FIXED-BED/MOVING-BED TWO STAGE CATALYTIC REFORMING

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a two stage process for catalytically reforming a gasoline boiling range hydrocarbonaceous feedstock. The reforming is conducted in two stages wherein the first stage is operated in a fixed bed mode, and the second stage is operated in a moving-bed continual catalyst regeneration mode. A gaseous stream comprised of hydrogen and predominantly C₄^- hydrocarbon gases are separated between stages and at least a portion of it is recycled.

BACKGROUND OF THE INVENTION

[0002] Catalytic reforming is a well established refinery process for improving the octane quality of naphthas or straight run gasolines. Reforming can be defined as the total effect of the molecular changes, or hydrocarbon reactions, produced by dehydrogenation of cyclohexanes, dehydroisomerization of alkylcyclopentanes, and dehydrocyclization of paraffins and olefins to yield aromatics; isomerization of substituted aromatics; and hydrocracking of paraffins which produces gas, and inevitably coke, the latter being deposited on the catalyst. In catalytic reforming, a multifunctional catalyst is usually employed which contains a metal hydrogenation-dehydrogenation (hydrogen transfer) component, or components, usually platinum, substantially atomically dispersed on the surface of a porous, inorganic oxide support, such as alumina. The support, which usually contains a halide, particularly chloride, provides the acid functionality needed for isomerization, cyclization, and hydrocracking reactions.

[0003] Reforming reactions are both endothermic and exothermic, the former being predominant, particularly in the early stages of reforming with the latter being predominant in the latter stages. In view thereof, it has become the practice to employ a reforming unit comprised of a plurality of serially connected reactors with provision for heating the reaction stream as it passes from one reactor to another. There are three major types of reforming: semi-regenerative, cyclic, and continuous. Fixed-bed reactors are usually employed in semi-regenerative and cyclic reforming, and moving-bed reactors in continuous reforming. In semi-regenerative reforming, the entire reforming process unit is operated by gradually and progressively increasing the temperature to compensate for deactivation of the catalyst caused by coke deposition, until finally the entire unit is shut-down for regeneration and reactivation of the catalyst. In cyclic reforming, the reactors are individually isolated, or in effect swung out of line, by various piping arrangements. The catalyst is regenerated by removing coke deposits, and then reactivated while the other reactors of the series remain on stream. The "swing reactor" temporarily replaces a reactor which is removed from the series for regeneration and reactivation of the catalyst, which is then put back in the series. In continuous reforming, the reactors are moving-bed reactors, as opposed to fixed-bed reactors, with continuous addition and withdrawal of catalyst. The catalyst descends the reactor in an annular bed and is passed to a regeneration zone where it is regenerated, the sent back to the reforming zone. This cycle is continuously repeated.

[0004] With the gradual phasing out of lead from the gasoline pool and with the introduction of premium grade lead-free gasoline in Europe and the U.S., petroleum refiners must re-evaluate how certain refinery units are run to meet this changing demand. Because catalytic reforming units produce product streams which represent the heart of the gasoline pool, demands are being put on these units for generating streams with ever higher octane ratings.

[0005] U.S. Patent No. 3,992,465 teaches a two stage reforming process wherein the first stage is comprised of at least one fixed-bed reforming zone and the second stage is comprised of a moving-bed reforming zone. The teaching of U.S. Patent No. 3,992,465 is primarily to subject the reformate, after second stage reforming to a series of fractionations and an extractive distillation of the C₆-C₇ cut to obtain an aromatic-rich stream.

[0006] While these process schemes have commercial promise, the partially reformed stream must still undergo a separation between stages to remove the heavier components before they can be passed to a low pressure stage. This is because reforming reactors operated in semiregenerative and cyclic modes cannot operate with a full range first stage product stream at low pressure and low hydrogen/oil ratio typified by such processes. A full range product stream at such conditions would cause too much carbon, or coke, to deposit on the catalyst, thus leading to rapid catalyst deactivation.

[0007] Therefore, there still remains a need in the art for improved reforming processes which can overcome such disadvantages.

[0008] GB-A-1469681 discloses and claims a multiple-stage process for the catalytic reforming of a hydrocarbon feed stream which comprises the steps of:

(a) reacting said feed stream in a plurality of catalytic first reaction zones containing non-movable fixed beds of catalyst, said feed stream contacting the individual fixed beds of catalyst in lateral, radial flow, and said fixed beds being arranged in series flow with each other;

(b) introducing at least a portion of the resulting first zone effluent downwardly into a second reaction zone containing a bed of catalyst movable downwardly therethrough via gravity-flow, and further reacting said effluent in contact with said movable catalyst;

(c) withdrawing, at least periodically, catalyst from said second reaction zone, while simultaneously recovering converted hydrocarbon effluent therefrom; and,

(d) at least periodically adding fresh, or regenerated catalyst to said second reaction zone.

