Reforming process for the catalytic conversion of petroleum fractions to a mixture of hydrocarbons rich in aromatics

The process disclosed is for the improved reforming of petroleum fractions by catalytic conversion to a mixture of hydrocarbons rich in aromatics. In the process, naphtha fraction is contacted with two types of catalysts (1) a conventional reforming catalyst and (2) an acidic reforming catalyst containing a crystalline iron silicate. Splitting the reformate into two fractions and recycling the same to the two different reaction zones containing the two types of catalysts. The fraction recycled to the acidic reforming catalyst is rich in aromatics.

The present invention relates to an improved reforming process for the 
catalytic conversion of petroleum fractions to a mixture of hydrocarbons 
rich in aromatics. More specifically, it relates to a reforming process 
wherein the naphtha fraction is contacted with two types of catalysts one 
of which contains a crystalline iron silicate and recycling two different 
fractions of the reformate to the two different reaction zones containing 
the two types of catalysts. 
Reforming processes using solid catalysts are in practice in the petroleum 
industry for the manufacture of high octane motor gasoline and aromatic 
compounds like benzene, toluene and xylenes. In prior-art, it has been 
known to contact various hydrocarbon feedstocks, especially the naphtha 
fractions obtained by the fractional distillation of crude petroleum oil 
in admixture with hydrogen over bifunctional catalysts containing metallic 
and acidic functions and, in particular, solid aluminous acidic catalysts 
containing metals like platinum, for upgrading them into very high octane 
motor fuel blendstock or to products rich in aromatics suitable for 
manufacture of pure aromatics, especially, benzene, toluene and xylenes, 
by extraction techniques. These conversion processes are classified as 
naphtha reforming. In general, these processes contact petroleum 
hydrocarbon fractions preferably, the naphtha fraction boiling between 
60.degree. to 150.degree. C. with a catalyst composite material consisting 
of an acidic chlorided alumina, containing about 0.1 to 0.8 wt. % of a 
metal like platinum along with 0.1 to 0.8 wt. % of one or more promoters 
like rhenium, iridium, tin and germanium, under suitable reforming 
conditions of temperature, pressure and space velocity. 
The reactions occurring in catalytic naphtha reforming are varied and 
complex and depend upon the dual catalytic function of both the metal and 
the acidic support. In one mode of operation, suitable for the manufacture 
of motor gasoline, the normal alkane components of the feedstock are 
converted into isoalkanes, cycloalkanes and aromatics. In another mode of 
operation, especially suited for the manufacture of aromatic hydrocarbons, 
the isoalkanes and cycloalkanes are also converted into aromatics, 
typically benzene, toluene and xylene. The conversion of alkanes into 
aromatics is called dehydrocyclization, and, this by far, is the most 
difficult to accomplish and the activity of a reforming catalyst is best 
judged by its ability to convert alkanes into aromatics. The 
dehydrocylization reactions which convert alkanes into aromatics can take 
place either on the metal alone as a monofunctional reaction or on both 
the support acid sites and the metal as a bifunctional reaction. 
The prior-art reforming catalysts are broadly classified into two 
categories viz. monometallic catalysts containing only platinum (the 
monometallics) and multimetallic catalysts containing platinum and one or 
more of the promoters. The former catalysts operate well at low severity 
conditions (like high pressures, low temperatures, and large H.sub.2 /HC 
ratios) under which conditions aromatics yields are lower due to 
thermodynamic constraints. These catalysts can operate at high sulphur 
contents in the feed material up to 10 ppm. On the other hand, the bi- and 
multimetallic catalysts operate well (without significant activity loss) 
at higher severity conditions (like low pressures, high temperatures and 
low H.sub.2 /HC ratios) which are conductive to larger aromatic yields. 
However, the catalysts used in the later processes are easily poisoned by 
feed sulphur and require feeds with less than 1 ppm sulphur for economical 
run lengths. 
