Catalytic Activity For Carbon Monoxide Oxidation Research Articles

Carbon Monoxide and Propylene Catalytic Oxidation Activity of Noble Metals (M = Pt, Pd, Ag, and Au) Loaded on the Surface of Ce0.875Zr0.125O2 (110)

With the advances in engine technology, the exhaust gas temperature of automobiles has further reduced, which in turn leads to an increase in the emissions of carbon monoxide (CO) and hydrocarbons (HCs). In order to understand the influence of CeO2-based catalysts loaded with different noble metals on the catalytic oxidation activity of CO and HCs, this study constructed catalyst models of Ce0.875Zr0.125O2 (100) surfaces loaded with Pt, Pd, Ag, and Au. The electronic density and state density structures of the catalysts were analyzed, and the reaction energy barriers for CO oxidation and C3H6 dehydrogenation oxidation on the catalyst surfaces were also calculated. Furthermore, the activity sequences of the catalysts were explored. The results revealed that after loading Pt, Pd, Ag, and Au atoms onto the catalyst surfaces, these noble metal atoms exhibited strong interactions with the catalyst surfaces, and electron transfer occurred between the noble metal atoms and the catalyst surfaces. Loading with noble metals can enhance the catalytic activity of CO oxidation, but it has little effect on the dehydrogenation oxidation of C3H6. Of the different noble metals, loading with Pd exhibits the best catalytic activity for both CO and C3H6 oxidation. This study elucidated the influence of noble metal doping on the catalytic activity of catalysts at the molecular level, providing theoretical guidance for the design of a new generation of green and efficient catalysts.

High catalytic performance of CuCe/Ti for CO oxidation and the role of TiO2

CuCe/Ti-A and CuCe/Ti-R catalysts were prepared using anatase TiO2 (TiO2-A) and rutile TiO2 (TiO2-R) as supports using the incipient wetness impregnation method for the carbon monoxide (CO) oxidation reaction and were compared with a CuCe-C catalyst prepared using the co-precipitation method. The CuCe/Ti-A catalyst exhibited the highest activity, with complete CO conversion at 90 °C, when the gas hourly space velocity was 24000 ml·g−1·h−1 and the CO concentration was approximately 1% (vol). A series of characterizations of the catalysts revealed that the CuCe/Ti-A catalyst has a larger specific surface area, more Cu+ species and oxygen vacancies, and the Cu species of CuCe/Ti-A catalyst is more readily reduced. In situ FT-IR results indicate that the bicarbonate species generated on the CuCe/Ti-A catalyst have lower thermal stability than the carbonate species on CuCe/Ti-R, and will decompose more readily to form CO2. Therefore, CuCe/Ti-A has excellent catalytic activity for CO oxidation.

The Enhancement of CO Oxidation Performance and Stability in SO2 and H2S Environment on Pd-Au/FeOX/Al2O3 Catalysts.

Carbon monoxide (CO) is a colourless, odourless, and toxic gas. Long-term exposure to high concentrations of CO causes poisoning and even death; therefore, CO removal is particularly important. Current research has focused on the efficient and rapid removal of CO via low-temperature (ambient) catalytic oxidation. Gold nanoparticles are widely used catalysts for the high-efficiency removal of high concentrations of CO at ambient temperature. However, easy poisoning and inactivation due to the presence of SO2 and H2S affect its activity and practical application. In this study, a bimetallic catalyst, Pd-Au/FeOx/Al2O3, with a Au:Pd ratio of 2:1 (wt%) was formed by adding Pd nanoparticles to a highly active Au/FeOx/Al2O3 catalyst. Its analysis and characterisation proved that it has improved catalytic activity for CO oxidation and excellent stability. A total conversion of 2500 ppm of CO at -30 °C was achieved. Furthermore, at ambient temperature and a volume space velocity of 13,000 h-1, 20,000 ppm CO was fully converted and maintained for 132 min. Density functional theory (DFT) calculations and in situ FTIR analysis revealed that Pd-Au/FeOx/Al2O3 exhibited stronger resistance to SO2 and H2S adsorption than the Au/FeOx/Al2O3 catalyst. This study provides a reference for the practical application of a CO catalyst with high performance and high environmental stability.

