Thermal Degradation of Aviation Synthetic Lubricating Base Oil

The thermal degradation, under oxidative pyrolysis conditions, of two synthetic lubricating base oils, poly-α-olefin (PAO) and di-ester (DE), was investigated. The main objective of the study was to characterize their behavior in simulated “areo-engine” conditions, i.e. compared the thermal stability and identified the products of thermal decomposition as a function of exposure temperature. Detailed characterizations of products were performed with Fourier transform infrared spectrometry (FTIR), gas chromatography/ mass spectrometry (GC/MS), viscosity experiments and four-ball tests. The results showed that PAO had the lower thermal stability, being degraded at 200°C different from 300°C for DE. The degradation also effected the tribological properties of lubricating oil. Several by-products were identified during the thermal degradation of two lubricants. The majority of PAO products consisted of alkanes and olefins, while more oxygen-containing organic compounds were detected in DE samples according to the observation of GC/MS analysis. The related reaction mechanisms were discussed according to the experimental results.     

Determination of the Thermal Decomposition Products of Terephthalic Acid by Using Curie-Point Pyrolyzer

The thermal decomposition behavior of terephthalic acid (TA) was investigated by thermogravimetry/differential thermal analysis (TG/DTA) and Curie-point pyrolysis. TG/DTA analysis showed that TA is sublimed at 276°C prior to decomposition. Pyrolysis studies were carried out at various temperatures ranging from 160 to 764°C. Decomposition products were analyzed and their structures were determined by gas chromatography–mass spectrometry (GC-MS). A total of 11 degradation products were identified at 764°C, whereas no peak was observed below 445°C. Benzene, benzoic acid, and 1,1′-biphenyl were identified as the major decomposition products, and other degradation products such as toluene, benzophenone, diphenylmethane, styrene, benzaldehyde, phenol, 9H-fluorene, and 9-phenyl 9H-fluorene were also detected. A pyrolysis mechanism was proposed based on the findings.     

Kinetics of Thermal Decomposition of Ammonium Perchlorate by TG/DSC-MS-FTIR

The method of thermogravimetry/differential scanning calorimetry–mass spectrometry–Fourier transform infrared (TG/DSC-MS-FTIR) simultaneous analysis has been used to study thermal decomposition of ammonium perchlorate (AP). The processing of nonisothermal data at various heating rates was performed using NETZSCH Thermokinetics. The MS-FTIR spectra showed that N₂O and NO₂ were the main gaseous products of the thermal decomposition of AP, and there was a competition between the formation reaction of N₂O and that of NO₂ during the process with an iso-concentration point of N₂O and NO₂. The dependence of the activation energy calculated by Friedman's iso-conversional method on the degree of conversion indicated that the AP decomposition process can be divided into three stages, which are autocatalytic, low-temperature diffusion and high-temperature, stable-phase reaction. The corresponding kinetic parameters were determined by multivariate nonlinear regression and the mechanism of the AP decomposition process was proposed.     

Catalyst Effects of Nanometer CuCr2O4 on the Thermal Decomposition of TEGDN Propellant

The catalyst effects of nanometer CuCr₂O₄ on the thermal decomposition of triethyleneglycol dinitrate (TEGDN) propellant were investigated using thermogravimetric analysis, differential scanning calorimetry, mass spectrometry, and Fourier transform infrared spectroscopy. The Ozawa equation and step integral equation were used to calculate the activation energy. The results showed that the thermal decomposition reaction of TEGDN propellant can be seen as two reactions. Nanometer CuCr₂O₄ added in TEGDN propellant reduced the activation energy of the second reaction step; therefore, the second reaction step was sped up. Mass spectrometry, Fourier transform infrared spectrometry and the combustion residue analysis results also supported this conclusion.     

硫醚类硫化物的热解及腐蚀性研究

采用高压釜热解法研究了硫醚类硫化物的热解规律。研究表明:硫醚类硫化物的热解产物主要是硫化氢和元素硫,结构不同的硫醚分解温度和分解产物也不同,具体的反应过程取决于自身的分子结构和反应条件。同时采用金属粉末腐蚀法研究了硫醚类硫化物的腐蚀性,结果表明硫醚腐蚀性是由于自身在高温条件下发生热解生成腐蚀性很强的"活性硫"造成的。     

Synthesis and Thermal Decomposition Mechanism of the Energetic Compound 3,5-Dinitro-4-nitroxypyrazole

A novel energetic material, 3,5-dinitro-4-nitroxypyrazole (DNNP), was synthesized via nitration and nucleophilic substitution reaction using 4-chloropyrazole as raw material. The structure of DNNP was characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and elemental analysis. Its detonation properties were calculated and compared with those of other commonly used energetic compounds. The thermal decomposition mechanism of DNNP was studied by means of thermogravimetry and differential scanning calorimetry coupled with a mass spectrometry (DSC-MS). The results show that the detonation properties of DNNP were better than those of TNT and comparable to those of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). In addition, the thermal decomposition mechanism of DNNP was supposed. Initially, the O–NO₂ bond was broken, thereby producing a nitropyrazole oxygen radical. Subsequently, the nitropyrazole oxygen radical was decomposed by free radical cleavage of nitro or isomerized to nitritepyrazole and subsequently decomposed by free radical cleavage of the nitroso group. Finally, pyrazole ring fission occurred and produced N₂, NO, N₂O, and CO₂.     

