Synthesis of vanillin in water by TiO2 photocatalysis

The photoproduction of vanillin is studied in aqueous medium starting from trans-ferulic acid, isoeugenol, eugenol or vanillyl alcohol by using both commercial and home prepared TiO2 samples as photocatalysts and batch Pyrex photoreactors. The photo-oxidation at room temperature of these compounds produces vanillin with a selectivity ranging from 1.4 to 21 mol% with respect to the converted substrate. An investigation on the intermediates was performed in the case of trans-ferulic acid; for this substrate the most important intermediates were homovanillic acid, vanillyl mandelic acid, trans-caffeic acid, formic acid, acetic acid, and oxalic acid. The carbon mass balance, including CO2 derived from the mineralization, was made for all of the substrates at irradiation times corresponding to the highest selectivity to vanillin. High closure of the carbon balance was obtained with vanillyl alcohol (ca. 90%) and trans-ferulic acid (ca. 80%).

The photoproduction of vanillin is reported in aqueous medium starting from trans-ferulic acid, isoeugenol, eugenol or vanillyl alcohol by using both commercial and home prepared TiO2 samples as the photocatalysts and batch photoreactors. Crystals of vanillin were obtained by pervaporation under ambient temperature with a high degree of purity.Figure optionsDownload as PowerPoint slideHighlights
► Photocatalytic synthesis of vanillin.
► Trans-ferulic acid, isoeugenol, eugenol, vanillyl alcohol, used as substrates.
► Commercial and home prepared TiO2 samples for partial photo-oxidation.