Advanced Materials Research Vols. 550-553

Abstract: Heteropolymolybdates-modified zirconia solid acid catalysts were prepared by dispersing molybdophosphoric acid (MPA) on zirconium hydroxide (ZH) and calcining the MPA/ZH materials at 750 °C. The initial loadings of MPA on ZH were 5-25 wt%. The catalysts were characterized by N₂ adsorption, XRD, FTIR, Py-IR, and NH₃-TPD analysis, and they were used as catalysts for the ring-open polymerization of tetrahydrofuran. The results show that, after calcination at 750 °C, the major molybdenum species are zirconia-anchored polymolybdate surface species and ZrMo₂O₈. The catalysts show both Brönsted and Lewis acidities, and the catalyst with 15% loading has the highest total acidity and catalytic activity because of the near-saturation coverage of the surface molybdenum species on support. Under the reaction conditions of 40 °C for 20 h, the catalyst sample, 15MPZ-750, gives a high polymer yield of 49% and a desirable number average molecular weight of 2262. A preliminary recycle study indicates a good reusability of these materials.

Abstract: The acetalization reaction of ethyl acetoacetate (EAA) with 1,2-propanediol (PPO) was performed efficiently in ionic liquid using aluminium sulfate as catalyst. The synergistic effect between aluminium sulphate and ionic liquid [bmim]BF4 on the acetalization was observed. An EAA conversion of 89.6% with the fructone selectivity of above 99.0% was achieved under the optimized reaction conditions. After the reaction was completed, the products could be easily separated from the reaction mixture extracted by dimethyl ether, and the catalyst and ionic liquid could be directly recycled several times without a significant decrease in the activity and selectivity towards fructone.

Abstract: Keggin-type 12-phosphomolybdic acid with molybdenum partially substituted by vanadium and protons partially substituted by alkali and transition metals was synthesized for the selective oxidation of methacrolein to methacrylic acid. The structures of the catalysts were studied by FT-IR, XRD, TG-DTA and BET. The effects of the additive amount of PEG400, calcination temperature and the content of Cs on the catalytic performance were investigated. Results show that specific surface areas of the catalysts increase with the increase of PEG400 amount; PEG400 is removed at 250 °C and the primary structure of the catalysts is not changed with the addition of PEG400. The conversion and selectivity increase with the Cs content, and then decrease. The catalyst with the ratio of Cs⁺: heteropoly anion=1:1 exhibits good catalytic performance for the selective oxidation of MAL. Under the optimum conditions, the conversion of MAL and selectivity of MAA are 76.4% and 83.6% respectively.

Abstract: Different platinum catalysts patterns such as dots array and films were successfully fabricated by directly inkjet printing of catalyst precursor inks on the substrate. It offers a feasible way for platinum catalyst deposition by precise control of catalyst loading, deposition position, and morphology. The effects on drying behavior of printed catalyst droplet on the catalytic performance of low temperature methanol catalytic combustion were investigated. The results show that the conversion of methanol over printed Platinum patterns in the catalytic combustion is approximately 85% at 100°C.

Abstract: The photocatalyst Fe doped K2La2Ti3O10 for hydrogen production was prepared by three methods such as sol-gel, hydrothermal and solid solution. The effects of preparation method, doped element, sacrificial agent on photocatalytic activity were studied, the properties of samples were characterized with X-ray diffraction(XRD) and UV-Vis diffuse reflectance spectra(DRS). The photocatalytic activity evaluation measurements showed that the photocatalyst prepared by sol-gel has the highest catalytic activity, and methanol was the best sacrifice agent for hydrogen production from water splitting. UV-Vis DRS results indicated that the doping of Fe could expand the absorbing range to visible light. XRD results showed that the doping of Fe hadn’t change the main construction of catalysts.

Abstract: Commercial catalysts were characterized by SEM and XRD. The dendrites of catalysts were clear. Some promoters were solid-solute in crystallites uniformly in the form of f-phase, which blocked the crystallites from growing to improve the activity and thermostability of the catalyst. The reduced catalyst is an (α+f) multi-phase porous alloy. The larger specific surface area and the more active poαsition resulted in excellent activity of catalysts.

Abstract: The textural properties and microstructures of Co-modified Cu-based catalysts were investigated by N₂ physisorption, X-ray diffraction (XRD), temperature-programmed reduction/desorption of hydrogen (H₂-TPR/TPD) and scanning electron microscopy (SEM). Higher alcohols synthesis (HAS) was performed in a fixed bed reactor. The characterization results indicated that incorporation of cobalt in the Cu/γ-Al₂O₃ catalyst promoted the formation of CuCo₂O₄ crystallites, causing the decrease in BET surface area and pore volume. The gradual increase of CuCo₂O₄ concentration enhanced the adsorption of hydrogen on the surface layers, facilitating the formation of the well dispersed bimetal Cu-Co sites. In the HAS reaction, the catalytic activity of CO hydrogenation and space time yield of total alcohols presented an increasing trend with the increase in Co concentration. As the ratio of Co/Cu increased to 1, the catalyst produced the space time yield of 0.38 g.ml^-1.h^-1 and the selectivity of 65% for total alcohols, respectively. Moreover, higher Co concentration facilitated the product distribution shifting towards C₂⁺OH.

Abstract: Nano-TiO₂ powder was synthesized by the continous-orderly-controlled-explosive nucleation method [1]. The experiment has effectively degenerated the n-amyl alcohol gas, and investigated its influencing factor by using the Nano-TiO₂ photocatalytic activity[2]. When the initial density of the n-amyl alcohol gas is 1714.7mg/m3, the TiO₂ calcination temperature is 450°C, the dosage of catalyst is 9.98g. The experiment reacts 40 minutes later, degeneration rate of the n-amyl alcohol achieves above 98%, and the degeneration rate increases constantly with the extension of reaction time. This study provides a solution for the environment pollution problem which the n-amyl alcohol produces.

Abstract: The effects of different temperatures on catalytic hydrolysis of polyethylene terephthalate(PET) by solid super acids SO₄^2- /γ-Al₂O₃ as a catalyst under microwave irradiation were studied, and in the meantime, the morphology analysis of the undepolymerized PET under the same temperature was investigated by SEM. The results indicate that the depolymerization rate of PET is seriously influenced by reaction time and temperature. The depolymerization mechanism is changed by the solid super acid SO₄^2- /γ-Al₂O₃, and the depolymerization rate is higher than that of with no catalyst in the whole process of reaction.

Abstract: Unsupported MoS₂ hydrodesulfurization(HDS) catalysts is sulfide in its original state, so there is no need to add toxic sulfur compounds to presulfurize the hydrogenation catalyst, which has ultra-high capacity to HDS and causing attentions. This paper focuses on summarizing the preparation, characterization and desulfurization mechanism of unsupported nano MoS₂ catalyst and provides its future research directions.