ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT where it was employed, the generators responded with a rise in efficiency. The general practice of running vinegar generators calls for holding the nutrients a t a level where the organisms are maintained but not st,imulatedto form slime. I n applying the results of these experiments, therefore, the amounte of nutrient should be kept a t the minimum required to give good generator activity. I t is believed that stimulat,ion of bacterial multiplication is required by coke and ceramic saddle packings because the film of organisms sluffs off, whereas beechwood shavings not’ only present more surface per unit volume, but present a surface to which the bacteria can readily adhere. Packings ot,her than shavings may be used to obtain performance equal to beech shavings, volume for volume. However, the nutrient level may have to be raised in order to maintain an
adequate alcohol-converting bacterial film in the generator when certain hard surface packing materials are employed. literature Cited (1) Allgeier. R. J., Wisthofi, R. T., and H l l d e b r a n d t , F. >I,, 1311. EN&.C H E M . ,44, 669-72 (1952,. (2) Ihid., 45, 489-94 (1953).
(3) Hildebrandt, F. >I., Food Inds., 13, No. 8, 47-8 (1941) Myers, R. P., and Speck, 31. L , C . S.Patent 2,448,690 (Sept. 7, 1918). ( 5 ) Gnderkofler, 1,. A . , and Hickey, R. J.. “Industrial Fermentations,” Vol. 1, pp. 510-11, 516-17, Chemical Publishing Co., Kew York, 1954. (6) Wustenfeld, H., “Lehrbuch der Essigfabrikation,” pp, 100-2, Paul Parey. Berlin, 1930. (4)
RECEIVED for review April 2, 1954
ACCEPTEDJune 4 , 1954.
Manufacture over Platforming Catalyst EFFECT O F SULFUR ON CATALYST LIFE WILLIAM K. MEERBOTT, ALAN H. CHERRY, BENJAMIN CHERNOFF, JAMES CROCOLL, JULIUS D. HELDMAN’, AND CYRIL J. KAEMMERLEN2 Shell Oil Co., Houston Manufacfuring-Research loborofory, Housfon, Jew.
I
KCREBSIXG demand? on the petroleum industry for monocyclic aromatics and for higher octane fuels have h m u l a t e d extensive investigations in the field of catalytic reforming. Recently, several new processes have been described ( 1 , 4, 6 , 7 , 3, 14, 16, 17, 80, 21, 25, 25) whereby narrow boiling petroleum fractions or wider boiling range petroleum naphthas may be converted into monocyclic aromatics such as benzene, toluene, or xylenes, or into fuels of improved octane rat’ing. The catalytic reforming processes involve (1) dehydrogenat,ion of naphthenes t,o aromatics, (2) isomerization of naphthenes and paraffins, (3) hydrocracking of paraffine, (4) desulfurization, and ( 5 ) dehydrocyclization of paraffins. The mechanisms of these reactions have been discussed by several authors in recent years (3, 8, 10, 28). Most of the st,udieshave been carried out in ehort processing periods, eit8herx i t h pure hydrocarbons or with synthetic mixtures of these materials. Only limited information has been available on the effect of operating variables on catalyst life in the production of aromatics via catalytic reforming. This paper is concerned particularly Tvith the pilot plant preparation of concentrates of benzene and t’oluene using the Plat’forniing process developed by the Universal Oil Products Co., including pilot plant, produetion of aromatics from a narrow boiling Cg t o C7 (140’ to 228” F.) East-Kest Texas (ETVT) crude oil fraction, and the factors involved in the selection of operating conditions for an optimum aromatic yield-catalyst life relationship.’ laboratory Recycle Hydrogen Platforming Unit Is Used in lnvestigalions
The experimental apparatus, based on a design supplied by the Universal Oil Products Co., consists of an oil feed system, recycle gas compressor and metering facilities, and a dual external 1 2
Present address, Shell Oil Co., New P o r k , K. Y . Present address, Celanesc Corp. of America, Charlotte, N. C.
