Process for upgrading light apparatus

The present invention relates to a process for producing aromatic compounds from a hydrocarbon gas containing C.sub.3 through C.sub.5 paraffinic hydrocarbons under conversion conditions in the presence of a catalyst comprising a gallosilicate molecular sieve, a platinum metal component, and a rhenium metal component.

Background of the Invention 
The present invention is directed to a process for upgrading light 
paraffins such as propane, and butanes. Interest in upgrading these light 
paraffins has been growing due to recent and anticipated changes in 
refinery processing schemes which resulted and will result in a greater 
supply of such light paraffins. These changes include: the higher severity 
operation of the reforming process in order to maintain a high octane 
rating in the absence of or reduction of the lead content in gasoline; the 
lowering of reid vapor pressure (RVP) specifications; the increased use of 
oxygenates such as methyl tertiary butyl ether (MTBE) and ethanol 
resulting in the removal of butanes from the gasoline pool; the increased 
demand for jet fuel necessitating increased gas oil hydrocracking 
resulting in more light gas production, and the increase in operating 
temperatures in fluidized catalytic crackers resulting in more light gas 
production. Thus, there is great incentive to investigate means for 
converting these materials into more valuable liquids such as 
transportation fuels or chemical feedstocks. 
The upgrading or conversion of light paraffinic gases and synthesis gas has 
previously been carried out in the presence of gallium-based or 
gallium-containing catalysts. 
U.S. Pat. No. 4,543,347 (Heyward et al.) discloses a catalyst composition 
suitable for converting synthesis gas to hydrocarbons which is a mixture 
of zinc oxide and an oxide of at least one metal selected from gallium and 
iridium, an oxide of at least one additional metal collected from the 
elements of Group IB, II through V, VIB and VIII including the lanthanides 
and actinides and a porous crystalline tectometallic silicate. 
U.S. Pat. No. 4,490,569 (Chu et al.) discloses a process for converting 
propane to aromatics over a zincgallium zeolite. This zeolite optionally 
may also contain palladium. More specifically, the catalyst composition 
used in the instant patent consists essentially of an aluminosilicate 
having gallium and zinc deposited thereon or an aluminosilicate in which 
cations have been exchanged with gallium and zinc ions wherein the 
aluminosilicate is selected from the group known as ZSM-5 type zeolites. 
U.S. Pat. No. 4,585,641 (Barri et al.) discloses crystalline gallosilicates 
which may be impregnated, ion exchanged, admixed, supported or bound for 
catalyzing a reaction such as alkylation, dealkylation, 
dehydrocyclodimerization, transalkylation, isomerization, dehydrogenation, 
hydrogenation, cracking, hydrocracking, cyclization, polymerization, 
conversion of carbon monoxide and hydrogen mixtures through hydrocarbons 
and dehydration reaction. The metal compounds which may be used for ion 
exchange or impregnation may be compounds of any one of the groups of 
metals belonging to Groups IB, IIB, IIIA, IVA, VA, VIB, VIIB and VIII 
according to the Periodic Table. Specifically, preferred compounds include 
copper, silver, zinc, aluminum, gallium, indium, vanadium, lead, antimony, 
bismuth, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, 
ruthenium, rhodium, palladium, iridium, platinum, radium, thorium and the 
rare earth metals. Patentees describe their gallosilicate as "Gallo 
Theta-1" in contradistinction to an MFI-type gallosilicate which has a 
substantially different X-ray diffraction pattern. 
U.S. Pat. No. 4,350,835 (Chester et al.) relates to a catalytic process for 
converting gaseous feedstocks containing ethane to liquid aromatics by 
contacting the feed in the absence of air or oxygen under conversion 
conditions with a crystalline zeolite catalyst having incorporated therein 
a minor amount of gallium thereby converting the ethane to aromatics. The 
gallium is present in the catalyst as gallium oxide or as gallium ions if 
cations in the aluminosilicate have been exchanged with gallium ions. The 
patent further discloses that the original alkali metal of the zeolite, 
when it has been synthesized in the alkali metal form, may be converted to 
the hydrogen form or be replaced by ion exchange with other suitable metal 
cations of Groups I through VIII of the Periodic Table, including nickel, 
copper, zinc, palladium, calcium or rare earth metals. 
European Patent Application 0 107 876 discloses a process for producing an 
aromatic hydrocarbon mixture from a feedstock containing more than 50 wt.% 
C.sub.2 through C.sub.4 paraffins. Specifically the process is carried out 
in the presence of crystalline gallium-silicate having a SiO.sub.2 
/Ga.sub.2 O.sub.3 molar ratio of 25 to 250 and a Y.sub.2 O.sub.3 
/GaO.sub.3 molar ratio lower than 1 where Y can be aluminum, iron, cobalt 
or chromium. The disclosure also teaches a two-step silicate treatment 
comprising a coke deposition and a coke burn-off with an oxygen-containing 
gas. 
