二苯甲烷二氨基甲酸甲酯热解制备异氰酸酯反应过程机理的ReaxFF反应分子动力学研究

The thermal decomposition of methylene-4,4-di(ethylphenyl-carbamate) (MDC) is the most promising method for producing methylene-4,4-di(phenylisocyanate) (MDI). However, it is difficult to improve the yield of MDI. One important reason is that the reaction mechanism of pyrolysis process is not clearly understood. This project is devoted to the study of the reaction mechanism of the thermal decomposition of MDC to MDI, by constructing a series of multi-level molecular simulation methods including ReaxFF reaction molecular dynamics and quantum chemistry. The project is mainly focused on finding the key factors of directional transformation MDC pyrolysis process effect mechanism and the main reaction effective regulation, the generation mechanism of a byproduct of the process and its influence on the reaction. Subsequently, The layered montmorillonite Brønsted catalytic pyrolysis and methanol adsorption separation coupling mechanism were studied. Finally, studying of the reaction process of solvent effect, we want to provide a theoretical guidance for the selection and design of solvent. It is anticipated that the project can provide helpful reference for the non-phosgene MDI technology development, and has important theoretical value and practical significance.

二苯甲烷二氨基甲酸甲酯（MDC）热解是目前非光气法合成异氰酸酯（MDI）最有前景的技术路线，但工艺开发过程中MDI产率的调控是技术难点，这主要是由于对热解过程的分子转化及反应机理认识不足。鉴于此，本项目拟采用以ReaxFF反应分子动力学为核心的多尺度方法模拟MDC热解反应过程，开发适合反应物及产物分子的ReaxFF反应力场，重点明晰MDC单分子可逆β-热消去反应过程本质及外加溶剂效应，探索液相热解过程副反应的发生及调控机制，明确多聚体PMDC副产物及杂质分子对MDC热解过程的影响。同时借助巨正则蒙特卡罗方法开展层状蒙脱石Brønsted酸催化热解及甲醇吸附分离耦合作用机理研究，为催化剂设计提供支撑。本项目的分子模拟研究可为MDC热解过程中MDI产率调控方案的设计提供可靠的理论指导。

本项目以明晰MDC热解过程反应机理为目标，建立了以ReaxFF反应分子动力学为核心，量子化学等为辅助的多尺度分子模拟方法体系，重点明晰了MDC单分子可逆β-热消去反应过程本质及外加溶剂效应，探索了液相热解过程副反应的发生及热力学调控机制，明确了多环MDC副产物及杂质分子对MDC热解过程的影响。同时借助GCMC方法开展层状蒙脱石Brønsted酸催化热解及甲醇吸附分离耦合作用机理研究，为催化剂设计提供支撑。通过本项目的理论模拟研究，开发了适用于氨基甲酸酯、异氰酸酯类有机物质的ReaxFF反应力场参数，明晰了苯氨基甲酸酯类有机物质可逆热消去反应本质，从而为非光气法制备MDI工艺开发提供重要支撑，具有重要的理论价值与实际应用意义。