Catalytic Effect Of Metal Oxides Research Articles

Catalytic effect of metal oxides on CO2 absorption in an aqueous potassium salt of lysine

We report the catalytic effects of metal oxides on the CO2 absorption rate in an aqueous potassium salt of l-lysine-HCl using the vapor liquid equilibrium method. The best CO2 absorption rate obtained through testing metal oxides in a highly concentrated potassium salt of amino acids (2.0M) was identified using CuO. The recyclability of the metal oxides was tested over three cycles. The catalyst CuO was found to enhance the absorption rate of CO2 by 61%. A possible mechanism was proposed based on NMR spectroscopy studies. Further, the effect of change in liquid absorbent viscosity on CO2 absorption is discussed.

Experimental Research on Catalytic Combustion Characteristics of Inferior Coal and Sludge Mixture

Catalytic effects of metal oxides on combustion characteristics of inferior coal, sludge, and their mixture were investigated by thermogravimetric analysis. Combustion and thermal dynamic characteristics including ignition temperatures, apparent activation energy, and frequency factors of inferior coal, sludge, and their mixture were observed. The catalytic effects and mechanism of combustion were discussed. Results showed that thermal gravity analysis (TG) and derivative thermogravimetric analysis (DTG) curves of coal and sludge shifted to lower temperature side, the weight losses increased, and the ignition performance was improved with the addition of metal oxides CaO, Al2O3, and K2O. The combustion dynamics analysis showed that the apparent activation energy of cocombustion of coal blending sludge decreased by 11–20% and the frequency factors increased by 20–30%. The minimum apparent activation energy and the maximum frequency factors were obtained in the presence of K2O, indicating that the catalytic effect of K2O was most significant.

Synergistic effect of water content and composite conditioner of Fenton's reagent combined with red mud on the enhanced hydrogen production from sludge pyrolysis

This study investigated the synergistic effect of water content and a composite conditioner of Fenton's reagent combined with red mud (Fenton-RM) on the pyrolytic products (fuel gas, tar, and solid char) of deep-dewatered sludge. The catalytic effect of metal oxides in Fenton-RM could be promoted by the presence of water during sludge pyrolysis, showing higher gas yield with increased water content. Maximum gas outputs of the deep-dewatered sludge conditioned with Fenton-RM (S-Fenton-RM) and the conventional dewatered sludge conditioned with polyacrylamide (S-PAM), both appeared at 900 °C with a water content of 65 wt%, and were 0.257 and 0.189 L/g dry solid (DS), respectively. At the same temperature and with the same water content, the hydrogen (H2) yields of the S-Fenton-RM samples were always higher than those of the S-PAM samples. At 900 °C, the maximum H2 yield of the S-Fenton-RM samples was 0.102 L/g DS, which was 85.5% higher than that of the S-PAM samples. The results indicated that water in the wet sludge provided the steam atmosphere for pyrolysis, and the water vapor then involved in secondary cracking reformation of tar and char gasification reactions, which would be catalyzed by the presence of metal oxides in the Fenton-RM conditioner, thus increasing the yield of fuel gas, especially hydrogen. The H2 production cost from the S-Fenton-RM system is less than that from the S-PAM system. The results suggest that pyrolysis of the wet deep-dewatered sludge conditioned with Fenton-RM is an economical and promising alternative for sewage sludge dewatering and disposal/reuse.

Pyrolysis of oil sludge with oil sludge ash additive employing a stirred tank reactor

The pyrolysis of oil sludge with addition of oil sludge ash, Al2O3, Fe2O3, CaO and SiO2 was carried out under inert condition employing a stirred tank reactor to investigate the catalytic effect of metal oxides on the oil product quality. Thermogravimetric scale experiments were conducted for searching the optimal reaction temperature. The reaction condition was set at: 450°C-5rpm finally. Quality of the oil products was determined based on the results of four main fractions separation method, the H/C mole ratio, the carbon residue and the elemental analysis. Addition of oil sludge ash, Al2O3, Fe2O3 and CaO decreased the carbon residue and the migration of S, N and O from the oil sludge to the oil product. We inferred that these oil quality improvements were due to the catalytic effect of Al2O3, Fe2O3 and CaO composition in oil sludge ash. The possible catalytic mechanism was proposed based on the FTIR (fourier transform infrared spectroscopy), NMR (nuclear magnetic resonance) and GCMS (gas chromatography mass spectrometry) analysis results of the oil product.