2026
preheater-react,or system, together with condensing and produrt recovery vessels. A simplified flow diagram of t,he apparatus is shown in Figure 1. The recycle gas stream, consisting principally of hydrogen, is passed over sodium-calcium hydrate for the rcmoval of hydrogen sulfide and gaseous mercaptans prior to re-use in the process. I n order to simulate the pressure drop that occurs in a commercial installation an interstage pressure control is used between tEir, two laboratory reactors to provide a differential of 50 pounds por square inch. Miniature motor valves and pressure controllers, manufactured by the Research Control Instrument Co. of Tulsa,, Okla., are used for pressure control. The reactor temperature control is semiadiabatic. An aluminum block furnace, into Tvhich the reactor is inserted, is maintained a t a constant block temperature by mean3 of a Celectray temperature controller. Homver, because of the endothermic nature of the dehydrogenation reactions and the type of reactor and furnace construction, it is impracticable to control temperntures within the catalyet bed. During a catalyst life study, a temperature profile of the catal>rst bed is recorded once every 24 hours. Temperature3 a t selectrd points are recorded hourly, as are other process measurements. The temperature profile of the catalyst bed gives an excellent indication of the catalyst activity decline. Catalyst. Universal Oil Products Co. Type R-5 spherical Platforming catalyst is used in all experiments. The total cat,alyst charge is divided equally betv-een the two reactors. Analyses. The recycle gas stream is analyzed by mass spectrometer. The unstabilized liquid product is fractionated by low temperature Podhielniak distillation into a ‘(‘2; and lighter” and a “hexanes plus” cut. Mass spectrometer analyses are obtained on both fractions. The hexanes plus material is analyzed for total aromatics by a fluorescent indicator adsorption technique (5). Individual aromatics are calculated from the
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 10
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT any commercial nonregenerative process, such as Platforming, operating conditions must be employed that will give an economically feasible catalyst life. Therefore, a lower temperature and higher hydrogen partial pressure than indicated by the thermodynamics for optimum yields rl I only might be anticipated to prevent rapid Gas Meter catalyst deactivation. A catalyst life of Rotameter a t least 3 to 4 months, corresponding Product to more than 25 barrels of feed per Cooler pound of catalyst, would be considered reasonable for commercial aromatics production. Liquid Level The dehydrogenation of cyclohexane Control Valve Recycle H2 P m p and alkylcyclohexanes to the respective aromatics proceeds rapidly and with High Pressure high yields over known dehydrogenaReceiver' tion catalyst (16). The alkylcyclopentanes are more slowly converted to aroPCV :Pressure Control Valve Hydrocarbon $!q l uId Progct Receiver matics than the cyclohexylnaphthenes Charge Pump ( 1 2 , 9 3 ) and have a less favorable therOebutanlzlng Calurnn modynamic equilibrium conversion to aromatics (15). Since alkylcyclopenFigure 1 . Laboratory Recycle Hydrogen Platforming Unit tanes constitute about 50% of the total naphthcnes in the feed (Table I), it is arumatics ratio obtained in the mass spectrometer analysis of cssential that conditions be selected that favor the dehydrothis hexanes liquid product. isomerization of these components. Since methylcj-clopentane is a major constituent in the feed and is, furthermore, the Feed Stock. A 200-barrel lot of 140' to 235" F. fraction prepared in refinery distillation columns from E W T crude oils is stored under nitrogen for experimental use. The plant feed is redistilled in a laboratory column to a 140' to 228' F. fraction just prior to use in the Platforming experiments. This is done to eliminate possible polymer formation, reeulting from long-time storage, which could deactivate the catalyst. A hydrocarbontype analysis of the redistilled 140" to 228" F. EWT feed stock is shown in Table I. Eastman Kodak I-Butanethiol (n-butyl mercaptan) is added as necessary to increase sulfur concentration of the feed material. il synthetic feed consisting of 22.2 volume % niethylcycloCYCLOHYXANE pentane, 22.3 volume % methylcyelohexane, and 55.5 volume % l coo 600 800 n-heptane is used in some experiments. The naphthenic comPARTlA- PRESSJRE rit, P S k ponents, of 95 mole % ' purity, and the n-heptane, of 99 mole % Figure 2. Equilibrium for Benzene-Methylpurity, were obtained from Phillips Petroleum Corp. Excess Recycle Gas
Recycle Gas
R
'on
7 Sornpflng
hL
+
cyclopentane-Cyclohexane a t 890' F.
Minimum Hydrogen Partial Pressure to Maintain Catalyst Life I s Function of Total Sulfur in Feed
Thermodynamic considerations show the desirability of utilizing elevated temperature and low hydrogen partial pressure for the conversion of naphthcnes to aromatics. However, in
Table
I.
Composition of East-West Texas Cg to C7 Feed Stock (140' t o 228'
Hydrocarbon Type C BParaffins C T Paraffins CPParaffins Cyclopentane Co Naphthenes Methylcyclopentane Cyclohexane Ci Naphthenes Dimethylcyclopentanes hZethylcyclohexane Cs Naphthenes Benzene Toluene
F.fraction) Volume % 23.6 25.9
4.4 -
53.8
0.5 6.9 6.8
10.9 11.9 4.0 _-
1.2 4.2
40.8 5.4
100.0
October 1954
