制备方法对Cu-SiO_2催化剂结构及其生物基木糖醇选择氢解性能的影响  

Effect of Preparation Methods on the Structure and Catalytic Performance of Cu-SiO_2 Catalysts in the Selective Hydrogenolysis of Biomass-derived Xylitol

作　　者：黄志威[1] 刘海龙[1,2] 贾玉庆[3] 夏春谷[1] 陈静[1] 刘海超[3] 

机构地区：[1]中国科学院兰州化学物理研究所羰基合成与选择氧化国家重点实验室,甘肃兰州730000 [2]中国科学院大学,北京100039 [3]北京大学化学与分子工程学院北京分子科学国家实验室,北京100871

出　　处：《分子催化》2015年第3期207-217,共11页Journal of Molecular Catalysis(China)

基　　金：国家自然科学基金(21203221,21473224);甘肃省自然科学基金(1308RJZA281);北京分子科学国家实验室开放课题基金

摘　　要：生物质基高碳多元糖醇选择氢解制备高附加值的C2、C3小分子多元醇具有重要的科学意义和应用前景.采用常规浸渍法(IM)、沉淀凝胶法(PG)、尿素水解沉积沉淀法(UHDP)、蒸氨沉积沉淀法(AEDP)和异相沉积沉淀法(HTDP)等5种不同方法制备了纳米Cu-Si O2催化剂,通过XRD、XPS、H2-TPR、BET和N2O化学吸附等不同方法对催化剂结构进行了表征,以Ca(OH)2为助剂考察了催化剂在生物基木糖醇选择氢解制备乙二醇和1,2-丙二醇反应中的催化性能.结果显示:制备方法不同Cu-Si O2催化剂的表面和体相组成不同,IM催化剂焙烧样品表面主要以Cu O存在,AEDP和HTDP焙烧样品的表面主要是页硅酸铜,而PG和UHDP焙烧样品的表面Cu O和页硅酸铜共存;IM和UHDP焙烧样品的体相以团聚的大颗粒Cu O为主,PG和HTDP样品以高分散Cu O为主,AEDP样品体相以高分散无定形页硅酸铜存在.受样品中物相组成的影响,不同方法所制备催化剂的分散度按AEDP>PG>HTDP>UHDP>IM顺序递减,经H2还原活化后,催化剂中Cu0颗粒尺寸按相反顺序递增.催化剂的木糖醇氢解反应活性和二元醇目标产物选择性受制备方法影响十分明显,均按AEDP、PG、HTDP、UHDP和IM的顺序先增高后降低,以UHDP法制备的Cu颗粒尺寸在12 nm左右的催化剂表现最佳,主要原因是该反应为结构敏感型反应,活性和选择性依赖于Cu颗粒尺寸.The selective hydrogenolysis of biomass-derived polyols to value-added etheylene glycol and propylene glycol has important scientific significance and application prospects.Five different methods including conventional impregnation (IM),precipitation-gel (PG),urea hydrolysis deposition-precipitation (UHDP),ammonia-evapora-tion deposition-precipitation (AEDP)and heterogeneous deposition-precipitation (HTDP)have been applied to prepare Cu-SiO2 catalysts.The catalysts were characterized by XRD、XPS、H2-TPR、BET and N2 O chemisorption. The catalytic performances of the catalysts were investigated in the selective hydrogenolysis of biomass-derived xyli-tol to ethylene glycol and propylene glycol in the presence of Ca(OH)2 .The results showed that the surface and bulk composition of the Cu-SiO2 catalysts differ greatly by preparation methods:CuO was the predominant Cu spe-cies on the surface of calcined IM sample,mainly copper phyllosilicate was present on the surface of calcined AEDP and HTDP samples,while both CuO and copper phyllosilicate were present on the surface of calcined PG and UHDP samples.Differently,for bulk samples,mainly CuO with large aggregates was present in the calcined IMand UHDP samples,CuO with high dispersion was the main species in the calcined PG and HTDP sample, while copper phyllosilicate with amorphous structure was mainly present in calcined AEDP.Due to the influence of the phase composition,the dispersion of the catalysts decreased by AEDP>PG>HTDP>UHDP>IM,while the Cu0 particle sizes after reduction in H2 increased on the opposite trend.The catalytic activity and selectivity to the target glycols of the Cu-SiO2 catalysts differ obviously by preparation methods,which increased with the trend AEDP <PG<HTDP and showed a maximum on UHDP then declined on IM.Such behavior of the catalysts is most likely due to the structure-sensitive nature of the reaction,with the UHDP catalyst having Cu particles of around 12 nm demonstrated the highest turnover frequency and glycol selectivity.

关 键 词：高碳多元醇 选择氢解 乙二醇 丙二醇 纳米Cu催化剂 

分 类 号：TQ223.1[化学工程—有机化工]