Activity For CO Preferential Oxidation Research Articles

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.

In situ construction of a highly active surface interface for a Co3O4|ZrO2 catalyst enhancing the CO-PrOx activity

Employing a reduction–oxidation pretreatment led to the modification of the Co3O4|ZrO2 catalyst surface for the preferential oxidation of CO. It was shown, using XPS and temperature-programmed studies (O2-, CO-, CO2-TPD), that the amount of Co2+ species, O2 activation, CO2 desorption and CO adsorption sites improved. This was due to the restructuring of Co3O4 to more CoO species on the ZrO2 surface forming a highly active Co3O4–CoO|ZrO2 interface. This restructuring was supported by in situ XRD and XPS analysis which showed a decrease in the Co3O4 phase, without the emergence of metallic cobalt. The stabilization of more CoO species on the catalyst surface led to more basic sites being available on the surface, due to more oxygen anions/OH species, leading to improved CO2 desorption sites, which enhanced the CO oxidation activity. The balancing of these properties led to a 100% CO conversion (under dry and wet conditions) and excellent CO selectivity of 80% under wet conditions was achieved. The present finding highlights the importance of surface modification for improving CO preferential oxidation activity.

Purification of H2-rich streams by CO preferential oxidation over Pt nanoparticles supported on ordered porous silica

In this work, the performance of mesostructured Pt catalysts is studied for the preferential oxidation of CO in H2-rich environments under a wide range of operating conditions. The catalysts were synthesized by incipient wetness impregnation and characterized by nitrogen sorptometry, transmission electron microscopy, X-ray diffraction, temperature-programmed reduction by hydrogen, H2 chemisorption and inductively coupled plasma-atomic emission spectroscopy. The influence of Pt content, the presence of aluminium in the mesoporous structure, as well as different catalyst preteatments were studied. The samples showed promising results in terms of activity, selectivity and stability. Pt (1%)/Al-MCM-41 exhibits high activity for CO preferential oxidation at 120 °C, when pretreated with hydrogen and shows stability for 80 h on-stream, even when steam and CO2 is fed in the inlet stream.

Enhanced Activity for CO Preferential Oxidation over CuO Catalysts Supported on Nanosized CeO2 with High Surface Area and Defects

Nanosizedceria (n-CeO2) was synthesized by a facile method in 2-methylimidazolesolution. The characterization results of XRD, N2 adsorption-desorption, Raman and TEM indicate that n-CeO2 shows a regular size of 10 ± 1 nm, a high surface area of 130 m2·g−1 and oxygen vacancies on the surface. A series of CuO/n-CeO2 catalysts (CuCeOX) with different copper loading were prepared for the preferential oxidation of CO in H2-rich gases (CO-PROX). All CuCeOX catalysts exhibit a high catalytic activity due to the excellent structural properties of n-CeO2, over which the 100% conversion of CO is obtained at 120 °C. The catalytic activity of CuCeOX catalysts increases in the order of CuCeO12 < CuCeO3 < CuCeO6 < CuCeO9. It is in good agreement with the order of the amount of active Cu+ species, Ce3+ species and oxygen vacancies on these catalysts, suggesting that the strength of interaction between highly dispersed CuO species and n-CeO2 is the decisive factor for the activity. The stronger interaction results in the formation of more readily reducible copper species on CuCeO9, which shows the highest activity with high stability and the broadest temperature “window” for complete CO conversion (120–180 °C).

