关键词: 渣油 , FCC催化剂 , SiO₂ 模型催化剂 , 有效扩散系数 , 扩散受阻因子

Abstract: Through the measured effective diffusion coefficient of Dagang vacuum residue supercritical fluid extraction and fractionation(SFEF)fractions in FCC catalysts and SiO₂ model catalysts the restricted diffusion factor was calculated.The restricted diffusion factor in FCC cataly stsisless than 1 and it is 2~3 times larger in large pore catalyst than in the conventional FCC catalyst.The results show that the diffusion of SFEF fractions in the two FCC catalysts is restricted by the pore.When the average molecular diameter is less than 1.8 nm,the diffusion of SFEF fractions in SiO₂ model catalyst which average pore diameter bigger than 5.6 nm is unrestricted.The diffusion is restricted in the catalyst pores of less than 8 nm for SFEF fractions which diameter more than 1.8 nm.The tortuosity factor of SiO₂ model catalyst was obtained to be 2.87,within the range of empirical value.The effective diffusion coefficient of the SFEF fractions in SiO₂ model catalyst was two orders of magnitude bigger than that in FCC catalyst with the same average pore diameter.It indicates that besides the ratio of molecular diameter to the pore diameterλ,the effective diffusion coefficient is also closely related to the pore structure of catalyst.Because SiO₂ model catalyst has uniform poresize,the diffusion coefficient can be precisely correlated with pore size of catalyst,so it is a good model materia lfor catalyst internal diffusion investigation.

Key words: Residue , FCC catalyst ,  SiO₂ model catalyst , Effective diffusion coefficient , Restricted diffusion factor Corresponding author