INDUSTRIAL AND ENGINEERING CHEMISTRY
January, 1934
Triisobutylene is also found to contain 2,4,4,6,6-pentamethyl-1-heptene (K) and 2,4,4,6,6-pentamethyl-2-heptene (L) ( 7 ) . The unsolved tetraisobutylene mixture may be predicted to consist of olefins from the following combinations: (B) (H), (B) (K), (A) (F), and (A) (J). The less probable union of (C) and (D) would give the same products as (B) and (K). The determination of the structures of the hexadecenes in tetraisobutylene will throw light on such additions. The structures of the polyisoamylenes have also never been solved. Here the problem is complicated by the fact that catalysts for polymerization can also cause rearrangement of the olefin,’ thus increasing the number of substances to which the tert-amyl group can add. The most probable products in the diisoamylenes would be 3,5,5-trimethyl-Zheptene and -3-heptene, 2,3,4,4-tetramethyl-l-hexeneand -2-hexene, and 2-ethyl-4,4-dimethyl-l-hexene. Polymerization processes are complicated by the possible reversal of the addition of a positive tertiary group to an olefin (6). A further complication may be caused by re-
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arrangements of the positive fragments formed by additions to the olefins (4). Such changes accompany the polymerization of tetramethylethylene ( 3 ) . I n conclusion it may be stated that the present theory is proving a valuable tool in laboratory studies of polymerieation.
LITERATURE CITED (1) Brooks, B. T., paper presented before Division of Organio Chemistry, 85th Meeting of American Chemical Society, Washington, D . C., March 26 to 31, 1933; Norris and Joubert, J. Am. Chem. SOC.,49, 879 (1927). (2) McCubbin, Zbid., 53, 356 (1931). (3) Meunier, P. L., unpublished data. (4) Whitmore, J. Am. Chem. SOC.,54, 3276 (1932). (5) Whitmore and Church, Ihid., 54, 3711 (1932). (6) Whitmore and Stahly, Ibid.. 55, 4153 (1933). (7) Wilson, C. D., unpublished data. RECEIVED December 6, 1933. This paper is a aummary of the address by the author aa retiring chairman of Section C at the meetinn of the American Association for the Advancement of Science, Boaton. Maes., December 29, 1933.
Fused Cobalt Oxide as a Water Gas Catalyst ERNESTC. WHITEAND J. F. SHULTZ, Bureau of Chemistry and Soils, Washington, D. C.
R
E C E N T years have witnessed a n increase in the number of industrial installations for the manufacture of hydrogen by the catalytic conversion of w a t e r g a s with steam according t o the wellknown reaction, CO
+ H20= COz 4-HZ (1)
Catalysts made by the fusion of cobalt oxide will, ulhen properly reduced in hydrogen, effeclively catalyze the water gas reaction to equilibrium at temperatures as low as 283” c. and space velocities as high as 1800. The addition of oarious promoters Seems capable of largely repressing the simultaneous formation of methane. Iron in quantities as high as 3 p e r cent appears to inhibit the formationof methane without cutting down appreciably the activity toward the water gas reaction. Copper as a promoter gives promising results. A cobalt catalyst containing38 per copper is particularly actiue as a water gas synthesizing sign*cant quantities of methane.
and the advantages of producing hydrogen-nitrogen mixtures by this method, especially for use in the direct synthesis of ammonia, h a v e s t i m u l a t e d the search for better catalysts than those originally employed in the Bosch process. Earlier studies in this laboratory have been reported by Evans and Newton (2) who prepared a number of precipitated metal oxides, with and without promoters, and noted the superior activity of cobalt when used with a sulfur-free gas. The known excellence of fused catalysts for ammonia synthesis and other reactions prompted the present authors to investigate the merits of fused cobalt oxide as a water gas catalyst and t o ascertain whether by proper addition of promoters the concomitant synthesis of methane according to the following reaction could be satisfactorily suppressed: CO
+ 3H2 = CH, + HzO
(2)
For extraneous reasons the investigation was interrupted before all of its objectives were attained. It is believed, however, that it contributes in a measure to the background of information useful to investigators in this field of catalysts.
