Thermal degradation of polyesters by simultaneous TG-DTA/FT-IR analysis

A combination system of thermogravimetric/differential thermal analysis (TG-DTA) and Fourier-transform infrared absorption spectroscopy (FT-IR) was described. This simultaneous TG-DTA/FT-IR technique gave spectroscopic and weight loss information about the thermal degradation process of engineering polyesters; poly(ethylene terephthalate)(PET) and poly(butylene terephthalate)(PBT). The evolved gases from PET were benzoic acid, carbon dioxide and carbon monoxide, while those from PBT were terephthalic acid esters and benzoic acid esters.

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Zusammenfassung Es wird ein kombiniertes System aus TG-DTA und FT-IR beschrieben. Mit dieser simultanen TG-DTA/FT-IR-Technik wurden spektroskopische und Massenverlustangaben über die thermische Zersetzung technisch wichtiger Polyester, namentlich von Poly(ethylenterephthalat) (PET) und Poly(Butylenterephthalat) (PBT) ermittelt. Die aus PET freigesetzten Gase waren Benzoesäure, Kohlendioxid und Kohlenmonoxid, die aus PBT freigesetzten Gase hingegen Terephthalsäureester und Benzoesäureester.

     

Basic aluminium succinate: An alumina precursor formed by precipitation from homogeneous solution

Precipitation from a homogeneous solution of aluminium nitrate by neutralisation using urea in presence of succinic acid leads to the formation of a well-defined alumina precursor, basic aluminium succinate, which on calcination yields microspheroidal γ-alumina with excellent free-flowing characteristics.     

Molecular structure and properties of oxime phosphonates: an FTIR and quantum chemical study

Peculiar features of the molecular structure, isomeric composition, and hydrogen bonding in new, potentially physiologically active γ-oxime alkylphosphonates were established. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1253–1258, July, 2007.     

Sequential coordination of orthosemiquinone radical ligands by surface centers on γ-Al2O3

The kinetics of sequential generation of mono-, bi-, and triradical centers in heterogeneous reactions of toluene solutions of orthoquinones, catechols, and their mixtures with γ-Al₂O₃ was studied. The localization of mono- and biradical centers on the solid oxide surface and the transfer of triradical Al³⁺ (Q⁻)₃ complexes (Q⁻ is the corresponding 3,6-di-tert-butylsemiquinone radical) to a solution (extraction of Al from the solid phase) were proved. The number of the triradical complexes extracted is considerably higher than that of active surface centers accessible for coordination with radical ligands. The conditions favoring the formation of the radical complexes on the Al ions were established. Possible mechanisms of these processes were proposed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2223–2227, November, 1998.     

Probing the surface acidity of modified γ-alumina with1H and15N high-resolution solid state NMR spectroscopy

¹H MAS NMR and¹⁵N NMR studies of adsorbed N₂ and N₂O molecules were used to characterize Br?nsted and Lewis acidic sites of unmodified γ-Al₂O₃ and γ-Al₂O₃ modified with NaOH. Changes in the concentrations of surface hydroxyls with the increase in the number of more “basic” OH groups for NaOH/γ-Al₂O₃ have been found by¹H MAS NMR experiments. Two different types of Lewis acidic sites in γ-Al₂O₃ have been revealed using¹⁵N NMR studies. The strongest sites are poisoned even at small NaOH concentrations (ca. 0.05 wt.%). Not only the number of electron-accepting sites but also their strength are supposed to decrease for modified γ-alumina.     

芳香烃异构体的毛细管柱气相色谱－傅里叶变换红外光谱联用技术分析

采用国产色谱仪与进口红外光谱仪及接口组成的气相色谱－傅里叶变换红外光谱（ＧＣ／ＦＴＩＲ）分析仪，使用大口径毛细管柱，分析了乙苯与苯乙烯固相催化反应液的复杂芳香烃异构体组成，讨论了ＧＣ／ＦＴＩＲ分析中随机噪声和基线漂移的去除方法。采用等高线图（ＣＴＤ）分析技术得到了混合液中各组分的纯气相红外光谱图，最后鉴定了１４个气相色谱峰中的９个，占整个色谱峰面积９９％以上。     

