INDUSTRIAL AND EN( NEERING CHEMISTRY
169
that of treatment of the oil with the adsorbent in successive portions. )n the writers' decolorization results adsorption of pure substances from a are, however, examples which apely the conditions for decolorization are especially the decolorization of sugar solutions and of vegetabie oils.- SandereI6 and Teeple and ?*'IahlerL7 have recently shown that the devolorization of these subst,mces follows Freundlich's law, and a striking similarity b:tween their curves and those in Figures 3, 4,
oils, and mineral oils is complete; each involves the determination of the amount of unknown materials adsorbed by measurement of color removal.
Teeple and Mahler for vegetable oils
rate method of evaluating the decolorizing power of adsorb-
t the analogy between the results s on sugar solutions, vegetable
from those for the adsorption of pure compounds from solution. 5-Color formation in cracked kerosene is catalyzed by fuller's earth and is due t o oxidation.
'
Conclusions
1-The method of color measurement of oils proposed by Parsons and Wilson is satisfactorv for auantitative decolorization tests when sufficient precaution is*taken in the choice of a standard. 2-Freundlich's adsorption equation applies to the decolorization of all types of petroleum products by various adsorb-
urn Refining Agents on Naphtha ganic Sulfur Compounds' , E . Wood, Clyde She'ely, and A . W . Trusty MISSISSIPPI COLLEGE, CLINTON,MISS.
A study of the basic troleum-refining agents fur, isoamyl mercaptan,
and n-butyl sulfone.
Flash point, 42' C. Iodine number, 3.50 Initial boiling point, 152O C. D r y point, 237' C.
The refinin
ment), sodium hydroxide solution, silica gel, fuller's earth, aluminium oxide, and sulfuric acid of three strengthsfuming, 66 B6., and 53 BB.
T
HIS paper is a continuation of some previously reported work by Wood, Lowy, and Faragher,2and represents a
quantitative study of the action of petroleum-refining agents on naphtha solutions of free sulfur, mercaptans, hydrogen sulfide, alkyl suli ates, sulfonic acids, carbon disulfide, alkyl sulfides, alkyl disulfides, sulfoxides, sulfones, and thiophene. The sulfoxides and sulfones have never been identified in petroleum distillates or residues. Free sulfur and the other cornpounds listed have been identified by various investigators in certain petroleum distillates and residues, but the evidence is not so convincing in many cases as one could wish. The refining agents acid Of three strengths-funlingi 66 B B . ~ 53 Bk.-sodium plumbite, sodium hydroxide, silica gel, earth, and aluminium oxide. It is hoped that investigations of basic reactions or effects of standard refining agents on naphtha solutions of typical sulfur compounds will yield information of value to the industry and thus serve to remove some of the empiricism long prevalent in petroleum-refining operations, Materials
The naphtha used for making the solutions had the fol]om,ing properties: 1
Color, water-white Acidity, none Halogens, none Sulfur, none Specific gravity, 0 77 a t 20' C.
Received August 1, 1925. THISJOURNAL, 16, 1116 (1924).
STOCKSOLUTION Free sulfur Isoamyl mercaptan Hydrogen sulfide Dimethyl sulfate Methyl p-toluene sulfonate Carbon disulfide n-Butyl sulfide n-Propyl disulfide Thiophene Diphenyl sulfoxide n-Butyl sulfone
PERCENT SULFUR 0 26 0.29 0 034 0 04 0.15 0 08 0.30 0 38 0.09 0 05 0 08
General Methods DETERRIIsATIOS OF sULFUR-ThiS was made by the lamp method as described in TechnicalPaper 298, s. Bureau of R.Iines. D E T E R ~ l I x ~ L T ~ o xO F DEScLFURIZING EFFECyT1,is carried out in a closed system in a specially constructed apparatus Jvhich was described in detail by J\7ood, Lolvy, and Faragher.2 The desulfurizing effectof the refining agent Tvasdetermined from the sulfur content of the naphtha solution before and after treatment. Duplicate and in many a larger number of experiments ere made.
