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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Additional Recent Literature on Corn-Waste Utilization Atkinson, U. S. Patents 1,472,318 (October 30, 1923); 1,538,505(May 19, 1925); 1,572,510(February 9,1926). Bache-Wiig, U. S. Patent 1,455,471(May 15,1923). Bcrntson. U. S.Patent 1,516,701(November 25, 1924). Burkey. Iowa State Coll. J . Sci., 3, 57 (1928). Burtt-Davy, S. African J . Ind., 6, 357 (1922). Clemen, Iowa Agr. Expt. Sta., Circ. 339 (1929). Darling, Raw Material, 6, 97 (1922). Ditman, U. S. Patents 1,456,540(May 29, 1923); 1,522,618(January 13, 1925). Dorner. British Patent 286,211 (February 28, 1927). Emley, Paper Trade J., 88,No. 25,61 (1929). Fred and Peterson, J. IND. END.CRBM.,13, 211 (1921). Hinde, U. S. Patent 1,623,184(April 5, 1926); British Patent 304,171 (July 14, 1927). Hulbert. Paper Trade J.. 87, No. 13, 51 (1928); P a p n Mill, 61, No. 39, 12, 38 (1928). Jackson, Pulp Paper Mag. Can., 26, 713 (1928); Paper Mill, 60, N o . 36, 2, 20 (1927).
Vol. 22, N o . 12
Kirkpatrick. Chem. Met. Eng., 38, 401 (1928). La Forge, J. IND.ENG. CHSM., 10, 925 (1918); 13, 1024 (1921); 16, 499
(1923);16, 130 (1924). La Forge and Mains, I b i d . , 16,823,1057(1923). Ling and Nanji, J . Chcm. Soc., 123,620 (1923). Mains and La Forge, IND.ENG.CHEM.,16,356 (1924). Marsh, Jbid., 13, 296 (1921). Maxwell, Proc. Iowa Acad. Sci., 33, 174 (1926). Naudain, A m . Food J . BO, 508 (1925). Naylor, U. S. Patent 1,573,734(February 16, 1926). Peterson, Fred, and Verhulst, J. IND.END.CHBM.,18,757 (1921). Peterson and Hixon, Ibid., Anal. Ed., 1, 65 (1929). Phillips, J . A m . Chcm. Soc., 49,2037 (1927);60,1986 (1928). Rommel, IND.ENC. CHBM., 20, 587, 716 (1928); "Farm Products in Industry,'' Rae D. Henkle Co.. Inc.. New York. 1929. Skolnik. U. S.Patent 1.599.253 (September 7, 1926). Spirindelli, Notis. chim. ind.. 1, 412 (1926). St. Klein, Wochbl. Papierfnbr., 69, 1175 (1928). Sweeney, U.S. Patent 1,639,152(August 16.1927). Taylor. Chcm. Age (N.Y.),81, 549 (1923). Webber, Proc. Iowa Acad. Sci., S i , 290 (1924). Williamson, Burr, and Davison, IND. END.CHSM., 16,734 (1924).
Catalytic Reactions of Sulfur Compounds Present in Petroleum' I-High-Sulfur Naphthas in Contact with Nickel and Iron Catalysts J. C. Elgin, G. H. Wilder, and H. S. Taylor FRICK CHEMICAL LABORATORY OB PRINCETON UNIVERSITY, PRINCETON, N. J.