T-Jump/FTIR技术研究3,4-二硝基呋咱基氧化呋咱快速热裂解

采用温度快速跃迁原位池与快速扫描傅里叶变换红外联用(T-Jump/FTIR)技术在0.1-0.4MPa压强范围内研究了3,4-二硝基呋咱基氧化呋咱(DNTF)的快速热裂解.试验是以1000℃·s-1的升温速率在800和1000℃的温度下进行,用快速扫描傅里叶变换红外光谱实时跟踪分析DNTF裂解的气相产物.结果表明,DNTF快速热裂解的主要产物CO、CO2、NO和NO2的相对摩尔浓度c*与温度和压强有关,通过分析相对摩尔浓度比(c*NO/c*NO2)随温度和压强的变化,揭示了DNTF中碳硝基C—NO2存在均裂生成NO2和异构化生成NO两条竞争分解的可能途径,同时压强可能抑制呋咱环和氧化呋咱环生成NO的可能性.压强升高使c*CO和c*CO2升高,而使c*CO/c*CO2下降,证明DNTF的分解中存在非均相的气相/凝聚相反应和均相的气相产物间反应的二次或三次过程.     

不分流进样/Cu~(2 )预柱-毛细柱GC/FTIR鉴定环境水中痕量有机污染物

本文介绍一种新的分离分析技术,即不分流进样/Cu~(2 )预柱-毛细柱GC/FTIR,它能彻底消除溶剂影响,实现大容量进样,系统灵敏度比现行GC/FTIR系统高约1～2个数量级。这种技术已成功地用于长江水中痕量有机污染物的分析。     

Sol-Gel Synthesis of Transparent Alumina Gel and Pure Gamma Alumina by Urea Hydrolysis of Aluminum Nitrate

-Alumina was synthesized by a sol-gel method with the aluminum ion hydrolysis control performed by urea. The initial saturated Al³⁺/urea solution presented urea coordinated with the aluminum ion, as shown in the ¹³C NMR and ²⁷Al NMR spectra and longitudinal relaxation times, T ₁, from the latter. The substitution of water molecules in the Al³⁺ coordination shell by urea controlled the hydrolysis process and provided an extensive nucleation during the initial steps of the aluminum hydroxide formation due to urea thermolysis at 90°C. The resulting sol, composed of Al(OH)₃ nanoparticles, coalesced and became a transparent gel permeated by a solution of urea and the polycation ion [Al₁₃O₄(OH)₂₄(H₂O)₁₂]⁷⁺. The freshly prepared gel was transformed, under heating at 300°C, directly to -alumina, characterized by FTIR, ²⁷Al-MAS-NMR and S_BET techniques, without - or -phases, as a consequence of the high degree of homogeneity of the -alumina precursor.     

氨基聚酯树脂固化过程的FTIR跟踪

用FTIR内标法跟踪氨基聚酯树脂的固化过程,选取815cm~(-1)的三嗪环面外振动峰作内标峰,913cm~(-1)处的甲氧基变形振动峰和3500cm~(-1)左右的羟基伸缩振动峰为特征吸收峰。结果表明,随着固化的进行,涂膜的羟基、甲氧基和羧基递减,醚键和羰基递增,说明固化过程是以交联反应为主,伴有自缩合反应和酯化反应的复杂过程。     

添加三甲基乙氧基硅烷制备耐高温硅/铝复合气凝胶

以仲丁醇铝(ASB)和三甲基乙氧基硅烷(TMEO)为前驱体,采用溶胶-凝胶法,经乙醇超临界干燥制备了耐温高、成型性好的硅/铝复合气凝胶。用透射电子显微镜、N₂吸附分析仪、红外光谱仪、X射线衍射仪、hot disk热分析仪等仪器表征了气凝胶的形貌、孔结构、表面基团、晶相、热学等性能。在溶胶-凝胶过程中,通过添加TMEO在氧化铝纳米颗粒表面引入了-Si-(CH₃)₃基团,该基团经高温热处理后会在Al₂O₃表面形成SiO₂纳米颗粒,有效地抑制了Al₂O₃纳米颗粒在高温下的晶体生长,使得该复合气凝胶具有优异的耐温性能。在1 200 ℃高温处理后,线性收缩低至16%,比表面积可达141 m²·g^-1,这将进一步促进气凝胶材料在高温保温隔热、吸附、催化等领域的广泛应用。     

添加三甲基乙氧基硅烷制备耐高温硅/铝复合气凝胶

以仲丁醇铝(ASB)和三甲基乙氧基硅烷(TMEO)为前驱体,采用溶胶-凝胶法,经乙醇超临界干燥制备了耐温高、成型性好的硅/铝复合气凝胶。用透射电子显微镜、N2吸附分析仪、红外光谱仪、X射线衍射仪、hot disk热分析仪等仪器表征了气凝胶的形貌、孔结构、表面基团、晶相、热学等性能。在溶胶-凝胶过程中,通过添加TMEO在氧化铝纳米颗粒表面引入了-Si-(CH_3)_3基团,该基团经高温热处理后会在Al_2O_3表面形成SiO_2纳米颗粒,有效地抑制了Al_2O_3纳米颗粒在高温下的晶体生长,使得该复合气凝胶具有优异的耐温性能。在1 200℃高温处理后,线性收缩低至16%,比表面积可达141 m~2·g~(-1),这将进一步促进气凝胶材料在高温保温隔热、吸附、催化等领域的广泛应用。     

