Combination reforming and isomerization process Number:7,435,329 from the United States Patent and Trademark Office (PTO) owispatent A reforming and isomerization process has been developed. A reforming feedstream is charged to a reforming zone containing a reforming catalyst and operating at reforming conditions to generate a reforming zone effluent. Hydrogen and an isomerization feedstream is charged into an isomerization zone to contact an isomerization catalyst at isomerization conditions to increase the branching of the hydrocarbons. The isomerization catalyst is a solid acid catalyst comprising a support comprising a sulfated oxide or hydroxide of at least an element of Group IVB, a first component being at least one lanthanide series element, mixtures thereof, or yttrium, and a second component being a platinum group metal or mixtures thereof. The reforming zone effluent and the isomerization zone effluent are each separated to form a light ends stream and a product stream. The light ends streams are combined for processing in a net gas re-contacting zone.<H isomerization, Combination, Combination, ref, 7435329.html, Patent, pto, 7435329

Title: Combination reforming and isomerization process

Abstract: A reforming and isomerization process has been developed. A reforming feedstream is charged to a reforming zone containing a reforming catalyst and operating at reforming conditions to generate a reforming zone effluent. Hydrogen and an isomerization feedstream is charged into an isomerization zone to contact an isomerization catalyst at isomerization conditions to increase the branching of the hydrocarbons. The isomerization catalyst is a solid acid catalyst comprising a support comprising a sulfated oxide or hydroxide of at least an element of Group IVB, a first component being at least one lanthanide series element, mixtures thereof, or yttrium, and a second component being a platinum group metal or mixtures thereof. The reforming zone effluent and the isomerization zone effluent are each separated to form a light ends stream and a product stream. The light ends streams are combined for processing in a net gas re-contacting zone.

Patent Number: 7,435,329 Issued on 10/14/2008 to Nafis, et al.

Inventors: Nafis; Douglas A. (Mount Prospect, IL), Maher; Gregory F. (Aurora, IL), Rice; Lynn H. (Arlington Heights, IL), Schlueter; William D. (Lake in the Hills, IL), Gillespie; Ralph D. (Gurnee, IL), Cohn; Michelle J. (Glenview, IL)
Assignee: UOP LLC (Des Plaines, IL)

Appl. No.: 11/220,127

Filed: September 6, 2005

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
10872642	Jun., 2004	6979396
10872581	Jun., 2004	7015175
10804358	Mar., 2004	7022889
10718050	Nov., 2003	6927188
10717812	Nov., 2003	6881873
09942237	Aug., 2001	6706659
09942237	Aug., 2001	6706659

Current U.S. Class: 208/63 ; 208/66

Current International Class: C10G 35/04 (20060101); C10G 35/085 (20060101); C10G 35/09 (20060101)

Field of Search: 208/63,66

References Cited [Referenced By]

U.S. Patent Documents


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Primary Examiner: Dang; Thuan Dinh
Attorney, Agent or Firm: Maas; Maryann

Government Interests

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This work was performed under the support of the U.S. Department of Commerce, National Institute of Standards and Technology, Advanced Technology Program, Cooperative Agreement Number 70NANB9H3035. The United States Government has certain rights in this invention.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation-In-Part of application Ser. Nos. 10/872,642 and Ser. No. 10/872,581 both filed Jun. 21, 2004, now U.S. Pat. No. 6,979,396 and U.S. Pat. No. 7,015,175, respectively, which applications are a Continuation-In-Part of application Ser. No. 10/804,358 filed Mar. 19, 2004, now U.S. Pat. No. 7,022,889, which application is a Continuation-In-Part of application Ser. No. 10/718,050 and Ser. No. 10/717,812 both filed Nov. 20, 2003, now U.S. Pat. No. 6,927,188 and U.S. Pat. No. 6,881,873, respectively, which applications are a Continuation and a Division, respectively, of application Ser. No. 09/942,237 filed Aug. 29, 2001, now U.S. Pat. No. 6,706,659, the contents of all are hereby incorporated by reference in their entirety.

