zeolite

For microporous molecular sieves, the particle size has little effect on the surface area. The specific surface area of the microporous molecular sieve is mainly contributed by the inner surface (pore surface), and the proportion of the outer surface to the total surface is generally not more than 10%. As for the particle diameter 2~3(mm?), 3~5, 5~7, this difference can be completely ignored. Catalytic reaction involves both mass transfer and diffusion control and reaction kinetics control. For the same type of microporous molecular sieve, the reaction kinetics control is the same. At this time, the influence of mass transfer diffusion on the adsorption desulfurization reaction depends on the catalyst particles. Diameter, molecular sieve aperture and molecular dynamics effective cross-sectional diameter of the reactants, the latter two are fixed values, and their influence is difficult to eliminate. The former is related to the mass transfer and diffusion of the reactants in the secondary pores. Theoretically, the particle size increases or decreases. The decrease of the pore size of the graded pores all lead to the decrease of the mass transfer and diffusion rate, which is unfavorable to the reaction. Generally, the secondary pore size is much larger than that of the molecular sieve micropores. The diffusion of gas reactant molecules in the molecular sieve micropores is Knudson diffusion or crystal diffusion, while the diffusion in the secondary pores is roughly free diffusion. The influence of mass transfer diffusion can be reduced to a stable level by changing the reaction conditions (such as space velocity, temperature), catalyst particle size and bed height-to-diameter ratio, but basically cannot be completely eliminated. In this sense, catalyst particles The diameter reduction may help to improve the adsorption desulfurization effect,