most difficult of the alkylcyclopentanes to convert, a study of the thermodynamic equilibrium for benzene cyclohexane, and methylcyclopentane was necessary to establish desirable operating conditions. Figure 2 presents the equilibrium composition for the system benzene-methylcyclopentane-cyclohexane a t 890" F. For high benzene production it is preferable to operate a t hydrogen partial pressures of less than 250 pounds per square inch absolute. However, the effect of these conditions on the life of the Platforming catalyst still had not been established. Since organic sulfur compounds, which exist in many petroleum fractions, are known poisons for metallic catalyst ( I ? ) > an investigation of the influence of sulfur concentration in Platformer feed was included. Two catalyst life tests were carried out with the same Cg to C I EWT feed at comparable conditions-900" F. furnace temperature and 2 L.H.S.V. (volumes of feed per volume of catalyst per hour), with variation in the hydrogen partial pressure. The hydrogen partial pressures a t the outlet of the second reactor for the two catalyst life tests were 180 and 230 pounds per square inch. The total pressures for reactors S o . 1 and 2 a t 180 pounds per square inch hydrogen partial pressure were 290 and 240 pounds per square inch absolute and a t 230 pounds per square
INDUSTRIAL AND ENGINEERING CHEMISTRY
2027
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT quarter of the experiment was carried out under conditions of greater severity than origi(0.02 Wt. % sulfur in EWT feed) Outlet hydrogen partial pressure, nal operating conditions. 230 230 180 180 Ib./eq. inch 4.C 16 6 4 0 16.6 Catalyst age, bbl. feed/lb. catalyst Since the sulfur content of Operating Conditions the feed was considered to have an important effect on Reactor KO.1 340 340 290 290 Preesure, lb / 3 q . inch abs aromatics yields and catalyst TemRerature, F. 900 900 900 900 Furnace decline rate, additional data 89 5 88i 880 890 Inlet oil 863 880 852 869 mere obtained in two runs a t Outlet oil 830 844 866 837 -4v.catalyst about 230 pounds per square Reactor KO.2 290 290 240 260 Pressure, Ib /sq inch abs. inch hydrogen partial presTemperature, F. 900 900 900 Furnace sure. I n one test the feed 89 4 89 G 895 Inlet oil contained 0.055 weight % sul8cI 0 888 887 Outlet oil 887 887 889 Av. catalyst fur and in the second the feed 866 862 878 A v catalyst temperature, O F. 2.0 2.0 2 0 L.H.5 V.O had been desulfurized to 0.005 3.2 4.4 4.2 Hydrogen/oil mole ratio weight sulfur. A compari98.8 98.4 98 1 Recovery (actual) mt. 56 charge __ son of the effect of sulfur in Yield, Charge Basis ;Yo Loss), % the feed on aromatics yield Yol, Wt. T'ol. wt. and decline rate is shown in 1.0 2.0 1.8 ... 2 0 ... Hydrogen Figure 4 and Table 111. Fig0.3 '5'8 0.3 0.5 0.1 0.8 0 3 0.2 Methane 0.5 1.0 0.6 1.2 0. D 0.9 1.2 0.4 Ethane ure 4 shows that there is a 1.5 1.0 0.G 1.6 2.3 2.2 1.6 0.8 Propane 0.9 1.6 0.6 1.0 1.2 2.0 1.3 1.5 Isobutane substantial reduction in aro0.9 1.5 0.0 1.4 1.1 0.6 1.2 1.7 n-Butane matics yield when the feed con2.1 2.1 L4 1.8 1.8 1.1 1.7 1.0 Isopentane 10 0.0 1.2 1 4 1.3 0.9 1.1 1 6 n-Pentane tains 0.055 weight % sulfur. 9 1 . 3 8 8 . 8 0 2 . 6 9 1 . 1 9 1 . 5 87.0 86.6 89.6 Hexanes i Xoreover, the catalyst activity 31.3 33.5 36 0 22.9 Total aromatics, VOI. "c 9.1 5.6 8.1 7.6 Benzene decline rate with the high sul23.7 15.; 23.1 22.7 Toluene fur feed a t 230 pounds per 2.8 3.0 2.4 1 . t CS $2 0.2 0.8 0.5 COL square inch hydrogen partial ' .3 8.5 Z.1 19.7 h'aphthenes, vol. %c 46.0 48.8 Paraffins, vol. % 45.5 47.0 pressure is greater than in the runs with the feed containing 5 Liquid hourly space velocity, volumes of f r e d per rolume of catalyit per hour. lower sulfur concentrations a t otherwise constant conditions. The rates of catalyst activity inch hydrogen partial pressure were 340 and 290 pounds per square decline for three runs with Cg to C, EKT feed are summarized in Tahle IT. inch absolute, respectively. Total reactor sulfur for both runs The effect of desulfurization of Ce to C i E W T feed (0.005 was 0.02 weight % of the hydrocarbon feed. weight % sulfur remaining) at 230 pounds per q u a r e inch .Z comparison of the life test data for the two runs is presented in Figure 3 and Table 11. The activity of the catalyst in the hydrogen partial pressure on yield and catalyst life is shown also run a t 180 pounds per square inch hydrogen partial p r w x ~ r e in Figure 4 and in Table 111. These data reveal that desulfurdeclined more rapidly than would be satisfactory for commercial ized feed gave an initial aromatics yield improvement of about operation. However, in the run with an outlet partial pressure of 1 volume %, compared to the run with 0.02 weight % eulfur in the feed. Xoreover, with desulfurized feed the catalyst 230 pounds per square inch of hydrogen, the catalyst exhibited decline rate is practically negligible for the period of the test only minor loss in activity. This test was extended over 50 Comparison of the data from different cxperimcnts prcsented barrels of feed per pound of catalyst, about 8 months of continuous operation, without evidence of seiious decline in catalyst in Figure 4 shows that the greatest improvenient in aromatics yield was achieved when the sulfur concentration v-as reduced activity. I n this experiment total aromatics production only declined from an initial yield of 34 to 30 volume % (basis feed) from 0.055 to 0.02 weight %. This conclusion is further illusa t the conclusion of the run, even though approximately one trated in Figure 5, where the aromatics yield is related to the Table II.
Effect of Hydrogen . - Partial Pressure
, I .
I 0
1
4
e
1
I2
16
1
20
MRRELS FEED / LB CATALYST
Figure 3. EffectIof Sulfur and Hydrogen Partial Pressure on Platforming of East-West Texas Feed 1,3. Conditions of Table I1 2. Conditions of Table Ill
2028
Figure 4. Effect of Sulfur on Platforming of East-West Texas Feed at 230 Lb./Sq, Inch Hydrogen Partial 2ressure 1,3. Conditions of Table 111 Conditions of Table I1
2.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 10
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT sulfur concentration in the feed a t constant conditions. Figure 5 shows that (at 230 pounds per square inch hydrogen partial pressure) there is a noticeable reduction in the aromatics yield when the concentration of sulfur in the feed stock exceeds 0.03 weight %.