化学修饰氧化铝负载钴基催化剂吸附与反应行为的研究

提出了一种改进催化剂活性和C₅⁺烃选择性的方法,利用原位红外光谱、TPSR和费-托合成反应考察了催化剂的还原、分散、吸附与反应行为的关系.研究表明,载体处理的差异决定了CO在催化剂表面上的吸附形态,钴负载在氨修饰氧化铝上有利于桥式CO吸附,而醋酸改性氧化铝则增进了金属钴与载体之间的相互作用,催化剂以线形吸收态为主.CO加氢反应表明,氨修饰氧化铝负载钴催化剂能促进活性和C+5烃选择性的提高,而醋酸修饰氧化铝可抑止钴催化剂的活性和碳链增长.     

Multilevel profiling and identification of Dalbergia odorifera and Dalbergia stevensonii by FTIR,NMR and GC/MS

Chemical differences of the extractives revealed by FTIR methods can be further confirmed by ¹H NMR and ¹³C NMR. Meanwhile, the volatile compounds in the extractives can be identified by GC/MS     

Detection of new radiolysis products in γ-irradiated,methanolic medazepam by GC-FTIR

Summary A methanolic solution of 2% medazepam was irradiated with a dose of 50 kGy. A capillary gas chromatograph with a Fourier Transformation Infrared Spectrophotometer (FTIR) was used to investigate the radiolysis products in the solution. The changed products found earlier were confirmed and new ones identified. The radiolytic scheme can be improved and enlarged.     

Analysis of the metal-catalyzed decomposition of γ- and δ-haloesters by GC/FT-IR

Summary The decomposition of γ- and δ-haloesters has previously been observed to take place within a commercial GC/FT-IR light-pipe system. Using a home-built light-pipe interface, an analysis of this same class of compounds was conducted from which the source of the decomposition was determined to be a brass fitting central to the commercial system's assembly. It is proposed that the reaction is due to a weakening of the carbon-halogen bond by metal interaction thereby allowing lactonization to occur.     

Thermal cracking characteristics of PEEK under different environments by the TG/FTIR technique

The thermogravity/Fourier transform infrared (TG/FTIR) system was used to analyze the mechanism and kinetics of the thermal cracking of poly(ether ether ketone) (PEEK) under different environments. The thermal cracking of PEEK in a helium atmosphere showed that there were two stable cracking reaction regions. In the first-stage reaction, the thermal stability of the ketone group in PEEK was thermally more stable than the ether group. The cracking of the fluorenone structure in the carbonization showed it dominated the cracking scheme in the second-stage reaction. The thermal cracking of PEEK in air was governed by a random main-chain-scission and carbonization mechanism that increased with the cracking temperature under the influence of an increased thermal-oxidation mechanism. This mechanism predominated the PEEK solid reaction system until the compound completely was combusted. In air, the solid reaction rate of PEEK that produced a stable fluorenone structure was faster than that in helium and imparted a higher retarding effect on cracking in the initial lower temperature region. By means of the stable average activation energy for the kinetic parameter calculation for the order of reaction and pre-exponential factor, the theoretical TG curve was calculated and found to be identical to the observed TG curve. The kinetic model for thermal cracking of PEEK in air also is discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4582–4590, 1999     

负载型Cu/Al2O3和Cu/ZnO催化剂上CO2加氢的原位FTIR及准原位XPS/HS-LEIS研究

铜基催化剂是工业合成甲醇中常用的催化剂,其主要包含Cu,ZnO,Al2O3三种组分,研究各组分在催化合成甲醇过程中的本质作用及其相互间的协同作用不仅是一个催化基础科学问题,同时对于设计和合成新型高性能的铜基催化剂也有重要指导作用.以往的研究主要针对Cu和ZnO二元组分,关于Al2O3的作用很少有报道,主要观点认为Al2...     

用毛细管GC／MS和GC／FTIR研究挥发油的化学成分

本文用毛细管GC/MS和GC/FTIR对异叶青兰和鼠曲草两种植物挥发油的化学成分进行了研究,讨论了两种方法分析挥发油化学成分的优点和局限性。