I,VDUSTRIAL A S D ENGINEERING CHEMISTRY
October, 1929
was found that the relationships could be expressed by the following equations:
or
C,
=
c,
=
(4.0s) ~ ~ (1.8t 5+ 0 702)
~
(4.0 - S) 6460 (t
+ 670)
where C, = specific heat at atmospheric pressure S = specific gravity at 16 5' C (6!" F ) t = temperature [ " C in (1) and F. in (2)]
Values for the specific heat calculated by these equations are in good agreement with the experimental ones as will be seen in Figures 2 to 6 where the results calculated from the equations are s h o ~ ~by i i the dashed line. For the low molecular-weight hydrocarbons the calculated values agree fairly well with the observed values a t the average temperature of the determination ( 2 ) as is shown in Table 11. Table 11-Specific
Heats a t 50' C.
At temperatures inuch different from this, however, the agreement with the equation proposed by Lewis and McAdams is not so good, because the temperature coefficient of the two equations is different. The equation proposed here should be considered to apply to distillates froin midcontinent crude a t atmospheric pressure and in the temperature range from that a t which the distillate is just completely vaporized to temperatures where thermal decomposition sets in. Its applicability t o distillate, froin crudes other than midcontinent has not been shown. HOWever, it would probably give results not much in error. It will be noted that the equation is similar to that of Fortsch arid Whitman ( 1 ) for the specific heat of the liquids. The comparison of the calculated values for liquid and vapor is shown in Figure 7 . Ackncwledgment
The writers are indebted to W.H. hlcAdams aiid W.G. Whitman for suggestions in the development of the empirical equations.
LEWISA N D MCADAMS BAHLKEA X D K A Y Propane Butane
0 434 0 410
0 428 0 420
945
Literature Cited (1) Fortsch and Whitman, INDEVG CHEM 18, 795 (1926) ( 2 ) Lenis and Ivlc4dams, Chem .Vel Eng , 36, 336 (1929)
Thermal Treatment of Natural Gas' D. S. Chamberlin and E. B. Bloomz LEHICHUNIVERSITY, BETHLEHEX, Pa.
vv
cubic meters in a horizontal Natural gas was thermally treated in tubes of silica, 'HILE studying some steel, copper, iron, nickel, monel, and clay. Between reaction tube of quartz, 3 cin. of the characterisinside diameter. Copper extemperatures of 500" and 900" C., the various tubes tics of natural gas erted little catalytic effect on had different effects on converting methane to benzene, as found in various parts of the decomposition; with an naphthalene, anthracene, acetylene, etc. All these this country, it was observed iron tube no c o n d e n s a b l e materials except nickel gave yields of benzene varying that when natural gas was p r o d u c t s of decomposition from 4.00 to 40.00 liters per thousand cubic meters gas thermally treated clouds of oil were obtained. The yield of treated. Nickel catalyzed methane, causing a breakvapors were formed and that aromatic hydrocarbons dedown to carbon and hydrogen. benzene as one of the chief creased as the hydrogen diluThe effects of temperature, surface, dilution, and constituents of the treated gas tion increased. other factors were studied. Various units are discussed could be recovered by adsorpBetween 1000" aiid 1200" ranging from laboratory-size apparatus to a semition. C., Stanley arid Sash (3)have commercial installation. Bone and Coward ( I ) made concluded that comparatively This work shows that carbon which is formed in the these observations in their long heating periods and t h e treatment tubes is responsible for the specific catalytic study of the decomposition presence of such active mateeffect in changing natural gas to aromatic hydrocarof methane, but little regard rials as iron and nickel cause bons. The CH residue is not necessary in the conwas given to this mist formainethane to deco1npo.e into version but no doubt takes place in the polymerization tion. carbon and hydrogen. On to aromatics. Fischer ( 2 ) found that a t the other hand. shorter heattemperatures around 1000 O C. and- a high gas velocity satisfactory yields of tar and light ing periods and the presence of such materials ab porcelain, oil were obt>ained. Quartz and porcelain were suitable tubes silica, and beryllia are much less active in proriiotiiig this for this synthesis, while iron and copper tubes favored the decomposition. This investigation on the heat treatment of iiatural gas, formation of carbon. On diluting methane with other gases, a high temperature of conversion mas necessary to bring which has been under way for the last four years, has conabout the same degree of conversion. The tar contained sidered the practical treatment of natural gas in apparatus naphthalene, phenanthracene, and the light oil, benzene and of large table size as well as semi-conimercial uiiitq, to examine the mechanism of thermal treatment as regarding toluene. \\-heeler and Wood (4)found that benzene was an iinpor- surface, materials of construction and conrersion, and t h e t a n t product of the pyrolysis of methane between 8i5" and economic thermal conditions necessary to give a practical 1000" C. The optimum temperature for the productioii of conversion. benzene was about 1050" C., yielding 27 liters per 1000 Materials, Apparatus, and Method Presented before the Division of Gas and 1 Received April 11, 1929. Fuel Chemistry at t h e 77th Meeting of t h e American Chemical Society, Columbus, Ohio, April PO to M a y 3, 1929. 2 Columbidn Carbon Fellow, Lehigh University.
