NewJ.Chem., 2015,39,8006

High activity of aluminated bifunctional mesoporous
silica nanoparticles for cumene hydrocracking and
measurement of molar absorption coefficient†

Bifunctional mesoporous silica nanomaterials (MSN) with various Si/Al molar ratios of 7, 10, 20 and 50 in
platinum supported (Pt/HAlMSN) were synthesized using sol–gel methods followed by post-synthesis
methods. XRD and nitrogen sorption results confirmed the mesoporous structure with surface areas of
537–775 m2 g1. 27Al NMR spectroscopy confirmed aluminium loading with tetrahedral, pentahedral and
octahedral structures. Pyridine adsorption IR results indicated that incorporation of aluminium led to the
generation of strong Brønsted and Lewis acidic sites. Catalytic activity was investigated for cumene
hydrocracking in a pulse microcatalytic reactor in the temperature range of 323–573 K which revealed
that this activity depends on the number of Lewis and Brønsted sites. The high yield of cumene conversion
increased from Si/Al molar ratios of 50 to 10 and decreased for the Si/Al molar ratio of 7 due to the
presence of pentahedral Al and/or inactive tetrahedral Al atoms in Pt/HAlMSN-7. The high selectivity of
a-methylstyrene showed the important role of Lewis acid sites in these bifunctional catalysts. In spite of the
coke formation in the Pt/HAlMSN catalysts, reactivation recovered the activity of the catalysts after 100 h of
reaction. The molar absorption coefficients of Pt/HAlMSN were measured using pyridine followed by water
adsorption monitored by FTIR.