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1.
Pyrolysis of N-doped organic xerogels prepared from different N-containing precursors has been studied by TG–MS. The pyrolytic process has been ascertained to consist of three steps. The first step (up to cca. 250 °C) has been interpreted as water loss (humidity, fixed water from pores) and in some cases as formaldehyde loss. The second step has been connected with volatile substances evolution (cca. 250–450 °C) with predominant release of NH3, CO2 and products of melamine (M) or urea decomposition. Reaction/pore water and formaldehyde have also been detected in this step. The third step of pyrolysis (450–1,000 °C) has been ascribed to carbonization reaction when the other releases of NH3, CO2, reaction/pore water and M decomposition products have continued. This was accompanied with evolution of H2 and 3-hydroxypyridine. On the basis of TG measurements, it was found that increasing time of condensation of organic xerogels and amount of used catalyst lead to higher yield of carbonaceous products. In addition, adsorption experiments of Pb(II) on N-doped carbon xerogels proved that relationship between adsorption properties of xerogels and nitrogen loss during pyrolysis exists. When the sample contains only amino groups, they are lost during pyrolysis as ammonia and the adsorption ability is low, while nitrogen comprised in the aromatic rings of N-precursors stays in the structure and causes enlarging of adsorption capacity. 相似文献
2.
Sanjiv Arora Mahesh Kumar Mahender Kumar 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1277-1286
Wood, one of the flammable material, was treated with aqueous solution of guanidine nitrate (GUN) and also with small amount
of bases like N,N-dimethylformamide, 4-dimethylaminopyridine, pyridine, and triethylamine in the treating solution. These bases catalyze the
impregnation of GUN as indicated by increase in mass gain percentage, elemental analysis, and scanning electron microscopy.
To study their thermal behavior, dynamic thermogravimetry (TG) and derivative thermogravimetry (DTG) analysis under nitrogen
atmosphere have been applied from ambient temperature to 973 K on all samples, at multiple linear heating rates 2.5, 5, 10,
and 20 K min−1. Non-isothermal, “model free” iso-conversional multiple heating rate methods, Ozawa–Flynn–Wall (O–F–W) and modified Coats–Redfern
are used to calculate activation energy of samples. The activation energy of samples is found in the range 109–208 kJ mol−1. Thermal parameters like overall pyrolysis duration, maximum mass loss rate, corresponding to DTG peak maximum and percentage
char yield calculated at 873 K from TG curves are used to appraise the flammability of samples. Also, flammability of samples
is determined by reliable methods namely limiting oxygen index and underwriters laboratories 94 (UL 94) test. The aforesaid
study indicates that base catalyzed impregnated samples are less flammable than those impregnated with only GUN and untreated
ones. 相似文献
3.
B. Ravindran G. Madhurambal M. Mariappan S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2011,104(3):893-899
Thiourea Urea Zinc (II) Chloride (TUZC), a new semiorganic non-linear optical material has been synthesized. The solubility
studies have been carried out at room temperature. Single crystals of different proportions of TUZC have been grown by slow
evaporation of saturated aqueous solution at room temperature. The FTIR and UV spectral bands have been compared with urea,
thiourea and bis Thiourea Zinc Chloride (BTZC). The TG curve showed a two steps mass loss on heating the compound between 30 and 800 °C corresponding
to two exothermic DTA peaks at 181–183 and 250–252 oC. 相似文献
4.
Co-pyrolysis of olive residue with poly(vinyl chloride) using thermogravimetric analysis 总被引:1,自引:1,他引:0
Pyrolytic process has a promising potential for the environmentally friendly upgrading of lignocellulosic materials and plastic
waste. The co-pyrolysis of olive residue and poly(vinyl chloride) was investigated under nitrogen atmosphere by dynamic thermogravimetric
analysis in the temperature range of 300–975 K. Two main stages of mass loss have been evidenced by TG analysis. The first
occurs in the temperature range of 420–684 K, and the second occurs at 631–840 K. This research was focused on the interaction
between olive residue and poly(vinyl chloride) during the pyrolysis process. Discrepancies between the experimental and calculated
TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis. It was found that
reactivity of olive residue was increased in olive residue/PVC mixture. In addition, a kinetic analysis was performed to fit
thermogravimetric data, the mixture is considered as multistage process. A reasonable fit to the experimental data was obtained
for all materials and their mixture by isoconversional Friedman method. 相似文献
5.
