Organic environments on Saturn’s moon,Titan: Simulating chemical reactions and analyzing products by FT-ICR and ion-trap mass spectrometry

Laboratory simulations have been carried out to model chemical reactions that possibly take place in the stratosphere of Saturn's moon, Titan. The aerosol products of these reactions (tholin samples) have been systematically analyzed by mass spectrometry using electrospray ionization (ESI) and laser desorption (LD). A wide variety of ions with a general formula C(x)H(y)N(z) detected by ultrahigh resolution and accurate mass measurements in a Fourier transform/ion cyclotron resonance (FT-ICR) cell reflect the complexity of these polymeric products, both in chemical compositions and isomeric distributions. As a common feature, however, tandem mass spectral (MS/MS) data and H/D exchange products in the solution phase support the presence of amino and nitrile functionalities in these (highly unsaturated) "tholin" compounds. The present work demonstrates that ESI-MS coupled with FT-ICR is a suitable and "intact" method to analyze tholin components formed under anaerobic conditions; only species with C(x)H(y)N(z) are detected for freshly prepared and harvested samples. However, when intentionally exposed to water, oxygen-containing compounds are unambiguously detected.     

Determination of short-chain branching content in polyethylene by pyrolysis comprehensive multidimensional gas chromatography using low thermal mass column technology

A research effort was undertaken to utilize the pyrolysis process to create fragments of polyethylene that could be indicative of branching, and allow quantitiation of said short-chain branches by pyrolysis comprehensive 2-D GC (Py-GC x GC). Several strategies for sample introduction and pyrolysis such as the in-column pyrolysis device and the programmed temperature vaporizer (PTV) were studied. The chromatographic separations were executed using low-thermal mass (LTM) comprehensive 2-D GC (GC x GC). A series of polyethylene-co-hexene samples were analyzed and a linear correlation of 1-hexene content with branching peak ratio was found. Correlation coefficients were determined as 0.97 for the measurements performed.     

同时裂解甲基化气相色谱法鉴别合成胶粘剂

 应用同时裂解甲基化气相色谱法 (Py Me GC)对合成胶粘剂进行了鉴别。采用热丝型裂解器、氢火焰离子化气相色谱仪、FFAP毛细管柱、程序升温方式及季铵盐甲基化试剂 ,对刑事案件中常见的丙烯酸酯类及其改性体、醋酸乙烯酯、聚乙烯醇等合成胶粘剂进行了测定 ,并对样品裂解各主要组分峰进行了GC/MS定性分析 ,同时比较了相同样本用常规裂解气相色谱法 (Py GC)测定的结果。结果表明 :Py Me GC法比Py GC法可获得更多的物质组分信息 ,是一种适用于法庭科学鉴定的方法。     

压力对塔里木原油四组分热解性能的影响

压力对深层油藏原油热化学过程的影响尚存在较大争议,为研究其在油藏原油热解成气过程中的作用机理,我们在450℃、5~40 MPa压力下对塔里木原油四组分(饱和分、芳香分、胶质和沥青质)进行了封闭体系的热解实验,通过气相色谱(GC)和气相色谱/质谱(GC/MS)分别对原油四组分热解反应的气体产物及饱和分热解过程的液态产物进行了分析。结果表明,在450℃、24 h及不同压力下,沥青质热解产气率高于胶质、芳香分和饱和分;四组分的气相热解产物中,C1的产率明显高于C2~C5组分。增大压力抑制沥青质、胶质及芳香分的热解产气过程而促进饱和分的热解产气过程。随压力的增大,饱和分热解的液态产物的主峰组分碳数先减小,再增大。压力低于20 MPa时,饱和分热解过程中以裂解反应为主;高于30 MPa时,增大压力有利于缩合反应。研究结果可为认识深层油藏原油的稳定程度及天然气的成因提供一定的理论参考。     

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。     

Universal and discriminative detection using a miniaturized pulsed discharge detector in comprehensive two-dimensional GC

A miniaturized pulsed discharge detector (Mini-PDD) has been successfully demonstrated for comprehensive 2-D GC (GC x GC) analysis of pyrolysis gasoline and the pyrolysis GC x GC analysis of a polyethylene copolymer. The detector cell volume of the Mini-PDD is reduced to 25% of the Valco plug-in PDD D-3. An n-C11 peak width at base is 96 ms for the Mini-PDD, about 23% larger than a peak width of 78 ms detected by a flame ionization detector (FID). The Mini-PDD has sufficient response time for most GC x GC applications. When Mini-PDD is operated in helium photoionization mode (Mini He-PDD), it is a universal detector for both inorganic and organic compounds. This is especially useful when detection of water is needed in GC x GC applications. When krypton is doped in the helium discharge gas (Mini Kr-PDD), it can suppress signals of compounds having higher ionization potentials and enhance relative signal intensities of aromatic compounds. The determination of aliphatic to aromatic hydrocarbon ratios is essential to the operation of petroleum crackers. Comparison of the signal from two modes of the Mini-PDD is a simple and fast way to verify the location of aromatics in comprehensive 2-D gas chromatograms.     

