CA2077457A1 - Multi-stage reforming process - Google Patents

Abstract

A multi-stage reforming process is described in which a conventional reforming catalyst (12) is used upstream of an intermediate pore size crystalline silicate containing a Group VIII metal (14).
The conventional catalyst is operated at typical reforming conditions and the crystalline silicate is operated at lower pressures. At least a portion of the hydrogen and substantially all of the hydrogen sulfide present is removed (18) from the penultimate stage reformate before it is used in the feed to the final stage.

Description

W091/13127 2 0 7 7 4 ~ 7 PCT/US91/01~S

MULTI-9 _ ROCES~

~ackground Of The Invent~Qn The present inventlon is a multi-stage S reforming process for upgrading a hydrocarbon feed and increasing its octane rating. More specifically, two catalysts are used in sequential operation to reform a naphtha hydrocarbon feed.
Catalytic reforming is well known in the petroleum industry and refers to the treatment of naphtha fractions to improve thelr octane rating.
There are at least three important hydrocarbon reactions that occur during reforming operation.
These include: l) dehydrogenation of cyclohexanes to aromatics; 2) dehydroisomerization of alkylcyclopentanes to aromatics; and 3) dehydrocyclization of acyclic hydrocarbons to aromatics. A number of other reactions also occur, including the following: alkylbenzene dealkylation, paraffin isomerization, aromatic disproportionation and hydrocracking reactions which produce light gaseous hydrocarbons, e.g., methane, ethane, propane and butane. Hydrocracking reactions are to be particularly minimized during reforming as they decrease both the product yield in the gasoline boiling range and the product yield of hydrogen.
Naphthene dehydrogenation to aromatics is the most thermodynamically favorable aromatization reaction at reforming conditions. It yields higher ratios of aromatic product/nonaromatic reactant than the dehydrocyclization or dehydroisomerization reactions at a given reaction temperature and pressure. Moreover, it i8 also the fastest of the three aromatization reaction6. Conse~uently, the ~èlectivity for naphthene dehydrogenation is ~:IJF~!3TlTI~T~ E~

wo 91/13127 Pcr/l,s91/o ~5 generally hlgher than that for the other two aromatization reactlons.
senzene, al~ylbenzenes, and hydrogen are lmportant products of catalytic reformlng. The aromatic hydrocarbons are valuable because they increase the gasoline octane number and because they can be used in the synthesis of other chemicals.
The hydrogen is useful elsewhere ln the refinery, for such tasks as: processing of high boillng feedstreams; removing heteroatoms; and other reforming operations.
The demand for high octane gasol~ne has stimulated extensive research for developing ~mproved reforming catalysts and catalytic reforming processes. Successful reforming catalysts must be selective for high octane aromatlc hydrocarbons without producing low yields or light gaseous hydrocarbons and sufficiently active to produce a certain quality product without an excessively high reaction temperature. Additionally, the catalysts should: be stable to retain their activity and selectivity characteristics during prolonged periods of operation; permit frequent regeneration without loss of performance; and be tolerant to common catalyst poisons, such as sulfur.
Catalysts comprising platinum supported on alumina are well known and widely used for naphtha reforming. However, other reforming catalysts typically contain a catalytic metal such as platinum, disposed on silica, silica/alumina, boria/silica, large pore zeolites, and a plethora of other natural and manmade crystalline silicates. One example of a crystalline silicate useful in reforming hydrocarbons is ZSM-5, particularly ZSM-5 which has a high silica:alumina (SiO2:A103) ratio and is sometimes referred to as silicalite. Examples of its methods of manufacture are shown in: Dwyer, et al., SUBSTITUTE S~IEET

2 ~ 7 7 1 j 7 U.S. Patents Nos. 3,941,871, iss~ed March 2, 1976 and 4,441,991, issued April 10, 1984; and Derouane, et al., EPO Applicatlon No. 186,479, published February 7, 1986, all of whlch are incorporated by reference lr.
their entirety.
Currently, conventional catalytic reformlng processes must operate at higher severity to produce higher octane products because lead can no longer be added to boost octane in gasolines. High severity operations produce high octane gasolines, but at the expense of liquid yield and reformer run length.
Thus, it is advantageous to develop a process which can produce a high octane gasoline while retaining a high liquid yield and run length. In accordance with the present invention a combination process is set forth which offers the flexibility needed to achieve this result.
The art contains combination reforming processes in which a hydrocarbon feed is converted ~0 with one or more different types of conversion catalysts. For example, U.S. Patents Nos. 4,440,628, 4,436,612 and 4,425,222 show two-stage reforming with platinum and rhenium on chlorided alumina catalysts, U.S. Patents Nos. 4,636,298 and 4,645,586 disclose two-stage processes using a conventional bifunctional catalyst (e.g., platinum/rhenium on alumina) ahead of a monofunctional catalyst (e.g., platinum on L
zeolite). U.S. Patent No. 4,190,5l9 shows a two-stage system for aromatics production using two different catalysts. They are platinum and rhenium on chlorided alumina and ZSM-5 in the H-form without a Group VIII metal. U.S. Patent No. 4,443,326 disclo~es reforming using a large pore zeolite having a Group VIII ~etal and then cracking low octane components in the reformate using an intermediate pore zeolite without Group VIII metal. U.S. Patent No. 4,370,219 discloses cracking low octane ~ T~Ç~ YFEr WO91/l3t27 ~ PCT/~S91/012X5 components to C~_CJ oleflns, followed by olefln oligomerlzation using ZSM-5. U.S. Patent No.
4,292,167 discloses reforming using a conventional noble metal reforming catalyst followed by shape selective cracking of reformate using ZSM-5 and then reformlng again. U.S. Patent No. 4,211,886 discloses a two-stage process wherein the first stage reforms a feed to produce aromatics and the final stage isomerizes and dealkylates the reformate using ZSM-5.
U.S. Patent No. 4,162,212 discloses a parallel process for reforming and isomerization using ZSM-5.
Australian Patent Application 65624/86 discloses a two-stage system for upgrading a hydrocarbon feedstock. A conventional reforming catalyst is used in sequence with a ZSM-5 type zeolite containing a metal from Groups IIS or IIIA (such as galliùm or beryllium). The ZSM-5 type catalyst is acidic and makes aromatics by forming C3~C~ olefins and then combining them.
However, even with the combination processes listed above, there is still a need for a process which will reform hydrocarbons to a high octane number while maintaining a correspondingly high liquid yield. That need has now been satisfied by the invention which is discussed below.

Brief Descri~t~on Of Drawing The invention will be better understood by reference to the drawing which schematically represents a process in accordance with the embodiments of the invention.