Claims

What is claimed is:

1. A process comprising: charging a reforming feedstream to a reforming zone containing a reforming catalyst and operating at reforming conditions to generate a reforming zone effluent; charging hydrogen and an isomerization feedstream comprising at least C.sub.5-C.sub.6 hydrocarbons into an isomerization zone to contact an isomerization catalyst at isomerization conditions to increase the branching of the feedstream hydrocarbons and produce the isomerization zone effluent comprising at least normal pentane, normal hexane, methylbutane, dimethylbutane, and methylpentane; wherein said isomerization catalyst is a solid acid catalyst comprising a support comprising a sulfated oxide or hydroxide of at least an element of Group IVB (IUPAC 4) of the Periodic Table, a first component selected from the group consisting of at least one lanthanide series element, mixtures thereof, and yttrium, and a second component selected from the group consisting of platinum group metals and mixtures thereof and wherein the atomic ratio of the first component to the second component is at least about 2; separating the isomerization zone effluent into an isomerization zone product stream and an isomerization zone light ends stream; separating the reforming zone effluent into a reforming zone product stream and a reforming zone light ends stream; combining at least a portion of the isomerization zone light ends stream and at least a portion of the reforming zone light ends stream to form a combined light ends stream; separating the combined light ends stream into a product stream enriched in C.sub.5 and heavier hydrocarbons and a stream enriched in C.sub.4 and lighter boiling compounds.

2. The process of claim 1 wherein the separating of the combined light ends stream comprises contacting the combined light ends stream with the reforming zone product stream in at least one re-contacting drum so that the product stream enriched in C.sub.5 and heavier hydrocarbons and the reforming zone product stream are formed as a combined product stream.

3. The process of claim 2 further comprising separating the isomerization zone product stream in a isomerization zone stabilizer to form an isomerate stream and an isomerization zone stabilizer overhead stream enriched in C.sub.4 and lighter boiling compounds and separating the combined product stream in a reforming zone stabilizer to form a reformate stream and a reforming zone stabilizer overhead stream enriched in C.sub.4 and lighter boiling compounds.

4. The process of claim 3 further comprising combining the isomerization zone stabilizer overhead stream and the reforming zone stabilizer overhead stream to form a combined stabilizer overhead stream and separating the combined stabilizer overhead stream in an overhead receiver to form a receiver gas stream further enriched in C.sub.4 and lighter boiling compounds and a receiver bottoms stream enriched in isomerate and reformate.

5. The process of claim 4 further comprising combining the receiver gas stream from the overhead receiver with the combined light ends stream.

6. The process of claim 3 further comprising blending a stream selected from the group consisting of the reformate stream, the isomerate stream, and a combination thereof into a gasoline pool to produce a motor fuel.

7. The process of claim 1 wherein the hydrogen charged to the isomerization zone is provided at least in part having passed through a net gas compressor in the reforming zone by the stream enriched in C.sub.4 and lighter boiling compounds.

8. The process of claim 1 wherein the reforming zone is operated in a mode selected from the group consisting of continuous catalyst regeneration (CCR) and semi-continuous regeneration.

9. The process of claim 1 wherein the isomerization catalyst further comprises from about 2 to about 50 mass-% of a refractory inorganic-oxide binder.

10. The process of claim 9 wherein the refractory inorganic-oxide binder has deposited thereon a component selected from the group consisting of the first component, the second component, and a sulfate component.

11. The process of claim 1 wherein the first component is selected from the group consisting of lutetium, ytterbium, thulium, erbium, holmium, terbium, combinations thereof and yttrium.

12. The process of claim 1 wherein the isomerization catalyst further comprises a third component selected from the group consisting of iron, cobalt, nickel, rhenium, and mixtures thereof.

13. The process of claim 1 wherein said reforming feedstream includes C.sub.6 and higher boiling hydrocarbons.

14. The process of claim 1 wherein said isomerization zone includes a series of two reactors, the first reactor operating at a temperature in the range of 120.degree. to 225.degree. C. and said isomerization zone effluent is recovered from a second reactor operating at a temperature in the range of 60.degree. to 160.degree. C.

Description

FIELD OF THE INVENTION

This invention relates generally to the parallel reforming and isomerization of hydrocarbons with integrated processing of the light ends of the reforming zone and the isomerization zone. This invention relates more specifically to the reforming of from C.sub.6 to C.sub.12 hydrocarbons and the isomerization of light paraffins using a novel solid catalyst in the isomerization zone.

BACKGROUND OF THE INVENTION

High octane gasoline is required for modern gasoline engines. Formerly it was common to accomplish octane number improvement by the use of various lead-containing additives. As lead is phased out of gasoline for environmental reasons, it has become increasingly necessary to rearrange the structure of the hydrocarbons used in gasoline blending in order achieve higher octane ratings. Catalytic reforming and catalytic isomerization are two widely used processes for this upgrading.

