Three V2O5/TiO2 catalysts with V2O5 loading of 3 wt% were fabricated by wet impregnation, in which the TiO2 supports had different crystal types, including the octahedral TiO2 (preferentially exposed anatase {101} facets, labeled as TiO2-O), the sheet TiO2 (preferentially exposed anatase {001} facets, labeled as TiO2-S), and the commercial TiO2 (TiO2-P25), giving the three corresponding catalysts, respectively. The activities and the effects of H2O and SO2 over the V2O5/TiO2 catalysts for the selective catalytic reduction (SCR) of NO by NH3 were investigated. It was found that the crystal facets of TiO2 nanoparticles played an essential role in the catalytic activity. The V2O5/TiO2-S catalyst exhibited the better catalytic activity than the V2O5/TiO2-O and V2O5/TiO2-P25 catalysts for the NH3-SCR reaction. The N2 sorption isotherm measurement (BET), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), temperature-programmed reduction (H2-TPR), temperature-programmed desorption (NH3-TPD), X-ray photoelectron spectra (XPS) and in-situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) characterizations showed that the good dispersion and reducibility of vanadium species, and the high concentration of chemisorbed oxygen of the V2O5/TiO2-S catalyst could be responsible for the enhancement in the activity of NH3-SCR reaction over the catalyst.

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.

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.

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.

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.SEM images of the fresh Pd/CeO2-UH catalysts with Pd loadings of 0.0 wt.%

It is of great interest to study the shape effect on the catalytic activity of metal nanocrystals, which exposed different crystallographic facets upon adopting various shapes. The investigations on shape-dependent catalysis of supported metal nanocrystals need to be conducted over nanocrystals with well-defined shapes and cleaned surface. The palladium nanocrystals with cubic, octahedral, and spherical morphologies were synthesized and well dispersed onto the inert silica support after removing the capping agents, which were used as the heterogeneous catalysts for carbon monoxide (CO) oxidation. It was found that the crystal facets of Pd nanoparticles played an essential role in determining the catalytic oxidation properties. As a result, the octahedral and spherical nanoparticles that predominantly exposed the Pd {111} crystal facets exhibited significantly better catalytic activity than the palladium nanocubes that possessed the Pd {100} crystal facets as the basal plane for the CO catalytic oxidation. It was inferred that the appropriate adsorption strength of CO molecules on Pd {111} planes was beneficial to the enhancement of the catalytic activity.

A new method called ultrasonic-assisted membrane reaction (UAMR) was reported for the fabrication of ceria-zirconia solid solution. A series of ceria-zirconia solid solutions with different Ce/Zr molar ratios were prepared by the UAMR method and characterized by X-ray diffraction (XRD), N2 adsorption, hydrogen temperature-programmed reduction (H2-TPR), scanning electron microscope (SEM), and transmission electron microscopy (TEM) techniques. The UAMR method proved to be superior, especially when the Ce/Zr molar ratio was lower than 1, in fabricating ceria-zirconia solid solutions with large BET surface area, high oxygen storage capacity (OSC), and low reduction temperature.

A novel process, i.e., ultrasound-assisted membrane reduction, was introduced and applied to synthesize Ag and Au nanocrystals. High-resolution transmission electronic microscopy and UV−vis spectra were adopted to observe and study the resulting colloids. The nearly spherical Ag and Au nanoparticles with mean diameters of 5.8 and 6.8 nm, respectively, were synthesized with the novel method. The silver nitrates/hydrogen tetrachloroaurate hydrate, sodium borohydride, and poly(N-vinyl-2-pyrrolidone) (PVP) were used as metal precursor, reductant, and stabilizer, respectively. The reverse mixing of silver nitrate and reductant resulted in larger Ag nanoparticles in the range of 5−24 nm. The addition of ethylenediaminetetraacetic acid (EDTA), which may serve as the second protecting agent together with PVP, could reduce the Au particle size to a mean value of 2.6 nm. By varying the NaBH4 injection rate in the process, a portion of the primary Au crystallites could be self-assembled to form decahedral Au nanocrystals with a diameter of ca. 24 nm. The two-dimensional networked gold nanowires with mean diameters of 5−10 nm could be fabricated by regulating the acidity of the reaction system to pH 10 with aqueous ammonia.

Biological control of odor gases has gained more attention in recent years. In this study, removal performance of a vertical bio-trickling filter inoculated with bacteria and fungi was studied. Bacteria and fungi were isolated from activated sludge in a sewage treatment plant. By adopting “three step immobilization method”, the bio-trickling filter could degrade pollutant immediately once hydrogen sulfide (H2S) passed. The optimal empty bed resident time was 20 s. The optimal elimination capacity was about 60 g H2S m−3 h−1 with removal efficiency of 95%. And the maximum elimination capacity was 170 g H2S m−3 h−1. Pressure drop was ranged between 5 and 15 mm H2O per bed over the whole operation. Removal efficiency was not affected obviously after terminating nutrient supply. The bio-trickling filter could recover back after shut down H2S gaseous and liquid supplies simultaneously. Microbial community structure in the bio-trickling filter was not changed significantly.Combining bacteria and fungi would be a better choice for inoculation into a bio-trickling filter because of the quickly degradation of H2S and rapid recovery under shut-down experiment. This is the first study attempting to combine bacteria and fungi for removal of H2S in a bio-trickling filter.Highlights► Bacteria and fungi mixed cultures as inoculation microorganisms for H2S removal. ► Three step immobilization method increase quantity of microorganisms on packings. ► Bacteria and fungi trickling filter start to degrade H2S quickly. ► Bacteria and fungi trickling filter robust enough after shut down experiment.

