石脑油中有机氯脱除的研究进展

石脑油中有机氯的脱除作为行业难题之一,国内外进行了大量有机氯脱除技术研究。现有有机氯脱除技术有吸附、催化加氢、萃取脱氯、微生物脱氯等,这些方法各有优缺点,但大部分技术处于实验室研究阶段,尚未实现工业化。本文综述了石脑油中有机氯化物的来源、危害,重点分析了吸附法、催化加氢法等有机氯脱除方法的反应机理和研究现状,并提出目前存在的问题及未来的研究方向。     

城市生活垃圾焚烧体系化学热力学平衡分析

采用化学热力学平衡分析方法，分析城市生活垃圾焚烧体系污染物的排放特性。主要计算了聚氯乙烯（PVC）及典型城市垃圾焚烧过程氯元素的化学平衡组成及其浓度，同时研究了脱氯剂对PVC及垃圾中氯转化的影响。计算结果表明，PVC热态反应的主要产物是HCl气体，在加入脱氯剂后温度低于600℃时，脱氯剂对HCl的脱除作用很明显；城市生活垃圾热解和燃烧过程中在温度超过600 ℃，垃圾中的有机氯和无机氯都将转化为HCl气体，而此时脱氯剂失去效果。由计算结果得到控制HCl生成，消除二口恶英污染物的生成反应工艺条件。     

煤中氯在亚临界水条件下的变迁

运用半连续反应装置对山西吴家坪煤和四川华蓥山煤中氯在亚临界水条件下的脱除规律及形态变化进行了研究。考察了反应温度和压力对氯脱除率的影响；同时还运用化学提取法对原煤及残渣中氯的形态进行了研究。研究结果表明,随着反应温度的升高，煤中氯的脱除率也增加，在410℃、15MPa、60min、水流量为580mL/h时，吴家坪煤中氯的脱除率为84.6%，华蓥山煤中氯的脱除率为72.4%。吴家坪煤中氯在15MPa时的脱除率最大。华蓥山煤中氯主要以有机氯的形态存在，而吴家坪煤中氯有8%为离子可交换态的无机氯，其余为有机结合的氯；在亚临界水萃取煤的过程中，离子交换态结合的有机氯比共价键结合的有机氯更容易挥发,有机氯要首先转化为无机氯然后再逸出。     

高温煤气净化高效脱氯剂的研究

在固定床反应器中对四种高温煤气脱氯剂进行了筛选研究。在５５０℃温度下,所有被测试的脱氯剂都能迅速与ＨＣｌ气体发生反应,在反应开始的一段时间同都能使混合气体中的ＨＣｌ从０．１％降低到０．０００１％以下。在相同的反应条件下,ＣＮ１脱氯剂具有最高的穿透时间,穿透氯容量和饱和氯容量。在３００￣７００℃之间,温度越高,ＣＮ１脱氯剂吸收氯容量越高,反应性越好,在高空速下,脱氯剂脱氯效果明显下降。     

二噁(英)降解方法的研究

二噁是一类剧毒有机氯化物 ,已被联合国环境署和世界卫生组织列为持久性有机污染物和一级致癌物质 ,能够对环境和人类的健康造成重大危害。脱氯降解是降低二毒性的有效途径。本文对二的光降解、热降解、生物降解和化学降解脱氯作了详尽的评述 ,比较了各种降解方法的优劣 ,指出多相催化加氢脱氯降解方法将是今后的发展方向     

二噁(英)降解方法的研究

二噁(左口右英)是一类剧毒有机氯化物,已被联合国环境署和世界卫生组织列为持久性有机污染物和一级致癌物质,能够对环境和人类的健康造成重大危害.脱氯降解是降低二噁毒性的有效途径.本文对二噁的光降解、热降解、生物降解和化学降解脱氯作了详尽的评述,比较了各种降解方法的优劣,指出多相催化加氢脱氯降解方法将是今后的发展方向.     

