MoCI_5在HZSM-5和APO-5上的负载及调变作用

MoCl_5在HZSM-5和APO-5上没有发生“双聚”,沸石的酸性对MoCl_5负载量的影响大于孔结构。APO-5负载MoCl_5后,仅生成数量和强度都很小的B酸中心。Mo-ZSM-5沸石在MTG反应中有Mo和Al的表面迁移,负载的MoCl_5通过氧化-还原及水解等过程产生羟基,增加了ZSM-5沸石的B酸量,通过B酸-L酸中心的电子协同效应增加载体的B酸强度,调变了催化剂的酸性分布。

MoCl5 LOADING AND MODIFICATION OF HZSM-5 AND APO-5 ZEOLITES

MoCl5 loaded on both HZSM-5 and APO-5 did not form Mo2Cl10.Both the pore structure and acid distribution of zeolites affected the adsorption of MoCl5,and the latter gave a greater effect than the former.In the MTG reaction,the surface migration of Mo and Al atoms/species on MoZSM-5 zeolite resulted in the proportion enhancement of aromatics in the product.The loading of MoCl5 increased the amount of Bronsted acid sites on ZSM-5 during the oxidation-reduction and hydrolysis processes,and increased the strength of B acid sites through the synergistic electronic effect of B and L acid sites,and thus the acid distribution of the catalyst was changed obviously.As a result,the proportion of aromatic products was almost doubled in the MTG reaction over MoZSM-5 zeolite.Compared with HZSM-5,when MoCl5 loaded on APO-5 zeolite,only a small amount of B acid sites was formed and most of them were weak in acidic strength,therefore,only those hydrocarbons with carbon chain shorter than C5 were produced in MTG reaction on MoAPO-5 zeolites.