atomizing diluent material will be discharged from the riser at a temperature in the range 482°C to 593°C (900°F to 1100°F) and more usually in the range 510°C to 566°C (950°F to 1050°F).

[0053] In applying the present process to the disclosure of US-A-4,434,044 in order to improve product selectivity and reduce coke deposition an important aspect of the combined process is related to the light gaseous product recovery steps of Figure 1 shown in that patent, wherein a fuel gas is recovered from a C_3-C₄ fraction. This fuel gas comprises hydrogen and when separated from the C₃-C₄ hydrocarbons is particularly suitable for use as the lift gas in accordance with the present invention. Thus the product recovery technique disclosed in US―A―4,434,044 and described therein with reference to Figure III is particularly useful in the present invention as the source of the dry lift gas, and reference should be made to that patent for further details.

[0054] In applying the present technique to the process disclosed in US-A-4,434,044, the apparatus shown in Figure V of that Patent, comprising a riser catalytic cracking zone adjacent to a sequence of two stage catalyst regeneration providing for cooling of catalyst passed from said first stage to said second stage of catalyst regeneration, is preferably modified to incorporate a riser reactor of larger diameter in an upper portion than in a lower portion thereof with the oil feed to be cracked being charged to a downstream section of the riser comprising the larger diameter poriton thereof. Such a riser design is shown in US-A-4,435,279 to which reference should be made for further details.

[0055] In summary the essential and preferred features of this invention include:

(a) using a refinery product gas known as dry gas (commonly derived from the conventional gas concentration unit, such as that shown in Figure III of US―A―4,434,044) comprising at least 10 vol.% of hydrogen but less than 10 vol.% of C₃ and.heavier hydrocarbons, as the lift gas for the hot freshly regenerated catalyst at a temperature of at least 704°C (1300°F). Optionally the dry gas may be supplemented with steam and/or water as a heat sink in an amount sufficient to reduce the regenerated catalyst temperature to the desired oil feed conversion temperature. The preferred dry gas compositions contain 15 to 40%, most preferably 20 to 35% hydrogen, and not more than 8%, most preferably 0 to 6% C₃ and higher hydrocarbon (percentages on a volume basis).

(b) the dry gas-steam-catalyst suspension is formed in the lower portion of the riser beneath the point of oil feed injection thereto and is retained therein for a residence time in the range 0.01 to 2 seconds sufficient to reduce meal oxides on the catalyst to a lower oxidation state or its metal state, but short enough to inhibit coke deposited on the regeneration catalyst particles exceeding about 0.25 wt% before contact with the charged oil feed boiling above about 343°C (650°F).

(c) a refinery product dry gas stream comprising less than 10 vol.% of C₃-plus material and from 10 to 40 vol.% hydrogen recoverable from a downstream aromatic desulfurization unit represents an economically attractive lift gas for use in the cracking operation of this invention. Hydrogen sulfide in this dry gas stream helps to form sulfide compounds with the metal contaminants.

(d) the processing of high carbometallic reduced crude oil feeds with catalyst comprising up to 20,000 ppm Ni + V metal contaminants accumulated on the catalyst may be accomplished with improved product selectivity using the techniques herein described especially when the catalyst is provided ith one or more metal additives for passivating the nickel and vanadium accumulated on the catalyst.

[0056] As a result an improved product selectivity is achieved and the substantially reduced slurry oil and coke deposition enables lower catalyst regeneration temperatures whether the regeneration is carried out in one or two stages. Thus regeneration temperatures can be employed not exceeding 760°C (1400°F) in either stage of regeneration. Thus, the hydrothermal catalyst deactivation normally encountered when the regenerated particles are contacted with steam added to the lift gas to form a rising catalyst suspension is measurably reduced to acceptable limits.

[0057] The invention is further described with reference to the accompanying drawings, in which:

Figure 1 is a graph comparing the hydrogen yields obtained using a wet recycle gas and a dry recycle gas as catalyst lift gas prior to converting the oil feed to products boiling below 221°C (430°F) ;

Figure 2 is a graph comparing the C₅ 221°C (430°F) gasoline yields obtained using a wet recycle gas and a dry recycle gas as a catalyst lift gas prior to converting an oil feed to products boiling below 221°C (430°F);

Figure 3 is a graph comparing the gasoline selectivity obtained using a wet recycle gas and a dry recycle gas as a catalyst lift gas prior to converting an oil feed to products boiling below 221°C (430°F);

Figure 4 is a graph comparing the coke yield obtained using a wet recycle gas and a dry recycle gas as catalyst lift gas when converting an oil feed to products boiling below 221°C (430°F).

Figure 5 is a graph comparing the reduced C₂- minus by-products obtained when using a wet recycle gas and a dry recycle gas as a catalyst lift gas prior to converting an oil feed to products boiling below 221°C (430°F).

Figure 6 shows a residual oil cracking unit comprising a catalytic cracking reactor or riser and an adjacent catalyst regenerator suitable for use in the present invention and being of the general type shown in US-A-4,435,279 and US-A-4,434,044, and to which reference should be made for full details.

[0058] Referring to the drawings a sequence of experiments has been carried out in which carbometallic containing residual oil feeds comprising Ramsbottoms carbon, sulfur, nickel and vanadium were brought into contact with a typical fluid cracking catalyst comprising a rare earth exchanged crystalline aluminosilicate (faujasite) containing cracking catalyst following regeneration treatment thereof at an elevated temperature, herein defined, with a hydrogen rich dry gas comprising less than 10% of C₃-plus materials, and for comparison a hydrogen rich wet gas obtained as a downstream product of catalytic cracking operation and comprising subatantial quantities of C₃, C₄ and C₅ hydrocarbons. The exact compositions of the dry and wet gas are set forth in Table I and Table II respectively.

[0059] Referring now to Figure 1, there is presented a plot of the data obtained with respect to hydrogen production obtained during conversion of a residual oil feed to 221°C (430°F) minus products after pretreatment of the cracking catalyst at a temperature of about 704°C (1300°F) using the hydrogen rich dry lift gas, Table I and the hydrogen rich wet gas, Table II. It will be observed from Figure 1 that the upper curve representing treatment of the catalyst with the wet gas product produced considerably more hydrogen during subsequent conversion of the residual oil feed with a catalyst suspension thereof than was obtained by using a dry gas as lift gas to form a suspension of high temperature catalyst of at least about 704°C (1300°F).

