Gold supported on metal oxides for carbon monoxide oxidation

Abstract

Au has been loaded (1% wt.) on different commercial oxide supports (CuO, La 2 O 3 , Y 2 O 3 , NiO) by three different methods: double impregnation (DIM), liquid-phase reductive deposition (LPRD), and ultrasonication (US). Samples were characterised by N 2 adsorption at -196 °C , high-resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectrometry, high-angle annular dark-field imaging (Z-contrast), X-ray diffraction, and temperature programmed reduction. CO oxidation was used as a test reaction to compare the catalytic activities. The best results were obtained with Au loaded by DIM on the NiO support, with an activity of 7.2 × 10 -4 mol CO· g Au -1 · s -1 at room temperature. This is most likely related to the Au nanoparticle size being the smallest in this catalyst (average 4.8 nm), since it is well known that gold particle size determines the catalytic activity. Other samples, having larger Au particle sizes (in the 2-12 nm range, with average sizes ranging from 4.8 to 6.8 nm), showed lower activities. Nevertheless, all samples prepared by DIM had activities (from 1.1 × 10 -4 to 7.2 × 10 -4 mol CO· g Au -1 · s -1 , at room temperature) above those reported in the literature for gold on similar oxide supports. Therefore, this method gives better results than the most usual methods of deposition-precipitation or co-precipitation.

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

“…According to the literature (Potoczna-Petru and Kepinski 2001), the peaks (Table 2) observed in the TPR spectra of Co 3 O 4 are due to the reduction of this species to CoO and the further reduction of the latter to Co. One single peak (Table 2) corresponding to the reduction of CuO to Cu (Solsona et al 2006;Carabineiro et al 2011b) was found for samples doped with this metal.…”

“…The resulting solid was washed repeatedly with distilled water for chloride removal (which is well known to cause sinterization of Au nanoparticles, thus turning them inactive (Bond and Thompson 1999;Bond et al 2006;Thompson 2007, 2010;Carabineiro et al 2010g;Santos et al 2010), and again dried in the oven at *100°C overnight, and used without any further treatment. As far as we know, LPRD has only been used by Sunagawa et al (2008) to prepare Pt and Au catalysts on Fe 2 O 3 , FeOOH, ZrO 2 and TiO 2 supports, and by us for Au/CeO 2 (Carabineiro et al 2010g), Au/CuO (Carabineiro et al 2011b), Au/La 2 O 3 (Carabineiro et al 2011b), Au/MgO (Carabineiro et al 2011a), Au/NiO (Carabineiro et al 2011b), Au/TiO 2 (Santos et al 2010) and Au/Y 2 O 3 (Carabineiro et al 2011b) catalysts. To the best of our knowledge, this is the first report on its use for alumina and doped alumina based supports.…”

Gold highlights on the 22nd Meeting of the Portuguese Society of Chemistry in Braga, Portugal, July 3–6, 2011

“…Samples were prepared by several techniques like DIM and LPRD [11], reduction with nitric acid [12] and sol immobilisation method [13]. The latter lead to the best results, as reported in literature for Au-activated carbon (AC) catalysts [14].…”

“…Au was deposited by double impregnation (DIM), liquid-phase reductive deposition (LPRD) and ultrasonication methods [11]. The best results were obtained with Au loaded by DIM on the NiO support.…”

“…Adrián Silva (University of Porto) presented a poster on 'Gold supported in Ce-Mn-O composite materials for the oxidation of CO', with different Ce/Mn ratios and loaded with Au by DIM [11]. CeO 2 and Mn 3 O 4 were detected by XRD.…”