US2054429A - Dewaxing hydrocarbon oil - Google Patents

Description

Patented Sept. 15, 1936 PATENT OFFICE.

DEWAXING HYDROCARBON OIL Edwin C. Knowles, Beacon, N. Y., assignor to The Texas Company, New York, N. Y., a cornotation of Delaware No Drawing. Application May 7, 1935, Serial No. 20,193

5 Claims.

This invention relates to dewaxing hydrocarbon oil and more particularly to the removal of wax from mineral lubricating oil stock for the production of low pour test lubricating oil.

The invention broadly contemplates dewaxing wax-bearing mineral oil with a solvent composed of mixed aliphatic ketones, and particularly a mixture composed of a high molecular weight member of the series of aliphatic ketones and a relatively low molecular weight member of the same series.

More specifically, the invention comprises -dewaxing oil with a mixture of an aliphatic ketone having around seven to ten carbon atoms and a relatively lower member of the series having up to six carbon atoms.

I have discovered that the higher members of the series of aliphatic ketones having from seven up to about ten carbon atoms have :a comparatively high solvent power for mineral oil "at temperatures of the'order of 0 F. and below. I have found that the solubility of mineral oil is greater in these higher members of the aliphatic ketones than in the relatively lower members of the series having fewer carbon atoms. Due to the high solubility of oil in these compounds, they are, therefore, suitable as good oil solvents and provide, when mixed with a wax anti-solvent liquid, a selective solvent liquid mixture which is particularly well adapted for the dewa'xing of hydrocarbon oil.

The aliphatic ketones having this characteristic 'of high oil solubility comprise dipropyl ketone, propyl isobutyl ketone, methyl normal hexy-l ketone, ethyl normal amyl ketone and ethyl iso-amyl ketone. Dipropyl ketone, for example, has the following chemical formula: C3H1COC3H'1, while methyl normal hexyl ketone, for example, has the formula: CH3COC6H13.

Higher molecular weight members of the series such as ethyl hexyl ketone, propyl hexyl ketone (containing nine and ten carbon atoms), even though they are solids at temperatures below about 25 F., may nevertheless be used in combination with a relatively lower member of the series to provide a satisfactory dewaxing solvent. For example, the solid point of a mixture of such high molecular weight ketone with acetone or methyl ethyl ketone is depressed below normal dewaxing temperatures.

The lower members of the series of aliphatic ketones which are suitable as wax anti-solvent liquids comprise acetone, methyl ethyl ketone and methyl isobutyl ketone.

Methyl isobutyl ketone which contains six carbon atoms combines the properties of wax antisolvent action and good oil solvent action to a considerable extent. However, I have found that when this compound is mixed with a higher member of the series of aliphatic ketones, such as dipropyl ketone, and which has a relatively higher solubility for oil, an improved dewaxi-ng solvent liquid mixture is obtained. Such a mixture may be used for dewaxing at relatively lower temperatures than methyl isobutyl ketone alone, 1 0 and when used at temperatures relatively below 0 F., this mixture continues to exert a solvent action upon substantially all of the liquid oil constituents.

My invention, therefore, comprises mixing wax- 15 bearing oil with a solvent composed of an aliphatic ketone having around seven to ten carbon atoms, and an aliphatic ketone having up to six carbon atoms, in such proportion that at temperatures of 0 F. and below, the solvent mix- .20 ture has substantially complete solvent action on the liquid constituents of oil, and substantially no solvent action upon the solid waxy constituents of the oil. This mixture of oil and solvent liquid is chilled to temperatures of 0 F. and below, depending upon the desired pour test of the dewaxed oil to precipitate the wax constituents. The wax constituents thus precipitated are then separated from the cold mixture by mechanical means, such as filtration, centrifuging, $0 or settling.

In order to more clearly describe the invention, reference will now be made to the following examples in which a wax-bearing distillate, solvent refined to remove naphthenic 'constitu- 335 ents, and derived from a Mid-Continent crude and also having the following tests, was dewaxed with a mixture comprising dipropyl ketone and a wax anti-solvent liquid, consisting of a relatively lower molecular weight ketone: 40

Gravity A. P. I 26.9 Saybolt universal viscosity seconds at 210 F 112 7 Pour test F 120 45 In the first example, one part of the above oil was mixed with four parts by volume of a solvent liquid mixture consisting of 20% dipropyl ketone and methyl isobutyl ketone. This mixture was then chilled to a temperature of --10 F. to precipitate wax constituents. Thereafter, the mixture was subjected to filtration to separate and remove the precipitated wax constituents.

