scholarly journals Kinetic Studies and Moisture Diffusivity During Cocoa Bean Roasting

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 770 ◽  
Author(s):  
Leydy Ariana Domínguez-Pérez ◽  
Ignacio Concepción-Brindis ◽  
Laura Mercedes Lagunes-Gálvez ◽  
Juan Barajas-Fernández ◽  
Facundo Joaquín Márquez-Rocha ◽  
...  
Keyword(s):  
Diffusion Coefficients ◽  
Kinetic Studies ◽  
Moisture Diffusion ◽  
Moisture Diffusivity ◽  
Cocoa Bean ◽  
Exponential Models ◽  
First Order ◽  
Roasting Process ◽  
Pseudo First Order ◽  
Semi Empirical

Cocoa bean roasting allows for reactions to occur between the characteristic aroma and taste precursors that are involved in the sensory perception of chocolate and cocoa by-products. This work evaluates the moisture kinetics of cocoa beans during the roasting process by applying empirical and semi-empirical exponential models. Four roasting temperatures (100, 140, 180, and 220 °C) were used in a cylindrically designed toaster. Three reaction kinetics were tested (pseudo zero order, pseudo first order, and second order), along with 10 exponential models (Newton, Page, Henderson and Pabis, Logarithmic, Two-Term, Midilli, Verma, Diffusion Approximation, Silva, and Peleg). The Fick equation was applied to estimate the diffusion coefficients. The dependence on the activation energy for the moisture diffusion process was described by the Arrhenius equation. The kinetic parameters and exponential models were estimated by non-linear regression. The models with better reproducibility were the pseudo first order, the Page, and the Verma models (R2 ≥ 0.98). The diffusion coefficients that were calculated were in the order of 1.26 to 5.70 × 109 m s−2 and the energy activation for moisture diffusion obtained was 19.52 kJ mol−1.

Kinetics of the Ozonation of Tetrabromobisphenol-A in Wastewater

2011 ◽  
Vol 383-390 ◽  
pp. 2945-2950 ◽  
Author(s):  
Jie Zhang ◽  
Shi Long He ◽  
Mei Feng Hou ◽  
Li Ping Wang ◽  
Li Jiang Tian
Keyword(s):  
Rate Constants ◽  
Apparent Rate Constant ◽  
Reaction Rate ◽  
Batch Reactor ◽  
Kinetic Studies ◽  
Tetrabromobisphenol A ◽  
First Order ◽  
Reaction Rate Constants ◽  
Pseudo First Order ◽  
Kinetics Of

The kinetics of TBBPA degradation by ozonation in semi-batch reactor was studied. The reaction rate constants of TBBPA with O3 and •OH were measured by means of direct ozone attack and competition kinetics, and the values of which were 6.10 l/(mol•s), 4.8×109 l/(mol•s), respectively. Results of kinetic studies showed that TBBPA degradation by ozonation under the different conditions tested followed the pseudo-first-order. The values of apparent rate constant of TBBPA degradation increased with the increase of ozone dosage and pH, but decreased with the increase of initial TBBPA concentration.

scholarly journals Adsorption isotherm, kinetic and mechanism studies of 2-nitrophenol on sedimentary phosphate

2015 ◽  
Vol 4 (6) ◽  
pp. 289-296 ◽  
Author(s):  
Hind Yaacoubi ◽  
Zuo Songlin ◽  
Mustapha Mouflih ◽  
Mina Gourai ◽  
Said Sebti
Keyword(s):  
Kinetic Studies ◽  
Intraparticle Diffusion ◽  
X Ray Diffraction ◽  
Equilibrium Isotherms ◽  
X Ray ◽  
First Order ◽  
Adsorption Data ◽  
Pseudo Second Order ◽  
Pseudo First Order ◽  
Equilibrium Adsorption Capacity

