INDUSTRIAL AND ENGINEERING CHEMISTRY
2702
These findings, in addition to their theoret,ical interest, have important applications to the extraction of sulfur compounds from petroleum.
ACKNOWLEDGMENT The authors wish to thank B. H. Shoemaker and R. F. Marschner of this laboratory and H. C. Brown of Purdue University for their advice and encouragement during the course of t,his work.
LITERATURE CITED (1) Am. SOC.T e s t i n g M a t e r i a l , “A.S.T.M. S t a n d a r d s on Petroleum Products and Lubricants,” p. 37, D 9-47T, Philadelphia, Pa.,
Vol. 41, No. 12
(3) Burk, R. E., U.S. Patent 2,343,841 ( M a r c h 7, 1944). (4) Evering, B . L., and d’Ouville, E. L , d . Am. Chem. &c.,
71, 440 (1949). (5) F o s t e r , A. L., Oil Gas J . , 44, 96 (June 15, 1946). (6) Hofrnann, F.,and St,egemarin, W., Brit. Patent, 292,432 (June
25, 1927). ( 7 ) Ingold, C. K . , Chem. Rev., 15, 225 (1934). (8) K l a t t , W., Z . anorg. u.allgem. Chem., 232, 404 (1937). (9) Lewis, J., J . Franklin In.st., 226, 293 (1938). (10) Scafe, E. T., Petroleum Refiner, 25, 413 (1946). (11) Schneider, K. W., and Gottsohall, H . , ErdBl u a Aohla, 1, 74 (1948)
~
(12) Schriner, R. L., a n d Berger, A., J . OTO.Chena., 6, 305 (1941). (13) Taniele, M . , a n d K y l a n d , L. B., IND. EXG.CHEM., ANAL.ED., 8, 16 (1036).
1947.
i2) Ibid., p , 472, D 894-46T.
RECJIVFD M a y 16, 1949
CATALYTIC DESULFURIZATIQN OF CRUD J. H.HALE, M. C. SIMMONS1, AND F. P.WHISENHUNT Petroleum Experiment Station, Bureau of Mines, Bartlesville, Okla. Experiments have indicated that the composition and Properties of crude oil can be improved greatly by catalytic desulfurization. Table I shows some of the changes that would be brought about by treating 100 barrels of Slaughter crude oil in a bauxite catalytic desulfurizer under the conditions given. The sulfur content of the oil would be reduced Sl.Sq’,. The most active types of sulfur compounds are the ones removed by the treatment ; therefore corrosion problems would be reduced in the subsequent refining of the oil. The products distilled from the oil would have improved properties. The gasoline would have
an A.S.T.M. motor-method clear octane number 6.8 units higher, and also an increased lead susceptibility. The volumes of gasoline and gas oil would be increased at the expense of the residual material, thus reducing the amount of bottoms from the distillation. A limited amount of experimental work using hydrogen and an operating pressure of 225 pounds per square inch gage with bauxite, cobalt molybdenum bauxite, and zinc molybdenumbauxite catalysts showed that better desulfurization could be obtained in this way and that the prepared catalysts give the best results.
ORK on the catalytic desulfurization of crude oil v a s an outgrowth of Bureau of Mines studies on desulfurization of aviation-gasoline base stocks during IVorld War 11. The idea was conceived that, if an entire crude oil could be desulfurized effectively corrosion problems would be minimized, subsequent desulfurization of the gasoline distillate would not be necessary, a.nd a cracking unit charge stock of low sulfur coiit,ent would be available. This report covers experiments on the desulfurization of Slaughter crude oil over bauxite to establish optimum limits for operating variables, such as temperature and liquid hourly space velocity. Data also were obt’ained for the effect of oil-catalyst ratio on the liquid products and catalyst deposits, but additional data on regeneration of the catalyst would be required to establish t h e maximum oil-catalyst ratio that should be used. Further development would require pilot scale evaluation of t,he process, preferably on a continuous or cycle basis. Such development, if t h e data !Tarrant it, is deemed outside the scope of the activity of the Bureau of Mines. Sccordiiigly, tlic data are presented as found as a basis for further development.
