Valero Energy Corp. has begun a significant maintenance program at its 180,000 barrel-per-day refinery in Memphis, Tennessee, with a focus on upgrading key gasoline-producing units, according to industry sources.

The refinery’s 65,000 bpd Fluid Catalytic Cracking Unit (FCCU) central to gasoline production was taken offline over the weekend for a planned overhaul. The shutdown also includes the 12,000 bpd alkylation unit, with work expected to be completed by November 1.

Additional equipment undergoing maintenance includes the flare gas recovery unit and a hydrotreater, which was idled for a catalyst replacement. These upgrades are designed to ensure operational reliability, enhance fuel quality, and maintain compliance with U.S. environmental standards.

The FCCU uses silica-based catalysts to convert gas oil into gasoline components, while the alkylation unit creates high-octane blending liquids critical for modern fuels. The flare gas recovery system improves efficiency by capturing gases that would otherwise be flared, and hydrotreaters remove sulfur from fuels to meet strict emissions regulations.