Pyrolysis of mixed polyolefins in a fluidised-bed reactor and on a pyro-GC/MS to yield aliphatic waxes

Polyolefins (PE, PP and PS) were pyrolysed in a fluidised-bed reactor on kilogram scale at 510°C. Pyrolysis products were analysed with GC, GC/MS and other methods. It was shown that valuable products, mostly aliphatic waxes, are received from polyolefins. It was also investigated if mixtures of different polyolefins (PE, PP, PS) interact with each other in fluidised bed pyrolysis yielding different pyrolysis products than received from the pure, individual polyolefins. The same polymer mixtures were also analysed using a pyro-GC/MS-device.     

硫酸盐法制浆黑液中主要有机组分的热解特性研究

采用管式炉对硫酸盐法竹子、阔叶木混合制浆黑液固形物(BLS)及其三种主要组分碱木素(AL)、多糖(PLS)和木素-碳水化合物复合体(LCC),在400~800℃进行热解,全面分析了各相热解产物组成与分布规律。结果表明,BLS及其三种主要组分的热解产物组成与分布规律存在明显差异。AL、PLS和LCC对BLS热解产生H₂和CO的产率影响不大,PLS热解生成CO₂的能力明显高于BLS、AL和LCC。BLS热解液相产物中的酚类和醚类主要是来自AL和LCC;酮类和酸类是由AL、PLS和LCC共同贡献的。BLS、AL、PLS和LCC热解半焦表面形貌存在明显差异。在BLS热解过程中,AL、PLS和LCC会相互影响、相互制约,共同决定着BLS的热解特性。     

The co-pyrolysis of flame retarded high impact polystyrene and polyolefins

The co-pyrolysis of brominated high impact polystyrene (Br-HIPS) with polyolefins using a fixed bed reactor has been investigated, in particular, the effect that different types of brominated aryl compounds and antimony trioxide have on the pyrolysis products. The pyrolysis products were analysed using FT-IR, GC–FID, GC–MS, and GC–ECD. Liquid chromatography was used to separate the oils/waxes so that a more detailed analysis of the aliphatic, aromatic, and polar fractions could be carried out. It was found that interaction occurs between Br-HIPS and polyolefins during co-pyrolysis and that the presence of antimony trioxide influences the pyrolysis mass balance. Analysis of the Br-HIPS + polyolefin co-pyrolysis products showed that the presence of polyolefins led to an increase in the concentration of alkyl and vinyl mono-substituted benzene rings in the pyrolysis oil/wax resulting from Br-HIPS pyrolysis. The presence of Br-HIPS also had an impact on the oil/wax products of polyolefin pyrolysis, particularly on the polyethylene oil/wax composition which converted from being a mixture of 1-alkenes and n-alkanes to mostly n-alkanes. Antimony trioxide had very little impact on the polyolefin wax/oil composition but it did suppress the formation of styrene and alpha-methyl styrene and increase the formation of ethylbenzene and cumene during the pyrolysis of the Br-HIPS.     

In situ modification of pyrolysis products of macromolecules in an analytical pyrolyser

An application of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) is presented for the fast on-line testing of solid catalysts activity in upgrading pyrolysis oils and/or gases of natural and synthetic polymers. Evaluation of the chemical conversion by a catalyst is simply and quickly performed in a Py-GC/MS instrument without any modification either of the micropyrolyser or the GC inlet. The pyrolysis products evolved from the sample pass through catalyst microbeds of some mm length and the GC/MS analysis of the converted products is performed on-line. Modification of polyolefin, styrene copolymer, polyester, polyamide, brominated epoxy resin and wood pyrolysate was carried out applying sodium type zeolite and medium acidic mesoporous aluminosilicate in the microbeds. The primary pyrolysis products are converted over the microbeds due to the catalytic activity of the bed material. Intramolecular hydrogen transfer reactions promoted by Na zeolite results in the isomerisation of alkenes and alkadienes evolved by pyrolysis from polyethylene and polypropylene. These basic catalysts were found to be effective for the elimination of brominated phenols from the pyrolysate of brominated epoxy resin. Cracking of alkane and alkene oligomer products of polyolefins to light isoalkenes occur over acidic mesoporous aluminosilicate. Certain compounds with polar groups evolved from polyester, polyamide, cellulose or lignin are removed by this catalyst. Alkenylaromatic compounds are simultaneously hydrogenated and polyaromatised in pyrolysis oils of styrene copolymers over both acidic and basic aluminosilicate catalysts tested.     

