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首页> 外文期刊>Chemical engineering journal >Catalytic conversion of glycerol to acrolein over modified molecular sieves: Activity and deactivation studies
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Catalytic conversion of glycerol to acrolein over modified molecular sieves: Activity and deactivation studies

机译：改性分子筛上甘油到丙烯醛的催化转化：活性和失活研究

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The catalytic conversion of glycerol to acrolein by liquid-phase dehydration over molecular sieves catalysts was studied. In order to understand the role of the acidity, structure and porosity, five structures were synthesized and evaluated. The lower the Si/Al ratio, the higher the activity; large pore molecular sieves, as HY showed high performance (conversion = 89.0%; selectivity to acrolein=99.5%), while siliceous molecular sieves such as SBA-15 possessing weak acidity, exhibited low conversion (40.6%) and decreased selectivity to acrolein (84.0%). The structure and the acidity govern the selectivity to acrolein and hydroxyacetone, the latter being a by-product mainly dependent on the amount of weak and medium strengths acidic sites, as in the case of Hp. The activity has almost the same order of the acidity: HY>Hβ>Mor>SBA-15>ZSM-23. Modifications of the most acidic and active catalysts by silanation (CVD) or Pt incorporation did not result in an enhanced conversion. The studies of reusability and the nature of the coke deposits indicated that heavy polycondensed and cyclic Cs compounds resulting from the reaction between glycerol and acrolein block the pores and the acidic sites. The blockage was the main cause of deactivation, whereas acidic site poisoning led to a less extensive deactivation of the surface active sites. From these results, it was possible to establish acidity-activity-deactivation relationships that allow to explain the behaviour of the catalysts.
机译：研究了分子筛催化剂上液相脱水法将甘油催化转化为丙烯醛。为了理解酸度，结构和孔隙率的作用，合成并评估了五个结构。 Si / Al比越低，活性越高。大孔分子筛，因为HY表现出较高的性能（转化率= 89.0％;对丙烯醛的选择性= 99.5％），而硅质分子筛（例如SBA-15）的酸度较弱，则转化率较低（40.6％），并且对丙烯醛的选择性降低（ 84.0％）。结构和酸度决定了对丙烯醛和羟丙酮的选择性，后者是一种副产物，主要取决于弱和中等强度酸性位点的数量，例如在Hp的情况下。活性的酸度几乎相同：HY>Hβ> Mor> SBA-15> ZSM-23。通过硅烷化（CVD）或掺入Pt对大多数酸性和活性催化剂的改性不会导致转化率的提高。对可再利用性和焦炭沉积物性质的研究表明，甘油与丙烯醛之间的反应产生的重质缩聚和环状Cs化合物会堵塞孔隙和酸性部位。堵塞是失活的主要原因，而酸性位点中毒导致表面活性位点的失活程度降低。从这些结果，可以建立允许解释催化剂行为的酸度-活性-失活关系。

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