The traditional gasoline blending pool normally includes C.sub.4 and heavier hydrocarbons having boiling points of less than 205.degree. C. (395.degree. F.) at atmospheric pressure. This range of hydrocarbon includes C.sub.4-C.sub.6 paraffins and especially the C.sub.5 and C.sub.6 normal paraffins which have relatively low octane numbers. The C.sub.4-C.sub.6 hydrocarbons have the greatest susceptibility to octane improvement by lead addition and were formerly upgraded in this manner. With eventual phase out of lead additives octane improvement was obtained by using isomerization to rearrange the structure of the paraffinic hydrocarbons into branched-chain paraffins or reforming to convert the C.sub.6 and heavier hydrocarbons to aromatic compounds. Normal C.sub.5 hydrocarbons are not readily converted into aromatics, therefore, the common practice has been to isomerize these lighter hydrocarbons into corresponding branched-chain isoparaffins. Although the C.sub.6 and heavier hydrocarbons can be upgraded into aromatics through hydrocyclization, the conversion of C.sub.6's to aromatics creates higher density species and increases gas yields with both effects leading to a reduction in liquid volume yields. Moreover, the health concerns related to benzene are likely to generate overall restrictions on benzene and possibly aromatics as well, which some view as precursors for benzene tail pipe emissions. Therefore, it is preferred to charge the C.sub.6 paraffins to an isomerization unit to obtain C.sub.6 isoparaffin hydrocarbons. Consequently, octane upgrading commonly uses isomerization to convert C.sub.6 and lighter boiling hydrocarbons.

Combination processes using isomerization and reforming to convert naphtha range feedstocks are well known. U.S. Pat. No. 4,457,832 uses reforming and isomerization in combination to upgrade a naphtha feedstock by first reforming the feedstock, separating a C.sub.5-C.sub.6 paraffin fraction from the reformate product, isomerizing the C.sub.5-C.sub.6 fraction to upgrade the octane number of these components and recovering a C.sub.5-C.sub.6 isomerate liquid which may be blended with the reformate product. U.S. Pat. No. 4,181,599 and U.S. Pat. No. 3,761,392 show a combination isomerization-reforming process where a full range naphtha boiling feedstock enters a first distillation zone which splits the feedstock into a lighter fraction which enters an isomerization zone and a heavier fraction that is charged as feed to a reforming zone. In both the '392 and '599 patents, reformate from one or more reforming zones undergoes additional separation and conversion, the separation including possible aromatics recovery, which results in additional C.sub.5-C.sub.6 hydrocarbons being charged to the isomerization zone.

The effluent from a reforming zone will contain a portion of hydrogen which may be used in the isomerization zone. Therefore combining the effluents to separate a stream containing hydrogen for recycle to the isomerization zone may be desirable, but a refiner may lose blending flexibility and may prefer to keep the isomerate and reformate separate from one another. Even while keeping the isomerate and reformate separate, cost savings may be achieved through integration of the net gas recovery zone between the reforming process and the isomerization process. The light ends from the isomerization zone effluent may be combined with the light ends of the reforming zone effluent and the combined light ends stream may be processed in a single net gas re-contacting zone. Portions of the resulting gas stream may be recycled.

The present invention involves a reforming zone and an isomerization zone where a portion of the isomerization zone light ends is directed to a net gas re-contacting zone in the reforming zone and where the isomerization zone uses a novel catalyst. Also, the reforming zone stabilizer overhead and the isomerization zone stabilizer overhead may use an integrated overhead receiver. The isomerization catalyst is a solid acid catalyst comprising a support comprising a sulfated oxide or hydroxide of at least an element of Group IVB (IUPAC 4) of the Periodic Table, a first component selected from the group consisting of at least one lanthanide-series element, mixtures thereof, and yttrium, and a second component selected from the group of platinum-group metals and mixtures thereof. In one embodiment of the invention, the atomic ratio of the first component to the second component is at least about 2. In another embodiment of the invention, the isomerization catalyst further comprises from about 2 to 50 mass-% of a refractory inorganic-oxide binder. In yet another embodiment of the invention, the isomerization catalyst further comprises from about 2 to 50 mass-% of a refractory inorganic-oxide binder having one or more platinum group metals dispersed thereon.