[0009] US-A-4985132 discloses and claims a process for the catalytic reforming of hydrocarbons comprising contacting the hydrocarbon feed in two sequential catalyst zones, wherein:

(a) an initial catalyst zone which is a fixed-bed system and contains an initial catalytic composite comprising a platinum component, a germanium component, a refractory inorganic oxide, and a halogen component; and

(b) a terminal catalyst zone which is a moving-bed system with associated continuous catalyst regeneration and contains a terminal catalytic composite having the essential absence of germanium and comprising a platinum component, a refractory inorganic oxide, a halogen component, and catalytically effective amounts of a metal promoter selected from one or more of the rhenium, tin, indium, rhodium, ruthenium, cobalt, nickel, and iridium.

[0010] In accordance with the present invention, there is provided a process for catalytically reforming a gasoline boiling range hydrocarbon reactant stream in the presence of hydrogen in a reforming process unit comprised of a plurality of serially connected reforming zones wherein each of the reforming zones contains a catalyst comprised of one or more Group VIII noble metals on a refractory support. The catalyst may be either monofunctional or bifunctional. The process comprises:

(a) reforming the reactant stream in a first reforming stage comprised of one or more serially connected reforming zones containing a fixed-bed of catalyst comprised of one or more Group VIII noble metals on a refractory support, which one or more reforming zones are operated at reforming conditions which includes a gauge pressure of about 100 to 500 psi (6.896 to 34.48 bar) and a H₂:C₅₊ mol ratio in the range of from 1 to 10, thereby producing a first effluent stream;

(b) passing said first effluent stream to a separation zone wherein a hydrogen-rich predominantly C₄^- hydrocarbon gaseous stream and a predominantly C₅⁺ effluent stream; are produced

(c) recycling a portion of the hydrogen-rich gaseous stream to said first reforming stage;

(d) reforming the C₅⁺ effluent stream with the remaining portion of the hydrogen-rich gaseous stream in a second reforming stage operated at a pressure which is at least 50 psi (3.45 bar) lower than that of the first reforming stage and a H₂:oil mol ratio of from 0.5 to 5.0 , which second reforming stage is comprised of one or more serially connected reforming zones which are operated in a moving-bed continual catalyst regeneration mode wherein the catalyst descends through the reforming zone, exits, and is passed to a regeneration zone where any accumulated carbon is burned-off, and wherein the regenerated catalyst is recycled to the one or more moving-bed reforming zones.

[0011] In preferred embodiments, the Group VIII noble metal for catalysts in all stages is platinum and the catalyst of the first stage is comprised of platinum and tin on substantially spherical alumina support particles.

[0012] In yet another preferred embodiment of the present invention, from about 50 to 85 vol.% of the hydrogen-rich gas separated between stages is recycled.

[0013] In still other embodiment of the present invention an aromatics-rich stream is separated and collected between stages and the remaining aromatics-lean stage is sent to second stage reforming.

BRIEF DESCRIPTION OF THE FIGURE

[0014] The sole figure hereof depicts a simplified flow diagram of a preferred reforming process of the present invention. The reforming process unit is comprised of a first stage which includes a lead reforming zone, which is represented by a lead fixed-bed reactor, and a first downstream fixed-bed reforming zone, which is represented by another fixed-bed reactor, which first stage is operated in semi-regenerative mode, but which may also be designed to operate in a cyclic mode. There is also a second stage which contains two serially connected moving-bed reforming zones in fluid communication with a regeneration zone, which reforming zones are represented by annular radial flow reactors wherein the catalyst continuously descends through the reactors and is transported to the regeneration zone, then back to the reactors, etc.

DETAILED DESCRIPTION OF THE INVENTION

[0015] Feedstocks, also sometimes referred to herein as reactant streams, which are suitable for reforming in accordance with the instant invention are any hydrocarbonaceous feedstocks boiling in the gasoline range. Nonlimiting examples of such feedstocks include the light hydrocarbon oils, boiling from about 70° F (21.1°C) to about 500° F (260°C), preferably from about 180° F (82.2°C) to about 400° F (204.4°C), for example straight run naphthas, synthetically produced naphthas such as coal and oil-shale derived naphthas, thermally or catalytically cracked naphthas, hydrocracked naphthas, or blends or fractions thereof.