PREPARATION OF MATERIALS CATALYSTS.In most cases cobalt oxide was prepared by ignition of cobaltous nitrate and was fused in an oxygen at-
mosphere by n ~ a n of s an OX!’hydrogen torch Playing directlv on the material contained in one of two s p e c i a l crucibles: The first was a 4-inch (10.2-cm.) iron crucible, t h e i n t e r i o r of which had been lined to a thickness O f a b o u t i n c h (1*27 cm.) with cobalt oxide by baking out a thick p a s t e of t h e ignited material. The second c r u c i b l e w a s m a d e from a casting of cobalt metal, the wall t h i c k n e s s being sufficient t o prevent melting by the flame used. Usually the minor components were added to the cobalt nitrate before i g n i t i o n in the form of nitrates or other suitable salts, but a few were introduced as oxide during the fusion. Two of the preparations (221 and 224) were made by burning cobalt metal. After the melt had cooled, it was crushed and screened to 10-14 mesh. I n Table I are shown the results of chemical analyses of the twenty-four preparations. It is worthy of note that nickel was never introduced purposely but appeared in association with the cobalt to an extent depending on the source of the latter, which is indicated in the final column. GAS. The water gas used in the tests was made in a semiworks generator, using a commercial coke. A regulated portion of the “blow” was introduced with the “run” so as to give a nitrogen content of about 25 per cent after removal of the carbon dioxide. After mixing in the holder, the gas was compressed and subjected to water scrubbing a t about 100 atmospheres t o remove carbon dioxide and hvdroeen sulfide. and Gas stored a t this pressure in cylinders. Analysis showed the percentage composition of the stored gas to be 32.6 carbon monoxide, 40.1 hydrogen, 26.1 nitrogen, 0.5 carbon dioxide, 0.5 oxygen, and 0.29 methane. O e 5
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Vol. 26, No. 1
TABLE I. CHENICAL ANALYSES OF CATALYSTS ( I n per cent) CATALYST Co Xi Fe A1203 cu Cr KzO CaO ZrOz M e 51n SOURCE' h 200 79.7 0.2 A 201 75.5 0.2 0730 3 :x7 .. .. . . . 76.8 202 0.2 0.69 2.28 0 : io .. 76.7 203 1.38 0.12 .. .. .. 0:26 ... .. 73.3 204 0.98 0.31 .. .. .. 0.40 c 77.6 205 1 :98 i:3 76.0 206 0.17 .. .. 4:56 e 207 72.7 0 : 40 2.75 208 73.8 0.2 0.20 3:37 .. .. A 209 60.4 0.16 19.00 0.2 .. .. .. ... A 210 8.5 0.20 0.03 75.5 .. .. .. .. .. B ... 211 7.2 0.16 0.05 .. 75.6 .. .. .. ... .. B 42.1 2 12 37.7 0.22 0.97 .. .. .. B 74.0 213 3.32 2.02 .. .. 0:14 B c 214 9.6 62.6 0.02 .. B 215 75.2 1.92 .. 1.06 B 74.5 216 1.76 .. 0.51 .. B . . . .. 70.5 217 .. 1.45 1.3 .. i:j3 .. B ... .. 67.1 218 0.95 2.25 4:o .. ,. .. C 66.9 219 .. 2.55 1.88 7.48 .. .. .. .. c 70.0 220 2.50 1.59 3.35 .. c 22 1 78.2 0.91 0.36 .. .. 0:48 D 222 88.1 5.92 0.85 .. .. ... 2.5 C 99.7 224d .. 0.10 0.04 o:o2 0:05 ... Trace E Sources of cobalt: A , specially purified cobaltous nitrate; B , commercial c. P. cobaltous nitrate, first make; C , commercial cobaltous nitrate, second make; D ,cobalt metal, commercial grade; E , cobalt metal, special grade obtained from Belgium. b Not determined b u t estimated from analysis of source t o be 0.2 per cent. C Method of ana!ysis included nickel with cobalt, b u t proportion assumed the same as t h a t found in catalysts from like source. d Belgian analysis of metal before fusion.
