US2193763A - Process for purification of crude light oil - Google Patents

Description

Patented Mar. 12, 1940 UNITED STATES PROCESS FOR PURIFICATION OF CRUDE LIGHT OIL Irvin H. Jones, Pittsburgh, Pa., assignor, by mesne assignments, to Koppers Company, a corporation of Delaware No Drawing. Application March 14, 1931,

Serial No. 522,780

'21 Claims. (01. 196-40) This invention relates to the refining or purification of crude light oil. More particularly, this invention relates to the treatment of crude light oil to remove gum forming and corrosive constituents thereof, and to leave in the refined oil those constituents which are beneficial or at least not harmful so far as the use of the light oil as a motor fuel is concerned.

One object of my invention is to provide an improved process for removing from crude light oil substantially all gum forming and corrosive constituents Without greatly decreasing the yield, and at the same time obtain a light oil which may beadvantageously used as a motor fuel. A fur- "ther object of my invention is to provide an improved process for refining or purification of crude light oil according to which substantially all, gum forming and corrosive constituents are removed while leaving unchanged in the refined oil substantially all of those unsaturated compounds whose presence is advantageous in the motor fuel.

In the production of illuminating gas or fuel gas or the like, whether by a producer or by the distillation of coal to form coke, a number of condensib-le hydrocarbon. compounds are givenv oil and carried along by the gas. It is customary in certain plants to recover from the gas certain of these compounds by washing the gas with a hydrocarbon liquid known as Wash oil. Various compounds such as benzol are washed out of the gas by the wash oil, and may be driven ofi from the wash oil by distillation. This distillation is carried to a temperature of 180 C. or the like;

crude-light oil.

Considerable demand has arisen for such lighoil as a fuel for internal combustion engines. It vaporizes readily, and contains unsaturated compounds which have valuable anti-knock properties. The Navy Department Specifications for motor fuel require that when 100 c. c. are evaporated to dryness on. an actively boiling steam bath, the gum residue shall not exceed 3 milligrams. To test for corrosiveness, the fuel is evaporated, as above described, in a copper crucible. The copper should not become discolored or blackened. An alternative test is to subject a strip of copper to boiling light oil to test for dis- 50 coloration or blackening by the sulphur compounds, which, it is generally considered, constitute the corrosive agency in the crude light oil.

Heretofore, crude light oil has been refined by 55 ,a process known as'the silica gel process. Crude 1 and the fraction thus driven ofi is known as 7 light oil contains a relatively high proportion of various unsaturated compounds which differ in their physical and chemical properties,.as Well I as their stability in storage.

Some are relatively stable compounds, not changing materially on 5 long standing, while others are so highly reactive and unstable that soon after production they begin to change from volatile oils to heavier materials which are lgummy and resinous in nature. Certain oi the more stab-1e unsaturates couldQwith advantage, be retained in'the refined product, if it is, to be sold as motor fuel, as they have high anti-knock value. On the other hand, no compounds must be left in the motor fuel which will, on long storage, change into gummy 15 in some step in the process. 25

The special feature of the silica gel process is considered to be that it removes from the crude light oil all gum forming and corrosive constitu ents; and that it leaves unchangedin the refined oil all those unsaturated compounds Whose pres- 30 once is advantageous in the motor fuel, since they are considered to have a certain anti-knock value. It should moreover be noted that due to the presencein the refined light oil of these unsaturated compounds the yield is increased by from 10% to 15%.

Crude light oil has heretofore been treated with concentrated sulphuric acidto produce refined motor fuel; but it has heretofore been customary to wash the. crude light oil with sufficient quantities of concentrated acid so that not only were all thegum forming constituents removed from the oil but all the unsaturated compounds which produce color with sulphuric acid were removed as Well. This had the disadvantage, 45 that the unsaturatedcompounds which have the valuable property of alleviating knocks in the motor were,to a considerable extent, lost during the refining process.

It has been discovered that the gum forming constituents of the light oil are particularly sensitive to the presence ofconcentrated sulphuric acid. By conforming my improved process to this attribute or quality of the gum forming constituents, I have'made it possible to polymerize all of the gum forming constituents present in the crude light oil without using sufficient acid to attack, to any substantial extent, the unsaturated compounds. Essentially, my improved process relies for the purification or refining of the crude light oil upon the selective separation of the more unstable unsaturates by washing of the crude light oil with only small qua titles of concentrated sulphuric acid so as to remove the gum forming and corrosive constituents without removing the highly desirable unsaturated compounds which have anti-knock value in the re fined motor fuel.

