Pd-Decorated CNT-Promoted Pd-Ga(2)O(3) Catalyst for Hydrogenation of CO(2) to Methanol

Abstract

A type of Pd-decorated CNT-promoted Pd-Ga catalysts was developed. The catalyst displayed excellent performance for CO(2) hydrogenation to methanol. Under the reaction conditions of 5.0 MPa and 523 K, the observed specific reaction rate of CO(2) 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 CO(2) 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.