Supported PdZn nanoparticles for selective CO2 conversion, through the grafting of a heterobimetallic complex on CeZrOx

Abstract

Controlling the stoichiometry of supported bimetallic nanoparticles is essential in many catalytic reactions, notably selective CO2 hydrogenation. Thus, a new strategy to ensure the preferred stoichiometry (1:1) of supported bimetallic PdZn nanoparticles is presented, involving the deposition of a heterobimetallic precursor, [PdZn(μ-OOCMe)4]2 on a CeZrOx support. After calcination and reduction, the material contained mainly a PdZn alloy, as revealed by powder XRD and XAFS, and further supported by XPS, TEM-EDX, elemental analysis and in-situ IR at low temperature using CO as probe molecule. Moreover, a minor phase of oxidized Zn was determined by XAFS. This PdZn/CeZrOx reduced catalyst was combined with SAPO-34 to form a tandem catalytic system for CO2 conversion to hydrocarbons. This system could readily convert CO2 and H2 at high temperature (380 °C) into hydrocarbons with a conversion of 24% and high relative selectivity in light hydrocarbons (C2–C3: 82%) with virtually no deactivation of the catalyst after 16 h on stream. Controlled experiments were performed with Pd/CeZrOx and Zn/CeZrOx in order to gain supplementary insights on this system: Pd/CeZrOx gave only methane and Zn/CeZrOx gave mainly CO under the same conditions. The latter clearly shows that the control of the formation of PdZn phase has great impact for the selective production of hydrocarbons.