Papers by Keyword: SO₂

Abstract: A catalyst, 8%Fe-10%MnOx-CeO2/ZrO2, was prepared and applied for selective catalytic reduction of NO with NH3 at low temperature. The effects of SO2 and H2O on the catalyst were studied. The results showed that in the absence of SO2 and H2O, the catalyst 8%Fe-10%MnOx-CeO2/ZrO2 has good activity and stability. The presence of SO2 and H2O make the catalyst deactivate, and the activity can be recovered mostly by heating at 400°C. Properties of the catalyst on different reaction stages were characterized by FT-IR to study the inactivation mechanism of the catalyst. The results showed that the catalyst deactivation is due to the deposition of ammonium sulfate on the catalyst and the sulphation of the metal oxides of the catalyst.

Abstract: Graphene oxide (GO), an oxygen-rich carbonaceous layered material, is produced by the strong oxidation of graphite. The GO aqueous suspension is very stable and can be fabricated to porous GO aerogels by a green method, unidirectional freeze-drying technology. GO shows catalytic activities in both solution and solid state. It can also act as reductant or oxidant depending on the reaction patterns. The product of the reaction was analyzed and the component change of the graphene oxide (GO) was monitored by x-ray photoelectron spectrometer, scanning electron microscopy and transmission electron microscopy. The results confirm that GO not only acts as the reactant in the reaction, but also as the catalyst to catalyze the reaction.

Abstract: A SO₂ on-line monitoring system (CEMS) has been developed by the author based on the principle of electrochemistry. This system consists of SO₂ mass concentration monitoring subsystem (the subsystem had been described in on-line system for monitoring SO₂ in fumes（1）) and SO₂ flow velocity and flow rate monitoring subsystem. In the paper, the working principle and procedure of SO₂ flow velocity and flow rate monitoring subsystem are described in detail. In the meantime, an advanced method for measuring average flow velocity of fumes by mean of “velocity field constant” is presented. A innovative device has been developed to detect velocity field constants automatically, which has resolved the technical difficulty in automated monitoring of fumes average velocity in the flue.

Abstract: In order to achieve the target of controlling SO₂ emissions in fumes in a short period of time in China, a SO₂ on-line monitoring system (CEMS) has been developed by the authorased on the principle of electrochemistry. This system consists of two subsystems: (1) SO₂ mass concentration monitoring and (2) SO₂ flow velocity and flow rate monitoring. In the paper, the procedure of system and working principle and method of SO₂ mass concentration monitoring subsystem are described in detail (SO2 flow velocity and flow rate monitoring subsystem is described by another paper).Two subsystems work synchronously to monitor and calculate the SO₂ emissions, then the on-line monitoring of SO₂ emissions is achieved. Through experiment and testing, monitoring result of the system is stable and reliable, which has reached the national monitoring standards and passed the appraisal.

Abstract: The aim of this paper is to study the adsorption characteristics of nitric oxide (NO) and sulfur dioxide (SO₂) on raw coal activated carbon over temperature ranged 298～343K using a static volumetric adsorption apparatus. The adsorption equilibrium data for NO and SO₂ were fitted to Freundlich, Dubinin-Radushkevich (D-R) and Sips adsorption isotherm model. Isosteric heat of adsorption was determined by the Clausius-Clapeyron equation. It was found that Sips adsorption isotherm model is more suitable for description of NO adsorption process at 298K, 313K and 328K and SO₂ adsorption process at 313K, 328K and 343K, however, D-R adsorption isotherm model is more suitable for description of the NO adsorption process at 343K and SO₂ adsorption process at 298K. The isosteric heat of adsorption values of SO₂ increase slightly as the adsorbed amounts increasing from 0.8 to 1.6mg/g, but the isosteric heat of adsorption values of NO show a converse trend. Meanwhile, NO and SO₂ adsorbed on coal activated carbon at the four temperatures may be a dominant of physical adsorption.