[0016] Referring to the sole Figure hereof, a gasoline boiling range hydrocarbon reactant stream, which is preferably first hydrotreated by any conventional hydrotreating method to remove undesirable components such as sulfur and nitrogen, is passed to a first reforming stage represented by heater or preheat furnaces, F₁ and F₂, and reactors R₁ and R₂. A reforming stage, as used herein, is any one or more of a particular type of reforming zone, in this figure reactors, and its associated equipment (e.g., preheat furnaces etc.). That is, each reforming stage will contain one or more of the same type of reactor, for example, fixed-bed or moving-bed, but not both. The reactant stream is fed into heater, or preheat furnace, F₁, via line 10 where it is heated to an effective reforming temperature. That is, to a temperature high enough to initiate and maintain dehydrogenation reactions, but not so high as to cause excessive hydrocracking. The heated reactant stream is then fed, via line 12, into reforming zone R₁ which contains a catalyst suitable for reforming. Such a catalyst typically contains at least one Group VIII noble metal, preferably platinum, with or without a promoter metal, on a refractory support, preferably alumina. Reforming zone R₁, as well as all the other reforming zones in this first stage, are operated at reforming conditions. Typical reforming operating conditions for the reactors of this first fixed-bed stage include temperatures from about 800° to about 1200° F (426.7 to 648.9°C); gauge pressures from 100 psig (6.896 bar) to 500 psig (34.48 bar), preferably from about 150 psig (10.34 bar) to about 300 psig (20.69 bar): a weight hourly space velocity (WHSV) of about 0.5 to about 20, preferably from about 0.75 to about 5 and a hydrogen to oil ratio of 1 to 10 moles of hydrogen per mole of C₅⁺ feed, preferably 1.5 to 5 moles of hydrogen per mole of C₅⁺ feed.

[0017] The effluent stream from reforming zone R₁ is fed to preheat furnace F₂ via line 14, then to reforming zone R₂ via line 16. Because reforming reactions are typically endothermic, the reactant stream must be reheated to reforming temperatures between reforming zones. The effluent stream from this first stage is sent to cooling zone K₁ via line 18 where it is cooled to condense a liquid phase to a temperature within the operating range of the recycle gas separation zone, which is represented in the Figure hereof by a separation drum S₁. The temperature will generally range from about 60° to about 300° F (15.6 to 148.9°C), preferably from about 80 to 125°F (26.7 to 51.7°C).The cooled effluent stream is then fed to separation zone S₁ via line 20 where a gaseous stream and a heavier liquid stream are produced. The preferred separation would result in a hydrogen-rich predominantly C₄^- gaseous stream and a predominantly C₅⁺ liquid stream. It Is understood that these streams are not pure streams. For example, the separation zone will not provide complete separation between the C₄^- components and the C₅⁺ liquids. Thus, the gaseous stream will contain minor amounts of C₅⁺ components and the liquid stream will contain minor amounts of C₄^- components and hydrogen.

[0018] A portion of the gaseous stream, which can be characterized as being a hydrogen-rich C₄^- gaseous stream, is recycled, via line 22, to line 10 by first passing it through compressor C₁ to increase its pressure to feedstock pressure. About 40 to 90 vol.%, preferably about 50 to 85 vol.%, of the hydrogen-rich gaseous stream will be recycled. Of course, during start-up, the unit is pressured-up with hydrogen from an independent source until enough hydrogen can be generated in the first stage for recycle. It is preferred that the first stage be operated in semi-regenerative mode, although a cyclic mode can also be used.

[0019] The remaining hydrogen-rich predominantly C₄^- gaseous stream from separation zone S₁ is passed to the second reforming stage via pressure control valve 26 where pressure is reduced to the level required for second stage operation. The amount of pressure reduction will depend on the operating pressure of the second stage separation zone S₂ and the pressure drop in furnaces F₃ and F₄, reactors R₃ and R₄, and the connecting piping. The reduced pressure gas from line 25 is mixed with the C₅⁺ liquid which passes from separation zone S₁ through a level control valve (not shown) and the mixture is then passed via line 24 to furnace F₃.

[0020] The heated stream from furnace F₃ is passed to reforming zone R₃ via line 28, which is operated in a moving-bed continual catalyst regeneration mode. Reforming conditions for the moving-bed reforming zones will include temperatures from about 800° to 1200° F (426.7 to 648.9°C), preferably from about 800° to 1000° F (426.7 to 537.8°C); pressures gauge from about 30 to 300 (2.07 to 20.68 bar), preferably from about 50 to 150 psig (3.5 to 10.3 bar); a weight hourly space velocity from about 0.5 to 20, preferably from about 0.75 to 6. Hydrogen-rich gas should be provided to maintain the hydrogen to oil ratio between the range of about 0.5 to 5, preferably from about 0.75 to 3. In the preferred embodiment, all of the hydrogen gas is supplied by the hydrogen-rich predominantly C₄^- gaseous stream which passes through pressure control valve 26. Instances may exist in which the gas flowing from the first stage is insufficient to supply the needed hydrogen to oil ratio. This could occur if the feedstock to the first stage was highly paraffinic or had a boiling range which included predominantly hydrocarbons in the 6 to 8 carbon number range. In these instances, hydrogen would need to be supplied from external sources such as a second reforming unit or a hydrogen plant. An additional, but less preferred source of hydrogen would be from compressing and recycling stream 56. This option would require additional compressor or a larger capacity compressor C₂.

