EFFECT OF PORE-SIZE OF MESOPOROUS MOLECULAR-SIEVES (MCM-41) ON AL STABILITY AND ACIDITY

A matrix of mesoporous molecular sieves (MCM-41) with various Si/Al ra tios and various pore sizes was synthesized. These were structurally c haracterized by X-ray diffraction, IR and Al-27 NMR. The relative acid ity of these materials was estimated catalytically based on the isomer ization selectivity of 2-methyl-2-pentene, The activity and selectivit y of this reaction are affected by both the Si/Al ratio and the pore s ize at fixed composition. The stability of Al in the wall structure (a s tetrahedral Al) is also affected by the pore size, the smallest pore size resulting in the most stable tetrahedral Al.