US2293162A - Solvent for dewaxing - Google Patents

Description

Patented Aug. 18, 1 942 SOLVENT FOR DEWAXING James V. Montgomery, Okmulgee, kla., Luke B. Goodson, Phillips, Tex., and- Robert W. Henry, Bartlesville, 0kla., assignors to Phillips Petroleum Company, a corporation of-Delaware No Drawing.

10. Claims:

This invention relates to the dewaxing of mineral oils and more particularly it relates to improved dewaxing solvents involving the use of hydrocarbons or hydrocarbon naphthas as a principal component thereof.

The use of petroleum hydrocarbons, particularly straight run naphthas, as diluentsfor wax containing oils in dewaxing processes has long been known. However, the use of these hydrocarbon solvents, with the exception of propane, has been limited to cold settling or centrifuging processes, either of which results in a comparatively poor separation between the oil. and wax. Furthermore, unless the solution to be dewaxed is slow chilled at a rate not exceeding 3 to 4 F. per hour, the wax crystals are small and poorly defined, which form makes them difficult to remove from the chilled oil-solvent solution. We have found it impossible to remove such wax crystals'by filtration methods even when the solutions are slow chilled under the most carefully controlled conditions. A, further disadvantage in using petroleum naphthas is the fact that these naphthas have such high solvent power for the wax component as well as the oil component even at the low temperatures necessarily employed, that suff cient wax remains in the solution to give pour points as much as 50 F. above the dewaxing temperature.

Acetone, methyl ethyl ketone and/or other aliphatic or aromatic ketones, furfural, nitrobenzene, pyridine, etc., are well known wax antisolvents. However, none of these antisolvents, when used with naphthas possess the proper degree of solvent action to give a dewaxing solvent which may be used with oils of different qualities or under a wide range of operating conditions. When a strong wax antisolvent such as acetone is blended with straight run naphtha, the low solvent power of the acetone for'oil makes it impossible to use sufficient acetone in the solvent mixture to lower the dewaxing differential appreciably without causing a phase separation which renders dewaxing difficult and expensive. Likewise, when a comparatively weak wax antisolvent such as pyridine or picolines is blended with naphtha, an excessive amount of said antisolvent is required to offset the high solventpower of the naphtha for wax. For illustration: (1) One volume of treated dewaxedMid-Continent residuum lube stock of 90 seconds Saybolt Universal viscosity at 210 F. and 85 viscosity index was mixed with one volume of solvent composed'of 80% of straight run naphtha and of acetone. On chilling, a phase separation occurred at +20%.

Application November 25, 1940 Serial No. 367,136.

(2) One volume of treated waxy Mid-Continent lubricating oil stock of '70 seconds Saybolt Universal viscosity at 210 F. and viscosity index was blended with three volumes of a solvent composed of 50% naphtha'and 50% picolines. The blend was warmed to insure complete solution, shock chilled to -25 F'., filtered, and the,

solvent removed by distillation. An oil having a pour, point of +l5 F. was obtained.

Thus, it can be seen from these illustrations that such single antisolvents are not suitable for use withnaphthas. However, by using a third solvent, one that possesses antisolvent powers for wax and a comparatively high solvent power for -oil, it is possible to use these abovementioned antisolvents with petroleum naphthas. A blend of acetone or other strong antisolvent, naphtha and such a solvent will give a solvent mixture which can be easily changed to meet the requirementsof different oils.

An object of this invention is to provide an improved solvent for the dewaxing of lubricating and other oil stocks.

Another object of this invention is to provide a dewaxing solvent in which oil and wax are miscible at normal atmospheric temperatures and in which the oily constituents are miscible at dewaxing temperatures.

Still another-object of this invention is to provide a new solvent mixture containing petroleum hydrocarbons as a principal component thereof which may be used for the dewaxing of mineral oils by shock chilling and filtering.

Still other objects and advantages will be apparent tothose skilled in the art from a study of the. following disclosure.

We have found that the saturated and partly saturated heterocyclic nitrogen bases such as piperidine, pipecoline, pyrroline, pyrrolidine, pyrazoline, pyrazolidine, etc., derivatives and homolog's thereof, possess solvent powers and other properties which make, them valuable for use in connection with petroleum naphtha and wax antisolvents; these compounds have such a high solvent power for oil that they offset to a remarkable degreethe low oil solvent powers of such strong wax antisolvents as acetone, methyl ethyl ketone, other. aliphatic ketones, aniline, furfural, nitrobenzene, etc., thus making it possible to use sufiicient quantities of said antisolvent to lower the dewaxing differential to 5 F. or less. The following examples illustrate the Wide range in the different types of oil which may be successfully dewaxed when using a solvent composed of petroleum naphtha, acetone and pipecoline.

