February, 1926
ILVDUSTRIAL AND ENGI-VEERING CHE.1IISTRY
bon disulfide, alkyl sulfide, alkyl disulfide, thiophene, sulfoxide, and sulfone. Both strengths of alkali effectively removed the hydrogen sulfide as Sa2S. The alkyl sulfate was completely removed by the 10 per cent solution and was partially removed by the 0.05 per cent solution as KazS04. Sixteen cubic centimeters of the 10 per cent alkali removed about 50 per cent of the mercaptan as sodium mercaptide. Sixteen cubic centimeters of the 0.05 per cent alkali solution removed about 25 per cent of the mercaptan. These facts probably explain why it is best to subject a cracked distillate of high sulfur content to an alkali wash or to a sodium plumbite treatment before using sulfuric acid. Severe cracking of a petroleum distillate containing sulfur yields hydrogen sulfide as the final product. However, in actual cracking operations it is probable that hydrogen sulfide is formed along with free sulfur, mercaptans, and other sulfur compounds. Tf an alkali treatment is employed with a distillate of this character, hydrogen sulfide will be completely and mercaptans partially removed. If sodium plumbite is used, hydrogen sulfide will be completely removed as lead sulfide and mercaptans will be transformed to the corresponding alkyl disulfides, provided enough free sulfur is in solution to react with the resulting lead mercaptide. If the free sulfur is not sufficient for this purpose, the necessary quantity of flowers of sulfur should be added. It is evident that either the alkali or sodium plumbite treatment will render more effective a subsequent acid treatment with a distillate of this character, since sulfuric acid does not remove sulfur when present as hydrogen sulfide and removes mercaptans, as previously indicated, with some difficulty.
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The reaction of naphtha solutions of mercaptans with sodium plumbite and flowers of sulfur has been explained by Wendt and Diggs3 and by Wood, L o w , and Faragher.2 Effect of Silica Gel, Fuller’s E a r t h , a n d A l u m i n i u m Oxide
The silica gel was used as received. The fuller’s earth came from Gadsen County, Florida, and was preheated for 2 hours a t 250” C. The aluminium oxide was preheated for 3 hours a t 1000° C. Since the degree of fineness, porosity, and heat treatment are vital factors which affect the desulfurizing properties of these materials, the results should not be considered as indicating desulfurizing efficiencies, but rather as indicating the types of sulfur compounds likely to be most affected. The experiments were carried out in the closed system in the usual manner using 4 grams of each material with 50 cc. of each stock solution for 1 hour a t room temperature. The naphtha was recovered without washing and the sulfur content determined. Tahle 111-Average Per cent of Sulfur in Naphtha Treated w i t h Silica Gel, Fuller’s Earth, and Aluminium Oxide STOCK Sorurrov Free sulfur Isoamyl mercaptan Hydrogen sulfide Dimethyl sulfate Methyl p-toluenesulfon ate Carbon disulfide n-Butvl sulfide
Silica gel 0.24
0.09 0.03 0.00 0.03 0.08 0.13 0.24 0.08 0.00 0.00
Fuller’s earth 0.25 0.28 0.03 0.00 0.05 0.08 0.29 0.32 0.08 0.00
0.00
Aluminium oxide 0.25 0.24 0.03 0.03 0.lA 0.08
0.30 0.36 0.09 0.05
0.07
The results shown in Table I11 indicate that silica gel is, in general, a more effective desulfurizing agent than fuller’s The sodium plumbite solution used in these experiments earth or aluminium oxide. The silica gel completely removed was prepared according to directions in Technical Paper 298, the alkyl sulfate, sulfoxide, and sulfone, removed about 75 E. S. Bureau of Mines. Carefully checked quantitative per cent of the mercaptan and the methyl p-toluenesulfonate, experiments were carried out in the closed system by treat- and removed smaller percentages of some of the others. The ing 50 cc. of each stock solution with 4 and 16 cc. quantities fuller’s earth completely removed the alkyl sulfate, sulfoxide, of sodium plumbite solution for 1 hour a t room temperature. and sulfone, and partially removed the methyl p-tolueneThe recovered naphtha was washed with water and the per sulfonate, but had little effect on the others. Aluminium oxide partially removed mercaptans and the alkyl sulfate, cent of sulfur determined. These results indicate that at room temperature the sodium but had little effect on the other sulfur compounds. The plumbite solution had no effect on free sulfur, methyl p- action in all cases seems to be due to adsorption. Free sulfur, toluenesulfonate, carbon disulfide, alkyl sulfide, alkyl disul- hydrogen sulfide, carbon disulfide, and thiophene were apfide, thiophene, sulfoxide, and sulfone. The addition of parently not affected by any of these materials. I n all these flowers of sulfur proportionately increased the sulfur content experiments it should be kept in mind that the sulfur was in the liquid phase a t room temperature and was shaken with of the naphtha in every case. The sodium plumbite removed the alkyl sulfate as PbS04 the material in a closed system, rather than filtered through and the hydrogen sulfide as PbS. The addition of flowers it as is frequently the custom. The sweetening action usually attributed to silica gel is of sulfur is unnecessary and only serves to increase the probably due to the ease with which it adsorbs mercaptans, sulfur content of the naphtha. Effect of S o d i u m P l u m b i t e
Arsenic in 1925 The production and sales of arsenic in the United States in 1925 nearly equaled the large output of 1924, according to Victor C. Heikes. of the Bureau of Mines. Four companies t h a t produced white arsenic in the United States in 1925, the American Smelting and Refining Company, United States Smelting, Refining and Mining Company, Anaconda Copper Mining Company, and the Jardine Mining Company, reported sales which amounted t o about 12,000 short tons which sold a t from 3 t o 6 cents a pound. Thc quantity sold is nearly equal to the total white arsenic produced About 8000 tons were reported in stock a t the end of the year. During 1925 about 9000 tons of white arsenic were imported into the United States, as shown by actual figures for ten months and a n estimate for the remainder of the year. Over 1000 t o m of white arsenic were imported in January and in June. Most of the imported white arsenic came from Mexico and from ports
in Germany and lesser amounts from Canada, Japan, and Southern Rhodesia. The total available white arsenic in the United States during 1925 therefore amounted to about 29,000 short tons. Most of the white arsenic was used in the manufacture of insecticides and for weed-killer. Very little calcium arsenate was manufactured for controlling boll weevil during 1925, as the ravages of t h a t pest had far less effect on this year’s cotton crop than on previous crops. The manufacturers of weedkiller used about 4 pounds of white arsenic t o the gallon of solution, of which over a million gallons were sold. The price of white arsenic in 1925, as quoted in journals published in New York City, ranged from j 3 / 4 cents in January, 4 3 / r cents in July, 3 3 / 4 cents in September, and 3 l / 4 cents a pound in December, with only an occasional carload being sold.