Sedimentary phosphate (SP) was used as an adsorbent for the removal of 2-nitrophenol from aqueous solutions in an attempt to investigate (the feasibility of) its application (to) in wastewater purification.  The adsorbent was characterized by X-ray diffraction (XRD), IR spectroscopy, Fluorescence X and BET.  The results indicated that the SP (was) is francolite (Ca10 (PO4,CO3)6F2) and mesoporous. The effect of the adsorption time and the pH of the solution were studied. The pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to fit adsorption data in the kinetic studies. The equilibrium isotherms were determined using the Langmuir, Freundlich and Dubinin-Radushkevich models. The results show that the Dubinin-Radushkevich isotherm had better agreement with the 2-nitrophenol adsorption on SP with a correlation coefficient of 0.98, an equilibrium adsorption capacity of 633 mg. g-1 and a corresponding contact time of 2 h. The results imply that intraparticle diffusion could be summarized as the basic rate-controlling mechanisms during 2-nitrophenol adsorption on SP.

Kinetic studies of Dakin oxidation of o- and p-hydroxyacetophenones

1977 ◽  
Vol 55 (1) ◽  
pp. 102-110 ◽  
Author(s):  
M. B. Hocking ◽  
J. H. Ong
Keyword(s):  
Hydrogen Peroxide ◽  
Fractional Order ◽  
Rate Constants ◽  
Kinetic Studies ◽  
Second Order ◽  
Simple Test ◽  
Alkaline Hydrogen Peroxide ◽  
Para Isomer ◽  
First Order ◽  
Pseudo First Order

Rates of oxidation of aqueous o-, and p-hydroxyacetophenone with alkaline hydrogen peroxide to yield catechol and hydroquinone, respectively, have been followed spectrophotometri-cally. Both ketones showed smooth pseudo first-order behaviour, the ortho isomer yielding rate constants in the range 2.6 to 6.6 × 10−2 min−1 at 0 °C, and the para isomer of 0.73 to 7.10 × 10−2 min−1 at 35 °C for the concentrations of hydrogen peroxide and base used. The order in hydrogen peroxide was, unexpectedly, found to be 1.4. A simple test established that this fractional order was probably not the result of hydrogen peroxide involvement in simultaneous first- and second-order processes of differing rates. Other plausible pathways to explain this are proposed.

scholarly journals Kinetic studies on the effect of uridine diphosphate galactose and manganous ions on the reaction between lactose synthetase A protein from human milk and p-hydroxymercuribenzoate

1974 ◽  
Vol 143 (3) ◽  
pp. 587-590 ◽  
Author(s):  
Barry J. Kitchen ◽  
Patrick Andrews
Keyword(s):  
Human Milk ◽  
Protective Effect ◽  
Rate Constants ◽  
Dissociation Constants ◽  
Kinetic Studies ◽  
Uridine Diphosphate ◽  
First Order ◽  
Pseudo First Order ◽  
Uridine Diphosphate Galactose

The inhibition of lactose synthetase A protein by p-hydroxymercuribenzoate at pH7.5 and 25°C, which involves the reaction of one molecule of inhibitor with each molecule of enzyme, was decreased in rate by UDP-galactose, especially in the presence of Mn2+. Pseudo-first-order rate constants for the reaction between 0.1mm-p-hydroxymercuribenzoate and free enzyme, the enzyme–UDP-galactose complex and the enzyme–Mn2+–UDP-galactose complex were 4.4×10−2, 1.9×10−2 and 0.3×10−2min−1 respectively. The results also indicated that dissociation constants for UDP-galactose in the enzyme–UDP-galactose and enzyme–Mn2+–UDP-galactose complexes were 313 and 16μm respectively, the latter value being similar to the Km for UDP-galactose in the lactose synthetase reaction. The protective effect of UDP-galactose and the role of Mn2+ ions in lactose synthetase are discussed.

scholarly journals Kinetic Studies for the Biosorption of Chromium Using Cherry Leaves (Muntingia calabura L.)