The prior-art reforming processes are broadly classified into 
semi-regenerative, cyclic and continuous regenerative types. For a given 
catalyst, the severity level of economic operation increases in the order 
semi-regenerative&lt;cyclic&lt;continuous regenerative process. Therefore, for 
the given catalyst, the aromatics production increases in the same 
abovementioned order. Also, the operating cost of the process and the 
installation costs also increase in the same order, thus partially 
off-setting the economic advantage of increased aromatics production. One 
limitation of the prior-art processes is that the amount of aromatics 
produced in the process is limited by the nature of the components present 
in the feedstock. Components in the feedstock or in the recycle gases 
which contain less than six carbon atoms in the molecule cannot undergo 
conversion into aromatic. 
Another limitation of the prior-art processes is that the number of carbon 
atoms in the aromatic molecules is limited by the number of carbon atoms 
in its paraffinic precursor. Alkylation reactions of aromatics by 
molecules in the naphtha fraction containing less than six carbon atoms do 
not occur to any significant extent. 
Yet another limitation of the prior art processes is their inability to 
utilize gaseous olefins or olefin precursors, like alcohols, as additional 
feedstock to enhance the total yield of high octane motor fuel blendstock, 
and to enhance the aromatic content. 
Yet another limitation of the prior art processes using prior art catalysts 
is that they can neither oligomerize the cracked low molecular weight 
products present in the recycle gas into useful aromatic compounds nor 
convert added olefinic gases (obtained from other sources in the refinery 
like the fluid catalytic cracker) into aromatic products. 
Yet another limitation of the prior art processes is that the coke lay down 
on the prior art catalysts is rapid thereby demanding the use of 
relatively high partial pressures of hydrogen during the reforming of 
hydrocarbons, thereby incurring a high expenditure of energy in operating 
the gas recycle compressors. 
Yet another limitation of the prior art processes is their low liquid yield 
due to the high propensity for hydrocracking of the conventional catalysts 
used therein. 
Yet another limitation of the prior art processes is the necessity to 
inject a chlorine containing molecule continuously along with the naphtha 
feedstock to maintain adequate catalyst acidity necessary for the 
isomerisation reactions thereby necessitating a rigid control of the 
moisture content of the feedstock. 
The process of the present invention provides for the use of a catalyst 
material wherein it has been found possible to convert molecules 
containing less than five carbon atoms and feedstock containing naphtha in 
admixture with olefins and olefin-precursors such as methyl and ethyl 
alcohols including higher alcohols into high octane motor fuel rich in 
aromatics. The process also provides for the conversion into aromatics of 
low molecular weight gases produced during naphtha reforming or added to 
recycle gas stream. 
Various improvements have been made in such processes to improve the 
performance of reforming catalysts. The possibility of using carriers 
other than alumina has also been studied. Molecular sieves such as X, L 
and Y zeolites were studied as catalyst support. U.S. Pat. No. 3,926,780 
discloses a method for preparing reforming catalysts containing such 
zeolites. U.S. Pat. No. 4,615,793 discloses the use of L, X and Y zeolites 
in a reforming process. U.S. Pat. No. 4,645,586 discloses a reforming 
process using two reforming catalysts wherein the second reforming 
catalyst is a non-acidic catalyst comprising a type L zeolite containing 
platinum. However, catalysts based upon these molecular sieves have not 
been commercially successful. Variations have been made in the amounts and 
kinds of catalyst charged to the different reforming reactors of a series 
to modify or change the nature of the product or to improve C.sub.5.sup.+ 
liquid yields. Different catalysts, with differing catalytic metal 
components have also been used in the different reactors of a series. 
European Patent Application No. 0083875 disclosed such a process for 
naphtha reforming wherein the catalyst in the forward most reforming zone 
contains more platinum while the catalyst in the rearward most reforming 
zone contains more rhenium in mixture containing both platinum and 
rhenium. 
