Selective Hydrogenolysis of C–O Bonds Using the Interaction of the Catalyst Surface and OH Groups

Abstract

Hydrogenolysis of C-O bonds is becoming more and more important for the production of biomass-derived chemicals. Since substrates originated from biomass usually have high oxygen content and various kinds of C-O bonds, selective hydrogenolysis is required. Rhenium or molybdenum oxide modified rhodium and iridium metal catalysts (Rh-ReO(x), Rh-MoO(x), and Ir-ReO(x)) have been reported to be effective for selective hydrogenolysis. This review introduces the catalytic performance and reaction kinetics of Rh-ReO(x), Rh-MoO(x), and Ir-ReO(x) in the hydrogenolysis of various substrates, where selectivity is especially characteristic. Based the model structure of the catalysts and the reaction mechanism, the role of the oxide components is to make the interaction between the OH groups in the substrates and the catalyst surface, and the role of metal components is to dissociate hydrogen molecule heterolytically to give hydride and proton.

Role of Re Species and Acid Cocatalyst on Ir-ReOx/SiO2in the C-O Hydrogenolysis of Biomass-Derived Substrates

“…[41] In the case of the reactions mentioned above, it is important to dissociate and maintain C-O bonds selectively, and this is regarded as partial C-O hydrogenolysis. From the studies on the partial C-O hydrogenolysis over Ir-ReOx/SiO2, it was found that Ir-ReOx/ SiO2 did not catalyze the C-C bond hydrogenolysis.…”

“…Ir-ReOx/SiO2 catalyzed the C-O bond hydrogenolysis utilizing the interaction between OH groups in the substrates and the Re species on the catalyst surface. [41] In the case of the reactions mentioned above, it is important to dissociate and maintain C-O bonds selectively, and this is regarded as partial C-O Scheme 8. Attack by the hydride on Ir metal to the glycerol adsorbed on Re species, assisted by protonation under acidic conditions.…”

Glycerol hydrogenolysis into useful C3 chemicals

“…However, the reviews have focused mainly on the liquid-phase reactions, while vapor-phase reactions are less 5 discussed. Although new achievements are summarized in review papers for the recent 5 years [56][57][58][59][60][61][62][63][64][65], the advantages and disadvantages of vapor-and liquid-phase reactions are less discussed. In addition, some important achievements have been reported in the past 5 years.…”

Influence of acid pretreatment on the hydrodeoxygenation performance of carbon supported RuMo bimetallic catalysts on sorbitol conversion

“…The challenge to reconstitute biomass resources is their polyoxygenated nature (CHO)n, which requires the transformation of C-O bond for oxygen removal or substitution [1][2][3]. However, the thermodynamic data showed that the bond-dissociation for C-O bonds (CH 3 -OH 381 kJ/ mol, CH 3 CH 2 -OH 381 kJ/mol, CH 3 CH 2 CH 2 -OH 381 kJ/mol) were higher than that of C-C bonds (CH 3 -CH 3 368 kJ/mol, CH 3 CH 2 -CH 3 356 kJ/mol, CH 3 CH 2 -CH 2 CH 3 381 kJ/mol) [4][5][6]. Thus, the control of relative activity in cracking reaction of C-C and C-O bonds is one of the most important themes of the design of hydrodeoxygenation catalysts as most metal catalysts can crack both C-C and C-O bonds [7,8].…”