[0060] Figure 2 compares the C₅ to 221°C (430°F) gasoline yield using the dry lift gas and the wet lift gas. It is significant to note from this Figure that the use of dry gas as a lift gas provided higher yield of gasoline product than was obtained when using the wet gas as a lift gas. Thus the gasoline product selectivity is considerably improved.

[0061] Figure 3 compares the gasoline selectivity obtained when using the dry lift gas and the wet lift gas.

[0062] Figure 4 is a further plot of the experimental data obtained showing the coke production obtained when converting a residual oil to 221°C (430°F) minus product in the presence of catalyst initially contacted dry or wet lift gas as the case may be. It will be observed from the plot of Figure 4 that the use of a hydrogen rich wet recycle gas comprising C₄ and C₅ hydrocarbons in substantial amounts produced considerably more coke in the catalyst than was obtained when using a hydrogen rich dry recycle gas. The high coke deposition contributes to obtaining high catalyst regeneration temperatures exceeding 760°C (1400°F).

[0063] Figure 5 shows the reduced amount of C₂- minus by product obtained using the dry lift gas as opposed to the wet lift gas.

[0064] The above data identifies beyond any reasonable doubt that a wet recycle gas comprising substantial amounts of C₃ and higher hydrocarbons found in a wet gas contributes coke to the cracking catalyst, thereby reducing the catalyst cracking activity and selectivity as shown by the yield difference obtained in C₅ plus gasoline and light cycle oil yield. Using a dry gas, on the other hand, comprising very little C₃ and higher hydrocarbons provided improved yields. It is further noted that when using a dry gas composition defined herein permits one to use from about 12 to 15 weight percent more lift gas relative to feed in a given riser cracking operation.

[0065] When the lift gas comprises a significant quantity of C₃ plus material comprising C_s hydrocarbons which are cracked to deposit coke on the hot freshly regenerated catalyst prior to contact with the residual oil feed, a signficant reduction occurs in the catalyst cracking activity and selectivity and this contributes to a resultant loss in C₅ plus gasoline product material evaluated to amount to at least 3 to 5 vol.% of desired gasoline forming product material.

[0066] It is thus clear from the experimental evidence that it is essential to more efficient cracking of oil feeds to use a lift gas initially in contact with hot freshly regenerated catalyst which contributes little, if any, coke deposition on the hot catalyst particles prior to contact with the oil feed to be converted. This operating concept is accomplished as determined by the experimental evidence herein provided by using an economically obtainable commercial dry gas product of a refinery operation such as the cracking operation comprising hydrogen and preferably less than about 10% of C₃ plus hydrocarbons. Another lift dry gas suitable for the purpose is one consisting of hydrogen, methane and ethane. However, such a recycle lift gas product stream of a cracking or refinery operation is difficult to obtain economically from a commercial operation. A hydrogen-containing gas stream obtained from desulfurizing an aromatic oil product of coal processing may be used provided the C₃ plus hydrocarbons therein are less than 10 vol.%.

[0067] It is concluded further from the available evidence that the regenerated catalyst should be reduced to a residual coke level of at least 0.10 wt.% and preferably to at least 0.05 wt.%. The formed catalyst suspension with dry gas and comprising hydrogen prior to contact with the oil feed to be converted should be restricted to a coke level not to exceed about 0.25 wt.% and preferably should not be above about 0.15 wt.% to reap the significant benefits herein identified.

[0068] As indicated the process of the present invention is applicable to a fluidized catalytic cracking operation of the type disclosed in US-A-4,434,044 and using apparatus of the type disclosed therein and comprising a verticaly oriented riser and an adjacent catalyst regeneration recovery system.

[0069] One such specific apparatus combination is shown herein in Figure 6. This comprises a riser reactor 1 with an expanding transition section in an upper portion thereof which terminates in a larger diameter portion 2 of the riser there above. Conversion of the charged oil feed such as a residual oil feed by one of 5, 7 or 9 feed inlets is particularly effective. The expanded or larger diameter portion of the riser 2 is provided with a plurality of feed inlet nozzles means 6 adjacent the upper edge of the transition section which are used in a preferred embodiment to charge the oil feed. The vertically spaced apart feed inlet means 5, 7 and 9 provides the operator considerably more latitude in feed contact time with the dry gas-catalyst suspension within the riser reactor before separation of a resultant formed suspension of hydrocarbon product vapours, catalyst and lift gas available as herein discussed. Thus, the riser 1-2 configuration of Figure 6 permits achieving relatively high temperature zeolite catalytic upgrading of an oil feed charged to a bottom, intermediate or upper portion of the riser conversion zone but downstream of the formed dry gas-regenerated catalyst suspension to restrict the oil feed contact time with catalyst within the range of a fraction of a second up to 1, 2 or even 3 seconds contact time.

[0070] In this riser arrangement, the hot regenerated catalyst at a temperature within the range of 649°C (1200°F) to 816°C (1500°F) is intially mixed with a dry lift gas or fluidizing gas as herein provided with the addition of steam and/or water as heat sink material to form an upflowing suspension in the restricted diameter portion thereof at a temperature suitable for effecting catalytic cracking of a downstream charged residual oil feed as by 7 or 9. Thus, feed inlet means 5,7 and 9 with diluent inlets 6, 8 and 10 permit a substantial variation in feed atomization and partial pressure and contact time as above identified between oil feed and the dry gas-steam suspended catalyst particles. Furthermore, a bottom portion of the riser reactor permits adjustment of the regenerated catalyst temperature by the addition of steam and/or water as a heat sink along with the dry lift gas of a composition particularly identified herein.

