Reaction & Synthesis / Water/Wastewater

New catalyst promises better way to biodiesel


Aug 21, 2007

A heterogeneous catalyst developed at Iowa State University, Ames, Iowa, avoids some serious downsides of the current production of biodiesel using homogeneous catalyst, says Victor Lin, a professor of chemistry at the university. The homogeneous catalyst isn’t reusable, while the processing involves many steps and leads to the generation of 0.5-1 gallon of wastewater for every gallon of biodiesel, he says. A startup company, Catilin Inc. in Ames, with funding from venture capitalists and the university research foundation, now is working to commercialize a route based on the heterogeneous catalyst, he adds.

“The technology could change how biodiesel is produced,” claims Lin.

Heterogeneous catalysts haven’t found a role in the burgeoning production of biodiesel because of their slow kinetics, Lin notes, adding that the new nanostructure material boasts far faster kinetics than other such catalysts. The reaction speed still lags that provided by conventional catalyst, sodium methoxide, but the new material eliminates the need for acid neutralization after the reaction and the subsequent water-washing and separation steps, he explains.

So, production of biodiesel using the new catalyst takes four hours, compared to 13 hours for the conventional route, says Lin. Moreover, the nanostructure catalyst doesn’t pose the toxicity, corrosivity and flammability issues of sodium methoxide, he adds.

The catalyst has a honeycomb nanostructure with a high surface area, more than 1,000 m2/gm, with a lot of active sites, both acidic and basic, notes Lin. It is completely different from conventional acidic catalysts, he says.

The catalyst can be used with the vegetable oils now serving as biodiesel feedstocks. However, it also can work with less costly animal fats — poultry fat is half the cost of soybean oil, Lin estimates — and even with used cooking oils, which are waste materials now.

After processing, the catalyst can be recovered by filtration and reused without washing, he says — for soybean oil feed up to 20 times without activity loss and for animal fats up to 12 times with the original reactivity.

The researchers are manufacturing the catalyst themselves in a laboratory at the university and aim to produce enough for a pilot plant to be built at the Iowa Energy Center’s Biomass Conversion Facility in Nevada, Iowa. That unit, which should be operating in the summer of 2008, will contain a 100-gal. continuous stirred-tank reactor, which will be able to produce 0.5 to 1 million gallons of biodiesel per year, says Lin. The solid catalyst will be confined in a separate compartment within the reactor. The pilot plant will test a variety of feedstocks, including palm oil, which is important in Asia but which contains a lot of free fatty acids and can’t be used directly in conventional processes, he adds.

The route, like conventional ones, yields glycerol as byproduct. While finding an outlet for all the glycerol from biodiesel is a concern (see, Lin notes that the byproduct is salt-free and so is better quality than that made conventionally and eliminates the potential for emulsion problems during separation.

Lin reckons that petroleum-based diesel costs $1.50 to $2.50/gal to produce, while soy-based biodiesel made via conventional processes runs $2.35 to $2.65. In contrast, the new route will boast production costs of $1.80/gal for soybean oil and $1.40 for animal fats, he hopes.

Catilin now is weighing whether to make biodiesel itself, license the technology or sell catalyst, says Lin.