Strong metal-support interaction promoted via constructing biocarbon membrane for enhanced CO preferential oxidation activity of Rh/CaCO3@biocarbon

Precious metal nanoparticles, widely used as heterogeneous catalysts, are easy to aggregate and deactivate, restricting their applications in many important catalytic fields like preferential CO oxidation (CO-PROX) in H2-rich stream. In this work, well dispersed Rh nanoclusters anchored on CaCO3@biocarbon derived from waste eggshell (ESMC) were synthesized through a step carbonization and incipient wetness impregnation process. The obtained catalysts exhibited 3D macroporous architecture, which is favorable for exposure of more nucleation sites of precious metal Rh, thus minimizing the aggregation of Rh particles. Furthermore, a thick carbon shell attached to eggshells, with interesting electronic structure and surface chemistry, efficiently transfers electrons between Rh and biocarbon@CaCO3 support, and enhances the interaction between Rh NPs and support. Both effects synergistically allow Rh/ESMC to equip more active adsorption sites-asymmetric Rh(CO)2 gem-dicarbonyl, thus greatly promoting the catalytic performance of Rh/ESMC in CO-PROX (operation temperature window: 140–240 °C). The present finding offers an environmentally friendly approach to fabricate well dispersed Rh nanoclusters catalysts, and it can be extended to rationally design other supported metal nanoparticle catalysts.

Retraction of “Enhanced Activity for CO Preferential Oxidation via the CeO2–LaCoO3 Interaction”

ADVERTISEMENT RETURN TO ISSUEPREVRetractionNEXTRetraction of “Enhanced Activity for CO Preferential Oxidation via the CeO2–LaCoO3 Interaction”Yuhao WangYuhao WangMore by Yuhao Wang, Yane Zheng*Yane ZhengMore by Yane Zheng, Hua WangHua WangMore by Hua Wang, Kongzhai LiKongzhai LiMore by Kongzhai Li, Xing ZhuXing ZhuMore by Xing Zhu, Yonggang WeiYonggang WeiMore by Yonggang Wei, Yaming WangYaming WangMore by Yaming Wang, Lihong JiangLihong JiangMore by Lihong Jiang, and Dong TianDong TianMore by Dong TianCite this: Ind. Eng. Chem. Res. 2019, 58, 11, 4710Publication Date (Web):January 4, 2019Publication History Received17 November 2018Accepted28 December 2018Revised26 December 2018Published online4 January 2019Published inissue 20 March 2019https://doi.org/10.1021/acs.iecr.8b05727Copyright © 2019 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1149Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (169 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Enhancing the CO Preferential Oxidation (CO-PROX) of CuO–CeO2/Reduced Graphene Oxide (rGO) by Conductive rGO-Wrapping Based on the Interfacial Charge Transfer

Reduced graphene oxide supported CuO–CeO2 nanospheres (CuO–CeO2/rGO) were prepared by a facile hydrothermal method. The chemically bonded CuO–CeO2/rGO composites effectively enhanced their activity in the CO preferential oxidation (CO-PROX), while moderate rGO content (7 mg) exhibited an improvement on the catalytic activity. The prepared composite with 14 wt% rGO showed the highest catalytic activity, exceeding that of pure CuO–CeO2 and mechanically mixed CuO–CeO2 and rGO, respectively. The enhancement in the CO-PROX activity was attributed to the synergetic effect between rGO and CuO–CeO2 nanospheres. Besides supported rGO layers as excellent electron transporters, CuO–CeO2 nanospheres in turn act as the skeleton to brace two-dimensional structure to prevent from further curling, crumpling and aggregation of rGO. In the presence of capping agents during synthesis, limited catalytic activities of CuO–CeO2/rGO was observed due to the restrained interfacial charge transfer between CuO–CeO2 and rGO layers. This work, focusing on effective CO-PROX through a chemically bonded interface between CuO–CeO2 and rGO, can provide a new insight for design of new heterogeneous catalysts. Chemical bonded CuO–CeO2/rGO nanocomposites synthesized by a facile hydrothermal approach have shown high CO-PROX activity. Excellent charge transport between rGO layers and CuO–CeO2 nanospheres via their interfaces leads to enhanced catalytic activity for CO-PROX.

