ANALYSIS OF THE CATALYTIC ACTIVITY OF 2-ETHYLHEXANOATES OF METALS OF THE 2ND AND 12TH GROUPS IN ETHYLBENZENE OXIDATION USING KINETIC MODELING
Journal: HERALD OF TECHNOLOGICAL UNIVERSITY
Rubrics: 2. CHEMICAL TECHNOLOGY
Authors:
1.
Kazan National Research Technological University
2.
Kazan National Research Technological University
3.
KNITU
4.
KNITU
5.
Kazan National Research Technological University
(Department of General Chemical Technology, Assistant)
employee from 01.01.2024 to 01.01.2025
Kazan, Kazan, Russian Federation
employee from 01.01.2024 to 01.01.2025
Kazan, Kazan, Russian Federation
6.
KNITU; KNRTU
7.
KNITU
8.
Kazan National Research Technological University
(General chemical technology, associate professor)
9.
Kazan National Research Technological University
10.
KNRTU
11.
Kazan National Research Technological University
Russian Federation
Russian Federation
Type:
Article
Pages:
from 51
to 57
Status:
Language:
Russian
Keywords:
ETHYLBENZENE HYDROPEROXIDE, HOMOGENEOUS CATALYSIS, KINETIC MODELING, ETHYLBENZENE OXIDATION
Funding:
Issledovanie vypolneno za schet granta Rossiyskogo nauchnogo fonda №22-13-00461, https://rscf.ru/project/22-13-00461/.
Abstract:
The kinetics of accumulation of ethylbenzene hydroperoxide and by-products during ethylbenzene oxidation has been studied in the presence of homogeneous catalysts - 2-ethylhexanoates of metals of the 2nd and 12th groups (Mg, Ca, Sr, Ba, Zn and Cd). The catalytic ethylbenzene oxidation by molecular oxygen was carried out in a column-type glass reactor at the atmospheric pressure in the temperature range of 363-393 K. The catalytic decomposition of ethylbenzene hydroperoxide was investigated by ampoule method at 403 K in chlorobenzene medium. A photometric analysis method was used to determine the concentration of ethylbenzene hydroperoxide. To determine the concentrations of ethylbenzene oxidation products and decomposition of ethylbenzene hydroperoxide, a chromatographic analysis method was used (chromatograph Chromatek-Crystal 5000.2, capillary column Sol Gel Wax 30 m long, 0.53 mm diameter, carrier gas was helium). It has been shown that the main products of ethylbenzene oxidation in the presence of the studied catalysts are ethylbenzene hydroperoxide, acetophenone and methyl phenyl carbinol. In this work, the kinetic scheme was proposed based on the analysis of the literature and experimental data obtained. This scheme is common for the ethylbenzene oxidation and ethylbenzene hydroperoxide decomposition in the presence of 2-ethylhexanoates of metals of the 2nd and 12th groups. It consists of classical reactions of initiation, propagation and termination of the chains, reactions of formation of the intermediate adducts "component of the reaction mixture + catalyst", reactions of initiation and propagation of chains involving intermediate adducts, reactions of deactivation of the catalyst. Based on the proposed scheme, a kinetic model has been made, which was written using the mass action law in the form of a system of nonlinear differential equations. The Arrhenius equation was used to describe the functions of the reaction rate coefficients on temperature, and the parameters of the functions where determined as a result of solving the inverse kinetic problem by the method of direct zero-order search. This kinetic model describes the experimental data within an average relative error of 25%, which confirms the overall correctness of the reaction scheme embedded in the model. According to the scheme embedded in the model, during the ethylbenzene oxidation, only peroxyl radicals, which are formed directly from ethylbenzene radicals, are directly involved in the formation of the target product (ethylbenzene hydroperoxide). Using kinetic modeling, the following has been shown: 1) according to the average integral sum of the reaction rates of the ethylbenzene and peroxyl radicals formation in the ethylbenzene oxidation, the catalysts in question are arranged in a row Cd > Sr » Mg » Ba > Ca > Zn, and it has been experimentally shown that the catalysts in terms of their activity level (which can be estimated by the tangents of the angles of inclination of kinetic curves at the initial oxidation moment) are arranged in the same row; 2) the catalytic activity of 2-ethylhexanoates of metals of the 2nd and 12th groups in ethylbenzene oxidation is due to their ability to increase the quasi-stationary concentration of radicals due to the formation of intermediate adducts with molecules of oxidized hydrocarbon and its hydroperoxide and a faster decay of these adducts compared to the decay of the initial molecules of oxidized hydrocarbon and its hydroperoxide; 3) using the example of Cd 2-ethylhexanoate (the best catalyst among those considered in terms of activity), it was found that its catalytic activity in ethylbenzene oxidation is determined primarily by the reaction of the intermediate adduct "ethylbenzene + catalyst" with oxygen, leading to the formation of ethylbenzene radical.