Example I One volume of treated dewaxed Mid-Continent residuum lube stock of 90 seconds Saybolt Universal viscosity at 210 F. and 85 viscosity index was mixed with one volume of a solvent composed of 50% of straight run naphtha, 20% of pipecoline, and 30% of acetone. On chilling, a phase separation occurred at +11 F.

Example II One volume of the same lube stock as in Example I was mixed with one volume of a solvent mixture composed of 30% of straight run naphtha, 40% of pipecoline, and 30% of acetone. On chilling, a phase separation occurred at 11 F. These miscibility relations show how the properties of the solvent may be changed, and, even though the above examples are limited to one type of oil, it is evident that the solvent may be easily varied to meet the requirements of different oils.

We have also found it possible to use these solvents composed of naphtha, pipecolines, and acetone or other wax antisolvent, under a wide range of operating conditions. By operating conditions, such variables as solvent to oil ratio, cooling rate, blending temperature, etc., are included, We have found that 3 t l solvent to oil ratios give good results and that excellent filter rates can be obtained even when the solution mixtures are shock chilled as in Carbondale chillers. Using these solvents as described below Will give substantially wax-free oils having low pour points.

The following example will serve to demonstrate one phase of our invention.

Example III One volume of treated Waxy Mid-Continent lubricating oil stock of '70 seconds Saybolt Universal viscosity at 210 F. was mixed with three volumes of a solvent composed of 30% of straight run naphtha, 35% of pipecolines,:and 35% of acetone and the mixture heated to insure rapid and complete solution. The mixture was then shock chilled to F. to precipitate the wax and filtered in a conventional manner with an excellent filter rate. After removing the solvent by distillation, oil having a pour point of +5 F. was obtained.

The wax crystals obtained from chilled solutions of waxy oil in our solvent are large, well defined crystals which do not tend to pack into an amorphous mass as do those obtained when naphtha alone is used as a diluent. This superior crystalline structure, which permits excellent filter rates, coupled with the decrease in refrigeration costs due to the superior dewaxing differential and shock chilling, results in a marked decrease in overall dewaxing costs. A further advantage in using our solvent is that essentially oil-free wax cakes are obtained with Y a minimum of washing. This results in a marked increase in oil yields as well as a decrease in solvent costs.

Furthermore, we have found that solvent blends using unsaturated hydrocarbons such as amylene, hexylene, etc., and saturated hydrocarbons such as pentane, hexane, etc., may be used instead of straight run naphtha. The unsaturated hydrocarbons such as amylene, hexylene, etc., or mixtures thereof, offer an advantage in that they possess a higher oil-solvent power without the usual corresponding increase in Wax solvent power,

The following examples demonstrate this phase of our invention.

Example IV One volume of treated waxy Mid-Continent lubricating oil stock of 70 seconds Saybolt Universal viscosity at 210 F. was mixed with three volumes of a solvent composed of 30% of mixed amylenes (50% of trimethyl ethylene and 50% of pentene-Z), 35% of pipecoline, and 35% of acetone. The mixture was shock chilled to 0 F. to precipitate the wax and filtered in a conventional manner with an excellent filter rate. After removing the solvent by distillation, an oil having a pour point of +5 F. was obtained.

Example V One volume of the treated waxy Mid-Continent lubricating oil stock of Example IV was mixed with three volumes of a solvent composed of 30% of pentane, 35% of pipecoline, and 35% of acetone, and mixed thoroughly. The mixture was then shock chilled to 0 F. to precipitate thev wax and filtered in a conventional manner with an excellent filter rate. After removing the solvent by distillation, an oil having a pour point. of +15 F. remained. Likewise, it should be un-- derstood that such solvents as cracked naphthas,', hydrogenated naphtha extracts, etc., may be used in the same manner as the abovernentioned hydrocarbon diluents.

