Preferential Oxidation In H2-rich Stream Research Articles

Oxygen vacancy-regulated atomic dispersed Au on CeFeOx for preferential oxidation of CO in H2-rich stream

CO preferential oxidation in H2-rich stream (CO-PROX) is a critical reaction for H2 purification in emerging hydrogen economy including advanced fuel cell technology. Au-based catalysts are viewed as some of the most promising catalysts but achieving high catalytic efficiency and selectivity is still challenging. Defect engineering is deemed as a powerful strategy to improve the intrinsic catalytic activity. Herein, CeFeOx-supported Au catalysts with controllable oxygen vacancy (Ov) concentrations were obtained and applied to CO-PROX. The results of characterizations showed that the Ovs were preferentially generated in conjunction with Au single atoms (SAs) rather than nanoparticles (NPs), which further modulated the surface electronic properties via surplus electrons in Ovs and enhanced the interfical interaction between Ovs and Au SAs. The CO-PROX results indicated that the reduced Au SA catalyst (Au1/CeFeOx-R) with the highest Ov concentration completely converted CO at temperature of 80 °C with relatively low reactivity towards H2 oxidation. The remarkable catalytic activity and selectivity were attributed to the modified electronic properties by Ovs that played a bridging role in electron transfer and accelerated reaction process, as well as the coupling effect of Ovs and Au SAs that enhanced the dissociative adsorption of O2 and the adsorption-oxidation of CO, resulting in a reduced reaction energy barrier and making CO oxidation more favorable than H2 oxidation. This research opens up an alternative strategy to simultaneously stabilize and activate single-atom catalysts.

Effect of acid treatment on the catalytic performance of CuO/Cryptomelane catalyst for CO preferential oxidation in H2-rich streams

The effect of acid treatment on the catalytic performance of CuO/Cryptomelane (CuO/CR) for CO preferential oxidation (CO-PROX) in H2-rich streams has been investigated. The CR supports are synthesized via the sol-gel approach. The hydrochloric acid or water is used to treat the CR support, and the corresponding CuO/CR catalysts are prepared by an initial wet impregnation method. Compared with the pristine CuO/CR and water-treated CuO/CRW catalysts, the acid-treated CuO/CRH exhibits the best catalytic activity with almost 100% of CO conversion at 110 °C, which can be maintained at least 100 h. The characterization results show that acid treatment decreases the K+ content in the CuO/CRH catalyst, which is conducive to the formation of more oxygen vacancies, thereby promoting the reducibility of CuO/CRH. This is the main reason for the high catalytic activity of the acid-treated CuO/CRH catalyst. Moreover, the abundant Brönsted acid sites on CuO/CRH are favorable for the desorption of acidic product CO2, which also could result in the significant promotion of the catalytic activity for CO-PROX. This study sheds a light on the importance of acid treatment for cryptomelane and provides an efficient catalyst for hydrogen purification.

CO preferential oxidation in H2-rich stream over the CuO-MnOx mixed oxide catalysts prepared by a facile mechanochemical preparation method

The CuMn samples with various CuO weight percentages were synthesized by the mechanochemical route. The catalytic activity of the prepared samples was determined in the preferential oxidation of CO process (CO-PROX) in the temperature range of 40–250 °C. According to the XRD results, the 5CuMn and 10CuMn samples exhibited the spinel phase in their structures. The spinel phase formation enhanced the CO adsorption active sites and modified the redox properties. The results indicated that the copper incorporation into the manganese oxide modified the catalytic activity and structural properties. The 5CuMn catalyst with the highest BET area (72.1 m2 g−1) possessed 96% CO conversion and 50% CO2 selectivity at 70 °C (GHSV = 30,000 ml/h.gcat) and significant resistance in the presence of water due to the formation of hydroxyl groups over the catalyst surface. The catalyst activity remained stable for 14 h at 130 °C. Furthermore, the influence of calcination temperature, feed composition, and GHSV value on the catalytic performance of the 5CuMn catalyst was studied.

