Performance enhancement of NH3-SCR via employing hydrotalcite-like precursor to induce the decoration of NiO by TiO2 phase

Optimizing study on the NH3-SCR activity of Ce-W-Ti@g-C3N4 catalyst: influence of graphite carbon nitride types

Herein, three g-C3N4(MCN/TCN/UCN), obtained by the direct pyrolysis of melamine/urea/thiourea respectively, were introduced as supports to optimize the NH3-SCR activity of Ce-W-Ti catalyst. Compared to CWT-400-Air, CWT@g-C3N4(2)-300-N2 exhibits lower crystalline anatase TiO2 and larger specific surface area, which improves the dispersion of Ce/W/Ti species on catalysts surface. Furthermore, the introduction of g-C3N4 as supports also contributes to doping C/N elements into Ce-W-Ti catalyst and increases the Ce3+/(Ce3++Ce4+) and Oα/(Oα+Oβ) molar ratios on catalyst surface. These all are advantageous to the NH3-SCR activity. However, UCN shows better promotional effect than MCN and TCN. This might be mainly attributed to the loose and porous stacked layered fold structure of UCN, the larger BET surface area, higher dispersion of Ce/W/Ti species and moderate weak/medium-strong acid sites of CWT@UCN(2)-300-N2. At the same time, the influence of carbon nitride amount, calcination atmosphere and calcination temperature on the NH3-SCR activity of CWT@g-C3N4 catalyst were also investigated.

DeNO x performance enhancement of Cu-based oxides via employing a TiO2 phase to modify LDH precursors

CuAl-LDO, CuAl-LDO/TiO2 and CuAl-LDO/TiO2NTs catalysts were obtained from TiO2 modified LDHs precursor which were prepared by in situ assembly method. Then catalysts were evaluated in the selective catalytic reduction of NO x with NH3(NH3-SCR), and the results showed that the CuAl-LDO/TiO2NTs catalyst exhibited preferable deNO x performance (more than 80% NO x conversion and higher than 90% N2 selectivity at a temperature range of 210-330 °C) as well as good SO2 resistance. With the aid of series of characterizations such as XRD, N2 adsorption/desorption, XPS, NH3-TPD, H2-TPR, and in situ DRIFTS, it could be concluded that, doping TiO2NTs afforded the catalyst larger specific surface area, more abundant surface chemisorption oxygen species and more excellent redox performance. Meanwhile, In situ DRIFTS evidenced that CuAl-LDO/TiO2NTs catalyst has a strong adsorption capacity for the reaction gas, which is more conducive to the progress of the SCR reaction.

Fabrication of a multi-dimensional CoFeOx catalyst for the efficient catalytic oxidation elimination of o-dichlorobenzene

Multi-dimensional CoFeOx/CoOx with a 2D/1D structure exhibited outstanding catalytic activity and thermal stability in the catalytic elimination of o-DCB.

Nanozyme with Robust Catalase Activity by Multiple Mechanisms and Its Application for Hypoxic Tumor Treatment

Utilizing catalase-mimicking nanozymes to produce O₂ is an effective method to overcome tumor hypoxia. However, it is challenging to fabricate nanozymes with ultrahigh catalytic activity. Palladium nanosheet (Pd NS), a photothermal agent for photothermal therapy (PTT), has superior catalase-mimicking activity. Here, titanium dioxide (TiO₂ ) is used to modify Pd NS (denoted Pd@TiO₂ ) by a simple one-step method to improve its catalytic activity about 8 times. The enhancement mechanism's fundamental insights are discussed through experiments and density functional theory calculations. Next, zinc phthalocyanine is loaded on Pd@TiO₂ to form a nanomotor (denoted PTZCs) with the synergistic activities of photodynamic therapy and PTT. PTZCs inherit the catalase activity of Pd@TiO₂ to facilitate the decomposition of endogenous H₂ O₂ to O₂ , which can relieve tumor hypoxia and propel PTZC migration to expand the reach of PTZCs, further enhancing its synergistic treatment outcome both in vitro and in vivo. It is proposed that this work can provide a simple and effective strategy for catalytic activity enhancement and bring a critical new perspective to studying and guiding the nanozyme design.

