Base-catalysed reduction of pyruvic acid in near-critical water

2013 ◽  
Vol 67 (5) ◽  
Author(s):  
Li Luo ◽  
Zhi Hou ◽  
Yuan Wang ◽  
Li Dai
Keyword(s):  
Activation Energy ◽  
Formic Acid ◽  
Pyruvic Acid ◽  
Sodium Acetate ◽  
Reaction Rate ◽  
Arrhenius Equation ◽  
Base Catalyst ◽  
Acid Yield ◽  
Exponential Factor ◽  
Reaction Rate Constants

AbstractThe reduction of pyruvic acid in near-critical water has successfully been conducted under conditions of various temperatures, pressures, reaction time and the presence of formic acid as the reducing agent. In this work, additives (K2CO3, KHCO3, and sodium acetate) used in the reduction of pyruvic acid were also investigated. The results showed that by adding K2CO3 (25 mole %) a markedly higher lactic acid yield (70.7 %) was obtained than without additives (31.3 %) at 573.15 K, pressure of 8.59 MPa, 60 min, and in the presence of 2 mol L−1 formic acid. As a base catalyst, K2CO3 definitely accelerated the reduction of pyruvic acid. The reaction rate constants, average apparent activation energy and pre-exponential factor were evaluated in accordance with the Arrhenius equation. The reaction mechanism of the reduction was proposed on the basis of the experimental results.

Kinetics of Bamboo Fiber Hydrolysis Reaction in Saturated Formic Acid

2012 ◽  
Vol 531-532 ◽  
pp. 679-683 ◽  
Author(s):  
Jun Ping Zhuang ◽  
Lu Lin ◽  
Chun Sheng Pang ◽  
Ying Liu
Keyword(s):  
Activation Energy ◽  
Hydrochloric Acid ◽  
Acid Solution ◽  
Formic Acid ◽  
Arrhenius Equation ◽  
Bamboo Fiber ◽  
Hydrolysis Reaction ◽  
Exponential Factor ◽  
Practical Applications ◽  
And Performance

Kinetic models can have practical applications for the optimization of the process and performance analysis, or economic estimations, so investigate the bamboo fiber kinetics is necessary. In this paper, effects of temperature and time on bamboo fiber hydrolysis in saturated formic acid with 4% hydrochloric acid solution reaction kinetics have been investigated. The rate constants, average apparent activation energy and frequency factors were evaluated according to the Arrhenius equation. The results showed that the hydrolysis velocities of bamboo fiber were 1.63×10-2 h-1 at 55 °C, 2.59×10-2 h-1 at 60 °C, 4.56×10-2 h-1 at 65 °C, 6.75×10-2 h-1 at 70 °C and 0.10 h-1 at 75 °C in formic acid solution with 4 % hydrochloric acid. The degradation velocities of glucose were 6.57×10-3 h-1 at 55 °C, 1.98×10-2 h-1 at 60 °C, 2.53×10-2 h-1 at 65 °C, 7.47×10-2 h-1 at 70 °C and 0.14 h-1 at 75 °C. The pre-exponential factor of Arrhenius equation of bamboo fiber hydrolysis reaction and glucose decomposition was 1.48×1014 h-1 and 2.32×1020 h-1 respectively. The activation energy of bamboo fiber hydrolysis was 87.65kJ/mol, and the activation energy of glucose degradation was 141.44kJ/mol.

scholarly journals Instantaneous activation energy of alkali activated materials

2019 ◽  
Vol 3 ◽  
pp. 121-123
Author(s):  
Shiju Joseph ◽  
Siva Uppalapati ◽  
Ozlem Cizer
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Reaction Rate ◽  
Arrhenius Equation ◽  
Isothermal Calorimetry ◽  
Traditional Methods ◽  
Cement Based Materials ◽  
Different Temperatures ◽  
Higher Temperature ◽  
Alkali Activated

Alkali activated materials (AAM) are generally cured at high temperatures to compensate for the low reaction rate. Higher temperature accelerates the reaction of AAM as in cement-based materials and this effect is generally predicted using Arrhenius equation based on the activation energy. While apparent activation energy is calculated from parallel isothermal calorimetry measurements at different temperatures, instantaneous activation energy is typically measured using a differential scanning calorimeter. Compared to the apparent activation energy, instantaneous activation energy has minimal effects on the microstructural changes due to the variation in temperature. In this work, the evolution of activation energy was determined by traditional methods and was compared with the instantaneous activation energy. It was found that while the activation energy changed with the progress of reaction over traditional methods, the instantaneous activation energy did not show any changes / or remained the same. The instantaneous activation energy was also found to be higher compared to the apparent activation energy determined with traditional methods.

scholarly journals Finding of kinetic characteristics of the process co-gasification of heavy coal tars with lignite and walnut shell