Effect of Sulfuric Acid
ill1 these experiments were carried out in the previously described closed system using three strengths of sulfuric acid-fuming, 66 B6., and 53 B6. Fifty cubic centimeters of each naphtha stock solution were treated with 4 and 16 cc. quantities of acid of the indicated strength for 1 hour. The naphtha recovered from the acid treatment was washed
INDUSTRIAL A N D ENGl'NEERING CHEMISTRY
170
to the neutral point with a 1 per cent solution of sodium hydroxide, using phenolphthalein as an indicator. Per c e n t of S u l f u r in N a p h t h a T r e a t e d w i t h Sulf u r i c Acid -Fuming---66 BC.--53 Be.-NAPHTHA SOLUTION 4cc. 16cc. 4cc. 16cc. 4cc. 16cc. Free sulfur 0.26 0.26 0.00 0.27
T a b l e I-Average
0.03 0.00
n-Butyl sulfide n-Propyl disulfide Thiophene Diphenyl sulfoxide n-Butyl sulfone
0.00 0.08 0.00 0.00
0.00 0.00 0.00
NAPHTHA
Free sulfur Isoamyl mercaptan
Dimethyl sulfate
{
Methyl p-toluenesulfonate Carbon disulfide n-Butyl sulfide n-Propyl disulfide
{ ReZZ& {
{
Thiophene Diphenyl sulfoxide n-Butyl sulfone
{ {
H \
0 \ /
*
P-'
//
0.15 0.08 0.2s 0.34 0.08 0.006 0.008
The 53 BB. acid removed most of the alkyl s i r i f a t e siilfnuide, and sulfone, but had little effect on the ni These results indicate that the desulfui sulfuric acid is a factor of its concentrati0n.d is not an effective desulfurizing agent. Id a cracked distillate containing appreciah drogen sulfide should be subjected to a an acid treatment; otherwise free I stance, is introduced into the naphth Cmay be removed from a distillate by redis Zreatment with an alkaline lead mercaptid gested by Wendt and D i g g ~ . ~The prior alkali would also remove some of the mercau d be an additional advantage for the acidd J
T a b l e 11-Average Per c e n t P e r c e n t Sod4 NAPHTHA SOLUTION bv - i Free sulfur Isoamyl mercaDtan
ha T r e a t e d w i t h 10
b.
AOH SOLUTION16 cc.
0.00
i
-
0.00
0.03
0.00
0.09 0.05 0.08
0.09 0.04 0.08
.. -.
Sodium Hydroxide
7
:re carried out in the previously described closed s y s m u s i n g sodium hydroxide of two strengths, 10 and 0.05 per cent. I n carrying out the experiments, 50 cc. of each stock solution were treated for 1 hour with 4 cc. and 16 cc. quantities of each strength of alkali. The treated naphtha was then washed with water to remove the excess of alkali and the per cent of sulfur determined. (Table 11) The results from these experiments indicate that the alkali had no effect on free sulfur, methyl p-toluene sulfonate, car8
THISJOURNAL, 16, 1113 (1924).
Effects of Refining Agents o n N a p h t h a Solutions of S u l f u r a n d S u l f u r C o m p o u n d s -DESC.LQURIZINGSULFURIC Ac1o-7 Fuming 66 BC. 53 BC. SAZPBOZ NAZPBOZ 4- S NAOH SILICA GEL FULLER'S EARTH A L z O ~ None None None None None None None None Removes as Removes as ?one Removes Forms Removes Removes None Removes disulfides disulfides partially naphtha partially as fairly sparingly as lead solution of sodium well mercaptides disulfides mercaptides None Forms Forms No oxidaRemoves Removes Removes None None Removes' sparingly as PbS as PbS as NaaS naphtha naphtha tion to solution of solution of free sulfur free sulfur free sulfur Removes Removes Removes Removes Removes Removes Removes Removes sparingly readily fairly well as PbSOi as PbSOi as NazSOi Removes None None None None Removes fairly well fairly well None None None h-one None None None None None None None None Removes None None None Re~n~nz; Removes partially Sone None None Removes Removes None Removes hrone R!% :; fairly well partially sparingly None Sone Sone None None Sone Rerr.oves as Removes as None thiophenethiophenesulfonic sulfonic acid acid Removes Removes None None None Removes Removes Removes fairly well sparingly R% : %; None None Removes Removes Removes R;E~; Removes Removes None fairly wrll sparingly
i
Hydrogen sulfide
H-0
0.008