This paper presents results obtained in a study of the action of nickel and iron contact catalysts on the sulfur content of high-sulfur naphthas, carried out as the preliminary investigation in a systematic study of the catalytic reactions of the sulfur compounds in petroleum. Experiments have been made in the vapor phase a t 300' and 400' C., a t atmospheric pressure, and with and without added hydrogen. Adsorption of sulfur from the naphthas in the liquid phase has also been determined. It is shown that a reduction in the sulfur content of naphthas is effected by passage, in the vapor phase, over a nickel or an iron catalyst, nickel being the more efficient. Sulfur may be completely removed in contact with the initially sulfur-free nickel catalyst, but the catalyst undergoes a decrease in activity as sulfurization proceeds. It reaches a state in which it possesses a constant, definite, though reduced activity. Sulfur removed is converted to hydrogen sulfide. Hydrogen added to the vapor stream
tends to increase the extent to which sulfur is removed, and effects the removal of sulfur not affected by t h e catalyst in its absence. The percentage of sulfur removed under a fixed set of conditions varies with the naphtha sample studied. This is attributed to variations in the nature of the sulfur compounds present in the naphthas. All of the sulfur present in the naphthas studied is not removed under t h e present experimental conditions. Nickel and iron catalysts do not adsorb from the liquid phase all sulfur present in the naphthas. The preliminary results suggest that, with addition of hydrogen, alternate sulfide formation with the catalyst surface and its reduction by hydrogen may play an important role in the removal of sulfur and, in consequence, that variation in the ratio of hydrogen pressure to t h e sulfur compound pressure may increase the effectiveness of the catalyst action.
. . . . . . , . , . . .. HE present communication is concerned with results obtained in the first phase of an investigation which lias for its object a complete study of the reartions of sulfur compounds in petroleum in the presence of contact catalysts, alone, or with the addition of hydrogen The fact that metallic hydrogenation catalysts exhibit a specific affinity for sulfur suggested that the actian of a metallic nickel catalyst be studied first. The action of an iron catalyst, very active in the synthesis of ammonia, has also been studied. Since there is available very little fundamental information
T
1 Received October 18. 1930. Thrse papers contain rrsults obtained in an investination on 'Specific Absorbents for Sulfur Compounds in Pe-
troleum" listed a* Project No. 40 of American Pet-oleum Institute Research Financial assistance in this work has been received from a research f u n d donated by John D Rockefeller This fund is being administrred by the inst:tute with the coliperation of the Central Petroleum Committee of the National Rrsearch Council. Hugh S. Taylor, of Princeton University, is director of Project hTo. 40.
pertaining to this field, the preliminary investigations have been carried out with high-sulfur naphthas. In Part I1 the study will be continued with mixtures of pure-sulfur compounds in definite hydrocarbon materials. Cata!ysts NrcmL-The metallic nickel catalysts employed were obtained from two sources. One material was prepared in several batches in this laboratory by the following method (4). Nickel was precipitated on a kieselguhr support as the hydroxide by expelling excess ammonia from a suspension of kieselguhr in ammoniacal nickel nitrate solution in a current of air at 70' C. The precipitate was filtered, dried in air at 100" C., and reduced in hydrogen. The temperature during reduction was raised slowly to 500" C. over a period of 5 hours and maintained at this temperature until reduction
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I N D U S T R I A L A N D ENGINEERING CHEMISTRY
was complete. The material thus obtained is a fine black powder. As it readily oxidizes when exposed to air. it was preserved under thiophene-free benzene during the investigation. This material is known to be an extremely active hydrogenation catalyst. It was prepared in several batches of several hundred grams each. The results obtained with samples from various batches were uniform. b The second catalytic material was obtained in quantity through the courtesy of E. I. du Pont de Nemours and Company. It had been prepared by sodium carbonate precipitation on kieselguhr from a nickel sulfate solution, and had been compressed into tablets. This rendered it more suitable for vapor-phase experiments. The material was obtained in unreduced form and the reduction carried out in this laboratory as described above. This material is also known to be a very active hydrogenation catalyst. Both materials exhibited practically the same adsorptive capacity for the sulfur in naphthas. IRoN-This catalyst was promoted with potassium and aluminum oxides and is known to be very active in the synthesis of ammonia. It was obtained through the courtesy of P. H. Emmett, of the Fixed Nitrogen Research Laboratory. It was screened to a uniform size and reduced in hydrogen before use.
