Adsorption of fluoride from water by amorphous alumina supported on carbon nanotubes

A new candidate for fluoride adsorption from water, amorphous Al₂O₃ supported on carbon nanotubes (Al₂O₃/CNTs), is reported in this Letter. The adsorption isotherms show that the best fluoride adsorption of Al₂O₃/CNTs occurs at a pH range of 5.0–9.0. The adsorption capacity for Al₂O₃/CNTs is about 13.5 times higher than that of AC-300 carbon, 4 times higher than that of γ-Al₂O₃ at equilibrium fluoride concentration of 12 mg/l. The broad range of the pH values and high adsorption capacity of Al₂O₃/CNTs make it very suitable for potential applications in fluoride removal from water.     

负载Cu氧化铝纳米管合成及在NO+CH4反应中催化性能研究

采用过氧化氢调节反应条件,在水热体系中合成了新型的勃姆石纳米管,经520℃焙烧2h后,晶型由AlOOH转化为γ-Al2O3;采用XRD、氮吸附、TEM等对合成的纳米管进行表征.结果表明,合成的γ-Al2O3纳米管长约300nm,外径20nm,比表面积达到230m2/g以上.以此为载体,采用等体积浸渍法用Cu(NO3)2...     

TPAOH处理制备的微介孔催化剂物化性质与噻吩烷基化性能研究

采用不同浓度的TPAOH溶液处理不同SiO_2/Al_2O_3物质的量比的HZSM-5分子筛,制备了微孔-介孔多级孔HZSM-5催化剂。结果表明,采用不同浓度的TPAOH溶液处理不同SiO_2/Al_2O_3物质的量比的HZSM-5分子筛能够脱出HZSM-5分子筛的骨架硅而产生介孔,介孔孔径随TPAOH溶液浓度和SiO_2/Al_2O_3物质的量比的增大而增大;TPAOH溶液处理能够调变HZSM-5催化剂的酸性。采用不同浓度的TPAOH溶液处理SiO_2/Al_2O_3物质的量比分别为50、80和150的HZSM-5分子筛,其中,SiO_2/Al_2O_3物质的量比为50的HZSM-5弱中酸酸强度、相对酸量、B酸和L酸含量明显高于SiO_2/Al_2O_3物质的量比为80和150的HZSM-5分子筛。经不同浓度的TPAOH溶液处理后SiO_2/Al_2O_3物质的量比为50的HZSM-5催化剂具有最佳的噻吩烷基化反应性能。     

Al2O3孔结构对纳米HZSM-5基催化剂改质FCC汽油性能的影响

采用NH₃-TPD、FT-IR、N₂吸附-脱附等手段对两种不同来源的氧化铝样品进行了表征。结果表明,两种Al₂O₃的总酸量及酸强度没有明显差别,酸类型均以Lewis酸为主,其中,Al₂O₃ (b)的平均孔径及孔体积较大。在固定床微型反应装置上考察了以两种Al₂O₃为载体制备的纳米HZSM-5基催化剂改质全馏分FCC汽油的性能。实验结果表明,以大孔Al₂O₃为载体的HZSM-5基催化剂具有较好的降烯烃、芳构化、异构化活性及稳定性。改性纳米HZSM-5负载的LaNiMo催化剂对FCC汽油的300 h评价结果表明,烯烃饱和率为83%,脱硫率为87%,同时维持了油品的辛烷值。     

Synthesis of Fe2O3 nanowires by oxidation of iron

By carefully controlling the reacting conditions, including atmosphere, temperature, and reacting time, we managed to prepare the nanowires of Fe₂O₃ by oxygenating pure iron. X-ray and transmission electronic microscope analyses demonstrate that the Fe₂O₃ nanowires are of rhombohedral structure, i.e., -Fe₂O₃. It is shown by our study that the -Fe₂O₃ nanowires have a diameter ranging from 15 to 75 nm and their typical lengths are in the range 10–20 μm. Within our knowledge it is the first report on nanowires of Fe₂O₃. The Fe₂O₃ nanowires are expected to present special magnetic, optical and electrical properties, and facilitate future nanoscale device applications.     

