INDUSTRIAL AND ENGINEERING CHEMISTRY
2202
TABLE Ix. EQUILIBRIUM I N CARBON-HYDROGEX-hfETHANE Run G-19 G-19 G-20 G-20 G-20 G-22 G-22 G-22 G-20 G-22 Average Average
2
Approach from CHa Side Temp., O F. 1.29 1115
1
1.31
Sample No.
KP
...
3 2 3
2.2
1
2 3
,..
4
... ... ...
0.21
i3k5 (i29' C.)
1.30
1'1'20 (604" C.)
...
4
...
1126 1115
.
(6) Day, J.
... ...
...
1116
...
Schultz, J. F., J . Am. Chem. Soc., 51, 3249 (1929).
(8) Fonda, G. R.. and Van
0.6
l i l 0 (599' C.)
1.5
0.3 1.6 1.6
0.11
1'70 (799' C.)
1.0 1.0
0.22
1315 (713' C.)
, . .
Aernem, H. N., IKD. ENG. CHEM., 14, 539 (1922). (9) F r a n k e n b u r g , Tir. G . , Komarewsky, V. I., and Rideal, E. K. (editors), Advances in Catalysis,
1.6
1320 1310 1316
0.22 0.26
235 (1936). (7) E m m e t t , P . H . , a n d
Esid. % Carbon on Catalyst 1.5 1.6
, . .
1.18
0.19
E., IKD.ENG.
CHEXI.,28,
SYSTEN
Approach from Hz Side KP Temp., F. 0.62
Vol. 46, No. 10
(IO) Ibid., 111, p. 280.
Hagerbaumer, W. A , and Lee, R., T r a n s . Am. Soc. N e c h . Engrs., 69, 780 (1947). Harris, G. PI., Nauture, 160, S71 (1947). Hofer, L. J. E., U. S. Bur. Mines, Rept. Invest.. 3770, 1944. Hutchinson, W.S.. 11.8.thesis, chemical engineering, M.I.T., (11)
in excess of the quantity expected for equilibrium. When sufficient oxygen had accumulated on the metal to form detectable amounts of oxide, the expected ratio of hydrogen to water vapor was obtained. If a n appreciable fraction, say lo%, of the metal surface must be covered by carbon t o obtain consistent equilibrium values for the carbon, a catalyst with an area of 500 square meters per gram would require a deposit of more than lyocarbon. Troesch ( S I ) , studying the methane equilibrium, probably had only a small fraction of nickel surface covered with carbon. In a typical run, the carbon deposited could cover only 1 square meter of the total surface available in the 2 grams of catalyst (perhaps 50 to 200 square meters). I n a fexv runs in which he allowed carbon to accumulate on the surface, the measured per cent methane at equilibrium incieased with the amount of carbon present. 111. CARBIDEFORMATIOS. Another eriect t o consider when metal catalysts are used is the possibility of carbide formation. Cobalt and nickel carbides are endothermic compounds a hich are stable only a t high temperatures (800" t o 1000" C.), b u t they can be formed from the metals and some carbon compounds a t low temperatures (300" C.). Examination of literature data ( 3 , 13> 96, $6,28) indicates that little if an) carbide vould be formed in depositing carbon from either methane or carbon monoxide under the conditions of the experiments reported in this work. Experimental Results. Three equilibrium runs were made by recirculating hydrogen-methane mixtures through the reactor a t atmospheric pressure after some caibon had been deposited on the catalyst by cracking methane. The results are given in Table IX, and the average R,'s for each temperature are plotted in Figure 10. Equilibrlum was approached from both sides. I n run G-19 pure hydrogen and methane were used as starting gases. I n runs G-20 and G-22 mixtures of methane and hydrogen close t o the equilibrium composition were used. T h e direction in which the reaction Was proceeding was noted by measuring the molecular weight of the gas a t 3-minute intervals with a weighing bulb. T h e gas composltion was gradually adjusted until the reaction started to go in the other direction, and then a sample was taken for Orsat analysis. T h e K,'s for the formation of methane were calculated from the Orsat analyses. The values of K , are 2.3 t o 2.6 times those given for graphite (23). Contrary t o expectations, the K, values did not show any significant change with the per cent carbon on the catalyst. T h e K,'s for the deposited carbon correspond t o a free energy of 1500 calories per gram-atom greater than t h a t for graphite. It is felt t h a t this free energy is primarily a result of the large surface presented b y the carbon, or the fact t h a t nearly every carbon atom is on the surface and does not have all its valences satisfied. LITERATURE CITED
(1) Berl, E., and Bemmann, R., 2. phyailz. Chem., A162, 71 (1932). (2) Browning, L. C., and Emmett, P. H., J . Am. Chem. Soc., 73, 581 (1951). (3) I b i d . , 74, 1680 (1952). (4) Coward, H. F., and Wilson, S. P., J . Chem. Soc., 115, 1380 (1919).
( 5 ) Dart, J. C., Savage, R. T., and Kirkbride, C. G., Chem. Eng.
Prop., 102 (1949).
1949,
Jley, R., and Riley, H. S.,J . Chem. Soc.. 1948, p. 1362. Lewis, W. K., Gilliland, E. R., and associates, IND.ENG. CHEX., 42, 1326 (1950). Lexis, \Ti. K., Gilliland, E . R., and Hipkin, H., I b i d . , 45, 1697 (1953). >
,
&I., and Altmayer, V., Ber., 40, 2134 (1907). Pring, J. K,, J . Chem. Soc., 97, 499 (1910). Pring, J. Tu'.,and Fairlie, D. AI., Ibid., 99, 1796 (1911); 101, 91 hIayer,
(1912).
Randall, RI., and Mohammad, A , IND.ENG.CHEM.,21, 1048 (1929).
Rilev. H. L.. J . Chem. Phvs.. 47. 565 (1950). Rosjini, F. D., and associates: Xatl. Bur. Standards, Circ. C461, 1946.
Scheffer, F. E. C., Dokkum, T., and A1, J., Rec. traw. chim., 45, 8 0 3 (1926).
Schmidt, V. J.. 2. anorg. u. allgem. Chem., 216, 85 (1933). Storch, H. H., "The Fischer-Tromch Synthesis," Wiles, New York, 1951.
Szabo, Z., J . Am. Chem. Soc., 72, 3497 (1950). Tebboth, J. A . , S O C .C h e n . I n d . ( L o n d o n ) , 67, 62 (1948) Travers, hI.. T ~ a n s Faraday . Soc., 34, 580 (1938). Troesch, A , J . C h i m P h y s . , 47, 148 (1950).
Ibid., p. 274. Wright, bI. >I., and Taylor, H. S., Can. J . Research, 27B, 303 (1949). RECEIVED for review Augusi 6, 1963. ACCEPTED June 1, 1954, Presented a t the meeting of the Gas and Fuels Division of the AMERICAN CHEMICAL SOCIETY a t Pittsburgh, Pa., April 1953.
Aggregation of Suspensions by Polyelectrolytes-Correction I n the article on L'Aggregation of Guepensions by Polyelectrolytes" [IsD. EXG.CHEII., 46, 1485 (1954)] the third column of Table I should read:
[?I 0 38 0.19
ALAXS.MICHAELS
....... Toxicity of Various Refinery Materials to Fresh Water Fish-Correction I n the article on "Toxicity of Various Refinery Materials t o Fresh Water Fish" [Turnbull, Harry, D e h n n , J. G., and Weston, R. F., TND. EYG.CHEM, 46, 324 (1954)], the material referred t o in the second paragraph below Table I V on page 329 should have been cupric chrome glurosnte.
