Hopcalite Catalyst Research Articles

A Ce/hopcalite catalyst for low-temperature oxidation of CO:Preparation, performance and mechanism

The utilization of atomic-scale doping in catalysts has been recognized as an effective strategy for enhancing CO oxidation catalytic activity. This work adjusted the lattice structure of hopcalite (CuMnOx) catalysts via Ce-doping. Ce species was uniformly dispersed on the surface of amorphous porous catalysts, which built abundant interfaces along with many active sites. The lattice distortion degree can be regulated by changing Ce dosage. The modified catalysts with 7.5 wt%Ce-doping exhibited the optimal intrinsic activity for CO oxidation. Compared with the original sample, the CO conversion increased by 50 % at room temperature, and the reaction rate was eight-fold faster, superior to most reported hopcalite catalysts. Integrating with the various characterizations, the enhancing of low-temperature activity mainly originates from the weakened binding of oxygen atoms by lattice distortions. Moreover, the experiments and characterization results revealed that the reactivity of both adsorbed and lattice oxygen is enhanced on Ce-modified samples at low temperature. This work provides new insights into the rational modulation of reactive oxygen species and reinforces the utility of hopcalite catalysts for oxidizing CO at low temperature.

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.

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.

To optimized various parameters of Hopcalite catalysts in the synthetic processes for low temperature CO oxidation

Carbon monoxide (CO) is very poisonous gasses present in the atmosphere and lower temperature complete oxidation of CO is very important processes for all life support. The automobile vehicles exhaust is one of the major sources of CO produced into the environment. The application of catalytic converter in automobile vehicles reduces the toxic gasses emission. There are lots of catalysts used in the catalytic converter for CO oxidation purposes among these catalysts the Hopcalite (CuMnOx) is one of the oldest and best-known catalysts for low temperature CO oxidation. The hopcalite catalyst is prepared by the co-precipitation method and preparation parameters like magnetic shaker shaking speed, shaking time, shaking temperature and pH has an influence on the activity of resultant catalysts. The activity of catalyst was measured in reactive calcinations (RC) conditions at the presence of (1.5% CO) and air. The reaction temperature was increased from room temperature to higher temperature at which the total oxidation of CO was achieved. The characterizations of catalysts are done by several techniques like XRD, FTIR, BET and SEM-EDX. These results are interpreted in terms of structure the active catalyst. The reusability of CuMnOx catalyst was also tested and also found that this catalyst does not show any high level of significant change in its catalytic performances even after reuses.

CONCEPTUAL APPROACHES TO THE DEVELOPMENT OF CATALYSTS FOR LOW-TEMPERATURE CARBON MONOXIDE OXIDATION WITH AIR OXYGEN

Actual questions concerning the modern stage of development of catalysts for low-temperature carbon monoxide oxidation and their application in the personal respiratory protective equipment (PRPE) have been analyzed. Some approaches contributing to purposeful control of activity of Wacker type catalysts consisting of both palladium(II) and copper(II) salts and sorbents of different origin as well as their possible use in several environment protection devices have been considered. Despite some progress in the development of new catalysts for low-temperature CO oxidation, Hopcalite catalysts characterized by well-known disadvantages are as usual used in the series-produced PRPE. In our opinion, Au containing nanocatalysts and Pd(II)-Cu(II) catalysts based on modified natural sorbents such as Tripoli and clinoptilolite (Ukraine) are more perspective for this purpose. Available data concerning test conditions and activity parameters for some commercial catalysts at comparable CO inlet concentrations commonly used in PRPE, i.e. 130-300 mg/m3, were summarized. For comparison of their activity and evaluation of their applicability in PRPE, their air purifying ability (down to MPCCO in the air of work area) was used. It can be seen that the Au containing Nanoqold Cat (0.57 % Au/TiO2/AC) nanocatalyst demonstrates the highest activity providing the almost complete air purifying from CO: at CO inlet concentration of 625 mg/m3 and the residence time value of 0.04 s, the outlet concentrations are 1.25‑7.5 mg/m3 for 12 h. For NanAuCat (0.57 % Au/TiO2/AC) and AUROlite (1 % Au/TiO2), CO conversion values were equal to 48 % and 22 %, respectively, however, in this case the residence time value was lower by an order of magnitude. STC catalyst (Pt/SnO2) and AK-62 (2.4 % Pd/Al2O3) catalyst are less active than the above mentioned Au containing catalysts. The Wacker type catalysts are characterized by similar parameters however KNO-CO/MT is somewhat better showing the air purification down to MPC even at the residence time of 0.29 s. The residence time is a parameter determining the catalyst weight necessary to achieve a required CO conversion and dimensions of an applicable gas mask filter. Hopcalite catalysts used in the PRPE produced by the main companies over the world are the cause of large dimensions and weights of PRPE cartridges and canisters. Thus, low values of catalyst weights in “Platan” and “Suprovidnyk” devices, i.e. 50 g and 97 g, respectively, and high levels of protection from CO are their great advantages.