SUMMARY OF THE INVENTION

The invention is a process having both a reforming zone and an isomerization zone involving charging a reforming feedstream to a reforming zone containing a reforming catalyst and operating at reforming conditions to generate a reforming zone effluent and charging hydrogen and an isomerization feedstream comprising C.sub.5-C.sub.6 hydrocarbons into an isomerization zone and contacting said hydrogen and feedstream with an isomerization catalyst at isomerization conditions to increase the branching of the feedstream hydrocarbons and produce an isomerization effluent stream comprising at least normal pentane, normal hexane, methylbutane, dimethylbutane, and methylpentane. The isomerization catalyst is a solid acid catalyst comprising a support comprising a sulfated oxide or hydroxide of at least an element of Group IVB (IUPAC 4) of the Periodic Table, a first component selected from the group consisting of at least one lanthanide-series element, mixtures thereof, and yttrium, and a second component selected from the group of platinum-group metals and mixtures thereof. The reforming zone effluent is separated into a light ends stream and a reformate stream and the isomerization zone effluent is separated into a light ends stream and an isomerate stream. The reforming zone light ends stream and the isomerization zone light ends stream are combined and further processed in a net gas re-contacting zone.

The atomic ratio of the first component of the isomerization catalyst to the second component of the isomerization catalyst may be at least about 2, and the catalyst may further comprise from about 2 to 50 mass-% of a refractory inorganic-oxide binder. The first component of the isomerization catalyst may be selected from the group consisting of lutetium, ytterbium, thulium, erbium, holmium, terbium, combinations thereof, and yttrium. The isomerization catalyst may further comprise a third component selected from the group consisting of iron, cobalt, nickel, rhenium, and mixtures thereof.

Additional objects, embodiments and details of this invention can be obtained from the following detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of the process of this invention where the reforming zone is operated in the continuous regeneration mode.

FIG. 2 is a plot of the octane number of the isomerized product streams versus temperature for an isomerization process using an available sulfated zirconia catalyst as compared to the isomerization catalyst the present invention.

FIG. 3 is a plot of the PIN number in a product stream versus temperature for an isomerization process using an available sulfated zirconia catalyst as compared to the isomerization catalyst of the present invention.

FIG. 4 is a plot of the percent of cyclic components converted to non-cyclic components versus temperature for an isomerization process using an available sulfated zirconia catalyst as compared to the isomerization catalyst of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In general terms, one embodiment of the invention comprises both a reforming zone and an isomerization zone operating concurrently, wherein a portion of the light ends from each zone are combined for further processing using a common net gas re-contacting zone thereby reducing equipment and operating costs. Other beneficial process integrations, such as a common stabilizer overhead receiver, will also be described below.

With respect to the reforming zone, a wide variety of reforming zone feed stocks may be used. In general, the reforming zone feed stock contains from C.sub.6 to about C.sub.11 or C.sub.12 hydrocarbons with a boiling point range from about 82 to about 240.degree. C. Specific reforming zone feedstocks may be generated using separation techniques. For example, a naphtha feedstock may be introduced into a separation zone comprising one or more fractional distillation columns to separate a heart-cut naphtha fraction from a heavy naphtha fraction. The lower-boiling heart-cut naphtha may contain a substantial concentration of C.sub.7 and C.sub.8 hydrocarbons, which can be catalytically reformed to produce a reformate component suitable for blending into current reformulated gasolines. This heart-cut naphtha also may contain significant concentrations of C.sub.6 and C.sub.9 hydrocarbons, plus smaller amounts of lower- and higher-boiling hydrocarbons, depending on the applicable gasoline specifications and product needs. The heart-cut naphtha end point may range from about 130.degree. to 175.degree. C., and preferably is within the range of about 145.degree. to 165.degree. C. The higher-boiling heavy naphtha may contain a substantial amount of C.sub.10 hydrocarbons, and also may contain significant quantities of lighter and heavier hydrocarbons depending primarily on a petroleum refiner's overall product balance. The initial boiling point of the heavy naphtha is between about 120.degree. and 175.degree. C., and preferably is between 140.degree. and 165.degree. C.

