Esterification via saccharine mediated silica solid catalyst

Saccharine (Sac) was immobilized onto rice husk ash (RHA) silica via 3-(chloropropyl)triethoxysilane (CPTES) to form a new catalyst, RHAC-Sac. The saccharine loading on the silica was found to be ca. 82%. The Si-29 MAS NMR showed the presence of T-2, T-3, Q(3) and Q(4) silicon centers. The C-13 MAS NMR showed that RHAC-Sac had three chemical shifts consistent with the three carbon atoms of the propyl group and a series of chemical shifts consistent with the presence of the aromatic ring. RHAC-Sac had a specific surface area of 250 m(2) g(-1) and a narrow average pore size of 3.28 nm. RHAC-Sac was used as a catalyst in the esterification reaction between ethyl alcohol and acetic acid. A 66% conversion was achieved at 85 degrees C with 100% selectivity for the ester. The stoichiometric composition of acid:alcohol = 1:1 was found to give the highest conversion. The use of Sac as a homogeneous catalyst also gave similar results to that of RHAC-Sac. RHAC-Sac could be reused several times by regenerating at 150 degrees C. (C) 2009 Elsevier B.V. All rights reserved.