The possibility of using reforming catalysts containing crystalline 
silicates other than aluminosilicates have also been studied. European 
Patent No. EP 21475 discloses the use of a crystalline silicate 
characterised by a specific x-ray powder diffraction pattern and having 
following composition: 
EQU P(0.9+0.3) OM.sub.2/n 0.P(aX.sub.2 O.sub.3 bY.sub.2 O.sub.3)SiO.sub.2 
wherein 
M=H, alkali and/or alkaline earth metal, 
X=Rh, Cn and/or Sc 
Y=Al, Fe and/or Ga 
a&gt;0.5, b&gt;0, a+b=1&lt;P&lt;0.1 
Similarly, European Patent Nos. EP 24147 and EP 50499 disclose reforming 
catalysts containing gallium containing aluminosilicates. However, 
catalysts based upon these non-aluminium containing crystalline silicates 
have not been commercially successful in naphtha reforming processes, so 
far. 
Improvements in reforming processes have also been proposed. U.S. Pat. No. 
4,615,793 discloses a reforming process wherein a hydrocarbon feed is 
contacted with a reforming catalyst comprising type L zeolite in a 
reaction vessel to produce a reformate; hydrogen, methane and ethane are 
stripped from the reformate in a first separator, C.sub.3 -C.sub.5 
hydrocarbons are stripped from the stripped reformate in a second 
separator and then a portion of the hydrogen, methane and ethane and 
substantially all of the C.sub.3 -C.sub.5 hydrocarbons are recycled to the 
reaction vessel as heat carrier. 
The above variations and modifications have the objective of improving the 
process with respect to one selected performance objective or another. 
It is an object of the present invention to provide a further improved 
process, particularly, a process capable of enhancing the yield of 
aromatic hydrocarbons in contrast with prior art processes. 
SUMMARY OF THE INVENTION 
The present invention overcomes the deficiencies of the prior art by: 
1. Using, in combination, a first conventional reforming catalyst 
comprising an alumina support having disposed therein one or more Group 
VIII metals and a second acidic reforming catalyst comprising a mixture of 
alumina and a crystalline iron silicate having dispersed therein platinum, 
rhenium, iridium, tin, zinc, copper mixtures thereof, as disclosed and 
claimed in an Indian Patent application No. 160212 (published on 24.6.88), 
and copending application No. 222/DEL/88. Indian Patent Application No. 
160212 discloses a novel crystalline catalyst material having a 
composition in terms of mole ratio of oxides of formula 
EQU 1.0.+-.0.2M.sub.2 O: Fe.sub.2 O.sub.3 :30-300SiO.sub.2 :ZH.sub.2 O 
Wherein M is a monovalent cation and Z is 0-20 whereas Indian Patent 
Application No. 222/DEL/88 discloses a crystalline ferrosilicate having a 
composition of the formula 
EQU 0-0.4 Na.sub.2 O: Fe.sub.2 O.sub.3 :30-300SiO.sub.2 : 0-10H.sub.2 O 
which latter when used in the reforming process of a hydrocarbon feedstock 
is effected in the presence of catalyst composite material consisting of 
alumina and one or two noble metals selected from platinum, rhenium, 
iridium or mixtures thereof. 
2. Splitting the recycle hydrocarbon stream into two fractions, passing the 
first fraction comprising of hydrogen, methane and ethane into the first 
reaction zone containing the conventional reforming catalyst and passing 
the second fraction comprising propane and butanes into the second 
reaction zone containing the second acidic reforming catalyst containing a 
crystalline iron silicate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In its broadest aspects, the present invention involves the use of a first 
catalyst which is a conventional reforming catalyst and a second catalyst 
which is an oligomerisation catalyst containing a crystalline iron 
silicate in the reforming of hydrocarbons as described in the above said 
application Ser. No. 160212 and copending application Ser. No. 222/DEL/88. 
