Mechanism of the dehydration of 1-butanol over zeolites

1985 ◽  
Vol 50 (8) ◽  
pp. 1834-1841 ◽  
Author(s):  
O. Olaofe ◽  
P. L. Yue
Keyword(s):  
Experimental Data ◽  
Reaction Mechanism ◽  
Product Distribution ◽  
Preferential Formation ◽  
Reaction Proceeds ◽  
Increasing Temperature ◽  
Positively Charged

The product distribution from the dehydration of 1-butanol over zeolites (13X, 4A, ZNa) has been investigated to gain insight of the reaction mechanism. The formation of 2-alkenes (cis-2-butene and trans-2-butene) in the absence of isomerization reactions during the catalytic dehydration of 1-butanol over zeolites is unambiguous evidence in favour of a positively charged intermediate, indicating that reaction proceeds via a E1 type of mechanism. Experimental data also showed the preferential formation of cis-2-butene over that of trans-2-butene. The predominance of E1 type mechanism increases with increasing temperature.

Vinyl ether hydrolysis. XVII. Oxacyclonon-2,8-diene and the question of the unorthodox reaction mechanism for 9-methoxyoxacyclonon-2-ene

1984 ◽  
Vol 62 (1) ◽  
pp. 74-76 ◽  
Author(s):  
R. A. Burt ◽  
Y. Chiang ◽  
A. J. Kresge ◽  
S. Szilagyi
Keyword(s):  
Reaction Mechanism ◽  
Vinyl Ether ◽  
Membered Ring ◽  
Specific Rate ◽  
Ether Group ◽  
Reaction Proceeds ◽  
Great Reactivity ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The acid-catalyzed hydrolysis of the nine-membered ring cyclic vinyl ether, oxacyclonon-2,8-diene, occurs with a normal isotope effect, [Formula: see text], which indicates that this reaction proceeds by the conventional vinyl ether hydrolysis mechanism involving rate-determining proton transfer to carbon. The specific rate of this reaction, [Formula: see text], may then be used to show that there is no significant ring-size effect on the rate of hydrolysis of a vinyl ether group in a nine-membered ring. The previously noted unusually great reactivity of the vinyl ether group in 9-methoxyoxacyclonon-2-ene, for which an unorthodox reaction mechanism has been claimed, must therefore be due to some other cause.

scholarly journals Kinetics of drying of basil leaves (Ocimum basilicum L.) in the infrared

2012 ◽  
Vol 16 (12) ◽  
pp. 1346-1352 ◽  
Author(s):  
Renata C. dos Reis ◽  
Ivano A. Devilla ◽  
Diego P. R. Ascheri ◽  
Ana C. O. Servulo ◽  
Athina B. M. Souza
Keyword(s):  
Experimental Data ◽  
Ocimum Basilicum ◽  
Coefficient Of Determination ◽  
Chisquare Test ◽  
The Mean ◽  
Drying Curves ◽  
The One ◽  
Increasing Temperature ◽  
Air Circulation ◽  
Kinetics Of

The objective of this paper was to model the drying curves of the leaves of basil (Ocimum basilicum L.) in the infrared at temperatures of 50, 60, 70 and 80 ºC and to evaluate the influence of drying temperature on the color of dried leaves. Drying was conducted in infrared dryer with temperature and greenhouse air circulation. Experimental data were fitted to eight mathematical models. The magnitude of the coefficient of determination (R²), the mean relative error (P), the estimated mean error (SE) and chisquare test (χ2) were used to verify the degree of fitness of the models. From the study it was concluded that: a) the behavior of the drying curves of basil leaves was similar to most agricultural products, the drying times in the infrared were less than the drying times in an oven with air circulation, b) the mathematical drying model proposed by Midilli et al. (2002) was the one which best adjusted to the experimental data, c) the diffusion coefficient ranged from 9.10 x 10-12 to 2.92 x 10-11 m² s-1 and d) the color of the samples was highly influenced by drying, becoming darker due to loss of chlorophyll with increasing temperature.

scholarly journals Mathematical modeling of pequi pulp drying and effective diffusivity determination

2017 ◽  
Vol 21 (7) ◽  
pp. 493-498 ◽  
Author(s):  
Elisabete P. de Sousa ◽  
Rossana M. F. de Figueirêdo ◽  
Josivanda P. Gomes ◽  
Alexandre J. de M. Queiroz ◽  
Deise S. de Castro ◽  
...  
Keyword(s):  
Experimental Data ◽  
Effective Diffusivity ◽  
Drying Kinetics ◽  
Convective Drying ◽  
Drying Time ◽  
Air Speed ◽  
Drying Curves ◽  
Increasing Temperature ◽  
Kinetics Of ◽  
Best Fit

