In our previous research (Liu et al., J Anal Appl Pyrol 63:303–325, 2002), the pseudo bi-component separated-stage model (PBSM) was suggested for the kinetic analysis on the decomposition of lignocellulosic materials in air at relatively lower heating rates. As a continuing work, this paper is intended to investigate the applicability of PBSM at different heating rates by experimental analyses. Decomposition of oil tea wood has been studied by means of non-isothermal thermogravimetric analysis in air atmosphere at 10–25 K min−1 heating rates. A two-step parallel reaction kinetic model is used to optimize the kinetic parameters of these materials in air. Meanwhile, an improved PBSM is developed to describe the thermal degradation process of oil tea wood. Furthermore, a comparison between the kinetic results of parallel model and PBSM reveals realistic applicability of PBSM. It is concluded that the PBSM has relatively high accuracy for the first decomposition step in the lower temperature range, while fails to predict the thermal decomposition behavior in the char oxidative process which occurs in the higher temperature range.
Authors:C. Chang, Y. Chou, J. Tseng, M. Liu, and C. Shu
Many concerns over unsafe or unknown properties of multi-walled carbon nanotubes (MWNTs) have been raised. The thermal characteristics
regarding stability would represent potential hazards during the production or utilization stage and could be determined by
calorimetric tests for various thermokinetic parameters. Differential scanning calorimetry (DSC) was employed to evaluate
the thermokinetic parameters for MWNTs at various compositions.
Thermoanalytical curves showed that the average heat of decomposition (ΔHd) of the MWNTs samples in a manufacturing process was about 31,723 J g−1, by identifying them as an inherently hazardous material. In this study, significant thermal analysis appeared in the presence
of sulfuric acid (H2SO4). From the DSC experiments, the purification process of MWNTs could induce an unexpected reaction in the condition of batch
addition with reactants of H2SO4. The results can be applied for designing emergency relief system and emergency rescue strategies during a perturbed situation
Due to the experimental errors, the chemical effect of minor reactions, and some physical effects of heat and mass transfer,
there usually exists much noise in the mass loss data resulted from thermal decomposition experiments, and thus high quality
smoothing algorithm plays an important role in obtaining reliable derivative thermogravimetric (DTG) curves required for differential
kinetic analysis. In this paper three smoothing methods, i.e. Moving Average smoothing, Gaussian smoothing, and Vondrak smoothing,
are investigated in detail for pre-treatment of biomass decomposition data to obtain the DTG curves, and the smoothing results
are compared. It is concluded that by choosing reasonable smoothing parameters based on the spectrum analysis of the data,
the Gaussian smoothing and Vondrak smoothing can be reliably used to obtain DTG curves. The kinetic parameters calculated
from the original TG curves and smoothed DTG curves have excellent agreement, and thus the Gaussian and Vondrak smoothing
algorithms can be used directly and accurately in kinetic analysis.
Authors:Shang-Hao Liu, Chun-Ping Lin, and Chi-Min Shu
The thermokinetic parameters were investigated for cumene hydroperoxide (CHP), di-tert-butyl peroxide (DTBP), and tert-butyl peroxybenzoate (TBPB) by non-isothermal kinetic model and isothermal kinetic model by differential scanning calorimetry (DSC) and thermal activity monitor III (TAM III), respectively. The objective was to investigate the activation energy (Ea) of CHP, DTBP, and TBPB applied non-isothermal well-known kinetic equation to evaluate the thermokinetic parameters by DSC. We employed TAM III to assess the thermokinetic parameters of three liquid organic peroxides, obtained thermal runaway data, and then used the Arrhenius plot to obtain the Ea of liquid organic peroxides at various isothermal temperatures. In contrast, the results of non-isothermal kinetic algorithm and isothermal kinetic algorithm were acquired from a highly accurate procedure for receiving information on thermal decomposition characteristics and reaction hazard.
Authors:Wang Rong-shu, Liu Zhong-wen, Chen Jia-xiu, Chen Lei, and Mao Wen-shu
Some results of tests on removing radium from liquid phase by adsorption on barytes are described. The paper demonstrates the mechanism for removal of radium, which is basically a chemical exchange between radium and barium ions on solid surface.
Authors:Mei-Li You, Jo-Ming Tseng, Ming-Yang Liu, and Chi-Min Shu
Pooling lauroyl peroxide (LPO) with nitric acid, we used differential scanning calorimetry (DSC) to assess the thermokinetic
parameters, such as exothermic onset temperature (T0), heat of decomposition (ΔHd), frequency factor (A), and the other safety parameters. When LPO was contaminated with nitric acid (HNO3), we found the exploder 1-nitrododecane. Obvious products were sensitive and hazardous chemicals. Concentration reaching
1–12 N HNO3 emitted a large amount of heat. This study combined with curve-fitting method to elucidate its unsafe characteristics and
thermally sensitive structure to help prevent runaway reactions, fires and explosions in the process environment. According
to the findings and the concept of inherently safer design, LPO runaway reactions could be adequately prevented in the relevant
Authors:Zhiyong Wei, Wanxi Zhang, Guangyi Chen, Jicai Liang, Shu Yang, Pei Wang, and Lian Liu
In this study, α-phase nucleating agent (NA) 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS), β-phase rare earth NA
(WBG), and their compound NAs were introduced into isotactic polypropylene (iPP) matrix, respectively. Crystallization kinetics
and subsequent melting behavior of the nucleated iPPs were comparatively studied by differential scanning calorimetry (DSC)
under both isothermal and nonisothermal conditions. For the isothermal crystallization process, it is found that the Avrami
model successfully described the crystallization kinetics. The active energy of nonisothermal crystallization of iPP was determined
by the Kissinger method and showed that the addition of nucleating agents increased the activation energy. Melting behavior
and crystalline structure of the nucleated iPPs are dependent on the nature of NAs and crystallization conditions. Higher
proportion of β-phase can be obtained at higher content of β-nucleating agent and lower crystallization temperature or lower
Authors:Zhong-Suo Liu, Qi Wang, Zong-Shu Zou, and Guang-Lei Tan
Experiments of carbon (graphite) gasification in CO2 have been carried out by thermal analysis techniques (TG-DTG-DSC) under non-isothermal conditions. The results indicate that the entire carbon gasification process can be divided into an exothermic slow gasification stage during the initial period and an endothermic fast gasification later. The analyses of energy conservation and non-isothermal kinetics arrive at the following conclusions; (1) The exotherm of the initial stage is caused by the combined effect of the exothermic chemisorption and the endothermic chemical reaction. The gasification reaction may be expressed by the series of chemisorption and chemical reaction and the overall process is controlled by interface reaction via chemisorption. (2) The endothermic effect of fast gasification stage is almost equal to the reaction heat of carbon gasification, which implies that the chemisorption step disappears. The gasification process can be expressed by a simple interface reaction.
A new system for simultaneous electrodeposition of U, Np, Pu, Am and Cm has been developed. The system consists of (NH4)2C2O4–H2SO4–HCl. The effects on recovery of pH, current density, interfering ions and the amount of added HCl have been studied. The optimum condition for simultaneous electrodeposition of actinides has been recommended. Under the recommended condition recoveries of U, Np, Pu, Am and Cm have been obtained by using232U,237Np,241Am,242Pu and244Cm. The counting sources prepared are uniform, adherent and suitable for -spectrometry.