Synthesis and structure of grafted layer of silicas modified with alkanesulfonic acid

A convenient method for preparation of silicas modified with alkanesulfonic acid through the reaction of NaHSO3 with the C2H3 groups grafted on the SiO2 surface was proposed. The influence of the carrier and the structure of the grafted layer on the modification process was studied by DRIFT, MAS NMR, and temperature-programmed desorption mass spectrometry (TPD-MS). It was found that at most 40% of the C2H3 groups transform to the acid sites, which mostly have the structure of 2-Si-ethanesulfonic acid. The mechanism of the thermal decomposition of the grafted groups, which are stable up to 240 degreesC, was proposed. The monomeric structure of the grafted layer leads to partial olygomerization of the C2H3 groups through the C=C bonds.