September, 1929
INDUSTRIAL A S D ENGIXEERISG CHEMISTRY
I n Chart I are presented the data of the calcium cyanide with the smallest particle used, a very fine dust, 80 per cent of it passing through a 200-mesh sieve. It contained calcium cyanide equivalent to 23.49 per cent hydrocyanic acid, and in addition considerable quantities of calcium carbonate and sodium chloride and small quantities of calcium carbide and calcium sulfide. The curve for 80 per cent relative humidity so closely approximates the 100 per cent that it is not shown. With both these humidities 95 per cent of the total hydrocyanic acid content is evolved in 2 hours. With 56 per cent relative humidity 4 hours are required to evolve 95 per cent of the hydrocyanic acid. whereas with 45 per cent relative humidity about 85 per cent evolution is reached in 47 hours, and with 26 per cent relative humidity 38 per cent is evolved in 47 hours. (Because of the experimental difficulties of determining the very small quantities of hydrocyanic acid involved, none of the experiments was carried past 95 per cent.) The material used in obtaining the data shown in Chart I1 was of the same general nature chemically as the preceding. It contained the equivalent of 25.27 per cent hydrocyanic acid. It \vas not so finely ground (about like 'ea sand), 80 per cent of it being retained on an 80-mesh sieve. The evolution of gas was slightly slower than with the more finely divided material, 100 per cent relative humidity evolving 95 per cent of the total hydrocyanic acid in about 31/2 hours instead of 2 hours. The lower relative humidities give approximately the same evolution of gas with both materials. The calcium cyanide the behavior of which is shown in Chart I11 was the same chemically as in the two preceding, containing 25.11 per cent hydrocyanic acid. It mas much coarser, however, consisting of small flakes about 0.8 mm. (1/32 inch) thick and a maximum of 6 by 13 mm. ( l / d by '/z
863
inch). The evolution of hydrocyanic acid was much slower than with either of the preceding. With 100 per cent relative humidity, 95 per cent of the total hydrocyanic acid was evolved in 12 hours (not shown on the chart). With the lower humidities the evolution was very slow, 26 per cent humidity producing less than 10 per cent evolution of hydrocyanic acid in 49 hours. The fourth material used (Chart IV) was very different chemically from the preceding three. It consisted of about 30 per cent calcium cyanide (hydrocyanic acid 17.67 per cent), the rest of the material being calcium hydrate. It was very finely powdered, similar to the material described in Chart I. The results were, for the higher relative humidities, similar to those shown in Chart I. For the lower humidities, however, there was a considerably greater evolution of hydrocyanic acid. With the material described in Chart I, 26 per cent relative humidity produced 38 per cent evolution of the total hydrocyanic acid present, whereas with the material described in Chart IV it produced 60 per cent. The differences shown by the four grades of calcium cyanide examined are very probably to be attributed to differences in the degree of fineness of the material. Summary
With any given calcium cyanide the rate of evolution of hydrocyanic acid increases with increasing relative humidity. With a calcium cyanide, 80 per cent of which will pass through a 200-mesh sieve, commercially satisfactory evolution of hydrocyanic acid (90 per cent or more) will occur in about 2 hours, with a relative humidity of 50 per cent or more. Literature Cited (1) New Jersey Agr Expt. Sta., Ann. Rpt., 1919, p. 442.
Purification and Preservation of Ether for Anesthetic Use' S. Palkin and H. R. Watkins DRUGCONTROL LABORATORY, FOOD,DRUG,AND IXSECTICIDE ADMINISTRATION, U. S. DEPARTMENT OF AGRICULTURE, WASHINGTON, D . C.