Ceria-silica mesoporous catalysts for CO preferential oxidation in H2-rich stream: The effect of Ce:Si ratio and copper modification

In this work mesoporous CeO2-SiO2 catalysts with the Ce:Si molar ratios of 1:1 and 4:1 were synthesized by template method and modified with copper to elucidate the role of copper-ceria and ceria-silica interactions in the catalyst efficiency in CO-PROX. The catalysts were characterized by SEM-EDS, AAS, XRD, TPR-H2, TEM, and spectroscopic methods (Raman, EPR and in situ DRIFT of adsorbed CO). The binary catalyst with the equimolar Ce:Si ratio demonstrated better catalytic performance in CO-PROX due to its favorable textural properties and strong ability to anion vacancy formation as confirmed by N2 physisorption and Raman spectroscopy. CuOx/CeSiOy (Ce:Si = 4:1) demonstrated better low-temperature activity, CO2 selectivity and stability than CuOx/CeSiOy (Ce:Si = 1:1) and both binary systems because of its unique structure, comprising fine CeO2 particles with a narrow size distribution of 2–3 nm well dispersed on a large surface area, high concentration of the most active in CO oxidation Cu+ sites, formed on CuOx-CeO2 interfaces, and improved ability to surface reoxidation after reduction with the reagents resulted in the decreased Ce3+ concentration. It was also stable in the presence of CO2 and H2O in the reaction mixture. These properties would be difficult to achieve via template preparation methods without SiO2 addition.

Catalytic performance of copper oxide supported α-MnO2 nanowires for the CO preferential oxidation in H2-rich stream

In this article, the catalytic activity of the copper catalysts with different loadings of copper oxides supported on α-MnO2 nanowires prepared by the simple hydrothermal route was studied in the CO preferential oxidation reaction. The x-ray diffraction (XRD), N2 adsorption/desorption, Fourier transform infrared (FT-IR) spectroscopy, H2-temperature-programmed reduction (H2-TPR), and scanning electron microscopy (SEM) analyses were used to characterize the synthesized samples. The obtained results showed that the 10 wt% CuO/MnO2 catalyst with the highest specific surface area and the lowest particle size demonstrated the highest CO conversion and CO2 selectivity in this reaction. The good catalytic performance of this catalyst was due to the beneficial synergistic interaction between copper and manganese. However, adding CO2 and/or H2O to the feedstock decreased the conversion and selectivity. Moreover, the effect of different parameters such as calcination temperature, O2/CO ratio, gas hourly space velocity (GHSV), and pretreatment conditions were investigated.

Low-temperature CO preferential oxidation in H2-rich stream over iron modified Pd–Cu/hydroxyapatite catalyst

The effect of FeCl3 addition on the catalytic property of Pd–Cu/hydroxyapatite (Pd–Cu/HAP) for low-temperature CO preferential oxidation (CO-PROX) under H2-rich condition has been investigated. It can be found that CO conversion of Pd–Cu/HAP rapidly decreases from 56% to 21% within 2 h at 30 °C in the presence of water, however, the Pd–Cu–Fe/HAP with the Fe/Cu atomic ratio of 1:1 presents a stable CO conversion of 40% and CO2 selectivity of 100% under the same reaction conditions. The characterization results display that the addition of FeCl3 to Pd–Cu/HAP causes the formation of Fe2O3 species, and the strong interaction presents between Fe2O3 species and Pd–Cu/HAP. Thus, the Pd0 species generated during CO-PROX over Pd–Cu–Fe/HAP can be more easily oxidized than that over Pd–Cu/HAP, which could avoid H2 adsorption on Pd0 species and maintain CO adsorption and activation.

Sn-induced CuO–CeO2 catalysts with improved performance for CO preferential oxidation in H2-rich streams

Sn modified CuO–CeO2 catalysts with different Sn loadings were prepared by a facile, green and solvent-free method. The effect of Sn/Ce ratio over Sn–Cu–Ce-x (x = 0, 1, 2.5, 5, 7.5) samples on CO activity and O2 selectivity was investigated. The samples were characterized by various techniques using N2-adsorption/desorption, XRD, H2-TPR, XPS, Raman and in-situ DRIFTS. It was revealed that stronger interaction between acitve sites and support, higher amounts of Sn2+ and Ce3+, associated with increased amount of oxygen vacancies, were observed on the catalyst of Sn–Cu–Ce-5. As a result, the optimized catalyst displayed an excellent catalytic performance even in the presence of CO2 and H2O. In this sense, probing the Sn modified CuO–CeO2 catalyst can elucidate some useful keys for the development of high CO2 and H2O-resistance catalyst during CO-preferential oxidation in H2-rich streams.

