Catalytic conversion of glycerol to acrolein over modified molecular sieves: Activity and deactivation studies
Catalytic conversion of glycerol to acrolein over modified molecular sieves: Activity and deactivation studies
复制标题
DOI：
10.1016/j.cej.2010.09.029
复制
发表时间：
2011-04-01
影响因子：
15.1
通讯作者：
Oliveira, Alcineia C.
中科院分区：
文献类型：
--
作者：
de Oliveira, Aldenor S.;Vasconcelos, Santiago J. S.;Oliveira, Alcineia C.
研究了甘油在分子筛催化剂上液相脱水制丙烯醛的反应。为了理解酸性、结构和孔隙率的作用，合成并评价了五种结构。Si/Al比越低，活性越高;大孔分子筛如HY表现出高性能（转化率=89.0%;丙烯醛选择性=99.5%），而硅质分子筛如SBA-15具有弱酸性，表现出低转化率（40.6%）和降低的丙烯醛选择性（84.0%）。结构和酸度决定了对丙烯醛和羟基丙酮的选择性，后者是副产物，主要取决于弱和中等强度酸性位点的量，如在H β的情况下。催化剂的活性与酸性大小顺序基本相同：HY > H β>莫尔> SBA-15 > ZSM-23。通过硅烷化（CVD）或Pt掺入的最酸性和活性催化剂的改性没有导致转化率提高。重复使用性和焦炭沉积物的性质的研究表明，从甘油和丙烯醛之间的反应产生的重缩聚和环状C-6化合物堵塞的孔和酸性位点。堵塞是失活的主要原因，而酸性位中毒导致的表面活性位的失活范围较小。根据这些结果，可以建立酸性-活性-失活关系，从而解释催化剂的行为。(C)2010 Elsevier BV保留所有权利。
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 H beta. The activity has almost the same order of the acidity: HY > H beta > 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 C-6 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. (C) 2010 Elsevier B.V. All rights reserved.