Catalytic Performance For Preferential Oxidation Research Articles

Tailoring Ir-FeOx interactions and catalytic performance in preferential oxidation of CO in H2 via the morphology engineering of anatase TiO2 over Ir-FeOx/TiO2 catalysts

Ir-FeOx/TiO2 catalysts with both Ir and Fe contents of ∼1% wt. employing anatase TiO2 nanocrystals predominantly exposing either {100}, {101}, or {001} facets as the support were prepared and a comprehensive study was conducted on their interactions in pairs that are strongly dependent on the TiO2 morphology. The strongest FeOx-TiO2 interactions occurred over TiO2{001} support while TiO2{101} support contributes to the strongest Ir-TiO2 and Ir-FeOx interactions. Catalytic performance of the Ir-FeOx/TiO2 catalysts in preferential oxidation of CO in H2 is not only affected by the CO reactivity, but also determined by the Ir-FeOx interfaces. Ir-FeOx/TiO2{101} catalyst exhibits the highest CO conversion and best O2 selectivity over the three Ir-FeOx/TiO2 catalysts, which could be ascribed to stronger Ir-FeOx interactions that contribute to the enhancement of a H-spillover effect and subsequently facilitate the transformation of surface carbonaceous intermediates into CO2. These results add the versatility of the morphology engineering strategy in tailoring the structures and catalytic performance of oxide-based catalysts, and broaden the concept of morphology-dependent catalysis of oxide-based nanocrystal catalysts.

Insights into the structure-performance relationship of CuOx-CeO2 catalysts for preferential oxidation of CO: Investigation on thermally induced copper migration process

A series of CuOx-CeO2 catalysts is designed by coating composite copper-ceria precursor with different thickness of CeO2, followed by thermal treatment at 500 and 700 °C respectively to investigate the outward migration phenomenon of Cu species induced by high temperature thermal treatment. For the CuOx-CeO2 catalysts calcined at 500 °C, the coating of CeO2 covers the active surface Cu entities and degrades the low temperature catalytic performance for preferential oxidation of CO (CO-PROX). However, thermal treatment at 700 °C induces the migration of large amounts of Cu entities from bulk to the surface of CeO2 nanoparticles and recovers the low temperature catalytic performance. In addition, 700 °C thermal treatment of CuOx-CeO2 catalyst without CeO2 coating causes excessive outward migration of Cu species and severe CuO agglomeration, which decreases the catalytic performance at low reaction temperature, but broadens the high temperature operation window on account of the formation of inverse CeO2-CuO structure. This work provides deeper insight into the regime of thermally induced Cu migration phenomenon, and illuminated the structure-performance relationship of copper-ceria based catalysts for CO-PROX.

Precise Tailoring of Ir-FeOx Interfaces for Improved Catalytic Performance in Preferential Oxidation of Carbon Monoxide in Hydrogen

Preferential oxidation of CO in H2 (PROX) has been regarded as the most promising on-board approach to remove the trace levels of CO (∼1%) present in hydrogen fuels and thus to protect the Pt elect...

Facile synthesis of multi-shelled hollow Cu CeO2 microspheres with promoted catalytic performance for preferential oxidation of CO

Abstract Preferential oxidation of CO is beneficial to the removal of residual poisonous CO in reformate gas for proton exchange membrane fuel cell. Cu CeO2 has been widely studied as a promising catalyst for this application. Herein, we have synthesized multi-shelled hollow Cu CeO2 microspheres by a facile and one-step aerosol spray pyrolysis. Repeated and asynchronous combustion of carbon during the pyrolysis process results in the formation of multi-shelled hollow structure. Meanwhile, surface enrichment and high dispersion of copper species are achieved. This novel Cu CeO2 catalyst exhibits full CO conversion in H2-rich stream within a rather wide temperature window from 130 °C to 190 °C and a satisfying O2 selectivity. In addition, it displays a decent catalytic stability, with a slight conversion decay of 3.3% and a high O2 selectivity around 94% in continuous flow for 20 h. Based on the synergetic mechanism of copper-ceria catalysts, highly dispersed copper species and abundant CuOx/CeO2 interfaces in multi-shelled hollow microspheres give rise to the changes of redox properties and CO adsorption properties, and thus result in promoted catalytic performance.