An advantageous feature of the present invention is that the products of 
the reforming process, after separation of the C.sub.5 plus reformate, are 
separated into two fractions, a first fraction comprising hydrogen, 
methane and ethane which is recycled back to the first conventional 
reforming catalyst zone and a second fraction comprising propane and 
butanes which is recycled to the second reaction zone. The process of the 
present invention enables to convert molecules containing less than 5 
carbon atoms and feedstock containing naphtha in admixture with such 
hydrocarbons into high octane motor fuel rich in aromatics. The process 
also provides for the conversion into aromatics of low molecular weight 
gases produced during naphtha reforming or added to recycle gas stream. 
According to the present invention, the reforming reactions are carried out 
in two stages. In stage 1, the naphtha fraction is reformed using a mono- 
or bi-or multimetallic catalyst. The reformate is then contacted with a 
catalyst composite material containing a crystalline iron silicate in 
admixture with a Group VIII metal and an inorganic oxide binder. The 
preparation of the said crystalline iron silicate is more fully described 
in Indian Patent Application No. 160212 the contents of which are hereby 
incorporated to show the catalyst composite material useful in the present 
invention. The recycle gas steam used in the second stage can be 
additionally mixed with low molecular weight gases from other sources 
(like fluid catalytic cracker OFF gas) prior to contacting the catalyst 
composite material hereinbefore mentioned. 
According to a feature of the present invention the naphtha feed is mixed 
with olefinic precursors like alcohols and or olefins and the mixture is 
passed along with hydrogen over a catalyst material consisting of alumina 
and, if necessary, one or more metals selected from platinum, iridium, 
rhenium, silver, gold or tin under dehydrogenating and dehydration 
conditions. The product from the above reaction is further contacted in 
the presence of hydrogen with the catalyst composite material containing 
the crystalline iron silicate. 
Another feature of the process of the present invention is that the 
reactions of stages 1 and 2 mentioned earlier are operated in fixed bed 
mode. The embodiments of the process are the total pressure of the 
reaction is in the range 1 atm-30 atm, preferably 5-20 atms more 
preferably 7-10 atms, the temperatures are in the range 
200.degree.-500.degree. and more preferably 450.degree.-530.degree. C., 
the WHSV's (weight hourly space velocities) are typically in the range 0.1 
to 5.0 hr.sup.-1 more typically in the range 0.5 to 2.00 hr.sup.-1 and 
most typically in the range 1.0 to 2.0 hr.sup.-1. 
Yet another feature of the present invention is that the cracked gaseous 
products and any added olefinic material or precursors (like alcohols) are 
converted into aromatics through oligomerization reactions, thereby 
increasing the aromatics yield to levels not attainable by the earlier 
conventional processes. 
An advantageous feature of the present invention is that the catalyst 
composite material used in the process of the present invention can 
operate at very high severe conditions, with low deactivation rates and at 
the same time tolerate sulphur levels as high as 10 ppm. Their operation 
at high severe conditions leads to larger aromatics yields due to 
thermodynamic advantages. A novelty of the process of the present 
invention is that highly olefinic stocks like coke and cracker gasolines 
can be used as feed materials for the production of aromatics. This was 
hitherto not economically feasible in conventional processes due to the 
rapid deactivation, of the catalysts used therein when using olefinic 
feedstocks. 
Another novelty of the processes of the present invention is that the 
process parameters can be adjusted to yield liquid products which consist 
almost completely of the aromatic compounds. This is an important 
advantage if the reformate is to be utilized later for aromatics 
extraction, as this will not only reduce considerably the load of the 
extraction unit but will also lead to greater purity of the aromatics 
produced. 
Yet another novel and advantageous feature of the process of the present 
invention is that the reformate has little or no C.sub.9 paraffins which 
is again desirable in subsequent aromatics extraction processes. 
Yet another advantageous feature of the process of the present invention is 
that the gaseous products consist primarily of C.sub.3 and C.sub.4 
hydrocarbons with very little C.sub.1 and C.sub.2 hydrocarbons. 
