The development of supported vanadia catalysts for the combined catalytic removal of the oxides of nitrogen and of chlorinated hydrocarbons from flue gases

Development of Pharmaceutical VOCs Elimination by Catalytic Processes in China

As a byproduct of emerging as one of the world’s key producers of pharmaceuticals, China is now challenged by the emission of harmful pharmaceutical VOCs. In this review, the catalogue and volume of VOCs emitted by the pharmaceutical industry in China was introduced. The commonly used VOC removal processes and technologies was recommended by some typical examples. The progress of catalytic combustion, photocatalytic oxidation, non-thermal plasma, and electron beam treatment were presented, especially the development of catalysts. The advantages and shortages of these technologies in recent years were discussed and analyzed. Lastly, the development of VOCs elimination technologies and the most promising technology were discussed.

V-Containing Mixed Oxide Catalysts for Reduction–Oxidation-Based Reactions with Environmental Applications: A Short Review

V-containing mixed oxide catalytic materials are well known as active for partial oxidation reactions. Oxidation reactions are used in industrial chemistry and for the abatement of pollutants. An analysis of the literature in this field during the past few years shows a clear increase in the use of vanadium-based materials as catalysts for environmental applications. The present contribution makes a brief revision of the main applications of vanadium containing mixed oxides in environmental catalysis, analyzing the properties that present the catalysts with a better behavior that, in most cases, is related with the stabilization of reduced vanadium species (as V4+/V3+) during reaction.

Gas-phase and particle-phase PCDD/F congener distributions in the flue gas from an iron ore sintering plant

The activated carbon injection-circulating fluidized bed (ACI-CFB)-bag filter coupling technique was studied in an iron ore sintering plant. For comparison, the removal efficiencies under the conditions without or with ACI technology were both evaluated. It was found that the polychlorinated dibenzo-p-dioxins and dibenzofuran (PCDD/F) removal efficiency for total international toxic equivalence quantity (I-TEQ) concentration was improved from 91.61% to 97.36% when ACI was employed, revealing that ACI was very conducive to further controlling the PCDD/F emissions. Detailed congener distributions of PCDD/Fs in the gas-phase and particle-phase of the Inlet and Outlet samples were determined. Additionally, the PCDD/F distribution for the Fly ash-with ACI sample of was also studied.

Simultaneous removal of PCDD/Fs and NOx from the flue gas of a municipal solid waste incinerator with a pilot plant

The pilot-scale plant on the simultaneous removal of PCDD/Fs and NOx from the flue gas of a municipal solid waste incinerator is presented. In order to research the influence of temperature on the catalytic decomposition of PCDD/Fs and the selective catalytic reduction of NOx, the experiments were performed at 220 °C, 260 °C, and 300 °C, and the congener profiles of PCDD/Fs for the samples collected at the inlet and outlet were illustrated. Noteworthy, the detailed congener distributions of PCDD/Fs in the gas-phase and particle-phase of the inlet and 300-outlet (decomposition temperature = 300 °C) samples are presented, and the removal efficiencies η(g-I-TEQ) and η(p-I-TEQ) reached to 94.94% and 99.67%, respectively. The effect of the SCR process on the removal of PCDD/Fs was also studied at a relatively low temperature of 220 °C. Additionally, the NOx emissions and the SCR efficiencies were investigated.

State of the art in catalytic oxidation of chlorinated volatile organic compounds

Chlorine-containing organic compounds (Cl-VOC) require special attention due to their distinct toxicity, high stability and persistence in the environment. Removal of Cl-VOC by catalytic oxidation over a wide variety of catalysts has been presented in literature. This paper reviews the state of the art in this subject, including different model compounds, nature of catalysts, and oxidation activity. Catalyst selectivity (CO2 vs. CO and HCl vs. Cl2), by-products formation and the causes of deactivation are also analyzed as the most important factors in the catalyst selection for practical applications.

