Daniel S. Sanders, 64, president of ExxonMobil Chemical since Exxon and Mobil merged in December 1999, is retiring at the end of August. Michael J. Dolan, 50, current deputy to the president of ExxonMobil Refining & Supply Co., has been named Sanders' replacement. Sanders, also a vice president of Exxon Mobil Corp., served with ExxonMobil and its predecessor companies for more than 43 years, beginning with a stint as an engineer at its Baton Rouge, La., refinery. He later worked in Exxon's chemical operations in Baton Rouge and Linden, N.J. His past roles include president of Exxon Chemical Asia-Pacific and chairman of the American Chemistry Council. Dolan comes from the Mobil side of Exxon Mobil, having joined Mobil in 1980 at its Paulsboro, N.J., research labs. He started working at Mobil Chemical in 1993, becoming vice president and general manager for petrochemicals for the Americas in 1998.