Structural and catalytic properties of Fe and Ni doping on CuMnOx catalyst for CO oxidation

The application of iron (Fe) or nickel (Ni) doping over hopcalite (CuMnOx) catalyst highly effects on their structural properties and catalytic performance for ambient conditions carbon monoxide (CO) oxidation have been investigated. The NiO and Fe2O3 phases are easily isolated over the CuMnOx catalyst. The (Fe or Ni) doping was done in the range of (0.5–5 wt%) in CuMnOx catalyst. The better catalytic activity was observed at 3.50 wt% of Fe, and 4.0 wt% of Ni loading in CuMnOx catalyst was separately found. However, the catalytic performance of CuMnOx catalyst was also depended on the promoters’ percentages rate. The smaller percentages of promoters carry out superior result than the higher ones. The size of catalytic material was also decreases, and specific surface area was also increased; therefore, the formation of active sites for CO conversion improved highly. The calcination strategies (reactive calcinations and traditional calcinations) highly affect on the performance of final catalysts. The reactive calcinations prepared catalysts that show the most excellent catalytic performances for CO conversion as compared to the other ones. The activity of catalysts was also matched with their characterization results.

Synthesis of Hopcalite catalysts by various methods for improved catalytic conversion of carbon monoxide

The conversion of carbon monoxide (CO) at ambient condition is major procedure for human life protection. The Hopcalite (CuMnOx) is one of the best known catalysts for lower temperature CO conversion. The synthesis of hopcalite catalysts by various methods including Co-precipitation (CP), Sol-gel (SG), Reactive grinding (RG), Impregnation (I) and Pyrolysis (P) highly effects on the performance of final catalysts for CO conversion. In this experimental work various types of hopcalite catalysts prepared by various methods (CP, SG, RG, I, and P) followed by calcination in reactive (CO-air) mixture and traditional calcination conditions. The performance of different hopcalite catalysts for CO conversion reaction was as follows: CuMnCP > CuMnRG > CuMnSG > CuMnP > CuMnI. The Co-precipitation method synthesized hopcalite catalyst followed by reactive calcination conditions represents that the most excellent catalytic performance for complete conversion of CO at 80 °C. The order of synthetic conditions based on the activity of hopcalite catalysts matched with their characterization. Our effort to demonstrates that the simplistic and potential strategy for improvement of catalytic perfromances over hopcalite catalysts, which should be suitable for different chemical reactions. Hopcalite is a lower cost, simply aviliable and recycle catalysts for application in catalytic converter for CO conversion purposes.

Application of hopcalite catalyst for controlling carbon monoxide emission at cold-start emission conditions

Abstract Carbon monoxide (CO) is a poisonous gas particularly to all leaving being present in the atmosphere. An estimate has shown that the vehicular exhaust contributes the largest source of CO pollution in developed countries. Due to the exponentially increasing number of automobile vehicles on roads, CO concentrations have reached an alarming level in urban areas. To control this vehicular exhaust pollution, the end-of-pipe-technology using catalytic converters is recommended. The catalysts operating efficiently in a catalytic converter are a challenging class of materials for applications in cold start of engines to maintain indoor air quality. In the cold start period, the catalytic converter was entirely inactive, because the catalytic converter had not been warmed up. The cold start phase is also depending upon the characteristics of vehicles and property of catalysts. The increasing cost of noble metals with the increasing number of vehicles motivates the investigation of material concepts to reduce the precious metal content in automotive catalysts or to find a substitute for noble metals. Hopcalite (CuMnOx) catalyst could work very well at the low temperature; thus, it can overcome the problem of cold-start emissions if used in a catalytic converter. Further, low cost, easy availability and advanced synthesis methods with stabilizer, promoter, etc., advocates for the use of hopcalite as an auto exhaust purification catalyst. Although there are numerous research articles present on this topic until now, no review has been presented for demanding this issue. So there is a space in this area, and it has been made an attempt to seal this hole and progress the future scope for hopcalite catalyst for purification of exhaust gases by this review.