Insights into the essential roles of tin and chloride species within Cu–CeO2 based catalysts for CO preferential oxidation in H2-rich stream

Sn modified Cu–Ce catalysts have been synthesized by the solvent-free combustion method for preferential oxidation of CO in H2-rich stream (CO-PROX) and characterized by N2 adsorption-desorption (BET), H2 temperature-programmed reduction (H2-TPR), X-ray diffraction (XRD), Raman, in-situ DRIFTS, X-ray photoelectron spectroscopy (XPS), and Oxygen storage capacity (OSC). The results show that the incorporation of Sn species accelerates the redox cycle among Sn, Cu and Ce, thus strengthening the Cu–Ce interaction and promoting the formation of surface and bulk lattice Cu-[Ox]-Ce structures Meanwhile, to balance the charge, more oxygen vacancies are formed and thus facilitate the migration of oxygen species. Combined with the more strong absorbed ability of SnO2 for O2, active Cu-[Ox]-Ce structures promotes the easier conversion of more CO into CO2. However, the existence of Cl ions decreases catalytic performance because the formation of CuCl makes the Cu–Ce interaction weakened, resulting in the formation of fewer Cu-[Ox]-Ce structures and oxygen vacancies. Although CuCl is prone to be in favor of absorbing more CO, there are not enough O species available, hence a decrease in performance is observed.

Au-Decorated Ce-Ti Mixed Oxides for Efficient CO Preferential Photooxidation.

We investigated the photocatalytic behavior of gold nanoparticles supported on CeO2–TiO2 nanostructured matrixes in the CO preferential oxidation in H2-rich stream (photo-CO-PROX), by modifying the electronic band structure of ceria through addition of titania and making it more suitable for interacting with free electrons excited in gold nanoparticles through surface plasmon resonance. CeO2 samples with different TiO2 concentrations (0–20 wt %) were prepared through a slow coprecipitation method in alkaline conditions. The synthetic route is surfactant-free and environmentally friendly. Au nanoparticles (<1.0 wt % loading) were deposited on the surface of the CeO2–TiO2 oxides by deposition–precipitation. A benchmarking sample was also considered, prepared by standard fast coprecipitation, to assess how a peculiar morphology can affect the photocatalytic behavior. The samples appeared organized in a hierarchical needle-like structure, with different morphologies depending on the Ti content and preparation method, with homogeneously distributed Au nanoparticles decorating the Ce–Ti mixed oxides. The morphology influences the preferential photooxidation of CO to CO2 in excess of H2 under simulated solar light irradiation at room temperature and atmospheric pressure. The Au/CeO2–TiO2 systems exhibit much higher activity compared to a benchmark sample with a non-organized structure. The most efficient sample exhibited CO conversions of 52.9 and 80.2%, and CO2 selectivities equal to 95.3 and 59.4%, in the dark and under simulated sunlight, respectively. A clear morphology–functionality correlation was found in our systematic analysis, with CO conversion maximized for a TiO2 content equal to 15 wt %. The outcomes of this study are significant advancements toward the development of an effective strategy for exploitation of hydrogen as a viable clean fuel in stationary, automotive, and portable power generators.

The catalytic performance of isolated-dispersed Au on nanosized CeO2 for CO preferential oxidation in H2-rich stream

Nanosized CeO2 and supported Au catalysts were synthesized and their catalytic performance for CO preferential oxidation in H2-rich streams was evaluated. Transmission electron microscope (TEM), N2 isothermal adsorption/desorption, X-ray diffraction (XRD), temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and in-situ DRIFTS techniques were adopted to characterize their structure property, redox property as well as dispersion and valence states of the active Au species. The results demonstrate the strong interaction between highly dispersed gold species (grain size <2 nm) and CeO2 in catalysts with low gold loading, which promotes the reduction of surface and sub-surface oxygen and the stabilization of high-valent Au3+ species. Meanwhile, it creates more lattice defects and benefits to the enhanced mobility of lattice oxygen and the activation of gas oxygen, thus contributing to the low-temperature CO preferential oxidation. However, over high Au content (≥0.6%) would lead to the agglomeration of gold nanoparticles and the formation of Au0 species, which weakens the gold-ceria interaction and decreases the active sites. On the other hand, the formation of Au0 species with large grain size would accelerate the dissociation of H2, which is the main reason for the decreasing of O2 selectivity toward CO over Au/CeO2 catalysts.