Meso-macroporous monolithic CuO–CeO2/γ-Al2O3 catalysts and their catalytic performance for preferential oxidation of CO

Meso-macroporous monolithic CuO–CeO2/γ-Al2O3 catalysts were prepared and tested for preferential oxidation of carbon monoxide in hydrogen-rich gases. The catalysts were characterized with photographs, SEM, N2 adsorption–desorption, XRD, HRTEM, and TPR techniques. CuO–CeO2 catalysts were evenly coated onto the walls of γ-Al2O3 monolith macropores with ceria and copper oxide highly dispersed. The prepared meso-macroporous monolithic CuO–CeO2/γ-Al2O3 catalysts can remove CO from H2-rich gases to ppm level at high space velocity, indicating that they are a kind of promising structured catalyst.

Meso–macroporous monolithic CuO–CeO 2/γ/α-Al 2O 3 catalysts for CO preferential oxidation in hydrogen-rich gas: Effect of loading methods

Meso–macroporous alumina supported CuO–CeO 2 catalysts were prepared by citrate, urea combustion and impregnation methods. The effect of loading methods on the microstructure of the catalysts, the interaction between copper and ceria and the catalytic performance for preferential oxidation of CO in hydrogen-rich gases was investigated. The prepared monolithic catalysts were characterized by using techniques of N 2 adsorption and desorption, SEM, XRD, HRTEM and TPR. The results showed that the loading methods markedly influenced the catalyst structure and the catalytic performance. The citrate and urea combustion methods favored the formation of the interaction between copper and ceria. Compared with the urea combustion method, the citrate method led to smaller ceria particles on the alumina support. The meso–macroporous monolithic catalysts prepared by the citrate method maintained the structural characteristics of the highly active CuO–CeO 2 catalysts, and showed good catalytic performance in CO preferential oxidation in the simulated reformate gases containing water and CO 2.

Preferential oxidation of CO in H2 rich stream over Au/CeO2–Co3O4 catalysts

Au/CeO2–Co3O4 catalysts with a Ce/Co atomic ratio from 0.1 to 0.6 were prepared by deposition–precipitation; their catalytic performance in preferential oxidation (PROX) of CO in H2 rich stream was investigated. Au/CeO2–Co3O4 exhibits much higher catalytic activity in CO PROX than Au/Co3O4 and Au/CeO2; over Au/CeO2–Co3O4, 100% CO conversion with 75% selectivity to CO2 can be achieved even at ambient temperature. Typically, for CO PROX at 80 °C over oxidation pretreated Au/CeO2–Co3O4 (Ce/Co = 0.2), 91% CO conversion and 51% selectivity to CO2 can last for 260 h.

Catalytic processes during preferential oxidation of CO in H 2-rich streams over catalysts based on copper–ceria

Nanostructured catalysts based on combinations between oxidised copper and cerium entities prepared by two different methods (impregnation of ceria and coprecipitation of the two components within reverse microemulsions) have been examined with respect to their catalytic performance for preferential oxidation of CO in a H 2-rich stream (CO-PROX). Correlations between their catalytic and redox properties are established on the basis of parallel analyses of temperature programmed reduction results employing both H 2 and CO as reactants as well as by XPS. Although general catalytic trends can be directly correlated with the redox properties observed upon separate interactions with each of the two reductants (CO and H 2), the existence of interferences between both reductants must be considered to complete details for such activity/redox correlation. Differences in the nature of the active oxidised copper–cerium contacts present in each case determine the catalytic properties of these systems for the CO-PROX process.