1. Field of the Invention
The present invention relates to a process for the production of carbon monoxide of high purity by pyrolyzing of methyl formate. More particularly, the present invention relates to a process for the production of carbon monoxide wherein methyl formate alone in a mixture of methyl formate and methanol is selectively subjected to catalytic pyrolysis to obtain carbon monoxide of high purity and methanol.
2. Description of the Prior Arts
Usually known as a process for producing methyl formate are a process wherein methanol is reacted with carbon monoxide (CH.sub.3 OH+CO.fwdarw.HCOOCH.sub.3), a process wherein formic acid is esterified with methanol (HCOOH+CH.sub.3 OH.fwdarw.HCOOCH.sub.3 +H.sub.2 O) and a process wherein methanol is subjected to dehydrogenation reaction (2CH.sub.3 OH.fwdarw.HCOOCH.sub.3 +2H.sub.2). In these reactions, the conversion of methanol is not so high that the resultant reaction mixture substantially is a mixture of unreacted methanol and the produced methyl formate. If methyl formate alone in such mixture of methyl formate and methanol is selectively decomposed to carbon monoxide and methanol, it will be of very industrial significance in that carbon monoxide of high purity can directly be obtained from the mixture of methyl formate and methanol without eliminating methanol from the reaction mixture in the synthesis of methyl formate or without isolating methyl formate from the reaction mixture.
On the other hand, known prior art processes of the pyrolysis of methyl formate involve (i) a process wherein methyl formate is subjected to pyrolysize in vapor phase conducted at 200.degree.-500.degree. C. in the presence of a solid catalyst comprising an alkaline earth metal oxide such as barium oxide or calcium oxide (U.S. Pat. No. 3,812,210), (ii) a process wherein methyl formate is pyrolyzed at a temperature of 200.degree.-550.degree. C. by the aid of active carbon as catalyst (Japanese Laid-Open Patent Appln. No. 36609/77) and (iii) a process wherein methyl formate in the co-existence of methanol is pyrolyzed under a pressure of at most 250 psig (175 kg/cm.sup.2) and at a temperature of 35.degree.-200.degree. C., using a catalyst sodium methylate which has been used for the synthesis of methyl formate from methanol and carbon monoxide (U.S. Pat. No. 3,716,619).
Among the above mentioned three processes, however, the processes (i) and (ii) are effective only in case of using pure methyl formate free from methanol as starting material and show a slow reaction velocity when applied to methyl formate in a mixture of methanol and methyl formate utilized for the present invention. Further, in case of applying the process (ii), a large amount of hydrogen is included in the evolved gas, thus making it impossible to obtain carbon monoxide of high purity. In the process (iii) sodium methylate used as catalyst is reacted within the adopted temperature range of 35.degree.-200.degree. C. with methyl formate and easily converted into other compounds so that methyl formate is wasted to reduce selectivity of methyl formate to carbon monoxide, and at the same time, dimethyl ether evolved in this reaction contaminates carbon monoxide. In the above mentioned processes (i)-(iii), methyl formate alone in a mixture of methyl formate and methanol could not selectively be pyrolyzed at such a space velocity as adopted in the present invention and as a result carbon monoxide of high purity could not be obtained.