[0071] Generally speaking the contact time between a residual oil feed and catalyst in the riser depending on feed composition and source will be restricted to within the range of 0.5 to about 2 or 3 seconds when contacting an oil feed with catalyst at a temperature in the range of 704°C (1300°F) to 760°C (1400°F) to provide a riser outlet temperature within the range of 510°C (950°F) to 593°C (1100°F) and more usually not above 566°C (1050°F). The riser reactor may be substantially any desired vertical length which will be compatible with the adjacent catalyst regeneration apparatus whether of single or multiple sages of regeneration as shown, catalyst stripping and catalyst transfer conduit means essential to the combination.

STRIPPING

[0072] The upper portion of riser 2 passes upwardly through a stripping zone 6 to form an annular stripping zone therewith into an upper portion of a larger diameter catalyst disengaging zone in open communication with the annular stripping zone 16. Stripping gas such as steam or other suitable gas is charged to a bottom portion of the stripping zone by conduit 17 for flow upwardly therethrough and counter-current to downflowing catalyst particles.

REGENERATION

[0073] The stripped catalyst is then passed by conduit 19 to catalyst regeneration shown as a sequence of catalyst beds 20 and 36 being regenerated in separate zones to remove carbonaceous deposits of conversion by combustion without exceeding an elevated temperature below about 816°C (1500°F) and preferably restricted to within the range of about 649°C (1200°F) to 816°C (1500°F) and more usually within the range of 704°C (1300°F) to 760°C (1400°F)

CATALYST SEPARATION

[0074] An important aspect of the riser system is the method and means for separating the upwardly flowing suspension at the riser upper open end. That is, the suspension of hydrocarbon vapours, catalyst, lift gas and steam is discharged from the upper open end of the riser at a velocity which will impart a great er momentum to the particles of catalyst than to that imparted to the vapourous constituents whereby an upwardly flowing trajectory is established which separates catalyst particles from vaporous material. The vaporous material mixture, often referred to as gasiform material in the prior art, passes into an annular cup 11 withdrawal passageway open in the top thereof and thence through radiating conduit means in open communication with cyclone separation means 12 on the other end of each of said radiating conduits. Vapors separated from entrained catalyst fines in cyclones 12 are recovered by conduits communicating with plenum chanber 13 and product withdrawal conduit 14 for passage to product fractionation and separation in means not shown. Catalyst fines separated in cyclones 12 are removed by diplegs for passage to catalyst stripping and regeneration discussed below.

CATALYST

[0075] The hydrocarbon conversion operation contemplated to be accomplished in the riser zone herein discussed relies upon the use of fluidizable particles of catalyst of a particle size in excess of 10 x 10-⁶ metres (10 microns) and usually providing an averge particle size within the range of 60 to 100 x 10-⁶ metres (60 to 100 microns) and more usually below about 85 x 10-⁶ metres (85 microns). The catatyst is preferably one comprising a crystalline alumisilicate or crystalline zeolite which has been rare earth and/or ammonia exchanged to provide a catalytically active material which is dispersed in a matrix material which may or may not have catalytic activity. A catalyst particularly suitable for use in the process of this invention is a rare earth exchanged faujasite crystalline zeolite comprising a catalyst pore volume and matrix pore size openings which will collect and/or accumulate substantial quantities of metal contaminants and yet retain substantial catalyst cracking activity and selectivity as herein provided.

FEEDS

[0076] The oil feed such as a residual portion of crude oil charged by feed inlet 5 or 7 may be mixed with steam and/or water such as product sour water charged by conduits 6 or 8. On the other hand, when charging the oil feed by feed inlet 9, the steam-water mixture may be added by conduit 10. The bottom portion of riser 2 is provided with dry lift gas inlet conduit 4 for charging the lift gas to form an upflowing suspension with hot regenerated catalyst particles charged to a bottom portion of the riser by conduit 3. The dry lift gas may be charged to the riser alone or in combination with steam and/or water introduced by conduit 43.

[0077] The lower portion of the riser of restricted diameter may be used to serve several different functions beyond the formation of an upflowing suspension of a desired catalyst particle concentration within the range of 16 to 44 kilograms per cubic metre. That is, the use of a hydrogen containing dry gas herein identified as lift gas may be used as a contaminant metals passivation material to which a passivating metal compound is added to passivate Ni and V. Antimony may be added to passivate accumulated nickel deposits. Vanadium oxide may be passivated by the combination of hydrogen reduction to a lower oxide state providing a high melting point oxide thereof alone or. in conjunction with the addition of titanium, alumina and rare earth metals rich in lanthanum. Thus, whatever use is made of the lower portion of the riser reactor prior to oil feed atomized injection, it is essential to the concepts of this invention that the use of a hydrogen containing product recycle dry gas be of a composition which severely limits the C3 and higher components of the dry gas to a level inhibiting any significant coking of the catalyst therewith and prior to contact with the heavy oil feed to be cracked. As particularly discussed, herein, restricting the hydrogen containing dry gas to a C₃ plus content less than 10%, more preferably less than 8% and most preferably less than 6%, improves the gasoline yield, reduces the yield of hydrogen, increases the yield of light cycle oil and reduces the yield of slurry oil and coke. These findings obtained by experimental evidence were unexpected and not predictable. A further significant economic aspect of the operating concept is the use of readily available refinery product gases or other source gases comprising from 10 to 40 vol.% of hydrogen in the dry gas.

[0078] In a particular operating embodiment, a dry gas product of the cracking operation is employed comprising at least 15 vol.% hydrogen, less than 10 vol.% of C₃ plus hydrocarbons in admixture with water in an amount sufficient to partially cool the regenerated catalyst to a desired low oil feed conversion level before contact with atomized preheated residual oil charged to the rising dry gas-steam-catalyst suspension. The fluid catalytic cracking of the charged hydrocarbons is effected at a riser pressure above atmospheric pressure and the riser cracking operation of this invention may be effected at a pressure of about 172 x 10³ to 1,137 x 10³ Pascals (about 10 to 150 psig) pressure. However, the atomized oil feed hydrocarbon partial pressure will be substantially reduced by the lift gas-steam mixture and the oil feed atomizing diluent material. Thus, the oil feed partial pressure may be in the range of 27.6 to 172 x 10³ Pascals and the catalyst to oil ratio may be within the range of about 5 to 15, more preferably 6 to 12, and providing for intimate contact between catalyst particles and the atomized oil feed.