The natural gas as used in these experiments was obtained from near Charleston, W. Va., and from the Monroe field of Louisiana. These gases were compressed a t the wells into
INDUSTRIAL AND ENGINEERING CHEMISTRY
946
cylinders of 6.23 cubic meters a t pressures up to 141 kg. per sq. cm. The analysis of the two gases is given in Table I. Table I-Analyses of Gases Studied WEST VIRGINIA GAS LOUISIANA GAS P e r cent Per cent COl CHI C2HI Na
0.80 71.20 23.30 4.70
0.50 94.12 3.44 1.94
The tubes in which the thermal treatment of the gas was carried on were nine in number and were of materials and dimensions as shown in Table 11. Table 11-Materials and Dimensions of Tubes TUBE INTERNAL DIAMETFIR HEATED LENGTH Cm. Cm. Fused silica 30 Fused silica 45 Steel 45 Nickel 45 Monel 45 Copper 45 Fused silica 45 Steel 275 Clay 275
I n all cases furnaces were built for the particular tubes; in the f i s t seven cases the source of heat was electrical and in the last two heating was obtained from a coal grate. The general experimental layout is shown in Figure 1. The cylinder of gas, A , is expanded into a gas-holder and pressure regulator, R. From this point the gas can be forced, a t pressure consistent with practice, through the rest of the system. At two coconut shell carbon towers remove any gasoline vapors from the gas. A wet gas meter a t E, or a flow gage, meters the gas to 0.0003 cubic meter. If it is necessary to dry the gas, drying agents can be placed between E and F. I n every case the electric (Figure 2) or coal furnace was inserted a t F and the temperature of the furnace controlled by standardized noble-metal couples. The velocity of flow of the treated gas was reduced temporarily a t H to allow heavy tars and naphthalene to condense out. At K the fixed oil vapors as benzene, toluene, etc., were adsorbed in active carbon towers. I n many cases, since some of the oil fog was not scrubbed out in the carbon towers, the final traces of aromatics were thrown down by precipitation in a small Cottrell unit. The carbon that formed in the tube was recovered by
Vol. 21, No. 10
a temperature of 200" C. The gas was analyzed by either 8 modified Burrell or by the Bone and Wheeler gas apparatus. Fused Silica Tube-1.9
cm.
