裂解气相色谱-质谱联用法分析聚醚酰亚胺的裂解产物

应用裂解气相色谱及质谱联用法研究了3种聚醚酰亚胺(PEIM′s)的裂解行为,并根据裂解产物的结构及其相对产率推断了裂解的机理。取3种PEIM样品置于石英裂解管中,分别在550℃,650℃,750℃条件下裂解,所得产物用气相色谱-质谱联用法分析。分析中采用DB-5毛细管色谱柱,电子轰击离子源(200℃,70eV)及在m/z 29～500范围内全扫描方式,并用NIST谱库进行检索和用归一化法计算峰面积进行定量。由试验结果可知:选择在750℃进行裂解较好,在此条件下获得主要裂解产物存在的更明显的信息,有利于对产物进行详细分析和鉴定。     

废弃印刷电路板材料裂解产物的高分辨裂解气相色谱-质谱分析

采用高分辨裂解气相色谱-质谱法(PyGC-MS)分析了FR-4型印刷电路板粉末样品的裂解产物。在氦气氛围中,分别在350,450,550,650和750 ℃下对印刷电路板粉末样品进行热裂解,并通过毛细管气相色谱-质谱对裂解产物进行分析,研究了不同裂解温度下裂解产物分布以及主要裂解产物的产率与裂解温度的关系,根据热分解产物的组成,探讨了热分解反应机理。     

管式炉裂解色谱法定量分析聚醚酰亚胺的组分配比

本工作利用管式炉裂解色谱法探索了聚醚酰亚胺的裂解产物苯酚、苯胺等特征峰与其组分配比的定量关系。 实验 (一)仪器 LJ—001型管式炉裂解器和SP—2305E型气相色谱仪,联用SIGMA10B计算机。     

裂解气相色谱-质谱法研究壬酸香草酰胺的热裂解

采用在线热裂解/气相色谱-质谱联用技术(Py/GC-MS)对壬酸香草酰胺(PAVA)的热裂解行为进行了研究,在氦气氛围中考察了不同裂解温度和裂解时间对PAVA裂解的影响,通过GC-MS对裂解产物进行定性和半定量分析。结果表明,随着裂解温度的升高,PAVA裂解率快速提高,裂解产物也进一步增多,当裂解温度达到700℃以上时,可裂解出壬酰胺、2-甲氧基-4-甲基苯酚、1-己烯、壬基腈、壬醛等14种产物。同一温度下随着裂解时间的延长,PAVA的裂解率逐步升高,裂解产物发生了进一步的裂解。根据热裂解产物及主要裂解产物的含量变化,初步推断了PAVA的裂解规律。     

裂解气相色谱-质谱法研究聚苯硫醚热分解

采用裂解气相色谱一质谱法研究了在350～750℃之间聚苯硫醚（PPS）的裂解行为。350℃时裂解，仅检测到4种裂解产物。随裂解温度上升，裂解产物急剧增加。在750℃时，检测到25种裂解产物，主要特征裂解产物为硫化氢、苯、苯硫醇、1，4-苯二硫醇、二苯硫、二苯并噻吩、1，4-苯二硫醇基苯、噻茚等。聚苯硫醚裂解过程中，发生链剪切作用，由聚合物链断裂成苯硫醇单体、二聚体和三聚体等化合物。裂解过程还会发生重排，环化，次级反应等形成了各种裂解产物。     

乙苯与二甲苯在超临界压力下的热裂解研究

采用连续流动装置, 在压力为4 MPa, 温度分别在700, 750和780 ℃条件下, 开展了乙苯和二甲苯在超临界压力条件下热裂解反应的实验研究. 对乙苯和二甲苯裂解的气相产物, 采用在线气相色谱进行分析; 而裂解的液相产物则通过色质联用仪进行定量分析. 研究发现乙苯和二甲苯裂解的气相产物组成基本相同, 而液相产物组成相差较大, 但都是芳香烃类化合物. 乙苯和二甲苯的转化率都随温度升高而增加; 在相同温度下, 乙苯比二甲苯转化率高. 此外, 裂解过程并未发现明显的结焦现象, 说明纯芳香烃物质的热裂解并不会导致严重积炭. 同时, 本文还采用密度泛函方法在BHandHLYP/6-31+G(d, p)水平上, 对乙苯和甲苯分别进行结构优化并计算相关的键能. 计算结果表明: 乙苯侧链乙基中的C—C键的键能最小, 从而说明乙苯侧链烷基更容易发生断键反应, 理论结果很好地解释了乙苯比二甲苯裂解转化率高的实验现象. 本文的工作对燃料裂解结焦机理的重新认识有重要的意义.     

