介孔Co3O4-CeO2复合氧化物的制备及在CO选择性氧化中的应用

以硝酸钴和硝酸铈为前驱物，SBA-15为硬模板，利用双溶剂法制备了Co3O4-CeO2介孔复合氧化物，通过X-射线衍射、N2吸脱附测试、程序升温还原和透射电子显微镜等技术对活性组分及载体进行了表征，并且与浸渍法和共沉淀法所制备的催化剂进行了对比分析。结果表明，相比于浸渍法和共沉淀法，采用双溶剂法制备的介孔Co3O4-CeO2复合氧化物具有均匀的介孔结构、较小的颗粒尺寸、较大的比表面积和较高的活性组分分散度。此外，CO氧化脱除评价显示与常规的共沉淀法和浸渍法所制备的催化剂相比该介孔复合氧化物具有较高的反应活性和选择性，其高活性主要归因于较高的比表面积和活性组分的高分散度。     

介孔氧化硅球负载钴基催化剂在费托合成中的应用

以介孔氧化硅空心球(HMSS)为载体, 采用双溶剂法浸渍硝酸钴溶液制备了高分散度的钴催化剂, 并表征了催化剂中Co3O4颗粒的负载情况和费托(F-T)反应性能. 结果表明: Co3O4颗粒在介孔硅球孔道内形成100～200 nm左右分散良好的簇团, 将催化剂压碎和刻蚀后的透射电子显微镜(TEM)证实, 这些簇团是由尺寸约为10～15 nm大小均匀的Co3O4单分散颗粒组成, 这些单分散颗粒锚定在介孔硅球孔道内, 彼此之间被相邻孔壁隔开; 催化剂中钴-硅作用很弱, 在600 K下即可被还原; F-T反应评价表明, 所得产物保持了良好的烃分布, 主要集中于C5～C18烃, 选择性在60%左右, C5＋选择性达到80%以上.     

不同方法制备的Cu-Cr/γ-Al2O3的结构及其对糠醛加氢制2-甲基呋喃反应的催化性能

 利用普通浸渍法、共沉淀法和溶剂化金属原子浸渍法制备了一系列Cu－Cr／γ－Al2O3催化剂，并用X射线衍射、扫描电镜、透射电镜和X射线光电子能谱等技术对这些催化剂进行了表征．结果表明，不同方法制备的催化剂的金属粒度的顺序为溶剂化金属原子浸渍法＜共沉淀法＜普通浸渍法；金属还原程度的顺序为溶剂化金属原子浸渍法＞普通浸渍法≈共沉淀法．糠醛加氢反应实验结果表明，催化活性顺序为溶剂化金属原子浸渍法＞普通浸渍法＞共沉淀法；生成2－甲基呋喃选择性顺序为共沉淀法＞普通浸渍法＞溶剂化金属原子浸渍法．     

介孔Co-Al2O3催化剂上甲烷部分氧化制合成气

采用一锅法制备了介孔Co-Al2O3催化剂,并首次用于甲烷部分氧化制合成气反应. 结果表明,与普通浸渍法相比,一锅法制备的Co-Al2O3催化剂表现出更为优异的催化性能. 合成的介孔Co-Al2O3催化剂具有大的比表面积和孔体积,以及规整有序的六方介孔孔道,Co物种高度分散,从而导致还原后高的金属分散度,而介孔孔道对金属纳米颗粒的约束作用可有效增强金属的抗烧结能力.     

各种形貌纳米Co_3O_4的制备及其应用

本文综述了各种形貌的纳米Co3O4的制备及其应用。制备纳米Co3O4的方法有很多,包括热分解、水热法、溶剂热法、化学喷雾热分解、化学气相沉积和溶胶-凝胶法。制备得到的Co3O4有各种形貌,如纳米球、纳米立方体、纳米管、纳米棒、纳米片、纳米纤维和介孔结构。Co3O4是一种重要的磁性p型半导体,在锂离子电池、超级电容器、电致变色、磁性材料、气体传感器和催化剂等诸多领域有较广泛的应用。     

介孔氧化铝复合材料负载铂催化剂上丙酮酸乙酯的不对称氢化反应

采用固相研磨法制备了有序介孔树脂FDU-14孔道限阈分散的Al2O3复合材料Al2O3@FDU-14.以其为载体,采用浸渍法制备了4.0％ Pt/Al2O3@FDU- 14催化剂,并利用X射线衍射、透射电子显微镜和N2吸附等手段对催化剂进行了表征.结果表明,Pt/Al2O3@FDU- 14催化剂保持了FDU-14的介孔...     