West Virginia natural gas was passed through a new silica tube a t the.rate of 0.085 cubic meter per hour and a temperature of 800-850" C. At first no fumes were observed, but after about 0.142 cubic meter of gas had passed through, light brown fumes started to form. At this point a thin film of carbon was observed over the tube in the heating zone. As the experiment proceeded naphthalene crystals built up on the walls of the air condenser, and finally a brown oil collected in droplets. Some portion of the fumes failed to condense out and even passed through the carbon absorbers, showing that some of the oils formed were not wetted and were therefore lost to the end gas. The products recovered were 8.0 per cent carbon in the silica tube, 5.40 per cent oils, and naphthalene condensed in the air condenser, the remaining gas and suspended oils amounting to 86.6 per cent. This final gas showed that 42.0 per cent of the natural gas had been decomposed, and when examined for benzene oils was found to contain 43.73 liters per thousand cubic meters. This benzene oil was of about the same composition as a 90 per cent benzene. On repeating this experiment several times, it was found that the optimum rate was 4.57 cubic meters per hour per square meter of heated area in a tube as above a t 800-850" C. At any one temperature the lower the rate the higher the yield of oils, carbon, and tar, and the greater the decomposition of the natural gas. If the precautions were observed to cool the furnace containing the tube in the presence of the natural gas or its products, the formation of fumes was always instantaneous on passing the gas through the tube, when the proper temperatures were attained. On the other hand, if the tube was subjected to air while in a heated condition, and a t some later time was used for a thermal treatment of natural gas, in each case there was necessary a passage of 0.142 cubic meter or more of gas before the tube attained an activity that would cause the formation of vapors. To determine whether carbon had an effect on the con-
--L
L
.
Figure 1-Apparatus for Thermal Treatment of Natural Gaa
U
weighing the tube before and after treatment. Heavy tars and oils were recovered from the air condenser and the lines running thereto, by washing in volatile solvents. The condensable vapors as caught by the active carbon were recovered by placing the carbon in a distillation flask, wetting the carbon with pure glycerol, and carefully distilling off the benzene, toluene, and anthracene up to I
version of methane and ethane to aromatic hydrocarbons, several tests were run by placing various types of carbon in the tube as layers or granules. Carbon black, petroleum coke, graphitic carbon, and coconut shell carbon were noneffective a t the operating temperatures until 0.142 cubic meter or more gas had been passed through. The fog would then form, but in no case t o the same extent as when the tube itself had been coated. Examination of the carbons
INDUSTRIAL A N D EN6TNEERING CHEMISTRY
October. 1929
in the tube showed that a film of carbon had formed over each of the particles or on the surface of the tube. It was apparent that carbon first had to be formed from the decomposition of methane and ethane, and when this carbon had coated the tube in a thin film, oil fogs would start to appear. This carbon film did not accumulate rapidly, as carbon that did form later from the gas was to a great extent carried 'out of the reaction tube in the oil fog. In this small tube oil vapors were visible at temperatures as low &s 650' C. On attaining temperatures much above 850' C., vapors that came over were mostly tar holding a great deal of carbon.
847
Steel Tube--3.5
cm.
Iron tubes were first used, but in no case were any'oil fumes observed. Iron catalyzed the reaction according to 2H2, and the tubes rapidly decomposed. CH, = C At temperatures around 630" C. fumes of oil were first visible a t gas rates from 0.057 to 0.19 cubic meter per hour. At 890" C. the fumes turned dark brown. On cooling down the furnace and then heating it up the next day, fumes were not formed a t any temperature. After removing the carbon from the tube, at a temperature of 800" C. and a rate of 0.198 cubic meter per hour, 24.6 liters of benzene per 1000 cubic meters of gas were obtained.
+
Fused Silica Tube-3.6 cm. I n order to study the effect of surface, increase in gas rate, and the type of gas used, a larger silica tube was placed in a furnace with a larger heating surface. Gas that had a minimum ethane content was obtained, to determine whether the reduction of ethane in any way reduced the yield. Louisiana gas was run through the silica tube a t a rate of 0.10 cubic meter per hour and the temperature held a t various points to determine a t what point fumes were formed and the degree of breakdown of methane. By analysis, the unsaturates decreased from 1.7 per cent at low temperatures to 1.0 per cent at high temperatures. The acetylene content remained nearly constant at 1.1 per cent. In this scrim of experiments fumes appeared a t 600" C. The practical decomposition of natural gas a t 900" C. was determined by running the gas through the treatment tube at a rate of 0.093 cubic meter per hour and, after a quantity of treated gas had accumulated, running this gas back through the tube. The gas was analyzed after each t.rmtment. I n five thermal treatments the methane content reduced as follows: 75.4, 69.7, 61.6, 59.2, 60.6 per cent, and after the tenth treatment the methane content was 48.2 per cent. A gas mixture was made up containing 41.4 per cent methane and 57.9 per cent hydrogen. This mixture, after a thermal treatment under the same conditions as above, yielded 40.0 per cent, methane and 56.3 per cent hydrogen. No oil fumes were formed, but acetylene was formed to the extent of 0.7 per cent, showing that the Fnmes are not entirely dependent on the polymerization of the CH residue. Several rnns were made using Louisiana natural gas to show the effect of temperature on the yield, with other factors constant. Table 111 gives a comparison of benzene yields with methane decompositions. Table IV shows, as a comparison with Table 111, a collection of data on West Virginia gas run under similar conditions. Table 111-Effect of Temperature on Benzene Ylelda from Louisiann Natural Gas
686
nzo '
7 s
0 . ~ 1 0.10 0.836
0.10
1.20 7.23 16.23
24.05
T=C~
282.70 282.70
1oon.m
None N~~~ None
None Light Considerable heavy fog
Silica tubea seemed t o work the most satisfactorily, for after a thin 6hn of carbon formed on the inside of the tube this film increased very little in thickness. Any carbon that did form was in a finely powdered state and was carried out in the w.
