US1722872A - Process for separating oil from coal tar - Google Patents

Description

Patented July 30, 1929.

ANTON WEINDEL, F ESSEN-RUHR, GERMANY,

ASSIGNOR TO ZEGHE MATHIAS STINNES, OF ESSEN-RUHR, GERMANY.

PROCESS FOR SEPARATING OIL FROM COAL TAR.

No Drawing. Application filed December 12, 1924, Serial No. 755,554, and in Germany December 27, 1923.

)Vhcn coal tar is worked it is usually subjected to distillation at atmospheric or decreased pressure with or without the use of steam. The dist-illates of the tar of a high boiling point are partly used as a so called fatty tar oil for lubricating purposes. During the distillation of the tar the viscous oils present in the tar itself are however turned into less viscous products which accordingly 10 are found in the aforementioned fatty tar oils.

I'have succeeded in finding a mode of working by means of which the materials present in the tar may be isolated without being exposed to high'temperatures which cause dissociation.

The process works in the following manner:

The tar is thoroughly mixed with double or treble its quantity of petroleum benzine at the ordinary room temperature and is then allowed to stand at the same temperature or preferably at a somewhat lower temperature about 0 C. to 10 C. by which measure all- 5 asphaltic substances present in the tar are deposited on the bottom of the reservoir in a solid or plastic form. The benzine like solution is poured off, the benzine is removed by distillation and after its condensation it is used again for the same purposes. The residue of distillation which as to quantity varies according to the quality of the tar and which for instamx: in case of a tar of good quality amounts toabout from 60-65%, consists of an oil which may be employed for crude lubricating purposes. The solidifying point lies at 10 (1., the viscosity being 1, 7

Engler at 50 C.

When it is intended to produce from the residue of distillation oils of a greater viscosity it suflices to drive off from the oil the components of lower boiling points at normal or decreased pressure. If for in, stance by distilling off those constituents volatile up to 225 0., about 15% are distilled over and the result is an oil having a a viscosity of 4,9 Engler at 50 C. and a flash point of 125 C. If the distillation is continued up to a temperature of 250 C. about from'2022% are distilled over and the resuit is an oil having the following constant properties:

Viscosity=6 Engler, at 50 C. flash point'g 130 C. and a solidifying point= 8 I The driving off of the fraction of a low boiling point from the tar has the advantage that the naphthalene inclined to crystallize at low temperatures is removed in this manner.

The anthracene of the tar, some of which will be present in the oil also present in larger quantities-in the fatty tar oil may give rise to the formation of sediments. This can be easily removed in several ways. I, for instance, cool the oil above described to 0 C. to 10 C. after the naphthalene fraction has been driven ofl and allow it to stand for several days. The anthracene may then be separated from the oilby filtration or by means of centrifugal action.

1 The advantages of this process are asv folows:

(1) A considerable part of the anthracene and of the intermediary products of the phenols are for the greater part removed Withthe asphalts which have agreat tendency to become resinous;

(2) The Viscous components of the tar which normally during the distillation process become chiefly decomposed-which process is accompanied by the formation of nonviscous products-remain fully preserved.

. (3) For this reason the present products are of a greater viscosity than fatty tar oils; it is no longer necessary to solidify them artificially as such is done by treatlng them with oxygen or by the dehydrogenatmg by means of sulphur.

(4) Losses of benzine are only small, the

bulk thereof being recovered and used again.

The process can not only be applied to primary tar and coke oven tar but may also be used for other tars such as generator tar and gas works tar.

I am also not restricted to the methods of working mentioned in the example. Thus by extending the driving off still further, oils of considerably greater viscosity may be obtained and Ialso may, in order to obtain refined substances, distill the oil preferably in a vacuum. If it is intended to obtain products of a better quality, the following method may be employed:

The crude coke oven tar contains as 1t 15 generally known a light oil consisting of benzol and its homologues. If the asphaltio substances are separated from the crude tar by means of petroleum benzine, the benzine 110 when it has been repeatedly used, must becomeenriched by the light oil which for its greater part has a similar boiling point, and in the course of time it becomes more and. more unsuitable for. the separation of asphalt, as the light oils of the tar tend to dissolve the asphalts. Since the petroleum benzines and the light oils of the tar cannot be separated by fractioning it would be necessary to add fresh benzine to the mixture after a relatively small number of operations. According to my invention I preferably first free the crude tar from water and light oil by employing the customary distillation process up to a temperature of 200" C. and then I treat the tar free from the light oil cooled down to the ordinary temperature, with benzine. In this manner the valuable light oil of the tar is recovered while the benzine maybe used for a practically unlimited number of operations and in consequence of the difference between the boiling points of the benzine and the tar it may be easily completely recovered again.

