US2185291A - Process for refining mineral oils - Google Patents

Description

Patented Jan. 2, 1940 UNITED STATES PATENT OFFICE PROCESS FOR REFINING MINERAL OILS No Drawing.

Original application November 6,

1933, Serial No. 696,910. Divided and this application January 19, 1938, Serial No. 185,690. In the Netherlands July 23, 1928 8 Claims. (01. 196-13) This invention relates to extraction methods of refining mineral oils, and is particularly concerned with methods for extracting such oils by means of a selective solvent in the presence of chloroform. This application is a division of our application, Serial No. 696,910, filed. November 6, 1933, on which Patent No. 2,124,606 was issued July 26, 1938.

It has been known in the art that crude petroleum oils, lubricating, transformer and spindle oils, kerosenes, heavy or light naphthas, etc, can

be separated into groups of components by ex-- traction with suitable selective solvents. A large number of such solvents are available for the purpose. The present invention is particularly (but not exclusively) directed to an improvement in methods of extracting mineral oils with furiural or acetone, which improvement is analogous to the one claimed for S02 in Patent No. 1,945,516, which issued upon our application, Serial No. 379,310, filed July 18, 1929, of which this is a continuation-in-part.

The invention is based on the discoverythat the extraction characteristics of substantially any solvent which is capable of separating a mineral oil into two component groups-one more soluble therein than the other-can be markedly modified by introducing chloroform into the extraction mixture.

The type of selective solvents whose efiectiveness as the extracting agents in refining mineral oils can be improved by practicing this invention is illustrated by liquid S02, furfural, and acetone. These specific examples represent, however, only typical solvents of a large number of known selective solvents capable of separating mineral oils into aromatic and non-aromatic components (sometimes referred to as naphthenic and paraffinic or as non-paraffinic and parafiinic) which solvents are intended to be within the scope of this invention.

Likewise, the auxiliary solvent, whose presence in the extraction mixture improves the efficacy of extraction consists predominantly of chloroform, i. e., it may consist entirely of chloroform or it may contain chloroform in admixture with minor proportions of such related solvents as ether, benzol or toluol, or with a relatively volatile liquid chemically or physically related to benzol, such as aromatic hydrocarbons, which related solvents usually are miscible in all proportions with the main solvent and can be relatively easily separated from the material being treated, for example by distillation, and have no detrimental efiect on the refined products.

It will be understood, therefore, that the pres ent invention is to include within its scope the extraction processes employing a selective solvent which may be a single substance or a mix: ture of suitable substances) and wherein extrac- 5 tion is carried out in the presence of an auxiliary solvent consisting predominantly of chloroform and having an action similar to that of benzol,

i. e., causing an increase in the efficiency of separating a mineral oil into its components, 10 which may be the naphthenic and parafiinic portions of the oil.

Generally speaking, the efficiency of extraction is determined by the solvent power and the selectivity of the solvent (or solvent mixture) with 16 regard to the components oi the mixture being extracted. The efiiciency may be measured by and compared with the relative yields of the raffinate of the desired purity in cases where the mass or volume of the main or selective solvent is -20 kept constant.

If the extraction efficiency is to be compared in cases where the relative yield is fixed, whilst also the mass or volume of the main or selective solvent is kept constant, then the quality of the 25 rafiinate may be taken as the measure of the efficiency. i

The efficiency of the various extractions may also be measured by comparing the extent to which the solvent is conserved, if the same raf- 30 finate is made with or without the useof the auxiliary solvent described in this specification.

By applying this invention, i. e., by using a main solvent in the presence of an auxiliary solvent, it becomes possible, therefore, in extracting .35 hydrocarbon oils to improve the quality and/or quantity of the raffinate and/or to conserve the main solvent.

The method of this invention also provides a means for improving mineral oils having rela 40 tively low contents of naphthenic (aromatic) components, which contents it is difficult or impossible to reducestill further by extraction with the main solvent alone.

The improved qualities of the raflinate may be 45 controlled, e. g., by determining the viscosity index, the no, or refractive index, or the stability against oxidation. All these properties are dependent on the ratio between aromatics (nonparaii'ins) and the parafiins.

The increased extraction efficiency of the mixed solvent process, as compared with the efficiency of the corresponding single solvent process, is apparently due to the favourable eifect of the mixed solvent on the distribution ratios of 55 the non-paraffinic and paraflinic components of the oil in the extract and raflinate phases; in other words, the content of the components pref erentially soluble in the selective solvent as compared with that in the rafiinate phase is increased in the presence of the auxiliary solvent, so that when a mixed solvent is used it becomes possible sometimes, under suitable temperature conditions, to produce from an oil a greater quantity of the raihnate, which is richer in parafiinic components than it would have been possible to obtain if only the main solvent were used.

