PLANTOF STANDARD ALCOHOL
Synthetic Alcohols and Related Products from Petroleum BENJAXN T. BROOKS, 114 East 32nd Street, New York, N. Y
I. Olefin Raw Materials Cracked oil gas is the cheapest source of the simple olefins. New data are presented f o r Ihe yield and composition of gas made by vaporphase cracking at temperatures higher than are employed for maximum gasoline production.
S
YNTHESIS of useful materials from petroleum and oil gas has beccme a n important American industry during the past decade. Built upon the utilization of the bountiful supply of raw materials made available by the spread of cracking processes in gasoline manufacture, the new industry has grown primarily through the development of improved methods of cracking and of separating chemical individuals from refrnery waste gases which have enabled it t o produce its products in a high state of purity. Even so cheap a solvent as ethyl alcohol, fermented from molasses, has felt competition from the synthetic products from ethylene; and numerous other synthetics were never available commercially before, either as to price or quantity. Kew estimates of the extent of our petroleum reserves are continually enlarging the expected supply of this essential raw material. Rather the bountiful supply of petroleum available has tended to force prices lower instead of higher. The most prolific source of the preferred raw materials for synthesiscracking gases-is growing rather than shrinking and will con-
tinue to do so if and when a shortage of crude oil require5 the production of more gasoline by cracking than a t present. Important though the new industry is and may become in magnitude, the enormous volumes of petroleum now annually processed are more than ample to yield the raw material to produce all of the common compounds and solvents now knon-n which could conceivably be made from petroleum without in any way interfering with the adequate supply of present refinery products. From the point of view of 1934, it is hardly conceivable that the demand for synthetic derivatives of petroleum could ever reach the point of affecting its basic price structure. In the long run, the ultimate prices of petroleum and its products will be more influenced by the price of coal than by any demands likely to be created by the new industry of synthetics. Recent reports from Russia state that a promising synthesis of rubber has been developed there, using butadiene made catalytically from ethyl alcohol. While butadiene may be isolated from the products of high-temperature cracking of petroleum, as shown in the present paper, it is more probable that, if the butadiene rubber is satisfactory, the butadiene will be made from synthetic ethyl alcohol rather than from fermentation ethyl alcohol or from the butadiene separated from the products of petroleum cracking. Most of the important developments so far undertaken in this field have been fitted into existing refinery operations. One company producing a series of alcohols and related derivatives utilizes the by-product still gases produced by a pressure cracking operation. Another company produces ethylene
278
COMPASY,BAYWAY, %. .J.
glycol and ethyl alcohol from the by-product gas of a vaporphase cracking plant. Thus the utilization of uncondensed cracked gases, formed incidentally in cracking for gasoline (the principal product), bears the same economic relation to petroleum refining as the manufacture of coal-tar light oil and its derivatives does to the coking of coal. Striking though the growth of the new industry has been, sereral important factors have operated to delay its beginnings and still impede its progress. Among thew, the most important are.
tertiary alcohols, and the investigation was extended to a number of pure amylenes, hexenes, and other olefins. Ellis and Cohen (12) suggested that acid more dilute than the customary 66" BB. be used for refining cracked gasoline, thus reducing the loss by polymerization. The first production of alcohols industrially from oil gas and cracked gasoline was made by Ellis and his co-workers (9). The development of synthetic ethyl alcohol in Europe, beginning about 1919, was focused on the utilization of the ethylene in coal gas in the plant of the Skinningrove Iron Company in England, and a t Bethune in France. 1. The complexity of petroleum oils and the difficulty of On the basis of a group of patent; issued to Ellis and his separating pure compounds either from the raw material or from the products of reactions. associates, the Standard Oil Company of S e w Jersey began t h e 2. The widely varying nature of crude oils from different fields. commercial manufacture of isopropyl alcohol about 1920. 3. Lack of exact knowledge of the chemistry of all but the The Doherty Research Corporation later made isopropyl alcosimplest petroleum hydrocarbons. hol on a small commercial scale a t the plant of the Empire These handicaps are now being rapidly overcome as a result of Refineries a t Okmulgee, Okla. The Petroleum Chemical Corthe acceleration of reqearch caused by interest tiroused by poration, originally under the technical direction of Arthur initial commercial suwesseq, and by the much larger number D. Little, Inc., erected a plant a t Tiverton, R. I., in 1925-26 for the manufacture of isopropyl and other alcohols, but after of chemiqts employed in the industry. six months of operation this plant was closed and later disEARLY DEVELOPMENT mantled. The Petroleum Chemical Corporation, continuing As early a> 1862 a liter of ethyl alcohol, said to have been its synthetic alcohol research and development under t h e made from the ethylene of coal gas, was shown a t the London writer's direction, later erected a small commercial plant a t Exhibition of that year. This achievement, if true, was in the Barnsdall, Okla., and a plant for producing light olefin fracnature of a stunt and had no industrial significance. Synthetic tions in the refinery of the Pure Oil Company a t Muskogee, ethyl ether was made on a amall commercial scale a t Rich- Okla. These plants continued in operation until 1932 when mond, Va., in 1896 by Fritzsche (15). The commercial intro- the Petroleum Chemical Corporation was merged with the duction of oil cracking proceqses in 1912 may be said to have intereqtq of the Standard Oil Company of S e w Jersey to form greatly stimulated petroleum research and opened the way for the Standard Alcohol Company. Oil gas made by the Pintsch the precent development of petroleum synthetics, since the retort method and purified by cooling and compression to refining of cracked gasoline and the utilization of the by- remove higher olefins was used by the writer to produce ethylproduct cracked gas presented new problems which later de- ene and propylene chlorohydrins and glycols ( 2 ) . This developed into the present industry. Application of the stand- velopment by the Commercial Research Company, in 1917-18, ard method of refining by sulfuric acid to the treatment of was later acquired by the Carbide and Carbon Chemicals Corcracked gasoline containing 30 per cent or more of olefins, poration, which company improved the manufacture of ethylgave a n acid extract from which a n oil separated on dilution. ene and propylene derivatives, including ethylene glycol, isoI n a study of this problem in 1918, the writer with Hum- propyl alcohol, synthetic ethyl alcohol, and other products a t phrey ( 4 ) showed t h a t this acid oil contained secondary and its plant a t Charleston, SV. Va. 279
280
I N D U S T R I A L A N D E N G I PU- E E R I N G C H E M I S T R Y
The principal synthetic petroleum products find their largest uses as solvents and as such have contributed t o the growth of the lacquer and other solvent-using industries. Alcohols from ethyl to and including hexyl alcohol, their esters, and the ketones derived from them, are particularly important as solvents for the cellulose esters and ethers. Acetone, formerly obtained from fermentation and wood distillation, is now made cheaply from isopropyl alcohol. Methyl ethyl ketone, methyl propyl ketone, and methyl butyl ketone, made catalytically from the appropriate secondary alcohols and not heretofore available commercially, have taken their places among the important lacquer solvents. Synthetic ethyl alcohol, in a period of unprecedently low molasses prices, and isopropyl alcohol, mixed with 35 per cent synthetic methyl alcohol, have both invaded the antifreeze market which for many years has been the largest commercial field for ethyl alcohol. The development of this industry has been closely dependent on the development of methods of producing and treating olefin fractions. Hence, in this paper attention will be given first to the preliminary treatment of olefins from oil gas and cracking still gases.