The abatement of major pollutants in air and water by environmental catalysis

This review reports the research progress in the abatement of major pollutants in air and water by environmental catalysis. For air pollution control, the selective catalytic reduction of NO x (SCR) by ammonia and hydrocarbons on metal oxide and zeolite catalysts are reviewed and discussed, as is the removal of Hg from flue gas by catalysis. The oxidation of Volatile organic compounds (VOCs) by photo- and thermal-catalysis for indoor air quality improvement is reviewed. For wastewater treatment, the catalytic elimination of inorganic and organic pollutants in wastewater is presented. In addition, the mechanism for the procedure of abatement of air and water pollutants by catalysis is discussed in this review. Finally, a research orientation on environment catalysis for the treatment of air pollutants and wastewater is proposed.

Nitrous oxide emissions from waste incineration

EU energy and environmental policy in waste management leads to increasing interest in developing methods for waste disposal with minimum emissions of greenhouse gases and minimum environmental impacts.

From the point of view of nitrous oxide (N2O) emissions, waste incineration and waste co-combustion is very acceptable method of waste disposal. Two factors are important for attaining very low N2O emissions from waste incineration, particularly for waste with higher nitrogen content (e.g. sewage sludge, leather, etc.): temperature of incineration over 900°C and avoiding selective noncatalytic reduction (SNCR) de-NOx method based on urea. For reduction of N2O emissions retrofitting such plants to ammonia-based SNCR is recommendable. The modern selective catalytic reduction facilities for de-NOx at waste incineration plants are only negligible source of N2O.

Nitrous oxide (N2O) emissions from waste and biomass to energy plants

Following the Kyoto protocol with respect to reducing emissions of greenhouse gases emissions, and EU energy policy and sustainability in waste management, there has been an increased interest in the reduction of emissions from waste disposal operations. From the point of view of nitrous oxide (N2O) emissions, waste incineration and waste co-combustion are very acceptable methods for waste disposal. In order to achieve very low N2O emissions from waste incineration, particularly for waste with higher nitrogen content (e.g. sewage sludge), two factors are important: temperature of incineration over 900 degrees C and avoiding the selective non-catalytic reduction (SNCR) de-NO(X) method based on urea or ammonia treatments. The more modern selective catalytic reduction (SCR) systems for de-NO(X) give rise to negligible sources of N2O.

Development of new vanadium-based oxide catalysts for decomposition of chlorinated aromatic pollutants

Supported transition metal oxides and vanadium-containing multi-metallic oxides were investigated to develop new catalysts for the catalytic destruction of highly toxic polychlorinated aromatic pollutants such as polychlorinated benzenes, polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and/or biphenyls (PCBs) from waste gases. The decomposition of 1,2-dichlorobenzene (Cl2Bz) was chosen as a model reaction. Titania-supported vanadium catalyst (VOx/TiO2) showed the highest activity and stability among the binary oxides tested even in the presence of water vapor. The optimum loading of vanadia was 5 wt %, corresponding to half a monolayer, suggesting that the active species are tetrahedral vanadyl species on titania. Characterizations of the VOx/TiO2 catalysts were carried out with XRD, laser Raman spectroscopy, and TPR. Multi-metallic VOx/TiO2 catalysts prepared by incorporating Mo, W, or Cr showed enhanced activities for Cl2Bz oxidation. Among the tested catalysts, V-Mo-Ox/TiO2 catalysts wash-coated on the cordierite honeycomb showed a good activity for the decomposition of the toxic PCDDs/PCDFs in the flue gas emitted from a municipal solid waste incinerator (MSWI).

Effects of flue gas composition on the catalytic destruction of chlorinated aromatic compounds with a V-oxide catalyst

When using catalytic flue gas cleaning, several flue gas compounds may influence oxidation reactions of hazardous volatile organic compounds, possibly leading to lower reaction rates and, thus, to an incomplete destruction. Experimental investigations were performed with regard to the influence of selected flue gas compounds, like hydrogen chloride, sulfur dioxide, oxygen, and water vapour, on the catalytic destruction behavior of chlorobenzenes under flue gas cleaning conditions of an incineration plant. For this purpose, a metal oxide catalyst was operated at different temperatures at a space velocity of 3600 h-1 in a laboratory-scale fixed bed reactor with model flue gases, and with real flue gases generated from the TAMARA waste incineration plant. The results obtained from the studies with model flue gas were analyzed with respect to reaction kinetics. These kinetics were applied for comparison with the experimental data gained in the real flue gas.