A light naphtha fraction may also be separated from the naphtha feedstock in a separation zone. The light naphtha comprises pentanes, and may comprise C.sub.6 and possibly a limited amount of C.sub.7 hydrocarbons. This fraction may be separated from the heart-cut naphtha because pentanes are not converted efficiently in a reforming zone, and optionally because C.sub.6 hydrocarbons may be an undesirable feed to catalytic reforming where they are converted to benzene for which gasoline restrictions are being implemented. The light naphtha fraction may be separated from the naphtha feedstock before it enters the separation zone, in which case the separation zone would only separate heart-cut naphtha from heavy naphtha. If the pentane content of the naphtha feedstock is substantial, however, separation of light naphtha generally is desirable. This alternative separation zone generally comprises two fractionation columns, although in some cases a single column recovering light naphtha overhead, heavy naphtha from the bottom and heart-cut naphtha as a side stream could be suitable.

For purposes of describing this invention, the reforming zone feedstock will contain from C.sub.6 to about C.sub.12 hydrocarbons with a boiling point range from about 82 to about 204.degree. C. The reforming zone feedstock is introduced to a heat exchanger to exchange heat with the reforming zone effluent stream. The heated reforming zone feed stream is then conducted to the reforming zone. The reforming zone upgrades the octane number of the reforming feed stream through a variety of reactions including naphthene dehydrogenation and paraffin dehydrocyclization and isomerization. The product reformate, which may contain a small amount of isomerate, may be used for gasoline blending to form motor fuel or may be further processed.

Reforming operating conditions used in the reforming zone of the present invention include a pressure of from about atmospheric to about 6080 kPaa, with the preferred range being from atmospheric to about 2026 kPaa and a pressure of below 1013 kPaa being especially preferred. Hydrogen is generated within the reforming zone, but additional hydrogen may be directed, if necessary, to the reforming zone in an amount sufficient to correspond to a ratio of from about 0.1 to 10 moles of hydrogen, but generated and added, per mole of hydrocarbon feedstock. The volume of the contained reforming catalyst corresponds to a liquid hourly space velocity of from about 1 to 40 hr.sup.-1. The operating temperature generally is in the range of 260.degree. to 560.degree. C.

The reforming catalyst comprises a supported platinum-group metal component. This component comprises one or more platinum-group metals, with a platinum component being preferred. The platinum may exist within the catalyst as a compound such as the oxide, sulfide, halide, or oxyhalide, in chemical combination with one or more other ingredients of the catalytic composite, or as an elemental metal. Best results are obtained when substantially all of the platinum exists in the catalytic composite in a reduced state. The preferred platinum component generally comprises from about 0.01 to 2 mass % of the catalytic composite, preferably 0.05 to 1 mass %, calculated on an elemental basis.

It is within the scope of the present invention that the catalyst may contain other metal components known to modify the effect of the preferred platinum component. Such metal modifiers may include Group IVA (14) metals, other Group VIII (8-10) metals, rhenium, indium, gallium, zinc, uranium, dysprosium, thallium and mixtures thereof. A preferred metal modifier is a tin component. Catalytically effective amounts of such metal modifiers may be incorporated into the catalyst by any means known in the art.

The reforming catalyst conveniently is a dual-function composite containing a metallic hydrogenation-dehydrogenation component on a refractory support which provides acid sites for cracking and isomerization. The refractory support of the reforming catalyst should be a porous, adsorptive, high-surface-area material which is uniform in composition without composition gradients of the species inherent to its composition. Within the scope of the present invention are refractory supports containing one or more of: (1) refractory inorganic oxides such as alumina, silica, titania, magnesia, zirconia, chromia, thoria, boria or mixtures thereof; (2) synthetically prepared or naturally occurring clays and silicates, which may be acid-treated; (3) crystalline zeolitic aluminosilicates, either naturally occurring or synthetically prepared such as FAU, MEL, MFI, MOR, MTW (IUPAC Commission on Zeolite Nomenclature), in hydrogen form or in a form which has been exchanged with metal cations; (4) non-zeolitic molecular sieves as disclosed in U.S. Pat. No. 4,741,820, incorporated by reference; (5) spinels such as MgAl.sub.2O.sub.4, FeAl.sub.2O.sub.4, ZnAl.sub.2O.sub.4, CaAl.sub.2O.sub.4; and (6) combinations of materials from one or more of these groups.

The preferred refractory support for the reforming catalyst is alumina, with gamma- or eta-alumina being particularly preferred. Best results are obtained with an alumina is that which has been characterized in U.S. Pat. No. 3,852,190 and U.S. Pat. No. 4,012,313 as a byproduct from a Ziegler higher alcohol synthesis reaction as described in Ziegler's U.S. Pat. No. 2,892,858. For purposes of simplification, such an alumina will be hereinafter referred to as a "Ziegler alumina." Ziegler alumina is presently available from the Vista Chemical Company under the trademark "Catapal" or from Condea Chemie GMBH under the trademark "Pural." This material is an extremely high purity pseudo-boehmite powder which, after calcination at a high temperature, has been shown to yield a high-purity gamma-alumina.