Catalytic performance of Cu/hydroxyapatite catalysts in CO preferential oxidation in H2-rich stream

Abstract A series of Cu/HAP catalysts was prepared by impregnation and characterised by TEM, BET, DRS, XPS, H2-TPR, XRD, TEM and FTIR techniques. H2-TPR and DRS data revealed that at low concentration ( The activity of the reduced samples in COTOX and COPROX processes revealed remarkable differences when the Cu content was increased from 0.8 to 14.8%. For instance, analysing the TOF values calculated for the two processes and the characterisation data, it was concluded that the catalysts with low Cu loadings (0.8% and 3.6%) were the most active ones and their sites involved in the CO oxidation reaction were almost similar. The addition of CO2 and water seemed to affect the performances of the two catalysts via different pathways. Indeed, in contrast to the Cu(4)/HAP, the Cu(1)/HAP catalyst became more selective in the presence of CO2 and water. Moreover, under these realistic COPROX conditions, the latter was 6.6 times more active than the former. A correlation with the characterisation data showed that the most efficient species consisted of those presenting strong interaction with the HAP support. By contrast, the sites exhibiting high concentration of Cu lattice imperfections showed a relatively low activity.

Catalytic performance of transition metals (Co, Ni, Zn, Mo) doped CuO-Ce0.8Zr0.2O2 based catalysts for CO preferential oxidation in H2-rich streams

CuO-Ce0.8Zr0.2O2 composites (CuCZ) doped by transition metals (Co, Ni, Zn, Mo) as well as Co-doped CuCZ with different molar ratios of Co/Cu were prepared by a facile urea grind combustion (UGC) method and applied for CO preferential oxidation (CO-PROX) reaction in the hydrogen-rich gas mixtures. The characterizations of XRD, N2 adsorption-desorption, SEM, TEM, XPS and H2-TPR were used to investigate the difference in the catalytic behavior. Activity results found that the modification of Co had a positive influence on the catalytic activity of CuCZ and the optimal ratio of Co/Cu was 1/10, while the addition of Ni, Zn and Mo resulted in the decrease in the catalytic activities. XRD, SEM, H2-TPR and XPS results proved that the catalytic behavior of CuCZ based catalysts largely depended on the properties and types of transition metals. The addition of Co into CuCZ led to the isomorphous substitution of Cu2+ and Ce3+ species via Co2+ and Co3+, and the redispersion of Cu species over CeO2 support promoted the generation of the highly dispersed Cu oxides. As a result, large amount of active Cu+ sites and the surface active oxygen were available. The negative effects caused by Ni, Zn and Mo species were originated from the decreased amount of highly dispersed Cu oxides, possibly due to the differences in the oxidation-reduction property, the ion radius, the metal-support interaction as well as the nucleation rate and the size growth of particles during the preparation process. Consequently, the structure-property relationship was established, and the catalytic activity was suggested to be correlated with the amount of highly dispersed Cu oxides. Furthermore, 1/10Co-CuCZ showed excellent stability in terms of both CO conversion and CO2 selectivity during 120 h time-on-stream test.

Preferential Oxidation of CO in H2-Rich Stream Over Au/CeO2–NiO Catalysts: Effect of the Preparation Method

Two methods, viz., the hydrothermal (HT) and co-precipitation (CP) methods, were used to prepare CeO2–NiO composite oxides; with them as the supports, Au/CeO2–NiO catalysts were prepared by the colloidal deposition method and used in the preferential oxidation (PROX) of CO in H2-rich stream. Various characterization measures such as N2 sorption, XRD, TEM, H2-TPR, Raman spectroscopy and XPS were used to clarify the influence of preparation method on the structure of CeO2–NiO support and the performance of Au/CeO2–NiO catalyst. The XPS and TEM results reveal that the CeO2–NiO(HT) support prepared by hydrothermal method displays a uniform rod-like shape and exposes preferentially the (110) and (100) planes of CeO2, whereas the CeO2–NiO(CP) support prepared by co-precipitation method is composed of nanorods and irregular nanoparticles dominated by (111) facets of CeO2. After deposition of gold, both the Au/CeO2–NiO(HT) and Au/CeO2–NiO(CP) catalysts are alike in the state and size distribution of deposited Au nanoparticles. The H2-TPR results indicate that the presence of Au strongly promotes the reduction of CeO2 in the Au/CeO2–NiO catalyst. Raman spectra illustrate that the incorporation of Ni ions into CeO2 remarkably increases the amount of oxygen vacancies in the CeO2–NiO supports, especially in CeO2–NiO(HT) prepared by hydrothermal method, which is beneficial to the dispersion and stabilization of gold species. The structure of CeO2–NiO support and catalytic activity of Au/CeO2–NiO in CO PROX is strongly related to the preparation method; Au/CeO2–NiO(HT) exhibits much higher activity than Au/CeO2–NiO(CP). The larger fraction of (110) and (100) CeO2 facets in CeO2–NiO(HT) can promote the dispersion of gold species, formation of oxygen vacancies and migration of oxygen species, which are effective to enhance the redox capacity and activity of the obtained Au/CeO2–NiO(HT) catalyst for CO PROX in H2-rich stream. Au supported on CeO2–NiO nanorods prepared by hydrothermal method exhibits much higher catalytic activity for CO PROX in H2-rich stream.

