Simulation Study On The Diffusion And Reaction Coupling Mechanism In Catalyst Pores

The diffusion of molecules in the pores of catalyst particles has significant effect on the reaction process and catalytic performance.It is of great importance to study the coupling mechanism between the diffusion and reaction in catalyst pores for optimizing the structure of catalysts.In this paper,the diffusion-reaction coupling in nano-and micro-scale pores is studied.The dynamic distribution characteristics of components caused by the diffusion-reaction coupling are analyzed.Furthermore,it reveals that the coupling mechanism is different from that of macroscopic continuum description.The algorithm for the coupling of hard sphere and pseudo-particle methods in molecular dynamics simulations is improved,and typical simple reaction models are introduced and its parallel algorithm is improved.Then,the diffusion and reaction processes in micro-scale confined space are studied.The simulation results show that the component concentration near the catalytic active site shows obvious non-random fluctuation in temporal and spatial distribution,which is significantly different from the steady-state distribution predicted by the traditional continuum model.The relationship between the fluctuation and the diffusion-reaction coupling is quantitatively characterized by introducing the diffusion and reaction factors.The mechanism of diffusion and reaction coupling in simple pores with uniform distribution of active sites is then studied,and the pore structure for maximum yield at the same pore volume is determined.The above results and understandings have also been applied to simulate the diffusion and reaction processes in complex pores,revealing the different deactivation phenomena process caused by two coke distribution models in ZSM-5 zeolite catalysts,and explaining the related experimental phenomena.The work is expected to provide an effective simulation method and analysis tool for the design and optimization of catalyst structures.