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(11) | EP 0 032 414 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Reformate upgrading |
| (57) A process for upgrading reformate or reformer effluent comprising contacting it with
or without the presence of added hydrogen with a catalyst comprising highly siliceous
zeolites having a silica to alumina mole ratio of at least 200 to 1 and a constraint
index in the approximate range of 1 to 12, with or without a hydrogenation/dehydrogenation
component. |
[0001] This invention relates to a process to upgrade reformate. More particularly, the present invention is directed towards a process for increasing the octane number of reformate.
[0002] The upgrading of reformates to improve the octane number of gasolines, as well as the yield-octane relationship, has been the subject of much activity in the petroleum industry over the years. Recently, however, because of the greater awareness of the problem of environmental control, as well as air pollution, greater impetus has been given to investigations directed towards increasing the octane number of gasoline without the use of lead.
[0003] In order to reduce automobile exhaust emissions to meet federal and state pollution requirements, many automobile manufacturers have now equipped the exhaust systems of their vehicles with catalytic converters which contain catalysts which are poisoned by lead. Since lead has been widely used in the past to boost the octane number of gasoline, refiners now have to turn to alternate means to improve gasoline octane number. One method to boost gasoline octane number is to boost the octane number of the various constituents of gasoline, such as reformate.
[0004] It has long been known to upgrade a reformate by a wide variety of techniques including treatment with crystalline zeolites. The treatment of a reformate with crystalline zeolites heretofore practiced has included both physical treatment such as selective adsorption, as well as chemical treatments such as selective conversion.
[0005] U.S. Patents 3,729,409 and 3,767,568 disclose methods of improving the yield-octane number of reformate or reformer effluent by contacting same with crystalline zeolites, such as ZSM-5.
[0006] In order to use conventional ZSM-5 zeolite, e.g. silica to alumina mole ratio of about 70 to 1, to boost the octane number of reformate in an existing reformer unit, the reformate must be cooled from about 900°F (483°C) to about 600-700°F (316-372°C). Thus there would have to be additional capital expenditure for existing reforming units to boost octane using conventional ZSM-5, since extra equipment would be required to cool the reformate.
[0007] One object of the instant invention is to upgrade the octane number of a full-range reformate. Another object of the present invention is boost the octane number of reformate using existing equipment without undue construction delay or capital expenditure.
[0008] It has now been discovered that the octane number of reformate or reformer effluent can be dramatically increased by contacting same with a catalyst comprising a highly siliceous zeolite, with or without a hydrogenation component. Such highly siliceous zeolites are characterized by a silica to alumina mole ratio of at least 200 to 1 and a constraint index in the approximate range of 1 to 12. The significance and manner of determination of "constraint index" is described in our G.B. Specification No. 1,446,522.
[0009] The highly siliceous zeolite containing catalysts can be used in conjunction with existing reforming units, since they can operate at the temperatures and pressures of such units. They may be utilized in the last reactor of the string of reforming reactors in existing units without extensive time delay or any additional capital expense.
[0010] According to the invention, the octane number of full-range reformate can be extensively increased, for example, from about 96 to about 101 R+0 (research octane number with no added lead) at temperatures in the range of between about 800°F (427°C) and about 900°F (483°C).
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
FIGURE 1 is a plot of benzene yield versus C5+ octane no. (R+0) for a 1600/1 silica to alumina mole ratio zeolite and a 140/1 silica to alumina mole ratio zeolite used as catalysts to upgrade reformate.
FIGURE 2 is a plot of toluene yield versus C5+ octane no. (R+0) for the same two zeolites utilized in FIGURE 1 to upgrade reformate.
FIGURE 3 is a plot of C8 aromatic yields versus C5+ octane no. (R+0) for the same two zeolites utilized in FIGURE 1 to upgrade reformate.
FIGURE 4 is a plot of C9 aromatic yields versus C5+ octane no. (R+0) for the same two zeolites utilized in FIGURE 1 to upgrade reformate.
[0012] Reformates or reformer effluents which are composed substantially of aromatic and paraffinic constituents can be prepared according to conventional reforming technology by contacting any suitable material such as a naphtha chargestock boiling in the range of about C5 and preferably from about C6 up to about 380°F (194°C) and higher with hydrogen at least initially in contact with any conventional reforming operation. A conventional reforming operation is described in United States Patent 3,395,094.
[0013] Conventional reforming catalysts include, for example, alumina in the eta, chi, or gamma form and mixtures thereof in combination with a chromium, molybdenum, or noble metal. Platinum type includes, for example, the metal series which includes platinum, palladium, osmium, iridium, ruthenium or rhodium and mixtures thereof deposited on a suitable support. Metals of Group VIIA, including'rhenium, may be used in combination with platinum- type metals. Generally, the major portion of the catalyst will be alumina, which may comprise as much as about 95% by weight or more of the catalyst. Other components may be combined with the alumina carrier, such as the oxides of silica, magnesium, zirconium, thorium, vanadium, titanium, boron or mixtures thereof. The platinum-alumina combination, either with or without one or more of the above-listed components such as silica, etc., may also be promoted with small amounts of halogen such as chlorine and fluorine, in amounts ranging from about 0.1% up to about 5% by weight. Generally, less than about 3% of halogen is employed with the platium type catalyst. In a preferred embodiment, the reforming catalyst carrier material is a relatively high surface area material, preferably an eta alumina material of at least about 100 square meters per gram.