~;UB~T~TIÇTe 5~1EET

WO91/13127 2 0 7 7 ~ j 7 PCT/~S91/0128s Summary Of Invention Accordlng to the present lnvention a staged process lS provlded for reforming hydrocarbons. It comprises contacting a hydrocarbon feed with a conventional reforming catalyst in a penultimate reformlng zone under reforming conditlons to produce a reformate, separating at least some of the hydrogen from the penultimate reforming zone along with any hydrogen sulfide present from the reformate to provide a hydrogen content substantially reduced and substantially hydrogen sulfide free reformate hydrocarbon fraction and contacting the reformate hydrocarbon fraction with a final catalyst which comprises a Group VIII metal on a nonacidic lS intermediate pore size crystalline silicate in a final reforming zone. The crystalline silicate catalyst is contacted with the reformate hydrocarbon fraction at a temperature between 550 and 1200#F, a space velocity between 0.1 and 20 LHSV and a pressure between 0 and about 100 psig. Preferably, the crystalline silicate is silicalite.
Among other factors, the present invention is based on the discovery that the multi-stage sequential process of the invention, using a conventional reforming catalyst and a silicalite catalyst under specified conditions, produces a relatively high octane product at a relatively high liquid yield. The combined high octane and high Csl liquid yield from this multi-stage process is greater than the com~ined octane and liquid yield for either of the two individual catalysts. Thes.e advantages are believed to result from a combination of the conventional catalystts ability to selectively catalyze cyclohexane dehydrogenation, alkylcyclo-hexane dehydrogenation and alkylcyclopentane - dehydroisomerization, and the silicalite catalyst's ability to selectively catalyze paraffin dehydro-~lIR~Tr~s~ ~ ~ F~-WO 91/13127 PC~ 'S91/n~8S

r ;~

cyclizatlon.
In accordance with an embodlment of the lnventlon it is not necessary to contact the platlnum/silicalite catalyst in the final sta~e wltr.
recycle hydrogen. In this embodiment the absence of added hydrogen favors aromatics prod~ction and relative activity which increases llquid yield at a given octane.
In accordance with another embodimen~ of the invention some hydrogen is recycled. This increases catalyst life and allows some heat to be returned to the catalyst beds.
A specific embodiment of the present invention comprises contacting a catalyst, which comprises between O.l and 2.5 weight percent platinum, 0.1 and 5.0 weight percent rhenium and 0.5 and 1.5 weight percent chloride on alumina, the ratio of rhenium to platinum being between 1:1 and 6:1, in a penultimate reforming zone with a feed having less than 1 ppm sulfur, at a temperature between 800 and 1100'F, a liquid hourly space velocity tLHSV) between 0.5 and 6, a pressure between 50 and 500 psig, and a hydrocarbon recycle ratio between 1 and 20 H2/HC, to form a reformate; separating at least a portion of the gaseous hydrogen along with hydrogen sulfide from the reformate to form a hydrogen content substantially reduced and substantially hydrogen sulfide free reformate hydrocarbon fraction; and contacting the reformate hydrocarbon fraction in a final reforming zone with a catalyst which comprises between 0.1 weight percent to 2.5 weight percent platinum on silicalite and an alkali or alkaline earth metal, at a temperature between 700 and 1100-F, a space velocity between 0.3 and 5 LHSV and a pressure between 15 and 75 psig.
Detail~ed De~ $lon Of The Inven~Qn The present invention i8 a multi-stage WO91/13127 ~ 7 PCT/~S91/01 process show~ generally as 10 in the drawlng which uses a conventlonal reforming catalyst in the penultimate stage or zone 12 and an intermediate pore size crystalllne silicate catalyst ln the ~inal stage or zone 14. It should be noted that while only two reforming zones, 12 and 14, are illustrated, additional reforminq zones can precede the penultimate zone 12. A hydrocarbon feed is introduced via line 16 to the penultimate reforming zone 12 where it is contacted with the conventional reforming catalyst in the penultimate reforming zone at less severe conditions than those needed to produce a reformate of the desired octane of the overall process. At least a portion of the hydrogen and substantially all of the hydrogen sulfide are separated by a separator 18 from the reformate exiting the penultimate zone 12 via line 20. The remaining reformate Cs~ hydrocarbon fraction is introduced via line 22 and is upgraded to the desired octane rating in the final stage 14. The reformate from the penultimate stage 12 is upgraded in the final reforming stage 14 at low pressure. The multi-stage process produces a relatively high octane product at a relatively high liquid yield.
Co~y~Lç~ S~talys~ (Penultimate Reforming Zone 12 The conventional reforming catalyst used in the penultimate reforming zone 12 comprises a Group VIII metal, more preferably a noble metal, most preferably platinum. Preferably, the conventional reforming catalyst also comprises a promoter metal, such as rhenium, tin, germanium, cobalt, nickel, iridium, rhodium, ruthenium, or combinations thereof.
More preferably, the promoter metal is rhenium or tin. These metals are disposed on a support.
Preferable Supports include alumina, silica/alumina, silica, natural or man-made zeolites. More 1T~l'~ S~IF~

W091/13127 ~ PCT/~Sgl/01~5 preferably, the support lS alumlna. ~he cataiyst may also include between 0 1 and 3 weight percent chloride, more preferably between 0.5 and 1.; welgh~
percent chloride. The catalyst, if it 1ncludes a promoter metal, suitably includes sufficlent promoter metal to provide a promoter to platinum ratlo between O.S:l and lO:l, more preferably between 1:1 and 6:1, most preferably between 2:1 and 5:1. The preclse conditions, compounds, and procedures for catalyst manufacture are known to those persons skilled ln the art. Some examples of conventional catalysts are shown in U.S. Patents Nos. 3,631,216; 3,415,/37; and 4,511,746, which are hereby incorporated by reference in their entireties.
Crystalline Silicates (Final Reformina Zone 14) The final stage catalyst of the present process comprises an intermediate pore size crystalline silicate.
By "intermediate pore size", as used herein, is meant an effective pore aperture in the range of about 5 to 6.5P when the molecular sieve is in the H-form. Molecular sieves having pore apertures in this range tend to have unique molecular sieving characteristics. Unlike small pore zeolites such as erionite and chabazite, they will allow hydrocarbons having some branching into the molecular sieve void spaces. Unlike larger pore zeolites such as the faujasites and mordenites, they can differentiate between n-alkanes and slightly branched alkanes on the one hand and larger branched alkanes having, for example, quaternary carbon atoms.

SuBsT1Tl~T~ F~r WO91/13127 PCT/~S91/OI~S
2077 1r;~7 The effectlve pore size of the molecular sieves can be measured using standard adsorptlon technlques and hydrocarbonaceous compounds of known mlnimum kinetic dlameters. See Breck, Zeolite Molecular Sieves, 1974 (especially Chapter 8) and Anderson, et al., J. Catalysis 58, 114 (1979), both of which are incorporated by reference.
Intermediate pore size molecular sieves in the H-form will typically admit molecules having kinetic diameters of S.0 to 6.5P with little hindrance. Examples of such compounds (and their kinetic diameters in P) are: n-hexane (4.3), 3-methylpentane (5.5), benzene (5.85), and toluene (5.8). Compounds having kinetic diameters of about 6 to 6.5P can be admitted into the pores, depending on the particular sieve, but do not penetrate as quickly and in some cases are effectively excluded. Compounds having kinetic diameters in the range of 6 to 6.5P include:
cyclohexane (6.0), 2,3-dimethylbutane (6.1), 2,2-dimethylbutane (6.2), m-xylene (6.1) and 1,2,3,4-tetramethylbenzene (6.4). Generally, compounds having kinetic diameters of greater than about 6.5P do not penetrate the pore apertures and thus are not absorbed into the interior of the molecular sieve lattice. Examples of such larger compounds include: o-xylene (6.8), hexamethylbenzene (7.1), 1,3,5-trimethylbenzene (7.5), and tributylamine (8.1).
The preferred effective pore size range is from about 5.3 to about 6.2P. Among the materials falling within this range are the crystalline silica polymorph, silicalite, RE 29,948 organosilicates, and the chromia silicate CZM.
In performing adsorption measurements to determi~e pore size,- standard techniques are used.
It is convenient to consider a partlcular molecule as SVBSTIT~JTE S~EET

WO91/13127 PCT/~S91/n'~5 '1.~' excluded if it does not reach at least 95% of lts equilibrium adsorption value on the zeollte ln less than about 10 minutes (p/po = 0.5; 25 C.).
By "crystalline silica polymorphs~, as used herein, is meant materlals having very low alumlnum contents (or high silica:alumina mole ratios).
Aluminu~ contents of these materials are generally less than about 4000 ppm, preferably less than about 2000 ppm, more preferably less than about 1000 ppm.
Intermediate pore size crystalline silica polymorphs useful in the present invention include silicalite, as disclosed in U.S. Patent No.

