Zn Promoted Mg-Al Mixed Oxides-Supported Gold Nanoclusters for Direct Oxidative Esterification of Aldehyde to Ester

Abstract

The synthesis of ester compounds is one of the most important chemical processes. In this work, Zn-Mg-Al mixed oxides with different Zn2+/Mg2+ molar ratios were prepared via co-precipitation method and supported gold nanoclusters to study the direct oxidative esterification of aldehyde and alcohol in the presence of molecular oxygen. Various characterization techniques such as N2-physical adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and CO2 temperature programmed desorption (TPD) were utilized to analyze the structural and electronic properties. Based on the results, the presence of small amounts of Zn2+ ions (~5 wt.%) provoked a remarkable modification of the binary Mg-Al system, which enhanced the interaction between gold with the support and reduced the particle size of gold. For oxidative esterification reaction, the Au25/Zn0.05MgAl-400 catalyst showed the best performance, with the highest turnover frequency (TOF) of 1933 h−1. The active center was believed to be located at the interface between metallic gold with the support, where basic sites contribute a lot to transformation of the substrate.

Highly Selective and Stable Cu Catalysts Based on Ni–Al Catalytic Systems for Bioethanol Upgrading to n-Butanol

“…Thus, to evaluate the acid-base property, CO2-TPD and NH3-TPD were conducted, respectively, for different supported Cu catalysts. As displayed in Figure 5a, all catalysts show a desorption peak of CO2 at 350~400 °C, implying the presence of mediumstrong basic sites [49]. Notably, for the Cu/Ni3AlOx and Cu/Ni1AlOx, the total amount of CO2 adsorption is obviously larger than that of the Cu/NiO and Cu/Al2O3, implying the catalysts possess much more basic sites than those of the Cu/NiO and Cu/Al2O3, which are derived from the abundant interlayer hydroxyl groups of Ni-Al-LDH.…”

Ag substituted Au clusters supported on Mg-Al-hydrotalcite for highly efficient base-free aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

“…This suggested that the interlayer distance of MgAl-HT decreased correspondingly owing to the collapse of the lamellar hydrotalcite structure after heat treatment. 48,49 Nevertheless, the deposition of Au and Au-Ag NCs onto the support could greatly enhance the stability of hydrotalcite after calcination, since the diffraction peaks of (006) appeared again in the patterns, and the values of d 003 were between that of MgAl-HT and MgAl-300. Besides, no obvious diffraction peaks assigned to metallic Au or Ag could be observed in the spectra, indicating that Au and Au-Ag particles were highly dispersed in the catalysts.…”

Multifunctional Nanomaterials: Synthesis, Properties and Applications

“…Furthermore, in the eleventh published research article, Yuan Tan et al [ 11 ] reported that Zn promoted Mg-Al mixed oxides-supported gold nanoclusters for the direct oxidative esterification of aldehyde to ester. In the last, i.e., twelfth, published research article, Florian Grüner et al [ 12 ] discuss a numerical study on the feasibility of monitoring tumor response by tracking nanoparticle-labelled T cells by utilizing the X-ray fluorescence imaging technique.…”