Several factors can influence mass transfer limitations:
Particle Size: Smaller particles have a higher surface area-to-volume ratio, reducing external mass transfer resistance. However, very small particles can result in pressure drop issues in packed bed reactors. Pore Structure: The size, shape, and connectivity of pores within the catalyst influence internal diffusion. Microporous and mesoporous materials have different diffusion characteristics. Fluid Dynamics: The flow rate and pattern of the fluid (gas or liquid) around the catalyst particles affect the external mass transfer. Turbulent flow generally enhances mass transfer. Temperature: Higher temperatures increase the diffusion coefficients, potentially reducing mass transfer limitations but may also affect reaction kinetics and catalyst stability. Concentration Gradients: Steep concentration gradients can arise in systems with significant mass transfer limitations, leading to non-uniform reactant distribution.
