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We first present preparation of MnO x -CeO 2 -Al 2 O 3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis (SHS) method, and studied the application of these catalysts to the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR). Using the catalyst with 18 wt.% Mn (18MnCe1Al2), 100% NO conversion was achieved at 200°C and a gas hourly space velocity of 15384hr -1 , and the high-efficiency SCR temperature window, where NO conversion is greater than 90%, was widened to a temperature range of 150-300°C. 18MnCe1Al2 showed great resistance to SO 2 (100 ppm) and H 2 O (5%) at 200°C. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller (BET) analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and H 2 temperature programmed reduction. The characterization results showed that the surface atomic concentration of Mn increased with increasing Mn content, which led to synergism between Mn and Ce and improved the activity in the SCR reaction. 18MnCe1Al2 has an extensive pore structure, with a BET surface area of approximately 135.4m 2 /g, a pore volume of approximately 0.16cm 3 /g, and an average pore diameter of approximately 4.6 nm. The SCR reaction on 18MnCe1Al2 mainly followed the Eley-Rideal mechanism. The performances of the MnO x -CeO 2 -Al 2 O 3 catalysts were good, and because of the simplicity of the preparation process, the SHS method is applicable to their industrial-scale manufacture., (Copyright © 2018. Published by Elsevier B.V.)

An in situ technique is employed to tailor the valence states of copper in CuOδ/γ-Al2O3 catalysts with the purpose of inducing superior catalytic performance for simultaneous elimination of NO and CO. The catalyst with zero-valent copper exhibits excellent catalytic performance, which is comparable with the conventional supported noble-metal catalysts.

Abstract: High surface area Ti0.5Sn0.5O2 mixed oxide with rutile phase was prepared by a coprecipitation method. The surface area of Ti0.5Sn0.5O2 sample is 76.7m2 g−1, and VO x /Ti0.5Sn0.5O2 catalysts were prepared using the mixed oxide as support. Characterizations using XRD, FT-IR, LRS, EPR, UV–vis, and TEM demonstrated that vanadium oxide species are highly dispersed on the surface of Ti0.5Sn0.5O2 support when the loading amount of vanadium oxide is ≤1.5mmolV/100m2 Ti0.5Sn0.5O2. The dispersed vanadium oxide species form epitaxial-growth layer on the support. In situ FT-IR (NH3 adsorption), combined with NH3-TPD, indicate that the catalyst with vanadium loading amount of 1.5mmolV/100m2 Ti0.5Sn0.5O2, which equals to the dispersion capability, possesses a maximum amount of Brønsted acid sites. The 1.5V/Ti0.5Sn0.5O2 catalyst exhibits the best catalytic performance and good resistance to water vapor poison for the “NO+NH3 +O2” reaction, indicating that surface dispersed polymeric vanadium oxide species are the primary active species. A possible reaction mechanism is proposed on the basis of in situ FT-IR results. [Copyright &y& Elsevier]

Graphical abstract Highlights • Sm doped CeO 2 -TiO 2 catalyst presents excellent NH 3 -SCR activity in range of 250–425 °C. • The acidity and redox property are adjusted with appropriate balance by Sm doping. • Redox cycle of Ce4++Sm2+⇌Ce3++Sm3+ is responsible for the good SO 2 tolerance. Abstract The Sm doped CeO 2 -TiO 2 mixed oxide catalyst, which exhibited excellent activity and tolerance to H 2 O and SO 2 in the NH 3 -SCR reaction, was synthesized. The reasons for the high activity and SO 2 resistance of the catalyst were investigated by a series of characterization. The H 2 -TPR and O 2 -TPD results suggested that the reducibility and oxygen storage capacity (OSC) of CeTi catalyst were promoted by the addition of Sm species, which was beneficial for improving the activity of catalyst. The in situ DRIFTS results revealed that the adsorptive ability of NO x species and activation ability of NH 3 were enhanced by Sm doping, which was also propitious to enhance the activity. XPS combined with DFT calculated results confirmed that the transfer of electron by Sm2++Ce4+⇌Sm3++Ce3+ circles occurred in the SmCeTi catalyst. The redox circles may be the reason of the good SO 2 tolerance of the SmCeTi catalyst, for which suppressed the electron transferring from adsorbed SO 2 to Ce4+. Through in situ DRIFTS and TG-DSC results, it can be concluded that the sulphation of catalyst was lowered by samarium doping into CeTi catalyst. Consequently, the SmCeTi catalyst exhibited significant SO 2 tolerance ability. [ABSTRACT FROM AUTHOR]

