Conductance of KCI-Glycerol Solutions: Test of the Fuoss Paired Ion Model

Abstract

The electrical conductance of KC1 in glycerol solutions has been measured at concentrations between 1.5 mol m^?3 and 353 mol m^?3 at 22°C. The results are compared with the Fuoss paired ion model and fits to the data are obtained assuming a Gurney co-sphere having a radius in the approximate range 6 ± 10^?10 m to 9 ± 10^?10 m. The model leads to an estimate of ionic association which is less than that given by the theory of Bjerrum.     

Selective enzyme amplification of NAD/NADH using coimmobilized glycerol dehydrogenase and diaphorase with amperometric detection

A flow system for substrate recycling of NAD⁺/NADH was set up with an enzyme reactor containing coimmobilized glycerol dehydrogenase (GDH) and diaphorase. The product from the diaphorase catalysis, hexacyanoferrate(II), aws detected amperometrically at a glassy carbon electrode. The amplification factor was 150 for a reactor volume of 100 μ l at a flow-rate of 0.5 ml/min. With a stopped flow of four minutes, the signal increased another 88 times, resulting in a signal amplification of 13 300 times. Equations are derived for the amplification factor and used for a discussion of the optimization of amplification systems. The K_m for GDH with glycerol as a substrate was found to be 5 × 10⁻³ M at pH 8.0. GDH from Cellulomonas sp. was purified on a gel filtration column and the purified enzyme showed a specificity toward NAD⁺, compared to NADP⁺, that was higher than 99.9%. Due to the NAD⁺ specificity of the purified GDH, the enzyme amplification system reported here could be used in detection systems for enzyme immunoassays when using alkaline phosphatase as a label and NADP⁺ as a substrate. The stability of immobilized GDH and diaphorase is several orders of magnitude better than that of alcohol dehydrogenase, which is the enzyme commonly used for NAD⁺-specific detection in these applications.     

聚丙烯共混物反应挤出过程中的降解抑制

聚丙烯／（丙烯腈－苯乙烯）共聚物在过氧化二异丙苯存在下反应共混挤出时，加入亚油酸三甘酯可以有效地抑制过程的降解，从挤出物中分离出聚丙烯组分测试熔体流动速率表明，加入亚油酸三甘酯后，其熔体流动速率有很大下降，扫描电子显微镜的观察表明，调节过氧化二异丙苯和亚油酸三甘酯的加入量，可有效控制降解并生成较多的接枝物相容性，显著改善相形态。     

Determination of anionic trace impurities in glycerol by capillary isotachophoresis with enlarged sample load

Glycerol of different quality classifications served as a model for a neutral excess component in the isotachophoretic determination of low-molecular-mass anionic trace impurities. Potential anionic contaminants such as nitrate, sulphate, chlorate, nitrite, oxalate, fluoride formate and phosphate were analysed up to an analyte-to-excess ratio of 1:4·10⁷, thus providing the possibility of checking the sample for the mentioned analytes in the order of 2.5·10⁻⁶–9.5·10⁻⁶%. Because we used a column-coupling isotachophoretic instrument the electrolyte system consisted of two different leading electrolytes, one for the pre-separation (10 mmol/l HCl, β-alanine, pH 3.2) in the first capillary and one for the final separation (5 mmol/l HCl, 1,3-bis[tris(hydroxymethyl)methylamino]propane, β-alanine, pH 3.6) in the second capillary. The terminating electrolyte was citric acid. Due to an increased injection volume of 300 μl, limits of detection (LODs) in the nanomolar range were realised by conductivity detection. The developed method allows simultaneous analysis without sample preparation and/or preconcentration within 25 min and is for that reason suitable for in-place process control.     

CuI/l-proline catalyzed click reaction in glycerol for the synthesis of 1,2,3-triazoles

Despite the apparent simplicity of the copper(I) iodide catalyzed CuAAC reaction, the conversion of the catalytic species, i.e. Cu(I) to thermodynamically more stable Cu(II), via aerial oxidation or disproportionation is a major issue. To stabilize the Cu(I) species, the reaction is ideally carried out under an inert atmosphere in the presence of additives such as alcohols, amines, thiols, and aldehydes. Herein, we report the first CuI catalyzed click reaction without an inert atmosphere by employing the CuI/l-proline system in glycerol. The method showed remarkable stability towards sensitive functional groups such as acetonides and 1,2,4-trioxanes.     

