Controlling selectivity in catalysis: Selective greener oxidation of cyclohexene under microwave conditions

A smart and greener microwave approach to the selective oxidation of cyclohexene is reported whereby, depending on the reaction conditions, the epoxide (65% conversion, 75% selectivity), the enol (70% conversion, 80% selectivity) or the enone (>99% conversion, 89% selectivity) can be obtained in a short period of time ranging from 1 to 20 min. A cobalt-salen-SBA-15 material was employed as catalyst. The reported solventless microwave protocol was simple, greener and more efficient compared to any other reported cyclohexene oxidations.     

Etching characteristics of Al2O3 thin films in inductively coupled BCl3/Ar plasma

The investigation of Al₂O₃ etch characteristics in the BCl₃/Ar inductively coupled plasma was carried out in terms of effects of input process parameters (gas pressure, input power, bias power) on etch rate and etch selectivity over poly-Si and photoresist. It was found that, with the changes in gas pressure and input power, the Al₂O₃ etch rate follows the behavior of ion current density while the process rate is noticeably contributed by the chemical etch pathway. The influence of input power on the etch threshold may be connected with the concurrence of chemical and physical etch pathways in ion-assisted chemical reaction.     

催化汽油选择性加氢技术现状及进展

在阐述催化汽油加氢技术的原理后介绍了国内外该技术的现状以及部分工艺,重点介绍了Gardes工艺技术.通过分析对比后发现Gardes工艺技术有以下特点:较高脱硫活性和辛烷值保持能力、整个工艺流程较其他工艺简单,加氢产物直接调和.预计Gardes工艺将成为今后国内生产清洁汽油的主要工艺.     

涤纶织物渗透碱减量工艺的探讨

本文主要介绍适宜在ＹＨ４００、６００、８００型液汉式自动碱减量机上进行涤纶织物渗透碱减量加工工艺。通过对桃皮绒、卡丹绒、水洗绒、华达呢等１０种织物的碱减量试验，筛选了适应涤纶减量的渗透剂，获得了各种织物碱减量试验数据，以指导实际生产。     

纯棉及棉／亚麻交织布前处理工艺的探索

本文对纯棉及棉／亚麻交织布实施高效短流程前处理工艺进行了讨论，采用正交设计法从６只国产稳定剂中优选出新型高效的非硅双氧水漂白稳定剂ＡＲ－７５０，并在不同前处理设备上进行生产性应用试验，获得了理想的结果。     

Attainable regions of reactive distillation—Part III. Complex reaction scheme: Van de Vusse reaction

The main underlying principle behind the application of reactive distillation (RD) for selectivity enhancement is to facilitate the separation of selected components and favorably manipulate the composition profiles in the reactive zone to expedite the desired reaction. In this paper, a geometric approach of attainable region (AR), which is already developed for conventional reactor network, is extended further to include few representative RD configurations. We define new RD building blocks and the corresponding composition vectors that indicate a need of networking of RD units among themselves and with conventional reactors to enlarge the set of attainable compositions. A model reaction scheme of van de Vusse type ) is studied as an illustrative example and an algorithm is developed to obtain the attainable region for the given kinetics, feed composition and relative volatilities. In almost all the different cases, which are studied by varying the kinetics and volatility pattern, network consisting of RD units performs better than the conventional reactor network.     

Proton conducting hydrocarbon membranes: Performance evaluation for room temperature direct methanol fuel cells

The methanol permeability, proton conductivity, water uptake and power densities of direct methanol fuel cells (DMFCs) at room temperature are reported for sulfonated hydrocarbon (sHC) and perfluorinated (PFSA) membranes from Fumatech^®, and compared to Nafion^® membranes. The sHC membranes exhibit lower proton conductivity (25–40 mS cm⁻¹ vs. ∼95–40 mS cm⁻¹ for Nafion^®) as well as lower methanol permeability (1.8–3.9 × 10⁻⁷ cm² s⁻¹ vs. 2.4–3.4 × 10⁻⁶ cm² s⁻¹ for Nafion^®). Water uptake was similar for all membranes (18–25 wt%), except for the PFSA membrane (14 wt%). Methanol uptake varied from 67 wt% for Nafion^® to 17 wt% for PFSA. The power density of Nafion^® in DMFCs at room temperature decreases with membrane thickness from 26 mW cm⁻² for Nafion^® 117 to 12.5 mW cm⁻² for Nafion^® 112. The maximum power density of the Fumatech^® membranes ranges from 4 to 13 mW cm⁻¹. Conventional transport parameters such as membrane selectivity fail to predict membrane performance in DMFCs. Reliable and easily interpretable results are obtained when the power density is plotted as a function of the transport factor (TF), which is the product of proton concentration in the swollen membrane and the methanol flux. At low TF values, cell performance is limited by low proton conductivity, whereas at high TF values it decreases due to methanol crossover. The highest maximum power density corresponds to intermediate values of TF.     

