Site requirements of supported W_(2)C nanocatalysts for efficient hydrodeoxygenation of m-cresol to aromatics  

用于间甲酚高效加氢脱氧制芳烃的负载型W_(2)C纳米催化剂的活性位研究

作　　者：Yanling Yang Peijie Han Yuanbao Zhang Jingdong Lin Shaolong Wan Yong Wang Haichao Liu Shuai Wang 杨艳玲;韩沛杰;张元宝;林敬东;万绍隆;王勇;刘海超;王帅(固体表面物理化学国家重点实验室,能源材料化学协同创新中心,厦门大学化学化工学院,福建厦门361005;集美大学轮机工程学院,福建厦门361000;厦门市海洋腐蚀与智能防护材料重点实验室,福建厦门361000;华盛顿州立大学化学工程与生物工程学院,华盛顿州,美国;北京大学化学与分子工程学院,北京分子科学国家研究中心,北京100871)

机构地区：[1]State Key Laboratory for Physical Chemistry of Solid Surfaces,Collaborative Innovation Center of Chemistry for Energy Materials,and College of Chemistry and Chemical Engineering,Xiamen University,Xiamen 361005,Fujian,China [2]College of Marine Engineering,Jimei University,Xiamen 361000,Fujian,China [3]Key Laboratory for Marine Corrosion and Intelligent Protection Materials of Xiamen,Jimei University,Xiamen 361000,Fujian,China [4]Voiland School of Chemical Engineering and Bioengineering,Washington State University,Pullman,WA 99164,United States [5]Beijing National Laboratory for Molecular Sciences,College of Chemistry and Molecular Engineering,Peking University,Beijing 100871,China

出　　处：《Chinese Journal of Catalysis》2024年第12期91-101,共11页催化学报(英文)

基　　金：国家重点研发计划(2021YFA1501104);国家自然科学基金(21922201,22202041,21872113);中央高校基本科研基金(20720220008).

摘　　要：Selective hydrodeoxygenation of lignin derivatives into aromatic compounds is a promising route for the upgrading of lignin feedstocks.Metal carbide catalysts have exhibited excellent selectivity in hydrodeoxygenation reactions,while their structure-activity relationship is still in ambiguity.Herein,a liquid-phase atomic layer deposition method was employed to synthesize W_(2)C/SiO_(2) catalysts with uniform and size-controllable W_(2)C nanoparticles.For gas-phase hydrodeoxygenation of lignin-derived m-cresol at 350℃,these W_(2)C/SiO_(2) catalysts showed superior toluene selectivities(>95%)regardless of the W_(2)C particle size.An optimal W_(2)C particle size of~7 nm was obtained for achieving the highest W_(2)C-based hydrodeoxygenation rate.In contrast,the turnover rate per surface W site increased almost monotonously as the W_(2)C particle size increased within 0.7-15 nm,attributable to high-index planes appeared on the larger W_(2)C nanoparticles.Kinetic effects of m-cresol and H_(2),taken together with temperature-programmed desorption of probe molecules and theoretical treatments,further indicate that the W_(2)C surface is nearly saturated by adsorbed m-cresol or its derivates under the reaction condition and the H-addition of the C7H7*intermediate to form toluene,instead of the initial C-O cleavage in m-cresol,acts as the rate-determining step.A side-by-side comparison between W_(2)C(102)and W_(2)C(001)catalyst surfaces in theoretical simulations of m-cresol hydrodeoxygenation verifies that high-index planes can stabilize kinetically-relevant transition states more effectively than the low-index ones,as a result of more available less-coordinated active sites on the former.The above findings bring new mechanistic insights into the site requirements of supported W_(2)C nanocatalysts,distinct from those metal-catalyzed hydrodeoxygenation of oxygenates.生物质作为地球上最主要的可再生有机碳资源,其高效转化制取液体燃料和化学品对推动“碳中和”具有重要意义.木质素是仅次于纤维素的第二大类生物质组分,含有丰富的含氧官能团和芳香环结构.将木质素衍生物通过选择性加氢脱氧反应制取芳香族化合物为木质素资源的优化利用提供了一条极具潜力的途径.加氢脱氧反应通常使用过渡金属为催化剂,但该类催化剂在促进木质素衍生物中C–O键断裂的同时,往往会造成芳香环的过度加氢,导致反应选择性不理想.近年研究表明,金属碳化物催化剂兼具较好的促进C–O键氢解能力和抑制C=C键加氢能力.但这些研究多以块体催化剂为主,对催化剂的构-效关系尚缺乏深入认识,严重阻碍了金属碳化物催化剂的合理设计与优化.合成粒径均一且可调变的金属碳化物纳米粒子有利于深入考察金属碳化物催化剂在加氢脱氧反应中的构-效关系.本文采用液相原子层沉积法在较宽的负载量范围(WO_(3):1.0 wt%-50 wt%)内将WO_(3)前驱体嫁接于SiO_(2)载体表面.紫外-可见光谱和高分辨透视电镜表征结果证实,此合成方法可将WO_(3)均匀分散在SiO_(2)载体上.以此为基础,在优化条件下对WO_(3)/SiO_(2)前体进行碳化处理,获得了相应W_(2)C粒径均一且可在0.7-15 nm范围调控的W_(2)C/SiO_(2)催化剂.以木质素衍生物间甲酚的加氢脱氧转化为模型反应,不同W_(2)C粒径的W_(2)C/SiO_(2)催化剂在350℃下均表现出较好的甲苯选择性(>95%).在其他氧化物载体上负载W_(2)C催化剂(如TiO_(2),ZrO_(2)等)或以其他木质素衍生物为加氢脱氧反应的底物(如苯甲醇、苯甲醚、愈创木酚等)同样可获得高C–O键氢解选择性,体现了W_(2)C在催化C–O键氢解反应中的优越性.基于W_(2)C单位质量考察催化活性,粒径为~7 nm的W_(2)C/SiO_(2)催化剂上的加氢脱氧速率最高;而将催化活性为归结至催化剂表面暴

关 键 词：Lignin derivative HYDRODEOXYGENATION Tungsten carbide Heterogeneous catalysis Structure-activity relationship Size effect Kinetics Density functional theory calculation 

分 类 号：O64[理学—物理化学]