新型二氧化硫被动采样器的研制

研究了一种新型二氧化硫被动采样器。考察了无纺布、定性滤纸和定量滤纸等吸收剂的载体在相同情况下对二氧化硫和二氧化氮的吸收效果 ,对吸收载体进行了优选。并针对低温地区和高温高湿的气候条件 ,确立了以三乙醇胺(TEA)为吸收主体 ,分别以乙二醇、丙三醇为添加剂的吸收体系。     

Ambient γ-Rays-Mediated Noble-Metal Deposition on Defect-Rich Manganese Oxide for Glycerol-Assisted H2 Evolution at Industrial-Level Current Density

Developing novel synthesis technologies is crucial to expanding bifunctional electrocatalysts for energy-saving hydrogen production. Herein, we report an ambient and controllable γ-ray radiation reduction to synthesize a series of noble metal nanoparticles anchored on defect-rich manganese oxides (M@MnO_2-x, M=Ru, Pt, Pd, Ir) for glycerol-assisted H₂ evolution. Benefiting from the strong penetrability of γ-rays, nanoparticles and defect supports are formed simultaneously and bridged by metal-oxygen bonds, guaranteeing structural stability and active site exposure. The special Ru−O−Mn bonds activate the Ru and Mn sites in Ru@MnO_2-x through strong interfacial coordination, driving glycerol electrolysis at low overpotential. Furthermore, only a low cell voltage of 1.68 V is required to achieve 0.5 A cm⁻² in a continuous-flow electrolyzer system along with excellent stability. In situ spectroscopic analysis reveals that the strong interfacial coordination in Ru@MnO_2-x balances the competitive adsorption of glycerol and OH* on the catalyst surface. Theoretical calculations further demonstrate that the defect-rich MnO₂ support promotes the dissociation of H₂O, while the defect-regulated Ru sites promote deprotonation and hydrogen desorption, synergistically enhancing glycerol-assisted hydrogen production.     

VLE of CO2 + glycerol + (ethanol or 1-propanol or 1-butanol)

Vapour-liquid equilibrium of CO₂ + [0.00871 glycerol + 0.99129 (ethanol or 1-propanol or 1-butanol)] mixtures was measured at the temperatures of 313.15 K and 333.15 K, and close to the critical line, at pressures up to 12 MPa. On the liquid side, the bubble points measured for these ternary mixtures follow closely the behaviour of VLE reported by several authors for the corresponding binary mixtures without glycerol. On the vapour side, however, dew points for the ternary mixtures deviate significantly from VLE results for the binaries. A correlation of the results obtained for the CO₂ + glycerol + ethanol mixture with the Peng-Robinson equation of state, admitting quasi-binary behaviour, equally yields good agreement on the liquid side, and significant deviations on the vapour side.     

