正戊烷与SO2气相光化学反应自由基机理的ESR验证

烷烃与SO2的气相光化学作用为自由基反应[1].Penzhorn等[2]对C4以下的气相烷烃与SO2光化学反应产物的复杂性和多样性进行了推测,此后对该光化学反应机理的研究均以反应产物(特别是凝聚态产物)为基础进行的[3].为验证烷烃与SO2光化学反应体系中确实存在自由基,Makarov等[4]向正戊烷与SOz光化学反应体系中引入NO,通过对反应起始阶段的产物的光谱分析和反应动力学研究,论证了该反应的自由基过程.ESR技术是检测自由基的有效方法,Stokes等[5]利用自旋捕集-ESR技术成功地测得了气相羟基自由基的存在.     

用吹扫捕集-热脱附-气相色谱-质谱法分析生活污水中挥发性有机物

介绍了用于分析生活污水中挥发性有机物的方法,分析物以吹扫捕集法取样,混合吸附剂富集,然后热脱附-气相色谱分析.混合吸附剂是由TenaxGC和活性炭组成,二者体积比为2∶1.对吹扫捕集流速和捕集时间进行了优化,并测定了标准分析物的回收率.利用该法,从生活污水中检出37种挥发性有机物,其中8种列在我国环境优先污染物名单中.     

基于壳层隔绝纳米粒子和在线裂解-吹扫捕集的血液氰化物表面增强拉曼光谱快速检测方法

建立了一种快速、简便的基于壳层隔绝纳米粒子和在线裂解捕集技术的血液氰化物表面增强拉曼光谱(SERS)检测方法.构建了新型在线裂解-吹扫捕集装置,通过浓H2SO4酸化,将全血中结合态氰化物裂解,并转化为挥发性的HCN气体,经N2吹扫至碱液中形成NaCN,实现了中毒血液中氰化物的高效裂解与捕集;在强碱性条件下,以壳层隔绝金纳米粒子为基底,极大地削弱了氰化物的溶金效应,使得检测信号稳定,存在时间由普通金纳米粒子的5 min提高至1 h;方法检出限达10 μg/L,线性范围为100~2000 μg/L.将此方法应用于氰化物染毒大鼠及真实氰化物中毒患者全血的快速检测,为氰化物中毒快速检测提供了一种灵敏、特异、可靠的新方法.     

离子交换树脂优化生物柴油中金属离子含量的研究

本研究旨在利用离子交换树脂优化降低小桐子油生物柴油中的金属离子含量。利用GCMS测量了小桐子油生物柴油经离子交换树脂捕集前后成分变化,并研究了离子交换树脂在不同油酸含量、不同氧化程度的小桐子油生物柴油对K~+、Ca~(2+)、Na~+和Mg~(2+)等金属离子的捕集效率。结果证明,离子交换树脂可有效降低小桐子油生物柴油中金属离子含量且不会产生对环境及人体有害的物质;小桐子油生物柴油油酸含量和氧化程度的增加,可促进离子交换树脂对生物柴油中Na~+和K~+的捕集,同时抑制离子交换树脂对生物柴油中Ca~(2+)和Mg~(2+)的捕集。     

氨水捕集模拟烟气中二氧化碳的实验与理论研究

介绍了氨水捕集CO₂的反应原理, 利用鼓泡反应器开展了氨水碳捕集实验研究. 研究了氨水浓度、CO₂浓度、温度等因素对脱除效率的影响. 研究发现, 提高氨水质量分数和pH值均可增大CO₂脱除效率|增大CO₂浓度和入口气体流量后脱除效率呈现下降趋势|最佳脱除温度为45 ℃. 红外光谱分析表明, 氨水吸收后的主要成分是碳酸氢铵. 研究结果对进一步开展氨法捕集CO₂研究有较大的参考价值.     

