Catalyst particles can migrate into ceramic support layers when the void structure is too coarse or catalyst fragments during service. Properly graded transition layers reduce penetration without creating excessive pressure drop.

Support-ball diameter and layer depth influence reactor pressure drop. Larger balls preserve open flow area, while smaller transition balls retain catalyst particles. Grading balances hydraulic capacity with particle support.

Higher-alumina ceramic balls provide benefits in demanding temperature, wear, strength or purity service, but conventional inert ceramic grades remain appropriate for many catalyst beds. Select alumina content from process requirements rather than automatically choosing the highest percentage.

Ceramic support-ball crushing strength should provide adequate margin for catalyst-bed load and operating conditions. Do not compare or specify crushing values without identifying ball diameter, material grade and test method.

Bottom ceramic balls support and transition the catalyst bed to the structural grid, while top balls stabilize and protect the catalyst surface. Their required size, depth and sometimes material grade may therefore differ.