This invention is not to be limited in any manner by the above examples which are given for illustration only. It should be understood that the saturated and partly saturated heterocyclic nitrogen bases including such compounds as: piperidine, pyrroline, pyrrolidine, hydrogenated pyridines, pyrazoline, pyrazolidine, etc., and their alkyl derivatives such as the pipecolines,, methyl pyrrolidines, etc., or such as exist'with-- in suitable melting point range for use at dewax-- ing temperatures, or within suitable boiling point; range as to permit separation from the 'oil and: wax without decomposition, are suitable within: degree for use in our process as herein disclosed. Obviously, mixtures of any or all of the abovementioned compounds are suitable as well as the individuals. Such mixtures may be obtained by hydrogenation or partial hydrogenation of commercial pyridines, picolines, or selected fractions thereof, selected cuts of nitrogen compounds from coal tar oils, or hydrogenation of the nitrogen bases recovered from petroleum. A convenient method of obtaining useful dewaxing solvents consisting of blends'of saturated and partially saturated heterocyclic nitrogen bases in pyridine, picoline, or selected fractions thereof, etc., is to hydrogenate the said pyridine, picoline or selected fractions thereof, etc., in such a man ner as to produce a mixture of hydrogenated, partly hydrogenated and unhydrogenated materials.

It is also possible to use the unsaturated heterocyclic nitrogen bases such as pyridine, picolines, etc., but in such cases a greater differential between dewaxing temperatures and pour points of the dewaxed oils results from the comparatively low oil solventpower of the pyridine, picolines, etc., which limits the proportion of acetone or other wax antisolvent which may be used. For illustration: One volume of treated WaxyMid- Continent lubricating oil stock of 70 seconds Saybolt Universal viscosity at 210 F. was mixed with. 1 three volumes of a solvent composedofv 50% of straight run naphtha, 30% of picolines and 20% ,of acetone, and, the mixture ,heated to; n r rapid and complete solution. The mixture was thenshock chilled to, F. ,toprecipitatethe wax and filtered in a conventional manner. After removing the solvent by distillation, an oil having a pour point of +15 F. remained.

We have found that the aforementioned hydrogenated and partially hydrogenated heterocyclic nitrogen base compounds and petroleum naphthas or hydrocarbons may be used with acetone as a wax antisolvent, or other wax antisolvents such as methyl ethyl ketone, diethyl ketone, dipropyl ketone, dibutyl ketone, or other aliphatic ketones, pyridine, .picolines, furfural, aniline,

.nitrobenzene, etc., with exceptionally good results. i In carrying out our invention, we do not wish to be limited by any special type of dewaxing apparatus, since essentially standard dewaxing equipment is satisfactory. For dewaxing of the abovementioned Mid-Continent lubricating oil stock at 0 F., for example, one volume of the oil to be dewaxed is mixed with three volumes of solvent as hereindisclosed, the mixing being carried out inessentially any type of mixer at slightly elevated temperature, say 120 to 140 F., to insure complete and rapid solution. The warmed oil-solvent solution is shock chilled to 0 F., as in Carbondale chillers, and filtered in conventional filters. The filtration is rapid since the wax crystals formed in our solvent are distinct and sharp-edged and do not form an amorphous mass in the filters. The wax cakes may be washed with additional solvent at dewaxing temperature to remove adhering oil-solvent solution, and the combined filtrate solution and washings comprising dewaxed oil and solvent mixture are conducted to a solvent-oil separating apparatus. This separating apparatus may comprise a conventional pipe heater and fractionating tower from which solvent mixture is removed overhead as vapors and the oil passes from the lower portion thereof and is conducted to storage. The solvent vapors from the above-mentioned fractionator are condensed and led to intermediate storage preparatory to reuse.

By using our solvent compounds or compositions as described above, we obtain substantially wax-free oils having pour points from 5 to 15 F. above the dewaxing temperatures, and in every case the pour points are Well within the range of effectiveness of commercial pour point depressors.

We have found it possible to use these saturated and partly saturated heterocyclic nitrogen bases with diluents and wax antisolvents under a wide range of operating conditions. By operating conditions such variables as solvent mixture to oil ratio, solvent to wax antisolvent ratio, cooling rate, blending temperature, etc., are included. To one skilled in the art, it will be apparent that our solvents may be used in a wide range of solvent to oil ratios, as well as differentconcentrations of the components comprising the solvent, depending upon the nature of the oil to be dewaxed and on the method of separating the wax from the solution. The use of a 3 to 1 solvent mixture to oil ratio gave good results regarding pour point of the finished oil and filter rates of the chilled oil-solvent-wax mixture. Good filter rates are made possible since the wax crystals are large and sharply defined. The boiling points of our saturated and partly saturated heterocyclic nitrogen base materials are sufiiciently low as to permit complete separation of solvent from oil,

' and solventfrom wax fractions without decomposition or deterioration in any manner.