Aouad A. Bilali L. Benchanâa M. Mokhlisse A. 《Journal of Thermal Analysis and Calorimetry》2002,67(3):733-743
The natural phosphate and its demineralization products from Moroccan deposit were pyrolysed in a thermogravimetric analyser
(TG) to examine the influence of the heating rate and mineral matter on their thermal decomposition. The heating rates investigated
in the TG were 5–100°C min−1 to final temperature of 1200°C. The integral method was used in the analysis of the TG to determine the kinetic parameters.
It has been found that for the natural phosphate and corresponding kerogen analysed in the TG, the increase of the heating
rate shifts the maximum rate loss to higher temperature. A first order reaction was found to be adequate for pyrolysis in
the range 150–600°C which was attributed to kerogen decomposition. In addition, the results indicate that the removal of mineral
matter affected the kinetic parameters found for kerogen in the natural phosphate.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
Jürgen Paulsdorf Hans-Dieter Wiemhöfer Andrej Orinák Petr Zámostný Zdeněk Bělohlav David Baxter 《Central European Journal of Chemistry》2007,5(1):271-290
Polyphosphazenes represent a unique class of polymers with a backbone composed of alternating phosphorous and nitrogen atoms.
The thermal behaviour and decomposition of a variety of polyphosphazenes depends on the type of side groups present. Especially
those that bear aryloxy side groups, possess a high temperature stability as well as excellent flame resistance. Pyrolysis-capillary
gas chromatography has been used in a study of three polyphosphazene samples for thermal stability characterisation. Degradation
products were detected with three single detectors for flame ionisation (FID), nitrogen-phosphorous sensitivity (NPD) and
mass spectrometry (MSD) at different pyrolysis temperatures ranging from 300°C up to 800°C. The NPD responses for phosphorous
or nitrogen fragments of polyphosphazenes have been used for the construction of degradation product schemes and the examination
of the thermal stability of the polyphosphazene’s backbone. Partial identification of the degradation products present in
the gaseous phase was achieved by MSD. The polyphosphazenes thermal degradation conversion rates were at a maximum at 450–500°C.
At various pyrolysis temperatures, the calculated N/P peak area ratio is a function of the degree of polyphosphazene-N=P-chain
degradation, and reflective of the nitrogen — phosphorous detector sensitivity. NPD proved to be suitable tool for characterization
of polyphospazene thermal stability. 相似文献
7.
Hou-yin Zhao Yan Cao Song P. Sit Quentin Lineberry Wei-ping Pan 《Journal of Thermal Analysis and Calorimetry》2012,107(2):541-547
The pyrolysis behavior of bitumen was investigated using a thermogravimetric analyzer–mass spectrometer system (TG–MS) and
a differential scanning calorimeter (DSC) as well as a pyrolysis-gas chromatograph/mass spectrometer system (Py-GC/MS). TG
results showed that there were three stages of weight loss during pyrolysis—less than 110, 110–380, and 380–600 °C. Using
distributed activation energy model, the average activation energy of the thermal decomposition of bitumen was calculated
at 79 kJ mol−1. The evolved gas from the pyrolysis showed that organic species, such as alkane and alkene fragments had a peak maximum temperature
of 130 and 480 °C, respectively. Benzene, toluene, and styrene released at 100 and 420 °C. Most of the inorganic compounds,
such as H2, H2S, COS, and SO2, released at about 380 °C while the CO2 had the maximum temperature peaks at 400 and 540 °C, respectively. FTIR spectra were taken of the residues of the different
stages, and the results showed that the C–H bond intensity decreased dramatically at 380 °C. Py-GC/MS confirmed the composition
of the evolved gas. The DSC revealed the endothermic nature of the bitumen pyrolysis. 相似文献
8.