Fabrication of supported Pt/CeO2 nanocatalysts doped with different elements for CO oxidation: theoretical and experimental studies.

Supported Pt/CeO2 catalysts have been widely used in carbon monoxide (CO) oxidation; however, the high oxygen vacancy formation energy (Evac) in the process leads to the poor performance of these catalysts. Herein, we explored different element (Pr, Cu, or N) doped CeO2 supports using Ce-based metal-organic frameworks (MOFs) as precursors via calcination treatment. The obtained CeO2 supports were used to load Pt nanoparticles. These catalysts were systematically characterized by various techniques, and they showed superior catalytic activity for CO oxidation compared to undoped catalysts which could be attributed to the formation of Ce3+, and high amounts of Oads/(Oads + Olat) and Ptδ+/Pttotal. Moreover, density functional theory calculations with on-site Coulomb interaction correction (DFT+U) were performed to provide atomic-scale insights into the reaction process by the Mars-van Krevelen (M-vK) mechanism, which revealed that the element-doped catalysts could simultaneously reduce the adsorption energies of CO and lower reaction energy barriers in the *OOCO associative pathway.

Influence the performances of hopcalite catalysts by the addition of gold nanoparticle for low temperature CO oxidation

The catalytic conversion of carbon monoxide (CO) into carbon dioxide (CO 2 ) at a low temperature is very important procedure for all living beings present in the environment. The present study represents that the addition of gold (Au) nano-particles, by the deposition-precipitation method into the hopcalite (CuMnOx) catalyst has been improving their performances for CO oxidation. The CuMnOx catalyst loading by 0.75 wt% Au was representing that the best catalytic activity for CO oxidation than the other catalysts loading by 0.25, 0.5 and 1 wt% Au. The small amount of Au doping (0.75 wt%) in CuMnOx catalyst improves their performances for CO oxidation at an ambient conditions. The gold nano-particles will be introducing the new active sites into the CuMnOx catalyst surfaces and decreases the deactivation of catalyst. The lattice oxygen movement was a major important factor which can influences the performances of hopcalite catalyst for CO oxidation. The calcinations strategies (reactive calcinations and traditional calcinations) of the precursor have huge impacts on the performances of resulting catalysts. The reusability of Au promoted CuMnOx catalyst was also measured and found that this catalyst does not have any major changes in its catalytic performances still after the reuses.

Highly efficient Au/Fe2O3 for CO oxidation: The vital role of spongy Fe2O3 toward high catalytic activity and stability

Supported gold catalysts have drawn great attention for many decades due to their outstanding performance in remedying the environment from carbon monoxide (CO) pollution. In this study, due to the large surface area of spongy Fe2O3, fabricated by salt-assisted ultrasonic spray pyrolysis, a considerable amount of Au was loaded on spongy Fe2O3 compared to low-surface-area non-spongy Fe2O3. It is seen that the spongy Fe2O3 catalyst loaded with Au has an interface that can be extremely active for CO desorption and O2 activation. That means it has high catalytic activity in CO oxidation than non-spongy and low surface area Fe2O3 loaded with Au. Also, the incorporation of Au in low alkaline condition further enhances the interaction between Au and Fe2O3, providing more active sites. This made the catalyst to have better activity, good stability over 60 hrs, and there was no carbonate on its surface. It had full conversion at 30 °C on 120 L g-1h−1 with high TOF (2.2 s−1).

Catalytic oxidation of CO on noble metal-based catalysts.

