Oxidative Ammonolysis of Technical Lignins. Part 1. Kinetics of the Reaction under Isothermal Condition at 130°C

Holzforschung ◽  
2001 ◽  
Vol 55 (4) ◽  
pp. 397-404 ◽  
Author(s):  
Ewellyn A. Capanema ◽  
Mikhail Yu. Balakshin ◽  
Chen-Loung Chen ◽  
Josef S. Gratzl ◽  
Adrianna G. Kirkman
Keyword(s):  
Reaction Time ◽  
Isothermal Condition ◽  
Reaction Times ◽  
Molar Ratio ◽  
Second Phase ◽  
Spectroscopic Techniques ◽  
Oxidative Ammonolysis ◽  
Nitrogen Incorporation ◽  
Two Phases ◽  
Kinetics Of

Summary Investigations were conducted on the oxidative ammonolysis of REPAP organosolv lignin at 130 °C in 0.8M NH4OH solution under oxygen pressure of 12 bar. The lignin was completely solubilized at the reaction time of 165 min. The kinetics of the nitrogen incorporation consists of two phases. The first phase is up to the reaction time of approximately 35 min including 15 min heating up period. The rate of nitrogen incorporation in the first phase is 2.3 times higher than that in the second phase: κ1 = 4.58 × 10−4 s−1 versus κ2 = 1.90 × 10−4 s−1. The oxygen uptake and CO2 formation in the reaction is rather high. When the nitrogen incorporation was ceased after reaction for 255 minutes, more than 4 moles of oxygen/C9-unit of lignin were consumed and approximately 1.5 moles of carbon dioxide/C9-unit of lignin were released. In addition, extensive O-demethylation of methoxyl groups occurred. The molar ratio of the nitrogen incorporation to the methoxyl group eliminated is approximately 1.4 and 0.7 for the soluble and insoluble N-modified lignins, respectively. Structural analyses of the soluble N-modified lignins by FTIR and 1H NMR spectroscopic techniques showed only quantitative differences in the spectra obtained at different reaction times. This indicates that the reaction pathways do not change in the course of the oxidative ammonolysis. Possible reaction mechanisms of the oxidative ammonolysis are discussed on the basis of the experimental data.

Cardiac Cycle Phase and Movement and Reaction Times

1976 ◽  
Vol 42 (3) ◽  
pp. 767-770 ◽  
Author(s):  
Matti J. Saari ◽  
Bruce A. Pappas
Keyword(s):  
Reaction Time ◽  
Cardiac Cycle ◽  
Visual Stimuli ◽  
Reaction Times ◽  
Reaction Time Task ◽  
Stimulus Presentation ◽  
Stimulus Onset ◽  
Cycle Phase ◽  
Second Phase ◽  
Time Task

The EKG was recorded while Ss differentially responded to auditory or visual stimuli in a reaction time task. The EKG record was analyzed by dividing each R-R interval encompassing a stimulus presentation into 9 equal phases. Reaction times were determined as a function of the phase encompassing stimulus onset while movement times were determined for the phase in which the response was initiated. Only reaction time significantly varied with cardiac cycle, with reactions during the second phase being slower than later phases.

scholarly journals COMPARATIVE KINETICS OF HEMOLYSIS INDUCED BY BACTERIAL AND OTHER HEMOLYSINS

1947 ◽  
Vol 30 (4) ◽  
pp. 337-353 ◽  
Author(s):  
Alan W. Bernheimer
Keyword(s):  
Maximum Rate ◽  
Sodium Taurocholate ◽  
Second Phase ◽  
Pyridinium Chloride ◽  
Cetyl Pyridinium Chloride ◽  
Streptolysin S ◽  
Streptolysin O ◽  
Cetyl Pyridinium ◽  
Two Phases ◽  
Kinetics Of

