Haze-free base oils with high paraffinic content

Abstract

The present invention relates to a method for reducing the cloud point of a base oil with high saturates/paraffinic content to below 0° C., wherein the method comprises subjecting said base oils to a cloud point reduction step comprising adding said base oil to a solvent mixture, wherein the solvent mixture comprises a paraffin naphtha fraction and a co-solvent to obtain a solvent treatment mixture; and subjecting the solvent treatment mixture to a solvent de-waxing step.

Claims

1. A method for reducing the cloud point of a base oil comprising a high saturates and paraffinic content to below 0° C., the method comprising: (a) combining the base oil with a solvent and a co-solvent to form a treatment mixture, wherein the solvent comprises a paraffinic naphtha fraction, and wherein the co-solvent comprises one or more of methyl isobutyl ketone, methyl butyl ketone, methyl propyl ketone, and methyl isopropyl ketone; and (b) cooling the treatment mixture to a temperature of less than −20° C. to form a wax crystal and a de-waxed mixture comprising a portion of the solvent and a de-waxed oil; (c) separating the wax crystal from the de-waxed mixture to form a separated de-waxed mixture comprising the portion of the solvent and the de-waxed oil; (d) distilling the separated de-waxed mixture to form a distilled solvent and a de-waxed oil, wherein the de-waxed oil comprises a cloud point below 0° C.

2. The method according to claim 1, wherein the paraffinic naphtha fraction comprises paraffinic molecules comprising carbon chain lengths in the range of from 5 to 11.

3. The method according to claim 1, wherein the paraffinic naphtha fraction comprises paraffinic molecules of at least one of carbon chain length 6, 7 and 8.

4. The method according to claim 1, wherein the paraffinic naphtha fraction comprises paraffinic molecules of carbon chain length comprising one or more of 5, 6, 7, 8, 9, 10, and 11.

5. The method according to claim 1, wherein the co-solvent further comprises methyl ethyl ketone.

6. The method according to claim 1, wherein the weight ratio of the naphtha fraction to the co-solvent is from 70:30 to 30:70.

7. The method according to claim 1, wherein the combining the base oil with the solvent is done at a ratio of base oil to solvent of from 1:3 to 1:6, and wherein the combining the base oil with the solvent is done at a temperature from 20° C. to 150° C.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) The present invention concerns a method for reducing the cloud point of a base oils with high saturates/paraffinic content to below 0° C., wherein the method comprises subjecting said base oils to a cloud point reduction step comprising (a) adding said base oils to a solvent mixture, wherein the solvent mixture comprises a paraffinic naphtha fraction and a co-solvent to obtain a solvent treatment mixture; and (b) subjecting the solvent treatment mixture to a solvent de-waxing step.

(2) With respect to the present invention, base oils with high saturates/paraffinic content may be base oils with more than 90% saturates/paraffinic content, such as Group II and Group III base oils (according to the API categories). Suitably, base oils with high saturates/paraffinic content may be also base oils with more than 95% saturates/paraffinic content. Suitably, base oils with high saturates/paraffinic content may be also base oils with 98% or more saturates/paraffinic content.

(3) As used herein, references to “paraffinic(s)” refer to alkanes, and references to “saturates” refer to carbon compounds devoid of double and triple carbon-carbon bonds. Preferably, the base oil comprises more than 90 wt. % of paraffins and more than 90 wt. % of saturates.

(4) As discussed earlier, at ambient temperature, and particularly at 0° C. and below, base oils with high saturates/paraffinic content can suffer from the undesirable presence of a waxy haze, and the inventors of the present method surprisingly discovered that the cloud point of base oils with high saturates/paraffinic content can be reduced to below 0° C. using a naphtha fraction. Suitably, the naphtha fraction is a Fischer-Tropsch process derived paraffinic fraction.

(5) It is known in the art that the Fischer-Tropsch process enables the manufacture of paraffinic molecules from gaseous hydrocarbon feedstock by first breaking down the hydrocarbon feedstock to carbon monoxide and hydrogen, then by building them up to larger paraffinic molecules, followed by subjecting the larger paraffinic molecules to hydroisomerization/hydrocracking whereby long chain normal-paraffins and slightly branched paraffins are removed and/or rearranged/isomerized into more heavily branched iso-paraffins.

(6) It is also known in the art that the more heavily branched iso-paraffins may be fractionated, such as by atmospheric distillation, to commercially useful fractions such as kerosene and diesel.

(7) The inventors of the present method surprisingly discovered that the naphtha fraction may be obtained from said atmospheric distillation, which is conventionally used to fractionate the more heavily branched iso-paraffins into, for example, kerosene and diesel.

(8) Suitably, the naphtha fraction that may be obtained from said atmospheric distillation comprises paraffinic molecules with boiling points less than 200° C. at ambient atmospheric pressure. Preferably, the lower boiling point fraction comprises paraffinic molecules with boiling points between 35° C. and 200° C., more preferably boiling points between 40° C. and 200° C., and even more preferably boiling points between 70° C. and 170° C., all boiling points being at around ambient atmospheric pressure. Preferably, the paraffinic naphtha fraction according to the present invention comprises less than 5 wt. % of aromatics and a content of paraffins of more than 90 wt. % according to ASTM D6839. More preferably, the paraffinic fraction comprises at least 90 wt. % paraffins, at most 5 wt. % aromatics and at most 1 wt. % olefins. Even more preferably, the paraffinic naphtha fraction comprises n-paraffins in a range of from 40 to 50 wt. %, iso-paraffins in a range of from 50 to 60 wt. %, naphthenes in a range of from 2 to 3 wt. % and aromatics in a range of from 0 to 0.1 wt. %.