Computation-Guided Development of Platinum Alloy Catalyst for Carbon Monoxide Preferential Oxidation

Carbon monoxide preferential oxidation (PROX) in an H2-rich stream represents one promising H2 purification technology but requires the development of active and selective catalysts to make the technology viable. We conducted density functional theory simulations of CO PROX catalysis on model Pt alloy systems to establish correlations between the catalyst parameters and the catalytic properties, which validated EA,COOR and EA,HOR as descriptors for CO oxidation and H2 oxidation kinetics, ΔEA as a descriptor for CO PROX selectivity, and ed as a catalyst parameter descriptor for the activation energy barriers. We discovered an interesting compromising relationship between the CO PROX activity and selectivity properties. Pt-Ni and Pt-Mn nanoparticle catalysts were selected for synthesis on the basis of the computational data and tested for their properties, which matched well with the DFT calculations and verified the effectiveness of the computational findings. The use of computation-guided methods and the ...

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.

Comparative studies of leached Pt-Fe and Pt-Co catalysts for CO oxidation reactions

Leached Pt-Fe and Pt-Co catalysts were prepared by acid leaching the reduced catalysts in acid solution. Oxidation treatments of leached catalysts produced the structure of metal oxides decorating the surface of nanoparticles. The fully oxidized Fe 2 O 3 and Co 3 O 4 species on Pt nanoparticle surfaces result in the low performance of the CO complete oxidation (COOX) reaction. In contrast, unsaturated FeO and CoO surface species can be formed during exposure to the CO preferential oxidation (CO-PROX) reaction with an excess of H 2 , leading to a high O 2 activation ability and enhancing the CO-PROX activity. The FeO x surface structures can be transformed between these two states by varying the reactive gas environments, exhibiting oscillating activity in these two reactions. Conversely, the CoO surface structure formed in the H 2 -rich atmosphere is stable when exposed to the COOX reaction and exhibits similar activity in these two reactions. It is hoped that this work may assist in understanding the important role of surface oxides in real reactions. The structure of metal oxides on nanoparticle surfaces can be obtained by oxidizing the leached Pt-Fe and Pt-Co catalysts. The relationship between surface oxides and the catalytic performance for CO oxidation reactions was studied.

Improved Low-Temperature Activity of CuO–CeO2–ZrO2 Catalysts for Preferential Oxidation of CO in H2-Rich Streams

In this work, CuO–CeO2–ZrO2 catalysts for CO preferential oxidation have been prepared by ultrasound assisted reverse coprecipitation and slow coprecipitation, and characterized via BET, XRD, XPS and H2-TPR techniques, respectively. It is found that the catalyst prepared with ultrasound assisted reverse coprecipitation preserves large specific surface area, fine crystalline grain and high dispersion of active copper species. Meanwhile, the reducibility is improved significantly and more active copper species and oxygen vacancies are formed in the copper–ceria boundaries. The ultrasound assisted reverse coprecipitation prepared CuO–CeO2–ZrO2 catalyst exhibits superior low-temperature activity and CO2 selectivity, over which the temperature responding to 50 % CO conversion is as low as 67 °C, and the temperature window of full CO conversion is significantly widen from 100 to 160 °C. The ultrasound assisted reverse coprecipitation prepared CuO–CeO2–ZrO2 catalyst exhibits superior low-temperature activity for CO preferential oxidation and wide temperature window of full CO conversion comparing with the catalyst prepared with slow coprecipitation.

Synergy between hydrogen and ceria in Pt-catalyzed CO oxidation: An investigation on Pt–CeO2 catalysts synthesized by solution combustion

