查找使用阿拉丁产品的科研文献

In-plasma-catalysis for NOx degradation by Ti3+ self-doped TiO2−x/γ-Al2O3 catalyst and nonthermal plasma

Xingdong Yang,Jiyan Qu,Linxi Wang,Jianhong Luo

In an attempt to realize the efficient treatment of NOx, a mixed catalyst of Ti3+ self-doped TiO2−x and γ-Al2O3 was constructed by reducing commercial TiO2. The degradation effect on NOx was evaluated by introducing the mixed catalyst into a coaxial dual-dielectric barrier reactor. It was found that the synthesized TiO2−x could achieve considerable degradation effects (84.84%, SIE = 401.27 J L−1) in a plasma catalytic system under oxygen-rich conditions, which were better than those of TiO2 (73.99%) or a single plasma degradation process (26.00%). The presence of Ti3+ and oxygen vacancies in TiO2−x resulted in a relatively narrow band gap, which contributed to catalyzing deeply the oxidation of NOx to NO2− and NO3− during the plasma-induced “pseudo-photocatalysis” process. Meanwhile, the TiO2−x showed an improved discharge current and promoted discharge efficiency, explaining its significant activation effect in the reaction. Reduced TiO2−x could achieve an impressive degradation effect in a long-time plasma-catalysis process, and still maintained its intrinsic crystal structure and morphology. This work provides a facile synthesis procedure for preparing Ti3+ self-doped TiO2−x with practical and scalable production potential; moreover, the novel combination with plasma also provides new insights into the low-temperature degradation of NOx.

Irregular influence of alkali metals on Cu-SAPO-34 catalyst for selective catalytic reduction of NOx with ammonia

Guangpeng Yang,Xuesen Du,Jingyu Ran,Xiangmin Wang,Yanrong Chen,Li Zhang,Vladislav Rac,Vesna Rakic,John Crittenden

SCR activity of Cu-SAPO-34 catalyst was reduced by alkali metal ions. The alkali metals ions (Li + , Na + and K + ) have shown irregular influences on Cu-SAPO-34. The order of poisoning strengths under 400 °C was found to be: Na +  > K +  > Li + , which is not consistent with the basicities of their corresponding metals. Experimental results and calculations showed that the alkali metal ions readily replace H + and Cu 2+ /Cu + ions. These exchanges result in the loss of Brønsted acid sites and migration of isolated Cu 2+ ions in Cu-SAPO-34, which decrease the NH 3 -SCR activity. Both the basicity and ion diameter will affect the exchanging behavior of an alkali ion. Na + and Li + ions will influence both H + and Cu 2+ /Cu + ions but K + ions only preferably replace the H + . We hypothesize that K + cannot enter into a small ring (6-membered ring) to replace a Cu 2+ /Cu + ion because of its large ion diameter. The displaced Cu 2+ /Cu + ions will transfer to adjacent unbonded Al site to form a CuAlO 2 species.

In situ regeneration of sulfated Cu/SAPO-34 catalyst for the selective catalytic reduction of NOx with NH3

Yu Qifan,Liu Xuesong,Chen Hongfeng,Liu Shuang,Jiang Peng

The regeneration mechanism of sulfated Cu/SAPO-34 catalysts in reducing atmospheres (5% H 2 /Ar and NH 3 /Ar at 600 °C) was investigated by using a series of characterization methods. Hydrogen regeneration improved the catalysts’ NH 3 -SCR activity from 150 to 550 °C remarkably, while ammonia regeneration exhibited relatively less obvious promotion effect. The TPR of hydrogen and EPR spectra data show that the regeneration process affects the amount and the coordination of the active isolated Cu 2+ species significantly. The desulfation increases the amount of isolated copper ions and improves the catalytic activity of SCR.

