Synthesis of Phenyl Esters Using SiO2-SO3H Catalyst in Conventional Heating and Microwave-Irradiated Esterification Processes.

A SiO2-SO3H amorphous catalyst containing a small surface area of 115.0 m²g-1 and 1.32 mmol H+/g was prepared from fine construction sand and sodium carbonate and sulfonated with H2SO4. In a 10% (w/w) basis, it is very efficient for catalyzing the esterification of carboxylic acids with phenol. The reaction processes were performed using conventional heating and under microwave irradiation. The yields were higher in the microwave-irradiated esterification. The catalyst could be used for three esterification sequences in both processes.

The preparation of benzyl esters using stoichiometric niobium (V) chloride versus niobium grafted SiO2 catalyst: A comparison study.

Two solvent free methods of a one-to-one alcohol/acid mol ratio synthesis of benzyl esters of the formic, acetic, benzoic, salicylic, nicotinic, and oxalic acids are described. The stoichiometric reactions used 1.5 mol ratio solid NbCl5 as the reagent and required from two to three hours for completion at room temperature; for the catalytic processes, NbCl5 was grafted directly, at room temperature, onto a silica gel of specific area of 507 m2g-1, produced from construction sand and sodium carbonate, forming a 5.4% Nb w/w SiO2-Nb gel with a specific area of 412 m2g-1. At 10% w/w catalyst/alcohol ratio, this SiO2-Nb catalyst gave similarly very good yields but required from 6 to 9 hours at the reflux temperature of the slurry. The catalyst could be re-used three times.