Vapor phase esterifation of acetic acid with n-butanol over H3PO4/MCM-41

Several mesoporous aluminosilicate molecular sieves with the MCM-41 structure (SiO2/Al2O3 = 20-200) have been synthesized using different aluminum sources and modifying several synthesis parameters during the preparation process, such as the temperature and the content of water and sulphuric acid in the gel mixture. All samples were characterized by element chemical analysis, X-ray diffraction, N2 physisorption, thermal analyses and electron microscopy. These Al-MCM-41 materials have BET surface areas up to 1000 m2/g. The catalytic properties of their H3PO4-treated derivatives for esterification of acetic acid with nbutanol have been evaluated. This reaction preferentially gave n-butyl acetate. The conversion of acetic acid to n-butyl acetate increased with increasing the H3PO4 content in the catalysts and reached a maximum value for a H3PO4 loading of 20%, a further increase in H3PO4 leading to a decrease in the activity for esterification. The acidic properties and the pore network of the catalysts were key factors conditioning their catalytic performance. The effect of reaction temperature, H3PO4 content, feed ratio of acetic acid to nbutanol, WHSV and carrier gas flow rate was also investigated.