The Di-t-butylation of p-cresol with t-butanol in Supercritical CO2 over Tungstophosphoric Acid Supported on Ordered Mesoporous Silica

Tungstophosphoric acid (HPW) supported on MCM-41 was an excellent catalyst for the t-butylation of p-cresol to 2,6-di-t-butyl-4-methylphenol (2,6-DTBPC) in supercritical CO2; however, zeolites, H-Y and H-Beta, only gave 2-t-butyl-4-methylphenol (2-TBPC) because of their limitation in pore size. The yield of 2,6-DTBPC was maximized at 110 °C, and further increase in temperature rather decreased the yield. The yield of 2,6-DTBPC was maximized at 10–11 MPa CO2 pressure, and further increase of the pressure decreased in the conversion of phenol and the yield of 2,4-DTBC. The thermogravimetric analysis of used catalysts showed that the coke-formation was minimized in supercritical CO2 compared to the other reaction media such as in liquid phase and in N2 atmosphere.