[0014] In the reforming process, typical reforming operating conditions including temperatures in the range of from about 800°F (427°C) to about 1,000°F (538°C), preferably from about 890°F (477°C) up to about 980°F (527°C), liquid hourly space-velocity in the range of from about 0.1 to about 10, preferably from about 0.5 to about 5; a pressure in the range of from about atmospheric up to about 800 psig (5618 kPa) and higher, preferably from about 100 psig (791 kPa) to about 600 psig (4239 kPa); and a hydrogen-hydrocarbon ratio in the range of from about 0.5 to about 20 and preferably from about 1 to about 10.
[0015] In the process of this invention, the reformate or reformer effluent is contacted with or without added hydrogen over the highly siliceous zeolite containing catalysts of the instant invention. The production of reformate via a reforming reaction always results in the production of hydrogen. Practically, it is undesirable to separate out the hydrogen because it would add to processing cost. It is to be immediately understood, however, that it is not necessary to have a hydrogenation/dehydrogenation component associated with the catalyst, although such is a preferred embodiment of this invention. Thus, in its broadest form this invention includes/processing of a reformate or reformer effluent either in the absence or in the presence of hydrogen over the zeolite catalysts of the present invention with or without an added hydrogenation component.
[0016] The amount of the hydrogenation/dehydrogenation component employed is not narrowly critical and can range from about 0.01 to about 30 weight percent based on the entire catalyst including binder. A variety of hydrogenation components may be combined with either the zeolite and/or matrix in any feasible manner which affords intimate contact of the components, employing well known techniques such as base exchange, impregnation, coprecipitation, cogellation, mechanical admixture of one component with the other, and the like. The hydrogenation component can include metals, oxides, and sulfides of metals of the Periodic Chart which fall in Group VIA including chromium, molybdenum, tungsten and the like; Group IIB including zinc cadmium, Group VIIA including manganese and rhenium and Group VIIIA including cobalt, nickel, platinum, palladium, ruthenium, rhodium and the like, and combinations of metals, sulfides and oxides thereof, including the combination of the metals of Group VIA and VIIIA, such as nickel-tungsten-sulfide, cobalt oxide-molybdenum oxide and the like. Any reference to "Periodic Table", "Periodic Chart" or "Group" as used herein shall refer to the "Periodic Chart of the Elements" of the Fisher Scientific Company, Cat. No. 5-702-10, 1978.
[0017] Conversion in accordance with the present process is generally carried out at a temperature between about 800°F (427°C) and about 1,050°F (566°C) and preferably between about 850°F (455°C) to 950°F (510°C). The hydrogen pressure, if such is used, in such operation is generally within the range of between about 50 psig (447 kPa) and about 1000 psig (6996 kPa) and preferably between about 200 psig (1481 kPa) to about 500 psig (3549 kPa). The liquid hourly space velocity, i.e., the liquid volume of hydrocarbon per hour per volume of catalyst is between about 0.1 and about 10, and preferably between about 1 and 5. In general the molar ratio of hydrogen to hydrocarbon charge i.e. reformate, employed is between about 1 and about 80, and preferably between about 2 and 15.
[0018] The silica to alumina mole ratio referred to may be determined by conventional analysis. This ratio is meant to represent, as closely as possible, the ratio in the rigid anionic framework of the crystal and to exclude aluminum in the binder or in cationic or other form within the channels. In highly siliceous zeolites, the upper limit of silica to alumina mole ratio is unbounded. ZSM-5, is one such example wherein the silica to alumina mole ratio is at least 5, but can be 100, 1,000, 10,000, or even greater, i.e. up to and including infinity. The highly siliceous zeolites of this invention are characterized by a silica to alumina mole ratio of at least 200 and it is preferred that the silica to alumina mole ratio be higher, e.g. silica to alumina mole ratios of 500 to 1, 1,000 to 1, 1,400 to 1, 1,600 to 1 and greater.
[0019] The preferred zeolites, after activation, acquire an intracrystalline sorption capacity for normal hexane which is greater than that for water, i.e. they exhibit "hydrophobic" properties. It is believed that this hydrophobic character is advantageous in many instances.
[0021] There may be situations where the activity is so low, i.e., silica to alumina mole ratio approaching infinity, that the Constraint Index cannot be adequately measured, if at all. In such situations, Constraint Index is to mean the Constraint Index of the same zeolite (same crystal structure as determined by X-ray diffraction pattern) in an alumina-containing form.
[0023] Highly siliceous ZSM-5 is described in greater detail in U.S. Patent Re. No. 29,948. The significant (strong) lines of the X-ray diffraction patent of ZSM-5 are as follows:
[0024] Highly siliceous ZSM-11 is more particularly described in U.S. Patent Applications Serial Nos. 003,143 and 003,145.