Figore 2-Collocfion
of Furnaces and Tubes Used in the Tests
When a new steel tube was used for the thermal treatment of Louisiana gas, the tube was heated to 750" C. and gas was passed through the tube at a rate of 0.102 cubic meter per hour. After 0.396 cubic meter of gas had passed through the tube, fumes began to form. Benzene was recovered to the extent of 27.00 liters per 1000 cubic meters and naphthalene oils to the amount of 714.00 grams per 1000 cubic meters, The gas, on analysis, showed methane 49.4 per cent, hydrogen 50.6 per cent. Table IV-Effect
of Temperature on Benzene Yields from West Virginla Natural Gas
CnHaTBUP. RATS RBNZBNB TARS 0 c. cu. m./ Liters/ cram*/ hour I000 LU. m, IOW LU. m. 050- 0.071 6.05 None 750' 0.08 4.01 2401.10 860' 0.091 4.01 2401.10 sfin6 0.08 28.10 9004.30 1040b 0.082 38.90 1usc4.10 80Ub 0.085 20.20 , , , ... 7 M b 0.082 2.07 . ., . . , R26r 0.042 41.95 . .. .. .
N O N C O N D R N E A B L ~For,
Whitevapors Brownfumes
H**T*D
LshiorH Cm. 46 40
Anfhraceneinfumes 46 ~ e a v y p i t c hblpwniumes , 48 ~~~~ftrellprenplta 187846 tor Heavy pitch withearbon 46 Yellow fumes, red oil 46 Heavy dark fumes, carbon 0 2
Nickel Tube-3.8 cm.
Nickel caused a breakdown in every case to carbon and hydrogen a t all rates and temperatures u p to 880" C. At 880" C. a t a rate of 0.10 cubic meter per hour, 217 kg. of carbon were deposited in the tube per 1000 cubic meters of gas. The carbon was very fine and fluffy and contained nickel. No oil fumes were formed and, after the tube had been subjected to several runs, the carbon yield fell off t o negliable quantities. When pure nickel gauze was placed in a 3.5-cm. silica tube, West Virginia gas at 700' c. gave 66.60 kg. d Ertrbon per 1000 cubic meters in the tube. A similar test &s rtbo~ewith Louisiana gas gave 17.64 kg. of carbon. I n each esse t h e
948
INDUSTRIAL A N D ENGINEERING CHEMISTRY
nickel gauze was decomposed, resulting in a nickel-carbon combination. Monel Metal Tube-3.5 cm.