Pyrolysis studies on polyalkylene phthalates

The synthesis and identification of pyrolysis products of five polyalkylene phthalates are reported. The pyrolysis products are separated in a capillary gas chromatograph and the products are identified using a mass selective detector. The major degradation products for the polyesters now investigated are phthalic anhydride and the appropriate diol. In nearly all the polyesters studied, cyclic ether from the diol and the cyclic diester formed from phthalic anhydride and the diol are detected. A wide variety of low molecular weight compounds and considerable quantities of complex mono- and diesters of phthalic acid are identified among the pyrolysis products. The mode of formation of the products identified by GC/MS analysis are discussed with reference to the general polyester degradation mechanism.     

Determination of the antioxidant alurofen in synthetic rubbers by pyrolysis-gas chromatography

A pyrolysis—gas chromatographic (Py—GC) method for the determination of the antioxidant Alurofen in synthetic rubbers was developed. The Alurofen was extracted from the rubber, then pyrolysed as 873 K in continuous-mode furnace pyrolyser in 20 s. Chromatographic conditions for the separation of the pyrolysis products were established. The pyrolysis of the Alurofen at several temperatures was investigated by measuring the yields of the pyrolysis products. It was observed that 2-phenyl-2-(4-hydroxyphenyl)propane was produced in the greatest, amounts, and the effect of the pyrolysis temperature on the yield of this compound was studied. The overall Py—GC method for the determination of the Alurofen content of rubbers had a mean relative error of 2.7% and a relative standard deviation of 2.94%.     

A Review of Synthetic Polymer Characterization by Pyrolysis–GC–MS

Pyrolysis–GC with mass spectrometry detection (Py–GC–MSD) study of the thermal degradation products of synthetic polymers is reviewed. Due to the high heating speed, accurate temperature reproducibility and a wide temperature range, Py–GC–MSD has been applied successfully for polymer characterization. Introduction of samples using the pyrolysis carrier gas through the split injection port, followed by sub-ambient cryofocusing of the pyrolysis products, has shown to give reproducible chromatograms (pyrograms). One of the advantages of this method is that all compositions of the polymers and additives can be investigated without any pretreatment, providing important compositional and structural information in a simple way. The method is a convenient method for compositional analysis of complex polymer materials. The aim of this review is to describe the kinds of applications for which Py–GC–MSD has been found to be suitable; to present guidelines for method optimization; to survey innovations that have recently been developed or are currently being researched; to point to problems in our understanding of the pyrograms; and to suggest areas in which research efforts might be most effective in realizing the full potential of this technique.     

Analysis of cyclic pyrolysis products formed from amino acid monomer

Amino acid was mixed with silica and tetramethylammonium hydroxide (TMAH) to favor pyrolysis of amino acid monomer. The pyrolysis products formed from amino acid monomer were using GC/MS and GC. 20 amino acids of alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine were analyzed. The pyrolysis products were divided into cyclic and non-cyclic products. Among the 20 amino acids, arginine, asparagine, glutamic acid, glutamine, histidine, lysine, and phenylalanine generated cyclic pyrolysis products of the monomer. New cyclic pyrolysis products were formed by isolation of amino acid monomers. They commonly had polar side functional groups to 5-, 6-, or 7-membered ring structure. Arginine, asparagine, glutamic acid, glutamine, histidine, and phenylalanine generated only 5- or 6-membered ring products. However, lysine generated both 6- and 7-membered ring compounds. Variations of the relative intensities of the cyclic pyrolysis products with the pyrolysis temperature and amino acid concentration were also investigated.     

Analysis of products from the pyrolysis of plastics recovered from the commercial scale recycling of waste electrical and electronic equipment

Three plastic fractions from a commercial waste electrical and electronic equipment (WEEE) processing plant were collected and investigated for the possibility of recycling them by batch pyrolysis. The first plastic was from equipment containing cathode ray tubes (CRTs), the second plastic was from refrigeration equipment, and the third plastic was from mixed WEEE. Initially, the decomposition of each of the plastics was investigated using a TGA linked to a FT-ir spectrometer which showed that the CRT plastic decomposed to form aliphatic and aromatic compounds, the refrigerator plastic decomposed to form aldehydes, CO₂, aromatic, and aliphatic compounds, and the mixed WEEE plastic decomposed to form aromatic and aliphatic compounds, CO₂, and CO. Each plastic mixture was also pyrolysed in a batch reactor to determine the halogen and metal content of the pyrolysis products, additionally, characterisation of the pyrolysis oils was carried out by GC–MS and the pyrolysis gases by GC–FID and GC–TCD. It was found that the halogen content of the oils was relatively low but the halogen and metal content of the chars was high. The pyrolysis oils were found to contain valuable chemical products and the pyrolysis gases were mainly halogen free, making them suitable as a fuel.     

