H2 Temperature-programmed Reduction Research Articles

Nickel Nanoparticles Anchored on Activated Attapulgite Clay for Ammonia Decomposition to Hydrogen

Ammonia decomposition to hydrogen technique is an effectively way to solve the problems associated with the storage and transportation of hydrogen, but the development of a high-performance catalyst for ammonia decomposition is a great challenge. Ni species supported on activated attapulgite clay (AATP) is prepared by a homogeneous precipitation method for ammonia decomposition to COx-free H2. The structural properties of the Ni/AATP catalysts are characterized by thermogravimetric analysis, X-ray diffraction, scanning and transmission electron microscopy, H2 temperature-programmed reduction, and N2 sorption technique. It is revealed that the porous structure and high surface area of rod-like symmetric AATP results in highly dispersed NiO particles because the presence of a strong interaction between AATP and NiO particles. In particular, the Si-OH in AATP can react with Ni species, forming Si-O-Ni species at the interface between Ni and AATP. The Ni/AAPT catalysts are used for ammonia decomposition, the 20%-Ni/ATTP catalyst shows a 95.3% NH3 conversion with 31.9 mmol min−1 gcat−1 H2 formation rate at 650 °C. This study opens a new way to utilize natural minerals as an efficient support of catalysts towards ammonia decomposition reaction.

An amine-modified Pd-based catalyst for highly-efficient 2-amylanthraquinone hydrogenation

The development of anthraquinone (AQ) hydrogenation catalysts with high activity and selectivity remains a challenge, but it is critical in industrial applications from both economic and environmental perspectives. In this work, an amine-modified catalyst, i.e., Pd/A/SiO2, was designed and synthesized via grafting 3-aminopropyltrimethoxysilane (APTMS) onto silica support and then loading Pd via the Shiff-base reaction. Multiple techniques were used to thoroughly characterize and analyze the catalysts' structural and electronic properties, such as transmission electron microscopy (TEM), H2 temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS), etc. The Pd particle size (3.86 nm) in Pd/A/SiO2 was found to be very close to the reported optimal value, which balances well between the number of active sites and the required size for AQ adsorption; also, the residual carbon species from APTMS improves the hydrophobic properties of the support, which benefits AQ adsorption and anthrahydroquinone (AQH2) desorption; and furthermore, the electron transferred from N to Pd increases the electron density of the latter, favoring the activation of the CO bond in AQ. These factors combine to give a very superior performance of Pd/A/SiO2 for AQ hydrogenation, including a hydrogenation efficiency as high as 15.7 g/L with an intriguing selectivity of 96.1 %, and a good reusability merit within a six-run test, all of which are among the best results reported so far. This work, we believe, provides food for thought in the development of a highly efficient catalyst for AQ hydrogenation.

Experimental and theoretical studies of carbon monoxide oxidation over W/Cu/Ce trimetallic oxides: the effect of W addition

It is a significant method to prepare highly dispersed polymetallic oxides using in-situ doping metal organic frameworks as precursors. Herein, a series of straw-like W/Cu/Ce trimetallic oxides were prepared by using phosphotungstic ionic liquid@Ce-based metal organic framework adsorbing with copper acetylacetonate as precursors. The effect of W content on catalytic activity of W/Cu/Ce trimetallic oxides for carbon monoxide (CO) oxidation was well-investigated. Comprehensive characterization methods and density functional theory calculations were adopted to reveal the property changes of Cu/CeO2 catalyst by the addition of W. The results demonstrated that W, Cu, and Ce are highly dispersed in the prepared W/Cu/Ce trimetallic oxides, and adding proper amount of W can improve the activity of the catalyst. H2 temperature-program reduction profiles, X-ray photoelectron spectroscopy, in-situ diffuse reflectance infrared Fourier transform spectroscopy, and density functional theory calculations clearly revealed that after the addition of W, the strength of Ce-O bond is weakened, the oxygen vacancy is increased, and the adsorption of CO is enhanced, respectively, which are vital reasons for its high catalytic activity. In addition, the CO oxidation reaction pathway over prepared W/Cu/Ce trimetallic oxides based on the Mars-van Krevelen mechanism was studied, and the results exhibited that CO can wrest the lattice oxygen of W/Cu/Ce trimetallic oxides to form CO2, which is also proved to be the rate-determining step in reaction process.

