BILLIONS
STAFF
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ACETYLENE PRODUCTION
REPORT
Calcium carbide a n d n a t u r a l gas vie f o r f a v o r as starting materials, but e i t h e r w a y , say users, as long as it m e a n s m o r e . . .
ACETYLENE T HE approaching developnierxt of commercial processes for productions: of acet\lene from natural gas or other h\drocarhons by a thermal cracking zamethod is expected to pose a serious challenge to t h e calcium carbide process, wliich starts with coke and lime. T h e r e is little likelihood that the calcium carbide route will be rendered obsolete, however. Big news in t h e chemical industry today is the development of aerylonitzrile fibers. But t h e story b e h i n d the fiber news concerns acetylene, one of the sraw materials used in t h e synthesis of acrylonitrile. In this connection, the industr-y is wrestling with two complex problems: ( 1 ) Can a process for economic production of acetylene from natural gas be developed? and ( 2 ) Can an investment ira new calcium carbide capacity b e jusrtified economically in view of the possible emergence of hydrocarbon acetylenes? Answers to these questions will shape t h e face of a large segment of chemical isndustry for some t i m e to come. In answer to t h e first quesrtion, Monsanto Chemical Co. is planning a $30 million program at Texas City to include acrylonitrile production from acetylene. T h e acetylene will be derived from methane and oxygen by partial combustion followed by solvent extraction. Of further importance, the Wulff IProcess Co., a holding company for t h e Wulff patents, will launch a small demonstration unit to p r o d u c e 1 million cubic feet of acetylene a m o n t h for cylinder g a s . Located just outside Los Angeles, Calif., the plant, w h i c h will begin operation late this month, will use natural gas feed or propane w h e n gas supplies a r e interrupted. These projects, the first chinks in t h e car~bide armor, have still a long way to g o , ho^^ever. Several pilot plants have already fallen by t h e wayside attempting to zresolve the problems involved in producing acetylene from hydrocarbons economically. Will It P a y Off? Some companies with a s t a k e in calcium carbide are wondering w h e t h e r further expansion is justified. Ora one hand, American Cyanamid Co. is contemplating construction of a large carbicie plant in Virginia, as p a r t of a program to expand
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acrylonitrile capacity. " O n t h e fence" is Air Reduction Co., w h i c h had originally planned a $10 million outlay for calcium carbide production near P a d u c a h , Ky. At present, the timing element may not b e favorable for this undertaking. However, the project, which was to incorporate new design features promising substantial o p erating economies, could b e revived. Union Carbide says it is planning a substantial expansion of carbide capacity at existing plant and power developments—this w o u l d point to Sault Ste. Marie a n d Niagara Falls as the most likely possibilities. While all indications point to some expansion of carbide facilities in certain selected areas, at the same time t h e chemical industry seems to b e favoring the eventual adoption of a thermal cracking process for acetylene. T h e problems to b e surmounted are formidable, a n d until thinking h a s crystallized on the subject of acetylene sources, it is probable that acetylene will continue to be in short supply. An a c e in calcium carbide's # corner is carbide's suitability for shipment in simple containers for generation of acetylene wherever needed. T o illustrate the advantages of t h e carbide-acetylene system, one only needs to compare estimated investment costs: $6.00 per thousand cubic feet of annual capacity for a carbide facility and acetylene generating units at scattered locations, versus a n engineering estimate of $8.95 for hydrocarbon acetylene. Thus, hydrocarbon acetylene is usually visualized as a potential material for large-scale chemicals syntheses. For the chemical (as opposed to cylinder gas) market, acetylene from m e t h a n e offers a favorable, t h o u g h as yet u n d e m onstrated, economic potential. T h e challenge of acetylene from this source is sharpened by cost estimates of 7 to 8 cents a pound for t h e Wulff system. This estimate, while highly speculative considering the unproved nature of the process, includes t h e cost of separation by Hypersorber and selective solvent, 5 year writeoff of investment, a n d natural gas at 9 t o