[0079] The combustion apparatus of Figure 6 provides a unique catalyst particle regeneration arrangement permitting close temperature control to minimize particularly hydrothermal deactivation of catalyst particles during the removal of coke deposits by combustion and contributed particularly by gas oil catalytic conversion and/or higher boiling components of residual oil including vacuum resid.

[0080] Referring now particularly to the catalyst regeneration apparatus and its method of utilization there is provided a unique arrangement in that the upper chamber portion thereof is of a larger diameter than a bottom chamber portion and separated from one another by a regeneration gas distributor chamber 24 centrally located and supported by an annular baffle member 40 provided with gas flow through passageways 41. A . plurality of radiating arm means 25 from chamber 24 are provided for introducing regeneration gas to a lower bottom portion of catalyst bed 20 being regenerated. Regeneration combustion supporting gas such as air or an oxygen modified gas in conduit 22 admixed with steam in conduit 23 provides a desired concentration of oxygen and partial removal of carbonaceous deposits from the charged catalyst particles whereby combustion temperatures encountered can be restricted to within a desired range are charged by plenum 24 and radiating arms 25. In this first stage of catalyst regeneration comprising combustion of hydrocarbonaceous deposits effected in the presence of oxygen, carbon dioxide and steam as desired, the regeneration temperature is preferably kept to a low value in the range of 593°C (1100°F) to 871°C (1600°F), preferably 649°C (1200°F) to 815°C (1500°F) and more usually in the range of about 690°C (1275°F) to 760°C (1400°F).

[0081] A partial removal of carbonaceous material is removed in catalyst bed 20 under conditions producing CO rich containing product flue gases and comprising carbon dioxide, sulfur, nitrogen and water vapour. The thus-generated flue gases pass through one or more combination of cyclones represented by cyclones 26 to remove entrained catalyst fines recovered by diplegs provided. The flue gases then pass from cyclones 26 to a plenum chamber 27 or recovery therefrom by conduit 28. Such CO rich containing flue gases are normally passed to a CO boiler not shown to generate process steam.

[0082] The partially regenerated catalyst comprising bed 20 is removed from a bottom portion thereof for downflowthrough an external catalyst cooling zone 29 in indirect heat exchange with bayonnet type heat exchange tubes 30 provided and substantially vertically extending therein. High pressure steam of the order of about 3.1 x 10⁶ Pascals (450 pounds) steam is generated and recovered as by conduit 34 when charging boiler feed water by conduit 31 to a distributor chamber in the bottom of cooler 29 communicating with said heat exchange tubes 30. The catalyst partially cooled in chamber 29 by an amount in the range -of 28°C to 111°C (50°F to 200°F) and more usually in the range of 55°C to 83°C (100°F to 150°F) is withdrawn and passed by conduit 35 to a bed of catalyst 36 retained in the second stage of catalyst regeneration in chamber 37 A stand pip 42 communicating between bed 20 and 36 is provided for direct passage of catalyst without cooling from the upper bed to the lower bed when required. However, the main or primary flow of catalyst between beds is through cooler 29 to maintain desired catalyst temperature restraints in the sequential regeneration system. A temperature restraint in the second stage comprising bed 36 is restricted within the range of 649°C to 816°C (120°F to 1500°F) and more usually within the range of 704°C to 760°C (1300°F to 1400°F). The temperature of the regenerated catalyst in dense fluid bed 36 may be equal to, above or below the temperature maintained in dense fluid catalyst bed 20 in the first stage of catalyst regeneration. In one embodiment, the amount of air or oxygen modified gas charged to catalyst bed 36 by conduit 38 and passing through grid 39 may be equal to or more than that required to complete combustion of residue carbon on the partially regenerated catalyst and provide a CO₂ rich flue gas product which may or may not comprise some unconsumed oxygen. It is preferred that the flue gas passed from the upper dense phase of catalyst bed 36 be free of combustion supporting amounts of CO to prevent after burning from occurring therein. The C0₂ rich flue gas product of the second stage of catalyst regeneration at an elevated temperature passes through openings 41 in baffle 40 into a bottom portion of bed 20 for admixture with the regeneration gas charged by distributor arms 25 thereby contributing heat to the first stage of catalyst regeneration. All of the flue gas combustion products of the second stage of catalyst regeneration to reduce the coke residue to about 0.05 wt.% or as low as about 0.01 wt.% coke on regenerated catalyst particles passes through catalyst bed 20 of the first stage of regeneration. Regenerated catalyst obtained as above provided is withdrawn from an upper catalyst bed 36 for passage by conduit 3 to a bottom portion of riser 1 for use as above discussed.

[0083] In an apparatus arrangement disclosed and discussed with respect to Figure 6 it is contemplated employing a riser reaction zone of a vertical length of about 49 metres (about 160 feet) through which a catalyst suspension is passed at a velocity in the range of 18 to 31 metres/sec (60 to 100 ft/sec.). In a specific embodiment employing a velocity of about 24.5 metres/sec. (80 ft/sec.) the suspension traverses the riser in about 2 seconds. In such an operation the dry gas-steam-catalyst suspension initially formed consumes a residence time of a fraction of a second up to 0.5 second before contact with the atomized oil feed and providing a hydrocarbon residence contact time with catalyst particles up to about 1 or 1.5 seconds. The short residence times identified are not detrimental to the process and may be used with considerable advantage to maintain desired product selectivity by reducing any tendency of over-cracking to occur.

