Selective oxidation of benzyl alcohol to benzaldehyde in “supercritical” carbon dioxide

Palladium Supported on an Acidic Resin: A Unique Bifunctional Catalyst for the Continuous Catalytic Hydrogenation of Organic Compounds in Supercritical Carbon Dioxide

“…The selectivities to 2 exceeded 99% for the commercial catalysts. The present results with 1% Pd/C are in accordance with the former data published by Arunajatesan et al [2e] Palladium immobilized on an acidic resin of Amberlyst 15 (Pd/Amberlyst-15) also exhibited high activity (entries [3][4][5]. The activity strongly depended on the amount of palladium loaded, and the catalyst containing 1% palladium showed the highest activity (entry 4).…”

“…These features, together with the low viscosity and high diffusivity, render scCO 2 suitable particularly for heterogeneous catalytic hydrogenations and oxidations. [1][2][3] Most catalysts used so far under such conditions were conventional ones, while corresponding studies based on specifically developed new catalysts are still scarce. Amberlyst 15 is a commercially available, strongly acidic cation exchange resin composed of styrene-divinylbenzene matrix with sulfonic acid groups and has been used as a heterogeneous acid catalyst with great success.…”

Solvent-Free Aerobic Oxidation of Alcohols Catalyzed by an Efficient and Recyclable Palladium Heterogeneous Catalyst

“…[6] They were also higher than that observed for a commercial 0.5 wt % Pd/Al 2 O 3 (1585 h À 1 ) working with supercritical CO 2 . [17] Only the 0.3 wt % Pd/hydroxyapatite showed a higher TOF (9800 h À 1 ) at a relatively higher temperature (160 8C) for the oxidation of 1-phenylethanol but not benzyl alcohol. [11] On the other hand, as shown in Table 1, the corresponding Pd/Al 2 O 3 -imp only provided a very low conversion of benzyl alcohol (8%) at 88 8C.…”

“…Pd/Al 2 O 3 is a simple catalyst and is generally prepared by conventional wet impregnation. A few studies have mentioned the use of Pd/Al 2 O 3 for the oxidation or dehydrogenation of alcohols, [11,16,17,19] but Pd/Al 2 O 3 prepared by the impregnation (Pd/Al 2 O 3 -imp) exhibits lower activities in the aerobic oxidation of alcohols as compared with Pd/hydroxyapatite or Pd/MgO. [11,16] In this communication, we report the superior catalytic performances of the Pd/Al 2 O 3 -ads catalyst prepared by the adsorption method for the solvent-free oxidation of alcohols with molecular oxygen.…”

Catalysing Sustainable Fuel and Chemical Synthesis

“…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].…”