NOx Removal Rate Research Articles

Sludge Recycling from Non-Lime Purification of Electrolysis Wastewater: Bridge from Contaminant Removal to Waste-Derived NOX SCR Catalyst

Catalysts for the selective catalytic reduction (NOX SCR) of nitrogen oxides can be obtained from sludge in industrial waste treatment, and, due to the complex composition of sludge, NOX SCR shows various SCR efficiencies. In the current work, an SCR catalyst developed from the sludge produced with Fe/C micro-electrolysis Fenton technology (MEF) in wastewater treatment was investigated, taking into account various sludge compositions, Fe/C ratios, and contaminant contents. It was found that, at about 300 °C, the NOX removal rate could reach 100% and there was a wide decomposition temperature zone. The effect of individual components of electroplating sludge, i.e., P, Fe and Ni, on NOX degradation performance of the obtained solids was investigated. It was found that the best effect was achieved when the Fe/P was 8/3 wt%, and variations in the Ni content had a limited effect on the NOX degradation performance. When the Fe/C was 1:2 and the Fe/C/P was 1:2:0.4, the electroplating sludge formed after treatment with Fe/C MEF provided the best NOX removal rate at 100%. Moreover, the characterization results show that the activated carbon was also involved in the catalytic reduction degradation of NOX. An excessive Fe content may cause agglomeration on the catalyst surface and thus affect the catalytic efficiency. The addition of P effectively reduces the catalytic reaction temperature, and the formation of phosphate promotes the generation of adsorbed oxygen, which in turn contributes to improvements in catalytic efficiency. Therefore, our work suggests that controlling the composition in the sludge is an efficient way to modulate SCR catalysis, providing a bridge from contaminant-bearing waste to efficient catalyst.

Development and Optimization of A Low-Pressure Microbubble Scrubber for Air Pollutants Removal Using CFD

A microbubble scrubber is a hybrid type scrubber that combines the advantages of a general scrubber with the advantages of the microbubble. Microbubble which has generally under 50 μm diameter is one of the effective ways to remove air pollutants, like PM, NOx, and SOx. The low-pressure microbubble (LPMB) scrubber is a low-power, high-efficiency method that uses a blower to draw flue gas into the solution and generate microbubbles in the water by using low-pressure or negative pressure. The objective of this study was to enhance the removal efficiency of air pollutants in an LPMB scrubber by determining its optimal operating conditions for generating a large number of microbubbles. To achieve this, we developed a CFD model based on a pilot-scale LPMB scrubber and conducted case studies under different operating conditions using fluid flow analysis. The case study consisted of 12 cases according to the pressure difference (1,000, 3,000, 5,000, and 7,000 Pa) between the scrubber inlet and outlet and the initial water level (–0.2, 0, and +0.2 m). The simulation results showed that the optimal operating conditions were a pressure difference of 5,000 Pa and an initial water level of –0.2 m. The removal rates of PM, NOx, and SOx were 99.9, 92.6, and 99.0%, respectively when operating under the optimal operating conditions of the LPMB scrubber. The results suggest that the proposed optimal operating conditions can effectively enhance the removal efficiency of the LPMB scrubber.

Actual NOX and SOX removal rates in the atmospheric environment of concrete permeable blocks containing TiO2 powders, coconut shell powders, and zeolite beads