OILGAS Although oil gas has long been known, its production a t low cost was hardly possible prior to the development of vaporphase or high-temperature cracking processes in recent years. The old Pintsch gas retorts were very inefficient and were operated over a wide range between maximum and minimum temperatures. Close temperature regulation, particularly in high-temperature cracking, was appreciated by W.A. Hall, one of the pioneers of oil cracking, and this feature was greatly improved by Luis de Florez, the inventor of a cracking process adapted to vapor-phase operation. During the World War the Hall process was operated a t high temperatures for the conversion of petroleum to benzene and toluene. I n the Hall process, cracking a t 605' C. (1120" F.) gave 17.7 per cent gas containing 49 to 50 per cent olefins; a t 725' C. (1337' F.) 66 per cent of the oil was gasified, the gas containing 40 per cent total olefins (3). It has long been known that the olefins are unstable at the temperatures employed to produce them by cracking. This was particularly pointed out by Whitaker and Rittman (B) and Whitaker and Alexander (27). Also in more recent work by Frey and his associates ( I S ) it is shown that when propane and butane are cracked to produce a maximum of olefinsi. e,, a t about 850' C. (1560' Fa)-an exothermic reaction quickly ensues, a further temperature rise of 94' C. (201' F.) having been observed. During this exothermic period benzene and other condensable hydrocarbons are formed and the yield of olefins is considerably decreased. Most of the research and development in this field of hightemperature cracking of the simple paraffins, methane t o butane, inclusive, has been carried out with the object of producing benzene or for the purpose of enriching lean gas such as water gas. This subject and the pyrolysis of individual hydrocarbons have recently been well reviewed by Ellis ( I O ) . The pyrolysis of ethane t o produce ethylene has been repeatedly investigated and is reported to have been carried out on a large scale which has, however, now been abandoned. Owing to the potentially enormous quantities of propane and butane which are available as by-products of the stabilization of gasoline, the cracking of propane and butane to produce gaseous olefins has industrial promise. Podbielniak (18) and others have obtained a maximum ethylene yield a t about 815" C. (1500' E'.) from commercial propane. One volume of commercial propane, in the form of stabilizer tops, gave about 1.8 volumes of cracked gas containing 26 to 28 per cent ethylene. The results of Podbielniak are of significance since they were obtained on an industrial unit scale. There appears
\-01.
?I, x o . 3
to be no reason why propane and butane cannot be cracked for ethylene and propylene industrially wherever an adequate and reasonably permanent supply of such raw material is available. Stabilizer gas produced a t large refineries or by gasoline recovery plants situated on large gas transmission lines are the most permanent sources of supply. The temporary character of the great majority of gasoline recovery plants situated in the oil and gas fields practically precludes consideration of these sources of propane and butane for the manufacture of synthetic solvents a t low cost. Much of the published data with respect to yields of oil gas by cracking a t particular temperatures is of very little value; many important factors are usually neglected, such as time of passage, diameter of heating tubes, composition of the heating tubes, ratio of recycled oil to fresh charging stock, nature of the charging stock, etc. None of the older results gives analyses showing the percentages of the individual olefins. The figures from the literature (3) do show, however, the rapidly increasing gas yields as the cracking temperature is increased (Table I). TABLEI. YIELDSOF OLEFINSBY CRACKIXG GASPER 42 GAL.
TEMP.
NO.
C.
1 2 3 4
5 6
7
8 9
10 11
O
F.
593 (1099) 650 (1202) 682 (1260) 700 (1292) 743 (1369) 743 (1369) 750 (1382) 760 (1400) 782 (1440) 800 (1472) 850 (1562)
OF OIL Cu ~. ft. 1260 1887 2490 2520 2990 3136 2884 2968 3365 2870 3256
OLEFINS
REMI R K @
"7,
,I
45-48 43.6 35.8 36.5 36.6 33.5 30.6 30.1 27.7 46.2 43.1
So many factors are changed when small-scale experimental operations are enlarged to commercial unit operations that it is not safe to base projected commercial operations on smallscale results. The Gyro process is the best known vaporphase cracking which is operated on a large commercial scale, although the de Florez plants can be operated a t the low pressures and the temperatures characteristic of this type of operation, if desired. Some of the earlier results, reported by Wagner (26), for vapor-phase cracking showed 30 per cent or more of the charging stock converted to wet gas. Gas formation has since been reduced in the Gyro operations. Gas from one of these plants in 1931 showed the following analyses: TABLE 11. COMPOSITION OF GAS BY VAPOR-PHASE CRACKING
++ H& H2 Ethylene COn
CH,
Ethane Propane
I 0.89 29.6 23.1 13.3 4.9
(In per cent by volume) I1 0.28 Butenes and butane 28.5 CS 23.1 Above Ca 15.7 Total olefins 4.4
I 8.3
4.1
3.9
47.2
I1 10.1 4.0 3.1 48.4
The quantity of available olefins produced by a typical vapor-phase cracking plant, yielding 4,500,000 cubic feet of gas per day, is as follows (in tons): ethylene 40.4, propylene 38, butenes 29.9, amylenes 19.7, hexenes and gasoline 15.5 (about 5000 gallons). The following results recently obtained on a small-size vapor-phase unit are of interest as showing that in the cracking temperature range 580" t o 610'C. (1075'to 1130'F.) the composition of the pentane-free gas remains very little changed when the rate of feed is increased with increasing cracking temperature, thus decreasing the time of passage through the cracking zone. If the feed rate had been kept constant with increasing cracking temperatures, the yield of gas would have been much greater and the gasoline yield much smaller. The higher gas yields necessarily result from cracking of gasoline, which a t least for most purposes is uneconomical.
March, 1935
INDUSTRIAL ABD ENGIXEERING
CHE,MISTRY
"81
The East Texas reduced crude (26.1" A. P. I.) represented 60 per cent of the original crude and contained about 24 per cent residual fuel oil not volatilized in the apparatus. The figures in Table I11 were obtained by analyses of the dry residual gas, the stabilizer overhead product, mainly three- and four-carbon hydrocarbons, and the stabilized endpoint gasoline.
mental scale results given in Table 111, these ratios are as follows :
TABLE111. YIELDSAND COMPOSITION OF GAS AKD GASOLINE BY CRACKING EAST TEX.4S REDUCED CRUDE AT ATMOSPHERIC 1 PRESSURE
Propylene-propane ratio a Large scale.
Cracking t e m p , C. ( " F ) Pentane-free gas: Wt. % of feed Cu. ft./bbl. of feed Cu. ft./bbl. gas oil Composition, vol. %: Methane a n d hydrogen Ethylene Ethane Propylene Propane C I hydrocarbons Gasoline, 9.6 lb. Reid vapor pressure, 400° F. end point: Vol. 5% of feed Vol. O0 of gas oil A. I. Gasoline compn., vol. %: Butenes Butanes Pentenes Pentanes Ce hydrocarbons C;hydrocarbons plus
6.
580 (1075)
600 (1110)
610 (1130)
22.5 855 1125
24.9 990 1300
26.5 1025 1350
27.4 22.2 14.4 19.8 6.9 9.2
32.5 23.9 13.4 16.8 4.9 8.5
30.5 23.4 12.4 19.0 5.6 9.0
41.9 55.1 58.9
40.0 52.6 58.0
34.1 44.9 57.0
5.9 2.1 7.7
6.3 2.3 7.4 4.5 16.1 63.4
6.0 2.2
Cracking temp C (" F ) Ethylene-ethank ratio
550 (1076)
100/65
600 (1112) 100/56
610 111301 100/53
The propylene-propane ratio. are as follows : Cracking temp., ( " F.)
C.
