Hydrogen production by catalytic supercritical water gasification of nitriles

摘要

Supercritical water gasification (SCWG) of nitriles was studied in a tubular flow reactor at different temperatures. This article focuses on the product distributions and corresponding reaction pathways influenced by addition of Na_2CO_3 catalyst. Results showed that gas yield for both acetonitrile and acrylonitrile can be greatly enhanced by adding Na_2CO_3 catalyst. Especially, H_2 gasification efficiency can reach 55.4% and 123.3% at 550 ℃, respectively. But the catalytic effect on the gas yield of benzonitrile was relatively insignificant. Na_2CO_3 can also accelerate the hydrolysis of cyanogen and amido as a base catalyst. Benzene and acetic acid were the primary intermediate products during the SCWG of benzonitrile and acetonitrile, respectively. The conversion of acrylonitrile was more complicated because of the activity of double bond. It is possible that 3,3' iminodipropionitrile was formed by Na_2CO_3 catalyzed in the range of 490-520 ℃, which dominated two thirds of pathways for the subsequent formation of acetic acid. Ammonia-nitrogen content in the liquid effluent was limited by the hydrolysis degree of cyano-group and the possible polymerization reaction of intermediate products. There was no obvious trend to reveal that NH_3 was converted into nitrogen under our experimental conditions.