Waxy Woes of Winter

Remember winter? When you can't get a truck started in the morning because the engine is clogged up and your skin cream hardens if you leave it out in the cold? These and other phenomena are caused by crystals forming in the wrong place at the wrong time. In the case of the truck engine, for example, it's the hydrocarbons contained in gasoline that crystallize into wax -- a process that also clogs up pipes used for transporting diesel fuels.

Research that may help prevent formation of such unwanted crystals is being conducted by Profs. Meir Lahav and Leslie Leiserowitz of the Weizmann Institute's Materials and Interfaces Department. Together with colleagues at the Institute and elsewhere, they have now conducted the first detailed study of processes occurring at the very onset of crystallization.

In experiments conducted at DESY, the synchrotron radiation facility in Hamburg, Germany, the researchers found that at the beginning of wax build-up, shorter hydrocarbon molecules produce more massive, multi-layered crystal structures, while longer varieties form only a single layer of wax molecules. They also showed that the multi-layer build-up of the wax crystals can be prevented by addition of a long-chain alcohol.

These findings may serve as a basis for designing better fuel additives, or flow improvers, which avert the clogging up of fuel pipes and for preventing crystals from forming in other situations. Conversely, this research may also be used to promote the nucleation of crystals when needed, as in enhancing rainfall by artificial cloud-seeding.