Pt–CeO2 catalysts were prepared by solution combustion synthesis (SCS), a simple and fast one-pot method, using glycine or oxalyl dihydrazide (ODH) as the fuel and Pt chloride or nitrate as the metal precursor. The samples were characterized by ICP-OES, N2 volumetry, XRD, XPS, aberration-corrected (S)TEM, CO-DRIFTS and microRaman spectroscopy. The SCS catalysts were evaluated in CO oxidation and preferential oxidation (PROX) of CO in H2 excess, and compared to Pt/CeO2 and Pt/Al2O3 catalysts prepared by incipient wetness impregnation. The glycine fuel yields better results than ODH in terms of Pt dispersion and catalytic performance. The fresh Cl-containing catalysts consist of PtO nanoparticles poorly active in CO oxidation, while the catalysts synthesized from Pt nitrate contain highly active Ptδ+ (0<δ<2) species in interaction with ceria. Consistently, the most efficient catalyst for H2-free CO oxidation is the one synthesized from glycine and Pt nitrate. For PROX, the selectivity to CO2 is 100% at low temperature and decreases in a similar way for all the Pt–CeO2 catalysts above ca. 100°C. With respect to H2-free conditions, the CO PROX activity of the Pt–CeO2 catalysts is considerably enhanced (activity multiplied by up to 60at 110°C), while the activity gain is comparatively minor for Pt/Al2O3. We conclude that hydrogen, by increasing the mobility of oxygen species at the surface of ceria, promotes the support-assisted pathway of CO oxidation.

Three dimensionally ordered macroporous Au/CeO2 catalysts synthesized via different methods for enhanced CO preferential oxidation in H2-rich gases

Three dimensionally ordered macroporous (3DOM) Au/CeO2 catalysts were synthesized via a thermal decomposition-assisted colloidal crystal templating method following different synthetic procedures using citric acid and oxalic acid as chelating ligands and CeCl3 and Ce(NO3)3 as cerium salt precursors. All 3DOM Au/CeO2 catalysts possess well-defined 3DOM skeletons composed of well-crystallized CeO2 nanoparticles, based on the different synthetic procedures, the 3DOM Au/CeO2 catalysts show variations in surface elemental compositions, particle sizes of CeO2, macroporous and mesoporous structures, and valence states of Au. The mesoporous walls with nanopores ∼3–4 nm on 3DOM Au/CeO2 skeletons can be created when using Ce(NO3)3 as precursor. The catalytic performance of 3DOM Au/CeO2 catalysts for CO preferential oxidation in H2-rich gases was systematically investigated. The catalytic performance is closely correlated to surface elemental compositions, particle sizes of CeO2, macroporous and mesoporous structures, and valence states of Au due to the different synthetic procedures. The 3DOM Au/CeO2 catalysts prepared using oxalic acid as chelating ligand and Ce(NO3)3 as cerium salt precursor show the highest catalytic activity for CO preferential oxidation in H2-rich gases with 90.1% CO conversion and 59.9% CO2 selectivity at 50 °C, and 88.3% CO conversion and 59.3% CO2 selectivity at 80 °C, respectively. The obtained 3DOM Au/CeO2 catalysts may be of importance for guiding the design of efficient catalysts with desired porous structures that are potentially applicable in polymer electrolyte membrane fuel cells.

Study of the synthesis of CeO2 nanoparticles for their use in CO preferential oxidation (COPrOx)

CeO2 nanoparticles were synthesized by the controlled precipitation method from a Ce(NO3)3 solution. To this end, two additives were used alternatively: ethylene glycol (EG) and tetramethylammonium hydroxide (TMAH). Their function was to reduce the particle size obtained after the synthesis. After precipitation and drying, nitrate and organic residuals must be removed, and the method employed for this step could affect the structure and size of the particles. This is an important issue for achieving contaminant-free measurements in catalytic tests. In order to optimize the residuals removing process, a thorough study of the species present and/or eliminated was carried out. Our findings show that a calcination temperature of at least 500°C is necessary in order to accomplish the complete removal of solvent and precursors such as NO3-. Among the catalysts studied, the one prepared with EG showed the best activity for CO preferential oxidation. In order to study the effect of the residuals upon the catalytic activity, samples prepared using EG were calcined at different temperatures and tested for the COPrOx reaction. CO conversions for all the samples were between 80% and 93% at different temperatures. The best activity was obtained with the sample calcined at 500°C, which is in agreement with the minimum temperature necessary for the total elimination of residuals.