[0021] Such reforming zones, or reactors, are well known in the art and are typical of those taught in U.S. Patent Nos. US-A-3,652,231; 3,856,662; 4,167,473; and 3,992,465.

[0022] The general principle of operation of such reforming zones is that the catalyst is contained in a annular bed formed by spaced cylindrical screens within the reactor. The reactant stream is processed through the catalyst bed, typically in an out-to-in radial flow, that is, it enters the reactor at the top and flows radially from the reactor wall through the annular bed of catalyst 30 which is descending through the reactor, and passes into the cylindrical space 32 created by said annular bed. It exits the bottom of the reforming zone and is passed, via line 34, to furnace F₄, then to reforming zone R₄ via line 35. Again, as in reforming zone R₃, the reactant stream passes out-to-in radially through the catalyst bed and into the cylindrical space 44 defined by said annular bed of catalyst. The effluent stream from reforming zone R₄ is passed via line 46 to cooling zone K₂ where the temperature of the stream is dropped to about 60° to 200°F (15.6 to 93.3°C), preferably from about 80° to 125°F (26.7 to 51.7°C). It is then passed into separation zone S₂ via line 52 where it is separated into a light hydrogen-rich C₄^- gaseous stream and a C₅⁺ liquid stream. The C₅⁺ stream is collected for blending in the gasoline pool via line 54, and the light hydrogen-rich C₄^- gaseous stream is sent through compressor C₂ via line 56 and used as a product gas.

[0023] Fresh and/or regenerated catalyst is charged to reforming zone R₃ by way of line 33 and distributed in the annular moving-bed 30 by means of catalyst transfer conduits 36, the catalyst being processed downwardly as an annular dense-phase moving bed. The reforming catalyst charged to reforming zones R₃ and R₄ is comprised of at least one Group VIII noble metal, preferably platinum; and one or more promoter metals, preferably tin, on spherical particles of a refractory support, preferably alumina. The spherical particles have an average diameter of about 1 to 3 mm, preferably about 1.5 to 2 mm, the bulk density of this solid being from about 0.5 to 0.9 and more particularly from about 0.5 to 0.8. The annular moving bed of catalyst exits from the bottom section of reforming zone R₃ and is passed via line 38 to reforming zone R₄ where it is distributed into the annular moving catalyst bed 42 by transfer from conduits 40.

[0024] The catalyst of reforming zone R₄ descends through the zone where it exits and is passed to catalyst regeneration zone CR via line 48 and transfer conduit 50 where the catalyst is subjected to one or more steps common to the practice of reforming catalyst regeneration. The catalyst regeneration zone CR represents all of the steps required to remove at least a portion of the carbon from the catalyst and return it to the state needed for the reforming reactions occurring in reforming zone R₃. The specific steps included in CR will vary with the selected catalyst. The only required step is one where accumulated carbon is burned-off at temperatures from about 600° to 1200°F (315.6 to 648.9°C) and in the presence of an oxygen-containing gas, preferably air. Additional steps which may also be contained in the catalyst regeneration equipment represented by CR include, but are not limited to, adding a halide to the catalyst, purging carbon oxides, redispersing metals, and adding sulfur or other compounds to lower the rate of cracking when the catalyst first enters the reforming zone.

[0025] The regenerated catalyst is then charged to reforming zone R₃ via line 33 and the cycle of continuous catalyst regeneration is continued until the entire reforming unit (both stages) is shut down, such as for catalyst regeneration of first stage (fixed-bed) reforming, which if operated in a semi-regenerative mode would need to be regenerated from time to time by shutting off the feed and raising the reactors to regeneration temperatures in the presence of an oxygen-containing gas. It is to be understood that the catalyst in the moving-bed reforming and regeneration zones may not be constantly moving, but may only move intermittently through the system. This may be caused by the opening an closing of various valves in the system. Thus, the word "continuous" is not to be taken literally and the word "continual" is sometimes used interchangeably with "continuous".

[0026] The moving-bed zones of the second stage may be arranged in series, side-by-side, each of then containing a reforming catalyst bed slowly flowing downwardly, as mentioned above, either continuously or, more generally, periodically, said bed forming an uninterrupted column of catalyst particles. The moving bed zones may also be vertically stacked in a single reactor, one above the other, so as to ensure the downward flow of catalyst by gravity from the upper zone to the next below. The reactor then consists of reaction zones of relatively large sections through which the reactant stream, which is in a gaseous state, flows from the periphery of the interior of the reactor (although a reactor may be designed to have the reactant stream flow from the center to the periphery) to the center (or from the center to the periphery) interconnected by catalyst zones of relatively small sections, the reactant stream issuing from one catalyst zone of large section divided into a first portion (preferably from 1 to 10%) passing through a reaction zone of small section for feeding the subsequent reaction zone of large section and a second portion (preferably from 99 to 90%) sent to a thermal exchange zone and admixed again to the first portion of the reactant stream at the inlet of the subsequent catalyst zone of large section.