A study has been made of the kinetics of lysis induced by various hemolytic agents. The course of bemolysis was followed by mixing lysin with washed human erythrocytes, removing samples from the mixture, and estimating colorimetrically the hemoglobin in the supernatant fluid of the centrifuged samples. Most of the curves (but not all of them, e.g. tyrocidine) obtained by plotting degree of hemolysis against time, were S-shaped. The initiation of lysis by streptolysin S' was delayed, and in this property, streptolysin S' was similar to Cl. septicum hemolysin. None of the other lysins studied exhibited a long latent period preceding lysis. The maximum rate of hemoglobin liberation was found, in the range of lysin concentrations studied, to be a linear function of concentration when theta toxin of Cl. welchii, pneumolysin, tetanolysin, or streptolysin S' was the lytic agent. With comparable concentrations of saponin, sodium taurocholate, cetyl pyridinium chloride, tyrocidine, duponol C, lecithin-atrox venom mixture, or streptolysin O, the relation between rate and concentration was non-linear. The critical thermal increment associated with hemolysis was determined for systems containing pneumolysin, theta toxin, streptolysin S', streptolysin O, tetanolysin, and saponin. The findings concerning the effect of concentration and temperature on the rate of hemolysis provide a basis for classifying hemolytic agents (Tables I and II). Hemolysis induced by Cl. septicum hemolysin was found to be preceded by two phases: a phase of alteration of the erythrocytes and a phase involving swelling. Antihemolytic serum inhibited the first but not the second phase while sucrose inhibited the second but not the first phase.

scholarly journals Universal kinetics of imperfect reactions in confinement

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Thomas Guérin ◽  
Maxim Dolgushev ◽  
Olivier Bénichou ◽  
Raphaël Voituriez
Keyword(s):  
Reaction Time ◽  
Transport Process ◽  
Reaction Times ◽  
Complex Environments ◽  
Analytical Treatment ◽  
Volume Limit ◽  
Normal Diffusion ◽  
The Mean ◽  
Kinetics Of ◽  
Mean Reaction Time

AbstractChemical reactions generically require that particles come into contact. In practice, reaction is often imperfect and can necessitate multiple random encounters between reactants. In confined geometries, despite notable recent advances, there is to date no general analytical treatment of such imperfect transport-limited reaction kinetics. Here, we determine the kinetics of imperfect reactions in confining domains for any diffusive or anomalously diffusive Markovian transport process, and for different models of imperfect reactivity. We show that the full distribution of reaction times is obtained in the large confining volume limit from the knowledge of the mean reaction time only, which we determine explicitly. This distribution for imperfect reactions is found to be identical to that of perfect reactions upon an appropriate rescaling of parameters, which highlights the robustness of our results. Strikingly, this holds true even in the regime of low reactivity where the mean reaction time is independent of the transport process, and can lead to large fluctuations of the reaction time - even in simple reaction schemes. We illustrate our results for normal diffusion in domains of generic shape, and for anomalous diffusion in complex environments, where our predictions are confirmed by numerical simulations.

Oxidative Ammonolysis of Technical Lignins. Part 2. Effect of Oxygen Pressure

Holzforschung ◽  
2001 ◽  
Vol 55 (4) ◽  
pp. 405-412 ◽  
Author(s):  
Ewellyn A. Capanema ◽  
Mikhail Yu. Balakshin ◽  
Chen-Loung Chen ◽  
Josef S. Gratzl ◽  
Adrianna G. Kirkman
Keyword(s):  
Oxygen Uptake ◽  
Oxygen Pressure ◽  
Minor Effect ◽  
Oxidative Ammonolysis ◽  
First Order ◽  
Rate Determining Step ◽  
Nitrogen Incorporation ◽  
Two Phases ◽  
Modified Lignin ◽  
Effect Of Oxygen

Summary Investigations were conducted on the effects of oxygen pressure on the oxidative ammonolysis of REPAP organosolv lignin at 130 °C under oxygen pressure of 5, 8 and 12 bar. The rates of reactions monitored, such as nitrogen incorporation, lignin solubilization, oxygen uptake and CO2 formation, increase with increasing oxygen pressure. Kinetics of nitrogen incorporation under different oxygen pressure consists of two phases and follows a first order law in each phase. Linear correlation between the rate of nitrogen incorporation and oxygen pressure implies that the reaction is first order with respect to oxygen concentration. This indicates that oxygen participates directly in the rate-determining step of nitrogen incorporation. The rate of lignin solubilization also linearly increases with increasing oxygen pressure, implying that the rate of lignin degradation directly depends on oxygen pressure. The nitrogen incorporation is linearly correlated with the oxygen uptake, CO2 formation, oxygen incorporation into lignin, loss of carbon and methoxyl group content under all values of oxygen pressure and during the entire reaction period. This suggests that the reactions in the oxidative ammonolysis of lignin proceed via the same pathways in the different kinetic phases. In addition, the changes in the oxygen pressure were found to have only minor effect upon the coefficients of these linear correlations. This is in good agreement with the structures of N-modified lignin elucidated from FTIR and indicates that oxygen pressure affects only the reaction rate, but not the reaction mechanism.