Carbon monoxide (CO) catalytic oxidation has gained increasing interest in recent years due to its application prospects. The noble metal catalysts commonly exhibit outstanding CO catalytic oxidation activity. Therefore, this article reviewed the recent research on the application of noble metal catalysts in the catalytic oxidation of CO. The effects of catalyst support, dopant, and physicochemical properties on the catalytic activity for CO oxidation are summarized. The influence of the presence of water vapor and sulfur dioxide in the reaction atmosphere on the catalytic activity in CO oxidation is emphatically discussed. Moreover, this paper discussed several reaction mechanisms of CO catalytic oxidation on noble metal catalysts. Finally, the challenges of removing CO by catalytic oxidation in practical industrial flue gas are proposed.

Bimetallic Pt-Co Nanoparticle Deposited on Alumina for Simultaneous CO and Toluene Oxidation in the Presence of Moisture

Carbon monoxide (CO) and hydrocarbons (HCs) generally have competitive adsorption on the active site of noble-metal nano-catalysts, thus developing an effective way to reduce the passivation of competitive reaction with each other is an urgent problem. In this study, we successfully synthesized transition metal-noble metal (Pt-M) alloys via introducing inexpensive metal elements (M = Ni, Co and Cu) into Pt particles and then deposited on alumina support to form Pt-based catalysts. Subsequently, we choose CO and toluene as polluting gases to evaluate the catalytic activities of Pt-M/Al2O3 catalysts. Introducing inexpensive metal elements (M = Ni, Co, and Cu) significantly changed the physicochemical properties and catalytic activities of these Pt-based catalysts. It can be found that the Pt-Co/Al2O3 catalyst exhibited outstanding catalytic activity for CO and toluene oxidation under mixed gas atmosphere, compared with other Pt-based catalysts, which is due to the higher dispersity, more surface adsorption oxygen, and well redox ability. Surprisingly, H2O could promote the catalytic activities for CO/toluene co-oxidation over the Pt-Co/Al2O3 catalyst. Thus, the present synthetic strategy not only opens an avenue towards the synthesis of noble metal-based catalysts, but also provides an excellent tolerance to H2O in the catalytic process.

Selection of Manganese oxide catalysts for catalytic oxidation of Carbon monoxide at ambient conditions

Abstract Carbon monoxide (CO) is one of the very poisonous gases present in the atmosphere and low temperature complete oxidation CO is very important process for all human being present in the environment. A catalytic converter was an emission control device that converts more toxic gases present in the automobile exhaust into less toxic gases by the catalytic reactions. The manganese oxide catalysts i.e. (XMn2O x , X = Ce, Co, Fe, Cu) are prepared into laboratory by the co-precipitation method followed by calcinations in reactive CO–air mixture and traditional calcinations conditions. The activity order of catalysts for CO oxidation is as follows: CuMn2O2 > CeMn2O2 > CoMn2O2 > FeMn2O2. Among all the prepared catalysts, the CuMn2O2 has showed that the best catalytic activity for CO oxidation at the low temperature. The complete oxidation of CO was achieved at 85 oC over CuMn 2RC catalyst. The calcinations strategies of precursors have great influenced on the activity of resulting catalysts. The CO oxidation activity was recognized to be a combination of factors including high surface area, active surface oxygen species and Mn(IV) cations. These results provide a novel thought to design the highly active CuMn2O2 catalyst.

Synthesis of CuMnOx catalysts by novel routes for selective catalytic oxidation of carbon monoxide

The ambient temperature catalytic oxidation of carbon monoxide (CO) is very important process for all living beings present in the atmosphere. Hopcalite (CuMnOx) is a mixed oxide of copper and manganese has been efficiently applied as a catalyst in the catalytic converter for CO oxidation. All the catalysts are prepared by the Co-precipitation method and characterized by the SEM-EDX, XRD, FTIR, BET and XPS technique. The ratio of Cu:Mn in CuMnOx catalyst was divided into three equal parts (Cu:Mn = 1:2, Cu:Mn = 1:1 and Cu:Mn = 2:1) and their performances for CO oxidation was also measured. The activity order of catalysts for CO oxidation was as follows: Cu2Mn1 < Cu1Mn1 < Cu1Mn2. In these catalysts the Cu1Mn2 has showed that the best catalytic activity for CO oxidation at a lower temperature. The calcinations strategies of precursors have great influences on the activity of resultant catalyst. All the catalysts are prepared in different calcinations conditions like reactive calcinations (RC) and traditional calcinations. The reactive calcinations strategy is one of the best calcinations strategies for the preparation of highly active catalysts. The stability of CuMnOx catalyst is also investigated in this research work.

