US2143474A - Treatment of residual oils - Google Patents

Description

Patented Jan. 10, 1939 TREATMENT OF RESIDUAL OILS H. Carmody, Pittsburgh, Pa., assignor to The Neville Company, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application November 3, 1936, Serial No. 108,963

3Claims.

This invention relates to the treatment of still residues recovered in the purification and refining of light oils obtained in the operation of byproduct coke ovens, and a major object of the 5 invention is to provide a simple, efficient and easily performed method of converting such materlal into products of greater utility.

The term pure still residues as used herein has reference to material recovered from still resl idues produced in the recovery of coke oven light oils. In the high temperature carbonization of coal in by-product coke ovens the common practice is to scrub out the light oils from the gases with a high boiling petroleum wash oil thus prol ducing a. solution of the aromatic light oils in the wash oil. .This is then distilled to give a mixture of light oils, chiefly benzol, toluol, xylol, and solvent naphtha, which mixture is then fractionated to obtain the individual constituents as 201 somewhat impure cuts of rather narrow boiling range. a

The crude fractions, or cuts, are then commonly acid washed by vigorously agitating them with a small amount of strong sulfuric acid,

. 25 which polymerizes the unsaturated constituents and produces a mixture of high boiling oils and resinous bodies, and because the temperature is not controlled in this step, rise in temperature may cause other reactions to take place with for- 80 mation of other oils and resins. After separation from the sulfuric acid stratum, the oil is then washed with alkali, to neutralize acid, following which it is distilled to produce commer: cially pure solvent, leaving in the still a residue 88 of a mixture of the polymers and high boiling oils referred to. Commonly sufiicient solvent is left in the residue to permit it to be removed from the still and handled in the liquid state.

These residues of polymers and high boiling 40 oils from the various cuts are then combined and subjected to distillation to strip out all of the content of solvent oil, such as benzol and the like. The residue from this operation forms what is known in the trade as pure still residue. It com- 46 prises chiefly polymers of unsaturated com- I pounds, appearing chiefly as resins, and other reacted bodies appearing as high boiling oils. Resolution of this mixture into its individual components has not been possible heretofore, at least 50 by ordinary or commercially practicable means, and the material has been of low market value, being either disposed of conveniently by adding it to coke oven tar, or burned as a fuel, for lack of a more profitable mode of handling it.

I! In my copending application Serial No. 85,747,

filed June 17, 1936, I have disclosed and claimed a process of treating such pure still residue for the recovery of products of increased value. According to that process the still residue is steam distilled, for instance at 300 C., to strip it of 5 its content of high boiling oils. Thereby there is obtained a distillate consisting of the oils and water, and a resinous residue. The oil in the condensate is separated from the water, preferably by heating the mixture almost to the boiling in point of water, and allowing it to stand for settling, following which the water is drawn off from the supernatant oil layer. The oil is then heated somewhat above the boiling point of water,

say to a temperature above 100 and not exceeding about 150 C., whereupon the residual water in the oil distills ofi together with a small amount of low boiling light gravity distillate.

The oil remaining in the still is now dry and may be fractionated, suitably after addition of caustic soda in an amount at least sufficient to combine with free acid contained in the oil. The distillation is carried out at atmospheric pressure, or under slightly reduced pressure. The distillate may be separated into more or less definite cuts having useful solvent action. For instance, in treating still residue from one source the out boiling from 150 to 200 C., which may amount to about 10 per cent of the oil,.has a sharp characteristic odor resembling that of hen Z01 fore-runnings or cyclopentadene; this may be considered a crude solvent naphtha. A second cut boiling from 200 to 250 C. affords a light amber colored oil which possesses a characteristic odor that can be described as sour or musty. It is lighter than water, from which "it separates readi1y, an'd it may amount to about 15 per cent of the original oil. The properties of this oil are similar to those of the cut boiling from 275 to 300 C., constituting about 60 per cent of the 40 original dry oil, which has a specific gravity of about 0.98, and an aniline point of 26 C., indicating that the oil is of aromatic character and of high solvent power. Finally, there is obtained a cut boiling from 300 to 360 C., which is rather viscous and constitutes about 15 per cent of the original dry oil. Above 360 C. decomposition occurs.

, The aniline points referred to herein were determined in accordance with the method used by The Neville Company,-of Pittsburgh, Pa. In accordance with this method there is prepared a test mixture by weighing into a small flask, say of to ml. capacity, 10' grams of the material whose aniline polnt is to be determined and 55 to M 20 grams of a standard petroleum benzine diluent. The two materials are mixed thoroughly and 2.5 ml. of the test mixture are pipetted into a test tube of about ,41 or M; inch diameter and 5 6 or 7 inches in length into which there has been placed 5 ml. of freshly distilled. reagent quality aniline, which should be of pale yellow color. "Into the mouth of the test tube there is placed a vented cork stopper carrying a thermometer 10 having a suitable scale, say minus 30 C. to plus 50C. The thermometer is adjusted so that the bulb is completely covered by the solution but does not quite touch the bottom of the test tube. The mixture is then warmed gently with constant I agitation until it becomes entirely homogeneous.