Advanced treatment of high strength opium alkaloid industry effluents

2002 ◽  
Vol 46 (9) ◽  
pp. 323-330 ◽  
Author(s):  
A.F. Aydin ◽  
M. Altinbas ◽  
M.F. Sevimli ◽  
I. Ozturk ◽  
H.Z. Sarikaya
Keyword(s):  
Reaction Time ◽  
Treatment Plant ◽  
Operating Conditions ◽  
Treatment System ◽  
Molar Ratio ◽  
Optimum Operating ◽  
Second Phase ◽  
Fenton’S Oxidation ◽  
Fenton's Oxidation ◽  
Opium Alkaloid

The purpose of this study was to investigate an effective treatment system which can be applicable to treat opium alkaloid industry (OAI) effluents characterised with high COD, TKN, dark color and non-biodegradable organic pollutants. In the first phase of the study, lab-scale anaerobic (UASBR) + aerobic (SBR) treatability studies were carried out on opium processing industry effluents. Effluent CODs from the two staged biological treatment system were relatively high (∼700 mgl−1) and additional post treatment was required. Physico-chemical treatability studies previously carried out on the effluent of opium alkaloid wastewater treatment plant, were not effective in removing residual COD and color. In the second phase of the study, the refractory organics causing higher inert COD values in the SBR effluent were additionally treated by using Fenton's Oxidation. The batch tests were performed to determine the optimum operating conditions including pH, H2O2 dosage, molar ratio of Fe2+/H2O2 and reaction time. It was found that removal efficiencies of COD and color for 30 minutes reaction time were about 90% and 95%, respectively. The ratio of H2O2/FeSO4 was determined as 200 mgl−1/600 mgl−1 for the optimum oxidation and coagulation process at pH 4. Experimental results of the present study have clearly indicated that the Fenton's oxidation technology is capable to treat almost all parts of the organics which consist of both soluble initial and microbial inert fractions of COD for opium alkaloid industry effluents. Effluents from the Fenton's Oxidation process can satisfy effluent standards for COD and color in general.

scholarly journals Pressure-induced depolymerization of spindle microtubules. I. Changes in birefringence and spindle length.

1975 ◽  
Vol 65 (3) ◽  
pp. 603-614 ◽  
Author(s):  
E D Salmon
Keyword(s):  
Initial Phase ◽  
Polarized Light ◽  
Meiotic Metaphase ◽  
Second Phase ◽  
Complete Disappearance ◽  
Spindle Microtubule ◽  
Spindle Microtubules ◽  
Optical Pressure ◽  
Two Phases ◽  
Kinetics Of

Changes in birefringence retardation (BR) and length of Chaetopterus meiotic metaphase-arrested spindles produced by increased hydrostatic pressure were observed with polarized-light microscopy using a newly developed optical pressure chamber. Increased pressure produced rapid, reversible decreases in spindle BR and length. Pressures of 3,500 psi or higher at 22 degrees C caused complete disappearance of spindle BR within 3 min. Up to 6,000 psi, the rates of both BR decay and spindle shortening increased progressively with increasing pressure. At 6,000 psi or above, the BR decreased rapidly but there was no evidence of spindle shortening. The general observations are consistent with results of earlier classical experiments on effects of pressure on mitosis, and with experiments that used colchicine or low temperature as microtubule-depolymerizing agents. The kinetics of spindle depolymerization and repolymerization showed two phases: an initial phase of rapid decreases or increase in half-spindle microtubule BR; and a second phase of nearly constant BR during which most of the spindle shortening or growth occurs. BR is assumed to be directly related to the number of microtubules in a spindle cross section. It is hypothesized that microtubules in the spindle have different stabilities depending on the attachment of nonattachment of their ends. This hypothesis is used to explain the two phases of spindle depolymerization and repolymerization as well as several other observations.

scholarly journals Kinetics of Biodiesel Synthesis Using Used Frying Oil through Transesterification Reaction

2020 ◽  
Vol 9 (1) ◽  
pp. 1-11
Author(s):  
Agus Haryanto ◽  
Amieria Citra Gita ◽  
Tri Wahyu Saputra ◽  
Mareli Telaumbanua
Keyword(s):  
Reaction Time ◽  
Frying Oil ◽  
Transesterification Reaction ◽  
Biodiesel Production ◽  
Molar Ratio ◽  
Order Kinetic ◽  
Used Frying Oil ◽  
First Order ◽  
Biodiesel Synthesis ◽  
Kinetics Of