European Patent Application 0 107 875 similarly discloses a process for 
producing an aromatic hydrocarbon mixture from a feedstock comprising more 
than 50 wt.% of C.sub.2 through C.sub.4 paraffins. This process is carried 
out in the presence of a crystalline gallium-silicate, having a SiO.sub.2 
/Ga.sub.2 O.sub.3 molar ratio of 25 to 100 and a Y.sub.2 O.sub.2 /Ga.sub.2 
O.sub.3 molar ratio lower than 1 where Y can be aluminum, iron, cobalt or 
chromium. 
U.S. Pat. No. 4,629,818 (Burress) discloses an aromatization catalyst that 
contains gallium and thorium incorporated with a ZSM-5 or ZSM-11 
component. 
Similarly, U.S. Pat. No. 4,350,835 (Chester et al.) discloses a catalyst 
suitable for converting ethane to benzene, toluene, and xylene with a 
catalyst comprising gallium and a zeolite such as ZSM-5, ZSM-11, ZSM-12, 
ZSM-35, and ZSM-38. Along the same vein, U.S. Pat. No. 4,766,264 (Bennett 
et al.) discloses a gallium-loaded zeolite aromatization catalyst. 
Light paraffinic gases have also been upgraded to liquid aromatics in the 
presence of crystalline aluminosilicate zeolite catalysts having 
incorporated therein a minor amount of a metal selected from Groups VIII, 
IIB, and IB of the Periodic Table. For instance, U.S. Pat. No. 4,120,910 
(Chu) discloses copper-zinc-HZSM-5, platinum-HZSM-5, copper-HZSM-5, and 
zinc-HZSM-5 catalysts suitable for upgrading a gaseous paraffinic 
hydrocarbon feed to aromatic compounds. 
U.S. Pat. No. 4,704,494 (Inui) discloses a process for the conversion of 
low molecular paraffin hydrocarbons to aromatic hydrocarbons in the 
presence of metallosilicates wherein the metal is Al, Ga, Ti, Zr, Ge, La, 
Mn, Cr, Sc, V, Fe, W, Mo, or Ni. 
International Application No. PCT/GB84/00109 (International Publication 
Number: W084/03879) (Barlow) discloses an aromatization process utilizing 
a catalyst having a Group VIII metal in combination with a 
galloaluminosilicate. 
It is also known to employ a rhenium component and a platinum component in 
reforming and light paraffin dehydrocyclization catalysts. 
U.S. Pat. No. 4,416,806 (Bernard et al.) discloses a paraffin 
dehydrocyclization catalyst that contains a zeolitic crystalline 
aluminosilicate such as faujasite X, faujasite Y, zeolite L, zeolite 
omega, and zeolite ZSM-4. This catalyst also contains a rhenium component 
incorporated in the form of a carbonyl, a sulfur component and a platinum 
component. 
U.S. Pat. No. 4,105,541 (Plank et al.) broadly discloses an aromatization 
catalyst containing ZSM-38 that can have its original cations replaced by 
ion exchange with a mixture of cations selected from the group consisting 
of hydrogen, rare earth metals and metals from Groups IIA, IIIA, IVA, IB, 
IIB, IIIB, IVB, VIB, and VIII. 
U.S. Pat. No. 4,613,716 (McNiff) discloses a process for aromatizing ethane 
and/or ethylene with a catalyst containing an aluminosilicate loaded with 
gallium compounds or ions and a compound of a metal from Group VIIB or 
Group VIII specifically rhenium or iridium. 
Finally, U.S. Pat. No. 4,766,265 (Desmond) teaches a process for the 
conversion of ethane to liquid aromatic compounds using a catalyst 
containing a gallium impregnated molecular sieve with both a rhenium 
component and a metal selected from the group consisting of nickel, 
palladium, platinum, rhodium and iridium. The molecular sieve can be an 
alumino-, gallo-, or borosilicate. Silica is the preferred binder material 
for the catalytic composite. The '265 process is directed to handling 
ethane-rich, ethane feedstocks ranging from 100% ethane to a feedstock 
containing only minor amounts of ethane in a feedstock predominantly of 
hydrogen, methanol, and relatively minor amounts of C.sub.2 -C.sub.5 and 
C.sub.3 -C.sub.5 paraffins. 
In contrast to the '265 process, the process of the present invention, is 
directed to the conversion of a hydrocarbon gas rich in C.sub.3 through 
C.sub.5 light paraffins, preferably a feedstock rich in either C.sub.3 
and/or C.sub.4. Further, the process of the present invention does not 
require the ion exchange or impregnation of the molecular sieve contained 
in the catalyst with a gallium compound. 
It has now been discovered that C.sub.3 through C.sub.5 light paraffins can 
most effectively be upgraded by the catalytic process of the present 
invention minimizing methane and ethane production while simultaneously 
maximizing benzene, toluene and xylene production. 
SUMMARY OF THE INVENTION 
Briefly stated, in a broad aspect, this invention relates to a process for 
producing aromatic compounds from a hydrocarbon gas rich in paraffinic 
hydrocarbons ranging from C.sub.3 to C.sub.5 under conversion conditions 
in the presence of a catalyst comprising a gallosilicate molecular sieve, 
a platinum metal component, and a rhenium metal component. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention deals with the conversion of a hydrocarbon gas rich 
in paraffinic hydrocarbons ranging from C.sub.3 to C.sub.5 to aromatics. A 
particularly suitable feedstock for use in the present invention contains 
C.sub.3 and/or C.sub.4 paraffins. The feedstock suitable for use in the 
present invention preferably contains less than 10% ethane and most 
preferably a relatively minor amount of ethane such as less than 5%. Minor 
amounts of methane can also be present. In addition to the above-mentioned 
paraffins, the feedstock may contain other light gases such as propylene, 
butene, isobutene, butadiene, and paraffins and olefins with five or more 
carbon atoms per molecule. These feedstocks are generally available from 
several sources in a refinery as elucidated above. 
