Urea dewaxing of low n-paraffin content oils

In a process for dewaxing liquid mineral oils comprising reacting said liquid mineral oils with urea in the presence of an organic solvent to form solid, n-paraffin-urea adducts, separating said adducts from the solution of the dewaxed mineral oil, decomposing or extracting the separated adducts, recovering and recycling the urea and, optionally, recovering the n-paraffins, the improvement which comprises:

• a. diluting a mineral oil containing less than 2 weight percent of a n-paraffins with an organic solvent, said solvent being one which does not form an adduct with urea, in which urea is substantially insoluble and which has a density substantially below that of the n-paraffin-urea adduct,
• b. combining the mineral oil solution with solid urea, the amount of urea being a multiple of the amount required for the completed conversion of the n-paraffins into n-paraffin-urea adduct,
• c. vigorously mixing the mixture of mineral oil solution and urea by pumping the mixture of mineral oil solution and urea through a closed loop whereby said mixture is continuously circulated for a period of time sufficient to form n-paraffin-urea adduct,
• d. separating from the mixture of step (c) a solids-free solution of dewaxed mineral oil, and
• e. recovering from said solids-free solution the organic solvent and a dewaxed mineral oil product having a reduced n-paraffin content,
• f. continuously removing a portion of said circulating mixture,
• g. removing the solids from said portion,
• h. returning said solids-free portion to said circulating mixture,
• i. recovering the urea from the separated solids of step (g) by decomposing the adduct in said solids, and
• j. returning the recovered urea to the circulating mixture.