ABSTRACT

This article provides a comprehensive and critical review of the latest studies on catalytic glycerol dehydration-oxidation to acrylic acid. The two-bed catalytic system in one or two reactors involves glycerol dehydration to acrolein and subsequent oxidation of acrolein to acrylic acid. Zeolites, metal oxides, heteropoly acids, and phosphates are effective in the dehydration of glycerol to acrolein. Mo–V–O catalysts appear active in the acrolein oxidation to acrylic acid. The glycerol can be completely converted to acrolein with 98% selectivity. In such a two-step process, the step of catalytic dehydration is thought to be critical. A few recent studies reveal that the conversion of glycerol to acrylic acid in two reactors can be also achieved via allyl alcohol as intermediate. For the one-bed catalytic glycerol oxydehydration to acrylic acid, a single catalyst must possess both active acid sites and active redox sites. Mo–V–O, W–V–O, Mo–V–W–O, W–V–Nb–O oxide catalysts, and heteropoly acid catalysts are particularly promising. Currently, a 60% yield of acrylic acid can be achieved over H_0.1Cs_2.5(VO)_0.2(PMo₁₂O₄₀)_0.25(PW₁₂O₄₀)_0.75 at 340°C. However, all the catalysts rapidly deactivate due to coking. Coking usually occurs during the glycerol oxydehydration step. Optimizing reaction conditions such as increasing water and oxygen feeding, lowering reaction temperature, tuning the catalysts by finely doping, adjusting the surface acidity and enlarging pores of the solid catalysts can inhibit coking to some extent by slowing the deactivation of catalyst. Yet coking over catalysts is a major obstacle when conducting glycerol oxydehydration on a large scale. We suggest that future work should place an emphasis on revealing the essence of coking, further designing coking-resisting catalysts, and developing an efficient reaction and separation system.

摘要

本文提供了有关催化甘油脱水氧化为丙烯酸的最新研究的全面而严格的综述。在一个或两个反应器中的两床催化系统涉及甘油脱水成丙烯醛和随后将丙烯醛氧化成丙烯酸。沸石，金属氧化物，杂多酸和磷酸盐可有效地将甘油脱水成丙烯醛。Mo–V–O催化剂在丙烯醛氧化成丙烯酸中表现出活性。甘油可以98％的选择性完全转化为丙烯醛。在这样的两步过程中，催化脱水步骤被认为是至关重要的。最近的一些研究表明，在两个反应器中甘油也可以通过烯丙醇作为中间体来实现丙烯酸的转化。对于单床催化甘油氧化脱水为丙烯酸，单一催化剂必须同时具有活性酸位和活性氧化还原位。Mo–V–O，W–V–O，Mo–V–W–O，W–V–Nb–O氧化物催化剂和杂多酸催化剂特别有前途。目前，在H上可以达到60％的丙烯酸收率_0.1 Cs _2.5（VO）_0.2（PMo ₁₂ O ₄₀）_0.25（PW ₁₂ O ₄₀）_0.75在340°C下。但是，所有催化剂由于焦化而迅速失活。焦化通常发生在甘油氧化脱水步骤中。优化反应条件，例如增加水和氧气的进料，降低反应温度，通过精细掺杂来调节催化剂，调节表面酸度和扩大固体催化剂的孔，可以通过减缓催化剂的失活在某种程度上抑制焦化。然而，当大规模进行甘油氧化脱水时，催化剂的焦化是主要障碍。我们建议未来的工作应着重于揭示焦化的本质，进一步设计抗焦化催化剂，以及开发有效的反应和分离系统。