Supported palladium nanoparticles on hybrid mesoporous silica: Structure/activity-relationship in the aerobic alcohol oxidation using supercritical carbon dioxide

Catalysing sustainable fuel and chemical synthesis

“…Pd nanoparticles confined within such mesoporous silicas demonstrate good selectivity in crotyl and cinnamyl alcohol selox to their respective aldehydes ([70 %), and excellent TOFs of 7,000 and 5,000 h -1 for the respective alcohols. Similar activities are reported for secondary and tertiary allylic alcohols, highlighting the versatility of silica supported Pd nanoparticles [51,135,136,[180][181][182]. Incorporation of macropores into SBA-15 via dual hard/soft templating to Fig.…”

“…For example, continuous flow microreactors have been implemented in both homogeneous and heterogeneous aerobic selox, providing facile catalyst recovery from feedstreams for the latter [42,43], but their scale-up/out requires complex manifolding to ensure adequate oxygen dissolution uniform reactant mixing and delivery [44,45]. Efforts to overcome mass transport and solubility issues inherent to 3-phase catalysed oxidations have centred around the use of supercritical carbon dioxide to facilitate rapid diffusion of substrates to and products from the active catalyst site at modest temperatures [46] affording enhanced turnover frequencies (TOFs), selectivity and on-stream performance versus conventional batch operation in liquid organic solvents [47][48][49][50][51].…”

Aerobic Oxidations in Continuous Flow

“…In an alternative approach, 2,2 0 -dipyridylamine (16) was installed as a linker unit instead of PEG to immobilize and simultaneously stabilize the Pd nanoparticles on mesoporous silica for a catalytic aerobic oxidation in scCO 2 [104]. Similar to the 180 ] and PEG-1000 before (a) and after (b) the aerobic oxidation.…”

Functionalized Poly(ethylene glycol)-Stabilized Palladium Nanoparticles as an Efficient Catalyst for Aerobic Oxidation of Alcohols in Supercritical Carbon Dioxide/Poly(ethylene glycol) Biphasic Solvent System

“…For example, the Pd clusters [Pd 561 phen 60 (OA) 180 ] have been stabilized in PEG matrix, and the Pd nano-catalysts show both high activity and good recyclability for the aerobic oxidation of alcohols in scCO 2 /PEG biphasic system [23]. Moreover, the palladium nanoclusters stabilized and immobilized in PEG-modified silica, in combination with supercritical carbon dioxide (scCO 2 ) as reaction medium have also been employed for oxidation of alcohols under continuous-flow conditions [10,24]. Herein, we continue on the previous work by designing and preparing bidentate nitrogen ligand (2,2 0 -dipyridylamine) tethered covalently to the tip of PEG, and then we expect that the functionalized PEG could stabilize palladium nanoparticles.…”