在线热裂解/气相色谱-质谱分析3-吡啶甲酸茴香酯的热裂解产物

采用在线热裂解/气相色谱-质谱(Py/GC-MS)联用技术对3-吡啶甲酸茴香酯进行热裂解分析。通过酰氯化和酯化反应合成了新型目标化合物3-吡啶甲酸茴香酯,其分子式为C14H14NO3。目标化合物的结构经核磁氢谱(1H NMR)、核磁碳谱(13C NMR)、红外光谱(IR)和高分辨质谱(HRMS)进行确证,并通过热重-微热重-差示扫描量热(TG-DTG-DSC)分析方法对目标化合物的热稳定性进行分析。在空气氛围中,将目标化合物分别于300,600,900℃下进行热裂解,并通过气相色谱-质谱法对其挥发性热裂解产物进行定性和半定量分析。研究显示:目标化合物共经历了两次失重过程。第一次失重在129.9~158.9℃之间,失重2.3%;第二次失重在158.9~274.9℃之间,失重达90.1%,230.1℃时失重率最大。热裂解共产生44种产物,包括具有香味特征的大茴香醛、对甲基苯酚、松油醇、D-香茅醇、大茴香醚和茴香醚等化合物。其中裂解温度对裂解产物的种类和相对含量具有明显影响。300℃时α-二去氢菖蒲烯的相对含量最高,600,900℃时,相对含量最高的分别是大茴香醛和对甲基苯酚。苯甲醛、茴香醚和大茴香醚的相对含量随着温度的升高呈先增加后降低趋势;而对甲基苯酚含量则随着温度的升高而增加。根据主要裂解产物及其相对含量的变化,对目标化合物的裂解机理进行了初步探讨。     

PC/ABS共混物的PGC-MS定量分析

采用裂解/气相色谱-质谱联用方法(PGC-MS)对制备的一系列已知配比的PC/ABS共混物进行分析。实验比较了650、750℃裂解温度下共混物的裂解质谱总离子流图,选择PC/ABS共混物的快速鉴定的裂解温度为750℃;通过对已知PC/ABS配比的共混物的特征裂解碎片进行定量分析,发现当共混物中ABS和PC的质量比不大于20∶100时,特征裂解碎片苯乙烯与苯酚的峰面积之比与共混物中ABS/PC的配比呈线性关系,该现象可作为PC/ABS共混物定量分析的依据。     

热裂解气相色谱-质谱法对聚四氟乙烯涂层的热裂解产物分析

提出了热裂解气相色谱-质谱法(Py-GC-MS)研究聚四氟乙烯涂层的热裂解性质。采用管炉型热裂解装置和不锈钢毛细管柱,根据样品的复杂程度进行分阶段释放气体分析,得到聚四氟乙烯涂层不同热裂解阶段的释放气体色谱图。结果表明:聚四氟乙烯涂层在100～300℃热裂解温度下检测到的热裂解产物为1,4-二甲基-2,5-二乙基苯、异丙氧基苯胺、双酚A;在300～380℃热裂解温度下检测到的热裂解产物为苯乙烯、α-甲基苯乙烯、4,4′-二甲基苯胺;在380～460℃热裂解温度下检测到的热裂解产物为苯酚、苯胺、对氨基甲苯、二苯醚;在460～600℃热裂解温度下检测到的热裂解产物为四氟乙烯单体。     

在线裂解气相色谱/质谱联用法研究4-氧代-β-大马酮的热裂解行为

用在线裂解气相色谱/质谱法(PyGC/MS)研究了4-氧代-β-大马酮的热裂解行为。在氦气氛围中,将4-氧代-β-大马酮分别在350,450,550,650,700和750 ℃下进行热裂解,并以GC/MS对其裂解产物进行定性和半定量分析。结果表明,不同的裂解温度直接影响生成产物的类型和相对含量。4-氧代-β-大马酮可裂解出β-大马酮、4-氧代-β-紫罗兰酮、3,4,4-三甲基-环己-2-烯-1-酮和2,5,5-三甲基-环己-3-烯-1-酮等54种裂解产物。在550 ℃以下时,只有少量4-氧代-β-大马酮发生裂解; 在750 ℃时,几乎完全裂解,转移率达99.74%, 裂解产物达45种之多。随着裂解温度的升高,裂解产物越来越复杂,并出现有害物质如苯、甲苯、蒽和菲等。根据4-氧代-β-大马酮裂解产物相对含量的变化规律,对其裂解产物的形成机理进行了探讨,认为4-氧代-β-大马酮可能按照4种途径发生裂解。     

Very Low-Pressure Pyrolysis (VLPP); A Versatile Kinetic Tool

The theory and applications of the very low-pressure pyrolysis technique to the study of the rates and mechanisms of unimolecular reactions, radical-radical, and radical-molecule bimolecular reactions, surface recombination of atoms, heterogeneous reactions, and vibrational energy transfer are reviewed.     

