The Texas environmental agency has rejected a request by oil giant Valero for a large tax break and potential $92 million refund at six refineries that installed equipment designed to remove sulfur dioxide from crude oil.

Valero’s requests were first made in 2007. The company had argued that the hydrotreater equipment should be exempt because they help reduce pollution. The Texas Commission on Environmental Quality on Dec. 14 turned down a second request for a partial exemption, according to letters written to Valero and obtained by The Associated Press on Wednesday.

Texas grants tax breaks to companies that install pollution-reducing equipment.

Valero wanted the break for the hydrotreaters that were installed after the U.S. Environmental Protection Agency in 2006 began requiring refineries to remove sulfur dioxide from crude oil.