This study examined actual nitrogen oxide (NOX) and sulfur oxide (SOX) removal rates of concrete permeable blocks in the atmospheric environment. To give the concrete permeable block a NOX and SOX removal function, TiO2 submicron particle or coconut shell powder was embedded in the surface layer, and zeolite bead was embedded in the base layer. Using an actual factory production line, concrete permeable block specimens were prepared by adding TiO2 submicron particles and coconut shell powder to the surface layer of the concrete permeable block. The prepared concrete permeable block specimens were placed in a parking lot, and then NOX and SOX removal rates were directly measured for 6 months on the concrete permeable block specimens placed in the parking lot. Test results showed that the clear day removal rates of NOX and SOX for the concrete permeable block specimens embedded with TiO2 submicron particles during the day was 84% and 70%, respectively. Compared to the concrete permeable blocks embedded with coconut shell powder, the NOx removal rate of the specimens embedded with TiO2 submicron particles was 1.45 times higher, while the SOx removal rate was similar. However, during cloudy days and nights, the NOX removal rate of the concrete permeable block specimens embedded with TiO2 submicron particles was zero. On the other hand, NOX and SOX removal rates of the concrete permeable block specimens embedded with coconut shell powder and zeolite bead were maintained at approximately 51% and 77% for 6 months, respectively, in the atmospheric environment regardless of weather and day light conditions. Consequently, the coconut shell powder added to the surface layer of the concrete permeable block is a practically promising material in reducing the NOX in the atmospheric environment regardless of weather and day light conditions.

NOx removal and copper recovery from the leaching process for waste printed circuit boards: performance evaluation and potential environmental impact assessment.

Resource recovery is crucial for small- and medium-sized enterprises to attain a circular economy. The economic benefits of recovering precious metals from electronic waste, such as waste printed circuit boards (WPCBs), are hindered by secondary pollutant emissions from pretreatment processes. This study aims to recover copper from the WPCB acid leaching process and reduce NOx emissions through the use of a high gravity rotating packed bed (RPB). The results indicate that the copper recovery ratio increases to 99.75% through the displacement reaction between iron powder and copper nitrate. The kinetic analysis of copper dissolution was employed to simulate the NOx emissions during acid leaching, with an R-squared value of 0.872. Three oxidants, including H2O2(aq), ClO2(aq), and O3(g), with pH adjusted to different NaOH concentrations, were used to remove NOx. The greatest NOx removal rate was achieved using a 0.06M NaOH solution, with a removal rate of 91.2% for ozone oxidation at a 152-fold gravity level and a gas-to-liquid (G/L) ratio of 0.83. The gas-side mass transfer coefficients (KGa) for NOx range from 0.003 to 0.012 1/s and are comparable to previous studies. The results of a life cycle analysis indicate that the NOx removal rate, nitric acid recycling rate, and copper recovery rate are 85%, 80%, and 100%, respectively, reducing the environmental impact on the ecosystem, human health, and resource depletion by 10% compared to a scenario with no NOx removal.

One-pot synthesis of bimetallic CeCu-SAPO-34 for high-efficiency selective catalytic reduction of nitrogen oxides with NH3 at low temperature

NH3 selective catalytic reduction (SCR) has been widely recognized as a promising technique for reducing nitrogen oxides from diesel vehicle exhausts. High-efficiency SCR catalysts that could perform at low temperatures are essential to denitration. In this work, a series of bimetallic CeCu-SAPO-34 molecular sieves were synthesized by one-step hydrothermal method. The CeCu-SAPO-34 maintained good crystallinity and a regular hexahedron appearance of Cu-SAPO-34 after introducing Ce species, while exhibiting a higher specific surface area and pore volume. The as-prepared CeCu-SAPO-34 with 0.02% (mass) Ce constituent exhibited the best catalytic activity below 300 oC and a maximum NOx conversion of 99% was attained; the NOx removal rates of more than 68% and 94% were achieved at 150 °C and 200 °C, respectively. And the introduction of cerium species in Cu-SAPO-34 improves the low-temperature hydrothermal stability of the catalyst towards NH3-SCR reaction. Additionally, the introduced Ce species could enhance the formation of abundant weak Brønsted acid centers and promote the synergistic effect between CuO grains and isolated Cu2+ to enhance the redox cycle, which benefit the NH3-SCR reaction. This work provides a facile synthesis method of high-efficiency SCR denitration catalysts towards diesel vehicles exhaust treatment under low temperature.

