Kinetics of 1-butanol, di-(1-butyl) ether and 1-butene reactions on aluminas partially deactivated by sodium

1989 ◽  
Vol 54 (11) ◽  
pp. 2985-2997 ◽  
Author(s):  
František Krampera ◽  
Ludvík Beránek
Keyword(s):  
Vapour Phase ◽  
Reaction Rates ◽  
Product Formation ◽  
Sodium Content ◽  
Butyl Ether ◽  
Deactivation Kinetics ◽  
Two Factors ◽  
Best Fitting ◽  
The Individual ◽  
Kinetics Of

The initial rates of six reactions taking place in 1-butanol dehydration at 260 °C in vapour phase were measured on aluminia samples differing in sodium content. The reactants were 1-butanol, di-(1-butyl) ether and 1-butene, resp. The parameters of the best fitting rate equation for each reaction were evaluated. The reaction rates as well as the rate constants and adsorption coefficients of the individual reactions show different sensitivity to datalyst acidity. Therefore, the selectivity of product formation can be influenced by sodium content of the catalyst. The selectivities (with the exception of 1-butene izomerization) strongly depend also on the partial pressure of the starting reactants. Thus, these two factors can be used to control the selectivity for preparative purposes. The results of this paper clearly demonstrate the nonseparability of the deactivation kinetics in 1-butanol dehydration on sodium poisoned aluminas.

Kinetics of esterification of monoisopropylphenols with phosphoryl trichloride

1989 ◽  
Vol 54 (5) ◽  
pp. 1311-1317
Author(s):  
Miroslav Magura ◽  
Ján Vojtko ◽  
Ján Ilavský
Keyword(s):  
Liquid Phase ◽  
Rate Constants ◽  
Reaction Rates ◽  
Activation Energies ◽  
The Individual ◽  
Kinetics Of

The kinetics of liquid-phase isothermal esterification of POCl3 with 2-isopropylphenol and 4-isopropylphenol have been studied within the temperature intervals of 110 to 130 and 90 to 110 °C, respectively. The rate constants and activation energies of the individual steps of this three-step reaction have been calculated from the values measured. The reaction rates of the two isomers markedly differ: at 110 °C 4-isopropylphenol reacts faster by the factors of about 7 and 20 for k1 and k3, respectively. This finding can be utilized in preparation of mixed triaryl phosphates, since the alkylation mixture after reaction of phenol with propene contains an excess of 2-isopropylphenol over 4-isopropylphenol.

Kinetics of Triplet Sublevel Selective Photochemical Reactions in the Solid State

1981 ◽  
Vol 36 (7) ◽  
pp. 743-750
Author(s):  
Manfred Gehrtz ◽  
Christoph Bräuchle ◽  
Jürgen Voitländer
Keyword(s):  
Solid State ◽  
Reaction Rates ◽  
Photochemical Reactions ◽  
Solid State Reactions ◽  
Physical Activation ◽  
Zero Field ◽  
Excited Triplet ◽  
The Individual ◽  
Activation Rates ◽  
Kinetics Of

Abstract A detailed description of the overall kinetics of photochemical reactions has to deal with photo-physical activation and de-activation rates as well as with true photochemical rates. Based on the hypothesis that for photoreactions involving the lowest excited triplet state the chemical reaction rates of the individual triplet zero-field levels have different values, a method is presented for the evaluation of these rates from bulk measurements under steady state illumination conditions. The complications arising from the detection of solid state reactions are discussed, and a simple solution is given, illustrated by a numerical example.

Kinetics of hydrogenation of alkynes and dienes on palladium catalyst

1987 ◽  
Vol 52 (12) ◽  
pp. 2909-2917 ◽  
Author(s):  
Libor Červený ◽  
Šárka Řehůřková
Keyword(s):  
Activated Carbon ◽  
Palladium Catalyst ◽  
Atmospheric Pressure ◽  
Reaction Rates ◽  
Initial Reaction ◽  
Hydrogenation Rate ◽  
Substrate Structure ◽  
The Individual ◽  
Kinetics Of ◽  
Relative Adsorption

Alkynic and dienic substrates (C6-C10) in hexane and methanol were hydrogenated over a catalyst of 3% Pd on activated carbon at 20 °C and atmospheric pressure. The initial reaction rates were measured for the individual substrates; the hydrogenation rates of the olefinic substances formed were also determined if the hydrogenation was selective. The selectivities in competitive hydrogenations of substrate pairs were established and the relative adsorption coefficients of the substrates were calculated from them. The effect of the substrate structure and the solvent effect on the hydrogenation rate and relative adsorptivity are discussed for the alkynic and dienic substances studied.