[0027] When using one or more reaction zones with a moving bed of catalyst, said zones as well as the regeneration zone, are generally at different levels. It is therefore necessary to ensure several times the transportation of the catalyst from one relatively low point to a relatively high point, for example from the bottom of a reaction zone to the top of the regeneration zone, said transportation being achieved by any lifting device simply called "lift' (not shown on the Figure hereof). The fluid of the lift used for conveying the catalyst may be any convenient gas, for example nitrogen or still for example hydrogen and more particularly purified hydrogen or recycle hydrogen.

[0028] Catalysts suitable for use in any of the reactors of any of the stages include both monofunctional and bifunctional, monometallic and multimetallic noble metal containing reforming catalysts. Preferred are the bifunctional reforming catalysts comprised of a hydrogenation-dehydrogenation function and an acid function. The acid function, which is important for isomerization reactions, is thought to be associated with a material of the porous, adsorptive, refractory oxide type which serves as the support, or carrier, for the metal component, usually a Group VIII noble metal, preferably Pt, to which is generally attributed the hydrogenation-dehydrogenation function. The preferred support for both stages of reforming is an alumina material, more preferably gamma alumina. It is understood that the support material for the second stage reforming must be in the form of particles which are substantially spherical in shape, as previously described. One or more promoter metals selected from metals of Groups IIIA, IVA, IB, VIB, and VIIB of the Periodic Table of the Elements may also be present. The promoter metal, can be present in the form of an oxide, sulfide, or in the elemental state in an amount from about 0.01 to about 5 wt.%, preferably from about 0.1 to about 3 wt.%, and more preferably from about 0.2 to about 3 wt.%, calculated on an elemental basis, and based on total weight of the catalyst composition. It is also preferred that the catalyst compositions have a relatively high surface area, for example, about 100 to 250 m²/g. The Periodic Table of which all the Groups herein refer to can be found on the last page of Advanced Inorganic Chemistry, 2nd Edition, 1966, Interscience publishers, by Cotton and Wilkinson.

[0029] The acid function of the catalyst is typically provided by a halide component which may be fluoride, chloride, iodide bromide, or mixtures thereof. Of these, fluoride, and particularly chloride, are preferred. Generally, the amount of halide is such that the final catalyst composition will contain from about 0.1 to about 3.5 wt.%, preferably from about 0.5 to about 1.5 wt.% of halogen calculated on an elemental basis.

[0030] Preferably, the Group III noble metal, the most preferred which is platinum, will be present on the catalyst in an amount from about 0.01 to about 5 wt.%, calculated on an elemental basis, of the final catalytic composition. More preferably, the catalyst comprises from about 0.1 to about 2 wt.% platinum group component, especially about 0.1 to 2 wt.% platinum. Other preferred platinum group metals include palladium, iridium, rhodium, osmium, ruthenium and mixtures thereof.

[0031] By practice of the present invention, reforming is conducted more efficiently and results in increased hydrogen and C₅⁺ liquid yields. The first stage reactors are operated at conventional reforming temperatures and pressures in semiregenerative or cyclic mode while the reactors of the second stage are moving bed reactors operated substantially at lower pressures. Such (gauge) pressures in the second stage may be from as low as about 30 psig to about 100 psig (2.07 to 6.89 bar). More particularly, the downstream reactors can be operated in once-through gas mode because there is an adequate amount of hydrogen generated, that when combined with the hydrogen-rich gas stream from the first stage, is an adequate amount of hydrogen to sustain the reforming reactions taking place.

[0032] The second stage reactors, when operated in a once-through hydrogen-rich gas mode, permit a smaller product-gas compressor (C₂ in the Figure) to be substituted for a larger capacity recycle gas compressor. Pressure drop in the second stage is also reduced by virtue of once-through gas operation. Of course, the second stage reactors can be operated in a mode wherein the hydrogen-rich gas is recycled.

[0033] It is also within the scope of this invention that an aromatics separation unit where aromatic materials are separated in one or more steps to produce an aromatics-rich stream, an aromatics-lean stream, and optionally a stream containing predominantly C₅ and lighter hydrocarbons which comprise a portion of the aromatics-lean stream. This optional stream might be required to effect an economical separation of the remaining C₆⁺ product and can be removed as product or may be mixed back with the aromatics-rich stream for processing in the second stage. The terms "aromatics-rich" and "aromatics-lean" as used herein refer to the level of aromatics in the liquid fraction reaction stream after aromatic separation relative to the level of aromatics prior to separation. That is, after a reaction stream is subjected to an aromatics separation, two fractions result. One fraction has a higher level of aromatics relative to the stream before separation and is thus referred to as the aromatics-rich fraction. The other fraction is, of course, the aromatics-lean fraction which can also be referred to as the paraffin-rich fraction. Aromatics separation can be accomplished by any suitable method. Non-limiting methods suitable for use herein for aromatics separation include: extraction, extractive distillation, distillation, flashing, adsorption, and by permeation through a semipermeable membrane, or by any other appropriate aromatics or paraffins removal process. Preferred are extractive distillation, distillation, and flashing.