Ordinarily ether shows a marked tendency to develop the presence of peroxide and aldehydes during storage. This tendency appears to be evident in ether which has been especially purified even when it is stored in a cool, dark place and access of air is prevented. A process of purification and preservation of ether is here described which has kept the ether in a good state of preservation for over a year, even when exposed to light and elevated temperature, conditions which ordinarily bring about rapid development of aldehyde and peroxide. Such ether, furthermore, has not become contaminated with the preservative agent in any other way. Two types of such agents have been found serviceable, pyrogallol and
permanganate, fixed in very strong alkali and spread over asbestos. A small quantity of asbestos impregnated with either of these agents may be placed in the vessel containing the purified ether. From this the ether may be poured for use without resort to filtration. The purification of ether is carried out by distilling the contaminated ether over either of these agents and passing a fine spray of the condensed ether through a column of strong alkaline solution of either of these agents by means of an apparatus similar to that described by the authors for extraction of liquid by means of immiscible organic solvents (18).
HE marked tendency for the development of aldehyde
these impurities in the low concentration ordinarily met (0.005 to 0.01 per cent peroxide) (90,there can be no question as to the desirability of using for anesthesia only ether of the highest purity obtainable. KO consideration will be given in this paper to the pharmacological studies on the impurities in ether. Compliance with the tests and standards for purity setup by the U. S. Pharmacopeia constitutes the legal requirements for ether. These place maximum limits upon the quantities of aldehyde and peroxide it may contain. Ether
...... ......
T
and peroxide in ether, particularly under the catalytic influence of light, is a matter of common knowledge. The possibility of harmful effects of such impurities in ether intended for anesthetic use has been studied by several investigators (9, 10, 12, 14). While no unanimity of opinion exists with regard to the potential danger of ether containing 1 Presented before the Division of Medicinal Chemistry at the 76th Meeting of the American Chemical Society, Swampscott, Mass., September 10 to 14, 1928.
Ih-D USTRIAL A-VD ESGIiYEERING CHEXISTRY
864
containing any impurities as revealed by the pharmacopeia1 tests is considered adulterated under the federal food and drugs act. The character of such impurities, the probable cause of their development, and means for their prevention have been studied by Baskerville and Hamor ( I ) , Clover ( 3 ) ,Rowe (go), LIallinckrodt ( 7 ) , recently by Sitardy ( I T ) , and many others (6, 6, 23). Various preservative agents, such as inert gas aiid niore particularly metals that do not enter into solution in ether (%), have been tried. Some aromatic compounds, such as benzidine (1.5) and pyrogallol (g), have also been used for this purpose. The reactivity of the latter x i t h aldehyde and peroxide mould doubtless make them effective agents against the development of those impurities were it not that these reagents themselves become contaminants. Table I-Storage
the reagents with the aid of a n apparatus similar to that used for the extraction of substances from solution by means of immiscible solvents (18). I n order t o ascertain incidentally what influence the type of containers may have on the keeping qualities of ether, the experiments were carried out in a variety of glass containers, and also in tin cans. The glass bottles used in the storage experiments included colorless flint aiid amber of American manufacture and several types of foreign origin. The latter were obtained in connection with the study of imported ethers which had shown remarkable freedom from aldehyde and peroxide. The tin cans were “used” cans from wellknown brands of ether. They were thoroughly cleansed, washed with alcohol and then with pure ether, and dried before using. I n the absence of facilities for sealing the cans
Experiments w i t h Ether Exposed t o Direct S u n l i g h t a n d S u b j e c t t o Elevated T e m p e r a t u r e .
T e s t s for Peroxide
1928
SERIES COSTAISER January
Pu‘o preservative: A Colorless-0 Colorless-E Amber - M c Amber -E Amber -bl Amber -K C Colorless-F Colorless-0 S m b e r -0 Amber -D Amber -24 .4mber -K With preservative B Colorless--E Amber --E D Colorless-0 Colorless-0 Amber -E Amber -E
VOl. 21, No. 9
13
20
27
I
I
February
7
14
21
28
1
March 13
20
/Auril
May
July
AUK. Seut.
Nov.
Dec.
2i
-- + +
+ +
-
+ + +
T A
-
+
+
+
-
-
Na K Na
K
Aldehyde negative in all tests. Contents of container exhausted.
