US2054750A - Refining of petroleum oils - Google Patents

Description

Patented Sept. 15, 1936 REFINING OF PETROLEUM OILS Eric B. Hjerpe, Pittsburgh, and William A; Gruse,

' Wilkinsburg, Pa., assignors to Gulf Research &

' Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Application November 2, 1934, Serial No. 751,258

6 Claims, (Cl. 19617) This invention relates to the refining of petroleum oils and it comprises improved unitary methods of extracting and dewaxing such oils with the aid of solvents wherein the oil is first extracted with a mixture containing ethylene pletely refined oil, heretofore no single process 5 dichloride, benzol andSOz and then the refined. was avai ab e-by hi b of these refinements oil is dewaxed in the presence'of the benzol and Could be Obtain d n a S p unitary mannerethylene dichloride; the S02 being removed from Of course, the oil couldbe first dewaxed and then the oil after the mixture has been Stratified into refi d Vice Versa b tea 0f the p d e s an oil layer and a solvent layer but before the oil entirely ind pend nt of the other nd constitutes 1o diluted with the remaining solvents is subjected a Separate process employing distinct solvents or. to temperatures sufficient to precipitate the wax; Solvent mixtures- Further, the prior-dewaxing all as more fully hereinafter set forth and as a d Solvent x on Processes in commercial claimed. practice are subject to one or more disadvantages Some petroleum oils primarily are composed of r d ffi lt In y v n n pri practice, i

paraflinic oils, naphthenic oils and 'petrolatum which is av mixture of high and low melting waxes and resins. It is known that'by dewaxing the'oil and removing the poly-.naphthenic materials; oils improved for certain uses can be obtained.

Petroleum oil being more or less a heterogeneous mixture, its behavior when treated with solvents varies with the particular solvent. Some solvents such as benzol and naphtha arecomresidual solvent. An equivalent continuous process may be employed.

Although it is necessary to remove both thewax and the naphthenic bodiestov obtaina comwas necessary tocomplet'ely remove the dewaxing.

solvent before proceeding with the solvent extrac-. tion or vice versa. l V

By the present invention weobtain a substantially complete refining of the oil in an improved 2 manner which is free of the disadvantages and difficulties of the prior methods. In the present process the solvent extraction and the dewaxing are effectively correlated into a unitary. simple pletely miscible with the oil but when the solution Process having y tagesv is cooled the waxes or-petrolatum becomeinsol- In Livingstone Patent 1,343,636, an uble at certain temperatures and may be sepaadvantageous od of re' 0 W th a rated from the oil dilutediwith the solvent. such mixture of lo(in-Z01 and ethylene dichloride is solvents re known i t a t as good solvents closed. In the present processes, the principles because they hold the oil in solution even at low of that process used t0 advantage in a 3 temperature. plete process in refining the oil. .The present On the other hand thereis another class of sol- F P is in a Sense n improvement upon the vents which are not completely miscible with the Llvmgstone process" oil. Such solvents when admixed with the oil at 1 We have found that by extractmethe 011 Wlth elevated temperatures do form homogeneous a mixed solvent containing ethylene .dichloride, cible mixtures. But when the mixture is cooled benzol and improved Oils are obtained and below a definite miscibility temperature, it stratithe Oil layer, after SQPaIatiQH f t fi l fies into an oil layer and a solvent layer. The layer and removal of S02, Ideally l for poly-naphthenic portion of the oil is soluble in deWaXine by the procedures of the Livlhgstone th s 1 t and appears the Solvent wn patent since it constitutes a solution. of 011 to be 40 The paraffinie oil are 1 1 11 1 and constitute dewaxed in thesolvent of the Livingstone process. t of t 11 layer when it is form d Likewise the present methods constitute an 11: h b proposed t 'dewax petroleum oils improvement upon the solvent extraction methods by mixing the oil with such goodv solvents and disclosed and claimed in our copending applicacooling the mixture to precipitate the wax. The tions Serial 721,256 and 751,259- In serial wax is separated from the oil diluted with solvent 751,256 We disclose processes for extracting either by filter pressing or centrifuging, oils with ethylene dichloride wherein the ethylene Likewiseit has been proposed to refine 0115 by dichloride is mixed with the oil and the mixture solvent extraction using the other type of solvents coolefl to sultajble temperature to fafiect strain which function as differential solvents. In these 'g z s gi i g gzigg fizf g g gii i g 32 1; 3523353 3; 322 2? g zfi z figsg i gg ethylene dichloride and S02 are used in extracttemperaturesat which the oil layer and the sol- In the present invention We gain in addition f layer are o i l Alternatwelyi the to all the advantages of' our other processes deoil and solvent may be mixed at the temperature scribedrin said applications, further advantages t at which separation is to be effected, equilibrium and improvements 7 being a t y agitetioh- The Oil layer is s p- Oils have been extracted with S0; alone or in mated from the Solvent aye o ta ng eX- admixture with benzol, but. those processes have tracted naphthenic oil and the'oil layer freed of not been entirely satisfactory in commercial practice and do not give the advantages obtained in the present process.