A Review of Synthesis, Structure and Applications in Hopcalite Catalysts for Carbon Monoxide Oxidation

Carbon monoxide (CO) is a poisonous atmospheric pollutant. It highly affects human beings, plants, animals and environment. Automobile exhaust is the largest source of CO emission in the environment. To control this automobile exhaust pollution, the catalytic converters are used. Many types of catalysts have been investigated for CO oxidation purposes, i.e., noble metal, base metal, rare earth, perovskite, spinel and mixed transient metal oxides. These catalysts are widely used in a catalytic converter. Among the various metal oxide catalysts, hopcalite (CuMnOx) is one of the most efficient catalysts for low-temperature CO oxidation. Hopcalite catalysts have been reported to be good from economical, thermal, activity, selectivity and availability points of view. The activity of hopcalite catalysts is strongly dependent on the surface area, crystallite size and binding energy of the catalysts. This study will provide a scientific basis for designing future application of hopcalite catalysts for low-temperature CO oxidation. This manuscript provides a summary of published information regarding pure and substituted hopcalite catalyst, synthesis methods; properties and application for CO emissions control. A number of papers associated with CO oxidation over the hopcalite catalysts have been available, but no review papers appear in the literature that is dedicated to CO oxidation. Therefore, in an attempt to fill this gap, the present review updates and evaluates the progress and future scope of hopcalite catalyst for purification of exhaust gases.

Ambient temperature complete oxidation of carbon monoxide using hopcalite catalysts for fire escape mask applications

Carbon monoxide (CO) is one of the most poisonous gases present in the atmosphere. It also called the silent killer of twenty-first century. CO is produced into the environment by incomplete combustion of carbon containing compounds. It causes lots of people die every year including the firefighters. The main aim of this work to find out the literature study of standard respiratory escape masks for ambient temperature CO oxidation purposes. The research under concern is applicable for developing respiratory protection systems for military, mining, and space devices. There are many catalysts which are active for this process under different conditions. Among these catalysts, the hopcalite (CuMnOx) is one of the best-known catalysts for low-temperature CO oxidation. It is a low-cost, easily available, and highly stable catalyst. The hopcalite catalyst is active for a longer time and would be tolerant of moisture and impurities in reacting gases. The catalyst surface and reacting gases forever play a key role in catalytic reactions. Hopcalite is an ideal catalyst for use in next-generation respiratory protection devices. Although there are numerous research papers present on this topic until now no one review are present for demanding this issue. So there is a space in this area; it has been made an attempt to seal this hole by this review.

The choice of precursors in the synthesizing of CuMnOx catalysts for maximizing CO oxidation

The hopcalite (CuMnOx) catalyst is a well-known catalyst for CO oxidation at a low temperature and it is synthesized by the co-precipitation method with different types of precursors. Activity of the CuMnOx catalysts for CO oxidation is strongly dependent upon the combination of precursors, ranking in order {Mn(Ac)2 + Cu(NO3)2} > {Mn(Ac)2 + Cu(Ac)2} > {Mn(NO3)2 + Cu(NO3)2} > {Mn(NO3)2 + Cu(AC)2}. All the precursors were precipitated by KMnO4 solution and the precursors mostly comprised of MnO2, Mn2O3 and CuO phases. Keeping the same precipitant while changing the precursors caused a change in the lattice oxygen mobility which influenced the CO oxidation activity. The calcination strategy of the precursors has great influence on the activity of resulting catalysts. The reactive calcination (RC) conditions produce multifarious phenomena of CO oxidation and the precursor decomposition in a single-step process. The activity order of the catalysts for CO oxidation was as follows: reactive calcination (RC) > flowing air > stagnant air. Therefore, we recommended that the RC route was the more appropriate calcination route for the production of highly active CuMnOx catalysts. All the catalysts were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller analysis, X-ray photoelectron spectroscopy and scanning electron microscopy technique. The influence of precursors on the structural properties and the catalytic activity of co-precipitation derived binary CuMnOx catalysts for CO oxidation has been investigated.

Cobalt doped CuMnOx catalysts for the preferential oxidation of carbon monoxide

Carbon monoxide (CO) is a poisonous gas, recognized as a silent killer for the 21st century. It is produced from the partial oxidation of carbon containing compounds. The catalytic oxidation of CO receives a huge attention due to its applications in different fields.In the present work, hopcalite (CuMnOx) catalysts were synthesized using a co-precipitation method for CO oxidation purposes. Also, it was doped with the cobalt by varying concentration from 1 to 5wt%. It was observed that the addition of cobalt into the CuMnOx catalyst (by the deposition-precipitation method) improved the catalytic performance for the low-temperature CO oxidation. CuMnOx catalyst doped with 3wt% of cobalt exhibited most active performance and showed the highest activity than other cobalt concentrations. Different analytical tools (i.e. XRD, FTIR, BET, XPS and SEM-EDX) were used to characterize the as-synthesized catalysts. It was expected that the introduction of cobalt will introduce new active sites into the CuMnOx catalyst that are associated with the cobalt nano-particles. The order of calcination strategies based on the activity for cobalt doped CuMnOx catalysts was observed as: Reactive calcinations (RC) > flowing air > stagnant air. Therefore, RC (4.5% CO in air) route can be recommended for the synthesis of highly active catalysts. The catalytic activity of doped CuMnOx catalysts toward CO oxidation shows a correlation among average oxidation number of Mn and the position and the nature of the doped cobalt cation.