Since nickel readily decomposed methane into its elements the question arose as to whether alloys of nickel would do the same. Monel metal, mainly an alloy of nickel and copper, was employed as a treatment tube. At a rate of 0.156 cubic meter per hour vapors were first visible at 670" C., and a t 700-750" C. appeared in large quantities as dark brown vapors. After the carbon layer had been formed, fumes repeatedly came over above 670" C. up to a rate of 0.28 cubic meter per hour. The yield of benzene at 0.156 cubic meter per hour was 24 to 27 liters per 1000 cubic meters of gas treated. Little carbon was formed in the tube and the methane content of the natural gas from Louisiana was decreased 30 per cent. As the tests were repeated on the tube, the oil yield dropped off, the tube finally became inert, and vapors could not be obtained. Sickel carbide was found in the soft carbon that accumulated in the end of the tube. Little naphthalene was formed under any of the above conditions, but anthracene was formed and extracted from the adsorbent carbon after the benzene passed
VOl. 21, N o . 10
900" C. the fumes started to turn yellow and a t 990" C. drops of oil and tar condensed in the air condenser. As compared with the 3.5-cm. tube, it required 150" C. higher temperature to attain the same visible conditions. At 880" C. at a rate of 0.136 cubic meter per hour, a yield of 6.67 liters of benzene per 1000 cubic meters was obtained. This and other experiments indicated that thermal treatment in the gas phase, as well as an active surface condition, is necessary for good conversions of natural gas into aromatic hydrocarbons. Large-Scale Unit-Steel
Tubes 15.2 cm., Clay Tube
15.2 cm.
In June, 1926, a large-scale unit was erected at Tacony, Philadelphia, at the carbon plant of the L. Nartin Co., that would treat thermally 1.4 to 2.8 cubic meters of natural gas per hour. The general layout of the plant was similar to Figure 1 and was constructed entirely of steel. The heating unit consisted of three steel pipes 2.40 meters long and lying horizontally, one above the other, over a coal grate. The heated length of each pipe was 1.83 meters and the temperature of each treatment tube was controlled by a base-metal couple fitted into the center of the middle porOff. tion of each pipe. The gas was completely stripped of oil Cppper Tube-3.5 cm. vapor before and after treatment by running it through Copper being one of the principal metals in monel metal, 27.30 kg. of adsorptive carbon. The three retorts were so connected that the natural gas could be run through the a copper tube was next tried as a treatment tube. When 5.49 linear meters of heated retorts, through any one retort, a high-ethane West Virginia gas was passed through the or parallel through all three retorts. heated tube a t a rate of 0.10 cubic meter per hour, after the The benzene vapors were recovered from the carbon towers tube was coated with a layer of carbon, dense fumes came by steaming them out with high-pressure steam and then off as low as 565" C. The fumes were light colored at first, condensing the steam in a pipe cooler. The final vapors but as the temperature increased t o 645" C. they became after the benzene vapors were taken out were recovered from darker and denser. the gas by passing the vapors through a refrigerated coil. When a high-methane Louisiana gas was passed through On account of the large condensing surface of this plant, the treatment tube a t a rate of 0.085 cubic meter per hour, the lower point at which vapors were first visible was hard t o white fumes were just visible a t 450" C. and there was little determine. At a mean temperature of 760" C. a yield of change in density a t 500" C. At 575" C. the fumes changed benzene and lighter oils amounting to 13.73 liters per 1000 definitely brown and increased greatly in quantity. At this cubic meters was obtained a t a gas rate of 2.265 t o 2.832 last temperature the gas after treatment contained methane cubic meters of gas per hour. 68.2 per cent, hydrogen 25.0 per cent, acetylene 0.9 per cent, As these tests continued, the gas rate started to fall off unsaturates 1.2 per cent. At 600" C. and a 0.085 cubic and finally stopped. On examining the retorts, after a meter rate the benzene yield was 13.3 liters per 1000 cubic temperature drop from 616" C. in the top, 705" C. in the meters. Temperatures above 650" C. were not studied middle, and 782" C. in the bottom retort, it was found that because of the high conductivity of copper and its heat the bottom tube was filled with a granular grayish carbon. radiation to the air. This graphitic carbon varied from the bottom to the top T o determine whether a greater surface of copper would retort in the ratio of 7:3: 1. After this carbon had been reduce the temperature of gas breakdown into oil vapors, cleaned out the activity