Microwave assisted synthesis of PQ-GDY@NH2-UIO-66(Zr) for improved photocatalytic removal of NOx under visible light

Pyrazinoquinoxaline-based graphdiyne (PQ-GDY) contains a fixed number of sp−sp2 hybridized carbon atoms and pyrazine-like sp2 hybridized N atoms. In this paper, NH2-UIO-66(Zr) on PQ-GDY substrate was successfully constructed with the help of microwave-assisted heating. PQ-GDY surface acts as a microwave antenna under microwave irradiation to rapidly absorb microwave energy and form hot spots (hot spot effect), which facilitates the formation of well-dispersed NH2-UIO-66(Zr) with good crystallinity. Transient absorption spectra show that high hole transport property of PQ-GDY can accelerate the migration of photogenerated holes from NH2-UIO-66(Zr) to PQ-GDY and greatly reduce the recombination rate of photogenerated electrons and holes due to the strong interaction between PQ-GDY and NH2-UIO-66(Zr). Under visible light (λ ≥ 420 nm), PQ-GDY@NH2-UIO-66(Zr) shows high photocatalytic stability and high NOx removal rate up to 74%, which is 44% higher than that of primitive NH2-UIO-66(Zr). At the same time, it inhibits the formation of toxic by-products (NO2) and limits its concentration to a low level.

Alkali and Heavy Metal Copoisoning Resistant Catalytic Reduction of NOx via Liberating Lewis Acid Sites.

The catalyst deactivation caused by the coexistence of alkali and heavy metals remains an obstacle for selective catalytic reduction of NOx with NH3. Moreover, the copoisoning mechanism of alkali and heavy metals is still unclear. Herein, the copoisoning mechanism of K and Cd was revealed from the adsorption and variation of reaction intermediates at a molecular level through time-resolved in situ spectroscopy combined with theoretical calculations. The alkali metal K mainly decreased the adsorption of NH3 on Lewis acid sites and altered the reaction more depending on the formation of the NH4NO3 intermediate, which is highly related to NOx adsorption and activation. However, Cd further inhibited the generation of active nitrate intermediates and thus decreased the NOx abatement about 60% on potassium-poisoned CeTiOx catalysts. Physically mixing with acid additives for CeTiOx catalysts could significantly liberate the active Lewis acid sites from the occupation of alkali metals and relieve the high dependence on NOx adsorption and activation, thus recovering the NOx removal rate to the initial state. This work revealed the copoisoning mechanism of K and Cd on Ce-based de-NOx catalysts and developed a facile anti-poisoning strategy, which paves a way for the development of durable catalysts among alkali and heavy metal copoisoning resistant catalytic reduction of NOx.

Investigation of Inactivatioin and Electrostatic Precipitation Effects by Corona Discharge

In recent years, infectious diseases have caused social and economic problems. To control such infectious diseases, various techniques are being developed and tested. In this study, the experimental apparatus as air purifier with corona discharge electrodes intersect to the gas flow was verified. We examined how the effects of air volume on O3 and NOx concentration and removal rate of virus. We found that the O3 and NOx concentrations decreased with air volume. The amount of viruses was decreased 84% by circulating air with viruses through the experimental apparatus four times.

Performance evaluation of Mn-Ce/cordierite catalyst modified by green surfactant to remove NOx in underground mines at low temperatures

An environment-friendly and low temperature performance catalyst is important to protect the working environment under the mine. We choose cordierite as the carrier of catalyst and modified by green surfactant to increase the specific surface area and catalytic activity, which also provides environmental protection for the catalyst. The most suitable surfactant is selected based on its saturated adsorption curve, surface tension, and denitration efficiency. Analyze the adsorption process of surfactant molecules on cordierite surface and the micro mechanism of improving the removal rate of NOx. In order to improve the NOx removal rate to a step further, the surfactant is used as a coating to prepare a new Mn-Ce/surfactant-cordierite monolithic catalyst, which is characterized by Fourier transform infrared spectroscopy, energy-dispersive x-ray spectroscopy, X-ray diffraction, and H2 temperature programmed reduction. Its selective catalytic reduction and denitration activity are studied. Experimental results: (1)Green surfactants can effectively improve the conversion efficiency of cordierite for NOx.(2)Among the four surfactants, cetyltrimethyl ammonium bromide (CTAB) can most significantly improve the conversion efficiency of NOx and its optimum concentration is 0.04%.(3)The NOx removal efficiency of the new Mn-Ce/CTAB-cordierite monolithic catalyst can reach 95% at 150 ℃.

