酸碱双功能催化剂及其在制备α,β不饱和酯反应中的协同效应

Synthesis of α, β-unsaturated ester by aldol condensation of corresponding ester with formaldehyde over acid–base bifunctional catalysts has important theoretical significance and practical value in broaden product route of the fine chemistry and environmental protection. In this study, the research is focused on improving the adsorption and diffusion capacity of formaldehyde and ester on catalyst, to achieve more efficient ability on activation of carbon-hydrogen and carbon-oxygen bonds by changing the ingredient, preparation method and technology of the catalysts. By adjusting the strength，the concentration and ratios of acid-base sites on the catalytic surface , the activation of base sites on α-positional carbon-hydrogen bond can well coordinate with the dehydrogenation reaction catalyzed by acidic sites，the reaction of formaldehyde and ester will follow the mechanisms of dehydrogenation- condensation- dehydration. Micro-mechanism of the condensation-dehydration reaction will be verified. The relationships between physico-chemical properties (such as: strength, concentration of acidic-base, specific surface area, pore structure of catalyst) and the catalytic activity, stability as well as product selectivity will be investigated. The effect of reaction conditions (such as: temperature, pressure, reaction time and ingredients) and reaction technology on the condensation-dehydration properties, stability and life of the catalyst will be investigated.

利用两性固体催化剂催化甲醛和酯缩合制备α, β不饱和酯对于拓宽精细化工产品的生产途径、改善环境具有重要的理论意义和现实价值，本课题重点开展以下研究内容：通过改变催化剂配方、制备方法和制备工艺，改变两性催化剂表面的吸附性能和孔结构,使其对甲醛和酯类反应物具有较强的吸附和扩散能力，具有更加有效的活化碳氢键和碳氧键的能力; 通过调整两性催化剂表面酸、碱中心的强度和浓度，使碱中心对α碳氢键的活化作用和酸中心对缩合产物的脱水反应能有效地协同进行；使甲醛和酯类原料按照脱氢-缩合-脱水的机理连续进行。确认缩合-脱水反应的微观作用机理，研究催化剂酸碱相对强度、相对浓度、比表面、孔结构以及其它物理化学性质与缩合-脱水反应过程的催化剂活性、稳定性、产品选择性之间的关系，探讨反应条件(如: 温度、压力、反应时间和组成等)、反应工艺等对催化剂缩合-脱水性能、稳定性和再生性能的影响。

丙烯酸及其酯是重要的有机合成原料和合成树脂单体，其聚合物用于合成树脂、纤维，也用于建材、涂料等工业部门，本文开发了钒系金属氧化物催化剂，以煤基工业路线副产物醋酸（甲酯）和甲醛为原料，经羟醛缩合反应一步合成丙烯酸（甲酯），实现其高效绿色合成。主要研究内容及结果如下：.利用有机溶剂还原法制备了钒磷氧化物（VPO）和负载型VPO催化剂。利用不同表征手段（XRD、BET、SEM、TG/DTA、XPS、NH3-和CO2-TPD、EPR）分析VPO与VPO-M催化剂的物理化学性质，在固定床反应器中评价其催化醋酸甲酯与甲醛合成丙烯酸甲酯的活性。研究发现，IV4+/IV5+比例在0.4-0.8的范围内，VPO-Zr-2%催化剂表现出最优的催化活性，丙烯酸甲酯收率达到40%，选择性为85%; V2%-P4%/SiO2（焙烧温度500 ℃）催化剂有最优的催化活性，其IV4+/IV5+比例为0.58，且结构性质适宜，丙烯酸收率为22%，选择性为98%。运行＞200 h时间范围内催化剂活性稳定，表现出良好的再生性能。用经验公式Voorhies和Arrhenius方程拟合催化剂积碳量与反应时间、反应温度的关系，建立了积碳反应动力学方程。