Calumet Specialty Products Partners L.P. announced that Tim Go notified its board of directors that he will resign as CEO effective June 1 to pursue other interests closer to his family in Texas. The Indianapolis-based company appointed Steve Mawer, a current board member, to take over as CEO upon successful completion of an orderly transition process. Jonathan ODwyer joined Dalton, Georgia-based specialty chemical manufacturer MFG Chemical as vice president of commercial operations.