离子液体的制备及应用*

离子液体由于具有独特的物理化学性质而成为一种新型的绿色溶剂,近年来成为国际上研究的前沿和热点。它为开发新型绿色工艺、实现传统重污染、高能耗工业过程的升级换代提供了新机遇。本文介绍了离子液体的合成与制备方法,以及离子液体在CO2捕集分离及转化利用、电解/电镀铝、SO2吸收、废水处理以及废旧塑料降解循环利用中的应用,展望了离子液体的发展前景。     

以离子液体为介质的H_2S捕集与转化研究进展

从能源气中脱除硫化氢(H_2S)是能源化工的基础工艺,具有重要的科学和现实意义.离子液体是一类在室温附近呈液态的有机熔融盐,可用作捕集H_2S的新型介质.综合国内外学者和本课题组在该领域内的多年研究积累,本文介绍了H_2S在离子液体中的捕集和转化研究进展,讨论了捕集与转化流程工艺,并分析了当前离子液体用于H_2S捕集与转化的发展趋势.     

静态和动态收集与富集挥发性有机物的方法在法医中的应用

引言捕集和富集挥发性化合物近来已成为制备试样的一种标准方法,但很少用以取得法庭物证。在文献报导的几乎所有应用中,都是将小量挥发性化合物捕集在过量的吸附剂上,但在物证中挥发物的量很容易超过吸附剂的容量,使试样失去代表性。法庭分析工作者可以根据由下列四个参数的排列组合而得到的十六种情况来设计、使用和评价试样中挥发物的富集方法: 1.试样是由动态的“吹洗和捕集”还是由静态扩散来富集? 2.吸附剂容量是否足以定量捕集所有挥发性化合物?     

基于MEA的CO_2相变化吸收剂的开发

化学吸收法是碳捕集技术中最为成熟的技术之一,单乙醇胺(MEA)是最常用的化学吸收剂.然而由于MEA的解吸能耗较高,造成CO_2捕集成本居高不下.本文提出了一种利用盐析效应开发新型CO_2相变化吸收剂的方法,并开发了吸收剂组成为"MEA+叔丁醇+水"的新型CO_2相变化吸收剂.实验考察了不同配比下吸收剂的分相情况、循环负载量以及吸收剂的物理性质,并用气相容积法测定了40℃、0～0.5 MPa下,CO_2在相变化吸收剂中的溶解度.研究表明,MEA/叔丁醇相变化吸收剂的循环负载量最高为2.84 mol CO_2/kg,相比于30%MEA水溶液提高了40%,进入解吸塔的吸收剂体积降低了65%,有望大幅降低CO_2捕集能耗.     

简易吹扫-捕集装置在化学实验教学中的适用性探讨

在测定水中微量的挥发性有机物时,常利用吹扫-捕集技术对水样进行预处理,以浓缩分离待测物质,使其达到后续分析仪器的检测限值。吹扫-捕集装置通常价格昂贵,难以在分析化学、环境监测等实验教学中普遍配备。介绍了一套经过改造的简易吹扫-捕集装置,用以展示其工作原理。改造后的吹扫-捕集装置以低温有机溶剂捕集代替了原常规装置中的吸附剂捕集,简化了实验流程。对水中甲基叔丁基醚（MTBE）的预处理实验结果表明,该装置操作简单,原理展示清晰,实验数据相对精确,可有效加强学生对吹扫-捕集技术的理解。     

硫中毒对Cu/γ-Al_2O_3催化含硫低浓度甲烷燃烧特性的影响

采用浸渍法制备了质量分数11.32%Cu/γ-Al2O3催化剂,采用固定床反应器,考察了SO2浓度(0~0.02%)对低浓度甲烷(体积分数,3%)催化燃烧特性的影响,通过反应前后催化剂的微观结构及化学成分检测,结合理论分析,探讨了催化反应的硫中毒原因。研究表明,SO2的通入导致了Cu/γ-Al2O3催化剂活性及稳定性的降低,在同一反应温度下,甲烷转化率随着SO2浓度的增加而下降。SEM、EDS、FT-IR、XRD表征结果表明,SO2会导致Cu/γ-Al2O3催化剂表面出现结块现象,催化剂表面有硫元素的累积,且以硫酸盐的形式存在,其主要成分为硫酸铜(CuSO4)。在富氧条件下,SO2分子及氧离子在Cu2+上吸附所形成的硫酸铜,附着在催化剂表面,形成一层坚硬的外壳,是产生硫中毒现象的根本原因。     

