Silver News

New Silver/Copper System Benefits Plastics Industry

One of the great achievements of chemistry was the discovery that the production of chemicals could be greatly improved in the presence of certain metals called catalysts. A hundred years ago it was discovered that silver was one of these metals, and since then silver has been a key metal in the production of chemicals for the $300 billion plastics industry.

It is estimated that 700 tons of silver are in constant use worldwide for two chemical reactions essential to the plastics industry. The first reaction produces ethylene oxide used to make flexible plastics. In this instance, silver is the exclusive catalyst for this reaction. The second reaction is in the production of formaldehyde used to make solid plastics, but here silver has competitors. Now a combination with copper has increased the competitive advantage of silver for this reaction.

"A stream of gaseous methanol (wood alcohol) over silver crystals will result in 90 percent conversion to formaldehyde. By conducting the products of this stream over an additional bed of copper crystals the total conversion becomes better than 93 percent," says Israel E. Wachs, Professor of Chemical Engineering, Lehigh University, Bethlehem, Pennsylvania. "At first glance, this may appear small, but considering the amounts involved (15 million tons per year) it is economically a significant benefit to the industry."

The main benefits to the plastics industry are that less energy is needed to produce more formaldehyde and fewer products are wasted. As the plastics industry continues to grow, the use of silver as a catalyst will increase, too.

Formaldehyde produces plastics for impact-resistant dinnerware and tableware, finishes that increase the strength of paper products and textiles, surface coatings that resist heat and scratches, casings for electronic equipment and appliances, and high-strength adhesives for structural laminated wood beams.

Silver News - June / July 2001