Synthesis And Catalytic Properties Of Hierarchical Mordenite Zeolites

As a zeolite has been applicated in chemical industry, Mordenite (MOR) is used as catalysts for hydro cracking, hydroisomerization, alkylation and reforming etc. However, its small pore diameter limits the diffusion rate of reactants and products in the pores. It is the reason for the low usage of active sites and the high carbon deposit. In recent years, inspirited by the advantages of and the mesoporous molecular sieve, the synthesis of the hierarchical Mordenite has been focused. In this paper, we synthesized a series of hierarchical mordenite samples by different mathods. Their catalytic performances were evaluated by the alkylation of benzene and benzyl alcohol.The main conclusion has been drawn as follows:(1) The hierarchical mordenite samples were synthesized by soft template method using Al2(SO4)3as aluminum source and adding MOR seeds. Cetytrimethylammonium bromide (CTAB), polyquaternium-6and polyquaternium-7were used as templates. The samples synthesized with CTAB as template presents flaky particles with irregular morphology. The BET surface area is472.5m2/g with a mesoporous/microporous volume ratio of0.3. While the polyquaternium-6was employed as template, the samples present as nanocrystal aggregates. The BET surface area is301.2m2/g with a mesoporous/microporous volume ratio of7.0. Then mesoporous can be adjusted by the content of the template agents.(2) The hierarchical mordenites were also synthesized by using multi-wall carbon nanometer tubes and self-synthesizd FeOOH particles as templates.The crystal size of the samples synthesized with the multi-wall carbon nanometer tubes are about20μm. Whlie the FeOOH was employed as template, the samples are about4um in size. The BET surface area is458.8m2/g with a mesoporous/microporous volume ratio of0.3.(3) After treated by HC1solution, all of the hierarchical mordenite samples synthesized by soft and hard templates possessed higher Si/Al molar ratio. They showed better catalytic performance than the usual MOR in the alkylation of benzene and benzyl alcohol. The conversion of benzyl alcohol was28.5%over the sample synthesized with CTAB as template, and26.8%over the sample synthesized with FeOOH as template.