Thermal decomposition of RDX: A critical review

A critical assessment is given of the likely modes of thermal decomposition of RDX. Previous publications by other authors report that thermally decomposed RDX produces nitroxide and nitronylnitroxide radicals as intermediates. These results are discussed, and it is suggested that these radicals are not primary decomposition products, but are formed by the reaction of the radical products of thermal decomposition with molecular oxygen.     

Influence of Aluminum Particle Size on Thermal Decomposition of RDX

The effect of aluminum particle size (10.7 µm, 2.6 µm, and 40 nm) on the thermal decomposition of 1,3,5-trimethylene trinitramine (RDX) was investigated using differential scanning calorimetry (DSC), thermogravimetry–derivative thermogravimetry (TG-DTG), and DSC-TG–mass spectrometry (MS)–Fourier transform infrared (FTIR) spectroscopy, respectively. The results showed that the first exothermic peak (512 K) of RDX diminishes gradually with an increase in the nanosize aluminum content and is overcome by the second exothermic peak when the content of nano-Al reaches 30 wt%. The reaction mechanisms demonstrated by the nonisothermal kinetics of RDX in the absence and presence of 30 wt% Al were conformed to the Avrami-Erofeev equations for all of the RDX compositions. The nucleus growth factor for the RDX/40 nm Al mixture was found to be n = 2/3 compared to n = 3/4 for RDX with and without the microsized Al. The MS and FTIR analyses indicated that the thermal decomposition of RDX in the presence of Al nanopowders favors C-N bond cleavage over N-N bond cleavage as the rate determining step.     

Thermal Decomposition Behaviors and Burning Characteristics of AN/Nitramine-Based Composite Propellant

Ammonium nitrate (AN) has attracted much attention due to its clean burning nature as an oxidizer. However, an AN-based composite propellant has the disadvantages of low burning rate and poor ignitability. In this study, we added nitramine of cyclotrimethylene trinitramine (RDX) or cyclotetramethylene tetranitramine (HMX) as a high-energy material to AN propellants to overcome these disadvantages. The thermal decomposition and burning rate characteristics of the prepared propellants were examined as the ratio of AN and nitramine was varied. In the thermal decomposition process, AN/RDX propellants showed unique mass loss peaks in the lower temperature range that were not observed for AN or RDX propellants alone. AN and RDX decomposed continuously as an almost single oxidizer in the AN/RDX propellant. In contrast, AN/HMX propellants exhibited thermal decomposition characteristics similar to those of AN and HMX, which decomposed almost separately in the thermal decomposition of the AN/HMX propellant. The ignitability was improved and the burning rate increased by the addition of nitramine for both AN/RDX and AN/HMX propellants. The increased burning rates of AN/RDX propellants were greater than those of AN/HMX. The difference in the thermal decomposition and burning characteristics was caused by the interaction between AN and RDX.     

氨基甲酸酯热分解法制备对氯苯基异氰酸酯

对氨基甲酸酯热分解法制备对氯苯基异氰酸酯(4CPI)的工艺进行了研究。以对氯苯胺和碳酸二甲酯为原料,合成了热分解前体对氯苯基氨基甲酸甲酯(M4CPC);通过核磁共振氢谱、傅里叶变换红外光谱和热重分析对M4CPC的结构和性能进行了表征,确定了适宜的M4CPC热分解温度为150～200℃。常压下对M4CPC热分解溶剂的考察结果表明,高介电常数的有机溶剂对M4CPC的分解比较有利。M4CPC热分解制备4CPI的主要副产物为N,N′-双(4-氯苯基)脲。以低毒的N,N′-二甲基乙酰胺为溶剂,在M4CPC的摩尔分数为10%、催化剂用量为m(Bi2O3)∶m(M4CPC)=0.05、反应温度162～164℃、反应时间1h的优化条件下,M4CPC的转化率为90.4%,4CPI的选择性为66.0%。     

Deuterium isotope effects during the thermal decomposition of 1,4-butanediammonium dinitrate and selected composites with ammonium and potassium nitrates