[0025] In U.S. Application Serial No. 003,143, filed January 15, 1979, a highly siliceous ZSM-11 composition can be identified in terms of mole ratios of oxides as follows:
(0-10)M2/nO : (0-0.5)Al2O3 : (100) SiO2
wherein M is at least one cation having a valence n, and is further characterized by the X-ray diffraction pattern of ZSM-11, as shown in Table 1 herein.[0026] In the as synthesized form, this highly siliceous ZSM-11 has a formula, on a water-free basis, in terms of moles of oxides, per 100 moles of silica, as follows:
(0-10)R2O . (0-10)M2/nO : (0-0.5)Al2O3: (100)Si02
wherein M is an alkali or alkaline earth metal, R20 is an organic compound of Group VB element of the Periodic Chart of the Elements, Fisher Scientific 'Co., Cat. No. 5-702-10, 1978, preferably nitrogen or phosphorous, containing at least one alkyl or aryl group having between 1 and 7 carbon atoms, preferably between 2 and 5, carbon atoms, preferably containing at least one ethyl or butyl group and still more preferably R20 is a quaternary ammonium compound.[0027] This highly siliceous ZSM-11 can be prepared from a reaction mixture containing a source of silica, R20, an alkali metal oxide, e.g. sodium, water, and no added alumina, and has a composition, in terms of mole ratios of oxides, falling within the following ranges:
wherein R20 is the oxide form of an organic compound of an element of Group VB of the Periodic Chart and can be a compound containing one butyl group, M is an alkali or alkaline earth, and maintaining the mixture, at crystallization temperatures, until crystals of the ZSM-11 are formed. As mentioned above, no alumina is added. The only aluminum present occurs as an impurity.
[0028] In U.S. Application Ser. No. 003,145, filed January 15, 1979, a highly siliceous ZSM-11 composition can be identified in terms of mole ratios of anhydrous oxides per 100 moles of silica as follows:
(0-10)M2/nO: [(a)Cr203 + (b)Fe2O3+(c)Al2O3]: 100 SiO2,
wherein M is at least one cation having a valence n, a=0-4, b=0-5, c=0.001-0.5 and is further characterized by the X-ray diffraction pattern of ZSM-11, as shown in Table 1 herein. However, "a" and "b" cannot both be equal to 0 at the same time; when one equals 0 the other must be greater than the value of "c". The chromium and iron oxide need not all occur as Cr2O3 or Fe203 but are so calculated in the formula.[0029] In the as-synthesized form, this highly siliceous ZSM-11 has a formula, on a water-free basis, in terms of moles of oxides, per 100 moles of silica, as follows:
(0-3)R2O:(0-8)M2/nO:[(a)cr2O3 + (b) Fe203 + (c)Al2O3):100 Si02,
wherein M is an alkali or alkaline earth metal, R20 is an organic compound of Group VB element of the Periodic[0030] Chart, preferably nitrogen or phosphorous, containing at least one alkyl or aryl group having between 1 and 7 carbon atoms, (preferably between 2 and 5, carbon atoms) preferably containing at least one butyl group and still more preferably R20 is a quaternary ammonium compound containing at least one butyl group, "a"=0-4, "b"=0-5, and "c"=0.001-0.4. However, "a" and "b" cannot both be equal to 0 at the same time. When one equals 0'the other must be greater than 0 and greater than the value of "c".
[0031] This highly siliceous ZSM-11 can be prepared from a reaction mixture containing a source of silica, R20, an alkali metal oxide, e.g. sodium, a chromium or iron compound, water, and no added alumina, and having a composition, in terms of mole ratios of oxides, falling within the following ratios:
wherein R20 is the oxide form of an organic compound of an element of Group VB of the Periodic Chart and can be a compound containing one butyl group, and M is an alkali or alkaline earth metal, and maintaining the mixture until crystals of the ZSM-11 are formed. As mentioned above, no alumina is added. The only aluminum present occurs as an impurity.
[0032] The parenthesis around lines 3.07 and 3.00 indicate that they are separate and distinct lines, but are often superimposed. These values were determined by standard technique. The radiation was the K-alpha doublet of copper, and a diffractometer equipped with a scintillation counter (or a geiger counter spectrometer) and a strip chart pen recorder can be used. The peak heights, I, and the positions as a function of 2 theta, where theta is the Bragg angle, were read from the diffractometer chart. From these, the relative intensities, 1001/1 , where Io is the intensity of the strongest line or peak, and d (obs.), the interplanar spacing in A, corresponding to the recorded lines, were calculated. The intensity in Table 1 is expressed as follows:
m = medium, w = weak and vs = very strong.
[0033] ZSM-11 is similar to ZSM-5 with the notable exception that whereas ZSM-5 contains a doublet at about 10.1, 3.73, 3.00 and 2.01 A interplanar spacing, ZSM-11 shows a singlet at these values. This means that the crystal class of ZSM-11 is different from that of the other zeolites. ZSM-11 is tetragonal whereas ZSM-5 tends to be orthorhombic.
[0034] The sodium form as well as other cationic forms reveal substantially the same pattern with minor shifts in interplanar spacing and variation of relative intensity.
[0035] Other minor variations can occur depending on the silicon to aluminum mole ratio of the particular sample as well as on its degree of thermal treatment.
[0036] Highly siliceous ZSM-12 is more particularly described in U.S. Patent Applications, Serial Nos. 003,146 and 003,144.