4,061,724, and the "RE 29,948 organosilicates~l, disclosed in RE 29,948, both of which are incorporated by reference. The essentially alumina-free chromia silicate, CZM, is disclosed in Serial No. 160,618, Miller, filed June 28, 1980, incorporated by reference.
Intermediate pore size zeolites include materials such as C2H-5 and members of the ZSM
series, e.g., ZSM-5, ZSM-11, ZSM-12, ZSM-21, ZSM-22, ZSM-23, ZSM-35, and ZSM-38. ZSM-5 is described in U.S Patents Nos. 3,702,886, Re. 29,948 and 3,770,614; 2SM-11 is described in U.S. Patent No.
3,709,979 (See also, Bibby, et al., Nature, 280, 664-665 (August 23, 1980) which reports the preparation of a crystalline silicate called "silicalite-2");
ZSM-12 is described in U.S. Patent No. 3,832,449;
ZSM-21 and ZSM-38 are described in U.S. Patent No.
3,948,758; ZSM-22 is described in U.S. Patents Nos.
4,481,177 and 4,556,477; ZSM-23 is described in U.S.
Patent No. 4,076,842; ZSM-35 is described in U.S.
Patent No. 4,016,245; ZSM-38 is described in U. S.
Patent No. 4,046,859; ZSM-48 is described in U. S.
Patent No. 4,397,827 and CZH-5 is disclosed in Serial No. 166,863, Hickson, filed July 7, 1980. All of - the~e patent~, publications and 5pecifications which SIIBS~T' '~ !;!tEE-r WO91/13127 ~j 7 PCT/~591/01~5 have not previously already been lncorporated hereln by reference are hereby so lncorporated. The ntermediate pore slze zeolites can include ~crystalline admixtures~' which are thought to be the result of faults occurring within the c_ystal or crystallite area durlng the synthesls of the zeolites. The "crystalline admixtures~' are themselves zeol~tes but have characteristics ln common, in a uniform or nonuniform manner, to what the literature reports as distinct zeolites.
Examples of crystalline admixtures of ZSM-5 and ZSM-11 are disclosed and claimed in U.S. Patent No.
4,229,424, Kokotailo, October 21, 1980 (incorporated by reference). The crystalline admixtures are themselves intermediate pore size zeolites and are not to be confused with physical admixtures of zeolites in which distinct crystals or crystallites of different zeolites are physically present in the same catalyst or hydrothermal reaction mixture.
Additionally, zeolites SSZ-20 and SSZ-23 are preferred catalysts. SSZ-20 is disclosed in U.S.
Patent No. 4,483,835, and SSZ-23 is disclosed in U.S.
Patent No. 4,859,442, both of which are incorporated herein by reference.
"Crystalline silicate" as used herein refers -to silicates having a rigid, three-dimensional network of SiO4 tetrahedra in which the tetrahedra are crosslinked by the sharing of oxygen atoms.
Preferably, the crystalline silicates are non-acidic and substantially alumina-free, but they may contain minor amounts of alumina re6ulting from impurities in the starting materials or contamination of the reaction vessel6. ~he preferred intermediate pore size cry~talline silicate is silicalite, examples of which are disclosed in the U.S. Patent No. 4,061,724 and U.S. Patent No. Re. 29,948. The silica:alumina molar ratio of the crystalline silicates of the Q~t ~T~J~ SHEEl wo 91/13127 " ~ PCr/l,~91/~ ~5 q Q~

present invention are preferably greater than about 200:1, more preferably greater than about 500:1 and most preferably greater than about 1000:1 The crystalline sillcates also preferably have speclflc gravities, in the calcined form, between about 1.50 and about 2.10 g/cc and a refractive index between about 1.3 and about 1.5.
The crystalline silicate may be in the form of a borosilicate, where boron replaces at least a portion of the aluminum of the more typical aluminosilicate form of the silicate. Borosilicates are described in U.S. Patent Nos. 4,26a,420;
4,269,813; 4,327,236 to Klotz, the disclosures of which patents are incorporated herein, particularly that disclosures related to borosilicate preparation.
In the borosilicate, the preferred crystalline structure is that of ZSM-5, in terms of X-ray diffraction pattern. Boron in the ZSM-5 type borosilicates takes the place of aluminum that is present in the more typical ZSM-5 crystalline aluminosilicate structures. Borosilicates contain boron in place of aluminum, but generally there are some trace amounts of aluminum present in crystalline borosilicates.
Still further crystalline silicates which can be used in the present invention are iron silicates and gallium silicates.
Borosilicates and aluminosilicates are the more preferred silicates for use in the present invention. Aluminosilicates are the most preferred.
The following sets forth the relevant details and methods of manufacture for the preferred catalyst. As noted above, crystalline silicates which can be used in the process of the present 35 invention have been reported in the literature. As -- ~ynthesized, sil-icalite (U.S. Patent No. 4,061,724) ha8 a ~pecific gravity at 77'F of 1.99 % 0.05 g/cc as SUE3STITUTE S~EET

WO91/13127 PCT/~591/0128~
2077 4lj7 measured by water displacement. In the calcined form (1112-F in air for one hour), silicalite has a speciflc grav~ty of 1.70 % 0.05 g/cc. With respect to the mean refractive lndex of sil1calite crystals, values obtained by measurement of the as syntheslzed form and the calcined form (1112'F in alr for one hour) are, 1.48 % 0.01 and 1.39 % 0.01, respectively.
The X-ray powder diffraction pattern of silicalite (1112-F calcination in air for one hour) has six strongest lines (i.e., interplanar spacings).
They are set forth in Table k ("S"-strong, and ~'VS'~-very strong):

TABLE A
15 d-P Relative Intensity 11.1 % 0.2 VS
10.0 % 0.2 VS
3.85 % 0.07 VS
3.82 % 0.07 S
203.76 % 0.05 S
3.72 % 0.05 S

Table B shows the X-ray powder diffraction pattern of a typical silicalite composition containing 51.9 moles of SiO2 per mole of tetrapropylammonium oxide (TPA) 2 ~ prepared according to the method of U.S. Patent No. 4,061,724, and calcined in air at 1112-F for one hour.

