Vesna Tomašić

Catalytic reduction of NOx over Cu/ZSM-5 catalyst

Catalytic decomposition of NO on Cu/ZSM-5 catalyst was carried out in tubular fixed-bed reactor at atmospheric pressure. The influence of temperature and flow rate on the reaction rate was investigated. The kinetic model of reaction was proposed and compared with the literature results. The formation of NO2 during the catalytic decomposition of NO was also monitored. Therefore, additional experiments were performed aimed at examining the kinetics of NO oxidation under the same reaction conditions. Both kinetic models were used to develop the reactor model and to describe quantitatively the behavior of the overall reaction system. Satisfactory degree of correlation between experimental data and values predicted by reactor model has been achieved.

Reaction and Mass Transfer Effects in a catalytic monolith reactor

Zeolite-based monoliths (Cu/ZSM-5 on cordierite) are prepared and used to catalyze direct decomposition of nitrogen monoxide. Two-dimensional heterogeneous model is applied to describe the behavior of the monolith reactor, with the emphasis on the features introduced due to coupling of flow, mass transfer and chemical reaction. The proposed model has been verified by comparing computer simulation data with laboratory experimental data. It is shown that both inter- and intraphase diffusion limitations have to be considered when modeling complex reactor configuration, such as monolith reactors, especially when monolith with thicker catalytic layer are used at higher temperatures.

Kinetics of no decomposition over Cu/ZSM-5 catalyst

AbstractThe kinetics of catalytic decomposition of NO over Cu/ZSM-5 catalyst has been studied in an integral flow reactor at atmospheric pressure. Kinetic analysis is based on the assumption that the surface reaction represents the rate-determining step. On the basis of theoretical considerations of different interactions between reactants and catalyst, and experimental evidences, three different mechanistic kinetic models were chosen. Also a power-law model was tested. The best agreement has been achieved with the model

Synthesis and characterization of Cu-MFI catalyst for the direct medium temperature range NO decomposition

r_S = \frac{{k \cdot C_{NO} ^2 }}{{\left( {1 + \sqrt {K_D ^1 \cdot C_{O_2 } } } \right)^2 }}

State-of-the-art in the monolithic catalysts/reactors

This work reports the results of experimental and theoretical investigation of toluene oxidation on different metal oxide based catalysts (manganese oxide, MnOx, mixed manganese-iron oxide, MnFe, perovskite-type manganese oxide, LaMnO3 and commercial Pt-Al2O3 catalyst). Particular attention was devoted to single and mixed manganese based oxides and ceria based materials as alternatives to conventionally used noble metal containing catalysts. Toluene oxidation was performed under steady-state conditions in an integral fixed bed reactor operating over a wider range of reaction temperatures and at various space times. The influence of reaction variables on the rate of toluene oxidation was examined using the simple first-order kinetic model and the one-dimensional (1D) pseudo-homogeneous model to describe the reaction system. The proposed model was verified comparing the theoretical predictions with the experimental laboratory results. The results of catalytic tests indicated that the mixed manganese-iron oxide (MnFe) exhibited remarkable catalytic activity for the toluene oxidation, almost comparable with the activity of the commercial Pt-Al2O3. The reaction temperature T50 corresponding to 50% of the toluene conversion was observed at 419 K for the MnFe oxide and at 405 K for the Pt-Al2O3. A very good agreement of experimental data with the proposed 1D model was obtained. Based on the shape of the light-off curve and the values of the apparent activation energies, which decreased from 120.36 kJ/mol to 16.88 kJ/mol with reaction temperature increase, it was concluded that the reaction rate was probably limited by the mass transfer, no matter the relatively small catalyst particle size fraction employed in this study (315 400μm).

Photocatalytic oxidation of toluene in the gas phase: Modelling an annular photocatalytic reactor

Abstract In this study the physico-chemical and catalytic properties of copper bearing MFI zeolites (Cu-MFI) with different Si/Al and Si/Cu ratios were investigated. Two different methods for incorporation of metal ions into the zeolite framework were used: the ion exchange from the solution of copper acetate and the direct hydrothermal synthesis. Direct synthesis of a zeolite in the presence of copper-phosphate complexes was expected to generate more active copper species necessary for the desired reaction than the conventional ion exchange method. Direct decomposition of NO was used as a model reaction, because this reaction still offers a very attractive approach to NOX removal. The catalytic properties of zeolite samples were studied using techniques, such as XRD, SEM, EPR and nitrogen adsorption/desorption measurements at 77 K. Results of the kinetic investigation revealed that both methods are applicable for the preparation of the catalysts with active sites capable of catalyzing the NO decomposition. It was found out that Cu-MFI zeolites obtained through direct synthesis are promising catalysts for NO decomposition, especially at lower reaction temperatures. The efficiency of the catalysts prepared by both methods is compared and discussed.

Application of the monoliths in DeNOx catalysis

ABSTRACT This paper is focused on development of the metal monolithic structure for total oxidation of toluene at low temperature. The well-adhered catalyst, based on the mixed oxides of manganese and nickel, is washcoated on the Al/Al2O3 plates as metallic support. For the comparison purposes, results observed for the manganese–nickel mixed oxide supported on the metallic monolith are compared with those obtained using powder type of the same catalyst. Prepared manganese–nickel mixed oxides in both configurations show remarkable low-temperature activity for the toluene oxidation. The reaction temperature T50 corresponding to 50% of the toluene conversion is observed at temperatures of ca. 400–430 K for the powder catalyst and at ca. 450–490 K for the monolith configuration. The appropriate mathematical models, such as one-dimensional (1D) pseudo-homogeneous model of the fixed bed reactor and the 1D heterogeneous model of the metal monolith reactor, are applied to describe and compare catalytic performances of both reactors. Validation of the applied models is performed by comparing experimental data with theoretical predictions. The obtained results confirmed that the reaction over the monolithic structure is kinetically controlled, while in the case of the powder catalyst the reaction rate is influenced by the intraphase diffusion.