ZrO2修饰Al2O3纳米片负载钴催化剂的制备及其费托反应性能研究

通过水热法合成了Al₂O₃纳米片（Al₂O₃-CN）,采用浸渍法制备20%（质量分数）钴基催化剂,并应用于费托合成反应。制备的Al₂O₃-CN（226 m²/g）与商业氧化铝（Al₂O₃-C,249 m²/g）具有相近的比表面积,但Al₂O₃-CN孔尺寸分布更加集中。浸渍钴后,与Co/Al₂O₃-C催化剂相比,Co/Al₂O₃-CN催化剂表现出较高的还原度及更均匀的钴颗粒粒径分布。因此,Co/Al₂O₃-CN催化剂表现出更高的CO转化率和低的甲烷选择性。为了进一步提高Co/Al₂O₃-CN的催化性能,采用不同含量ZrO₂对Al₂O₃-CN进行修饰。表征结果表明,随着ZrO₂修饰量的增加,Al₂O₃-CN载体比表面积变化不明显,孔体积和孔径增大;相对应催化剂的钴颗粒粒径减小,活性位点数目增加。在相同反应条件下,经ZrO₂修饰催化剂CO转化率进一步提高,甲烷选择性降低。     

Selective Oxidation of CO in Excess H2 over Ru/Al2O3 Catalysts Modified with Metal Oxide

The Ru/Al_2O_3 catalysts modified with metal oxide(K_2O and La_2O_3)were prepared via incipient wetness impregnation method from RuCl_3·nH_2O mixed with nitrate loading on Al_2O3 support. The activity of catalysts was evaluated under simulative conditions for the preferential oxidation of CO (CO-PROX)from the hydrogen-rich gas streams produced by reforming gas,and the performances of catalysts were investigated by XRD and TPR.The results showed that the activity temperature of the modified catalysts Ru-K_2O/Al_2O3 and Ru-La_2O_3/Al_2O_3 were lowered approximately 30℃compared with pure Ru/Al_2O_3,and the activity temperature range was widened.The conversion of CO on Ru-K_2O/Al_2O_3 and Ru-La_2O_3/Al_2O_3 was above 99% at 140-160℃,suitable to remove CO in a hydrogen-rich gas and the selectivity of Ru-La_2O_3/Al_2O_3 was higher than that of Ru-K_2O/Al_2O_3 in the active temperature range. Slight methanation reaction was detected at 220℃and above.     

Post-modification using aluminum isopropoxide after dye-sensitization for improved performance and stability of quasi-solid-state solar cells

In this study, dye-sensitized TiO₂ electrodes were immersed into a solution of aluminum isopropoxide and after hydrolysis quasi-solid-state solar cells were fabricated. The interaction between the dye and the resulting Al₂O₃ overlayer was investigated by ultraviolet–visible (UV–vis) spectrum, Fourier transform infrared (FTIR) spectrum and X-ray photoelectron spectrum (XPS). The current density–voltage (I–V) characteristics showed that the overlayer increased the photovoltage and decreased the photocurrent under low intensity irradiation, and increased both the photovoltage and photocurrent under AM 1.5 irradiation. The Al₂O₃ overlayer at the dye/electrolyte interface resulted in a 28% improvement in overall photo-to-electrical conversion efficiency from 2.60 to 3.32%. Dark current measurements showed that Al₂O₃ acted as an insulator barrier to retard recombination between the TiO₂ and dye/quasi-solid-state electrolyte interface. Without encapsulation, dye-sensitized solar cells with Al₂O₃ coating after sensitization also exhibited improved stability compared to cells without coating.     

吸附剂修饰铁基氧载体的氧化动力学研究

研究了吸附剂修饰合成Fe_2O_3/Al_2O_3的氧化动力学。其中,吸附剂(K_2O、Na_2O、CaO)用于控制化学链燃烧过程中有毒氯化物、硫化物以及重金属的排放。首先在热重分析仪(TGA)上利用合成气作为还原气氛使氧载体呈还原态(FeO/Al_2O_3),在空气气氛下进行了原FeO/Al_2O_3以及三种吸附剂修饰FeO/Al_2O_3的氧化实验,实验温度分别为850、875、900和925℃。通过八种等温动力学模型对900℃下原FeO/Al_2O_3的氧化过程进行了分析。结果表明,phase boundary-controlled(contracting cylinder)模型能够很好地描述其氧化过程(FeO向Fe_2O_3转化过程)。利用该模型分别计算了原FeO/Al_2O_3、K_2O修饰FeO/Al_2O_3、Na_2O修饰FeO/Al_2O_3和CaO修饰FeO/Al_2O_3的氧化动力学参数,其表观活化能分别为13.71、20.21、21.62和24.20 k J/mol。通过进行比较依据动力学参数计算得到的转化率随时间的函数以及实验获得的转化率随时间的函数,进一步证实了phase boundary-controlled(contracting cylinder)模型的可靠性以及相应动力学参数的准确性。     

