Kinetics and Mechanism Study of Low-Temperature Selective Catalytic Reduction of NO with Urea Supported on Pitch-Based Spherical Activated Carbon

Nitrogen oxide gas purification using carbon in water as reducing reagent with the aid of microbial fuel cell

Microbial Fuel Cell (MFC) can degrade the organic matter (OM) in wastewater at the anode and transfer electrons to the cathode. In this work, the harmful NO_X gas was used as electron acceptor in MFC and converted to harmless N₂. The OM in water was indirectly used as a zero-cost reducing agent for NOx removal. More than 80% of NO_X was removed continuously by MFC at room temperature. The NO_X was directly reduced to N₂ at MFC cathode and the cathode activity played a key role on enhancing the NO_X removal. The NO_X removal efficiency by the cathode of high potential was 1.37 times that by the cathode of low potential. When O₂ coexisting with NO as the electron acceptor, not only the NO_X removal but also the power output of MFC was improved greatly. The presence of NO_X did not decrease the power generation of MFC under the same O₂ concentration. The MFCs showed good stability for NO_X treatment and power output. Moreover, the possible pathways and advantages of NO_X removal by MFC were discussed in detail. These results indicated that the MFC system has the potential to treat wastewater, purify flue gas and recover energy simultaneously.

Low temperature selective catalytic reduction of nitric oxide with urea over activated carbon supported metal oxide catalysts

Selective catalytic reduction of nitrogen oxides (SCR) with loaded urea is a method for removing NO under oxygen-rich and low-temperature conditions, which can solve the inhibitory effect of oxygen on the catalyst and the slip of ammonia. In present study, a series of activated carbon (wo-AC, co-AC, cs-AC and nu-AC) supported metal (Mn, Fe, Co, Cu and Zn) oxide catalysts with loading urea were prepared by ultrasonic assisted impregnation. The catalysts were used for NO removal at 50-120°C and characterized by XRD, SEM, GFAAS, EDS, XPS, BET and FTIR techniques. The effects of activated carbon type, loaded active element, metal oxides loading, temperature fluctuation on catalytic activity and the catalytic stability were also studied in this paper. The results indicated that nutshell-based activated carbon was more suitable as a carrier than other activated carbons, and urea-10Mn/nu-AC catalyst yielded a higher NO conversion than other catalysts. Besides, for used activated carbons, the larger specific surface area, more micropores distribution and the larger number of hydroxyl group and cyano terminal group are beneficial to the catalytic process. Moreover, the downward trend of NO conversion with increasing temperature suggested the adsorption of reactant gases played a crucial role in the catalytic process of urea-SCR.

Catalytic Degradation of Ortho-Chlorophenol Using Activated Carbon Modified by Different Methods

The performance of activated carbon (AC) modified by different methods was compared for its catalytic degradation of ortho-chlorophenol (o-CP). For the chemically treated AC, the catalytic effect of AC–NH3·H2O was superior to the other catalysts examined, having an o-CP removal efficiency of 82.2% at 330 °C. For the metal-modified catalysts, AC–V and AC–Co showed similar removal performances of 93.2% at 330 °C. N2 adsorption-desorption isotherms, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and gas chromatography—mass spectrometry (GC-MS) analyses were used to characterize the reaction products, and different reaction mechanisms were proposed for both AC–NH3·H2O and AC–V according to the results. Complete oxidative degradation of o-CP was achieved by AC–V, with AC–NH3·H2O leading to the formation of additional dioxins. It can be deduced that a risk of dioxin synthesis and escape during the regeneration process is possible when nitrogen-modified carbon is used in selective catalytic reduction (SCR) denitrification reactions, especially in the presence of chlorine atoms, benzene rings, and oxygen.

Catalytic oxidation of nitric oxide (NO) with carbonaceous materials

This paper reviewed recent progress in catalytic oxidation of nitric oxide (NO) over various carbonaceous materials, such as activated carbon, carbon nanofibers with the aim of NO abatement.

Design of a dual-bed catalyst system with microporous carbons and urea-supported mesoporous carbons for highly effective removal of NOx at room temperature

A dual-bed catalyst system is designed for highly effective remove of NO_x at room temperature, which consists of a microporous spherical activated carbon (SAC) layer and a urea-supported spherical mesoporous carbon (SMC) layer.