New process for silicon production

Professor Richard Laine of the University of Michigan has discovered an inexpensive and relatively non-toxic method for producing a variety of silicon-based chemicals from sand or rice hull ash and antifreeze.

Once implemented, the new technology has the potential to enable manufacturers to create silicon-based compounds without expensive, high-temperature processing and toxic by-products.

In his original experiments, Laine and several students used beach sand, ethylene glycol (antifreeze) and a caustic to produce silicon-based chemicals that included transparent conducting polymers, flame-resistant polymers, liquid crystalline polymers, and silicate glasses.

Dr Cecil Frye of the Dow Corning Company inspired Laine’s latest work. Based on Frye’s findings, Laine saw the potential for making his process ‘greener’ by reducing the amount of caustic and creating a catalytic reaction.

Laine’s research group believed that this new catalytic approach would open up the process dramatically, making it possible to use almost any source of silica and thus produce a wider range of compounds.

One of those sources was rice hull ash, created as a by-product in the routine burning of thousands of tons of brown rice hulls daily.

Laine’s work has shown that this waste product is capable of yielding numerous novel and common silicon-containing chemicals, polymers, plastics, and even very pure silica which can be employed as a filler for polymers, in paper making and the production of optical glass.

Many polymers and plastics are made from petroleum-derived chemicals rather than silicon. This despite the fact that petroleum comprises less than one percent of the earth’s natural resources while silicon-containing materials account for some 25 percent of the minerals on the planet.

Current technology for producing silicon-based materials is said to use a very old metallurgical process that requires heating minerals such as quartz sand in a furnace at extremely high temperatures, then using an electric current and a carbon compound to remove the oxygen and create an impure silicon metal.

Surprisingly, the process of producing silicon-containing chemicals often involves returning the silicon metal to something approximating its original chemical state. Studies at Dow Corning suggest that 70 percent of the energy consumed in producing these silicon-based chemicals, including silicone rubbers, is lost as gases during the process.

‘We have discovered an extremely low-cost route to silicon-containing chemicals and polymers, with very few of the environmental hazards that are extant in current processes,’ said Laine when comparing traditional manufacturing methods with his new process.

‘Rather than relying on expensive high-temperature processing that generates by-products, we’re looking at a relatively eco-friendly process—one that uses rice hull ash, low-toxicity antifreeze and trace amounts of caustic chemicals to produce a high-quality silica and silicon-containing chemicals, polymers and plastics.’

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