Encapsulation of ultra-small Cu–Fe into ZSM-5 zeolites for NH3-SCR with broad reaction-temperature ranges

En-Hui Yuan,Meng Li,Ming-Hui Yang,Xiaosheng Huang,Kun Zhang,Weiliang Han,Zhicheng Tang,Zhong-Wen Liu

A direct hydrothermal synthesis strategy is developed to prepare the Cu–Fe-ZSM-5 zeolites by using the ethylenediaminetetraacetic acid disodium dihydrate (EDTA-2Na·2H 2 O) chelated Cu 2+ and Fe 3+ precursors as metal sources. During the crystallization, the metal chelates were spontaneously embedded into the ZSM-5 crystals and subsequently transformed to the zeolites encapsulated copper and iron species after removing the chelating agent via the high-temperature calcination . Rigorous characterizations indicate that the resulted Cu 2+ /Cu + and Fe 3+ /Fe 2+ species are formed ultra-small nano-composites with an average diameter of ∼2.2 nm and highly dispersed in the ZSM-5 zeolite crystals. The acidity of the ZSM-5 zeolites is subtly modulated by the encapsulated Cu–Fe nano-composite. As expected, the as-prepared Cu–Fe-ZSM-5 exhibits outstanding catalytic performance for the selective catalytic reduction of NO x with ammonia (NH 3 -SCR) in the broad reaction temperature ranges of 220–480 °C, which is much better than the Cu–Fe/ZSM-5 prepared with the conventional wetness impregnation method. Furthermore, the resultant zeolites show high stability and good tolerance to H 2 O and SO 2 , and it is very competitive for practical application to eliminate NO x . The developed one-pot hydrothermal synthesis route by using EDTA-2Na·2H 2 O as chelating agent is very convenient and easily reproducible, providing a general guideline to design and fabricate the superior transition metal modified zeolite catalysts for NH 3 -SCR and the related reactions.

Low-temperature SCR of NOx by NH3 over MnOx/SAPO-34 prepared by two different methods: a comparative study

Chenglong Yu,Lifu Dong,Feng Chen,Xiaoqing Liu,Bichun Huang

Wet de-NOx Process of the Composite Phosphate Rock/H2O2 Slurry by Calcination Modification: Key Components and Radical Generation

Yaqiong Luo,Jiacheng Bao,Xin Yan,Lei Shi,Fei Wang,Xin Sun,Kai Li,Ping Ning

Wet flue gas denitrification offers a new route for converting industrial nitrogen oxides (NOx) into highly concentrated nitrate wastewater. This study presents a novel H2O2-based advanced oxidation process that utilizes the composite calcined phosphate rock to activate H2O2 for efficient NOx removal. The calcination treatment for composite phosphate rocks was found to enhance de-NOx efficiency and capacity by varying the CaMg(CO3)2 and Ca5(PO4)3OH contents and creating oxygen vacancies. A systematic investigation of the phase structural evolution under alkaline H2O2 conditions identified CaMg(CO3)2 and Ca5(PO4)3OH as the primary active components, with CaMg(CO3)2 preferentially participating in the reaction. Radical quenching experiments and time-resolved electron paramagnetic resonance (EPR) analysis confirmed the predominant roles of superoxide radicals (O2•–) and surface-bound hydroxyl radicals (•OHsurface) in NOx oxidation. A mechanistic pathway was proposed, highlighting the synergistic effects of reactive oxygen species (ROS) and mineral phase transitions on NOx removal. The proposed NOx purification method offers a promising option for nitrogen recovery and NOx pollution control.

Enhancements of activity and hydrothermal stability of FeTi catalyst from solid acid sites for selective catalytic reduction of NOx

Zhipeng Yang,Siru Lu,Tianyu Wu,Hong Yao,Changan Zhou,Chao Wang,Kui Ma,Lei Song,Hairong Yue

Acid sites and redox sites with high thermal stability are crucial for the NH 3 -SCR catalyst for diesel vehicles. The surface acidity of FeTi catalysts is improved by modified with the solid acid of PO 4 3- or WO 3 . The acid-modified FeTi catalysts show superior NH 3 -SCR activity hydrothermal stability with a wide temperature window. The introduction of acid groups not only provides a large number of Brønsted acid sites but also promotes high dispersion of the active species of redox sites due to the formation of the structure P-O-Fe/W-O-Fe. The P-O-Fe/W-O-Fe structure can also improve the redox properties of the FeTi catalysts and inhibit the phase transformation of the TiO 2 support during high-temperature hydrothermal process. The reaction kinetics indicate that the reaction rate is primarily related to the concentration of NO. The mechanistic study indicates that the catalytic reaction is primarily governed by the Eley-Rideal mechanism.

