Catalytic Oxidation Of Carbon Monoxide Research Articles

Catalytic oxidation of carbon monoxide at low temperature using AuRh/TiO2 bimetallic catalysts: Effect of the synthesis method

AuRh nanoparticles supported on TiO2 P25 were synthesized by two sequential deposition methods: sequential deposition-precipitation with urea (DPU) and impregnation (IMP)-DPU. Segregated nanoparticles (RhcoreAushell ball-cup-type, and Janus-type arrangements) were observed in gold-rhodium bimetallic catalysts, but mainly ball-cup-type and Janus-type nanoparticles were found on catalysts prepared by IMP-DPU. XPS analysis of gold-rhodium bimetallic catalysts, before and after reaction allowed concluding that gold-rhodium interaction on metallic state was an important factor to avoid the oxidation of rhodium during CO oxidation. However, this effect of stabilization of the rhodium metallic phase by gold does not fully explain the promoting effect observed for some bimetallic catalysts on CO oxidation. Some structural aspects such as the atomic arrangement of the bimetallic nanoparticles and the type of active sites, determined by DRIFTS-CO, were also considered. TPR and UV–visible DR spectroscopy characterizations also showed differences in the gold-rhodium interactions.

Oxygen vacancies promote the activation of O2 in transition metal oxide doped ε-MnO2 for low-temperature CO oxidation

Carbon monoxide (CO), a toxic pollutant usually formed from incomprehensive combustion especially at low temperature, has harmful effects on human health. Therefore, the catalytic oxidation of CO always receives widespread attention. Herein, we reported transition metal (Cu, Co, Ni, Fe) doped ε-MnO2 as CO catalysts using a hydrothermal-deposition method. Physiochemical properties for CO oxidation were meticulously analyzed employing characterization techniques such as SEM, XRD, BET, XPS, EPR, CO-TPR. The doped ε-MnO2 catalyst showed expanded BET surface area, increased oxygen vacancy defects, more active sites, enhanced adsorption, and faster electron transfer. Catalytic activity tests indicated that the ε-MnO2 catalyst doped with transition metals exhibited exceptionally high catalytic activity, with the Cu-doped catalyst showing the fastest chemical reaction rate and the lowest complete conversion reaction temperature (TOF of 9.92 × 10−3 s−1, at 65℃). Density Functional Theory (DFT) calculations indicated that Cu doping more effectively induced oxygen vacancy defects compared to Co, Ni, Fe, and raw ε-MnO2 catalysts. It identifies the CO oxidation reaction and improved the CO adsorption capacity of the catalyst. Furthermore, a novel potential reaction pathway for the M-vK mechanism in transition metal oxides was proposed.

Enhanced Catalytic Performance and Tolerance to Carbon Monoxide Poisoning of CoO/PtPd/r‐GO Nanocomposite Thin Film for Methanol Fuel Cells

This study presents the facile synthesis of CoO/PtPd and CoO/PtPd/reduced‐graphene oxide (r‐GO) nanocomposites, highlighting their significant role in methanol fuel cells. To create a CoO/PtPd thin film at the toluene/water interface, we employed NaBH4 to effectively reduce PtCl2(COD), PdCl2(COD), and Co (acac)3 (COD = cis,cis‐1,5‐ cyclooctadiene, acac = acetylacetonate). The two nanocomposites were analyzed using XRD, FE‐SEM, AFM, XPS, BET, and TEM techniques. In the electrooxidation of methanol in the anodic part of fuel cell, cobalt (II) oxide can serve as an oxygen source in the catalytic oxidation of carbon monoxide (CO) or it can play a role in producing the HO‐CoO intermediate to facilitate the oxidation of CO‐PtPd to carbon dioxide (CO2). This reaction can help eliminate CO, which is a common poison for Pt‐based catalysts in methanol oxidation. Our research reveals significant improvements in current densities and catalyst tolerance when using the CoO/PtPd/r‐GO nanocomposite thin film. The observed current density for CoO/PtPd/r‐GO is 263.33 mA.cm−2, surpassing the reported value of 30.00 mA.cm−2 for PtPd/r‐GO. The jf/jb ratios, commonly used to evaluate catalyst tolerance, are approximately 2.80 for CoO/PtPd and 4.98 for CoO/PtPd/r‐GO, in contrast to ratios larger than 0.99 for ETEK Pt and 0.58 for other types of commercial Pt/C. These findings indicate that the CoO/PtPd/r‐GO thin film exhibits enhanced catalytic performance and improved tolerance to CO poisoning. Furthermore, the power output calculated for CoO/PtPd/r‐GO is 104.5 mW·cm−2, which is comparable to the reported value of 48.03 mW·cm−2 for commercial Pt/C. These results demonstrate the potential of the CoO/PtPd/r‐GO nanocomposite thin film as a promising alternative to traditional catalyst materials in methanol fuel cells.

