金属改性结合核壳结构协同调控酶解木质素催化热解液体产物分布的研究

Regulation of Metal Modification Combined with Core-Shell Structure on Liquid Products During Catalytic Fast Pyrolysis of Enzymatic Hydrolysis Lignin

针对催化热解中目标产物单环芳烃收率低、催化剂易失活等问题,制备4种金属改性分子筛催化剂,并提出结合金属改性和核壳结构的新型催化剂制备手段.将改性催化剂应用于酶解木质素催化热解制取液体燃料中,Fe改性的分子筛催化剂具有较高单环芳烃选择性和MAHs/PAHs比值,以其为微孔内核进行介孔壳层的包覆能够提高反应物和产物的扩散速率.在金属改性结合核壳结构催化剂的制备中,金属负载与介孔包覆顺序对于液体产物具有不同调控机制.研究结果表明,“先负载,后包覆”的催化剂能够降低多环芳烃选择性,提高MAHs/PAHs至2.38.“先包覆,后负载”的制备方法保留了酸性位点优势,促进芳构化反应和烷基化反应,单环芳烃质量收率提升至8.06%.

In order to solve the problems of low yield of target monocyclic aromatic hydrocarbons and deactivation of catalysts in catalytic fast pyrolysis,four metal modified molecular sieve catalysts were prepared and a novel catalyst preparation method combining metal modification and core-shell structure was proposed.Catalytic fast pyrolysis of enzymatic hydrolysis lignin was conducted over the modified catalysts to produce liquid products.Femodified zeolite catalysts had higher selectivity of monocyclic aromatic hydrocarbons and MAHs/PAHs ratio.The diffusion rate of reactants and products could be improved by coating mesoporous shell with Fe-modified zeolite as microporous core.During the preparation of metal modification combined with core-shell structure catalysts,metal incorporation and mesoporous coating sequence had different regulation mechanisms on liquid products.The results showed that‘metal incorporation followed by mesoporous coating’could reduce the selectivity of PAHs and increase the MAHs/PAHs ratio to 2.38.The preparation method of‘mesoporous coating first,then metal introduction’retained the advantages of acid sites distribution and promoted the aromatization and alkylation reactions,leading to the increase of the mass yield of MAHs to 8.06%.