The alumina powder may be formed into any shape or form of carrier material known to those skilled in the art such as spheres, extrudates, rods, pills, pellets, tablets or granules. Preferred spherical particles may be formed by converting the alumina powder into alumina sol by reaction with suitable peptizing acid and water and dropping a mixture of the resulting sol and gelling agent into an oil bath to form spherical particles of an alumina gel, followed by known aging, drying and calcination steps. The alternative extrudate form is preferably prepared by mixing the alumina powder with water and suitable peptizing agents, such as nitric acid, acetic acid, aluminum nitrate and like materials, to form an extrudable dough having a loss on ignition (LOI) at 500.degree. C. of about 45 to 65 mass %. The resulting dough is extruded through a suitably shaped and sized die to form extrudate particles, which are dried and calcined by known methods. Alternatively, spherical particles can be formed from the extrudates by rolling the extrudate particles on a spinning disk.

The reforming catalyst optimally contains a halogen component. The halogen component may be either fluorine, chlorine, bromine or iodine or mixtures thereof. Chlorine is the preferred halogen component. The halogen component is generally present in a combined state with the inorganic-oxide support. The halogen component is preferably well dispersed throughout the catalyst and may comprise from more than 0.2 to about 15 mass %, calculated on an elemental basis, of the final catalyst. Further details of the preparation and activation of embodiments of the above reforming catalyst are disclosed in U.S. Pat. No. 4,677,094, which is hereby incorporated by reference in its entirety.

In an advantageous alternative embodiment, the reforming catalyst comprises a large-pore molecular sieve. The term "large-pore molecular sieve" is defined as a molecular sieve having an effective pore diameter of about 7 angstroms or larger. Examples of large-pore molecular sieves which might be incorporated into the present catalyst include LTL, FAU, AFI and MAZ (IUPAC Commission on Zeolite Nomenclature) and zeolite-beta.

Preferably the alternative embodiment of the reforming catalyst contains a nonacidic L-zeolite (LTL) and an alkali-metal component as well as a platinum-group metal component. It is essential that the L-zeolite be nonacidic, as acidity in the zeolite lowers the selectivity to aromatics of the finished catalyst. In order to be "nonacidic," the zeolite has substantially all of its cationic exchange sites occupied by nonhydrogen species. Preferably the cations occupying the exchangeable cation sites will comprise one or more of the alkali metals, although other cationic species may be present. An especially preferred nonacidic L-zeolite is potassium-form L-zeolite.

It is necessary to composite the L-zeolite with a binder in order to provide a convenient form for use in the catalyst of the present invention. The art teaches that any refractory inorganic oxide binder is suitable. One or more of silica, alumina or magnesia are preferred binder materials of the present invention. Amorphous silica is especially preferred, and excellent results are obtained when using a synthetic white silica powder precipitated as ultra-fine spherical particles from a water solution. The silica binder preferably is nonacidic, contains less than 0.3 mass % sulfate salts, and has a BET surface area of from about 120 to 160 m.sup.2/g.

The L-zeolite and binder may be composited to form the desired catalyst shape by any method known in the art. For example, potassium-form L-zeolite and amorphous silica may be commingled as a uniform powder blend prior to introduction of a peptizing agent. An aqueous solution comprising sodium hydroxide is added to form an extrudable dough. The dough preferably will have a moisture content of from 30 to 50 mass % in order to form extrudates having acceptable integrity to withstand direct calcination. The resulting dough is extruded through a suitably shaped and sized die to form extrudate particles, which are dried and calcined by known methods. Alternatively, spherical particles may be formed by methods described hereinabove for the first reforming catalyst.

An alkali metal component is an essential constituent of the alternative reforming catalyst. One or more of the alkali metals, including lithium, sodium, potassium, rubidium, cesium and mixtures thereof, may be used, with potassium being preferred. The alkali metal optimally will occupy essentially all of the cationic exchangeable sites of the nonacidic L-zeolite. Surface-deposited alkali metal also may be present as described in U.S. Pat. No. 4,619,906, incorporated herein by reference.

