The Synthetic Aliphatic Industry—II HARRY
B.
MCCLURE,
Vice President, and ROBERT L. BATEMAN, Manager, Fine Chemicals Division, Carbide and Carbon Chemicals Corp., New York, Ν . Υ.
changing I n P a r t II o f t h e i r s t o r y , the authors discuss the source picture, principal u s a g e s, a n d t h e i m p o r t a n t p a t h s o f f u t u r e d e v e l o p m e n t s i n t h e g r o wi n g s y n t h e t i c a l i p h a t i c i n d u s t r y U U R I N G the 20-year period the sources of aliphatic chemicals have changed mark edly. According to Fig. 6, in 1925 the fermentation of sugars, such as those de rived from molasses and corn, accounted for 85% of all aliphatics made. These were principally ethyl alcohol, butyl alcohol, and acetone. T h e next most important source of aliphatics—also a degradative process—was the distillation of wood, principally for the manufacture of acetone, methyl alcohol, and acetic acid. I n 1925 the amount made from petroleum and nat ural gas was less than 0 . 1 % of the total produced. B y 1945 the picture h a d changed radi cally and half of the tonnage was made from the petroleum sources. T h e fer mentation segment shrank to 28%. Even this is swollen because it includes fermenta tion ethyl alcohol required for the manu facture of 500 million l b . of butadiene. Since it took almost three lb. of alcohol to make a pound of butadiene, the consump tion of alcohol was 1.5 billion lb. The size of the fermentation segment in future years will be dependent o n the world availability and world prices of nat ural sugars and starches. With molasses selling as high as 25 to 3 5 cents per gal. today, it results in high cost chemicals. But if it returns to the prewar price of three to six cents per gal., there are many who predict that fermentation will be a t least partially restored as an important source of aliphatic chemicals a n d this m a y par tially counterbalance the reduction of fer mentation alcohol. Twenty-one per cent of the aliphatic chemicals were derived from coal in 1945. Coal is ordinarily regarded as a source of aromatic chemicals, but important quanti ties of many aliphatics are made from coal by way of acetylene and water-gas. Among those made from acetylene are acetaldehyde, acetic acid, and trichlorethylene, while those made from water-gas include methyl alcohol, urea, and ethylene glycol. Natural
Gas and
cal industry became important at a later date than the aromatic chemical industry. The three principal methods of attack are dehydrogenation, «hlorination, and oxidation. T o be entirely complete, wo should also show nitration. Commercial Solvents Corp. and the chemists at Purdue University have made progress in attack ing ethane, propane, and butane with oxides of nitrogen. Also the patent litera ture indicates some success on the part of Sinclair and Phillips in the amination of hydrocarbons under rather vigorous con ditions. In addition, certain detergents are now being made by the sulfonation of aliphatic hydrocarbons. Dehydrogenation is usually accom plished by the use of high temperatures, commonly known as cracking, t o produce olefins such as ethylene, propylene, aud butylène. T h e olefins in turn may be converted to other chemicals by one of three steps. The hydration step is usually carried out by absorption in sulfuric acid. This is followed by hydrolysis to yield the simple alcohols—ethyl alcohol, isopropyi alcohol, and sec-butyl alcohol. From these three basic alcohols, by dehydrogenation, acetaldehyde, acetone, or methyl ethyl ketone are produced and from these there is a whole host of chemicals that can be made. This approach was developed principally b y Carbide and Carbon Chemicals Corp., Shell Chemical Corp., ami Standard Oil (N. J.). Halogenation is the second method of converting the olefins to useful chemicals. Chlorine is the principal reactant, although ethylene dibromide is also made by this Fig. 6. 1925
Sources
of a.'mhatic
Natural Gas and Petroleum Less Than 0.1%
Petroleum.
