表面修饰的级孔ZSM-5催化烃类裂解制备低碳烯烃的积炭行为研究

Catalytic cracking of naphtha and heavy oil, as the new technology for light olefins production, has attracted wide attention from the academic world; while, catalyst deactivation caused by coke deposit limited its industrial application. In this work, the formation and inhibition mechanisms of coke deposit are systematically investigated for hydrocarbon catalytic cracking over the SO42-/TiO2 surface-modified hierarchical ZSM-5 zeolites to produce light olefins. Via the alkali treatment and chemical liquid deposition methods, the mesoporous structure and SO42-/TiO2 surface modification of ZSM-5 zeolites are simultaneously achieved. Influences of the molecular structure of reactants and composition of model oils on the catalytic cracking have been investigated, and a particular attention has been paid to the measurement of light olefins, aromatics, coke deposit, etc. Then, the formation mechanism of coke deposit for hydrocarbon catalytic cracking over ZSM-5 zeolites is established. On the basis of the mechanism of coke formation and the evaluation and characterization results of ZSM-5 based catalysts, the structure-activity relationship between the reaction routes to coke deposit and ZSM-5 zeolites with different pore and surface structures is revealed. It directs the design and preparation of the highly anti-coking ZSM-5 based catalysts, which is evaluated by naphtha catalytic cracking. This project focuses on the roles of ZSM-5 zeolites with different pore and surface structures in the coke formation during the catalytic cracking of the straight-chain alkanes, branched alkanes, cycloalkanes, aromatics and model oils. The pore and surface structures of ZSM-5 zeolites are optimized to improve the coke resistance, and thus promote the industrialization of naphtha and heavy oil catalytic cracking to produce light olefins.

石脑油、重油等催化裂解是新兴的低碳烯烃制备技术，然而，催化剂积炭失活阻碍其工业应用。本课题拟针对SO42-/TiO2表面修饰的级孔ZSM-5催化烃类裂解制备低碳烯烃的积炭形成及抑制机理进行深入研究。同时采用碱处理法和化学液相沉积法，实现ZSM-5的级孔结构调控和SO42-/TiO2表面修饰，考察反应物分子结构、模型油组成对低碳烯烃、芳烃和积炭等裂解产物的影响，建立ZSM-5分子筛催化烃类裂解的积炭形成机理，结合ZSM-5基催化剂的评价及表征结果，探索具有不同孔、表面结构的ZSM-5与积炭反应的构效关系，指导设计、制备高效抗积炭ZSM-5基催化剂，并通过石脑油裂解工艺验证其催化性能。本项目重点讨论具有不同孔、表面结构的ZSM-5对直链烷烃、支链烷烃、环烷烃、芳烃和模型油等催化裂解积炭的作用机制，通过优化ZSM-5结构性质，提升其抗积炭能力，加速石脑油、重油等催化裂解制备低碳烯烃的工业化进程。

乙烯、丙烯作为化工行业的重要基础原料，与国民日常生活、国家经济发展息息相关。石脑油催化裂解技术具有良好的原料适应性和烯烃收率，然而催化剂积炭失活阻碍了该技术的发展和应用。由于石脑油组成过于复杂，其催化裂解积炭形成机理尚不明确。.本项目针对石脑油裂解制备低碳烯烃工艺进行深入研究。建立了由固定床反应器和双通道气相色谱仪在线连接的石脑油裂解评价体系，考察了分子筛催化剂、反应条件、反应物分子结构和原料组成等对烃类化合物裂解制备低碳烯烃的影响，分析了催化剂、反应条件、反应物分子结构、特征产物和关键反应路径之间的内在联系，揭示了石脑油催化裂解的积炭形成机理；在此基础上，考察了分子筛催化剂酸性质和结构性质对积炭反应、催化剂失活的影响，指导设计、制备抗积炭分子筛催化剂，并借助MATLAB和Python等软件，建立石脑油裂解制备低碳烯烃工艺的经验模型、智能模型，预测低碳烯烃产量和原料消耗，为低碳烯烃制备工艺的设计和优化提供理论指导。围绕本项目的研究成果，累计发表学术论文12篇，3项发明专利正在准备中；与此同时，结合承担单位相关专业的研究生教育和学科建设，培养硕士生6名。.本项目使用的分子筛催化剂提高了乙烯、丙烯收率，乙烯和丙烯的加和收率最高可达到65%以上。通过调控反应条件和催化剂性质能够改善低碳烯烃选择性和催化剂稳定性。本项目建立的石脑油裂解的积炭形成、催化剂失活机理，有助于推动石脑油催化裂解工艺的不断完善，加快其工业化进程。本项目建立的数学模型适用于多种原料的裂解工艺，能够在较宽泛的条件内预测原料转化率和烯烃收率，绝对误差控制在可接受的范围之内，扩展石脑油裂解及相关领域研究的深度与广度。因此，本项目已完成的工作，具有重要的科学意义和工程价值。