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Methods and Apparatus
The determinations of sulfur removed from the n a p h t h a in liquid phase by the catalytic materials were made by agitation of known weights of catalyst with measured quantities of naphtha in a closed flask, and analyzing for sulfur before and after. Adsorption was apparently instantaneous. As the catalyst was preserved under benzene, care was taken to prevent contact with air and the addition of appreciable amounts of benzene in transferring it to the naphtha. One experiment was carried out in which the naphtha was filtered through a column of catalyst under slightly increased pressure. The vapor-phase catalytic experiments were carried out in a flow system. The apparatus underwent several stages of development with minor alterations in each. I n final form it consisted of an electrically heated vaporizing chamber (in early experiments this was direct-fired but in order to obtain closer temperature control electrical heating was substituted) into which the naphtha was passed at a measured rate and in which it was completely vaporized as rapidly as it entered; a reaction tube containing the catalyst and maintained at the desired temperature in an electric furnace; a water-cooled condenser; a receiver and draw-off for the condensate; and a trap surrounded by a freezing mixture, through which exit gases passed to a gas scrubber containing cadmium chloNaphthas Investigated ride or lead acetate solution in which hydrogen sulfide wan Two straight-run and a cracked naphtha, obtained through determined. A thermometer was placed in the catalyst. the courtesy of J. B. Hill, of the Atlantic Refining Company, The temperature of the vaporizing chamber necessary to have been studied. The properties of these naphthas are insure complete flash vaporization was determined for each naphtha. Temperatures between 350" and 400" C. were summarized in Table I. satisfactory. Table I-Properties of Naphthas Investigated While under investigation a catalyst was preserved under STRAIGHT-RUN CRACKED benzene between experiments. Before each run the appaPROPERTY 2 3 1 ratus was swept out and all benzene distilled off in a current of purified nitrogen. At the end of each run the catalyst was Per cent Per cenl Per cent cooled in nitrogen before immersion in benzene. It was Sulfur: 0.410 0.278 0.357 Raw necessary to proceed in this manner in order to prevent 0.320 0.352 0.281 NaOH washed Hydrogen sulfide and free sulfur: oxidation of the catalyst. 0.03 0.035 0.043 After 3 months' standing The naphthas were vaporized and passed over the catalyst ... 0.05 ... After 8 months' standing Mercaptan sulfur: at the rate of 100 cc. of liquid per hour, I n the vapor-phase 0.015 0.041 Method of Faragher, Morrell, and Monroe 0.057 0.09 ... ... Method of Borgstrom and Reid experiments the weight of the catalyst sample was 20 grams, Sour Sour Sour Doctor except in one series of experiments in which it wao varied. 9 Saybolt - 5 Saybolt Yellow Color 49.3 50.6 53.8 Gravity, * A. P. I. This weight of the material was 3.0 cm. in diameter and 3.5 c. c. c. cm. high, giving an apparent volume of approximately 25 CC. Assay distillation: 4s 42 30 I. B. P. I n experiments where hydrogen was added the rate of flow 100 116 110 25 per cent over of this gas was 100 cc. per minute. The naphtha condensed 190 212 180 75 per cent over 299 234 268 F. B. P. after passing the catalyst was caught in separate 25-cc. portions and the sulfur content of each separately determined. The straight-run naphthas, 1 and 2, came from the same Changes in the action of the catalyst in removing sulfur during crude, but the stills were being run under different conditions a run were thus followed. The evolution of hydrogen sulfide at the times when the samples were obtained. Determina- was qualitatively determined by leading the exit gases through tions made at intervals during the period of the research cadmium chloride or lead acetate solution. The A. S. T. M. lamp method was employed to determine showed no detectable change in total-sulfur content of the naphthas. Sulfur removed by a cadmium chloride solution sulfur content of the naphthas. I n several cases it was neceswas taken as hydrogen sulfide and that by elementary mer- sary to use the modification suggested by Edgar and Calincury as free sulfur. The determination of mercaptan sulfur gaert ( 2 ) , in which the wick tube is surrounded by a copper was made by the method recommended by Faragher, Morrell, collar, to control the height of the flame. Checks on the and Monroe (3). The method developed by Borgstrom and determinations were generally made. I n determining reReid (1) for determination of mercaptans present alone in action to doctor both aqueous and alcoholic plumbite soluhydrocarbon materials was also applied to their determination tions were used, A negative test was taken to indicate in these naphthas, but it could not be successfully used with absence of mercaptans. Color and odor of treated naphthas the cracked naphtha. The applicability of the latter method were observed and recorded. When Engler distillations in case of naphthas is unknown and the confidence to be were made on the treated naphthas the standard method was placed in results obtained by either is uncertain. They used. apparently, however, should give order of magnitude. An Removal of Sulfur from Naphthas in Vapor Phase interval of about 6 months intervened between the liquidNICKEL CATALYSTS-NO Hydrogen Added. The curves of phase adsorption experiments and the determination of Figure 1 show typical results obtained when the naphthas mercaptan sulfur.
