Pd/MoO3-TiO2/SiO2光催化CO2与C2H6合成烃类氧化物的反应性能

 采用化学反应改性和等体积浸渍法制备了负载型Pd/MoO3-TiO2/SiO2催化剂,并用IR,FT-Raman,TPD-MS,UV-Vis DRS和活性评价等方法研究了催化剂的表面结构、光吸收性能、化学吸附性能及光催化CO2与C2H6合成烃类氧化物的反应性能. 结果表明,SiO2负载的MoO3和TiO2之间存在着强相互作用,并能部分形成Mo-O-Ti键联,使得两种氧化物微粒均匀分布于载体表面; 表面MoO3和TiO2的复合作用使TiO2/SiO2的吸光带边红移,扩展了其吸光域,Pd的引入明显提高了固体材料的可见光吸收率; CO2和C2H6能较好地吸附在催化剂表面,在紫外光的激发下,CO2吸附态能解离生成CO,而C2H6单位吸附态能部分转化为C和H同时吸附在两个晶格氧上的双位吸附态; 光促CO2和C2H6反应主要生成丙醛、乙醇和乙醛; 在合适的条件下,烃类氧化物的选择性可超过90%.     

不同CuO/CeO2催化剂上CO低温氧化反应

 分别用热解硝酸铈法和浸渍法制备了不同物性的CeO2粉体和相应的CuO/CeO2催化剂,并用XRD, HRTEM和TPR等对样品进行了表征,利用微反-色谱装置考察了其催化CO低温氧化的活性. 结果表明,热解温度影响CeO2的物性(形貌、粒度大小及分布等). 相同条件下,不同物性的CeO2载体上CuO的负载情况不同, 500 ℃热解获得的CeO2载体上非晶态CuO负载量最高,相应的CuO/CeO2催化剂活性也较高. 非晶态CuO一部分进入CeO2晶格,另一部分高度分散于CeO2表面上. 焙烧温度较低时(≤ 600 ℃), 催化剂活性受焙烧温度的影响较小,而高温(800 ℃)焙烧后,催化剂则因载体粒度增大和CuO烧结团聚等因素导致催化活性明显降低.     

Analytical Biosensing of Hydrogen Peroxide on Brilliant Cresyl Blue/Multiwalled Carbon Nanotubes Modified Glassy Carbon Electrode

A cationic quinine‐imide dye brilliant cresyl blue (BCB) and horseradish peroxidase (HRP) were co‐immobilized within ormosil on multiwalled carbon nanotubes modified glassy carbon electrode for the fabrication of highly sensitive and selective hydrogen peroxide biosensor. The presence of epoxy group in ormosil as organic moiety improves the mechanical strength and transparency of the film and amino group provides biocompatible microenvironment for the immobilization of enzyme. The presence of MWCNTs improved the conductivity of the nanocomposite film. The surface characterization of MWCNT modified ormosil nanocomposite film was performed with scanning electron microscopy (SEM) and atomic force microscopy (AFM). Cyclic voltammetry and amperometry measurements were used to study and optimize the performance of the resulting peroxide biosensor. The apparent Michaelis–Menten constant was determined to be 1.5 mM. The proposed H₂O₂ biosensor exhibited wide linear range from 3×10^?7 to 1×10^?4 M, and low detection limit 1×10^?7 M (S/N=3) with fast response time <5 s. The probable interferences in bio‐matrix were selected to test the selectivity and no significant response was observed in the biosensor. This biosensor possessed good analytical performance and long term storage stability.     

A Flexible Pro‐porous Coordination Polymer: Non‐conventional Synthesis and Separation Properties Towards CO2/CH4 Mixtures

The novel coordination polymers [Cu(Hoxonic)(H₂O)]_n ( 1 ) and [Cu(Hoxonic)(bpy)_0.5]_n ? 1.5 n H₂O ( 2?H₂O ) (H₃oxonic: 4,6‐dihydroxy‐1,3,5‐triazine‐2‐carboxylic acid; bpy: 4,4′‐bipyridine) have been isolated and structurally characterised by ab initio X‐ray powder diffraction. The dense phase 1 contains 1D zig‐zag chains in which Hoxonic dianions bridge square‐pyramidal copper(II) ions, apically coordinated by water molecules. On the contrary, 2?H₂O , prepared by solution and solventless methods, is based on 2D layers of octahedral copper(II) ions bridged by Hoxonic ligands, further pillared by bpy spacers. The resulting pro‐porous 3D network possesses small hydrated cavities. The reactivity, thermal, magnetic and adsorptive properties of these materials have been investigated. Notably, the adsorption studies on 2 show that this material possesses unusual adsorption behaviour. Indeed, guest uptake is facilitated by increasing the thermal energy of both the guest and the framework. Thus, neither N₂ at 77 K nor CO₂ at 195 K are incorporated, and CH₄ is only minimally adsorbed at 273 K and high pressures (0.5 mmol g^?1 at 2500 kPa). By contrast, CO₂ is readily incorporated at 273 K (up to 2.5 mmol g^?1 at 2500 kPa). The selectivity of 2 towards CO₂ over CH₄ has been investigated by means of variable‐temperature zero coverage adsorption experiments and measurement of breakthrough curves of CO₂/CH₄ mixtures. The results show the highly selective incorporation of CO₂ in 2 , which can be rationalised on the basis of the framework flexibility and polar nature of its voids.     