displacement charge pump with adjushble stroke furnished the desired rates of pumping. The preheater consists of 15 feet of ‘/*-inch, standard black iron pipe coiled so t h a t the coil fits smoothly over a 2-inch pipe placed concentrically in a 4-inch pipe with the bottom closed and the annular space filled with lead. The lead is heated by two 1000-watt strip heaters, cont,rolled by a variable transformer, clamped on opposite sides of the 4-inch pipe. The outside is insulated with high-temperahre pipc insulation. The catalyst chamber is a 5-foot section of 2-inch extra strong pipe with a concentric thermomell made of 1/4-inchpi e extending from the tee at the top of the column to a point 6 incies from the bottom of the chamber. Eight, t’hermocouples are equally spaced throughout the length of the thermowell. The volume of the catalyst chamber is about 2700 ml., of which 2400 ml. are filled with catalyst. As shown in Figure 1, one layer of a,sbcstos listing on the column furnishes the base for a layer of Alundum cement. Three Nichrome-wire heating elements, each covcring a separate vertical portion of the chamber, are wound over the layer of Alundum cement, which is built up between the coils of the heating element and holds them in place. Two layers of asbestos listing and a n outside covering of pipe insulation covcr the heating wires. The condensers are st,raight tubes with an outer jacket in which refrigerated water is circulated. The liquid-product receiver is a 2-gallon screwcap bottle like the charge bottle. A smaller receiving bottle is used when the total charge for a run is less than 1 gallon. The gas-washing bot,tles have plastic screw caps with connections for rubber tubing.
APPARATUS Figure 1 shows diagrammatically the small scale bauxitedesulfurization unit used. A 2-gallon screw-cap bottle is the container for the charge. Two 500-ml. Pyrex graduated cylinders, closed at the ends by gasketed-steel plates, drilled and tapped for pipe connections, provide a measure of the volume of oil charged. A positive1
Present address, Shell Oil Company, Houston, Tex.
-
-
-
EXPERIMENTAL PROCEDURE A 2-gallon bottle is placed on the charge line wit,h enough sample to fill the charge lines to the top of the catalyst chamber and to adjust the pumping rate. One of the graduated cylinders is pumped down to the bottom graduation mark, and while the other cylinder is pumping down, the charge bottle is replaced wit,h one containing a weighed aniount of sample. The empty
INDUSTRIAL AND ENGINEERING CHEMISTRY
December 1949
2703
Table I. Bauxite Desulfurization of S l a u g h t e r C r u d e Oil (Basis, 100 barrels of crude charged. Conditions,. 750° F., 0.33 LHSVa, 2.08 oil-catalyst b ratio, and atmospheric pressure) Sulfur, Untreated Treated .- Wt. % Crude Crude Before After Total bbi Gasoline (110-400° F.), bbl. Cas oil (400-630° F . ) , bbl. Residuum (650 F.), bbl. Gas cu. feet Cok; lb. Oil 0; catalyst, lb;
+
Octane No. of gasoline0 Clear 1 nil. T E L 3 ml. T E L
++
a
100.0 35.0 25.0 40.0
... ... ..
.,
48.5 54.6 61.1
92.0 39.2 31.0 21.8 14,120 1,268 1,420
2.06 0.31 1.49 3.20
1.00 0.17 1.27 1.92
STEAM INLET HCRMCCOUPLE
55.3 63.3 71.2
Liquid hourly space velocity, volume of oil charged per hour per volume
of catalyst. b C
2.08 volumes of oil charged t o 1 volume of catalyst. A.S.T.M. motor method (F-2).
*
cylinder is filled with the weighed sample bottle preparatory to starting the sample through the catalyst chamber. As soon as the other cylinder is pumped down to the bottom graduation mark, its valve is closed and the valve t o the full cylinder is o ened. Simultaneously the feed is switched from a bypass to t i e top of the catalyst chamber, thus starting the run with sample memured from the weighed charge bottle. The temperature of the sample is raised t o a maximum of about 525 O F. in the preheater without evidence of cracking and heated further t o the selected reaction temperature in the top portion of the cat.alyst chambcr. The chamber is held at this tem erature aa the oil passes down through the catalyst bed. ,On Eaving the catalyst chamber, the oil passes through the two condensers a t the bottom of the chamber where vapors are condensed, and the liquid is cooled t o about 40' F. The liquid product is collected in the receiving bottle, and the noncondensable gas is vented through the two gas-washing bottles t o remove hydrogen sulfide. The first bottle contains a 5% by weight sodium hydroxide solution, and the second bottle contains water. The "sweetened" gas is metered and collected in a gasometer. At the end of each run, before the receiving bottle is removed, steam is passed through the catalyst chamber to remove as much oil and va or as possible, and the cooling water t o the condensers is shut ofpto warm these enough to melt any accumulated wax. The weights of charge and of liquid products are determined by weighing the charge and receiving bottles.