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Volume ofNaphiho Posed oyer Cotalysf Figure 1-No Hydrogen Added
- cc
8.
4 03 4
B
$02 x
d
5
0.1
4
4
300 400 500 600 700 800 900 /#OO Volume of Nakhiho Passed over Catulysf CC. Figure 2--Hydrogen Added Removal of Sulfur f r o m Naphthas in Vapor Form in Contact with Metallic Nickel Catalysts Temperature, 300' C. Curves 1.2, and 3 show the results with naphthas 1, 2, and 3, respectively. The initial sulfur contents were 0.41, 0.278, and 0.367 per cent, respectively.
0
IO0
200
-
studied were passed in vapor form over initially sulfur-free nickel catalysts a t 300' C. The sulfur content of each successive 25-cc. volume of the condensed product is plotted against the total volume of naphtha which has passed over the catalyst from the start of the run. The curves for the different naphthas possess the same general characteristics. After passing in contact with the catalyst, the f i s t portions of naphtha contained extremely little sulfur. The sulfur content of the product first underwent a rapid increase, than a slower rise up to a point after which no further change occurred. Thereafter, the sulfur content was independent of the volume of naphtha which had been passed over the catalyst. This condition is called in this paper the "steady state."
Vol. 22, No. 12
nature and reactivity of the sulfur compounds present. When hydrogen was not added to the naphtha vapor, no hydrogen sulfide was evolved until the steady state was approached. At the sharp bend in the curves of Figure 1its evolution commenced. It then increased slowly, finally reaching a constant rate, which thereafter continued as long as the catalyst was used. I n the case of naphtha 1 the product was sweet to doctor up until 475 cc. had passed over the catalyst. At this point the sulfur content was 0.202 per cent. Thereafter the product was sour to doctor, but its reaction in this respect was very considerably improved in comparison with the untreated naphtha. As will be subsequently seen, when the sulfur content of naphtha 1 had been reduced to 0.202 per cent, it was always sweet to doctor. These results indicate that all mercaptans may be removed in contact with the catalyst, and that nearly complete removal is effected in a single passage a t the steady state. I n the case of naphtha 2 the product was always sweet to doctor and with the cracked naphtha, No. 3, sour after the first 75 cc. Comparison of the reductions in sulfur effected at the steady state, given in Table 11, with the quantities of mercaptan sulfur present in each naphtha, given in Table I, shows conclusively that the catalytic decomposition of sulfur compounds other than mercaptans is effected in contact with the catalyst.
Nofs-Preliminary results with solutions of pure sulfur compounds in sulfur-free naphtha show that butyl and isobutyl mercaptans and propyl sulfide are decomposed in contact with the catalyst a t the steady state with the evolution of hydrogen sulfide.