I have further found it to be preferable to distill the naphthalene-fraction imirnediately after the light oil has been driven off, and then to free the tar (from which constituents boiling at temperatures up to approximately245 C. have been removed) from asphalt by means of benzine. A special advantage which accompanies this method of working consists therein, that in addition to the napthalene nearly all phenols are also removed from the oil and recovered.

The anthracene present in the coke oven tar has, as it is generally known, a tendency to separate therefrom in the form of crystalswhich for instance is also the case with fatty tar oil. Although this formation of sediment is not so great in case of m products, since the asphalt carries ant racene along with it, it has nevertheless proved to be necessary in order to secure the best product to remove even the small quantities of anthracene, as especially these quantities detrimentally aifect the quality of the oils.

The anthracene is far more soluble in the tar oil than it is in benzine but also the benzine is capable of dissolving a few percent of anthracene. I employ such a quantity of benzine which is only just sufficient. to completely separate the asphalts and I have found by experiments that benzine equal to about double the weight of the tang will suffice. When cooling the benzine solution which results from the process of removing the asphalt, a considerable part of the anthracene will separate out and can be removed by filtration or centrifugal action. Small quantities of benzine therefore reduce the solubility of the tar oil with regard to anthracene, while greater quantities of benzine neutralize this effect, since benzine is also capable of dissolving anthracene. The

for the separation of asphalt has however also the great advantage that apparatus of a small size sufiices and that considerable savings in the costs of distillation for the recovery of the benzine are made.

For producing high class lubricating oils the following methods of working have proved to be very satisfactory:

In addition to the light oil and the naphthalene fraction also fractions of a higher boiling point (anthracene oil) can be driven off the tar. Thedistillates obtained boiling at temperatures higher than the naphthalene fraction are cooled, filtered and added again to the residue of distillation of the tar and dissolved by slightly heating it, whereupon the asphalt is removed in the aforementioned manner. manner due consideration is given to the fact that components of the tar which have a tendency to form asphalt become quickly thickened in consequence of the high temperatures of distillation which are now em ployed and are also separated out during the subsequent removal of asphalt. It is evident that in this manner the yield of oil is decreased, (relatively it is still very high) .but the quality of the oils is considerably improved. A11 oil produced in this manner must be usable even at high temperatures, since the part, which polymerizes in the heat and is the cause of an undesired thickening have already been removed by this new mode of treatment. It has been proved to be advantageous to carry on the driving off of the low boiling constituents not to an excessive height of temperature as otherwise also viscous components will be destroyed. Without being restricted to definite limits the end temperature is preferably fixed approximately at 325 C.

Instead of the petroleum benzines the benzines of the pit coal primary tar may also be employed. As the primary tar bcnzines separate out fewer kinds of asphalt (appar ently the hard asphalts only) the oils obtained have a slightly greater viscosity while the other qualities are similar. My methods of working are not so strictly tied to the conditions of experiments mentioned and they may as such, as will be readily understood be varied within long ranges. The figures given in the following examples apply to a special coke oven tar while in caseof other kinds of tar the results 'will be different.

Example 1.1000 parts by weight of crude tar are heated to drive off fractions volatile at a temperature of 200 (1, whereby 50 parts by weight of water and light oil are distilled off. The remaining 950 parts by Weight of residue of distillation are, after cooling, thoroughly agitated together with 1900 parts of petroleum benzine and Flash point Asphalt=480 parts by weight= 43% of.

the crude tar,

Lubricating oil=480 48% of the crude tar.

