均匀设计法应用于NaZSM-5分子筛无机酸交换条件的优化

Optimization of inorganic acid exchange conditions of NaZSM-5 zeolite by uniform design

采用无胺法水热合成NaZSM-5分子筛,分别用盐酸和硝酸将Na ZSM-5分子筛交换为HZSM-5,考察酸浓度、交换时间及温度、液固比(V(交换液)∶m(催化剂))等对其催化环己烯水合制环己醇性能的影响。采用XRD、XRF、NH3-TPD、SEM和N2吸附-脱附等技术对试样进行表征。运用均匀设计法对分子筛无机酸交换条件进行优化。实验结果表明,无机酸交换方法较传统铵盐交换方法简便、节能和高效。最优盐酸交换条件为:盐酸浓度1.2 mol/L、交换温度80℃、交换时间3 h、液固比11 mL/g,环己醇理论收率为9.29%,实际收率为8.71%。最优硝酸交换条件为:硝酸浓度1.2 mol/L、交换温度63℃、交换时间3 h、液固比为11 mL/g,环己醇理论收率为8.92%,实际收率为8.90%。理论收率与实际收率较吻合,说明均匀设计法在分子筛无机酸交换条件优化上具有较高的实用价值。

NaZSM-5 zeolite was synthesized in an amine-free system by hydrothermal method, and HZSM-5 catalysts were prepared through the inorganic acid exchange of the NaZSM-5 zeolite with HC1 and HNO3 separately. The effects of acid concentration, exchange time, exchange temperature and exchange liquid volume on the performances of the HZSM-5 catalysts in the hydration of cyclohexene to cyclohexanol were studied. The HZSM-5 catalysts were characterized by means of XRD, XRF, NH3-TPD, SEM and N2 adsorption-desorption. The exchange conditions were optimized by means of uniform design. The results showed that the inorganic acid exchange method was simple, energy saving and high efficient compared with the traditional ammonium salt exchange method. Under the optimal HC1 exchange conditions of HC1 concentration of 1.2 mol/L, exchange temperature of 80 %, exchange time of 3 h and exchange liquid volume of 11 mL/g, the theoretical and actual yields of cyclohexanol were 9.29% and 8.71%, respectively. Under the optimal HNO3 exchange conditions ofHNO3 concentration of 1.2 mol/L, exchange temperature of 63 ℃, exchange time of 3 h and exchange liquid volume of 11 mL/g, the theoretical and actual yields of cyclohexanol were 8.92% and 8.90%, respectively.