Ethanal is manufactured by reacting ethene, C₂H₄, with steam - OCR Gateway - GCSE Chemistry - Question 19 - 2018 - Paper 1

The conditions used in the production of ethanol from ethene and steam are critical to optimize the reaction and achieve maximum yield.

1. High Temperature: The reaction occurs at a temperature of 300°C, which provides sufficient kinetic energy for the reactants, allowing them to effectively collide and react. In exothermic reactions like this one, high temperatures shift the equilibrium position to favor the reactants. However, in this process, the heat is beneficial as it aids both the rate of reaction and also allows for a reasonable yield before losing the ethene as gas.

2. High Pressure: The reaction is conducted at pressures between 60 to 70 atm. High pressures favor the formation of ethanol (product) by shifting the equilibrium to the right due to a decrease in the number of moles of gas from reactants to products (2 moles of gas reactants producing 1 mole of liquid product). This results in higher conversion rates and overall yields.

3. Use of Catalyst: A phosphoric(V) acid catalyst is employed to speed up the reaction without affecting the position of equilibrium. This allows the reaction to reach equilibrium faster and increases productivity.

4. Removal of Product: Continuously removing ethanol from the system pushes the reaction toward the production of more ethanol, effectively shifting the equilibrium further to the right in accordance with the Le Chatelier's principle.

5. Cooling of Gases: After the reaction, cooling the gases allows ethanol to condense into a liquid, ensuring that it can be efficiently collected. This is essential for maintaining a high yield over the multiple passes through the reactor.