http://news.dow.com/dow_news/corporate/2008/20080710b.htm

Both Dow Chemical and Rohm & Haas make ion exchange resins for cleaning biodiesel.

Just an update on this - apparently the finality of this deal is under question since Dow was going to use the sale of one of its assest to China did not go through, therefore the money they had counted on to buy Rohm and Haas is not available and the deal hasn't went down...