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10 cents per thousand c u b i c feet. W h e r e gas is delivered from 25 to 3 0 cents, total acetylene cost will run an estimated. 9.5 to 10.5 cents per pound. Starting with calcium carbide, acetylene can b e m a d e to sell for about 11 cents p e r pound with some range based on power costs. Breakeven cost is probably as low as 7.5 cents. Present feeling in industry points t o the eventual ascendancy of a t h e r m a l cracking process for acetylene in locations close to natural gas fields, while calcium carbide may be expected t o hold its o w n in areas of low power cost and plentiful supplies of coal a n d lime. Much depends on t h e further development of acetylene markets for acrylonitrile, as well as high pressure (Reppe) acetylene derivatives, polyvinyl chloride, and others. Reluctant to b e the guinea pig for a thermal cracking process, many acetylene p r o d u c e r s will place immediate d e p e n d e n c e o n the calcium carbide process. Actually, ethylene right now offers stronger competition to acetylene from carbide than does the thermal cracking process. Hydrocarbon Acetylene Industry experts are almost u n a n i m o u s in feeling t h a t an electric arc p r o c e s s for producing acetylene from m e t h a n e or other hydrocarbons h a s some possibility where only limited quantities of acetylene are needed a n d power costs are low. One such is the Schoch process developed a t the University of Texas. F a r more interest is exhibited in a Wulff regenerative process, perhaps using propane, and in partial combustion systems involving m e t h a n e and either air or tonnage oxygen. W i t h a methane feedstock, cracked gases from the quencher would have the following approximate composition: Constituents Mol H2 N2 CO CH* COz
%
C2H2 C2H4 Heavier C 2 H 2
AND
Partial Combxistion Air Oxygen 24 48 10 9.4 4.5 3.9 0.2
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.53
2 0_ .5 10.4 5.5
10.0 0.6
—
ENGINEERING
Regenerative 33.8 43.3 8.6 4.6 1.7 7.3 0.4 0.3
NEWS
T h e WuLff process has the advantage that ethylene can also be produced in substantial amounts if propane is cracked in the regenerative furnace. Using propane, this process is reported to yield up to 14.8'v acetylene and 15.7Vr ethylene in the cracked gases. Further, use of off-gases reduces the cost of heat energy required. A partial combustion process in which methane a n d oxygen ai e ignited in rerraetory burners is reported to produce as much as 18 volumes of acetylene in the product gases per 100 volumes of methane h-d; a plant at Oppau. Germany, produced a cracker stream containing 8r/r by volume of acetylene with a yield of 32 r/ r based on methane. Comparable yields were obtained starting with propane. T h e separation problem is such that, for maximum recoveries, production capacity of 290 million cubic feet of acetylene a \ ear is a minimum requirement. W h e r e a separation between C 2 fractions is desired, a solvent absorption system, using a selective solvent such as dimethyl formamide, lias b e e n suggested. Such a system produces high-purity acetylene, although carryover loss ol an expensive solvent presents a problem. Economic estimates of 7 to 8 cents a pound for hydrocarbon acetylene are regarded as sufhcientlv attractive to entice prospective users of acetylene to Texas. Monsanto will be first in t h e field at Texas City, and General Aniline is regarded as a potential second candidate. Tennessee Eastman, n o w constructing a chemical plant at Longvievv, Tex., not only says that acetylene is a future possibility, b u t has succeeded in improving on the Wulff process. Indeed, there are few chemical companies which have not investigated the feasibility of one or more of these acetylene processes. Based on calcium carbide, acetylene can now be produced for an estimated 11 cents a pound, including all costs, in an efficient plant. Notwithstanding estimates of low cost acetylene via t h e as yet uncertain natural gas route, t h e carbide industry feels t h a t it has a superior p r o c e s s indeed a process of proved worth.
