固体酸催化剂烷基化反应动力学性能与酸性的关联

RELATIONSHIP BETWEEN ACIDITY AND REACTION KINETIC PERFORMANCE OF SOLID ACID CATALYST FOR ALKYLATION

在确定非稳态反应动力学模型基础上,通过反应实验及数据处理,建立了用一套连续反应实验数据考察外扩散对多相反应过程影响及确定消除外扩散影响实验条件的新方法。结果表明,随着活化温度的提高,催化剂失活级数增大,即催化剂表面活性中心失活难易程度的分布变宽;催化剂活性先增大后降低,在250℃时为极大值;而催化剂活性稳定性先变差后变好,在350℃时为最差。TPD表征结果表明.催化剂表面酸强度和酸密度均随着活化温度的提高先增大后降低,分别在350℃和250℃时达到极大值。动力学性能与酸性的关联指出,催化剂的活性随着催化剂酸密度的提高而提高,催化剂活性稳定性随着其酸强度的增大而变差,即酸密度大、酸强度较低的催化剂是活性稳定性较好的催化剂。

The aim of this work is to study relativity between acidity and reaction kinetic performance of zeolite solid acid catalysts for alkylation of benzene with long chain olefins (C10-C14) in liquid-solid reaction system. Based on the determined kinetic model equation of non-steady reaction, the new method for obtaining experimental data of single continuous run to be used to evaluate the effect of external diffusion on multiphase reaction and to determine experimental conditions of eliminating external diffusion effect was developed through experiments and kinetic simulation. TPD acidity characterization and reaction kinetic model investigation for zeolite solid acid catalysts activated at temperatures from 200°C to 400°C in N2 stream were carried out. The results of kinetics study show that the order of catalyst deactivation in independent deactivation mechanism enlarges with the temperature rise of catalyst activation, i.e., the active site distribution on catalyst surface for coking deactivation is broadened with the temperature rise of catalyst activation. TPD characterization of n-propylamine temperature programmed desorption indicates that the acid density and acid strength of the catalyst acid sites change with the temperature rise of catalyst activation and reached a maximum at 250°C and 350°C, respectively. Catalyst activity rises with the increase of catalyst acid density and weaker acid strength of catalyst provides better activity stability.