[0037] In U.S. Application Ser. No. 003,146, filed January 15, 1979, a highly siliceous ZSM-12 composition in its calcined form can be identified, in terms of moles of oxides per 100 moles of silica as follows:
(0-10)M2/nO : (0-0.5)A1203 : 100 SiO2 wherein M is at least one cation having a valence n, and is further characterized by the X-ray diffraction pattern of ZSM-12, as shown in Table 2 herein.
[0038] In the as-synthesized form, this highly siliceous ZSM-12 has the formula, on a water-free basis, in terms of moles of oxides per 100 moles of silica, as follows:
(0-10)R2O : (0-10)M2/nO : (0-0.5)Al2O3 : (100)SiO2
wherein R20 is the tetraethyl derivative of an element of Group VB, e.g. N, P, As, Sb, preferably N or P, more preferably N, and M is an alkali or alkaline earth metal.[0039] This highly siliceous ZSM-12 can be prepared from a reaction mixture containing a source of silica, R20, an alkali metal oxide, e.g. sodium, water and no added alumina, and having a composition in terms of mole ratios of oxides, falling within the following ratios:
wherein R20 is the oxide form of the tetraethyl derivative of an element of Group VB of the Periodic Chart and M is alkali or alkaline earth metal and maintaining the mixture at crystallization temperature until crystals of the ZSM-12 are formed. As mentioned above, no alumina is added. The only aluminum present occurs as an impurity.
[0040] In U.S. Application Ser. No. 003,144, filed January 15, 1979, a highly siliceous ZSM-12 composition in its anhydrous form can be identified, in terms of moles of oxides per 100 moles of silica as follows:
(0-8)M2/n0: [(a)Cr2O3 + (b)Fe2O3+(c)Al2O3]: 100 SiO2,
[0041] in the dehydrated state, wherein M is at least one cation having a valence n, "a" = 0-4, "b" = 0-5, "c" = 0.001-0.5 and is further characterized by the X-ray diffraction pattern of ZSM-12, as shown in Table 2 herein. The chromium and iron need not all occur as Cr2O', or Fe2O3 but are so calculated in the formula. However, "a" and "b" cannot both be equal to 0 at the same time. When one is zero, the other must be greater than the value of "c".
[0042] This highly siliceous ZSM-12 can be prepared from a reaction mixture containing a source of silica, R20, and alkali metal oxide, e.g. sodium, a chromium or iron compound, water, and no added alumina, and having a composition, in terms of mole ratios of oxides, falling within the following ratios:
wherein R20 is the oxide form of an organic compound of an element of Group VB of the Periodic Chart and can be an organic compound containing at least one ethyl group and M is alkali or alkaline earth metal and maintaining the mixture at crystallization temperature until crystals of the ZSM-12 are formed. As mentioned above, no alumina is added. The only aluminum present occurs as an impurity.
[0043] These values were determined by standard techniques. The radiation was the K-alpha doublet of copper and a diffractometer equipped with a scintillation counter and a strip chart pen recorder was used. The peak heights, I,and the positions as a function of 2 theta, where theta is the Bragg angle, were read from the diffractometer chart. From these, the relative intensities, 100 I/I0, where I is the intensity of the strongest line or peak, and d(obs.), the interplanar spacing in A, corresponding to the recorded lines, were estimated. In Table 2,' the relative intensities are given in terms of the symbols m = medium, w = weak
and vs = very strong. It should be understood that this X-ray diffraction pattern is characteristic of all the species of ZSM-12 compositions. The sodium form as well as other cationic forms reveal substantially the same pattern with some minor shifts in interplanar spacing and variation in relative intensity. Other minor variations can occur depending on the silicon to aluminum mole ratio of the particular sample, as well as its degree of thermal treatment.
[0044] Crystallization of the aforementioned substances described in U.S. Application Ser. Nos. 003,143; 003,145; 003,146; and 003,144 can be generally carried out at either static or stirred conditions. Static conditions can be achieved using polypropylene jars at about 100°C or.teflon-lined stainless steel autoclaves at about 160°C. Static conditions can also be carried out under pressure in a static bomb reactor. The total useful range of temperatures is about 80°C to about 180oC for about 6 hours to 150 days. Thereafter, the zeolites are separated from the liquid and recovered. The composition can be prepared utilizing materials which supply the appropriate oxides. Depending on the particular zeolite formulation desired, reaction mixtures can include sodium, silicate, silica hydrosol, silica gel, silicic acid, sodium hydroxide, chromic potassium sulfate, or ferric ammonium sulfate. The organic compounds can include any element of Group VB such as nitrogen, phosphorous, arsenic, antimony, or bismuth, preferably nitrogen or phosphorous.
[0045] However, in the case of Application Ser. No. 003,146, the organic compounds include the tetraethyl derivatives of Group VB elements.
[0046] The preferred compounds are quaternary compounds generally expressed by the following formula:
[0047] wherein "L" is an element of Group-B of the Periodic Chart, preferably nitrogen, and each "R" is an alkyl or aryl group having between 1 and 7 (preferably between 2 and 5) carbon atoms. It may be preferable in some formulations that at least one "R" group be an ethyl group or a butyl group.