595 (1103)a 100/32
550 (1076) 600 (1112) 610 (1130) 100/35 100/29 100/29
The material used industrially for the manufacture of isopropyl alcohol is the overhead gas produced when stabilizing cracked gasoline, made by pressure cracking, and contains approximately 18 per cent propylene. The butene fraction separated on an industrial scale from gas produced by vapor-phase cracking contained the following: % Butanes Isobutene n-Butenes
10-12 20-24 50-55
Butadiene Cs and Ca
12-14 2.0
The analytical procedure was to remove isobutene by treating with 65 per cent sulfuric acid a t 5" to 10" C. (41" to 50" F.) 9.0 and to remove butadiene by treating with an excess of a 5.8 4.9 15.7 17.1 solution of cuprous chloride in 10 per cent ammonium chloride 62.5 60.7 solution, followed by removal of the normal butenes byreaction The results of cracking a Pennsylvania gas oil 690" to with 75 per cent sulfuric acid a t 10" to 15" C., collecting, and 705°C. (12'75" to 1300°F.) are of interest although not redistilling the residual butanes. The three- and five-carbon strictly comparable with those shown in Table 111, since the hydrocarbons werc estimated from a Podbielniak analysis of cracking was done in a once-through operation in a different the original fraction. The percentage butadiene, as indicated apparatus. The approximately constant ethylene content of by the cuprous chloride reaction alone, is not reliable, this the gas throughout a wide range of temperature conditions reagent reacting slowly with butenes, hut these figures were and gas yields is striking. The gasoline distillate was not confirmed by separating the butadiene tetrabromide. Several stabilized; the wet gas gave the analysis shown below. years ago, Then more gas was produced in vapor-phase crackThe products were 38 per cent gas, 32.6 per cent distillate, ing, the butadiene content of the four-carbon fraction was and 22.8 per cent fuel oil. The wet gas had t l ~ efollowing found to be as high as 18 per cent. The formation of synthetic resins from such material is reported to be of some promire composition (in per cent by volume):' (28. Cd hydrocarbons 7.9 Methane and hydrogen 34.7 Other types of oil gas contain these same hydrocarbons in 1 ,ti Ethylene 22.6 Cs hydrocarbons varying amount, the gases made by cracking a t lower temEthane 15.3 C Bhydrocarbons 1 09 (gal. per t houeand) Propylene and propane 1 7 . 9 peratures and under pressure containing much more butane Similar results have been reported by Geniesse and Reu- and little or no butadiene. A four-carbon fraction made by ter (16) who cracked Midcontinent gas oil in a small experi- the Cross cracking process shox-ed 22 per cent buteneq and no mental apparatus. The ethylene content of the gas was found butadiene. Of the normal butenes present, 2-butene predominates; to be nearly constant through the temperature range 600" to 630" C. (1110" to 1185" F.), the time of cracking being de- this is also shown by fractionation analyses made by Frey and Hepp (14) of butenes made by cracking. The initial product creased as the temperature was increased. Egloff and Morrell (8) have recently shown that the gas, is doubtless I-butene which is rearranged t o 2-butene. The made by cracking a variety of blended charging stocks under butenes made by small-scale experimental cracking, where the I50 to 200 pounds pressure and a t 495" to 506" C. (923" to cracking time is very short, yield larger proportions of 1943" F.) in a large industrial cracking unit, and separating the butene. The relative proportion of I-butene is of considerable gas from the condensate under 30 pounds per square inch importance for certain synthetic applications, though both pressure averaged 2.37 per cent ethylene; the gas separated yield 2-butanol exclusively in the sulfuric acid-alcohol from the condensate under 200 pounds pressure averaged 2.0 method. The pentene-pentane fraction made by large-scale vaporper cent ethylene. These figures are probably fairly representative of the ethylene content of large-scale pressure- phase cracking contains 18 to 25 per cent of pentanes; the cracking processes, and the ethylene content is approximately product of the small-scale fraction contains a larger proportion of pentanes. The pentene-pentane fraction, made by the same as for coal gas. pressure cracking for gasoline, contains 25 to 33 per cent pentenes, depending upon the temperatures and possibly the time COMPOSI~O OFKOLEFIN-PARAFFIN FRACTIONS factor in the cracking process employed. I n the separation of the simpler olefins by fractional disThe "amylene" reported in the early literature usually retillation or similar methods, it is usually not feasible or par- ferred to amylene made by the decomposition of amyl alcohol ticularly desirable to separate the olefins from the correppond- or fusel oil and contained large proportions of trimethyl ing paraffins. ethylene; accordingly it was reported to yield chiefly tertI n the case of ethylene-ethane (the gas made by industrial amyl alcohol when treated with sulfuric acid under suitable vapor-phase cracking a t 595 " C. (1103" F.) noted in Table 11), conditions. the ratio of ethylene t o ethane is 100 to 51. I n the experiThe pentene-pentane fraction contains I-pentene, 2-pen1 Published by courtesy of Aloo Products, Inc. tene, trimethyl ethylene, isopropyl ethylene, probably asym-
.
282
INDUSTRIAL AND ENGINEERING CHEMISTRY
methyl ethyl ethylene and only very small proportions (about 1 per cent) of dienes. The much smaller proportion of dienes found in the five-carbon fraction, as compared with the butene fraction made in the same cracking operation, is perhaps to be explained by the generally greater reactivity and ease of polymerization of isoprene, as compared with butadiene. Also the proportion of pentenes yielding tert-amyl alcohol ( 2 to 4 per cent in material of vapor-phase origin) is much smaller than the isobutene content of the butene fraction. Isopropyl ethylene is one of the major constituents of the pentenes produced by either vapor-phase or pressure cracking. The composition of the hexene-hexane fraction, made by vapor phase or by pressure cracking, is not known. The alcohols made from this fraction are derived from the normal hexenes. CONCENTRATIOX AND PURIFIC.4TION O F OLEFINS
For most chemical reactions, as for example absorption in sulfuric acid, there are obvious advantages in using gas rich in olefins. Since in the earlier work on the manufacture of ethyl alcohol from ethylene, coal gas was employed, many methods of concentrating the ethylene were tried. Bury and Ollander (6) tried the method of partially selective adsorption by charcoal, patented by Soddy ( % I ) , but abandoned it. Berl and Schmidt (1) have reported quantitative experiments with this method. The process of Claude, primarily directed to the purification of the hydrogen of coal gas, liquefies the ethylene and a portion of the methane a t -140' C. (-220' F.). This method was tried a t Bethune, France, and a fraction was obtained containing 20 to 30 per cent of ethylene (24). The Soci6t6 Anonyme d'Explosifs (20) employed both pressure and cooling to separate a series of hydrocarbon fractions, and a liquid ethylene-ethane fraction. The advantages of absorption in a hydrocarbon oil, followed by rectification in the presence of the solvent oil, has been patented by Curme ( 6 ) ,and Voorhees and Youtz (25) concentrate ethylene by utilizing its greater solubility, as compared with methane and ethane, in ethyl alcohol under pressure. It is doubtful if there is any practical utility, so far as ethyl alcohol is concerned, in concentrating or isolating ethylene if residual oil gas, freed from other olefins and containing 20 to 30 per cent ethylene, is the available raw material. Thus Bury and Ollander found that with reasonably good surface contact between the acid and the gas, 71 per cent of the 2.5 per cent ethylene originally present in the coal gas could be absorbed in 2 minutes by 95 per cent sulfuric acid a t 60" to 80" C. (140" to 175' F.). Tideman reported that SO to 90 per cent of the ethylene was absorbed under the same conditions in 3 minutes. In his early work, Fritzsche (16) removed the ethylene homologs from oil gas by concentrated sulfuric acid below 40" C. (104' F,). Ellis (11) described the removal of propylene by treating with sulfuric acid of specific gravity 1.80 a t low temperatures, followed by reaction of the ethylene with more concentrated acid above 60' C. Isham and Born (17) and Taveau (29) have described similar methods of successively removing butenes, propylene, and ethylene. It has long been known that isobutene is much more reactive to dilute mineral acid than the normal butenes, readily yielding tert-butyl alcohol, and that trimethyl ethylene is much more reactive than the normal pentenes and may be selectively removed from olefin mixtures containing the isomeric pentenes. The relative reaction rates of these olefins with sulfuric acid have been reported by Davis and Schuler ( 7 ) . These reaction rates are so different that the separation of the olefin yielding tertiary alcohols from the normal butenes and pentenes, which yield secondary alcohols, has been carried out
Vol. 27, No. 3
industrially. Hydrochloric acid has been proposed for the same purpose but has not been thus used industrially. It was early recognized by Ellis that hydrogen sulfide and mercaptans should be removed or the alcohols, made by reaction with sulfuric acid, contain mercaptans. The presence of malodorous mercaptans in isopropyl alcohol, made from unpurified gas, has been considered desirable by the U. S.government authorities, when this alcohol is used for denaturing ethyl alcohol. Selective removal of butadiene from the butene fraction, when made by vapor-phase cracking, is advantageous to the butyl alcohol process as will be noted later. It can be selectively removed by cuprous chloride as mentioned above. In Part I1 the alcohol processes will be described. LITERATURE CITED Berl, E., and Schmidt, O., 2. angew. Chem., 36, 247 (1923). Brooks, B. T., Chem. & Eng., 22, 631 (1920). Brooks, B. T., Chem. Rev., 2, 369 (1926). Brooks, B. T., and Humphrey, I. W., J . Am. Chem. SOC.,40, 822 (1918).