Study of Hopcalite (CuMnOx) Catalysts Prepared Through A Novel Route for the Oxidation of Carbon Monoxide at Low Temperature

Carbon monoxide (CO) is a poisonous gas, recognized as a silent killer. The gas is produced by incomplete combustion of carbonaceous fuel. Recent studies have shown that hopcalite group is one of the promising catalysts for CO oxidation at low temperature. In this study, hopcalite (CuMnOx) catalysts were prepared by KMnO4 co-precipitation method followed by washing, drying the precipitate at different temperatures (22, 50, 90, 110, and 120 oC) for 12 h in an oven and subsequent calcination at 300 oC in stagnant air, flowing air and in a reactive gas mixture of (4.5% CO in air) to do the reactive calcination (RC). The prepared catalysts were characterized by XRD, FTIR, SEM-EDX, XPS, and BET techniques. The activity of the catalysts was evaluated in a tubular reactor under the following conditions: 100 mg catalyst, 2.5% CO in air, total flow rate 60 mL/min and temperature varying from ambient to a higher value, at which complete oxidation of CO was achieved. The order of calcination strategies based on activity for hopcalite catalysts was observed to be as: RC > flowing air > stagnant air. In the kinetics study of CuMnOx catalyst prepared in RC conditions the frequency factor and activation energy were found to be 5.856×105 (g.mol)/(gcat.h) and 36.98 kJ/gmol, respectively.

Effect of Preparation Conditions on the Catalytic Activity of CuMnOx Catalysts for CO Oxidation

The hopcalite (CuMnOx) catalyst is a well-known catalyst for oxidation of CO at ambient temperature. It has prepared by co-precipitation method and the preparation parameters were like Copper/Manganese (Cu:Mn) molar ratios, drying temperature, drying time, calcination temperature and calcination time has an influence on activity of the resultant catalyst. The activity of the catalyst was measured in flowing air calcinations (FAC) conditions. The reaction temperature was increased from ambient to a higher value at which complete oxidation of CO was achieved. The particle size, weight of catalyst and CO flow rate in the air were also influenced by the activity of the catalyst for CO oxidation. The characterizations of the catalysts were done by several techniques like XRD, FTIR, BET, SEM-EDX and XPS. These results were interpreted in terms of the structure of the active catalyst. The main aim of this paper was to identify the optimum preparation conditions of CuMnOx catalyst with respect to the performance of catalyst for CO oxidation.

Influence of the preparation method on the activity of copper-manganese oxides for toluene total oxidation

Copper manganese oxides were prepared either by a co-precipitation method using metal nitrates as precursors, tetramethylammonium hydroxide (TMAH) as precipitant or by a redox-precipitation method using manganese acetate and copper nitrate as precursors, permanganate of potassium as oxidant. Copper manganese oxides synthesized by the redox method and calcined at 300°C were also doped with Pt and Pd (0.5wt%). The materials were characterized by ICP-OES, X-ray powder diffraction, N2 adsorption/desorption analysis, temperature-programmed reduction, X-ray photoelectron spectroscopy and time-of-flight secondary-ion mass spectrometry. The catalyst properties were assessed in total oxidation of toluene and compared with those of the corresponding single oxides and of a commercial Hopcalite catalyst. Copper manganese oxides were proved to be more active than the single oxides whatever the method of preparation used. CuMnOx prepared via redox method were more active than the catalyst prepared by co-precipitation and compared favorably with the commercial Hopcalite. The overall characterization results revealed that the redox method can ensure a good dispersion of copper in close interaction with manganese preserving more active sites at the outermost layers of the catalyst in comparison with the catalyst obtained via co-precipitation. However all the catalysts deactivate to some extent at the earlier stages of the reaction before to reach a steady-state. For redox catalysts calcined at 300°C, although the dispersion of trace amount of noble metals does not ensure a better activity, adding Pt allows to get a better resistance to deactivation. Additionally it is to be noticeable that the catalyst using redox-precipitation method calcined at 200°C outperforms the commercial hopcalite overtime on stream.

