Nanocrystalline gold supported on Fe-, Ti- and Ce-modified hexagonal mesoporous silica as a catalyst for the aerobic oxidative esterification of benzyl alcohol

Synthesis of Gold Catalysts Supported on Mesoporous Silica Materials: Recent Developments

“…The suspension was stirred for 2 h, followed by filtration, washing with deionized water, drying at 110 °C overnight and calcination at 400 °C for 4 h. The resulting catalysts, showing average Au particle sizes of 4.9 ± 1.3, 7.3 ± 1.6 and 6.7 ± 2.1 nm for SBA-15, SBA-16 and MCM-41 materials, respectively, were active for ethanol oxidation. Parreira et al [131] synthesized gold catalysts supported on pure and metal-modified hexagonal mesoporous silica (HMS, HMS-M, where M = Ce, Ti, Fe), using [Au(en) 2 ]Cl 3 as gold precursor. The HMS and the metal-modified HMS, synthesized by direct synthesis via co-precipitation using appropriate metal salts, were mixed with an aqueous solution of [Au(en) 2 ]Cl 3 maintaining the pH value at ca.…”

Formation of silver active states in Ag/ZSM-5 catalysts for CO oxidation

“…It is important for preparation of catalytically stable bimetal Au-Ag systems. Some supports and modifying additives of transient metal oxides can stabilize the active sites both silver and gold [31][32][33][36][37][38][39][40][41][50][51][52]. At higher temperatures (>300-400°C) formation of the metal active states follows other way; in this case big metal particles, metal crystals and films can also catalyze oxidation reactions (for example, methanol selective oxidation [33,53]).…”

Gold nanoparticles supported on magnesium oxide as catalysts for the aerobic oxidation of alcohols under alkali-free conditions

“…Nevertheless, several gold-containing catalysts have been developed for the aerobic oxidation of alcohols under base-free conditions [14][15][16][17][18][19][20][21][22][23]. One of the recently suggested approaches to prevent the consumption of base in stoichiometric amounts due to the formation carboxylic acid salts is performing the reaction in methanol solutions [24][25][26][27][28][29][30]. In these systems, carboxylic acids are trapped by methanol, which itself is rather inert to aerobic oxidation, so that methyl esters are formed as final products.…”

“…Only a few catalysts capable to promote direct transformations of alcohols into methyl esters using molecular oxygen as a final oxidant have been reported, with all of them being based on gold NPs, as far as we know [24][25][26][27][28][29][30]. In a previous work, we found that gold NPs supported on Ce-or Ti-modified hexagonal mesoporous silica (HMS) efficiently performed the one-pot aerobic oxidative esterification of benzyl alcohol [30]. However, the systems were active only in the presence of the base co-catalyst (potassium carbonate), likewise most of other gold systems reported for the oxidative esterification of alcohols.…”