微波辅助甘油催化脱水制备丙烯醛的强化机制研究

Acrolein is an important downstream product from glycerol, which can be used to produce high value-added products such as resin, medicine and paint. Considering the issues existing in conventional gas-phase catalytic dehydration of glycerol for acrolein production, including uneven temperature distribution in reactor and unstable catalyst, applicants proposed a novel method of microwave heating coupled with microwave absorbing catalyst, which effectively improved the catalyst stability and meanwhile increased the reaction rate. With the aim of deeply examining the mechanism of microwave influencing the glycerol dehydration process, the strengthening mechanism of microwave-assisted catalytic dehydration of glycerol to acrolein will be revealed, from the perspectives of heat transfer, mass transfer and reaction, in this project by means of both simulation and experimental research. The strengthening mechanism of microwave in heat transfer of both catalyst particle and catalyst bed will be explored through multi-physical simulation and experimental studies. The strengthening mechanism of microwave in mass transfer of both reactant and product molecules on the catalyst will be investigated through the determination of diffusion coefficients under various conditions. The strengthening mechanism of microwave in dehydration reaction will be studied through molecular dynamics simulation combining with experimental verification. A glycerol dehydration process of high reaction rate, high acrolein yield and high catalyst stability is expected to be achieved through the studies in this project. The results will also provide new research idea and theoretical basis for other gas-phase high temperature catalytic reactions.

丙烯醛是甘油重要的下游产品，可用于生产树脂、医药、涂料等高附加值产品。针对传统气相甘油催化脱水制备丙烯醛工艺中存在反应器内温度分布不均匀、催化剂易失活等不足，申请者提出的微波加热耦合吸波催化剂的方法，能够有效提高催化剂的稳定性，同时可以提高反应速率。为了深入探究微波在甘油脱水过程中的作用机制，本课题拟通过模拟仿真和实验研究相结合的手段，从传热、传质和反应的角度揭示微波辅助甘油催化脱水制备丙烯醛的强化机制。采用多物理场仿真和实验研究，探究微波对催化剂颗粒和床层传热的强化机制；通过测定不同工艺条件下的扩散系数，研究微波对反应物和产物分子在催化剂上传质的强化机制；采用分子动力学模拟并结合实验验证，探究微波对脱水反应的强化机制。以期通过本课题的研究，实现甘油脱水过程的高反应速率、丙烯醛的高收率和催化剂的高稳定性。研究结果也将为其它气相高温催化反应提供新的研究思路和理论依据。

丙烯醛是甘油重要的下游产品，可用于生产树脂、医药、涂料等高附加值产品。针对传统气相甘油催化脱水制备丙烯醛工艺中存在反应器内温度分布不均匀、催化剂易失活等不足，本项目利用微波加热耦合吸波催化剂的方法进行气相甘油催化脱水研究，并通过模拟仿真和实验研究相结合的手段，从传热、传质和反应的角度探究微波辅助甘油脱水过程的强化机制。通过开展上述研究，获得如下重要结果和关键数据：（1）数值模拟结果显示传统电加热管式反应器中催化剂床层内温度梯度较大，当反应器管径为20 mm时反应器中心与壁面温差最大为57 ºC；而微波管式反应器中整个催化剂床层内部温度分布较均匀，不同管径的反应器内外最大温差均在8~15 ºC；（2）通过对比搅拌速度对微波加热和常规加热下液固丙烯醛催化水合反应的影响可以看出，微波辐射能够在一定程度上促进反应物分子在固体催化剂上的扩散传质；（3）利用九种不同的双金属氧化物吸波催化剂进行气相甘油催化脱水实验研究，结果表明对于所有九种催化剂和250 ºC、300 ºC两个反应温度，微波加热条件下催化剂稳定性均明显优于电加热下的结果，而且不同反应器管径微波加热下催化剂稳定性基本相同，而电加热下催化剂稳定性随反应管尺寸的增大而明显下降；（4）分子动力学模拟结果表明微波辐射可以增加反应物分子在固体催化剂表面的吸附能，降低反应能垒，从而降低反应活化能。通过上述研究，探明了微波对于传热、传质和反应的强化机制，实现了甘油脱水过程的高反应速率、丙烯醛的高收率和催化剂的高稳定性。研究结果也将为其它气相高温催化反应提供新的研究思路和理论依据。