Effect of MnOx modification on the activity and adsorption of CuO/Ce0.67Zr0.33O2 catalyst for NO reduction

Enhancing the catalytic oxidation of elemental mercury and suppressing sulfur-toxic adsorption sites from SO2-containing gas in Mn-SnS2

It is difficult to stabilize gaseous elemental mercury (Hg°) on a sorbent from SO₂-containing industrial flue gas. Enhancing Hg° oxidation and activating surface-active sulfur (S*) can benefit the chemical mercury adsorption process. A Mn-SnS₂ composite was prepared using the Mn modification of SnS₂ nanosheets to expose more Mn oxidation and sulfur adsorption sites. The results indicate that Mn-Sn₂ exhibits better Hg° removal performances at a wide temperature range of 100-250 °C. A sufficient amount of surface Mn with a valance state of Mn⁴⁺ is favorable for Hg° oxidation, while the electron transfer properties of Sn can accelerate this oxidation process. Oxidized mercury primary exists as HgS with surface S*. A larger surface area, stable crystal structure, and active valance state of each element are favorable for Hg° oxidation and adsorption. The Mn-SnS₂ exhibits an excellent SO₂ resistance when the SO₂ concentration is lower than 1500 ppm. The effects of H₂O and O₂ were also evaluated. The results show that O₂ has no influence, while H₂O and SO₂ coexisting in the flue gas have a toxic effect on the Hg° removal performance. The Mn-SnS₂ has a great potential for the Hg° removal from SO₂-containing flue gas such as non-ferrous smelting gas.

Unravelling the structure sensitivity of CuO/SiO2 catalysts in the NO + CO reaction

CuO/SiO₂ catalysts with vast difference in copper dispersion were prepared by impregnation and ammonia-evaporation methods and used for exploring the structure sensitivity of CuO/SiO₂ catalysts in the NO + CO reaction.

Insights into the precursor effect on the surface structure of γ-Al2O3 and NO + CO catalytic performance of CO-pretreated CuO/MnOx/γ-Al2O3 catalysts

NO reduction by CO was investigated over CO-pretreated CuO/MnO_x/γ-Al₂O₃ catalysts with different metal precursors (nitrate and acetate). It was found that the catalyst prepared from acetate salts (Cu/Mn/Al-A) exhibited significantly higher activity than counterpart catalyst from nitrate precursors (Cu/Mn/Al-N). XRD, XPS and in situ DRIFT were carried out to approach the nature for the different catalytic performance. For both catalysts, copper mainly existed as CuO, but the status of manganese oxide was markedly different. Mn(IV) was predominant in Cu/Mn/Al-N and Mn(III) was enriched in Cu/Mn/Al-A. As a result, different dispersion behaviors of manganese oxide on γ-Al₂O₃ were displayed, which induced inconsistent Cu-Mn contact. The catalyst obtained from acetate precursor exhibited enriched Cu-Mn contact and thus more Cu⁺-□-Mn^3+/2+ entities would be produced after CO pretreatment, leading to promoted NO dissociation and favorable performance in NO reduction by CO. The present study sheds light on the effective tuning of Cu-O-Mn interfacial sites in CuO/MnO_x/γ-Al₂O₃ via modulating the dispersion behaviors of surface components.

Low temperature CO oxidation catalysed by flower-like Ni–Co–O: how physicochemical properties influence catalytic performance

In this work, mesoporous Ni–Co composite oxides were synthesized by a facile liquid-precipitation method without the addition of surfactant, and their ability to catalyse a low temperature CO oxidation reaction was investigated. To explore the effect of the synergetic interaction between Ni and Co on the physicochemical properties and catalytic performance of these catalysts, the as-prepared samples were characterized using XRF, XRD, LRS, N₂-physisorption (BET), SEM, TEM, XPS, H₂-TPR, O₂-TPD and in situ DRIFTS characterization techniques. The results are as follows: (1) the doping of cobalt can reduces the size of NiO, thus massive amorphous NiO have formed and highly dispersed on the catalyst surface, resulting in the formation of abundant surface Ni²⁺ ions; (2) Ni²⁺ ions partially substitute Co³⁺ ions to form a Ni–Co spinel solid solution, generating an abundance of surface oxygen vacancies, which are vital for CO oxidation; (3) the Ni_0.8Co_0.2 catalyst exhibits the highest catalytic activity and a satisfactory stability for CO oxidation, whereas a larger cobalt content results in a decrease in activity, suggesting that the amorphous NiO phase is the dominant active phase instead of Co₃O₄ for CO oxidation; (4) the introduction of Co can alter the morphology of catalyst from plate-like to flower-like and then to dense granules. This morphological variation is related to the textural properties and catalytic performance of the catalysts. Lastly, a possible mechanism for CO oxidation reaction is tentatively proposed.

The flower-like catalyst possesses highly dispersed amorphous NiO and a high concentration of surface oxygen vacancies which are the central points for CO oxidation.

Investigation of the interactions in CeO2–Fe2O3 binary metal oxides supported on ZSM-5 for NO removal by CO in the presence of O2, SO2 and steam

The 10Ce–10Fe/ZSM-5 catalyst exhibits superior resistance to O₂ and SO₂ due to the interaction between Fe₂O₃ and CeO₂.

Catalytic oxidation of NO by O2 over CeO2–MnOx: SO2 poisoning mechanism

The catalytic oxidation of NO by O₂ was performed over a series of CeO₂–MnO_x catalysts with different molar ratios of Mn/Ce, which were prepared by the sol–gel method.

NO reduction by CO over CuO supported on CeO2-doped TiO2: the effect of the amount of a few CeO2

This work is mainly focused on the investigation of the influence of the amount of a few CeO₂ on the physicochemical and catalytic properties of CeO₂-doped TiO₂ catalysts for NO reduction by a CO model reaction.

Effects of different manganese precursors as promoters on catalytic performance of CuO–MnOx/TiO2 catalysts for NO removal by CO

Since the formation of the surface synergetic oxygen vacancy SSOV (Cu⁺–□–Mn³⁺) in the xCuyMn(N)/TiO₂ catalyst is easier than that (Cu⁺–□–Mn²⁺) in the xCuyMn(A)/TiO₂ catalyst, the activity of the xCuyMn(N)/TiO₂ catalyst is higher than that of the xCuyMn(A)/TiO₂ catalyst.