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采用密度泛函理论研究了ZrO2负载的Ru基、Rh基以及Re改性的Rh基、Ir基催化剂上甘油氢解生成1,2-丙二醇和1,3-丙二醇的热力学过程, 重点考察了ReOx调变催化剂活性和选择性的作用机制. 结果表明, Ru/ZrO2和Rh/ZrO2催化剂上甘油分解经由脱水-加氢反应途径, 1,2-丙二醇的生成是热力学有利过程, 其中Ru基催化剂活性更高. 在Re修饰的Rh基和Ir基催化剂上, 反应遵循直接氢解机理, 其中金属表面解离的氢原子进攻ReOx团簇上与醇盐紧邻的C-O键是催化甘油转化为丙二醇最核心的步骤. Re-Ox-Rh/ZrO2催化剂上1,2-丙二醇为主要产物, 并伴随1,3-丙二醇的生成, ReOx的修饰则显著提高了Ir/ZrO2催化剂上1,3-丙二醇选择性. 与单金属催化剂上发生的间接氢解机理相比, 修饰催化剂上1,3-丙二醇选择性的提高可主要归因于Rh(Ir)-Re协同催化的直接氢解反应过程, 其中羟基化铼官能团有利于末端醇盐中间体的生成. ReOx-Ir/ZrO2催化剂上较大的Ir-Re团簇使得末端金属醇盐的立体优选性比次级醇盐更为突出, 从而具有最高的1,3-丙二醇选择性.
The thermodynamic processes of hydrogenolysis of glycerol to 1,2-propanediol and 1,3-propanediol over RuO2-supported and Rh-based and Ir-based catalysts on ZrO2 were investigated by using density functional theory. The effects of ReOx The results show that the formation of 1,2-propanediol is a thermodynamic favorable process for the dehydration-hydrogenation of glycerol on Ru / ZrO2 and Rh / ZrO2 catalysts, and the activity of Ru-based catalyst Higher Re on the modified Rh-based and Ir-based catalysts, the reaction follows the direct hydrogenolysis mechanism, in which dissociated hydrogen atoms on the metal surface attack ReOx cluster with the alkoxide immediately CO bond is the catalytic core of glycerol into propylene glycol Of 1,2-propanediol on Re-Ox-Rh / ZrO2 catalyst with the formation of 1,3-propanediol, the modification of ReOx significantly enhanced the selectivity of 1,3-propanediol on Ir / ZrO2 catalyst The improvement of the 1,3-propanediol selectivity over the modified catalysts can be attributed to the direct hydrogenolysis reaction catalyzed by Rh (Ir) -Re, compared with the indirect hydrogenolysis mechanism that occurs on the monometallic catalysts, in which the hydroxylation Rhenium functional groups favor terminal alkoxides Generated between the body. ReOx-Ir / ZrO2 catalyst Ir-Re large clusters of such end perspective preferably a metal alkoxide salt is more prominent than a secondary alcohol, so as to have the highest selectivity of 1,3-propanediol.