The kinetics of accumulation of ethylbenzene hydroperoxide and by-products during ethylbenzene oxidation has been studied in the presence of homogeneous catalysts - 2-ethylhexanoates of metals of the 2nd and 12th groups (Mg, Ca, Sr, Ba, Zn and Cd). The catalytic ethylbenzene oxidation by molecular oxygen was carried out in a column-type glass reactor at the atmospheric pressure in the temperature range of 363-393 K. The catalytic decomposition of ethylbenzene hydroperoxide was investigated by ampoule method at 403 K in chlorobenzene medium. A photometric analysis method was used to determine the concentration of ethylbenzene hydroperoxide. To determine the concentrations of ethylbenzene oxidation products and decomposition of ethylbenzene hydroperoxide, a chromatographic analysis method was used (chromatograph Chromatek-Crystal 5000.2, capillary column Sol Gel Wax 30 m long, 0.53 mm diameter, carrier gas was helium). It has been shown that the main products of ethylbenzene oxidation in the presence of the studied catalysts are ethylbenzene hydroperoxide, acetophenone and methyl phenyl carbinol. In this work, the kinetic scheme was proposed based on the analysis of the literature and experimental data obtained. This scheme is common for the ethylbenzene oxidation and ethylbenzene hydroperoxide decomposition in the presence of 2-ethylhexanoates of metals of the 2nd and 12th groups. It consists of classical reactions of initiation, propagation and termination of the chains, reactions of formation of the intermediate adducts "component of the reaction mixture + catalyst", reactions of initiation and propagation of chains involving intermediate adducts, reactions of deactivation of the catalyst. Based on the proposed scheme, a kinetic model has been made, which was written using the mass action law in the form of a system of nonlinear differential equations. The Arrhenius equation was used to describe the functions of the reaction rate coefficients on temperature, and the parameters of the functions where determined as a result of solving the inverse kinetic problem by the method of direct zero-order search. This kinetic model describes the experimental data within an average relative error of 25%, which confirms the overall correctness of the reaction scheme embedded in the model. According to the scheme embedded in the model, during the ethylbenzene oxidation, only peroxyl radicals, which are formed directly from ethylbenzene radicals, are directly involved in the formation of the target product (ethylbenzene hydroperoxide). Using kinetic modeling, the following has been shown: 1) according to the average integral sum of the reaction rates of the ethylbenzene and peroxyl radicals formation in the ethylbenzene oxidation, the catalysts in question are arranged in a row Cd > Sr » Mg » Ba > Ca > Zn, and it has been experimentally shown that the catalysts in terms of their activity level (which can be estimated by the tangents of the angles of inclination of kinetic curves at the initial oxidation moment) are arranged in the same row; 2) the catalytic activity of 2-ethylhexanoates of metals of the 2nd and 12th groups in ethylbenzene oxidation is due to their ability to increase the quasi-stationary concentration of radicals due to the formation of intermediate adducts with molecules of oxidized hydrocarbon and its hydroperoxide and a faster decay of these adducts compared to the decay of the initial molecules of oxidized hydrocarbon and its hydroperoxide; 3) using the example of Cd 2-ethylhexanoate (the best catalyst among those considered in terms of activity), it was found that its catalytic activity in ethylbenzene oxidation is determined primarily by the reaction of the intermediate adduct "ethylbenzene + catalyst" with oxygen, leading to the formation of ethylbenzene radical.
Keywords:
ETHYLBENZENE HYDROPEROXIDE, HOMOGENEOUS CATALYSIS, KINETIC MODELING, ETHYLBENZENE OXIDATION
ETHYLBENZENE HYDROPEROXIDE, HOMOGENEOUS CATALYSIS, KINETIC MODELING, ETHYLBENZENE OXIDATION