Simultaneous catalytic oxidation of toluene and CO over Cu-V/Al-Ce catalysts: Physicochemical properties-activity relationship and simultaneous oxidation mechanism

Cu-V/Al-Ce with varying ratios of Al2O3/CeO2 were prepared to study the simultaneous catalytic oxidation of toluene and CO. Experimental results show that Cu-V/20Al-80Ce exhibits optimal simultaneous oxidation activity and good durability. This superior performance is related to Cu-Ce, V-Ce, and Al-Ce interactions, which facilitate the exposure of active centers, the creation of oxygen vacanicies, and efficient electron transfer. The mutual influence between toluene and CO during the simultaneous oxidation is then demonstrated. Toluene hinders CO oxidation through the competitive adsorption and the consumption of reactive oxygen species. CO enhances toluene oxidation, which is comprehensively explained by affecting the competition between the desorption and oxidation of benzaldehyde. Despite the mutual influence between toluene and CO, the pathways of CO and toluene oxidation are mutually independent. Toluene oxidation proceeds sequentially from toluene to benzyl alcohol, benzaldehyde, benzoate, and finally to CO2. Before being completely oxidized to CO2, CO is initially converted to carboxylic acid, hydrogen carbonate, free carbonate ion, bidentate formate, and monodentate carbonate.

Enhancing the Catalytic Oxidation of Carbon Monoxide Using K-OMS-2 by Surface Modification with Binary Oxides of Copper and Other Metals

Enhancing the Catalytic Oxidation of Carbon Monoxide Using K-OMS-2 by Surface Modification with Binary Oxides of Copper and Other Metals

Incorporation of Epoxy Carbon onto CeO2-Supported Pt to Tackle the CO Self-Poisoning Issue.

The catalytic oxidation of carbon monoxide (CO) under ambient conditions plays a crucial role in the abatement of indoor CO, which poses risks to human health. Despite the notable activity exhibited by Pt-based catalysts in CO oxidation, their efficacy is usually diminished by the CO self-poisoning issue. In this work, three different Pt/CeO2-based catalysts, which have distinct coordinative environments of Pt but an identical Pt/CeO2 substrate structure, were synthesized by activating the catalyst with CO using different temperatures and durations. Compared with clean and graphite-covered Pt on CeO2, the one modified by epoxy carbon showed higher activity and stability. The combination of characterizations and density functional theory modeling demonstrated that the clean Pt on CeO2 rapidly deactivated due to the CO self-poisoning albeit high initial activity, and conversely, low initial activity was observed for the more stable graphite-covered catalyst due to the obstruction of the Pt site. In contrast, epoxy carbon species on Pt shifted the d-band of Pt to lower energy, weakening the Pt-CO binding strength. Such a modification mitigated the self-poisoning effect while maintaining ample active sites and enabling the complete oxidative removal of CO under ambient conditions. This work may provide a general approach to tackling the self-poisoning issue.

Simultaneously accomplishing selective catalytic reduction of NO and catalytic oxidation of CO in a catalyst coupling system

Considering that nitrogen oxides (NOx) and carbon monoxide (CO) usually meantime exist in industrial flue gas, it is meaningful to develop a collaborative control technology for the simultaneous purification of NOx and CO. In this work, the catalysts xCu-1V-5W/Ti were evaluated in the simultaneously selective catalytic reduction by NH3 (NH3-SCR) and CO oxidation. The introduction of CuO provided the active sites for the oxidation of CO, while inhibited the NH3-SCR process and facilitated the generation of N2O by-product at high temperature. Accordingly, a catalyst coupling system was designed by employing 1V-5W/Ti and 2Cu-1V-5W/Ti catalysts in one reactor, and high NO conversion (>90 %) and CO removal efficiency (>80 %) could be simultaneously realized within 350–500 °C. This work would provide valuable insights for achieving simultaneous removal of NOx and CO using the catalyst coupling method.