ABSTRACT The aim of this work was to study the drying kinetics of pequi pulp by convective drying at different conditions of temperature (50, 60, 70 and 80 °C) and thickness (0.5, 1.0 and 1.5 cm) at the air speed of 1.0 m s-1, with no addition of adjuvant. The experimental data of pequi pulp drying kinetics were used to plot drying curves and fitted to the models: Midilli, Page, Henderson & Pabis and Newton. Effective diffusivity was calculated using the Fick’s diffusion model for a flat plate. It was found that, with increasing thickness, the drying time increased and, with increasing temperature, the drying time was reduced. The Midilli model showed the best fit to the experimental data of pequi pulp drying at all temperatures and thicknesses, presenting higher coefficients of determination (R2), indicating that this model satisfactorily represents the pequi pulp drying phenomenon. There was a trend of increase in the effective diffusivity with the increase in pulp layer thickness and temperature.

Research on Additives Assisted Catalytic Cyclo-Dehydration of 1, 4-Butanediol to Tetrahydrofuran in Near-Critical Water

2012 ◽  
Vol 550-553 ◽  
pp. 693-698 ◽  
Author(s):  
Yan Yang ◽  
Li Yi Dai ◽  
Jin Shou Wang ◽  
Hong Yan Zhou
Keyword(s):  
Catalytic Activity ◽  
Reaction Mechanism ◽  
Maximum Yield ◽  
Experimental Results ◽  
Time Range ◽  
Temperature Range ◽  
Experimental Parameters ◽  
Increasing Temperature ◽  
Water Ratio

We herein report the cyclo-dehydration of 1,4-butanediol (BD) assisted with additives to form tetrahydrofuran (THF) in near-critical water (NCW).Three additives including Fe2(SO4)3,ZnSO4 and NaHSO4 were screened. Effects of various experimental parameters such as temperature (260-340°C), time (60-180min), reactant/water ratio (r/w, 1:10-1:40) and pressure (15-25MPa) on the yield of THF were examined. Without the presence of additives, the results showed that increasing temperature favored the cyclo-dehydration of BD to form THF. The maximum yield (52.61 wt. %) was obtained at temperature of 340°C and time of 180 min. With the presence of additives, at temperature range of 260~300°C and time range of 60~130min, all the additives selected can promote the cyclo-dehydration of BD to yield THF. However, with further increasing temperature and time, the additives would suppress the formation of THF. The catalytic activity toward the production of THF in the order of Fe2(SO4)3> ZnSO4> NaHSO4. The maximum yield of THF assisted with Fe2(SO4)3 could reach as high as 59.85 wt. % at 320°C, 120 min. Large reactant/water ratio would not benefit the yield of THF because of the dilution of additive. Increasing the pressure will slightly increase the yield of THF. Base on experimental results, a possible reaction mechanism and pathway of dehydration of BD was proposed in NCW.

scholarly journals Raman Spectroscopy and Statistical Analysis of the Silicate Species and Group Connectivity in Cesium Silicate Glass Forming System

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Armenak Osipov ◽  
Leyla Osipova ◽  
Rimma Zainullina
Keyword(s):  
Experimental Data ◽  
Raman Spectroscopy ◽  
Statistical Analysis ◽  
Raman Spectra ◽  
Dynamic Equilibrium ◽  
Structural Units ◽  
Melt Temperature ◽  
Deconvolution Analysis ◽  
Glass Forming ◽  
Increasing Temperature

The Raman spectra of x%Cs2O-(100 − x)%SiO2 (x=17, 22, 27, 33, and 37 mol%) glasses and melts were measured in the temperature range of 293 to 1553 K. The concentrations of the Qn species were calculated as a function of the composition and temperature based on the deconvolution analysis of the spectra. It was found that a dynamic equilibrium among structural units in the melts with x>17 mol% can be described by disproportionation reaction Q3⇔Q4+Q2. The enthalpy of this reaction was found to be equal to 32 ± 6, 43 ± 8, 56 ± 10, and 52 ± 9 for x=22, 27, 33, and 37 mol%, respectively. The nonideal entropy of mixing (ΔSmix) depends on the melt temperature and increases almost linearly with increasing temperature. The Qn, Q2–Q2, and Qn,ijkl distributions with x ranging from 0 to 55 mol% were modeled using experimental data for the concentrations of the Qn units.

