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首页> 外文期刊>Catalysis science & technology >Mechanistic insight into the selective hydrogenolysis of sorbitol to propylene glycol and ethylene glycol on supported Ru catalysts
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Mechanistic insight into the selective hydrogenolysis of sorbitol to propylene glycol and ethylene glycol on supported Ru catalysts

机译：机械的洞察选择性山梨糖醇,丙二醇的氢解作用和支持俄文催化剂乙二醇

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Supported Ru clusters efficiently catalyzed the selective hydrogenolysis of sorbitol to ethylene glycol and propylene glycol in the presence of Ca(OH)(2). Ru/C was more selective to the two target glycols than Ru catalysts on MgO, Al2O3, ZrO2 and TiO2 with similar Ru particle sizes (similar to 2 nm). The reaction parameters, including the amount of Ca(OH)(2), H-2 pressure and temperature, strongly influenced the activity and selectivity of Ru/C, which reflects the bi-functional requirements of sorbitol hydrogenolysis that involves the competitive Ru-and base-catalyzed reactions of ketose or aldose intermediates, derived primarily from sorbitol dehydrogenation. Kinetic isotopic studies with different deuterated sorbitols confirmed that such a sorbitol dehydrogenation step was kinetically relevant to the hydrogenolysis reaction, which most likely proceeded by preferential activation of its C(5)-H bond on the Ru surfaces, as indicated by the more noticeable kinetic isotope effect with sorbitol deuterated at its C-5 position than those at the other C positions. Moreover, it was found that the hydrogenolysis of hexitols with different configurations showed large differences in their activities and selectivities. Erythro sequences of the vicinal hydroxyl groups adjacent to the primary carbons in the hexitol molecules, compared to threo sequences, tended to facilitate the hydrogenolysis reaction and the formation of C-3 products over C-2 products, most likely as a result of the effects of the different sequences of the hydroxyl groups on the adsorption and C-H bond activation of hexitols on Ru. Clearly, these findings and understanding demonstrate the feasibility of effective synthesis of ethylene glycol and propylene glycol from sorbitol and other largely available polyols, for example, by rational design of more efficient catalysts and tuning of polyol adsorption configurations.
机译：支持俄文集群有效地催化山梨糖醇的选择性氢解作用乙烯乙二醇和丙二醇的存在Ca (OH)(2)。目标比俄罗斯乙二醇催化剂分别,氧化铝,锆和二氧化钛的俄文粒子大小相似(类似于2海里)。包括Ca的数量(哦)(2),2的压力和温度,强烈影响的活动和选择性的俄文/ C,它反映了bi-functional山梨糖醇的需求氢解作用,涉及到竞争力酮糖或钌和base-catalyzed反应醛糖中间体,主要来自山梨糖醇脱氢。研究不同氘山梨糖醇证实,山梨糖醇脱氢一步是活动相关氢解反应,最有可能接着通过优惠的激活C (5) - h键俄文表面,如所示动力学同位素效应越明显山梨糖醇比氘的c - 5位置那些在其他C的位置。发现己糖醇的氢解作用不同的配置显示巨大差异在他们的活动和选择性。序列的附近的羟基邻边在己糖醇的主要碳分子,threo序列相比,倾向于促进氢解反应的形成颈- 3产品在c - 2产品,最有可能的作为不同序列的影响的结果吸附的羟基和碳氢键键激活己糖醇的俄文。发现和理解证明有效的乙烯合成的可行性从山梨糖醇,乙二醇和丙二醇其他大部分可用的多元醇,例如,通过理性的设计更高效的催化剂和调优的多元醇吸附构型。

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