To those skilled in the art, many applications and uses of the above-disclosed solvents will be apparent and we do notwish to be limited by the particular examples given since many materials and combi-nationof materials having the abovedescribedcharacteristics and properties may be successfully employed in practicing our invention and yet remain within itsintended scope, and we wish to belimited only by the following claims.

We claim;

1. The process of. dewaxing mineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising three components, namely, a petroleum naphtha solvent, a wax antisolvent, and athird component possessing combined oil solventjproperties and wax antisolvent properties, said third component being selected from a group consisting of saturated and partially saturated heterocyclic nitrogen bases,

chilling the mixture of oil and dewaxing solvent to precipitate the wax, and removing the precipitated wax.

2. The process ofdewaxing mineral oils including the steps of mixing thewaxy oil with a dewaxing solvent comprising three components, namely, a petroleum naphtha solvent, a wax antisolvent, and a third component possessing combined oil solvent properties and wax antisolvent properties, said third component being a hydrogenated commercial pyridine, chilling the mixture of oil and dewaxing solvent to precipitate the wax, and removing the precipitated wax.

3. The process of dewaxing mineral oils including the steps of mixing .the waxy oil with a dewaxing solvent comprising three components, namely, a straight run petroleum naphtha solvent, a wax antisolvent in which the antisolvent is acetone, and a third component possessing combined oil solvent properties and wax antisolvent properties, said third component being a hydrogenated commercial pyridine, chilling the mixture of oil and dewaxing solvent to precipitate the wax, and removing the precipitated wax.

4. The process of dewaxing mineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising three components, namely, a cracked petroleum naphtha solvent, a wax antisolvent in which the antisolvent is acetone, and a third component possessing combined oil-solvent properties and. wax antisolvent properties, said third component being a hydrogenated commercial pyridine, chilling the mixture of oil and dewaxing solvent to precipitate the wax, and removing the precipitated wax.

5. The process of dewaxing mineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising three components, namely, a petroleum naphtha solvent, a wax antisolvent, and a third component possessing combined oil solvent properties and wax antisolvent properties, said third component being a selected fraction of hydrogenated commercial pyridine, chilling the mixture of oil and dewaxing solvent to precipitate the wax, and removing the precipitated wax.

6. The process of dewaxing mineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising three components, namely, a straight run petroleum naphtha solvent, a wax antisolvent in which the antisolvent is acetone, and a third component possessing combined oil solvent properties and wax antisolvent properties, said third component being a selected fraction of hydrogenated commercial pyridine, chilling the mixture of oil and dewaxing solvent to precipitate the wax, and removing the precipitated wax. '7. The process of dewaxingmineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising three components, namely, a cracked petroleum naphtha solvent, a wax antisolvent in which the antisolvent is acetone, and a, third component possessing combined oil solvent properties and. wax antisolvent properties, said third component being a selected fraction of hydrogenated commercial pyridine, chilling the mixture of oil and dewaxing solvent to precipitate .the wax, and removing the precipitated Wax. I

8. The process of dewaxing mineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising three components, namely, a petroleum naphtha solvent, a wax antisolvent, and a third component possessing combined oil-solvent properties and wax antisolvent properties, said third component being pipecoline, chilling the mixture of oil and dewaxing solvent to precipitate the wax, and removing the precipitated wax.

' 9. Th process of dewaxing mineral oils includ--' ing the steps of mixing the waxy oil with a dewaxing solvent comprising three components, namely, a straight run petroleum naphtha, a wax antisolvent in which the antisolvent is acetone, and a third component possessing combined oil-solvent properties and wax antisolvent properties, said third component being a pipecoline, chilling the mixture of oil and dewaxing solvent to precipitate the wax, and removing the precipitated wax. V

10. The process of dewaxing mineral oils including the steps of mixing the waxy oil with a dewaxing solvent comprising three components, namely, mixed amylene solvent, a wax antisolvent in which the antisolvent is acetone, and a third component possessing combined oil-solvent properties and wax antisolvent properties, sai l third component being a pipecoline, chilling t mixture of oil and dewaxing solvent to precipitat the wax, and removing the precipitated wax. i

JAMES V. MONTGOMERY. LUKE B. GOODSON. ROBERT W. HENRY.