S~STIT~I~r ~

wo 91/1312~ PC~/~,S91/~"~8 TABLE B
Relatlve Relatlve d-P Intenslty d-P Inten~it~
11.1 100 4.3s 5 10.02 64 4.25 7 9.73 16 4.08 3 8.99 1 4.00 3 10 8.04 0.5 3.85 59 7.42 1 3.82 32 7.06 0.5 3.74 24 6.68 5 3.71 27 6.35 9 3.64 12 15 5.98 14 3.59 0.5 5.70 7 3.48 3 5.57 8 3.44 5 5.36 2 3.34 11 5.11 2 3.30 7 20 5.01 4 3.25 3 4.98 5 3.17 0.5 4.86 0.5 3.13 0.5 4.60 3 3 05 ~ 5 4.44 0.5 2.98 10 Silicalite crystals in both the "as synthesized" and calcined forms are generally orthorhombic and have the following unit cell parameters, in Angstroms: a = 20.05, b = 19.86, c = 1~.36 (all values % 0.1 Angstrom).
The pore diameter of silicalite is about 6P
and its pore volume is 0.18 cc/gram as determined by adsorption. Silicalite adsorbs neopentane (6.2P
kinetic diameter) slowly at ambient room temperature.
The uniform pore structure imparts size-selective molecular sieve properties to the composition, and the pore size permits separation of p-xylene from o-xylene, m-xylene and ethylbenzene as well as separations of compound8 having guaternary carbon atoms from those having carbon-to-carbon linkages of lower value (e.g., normal and slightly branched - paraffins).

~UBSTITUT~ SH~E~

WO 91/13127 PCr/( S91/01285 2077 il~37 The crystalline silicates of U.S. Patent Nc.
Re. 29,948 are disclosed as ~avlng a composlt~on, in the anhydrous state:

S 0.9 % 0.2 ~x~0 (1 - x)M2/~0]: <.005 Al20~:>1 SiO2 where M lS a metal, other than a metal of Group IIIA, n is the valence of said metal, R is an alkyl ammonium radical and x is a number greater than 0 but not exceeding 1. The crystalline silicate is characterized by the X-ray diffractlon pattern of Table C.

TABLE C
15~n~r~lanar SDacing d~P) Relative Intensity 11. 1 S
10.0 S
7.4 W
7.1 w 20 6.7 W

6.4 W
5.97 W
5.56 W
5.01 W
254.60 W
4.25 W
3.85 VS
3.71 S
3.04 W
302.99 W
2.94 W
The following discloses crystalline silicates that are related to silicalite. The crystalline silicate polymorph of U.S. Patent No.
4,073,865 is disclosed as having a specific gravity of 1.70 % 0.05 g/cc and a mean refractive index of 1.39 ~ 0.01 after calcination in air at 600 C, as prepared by a hydrothermal process in which fluoride anions are included in the reaction mixture. The crystals, which can be as large as 200 microns, éxhibit a substantial absence of infrared adsorption in the hydroxyl-stretching region and also exhibit an W091/13127 ,,~ PCT/~S91/~''85 j~ ~r~
'1.~

exceptional degree of hydrophoblcity. They exhiblt the X-ray diffraction pattern of Table D.

- ~IIBS~IT~5 ~ E SHEI~

- W091/13127 PCT/US9~/Ot~S
2077~ 7 TA~ D

d(P) In~nsity 11.14 91 10 . 01 100 9.75 17 8.99 8.01 0.5 7.44 0.5 7.08 0.2 6.69 4 6.36 6 5 . 9 9 10 5.71 s 5.57 5 5.37 5.33 5.21 ~.3 5.12 1.5 5.02 3 4.97 6 4.92 0.6 4.72 0.5 4.62 2 4-47 0.6 4.36 3 4.25 4 4.13 0.5 4.08 1.5 4.00 3 3.85 44 3.82 25 3.71 21 3.65 5 3.62 5 3.59 3.48 1.5 3,45 3 3.44 3 3.35 3 3.31 5 3.25 1.5 3.23 0.8 3.22 0.5 The literature also describes other intermediate pore size crystalline silicates and their method of preparation. For example, sllicallte-2 is de~cribed in Nature, August, 1979 and i~ totally incorporated by reference. The SUBS'r!-'~'T'~ EQ

WO91/13127 ~ PCT/~591/~"85 ~,~,", .) Nature article discloses the method of preparlr.g silicalite-2 and shows that the major dlfferences between the patterns of sllicalite and silicalite-2 are that peaks at 9.06, 1~.9, 15.5, 16.5, 20.8, 2~.7, 22.1, 24.4, 26.6 and 27.0 degrees 2R (CuK alpha radiation) in the silicalite X-ray diffraction pattern are absent from the silicalite-2 pattern.
Also, peaks at 8.8, 14.8, 17.6, 23.1, 23.9 and 29.9 degrees are singlets in the silicalite-2 pattern rather than doublets as in the silicallte pattern.
These differences are reported as being the sa~e as those found between the diffraction patterns of the aluminosilicalites, orthorhombic ZSM-5 and tetragonal ZSM-11. Unit cell dimenslons reported as calculated on the assumption of tetragonal symmetry for silicalite-2 are (in Angstroms) a = 20.04;
b = 20.04; c = 13.38. The measured densities and refractive indices of silicalite-2 and its precursor are reported as 1.82 and 1.98 g/cc and 1.41 and 1.48 respectively.
It is envisioned that the definition of silicalite includes these variants and others whlch may function as described by the present invention even though there are differences in such things as X-ray diffraction pattern or refractive index.

Preparation of Intermediate Pore S~ e~iljgates The preparation of crystalline silicates of the present invention generally involves the hydrothermal crystallization of a reaction mixture comprising water, a source of silica and an organic templating compound at a pH of 10 to 14.
Repre8entative templating moieties include quaternary cation8 such as XR~ where X is phosphorous or nitrogen and R is an alkyl radical containing from 2 to 6 carbon atom~, e.g., tetrapropylammonium -5t~E~ST~UTE SH~El WO91/13lZ7 2 ~ 7 7 !1 .i 7 hydroxide (TPA-OH) or hallde, as well as alkyl hydroxyalkyl compounds, organlc amlnes and dlamlnes, and heterocycles such as pyrrolidine.
When the organic templating compound (l e., TPA-OH) is provided to the system ln the hydroxide form in sufficlent quantity to establlsh a baslcity equivalent to the pH of 10 to 14, the reactlon mixture need contain only water and a reactive form of silica as additional ingredients. In those cases in which the pH must be increased to above 10, ammonium hydroxide or alkali metal hydroxides can be suitably employed for that purpose, particularly the hydroxides of lithium, sodium and potasslum. The ratio R~/(Rt I Mt), where R is the concentration of organic templating cation and M- is the concentration of alkali metal cation, is preferably between 0.7 and 0.98, more preferably between 0.8 and 0.98, most preferably between 0.85 and 0.98.
The source of silica in the reaction mixture can by wholly, or in part, alXali metal silicate but should not be employed in amounts greater than that which would changé the molar ratio of alkali metal to organic templating compound set forth above. Other silica sources include solid reactive amorphous silica, e.g., fume silica, silica sols, silica gel, and organic-orthosilicates. One commercial silica source is Ludox AS-30 available from DuPont.
Aluminum is easily incorporated as an impurity into the crystalline silicate. Accordingly, care should be exercised in selecting the silica source to minimize alumina uptake. Commercially available silica sols can typically contain between 500 and 700 ppm Al203, whereas fumed silica can contain between 80 and 2000 ppm of Al203 impurity.
As explained above, the 6ilica to alumina molar ratio in the crystalline silicate is preferably greater than 200:1, more preferably greater than 500:1, most S~B~T!r~ ;HFF'I-Wo 91/131Z7 " "l PCJ/~,S91/'~'t85 C~