Claims

1. A process for catalytically reforming a gasoline boiling range hydrocarbon reactant stream in the presence of hydrogen In a reforming process unit comprised of a plurality of serially connected reforming zones wherein each of the reforming zones contains a reforming catalyst comprised of at least one Group VIII noble metal on a refractory support, which process comprises;

(a) reforming the reactant stream in a first reforming stage comprised of one or more serially connected reforming zones containing a fixed-bed of catalyst comprised of one or more Group VIII noble metals on a refractory support, which one or more reforming zones are operated at reforming conditions which includes a (gauge) pressure of from 100 to 500 psig (6.896 to 34.48 bar), and a H₂:C₅⁺ mol ratio in the range of from 1 to 10, thereby producing a first effluent stream;

(b) passing said first effluent stream to a separation zone wherein a hydrogen-rich predominantly C₄^- hydrocarbon gaseous stream and a predominantly C₅⁺ effluent stream; are produced

(c) recycling a portion of the hydrogen-rich gaseous stream to said first reforming stage;

(d) reforming the C₅⁺ effluent stream, with the remaining portion of the hydrogen-rich gaseous stream, in a second reforming stage operated at a pressure which is at least 50 psi (3.45 bar) lower than that of the first reforming stage and a H₂:oil mol ratio of from 0.5 to 5.0, which second reforming stage is comprised of one or more serially connected reforming zones which are operated in a moving-bed continual catalyst regeneration mode, which catalyst is comprised of at one or more Group VIII noble metals on substantially spherical refractory support particles, wherein the catalyst continually descends through the reforming zone, exits, and Is passed to a regeneration zone where it is regenerated by burning-off at least a portion of any accumulated carbon, and wherein the regenerated catalyst is continually recycled back to the one or more reforming zones.

2. The process of claim 1 wherein the catalyst in each of the reforming zones of the first stage is comprised of from 0.01 to 5 wt.% platinum, and from 0.01 to 5 wt.% of at least one metal selected from the group consisting of iridium, rhenium, and tin.

3. The process of claim 1 or claim 2 wherein: (i) the first reforming stage contains 2 or 3 fixed-bed reforming zones, and (ii) the second reforming stage contains one or two moving-bed reforming zones, with the proviso that when two moving-bed reforming zones are employed, the catalyst descends through a first moving-bed reforming zone, is passed to a second moving-bed reforming zone where it descends through said second moving-bed reforming zone, then is passed to a regeneration zone where any accumulated carbon is burned-off, after which the regenerated catalyst is recycled to said first moving-bed reforming zone.

4. The process of any one of claims 1 to 3 wherein: (i) aromatics are separated from at least a portion of the reaction stream of the first reforming stage thereby producing an aromatics-rich stream and an aromatic-lean stream; and (ii) passing at least a portion of the aromatics-lean stream to the second stage reforming stage.

5. The process of claim 4 wherein the aromatics separation between stages is accomplished by a technique selected from extractive distillation, distillation, and flashing.

6. The process of claim 4 or claim 5 wherein the separation between stages produces three streams, one of which is a C₉⁺ aromatics-rich stream which is collected; a C₅^- stream which is also collected; and the remaining fraction which is sent to the second stage reforming.

7. The process of any one of claims 1 to 6 wherein a C₆ heartcut is separated from the feedstock before it enters a reforming zone and is directed to the lead reactor of the second reforming stage.

8. The process of any one of claims 1 to 7 wherein the catalyst in each of the reforming zones of the first stage is comprised of from 0.1 to 2 wt.% platinum, and from 0.1 to 3 wt.% of at least one metal selected from the group consisting of iridium, rhenium, and tin.

Ansprüche

1. Verfahren zum katalytischen Reformieren eines Kohlenwasserstoffreaktantstroms aus dem Gasolinsiedebereich in Gegenwart von Wasserstoff in einer Reformierungsverfahrenseinheit, die eine Vielzahl von in Reihe miteinander verbundenen Reformierungszonen umfaßt, wobei jede der Reformierungszonen einen Reformierungskatalysator enthält, der mindestens ein Edelmetall der Gruppe VIII auf einem feuerfesten Träger umfaßt, bei dem:

(a) der Reaktantstrom in einer ersten Refomierungsstufe reformiert wird, die eine oder mehrere in Reihe miteinander verbundenen Reformierungszonen umfaßt, die einen Festbettkatalysator enthalten, der ein oder mehrere Edelmetalle der Gruppe VIII auf einem feuerfesten Träger umfaßt, wobei eine oder mehrere Reformierungszonen bei Reformierungsbedingungen betrieben werden, die einen Manometerdruck von 100 bis 500 psig (6,896 bis 34,48 bar) und ein H₂:C₅⁺ Molverhältnis im Bereich von 1 bis 10 umfassen, wodurch ein erster Austrittsmaterialstrom erzeugt wird,

(b) der erste Austrittsmaterialstrom in eine Trennzone geführt wird, in der ein gasförmiger wasserstoffreicher überwiegend C₄^-Kohlenwasserstoffstrom und ein überwiegend C₅⁺-Austrittsmaterialstrom gebildet werden,

(c) ein Teil des gasförmigen wasserstoffreichen Stromes zu der ersten Reformierungsstufe zurückgeführt wird,

(d) der C₅⁺-Austrittsmaterialstrom mit dem verbleibenden Teil des gasförmigen wasserstoffreichen Stromes in einer zweiten Reformierungsstufe reformiert wird, die bei einem Druck, der mindestens 50 psi (3,45 bar) niedriger ist als derjenige der ersten Reformierungsstufe, und bei einem H₂:Öl-Molverhältnis von 0,5 bis 5,0 betrieben wird, wobei die zweite Reformierungsstufe aus einer oder mehreren in Reihe miteinander verbundenen Reformierungszonen besteht, die in einem kontinuierlichen Katalysatorregenerationsmodus mit sich bewegendem Bett betrieben werden, wobei der Katalysator ein oder mehrere Edelmetalle der Gruppe VIII auf im wesentlichen kugelförmigen feuerfesten Trägerteilchen umfaßt, wobei sich der Katalysator kontinuierlich durch die Reformierungszone abwärtsbewegt, austritt und in eine Regenerationszone geführt wird, in der er durch Ausbrennen mindestens eines Teils von jeglichem angesammeltem Kohlenstoff regeneriert wird, und wobei der regenerierte Katalysator kontinuierlich in eine oder mehrere Reformierungszonen zurückgeführt wird.

2. Verfahren nach Anspruch 1, bei dem der Katalysator in jeder der Refomierungszonen der ersten Stufe 0,01 bis 5 Gew.-% Platin und 0,01 bis 5 Gew.-% mindestens eines Metalls ausgewählt aus der Gruppe bestehend aus Iridium, Rhenium und Zinn umfaßt.

3. Verfahren nach Anspruch 1 oder Anspruch 2, bei dem (i) die erste Refomierungsstufe zwei oder drei Festbettreformierungszonen enthält und (ii) die zweite Reformierungsstufe ein oder zwei Reformierungszonen mit sich bewegendem Bett enthält, mit der Maßgabe, daß, wenn zwei Refomierungszonen mit sich bewegendem Bett verwendet werden, sich der Katalysator durch eine erste Reformierungszone mit sich bewegendem Bett abwärtsbewegt, in eine zweite Refomierungszone mit sich bewegendem Bett geführt wird, wo er sich durch die zweite Reformierungszone mit sich bewegendem Bett abwärtsbewegt, wird, dann in eine Regenerierungszone geführt wird, wo jeglicher angesammelter Kohlenstoff abgebrannt wird, woraufhin der regenerierte Katalysator zu der ersten Refomierungszone mit sich bewegendem Bett zurückgeführt wird.

4. Verfahren nach einem der Ansprüche 1 bis 3, bei dem (i) Aromaten von mindestens einem Teil des Reaktionsstromes der ersten Refomierungsstufe abgetrennt werden, wodurch ein aromatenreicher Strom und ein aromatenarmer Strom gebildet werden, und (ii) mindestens ein Teil des aromatenarmen Stroms zu der zweiten Refomierungsstufe geführt wird.

5. Verfahren nach Anspruch 4, bei dem die Aromatenabtrennung zwischen den Stufen durch eine Technik bewirkt wird, die ausgewählt ist aus extraktiver Destillation, Destillation und Schnellverdampfung (flashing).

6. Verfahren nach Anspruch 4 oder Anspruch 5, bei dem die Abtrennung zwischen den Stufen drei Ströme erzeugt, wobei einer davon ein C₉⁺ aromatenreicher Strom ist, der gesammelt wird, einer ein C₅^--Strom ist, der ebenfalls gesammelt wird, und einer die verbleibende Fraktion ist, die zu der zweiten Refomierungsstufe zurückgeführt wird.

7. Verfahren nach einem der Ansprüche 1 bis 6, bei dem ein C₆-Herzschnitt aus dem Einsatzmaterial abgetrennt wird, bevor es in eine Refomierungszone eintritt, und zu dem Führungsreaktor der zweiten Reformierungsstufe geführt wird.

