Abstract: Volatile acids present in n-methyl pyrrolidone vapor from solvent extraction processes can be reacted with sacrificial metals such as magnesium to concentrate the acid salts into a small volume of oil/NMP. Steam stripping removes NMP from the oil/NMP mixture while simultaneously springing a portion of the light carboxylic acids from their salts, the acids going with the NMP. This condensed NMP stream containing the light carboxylic acids is contacted with an ion exchange resin which removes the acids from the NMP. The purified small volume of NMP is returned to the extraction process.

Abstract: Corrosion of the process equipment in solvent extraction units utilizing N methyl-2-pyrrolidone as the selective extraction solvent is significantly reduced by means of a sacrificial metal contacting zone or bed containing a metal or metal alloy with a higher electro chemical potential than the metals used in the extraction unit vessels and lines. Preferred sacrificial metals are magnesium, zinc, calcium, barium, and strontium, most preferably magnesium, as metal strips, shavings, ribbons, sponge, filings, chips, blocks, bricks, etc.

Abstract: An improved rotary drum filter is described. The filter includes a liquid collection means communicating with at least a plurality of fluid conduits. The collection means collect and discharge residual liquid remaining in the fluid conduits during each rotation of the filter drum to decrease the erosive effects of the residual liquid on the filter cloth.

Abstract: An improved process for removing H.sub.2 S from a hydrofiner tail gas wherein said tail gas is passed into a scrubbing zone wherein it is contacted with liquid NMP to remove most of the H.sub.2 S from the gas to form an H.sub.2 S-rich NMP solution and the H.sub.2 S-rich NMP solution is heated and passed into a stripping zone to remove most of the H.sub.2 S from the NMP to form an H.sub.2 S-lean NMP solution, extracting a hydrocarbon oil with an NMP solution, recovering hot liquid, NMP from said extracted oil and combining it with said H.sub.2 S-lean NMP solution and wherein said combined solution comprises at least a portion of said NMP solution used to extract said oil, wherein the improvement comprises heating the H.sub.2 S-rich NMP solution to the required stripping temperature by indirectly contacting same, in heat exchange relationship, with at least a portion of said combined NMP solution.This process is especially useful for scrubbing H.sub.

Abstract: An asphalt containing mineral oil is simultaneously deasphalted and extracted in a combination zone by contacting the oil with a solvent comprising N-methyl-2-pyrrolidone (NMP) containing from 0-5 LV% water and a light hydrocarbon to produce a raffinate and extract phase, with the raffinate phase containing the desired oil, most of the hydrocarbon solvent and some NMP. The raffinate is then passed to a reduced pressure zone to remove most of the hydrocarbon solvent therefrom. The remaining raffinate oil and NMP solution is then chilled to produce bulk liquid-liquid immiscibility between the oil and NMP. The chilled oil and NMP are then passed to a settling zone wherein the NMP is separated from the oil and recycled back into the combination zone.

Abstract: N-methyl-2-pyrrolidone is recovered from the raffinate and extract phases produced by its use in hydrocarbon extraction processes, particularly lube oil extraction, through the use of flash evaporation and/or distillation followed by gas stripping. Water buildup in the recovered solvent is prevented by employing solvent dehydration means in the solvent recovery line after gas stripping. Proper control of process parameters enables the dehydration means to remove excess water without requiring additional heat input to the process.