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Selective catalytic reduction

About: Selective catalytic reduction is a research topic. Over the lifetime, 10502 publications have been published within this topic receiving 226291 citations.


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Journal ArticleDOI
TL;DR: In this paper, the role of active supports in the catalytic hydrogenation of nitrates in the liquid phase using a PdCu/Mg/Al hydrotalcite is studied.

119 citations

Journal ArticleDOI
TL;DR: The catalyst reduced the toxicity measured in chemical and cellular assays suggesting a pathway for an inverse correlation between particle number and toxicity.
Abstract: Four heavy-duty and medium-duty diesel vehicles were tested in six different aftertreament configurations using a chassis dynamometer to characterize the occurrence of nucleation (the conversion of exhaust gases to particles upon dilution). The aftertreatment included four different diesel particulate filters and two selective catalytic reduction (SCR) devices. All DPFs reduced the emissions of solid particles by several orders of magnitude, but in certain cases the occurrence of a volatile nucleation mode could increase total particle number emissions. The occurrence of a nucleation mode could be predicted based on the level of catalyst in the aftertreatment, the prevailing temperature in the aftertreatment, and the age of the aftertreatment. The particles measured during nucleation had a high fraction of sulfate, up to 62% of reconstructed mass. Additionally the catalyst reduced the toxicity measured in chemical and cellular assays suggesting a pathway for an inverse correlation between particle number and toxicity. The results have implications for exposure to and toxicity of diesel PM.

119 citations

Journal ArticleDOI
TL;DR: In this article, the thermal deactivation of a commercial de-NO x V 2 O 5 WO 3 /TiO 2 catalyst is investigated, and the structural, morphological and chemico-physical changes caused by calcination at high temperatures are investigated by XRD, BET and Hg porosimetry measurements.
Abstract: In the present paper, the thermal deactivation of a commercial de-NO x V 2 O 5 –WO 3 /TiO 2 catalyst is investigated. In order to simulate long-term operation in gas firing samples of the catalyst are calcined at different temperatures from 773 to 1173 K. The structural, morphological and chemico-physical changes caused by calcination at high temperatures are investigated by XRD, BET and Hg porosimetry measurements, FT-IR, FT-Raman and EPR spectroscopies, and the activity in the reduction of NO with ammonia, the direct oxidation of ammonia and the oxidation of SO 2 is measured over the different catalyst samples. It is shown that sintering of the TiO 2 support leads to aggregation of isolated vanadium ions; this favours the selective catalytic reduction (SCR) reaction at low temperatures, the oxidation of ammonia at high temperatures and the undesired oxidation of SO 2 as well. Thus, it is expected that catalysts operated for long-term in gas firing at high temperatures are no longer appropriate for commercial use in the SCR process, because in spite of the greater activity in the de-NO x reaction, the temperature window is too narrow and the activity in the oxidation of SO 2 is too high.

119 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive review of the synergistic mechanism between bi-metal or multi-metal oxides is presented, and several possible directions for further research are presented finally.
Abstract: Atmospheric pollutants of nitrogen oxides (NOx) can be reduced by selective catalytic reduction (SCR). SCR of NOx with ammonia (NH3) at low temperatures has attracted much interest for high nitric oxide (NO) conversion, and this method is dominated by catalysts. Manganese (Mn)-containing oxide catalysts exhibit high activity and selectivity for the unique redox property of manganese oxides (MnOx). The reaction mechanisms and deactivation processes are summarized in this review. SCR of NOx with NH3 follows both the Langmuir–Hinshelwood and the Eley–Rideal mechanisms, which also contribute to the nitrous oxide formation. Fast SCR has a higher reaction rate than standard SCR. Mn-containing catalysts could also be deactivated by sulfur oxides and water vapor. The deactivation process of sulfur dioxide can be classified into two categories: deposition of (NH4)2SO4 and sulfation of active sites. The deactivation caused by water vapor can be attributed to the competitive adsorption. The adsorption of water on catalysts' surface blocked the active sites, which are provided for the adsorption of NH3 and NO. Alkali, alkaline earth and heavy metal ions existing in fine fly ash can also damage the catalysts' acid sites. A notable improvement on performance was obtained when Mn-containing catalysts were doped with a transition metal, for these enhanced its adsorption capacity and oxidation ability. Furthermore, this review gives a comprehensive discussion of the synergistic mechanism between bi-metal or multi-metal oxides. Major conclusions and several possible directions for further research are presented finally.

119 citations

Journal ArticleDOI
TL;DR: In this paper, four different supports of varying degree of Bronsted and Lewis acid sites and textural properties were used to evaluate the influence of degree of ammonia interaction and Mn species formation in the catalysts and its effect on NOx conversion.

119 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023311
2022632
2021546
2020583
2019604
2018595