Abstract: The catalyst of MnO_x-CeO_x/ACF prepared by impregnation method was used for low-temperature selective catalytic reduction (SCR) of NO with NH₃, and more than 90% NO conversion was obtained at 230°C. Fe、Cu or V was used respectively to prepare transition metal modified MnO_x-CeO_x/ ACF catalysts which had lower catalytic activity than that over MnO_x-CeO_x/ACF. SEM, N2 adsorption and NH₃-TPD were used to analyze the catalysts. The results showed that transition metal modified catalysts had a reduced surface area, pore volume and surface acidity. SO₂ had a negative effect on SCR performance of the catalysts. Fe modified catalyst exhibited SO₂ tolerance in the first 6h in the presence of 100ppm SO₂. Thermal treatment in N₂ at 350°C was used to regenerate the deactivated catalysts by SO₂. The decomposition of ammonium salts recovered the catalytic activity to some extent. The sulfated active components in deactivated catalysts after the thermal treatment enhanced the surface acidity of the catalysts.

Abstract: The purpose is to study the temporal and spatial distribution features of SO₂ and its relationship with impact factors such as wind, humidity and precipitation in urban areas of Yantai. The results demonstrate that the emission of SO₂ had been capable controlled from 2008 to 2010. The meteorological conditions also take the key part in spread of SO₂, wind and precipitation are the main factors affecting of it in Yantai. Concentrations change significantly with seasons, which remain low in vast majority of periods. Contamination is generally concentrated in the range of major pollution sources within 7 kilometers. And it implies that after the reduction of SO₂ pollutant concentrations, the planning and adjustment of industrial areas and residential areas still need to be paid attention.

Abstract: Palygorskite is widely used as industrial adsorbent and also potential for flue gas desulfurization by adsorption of SO₂. The effect of thermal treatment on Palygorskite’s structural properties and its performance in SO₂ adsorption were investigated. The textural and structural properties of the prepared palygorskite adsorbent were characterized by X-ray diffraction, transmission electron microscopy and temperature programmed desorption. The result showed the channel of Palygorskite is partial collapsed and the structure is not changed ultimately when thermally treated below 300 °C. The structure of Palygorskite is Gradually changed when the treating temperature is higher than 300 °C and is damaged entirety till 800 °C. As a result, the adsorption capacity of SO₂ on Palygorskite decreased drastically. It is suggested that the presences of surface adorbed water and zeolitic water which occupy a large number of adsorption sites are disadvantage for the adsorption of SO₂, and dissimilarly the presence of crystal-bonded water is favorable.

Abstract: NiMgAlO catalysts were prepared by two methods: coprecipition and impregnation. They were used to simultaneously adsorb SO₂ and NO with O₂ in a fixed bed at atmospheric pressure. Typically the molar composition of the feed gas was 1% SO₂, 0.2% NO and O₂ with ultra-high purity Ar as the diluent. The results showed the catalysts were excellent materials for the simultaneous oxidation adsorption of SO₂ and NOx. The two kinds of catalysts were compared for the SO₂ and NOx adsorption capacity. The NiMgAlO catalyst prepared by coprecipition had better adsorption than impregnation. When NiMgAlO catalysts with 10 wt-% Ni content were calcined at 550°C, adsorption capacity was the largest at 120°C adsorption temperature: 1.392 mmol SO₂ and 0.213 mmol NOx were adsorbed on 1 g catalyst prepared by the coprecipition method. The causes are seen by the XRD, surface area and porous size analysis.

Abstract: Two catalysts, MnOx and ceria modified MnOx were prepared by deposition-precipitation method and used for low-temperature selective catalytic reduction (SCR) with NH₃ in the presence of SO₂. The catalysts were characterized by X-ray diffraction (XRD), surface area measurement (BET) and thermal gravimetry analysis(TG). The deactivation of MnOx and MnOx-CeO₂ by SO₂ was observed during SCR process. It was found that the resistance to SO₂ could be greatly enhanced for Ce modified MnOx. It was because that the formation of Mn(SO₄)x was prevented and the depositions of (NH₄)₂SO₄ and NH₄HSO ₄ were significantly inhibited with the doping of ceria.