Solvent recovery process for N-methyl-2-pyrrolidone in hydrocarbon extraction

An improved process for removing minor amounts of water extraneously introduced into a lube oil extraction solvent comprising NMP and minor amounts of water, said process comprising removing most of said solvent from a lube oil extract, as a first solvent vapor, by flash evaporation, simple distillation, rectification or combination thereof and stripping residual solvent from said extract with a non-aqueous stripping gas to form a mixture of solvent vapor and stripping gas, separating said solvent from said gas and recovering said solvent, wherein the improvement comprises the steps of:

• a. combining said first solvent vapor with said mixture;
• b. passing said combined mixture which contains extraneous and non-extraneous water through a first condensing zone wherein most of the solvent in said mixture is condensed to a liquid to form a mixture of condensed solvent, stripping gas and vapor and wherein said vapor contains NMP and said extraneous water;
• c. passing said second mixture to a separating zone to separate said condensed solvent from said vapor and stripping gas;
• d. passing at least a portion of the separated vapor and stripping gas from said separating zone to a rectifying zone wherein said NMP in said vapor is condensed and separated from said extraneous water and stripping gas;
• e. passing said extraneous water vapor and stripping gas from said rectifying zone to a second condensing zone to condense the extraneous water and separate same from the stripping gas;
• and
• f. returning a portion of said condensed water from the second condensing zone back to said rectifying zone to act as reflux therein.