Abstract

The thermal decomposition of 1,4-butanediammonium dinitrate (BDD), selected BDD-based composites with ammonium/potassium nitrates (BAK), and specifically deuterated analogs, was investigated. A previous study showed that molten BDD decomposes thermally via a multistep process that produces a variety of condensed phase and gaseous products. The nature of the products suggested that proton transfer from cation to anion followed by C-N bond rupture occurred early in the decomposition process. During the present investigation condensed phase DSC induction period studies performed using specifically deuterated BDD analogs generally displayed inverse deuterium isotope effects. Impact sensitivities, times to explosion and critical temperatures were also determined for BDD, the BAK composites, and many of their N-deuterated analogs. While these studies did not unequivocally reveal the specific covalent bond rupture responsible for generating the conditions favorable for exothermic decomposition, they did provide a direct relationship between induction period chemistry and macroscopic thermal sensitivity properties.     

Nanoscale Effect on Thermal Decomposition of 2,2′,4,4′,6,6′-Hexanitrostilbene by Dynamic Pressure Measuring Thermal Analysis

2,2′,4,4′,6,6′-Hexanitrostilbene (HNS) was prepared into nano- and microscale particles. The thermal decomposition behaviors were investigated using dynamic pressure measuring thermal analysis. The released gas amount and apparent activation energy show that the nanoparticles (NPs) have higher reaction activity and faster reaction rate and experience more drastic autocatalytic reaction than the microparticles (MPs). A reduction in particle size to nanoscale decreases the energy barrier of thermal decomposition and influences the reaction mechanism. The “trinitrotoluene mechanism,” which is the homolysis via hydrogen transfer to form a six-membered transition state, corresponds to the initial decomposition of HNS. The nanoscale effect is attributed to the surface properties of NPs, including high surface energy, rapid mass and heat transfer, and numerous active reaction sites on the reactant interface.     

Thermal characteristics of alkali metal dinitramide salts

Abstract

A thermal study of the dinitramide salts of lithium, sodium, potassium, rubidium and cesium is presented. The series displayed a complex set of DSC exothermic decays with the exception of the lithium salt which showed two simple exothermic decomposition reactions. All five salts thermally decomposed to the equivalent nitrate salt as evidenced by DSC melting endotherms and TGA stoichiometric mass losses. Physical changes due to thermal heating were able to be followed by hot stage microscopy. Thermal decay was accompanied by gas evolution.     

Decomposition of Azo- and Hydrazo-Linked Bis Triazines

In a search for novel energetic materials, azo-linked bis triazines were pursued. Herein the thermal decomposition of 14 simple triazines and 16 hydrazo- or azo-linked bis triazines were studied using mass spectrometry, permanent gas evolution, and differential scanning calorimetry. At temperatures far above the melting/decomposition point, decomposition was complete. Lower temperatures provided insight into the stability of the functional groups pendant to the triazine rings. Decomposition gases were identified by chromatography; they indicated little degradation of the triazine rings. The s-triazine ring system appears very stable, resisting decomposition up to 550°C while its substituents undergo relatively isolated chemistry.     

高温原位XRD和TG-MS法研究S Zorb工业吸附剂热解行为

从某S Zorb工业装置上采集了两个具有不同脱硫活性的工业吸附剂,利用XRD、碳硫分析和SEM表征其晶体结构、化学组成和形貌,利用高温原位XRD表征了吸附剂在受热过程中晶体结构的变化规律,TG-MS和DTA表征其热分解过程和产物。研究表明,Zn2SiO4的形成显著影响了吸附剂的化学组成、脱硫活性和稳定性、分解温度、失重量。吸附剂的热解主要包括5个阶段,主要为物理吸附水和吸附物的挥发、Ni物相的氧化、积炭的燃烧、ZnS热解和晶相转变等。高温和酸性环境会导致Zn2SiO4物相的进一步生成。最后详细阐述了吸附剂的热解机理,以期为S Zorb工业生产和科研提供信息。     

Ammonium perchlorate decomposition: Neat and solution1

Abstract

The thermal decomposition of ammonium perchlorate (AP) was examined over a broad temperature range (215°C to 385°C) in solution and condensed phase. Over the entire temperature range, the decomposition, as monitored by loss of ammonium ion, appeared first-order out to 70% decomposition. Up to about 350°C the decomposition of AP in methanol (5wt% AP) proceeded at a rate similar to neat AP, but the AP in aqueous solution (20wt%) decomposed considerably slower than the neat material. Activation energies and frequency factors were determined for each experimental condition. In addition, decomposition products, both gaseous and condensed phase, were identified and quantified. For neat AP decomposition, the following reaction stoichiometries were determined.