It is then cooled slowly and carefully with constant agitation until the solution becomes just sufficiently cloudy-to obscure the outline of the thermometer bulb. This temperature is recorded. There is then added an additional05 ml. of the test mixture, and this procedure repeated. The addition of 0.5 ml. of the'test mixture is repeated until a maximum temperature of clouding has been reached, and the cloud point begins to drop. The maximum temperature of clouding is taken as the aniline point, and usually three 0.5 ml. additions of the test mixture will be sufficient. The standard petroleum benzine diluent is made from industrial pure as toluol and a .low boiling petroleum naphtha known as petroleum benzine; its specific gravity is usually 0.725 to 0.730, and it distills completely between about 85 C. and 125 to 130 C. A. mixture of these two in the proportion of ap- 5 proximately 92 per cent of petroleum benzine and 8 per cent of toluol is prepared. This is then standardized against industrial pure toluol by the foregoing procedure. Toluol should show an aniline point by this procedure of exactly 21 C.

40 In case the standard diluent fails to do this the proportions must be varied until the standard diluent shows an aniline point of 21 C. If the mixture as prepared has an aniline point lower than 21 C., the percentage of petroleum benzine must be raised, while in case the aniline point is above 21 C., the percentage of toluol is to be increased.

The various fractions thus obtained from pure still residue possess solvent properties which render them more valuable as an article of commerce than the original still residue. 'Also, the resin resulting from steam distillation in an amount of 40 per cent of the still residue in the case of material from one source, possesses properties making it desirable for various uses, as described more fully in my aforesaid application.

My investigations have shown that the oils isolated by'steam distillation of pure still residue, as'just described, are highly stable. They appear .3 to be of saturated character, and sulfuric acid forwhich there is a constant demand and which are of material commercial utility and value. More specifically, I have found that by heating and catalytically cracking the pure still residues arcane there is produced a mixture of simple aromatic oils, such as benzol, toluol, xylol and solvent naphtha, which may be recovered and easily separated by distillation and fractionation, together with a new resinous material.

In the preferred practice of the invention the pure still residues or a fraction thereof is heated moderately in the presence of a cracking catalyst,

most suitably a metallic chloride cracking catalyst, examples being aluminum chloride and ferric chloride. Thereby the pure still residue is easily and rapidly broken down with production of unsaturated units and active hydrogen. Some of the unsaturated substances thus produced become polymerized in the presence of the catalyst, with production of a resinous materiahwhile others become hydrogenated with a comparatively small amount of hydrogen to produce welldefined and valuable aromatic solvents, chiefly benzol, toluol, xylol and solvent naphtha. Some of the uncracked constituents appear to become hydrogenated, producing oils resistant to cracking.

As exemplifying the practice of the invention reference may be made to its application to the 275 to 300 C. out of pure still residue as de scribed in connection with my aforesaid invention. This'material was mixed with anhydrous aluminum chloride in the proportion of 500 cc. of oil to 25 grams of catalyst, and the mixture of the two materials was then slowly and, progressively warmed in a still, the vapors evolved being withdrawn from the still and condensed. The condensed liquid was found to be a mixture of benzol, toluol, xylol and solvent naphtha, with little or no content of other substances; During this run benzol first appeared when the temperature of the liquid in the still was about Q, toluol when the liquid temperature was about C., and xylol when the liquid was at C. At a temperature in the cracking mixture of 250 C. the cracking and distillation were apparently complete.

It thus appears that the cracking not only takes place readily, but also that it occurs at low'temperatures, apparently at or below the boiling points of the aromatic oils produced, which is advantageous as will be recognized by those concerned with this art.

The distillate was carefully washed with sodium hydroxide to eliminate hydrochloric acid, followed by washing with water and drying. It was then carefully refractionated with production of a cut boiling between 45 and 1230 C., and consisting mainly of benzol and toluol. This mixture amounted to about 17 per cent of the total distillate obtained in refractionation, and it had. a specific gravity of 0.874 at 155, and an aniline point of 25 S. The next out boiled between 120 to 6.; it consisted chiefly of xylol and amounted to about 54 per cent of the redistilled material. Its specific gravity .at C. was 0.87, and its aniline point was 21 C. The last out boiled from 150 to 208 0., had an aniline point of 24 0., and was chiefly solvent naphtha.

point was about 75 C. its color may be made somewhat lighter by treatment with alkali, say soda ash. It is useful for the purposes to which resins are applied. I now believe that the uncracked oil resulted from hydrogenation of one or more constituents of the original pure still residues, with production of materials resembling cyclic parafilns. This is indicated by its aniline point of 38 to 40 C. which-coupled with its high boiling point indicates a loss of aromatic nature. The original pure still residues used had an aniline point of 26-27 C., while a petroleum oil of the same boiling point has an aniline point of about 50 0.

