Activity Enhancement by the Support in the Hydrogenation of C=C Bonds over Polymer-Supported Palladium Catalysts

Abstract

Four synthetic ion-exchange resins (AH, BH, CH, DH) of different hydrophilic/hydrophobic properties were used as supports for heterogeneous palladium catalysts (A, B, C, D). The resins contained styrene (STY) and 2-(methacryloxy)ethylsulfonic acid (MESA) as the comonomers. Either divinylbenzene (DVB: CH, DH resins) or N,N'-methylenebisacrylamide (MBAA: AH, BH resins) were used as the cross-linker. AH contained also N,N-dimethylacrylamide (DMAA) as the third comonomer. The catalysts (Pd 0.25-0.45% w/w) were obtained by ion-exchanging the acidic forms of the resins with [Pd(OAc)2] and reducing palladium(II) with excess sodium borohydride. The use of NaBH4 also ensured the neutralization of the acidic sites of the supports. No effect of the hydrophilic/hydrophobic properties of the supports was observed in the hydrogenation of cyclohexene and 2-cyclohexen-1-one in methanol, at 25 degrees C and 0.5, 1, and 1.5 MPa, respectively. However, catalysts A and B, containing amido groups provided by either DMAA or MBAA, proved to be more active than C and D. The observed activity enhancement was directly proportional to the nitrogen/ palladium molar ratio in the catalysts. This finding suggests that amido groups promote palladium through a direct interaction with the metal surface.

A Covalently Immobilized Triphenylphosphine Rhodium Complex: Synthesis, Characterization, and Application in Catalytic Olefin Hydrogenation

“…To compare supports with different surface hydrophobicities, we also used a 1,4‐(bistriethoxysilyl)benzene derived periodic mesoporous organosilica support (PMO). However, the catalytic results confirmed that the hydrophobicity of the support surface should not play an important role in the hydrogenation reaction according to findings of Zecca et al 19…”

Metal nanoparticles immobilized on ion-exchange resins: A versatile and effective catalyst platform for sustainable chemistry

“…PdNP@resins are effective catalysts, including as bifunctional catalysts [68,69], for a variety of processes and are at the core of the large scale manufacture of methyl isobutyl ketone and methyl-tert-butyl ether [70,71]. Common precursors employed for the PdNP@resin synthesis are either [Pd(NH3)4] 2+ or Pd(CH3CO2)2, for cation exchange resins, and PdCl4 2-, for anion exchange resins, which require high temperature treatment or large excesses of sodium borohydride for their conversion to Pd metal [72,73].…”

Chemoselective Hydrogenation of the Olefinic Bonds Using a Palladium/Magnesium‐Lanthanum Mixed Oxide Catalyst

“…[ 12] Ihm and co‐workers reported the hydrogenation of olefinic double bonds by using gel‐like and macroporous polymer‐supported palladium(II) complexes13a while Zecca et al. used the ion‐exchange resins‐supported palladium catalyst for the same reaction 13b. Manorama and co‐workers reported the Pd immobilized on amine‐terminated ferrite nanoparticles for hydrogenation of aromatic nitro and azide compounds 14.…”