Cu-Mn Catalysts Research Articles

Study on the catalytic mechanism and water resistance of Cu-Mn-Snx catalyst for CO elimination

CO in coal mine underground spaces can easily cause casualties among miners. The humidity in coal mines is relatively high, and traditional Cu-Mn catalysts are prone to deactivation. Compared to traditional Cu-Mn catalysts, doping with Sn enhances the activity and water resistance of Cu-Mn catalysts. The Cu-Mn-Sn catalyst was tested using XPS, FTIR, and a self-made Activity Test Experimental System, with partial data processed using the Avantage software. The results show that Sn increases the number of active sites (Cu+) on the Cu-Mn catalyst and the proportion of surface adsorbed oxygen (Oads) and surface lattice oxygen (Olat) in O 1s, which is the reason for the improved activity of the Cu-Mn-Sn catalyst. Sn weakens the coordination bond between Cu2+ and H2O, reducing the formation of CO32−, which is the reason for the improved water resistance of the catalyst.

Suspension-washcoat optimization for preparing copper-manganese oxide structured catalyst towards flue gas CO purification

Structured catalysts play significant role in nowaday environmental industry. The copper-manganese oxide (Cu-Mn) is a low cost and efficient catalyst for CO purification from flue gas, for which a robust preparation regarding stabilized suspension and washcoat process is still lacked. This work addressed this challenge by constructing the catalyst suspension by introducing absorbent polymer (SAP), polyvinyl alcohol (PVA), and nano-silica sol (SiO2-NA). The effects of the dosage of SAP, PVA, and SiO2-NA on suspension properties including viscosity, water-retention capacity and stability were systematically studied. The combined effect of the three additives regarding electrostatic-sterical stability and regionalized coating is demonstrated to avoids the destruction of connection between SiO2-NA and Cu-Mn due to the thermal stress during the drying process. After calcination, SiO2-NA is efficiently utilized, evenly distributed and tightly bonded to Cu-Mn catalyst, rendering strongly-attached, crack-free and compact washcoated layer. The optimized structured catalyst shows appreciable balance of loading (up to 182 kg/m3) and strength (powder shedding rate <1 wt%) without blockage. The potential of practical application was verified by CO purification from realistic iron-ore sintering flue gas with catalytic efficiency of above 90 % for 240 h. These findings indicated a promising strategy to design Cu-Mn structured catalysts efficient for industrial use.

Staggered distribution structure Cu-Mn catalysts for mitigating smoke and gas toxicity in combustion: Unravelling mechanistic insight through operando studies

The integration of flame retardancy and environmental friendliness can be achieved by designing cost-effective, stable, and efficient catalysts to reduce smoke and toxicity during the combustion of polymeric materials. This work reports the development of non-precious metal catalysts for thermoplastic polyurethanes (TPU), which exhibit a significant reduction in smoke and gases toxicity while providing flame retardancy. The use of MgB2 as a support enables the in-situ growth of highly efficient Cu-Mn based catalysts, resulting in a remarkable 51.5 % decrease in total smoke release and a 49.1 % reduction in peak rate of CO generation of TPU according to cone calorimeter test results. Furthermore, Cu-Mn/MgB2 demonstrates an impressive 83.1 % reduction in total CO production rate during the steady-state tube furnace test. Additionally, density functional theory is employed to analyze the binding energy between catalysts and TPU as well as the adsorption energy of gases. This elucidates the rational reaction mechanism behind the catalyst and smoke inhibiting process. By combining transition metal oxide catalyzed CO oxidation reaction with polymeric material combustion, this study presents a promising approach for efficient smoke suppression with potential applications.

Engineering Grain Boundary and Surface Sites of Binary Cu-Mn Catalysts to Boost CO Oxidation

The catalytic oxidation of CO over Cu-based catalysts has garnered significant interest due to their promising potential in addressing environmental pollution and enhancing industrial processes. Herein, we report a dual-stimuli...

Hydrogen production via methanol steam reforming using sepiolite-derived Cu-based spherical micro-mesoporous catalysts

Hydrogen production via MSR has been achieved over spherical micro-mesoporous supported CuMn catalysts using sepiolite-derived silica. Cu–MnOx interfaces inhibit the excessive oxidation of Cu0 to supply active Cu+ and oxygen vacancies.

