Solid-phase Hydrogenation of Organic Compounds over Metal Catalysts

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Study on the solid-phase hydrogenation over a metal catalyst was carried out, using disodium fumarate and maleate as substrates and fine nickel powder as a catalyst. In the course of this study, it was found that the substrates were hydrogenated to disodium succinate even in the process of product analysis in the liquid phase. Thus, the development of a product analysis procedure to estimate the amount of disodium succinate formed in the solid phase was strongly required. An inhibitor treatment of the nickel catalyst was found to satisfy the requirement. A typical experimental procedure is as follows ; after the solid phase reaction, a methanol solution of catalyst inhibitor(e. g., sodium iodide and cysteine methyl ester hydrochloride) is added to the reaction mixture(Ni+substrate+product(s)). The inhibitor treatment of the nickel catalyst is followed by the extraction of the substrate and product(s) with H_2O *the esterification of the substrate and product(s)*GLC analysis. By the application of this procedure it was made clear that the amount of succinate formed in the solid phase was only 0.04mmol/g Ni in the maximum at 30ﾟC and at 1x10^5Pa hydrogen pressure, although a large excess of hydrogen gas was present in the reaction system. This finding suggests that a small amount of the substrate would be hydrogenated with dissociated hydrogen on the nickel surface and the hydrogen gas in the reaction system could not be consumed for the solid phase reaction under the above reaction conditions. The studies on the solid phase hydrogenation under severer conditions (higher temperature, higher pressure) are now in progress.