AM-00-54 REMOVAL OF SULFUR FROM LIGHT FCC GASOLINE STREAM

Description:

Refiners throughout the world are evaluating sulfur removal technologies and strategies for meeting future government dictated gasoline sulfur requirements. These requirements will vary depending upon the location of the refinery’s gasoline market and the sulfur reduction schedule mandated by the various governments of the market. For Europe and North America, the sulfur content of finished gasoline must be reduced by about 90% down to an average level of 30 wppm. The major finished gasoline component in Europe and North America is full boiling range fluid catalytic cracked (FCC) gasoline. It is documented that FCC gasoline contributes about 98% of the sulfur that is contained in today’s finished gasoline. The octane of full boiling range (C5–400 °F) FCC gasoline comes from the olefins in the light FCC portion (C5–158 °F)and the aromatics in the heavy FCC portion (158–400 °F). Therefore, hydrotreating can be used to reduce the sulfur of the heavy FCC gasoline. Since olefins are destroyed by hydrotreating, it is not an economically acceptable process for the light FCC gasoline portion. Fortunately, the sulfur can be removed from the light FCC gasoline via caustic treating, which does not effect the olefins in any way. Our presentation will describe the types of sulfur compounds present in light FCC gasoline, the sulfur removal possibilities with caustic and a process description of a light FCC gasoline extractive caustic treating system. Commercial experience of seven actual sulfur reduction operating units will also be described. Methods of caustic treating recombinant mercaptans produced by hydrotreating heavy FCC gasoline streams will also be discussed.