CO PROX Research Articles

Binary metal (Ti, Cu) oxyhydroxy–organic (terephthalate) framework: An interface model nanocatalyst for hydrogen purification

The importance of metal–support interfaces is widely known in commercial and fundamental heterogeneous catalysis; however, it is difficult to characterize the active interface sites. In this study, we synthesize a new class of compound comprising tetragonal [Ti8O8(OH)4]12+ clusters interlinked by terephthalates (bdc) and [Cu2(OH)6]2− linkers {Ti8O8(OH)4·(bdc)2·[Cu2(OH)6]4}. The crystalline structure was refined for X-ray diffraction and direct links between [Cu2(OH)6]2− and [Ti8O8(OH)4]12+ are confirmed by extended X-ray absorption fine structure. This compound functions very well (k=0.117min−1 in CO 63Pa+O2 76Pa at 323K) as a catalytic model of interface Cu sites on ultra-dispersed Ti [hydro]oxide for preferential oxidation of CO in predominantly H2 gas, that is important for the purification of hydrogen used in fuel cells. In comparison, mean 1.7-nm CuO nanoparticles embedded inside the pores of MIL125 were inert (k=0.0035min−1) because of the absence of links between Cu and [Ti8O8(OH)4]12+ clusters. In CO 0.51kPa+O2 0.51kPa at 323K, the conversion to CO2 and CO PROX selectivity using Ti8O8(OH)4·(bdc)2·[Cu2(OH)6]4 (76% and 99%) was significantly higher than that using CuO/CeO2 (28% and 96%, respectively) for 24h.

Influence of the partner oxide on the catalytic properties of Au/CexZr1−x highly loaded gold catalysts

Since the ability to provide lattice oxygen should be an important factor dictating the catalytic activity of supported gold catalysts, we synthesized, simply by oxidation of the primary AuCe, AuZr, AuCeZr alloys, intimate mixtures of nanostructured Au with CeO2, ZrO2 or Ce–Zr mixed oxides which have unique redox properties and high mobility of lattice oxygen. This makes it possible to accurately study the influence of the support identity on the catalytic activity. A detailed investigation of the preferential oxidation of CO (PrOx) in the presence of H2 was undertaken also with the oxidation of CO and the oxidation of H2. For CO oxidation, it immediately appears that the nature of the oxide affects significantly the activity of gold, ceria being the best whereas for H2 oxidation no or only slight support effect has been observed. Catalytic performances in the PROX reaction were compared with those in the oxidation of CO. A change in the conversion of CO was observed in the presence of H2 at low temperature for all system, the effect depending on the support identity. A boost is clearly observed on Au/ZrO2 whereas the samples containing ceria present an opposite effect: when H2 is introduced in the reactive mixture, the CO conversion rate is drastically decreased. According to a Mars–van Krevelen mechanism, implying lattice oxygens of the cerium oxide it was suggested that the presence of H atoms in the vicinity of gold should reduce considerably the oxygen spillover activity. At higher temperature, hydrogen can desorb from ceria and the opposite trend is observed. Whereas the rate of CO’s oxidation decreases in a regular and fast way with the temperature for AuZr, it decreases more slowly when ceria is present. This could explain the better selectivity obtained with ceria containing gold catalysts as compared to gold–zirconia material in the high temperature range. Indeed when H2 is no longer present on the support, oxygen spillover activity should be recovered and CO oxidation favored. In any case we showed that Au/CeO2, in our conditions, is not active in the WGS reaction.

Copper as promoter of the NiO–CeO2 catalyst in the preferential CO oxidation

This study investigated the influence of the addition of copper on the catalytic performance of the NiO–CeO2 system for preferential CO oxidation reaction (CO–PROX) in hydrogen excess. A systematic structural characterization was performed employing various techniques (XRD, H2-TPR, Raman spectroscopy, HRTEM and XPS) in order to understand the structure–activity relationship. XRD, Raman and HRTEM analysis showed that part of Ni is introduced into the CeO2 structure forming a Ce1−xNixO2 solid solution and maintaining the fluorite structure, while Cu species added a posteriori are dispersed on the ceria surface. The catalytic performance of NiO–CeO2 system was significantly improved by addition of copper. This enhance in CO activity was attributed to synergetic interaction between dispersed copper species and surface oxygen vacancies of ceria support. Conversely, the effect of the presence of copper was not beneficial to the stability. XRD patterns of the catalyst post reaction indicate that metallic Cu and Ni were formed during the course of CO–PROX reaction, while Raman analysis demonstrates the both catalysts presented high resistance to carbon deposition. These results suggest that the decline in CO conversion and CO2 selectivity observed during the stability tests was caused by partial reduction of nickel and copper oxides sites (favored at higher temperatures). In addition, the influence of H2O and CO2 affected severely the reaction rate, however it is totally reversible.