Claims

Claims for the following Contracting State(s) : s: AT DE FR GB IT NL

1. A process for catalytic cracking of hydrocarbon feedstocks, which comprises establishing in the bottom of a vertically oriented riser an upflowing stream of hot, regenerated catalyst particles, comprising a crystalline zeolite, suspended in a lift gas, introducing the hydrocarbon feedstock into the upwardly flowing stream of regenerated catalyst particles, passing the mixture upwardly through the riser to effect catalytic cracking of the feedstock, separating the catalyst particles from the cracked product stream recovered from the top of the riser, and passing the separated particles through a catalyst regeneration zone wherein they are regenerated with a hot oxygen-containing gas effective to burn off carbon deposited on the used catalyst particles prior to recycle to the bottom of the riser, characterized in that:

(a) the lift gas comprises a hydrocarbon-containing dry gas stream containing at least 10 vol.% hydrogen but less than 10 vol.% C₃ and heavier hydrocarbons, contact between the hot regenerated catalyst particles and said lift gas being maintained for a short period of from 0.01 to 2 seconds prior to the introduction therein of said hydrocarbon feedstock thereby to limit coke deposition on the regenerated catalyst particles to 0.25 wt.% or less prior to contact with the hydrocarbon feedstock,

(b) the hydrocarbon feedstock is a residual crude oil fraction boiling above 650°F (343°C) having a heavy metal content, calculated in terms of Nickel Equivalent, of at least 4, and a carbon residue on pyrolysis of at least 1%, and

(c) the regenerated catalyst comprises from 1,000 to 50,000 ppm accumulated heavy metal.

2. A process according to claim 1, characterized in that, after separation of the used catalyst particles, the cracked product stream from the riser is treated to separate a liquid product stream and a gaseous product stream, which gaseous product stream is then further treated to obtain a hydrocarbon-containing hydrogen rich dry gas product stream containing less than 10 vol.% C₃ and heavier hydrocarbon and which is then recycled to the riser to provide said lift gas.

3. A process according to claim 2, characterized in that the hydrocarbon-containing, hydrogen rich dry gas product stream recycled to the riser as said lift gas contains a proportion of hydrogen sulfide and is a product recovered from an aromatic desulfurization unit downstream of the riser.

4. A process according to any one of claims 1 to 3, characterized in that the dry gas stream contains 15 to 40, preferably 20 to 35 vol.% hydrogen.

5. A process according to any one of claims 1 to 4, characterized in that the dry gas stream contains less than 8 vol.% C₃ and heavier hydrocarbon, preferably 0 to 6 vol.%.

6. A process according to any one of claims 1 to 5, characterized in that the temperature of the lift gas stream containing the suspended, hot regenerated catalyst particles is adjusted prior to injection therein of said feedstock by injection of steam and/or water.

7. A process according to any one of claims 1 to 6, characterized in that the feedstock has a Nickel Equivalent of at least 5, preferably at least 5.5.

8. A process according to any one of claims 1 to 7, characterized in that the feedstock has a carbon residue on pyrolysis of at least 2% by weight.

9. A process according to any one of claims 1 to 8, characterized in that the regenerated catalyst particles have a heavy metal accumulation in the range 1,000 to 20,000 ppm Ni + V.

Claims

Claims for the following Contracting State(s) : s: BE SE

1. A process for catalytic cracking of hydrocarbon feedstocks, which comprises establishing in the bottom of a vertically oriented riser an upflowing stream of hot, regenerated catalyst particles, comprising a crystalline zeolite, suspended in a lift gas, introducing the hydrocarbon feedstock into the upwardly flowing stream of regenerated catalyst particles, passing the mixture upwardly through the riser to effect catalytic cracking of the feedstock, separating the catalyst particles from the cracked product stream recovered from the top of the riser, and passing the separated particles through a catalyst regeneration zone whereim they are regenerated with a hot oxygen-containing gas effective to burn off carbon deposited on the used catalyst particles prior to recycle to the bottom of the riser, characterized in that the lift gas comprises a hydrocarbon containing dry gas stream containing at least 10 vol.% hydrogen but less than 10 vol.% C₃ and heavier hydrocarbons, contact between the hot regenerated catalyst particles and said lift gas being maintained for a short period of from 0.01 to 2 seconds prior to the introduction therein of said hydrocarbon feedstock thereby to limit coke deposition on the regenerated catalyst particles to 0.25 wt.% or less prior to contact with the hydrocarbon feedstock.

2. A process according to claim 1, characterized in that, after separation of the used catalyst particles, the cracked product stream from the riser is treated to separate a liquid product stream and a gaseous product stream, which gaseous product stream is then further treated to obtain a hydrocarbon-containing hydrogen rich dry gas product stream containing less than 10 vol.% C₃ and heavier hydrocarbon and which is then recycled to the riser to provide said lift gas.

3. A process according to claim 2, characterized in that the hydrocarbon-containing, hydrogen rich dry gas product stream recycled to the riser as said lift gas contains a proportion of hydrogen sulfide and is a product recovered from an aromatic desulfurization unit downstream of the riser.

4. A process according to any one of claims 1 to 3, characterized in that the dry gas stream contains 15 to 40, preferably 20 to 35 vol.% hydrogen.

5. A process according to any one of claims 1 to 4, charcterized in that the dry gas stream contains less than 8 vol.% C₃ and heavier hydrocarbon, preferably 0 to 6 vol.%.

6. A process according to any one of claims 1 to 5, characterized in that the temperature of the lift gas stream containing the suspended, hot regenerated catalyst particles is adjusted prior to injection therein of said feedstock by injection of steam and/or water.

7. A process according to any one of claims 1-6, characterized in that the hydrocarbon feedstock is a residual crude oil fraction boiling above 650°F (343°C) having a heavy metal content, calculated in terms of Nickel Equivalent, of at least 4, and a carbon residue on pyrolysis of at least 1 % and in that the regenerated catalyst comprises from 1,000 to 50,000 ppm accumulated heavy metal.

8. A process according to claim 7, characterized in that the feedstock has a Nickel Equivalent of at least 5, preferably at least 5.5.

9. A process according to claim 7 or 8, characterized in that the feedstock has a carbon residue on pyrolysis of at least 2% by weight.

10. A process according to any one of claims 7, 8 or 9, characterized in that the regenerated catalyst particles have a heavy metal accumulation in the range 1,000 to 20,000 ppm Ni + V.

