scholarly journals Pyrolysis and Oxidation of PAN in Dry Air. Thermoanalytical Methods

1970 ◽  
Vol 17 (1) ◽  
pp. 38-42
Author(s):  
Anna BIEDUNKIEWICZ ◽  
Pawel FIGIEL ◽  
Marta SABARA
Keyword(s):  
Temperature Increase ◽  
Heating Rates ◽  
Linear Change ◽  
Dry Air ◽  
Isothermal Conditions ◽  
Gaseous Products ◽  
Heterogeneous Processes ◽  
Temperature Ranges ◽  
Higher Temperature ◽  
Kinetics Of

The results of investigations on pyrolysis and oxidation of pure polyacrylonitrile (PAN) and its mixture with N,N-dimethylformamide (DMF) under non-isothermal conditions at linear change of samples temperature in time are presented. In each case process proceeded in different way. During pyrolysis of pure PAN the material containing mainly the product after PAN cyclization was obtained, while pyrolysis of PAN+DMF mixture gave the product after cyclization and stabilization. Under conditions of measurements, in both temperature ranges, series of gaseous products were formed.For the PAN-DMF system measurements at different samples heating rates were performed. The obtained results were in accordance with the kinetics of heterogeneous processes theory. The process rates in stages increased along with the temperature increase, and TG, DTG and HF function curves were shifted into higher temperature range. This means that the process of pyrolysis and oxidation of PAN in dry air can be carried out in a controlled way.http://dx.doi.org/10.5755/j01.ms.17.1.246

scholarly journals Kinetic study of Mongolian coals by thermal analysis

2018 ◽  
Vol 18 (44) ◽  
pp. 20-23
Author(s):  
Jargalmaa S ◽  
Tsatsral G ◽  
Battsetseg M ◽  
Batkhishig D ◽  
Ankhtuya A ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Thermal Characterization ◽  
Low Rank ◽  
Weight Changes ◽  
Heating Rates ◽  
Weight Losses ◽  
Brown Coals ◽  
Temperature Ranges ◽  
Kinetics Of

Thermal analysis was used for the thermal characterization of the coal samples. The experiments were performed to study the pyrolysis and gasification kinetics of typical Mongolian brown coals. Low rank coals from Shivee ovoo, Ulaan ovoo, Aduun chuluun and Baganuur deposits have been investigated. Coal samples were heated in the thermogravimetric apparatus under argon at a temperature ranges of 25-1020ºC with heating rates of 10, 20, 30 and 40ºC/min. Thermogravimetry (TG) and derivative thermogravimetry (DTG) were performed to measure weight changes and rates of weight losses used for calculating the kinetic parameters. The activation energy (Ea) was calculated from the experimental results by using an Arrhenius type kinetic model.

Study on the Pyrolysis Kinetics of HCl-Pretreated Soybean Stalk

2014 ◽  
Vol 953-954 ◽  
pp. 261-266
Author(s):  
Dong Yu Chen ◽  
Yan Qing Hu ◽  
Qing Yu Liu
Keyword(s):  
Heating Rate ◽  
Temperature Increase ◽  
Loss Rate ◽  
High Efficiency ◽  
Three Dimensional ◽  
Pyrolysis Kinetics ◽  
Heating Rates ◽  
Acid Washing ◽  
Shoulder Peak ◽  
Kinetics Of

To study the influences of the acid-washing on the characteristics of soybean stalk pyrolysis , and search the high-efficiency catalyst for biomass pyrolysis, pyrolysis experiments of soybean stalk pretreated by 0.1mol/L HCl acid solution were performed by nonisothermal thermogravimetric analysis (TGA) at five different heating rates. The results showed the pyrolysis process of HCl-washed soybean stalk can be separated into four stages (water loss, depolymeri-zation and vitrification, thermal decomposition, and carbonization). At the same heating rate, the maximum pyrolysis rate of HCl-washed is larger than untreated soybean stalk, but the corresponding temperature is higher. All the DTG (differential thermogravimetric) curveas appear a smaller shoulder peak respectively. With the heating rate increasing, the main pyrolysis zone of the TG (thermogravimetric) and DTG curves move to the high-temperature direction, and the maximum pyrolysis rate and its corresponding temperature increase too. HCl-wahsed makes the weight loss rate of the final temperature increase 5% approximately. The value area of activation energy of the main pyrolysis area is 140.19~174.59 kJ/mol calculated by the method of Ozawa. The Šatava method inferred the most possible mechanism function of HCl-wahsed soybean stalk is Zhuralev-Lesakin-Tempelman equation, which is three-dimensional diffusion.

