甲醇制烯烃过程中介尺度催化剂积碳机理及调控机制研究

DMTO, which provides an alternative way for light olefins production, is of great significance in ensuring the safety of the national energy strategy. Currently the design of DMTO fluidized bed reactor learns a lot from the FCC unit design, which remains a lot of room for improvement. In this project we will study the catalyst coking process in DMTO multiphase catalytic reactor, with a focus on the meso-scale effect. The study will be based on two different levels, i.e. the catalyst level and reactor level. At the catalyst level, we will try to learn the gas diffusion and coking mechanism in a catalyst solid that composed of a huge amount of zeolite crystal and void channels in between. As the gas diffusion and coking were studied inside a single zeolite crystal, less is known about the gas diffusion and coking in the void channels and crystal clusters, which is the so-called meso-scale. A 3D network model together with NMR technique will be used to study how the gas diffuses and how the coke forms at the meso-scale. At the level of reactor, non-uniform structures such as particles agglomerates and bubbles are considered very important in controlling catalyst residence time distribution. Since the catalyst residence time distribution can dominate the distribution of coke-in-catalyst, and the latter is very important for light olefins selectivity in DMTO reactor, there rises a desire to understand the non-uniform structures in the fluidized bed reactor. These non-uniform structures are again meso-scale structures if we define the catalyst solid as the low scale and the reactor as the high scale. A comprehensive study, including cold flow experiments, reaction experiments, and DEM (discrete element model) simulations, will be carried out in this project to study the formation and evolution of these non-uniform structures. We will find the methods to regulate catalyst residence time distribution in the reactor by controlling the meso-scale structures. Along this line, we would like to propose the design philosophy for high efficient DMTO fluidized bed reactor.

DMTO作为煤转化制化学品领域的一个重要新工艺，在保证国家能源战略安全方面具有重要意义。目前DMTO流化床反应器主要借鉴FCC装置的设计，还有很大的优化改进余地。本项目针对DMTO气固多相反应体系，从催化剂和反应器两个层面对催化剂积碳过程进行研究。着重1) 研究DMTO催化剂颗粒内介尺度结构（如分子筛晶体以及晶体间孔隙）对气体扩散和积碳反应的影响，以及单个催化剂颗粒内气体扩散及积碳反应机理。建立催化剂积碳与间催化剂颗粒大小、分子筛含量与分布及反应条件之间的关联；2) 研究DMTO流化床反应器中介尺度非均匀结构如气泡颗粒聚团等的形成机理，及其对催化剂停留时间分布的影响。根据催化剂停留时间与催化剂积碳分布之间的关联，研究催化剂积碳分布的调控机制，提出DMTO流化床反应器的优化设计理论基础。

MTO工艺是煤制化学品路线的一个重要环节，在保证国家能源战略安全方面具有重要意义。目前，MTO装置设计主要借鉴了FCC的设计思想，还有很大的优化改进余地。本项目针对MTO工艺基于催化剂颗粒和反应器的两个层面考察了MTO的积碳过程：基于Maxwell-Stefan扩散理论和理想溶液吸附理论，建立了用于描述单个催化剂颗粒内介尺度几何拓扑结构的三维网络模型；开展MTO催化剂颗粒内部的Uptake吸附研究和核磁共振技术测量研究，探索了MTO过程主要组分的扩散机制；基于双循环机理，建立MTO的反应动力学模型，定量描述MTO过程的产物选择性和和甲醇转化率；建立热膜/光纤式高速内窥摄像系统，实现了DMTO反应器内气固两相系统速度和浓度的同时测量；搭建了小型循环流化床实验装置，建立了流化床运行参数与流化扩散系数之间的关联式；搭建了微波加热-颗粒示踪实验平台，对流化床内颗粒扩散过程进行了系统测量；提出催化剂的积碳分布模型，针对MTO反再系统建立适合中试、示范性装置和工业装置的多尺度的MTO反应器模型。本项目研究了DMTO催化剂颗粒和反应器的介尺度结构以及催化剂积碳分布的调控机制，对DMTO流化床反应器的优化设计具有指导意义。