Dynamic fluorescence imaging deciphers the particle size-acid accessibility trade-off in FCC catalysts toward optimized synthesis

In the synthesis of fluid catalytic cracking (FCC) catalysts, particle size is a critical factor governing acid site accessibility. This study takes different sieve-sized catalysts CAT-1 to CAT-6 as the research objects and combines conventional characterization techniques (e.g., SEM, XRD, N₂ adsorption–desorption, NH₃-TPD, Py-FTIR) with spatiotemporally resolved fluorescence imaging to systematically elucidate the mechanistic link between catalyst particle size and acid site accessibility. The results demonstrate that smaller catalyst particles (e.g., CAT-1: 10–20 μm), characterized by abundant submicron pore structures (0–0.2 μm), achieve complete (100%) acid site accessibility and superior spatial utilization efficiency within markedly shorter timeframes, significantly enhancing mass transfer performance. In contrast, larger particles (e.g., CAT-6: 120–180 μm) exhibit diminished catalytic activity due to mass transfer limitations imposed by elongated diffusion pathways and inadequate submicron pore structures. These findings provide a pivotal foundation for optimizing particle size design in industrial FCC catalyst synthesis, effectively balancing acid accessibility with particle dimensions to maximize overall catalytic efficiency.