Solid-State MAS NMR Studies of Sulfonic Acid-Functionalized SBA-15

Abstract

Solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) was used to characterize propylsulfonic acid-functionalized SBA-15 materials prepared by the cocondensation method. The propylsulfonic acid-group concentration and distribution was systematically varied from 2.5 to 10%. As a way of coupling two acid sites and controlling the acid site spatial distribution, tethered propylsulfonic acid groups were incorporated into SBA-15. 13C, 29Si and 1H MAS NMR were used to determine the extent of functionalization. Probe molecules, such as triethylphosphine oxide and diphenyldiphosphines were used to evaluate acid site strength and acid site distributions, respectively.