THERMOCOUPLE
2"EXTFIA STRONG PIPE
O N E LAYER ASBESTOS LISTING NE LAYER ALUNDUM LAYERS ASBESTOS
WASHING WTTLES
TEMPERATURE A series of four runs a t 450°J 600°, 750°, and 850" F. and a t
atmospheric pressure was made to determine the effect of temperature in desulfurizing Slaughter crude oil (2.04% sulfur). For each run, new 14- to 20-mesh Arkansas bauxite of the following approximate analysis was used: % b y Weight
+
5.65 2.59
+ titanium
LISTING
COOLING WATER OU
OPERATING VARIABLES
Moisturea Loss on ignitionb Silica Total iron oxides RzOa alumina
LEADS
28.06 8.41 54.46
91
Dried t o constant weight a t 140° C. b Ignited to constant weight a t llOOo C.
a
o i l at a volume rat,io o f 1.8 per volume of catalyst was charged was at 1.00 LHSV (liquid hourly space velocity) and the washed free of hydrogen sulfide with an aqueous solution of sodium hydroxide (5% by weight). The sulfur content of the liquid product as compared with Slaughter crude oil was reduced 20% a t 450" F., 30% a t 600" F., 50% a t 750" F., and 55% at 850' F. The qualitativechangesin ,composition caused by the treatments were compared on the basis of Bureau of Mines routine crude-oil analyses (1, 9) made on the crude oil and liquid products. It was found that a sub,stantial portion of the residual material in the crude-oil charge was converted to hydrocarbons of lower boiling range. On a volumetric basis, the percentage of residuum (790" F. initial
TWO- GALLON RECEIVING EOTTLE
F i g u r e 1.
Catalytic Desulfurization U n i t for C r u d e Oil
boiling point) was reduced from 25.6 for the charge material to 20.7 for the 450" F. product; 15.9 for the 600" F. product; 12.0 for the 750" F. product; and 5.1 for the 850' F. product. The percentages of gasoline and gas oil, which constitute a large portion of the crude, are definitely increased by bauxite treatment. This conversion is greater as the treating temperature is raised, but comparison of the properties of crude oil treated at 750" and 850" F. indicated that thermal cracking is much more evident a t 850' F. The excessive coking and loss of material that resulted from the cracking were undesirable as far as this study is c ~ r m ~ n e dConsequently, . a temperature of 750" F. was chosen for further investigation. VELoCITY
An effort to determine the effect of liquid hourly space velocity was next attempted with a series of runs a t 750" F. and atmospheric pressure with liquid hourly space velocity values of 1.00; 0.67,0.33, and 0.10, respectively. Other conditions remained the same as those used in the investigation of temperature effect. Results indicated t h a t reduction of liquid hourly space velocity affects the desulfurization and conversion in much the same manner as increasing the treating temperature, except that the changes
INDUSTRIAL AND ENGINEERING CHEMISTRY
2704
Vol. 41, No. 12
oil, there is a simultaneous conversion of low-value residuum material into gasoline and gas oil, and the products obtained from the treated crude oil are of improved quality. For example, the F-3 clear octane numbers of the gasoline fractions obtained from treated crude are higher than the clear octane number of the gasoline obtained from untreated crude. CATALYST LIFE
3 SERIES
5
1.0 I-
During the evaluation of operating condit,ions it was noted that the color, gravity, and other properties of the treated product rapidly changed during the course of a run from those similar to a light gas oil to those more typical of the crude oil charge. This phenomenon evidenced a rapid decline in act,ivity of the catalyst and the need for a more thorough study of catalyst on-stream period. INFLUENCE OF CATALYST ON-STREAM PERIOD AT 150" F. AND 0.33 LHSV
Gl
3
5 .a V
LL
0
5 .6 w
V
a W
a I-4
r 0
$ 2
.O 3 SERIES
I
Figure 2.
Catalyst Deposits
5
T o determine the influence of cat,alyst on-si ream period, three series of runs ryere made a t 750" F. treating temperature, atmospheric pressure, and 0.33 liquid hourly spa,ce velocity. In the following discussion, these series are referred to as serics 1, in which 1 liter of crude was charged t,o 2400 ml. of new bauxite; series 3, in which 3 liters of crude were charged t o 2400 ml. df new bauxite; and series 5, iri xhich 5 liters of crude were charged to 2400 ml. of new bauxite. Data on uiitreat,ed Slaughter crude are presented for comparison wit,h t,he dnta on samples from each series of runs, and the untreated crude oil is referred t,o as original crude. Composition and Properties of Product. The treating conditions used and Bureau of Mines crude-oil analyses data for the product from each series as m-ell as for the original crude are given in Table 111. These data show t x o major facts: (1)The product definitely differs from the charge in having a lower sulfur content, higher A.P.I. gravity, higher content of gasoline and gas oil, and less residuum; (2) t'he catalyst activity decreases with increase of total charge as evidenced by the gyadual increase in sulfur, decrease in 4.P.I. gravity, decrease in gasoline and gas oil, and increase in residuum in proceeding from series 1 to series 5, Most of the other data recorded also follow these two general trends, showing a marked increase or decrea,se caused by the catalytic t,reatment and a gradual change ae ca,talyst activity decreases.