Table 111.
Effect of Sulfur in Feed Stock
(Hydrogen partial pressure 230 Ib./sq. inch) Feed sulfur, wt. % Catalyst age, bbl. feed/lb. catalyst
0.055 4.0
0.055 14.0
0,005
340
340
900 865
844
4.0
Operating Conditions
Reactor No. 1 Pressure, lb./sq. inch Temperature, F. Furnace Av. catalyst Reactor No. 2 Pressure, Ib./sq. inch Temperature, F. Furnace Av. catalyst Av. catalyst Temperature, F. L.H.S.V. Hydrogen/oil mole ratio Recovery (actual), wt. % charge
Threshold Range of Sulfur in Reactor Feed Marks Point of Rapid Decline in Catalyst Activity
The problems arising from the presence of 0.05 weight % sulfur in the feed were investigated further in an attempt to minimize both the initial reduction in aromatics yield and the accelerated activity decline caused by sulfur poisoning of the catalyst. Whether the deactivation of the platinum on the catalyst is caused by the formation of a chemical compound between platinum and sulfur or by a chemisorption of hydrogen sulfide on the platinum surface, it was felt that an additional increase in hydrogen partial pressure would be beneficial in suppressing the effect of higher sulfur concentrations on the Platforming catalyst. I n c r e a s e d pressure, however, is thermodynamically less favorable for m e t h y l c y c l o pentane conversion 28 I , 000 0 02 0 04 006 to benzene a t con%Wr.SULFUR IN FEED stant temoerature. Consequently, t o Figure 5. Effect of Sulfur on Platoffset the loss in forming of East-West Texas Feed a t aromatics yield due Constant Catalyst Life to higher pressure, 4 Bbl. feed/lb. catalyst a higher reactor Conditions of Table 111 temperature is required. The over-all reaction severity, as measured by the extent of hydrocracking (yield of Cg and lighter gases), was held constant by increasing the liquid hourly space velocity from 2 to 3. A series of runs was carried out a t 935' F., 3 L.H.S.V., and at hydrogen partial pressures of 230 and 285 pounds per square inch with the CSto C? EWT feed containing 0.015 and 0.05 weight % ' sulfur. The results of these experiments are presented in Figure 6 and Table V. With the low sulfur feed, increasing the hydrogen partial pressure resulted in a loss of 3.2 volume % total aromatics as given in a smoothed curve, due to the less favorable thermodynamic equilibrium. However, when the feed contained 0.05 weight % sulfur, the effect of the sulfur inhibition of the catalyst a t 230 pounds per square inch hydrogen partial pressure was to reduce the aromatics yield to the same level (32.5 volume %, feed basis) obtained a t 285 pounds per square inch of hydrogen. The suppression of aromatics formation by 0.05 weight % sulfur a t 285 pounds per square inch hydrogen partial pressure is practically ncgligible. Moreover, the catalyst activity decline rate, as shown in Figure 6, is affected less a t the higher pressure. For a given combination of operating conditions there appears to be a maximum concentration of sulfur in the feed stock which can be tolerated without undue catalyst activity decline a t the sacrifice of a small loss of aromatics yield. When the threshold is overstepped the loss in catalyst activity and aromatics yield is large. I n general, when the sulfur level in the feed stock increases, the deleterious effect on the Platforming catalyst can be counteracted by increasing hydrogen partial pressure, although a t some loss in aromatics yield. When this loss becomes excessive, because of the lower equilibrium concentrations of aromatics a t higher pressures, a feed desulfurization process merits consideration.
I
October 1954
340
goo
290
290
290
900 881 871 2.0 3.7 98.4
900 883 874 2.0 3.6 87.9
900 893 868 2.0 4.3 98.6
10.7 86.1 27.4 5.2 18.9 2.8 0.5 12.9 45.8
9.5 86.0 34.9 8.2 23.2 3.2 0.2 7.5 43.6
Yield, Charge Basis (No Loss)
Cr and lighter wt. % Hexanes $01. %
8.8 87.7 30.4 6.2 20.7 3.1 0.4 11.3 46.0
+
Total arornktics, vol. % Benzene Toluene Ca
Caf Naphthenes vol. % paraffins, v d ~ % .
Table
IV.
Rates of Catalyst Activity Decline
Outlet hydrogen partial pressure, Ib./sq. inch 180 230 Total sulfur (feed basis), wt. % 0.02 0.02 Decline ratea vol. % aromatics loss per bbl. feed& catalyst 0.73 0.04 a From smooth curve between 4 and 14 bbl. feed/lb. catalyst.
230 0,055
0.18
Figure 3 shows that Platforming a t 180 pounds per square inch hydrogen partial pressure with 0.02 weight % ' sulfur in the feed results in a rapid catalyst activity decline. Since this sulfur level appeared too high for economical low pressure operation, another test run was made with a desulfurized feed, 0.005 weight % sulfur. D a t a from the test run are compared with the previous run at the same conditions. The results indicate that sulfur removal is beneficial, but the rate of catalyst activity decline
-
u.