[0048] Normally each alkyl or aryl group will be the same, however it is not necessary that each group have the same number of carbon atoms in the chain. The oxide of the quaternary compound is generally supplied by introducing into the reaction mixture a composition such as the tetraethyl (or tetrabutyl as the case may be) hydroxide or chloride of the desired VB element. In preparing an ammonium species, the organic substituted chloride, bromide, or hydroxide is useful. In preparing the phosphonium species of the zeolite, tetraethyl (or tetrabutyl as the case may be) phosphonium chloride is particularly desirable as a means of incorporating the quaternary compound in the zeolite. The other elements of Group VB behave similarly and thus zeolites containing the same can be prepared by the same manipulative procedure substituting another Group VB metal for nitrogen. It should be realized that the oxide can be supplied from more than one source. The reaction mixture can be prepared either batchwise or continuously. Crystal size and crystallization time of the zeolite composition will vary with the nature of the reaction mixture employed and the crystallization conditions.
[0049] The quaternary compounds need not be used as such. They may be produced in situ by the addition of the appropriate precursors. These precursors comprise a compound characterized by the formula RlR2R3L where Rl, R2 and R3 are selected from alkyl, substituted alkyl, aryl, substituted aryl, cycloalkyl, substituted cycloalkyl and hydrogen and L is an element of Group VB and a compound of the formula R4L where R4 is alkyl, substituted alkyl, cycloalkyl, substituted cycloalkyl, aryl and substituted aryl and L is an electronegative group. According to a special embodiment, the method of the zeolite preparation can be practiced using the compound R1R2R3L alone. Thus, in specific embodiments one may use as the source of R20, amines or phosphines either primary, secondary or tertiary as well as diamines without addition of any R4X.
[0050] Zeolite preparation is facilitated by the presence of at least 0.001%, preferably at least 0.01%, and still more preferably at least 0.1% seed crystals (based on total weight of crystalline product).
[0052] ZSM-48 can be identified, in terms of moles of anhydrous oxides per 100 moles of silica as follows:
(0 to 1-15)RN : (0 to 1.5)M2/n0 : (0 to 2)A1203 : (100)SiO2
wherein M is at least one cation having a valence n, RN is a Cl-C20 organic compound having at least one amine functional group of pK >7, and wherein the composition is characterized by the distinctive X-ray diffraction pattern as shown in Table 3 below.[0053] It is recognized that, particularly when the composition contains tetrahedral, framework aluminum, a fraction of the amine functional groups may be protonated. The doubly protonated form, in conventional notation, would be (RNH)20 and is equivalent in stoichiometry to 2RN + H20.
[0055] These values were determined by standard techniques. The radiation was the K-alpha doublet of copper, and and a scintillation counter spectrometer with a strip chart pen recorder was used. The peak heights, I, and the positions as a function of 2 times theta, where theta is the Bragg angle, were read from the spectrometer chart. From these, the relative intensities, 100 I/Io, where 10 is the intensity of the strongest line or peak, and d (obs.), the interplanar spacing in A, corresponding to the recorded lines, were calculated. In Table 3 the relative intensities are given in terms of the symbols W = weak, VS = very strong and W-S = weak-to-strong. Ion exchange of the sodium ion with cations reveals substantially the same pattern with some minor shifts in interplanar spacing and variation in relative intensity. Other minor variations can occur depending on the silica to alumina mole ratio of the particular sample, as well as if it has been subjected to thermal treatment.
[0056] Highly siliceous ZSM-48 can be prepared from a reaction mixture containing a source of silica, RN, an alkali metal oxide, e.g. sodium and water, and having a composition, in terms of mole ratios of oxides, falling within the folowing ranges:
wherein RN is a Cl-C20 organic compound having amine functional group of pKa >7, and maintaining the mixture at 80-2500C until crystals of ZSM-48 are formed. H+(added) is moles acid added in excess of the moles of hydroxide added. In calculating H+(added) and OH values, the term acid (H+) includes both hydronium ion, whether free or coordinated, and aluminum. An amine hydrochloride would be a mixture of amine and HCl. In preparing the highly siliceous form of ZSM-48 no alumina is added. The only aluminum present occurs as an impurity.
[0057] Preferably, crystallization is carried out under pressure in an autoclave or static bomb reactor, at 80 to 250°C. Thereafter, the crystals are separated from the liquid and recovered. The composition can be prepared utilizing materials which supply the appropriate oxide. Such compositions include sodium silicate, silica hydrosol, silica gel, silicic acid, RN, sodium hydroxide, sodium chloride, etc. RN is a C1-C20 organic compound containing at least one amine functional group of pKa≥7 and includes such compounds as C3-C18 primary, secondary, and tertiary amines, cyclic amine, such as piperidine, pyrrolidine and piperazine, and polyamines such as NH2-CnH2n-NH2 wherein n is 4-12.
[0058] Many of the specific zeolites described, when prepared in the presence of organic cations, are unsuitable for use herein, possibly because the intracrystalline free space is occupied by organic cations from the forming solution. Such zeolites may be made suitable by heating in an inert atmosphere at 540°C for one hour, for example, followed by base exchange with ammonium salts followed by calcination at 540°C in air. The presence of organic cations in the forming solution may not be absolutely essential to the formation of this type zeolite; however, the presence of these cations does appear to favor the formation of many members of this special class of zeolite. More generally, it is desirable to activate this type zeolite by base exchange with ammonium salts followed by calcination in air at about 540°C for from about 15 minutes to about 24 hours.
