New Insights on the Dynamic Role of the Protecting Agent on the Reactivity of Supported Gold Nanoparticles

Abstract

A very efficient catalyst (AuCePVA) was prepared by depositing gold colloids on CeO2 and using polyvinyl alcohol (PVA) as protective agent. Complete conversion and selectivity in furfural (2‐FA) oxidative esterification to methyl‐2‐furoate (Me‐2‐F) was obtained without base under conventional heating at 120 °C. AuCePVA was compared with Au/CeO2 obtained by deposition‐precipitation method, pointing out that along with the size of the Au nanoparticles and the surface sites of the ceria support, also PVA chains played a role during reaction. In situ FTIR spectroscopy measurements of adsorbed molecules at controlled temperature and pressure demonstrated that PVA acted not merely as gold stabilizer, but also as mediator during the 2‐FA oxidative esterification, leaving both Au and ceria sites available for catalysis at the reaction temperature. In a perspective of process intensification, the microwave‐assisted (MW‐assisted) 2‐FA oxidative esterification was carried out. Depending on the reaction time and temperature, AuCePVA favoured the oxidation of the hemiacetal into the ester rather than the re‐oxidation of the acetal into the ester, due to the formation of Ce3+ sites under MW irradiation.

Au Nanoparticle Catalysts on NiO-Decorated MgO–Al2O3 Supports for Efficient Oxidative Esterification of Methylacrolein to Methyl Methacrylate

“…As for Au 1 Ni 0.5 /MA-353, although the nanoparticles were also very small, the protective agent PVA added in the preparation process was not completely removed during the calcination process. This affected the adsorption of the substrate on the active metal, resulting in relatively poor performance …”

Efficient and selective oxidation of furfural into high‐value chemicals by cobalt and nitrogen co‐doped carbon

“…These results also align with those reported by Cheng et al, who confirmed that cobalt chelate complexes in a graphene lattice are dominant active sites for aerobic oxidative esterification. [ 12 ]…”

“…The highly efficient activity of Co SAs‐N@C is probably attributed to uniformly dispersed Co‐N x species. [ 4,12 ] In order to demonstrate the influence of N resources in Co SAs‐N@C on the conversion and selectivity, various N‐containing compounds, including dicyanodiamide, melamine, urea, g‐N 3 C 4 derived from melamine, and urea, were investigated during catalyst synthesis. Among these N‐containing compounds, the catalytic reactivity of catalysts was found to be in the order of dicyanodiamide ≈ melamine ≧ g‐N 3 C 4 derived from melamine > g‐N 3 C 4 derived from urea ≈ urea (Figure S6).…”

“…In addition, the XAFS analyses pointed out that Co atoms are isolated and predominantly coordinated with N and/or C atoms in Co SAs-N@C (Figure 2F). The homogeneous dispersion property of the Co-Nx species probably contributed to the high catalytic activity of Co SAs-N@C. [4,11,12] XPS was conducted to further verify the chemical state of the Co element. The results are shown in Figure 3.…”

“…It has been comprehensively confirmed that Co-based, N-doped carbon material is one of the most promising catalysts for oxidative esterification reactions. [4,12,13,25] Therefore, the supported Co-based catalyst was screened for aerobic oxidation of FUR in the following experiments.…”