Modifying Hopcalite catalyst by SnO2 addition: An effective way to improve its moisture tolerance and activity for low temperature CO oxidation

To improve the water tolerance and activity of traditional Hopcalite catalyst, a series of CuMnOx catalysts with a typical Hopcalite composition, but with part of the Mn element replaced by Sn were prepared and evaluated for low temperature CO oxidation. It is revealed that with suitable Sn replacement, both the moisture tolerance and activity of the catalysts have been evidently enhanced. The best performance is achieved with 8.5wt% Sn addition. With the incorporation of Sn, the morphologies of the catalysts were changed accompanying the formation of a larger amount of intra-particle mesopores, thus resulting in catalysts with much higher surface area. In addition, more active oxygen species has been formed in the catalysts, as evidenced by H2-TPR, O2-TPD and XPS results. Furthermore, the catalyst surface has more exposed Cu2+ cations, thus having stronger ability to adsorb CO molecules. Most importantly, FTIR and H2O-TPD results have testified that the addition of SnO2 can significantly suppress the adsorption of H2O molecules on the surface of the catalysts, hence improving their water resistance at low temperature dramatically. In conclusion, these are believed to be the major reasons accounting for the remarkably improved moisture tolerance as well as activity for Hopcalite catalysts by SnO2 addition.

Hopcalite nanoparticle catalysts with high water vapour stability for catalytic oxidation of carbon monoxide

Hopcalite catalysts (copper manganese oxides) with high catalytic activity in CO oxidation catalysis under humid conditions were obtained via flame spray pyrolysis. While commercial hopcalites, for example produced by precipitation methods, immediately deactivate under humid conditions, the new catalysts show significantly reduced deactivation at humidity levels up to 75% and are thus promising materials for personal respiratory protection in respiratory filters for fire fighters and miners. The hopcalite catalysts were obtained by a scalable production route using flame spray pyrolysis (FSP) of mixtures of oleates, 2-ethylhexanoates as well as nitrates dispersed by a surfactant. The textural compositional and also catalytic properties of the FSP-hopcalites were found to be highly tuneable by the type of precursor and the spraying parameters. Adjusting the spraying conditions lead to catalysts with specific surface areas as high as 180m2g−1 being mainly composed of Cu1.5Mn1.5O4 by applying 2-ethylhexanoates as precursors. Microemulsions and 2-ethylhexanoates were found to yield hopcalite nanoparticles with very high activity for the catalytic oxidation of carbon monoxide at ambient temperature. The humidity tolerance is attributed to carbon deposits exhibiting a hydrophobic characteristic as indicated by physisorption measurements using water vapour and nitrogen as adsorbates.

Microemulsion flame pyrolysis for hopcalite nanoparticle synthesis: a new concept for catalyst preparation.

A new route to highly active hopcalite catalysts via flame spray pyrolysis of an inverse microemulsion precursor is reported. The nitrate derived nanoparticles are around 15 nm in diameter and show excellent conversion of CO under ambient conditions, outperforming commercial reference hopcalite materials produced by co-precipitation.

Catalytic Decomposition of Ozone by CuO/MnO2-Performance, Kinetics and Application Analysis

Ozone as a major ambient gas pollutant needs to be removed for many indoor environments due to its adverse health effect. The objective of this study is to investigate the ozone removal performance of a Hopcalite catalyst CuO/MnO2 under different operation conditions. The effect of relative humidity (15-80%), temperature (30-160°C) and ozone concentration (200-2000ppb) was experimentally tested. Then the catalyst was coated on fiberglass media for application. The influence of preparation method was also investigated. Finally, the application analysis of such material is discussed for building environment control situation.

Performance and kinetics of catalytic oxidation of formaldehyde over copper manganese oxide catalyst

Thermo-catalytic oxidation (TCO) has a great potential for formaldehyde removal in terms of both efficiency and lifetime. This study investigated the performance and kinetics of hopcalite catalyst (CuO–MnO2) for indoor formaldehyde removal. The effect of inlet concentration (typical indoor level: 180–1300 ppb) and moisture concentration (typical indoor level: 2000–30,000 ppm) on the reaction rate was studied at four temperature levels (25–180 °C). The relative humidity shows significant influence on the catalytic oxidation of formaldehyde by CuO/MnO2, especially at room temperature level. The catalytic oxidation of formaldehyde by CuO/MnO2 follows the traditional L–H model. The L–H model described the reaction process best. Furthermore, the reaction kinetics considering multiple parameters including concentration, moisture concentration and temperature was proposed based on the L–H model. Good agreement was found between experimental data and the prediction with the modified L–H model.