Abstract
Ethylene oxidation reactions were studied in a Berty reactor (an example of a continuously stirred tank reactor (CSTR)) using a commercial silver catalyst supported on α-alumina. Reaction rates were measured using a gas feed containing ethylene (3% – 6.5%) and oxygen (18% – 19.5%), the balance being nitrogen. The reactions were carried out at a pressure of 2170 kN m
−2 and at a temperature varying from 513 to 593 K. The Berty reactor used in this investigation was found to behave as a CSTR with perfect mixing. The kinetic data obtained for the ethylene oxidation were free from external and internal mass- and heat-transfer limitations. Rate expressions for ethylene conversion to ethylene oxide and to carbon dioxide were obtained as follows.
(1) Rate of ethylene oxide production (mol (g cat.)
−1 h
−1) r
C
2H
4O
=
(2.259 × 10
7) exp(—9010
T)(P
O
2
)
0.5(P
C
2H
4
)
0.61 + (1.985 × 10
2) exp(2400T)(P
CO
2
)
(2) Rate of carbon dioxide production (mol (g cat.)
−1 h
−1) r
CO
2
=
(4.34 × 10
7) exp(—10800
T)(P
O
2
)
0.5(P
C
2H
4
)
0.51 + (1.08 × 10
2) exp(1530T)(P
CO
2
)
It was observed that the catalyst selectivity towards ethylene oxide decreased with an increase in the total ethylene conversion, and the temperature was found to have a negligible effect on selectivity. Carbon dioxide was found to have an inhibiting effect on both ethylene oxide and carbon dioxide reaction rates.