In order to illustrate my improved process, the following example is given: Treat crude light oil for twenty minutes with an acid wash of B. H2804 1% by volume, using sufficient agitation to insure thorough contact. After settling, remove this light acid wash. By this treatment, the suspended water and any alkaline bodies, such as ammonia or pyridine, are removed. The crude light oil is then treated with 0.4% by volume of concentrated H2804 and the mixture agitated for at least an hour, so as to obtain thorough contact of the crude light oil with the acid. The acid sludge is allowed to settle, and is then removed. By this second treatment, the more unstable unsaturated compounds are polymerized and, therefore, are not sufiiciently volatile to pass over with the refined motor fuel during the subsequent distillation. The polymerized unsaturated compounds are left behind in the still residue. In the case of those crude light oils which contain a high percentage of coumarone and indene fractions, it is distinctly advantageous to heat the oil to -70 C. after the treatment with concentrated sulphuric acid and after the separation of the acid sludge. This heat treatment carries the polymerization of the unsaturated compounds more nearly to completion and, therefore, makes a more stable product. The polymerized oils are then alkali washed and steam distilled at 98-99 C. The condensate is then fractionated, taking the fraction distilled up to and including a vapor temperature of 180 C. The proportion of concentrated sulphuric acid to be used in my improved process may vary from as little as 0.3% to as high as 0.8%. Where the yield is to be as high as possible and the tolerance for the amount of gum forming and corrosive constituents is high, only a small amount of concentrated sulphuric acid is required. With the use of greater quantities of concentrated sulphuric acid, the yield of refined motor fuel is decreased slightly and the quantity of gum forming and corrosive constituents left in the refined motor fuel is substantially decreased. I prefer to use between 0.4% by volume and 0.6% by volume of concentrated sulphuric acid.

Tests show that a crude light oil when treated in accordance with my improved process will produce a motor fuel which is relatively stable in storage in the dark, whether dehydrated, or in the presence of water, or in the presence of water and iron filings. This motor fuel after fifteen months in storage retains its water-white color, and has changed in gum content from a maximum of .003 gram to only .008 gram per 100 00., as determined by the copper dish test. Moreover, the motor fuel at the end of such storage is practically non-corrosive in response to the copper test. It is not known whether the sulphur compounds to which corrosion is ordinarily attributed, are still in the light oil; but if so, they are not in such form as to attack copper.

While I have described one specific manner of performing my improved process, it will be understood that the invention is not restricted to the particular details of the steps outlined, but may be variously modified within the contemplation of the invention and under the scope of the following claims.

I claim:

1. In the refining of crude light oil comprising essentially a mixture of motor fuel fractions to make motor fuel therefrom, the process which comprises subjecting the crude light oil to treatment to polymerize unsaturates, said treatment consisting of washing the oil with an amount, between 0.3 and 0.8 per cent by volume of concentrated sulphuric acid sufficient to polymerize the gum forming unsaturates but insufficient to polymerize the other unsaturates, separating the light oil from the acid sludge, heating the treated light oil to between 60 and C., washing with alkali, and removing volatile constituents of the light oil by distillation at 98-99 C. while still containing the more stable unsaturates in unpolymerized condition in the oil.

2. In the refining of crude light oil essentially comprising a mixture of motor fuel fractions to make motor fuel therefrom, the process which comprises: subjecting the crude light oil to treatment in the absence of adsorbent agents to remove unsaturated compounds therefrom, said treatment consisting of washing the oil with an amount of mineral acid sufiicient to polymerize all of the gum forming unsaturates present in the crude light oil but insufficient to attack to any substantial extent the other unsaturates in the oil then separating acid sludge from the refined oil and washing with alkali prior to distillation to remove the so polymerized gum formers from the refined oil, and completing the separation of the polymerized gum formers from the oil by distillation while still containing the other unsaturated compounds in unpolymerized condition in the oil and recovery of the refined distillate as motor fuel oil containing the other unsaturates unpolymerized.

In the refining of crude light oil essentially comprising a mixture of motor fuel fractions to make motor fuel therefrom, the process which comprises: subjecting the crude light oil to treatment in the absence of adsorbent agents to remove unsaturated compounds therefrom, said treatment consisting of selectively separating the more unstable unsaturates by washing the crude light oil with a small quantity of concentrated sulphuric acid sufficient to remove the gum forming and corrosive constituents but insuificient to remove the highly desirable unsaturated compounds which have anti-knock value in the re fined motor oil, removing the acid sludge, washing with alkali, and then completing the separation of the refined motor fuel from the polymerized gum formers in the oil by distillation there of while still containing said highly desirable unsaturated compounds therein in unpolymerized condition.

