HZSM-5/Y复合分子筛的制备、表征及催化裂化性能研究

以商用HZSM-5分子筛为母体,采用NaOH溶液对其进行预处理,在添加铝源和Y导向剂的作用下合成了HZSM-5/Y复合分子筛,并对其进行XRD、SEM和BET表征。考察了NaOH溶液浓度对复合分子筛结构和形貌的影响。进一步考察了该复合分子筛催化剂在油酸裂化反应中的催化特性,并与商用HZSM-5分子筛的催化特性作了比对。结果表明:当NaOH溶液浓度为1. 5mol/L时制备的HZSM-5/Y复合分子筛具有良好的分子筛结构,并且在催化裂化反应中表现出良好的性能。当使用该分子筛时,在反应温度475℃、质量空速6. 99 h-1条件下,液体产物产率达到了54. 2%,油酸脱氧率为38. 5%,液体产物酸价(KOH)为2. 6 mg/g;与使用商用HZSM-5分子筛相比,该复合分子筛对5~12个碳原子的链烃类的选择性更高,其裂化液体产物酸价更低,但重复使用效果较差。

Preparation,characterization and catalytic cracking properties of HZSM-5/Y composite molecular sieve

The commercial HZSM-5 molecular sieve was used as the precursor and pretreated with NaOH solution to synthesize HZSM-5/Y composite molecular sieve by the addition of aluminum source and Y-directing agent,and the HZSM-5/Y composite molecular sieve was characterized by XRD,SEM and BET. The effect of NaOH solution concentration on the structure and morphology of the composite molecular sieve was investigated. The catalytic properties of the composite molecular sieve in the cracking oleic acid reaction were further investigated and compared with the catalytic properties of commercial HZSM-5 molecular sieve. The results showed that the HZSM-5/Y composite molecular sieve prepared with 1. 5 mol/L NaOH solution had a selected molecular sieve structure and exhibited good performance in the catalytic cracking reaction. When the molecular sieve synthesized was used,the liquid product yield reached 54. 2%,the oleic acid deoxidation rate was 38. 5%,and the acid value of the liquid product was 2. 6 mgKOH/g at reaction temperature of 475 ℃ and mass space velocity of 6. 99 h-1. Compared with the commercial HZSM-5 molecular sieve,the composite molecular sieve had higher selectivity to acyclic alkane of 5-12 carbon atoms,and the cracked liquid product had lower acid value,but the life of the composite molecular sieve was poor.