Synthesis of hydrophobic bifunctional mesoporous solid acid catalysts and their performance evalution in the esterification reaction of acetic acid with ethanol

Single-step synthesis of bifunctional mesoporous solid acid materials SBA-15-SO₃H－(CH₃)_x containing different hydrophobic alkyl (methyl, dimethyl or trimethyl) was carried out by hydrothermal treatment of gels. The catalysts were characterized by XRD, N₂ adsorption, elementary analysis, and were tested in the esterification reaction of acetic acid with ethanol. The results revealed that the hydrophobicity of the as-prepared materials increased with the increase of methyl number of hydrophobic precursors, and the catalytic activity increased with the hydrophobicity of the materials. Among these materials, SBA-15-SO₃H－(CH₃)₃ showed good performance toward the esterification reaction. Effects of reaction temperature, catalyst amounts, reaction time and the molar ratios of acetic acid/ ethanol over the catalyst SBA-15-SO₃H－(CH₃)₃ were also studied. Under the optimal reaction conditions of temperature 120℃, n(acetic acid)∶ n(ethanol) = 4∶1, catalyst 1%, time 1h, the conversion of ethanol and the selectivity of ethyl acetate were 93% and 100%, respectively.