L-3T-
0.0509r.WT. s-'
OUTLET HYDROGEN PARTIAL PRESSURE 230 PSJ. 285 PSI.
---
20 l
0
4
I
I
I
8 12 16 BARRELS FEED/LB, CATALYST
I 20
Figure 6. Effect of Hydrogen Partial Pressure on Platforming of East-West Texas Feed Conditions of Table V
(0.47 volume % aromatics per barrel of feed per pound catalyst) is still too high for satisfactory catalyst life. I t may be concluded, therefore, that Platforming the E W T feed stock for Ce to C, aromatics requires hydrogen partial pressure greater than 180 pounds per square inch to reduce catalyst deactivation not caused by sulfur poisioning but due, apparently, to coke-forming reactions. It was observed in these experiments that an increase in sulfur concentration in the feed stock has two principal effects-initial
INDUSTRIAL AND ENGINEERING CHEMISTRY
2029
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT
Table V.
Effect of Hydrogen Partial Pressure at Increased Space Velocity
Outlet hydrogen partial pressure. 230 230 lb./sq. inch 0.015 0 05 Feed sulfur, nt. '% 4.0 4.0 Catalystage, bbl.feed,'lb. catalyst Ogeratine CondiGionn Reactor No. 1 340 340 Pressure, lh./sq. inch Temperature, F. 933 935 Furnace 858 870 Av. Catalyst Reactor KO. 2 290 290 Pressure, Ih./sq. inch Temperature, O I'. 935 937 Furnace 922 922 -4v. Catalyst 896 890 Av. Catalyst Temperature, ' B. 3.0 3 0 L.H.S.V. 4 2 3.6 Hydrogen/oil mole ratig 98 9 98.9 Recovery (actual),wt. ,c of cliarge Yield. C!iaree Basis I N o Loss) 13.0 13 5 82 0 36.0 9.1 23.3
3 3 0.3
CBt
Xaphthenes, 1701. 70 Paraffins, vol. 70
5.1
40.6
82 3 31 8 7.3 21.2 2 8 0 5 11 1 39 4
283 0.015 4.0
285 0.0; 16 2
390
390
535
536 865
8.57 340
340
935 908 883
935
5 7 97.7
5.1 99 0
9.7 86.3 33.0 7.8 22.2 2.9 0.1 7.8 46.6
10.6 85 4 31 8 7.3 21.6 2 7 0 2 11 0 42 6
2 9. -
90.5 885 3.0
inhibit,ion of aromat,ics formation, and accelerated catalyst activity decline rate. The inhibition of Platforming catalyst. by sulfur appears to be a reversible reaction. Exposure of Platforming catalyst to several 4-day cycles of alternate processing of 0.026 and 0.053 veight % sulfur in the feed showed this reversible effect of sulfur inhibition. Table 1'1 illustrates this effect and shows the variation in aromatics yield n-ith changes in sulfur concentration. While there is some indication of a catalyst activity decline in Table TI, no attempt was made to determine the decline rate during this experiment.
Table VI. Catalyst Age. Bbl./Lb. 3.7--4 1 4.2-5 2 2.3-6 2 , ,6436 8.7-9 6 9.7-10.3
sisting of a blend of methj Icyclopentane, methylel clohexane, and n-heptane was used. In the other life test, a Cs to C7 CWT feed stock containing 0.02 weight % sulfur was used. However, a t intervals of about 1.5 to 2.0 barrels of feed per pound of catalyst, during the latter life study, a 24-hour test period was made with the three-component synthetic blend. A comparison of thp synthetic feed test data is presented in Figure 8 and Table T'II. The niethylcyclopentane conversion (the dehydroisomerization reaction) suffered early in the run from exposure of the catalyst to sulfur in the feed. Only after the catalyst deactivation was considerably advanced, as measured by loss of niethylcyclopentane conversion, was the conversion of methglcyclohexane to toluene noticeably affected.
Table VII.
Effect of Sulfur on Aromatic Synthetic Feed Furnace temperature, 900° F.
Yields from
Pressure, 290 and 240 lh./aq. inah L.H.S.V., 2 Hydrogen/oil, mole ratio, 3 Run Run Run Run Run Run Aa Aa Bb Bb Ala Bb Catalyst age, hhl./lb. 4 4 .1.4 14.4 14 4 23 2 c 1 0 ; c Yields, vol. 3' 2 Total aromatics 3 2 . 3 30 4 29 5 26 1 27.9 16.6 Benzene 9 9 7.3 7.6 4.8 6 3 2.7 Toluene 21.2 20 5 21 6 20 2 1H 7 12.4 Hexanes 484.5 84 4 86.5 88 0 86 0 00.6 Hpdropracking, i y t . % feed Cs and lighter 11 0 10.1 11 6 9.2 9.6 7.1 Ai,oniatics activity 70a t 4.4hbl.feed/lh. datalysG 100 100 91 86 87 55 a Catalyst life teat with synthetic feed containing 22.3 vo1. $; mctllylcyclohexane, 22.2 1.01. % methylcyclopentane, and 5 5 . 5 v01. Tc 7i-lieptane. b 24-Hour test period made with synthetic feed during catalyst life teet ~ ~ 1 EWT ~ 1 1 feed containing 0.02% sulfur. c E n d of run.
