William Ingraham "Bill" Koch, a billionaire oil man behind the Alliance to Protect Nantucket Sound group, has purchased a 4,690-square-foot home in Osterville.

The home at 217 Seapuit Road, which has four bedrooms and 4.5 bathrooms, sold for $8.4 million, according to data from The Warren Group, publisher of Banker & Tradesman. 217 Seapuit River Road Rt and FW Wrightson are listed as the sellers.

Koch has also owned land on Seapuit Road since 2000, valued at more than $2 million, according to public records. He recently sold land at 390 Grand Island Drive in Osterville for $1.65 million.

Koch’s family founded the business empire Koch Industries based on oil refining that became the largest privately owned company in America. He later became the founder and president of the Oxbow Group, an energy development holding company based in West Palm Beach, Fla. He also co-chairs the group formed to fight the Cape Wind project to build an offshore wind farm of 130 turbines.