Efficient catalytic ozonation of ethyl acetate over Cu-Mn catalysts: Further insights into the reaction mechanism

A series of Cu-Mn oxides were synthesized by the redox-precipitation method with different precipitants to evaluate the catalytic ozonation of ethyl acetate (EA). It was found that CuMn-II (with H2C2O4 as precipitant) exhibited the best catalytic activity, which achieved an EA conversion of 99 % at 120 °C with an O3/EA molar ratio of 10. The reaction temperature, O3/EA molar ratio, ozone utilization rate, and COx selectivity were also discussed. Meanwhile, many characterizations were conducted to reveal the properties of catalysts, such as SEM, XRD, BET, XPS, H2-TPR and NH3-TPD. Abundant surface defects, plentiful oxygen vacancies, larger specific surface area, higher content of Mn3+ and more acid sites contributed to the superior performance of CuMn-II. Catalyst poisoning occurred when SO2 was added, however, the conversion of EA could gradually recover to 88 % once SO2 was stopped. In-situ DRIFTS measurement was carried out to reveal the formation of intermediate species during the reaction. Combined with DFT calculations, a reaction mechanism for the catalytic ozonation of EA over CuMn2O4 catalysts was proposed.

The promotional roles of multivalent metal ions and oxygen vacancies on nitrogen-doped carbon-combined CuMn-based catalysts for cyclohexylbenzene oxidation

In this work, we fabricated nitrogen-doped carbon (NC)-combined CuMn-based catalysts derived from layered double hydroxide and melamine mixture precursor and further explored their activity in the aerobic oxidation of cyclohexylbenzene (CHB) to produce cyclohexylbenzene-1-hydroperoxide (CHBHP) using molecular oxygen as the oxidant. Series of structural characterizations demonstrated that multivalent Cu and Mn species and abundant surface defective oxygen vacancies could form in catalysts, due to comprehensive redox processes between Cu and Mn atoms upon high-temperature calcination of precursors under inert atmosphere, as well as the promotional effect of melamine added on the reduction of metal ions. As-fabricated NC-combined CuMn catalyst bearing a 1:1 Cu:Mn molar ratio showed a higher catalytic oxidation activity, in comparison to other NC-decorated CuMn-based catalysts, NC-free CuMn-based one, and pure single metal oxides (i.e., CuO, MnO2). It was revealed that the presence of favorable multivalent Cu and Mn ions and abundant oxygen vacancies was conducive to the effective adsorption and activation of CHB and oxygen molecules, thus accelerating the selective oxidation of CHB to form CHBHP. Moreover, surface NC overlayer on catalysts could protect surface structures of catalysts during the oxidation. The present study provides deep understanding of the roles of surface-active metal species and oxygen vacancies of CuMn-based catalysts for efficient oxidation of CHB to form CHBHP.

Evaluation of the Flexibility for Catalytic Ozonation of Dichloromethane over Urchin-Like CuMnOx in Flue Gas with Complicated Components.

The evaluation of the poisoning effect of complex components in practical gas on DCM (dichloromethane) catalytic ozonation is of great significance for enhancing the technique's environmental flexibility. Herein, Ca, Pb, As, and NO/SO2 were selected as a typical alkaline-earth metal, heavy metal, metalloid, and acid gas, respectively, to evaluate their interferences on catalytic behaviors and surface properties of an optimized urchin-like CuMn catalyst. Ca/Pb loading weakens the formation of oxygen vacancies, oxygen mobility, and acidity due to the fusion of Mn-Ca/Pb-O, leading to their inferior catalytic performance with poor CO2 selectivity and mineralization rate. Noticeably, the presence of As induces excessively strong acidity, facilitating the inevitable formation of byproducts. Catalytic co-ozonation of NO/DCM is achieved with stoichiometric ozone addition. Unfortunately, SO2 introduction brings irreversible deactivation due to strong competition adsorption and the loss of active sites. Unexpectedly, Ca loading protects active sites from an attack by SO2. The formation of unstable sulfites and the released Mn-O structure offset the negative effect from SO2. Overall, the catalytic ozonation of DCM exhibits a distinctive priority in the antipoisoning of metals with the maintenance of DCM conversion. The construction of more stable acid sites should be the future direction of catalyst design; otherwise, catalytic ozonation should be arranged together with post heavy metal capture and a deacidification system.

