Objective In order to remove paraffin from white oil and reduce its cloud point, filter aids were applied to methyl ethyl ketone(MEK)-toluene dewaxing process of the white oil.

Methods The influences of the volume percentage of MEK in the mixed solvent, the volume ratio of solvent to white oil, and the dewaxing temperature on the dewaxing effect were studied. Three types of comb-type copolymers denoted AMAC, EMAC and Azo-MAC were obtained by the reaction of maleic anhydride-α-octadecene copolymers with aniline, phenylethylamine and amino-azobenzene, respectively. The effects of polymer types and addition amount on the MEK-toluene dewaxing were studied.

Results The optimum dewaxing effect was obtained at a MEK ratio of 55%, a solvent ratio of 3.0∶1, and a dewaxing temperature of -14 ℃ without filter aids, the wax yield was 5.6% and the cloud point was -2 ℃. Under the optimal process conditions, the wax yield was improved to 5.9% and 6.0% and the cloud point reduced to -4 ℃ by adding 100 μg/g of AMAC and EMAC with a molar ratio of side chain to main chain of 2∶1, respectively.

Conclusions Polymer AMAC and EMAC show the characteristics of filter aids. Adding the filter aids AMAC and EMAC in the MEK-toluene dewaxing process of white oil can improve the dewaxing effect and increase the wax precipitation point.