Catalytic oxidation of carbon monoxide over copper oxide with interfering gases involved for industrial buildings: An experimental and theoretical study

With the intention of thoroughly eliminating carbon monoxide (CO) from indoor environment, it is one of the most promising methods of converting it into carbon dioxide (CO2) via catalytic oxidation processes. Therefore, in this study, catalytic oxidation mechanisms of CO over copper oxide (CuO) with interfering gases involved are investigated via theoretical calculations and experimental verification, which mainly include basic catalytic oxidation processes over CuO, effects of different interfering gases and analyses of thermodynamic features. According to results, catalytic oxidation of CO over CuO can be performed in three different routes and rate-determining transition-state (TS) energy barriers vary a lot from route to route at high temperature owing to different thermal stability. In the meantime, SO2, H2O and NO are theoretically proved to affect catalytic oxidation of CO via competitive adsorption, high oxidizability and hydrogen bonds, which are accompanied with different sensitivities to changes of temperature or temperature power exponents. In experiments, it is found that impurity of lattice planes and small specific surface areas in CuO are key to restricting catalytic oxidation performances. What is more, some extra chemical reactions in experiments (e.g. SO2 + O2 + CuO → CuSO4, NO + O2 + CO → CO2 + NO) caused by interfering gases colossally affect catalytic oxidation performances of CuO. The whole study provides crucial information for indoor air purification in industrial buildings by using cheap adsorbents/catalysts.

Ultrathin 3D CoMn nanoflowers coupled diatomite for highly efficient catalytic oxidation of CO and propane

Manganese oxides are promising catalysts for the treatment of VOC gas pollutants due to variable valences and abundant oxygen vacancies. The surface properties of manganese oxides significantly affect their catalytic activity. Thus, the development of appropriate modulation strategies for manganese oxides is of great significance. Herein, ultrathin (1–2 nm) three-dimensional (3D) CoMn nanoflowers have been in-situ planted on the surface of a naturally abundant resource – diatomite. Due to the open diffusion channels of diatomite and 3D coordination of CoMn nanoparticles, more open space and exposed sites are created for the transport and migration of O2, CO and propane. Compared to the pure CoMn, the obtained cobalt-manganese/diatomite (CoMn/Dia) composite contains more surface defect sites and oxygen vacancies, resulting in 90 % of carbon monoxide (CO) and propane (C3H8) conversion at as low as 108 °C and 250 °C, respectively. Density functional theory (DFT) results demonstrate that the doping of Co elements and the ultrathin structure of CoMn nanoflowers induce the formation of oxygen vacancies and weaken the Mn-O-Co bond in CoMn/Dia composites, which significantly accelerate the oxygen cycling during the oxidation reactions of CO and propane. In addition, the prepared CoMn/Dia catalyst exhibits excellent stability with consistent catalytic efficiency achieved for 70 h. Due to the simple synthesis method and lower cost raw materials, this research provides new insight into the scale-up production of efficient and economical Mn-based catalysts.

Enhanced CO oxidation performance over hierarchical flower-like Co3O4 based nanosheets via optimizing oxygen activation and CO chemisorption

Enhancing low-temperature activity is a focus for carbon monoxide (CO) elimination by catalytic oxidation. In this work, the hierarchical flower-like silver (Ag) modified cobalt oxides (Co3O4) nanosheets were prepared by solvothermal method and applied into catalytic CO oxidation. The doped Ag species in the form of AgCoO2 induced the prolongated surface Co–O bond and weaker bond intensity. Consequently, the oxygen activation/migration ability and redox capacity of Ag0.02Co were enhanced with more oxygen vacancies. The chemisorbed CO was preferentially converted to CO2 but not carbonates. The inhibited carbonates accumulation could avoid the coverage of active sites. According to Density functional theory (DFT) calculations, the electron transfer from AgCoO2 to Co3O4 promote electron donation ability of Co3O4 layer, benefiting for oxygen activation. Moreover, the longer Co–C and C–O bond length suggest the weakened chemisorption strength and higher active of CO molecule. The Ag modified Co3O4 exhibited more satisfactory activity at lower temperature. Typically, it realized 100% CO conversion at 90 °C, and displayed 6.3-fold higher reaction rate than pristine Co3O4 at 40 °C. Moreover, the Ag0.02Co exhibited outstanding long-term stability and water resistance. In summary, the optimized oxygen activation, CO chemisorption and interfacial electron transfer synergistically boosted the CO oxidation activity on Ag modified Co3O4.

