铜基/氧化锆催化剂的应用及改性研究进展

ZrO2具有弱酸碱性、氧化还原性、良好的热稳定性和机械强度,在催化领域得到广泛应用。以Zr O2为载体的铜基催化剂因其活性高,选择性好,性能稳定,受到越来越多的关注。本文介绍了Cu/Zr O2催化剂在醇类的水蒸气重整制氢、CO/CO2加氢合成低碳醇、二乙醇胺脱氢、乙醇直接合成乙酸乙酯和低温水煤气变换方面的应用。综述了添加不同助剂对Cu/Zr O2催化剂物化及催化性能的影响。     

Water Formation in Non-Hydrolytic Sol–Gel Routes: Selective Synthesis of Tetragonal and Monoclinic Mesoporous Zirconia as a Case Study

Several non-hydrolytic sol–gel syntheses involving different precursors, oxygen donors, and conditions have been screened aiming to selectively produce mesoporous t-ZrO₂ or m-ZrO₂ with significant specific surface areas. The in situ water formation was systematically investigated by Karl Fisher titration of the syneresis liquids. XRD and nitrogen physisorption were employed to characterize the structure and texture of the ZrO₂ samples. Significant amounts of water were found in several cases, notably in the reactions of Zr(OnPr)₄ with ketones (acetone, 2-pentanone, acetophenone), and of ZrCl₄ with alcohols (benzyl alcohol, ethanol) or acetone. Conversely, the reactions of Zr(OnPr)₄ with acetic anhydride or benzyl alcohol at moderate temperature (200 °C) and of ZrCl₄ with diisopropyl ether appear strictly non-hydrolytic. Although reaction time and reaction temperature were also important parameters, the presence of water played a crucial role on the structure of the final zirconia: t-ZrO₂ is favored in strictly non-hydrolytic routes, while m-ZrO₂ is favored in the presence of significant amounts of water. ¹H and ¹³C NMR analysis of the syneresis liquids allowed us to identify the main reactions responsible for the formation of water and of the oxide network. The morphology of the most interesting ZrO₂ samples was further investigated by electron microscopy (SEM, TEM).     

Synthesis and characterization of TENORM-free nano zirconia from zircon sand

To avoid radiation exposure in the use of nano zirconia in the ceramics and dentistry industries, a Technologically Enhanced Natural Radioactive Materials (TENORM)-free nano zirconia was required. The purpose of this research was to obtain an environmentally friendly TENORM-free nano zirconia prototype. TENORM-free nano zirconia synthesis consists of processing zircon sand into sodium zirconate, leaching of sodium zirconate to form zirconyl chloride solution, separation of impurities (silica, ThO₂, U₃O₈, etc.), crystallization of zirconyl chloride, zirconyl-oxalate sol-gel formation, and calcination. The quality test of nano zirconia products was characterized by XRD, FT-IR, SEM, and Surveymeter, while the composition test was carried out by the XRF method. The results of this research obtained an environmentally friendly TENORM-free nano zirconia prototype, that has the chemical compound of ZrO₂, the crystal size was 15.09 nm, the average particle size was 91.33 nm, free of radiation exposure, and its composition includes ZrO₂: 96.599%, HfO₂: 2.899%, and CaO: 0.303%. This synthesis can process zircon sand containing TENORM (ThO₂: 0.070% and U₃O₈: 0.047%) into TENORM-free nano zirconia and increase the added value by increasing the zirconia content from 40.493% to 96.599%.     

Crystal growth,structure and optical properties of Pr~(3+) -doped yttria-stabilized zirconia single crystals

The development of blue semiconductor light-emitting diodes(LEDs) has produced potential applications for Prdoped materials that can absorb blue light, especially crystals, and we now report structure and optical properties for high-quality Pr-doped single crystals of yttria-stabilized zirconia(YSZ) grown by the optical floating zone(FZ) method.X-ray diffraction(XRD) and Raman spectroscopy showed that all of the single crystal samples were in the cubic phase,whereas the corresponding ceramic samples contained a mixture of monoclinic and cubic phases. X-ray photoelectron spectroscopy(XPS) and electron paramagnetic resonance(EPR) spectroscopy showed that Pr was present as the Pr~(3+) ion in ceramic rods and single crystals after heating to high temperatures. The absorption and photoluminescence excitation(PLE) spectra of the Pr-doped YSZ crystals measured at room temperature showed strong absorption of blue light, while their photoluminescence(PL) spectra showed five emission peaks at 565 nm, 588 nm, 614 nm, 638 nm, and 716 nm under450 nm excitation. The optimum luminescence properties were obtained with the crystal prepared using 0.15 mol% Pr_6O_(11),and those with higher concentrations showed evidence of quenching of the luminescence properties. In addition, the color purity of Pr-doped YSZ single crystal reached 98.9% in the orange–red region.     

