Highly Selective Lewis Acid Sites in Desilicated MFI Zeolites for Dihydroxyacetone Isomerization to Lactic Acid
Highly Selective Lewis Acid Sites in Desilicated MFI Zeolites for Dihydroxyacetone Isomerization to Lactic Acid
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DOI：
10.1002/cssc.201200703
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发表时间：
2013-05-01
期刊：
影响因子：
8.4
通讯作者：
Perez-Ramirez, Javier
中科院分区：
文献类型：
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作者：
Dapsens, Pierre Y.;Mondelli, Cecilia;Perez-Ramirez, Javier
研究了工业MFI型(ZSM-5)分子筛在碱金属氢氧化物溶液中的脱硅反应，得到了用于生物基二羟基丙酮(DHA)水相异构化合成乳酸(LA)的高选择性多相催化剂。最好的分级ZSM-5样品的LA选择性超过90%，与最先进的催化剂(即锡-贝塔沸石)相当；这种优化的分级催化剂可循环使用三次。通过脱硅和引入介孔产生的Lewis酸位被证明在所需产品的形成中起着关键作用；这些作用不能通过使用其他合成后方法来实现，例如蒸汽或浸渍铝物种。其他金属硅酸盐的脱硅，如GaMFI，也导致了高的LA选择性。在硝酸铝等可溶铝源存在的情况下，碱辅助铝化可以在全硅MFI分子筛中引入这些独特的Lewis酸中心。这些发现突出了沸石在生物质转化为化学领域的潜力，并扩大了脱硅产生选择性催化中心的适用性。
Desilication of commercial MFI-type (ZSM-5) zeolites in solutions of alkali metal hydroxides is demonstrated to generate highly selective heterogeneous catalysts for the aqueous-phase isomerization of biobased dihydroxyacetone (DHA) to lactic acid (LA). The best hierarchical ZSM-5 sample attains a LA selectivity exceeding 90%, which is comparable to that of the state-of-the-art catalyst (i.e., the Sn-beta zeolite); this optimized hierarchical catalyst is recyclable over three runs. The Lewis acid sites, which are created through desilication along with the introduction of mesoporosity, are shown to play a crucial role in the formation of the desired product; these cannot be achieved by using other post-synthetic methods, such as steaming or impregnation of aluminum species. Desilication of other metallosilicates, such as GaMFI, also leads to high LA selectivity. In the presence of a soluble aluminum source, such as aluminum nitrate, alkaline-assisted alumination can introduce these unique Lewis acid centers in all-silica MFI zeolites. These findings highlight the potential of zeolites in the field of biomass-to-chemical conversion, and expand the applicability of desilication for the generation of selective catalytic centers.