Synthesis of Inexpensive Ternary Metal Oxides by a Co-Precipitation Method for Catalytic Oxidation of Carbon Monoxide.

By using a simple co-precipitation method, new Fe2 O3 -based nanocatalysts (samples) were synthesized. The samples were composites of two or three transition metal oxides, MOx (M=Fe, Mn, Co, Ni, and Cu). The average size of CuO crystallites in the composites composed of two oxide components (CuO-Fe2 O3 ) was about 14.3 nm, while in those composed of three (CuO-MnOx -Fe2 O3 ), the composite's phase compositions were almost in the amorphous form when annealing the sample at 300 °C. The latter sample had a specific surface area higher than that of the former, 207.9 and 142.1 g/m2 , respectively, explaining its higher catalytic CO oxidation. The CO conversion over the CuO-MnOx -Fe2 O3 -300 catalyst (1 g of catalyst, 2600 ppm of CO concentration in air, and 1.0 L/min of gas flow rate) begins at about 40 °C; the temperature for 50 % CO conversion (t50 ) is near 82 °C; and CO removal is almost complete at t99 ≈110 °C. The activity of the optimal sample was tested in different catalytic conditions, thereby observing a high durability of 99-100 % CO conversion at 130 °C. The obtained results were derived from XRD, FTIR, BET, SEM, elemental analysis and mapping, as well as catalytic experiments.

Hydrothermal synthesis of highly dispersed Bi–Ni–Sb–O pyrochlore for catalytic oxidation of carbon monoxide

The highly dispersed Bi–Ni–Sb–O pyrochlore was prepared under hydrothermal conditions with and without microwave treatment. Composite samples of NiO/(Bi–Ni–Sb–O pyrochlore) demonstrated consistently high activity without pretreatment in CO oxidation

CO Oxidation Catalyzed by Au Dispersed on SBA-15 Modified with TiO2 Films Grown via Atomic Layer Deposition (ALD)

It has been established that gold, when in nanoparticle (NP) form and in contact with reducible oxides, can promote oxidation reactions under mild conditions. Here, we report results from our exploration of the catalytic oxidation of carbon monoxide using catalysts where Au NPs were combined with thin titanium oxide films deposited on SBA-15 using atomic layer deposition (ALD). Both orders of deposition, with TiO2 added either before or after Au dispersion, were tested for two titania film thicknesses amounting to about half and full TiO2 monolayers. The resulting catalysts were characterized using various techniques, mainly electron microscopy and N2 adsorption–desorption isotherms, and the kinetics of the oxidation of CO with O2 were followed using infrared absorption spectroscopy. A synergy between the Au and TiO2 phases as it relates to the bonding and conversion of CO was identified, the tuning of which could be controlled by varying the synthetic parameters. The ALD of TiO2 films proved to be an effective way to maximize the Au-TiO2 interface sites, and with that help with the activation of molecular oxygen.

Promoting mechanism of CuO on catalytic performance of CeFe catalyst for simultaneous removal of NOx and CO

Nitrogen oxides (NOx) and carbon monoxide (CO) coexisted in numerous industrial waste gases. And selective catalytic reduction of NOx with ammonia (NH3-SCR) and CO catalytic oxidation were considered as the effective technologies for simultaneous elimination of NOx and CO, respectively. However, an efficient bifunctional catalyst was crucial for achieving simultaneous removal of NOx and CO. Herein, we developed a series of Cu-modified CeFe catalysts for simultaneous removal of NOx and CO. The results demonstrated that 5Cu-CeFe catalyst presented the best catalytic performance, achieving approximately 81% NOx removal efficiency and nearly 99% CO conversion rate at 200 °C under a gas houely space velocity of 90,000 h−1. The XPS analysis demonstrated that copper oxides played a critical role in promoting the formation of Ce3+ and Oβ, thereby facilitating the NH3-SCR catalytic performance and CO catalytic oxidation. Moreover, the copper oxide modification of CeFe catalyst attained a trade-off between the surface acidity and redox ability, resulting in improving adsorption and activition capacity of the reactant gases. In situ DRIFTS experiments revealed that the NH3-SCR process primarily obeyed the Eley-Rideal (E-R) pathway over both CeFe and 5Cu-CeFe catalysts, while Langmuir-Hinshelwood (L-H) pathway hardly participated in NH3-SCR process. The presence of Cu+–CO species and surface lattice oxygen was crucial for CO oxidation, and both Mars-van Krevelen (M−K) and L-H pathways might be involved in the CO catalytic oxidation process over 5Cu-CeFe catalyst.

