US2384866A - Motor fuel - Google Patents

Description

. Patented Sept. 18, 1945 UNITED STATES PATENT oFFlcE" 2,384,866 Moron FUEL Sol B. Wiczer, Washington, D. C.

No Drawing. Application March 24, 1942, Serial No. 436,019

8 Claims.

The present invention relates to a method of treating a crude naphtha distillate containing substantial quantities of undesirable unsaturates of the type resulting from gas oil cracking, and boiling in the range from about 80 F. to 800 F. and, thus, includes within its scope commercial cracked gasolines, Diesel fuels, and light distilled nin or ran e oils such as kerosene.

The unsaturated hydrocarbon content, as contained in cracked gasoline, or the lower boiling distillate (80 F.-400 F.) as usually used as motor fuel in spark firedcycle motors, represents a valuable component because of its high anti-knock character. It has the disadvantage that it forms gums in storage and in the motors. The unsaturated content is substantial and may range from 2060%, dependent upon the method of cracking.

For ordinary automobile motors, cracked gasoline in present day practice is treated by polymerization, filtration, through clay, or by dilute acid washing to remove a, portion of the most active gum-forming components which, incidentally, are of the most valuable anti-knock character. The remainder of the fuel is then doped with strong anti-oxidants to prevent oxidation over a period of a few months to allow marketing. Such fuel is not entirely gum-free and must often be used with special heavy solvents to keep the gum in suspension and remove it together with occluded carbon from the combustion chambers. This product, therefore, represents a, refiner's compromise to lose as little of the fuel as possible while stabilizing it to a degree only satisfactory for quick use in commercial transportation.

Cracked gasoline is not susceptible to substantial improvement in anti-knock value by doping with lead tetraethyl because of its unsaturated hydrocarbon content. Hence, it cannot be used in aviation motors both because it cannot be doped to the super high octane anti-knock value required for high compression aviation motors and because the gum-forming unsaturated constituents cannot be adequately stabilized for aviation motor requirements wherein any gum deposition could not be tolerated.

it has been the practice for aviation fuel blends to avoid use of the present great bulk fuel supply of cracked gasoline because of its unsaturated character and to rely largely upon special synthetic isoparafflns formed from alkylation and hydropolymerization of the C3-C4 fraction of the by-product gases produced in gas oil cracking. Hence, the high anti-knock aviation fuel supply has substantially been restricted to the l or 2 per cent of waste gas by-product of the normal cracked gasoline motor fuel supply. The synthetic isoparaflins must be blended with a fuel base which must be specially refined and is of poor anti-knock character and of relatively limited supply.

In the cracked higher boiling naphtha fractions of the kerosene type, unsaturated hydrocarbonconiponents are undesirable for both Diesel fuel and burning oil purposes not only because of the gum-forming character but also because, in

' the case of Diesel fuel, the high anti-knock unsaturates are undesirable because they do not burn properly in the Diesel cycle of combustion, resulting in a lower cetane number of the fuel, and in the case of burning oils, the unsaturates burn with a. smoky flame, resulting in carbon and soot deposition. Thus, it is desirable to replace unsaturates in any type of motor fuel or burning oil with saturated products.

In its broadest aspect the present invention embraces the treatment of unsaturated cracked petroleum naphthas boiling in the gasoline, Diesel fuel, and burning oil range to remove substantially all of the unsaturated constituents and converting all or a substantial portion thereof to ethers, esters, and ketones and returning the same to the rafilnate fuel base.

The unsaturates are first extracted from the cracked naphtha by treating the naphtha with an extraction medium such as strong mineral acids, for example, -l00% H2804, or with other known extraction solvents such as liquid sulfur dioxide, phenol, furiural, Chlorex, polyglycol ethers,- etc.

' i In operating the present process, this extract may be acted on in its entirety as hereinafter described to convert all of the active components to ethers, esters, and ketones, and all of the crude reacted products may be recycled to the extracted fuel base or rafiinate; or any desirable fraction of the reaction product may be so recycled or reblended with the rafilnate.

It is preferable, however, to first fractionate the extract to produce a low or high boiling fraction, depending upon the particular fuel for which it is intended. For example, for high antiknock spark-fired motor fuel, the lower ing oils, the use of the higher boiling fractions from 200 F. to the end point oi 500 to 800? F. would be preferred.

It is further desirable to extract from any particular fraction the more readily reactable unsaturates, for example, the tertiary olefins, so that a higher yield of ethers, esters, or ketone may be produced by more rigid control of reaction conditions upon easily reactable olefins as distinguished from the less easily reactable unsaturates, each being subjected to optimum reaction conditions for its type. Tertriary olefins are readily separated by treating the original extract or fraction thereof with 60-65% H2504 or a selective solvent such as phenol. In an alternative method, suitable catalysts, such as, boron fluoride, BFs in alcohol or acetic acid solution may be used which reacts selectively with only the tertiary oleiins, the secondary or less reactive olefin being reacted at a later stage or discarded.

