Consider a process for the partial oxidation of benzene to produce maleic anhydride (C4H4O4) using air. There are two reactions to be concerned with: The first partially oxidizes the Benzene to produce maleic anhydride along with carbon dioxide and water.
The second, undesired reaction fully oxidizes the benzene. The process used is as follows:
1) Benzene Purification: The benzene flows into a pressurized still with water at 23.2
psia. The liquid in the still is 80% benzene by mass. Energy is supplied to keep the mixture at its boiling point (180°F) resulting in a vapor mixture of pure water (partial pressure = 7.52 psia) and pure benzene (partial pressure = 15.68 psia). The contaminates along with waste benzene flow out as a liquid.
2) Reaction: The vapor stream is mixed with enough air (T = 150°F, 1 atm, 50% relative humidity) to provide an 18/1 molar ratio of oxygen/benzene entering the reactor. At the exit to the reactor an analysis of the gasses (mole, dry basis) shows 0.76% C4H4O4, and 80.0% nitrogen.
3) Stripping: The exit gasses from the reactor flow into a water scrubber operating at 1 atm. Pure water enters the top of the column and the reactor outlet gas enters the bottom. The water "scrubs" out the maleic anhydride where it exits as a liquid at the bottom of the column with a concentration of (mole %) 12% C4H4O4, 88% water.
Exiting the top of the column as a gas are all of the unreacted benzene, oxygen, carbon dioxide, and nitrogen. This gas stream exits at 142°F saturated with water.
4) Drying: The liquid stream from the scrubber goes to a dryer where the water is driven off leaving pure maleic anhydride. What is (use pound moles):
a) The moles of benzene that are completely oxidized in the reactor per mole of benzene fed into the reactor? (i.e. the moles benzene used in the second reaction per mole fed)
b) The pounds of water leaving the dryer per mole of benzene fed into the reactor?
c) The composition of the gas leaving the scrubber (mole percent, wet basis)?
d) The pounds of water added to the top of the scrubber per mole of benzene fed into the reactor?