异丁醇脱水制备异丁烯反应热力学

异丁醇脱水制备异丁烯是又一条增产高纯异丁烯的可行性技术路线,文章采用平衡常数法计算异丁醇脱水制备异丁烯反应过程的反应热力学数据,如标准摩尔焓变Δ_rH~■_m、标准摩尔吉布斯自由能变Δ_rG~■_m和标准平衡常数K~■_P。采用吉布斯自由能最小化法,系统探讨了反应温度、压力、稀释剂对异丁醇脱水平衡转化率和异丁烯平衡产率的影响规律。热力学平衡计算结果说明:温度高于150℃时异丁醇脱水反应平衡转化率高于99.5%,温度和压力变化对异丁烯平衡产率的影响较大,异丁醇原料含水量对异丁烯平衡产率有促进作用。以热力学角度而言,开发异丁醇脱水制备高纯异丁烯工业化技术,无需对异丁醇原料进行脱水处理,原料异丁醇中添加适量的水有利于提高异丁烯产率。     

CO气相偶联合成草酸二乙酯反应热力学分析

采用Joback基团贡献法推导了亚硝酸乙酯的摩尔定压热容与温度的关系式,并估算了亚硝酸乙酯和碳酸二乙酯的标准摩尔生成吉布斯自由能.综合物性手册中各化合物的热力学函数,计算了CO偶联合成草酸二乙酯反应中主反应和副反应的反应热、反应吉布斯自由能和平衡常数,并对此进行了分析,发现较低的反应温度有利于草酸二乙酯的生成,且主反应...     

丁烯氧化脱氢制丁二烯体系的热力学计算与分析

计算了正丁烯氧化脱氢制丁二烯体系中各反应的标准摩尔反应焓、标准摩尔吉布斯自由能、平衡常数,并利用Gibbs自由能最小法计算了反应体系的热力学平衡组成。结果表明,正丁烯的氧化脱氢与完全氧化反应在热力学上均可完全进行,但是丁二烯的产率受热力学平衡限制。因此,提高丁二烯产率的关键在于开发高性能的催化剂,从动力学上角度充分抑制COx的生成反应。     

悬浮床加氢脱硫尾气水蒸气转化制氢热力学

以悬浮床加氢脱硫尾气为水蒸气转化制氢原料,采用改进的原子序数矩阵法构建了包含6个独立反应的化学反应体系。分别考察各个独立反应在不同反应温度下,标准摩尔反应焓、吉布斯自由能变及平衡常数的变化规律;借助HYSYS流程模拟软件中的GIBBS反应器,研究反应器出口温度、反应压力及水碳物质的量之比对产物平衡组成的影响。热力学研究结果表明：烷烃碳数越高,水蒸气转化反应的平衡常数、吉布斯自由能变和标准摩尔焓对温度的敏感性越高,达到相同转化效果所需的反应温度越低。HYSYS模拟确定该体系下最适宜的反应条件为反应器出口温度700℃、反应压力100kPa、水碳物质的量之比4。     

异丙醇脱水制备丙烯反应热力学分析

采用吉布斯自由能最小化法,系统探讨了反应温度、压力、原料含水量对异丙醇脱水反应和丙烯二聚副反应的平衡转化率的影响规律。热力学平衡计算结果说明,高温、低压有利于促进异丙醇脱水生成丙烯的目标反应,同时可抑制丙烯二聚生成甲基戊烯的副反应。当反应温度高于300℃时,异丙醇原料的含水量对异丙醇脱水反应平衡转化率的影响可以忽略。因此,采用高温常压异丙醇脱水工艺,在使用耐水蒸汽催化剂的前提下,可采用异丙醇和水共沸物作为原料,可降低原料的获得成本。     

焦化干气加氢热力学研究及其工业应用

计算了焦化干气加氢中各反应的标准摩尔生成焓以及反应温度范围内的吉布斯自由能和平衡常数。结果表明,温度是影响反应热力学的重要因素。此外,为了减少温度对反应平衡的影响,应该采用提高反应压力、降低反应温度的方法使烯烃和氧加氢反应达到一定深度。因此,焦化干气加氢热力学研究对焦化干气加氢技术的工业化应用有重要的指导意义,根据其研究结果选定的工艺条件能够满足工业装置的正常运行及指标要求。     

