Catalytic process that could help paper mills save millions of dollars a year by converting a polluting by product into formaldehyde, a useful product, has been discovered and patented by an engineering professor at Lehigh University in Bethlehem. Israel E. Wachs, professor of chemical engineering, says his method, which was tested by Georgia-Pacific Corp. (G-P) in mobile pilot plants for two years, succeeded in converting a methanol-water waste stream contaminated by sulfur compounds and small amounts of hydrocarbons known as terpenes into formaldehyde. The process also significantly minimizes most of the emissions of carbon dioxide (CO2) and sulphur dioxide (SO2), two potentially harmful by-products of traditional pollution-control methods, Wachs says.

Methanol and sulphur compounds called mercaptants, are produced at paper mills when logs are digested under intense heat and pressure with a caustic solution in sulphite. The process separates lignin, a polymeric resin that holds together the cell walls of plants, from cellulose the material used to make paper. Methanol and mercaptans foul-smelling compounds, were once released by paper mills into streams.

The conventional method now of disposing of methanol and meracaptans is incineration at 1500 degrees Fahrenheit, an expensive process often requiring additional fuel-usually natural gas that emits CO2, a greenhouse and SO2, an ingredient in acid rain.

"Using conventional pollution-control methods," Wachs says, " paper mills at best can only convert an extremely bad pollutant, contaminated methanol waste streams, into moderately bad pollutants, CO2 and SO2 and at a major cost.

Consequently, the paper mills are not completely solving the pollution emissions, but just taking a band-aid approach." Wachs's process also produces formaldehyde, a reactive compound important to the paper mill industry used to make the resins in particle board, and also to make molding compounds, brake innings and other products.

Existing methanol-oxidation catalysts made of bulk metal oxides of metallic silver, Gibson says, were useless in paper mills because they were deactivated by the sulphur compounds and by the high stream concentration present in the stripper overhead gases containing the methanol. Wachs conducted experiments in the microreactors at Lehigh's Zettlemoyer Center for Surface Studies using tiny amounts - about 100 mg-of a catalyst of vanadium pentoxide on a Titania support.

Not only did his catalyst incinerate the waste streams to CO2 to SO2 at about 600 degrees F., much lower than the 1500 degrees f. using conventional non-catalytic methods, but the catalysts was not poisoned by the sulphur compounds and high concentration of water ( 50 per cent ). But two things the rapid catalytic reaction and the total conversion to CO2 and SO2 made Wachs suspect that he was failing to notice intermediate reaction steps and products.

"It seemed to me that the reaction was being pushed so quickly from step A step C that it was not possible to detect the intermediate reaction step B. So the reaction slowed down and it was discovered that in that sep for maldehyde was being made in very high concentration.

This was the discovery of a new catalytic reaction that was previously unknown and was a new way of making formaldehyde that was economically and ecologically favorable.

To further improve the efficiency of the catalyst, Wachs deposited the active vanadia-titania catalytic material on an inter ceramic, which minimized over-oxidation of the desired formaldehyde and minimized the negative influences of excessive exothermic heat of this reaction.

Different versions of the paper will be published by the Technical Association of the Pulp and Paper Industry (TAPPI) Journal and AICHe Environmental Progress in the coming year.