Successive treatment of benzene and derived byproducts by a novel plasma catalysis-adsorption process

Gas discharge plasma (catalysis) process (GDPP/GDPCP) is efficient for degrading VOCs at ambient temperature and atmospheric pressure, but the process also leads to the emission of gaseous byproducts including organic aerosols, NOx and O3. In this paper, a novel double-chamber dielectric barrier discharge (DBD) catalysis reactor, which was consisted of a gas phase packed-bed discharge chamber and a gas-liquid phase discharge chamber in series, was designed to enhance the benzene degradation and inhibit the emission of gaseous byproducts. Mn-Cu/Al2O3 catalyst was employed as the packed material in gas phase discharge chamber due to their good catalytic performance in VOCs degradation. Persulfate was added in the water of gas-liquid phase discharge chamber to reduce the emission of gaseous byproducts. The results show that Mn-Cu/Al2O3 (1:1) catalysts improved benzene degradation and CO2 selectivity compared to discharge plasma treatment alone, and the emission of O3 and NO2 was effectively reduced; moreover, an addition of persulfate in water also enhanced the degradation of benzene due to the formation of stronger active radicals via an activation of persulfate by discharge plasma. The characterization of Cu-Mn catalyst by XRD, SEM and XPS shows that Cu1.4Mn1.6O4 is one of important components of Cu-Mn composite catalyst, and the derived redox couples of Mn4+ /Mn3+ and Cu2+/Cu+ with more vacancies are helpful for adsorbing oxygen or ozone and then enhancing the degradation of benzene.

Lanthanum-doped Cu[sbnd]Mn composite oxide catalysts for catalytic oxidation of toluene

CuMn mixed oxides catalysts doped with La were prepared following a co-precipitation method and used for the catalytic oxidation of toluene. Catalysts properties of the catalysts were investigated by X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, H2-temperature-programmed reduction (H2-TPR), O2-temperature-programmed desorption (O2-TPD) and X-ray photoelectron spectroscopy techniques. Characterization data reveal that the phase change and decrease in crystallinity of the La-doped catalysts increase the number of oxygen vacancies. Improvements in reducibility and an increase in the amount of chemisorbed oxygen of the La-doped catalysts were also verified by H2-TPR and O2-TPD. The activity of the CuMn mixed oxides catalysts is significantly improved by the addition of a nominal amount of La. The CuMn/La-4 mol% catalyst exhibits the best catalytic activity, with a 90% conversion temperature of 255 °C, attributed to a high Mn3+ratio, superficial chemisorbed oxygen, and high surface area. This study indicates La to be a promising dopant for CuMn catalysts toward toluene oxidation.

Cu-Mn catalysts modified by rare earth lantnaum for low temperature water-gas shift reaction

The Cu-Mn catalysts doped with different amounts of lanthanum (La) for water-gas shift reaction (WGSR) were prepared, and characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), temperature-programmed reduction of oxidized surfaces (s-TPR), temperature-programmed desorption of CO2 (CO2-TPD), infrared spectrum (FT-IR) and X-ray photoelectron spectroscopy (XPS). Catalytic activities were tested for a water-gas shift reaction. The results showed that the introduction of 0.5 mol.% La could significantly improve the catalyst activity for low-temperature shift reaction compared with the undoped catalyst, which might be from the introduction of La making the Cu and Mn components distribute uniformly and the synergistic effect between Cu and Mn increasing the dispersion of Cu on the surface of the catalyst. The apparent CuO phases besides Cu1.5Mn1.5O4 were found in the samples with at least 3.0 mol.% La content, and the basic sites increased with the increasing of La contents at a decreased rate. With excessive La doping, La particles would aggregate and cover some active sites, resulting in that Mn could not effectively inhibit the gathering together and growing up of Cu crystalline grain, and decreased the dispersion of Cu on the surface, which resulted in the poor activity of the catalyst for WGSR.