900
I
I
I
I
I
I
I
1
Effect of Sulfur on Aromatic Yields at Constant Condiiions Ca and S~ilfur, Lighter, 1 ~ ~ . c~ Feed Feed 0.026 10 4 0.052 8.9 0 026 8.3 0.026 5 4 0.052 '3.7 0.026 9.0
Hexanes vel.
+, w
Feed 85.2 8i 1 86.5 86.6 86.3 86 9
Aromatics, Vol. % Feed Total Benzene Toluene 37.2 33 5 35.7
7 7 6.7 7.2
32 3 34.1
6.2 7 0
31.6
7 3
23.8 21 9 23 2 22.4 21 0 22.3
-00554.W~
S
0020ZWr
800 0
s
50 PER C E N T OF CATALYST BED
100
figure 7. Effect of Sulfur on Temperature Profile Experiments with Sulfur-Free Synthetie Feed Lead to Explanation of Effects of sulfur Poisoning of catalyst
The actual niechanisni of sulfur poisoning has been considered by Peveral workers ( 1 3 , 1 8 , $0). They have shown that organic sulfur conipounds impair the dehydrogenation activity of the platinum-containing catalysts. Moreover, Heinemann and associates ( 1 3 ) have s h o w , in short term experiments n.ith Houdriforining catalyst, the deactivating effect of sulfur on the dehydrogenation propertmyof the catalyst, a threshold value for sulfur poisoning, and the reversibilit,y of the sulfur inhibition reaction. Evidence present,ed in this paper indicates that the Platforming catalyst is affected in a similar manner. Sapht'hene dehydrogenation, an endothermic reaction, is evidenced in adiabatic operation by a marked temperature drop in the cat,alyst bed. Figure 7 presents a comparison of react>or' temperature profile measurenients for runs a t two sulfur levels. The yield dat,a (Figure 4), as well as the profilee in Figure 7, show that dehydrogenation is inhibited by sulfur. This same effect was demonstrated in txyo catalyst life tests with Platforming catalyst. I n one experiment, a sulfur-free synthetic feed con2030
East-Wesf Texas Feed 9.0 Bbl. feed/lb. catalyst
The data in Table VII, taken a t the end of the runs, show that run A (synthetic feed) still retained 87% of the aromatics production activity exhibited a t 4.4 barrels ol feed per pound of catalyst,. Run B EWT feed Tvith synthetic feed k s t periods, as presented in Table VII, shows the loss of considerable activity. At the end of the run tthe catalyst possessed only 55% of the aromatics producing activity which it had at' 4.4 barrels of ferd per pound of catalyst. At the conclusion of bot,h runs the catalyst from each reactor v a s tested for act,ivity with the eynthetic feed, after which each batch of catalyst wa8 analyzed for chemical composition. The catalyst analyses showed no evidence of metallic contamination or significant differences in composition. The activity test data and the carbon content of the aged catalysts are presenkd in Table TrIII. Although the average catalyst hrd temperature differed in the tests shown in Table ITII, the outlet hed temperatures, which would be expected t'o clet'ermine Ihe equilibrium quantities of benzene and toluene in the product, were the snine.
INDdUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 10
ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT
Table VIII.
Activity Tests of Aged Catalyst
Synthetic feeda Furnace temperature, 900° F. Pressure, 240 Ib./ay inch L.H S.V., 2 Hydrogen/oil mole ratio, 3 Run A
Run B Reactor N o . 1 2 1 2 4.3 0.91 2.8 Carbon, wt. % ‘ catalyst 0.67 880 883 882 Outlet catalyst bed temp., F. 879 A v . catalyst bed temp., F. 842 867 859 880 Yield, Charge Basis (No Loss) CSand lighter, wt. yo 8.6 11.6 10.0 10.2 Hexanes +, yol. % 87.6 86.0 86.8 88.3 Total aromatics, vol. ?& 30.2 19.9 25.2 11.4 Benzene 8.2 4.8 5.0 1.8 Toluene 20.4 12.6 18.5 7.4 2.5 1.7 2.2 1.6 Ca Rensene/toluene, vol. ratio 0.40 0.38 0.27 0.24 a Containing 22.3 vol. % methylcyclohexane, 22.2 vol. % methyloyolopentane, and 55.5 vol. % n-heptane.