γ-Fe 2O 3-supported Pt-Cu nanoparticles synthesized by radiolytic process for catalytic CO preferential oxidation

Pt-Cu bimetallic nanoparticles immobilized on γ-Fe 2O 3 support were synthesized by a unique radiolytic process and their physical properties and catalytic activity for CO preferential oxidation were investigated for various Pt/Cu atomic ratios. The chemical composition of the catalysts measured by inductively coupled plasma revealed most of the platinum and copper aqueous precursors were deposited on to the γ-Fe 2O 3 support after irradiation with electron beam. Crystallographic analysis of the catalysts by X-ray diffraction showed Pt-Cu alloy is formed for wide range of Pt/Cu ratio. From the lattice parameter of this Pt-Cu alloy, it was found that Cu can be incorporated into Pt lattice up to 30 at% with the present irradiation condition. The rest of Cu for high-Cu (low-Pt) samples was identified as divalent oxide with poor crystallinity by XANES spectrum. Detailed STEM-EDX analyses further confirmed that Pt-Cu alloy exists as nanoparticles with a few nanometers in diameter and CuO with low crystallinity distributes on entire surface of the γ-Fe 2O 3 support. The PROX activity showed different trends between high-Pt and high-Cu samples. The CO conversion decreased as the Pt loading was decreased to 50 at%, and it monotonically decreased with increasing temperature. However, as the Pt loading was further decreased, the activity increased with temperature by contraries, and reached the maximum conversion at 100 °C. Regardless of the low Pt loading, the sample with 10 at% Pt and 90 at% Cu exhibited the highest activity at 100 °C, which is preferable for low temperature fuel cell applications. This enhanced activity was attributed to oxygen supply via the copper of low crystallinity from the O 2-poor atmosphere to Pt-Cu alloy particles that chemisorbs CO molecules.

Reaction and Surface Characterization Studies of Ru/Al2O3 Catalysts for CO Preferential Oxidation in Reformed Gas

In order to investigate the reasons the activation of a Ru/Al2O3 catalyst by heating in a H2/N2 mixed gas improves the CO preferential oxidation (PROX) activity, the oxidation state of the Ru on the catalyst surface was studied by using ESCA. As the ratio of Ru(0) to total Ru on the surface was increased, the temperature window of the Ru catalyst, where CO was reduced to below 10 ppm, was expanded to the lower temperature side. The activity of CO oxidation by O2 of the Ru catalyst at lower temperatures was improved by increasing the ratio of Ru(0). However, the selectivity for CO oxidation hardly varied with the change in the surface Ru(0) ratio at these low temperatures. It is considered that O2 activation on Ru(0) plays an essential role in CO PROX activity on the Ru catalyst at low temperatures.

A study of CO removal on an activated Ru catalyst for polymer electrolyte fuel cell applications

The influence of pre-treatment of a Ru/Al 2O 3 catalyst on the CO preferential oxidation activity was studied for the residential polymer electrolyte fuel cell (PEFC) cogeneration system. When a Ru/Al 2O 3 catalyst was heated in a H 2/N 2 mixed gas flow as the pre-treatment, the CO oxidation activity was highly improved at a low temperature range. When an activated Ru/Al 2O 3 catalyst was used with the pre-treatment, CO was removed from the simulated reformed gas to less than 6 ppm at [O 2]/[CO]=1.0 and to less than 0.5 ppm at [O 2]/[CO]=1.5. However, CO was not removed to below 10 ppm at [O 2]/[CO]=1.5 on a non-activated Ru/Al 2O 3 catalyst without the pre-treatment. The temperature window, where CO was removed to below 10 ppm, of the activated Ru/Al 2O 3 catalyst was between ca. 90 °C and ca. 140 °C at [O 2]/[CO]=1.0 and between ca. 85 °C and ca. 170 °C at [O 2]/[CO]=1.5, while that of the non-activated Ru catalyst was between ca. 155 °C and ca. 180 °C at [O 2]/[CO]=3.0.