The process of the invention provides for the direct conversion of the 
light paraffinic gases to valuable aromatic hydrocarbons such as benzene, 
toluene, and xylenes. These aromatics can be used as an additive component 
to increase the octane number of gasoline or as raw materials in the 
petrochemical industry. 
The process of the invention selectively provides for a high yield of 
benzene, toluene, and xylenes in the C.sub.4 +product fraction while 
minimizing the yield of light C.sub.1 and C.sub.2 gases and C.sub.9 + 
aromatic compounds in the product fraction. 
Broadly, the catalyst employed according to the process of the present 
invention comprises a gallosilicate molecular sieve component and a 
platinum metal component. The gallosilicate can be prepared using 
conventional methods known to those skilled in the art. A suitable method 
is disclosed in European Patent Application 01 107 875 which is 
incorporated herein by reference. 
In another method the gallosilicate crystalline molecular sieves of this 
invention are characterized by the representative X-ray pattern listed in 
Table I below and by the composition formula: 
EQU 0.9.+-.0.2 M.sub.2/n O: Ga.sub.2 O.sub.3 : ySiO.sub.2 : zH.sub.2 O 
wherein M is at least one cation, n is the valence of the cation, y is 
between 4 and about 600, and z is between 0 and about 160. It is believed 
that the small gallium content of the sieves is at least in part 
incorporated in the crystalline lattice. Various attempts to remove the 
gallium from the gallosilicate sieves by exhaustive exchange with sodium, 
ammonium, and hydrogen ions were unsuccessful and therefore, the gallium 
content is considered nonexchangeable in the instant sieves prepared 
according to the present method. 
TABLE I 
______________________________________ 
Assigned Assigned 
d-Spacing .ANG. (1) 
Strength (2) 
d-Spacing .ANG. (1) 
Strength (2) 
______________________________________ 
11.10 .+-. 0.20 
VS 3.84 .+-. 0.10 
MS 
9.96 .+-. 0.20 
MS 3.71 .+-. 0.10 
M 
6.34 .+-. 0.20 
W 3.64 .+-. 0.10 
W 
5.97 .+-. 0.20 
W 2.98 .+-. 0.10 
VW 
5.55 .+-. 0.20 
W 
4.25 .+-. 0.10 
VW 
______________________________________ 
(1) Copper K alpha radiation 
(2) VW = very weak; W = weak; M = medium; MS = medium strong; VS = very 
strong 
A gallosilicate molecular sieve useful in this invention can be prepared by 
crystallizing an aqueous mixture, at a controlled pH, of a base, a gallium 
ion-affording material, an oxide of silicon, and an organic template 
compound. 
Typically, the molar ratios of the various reactants can be varied to 
produce the crystalline gallosilicates of this invention. Specifically, 
the molar ratios of the initial reactant concentrations are indicated 
below: 
TABLE II 
______________________________________ 
Most 
Broad Preferred 
Preferred 
______________________________________ 
SiO.sub.2 /Ga.sub.2 O.sub.3 
4-200 10-150 20-100 
Organic base/SiO.sub.2 
0.5-5 0.05-1 0.1-0.5 
H.sub.2 O/SiO.sub.2 
5-80 10-50 20-40 
Template/SiO.sub.2 
0-1 0.01-0.2 0.02-0.1 
______________________________________ 
By regulation of the quantity of gallium (represented as Ga.sub.2 O.sub.3) 
in the reaction mixture, it is possible to vary the SiO.sub.2 /Ga.sub.2 
O.sub.3 molar ratio in the final product. In general, it is desirable to 
have the gallium content of the gallosilicate sieve of this invention 
between about 0.1 and about 8 percent by weight of gallium. More 
preferably, the amount of gallium should be between about 0.2 and about 6 
weight percent gallium and, most preferably, between about 0.3 and about 4 
weight percent of gallium. Too much gallium in the reaction mixture 
appears to reduce the sieve crystallinity which reduces the catalytic 
usefulness of the sieve. 
More specifically, a material useful in the present invention is prepared 
by mixing a base, a gallium ion-affording substance, an oxide of silicon, 
and an organic template compound in water (preferably distilled or 
deionized). The order of addition usually is not critical although a 
typical procedure is to dissolve the organic base and the gallium 
ion-affording substance in water and then add the template compound. 
Generally, the silicon oxide compound is added with mixing and the 
resulting slurry is transferred to a closed crystallization vessel for a 
suitable time. After crystallization, the resulting crystalline product 
can be filtered, washed with water, dried, and calcined. 
