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BACKGROUND The 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). RESULTS Steady 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. CONCLUSIONS The 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 [ABSTRACT FROM AUTHOR]

BACKGROUND Environmental regulations are moving to tighter control of NOx emissions produced at both stationary and mobile sources. Selective catalytic reduction ( SCR) of NOx with NH3 is an efficient treatment technique capable of operating at high gas flow rates (e.g. using monolithic catalysts) and a wide range of NO concentrations. The aim of this work is to provide guidelines for designing this kind of reactor taking into account both intrinsic kinetics and mass transfer. RESULTS Experiments have been done in lab-scale (0.5 g) and bench-scale (430 g) reactors operating under different conditions: temperature (150-320 °C), space velocity ( WHSV 5360-16100 mol h−1 kgcat−1), oxygen concentration (0-21%) and NH3/ NO ratio (0.2-1.2). Temperature has a great influence on the reaction rate, and at least 300 °C is required at a WHSV of 16100 mol h−1 kgcat−1. Oxygen is required in the feed because it participates as reactant in SCR. CONCLUSIONS Data obtained from the lab-scale reactor in the absence of mass transfer limitations have been used to fit an intrinsic kinetic model of the SCR reaction. A more complex model has been used for the bench-scale reactor accounting for reaction kinetics and mass transfer (internal effectiveness factor was determined) in the monolithic catalyst. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: The performance of a 0.5wt.% Pd on alumina catalyst used for the hydrodechlorination of tetrachloroethylene, in presence of model organosulphur (thiophene and butanethiol) organonitrogen (quinoline and n-butylamine) and organooxygen (tetrahydrofurane, isobutanol) compounds, was studied in this work. Experiments were carried out in a continuous fixed bed reactor (space time of 1.8ming/mmol of TTCE) at a pressure of 0.5MPa and a temperature range of 200–300°C. Concentrations of heteroatomic molecules in the range 0.5–5% were used in this study. Organosulphur compounds produce strong inhibition on the TTCE hydrodechlorination, decreasing the conversion and increasing the selectivity for partially dechlorinated compounds (trichloroethylene). However, this effect is shown to be highly reversible, the catalyst almost recovering its initial activity when the sulphur source is removed from the feed. Organonitrogen compounds cause a fast and fatal deactivation of the catalysts, being this effect completely irreversible. Different regeneration procedures were tested, being the treatment with hydrogen at 400°C the only way to partially recover catalytic activity. Finally, organooxygen compounds hardly affect catalyst performance. [Copyright &y& Elsevier]

Abstract: The deactivation of a 0.5wt.% Pd on alumina catalyst used for the hydrodechlorination of tetrachloroethylene (TTCE), chlorobenzene (CBZ) and dichloromethane (DCM) in organic matrix in gas phase has been studied in this work. Experiments were carried out in a continuous fixed bed reactor, at a pressure range of 0.1–2MPa. It was found that the reactivity and stability of the catalyst increases as pressure increases. Different compounds present quite different deactivation patterns: fast initial deactivation followed by a plateau for DCM and CBZ, continuous moderate deactivation for TTCE. The effect of hydrogen chloride was studied by adding to the reactor feed different amounts of hydrogen chloride, working at 225–300°C. Fresh and used catalysts were characterised by nitrogen porosimetry, X-ray diffraction, transmission electronic microscopy, scanning electronic microscopy, thermogravimetry and temperature-programmed oxidation. Results indicate that carbonaceous deposits play a key role in the catalyst deactivation, being this phenomenon promoted by the presence of HCl. [Copyright &y& Elsevier]