Untersuchung der alkalischen Hydrolyse des Benzoesäurebenzylesters in Wasser-Äthanol 1 : 1 / Study of the Basic Hydrolysis of Benzyl Benzoate in Water-Ethyl Alcohol 1:1

1974 ◽  
Vol 29 (11) ◽  
pp. 1697-1698 ◽  
Author(s):  
F. Mansilla ◽  
P. Martinez ◽  
J. Sancho
Keyword(s):  
Experimental Data ◽  
Reaction Mechanism ◽  
Order Rate Constant ◽  
Benzyl Benzoate ◽  
Conductometric Method ◽  
Alcohol Medium ◽  
Basic Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Water Alcohol

By using a conductometric method, the kinetics of the basic hydrolysis of benzyl benzoate in water-alcohol medium has been investigated. The second order rate constant follows the equation K = A exp {-E/RT} with A = 1.35·1010 l mol-1 min-1 and E = 14.5 kcal mol-1. A reaction mechanism is postulated, which is consistent with the experimental data.

scholarly journals DFT Study of Stereoselective Ketene-imine Cycloadditions, Evaluation of Possible Solvent Effects with IEF-PCM

2018 ◽  
Vol 62 (4) ◽  
Author(s):  
Balázs Komjáti ◽  
Bianka Szokol ◽  
Benjámin Kováts ◽  
Péter Kegye ◽  
József Nagy
Keyword(s):  
Experimental Data ◽  
Solvent Effects ◽  
Substituent Effects ◽  
Chiral Auxiliary ◽  
Electrostatic Repulsion ◽  
Chiral Auxiliaries ◽  
Reaction Parameters ◽  
Reaction Proceeds ◽  
Stereoselective Reactions ◽  
Main Factor

The formal [2+2] cycloaddition of ketenes and imines, also known as Staudinger synthesis, is a facile method for the synthesis of biologically important β-lactam derivatives. In this paper two previously reported stereoselective reactions were investigated with computational methods. Our computations support experimental data that a chiral imine, derived from d-glyceraldehyde reacting with ketenes, yields almost exclusively one out of the possible four diastereomers. The reaction proceeds stepwise, first addition of the imine to the ketene yields an intermediate, then the product is formed in a conrotatory electrocyclization. Results indicate that the electrostatic repulsion of the chiral auxiliary group is the main factor of the stereoselectivity, but solvent and substituent effects are not negligible. Calculations were performed at M06-2X/6-31+G** level of theory combined with IEF-PCM solvation, in common solvents such as toluene, THF, dichloromethane, acetonitrile and water. These results provide useful insight for the development of new chiral auxiliaries and optimizing reaction parameters.

scholarly journals Deoxydehydration of vicinal diols by homogeneous catalysts: a mechanistic overview

2019 ◽  
Vol 6 (11) ◽  
pp. 191165 ◽  
Author(s):  
Kayla A. DeNike ◽  
Stefan M. Kilyanek
Keyword(s):  
Reaction Mechanism ◽  
Product Distribution ◽  
Catalytic Cycle ◽  
Reaction Conditions ◽  
Homogeneous Catalysts ◽  
Commodity Chemicals ◽  
Reduction Methods ◽  
Vicinal Diols ◽  
Catalyst Systems

Deoxydehydration (DODH) is an important reaction for the upconversion of biomass-derived polyols to commodity chemicals such as alkenes and dienes. DODH can be performed by a variety of early metal-oxo catalysts incorporating Re, Mo and V. The varying reduction methods used in the DODH catalytic cycle impact the product distribution, reaction mechanism and the overall yield of the reaction. This review surveys the reduction methods commonly used in homogeneous DODH catalyst systems and their impacts on yield and reaction conditions.

Well-defined nickel(II) tetrazole-saccharinate complex as homogeneous catalyst on the reduction of aldehydes: scope and reaction mechanism

2020 ◽  
Vol 92 (1) ◽  
pp. 151-166 ◽  
Author(s):  
Luís M. T. Frija ◽  
Bruno G. M. Rocha ◽  
Maxim L. Kuznetsov ◽  
Lília I. L. Cabral ◽  
M. Lurdes S. Cristiano ◽  
...  
Keyword(s):  
Experimental Data ◽  
Reaction Mechanism ◽  
Transition Metal ◽  
Dft Calculations ◽  
Microwave Power ◽  
Low Temperatures ◽  
Nickel Complex ◽  
Transition Metal Catalysts ◽  
Homogeneous Catalyst ◽  
First Time

AbstractA new (tetrazole-saccharin)nickel complex is shown to be a valuable catalyst for the hydrosilative reduction of aldehydes under microwave radiation at low temperatures. With typical 1 mol% content of the catalyst (microwave power range of 5–15 W) most reactions are complete within 30 min. The Ni(II)-catalyzed reduction of aldehydes, with a useful scope, was established for the first time by using this catalyst, and is competitive with the most effective transition-metal catalysts known for such transformation. The catalyst reveals tolerance to different functional groups, is air and moisture stable, and is readily prepared in straightforward synthetic steps. Supported by experimental data and DFT calculations, a plausible reaction mechanism involving the new catalytic system is outlined.

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