不同形貌MgAl LDH的制备及Pt/LDH的催化加氢性能

Preparation of MgAl LDH with Various Morphologies and Catalytic Hydrogenation Performance of Pt/LDH Catalysts

如何制备性能高效、稳定的纳米Pt催化剂,对提高肉桂醛C=O加氢选择性具有重要的实际价值和科学意义。本研究采用共沉淀法和水热法制备不同形貌的MgAl水滑石(LDH),用等体积浸渍法制备负载型Pt/LDH催化剂,研究不同形貌的LDH对Pt催化肉桂醛选择加氢性能的影响。利用不同表征方法对催化剂结构、形貌、表面理化性能进行分析。结果表明,LDH载体的形貌对Pt/LDH催化剂的结构和性能影响较大,具有片层结构的LDH纳米片与活性组分Pt之间的相互作用易于贵金属Pt的分散和稳定。同时,LDH载体中存在丰富的碱性位点和表面羟基,有利于提高催化加氢活性和稳定性。催化性能评价表明,在反应温度为40℃、反应压力为1 MPa、反应时间为120 min的条件下,肉桂醇(CMO)的选择性为82.1%,肉桂醛的转化率为79.8%,经过5轮循环测试,催化剂仍具有较好的稳定性。

How to design and fabricate highly efficient and stable Pt nano-catalyst is of important practical value and scientific significance for improving the C=O hydrogenation selectivity of cinnamaldehyde.In present study,a series of MgAl hydrotalcite(LDH)supports with various morphologies were synthesized by co-precipitation and hydrothermal methods.The supported Pt/LDH catalysts were prepared by incipient wet impregnation(IMP)method with LDH supports,and used for cinnamaldehyde selective hydrogenation reaction,and influences of LDH with different morphology for the catalyst activity were studied.The structure,morphology,surface physicochemical properties of these catalysts were characterized.The results show that the morphology of different supports exerts a significant influence on the structure and properties of Pt/LDH catalysts.Interaction between lamellae LDH nanosheet and active component Pt facilitates dispersing and stabilizing of Pt nanoparticles.Meanwhile,there are abundant alkaline sites and surface hydroxyl groups in the LDH support,which are beneficial to improve the catalytic hydrogenation activity and stability.Results of catalytic performance show that selectivity of cinnamon alcohol(CMO)and conversion of cinnamon aldehyde(CMA)at reaction temperature of 40℃,reaction pressure of 1 MPa,and reaction time of 120 min were 82.1%and 79.8%,respectively.After 5 rounds of cycle tests,the Pt/LDH catalyst still has excellent stability.