Intraparticle diffusion is a crucial factor for heterogeneous catalytic processes. Heavy oils are significantly influenced by diffusional transport in catalyst

which reduces the efficient conversion of the feedstocks and the effective utilization of the catalyst. An overview of the methods (diaphragm diffusion cell

adsorptive uptakeand reactive kinetic methods) and advances in diffusivity of heavy oils in pores is presented. Key factors of diffusion of heavy oils

such as temperature

concentration

molecular configuration and catalyst deactivation are discussed. At last

the directions of future development indiffusion of heavy oils are suggested.