are not as pronounced. The sulfur content of the Slaughter crude oil was decreased 50% a t a liquid hourl? space velocity of 1.00, 51% a t 0.67, 57% a t 0 33. and 58% a t 0.10. Conveision to gasoline and gas oil also was increased somewhat by lowering the liquid hourly space velocity, but it n as considered impractical to employ a liquid hourly space velocitv lon el than 0.33. The general effects of operating conditions on the desulfurization of Slaughter crude oil a t atmospheric pressure with bauxite are illustrated bv the selected data in Table 11: These data show that (1) temperature has Table 11. Effects of O p e r a t i n g Variables o n Desulfurization of S l a u g h t e r a greater effect on desulfurizaC r u d e Oil w i t h Bauxite tion and conversion than does Original Effect of LHSVEffect of Teinperature Crude liquid hourly space velocity; 450 600 750 850 760 750 750 750 Temperature of treatment, ' F. (2) 750" F. is a tempera1 1 1 1 1 0.67 0.33 0.10 LHSV 1 . 8 1 . 8 1 . 8 1 . 8 1 . 8 1 . 8 1 . 8 1.8 Col. of crude chgd./vol. of bauxite ture a t which good desulfuiiProperties 2.04 1.64 1.42 1.03 0.91 1 . 0 3 0.99 0.87 0.86 zation can be obtained and Bomb sulfur, wt. A.P.I. gravity 32.7 36.8 37.8 39.2 89.0 39.2 3'3.2 40.6 39.8 is low enough to avoid the Volumetric composition, from Bureau excessive coke formation that of Mines orude-oil analyses 44.5 44.1 41 4 40.1 42.7 42.7 41.0 39.8 31.5 Gasoline and naphtha accompanies the increased 5.9 5.7 6.0 6.6 5.7 5.3 5.7 5.0 5.0 Kerosene 27.1 23.1 23.8 24.7 25.5 23.1 18.1 2 0 . 5 18 3 Gas oil thermal cracking experienced 12.7 11.5 Q . 6 1 3 . 2 1 0 . 8 9 . 6 9 . 7 7 . 5 6 . 9 Light lube distillate 5.3 5.9 6.9 5.3 4.7 4.2 4.7 3.7 4.5 a t higher temperatures, and Medium lube distillate 3.9 3 1 2.1 1.0 .... 1.0 .... . . . . 0.8 Heavy lube distillate 5.4 3.4 7.3 (3) very little is gained by 5,1 12.0 15.9 12.0 20:7 25.6 Residuum 1.8 1.7 1.4 0.6 1.2 1.2 2.7 1.3 3.7 Distillation loss reducing the liquid h o u r k Properties of 150-275O F. fraction space velocity below 0.33. Lamp sulfur, wt. % 0.129 0.090 0.061 0.049 0.042 0.04!l 0.049 0.053 0.055 16.9 10,: 10.3 19.6 23.0 0.60 2.49 1 0 . 0 0.75 Bromine number I n general, the information 64.0 64.4 63.0 63.4 63.6 3 . 2 6 0 . 4 5 9 . 2 6 0 . 2 F-3 clear octane numbera gained from these prelimiProperties of residuum 1.73 1.92 1.46 2.18 2.29 2.29 3.55 3.43 3.72 Bomb sulfur, wt. % nary qualitative experiments 10.3 13.2 13.9 16.2 14.7 16.2 18.6 19.5 18.1 A.P.I. gravity 13.7 9.7 8.9 5.6 1.5 5.6 3.2 2.2 1.3 showed that in addition to Carbon residue removal of more than 50% Calculated from blended octane number. of the sulfur present in the
December 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
Deposit on Used Bauxite catalyst. The deposit on the bauxite catalyst may be classified as coke, oil, and sulfur. It was found t h a t the extracted oil contained sulfur or sulfur compounds and t h a t sulfur also was present in the coke deposit. Analyses of catalyst samples gave the following data:
Carbon Oil Sulfur i n coke deposit Sulfur in oil deposit Total sulfur
1
-
Series 1 2.15 3.75 0.19 0.10 0.29
Weight % of Catalyst Series 3 Series 5 4.63 7.25 7.26 8.16 0.35 0.49 0.29 0.23 0.64 0.72
These data are plotted in Figure 2 to show more clearly the trend of the deposits. The carbon from the coke deposit is virtually a rectilinear function of the volume of crude oil charged over the range studied, whereas the oil deposit appears t o reach a maximum where no additional oil will adhere t o the catalyst. Similarly, the sulfur combined with the coke is virtually rectilinear with the volume of crude oil charged, whereas the sulfur content of the oil deposit reaches a maximum a t a point corresponding t o series 3 runs. The total sulfur in the catalyst deposits apparently reaches a maximum percentage not much greater than that of series 5 . Sulfur-Balance Data. Sulfur removal from Slaughter crude oil occurred in two ways-as hydrogen sulfide and as sulfur-bearing deposits on the catalyst. The hydrogen sulfide formed during desulfurization was not measured, but the amount of sulfur going t o hydrogen sulfide was calculated from the quantities of sulfur in the charge, in the catalyst deposits, and in the product oil. T h e difference