*
Some authorities have stressed the manner of purification itself as a criterion for the keeping qualities of ether, and several patents have been taken out for special purification processes (4, 8, 1 1 , 16). Experimental Procedure
The serviceability of the methods of preservation of ether here described is based on the experimental proof that strong alkali and certain reagents, such as pyrogallol or permanganate fixed in strong alkali, will not enter into solution in ether reasonably free from alcohol in more than mere traces for Schobig (21) points out that ether containing several per cent of alcohol is capable of dissolving an appreciable quantity of potassium hydroxide and of aldehyde resin formed by the alkaline treatment. These substances, alkali for the aldehyde and pyrogallol or perniangaiiate as antioxidants, have been found to be exceedingly effective, not only for purposes of preservation of ether, but for the purification of ether already contaminated with aldehyde, peroxide, or acid. Either of these two types of agents iq employed in the form of strong alkali solution spread over asbestos, a sinall quantity of the impregnated asbestos reagent being placed in the vessel containing the purified ether. The data presented in this paper, particularly the results on preservation, are taken from experiments conducted over a period of about a year. These iiiclude storage experiments under extremely adverse conditions (exposure to light and elevated temperature) which ordinarily ,ring about rapid development of aldehyde and peroxide. Contaminated ether is purified by distilling over either one of these agents and a fine spray of the condensed ether is passed through a column of strongly alkaline solutio11 of
n i t h metal, corks lined with tin foil lvere ubed for stoppering the cans. The glass bottles were similarly stoppered. The use of alkaline pyrogallol is based on the well-known avidity of this reagent for oxygen and oxidizing substances. Its presence as a preservative agent is considered to be a continuous safeguard against accumulation of oxygenating compounds. Khile with the prevention of peroxide formation development of aldehyde should automatically be excluded ( 3 13), the presence of strong alkali, iiormally an excellent teqt reagent for aldehyde, should be an added safeguard. The use of permanganate depends upon its well-known reaction with peroxide (involving mutual destruction) and, in alkaline medium, liberation of reaction productq, such a< lower oxides of manganese, which do not offer in themselves danger of contamination. The asbestos with either type of reagent provides a large surface and serves as a retaining medium both for the reagent and the reaction products, so that the ether present may be taken from the container merely by decantation and without resort to filtration. The alkaline pyrogallol reagent Tvas prepared as follovi-.: One gram of pyrogallol was dissolved in 15 cc. of potaisiuni hydroxide solution (1 part potassium hydroxide sticks, 2 parts mTater by weight). Purified long-fiber asbestos wai impregnated with this reagent to such a degree as to be mol-t but not “soaked,” and when throw1 in the ether was in :i comparatively loose fibrous form. In the preservatioll experiments several grams of this impregnated asbestos n ere added to each container. The permanganate reagent was prepared in two formain strong potassium hydroxide and in strong sodium hydroxide-because of the comparatively low solubility of potassium permanganate and further solubility-depressing effect
IA4-DCSTRIALA S D ESGIXEERING CHEMISTRY
September, 1929
of potassium hydroxide. To 5 cc. of a saturated solution of the permanganate were added 15 cc. of strong alkali (1 part potassium or sodium hydroxide and 2 parts water). and the precipitated permanganate due t o supersaturation was removed by filtration through asbestos filter. The alkaline permanganate filtrate was then used to impregnate the purified asbestos in a manner described under alkaline pyrogallol reagent. Similar quantities of the prepared asbestos reagent (several grams) were used in the preserrative experiments as in the case of the alkaline pyrogallol. I n order to deterniine to what extent the method3 of purification here described TTere in theniselves effective in preserving ether, a series of purified ether samples was storr>dm-ithout added preservative. These included ether purified by means of pyrogallol and that purified by means of permanganate. The storage experiments, therefore, included a series representing ether which had been prepared by purification vith alkaline pyrogallol and stored (A) without added preservative and (B) with preservative agent; another series representing ether prepared by purification with alkaline permanganate and stored (C) without added preservative agent, and (D) with added preservative agent. The last experiment (D) was further subdivided into two groups, one in which sodium hydroxide was used in preparation of the preservatire agent and the other in which potassium hydroxide was used. I n order to test the practicability of the proposed methods, both from the standpoint of purification and preservation, the ether used in these experiments was obtained from a mixture of ethers from several different manufacturers. These ranged in quality from very pure ether to that very highly contaminated with aldehyde, peroxide, and other impurities. The batches of this ether were prepared by the iiiethods of purification described earlier and then examined by pharmacopeia1 and other tests, paging particular attention to aldehyde and peroxide. Both the ether purified by the pyrogallol method and that purified by the permanganate method gave negative tests for peroxide, aldehyde, ;ind acidity and showed lion-volatile residues of 0.3 mg. and 0.1 mg. (per 50 cc ) and specific gravities of 0.7129 and 0.7119, respectively.
