Novel Silica-Encapsulated Cu–Al Hydrotalcite Catalyst: Oxidative Decarboxylation of Vanillyl Mandelic Acid to Vanillin in Water at Atmospheric Pressure

Abstract

Vanillin is a versatile chemical, having characteristics such as antimicrobial, antioxidant, anticarcinogenic, antimutagenic, hypolipidemic, and antisickling activities and is an intermediate for synthesis of fine chemicals such as vanilla flavoring. Vanilla is the second most expensive spice; it is extracted from vanilla beans and is in short supply. Therefore, to meet demand of vanilla flavor, the synthesis of vanillin via chemical routes is necessary. In this regard, a novel silica-encapsulated copper aluminum hydrotalcite (SECuAlHT) was synthesized. Different techniques such as XRD, FTIR, N2 adsorption–desorption, TGA-DSC, NH3 TPD, CO2 TPD, H2 chemisorption, TEM, and SEM-EDXS were used to characterize SECuAlHT. Its catalytic activity for oxidative decarboxylation of vanillyl mandelic acid (VMA) was investigated. Vanillin was obtained from VMA by oxidative decarboxylation using SECuAlHT in water as a solvent and atmospheric air under base-free conditions. The presence of basic sites in the catalyst was...