Bury, E., and Ollander, O., Gas J., 148, 718 (1919). Curme, G., U. S. Patent 1,422,193 (1922). Davis, H. S., and Schuler, R., J . Am. Chem. SOC.,52, 721 (1930). Egloff,G., and Morrell, J., IND. ENG.CHEY.,26, 940 (1934). Ellis, C., Chem. &. Met. Eng., 23, 1230 (1920). Ellis, C., "Chemistry of Petroleum Derivatives," p. 161, New Tork, Chemical Catalog Co., 1934. Ellis, C., U. S.Patent 1,464,153 (1923). Ellis, C., and Cohen, M. J., U. 9. Patent 1,486,646 (1924). Frey, F. E., et al., U. S. Patent 1,847,235 (1932). Frey, F. E., and Hepp, H. J., ISD.ENG.CHEW,24, 282 (1932). Fritasche, P., Chem. I d . , 20, 266 (1897); 21, 33 (1895). Geniesse, J. C., and Reuter, R., IND. ENG.CHEW., 24, 219 (1932). Isham, R. M., and Born, S.,U. S. Patents 1,744,164 (1930) and 1,744,207 (1930); Isham, R. M.,Ibid., 1,729,782 (1929) and 1,744,227 (1930).
Podbielniak, W. J., Oil Gas J., 29, 22 (May 14, 1931). Schutt, H. C., Proc. Am. Petroleum I n s t , 1933, 132. SOC. Anon. Explosifs, British Patent 251,652 (1926). Soddy, F., U. S. Patent 1,422,007 (1922). Taveau, R. M., U. S. Patent 1,810,192 (1931). Thomas, C. A., and Carmody, W. H., IND. ENG.CHEM.,24,1125 (1932); J . Am. Chem. SOC.,54, 2480 (1932). Valette, F., Chimie &- industrie, 13, 718 (1925); Damm, P., Chem. Zentr., 1928, 11, 2208. Voorhees, V., and Youts, M. -4., U. S. Patent 1,875,311 (1932). Wagner, C. R., Refiner, 8 ( l l ) , 80 (1929). Whitaker, M. J., and Alexander, C. M., J. ISD.ENG.CREM.,7, 454 (1915).
Whitaker, M. J., and Rittman, W., Ibid., 6, 479 (1914). * * * e *
11. Manufacture of Alcohols and Esters The effect of pressure in promoting the absorpiion of ethylene in sulfuric acid is shown. The formation of ethyl ether by the reaction of diethyl sulfate and ethyl alcohol, and the state of our knowledge of the chemical reactions involved i n producing alcohols from olefins is reviewed. Hydrolysis of these sulfates is rapid in acid solutions; in alkaline solutions theyarerelativelystable.
T
HE brevity and simplicity of textbooks might lead one t o suppose that the conversion of olefins to alcohols involves merely reaction with sulfuric acid and hydrolyjis of the alkyl sulfate to alcohol, substantially as shown by Faraday and Hennel a century ago. Yet the simpler alcohols have been made from the olefins on a n industrial scale only
INDUSTRIAL AND ENGINEERING CHEMISTRY
March, 1935
since the World War. Some of the difficulties which have been overcome have naturally been of a chemical engineering nature, but all of the organic chemistry involved is by no means entirely clear even now.
CHEMIC.AL BASISOF THE PROCESSES XATUREOB REAGENTS FOR OLEFIN HYDRATION. Sulfuric acid is the only reagent now used industrially for the conversion of olefins to alcohols. Other reagents of an acid character have been proposed, but for various reasons (mostly poorer yields) they are not used.
201
'
20
4a
I I 60 BO T i m e . minutes.
I
IOO
,
120
140
reached in forming the dialkyl sulfate, caused by the liberation of water, ROS03H,Hz0
+ R (olefin) +(R0)2S02+ H 2 0
(2)
as is clearly shown in Figure 1. Thus, on agitating ethylene for 50minuteswith 98per cent sulfuric acid a t 80" C. (176" F.) under 500 pounds per square inch pressure, the yield of diethyl sulfate was 80 per cent of the theoretical (2 moles of ethylene to 1 of sulfuric acid); with 90 per cent acid under the same conditions, the yield of diethyl sulfate was 45 per cent. DIALKYL SULFATEFORMATIOX. The formation of monoand dialkyl sulfates proceeds simultaneously. For example,
I n the case of ethylene, appreciable amounts of diethyl sulfate are formed when the acid has reacted with about onethird molecule (32). This has the result that, on treating a cracked naphtha or a mixture of olefins and paraffins, part of the dialkyl sulfate formed passes into the residual naphtha, usually requiring redistillation of the residual naphtha before blending with gasoline. The higher dialkyl sulfates (dibutyl and diamyl sulfates, etc.) are miscible with hydrocarbon solvents, and i t was shown by the writer with Humphrey (9) in 1918 that cracked gasoline, refined by treating with concentrated sulfuric acid, always contains dialkyl sulfates which are decomposed on redistilling.
I
I(W
FIGURE 1. EFFECTOF ACID CONCEYTRATTON ON ETHYLENE ABSORPTIOYA T 50" c. (122' F.) AND 450
283
I
I
I
I
I
I
I / I
I
I
I
I
00
100
110
I
P O U N D S PER SQUARE INCH PRESSURE
The writer belieres that in all cases the acid reagents first combine with the olefins to form definite chemical compounds which are simultaneously, or more often later, hydrolyzed to give alcohols. I n an effort to avoid the use of more or less concentrated sulfuric acid, a number of processes have been proposed which describe the hydration of the olefin (ethylene) as "catalytic" or "direct;" most of these processes employ a dilute acid or an acid salt, usually with steam under high pressures. I t seems more consistent with all of the known facts to suppose that in such processes the function of the acid reagent is initially the same as in the more familiar reactions with concentrated acid-i.e., compound formation followed by hydrolysis. Anhydrous or 100 per cent sulfuric acid causes carbonization even with ethylene, and temperature control is difficult. The function of the water in less concentrated :wid is more than that of a mere diluent. I n the concentrations commonly employed for secondary hexyl, amyl, butyl, and isopropyl alcohols, the reagent chiefly used is the hydrate HzSOh.Hz0; the equilibrium, HzSO,
+ HzO + HzSOa.Hz0
(1)
is generally believed to exist in acid corresponding to this composition. The stability of the substance H !SOd.HzO is indicated by its large heat of formation, which is also consistent with the fact that, when this so-called hydrate reacts with an olefin, the alkyl sulfate ROSO~H~HzO is formed without loss of water, as is indicated by the composition of a large number of salts, such as Ba(OS03CzH6)z.2Hz0.Also when a solution containing 85 per cent sulfuric acid reacts with an olefin, there is no decrease in the reaction rate as the reaction proceeds, proving that there is no increase in the proportion of water to uncombined acid. When dialkyl sulfates are formed by the reaction of a monoalkyl sulfate (RSO3H.H2O)with a n olefin, the resulting dialkyl sulfate, (RO)zSOz,is anhydrous; this explains the fact that the sensible heat of reaction is very small compared with that of forming the monosulfate, and that, when using 90 to 96 per cent sulfuric acid, equilibria are
20
40
60
Time.
I+O
minutes.