Facile hydrothermal preparation of a ZnFe2O4/TiO2 heterojunction for NOx removal

Titanium dioxide (TiO2) has become the most promising photocatalyst. It is non-toxic and has a wide range of sources, but its application is limited due to its weak visible light absorption capacity. Compounding with other materials to form heterojunctions has proven to be effective strategies for enabling high photocatalytic performances under visible light. Here, the ZnFe2O4/TiO2 composites had been synthesized by a facile hydrothermal method to realize efficient visible light photocatalytic activity of NOx removal. A series of characterizations, such as XRD, ESR, in-situ DRIFTS, etc., were used to analyze the physical and chemical properties of the photocatalyst, which demonstrated that the composite material had more active sites and a faster electron transfer rate. The optimal sample (12 wt% ZnFe2O4/TiO2) had a NOx removal rate of 54 % nearly 11 times higher than that of original TiO2. On the basis of the above photocatalytic experimental results and characterizations, a possible mechanism or pathway was proposed and illustrated. This work can provide a feasible strategy to prepare TiO2-based composite materials with magnetic separation properties to effectively remove NOx.

Highly-efficient green photocatalytic cementitious materials with robust weathering resistance: From laboratory to application.

The combined use of nano-TiO2 with cementitious materials offers an environmentally-friendly way to combat the air pollution problem. However, a trade-off between a high efficiency and a robust weathering resistance has often to be made for most of the attempted nano-TiO2 incorporation methods. This paper developed a simple and effective "spraying" method to coat nano-TiO2 particles on the surface of concrete surface layers (CSL). The results showed that the NOx removal rate of the samples increased with an increase in both the concentrations of nano-TiO2 solutions and the number of times of the spraying action. And the conditions for preparation of the Spray AB (the CSL were first sprayed with the 30gL-1 TiO2-solution 20 times, followed by mechanical compaction, and for another 20 times after the compaction) were found to be optimal in terms of NOx removal performance and weathering resistance. The Spray AB was superior to the 5% TiO2-intermixed samples with respect to photocatalytic NOx removal ability. Compared with TiO2-dip-coated samples, the Spray AB samples had better and robust weathering resistance. A case study on the factory-fabricated green Eco-blocks (produced by the laboratory-developed spray method and the conventional intermix method) was performed. Examination and comparison on their respective photocatalytic NOx removal further verified the advantages of the spray method over the intermix method.

Effect of Cu, Cr, S Doped TiO2 for Transparent Plastic Bar Reinforced Concrete

In this study, after firing and powdering Cu, Cr, and S with NP-400 TiO2, an NOx removal rate test was performed according to the ISO test method to analyze the photocatalytic reactivity in visible light. The distribution of the photocatalyst and visible light reactivity on the surface of the test specimen were confirmed through SEM (Scanning electron microscope), EDS (Energy dispersive spectroscopy), XRD (X-ray diffraction), UV-visible absorption spectrum and energy band gap tests. The flowability of UHPC (Ultra high performance concrete) slightly decreased due to the increase in the photocatalyst mixing rate, but both J-Ring and L-Box test results showed that there is no problem when concrete is placed. As a result of SEM and EDS tests, good microstructure and peak values were confirmed in the test specimens doped with Cu, and as a result of the XRD test, anatase and rutile peaks were confirmed in the Cu, Cr, and S specimens. In the UV-visible absorption spectrum analysis, it was confirmed that only the specimen doped with Cu maintains a high absorption power of 0.8 up to 700 nm, and the inherent band gaps are reduced to 2.9 eV, thereby increasing the possibility of reaction in visible light. Finally, as a result of the NOx removal test by the ISO test method, about 15.8% was removed for 5 h in the specimen doped with Cu, and the removal efficiency is estimated to be possible up to about 25% when applied with the TPBRC (transparent plastic bar reinforced concrete).