预处理温度对甘油氢解双金属Ir-Re催化剂性能的影响

在生物柴油生产过程中大量副产的甘油是重要的生物质转化平台化合物.通过甘油氢解制备高附加值的1,3-丙二醇是甘油的资源化利用的重要途径,能够显著提高生物柴油产业的经济效益,同时也是探究更复杂的糖醇类化合物氢解的模型反应.因此,甘油氢解制备1,3-丙二醇成为当前学术界的研究热点.通常,以Re或W为助剂修饰的贵金属催化剂是有效的甘油选择性氢解制1,3-丙二醇的催化剂,其中,双金属Ir-Re催化剂是目前最高效的催化剂之一.甘油氢解反应是典型的结构敏感性反应,它的催化性能依赖于双金属催化剂的结构,而后者受制备工艺条件如热处理方式及条件的影响.最近,我们报道了以直接还原法(即浸渍-还原法)制备的Ir-Re催化剂为合金结构,在甘油氢解中表现出更为优越的反应活性及目前报道中最高的1,3-丙二醇生成速率,并提出了可能的双功能反应机理,即催化剂表面的Re-OH酸性位和Ir均为甘油氢解的活性位.本文采用直接还原法制备KIT-6(具有三维有序介孔孔道结构的SiO2)负载的双金属Ir-Re催化剂,进一步研究还原温度对Ir-Re/KIT-6的结构及其催化性能的影响,揭示催化剂表面酸性在甘油氢解反应中的重要作用并阐明其构-效关系.结果显示不同还原温度(400–700 oC)制备的催化剂的比表面积、孔体积及孔径数据基本一致,表明还原温度对Ir-Re/KIT-6的织构性质的影响很小.根据程序升温还原和透射电镜-能量散射点扫描结果可知,不同温度还原后的催化剂表面Ir和Re均以金属态形式存在,同时两者存在直接的相互作用,形成了Ir-Re合金;而漫反射红外图谱上CO吸附峰的红移以及峰形的显著变化也印证了Ir-Re合金结构的形成. TEM结果显示,在400–700oC还原后得到的Ir-Re合金纳米粒子均匀分布于KIT-6上,尺寸基本一致(2.5–2.8 nm),与CO化学吸附结果一致.此外, NH3-程序升温脱附结果表明催化剂的酸量随着还原温度的升高而逐渐增大,但酸强度没有明显变化,这可能是由于高温还原进一步促进了Ir和Re的相互作用,在原子尺度上混合更为均匀所致. Ir-Re催化剂上甘油氢解反应结果显示,随着还原温度由400提高到600 oC,所制催化剂的活性先增加而后趋于稳定.由此可以认为Ir-Re催化性能的差异与Ir分散度和酸强度的关联较小,主要是由于催化剂表面酸量所致.直接关联酸量与反应活性(以反应时间内的平均1,3-丙二醇生成速率表示)可以看到,反应活性随着酸量的增加而线性增大,表明Ir-Re/KIT-6的表面酸量直接影响了甘油氢解反应速率的快慢,即酸位Re-OH直接参与了催化反应.众所周知, Re金属活化H2的能力很弱,而金属Ir在反应中起到催化加氢的作用.实验结果很好地印证了Ir-Re合金催化甘油氢解反应的双功能反应机理,即酸位Re-OH与金属Ir协同参与氢解反应,分别作为甘油吸附位和H2活化中心,因此提高催化剂的表面Re-OH的数量将是进一步提高催化活性的途径之一.总的来说,在400–700 oC还原得到的Ir-Re/KIT-6催化剂具有Ir-Re合金结构.还原温度对催化剂的织构性质、金属纳米粒子的尺寸、Ir的分散度及表面酸强度的影响不大,但还原温度的升高有利于Ir和Re的相互作用,显著提高了催化剂的表面酸量,因而提高催化活性.此外,表面酸量和反应活性的线性关系表明酸位Re-OH参与Ir-Re合金催化甘油氢解反应,印证了双功能反应机理.     

气-液半间歇反应器中甘油氯化:用于生产氯代醇的新型催化剂(英)

Glycerol from biodiesel production can be an important industrial feedstock for chemical commodities as it can be used in the food,cosmetic,pharmaceutical and tobacco industries.However,crude glycerol derived from biodiesel production has a low value because of impurities.The purification of this glycerol into a high grade involves high costs and is not economically feasible for small and medium size plants.The glycerol conversion into chlorohydrins was studied using new homogeneous catalysts and hydrochloric acid as chlorination agent.This is an interesting alternative route to epichlorohydrin and then to epoxy resins.The behavior of two series of homologous catalysts,glycolic acid series(glycolic acid,di-glycolic acid and thio-glycolic acid) and amminoacid series(glutamic acid,aspartic acid and cysteine),were investigated for their activity and selectivity.Glycolic acids were more active than amminoacids.The pK_a values had a strong influence on selectivity(mono-chlorohydrins/di-chlorohydrins) for the amminoacid series,which was not observed for the glycolic acids.A kinetic model and reaction mechanism developed in a previous work were used for interpreting the kinetic runs.