US1981758A - Process for dewaxing petroleum oil - Google Patents

Description

Nov. 20, 1934. H. SVANOE 1,

PROCESS FOR DEWAX ING PETROLEUM OIL Filed Aug. 24, 1951 1 UHDEWAXED OIL I 2 MIXING WITH THIHHIHG AND/0k DEWAXING AGENT CHILLING T0 32F AND LOWER 14: I RETURN or 4 DEWAXING AGENT 5 WAX SEPARATION WAX ADDITION OF EXTRACTING LIQUID CONTAINING SOME 12 DEWAXIHG AGENT EXCESS EXTRACTING 11 7 LIQUID REMOVED 5OLVEHT SEPARATION OF OIL g'fifimg 'g ff DY DISTILLATIOH LAYER AND SOLVfNTIAYERS DEWAXING AGENT 13 8 EXTRACTIHG OIL LAYER WASHED LIQUID CONDEHSATE WITH EXTRACTIIIEI LIQUID TRACES OFSOLVEHT REMOVED BY DISIILLATION OIL TO STORAGE INVENTOR. 7{an4, 5 trance Patented Nov. 20, 1934 UNITED STATES PROCESS FOR DEWAXING PETROLEUM OIL Hans Svanoe, Fairville, Pa.,- assignor to E; I. du Pont de Nemours & Company, Wilmington, Del., a corporationv of Delaware Application August 24, 1931, Serial No. 559,025

11' Claim.

This invention relates toa process for the dewaxing of oils and particularly to the separationv of mineral wax, such as paraffin, from a petro leum oil containing the same by chilling in the presence of a solvent.

In refining lubrication oil the crude is generally distilled to remove the lighter fractions. This treatment results in a concentration of the paraflin wax in" the residual heavy oils. A number of methods are employed for separating the wax from the oil, the nature of the process being governed by the grade of oil it is desired to produce. For example, if a medium pour test machine oil is to be prepared, the concentrate may 15 be diluted with naphtha, say 3 parts of naphtha to 1 part of oil, and the resulting mixture chilled to a few degrees below F., at which temperature a portion of the wax crystallizes out and is filtered and/or centrifuged from the oil. Owing to the solubility of the wax in the naphtha at this temperature, much remains in the finished oil. To obtain a zero pour test oil, the naphthaoil mixture must be chilled to very low temperatures, such as, for example, to F. or lower, an operation which is very expensive. The oil must also be very slowly cooled, due to the fact that rapid cooling of a naphtha-oil mixture separates a wax difficult and often impossible of separation from the mixture.

The great disadvantage inherent in the use of 30 naphtha per se as a dewaxing agent is due to its high relative solubility of the wax even at very low temperatures. To obtain by its use alone, therefore, a high-grade, wax-free oil is a very expensive operation.

An object of the present invention is to provide an improved process for the dewaxing of lubricating oils. Another object of the invention is to provide a wax-immiscible solvent for the dewaxing of lubricating oils whereby high-grade advantages will hereinafter appear. v

I have found that high-grade, substantially wax-free, lubricating oils canbe prepared from wax-bearing heavy oils by employing in con- 45 junction with naphtha a water-insoluble aliphatic' alcohol with -or without an organic liquid which is soluble in the. alcohol but substantially insoluble in mineral oil. By dewaxing with my dewaxing agents and by the processas willhereinafter be more fully described, high-grade oils can be obtained by chilling to but medium low temperatures; while if naphtha were the sole dewaxing agent, a lubricant containing a large amount of wax would be obtained under the same conditions.

lubricants can be produced, Other objects and I have made the surprising discovery that when naphtha 1 is mixed with a water-insoluble aliphatic alcohol in amounts ranging preferably from 20 to'80% naphtha, the solubility of the solution for the mineral oil wax is so markedly decreasedv that high-grade lubricating oils can be obtained from crudes, having high wax content, by chilling the crude oil-naphtha-alcohol mixture to temperature but slightly below 0 F. Without the presence of these alcohols, a considerably lower temperature is required to give as good a dewaxing.

Furthermore, I have found that the solubility of the naphtha for the mineral wax can be still further decreased by having present an organic liquid wax precipitating agent, such as methanol, ethanol, acetone, etc., in amounts up to organic liquid, lubricating oils of superior quality can be prepared at an extremely low cost.

I have developed a still further advantage which when utilized in my preferred dewaxing process, renders the separation of the solvents from the dewaxed oil more economical than the simple distillation processes which would ordinarily be used. This process may be more readily comprehended by reference to the accompanying fiow sheet divisions of which will hereinafter be referred to by numbers, and the following description of my preferred dewaxing process which is descriptive of one manner of carrying out my invention, but which will not limit in any way the scope thereof.

