Gold nanoparticle-catalyzed oxidative esterification of furfural: Enhancement by NaOH-etched γ-Al2O3 support

[Display omitted] •The pore structure of the existing carrier was adjusted by NaOH etching.•Catalysts with varied etching times were prepared via a urea deposition–precipitation method.•Au/γ-Al2O3-2 achieves a conversion of 99.6% and a selectivity of 99.5% under optimal conditions.•The mechanism for the conversion of furfural to methyl furoate and by-products was proposed.•The catalytic system is suitable for the oxidative esterification of aromatic aldehydes and alcohols. Furfural, a key biomass-derived compound, can be transformed into high-value chemicals, including methyl furoate, through oxidative esterification. This process finds broad applications across various industries. In the current study, gold nanoparticles were deposited on γ-Al2O3 pretreated with NaOH etching, utilizing the urea deposit-precipitation method followed by reduction in a hydrogen atmosphere. This approach resulted in a highly active Au catalyst, which was thoroughly characterized using multiple analytical techniques. The optimization of NaOH etching enhanced the pore structure and improved the dispersion of the active metal on the support. Notably, the Au/γ-Al2O3-2 catalyst, prepared with a 2-hour etching duration using 1 M NaOH, exhibited uniformly dispersed gold nanoparticles with an average size of 2.8 nm. The smaller particle size and enhanced dispersion of these Au nanoparticles significantly contributed to the catalyst’s superior catalytic activity and recyclability. Under optimized reaction conditions, the Au/γ-Al2O3-2 catalyst achieved nearly complete conversion of 1 mmol of furfural to methyl furoate within 4 h, with both conversion and selectivity exceeding 99 %. The study also proposed a mechanism for the oxidative esterification of furfural to methyl furoate catalyzed by Au/γ-Al2O3-2. Additionally, the catalyst’s effectiveness in the oxidative esterification of various substrates was investigated, demonstrating its robust activity for aromatic aldehydes and alcohols. This broadens the potential applications of the catalyst in the synthesis of diverse valuable esters.