基于ASPEN PLUS的甲醇和苯烷基化反应热力学分析

利用ASPEN PLUS软件进行了甲醇和苯烷基化过程的热力学研究,计算了非标准状态下的反应焓、反应熵及反应吉布斯自由能变,为该反应体系提供了非标准状态下的热力学依据。研究结果表明,利用ASPEN PLUS软件的纯组分物性分析计算非标准状态的热力学数据可以大大减少人工计算量。甲醇和苯烷基化反应的反应焓变、反应熵变和反应吉布斯自由能变随压力变化不大,温度一定时,该体系中主副反应的热力学数据均可当作常数。该体系的主副反应均为放热反应,反应启动后,可以依靠体系放出的热量维持反应进行。除生成甲苯的反应为熵增反应外,其余反应均为熵减反应。从平衡常数看,该反应体系中乙苯、丙苯、异丙苯、二甲醚等副产物很可能不存在,甲醇作为原料并没有全部参与烷基化反应。     

缩合法合成甲基苯基二氯硅烷反应热力学研究

本工作研究了氯苯和甲基二氯硅烷气相缩合生成甲基苯基二氯硅烷反应体系,指出在温度低于600℃时,反应体系可由一个主反应和两个副反应组成的反应网络描述,并给出了此三个反应的平衡常数和反应热.利用吉布斯自由能最小化原理计算了热力学平衡组成和产品的平衡收率.计算表明由于副反应的平衡移动,温度升高有利于提高甲基苯基二氯硅烷的平衡...     

HFC-245fa催化裂解合成HFO-1234ze和HFO-1234yf的热力学研究

采用密度泛函理论(DFT)方法,使用Materials Studio的DMol 3模块,计算了1,1,1,3,3-五氟丙烷(HFC-245fa)气相裂解脱氟化氢生成1,3,3,3-四氟丙烯(HFO-1234ze)和2,3,3,3-四氟丙烯(HFO-1234yf)反应及其副反应体系中各物质的标准摩尔焓和标准摩尔吉布斯自由能。通过比较不同温度下各反应的标准摩尔焓变和标准摩尔吉布斯自由能变,对反应过程进行了热力学分析。结果表明:HFC-245fa脱HF生成HFO-1234ze的反应为吸热反应,标准摩尔吉布斯自由能变随着温度的升高而减小;当反应温度更高时,E构型的HFO-1234ze能异构化反应合成HFO-1234yf;高温有利于HFO-1234yf的生成。     

烷基胺羰基化反应的热力学计算与分析

利用基团贡献法估算了烷基胺类化合物与CO羰基化反应生成N-烷基甲酰胺的标准生成焓、标准熵和摩尔定压热容,对反应体系的热力学性质进行计算,得到不同反应温度下的反应焓变、吉布斯自由能变以及反应平衡常数等热力学数据。分析了反应的方向与限度,考察了温度对反应焓变、吉布斯自由能变和反应平衡常数的影响,比较了热力学数据随反应物分子结构的变化规律。结果表明:在323 K到473 K的温度区间内,文中涉及的烷基胺羰基化反应均为放热反应,随反应温度的升高,反应由自发向右进行转变为非自发反应。烷基胺N原子上取代基个数和结构的不同对反应热、反应方向与限度均产生影响。     

短链氯化石蜡的研究进展

短链氯化石蜡(SCCPs)是一类碳原子数为10~13的正构烷烃氯化衍生而成的复杂混合物,具有环境持久性、生物蓄积性和生物毒性,可长距离迁移。作为《关于持久性有机污染物的斯德哥尔摩公约》拟增列持久性有机污染物(persistent organic pollutants,POPs)之一,短链氯化石蜡的生物毒性、环境和人体健康风险及环境污染现状等的研究备受关注。本文概述了SCCPs的物理化学性质;详细比较了国内外对SCCPs的分析方法的优缺点,包括气相色谱-电子捕获检测器(GC-ECD)、气相色谱-电子轰击串联质谱(GC-EI/MS)、气相色谱-低分辨电子捕获负化学离子源质谱(GC-ECNI-LRMS)等;重点综述了SCCPs在全球环境介质(大气、土壤、底泥、水)及生物体中的污染现状;总结了SCCPs现有的污染控制技术,包括生物降解、光降解、吸附等;同时,针对目前存在的问题,对SCCPs今后的研究方向进行了展望,以期为该领域相关的研究工作提供参考。     

环境中短链氯化石蜡去除方法的研究进展

短链氯化石蜡（SCCPs）是2017年新定义的持久性有机污染物（POPs）,能对人体健康及生态环境造成重大危害。现阶段国内外关于SCCPs的研究工作主要集中在环境中SCCPs的分析检测方法和浓度水平分布规律,对SCCPs的高效去除方法及去除机理的研究较少。本文主要综述了现阶段SCCPs的有效去除方法,包括物化法（一般物化法和高级氧化处理）和生物法（细菌降解和植物吸收法）,对比分析了这些方法的优缺点,讨论了不同方法去除SCCPs的影响因素、可能降解机理及途径,并通过类比借鉴,提出了其他具有可行性的去除SCCPs的方法。总体而言,虽然物化法去除效率高,但是成本高且操作条件苛刻,微生物法因经济环保而具有更大的发展潜力,但若将微生物法与物化法联用,则有可能发展成为最佳去除工艺。最后展望了环境中SCCPs去除方法的研究重点。     