+
A comparison of the data in Table VIII indicates that reactor No. 1 catalysts were more active than the second reactor catalysts
II
and showed only a small loss in dehydrogenation activity as measured by the methylcyclohexane conversion to toluene. The greater activity of reactor No. 1 catalysts can be explained by their low carbon content, which probably resulted from the lower temperature in the catalyst bed due to the endothermic reactions and the operation at 50 pounds per q u a r e inch higher pressure. The aromatics producing activity of the catalyst in reaction No. 2 of run A is reduced appreciably by the high carbon content on the catalyst, but the ratio of the dehydroisomeriaation to dehydrogenation reactions, as measured by the benzene to toluene production ratio, is unaffected by the carbon level. The evaluation of the catalyst in run B shows the same trend. I n run A the loss in catalyst activity can be attributed to carbon formation on the catalyst, whereas in run B both carbonization and sulfur poisoning have a part in the deactivation of the catalyst. A comparison of benzene to toluene ratios between runs A and B indicates that the exposure of the Platforming catalyst to sulfur in the feed has more effect on the reaction8 converting methylcylcopentane to benzene than on the dehydrogenation of methylcyclohexane to toluene. Data in Tables VII, VIII, and Figure 9 indicate that prolonged exposure of the catalyst to sulfur results in permanent loss of some dehydrogenation activity. The extent of the loss of activity depends on operating conditions and especially hydrogen partial pressure. Ciapetta ( 2 ) and Mills and associates (19), in discussing alkylcyclopentane conversion to aromatics over multifunctional catalysts, postulated the following series of successive reactions: Methylcyclopentane
-H z methylcyclopentene + +
I
I1 -2H2 cyclohexene _i) benzene I11
Reaction I11 is common to the Conversion of both alkylcyclopentanes and alkylcyclohexanes to aromatics. Results obtained with methylcyclohexane indicate that this reaction proceeds rapidly and reaches equilibrium under Platforming run conditions. Hence reaction I11 should not be the rate limiting step in the conversion of methylcyclopentane. Therefore, either reaction I or I1 is rate controlling, but it is not possible to determine from the present data which step is rate limiting. Mills and associates (18) have shown that the use of methylcyclopentane with either an isomerization or dehydrogenation catalyst separately, under reforming conditions, resulted in little aromatic or olefin production. However, processing over the dual functional catalyst resulted in an appreciable conversion of methylcyclopentane to aromatics. I t is possible that a close proximity of platinum and acid sites is required for alkylcyclopentane conversion to aromatics. For cyclohexylnaphthenes any active platinum site will satisfy the conditions for aromatics formation. The poisoning of the Platforming catalyst by sulfur deactivates a portion of the dehydrogenation sites, including some of the platinum-acid combination sites. This loss of dual site activity further retards an already rate limited step (reactions I and 11). In addition, sulfur poisoning also inhibits the rate of dehydrogenation in reaction I[I. Thus, in the conversion of methylcyclopentane to benzene there is a double dependence on the platinum activity of the catalyst and the effect of sulfur shows up almost immediately in the lower yield of benzene. Ac knowledgrnent
The authors wish to acknowledge certain technical information and the basic design of and operational techniques for the experimental apparatus, obtained through private correspondence from Universal Oil Products Co. to Shell Oil Co. The authors also wish to express their appreciation to the Shell Oil Co. for permission to publish the results of this investigation, and to A. C. Hogge, Wm. A. Bailey, Jr., and F. Kunreuther for their valuable comments and advice. Acknowledgment is also gratefully accorded to J. SV. Ferry and Martha Hills for experimental assistance and calculations and to the operating and analytical groups for their contribution to this work. literature Cited
(5)
~I
(6)
(7) (8)
(9) (10) (11) (12) (13) BARRELS FEED/LB.
Figure 8.
---
Effect of
C~TALYST
Sulfur on Platforming Catalyst
Synthetic feed (Run A of Table VII) Data from synthetic feed periods of run with East-West Texas feed (Run B of Table VU)
October 1954
Berg, C., Petroleum Refiner, 31, No. 12, 131 (1952). Ciapetta, F. G., IND.ENG.CHEM.,45, 162 (1953). Ciapetta, F. G., and Hunter, J. B., Ibid., 45, 147 (1953). Connor, J. E., Jr., Ciapetta, F. G., and associates, presented before the Division of Petroleum Chemistry at the 124th Meeting, ACS, Chicago, Ill., September 1953. Griddle, D. W., and LeTourneau, R. L., A n a l . Cheni., 23, 1620 (1951). Forrester, J. H., Conn, A. L., and Nalloy, J. B., Oil Gas J., 52, Yo. 49, 139 (1954). Fowle, M. J., Bent, R. D., and associates, Ibid., 51, No. 3, 131 (1952); Petroleum Refiner, 31, No. 4, 156 (1952). Greensfelder, B. S.,Archibald. R. C.. and Fuller. D. L.. Chem. Eng. PrOgr., 43, 561 (1947): Haensel, V., Oil Gas J., 48, No. 47, 82 (1950); Petroleum Processing, 5, No. 4, 356 (1950). Haensel, V., and Donaldson. G. R., IND.Esd. CHEX, 43, 2102 (1951). Heinemann, H., Ibid., 43, 2098 (1951). Heinemann, H., Mills, G. A., and associates, Ibid., 45, 130 (1953). Heinemann, H., Shalit, H., and Briggs, W. D., I b i d . , 45, 800 (1953). Kastens, M. L., and Sutherland, R. E., I b i d . , 42, 582 (1950). Kilpatrick, J. E., Werner, H. G., and associates, J . Research N a t l . Bur. Standards, 39,523 (1947). Kirkbride, C . G., Petroleum Refiner, 30, No. 6 (1951). McGrath, H. G., Oil Gas J., 50, No. 34 (1951); Petroleum Refiner, 30, No. 12, 102 (1951). Maxted, E. B., “Advances in Catalysis,” Vol. 111, p. 129, Academic Press, New York, 1948.
