碱改性介-微孔HZSM-5分子筛催化乙醇脱水制乙烯性能

摘要

对两种不同硅铝比的HZSM-5分子筛进行碱处理,制备介-微孔复合HZSM-5分子筛,研究乙醇脱水制乙烯的催化性能,并考察碱溶液浓度和处理温度对HZSM-5分子筛孔结构和表面酸性的影响.结果表明,适宜的碱处理条件有利于分子筛发生骨架脱硅和脱铝,从而形成介孔.碱处理对硅铝比低的HZSM-5分子筛酸性质影响明显,而硅铝比高的HZSM-5分子筛在碱处理过程中酸性质变化不明显,更易发生脱硅和脱铝而形成更多介孔.碱改性介-微孔HZSM-5分子筛催化剂使乙醇脱水制乙烯催化性能得到改善,尤其低温催化活性提高,这主要归功于碱处理中介孔的形成和表面酸性的调变.%Meso-microporous HZSM-5 zeolites with different Si/Al ratios were prepared through alkali treatment,and their catalytic performance for ethanol dehydration to ethylene was studied.The effects of alkali concentrations and treatment temperatures on the pore structure and surface acidity of HZSM-5 zeolites were investigated.The results showed that appropriate conditions of alkali treatment were beneficial to the removal of framework Al species and Si species of HZSM-5 zeolites,thus forming more mesopores.Alkali treatment had the greater effects on the acidity of HZSM-5 zeolite with low Si/Al ratio than that with high Si/Al ratio.After alkali treatment,more mesopores could be formed on HZSM-5 zeolite with high Si/Al ratio due to the removal of Al and Si.The catalytic performance of meso-microporous HZSM-5 zeolite for ethanol dehydration to ethylene was improved,especially its low-temperature catalytic activity was increased,which could be attributed to the newly formed mesopores and modulated surface acidity during alkali treatment.