Annual statistics are shown Table i. Untied S t a t e s Production of Calcium in Table I. Uses for carC a r b i d e and Acetylene bide, aside from acetylene CARBIDE E Q I J V A manufacture, are as a moisCALCIWJ ACETVI EXE I E N T O F ACETYture determinant and dryCARBIDE (Thous. Cub:/'i is in power supply a n d t h e use of cjf »r coke or lime ( w h i c h cause h i g h e r 1 - "-le consumption) h a v e a n a d v e r s e on process economics. •or pipeline acetylene, cost t o a large * finical consumer is estimated a t 1 1 cents a pound, based on c a r b i d e a t $ 6 0 a ton. T h e acetylene estimate assumes t h a t t h e consumer bears all costs including profit o n investment in g e n e r a t i n g facilities. Normally, commercial calcium car 1'.J e p r o vides 9,000 t o 9,400 cubic feet of acetylene p e r ton of carbon. Taking into a c c o u n t possible improvements in furnace design a n d process o p eration, and under conditions of favorable
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power costs, acetylene cost of 9 . 5 cents a p o u n d could be realized. For the cylinder gas market, the economics are entirely different and bear little relation to the estimated cost of 11 cents a p o u n d for pipeline acetylene. This market is sizable in the aggregate, and carbide is strongly entrenched. Acetylene generating units are positioned a t scattered locations for local distribution of cylinder gas. Thus, acetylene costs for t h i s service must include cost of transporting carbide, packaging acetylene in small containers, a n d depreciation of a larger investment p e r unit of product. Acetylene Markets While acrylonitrile and the R e p p e synthesis will probably a d d importantly to t h e d e m a n d for acetylene, r e a l impetus b e h i n d acetylene development has been t h e introduction of synthetic aliphatic derivatives—acetaldehyde, acetic a c i d a n d anhydride—and of polyvinyl plastics. Acetylene production as shown in Table I reveals a strong u p w a r d t r e n d which was accelerated during w a r t i m e b y increascvi requirements for welding and cutting, a n d for the neoprene program. T h e 1949 recession is also indicated. T h e array of calcium carbide plants s h o w n m Table III indicates geographic centers of acetylene consumption—each with its own particular pattern of supply a n d d e m a n d . Excluding t h e w e l d i n g industry, important consuming areas are Niagara Falls, N. Y., site of Goodrich and Goodyear polyvinyl chloride plants and Niacet Chemicals' production of acetic acid, vinyl acetate, acetaldehyde, and o t h e r acetylene derivatives; Ashtabula, O h i o , w h e r e Hooker-Detrex makes trichloroethylene, a n d nearby Painesville, w h e r e U. S. Rubber produces polyvinyl chloride; a n d Louisville, Ky., where Goodrich has a large P V C p l a n t a n d Du Pont centers its neoprene activities. With t h e construction of Mathieson C h e m i c a l Co.'s ethylene oxide and glycol
plant near Brandenburg, Ky., a n d d i e possibility of Airco's P a d u c a h plant, t h e Ohio River Valley from Louisville to P a d u c a h seems t o be s h a p i n g up as a n important chemicals center. Mathieson's project for production of 50 million p o u n d s a year of glycol, starting from e t h a n e extracted from natural gas, h a s m a n y implications Eth\ lene oxide, for example, will react with hydrogen cyanide to form ethylene eyanohydrin, which is d e h y d r a t e d to acrylonitrile. Mathieson m a y well h a v e an eye on acetylene chemicals; for entry into this field either ^alcuim carbide or natural gas is or can b e m a d e available. Mathieson's decision to '.ocate near Brand e n b u r g , and balance transmissions costs on n a t u r a l gas against freight o n its finished products, can be regarded as one of t h e year's more significant developments. Shawinigan Chemicals T h e largest a n d most important center of aliphatic chemicals derived from acetylene is Shawinigan Falls, Q u e b e c , C a n a d a . At this location, low cost electric p o w e r , proximity of limestone, a n d a d v a n c e d plant design offer economic advantages which permit Shawinigan Chemicals, Ltd., to p r o d u c e , in volume, derivatives of acetylene at low cost. I n spite of a $10a-ton tariff on calcium carbide, t h e company could compete w i t h U n i t e d States producers if necessary. However, approximately 8 0 % of the carbide produced a t Shawinigan Falls is u s e d to g e n e r a t e acetylene. In t h e postwar period, plant capacity has b e e n a d d e d for the m a n u facture of acetaldehyde, acetic a n h y d r i d e , and acetylene black, while new plants have b e e n built for t h e manufacture of b u t y r a l d e h y d e a n d monochloroacetic acid. Shawinigan Chemicals p r o d u c e s 20 derivatives of acetylene, from the a c e t a l d e h y d e series to butylated chemicals. I n t h e U n i t e d States, acetic acid a n d anhydride production from acetylene h a s lost g r o u n d to t w o alternative routes. Most important is t h e ethylene-to-ethyl alcohol
Competitive Interrelation of Acetylene and Ethylene
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Table III.