scholarly journals The non-isothermal kinetics of hydroxyapatite formation in kaolin - natural phosphate mixtures

2019 ◽  
Vol 9 (1) ◽  
pp. 1-7
Author(s):  
Fateh Chouia ◽  
Hocine Belhouchet ◽  
Toufik Sahraoui
Keyword(s):  
Activation Energy ◽  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Exothermic Peak ◽  
Isothermal Kinetics ◽  
Heating Rates ◽  
Natural Phosphate ◽  
Isothermal Conditions ◽  
Kinetics Of ◽  
Hydroxyapatite Formation

In this work, the activation energy of hydroxyapatite formation in different composites under non-isothermal conditions was determined using differential thermal analysis (DTA). Seven compositions were prepared and studied while varying the percentage of the kaolin from 20 to 80 wt.% at 10% increments. The DTA conducted at heating rates of 10, 20 and 30 K min−1 showed an exothermic peak in all composites in the region 700°C–750°C associated with hydroxyapatite formation. The activation energies measured from non-isothermal treatments for seven compositions (20, 30, 40, 50, 60, 70 and 80 mass% of kaolin) were 194, 178, 178, 209, 162, 146 and 121 kJ mol−1, respectively.   Keywords:energy, kinetics,  kaolin - natural, phosphate mixtures

Thermogravimetric Analysis of KCl-Pretreated Soybean Stalk

2015 ◽  
Vol 1092-1093 ◽  
pp. 118-121
Author(s):  
Dong Yu Chen ◽  
Qing Yu Liu
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Metal Salts ◽  
Pyrolysis Kinetics ◽  
Ozawa Method ◽  
Heating Rates ◽  
Energy Value ◽  
Lower Activation ◽  
Higher Temperature ◽  
Kinetics Of

To study the influence of KCl pretreating on the pyrolysis kinetics of soybean stalk, the pyrolysis of soybean stalk pretreated by different concentration KCl solutions were performed by nonisothermal thermogravimetric analysis (TGA) at five different heating rates. The Ozawa method was employed to calculate the activation energy. The results showed that the pyrolysis process of the soybean stalk pretreated by 3% and 10% KCl solution can be separated into four stages (water loss, depolymerization and vitrification, thermal decomposition, and carbonization). With the heating rate increasing, the main pyrolysis zone of the TG (thermogravimetric) and DTG curves move to the higher temperature region, and the maximum pyrolysis rate and its corresponding temperature increase too. A small amount of metal salts addition is conducive to the formation of volatile, and a certain amount of metal salts can improve the charcoal yield. More KCl additive makes the lower activation energy value, and the obtained activation energy value increases with the reaction degree.

scholarly journals Thermogravimetric Kinetics of Selected Energy Crops Pyrolysis

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3977
Author(s):  
Magdalena Matusiak ◽  
Radosław Ślęzak ◽  
Stanisław Ledakowicz
Keyword(s):  
Activation Energy ◽  
Energy Crops ◽  
Pyrolysis Kinetics ◽  
Heating Rates ◽  
Exponential Factor ◽  
Miscanthus Giganteus ◽  
Temperature Ranges ◽  
The Given ◽  
Kinetics Of ◽  
Derivative Thermogravimetry

