A method for regenerating a caustic solution comprising: providing a rich caustic liquid containing mercaptans; mixing the rich caustic liquid with a liquid catalyst to form a liquid caustic catalyst admixture; directing the liquid caustic catalyst admixture into a bottom section of a vertical column configured to cause the liquid caustic catalyst admixture to flow upward inside the column; injecting or sparging an oxygen containing gas into the liquid caustic catalyst admixture to form a gas liquid mix that flows upward inside the column entering a first reaction zone; oxidizing the mercaptans to disulfide oil in the first reaction zone forming an oxidized gas liquid mix; directing the oxidized gas liquid mix into a conduit positioned between a top tray and a bottom tray such that a liquid mix of disulfide oil and caustic exits the conduit onto an upper surface of the top tray that is fixedly attached to an upper section of the column; directing the liquid mix of disulfide oil and caustic into a shroud connected to a lower surface of the top tray where the liquid mix of disulfide oil and caustic contacts a bundle of vertical hanging fibers such that the liquid mix of disulfide oil and caustic flows down individual fibers in the bundle and into a second reaction zone; maintaining the second reaction zone as a gas continuous phase comprising from 20% to 100% by volume vapor; oxidizing mercaptans in the liquid mix of disulfide oil and caustic while the liquid mix of disulfide oil and caustic flows down the fibers in the second reaction zone to form a regenerated caustic and disulfide oil admixture; collecting the regenerated caustic and disulfide oil admixture on the bottom tray to allow separation of the disulfide oil from the regenerated caustic; and separately removing from the column a continuous stream of disulfide oil and a stream of regenerated caustic. providing a rich caustic liquid containing mercaptans; mixing the rich caustic liquid with a liquid catalyst to form a liquid caustic catalyst admixture; directing the liquid caustic catalyst admixture into a bottom section of a vertical column configured to cause the liquid caustic catalyst admixture to flow upward inside the column; injecting or sparging an oxygen containing gas into the liquid caustic catalyst admixture to form a gas liquid mix that flows upward inside the column entering a first reaction zone; oxidizing the mercaptans to disulfide oil in the first reaction zone forming an oxidized gas liquid mix; directing the oxidized gas liquid mix into a conduit positioned between a top tray and a bottom tray such that a liquid mix of disulfide oil and caustic exits the conduit onto an upper surface of the top tray that is fixedly attached to an upper section of the column; directing the liquid mix of disulfide oil and caustic into a shroud connected to a lower surface of the top tray where the liquid mix of disulfide oil and caustic contacts a bundle of vertical hanging fibers such that the liquid mix of disulfide oil and caustic flows down individual fibers in the bundle and into a second reaction zone; maintaining the second reaction zone as a gas continuous phase comprising from 20% to 100% by volume vapor; oxidizing mercaptans in the liquid mix of disulfide oil and caustic while the liquid mix of disulfide oil and caustic flows down the fibers in the second reaction zone to form a regenerated caustic and disulfide oil admixture; collecting the regenerated caustic and disulfide oil admixture on the bottom tray to allow separation of the disulfide oil from the regenerated caustic; and separately removing from the column a continuous stream of disulfide oil and a stream of regenerated caustic.