Calcium Carbide Industry
PLAJVT L O C A T I O N
POTENTIAL ANNUAL CAPACITY (Tons )
Air Reduction Co., National C a r b i d e Division Louisville, Ky. 144,000 Keokuk, Iowa 36,000 Ivanhoe, V a . 79,000 Ashtabula, Ohio (Government owned) 81.000 Union Carbide & Carbon Co. Electro Metallurgical Division: Niagara Falls, N . Y. 115,000" Sault Ste. Marie, Mich. 90,000« Ashtabula, Ohio 108.000° Portland, O r e g o n 17,000" Shawinigan Chemicals, Ltd. Shawinigan Falls, C a n a d a 220,000 Tennessee Valley Authority Muscle Shoals, Ala. 85.000 Mid-West Carbide Corp. Keokuk, Iowa 50,000 Monsanto Chemical C o . Anniston, Ala. 22,000 Pacific Carbide Co. Portland, O r e . 15.000 American Carbide Co. Arkansas City, Kan. 3,000 1,065,000 ° Estimated N o t e : Union C a r b i d e , Portland, Ore., plant also produces ferro-alloys. TVA and A i r Reduction, Ashtabula, Ohio, plants are in standby condition. American Cyanamid, Niagara Falls, Ontario production is captive; output of calcium cya n a m i d e is presently 2 5 0 , 0 0 0 tons per year. Mid-west Carbide Corp. is jointly owned by Shawinigan Chemicals and National Cylinder Gas
Co.
acetylene. The competition between these raw materials is made manifest in a number of interesting ways. For example, several polyvinyl chloride plants use vinyl chloride monomer made from ethylene and chlorine, instead of producing the monomer from acetylene and hydrogen chloride. Dow Chemical sells vinyl chloride based on ethylene for only 10 cents a pound, a price which reflects competitors' costs of producing the monomer from acetylene. Thus, ethylene and acetylene have been equated for this particular use. In another instance, ethylene and acetylene can team up to produce vinyl chloride. Shell Oil Co. has patented a process which proceeds by several stages. Ethylene and chlorine are reacted t o ethylene dichloride, which is then cracked to vinyl chloride and hydrogen chloride. More vinyl chloride is produced by reaction of the by-product hydrogen chloride with acetylene. The complementary relationship of ethylene and acetylene in this instance simply points up the fluid nature of the chemical industry. Usage of acetylene for the PVC industry, operating at full capacity, would amount to about 2.2 billion cubic feet a year.
Polyvinyl Chloride One of the most rapidly developing products derived from acetylene is polyvinyl chloride. The polyvinyls, including the acetate, constitute one of the largest groups of plastics and one of the most expensive by comparison with phenolic, alkyd, and polystyrene resins. • With respect to raw materials availability and stability, the vinyl resins are in a better position than the other groups as they are not dependent upon supplies of aromatics. Postwar plant expansions, primarily by Carbide & Carbon and B. F. Goodrich, have brought polyvinyl capacity up to 325 million pounds a year. Goodrich recently announced plans for a new u n i t its third plant—at Avon Lake, Ohio, which is expected to b e in operation by mid1951. U. S. Rubber Co. will expand the capacity of the Painesville, Ohio, plant shortly. Goodyear expects to have enlarged capacity costing $2,250,000 in operation at Niagara Falls, N. Y., early in 1951, and other rubber companies, including Firestone and General Tire, are known to be interested in participating more fully in the vinyl business.
