Measurements and distinguishment of mass transfer processes in fluid catalytic cracking catalyst particles by uptake and frequency response methods

•D/r02 of guest molecular in REUSY zeolite are smaller than that in FCC catalyst particles.•The intraparticle diffusion play a dominant role in transfer limitation in FCC catalyst particles.•The mass transfer processes in particles can be detected and distinguished by FR technique.•Molecular transfer at the zeolite–matrix interface in FCC catalyst particles is the limiting step.

The mass transfer processes in REUSY zeolites and fluid catalytic cracking (FCC) catalyst particles have been measured and distinguished in this study by uptake method with an intelligent gravimetric analyser (IGA) and by the frequency response (FR) technique. The results indicate that the diffusion time constants in the FCC catalyst particles are smaller than those in the REUSY zeolites, and the limiting steps for the overall mass transfer processes in the FCC catalyst particles are the diffusion process in the length scale of macropore of the matrix or/and the mass transfer at the zeolite–matrix interface rather than the intracrystalline diffusion one in the micropores of the zeolite crystals.

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