Catalytic effect of metal oxides on pyrolysis of sewage sludge

The effect of metal oxides (Al 2O 3, CaO, Fe 2O 3, TiO 2, and ZnO) on the pyrolysis of sewage sludge was investigated. The experiments were performed in a thermogravimetric analyzer (TGA) to check the pyrolysis behavior of raw sludge, demineralized sludge and demineralized sludge with metal oxides added, respectively. The results showed that the presence of Fe 2O 3 and ZnO probably inhibited the decomposition of organic matters in demineralized sludge samples to generate more solid residues, while Al 2O 3, CaO, and TiO 2 promoted the degradation of organic matters throughout the whole pyrolysis temperature ranges. All the metal oxides studied accelerated the initial decomposition of sludge samples. Al 2O 3 and TiO 2 might decrease the total pyrolysis time, while CaO, Fe 2O 3, and ZnO prolong pyrolysis time. The structure of demineralized sludge samples might be changed due to the addition of CaO, TiO 2, and ZnO. Between 550 K and 750 K, the conversion of organic matters (mainly cellulose and lignin) in sludge samples was enhanced by Al 2O 3 and TiO 2, but inhibited by CaO, Fe 2O 3, and ZnO. The effects of metal oxides on the weight loss rate of cellulose in demineralized sludge samples presented the following decreasing order of DE–ZnO > DE–TiO 2 > DE–SS > DE–Al 2O 3 > DE–Fe 2O 3 > DE–CaO.

Catalytic effect of metal oxides on the oxidation resistance in carbon nanotube–inorganic hybrids

Hybridising carbon nanotubes (CNTs) with metal oxide nanostructures creates a new class of multifunctional materials with greatly enhanced performances as photocatalysts, chemical sensors, and in fuel cells and batteries. The low resistance of CNT towards oxidation often limits their applicability. On the other hand, exactly this ability to degrade CNTs at low temperatures is beneficial when using them as sacrificial templates for the synthesis of inorganic nanotubes. In this work, we investigate the oxidation resistance of 20 new hybrids and reveal that the presence of metal oxides can both inhibit and catalyse the oxidation of CNTs. As a result, the oxidation temperatures range from nearly 800 °C with Al2O3 to values as low as 330 °C with PbO and Bi2O3. We further demonstrate that the catalytic activity of the metal oxides correlates directly with their reducibility, i.e. the ability to create oxygen vacancies, and propose a mechanistic model based on Mars and van Krevelen, which allows prediction of the chemical stability of a wide range of CNT–metal oxide hybrids.

Quantitative approach to the understanding of catalytic effect of metal oxides on the desorption reaction of MgH2

AbstractThe hydrogen desorption reaction of magnesium hydride (MgH2), MgH2→Mg+H2, is accelerated by mixing catalytic metal oxides (e.g., Nb2O5). This catalytic effect of metal oxides, MxOy, is theoretically estimated in a quantitative way using atomization energy concept. The atomization energies, ΔEM for metal ion and ΔEO for oxide ion in various metal oxides are evaluated using the energy density analysis of the total energy. It is shown that the hydrogen desorption rate increases monotonously with increasing y ×ΔEO values of metal oxides. This indicates that the oxide ion in MxOy interacts mainly with hydrogen atoms in MgH2. The y × ΔEO value is a measure of the magnitude of the OH interaction operating between MxOy and MgH2, and hence, it is indeed a good parameter to show the catalytic activities of metal oxides. This approach is useful for the analysis of other catalyst and catalytic reactions. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009

Effects of metal oxides addition on the performance of La1.3CaMg0.7Ni9 hydrogen storage alloy

