The ethylene epoxydation is to be carried out using a cesium-doped silver catalyst in a packed bed reactor.
Along with the desired reaction, the complete combustion of ethylene also occurs
[M. Al-Juaied, D. Lafarga, and A. Varma, Chem. Eng. Sci. 56, 395 (200 I)]. It is proposed to replace the conventional PBR with a membrane reactor in order to improve the selectivity. As a rule of thumb, a 1% increase in the selectivity to ethylene oxide translates to an increase in profit of about
2 million/yr. The feed consists of 12% (mole) oxygen, 6% ethylene, and the remainder nitrogen at a temperature of 250"C and a pressure of 2 atm. The total molar flow rate is 0.0093 mol/s to a reactor containing 2 kg of catalyst.
(a) What conversion and selectivity,
, are expected in a conventional PBR?
(b) What would be the conversion and electivity if the total molar flow rate were divided and the 12% oxygen stream (no ethylene) were uniformly fed through the sides of the membrane reactor, and 6% ethylene (no oxygen) were fed at the entrance?
(c) Repeat (b) for a case when ethylene is fed uniformly through the sides and oxygen is fed at the entrance. Compare with parts (a} and (b).