金属氧化物改性的HZSM-5催化热解木质素定向制备对二甲苯（英文）

Catalytic Pyrolysis of Lignin for Directional Production of p-Xylene over Metal Oxides-Modified HZSM-5 Catalysts

对二甲苯是石化行业中一种重要的大宗化学品,而且生物质基对二甲苯的制备在学术和工业领域都具有重要意义.对木质素和甲醇在不同金属氧化物改性的HZSM-5催化剂作用下共催化热解一步法制备可再生的对二甲苯的过程进行了研究.研究结果表明,在HZSM-5催化剂中引入La,Mg,Ce和Zn元素可以调节催化剂的酸强度和强酸性位点,进而促进轻芳烃(如苯和甲苯)烷基化形成对二甲苯以及间/邻二甲苯向对二甲苯的异构化.木质素和甲醇的共催化热解显著地提高了对二甲苯的产率.在20%La_2O_3/HZSM-5催化剂作用下,木质素与33 wt%甲醇共催化热解获得的对二甲苯的最高收率为13.9%,对二甲苯/二甲苯比率为82.7%.并且基于产物的分析以及催化剂的表征,提出了由木质素制备对二甲苯的可能反应途径.

Para-xylene（p-xylene） is an important bulk chemical in petrochemical industry, and the production of biomass-based p-xylene is of great significance in both academic and industrial arenas. This work proves the one step process for the production of p-xylene through the catalytic pyrolysis of lignin into the aromatic monomers, together with the alkylation of light aromatics and the isomerization of xylenes isomers into p-xylene over metal oxides-modified HZSM-5 catalysts. The modified catalysts by adding the La, Mg, Ce, and Zn elements into HZSM-5 promoted the alkylation of light aromatics（like benzene and toluene） into xylenes, and the isomerization of m-/o-xylenes to p-xylene, due to the modulations of the acid strength and the strong acid sites. Co-catalytic pyrolysis of lignin and methanol significantly enhanced the production of p-xylene during the catalytic pyrolysis of lignin. The highest p-xylene yield of 13.9% with a p-xylene/xylenes ratio of 82.7% was obtained by the co-catalytic pyrolysis of lignin with 33 wt% methanol over the 20% La2_O_3/HZSM-5 catalyst. The reaction pathway for the formation of p-xylene from lignin was addressed based on the identified products and the characterization of catalysts.