2014 ◽  
Vol 25 ◽  
pp. 6-11 ◽  
Author(s):  
R. Aathithya ◽  
J. Rajani Sowparnika ◽  
V. Balakrishnan
Keyword(s):  
Regression Coefficient ◽  
Kinetic Studies ◽  
Order Reaction ◽  
First Order Reaction ◽  
Standard Errors ◽  
Second Order Reaction ◽  
Pseudo First Order Reaction ◽  
First Order ◽  
Pseudo First Order ◽  
Muntingia Calabura

Biosorption is an attractive technology which is used for the sorption of substances by a biomaterial. In this present work the heavy metal chromium was subjected to biosorption because of their non-degradability nature and causes water and land pollution. Cherry leaves were used as a biomaterial for the biosorption. Kinetic studies were performed for the biosorption experiment. From the experiment it was found that the reaction follows pseudo first order reaction because of the larger value of regression coefficient R2 and lower value of standard errors (χ2) for pseudo first order reaction than second order reaction.

scholarly journals Kinetics and DFT Studies of the Hydrogenation Reactions of Alkenes and Alkynes Catalyzed by (Benzoimidazol-2-ylmethyl)amine palladium(II) Complexes

2018 ◽  
Author(s):  
Thandeka Tshabalala ◽  
Stephen Ojwach
Keyword(s):  
Density Functional ◽  
Complex Structure ◽  
Kinetic Studies ◽  
Active Species ◽  
Functional Theory ◽  
Catalytic Activities ◽  
First Order ◽  
Mild Conditions ◽  
Hydrogenation Reactions ◽  
Pseudo First Order

A series of (benzoimidazol-2-ylmethyl)amine palladium(II) complexes have been employed as catalysts in the homogenous hydrogenation of alkenes and alkynes under mild conditions. A correlation between the catalytic activity and the nature of the ligand was established. Kinetic studies of the hydrogenation reactions of styrene established pseudo-first-order dependence on styrene substrate. On the other hand, partial orders with respect to H2 and catalyst concentrations were obtained consistent with the formation of palladium(II) monohydride species as the active species. The nature of the solvent used influenced the hydrogenation reactions, where coordinating solvents resulted in lower catalytic activities. Density functional theory investigations provided valuable insights into the reactivity trends and influence of complex structure on the hydrogenation reactions.

Degradation Kinetic of Oxytetracycline Antibiotic inside UV Reactor in the Presence of H2O2

2014 ◽  
Vol 625 ◽  
pp. 901-906
Author(s):  
Anisa Ur Rahmah ◽  
Sabtanti Harimurti ◽  
Abdul Aziz Omar ◽  
Thanabalan Murugesan
Keyword(s):  
Experimental Data ◽  
Kinetic Study ◽  
Regression Coefficient ◽  
Kinetic Studies ◽  
Second Order ◽  
Degradation Kinetic ◽  
First Order ◽  
Uv Reactor ◽  
Pseudo First Order ◽  
Veterinary Antibiotic

–Oxytetracycline (OTC), a widely used of veterinary antibiotic, was degraded inside a UV/H2O2system. Kinetic study was conducted at 30°C of temperature and pH 6.37, as suggested by the previous optimization experiment. About 250, 375 and 500 ppm initial OTC concentration were used for the kinetic studies, at H2O2concentration of 0.116 M. The experimental data were plotted against the pseudo zero-th, first and second order of kinetic. Based on regression coefficient value, the data was well fitted with the pseudo first order of kinetic. The calculated value ofkobswas 0.181 min-1.

scholarly journals Moisture diffusion coefficient estimation in peas drying by means of a modified Hawlader and Uddin method

2018 ◽  
Author(s):  
Carlos Martínez-Vera ◽  
Mario Vizcarra-Mendoza
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Equation ◽  
Diffusion Coefficients ◽  
Moisture Diffusion ◽  
Moisture Diffusivity ◽  
Second Step ◽  
Drying Process ◽  
Moisture Diffusion Coefficient ◽  
Coefficient Estimation ◽  
Constant Diffusion