Un'dewaxed lubricating oil, such as residual unfiltered cylinder stock! (1) is diluted (2) wltlf my preferred dewaxing agent to give a mixture containing '70 parts by volume of the dewaxing agent to 30 parts by volume of the oil. The

resulting very fluid mixture is filtered through fullers earth and then chilled (3) as rapidly as desired to approximately 32 F. or lower, depending upon the grade of lubricating oil being made.- The precipitated wax is separated (4) from the oil-dewaxing agent mixture by filtration, gravity and/or centrifugal means. The dewaxing agent may be separated from the oil in any suitable manner, such as by distillation, extraction, etc., but I prefer to separate it by the following novel process.

An alcohol-miscible but oil-immiscible liquid, such as methanol, ethanol, acetone, or mixtures eat thereof, or a liquid having like qualities, is added (6), as an extracting liquid, to the mineral oildewaxing agent mixture until two layers separate. This will generally be effected, for example, when approximately 15% methanol has been added; on the other hand, 30% ethanol and 16% acetone are generally required to effect the desired separation. (The percentage is calculated as percentage by volume of the separating liquid to the total volume of mineral oil+dewaxing agent.) It is to be understood that the percentage may vary 5 to 10% either way, and in some cases more according to the type of oildewaxing agent mixture being treated. By adding methanol, an oil layer will separate (7) containing the major part of the original oil which can readily be decanted and washed with methanol (8) to recover the small amount of dewaxing agent contained therein, the methanol washings (15) being subsequently used with fresh extracting liquid. The last traces of the solvent may be, if thought necessary, stripped from the dewaxed lubricating oil by distillation (9). The thus purified and dewaxed oil may now be sent to storage (10).

The solvent layer may, if desired, be distilled (12) to remove the excess of the extracting liquid. Complete removal of the extracting liquid is not necessary, as will be more fully explained hereinafter. The extracting liquid condensate (13) may be employed for washing the dewaxing agent from the dewaxed oil layer and the dewaxing agent residue (14) used in the next batch of oil to be treated.

My dewaxing agent should contain such a proportion of naphtha and alcohol, or other suitable solvents, and be added to the crude oil in such amounts, that the desired dewaxing is effected at the highest temperature possible and the fluidity of the oil-dewaxing agent mixture at the precipitation temperature, i. e. the temperature at which the desired amount of wax has been separated, should be such that rapid and eflicient filtering and/or centrifuging operations may be effected. I have found that no optimum proportion can be given which will be satisfactory for all types of crude. It may be stated generally, however, than an oil to dewaxing agent ratio of from 1 to 1.5 to l to 5, with the mean ratio of 1 to 3 as usually most satisfactory, will give good results. My dewaxing agent may contain no naphtha but comprise only one or more water-insoluble alcohols, with or without an oil-immiscible organic liquid. As such a dewaxing agent is, under some conditions, not always sufiiciently fluid, I generally prefer to also have naphtha or like hydrocarbons pres- The percentage of naphtha in the naphthaalcohol dewaxing agent, may vary from approximately 20 to and when a wax precipitating agent is present the latter may constitute up to approximately 10% of the composition of the dewaxing agent. I have found it to be of advantage to use as the extracting liquid the same liquid that is present in the dewaxing agent as a wax precipitating agent. Methanol, ethanol, acetone and liquids which are substantially oilimmiscible and in which the wax is insoluble are well suited for this purpose. Their presence with the dewaxing agent tends to decrease the solu-' bility of wax in that agent, particularly at low temperatures. It is not necessary, therefore, to completely separate the extracting liquid from the dewaxing agent, after the latters decanta- I ter-insoluble alcohol.

tion from the oil, as up to 10% may be left with the dewaxing agent.

The water-insoluble aliphatic alcohols which I prefer to use are those containing seven or more carbon atoms and particularly mixtures of such alcohols. A mixture of alcohols of this nature which is particularly well-fitted for this work is the higher fraction of oxygenated organic compounds resulting from the catalytic hydrogenation of the oxides of carbon under pressure. In the organic synthesis described in the copending application of Roger Williams, Serial No. 185,339, a method of synthesizing such compounds is described. The organic compounds synthesized by this process cover a boiling rangeup to approximately 410 F. and include such alcohols as methyl, ethyl, propyl, butyl, amyl, hexyl, etc., the alcohols above ethyl having both straight and side-chain groupings. The fraction of this mixture which I prefer to use either alone or together with naphtha and/or an alcohol-miscible and oilimmiscible liquid, boils from approximately 290 F. up to approximately 410 F. and is substantially water insoluble.

The wax (5) separated by filtration or centrifugal means will contain, of course, some oil and dewaxing agent. I remove the oil by washing with the dewaxing agent, using the resulting oilcontaining dewaxing agent, without separation of the oil, for subsequent dewaxing treatment of the crude. The dewaxing agent remaining in the wax may be removed by simple evaporation.

