Cheap catalysts

researchers in Japan have developed a better way to produce biodiesel from vegetable oils by using common, inexpensive sugars, such as glucose and sucrose, as catalysts. The new catalysts are not only highly efficient but also cheap -- one-tenth to one-fiftieth the cost of conventional catalysts.

Any vegetable oil, edible or non-edible, can be turned into fuel after its fatty acids are converted to chemical compounds called esters. To achieve this, two types of catalysts are commonly used -- liquid acid or solid. The use of liquid acid catalysts, such as sulphuric acid, is prohibitively expensive because not only does it involve high consumption of energy, but the recovery of the catalysts for reuse is also difficult. Solid catalysts are easy to recycle, but they are costly and tend to rapidly lose their catalytic activity.

The new class of catalysts, developed by Michikazu Hara of the Tokyo Institute of Technology in Yokohama and his team, is prepared by partially burning sugar, starch or cellulose in the absence of air. This produces small, polycyclic carbon compounds, which when treated with sulphuric acid, yield the catalyst in powdery form.

The catalyst can be moulded into hard pellets or thin flexible films. It is capable of producing high-grade biodiesel by esterification of the vegetable-oil constituents oleic acid and stearic acid. The findings were published in the November 10 issue of Nature (Vol 438, No 7065).

The activity of new carbon-based catalysts is more than half of a liquid sulphuric acid catalyst but higher than what can be achieved by conventional solid acid catalysts such as nafion. Besides, there was no loss of activity, even for samples subjected to repeated reactions at 80-180 c.

The discovery couldn't have come at a better time. There is a renewed interest in biodiesel the world over, thanks to increasing awareness about fossil fuels' contribution to enhancing global warming and spiraling energy costs.

According to a report published by a team of scientists from University of Nebraska, led by M A Hanna, in the November issue of Journal of Industrial and Scientific Research (Vol 64, No 11), the world currently has feedstock of over 100 million tonnes for producing biodiesel. This can yield 30-35 million tonnes of biodiesel. The current global consumption of diesel stands at 1 billion tonnes a year.