A Novel Pd-decorated Carbon Nanotubes-promoted Pd-ZnO Catalyst for CO2 Hydrogenation to Methanol

作者：Liang, Xue-Lian^*; Xie, Jian-Rong; Liu, Zhi-Ming

来源：Catalysis Letters, 2015, 145(5): 1138-1147.

DOI：10.1007/s10562-015-1505-8

• Carbon nanotubes
• Pd-ZnO catalyst doped by Pd-decorated CNTs
• CO2 hydrogenation
• Methanol synthesis

A novel metallic palladium-decorated CNTs-promoted Pd-ZnO catalyst was developed, with excellent performance for hydrogenation of CO2 to methanol. Over a composition-optimized catalyst, Pd0.1Zn1-10 %(5.0 %Pd/CNTs), under reaction conditions of 5.0 MPa, 543 K, V(H-2)/V(CO2)/V(N-2) = 69/23/8, GHSV = 15,000 mL g(-1) h(-1), the conversion of CO2 hydrogenation and the corresponding space-time-yield of methanol (STY(CH3OH)) reached 6.98 % and 343 mg g(-1) h(-1), respectively. This STY(CH3OH) value was 1.7 times that (202 mg g(-1) h(-1)) of the corresponding (5.0 %Pd/CNTs)-free counterpart, Pd0.1Zn1, under the same reaction conditions. Addition of a minor amount of the Pd-decorated CNTs into the Pd-ZnO host catalyst caused little change in the apparent activation energy for the CO2 hydrogenation. The Pd-decorated CNTs or the simple CNTs as promoter function through their excellent performance of adsorbing/activating H-2 to generate a surface micro-environment with higher stationary-state concentration of H-adspecies at the surface of functioning catalyst. This resulted in a marked increase of surface concentration of the Pd-0-species in the form of PdZn alloys, a kind of catalytically active Pd-0-species closely associated with the formation of methanol. On the other hand, those active H-species adsorbed on the CNTs (or Pd-decorated CNTs) could be readily transferred to Pd (i) Zn (j) active sites via the CNTs-assisted hydrogen spillover. The aforementioned two factors both were conducive to increasing the rate of hydrogenation-conversion of CO2.
Hydrogenation of CO2 to methanol over Pd-decorated CNT-promoted Pd-ZnO catalyst.
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• 出版日期2015-5
• 单位厦门大学