Further details of the preparation and activation of embodiments of the alternative reforming catalyst are disclosed, e.g., in U.S. Pat. No. 4,619,906 and U.S. Pat. No. 4,822,762, which are incorporated into this specification by reference.

The final reforming catalyst generally will be dried at a temperature of from about 100.degree. to 320.degree. C. for about 0.5 to 24 hours, followed by oxidation at a temperature of about 300.degree. to 550.degree. C. in an air atmosphere for 0.5 to 10 hours. Preferably the oxidized catalyst is subjected to a substantially water-free reduction step at a temperature of about 300.degree. to 550.degree. C. (preferably about 350.degree. C.) for 0.5 to 10 hours or more. The duration of the reduction step should be only as long as necessary to reduce the platinum, in order to avoid pre-deactivation of the catalyst, and may be performed in-situ as part of the plant startup if a dry atmosphere is maintained.

The reforming zone feed stream may contact the reforming catalyst in either upflow, downflow, or radial-flow mode. The catalyst is contained in a fixed-bed reactor or in a moving-bed reactor whereby catalyst may be continuously withdrawn and added. These alternatives are associated with catalyst-regeneration options known to those of ordinary skill in the art, such as: (1) a semi-continuous regenerative unit containing fixed-bed reactors maintains operating severity by increasing temperature, eventually shutting the unit down for catalyst regeneration and reactivation; (2) a swing-reactor unit, in which individual fixed-bed reactors are serially isolated by manifolding arrangements as the catalyst become deactivated and the catalyst in the isolated reactor is regenerated and reactivated while the other reactors remain on-stream; (3) continuous regeneration of catalyst withdrawn from a moving-bed reactor, with reactivation and substitution of the reactivated catalyst, permitting higher operating severity by maintaining high catalyst activity through regeneration cycles of a few days; or: (4) a hybrid system with semi-continuous regenerative and continuous-regeneration provisions in the same unit. The preferred embodiment of the present invention is a moving-bed reactor with continuous catalyst regeneration, in order to realize high yields of desired C.sub.5+ product at relatively low operating pressures associated with more rapid catalyst deactivation. The total product stream from the reforming zone generally is conducted to the heat exchanger to exchange heat with the reforming zone feedstock.

Concurrently with the conversion occurring the in the reforming zone, isomerization is occurring in the isomerization zone. The feedstock to the isomerization zone includes a hydrocarbon fraction rich in C.sub.4-C.sub.7 normal paraffins. The term "rich" is defined to mean a stream having more than 50% of the mentioned component. Preferred feedstocks are substantially pure normal paraffin streams having from 5 to 6, and some having 7 carbon atoms or a mixture of such substantially pure normal paraffins. Other useful feedstocks include light natural gasoline, light straight run naphtha, gas oil condensate, light raffinates, light reformate, light hydrocarbons, field butanes, and straight run distillates having distillation end points of about 77.degree. C. and containing substantial quantities of C.sub.4-C.sub.6 paraffins. The feed stream may also contain low concentrations of unsaturated hydrocarbons and hydrocarbons having more than 6 carbon atoms.

Hydrogen is admixed with the feed in an amount that will provide a hydrogen to hydrocarbon ratio equal to from about 0.05 to about 5.0 in the effluent from the isomerization zone. Hydrogen may be consumed in the isomerization zone, especially in the saturation of benzene. Additionally, the isomerization zone will have a net consumption of hydrogen often referred to as the stoichiometric hydrogen requirement which is associated with a number of side reactions that occur. These side reactions include cracking and disproportionation. Other reactions that will also consume hydrogen include olefin and aromatics saturation. For feeds having a low level of unsaturates, satisfying the stoichiometric hydrogen requirements demands a hydrogen to hydrocarbon molar ratio for the inlet stream of between 0.05 and 5.0. Hydrogen in excess of the stoichiometric amounts for the side reactions is maintained in the reaction zone to provide good stability and conversion by compensating for variations in feed stream compositions that alter the stoichiometric hydrogen requirements.

Hydrogen may be added to the feed mixture in any manner that provides the necessary control for the addition of small hydrogen quantities. Metering and monitoring devices for this purpose are well known by those skilled in the art. A control valve may be used to meter the addition of hydrogen to the feed mixture. The hydrogen concentration in the outlet stream or one of the outlet stream fractions is monitored by a hydrogen monitor and the control valve setting position is adjusted to maintain the desired hydrogen concentration. The hydrogen concentration at the effluent is calculated on the basis of total effluent flow rates.