As indicated in the above general process, I prefer to' add the naphtha and/or water-insoluble alcohols prior to the filtration of the crude. In 110 some instances, however, it may be advantageous to first thin the crude with naphtha. or other thinning agent and after filtration and prior to wax removal, add the required amount of the wa- There are numerous other substances which may be used-in lieu of naphtha such, for example, as ethylene chloride, benzol, butyl formate, etc. Any liquid which will give, at the temperature of precipitation of the wax, suflicient fluidity to the mixture, and preferably one in which the wax is substantially insoluble at that temperature, may be considered an equivalent thereof.

Various changes may be made in the process for dewaxing oils, or in the dewaxing agents or extracting liquids employed, without departing from this invention or sacrificing any of the advantages that may be derived therefrom.

I claim:

1. In a process of separating wax from a waxbearing oil, the steps which comprise diluting the oil with a dewaxing agent containing a mixture of water-insoluble alcohols boiling between ap proximately 290 F. and approximately 410 F.

and obtained by the catalytic hydrogenation of carbon oxides under high pressure, chilling the resulting mixture to a temperature of 32 F. or lower, separating the precipitated wax from the oil and dewaxing agent, and recovering the dewaxing agent from the oil and wax.

2. In a process of separating wax from a waxbearing oil, the steps which comprise diluting the oil with a dewaxing agent containing a mixture of water-insoluble alcohols boiling between approximately 290 F. and approximately 410 F. and obtained by the catalytic hydrogenation of carbon oxides under high pressure, and an alcohol-miscible and substantially oil-immiscible precipitating agent, chilling the resulting mixture in order to precipitate the wax, separating the pre- 150 chilling the resulting mixture to a temperature of 32 F. or lower, separating-the precipitated wax from the oil and dewaxing agent, and recovering the dewaxing agent from the oil and wax.

4. In a process of separating wax from a waxbearing oil, the steps which comprise diluting the oil with a dewaxing agent containing a mixture of water-insoluble alcohols, boiling between approximately 290 F. and approximately 410 F. and obtained by the catalytic hydrogenation of carbon oxides under high pressure, and naphtha mixture containing 20-80% naphtha, chilling the resulting mixture to a temperature of 32 F. or lower, separating the precipitated wax from the oil and dewaxing agent, and recovering the dewaxing agent from the oil and wax.

-5. In a process of separating wax from a waxbearing oil, the steps which comprise diluting the oil with a dewaxing agent containing a mixture of alcohols having a boiling range from approximately 290 F. to approximately 410 F., said alcohols having been obtained by the catalytic hydrogenation of a carbon oxide under high pressure, chilling the resulting mixture in order to precipitate the wax, separating the precipitated wax from the oil and dewaxing agent, and recovering the-dewaxing agent from the oil and wax.

6. In a process according to claim 1, after separating the precipitated wax, adding to the dewaxed oil an organic liquid which is soluble in the alcohol but substantially insoluble in the oil,

whereby the oil and dewaxing agent separate in two layers, and separating the oil layer from the layer containing the dewaxing agent.

7. In a process according to claim 1, after separating the precipitated wax, adding to the dewaxed oil an alcohol having less than'ioui' carbon atoms, wherebythe oil and dewaxing agent separate in two layers, and separating the oil layer from the layer containing the dewaxing agent.

8. In' a process according to claim 1, after separating the precipitated wax, adding to the dewaxed oil methanol, whereby the ofl and dewaxing agent separate in two layers, and separate ing the oil layer from the layer containing the dewaxing agent.

9. In a process according to claim v2, after separating the precipitated wax, adding to the dewaxed 611 an organic liquid which is soluble in the "alcohol but substantially insoluble in the oil,

whereby the oil and dewaxing agent separate in two layers, and separating the oil layer from the. layer containing thedewaxlng agent.

10. In a process of separating wax from a waxbearing oil, the steps which comprise diluting the oil with a dewaxing agent consisting of a mixture of oxygenated organic compounds boiling between approximately 290 F. and approximately 410 F. and obtained from the catalytic hydrogenationbf carbon oxides under elevated tem-, peratures and pressures, filtering the resulting mixture to precipitate the wax, and afterseparating the wax from the oil-dewaxing agent mixture, adding a given quantity of methanol to the mixture suilicient to separate the oil from thedewaxing agent and methanol.

11. In a process of separating the constituents 110 of a mixture containing an oil and a mixture of alcohols having a boiling range from approximately 290 F. to approximately 410 F., said alcohols having been obtained by the catalytic hydrogenation of a carbon oxide under high pressure, which comprises adding methanol to the mixture. J

HANS BVANOE.

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