What are the challenges in scaling up catalyst performance from lab to commercial scale?

Scale-up challenges: mass transfer regime may change (lab kinetically-controlled, plant diffusion-limited), heat transfer limitations develop in larger particles or tubes, flow distribution becomes non-ideal (bypassing, maldistribution), pressure drop increases with bed depth, and external gradients develop. Strategies: use representative particle size in lab, include transport calculations (Weisz-Prater criterion, Mears criterion), pilot at intermediate scale, develop models validated across scales, and account for flow maldistribution. Full-scale catalyst loading and startup procedures also differ.