Ag-Hollandite型MnO2催化剂催化草酸二乙酯加氢制备乙醇酸乙酯的研究

Ethyl glycolate is an important chemical product and intermediate, which can be used to synthesize glycolic acid, malonic acid, penicillin and allantoin. In view of the limited source of raw materials, the high pollution of catalysts and waste liquid, this project utilizes the catalytic hydrogenation of diethyl oxalate to realize the preparation of ethyl glycolate with high efficiency, environmental protection and economy. Ag-Hollandite type MnO2 catalysts are prepared on the basis of regulating the formation of Ag-O-Mn active units and silver nanoclusters, improving the adsorption and activation of H2 and diethyl oxalate, and thus promoting the catalytic activity. On this basis, on-line research, in-situ, off-line characterization and theoretical calculation are used to analyze the generation of Ag-O-Mn unit and silver nanocluster as well as the regulating mechanism for the catalytic activity, adsorption activation and reaction mechanism of H2 and diethyl oxalate on Ag-O-Mn unit and silver nanocluster, competitive adsorption mechanism between trace by-products (diethyl carbonate and ethyl acetate) and diethyl oxalate at active sites, and kinetics of catalytic hydrogenation of diethyl oxalate to ethyl glycolate. Thus, the research and development of the technology on the low-cost and green ethyl glycolate production will be promoted.

乙醇酸乙酯是一种重要的化工产品和中间体，可用于合成乙醇酸、丙二酸、青霉素和尿囊素等。本项目针对目前乙醇酸乙酯生产过程中原料来源受限、催化剂和废液污染大等问题，采用催化草酸二乙酯加氢方法，实现高效、环保、经济乙醇酸乙酯制备。以调控Ag-O-Mn活性单元和纳米银簇的生成改善H2和草酸二乙酯吸附活化促进催化反应活性为依据，制备Ag-Hollandite型MnO2催化剂。在此基础上，采用在线研究、原位和离线表征并结合理论计算，探明Ag-O-Mn活性单元和纳米银簇生成及其对催化反应活性调控的机制，H2和草酸二乙酯在Ag-O-Mn活性单元和纳米银簇上的吸附活化及反应机理，反应原料中微量碳酸二乙酯和乙酸乙酯等副产物与草酸二乙酯在活性位点上的竞争吸附机制，以及草酸二乙酯催化加氢制备乙醇酸乙酯的反应动力学，获得Ag-Hollandite型MnO2催化剂最佳制备方法，推进低成本乙醇酸乙酯绿色制备技术的研发。

本项目针对目前乙醇酸乙酯生产过程中原料来源受限、催化剂和废液污染大等问题，采用了催化草酸二乙酯加氢方法，利用银锰复合催化剂，实现了高效、环保、经济乙醇酸乙酯制备。研究结果表明，银原子具有显著的热迁移特性，在热作用下，银原子迁移进入HMO晶格通道内形成Ag-O-Mn结构单元。Ag-O-Mn结构单元内银原子和氧原子发生d2sp杂化，致使d轨道空缺，从而增强了氢气在银原子上的吸附活化。基于银原子的氢溢流特性以及锰原子的氢传递特性，活化氢会逐步迁移至催化剂表面与活化解离的草酸二乙酯发生反应生成乙醇酸乙酯和乙醇。草酸二乙酯易吸附在酸性位点上，Ag-O-Mn结构单元中银和氧原子的杂化牵引电子整体向银原子转移，诱导Mn原子上的电子向Mn-O化学键转移，Mn位点上的酸性提升，草酸二乙酯在催化剂表面吸附活化和解离为乙氧基化合物和双羰基化合物，这两种物质与活化氢发生反应后生成乙醇酸乙酯和乙醇。通过研究获得了银锰复合催化剂的最佳制备方法及其形成机制，以及草酸二乙酯在银锰复合催化剂表面的演化过程机制，推进了低成本乙醇酸乙酯绿色制备技术的研发。