Reactivity of the surface hydroxyl groups of MCM-41 towards silylation with trimethylchlorosilane

Two solid-state NMR methods are proposed to study the degree of silylation of MCM-41 with trimethylchlorosilane (TMCS). Both Si-29 MAS NMR and H-1 MAS NMR provide an accurate estimation of the amount of trimethylsilane attach ed to MCM-41. A silylation degree of 1.1 mmol per gram MCM-41 evacuated at 388 K was found. No external reference is required when Si-29 MAS NMR is us ed, this in contrast to(1)H MAS NMR. The reactivity of the surface hydroxyl s is easily analysed by means of H-1 MAS NMR spectroscopy. Only the isolate d silanol groups of MCM-41 are reactive for silylation with TMCS. (C) 2001 Elsevier Science B.V. All rights reserved.