chemicals 1945
Fermentation 28%
Coal 21%
Fig. 7 outlines the several basic methods for attacking the aliphatic hydrocarbons to convert them to a multitude of chemi cals. The word aliphatic is of Greek deri vation and means "inert." I n general, vigorous means must be used to convert these hydrocarbons, and possibly this is one of the reasons why the aliphatic chemi-
3286
process. The word halogenation is used here to cover not only the addition of chlorine itself, but also hypochlorous acid. Thus not only is ethylene dichloride made by the chlonnation of ethylene b u t ethylene chlorhydrin is made by its hypochlorination. From the resulting chlorhydrins, there stems a whole family of compounds, such as ethylene oxide, ethylene glycol and their various ethers, esters, and ethanolamines. The main companies that have pioneered in this field are Carbide arid Carbon Chemicals Corp. and D o w Chemical Co. Shell Chemical Co. has succeeded in hot chlorinating propylene to ally I chloride m a k i n g possible the commercial synthesis of allyl alcohol and glycerol. Lastly, i t is possible, under certain conditions, t o oxidize ethylene directly to its oxide. However, this catalytic oxidation is not particularly efficient and is costly in that excessive quantities of ethylene are burned to carbon dioxide. T h e second method of attacking the saturated hydrocarbons is by direct chlorination. Sharpies has pioneered the chlorination of pentanes t o form amyl chlorides which on subsequent hydrolysis gave amyl alcohols, from which m a n y other chemicals are made. The Ethyl Corp. is chlorinating ethane to make ethyl chloride and ethylene dichloride. D o w is chlorinating methane t o produce the methylene dichloride, chloroform, and carbon tetrachloride. T h e third method of converting the saturated hydrocarbons is by direct oxidation. This is done in several w a y s and is one of the oldest as well as the most recently exploited method of attack. Cities Service Oil Co. oxidized methane t o formaldehyde i n 1926, and it was a beautiful example of making a virtue out of a necessity. Originally, their natural gas lines
CHEMICAL
AND
ENGINEERING
NEWS
suffered excessive corrosion due to the presence of small quantities of oxygen in the methane. To remove this oxygen they passed the natural gas over certain catalysts at elevated temperatures, but in doing so they obtained, as a coproduct commercially useful grades of formaldehyde. The newest entry in this field is the Celanese Corp. which has completed a large plant in Bishop, Tex., where they are oxidizing saturated hydrocarbons to mixtures of formaldehyde, acetaldehyde, acetone, methyl alcohol, and propyl alcohol. Many of these are used in their production of acetate rayon and plastics. In the case of the second oxidation method, steam and carbon dioxide are used as the oxidizing agents for producing •water gas—that is, one volume of carbon monoxide to two volumes of hydrogen. Until now, Du Pont has obtained their water gas only from coal. However, they now are building a plant in Orange, Tex., to carry out this process from natural gas. Carbide and Carbon Chemicals Corp. has been doing the same thing for several years at Charleston, W. Va. The third oxidation method is shown as a dotted line since the commercial planta are planned but will not be in operation for a year or two. Carthage-Hydrocol and Stanolind plan to use oxygen for converting methane to water gas for their FischerTropsch plants. While the plans are primarily to produce gasoline and Diesel fuel, it is reported that important quantities of alcohols, aldehydes, and ketones will be produced concurrently.
Fig. 8.
Methods of Manufacture from Coal Fig. 8 indicates the several methods of converting coal to aliphatic chemicals. First, coal may be converted to calcium carbide for the generation of acetylene. Subsequently, the acetylene is catalytically hydrated to acetaldehyde. This can be oxidized to acetic acid or converted to a host of other aliphatic chemicals. Niacet Fig. 7.
Basic
methods
for
Dupont Goodrich
Niocet (UCC) Shawinigan
Methods
and Shawinigan have pioneered in this work. The use of chlorine for converting acetylene into useful chemicals has grown rapidly during the last 10 years. The Du Pont Co. dimerizes acetylene to vinyl acetylene which, on the addition of hydrogen chloride, gives monochlorobutadiene, the monomer from which Neoprene is made. Carbide and Carbon Chemicals Corp., Du Pont, and Goodrich have also been making important quantities of vinyl chloride by the addition of hydrogen chloride to acetylene. There really should be an additional leg under acetylene in this diagram because vinyl acetate is now being made on a commercial scale by the catalytic addition of acetic acid to acetylene. By far the oldest method of making water gas is by blowing steam through coke. Du Pont has had a large plant to make it by this procès* at Belle, W. Va.f for many years, while Carbide and Carbon Chemicals Corp. has been making water gas from carbon monoxide from the Electro Metallurgical Co. furnaces at
attacking
aliphatic
hyilrocarbons
NATURAL GAS A N D PETROLEUM
of converting
coal
Niagara Palls. Of course, the carbon in the carbon monoxide was originally from coal. The Fischer-Tropsch reaction for making gasoline from coal has always been too expensive for commercialization in the United States. However, the Germans, lacking sufficient petroleum sources, carried it out on a large scale before and during the war for the manufacture of gasoline. And yet there seems to be no evidence that they made appreciable quantities of oxygenated chemicals by this method. Raw Materials Table IX is an attempt to evaluate the future availability of raw materials for the aliphatic industry. The data were collected from various sources but principally from two hearings before the Senate committees during the summers of 1943 and 1944. The Bureau of Mines was justifying its request for funds for developing synthetic gasoline b y the hydrogénation of coal. As will be noted, the prr «*d reserves of coal are hundreds of times those of either natural gas or petroleum. The second column is derived from the first by dividing the known reserves by our present annual consumption of each of these three raw materials. As will be noted there is sufficient coal at present rates to last 5,000 years; natural gas about a little more than 30 years and petroleum about 12 years. Before becoming alarmed at these last two figures, we should point out that these are only the proved reserves.Geologists usually estimate that the unproved reserves will yield three to five times these figures. Table IX. Supply of Raw Materials for Synthetic Aliphatic Chemicals
ctccc
SMI St. N. J .
