HZSM-5分子筛的改性及其催化裂解废轮胎制备低碳烯烃

用不同浓度氢氧化钠溶液对硅铝比为200的商业HZSM-5分子筛进行了扩孔改性，利用粉末X射线衍射、扫描电镜、NH₃程序升温脱附和N₂吸脱附对改性分子筛的晶体结构、孔结构、形貌和酸性进行了表征，考察了改性HZSM-5分子筛在催化裂解废轮胎反应中的性能.结果表明，通过改变氢氧化钠溶液的浓度，可以一定程度调控分子筛晶体的孔结构和酸量.随着碱浓度增大，改性HZSM-5分子筛平均孔径增大，而介孔孔容和酸量先增加后减少.经0.4 mol/L氢氧化钠溶液改性处理后的HZSM-5分子筛催化剂，介孔孔容及酸量最大，其催化裂解废轮胎低碳烯烃选择性最高，达到了32.39%，远高于商业HZSM-5分子筛. 

Modification of HZSM-5 Zeolites and Their Catalytic Performances for Cracking Waste Tires to Produce Light Olefins

Commercial HZSM-5 molecular sieves with SiO₂/Al₂O₃ ratio of 200 were modified using different concentrations of sodium hydroxide solution.Their crystal structures, pore structures, morphologies and acidity were characterized by XRD, SEM, NH₃-TPD and N₂ adsorption and desorption measurements.The catalytic performances of the modified HZSM-5 molecular sieves for the catalytic cracking of waste tires were investigated. The results show that pore structure and acidity of modified HZSM-5 can be adjusted by changing the concentration of sodium hydroxide solution. With the increase of the concentration of sodium hydroxide solution, the average pore size of HZSM-5 increases gradually, while the mesoporous volume and the amount of acid increases at first and then decreases.The HZSM-5 zeolite modified with 0.4 mol/L of sodium hydroxide solution shows the most mesoporous pore volume and acid content. When it was used to catalyze the cracking of waste tires, the selectivity of light olefins is high up to 32.39%, being much higher than that of commercial HZSM-5 zeolites.