For purposes of converting the unsaturate to ether, ester, or ketone, in the case of spark-fired anti-knock motor fuel, only the lower ethers, esters, and ketones are used, such as methyl ether, acetate esters, and methyl ketones formed of a low boiling fraction of the extract, such as methyl ethers, acetate esters, and methyl ketones of the extracted fraction boiling from 80 to 150 F. or 200 F. Such products are obtained by reactions of methyl alcohol, acetic acid, or acetaldehyde upon the unsaturated product in thepresence of catalysts such as mineral acids, boron fluoride, and aluminum chloride. Other standard reactions for conversion of unsaturates to these ethers, esters, and ketones may be used, as will be apparent to one skilled in the art.

The following equations will illustrate the reactions for converting the unsaturates to methyl ethers, acetate esters, and methyl ketones:

Ethers CHs c=cm+cmon (L-Om R 0595-7695 where R and R have a similar significance as above. I

Ketones R ,.R'/ EH13 I where R and R have a similar significance as above. Other commerciai'methods of converting unsaturates to ethers, esters, and ketones may be used. A convenient commercial source of- 81 20- hols, acids, etc., is the water gas synthesis by hydrogenation of carbon monoxide. A water-gas converter may be operated from any source of hydrocarbon such as coal and waste petroleum oils and. gases. For example, as shown in U. S. Patents Nos. 1,844,857, 1,201,850 and 1,271,013, carbon monoxide and hydrogen are passed over catalysts to produce a mixture of methyl alcohol and higher alcohols in controlled proportions. The meth! nol may be distilled from the higher alcohols produced and used for direct synthesis of methyl ethers with the olefin extract. To make up extra methyl ether for blending with ramnate, a part of the methanol may be reacted with the higher alcohols, most of which are branched chain to make additional methyl branched alkyl ethers. The same water gas synthesis may be controlled for making acids such as acetic acid, for example, as taught in U. S. Patents Nos. 1,864,531 and 1,864,643.

As pointed out, acetic acid reacted with an olefin fraction in the presence of boron fluoridewill form acetate esters of the olefin. In the case of ketones, a direct addition of acetone as shown in U. S. Patent No. 1,757,830 is effected.

It is to be noted that in each case of synthesis of ether, ester, or ketone, several results are simultaneously efiected:

1. The valuable olefin component is not lost as in ordinary refining.

2. Nor is the olefin retained as such, necessitating a partial loss by filtration or weal: acid treatment to remove more active olefins according to present day practice and requiring further stabilization with gum inhibitors.

3. The olefin is returned not only in a stabl form as ether, ester, and ketone, but in a superior form for use as motor fuel or burning oil.

a. For motor fuel the ethers, esters, and ketones are superior anti-knock agents to olefin and possess far greater lead susceptibility.

5. Not only do the olefins otherwise wasted provide a source from which the ethers, esters, and ketones may be prepared for blending with motor fuels, but the very method of obtaining the olefin by extraction from the naphtha provides a saturated blending base fuel containing no undesirable olefins, a characteristic which makes the present process of outstanding value for preparation of 100 plus aviation fuels.

Example 1 A raw vapor phase cracked gasoline boiling from 80 to 400 F. was extracted with liquid sul fur diom'de according to the Edeleanu process. After removal of sulfur'dioxlde, the extract was fractionated to obtain a cut boiling from 80 to 175 F. The light olefin out is mixed with an equal volume of methanol, and a further euan== tity of about equal proportions with the olefin of 70% sulfuric acid is added, and the mixture is heated at C. for about five hours. The batch is then azeotropically distilled to remove the methyl ether derivativeof the olefin. The synthetic ether is then reblended with the cracked gasoline ramnate in proportions of 10 to 50%. To further improve the anti-lmock value 1-4; cc. of lead tetra ethyl may be added. In this reaction the concentration of acid may be varied from to H2804, and the volume of acid'based on alcohol may vary from .75 to 1 /2 parts. The time of contact may be varied from 30 minutes to 10 hours, and the temperature may be varied from 20 to C. It will be apparent that theyield of ether will vary with low 400 F.

the exact conditions. At higher temperatures and acid concentrations the reaction will run more rapidly, but excessive olefin polymerization may not be avoided. It will be apparent that by adjustment of flow rates the reaction may be carried out continuously instead of in batches.

Example 2 This is the same as Example 1 except that the etherification reaction is performed upon the whole olefine extract, the final ethers produced being fractionated to separate a cut boiling be- Earample 3 The raw total olefin extract produced as in Example 2 is washed with 65% H2804 to extract tertiary olefins. To the tertiary extract are added 65% H2804 and volume of methyl alcohol, and heat is applied at 55 C. for 5 hours. A

similar reaction is applied to the secondary olefin residue using 70% H2504 and a temperature of 75 C., heating for 7 hours. Methyl ethers are separated from both reactions. Either or both may be returned to the same or different gasoline rafilnates as anti-knock, the tertiary olefin ethers, however, being substantially superior in anti-knock improvement.