From the nature of the auxiliary solvents it may be seen that their addition to the main solvent would normally produce a solvent mixture with a greater solvent power for the oil than that of the main solvent, so that the selectivity of the solvent and the yield of the rafilnate may be impaired, Although this is not necessarily a disadvantage, as a main solvent with an auxiliary solvent added thereto in any case will be useful in increasing the extraction efiiciency so far as the quality of the rafiinate is concerned, it is possible to improve this impaired selectivity by suitably lowering the temperature of extraction with the resultant additional increase in the, efficiency of extraction so far as, e. g., the yield of the rafiinate is concerned. In general, the extraction temperature is so selected as to create optimum conditions from the view points of' economy, yield, purity of the products, etc.

The operating details of putting the invention 1 into practice, such as temperatures, pressures, etc., may vary in different cases, depending upon specific properties of the substances used in each case, or may be controlled by some other consideration. For example with a so-called batchextraction the auxiliary solvent may be mixed with the oil undergoing treatment either before, or at the time the oil is contacted with the main solvent; the whole or a part of the auxiliary solvent may be mixed with the main solvent prior to contacting it with the oil.

It is preferable, although not necessary, to operate the process of this invention in a continuous countercurrent manner, i. e., passing the main solvent countercurrently to and in contact with the oil being extracted through a mixingse-ttling zone and adding at least a portion of the auxiliary solvent to the oil-main solvent mi;- ture at a point, or points, along the mixing-settling zone, and preferably at such a place where such an addition of the auxiliary solvent would be most eifective. The extract and raifinate phases are separated, usually by gravity, and the main and auxiliary solvents or the main solvent only are then removed from each of the phases by distillation (both solvents being removed together or in separate stages) or by some other suitable means. The separated solvents may be continually reused. The auxiliary solvent may be left in the raffinate if this solvent improves the quality of the raffinate, e. g., its anti-knock property in case of the extraction of relatively heavy hydrocarbons with the aid of benzol as a constituent of the auxiliary solvent.

In order to demonstrate the effectiveness of the new process the following example may be set forth.

A number of samples ofa lubricating oil having viscosity index 59 (indicating that the oil had a relatively high content of aromatics or a low content of parafiinic hydrocarbons) were thoroughly contacted with various quantities of furfural, of furfural-benzol, and of furfuralchloroform mixtures; in each case the raflinate (upper) layers were separated, and the viscosity and refracting indices of solvent-free portions (rafiinates) were determined. The following table contains the pertinent data:

These results show that the presence of an auxiliary solvent, such as benzol, or chloroform,

causes a marked improvement in the refined product; the results also demonstrate that non-parafiinic components are extracted in preference to parairlnic components when furfural-benzol mixture is used instead of furfural alone.

The following example further illustrates some of the effects of extraction temperature upon the efficiency of extraction when a motor oil having a viscosity index -5 is extracted.

Fur- Ben- Ohloro- Tempem' Ramnate Oil ture of arts fuml Z01 form Extracp parts parts parts tion 00 Percent Viscosity yield index These data demonstrate that the yield and the degree of refinement of the rafiinate may be controlled at will by regulating the extraction temperature and the relative quantity and the composition of the mixed solvent, and the selective solvent can be conserved, when used with an auxiliary solvent for producing the raffinate having a fixed viscosity index.

Similar results may be obtained when extracting mineral oils with other selective solvents, such as acetone, in the presence of an auxiliary solvent containing a predominant quantity of chloroform.

It has been also found that various mixtures of selective solvents, such, for example, as liquid SOs-flil'flll'tl, can be successfully used for extracting mineral oils in the presence of either chloroform or its mixtures with solvents or the type of benzol, as outlined heretofore.

While it is practical and may be desirable in some cases to carry out the extraction of mineral oils by means of the main and auxiliary solvents at such temperatures, at which the auxiliary solvent is only partially soluble in either the main solvent or the oil being extracted, or in both, it should be noted that the extraction. process of this invention may be operated at the temperatures at which the auxiliary solvent becomes miscible in all proportions with either the main, i. e., selective, solvent or the oil, or both.

The main solvents used in this extraction process to separate a mineral oil into two component groups as defined, have the common characteristic that, like liquid S02, acetone or furfural, at the extraction temperature they are completely miscible only with the non-paraffinic component group. With the parafiinic component group they are miscible only to a limited extent. Examples of suchlike selective solvents are: nitromethane, propionitrile, dimethyl sulphate, dimethyl sulphite, methyl formiate and several alcohols or esters at suitable temperatures.

