Catalysis Letters, Vol.141, No.6, 886-894, 2011
Pd-Decorated CNT-Promoted Pd-Ga2O3 Catalyst for Hydrogenation of CO2 to Methanol
A type of Pd-decorated CNT-promoted Pd-Ga catalysts was developed. The catalyst displayed excellent performance for CO2 hydrogenation to methanol. Under the reaction conditions of 5.0 MPa and 523 K, the observed specific reaction rate of CO2 hydrogenation reached 2.23 mu mol s(-1) (m(2)-Pd)(-1), which was 1.39 times that (1.60 mu mol s(-1) (m(2)-Pd)(-1)) of the non-promoted Pd-Ga host. The addition of a small amount of the Pd-decorated CNTs to the Pd-Ga host catalyst did not cause a marked change in the E (a) of the CO2 hydrogenation reaction. The function of the CNT-promoter was mainly in increasing the molar percentage of the catalytically active Pd-0-species in the total Pd-amount at the surface of the functioning catalyst, and in improving the capability of the catalyst to adsorb and activate H-2 (one of the reactants). Compared to the "Herringbone-type" CNTs, the "Parallel-type" CNTs possess less active surface (with less dangling bonds), and thus, lower capacity for adsorbing H-2, resulting in the rather limited promoter effect.
Keywords:Carbon nanotubes;Pd-decorated CNTs;CNT-promoted Pd-Ga2O3 catalyst;CO2 hydrogenation;Methanol synthesis