STUDY ON PYROLYSIS OF POLYPHENYLSILSESQUIOXANE

X-ray photoelectron spectroscopy and Raman spectroscopy were used to determine the chemical change ofpolyphenylsilsesquioxane (PPSQ) during pyrolysis in flowing nitrogen. Two temperature ranges were found for pyrolysedPPSQ below and above 600℃, respectively. The former is related to the rearrangement of PPSQ backbone and the latterreflects that most of backbone structure of PPSQ might be broken down and unorganized. Carbon formed in carbonization ofPPSQ sample pyrolysed at 900℃ should be sp~3 bonded carbon with crystallite size effects or defects.     

系列新型咔哚聚芳醚砜结构的裂解色谱—质谱研究

利用裂解色谱－质谱对４个同一系列新型咔哚聚芳醚砜样品的裂解规律进行了研究，分别得到了各自链节的裂解特征碎片，证明了各聚合物确实发生了缩聚反应。     

Homogeneous pyrolysis kinetics of ethyl 3-hydroxy-3-methylbutanoate in the gas phase

The pyrolysis kinetics of ethyl 3-hydroxy-3-methylbutanoate have been examined over the temperature range of 286–330°C and pressure range of 29–108 Torr. In a seasoned vessel and in the presence of the free radical inhibitor cyclohexene or toluene the reaction is homogeneous, unimolecular and obeys a first-order rate law. The elimination products are mainly acetone and ethyl acetate, and very small amounts of ethyl 3-butenoate, acetic acid, ethylene and H₂O. The rate coefficient is expressed by the following equation: log k₁(s^–1)=(12.39±0.46)–(174.5±5.2) kJ mol^–1 (2.303RT)^–1. The mechanism appears to proceed via a six-membered cyclic transition state, where polarization of the (CH₃)C(OH)^+...-CH₂COOCH₂CH₃ bond is rate determining.     

Flame retarding of wood by impregnation with boric acid - Pyrolysis products and char oxidation rates

The pyrolysis of fir wood impregnated with boric acid (0-5.4%) has been investigated for heating temperatures of 650 and 800 K by examining the yields of char, water, permanent gases (CO₂, CO, CH₄) and total organic products (together with 32 compounds). The yields of the last product class continuously decrease to the advantage of char and water, but the most significant modifications occur for acid contents below 2%. The formation of levoglucosan (with 2-acetylfuran, 5-methyl-2-furaldehyde and other minor species) first and levoglucosenone (with 2-furaldehyde) afterwards is favoured, whereas other compounds generated from the holocellulosic (hydroxyacetaldehyde, hydroxypropanone, acetic acid and minor carbohydrates) and lignin (phenols, cresols) fractions generally decline. Conversion times become longer and volatilization rates are reduced. The oxidation characteristics of char have been studied by means of thermogravimetric analysis and interpreted according to a three-step reaction mechanism. The boric acid treatment lowers the activation energy and reaction order of the most important step (145 versus 226 kJ/mol and 1.2 versus 0.86, respectively) which also shows lower rates and is slightly delayed.     

Pyrolysis of solid waste in a rotary kiln: influence of final pyrolysis temperature on the pyrolysis products

Temperature is one of the most important parameters in pyrolysis reaction. In present work, an externally heated laboratory-scale rotary-kiln pyrolyser was designed and developed. The influence of final pyrolysis temperature (FPT) on the pyrolytic products of solid wastes has been studied. Raising FPT caused increasing gas yield and decreasing semi-coke yield. The average heat value of the gas also changed with FPT. The content of aliphatic hydrocarbons in PE tar increased initially and then decreased with increasing FPT. Parallel to this, the content of aromatic ring changed conversely. FPT had obvious influence on the primary and elemental analysis data of the semi-cokes. The CO₂ reactivity of the semi-cokes also varied with the FPT. The kinetic parameters of the semi-cokes were different for the same material at the different FPT.     