Bharti U. N. Verma Kingsuk Mukhopadhyay 《Journal of Thermal Analysis and Calorimetry》2011,104(3):1071-1075
The ligand [2-(1,2,3,4-thiatriazole-5-yliminomethyl)-phenol] (L) is a schiff base derived from condensation reaction of 1,2,3,4-thiatriazole-5-ylamine
and Salicylaldehyde. Synthesis of the ligand (L) and the complex [Cu(II)(L)2]·2H2O have been studied in our previous work (Bharti et al., Asian J Chem 23(2):773–776, 2011). Thermal decomposition behavior
of synthesized Cu(II) complex has been investigated by thermo gravimetric (TG) analysis at heating rate of 10 °C min−1 under nitrogen atmosphere. The mechanism of decomposition of Cu(II) complex has been established from TG data. Kinetic parameters
such as order of reaction (n), activation energy (E
a), frequency factor (Z) and entropy of activation (∆S
≠) were calculated by using Freeman and Carroll (J Phys Chem 62:394–397, 1958) as well as Doyle’s methods as modified by Zsako
(J Phys Chem 72(7):2406–2411, 1968). 相似文献
9.
Manoj Kumar J. Udhayakumar Ashutosh Dash 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(1):53-58
Aiming the selective recovery of palladium from high level radioactive liquid waste (HLW), a chelating thiamide type sorbent,
CWP–TU, was prepared by the modification of Japanese cedar wood powder (CWP). Convection oven and microwave heating were separately
used for modification purpose and found that microwave heating is more effective over oven heating. CWP–TU was extensively
studied for the adsorption of Pd(II) from nitric acid medium. The batch test showed that nitric acid concentration of 3 M
or higher is favorable for Pd(II) loading. Consistent adsorption of Pd(II) under gamma irradiation condition demonstrated
the feasibility of using CWP–TU in real HLW. Also, Pd(II) only adsorption from simulated HLW solution verified the palladium
only selectivity of the sorbent as well as the lack of influence of coexisting metal ions on its affinity toward Pd(II). CWP–TU
holds maximum Pd(II) loading capacities of 0.98 mol/kg at 30 °C and 1.04 mol/kg under gamma irradiation. A comparative study
using some ion exchange resins revealed that the resins are either ineffective in nitrate medium or lack stability under irradiation. 相似文献
10.
K. Muraleedharan M. P. Kannan T. Ganga Devi 《Journal of Thermal Analysis and Calorimetry》2011,103(3):943-955
The thermal decomposition of potassium iodate (KIO3) has been studied by both non-isothermal and isothermal thermogravimetry (TG). The non-isothermal simultaneous TG–differential
thermal analysis (DTA) of the thermal decomposition of KIO3 was carried out in nitrogen atmosphere at different heating rates. The isothermal decomposition of KIO3 was studied using TG at different temperatures in the range 790–805 K in nitrogen atmosphere. The theoretical and experimental
mass loss data are in good agreement for the thermal decomposition of KIO3. The non-isothermal decomposition of KIO3 was subjected to kinetic analyses by model-free approach, which is based on the isoconversional principle. The isothermal
decomposition of KIO3 was subjected to both conventional (model fitting) and model-free (isoconversional) methods. It has been observed that the
activation energy values obtained from all these methods agree well. Isothermal model fitting analysis shows that the thermal
decomposition kinetics of KIO3 can be best described by the contracting cube equation. 相似文献
11.
混甲酚甲醛炭气凝胶的制备及表征 总被引:5,自引:0,他引:5
以混甲酚和甲醛为原料,经溶胶-凝胶民、酸洗老化、超临界干燥得有机气凝胶,密度0.1507g/cm^3,进一步炭化得炭气凝胶。采用正交试验方法重点考察了炭化工艺条件对炭气凝胶结构和性能的影响,并用TEM、TG、低及附等手段进行了表征。结果表明,炭化工艺条件影响因素顺序为:升温速率〉炭化终温〉维温时间,最佳炭化条件下炭气凝胶密度为0260g/cm^3,幽静面积人1022m^2/g,平均戏5.6mm。T 相似文献
12.