Preferential oxidation of carbon monoxide over Pt–FeOx/CeO2 synthesized by two-nozzle flame spray pyrolysis

Pt–FeOx–CeO2 catalysts for the preferential oxidation of CO (CO-PROX) with controllable segregation between the Pt/FeOx and CeO2 components were synthesized by two-nozzle flame spray pyrolysis. This was achieved by flame-spraying the two active components independently in two interfacing flames. By adjusting the intersection distance between the two aerosol flames, it was possible to tune the morphology and the reducibility of the catalysts. Intimate interactions between Pt/FeOx and CeO2 (without oversintering the two components) achieved at the greatest flame distance gave reducibility at the lowest temperature, as corresponding to the formation of oxygen vacancies around the Pt (from H-spillover). Maximum CO conversion (>99.5%) for the two-nozzle synthesized catalysts was achieved below 90°C, which is 30°C lower than for mechanically mixed Pt/FeOx and CeO2. While high CO2 selectivity was attained at lower temperatures, it was limited by the adsorption of reactive oxygen. The oxygen vacancies on the Pt–FeOx–CeO2 catalyst were gradually oxidized at low temperatures due to unconsumed O2, and this led to a decrease in CO conversion with time on stream. In contrast, complete consumption of O2 and excess of dissociated H2 sustained the high oxygen vacancies content at high temperatures and hence high activity (although nonselective) was achieved. We further identified the loss of CO2 selectivity at high temperature as originating from the weakened CO adsorption compared to that of H2 in the presence of oxygen vacancies.

Influence of the structure and morphology of CuO supports on the amount and properties of copper–cerium interfacial sites in inverse CeO2/CuO catalysts

The CuO supports with different morphologies were prepared and the inverse CeO2/CuO catalysts were synthesized by the impregnation method. The catalysts were characterized via SEM, XRD, H2-TPR, in situ DRIFTS, XPS, TEM and N2 adsorption–desorption techniques. It is found that the CeO2/CuO-X catalysts present good catalytic performance in the CO–PROX reaction. Catalytic performance is related to BET specific surface area, Ce3+ content and reduction temperature of CuO. Cu+ species is CO adsorption site over the CeO2/CuO catalysts. The carbonate and hydrogen carbonate species cover the surface of CeO2/CuO catalysts at high temperature, and these species could cause the deactivation of the catalysts. The CuO particles are reduced into the metallic copper with large crystallite sizes after the reaction. The metallic copper is oxidized into CuO again, while the crystallite sizes of CeO2 and CuO both increase via regeneration. There are two possible ways to solve the problem of deactivation. One is to control the reaction temperature, and the other is to prevent the generation of metallic copper by promoting structure and morphology of the CuO support.

Capillary microreactors based on hierarchical SiO2 monoliths incorporating noble metal nanoparticles for the Preferential Oxidation of CO

Novel hierarchical SiO2 monolithic microreactors loaded with either Pd or Pt nanoparticles have been prepared in fused silica capillaries and tested in the Preferential Oxidation of CO (PrOx) reaction. Pd and Pt nanoparticles were prepared by the reduction by solvent method and the support used was a mesoporous SiO2 monolith prepared by a well-established sol–gel methodology. Comparison of the activity with an equivalent powder catalyst indicated that the microreactors show an enhanced catalytic behavior (both in terms of CO conversion and selectivity) due to the superior mass and heat transfer processes that take place inside the microchannel. TOF values at low CO conversions have been found to be ∼2.5 times higher in the microreactors than in the powder catalyst and the residence time seems to have a noticeable influence over the selectivity of the catalysts designed for this reaction. The Pd and Pt flexible microreactors developed in this work have proven to be effective for the CO oxidation reaction both in the presence and absence of H2, standing out as a very interesting and suitable option for the development of CO purification systems of small dimensions for portable and on-board applications.

In-situ DRIFTS and XANES identification of copper species in the ternary composite oxide catalysts CuMnCeO during CO preferential oxidation

A series of CuMnCeO catalysts with 10% CuO (weight loading) and variable atomic ratios of Mn/Mn + Ce (0, 0.02, 0.05 or 0.10) were synthesized by co-precipitation and employed for CO preferential oxidation (CO PROX). After doping a small amount of manganese into ceria, the catalysts show improved catalytic performance as compared with the undoped one, especially the catalyst with the Mn/Mn + Ce atomic ratio of 0.05 (CMC-0.05) which displays the lowest temperatures for half CO conversion (T50 = 73 °C) and full CO conversion (T100 = 108 °C). In addition, it also exhibits the widest temperature window of full CO conversion (108–149 °C) and 100% selectivity of oxygen to CO2 below 117 °C. As revealed by XRD and UV-Raman, the presence of appropriate amount of Mn cannot only enhance the formation of Ce–Cu–Mn–O ternary oxide solid solution with fluorite structure, inhibiting the growth of CeO2 crystallite size, but also increase the oxygen vacancies. The results of H2-TPR and XPS indicate that the reducibility and amount of surface oxygen species of CMC-0.05 are also improved, both of which are beneficial to catalytic performance. In situ XANES results suggest that the bulk copper species still remain as Cu2+ ions below 200 °C even in H2-rich CO PROX atmosphere; however, the in-situ DRIFTS spectra indicate that during CO PROX below 120 °C the surface copper species are Cu+ ions which are regarded as the main active sites for CO PROX; above 120 °C Cu0 species appear, which enhance H2 oxidation, decreasing the oxygen to CO2 selectivity.

Preferential carbon monoxide oxidation on Ag/Al-SBA-15 catalysts: Effect of the Si/Al ratio

In this work, mesoporous aluminosilicate supports (Al-SBA-15) were prepared using in situ “pH-adjusting” method, and Ag nanoparticles were supported on Al-SBA-15 supports by using the simple impregnation method. The effect of the Si/Al ratios of mesoporous support on the structure of Ag catalysts and the catalytic performance for the preferential oxidation of CO (CO PROX) in H2-rich gases was investigated. The Ag/Al-SBA-15 catalyst with an appropriate Si/Al molar ratio of 200 has been found to show highly catalytic activity, selectivity and stability. A series of supports and corresponding supported Ag catalysts with different Si/Al ratios were characterized by ICP-AES, XRD, N2 adsorption–desorption, 27Al NMR, FT-IR of adsorbed pyridine, TEM, H2-TPR and XPS. The results indicated that the addition of a small amount of Al is beneficial to the formation of small sized highly dispersed metal Ag particles in the channel, consequently improving the catalytic activity. In addition, the Ag/Al-SBA-15 (200) catalyst also exhibited better catalytic activity under the presence of H2O and CO2 in the stream.

Trends in the CO oxidation and PROX performances of the platinum-group metals supported on ceria

PGM–CeO2 (PGM=Pt, Pd, Ir, Rh, Ru) catalysts were prepared by one-step solution combustion synthesis (SCS) and characterized by elemental analysis, N2 volumetry, aberration-corrected HRTEM, X-ray diffraction, and CO-DRIFTS. The samples, consisting of 2–6nm metal nanoparticles supported on mesoporous ceria, were tested in CO oxidation in absence and presence of hydrogen (PROX). To our knowledge, this work presents the first comparison of all the platinum-group metals (except Os) for these reactions in the same conditions. The as-prepared SCS catalysts are active in CO oxidation and a reducing treatment has no significant effect on their performances. While the best catalyst in H2-free CO oxidation is Rh–CeO2, the addition of a high hydrogen excess decreases the Rh catalyst activity but enhances the CO oxidation rate on all other systems, including alumina-supported metals employed as reference catalysts. The resulting PROX turnover frequencies (Pt>Pd>Rh>Ir>Ru) follow the trends predicted by published density-functional-theory calculations considering the COad+Oad elementary reaction as the rate-determining step. Pt–CeO2 is not only the most active but also the most selective catalyst, reaching near 100% CO2 at low temperature (ca. 100°C). The alumina-supported catalysts appeared less active than their ceria-supported counterparts in both reactions. The effect of heating/cooling cycles on the reaction kinetics was also investigated. Whereas the Pt, Pd and Ir ceria-supported catalysts were stable throughout PROX cycles, Rh and Ru ones exhibited apparently chaotic behaviors above ca. 200°C, which are proposed to be induced by favorable CO dissociation and methanation pathways and/or variable metal oxidation states.

CO PROX over Pt–Sn/Al2O3: A combined kinetic and in situ DRIFTS study

Preferential oxidation of CO (PROX) in hydrogen-rich mixtures was studied over alumina-supported Pt and Pt–Sn catalysts, which exhibited a well-defined metal particle size. The reaction rate was much faster over Pt–Sn/Al2O3 than over Pt/Al2O3. Significantly different apparent activation energies and oxygen reaction orders were found for both samples. Whereas the CO PROX kinetics over Pt/Al2O3 could be described by oxygen adsorption as being rate-determining step, this was not the case for Pt–Sn. In situ Diffuse Reflectance Infrared Fourier Transformed Spectroscopy (DRIFTS) showed that Pt–Sn, initially under a mixture of 1% CO/80% H2, segregated upon the introduction of 2% O2, even at temperatures where the alloy was stable under reducing conditions. For the CO PROX reaction over Pt–Sn/Al2O3 a bifunctional mechanism is proposed with CO and H being adsorbed on the platinum sites and oxygen being channeled from neighboring SnOx sites. This work suggests a Mars–Van Krevelen type of mechanism for the SnOx site, in agreement with the low value of 0.2 for the oxygen reaction order over Pt–Sn.

On the mechanism of the preferential oxidation of carbon monoxide over Cu n Pd (n = 3–12) catalysts

Preferential oxidation of CO (CO-PROX) is an important practical process for the purification of H2 for use in proton exchange membrane fuel cells. In order to clarify the mechanism of CO-PROX, the reaction promoted by CunPd (n = 3–12) clusters has been studied by density functional theory calculations. The CO-PROX reaction via carboxylic and hydroxyl intermediates is found to be the most likely mechanism. The theoretical results show that CO oxidation is promoted by the attack of surface OH groups, which is different from the usual oxidation of CO with O2. The Cu6Pd cluster is predicted to have a lower activation barrier compared with other CunPd clusters and is therefore proposed as the most effective nanocatalyst. To gain insights into the high catalytic activity of the CunPd nanoparticles, the nature of the interaction between adsorbate and substrate has been analyzed by the detailed electronic local density of states. The results should be helpful in developing efficient catalysts for the CO-PROX reaction.

The graphene-meso-macroporous SiO2 supported Pt–Ni alloy nanocatalyst for preferential oxidation of CO in H2-rich gases

In this work, nanoparticles of Pt–Ni alloy were supported on a new kind of composite which composed of graphene sheets and meso-macroporous SiO2, and the composite supported Pt–Ni catalyst was applied to the preferential oxidation of CO (CO-PROX) in H2-rich gases. The bimetallic Pt–Ni alloy catalyst was characterized by using techniques of SEM, TEM, XRD, TPR, CO chemisorptions and XPS. The catalyst showed excellent catalytic performance for CO-PROX with high activity at low temperature, high selectivity and very good stability, which was attributed to the following characters of the catalyst: Pt–Ni nanoparticles were in alloy state and highly dispersed, Pt–Ni nanoparticles were preferentially loaded on the surface of graphene sheets, and the meso-macroporosity of the composite markedly improved the mass transferring ability. This is a case study, and this kind of catalysts can be extended to other gas–solid catalytic reactions.

Novel Co‐Mn‐O nanosheet catalyst for CO preferential oxidation toward hydrogen purification

Co‐Mn‐O composite oxide nanosheet catalyst was successfully prepared using a facile urea‐assisted one‐step hydrothermal method in the absence of organic or organic templating reagent. Co‐Mn‐O nanosheet catalyst was optimized by varying hydrothermal process parameters such as molar ratio of Co‐Mn to urea, hydrothermal temperature, and hydrothermal time. Various characterization techniques including scanning electron microscopy, X‐ray diffraction, nitrogen adsorption, X‐ray photoelectron spectroscopy, Raman spectroscopy, and H2 temperature‐programmed reduction were used to reveal the relationship between catalyst nature and catalytic performance in CO preferential oxidation (CO PROX) in excess H2. The developed Co‐Mn‐O nanosheet catalyst have demonstrated much superior catalytic performance to Co‐Mn‐O nanoparticle, particularly in the low temperature range, and 100% CO conversion over the developed Co‐Mn‐O nanosheet can be achieved in temperature range of 50 to 150°C at 10,000 mL g−1 h−1 of gas hourly space velocity in the standard feed. Furthermore, the almost complete CO removal over Co‐Mn‐O nanosheet at 125°C of low temperature with 94.9% selectivity can be achieved even in the simulated reformed gas. The excellent catalytic performance is ascribed to nanosheet morphology, more surface Co3+, smaller average crystallite size, higher reducibility, and strong Co‐Mn interaction. Catalytic stability investigation indicates the developed nanostructured catalyst exhibits high catalytic stability for CO PROX reaction in simulated gas. The developed Co‐Mn‐O nanosheet catalyst can be a potential candidate for catalytic elimination of trace CO from H2‐rich gas for Proton exchange membrane fuel cell applications. © 2014 American Institute of Chemical Engineers AIChE J, 61: 239–252, 2015

Highly dispersed Ru on K-doped meso–macroporous SiO2 for the preferential oxidation of CO in H2-rich gases

In this work, highly dispersed Ru nanoparticles which had a uniform small nanoparticle size were supported on K-promoted meso–macroporous SiO2 by using the simple impregnation method. The effect of the size of Ru nanoparticle on the catalytic performance for the preferential oxidation of CO (CO-PROX) in H2-rich gases was investigated. Meanwhile, the related mechanism on size effect was discussed. The catalysts were characterized by using techniques of transmission electron microscopy, temperature-programmed reduction and CO-chemisorption. The results indicate that the K-promoted Ru/SiO2 catalyst with the size of metal Ru particles at about 7 nm showed obviously higher turnover frequency (TOF) than that of K-Ru/SiO2 with smaller size of Ru particles of around 2 nm. As for oxidizing CO to CO2 on specific weight of ruthenium, the catalyst with the smaller size of metal Ru exhibited better performance owing to its much higher specific surface area of metal Ru. The catalyst with the smaller size of Ru nanoparticles showed much better methanation formation resistance for CO and CO2. The K-promoted and highly dispersed Ru on SiO2 exhibited excellent activity and selectivity for the CO-PROX reaction.

Superior catalytic performance of non-stoichiometric solid solution Ce1 − xCuxO2 − δ supported copper catalysts used for CO preferential oxidation

A series of Ce1−xCuxO2−δ non-stoichiometric solid solutions and their supported copper catalysts CuO/Ce1−xCuxO2−δ (x=0, 0.005, 0.022, 0.043) were prepared by co-precipitation and deposition–precipitation, respectively. The CuO/Ce1−xCuxO2−δ catalysts show high performance for CO preferential oxidation (CO PROX). Multiple techniques of N2 sorption (BET), XRD, Laser Raman spectroscopy (LRS), HRTEM, H2-TPR, O2-TPO, N2O chemisorption and in-situ DRIFTS were used for catalyst characterization. The results of XRD, LRS and H2-TPR conformably indicate that a small amount of Cu2+ ions can be incorporated into the lattice of CeO2, forming non-stoichiometric solid solutions Ce1−xCuxO2−δ, which shows much better reducibility than pure CeO2. The supported CuO/Ce1−xCuxO2−δ catalysts exhibit remarkably enhanced activity for CO PROX as compared with CuO/CeO2, especially the catalyst CuO/Ce0.978Cu0.022O2−δ containing 15% Cu, which displays the best CO PROX performance, showing not only the lowest temperature (115°C) for CO total conversion, but also the 100% selectivity of O2 to CO2 at this temperature. Several aspects including the presence of more oxygen vacancies, the improved reducibility, and stronger capability for CO chemisorption of this catalyst account well for its superior performance for CO PROX. Based upon the in-situ DRIFTS study, it is revealed that Cu+ is the main active site for CO oxidation, while Cu0 is more active for H2 activation and oxidation.

Synthesis of mesoporous Co–Ce oxides catalysts by glycine-nitrate combustion approach for CO preferential oxidation reaction in excess H2

Preferential oxidation of CO (CO-PrOx) is an important step to meet the need of the proton exchange membrane (PEM) fuel cell without the Pt anion poison. A glycine-nitrate approach was used for the synthesis of Co/CeO2 nanoparticle for preferential oxidation of CO, which a precursor solution was prepared by mixing glycine with an aqueous solution of blended nitrate in stoichiometric ratio. Then the glycine-mixed precursor solution was heated in a beaker for producing nanosized porous powders. Catalytic properties of the powders were investigated and results illustrate that the Co-loading of 30 wt.% catalysts exhibits excellent catalytic properties. Various characterization techniques like X-ray diffraction, SEM, BET, Raman and TPR were used to analyze the relationship between catalyst nature and catalytic performance. The X-ray diffraction patterns and SEM micrographs indicate that catalysts prepared by glycine-nitrate combustion own mesopore structure. The BET, Raman and TPR results showed that the high activity of the 30 wt.% Co-loading of Co/CeO2 catalysts is related to the high BET surface and the strongly interaction between fine-dispersed Co species and CeO2 support.

Preparation of Ru/graphene-meso-macroporous SiO2 composite and their application to the preferential oxidation of CO in H2-rich gases

Preparation for graphene (GE)-meso-macroporous SiO2 composite was studied, the composite was used as the support for Ru and the resulted catalyst was applied to the preferential oxidation of CO (CO-PROX) in H2-rich gases. The composite was characterized by using techniques of SEM, TEM, XRD, TPR, N2 adsorption/desorption and XPS. In the preparation, polystyrene foam and a tri-block copolymer of P123 were used as the template for the macropores and the mesopores, respectively. In addition to the macro and the meso pores, there are narrow slit-like pores with width of several nanometers between GE and SiO2. The highly dispersed Ru nanoparticle can be loaded on the surface of GE in the composite by impregnating. Thus prepared Ru/GE-SiO2 showed very good catalytic performance for CO-PROX, especially exhibited high activity at low temperature. The GE-SiO2 composite should possess the properties of both meso-macroporous oxides and graphene, and is a kind of new promising material, in which SiO2 can be replaced by other oxides.

The supported CeO2/Co3O4–MnO2/CeO2 catalyst on activated carbon prepared by a successive-loading approach with superior catalytic activity and selectivity for CO preferential oxidation in H2-rich stream

The supported CeO2/Co3O4–MnO2/CeO2 catalyst on activated carbon (AC) prepared by a successive loading approach to support ceria, cobalt-manganese oxide and ceria on activated carbon exhibits superior catalytic activity and selectivity to Co3O4–MnO2–CeO2/AC prepared by a one-step loading for CO preferential oxidation in H2-rich stream, although the same loading of Co, Mn and Ce was used, which illustrates that the addition of ceria doesn't always enhance catalytic performance in CO PROX reaction, and appreciate supporting method is essential. The superior catalytic activity and selectivity of developed catalyst can be ascribed to high reducibility, well dispersion, unique porous structure, and strong interaction between Co3O4–MnO2 and CeO2.

Promoting effect of MnOx on the performance of CuO/CeO2 catalysts for preferential oxidation of CO in H2-rich gases

A series of CuO/CeO2–MnOx catalysts with the Mn/(Ce + Mn) atomic ratios of 0, 0.2, 0.4, 0.6 and 1.0 were prepared and characterized by means of N2 adsorption, XRD, H2-TPR and XPS. The promoting effect of MnOx on the performance of CuO/CeO2 catalyst for the CO preferential oxidation in H2-rich gases (CO PROX) was investigated. The results show that the addition of MnOx can improve the catalytic activity of CuO/CeO2 catalyst. CuO/CeO2–MnOx catalysts exhibit much higher activity in the preferential oxidation of CO than CuO/CeO2 and CuO/MnOx. The CuO/CeO2–MnOx catalyst with the Mn/Ce + Mn atomic ratio of 0.4 is the most active, over which 100 % conversion of CO with selectivity of 83 % is obtained at 140 °C. The presence of MnOx in CuO/CeO2–MnOx catalysts can promote the release of oxygen species from ceria to active copper species and increase the highly dispersed copper species. XPS characterization further revealed that the surface hydroxyls/carbonates of catalysts decrease with the amount of Mn, which should be greatly responsible for the higher activity of CuO/CeO2–MnOx catalysts.

Hierarchically nanoporous Co–Mn–O/FeOx as a high performance catalyst for CO preferential oxidation in H2-rich stream

A novel and highly-efficient hierarchically nanoporous Co–Mn–O/FeOx catalyst fabricated by a hard/soft dual-templating and subsequent deposition–precipitation (HSDT/DP) approach demonstrates unexpectedly high catalytic activity with 100% CO conversion at 75°C and wide temperature window of 75–200°C with complete CO removal for CO preferential oxidation (CO PROX), ascribed to the unique microstructure and strong interaction between finely dispersed cobalt–manganese and FeOx. The excellent catalytic performance allows it to be a practical candidate for CO elimination from H2-rich stream.