Platforming of Pure Hvdrocarbons J VLADIMIR HAENSEL AND GEORGE R. DONALDSON Universal Oil Products Co., Riverside, I l l . T h e Platforming process is a process for converting naphthas into high octane gasolines and for producing aromatic hydrocarbons. The Platforming process uses a platinum-containing catalyst, the properties of which are discussed herein. The results obtained in processing pure hydrocarbons over the Platforming catalyst are presented. In the case of n-heptane, isomerization and hydrocracking occur to a large extent. The hydrocrackingreaction proceeds to give propane and isobutane as the major products. For npentane the isomerization to isopentane is the predominant reaction. Isopropylbenzene (cumene) undergoes hydrocracking to propane and benzene, the latter in
turn producing cyclohexane and methylcyclopentane. At the same time appreciable quantities of all isomeric Cg aromatics and smaller quantities of isomeric Co naphthenes are formed. The yield of toluene and xylenes is low. Methylcyclohexane produces toluene and isomeric alkylcyclopentanes and under selected conditions mixtures of toluene and methylcyclohexane can be converted to the isomeric alkylcyclopentanes. By modifying the condition it is possible to con'vert methylcyclohexane almost quantitatively into toluene. The results indicate the versatility of the Platforming catalyst in promoting reactions of dehydrogenation, hydrocracking, isomerization, and hydrogenation.
T
tanizer overhead gas streams. The units were equipped with automatic controllers t h a t held the block furnace at the desired temperature (f 1O C.), and the reactor at the desired pressure (It: approximately 5 pounds per square inch gage). The analytical procedure consisted of fractionation into selected cuts followed by infrared and ultraviolet analyses. In addition, the physical froperties of the cuts were determined, including refractive in ex and dispersion measurements, on a Pulfrich refractometer. The lower boiling range compounds (C, t o C5) were analyzed by means of a mass spectrometer.
HE Platforming process developed by Universal Oil Products Co. is a process for the conversion of naphthas into
high octane gasolines and for the production of aromatic hydrocarbons. T h e process is carried out in the presence of recycled hydrogen and utilizes a platinum-containing catalyst. I n previous publications on the process (2,3) i t was pointed out t h a t the following reactions take place: 1. 2. 3. 4. 5.
Dehydrogenation Hydrocracking Isomerization Desulfurization Dehydrocyclization
Source of Materials n-Pentane n-Heptane C u mene Methylcyclohexane
The extents of the reactions taking place are balanced t o ensure high yields of the desired product. The present paper deals Rith the reactions of pure hydrocarbons under Platforming conditions. APPARATUS AND PROCEDURE
T h e reactor used in conducting this investigation consisted of a stainless steel tube ?/&nch inside diameter, li/4-inch outside diameter, 45 inches long with a '/,-inch outside diameter axial thermowell in an electrically heated aluminum bronze block furnace. The upper section of the reactor contained a spirally grooved, stainless steel preheat section while the space below the catalyst bed was filled with stainless steel spacers. T h e hydrocarbon was fed t o the reactor using a plunger-type charge pump a t rates on the order of 100 ml. per hour. The hydrogen charge to the reactor was either from a high pressure calhrated hydrogen cylinder, in the case of the once-through-type units, or from a recycle gas compressor which pumped the off-gas from the high pressure receiver t o the reactor a t rates of approximately 5 to 10 standard cubic feet per hour in the case of the recycle-type units. The reaction products were condensed, cooled t o room temperature, and a phase se aration was effected in a high pressure receiver. The liquid pEase from the high pressure receiver was either collected in a n atmos heric pressure glass receiver and then combined batchwise wit[ the condensate collected at dry ice temperature from the off-gas from the atmospheric pressure receiver, or was sent t o a continuous debutanizer in which a split between Cc and C5 was effected. I n the former case the total liquid roduct was then fractionated in a batch column. Conventiona? equipment was used t o sample and meter the gas stream. I n the case of the once-throu h units, t h e one gas stream metered and sampled consisted combined streams of the high pressure receiver off-gas and the gas from the atmos heric pressure receiver t h a t passed through the dry ice traps. f n the case of the recycle units, the excess off-gas from the high pressure receiver was vented from the unit to maintain the desired re8 sure and was sampled and metered separately from the Lbu:
07
Toluene
Phillips Petroleum Co., 99% pure Phillips Petroleum Co., ASTM n-heptane Dow Chemical Co. (redistilled) From hydrogenation of C.P. toluene over UOP nickel hydrogenation catalyst C.P. Merck
RESULTS AND CONCLUSIONS
%-HEPTANE.Normal heptane was processed over the Platforming catalyst at a pressure of 500 pounds per square inch gage, a n average catalyst temperature of 459' C., 2.0 hourly liquid space velocity, and a cylinder hydrogen-to-hydrocarbon ratio of 3.3. Table I gives the composition of the total product, exclusive of a small amount of toluene formed, amounting t o approximately 2% of the charge. The results of Table I can be summarized in the following manner:
C -C -C -C -C
t
C1
+ Ce
J Ct
+ CS
C?