between the quantity of sulfur in the total charge and that in the catalyst deposits and product provides a value for the amount of sulfur which is removed as hydrogen sulfide during the catalytic treatment. Figure 3 shows the sulfur balance data in graphic form, and indicates t h a t catalytic sulfur removal, or hydrogen sulfide formation, remains virtually constant in the three series. The decreased percentage of sulfur in the catalyst deposits accounts for the decreased efficiency of desulfurization in series 3 and series 5 . Material Balance Data. Data are presented in Figure 4 t o show a weight balance of the crude oil charged and the products received from the desulfurizer. The weight per cent of desulfurized oil recovered is less than 1 0 0 ~ oof the charge because of sulfur removal, and some cracking of heavy material which forms a certain amount of gas and leaves a coke deposit on the cataI 3 5 lyst. A film of very SERIES heavy oil also is adsorbed on the surface Figure 3. Sulfur Balance Date
2705
Table 111. Effect of Volume Charged on Composition and Properties of Products Original Crude Temperature of treatment, F. LHSV Vol. of charge, liters Vol. of crude chgd./vol. of bauxite Properties4 Bomb sulfur, wt. % A.P.I. gravity Volumetric compositiona Gasoline and naphtha Kerosene Gas oil Light lube distillate Medium lube dietillate Heavv lube distillate Residuum Distillation loss Properties of residuum" A.P.I. gravity Carbon residue a
Series 1 Series 3 750 750 0.33 0.33 1 3 1.25 0.42
Series 5 750 0.33 5 2.08
2.06 32.5
0.71 41.1
0.88 39.2
1.00 38.2
31.4 4.4 18.6 8.36 1.25
46.3 6.9 27.5 9.9 4.4
42.8 6.3 25.9 11.8 6.7
39.1 5.8 26.3 12.2 7.0
4.2 0.8
6.0 0.5
9.3 0.3
U. I
27.3 2.0 11.3 14.3
....
15.9 2.4
....
17.8 2.4
....
19.4 2.5
From Bureau of Mines crude oil analyses.
of the catalyst. The percentage of oil recovered is progressively higher as the total crude-oil charge is increased, caused partly by a decrease in the percentage of the charge deposited on the catalyst. Analysis of Gas Samples. Noncondensable gas samples representative of each series of runs were analyzed b y low temperature distillation. The results are tabulated in Table IV. Quantity and Quality of Products from Treated Slaughter Crude Oil. Ten liters each of original Slaughter crude, series 1 product, series 3 product, and series 5 product were distilled. The following fractions were made: a gasoline boiling from 110" to 415' F.; a gas oil boiling from 415" to 650' F.; and residue consisting of the material boiling a b o v e 650 O F . The weight per cent sulfur was determined for all the distillation p r o d u c t s , and A.S.T.M. motor octane numbers, both clear and with tetraethyllead added, were determined on the gasoline fractions. Figure 5 presents data which show the weight per cent loss incurred by treating Slaughter crude oil before distillation, and the concurrent increase in SERIES quantity and quality of the gasoO I L ON CATALYST PRODUCT OIL line and gas oil. A COKE / UNACCOUNTED FOR substantial portion of the sulfur was Figure 4. Material Balance Data
INDUSTRIAL AND ENG INEERING CHEMISTRY
2706
Vol. 41, No. 12,
ehrniriating thc lad two steps in the p r o ~ e . f u i TI< herein ~ the ah. phatic sulfides and aromatic sulfides are dcteimined. These steps were omitted because the chemicals used for these t\vo steps also n 111 r m c t with olefins in thc sample, and sometimes the rcactiora i s violent enough to be dangerous. Therefore, in these sample. ana1)zed by the modified method, the residual sulfur might be assumed to be of the aliphatic and aromatic sulfide typcc. The method worked very well for the gasoline from the origirlal crude oil, but the gasoline from the treated crude of seiies J 3 and 5 had such low concentrations of the types of sulfur coni pounds for which analyses were made that none could be dcxtected. Thus the sulfur compounds in the gasoline fractiont from treated crude oil are shown as residual-type sulfur conipounds in Figure 6, This figure shows the percentage of different types of sulfur compounds found in the gasoline from originai ciude, and the relative amounts of sulfur in the seiies 1, 3, and 5 samples. The gasolines from the catalytically treatcd crude oit contain less of the residual-type sulfur