Selective hydrodesulfurization of FCC gasoline to below 10 ppm sulfur

A system for reducing the sulfur content of a hydrocarbon stream, the system comprising:

• a hydrogenation reactor for contacting a full range cracked naphtha with a hydrogenation catalyst to convert at least a portion of the dienes and mercaptans to thioethers and to hydrogenate at least a portion of the dienes;
• a separation system for fractionating the full range cracked naphtha into:
• a light naphtha fraction having a boiling range end point in the range from about 140° F. to about 150° F. and a sulfur content of less than about 15 ppm, and a heavy fraction;
• a separation system for, in the absence of catalyst, fractionating the heavy fraction into:
• a medium naphtha fraction having initial boiling point in the range from about 140° F. to about 150° F. and a boiling range, end point temperature in the range from about 230° F. to about 270° F.;
• and
• a heavy naphtha fraction having an initial boiling point in the range from about 230° F. to about 270° F.;
• a hydrodesulfurization reactor for hydrodesulfurizing the heavy naphtha fraction to produce a hydrodesulfurized heavy naphtha fraction has a sulfur content of less than about 12 ppm;
• a mixer for mixing the medium naphtha fraction with hydrogen and a gas oil to form a mixture;
• a heater for heating the mixture;
• a hydrodesulfurization reactor for contacting the heated mixture with a hydrodesulfurization catalyst to produce a reactor effluent comprising hydrogen sulfide, unreacted hydrogen, and a medium naphtha fraction having a reduced sulfur concentration;
• a separation system for separating the medium naphtha fraction having a reduced sulfur concentration from the gas oil, the unreacted hydrogen, and hydrogen sulfide to produce a medium naphtha fraction having a reduced sulfur concentration has a sulfur content of less than about 5 ppm;
• a mixer for mixing the light naphtha fraction, the medium naphtha fraction having a reduced sulfur concentration, and the hydrodesulfurized heavy naphtha fraction to produce a full range naphtha product having a sulfur content of equal to or less than about 10 ppm.

A system for reducing the sulfur content of a hydrocarbon stream, the system comprising:

• a catalytic distillation reactor system for concurrently:
• contacting a full range cracked naphtha with a hydrogenation catalyst to convert at least a portion of the dienes and mercaptans to thioethers and to hydrogenate at least a portion of the dienes;
• fractionating the full range cracked naphtha into a light naphtha fraction and a heavy fraction at an overhead temperature of less than 165° F.;
• a separation system for, in the absence of catalyst, fractionating the heavy fraction into a medium naphtha fraction having a boiling range, end point temperature minus initial boiling point temperature, of less than 105° F., and a heavy naphtha fraction;
• a hydrodesulfurization reactor for hydrodesulfurizing the heavy naphtha fraction;
• a mixer for mixing the medium naphtha fraction with hydrogen and a gas oil to form a mixture;
• a hydrodesulfurization reactor for contacting the mixture with a hydrodesulfurization catalyst to produce a reactor effluent comprising hydrogen sulfide, unreacted hydrogen, and a medium naphtha fraction having a reduced sulfur concentration;
• a separation system for separating the medium naphtha fraction having a reduced sulfur concentration from the gas oil, the unreacted hydrogen, and hydrogen sulfide, wherein the medium naphtha fraction has a reduced sulfur concentration of less than about 5 ppm;
• and
• a mixer for mixing the light naphtha fraction, the medium naphtha fraction having a reduced sulfur concentration, and the hydrodesulfurized heavy naphtha fraction to produce a full range naphtha product having a sulfur content of equal to or less than about 10 ppm.