Ethylene oxide $(C_2{H}_{4}O)$ is used primarily as a sterilizing agent for medical equipment and supplies, and as a chemical intermediate in the production of ethylene glycol and other chemicals. It is produced by the catalytic oxidation of ethylene $(C_2{H}_4)$ :

$2C_2{H}_4+O_{2}2C_2{H}_{4}O,\{\begin{array}{c}\text{:}[H-8]\\ 0-2\end{array}$

The feed to the reactor $($R$1)($not the fresh feed to the process$)$ contains $75$mol$\%$ of ethylene and the balance oxygen $(O_2).$ The production is designed for $30\%$ of single pass conversion. Product stream exit at R$1$ enters a two$-$stage separator unit. The two$-$stage separator unit is functioned to separate the ethylene oxide $($stream exit the R$1)$ from other components. The product stream exit R$1$ enters the first$-$stage separator $($S$1).$ The S$1$ top product contains ethylene and oxygen only, while the $S1$ bottom product consists of ethylene and ethylene oxide only. The top product of $S1$ is recycled to the reactor. The bottom product of $S1$ enters second$-$stage separator $($S$2).$ At separator S$2,95\%$ of ethylene fed to the S$2$ will exit the S$2$ as top product. Only ethylene present at S$2$ top product. Meanwhile, S$2$ bottom product contains $97\mathrm{.}7$mol$\%$ of ethylene oxide and the balance ethylene. It is noted that the production rate is refer to the molar flowrate of $S2$ bottom product.

The basic process flow diagram is presented in Figure $1.$