During preparation, acidic conditions should be avoided. Advantageously, 
the pH of the reaction mixture falls within the range of about 9.0 to 
about 13.0; more preferably between about 10.0 and about 12.0 and most 
preferably between about 10.5 and 11.5. 
Examples of oxides of silicon useful in this invention include silicic 
acid, sodium silicate, tetraalkyl silicates, and Ludox, a stabilized 
polymer of silicic acid manufactured by E. I. DuPont de Nemours & Co. 
Typically, the oxide of gallium source is a water-soluble gallium compound 
such as gallium nitrate or gallium acetate or another gallium compound, 
the anion of which is easily removed during sieve calcination prior to 
use. Water insoluble gallium compounds such as the oxide can be used as 
well. 
Cations useful in the formation of the gallosilicate sieves include the 
sodium ion and the ammonium ion. The sieves also can be prepared directly 
in the hydrogen form with an organic base such as ethylenediamine. 
The acidity of the gallosilicate sieves of this invention is high as 
measured by the Hammett H.sub.o function which lies in the neighborhood of 
about -3 to about -6. 
Organic templates useful in preparing the crystalline gallosilicate include 
alkylammonium cations or precursors thereof such as tetraalkylammonium 
compounds, especially tetra-n-propylammonium compounds. A useful organic 
template is tetra-n-propylammonium bromide. Diamines, such as 
hexamethylenediamine, can be used. 
The crystalline gallosilicate molecular sieve can be prepared by 
crystallizing a mixture of sources for an oxide of silicon, an oxide of 
gallium, an alkylammonium compound, and a base such as sodium hydroxide, 
ammonium hydroxide or ethylenediamine such that the initial reactant molar 
ratios of water to silica range from about 5 to about 80, preferably from 
about 10 to about 50 and most preferably from about 20 to about 40. In 
addition, preferable molar ratios for initial reactant silica to oxide of 
gallium range from about 4 to about 200, more preferably from about 10 to 
about 150 and most preferably from about 20 to about 100. The molar ratio 
of base to silicon oxide should be about above about 0.5, typically below 
about 5, preferably between about 0.05 and about 1.0 and most preferably 
between about 0.1 and about 0.5. The molar ratio of aklylammonium 
compound, such as tetra-n-propylammonium bromide, to silicon oxide can 
range from 0 to about 1 or above, typically above about 0.005, preferably 
about 0.01 to about 0.2, most preferably about 0.02 to about 0.1. 
The resulting slurry is transferred to a closed crystallization vessel and 
reacted usually at a pressure at least the vapor pressure of water for a 
time sufficient to permit crystallization which usually is about 0.25 to 
about 25 days, typically is about one to about ten days and preferably is 
about one to about seven days, at a temperature ranging from about 
100.degree. to about 250.degree. C., preferably about 125.degree. to about 
200.degree. C. The crystallizing material can be stirred or agitated as in 
a rocker bomb. Preferably, the crystallization temperature is maintained 
below the decomposition temperature of the organic template compound. 
Especially preferred conditions are crystallizing at about 165.degree. C 
for about three to about seven days. Samples of material can be removed 
during crystallization to check the degree of crystallization and 
determine the optimum crystallization time. 
The crystalline material formed can be separated and recovered by 
well-known means such as filtration with aqueous washing. This material 
can be mildly dried for anywhere from a few hours to a few days at varying 
temperatures, typically about 50.degree. to about 225.degree. C., to form 
a dry cake which can then be crushed to a powder or to small particles and 
extruded, pelletized, or made into forms suitable for its intended use. 
Typically, materials prepared after mild drying contain the organic 
template compound and water of hydration within the solid mass and a 
subsequent activation or calcination procedure is necessary, if it is 
desired to remove this material from the final product. Typically, the 
mildly dried product is calcined at temperatures ranging from about 
260.degree. to about 850.degree. C. and preferably from about 425.degree. 
to about 600.degree. C. Extreme calcination temperatures or prolonged 
crystallization times may prove detrimental to the crystal structure or 
may totally destroy it. Generally, there is no need to raise the 
calcination temperature beyond about 600.degree. C. in order to remove 
organic material from the originally formed crystalline material. 
Typically, the molecular sieve material is dried in a forced draft oven at 
165.degree. C. for about 16 hours and is then calcined in air in a manner 
such that the temperature rise does not exceed 125.degree. C. per hour 
until a temperature of about 540.degree. C. is reached. Calcination at 
this temperature usually is continued for about 4 hours. The gallosilicate 
sieves thus made generally have a surface area greater than about 300 sq. 
meters per gram as measured by the BET procedure. 
Although not required, it is preferred to employ the above-described 
gallosilicate molecular sieve combined, dispersed or otherwise intimately 
admixed in a matrix of at least one non-molecular sieve, porous refractory 
inorganic oxide matrix component, as the use of such a matrix component 
facilitates the provision of the ultimate catalyst in a shape or form well 
suited for process use. Useful matrix components include alumina, silica, 
silica-alumina, zirconia, titania, etc., and various combinations thereof. 
