Highly Active Gold and Gold–Palladium Catalysts Prepared by Colloidal Methods in the Absence of Polymer Stabilizers

Abstract

Supported gold and gold–palladium nanoparticles were found to be effective catalysts for the selective oxidation of glycerol and benzyl alcohol. The properties and stabilities of catalysts are often sensitive to factors such as the dimensions, shape, and composition of the metal nanoparticles. Although colloidal methods provide an easy and quick way to synthesize supported metal catalysts, they typically involve the use of polymers such as polyvinyl alcohol and polyvinylpyrrolidone as steric stabilizers, which can sometimes be detrimental in subsequent catalytic reactions. Herein, we report the synthesis of supported gold and gold–palladium nanoparticles without the addition of stabilizing polymers. The catalysts prepared with and without the addition of polymers performed very similarly in the selective oxidation of glycerol and benzyl alcohol, which suggests that polymers are not essential to make active catalysts for these reactions. Thus, this new stabilizer‐free method provides a facile and highly effective way of circumventing the inherent problems of polymer stabilizers in the preparation of gold and gold–palladium catalysts.

Glycerol Oxidation Using MgO‐ and Al2O3‐supported Gold and Gold–Palladium Nanoparticles Prepared in the Absence of Polymer Stabilizers

“…Similar observations were made for Au/TiO 2 catalysts prepared with and without PVA in our previous report . The activity of the catalysts reported there seems to be comparable to the activity of the monometallic catalysts presented herein, which might imply that the support does not play a pivotal role for the reaction.…”

“…Glyceraldehyde is an unstable intermediate which is readily oxidized to glyceric acid, which also can be further oxidized to form tartronic acid as consecutive product. It has to be noted that, based on the catalytic results obtained herein and reported in our previous publication, tartronic acid is likely to be also a primary product formed at the catalyst surface. Subsequently, either from glyceric acid or eventually from tartronic acid, C−C cleavage products are formed such as glycolic and oxalic acid.…”

“…We initially prepared Au colloidal solutions both in the presence and absence of a PVA stabiliser (PVA:metal=0.65 by weight) before immobilisation on various MgO (NanoActive MgO plus (MgO nano ), Nanoscale Corporation, and MgO BDH (MgO BDH ), Analar) and Al 2 O 3 (α‐Al 2 O 3 , Aldrich, and γ‐Al 2 O 3 , Alfa Aesar) support materials to give a nominal metal loading of 1 wt %. This method was investigated for the general applicability of preparing catalyst materials in the absence of polymers on supports other than TiO 2 , since we could show that TiO 2 supported Au and AuPd nanoparticles (NPs) prepared without capping agent exhibited similar catalytic performances compared to the catalysts prepared with capping agent for benzyl alcohol and glycerol oxidation . In addition, bimetallic AuPd catalysts were also prepared on MgO nano with and without the addition of PVA.…”

“…Recently, the preparation of gold and gold palladium nanoparticles by colloidal methods in the absence of polymer stabilisers has been reported for both quasi‐homogeneous catalysts in solution phase reduction of 4‐nitrophenol and supported catalysts for selective oxidation . We reported that despite a larger particle size distribution, catalysts prepared without the addition of polymers were similar in activity to catalysts prepared by the extensively reported method . However, the selectivity was affected by the absence of the polymer stabilisers suggesting that the presence of polymer additives can control the reaction pathways occurring on the metal particle surface.…”

Gold as a Catalyst for the Ring Opening of 2,5-Dimethylfuran

“…Recently there has been considerable interest in the use of supported gold as catalysts for oxidation reactions [1][2][3][4][5][6]. This is due to its high activity and the green nature of using catalysis for chemical transformations.…”