Mesocellular aluminosilicate foams (MSU-S/F) and large pore hexagonal mesostructures (MSU-S/H) assembled from zeolite seeds: hydrothermal stability and properties as cumene cracking catalysts

摘要

Mesostructured aluminosilicate foams (pore size > 20 nm) and very large pore hexagonal SBA-15 analogs (pore size >8 nm), denoted MSU-S/F and -S/H, respectively, were assembled from aluminosilicate nanoclusters that seed the crystallization of zeolites Y, ZSM-5 and Beta. Although the zeolite seeds are nucleated under basic pH conditions and the mesostuctures are assemble at acidic pH, the results of hydrothermal stability tests in steam at 800°C and in boiling water for 250 h reveal that MSU-S/F and MSU-S/H aluminosilicates are much more hydrolytically stable than their Al-MCF and Al-SBA-15 analogues. ~(27)Al MAS NMR spectra indicate that calcined MSU-S/F and MSU-S/H mesostructures retained between 80 and 95% of the aluminum centers in tetrahedral framework sites at an overall Si/Al ratio of 50. Both mesostructures showed high activity for acid - catalyzed cumene cracking at 300 °C.