In a specific embodiment of the present invention silica is the most 
preferred inorganic refractory oxide. The matrix components also can 
contain various adjuvants such as phosphorus oxides, boron oxides, and/or 
halogens such as fluorine or chlorine. Usefully, the molecular 
sieve-matrix dispersion contains about 1 to 99 wt.% of a sieve component, 
preferably 20 to about 90 wt.% and most preferably 30 to 80 wt.% of a 
sieve component based upon the sieve-matrix dispersion weight. 
Methods for dispersing molecular sieve materials within a matrix component 
are well-known to persons skilled in the art and applicable with respect 
to the gallosilicate molecular sieve materials employed according to the 
present invention. A method is to blend the molecular sieve component, 
preferably in finely-divided form, in a sol, hydrosol or hydrogel of an 
inorganic oxide, and then add a gelling medium such as ammonium hydroxide 
to the blend, with stirring, to produce a gel. The resulting gel can be 
dried, shaped if desired, and calcined. Drying preferably is conducted in 
air at a temperature of about 80.degree. to about 350.degree. F. (about 
27.degree. to about 177.degree. C.) for a period of several seconds to 
several hours. Calcination preferably is conducted by heating in air at 
about 800.degree. to about 1,200.degree. F. (about 427.degree. to about 
649.degree. C.) for a period of time ranging from about 1/2 to about 16 
hours. 
Another suitable method for preparing a dispersion of the molecular sieve 
component in a porous refractory oxide matrix component is to dry blend 
particles of each, preferably in finely-divided form, and then shape the 
dispersion if desired. 
Alternatively, in another method, the sieve and a suitable matrix material 
like alpha-alumina monohydrate such as Conoco Catapal SB Alumina can be 
slurried with a small amount of a dilute weak acid such as acetic acid, 
dried at a suitable temperature under about 200.degree. C., preferably 
about 100.degree. to about 150.degree. C. and then calcined at between 
about 350.degree. and about 700.degree. C., more preferably between about 
400.degree. to about 650.degree. C. 
Silica-supported catalyst compositions can be made by dry mixing the 
gallosilicate sieve with a silica source such as Cab-0-Sil, adding water 
and stirring. The resulting solid is then dried below about 200.degree. C. 
and finally calcined between about 350.degree. C. and 700.degree. C. 
The platinum metal component of the catalyst employed according to the 
present invention can be present in elemental form, as oxides, as 
nitrates, as chlorides or other inorganic salts, or as combinations 
thereof. While other Group VIII metals can be employed in the present 
invention, platinum is preferred because it is relatively inactive for 
hydrogenolysis which would result in undesirable increased yields of 
C.sub.1 and C.sub.2. 
The platinum metal component content preferably ranges from about 0.01 to 
about 10 wt.%, calculated as a zero valent metal and being based on the 
total weight of the catalytic final composite, with about 0.01 to about 5 
wt.% being more preferred, with a range of 0.05 to 1.0 wt.% being most 
preferred. Higher levels of platinum can be employed if desired, though 
the degree of improvement resulting therefrom typically is insufficient to 
justify the added cost of the metal. 
The rhenium metal component content employed according to the present 
invention can be present in elemental form, as oxides, as nitrates, as 
chlorides, or other inorganic salts, or combinations thereof. 
The rhenium metal component content preferably ranges from about 0.01 wt.% 
to about 10 wt.% calculated as a zero valent metal and being based on the 
total weight of the catalytic final composite, with a range of about 0.01 
wt.% to about 5 wt.% being more preferred, with a range of about 0.05 wt.% 
to about 2 wt.% being most preferred. 
The platinum metal and rhenium metal components of the catalyst employed 
according to this invention can be associated with the sieve component by 
impregnation of the sieve component, or the sieve component can be 
dispersed in a porous refractory inorganic oxide matrix, with one or more 
solutions of compounds of the platinum and rhenium, metal components which 
components are convertible to oxides on calcination. It also is 
contemplated, however, to impregnate a porous refractory inorganic oxide 
matrix component with such solutions of the platinum metal and rhenium 
metal components and then blend the sieve component with the resulting 
impregnation product. Accordingly, the present invention contemplates the 
use of catalysts in which the platinum metal and rhenium metal components 
are deposed on the sieve component, on a sieve matrix component dispersion 
or on the matrix component of a sieve matrix component. The order of 
incorporation of the metal components with the sieve component or sieve 
component and refractory inorganic oxide matrix component is not material. 
The mechanics of impregnating the sieve component, matrix component or 
matrix composite with solutions of compounds convertible to metal oxides 
on calcination are well-known to persons skilled in the art and generally 
involve forming solutions of appropriate compounds in suitable solvents, 
preferably water, and then contacting the sieve matrix component or sieve 
matrix dispersion with an amount or amounts of solution or solutions 
sufficient to deposit appropriate amounts of metal or metal salts onto the 
sieve or sieve matrix dispersion. Useful metal compounds convertible to 
oxides are well-known to persons skilled in the art and include various 
ammonium salts as well as metal acetates, nitrates, anhydrides, etc. 
In another embodiment of the present invention the catalyst of the present 
invention also contains chloride. The addition of chloride to the catalyst 
serves to increase the conversion and selectivity of the process of the 
invention to aromatics. A convenient method of adding the chloride is to 
include a predetermined volume of a solution containing a predetermined 
concentration of hydrochloric acid in the impregnating solution used to 
incorporate the platinum metal component with the catalyst. 