865
The ether purified with perinanganate thus showed a specific gravity slightly lower than the U. S.Pharmacopeia minimum. The batches of ether thuq prepared mere then packed in the various containers described. Portions of these experimental batches were stored in a dark room simulating storage conditions ordinarily prevailing in the trade, and other portions were stored on an open shelf Some 10 feet above the floor, exposed to diffused sunlight iiiost of the day and to direct sunlight part of the day, and subject to considerable mriation in temperature at times reaching about 30" C. Storage Experiments with Ether Exposed t o Sunlight
STORED JT ITHOUT ADDED PRESERI ITIT E (A LXD C)-Tebts for aldehydes and peroxide mere macle weekly from the fir-t day of storage, December 13. 1927. to April 10, 1928, then inonthly to August 28, when the contents of the major portion of the containers were exhausted, owing particularly to loss of ether by evaporation in Tiex of the elevated temperature prevailing on the shelf. ;\Ionthly testing was coiitinued on those remaining, until January 19, 1929. (Table I) With the exception of those put up in t-ivo types of aniber bottles of foreign manufacture, all developed peroxides vel y promptly and continued to show peroxide throughout. This v a s true for both the ether purified with pyrogallol and that purified with permanganate. Of the ether in these two types of amber containers, that which was purified with permanganate began to show the presence of peroxide by April 10, that purified with pyrogallol lasted until the sample was exhausted, August 28, 1928. From these experiments it is obvious that the purification treatments n-ere in theniselves not sufficient to insure against deterioration under all conditions and in all types of coiitainers. The comparatively long period of freedom froin peroxides in the case of ether stored in the foreign containers mentioned indicates very decidedly a marked preserving effect exercised by the container itself. This is particularly true in view of the extremely adverse conditions of storage under which this stability is exhibited. Further invejti-
T a b l e 11--Experiments w i t h Ether Stored in Dark R o o m S u b j e c t to R o o m T e m p e r a t u r e .
T e s t s for Peroxide -
1928 SERIES
COSTAIKER
January
1029
February
S o preservative:
Purified with alkaline pyrogallol: A Colorless-0 Colorless-E Amber -E Amber -1Ic Tin -1 . , Tin ., Colorless-F Amber --I1 Amber -K Purified with alkaline permanganate: C Colorless-0 Amber -0 Tin -;, Tin -.jz Amber -D Colorles.;-F Amber -31 .41nber -K TViih prerrrvativp: I( Colorless-E Amber -E Tin -1 Tin -1 ,',D Colorless-0 S a Colorless-0 K Tin -1 S a Tin -1K -1,'~ Sa Tin Tin -I,'? K Amber -E Sa Amber -E K -A
2 1I -+ 1' -
+
. .
, 1:
1
._
Aldehyde-Positive tests were obtained in Tins 1 and r e r e negative a t other periods. * Contents of container exhausted.