Asymmetric support-side deposition strategy for high-permeance tubular CePO4/SiC catalytic membranes enabling synergistic PM and NOx removal

Yiqing Zeng,Guangyu Zhou,Jiangxiao Qiao,Yunqi Shi,Jicheng Han,Xiangsen Xu,Junwei Wu,Zhaoxiang Zhong,Weihong Xing

Catalytic membranes are promising multifunctional materials for integrated pollutant control. However, conventional impregnation-based catalyst loading strategies often allow catalytic particles to infiltrate the separation layer, resulting in severe pore blockage and reduced permeance. Herein, we develop a rapid and low-cost asymmetric support-side deposition approach to fabricate tubular CePO 4 /SiC–S catalytic membranes, which effectively prevents catalyst penetration into the separation layer, minimizes pore blockage, and thereby enhances the permeance. The results indicate that CePO 4 catalysts are mainly anchored within the pores of the SiC support, rather than in the separation-layer pores, thereby preserving efficient gas transport pathways and avoiding direct contact between particulate matter (PM) and catalytic sites. Compared with conventional vacuum impregnation, the proposed method achieves comparable ammonia selective catalytic reduction (NH 3 -SCR) activity while reducing permeance loss from 35.44% to only 20.09%. The membrane demonstrated exceptional stability during a 240 h continuous operation at 350 °C, maintaining a dust rejection rate of >99.99% and NO conversion >90%. Notably, dust cake formation was found to further enhance catalytic efficiency, particularly under low filtration velocities (0.5 m min −1 ). Computational fluid dynamics (CFD) simulations revealed that moderate cake deposition promotes uniform flow distribution and extends residence time, thereby improving catalyst utilization. This work provides a scalable fabrication strategy for high-permeance catalytic membranes, offering a practical pathway for synergistic control of multiple pollutants at high temperatures.

Unveiling the complex effect of Fe2O3 on NOx precursors evolution mechanism during sludge protein pyrolysis based on product characteristics

Jiangtao Meng,Jing Wang,Fengling Yang,Fangqin Cheng

The multiple influence mechanisms of Fe 2 O 3 on nitrogen evolution during sewage sludge pyrolysis were systematically investigated by correlating temperatures. The results showed that Fe 2 O 3 promoted the pyrolysis of the sludge. The activation energy of the pyrolysis was reduced by 12–110 kJ/mol. Fe 2 O 3 acted oxidatively on sludge nitrogen in the following order Fe 2 O 3 →Fe 3 O 4 ( ca. 528 K)→Fe x N y ( ca. 763 K)→Fe x C ( ca. 1023 K). The oxidation target of Fe 2 O 3 on nitrogen containing compounds varied as a function of temperature. At temperatures of 528 K and 623 K, Fe 2 O 3 hindered the deamination of proteins in char to NH 3 , facilitated the condensation of pyridines to nitrile, and impeded the generation of HCN. At temperatures of 763 K and 1023 K, Fe 2 O 3 facilitated the cleavage of amines, heterocycles, and nitrile in char. Additionally, it promoted the breaking of chains and cyclization of long chain amines in tar. This process theoretically leads to the production of a great amount of NH 3 and HCN at the front. Overall, Fe 2 O 3 inhibited the release of NOx precursors through inhibition of deamination, fixation of nitrogen in char and consumption of NH 3 and HCN. This study will establish the effect mechanism of action of Fe 2 O 3 on the nitrogen conversion of sewage sludge pyrolysis at relevant temperatures. It will provide a theoretical foundation for controlling NOx and the targeted regulation NH 3 (carbon-free hydrogen energy carriers) in the high-value conversion of nitrogen-rich biomass.