- C - C100moles
+ CC C7 isomers
n-Cr unconverted
These data show a pronounced tendency t o produce larger fragments which is indicative of a carbonium ion mechanism. However, i t is thought that the reaction is somewhat different due t o the very rapid quenching by hydrogen of the ions formed thus eliminating secondary decomposition. The good agrecment in the yields of methane and hexanes, ethane and pentanes, and, finally, propane and butanes indicates t h a t t h e fragments apparently do not undergo further hydrocracking.
2102
September 1951
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
TABLE I. PLATFORMING OF TL-HEPTAKE Compound
Wt. % of Charge
hl e t hane Ethane Propane Is o b 11 t a m n-Butane 1-opentane Ti-Pentane fiexanes 2,2.3-Tritnethylbutane 2.2-Dirnet hylpentane 3.3-Di methyl pentane 2.4-Diinethvloentane 2.3-Dimethylpentane 2-Methylhexane 3-Met.hylhexane n-Heptane Bottoms Total Ilydrogen consunied
0 5 1.6 11 0 10 7 4 8 2 7 1 6 2.6 1.4 1 6 1 8 1.6 6.0 19.0 20.4 12 5 1.6 __ 101.4 1.4
100.0
hfoles/100 Moles of Charge 3.1 5 2 25 1 18 8 52 3.8
2103
The selectivity of the hydrocracking reaction is well illustrated by the very extensive formation of benzene and propane as compared to the formation of toluene, xylene, methane, and ethane. There a r e a number of alternatives for the formation of t,oluene which includes the hydrocracking of ethyltoluene to give toluene and ethane.
2.3
3.0 1.4 1.6 1.8 1.6 6.0 19 0 20.4 12.5 1.6 135.1
-
The composition of the heptane fraction is of interest from the standpoint of approach t o equilibrium. Table I1 gives the composition of the heptane fraction and t h a t of a n equilibrium mixture at 459" C. The comparison given in Table I1 indicates a fair approach to an equilibrium mixture, particularly when i t is considered that some of the more reactive isomers are being removed by the hydrocracking reaction. n-PEmANE. n-Pentane was processed over the Platforming catalyst a t a pressure of 950 pounds per square inch gage, an average catalyst temperature of 432O C., a liquid hourly space velocity of 1, and a cylinder hydrogen-to-hydrocarbon ratio of 2.9. Table I11 gives a n analysis of the total product, the recovery of which amounted t o 97.87, by weight of the charge. The isomerization is relatively clean-cut and the approach t o equilibrium amounts t o about 60%. CUMENE(ISOPROPYLBENZENE). Cumene was selected as a suitable aromatic hydrocarbon for determining the reactions occurring in the presence of the Platforming catalyst, since both hydrocracking and isomerization were considered as possiblc reactions. The processing of cumene was carried out at 500 pounds per square inch gage, an average catalyst temperature of 459' C., a liquid hourly space velocity of 2, and a cylinder hydrogen-to-hydrocarbon ratio of 3.4. Table I V gives the composition of the total product, exclusive of the excess hydrogen used in the processing. These results can be summarized as follows:
TABLE 11. P OM POSITION
OF
c, FRACTION
Ohervcd 2 1 2 5 2 8 2 5 9 4 29.6 31.7
2-Methylhexane 3-Met,hylhexane 3-Ethylpentane n-Heptane
Equilibrium ( I )
3 5 7
5
23 17 24 3 13
...
19,4
TABLE111. PROCESSING O F TL-I'EST~NE OVER
THE
PLATFORM-
I N O C A T 4 1 YST
1Ioie %
Compound