Synthesis and characterization of saturated and unsaturated polysulfide polymers and their thermal degradation processes investigated by flash pyrolysis–gas chromatography/mass spectrometry

The synthesis of polysulfide polymers with unsaturated and saturated units in the backbone and their characterization by Fourier transform infrared, NMR, gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry are reported. This is the first report on an analysis of the thermal degradation of an unsaturated polysulfide polymer [poly(2‐butene sulfide)] carried out by pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). A unique phenomenon of exothermic degradation has been detected by differential thermal analysis and has been attributed to the energetics of the unsaturated polysulfide linkage during degradation. The thermal degradation products studied by Py–GC/MS indicate that the formation of sulfur‐containing products is more favored than the formation of non‐sulfur‐containing products. Furthermore, a comparative study of the thermal degradation of unsaturated and saturated polysulfide polymers has been conducted with thermogravimetry and Py–GC/MS analyses. These analyses have shown that the mechanisms of degradation of these polymers are different, and the lower number of pyrolysis products indicates a selective cleavage of the polymer during degradation in the saturated polysulfide polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 638–649, 2005     

A thermogravimetry/differential thermal analysis and pyrolysis/gas chromatography—mass spectrometry study of several tin(IV) dithiocarbamate complexes in an air atmosphere

Our P/GC—MS system has been modified such that pyrolysis can be performed in an air atmosphere. Several tin(IV) dithiocarbamate complexes have been prolysed in air in order to rationalise the precise role oxygen in the decomposition process. Further, the effectiveness of the P/GC—MS technique in separating pyrolysis products from individual decomposition stages was investigated using tetrakis(diethyldithiocarbamato)tin(IV) which, from standard TG studies, is known to decompose in air in two stages. It is doubtful, whether complete separation was achieved due to the similarity of products obtained from each stage of decomposition, however, the general method has potential.     

Impact of landuse change on the molecular composition of soil organic matter

The conversion of grassland into cultivated land is a common agricultural practice, generally leading to the decrease of the soil organic matter (SOM) content. In this study, we analysed quantitative changes in carbon content. Additionally qualitative changes occurring in the soil organic matter composition on a molecular basis were assessed using Curiepoint pyrolysis coupled to gas chromatography and mass spectrometry (pyrolysis GC/MS). The aim of the study was to follow the development of SOM in grassland soil, after conversion into arable soil.Soil was sampled before the conversion (0 month) as well as 3 months, and 1 year after the conversion. The samples were treated with 10% HF to remove mineral material before being subjected to analysis of the bulk chemical composition by pyrolysis GC/MS. The relative contributions of single molecules were obtained by the integration of the total ion chromatogram.Pyrolysis products derived from lignins, proteins and polysaccharides were identified in all samples. SOM under grassland, arable land and converted grassland released similar pyrolysis products. Three months after the conversion, lignin-derived pyrolysis products were found at lower concentrations in the converted grassland soil. Principal component analysis showed that arable land, grassland and the converted grassland could be distinguished using the score plot of the 2nd and 3rd principal components. The differences induced by grassland conversion are only transitory and 1 year after the conversion, SOM has a similar composition as SOM of the initial grassland soil.     

聚氨酯醇酸的裂解气相色谱-质谱研究

人工合成聚氨酯醇酸,用裂解气相色谱－质谱（ＰＧＣ－ＭＳ）法详细研究其热裂解产物的化学组成,探索其热裂解机理。裂解的主要产物为合成所用的单体甲苯二异氰酸酯（ＴＤＩ）、邻苯二甲酸酐及油脂相应的脂肪酸。     

Identification of polymer building blocks by Py–GC/MS and MALDI-TOF MS

The main goal of this work is to identify polyurethane (PU) building blocks by pyrolysis gas chromatography/mass spectrometry (Py–GC/MS) and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). Toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI) are widely used polymer building blocks. Py–GC/MS and MALDI-TOF MS were proved to be powerful methods to distinguish TDI-PU and MDI-PU according to the characteristic pyrolysis products and the different repeated units, respectively. In Py–GC/MS, the specific pyrolyzates are TDI for TDI-PU and MDI for MDI-PU. In MALDI-TOF MS, the weights of repeated units are 264?g/mol for TDI-PU and 340?g/mol for MDI-PU.