[0059] Natural zeolites may sometimes be converted to this type zeolite by various activation procedures and other treatments such as base exchange, steaming, alumina extraction and calcination, alone or in combinations. Natural minerals which may be so treated include ferri- erite, brewsterite, stilbite, dachiardite, epistilbite, heulandite, and clinoptilolite.
[0060] In a preferred aspect, the zeolites hereof are selected as those having a crystal framework density, in the dry hydrogen form, of not less than about 1.6 grams per cubic centimeter.
[0061] Crystal framework densities of some typical zeolites, including some which are not within the purview of this description, are:
[0062] A preferred embodiment of this invention resides in the use of a porous matrix together with the highly siliceous zeolites previously described. The highly siliceous zeolite can be combined, dispersed or otherwise intimately admixed with a porous matrix in such proportions that the resulting product contains from one to 95 percent by weight, and preferably from 10 to 70 percent by weight of the highly siliceous zeolite in the final composite.
[0063] The term "porous matrix" includes inorganic compositions with which the zeolites can be combined, dispersed or otherwise intimately admixed wherein the matrix may be active or inactive. It is to be understood that the porosity of the compositions employed as a matrix can either be inherent in the particular material or it can be introduced by mechanical or chemical means. Representative matrices which can be employed included metals and alloys thereof, sintered metals and sintered glass, asbestos, silicon carbide aggregates, pumice, firebrick, diatomaceous earths, alumina, and inorganic oxides. Inorganic compositions, especially those of a siliceous nature, are preferred. Of these matrices, inorganic oxides such as clay, chemically treated clay, silica, silica-alumina, etc. are particularly preferred because of their superior porosity, attrition, resistance, and stability.
[0064] Techniques for such incorporation of highly siliceous zeolites in a matrix are conventional in the art. The incorporation of zeolites in a matrix is set forth in United States Patent No. 3,140,253.
[0065] The novel process of this invention can be carried out in a wide variety of techniques utilizing the process parameters previously set forth. Thus, it is possible to carry out this selective conversion in a separate reactor. In this embodiment a conventional reformer is operated so as to yield a reformate of the type previously set forth and then the reformate or reactor effluent, together with added hydrogen is passed into a separate reactor containing the zeolite catalyst previously set forth with or without a hydrogenation component in the manner previously set forth. In another embodiment of this invention a separate reactor need not be employed, but rather, the last reactor in a conventional three reactor reforming operation can be filled with a conventional platinum reforming catalyst and with the zeolite catalyst previously set forth so that hydrocarbon feed first contacts the conventional platinum reforming catalyst and then zeolite catalyst. Thus, a feed material would undergo conventional reforming in the first two stages of a conventional reactor and then would enter into a third stage wherein conventional reforming would be carried out at the top of the reactor followed by the selective conversion in the bottom of the reactor with the zeolite catalyst. This embodiment has the advantage of utilizing existing equipment and carrying out the novel process of this invention. In a further embodiment of the instant invention, the novel process described herein can take place in a reforming unit which employs an extra reactor ("swing reactor"). This extra reactor is usually the last of four reactors in a reformer unit.
[0066] The novel catalyst of this invention can be employed under typical reforming conditions, e.g. 900°F (483°C) temperature, 1.7 LHSV, 350 psig (2515 kPa) pressure and 7 H2/HC. There is no need to cool the reformate down to between about 600°F (316°C) and 700°F (372°C) as would be required for conventional ZSM-5, e.g. ZSM-5 with a silica to alumina mole ratio of about 70 to 1. The novel catalyst of the instant invention boosts reformate octane and exhibits high selectivity for cracking normal and mono-branched paraffins of typical reforming operating conditions.
[0067] The shape selectivity for the highly siliceous zeolite containing catalysts of this invention is comparable to conventional zeolite catalysts having the same constraint index. For example, highly siliceous HZSM-5 is just as shape selective for paraffin cracking as the conventional HZSM-5 catalyst. The amounts of methane and butane produced are comparable and more ethane and propane is produced. When operating under typical reforming conditions, the catalyst of the instant invention does more dealkylation than conventional HZSM-5 catalysts. Lower boiling aromatics are formed by the dealkylation reaction, resulting in a higher volatility gasoline than that made by conventional HZSM-5 at the same octane number. Also, greater dealkylation is desirable where an objective is to maximize benzene and/or toluene yield.
Example
[0069] This example illustrates the preparation of a highly siliceous HZSM-5 with a silica to alumina mole ratio of about 1600 to 1.
Prereacted Organics Preparation
[0070] The following materials were charged to an autoclave: 0.30 parts methylethyl ketone, 0.18 parts tri-n-propylamine and 0.15 parts n-propyl bromide. The contents were mixed with gentle agitation for 15 minutes. The agitation was stopped and 1 part water was charged to the autoclave. The autoclave was sealed and heated to 220°F (105°C) and held at 220°F (105°C) for 15 hours. After this reaction period the temperature was raised to 320°F (160°C) and the unreacted organics were flashed off. The aqueous phase was removed containing the prereacted organics and contained 1.44% wt. nitrogen.