三氯新中二噁英同类物的指纹特征

作为三氯新生产过程中的一种副产物,二口恶英污染物在三氯新中的存在已经引起了广泛关注。采用高分辨气相色谱-质谱测定了三氯新样品中的二口恶英同类物,共检测到7种2,3,7,8位氯取代同类物,即2,3,7,8 TCDD(四氯代二苯并二口恶英)、1,2,3,7,8 PeCDD(五氯代二苯并二口恶英)、1,2,3,4,6,7,8 HpCDD(七氯代二苯并二口恶英)、2,3,7,8 TCDF(四氯代二苯并呋喃)、1,2,3,7,8 PeCDF(五氯代二苯并呋喃)、2,3,4,6,7,8 HxCDF(六氯代二苯并呋喃)、1,2,3,4,6,7,8 HpCDF(七氯代二苯并呋喃),其含量分别为0 25、0 44、2 65、0 88、2 15、1 02和4 21pg·g-1。四至八氯代二口恶英总量中,四氯代二苯并呋喃最多。在检测到的7种有毒二口恶英中,对毒性当量贡献较大的同类物有2,3,7,8 TCDD和1,2,3,7,8 PeCDD。三氯新样品中二口恶英同类物分布的指纹特征与环境样品差别较大,二口恶英类污染物的产生与三氯新的生产工艺有关。     

Formation and emission characteristics of VOCs from a coal-fired power plant

On-site measurements of volatile organic compounds (VOCs) in different streams of flue gas were carried out on a real coal-fired power plant using sampling bags and SUMMA canisters to collect gas samples,filters to collect particle samples,Gas chromatography-flame ionization detector/mass spectrometry and gas chromatography-mass spectrometry was the offline analysis method.We found that the total mass concentration of the tested 102 VOC species at the outlet of wet flue gas desulfuration device was (13456 ± 47) μg·m-3,which contained aliphatic hydrocarbons (57.9％),aromatic hydrocarbons(26.8％),halogen-containing species (14.5％),and a small amount of oxygen-containing and nitrogen-containing species.The most abundant species were 1-hexene,n-hexane and 2-methylpentane.The top ten species in terms of mass fraction (with a total mass fraction of 75.3％) were mainly hydrocarbons with a carbon number of 6 or higher and halogenated hydrocarbons with a lower carbon number.The mass concentration of VOC species in the particle phase was significantly lower than that in the gas phase.The change of VOC mass concentrations along the air pollution control devices indicates that con-ventional pollutant control equipment had a limited effect on VOC reduction.Ozone formation potential calculations showed that aromatic hydrocarbons contributed the highest ozone formation (46.4％) due to their relatively high mass concentrations and MIR (maximum increment reactivity) values.     

Structural Elucidation and Biological Activity of Acyl-homoserine Lactones from the Phytopathogen Pantoea ananatis Serrano 1928

In Gram-negative bacteria, the acyl-homoserine lactones (acyl-HSLs) are the main signaling substances employed in cell-to-cell communication systems. This paper describes the chemical characterization of acyl-HSLs produced by the worldwide-spread phytopathogen Pantoea ananatis (Serrano 1928) by using gas chromatography-electron impact mass spectrometry. The absolute configuration of the major identified substance, (S)-(−)-N-hexanoyl-HSL, was determined with gas chromatography-flame ionization detection with a chiral capillary column. Biological activities of extracts, fractions, and synthetic products were evaluated with the specific reporter Agrobacterium tumefaciensNTL4(pZLR4) in β-galactosidase expression assays.     

Chlorinated poly(vinyl chloride) and plasticized chlorinated poly(vinyl chloride)—thermal decomposition studies

The thermal decomposition of chlorinated poly(vinyl chloride) and three plasticized chlorinated poly(vinyl chloride) systems has been investigated. The routes of decomposition of these systems have been elucidated by investigating char formation and by using a combination of thermogravimetric analysis (TGA) and prolysis/gas chromatography/mass spectroscopy methods (Py/GC/MS). The effects of the charforming/smoke‐suppressing iron(III) compound FeOOH in these polymer systems has also been investigated. The structure of both CPVC polymer and plasticzer determine the path of thermal decomposition and also the quantity and nature of the decomposition compunds formed. Changes in oxygen index and the formation of smoke during burning in these systems have been related to the char that is formed and also to the chemical nature of the decomposition products.     

