摘要: Aqueous phase reforming (APR) of methanol is a potential pathway for the effective hydrogen production under relatively mild conditions. The Pt/CeO2 and a series of Pt-MOx/CeO2 (M = Fe, Cr, Mg, Mn) catalysts were prepared by sequential impregnation method and their APR reaction performances were studied. The catalyst properties including valence state of the promoters, the amount of oxygen vacancies, the metal distributions, the adsorption properties of CO and the acidity/basicity of catalysts were characterized and analyzed by XPS, XRD, TEM, CO-TPD, NH3-TPD, CO2-TPD, etc. It was found that the addition of MOx weakened the Pt-CeO2 interaction and promoted the generation of Ptδ + species with lower valence state, which contribute to the C−H bond cleavage and facilitate methanol conversion. The highest hydrogen production (164.78 mmol) and relatively low CO and CH4 selectivities were obtained over the Pt-MgO/CeO2, while the highest CH4 selectivity was obtained over the Pt-CrOx/CeO2 (2.21%). Over the Pt/CeO2 and Pt-MOx/CeO2 (M = Fe, Cr, Mg, Mn) catalysts, CO2/CH4 ratio correlated well with the catalyst basicity, indicating that the basicity promotes the dissociation adsorption of H2O as well as the water-gas shift (WGS) reaction activity and decreases the methanation activity.
摘要: The photocatalysis of direct dehydrogenation of benzyl alcohol to benzaldehyde is an energy saving way to synthesize fine chemicals and pure hydrogen by using solar energy. The CdS-based catalysts were one of the typical kinds of photocatalysts for this reaction. The morphology of CdS could be easily tuned, which could greatly influence the photocatalytic performances. However, the morphology effect of CdS on the photocatalytic behaviour of the direct dehydrogenation of benzyl alcohol has not been investigated yet. In this work, we synthesized CdS with two different morphologies (nanosheet (NS) and nanowire (NW)) and found the CdS-NS showed much higher photocatalytic activity for converting the benzyl alcohol than the CdS-NW, but the selectivity to benzaldehyde over the two supports was very low. By depositing Au25 nanoclusters on the CdS-NW and CdS-NS, the morphology effect of the CdS support could be mitigated and their catalytic activity and selectivity could be greatly boosted for the photocatalytic anaerobic dehydrogenation of benzyl alcohol to benzaldehyde and H2. The results of this work would provide new insight into the design of efficient photocatalysts for synthesizing fine chemicals.
摘要: The selective catalytic reduction (SCR) NH3 catalyst is mainly used in industrial production and automobile exhaust cleaning. In this study, a novel α%Fe2O3/ZrTiO4 (α=0, 8, 12, 15) catalyst was prepared by the coprecipitation impregnation method. The results show that the NOx conversion rate of 12%Fe2O3/ZrTiO4 catalyst with the optimal composition is high above 80% at 250−400 °C, close to 100% at 300 °C, and N2 selectivity is high above 90% at 200−450 °C. The redox properties, surface acidity, and Oβ/(Oα + Oβ) ratio of ZrTiO4 catalysts are improved after loading Fe2O3 on the ZrTiO4 surface, which is attributed not only to the porous structure of α%Fe2O3/ZrTiO4 catalyst but also to the synergistic interaction between the active component Fe2O3 and the support ZrTiO4. In addition, in-situ DRIFT reactions show that the NH3-SCR reaction of 12%Fe2O3/ZrTiO4 catalyst follows the Eley-Rideal mechanism. A clear reaction mechanism is conducive to a deeper understanding of the reaction process of NOx conversion during SCR. This work provides a feasible strategy for Fe-based SCR catalysts to replace V-based catalysts in the medium temperature range in the future.
