Adsorption and diffusion behavior of n-butane and butene-1 on ZSM-5 zeolite with different Si/Al ratios and temperatures

Adsorption and diffusion behavior of C4 fractions (n-butane and butene-1) on special shape-selective and acidic ZSM-5 zeolite with different Si/Al ratios, which is used as catalyst in olefins catalytic cracking (OCC) technology, was investigated using an intelligent gravimetric analysis apparatus (IGA-003, HIDEN) at 275, 288 and 300 K. The double Langmuir model was applied to simulate the adsorption of n-butane and butene-1 on ZSM-5 zeolite samples. The diffusion coefficients of n-butane and butene-1 were correlated in terms of the Fick diffusion model. The results indicate that the diffusion of n-butane and butene-1 on ZSM-5 zeolites are intracrystalline diffusion, and the diffusion coefficients are of the order of magnitude 10-14 m2/s. In addition, the diffusion coefficients of n-butane are larger than those of butene-1 on ZSM-5 zeolites at the same temperature and pressure. Moreover, the diffusion coefficients of n-butane and butene-1 on ZSM-5 zeolites all increase with temperature, and increase with pressure first and decrease at high pressure. In addition, the diffusion coefficients of n-butane all increase with the Si/Al ratio. The results are applicable in the C4 olefins catalytic cracking technology.