碱促进剂在Ru/CNFs催化山梨醇氢解制备二元醇中的作用

Hydrogenolysis of sorbitol to glycols over carbon nanofibers-supported ruthenium catalyst:The role of base promoter

研究了NaOH,KOH,Mg(OH)_2,Ba(OH)_2和CaO等5碱促进剂在Ru/CNFs催化山梨醇氢解过程中的作用机制.结果表明,这些碱均能显著提高山梨醇的转化率,但生成二元醇的选择性随碱种类而有所差异,其中以CaO促进的催化剂二元醇选择性最高.CaO提供了用以催化C—C键断裂的OH^-,同时与中间产物形成络合物从而影响反应历程.提出了CaO作为促进剂时山梨醇氢解生成二元醇的反应历程,并由此进一步优化了山梨醇浓度、Ru催化剂用量和碱促进剂用量之间的匹配以达到更高的二元醇产率.

Sorbitol hydrogenolysis over carbon nanofibers-supported Ru （Ru/CNFs） was carried out with different bases （NaOH, KOH, Mg（OH）2, Ba（OH）2, and CaO） to investigate the role of base promoter. The results indicated that all the bases used significantly enhanced the sorbitol conversion while the glycol selectivities varied with the base type and amount. CaO was the best base in terms of glycol selectivity for two reasons. CaO provided OH-for the base-promoted cleavage of C-C bonds, while it also supplied Ca2＋ for complexation with the intermediate aldehydes, thus affecting the reaction pathways. We identified an optimum ratio among sorbitol concentration, Ru/CNFs catalyst, and CaO to achieve favorable glycol selectivities in sorbitol hydrogenolysis. Reaction pathways for sorbitol hydrogenolysis into glycols in aqueous solution in the presence of CaO have been proposed based on the mechanistic study.