糠醛制γ-戊内酯的高选择性Cu-Ni/铌固体酸多功能催化剂的制备及协同效应研究

Catalytic conversion of furfural to the high value-added γ-valerolactone (GVL) is one of the most promising pathways in the highly efficient utilization of biomass, including hydrogenation of furfural, alcoholysis of furfuryl alcohol, hydrogenation and dehydration of levulinate ester. in the project the alcoholysis of furfuryl alcohol on niobic solid acid is important among three above reactions by our recently studies and references. Therefore, we intend to explore catalytic alcoholysis mechanism in-depth by kinetics studies of the reaction, in situ characterization and DFT theoretical calculation, and study the interaction between the various reactions; On this basis, design and prepare niobic solid acid supported Cu-Ni bimetallic multifunctional catalyst through regulating the surface acid sites and intensity of niobic solid acid, preparation of Cu-Ni nano hydrogenation component and taking advantage of the synergetic effects between the two active sites; Integrate all the intermediate reaction steps of hydrogenation, alcoholysis, hydrogenation and dehydration in the furfural conversion by virtue of designing and preparing niobic solid acid supported Cu-Ni bimetallic multifunctional catalyst, and finally realize the highly efficient one-pot synthesis of GVL; Determine the rate-determining step of the process through kinetic studies and DFT theoretical calculation on Cu-Ni/Nb solid acid composite catalyst; Understand the coupling effects among different steps in whole the reactions. On the whole, the development of Cu-Ni/niobic solid acid multi-functional catalysts in this project would be believed to provide a novel idea for the highly efficient, low-cost and green synthesization of GVL.

由糠醛催化转化制高附加值的γ-戊内酯是一条极具前景的生物质利用途径，包含糠醛选择性加氢到糠醇，糠醇醇解制乙酰丙酸酯以及乙酰丙酸酯加氢脱水至γ-戊内酯三步反应。本项目结合前期研究结果及文献调研，得出铌固体酸上的糠醇催化醇解在三步反应中尤显重要。因此，通过反应动力学研究、原位反应表征设计及DFT理论计算，深入探讨醇解催化反应机理，同时对各反应间的相互影响进行研究；在此基础上，通过对铌固体酸表面酸中心的种类和强度的调节、Cu-Ni加氢组分的纳米化制备，利用二者之间的协同作用，设计制备出多功能的铌固体酸负载纳米Cu-Ni的复合催化剂，实现糠醛一釜制备γ-戊内酯的高效催化过程；并通过Cu-Ni/铌固体酸复合催化剂上糠醛制γ-戊内酯反应的动力学研究及DFT理论计算，确定整个反应过程的速控步骤，揭示多步反应间的耦合效应，为高效、绿色、低成本合成γ-戊内酯提供新思路。

一锅法催化转化糠醛制备高附加值的γ-戊内酯是一条极具前景的生物质资源高效利用途径。本项目首先对糠醛一锅法制备γ-戊内酯的过程中的三步催化反应——糠醛加氢至糠醇、糠醇醇解至乙酰丙酸酯及乙酰丙酸酯加氢至γ-戊内酯分别进行了研究：1）分别用多元醇原位还原和共沉淀的方法制备了不同CuNi比例的Cu-Ni-Zr-O催化剂，通过优化CuNi比例，发现共沉淀法制备的Cu1-Ni1-Zr-O催化剂用于糠醛加氢至糠醇反应，糠醇的收率大于99%。2）系统研究了制备条件及助剂等对铌固体酸载体酸性的影响，实现B酸/L酸强度的可控调变，当制备体系pH为1时，得到的铌固体酸载体具有较多的B酸，在糠醇醇解至乙酰丙酸酯反应中表现出较高的乙酰丙酸酯的选择性；类似的，含有较高B酸量的商业低硅铝比ZSM-5也表现出较好的糠醇醇解至乙酰丙酸酯催化活性。3）将糠醛加氢至糠醇反应中Cu1-Ni1-Zr-O催化剂应用于乙酰丙酸酯加氢至γ-戊内酯反应中，γ-戊内酯收率大于96%；通过DFT计算得到乙酰丙酸酯的吸附活化是此反应的速控步骤。接着，在上述研究基础上尝试了催化加氢和醇解多功能催化剂的复配制备，发现复配后催化剂的加氢性能与酸催化性能在一定程度上会相互抑制，尤其是加氢活性组分的加入对铌固体酸载体的酸性有很大影响。通过优化，最终选择Cu1-Ni1-Zr-O和商业的ZSM-5按质量比例5:8混合为催化剂，对糠醛进行一锅法催化转化，以95%的乙醇水溶液为溶剂，3 MPa氢压，180 oC反应25小时，糠醛转化率大于99%，γ-戊内酯收率为63%。