Thesis (M.Eng.)--Chulalongkorn University, 2008

This research studied the direct synthesis of benzaldehyde from toluene and hydrogen peroxide using titanium silicalite-1 catalysts modified with different amount of Al. The reaction is carried out at reaction temperature 70°C and 90°C, and toluene per hydrogen peroxide molar ratios 1:1 and 2:1. It is found that all modified catalysts yield benzaldehyde as the major product with o-cresol and p-cresol as by products. The experimental results also show that Al added into TS-1 promotes the formation of benzaldehyde and suppresses the formation of cresols. Too much Al added, however, will decrease the catalytic activity of the modified catalysts. Benzaldehyde selectivity increases with the increase in reaction temperature. On the contrary, benzaldehyde selectivity decreases if toluene per hydrogen peroxide molar ratio is increased from 1:1 to 2:1. This is due to toluene will cover the catalyst surface, leaving lesser hydrogen peroxide on the catalyst surface. The formation of benzaldehyde which requires twice amount of hydrogen peroxide than the formation of cresol, therefore, decreases