Jeya Rajendran T. Lekshmana Thanu Lingam M. Jose S. Jerome Das 《Journal of Thermal Analysis and Calorimetry》2011,103(3):845-851
A single crystal of heptaaqua-p-nitrophenolatostrontium(II) nitrophenol (HNSN) was grown, and the structure was confirmed by UV–Vis–NIR, FT-IR, FT-NMR, and
high-resolution X-ray diffraction (HRXRD) analyses. The dielectric loss, dielectric constant, and the mechanical strength
of the crystal have already been reported. The dynamic, non-isothermal thermal analysis was carried out at different heating
rates, and TG and DTG data were used for the interpretation of the mechanisms and kinetics of decomposition by means of a
model fitting method, Coats–Redfern equation, and a model-free method, Kissinger and Flynn–Wall method. The values of activation
energy (E) and the pre-exponential factor (ln A) of each stage of thermal decomposition at various linear heating rates were calculated. 相似文献
13.
In this work, a kinetic study on the thermal degradation of carbon fibre reinforced epoxy is presented. The degradation is
investigated by means of dynamic thermogravimetric analysis (TG) in air and inert atmosphere at heating rates from 0.5 to
20°C min−1 . Curves obtained by TG in air are quite different from those obtained in nitrogen. A three-step loss is observed during
dynamic TG in air while mass loss proceeded as a two step process in nitrogen at fast heating rate. To elucidate this difference,
a kinetic analysis is carried on. A kinetic model described by the Kissinger method or by the Ozawa method gives the kinetic
parameters of the composite decomposition. Apparent activation energy calculated by Kissinger method in oxidative atmosphere
for each step is between 40–50 kJ mol−1 upper than E
a calculated in inert atmosphere.
The thermo-oxidative degradation illustrated by Ozawa method shows a stable apparent activation energy (E
a ≈130 kJ mol−1 ) even though the thermal degradation in nitrogen flow presents a maximum E
a for 15% mass loss (E
a ≈60 kJ mol−1 ).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Bhojya Naik H. S. Siddaramaiah Ramappa P. G. 《Journal of Thermal Analysis and Calorimetry》1999,55(3):841-849
The complexes of cobalt(II) with dothiepin (DOT) hydrochloride have been studied for kinetics of thermal degradation by thermogravimetric
analysis (TG) and derivative thermogravimetric studies (DTG) in a static nitrogen atmosphere at a heating rate of 10° C min−1. A general mechanism of thermal decomposition is advanced involving dehydration and decomposition process for both organic
and inorganic ligands. The thermal degradation reactions were found to proceed in three steps having an activation energy
in the range 6.75–170 kJ mol−1. Thermal decomposition kinetics parameters were computed on the basis of thermal decomposition data.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
The pyrolysis of wheat straw has been carried out by means of thermogravimetric analysis in inert atmosphere. The samples
were heated over a range of temperatures that includes the entire range of pyrolysis with three different heating rates of
5, 10 and 20 K min−1. The activation energy values as a function of the extent of conversion for the pyrolysis process of wheat straw have been
calculated by means of the Flynn–Wall–Ozawa isoconversional method, the Vyazovkin–Sbirrazzuoli isoconversional method and
an iterative isoconversional method presented in this article. The results have showed that there are small differences between
the activation energy values obtained from the three methods, and the pyrolysis process reveals a dependence of the activation
energy on conversion and have indicated the validity of the iterative integral isoconversional method. The effective activation
energy for the pyrolysis of wheat straw is 130–175 kJ mol−1 in the conversion range of 0.15–0.85. Furthermore, the prediction of the pyrolysis process under isothermal conditions from
the dependence of the activation energy on the extent of conversion has been presented. 相似文献
16.