(14) (15) (16) (17)
(18)
INDUSTRIAL AND ENGINEERING CHEMISTRY
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ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT (19) Mills, G. A., Heinemann, H., and associates, IND.ENQ.CHEM., 45, 134 (1953). (20) Minachev, Xh. M., and associates, Izvest. A k a d . Na'auk S.S.S.R., OtdeE. Khim. iVauk, 1952, No. 4, pp. 603-15. (21) Murphree, E. V., Petroleum Refiner, 30, No. 12, 97 (1951). (22) Nelson, E. F., presented at the 37th Annual hIeeting of the
Western Petroleum Refiners Assoc., San Antonio, Tex., March 1949; Petroleum Processing, 4 , No. 5, 553 (1949). (23) Oblad, A. G., Llarschner, R. F., and Hear, L., J. Am. Chem. SOC., 62, 2066 (1940).
(24) Payne, J. W., Evans, L. P., and associates, Petroleum Refiner, 31, No. 5, 117 (1952). (25) Teter, J. W., and associates, Oil Gas J., 52, No. 23, 118 (1953). (26) Zelinski:, N. D., and Shuikin, N. I., Compt. rend. acad. sci. U.R.S.S., 3 , 255 (1934). RECEIvED for review January 4, 1954. Acomr5n hfay 28, 1054. Presented before the Divisions of Petroleum Chemistry and Industrial and Engineering Chemistry a t the Southwest Regional Conclave of the AMERICAN CHEMICAL SOCIETY, S e w Orleans, La., December 1953.
Fuels and Chemicals from Coal Hydrogenation E.
E. DONATH
Kopperr Co., Inc., Pitfsburgh, Pa.
I
N A previous paper ( 1 ) a projected coal hydrogenation plant was described with capacity to produce about 30,000 barrels
per day of chemicals and fuels. I n this plant Illinois coal is processed in two hydrogenation stages by liquid and vapor phase hydrogenation. The other main processing units include plants for coal preparation, residue coking combined with liquid phase hydrogenation, tar acids recovery from liquid phase oil, vapor phase gasoline fractionation combined with aromatics extraction, and Platforming and hydroforming. The main products, as shown in Table I, are tar acids from phenol to xylenols, aromatics from benzene to naphthalene, liquefied petroleum gas (LPG) and gasoline, predominantly motor gasoline.
creased if they were produced on a large scale and in constant quality or if they were offered at somewhat reduced prices. Another approach t o the utilization of these higher boiling aromatics and tar acide is the conversion within the coal hydrogenation plant into chemicals for which a large market already exists. The inherent flexibility of the coal hydrogenation process can be used to effect the desired change in the product distribution pattern. This paper discusses such possibilities, particularly with regard to increased production of phenol and benzene. If such an increase can be achieved at low expense, it will markedly improve the economics of the process. Rehydrogenation of Higher Boiling Tar Acids
Is Proposed to Increase Phenol Production Table I.
Chemicals and Fuels from 30,000 Barrel-per-Day Coal Hydrogenation Plant
Broinatios Benzene Toluene Xylenes Mixed aromatics Ethylbenzene S a p hthalene
2,210 3,770 4,190 1,780 750 316,000
--790
-
7,300
16.4
5,260 3,660 8,920
11.1 __
13,490
Liquefied petroleum gas
Gasoline Motor Aviation Total Ammonium sulfate, t o n s i d a s Sulfuric acid, tons/day
8 2 13.9 15 4 6 8 2 8 3 7 50 8
v
31,090 450 89
15.6
26.7
100.0
Forecasts for the demand for chemicals in the United States indicate that most of the chemicals produced in such a plant would find a ready market. This is especially true for benzene, phenol, ammonia, and sulfuric acid. However, the higher boiling aromatics and tar acids would be produced in amounts which constitute a major proportion of the anticipated future production. It can be assumed that the sale of these chemicals could be in-
2032
Increased production of phenol by the further hydrogcnntion The product of the liquid phase hydrogenation is the main source of tar acids. It contains about 20Y0 total tar acids of n-hich one third are phenol, cresols, and xylenole. I n the proposed plant ( I ) , only the latter were recovered. The higher boiling tar acids remained in the liquid phase product and Fere converted in the vapor phase into gasoline and aromatics. Perhaps in the future, satisfactory methods for the separation of the components of these higher tar acids can be developed and attractive markets found. I n this case these tar acids would be extracted and separated into marketable products. The lack of the necessary technical and market information makes an economic evaluation of such processing unreliable. Therefore, it appears of interest to investigate conversion of these high boiling tar acids into phenol, cresols, and xylenols. The highw tar acids from coal hydrogenation products ohtained in a pilot plant have been shown t o consist primarily of polyalkyl phenols (6'). The dealkylation of such higher boiling tar acids by hydrogenolysis is probable ( 3 ) ,and 32.5% conversion of tar acids in the 235O t o 280' C. range into lower boiling tar acids in the phenol to xylenol range has been obtained in a oncethrough operation in autoclaves. Indirect data for the dealkylation of higher boiling tar acids in continuous hydrogenation experiments are also available. Pasting oils containing various amounts of middle oil and tar acids were used in liquid-phase coal hydrogenation and permitted evaluation of the rate of tar acid dealkylation in a continuous process. These data indicate that a 30y0 conversion of tar acids in the boiling range 225" to 275" C. into phenols, cresols, and xylenols is a conservative figure. On this basis a calculation was made of the yields obtainable by methanol evtraction of a middle oil fraction, followed
of higher boiling tar acids is one possibility.
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 46, No. 10
