Hardwood pulping kinetics of bulk and residual phases

The kinetics of the bulk and residual delignification phases of Eucalyptus nitens, E. globulus, E. benthamii, acacia, maple, and loblolly pine were determined in an effort to improve the use of various hardwoods. Kinetic experiments were performed using a microwave digestion system for fast heating of the kraft liquor. Delignification rates were obtained for three different temperatures (150°C, 160°C, and 170°C) and correlated with the wood’s syringyl-to-guaiacyl ratio. A linear correlation between the kraft delignification rate and the syringyl-toguaiacyl ratio was found to exist.

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Kinetics of Thermolysis of Nickel(II) Perchlorate Complex with n-Propylamine

Indian Journal of Materials Science ◽

10.1155/2014/787306 ◽

2014 ◽

Vol 2014 ◽

pp. 1-5 ◽

Cited By ~ 1

Author(s):

Chandra Prakash Singh ◽

Abhishek Singh

Keyword(s):

Model Fitting ◽

Isoconversional Method ◽

Nitrogen Atmosphere ◽

Molecular Formula ◽

Fast Heating ◽

Isothermal Tg ◽

Model Free ◽

Different Temperatures ◽

Explosion Delay ◽

Kinetics Of

Complex of nickel perchlorate with n-propylamine has been synthesised with molecular formula [Ni(n-pa)3(ClO4)(H2O)]ClO4. It has been characterised by elemental analysis, thermogravimetry, UV-VIS, and IR spectroscopic data. Thermal properties have been investigated by thermogravimetry (TG) in static air and by simultaneous thermogravimetry-derivative thermogravimetry-differential thermal analysis (TG-DTG-DTA) in flowing nitrogen atmosphere. Kinetics of thermolysis has been analysed applying model-fitting and model-free isoconversional method on isothermal TG data recorded at five different temperatures. To observe the response of complex towards fast heating, explosion delay time has been recorded at various temperatures and kinetics of explosion has been studied using these data.

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Comparative Labelling and Biokinetic Studies of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn)

Nuklearmedizin ◽

10.1055/s-0037-1620603 ◽

1977 ◽

Vol 16 (01) ◽

pp. 30-35 ◽

Cited By ~ 1

Author(s):

N. Agha ◽

R. B. R. Persson

Keyword(s):

Complex Formation ◽

Significant Influence ◽

Room Temperature ◽

Ph Value ◽

Maximum Activity ◽

Reduction Step ◽

Labelling Yield ◽

Different Temperatures ◽

Kinetics Of

SummaryGelchromatography column scanning has been used to study the fractions of 99mTc-pertechnetate, 99mTcchelate and reduced hydrolyzed 99mTc in preparations of 99mTc-EDTA(Sn) and 99mTc-DTPA(Sn). The labelling yield of 99mTc-EDTA(Sn) chelate was as high as 90—95% when 100 μmol EDTA · H4 and 0.5 (Amol SnCl2 was incubated with 10 ml 99mTceluate for 30—60 min at room temperature. The study of the influence of the pH-value on the fraction of 99mTc-EDTA shows that pH 2.8—2.9 gave the best labelling yield. In a comparative study of the labelling kinetics of 99mTc-EDTA(Sn) and 99mTc- DTPA(Sn) at different temperatures (7, 22 and 37°C), no significant influence on the reduction step was found. The rate constant for complex formation, however, increased more rapidly with increased temperature for 99mTc-DTPA(Sn). At room temperature only a few minutes was required to achieve a high labelling yield with 99mTc-DTPA(Sn) whereas about 60 min was required for 99mTc-EDTA(Sn). Comparative biokinetic studies in rabbits showed that the maximum activity in kidneys is achieved after 12 min with 99mTc-EDTA(Sn) but already after 6 min with 99mTc-DTPA(Sn). The long-term disappearance of 99mTc-DTPA(Sn) from the kidneys is about five times faster than that for 99mTc-EDTA(Sn).

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Thermodynamic and detailed kinetic study of the formation of orthophthalaldehyde-agmatine complex by fluorescence intensities

Journal of Analytical Science & Technology ◽

10.1186/s40543-020-00238-2 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

Khémesse Kital ◽

Moumouny Traoré ◽

Diégane Sarr ◽

Moussa Mbaye ◽

Mame Diabou Gaye Seye ◽

...