Assessment of Manganese Oxide and Cobalt Oxide Catalysts for Three Way Catalytic Converter

Raising number of vehicles emits pollutants responsible for one third of total air pollution. Carbon monoxide (CO), unburned hydrocarbons (HC), and nitrogen oxides (NOx) are the main pollutants from petrol engines. It requires stringent vehicular emission norms to be followed for controlling it. Three Way Catalytic Converter (TWCC) contain Platinum Group Metals (PGMs) as catalyst to reduce exhaust emission and is widely used method that fulfills these standards. Because of high cost of PGMs and considerable advancement in metal oxide preparatory methods, metal oxide catalysts have gained more attraction. Manganese oxide (MnOx) and Cobalt Oxide (CoOx) have displayed impressive redox reactions at lower temperature. MnOx seems to be a suitable contender of Oxygen Storage Capacity (OSC) and Cobalt oxide (CoOx) has displayed an excellent catalytic activity for HC and CO oxidation. Hence, these catalysts attract the attention of researchers. Present paper assesses the prospect of MnOx and CoOx as catalysts for the TWCC for redox reactions of CO, HC and NOx and also in terms of OSC and T50 temperature. It is found that CoOx and MnOx both low cost metal oxide catalysts stand a good chance to replace the noble metals for TWCC.

Synthesis and applications of titanium oxide catalysts for lower temperature CO oxidation

Carbon monoxide (CO) is one of the very poisonous gasses and major sources of CO produced into the environment by the automobile vehicles exhaust. There are various types of catalysts have been used in the catalytic converter for CO oxidation. The titanium dioxide (TiO2) is one of the best transitional metal oxides catalysts for lower temperature CO oxidation. A small amount of TiO2 was deposited on the mesoporous Al2O3 using atomic layer deposition and subsequent oxidation at the different temperatures. The lightly reduced support improves the high catalytic activity of the adparticles, a strongly reduced one quenches the CO oxidation. The quenching is due to thermally activated diffusion of Ti3+ interstitials from the bulk to the surface where they deplete the oxygen adsorbed onto the clusters by the formation of TiOx (x ​≃ ​2) structures. The additions of promoters and support in titanium oxide catalysts improved their performances and reduced their stability. The bulk reduction state of TiO2 strongly affects the catalytic activity of supported metal clusters in the chemical reactions between oxygen and other molecules. The certain attention has been paid on the recovery of TiO2 catalysts from reaction systems and their reuse for various times without losses of catalytic activity in CO oxidation. This investigation will shown scientific basis for potential design of Ti-oxide nano-particle catalysts for lower temperature CO oxidation.

Improved Catalytic Performance of Au/α-Fe2O3-Like-Worm Catalyst for Low Temperature CO Oxidation.

The gold catalysts supported on various morphologies of α-Fe2O3 in carbon monoxide (CO) oxidation reaction have been studied for many researchers. However, how to improve the catalytic activity and thermal stability for CO oxidation is still important. In this work, an unusual morphology of α-Fe2O3 was prepared by hydrothermal method and gold nanoparticles were supported using a deposition-precipitation method. Au/α-Fe2O3 catalyst exhibited great activity for CO oxidation. The crystal structure and microstructure images of α-Fe2O3 were carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and the size of gold nanoparticles was determined by transmission electron microscopy (TEM). X-ray photoelectron spectra (XPS) and Fourier transform infrared spectra (FTIR) results confirmed that the state of gold was metallic. The 1.86% Au/α-Fe2O3 catalyst calcined at 300 °C had the best catalytic performance for CO oxidation reaction and the mechanism for CO oxidation reaction was also discussed. It is highly likely that the small size of gold nanoparticle, oxygen vacancies and active sites played the decisive roles in CO oxidation reaction.

