Dow Chemical Co. plans to generate $1.5 billion from selling assets including polypropylene-producing technology as the biggest U.S. chemical maker focuses on its most profitable units. Dow plans to complete the sales in the next 18 months, the Midland, Michigan-based company said today in a statement. The divestitures exceed a forecast on Dec. 3, when Chief Executive Officer Andrew Liveris said the company expected to unload as much as $1 billion of assets.