of the retorts was renewed. a copper box 7.62 X 7.62 X 30.48 cm. was constructed. . It was found that when the gas passed through all three This copper box had an exposed surface four times that of the retorts the higher the carbon accumulation the less the vapor usual tube used. On heat-treating the gas a t the rate of formation. By passing the gas through the hottest retort 0.085 cubic meter per hour, the low temperature of 450" C. only, the less the carbon yield in the retort the higher the was attained a t which fumes formed, and the yields changed vapor production. As steel favored the breakdown of methlittle from the tube treatment. ane into its elements, a clay tube was placed in the position Copper retained its activity as long as the surfaces were of the hottest retort. covered with carbon, but the copper tube finally decayed. By passing the natural gas through this clay retort at The carbon layer apparently combined with the copper in 800" C., oil mist was visible before the gas entered the carbon thin films as a carbide. These films peeled off from the towers. On recovering the oil from the carbon, the oil tube interior and a new carbon surface was formed. The proved to be benzene with some higher fractions. On exbreakdown of methane into its elements was low in copper amining the clay retort after several runs, it was found to a s compared with the other metals. contain only a film of carbon on the inner surface with a little Fused Silica Tube--10.2 cm. accumulation of a semi-graphitic black. To determine the effect of cross-section area of the treatment tube on methane breakdown and oil vapor formation, a large tube 91.5 cm. long was used as the treatment tube. At a rate of 0.142 cubic meter per hour fuines were first visible from high-methane gas at 830" C. They increased i n density up to 895" C., but were still light in color. At
Discussion
Olle of the outstanding differences between these euperiments and those of other investigators herein cited is that the tubes for thermal treatment were of such sizes that large volumes of natural gas could be treated and the rates could
October, 1929
ISDUSTRIAL A-VD EAVGINEERIAVGCHEMISTRY
be controlled t o such minima that maximum yields of recoverable aromatic hydrocarbons could be obtained. Contrary t o Fischer ( 2 ) , Wheeler and Wood ( 4 ) , Stanley and Nash (J), and others, temperatures were used a t 900" C. and lower. Their yields were duplicated, and in many instances bettered, a t temperatures under 900" C. In that it requires quite closely the heating value of 1.0 cubic meter of natural gas to treat 1.0 cubic meter of gas thermally, the actual economy of recovery is only one-half of the actual results obtained. I n order t o obtain the maximum converbion of natural gas into aromatic hydrocarbons, the operation must he conducted a t as low a temperature as possible. I t has been shown that yields can be duplicated on various metal tubes that have been reported to catalyze methane. Theie rewlts n-ere made possible by the use of tubes of large diameters, in which conditions were obtained. by the passage of large volumes of gas, which were not reached by other investigator.. The fact that carbon is catalytic has been shown m-hen it is in the many forms common to us. When carbon is formed on the surface of the treatment tube by decompoqition of the paraffin hydrocarboils a t low temperatures-e. g., 600 " to 900" C.-it ha. a specific activity in the conversion of natural gas into aromatics. If this carbon alloys with a metal or iq partially oxidized, its activity is lost and graphitic carbon results. The gas that results from these thermal treatments very closly approximates that from the distillation of coal in the by-product coke oven, in that it attains about 50 per cent hydrogen, 40 per cent methane, and the remainder ethylene, olefins, benzene; etc. The benzene yields are analogous, for in coke-oven practice a light oil yield of 27.0 liters per 1000 cubic meters of gas is fair practice. It is apparent that a similar yield from natural gas is the optimum result to be expected. Wheeler and Wood ( 4 ) found that diluting the natural gas with hydrogen decreased the oil yields. These results were checked in these experiments in that it was found that when hydrogen finally attained a concentration of 50 to 60 per cent the conversion practically ceased. S u m m a r y of R e s u l t s
1-The aromatic hydrocarbons, principally benzene, naphthalene, anthracene, along with acetylene, ethylene, and the
949