In one embodiment of the present invention, the catalyst used in the first 
reforming zone consists of alumina containing platinum alone or with one 
or more of the promoters chosen from the group rhenium, iridium, 
germanium, tin, manganese, lead, gold, palladium, zinc and copper. In the 
present embodiment of this invention, the catalyst composite material 
employed in the second reforming zone contains 0.5-20% of the iron 
silicate zeolite material, 0.1-1% of platinum, and 0-2% wt. of the 
promoters mentioned hereinabove, the balance being alumina. The catalyst 
may also contain 0.1-2% wt. of chlorine, incorporated therein during its 
preparation. 
In a preferred embodiment of the process of the present invention, the 
product of contacting the petroleum naphtha with the said iron silicate 
containing catalyst is separated into a first light hydrocarbon fraction 
containing molecules with one to two carbon atoms, of second hydrocarbon 
fraction containing molecules with 3 to 4 carbon atoms, and a heavy 
hydrocarbon fraction containing molecules with more than four carbon atoms 
and recycling the first light hydrocarbon fraction in admixture with 
hydrogen to the inlet of the first reaction zone containing the 
conventional reforming catalyst, recycling the second hydrocarbon fraction 
to the inlet of the second reaction zone containing the second said 
crystalline iron silicate and processing the heavy hydrocarbon fraction 
containing molecules with more than four carbon atoms to recover the high 
octane gasoline containing significant amounts of aromatics. 
In naphtha reforming processes, hydrogen is normally used in an amount of 
hydrogen to hydrocarbon mole ratio of 2 to 10 and preferably from 3 to 6. 
The hydrogen usually comes from the hydrogen rich gas stream recycled from 
the exit of the reforming zone after removal of the C.sub.5 plus 
hydrocarbons. This recycle gas stream comprises hydrogen, methane, ethane, 
propane and butanes and a significant part of it is recycled to the inlet 
of the reforming zone without any separation or splitting. Modifications 
to this conventional recycle process are also known. U.S. Pat. No. 
4,615,793 discloses a reforming process comprising (1) stripping a first 
fraction from the reformate in a first separator, (2) stripping a second 
fraction from said stripped reformate in a second separator, and (3) 
recycling a portion of said first fraction comprising methane, ethane and 
hydrogen and substantially all of said second fraction comprising C.sub.3 
-C.sub.5 hydrocarbons to the inlet of the reforming zone. The inclusion of 
C.sub.5 hydrocarbons in the recycle stream was claimed to increase the 
heat capacity per unit of reactant and thereby allow a higher conversion 
for the same temperature. 
In a preferred embodiment of the present invention, there are two recycle 
gas streams, a first recycle gas stream separated in a first high pressure 
gas-liquid separator comprising hydrogen, methane and ethane and a second 
recycle gas stream separated in a second low pressure gas-liquid separator 
comprising propane and butane. The first recycle gas stream is recycled to 
the inlet of the first reactor in a multireactor reforming zone and the 
second recycle gas stream is recycled to the inlet of the last reactor of 
the said reforming zone. The splitting of the recycle into two fractions 
and selectively recycling the second fraction comprising propane and 
butane to the last reactor containing the crystalline iron silicate 
enables the conversion by oligomerisation over the crystalline iron 
silicate of the said propane and butane into high octane gasoline 
containing large quantities of aromatics thereby constituting a 
substantial improvement over the prior art reforming processes. 
In another embodiment of the present invention, the catalyst used in the 
second stage of the reforming process contains therein a crystalline iron 
silicate described in Indian Patent Application No. 160212. 
The practice of the present invention will be further illustrated with the 
following examples which are for illustrative purposes only and not to be 
construed as limitations on the practice of the present invention. 
EXAMPLE 1 
This example illustrates the preparation of a bimetallic reforming catalyst 
of the prior-art. A commercially available alumina monohydrate (water 
content 30%) solid under the trade name CATA B was sieved using a 200 
mesh (ASTM) screen 180 g of the 200 mesh material was kneaded with 50 ml 
of dilute nitric acid containing 3 ml of concentrated HNO.sub.3 of Sp. gr. 
