乙醇-环己烷体系中NaI活度系数的测定与计算

由于非水溶剂的应用日趋广泛,促使物理化学工作者对于溶剂和溶液性质进行研究,同时开展了有关物理化学数据的测定和积累工作,以利于指导实践[1]。目前文献报道含水混合溶剂中的电解质活度系数较多,但非水混合溶剂中电解质活度系数报道较少。电解质浓溶液活度系数的计算方法目前应用较广的是Pitzer半经验算法[2]。Pitzer的算法中具体物系的β(0)、β(1)等系数需从实测活度系数数据拟合求得。孙仁义等通过测定汽液平衡盐效应的方法研究了盐在混合溶剂中的活度系数[3-4]。最近孙仁义等[5]提出了双液比固定条件下含盐体系汽液平衡数据热力学一…     

乙醇在双功能Pd－Cu／分子筛催化剂上气相氧化酯化一步合成乙酸乙酯

研究了乙醇在双功能Ｐｄ－Ｃｕ／分子筛催化剂上一步合成乙酸乙酯的反应，发现Ｐｄ是氧化活性中心的主组分，ＣＵ主要对Ｐｄ的氧化功能起调变作用，以减少乙醇深度氧化副反应，提高酯化选择性．分子筛的酸性强弱对活性，特别是对酯化选择性有明显的影响，酯化要求在较强的酸中心上进行．探讨了氧化活性中心和酸中心的匹配关系以及ＣＵ对Ｐｄ的调变作用，提出了乙醇氧化酯化机理．     

乙醇水汽重整制氢反应中钯铜合金膜的透氢性能

 采用真空化学镀技术制备了厚度较薄的具有 fcc 结构的 Pd0.9Cu0.1/Al2O3 合金复合膜, 在 250~500 °C, 160~310 kPa 的乙醇水汽重整制氢模拟反应条件下, 考察了不同醇/水比的 H2-Ar-C2H5OH-H2O 混合气体系中该膜的透氢性能. 结果表明, 乙醇和水的存在均相同程度地降低了膜的透氢性能, 但测试条件下 Pd-Cu 合金膜仍保持完整的膜致密性和稳定的相结构. 在 500 °C, 310 kPa, H2-Ar-C2H5OH-H2O (H2:Ar:(C2H5OH+H2O) 体积比为 60:30:10) 混合气中, 膜的最大透氢量为 11.3 m3/(m2?h), H2 回收率大于 62.5%. Pd-Cu 合金膜在乙醇水汽重整制氢反应中具有潜在的应用前景.     

植物还原法制备负载型金纳米催化剂催化乙醇选择氧化反应

采用侧柏叶提取液还原氯金酸制备负载型金纳米催化剂,通过乙醇选择氧化反应,筛选出催化性能较好的TiO2载体。以TiO2载体为载体,考察了Au负载量、焙烧温度、催化剂用量、碳酸氢钠添加量及催化剂反应条件(时间、温度、压力)等因素对乙醇选择氧化反应的影响。结果表明,1.5%Au/TiO2催化剂(Au负载量为1.5%,质量分率,下同)催化乙醇选择氧化反应性能最佳,产物为乙醛、乙酸乙酯和缩醛,0.5%碳酸氢钠添加剂可抑制缩醛的生成,并可显著提高乙醇转化率和乙酸乙酯选择性。通过优化催化反应条件(1.5%Au/TiO2催化剂焙烧温度为400℃、用量为0.4 g、反应温度为100℃、氧气压力为3 MPa、反应时间为3 h时),乙醇转化率为47.9%,乙酸乙酯选择性为89.1%。     

液相色谱-同位素比质谱法同时测定葡萄酒中甘油和乙醇的δ13C值

采用液相色谱-同位素比质谱(LC-IRMS)技术建立了同时测定葡萄酒中甘油和乙醇δ13C值的分析方法。优化了葡萄酒中影响甘油和乙醇色谱分离的条件。方法的精密度和准确度分别为0.15‰~0.26‰和0.11‰~0.28‰。对40个葡萄酒样品进行了测定,甘油和乙醇的δ13 C值分别为-26.87‰~-32.96‰、-24.06‰~-28.29‰,两者具有较强的相关性(R=0.82)。该方法不需要复杂的样品预处理,在相同条件下同时测定甘油和乙醇的δ13C值,较传统方法简单、快速。     

Electrocatalytic activity of porous nanostructured Fe/Pt-Fe electrode for methanol electrooxidation in alkaline media

An electrochemical approach to fabricate a nanostructured Fe/Pt-Fe catalyst through electrodepo-sition followed by galvanic replacement is presented. An Fe/Pt-Fe nanostructured electrode was prepared by deposition of Fe-Zn onto a Fe electrode surface, followed by replacement of the Zn by Pt at open-circuit potential in a Pt-containing alkaline solution. Scanning electron microscopy and energy-dispersive X-ray techniques reveal that the Fe/Pt-Fe electrode is porous and contains Pt. The electrocatalytic activity of the Fe/Pt-Fe electrode for oxidation of methanol was examined by cyclic voltammetry and chronoamperometry. The electrooxidation current on the Fe/Pt-Fe catalyst is much higher than that on flat Pt and smooth Fe catalysts. The onset potential and peak potential on the Fe/Pt-Fe catalyst are more negative than those on flat Pt and smooth Fe electrodes for methanol electrooxidation. All results show that this nanostructured Fe/Pt-Fe electrode is very attractive for integrated fuel cell applications in alkaline media.     