Guiying Xu Baizeng Fang Guogang Sun 《Journal of Thermal Analysis and Calorimetry》2012,108(1):109-117
Thermal characteristics of wheat distiller grains (WDGs) and steam gasification kinetics of the corresponding pyrolysis char
were studied by thermogravimetric analysis. The pyrolysis process of WDGs can be divided into three stages including the drying,
devolatilization, and carbonation. The heating rate and final temperature are the most important factors influencing the WDGs
decomposition. The ultimate mass loss increases with increasing final temperature while the mass loss rate and the characteristic
temperature for the maximum reaction rate increase with the increasing heating rate. For the pyrolysis of WDGs, the average
activation energy was calculated as 77.45 kJ mol−1 by Coats–Refern method. While for the steam gasification of the pyrolysis char, the shrinking-core model fits the gasification
behavior better than the volumetric reaction one and the activation energy, and the pre-exponential factor were calculated
to be 199.19 kJ mol−1 and 7.21 × 106 s−1, respectively, with the former model. 相似文献
17.
G. V. Plaksin V. A. Semikolenov V. I. Zaikovskii E. M. Moroz V. Yu. Gavrilov 《Reaction Kinetics and Catalysis Letters》1998,63(1):157-163
Cellular carbon has been prepared by pyrolysis of a propane—butane mixture in a flow reactor at 700–1250 K. Its structural
characteristics were studied by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction
and adsorption methods. It was shown that cell-type carbon possesses a unique structure in contrast to carbon composite “Sibunnit”
and filamentous carbons and it may be a promising support for catalyst preparation. 相似文献
18.
P. Budrugeac Carmen Racles V. Cozan Maria Cazacu 《Journal of Thermal Analysis and Calorimetry》2008,92(1):263-269
Thermal and thermo-oxidative stability of some poly(siloxane-azomethine)s obtaining starting from bis(formyl-p-phenoxymethyl)tetramethyldisiloxane and different organic diamines have been investigated by TG+DTG+DSC simultaneous analyses
performed in argon flow and air static atmosphere, respectively. TG, DTG and DSC curves of each polymer showed three or four
successive degradation steps at different temperatures according to the composition of the sample and the gaseous atmosphere
in which the thermal analysis was performed. For each process, the following parameters were evaluated: total mass loss, temperature
corresponding to the maximum reaction rate, maximum reaction rate, temperature corresponding to certain mass loss. In order
to determine the thermal and thermo-oxidative stabilities of investigated polymers, the following values were determined:
T
x% — temperature corresponding to x% mass loss, and %Δm
T — mass loss at a given temperature T. The obtained orders of stability were correlated with the structure of investigated polymers. 相似文献
19.
升温速率对生物质热解的影响 总被引:4,自引:0,他引:4
稻壳、稻秆及麦秆是中国主要的农业废弃物,如何综合、有效地利用这些农业废弃物进行资源化研究显得十分必要。热解是热化学转化中最为基本的过程,是气化、液化及燃烧过程的初始和伴生反应,对热解的分析有助于热化学转化过程控制及高效转化工艺的开发。目前,国内外对生物质及其组分的热解已有大量的研究,但对中国主要的农业废弃物稻壳、稻秆及麦秆的研究较少。本研究利用热重和红外联用技术深入研究了升温速率对三种典型生物质热解气体产物的影响,并对生物质的热解动力学及热解气体产物的析出规律进行实时在线分析。 相似文献
20.
In this research, pyrolysis and combustion behavior of three different oil shale samples from Turkey were characterized using
thermal analysis techniques (TG/DTG). In pyrolysis experiments, two different mechanisms causing mass loss were observed as
distillation and cracking. In combustion experiments, two distinct exothermic peaks were identified known low and high temperature
oxidation. On the other hand, determination of activation energies are required for the estimation of oil extraction conditions
from the oil shales. Differential methods are used to determine the activation energies of the samples where various f(α) models are applied from the literature. It was observed that the activation energies of the all oil shale samples are
varied between 13.1–215.4 kJ mol−1 in pyrolysis and 13.1–408.4 kJ mol−1 in combustion experiments which are consistent with other kinetic results. 相似文献