Photocatalytic conversion of NOx on AgCl/Al2O3 catalyst

The rate of NO conversion under UV illumination was evaluated over Ag/Al₂O₃ and AgCl/Al₂O₃ catalysts at room temperature. The AgCl/Al₂O₃ catalyst is highly active for the conversion of NO_x. The conversion is enhanced in the presence of O₂ and further enhanced when oxygen coexists with hydrocarbons. Diffuse reflectance spectra of AgCl/Al₂O₃ and Ag/Al₂O₃ show an absorption band at 250 nm, and a weak and broad band at 230 nm, respectively. The high photocatalytic NO_x conversion is achieved over the AgCl/Al₂O₃ catalyst. The conversion level of NO_x is maintained above 60% over 5 h in the presence of O₂ and hydrocarbons under UV-irradiation. The absorption band at 250 nm is ascribed to the band gap energy of crystallized AgCl particles on Al₂O₃. These results suggest that high photocatalytic NO_x conversion proceeds on crystallized AgCl particles formed on Al₂O₃.     

Polypyrrole Hollow Nanotubes Loaded with Au and Fe3O4 Nanoparticles for Simultaneous Determination of Ascorbic Acid,Dopamine, and Uric Acid

An ultrasensitive electrochemical biosensor was fabricated for electroanalytical determination of ascorbic acid(AA), dopamine(DA) and uric acid(UA) individually and simultaneously based on polypyrrole hollow nanotubes loaded with Au and Fe₃O₄ nanoparticles(NPs) uniformly(PPy@Au-Fe₃O₄). The PPy@Au-Fe₃O₄ nanotubes were synthesized in one-pot using MoO₃ nanorods as templates and the polymerization of Py, the formation of Au and Fe₃O₄ NPs and the removel of MoO₃ templates took place stimultaneously. Electrochemical studies reveal that PPy@Au-Fe₃O₄modified glassy carbon electrode(GCE) possesses excellent electro-catalytic activities toward the oxidation of AA, DA and UA. Their oxidation peak currents increase linearly in the concentration ranges of 1-2000 μmol/L for AA, 0.01-25 and 25-300 μmol/L for DA and 0.1-300 μmol/L for UA. Their detection limit values(S/N=3) were calculated as 0.45, 0.0049, and 0.051 μmol/L for AA, DA and UA in the individual detection. By changing the concentrations simultaneously, the calibration curves showed linearity to 1000, 200, and 200 μmol/L with detection limit of 0.39, 0.0060, and 0.060 μmol/L for AA, DA, and UA, respectively. Finally, the obtained biosensor was successfully applied to the detection of AA, DA, and UA with satisfactory results on actual samples.     

三维有序In2O3纳米线阵列的合成及纳米结构有序度对气敏性能的影响

采用SBA-15硬模板复制技术合成出三维有序纳米线阵列结构的In₂O₃, 通过离心分离获得了2个尺寸不同的块状颗粒样品. 利用XRD、 SEM和紫外-可见光谱对样品的晶体结构、 晶粒尺寸、 形貌及带隙宽度进行了分析. 结果表明, 2个样品具有相同的纳米微结构, 均为由晶粒尺寸约12 nm的近球形In₂O₃晶粒规则有序排列生长而成的三维纳米线阵列结构, 纳米线的直径约为12 nm, 间距约为2 nm, 且块状尺寸较大样品的带隙宽度略大. In₂O₃样品对乙醇气体的气敏性能测试结果显示, 当乙醇气体在空气中的体积分数为100×10^-6, 温度为320 ℃时, A样品的灵敏度达到50. 6, 优于尺寸较小的B样品. 通过对比研究发现该纳米结构样品的气敏性能明显优于同级别纳米颗粒和介孔结构材料, 纳米材料的气敏性能随纳米结构形态有序度的增加而提高.     