Zeolite Synthesis
Solution Preparation
Silicate-Solution
Acid Solution
Additional Solids
Additional Liquid
Procedure
[0075] The silicate solution and acid solution were mixed in a mixing nozzle to form a gel which was discharged into an autoclave to which 0.029 parts water had been previously added. The gel was whipped by agitation and 0.14 parts NaCl were added and thoroughly blended. The autoclave was sealed and heated t ~ 220°F (105°C) with agitation at 90 rpm and held for 54.3 hours until crystallization was complete. The contents of the autoclave were cooled and discharged. The crystallized product was analyzed by X-ray diffraction and was found to be 100% wt. ZSM-5. The chemical analysis of the thoroughly washed crystalline product was:
Catalyst Preparation
[0076] After drying the zeolite was mixed with alpha alumina monohydrate (Catapal SB, Continental Oil Co.) and water to an extrudable consistency to form a 65% zeolite - 35% alumina mixture and formed into 1/16" extrudates. The extrudates were dried, calcined in flowing N2 for 3 hours at 1000°F (538°C) then ion exchanged twice with 1 N NH4NO3 solution (5 parts NH4N03 solution/l part zeolite) for one hour at ambient temperature. The extrudate was then exchanged for four hours with nickel nitrate solution (5cc in Ni (NO3)2 ' 6 H20/g catalyst) at 80-90°C and then for four hours with fresh nickel nitrate solution at room temperature. The extrudate was washed, dried and calcined for 3 hours in flowing air at 538°C, then sulfided with a flowing mixture of 2% H2S in hydrogen at 750°C.
Examples·2·to·10
[0078] The following examples will illustrate the novel process of this invention. In each case, the chargestock was a reformate obtained by contacting naphtha together with hydrogen over a platinum reforming catalyst at about 800°F (427°C) to 1000°F (538°C), a pressure of about 350 psig (2515 kPa) and 7 H2/HC. The properties of this chargestock are given in Table 4. In Examples 3 to 10, the reformate was contacted with a catalyst representative of the novel catalyst of this invention. Said catalyst was prepared according to Example 1. The catalyst was contacted with the reformate at temperatures in the range between about 800°F (427°C) and 900°F (483°C) and space velocities in the range between about 1.5 and 6.5. The results for Examples 2 to 10 are given in Table 5.
[0079] Example 2 was a blank thermal run charging the lowest feed rate (7 ml/hr) over 8-14 mesh T-61 alumina (manufactured by Alcoa). Said alumina served as the diluent for the ZSM-5 extrudate in the other examples.
[0080] Examples 3, 4 and 5 employed 1.08 g (2.0cc) of the catalyst prepared according to Example 1 and mixed with 15.5g (8.0cc) of 8-14 mesh T-61 alumina. Examples 7, to 11 utilized 2.82g (5.0cc) of the catalyst prepared according to Example 1 and mixed with 9.2g (5.0cc) of 8-14 mesh T-61 alumina.
[0081] The results for Examples 2 to 10 are given in Table 5 (the LHSV for Example 2 was based on 10 cc of T-61 alumina of 8-14 mesh; the LHSV for Examples 3 to 10 was based on ZSM-5).
[0082] As shown in Table 5, the blank thermal run over T-61 alumina showed only a very small amount of cracking thus establishing that the 1400/1 SiO2/Al2O3 Ni/HZSM-5 has catalytic activity.
Example 11
[0083] This example illustrates the preparation of HZSM-5 with Si02/A1203 mole ratio of about 140 to 1.
[0084] A sodium silicate solution was prepared by mixing 33.5 parts water and 57.8 parts sodium silicate (28.7 wt. % SiO2, 8.9 wt. % Na20, 62.4 wt. % H20).
[0085] An acid solution was prepared by adding 1 part aluminum sulfate (17.2 wt. % A1203) to 34.3 parts water followed by 5.3 parts sulfuric acid (~ 97 wt. % H2SO4) and 6.8 parts NaCl.
[0086] These solutions were mixed in an agitated vessel and 4.0 parts NaCl were added. The gel molar ratios expressed as oxides are the following:
[0087] An brganic solution was prepared by adding 3.3 parts n-propyl bromide and 6.4 parts methyl ethyl ketone to 3.9 parts tri-n-propylamine. Agitation was stopped and this solution was added to the above formed gel. The mixture was heated to about 95-110°C and held for about 16 hours, then severe agitation was resumed. When more than 65% of the gel was crystallized, the temperature was increased to 150-170°C and held there until crystallization was complete. Unreacted organics were removed by flashing and the remaining contents cooled.
[0088] The zeolite was separated from the liquor by filtration. The wet cake was reslurried and filtered until the sodium level was reduced to 1.3% wt. The final wet cake was dried.
[0089] The dried zeolite was then mixed with alumina and water. It was then extruded into 1/16" pellets and dried. The extruded material contained 65 parts ZSM-5 per 35 parts alumina.
