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[en] TPD / TPR techniques are used to titrate the active species of a catalyst for determining its activity towards a specific reaction. After discussing the basic features of the different techniques, the paper shows some significant example of application to acid catalysts, metallic copper, metals supported on alumina
[en] Highlights: • An absorption based laser sensor for the investigation of dynamically changing liquid film thicknesses is proposed. • The used laser wavelength was optimized to prevent dependence to the temperature. • The sensor can be used in two configurations, which leads to a higher flexibility regarding different boundary conditions. • The laser based sensor could successfully be validated in both configurations against a commercially available chromatic confocal resonance (CHR) sensor. - Abstract: In this work, an absorption based laser sensor for the investigation of dynamically changing liquid film thicknesses is developed and validated. For the wavelength selection of the single-ended, fibre-coupled, diode-laser sensor, near-infrared spectra of liquid water are measured at various thicknesses and temperatures. To reduce the influence of the film temperature, the evaluation is supported by a calibration procedure. Unknown film thicknesses of up to 440 µm could then be measured. To adapt the sensor to particular boundary conditions of different systems, the single-ended setup can be changed to a transmissive configuration. The sensor is validated in both configurations against a commercially available chromatic confocal resonance (CHR) sensor. A comparison with respect to the CHR sensor leads to an accuracy of 2.8 µm and a precision of 3.9% of the new laser based sensor.
[en] Criteria for designing the most suitable experimental setup for TPD / TRP measurements are discussed in detail. Interfacing the control and measurement components with a PC represents a crucial step in this operation. Two different approaches are considered: the first based on a computer-linked gas chromatographic integrator, the second featuring an analogic/ digital conversion module. When complex probe molecules or chemical reactions are involved, combining selective detectors such as GC and MS is recommended as the best solution
[en] Fast selective catalytic reduction (SCR) is regarded as a good choice to improve the SCR denitrification efficiency and reduce the using of catalyst. For a good understanding and further improvement, the investigation on the mechanism of SCR and fast SCR is essential. A four-step catalytic mechanism for SCR and fast SCR catalyzed by ZSM5 doped with Mn/Co–Al/Ce is proposed in this paper, and the catalytic mechanism is studied in detail by using the method of quantum chemistry. Results show that, by using ZSM5–Mn/Co catalyst, the activation energy of fast SCR (83.35/87.55 kJ/mol) is much lower than that of SCR (154.98/219.70 kJ/mol). This indicates that fast SCR has a better catalytic effect and higher denitration efficiency. Moreover, when Al/Ce is added into ZSM5–Mn/Co, the active center Si is replaced by Al/Ce, and the activation energy of fast SCR is further decreased to about 40–60 kJ/mol. This shows that the catalysts for SCR and fast SCR not only relate to the supported transition metal such as Co and Mn, but also highly relate to the activity center such as Al and Ce.
[en] Nitrogen oxides (NOx) are one of the most hazardous air pollutants arising from the combustion processes. Because of the implementation of strict emission limits many NOx removal technologies have been developed. In the present work post combustion NOx removal technique that is Selective Non-Catalytic Reduction (SNCR) has been investigated in a pilot scale 150 kW combustion rig facility. Investigation has been performed using some novel NOx reducing reagents like urea, ammonium carbonate and mixture of their 50%-50% aqueous solution within the temperature range of 700 to 1200 deg. C., at 1.1% excess oxygen and background NOx level of 500 ppm. The effects of these reagents were determined in term of their temperature characteristics and molar ratio. Among the reducing reagents used urea solution gave the highest NOx removal efficiency (81%) and was attractive due to its superior high temperature (1000 to 1150 deg. C) performance, ammonium carbonate was more effective at lower temperature range (850 to 950 deg. C) though its efficiency (32%) was lower than urea, while 50-50% solution of urea and ammonium carbonate gave higher efficiency than ammonium carbonate but slightly lesser than urea within a wide temperature range (875 to 1125 deg. C). It was also observed that the NOx removal efficiency was increased with increasing the molar ratio. (author)
[en] Highlights: ► We propose a new approach to correct gas/particle partitioning of flue gas PCDD/Fs. ► Validity of correction is assessed by examining the removal efficiencies of APCDs. ► After correction, PCDD/Fs in the flue gas is dominated by the gas-phase. ► After correction, the removal efficiencies of installed APCDs become more reasonable. - Abstract: This study was aimed at developing an approach for correcting the gas and particle partitioning of PCDD/F congeners for samples collected from the flue gas of an iron ore sinter plant. An iron ore sinter plant equipped with an electrostatic precipitator (EP) and a selective catalytic reduction (SCR) was selected. Flue gas samples were collected at EP inlet, EP outlet and SCR outlet. Both particle- and gas-phase PCDD/Fs were analyzed for each collected sample. PCDD/F contents in EP ashes (EPash) were also analyzed and used to correct the gas and particle partitioning of PCDD/F congeners of the collected flue gas samples. Results show that PCDD/Fs in the flue gas were dominated by the gas-phase. Before correction, the removal efficiencies for the gas- and particle-phase PCDD/Fs for EP were −58.1% and 64.3%, respectively, and SCR were 39.4% and 83.9%, respectively. The above results were conflict with the expected results for both EP and SCR indicating the need for correcting the gas and particle partitioning of PCDD/F congeners for all collected flue gas samples. After correction, the removal efficiencies become more reasonable for EP (=4.22% and 97.7%, respectively), and SCR (=54.7% and 62.0%, respectively). The above results confirm the effectiveness of the approach developed by this study.
[en] Korea Atomic Energy Research Institute (KAERI) has launched a decommissioning program of the uranium conversion plant in 2001. The treatment of the sludge waste, which was generated during the operation of the plant and stored in the lagoon, is one of the most important tasks in the decommissioning program of the plant. The major compounds of the lagoon sludge are ammonium nitrate, sodium nitrate, calcium nitrate, calcium carbonate, and uranium compounds. The minor compounds are iron, magnesium, aluminum, silicon and phosphorus. A treatment process of the sludge was developed as figure 1 based on the results of the sludge characteristics and the developed treatment technologies. A treatment of off-gas evolved from the nitrate salts thermal decomposition is one of the important process. Off-gas treatment by using a selective catalytic reduction (SCR) method was investigated in this study
[en] L-lactic dehydrogenase, LDH, is well known catalyst in reduction of phenyl pyrogronic acid. The aim of communication is to present the results of studies on the solvent isotopic effects (SIE) in the above mentioned reaction in the deuterised solvents. Obtained dependence of the reaction rate on the substrate concentration were applied for optimization of the kinetic parameters, kcat and kcat/Km, in the Michaelis-Menten equation. As a result - better understanding of the L-DOPA creation can be achieved
[en] With the development of bio electrochemistry, researches appeared on the enzymes immobilization at the surface of electrodes for the realization of bioreactors and bio sensors. One of the main challenges is the development of host matrix able to immobilize the protein material preserving its integrity. In this framework the authors developed graphite electrodes modified by clay films. These electrodes are examined for two enzyme reactions involving proteins of sulfate-reduction bacteria. Then in the framework of the hydrogen biological production and bioreactors for the environmental pollution de-pollution, the electrochemical behavior of the cytochrome c3 in two different clays deposed at the electrode is examined