Pd/Co3O4纳米颗粒负载于Al2O3纳米片高效催化甲烷燃烧

We report an efficient catalyst composed of ternary components prepared by inlaying Pd/Co₃O₄ nanoparticles in alkaline Al₂O₃ nanosheets for catalytic oxidation of methane. Pd/Co₃O₄ inlaid in alkaline Al₂O₃ exhibited a higher ability to break the C-H bond of methane than Pd/Co₃O₄ supported on SiO₂, ZrO₂, CeO₂, and acidic or neutral Al₂O₃. Our results show more oxygen vacancies and higher amounts of surface adsorbed oxygen on the surface of Pd/Co₃O₄/alkaline Al₂O₃ than on other catalysts, which is responsible for methane activation and conversion. Further, the Pd/Co₃O₄/alkaline Al₂O₃ catalyst can almost restore to its initial value in the absence of water when 5% (volume fraction) vapor water was cut off, although a decrease in activity occurred when water vapor was introduced to the reaction system. Even under a condition similar to the exhaust of a lean-burn natural gas engine, the catalytic performance of the Pd/Co₃O₄/alkaline Al₂O₃ catalyst is excellent, that is, methane could be completely converted when the sample temperature in the reaction atmosphere was ramped to 400℃.     

结构强健的Al2O3-SiO2气凝胶的 制备及可重复使用性能

通过纳米晶组装技术, 构筑了Al₂O₃-SiO₂复合气凝胶; 利用不同组分耐温性的差异, 经过热处理过程得到了骨架强健的Al₂O₃-SiO₂气凝胶. 研究了不同配比及热处理温度对材料微观结构和组分的影响, 确定了最佳制备条件, 得到了比表面积为123.9 m ²/g, 密度为 0.25 g/cm ³, 导热系数为0.029 W·m ^-1·K ^-1的气凝胶材料. 在泡水和冰冻等极端环境下, 气凝胶材料未发生结构的破坏, 模拟10次重复隔热应用(800 ℃, 30 min)后导热系数保持不变. 该隔热性气凝胶的开发有望解决未来飞行器隔热材料需重复使用的技术瓶颈, 为开发新型气凝胶隔热材料提供了新思路.     

负载型铂催化剂中的载体效应

本文用程序升温热脱附法和氢氧滴定法研究了SiO₂、SiO₂·Al₂O₃、Al₂O₃、SiO₂·SnO₂和Al₂O₃·SnO₂等和Pt的相互作用,表明Pt和载体作用强弱的顺序为:Al₂O₃>SiO₂·Al₂O₃>SiO₂;发现SnO₂具有强化SiO₂和Al₂O₃载体效应的作用;提出Pt和载体相互作用较强部位可能是Pt和缺氧氧化物所形成的表面络合物--Pt-[Al₂O_x]和Pt-[SnO_x]。     

Alumina/Polyimide Composite Porous Nanosolid: Dielectric Characteristics and Compressive Strength

Al₂O₃ porous nanosolid was prepared via solvothermal hot-press(SHP) method. The dielectric constant of Al₂O₃ porous nanosolid is as low as 2.34, while its compressive strength is very poor. In order to improve the compressive strength and maitain low dielectric constant, polyimide was introduced to prepare Al₂O₃/polyimide composite porous nanosolid. Compared to Al₂O₃ porous nanosolid, Al₂O₃/polyimide composite porous nanosolid possesses much higher compressive strength, which reaches its saturation value when the mass loading of polyimide is 7.75%. In addition, the in situ Fourier transformation infrared(FTIR) monitoring result reveals that Al₂O₃/polyimide composite porous nanosolid is stable up to 400℃.     

碱土Sr对Co/Al2O3催化剂甲烷部分氧化反应的影响

以γ-Al₂O₃为载体,采用共浸渍法制备了Sr-Co/Al₂O₃系列催化剂,研究了助剂Sr对Co/Al₂O₃催化剂上甲烷部分氧化(POM)制合成气反应的影响,并利用N₂物理吸附、X射线衍射、H₂-程序升温还原和热重等技术对催化剂的理化性质进行了表征。结果表明,未添加助剂的Co/Al₂O₃和800℃焙烧的Sr-Co/Al₂O₃催化剂在POM反应初期催化活性很低,然而,当添加Sr的质量分数高于2%时,催化剂表现出很好的催化活性和稳定性。焙烧后的新鲜催化剂上主要存在两类Co物种,一类是与载体相互作用较弱、易被H₂还原为单质的Co₃O₄;另一类是与载体相互作用较强、难还原、无催化活性的CoAl₂O₄尖晶石。在焙烧过程中,Sr易形成Sr₄Al₁₄O₂₅,从而削弱Co与Al₂O₃之间的相互作用,能在一定程度上抑制CoAl₂O₄物种的形成,提高催化剂的稳定性和活性。未添加Sr的Co/Al₂O₃在反应时易发生物相改变生成尖晶石,导致催化剂迅速失活;但当焙烧温度达到800℃时,添加有限量的Sr还是无法阻止CoAl₂O₄的产生。     

