科研之友
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摘要
Mechanistic pathways for catalytic hydrogenolysis of glycerol to propylene glycol, ethylene glycol, and lactic acid over supported metal catalyst are proposed and substantiated by conversion studies, isotopic labeling, reaction studies of proposed intermediates, and computational molecular modeling. Contrary to the naive expectation of hydrogenolysis as the simple replacement of OH by -H, the first step of reaction is the dehydrogenation of glycerol to glyceraldehyde. This aldotriose then reacts further via one of two paths: (1) retroaldol cleavage to the enediol of hydroxyacetaldehyde, which, with or without tautomerization, is reduced to ethylene glycol, or (2) keto-enol tautomerization to the enediol, which then dehydrates and tautomerizes to pyruvaldehyde. Subsequent hydrogenation or water addition and rearrangement leads to propylene glycol or lactic acid, respectively. The presence of base promotes both pathways but favors enolization and dehydration of the glyceraldehyde, which leads to propylene glycol and lactate formation.
- 出版日期2015-8
