Active centres on chromium oxide-zinc oxide catalysts for dehydrogenation

1976 ◽  
Vol 41 (12) ◽  
pp. 3563-3571 ◽  
Author(s):  
M. Kraus ◽  
Z. Žitný ◽  
D. Mihajlova ◽  
A. Andreev
Keyword(s):  
Zinc Oxide ◽  
Chromium Oxide ◽  
Oxide Catalysts ◽  
Active Centres

Dehydrogenation of Substituted Alcohols to Aldehydes on Zinc Oxide-Chromium Oxide Catalysts

1992 ◽  
Vol 57 (11) ◽  
pp. 2215-2226 ◽  
Author(s):  
Daniela Gulková ◽  
Miloš Kraus
Keyword(s):  
Zinc Oxide ◽  
Chromium Oxide ◽  
Substituent Effects ◽  
Oxide Catalysts ◽  
Catalytic Dehydrogenation ◽  
Primary Alcohols ◽  
Solid Catalysts ◽  
Type Rate ◽  
Chromium Oxide Catalysts ◽  
Kinetics Of

Sixteen primary alcohols of the structure RCH2OH (R = CH3, C2H5, (CH3)2CH, (CH3)3CCH2, HOCH2, CH3OCH2, C6H5, C6H5CH2, C6H5OCH2, ClCH2, BrCH2, F3C, CNCH2, (CH3)2NCH2, (C2H5)2NCH2 and tetrahydrofurfuryl) were explored for the possibility of obtaining the corresponding aldehydes by dehydrogenation on solid catalysts. Various catalysts were tested and two zinc oxide-chromium oxide catalysts were selected for further work because their activity and selectivity was satisfactory; moreover, the selectivity could be improved by addition of sodium into the catalysts and of water into the feed. The reaction was performed in the temperature range 250-450 °C and at atmospheric pressure. 2-Chloroethanol, 2-bromoethanol, ethylene glycol, 2-cyanoethanol and 2-(N,N-diethylamino)ethanol decomposed and deactivated the catalyst. The other alcohols were studied from the point of kinetics of dehydrogenation, which was described by a Langmuir-Hinshelwood type rate equation (3), and of substituent effects on rate, which were correlated by Taft equation (1) with the slope ρ = -1.46. The preparative value of catalytic dehydrogenation for obtaining substituted aldehydes was confirmed by prolonged runs and isolation of the aldehydic product by distillation using as the feeds 2-methoxyethanol and 2-(N,N-dimethylamino)ethanol, respectively.

scholarly journals Alkane dehydrogenation over supported chromium oxide catalysts

1999 ◽  
Vol 51 (2) ◽  
pp. 223-232 ◽  
Author(s):  
Bert M Weckhuysen ◽  
Robert A Schoonheydt
Keyword(s):  
Chromium Oxide ◽  
Oxide Catalysts ◽  
Alkane Dehydrogenation ◽  
Chromium Oxide Catalysts

scholarly journals STUDY OF CARBON DIOXIDE ADSORPTION ON CHROMIUM OXIDE AND GALLIUM OXIDE CATALYSTS ON BASIS OF NON-LINEAR RELAXATION TIMES

2018 ◽  
Vol 61 (2) ◽  
pp. 46 ◽  
Author(s):  
Nikolay I. Kol'tsov
Keyword(s):  
Carbon Dioxide ◽  
Relaxation Time ◽  
Chromium Oxide ◽  
Rate Constants ◽  
Gallium Oxide ◽  
Relaxation Times ◽  
Oxide Catalysts ◽  
Linear Relaxation ◽  
Adsorption And Desorption ◽  
Non Linear

Recently the analysis of transient regimes of chemical reactions is paid much attention. This is due to the fact that the time-dependent relaxation modes prior to achieving steady states contain important information about the features of the reactions. During unsteady mode the changes in reactant concentrations and rate of the reaction in time are observed. These changes are due to their own relaxation processes, depending on the structure of the reaction mechanism. A complete study of the reaction mechanism involves the study of the relaxation characteristics both near and away from the stationary state. Linear relaxation time describes the local transient modes near the steady state and it is calculated as the time decrease deviations of reactant concentrations from steady-state values in the e-times. Non-linear relaxation time describes the overall behavior reactions and it can be evaluated through the reaction time from the initial state to a stationary. Depending on the structural features of reactions ratio to determine the non-linear relaxation time through of reactions parameters (rate constants stages and reactant concentrations) differ significantly. The establishment of such ratio for a particular reaction allows getting more information to identify the mechanism and the constituent rate constants of its stages. The mechanism of any catalytic reaction involves stages adsorption of one or more of the starting materials on the catalyst surface. As a rule these stages are initial remaining stages of chemical transformation of reactants adsorbed forms follow them. Therefore, it is necessary to have the data on these stages and rate constants of adsorption of reagents on the catalyst surface. Earlier by author the method for estimating the values of the rate constants of adsorption and desorption by linear relaxation times was described. This method was used for determine of mechanism and kinetic parameters of process of adsorption of carbon dioxide on the chromium oxide and gallium oxide catalysts. In this article the method for estimating the values of the rate constants of adsorption and desorption by non-linear relaxation times for this process is described. The previously found CO2 dissociative adsorption mechanism was proved by the obtained results. The intervals of values changes of the rate constants of adsorption and desorption of carbon dioxide on the gallium oxide and chromium oxide catalysts were defined.Forcitation:Kol’tsov N.I. Study of carbon dioxide adsorption on chromium oxide and gallium oxide catalysts on basis of non-linear relaxation times. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 2. P. 46-52

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