The main purpose of this paper was to compare the pyrolysis kinetics of three types of energy crops: Miscanthus giganteus, Sida hermaphrodita, and Sorghum Moench. Studies were conducted in thermobalance. Feedstock samples were heated up from ambient temperature to 600 °C under an inert argon atmosphere. Three heating rates of β = 5, 10, and 20 °C/min were applied. Reactions occurring in the given temperature ranges were grouped together into so-called lumps identified by the deconvolution of derivative thermogravimetry (DTG) curves that corresponded to biomass compositions (hemicellulose, cellulose, and lignin). For the estimation of the activation energy and pre-exponential factor, the Friedman and Ozawa–Flynn–Wall methods were used. The final kinetic parameters were determined by nonlinear regression assuming that thermal decomposition proceeded via three parallel independent reactions of the nth order. The activation energy of hemicellulose, cellulose and lignin was determined to be in the range of 92.9–97.7, 190.1–192.5, and 170–175.2 kJ/mol, respectively. The reaction order was in the range of 3.35–3.99 for hemicellulose, 1.38–1.93 for cellulose, and 3.97–3.99 for lignin. The obtained results allow us to estimate the pyrolytic potential of energy crops selected for this study, and can be used in designing efficient pyrolizers for these materials.

Kinetics of agglomeration of NiSi and NiSi2 phase formation.

2002 ◽  
Vol 745 ◽  
Author(s):  
C. Detavernier ◽  
A. Özcan ◽  
C. Lavoie ◽  
Jean-Jordan Sweet ◽  
J. M. E. Harper
Keyword(s):  
Phase Formation ◽  
Nucleation Site ◽  
Silicon On Insulator ◽  
X Ray Diffraction ◽  
Heating Rates ◽  
Site Density ◽  
Device Applications ◽  
Higher Temperature ◽  
Kinetics Of

ABSTRACTWe have studied the kinetics of NiSi agglomeration and NiSi2 phase formation during heating of NiSi on Si, using simultaneous in situ measurements of resistance, light scattering and x-ray diffraction. NiSi is a desirable contact to Si because of its low resistivity, limited Si consumption and low formation temperature. However, the formation of the higher resistivity phase NiSi2 must be avoided for device applications. Ni thin films 5 to 30 nm thick were deposited on substrates of poly-Si and silicon-on-insulator (SOI) and were studied using heating rates from 0.3 to 27 °C/s. At low heating rates and for the thinnest films studied, NiSi agglomeration precedes NiSi2 nucleation by as much as 350°C. The agglomeration temperature decreases with decreasing film thickness and linewidth. Once the film is agglomerated, the formation of NiSi2 is delayed to higher temperature by its low nucleation site density and decreased contact area. We conclude that agglomeration is the primary failure mechanism limiting the morphological stability of NiSi as a contact material to Si devices.

Factors Limiting the Rate of Dry Matter Accumulation in the Grain of Wheat Grown at High Temperature

1980 ◽  
Vol 7 (4) ◽  
pp. 387 ◽  
Author(s):  
IF Wardlaw ◽  
I Sofield ◽  
PM Cartwright
Keyword(s):  
High Temperature ◽  
Temperature Increase ◽  
Dry Matter ◽  
Flag Leaf ◽  
Dry Weight ◽  
Dry Matter Accumulation ◽  
Grain Development ◽  
Temperature Ranges ◽  
Higher Temperature ◽  
Lower Temperature

Increasing temperatures from 21/16°C to 30/25°C, during the period of development from anthesis to maturity, substantially reduced grain dry weight in wheat. Although this was associated with a shorter duration of grain development, the failure to obtain any compensating increase in the rate of dry matter accumulation, as occurs in the lower temperature ranges, was also considered important. There was no evidence that night temperatures were more important than day temperatures. Analysis of the movement of 14C-labelled photosynthate from the flag leaf to the ear indicated a faster rate of import of photosynthate by the grain at the higher temperature. However carbon lost through respiration is a component of the ear demand for photosynthate and it appears that increase in movement of photosynthate was balanced by greater respiratory losses. This additional carbon lost through enhanced respiration at high temperature could, however, only account at the most for 25% of the reduction in grain dry weight that occurred with the temperature increase from 21/16°C to 30/25°C. Altering either the demand for photosynthate by grain removal, or the supply of photosynthate by a defoliation and shading treatment, did not prevent the reduction in grain dry weight due to high temperature and this is a further indication that the temperature effect occurred mainly within, or close to, the grain itself, and did not result from an effect on the availability of photosynthate.