FIGURE 2. ABSORPTION OB ETHYLENE
Large yields of dialkyl sulfate are favored by the solution of excess olefin in the monoalkyl sulfate-acid mixture which, in the case of ethylene, is readily effected by pressure (Figure 2). Thus, using 98 per cent acid a t 80" C. (176" F.),ethylene under 500 pounds per square inch pressure gave 80 per cent of 2 moles ethylene combined in 50 minutes, as compared with 59 per cent of 2 moles under 20 pounds pressure (Figure 1). I n the case of the pentenes the excess of olefin is readily soluble in the monoalkyl sulfate-acid mixture and reacts readily a t 20" C. (68' F.) to form large yields of diamyl sulfate. Dialkyl sulfates are also formed by the following type of reaction: 2CzH6OSOaH +(C~H~O)zSOz HzSOc (5)
+
which reaction, in fact, has been a well-known method of preparing diethyl sulfate; on heating ethyl sulfuric acid under vacuum, diethyl sulfate is distilled from the mixture. POLYMER FORMATIOX.The formation of polymers, XCBHIO --f CioHio
+ CISHIO,etc.
(6)
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284
is insignificant in the case of ethyl below 80” C. (176” F.) and acid concentrations below 96 per cent. With higher temperatures and more concentrated acid, secondary reactions, decomposition, carbonization, and formation of sulfur dioxide and tar are noted. Polymerization of propylene and the higher olefin homologs may be a serious loss if the conditions of acid concentration and temperature are too severe. The reason for increasing polymer formation with increasing acid
VOl. 27,
KO.
3
cated by the isolation of octane sultone by Baldeschwieler and Cassar (1) from the residual polymers made in the alcohol plant of the Standard Alcohol Company. They give the following reaction for its formation:
+
CdHgCH :CHCHzCHs 2HzS04 + CdHgCHzCHCHzCHzSOsH ----t CIH~CHZCHCH~CHZSO~ (8) bSO3H SOsHCH2CHzOS03H
+ HzO e
b-.J +
SOIHCHZCH~OH HzSOd (9)
* 30
O
i
I
l
2
/
3
T i m e Hour=,
FIGURE3. HYDROLYSIS OF sec-AiMyL HYDROGEN SULFATEAT 100” C. (212” F.) concentration is not known. I n a mixture of olefins one olefin may polymerize and couple with it another olefin which by itself is not polymerized. Thus, when butadiene is polymerized by 75 per cent sulfuric acid in the presence of normal butenes, viscous high-boiling polymers are formed in about double the proportions of the butadiene present. Thomas and Carmody (40)have noted similar co-polymerization when mixtures of olefins and dienes are polymerized by anhydrous aluminum chloride. The polymerization of gaseous olefins by heat and pressure to give good yields of motor fuel has become industrially important, and certain polymers, such as triisobutene, are of value as turpentine substitutes and for other purposes. The most interesting of the various theories of polymerization which has been proposed is that of Whitmore (46) which is based upon modern theories of organic reactions. Whitmore’s theory was suggested as applying only to polymerization of olefins by acids and is predicated upon the initial addition of hydrogen ion. This theory takes no account of the polymerizations by anhydrous reagents (alkali metals such as sodium and potassium, fuller’s earth and similar adsorbents) or by heat and pressure alone. FORMATION O F SaTURATED HYDROCARBOKS. I n COnCentrated sulfuric acid, in addition to polymerization, Ormandy and Craven (81)and Kametkin and Abakumovskaja (SO) have shown that saturated hydrocarbons are formed. Whereas cyclohexene gives good yields of cyclohexanol with 80 to 85 per cent sulfuric acid, diluting, and hydrolyzing, concentrated sulfuric acid yields two saturated hydrocarbons, C1;H22 and C1&. No satisfactory theory has as yet been advanced for these results :
+
XC~HIO (cyclohexene) +CIZHZZ C18H32
+ (1)
(7)
SULTONE AND CARBYL SULFATE FORMATION. Carbyl sulfate is not known to be formed by the reaction of ethylene and sulfuric acid of less than 100 per cent sulfuric acid. With ethylene homologs similar anhydrides are apparently formed more readily, with moderately concentrated acids, as is indi-
The formation of carbon on concentrating the diluted sulfuric acid used in alcohol manufacture is in all probability due to sulfonic derivatives of the unhydrolyzable isethionic acid type. HYDROLYSIS OF ALKYLSULFATES. Alkyl sulfates are fairly stable in the presence of water at ordinary temperatures. On heating with water, they are readily hydrolyzed and this hydrolysis is promoted by hydrogen ion. The effect of excess sulfuric acid on the hydrolysis of alkyl sulfates in the diluted acid product obtained in large-scale practice is very marked, being more rapid when excess free sulfuric acid is present. There is some confusion in the literature regarding the effect hydrogen and hydroxyl ions have on the hydrolysis of such esters. Kreman (24) reported that the hydrolysis of barium ethyl sulfate was retarded by hydrochloric acid, but Drushel and Linhart (14) clearly showed the contrary. Rice (34) noted the work of Kreman; commenting on results obtained by others for the hydrolysis of benzyl chloride, n-butyl chloride, isobutyl chloride, certain esters of phosphoric acid, monochlorohydrin, and certain lactones, he concluded that hydrogen ion has no effect on the hydrolysis of these compounds and that this behavior “appears to be common to the esters of all strong mineral acids.” Rice also states that these esters are fairly easily hydrolyzed by water alone and that “this fact, together with the fact that these esters are readily hydrolyzed by alkali, suggests that only hydroxyl ion is effective in promoting the hydrolysis.’’ The foregoing generalizations are contrary to the behavior of barium ethyl sulfate in neutral and acid solutions noted by Drushel and Linhart, and to the hydrolysis of isopropyl, seebutyl, and see-amyl sulfates noted in the manufacture of these alcohols and in special laboratory studies of their hydrolysis. The monoalkyl sulfates mentioned are most stable in excess caustic alkali solution and may be boiled in such solutions with only very slow hydrolysis, but in acid solution the hydrolysis is increasingly rapid with increasing acid concentration, as shown in Figures 3 and 4. Also Plimmer and Burch (53) have reported no detectable hydrolysis of barium diethyl and barium dipropyl phosphates on heating a t 90” C. (194’ F.) with 2 N sodium hydroxide for 96 hours, but hydrolysis was effected in dilute acid (2 N sulfuric). I n moderately concentrated acid solutions the following equilibria may be assumed : ROS03H (R0)zSOz
+ HzO % ROH + HzSO, + HzO ROSOiH + ROH
(10) (11)
These equilibria have not been investigated, with the exception of Equation 10 for ethyl alcohol and sulfuric acid. It is sometimes considered desirable to minimize reversion to olefin by hydrolyzing the alkyl sulfates prior to distillation (19).The hydrolysis of the dialkyl sulfates is complicated by ether formation. ETHER FORMATION. I n the manufacture of butyl and amyl alcohols, the sulfating reaction is usually not carried beyond the formation of the monoalkyl sulfate, and ether formation is not appreciable. I n the case of ethyl and isopropyl alcohols
INDUSTRIAL AND ENGINEERING CHEMISTRY
March, 1935
the dialkyl sulfates are more readily formed; when the acid reaction product, containing disulfates, is diluted, hydrolyzed, and distilled, ethers are formed. These ethers are formed mainly, and perhaps entirely, by the reaction of the dialkyl sulfates with alcohol:
+ CZHsOH +(C2Hs)zO + CzHaOSOaH
(CzHsO)*SOZ
(12)
Thus, ethyl alcohol may be distilled from a 40 per cent solution of sulfuric acid without appreciable ether formation, but, when diethyl sulfate is added to such a mixture, as much as 32 per cent of the diethyl sulfate is converted to ethyl ether. The formation of ethyl ether in this way can be minimized by separating the diethyl sulfate from the acid reaction product and hydrolyzing it separately with water or dilute acid, with vigorous agitation or by adding the ester gradually to boiling water in which the concentration of alcohol is kept low by distilling the alcohol as fast as it is formed. Ethyl ether and dikopropyl ether are available in large quantities as by-products of the manufacture of synthetic alcohols. Other work by the writer, in preparation, indicates that reaction 12, discovered long ago by Erlenmeyer, is mainly or wholly responsible for the formation of ethyl ether in the customary method of preparation, by the action of sulfuric acid and alcohol and not the reactions usually given in organic texts. DECOMPOSITION OF ALKYLSULFATES.The reverse of reaction 3, decomposition to olefin by heating, is a well-known method of preparation of the simple olefins. With the exception of ethyl alcohol -+ ethylene, rather dilute sulfuric acid (50 per cent or less) is used for this purpose. I n the case of ethyl and isopropyl alkyl sulfates, hydrolysis and distillation may be carried out in solutions of 35 per cent sulfuric acid without appreciable decomposition t o olefin. In the case of butyl, amyl, and hexyl alcohols, decomposition of the alkyl sulfates to olefins is an important factor in industrial operations. The dialkyl sulfates carbonize on decomposition by heat, giving sulfur dioxide and small yields of olefin. As shown by Nef, no ether is formed by the decomposition of diethyl sulfate by heat. The dialkyl sulfates are stable a t the low temperatures a t which they are formed; when dissolved in neutral hydrocarbon oil, rapid decomposition is noted at 140" t o 150" C. (2$4Oto 302" E'.).
