Co/Ni纳米粒子负载型SiAlON乙醇重整制氢催化剂的制备与应用研究

Hydrogen evolution from catalytic ethanol steam reforming (ESR) is an efficient way of development of hydrogen energy, but ethanol is prone to dehydration to form carbon coke on the surface of support such as Al2O3 and leads to deactivation of catalysts. In addition, the uniform chemical composition of support results in significant difficulty in adjusting electronic structures of metal catalysts, thus relatively low activity and product selectivity in ESR reaction. Our preliminary studies have found that the introduction of Si3N4 can decrease the acidity of Al2O3 efficiently, so the catalytic ethanol dehydration, carbon coke formation and undesirable side reactions can be significantly minimized, and hydrogen evolution selectivity would thus be improved. This project aims for preparation of SiAlON solid solution by introducing Si3N4 into Al2O3 using molten-salt-assisted nitridation method, and then loading Co/Ni nanoparticle to catalyze ethanol steam reforming. The SiAlON has high-temperature stability and the merit of both oxides and nitrides, the electronic structure of loaded Co/Ni nanoparticle and the surface properties of catalysts can be adjusted by variation in composition of SiAlON, and thus improve the activity, stability of product selectivity of the catalysts. The development of stable and high-efficiency Co/Ni nanoparticle-loaded SiAlON catalysts, systematic exploration of the structure-efficiency relationship of SiAlON catalyst, would afford new catalytic material, technology and method for hydrogen evolution from ethanol steam reforming reaction.

乙醇催化重整制氢是开发氢能源的有效途径，但乙醇在氧化物载体（如Al2O3）表面易脱水、结焦，导致催化剂易失活。此外，由于载体组分单一，难以对所负载金属催化剂电子结构进行有效调控，催化剂活性和选择性不够理想。前期研究发现Si3N4的引入，可有效降低Al2O3的酸性，从而显著降低Al2O3对乙醇脱水的催化效应，抑制结焦及副反应，提高产氢选择性。本项目拟采用熔盐氮化法，向传统的Al2O3载体中引入Si3N4，合成SiAlON固溶体。进一步负载Co/Ni纳米粒子，用于乙醇催化重整制氢。该SiAlON催化剂载体高温稳定、兼具氧化物和氮化物载体优点，通过调节其化学组成，可有效调控载体表面特性及负载Co/Ni纳米粒子电子结构，进而改善催化剂活性、选择性和稳定性。发展稳定、高效的Co/Ni纳米粒子负载型SiAlON催化剂，系统探讨催化剂结构与性能之间构效关系，为乙醇催化重整制氢提供新材料、新技术和新方法。

利用高效稳定催化剂催化乙醇重整制氢是利用生物质开发氢能的重要途径，但乙醇重整过程中催化剂的活性和耐受性仍是目前制约乙醇重整产氢效率的瓶颈，通过调控催化剂载体组成和物理化学性质，调节所负载金属催化剂与载体的相互作用和催化剂的电子结构是开发高效耐久型催化剂的重要研究方向。基于此，通过高温氮化法制备了系列Si6-zAlzOzN8-z(z=1，2，3，4)材料，并以其为载体合成了Si6-zAlzOzN8-z负载Ni/Co金属催化剂，通过Al/Si固溶比调节金属催化剂与载体间相互作用、电荷转移效应和金属催化剂的电子结构，提高了Si6-zAlzOzN8-z负载金属催化剂催化乙醇重整制氢活性以及产物选择性和C-C键断键选择性，获得了高效稳定的乙醇重整产氢催化剂，其中催化剂Co/Si4Al2O2N6-5w催化产氢产率达到90%，产物中C1组分产率达98%，表明SiAlON负载金属催化剂可显著提高乙醇重整制氢效率，催化反应产物中高含量C1产物表明其具有优良的C-C键裂解能力，可有效抑制催化剂表面的积炭，显著提高催化剂的耐受性。此外，对介孔氧化硅和取向性晶面暴露氧化铈负载型Co金属催化剂的催化乙醇重整制氢性能进行了研究，基于氧化物载体开发一系列提高乙醇重整催化产氢效率的策略。本项目工作为开发新型高效稳定乙醇重整制氢催化剂提供了新思路，研发的SiAlON负载Co/Ni催化剂可望转化成为高效的工业乙醇重整产氢催化剂，为氢能开发和生物质利用做出重要贡献。