Highly reactive methyl group drives selective catalytic reduction of NOx by methanol on bismuth oxide nanoparticle implanted FER zeolite

Han Sun,Fei Han,Lu Sun,Shinya Mine,Takashi Toyao,Yunpeng Liu,Zhonghua Wu,Masaaki Kitano,Masaya Matsuoka,Weiwei Liu,Yongqiang Dai,Meiqing Shen,Haijun Chen

Selective catalytic reduction by methanol (Methanol-SCR) is a promising technology for the deNO x treatment of the exhaust with high concentration of sulfur. Herein, nano-bismuth oxide implanted FER zeolites (Bi-FER) have been successfully synthesized as Methanol-SCR catalysts, on which the optimum reaction temperature shows a big shift from 450 down to 300 °C comparing with state of the art. The catalytic active species of Bi-FER catalyst have been investigated by multi-characterization methods combined by theoretical simulation. Methyl groups generated on Brønsted acid sites neighboring with nano-bismuth oxide were demonstrated to exhibit extraordinary reactivity towards NO x , resulting in a high deNO x performance at low temperature. A strategy by the activation of methanol to produce reactive methyl groups was put forward for the development of Methanol-SCR catalysts.

Performance of Fe-Ni-W exchanged zeolite for NOx reduction with NH3 in a lab-scale circulating fluidized bed

Hanzi Liu,Yi Zhang,Haiming Wang,Changfu You

Selective non-catalytic reduction of NOx (SNCR) with NH 3 is commonly used in industrial facilities like circulating fluidized bed (CFB) furnaces. However, the strongly temperature-dependent de-NOx feature confines its applications in a specific temperature range (900–1050 °C). Here, we report a new strategy on using Fe-Ni-W exchanged zeolite (0.5FNW-H) as a catalyst to extend the SNCR temperature window. In the CFB reactor, a significant NOx conversion improvement ranging from 14.1% to 80.9% was achieved at 700 to 850 °C by applying the developed catalyst. Catalyst dosage of 4500 h −1 (GHSV), a particle diameter of 0.1–0.3 mm, and NH 3 injection position at the dense-phase zone were found preferred for NOx reduction with the highest efficiency of ~85% at 700 °C. The physicochemical properties of the catalysts remained stable after the circulating reactions in the CFB reactor. The developed catalyst is particularly applicable for improving the SNCR performance when the thermal power plants are operated at low loads.

Reaction Behaviors of NOx and Methanol Simultaneous Abatement over a Ceria-Based NH3–SCR Catalyst at Low-Medium Temperatures

Yanye Zhu,Fangyuan Zhou,Xiaoqiang Wang,Yue Liu,Zhongbiao Wu

The NH3–SCR process could provide cobenefits for VOCs abatement from industrial sources. Ceria-based catalysts have received considerable attention for NOx removal at low-medium temperatures. In this study, the reaction behaviors of the simultaneous control of NOx and methanol over the Sb0.5CeZr2Ox catalyst were investigated. It was found that the presence of methanol reduced NOx conversion at low temperatures, while the methanol mineralization rate was promoted in the SCR reaction environment. This effect weakened as the temperature increased, and both NOx and methanol could be effectively removed (with efficiencies more than 90%) within 250–350 °C at a CH3OH/NO ratio of no more than 1:1. NO adsorption and oxidation were greatly suppressed by methanol, thereby inhibiting the SCR reaction via the Langmuir–Hinshelwood (L-H) mechanism. Meanwhile, the formation of formamide via NH3 and intermediates of methanol oxidation was also responsible for the deactivation effect on the SCR reaction at low temperatures. The presence of NO was found to be the main reason for enhanced methanol deep oxidation as NO can promote the rehealing process of active oxygen species.