Therrnatornic Process for Cracking of Gaseous Hydrocarbons ROBERTL. MOORE,Thermatonzic Carbon Company, Pittsburgh, Pa. magnetic separators which clean T H E PROCESS may be described i n four out any metallic scale or rust which tion of a gaseous hydroparts-namely, ( 1 ) the cracking units, consisting might possibly come off the colleccarbon, such as methane, tor hoppers or c o n v e y o r s . The of checkerwork furnaces, ( 2 ) the coolers, ( 3 ) fhe in the absence of air produces carbon is then air-floated through carbon collectors, and ( 4 ) packing. The furnaces fine-mesh wire s c r e e n s . Large carbon and hydrogen according rotors w i t h r u b b e r flippers atbeing used at present are 14 feet in diameter and to the equation: tached throw the carbon centrifu25 feet high, and consist of a rireied steel shell, C H I (upon heat clacking) gally t h r o ug h t h e s c r e e n i n g , +C 2Hg From the sifters the carbon falls insulated and lined with refractory brick and filled into the packing hoppers where it Theoretically from every thouwith checkwbrick, similar to a blast-f urnace stoae. is accurately weighed and packed sand cubic feet of methane thus in 30-pound paper bags. The temperature range in thejurnace is from 900” treated 31.82 pounds of carbon to 1400“ C. The process is intermittent, the The abore description is of the are formed as 11-ell as 2000 cubic checkerwork being first heated by a blast of natural p r o c e s s w h i c h p r o d u c e s the feet of hydrogen. I n order to Thermax brand of Thermatomic gas and air introduced at the bottom, after which create s u f f i c i e n t heat to carry carbon. This is the p i o n e e r on t h i s c r a c k i n g , which is a n the stack is closed and natural gas is added from “soft” carbon, having been proendothermic r e a c t i o n , part of the top of /he furnace f o r the decomposing pari of duced commercially in Louisiana the methane, or gaseous hydrothe cycle. since 1922 by the thermal decomcarbon b e i n g u s e d , m u s t be The smoke from the furnace is passed through a p o s i t i o n of natural gas. Reb u r n e d w i t h a i r t o h e a t the cooler chamber where su@cient water is sprayed cently a new improved brand, system to craEking temperature. called P-33, has been put on the The p o r t i o n c o n s u m e d for countercurrent to the gas stream to cool the smoke market. This carbon is blacker this purpose depends on the suflciently to allow it to be safely jltered through and finer than Thermas and is process used as well as on the the cloth bags in the collectors and yet not wet also a soft carbon. I t is made by efficiency of o p e r a t i o n . The either ihe bags or the carbon. a process essentially the same as amount of carbon e n t r a i n e d Thermax. the difference being during the decomposing period and the space velocity are also important factors. So much that, in making P-33, a portion of the resultant gas is recircuhas been written on the subject of this reaction that it hardly lated and acts aq a diluent for the natural gas heing decomseems necessary to elaborate further here ( 2 , 3 , 6 ,8-11,15, 18). posed, thereby allowing the particles of carbon to be formed in A typical cheinical analysis of the natural gas being used a t a more dilute atmosphere (4). This dilution principle is so the Sterlington, La., plant, and the resultant gas obtained effective as to reduce the average particle size of 1’-33 to about therefrom is as follows: one-fifth that of Thermas. I n the study of the patent literature pertaining to the manuVOLCME \‘OLUME facture of carbon, one is struck by the fact that most processes N.ATURAL G.is RESCLTLNTG A S are described quite fully, and the product formed i. merely % % Carbon dioxide 0.4 0.9 mentioned as a soot or a lampblack. The fact that the Illuminants 0.7 1.3 carbons produced from hydrocarbons differ widely in their Hydrogen .. 85.4 Carbon monoxide 1.1 physical properties and effect on ruliber, paint, oils, etc., AI ethane 9318 5.0 Kitrogen 5.1 6.3 hay led to the publication recently of several article. on the subject (1, 5, 7 , 12, 1 $, 16, 17, 19). I n these articles reference A general arrangement of the equipment is seen in Figure 2 ( 2 3 ) . is made to “Thermatomic carbon,” which, in all cases where The furnaces being used at present are 14 feet in diameter and is now known as Therrnax brand. 