An examination of Table I shows that free sulfur and carbon disulfide are not affected by sulfuric acid of any strength. The mercaptans were readily removed by the fuming, less readily by the 66 BB., and very sparingly, if a t all, by the 53 BB. acid. Several other strengths of acid were tried on the mercaptan solution: 16 cc. of 63 BB. acid removed about 20 per cent of the mercaptan; 44 BB. and 24 BB. acid did not affect the mercaptan. These results can be readily explained on the basis of the oxidizing and solvent action of sulfuric acid. Fuming sulfuric acid, being the best oxidizing and dissolving agent, readily converts the mercaptan to the corresponding disulfide and dissolves it as such. The 66 BB. acid is not so strong an oxidizing agent, but when used in sufficient quantity will convert and remove the mercaptan in the form of the disulfide. In the oxidation of the mercaptan to the disulfide, the alkyl acid thiosulfate and the alkyl dithiosulfate are perhaps formed as intermediate products.2 The quantity of acid used must be sufficient to carry the oxidation through these intermediate steps and then dissolve the resulting disulfide. As the acid becomes more and more dilute, the oxidizing and dissolving power gradually decreases. This fact probably accounts for the ineffectiveness of the 53 BB. acid. The fuming and 66 BB. acids oxidize hydrogen sulfide to free sulfur, in which form it is left in the naphtha. The effect of the 53 BB. acid could not be accurately checked because the acid was apparently too dilute to oxidize the hydrogen sulfide which the subsequent alkaline wash would remove. Dimethyl sulfate, methyl p-toluenesulfonate, n-butyl sulfide, n-propyl disulfide, thiophene, diphenyl sulfoxide, and n-butyl sulfone were removed by the fuming and 66 BB. acids. The thiophene was removed as thiophenesulfonic acid, while the others were dissolved apparently unchanged. These results would indicate that, while concentrated sulfuric acid is a sufficiently strong oxidizing agent to convert
SOLUTION
the mercaptan to the disulfide and to eo fide to free sulfur, it is not strong enough solutions of any of the alkyl sulfides to the s sulfone. The oxidizing reaction of sulfuri lows:
February, 1926
ILVDUSTRIAL AND ENGI-VEERING CHE.1IISTRY
171
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.
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 S o d i u m P l u m b i t e
The results shown in Table I11 indicate that silica gel is, in general, a more effective desulfurizing agent than fuller’s earth or aluminium oxide. The silica gel completely removed the alkyl sulfate, sulfoxide, and sulfone, removed about 75 per cent of the mercaptan and the methyl p-toluenesulfonate, and removed smaller percentages of some of the others. The fuller’s earth completely removed the alkyl sulfate, sulfoxide, and sulfone, and partially removed the methyl p-toluenesulfonate, but had little effect on the others. Aluminium oxide partially removed mercaptans and the alkyl sulfate, but had little effect on the other sulfur compounds. The action in all cases seems to be due to adsorption. Free sulfur, hydrogen sulfide, carbon disulfide, and thiophene were apparently not affected by any of these materials. I n all these experiments it should be kept in mind that the sulfur was in the liquid phase a t room temperature and was shaken with the material in a closed system, rather than filtered through it as is frequently the custom. The sweetening action usually attributed to silica gel is probably due to the ease with which it adsorbs mercaptans,
The sodium plumbite solution used in these experiments was prepared according to directions in Technical Paper 298, E. S. Bureau of Mines. Carefully checked quantitative experiments were carried out in the closed system by treating 50 cc. of each stock solution with 4 and 16 cc. quantities of sodium plumbite solution for 1 hour a t room temperature. The recovered naphtha was washed with water and the per cent of sulfur determined. These results indicate that at room temperature the sodium plumbite solution had no effect on free sulfur, methyl ptoluenesulfonate, carbon disulfide, alkyl sulfide, alkyl disulfide, thiophene, sulfoxide, and sulfone. The addition of flowers of sulfur proportionately increased the sulfur content of the naphtha in every case. The sodium plumbite removed the alkyl sulfate as PbS04 and the hydrogen sulfide as PbS. The addition of flowers of sulfur is unnecessary and only serves to increase the sulfur content of the naphtha.
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 c e n t of Sulfur in Naphtha Treated w i t h Silica Gel, Fuller’s Earth, a n d Aluminium Oxide Silica Fuller’s Aluminium STOCK Sorurrov gel earth oxide Free sulfur 0.24 0.25 0.25 0.28 0.09 Isoamyl mercaptan 0.24 0.03 0.03 Hydrogen sulfide 0.03 0.00 0.00 Dimethyl sulfate 0.03 0.03 0.05 0.lA Methyl p-toluenesulfon ate Carbon disulfide 0.08 0.08 0.08 0.13 0.29 n-Butvl sulfide 0.30 0.24 0.32 0.36 0.08 0.08 0.09 0.00 0.00 0.05 0.00 0.00 0.07
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.