Alternatively, the chloride can also be added during the impregnation of 
the metal salt if the metal salt contains chloride, such as hydrogen 
hexachloroplatinate (H.sub.2 PtCl.sub.6.6H.sub.2 0). If the chloride 
content in the chloridecontaining metal salt is not sufficiently high, 
additional chloride can be added by the addition of hydrochloric acid to 
the impregnating solution. 
In the instant embodiment of the invention, the catalyst broadly contains 
0.1 to 10 wt.% chloride, preferably 0.5 to 5 wt.% chloride and most 
preferably 0.5 to 1.5 wt.% chloride based on the final catalyst weight. 
Also contemplated within the purview of the present invention, chloride can 
be incorporated into the catalyst by the addition of chloride-containing 
compounds to the feed stream such as carbon tetrachloride, hydrochloric 
acid, in amounts such that the final catalyst contains the above 
prescribed amount of chloride. 
The above-described catalysts can be employed in any suitable form such as 
spheres, extrudates, pellets, or C-shaped or cloverleaf-shaped particles. 
The process of the present invention is carried out under suitable 
operating conditions set out below in Table III under which the feed is 
contacted with the above-described catalyst. It is also contemplated that 
a portion of the unconverted effluent stream can be recycled to the feed 
after separation from the aromatic products. 
TABLE III 
______________________________________ 
Most 
Broad Preferred 
Preferred 
______________________________________ 
Conditions 
Temperature, .degree.F. 
700-1400 800-1200 850-1150 
Total Pressure, psig 
0-500 0-300 0-100 
WHSV, h.sup.-1 
0.1-100 0.1-40 0.1-20 
______________________________________ 
The present invention is described in further detail in connection with the 
following examples, it being understood that the same are for purposes of 
illustration only and not limitation.

EXAMPLE I 
The present example serves to demonstrate the process of the present 
invention. A gallosilicate molecular sieve was first impregnated to 
incipient wetness with an aqueous solution of ammonium perrhenate with a 
concentration calculated to yield 1.0 wt% elemental Re. The dried 
Re-loaded gallosilicate was then impregnated to incipient wetness with an 
aqueous solution of tetraamine platinum nitrate having a concentration 
calculated to yield 1.0 wt% elemental Pt. The dried Pt- and Re-loaded 
gallosilicate was then uniformly mixed with Catalpal alumina (alpha 
alumina monohydrate), then slurried with water to form a paste, and 
finally extruded to yield 1/16" extrudate. The extrudate was dried and 
calcined. The amount of Catalpal alumina used was calculated to yield 60 
wt% molecular sieve and 40 wt% alumina in the dried extrudate. The 
elemental metal loadings were 0.6 wt% Pt and 0.6 wt% Re with respect to 
the final extrudate catalyst. The 1/16" extrudate was then passed through 
a set of sieves to obtain 10-20 mesh particles for testing. 
This catalyst was then tested for n-butane conversion in accordance with 
the present invention in a conventional tubular fixed-bed once-through 
reactor, which had not been exposed to sulfur. The catalyst was reduced in 
the presence of hydrogen at 900.degree. F. prior to charging the n-butane. 
The feed was 100% n-butane. Gas and liquid products were separated and 
analyzed by gas chromatography. Process parameters and results are 
summarized in Table IV below. 
EXAMPLE 2 
The platinum/rhenium/gallosilicate catalyst prepared as described in 
Example 1 was sulfided in situ after reduction with a hydrogen stream 
containing 500 ppm hydrogen sulfide at 900.degree. F. until hydrogen 
sulfide breakthrough. Weakly-adsorbed sulfur was then purged with hydrogen 
at 900.degree. F. This sulfided catalyst was then tested for n-butane 
conversion as in Example 1. Process parameters and results are summarized 
in Table V below. 
EXAMPLE 3 
A platinum/gallosilicate extrudate catalyst was prepared as described in 
Example 1 except that the rhenium component was omitted not in accordance 
with the present invention. The extrudate contained 60 wt% molecular sieve 
and 40 wt% alumina binder. The elemental Pt loading was 0.6 wt% with 
respect to the final catalytic composite. As in Example 1, 10-20 mesh 
particles were obtained for catalytic testing. Process parameters and 
results are summarized in Table VI below. 
EXAMPLE 4 
In the present Example a platinum/gallosilicate extrudate catalyst was 
prepared. The present catalyst is the same as the catalyst in Example 1 
except that the rhenium compound was omitted. The extrudate contained 60 
wt% molecular sieve and 40 wt% alumina binder. The elemental Pt loading 
was higher at 1.0 wt% with respect to the final extrudate. As in Example 
1, 10-20 mesh particles were obtained for the testing. The process 
parameters and results are summarized in Table VII below: 
TABLE IV 
______________________________________ 
Pt/Re/Gallosilicate Extrudate Catalyst (0.6% Pt-0.6% Re) 
______________________________________ 
Temperature: 900.degree. F. 
