Liquid-Phase Partial Hydrogenation of Phenylacetylene at Ambient Conditions Catalyzed by Pd-Fe-O Nanoparticles Supported on Silica

Catalysts with no hazardous or toxic components are required for the selective hydrogenation of acetylenic bonds in the synthesis of pharmaceuticals, vitamins, nutraceuticals, and fragrances. The present work demonstrates that a high selectivity to alkene can be reached over a Pd-Fe-O/SiO2 system prepared by the co-impregnation of a silica support with a solution of the metal precursors (NH4)3[Fe(C2O4)3] and [Pd(NH3)4]Cl2 followed by thermal treatment in hydrogen or in air at 400 °C. A DRIFT spectroscopic study of CO adsorption revealed large shifts in the position of the Pdn+-CO bands for this system, indicating the strong effect of Fen+ on the Pd electronic state, resulting in a decreased rate of double C=C bond hydrogenation and an increased selectivity of alkyne hydrogenation to alkene. The prepared catalysts consisted of mono- and bimetallic nanoparticles on an SiO2 carrier and exhibited a selectivity as high as that of the commonly used Lindlar catalyst (which contains such hazardous components as lead and barium), while the activity of the Fe-Pd-O/SiO2 catalyst was an order of magnitude higher. The hydrogenation of a triple bond over the proposed Pd-Fe catalyst opens the way to selective hydrogenation over nontoxic catalysts with a high yield and productivity. Taking into account a simple procedure of catalyst preparation, this direction provides a rationale for the large-scale implementation of these catalysts.

Hydrodechlorination of carbon tetrachloride with nanoscale nickeled zero-valent iron @ reduced graphene oxide: kinetics, pathway, and mechanisms

In recent years, carbon tetrachloride (CT) has been frequently detected in surface water and groundwater around the world; it is necessary to find an effective way to treat wastewater contaminated with it. In this study, Ni/Fe bimetallic nanoparticles were immobilized on reduced graphene oxide (NF@rGO), and used to dechlorinate CT in aqueous solution. Scanning electron microscopy (SEM) demonstrated that the two-dimensional structure of rGO could disperse nanoparticles commendably. The results of batch experiments showed that the 4N₄F@rGO (Fe/GO = 4 wt./wt., and Ni/Fe = 4 wt.%) could reach a higher reduction capacity (143.2 mg_CT/g_catalyst) compared with Ni/Fe bimetallic nanoparticles (91.7 mg_CT/g_catalyst) and Fe⁰ nanoparticles (49.8 mg_CT/g_catalyst) respectively. That benefited from the nickel metal as a co-catalyst, which could reduce the reaction activation energy of 6.59 kJ/mol, and rGO as an electrical conductivity supporting material could further reduce the reaction activation energy of 4.73 kJ/mol as presented in the conceptual model. More complete dechlorination products were generated with the use of 4N₄F@rGO. Based on the above results, the reductive pathway of CT and the catalytic reaction mechanism have been discussed.

Heterogeneous iron-containing nanocatalysts – promising systems for selective hydrogenation and hydrogenolysis

Bimetallic catalytic systems Fe–Me (Pt, Pd, Cu) demonstrate synergy in the activity/selectivity pattern in reactions involving hydrogen: selective hydrogenation of CC bonds, NO₂ and carbonyl groups and hydrogenolysis of C–O bonds.

Mesoporous silica supported bimetallic Pd/Fe for enhanced dechlorination of tetrachloroethylene

Immobilization of Pd–Fe nanoparticles on mesoporous SiO₂microspheres increases the reactivity for tetrachloroethylene dechlorination and enhances the mobility and permeability forin situremediation of chlorinated hydrocarbons in porous media.