The hydrogen may be provided as part of a stream generated through the separation of a combined light ends stream having a portion of the light ends from the reforming zone and a portion of the light ends from the isomerization zone. The generated stream will contain hydrogen from the reforming process which may supplement or replace an independent hydrogen source for the isomerization zone.

The hydrogen and hydrocarbon feed mixture is contacted in the isomerization zone with a novel isomerization catalyst. The novel isomerization catalyst comprises a sulfated support of an oxide or hydroxide of a Group IVB (IUPAC 4) metal, preferably zirconium oxide or hydroxide, at least a first component which is a lanthanide element or yttrium component, and at least a second component being a platinum-group metal component. Preferably, the first component contains at least ytterbium and the second component is platinum. The catalyst optionally contains an inorganic-oxide binder, especially alumina. The catalyst is fully described in U.S. Pat. No. 6,706,659 which is hereby incorporated by reference in its entirety.

The support material of the isomerization catalyst of the present invention comprises an oxide or hydroxide of a Group IVB (IUPAC 4). In one embodiment the Group IVB element is zirconium or titanium. Sulfate is composited on the support material. A component of a lanthanide-series element is incorporated into the composite by any suitable means. A platinum-group metal component is added to the isomerization catalytic composite by any means known in the art to effect the catalyst of the invention, e.g., by impregnation. Optionally, the catalyst is bound with a refractory inorganic oxide. The support, sulfate, metal components and optional binder may be composited in any order effective to prepare a catalyst useful for the isomerization of hydrocarbons.

Production of the support of the isomerization catalyst is described in U.S. Pat. No. 6,706,659 and not reproduced here. A sulfated support is prepared by treatment with a suitable sulfating agent to form a solid strong acid. Sulfate ion is incorporated into a catalytic composite, for example, by treatment with sulfuric acid in a concentration usually of about 0.01-10N and preferably from about 0.1-5N. Compounds such as hydrogen sulfide, mercaptans or sulfur dioxide, which are capable of forming sulfate ions upon calcining, may be employed as alternative sources. Ammonium sulfate may be employed to provide sulfate ions and form a solid strong acid catalyst. The sulfur content of the finished catalyst generally is in the range of about 0.5 to 5 mass-%, and preferably is from about 1 to 2.5 mass-%. The sulfated composite is dried, preferably followed by calcination at a temperature of about 500 to 800.degree. C. particularly if the sulfation is to be followed by incorporation of the platinum-group metal.

A first component, comprising one or more of the lanthanide-series elements, yttrium, or mixtures thereof, is another essential component of the present catalyst. Included in the lanthanide series are lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium. Preferred lanthanide series elements include lutetium, ytterbium, thulium, erbium, holmium, terbium, and mixtures thereof. Ytterbium is a most preferred component of the present catalyst. The first component may in general be present in the catalytic composite in any catalytically available form such as the elemental metal, a compound such as the oxide, hydroxide, halide, oxyhalide, carbonate or nitrate or in chemical combination with one or more of the other ingredients of the catalyst. The first component is preferably an oxide, an intermetallic with platinum, a sulfate, or in the zirconium lattice. The materials are generally calcined between 600 and 800.degree. C. and thus in the oxide form. The lanthanide element or yttrium component can be incorporated into the catalyst in any amount which is catalytically effective, suitably from about 0.01 to about 10 mass-% lanthanide or yttrium, or mixtures, in the catalyst on an elemental basis. Best results usually are achieved with about 0.5 to about 5 mass-% lanthanide or yttrium, calculated on an elemental basis. The preferred atomic ratio of lanthanide or yttrium to platinum-group metal for this catalyst is at least about 1:1, preferably about 2:1 or greater, and especially about 5:1 or greater.

The first component is incorporated in the isomerization catalytic composite in any suitable manner known to the art, such as by coprecipitation, coextrusion with the porous carrier material, or impregnation of the porous carrier material either before, after, or simultaneously with sulfate though not necessarily with equivalent results.

A second component, a platinum-group metal, is an essential ingredient of the catalyst. The second component comprises at least one of platinum, palladium, ruthenium, rhodium, iridium, or osmium; platinum is preferred, and it is especially preferred that the platinum-group metal consists essentially of platinum. The platinum-group metal component may exist within the final catalytic composite as a compound such as an oxide, sulfide, halide, oxyhalide, etc., in chemical combination with one or more of the o