compounds than thc gasoIine from the charge material: this indicates that bauxite remove3 some of the more stable types of sulfur compounds but not as efficiently as it does the hydrogen sulfide, mercaptans, antJ elementary sulfur. Composition of Gasoline. The gasoline samples were analyzcci by sulfuric acid absorption method A.S.T.M. D 875, and by silica gel adsorption. No attempt was made t o obtain a paraffin naphthene split or a separation of olefins into one fraction by silica gel adsorption, but thc aromatic percentages obtained b: the acid and gel treatments checked well. The folloaing data weIc obtained by D 875 anal! srb of t h e wamples. ~
w
a 3 [L
u
LL
0 L
t w V
a
:: I-
I w
u_
3
ORIGINAL
I
Original
5
3
berieh I
Serles 8
Serles 5
SERIES
Figure 5. Quantity and Quality of Products removed from the gasoline and ficiin t,he reslduc, by treating the crude oil. The sulfur reduction in the gas oil range was not appreciable, which indlcates that the sulfur compounds i r i this boiling range are not of the unstable, corrosive types. Thcrc is a n appreciable increase in the clear octane numbers of the gasolines from series I, 3, and 5, as 11-ell as in the octane nurnberb when tetraethyllead is added. The increase is greater than could have been caused by desulfurization alone ( 4 ) ; therefore it must be the result of a change in composition of gasolines from treated crude oil. The octane numbers of thcsc gasolines with tetraethyllead added show that the lead susceptibility was improved. Another important factor is the increased yirld of these higher grade products. Group Sulfur Analysis of Gasoline Samples. A modification of a Bureau of Mines procedure for group sulfur analysis ( 2 ) in which hydrogen sulfide, mereaptans, elementary sulfur, disulfides, aliphatic sulfides, and aromatic sulfides (including thiophenes) are removed from the gasoline sample, was employed t o analyze the gasoline samples. Thp modification ronslstcd of
Table IV. Analyses of G a s Formed in Desulfurizing Slaughter Crude Oil at 0.33 LHSV and 750' F.O Scries 1 49.82 Hydrogen 13.95 Methane 1.94 Ethylene 3.93 Ethane 7.80 Propylene 6.50 Propane 4.18 Isobutylene and isobutane 7.60 n-Butylene and n-butane 2.07 Iaopentene and isopentane 2 34 n-Pentene and n-pentane 1.87 Hexane a H18 removed from gas before analyses.
Series 3
Series 5
54.10
68.05
16.86 1.61 4.32 4.97 2.53
12.77 1.56 7.32 4.10 3.93 1.63
5.98
6.20
4.22
1.76 1.97 1.68
1.66
1.90 1.90
The olefins in the gasoline samples from series 1, 3, and 5 depless the percentages of paraffins, naphthrnes, and aromatios in these samples, so that it is difficult to see the change in raticL of these three tgpes of compounds. On a n olefin-free basis the iatios of parafEns, naphthrnes, and aromatics mould he as show> in Figuie 7. This figuie indicate3 no change in the perccntago of naphthenes, xvhile the percentage of aroniatics shows an i n c r e a s ~ in the trratrd samples with a corresponding decrease in paraffins This increase in the ratio of aromatics to paraffins coupled m i t l ; the olefins present ~ o u l darcount for the greater part of the clear ortan? numbrr incwase in the gasolines from treated crude.
GASOLINE FORMED B Y CRACKING OF HEAVY MATERIAL To obtain data on the types oi compounds formed b) t h ~ cmcking of "heavy" material in the crude oil, a sample of the original crude was topped to 41 5' F.and then 1-liter charges of the topped crude, which contained 2 64% by !%eightsulfur and were the equivalent of about 1 4 liters of whole crude, were desulfurized. The topped and desulfurized sample \pas then subjected to a second distillation in which all material in the 110" to 415" F. boiling range was collected This matelial was formed entirely by the cracking reactions in the desulfuriaer. The percentage of cracked gasoline formed is compared with the increase obtained from srries 1, 3, and .5 treatments in the following tahle. Original Series 1 Series 3 Series 5 Topped crude after treatment
Gasullna, 29.32 65.41 40.49 37.57 14.91
74
Gain, % 16:09
11.17 8.25 14.91
Data givon are weight per cent of still charge.
These data show that, the percentage of gasoline formed by
2707
INDUSTRIAL AND ENGINEERING CHEMISTRY
0ecember 1949
(OLEFIN -FREE \
100
BASIS)
c
*
"
ORIGINAL
I
3 SERIES
Figure 6.