Example 4 The total olefin extract is reacted with volume of a methanol-boron fluoride solution at low temperatures -50 0., preferably 40 C. Only the tertiary olefin will react to form methyl tertiary alkyl ethers which are removed from the unreacted secondary olefins by steam distillation, fractionated to 400 F. end point, and blended with saturated raffinate. The secondary olefin is reacted with methanol and sulfuric acid as described in previous examples to form methyl isoalkyl ethers which are independently blended with gasoline rafinate or mixed with the tertiary alkyl ether ramnate blend.

. Ezrrmrple 6 Similar to Example 5 except that the extract is reacted with acetic acid solution of boron fluoride to form tertiary alkyl acetate esters of the tertiary olefin. These esters are separated by steam distillation from secondary olefin and fractionated to the motor fuel boiling range and added to the rafiinate. The remaining secondary olefins may be treated as in Examplefi.

Example 7 Methods similar to Examples 1-6 are performed upon range 011 kerosene, Diesel oil, illuminating oil, etc. These products of higher boiling nature than gasoline are similarly extracted to remove unsaturates. The unsaturates are converted to ethers boilingxin the range of the rafllnate to which it is ultimately returned. To all of, these The ether distillate is of a similar oils the tendency to formation of gummy sludges and discoloration is decreased. In the case of burning oils, smoking and formation soot -deposits are inhibited In the case of Diesel fuels, in addition to these improvements the cetane number is improved, and the pour point of the fuel is reduced, the water tolerance and cloud point increased and, most important, the cold starting properties of the fuel are increased.

Example 8 arately extracted with liquid sulfur dioxide and the rafiinates are reblended. The low boiling fraction is treated with 60-70% H2304, the extract is separated and reacted with methanol as previously described to form methyl tertiary alkyl ethers which alone are returned to the raflinate blend.

Example 9 The low boiling secondary olefines insoluble in.

65% H2SO4 of Example 8 are converted to methyl secondary alkyl ethers according to previous examplesand also added to the gasoline raflinate.

Example 10 A cracked gasoline of boiling range 80-550 F. is divided into two fractions and both are extracted to separate high and low boiling olefine fractions. Each extract is separately treated with dilute sulfuric acid to separate tertiary and secondary olefines which are separately converted in secondary and tertiary methyl ethers. The tertiary ethers are reblended with the low boiling raflinate fraction to produce a high anti-knock motor fuel for spark-fired aviation engines. Only secondary ether is fractionated further to remove low boiling constituents below 200 F. and the higher boiling secondary ethers are returned to the high boiling railinate to make a Diesel fuel or burning oil blend.

Example 11 An oleflne extract as produced by any of the previous examples, is passed together with an equal volume of acetone in & v p riz ixt at a temperature of 350 C. over a catalyst consisting of nickel oxide, zinc oxide or chromium oxide moistened with a suspension ferric chloride, vanadium oxide and reduced copper oxide at a pressure of 2500 pounds, as describedin. U. S. Patent No. 1,757,830. The condensed vapors are steam distilled to separate methyl ketones which are reblended with the naphtha raflinate. The new naphtha extract may be fractionated into suitable cuts before or after extraction to obtain products of desired boiling range.

Products prepared according to the present disclosure may be further treated to give them desired characteristics For example, a Diesel oil prepared according to the present disclosure may be further doped with primers, lubricants, dyes, etc. a motor fuel may be further treated with lead tetra ethyl or other desired anti-mock agents, lubricants, dyes and stabilizers, etc.

Having thus described my invention, I claim:

1. Method of forming stable liquid fuels comprising extracting unsaturates from the cracked hydrocarbon distillate to produce an extract and railinate, converting a portion of the extract to products selected from the group consisting of ethers, esters and ketones, and recycling a pcr-' tion thereof to the ratfinate to form products suitable for use as motor fuels for internal combustion engines of the Otto and Diesel cycle types and burning oils.

2. Method of reforming cracked hydrocarbon naphthas containing substantial quantities of unsaturate's comprising extracting the unsaturates to produce an extract anda r'aflinate, forming a substantial portion of the extract into a derivative selected from the group consisting of methyl with the saturated naptha raflinate.

4. Method of reforming cracked hydrocarbon naphtha comprising, extracting the unsaturated hydrocarbon components to produce an extract and a rafiinate, separating the tertiary olefines from the extract, independently converting the secondary and tertiary olefines to derivatives selected from the group consisting of methyl ethers, methyl ketones, and acetate esters, and blending the derivative with the saturated naphtha raffinate.

5. Method of converting cracked gasoline to high anti-knock motor fuel comprising extracting the unsaturates to produce an xtract and a' raflinate, converting a substantial portion thereof to derivatives selected from' the group consisting of methyl ethers, methyl ketones, and acetate esters, and recycling a substantial portion oi} the extract and a raflinate, separating the tertiary olefines from the extract, reacting the tertiary olefines with methyl alcohol to form methyl tertiary alkyl ethers, and reblending the methyl ter- 'tiary alkyl ethers with the gasoline rafllnate.

8. Method of converting cracked gasoline to high anti-knock motor fuel comprising extractstantialportion of the extract to form methyl I ethers therewith, converting the remaining mixture of methyl alcohol and higher alcohol to methyl ethers of the higher alcohols, and blending the methyl ethers with the gasoline rafinate.

SOL B. WICZER.