This research aims to study the first-order kinetics of biodiesel production from used frying oil (UFO) through transesterification with methanol. Used frying oil was collected from fried peddlers around the campus of the University of Lampung. Technical grade methanol and NaOH catalyst were purchased from a local chemical supplier. The experiment was carried out with 100 ml of UFO at various combinations of oil to methanol molar ratio (1:4, 1:5, and 1:6), reaction temperatures(30 to 55oC, the ramping temperature of 5o C), and reaction time of 0.25 to 10 minutes. First-order kinetic was employed using 126 data pairs (87.5%). The acquired kinetic model was validated using 18 data sets (12.5%) observed at a reaction time of eight min. Results show that biodiesel yield was increased with reaction time, its molar ratio, and temperature. The maximum return of 78.44% was achieved at 55oC and molar ratio of 1:6. The kinetic analysis obtains the reaction rate constant (k) in the range of 0.045 to 0.130. The value of k increases with the reaction temperature and molar ratio. The analysis also reveals the average activation energy (Ea) of the UFO transesterification reaction with methanol and NaOH catalyst to be 21.59 kJ/mol. First-order kinetic is suitable to predict biodiesel yield from UFO because of low %RMSE (3.39%) and high R2 (0.8454

scholarly journals Estudo da produção de biodiesel utilizando resina aniônica na presença cossolvente

2020 ◽  
Author(s):  
◽  
B. G. Bessa
Keyword(s):  
Reaction Time ◽  
Raw Materials ◽  
Ambient Pressure ◽  
Reaction Times ◽  
Climatic Conditions ◽  
Molar Ratio ◽  
Transport Sector ◽  
Residual Water ◽  
Mass Ratio ◽  
Alternative Sources

Brazil is a country with several options of energetic matrices, due to its favorable climatic conditions, availability of land for cultivation of different cultures, oil reserves, amongst many other alternative sources of raw materials that can be used as fuel. Biodiesel is an example of energy used in the transport sector and derived from renewable sources, such as vegetable and animal oils and fats It is generally produced using methanol as transesterifying agent in homogeneous catalysis with a base. This type of catalysis, however, generates waste due to the need to wash the generated biodiesel, in order to meet the product quality standards. Therefore, there is a need to develop different production routes that are more economical and that use catalysts that are easier to separate and recover, enabling their reuse. In this work we studied the methyl transesterification reaction of soybean oil with the anion exchange resin, Amberlyst®, as a heterogeneous catalyst. This reaction was conducted using the 9:1 molar ratio of alcohol/oil, 50 ºC, ambient pressure and 300 rpm of stirring. We studied the effects of the load of catalyst used, reaction time, previous drying of the resin, and the amount of added solvent. The first experiment showed a peak of conversion rate using 2,5% of resin, by mass and in relation to oil, resulting in 1,04 ± 0,01% after 90 minutes of reaction. However, an increase was noticed when the resin was dried at 50 ºC, in order to remove residual water from its pores, obtaining the result of 2,42 ± 0,01% at the same reaction time of 90 min. For longer reaction times there was no considerable improvement in conversion. In order to verify the influence of the presence of cosolvent in the reaction, (n-hexane), four different amounts of it were used (mass ratio of cosolvent in relation to mass of oil was 0.5, 0.6, 0.8 and 1), keeping constant the other conditions of the reaction. All the proportions of cosolvent resulted in increased conversion when compared to previous experiments. The highest conversion obtained was 53,66 ± 0,02% using 0,8 mass ratio of cosolvent. In conclusion, we observed the necessity of drying the resin before it is used in the reaction, and that the use of cosolvent helps to increase the conversion. The analysis via MEV showed that the resin particle is spherical and that its surface is plain, without great variation when it was in natura or dried

scholarly journals Pengaruh Waktu Reaksi Terhadap Yield dan Kandungan Metil Ester Sintesis Biodiesel Ampas Tahu Metode Elektrokatalitik

2021 ◽  
Vol 15 (1) ◽  
pp. 54-64
Author(s):  
Elli Prastyo ◽  
Dian Farkhatus S ◽  
Puji Astuti Ibrahim
Keyword(s):  
High Temperature ◽  
Reaction Time ◽  
Synthesis Method ◽  
Reaction Times ◽  
Acid Number ◽  
Molar Ratio ◽  
Energy Separation ◽  
Homogeneous Catalyst ◽  
Biodiesel Synthesis ◽  
Time Variables

