Au–Pd nanoalloys supported on Mg–Al mixed metal oxides as a multifunctional catalyst for solvent-free oxidation of benzyl alcohol

Abstract

Au-Pd nanoalloys supported on Mg-Al mixed metal oxides prepared using sol-immobilisation are found to be highly efficient and reusable catalysts for the solvent-free oxidation of benzyl alcohol using molecular oxygen under low pressure. When using this support alloying Pd with Au resulted in an increase in both activity and selectivity to benzaldehyde and moreover an improved resistance to catalyst deactivation compared with the monometallic Pd and Au catalysts. The turnover number for the Au/Pd 1:1 molar ratio catalyst achieved 13,000 after 240 min and the selectivity to benzaldehyde was maintained at 93%; this high catalytic activity can be retained in full after three successive uses. The ensemble and electronic effect of Au-Pd nanoalloys were studied by IR spectroscopy using CO chemisorption, XPS and HRTEM. Moreover, the bifunctional nature of the acid-base MgAl-MMO support was found to be important as the acid sites are considered to be responsible for the improvement of catalytic activity; while, the basic sites gave rise to high selectivity. A possible mechanism with Au-Pd nanoparticles as the active sites has been proposed, illustrating that the oxidation of benzyl alcohol can proceed through the cooperation between the Au-Pd nanoalloys and the base/acid sites on the surface of the support.

Platinum nanocrystals supported on CoAl mixed metal oxide nanosheets derived from layered double hydroxides as catalysts for selective hydrogenation of cinnamaldehyde

“…Layered double hydroxides (LDH) are a class of synthetic highly ordered two-dimensional anionic clays consisting of positively charged layers (two metallic ions) with charge-balancing anions, which are octahedrally coordinated in the sheets [17,18] and trivalent cations (Al 3+ , Fe 3+ ), respectively [19,20]. Mixed metal oxides (MMO) can be generated from LDH by thermal treatment (450-600°C), by which MMO not only inherits structural features of LDH, but possess high specific surface area, thermal stability, and tunable surface acidic/basic properties [21,22]. Based on these properties, they can be widely employed as promising heterogeneous catalysts and supports.…”

Facile synthesis of mesoporous hierarchical Co3O4–TiO2 p–n heterojunctions with greatly enhanced gas sensing performance

“…Much attention has been paid to LDH because of their adjustable chemical composition, anion exchange ability, tunable charge density, and multifuntionalities, and they have been widely used in the fields of catalysis, optics, electrochemistry, adsorption, anion exchange, and polymer additives. [36][37][38][39][40] LDH have already been used as precursors to prepare different kinds of mixed metal oxides, [41][42][43] however, to the best of our knowledge, they are seldom adopted to fabricate p-n heterojunctions.…”

Selective Aerobic Oxidation of Benzyl Alcohol Driven by Visible Light on Gold Nanoparticles Supported on Hydrotalcite Modified by Nickel Ion

“…Due to the LSPR effect of gold nanoparticles [23], which allowed for the strong absorption of visible light, they can be stimulated by visible light. Better activities on Au/Ni 3 Al HT by visible light and better recycling properties have occurred, compared with the results in other references [24][25][26][27]. The photocatalytic reaction can occur over Au supported on the hydrotalcite which can avoid the addition of alkaline substances.…”

“…Some changes appeared in the characteristic peak of Au (111) at 38.2 degrees. Its peak intensity was stronger and the peak shape was even sharper than that in Figure 1a, a result of the appearance of gold nanoparticles and the larger size of the gold nanoparticles [24]. The layer frame of the hydrotalcite support was not damaged.…”