ETHYL AND ISOPROPYL ALCOHOLS Synthetic ethyl ether was made on a small industrial scale in Richmond, Va., from the ethylene in oil gas by Fritzsche (20) in 1896. Apparently no attempt was made to utilize any of the ethylene homologs in the oil gas, since they were polymerized by the concentrated sulfuric acid used. Although Fritzsche reported a yield of ether equivalent to 70 per cent, based on the ethylene in the gas, his acid consumption was high. The entire cost of the operation was borne by the single product made. The results of Fritzsche have led many writers t o condemn the economics of the process, including the production of synthetic ethyl alcohol,1 and the latest edition of Ullmann's excellent book (41) repeats the heretofore prevailing opinion based on this work. Fritzsche recovered only one-third of the sulfuric acid used, much of this loss resulting from polymerization and tar formation from the ethylene homologs removed in the preliminary acid-scrubbing of the 1 There has been so much discussion about the use of alcohol, made from grain or molasses, as a blend with gasoline as a motor fuel that the costs of fermentation alcohol may be of interest. A modern distillery, whose costs are lower than average, made ethyl alcohol from molasses bought in 1930 at 10.1 cents per gallon at a net manufacturing coat (exclusive of denaturing, selling cost, and general administrative expense, varioualy estimated at 3.5 to 5.0 cents per gallon) of 29.75 cente per gallon.
285
gas and decomposition of the acid during subsequent reconcentration. His acid efficiency was also very low since, although he used 98 per cent acid a t 80" C. (176" F.) for absorbing the ethylene, the reaction was not carried beyond 0.64 mole of ethylene per mole of sulfuric acid. The chief factors which have changed the picture altogether with regard to commercial synthetic ethyl alcohol are the following. The development of efficient methods of removing butenes and propylene by sulfuric acid t o produce butyl and isopropyl alcohol, on the one hand, and the development of physical methods of separating ethylene and propylene make it feasible t o produce synthetic ethyl alcohol of very
I
ss*c.I
I
I
I
I
I
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INDUSTRIAL AND ENGINEERING CHEMISTRY
The use of catalysts to promote the reaction of ethylene and sulfuric acid has frequently been proposed. Silver and mercury salts do have a substantial catalytic effect on this reaction. The patent literature is well summarized by Ellis (16). However, the use of catalysts of this nature would present some difficulties in large-scale operation and would probably be lost in the process of acid recovery. Their advantages appear to be of doubtful value in view of the rapid reaction with concentrated sulfuric acid at about 80" C. (176" I?.) when carried out under pressures of 300 to 500 pounds per square inch. Numerous proposals have been made to use dilute acids a t high temperatures and pressures. One patentee describes passing a mixture of ethylene and steam through sulfuric acid of 60 to 85 per cent a t temperatures u p to 200" C. (392" F.) (26). The maximum conversion of ethylene to ethyl alcohol reported in the patent is 1.39 per cent. Another patentee employs 4.3 per cent hydrochloric acid and ethylene a t 220" C. (428" F.) and under high pressure (21). Other patentees (16, 26) claim the reaction of ethylene with very dilute acids a t temperatures of 150" to 250" C. (302" to 482" F.) and pressures of 70 to 200 atmospheres, and in the presence of silver or copper salts as catalysts. I n addition to the dilute acid-high pressure methods, the hydration-dehydration equilibrium and catalysts, known to be effective in the catalytic decomposition of ethyl alcohol, have been investigated by numerous patentees, but the results of Keyes (22) and of Sanders and Dodge (35) are of particular interest. The latter noted considerable polymerization under 135 atmospheres pressure, but this was largely avoided by operating at 70 atmospheres. At the temperatures employed, 360" to 380" C. (680" to 716" F.), a lining of Allegheny metal was required to withstand corrosion. Using ethylene and steam in the ratio of about 1 to 1mole, the product averaged about 2 per cent ethyl alcohol by weight. The first account of the manufacture of isopropyl alcohol from cracking-still gas was published in 1920 by Ellis (16). A gas richer in propylene than cracking-still gas and substantially free from butenes, obtained as stabilizer overhead gas, is now employed. This gas, containing 16 to 18 per cent propylene, is treated with sulfuric acid in a steel tower provided with cooling coils and in the presence of a n absorbent oil as shown in the patent to Lebo (25). At low operating pressures the use of an absorbent mineral oil greatly increases the capacity of the reaction tower. The absorption is normally carried out until the acid reaction product contains a substantial proportion of diisopropyl sulfate. After separating the neutral oil and acid product, the latter is hydrolyzed and distilled continuously with steam. On rectifying the crude isopropyl alcohol, isopropyl ether is obtained in the lower boiling fraction. The liquefied propylene-propane fraction, derived from the products of vapor-phase cracking, may contain as high as 80 per cent propylene to 20 per cent propane, and, since in the liquid condition this olefin-rich material may be agitated with acid for any length of time desired, i t is possible t o carry out the reaction with sulfuric acid of 80 to 85 per cent strength. When carried out under pressure (8) a t 15" to 20" C. (59" to 68" F.) and 85 per cent acid, the product is largely diisopropyl sulfate and the formation of polymers is almost entirely avoided. At the isopropyl plant of the Empire Refineries at Okmulgee, Okla., and a t the Tiverton, R. I., plant of the Petroleum Chemical Corporation, the absorption of gas containing propylene in concentrated sulfuric acid a t low temperatures was favored. The formation of diisopropyl sulfate by reacting upon sulfuric acid with an excess of propylene was first reported by Berthelot (2) who also noted its rapid hydrolysis, in acid solution, to the alcohol.
