硅灰基介孔ZSM-5分子筛合成及催化裂解性能研究

Synthesis of silica-ash-based mesoporous ZSM-5 molecular sieve and catalytic cracking performance

摘要:

采用工业废弃物硅灰为原料，淀粉为模板剂通过两步法制备出介孔ZSM-5分子筛，采用XRD，SEM，氮气吸脱附以及NH3-TPD对催化剂的晶型、形貌、孔道结构以及酸性特征进行了表征。发现合成的分子筛相对结晶度为73.4%，微观形貌是一个长轴在3 μm左右的柱状晶粒，它的孔径分布在3 ~ 5nm之间，总酸量为1.15 mmol/g。进一步将催化剂用于低密度聚乙烯（LDPE）和木质素（AL）的共裂解研究，结果表明，当对LDPE与AL（质量比1:1）进行共裂解时，BTEX选择性为91.86%，高于CZ（86.31%），也高于单独裂解LDPE与AL时的BTEX选择性。并且，共裂解时获得的BTEX产率（22.94%）也明显高于BTEX的理论产率（19.79%），说明催化共裂解过程中两种原料之间对提高BTEX生产有协同效应。

Abstract:

Mesoporous ZSM-5zeolite was synthesized by a two-step process using industrial waste silica fume as raw material and starch as template agent. The crystalline shape, morphology, pore structure and acidic characteristics of the catalyst were characterized by XRD, SEM, N2 adsorption and desorption as well as NH3-TPD. It is found that the relative crystallinity of the synthesized molecular sieve is 73.4%, and the microscopic morphology is a columnar grain with a long axis of about 3 μm, which has a pore size distribution between 3 ~ 5 nm and a total acid content of 1.15 mmol/g. The catalysts were further used for the co-cracking of low density polyethylene (LDPE) and lignin (AL). The results show that when co-cracking LDPE and AL (1:1 mass ratio), the BTEX selectivity is 91.86%, which is higher than that of CZ (86.31%), and also higher than that of caracking LDPE and AL alone. Moreover, the BTEX yield obtained during co-cracking (22.94%) was also significantly higher than the theoretical yield of BTEX (19.79%), indicating a synergistic effect between the two feedstocks in the catalytic co-cracking process to improve BTEX production.