This is about a LPG Merox unit in our refinery. Since the content of RSH(mercaptan) in the feedstock has more than doubled, this makes it difficult to regenerate the caustic. The content of mercaptide and disulphide in regenerated caustic has greatly increased. Frequent replacement of caustic and increased air flow and temperature in the oxidizer doesn't solve the problem. How can we solve the problem if we can not change the feedstock?