Oxygen vacancy modification of commercial ZnO by hydrogen reduction for the removal of thiabendazole: Characterization and kinetic study

The effect of temperature-programmed H2 reduction on modification of surface oxygen vacancies in commercial ZnO (C-ZnO) is investigated. The photocatalytic degradation of the fungicide thiabendazole was optimized by treating C-ZnO with 10% H2/Ar gas at 500 °C over 5 h. The formation of oxygen vacancies and their catalytic activity were compared before and after the reduction treatment based on their characterization analysis (e.g., TPR, FE-SEM, EDS, XPS, Tauc plot, XRD, and BET). Our most recent kinetic modeling was carried out on the experiments using C-ZnO and T500 at different pH values. The highest adsorption removal and photocatalytic degradation rate (and quantum yield) was occurred at pH 3 and 11, respectively. Good reusability of the optimal reduced catalyst was confirmed when tested over five cycles. A strong compatibility between the kinetic modeling results and all characterization analyses supports the potent role of reduction treatment for the modification of oxygen vacancies on photocatalysis.

NH3-NO SCR Catalysts for Engine Exhaust Gases Abatement: Replacement of Toxic V2O5 with MnOx to Improve the Environmental Sustainability

Mn-WO3/TiO2 catalysts were investigated for Selective Catalytic Reduction (SCR) of NO with NH3. The catalysts were synthesized by wetness impregnation method with different Mn loadings (1.5-3-12 wt%) on 8wt%WO3/TiO2. All three catalysts were compared with 8wt%WO3/TiO2 and bare MnOx oxide, used as references. The 1.5wt%Mn-8wt%WO3/TiO2 exhibited the highest performance in NO conversion and N2 selectivity. A commercial catalyst, based on titania supported vanadia and tungsta, (V2O5-WO3/TiO2), widely used for its high efficiency, was also investigated in the present work. The morphological, structural, redox and electronic properties of the catalysts and their thermal stability were studied by several techniques (N2 adsorption/desorption, X-ray diffraction, H2 temperature-programmed reduction, NH3 temperature programmed desorption, X-ray photoelectron spectroscopy).The aim of this paper is to study the effect of different Mn loadings on 8wt%WO3/TiO2 with the ambition to obtain highly active and selective catalysts in a large window of temperature. The replacement of toxic vanadium used in the classic V2O5-WO3/TiO2 catalyst with MnOx in the best performing catalyst, 1.5wt%Mn-8wt%WO3/TiO2, represents an important achievement to improve the environmental sustainability.

Ozone catalytic oxidation of low-concentration formaldehyde over ternary Mn-Ce-Ni oxide catalysts modified with FeOx.

Manganese oxide-based catalysts have attracted extensive attention due to their relatively low cost and remarkable performance for removing VOCs. In this research, we used the Pechini method to synthesize manganese-cerium-nickel ternary oxide catalysts (MCN) and evaluated the effectiveness of catalytic destruction of formaldehyde (HCHO) and ozone at room temperature. FeOx prepared by the impregnation method was applied to modify the catalyst. After FeOx treatment, the catalyst represented the best performance on both HCHO destruction and ozone decomposition under dry conditions and exhibited excellent water vapor resistance.The as-prepared catalystswere next characterized via H2-temperature programmed reduction (H2-TPR), temperature programmed desorption of O2 (O2-TPD), and X-ray photoelectron spectroscopy (XPS), and the results demonstrated that addition of FeOx increased Mn3+ and Ce3+ concentrations, oxygen vacancies and surface lattice oxygen species, facilitated adsorption, and redox properties. Based on the results of in situ diffuse reflectance infrared Fourier transform spectrometry (DRIFTS), possible mechanisms of ozone catalytic oxidation of HCHO were proposed. Overall, the ternary mixed-oxide catalyst developed in this study holds great promise for HCHO and ozone decomposition in the indoor environment.

