ANS:A - potassium isobutyrate

In the sweetening process of petroleum refining, the solutizer agent used with caustic alkali is typically methanol. Here's why:

• Sweetening Process: In petroleum refining, sweetening refers to the removal of mercaptans (thiols) from petroleum products, such as gasoline or diesel, to reduce their sulfur content. This process is often carried out using caustic alkali (sodium hydroxide or potassium hydroxide) in the presence of a solutizer agent.
• Solutizer Agent: Methanol is commonly used as a solutizer agent in the sweetening process. It helps to improve the solubility of mercaptans in the caustic solution, facilitating their removal from the hydrocarbon stream.
• Other Options:
  • Potassium isobutyrate: This is not typically used as a solutizer agent in the sweetening process.
  • Sodium plumbite: While historically used in sweetening processes, it is less common today due to environmental and health concerns associated with lead compounds.
  • Phenol: Phenol has uses in various chemical processes but is not commonly used as a solutizer agent in sweetening.