VOLUME
CACCC Dow Ethyl Corp. Shell
2 5,
NO.
CACCC
Dew Ethyl Corp. Sharpies
Celanese Cities Service
45 . N O V E M B E R
10,
Dupont CACCC
1947
Carlhag· Stanolind
Material Coal Natural Gas Petroleum
Proved Reserves (billion tons) 3200 3.4 3.1
Life of Proved Reserves a t Current Use Rates (Years) 5000 30+ 12
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Nevertheless the last column explains why there is such intense interest in making gasoline from natural gas and coal, since its proved reserves are much greater than those of petroleum. Two commercial plants are being built and will operate about two years from now, using natural gas for Fischer-Tropsch synthesis of gasoline. This would indicate that the goal of using natural gas is much nearer than that of using coal. The amount of coal, natural gas, and petroleum needed for the manufacture of aliphatic chemicals is less than 0.5% of the total quantities of these raw materials for fuel uses. However, a gradual diminution in supply of petroleum and natural gas should ultimately lead to higher prices for these commodities and result in higher costs of the chemicals made from them. The German
Aliphatic
Industry
Because of the lack of oil and gas, acetylene became the backbone of the German aliphatic industry. Acetylene from calcium carbide, the latter in turn derived from a plentiful supply of brown coal, served as the basic building block for the synthesis of a wide variety of industrial chemicals. Most of the butadiene was made by hydrating acetylene to acetaldehyde and then through aldol to 1,3-butylene glycol, and butadiene. Their chlorinated solvents, trichloroethylene aud perchloroethylene, were also derived from acetylene. Other solvents were obtained mostly via acetaldehyde. Among the important developments in t he German chemical industry which came to light in the postwar period may be mentioned the Fischer-Tropsch catalytic hydrogénation of carbon monoxide for the production of liquid hydrocarbons. This process uses a 1:2 mixture of carbon monoxide and hydrogen, obtained by burning brown coal with steam and oxygen. In the Oxo variation of the FischerTropsch synthesis, carbon monoxide and hydrogen were reacted with olefins at elevated pressure to produce aldehydes which were then reduced t o alcohols and sulfated for synthetic detergent manufacture. Considerable notice is being given the acetylene chemistry of J. W. Reppe, which involves the addition of acetylene directly to compounds with the retention of the triple bond or to others containing an active hydrogen to yield a vinyl compound. An example of the first is the production of butynediol from acetylene and formaldehyde. Butynediol is an intermediate in one of the two processes for the manufacture of butadiene. Also investigated was the preparation of vinyl ethers from acetylene and alcohols. Carbonylation reactions, such as the production of acrylic acid directly from acetylene and carbon monoxide constituted a third phase of Reppe chemistry. The economic aspects of these processes are now being studied by Ameri-
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Tablc X . C o m para l i v e Prod u c t i o n of Some I m p o r t a n t S y n t h e t i c A l i p h a t i c s German 1942 or 1943
U. S.
1942 Product Acetic anhydride 430 Acetic acid (excludes recovered 237 acid) 338 Acetone 18 JUitadicne 200 Ethylene glycols 8G Ethyl acetate 55 Ethyl ether Formaldehyde 3 4 7 (37%) t 370 Methyl alcohol 50 Tetrachlorethylene 150 Trichlorethylene Detergents (in31 cludes aromatics) 2.312 Totals
1945 524
48
267 349
1,229
250 106 77
136 32 180 66 49 14
509 493 70 200
440 555 47 53
161
75
4,235
1,695
can chemical industries with a view to their possible modification and adoption. Comparative
German
Aliphatics
Table X compares the production of some of the more important synthetic aliphatic chemicals in the United States and Germany. As a result of World War I, the lay press and, for that matter, even some of our own technical publications, have suggested that the German chemical industry was further advanced than ours, and it is timely to compare them. The figures for the German production may be open to question. They were compiled from various sources—principally the various Technical Intelligence Investigating Committee teams who followed our armies into Germany. I t was felt that 1942 and 1943 were the top years before bombing had a serious effect on -German production. Hence, we used the figures for either of those years—whichever was higher. In most cases the United States production was greater, but on the average about Fig. 9.