Analysis of coal tar and petroleum pitches by computerized pattern recognition

Pyrolysis gas chromatography (P/GC) has been successful in differentiating coal tar pitches which are used in the manufacture of high temperature graphite materials [1,2]. In the present study, coal tar and petroleum pitches received from five suppliers were readily differentiated using three distinct methods of polymer analysis: dynamic headspace and pyrolysis gas chromatography mass spectrometry (DH/GC/MS and P/GC/MS, [3]), and pyrolysis mass spectrometry (P/MS, [4,5]). All of these methods are appropriate for the analysis and pattern recognition study of coal and petroleum products; however, methods which incorporate GC usually necessitate long analysis times and are subject to problems associated with gas chromatographic reproducibility (e.g. active sites [6], and nonconstant retention times). As a fingerprint analysis method, P/MS is rapid and ideally suited to computerized pattern recognition study of pitches due to the simple format of P/MS data (computer tabulation of normalized intensities versus masses); whereas, in the present study, the normalized peak area versus retention time date from DH/GC/MS and P/GC/MS analyses were not suitable for direct input to a computerized pattern recognition analysis program, (due to non-constant retention times and improper data format). One limitation is that P/MS does not provide positive identification of thermally evolved products (as can DH/GC/MS and P/GC/MS) due to the complexity of the spectra of a mixture of compounds produced by P/MS. Within the limits of the commercial instrumentation and computer programs used in this study, a combination of all three techniques provided the greatest capability for the differentiation of the five coal tar and petroleum based pitches studied.     

Characteristics of soot particles formed by diesel pyrolysis

This experiment involving diesel fuel pyrolysis was performed to study the process of soot formation without oxidation. The effects of temperature, residence time, and lubricating oil presence on soot formation were investigated through measurement of particle size distribution, morphology, and C/H ratio as well as through thermal analysis. The results show that the formation of soot during diesel pyrolysis depended strongly on both temperature and residence time. The critical temperature for the creation of soot with a primary particle diameter of 20 nm was about 1100 °C. Greater temperatures and residence times resulted in diesel soot particles that were more mature, i.e., with a higher C/H ratio, larger particle size, and higher ignition temperature. The carbonization of diesel soot through pyrolysis was also weakly affected by the addition of 5% lubricating oil to the diesel fuel. The results of this experiment provide information for modeling the formation of diesel soot without oxidation as well as for developing soot generators for after-treatment systems.     

The Pyrolysis of Azides in the Gas Phase

The chemistry of the non-metallic elements has in recent years passed through a period of rapid development, often referred to as its “renaissance”. To emphasize just one of the key facets: numerous short-lived molecules containing multiple bonds to elements of the third and higher periods have been discovered, often accompanied by the planned synthesis of derivatives which are sterically shielded by bulky groups and thus kinetically stabilized. Thus today molecules such as silabenzenes H₆C_6?nSi_n and silaethenes H₂Si?CH₂ or R₂Si?CR₂, disilenes R₂Si?SiR₂ and diphosphenes RP?PR, silaphenylisonitrile H₅C₆? N?Si, or methylidyne-phosphanes R? C?P, are all well-known species. Sandwich compounds with P₆ rings or silicon centers demonstrate that there are now hardly any barriers to impede the imagination of the non-metal chemist. In sharp contrast is our lack of knowledge regarding the “microscopic” pathways of chemical reactions: thus apart from information provided for example by molecular beam experiments, or from exact numerical calculations involving species consisting of only a few atoms, it remains largely unknown from which directions medium-sized molecules must approach each other to successfully collide and form a “reaction complex”, in which way their structures are changed in such a process or which role is played by molecular dynamics in the energy transfer.–The pyrolysis of azides X? N₃, i.e. compounds which tend to explode violently when ignited in the condensed phase but can be heated in low-pressure gas flow systems without much risk, illustrates that studies of reactive intermediates are of interest not only because novel molecules may be discovered and isolated, and thereby possibilities for synthesis expanded. Moreover, some aspects of the “microscopic” pathways of these azide pyrolyses can be described satisfactorily on the basis of calculated energy hypersurfaces, and the influence of molecular dynamics becomes experimentally visible in the “chemical activation” of intermediates which leads to their “thermal explosion”.     

裂解色谱法分析苯乙烯-丙烯酰胺共聚物

本文报道了用裂解色谱法分析一种新型的苯乙烯-丙烯酰胺共聚物的研究结果。考察了裂解温度、共聚物组成同主要裂解产物之间的相关性。提出了用相关曲线对不同类型共聚物的组成进行定量测定和鉴别的方法。讨论了由于分子链结构的差别导致无规和嵌段共聚物的不同的裂解行为。