After my one Penn State laboratory class where we chilled different hydrocarbons to measure the cloud point (temperature at initial wax formation) and pour point (temperature at which hydrocarbon became practically solidified) it was determined that the cold resistance of fuel from forming wax was an important property of a hydrocarbon. In a real life application hydrocarbons are enhanced by additives to resist the wax (long-chain paraffin) formation. Before any additives are blended into fuels they undergo a solvent or catalytic dewaxing processes.

The first method for dewaxing is by using the physical process of solvent dewaxing. The two main solvents that are used in the solvent dewaxing process are propane and ketones (either methyl ketone with methyl isobutyl ketone or methyl ketone with toluene.) The object of solvent dewaxing to mix the solvents with the deasphaling oil, which will dilute the feedstock reducing viscosity, and then the mixture is cooled down until wax is formed. [1] Once the wax was formed it is sent into a rotating drum that forces the wax crystals to the outside where I can be extracted. The most economical way to perform this process is by using Dilchill dewaxing. Dilchill dewaxing is a process that injects cold solvent into DAO stream where it is highly agitated forcing the formation of larger wax crystals.[1]

Another way to extract wax from DAO is by Catalytic Dewaxing. Catalytic dewaxing is the chemical process that uses hydrocracking, performed by zeolite catalysts, to break apart the long chained n-paraffins to form branched i-paraffins. As mentioned before, this will cause the cloud point and pour point to be reduced. Going one step further, catalytic cracking can use two enzymes for the reduction of pour point and to also improve on the oxygen stability of the DAO. [1] Catalytic dewaxing the the preferred process compared to solvent dewaxing because it has a better yield and is a cheaper overall process.

Sources:
1. Gary, J. H., & Handwerk, G. E. (2007). Petroleum refining: technology and economics. New York: M. Dekker.