Effective removal of Fe(II) impurity from rare earth solution using surface imprinted polymer

Rare earth is a very important resource. But, impurities, such as Fe²⁺, have great influence on the properties of rare earth material. In this paper, a novel Fe²⁺-ionic imprinted polyamine functionalized silica gel adsorbent was prepared by a surface imprinting technique for selective adsorption of Fe²⁺ from rare earth solution. Firstly, functional macromolecule polyethyleneimine (PEI) was grafted onto the surfaces of silica gel particles, and the PEI/SiO₂ was formed. Secondly, the ionic imprinting process was carried out using Fe²⁺ ion as a template, and Cr³⁺ ionic imprinting polyamine IIP-PEI/SiO₂ was prepared. The adsorption and recognition properties of IIP-PEI/SiO₂ for Fe²⁺ were studied in detail, and the effects of main imprinting conditions, such as the amount of crosslinking agent and reaction time, on the adsorption property of the imprinted material IIP-PEI/SiO₂ were examined. The experimental results showed that the IIP-PEI/SiO₂ possesses strong adsorption affinity, specific recognition ability, and excellent selectivity for Fe²⁺. The adsorption capacity could reach to 0.334 mmol g⁻¹, and relative selectivity coefficients to Pr³⁺ and Ce³⁺ are 23.25 and 18.42, respectively. Besides, the IIP-PEI/SiO₂ was regenerated easily using diluted hydrochloric acid solution as eluent and IIP-PEI/SiO₂ possesses better reusability.     

Standard Reference Materials (SRMs) for the Determination of Polycyclic Aromatic Compounds--Twenty Years of Progress

In 1981 the National Bureau of Standards, now the National Institute of Standards and Technology (NIST), issued the first natural matrix Standard Reference Material (SRM) for the determination of polycyclic aromatic compounds (PACs), SRM 1580 Organics in Shale Oil. In the next 10 years, additional natural matrix SRMs were developed including air and diesel particulate matter, petroleum crude oil, coal tar, sediment, and mussel tissue. The SRMs represented the "first generation" of natural matrix SRMs for the determination of PACs. The SRMs had "certified" values for only 5 to 12 PACs; however, their development established the foundation for the implementation of the "two or more independent analytical techniques" approach for certification of individual PACs in environmental matrices. The requirement for use of different analytical techniques spurred the development of both gas chromatography (GC) and liquid chromatography (LC) approaches for the determination of PACs. Since the mid-1990s, the "second generation" of natural matrix SRMs has been issued by NIST with certified values for over 20 PACs in each material. The greater number of certified values in these SRMs was the result of the combination of measurements using reversed-phase LC with fluorescence detection, multidimensional LC, and GC with mass spectrometric detection using two or more stationary phases with different selectivity for polycyclic aromatic hydrocarbon (PAH) separations. This article discusses the significant developments in analytical methods and chromatographic separation of PAHs during the past 20 years that have resulted in the certification of over 25 SRMs, which are now used worldwide for the validation of analytical methods for the measurement of PACs in environmental matrices.     

Recent advances on ion-imprinted polymers

Selective recognition of metal ions is a real challenge for a large range of applications in the analytical field (from extraction to detection and quantification). For that purpose, ion-imprinted polymers (IIPs) have been increasingly developed during the last 15 years on the principle of molecularly imprinted polymers (MIPs). Those imprinted materials are designed to mimic the binding sites of biological entities and assure an improved recognition of the template species. The aim of this review is to give the current state of the art in the conception of IIPs from the components to the polymerization process. Some applications of those materials will be also discussed.