Study on the Effect of Different Preparation Methods on the Performance ofAgCl/Al2O3 Catalyst Used for Diesel Exhaust Treatment

In this study, AgCl/Al2O3 catalyst was prepared by the impregnation method to remove NOx in diesel exhaust gas, so as to achieve the purpose of purifying exhaust gas. The AgCl/Al2O3 catalyst is a kind of hydrocarbons selective catalytic reduction (HC-SCR) catalyst. The HC-SCR catalyst uses the unsaturated hydrocarbons and the oxygencontaining derivatives of the hydrocarbons as reducing agents to convert harmful NOx in the exhaust gas into N2. This kind of catalyst belongs to Ag type catalyst, and because of its simple preparation conditions, low cost and good catalytic activity of this catalyst, AgCl/Al2O3 catalyst is worth studying. in this research, the catalysts were prepared under four different conditions by changing the adding order of NH4Cl, AgNO3 and γ-Al2O3, as well as the drying and sintering times, and through the HC-SCR test that the working environment of the catalyst in diesel exhaust gas is simulated by introducing the gas into the device equipped with the catalyst and heating, then the relationship between the NOx conversion rate and the temperature was obtained. According to the result, it is found that the NOx removal rate of the four catalysts is close to 100% at 350°C to 400°C. The catalyst obtained by condition C and condition D maintains a high conversion rate of NOx in a wide temperature range. At the same time, the catalyst under condition D has good reproducibility after repeated heating and cooling experiments, therefore this catalyst is considered to have good application prospects.

Bio-inspired mineralization of nanostructured TiO2 on PET and FTO films with high surface area and high photocatalytic activity

Nanostructured TiO2 coatings were successfully formed on polyethylene terephthalate (PET) films and fluorine-doped tin oxide (FTO) films in aqueous solutions. They contained an assembly of nanoneedles that grow perpendicular to the films. The surface area of the coatings on PET films reached around 284 times that of a bare PET film. Micro-, nano-, or subnanosized surface roughness and inside pores contributed to the high nitrogen adsorption. The coatings on FTO films showed an acetaldehyde removal rate of 2.80 μmol/h; this value is similar to those of commercial products certified by the Photocatalysis Industry Association of Japan. The rate increased greatly to 10.16 μmol/h upon annealing in air at 500 °C for 4 h; this value exceeded those of commercial products. Further, the coatings showed a NOx removal rate of 1.04 μmol/h; this value is similar to those of commercial products. The rate decreased to 0.42 μmol/h upon annealing. NOx removal was affected by the photocatalyst’s surface area rather than its crystallinity.

Germanium-based polyoxometalates for the adsorption-decomposition of NOx

A series of germanium-based Keggin-type polyoxometalates (POMs), including H4GeW12O40 (HGeW), H5GeW11VO40 (HGeWV), H5GeMo11VO40 (HGeMoV) and H5GeW9Mo2VO40 HGeWMoV), were first synthesized and utilized as catalysts for removal of NOx. The fourier transform infrared spectroscopy (FT-IR) and temperature-programmed desorption-mass spectroscopy (TPD-MS) characterizations were carried out to investigate the adsorption-desorption behavior and decomposition mechanism of NOx. The adsorption experiments revealed that HGeW had the highest NOx adsorption capacity up to 16.2 mg NOx per gram catalyst. Two infrared characteristic bands appeared at 2210 and 1851 cm−1 after NOx adsorption, while the latter firstly discovered over NOx-absorbed POMs could be assigned to nitrosyl radical (NO·). The regeneration of HGeW could be realized via reducing the temperature in wet atmosphere to desorb NOx. TPD-MS was conducted to investigate the decomposition behavior of NOx over HGeW and tungstophosphoric acid (HPW). O2 was firstly detected among the decomposition products, besides N2 and N2O. According to conservation calculation based on N mass, NOx removal rate of 81.5 % and N2 selectivity of 68.3 % could be achieved for HGeW. While the NOx conversion rate and N2 selectivity for HPW reached 54.1 % and 53.4 %, respectively.