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APPARATUS AND PROCEDURE
equally as good in the less important range between 2 and 6 per cent. I n carrying out the experiments, water gas from a cylinder Analyses for methane in the effluent gas were made interwas passed through a tower of glass wool for dust and oil spray removal, through a tube containing copper heated to mittently by collecting a measured sample, burning with about 450" C. for removal of oxygen and sulfur, through a excess oxygen, absorbing the resultant carbon dioxide in chromic acid-sulfuric acid mixture for removal of oil vapors standard barium hydroxide solution, titrating back with and unsaturated hydrocarbons, and finally through a soda oxalic acid, and correcting for the known carbon monoxide lime tower for removal of acid spray. The desired mixtures content. KO better accuracy than ten parts per hundred of of water gas and steam were obtained by means of calibrated methane seemed attainable, judging from the results on flowmeters and an electrical steam boiler ( 3 ) . The gaseous samples collected in as rapid sequence as was possible. The catalyst tests may conveniently be classified into two mixture was finally passed via heated tubes and stopcocks through the catalyst bed and then to a water condenser, groups: The experiments of the first group consisted of short runs in which temperature, space velocity, and steam to carbon dioxide scrubber, and gas analysis apparatus. gas ratio were varied in fairly rapid succession, followed usuTABLE11. OBSERVEDCARBONMONOXIDEAND METHANE ally by redeterminations of the activity under the original operating conditions. The catalyst sample was reduced IN EFFLUENT GASDURING EARLY STAGES OF TESTING in situ with pure hydrogen a t 310" C. until a trial run showed ( A t 310° C. and a 3 t o 1 steam-gas ratio) a good conversion. The main test procedure was then begun. Space Velocity: 1800 6000 10,000 CHd CHI CHI Each set of conditions was maintained for a t least one hour, CITALYBT CO formed CO formed CO formed during which the carbon monoxide content of the effluent % % % % % % 0.21 1.88 0.32 1.36 0.40 207 gas was recorded frequently. I n most of the runs the meth0.21 4.31 0.32 2.19 0.44 205 ane content of the gas was also determined. The second 0.21 0.28 0.45 206O 0:09 0.38 0.44 0.51 3:+9 0:63 217 group comprised life tests on three of the more active catalysts 0.53 0.18 0.42 0.17 0.27 0.61 209 0.19 0.24 0.35 0.93 1.50 0.33 208 a t about 310" C. and 1800 space velocity, using a 3 to 1 0.00 0.30 0.35 1.01 0.72 0.00 216 steam-gas ratio in one case, and a 5 to 1 ratio in the others. 1.02 0.23 0.24b 210 0.24 0.31 0.23 0.24 0.391 1.06 202 0.29 0.25 The effluent gas was analyzed frequently for both carbon 1.32 0.36 0.19 2000 0 : i7 0.37 0.24 0:51 203 monoxide and methane. 1:39 0.73 0.27 0.21 201 0.27 1.44 0.42 0.26 218 0.34 1.46 3.97 1.17 0.21 0.00 0.06 212 6.35 0.00 215 1.56 0.19 0.00 .. 221 3.77 0.38 0.28 .. 0.51 0.90 211c 0.61 .. .. 213c 0.9 0.3 .. .. 220d 1.11 0.59 .. 2 19 1.83 .. .. 204 Transient activity only 222 Very erratic results, transient activity 224 214 No activity a t 444O C. Sup ly exhausted before methane tests were begun. Un&y high in view of other observations. At 1200 spa^ vdnri+v . Mean values, erratic fluctuations.
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The carbon dioxide-free effluent gas was analyzed for carbon monoxide by oxidation over iodine pentoxide, followed by absorption with standardized potassium hydroxide solution and conductometric measurement in an apparatus which has been described by one of the authors (4). The readings of this apparatus were continuous. They were estimated to be in error by not more than five parts per hundred of carbon monoxide indicated, within the range from 0.1 to about 2.0 per cent. On the same basis, the accuracy was
RESULTS OF EXPERIMENTS A summary of the tests made at 310" C. and various space velocities on 3 to 1 gas is given in Table 11. A majority of the catalysts were sufficiently active to convert the steamwater gas mixture to equilibrium at 1800 space velocity. Many, however, showed a tendency to form methane under these conditions. Accordingly about ten of the more promising catalysts were tested a t 1800 space velocity at 283", 310", 380", and 444" C. on both 3 to 1 and 4 to 1 steam-gas ratios with a view of finding the influence of temperature and steam-gas ratio on the rate of formation of methane. The results are summarized in Tables I11 and IV. I n all tests shown in these two tables the exit carbon monoxide value was practically at the equilibrium value. (According to calculations based on the equations of Chipman ( 1 ) for reaction 1, the equilibrium percentage of carbon monoxide in the effluent carbon dioxide-free gas in the present experiments would be 1.04, 0.57, 0.25, and 0.17 for 3 to 1 steam-gas ratio, and 0.77 0.42, 0.18, and 0.12 for 4 to 1 steam-gas ratio at 444O, 380",
I N D U S T R 1-4L A N D E N G I N E E R I N G C H E It1 I S T R Y
January, 1934
310", and 283" C., respectively.) The catalysts are arranged in Tables I11 and IV in order of decreasing desirability on the basis of their ability to suppress the formation of methane. The results consistently indicate that an increase in the temperature of operation or an increase in the steam-hydrogen ratio will markedly decrease the amount of methane formed by the catalysts. TABLE111. OBSERVEDCARBON MOSOXIDEASD METHANEIN EFFLCENT G A S AT 3 TO 1 STEAM-GAS R a T I O , 1800 S P l C E VELOCITY AND VARIOES TEMPERATURES 4440 c . 380' C. 310' C. 283' C. CAT.4LYBT
CHI
CO formed
7 6 %
CH