Promoted the reduction of Cu2+ to enhance CuO[sbnd]CeO2 catalysts for CO preferential oxidation in H2-rich streams: Effects of preparation methods and copper precursors

A series of CuOCeO2 catalyst samples synthesized by using various methods (CuCe-SF-N, CuCe-UGC-N, CuCe-SG-N and CuCe-ST-N) and copper precursors (CuCe-SF-N, CuCe-SF-C, CuCe-SF-A and CuCe-SF-S) were estimated for CO preferential oxidation in H2-rich streams. It was found that both synthesis routes and copper precursors have an important effect on catalytic behaviors of CuOCeO2 catalyst. Compared to CuCe-UGC-N, CuCe-SG-N and CuCe-ST-N, CuCe-SF-N exhibits the lowest temperature and the widest temperature window for 100% CO conversion (about 50 °C), which should be attributed to synergistic effects of smaller crystallite size, the formation of more Cu+ species together with the high ratio of Ce3+/(Ce3++Ce4+). Among the four catalysts prepared with different Cu precursors (CuCe-SF-N, CuCe-SF-C, CuCe-SF-A and CuCe-SF-S), the corresponding CO conversions of them are in the order of CuCe-SF-N > CuCe-SF-A > CuCe-SF-C » CuCe-SF-S. The lowest catalytic activity of CuCe-SF-S should be due to the presence of SO42− species covered on the surface of the catalyst, which not only results in the formation of the less Cu active species but inhibits the interaction between Cu species and CeO2. In addition, the optimal CuCe-SF-N catalyst displays relative stability during the 200 h time-on-stream test even in the presence of H2O and CO2.

Rapid synthesis of Fe-doped CuO-Ce0.8Zr0.2O2 catalysts for CO preferential oxidation in H2-rich streams: Effect of iron source and the ratio of Fe/Cu

Abstract A facile route (urea grind combustion method) is described for the rapid synthesis of Fe-doped Cu-Ce-Zr catalysts within 30 min through simple grinding and combustion. The effects of iron source and Fe/Cu mass ratio on the performances of the catalysts for CO preferential oxidation (CO-PROX) are evaluated. The influences of H 2 O, CO 2 , and their mixture on the activity as well as stability of the catalysts are also investigated. The samples are characterized by XRD, N 2 adsorption-desorption, H 2 -TPR, TEM, Raman and XPS. Fe(NO 3 ) 3 is found to be superior to FeCl 3 and Fe 2 (SO 4 ) 3 as the iron source for Fe-CuCZ catalyst. Among the different synthesized catalysts, 1/10Fe (N) -CuCZ is found to be the most active catalyst, indicating that the optimal Fe/Cu mass ratio is 1/10. The influences of H 2 O, CO 2 , and H 2 O + CO 2 on the catalytic performance of 1/10Fe (N) -CuCZ are in the order of CO 2 2 + H 2 O 2 O. 1/10Fe (N) -CuCZ exhibits excellent stability during a 228 h time-on-stream test. 1/10Fe (N) -CuCZ shows the highest catalytic activity and excellent stability even in the presence of H 2 O and CO 2. The excellent catalytic performance can be attributed to the synergy between the highly dispersed copper species and ceria, as well as the formation of more oxygen vacancies and reduced copper species.