1.42. Additional water was sprayed on to the mixture while continuously 
kneading the alumina hydrate into a hard dough. The dough was extruded. 
The extrudates were dried at room temperature (30.degree. C.) for 6 hrs., 
then at 110.degree. C. for 10 hrs. and calcined finally at 500.degree. C. 
for 6 hrs. in a flow of dry air. The weight of the extrudates was 123 g. 
1000 ml of a solution of hydrochloric acid in distilled water, containing 
1.9 g of chloride ions were taken in a 2 lit. beaker and the calcined 
extrudates added to it. The mixture was agitated occasionally for 2 hrs. 
At the end of 2 hours, the solution was decanted out and analyzed for 
chloride ions. The chloride ions picked up by the extrudates was 1.01 wt. 
%. The extrudates were next dried at 110.degree. C. for 6 hrs. 
b 2 liters of a solution containing 0.99 g. of dihydrogen 
hexachloroplatinate (IV) hexahydrate equivalent to 0.4 g. of platinum 
metal and 0.54 of perrhenic acid equivalent to 0.4 g of rhenium metal were 
taken in a 5 lit. beaker and the chlorinated extrudates added to it. The 
mixture was kept aside for 24 hrs. with occasional agitation. After 24 
hrs., the solution was decanted off and the extrudates dried at 
110.degree. C. for 10 hrs. followed by calcination at 550.degree. C. for 6 
hrs. The final composition of bimetallic catalyst was 0.33% platinum, 
0.32% rhenium, 1.0% chlorine, the rest being alumina. The diameter of the 
extrudates was 1/16 inch. 
EXAMPLE 2 
This example illustrates the preparation of the crystalline iron silicate 
used in the preparation of the reforming catalyst used in the second stage 
of the reforming process of present invention. 
To 20 g of sodium silicate (8.2% Na.sub.2 O, 27.2% SiO.sub.2), 10 ml of 
water is added to constitute solution A. 3.5 g of triethyl-n-butyl 
ammonium bromide is dissolved in 10 ml of water to yield solution B. 0.54 
g of ferric sulphate in water constitutes solution C. Solutions A, B and C 
are mixed and 1.75 g of H.sub.2 SO.sub.4 in water is added to the mixture 
and the gel formed is heated at 180.degree. C. for one day in an autoclave 
after which the solid product is filtered, washed with water, dried and 
finally calcined in air at 500.degree. C. for 8 hours. The chemical 
composition of the solid crystalline iron silicate zeolite material in the 
anhydrous form is Na.sub.2 O: Fe.sub.2 O.sub.3 : 72 SiO.sub.2. In the next 
stage, the sodium ions are replaced by ammonium ions by exchange with 
ammonium chloride solution. The ammonium ions are then partially replaced 
by platinum to yield a solid material containing 0.6 % wt. of platinum. 
EXAMPLE 3 
This example describes the preparation of the novel reforming catalyst 
disclosed in copending Application No. 222/DEL/88 containing the 
crystalline iron silicate zeolite whose preparation has been illustrated 
in the preceding example. 
166 grams of a commercially available alumina monohydrate of the 
pseudoboehmite type (Catapal B, supplied by CONOCO, USA) were mixed 
throughly with 4.3 g of the platinum containing iron silicate zeolite 
whose preparation has been described in example 2 and kneaded with a 
dilute solution of nitric acid such that a hard dough containing 3% wt. of 
nitric acid was obtained. This dough was extruded and the extrudates 
calcined at 500.degree. C. for 6 hrs. after drying the extrudates at room 
temperature and at 110.degree. C. The extrudates (1/16" size) were next 
loaded with 1 wt. % chloride ions by a procedure identical to the one 
described in Example 1. Subsequently, 120 g of these extrudates were 
soaked in 2 litres of a chloroplatinic acid solution containing 1.8 g of 
chloroplatinic acid equivalent to 0.72 g of platinum metal for 24 hours 
with occasional agitation. The extrudates were then decanted off and dried 
at 110.degree. C. prior to calcination at 550.degree. C. for 6 hours. The 
final catalyst contained 0.6% Pt, 4% crystalline iron silicate and 1.0% 
chlorine, the rest being alumina. 
