Noguchi catalyst

The Noguchi catalyst aids in splitting these bonds and stabilizing the radicals formed, but it does not promote the hydrogenation of the aromatic nuclei. This was considered as the reason for the production of a relatively small total number of separable simple compounds. 

Based on experience obtained by hydrogenating coal during World War II, the Noguchi Institute of Japan began to study lignin liquefaction. By 1952 they had discovered a superior catalyst which converted a substantial portion of the lignin into relatively few monophenols and substantially suppressed additional hydrogenation of the phenols. This catalyst was improved some years later and, based on these two catalysts,... 

If, by means of catalyst improvements which are not obvious at the present time, the monophenol yield could be improved by, say 50%, the process should become profitable. Another area of improvement lies in reducing lignin preparation costs still further. This is for the future, however. At present, the Noguchi process is the best hydrogenation procedure which has yet been developed for converting lignin into chemicals. 

Recently, electron-transfer catalysis by viologen compounds has attracted much attention. The compounds function as mediators of electron transfer and have been applied in the reduction of aldehydes, ketones, quinines, azobenzene, acrylonitrile, nitroalkenes, etc., with zinc or sodium dithionite in a monophase or a two-liquid phase system [13]. Noguchi et al. [13] found that a redox-active macrocyclic ionene oligomer, cyclobis(paraquat-/ -phenylene), acted as an electron phase-transfer catalyst for the reduction of quinines, as compared with acyclic benzyl viologen. The enhanced activity of this compound is due to the inclusion of the substrate into the catalyst cavity. 

Saruwatai T, YagishitaE, Mino T, Noguchi H, Hotta K, Watanabe K (2014) Cytochrome P450 as dimerization catalyst in diketopiperazine alkaloid biosynthesis. Chembioehem 15 6564559... 

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