Effect of carbon dioxide and water on the performances of an iron-promoted copper/ceria catalyst for CO preferential oxidation in H2-rich streams

The catalytic behavior of an iron-promoted copper/ceria catalyst towards CO-PROX reaction under feed mixtures containing variable concentrations of CO2 (0–15 vol.%) and H2O (0–10 vol.%) was compared to that of an unpromoted sample with the same copper loading. At low temperature both species inhibit CO conversion on Fe-promoted catalyst more than on the reference Cu/CeO2 catalyst, although the performance is restored more rapidly to that corresponding to CO2-free conditions by increasing the temperature. CO2 temperature programmed desorption tests were carried out and experimental curves modeled to evaluate quantitatively the active sites for CO and H2 oxidation. Iron addition significantly reduced the amount of H2 oxidation sites, likely promoting copper dispersion, leading to the observed better selectivity under CO2-free conditions. The inhibiting effect of CO2 was ascribed to the formation of quite stable CO2 adsorbed species blocking copper active sites. The different dependence on the temperature of CO2 desorption results in a higher inhibition at low temperature for the Fe-promoted catalyst, but also in an easier CO2 desorption at higher temperature restoring the performance under CO2-free conditions for this sample.

A novel and facile method to rapidly synthesize Ce0.8Zr0.2O2 nanoparticles for CO preferential oxidation in H2-rich stream.

A novel urea grind combustion (UGC) route was reported in this paper to rapidly prepare the ceria-zirconia nanoparticles (Ce0.8Zr0.2O2). For comparison, the conventional surfactant-assisted (SA) and sol-gel (SG) methods were also employed to prepare Ce0.8Zr0.2O2 nanoparticles. CO preferential oxidation in H2-rich stream (CO-PROX) was chosen as probe reaction to investigate the catalytic performance of these Ce0.8Zr0.2O2 catalysts prepared with different methods to highlight the superiority of UGC. It was found that Ce0.8Zr0.2O2-UGC showed the better reducibility and oxygen mobility than the Ce0.8Zr0.2O2 prepared by SA and SG, because the UGC route favored the more incorporation of zirconia into CeO2, leading to more serious distortion of the structure, and more defective sites in the Ce0.8Zr0.2O2. As a result, Ce0.8Zr0.2O2-UGC exhibited the higher CO conversion, better O2 selectivity, and excellent catalytic stability without any deactivation during 72-h reaction on stream. More importantly, the UGC method, as compared to the relatively complex and time-consuming SA and SG method, is simple, facile, low-cost, time-saving (within 30 minutes) and scalable, thereby, might be very promising for the application in many fields.

Highly active subnano Rh/Fe(OH)x catalyst for preferential oxidation of CO in H2-rich stream

A novel catalyst formulation of 3.1wt.% Rh/Fe(OH)x was prepared via a co-precipitation method and investigated for CO preferential oxidation in H2-rich stream. This catalyst exhibited a wider temperature range of 20–70°C for CO total removal and better resistance to CO2 and H2O compared with the standard gold catalyst, standing out as the best Rh-based catalyst ever. The Rh species were highly dispersed in a subnano scale of ∼1nm and improved the reducibility of Fe(OH)x support. The adsorption of O2 was thus promoted over the reduced support, together with the weakened CO adsorption over the Rh clusters, permitting a non-competitive Langmuir–Hinshelwood mechanism through the elementary reaction of CO(ad)+O(ad). The reaction rate equation of r=k[CO]0.73[O2]0.64 and small apparent activation energy of 24kJmol−1 were then derived from the kinetic studies.

Optimization of the preparation method of CuO/CeO2 structured catalytic monolith for CO preferential oxidation in H2-rich streams

Copper/ceria washcoated monoliths were prepared by a modified dip coating procedure and operated under CO-PROX conditions. Slurry preparation was suitably modified with respect to more conventional procedure in order to improve the washcoat adhesion onto the cordierite walls. Wet instead of dry milling of the powder ceria used to prepare slurry and colloidal ceria addition to the slurry significantly improved washcoat adhesion, due to partial penetration of the washcoat into the cordierite macropores. Moreover, ceria specific surface area and pore size distribution were affected by both preparation and composition of slurry. Samples prepared by modified slurries showed also improved copper dispersion with a consequent higher selectivity to CO2.

CuO/CeO2 based monoliths for CO preferential oxidation in H2-rich streams

Copper/ceria washcoated monoliths were prepared by means of a modified dip coating procedure and operated under CO-PROX conditions. The effect of the substrate properties (cell density and wall thermal conductivity) was studied. The significant role of the temperature profile on the performances (CO conversion and selectivity to CO2) was found by testing monoliths with different cell density and wall thermal conductivity. High cell density monoliths with substrate showing the higher thermal conductivity (SiC) appear the best option, providing the best thermal management of the process.