preferably greater than 1000:l. Aluminum ln the synthesls contributes acidity to the catalyst, which is undesirable.
The quantity of sillca in the reaction S system is preferably between about 1 and 10 moles SiO2 per mole-ion o_ the organic templatinq compound.
Water should be generally present in an amount between 20 and 700 mole per mole-ion of the guaternary cation. The reaction preferably occurs in an aluminum-free react~on vessel which is resistant to alkali or base attack, e.g., Teflon.
Strong catalyst acidity is undesirable because it promotes cracking which results in lower selectivity. To reduce acidity the catalyst preferably contains an alkali metal and/or an alkaline earth metal. The alkali or alkaline earth metals are preferably incorporated into the catalyst during or after silicalite synthesis. Preferably, at least 90% of the acid sites are neutralized by introduction of the metals, more preferably at least 95%, most preferably 100~.
Crystalline silicates are conventionally synthesized largely in the sodium or potassium form.
These cations are exchangeable, so that a given silicalite can be used to obtain silicalites containing other cations, such as alkaline earth metals or other alkali metals, by subjecting the silicalite to ion exchange treatment in an aqueous solution of the appropriate salts. The preferred alkali and/or alkaline earth metals are: lithium, sodium, potassium, rubidium, cesium, strontium and barium, more preferred metals are: sodium, potassium, rubidium and cesium.
To determine whether a zeolite is non-acidic, the following test may be conducted. Analiguot of catalyst, 0.1 - 0.5g, is mixed with lg of ac1d-washed and neutralized alundum and packed in a SUBSt'ITl)TE SHEET

- W091/13127 2 ~7 1 ~ PCT/~S91/OI~S

3/16 inch stainless steel reactor tube with the re~alning space filled wlth alundum. The reactor contents are calc~ned for one hour at 450 C. The reactor is then placed ~n a clam-shell furnace and the reactor outlet is connected to the lnlet of a gas chromatograph. The inlet is connected to the carrier gas line of the gas chromatograph. The reactor temperature is set at 427 C. Pulses of n-decane, 0.04 microliter each, are injected through a septum above the reactor and reaction products are determined by standard gas chromatographic analysis.
Blank runs with alundum should show no conversion under the experimental conditions, nor should a 100%
Catapal alumina catalyst.
A pseudo-first-order, cracking rate constant, k, is calculated using the formula:

k = 1 ln A 1 - x where A is the weight of zeolite in grams and x is the fractional conversion to products boiling below decane. The catalyst is substantially free of acidity when the value of ln k is less than about -3.8. The catalyst is low in acidity if ln k is less than about -2.3.
The crystalline silicate is preferably bound with a matrix or porous matrix. The terms "matrix"
and "porous matrix~ include inorganic compositions with which the silicate can be combined, dispersed, or otherwise intimately admixed. Preferably, the matrix is not catalytically active in a hydrocarbon cracking sense, i.e., is substantially free-of acid sites The matrix porosity can either be inherent or it can be cau~ed by a mechanical or chemical means.
Satisfactory matrices include diatomaceous earth and inorganic oxides. Preferred inorganic oxides include a?umina, sllica, naturally occurring and e- -Q~

WO91/13127 ~ b, 'j~ PCT/~S9~ ~5 conventionally processed clays, for example bentonite, kaolin, sepiollte, attapulglte and halloysite.
Compositing the crystall~ne sillcate with an inorganic oxide matrix can be achieved by any suitable known method wherein the silicate is intimately admixed with the oxide while the latter ls in a hydrous state (for example, as a hydrous salt, hydrogel, wet gelatinous precipitate, or in a dried state, or combinations thereof). A convenient method is to prepare a hydrous mono or plural oxide gel or cogel using an aqueous solution of a salt or mixture of salts (for example aluminum and sodium silicate).
Ammonium hydroxide carbonate (or a similar base) is added to the solution in an amount sufficient to precipitate the oxides in hydrous form. Then, the precipitate is washed to remove most of any water soluble salts and it is thoroughly admixed with the silicate which is in a finely divided state. Water or a lubricating agent can be added in an amount sufficient to facilitate shaping of the mix (as by extrusion).
The preferred crystalline silicate is silicalite. Assuming that the only crystalline phase in the silicalite preparation is silicalite, the silicalite preferably has a percent crystallinity of at least 80%, more preferably at least 90%, most preferably 95$. To determine percent crystallinity, an X-ray diffraction (XRD) pattern of the silicalite is made and the area under the 8 major peaks is measured in the angle interval between 20.5 and 25.0 degrees. Once the area under the curve is calculated, it is compared with the area under the curve for a 100% crystalline standard for silicalite.

Group VII~ Metals The catalysts useful in either stage of the ~UB8TITUTE SHEET

WO91/13127 2 0 7 7 ~ ~ 7 PCT/~Sg1/01~K

present lnventlon contain one or more Group VI~;
metals, e.g., nickel, ruthenium, rhodium, palladium, lridium or platinum. The preferred Group VIII metals are iridium, palladium, and particularly platinum.
The preferred percentage of the Group VIII metal, such as platinum, in the catalysts is between 0.1 weight percent and 5 weight percent, more preferably from 0.1 weight percent to 2.5 weight percent.
Group VIII metals are preferably introduced into the catalyst by impregnation, occlusion, or exchange in an aqueous solution of an approprlate salt. When it is desired to introduce two Group VIII
metals into the catalysts, the operation may be carried out simultaneously or sequentially.
Preferably, the Group VIII metal is finely dispersed within, and on, the catalysts.
~ y way of example, platinum can be introduced by impregnation with an aqueous solution of tetraammineplatinum (II) nitrate, tetraamine-platinum (II) chloride, tetraammineplatinum (II)hydroxide, chloroplatinic acid or dinitrodiaminoplatinum. In an ion exchange process, platinum can be introduced by using cationic platinum complexes such as tetraammineplatinum (II) chloride.
Platinum may be occluded into the catalyst by introducing a platinum complex into the synthesis mixture.
After the desired metal or metals have been introduced, the catalysts are preferably treated in air, or air diluted with an inert gas, and reduced in hydrogen. Catalysts containing platinum are typically 8ubjected to halogen or halide treatments to achieve or maintain a uniform metal dispersion.
Typically, the halide is a chloride compound. The conventional catalysts can be sub~ected to similar - treatments. The preferred crystalline silicate cataly8t wa~ not 8ub~ected to this treatment so as to ~;UE~TITl~T~ S~IE1~1 W09l/1312~ PCT/~S91/~12~5 ., ~

keep its acidity low, thereby keeping undeslrable side reactions which keeps C~- products tO a minimum.
Other metals can be added to the penult.~ate stage catalyst as promoters. These metals are preferably selected from Groups VIIB, IVA, IB or VIB.
More preferably, the additional metals may lnclude:
rhenium, tin, gold, germanium, iridium, or chromlum.
Preferably, the promoter metal comprises between 0.1 and 10 weight percent of the catalyst, more preferably between 0.1 and 5.0 weight percent of the catalyst.