4. In the process of making motor fuel from crude light oil obtained from coal and comprising essentially a mixture containing motor fuel fractions, which process comprises, treating the crude light oil in the absence of adsorbents to polymerize unsaturated compounds, said treatment comprising washing the oil with between 0.3 and 0.8 per cent by volume of concentrated sulphuric acid, removing the acid sludge and then washing with alkali; and then distilling the oil while still s eaves polymerized unsaturated compounds behind in the distillation step.

5. In the process of making motor fuel from crude light oil obtained from coal comprising, treating it in the absence of adsorbents to polymerize unsaturated compounds, said treatment comprising washing the oil with between 0.3 and 0.8 per cent by volume of concentrated sulphuric acid, removing the acid sludge and then washing with alkali, and then distilling the oil While still acontaining the more stable unsaturated compounds in unpolymerized condition in the oil at 98-99 C. leaving the polymerized unsaturated compounds behind in the distillation step.

6. In the process of making motor fuel from crude light oil obtained from coal comprising, washing it with between 0.3 and 0.8 per cent by volume of concentrated sulphuric acid, removing the acid sludge, heating the oil to 60-7 0 C., after the concentrated acid treatment and after the "separation of the acid sludge in the absence of a solid porous adsorbent material, to carry the polymerization of the unsaturated compounds more nearly to completion, then washing the oil with alkali and distilling it while still containing the more stable unsaturated compounds in I unpolymerized condition in the oil at 98-99 C.

7. In the process of making motor fuel from crude light oil obtained from coal comprising, washing the'oil with mineral acid in amount sufficient to initiate polymerization of gum forming .,.alkali and distilling while still containing the more stable unsaturated compounds in unpolymeriz'ed condition in .the oil to a temperature at which the polymerized gum formers are not sufiiciently volatile to pass over with the refined 50 rnotor fuel during the distillation.

8. In the process of making motor fuel from crude light oil obtained from coal comprising, treating the oil in the absence of adsorbents to polymerize the gum forming and corrosive constituents without removing the highly desirable unsaturated compoundswhich have anti-knock value in the refined motor fuel, said treatment comprising: washing it with between 0.3 and 0.8 per cent by volume of concentrated sulphuric acid, removing the acid sludge, heating the oil to 6040 C., after the concentrated acid treatment and after the separation of the acid sludge in the absence of a solid porous adsorbent material, to carry the polymerization of the unsaturated compounds more nearly to completion, then washing the oil with alkali and distilling it while still containing the more stable unsaturated compounds in unpolymerized condition in the oil at 9. In the process of making motor fuel from crude light oil obtained from coal comprising, treating the oil in the absence of adsorbents to polymerize the gum forming and corrosive constituents without removing the highly desirable unsaturated compounds which have anti-knock value in the refined motor fuel, said treatment comprising: washing the oil with mineral acid in amount sufficient to initiate polymerization of gum forming constituents but insuflicient to remove the more stable unsaturated compounds having anti-knock value in motor fuel, removing the acid sludge, heating the oil to elevated tem-' perature after the acid treatment and after the separation f the acid sludge, to carry the polymerization of the gum forming unsaturated compounds more nearly to completion, and thereafter distilling while still containing the more stable unsaturated compounds in unpolymerized condition in the oil to a temperature at which the polymerized gum formers are not sufiiciently volatile to pass over with the refined motor fuel during the distillation.

10. In the process of making motor fuel from crude light oil obtained from coal, the steps comprising: washing the crude light oil with mineral acid in amount suiiicient to initiate polymerization of gumeforming constituents but insufficient to remove a substantial amount of the more stable unsaturated compounds having high anti-knock value, removing the acid sludge, heating the oil in the absence of a solid porous adsorbent material to a temperature below the decomposition temperature of gum forming and corrosive constituents in order to complete the polymerization said gum forming constituents and raise their decomposition points and thereafter continuing the heating to distill while still containing the more stable unsaturated compounds in unpolymerized condition in the oil at higher temperatures but below the decomposition point of the polymerized constituents, and Washing the refined oil with alkali after the sludge removal step and before the final distillation step.

11. In the process of making motor fuel from crude light oil obtained from coal and containing gum forming and corrosive constituents, the steps comprising: washing the oil with mineral acid in amount sufficient to initiate polymerization of gum forming constituents but insuiiicient to remove a substantial amount of the more stable unsaturated compounds having high anti-knock value, removing the sludge, heatingthe oil at a relatively low temperature to polymerize said constituents, and thereafter continuing the distillation while still containing the more stable unsaturated compounds in unpolymerized condition in the oil at higher temperatures but below the decomposition points of the polymerized constituents, and washing the refined oil with alkali after the sludge removal step and before the higher temperature distillation step.

