Pd@Al₂O₃‐Catalyzed Hydrogenation of Allylbenzene to Propylbenzene in Methanol and Aqueous Micellar Solutions

Abstract

The palladium on alumina (Pd@Al2O3)‐catalyzed hydrogenation of allylbenzene to propylbenzene was studied in methanol and aqueous micellar solutions of sodium dodecyl sulfate (SDS), decyltrimethylammonium bromide (DTAB), and t‐octylphenoxypolyethoxyethanol (TX‐100). Over Pd@Al2O3, propylbenzene was obtained via direct hydrogenation of allylbenzene and isomerization to β‐methylstyrene which was hydrogenated afterwards. In aqueous micellar solutions, the reaction was faster than in pure water, but slower than in methanol due to lower hydrogen solubility. In the H2O/SDS system, a higher activation energy was obtained than in methanol. For the investigated surfactants, the initial reaction rate in the micellar systems decreased in the order SDS > TX‐100 > DTAB.

Procedural Rate Enhancement of Lean Aqueous Hydroformylation of 1‐Octene without Additives

“…To overcome this limitation, a considerable number of studies have been published focusing on the use of additives such as co‐solvents 13, 14, surfactants 15–18, dextrines 19, 20, ionic liquids 21–23 or ambiphilic ligands 15, 16 to increase interfacial area or solubility. Examples are presented in Scheme .…”

Ni-NHC Nanoparticles in Micelles as an Effective and Reusable Catalyst for Hydrogenations and Reductive-Aminations in Water

“…Therefore, our catalytic system was rather active and chemoselective but slower than previous studied Pd catalysts stabilized by surfactants. Indeed, by operating under 1 to 14 bar H 2 pressures ,− or through hydrogen transfer, ,, they reduced quantitatively alkenes within 0.5 to 12 h, at room temperature or higher in some cases.…”

“…Catalytic applications of metallomicelles appear promising for the sustainable synthesis of bulk and fine chemicals and catalyst recycling. For example, several systems based on Pd/C, Pd organometallics, or nanoparticles have been reported as effective catalysts for cross-coupling reactions, ,− transfer hydrogenations ,− and hydrogenations. − Indeed, such metallomicelles have hydrophobic/lipophilic inner cores that allow the solubilization of organic reagents, as well as the catalysis of their reactions, and hydrophilic exterior domains. The catalytic processes within their inner core can proceed in water, and a full separation of the organic products from the aqueous reaction medium is possible through extraction, decantation, or filtration.…”

Cucurbit[6]uril-Stabilized Palladium Nanoparticles as a Highly Active Catalyst for Chemoselective Hydrogenation of Various Reducible Groups in Aqueous Media

“…Pd/C is one of the most frequently used hydrogenation catalyst under organic solvents, but due to its very high activity, it always leads to poor selectivity and leaching of active Pd is the major problem. To address this issue different basic inorganic supports like MgO,, hydrotalcite, alumina and silica have been used with fair success. Besides these, nitrogen‐rich organic polymers were also successfully employed as a support for palladium catalyzed hydrogenation of various substrates .…”