Keyword(s):

Complex Formation ◽

Thermodynamic Parameters ◽

Initial Rate ◽

Reaction Medium ◽

Standard Entropy ◽

Step Size ◽

Formation Reaction ◽

Different Temperatures ◽

Kinetics Of ◽

Complex Formation Process

Abstract The aim of this work is to determine the thermodynamic parameters and the kinetics of complex formation between orthophthalaldehyde (OPA) and agmatine (AGM) in an alkaline medium (pH 13). Firstly, the association constant (Ka) between orthophthalaldehyde and agmatine was determined at different temperatures (between 298 K and 338 K) with a step size of 10 K. Secondly, the thermodynamic parameters such as standard enthalpy (ΔH°), standard entropy (ΔS°),and Gibbs energy (∆G) were calculated, where a positive value of ΔH° (+45.50 kJ/mol) was found, which shows that the reaction is endothermic. In addition, the low value of ΔS°(+0.24 kJ/mol) indicates a slight increase in the disorder in the reaction medium. Furthermore, the negative values of ΔG between −35.62 kJ/mol and −26.02 kJ/mol show that the complex formation process is spontaneous. Finally, the parameters of the kinetics of the reaction between OPA and AGM were determined as follows: when the initial concentration of AGM (5 × 10−6 M) is equal to that of the OPA, the results show that the reaction follows an overall 1.5 order kinetics with an initial rate of 5.1 × 10−7Mmin−1 and a half-life of 8.12 min. The partial order found in relation to the AGM is 0.8. This work shows that the excess of OPA accelerates the formation reaction of the complex.

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Torrefaction Thermogravimetric Analysis and Kinetics of Sorghum Distilled Residue for Sustainable Fuel Production

Sustainability ◽

10.3390/su13084246 ◽

2021 ◽

Vol 13 (8) ◽

pp. 4246

Author(s):

Shih-Wei Yen ◽

Wei-Hsin Chen ◽

Jo-Shu Chang ◽

Chun-Fong Eng ◽

Salman Raza Naqvi ◽

...

Keyword(s):

Kinetic Model ◽

Pso Algorithm ◽

Nitrogen Atmosphere ◽

Computational Method ◽

Weight Changes ◽

Design And Optimization ◽

Thermogravimetric Analyzer ◽

Model Free ◽

Different Temperatures ◽

Kinetics Of

This study investigated the kinetics of isothermal torrefaction of sorghum distilled residue (SDR), the main byproduct of the sorghum liquor-making process. The samples chosen were torrefied isothermally at five different temperatures under a nitrogen atmosphere in a thermogravimetric analyzer. Afterward, two different kinetic methods, the traditional model-free approach, and a two-step parallel reaction (TPR) kinetic model, were used to obtain the torrefaction kinetics of SDR. With the acquired 92–97% fit quality, which is the degree of similarity between calculated and real torrefaction curves, the traditional method approached using the Arrhenius equation showed a poor ability on kinetics prediction, whereas the TPR kinetic model optimized by the particle swarm optimization (PSO) algorithm showed that all the fit qualities are as high as 99%. The results suggest that PSO can simulate the actual torrefaction kinetics more accurately than the traditional kinetics approach. Moreover, the PSO method can be further employed for simulating the weight changes of reaction intermediates throughout the process. This computational method could be used as a powerful tool for industrial design and optimization in the biochar manufacturing process.

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Hydrothermal Ageing and Its Effect on Fracture Load of Zirconia Dental Implants

Materials ◽

10.3390/ma14113103 ◽

2021 ◽

Vol 14 (11) ◽

pp. 3103

Author(s):

Laurent Gremillard ◽

Agnès Mattlet ◽

Alexandre Mathevon ◽

Damien Fabrègue ◽

Bruno Zberg ◽

...

Keyword(s):

Dental Implants ◽

Fracture Load ◽

Accelerated Ageing ◽

Dental Ceramics ◽

X Ray Diffraction ◽

X Ray ◽

Dental Restorations ◽

Different Temperatures ◽

Mechanical Performances ◽

Kinetics Of

Due to growing demand for metal-free dental restorations, dental ceramics, especially dental zirconia, represent an increasing share of the dental implants market. They may offer mechanical performances of the same range as titanium ones. However, their use is still restricted by a lack of confidence in their durability and, in particular, in their ability to resist hydrothermal ageing. In the present study, the ageing kinetics of commercial zirconia dental implants are characterized by X-ray diffraction after accelerated ageing in an autoclave at different temperatures, enabling their extrapolation to body temperature. Measurements of the fracture loads show no effect of hydrothermal ageing even after ageing treatments simulated a 90-year implantation.

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Effects of additives on the cure kinetics of vinyl ester pultrusion resins

Journal of Composite Materials ◽

10.1177/00219983211001528 ◽

2021 ◽

pp. 002199832110015

Author(s):

Alexander Vedernikov ◽

Yaroslav Nasonov ◽

Roman Korotkov ◽

Sergey Gusev ◽

Iskander Akhatov ◽

...