Effect of various metal oxides phases present in CuMnOx catalyst for selective CO oxidation

Hopcalite (CuMnOx) is a highly efficient catalyst for low temperature oxidation of Carbon monoxide (CO). As synthesized by Co-precipitation method, it shows the high activity for CO oxidation. The coordination between CuO and MnOx in CuMnOx catalyst improves the catalytic activity for CO oxidation. In this research work, we investigate the individual catalytic activity of CuO and MnOx and compare with the multiphase CuMnOx catalyst. The performance of multiphase catalysts CuO and MnO2 were numerous times higher as compared to single phase CuMnOx. The activity order of catalysts for CO oxidation was as follows: CuMnOx> MnOx > CuOx. The success of CuMnOx catalyst has prompted a great deal of research work into each component and nature of active sites. In CuMnOx catalyst, the MnOx acts as an oxygen donor and CuO acts as an oxygen acceptor. The presence of MnOx is possible to assist in the reduction of CuO, due to the coordination between CuO and MnOx. The calcination strategies of precursors highly affect the physicochemical and catalytic properties of the catalysts for CO oxidation. The reactive calcination (RC) conditions (4.5% CO in air) for prepared catalysts showed the best activity result for CO oxidation, as compared to the traditional method of calcination.

High Surface Area M (M = La, Pr, Nd, and Pm)-Doped Ceria Nanoparticles: Synthesis, Characterization, and Activity Comparison for CO Oxidation

High surface area M (M = La, Pr, Nd, and Pm)-doped ceria nanoparticles have been synthesized by the citric acid-aided sol–gel method to check their catalytic activity for carbon monoxide (CO) oxidation. BET analysis revealed high specific surface areas of M-doped CeO2 catalysts (∼190–198 m2 g–1). XRD and TEM showed 3–6 nm size of particles of M-doped CeO2 catalysts. Raman results showed the highest amount of oxygen vacancy possessed by La-doped CeO2 compared to other dopants. The catalytic activity for CO oxidation follows the order La-CeO2 > Pr-CeO2 > Nd-CeO2 > Pm-CeO2 > CeO2. La-doped CeO2 exhibited the highest catalytic activity (T50 - 170 °C) due to the higher quantity of oxygen vacancies, larger specific surface area, smaller particle size, and enhanced oxygen storage capacity (OSC) comparison to other dopants. This catalyst also showed an excellent stability for CO oxidation reaction for a time-on-stream of 50 h.

Theoretical study on the Si-doped graphene as an efficient metal-free catalyst for CO oxidation

Abstract The reduction of noble metal used in carbon monoxide (CO) oxidation remains a challenge. Based on the first-principle methods, the geometry, electronic structure and catalytic properties of Si-doped graphene (Si-graphene) are investigated. The Si adatom has smaller adsorption energy on pristine graphene as compared with that of the Si dopant in graphene. The large atomic radii of Si dopant in graphene can induce the local surface curvature and modulate the electronic structure through inducing the charge redistribution. Besides, the metal-free Si-graphene can weaken the CO adsorption and facilitates the O2 adsorption, thus enhancing the catalytic activity for CO oxidation. It is found that the preadsorbed O2 molecule on the Si-atom can greatly enhance the interaction with CO molecule. Moreover, the complete CO oxidation reactions on the Si-graphene include a two-step process of the Eley–Rideal (ER) reactions, in which the first step has a low energy barrier of 0.43 eV and the second step exhibits an even negligible energy barrier of 0.07 eV. The results validate the reactivity of catalysts on the atomic-scale and initiate a clue for fabricating metal-free catalysts with low cost and high activity.

Atomic-structural synergy for catalytic CO oxidation over palladium-nickel nanoalloys.

