焙烧温度对氟改性纳米HZSM-5分子筛催化甲醇制丙烯的影响

在400-550℃的不同焙烧温度下,制备了氟改性的纳米HZSM-5分子筛催化剂。利用XRD、N2吸附/脱附和NH3-TPD技术对氟改性前后催化剂的结构和酸性进行了表征,并在固定床反应器上考察了其催化甲醇制丙烯反应的催化性能。结果表明,氟改性可明显降低酸中心的数量及强度,从而显著提高丙烯的选择性和催化剂的稳定性。由于在450℃下焙烧的催化剂出现了新的强酸,使催化剂的稳定性和丙烯的选择性都略有下降。当焙烧温度达到550℃时,由于比表面积和孔体积大大降低,导致催化剂的稳定性显著下降。

Influence of Calcination Temperature on the Performance of Fluorinated Nanoscale HZSM-5 Zeolite in the Conversion of Methanol to Propylene

A series of fluorinated nanoscale HZSM-5 zeolite catalysts were prepared by calcining at different temperatures in the range of 400-550 ℃.The structures and acidic properties of the samples before and after fluorination were investigated by XRD,N2 adsorption/desorption and NH3-TPD techniques.The performances of the catalysts in the reaction of methanol to propylene were evaluated in a fixed-bed micro-reactor.The results showed that the amount and intensity of the acid sites decreased after fluorination,which resulted in the significant increase of propylene selectivity and catalytic stability.It was found that new strong acid sites appeared in the sample calcined at 450 ℃.As a result,both the selectivity of propylene and stability of catalyst decreased slightly.When the calcination temperature was increased to 550 ℃,the stability of the fluorinated sample decreased distinctly due to the significant decrease of the surface area and pore diameter.