CuO decorated vacancy-rich CeO2 nanopencils for highly efficient catalytic NO reduction by CO at low temperature.

With the rapid development of transportation and vehicles, the elimination of NOx and CO has highly attracted public attention. In this work, vacancy-rich CeO2 nanopencil supported CuO catalysts (CuO/CeO2-NPC) were successfully prepared for NO reduction by CO. Importantly, CeO2 with nanopencil-like shape (CeO2-NPC) have been synthesis by solvothermal method for the first time. The physicochemical properties of all samples were studied in detail by combining the means of X-ray diffraction (XRD), Raman spectroscopy, electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), H2-temperature-programmed reduction (H2-TPR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N2 physisorption (Brunauer-Emmett-Teller), and NO and CO temperature-programmed desorption (NO-TPD and CO-TPD) techniques. Compared with CeO2 nanorods and nanoparticles supported CuO catalysts (CuO/CeO2-NR and CuO/CeO2-NP), the CuO/CeO2-NPC catalysts showed the highest catalytic activity, affording more than 90% NO conversion at 69°C as well as excellent H2O tolerance at 150°C, which is superior to catalysts previously reported. Characterization results indicated that the synergistic effect between the well-dispersed CuO and the CeO2 nanopencil support enables a favorable electron transfer between these components and enhances the density of surface oxygen vacancies and Cu+ species, which consequently accelerating the redox cycle. The results indicated that the morphology control of CeO2 support could be an efficient way to evidently enhance the catalytic performance for NO + CO reaction.

Sn-decorated CeO2 with different morphologies for direct dehydrogenation of ethylbenzene

Three Sn-decorated ceria catalysts with various morphologies (rods, particles, and cubes) were prepared and applied to the direct dehydrogenation of ethylbenzene. Multi-technology characterizations, including X-ray photoelectron spectroscopy (XPS), H2-temperature programmed reduction (H2-TPR), and Raman spectroscopy, prove that the oxygen vacancies are the active sites for ethylbenzene dehydrogenation, which can be regulated by engineering CeO2 morphology and enhanced via introducing metal Sn. Given the results of activity test, the catalytic activities for ethylbenzene dehydrogenation over different samples are closely dependent on the amount of oxygen vacancies. The reduced Sn-decorated CeO2 catalyst with nanoparticles morphology exhibits better dehydrogenation performance than the other two studied catalysts at 600 °C. This work provides an effective approach to regulate the active oxygen vacancies and further enhance the dehydrogenation activities through engineering the surface morphology of the catalyst and introducing suitable additives.

Co-Precipitated Mn0.15Ce0.85O2−δ Catalysts for NO Oxidation: Manganese Precursors and Mn-Ce Interactions

Two Mn0.15Ce0.85O2−δ mixed oxides were synthesized by a co-precipitation method using Mn(NO3)2 and KMnO4 as the manganese precursors, respectively. Structural analyses by X-ray powder diffraction and Raman spectroscopy reveal the formation of MnOx-CeO2 solid solutions. The Mn0.15Ce0.85O2−δ catalyst prepared from the high-valent manganese precursor exhibits higher activity for the catalytic oxidation of NO. The advantage of KMnO4 is related to the improved redox property of the catalyst as supported by H2 temperature-programmed reduction (TPR) and O2 temperature-programmed desorption (TPD). The Mn-Ce interactions create more Mn4+, Ce3+ and oxygen vacancies on the KMnO4-synthesized mixed oxides based on the Raman and X-ray photoelectron spectra (XPS).

