甲醇芳构化的研究Ⅱ.NaOH处理HZSM-5分子筛催化剂的性能

Aromatization of Methanol Ⅱ. Catalytic Activity of NaOH Treated HZSM-5 Catalyst

采用NaOH溶液处理HZSM-5分子筛并将其用于甲醇芳构化反应,考察了NaOH溶液浓度、反应温度和甲醇分压等对催化剂甲醇芳构化性能的影响,比较了NaOH溶液处理前后HZSM-5分子筛催化剂的活性及稳定性。实验结果表明,产物苯、甲苯和二甲苯(BTX)的分布随反应温度和甲醇分压的变化规律与热力学计算结果基本一致。NaOH溶液处理显著调变了HZSM-5分子筛的结构和酸性分布,从而影响其甲醇芳构化性能。在所考察的催化剂中,0.2 mol/L NaOH溶液处理的HZSM-5分子筛催化剂表现出较好的活性和稳定性,在400℃、甲醇分压20 kPa条件下进行甲醇芳构化反应,BTX收率达48.6%,反应12 h后BTX收率仍高于35%,这主要归因于该催化剂具有适宜的酸量和酸强度分布。

The aromatization of methanol over HZSM-5 zeolite treated with NaOH aqueous solution was studied. The effects of the NaOH solution concentration, reaction temperature and methanol partial pressure on the activity of the catalyst in the aromatization was investigated. The changes of the yields of benzene, toluene and xylene（BTX） over the catalyst with the reaction temperature and methanol partial pressure accorded with thermodynamic calculation. The NaOH treatment significantly modified the structure and acidity of the catalyst, which affected its catalytic activity. The yield of BTX reached 48.6% under the conditions of the temperature of 400 ℃, methanol partial pressure of 20 kPa and HZSM-5 zeolite treated by 0.2 mol/L NaOH solution, and the BTX yield maintain more than 35% after running for 12 h. The high activity and good stability of the catalyst was attributed to its appropriate acid amount and acid intensity distribution.