Vol. 27, No. 3
SECONDARY BL-TYL,AMYL,AXD HEXYLALCOHOLS.As slready noted, the butene fraction contains isobutene and the normal butenes, the pentene fraction contains the two normal pentenes and also isopropylethylene and trimethylethylene, and the hexene fraction contains a mixture of hexenes which have not been identified except indirectly from the alcohols made from them. Tertiary butyl alcohol was prepared from isobutene by Butlerow (11) by the action of dilute sulfuric acid. The relative reaction rates of the butenes with sulfuric acid of various concentrations has been reported by Davis and Schuler ( I S ) , from which the selective removal of isobutene from a mixture of butenes by 65 per cent sulfuric acid will readily be understood. The literature notes that tert-butyl alcohol is decomposed on warming with mineral acids as dilute as 0.02 normal, and early in this development it was thought necessary to neutralize the diluted acid product to obtain the tertiary alcohols. However, by rapid continuous distillation in a column (7) with steam, it has been found possible to recover 80 per cent of the tert-butyl alcohol present from acid solutions containing 35 t o 40 per cent sulfuric acid. The isobutene polymers, useful as solvents, as high-octane motor fuel, and for other purposes, can be recovered in good yields by heating the undiluted 65 per cent acid solution. Diisobutene is readily hydrogenated in the presence of nickel catalysts to the corresponding octane, and this is the only source of this well-known antiknock motor fuel standard. The butadiene content of the butene fraction, derived from vapor-phase cracking, has been mentioned. Although the butadiene content of this fraction is ordinarily 12 to 14 per cent, the butadiene yield cannot be materially increased except by cracking a t higher temperatures and sacrificing the yields of gasoline and other products. It is not probable that this interesting material will be availabIe for synthetic rubber or other chemical syntheses, except as a relatively minor byproduct of the utilization of the gases and light olefins made by vapor-phase cracking. Butadiene was isolated from this fraction on a small plant scale by means of its solid double compound with cuprous chloride. The butene fraction was agitated with a thin slurry of cuprous chloride in a 10 per cent solution of ammonium chloride, in a copper-lined vessel (4). The butenes and butane were then allowed to boil o f f , condensing them under a few pounds pressure, and the double compound was then decomposed by heating to 55" to 60" C. (131" to 140" F.) and condensing the liberated butadiene. Although cuprous chloride was found to react slowly with isobutene, the formation of the insoluble butadiene compound was so rapid as to be nearly quantitative and very selective. It rras found that, contrary to statements in the patent literature, isobutene could be selectively removed by 65 per cent sulfuric acid a t 10" to 15" C. (50" to 59" F.) without polymerizing the butadiene. If not removed, i t is completely polymerized by the more concentrated acid employed to react with the normal butenes. The resulting polymerization includes approximately one mole of normal butene to one of butadiene, to yield a high-boiling oil having iodine absorption numbers (Hanus method) as high as 240 (6). On exposure to air, these oils dry very slowly to soft, sticky films, and this drying behavior was not much improved by the addition of well-known driers such as lead, manganese, and cobalt resinates and naphthenates. Pure normal butenes give about 80 per cent of the theoretical yield of sec-butyl alcohol. When the sulfuric acid reaction mixture is diluted with ice or ice water, 20 to 24 per cent of the sec-butyl alcohol is liberated as such, and this is not increased by repeated extraction of the cold acid solution. The remainder of the alcohol may be liberated by hydroIyzing the acid alkyl sulfate by heating, The treatment of mixtures of olefins from cracked petro-
March, 1935
I ND U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
287
ACETYLATION OF SECONDARY ALCOHOLS The secondary alcohols are readily esterified and the acetates are quite stable. It is worth while calling attention to these facts since, a t the time the secondary alcohols were introduced as industrial solvents, certain solvent manufacturers reported unsatisfactory results when using the crude acetylation method then commonly employed for esterifying fusel oil. The method of manufacturing amyl acetate from fusel oil, then in use, consisted in heating the alcohol and acetic acid with large proportions of sulfuric acid. Although the efficiency of esterification processes in the presence of very small proportions of mineral acids as catalysts was clearly shown long ago, the idea persisted that large proportions of sulfuric acid were necessary as a dehydrating agent. Even in 1895 Fischer and Speier (29)wrote, "That small proportions of mineral acids serve the same purpose (as large proportions) appears to have been forgotten." When large proportions of concentrated sulfuric acid are used in esterifying secondary alcohols, the yield of ester is diminished by olefin and polymer formation. Practically theoretical yields (95 per cent) of secondary butyl and amyl acetates are obtained by using very small proportions (0.5 to 1.0 per cent) of sulfuric acid (to acetic acid) and utilizing the azeotropic mixtures of the ester, or alcohol and ester, with water to remove the latter completely from the system. The equilibrium resulting on heating sec-butyl alcohol with , equimolecuacetic acid was investigated by Menschutkin (68) lar proportions yielding a final concentration of 59.28 per cent butyl acetate in the mixture. Continuous removal of water with the ester (ethyl acetate) was described by Wade (43),and a similar continuous acetylation of amyl alcohol was mentioned by Senderens and Aboulenc (36). Maximum ester content of the distillate may be obtained by returning the upper layer of the distillate (alcohol and acetate) to the still until water ceases to appear (10) or, following well-known principles of chemical equilibria, by maintaining an excess of acetic acid in the still. Since the azeotropic mixture of water, ester, and small proportions of butyl or amyl alcohols contains more water than is formed in the ester formation, The sulfate of this alcohol, in acid of the concentrations rethe best performance of the rectifying column is obtained by quired t o react with a n olefin of this type, rapidly polymeradding the water necessary for the azeotropic mixture. Secizes. The relatively large proportions of the polymer oils ondary butyl acetate forms an azeotropic mixture with water, which are formed from cracked petroleum pentene fractions distilling a t 87.0" C. (188.6" F.) and containing 84.5 per cent suggests that, as in the case of butadiene, the polymerization by volume. The secondary amyl acetate azeotropic mixture, of a given olefin includes other olefins not by themselves polywith water, distills a t 92.0" C. (197.6" F.) and contains 74.5 merized under these conditions (lo), per cent ester by volume. Commercial sec-amyl alcohol is mainly 2-pentanol, with The process of directly combining olefins with anhydrous about 20 per cent of 3-pentanol. 1-Pentene yields exclusively acetic acid containing a small proportion of sulfuric acid does 2-pentanol; 2-pentene yields a mixture of alcohols containing not give satisfactory yields of ester with N butenes and N about 65 per cent 2-pentanol and 35 per cent 3-pentanol ( 3 ) . pentenes, when carried out a t ordinary temperatures as origiSecondary diamyl sulfate, not heretofore known, is readily nally proposed for the terpenes. By heating 2-butene under made, in yields of 70 to 75 per cent, by treating 90 per cent pressure at 115" to 120" C. (239" to 248" F.) with an excess sulfuric acid slowly, wihh cooling, with an excess of 2-pentene, of glacial acetic acid containing 10 per cent sulfuric acid, maintaining the temperature at 15" to 20". Dilution by yields u p to 60 per cent of the theoretical of sec-butyl acetate water precipitates dia,myl sulfate and dissolved pentene were obtained. Since treatment with sulfuric acid removes When a pentene-pentane mixture, or a cracked naphtha frac- the olefins from hydrocarbon mixtures and acetylation of the tion, is reacted upon with a small proportion of sulfuric acid, alcohols gives very satisfactory yields, the direct acetylation the dialkyl sulfate formed is distributed between the acid of petroleum olefins has not been practiced industrially. reaction mixture and the pentane or naphtha, being miscible The olefins, isobutene and trimethylethylene, which yield in both. tertiary alcohols are much more reactive and give good yields Secondary butyl and amyl alcohols are used industrially, of the tertiary acetates by the Bertram and Wahlbaum reacmainly in the form of their acetates and also for conversion to tion a t room temperatures. These acetates are best prepared the corresponding ketones. The ketones are made by cata- in this way, but the tertiary esters are of no value as industrial lytic dehydrogenation over a brass catalyst a t 455" to 485" C. solvents on account of their rapid hydrolysis. (851" to 905" F.) as described by Williams and White (46). The use of air introduces an exothermic effect n-hich is someLITERATURE CITED what difficult to control. Simington and Adkins (37) have re(1) Baldeschwieler, E. L , and Cassar, H. A., J . Am. Chem. SOC.,51, ported that, in catalytic oxidations of this type, silver and 2969 (1929). 80-20 brass give the best results. (2) Berthelot, M., Ann. chim. phus., (7) 4, 104 (1895). leum, containing butenes, with sulfuric acid of less than 1.84 specific gravity to produce butyl and other alcohols was first described by Ellis and Cohen (17). King (63) used 78 per cent sulfuric acid on pure butenes; and Weizmann and Legg (44), who were interested in converting n-butyl alcohol to sec-butyl alcohol through the butenes, recommended the use of 75 per cent sulfuric acid. Taveau (39) used 85 per cent and a resulfuric acid a t temperatures below 30" C. (86" F.), cent patent to Engs and Moravec (18) recommended 90 to 100 per cent sulfuric acid on purified butenes to produce mainly dibutyl sulfate. However, with increasing acid concentrations and high percentages of butenes in the hydrocarbon treated, temperature control becomes increasingly difficult; in the liquid phase the normal butenes are very rapidly sulfated with little or no polymerization by treating with 70 to 75 per cent sulfuric acid a t 20" to 30" C. (68" to 86" Fa). When diluted with lsrge proportions of saturated hydrocarbons, higher acid concentrations are advantageous. The composition of the amylene fraction by vapor-phase cracking has been noted. The pentenes in the five-carbon fraction, made by pressure cracking, equal about 30 per cent. The proportion of triniethyl ethylene, yielding terf-amyl alcohol, is so small that the selective removal of this pentene by dilute acid is seldom carried out. Pure normal pentenes give nearly theoretical yields of secondary amyl alcohols, when treated with sulfuric acid of 82 to 90 per cent sulfuric acid a t 15" t o 20" C. (59" to 68" F.). Similarly, trimethylethylene and asym-methylethylethylene with more dilute acid give nearly quantitative yields of tertamyl alcohol. The only pentene which tends mainly to polymerize under these conditions is isopropylethylene. The latter pentene yields not the secondary alcohol which might be expected, but tert-amyl alcohol:
INDUSTRIAL AND ENGINEERING CHEMISTRY Brooks, B. T., J . Am. Chem. Soc., 56, 1998 (1934). Brooks, B. T., U. S. Patent 1,879,599 (1932). Ibid., 1,885,585 (1932) and 1,919,618 (1933). Ibid., 1,894,661 (1933). Ibid., 1,904,200 (1933). Brooks, B. T ,and Cardarelli, E., Ibid., 1,919,617 (1933). Brooks, B. T.. and Humphrey, I. W., J. Am. Chem. Soc., 40, 822 (1918).