纳米Fe0降解2,4-二氯酚的影响因素及其机理

采用化学还原法制备了纳米Fe⁰, 并研究了不同条件下纳米Fe⁰对2,4-二氯酚(2,4-DCP)的降解情况, 探讨了纳米Fe⁰降解2,4-二氯酚的反应途径. 结果表明, 纳米Fe⁰对2,4-二氯酚的去除作用包括吸附、脱氯、开环三种机制. 其中脱氯作用是一种界面反应, 发生在氯酚分子被吸附到Fe原子表面之后. 2,4-二氯酚可以脱去一个氯原子生成2-氯酚或4-氯酚, 也可以脱去两个氯原子生成苯酚. 随着氯酚初始浓度的增大, 其相对去除率略有降低, 但绝对降解量有较大提高. 温度不仅影响脱氯速率, 而且影响氯酚的去除途径. 温度较高时脱氯作用占主导地位, 先脱氯后开环, 温度较低时吸附作用占主导地位, 较易发生先开环后脱氯的情况.     

盐酸多西环素的合成新方法

盐酸多西环素为重要的人兽两用药，其生产过程中的脱氯和不对称氢化反应对产品的收率和质量有重要影响。以11α-氯代甲烯土霉素为起始原料，自制钯炭为催化剂，经脱氯、氢化和转盐3步反应合成了盐酸多西环素，总收率达58.4%，其结构经¹H NMR确证。     

氯对钌基氨合成催化剂的影响

氯离子的脱除是制备高性能钌催化剂的一个重要步骤。本文综述了新型钌基氨合成催化剂制备过程中的脱氯环节。介绍了以RuCl₃·3H₂O作为活性前驱体的钌催化剂中氯离子的来源、氯在催化剂中的存在方式、它对催化剂的毒害作用以及去除氯离子的方法。     

纳米级Pd/Fe双金属体系对水中2,4-二氯苯酚脱氯的催化作用

 利用化学沉淀法制备了纳米级Fe和纳米级Pd/Fe双金属催化剂,研究了它们对2,4-二氯苯酚(2,4-DCP)还原脱氯的催化性能. 结果表明,纳米级颗粒具有较高的比表面积和表面反应活性,其BET比表面积可达12.4 m2/g,当Pd/Fe用量为6 g/L时,2,4-DCP脱氯率达到90%以上. 脱氯效率与pH值、温度、钯含量和Pd/Fe投加量等因素有关. 2,4-DCP在脱氯过程中先生成2-氯苯酚和4-氯苯酚,最终生成苯酚,而少量的2,4-DCP可直接降解成苯酚.     

Liquid chromatography–high-resolution mass spectrometry for identifying aqueous chlordecone hydrate dechlorinated transformation products formed by reaction with zero-valent iron

Chlordecone (CLD) is a persistent toxic chlorinated pesticide which contaminates different ecosystems in French West Indies. A soil remediation process including zero-valent iron (ZVI) has produced promising results but failed to completely degrade CLD, and the analytical procedures used yielded little information on the transformation products. To fill these gaps, dechlorination of aqueous CLD by micrometric particles of ZVI has been investigated. Aliquots of water with 25% (v/v) of acetone spiked with 100 ppm CLD were taken at different times during a 30-day ZVI treatment and directly analysed by ultra-high-performance liquid chromatography in negative electrospray ionisation mode. CLD has been totally transformed after 14 days into 14 dechlorinated degradation products, including 9 isomeric compounds. The maximum chloride concentrations appearing in the medium represent 44% of that which would result from total dechlorination of CLD. The CLD transformation products identified by accurate mass measurements on an ultra-high-resolution Q-TOF mass spectrometer (Q-TOF-MS) were C₁₀H₃Cl₉O₂, C₁₀H₄Cl₈O₂, C₁₀H₅Cl₇O₂, C₁₀H₆Cl₆O₂ and C₁₀H₇Cl₅O₂. The results show the interest of LC-Q-TOF-MS for identifying transformation products of organic contaminants, and the effectiveness of micrometric ZVI particles to totally transform CLD into less chlorinated products.     

