Advanced Materials Research Vols. 550-553

Abstract: This paper reveals that photocatalytic activity of Bi₂O₃ under visible light towards the decolorization of Methyl Orange solution can be greatly enhanced by doping Pr into the lattice of Bi₂O₃ using a sol-gel method. The photocatalysts were characterized by BET, UV-Vis diffuse reflectance spectroscopy and surface photovoltage spectroscopy (SPS), respectively. The result shows that 4%Pr doped Bi₂O₃ possesses the best photocatalytic activity under visible light.

Abstract: A series of chromium (III) Schiff base complexes immobilized on MCM-41 were prepared and used for the selective oxidation of cyclohexanol with 30% hydrogen peroxide. The results revealed that the immobilized complexes were active catalysts and exhibited much higher catalytic performance than their homogeneous analogue. This could be ascribed to the dispersion effect of the support. Simultaneously, the linker flexibility and the surface property of support were also found to play important roles in the catalytic performance of immobilized complexes.

Abstract: In this paper, we reported an approach to fabricate PAN/β-cyclodextrin (β-CD) composite nanofibre with copper nanoparticles (NPs) grown on the surface by the simple electrospinning process. In the experiment, electrospinning method, soaking and adsorption method, together with reduction method were used to achieve the aim of coating. The final product was characterized using scanning electronic microscope (SEM), and fourier transform infrared spectroscopy (FTIR).

Abstract: To study the effect of K and Mn substitution on simultaneous removal of NOx and particulate materials (PM), a series of La_1-xK_xCo_1-yMn_yO₃ (x, y=0.1, 0.2, 0.3, 0.4, 0.5) perovskite-type catalysts were synthesized by complex-combustion method. The catalytic performances of the catalysts were evaluated by temperature-programmed oxidation reaction (TPO). And the catalysts were characterized by XRD, FT-IR, H₂-TPR techniques. After introducing K and Mn to LaCoO₃ simultaneously, all the samples possess perovskite-type structures and the B-site ions form higher average oxidation state enhancing the catalytic performance obviously. La_0.8K_0.2Co_0.7Mn_0.3O₃ catalyst exhibits not only the lowest T _i(297 °C) temperature but also the lowest Tm (343 °C) temperature. Meanwhile, the NO reduction percentage over this catalyst can reach 97%.

Abstract: The transition-metal oxide(ZrO₂, Fe₂O₃) and rare earth-metal oxide(La₂O₃, CeO₂) promoted Ag/Al₂O₃ catalysts for selective catalytic reduction of NO by C₃H₆ were investigated. These catalysts were characterized by temperature programmed desorption of NO and O₂ (NO-TPD and O₂-TPD), N₂ adsorption/desorption isotherms (BET), and X-ray diffraction (XRD) techniques, respectively. The BET result indicates the ZrO₂ promoted sample possesses larger surface area, and the TPD analysis demonstrates the dispersity and amount of adsorbed NO and O₂ are improved, both the results are favorable for the catalytic activity, which can be attributed to the synergic interaction between zirconia promoter and alumina support shown in the XRD pattern.

Abstract: Impregnation and deposition-precipitation (DP) methods were employed for the preparation of Au nanoparticles supported on SBA-15, and the influences of various reductants were systematically surveyed. The dispersion and particle size of gold loaded on SBA-15 were determined by XRD, SEM and TEM. It has been found that reductants have effect on the size and dispersion of Au NPs, resulting in different catalytic properties for aerobic oxidation of glucose. The Au NPs on SBA-15 using KBH₄ as reductant was approximately 5-6 nm, which exhibited excellent catalytic activity.