The perovskite-type oxides La0.8Ce0.2Cu0.4Mn0.6O3 and La0.8Ce0.2Ag0.4Mn0.6O3 prepared by reverse microemulsion and sol–gel methods (denoted as R and S, respectively), have been investigated on their catalytic performance for the (NO + CO) reaction, and characterized by means of temperature-programmed desorption (TPD), X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). XRD measurements proved the presence of the perovskite phase with a considerable amount of CeO2 phase and the formation of CeO2 phase was restrained with the reverse microemulsion method. TEM investigations revealed that the La0.8Ce0.2Cu0.4Mn0.6O3-R nanoparticles were uniform spheres in shape with diameters ranging from 40 to 50 nm, whereas an aggregation of particles was found for the La0.8Ce0.2Cu0.4Mn0.6O3-S catalyst. The activity of NO reduction with CO decreased in the order of La0.8Ce0.2Cu0.4Mn0.6O3-R > La0.8Ce0.2Cu0.4Mn0.6O3-S > La0.8Ce0.2Ag0.4Mn0.6O3-R > La0.8Ce0.2Ag0.4Mn0.6O3-S. In NO-TPD experiments, the principal desorbed species detected in the effluent was NO with a trace amount of O2 and N2O, suggesting that the non-dissociated adsorption of NO on the surface of the perovskite-type oxides was dominant. The XPS results revealed that Ce4+ and Cu+ was the predominant oxidation state for Ce and Cu components in La0.8Ce0.2Cu0.4Mn0.6O3 and La0.8Ce0.2Ag0.4Mn0.6O3 catalysts. The existence of Cu+ ions and its redox reaction (Cu+ ↔ Cu2+) would benefit the NO adsorption and reduction by CO.

In the present work, the 1.0 wt% Pd/γ-Al2O3, 1.0 wt% Pd/10 wt% CeO2/γ-Al2O3 and 1.0 wt% Pd/10 wt% Ce0.6Zr0.4O2/γ-Al2O3 catalysts were prepared and used for the catalytic combustion of methane. The durabilities of the three catalysts were investigated based on the phenomena of SO2 poisoning in methane catalytic combustion. The presence of SO2 in the reaction gases resulted in an increase of 70–250 °C in light-off temperature for methane conversion over all the catalysts. The sulfates could be formed below and decomposed above 600–700 °C in the reaction over the catalysts, which led to the inhibition and recovery of the catalytic activity, respectively. The introduction of CeO2 or Ce0.6Zr0.4O2 decreased the decomposition temperature of sulfates by 50–100 °C. Sulfur accumulation on the catalyst surface was investigated by sulfur content analysis and TG measurements after pretreatment with SO2. The saturated sulfur contents were all about 5 wt% for the three catalysts. In spite of sulfur poisoning, no obvious changes in the particle morphologies and sizes were observed for the fresh and used catalysts.Graphical abstractPd/γ-Al2O3, Pd/CeO2/γ-Al2O3 and Pd/Ce0.6Zr0.4O2/γ-Al2O3 are prepared by impregnation method. Catalyst durability is investigated for methane combustion in the presence of SO2. It is found that catalyst poisoning is due to sulfate formation, CeO2 or Ce0.6Zr0.4O2 introduction lowers sulfate decomposition temperature by 50–100 °C, and the saturated sulfur content is about 5 wt% for each catalyst.Download high-res image (267KB)Download full-size imageHighlights► Pd/Al2O3, Pd/CeO2/Al2O3 and Pd/Ce0.6Zr0.4O2/Al2O3 are prepared by impregnation method. ► The durability of the catalysts is studied for methane combustion in the presence of SO2. ► The poisoning of the catalysts is due to the formation of sulfates on the catalyst surfaces. ► CeO2 or Ce0.6Zr0.4O2 introduction lowers sulfate decomposition temperature by 50–100 °C. ► The saturated sulfur content of each of the three catalysts is about 5 wt%.

It is of great interest to study the shape effect on the catalytic activity of metal nanocrystals, which exposed different crystallographic facets upon adopting various shapes. The investigations on shape-dependent catalysis of supported metal nanocrystals need to be conducted over nanocrystals with well-defined shapes and cleaned surface. The palladium nanocrystals with cubic, octahedral, and spherical morphologies were synthesized and well dispersed onto the inert silica support after removing the capping agents, which were used as the heterogeneous catalysts for carbon monoxide (CO) oxidation. It was found that the crystal facets of Pd nanoparticles played an essential role in determining the catalytic oxidation properties. As a result, the octahedral and spherical nanoparticles that predominantly exposed the Pd {111} crystal facets exhibited significantly better catalytic activity than the palladium nanocubes that possessed the Pd {100} crystal facets as the basal plane for the CO catalytic oxidation. It was inferred that the appropriate adsorption strength of CO molecules on Pd {111} planes was beneficial to the enhancement of the catalytic activity.