12. A process as claimed in claim 11 and in which concentrated sulphuric acid is employed as the mineral acid and in amount between 0.3 and 0.8 per cent by volume.

13. A process as claimed in claim 11 and in which sulphuric acid is employed as the mineral acid and in amounts equivalent to 0.4 to 0.6 per cent by volume.

14. A process as claimed in claim 11 and in which the low temperature to which the oil in the absence of a solid porous adsorbent material is heated is between 60-'l0 C. and the higher temperature to which the oil is subsequently heated is equivalent to 98-99 C.

15. A process as claimed in claim ,11 and in which concentrated sulphuric acid is employed as the mineral acid and in amounts between 0.3

to 0.8 per cent by volume, and in which the low temperature to which the oil is heated is equivalent to -70 C. and the higher temperature to which the oil is subsequently heated is equivalent to 98-99 C.

16. In the process of making motor fuel from crude light oil obtained from coal and containing gum forming and corrosive constituents, the steps comprising, treating the oil with weak sulphuric acid to remove suspended Water and alkaline bodies such as ammonia and pyridine, washing the oil with mineral acid in amount sufficient to initiate polymerization of gum formconstituents but insuilicient to remove a substantial amount of the more stable unsaturated compounds having high anti-knock value, removing the sludge, heating the oil in the absence of a solid porous adsorbent material at a relatively low temperature to polymerize said constituents, and thereafter continuing the distillation while still containing the more stable unsaturated compounds in unpolymerized condition in the oil at hi her temperatures but below the decomposition points of the polymerized consiituents, and washing the refined oil with alkali after the sludge removal step and before the higher temperature distillation step.

17. The method of refining liquid low boiling hydrocarbon distillates containing gum forming constituents consisting in treating the distillate with an acidic reagent of such concentration and in such quantity at ordinary temperature and atmospheric pressure as to polymerize only the more easily reactive of the gum forming contituents and form only a small amount of sludge, separating the sludge from the hydrocarbon, subjecting the treated hydrocarbon while containing the balance of the acid hydrocarbon reaction products resulting from said acid treatment in the absence or" a solid porous adsorbent material to an elevated temperature to polymerize the more difficultly reactive of the gum forming constituents, and then distilling to separate the treated hydrocarbon from the polymerized products, thereby obtaining a final product substantially freed of gum forming constituents.

18 A process of refining crude light oils comprising essentially motor fuel fractions and containing in admixture members of unsaturated hydrocarbon series belonging to the class distinguished by a relative stableness under normal conditions of storage and members of said series that belong to a class having a tendency to change to substances of higher molecular weight under similar conditions of storage, which comprises, the steps of subjecting said crude light oils at ordinary temperature and at atmospheric pressure to reaction with such concentration of sulphuric acid in an amount sufficient, not to exceed a quantity about one per cent by volume of the crude oil, to promote the formation of substances of higher molecular weight from the less stable unsaturates but insufiicient to prevent leaving substantially unaltered therein the unsaturated hydrocarbons possessed of relative stableness in storage, and thereafter separating volatile hydrocarbons from the so-treated light oil in the absence of solid adsorbents for aiding the removal of the substances of higher molecular weight.

19. In a process of preparing motor fuels from low-boiling oils derived from manufactured fuel gas and the like, said oils comprising essentially motor fuel fractions and containing in admixture compounds belonging to unsaturated series of which some exhibit relative stability and of which others tend to change into gummy substances under normal conditions of storage, the method of excluding sensitive gum-forming substances from motor fuels volatilized from said oils which comprises the step of bringing said low-boiling oils into intimate contact at ordinary temperatures and atmospheric pressure with a quantity of sulphuric acid in aqueous medium sufiicient to alter those members of the unsaturated series, that tend to form substantial quantities of gummy materials under normal conditions of storage, to substances which exclude them from motor fuels distilled from the acid treated oils, but insufficient in rsnount to prevent preserving unsaturates that are substantially stable in storage in the motor fuel volatilized from said oils, and thereafter separating by distillation but in the absence of solid adsorbents, the altered members from the unaltered members of the unsaturated series.

20. In the method of refining benzol crudes the step which comprises agitating the crudes with about 0.08 pound of 66 B. sulphuric acid per gallon of the crudes.

21. The method of refining crude benzol which comprises the step of agitating the crude material for a period of about one hour with about 0.08 pound of 66 B. sulphuric acid per gallon of crude benzol.

IRVIN H. JONES.