Kinetics of individual reactions in reaction network 1-butanol-di-(1-butyl) ether-butenes-water on alumina

1986 ◽  
Vol 51 (4) ◽  
pp. 774-785 ◽  
Author(s):  
František Krampera ◽  
Ludvík Beránek
Keyword(s):  
Complex System ◽  
Reaction Network ◽  
Rate Equations ◽  
Butyl Ether ◽  
Alcohol Dehydration ◽  
Consecutive Reaction ◽  
Best Fitting ◽  
Kinetics Of

The complex system of six reactions occurring when 1-butanol is dehydrated on alumina at 260 °C was investigated. Initial kinetics of 1-butanol, di-(1-butyl) ether and 1-butene transformations were analyzed and best fitting rate equations for all reactions were selected. The inhibiting effects of water on initial rates was quantitatively expressed. Very low conversion data provided additional evidence for the validity of the parallel-consecutive reaction network of alcohol dehydration. In all the alkene-forming reactions, 1-butene was the primary product which was then isomerized into a mixture of cis- and trans-2-butenes.

scholarly journals Kinetics methods for clinical epidemiology problems

2015 ◽  
Vol 112 (46) ◽  
pp. 14150-14155 ◽  
Author(s):  
Alexandru Dan Corlan ◽  
John Ross
Keyword(s):  
Clinical Epidemiology ◽  
Meta Analysis ◽  
Reaction Rates ◽  
Mass Action ◽  
Reaction Systems ◽  
Disease Epidemiology ◽  
Mass Action Law ◽  
The Individual ◽  
Kinetics Of ◽  
Stochastic Kinetics

Calculating the probability of each possible outcome for a patient at any time in the future is currently possible only in the simplest cases: short-term prediction in acute diseases of otherwise healthy persons. This problem is to some extent analogous to predicting the concentrations of species in a reactor when knowing initial concentrations and after examining reaction rates at the individual molecule level. The existing theoretical framework behind predicting contagion and the immediate outcome of acute diseases in previously healthy individuals is largely analogous to deterministic kinetics of chemical systems consisting of one or a few reactions. We show that current statistical models commonly used in chronic disease epidemiology correspond to simple stochastic treatment of single reaction systems. The general problem corresponds to stochastic kinetics of complex reaction systems. We attempt to formulate epidemiologic problems related to chronic diseases in chemical kinetics terms. We review methods that may be adapted for use in epidemiology. We show that some reactions cannot fit into the mass-action law paradigm and solutions to these systems would frequently exhibit an antiportfolio effect. We provide a complete example application of stochastic kinetics modeling for a deductive meta-analysis of two papers on atrial fibrillation incidence, prevalence, and mortality.

Kinetics and Mechanism of Decomposition of 1,3-Bis(4-methylphenyl)triazene Catalyzed with Substituted Benzoic Acids in 25% Aqueous Methanol-General or Specific Catalysis?

1994 ◽  
Vol 59 (9) ◽  
pp. 2029-2041
Author(s):  
Oldřich Pytela ◽  
Taťjana Nevěčná
Keyword(s):  
Benzoic Acids ◽  
Hammett Equation ◽  
Aqueous Methanol ◽  
Mechanism Of Decomposition ◽  
Kinetics Of Decomposition ◽  
Independent Variable ◽  
Amino Derivatives ◽  
Substituted Benzoic Acids ◽  
The Individual ◽  
Kinetics Of

The kinetics of decomposition of 1,3-bis(4-methylphenyl)triazene catalyzed with 13 substituted benzoic acids of various concentrations have been measured in 25 vol.% aqueous methanol at 25.0 °C. The rate constants observed (297 data) have be used as values of independent variable in a series of models of the catalyzed decomposition. For the catalytic particles were considered the undissociated acid, its conjugated base, and the proton in both the specific and general catalyses. Some models presumed formation of reactive or nonreactive complexes of the individual reactants. The substituent effect is described by the Hammett equation. The statistically best model in which the observed rate constant is a superposition of a term describing the dependence on proton concentration and a term describing the dependence on the product of concentrations of proton and conjugated base is valid with the presumption of complete proton transfer from the catalyst acid to substrate, which has been proved. The behaviour of 4-dimethylamino, 4-amino, and 3-amino derivatives is anomalous (lower catalytic activity as compared with benzoic acid). This supports the presumed participation of conjugated base in the title process.

A contingency perspective on learning and instruction in physical education

2021 ◽  
pp. 1356336X2098588
Author(s):  
Jonas Wibowo ◽  
Ben Dyson
Keyword(s):  
Physical Education ◽  
Learning Processes ◽  
Methodological Issues ◽  
Unit Of Analysis ◽  
Contingency Perspective ◽  
Two Factors ◽  
The Individual ◽  
Teaching Learning ◽  
The Relationship ◽  
Learning And Instruction

In this article, we focus on the contingency between learning and instruction in physical education (PE). We argue that the complex interconnectedness of teachers’ instruction and students’ learning processes should be studied using a unit of analysis that expresses the relationship between the two factors. A contingency perspective foregrounds the individual differences between different learners and how a teacher regards these differences. Furthermore, it has the potential to provide a precise lens for empirical research on how the students’ situations shape the evolution of the teaching--learning process. Based on scaffolding research and adaptive teaching research, which draws on socio-constructivist foundations, we call this unit of analysis ‘contingency’. We outline a framework of research that suggests depicting contingency dimensions, respective instructional continua, and contingency rules when investigating contingency in PE. Furthermore, autonomy as a core contingency dimension for PE and methodological issues will be discussed.

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

2011 ◽  
Vol 324 ◽  
pp. 166-169 ◽  
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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