Study on the Performance of the Zr-Modified Cu-SSZ-13 Catalyst for Low-Temperature NH3-SCR.

Cu-SSZ-13 and Zr-modified Cu-SSZ-13 catalysts with different Zr/Cu mass ratios were prepared by ion-exchange and impregnation methods, respectively. The NH3-SCR performance tests were performed using the catalyst performance evaluation device to investigate the effects of different Zr/Cu mass ratios on the catalyst ammonia-selective catalytic reduction (NH3-SCR) performance. X-ray diffraction, ICP-OES, BET, NH3 temperature-programed desorption (NH3-TPD), H2 temperature-programmed reduction (H2-TPR), X-ray photoelectron spectrometry, and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) were used to characterize the catalysts. The results show that the prepared Cu-SSZ-13 catalyst had good catalytic activity. Zr introduction was carried out on this basis. The results showed that proper Zr doping improved the catalytic activity at low temperatures and widened the high-temperature stage, with an optimal activity stage at a Zr/Cu mass ratio of 0.2. The NO x conversion efficiency was close to 100% at 200 °C and over 80% at 450 °C. The active species were well dispersed on the catalyst surface, and the metal modification did not change the crystal structure of the zeolite. The NH3-TPD results showed that the Zr-modified catalyst had more abundant acid sites, and the H2-TPR results indicated that the Cu species on the catalyst had excellent reducibility at low temperatures. The interaction between Cu and Zr could regulate the Cu+ and Cu2+ proportion on the catalyst surface, which facilitated the increase in the Cu+ for fast SCR reaction at low temperatures. With abundant acid sites and both SCR reactions following the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanism on the catalyst surface at a low temperature of 150 °C, more abundant acid sites and reaction paths created favorable conditions for NH3-SCR reactions at low temperatures.

Catalytic behavior of Mo–Bi–Fe–Co–K–M–O (M=Ce, Gd, CeGd) catalysts for selective oxidation of isobutene

The further improvement of methacrolein (MAL) selectivity from isobutene (IB) oxidation is crucial and challenging. In this study, based on the typical Mo–Bi–Fe–Co–K–O mixed metal oxide, the rare earth element Gd-doped, Ce-doped and CeGd co-doped catalysts were prepared by co-precipitation strategy to increase the selectivity of MAL from 47.9% to 49.8%, 64.2% and 68.6%, respectively. In order to elucidate in-depth the promoting effect of Ce and/or Gd, various characterizations were utilized including X-ray diffraction patterns (XRD), Raman, X-ray fluorescence spectrometry (XRF), X-ray photoelectron spectroscopy (XPS), O2-temperature programmed desorption (O2-TPD), H2-temperature programmed reduction (H2-TPR), CO2-temperature programmed desorption (CO2-TPD), IB-temperature programmed desorption (i-C4-TPD) and in-situ IB-Fourier transform infrared spectroscopy (IB-FTIR). Both Ce and Gd finely regulate the bulk and surface structure of the catalyst, thus altering the redox ability, oxygen mobility and storage ability and basicity. Compared with Ce, Gd addition slightly regulates the variation of Co2+/Co3+ redox couples, greatly enhances the interaction among the components on the catalyst, thus only increases the content of surface oxygen species and has little effect on their mobility. While Ce-containing catalyst performs stronger oxygen storage and migration ability, thus leading to the overproduction of surface Odefect species, which are proposed to be the active sites for the production of MAL and COx. The CeGd co-doped catalyst possesses the proper content of surface Odefect species, thus exhibits much higher MAL selectivity. Moreover, the promoting mechanism of Ce and/or Gd over IB oxidation is proposed. Therefore, this work is helpful for understanding the influence of rare earth elements on the structure of mixed metal oxides and the olefin selective oxidation reaction.