. For increasing the viscosity of the oil the parts by weight naphthalene fraction (up to about 245 C.) is distilled off from the oil and the oil after it has again been allowed to stand and while -it is being cooled is separated from the small amount of anthracene which thereby solidifies by filtration or centrifugal action.

Products obtained are:

Anthracene=7. parts by weight=0,7% of the crude tar.

Naphthalene fraction=100 parts by weight=10% of the crude tar.

Pure oil=373 parts by weight=37,3% of the crude tar.

The constant properties of the oil are: Viscosity 3 Engler at 50 C. solidifying point= 8 C.

The asphalt is utilized in the form of soft pitch.

Example 2.4000 parts by weight of crude tar, are distilled at a temperature up to 325 C. The distillates which begin to pass over at a temperature of 250 C. are cooled, filtered and then added to the residue of distillation. By heating and agitating the product it will be completely dissolved so as to form a thickly running mass which after cooling is freed from asphalt as described in the first example with the use of double the quantity of benzine. After allowing the oil to stand an'd cooling it and after any separated parts are removed by centrifugalaction, the following products are obtained from the 4000 parts by weight which were subjected to thetreatment-z Description of the oil:

Viscosity 3,9 Englcr up to Flash point 143 C.

solidifying point= 7 C.

The oil runs very well, is transparent, of a red colour and possesses a green fluorescence.

I claim as my invention:

1. In a process of treating coke oven tar to obtain lubricating oils without distillation of the main bulk thereof, the steps which comprise mixing thetar with a multiple quantity of petroleum benzine at ordinary temperature, allowing the mixture to stand for some time at below normal room temperature, separating the tar oils dissolved in the benzine from the separated asphalt materials, freeing the oils from the benzine by distilling off the latter, thereafter distilling the oils up to a temperature of 245 C.

whereby the light oils are removed.

2. In a process of treating coke oven tar to obtain lubricating oils without distillation of the main bulk thereof, the steps which comprise mixing the tar with a multiple quantity of petroleum benzine at ordinary temperature, allowing the mixture to stand for some time at not above ordinary temperature, distilling off such components as willdistill up to about 245 C. under atmospheric pressure, allowing the preferably cooled oil to stand for some time to separate out anthracene, and thereafter removing the separated anthracene.

3. In a process of treating coke oven tar to obtain lubricating oils, the steps which comprise mixing the tar with several times its own quantity of petroleum benzine at ordinary temperatures, allowing the mixture to stand for some time at not above ordinary temperature, separating the tar oils dissolved in the benzine from the separated asphalt materials, and-thereafter freeing the oil from the benzine by distillation, said distillation being continued up to a temperature of about 245 C. 1

4. In a process of treating coke oven tar to obtain lubricating oils, the steps which comprise distilling the crude tar to remove moval of the asphalt, treating the still residue with benzine at ordinarytemperature,

allowing the benzine solution to stand, and thereafter separating the benzine solution from the separated asphalt.

5. In a process of treating coke oven tar to obtain lubricating oils, the steps which comprise freeing the crude tar prior to the removal of asphalt from light oils and naphthalene fractions by distilling the tar up to 200 (1, cooling the still residue, treating said residue to several times its own weight of petroleum benzine, and thereafter separating the benzine at ordinary temperature solution from the separated asphalt.

6. In a process of treating coke oven tar to obtain lubricating oils, the steps which comprise freeing thecrude tar from light oils by distilling the tar ata temperature up to 200 0., addingto the still residue aboutdouble its weight of benzine, cooling the benzine solution, allowing said solution 'to stand, removing the separated asphalt from said benzine solution, and thereafter distilling ofl? the benzine.

7. In a process of treating coke oven tar to obtain lubricating oils, the steps Which comprise distilling the tar up to a temperature of about 325 0., filtering, recovering, and cooling the distilled fractions boiling above 250 Q, during said distillation, adding said distillates to the still residues of said distillation, heating and'agitating the mixture of the still residue whereby a Vis-' cous mass is obtained, cooling the said v1scous mass, adding benzine to said mass in double the quantity of said mass, separatlng ofl the asphalt material from the benzine DOKTOR ANTON WEINDEL.