Keyword(s):

Vinyl Ester ◽

Mean Squared Error ◽

Cure Kinetics ◽

Zinc Stearate ◽

Heating Rates ◽

Scanning Calorimetry ◽

Different Temperatures ◽

Predicted Values ◽

Kinetics Of ◽

Final Degree

Pultrusion is a highly efficient composite manufacturing process. To accurately describe pultrusion, an appropriate model of resin cure kinetics is required. In this study, we investigated cure kinetics modeling of a vinyl ester pultrusion resin (Atlac 430) in the presence of aluminum hydroxide (Al(OH)3) and zinc stearate (Zn(C18H35O2)2) as processing additives. Herein, four different resin compositions were studied: neat resin composition, composition with Al(OH)3, composition comprising Zn(C18H35O2)2, and composition containing both Al(OH)3 and Zn(C18H35O2)2. To analyze each composition, we performed differential scanning calorimetry at the heating rates of 5, 7.5, and 10 K/min. To characterize the cure kinetics of Atlac 430, 16 kinetic models were tested, and their performances were compared. The model based on the [Formula: see text]th-order autocatalytic reaction demonstrated the best results, with a 4.5% mean squared error (MSE) between the experimental and predicted data. This study proposes a method to reduce the MSE resulting from the simultaneous melting of Zn(C18H35O2)2. We were able to reduce the MSE by approximately 34%. Numerical simulations conducted at different temperatures and pulling speeds demonstrated a significant influence of resin composition on the pultrusion of a flat laminate profile. Simulation results obtained for the 600 mm long die block at different die temperatures (115, 120, 125, and 130 °C) showed that for a resin with a final degree of cure exceeding 95% at the die exit, the maximum difference between the predicted values of pulling speed for a specified set of compositions may exceed 1.7 times.

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Kinetics of Ion-Pair Effect of Aquation of Bromopentaammine Cobalt(III) Complex in Different Dicarboxylate Media

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.324.166 ◽

2011 ◽

Vol 324 ◽

pp. 166-169 ◽

Cited By ~ 1

Author(s):

Farah Zeitouni ◽

Gehan El-Subruiti ◽

Ghassan Younes ◽

Mohammad Amira

Keyword(s):

Free Energy ◽

Solvent Effect ◽

Compensation Effect ◽

Ion Pairing ◽

Reaction Rates ◽

Ion Pair ◽

Free Energy Of Activation ◽

Different Types ◽

Different Temperatures ◽

Kinetics Of

The rate of aquation of bromopentaammine cobalt(III) ion in the presence of different types of dicarboxylate solutions containing tert-butanol (40% V/V) have been measured spectrophotometrically at different temperatures (30-600°C) in the light of the effects of ion-pairing on reaction rates and mechanism. The thermodynamic and extrathermodynamic parameters of activation have been calculated and discussed in terms of solvent effect on the ion-pair aquation reaction. The free energy of activation ∆Gip* is more or less linearly varied among the studied dicarboxylate ion-pairing ligands indicating the presence of compensation effect between ∆Hip* and ∆Sip*. Comparing the kip values with respect of different buffers at 40% of ter-butanol is introduced.

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A Logistic Approach for Kinetics of Isothermal Pyrolysis of Cellulose

Processes ◽

10.3390/pr9030551 ◽

2021 ◽

Vol 9 (3) ◽

pp. 551

Author(s):

Jorge López-Beceiro ◽

Ana María Díaz-Díaz ◽

Ana Álvarez-García ◽

Javier Tarrío-Saavedra ◽

Salvador Naya ◽

...

Keyword(s):

Kinetic Model ◽

Time Derivative ◽

Inert Atmosphere ◽

Second Step ◽

Rate Parameter ◽

Thermogravimetric Data ◽

Different Temperatures ◽

Parameter Values ◽

Kinetics Of ◽

Logistic Functions

A kinetic model is proposed to fit isothermal thermogravimetric data obtained from cellulose in an inert atmosphere at different temperatures. The method used here to evaluate the model involves two steps: (1) fitting of single time-derivative thermogravimetric curves (DTG) obtained at different temperatures versus time, and (2) fitting of the rate parameter values obtained at different temperatures versus temperature. The first step makes use of derivative of logistic functions. For the second step, the dependence of the rate factor on temperature is evaluated. That separation of the curve fitting from the analysis of the rate factor resulted to be very flexible since it proved to work for previous crystallization studies and now for thermal degradation of cellulose.

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