The solvent liquid was then removed from the filtrate by distillation, leaving a dewaxed oil 55 which comprised about 61% of the wax bearing oil. This dewaxed oil had a pour test of 10 F., or a pour test corresponding to the temperature at which it was dewaxed. I

In the second example, one volume of the same wax-bearing oil was mixed with four volumes of a solvent liquid mixture consisting of equal parts of dipropyl ketone and methyl ethyl ketone. This mixture was chilled to a temperature of 0 F. to precipitate the wax constituents and at this temperature it was filtered. After removal of the solvent from the resulting filtrate, the dewaxed oil was found to have a pour test of 0 F.

The precipitate of slack was removed in the dewaxing of the above examples contained wax having a melting point of around to 147 F. and comprising about 41 to 44% of the slack wax precipitate removed from the solvent mixture.

Rapid rates of filtration were realized in each case, and the precipitated wax was found to be readily filterable.

While in the foregoing examples, dewaxing with solvent liquid mixtures composed of dipropyl ketone with methyl ethyl ketone and methyl isobutyl ketone have been specifically described, the invention is not restricted to these particular mixtures. As already indicated, dipropyl ketone may be used in conjunction with lower members of the series of aliphatic ketones as, for example, acetone. On the other hand, instead of dipropyl ketone, higher members of the aliphatic series may be employed, such as methyl 'hexyl ketone and ethyl amyl ketone.

Nor is the invention restricted to the dewaxing of solvent refined distillates, such as that referred to above, but may be applied to the dewaxing or separation of wax from other fractions of crude petroleum, either residual or distillate. Furthermore, the proportions of the individual solvents, comprising the dewaxing mixture as well as the proportion of the solvent mixture to the oil undergoing dewaxing, will vary, depending upon the oil and wax content of the particular material undergoing treatment.

7 Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the ap pended claims. Y

I claim: 7

1. In the dewaxing of wax-bearing mineral oil, the method which comprises mixing the oil with a solvent comprising an aliphatic ketone having around seven to ten carbon atoms in admixture with an aliphatic ketone having up to six carbon atoms in proportions such that at temperatures of 0 F. and below, the mixture has substantially complete solvent action on the liquid constituents of the oil and substantially no sol,- vent action upon the solid waxy constituents of the oil, chillingthe mixture to a temperature of 0 F. and below to precipitate the wax constituents, and separating the thus precipitated wax constituents from the cold mixture.

2. In the dewaxing of wax-bearing mineral oil, the method which comprises mixing the oil with a solvent composed of an aliphatic ketone having around seven to ten-carbon atoms in admixture with a wax anti-solvent liquid of the character of methyl ethyl ketone in proportions such that at temperaturesof 0 F. and below, the mixture has substantially complete solvent action on the liquid constituents of the oil and substantially no solvent action upon the solid waxy constituents of the oil, chilling the mixture to a temperature of 0 F. and below to precipitate the wax constituents, and separating the thus precipitated Wax constituents from the cold mixture;

3. In the dewaxing of wax-bearing mineral oil, the method which comprises mixing the .oil with a solvent liquid comprising dipropyl ketone, chilling the mixture to precipitate the wax constituents, and separating the thus precipitated wax constituents from the cold mixture.

4. In the dewaxing of wax-bearing. mineral oil,

the method Which comprises mixing the oil with a solvent composed of dipropyl ketoneandmethyl isobutyl ketone in proportions such that at temperatures of 0 Rand below the mixture has substantially complete solvent action on the liquid constituents of the oil .and substantially no solvent action upon the solid waxy constituents of the oil, chilling the mixture to a temperature of 0 F. and below to precipitate the wax constitue ents, and separating the thus precipitated wax constituents from the cold mixture.

5. In the dewaxing of wax-bearing mineral oil, the method which comprises mixing the oilwith a solv-entcomposed of dipropyl ketone and methyl ethyl ketone in proportions such that at. temperatures of 0 F. and below the mixture has substantially complete solvent action on theliquid constituents of the oil and substantially no solvent action upon the solid waxy constituents of the oil, chilling the .mixture to .a temperature of 0 F. and below to precipitate the wax constituents, and separating the thus'precipitated wax constituents fromthe cold mixture.

EDWIN C. KNOWLES.