Gold on oxide-doped alumina supports as catalysts for CO oxidation

Abstract

The effect of doping a commercial alumina support with metal oxides of Ce, Co, Cu, Fe, La, Mg, Mn, Ni and Zn was investigated. Doped d-Al 2 O 3 samples were obtained by simple physical mixture (PM) of the alumina with the desired commercial oxide and by traditional impregnation of alumina with precursor salts of the same metals followed by calcination (IC). The metal load (7% wt.) was the same in both cases. Gold (1% wt.) was loaded using a liquid phase reductive deposition method. The obtained materials were characterized by adsorption of N 2 at -196°C, temperature programmed reduction, X-ray diffraction, energy-dispersive X-ray spectrometry and transmission electron microscopy. Both samples prepared by PM and IC showed a mixture of the d-alumina phase with the respective metal oxide, but the BET surface areas of the IC samples were, in general, higher than those of the PM materials. The particle size of the oxide phases were larger for the PM samples than for the IC materials. Nevertheless, catalytic experiments for CO oxidation showed that PM samples were much more active than IC. That could be explained by the size of gold nanoparticles, well known to be related with catalytic activity, that was lower in samples prepared by PM (7-16 nm) than by IC (11-17 nm). Gold was found to be in the metallic state. The most active samples were aluminas containing Zn and Fe prepared by PM that had the smallest gold nanoparticles sizes (7-13 and 8-12 nm, respectively) and had room temperature activities for CO conversion of 0.62 and 1.34 mol CO h -1 g Au -1 , respectively, which are larger than those found in the literature for doped c-alumina samples.

Pure Hydrogen Production via PROX over Gold Catalysts on Alumina Supported Y-Doped Ceria: Effect of Support Preparation

“…Generally, the gold catalysts on CeO2/Al2O3 and Y-doped CeO2/Al2O3 supports prepared by MM exhibited better PROX behaviour as compared to the corresponding supports prepared by IM. These results are in agreement with the study of Carabineiro et al [13] showing that gold catalysts on supports obtained by simple physical mixture of commercial alumina and different metal oxides (including CeO2) were much more active in CO oxidation than the gold catalysts on corresponding supports prepared by traditional way of impregnation. The positive effect of yttrium [9] was confirmed by the higher activity of AuY20CeAlIM then that of Au20CeAlIM catalyst.…”

Supported Gold Nanoparticles as Catalysts for the Oxidation of Alcohols and Alkanes

“…These authors used this method to prepare Au/TiO 2 materials, and state that it represents an environmentally and economically favorable route to the production of highly active gold catalysts. This method has been used with great success for other supports, such as metal oxides and carbon materials by Carabineiro et al (2010a,b,c,e,f, 2011a,b, 2012a,b, 2013, 2016); Bastos et al (2012); Rodrigues et al (2012b); Silva C. G. et al (2014); Soria et al (2014); Pérez et al (2016). One example is shown in Figure 1b, where much smaller and better dispersed gold nanoparticles are seen on ceria.…”

Kinetics of the catalytic oxidation of morin on γ-Al 2 O 3 supported gold nanoparticles and determination of gold nanoparticles surface area and sizes by quantitative ligand adsorption

“…It has been conventionally described as a defect spinel (Fd-3m) with the idealized formula Al 21+1/3ᮀ2+2/3 O 32 , where ᮀ denotes a vacancy [21]. Many studies have been reported on oxide-doped alumina supported AuNPs [4,19,[22][23][24][25]. It was reported that lithium oxide (Li 2 O) has a promoting effect on the activity of the Au/␥-Al 2 O 3 catalyst in CO oxidation [4,25].…”