Pressure: 1 atm 
WHSV: 2 g butane/g catalyst-hour 
Time on stream: 1.2 h 
Conversion of n-butane, C % 
90.0 
Selectivity, C % 
Methane 4.6 
Ethane 17.8 
Ethylene 0.4 
Propane 11.9 
Propylene 3.6 
Isobutane 2.5 
Butylenes 10.2 
C.sub.5 + PON* 0.3 
Aromatics 48.7 
Aromatics distribution, wt % 
Benzene 21.2 
Toluene 36.4 
Xylenes 35.3 
C.sub.9 2.3 
C.sub.10 1.5 
C.sub.11 + 3.3 
Selectivity to H.sub.2, mol % 
31.7 
(mole of hydrogen produced per mole 
of hydrogen in the converted butane) 
Carbon mass balance, % 93.6 
______________________________________ 
*PON = Paraffins, Olefins, Naphthenes 
TABLE V 
______________________________________ 
(S) Pt/Re/Gallosilicate Extrudate Catalyst 
(0.6% Pt-0.6% Re) 
______________________________________ 
Temperature: 900.degree. F. 
Pressure: 1 atm 
WHSV: 2 g butane/g catalyst-hour 
Time on stream: 2.1 h 
Conversion of n-butane, C % 
81.5 
Selectivity, C % 
Methane 4.1 
Ethane 12.2 
Ethylene 1.0 
Propane 10.6 
Propylene 5.6 
Isobutane 3.4 
Butylenes 17.4 
C.sub.5 + PON* 1.7 
Aromatics 44.0 
Aromatics distribution, wt % 
Benzene 15.2 
Toluene 28.5 
Xylenes 45.2 
C.sub.9 4.0 
C.sub.10 3.3 
C.sub.11 + 3.8 
Selectivity to H.sub.2, mol % 
25.7 
(mole of hydrogen produced per mole 
of hydrogen in the converted butane) 
Carbon mass balance, % 95.4 
______________________________________ 
*PON = Paraffins, Olefins, Naphthenes 
TABLE VI 
______________________________________ 
Pt/Gallosilicate Extrudate Catalyst (0.6% Pt) 
______________________________________ 
Temperature: 900.degree. F. 
Pressure: 1 atm 
WHSV: 2 g butane/g catalyst-hour 
Time on stream: 2.0 h 
Conversion of n-butane, C % 
90.0 
Selectivity, C % 
Methane 4.6 
Ethane 20.9 
Ethylene 0.1 
Propane 19.7 
Propylene 0.8 
Isobutane 3.1 
Butylenes 3.5 
C.sub.5 + PON 0.4 
Aromatics 46.9 
Aromatics distribution, wt % 
Benzene 20.2 
Toluene 33.3 
Xylenes 37.0 
C.sub.9 3.2 
C.sub.10 2.8 
C.sub.11 + 3.5 
Selectivity to H.sub.2, mol % 
23.8 
(mole of hydrogen produced per mole 
of hydrogen in the converted butane) 
Carbon mass balance, % 95.4 
______________________________________ 
*PON = Paraffins, Olefins, Naphthenes 
TABLE VII 
______________________________________ 
Pt/Gallosilicate Extrudate Catalyst (1.0% Pt) 
______________________________________ 
Temperature: 900.degree. F. 
Pressure: 1 atm 
WHSV: 2 g butane/g catalyst-hour 
Time on stream: 2.0 h 
Conversion of n-butane, C % 
87.1 
Selectivity, C % 
Methane 4.5 
Ethane 18.9 
Ethylene 0.2 
Propane 17.8 
Propylene 2.1 
Isobutane 3.3 
Butylenes 8.5 
C.sub.5 + PON 0.6 
Aromatics 44.1 
Aromatics distribution, wt % 
Benzene 17.8 
Toluene 29.8 
Xylenes 43.2 
C.sub.9 4.1 
C.sub.10 2.7 
C.sub.11 + 2.4 
Selectivity to H.sub.2, mol % 
26.3 
(mole of hydrogen produced per mole 
of hydrogen in the converted butane) 
Carbon mass balance, % 96.0 
______________________________________ 
*PON = Paraffins, Olefins, Naphthenes 
DISCUSSION OF RESULTS 
A comparison of Tables IV and V show that the sulfided 
platinum/rhenium/gallosilicate (Table V) is not superior to the unsulfided 
invention Example 1 catalyst (Table IV) in both activity, selectivity to 
aromatics and selectivity to hydrogen. Thus, Pt/Re/gallosilicate does not 
require sulfidation for good catalytic performance. 
This is in contrast to a prior art naphtha reforming catalyst, namely, a 
platinum/rhenium/alumina catalyst which requires sulfidation to achieve 
acceptable performance of the catalyst as demonstrated in V. K. Shum et 
al., J. Catal. 96, 371-380 (1985). 
A comparison of Table IV with either Table VI or Table VII shows that the 
invention Pt/Re/gallosilicate is more selective towards relatively 
high-valued products than the prior art Pt/gallosilicate at either a 
comparable platinum metal loading or comparable total metal loading. These 
highly-valued products include aromatics (used as high-octane gasoline 
blending stock or chemical feedstocks), butylenes and isobutane (both used 
for alkylation to produce high-octane isoparaffinic gasoline blending 
stock), and hydrogen (used for refinery streams hydroprocessing). Methane, 
ethane and propane are relatively low-valued byproducts. 