High Performance of Mn-Doped MgAlOx Mixed Oxides for Low Temperature NOx Storage and Release

NOx storage-reduction (NSR) is a potential approach for the effective removal of NOx under the lean conditions in lean-burn engines. Herein, manganese-doped mixed oxides (Mn/MgAlOx) with high performance for low temperature NOx storage and release were derived from hydrotalcites precursors prepared by a facile coprecipitation method. The catalysts were characterized by X-ray diffraction (XRD), SEM, N2 adsorption-desorption, H2-TPR, FT-IR, and X-ray photoelectron spectroscopy (XPS) techniques. The Mn-doped MgAlOx catalysts exhibited high NOx storage capacity (NSC) at low temperature range (150–300 °C), which was related to their increased surface area, improved reducibility and higher surface Mn3+ content. The largest NSC measured, 426 μmol/g, was observed for NOx adsorption at 200 °C on Mn15 catalyst (the sample containing 15 wt% of Mn). The in situ DRIFTS spectra of NOx adsorption proved that the Mn-doped hydrotalcite catalysts are preferred for low temperature NOx storage and release due to their ability to store NOx mainly in the form of thermally labile nitrites. NSR cycling tests revealed the NOx removal rate of Mn15 sample can reach above 70% within the wide temperature range of 150–250 °C. Besides, the influence of CO2, soot, H2O and SO2 on NOx storage performance of Mn15 catalyst was also studied. In all, owning to their excellent NOx storage capacity, NSR cycling performance, and resistance to CO2, soot, SO2 and H2O, the Mn-doped MgAlOx NSR catalysts have broad application prospects in NOx control at low temperatures.

Plasma–Chemical Hybrid NOx Removal in Flue Gas from Semiconductor Manufacturing Industries Using a Blade-Dielectric Barrier-Type Plasma Reactor

NOx is emitted in the flue gas from semiconductor manufacturing plants as a byproduct of combustion for abatement of perfluorinated compounds. In order to treat NOx emission, a combined process consisting of a dry plasma process using nonthermal plasma and a wet chemical process using a wet scrubber is performed. For the dry plasma process, a dielectric barrier discharge plasma is applied using a blade-barrier electrode. Two oxidation methods, direct and indirect, are compared in terms of NO oxidation efficiency. For the wet chemical process, sodium sulfide (Na2S) is used as a reducing agent for the NO2. Experiments are conducted by varying the gas flow rate and input power to the plasma reactor, using NO diluted in air to a level of 300 ppm to simulate exhaust gas from semiconductor manufacturing. At flow rates of ≤5 L/min, the indirect oxidation method verified greater removal efficiency than the direct oxidation method, achieving a maximum NO conversion rate of 98% and a NOx removal rate of 83% at 29.4 kV and a flow rate of 3 L/min. These results demonstrate that the proposed combined process consisting of a dry plasma process and wet chemical process is promising for treating NOx emissions from the semiconductor manufacturing industry.

Improving simultaneous removal efficiency of SO2 and NOx from flue gas by surface modification of MgO with organic component

Using glucose and polyvinylpyrrolidone as raw materials, MgO-organic component materials were prepared by a one-step hydrothermal method. The material is used to improve the efficiency of simultaneous removal of SO2 and NOx, and to reduce the competitive adsorption of both. In the experiments, the adsorption of SO2 and NOx in simulated coal-fired flue gas was tested with MgO-organic component/pure MgO/MgO (PVP modified)/MgO (glucose modified), and the test results were compared. It is very noteworthy that the SO2 dynamic adsorption capacity of the MgO-organic component (the glucose/polyvinylpyrrolidone ratio is 1:3) was 0.3627 mmol/g; while that of NOx was 0.2176 mmol/g, and the adsorption breakthrough time (time taken when the NOx removal rate was 50%) was as long as 60 min (the total flow rate of simulated flue gas is 200 ml/min, the space velocity is 24000 h-1, the reaction temperature is 100 °C, the concentration of SO2 and NOx is 500 ppm and 300 ppm, respectively). In this study, the organic component enhances the simultaneous desulfurization and denitration performance of MgO from three aspects and is verified by different characterization tests. There are an increase in specific surface area, an increase in surface energy and the insert of active functional groups. In particular, the insert of –CO can greatly improve the adsorption efficiency of NOx. Meanwhile, the adsorption process under different operating conditions is discussed in order to provide theoretical support for industrial practice. The work presented here has profound implications for future studies of simultaneous desulfurization and denitration field. Moreover, the economy and sustainability of the technology meet the basic requirements of waste reduction in cleaner production.