MICROWAVE ACCELERATED TETRAHYDROPYRANYLATION AND DETETRAHYDROPYRANYLATION OF ALCOHOLS,PHENOLS, AND THIOLS CATALYZED BY HYDRATED ZIRCONIA

ABSTRACT

A solvent free and expeditious method for tetrahydropyranylation and detetrahydropyranylation of alcohols, phenols and thiols is described using hydrated zirconia and 3,4-dihydro-2H-pyran (DHP). A comparison of this microwave-accelerated reaction with conventional heating condition is also presented.     

二氧化钛含量对铈稳定立方氧化锆陶瓷的性能影响

本文用无压烧结法成功制备了高硬度的立方氧化锆陶瓷,研究了氧化锆陶瓷的物相,Vickers硬度,显微结构,相对密度等性能,主要分析了TiO2添加量对Zr0.8Ce0.2O2陶瓷硬度和相对密度的影响。结果表明:烧结助剂TiO2可以有效抑制陶瓷晶粒异常生长,加快气孔排除,促进氧化锆陶瓷烧结致密化,提高陶瓷硬度。最高维氏硬度为20.2 GPa,最高相对密度达到了99.8%。     

Characterization of laser sealed coatings of yttria partially stabilized zirconia

The present paper reports an experimental investigation based on X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and wavelength dispersive spectroscopy (WDS) analyses of phases formed after laser sealing of plasma sprayed coatings of 8.5 wt% yttria partially stabilized zirconia (YPSZ). X-ray diffraction and X-ray step-scanning analyses showed that the plasma sprayed and sealed coatings consisted mainly of t′ phase with a very small amount of monoclinic phase (m phase) in the plasma sprayed coatings. It was also found that the small amounts of m and cubic phases (c phase) present in the sealed coatings were dependent on laser processing specific energies (specific energy is equal to laser power/traverse speed x beam diameter). It was also found that rhombohedral (r) phase formed after laser sealing of coatings at higher specific energies. A direct relationship between c/a ratio of transformable tetragonal phase (t phase) produced by thermal treatment of sealed coatings and nontransformable tetragonal phase (t′ phase) and the amount of Yttria was obtained. A new equation was derived, which describes the relationship between Yttria concentration and the c/a ratio of tetragonal phases (t or t′).     

多级孔WO3/ZrO2固体酸催化剂的制备与表征

采用复合模板表面活性剂辅助水热法一步合成了WO3/ZrO2多级孔固体酸催化剂,并应用X射线衍射、低温N2吸附-脱附、拉曼光谱及NH3程序升温脱附对催化剂进行了表征.结果表明,WO3的引入使得WO3/ZrO2催化剂的比表面积增大,表面的酸中心明显增加.在乙酸和正丁醇的酯化反应中,WO3/ZrO2多级孔固体酸催化剂表现出较...     

高热稳定性介孔氧化锆的合成及表征

利用阴离子表面活性剂作模板,通过水热均匀沉淀方法成功合成了具有高热稳定性的介孔氧化锆.该方法以十二烷基苯磺酸钠(SDBS)作为介孔结构的导向剂,其含S基团在煅烧时起到了稳定剂的作用.采用透射电镜、氮气吸附-脱附、X射线粉末衍射、红外光谱测试手段对样品进行了表征.研究表明,以SD-BS为模板剂合成的介孔氧化锆具有蠕虫状介...     

Metal-reinforced sulfonic-acid-modified zirconia for the removal of trace olefins from aromatics

Metal-reinforced sulfonic-acid-modified zirconia catalysts were successfully prepared and used to remove trace olefins from aromatics in a fixed-bed reactor. Catalysts were characterized by ICP-OES, N₂ adsorption–desorption, X-ray diffraction, thermogravimetric analysis (TGA), and pyridine-FTIR spectroscopy. Different metals and calcination temperatures had great influence on the catalytic activity. Alumina-reinforced sulfated zirconia exhibited outstanding catalytic performance, stable regeneration activity, and giant surface area, and are promising in industrial catalysis. TGA showed that the decomposition of methyl could be attributed to Brønsted acid sites, and pyridine-FTIR spectroscopy proved the weak Brønsted sites on these synthesized metal-reinforced sulfated zirconia. Also, a relation between the reaction rate and weak Brønsted acid density is proposed.