It should be noted that fresh nickel catalyst is able to adsorb sulfur from the naphthas in liquid form after they have been passed in vapor form over the catalyst. For example, with naphtha 1 the product a t the 150-cc. point containing 0.132 per cent sulfur was reduced to 0.082 per cent, the product at the 400-cc. point, containing 0.194 per cent sulfur, was reduced to 0.104 per cent, and the product at the 550-cc. point, containing 0.218 per cent, was reduced to 0.147 per cent and rendered sweet to doctor by this method. A passage rate of 100 cc. of liquid per hour with 20 grams of catalyst, which occupied an apparent volume of 25 cc., Note-During use for a prolonged period a further slight decrease in corresponds roughly to a space velocity of 1800 cc. of vapor activity of the catalyst seems to occur. This, most probably, IS to be attributed to a poisoning of the catalyst by accumulation of heavy products per hour per cubic centimeter of catalyst, on the assumption from a slight cracking of the naphtha. That the sulfur-removing action that hexane represents the average molecular weight of the of the catalyst has actually reached a constant state and does not tend to naphtha, Tripling this space velocity by decreasing the become zero is shown still more conclusively in later experiments. weight of catalyst decreased the amount of sulfur removed Although the curves are of the same form, they show that, from the naphtha in a single passage over the catalyst. The quantitatively, the amounts of sulfur removed a t each stage passage velocity used represents about the upper limit at were dependent upon the naphtha in question. I n the case of which all removable sulfur is removed in a single passage. Experiments in which the catalyst tube was filled with naphtha 1the steady state was reached after 500 cc. had been passed in contact with the catalyst, but very little change ground Pyrex glass showed no marked reduction in the sulfur occurred after about 300 cc. (It is evident that the volume content of the naphthas due to purely thermal decompoof naphtha which must be passed before the steady state is sition. When passed in vapor form a t 300" C. over Pyrex reached will depend upon the weight of catalyst used.) glass the sulfur content of naphtha 1 was reduced only from Apparently it was reached in a shorter period with the other 0.410 per cent to 0.378 per cent. It is evident that a sulfur-free metallic nickel catalyst is two naphthas. The amounts of sulfur removed from each naphtha a t the able to remove entirely all sulfur from naphthas in the form of steady state are recorded in Table 11. It is evident that vapor. (With larger amounts of catalyst initial portions of the action of the catalyst toward the sulfur in naphthas is condensed product containing less than 0.01 per cent sulfur characteristic, but that the reduction in sulfur content effected were obtained.) With continued use the catalyst becomes will depend upon the naphtha. The difference exhibited by less efficient in its action, but it eventually reaches a steady different naphthas is undoubtedly due to variation in the state, and then its effectiveness in reducing the sulfur content
I N D U S T R I A L A N D ENGINEERTNG CHEMISTRY
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becomes constant. The results point to a mechanism of sulfur removal at the steady state different from that occurring while the catalyst surface is initially sulfur-free. Effect of Adding Hydrogen. The rate of hydrogen flow was 100 cc. (0" C., 760 mm.) per minute and of naphtha, 100 cc. of liquid per hour. Assuming its average molecular weight to be represented by hexane, the latter corresponds to a p proximately 370 cc. (0" C., 760 mm.) of naphtha vapor per minute. This means that a 3.7 to 1 mixture or a partial pressure of 600 mm. of naphtha and 160 mm. of hydrogen was employed. I n Figure 2 the results obtained when hydrogen was added to the naphtha in the above ratio are plotted. I n general, the curves exhibit the same characteristics as those where no hydrogen was added (Figure l), but the amounts of sulfur removed at each stage were increased. The sulfur content of the first 25 cc. of product was appreciably lower in this case, and a greater continuous removal of sulfur at the steady state was effected. The increased effectiveness of the catalyst in removing sulfur was most pronounced with naphtha 1 and least with naphtha 2. The percentage of the total sulfur removed from these two naphthas was roughly the same, but the additional reduction caused by addition of hydrogen was widely different. All mercaptans were removed, the product obtained throughout the run being sweet to doctor. Small quantities of dissolved hydrogen sulfide were present, but the change in total sulfur on washing with caustic soda was scarcely perceptible. The results obtained at the steady state with hydrogen added are given in Table 11. It is significant that with hydrogen added the evolution of hydrogen sulfide commenced near the beginning of a run. It increased somewhat as the steady state was approached and then remained constant. It is evident that the addition of hydrogen increases the effectiveness of the catalyst in removing sulfur. The naphthas still show the differences in behavior, but the characteristic action of the catalyst is the same. The relative effect of the addition of hydrogen on the effectiveness of the catalyst vanes Table 11-Removal
NAPHTHA
in the first passage, was reduced to 0.206 per cent on re-running. It was then sweet to doctor, indicating that mercaptans had been completely removed. Additional re-running did not further lower the sulfur content. Naphtha 3, the sulfur content of which was lowered to 0.317 per cent a t the steady state in the first passage, was reduced to 0.309 per cent on further re-running. It was still decidedly sour to doctor. Apparently the mercaptans in this naphtha are removed with difficulty by the catalyst. These results emphasize the fact that a certain portion of the sulfur present in each naphtha is not affected by the catalyst under the conditions thus employed. I n the first passage over the catalyst under the conditions employed the major portion of sulfur r e movable by this method was removed. Action of Catalyst ut Steady State. This was studied with a catalyst sample which had been carried to the steady state with naphtha 1 at 300" C. and no added hydrogen. It continuously reduced the sulfur content of this naphtha to 0.238 per cent. A series of experiments with each naphtha with and without hydrogen was then made with this catalyst. The results are summarized in Table 111. I n each experiment 300 to 500 cc. of naphtha were passed over the catalyst and the sulfur content of successive 25-cc. portions of the product was independently determined as in previously described experiments. The sulfur contents were practically constant throughout a run, and there was no initial period of change, as was the case with the freshly prepared nickel catalyst. Note-In the event that a run with no hydrogen added followed one at the higher temperature in which hydrogen had been added, there seemed to be a tendency for the sulfur content of the first portions of the product to be lower than the average. A gradual increase to a constant value then took place.
