Chapter 9, Problem 9.31P

Ethylene oxide is produced by the catalytic oxidation of ethylene:

   $C_2{H}_4\left(g\right)+\frac{1}{2}{O}_2\left(g\right)\to C_2{H}_{4}O\left(g\right)$

An undesired competing reaction is the combustion of ethylene to CO₂.

The feed to a reactor contains 2 mol C₂H₄/mol O₂. The conversion and yield in the reactor are respectively 25% and 0.70 mol $C_2{H}_{4}O$produced/mol C₂H₄consumed. A multiple-unit process separates the reactor outlet stream components: C₂H₄and O₂are recycled to the reactor, C₂H₄O is sold, and CO₂and H₂O are discarded. The reactor inlet and outlet streams are each at 450°C, and the fresh feed and all species leaving the separation process are at 25°C. The combined fresh feed- recycle stream is preheated to 450°C.

1. Taking a basis of 2 mol of ethylene entering the reactor, draw and label a flowchart of the complete process (show the separation process as a single unit) and calculate the molar amounts and compositions of all process streams.

Calculate the heat requirement (kJ) for the entire process and that for the reactor alone.

Data for gaseous ethylene oxide

   $\begin{array}{l}\Delta {\hat{H}}_f^{°}=-51.00kJ/mol\\ C_p\left[J/mol\cdot K\right]=-4.69+0.2601T-9.995\times {10}^{-5}{T}^2\end{array}$where T is in kelvins.

1. Calculate the flow rate (kg/h) and composition of the fresh feed, the overall conversion of ethylene, and the overall process and reactor heat requirements (kW) for a production rate of 1500 kg C₂H₄O/ day. Briefly explain the reasons for separating and recycling the ethylene-oxygen stream.
(d) One of the attributes of this process defined in the problem statement is extremely unrealistic. What is it?