A Comparative Study of Various Pretreatment Approaches for Bio-Ethanol Production from Willow Sawdust,Using Co-Cultures and Mono-Cultures of Different Yeast Strains

The effect of different pretreatment approaches based on alkali (NaOH)/hydrogen peroxide (H₂O₂) on willow sawdust (WS) biomass, in terms of delignification efficiency, structural changes of lignocellulose and subsequent fermentation toward ethanol, was investigated. Bioethanol production was carried out using the conventional yeast Saccharomyces cerevisiae, as well as three non-conventional yeasts strains, i.e., Pichia stipitis, Pachysolen tannophilus, Wickerhamomyces anomalus X19, separately and in co-cultures. The experimental results showed that a two-stage pretreatment approach (NaOH (0.5% w/v) for 24 h and H₂O₂ (0.5% v/v) for 24 h) led to higher delignification (38.3 ± 0.1%) and saccharification efficiency (31.7 ± 0.3%) and higher ethanol concentration and yield. Monocultures of S. cerevisiae or W. anomalus X19 and co-cultures with P. stipitis exhibited ethanol yields in the range of 11.67 ± 0.21 to 13.81 ± 0.20 g/100 g total solids (TS). When WS was subjected to H₂O₂ (0.5% v/v) alone for 24 h, the lowest ethanol yields were observed for all yeast strains, due to the minor impact of this treatment on the main chemical and structural WS characteristics. In order to decide which is the best pretreatment approach, a detailed techno-economical assessment is needed, which will take into account the ethanol yields and the minimum processing cost.     

Transition Metal Substituted Barium Hexaferrite-Modified Electrode: Application as Electrochemical Sensor of Acetaminophen

This study used substituted barium hexaferrites, which were previously prepared and reported by the authors, to detect acetaminophen by the modification of a conventional glassy carbon electrode (GCE), which led to promising results. The synthesis of this electrode-modifying material was conducted using a citrate sol gel process. A test synthesis using glycerin and propylene glycol revealed that glycerin produced a better result, while less positive anodic potential values were associated with the electrooxidation of N-acetyl-p-aminophenol (NAP). Excellent electroactivity was exhibited by the cobalt-substituted barium-hexaferrite-nanomaterial-modified electrode. A good linear relationship between the concentration and the current response of acetaminophen (paracetamol) was obtained with a detection limit of (0.255 ± 0.005) µM for the Ba_1.0Co_1.22Fe_11.41O_18.11 GCE, (0.577 ± 0.007) µM for the Ba_1.14Cu_0.82Fe_11.65O_18.02 GCE, and (0.595 ± 0.008) µM for the bare GCE. The levels of NAP in a real sample of urine were quantitatively analyzed using the proposed method, with recovery ranges from 96.6% to 101.0% and 93.9% to 98.4% for the modified electrode with Cobalt-substituted barium hexaferrites (CoF_M) and Copper-substituted barium hexaferrites (CuF_M), respectively. These results confirm the high electrochemical activity of Ba_1.0Co_1.22Fe_11.41O_18.11 nanoparticles and thus their potential for use in the development of sensing devices for substances of pharmaceutical interest, such as acetaminophen (NAP).     

Controlled pinewood fractionation with supercritical ethanol: A prerequisite toward pinewood conversion into chemicals and biofuels

The objective of this work was to investigate the ability of supercritical (SC) ethanol conditions to attack preferentially the lignin fraction against the carbohydrate fraction and their effects on the product distribution among gases, light products, bio-oils, and chars. In this study, the conversion of each pinewood component was determined by the analysis of solid residues to quantify cellulose, hemicellulose, lignin, and char contents. It is shown that, by tuning the temperature, hemicellulose and lignin are already transformed in subcritical ethanol conditions, lignin being more reactive than hemicellulose. In contrast, native wood cellulose is recalcitrant to liquefaction in SC ethanol near the critical point (T_c = 241 °C and P_c = 61 bar), but 20% of native wood cellulose is converted in SC ethanol at 280 °C. Besides, the severity of the conditions, in terms of temperature and treatment time, does not significantly influence the yields of gases, light products, and bio-oils but strongly enhances char formation. Interestingly, the increase in SC ethanol density does not change the conversion of biomass components but has a marked effect on bio-oil yield and prevents char formation. The optimum fractionation conditions to convert the lignin component, while keeping unattacked the cellulose fraction with a minimum formation of char, are dense SC ethanol, at 250 °C for 1 h, in batch conditions. However, although lignin is more reactive than hemicellulose under these conditions, these fractions are converted, in a parallel way, to around 50% and 60%, respectively.     

Bi2O3/FAp,a sustainable catalyst for synthesis of dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives through green strategy

The bismuth loaded on fluorapatite (Bi₂O₃/FAp) proved to be an excellent catalyst for the synthesis of novel dihydro-[1,2,4]triazolo[1,5-a]pyrimidine derivatives via a three-component reaction involving the mixture of 1H-1,2,4-triazol-5-amine, ethyl cyanoacetate or ethyl acetoacetate, and different benzaldehydes in ethanol at room temperature. The catalyst material was characterized by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis, Fourier-transform infrared, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy techniques. The efficacy of Bi₂O₃/FAp as a heterogeneous catalyst was evaluated with the loading of different wt% of bismuth on FAp. The 2.5% bismuth on FAp performed extremely well as a catalyst with a high yield of products (92%–96%) in a short reaction time (25–35 min). The catalyst was recovered by simple filtration. It showed undiminished activity up to five runs. Simple work-up, room temperature reaction, short reaction time, high yields, no column chromatography, and good reusability of catalyst are the merits of the proposed protocol. In addition, this process offers 100% carbon efficiency and 98% atom economy with noteworthy fiscal and environmental benefits.