共沉淀法制备氧化铝负载Co-Mo双金属氮化物催化剂

采用硝酸铝和硝酸钴的乙醇溶液与钼酸铵的碳酸铵水溶液共沉淀制备了Al2O3负载Co-Mo双金属氧化物前驱体,结合氨程序升温还原法制得了氮化物催化剂Co-Mo-N/Al2O3.利用X射线衍射和N2物理吸附方法表征了制备的前驱体和钝化态Co-Mo-N/Al2O3催化剂的晶相和孔结构,用程序升温脱附、程序升温表面反应及扫描电子显微镜考察了共沉淀法和浸渍法制备的催化剂的晶格稳定性、活性中心和表面形貌,用氨分解反应表征了Co-Mo-N/Al2O3催化剂的活性.结果表明,焙烧温度对催化剂比表面积有较大影响,低温焙烧的样品中活性组分散性较好,673K焙烧制得催化剂的氨分解活性最高.与浸渍法制备的Co-Mo-N/Al2O3催化剂相比,共沉淀法制备的催化剂具有更高的晶格稳定性、更均匀的活性组分分布和更高的氨分解活性.     

不同方法制备的介孔Ni/MgO催化剂上水蒸气重整苯酚制氢

利用浸渍法和水热共沉淀法两种方法,制备了介孔Ni/MgO催化剂,用于水蒸气重整生物质油模型物苯酚制取氢气;利用XRD、N2吸附/脱附、H2-TPR、TEM以及TG等手段对催化剂进行了表征。结果表明,以介孔MgO为载体,采用浸渍法制备的介孔NiO/MgO固溶体,具有较高的比表面积(60.6m2/g)以及较大的孔径(10.1nm)。与水热共沉淀法制备的催化剂相比,浸渍法制备的NiO/MgO前驱体经还原后的所得到介孔Ni/MgO催化剂Ni颗粒较小(5.0-6.0nm),分布均匀,具有较高的分散度(19.44%)。较大的比表面积能有效地促进活性金属颗粒的分散,而介孔有利于反应物和产物在催化剂孔道中的扩散。因此,该Ni/MgO催化剂在水蒸气重整苯酚制氢反应中具有较高的催化活性、稳定性和优异的抗积炭能力。     

介孔氧化铝负载钒催化剂上丙烷氧化脱氢制丙烯

 采用浸渍法制备了介孔氧化铝 (m-Al2O3) 负载钒催化剂 (V/m-Al2O3), 并考察了其催化丙烷氧化脱氢制丙烯反应活性. 通过 N2 吸附-脱附、透射电镜、X 射线粉末衍射、紫外-可见漫反射光谱、氢-程序升温还原和氨-程序升温脱附对催化剂进行了表征. 结果表明, 介孔氧化铝具有大比表面积、窄孔径分布和两维六方相结构, 在其上负载适量的 V 可实现 V 活性物种的高分散及催化剂的弱酸性, 从而有利于提高丙烷转化率和丙烯选择性. 与共合成法制备的含 V 介孔氧化铝 V/m-Al2O3(C) 和浸渍法制备的 V/?-Al2O3 相比, V/m-Al2O3 表现出更高的催化活性. 这与载体较弱的酸性和较大的比表面积以及 V 物种的高分散有关.     

模板法制备的有序介孔Co3O4的电化学电容行为

以介孔硅作为模板合成有序的介孔Co3O4, 在6 mol/L KOH电解液里进行电化学性能的测试. 结果表明具有有序介孔结构的Co3O4, 其比容量可以达到250 F/g, 大约为在550 ℃下直接煅烧Co(NO3)•6H2O所得的Co3O4容量的4倍. 其外该材料还表现出良好的倍率特性, 这一现象可归因于有序的介孔结构增大了有效的反应表面积, 同时有利于离子在其中传递.     