均相催化CO2/H2还原羰基化合成高值化学品研究进展

The efficient utilization of the greenhouse gas CO₂ as a C1 feedstock can effectively reduce its emission and create economic value. Hence, the efficient chemical conversion of CO₂ has been receiving intense attention. Due to the extremely low energy level of the CO₂ molecule, the high energy barrier is the primary challenge for the chemical conversion of CO₂. The chemical conversion of CO₂ is mainly carried out through non-reductive transformation in industrial. Yet, the new route of chemical synthesis based on CO₂ reductive transformation is an interesting topic to expand its resource utilization. In this context, homogeneous reductive carbonylation is a hot topic for the utilization of CO₂ via reductive transformation. In this process, the metal hydride intermediate derived from the activation of the hydrogen source is crucial to the CO₂ reduction. Hydrogen, a clean source with high atom economy, can be used as a reducing agent for the reductive conversion of inert CO₂ through carbonylation, to construct C―O, C―N, and C―C bonds and to synthesize aldehyde/alcohol, carboxylic acid, ester, amide, and other chemicals. These expand the scope of CO₂ high-value utilization and show great potential application in terms of resource utilization and environmental protection. This CO₂ utilization process is thought to involve cascading catalytic reactions of CO₂ reduction and carbonylation. The catalytic systems require the corresponding catalysts to efficiently promote each step and effectively inhibit undesired side reactions. Recently, considerable progress has been made in the homogeneous reductive carbonylation of CO₂ with H₂. However, this kind of reaction is mostly of the cascade type, and hence, requires harsh conditions and noble metal catalysts. The chemoselectivity is low because of the multiple competing reactions. In addition, due to the steric hindrance and electronic effects of the substrate, there are limitations on the types of substrates that can be employed. With the development of new characterization techniques and theoretical calculations, some progress has been made in revealing the reaction mechanism and in the activation of the carbon-oxygen bonds of CO₂. Therefore, there is an urgent need to develop a more efficient catalytic system that requires mild conditions for reductive carbonylation. In this review, we provide an overview of the groundbreaking studies and the recent breakthroughs that have demonstrated the potential of metal catalysts to utilize the combination of CO₂ and H₂ as a C1 synthon, including olefin carbonylation, amine carbonylation, and alcohol/ether carbonylation, while highlighting the effect of different types of metal catalysts on the reaction. We conclude with a perspective on the future prospects of the homogeneous reductive carbonylation of CO₂ with H₂, providing readers a snapshot of this rapidly evolving field.     

离子液体介导CO2化学转化研究进展

The efficient utilization of carbon dioxide (CO₂) as a C1 feedstock is of great significance for green and sustainable development. Therefore, the efficient chemical conversion of CO₂ into value-added products has recently attracted a lot of research attention in recent years. The transformation of CO₂ generally requires high-energy substrates, specific catalysts, and harsh reaction conditions due to its high thermodynamic stability and kinetic inertness. Consequently, several efforts have been dedicated toward the development of high-performance catalysts and new reaction routes for CO₂ conversion over the last few decades. To date, many routes of convert CO₂ into value-added chemicals have been proposed, together with the development of heterogeneous and homogeneous catalysts. Among the advanced catalysts reported to date, ionic liquids (ILs) have been widely investigated and show great potential for the efficient, selective, and economical conversion of CO₂ into highly valuable products under mild conditions, even under ambient conditions. Some task-specific ILs have been designed with unique functional groups (e.g., —OH, —SO₃H, —NH₂, —COOH, and —C≡N), which can act as the solvent, absorbent, activating agent, catalyst, or cocatalyst to realize the transformation of CO₂ under metal-free and mild conditions. In addition, a variety of catalytic systems composed of ILs and metal catalysts have also been reported for the transformation of CO₂, in which the combination of the IL and metal catalyst is responsible for CO₂ conversion with high efficiency. In this review article, we summarize the recent advances in IL-mediated CO₂ transformation into chemicals prepared via C—O, C—N, C—S, C—H, and C—C bond forming processes. ILs that can chemically capture CO₂ with high capacity are first introduced, which can activate CO₂ via the formation of IL-based carbonates or carbamates, thus realizing the transformation of CO₂ under metal-free and mild conditions. Recent progress in IL-mediated CO₂ transformations to form carbonates and various kinds of N- and S-containing compounds (e.g., oxazolidinones, ureas, benzimidazolones, formamides, methylamines, benzothiazoles, and other chemicals) as well as CO₂ hydrogenation to give formic acid, methane, acetic acid, low-carbon alcohols, and hydrocarbons has been summarized in this review with a focus on the reaction routes, catalytic systems, and reaction mechanism. In these reactions, ILs can simultaneously activate the substrate via strong H-bonding in addition to activating CO₂, and the cooperative effects among the ionic and molecular species and metal catalysts accomplish the reactions of CO₂ with various kinds of substrates to afford a wide range of value-added chemicals. Finally, the shortcomings and perspectives of ILs are discussed. In short, IL-mediated CO₂ transformations provide green and effective routes for the synthesis of high-value chemicals, which may have great potential for a wide range of applications.     