Catalytic Total Oxidation of SOFC Exhaust Gas on Cu-Mn Catalysts

SOFC exhaust gases, such as methane and carbon monoxide, cause environmental problems. However, extra energy can be realized from oxidizing these out-gases into CO 2 and H 2 O. This extra energy can be recycled in an SOFC system and increase the thermal efficiency. Thus the development of new catalysts that lower the oxidation temperature will make the SOFC system more efficient. CULLEN et. al.[1] reported high conversion rate of SOFC exhaust gas using a La-Cu-Mn impregnated alumina catalyst and a Pt-Pd catalyst in series. In this work, Cu-Mn catalysts that are used in the oxidation of methane or carbon monoxide were tested for SOFC exhaust gas oxidation. For determining the best ratio of Cu-Mn in catalysts, different ratios of La2O3-MnO-CuO/γ-Al2O3catalysts were prepared. The result shows approximtely 0.5 to 2 Cu/Mn ratio is the best composition for SOFC exhaust gas oxidation[Fig. 1]. Fig. 1. Conversion of CO(160℃), H2(240℃), CH4(460℃) with various Cu-Mn ratio. Cu-Mn perovskite and spinel supported catalysts were also tested. The perovskite supported catalysts showed much higher activity than the spinel supported. This was especially so for the case of methane conversion; the perovskite supported catalysts showed similar performance to alumina supported. The methane conversion of reference, CP and MP were 53.1%, 55.1% and 56.3% at 500℃, respectively.

Catalytic Total Oxidation of SOFC Exhaust Gas on Cu-Mn Catalysts

SOFC exhaust gas oxidation technology will contribute to reducing the pollutants and providing economically feasible SOFC systems. The Cu-Mn based materials, known as CO and H2 oxidation catalysts, were tested as novel metal-free SOFC exhaust gas oxidation catalysts. Catalysts are prepared with incipient wetness impregnation method using metal nitrate precursors on γ-Al2O3. Various Cu-Mn catalysts are also prepared to study the effect of CuO-MnO ratio on catalytic activity. The feed gas was synthesized as similar composition of SOFC exhaust gas. The optimized conversion was obtained when CuO and MnO had the same weight ratio(CuO/MnO wt. ratio = 1). The conversion of CO, H2 and CH4 is 43.4, 36.1 and 58.0, repectively.

Transition metal oxide catalysts as an alternative for the oxidation of nitrogen monoxide to nitrogen dioxide: kinetic modelling at high space velocity

AbstractBACKGROUNDThe oxidation of NO to NO2 is a key step in environmental pollution abatement techniques, such as ‘fast‐SCR’ or diesel engine catalytic traps. In both cases, the conversion of an important fraction of NO into NO2 is a key step. In this work, two commercially available transition metal oxide catalysts, CuMn and CuCr‐based, are studied as an alternative to noble metal catalysts (a Pt/Al2O3 catalyst is used as reference catalyst).RESULTSSteady NO conversion is obtained after the first 1–2 h of operation. The experiments, carried out in an isothermal fixed‐bed reactor operating at high space velocities (5.60 gcat min mol‐1, GHSVmonolith‐eq. = 83 000 h‐1) with 500 ppm NO and 20% oxygen, showed that the optimum operating temperature is 380 °C for the CuMn catalyst, 430 °C for the CuCr catalyst and 366 °C for a 0.5% Pt/Al2O3 catalyst.CONCLUSIONSThe CuMn catalyst performed very similarly to the 0.5% Pt/Al2O3 catalyst in the vicinity of 380 °C, being a good and cheaper alternative to noble metal catalysts. Kinetic measurements obtained under different conditions, e.g. 3.73–5.60 gcat min mol‐1 (GHSVmonolith‐eq. = 83 000–125 000 h‐1), 300–900 ppm NO, 1–20% oxygen concentration and 330–480 °C, have been found to fit a mechanistic kinetic model based on the reaction between gas nitrogen oxide and adsorbed oxygen. © 2014 Society of Chemical Industry

