Development And Application Of High-Pressure Catalytic Reactor Coupled With SR-PIMS

Catalysis is an essential part of modern chemical application and is a significant contributor to the development of national economy.Catalysis includes homogeneous,heterogeneous and other processes,for example,Synthetic ammonia,Methanol to Olefin and Fischer-tropsch synthesis in modern chemical industry are gas-solid two-phase catalytic processes.The reactants in heterogeneous catalysis usually diffuse to the surface of the catalyst where the chemisorption occurs,chemical reaction follows after activation,and then product desorption and diffusion happens.Therefore,in-situ detection and characterization of these desorption products,especially unstable intermediates and free radicals,are crucial for understanding the catalytic reaction mechanism and guiding the catalyst design.The stable and unstable gas phase products can be "frozen" by molecular beam mass spectrometry and analyzed in real time by mass spectrometry technology.Combined with synchrotron radiation photoionization,SR-PIMS also has the characteristics of little fragment ions and being able to distinguish isomers,which is particularly suitable for the study of complex gas phase reaction systems.For example,in-situ SR-PIMS was used to detect the key active intermediates such as ketene in the Fischer-Tropsch synthesis to lower olefins(FTO),which provided one of the pivotal evidences to reveal the new mechanism of catalytic reaction.In the study of oxidative coupling of methane(OCM),the existence of methyl free radicals was also detected in the gas phase,which confirmed the previous hypothesis that methyl free radicals would be generated by methane-activated dehydrogenation.In the process of methanol to hydrocarbon(MTH),SR-PIMS was used to study the change process of active intermediate formaldehyde in the induction,stabilization and inactivation period,which clarified the formation and evolution mechanism of formaldehyde in the reaction.However,the in-situ catalytic detection devices mentioned in the above experiments were only used to detect intermediates under low and atmospheric pressure environment,thus,it is impossible to detect and analyze the catalytic process and reaction products in-situ in the industrial catalytic process in real time and under high-pressure environment.Aiming to solve the above problems,this paper designed and developed an in-situ catalytic high-pressure reactor with synchrotron radiation photoionization mass spectrometry,and selected methyl acetate which prepared by dimethyl ether carbonylation catalyzed by mercerized zeolite molecular sieve(HMOR)as the catalytic experimental system,which proved the practicability of the reactor in in-situ high-pressure detection catalytic reaction.This paper was mainly divided into three chapters:The first chapter summarized the composition of mass spectrometry and its domestic and international development.This chapter introduced the synchrotron radiation photoionization mass spectrometry and the experimental combustion line station of NSRL.Furthermore,in-situ catalytic detection technique and the application of in-situ mass spectrometry in OCM,FTO and MTO processes was introduced.The second chapter mainly presented the structure design and safety calculation of this in-situ catalytic high-pressure reactor.In this design,gas dynamics theory and COMSOL Multiphysics software were applied for simulation,and the simulation results were verified by experimental measurements as well.In the third chapter,the reaction of methyl acetate prepared by carbonylation of dimethyl ether under different pressures near working conditions was studied by in-situ mass spectrometry.Two different pressure,0.1 MPa and 1.0 MPa,were selected to detect the reaction products by in-situ synchrotron radiation photoionization mass spectrometry.The result showed that the composition of reaction products under high pressure was obviously different from that under atmospheric pressure,and the selectivity of reaction products was highly dependent on the reaction pressure,which was consistent with previous literature.Besides,the formation process and reaction path of intermediates and stable products in the system at different temperatures were explored through programmed heating experiments.The experimental results showed that the inactivation mechanism of the reaction process was due to the carbon deposition in the MTO process,which confirmed the previous view.The methyl acetate produced at low temperatures was further converted to ketene at high temperatures,while the formation of formaldehyde may be due to the conversion of ketene or dimethyl ether at higher temperature.A series of experiments were carried out to verify the catalyst inactivation mechanism of the reaction system and to enrich the reaction path of the high-temperature part.In the fourth chapter,the classical F-T reaction was used as the high-pressure catalytic system,and two different pressures,0.16 MPa and 1.3 MPa,were selected for the time resolution experiment.The results showed that high pressure was conducive to the formation of long-chain hydrocarbons,which was consistent with the previous FTS mechanism,confirming the practicability of the reactor in the high-pressure catalytic system.The conclusion and prospect section summarized the work of this paper,and looked forward to the further improvement.