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The use of solvents for dewaxing paraffin-base crude oil
410 THE
U.S. USE
OF
BUREAU OF MINES NOTES.
SOLVENTS
FOR CRUDE
DEWAXING OIL.
[J.F.I.
PARAFFIN-BASE
By H. M. Smith.
IN STUDYING the chemistry of lubricating-oil fractions from so-called " paraffin-base " crudes, one of the first requisites is a method for the separation and removal of waxy material. A method utilizing solvents for this purpose is described in this report, together with preliminary experiments with solvents that led to its development. The solvents actually used are secondary butyl alcohol, acetone, and mixtures of these. Isopropyl alcohol was also studied. Test-tube experiments indicated that the isopropyl alcohol (CH.~- C H O H - CH3) as received did not offer any advantage ov'er acetone, but after dehydrating with solid N a O H and anhydrous CuSO4, it was an excellent solvent. The secondary butyl alcohol (CH~ - C H O H - C H 2 - CH::) had a boiling range of 94 ° to lO2 ° C. and had been dehydrated to about 98 per cent. by volume. This alcohol appeared to dissolve the oil readily and to give good separations of the oil and wax. Filtration in a small experimental Shriver filter press using paper with cloth backing was not successful, as the pressures developed by the pump forced the small crystals through the filtering medium. Centrifuging was very successful, but because of limited equipment was very slow for the handling of large amounts; to overcome this difficulty cold settling was tried. Various mixtures of oil and solvents were prepared, placed in Florence flasks and allowed to stand at a temperature of I to 2 ° C. for thirty-six hours. Best results were with the following mixture, so a largescale test was made. Fifteen gallons of oil, 2o gallons of secondary butyl alcohol, and IO gallons of acetone were thoroughly mixed in the tank, and then allowed to settle at I to 2 ° C. ( 3 4 - 3 6 0 F.). At the end of twenty-four hours, 3o gallons 66 2/3 per cent. of clear supernatant liquid were drawn off, the wax level being approximately as shown by line //V in Fig. I. Twenty-five gallons of solvent were then added to the wax, the mixture stirred and again allowed to settle. At the end of twenty-four hours the entire supernatant liquid was drawn off.
Sept., J927.]
U . S . BUREAU OF MI~ES NOTES.
411
The solvent is removed from both the oil and wax by distillation with natural gas. A 5-1itre flask in a bath of boiling water is a convenient still. A stream of natural gas is passed through the solution in the flask, and removes the solvent very rapidly. The recovered solvent may be used successfully for the wash mixture, especially when corrected for distillation loss by the addition of a small amount of acetone. Altogether I4O kg. of gasoline-free oil were treated in this manner, and the recoveries were as follows: Oil, 72.8 per cent.; wax, 25. 7 per cent.; loss, 1. 5 per cent. The wax separated in this manner from this particular crude oil is very similar to xellow vaseline. The pour-point test of the dewaxed oil is 15 ° F., as against 25 ° F. for the gasoline-free crude. The above experimefits indicate that secondary butyl alcohol has possibilities as a solvent for the removal of w a x from paraffinbase crudes. Its solvent properties may be utilized to their fullest extent, or they may be modified by the admixture of ano.ther solvent such as acetone. The manner in which it is used depends upon the method of dewaxing. Further details will be found in Serial 2822, just issued.
U.S. USE
OF
BUREAU OF MINES NOTES.
SOLVENTS
FOR CRUDE
DEWAXING OIL.
[J.F.I.
PARAFFIN-BASE
By H. M. Smith.
IN STUDYING the chemistry of lubricating-oil fractions from so-called " paraffin-base " crudes, one of the first requisites is a method for the separation and removal of waxy material. A method utilizing solvents for this purpose is described in this report, together with preliminary experiments with solvents that led to its development. The solvents actually used are secondary butyl alcohol, acetone, and mixtures of these. Isopropyl alcohol was also studied. Test-tube experiments indicated that the isopropyl alcohol (CH.~- C H O H - CH3) as received did not offer any advantage ov'er acetone, but after dehydrating with solid N a O H and anhydrous CuSO4, it was an excellent solvent. The secondary butyl alcohol (CH~ - C H O H - C H 2 - CH::) had a boiling range of 94 ° to lO2 ° C. and had been dehydrated to about 98 per cent. by volume. This alcohol appeared to dissolve the oil readily and to give good separations of the oil and wax. Filtration in a small experimental Shriver filter press using paper with cloth backing was not successful, as the pressures developed by the pump forced the small crystals through the filtering medium. Centrifuging was very successful, but because of limited equipment was very slow for the handling of large amounts; to overcome this difficulty cold settling was tried. Various mixtures of oil and solvents were prepared, placed in Florence flasks and allowed to stand at a temperature of I to 2 ° C. for thirty-six hours. Best results were with the following mixture, so a largescale test was made. Fifteen gallons of oil, 2o gallons of secondary butyl alcohol, and IO gallons of acetone were thoroughly mixed in the tank, and then allowed to settle at I to 2 ° C. ( 3 4 - 3 6 0 F.). At the end of twenty-four hours, 3o gallons 66 2/3 per cent. of clear supernatant liquid were drawn off, the wax level being approximately as shown by line //V in Fig. I. Twenty-five gallons of solvent were then added to the wax, the mixture stirred and again allowed to settle. At the end of twenty-four hours the entire supernatant liquid was drawn off.
Sept., J927.]
U . S . BUREAU OF MI~ES NOTES.
411
The solvent is removed from both the oil and wax by distillation with natural gas. A 5-1itre flask in a bath of boiling water is a convenient still. A stream of natural gas is passed through the solution in the flask, and removes the solvent very rapidly. The recovered solvent may be used successfully for the wash mixture, especially when corrected for distillation loss by the addition of a small amount of acetone. Altogether I4O kg. of gasoline-free oil were treated in this manner, and the recoveries were as follows: Oil, 72.8 per cent.; wax, 25. 7 per cent.; loss, 1. 5 per cent. The wax separated in this manner from this particular crude oil is very similar to xellow vaseline. The pour-point test of the dewaxed oil is 15 ° F., as against 25 ° F. for the gasoline-free crude. The above experimefits indicate that secondary butyl alcohol has possibilities as a solvent for the removal of w a x from paraffinbase crudes. Its solvent properties may be utilized to their fullest extent, or they may be modified by the admixture of ano.ther solvent such as acetone. The manner in which it is used depends upon the method of dewaxing. Further details will be found in Serial 2822, just issued.