2020 ◽  
Vol 3 (2) ◽  
pp. 46-52
Author(s):  
D. Yu. Bilets ◽  
◽  
D. V. Miroshnichenko ◽  
P. V. Karnozhitskiy ◽  
Yu. V. Nikolaichuk ◽  
...  
Keyword(s):  
Activation Energy ◽  
Flow Rate ◽  
Rate Constants ◽  
Reaction Rate ◽  
Walnut Shell ◽  
Kinetic Characteristics ◽  
Reaction Rate Constants ◽  
Gasification Process

Studied of co-gasification of heavy coal tars with lignite and walnut shell in the temperature ranged from 400 to 500 °С, the flow rate of oxidand (air) ranged from 0,0005 to 0,004 m3/min. It is established that the weigth loss of the sample mixtures in the gasification process has a S-shaped. Mathematical and graphical dependences of the influence of oxidant flow rate on the values of reaction rate constants and activation energy of gasification of experimental mixtures were developed.

scholarly journals Stability of vitamin C in broccoli at different storage conditions

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Nasser Al-Habsi ◽  
Sithara Suresh ◽  
Amani Al-Yhmedi ◽  
Marwa Al-Shoryani ◽  
Mostafa I. Waly ◽  
...  
Keyword(s):  
Activation Energy ◽  
Vitamin C ◽  
Reaction Rate ◽  
Storage Conditions ◽  
Order Reaction ◽  
Titration Method ◽  
First Order ◽  
Reaction Rate Constants ◽  
Different Temperatures ◽  
Thermal Stability Of

In this study, the retention of vitamin C in fresh broccoli stored at different temperatures (i.e. chiller, room, cooking, and roasting or baking; 5-120°C) was investigated. The thermal stability of vitamin C in broccoli was analysed at 5, 20, 45, 60, 70, 80, 110, and 120°C. The vitamin C content was measured by the indophenol titration method. Vitamin C was affected negatively at all stored temperatures. The degradation of vitamin C was modelled by first-order reaction kinetics and the reaction rate constants were observed as 9.03×10-8 and 5.65×10-3 s-1 when stored at 5°C and 120°C, respectively. The activation energy was estimated as 74.2 kJ/mol within the temperature range used in this study. The lowest decay of vitamin C was observed during the chilling condition. The data on retention of vitamin C in broccoli could be used to determine their stability, when stored as raw, and when heated at different temperatures.

scholarly journals Studies of Degradation Kinetics of a 5-HT3 Antagonist, Ramosetron Hydrochloride: Effects of Temperature

2018 ◽  
Vol 17 (2) ◽  
pp. 167-173
Author(s):  
Md Mokaram Hossain ◽  
Reza Ul Jalil ◽  
Mohammad A Rashid
Keyword(s):  
Reaction Rate ◽  
Arrhenius Equation ◽  
Degradation Kinetics ◽  
First Order ◽  
Reaction Rate Constants ◽  
First Order Kinetics ◽  
Antiemetic Activity ◽  
Effects Of Temperature ◽  
Kinetics Of ◽  
Subtype 3

Ramosetron hydrochloride is the hydrochloride salt of ramosetron, a selective serotonin (5-HT3) receptor antagonist with potential antiemetic activity. Upon administration, ramosetron selectively binds to and blocks the activity of 5-HT subtype 3 (5-HT3) receptors located in the vagus nerve terminal and the vomiting center of central nervous system (CNS), suppressing chemotherapy-induced nausea and vomiting. Degradation of Ramosetron HCl was conducted with 0.1N NaOH at 60°C, 70°C and 80°C to study the reaction kinetics. The reaction rate constants (k) for degradation at 60°C, 70°C and 80°C were -2.2680 molL-1s-1 , -3.3714 molL-1s-1 and -5.3686 molL-1s-1 for zero order and -1.05 x 10-2s-1, -1.60 x 10-2s-1 and -2.70 x 10-2s-1 for first order kinetics, respectively. The activation energy of Ramosetron HCl was found as 10.05 kcalmol-1 by using Arrhenius equation. Dhaka Univ. J. Pharm. Sci. 17(2): 167-173, 2018 (December)

Reduction Kinetics of Bayan Obo Coexisted Iron and Niobium Ore by Carbon-Bearing Pellet

2011 ◽  
Vol 418-420 ◽  
pp. 346-352 ◽  
Author(s):  
Fu Shun Zhang ◽  
Zeng Wu Zhao ◽  
Yan Li ◽  
Nai Xiang Feng
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Reaction Rate ◽  
Mass Loss Rate ◽  
Reduction Process ◽  
Inert Atmosphere ◽  
Reaction Rate Constant ◽  
Carbon Gasification ◽  
Reaction Rate Constants ◽  
Two Stages

The mass loss rate of carbon-bearing pellet of coexisted iron and niobium ore during reduction process was investigated between 900 and 1050°C in inert atmosphere. The reduction mechanism was studied by analyzing reaction rate constant, apparent activation energy，and the controlling step. The results show that temperature has the significant effect on the reduction of carbon-bearing pellet. The reduction processes include the faster reaction stage and the slower reduction stage, and respective reaction rate constants in two stages are k1=exp (21.025-40484/(RT)) and k2= exp (21.060-42516/(RT))，while respective apparent activation energy are 337 and 353 KJ/mol. Both steps are controlled by carbon gasification.