How do chlorinated poly(olefins) promote adhesion of coatings to poly(propylene)?

The mechanism by which chlorinated poly(olefin) (CPO) primer coatings promote adhesion of paints to poly(propylene) and thermoplastic poly(olefins) (TPO) has been examined by surface characterization techniques including electron spectroscopy for chemical analysis (ESCA), time-of-flight secondary ion mass spectrometry (ToFSIMS) and transmission electron microscopy (TEM). The coatings, their interfacial failures, and taper-cut cross sections were studied, using both waterborne and solventborne CPO primers. The results were then correlated with peel strength and crosshatch adhesion tests. CPO primers do not penetrate deeply into the poly(olefin) substrates, but are quite mobile following application of the topcoat. Solventborne CPO's generally showed adhesive failure at the CPO/poly(olefin) interface when dried at ambient temperatures. Test results are also reported for waterborne CPO adhesion promoters.     

A study of aromatic polyester/chlorinated polymer blends

A large number of studies have been devoted in recent years to the miscibility behavior of linear polyesters with chlorinated polymers, including poly(vinyl chloride) (PVC), chlorinated PVC, chlorinated poly(ethylenes), and copolymers of vinylidene chloride (Saran). However, similar studies with aromatic polyesters are lacking. It is the purpose of this paper to compare the properties of blends made of poly(ethylene terephthalate), poly(butylene terephthalate) or poly(hexamethylene terephthalate) and of various chlorinated polymers. It is shown that a high concentration of chlorine atoms is required to achieve miscibility. Moreover, there is a “miscibility window” in terms of the carbonyl concentration of polyesters, immiscibility being found for carbonyl concentrations outside this window, A similar behavior was observed before for linear polyester/chlorinated polymer blends and for polyester/polycarbonate blends. Solid state small-angle light scattering experiments were also conducted to follow the morphology of the blends as a function of composition. Spherulites were found but their size vary with composition.     

基于MDEA的烟气SO2捕集过程工艺参数和能量集成分析

有机胺吸收法是一种高效环保型烟气脱硫技术,而从系统工程的角度对烟气SO₂捕集工艺的分析、优化和能耗评估尚未有详细报道。对N-甲基二乙醇胺（MDEA）为吸收剂的烟气SO₂捕集过程工艺进行研究,考察了MDEA浓度、温度、SO₂解吸率对捕集效果的影响规律。结果显示,MDEA溶液浓度为30%（质量）、烟气温度不高于45℃、回流贫液温度不高于41℃时,SO₂吸收效果较好;增加SO₂解吸率是以降低解吸气中SO₂纯度和增大再沸器负荷为代价,水分汽化是再生能耗增高的主要原因。针对吸收剂再生过程能耗大的问题,采用热泵辅助精馏对解吸过程进行能量集成,吸收剂再生能耗可降低47%,年度总费用（TAC）可降低9.93%。本研究对有机胺体系的SO₂捕集系统工业化应用具有重要的指导作用。     

Selective Capture and Identification of Methicillin-Resistant Staphylococcus aureus by Combining Aptamer-Modified Magnetic Nanoparticles and Mass Spectrometry

A nucleic acid aptamer that specifically recognizes methicillin-resistant Staphylococcus aureus (MRSA) has been immobilized on magnetic nanoparticles to capture the target bacteria prior to mass spectrometry analysis. After the MRSA species were captured, they were further eluted from the nanoparticles and identified using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). The combination of aptamer-based capture/enrichment and MS analysis of microorganisms took advantage of the selectivity of both techniques and should enhance the accuracy of MRSA identification. The capture and elution efficiencies for MRSA were optimized by examining factors such as incubation time, temperature, and elution solvents. The aptamer-modified magnetic nanoparticles showed a capture rate of more than 90% under the optimized condition, whereas the capture rates were less than 11% for non-target bacteria. The as-prepared nanoparticles exhibited only a 5% decrease in the capture rate and a 9% decrease in the elution rate after 10 successive cycles of utilization. Most importantly, the aptamer-modified nanoparticles revealed an excellent selectivity towards MRSA in bacterial mixtures. The capture of MRSA at a concentration of 10² CFU/mL remained at a good percentage of 82% even when the other two species were at 10⁴ times higher concentration (10⁶ CFU/mL). Further, the eluted MRSA bacteria were successfully identified using MALDI mass spectrometry.