绿色双溶剂法制备高效稳定钙钛矿太阳能电池

采用毒性小、环境友好的乙二醇甲醚(ethylene glycol monomethyl ether,EGME)与水混合的双溶剂(体积比为1:1)溶解CsBr,通过提高CsBr的溶解度,减少了后续CsBr的甲醇溶液的旋涂遍数,简化了电池制备流程。通过优化CsBr的甲醇溶液的旋涂遍数发现,在旋涂1遍200 mg·mL^-1 CsBr的水/EGME溶液的基础上旋涂2遍15 mg·mL^-1 CsBr的甲醇溶液,所制备的CsPbBr₃钙钛矿太阳能电池(perovskite solar cells,PSCs)拥有最佳的性能,实现了1.44 V的开路电压(open-circuit voltage,V_OC),6.26 mA·cm^-2的短路电流密度(short circuit current density,J_SC),74.57%的填充因子(fill factor,FF)及最高6.72%的光电转换效率(photoelectric conversion efficiency,PCE)。     

Determination of nitrate and nitrite in mixtures with a nitrate ion electrode

A rapid method for the determination of nitrate and nitrite ions is described. The potential of a mixture of nitrate and nitrite was measured with a nitrate ion selective electrode. The nitrite in the mixture is then oxidized to nitrate with permanganate in acid solution, and the potential of the oxidized solution is also measured with the electrode. The fundamental equations for the response of the nitrate ion electrode to nitrate ion in the presence of interfering ions were used, and a new equation was developed for calculating the original nitrate concentration of the mixture. The absolute errors for solutions of known concentrations (2.5–100 p.p.m. each) were 1.8 p.p.m. nitrate and 2 p.p.m. nitrite. When the results are calculated by computer, five determinations can be performed in 30 min. The method was applied to the determination of the oxides of nitrogen in cigarette smoke as nitrite and nitrate after dissolution in basic solution.     

Direct Determination of Arsenic in Beet Sugar Molasses Using Nickel as Chemical Modifier by Electrothermal Atomic Absorption Spectrommetry

A simple electrothermal atomic absorption spectrometric (ETAAS) method is described for direct determination of arsenic in sugar beet molasses samples. Pyrolytic graphite tubes were used as atomizers. The compression between modifiers such as nickel nitrate, palladium nitrate and the mixture of palladium and magnesium nitrate were performed and nickel nitrate selected as the best chemical modifier. The effects of pyrolysis and atomization temperature were also studied and the pyrolysis temperature of 900 °C and atomization temperature of 2300 °C have been chosen for temperature program. The detection limit of the method was 1 ng/mL As in sugar beet molasses samples. The relative standard deviation for ten determination of a spiked sample with concentration of 50 ng/mL As was 2.4%. The accuracy of the method was confirmed by the analysis of spiked samples. The linear rang of calibration is in the range of 1‐100 ng/mL of arsenic.     

Polarographic determination of nitrate in vegetables

A polarographic method for the determination of nitrate in vegetables is presented. The method is based on the reduction of nitrate to nitric oxide which reacts in solution with colbalt (II) and thiocyanate ions forming an electroactive complex that is reduced at the dropping mercury electrode at -0.5 V (vs. SCE). The nitric oxide is generated outside the polarographic cell by addition of ferrous ammonium sulfate and ammonium molybdate in hydrochloric acid to the previously triturated vegetable matrices. The calibration graph was linear in the range of 2-12x10(-6) mol nitrate. The recovery of nitrate in vegetable matrices (broccoli, kale, lettuce, radish, red beet, spinach, turnip and watercress) varied from 85.4 to 107.4 % and the nitrate content, expressed as sodium nitrate, varied from 751 to 10 806 mg kg(-1) of fresh vegetable. The relative standard deviation for the proposed method is lower than 7% and considering a sample of 5.0 g, the determination limit was 39 mg of nitrate per kg fresh vegetable weight. The precision and accuracy of the polarographic method were comparable to those of the reference spectrophotometric method (official AOAC reference method for the determination of nitrate in foodstuffs).     

Circularly Polarized Luminescence of Achiral Carbon Dots in Bi-Solvent Systems Triggered by Supramolecular Self-Assembly

An innovative strategy for circularly polarized luminescence (CPL) of carbon dots (CDs) has been developed: The achiral CDs displayed contrary supramolecular chirality and opposite CPL in two different bi-solvent systems, which are due to the formation of self-assembled helical nanostructures with two diverse assembly modes (P and M) in aggregate state via intermolecular π-π interactions and differential hydrogen bonding (H-bonding) without the need of any additional element of chirality.     