EXAMPLE 4 
The reforming of a naphtha (110.degree.-140.degree. C. cut virgin, 
containing about 1 ppm sulphur) was carried out at 480.degree. C., 18 kg 
cm.sup.-2 pressure, WHSV=2 hr.sup.-1 and H.sub.2 /HC ratio of 6 with 
recycle of the gaseous products and H.sub.2 in a bench scale reactor with 
30 g catalyst samples. The reforming catalyst described in the Example 3 
and a prior-art bimetallic catalyst containing platinum, rhenium and 
chlorine and NOT containing the Fe silicate whose preparation was 
described in Example 3 were compared. The products were analysed by gas 
chromatography. Table 1 reports the data. 
TABLE 1 
______________________________________ 
Feed: Neat Ankleshwar Naphtha, 110-114 C 
cut PNA analysis of feed 
Carbon No. 
Paraffins Naphthenes 
Aromatics 
______________________________________ 
C.sub.6 -- 1.02 -- 
C.sub.7 7.14 12.89 3.78 
C.sub.8 36.00 23.65 6.54 
C.sub.9 5.94 2.66 0.38 
______________________________________ 
Product Analysis (cut/wt. %) 
Hours of stream 
52 hours 300 hours 
Arom. Yield 
Present Prior-art Present 
Prior-art 
______________________________________ 
C.sub.6 2.87 1.23 2.5 1.00 
C.sub.7 23.11 15.80 19.4 15.4 
C.sub.8 37.83 34.65 32.5 32.7 
C.sub.9 3.09 3.98 2.6 3.7 
Total 66.9 55.68 57.0 52.8 
______________________________________ 
Composition of C.sub.8 hydrocarbons in the reformate 
Wt. % 
Hours of stream 
52 300 
Present Prior-art Present 
Prior-art 
______________________________________ 
Paraffins 0.1 23.85 0.6 29.4 
Naphthenes 0.2 0.8 0.3 1.0 
Aromatics 37.8 34.65 32.5 32.7 
______________________________________ 
It is seen from the above table that the process of the present invention 
utilizing a catalyst containing a ferrisilicate zeolite produces more 
total aromatics than the prior-art sample both at 52 hours of operation 
and at 300 hours of operation. The total yields of aromatics are 66.9 and 
57.0% at 52 hours and 300 hours for the zeolite containing catalyst used 
in this invention while the values are only 55.68 and 52.8% for the 
prior-art catalyst at 52 and 300 hours respectively. 
The distribution of the aromatics also reveals that the present process 
yields more of the economically desirable C.sub.9 minus aromatics (BTX) 
while the yields of the commercially less important C.sub.9 plus aromatics 
are lower. 
Again, the composition of the C.sub.8 hydrocarbons in the reformate shows 
that the concentration of paraffins and naphthenes are very low in the 
product from the present process while they are present in large amounts 
in the reformate from the prior-art catalyst. This is a major advantage 
for extraction of C.sub.8 aromatics from the reformate. 
EXAMPLE 5 
This example illustrates the advantages of gas recycle while using the 
novel catalyst of the present invention. Table 2 compares the performance 
of the catalyst when it is operated under recycle of hydrogen and other 
gases obtained from the high pressure product separator and when it is 
operated in a single pass mode without recycle. 
TABLE 2 
__________________________________________________________________________ 
Feed: Neat Ankleshwar naphtha (S = 1 ppm) 
Conditions: T = 480.degree., P = 18 kg cm.sup.-2 
WHSV = 2 hr.sup.-1, H.sub.2 /oil = 6 (mole) 
Catalyst: Novel Catalyst of the present invention containing 4 wt. % 
ferrisilicate zeolite. 