Ionic Conductivity of Polycrystalline Li2GexSi1-xO3 (x = 0.0~1.0)

2010 ◽  
Vol 459 ◽  
pp. 27-31 ◽  
Author(s):  
Shinichi Furusawa ◽  
Shun Enokida
Keyword(s):  
Activation Energy ◽  
Solid State ◽  
Ionic Conductivity ◽  
Solid State Reaction ◽  
Arrhenius Equation ◽  
Ionic Conduction ◽  
Exponential Factor ◽  
Temperature Range

Polycrystalline Li2GexSi1-xO3 (x = 0.0~1.0) was synthesized by solid state reaction, and its ionic conductivity was studied as a function of x in a temperature range of 500–700 K. The ionic conductivity was found to depend on x and was enhanced at x = 0.2–0.7. Furthermore, the pre-exponential factor and activation energy in the Arrhenius equation were also found to depend on x. These results suggest that lithium ionic conduction in Li2GexSi1-xO3 is strongly influenced by the structure of the framework.

Effect of Cu on Al-Transition Metal Reaction Kinetics

1983 ◽  
Vol 25 ◽  
Author(s):  
H.-C. W. Huang ◽  
M. Wittmer
Keyword(s):  
Activation Energy ◽  
Transition Metal ◽  
Reaction Rate ◽  
Resistivity Measurement ◽  
Intermetallic Phases ◽  
Compound Formation ◽  
Reaction Rate Constants ◽  
Cu Content ◽  
Cu Film ◽  
Kinetics Of

ABSTRACTThe effect of Cu on the kinetics of compound formation between Al and transition metals such as Hf and Ti has been studied by resistivity measurement and Rutherford backscattering (RBS) in the temperature range of 325°C to 450°C. Thin film couples consisting of 150nm-thick transition metal film and 600nm-thick Al-Cu film were used, in which the Cu content was varied from 0 to 9 wt%. The intermetallic phases were found to grow as (time)1/2. Most interestingly, the reaction rate constants were found to decrease significantly with increasing Cu content, but to level off for Cu contents greater than about 2 wt%. The corresponding activation energy for a given Altransition metal reaction was found to increase with increasing Cu for Cu contents up to 2wt%. For example, when 4 wt% Cu is added to Al, the rate constant at 400°C for HfA13 is reduced by about a factor of 5, while the activation energy increases from 1.5 eV to 2.0 eV. RBS results indicate that the Cu addition seems to inhibit the diffusion of Hf into Al. Diffusive intermixing in the Al/Ti system is much smaller and, consequently, the effect of Cu additions in preventing Ti diffusion into the Al is also much smaller.

scholarly journals Kinetic Study on Acrylic Acid Polymerisations in Isopropanol

2021 ◽  
Vol 11 (20) ◽  
pp. 9719
Author(s):  
Kai C. Betz ◽  
Anna Westhues ◽  
Werner Pauer
Keyword(s):  
Activation Energy ◽  
Molecular Weight ◽  
Acrylic Acid ◽  
Rate Constants ◽  
Reaction Rate ◽  
Monomer Concentration ◽  
Similar Reaction ◽  
Reaction Conditions ◽  
Reaction Rate Constants ◽  
Linear Correlations

The radical polymerisation of acrylic acid is largely concentration dependent and affected by the type of the surrounding solvent. This work investigates reaction rate constants, the activation energy, heat flux and the molecular weight in the industrially relevant synthesis of low molecular mass acrylic acid polymers in 2‑propanol. The polymerisations were carried out isothermally in an RC1e calorimeter with inline Raman spectroscopy for monomer concentration monitoring. For a non-neutralised acrylic acid in isopropanol (150 g/L), a monomer reaction order of 1.73 ± 0.15, an activation energy of 58.6 ± 0.8 kJ/mol (0.5 mol% AIBN) and 88.5 ± 1.5 kJ/mol (1.0 mol% AIBN), and a reaction enthalpy of 66.4 ± 4.8 kJ/mol could be shown. This data is in accordance with the literature values for acrylic acid polymerisation in water. In addition, linear correlations between the respective reaction parameters and the molecular weight for customised polymer synthesis in the range from 1.2 to 1.7 × 104 g/mol could be established. In comparison with aqueous acrylic acid polymerisation, it was found that the reaction rate constants in isopropanol were slower by a factor of approximately 10 under similar reaction conditions.

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