At low temperatures, decomposition of ammonium perchlorate in methanol proceeded at a similar rate to that of neat AP. In contrast to decomposition of neat AP, the only nitrogen-containing decomposition product was nitrogen gas, while chlorine appeared only as chloride. The presence of CO and CO₂ as decomposition gases and chromatographic analysis of the solvent indicated interaction between methanol and AP. The decomposition of AP in water was slowed, but product distribution was not significantly different than that of neat AP.     

ZDDP热稳定性及其对抗磨性能的影响

使用热重法（TGA）和红外法（FTIR）研究了不同ZDDP的热稳定性能,Prim.ZDDP热稳定性能最好,其后依次为Sec.ZDDP-4,Sec.ZDDP-3,Mixed ZDDP,Sec.ZDDP-2,Sec.ZDDP-1。不同添加剂对ZDDP分解也有一定影响,其中清净剂能延缓ZDDP的分解;抗氧剂在短时间内表现不明显,氧化8 h则也能在一定程度上延缓ZDDP的分解;分散剂与抗氧剂效果相似,且同时能把分解的物质分散于油品中,在整个氧化过程中保持油品透明无沉淀。在单剂抗磨性能方面,表现最好的为Prim.ZDDP,Mixed ZDDP与Prim.ZDDP相差不大,其次为Sec.ZDDP-3,Sec.ZDDP-1/Sec.ZDDP-2,Sec.ZDDP-4。油品氧化后,其抗磨性能出现一个先升后降的过程,不同的ZDDP分解速率不一样,导致其在氧化不同时间后抗磨性能出现分化,表现最好的为Prim.ZDDP。     

实沸点蒸馏前后高酸重质原油的石油酸分布表征

The molecular transformations of carboxylic acids in heavy acidic SL crude before and after true boiling point distillation were examined by ultra-high resolution negative-ion electrospray ionization （ESI） Fourier transform ion cyclotron resonance mass spectrometry （FT-ICR MS）. The acid class （heteroatom number）, type （z numbers） and carbon number distributions were positively characterized. It was found out that the total acid number （TAN） of SL crude decreased after true boiling point distillation, and the abundance of O2 class in mass spectra was also found to be reduced from 67.6% to 34.5% in SL TBP mixed crude as measured by MS spectra, indicating to a potential carboxylic acid decomposition. However, it was interesting that the carboxylic acids type distribution in both oils was almost the same although their relative abundance in SL TBP mixed crude turned to be much lower, suggesting that various petroleum carboxylic acid types have the similar thermal decomposition reaction behavior. Furthermore, for each O2 type of acids in SL TBP mixed crude, the abundance of carboxylic acids with carbon number higher than 35 was reduced greatly, especially for those with carbon number higher than 60, the mass peaks of which were nearly totally removed, indicating that the large carboxylic acid molecules in heavy fractions decomposedmore significantly because of longer heating time during the true boiling point distillation process. As a result, the reduction ofTAN may be caused by the thermal decomposition of carboxylic acids especially those with high carbon number, suggesting that quick distillation or much lower pressure is required to avoid the thermal decomposition.     

Thermal Degradation of Asphaltene and Infrared Characterization of Its Degraded Fractions

Petroleum asphaltene and its thermally degraded fractions are characterized using thermal analysis and infrared spectrometry, respectively. Thermal analysis of asphaltene has demonstrated that heating rate is important in studying thermal degradation of asphaltene. Asphaltene goes through three stages of mass reduction under thermogravimetric analysis from 25 to 1,000°C at a heating rate of 1°C/min and below. The products from thermal degradation of asphaltene at three different temperature intervals are collected. The collected fractions are characterized using a Fourier transform infrared spectrometer. The fraction collected between 220 and 350°C demonstrates similar infrared spectrum to that of asphaltene, however, with less aromatic properties. The fraction collected between 350 and 450°C resembles the undegraded asphaltene most based on the infrared spectra obtained. The fraction collected between 450 and 650°C demonstrates a spectrum that is totally different from those of the undegraded asphaltene and the other two fractions. In addition, a high degree of oxidation is observed on all of the three degraded fractions of asphaltene.     

Particle Size Effects on Thermal Decomposition of Energetic Material

This work refers to a study of the thermal decomposition of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) by differential scanning calorimetry (DSC) under nonisothermal conditions, with heating rates from 5 to 20°C min^?1. The influence of the particle size in the thermal decomposition of HMX was verified. The activation energy for the decomposition of each sample was calculated using the peak temperature shift methods, proposed by Kissinger and Ozawa. A significant variation in the results was observed according to the range of the particle size used. The results showed that, as the particle size of HMX increased, the thermal decomposition temperature of HMX and the decompositional activation energies ranges enhanced. At the same time, at a constant heating rate, the decomposition temperatures of the smaller particles were lower than those of larger ones. The critical temperature for thermal explosion of each sample was calculated. Also, the values of ΔS^#, ΔH^#, and ΔG^# of reaction for each particle size were computed.