New Process Cleans up Detergent

Researchers in the chemical engineering department at the University of Waterloo, Ontario, have developed a new low-temperature process for making sulfur trioxide, an ingredient used in the manufacture of synthetic laundry detergents.

The new process stoichiometrically converts sulfur dioxide to sulfur trioxide using near super-critical or super-critical carbon dioxide as the reaction medium. The process can be integrated with a sulfonation or sulfation reactor for making linear alkyl sulfonates or long- chain alcohol sulfates, which are major components of synthetic laundry detergents.

The key to the new process is the discovery of the large solubility of sulfur trioxide in near super-critical or super-critical carbon dioxide. The team also found that the sulfonation and sulfation reactions proceed rapidly at temperatures below 60°C (140°F) in this medium.

Researchers find several benefits to using the dense, gaseous carbon dioxide as the reaction medium. The near super-critical or super-critical carbon dioxide can be recycled and reused, resulting in cost savings. The medium also allows the sulfonation or sulfation step to occur at low temperature, which appears to reduce the extent of parasitic reactions that lead to product discoloration. Additional cost savings are realized since the production of waste products or waste acids is reduced to levels below those found in conventional processes.