Various modifications in the practice of the process will occur to those skilled in the art. For instance, the mixture undergoing cracking may or may not be agitated. My tests have shown that in this manner the proportions of the simple aromatic oils recovered from the cracking operation may be varied although agitation does not have any substantial effect upon factory results.

the total amount of oils recovered. Thus, rapid agitation, with consequent more intimate contact of oil and catalyst, increases somewhat the amount of benzol and toluol recovered, at the expense of xylol. On the other hand, agitation produces less coke and residue adhering to the walls of the still, but it increases the content of uncracked oil.

My tests have shown further that when aluminum chloride is used, coating'of the catalyst by resin or the like so slows down the rate of cracking that less than about2 per cent of catalyst ordinarily will not produce economically satis- On the other hand, increasing the amount of catalyst up to about 7 per cent progressively increases the yield of solvent, as appears from the following tabulation representing data obtained in the practice of the invention applied to 500 cc. portions of the dried distillate, recovered by steam distillation of the still residue, as described above:

A101; used Total volume of arcmatics recovered c. c- 70 150 155 195 238 238 240 I. D 92 90 88 81 81 76 76 73 To 90 C O 0 0 l 1 2 2 2 To C 1 2 2. 5 2 2. 5 11 9 14 To C 3 3.5 5 12 17 43 43 42 To C.. 7 17 28 32 48 58 65 67 To C... 34 68 108 125 152 184 188 188 To C 38 73 117 129 162 188 192 195 To C 41 76 121 134 168 197 200 200 From the table it will be seen that the maximum yield is reached at about 7 per cent of aluminum chloride; greater amounts do not substantially increase the yields and thus serve merely to increase costs. Moreover, the data show how amounts from 2 to '7 per cent lower the temperature at which cracking begins, which is of further advantage, as will be recognized by those skilled in the art.

When ferric chloride is used as the catalyst the total yield of aromatic solvents and of resins is lower, and the yield of uncracked oil is higher, showing how the character of the result may be varied according to the product desired.

In the practice of the invention I may treat the composite pure still residues obtained by the method described in my above-identified patent application or, if desired for any reason, the

pure still residues may be fractionated in the manner referred to above, and any one or more of the cuts may be subjected individually to cracking. Also, the pure still residue from any of the individual light oil fractions may be treated in accordance with my aforesaid invention to produce an oil for treatment in accordance with the present invention. All such materials are contemplated by the term pure still residues as used herein. By such selection of starting material the proportion of simple solvent oil produced in the practice of the invention may be varied according to need. This is indicated by the following data obtained in actual practice of the present invention:

Product, percent Original oil Benzol Toluol Xylol 5:532:

Toluol residue 25 58 10 Xylol residuel 7. 4 57 17 200-250 Cut 1. 6 6. 4 3 11 276-300 Cut 0.7 11. 4 42 7 300360 Cut" 2 2 35 12 Residue of coke oven light oil recovery.

Fraction produced by treatment of total still residue according to my copending application.

According to the provisions of the patent statutes, I have explained the principle of my invention and have described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim:

1. That method of treating high boiling oils contained in pure still residues resultant from fractionation of the cuts of coke oven light oils which comprises heating a mixture of said high boiling oils and at least about 2 per cent of aluminum chloride to a temperature not substantially over about 265 C., and thereby producing a mixture of simple aromatic oils, such as benzol, toluol, xylol and naphtha, and a resinous material.

2. That method of treating high boiling oils contained in pure still residues resultant from fractionation of the cuts of coke oven light oils which comprises heating a mixture of said high boiling oils and at least about 2 per cent of a cracking catalyst of the group aluminum chloride and iron chloride to a temperature not substantially over about 265 0., thereby producing a mixture of simple aromatic oils, such as benzol, toluol, xylol and naphtha, and a resinous material, distilling off said simple aromatic oils, and

recovering said resinous material.

3., That method of treating high boiling oils contained in pure still residues resultant from fractionation of the cuts of coke oven light oils which comprises fractionating said high boiling oils to recover that cut distilling between about 275 to 300 C. at atmospheric pressure, and heating a mixture of said out and at least about 2 per cent by weight of aluminum chloride progressively to a temperature not substantially over about 265 (3., and thereby producing therefrom a mixture of simple aromatic oils, such as benzol, toluol, xylol and naphtha, and a resinous material.

' "WELIAM H. CARMODY.

Certificate of Correction; Patent No. 2,143,474. January 10, 1939.

WILLIAM H. OARMODY It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line 54,

for 1230 0. read 120 0.; line 59, for 25 S. read 25 0.; page 3, second column, lines 15 to 20 inclusive, strike out the headlng to the table and Insert instead the following:

Product, percent Original 011 Benzol Toluol Xylo] 5251211111;

and that the said Letters Patent should be read virith these corrections therein that the same may conform to the record of the case in the Patent Office.

Slgned and sealed this 14th day of March, A. D. 1939.

[SEAL] Henry Van Arsdale'.

Acting Commissioner of Patents.