EXAMPLE 5 
A platinum/rhenium/gallosilicate molecular sieve catalyst, in accordance 
with the present invention containing 0.45 wt% Pt and 0.45 wt% Re was 
mechanically mixed with Cab-0-Sil EH-5 grade silica at a ratio of 60 wt% 
sieve to 40% wt% silica. Water was added to the mixed powder to form a 
slurry, which was then vigorously agitated in a high-speed blender. The 
resulting uniformly-mixed slurry was then dried in an oven to obtain a 
cake, which was then calcined in air at elevated temperature. The cake was 
then crushed and passed through a sieve to obtain 10-20 mesh particles for 
testing. 
This silica-containing catalyst was then tested for n-butane conversion in 
accordance with the process of the present invention in a conventional 
tubular fixed-bed reactor. The feed was 100% n-butane. Gas and liquid 
products were separated and analyzed by gas chromatography. Process 
parameters and results are set out in Table VIII below. 
EXAMPLE 6 
The platinum/rhenium/gallosilicate catalyst described in Example 1 
containing 0.45 wt% Pt and 0.45 wt% Re was mechanically mixed with 
Catalpal alumina at a ratio of 60 wt% sieve and 40 wt% alumina. The mixed 
powder was slurried with water in a high-speed blender. The slurry was 
dried and calcined to form a cake which was crushed and passed through a 
sieve to obtain 10-20 mesh particles. 
This alumina-containing catalyst was then tested for n-butane conversion in 
accordance with the process of the present invention as set out in Example 
5. Process parameters and results are set out in Table IX below. 
EXAMPLE 7 
The platinum/rhenium/gallosilicate catalyst described in Example 1 
containing 0.45 wt% Pt and 0.45 wt% Re was pressed into tablets without 
any matrix (binder). The tablets were crushed and passed through a sieve 
to obtain 10-20 mesh particles for catalytic testing. 
This catalyst-containing no refractory inorganic oxide binder catalyst was 
also tested for n-butane conversion described in Example 5 in accordance 
with the process of the present invention. Process parameters and results 
are presented in Table X below. 
TABLE VIII 
______________________________________ 
Binder type Silica 
Temperature, .degree.F. 900 
Pressure, atm 1 
Time on stream, h 2 
WHSV (based on catalyst), /h 
2.0 
WHSV (based on molecular sieve), /h 
3.3 
Molecular sieve loading, wt % 
60 
Conversion of n-butane, C-wt % 
78.1 
Selectivity to aromatics, C-wt % 
37.2 
Carbon mass balance, % 96.4 
______________________________________ 
TABLE IX 
______________________________________ 
Binder type Alumina 
Temperature, .degree.F. 
900 
Pressure, atm 1 
Time on stream, h 2 
WHSV (based on catalyst), /h 
2.0 
WHSV (based on molecular sieve), /h 
3.3 
Molecular sieve loading, wt % 
60 
Conversion of n-butane, C-wt % 
44.9 
Selectivity to aromatics, C-wt % 
34.0 
Carbon mass balance, % 97.3 
______________________________________ 
TABLE X 
______________________________________ 
Binder type NA 
Temperature, .degree.F. 900 
Pressure, atm 1 
Time on stream, h 2 
WHSV (based on catalyst), /h 
2.0 
WHSV (based on molecular sieve), /h 
2.0 
Molecular sieve loading, wt % 
100 
Conversion of n-butane, C-wt % 
76.0 
Selectivity to aromatics, C-wt % 
30.7 
Carbon mass balance, % 96.6 
______________________________________ 
Discussion of Results 
A comparison of Tables VIII and X shows that when the silica-containing 
catalyst (60 wt% sieve) and all-sieve catalyst were tested under the same 
weight hourly space velocity (WHSV) based on the as-charged catalyst with 
other process parameters held constant, the silica-containing catalyst was 
at least as active as the "all-sieve" catalyst. The silica-containing 
catalyst was also more selective towards aromatics production. These are 
surprising results since the silica-containing catalyst contains 40 wt% 
less molecular sieve, and silica by itself is considered to be 
catalytically inert for the reactions involved in the process of the 
present invention. 
A comparison of Tables IX and X shows that when the alumina-containing 
catalyst (60 wt% sieve) and the "all-sieve" catalyst were tested under the 
same WHSV based on the as-charged catalyst with other process parameters 
held constant, the alumina-containing catalyst was about 60% as active as 
the all-sieve catalyst. This was expected, since the alumina-bound 
catalyst contains only 60 wt% of the molecular sieve contained in the "all 
sieve" catalyst. 
Thus, as shown in Tables VIII through X, all of the catalysts used in 
accordance with the process of the present invention possess light 
paraffin aromatization activity. The catalyst in Example 5 possesses 
enhanced light paraffin aromatization activity despite containing less 
sieve. Thus, in a preferred embodiment of the present invention the 
catalyst contains silica as the refractory inorganic oxide as the binder 
of matrix material. Thus, the use of silica permits the preparation of a 
catalyst having greater mechanical strength and less cost due to the 
decreased sieve content.