SE RlES
Sulfur Compounds in Gasolines
Figure 7. A.S.T.M. D 875 Analysis of Gasoline
treating the topped crude falls between the gain of ,series 1 and stirred into the bauxite-cobaltous nitrate mixture, forming a the gain of series 3 as expected, because the charge was equivalent precipitate on the surface of the bauxite. Heat was applied to t o 1.4 liters of whole crude. dry and oxidize the cobalt-molybdate coating on the surface of the bauxite. The Zn-Mo-Baux catalyst was prepared by subThe cracked material was analyzed for sulfur by the lamp stituting zinc chloride for the cobaltous nitrate in the ,above method. The sulfur content of the material was 0.569% by procedure. weight, which would indicate that the gasoline from series 1 Hydrogen and pressure were used with these catalysts and should have a sulfur content of about 0.19% by weight instead of bauxite was tried with hydrogen and prcssure. Bauxite, when the 0.12% by weight actually found. Thus the treatment of used a t a pressure of 225 pounds per square inch gage with a the topped crude indicates with a fair degree of Certainty that the sulfur found in the gasoline obtained from series 1, 3, and 5 samples comes largely Table V. Comparison of Efficiency of Catalysts for Desulfurizing Slaughter Crude Oil from the cracked material.
EXPERIMENTS WITH OTHER CATALYSTS A few catalysts other than bauxite have been tried in desulfurization experiments with Slaughter crude oil. Table V shows the extent of the experiments with these catalysts. The catalyst designated CoMo-Baux was prepared by wetting 3000 grams of 14- t o 20-mesh Arkansas bauxite with a water solution containing212 grams of cobaltous nitrate. A soIution of 128 grams of ammoniummolybdate containing 96 ml. of concentrated ammonium hydroxide was
Catalyst Pressure, lb./sq. inch gage Hydrogen rate, cu. feet/liter of charge Temperature Vol. of charge liters Vol. of char@;e)vol.of catalyst LHSV Sulfur, % by wt. Specific gravity, 60/60° F. A.P.I. gravity Visaosity a t looo F., seconds Volumetric composition, from Bureau of Mines crude oil analyses Gasoline and naphtha Kerosene Gas oil Light lube diatillate Medium lube distillate Heavy lube distillate kesiduum Distillation loss Blend cuts 1-7 (to 392' E'.) Sulfur % Aromdtics olefins Naphthenes Paraffins Bromine number Blend cuts 8-12 (392-646' F.) Sulfur, %
+
Untreated
Bauxite 0
.... . . I .
2.06 0.863 32.5 46
0 750 1 0.42 0.33 0.71 0.820 41.1 32
Bauxite 225 10 750 1
0.42 0.33 0.40 0,801 45.2 32
Co-MoBaux 225
10 750 1 0.42 0.33 0.17 0.810 43.2 34
00-Mo-
Co-MoBaux 225 1.5 750 1 0.42 0.33 0.30 0.803 44.7 32
0.42 0.33 0.35 0.809 43.4 32
B&ux 225 0 750
I
Zn-Mo Banx 225 10 750 1 0.42 0.33 0.32 0.798 45.8 32
31.4 4.4 18.6 8.35 7.25 0.7 27.3 2.0
46.3 6.9 27.5 9.9 4.4
55.3 7.8 30.6 4.4
49.4 8.3 34.1
56.8 7.4 25.4 6.9 1.3
50.6 7.3 27.0 11.2 0.2
59.9 7.8 27.6 2.9
4.2 0.8
1.1 0.9
4.1 0.6
1.2 1.0
1.1 2.6
1.4 0.4
0.31 22.6 31.0 46.4 1.86
0.12 36.1 26.8 37.1 23.89
.,.. ,...
1.49
1.19
, , . .
....
.... ....
,
..,
.... .,,.
0,0067 29.1 23.0 47.9 10.19
.....
,... .... ,,.. ....
..,. ..,.
.....
0.0263 26.6 18.3 55.1 7.45
0.0316 24.1 21.5 54.4 5.75
0.52
0 58
2708
INDUSTRIAL AND ENGINEERING CHEMISTRY
hydrogen flow rate of 10 cubic feet per litcr of oil charged, s h o w better desulfurizing efficiency and more efficiency in reforming the heavy material than it shows a t atmospheric pressure VI ithout hydrogen. Co-110-Raux demonstrated the greatest efficiency for desulfurization by reducing the sulfur content of the crude oil from 2.06 to 0.179;b by weight. Zn-hlo-Baux gave the greatest conversion by increasing the gasoline content of the oil from 31.4 t o .!19.97~ by volume. D 875 analyses of some gasoline blends from Hempel distillations show that the use of hydrogen pressure tends t o increase the percentage of paraffins and decrease the percentage of olefins as indicated by the bromine number. CONCLUSION I t is evident that the sulfur content of a crude oil can be reduced greatly by catalytic desulfurization. This preliminary sulfur reduction would aid in the prevention of corrosion in the subsequent steps of refining the oil. The products would be of higher quality and thus more valuable. However, t o be eco-
nomical, morc study ~ o u l dbe the coke formation during the of lower iron content or one of be possible to reduce the coke ment of the process is deemed of the Bureau of Mines.