Acrylonitrile A head-on battle between acetylene and ethylene for the promising acrylonitrile market seems to Ibe developing. So far, American Cyanamid has been the only producer of acrylonitrile for c-ommeicial distribution. Its plant at Warners, N. J., uses ethylene oxide as starting material. Carbide & Carbon has been reported to be constructing facilities at Institute, W. Va., for the production of acrylonitrile, also based on ethylene oxide. Acetylene is very much in the picture, however, with Monsanto's $30 million program and American Cyanamid's plans, both schedules involving acrylonitrile from acetylene. These projects may indicate that a catalyst with a longer life than the neoprene catalyst (copper chloride and ammonium chloride) has been developed. Additional hydrogen cyanide capacity will also have to be installed to complete the acrylonitrile reaction with either -ethylene oxide or acetylene. Doubtless, Monsanto will use the methane plus ammonia catalytic reaction, while Cyanamid will stay with calcium cyanide. The rushing development of fibers of acrylonitrile polymers and copolymers with other vinyls means that acrylonitrile will become a tonnage chemical, and soon. As an important specialty rubber, neoprene made by Du Pont at ^Louisville, Ky., absorbs 1.5 billion cubic feet of acetylene a year at peak operating rates. A substantial increase in capacity, now 60,000 long tons a year, has already been announced.
PVC Raw Materials Approximately 459& of the PVC capacity is based on ethylene and 5 5 % on
Reppe Synthesis Potentialities of the Reppe synthesis which General Aniline L Film Corp. has
method. The Oelanese direct oxidation of propane and butane may be considered second most important. The future availability of low cost acetylene from natural gas may improve the outlook for the acetylene process somewhat, but the Celanese system is believed to have an economic edge over the other two.
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exploited in a semicommercial unit a t Grasselli, N. J., are such that the company says, "We are considering a suitable location for a commercial plant to produce acetylene derivatives." If the plant is located in Texas, the acetylene required would ultimately be derived from a thermal cracking process and a natural gas feed stock. The significance of t h e Reppe high-pressure technique is that vinylation, ethynylation, a n d polymerization reactions have opened o p a new Held of chemistry by introducing such newproducts as polyvinyl pyrrolidene, butanediol, propargyl alcohol, cyclooctatetraene, and many other intermediates as yet unexplored. Vinyl ethers are considered! interesting prospects as intermediates o r for polymerization with other monomers. Butanediol offers an attractive raw material for nonfugitive plasticLzers and synthetic fibers of polyurethane, polyester, and poly amide types. While General Aniline has reached only the market-testingstage in its interest in these developments, the future for this field of acetylene chemistry appears excellent. Future Further expansion of acetylene markets(particularly for acrylonitrile production ) ,. together with plans for expanded polyvinyl chloride facilities and extension o r the Reppe high pressure reactions, will force a two-way show-dc^wn: between: acetylene from carbide and from natural gis; and between acetylene and ethylene. The competitive impact visualized will be softened by the enlargement of existing markets for both acetylene and ethylene. However, the future course of events will determine the competitive relationship of Monsanto's acrylonitrile from natural gas at Texas City, Cyanamid's acrylonitrile from calcium carbide, a n d Carbide & Carbon's acrylonitrile from ethylene. In the final analysis, choice of acetylene or ethylene for competing uses will b e based .on relative yields, reaction speeds, the number of process steps, and byproduct formation. Economics will weigh heavily in the balance. Acetylene will have to rely to some extent on versatility to offset costs of 4 to 6.5 cents per pound, for ethylene from ethane or propanecracking. References (1) Aalh Christian Hiorth, '"Calcium Carbide, Its Manufacture and Uses,**" Chemical Products, Jan.-Feb., 1945. (2) "Acetylene," Industrial Reference Service, U. S. Department of Commerce. (3) "Calcium Carbide," Industrial Reference Service, U. S. Department of Commerce. (4) "General Aniline & Film Unveils. Acetylene Pilot Plant," C&EN, 27„ No. 14 (April 4, 1949). (5) Herrly, C. J., "The Acetylene Chemical Industry in America," C&EN,. 27, No. 29 (July 18, 1949). (6) Kirk, R. E. and Othmer, D. F., "Encyclopedia of Chemical Technology," Vol. 1, pp. 101-123; Vol. 2, pp. 834-846. 424T