I/%,
Series A, and Amber 0 and D, Colorless F, and Tins 1 and
l / ~ in
Series C on August 28, tests
I,VDUSTRIAL AND ENGINEERISG CHEMISTRY
866
gation to determine the character of the glass of these containers is in progress. T a b l e 111-Non-Volatile
R e s i d u e i n Ether Stored w i t h Preservatives 1/25/28
SERIES CONTAINER
Tnfiltered
4/5/28
Filtered
7/11/28
~~
.vg
Pyrogallol: I3 Colorless-E Amber -E Tin -1 Permanganate: D Colorless-0 Colorless-0 Amber -E Amber -E Tin -1 Tin -1 Tin -1/2
K h-a K Na K Na K
.zlg
1
1.0
I
0.9
0.1
.vg
0.5 0.4 0.5 0.7
~
'
0 . 3 0 . 7 0.51
.ME 0.0 1.0
0 5
n 4
1 ,
0 0
0.2 0.3
,
0.7
STOR.EDWITH ADDEDPRESERVATIVE (B AND D)-Tests for aldehyde and peroxide on these samples were made a t the same intervals indicated for those without preservative and continued t o January 19, 1929. (Table I) Noiie of the samples exposed to these conditions showed the development of peroxide or aldehyde to the date of exhaustion of sample or t o the last day of test, January 19, 1929, regardless of the type of preservative used. Experiments with Ether Stored in a Dark Room Subject t o Ordinary Temperature
Biweekly (and in a few instances weekly) tests for aldehyde and peroxide were made from the first day of storage, December 27, 1927, to April 15, 1928, and approximately monthly tests thereafter to January 19, 1929. STORED WITHOUT ADDEDPRESERV.4TIVE (A AND C)-com-
Preservative D: Specific gravity: At C. At 25' C. Aldehydes Peroxides Acidity Odor Appearance .. Preservative R : Specific gravity: At C . At 25' C. -4ldehydes Peroxiles Acidity Odor Appearance
CAN 1/18/29
4/30/28
1/18/29
0 . 7 2 0 at 206 0.716
0 . 7 2 0 at 215 0.717
0 . 7 1 7 a t 22 0.715
0 718 a t 215 0.715
Clear
Vanilla Clear
0 . 7 1 7 a t 215 0.714
0 . 7 1 8 at 21 0.715
0 . 7 1 8 a t 205 0.714
ia'n'illa Clear
keg. ( ? )
Viiilla Clear
... ...
BROWNGLASS
WHITF:GLASS
4/30/28
I :::
I
uary 19, 1929, or to the time of exhaustion of the sample. (Table 11) Son-volatile residue tests on ether stored with preservatives iincluding that exposed to light) were made several times throughout the pe iod of storage. (Table 111) Regardless of type of container or whether the pyrogallol or permanganate type of preservative agent was used, none of the non-volatile residue determinations showed the presence of a residue exceeding the maximum of 1 mg. per 50 cc. permitted by the Pharmacopeia. Only in three instances was there a maximum of 1 mg. and most of the others were below 0.5 mg., ranging from 0 to 0.7 mg. Several samples of preserved ether (stored with added preservative in colorless and amber glass, and in tin containers), representing those in which purification was effected through both alkaline pyrogallol and alkaline permanganate preservatives, were submitted to the Evans Nemorial Hospital of Boston for storage testing. A report (Table Is') by R. S. Hunt of that institution shows that these samples of ether stored under most adverse conditions from April 30, 1928, t o January 18, 1929, remained free from aldehyde and peroxide and conformed in other respects to the requirements of the Pharmacopeia. I n a few instances it was thought that a vanilla-like odor was noted in the ether residue, on first testing April 30, 1928. This, however, was found negative in a subsequent test of January 18, 1929. In the case of the pyrogallol-preserved ether a slight opalescence was noted also in one of the cans and one of the flint glass containers. In the present writers' experiments several of the samples stored in glass containers also showed slight opalescence, as was observed by Doctor Hunt. This may be due to minute traces of silica, but the cause has not been definitely determined. Such samples, however, showed no peroxide, aldehyde, or excessive non-volatile residue.
Tests on Preserved E t h e r at Evans M e m o r i a l HOSDital
T a b l e IV-Storaee
I 1
Vol. 21, No. 9
... ... keg. (?)
...
.
I
.
Opalescent
...
...
...