The La1.3CaMg0.7Ni9 alloy was modified with various metal oxides (Fe2O3, TiO2, Cr2O3, ZnO), and the effects of metal oxides addition on the electrochemical properties of the La1.3CaMg0.7Ni9 hydrogen storage alloy were investigated. The catalytic effects of metal oxides are found. Not only the discharge capacity but also the high-rate dischargeability (HRD) is improved by addition of 5wt% TiO2, Cr2O3, and ZnO, while the cyclic stability does not change except for addition of Fe2O3. The low-temperature property is enhanced more obviously by addition of TiO2, Cr2O3, and ZnO. The electrochemical kinetics is also measured by the linear polarization and electrochemical impedance spectroscopy (EIS). In addition, the hydrogen absorption kinetic behavior is measured by gas–solid reaction.

Involvement of catalyst materials in nonthermal plasma chemical processing of hazardous air pollutants

Catalytic effects of metal oxides in nonthermal plasma chemical processing of hazardous air pollutants (HAPs) are discussed, relevant to their activities for the oxidation of HAPs in nonthermal plasma media and their selective control of active oxygen species derived from background O 2. In ferroelectric packed-bed reactors, the oxidation power of barium titanate (BaTiO 3) is not strong enough to oxidize HAPs and their carbon intermediates to CO 2. Only nitrous oxide (N 2O) was formed from background N 2 and lattice oxygen atoms in BaTiO 3. The catalytic effect of BaTiO 3 is negligible under aerated conditions. On the other hand, ozone (O 3) is formed from background O 2 in much higher concentrations in a silent discharge plasma reactor. Manganese dioxide (MnO 2)-catalyzed decomposition of O 3 promotes decomposition of benzene, which is less reactive than trichloroethylene and tetrachloroethylene. The acceleration of benzene consumption rate is ascribed to the promotion of its oxidative decomposition by the triplet oxygen atom. Catalytic control of in situ active oxygen species could be one of the most effective approaches to increase the energy efficiency of the nonthermal plasma reactor and to achieve the complete oxidation of the carbon atoms in HAPs.

Catalysis and inhibition of the combustion of ammonium perchlorate based solid propellants

Results of studies of the combustion of a composite solid propellant based on ammonium perchlorate are presented. The effect of additives of metal oxides is studied for the high and low-temperature decompositions, linear pyrolysis, and combustion of ammonium perchlorate, the decomposition of HClO4, isobutylene oxidation by oxygen and perchloric acid, and the combustion of propellants with various organic combustibles. It is shown that the efficiency of metal oxides in the reactions of oxidation of isobutylene and propellant combustion is related to the energy of the Me—O bond in the surface oxide layer or the enthalpy of formation of this bond. The extremal nature of the catalytic effect of metal oxides on the burning rate of the propellant is due to the small time of residence of the oxide particles in the zone of intense oxidation-reduction reactions. For this reason, the same additives of metal oxides has different effects on the combustion of the propellant with different organic, combustibles, and the most efficient catalyst can be chosen by a simplified algorithm. The potentials for affecting the composite solid propellant via gas-phase oxidation-reduction reactions is indicated by the effect of additives of organic sources of active species—amines and halides.

Catalytic effects of metal oxides on the decomposition of Potassium perchlorate

Catalytic effects of metal oxides with comparable surface areas on the decomposition of potassium perchlorate were studied by thermogravimetric analysis. The catalytic mechanism is discussed based on the relative activity of the metal oxides. It is found that the oxides containing transition metal cations with partially filled d-orbitals have the highest activities, the oxides containing transition metal cations with completely empty valence d-orbitals are moderately active, and the oxides containing metal cations with completely filled d-orbitals or noble gas configurations have the lowest activities. Differences between the decomposition of potassium perchlorate and the previously reported decomposition of sodium chlorate are explained by differences in the melting points and molecular structures of these salts.

Catalytic decomposition of potassium chlorate

Thermal decomposition of potassium chlorate in the presence of various additives is studied using thermogravimetric analysis and differential thermal analysis. Catalytic effects of metal oxides with comparable surface areas are compared, and the catalytic effects of a number of nonoxide additives are also studied. The nonoxide additives show catalytic activities similar to the corresponding metal oxides. Metal cations and their electron configurations determine the catalytic activity of various compounds. Metal cations with partially filledd shells have the highest activity, transition metal cations with completely emptyd orbitals are moderated active, and metal cations with completely filledd shells or noble gas configurations have minimum activity.