Abstract: A series of CuO/TiO₂ catalysts were prepared with sol-gel and impregnation method and characterized by TG-DSC、FTIR、XRD and H₂-TPR. The effect of calcination temperature of TiO₂ carrier on the performance of CuO/TiO₂ for the NO + CO reaction was investigated. The results showed that CuO/TiO₂ (500°C, 15%) catalyst had superior catalytic activity with NO conversion and N₂ selectivity of 99.5% and 82.3% at 350°C, respectively. The activities of the CuO/TiO₂ catalysts were in the sequence of CuO/TiO₂ (500) > CuO/TiO₂ (600) > CuO/TiO₂ (700) > CuO/TiO₂ (400). Combined with TG-DSC and XRD patterns, the anatase phase transform into rutial phase at 462.9°C to 800°C in the TG-DSC patterns, while only rutile phase was present at 700°C in the XRD patterns. It indicated that CuO had a positive effect on phase transformation of TiO₂ from anatase to rutial. The IR spectra demonstrated that there were some organic ingredients left in the surface of TiO2 gel before calcination. The results of H₂-TPR suggested that the highly dispersed CuO was present on the CuO/TiO₂ catalysts when the calcination temperature of TiO₂ gel was below 500°C. Mixed oxide of CuO and TiO₂ was formed when the calcination temperature of TiO2 gel was above 600°C.

Abstract: Fe-ZSM-5 catalysts were synthesized by hydrothermal method under different levels of iron loading. The result of XRD and TG/DTA showed that Fe-ZSM-5 catalysts were successfully obtained after calcination at 550 °C. The effects of Si/(Fe+Al) and Fe/Al ratio on the SCR performance of Fe-ZSM-5 catalyst were investigated in a simulated flue gas. When Si/(Fe+Al)=20 and Fe:Al=20 Fe-ZSM-5 catalyst showed excellent catalytic activity. Under the condition of 210 °C, [NH₃]/[NO] of 1.2, [O₂] of 6 vol%, [NOx] of 900×10-6, Si/(Fe+Al)=20 and Fe/Al=1, NOx conversion exceeds 98%. Besides, Fe-ZSM-5 catalyst was excellently resistant to SO₂ and H₂O in the SCR reaction.

Abstract: Biomass represents an abundant and relatively low cost carbon resource that can be utilized to produce platform chemicals such as levulinic acid. This study focused on the effect of SO₄^2-/TiO2-Al₂O₃-SnO₂ solid acid catalyst on the catalytic performance in levulinic acid production from biomass-derived carbohydrates glucose. The SO₄^2-/TiO₂-Al₂O₃-SnO₂ solid acid catalyst showed a high catalytic activity for the selective conversion of glucose to levulinic acid. Experimental results showed that SO₄^2-/TiO₂-Al₂O₃-SnO₂ solid acid had markedly catalytic effects on the conversion of glucose to levulinic acid. With SO₄^2-/TiO₂-Al₂O₃-SnO₂ solid acid as the catalyst, an optimized ethyl levulinic acid was obtained at 180 °C for 2 h with glucose dosage of 2 wt% and 3 g SO₄^2-/TiO₂-Al₂O₃-SnO₂ solid acid catalys and the levulinic acid yield was 74.05%.

Abstract: Phosphorus and boron-doped palladium nanoparticles supported on carbon nanotubes (P-Pd/CNTs and B-Pd/CNTs, respectively) were prepared and evaluated for oxygen reduction reactivity (ORR) in alkaline environments. The prepared catalysts were characterized by X-ray diffraction (XRD), electron probe microanalysis (EMPA), and X-ray photoelectron spectroscopy (XPS). The ORR activity, methanol tolerance, and durability of the prepared catalysts were evaluated in oxygen-saturated 0.1 M potassium hydroxide electrolytes via cyclic voltammetry (CV) and linear sweep voltammetry (LSV) on rotating disk electrodes. The mechanisms and kinetics of ORR were discussed. The results show that P-Pd/CNTs exhibit higher ORR activity than B-Pd/CNTs and Pd/CNTs, higher methanol tolerance than commercial Pt/C, and excellent durability with 90% of the original activity maintained after 1000 voltage cycles. The ORR on P-Pd/CNTs proceeds via a 4-electron reduction process with O2 reduced to H2O directly, during which the rate-determining step is charge transfer at low overpotential and then changes to mass transport at high overpotential.