Non-isothermal reduction kinetics and mechanisms by hydrogen of Cu[sbnd]Al spinel solid solution

The non-isothermal reduction kinetics by hydrogen of CuAl spinel solid solution was investigated using H2 temperature-programmed reduction at different heating rates methodology. The reduction process consists of four stages in terms of the reduction degree (α), corresponding to the reduction of non-spinel Cu2+, easily reducible spinel Cu2+, hardly reducible spinel Cu2+ (I), and hardly reducible spinel Cu2+ (II). The activation energy was between 83.2 and 122.1 kJ mol−1 when α < 0.72, but increased sharply to ∼500 kJ mol−1 at α = 0.95, leading to different reduction mechanisms for these Cu2+ species. Furthermore, the phase transformation, spinel structure evolution, as well as reduction mechanism were investigated.

Application of hollow promoted Ni-based catalysts in steam methane reforming

This work deals with the application of Y-promoted Ni-based catalysts supported on both bulk and hollow Al2O3 supports with spherical shape in the steam reforming of methane (SRM) process. For evaluating the influence of Ni and Y loadings, 15, 20, and 25 wt% Ni and 1.5, 3.0, and 4.5 wt% Y were loaded on both alumina supports. Furthermore, for enhancing the stability and activity of SRM Ni-based catalysts, reaction temperature (600, 650, and 700 °C) and steam to methane (S/M) molar ratio (1.5 to 3.0) are also adjusted in this research. Various characterizing techniques listed as X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), N2 adsorption/desorption, energy dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FESEM), H2 temperature programmed reduction (H2-TPR), and temperature programmed oxidation (TPO) were employed on the fresh and used catalyst. Improvements in metal dispersion, catalytic performance, and long-time stability in SRM were achieved with the aim of a hollow Ni-Y-Al catalyst. As a result, 20Ni-3.0Y/HAl depicted the highest methane conversion of 95.77 %, hydrogen yield of 97.74 %, and H2/CO molar ratio of 6.61 at 700 °C, which is probably due to the higher surface area of hollow alumina support in comparison with bulk one.

Effect of Holmium Oxide Loading on Nickel Catalyst Supported on Yttria-Stabilized Zirconia in Methane Dry Reforming.

The carbon dioxide reforming of methane has attracted attention from researchers owing to its possibility of both mitigating the hazards of reactants and producing useful chemical intermediates. In this framework, the activity of the nickel-based catalysts, supported by yttria-stabilized zirconia and promoted with holmium oxide (Ho2O3), was assessed in carbon dioxide reforming of methane at 800 °C. The catalysts were characterized by N2-physisorption, H2 temperature-programmed reduction, temperature-programmed desorption of CO2, X-ray diffraction, scanning electron microscopy (SEM) together with energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) techniques. The effect of holmium oxide weight percent loading (0.0, 1.0, 2.0, 3,0, 4.0, and 5.0 wt %) was examined owing to its impact on the developed catalysts. The optimum loading of Ho2O3 was found to be 4.0 wt %, where the methane and carbon dioxide conversions were 85 and 91%, respectively. The nitrogen adsorption-desorption isotherms specified the mesoporous aspect of the catalysts, while the SEM images displayed a morphology of agglomerated, porous particles. The TEM images of the spent catalyst displayed the formation of multiwalled carbon nanotubes. TGA of the 4.0 wt % of Ho2O3 catalyst, experimented over 7-hour time-on-stream, displayed little weight loss (<14.0 wt %) owing to carbon formation, indicating the good resistance of the catalyst to carbon accumulation due to the enhancing ability of Ho2O3 and its adjustment of the support.

Effects of Silica Modification (Mg, Al, Ca, Ti, and Zr) on Supported Cobalt Catalysts for H2-Dependent CO2 Reduction to Metabolic Intermediates.