Reformi~g and Dehydrocyclizina Both catalysts may be employed in the form of pills, pellets, granules, broken fragments, or various special shapes, disposed as a fixed bsd within a reaction zone, and the charging stock may be passed therethrough in the liquid, vapor, or mixed phase, and in either upward, downward or radial flow.
Alternatively, they can be used in moving beds, or in fluidized-solid processes, in which the charging stock is passed upward through a turbulent bed of finely divided catalyst. However, a fixed bed system or a dense-phase moving bed system are preferred due to catalyst attrition losses and other operational advantages. In a fixed bed system, the feed is preheated (by any suitable heating means) to the desired reaction temperature and then passed into a reaction zone containing a fixed bed of the catalyst.
This reaction zone may`be one or more separate reactors with suitable means to maintain the desired temperature at the reactor entrance. The temperature must be maintained because reforming reactions are typically endothermic in nature.
The reformer feed entering the penultimate ~tage 12 of the multi-stage process 10 via line 16 is SU8STI~ E 8HE~T

WO 91/13127 PCr/l,S9~tO128S
2o77 1~ ~7 prefe~ably a naphtha fraction boiling wlthin the range of 70 to 550 F and preferably from 120 to 400-F. This can include, for example, straight run naphthas, paraffinic raffinates from aromatic extraction or adsorption, and C6-C10 paraffin-rlch feeds, as well as paraffln-containing naphtha products from other refinery processes, such as hydrocracking or conventional reforming. The reformate from the penultimate stage 12 is separated by separator 18 into a hydrogen/hydrogen sulfide containing fraction (which usually includes C,-Cs hydrocarbons) which exits separator 18 via line 24 and a hydrocarbon fraction (generally Cs-) which exits separator 18 via line 22. The hydrocarbon fraction serves as the feed to the final stage 14 although additional feeds such as light straight run and pen-hex feeds (Cs and C6) can be added. Usually, the hydrogen/hydrogen sulfide containing fractlon is recycled to the penultimate stage 12 thereby reducing heating requirements.
A low sulfur feed is especially preferred in the present process. The feed preferably contains less than 5 ppm, more preferably less than 1 ppm, and most preferably less than 0.1 ppm sulfur. In the case of a feed which is not already low in sulfur, acceptable levels can be reached by hydrotreating the feed in a presaturation zone with a hydrotreating catalyst which is resistant to sulfur poisoning. An example of a suitable catalyst for this hydrotreating process is an alumina-containing support and a minor catalytic proportion of molybdenum oxide, cobalt oxide and/or nickel oxide.
A Group VIII metal (such as platinum) on alumina can al~o be used as the hydrotreating catalyst. A
~ulfur sorber is preferably placed downstream of the hydrotreating catalyst, but upstream of the penultimate or final reforming cataly6ts. It may -~

SU8STlTUTE SHEEl' W091/13127 ~ ~ PCT/1591/~ ~85 also be advantageous to place an additionai sulfur sorber between the penultimate and flnal reforming catalysts. Examples of sulfur sorbers are alkall or alkaline earth metals or Group VIII metals, e.g., Cu, Ni, on porous refractory inorganic oxides such as zlnc oxide, etc.
It is also preferable to llmit the nitrogen level in the feed to the penultimate reforming catalyst to less than 10 ppm nitrogen, or more preferably less than 1 ppm. Preferably, water in the feed is limited to less than 100 ppm H20, more preferably less than about 10 ppm H20. Catalysts a~d processes which are suitable for these purposes are known to those skilled in the art.
In the penultimate reforming stage 12 the conventional catalyst upgrades the feed. Although dependent on the feed RON (Research Octane Number), the RON of the Cs+ hydrocarbon fraction of the penultimate stage reformate is typically between 80 and 96 RON. Typically, the feed is heated by contact with a feed effluent heat exchanger (not illustrated) before entering the penultimate reforming stage. The temperature is preferably between 500 and 1200 F, more preferably between 800' and l100-F. The heated feed contacts the conventional catalyst at pressures between 50 psig and l000 psig, more preferably, between 50 psig and 500 psig, and most preferably between 50 and 300 psig. The liquid hourly space velocity (LHSV) is preferably between 0.2 and 20, more preferably between 0.5 and 6. The H2/HC ratio is preferably between l and 20, more preferably between l and 10, most preferably between 2 and 6.
The actual reforming conditions for both catalysts will depend largely on the feed used, whether highly aromatic, paraffinic or naphthenic and upon the desired octane rating of the product.
- After the feed has been partially reformed SUBST~TUTE SHEE~

wo 91t13~27 Pcr/~sg~/0128s 2077~ 7 in the penultimate stage 12, at least a port1on of the hydrogen and substantially all of the hydrogen sulfide present is separated from the l~quid product.
This can be accomplished by the separator 18 whlch can be, for example, a liquifier. As prevlously stated, it may be desirable or necessary to add a sulfur sorber to assure that the feed to the flnal reforming zone 14 is substantially sulfur free. The partially reformed product (generally Cs~) can be reheated and is passed to a final reforming stage 14.
The final stage 14 contains the intermediate pore size crystalline silicate catalyst.
In the final stage 14 the reformate is further upgraded to a higher RON. The pressure in the final stage 14 is preferably between 0 psig and 200 psiq, more preferably between 0 and 100 psig, and most preferably between 15 psig and 75 psig. The liquid hourly space velocity (LHSV) is preferably between about 0.1 to about 10 hr.-' more preferably between 0.3 and 5 hr.'. The temperature is preferably between about 550 F and about 1200'F, more preferably between 700 F and 1100 F. As is well known to those skilled in the dehydrocyclization art, the initial selection of the temperature (for either catalyst) is determined primarily by the desired conversion level of the acyclic hydrocarbon (considering the characteristics of the feed and of the catalyst). Thereafter, to provide a relatively constant value for conversion, the temperature is slowly increased during the run to compensate for any deactivation that occurs.
In accordance with one embodiment of the present invention the recycle H2/HC mole ratio in the final stage 14 i8 between 0 and 3, preferably between 0 and about 1. In a preferred mode the final stage 14 is operated in the absence of recycle hydrogen. The absence of recycle hydrogen favors SUE~STITUTE SHEET

W0 91/13127 ,~ PCI/1,'S91/0128 aromatics formation and lncreases liquid yleld a~ a glven octane by decreasing hydrocracking whlch lS
favored by high hydrogen partial pressures.
In accordance with another embodiment of the S inventlon hydrogen is recycled via dashed llne 26 from the final stage reformate to the final stage 1 in any deslred amount. In such an instance the hydrogen is, however, substantially sulfide free and does not come from the reformate from the penultimate stage 12. This mode of operation serves to increase catalyst life.
To insure relatively long catalyst life between regenerations of the final stage catalyst lt is important that the feed to the final stage be quite low in sulfur (including sulfur introduced with recycle hydrogen). Generally no more than about 2 ppm, preferably no more than about 1 ppm and more preferably no more than about 0.1 ppm sulfur should be in the final stage feed. For sulfur sensitive catalysts the sulfur should be no more than about 0.02 ppm in the final stage, whether introduced with the feed or recycle hydrogen. Since the feed to the penultimate stage 12 can have a higher sulfur content it is important to use the separator 18 and to exclude the hydrogen and hydrogen sulfide containing fraction exiting the separator 18 from the final stage 14.
After the product is removed from the final stage 14, it can be passed to a distillation section (not shown) to separate out the more desired products (e.g., high octane blend stocks, aromatics rich stock).
The relative amounts of each catalyst may be different. The conventional catalyst that is used in the penultimate stage 12 may be between 10 and 90 v~lume perceAt of the total catalyst, preferably between 25 and 75 volume percent. The silicalite -~