25 feet high, and consist of a riveted-steel shell, insulated and named, is what By the term “soft” carbon is meant one which, when added lined with refractory brick and filled with checkerbrick, similar t o a blast-furnace stove. The temperature ranqe in the furnace to rubber in any appreciable quantity, does not increase the is from 900” to 1400” C. The process is intermittent, the modulus (tensile strength a t either 300 or 500 per cent elongacheckerbrick being first heated by a blast of natural gas and air introduced at the bottom, after which the stack is closed, and tion) of the vulcanized rubber stock in a measure comparable natural gas is added from the top of the furnace for the de- to that obtained with a n equal quantity of channel carbon composing part of the cycle. black (13, 21). The term as used in the literature refers to The smoke from the furnace is passed through a cooler chamber the influence of the carbon on the vulcanized stock and not where water is sprayed countercurrent to the gas stream (30) to cool the smoke sufficiently to allow it to be safely filtered through to either the carbon itself or the uncured rubber stock. the cloth bags in the collectors and yet not wet either the bags Tables I and I1 illustrate the difference in physical properties or the carbon. produced in ruliber by channel black and I)-33 carbon. The collectors ( 2 2 ) comprise a battery of cotton bags enclosed Thermax has established itself in the rubber trade throughin a steel shell with hoppers underneath. The collectors are built along the general principles of the dust collectors commonly out the world and is being successfully used in tires, inner used by the powdered-coal and starch industries, and have been tubes, boots and shoes, hose, belts, and other mechanical highly successful. The smoke enters a bag through the bottom; goods. It improves the working or processing qualities of this open end of the bag is clamped tightly to a flange in a steel compounds containing large quantities of reclaim and, in plate which separates the upper shell of the collector and the hopper. The upper end of the filter bag is shaken intermittently fact, has been added to reclaim itself for the same reason. It by an air-hammer device. During this period the flow of gas is also being used in paints, automohile-top fabrics, carbon is shut off from the shaking bags, and the carbon falls from the brushes, and electrodes. cloth into the hopper. The filtered resultant gas is piped off P-33 carbon, as previously stated, is blacker and has a from the top of the collectors. After the carbon falls into the hoppers, it is then carried by much smaller average particle size than Thermax. It imparts screw conveyors to the sifters. Just ahead of the sifters are practically the same stiffening effect to rubber as Thermax,
T
HE thermal decomposi-
+
21
\'"I.
24, N o 1
T h e r m a x n n d 1'43 itre &n i n T a b l e 111. The giis p r u d u ce d l)y the Thcrniatoniic ~iri~ccss is of especial i 111p o r t a I I OI, rtt the Iiresixit time because of t.lii: iirbwst, in the iiydr~igeiiati~m iif pet,riilcum,tlie ri~frirmiiig d natiiral and refinery-still pscs, as well :is the synthesis of airiiiionia nnd mctlianol. 'l'liisgas canbereadily produced at any locution desired from aiiy gaseous or liquid lrydnrcarbon a n d does iiot present any IIC\V jiroblems in purification. The fact that the cracking units arc lorig-lived and free from troublesome i:oinplicatioris of npcration has been proved by nine years of i:ormnercial prodnctioii with natural gas in Louisiana where over 100 million poiinds of carbon and 12 hillion ciil)i(. fret of liydroyrnn h a ~ ebeen manufactured.
I N D U ST R I A L A N D E N G I N E E R I N G C H E M I ST R Y
January, 1932
TABLE111. PROPERTIES OF THERMAX A N D P-33 CARBON THERMAX
P 33
PHYSICAL
Specific gravity 1.80 Apparent gravity (bulking value), kg./cu. meter 481.5 (Ibs./cu. ft.) Tinting strength,a % Average particle size, micron 1.0b
1.80 356.1
(E;)
0.23C
CHEMICAL
Moisture, yo 0.25 0.25 0.05 0.15 Ash % BeLzol extract (16 hours' extraction), % 0.60 1.25 Determinations made with Keuffel and Esser color analyzer a t a concentration of 2 . 5 parts carbon t o 100 parts zinc oxide. (Cabots Certified Carbon = loo%.) b Average of 2000 count# a t 1940 diameters magnification. e Average of 1000 counts a t 1940 diameters magnification.
ACKI~O WLEDGMENT Grateful acknowledgment is made to P. h1. Torrance of the Thermatomic Carbon Company for the color analyses, and to W. J. Latimore of the same company for the microscopical determinations.
LITERATURE CITED (1) Beaver and Keller, IND. ENG.Cmnf., 20,817 (1928). (2) Berthelot, "Les Carbures d'Hydroghe," p. 34, GauthierVillars, 1901.