Ansprüche

Patentansprüche für folgende(n) Vertragsstaat(en) : AT DE FR GB IT NL

1. Verfahren zum katalytischen Kracken von Kohlenwasserstoff-Ausgangsmaterialien, welches umfaßt: das Schaffen, im unteren Teil eines senkrecht angeordneten Reaktors (Riser), eines aufwärts gerichteten Stroms von heißen regenerierten Katalysator-Teilchen, die einen kristallinen Zeolith suspendiert in einem Trägergas enthalten; die Einführung des Kohlenwasserstoff-Ausgangsmaterials in den aufwärts strömenden Strom regenerierter Katalysator-Teilchen; das Durchleiten der Mischung aufwärts durch den senkrechten Reaktor, um das katalytische Kracken des Ausgangsmaterials zu erreichen; das Trennen der Katalysator-Teilchen von dem Strom gespaltener Produkte, die am oberen Ende des senkrechten Reaktors austreten; und das Durchleiten der abgetrennten Teilchen durch eine Katalysator-Regenerations-Zone, in welcher sie mit einem heißen Sauerstoff enthaltenden Gas, das den auf dem gebrauchten Katalysator abgelagerten Kohlenstoff abbrennen kann, regeneriert werden, bevor sie in den senkrechten Reaktor rückgeführt werden; dadurch gekennzeichnet, daß:

(a) das Trägergas einen trockenen, Kohlenwasserstoff enthaltenden Gasstrom umfaßt, der mindestens 10 Vol.-% Wasserstoff, aber weniger als 10 Vol.-% an C₃- und schwereren Kohlenwasserstoffen enthält, wobei der Kontakt zwischen den heißen regenerierten Katalysator-Teilchen und dem Trägergas für eine kurze Zeitspanne von 0,01 bis 2 Sekunden aufrechterhalten wird, bevor das Kohlenwasserstoff-Ausgangsmaterial darin eingebracht wird, um die Koksablagerung auf den regenerierten Katalysator-Teilchen vor dem Kontakt mit dem Ausgangsmaterial auf 0,25 Gew.-% oder weniger zu beschränken,

(b) das Kohlenwasserstoff-Ausgangsmaterial eine Rohöl-Rückstandsfraktion mit einem Siedpunkt über 650°F (343°C) ist, die einen Schwermetallgehalt, berechnet als Nickeläquivalente, von mindestens 4 und einen Kohlenstoff-Rückstand nach der Pyrolyse von mindestens 1 % aufweist, und

(c) der regenerierte Katalysator 1000 bis 50000 ppm gesamtes Schwermetall enthält.

2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß nach der Abtrennung der gebrauchten Katalysator-Teilchen der Strom der gespaltenen Produkte aus dem senkrechten Reaktor behandelt wird, um ihn in einen Strom flüssiger Produkte und einen Strom gasförmiger Produkte zu trennen, wobei der Strom gasförmiger Produkte hierauf weiter behandelt wird, um einen trockenen, Kohlenwasserstoffe enthaltenden, Wasserstoff-reichen Strom gasförmiger Produkte zu erhalten, der weniger als 10 Vol.--% an C₃- und schwereren Kohlenwasserstoffen enthält, und der danach in den senkrechten Reaktor rückgeführt wird, um als Trägergas zu dienen.

3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß der trockene, Kohlenwasserstoffe enthaltende, Wasserstoffreiche Strom gasförmiger produkte, vder als Trägergas in den senkrechten Reaktor rückgeführt wird, einen Anteil Schwefelwasserstoff enthält und ein Produkt darstellt, welches aus einer aromatischen Entschwefelungseinheit, die dem senkrechten Reaktor nachgeschaltet ist, erhalten wird.

4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß der trockene Gasstrom 15 bis 40, vorzugsweise 20 bis 35 Vol.-% Wasserstoff enthält.

5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der trockene Gasstrom weniger als 8 Vol.-%, vorzugsweise 0 bis 6 Vol.-% an C₃- und schwereren Kohlenwasserstoffen enthält.

6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Temperatur des Trägergasstroms, der die suspendierten heißen regenerierten Katalysator-Teilchen enthält, vor dem Einbringen des Ausgangsmaterials durch Injizieren von Dampf und/oder Wasser eingestellt wird.

7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß das Ausgangsmaterial ein Nickeläquivalent von mindestens 6, vorzugsweise mindestens 5,5 aufweist.

8. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, daß das Ausgangsmaterial einen Kohlenstoff-Rückstand nach der Pyro- ly.se von mindestens 2 Gew.% aufweist.

9. Verfahren nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, daß die regenerierten Katalysator-Teilchen einen Belag von Schwermetall im Bereich von 1000 bis 20000 ppm Ni + V aufweisen.

Ansprüche

Patentansprüche für folgende(n) Vertragsstaat(en) : BE SE

1. Verfahren zum katalytischen Kracken von Kohlenwasserstoff-Ausgangsmaterialien, welches umfaßt: das Schaffen, im unteren Teil eines senkrecht angeordneten Reaktors (Riser), eines aufwärts gerichteten Stroms von heißen regenerierten Katalysator-Teilchen, die einen kristallinen Zeolith suspendiert in einem Trägergas enthalten; die Einführung des Kohlenwasserstoff-Ausgangsmaterials in den aufwärts strömenden Strom regenerierter Katalysator-Teilchen; das Durchleiten der Mischung aufwärts durch den senkrechten Reaktor, um das katalytische Kracken des Ausgangsmaterials zu erreichen; das Trennen der Katalysator-Teilchen von dem Strom gespaltener Produkte, die am oberen Ende des senkrechten Reaktors austreten; und das Durchleiten der abgetrennten Teilchen durch eine Katalysator-Regenerations-Zone, in welcher sie mit einem heißen Sauerstoff enthaltenden Gas, das den auf dem gebrauchten Katalysator abgelagerten Kohlenstoff abbrennen kann, regeneriert werden, bevor sie in den senkrechten Reaktor rückgeführt werden; dadurch gekennzeichnet, daß das Trägergas einen trockenen, Kohlenwasserstoff enthaltenden Gasstrom umfaßt, der mindestens 10 Vol.-% Wasserstoff, aber weniger als 10 Vol.-% an C₃- und schwereren Kohlenwasserstoffen enthält, wobei der Kontakt zwischen den heißen regenerierten Katalysator-Teilchen und dem Trägergas für eine kurze Zeitspanne von 0,01 bis 2 Sekunden aufrechterhalten wird, bevor das Kohlenwasserstoff-Ausgangsmaterial darin eingebracht wird, um die Koksablagerung auf den regenerierten Katalysator-Teilchen vor dem Kontakt mit dem Ausgangsmaterial auf 0,25 Gew.-% oder weniger zu beschränken.

2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß nach der Abtrennung der gebrauchten Katalysator-Teilchen der Strom der gespaltenen Produkte aus dem senkrechten Reaktor behandelt wird, um ihn in einen Strom flüssiger Produkte und einen Strom gasförmiger Produkte zu trennen, wobei der Strom gasförmiger Produkte hierauf weiter behandelt wird, um einen trockenen, Kohlenwasserstoffe enthaltenden, Wasserstoff-reichen Strom gasförmiger Produkte zu erhalten, der weniger als 10 Vol.-% an C₃- und schwereren Kohlenwasserstoffen enthält, und der danach in den senkrechten Reaktor rückgeführt wird, um als Trägergas zu dienen.

3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß der trockene, Kohlenwasserstoffe enthaltende, Wasserstoffreiche Strom gasförmiger Produkte, der als Trägergas in den senkrechten Reaktor rückgeführt wird, einen Anteil Schwefelwasserstoff enthält und ein produkt darstellt, welches aus einer aromatischen Entschwefelungseinheit, die dem senkrechten Reaktor nachgeschaltet ist, erhalten wird.

4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß der trockene Gasstrom 15 bis 40, vorzugsweise 20 bis 35 Vol.-% Wasserstoff enthält.

5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß der trockene Gasstrom weniger als 8 Vol.-%, vorzugsweise 0 bis 6 Vol.-% an C₃- und schwereren Kohlenwasserstoffen enthält.

6. Verfahren nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Temperatur des Trägergasstroms, der die suspendierten heißen regenerierten Katalysator-Teilchen enthält, vor dem Einbringen des Ausgangsmaterials durch Injizieren von Dampf und/oder Wasser eingestellt wird.

7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, daß das Kohlenwasserstoff-Ausgangsmaterial eine Rohöl-Rückstandsfraktion mit einem Siedpunkt über 650°F (343°C) ist, die einen Schwermetallgehalt, berechnet als Nickeläquivalente, von mindestens 4 und einen Kohlenstoff-Rückstand nach der Pyrolyse von mindestens 1% aufweist, und daß der regenerierte Katalysator einen Belag von 1000 bis 50000 ppm Schwermetall aufweist.

8. Verfahren nach Anspruch 7, dadurch gekennzeichnet, daß das Ausgangsmaterial ein Nickeläquivalent von mindestens 5, vorzugsweise mindestens 5,5 aufweist.

9. Verfahren nach Anspruch 7 oder 8, dadurch gekennzeichnet, daß das Ausgangsmaterial einen Kohlenstoff-Rückstand nach der Pyrolyse von mindestens 2 Gew.-% aufweist.

10. Verfahren nach einem der Ansprüche 7, 8 oder 9, dadurch gekennzeichnet, daß die regenerierten Katalysator-Teilchen einen Belag von Schwermetall im Bereich von 1000 bis 20000 ppm Ni + V aufweisen.

Ansprüche

Patentansprüche für folgende(n) Vertragsstaat(en) : AT DE FR GB IT NL

1. Un procede pour le craquage catalytique de charges d'alimentation d'hydrocarbures, qui comprend I'etablissement a la partie inferieure d'une colonne montante orientee verticalement d'un courant s'ecoulant vers le haut de particules de catalyseurs chaudes, regenerees, comprenant une zeolite cristalline, en suspension dans un gaz ascendant et l'introduction de la charge d'alimentation d'hydrocarbures dans le courant de particules de catalyseur regenere s'ecoulant vers le haut, l'envoi du melange vers le haut ä travers la colonne montante pour effectuer le craquage catalytique de la charge d'alimentation, la separation des particules de catalyseur du courant de produits craques recuperes au sommet de la colonne montante, et l'envoi des particules separees ä travers une zone de regeneration du catalyseur dans laquelle elles sont regenerees avec un gaz contenant de l'oxygène chaud, efficace pour eliminer par combustion le carbone depose sur les particules de catalyseur use avant le recyclage ä la partie inferieure de la colonne montante, caractérisé en ce que:

(a) le gaz ascendant comprend un courant de gaz sec contenant des hydrocarbures contenant au moins 10% en volume d'hydrogene mais moins de 10% en volume d'hydrocarbures en C₃ et superieurs, le contact entre les particules de catalyseur regenere chaudes et ce gaz ascendant etant maintenu pendant une courte duree de 0,01 a 2 secondes avant l'introduction dans celui-ci de cette charge d'alimentation d'hydrocarbures, limitant ainsi le depot de coke sur les particules de catalyseur regenere ä 0,25% en poids ou moins avant le contact avec la charge d'alimentation d'hydrocarbures,

(b) la charge d'alimentation d'hydrocarbures est une fraction d'huile brute residuelle bouillant au-dessus de 650°F (343°C), ayant une teneur en metal lourd, calculee en Equivalent de Nickel, d'au moins 4, et un residu de carbone par pyrolyse d'au moins 1 % et

(c) le catalyseur regenere comprend de 1000 a 50 000 ppm de metal lourd accumule.

2. Un procede suivant la revendication 1, caracterise en ce qu'apres separation des particules de catalyseur use, le courant de produits craques provenant de la colonne montante est traite pour separer un courant de produit liquide et un courant de produit gazeux, courant de produit gazeux qui est ensuite soumis a un traitement supplementaire pour obtenir un courant de gaz sec contenant des hydrocarbures, riches en hydrogene contenant moins de 10% en volume d'hydrocarbures en C₃ et superieurs, et qui est ensuite recycle dans la colonne montante pour donner ce gaz ascendant.