Our composite solvent used for solvent extraction has many advantages. It is composed of ethylene dichloride, benzol and S02, each of these ingredients cooperating with the others in a correlated manner to give superior results. Our composite solvent easily penetrates the oil to give a substantially complete extraction of the naphthenic material. It is highly selective in its action and a maximum of naphthenic bodies is removed with a minimum loss of paraflinic oil in the present process.

In the present processes, the oil is mixed with the composite solvent and permitted to stratify.

After the oil layer has been stratified and separated from the solvent layer, the S02 can easily be removed, leaving an oil dissolved in the ethylene dichloride-benzol mixture. This solution might be submitted directly to chilling and Wax separation, but for proper drainage of liquid from the wax crystals it is desirable to increase the proportion of ethylene dichloride-benzol mixture present.

The miscibility temperature of our new composite extraction solvent is such that it can be easily mixed with the oil at ordinary temperatures and then stratified directly. Thus, solvent extraction can easily be first performed and then the oil dewaxed in a simple unitary manner fully utilizing the advantages of these particular solvents.

In practicing the present processes, the oil is mixed with a composite solvent containing ethylene dichloride, benzol and liquid S02 at ordinary temperatures, usually 75 F. The mixture is permitted to stratify into an oil layer and a solvent layer and the oil layer is separated from the solvent layer. The oil layer may be subjected to one orv more similar extractions, or the process may be a continuous one, as for instance by the countercurrent method.

The final rafiinate layer so obtained (oil layer) is then flash distilled in a vacuum to remove S02. The raffinate solution so obtained, which is substantially free of S02, is then diluted with more of the composite solvent, usually a :30 mixture of ethylene dichloride and benzol. The diluted mixture is then cool-ed to temperatures suflicient to precipitate the wax. The wax is filtered ofi and the filtrate is then freed of solvent by distillation.

In these processes, a composite solvent containing 70 parts of ethylene dichloride and 30 parts benzol is advantageous. However, that ratio may be varied and composite solvent mixtures containing ethylene dichloride and benzol in ratios between 90:10 and 50:50 can be used.

Of course, the amount of sulfur dioxide added to the composite solvent to produce the mixed solvent necessary to effect stratification, may be varied in commercial operation. It is advantageous to use suflicient sulfur dioxide to give sulfur dioxide-ethylene dichloride ratios between 10 and 50:50. An advantageous mixed solvent useful in the extraction step has the following compositionc-Zl parts of ethylene dichloride, 9 parts of benzol and '70 parts of S02.

The oil layer which is subjected to the dewaxing operation is the oil layer obtained in the stratification step after the S02 has been removed. It contains some ethylene dichloride and benzol in approximately the original ratio; in removing theSOz, some of the composite solvent is lost but the ratio of its components is not Inaterially changed; this may be adjusted if necessary. In dewaxing, it is advantageous to obtain a dilute oil in which the diluent solvent contains ethylene dichloride and benzol in approximately the ratio 70:30. In the usual practice, the ethylene dichloride is present in major amounts.

In these processes, the solvent extraction or stratification can be effected at temperatures between 0 F. and 125 F.

In the dewaxing step, lower temperatures are used. Dewaxing may be effectively obtained at temperatures between -30 F. and +10 F. The temperature to be employed will depend on the extent of wax removal desired. To obtain an oil with a pour point of 0 F. a filtering temperature of minus 5 F. to minus 10 F. is suitable.

In these processes, an improved dewaxed refined oil is obtained and as byproduct, there is also obtained petrolatum or waxes and a useful naphthenic oil. The solvent removed from the oil layer and from the solvent layer by distillation is recovered and re-used in the processes.-

This invention is broadly applicable to refining petroleum oils and various embodiments thereof may be used in refining particular oil stocks to produce special refined oils. One advantageous embodiment of this invention which is typical and illustrative is as follows:-

Example 1 parts of overhead cylinder stock from Oklahoma crude is mixed at 75 with 9 parts of benzol, 21 parts of ethylene dichloride, and 70 parts of liquid S02. After a homogeneous mixture is obtained, it is permitted to stand until clean stratification into an oil layer and a solvent layer is obtained. Usually a half hour at 75 F. is sufficient.