With reference to what has been stated above in respect to the auxiliary solvents, it deserves notice that the particular effect of auxiliary solvents on the extraction efficiency is independent of the phenomenon of dilution of the mixture being extracted, which dilution may or may not take place, depending upon viscosities of theliquids involved. Therefore, the process is elfective not only with oils which may be viscous at extraction temperatures, but also with oils which are easy flowing or non-viscous at such temperatures. For example, when liquid S02 is used as 2! selective solvent, the extraction temperatures are relatively low, so that certain viscous oils may have to be diluted with light solvents, while less viscous oils can be extracted without being previously diluted. On the other hand, oil which may be regarded as being viscous at ordinary temperatures (say, over 80 seconds at 100 F. Saybolt Universal) would become easy flowing at the slightly elevated temperatures of extraction with furfural, for example, or some other selective solvent, so that their dilution for the purpose of reducing the viscosity would be unnecessary. The use of auxiliary solvents in these cases would serve only the purpose of improving the extraction efficiency through the effect of such solvents on the distribution of the components being extracted between the extract and rafrlnate phases, no dilution being necessary.

We claim as our invention:

1. In an extraction process for separating hydrocarbon oils into portions of different degrees of parafiinicity, the steps of bringing a liquid hydrocarbon oil into contact with a selective solvent for non-parafiinic hydrocarbons in the presence of chloroform, under conditions causing the formation of liquid extract and raffinate phases and separating the phases.

2. The process according to claim 1, wherein the oil is a mineral lubricating oil.

3. In an extraction process for separating hydrocarbon oils into portions of different degrees of paraffinicity, the steps of counterflowing' under extracting conditions streams of a liquid hydrocarbon oil fraction and a selective solvent for non-paraflinic hydrocarbon components of the oil, in the presence of chloroform, thereby forming liquid rafiinate and extract phases, and separating said phases from each other.

4. In an extraction process for separating lubricating mineral oils into portions of dilIer-ent degrees of paraffinicity, the steps of counterfiowing under extracting conditions concurrent streams of chloroform and a selective solvent for non-parafiinic hydrocarbon components of the oil, and a stream of liquid lubricating oil, thereby forming liquid rafiiuate and extract phases, and separating the said phases.

5. In an extraction process for separating a hydrocarbon oil into portions having different degrees of paraiiinicity, the steps of bringing a liquid hydrocarbon. oil into contact with furfural in the presence of an auxiliary solvent consisting predominantly of chloroform, under conditions causing the formation of liquid raffinate and extract phases, separating the said phases, the temperature of contact being lower than that required to produce a raflinate phase of the same quantity with the same relative quantities of furfural and oil in the absence of the auxiliary solvent. l

6. In an extraction process for separating a hydrocarbon oil into portions having different degrees of paraffinicity, the steps of bringinga liquid hydrocarbon oil into contact with acetone in the presence of an auxiliary solvent consisting predominantly of chloroform, under conditions causing the formation of liquid raffinate and extract phases, and separating the said phases, the temperature of contact being lower than that required to produce a raffinate phase of the same quantity with the same relative quantities of acetone oil in the absence of the auxiliary solvent.

'7. In an extraction process for separating a hydrocarbon oil into portions having different degrees of paraiiinicity, the steps of bringing a liquid hydrocarbon oil into contact with sulfur dioxide in the presence of an auxiliary solvent consisting predominantly of chloroform, under conditions causing the formation of liquid raftinate and extract phases, and (separating the said phases, the temperature of contact being lower than that required to produce a raffinate phase of the same quantity with the same relative quantities of sulfur dioxide and oil in the absence of the auxiliary solvent.

8. In an extraction process for separating a hydrocarbon oil into portions having difierent degrees of paraflinicity, the steps of contacting a stream of liquid hydrocarbon oil countercurrently with a stream of a selective solvent for non-paraffinic hydrocarbons under conditions causing the formation of liquid raifinate and extract phases in the presence of an auxiliary solvent ccnsisting predominantly of chloroform, a portion only of said auxiliary solvent being initially introduced into the counterflowing streams with the fresh selective solvent, and another portion being introduced into said streams at a point spaced from the point of introduction of the selective solvent in the direction of thepoint of introduction of the initial oil, and separating said phases, the temperature of the process being lower than that required to produce a raiiinate phase of the same quantity with the same relative quantities of selective solvent and oil in the absence of the auxiliary solvent.

JOHANNES ARNOLDUS BUCHEL. REYERUS NICOLAAS JAN SAAL.