Na2CO3处理制备复合孔ZSM-5分子筛及其丙烷脱氢制丙烯的催化性能

Preparation of hierarchical ZSM-5 zeolites treated by Na_2CO_3 and its catalytic performance for propane dehydrogenation to propylene

通过不同浓度的Na2CO_3溶液处理合成的HZSM-5分子筛,并采用X射线衍射、N2低温物理吸附和X射线荧光光谱分析仪对溶液处理前后的样品进行了表征。表征结果显示,适量浓度的Na_2CO_3溶液处理HZSM-5,能够形成介孔-微孔复合孔道,增加了分子筛介孔容积和外比表面积;同时不会明显破坏HZSM-5的MFI结构,从而保持较好的高温热稳定性。在上述碱处理后的载体上制备了Pt-Sn-K/HZSM-5分子筛催化剂,并在固定床反应器上考察了丙烷脱氢制丙烯的催化活性。结果表明,随着Na_2CO_3溶液浓度的增加,催化剂的初始活性增加,而稳定性先增加后减少。当采用Pt-Sn-K/HZSM-5(1.8)分子筛催化剂用于丙烷脱氢反应,其呈现了良好的脱氢活性和稳定性:反应100h后,其丙烷化率为35.53%,相比初始活性仅下降了2.8个百分点,丙烯选择为98.4%,基本保持不变。

HZSM-5 zeolites were treated with different concentrations of Na2CO3 solutions. The samples were characterized by XRD, N2 adsorption and XRF. The characterizations showed that under suitable concentrations of Na2 CO3 solution, the treatment could form meso-micropore channels, which enhanced the external surface area and mesoporous volume. At the same time, the MFI structure of HZSM-5 was not obviously destroyed, therefore better thermal stability was maintained. The Pt-Sn-K/HZSM-5 catalysts were prepared by subjecting HZSM-5 samples to alkali treatment, and their catalytic performances for propane dehydrogenation to propylene were evaluated in a fixed-bed reactor. The results showed that the initial activity of the catalyst increased with increasing Na2 CO3 solution concentration, while the stability of the catalyst increased at first and then decreased. When Pt-Sn-K/HZSM-5 （1.8） zeolite catalyst was used for propane dehydrogenation, it showed better activity and stability： after reacting for 100 hours, the conversion of propane only decreased by 2.8%, resulted in a conversion of 35.53%. The propylene selectivity maintained at 98.4% with no significant change.