Recent advances in layered double hydroxides (LDHs) derived catalysts for selective catalytic reduction of NOx with NH3

In recent years, layered double hydroxides (LDHs) derived metal oxides as highly efficient catalysts for selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) have attracted great attention. The high dispersibility and interchangeability of cations within the brucite-like layers make LDHs an indispensable branch of catalytic materials. With the increasingly stringent and ultra-low emission regulations, there is an urgent need for highly efficient and stable low-medium temperature denitration catalysts in markets. In this contribution, we have critically summarized the recent research progress in the LDHs derived NH₃-SCR catalysts, including their ability for NO_x removal, N₂ selectivity, active temperature window, stability and resistance to poisoning. The advantages and defects of various types of LDHs-derived catalysts are comparatively summarized, and the corresponding modification strategies are discussed. In addition, considering the importance of the catalyst's resistance to poisoning in practical applications, we discuss the poisoning mechanism of each component in flue gases, and provide the corresponding strategies to improve the poisoning resistance of catalysts. Finally, from the perspective of practical applications and operation cost, the regeneration measures of catalysts after poisoning is also discussed. We hope that this work can give timely technical guidance and valuable insights for the applications of LDHs materials in the field of NO_x control.

A comparative study on the NOx storage and reduction performance of Pt/Ni1Mg2Al1Ox and Pt/Mn1Mg2Al1Ox catalysts

A series of Ni₁Mg₂Al₁O_x, Mn₁Mg₂Al₁O_x, 0.5Pt/Ni₁Mg₂Al₁O_x and 0.5Pt/Mn₁Mg₂Al₁O_x catalysts were carefully prepared and their NO_x storage and reduction (NSR) performance including NO_x oxidation efficiency (NOE), NO_x storage capacity (NSC), NO_x conversion rate (X_NO), N₂ selectivity (S_N2), N₂O selectivity (S_N2O) and NH₃ selectivity (S_NH3), was systematically investigated. A SO₂ resistance test was also performed in the presence of 100 ppm SO₂. The NOE and NSC experimental results revealed that the Ni₁Mg₂Al₁O_x catalyst possesses a higher NSC, while the Mn₁Mg₂Al₁O_x catalyst possesses a better NOE. With regard to X_NO, 0.5Pt/Ni₁Mg₂Al₁O_x presented higher results at 200 °C and 400 °C, while 0.5Pt/Mn₁Mg₂Al₁O_x obtained the highest result at 300 °C, which was more than 60% for both. In addition, compared to 0.5Pt/Ni₁Mg₂Al₁O_x, 0.5Pt/Mn₁Mg₂Al₁O_x exhibited a relatively higher S_N2 and lower S_N2O and S_NH3. The NO_x-TPD and H₂-TPSR results indicated that NO_x adsorbed on Ni₁Mg₂Al₁O_x and 0.5Pt/Ni₁Mg₂Al₁O_x is more stable, and that NH₃ can be formed in large amounts in a lower temperature range. Both Pt-containing catalysts presented a quite stable X_NO in ten cycles in the presence of 100 ppm SO₂, and their S_N2 can be remarkably enhanced to more than 80%, which could be attributed to the reactions of NH₃-SCR and SO₂ + NH₃. We believe this new insight can provide a new way of thinking for the development of NSR catalysts.

A Critical Review of Recent Progress and Perspective in Practical Denitration Application

Nitrogen oxides (NOx) represent one of the main sources of haze and pollution of the atmosphere as well as the causes of photochemical smog and acid rain. Furthermore, it poses a serious threat to human health. With the increasing emission of NOx, it is urgent to control NOx. According to the different mechanisms of NOx removal methods, this paper elaborated on the adsorption method represented by activated carbon adsorption, analyzed the oxidation method represented by Fenton oxidation, discussed the reduction method represented by selective catalytic reduction, and summarized the plasma method represented by plasma-modified catalyst to remove NOx. At the same time, the current research status and existing problems of different NOx removal technologies were revealed and the future development prospects were forecasted.

Tunable preparation of highly dispersed Ni x Mn-LDO catalysts derived from Ni x Mn-LDHs precursors and application in low-temperature NH3-SCR reactions

A series of Ni x Mn bimixed metal oxides (Ni x Mn-LDO) were prepared via calcining Ni x Mn layered double hydroxides (Ni x Mn-LDHs) precursors at 400 °C and applied as catalysts in the selective catalytic reduction (SCR) of NO x with NH3. The DeNO x performance of catalysts was optimized by adjusting the Ni/Mn molar ratios of Ni x Mn-LDO precursors, in which Ni5Mn-LDO exhibited above 90% NO x conversion and N2 selectivity at a temperature zone of 180-360 °C. Besides, Ni5Mn-LDO possessed considerable SO2 & H2O resistance and outstanding stability. Multiple characterization techniques were used to analyze the physicochemical properties of the catalysts. The analysis results indicated that all catalysts had the same active species Ni6MnO8, while their particle sizes showed significant differences. Notably, the uniform distribution of active species particles in the Ni5Mn-LDO catalyst provided the rich surface acidity and suitable redox ability which were the primary causes for its desirable DeNO x property.