Platelet Graphite Nanofibers for Electrochemical Sensing and Biosensing: The Influence of Graphene Sheet Orientation

Here, we demonstrate that platelet graphite nanofibers (PGNFs) exhibit fast heterogeneous electron‐transfer rates for a wide variety of compounds such as FeCl₃, ferrocyanide, dopamine, uric acid, ascorbic acid, and the reduced form of β‐nicotinamide adenine dinucleotide. The electrochemical properties of PGNFs are superior to those of multiwalled carbon nanotubes (MWCNTs) or graphite microparticles (GMPs). Transmission electron microscopy and Raman spectroscopy reveal that this arises from the unique graphene sheet orientation of such platelet nanofibers, which accounts for their unparalleled high ratio of graphene edge planes versus basal planes.     

Kinetic and equilibrium adsorption of methylene blue and remazol dyes onto steam-activated carbons developed from date pits

Steam-activated carbons DS2 and DS5 were prepared by gasifying 600 °C-date pits carbonization products with steam at 950 °C to burn-off = 20 and 50%, respectively. The textural properties of these carbons were determined from the nitrogen adsorption at ?196 °C. The chemistry of the carbon surface was determined from the surface pH and from neutralization of the surface carbon–oxygen groups of basic and acidic type. The kinetic and equilibrium adsorption of MB and RY on DS2 and DS5 was determined at 27 and 37 °C and at initial sorption solution pH 3–7.DS2 and DS5 have expanded surface area, large total pore volume and contain both micro and mesoporosity. They have on their surface basic and acidic groups of different strength and functionality. This enhanced the sorption of the cationic dye (MB) and of the anionic dye (RY). The adsorption of MB and RY on DS2 and DS5 involves intraparticle diffusion and followed pseudo-second order kinetics. The adsorption isotherms were applicable to the Langmuir isotherm and high monolayer capacities for MB and RY dyes were evaluated indicating the high efficiencies of the carbons for dye adsorption.     

CO加氢Rh-Mn-Li/SiO2催化剂配比的优化及其CO脱附行为

通过优化Rh-Mn-Li/SiO2催化剂配比,大大地提高了其催化CO加氢合成C2含氧化合物的性能,并利用吸附CO的程序升温脱附(CO-TPD)和程序升温表面反应(TPSR)等方法考察了助剂Mn和Li对Rh基催化剂表面CO脱附行为的影响.结果表明,在543~573K内,Rh担载量为1.5%时催化剂的Rh效率(ERh)最高.少量Mn的添加显著地提高了Rh基催化剂的ERh,C2含氧化合物的时空收率(STYC2-oxy)和选择性(SC2-oxy).并且随着Mn含量增加,ERh和STYC2-oxy在Mn=0.53%时最高,但SC2-oxy一直缓慢增加.而随着Li含量增加,SC2-oxy显著增加,但是ERh和STYC2-oxy明显下降.CO-TPD和TPSR结果表明,助剂Mn和/或Li的添加改变了催化剂表面解离CO活性中心的数量及其解离CO的能力,从而影响催化剂的活性.另一方面,Mn和Li的添加提高了催化剂表面弱吸附CO的相对数量,从而使SC2-oxy提高.     

一种新的测定微粒的电化学技术

设计了一种由2个石墨电极短路相连组成工作电极的新的电化学池装置.操作时首先通过外力按压使极少量固体微粒粘附在其中一个石墨电极表面上,然后在溶液存在下将微粒夹紧并固定在2个石墨电极表面之间进行电化学测定.电化学转化过程中生成的可溶性物质被封闭在2个石墨电极表面之间而得到测定.用该技术对钯沉积在氧化铝上而组成的催化剂的电化学行为以及黄铁矿的电化学行为进行了研究.结果表明,其兼具可电解粘合剂碳糊电极和固体微粒伏安法(voltammetry of microparticles)技术的优点而避免了各自的缺点:即不使用粘合剂,从而消除了粘合剂中杂质产生的氧化或还原电流的影响;可测定电化学转化过程中生成的可溶性物质;分辨率好、易于操作.     

聚对氨基苯磺酸修饰玻碳电极不可逆双安培法测定酪氨酸

在玻碳电极上成功地制备了聚对氨基苯磺酸修饰电极(P-p-ABSA/GCE),研究了酪氨酸在该修饰电极上的电化学行为.将此修饰电极用于流动注射不可逆双安培体系的构建,建立了流动注射双安培法直接测定酪氨酸的方法.在0 V外加电压下,在0.005 mol/L硫酸载液中,酪氨酸的氧化峰峰电流与其浓度在2.0×10-6 ～2.0×10-4 mol/L范围内呈良好的线性关系,方法的检出限(S/N=3)为1.0×10-7 mol/L.连续测定1.00×10-5 mol/L的酪氨酸标准溶液,电流值的相对标准偏差(RSD)为1.48%(n=20).该方法具有较高的选择性和灵敏度,应用于测定复方氨基酸注射液中酪氨酸的含量的测定,结果比较满意.     

微波辅助有机过氧化物功能化修饰单壁碳纳米管

本文报道了微波辅助下,利用过氧化月桂酰分解得到的十一烷基,化学功能化修饰单壁碳纳米管。这种快速、高效的方法将反应时间缩短至10分钟,并得到了比传统回流方法具有更高接枝率的产物。利用傅立叶变换红外光谱(FT-IR),热失重分析(TGA),拉曼光谱,探究了不同的反应时间和微波功率对单壁碳纳米管的接枝率的影响。结果表明：过长的反应时间会导致部分的去功能化的发生,而过高的微波功率(大于900瓦),则会将单壁碳纳米管上起初键连上的十一烷基剥落下来。分散性照片和高分辨率透射电子显微镜(HRTEM)照片显示出,功能化后的单壁碳纳米管与原始的碳管相比,在有机溶剂中的分散性有了明显的提高。