The Mechanism Formation Of Ethylene
THE MECHANISM FORMATION OF ETHYLENE
AND MONOOXIDE OF CARBONEUM AT HETEROGENOUS OXIDATION OF ETHANE
V. Gomonay, I. Barenblatt, N. Golub, K. Szekeresh
Uzghorod National University, Uzghorod, Ukraine
The problem to find catalysts of high efficiency for obtaining synthetic benzine, plastic material and valuable oxygen compounds is very urgent nowadays, a perspective raw-material for this is natural gas, an important component of which is ethane.
That is why the objective of this thesis was to synthesize chromium phosphate, to investigate its physical-chemical and catalytic properties and ways of turning ethane into different products.
Chromium phosphate was synthesized by means of precipitating from nitrate salt according to method [1]. Physical-chemical properties were investigated with the help of XRD, TG-DTA, IR, chemical analysis, acidity characterization. The catalytic activity CrPO4 was studied in stationary and non-stationary (by the method of impulse chromatography) conditions. The initial blend and reaction products were analyzed chromatographically. As sorbents were used Porapak-Q and molecular sieves 13X (5A). As gas-carrier was used helium.
Table 1.Concentrations of gaseous products of ethane oxidizing on the CrPO4 from contact time dependence (air/ C2H6=4; T=773 K)
, c
concentration, vol. %
C2H6
O2
CO2
C2H4
CO
2,25
2,22
2,30
3,42
9,43
5,20
1,80
2,46
2,32
3,13
11,55
6,58
1,50
2,73
2,47
2,64
13,91
7,32
0,90
1,68
2,61
2,96
10,70
7,50
0,60
0,88
2,93
3,38
7,51
7,9
0,30
0,57
3,99
5,30
6,40
8,32
It was established, that the main products of ethane oxidizing in the temperature interval 623 – 823 K is ethylene, carbon mono- and dioxides, ethanol, formaldehyde, acetic acid. The results of the study of contact time influence the concentration of gaseous products are listed in Table 1. The optimal contact time for the formation of C2H4 is =1,5c.
The investigation of the influence of the composition of the reaction blend on the flow of the given process gives evidence that under the oxygen concentration increase in the reaction blend the ethylene and other products containins (CO, CH2O, C2H5OH) are decreased (Figure 1).
Fig.1. The dependence of CO concentration from there the C2H4 concentration on the CrPO4 (T=775K)
The connection of ethylene with carbon monooxide is presented in Fig.2, which points out that there is a clear linear increase of CO concentration depending on the balanced contain of C2H4 in the reaction blend in a broad interval of concentrations. Only under very high concentrations (over 25 %) the lack of oxygen in the reaction blend is perceived and appeares a break on the curve. Introducing a small amount of ethylene into the initial ethane-air blend contributes to the quick increase of CO and aldehyde concentration (practically 5 times more), revealing a promoting action.
The comparison of the data of stationary and non-stationary catalysed by turning ethane and ethylene gave the possibility to establish the correlation between the concentration of CO, ethylene and other products and to deduce kinetic equations of their formations.
Fig.2. Dependence of CO concentration: on C2H4 concentration (T=773 K)
The processes of ethylene and carbon monooxide formation are described by means of the following kinetic equations:
.
References
1. N. Golub, V. Gomonay, P. Gomonay and K. Szekeresh. Synthesis and modification of catalysts of partial oxidation of n-alkanes//Adsorption Science & Technology, 1999, vol.17, №5.- p.403-406.
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