Not so clean. MTBE, which makes gasoline burn more cleanly, is an environmental hazard itself.

Green Gas Gets Greener

Staff Writer

ORLANDO, FLORIDA--Kermit was right: It's not easy being green. The compounds that can help gasoline burn more cleanly often create their own environmental problems, or they are expensive and difficult to produce. Now, there's a way to make one of the most attractive gasoline additives--a product called dimethyl carbonate (DMC)--from cheap and nonhazardous starting materials.

"It's a very interesting result," says Michele Aresta, a chemist at University Campus in Bari, Italy. However, due to proprietary concerns, the researchers didn't reveal the details of the new process when they presented it here at a 9 April meeting of the American Chemical Society, and Aresta and others note that key details determining the process's commercial viability remain unknown.

Many U.S. cities currently use an oxygen-rich compound called MTBE to reduce smog-forming exhaust. But MTBE readily dissolves in water and has fouled groundwater supplies around the country. DMC is seen as a possible replacement, because it is nontoxic and it does an even better job at helping gasoline burn cleanly. But the most prevalent production scheme uses a poisonous gas called phosgene. Moreover, DMC synthesis generates a variety of chlorinated byproducts that can damage wastewater streams.

Chemist Yiling Tian at Tianjin University in China says he and his colleagues found a better way when they devised a catalyst that makes DMC from nontoxic ingredients: methanol, dimethyl ether--a cheap methanol derivative--and a pressurized form of CO2 called supercritical CO2. What is more, Tian says that the reaction works under mild conditions and turns out DMC in high yield with no harmful byproducts.

The new process could have other environmental benefits as well, Tian contends. The process could be designed to tap CO2 present in oilfields instead of releasing it to the atmosphere, and thereby prevent the buildup of excess greenhouse gases. According to Tian, the Chinese energy giant Sino Petroleum, which funds a portion of his work, is considering scaling up the new process. If it's successful, it may be a little easier for petroleum companies to follow Kermit's lead.

Related sites
Information about MTBE from the Environmental Protection Agency

Posted in Chemistry