Lubricating oil dewaxing with membrane separation
AssigneeMobil Oil Corporation
InventorsRonald M. Gould, Harold A. Kloczewski, Krishna S. Menon, Thomas E. Sulpizio, Lloyd S. White
Life of this patent
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Abstract
A semicontinuous process for solvent dewaxing a waxy petroleum oil feed stream including the steps of: diluting of the waxy oil feed stream with solvent; feeding cold oil/solvent/wax mixture to a filter to remove the wax and obtain an oil/solvent filtrate stream; contacting the oil/solvent filtrate stream with a selective semipermeable membrane to selectively transfer solvent through the membrane to obtain a solvent-rich permeate; and periodically directing a warm stream of recovered solvent onto the membrane surface to wash the membrane and remove impurities therefrom.
Claims15
A semicontinuous process for solvent dewaxing a waxy petroleum oil feed stream comprising the steps of:
- diluting of the waxy oil feed stream with solvent;
- cooling the waxy oil feed stream in successive heat exchange stages;
- feeding the oil/solvent/wax mixture to a filter to remove the wax and obtain an oil/solvent filtrate stream, contacting the oil/solvent filtrate stream at a temperature of -35.degree. C. to +20.degree. C. with one side of a selective semipermeable membrane in a membrane module to selectively transfer solvent through the membrane to obtain a solvent permeate stream on the other side of the membrane, the oil/solvent filtrate stream side of the membrane is maintained at a positive pressure relative to a pressure on the solvent permeate side of the membrane, and wherein the volume ratio of solvent in the permeate stream to retentate stream is 1:1 to 3:1;
- selectively transferring a major amount of solvent from the filtrate side of the membrane to the solvent permeate side of the membrane, and recycling the solvent permeate at a temperature of -35.degree. C. to +20.degree. C. to the filter feed;
- withdrawing a solvent-lean filtrate stream containing the remaining solvent from the filtrate side of the membrane module, contacting the filtrate stream by indirect heat exchange with the warm waxy oil feed;
- treating the withdrawn filtrate stream to recover the remaining solvent from the oil;
- recovering a dewaxed oil product stream and a wax product;
- and periodically directing a warm stream of recovered solvent onto the membrane surface to wash the membrane and remove impurities therefrom.
In the process for solvent dewaxing a waxy petroleum oil feed to obtain petroleum oil lubricating stock wherein waxy oil feed is treated with cold solvent to crystallize and precipitate wax particles, thereby forming a multiphase oil/solvent/wax mixture containing filterable wax particles, and wherein the multiphase mixture is filtered to remove filterable wax particles from the cold oil/solvent/wax mixture to recover a cold wax cake and a cold oil/solvent filtrate stream;
- the improvement which comprises:
- feeding the cold oil/solvent filtrate stream containing wax particles under operating pressure of at least 2750 kPa to a selective permeable membrane for selectively separating the cold filtrate into a cold solvent permeate stream and a cold oil-rich retentate stream which contains the dewaxed oil and the remaining solvent;
- and
- periodically interrupting flow of the filtrate stream to the membrane;
- and
- directing a warm stream of recovered solvent onto the membrane surface to wash the membrane and remove impurities therefrom.
Dependencies are inferred from the claim text.