WO 91tl31t7 PCr/l,S91/lJ128S
2077 ~i7 catalyst used ln the f1nal stage 14 may comprlse between 10 and 90 volume percent of the total catalyst, more preferably between 25 and 75 volume percent.
After a perlod of operation a catalyst can become deactivated by sulfur or coke. Coke and some sulfur can be removed by contactlng the catalyst with an oxygen-containing gas at an elevated temperature.
If the Group VIII metal(s) has agglomerated, then it can be redispersed by contacting the catalyst with a chlorlne-containing gas under conditions effective to redisperse the metal(s). The method of regenerating the catalyst will depend on whether there is a fixed bed, moving bed, or fluidized bed operation.
Regeneration methods and conditions are well Xnown in the art. An example of an oxychlorination regeneration procedure is shown in U.S. Patent No.
4,855,269 which is hereby incorporated by reference in its entirety. An example of a sulfur removal procedure is shown in U.S. Patent No. 4,851,380 which is hereby incorporated by reference in its entirety.
Without wishing to be bound by theory, it is believed that the octane advantage of this process comes from the conventional reforming catalyst's ability to convert the naphthenes to aromatics and the silicalite catalyst's ability to selectivity convert C~-C8 paraffins (in particular n-paraffins) to aromatics at low hydrogen pressure. It is believed to be best to operate the conventional reforming catalyst at low to moderate severity conditions which can produce a reformate havin~
between about 85 and about 96 RON tdepending on the feed). Under these conditions ~he conventional catalyst catalyzes the easier reactions, such as 3S cyclohexane and alkycyc;ohexane dehydrogenation, and keeps hydrocracking to a minimum. The penultimate stage conventional reforming catalygt also serves to ~

SUBSTITI~7E SHEEr WO91~13127 ~ ~ PCT/~S91/~12X5 ',~,Q ~

- ~o -reduce the sulfur level as it converts most organic sulfur compounds to hydrogen sulflde whlch can then be removed along with the hydrogen. Generally, when the conventional catalyst is used to dehydrocyclize paraffins under more severe conditions more llght gases are produced (i.e., the catalyst is not very selective for dehydrocycllzation). With the present invention, however, the partially reformed feed from the conventional catalyst, after hydrogen and hydrogen sulfide are removed, is passed to the silicalite catalyst which is more selective in dehydrocyclizing paraffins. Consequently, the catalysts are complimentary by their selectivities for different reactions and the entire process produces a high octane product at a relatively high liquid yield.
The present invention will be more fully understood by reference to the following examples.
They are intended to be purely exemplary and are not intended to limit the scope of the invention in any way.

Exa~le 1 Co~
A 2:1 rhenium to platinum catalyst was prepared beginning with the following solutions: a chloroplatinic acid solution containing 1.20 g of Pt as metal; a perrhenic acid solution containing 2.40 g of Re as metal; and HCl containing 5.36 g of chloride. These solutions were added together and d$1uted to a total volume of 340 ml with deionized water.
The combined solution was slowly added, with sha~ing, to a flask containing 400.0 g of calcined alumina extrudate. The impregnated alumina was allowed to stand for 16 hours, dried for 2 hours at 25Q'F and then calcined for 2 hours at 950-F in SU~STITUTI~ SHEET

WO91/13~27 PCT/~'S91/0l~S
2077 l.j'~

flowing, dry air. The resultlng catalyst comprlsed 0.30 weight percent Pt, 0.60 weight percent Re, and 1.2 percent Cl. The catalyst exhibited a bulk density of approximately 0.622 g/cc, a pore volume of approximately 0.68 cc/g, and a nitrogen surface area that was approxlmately 200 m2/g.

Exam~le 2 Silicalite Catalyst A Pt-impregnated silicalite catalyst was prepared as follows: NaNO3, 8.4 g, and 40 g of EDT~
were mixed into 80 ml of distilled water. Eight hundred (800) g of a 25% aqueous solution of TPA-OH
were added and the resultinq solution was mixed well for 15 minutes. Six hundred forty (640) g of Ludox AS-30 were added and mixed in with rapid stirring for 15 minutes. The pH of the mixture was 13.1. The mixture was poured into a Teflon bottle and kept at 100-C for 7 days, The resulting product was filtered and then dried overnight in a vacuum oven at 120'C.
Then it was calcined for 8 hours at 566 C in air.
The percent silicalite was 100% as measured by XRD
analysis. The product had an average crystallite size of about one micron in diameter (roughly spherical). Then the product was impregnated with o . a weight percent platinum by the pore-fill method using an aqueous solution of Pt(NH3)4(NO3)2. The catalyst was dried overnight in a vacuum oven at 120#C and calcined in dry air for 4 hours at 240 C, 4 hours at 288 C, 4 hours at 371-C and 4 hours at 427 C.
~his catalyst was exchanged once with a 5 wsight percent aqueous solution of KNO3 at 82 C for 2 hours. ~hen it was filtered, washed with distilled water, and dried overnight in a vacuum oven at 120-C. -The catalyst was calcined in dry air for 4 hours at 204 C and 4 hours at 2a8'c. The Kt level of the SUBSTITUTE SHE~T

W091/13127~ ~ PCT/US91l~'~5 catalyst was approxlmately 0.69 weight percent Na was 239 ppm.

Ex~m2L~ 3 Reforming With ~he Conventional Catalyst Under More Severe Conditions A commercially produced conventional platinum and rhenium on alumina reformlng catalyst similar to that of Example 1 but made on a commercial scale was used to reform hydrocarbons. A
hydrocarbon feed comprising a full boiling range naphtha was contacted with the catalyst at 20Q psig., a H2/HC recycle ratio of 3, and a space velocity of 2 LHSV. The catalyst average temperature was 920-F.
The product RON was 98.5 and the Cs~ liquid yield was 76 LV%.

SUBS~TU~ SHEET

W091/t3127 PCT/US~1/01~S
2077 l j7 Exam~le 4 Reforming With The Conventional Catalyst and the Silicalite Catalyst Under Less Severe Conditions Without ~ecycle Hydrogen A commercially produced conventional platinum and rhenium on alumina reforming catalyst was used to reform the same feed as in Example 3 under the following less severe conditions: 200 psig, 3H2/HC recycle ratio, and 3 LHSV. The catalyst average temperature was 890 F. The product RON was 91.4 and the Csl liquid yield was 83 LV~.
The Csl reformate from the conventional catalyst (after separation from the hydrogen/hydrogen sulfide fraction) was contacted with the silicalite catalyst of Example 2 at 50 psig, 0 H2/HC recycle ratio, and 1.5 LHSV. The catalyst average temperature was 840 F. The product RON was 101.6 and the Cs~ liquid yield was 91 LV% of the yield from the penultimate stage.
The results of Example 4 are shown in Table 1.