Abstrak Sintesis biodiesel umumnya melalui proses transesterifikasi suhu tinggi menggunakan katalis homogen yang membutuhkan energi cukup besar, pemisahan katalis yang cukup sulit dan terbuang sebagai limbah. Sintesis biodiesel metode elektrokatalitik memberi keuntungan efisiensi lebih daripada transesterifikasi suhu tinggi. Pada penelitian ini, sintesis biodiesel metode elektrokatalitik dilakukan menggunakan elektroda grafit suhu 28oC dan tegangan konstan 18,2 Volt. Variabel waktu reaksi selama 60 menit, 120 menit, dan 180 menit, rasio molar minyak – metanol 1:9, katalis BaO/CaO 2% b/b terimpregnasi dengan berat katalis 5% b/b terhadap minyak digunakan untuk mengevaluasi biodiesel yang dihasilkan. Produk biodiesel berupa metil ester asam lemak bebas dianalisis menggunakan GC-MS. Hasil penelitian menunjukkan yield yang dihasilkan dengan waktu reaksi 60 menit, 120 menit, dan 180 menit berturut – turut sebesar 88%, 94%, dan 90 dengan waktu reaksi optimum 120 menit. Dan terdapat empat kandungan utama metil ester di semua waktu reaksi yaitu: metil palmiat, metil oleat, metil linoleat, metil stearat. Karakteristik biodiesel yang dihasilkan dilihat dari nilai densitas, viskositas, dan bilangan asam memenuhi kualifikasi SNI Biodiesel 04-7182-2006. Abstract Synthesis of biodiesel generally uses a transesterification process at high temperature with homogeneous catalyst that requires a large amount of energy, separation of the catalyst is quite, and is wasted as waste. Electrocatalytic biodiesel synthesis method gives more advantages in high temperature transesterification. The reaction time variables were 60 minutes, 120 minutes, and 180 minutes, the oil-methanol molar ratio was 1: 9, the BaO / CaO 2% w / w catalyst was impregnated with a catalyst weight of 5% w / w to the oil used for the resulting biodiesel. The results showed that the results with a reaction time of 60 minutes, 120 minutes, and 180 minutes were 88%, 94%, and 90 minutes respectively with an optimal reaction time of 120 minutes. It showed that there were four main ingredients of methyl ester at all reaction times, namely: methyl palmyate, methyl oleate, methyl linoleate, methyl stearate. The characteristics of the resulting biodiesel seen from the density, viscosity, and acid number have met the SNI Biodiesel 04-7182-2006 qualifications.

Oxidative Ammonolysis of Technical Lignins. Part 3. Effect of Temperature on the Reaction Rate

Holzforschung ◽  
2002 ◽  
Vol 56 (4) ◽  
pp. 402-415 ◽  
Author(s):  
E. A. Capanema ◽  
M. Y. Balakshin ◽  
C.-L. Chen ◽  
J. S. Gratzl ◽  
A. G. Kirkman
Keyword(s):  
Reaction Temperature ◽  
Reaction Rate ◽  
Total Carbon ◽  
Reaction Pathways ◽  
Effect Of Temperature ◽  
Pseudo First Order Reaction ◽  
Oxidative Ammonolysis ◽  
Nitrogen Incorporation ◽  
Different Temperatures ◽  
Two Phases

Summary The effect of the reaction temperature on the kinetics and the reaction mechanism of oxidative ammonolysis of Repap organosolv lignin have been studied. The reaction was conducted in 0.8 M Nh4oh solution under oxygen pressure of 12 bar and at three different temperatures, 70 °C, 100 °C and 130 °C. The resulting N-modified lignins were analyzed by elemental and methoxyl group. About 20–25% of maximum nitrogen content is incorporated into the lignin very fast, in 1–2 min of the reaction. The reaction kinetics then follows a pseudo-first order reaction law and consists of two phases. The activation energies for nitrogen incorporation and lignin solubilization are rather low, in the range of 33–34 kJ/mol. Linear correlation between nitrogen incorporated into the lignin and molecular oxygen uptake, oxygen incorporation, CO2 formation, O-demethylation and total carbon loss was analyzed at the different reaction temperatures. On the basis of kinetic data obtained so far, we have postulated that the reaction temperature affects the reaction rate, but not the reaction pathways. The reaction temperature also affects the ratios between different reaction pathways, though the effect is not very strong. The results obtained are discussed in the terms of competitive reactions of lignin oxidation followed by nitrogen incorporation and lignin deactivation involving nitrogen

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