生物柴油合成反应中KNO3/Al2O3催化剂的活性物种与失活研究

制备了KNO₃/Al₂O₃负载型固体碱催化剂，通过XRD、DRIFT、低温氮吸附、ICP和碱度滴定等手段对催化剂表面性质进行了表征，研究了其对大豆油与甲醇酯交换制备生物柴油的催化性能，剖析了在反应过程中该催化剂的催化本质以及失活原因。结果表明，高温焙烧后Al₂O₃表面KNO₃完全分解，形成了大量偏铝酸钾分散在载体表面；在酯交换反应时Al₂O₃表面的偏铝酸盐等活性组分不断溶出并参与反应，这是该催化剂表现出高活性的主要原因。在反应过程中生成的产物生物柴油和甘油对催化剂的活性有很大影响，其中，生物柴油与活性物种发生的皂化反应是造成催化剂失活的主要原因。     

Co/Fe/Al2O3/cordierite催化C3H6选择性还原NO的实验研究

采用溶胶凝胶法和浸渍法制备了负载于蜂窝陶瓷上的Co/Fe/Al₂O₃/cordierite催化剂,在陶瓷管流动反应器上对其催化C₃H₆选择性还原NO的性能进行了测试。结果表明,该催化剂表现出最优脱硝性能,在模拟烟气条件下,当反应温度为550 ℃时可实现97%的脱硝效率。Co的引入可显著增强Fe/Al₂O₃/cordierite催化剂抗SO₂和H₂O的能力。在模拟烟气中同时引入0.02% SO₂和3% H₂O后,1.5Co/Fe/Al₂O₃/cordierite的脱硝性能受影响甚微,当反应温度高于500 ℃时1.5Co/Fe/Al₂O₃/cordierite催化C₃H₆还原NO的效率均可达到90%以上;相比之下,未经Co修饰的催化剂Fe/Al₂O₃/cordierite脱硝性能受到了严重的抑制,在整个反应温度区间（200-700 ℃）内,其催化C₃H₆还原NO的效率最高不足50%。XRD和SEM表征结果表明,经过适量的Co修饰后的1.5Co/Fe/Al₂O₃/cordierite表面变得更疏松,且形成了以钴铁和钴铝双金属氧化物为主要成分的球状晶粒。H₂-TPR结果表明,相比于Fe/Al₂O₃/cordierite,1.5Co/Fe/Al₂O₃/cordierite有更好的低温还原性能。Py-FTIR结果表明,Co的引入可使催化剂表面的Lewis酸明显增加,且生成了Brønsted酸。N₂吸附-脱附表征结果表明,Co可增大催化剂的比表面积。     

Cu/Co/Mn基氧载体释氧动力学及机理研究

以溶胶凝胶法制备了CuO/CuAl₂O₄、Co₃O₄/CoAl₂O₄以及Mn₂O₃/Al₂O₃氧载体,在流化床反应器中CO₂气氛下研究了不同温度下氧载体释氧特性,并通过分析得到各氧载体的释氧动力学机理函数、活化能及指前因子等重要参数。释氧过程中,氧载体CuO/CuAl₂O₄中CuO、CuAl₂O₄均为活性相,释氧后转化为Cu₂O及CuAlO₂,而Co₃O₄/CoAl₂O₄及Mn₂O₃/Al₂O₃中CoAl₂O₄和Al₂O₃均为惰性相,仅有Co₃O₄和Mn₂O₃参与释氧并分别转化为CoO和Mn₃O₄。三种氧载体的释氧过程均可由成核-核生长机理描述,释氧初期氧载体经化学反应形成新的活性核心,随后活性核心聚集形成还原态的氧载体团簇。各氧载体释氧的机理函数G(x)有不同的表达式,CuO/CuAl₂O₄、Co₃O₄/CoAl₂O₄、Mn₂O₃/Al₂O₃释氧的活化能E分别为226.37、130.06和65.90 kJ/mol,相对应的指前因子A分别为2.99×10⁶、4.96×10³和27.37 s^-1。