The figures in columns 4 and 5 represent the average sulfur content of the entire volume of naphtha passed over the catalyst in each run. The results demonstrate conclusively that a nickel catalyst attains a state in which its action in removing sulfur becomes constant and does not tend to lose its effectiveness entirely
of Sulfur from Naphthas i n Vapor Form a t 300'C. a t Steady State b y a Metallic Nickel Catalyst Which Was
~..--... ..SULFUR
Initially Sulfur-Free
0.410 0.278 0.367
HYDROGEN ADDED
NO H Y D R O G E N ADDED
Reaction to doctor
Sulfur
product Straight-run: 1 2 Cracked, 3
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70
%
0.19 0.188 0.047
46.3 67.6 13.1
Barely sour Sweet Sour
Sulfur 'Ontent productOf
Reduction
Sulfur removed
%
%
%
0.14 0.08 0.27
0.27 0.198 0.087
65.9 71.2 24.3
Reaction to doctor
YEo:'
hydrogen
% Sweet Sweet Sweet
0.08 0.01 0.04
In experiments cited in a later section it will be seen that repassage over the catalyst will reduce this t o 0.20 per cent, after which it is sweet to doctor. The sulfur content of this naphtha cannot be reduced below 0.20 per cent at the steady state unless hydrogen is added.
with different naphthas. There appears to be no simple relation between the sulfur contents of the naphthas and the reductions in sulfur effected with or without added hydrogen. Whether the effectiveness of the catalyst in removing sulfur at the steady state will be further increased by increasing the ratio of hydrogen to naphtha vapor was not investigated in the present experiments. This question will be studied in experiments now under way. Effect of Re-running the Naphthas. Re-running the naphthas over the catalyst a t the same temperature, after it had reached the state where its action became constant, was studied. I n each case only naphtha which had been passed over the catalyst after it attained the steady state activity was re-run. A further slight reduction in sulfur content was effected, but repetition of this treatment did not continue to reduce the sulfur content. Naphtha 1, whose sulfur content was reduced to 0.224 per cent a t the steady state
with continued use. They confirm the conclusion that sulfur is removed when hydrogen is added to the naphtha vapor which is not affected when it is not added. If the hydrogen was added to naphtha vapor passed in contact with the initially sulfur-free catalyst, a greater reduction in sulfur a t the steady state was effected than if, as in the experiments recorded in Table 111, the hydrogen was added after the catalyst had previously reached a steady state with naphtha vapor alone. Runs 1 to 4 show that at 300' C. the addition of hydrogen after the catalyst had attained the steady state with naphtha vapor alone effected no greater removal of sulfur than with no hydrogen added. It is possible that, if continued for a considerably longer period, runs 3 and 4 might have shown a very slow increase in the amount of sulfur removed. At 400" C. the addition of hydrogen effected a greater reduction in sulfur than when it was not added. Comparison
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of the results of runs 12 to 15 with those recorded in Table I1 shows that it was necessary to re-run the naphtha at 400" C. several times with hydrogen in order to reduce its sulfur e 03