Serpentinizing hydrothermal systems generate H2 as a reductant and harbor catalysts conducive to geochemical CO2 conversion into reduced carbon compounds that form the core of microbial autotrophic metabolism. This study characterizes mineral catalysts at hydrothermal vents by investigating the interactions between catalytically active cobalt sites and silica-based support materials on H2-dependent CO2 reduction. Heteroatom incorporated (Mg, Al, Ca, Ti, and Zr), ordered mesoporous silicas are applied as model support systems for the cobalt-based catalysts. It is demonstrated that all catalysts surveyed convert CO2 to methane, methanol, carbon monoxide, and low-molecular-weight hydrocarbons at 180 °C and 20 bar, but with different activity and selectivity depending on the support modification. The additional analysis of the condensed product phase reveals the formation of oxygenates such as formate and acetate, which are key intermediates in the ancient acetyl-coenzyme A pathway of carbon metabolism. The Ti-incorporated catalyst yielded the highest concentrations of formate (3.6 mM) and acetate (1.2 mM) in the liquid phase. Chemisorption experiments including H2 temperature-programmed reduction (TPR) and CO2 temperature-programmed desorption (TPD) in agreement with density functional theory (DFT) calculations of the adsorption energy of CO2 suggest metallic cobalt as the preferential adsorption site for CO2 compared to hardly reducible cobalt-metal oxide interface species. The ratios of the respective cobalt species vary depending on the interaction strength with the support materials. The findings reveal robust and biologically relevant catalytic activities of silica-based transition metal minerals in H2-rich CO2 fixation, in line with the idea that autotrophic metabolism emerged at hydrothermal vents.

Synergistic effect of copper and vanadium species on Hg0 removal of Cu-SCR catalyst: A DFT and experimental study

The synergistic effect of Cu and V species on the improved Hg0 removal performance of Cu-SCR catalyst was analyzed in depth by experiments and theoretical calculations based on density functional theory (DFT). Possible CuVOx/TiO2(001) surface models were constructed for Hg adsorption and oxidation calculations in the presence of O2. According to the results of partial density of states (PDOS) and charge populations, Cu transfers electrons to V through bridge O, and the strong hybridization of Cu 3d and O 2p orbitals facilitate the generation of O−. Although copper doping slightly promotes the Hg adsorption and oxidation ability of VOx species, the O− bonded with Cu provides the optimal adsorption sites and active centers. Strongly hybridized with CuO, Hg easily transfers charge to O− and generate HgO to desorb from the surface, and the oxygen vacancy thus formed can be supplemented by gaseous O2. Characterizations including Raman, fourier transform infrared spectroscopy (FTIR), H2 temperature program reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) verifies the formation of Cu-O-V structure and the higher involvement of CuOx in Hg0 oxidation, and Hg0 temperature program desorption (Hg0-TPD) were conducted to verify the reaction mechanism. This study reveals the good potential of copper species in Hg0 removal, and provides a reference for designing new materials for mercury control.

MESOPOROUS SILICOALUMINATE MATERIALS (MCM-41, SBA-15 AND MCF) BY ATRANE ROUTE FOR COBALT CATALYST

In this work, the synthesis of mesoporous silicoaluminum supports synthesized by the atrane route was performed. The obtained supports presented high homogeneity of the aluminum dispersion, high surface area and narrow pore size distribution. The synthesized mesoporous supports were: MCM-41, SBA-15 and MCF with 10% of Al2 O3 in the matrix of SiO2 . Twelve percent of cobalt was added to these supports by the incipient wetness impregnation method. These materials were characterized by adsorption of Nitrogen (BET-BJH), Scanning Microscopy Electron (SEM), X-Ray Diffraction (XDR), H2 Temperature-Programmed Reduction (TPR) and NH3 Temperature-Programmed Desorption (TPD). According to their structural properties of these catalysts, a promising application in the Fischer- Tropsch syntheses (FTS) is identified.