Transition Metal (Fe2O3, Co3O4 and NiO)-Promoted CuO-Based α-MnO2 Nanowire Catalysts for Low-Temperature CO Oxidation

As a toxic pollutant, carbon monoxide (CO) usually causes harmful effects on human health. Therefore, the thermally catalytic oxidation of CO has received extensive attention in recent years. The CuO-based catalysts have been widely investigated due to their availability. In this study, a series of transition metal oxides (Fe2O3, Co3O4 and NiO) promoted CuO-based catalysts supported on the α-MnO2 nanowire catalysts were prepared by the deposition precipitation method for catalytic CO oxidation reactions. The effects of the loaded transition metal type, the loading amount, and the calcination temperature on the catalytic performances were systematically investigated. Further catalyst characterization showed that the CuO/α-MnO2 catalyst modified with 3 wt% Co3O4 and calcined at 400 °C performed the highest CO catalytic activity (T90 = 75 °C) among the investigated catalysts. It was supposed that the loading of the Co3O4 dopant not only increased the content of oxygen vacancies in the catalyst but also increased the specific surface area and pore volume of the CuO/α-MnO2 nanowire catalyst, which would further enhance the catalytic activity. The CuO/α-MnO2 catalyst modified with 3 wt% NiO and calcined at 400 °C exhibited the highest surface adsorbed oxygen content and the best normalized reaction rate, but the specific surface area limited its activity. Therefore, the appropriate loading of the Co3O4 modifier could greatly enhance the activity of CuO/α-MnO2. This research could provide a reference method for constructing efficient low-temperature CO oxidation catalysts.

Analysis of copper nanomaterial as catalyst for reduction of NOx gases in diesel engine

In the automobile sector, the removal of pollutants (NOx) generated by diesel engines remains a fascinating scientific and technological issue. The emissions of the vehicle are in compliance with BS III standards. The Indian government came up with the Bharat Stage Emission Standards in order to place limitations on the amount of air pollution that can be released into the atmosphere by machinery that uses an internal combustion engine, such as automobiles. The central pollution control board, which is an agency under the ministry of environment and forests, is in charge of defining the requirements and the timetable for their implementation. The brake-specific fuel consumption decreased by 4.5% and 8%, while brake thermal efficiency rose by 5.5% and 14.6%. However, with CO additions of 1000 and 2000 ppm, respectively, nanoparticles increased the chemical processes and decreased the ignition delay time by 3.03% and 5.45%. The amounts of CO, HC, and NOx emissions decreased by 14.6%, 20.8%, 6.2%, and 13.4%, respectively. The catalytic oxidation of carbon monoxide is an important reaction in both commercial and academic settings. For the past years, hoplite, which is composed of copper-manganese oxides, has served as a low-cost and widely available carbon monoxide abatement catalyst.

Catalytic Oxidation of Propane and Carbon Monoxide by Pd Nanoparticles on Mn/TiO2 Catalysts

The present work shows experimental results on the catalytic oxidation of C3H8 and CO by Pd nanoparticles supported on MnOx/TiO2 synthesized by the sol–gel method. The results show a strong interaction between Pd and MnOx/TiO2; likewise, the annealing temperature of the TiO2 support modified the catalytic properties of the Pd–MnOx/TiO2 catalyst. In this line, the catalysts with 1 and 2 wt% of Pd loading supported on MnOx/TiO2 showed outstanding catalytic activity oxidizing C3H8 and CO within two temperature intervals: 200–400 °C and 25–200 °C, respectively. The Pd–MnOx/TiO2 catalyst also displayed very high stability during long-term tests and the addition of Pd nanoparticles reduced greatly the oxidation temperature of MnOx/TiO2. The outcomes revealed that the Pd–Mn interaction promoted the formation of new Pd0/Pd2+ active sites as well as the formation of oxygen vacancies and reduced Ti4+ to Ti3+ species, which led to the improvement of the Mn3+ and Mn4+ redox features, thus boosting the catalytic oxidation capacity of the Pd–MnOx/TiO2 catalyst.Graphical