3. Un procede suivant la revendication 2, caracterise en ce que le courant de gaz sec contenant des hydrocarbures, riche en hydrogene, recycle dans la colonne montante en tant que gaz ascendant, contient une certaine proportion d'hydrogene sulfure et est un produit recupere ä partir d'une unite de desulfuration aromatique en aval de la colonne montante.

4. Un procede suivant l'une quelconque des revendications 1 ä 3, caracterise en ce que le courant de gaz sec contient 15 a 40, de preference 20 ä 35% en volume d'hydrogene.

5. Un procede suivant l'une quelconque des revendications 1 ä 4, caracterise en ce que le courant de gaz sec contient moins de 8% en volume d'hydrocarbure en C₃ et superieurs, de preference de 0 ä 6% en volume.

6. Un procede suivant l'une quelconque des revendications 1 a 5, caracterise en ce que la temperature du courant de gaz ascendant comprenant les particules de catalyseur regenere, chaudes, en suspension, est ajustee avant l'injection dans celui-ci de cette charge d'alimentation par injection de la vapeur et/ou d'eau.

7. Un procede suivant l'une quelconque des revendications 1 a 6, caracterise en ce que la charge d'alimentation a un Equivalent de Nickel d'au moins 5, de preference d'au moins 5,5.

8. Un procede suivant l'une quelconque des revendications 1 ä 7, caracterise en ce que la charge d'alimentation a un residu de carbone par pyrolyse d'au moins 2 % en poids.

9. Un procede suivant l'une quelconque des revendications 1 ä 8, caracterise en ce que les particules de catalyseur regenere ont une accumulation de metallourd dans l'intervalle de 1000 ä 20 000 ppm de Ni + V.

Revendications

Revendications pour l'(les) Etat(s) contractant(s) suivant(s) : BE SE

1. Un procédé pour le craquage catalytique de charges d'alimentation d'hydrocarbures, qui comprend l'établissement à la partie inférieure d'une colonne montante orientée verticalement, d'un courant s'écoulant vers le haut, de particules de catalyseur régénéré, chaudes, comprenant une zéolite cristalline en suspension dans un gaz ascendant, l'introduction de la charge d'alimentation d'hydrocarbures dans le courant de particules de catalyseur régénéré s'écoulant vers le haut, l'envoi du mélange vers le haut à travers la colonne montante pour effectuer le craquage catalytique de la charge d'alimentation, la séparation des particules de catalyseur du courant de produits craqués, récupérés au sommet de la colonne montante et l'envoi des particules séparées à travers une zone de régénération du catalyseur dans laquelle elles sont régénérées avec un gaz contenant de l'oxygène chaud efficace pour éliminer par combustion le carbone déposé sur les particules des catalyseurs usés avant le recyclage au bas de la colonne montante, caractérisé en ce que le gaz ascendant comprend un courant de gaz sec contenant des hydrocarbures contenant au moins 10% d'hydrogène mais moins de 10% en volume d'hydrocarbures C₃ et supérieurs, le contact entre les particules de catalyseur régénéré chaud et ce gaz ascendant étant maintenu pendant une courte durée, de 0,01 à 2 secondes avant l'introduction dans celui-ci de cette charge d'alimentation d'hydrocarbures, limitant ainsi le dépôt de coke sur les particules de catalyseurs régénérés à 0,25% en poids ou moins avant le contact avec la charge d'alimentation d'hydrocarbures.

2. Un procédé suivant la revendication 1, caractérisé en ce que, après séparation des particules de catalyseur usé, le courant de produits craqués provenant de la colonne montante est traité pour séparer un courant de produit liquide et un courant de produit gazeux, courant de produit gazeux qui est ensuite soumis à un traitement supplémentaire pour obtenir un gaz sec riche en hydrogène, contenant des hydrocarbures, contenant moins de 10% en volume d'hydrocarbures en C₃ et supérieurs, qui est ensuite recyclé dans la colonne montante pour donner ce gaz ascendant.

3. Un procédé suivant la revendication 2, caractérisé en ce que le courant de gaz sec contenant des hydrocarbures, riche en hydrogène recyclé dans la colonne montante en tant que ledit gaz ascendant, contient une certaine proportion d'hydrogène sulfuré et est un produit récupéré d'une unité de désulfuration aromatique en aval de la colonne montante.

4. Un procédé suivant l'une quelconque des revendications 1 à 3, caractérisé en ce que le courant de gaz sec contient 15 à 40, de préférence 20 à 35% en volume d'hydrogène.

5. Un procédé suivant l'une quelconque des revendications 1 à 4, caractérisé en ce que le courant de gaz sec contient moins de 8% en volume d'hydrocarbures en C₃ et supérieurs, de préférence 0 à 6% en volume.

6. Un procédé suivant l'une quelconque des revendications 1 à 5, caractérisé en ce que la température du courant de gaz ascendant comprenant les particules de catalyseur en suspension, régénéré, chaud est ajustée avant l'injection dans celui-ci de cette charge d'alimentation par injection de vapeur et/ou d'eau.

7. Un procédé suivant l'une quelconque des revendications 1 à 6, caractérisé en ce que la charge d'alimentation d'hydrocarbures est une fraction d'huile brute résiduelle bouillant au-dessus de 650°F (343°C) ayant une teneur en métaux, lourds calculés en Equivalent de Nickel d'au moins 4 et un résidu de carbone par pyrolyse d'au moins 1 %, et en ce que le catalyseur régénéré de 1000 à 50 000 ppm de métal lourd accumulé.

8. Un procédé suivant la revendication 7, caractérisé en ce que la charge d'alimentation a un Equivalent de Nickel d'au moins 5, de préférence d'au moins 5,5.

9. Un procédé suivant la revendication 7 ou la revendication 8, caractérisé en ce que la charge d'alimentation a un résidu de carbone par pyrolyse d'au moins 2% en poids.

10. Un procédé suivant l'une quelconque des revendications 7, 8 ou 9, caractérisé en ce que les particules de catalyseur régénéré ont une accumulation de métal lourd dans l'intervalle de 1000 à 20 000 ppm de Ni + V.

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