... V a ' i [la Clear
paratively rapid dcveloprnent of peroxide was shown (see Table 11) in the ethers of all the various containers, with the exception of the two types of amber glass of foreign make mentioned previously, and one other, a colorless container also of foreign make. Ether purified with permanganate, in the latter containers, developed peroxide by April 15, while that purified with pyrogallol remained free to September 28, and in one case to Kovember 5 , or very nearly for a pear's time. The remarkable preserving effect exhibited by this type of container is again evident in this series of experiments. These ethers were also found t o be free from aldehyde, with the exception of 3 few glass and tin containers which showed the presence of aldehyde on August 28. STOREDWITH ADDEDPRESERVATIVE (B AND D)-All samples packed with preservative agents, whether of pyrogallol or permanganate type, remained free from peroxide and aldehyde throughout the entire period of the experiment to Jan-
1/18/29
0 720 a t 20 0.716
0 . 7 1 9 at 21 0.716
h-eg Clear
V'a'n'illa Clear
h-eg. Clear
0 . 7 1 8 a t 21 0.715
0 . 7 1 7 a t 21 0.714
0 . 7 1 4 a t 245 0.714
Ne';. ( ? I Opalescent
V'a'n'illa Clear
...
... ...
...
4/~1/28
... ...
...
...
...
Slightly acid ( ? ) Xeg. (?)
Clear
Acknowledgment
The authors wish to express their appreciation to A. W. Rowe and R. P. Hunt, of the Evans 11emorinl Hospital, Boston, for their kind codperation in making corroborative examination of samples of preserved ether. Literature Cited (1) Baskerville and Hamor, J. I N D . ENG.CHEM..3, 331, 378 (1911). (2) Bishop, J . Soc. Chem. I n d . , 43, 23T (1924). Clover, J . A m . Chem. Soc., 44, 1107 (1922). Flaherty, U. S. Patent 1,312,475; C. A , , 13, 2575 (1920). Garbarini, I n d . chim., 10, 250 (1910). Guerin, J . phavm. chtm., 6, 212 (1912). Mallinckrodt, J . Am. Chem. SOL.,49, 2655 (1927). Mallinckrodt, U. S. Patent 1,461,539; C. A , , 17, 2936 (1923); U. S. Patent 1,508,563; C. A . , 18, 3685 (1924). (9) Mendenhall, J . Pharmacol., 21, Proc. 213 (1923). (10) Mendenhall and Connolly, Ibid., 25, 145 (1925). (3) (4) (5) (6) (7) (8)
INDUSTRIAL A N D ENGINEERING CHEMISTRY
September, 1929 (11) (12) (13) (14) (15) (16) (17)
Michaelis, Canadian Patent 173,128; C. A , , 12, 155 (1918). Middleton, P k a r m . J . , 113, 98, 130 (1924). Middleton, Analyst, 63, 201 (1928). Mita, Arch. ezpcl. Paik. Pharmakol., 104, 276 (1924). Xijk, U.S. Patent 1,532,772; C. A , , 19, 1710 (1923). Nitardy, U. S. Patent 1,632,309; C. A , . 21, 2478 (1927). Nitardy and Tapley, Convention Am. Pharm. Assocn., Portland, Me. (August 20 t o 25, 1928).
(18) (19) (20) (21) (22) (23) (24) (25)
867
Palkiu, Murray, and Watkins, IND. ENG.CHEM..17, 612 (1925). Rowe, I N D . ENG.CKEY., 16, 896 (1924). Rowe, J . Pkarnacol., 21, Proc. 213 (1923). Schobig, J. A m . Chem. Soc., 2 2 , 210 (1894). Siler, Sck;'eii. Apolh. ZLg., 63, 257 (1925). Wasteson, Svensk F a r m T i d . , 26, 473 (1922). Wische and Zechner, Phavm. Monatsk., 6, 133 (1924). Zechner and Wische, I b i d . , 6, 464 (1924).
Catalysts for the Formation of Alcohols from Carbon Monoxide and Hydrogen IV-Decomposition
and Synthesis of Methanol by Catalysts Composed of Zinc and Chromium Oxides1 D. S. Cryder and Per K. Frolich
DEPARTMENT O F CHEYICAL ENGINEERING. MASSACHUSETTS IXSTITUTE OF TECHSOLOGY, CAMBRIDGE, ~IASS.