23
(3) Bone and Coward, J . Chem. SOC.(London), 93, 1197 (1908). (4) Canadian Patent 271,013 O l a y 24,1927); U. S. Patent 1,794,558 (March 3, 1931). ( 5 ) Careon and Sebrell, IND.ENG.CHEM.,21, 911 (1929). (6) Cartelo, J., Phus. Chrm., 28, 1036 (1924). (7) c o x and Park, IND.EA-G.C H E Y . , 20, 1088 (1928). (8) Ellis, "Hydrogenation of Organic Substances," 3d ed., Chap LIX, Van Nostrand, 1930. (9) Fischer, Intern. Conference Batuminous Coal, 2, 7S9 (1928). (10) Fischer and Tropsch, Brennstof-Chem., 9,39 (1928). (11) Francis, IND.ENQ.CHEM.,20,277 (1928). (12) Goodwin and Park, Ibid., 20,621, 706 (1928). (13) Granor. I n d i a Rubber J . , 70,64 (1925). (14) Lunn, Trans. Inst. Rubber Ind., 4, No. 5. 396 (1929). (15) Odell, Bur. Mines, Rept. Investigations 2991 (1930). (16) Parkinson, Trans. Inst. Rubber Ind., 5 , No. 4, 263 (1929). (17) Plummer and Beaver, IND.EA-G.CHmr., 20, 895 (1928). (18) Slater, J. Chem. SOC.(London), 109,160 (1916). (19) Spear and Moore, IND.EXG. CHEM.,18, 418 (1926); Rubber Age (London), 9, 123 (1928). (20) U. S. Patent 1,520,115 (Dee. 23, 1929). (21) Ibid., 1,638,421 (Aug. 9, 1927). (22) Ibid., 1,710,469 (April 3, 1929). (23) Ibid., 1,718,720 (June 25, 1929). RECEIYED August 24, 1931.
Conversion of Methane to Carbon IMonoxide and Hydrogen CHaRLES
0. HAWK,PAULL. GOLDEK, H. H. STORCH, AXD A.
c. FIELDNER, Pittsburgh Experiment Station,
Bureau of .Wines, Pittsburgh, Pa. A C Y C L I C process has been developed f o r to reaction temperature by blasting with a n air-gas conuerting methane. or gases containing methane, Jame. Catalysts can be prepared f o r this purpose to carbon monoxide and hydrogen by either of two which are quite durable, and will consistently proreactions with equally satisfactory results: duce conversions near the calculated equilibrium values. CHI + H20 +CO 3H2 Optimum experimental conditions have been deCH, CO, +2CO + 2Hz termined for producing maximum conversions and The process is one in which the heat of reaction is minimum contamination by the products of side resupplied to the gases by the catalyst bed, heated actions in the temperature range 900" to 1100" C.
+
+
T
H E conversion of hydrocarbons, especially methane (in natural or coke-oven gas), to carbon and hydrogen or to mixtures of carbon monoxide and hydrogen constitutes a problem which has already received considerable attention in the industrial world. Methane, although thermodynamically unstable a t temperatures as low as 550" C., does not thermally decompose rapidly except a t very much higher temperatures (1100-1300" C.). The United States Bureau 'of Mines has investigated the thermal decomposition of natural gas in the presence of incandescent carbon, in water-gas generators a t high temperatures, with and without the presence of steam (6). With the addition of steam, this reforming process is satisfactory for the production of fuel gas, but, for the conversion of methane to carbon monoxide and hydrogen for synthetic purposes, it is complicated by the appearance of side reactions whose end products are tarry substances, mixtures of simpler liquid hydrocarbons, and heavy members of the benzene series. The reactions by which methane may be converted to mixtures of carbon monoxide and hydrogen are as follows: CHn CHa
++HzO --+ CO + 3Hz COz +2CO + 2Hz
(1) (2)
Both of these reactions are highly endothermic. By similar reactions higher hydrocarbons may also be decomposed
t o give the same products. -4consideration of the thermodynamic properties of the methane reactions shows that, in the case of methane and steam used in the proportions of Reaction 1, the process must be carried out a t temperatures a t least as high as 900" C. t o obtain satisfactdry conversions. The free energy and equilibrium constants for this reaction a t various temperatures, calculated from free-energy data made available by the work of Eastman (3) and Storch ( 8 ) have the following values: T o K. AF
KP
1,073 -10,700 150.5
1,173 -16,722 1.296 X 108
1,273 -22,735 0.794 X 10'
An approximate calculation of the concentration of the various constituents in the equilibrium mixture a t 900" C. shows the methane content of the gas to be somewhere near 1 per cent, which corresponds to about 96 per w n t conversion of the original gases. Reaction 2 approaches completion more rapidly than Reaction 1, with increasing temperature; but again an approximate calculation of the proportions of the constituents of the equilibrium mixture at 900" C. shows that the conversions t o be expected are of the same order as in Reaction 1, the conversion of methane in this case being about 98 per cent. Values for the free energy and equilibrium constant calculated for Reaction 2 are as follows:
