Acrylic acid, conventionally produced via propylene (non-renewable fossil fuel route), is an industrially important chemical. The bio-based feedstock process employing glycerol (a by-product of biodiesel production) has attracted the attention of researchers due to its non-polluting and renewable characteristics. Bi/multifunctional catalysts using a combination of zeolites, metal oxides, heteropoly acids, and phosphates have been mainly studied for the glycerol oxydehydration process. Brønsted acid sites favour acrolein generation over Lewis acid sites, whereas the redox sites convert the generated acrolein to acrylic acid. So far, the maximum acrylic acid yields of 60% and 59% have been reported on heteropoly acid and mixed metal oxide catalysts, respectively. Some DFT studies also revealed the deprotonation energy of acid sites and further helped in designing efficient catalysts. Despite these accomplishments, catalyst deactivation because of coking and stability remains a major problem. In this paper, various bi/multifunctional catalysts employed in glycerol oxydehydration to acrylic acid are critically reviewed. Different catalyst forms, preparation techniques, reaction kinetics, reaction mechanisms, deactivation, reactivation, process operating parameters, and sustainability are considered. In addition, the challenges associated with each catalyst type and strategies to overcome low yield, deactivation, and future directions are discussed.

中文翻译：

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生物甘油双/多功能催化氧化脱水制丙烯酸的综述：催化剂类型、动力学和反应机理

传统上通过丙烯（不可再生化石燃料路线）生产的丙烯酸是一种工业上重要的化学品。使用甘油（生物柴油生产的副产品）的生物基原料工艺由于其无污染和可再生的特性而引起了研究人员的关注。主要研究了使用沸石、金属氧化物、杂多酸和磷酸盐组合的双/多功能催化剂用于甘油氧化脱水过程。与路易斯酸位点相比，布朗斯台德酸位点有利于丙烯醛的生成，而氧化还原位点将生成的丙烯醛转化为丙烯酸。迄今为止，已报道的杂多酸和混合金属氧化物催化剂的最大丙烯酸产率分别为 60% 和 59%。一些 DFT 研究还揭示了酸性位点的去质子化能量，并进一步有助于设计高效的催化剂。尽管取得了这些成就，但由于焦化和稳定性导致的催化剂失活仍然是一个主要问题。本文对用于甘油氧化脱水制丙烯酸的各种双/多功能催化剂进行了批判性综述。考虑了不同的催化剂形式、制备技术、反应动力学、反应机理、失活、再活化、工艺操作参数和可持续性。此外，还讨论了与每种催化剂类型相关的挑战以及克服低产率、失活的策略以及未来的方向。对用于甘油氧化脱水制丙烯酸的各种双/多功能催化剂进行了批判性审查。考虑了不同的催化剂形式、制备技术、反应动力学、反应机理、失活、再活化、工艺操作参数和可持续性。此外，还讨论了与每种催化剂类型相关的挑战以及克服低产率、失活的策略以及未来的方向。对用于甘油氧化脱水制丙烯酸的各种双/多功能催化剂进行了批判性审查。考虑了不同的催化剂形式、制备技术、反应动力学、反应机理、失活、再活化、工艺操作参数和可持续性。此外，还讨论了与每种催化剂类型相关的挑战以及克服低产率、失活的策略以及未来的方向。