The influence of Pt loading and dispersion on the NOx storage and reduction performance of Pt/K2CO3/Co1Mg2Al1Ox catalysts

Abstract For NOx storage and reduction (NSR) catalysts, Pt is necessary for the NO oxidation during the lean stage and the NOx reduction during the rich stage. However, due to its high price, synthesis of NSR catalysts with low Pt loading is highly demanded. In this contribution, Pt/K2CO3/Co1Mg2Al1Ox as NSR catalysts with low Pt loadings (0.15, 0.33 and 0.59 wt%) were prepared via co-precipitation and incipient wetness impregnation methods. The optimal of K2CO3 loading was determined to be 15 wt% for both samples. The influence of Pt particle size and Pt dispersion on the NOx storage capacity and the NSR cycling performance of Pt/K2CO3/Co1Mg2Al1Ox were then systematically and comparatively investigated. It was demonstrated that the samples prepared by CP method can result in higher isothermal NOx storage capacity, and higher NOx removal rate and better cycle stability during lean-rich cycling tests. By increasing the Pt loading or extending the rich period duration, the overall NOx removal rate can be promoted and became more stable. No matter what method was used for loading Pt, the N2 selectivity of all catalysts was higher than 95%. The results also indicated the samples prepared by CP method were more resistant to the effects of SO2, CO2 and H2O. CO-pulse and HR-TEM analyses confirmed that the 0.59 Pt/Co1Mg2Al1Ox (CP) possesses smaller Pt particle size (1.30–1.32 nm) and higher Pt dispersion (65.41%), while the values for 0.59 Pt/Co1Mg2Al1Ox (IWI) was 2.66–2.71 nm and 31.90%, respectively. All results indicated that the CP method, which can effectively improve Pt dispersion and reduce the Pt particle size, is superior to the traditional IWI for the preparation of highly efficient low Pt loading NSR catalysts.

Denitrification performance of non-pitch coal-based activated coke by the introduction of MnOx–CeOx–M (FeOx, CoOx) at low temperature

Modified activated coke was prepared by the introduction of MnOx, CeOx, and M (FeOx, CoOx) into non-pitch coal-based activated coke (NPAC) using a novel non-pitch binder. The modified non-pitch coal-based activated coke was characterized in detail by N2 physical adsorption, thermogravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, temperature-programmed reduction of H2, temperature-programmed desorption of NH3, and its catalytic activity was examined by the selective catalytic reduction of NO with NH3 at low temperature. In addition, the SO2 and H2O tolerance was investigated. The results indicated that compared to MnOx–CeOx–4.39, Mn–Ce–Co/NPAC-7 and Mn–Ce–Fe/NPAC-7 exhibit considerably higher catalytic activities while simultaneously maintaining NOx removal rates of 78.98% and 77.85%, respectively, at 150°C. The high catalytic performance of Mn–Ce–Co/NPAC-a and Mn–Ce–Fe/NPAC-a is related to several better properties compared to MnOx–CeOx–4.39, namely, considerably higher specific surface areas and percentages of Oα/(Oα+Oβ+Oγ) and Ce3+/(Ce3++Ce4+), more easily reduced of Mn species, high reducibility, and more acidic sites. Furthermore, Mn–Ce–Co/NPAC-7 and Mn–Ce–Fe/NPAC-7 exhibited specific resistance to SO2 and H2O poisoning, and the SO2 deactivation mechanism was proposed.