ChemInform Abstract: Catalytic Effects of Metal Oxides on the Thermal Decomposition of Sodium Chlorate.

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Catalytic effects of metal oxides on the thermal decomposition of sodium chlorate

The thermal decomposition of NaClO 3 in the presence of metal oxides was studied using thermogravimetric analysis. A number of metal oxides were prepared to have comparable surface areas, and their catalytic effects on NaClO 3 decomposition were compared. It was found that the catalytic activity depends on the electron configurations of the metal cations. Oxides containing metal cations with partially filled d-orbitals are all active catalysts for NaClO 3 decomposition. Transition metal cations with no d-electrons are moderately active. Metal oxides containing metal cations with completely filled d-orbitals or noble gas configurations have very little activity.

Role of semiconductor phenomena in boronizing

1. The catalytic effect of metal oxides on the process of boronizing has to do with the semiconductor properties of these oxides. The electron-hole conduction of metal oxides improves the electron interchange between reagents, accelerating oxidation of boton carbide and the boronizing process. 2. Acceleration of saturation with boron based on the oxygen activation ions with lower valency is caused predominantly by oxides that are p-type semiconductors in which the disordered structure and the proportion of electron-hole conduction are determined by the partial pressure of oxygen in the system. 3. The application of the tenets of the electron theory of heterogeneous catalysis of chemical processes to semiconductors together with thermodynamic analysis of redox reactions is an effective direction of searching for optimal activators for currentless boronizing and possibly also for other methods of TCT.

Oxidation of Coals in Liquid Phases. IX. Kinetics of the Base-Catalyzed Oxidation of Acetate Ion by Oxygen at Elevated Temperatures

Abstract The kinetics of the oxidation of the acetate ion by oxygen have been studied to clarify the mechanism of the formation of oxalate from coal in concentrated alkaline solutions at elevated temperatures. The rate for the oxidation in a nickel reactor in the presence of 3 g of iron powder was expressed as −dmAc⁄dt=k′ mAcmOH2Po2, where k′ is the apparent rate constant, mAc is the molality of acetate ion, mOH is molality of the hydroxide ion, and Po2 is the partial pressure of oxygen. This result indicates that the oxidation of the acetate ion proceeds according to a base-catalyzed mechanism. The activation energy was 160 kJ mol−1. In addition, the rate of oxidation was affected by the coexistence of the metal powder and the oxidation activity in the order Cu> Ni> Co> Mn \fallingdotseq Fe>Cr. The catalytic effect of metal oxides on the rate is discussed.

The catalytic effects of metal oxides on thermal decomposition reactions, III

The catalytic activity of a series of iron oxides on the thermal decomposition of potassium chlorate was investigated by methods of thermal analysis. Structural and electronic defects were introduced into the oxide by doping, heat treatment in different atmospheres, and irradiation withγ-rays. These induced defects changed in a systematic way the conductive properties of the iron oxides and correspondingly, their catalytic activity. The results are consistent with ann-type semiconductive behavior of the oxides.

Catalytic effect of metal oxides on thermal decomposition reactions. II. Catalytic effect of metal oxides on the thermal decomposition of potassium chlorate and potassium perchlorate as detected by thermal analysis methods

Catalytic effect of metal oxides on thermal decomposition reactions. II. Catalytic effect of metal oxides on the thermal decomposition of potassium chlorate and potassium perchlorate as detected by thermal analysis methods

Catalytic effect of metal oxides on thermal-decomposition reactions. I. The mechanism of the molten-phase thermal decomposition of potassium chlorate in mixtures with potassium chloride and potassium perchlorate

Catalytic effect of metal oxides on thermal-decomposition reactions. I. The mechanism of the molten-phase thermal decomposition of potassium chlorate in mixtures with potassium chloride and potassium perchlorate