镓改性的铜基疏水催化剂用于CO_(2)选择性加氢制二甲醚的研究  

Selective hydrogenation of CO_(2) into dimethyl ether over hydrophobic and gallium‐modified copper catalysts

作　　者：李航杰 肖月华 肖佳乐 范凯 李炳宽 李晓龙 王亮[1] 肖丰收[1] Hangjie Li;Yuehua Xiao;Jiale Xiao;Kai Fan;Bingkuan Li;Xiaolong Li;Liang Wang;Feng-Shou Xiao(Key Laboratory of Biomass Chemical Engineering of Ministry of Education,College of Chemical and Biological Engineering,Zhejiang University,Hangzhou 310028,Zhejiang,China;Key Laboratory of Applied Chemistry of Zhejiang Province,Department of Chemistry,Zhejiang University,Hangzhou 310028,Zhejiang,China;Shaanxi Rock New Materials Co.,Ltd.,Baoji 721306,Shaanxi,China)

机构地区：[1]浙江大学化学与生物工程学院生物质化学工程教育部重点实验室,浙江杭州310028 [2]浙江大学化学系浙江省应用化学重点实验室,浙江杭州310028 [3]陕西瑞科新材料股份有限公司,陕西宝鸡721306

出　　处：《Chinese Journal of Catalysis》2023年第11期178-187,共10页催化学报（英文）

基　　金：国家重点研发计划(2022YFA1503502);国家自然科学基金(22288101,U21B20101,22102142).

摘　　要：CO_(2)选择性加氢制二甲醚(DME)是实现CO_(2)资源化利用的重要途径之一.然而,该过程面临着多方面的挑战.比如,水分子会限制CO_(2)的高效转化并诱导铜颗粒的团聚,导致催化活性与稳定性不足.此外,沸石分子筛甲醇脱水催化剂的酸性过强容易造成甲醇过度脱水生成低碳烃,导致催化选择性不足.因此,开发高效稳定的CO_(2)加氢制DME催化剂十分必要.本文通过共水解法制备了一系列镓改性的疏水二氧化硅负载铜基催化剂,并通过优化疏水基团含量以及铜与镓的比例来进一步提高催化性能.通过X射线衍射、氢气程序升温还原、X射线光电子能谱和CO吸附红外光谱等方法进行表征,结果表明,镓物种对铜纳米颗粒的电子结构进行了调控,提升了催化剂上Cuδ+物种的含量,从而抑制了逆水煤气转换反应,实现了CO选择性的降低.此外,水蒸气等温吸附、水蒸气程序升温脱附和水滴接触角测试等结果表明,引入疏水甲基基团可以调控催化剂表面的浸润性,提升水分子的扩散速率并抑制其二次吸附.在镓改性和甲基基团疏水修饰的协同作用下,Cu/Ga-SiO_(2)-20Me催化剂上CO_(2)转化率从5.5%提升至9.7%,DME选择性达到59.3%,而CO选择性则从40%降至11.3%.在100h的长周期测试中,表现出较好的催化稳定性.通过研究CO_(2)加氢催化剂(Cu/SiO_(2)-20Me)和甲醇脱水催化剂(Ga/SiO_(2)-20Me)的混合方式,探讨了疏水环境下铜和镓物种之间的协同作用.结果表明,镓改性和疏水基团的协同作用有助于串联反应的同步进行,避免了甲醇中间体的气相扩散和二次吸附.对于物理混合催化剂,由于两种活性金属存在一定的空间距离,导致铜基催化剂上生成的甲醇必须气相扩散并二次吸附于镓催化剂表面以进行后续甲醇脱水生成二甲醚反应.然而,在疏水甲基基团的作用下,抑制了极性甲醇分子的二次吸附,导致了二甲醚选择性的降低.尽�Supported Cu catalysts are widely studied for the hydrogenation of CO_(2) to dimethyl ether(DME).However,they suffer from insufficient durability and DME selectivity.Herein,we overcome these issues by modulating the gallium species and hydrophobic methyl groups to obtain a silica-supported copper catalyst,achieving a Cu/Ga-SiO_(2)-Me catalyst with significantly improved DME selectivity and catalyst durability.Characterizations of the catalysts showed that the gallium species electronically modulated the Cu nanoparticles,resulting in abundant Cu^(δ+)species in the catalyst,which minimized the reverse water-gas shift reaction and thus reduced CO selectivity.In addition,the methyl groups contributed to the rapid removal of water from the catalyst surface,which hindered Cu sintering and accelerated catalysis.Consequently,the Cu/Ga-SiO_(2)-20Me exhibited a CO_(2) conversion of 9.7%,selectivities of DME and methanol of 59.3%and 28.4%,and CO selectivity of only 11.3%.The strategy used in this study may provide rational guidance for improving current industrial catalysts.

关 键 词：CO_(2)加氢 铜催化剂 疏水性调节 镓助剂 催化剂稳定性 

分 类 号：TQ2[化学工程—有机化工]