Selective Synthesis of p-Hydroxybenzaldehyde by Liquid-Phase Catalytic Oxidation of p-Cresol

Abstract

Liquid-phase oxidation of p-cresol over insoluble cobalt oxide (Co 3 O 4 ) catalyst under elevated pressure of air gave 95% selectivity to p-hydroxybenzaldehyde, an important flavoring intermediate. The selectivity to p-hydroxybenzaldehyde could be enhanced by manipulating the concentrations of p-cresol, sodium hydroxide, and catalyst and the partial pressure of oxygen in such a way that the byproducts normally encountered in this oxidation process were eliminated or minimized significantly.

Liquid Phase Oxidation of p-Cresol over Cobalt Saponite

“…Based on these observations, the reaction pathway of p-cresol oxidation is shown in Scheme 1. Unlike in our previous work on p-cresol oxidation in methanol as solvent [3,6,13], no formation of a non-oxidation product or alkylated product of p-HBALc was observed in this work. After establishing the product distribution in liquid phase oxidation of p-cresol, a Reaction conditions: temperature, 343 K; mole ratio, NaOH: p-cresol, 4; catalyst (Co content 13%) loading, 2.67 kg/m 3 ; total reaction volume, 7.5 9 10 -5 m 3 ; partial pressure of oxygen 0.42 Mpa, reaction time, 1 h systematic study on catalyst screening, and the effect of various reaction parameters on conversion of p-cresol and product selectivities for 13% Co-saponite catalyst was carried out.…”

“…Classical methods of oxidation of alkyl benzenes involve the use of stoichiometric quantities of reagents such as chromic acid or potassium permanganate and suffer from serious environmental drawback due to generation of excessive inorganic wastes. Several reports are available on direct oxidation of p-cresol using homogeneous as well as heterogeneous cobalt catalysts [6][7][8]. Heterogeneous catalysts have an obvious advantage of easy separation for subsequent reuses.…”

Heterogeneous Catalysis for Fine Chemicals in Dense Phase Carbon Dioxide

“…[25] Selective oxidation for the production of odorant molecules in carbon dioxide might soon find practical applications. [28] The process, however, leaves solvent residues that blind taste testing panels can distinguish. [26] As number of small modern scCO 2 extraction plants are being installed worldwide, [27] adding a small high-throughput reactor to these plants would not be problematic once synthetic processes are on place.…”

Mixed Co–Mn Oxide‐Catalysed Selective Aerobic Oxidation of Vanillyl Alcohol to Vanillin in Base‐Free Conditions

“…[9] These metals (Co and Mn) are commonly used for oxidation reactions and also are more economical than noble-metal-based catalysts. Despite the large number of studies on single-component manganese [10][11][12] and cobalt oxides [13][14][15][16] and very few on mixed cobalt and manganese oxides for oxidation of volatile organic compounds (e.g., benzene and toluene), there is no single report addressing the catalytic properties based on the structural attributes of combinations of these two oxides for the aerobic oxidation of vanillyl alcohol, which is an industrially important phenolic starting compound.…”