Effect of anions on the structure and catalytic properties of a La-doped Cu-Mn catalyst in the water-gas shift reaction

AbstractEffects of the anion type on the structure, thermal stability, and catalytic performance of La-doped Cu-Mn catalysts prepared by co-precipitation were characterized by X-ray diffraction, Brunauer-Emmett-Teller, temperature-programmed reduction, temperature-programmed reduction of oxidized surfaces, and temperature-programmed desorption. The Cu-Mn catalyst was tested for the water-gas shift (WGS) reaction. The main crystalline phase of samples prepared with sulfate, acetate, chloride, and nitrate as the starting materials was a Cu1.5Mn1.5O4 spinel structure, following the WGS reaction, the main crystalline phases were transformed into Cu and MnO. The sample prepared with acetate as the starting material showed the most obvious MnCO3 characteristic diffraction peaks, with better synergistic effects of Cu and MnO, increased adsorption of CO2 and improved dispersion of Cu on the catalyst surface; also, the best thermal stability and the highest low temperature catalytic activity were observed. The sample prepared with nitrate as the starting material maintained high thermal stability and catalytic performance in the range of 400°C to 450°C, but CO conversion decreased below 350°C. Catalytic performance of the sample prepared with sulfate and chloride as the starting materials was poor, ranging from 200°C to 450°C.

Effect of the Ration of Cu to Mn on the Activity and Stability of Copper-Manganese Mixed-Oxides for the Water Gas Shift Reaction

The effects of Cu/Mn ratio on the activity and stability of Cu-Mn catalysts for the water-gas shift reaction (WGSR) were investigated. Activity tests showed that the Cu-Mn catalyst while the ration of Cu to Mn is 1:1 displayed higher activity and better stability than that of others catalysts. The BET , XRD and TPR results revealed that the Cu-Mn catalyst while the ration of Cu to Mn is 1:1 led to higher surface area, a more stable catalyst structure and suitable reduction performance, in turn leading to better catalytic behavior for the Cu-Mn catalyst.

Effect of Alkali Precipitateing Agent on the Activity and Stability of Copper-Manganese Mixed-Oxides for the Water Gas Shift Reaction

This paper reports the effect of alkali precipitating agents, i.e. KOH and NaOH, on activity and stability of Cu-Mn based catalysts for the water gas shift (WGS) reaction. Structural and texture characteristics of the catalysts were characterized by low temperature N2 adsorption, X-Ray Diffraction (XRD) and TPR techniques. The XRD and low temperature N2 adsorption results showed the two types of precipitators produced different Cu-Mn phases during precipitation and drying. The KOH precipitator resulted in partial precipitation of copper ion and formation of hydrate basic copper sulfate, Cu4SO4(OH)6•H2O after drying; while the NaOH precipitator led to a completed precipitation of Cu ion and formation of relatively stable Cu2+1O and Mn3O4crystals after drying. These phases formed after precipitation by the KOH and NaOH, however, experienced the same phase change during calcination and activation, namely, they first changed to Cu1.5Mn1.5O4in calcination followed by the formation of microcrystalline Cu and MnO phases during activation. The Cu-Mn WGS catalysts prepared by the NaOH was found to have larger surface area and more content of Cu and MnO phases after activation, which might be the reasons of higher activity and better stability of the Cu-Mn catalyst.

Copper-Based Mixed Oxides Catalyst of Water-Gas Shift Reaction for Fuel Cells: The Role of Alkali Charge

The effects of alkali charge on the activity and stability of copper-based mixed oxides catalyst for the water-gas shift reaction (WGSR) were investigated. Activity tests showed that the copper-based mixed oxides catalyst while the 2[NaOH]/[Cu2++Mn2+] is above 1.2 displayed higher activity and better stability than that of others catalysts. The BET , XRD and TPR results revealed that the Cu-Mn catalyst while the 2[NaOH]/[Cu2++Mn2+] is above 1.2 led to higher surface area, a more stable catalyst structure and suitable reduction performance, in turn leading to better catalytic behavior for the Cu-Mn catalyst.