Desulfurization Process by GTC Technology

Application: GT-BTX PluS accomplishes desulfurization of FCC gasoline with no octane loss and decreased hydrogen consumption by using a proprietary solvent in an extractive-distillation system. This process also recovers valuable aromatics compounds, which can be used as petrochemical feedstock.

Description: The optimum feed is the mid fraction of FCC gasoline from 70°C to 150°C. This material is fed to the GT-BTX PluS unit, which extracts the sulfur and aromatics from the hydrocarbon stream. The sulfur-containing aromatic components are processed in a conventional hydrotreater to convert the sulfur into hydrogen sulfide (H2S). Because the portion of gasoline being hydrotreated is reduced in volume and free of olefins, hydrogen consumption and operating costs are greatly reduced. In contrast, conventional desulfurization schemes must process the majority of the gasoline through hydrotreating units to remove sulfur, which inevitably results in olefin saturation, octane downgrade and yield loss.

FCC gasoline is fed to the extractive distillation column (EDC). In a vapor-liquid operation, the solvent extracts the sulfur compounds into the bottoms of the column along with the aromatic components, while rejecting the olefins and non-aromatics into the overhead as raffinate. Nearly all of the non-aromatics, including olefins, are effectively separated into the raffinate stream. The raffinate stream can be optionally caustic washed before routing to the gasoline pool or to an aromatization unit to further increase benzene, toluene and xylene (BTX) production.

Rich solvent, containing aromatics and sulfur compounds, is routed to the solvent recovery column (SRC), where the hydrocarbons and sulfur species are separated and lean solvent is recovered in columns bottoms. The SRC overhead is hydrotreated by conventional means and either used as desulfurized gasoline or directed to an aromatics plant. Lean solvent from the SRC bottoms is recycled back to the EDC.

Process advantages:
• Eliminates FCC gasoline sulfur species to meet a pool gasoline target of 10 ppm sulfur.
• Rejects olefins from being hydrotreated in the HDS unit to prevent
loss of octane rating and to reduce hydrogen consumption.
• Fewer components (only the heavy-most fraction and the aromatic concentrate from the ED unit) are sent to hydrodesulfurization, resulting in a smaller HDS unit and less yield loss.
• Purified benzene and other aromatics can be produced from the aromatic-rich extract stream after hydrotreating.
• Olefin-rich raffinate stream (from the ED unit) can be directed to an aromatization unit to produce additional BTX or recycled to the FCC unit to increase the light olefin production.

Licensor: GTC Technology.