Liyun Song

Effects of synthesis methods on the performance of Pt + Rh/Ce0.6Zr0.4O2 three-way catalysts.

The 0.7 wt% Pt + 0.3 wt% Rh/Ce0.6Zr0.4O2 catalysts were fabricated via different methods, including ultrasonic-assisted membrane reduction (UAMR) co-precipitation, UAMR separation precipitation, co-impregnation, and sequential impregnation. The catalysts were physico-chemically characterized by N2 adsorption, XRD, TEM, and H2-TPR techniques, and evaluated for three-way catalytic activities with simulated automobile exhaust. UAMR co-precipitation- and UAMR separation precipitation-prepared catalysts exhibited a high surface area and metal dispersion, wide λ window and excellent conversion for NOx reduction under lean conditions. Both fresh and aged catalysts from UAMR-precipitation showed the high surface areas of ca. 60-67 m(2)/g and 18-22 m(2)/g, respectively, high metal dispersion of 41%-55%, and small active particle diameters of 2.1-2.7 nm. When these catalysts were aged, the catalysts prepared by the UAMR method exhibited a wider working window (Δλ = 0.284-0.287) than impregnated ones (Δλ = 0.065-0.115) as well as excellent three-way catalytic performance, and showed lower T50 (169°C) and T90 (195°C) for NO reduction than the aged catalysts from impregnation processes, which were at 265 and 309°C, respectively. This implied that the UAMR-separation precipitation has important potential for industrial applications to improve catalytic performance and thermal stability. The fresh and aged 0.7 wt% Pt + 0.3 wt% Rh/Ce0.6Zr0.4O2 catalysts prepared by the UAMR-separation precipitation method exhibited better catalytic performance than the corresponding catalysts prepared by conventional impregnation routes.

NOx selective catalytic reduction by ammonia over Cu-ETS-10 catalysts

Abstract Ion exchange method was used to fabricate Cu-ETS-10 titanosilicate catalysts, which possessed high activity, N 2 selectivity and SO 2 resistance for NO x selective catalytic reduction (SCR). N 2 sorption measurements indicated that the microporous catalysts had high surface areas of 288–380 m 2 /g. The Cu content and speciation were investigated by inductively coupled plasma atomic emission spectrometry, H 2 temperature-programmed reduction, and diffuse reflectance infrared Fourier transform spectroscopy. Various Cu species coexisted within the catalyst. Isolated Cu 2+ species were the active sites for NH 3 -SCR, the number of which initially increased and then decreased with increasing Cu content. The catalytic activity of Cu-ETS-10 depended on the isolated Cu 2+ species content.

Novel synthetic approaches and TWC catalytic performance of flower-like Pt/CeO2

A novel Ultrasonic Assisted Membrane Reduction (UAMR)-hydrothermal method was used to prepare flower-like Pt/CeO2 catalysts. The texture, physical/chemical properties, and reducibility of the flower-like Pt/CeO2 catalysts were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), N2 adsorption, and hydrogen temperature programmed reduction (H2-TPR) techniques. The catalytic performance of the catalysts for treating automobile emission was studied relative to samples prepared by the conventional wetness impregnation method. The Pt/CeO2 catalysts fabricated by this novel method showed high specific surface area and metal dispersion, excellent three-way catalytic activity, and good thermal stability. The strong interaction between the Pt nanoparticles and CeO2 improved the thermal stability. The Ce4+ ions were incorporated into the surfactant chains and the Pt nanoparticles were stabilized through an exchange reaction of the surface hydroxyl groups. The SEM results demonstrated that the Pt/CeO2 catalysts had a typical three-dimensional (3D) hierarchical porous structure, which was favorable for surface reaction and enhanced the exposure degree of the Pt nanoparticles. In brief, the flower-like Pt/CeO2 catalysts prepared by UAMR-hydrothermal method exhibited a higher Pt metal dispersion, smaller particle size, better three-way catalytic activity, and improved thermal stability versus conventional materials.

A Copper-Based Metal-Organic Framework as an Efficient and Reusable Heterogeneous Catalyst for Ullmann and Goldberg Type C–N Coupling Reactions

A highly porous metal-organic framework (Cu-TDPAT), constructed from a paddle-wheel type dinuclear copper cluster and 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine (H6TDPAT), has been tested in Ullmann and Goldberg type C–N coupling reactions of a wide range of primary and secondary amines with halobenzenes, affording the corresponding N-arylation compounds in moderate to excellent yields. The Cu-TDPAT catalyst could be easily separated from the reaction mixtures by simple filtration, and could be reused at least five times without any significant degradation in catalytic activity.