Synthesis of CeyMn(1-y)Ox solid solution catalysts with superior photothermal catalytic performance for acetone removal under ambient condition

Cerium-manganese solid solution catalysts were prepared by sol-gel method. X-ray diffraction, Raman, UV–Vis-IR diffuse reflectance spectroscopy, and H2 temperature programmed reduction (H2-TPR) were used to characterize the as-prepared catalysts. Introduction of Mnx+ into CeO2 lattice dramatically improved the full solar spectrum absorption ability, as well as the lattice oxygen mobility of the catalysts. The Ce0.25Mn0.75Ox catalyst presents much better low temperature reducibility due to the presence of readily reduced Mnx+ species in CeO2 lattice. Ce0.25Mn0.75Ox shows a superior photothermal catalytic activity for the degradation of gaseous acetone under visible-infrared irradiation (150 mW/cm2), which gives a reaction rate constant of 11.0 times higher than that with MnOx. During the whole process, the air temperature in catalytic system never exceeds 42 °C, suggesting the achievement of the efficient photothermal catalysis for acetone removal under ambient condition. This work provides an alternative strategy in environmental protection field for efficient volatile organic compounds removal in indoor environment.

Highly efficient removal of ozone by amorphous manganese oxides synthesized with a simple hydrothermal method

Amorphous manganese oxides (MnOx) were synthesized by facile hydrothermal reactions between potassium permanganate and manganese acetate. Synthesis parameters, including hydrothermal time and temperature and molar ratio of precursors, significantly affected the ozone removal performance and structure property of MnOx. Amorphous MnOx-1.5, which was prepared at the Mn2+/Mn7+ molar ratio of 1.5 under hydrothermal conditions of 120°C and 2 hr, showed the highest ozone removal rate of 93% after 480 min at the room temperature, RH (relative humidity) = 80% and WHSV (weight hourly space velocity) = 600 L/(g·hr). The morphology, composition and structure of catalysts were investigated with X-ray diffractometer (XRD), Raman spectra, N2 physisorption, field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR), O2 temperature-programmed desorption (O2-TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). It was confirmed that high catalytic activity of amorphous MnOx for ozone removal was mainly ascribed to its abundant oxygen vacancies, high oxygen mobility and large specific surface area.

Catalytic Oxidative Decomposition of Dimethyl Methyl Phosphonate over CuO/CeO2 Catalysts Prepared Using a Secondary Alkaline Hydrothermal Method

Bimetallic synergism plays an important role in lattice-doped catalysts. Therefore, lattice-doped bimetallic CuO/CeO2 catalysts were prepared by secondary alkaline hydrothermal reaction. During this process, the CeO2 nanomaterials were partially dissolved and recrystallized; thus, Cu ions were doped into the CeO2 lattice. The physical and chemical properties of CeO2, CuO/CeO2, and CuO were investigated. H2 temperature-programmed reduction characterization showed that the oxidation activity of CuO/CeO2 was significantly improved. X-ray photoelectron spectroscopy results showed that electron transfer occurred between Ce and Cu in the CuO/CeO2 catalyst. Additionally, Raman characterization confirmed the strong interaction between Cu and Ce. After CuO was loaded, the thermal catalytic decomposition performance of the catalyst was significantly improved with respect to the sarin simulant dimethyl methyl phosphonate (DMMP); with an increase in the Cu/Ce ratio, the performance first strengthened and then weakened. Additionally, the reaction tail gas and catalyst surface products were analyzed using mass spectrometry and ion chromatography, and the changes in the surface products during the thermal catalytic decomposition of DMMP were characterized at different temperatures using in situ diffuse reflectance infrared Fourier transform spectroscopy. Finally, the catalytic reaction pathways of DMMP on CeO2, CuO/CeO2, and CuO were inferred. The study results not only demonstrate an effective catalyst for the removal of nerve agent but also a feasible preparation method for lattice-doped bimetallic catalysts in the field of environmental protection.