Simultaneous determination of bromide, nitrite and nitrate ions in seawater by capillary zone electrophoresis using artificial seawater as the carrier solution

We describe capillary zone electrophoresis (CZE) for the simultaneous determination of bromide, nitrite and nitrate ions in seawater. Artificial seawater was adopted as the carrier solution to eliminate the interference of high concentrations of salts in seawater. The artificial seawater was free from bromide ion to enable the determination of bromide ion in a sample solution. For the purpose of reversing the electroosmotic flow (EOF), 3 mM cetyltrimethylammonium chloride (CTAC) was added to the carrier solution. A 100 microm ID (inside diameter) capillary was used to extend the optical path length. The limits of detection (LODs) for bromide, nitrite, and nitrate ions were 0.46, 0.072, and 0.042 mg/L (as nitrogen), respectively. The LODs were obtained at a signal to noise ratio (S/N) of 3. The values of the relative standard deviation (RSD) of peak area for these ions were 1.1, 1.5, and 0.97%. The RSDs of migration time for these ions were 0.61, 0.69, and 0.66%. Artificial seawater samples containing various concentrations of bromide, nitrite, and nitrate ions were analyzed by the method. The error was less than +/-12% even if the concentration ratio of bromide ion to nitrite or nitrate ion was 20-240. The proposed method was applied to the determination of bromide, nitrite, and nitrate ions in seawater samples taken from the surface and the seabed. These ions in other environmental waters such as river water and rainwater samples were also determined by ion chromatography (IC) as well as this method.     

A simple simultaneous flow injection method based on phosphomolybdenum chemistry for nitrate and nitrite determinations in water and fish samples

A direct spectrophotometric flow injection method for the simultaneous determination of nitrite and nitrate has been developed. The method is based on the oxidation of a phosphomolybdenum blue complex by the addition of nitrite and the decrease in absorbance of the blue complex is monitored at 820 nm. The injected sample is split into two segments. One of the streams was directly reacted with the above reagent and detected as nitrite. The other stream was passed through a copperised cadmium reductor column where reduction of nitrate to nitrite occurs, and the sample was then mixed with the reagent and passed through the cell of the spectrophotometer to be detected as nitrite plus nitrate. The conditions for the flow injection manifold parameters were optimised by experimental design and the concentration of nitrite and nitrate was determined in the linear range from 0.05 to 1.15 mug ml(-1) nitrite and 0.06 to 1.6 mug ml(-1) nitrate with a detection limit of 0.01 mug ml(-1) for nitrite and 0.025 mug ml(-1) for nitrate. The method is suitable for the simultaneous determination of nitrite and nitrate in fish and water samples with a sampling rate of 25+/-2 sample per hour.     

Simultaneous determination of nitrite and nitrate in human plasma by on-capillary preconcentration with field-amplified sample stacking

A simple method for the determination of nitrite and nitrate in human plasma has been developed using CZE with minimal sample preparation. Field‐amplified sample stacking (FASS) was used to achieve submicromolar detection by dilution of the plasma sample with deionized water. In CZE, the separation of nitrite and nitrate was achieved within 10 min without adding EOF modifier. The optimal condition was achieved with 50 mM phosphate buffer at pH 9.3. The ninefold diluted plasma samples were injected hydrodynamically for 40 s into a 60 cm×75 μm id uncoated fused‐silica capillary. The separation voltage was 20 kV (negative potential) and UV detection was performed at 214 nm. The linearity curves for nitrite and nitrate were obtained by the standard addition method. The estimated LODs for nitrite and nitrate in ninefold diluted plasma sample were 0.05 and 0.07 μM, respectively. The LODs for nitrite and nitrate in original plasma samples were 0.45 and 0.63 μM. The intra‐ and inter‐day precisions for both analytes were <2.6% and the recovery ranged between 92.3 and 113.3%. It was found that nitrite was more stable than nitrate in the plasma after the sample preparation. This proposed method was applied to a number of human plasma samples and the measured nitrite and nitrate concentrations in human plasma were consistent with the literature ranges.     

高比表面SiC的合成及其在CO氧化反应中的应用

采用蔗糖为碳源, 正硅酸乙酯(TEOS)为硅源, 分别以草酸、硝酸铁、硝酸镍为催化剂, 用溶胶-凝胶法制备碳化硅前驱体, 考察了制备过程中催化剂的种类以及反应温度和时间对凝胶形成的影响. 发现以硝酸铁为催化剂最有利于凝胶的形成, 碳/硅物质的量比为4的前驱体在氩气气氛1350 ℃下加热10 h, 碳热还原反应趋于完成. 以该条件下合成的多孔碳化硅(比表面积133 m2·g-1)作为催化剂载体, 通过等量浸渍法获得Pt/SiC催化剂, 将其应用于一氧化碳氧化的模型反应中. 研究结果表明该催化剂有较好的催化活性和稳定性. 引入镍助剂的PtNi/SiC催化剂能进一步提高一氧化碳催化氧化反应的活性.