[0090] The dried extrudate was calcined for three hours at 538°C in flowing nitrogen. After cooling, the extrudate was contacted twice with an ammonium nitrate exchange solution (about 0.4 lb. NH4N03/lb. extrudate) for one hour at ambient temperature. The extrudate was then contacted four times with an ammonium nitrate solution (about 0.4 lb. NH4N03/lb. extrudate) for one hour at about 80-90°C. The sodium level was 0.06 wt. %. The extrudate was then contacted with a nickel nitrate exchange solution (about 0.7 lb. Ni(N03)2 '6H20/lb. extrudate) for four hours at about 80-90°C. After this exchange, the extrudate was washed, dried and calcined in flowing air at 538°C for three hours, and sulfided according to the same procedure as given in Example 1.
Examples 12 to 21
[0091] In Examples 12 to 21, the feed employed was the same reformate chargestock as used in Examples 2 to 10, i.e. of Table 4. The catalyst used in Examples 12 to 21 was a conventional HZSM-5 with a silica to alumina mole ratio of 140 to 1 prepared according to Example 1. The purpose of these examples was to use them as a comparison to representatives of the novel catalysts of the instant invention as previously shown in Examples 3 to 10.
[0092] In Examples 12 to 21, 0.22g (0.33 cc) of sulfided 1/16" extrudate HZSM-5 with 0.8 wt % nickel was mixed with 19g (9.7 cc) of 8-14 mesh T-61 alumina. The catalyst was contacted with the chargestock at about 900°F (483°C). , The results for Examples 12 to 21 are shown in Table 6.
[0093] Referring now to FIGURE 1, there is shown a plot of benzene yields versus C5+ octane no. (Research) with no lead added using the data of Examples 6 to 10 and 12 to 21 described above. The 1600/1 SiO2/Al2O3 mole ratio ZSM-5 catalyst of Examples 6 to 10 clearly gave a higher benzene yield than the 140/1 SiO2/Al2O3 mole ratio ZSM-5 catalyst of Examples 12 to 21 at the same C5+ O.N. Likewise, FIGURE 2 shows a higher toluene yield for the 1600/1 Si02/A1203 catalyst; FIGURE 3 shows lower C8 aromatic yield for the 1600/1 SiO2/Al2O3 catalyst; and FIGURE 4 shows lower C9 aromatic yield for the 1600/1 Si02/A1203 catalyst.
1. A process for upgrading reformates and reformer effluents which comprises contacting
the same at a temperature between 800°F (427°C) and 1050PF (566°C), a pressure between 50 psig (447kPa) and 1000 psig (6996kPa), and a liquid
hourly space velocity between 0.1 and 10 with a catalyst comprising a zeolite having
a silica to alumina mole ratio of at least 200 to 1 and a constraint index within
the approximate range of 1 to 12.
2. A process according to Claim 1 wherein the zeolite is ZSM-5, ZSM-11, ZSM-12 or
ZSM-48.
3. A process according to Claim 1 or Claim 2 wherein said silica to alumina mole ratio
is at least 500 to 1.
4. A process according to any preceding Claim wherein said silica to alumina mole
ratio is at least 1000 to 1.
5. A process according to any preceding Claim wherein said silica to alumina mole
ratio is at least 1400 to 1.
6. A process according to any preceding Claim wherein said silica to alumina mole
ratio is at least 1600 to 1.
7. A process according to any preceding Claim which is carried out at a temperature
between 850°F (455°C) and about 950°F (510°C), a pressure between 200 psig (l48lkPa)
and 500 psig (3549kPa) and a liquid hourly space velocity between 1 and 5.
8. A process according to any preceding claim wherein a hydrogenation/dehydrogenation
component is associated with the zeolite.
9. A process according to Claim 8 wherein the hydrogenation/dehydrogenation component
constitutes from 0.01 to 30 weight percent of the catalyst.
10. A process according to Claim 8 or Claim 9 wherein the hydrogenation/dehydrogenation
component is a Group VIA, IIB, VIIA, and/or VIII metal, oxide and/or sulphide.
11. A process according to any of Claims 8 to 10 wherein the hydrogenation/dehydrogenation
component is nickel.
12. A process according to any preceding Claim wherein said reformate and said catalyst
are contacted in a separate reactor downstream of the reformer.
13. A process according to any of Claims 1 to 11 wherein said reformate or reformer
effluent and said catalyst are contacted in a conventional reforming operation containing
a series of reactors.
14. A process according to Claim 12 wherein said reactor is a swing reactor.
15. A process according to any preceding Claim wherein said reformate or r.eformer
effluent is contacted with said catalyst in the presence of hydrogen.
16. A process according to Claim 15 wherein the molar ratio of hydrogen to reformate
is between 1 and 80 and the hydrogen pressure is between 50 psig (447kPa) and 100
psig (791kPa).
17. A process according to Claim 15 or Claim 16 wherein the molar ratio of hydrogen
to reformate is between 2 and 15 and the hydrogen pressure is between 200 psig (148lkPa)and
500 psig (3549kPa).
18. A process according to any preceding Claim wherein the zeolite constitutes between
1 wt. % and 95 wt. % of a composite with a matrix.
19. A process according to Claim 18 wherein the zeolite constitutes between 20 wt.
% and 80 wt. % of a composite with a matrix.