Aliphatic
in proportion to the population of the two countries. The first three—acetic acid, acetic anhydride, and acetone—are due to our vastly larger cellulose acetate rayon industry. The case of butadiene is a special one due to the phenomenal job that was done in this country in building this industry in two years after Pearl Harbor. Ethylene glycol probably highlights the relative lack of motor cars in Europe. In the case of methyl alcohol and the formaldehyde made from it, the production figures are about equal. Some of this is explained by the fact that the second largest process in Germany for making butadiene was by the Reppe method of condensing two molecules of formaldehyde with acetylene to form the butynediol which was subsequently hydrogenated and dehydrated to butadiene. Of course, our total for 1945 for this dozen chemicals may be considered slightly distorted by the 1.25 billion lb. of butadiene. Even if this is eliminated, our aliphatic industry, is probably two t o three times as large. Aliphatic
Chemical
Usage
Fig. 9 was most difficult t o prepare in that present governmental statistics are not sufficiently detailed to permit breaking chemicals down by usage. However, up to the present time, the Bureau of Census has distributed interesting War Production Board "use" information concerning some 50 or more chemicals. Of course the figures were distorted by war conditions, but they were usually broken down so that allowance could be made for such distortion. This chart covers the whole aliphatic chemical industry and contains both synthetic and nonsynthetic products, since it is extremely difficult t o segregate the two in such a breakdown. It provides a clue as to the growth of the aliphatic inchemical
CHEMICAL
AND
usage—1945
ENGINEERING
NEWS
ustry since the four largest usages are in idustries that are relatively young and rowing. In this usage chart, pyramiding has been jduced as much as possible and corre>onds more nearly to sales tonnage rather lan the production tonnage. T h e circle ^presents about 6 billion pounds. The rubber segment is probably abonnai. In 1945, 900,000 tons of synthetic ibber were made. This went up slightly - t o a million tons in 1946—and plans in 947 are for about 500,000 tons. There is Ptlk that in subsequent years this might jvcl off at 250,000 tons. If it does, this îgment, instead of being 1.4 billion lb., 'ill be nearer 750 million. While this segîent is made up principally of butadiene, 'hich is three fourths of GR-S rubber, it Iso contains substantial quantities of hloroprenc monomer for the manufacture f Neoprene, isobutylene for the manufacurc of butyl rubber, and a much smaller uantity of acrylonitrilc for Buna N. The automotive segment is larger in 946 and will continue to be so in future ears. The products making up this segment arc mainly the glycols and alcohols ised in the antifreeze systems and the thylcne dibromide used in tetrae thy Head. is well as the ethylene dichloride and the ithyl bromide used for dissolving the •etraethyllead. The next use from the standpoint οι size s plastics and resins. This is probably the astest growing outlet for aliphatic chemijals. From the viewpoint of tonnage, ormaldehydc tops the list even if the water .hat the Tariff Commission retains in the 57% formalin is excluded. This is followed closely by acetic anhydride for making icetate plastics. The fastest growing group is the vinyl chemicals, such as vinyl chloride and vinyl acetate. T h e plastics segment also includes the acrylates, mclELminc, urea, polyethylene, and pentaerythritol. Interestingly enough, the 1945 Tariff Commission's estimates show that almost exactly an equal amount of aryl and aliphatic resins were made—both about 400 million lb. There are some plastic enthusiasts who would also adopt the next family—the synthetic fibers. In the case of rayon, each of the three most important types of fibers requires aliphatic chemicals—acetic anhydride and acetone to make cellulose acetate, carbon disulfide to make the xanthate type of fiber, and the polyamides to make nylon. T h e next in size, surface coatings, is also a close kin of the plastics group, in that the film-forming solids are frequently syn thetic resins. However, the quantities .of aliphatic derived resins are not nearly as important in this field as are the aryl de rived resins, due to the great popularity of the alkyd resins derived from phthalic anhydride, which in turn is derived· from coal tar naphthalene or petroleum derived o-xylenc. This 8.4% segment of aliphatic surface coatings is principally made up of
VOLUME
2 5,
NO.