Buc, H. E., and Clough, W. W., U. S. Patent 1,726,946 (1923). Butlerow, A., Ann., 144, 1 (1867): 180,245 (1875); Konowalow, D., Ber., 13, 2395 (1880). Curme. H. R., U. S.Patent 1,339,947 (1920). Davis, H. S., and Schuler, R., J . Am. Chem. Soc., 52, 721 (1930). Drushel,W. A., and Linhart, G. A,, Am. J . Sci., 32, 51 (1911). Ellis, C., Chem. & Met. Eng., 23, 1230 (1920). Ellis, C., “Chemistry of Petroleum Derivatives,” p. 301 et seq., New York, Chemical Catalog Co., 1934. Ellis, C., and Cohen, M. J., U. S. Patent 1,486,646 (1924). Engs, W., and Moravec, R. Z., Ibid., 1,864,581 (1932) and 1,912,695 (1933).
Fischer, E., and Speier, A,, Ber., 28, 3252 (1895). Fritzsche, P., Chem. Ind., 20, 266 (1897); 21, 33 (1898). Johannsen, O., and Gross, O., U. S. Patent 1,607,469 (1926). Keyes, D. B., Science, 77, 202 (1933). King, A. T., J . Chem. Soc., 115, 1404 (1919). Kreman, R., Monatsh., (3) 28, 13 (1907); 31, 165 (1910); 38, 5 3 (1917).
Lebo, R. M., U. S. Patent 1,865,024 (1932); Mann, M. D., and Williams, R. R.,Ibid., 1,365,043 (1921). McElroy, K. P., U. S. Patent 1,438,123; cj. Distillers Co., Ltd., British Patents 368,051 (1932) and 370,136 (1932); Rochlingsche Eisen v. Stahlw., British Patent 238,900 (1925). Maimeri, C., British Patent 215,000 (1924).
Vol. 27. No. 5
Menschutkin, N,,Ann., 197, 195 (1879). Merley, S. R., and Spring, O., U. 5. Patent 1,859,241 (1933); Basore, C. A., Ibid., 1,385,515 (1922). Nametkin, S., and Abakumovskaja, L., Ber., 66B, 358 (1933). Ormandy, W. R., and Craven, E. C., J . SOC.Chem. Ind., 47, 317T (1928).
Plant, S.G. P.. and Sidgwick, N., Ibid., 40, 14T (1921). Plimmer, R. H. A., and Burch, W. J. N., J . Chem. Soc., 1929, 288.
Rice, F. O., “Mechanism of Homogeneous Organic Reactions,” p. 117, New York, Chemical Catalog Co., 1928. Sanders, F. J., and Dodge, B. F., ISD. ENQ. CHEM..26, 208 (1933).
Senderens, J. B., and Aboulenc, J., Compt. rend., 152, 1672 (1911).
Simington, R. M., and Adkins, H., J . Am. Chem. Soc., 50, 1449 (1928).
Strahler J., and Hachtel, B., Brennstof-Chem., 15, 166 (1934). Taveau, R. M., U. S. Patent 1,845,007 (1932). Thomas, C. A., and Carmody, W. H., IND. ENG.CHEM., 24, 1125 (1932).
Ullmann, “EnsyclopLdie der technischen Chemie.” 2nd ed., Vol. 1, p. 717, Berlin, Urban & Schwarzenberg, 1928. Valette, F., Chimie & Industrie, 13, 718 (1925): Cie Bethune. British Patent 221,512 (1925); Compton, J., U. S. Patent 1,598,560 (1926).
Wade, J., J . Chem. Soc., 87, 1657 (1905). Weismann, C., and Legg, P. A,, U. S. Patent 1,408,320 (1922). Whitmore, F. C., IND.Esa. CHEM.,24, 1125 (1933). Williams, R. R., and White, D. H., U. S. Patent 1,460,878 (1923).
RECEIVED September
6, 1933.
Contribution of the Standard Alcohol
Company.
Initial Inflammability of Construction A method of testing the flaming tendency of V Materials combustible materials has been developed which G. E. LANDTAND E. 0. HAUSMANN Continental-Diamond Fibre Company, Newark, Del.
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HE selection of slow-burning materials for fire-resistant construction is of paramount importance to the engineer and architect. When possible, he eliminates the u8e of combustible materials, yet structural and use requirements are often such that he must rely on natural or manufactured materials which are combustible. From time to time empirical tests have been devised which are designed to permit the selection of materials on the basis of their flame-producing or flame-carrying properties. Such a characteristic test is given by the Navy Department and by the New York City Building Code (1); the Navy Department specification is as follows: A No. 2 Meeker gas burner shall be used. The flame shall be ‘/,inchin diameter and 4 inches high. The s ecimen shall be held horizontally, 3 inches above the to of t i e gas burner. The flame shall be applied to one corner orthe specimen (in the case of square rods) or to one side of the specimen (in the case of round rods and tubes) about 2 inches from one end. After the specimen has become well i ted it shall be withdrawn from the flame. The length of time E i n g which the material supports combustion after being withdrawn from the flame shall be determined.
The variables affecting the end result are very difficult to The fist requirements for the flaming test are that the rate of application of heat shall be constant and the rate control.
permits a classijlcation of these materials on the basis of this tendency. Data are presented to show that the spec$c heat of unit volume, the specific heat conductivity, and the existence of microscopic channels play a n important part in the rapidity with which flames derelop at the surface of combustible materials when subjected to intense heat. of heat dissipation by convection, conductance, and radiation shall be constant so as to permit a uniform rate of temperature increase on the sample under test. Such a method makes no allowances for the variables which may affect the end result, the accuracy with which gas flame can be regulated, the difference of B. t. u. contents of different gases or the influence of the surrounding air on the behavior of the sample, particularly the influence of air currents which may, depending on the circumstances of the test, exert an inhibiting influence on the burning, or may, on the other hand, stimulate it excessively. Truax and Harrison (2) have attempted t o standardize these variables. A simpler and more direct method of overcoming these objections was desired: The requirement of a specific and closely controllable heat source is achieved by passing a 110-volt current through a 7foot length of No. 30 B & S gage, nichrome wire (6.5 ohms per foot). The possible variations in heat developed by this wire are 2 per cent. Either alternating or direct current may be used, and, when necessary, the voltage is held a t the required value b y means of a rheostat in the circuit [Weiss and Price (3) acquired