. TABLE 1 Example 3 Example 4 Conventional Combination Catalyst Catalyst Process RON 98.5 101.6 Cs~ LV% 76 76 Yields:
H2, SCF/B 1170 1243 C~, SCF/B 150 265 C2, SCF/B 104 80 C3, SCF/B 103 65 C4, LV% 7.3 5.4 - It is evident that a higher RON is achieved SIIB~ TU~C SHEE T

WO 91/13127 PCr/l S91/''-~S
r~

~ ~ 3 4 with a comparable Cs~ liquid volume yield by the combinatlon process over the slngle conventlonal catalyst.

Ex~m~le 5 Reforming With The Conventional Catalyst and the Silicalite Catalyst Under Less Severe Condi~ions With Recy~le Hyd~ogen Another full boiling range naphtha was reformed over the catalyst of Example 1 to produce a reformate with a 90.7 RON and sulfur content less than 0.1 ppm. This reformate was then reformed further over a Pt/silicalite catalyst similar to that of Example 2 except that there was no K~-exchange and the final Na~ level was 0.96 wt.%. Run conditions were 50 psig pressure, a LHSV of 1.0, and a H2/HC
ratio of 1Ø At 790 F, a 101.5 RON product was made with a 92 wt.% Cs+ yield in the final stage.
This example demonstrates increased Cs~ RON
product with substantially equal yield and with added recycle hydrogen.

ExamRle 6 Reforming With The Conventional Catalyst and the Silicalite Catalyst Without Use Of S~arator To RemQVe Hyd~ogen To illustrate the importance of removing sulfur ahead of the final stage catalyst, H2S, at a S/Pt mole ratio of 0.5, was injected into the H
stream ahead of the Pt/silicalite catalyst of Example 5 and using the feed of Example 5 to the penultimate reforming stage. A 101.5 RON product ~ub~equently could not be produced even at a catalyst temperature of 980-F.

SIJBSTITUTE SHEET

WO 91/13127 PCr/l~S91/0128~

2077/~:~ 7 While the invention has been descrlbed 1n connection with specific embodiments thereof, it W1L1 be understood that it is capable of further modification, and this application is intended to S cover any variations, uses, or adaptatlons of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth, and as fall within the scope of the invention and the limits of the appended claims.

SVBSTITU7'~ Sf~lEET

Claims (23)

Claims That Which Is Claimed Is:

1. A staged reforming process, comprising:
contacting a hydrocarbon feed with a conventional reforming catalyst in a penultimate reforming zone under reforming conditions to produce a reformate;
separating some or all of the hydrogen along with any hydrogen sulfide present from the reformate to provide a hydrogen containing fraction and a substantially hydrogen content reduced and substantially hydrogen sulfide-free reformate fraction; and contacting the reformate fraction with a final catalyst which comprises a Group VIII metal on a non-acidic intermediate pore size crystalline silicate in a final reforming zone, under reforming conditions without substantial hydrocracking, the reforming conditions comprising a temperature between 550 and 1200°F, a space velocity between 0.1 and 20 LHSV and a pressure between 0 and 200 psig.

2. A staged reforming process as set forth in claim 1, wherein the reforming conditions in the final reforming zone include a hydrogen recycle ratio between 0 and 1 H2/HC.

3. A staged reforming process in accordance with claim 2, wherein the final catalyst is silicalite.

4. A staged reforming process in accordance with claim 3, further including:
recycling the hydrogen containing fraction to the penultimate reaction zone.

5. A staged reforming process in accordance with claim 3, wherein the penultimate reforming catalyst is contacted with the feed at a temperature between 500 and 1200°F, a pressure between 50 and 1000 psig, a space velocity between 0.2 and 20 LHSV, and a hydrogen recycle ratio between 1 and 20 H2/HC; and the final reforming catalyst is contacted with the reformate at a temperature between 700 and 1100°F, a pressure between 0 and 100 psig, a space velocity between 0.3 and 5 LHSV, and a hydrogen recycle ratio of zero.

6. A staged reforming process in accordance with claim 3, wherein the feed is partially reformed to between 85 and 96 RON by the penultimate reforming catalyst and then further upgraded by the final reforming catalyst.

7. A staged reforming process in accordance with claim 5, wherein the penultimate reforming catalyst comprises a Group VIII metal and a promoter on a porous refractory inorganic oxide support.

8. A staged reforming process in accordance with claim 3, wherein the feed has less than 10 ppm sulfur.

9. A staged reforming process in accordance with claim 3, wherein the feed has less than 1 ppm sulfur.

10. A staged reforming process in accordance with claim 3, wherein the feed has less than 0.1 ppm sulfur.

11. A staged reforming process in accordance with claim 3, wherein the silicalite reforming catalyst further comprises an alkali or alkaline earth metal.

12. A staged reforming process in accordance with claim 1, wherein the penultimate catalyst comprises platinum and rhenium on chlorided alumina and the final catalyst comprises platinum on silicalite which contains an alkali or alkaline earth metal.

13. A staged reforming process in accordance with claim 1, wherein the final catalyst is silicalite.

14. A staged reforming process in accordance with claim 13, further including:
recycling the hydrogen containing fraction to the penultimate reaction zone.

15. A staged reforming process in accordance with claim 13, wherein the penultimate reforming catalyst is contacted with the feed at a temperature between 500 and 1200°F, a pressure between 50 and 1000 psig, a space velocity between 0.2 and 10 LHSV, and a hydrogen recycle ratio between 1 and 20 H2/HC; and the final reforming catalyst is contacted with the reformate at a temperature between 700 and 1100°F, a pressure between 0 and 100 psig, a space velocity between 0.3 and 5 LHSV, and a hydrogen recycle ratio of zero.

16. A staged reforming process in accordance with claim 13, wherein the feed is partially reformed to between 85 and 96 RON by the penultimate reforming catalyst and then further upgraded by the final reforming catalyst.

17. A staged reforming process in accordance with claim 14, wherein the penultimate reforming catalyst comprises a Group VIII metal and a promoter on a porous refractory inorganic oxide support.

18. A staged reforming process in accordance with claim 14, wherein the feed has less than 10 ppm sulfur.

19. A staged reforming process in accordance with claim 13, wherein the feed has less than 1 ppm sulfur.

20. A staged reforming process in accordance with claim 13, wherein the feed has less than 0.1 ppm sulfur.

21. A staged reforming process in accordance with claim 13, wherein the silicalite reforming catalyst further comprises an alkali or alkaline earth metal.

22. A staged reforming process comprising:
contacting a penultimate catalyst with a feed having less than 1 ppm sulfur at a temperature between 800 and 1100°F, a space velocity between 0.5 and 6 LHSV, a pressure between 50 and 500 psig, and a hydrogen recycle ratio between 1 and 20 H2/HC, to form a reformate, the penultimate catalyst comprises between 0.1 nd 2.5 weight percent platinum, between 0.1 and 5.0 weight percent rhenium, and between 0.5 and 1.5 weight percent chloride on alumina, the ratio of rhenium to platinum being in the range from 1:1 to 6:1;
separating the reformate into a gaseous hydrogen fraction and a hydrocarbon fraction; and contacting the hydrocarbon fraction with a final catalyst at a temperature between 700 and 1000°F, a space velocity between 0.3 and 5 LHSV, a pressure between 15 and 75 psig in the absence of recycle hydrogen, the final catalyst comprising between 0.1 and 2.5 weight percent platinum on silicalite and an alkali or alkaline earth metal.

23. A staged reforming process in accordance with claim 22, further comprising separating H2S out with the hydrogen.