(9) Suitably, the naphtha fraction comprises paraffinic molecules comprising carbon chain length of up to 11.

(10) Preferably, the naphtha fraction comprises paraffinic molecules comprising carbon chain length in the range of from 5 to 11, more preferably the naphtha fraction comprises paraffinic molecules comprising carbon chain lengths of from 6 to 10, even more preferably the naphtha fraction comprises paraffinic molecules comprising carbon chain lengths of from 6 to 9, and most preferably the naphtha fraction comprises paraffinic molecules comprising carbon chain lengths of from 6 to 8. Optionally, naphtha fraction may be a paraffinic molecule of carbon chain length of 7, such as heptane.

(11) Further, suitably, the naphtha fraction comprises paraffinic molecules of carbon chain length of 6, 7 and 8.

(12) Suitably, the naphtha fraction comprises paraffinic molecules of carbon chain length of either 5, or 6, or 7, or 8, or 9, or 10, or 11.

(13) Suitably, the naphtha fraction comprises a mixture of any combination thereof of paraffinic molecules of carbon chain length of either 5, or 6, or 7, or 8, or 9, or 10, or 11.

(14) Examples of the naphtha fraction a mixture of any combination thereof of paraffinic molecules of carbon chain length of either 5, or 6, or 7, or 8, or 9, or 10, or 11, may be for example, a paraffinic molecule of carbon chain length of 5 in a mixture comprising at least a paraffinic molecule of carbon chain length of 6, or 7, or 8, or 9, or 10, or 11; or paraffinic molecules of carbon chain length of 6 in a mixture comprising at least a paraffinic molecule of carbon chain length of 5, or 7, or 8, or 9, or 10, or 11; or paraffinic molecules of carbon chain length of 7 in a mixture comprising at least a paraffinic molecule of carbon chain length of 5, or 6, or 8, or 9, or 10, or 11; or paraffinic molecules of carbon chain length of 8 in a mixture comprising at least a paraffinic molecule of carbon chain length of 5, or 6, or 7, or 9, or 10, or 11; or paraffinic molecules of carbon chain length of 9 in a mixture comprising at least a paraffinic molecule of carbon chain length of 5, or 6, or 7, or 8, or 10, or 11; or paraffinic molecules of carbon chain length of 10 in a mixture comprising at least a paraffinic molecule of carbon chain length of 5, or 6, or 7, or 8, or 9, or 11; or paraffinic molecules of carbon chain length of 11 in a mixture comprising at least a paraffinic molecule of carbon chain length of 5, or 6, or 7, or 8, or 9, or 10.

(15) In the method of the present invention, the cloud point of the base oil with high saturates/paraffinic content is reduced to below 0° C.

(16) The method of the present invention comprises the steps of subjecting the base oil with high saturates/paraffinic content to a cloud point reduction step comprising mixing the base oil with high saturates/paraffinic content with a solvent mixture, wherein the solvent mixture comprises a naphtha fraction and a co-solvent, and subjecting the solvent treatment mixture to a solvent de-waxing step.

(17) Suitably, the co-solvent is methyl ethyl ketone. Suitably the co-solvent may also be methyl isobutyl ketone or methyl butyl ketone or methyl propyl ketone or methyl isopropyl ketone.

(18) In the method of the present invention, suitably the weight ratio of the naphtha fraction to the co-solvent in the solvent mixture is in the range of from 70:30 wt % to 30:70 wt % respectively. Preferably, the weight ratio of the naphtha fraction to the co-solvent in the solvent mixture may be in the range of from 60:40 wt % to 40:60 wt % respectively, and more preferably, the weight ratio of the naphtha fraction to the co-solvent in the solvent mixture may be 50:50 wt % respectively.

(19) In the method of the present invention, suitably the base oil with high saturates/paraffinic content is mixed with the solvent mixture in the weight ratio range of from 1:3 to 1:6 respectively at a temperature in the range of from 20° C. to 150° C. to provide a solvent treatment mixture.

(20) Preferably, the weight ratio in which the base oil with high saturates/paraffinic content is mixed with the solvent mixture is 1:4 respectively.

(21) Suitably, the temperature at which the base oil with high saturates/paraffinic content is mixed with the solvent mixture may be in the range of from 30° C. to 150° C.

(22) Suitably, the temperature at which the base oil with high saturates/paraffinic content is mixed with the solvent mixture may be also in the range of from 40° C. to 120° C.

(23) Following the mixing of the base oil with high saturates/paraffinic content with the solvent mixture, suitably the solvent treatment mixture is cooled to below at least 0° C. to obtain a mixture comprising a wax fraction and a de-waxed fraction, wherein the de-waxed fraction comprises the base oil with high saturates/paraffinic content and the solvent mixture. Preferably, the solvent treatment mixture is cooled to below −20° C. to enable the formation, and removal, of wax crystals.

(24) Preferably, the solvent treatment mixture is cooled to below −20° C. to enable the formation, and removal, of wax crystals.

(25) The wax crystals are removed from the solvent treatment mixture by subjecting the solvent treatment mixture to a mechanical treatment known in the art, such as by the use of a spinning drum to undertake a filtration process.

(26) Once the wax crystals are removed from the solvent treatment mixture, a de-waxed fraction remains, comprising the base oil with high saturates/paraffinic content and the solvent mixture.

(27) Suitably, the solvent mixture is removed from the de-waxed fraction by a distillation step to obtain a base oil with high saturates/paraffinic content with a cloud point below 0° C.