The aim of the present work is to determine the moisture diffusion coefficient in peas applying, in a first step, a methodology previously published in the literature by Uddin et al.[1] for determining constant diffusion coefficients taking in account the volume reduction associated to the drying process. Then, in a second step, refine it by means of an optimization step. The optimization step is justified because the methodology of Uddin et al. is based in a solution of the diffusion equation that is not mathematically valid for the drying-shrinking problem. Keywords: : moisture diffusivity; drying-shrinking; peas drying 

scholarly journals HYDROLYSIS AND DEUTERATION OF GLYCYLGLYCINE CATALYZED BY DINUCLEAR [BMXDCu 2]4+ COMPLEX

2007 ◽  
Vol 15 (15) ◽  
pp. 15-27
Author(s):  
Ana Cristina Franzoi ◽  
Gledir T. Stein Martins ◽  
Sérgio Duvoisin Jr. ◽  
Bruno Szpoganicz
Keyword(s):  
Rate Constants ◽  
Kinetic Studies ◽  
Peptide Bond ◽  
Reaction Rates ◽  
Active Species ◽  
Individual Species ◽  
Specific Rate ◽  
First Order ◽  
Parallel Reactions ◽  
Semi Empirical

Kinetic studies of hydrolysis and deuteration of glycylglycine by dinuclear [BMXDCu 2]4+ complexes were following by NMR1H. Two parallel reactions were observed for the ternary system BMXD-Cu 2-Glycylglycine: peptide bond hydrolysis and NCH2 deuteration reactions. The reaction rates show the first-order behavior to the concentration of the ternary [BMXDCu2Glycylglycine] complex. The specific rate constants for the hydrolysis reaction are: KLCu2HGG4+ (L = BMXD and GG = glycylglycine) = 1,8 x 10-6 s-1; KLCu 2GG3+ = 2,3 x 10-6 s-1; KLCu2H-1GG2+, KLCu 2(OH)H-1GG+ and KLCu 2(OH) 2H-1GG = 0, and the specific deuteration rate constants for individual species are: KLCu 2HGG4+ = 3,9 x 10-6 s-1; KLCu 2GG3+ = 4,3 x 10-6 s-1; KLCu2H-1GG2+, KLCu2(OH)H-1GG+ and KLCu2(OH)2H-1GG = 0. The results show that the most active species toward hydrolysis and deuteration reactions are the protonated and non-protonated species, the former being the most reactive species. Semi-empirical calculations for energy minimization showed that the binuclear [BMXDCu 2]4+) complexes adopt the boat-type conformation, in order to accommodate the dipeptide glycylglycine.

scholarly journals Nano-Catalytic Ozonation of 4-Nitrochlorobenzene in Aqueous Solutions

2012 ◽  
Vol 9 (4) ◽  
pp. 1968-1975 ◽  
Author(s):  
S. M. Tabatabaei ◽  
A. Mehrizad ◽  
P. Gharbani
Keyword(s):  
Particle Size ◽  
Degradation Rate ◽  
Batch Reactor ◽  
Kinetic Studies ◽  
Catalytic Ozonation ◽  
Main Role ◽  
Order Kinetic ◽  
Nano Zno ◽  
First Order ◽  
Pseudo First Order

In this paper, efficiency of nano-ZnO particles on catalytic ozonation of 4-nitrochlorobenzene (4NCB) using semi-batch reactor has been studied at various pHs. During the catalytic ozonation, TOC and concentration of nitrate ions was monitored. Results indicate that degradation of 4NCB was improved by combination of nano-ZnO with ozone. The effect of ZnO particle size and pH are also examined. According to the results, concentration of 4NCB decreased with increasing of particle size from nanosized to microsized and pH from 3.0 to 9.0. Based on the results, it suggests radical hydroxyl does not affect on the degradation of 4NCB in catalytic ozonation, but the surface of catalyst plays main role. Kinetic studies showed degradation of 4NCB followed pseudo-first-order kinetic and maximum degradation rate was observed at pH=3.

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