芬顿试剂改性ZSM-5分子筛上丙烯齐聚反应研究

Research on propene oligomerization reaction over the Fenton′s reagent modified ZSM-5

采用浸渍法分别制备了芬顿试剂及其原料FeSO4和H2O2改性的ZSM-5分子筛,并与未改性的母体ZSM-5分子筛进行了对比实验。通过一系列表征手段及丙烯齐聚反应考察了各催化剂的理化性质和催化性能。结果表明,芬顿试剂、FeSO4、H2O2的改性处理均会引起ZSM-5分子筛脱铝,从而导致其硅铝比升高。但与FeSO4改性相比,芬顿试剂由于其产生的大量羟基自由基更容易将Fe引入分子筛,形成新的活性中心,同时芬顿试剂改性还能使分子筛的比表面积和介孔的体积增大,调节催化剂的酸性。与母体ZSM-5相比,Fenton-ZSM-5催化剂具有优异的催化活性和稳定性。初始丙烯转化率和柴油选择性分别高达98.3%和92.4%,24 h内转化率和选择性维持在80%和82%以上。

ZSM-5 zeolite was modified by Fenton′s reagent,FeSO4 and H2O2 aqueous solutions using impregnation method,respectively.All these catalysts were characterized by XRD,ICP-OES,N 2 adsorption-desorption,NH 3-TPD,Py-FTIR and evaluated in propene oligomerization process.The results demonstrated that the framework of the parent ZSM-5 was well preserved after modification with Fenton′s reagent,FeSO4 or H2O2 solutions.However,the SiO2/Al2O3 ratios for all the modified ZSM-5 samples increased due to the dealumination.Furthermore,Fe was detected in Fenton-ZSM-5 while no Fe was observed for FeSO 4-ZSM-5 catalyst.The BET surface areas and total pore volumes of three modified catalysts significantly increased compared with the original ZSM-5 sample.Among them,the BET surface area of the Fenton-ZSM-5 increased by 17.86%.The increase of mesopores was probably caused by the removal of the residual organic template in the catalysts due to the generation of·OH radicals by Fenton′s reagent and H 2O 2.The Fenton-ZSM-5 catalyst formed new acid sites of Br nsted(B)and Lewis(L)with little change in the total calculated amount,which significantly changed the B/L ratio.Compared with the parent ZSM-5,the Fenton-ZSM-5 catalyst exhibited the best activity and stability for propene oligomerization reaction.The initial propene conversion and diesel selectivity were as high as 98.3%and 92.4%,respectively,and kept at>80%and>82%for about 24 h,respectively.