The complex, which is actually two historically separate refineries that were merged under the common ownership of Sunoco Inc., has struggled financially for a decade. Sunoco transferred much of its interest in 2012 to the Carlyle Group, a private equity investor, to form Philadelphia Energy Solutions. PES went through bankruptcy last year, and is now owned primarily by its former creditors, Credit Suisse Asset Management and Bardin Hill Investment Partners, according to the bankruptcy filing.