After stratification, the lower solvent layer is drawn off. The upper oil layer remaining in the apparatus is subjected to three more extractions in the same manner.

The final raffinate so obtained (upper oil layer) is then flashed at 75 F. in a vacuum of 50mm. to remove practically all the S02. The oil layer so obtained is then ready to be dewaxed.

The oil layer so freed of S02 is then mixed with 300 parts of a 70:30 mixture of ethylene dichloride and benzol. After a homogeneous mixture is obtained, it is cooled to 0 F. over a period of 2 hours. By this treatment the wax is rendered insoluble and is precipitated. The so cooled mixture is then filter-pressed at about 0 F. to remove the wax. The filtrate separated from the wax is then freed from the dewaxing solvent by distillation up to 400 F. to obtain an improved dewaxed refined oil. Fifty-six parts of a refined oil are obtained.

The improvement in the oil obtained by these processes is clearly discernible by comparison of its properties with those of the oil stock, as follows:

The solvent contained in the solvent layer in the extraction step is likewise recovered by distillation. The recovered solvent is re-used in the process. As byproduct, there is recovered from this distillation 35 parts of useful naphthenic oil.

Also, from the filter pressing operation, there is recovered 9 parts of useful petrolatum. This petrolatum can be further refined to obtain several gradesrof commercial wax.

In the commercial practice of these processes, suitable heat exchange is effected between the cold liquids and the hot liquids and vapors incident to the process.

In lieu of the exact procedure employed in the example given ante, the process may be varied as has been indicated in the foregoing disclosure, if desired.

The present processes are particularly advantageous for refining of relatively parafi'lnic stocks moderately low in wax content. With such stocks the extraction can be effectively performed at say about 75 F. and then the rafiinate dewaxed at a suitable temperature without precipitating oil with the wax, by these unitary processes, as described in detail ante.

What we claim is:

1. The process of refining petroleum oils which comprises first extracting the oil at a relatively high temperature with a composite solvent comprising ethylene dichloride, benzol and S02, separating the resultant oil and solvent layers, then removing S02 from the oil layer and chilling the resultant substantially SOz-free mixture to a relatively low temperature at which wax will precipitate and removing the precipitated wax from the oil in the presence of ethylene dichloride and benzol.

2. The process of claim 1 wherein said extraction is effected at temperatures between 0 F. and 125 F. and said dewaxing is effected at temperatures between 10 F. and minus 30 F.

3. The process of claim 1 wherein said mixed solvent contains ethylene dichloride and benzol in ratios between 90:10 and :50, said mixture containing suificient $02 to cause clean stratification at the extraction temperature, the ratio of $02 to ethylene dichloride being between 90: 10 and 50:50.

4. The process of claim 1 wherein during said dewaxing suflicient benzol is present in addition to the ethylene dichloride to prevent co-precipitation of paraffinic oil with the wax.

5. As an improvement in refining petroleum oils by which extraction and dewaxing with solvents is efiected in a unitary manner, the improved process which comprises extracting the oil at about 75 F. with a mixed composite solvent comprising 9 parts benzol, 21 parts ethylene dichloride and '70 parts S02, separating the oil layer from the solvent layer thus formed, removing the S02 from said oil layer, diluting the so treated oil layer with additional amounts of a mixed solvent comprising parts of ethylene dichloride and 30 parts of benzol, cooling the diluted mixture to approximately 0 F., separating the wax from the oil diluted with said composite solvent at said temperature and distilling the filtrate thus obtained to remove the said composite solvent and recover an improved dewaxed refined oil.

6. The process of refining petroleum oils which comprises first extracting the oil with a composite solvent comprising ethylene dichloride, benzol and S02, separating the resultant oil and solvent layers, flashing the oil layer after said separation to remove S02 therefrom, adding ethylene dichloride and benzol to the material from which S02 has been removed, and chilling the resultant mixture of paraflinic oil, ethylene dich1oride and benzol to a relatively low temperature to precipitate wax therefrom, and finally separating the thereby precipitated wax from the refined oil.

ERIC B. HJERPE. WILLIAM A. GRUSE.