Experiments on the decomposition of methanol in the presence of catalysts composed of the oxides of zinc and chromium show that an excess of chromium oxide gives rise to reactions producing appreciable amounts of carbon dioxide and unsaturated hydrocarbons. With catalysts containing excess zinc oxide the main products are carbon monoxide and hydrogen, a sharp maximum in activity occurring at a catalyst composition of about Zn,8Cr12.The relatively constant percentage of formaldehyde indicates its intermediate formation in the decomposition of methanol. Using the same catalysts for the reverse reaction, it is found that the production of methanol from carbon mon-
oxide and hydrogen parallels very closely the formation of carbon monoxide and hydrogen in the decomposition experiments. Those catalysts which give the highest percentages of carbon monoxide and hydrogen in the decomposition of methanol also give the maximum yield of alcohol in the synthesis. Besides throwing additional information on the reactions in question as well as on the general behavior of the type of catalysts involved, the results are in line with previous work on zinc-copper catalysts, demonstrating the suitability of the decomposition method as a criterion in the selection of catalysts for the high-pressure synthesis of methanol.
. . . . . .. . . . . . . . PREVIOUS paper from this laboratory (7) dealt with the atmospheric decomposition of methanol by catalysts composed of zinc and copper. The results showed that, other variables being kept constant, the extent to which the methanol was decomposed, as well as the type of products obtained, depended on the ratio of zinc to copper in the catalysts. A subsequent paper (8) giving the results of an investigation of the synthesis of methanol from carbon monoxide and hydrogen a t high pressures, using the same zinc-copper catalysts, proved that there exists a very close correlation between the two processes. Those catalysts which gave the highest percentage decomposition into carbon monoxide and hydrogen a t atmospheric pressure also gave the highest percentage conversion of carbon monoxide and hydrogen into methanol, when high pressures were employed. The present paper is a continuation of this work, being a discussion of catalysts composed of zinc and chromium oxides.
A
Previous Work
Some published data are available on the decomposition as well as the synthesis of methanol using the oxides of zinc and chromium. Sabatier, the first to study the decomposition of primary alcohols over metallic oxide catalysts, found that zinc oxide was more active than chroniium oxide in the decomposition of methanol and that zinc oxide was principally dehydrogenating in action while chromium oxide was principally dehydrating in character. Furthermore, the catalytic activity of chromium oxide when prepared from Received April 17, 1929. Presented before the Division of Industrial and Engineering Chemistry a t the 77th Meeting of the American Chemical Society, Columbus, Ohio, April 29 t o May 3, 1929 1
the trioxide differed from its activity when prepared from the hydroxide, while the specific dehydrating or dehydrogenating effect (18) depended on the temperature of calcination. Patart (14) observed that a combination of the two oxides as chromates gave better results in the decomposition of methanol than either oxide alone. More recently Smith and Hawk (20) have made a study of the decomposition of methanol using a wide variety of catalysts. Their results are of particular interest, from the fact that, out of thirty-six different mixtures of oxides used as catalysts, among the best is a catalyst which consists of zinc and chromium in the ratio of 4 to 1. Moreover, they showed by x-ray examination that the zinc oxide and chromium oxide are in actual chemical combination. Morgan, Taylor, and Hedley (16) have pointed out the superiority of a basic zinc chromate catalyst over one of zinc oxide alone in the synthesis of methanol from carbon monoxide and hydrogen. The patent literature contains numerous references to zinc oxide alone (6) or in combination with chromium oxide (2, 6, 10, 11, 12, 16, 24) for the production of methanol and other oxygenated compounds from carbon monoxide and hydrogen. One patent (22) mentions the particular use of a basic zinc chromate of the composition 4ZnO.lCr03. As in the case of zinc-copper catalysts, it is emphasized that the more basic oxide must be in preponderance and that the entering gases must be free from contact with iron. Preparation of Catalysts CATALYSTS CONTAINING hfORE THAX 50 MOL PER CEKT ZINC-Preliminary experiments were carried out as follows to determine the best methods for preparing a uniform catalyst with a high activity:
