Oxidation Of CO-PROX Research Articles

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.

Efficient fabrication of active CuO-CeO2/SBA-15 catalysts for preferential oxidation of CO by solid state impregnation

A facile solid state impregnation method was reported to prepare CuO-CeO2/SBA-15 catalysts for preferential oxidation of CO (CO-PROX). The catalysts were studied and compared with the counterpart from traditional wet impregnation. All catalysts together with a bulk CuO-CeO2 were characterized by XRD, N2 sorption, TEM, XPS, FT-IR of CO adsorption and H2-TPR. Results showed that: (1) both copper and ceria were well dispersed on SBA-15, and by adoption of a supported CuO-CeO2 configuration, the CO-PROX activities were greatly enhanced, which could be attributed to the distinct reduction of ceria size; (2) the optimum copper loading was 5wt%, and obvious decrease of CO2 selectivity was observed at higher loading; (3) in comparison with wet impregnation, the solid state impregnation displayed advantages of increased interfacial CuO-CeO2 entities and enhanced interaction between CuO and CeO2, which increased the active site and upgraded the CO-PROX activity resultantly. As well, the reason accounting for the different properties was tentatively discussed. On the basis of the preliminary results, it is supposed the solid state impregnation will find unique application in fabrication of multi-component heterogeneous catalysts.

Preferential oxidation of CO over Au/CuOx–CeO2 catalyst in microstructured reactors studied through CFD simulations

A computational fluid dynamics (CFD) simulation study of the preferential oxidation of CO (CO-PROX) in microstructured reactors consisting in square and semicircular microchannels coated with an Au/CuOx–CeO2 catalyst is presented. The CO content of the feed stream was set at 1vol.%. A parametric sensitivity analysis has been performed under isothermal conditions revealing that an optimal reaction temperature exists that leads to a minimum CO content at the microreactor exit. The influence of the space velocity, CO2 concentration and oxygen-to-CO molar ratio in the feed stream (λ), catalyst loading, and microchannel characteristic dimension (d) on the microreactor performance has been investigated. Under suitable conditions, the CO concentration can be reduced below 10ppm at relatively low temperatures within the 155–175°C range. A negative effect of the increase of d from 0.35mm to 2.8mm on the CO removal efficiency has been found and attributed to a more detrimental effect of the mass transport limitations on the oxidation of CO than that of H2. Non-isothermal CFD simulations have been performed to investigate the cooling of the CO-PROX reactor with air or a fuel cell anode off gas surrogate in parallel microchannels. Due to the very rapid heat transfer allowed by the microreactor and the strong influence of the reaction temperature on the exit CO concentration, a careful control of the coolant flow rate and inlet temperature is required for proper reactor operation. The microreactor behavior is virtually isothermal.

Potassium promoted Ru/meso-macroporous SiO2 catalyst for the preferential oxidation of CO in H2-rich gases

A series of potassium promoted Ru/meso-macroporous SiO2 catalysts were prepared and used for the preferential oxidation of CO (CO-PROX) in H2-rich gases. The catalysts were characterized by using techniques of TEM, SEM TPR, XPS, and N2 adsorption/desorption. The catalytic activity of Ru/meso-macroporous SiO2 was markedly improved by the introduction of potassium. The catalyst of K-5 wt.% Ru/meso-macroporous SiO2 with molar ratio of K:Ru = 5:7 exhibited relatively high activity and selectivity for CO-PROX. Nanoparticles of ruthenium species can be highly dispersed on the meso-macroporous SiO2 support by the simple impregnation method. The addition of potassium weakened the interaction between metallic Ru and the silica support. Lowering the reduction temperature of ruthenium ions could keep ruthenium in the state of metallic Ru, and it was proposed that potassium acted as an electron donating agent. The electron donating effect of potassium improved the low temperature activity for CO oxidation and increased the selectivity of O2 for CO oxidation, thus K-modified Ru/meso-macroporous SiO2 catalyst showed obviously a wide temperature window for CO elimination from H2-rich gases, meanwhile the related mechanism was discussed.

Recent Progress of Cu-Based Catalysts for Catalytic Elimination of CO

Catalytic elimination of CO mainly includes complete oxidation(CO-COOX) and preferential oxidation of CO(CO-PROX).First,combined with our group's research,a brief introduction to the active species and the interaction between components in Cu-based catalysts for CO-COOX was presented from the perspective of the catalyst system.Then recent progress in CO-PROX under H2-rich over Cu-based catalysts was systematically summarized.Influence of the preparation method,promoter,and support of CuO-CeO2 catalyst as well as transition metal ions doped support(CuO/Ce1-xMxO2),and inverse structure(CeO2/CuO) on the catalytic performance in CO-PROX was elaborated.Finally,the application problems and future research trend of Cu-based catalysts for catalytic removal of CO were discussed and summarized.

Copper catalysts prepared via microwave-heated polyol process for preferential oxidation of CO in H2-rich streams

The purposes of this study were to prepare a copper catalyst by the microwave-heated polyol (MP) process and subsequently to evaluate the feasibility of the preferential oxidation of CO (CO-PROX) in excess H2. A CeO2-TD support was firstly prepared by the thermal decomposition from Ce(NO3)3·6H2O precursor. For comparison, commercial ceria (CeO2-C) and activated carbon (AC) selected as support materials. Experimental results of CO-PROX indicated that the highest catalytic activity is achieved when the Cu/CeO2-TD used as catalysts. Correlating to the characteristic results, it is found that the CeO2-TD support prepared by the thermal decomposition has a large surface area and high mesoporosity; these properties contribute to the easy adsorption of pollutants and the effective dispersion of metal particles. Further investigation of feed composition found that Cu/CeO2-TD catalysts possess 100% CO conversion even existence of CO2 and H2O in H2-rich streams at 150 °C. Besides, a decrease in CO conversion was clearly observed above 175 °C for Cu/CeO2-TD catalysts due to the reverse water gas shift reaction tending to reform CO from CO2 and H2.

Preparation of meso-macroporous α-alumina using carbon nanotube as the template for the mesopore and their application to the preferential oxidation of CO in H2-rich gases

Meso-macroporous α-Al2O3 was successfully prepared by using acid-treated carbon nanotube as mesoporous forming agent and polystyrene foam as the template for the macropore. A series of Ru/meso-macroporous α-Al2O3 catalysts were prepared by the incipient wetness impregnation method and applied to the preferential oxidation of CO (CO-PROX) in H2-rich gases. SEM, N2 adsorption–desorption, H2-TPR techniques and TEM were employed to characterize the catalysts. The results indicate that the specific surface area was markedly elevated by introducing the mesopores, which led to the higher dispersion of ruthenium nanoparticles on the surface of α-Al2O3. The meso-macroporous α-Al2O3 supported ruthenium showed very high activity and selectivity for CO-PROX.

Preferential oxidation of CO on Ni/CeO2 catalysts in the presence of excess H2 and CO2

Preferential oxidation of CO (CO-PROX) was carried out over Ni supported on CeO2 prepared by the co-precipitation method. The influence of metal loadings (2.5, 5 and 10 wt.% Ni) and the reaction conditions such as reaction temperature and feed composition on CO oxidation and oxidation selectivity were evaluated by using dry reformate gas. No other reactions like CO or CO2 methanation, coking, reverse water gas shift (RWGS) reaction is observed in the temperature range of 100–200 °C on these catalysts. Hydrogen oxidation dominates over CO oxidation above the temperature of 200 °C. An increase in oxygen leads to an increase in CO conversion but a simultaneous decrease in the O2 selectivity. It has been noticed that 5 and 10 % Ni/CeO2 show better catalytic activity towards CO-PROX reaction. These catalysts were characterized by SBET, XRD, TEM, XPS and H2-TPR.

A Review on Preferential Oxidation of Carbon Monoxide in Hydrogen Rich Gases

In this review, recent works on the preferential oxidation of carbon monoxide in hydrogen rich gases for fuel cell applications are summarized. H2 is used as a fuel for polymer-electrolyte membrane fuel cell (PEMFC). It is produced by reforming of natural gas or liquid fuels followed by water gas shift reaction. The produced gas consists of H2, CO, and CO2. In which CO content is around 1%, which is highly poisonous for the Pt anode of the PEMFC so that further removal of CO is needed. Catalytic preferential oxidation of CO (CO-PROX) is one of the most suitable methods of purification of H2 because of high CO conversion rate at low temperature range, which is preferable for PEMFC operating conditions. Catalysts used for COPROX are mainly noble metal based; gold based and base metal oxide catalysts among them Copper-Ceria based catalysts are the most appropriate due to its low cost, easy availability and result obtained by these catalysts are comparable with the conventional noble metal catalysts. © 2011 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Doping effects of Ni–MgO on the structure and performance of carbon nanotube-supported Pt catalysts for preferential oxidation of CO in a H 2 stream

The preferential oxidation of CO (CO-PROX) in a H 2-rich stream is performed on a series of supported Pt catalysts doped with Ni–MgO. The characterizations of the catalysts by means of in situ X-ray diffraction, high resolution transmission electron microscopy, and scanning transmission electron microscopy–energy dispersive spectroscopy reveal that the nanocomposites of Pt–Ni alloys that intimately adjoined Ni–MgO solid solution are present on the surfaces of carbon nanotube (CNT). However, the Pt–Ni alloying is hardly detected when the same compositions are supported on other carriers like active carbon, graphite, TiO 2, SiO 2 and Al 2O 3 followed by identical treatment. The CNT-supported Pt 0.3Ni 1.0Mg 2.4 (Pt 0.3Ni 1.0Mg 2.5/CNT, the data at subscript stand for the Pt/Ni/Mg atomic ratio) catalyst with overall metal loading of 15 wt% affords 100% CO conversion and 50% O 2 selectivity in H 2 at temperatures ranging from 333 to 453 K, whereas the CNT-supported Pt catalyst and the other carriers-supported Pt 0.3Ni 1.0Mg 2.4 ones perform very low or insufficient activities under the same reaction conditions. Further, the Pt 0.3Ni 1.0Mg 2.4/CNT catalyst with a mean Pt–Ni particle size about 7.3 nm shows negligible drop in CO-PROX performance at 373 K for longer than 40 h on the streams either with or without H 2O vapor and CO 2. The deactivation of the catalyst is largely due to the accumulation of H 2O/OH − species and carbonates, which can be removed by calcination and reduction to get the regeneration of the CO-PROX performance as a result. The high performance of the catalysts is ascribed to the interaction between Pt and Ni with the formation of Pt–Ni alloy which is strongly interacted with Ni–MgO solid solution.

Preferential oxidation of CO (CO-PROX) over CuO x/CeO 2 coated microchannel reactor

The general aspects of the synthesis and characterization results of a CuO x /CeO 2 catalyst were presented. In addition the principal steps for manufacturing a microchannel reactor and for the coating of the CuO x /CeO 2 catalyst onto the microchannels walls, were also summarized. The catalytic activity of this microchannel reactor during the preferential oxidation of CO (CO-PROX) was evaluated employing a feed-stream that simulates a reformate off-gas after the WGS unit. Two activation atmospheres were studied (H 2/N 2 and O 2/N 2). The reducing pretreatment improved the resistance to deactivation by formation of carbonaceous species over the catalyst surface at high temperatures. The presence of H 2O and CO 2 in the feed-stream was also analyzed indicating that the adsorption of CO 2 inhibited the conversion of CO at lower temperatures because these compounds modified the active sites through the formation of carbonaceous species on the catalyst surface. Finally, the experimental results of the microreactor performance were compared with CFD simulations that were carried out using a kinetic for the CuO x /CeO 2 powder catalyst. The experimental results were reasonably well described by the model, thus confirming its validity.

Preparation, characterization and catalytic applications of ZrO2 supported on low cost SBA-15

This work presents some applications of ZrO2 supported over SBA-15 silica as promoter of sulfated zirconia and as support from CuO/CeO2 catalytic system for preferential oxidation of CO to CO2 in hydrogen rich streams, used as feed for proton exchange membrane fuel cells (PEMFC). Different amounts of ZrO2, from 10 to 30 wt.% were incorporated. These prepared materials were characterized by powder XRD, adsorption-desorption of N2 at 77 K, transmission and scanning electron microscopy (TEM and SEM) and X-rays photoelectron spectroscopy (XPS). The acidity was studied by thermo-programmed desorption of ammonia (NH3-TPD). These materials were tested, after treatment with H2SO4, by 2-propanol dehydration and 1-butene isomerization catalytic tests. The samples were found quite good catalyst with strong acid sites, the sample with 20 wt.% of ZrO2 being the better performing sample. Finally this material was successfully used as support for a CuO/CeO2 system, with 6 wt.% of Cu and 20 wt.% of Ce. The resulting catalyst was tested in the preferential oxidation of CO (CO-PROX) attaining conversions close to 100% and high selectivity to CO2.

Preferential Oxidation of CO in a Hydrogen-Rich Gas Through Au/NaY Catalytic Membranes

This paper describes novel Au/NaY catalytic membranes for preferential oxidation of CO (CO-PROX) in an H 2-rich gas. NaY zeolite membranes with a high CO 2/N 2 separation factor were loaded with nanosized Au particles using an ion-exchanged method. X-ray diffraction analyses showed that the structure of the NaY zeolite was not damaged by the ion exchange process. CO-PROX experiments showed that the catalytic membranes had excellent catalytic performance for selective oxidation of CO. The CO/H 2 molar ratio on the permeate side decreased with increasing operating temperature in the range of 80–200°C. At 200°C, almost no CO was detected from the permeate stream of a catalytic membrane with the feed containing 0.67% CO, 1.33% O 2, 32.67% H 2, and He in balance. Thus, these Au/NaY catalytic membranes show a promise for CO removal from hydrogen fuels.

CO Preferential Oxidation Activity of CuO/CeO2 Supported on Zirconium Doped Mesoporous MSU Type Silica

The activity of the CuO–CeO2 couple supported on a MSU silica doped with zirconium (Si/Zr = 7), was evaluated in the preferential oxidation of CO (CO-PROX) in hydrogen-rich gas stream (1.2% CO, 1.2% O2, 50% H2, 0–15% CO2, 0–10% H2O He balance) and the catalytic performance was compared with that of CuO–CeO2 supported on a pure MSU silica. The samples were characterized by X-ray powder diffraction (XRPD), N2 physisorption at 77 K, temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). Correlations between catalytic performances and physico–chemical properties of the materials have been made.

Hybrid catalytic-DBD plasma reactor for the production of hydrogen and preferential CO oxidation (CO-PROX) at reduced temperatures

Dielectric Barrier Discharges (DBD) operated at atmospheric pressure and working at reduced temperatures (T < 115 degrees C) and a copper-manganese oxide catalyst are combined for the direct decomposition and the steam reforming of methanol (SRM) for hydrogen production and for the preferential oxidation of CO (CO-PROX).