Product composition, wt. % Total 
Mode of 
C.sub.6 
C.sub.7 C.sub.8 C.sub.5 + 
aromatics 
operation 
P N A P N A P N A wt. % 
wt. % 
__________________________________________________________________________ 
Recycle 
1.7 
0.3 
2.9 
0.2 
0.4 
23.1 
0.1 
0.2 
37.8 
85.2 
66.9 
Single 
1.8 
0.1 
1.4 
0.2 
0.2 
15.4 
0 -- 38.0 
71.6 
57.8 
pass 
__________________________________________________________________________ 
It is noticed that the operation of the novel catalyst of the present 
invention in recycle mode produces more aromatics (66.9 wt. %) than when 
it is operated in the single pass mode (57.8 wt. %). Thus it is evident 
that to obtain maximum benefits out of the process of the present 
invention, it should be operated with recycle of the product gases 
including hydrogen. Also, it is noticed that the liquid yield (C.sub.5 +) 
increases with recycle (85.2% vs 71.6%). Obviously, during recycle part of 
the product gases (light hydrocarbons) undergo oligomerization and 
alkylation reactions over the novel catalyst to yield more aromatics and 
liquid products. 
This example illustrates a method for utilizing the novel catalyst of the 
present process more advantageously than heretobefore described. FIG. 1 of 
the drawing accompanying this specification presents a simplified scheme 
of the process incorporating split recycle. R1 is the first stage 
reforming reactor containing a conventional prior-art monometallic or 
bimetallic reforming catalyst. R2 is the second stage reforming reactor 
containing the novel catalyst of the present invention. The feed enters 
reactor 1 along with the recycle gas 1 from the high pressure separator. 
This recycle gas consists primarily of H.sub.2 and small amounts of 
hydrocarbon gases especially C.sub.1 and C.sub.2. The product of the first 
reactor and the recycle gas obtained from the low pressure separator (or 
splitter) are mixed and introduced into the second reactor R2. In the 
first reactor, the conventional catalyst converts most of the naphthenes 
and small amounts of paraffins in the feed into aromatics. In the second 
reactor, the catalyst containing iron silicate converts a large percentage 
of the remaining paraffins in the product into aromatics by three 
different routes namely: (1) direct dehydrocyclization of the paraffins, 
(2) cracking and alkylating the fragments and (3) cracking and 
oligomerizing the fragments. Thus the product leaving reactor 2 is 
enriched in aromatics beyond levels that would have been possible by 
conventional high severity operations. Also, the greater purity of the 
recycle gas of reactor 1 increases the life of the conventional catalysts. 
Table 3 compares the results obtained when operating the novel catalyst 
described in Example 3 as per the scheme in FIG. 1 by combining two bench 
scale reactors and when operating in a single recycle mode. The catalyst 
described in example 1 was loaded in R1 while the catalyst of example 3 
was loaded in R2. The other conditions of the reaction are temperature 
=480.degree. C., Press=18 kg cm.sup.-2, WHSV=2 hr.sup.-1, H.sub.2 
/oil=mole=6. Feed: Ankleshwar naphtha (S=1 ppm), Catalyst weight: 30 g in 
each reactor. 
TABLE 3 
______________________________________ 
Reforming of naphtha (110-114.degree. C.) by a split-recycle process 
Aromatic yield at 50 on stream (wt. %) 
C.sub.6 
C.sub.7 C.sub.8 C.sub.9 
Total 
______________________________________ 
Single recycle 
2.87 23.11 37.83 3.09 66.9 
Example 4 
Split recycle 
3.05 25.23 40.76 3.61 72.65 
(present) 
Conventional 
1.23 15.80 34.65 3.98 55.68 
bimetallic/ 
single recycle 
______________________________________ 
The above results show that a benefit of additional 5 wt. % aromatics can 
be obtained if the novel catalyst of the present invention is operated by 
the novel split recycle process described. Thus utilizing both the novel 
catalyst and the novel process, an aromatic yield enhncement exceeding 15 
wt. % has been obtained.