Abstract This article is intended to deepen the understanding of molecular shape selectivity of HZSM-5 in catalytic conversion of biomass pyrolysis vapors through the study of catalyst effective pore size. Ex-situ catalytic fast pyrolysis (CFP) of biomass over HZSM-5 with varied catalyst loadings were carried out using a continuous feeding two-stage fluidized-bed/fixed-bed combination reactor. Results showed that in addition to the shape selective reactions inside catalyst channels, cracking and aggregating reactions occur at the external surface of HZSM-5. The catalytic activity of HZSM-5 external surface for some heavy compounds was observed to be relatively low. On the basis of the molecular dimension information provided by quantum chemical calculations, it was found that HZSM-5 has an effective pore size which is significantly larger than its static pore size at CFP temperature. Catalytic alkylation of naphthalene with methanol over HZSM-5, HZSM-5@silicalite-1, HSAPO-34, HM, Hβ, HUSY and HMCM-41 were further compared to determine the effective pore size of HZSM-5. It is proposed that the effective pore size of HZSM-5 at CFP temperature is between the critical molecular diameters of 2,3- and 1,6-dimethylnaphthalene (between 7.520 and 7.961 A).

中文翻译：

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HZSM-5 在生物质热解蒸汽催化转化中的分子形状选择性：有效孔径

摘要 本文旨在通过对催化剂有效孔径的研究，加深对HZSM-5在生物质热解蒸汽催化转化中分子形状选择性的理解。使用连续进料两级流化床/固定床组合反应器，在不同催化剂负载的 HZSM-5 上对生物质进行异位催化快速热解 (CFP)。结果表明，除了催化剂通道内的形状选择反应外，HZSM-5 的外表面还发生了裂化和聚集反应。观察到 HZSM-5 外表面对一些重化合物的催化活性相对较低。根据量子化学计算提供的分子尺寸信息，发现 HZSM-5 的有效孔径明显大于其在 CFP 温度下的静态孔径。进一步比较了 HZSM-5、HZSM-5@silicalite-1、HSAPO-34、HM、Hβ、HUSY 和 HMCM-41 上的萘与甲醇的催化烷基化，以确定 HZSM-5 的有效孔径。建议在 CFP 温度下 HZSM-5 的有效孔径介于 2,3- 和 1,6- 二甲基萘的临界分子直径之间（介于 7.520 和 7.961 A 之间）。