Direct synthesis of N-sulfenylimines through oxidative coupling of amines with disulfides/thiols over copper based metal–organic frameworks

A highly porous metal–organic framework based on supramolecular building blocks with pcu-topology (pcu-MOF) has been tested for the oxidative coupling of amines and disulfides or thiols to afford the N-sulfenylimines directly in good yields without the formation of N-sulfinyl- and N-sulfonylimines. The pcu-MOF catalyst could be easily recovered from the reaction mixture by simple filtration, and could be reused at least five times without any substantial loss in the yield. The control experiments and mechanistic studies suggested that the oxidative coupling process involved the imine formation and the N–S coupling reaction.

Fabrication of a flower-like Pd/CeO2 material with improved three-way catalytic performance

Pd/CeO2 catalysts with flower-like morphology were fabricated via an ultrasonic-assisted membrane reduction (UAMR) and hydrothermal methods. The catalysts were physically characterized and evaluated for three-way catalytic activities versus traditional Pd/CeO2 catalysts. Flower-like Pd/CeO2 catalysts exhibited a higher catalytic performance and better thermal stability than the Pd/CeO2 prepared by conventional impregnation. The flower-like Pd/CeO2 catalysts were constructed from 20–50 nm thick nanosheet petals. These petals were in turn constructed from 10 nm CeO2 nanoparticles that self-assembled into the flower-like morphology resulting in abundant pores in all directions. The Pd nanoparticles were anchored and dispersed on both the interior and surface of the pores and had minimal sintering. When these catalysts were aged, the structure and morphology of the catalysts remained unchanged with important industrial implications for this new type of material including improved catalytic performance and high thermal stability. Regardless of the Pd loading, both the fresh and aged Pd/CeO2 catalysts prepared by the UAMR-hydrothermal method exhibited better performance than the corresponding samples prepared by conventional impregnation means.

Preparation of Ir@Pt Core–Shell Nanoparticles and Application in Three-Way Catalysts

The Ir@Pt core–shell spherical nanoparticles with Pt deposited on Ir cores were synthesized for the first time using successive reduction method based on epitaxial growth. The Ir@Pt/SiO2 core–shell structure catalysts were used in the three-way catalysts of controlling automobile exhaust emission, which exhibited high catalytic activity of NO reduction in three-way catalytic reaction.Graphical AbstractHAADF-STEM image (a) and definitive EDS line-scan spectrum (b) of Ir@Pt NPs with Ir/Pt molar ratio of 1/4FT-IR spectra of CO adsorption of Ir/SiO2 and Ir@Pt (1/1)/SiO2 catalysts

The Keggin Structure: An Important Factor in Governing NH3–SCR Activity Over the V2O5–MoO3/TiO2 Catalyst

Heteropolyacids and their salts have been effectively used in selective catalytic reduction because of the Keggin structure and extraordinarily strong acidity. Catalysts with and without the Keggin structure were synthesized to further investigate the effects of heteropolyoxometallate on low temperature NH3–SCR. XRD, BET, Raman, H2–TPR, NH3–TPD, FT-IR, and SO2–TPD techniques were used to characterize the physicochemical characteristics of the catalysts. Results indicate that catalysts with the Keggin structure had more surface Brönsted and Lewis acid sites, and these catalysts had significantly improved performances in the SCR reaction and in SO2 poisoning resistance.Graphical Abstract

Effects of SO 2 treatment of commercial catalysts on selective catalytic reduction of NO x by NH 3

Nitrogen oxide(NOx) emitted from stationary and mobile sources is a major air pollutant. Selective catalytic reduction(SCR) of NOx over a catalyst is a main technology for NOx elimination. Catalysts used for practical applications would be deactivated in flue containing SO2. In this work, three typical commercial catalysts were investigated before and after SO2 treatment. The catalysts were characterized by X-ray diffraction(XRD), X-ray fluorescene(XRF), temperature programme reduction(TPR), temperature programme desorption(TPD) and diffuse reflectance Fourier transform infrared(DRIFT) techniques. Results showed that SO2 treatment significantly influenced the performance of V2O5/TiO2 catalyst. The amount of V2O5 in the catalyst primarily affected the accumulation of sulfur species in the SO2 atmosphere. The performance of catalysts with small amounts of V2O5 could be improved under the same experimental conditions for acidity enhancement.