微波条件下固体酸催化剂催化酯化生物油的研究

以乙醇和乙酸的酯化作为反应模型,考察固体酸催化剂阳离子交换树脂、SO₄²-/ZrO₂和分子筛在微波加热条件下的酯化活性。结果表明,三类固体酸催化剂的活性顺序为Amberlite树脂﹥SO₄²-/ZrO₂﹥HZSM-5,催化剂活性与酸度一致;酯化反应中水的含量对催化剂的活性有不同程度的影响,水含量较高时催化剂SO₄²-/ZrO₂酯化活性明显变差,而阳离子交换树脂仍具有较高的酯化活性。采用阳离子交换树脂对生物油进行微波催化酯化提质后,原生物油中含有的大量不同种类的羧酸被有效地转化成各种酯类,酯类化合物由原油中的4种增加到13种。与传统加热条件下生物油催化提质比较,生物油微波提质具有明显优势,提质后生物油组分得到优化。     

平板式V_2O_5-MoO_3/TiO_2型SCR催化剂的中低温脱硝和抗中毒性能研究

针对中低温锅炉烟气脱硝技术需求的特点,采用等体积浸渍法,以V_2O_5为活性组分、MoO_3为助剂,制备了高钒高钼含量的V_2O_5-MoO_3/TiO_2型粉末和平板式SCR脱硝催化剂,考察了活性组分和助剂含量对催化剂活性以及抗SO_2和H_2O中毒性能的影响,对反应前后的催化剂进行了微观表征,并针对最优催化剂研究了其在不同烟气工况下催化剂的脱硝性能。结果表明,提升V_2O_5负载量可以有效提高催化剂的脱硝活性;MoO_3助剂的添加也可以提高催化剂的脱硝活性。XPS、XRF、FTIR等表征结果表明,MoO_3的含量会影响催化剂中V~(4+)/V~(5+)的比值,其相对含量的增加有利于催化剂中非化学计量钒物种的形成以及化学吸附氧比例的增加,钼与钒物种间的交互作用是抑制SO_2和H_2O对催化剂的毒化作用的关键。3V_2O_5-10MoO_3/TiO_2平板式催化剂在温度为200℃、空速为3 500 h~(-1)含SO_2和H_2O烟气条件下,经30 d连续反应,脱硝效率稳定维持在82%左右,该催化剂在中低温下具有优异的抗SO_2和H_2O中毒性能以及稳定性。     

NO reduction and CO oxidation over Cu/Ce/Mg/Al mixed oxide catalyst in FCC operation

Simultaneous NO reduction and CO oxidation in the presence of O₂, H₂O and SO₂ over Cu/Mg/Al/O (Cu-cat), Ce/Mg/Al/O (Ce-cat) and Cu/Ce/Mg/Al/O (CuCe-cat) were studied. At low temperatures (<340 °C), the presence of O₂ or H₂O enhanced the activity of CuCe-cat for NO and CO conversions, but significantly suppressed the activity of Cu-cat and Ce-cat. At high temperature (720 °C), the presence of O₂ or H₂O had no adverse effect on the NO and CO conversions over these catalysts. The addition of SO₂ to NO+CO+O₂+H₂O system had no effect on the reaction of CO+O₂ over Cu-cat, but deactivated this catalyst for NO+CO and CO+H₂O reactions; over Ce-cat, all of these reactions of NO+CO,CO+O₂ and CO+H₂O were suppressed significantly; over CuCe-cat, NO+CO and CO+O₂ reactions were not affected while the reaction of CO+H₂O was slightly inhibited.     