8. Verfahren nach einem der Ansprüche 1 bis 7, bei dem der Katalysator in jeder der Refomierungszonen der ersten Stufe 0,1 bis 2 Gew.-% Platin und 0,1 bis 3 Gew.-% mindestens eines Metalls ausgewählt aus der Gruppe bestehend aus Iridium, Rhenium und Zinn umfaßt.

Revendications

1. Procédé de reformage catalytique d'un courant de réactif hydrocarboné qui se situe dans la plage d'ébullition de l'essence en présence d'hydrogène dans une unité de traitement de reformage comprenant une pluralité de zones de reformage reliées en série, dans lequel chaque zone de reformage contient un catalyseur de reformage constitué d'au moins un métal noble du groupe VIII sur un support réfractaire, ledit procédé comprenant les étapes consistant:

(a) à reformer le courant de réactif dans un premier étage de reformage comprenant une ou plusieurs zones de reformage reliées en série contenant un lit fixe de catalyseur constitué d'un ou plusieurs métaux nobles du groupe VIII sur un support réfractaire, la ou lesdites zones de reformage fonctionnant dans des conditions de reformage qui comprennent une pression (manométrique) dans la plage de 6,896 à 34,48 bars (100 à 500 psig) et un rapport molaire H₂:C₅⁺ dans la plage de 1 à 10, produisant de la sorte un premier courant d'effluent,

(b) à faire passer ledit premier courant d'effluent dans une zone de séparation dans laquelle on produit un courant gazeux d'hydrocarbure riche en hydrogène, principalement en C₄^-, et un courant d'effluent principalement en C₅⁺,

(c) à recycler une partie du courant gazeux riche en hydrogène audit premier étage de reformage,

(d) à reformer le courant d'effluent en C₅⁺ avec la partie restante du courant gazeux riche en hydrogène, dans un second étage de reformage fonctionnant à une pression d'au moins 3,45 bars (50 psig) inférieure à celle du premier étage de reformage et un rapport molaire H₂:C₅⁺ dans la plage de 0,5 à 5,0, ledit second étage de reformage comprenant une ou plusieurs zones de reformage reliées en série qui fonctionnent en mode de régénération en continu du catalyseur à lit mobile, ledit catalyseur comprenant un ou plusieurs métaux nobles du groupe VIII sur des particules de support réfractaires sensiblement sphériques, le catalyseur descendant en continu à travers la zone de reformage, sortant et passant à une zone de régénération où il est régénéré en brûlant au moins une partie du carbone qui y est éventuellement accumulé et le catalyseur régénéré étant recyclé en continu vers la ou les zones de reformage.

2. Procédé selon la revendication 1, dans lequel le catalyseur dans chacune des zones de reformage du premier étage est constitué de 0,01% à 5% en poids de platine et de 0,01% à 5% en poids d'au moins un métal choisi dans le groupe constitué de l'iridium, du rhénium et de l'étain.

3. Procédé selon la revendication 1 ou 2, dans lequel (i) le premier étage de reformage contient deux ou trois zones de reformage à lit fixe et (ii) le second étage de reformage contient une ou deux zones de reformage à lit mobile à condition que, lorsqu'on utilise deux zones de reformage à lit mobile, le catalyseur descende à travers une première zone de reformage à lit mobile, passe à une seconde zone de reformage à lit mobile à travers laquelle il descend et passe ensuite dans une zone de régénération où le carbone qui y est éventuellement accumulé est brûlé, après quoi le catalyseur régénéré est recyclé vers ladite première zone de reformage à lit mobile.

4. Procédé selon l'une quelconque des revendications 1 à 3, dans lequel (i) les aromatiques sont séparés d'au moins une partie du courant de réaction du premier étage de reformage en produisant ainsi un courant riche en aromatiques et un courant pauvre en aromatiques et (ii) on fait passer au moins une partie du courant pauvre en aromatiques au second étage de reformage.

5. Procédé selon la revendication 4, dans lequel la séparation des aromatiques entre les étages se fait par une technique choisie parmi une distillation extractive, une distillation et une distillation éclair.

6. Procédé selon la revendication 4 ou 5, dans lequel la séparation entre les étages produit trois courants, à savoir un courant riche en aromatiques en C₉⁺ qui est recueilli, un courant en C₅^- qui est également recueilli et la fraction restante qui est envoyée au second étage de reformage.

7. Procédé selon l'une quelconque des revendications 1 à 6, dans lequel une fraction de coeur en C₆ est séparée de la charge de départ avant qu'elle ne pénètre dans une zone de reformage et est dirigée vers le réacteur principal du second étage de reformage.

8. Procédé selon l'une quelconque des revendications 1 à 7, dans lequel le catalyseur dans chacune des zones de reformage du premier étage comprend 0,1% à 2% en poids de platine et 0,1% à 3% en poids d'au moins un métal choisi dans le groupe constitué de l'iridium, du rhénium et de l'étain.

Drawing