Catalytic reduction of NO by CO was studied over a series of CuO-CoO x /γ-Al 2 O 3 catalysts prepared by co-impregnation with different copper and cobalt precursors (acetate and nitrate) to evaluate the structure–activity relationship. The obtained samples were characterized in detail by means of XRD, LRS, XPS, H 2 -TPR and in situ FT-IR technologies. Results indicate that copper oxide is agglomerated while cobalt oxide is dispersed on γ-Al 2 O 3 for the catalyst prepared from copper acetate and cobalt acetate precursors (CuACoA); Cu x Co 3-x O 4 spinel is formed and agglomerated on the catalyst prepared from copper nitrate and cobalt nitrate precursors (CuNCoN); while both copper oxide and cobalt oxide could be homogeneously dispersed for the catalyst prepared from copper nitrate and cobalt acetate precursors (CuNCoA), which exhibits the best activity for NO reduction by CO. Probably the synergistic effect between dispersed copper oxide and cobalt oxide is propitious to the oxygen transfer, which could be the reason for its high activities. Finally, a possible reaction mechanism was tentatively proposed to explore the different catalytic performances in NO reduction by CO model reaction. [ABSTRACT FROM AUTHOR]

A series of ultra-low content copper-modified TiO 2 /CeO 2 catalysts were prepared by wet impregnation method and tested for selective catalytic reduction of NO by NH 3 . The catalyst with a Cu/Ce molar ratio of 0.005 showed the best low-temperature activity and excellent sulfur-poisoning resistance. It was worth noting that the very small amounts of copper addition can lead to three times the activity at low temperature. The prepared catalysts were characterized by XRD, BET, Raman, XPS, NH 3 -TPD and the results revealed that the introduction of copper increased the amount of surface adsorbed oxygen and Ce 3+ species on the catalyst surface and generated more Brønsted acid sites. The redox and surface acidic properties were also improved by the addition of Cu. All these factors played important roles in enhancing NH 3 -SCR performance of TiO 2 -CuO/CeO 2 catalysts. Furthermore, in situ DRIFT experiments demonstrated that Cu doping enhanced the adsorption capacity of NH 3 while the appearance of CuO weakened the adsorption ability of bridging nitrates, both the two factors synergistically facilitated the NH 3 -SCR reaction proceed smoothly via the Eley-Rideal pathway. [ABSTRACT FROM AUTHOR]

Abstract: Acetic acid (HAc) aqueous was used as solvent in wetness impregnation to prepare CeO2-modified γ-Al2O3 support. With the help of HAc, the dispersion of CeO2 on γ-Al2O3 is significantly improved and the size of CeO2 nanoparticles can be controlled through tuning the concentration of HAc aqueous. XPS analysis shows that the percentages of Ce3+ in CeO2 nanoparticles will vary with the size. Then we load CuO on the as-prepared CeO2-modified γ-Al2O3 support and choose NO reduction with CO as a probe reaction to investigate the influences of impregnation solvent on the catalytic properties. The results demonstrate that the CuO/CeO2/γ-Al2O3 prepared in the solvent with volume ratio of 20:1 (H2O:HAc) has the highest activity in NO+CO reaction. Combing the structural characterizations and catalytic performances, we think that the size of the CeO2 nanoparticles should be a key factor that affects the activities of CuO/CeO2/γ-Al2O3. Furthermore, CuO dispersed on CeO2 nanoparticles with an average size of ca. 5nm should be the highest active sites for NO+CO reaction. [Copyright &y& Elsevier]

Highlights: [•] Sn4+ can be incorporated into the lattice of CeO2 to form uniform Ce x Sn1–x O2 solid solution when the mole ratio of Ce:Sn is not less than 2:1. [•] The incorporation of Sn4+ into the lattice of CeO2 is conducive to the decrease of crystallite size, the increase of lattice strain and the improvement of reduction behavior, which further promote the enhancement of catalytic performance. [•] The catalytic domain (CD, -Ce3+-□-Sn2+- species) in these Ce x Sn1–x O2 mixed oxides plays a key role in NO reduction by CO model reaction. [ABSTRACT FROM AUTHOR]