溶剂效应对Pt/MIL-100(Fe)催化肉桂醛选择性加氢性能的影响

Solvent Effect on the Catalytic Performance of Cinnamaldehyde Hydrogenation over Pt/MIL-100(Fe)

采用绿色环保的方法制备了MIL-100(Fe),通过双溶剂浸渍法将Pt纳米颗粒限域在MIL-100(Fe)的孔笼内部,经过盐酸质子化和甲醛还原制备出具有加氢中心及Lewis酸中心的双功能催化剂Pt/MIL-100(Fe).以肉桂醛选择性加氢为探针反应评价其催化性能,在60℃和1 MPa的最优条件下反应2 h,肉桂醛转化率为88.3%,肉桂醇选择性为84.9%.通过比较Cr,Al和Fe 3种金属中心的Pt/MIL-100催化肉桂醛加氢制肉桂醇及糠醛加氢制糠醇的反应性能发现,Fe中心有利于C=O加氢.重点研究了反应体系中水含量对肉桂醛选择性加氢反应的影响.表征和静态吸附实验结果表明,除去Pt/MIL-100(Fe)孔笼中的游离水有利于肉桂醛在孔道内直接富集,肉桂醛转化率提高;除去金属Fe簇上的络合水有利于肉桂醛C=O基团的吸附,肉桂醇选择性提高.在最优条件下,Pt/MIL-100(Fe)经过5次循环后,催化性能基本不变;X射线粉末衍射(XRD)、透射电子显微镜(TEM)及低温氮气吸附结果表明反应后催化剂结构仍保持稳定.

This study employs an environmentally-friendly method to synthesize MIL-100(Fe),and utilizes a double-solvent impregnation approach to confine Pt nanoparticles within the pores of MIL-100(Fe),subsequent to acidification with HCl and reduction with formaldehyde,a bifunctional catalyst,Pt/MIL-100(Fe),featuring hydrogenation and Lewis acid centers,is prepared.The catalytic performance is evaluated using the selective hydrogenation of cinnamaldehyde(CAL)as a probe reaction.Under optimal conditions(60℃,1 MPa H_(2)),the conversion of CAL reaches 88.3%in 2 h,with a cinnamyl alcohol(COL)selectivity of 84.9%.By comparing the reaction performance of Pt/MIL-100 catalysts with Cr,Al and Fe metal centers,it is revealed that the Fe center favors for the hydrogenation of C=O bonds in both CAL to COL and furfural to furfuryl alcohol.The impact of water content in the reaction system on the selective hydrogenation of CAL is extensively studied.Characterization and static adsorption experiments indicate that removal of free water from the pores of Pt/MIL-100(Fe)facilitates direct enrichment of CAL in the channels,leading to an enhanced conversion.Additionally,removal of coordinated water from the Fe cluster promotes the adsorption of the C=O group of CAL,resulting in an improved selectivity toward COL.After five catalytic cycles under optimal conditions,Pt/MIL-100(Fe)maintains the catalytic performance.Results of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and low-temperature nitrogenadsorption characterization confirm the stability of the catalyst structure after reaction.