短链氯化石蜡分析方法

短链氯化石蜡作为一类新型持久性有机污染物已经引起全球的关注,我国是氯化石蜡第一大生产国,但对其研究还处于起步阶段。氯化石蜡组成特别复杂,其定量分析面临巨大的挑战,已成为对氯化石蜡环境存在现状、降解途径以及毒性等进一步研究的瓶颈问题。本文从环境样品的制备、净化、仪器分析以及质量保证4个方面对国际上短链氯化石蜡分析方法的研究进行了评述,针对短链氯化石蜡的分析方法同样适用于中链氯化石蜡。     

二氧化碳参与的有机化学反应*

由于对日趋严重的温室效应的担忧,对廉价二氧化碳的固定和转化成为一个非常有吸引力的研究领域。本文主要介绍了二氧化碳参与的有机化学反应,包括与环氧化合物、胺类化合物、不饱和碳氢化合物以及醇类和烃类等化合物的反应。文章分别对这几类反应的发展历程、研究现状进行了总结,重点介绍了各反应所用到的催化剂体系及有关反应机理,并展望了该领域的研究前景。     

Assessing transformation processes of organic contaminants by compound-specific stable isotope analysis

The analysis of variations in stable isotope composition is becoming an essential approach for evaluating enzymatic and abiotic reactions of organic contaminants in soils and aquatic systems. Different, sometimes complementary analytical techniques are currently used and developed to determine stable isotope ratios in individual organic compounds. Anticipating an increasing demand for compound-specific isotope analysis, this survey compiles information for choosing the most promising analytical approach to an isotope-related problem. To this end, we review the principles of instrumentation for compound-specific isotope analysis and show how they can be exploited to assess contaminant transformation processes. Using chlorinated solvents and triazine herbicides as illustrative examples, we discuss how the isotope-sensitive techniques impact the investigation of stable isotope fractionation in environmental chemistry and microbiology.     

碳氢化合物的活化及氧化理论研究*

通过理论方法研究碳氢化合物的活化及氧化,可以对不同催化剂及氧化剂的反应机理形成深刻认识,从而指导设计合成更加高效的碳氢化合物活化及氧化催化剂。本文总结了近几年在碳氢化合物的活化及氧化领域的一些新进展,涉及的底物包括从甲烷到碳原子数等于6的烃类,而催化剂及氧化剂包括有机金属化合物和无机化合物（如分子筛催化剂、金属团簇和金属氧化物等）。文章底物的碳原子数为依据进行分类编排,对每一类底物的活化及氧化介绍不同催化剂及氧化剂的反应过程,着重比较了各类催化剂及氧化剂的异同。     

Enhancement of the reductive transformation of pentachlorophenol by polycarboxylic acids at the iron oxide-water interface

The enhancement effect of polycarboxylic acids on reductive dechlorination transformation of pentachlorophenol (PCP) reacting with iron oxides was studied in anoxic suspension. Batch experiments were performed with three species of iron oxides (goethite, lepidocrocite and hematite) and four species of polycarboxylic acids (oxalate, citrate, succinate, and tartrate) through anoxic abiotic reactors. The chemical analyses and morphological observation from scanning and transmission electron microscopy showed that different combinations between polycarboxylic acids and iron oxides produced distinct contents of Fe(II)-polycarboxylic ligand complexes, which significantly enhanced PCP transformation. Generation of the surface-bound Fe(II) depended on concentration of polycarboxylic acids. The optimal concentration for the enhancement was 2.0 mM oxalic acid. The dechlorination mechanism was further demonstrated by generation of chloride ions. The results suggest that surface-bound Fe(II) formed on the iron oxides surface appears to be a key factor in enhancing PCP transformation, and the mole ratio of oxalate to surface-bound Fe(II) (oxalate/Fe(II)) acted as an indicator of the enhancement effect. The enhancement mechanism attributes to strong nucleophilic ability and low reductive potential of the equivalent Fe(II)-polycarboxylate complexes. Therefore, the enhancement effects might be helpful for understanding the natural attenuation of reducible organic pollutants at the interface of contaminated soil in anoxic condition.     

