New Rh-ZnO/Carbon Nanotubes Catalyst for Methanol Synthesis

A new catalyst for methanol synthesis, ZnO-promoted rhodium supported on carbon nanotubes, was developed. It was found that the Rh-ZnO/CNTs catalyst had high activity of 411.4 mg CH3OH/g/cat/h and selectivity of 96.7 % for methanol at 1 MPa and 523 K. The activity of this catalyst is much higher than that of NC 207 catalyst at the same reaction conditions. It was suggested that the multi-walled structure CNTs favored both the couple transfer of the proton and electron over the surface of the catalyst and the uptake of hydrogen which was favorable to methanol synthesis.

Reduction-induced metal/oxide interfacial sites for selective CO_(2) hydrogenation

The interfacial structures of bimetallic-derived catalysts play an important role in promoting the activation of reactants such as CO_(2).In particular,both the physical property(e.g.,local bonding environment)and the electronic property(e.g.,oxidation state)can evolve from their native states under different environments,such as upon reduction and during the catalytic reaction.Hence,taking the CO_(2) hydrogenation reaction over Rh-based catalysts as a case study,the present work compares the interfacial structures in tuning the selectivity toward CH_(4) or CO.The combination of ex situ and in situ characterization reveals two representative interfacial structures:the Rh/CeO_(x) interface formed over Rh/CeO_(2) is active and selective to produce CH_(4)(~95%)by following a formate-mediated pathway;in comparison,the InO_(x)/Rh interface derived after reduction is active for CO_(2) activation and enables a redox mechanism for the exclusive formation of CO(~100%).This work provides insights into the environment-induced structural evolution at the metal−oxide interfaces,as well as the role of distinct interfacial active sites in tuning the selectivity of CO_(2) hydrogenation.

Active sites in CO2 hydrogenation over confined VOx-Rh catalysts

Metal oxide-promoted Rh-based catalysts have been widely used for CO2hydrogenation,especially for the ethanol synthesis.However,this reaction usually suffers low CO2conversion and alcohols selectivity due to the formation of byproducts methane and CO.This paper describes an efficient vanadium oxide promoted Rh-based catalysts confined in mesopore MCM-41.The Rh-0.3VOx/MCM-41 catalyst shows superior conversion（～12%）and ethanol selectivity（～24%）for CO2hydrogenation.The promoting effect can be attributed to the synergism of high Rh dispersion by the confinement effect of MCM-41 and the formation of VOx-Rh interface sites.Experimental and theoretical results indicate the formation of til-CO at VOx-Rh interface sites is easily dissociated into*CHx,and then*CHxcan be inserted by CO to form CH3CO*,followed by CH3CO*hydrogenation to ethanol.