Enhancing the Catalytic Activity of Mo(110) Surface via Its Alloying with Submonolayer to Multilayer Boron Films and Oxidation of the Alloy: A Case of (CO + O2) to CO2 Conversion

In-situ formation of boron thin films on the Mo(110) surface, as well as the formation of the molybdenum boride and its oxide and the trends of carbon monoxide catalytic oxidation on the substrates formed, have been studied in an ultra-high vacuum (UHV) by a set of surface-sensitive characterization techniques: Auger and X-ray photoelectron spectroscopy (AES, XPS), low-energy ion scattering (LEIS), reflection-absorption infrared spectroscopy (RAIRS), temperature-programmed desorption (TPD), electron energy loss spectroscopy (EELS) and work function measurements using the Anderson method. The boron deposited at Mo(110) via electron-beam deposition at a substrate temperature of 300 K grows as a 2D layer, at least in submonolayer coverage. Such a film is bound to the Mo(110) via polarized chemisorption bonds, dramatically changing the charge density at the substrate surface manifested by the Mo(110) surface plasmon damping. Upon annealing of the B-Mo(110) system, the boron diffuses into the Mo(110) bulk following a two-mode regime: (1) quite easy dissolution, starting at a temperature of about 450 K with an activation energy of 0.4 eV; and (2) formation of molybdenum boride at a temperature higher than 700 K with M-B interatomic bonding energy of 3.8 eV. The feature of the formed molybdenum boride is that there is quite notable carbon monoxide oxidation activity on its surface. A further dramatic increase of such an activity is achieved when the molybdenum boride is oxidized. The latter is attributed to more activated states of molecular orbitals of coadsorbed carbon monoxide and oxygen due to their enhanced interaction with both boron and oxygen species for MoxByOz ternary compound, compared to only boron for the Mox'By' double alloy.

Hydrodynamics and mass transfer around active particles in dense gas-fluidized beds

The hydrodynamics of bubbling fluidized beds of Geldart B granular solids operated at ambient temperature and at 500 °C are investigated by uncooled capacitance probes at different gas superficial velocities. Statistical analysis of the time-series of the local bed voidage generates Probability Density Functions (PDF) that display multimodal patterns. A remarkable bimodal character is apparent in the part of the PDF that refers to the emulsion phase when the gas superficial velocity is increased. It is inferred that two phases with different porosity co-exist in the emulsion phase: a lower voidage LV-phase and a higher voidage HV-phase. The link between the LV- and HV-phases as assessed from PDF of capacitance signals and the actual flow patterns induced in the emulsion phase by the bubbles is open to scrutiny.Along a different path, the influence of the bed hydrodynamics and expansion patterns of the emulsion phase on the gas mass transfer around a freely moving coarse active particle is investigated. To this end, mass transfer-limited reaction experiments are performed, consisting in catalytic oxidation of carbon monoxide at 450 °C over Pt-loaded γ-alumina spheres immersed in the fluidized bed. The mass transfer coefficient around the freely moving active particles is measured and worked out to calculate the particle Sherwood (Sh) number. Results obtained from reaction experiments confirm the close relationship between mass transfer and expansion patterns of the emulsion phase, and the need for proper hydrodynamic characterization of the bed. A Frӧssling-type equation, Sh=2·∊e+K·(Ree/∊e)1/2·Sc1/3, well correlates the results. Sh increases with fluidization gas velocity and a best fitting is obtained using the bed voidage of the HV-region of the emulsion phase in the correlation.

A review of catalytic oxidation of carbon monoxide over different catalysts with an emphasis on hopcalite catalysts

Hopcalite catalysts are reviewed showing highly active catalysts for low-temperature, low-cost and complete oxidation of CO.