Mechanism and influence factors of 2,4-D dechlorination by sodium citrate-activated bimetallic palladium-zero valent iron nanoparticles

Nanoscale zero-valent iron (nZVI) has high removal efficiency and strong reductive ability to organic contaminants, but this reactivity soon ceases and is attributed to rapid passivation of the nZVI surface due to the formation of iron oxides. In the present study, bimetallic palladium-zero valent iron nanoparticles were activated with sodium citrate (SC-nPd/Fe) to enhance 2,4-D dechlorination from aqueous solutions. FTIR and XRD analyses showed that there was no passivation layer on the surface of nZVI after the addition of SC, and XPS analysis confirmed the nZVI after the reaction still maintained high reactivity and surface Pd ratio. The existence of SC facilitated the transfer of electrons from Fe⁰ to contaminants, thus accelerating the reductive dechlorination of 2,4-D. The dechlorination efficiency of 2,4-D on nPd/Fe was only 56.4% in 210 min, while complete dechlorination could be achieved on SC-nPd/Fe under the same conditions, and simultaneously 97.1% of phenoxyacetic acid (PA) was generated. Moreover, the effect of reaction conditions on the dechlorination such as Pd ratio, SC dosage, initial pH and temperature was also investigated, and it was well described by pseudo-first-order kinetic model. In particular, The chelating abilities of SC is similar to EDTA, but it is an environmentally-friendly chelating agent. Findings from the present study suggested that the SC could be a promising substitute for application in the remediation of 2,4-D contained water.     

Effects of exogenic chloride on oxidative degradation of chlorinated azo dye by UV-activated peroxodisulfate

Recently, the degradation of organic compounds in saline dye wastewater by sulfate radicals (SO₄⁻)-based advanced oxidation processes (AOPs) have attracted much attention. However, previous studies on these systems have selected non-chlorinated dyes as model compounds, and little is known about the transformation of chlorinated dyes in such systems. In this study, acid yellow 17 (AY-17) was selected as a model of chlorinated contaminants, and the degradation kinetics and evolution of oxidation byproducts were investigated in the UV/PDS system. AY-17 can be efficiently degraded (over 98% decolorization) under 90 min irradiation at pH 2.0–3.0, and the reaction follows pseudo-first order kinetics. Cl^‒ accelerated the degradation of AY-17, but simultaneously led to an undesirable increase of absorbable organic halogen (AOX). Several chlorinated byproducts were identified by liquid chromatography-mass spectrometry (LC–MS/MS) in the UV/PDS system. It indicates that endogenic chlorine and exogenic Cl^– reacted with SO₄⁻ to form chloride radicals, which are involved in the dechlorination and rechlorination of AY-17 and intermediates. The possible degradation mechanisms of AY-17 photooxidative degradation are proposed. This work provides valuable information for further studies on the role of exogenic chloride in the degradation of chlorinated azo dyes and the kinetic parameters in the PDS-based oxidation process.     

丙二腈在多组分反应中的应用*

丙二腈分子中的氰基作为强吸电子基团活化亚甲基,也是良好的离去基团,以及氰基的碳氮三键可进行加成反应,使得丙二腈是一种非常特别的化合物。它具有非常丰富的反应性质,可以发生Knoevenagel缩合、Michael加成、环化和消去等反应,是进行多组分合成反应的优良试剂。由其参加的多组分合成反应已经成为合成众多碳环和杂环化合物的重要方法。本文综述了丙二腈在多组分反应中的研究进展,介绍了近年来丙二腈参加的多组分反应合成环状化合物的成功事例,展望了丙二腈反应的发展方向。     

从钒化合物生物效应的多样性看其作用机制*

本文对近年来关于钒化合物不同生物效应机制的研究进展进行了总结,着重于其类胰岛素和抗癌效应的信号转导机制以及两者之间的相关性。同时,基于钒化合物对磷酸转移反应的干预以及对细胞氧化还原状态的调节,讨论了钒化合物多样化的生物效应是否具有一个共同作用机制的可能性,并提出了未来钒化合物研究方向和所面临的挑战。