On the role of redox properties of CuO/CeO2 catalysts in the preferential oxidation of CO in H2-rich gases

Abstract CuO/CeO 2 catalysts with CuO content ranging from 0.5 wt.% to 8 wt.%, prepared by wet impregnation of commercial ceria, have been tested for the preferential oxidation of CO (CO-PROX) under H 2 -rich conditions at 70–210 °C. Catalytic activity increases up to 4 wt.% CuO content, with less concentrated catalysts showing higher intrinsic activity. Catalysts have been characterized by means of XRD, BET analysis and UV spectroscopy. Formation of segregated CuO clusters has been detected for Cu richest CuO/CeO 2 sample. Redox properties have been deeply investigated using TP analysis (H 2 TPR, CO TPR, TPO) of fresh or pre-treated samples. Participation of surface ceria, induced by the strong interaction with copper, to reduction/oxidation reactions in the temperature range explored (up to 430 °C) has been demonstrated. Different copper species and their reactivity towards H 2 and CO have been individuated by comparing TPR of fully oxidized catalysts with those of partially oxidized catalysts. Active species have been identified as copper-ceria sites able to oxidize CO even at room temperature and to be re-oxidized by O 2 at the same temperature. Transient experiments have been carried out at different temperature using a diluted mixture starting from oxidized or reduced catalysts and followed by a H 2 TPR of the used samples. The results of these tests have showed that active centres for CO oxidation contain copper in the +2 oxidation state. At T > 100 °C some reduced copper sites are stabilized which promote H 2 oxidation thus lowering the selectivity of the CO-PROX process.

Preferential CO oxidation (CO-PROX) over CuO-ZnO/TiO2 catalysts

Abstract A series of CuO-ZnO/TiO2 ternary catalysts was prepared by co-precipitation and characterized by X-ray powder diffraction (XRPD), N2 physisorption at 77 K, temperature-programmed reduction/oxidation (H2-TPR/TPO) and FT-IR measurements of low temperature adsorbed CO. The catalysts were tested and found active in the preferential oxidation of CO (CO-PROX) in hydrogen-rich gas streams and their catalytic performance was compared with that of the binary systems CuO/ZnO and CuO/TiO2.

Selective Oxidation of CO in Excess H 2 over Ru/Al 2O 3 Catalysts Modified with Metal Oxide

The Ru/Al 2O 3 catalysts modified with metal oxide (K 2OandLa 2O 3) were prepared via incipient wetness impregnation method from RuCl 3·nH 2O mixed with nitrate loading on Al 2O 3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO (CO-PROX) from the hydrogen-rich gas streams produced by reforming gas, and the performances of catalysts were investigated by XRD and TPR. The results showed that the activity temperature of the modified catalysts Ru-K 2O/Al 2O 3 and Ru-La 2O 3/Al 2O 3 were lowered approximately 30 °C compared with pure Ru/Al 2O 3, and the activity temperature range was widened. The conversion of CO on Ru-K 2O/Al 2O 3 and Ru-La 2O 3/Al 2O 3 was above 99% at 140–160 °C, suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La 2O 3/Al 2O 3 was higher than that of Ru-K 2O/Al 2O 3 in the active temperature range. Slight methanation reaction was detected at 220 °C and above.

Preferential oxidation of CO in a H 2-rich stream over CuO/CeO 2 and CuO/(Ce,M)O x (M = Zr, Tb) catalysts

Catalysts with the same copper oxide loading supported on cerium oxide and Ce–M (M = Zr or Tb) mixed oxides are examined with respect to their performance for preferential oxidation of CO (CO-PROX) in a H 2-rich stream. The catalytic activity results are analysed in combination with operando-DRIFTS tests done under similar conditions and characterization results obtained by XRD, XPS and XAFS techniques. The presence of essentially highly dispersed CuO entities strongly interacting with the corresponding supports and differing in their dispersion degree is evidenced by these techniques. The catalytic activity results reveal significant support effects affecting the conversion of either CO or H 2 as well as the selectivity for the CO-PROX process. These are explained on the basis of differences in the interfacial redox activities of the corresponding copper oxide-support contacts, while copper oxide particle size effects are proposed to be relevant to explain overall CO-PROX selectivities obtained.