Vol. 41, No. 12
required to find a way to reduce desulfurization. With a bauxite the synthetic catalysts, it should formation; but further developoutside the scope of the actlvity
ACKNOWLEDGMENT The authors wish to express their indebtedness to H. >I. Smith and C. C. Ward, under whose supervision the work was performed. LITERATURE CITED (1) Dean, E. W., Hill, H. H., Smith, N , 9. C., and Jdcobs, W. A.,
Bur. X i n e s Bull. 207 (1922). ( 2 ) Guthrie, Boyd, and Simmons, M. C., Bur. Mines, Rept. Invest. 3729 (1943). ( 3 ) Kraemer, A . J., and Lane, E. C , Bur. Milines Bull. 401 (1937). (4) Ryan, J. G., IND. ESG.C H E Y . , 34, 894-32 (1942). RECEIVED March 24. 1949.
Desulf urization-Hydrogenation of High-Sulfur Catalytically Cracked Cycle Stock ALEXIS VOORHIES,JR., AND W. M . SMITH Esso Laboratories, Esso S t a n d a r d Oil C o m p a n y , B a t o n Rouge, La. H y d r o g e n a t i o n a t 750 p o u n d s per s q u a r e i n c h pressure of a h i g h - s u l f u r , refractory, catalytically cracked cycle stock r e s u l t s i n p a r t i a l conversion of condensed-ring a r o m a t i c s t o single-ring a r o m a t i c s a n d virtually complete removal of s u l f u r . Hydrogenation catalyst activity is m a i n t a i n e d , hydrogenated product yield is 100 v o l u m e 70,a n d little change i n boiling r a n g e occurs. Catalytic cracking characteristics of t h e cycle s t o c k a r e improved by hydrogenation t o t h e point where it is a t least a s desirable a cracking stock a s t h e original virgin gas oil. S u l f u r removal prior t o cracking of a h i g h - s u l f u r stock is necessary for t h e production of a gasoline m e e t i n g s u l f u r specifications without further treating.
I
N A previous article ( 1j the hydrogenation of cycle stocks derived from the cat,alytic cracking of gas oils was discussed. I n that paper it was shown that cycle stocks from catalytic cracking contain refractory aromatic-type conipoiients which resist further cracking, and that hydrogenation of these aromatic-type components t,o naphthene ring derivatives provides an improved catalytic-cracking feed stock which is superior in quality even to the original virgin gas oil from which the cycle stock was derived. In comparing the quality of unhydrogenated and hydrogenat,ed cycle stocks as catalytic cracking feed stocks it was shown that, with a hydrogenated cycle stock, high conversions are obtaincd under similar cracking conditions; that, for a given degree of cracking, less carbon and more gasoline result; and that gssolines derived from the cat'alytic cracking of a hydrogenated cycle stock are a t least as good in quality (as evidenced by octane numbers) as the gasolines derived from the catalytic cracking of the virgin gas oil from which the cycle stock was originally obt,ained. Hydrcgenation conditions used for the conversion of aromatics
t o naphthenes ( 1 ) involved the use of a sulfur-resistant cat,alyst a t the high pressure of 3000 pounds per square inch. The use of high pressure was necessary in order to obtain complete hydrogenation of aromatics to naphthenes with the sulfur-resistant catalyst employed. Inasmuch as all feed stocks investigated contained appreciable amounts of sulfur, the use of a sulfur-resistant catalyst was required for the maintenance of a constant degree of catalyst activity and thereby a continuous and practicable hydrogenation process. Under these conditions, yields of hydrogenated cycle stock were 100 volume % or more in all cases, with little change in boiling range and virtually complete removal of sulfur. I n the previous article it n-as also shown t h a t under milder hydrogenation conditions (750 pounds pcr square inch instead of 3000), partial saturation of aromatics in catalytically cracked cycle stocks to naphthenes n-as obtained instead of the rather complete saturation u-hich resulted with the use of the higher pressure. Under these milder hydrogenation conditions catalyst activity was maintained and, in addition, rather complete sulfur removal resulted, even when the cycle stock used contained a large quant]ity of sulfur. This degree of desulfurization is especially notable because the sulfur-containing molecules in cycle stocks are very refractory, and sulfur removal from this type of material is difficult by ordinaiy methods. The present paper discusses further this lower pressure hydrogenation of high-sulfur catalytically cracked cycle stocks. Under low pressure hydrogenation conditions suitable for t,he maintenance of catalyst activity it is shown that: Despite only partial saturation of the cycle st,ock,it is superior t o the virgin gas oil in cracking characteristics, giving less carbon at equivalent conversion. However, this superiority is not as great as in the case of the completely saturated cycle stock. The