the ester and ketone solvents used to de posit protective coating films. The rest of the chart illustrates the rela tively unimportant part played by the ali phatic chemicals in the older industries. Relatively small quantities are used in metal processing and in foodstuffs. In the case of foods, which include agricultural uses as well as food processing, the seg ment includes such products as the Freon refrigerants and urea for fertilizer. In metal processing, the biggest products are the solvents used for the degrcasing of metals. In explosives the 4 % represents mainly the ethylene glycol used for making the lower freezing dynamite. It also in cludes some ether for the manufacture of smokeless powder. Although the tonnage going into the medicinal field is low, it is probable that the relative dollar value is much greater. Future
Developments
In the past, markets were developed by three principal methods. One was finding a new use for an old product, such as the use of triethylenc glycol for air steriliza tion. Another was the development of a new process making possible lower costs, and hence opening up new fields. A prime example of this occurred in cellulose ace tate rayon. When synthetic acetone was introduced, the price decreased from 14 to 7 cents per pound. The same thing happened to acetic anhydride and as a re sult, cellulose acetate rayon made from these raw materials is now selling at almost the same price as xanthate rayon. Thirdly, progress has been made by developing a product with a combination of properties of specific interest for particular applica
tion. A good example is the new tough ened Carbowax compounds. These three methods will pro-bably still be the important paths of future maxket development. In the future, probably there will be more custom building done, that is, more complicated molecules will be tailor-made for the need at hand. A good example is in the case of the resin plasticizers where it is now possible n o t onLy to get a good all-around plasticizer, sucli as 2-ethylhexyl phthalate, but also special plasticizers with either extremcLy good, lowtemperature characteristics, o r greater resistance to water extraction o r witfci in creased flame resistance. Another field in which a great deal of tailor making of molecules is necessary, and one that has been barely scratched, is the field of biological products. Vlany industrial research laboratories now have special divisions engaged in designing new molecules which will kill a fungus bu"t not injure green plant foliage; rcp»el a fly but not irritate human skin; immobilize air borne bacteria but not harm the human respiratory system, or possess some other useful combination of biological prope-rtics. The rapid growth of the synthetic ali phatic industry should continue and per haps accelerate. Each new coinpound may be regarded as a hand from Λνηίοη more chemical digits will grow. Acknowledg
merit
The authors wish to acknowledge the assistance of C . A. Sctterstrom and P. R. Rector in the compilation of s-tatistios and preparation of this paper. PRESENTED before the New York Section of the AMERICAN CHEMICAL SOCIETY and a n Chicago b e
fore the Technical Service Association of t h e Chemical Industry. Part I appeared in th.e Nov» 3 issue of C&EN.
Helium Isotopes Separated by Fluid-Plow J\. SINGLE-STEP process for the separation of helium 3 and helium 4 has been reported by a group at Ohio State University. The process utilizes the super-fluid flow characteristics of helium II and serves as partial verification for the suggestion that He 3 atoms do not partake in superflow, at least not within the limits of measurement. At temperatures near absolute zero liquid helium acquires the property of super-flow, that is, the ability to climb out of its container. This point is known as the λ-point. It is possible that the λ-point of He 3 is below that of He 4 and that when lower temperatures are reached it may also be capable of super-flow. In the experiments at Ohio State, liquid helium II at 1.5° K. was transported by super-fluid flow through a suprasurface film for a given period of time from one reservoir to another, contained within the first, with a resultant concentra tion of the rare He 3 isotope (normally present in atmospheric helium at about one part per million) in the initial res
45 . N O V E M B E R
10,
1947
ervoir. Work is now being carried ou-t on obtaining strong concentrations o i He 3 through the use of large quantities of liquid helium. Concentration of the He 3 isotope whichi is expected to differ greatly from He*, especially in the liquid state, will scrv« to make possible further investigation's into the many questions tluft have arise» in connection with the low-temperature characteristics of helium. Further,, it ha.s been observed in the course of these experiments, designed to studVy th.e mechano-caloric -effect in helium 1 1 , t h a t temperature differences of the order o f 10 "*2 could be obtained by mechanically altering the relative height o f the liquids in the two containers, "thus xnakir&g possible an exact measurement of tfcie entropy of super-fluid helium II. The Ohio State group which is workiog under contract with the Office o f Navel Research included J. G. Daunt, R. E . Probst, and H. L. Johnston.. A. O . Ni^r and L. T. Aldrich of the University of Minnesota also collaborated.
32*9