Alloying palladium (Pd) with other transition metals at the nanoscale has become an important pathway for preparation of low-cost, highly active and stable catalysts. However, the lack of understanding of how the alloying phase state, chemical composition and atomic-scale structure of the alloys at the nanoscale influence their catalytic activity impedes the rational design of Pd-nanoalloy catalysts. This work addresses this challenge by a novel approach to investigating the catalytic oxidation of carbon monoxide (CO) over palladium-nickel (PdNi) nanoalloys with well-defined bimetallic composition, which reveals a remarkable maximal catalytic activity at Pd:Ni ratio of ~50:50. Key to understanding the structural-catalytic synergy is the use of high-energy synchrotron X-ray diffraction coupled to atomic pair distribution function (HE-XRD/PDF) analysis to probe the atomic structure of PdNi nanoalloys under controlled thermochemical treatments and CO reaction conditions. Three-dimensional (3D) models of the atomic structure of the nanoalloy particles were generated by reverse Monte Carlo simulations (RMC) guided by the experimental HE-XRD/PDF data. Structural details of the PdNi nanoalloys were extracted from the respective 3D models and compared with the measured catalytic properties. The comparison revealed a strong correlation between the phase state, chemical composition and atomic-scale structure of PdNi nanoalloys and their catalytic activity for CO oxidation. This correlation is further substantiated by analyzing the first atomic neighbor distances and coordination numbers inside the nanoalloy particles and at their surfaces. These findings have provided new insights into the structural synergy of nanoalloy catalysts by controlling the phase state, composition and atomic structure, complementing findings of traditional density functional theory studies.

Control of Carbon Monoxide (CO) from Automobile Exhaust by a Dealuminated Zeolite Supported Regenerative MnCo2O4 Catalyst

We synthesized MnCo(2)O(4) catalyst with very high porosity on the surface of dealuminated zeolite molecular sieves (DAZMS) for CO oxidation under actual automobile conditions. The MnCo(2)O(4) catalyst was selected on the basis of preliminary DFT study using the software ADF BAND. The MnCo(2)O(4) catalyst had comparatively higher CO adsorption energy and very low oxygen vacancy formation energy. The synthesized MnCo(2)O(4)/DAZMS catalyst was characterized by XRD, XRF, BET, SEM, and Confocal Microscopy. The Confocal microscopic analysis revealed that porosity of the dealuminated zeolite surface was significantly enhanced after the catalyst loading process. The completely precious metal free and DAZMS-supported catalyst exhibited excellent CO oxidation ability with renewed activity for seven months under actual automobile conditions with reference to normal and cold start conditions. The synthesized MnCo(2)O(4)/DAZMS not only exhibited surprisingly high catalytic activity for CO oxidation at a temperature resembling a cold start period but was also sufficiently stable/active under actual automobile conditions and ambient conditions containing large amounts of CO,H(2)O,CO(2), and NO(x) at 155-715 °C. These significant results revealed the flexible use of the present catalyst system for a wide variety of automobiles from a small gasoline-fuelled vehicle to a large diesel-fuelled vehicle that may produce high CO-content exhaust.

Catalytic activity of CeO 2–ZrO 2 mixed oxide catalysts prepared via sol–gel technique: CO oxidation

CeO 2–ZrO 2 mixed oxide catalysts were prepared via a sol–gel technique and tested for carbon monoxide (CO) oxidation. Highly uniform nano-size solid solution particles of ceria–zirconia were attained under the conditions of this study (ca 100°C). The stabilization of the surface areas of the catalysts can be achieved by the addition of zirconium. The CO oxidation activity of the mixed oxides was found to be dependent on Ce/Zr ratio, which relates to the degree of reducibility. The catalytic activity for CO oxidation decreases with a decrease in Ce/Zr ratio. This might be due to the difference in phase compositions of the mixed oxides. It can be postulated that the cubic phase, fluorite structure, which is mainly found in Ce 1− x Zr x O 2 (where x<0.5) could be reduced easily than the tetragonal phase found in Ce 1− x Zr x O 2 (where x>0.5). Among the mixed oxide catalysts, Ce 0.75Zr 0.25O 2 was reported to exhibit the highest activity for CO oxidation.