The isothermal sulphation reactions of natural sorbents

The chemical reaction between sulphur dioxide and calcined limestone and dolomite particles was investigated using a thermogravimetric analyser. The samples used in this study originated from different parts of Turkey. Sulphation reactions were conducted under isothermal conditions in a gaseous mixture consisting of 15 vol% CO₂, 0.35 vol% SO₂ and a balance of dry air by volume. Before sulphation all samples were completely calcined in a gaseous atmosphere of 15 vol% CO₂ and 85 vol% dry air. It was observed that the sulphation reactions of samples are very rapid in their initial stage but after some reaction time, which varies depending on sample properties and temperature, the reaction rates quickly slow down. Also, the conversion-time results of sulphation experiments showed variations depending on the sulphation temperature, sorbent type and the physical properties of calcines.     

改性活性炭纤维可见光催化联合脱硫脱硝的研究

利用水合肼还原法制备的TiO₂/Cu₂O复合光催化剂对活性炭纤维(ACF)进行改性,利用SEM、XPS、BET以及XRD对其进行表征,研究改性后ACF的性质及其脱硫脱硝效果。研究表明,TiO₂/Cu₂O同时改性后的ACF表面孔径减小,但表面石墨碳和羰基(C=O)官能团增加,增强了ACF对NO和SO₂的吸附能力,从而提高了脱硫脱硝的效率,该催化剂在40℃、可见光的催化下脱硫效率达90%,脱硝效率达60%。     

CeTiOx脱硝催化剂的抗硫中毒性能

分别以Ce₂(C₂O₄)₃和Ce(SO₄)₂为Ce前驱体, 采用固相球磨法制备了Ce基选择性催化还原(SCR)脱硝催化剂CeTiO_x-A[以Ce₂(C₂O₄)₃为前驱体]和CeTiO_x-B[以Ce(SO₄)₂为前驱体]. 将2个催化剂分别在体积分数为0.15%的SO₂的气氛下反应40和60 h, 得到高硫条件下SCR反应后的CeTiO_x催化剂, 分别记为40CeTiO_x-A, 60CeTiO_x-A, 40CeTiO_x-B和60CeTiO_x-B. 考察了反应前后催化剂的NH₃-SCR反应活性. 采用X射线衍射(XRD)、 X射线荧光光谱(XRF)、 比表面积(BET)测试、 H₂程序升温还原(H₂-TPR)、 X射线光电子能谱(XPS)、 NH₃程序升温脱附(NH₃-TPD)及SO₂程序升温脱附(SO₂-TPD)等技术对样品进行了表征. 结果表明, CeTiO_x-A系列催化剂比CeTiO_x-B系列催化剂具有更高的NH₃-SCR反应活性和更好的抗硫抗水性能. 与CeTiO_x-B系列催化剂相比, CeTiO_x-A系列催化剂具有更大的比表面积和孔容, 更多的Ce³⁺和吸附氧(O_α)物种有助于NO的吸附和活化; CeTiO_x-A系统催化剂还具有更多的Lewis强酸性位数量, 可以吸附更多的NH₃分子, 有利于催化剂上NH₃-SCR反应的进行, 提高了CeTiO_x-A系列催化剂的NO转化率.     

Effects of SO2 Treatment of Commercial Catalysts on Selective Catalytic Reduction of NOx by NH3

Nitrogen oxide(NO_x) emitted from stationary and mobile sources is a major air pollutant. Selective catalytic reduction(SCR) of NO_x over a catalyst is a main technology for NO_x elimination. Catalysts used for practical applications would be deactivated in flue containing SO₂. In this work, three typical commercial catalysts were investigated before and after SO₂ treatment. The catalysts were characterized by X-ray diffraction(XRD), X-ray fluorescene(XRF), temperature programme reduction(TPR), temperature programme desorption(TPD) and diffuse reflectance Fourier transform infrared(DRIFT) techniques. Results showed that SO₂ treatment significantly influenced the performance of V₂O₅/TiO₂ catalyst. The amount of V₂O₅ in the catalyst primarily affected the accumulation of sulfur species in the SO₂atmosphere. The performance of catalysts with small amounts of V₂O₅ could be improved under the same experimental conditions for acidity enhancement.