Study of the Kinetics of Thermal Destruction of Crossed Polyethylene

2019 ◽  
Vol 5 (12) ◽  
pp. 37-46
Author(s):  
K. Chalov ◽  
Yu. Lugovoy ◽  
Yu. Kosivtsov ◽  
E. Sulman
Keyword(s):  
Total Yield ◽  
Calorific Value ◽  
High Heat ◽  
Process Temperature ◽  
Optimum Process ◽  
Quantitative Composition ◽  
Pyrolysis Gas ◽  
Gaseous Products ◽  
Liquid Products ◽  
Kinetics Of

This paper presents a study of the process of thermal degradation of crosslinked polyethylene. The kinetics of polymer decomposition was studied by thermogravimetry. Crosslinked polyethylene showed high heat resistance to temperatures of 400 °C. The temperature range of 430–500 °C was determined for the loss of the bulk of the sample. According to thermogravimetric data, the decomposition process proceeds in a single stage and includes a large number of fracture, cyclization, dehydrogenation, and other reactions. The process of pyrolysis of a crosslinked polymer in a stationary-bed metal reactor was investigated. The influence of the process temperature on the yield of solid, liquid, and gaseous pyrolysis products was investigated. The optimum process temperature was 500 °C. At this temperature, the yield of liquid and gaseous products was 85.0 and 12.5% (mass.), Respectively. Samples of crosslinked polyester decomposed almost completely. The amount of carbon–containing residue was 3.5% by weight of the feedstock. With increasing temperature, the yield of liquid products decreased slightly and the yield of gaseous products increased, but their total yield did not increase. For gaseous products, a qualitative and quantitative composition was determined. The main components of the pyrolysis gas were hydrocarbons C1–C4. The calorific value of pyrolysis gas obtained at a temperature of 500 °C was 17 MJ/m3. Thus, the pyrolysis process can be used to process crosslinked polyethylene wastes to produce liquid hydrocarbons and combustible gases.

Kinetics of temperature-programmed reactivation of a hydrodesulphurization catalyst

1983 ◽  
Vol 48 (12) ◽  
pp. 3340-3355 ◽  
Author(s):  
Pavel Fott ◽  
Pavel Šebesta
Keyword(s):  
Carbon Dioxide ◽  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Thin Layer ◽  
Kinetic Parameters ◽  
Diffusion Region ◽  
Reaction Heat ◽  
Gaseous Products ◽  
Temperature Programmed ◽  
Kinetics Of

The kinetic parameters of reactivation of a carbonized hydrodesulphurization (HDS) catalyst by air were evaluated from combined thermogravimetric (TG) and differential thermal analysis (DTA) data. In addition, the gaseous products leaving a temperature-programmed reactor with a thin layer of catalyst were analyzed chromatographically. Two exothermic processes were found to take part in the reactivation, and their kinetics were described by 1st order equations. In the first process (180-400 °C), sulphur in Co and Mo sulphides is oxidized to sulphur dioxide; in the second process (300-540 °C), in which the essential portion of heat is produced, the deposited carbon is oxidized to give predominantly carbon dioxide. If the reaction heat is not removed efficiently enough, ignition of the catalyst takes place, which is associated with a transition to the diffusion region. The application of the obtained kinetic parameters to modelling a temperature-programmed reactivation is illustrated on the case of a single particle.

Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst

1990 ◽  
Vol 55 (7) ◽  
pp. 1678-1685
Author(s):  
Vladimír Stuchlý ◽  
Karel Klusáček
Keyword(s):  
Carbon Monoxide ◽  
Reaction Rate ◽  
Catalyst Activity ◽  
Adsorbed Hydrogen ◽  
Reaction Products ◽  
Co Methanation ◽  
Molar Ratios ◽  
Rate Determining Step ◽  
Higher Temperature ◽  
Kinetics Of

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.

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