olefins, have been formed from natural gas by thermal treatment a t temperatures under 900' C. 2-Fused silica, clay, copper, and nionel metal do not catalyze methane and ethane to any great extent. Copper gives the highest yields a t the lowest temperatures, but the metal is consumed after R very short time in use. Silica gives high yields a t intermediate temperatures and is the most important inaterial here studied, as it is not changed by heat or products of the thermal treatment. 3-Iron and nickel readily decompose methane into itr elements and these metals are disintegrated by this reaction. 4--Various forins of carboii catalyze nwthane into its elements. 5-Carbon that is the result of the decompoiition of natural gas a t temperatures from 450" C. upward has a selective activity in the conversion of paraffins t o aromatics, etc. This activity is easily destroyed by partial oxidation or the formation of carbon-metal compounds. Graphitic. carbon is the final result of this loss in activity. 6-By a comparison of these thermal treatments nith that of gas manufacture in the by-product coke o m i . assuniing that the gases haTe reached an equilibrium, the practical yield of benzene has been obtained from natural gas aniounting to 27.0-40.0 liters per 1000 cubic meters of ga> treated. 7-The optimum temperature of benzene formation varies for each material and the method of carbon formation thereon. 8-When the concentration of hydrogen has attained 50 t o 60 per cent of the volume of the gas being treated, the oil yield becomes negligible. Acknowledgment
The authors wish to express their appreciation to the donors of the Columbian Carbon Fellowship, to G. C. Lewis, technical director of the Columbian Carbon Co., for his many helpful suggestions, and t o G. A. Lewis, assistant superintendent of the L. Martin Co., Philadelphia, for reconstructing and operating the semicommercial unit during 1926-27. L i t e r a t u r e Cited (1) Bone and Coward, J . Chem. Soc , 93, 1197 (1908). (2) Fischer, Brennstoff-Chem , 9, 309 (1928). (3) Stanley and Nash, J Soc C h e n I n d , 48 (1929). (4) .Wheeler and Wood, Fuel, 7, 535 (1928)
Manufacture of Rayon an Important U. S. Industry Rayon, the newest of the major textile fibers, has assumed a position of outstanding importance in the textile industry, production in 1927 amounting to $109,888,336, a gain of 24.8 per cent over the previous census year of 1925, according to the Textile Division, Department of Commerce. Although Europe was the birthplace of the industry and more than a decade elapsed before the manufacture of this fiber was introduced into the United States, greater progress has been made in this country than in any other, and the present productive capacity of American rayon plants is approximately 100 per cent greater than t h a t of our nearest foreign competitor. There arcfour separate and distinct processes now in commercial use in the manufacture of rayon, the resulting product of each process differing in certain respects from all the others. Irrespective of the process used, cellulcse obtained either from cotton linters or wood pulp, usually spruce, is the basic raw material. The four processes and the ratio of the 1928 domestic production accounted for by each are: viscose, 84 per cent; nitrocellulose, 9 per cent; cellulose acetate, 5 per cent; and cuprammonium, 2 per cent. According to the latest available census data on the industry, there were 19 establishments, employing 26,341 wage earners, engaged in the production of rayon and allied products during 1927, as compared with 14 establishments and 19,128 wage earners during the previous census year, 1925. I n 1927 wages paid
amounted to $28,649,441, an increase of 24.7 per cent over 1925, and the cost of materials, factory supplies, containers for products, fuel, and purchased power, $25,747,792, a gain of 39.3 per cent. The total value of products amounted to $109,888,336, a gain of 24.8 per cent, of which $106,468,752 represented yams, $342,749 waste, and $3,076,835 allied products, including sheets, etc. The rayon industry began in this country in 1911 and while increases in production have been registered each year since the inception of the industry, the greatest growth has been within the past few years. During the first ten years of the existence of the industry in the United States the capacity of American plants was augmented rather slowly, the average annual gains amounting to approximately 1,000,000 pounds. Although the industry began to expand a t a more rapid rate after 1921, the greatest strides have been made since 1925. During the period between 1921 and 1925 the annual output rose from about 15,000,000 pounds to almost 52,000,000 pounds, a gain of 37,000,000 pounds during the four-year period. I n 1926, there was an increase of 12,000,000 pounds, followed by increases of 12,000,000 and 22,000,000 pounds during 1927 and 1928, respectively, a total gain for the past three years of 46,000,000 pounds. According to unofficial estimates the 1929 production will be from 25,000,000 to 30,000,000 pounds heavier than last year, to be followed by a still greater enlargement in productive capacity in 19-30.
