US2376558A - Production of high octane fuels - Google Patents

Description

Patented May 22', 1945 UNITED PRGIWUC'ILEQN UIF HIGH @CTANEE FUELS N o Drawing.

Application January 13, Elli-ill, Serial No. Width)- 12 Claims. (Cl. 26683.5)

This invention relates to a method of improving the response of motor fuels and motor fuel stocks of high octane number to additions of lead alkyls or other antidetonants. More specifically it relates to a method of treating fuel stocks containing high concentrations of polymers and copolymers of propylene, isobutylene, butenes and the like to remove therefrom certain oxygenated and the like impurities which are detrimental to the antiknock characteristics of said fuels. It further relates to treating similar synthetic fuel stocks which contain paraflinic counterparts of said polymers and co-polymers.

In the preparation of motor fuels of very high octane number and closely controlled composition, such as '100 octane aviation fuels and the like, conventional manufacturing procedure has usually included the step of manufacturing a base stock containing high concentrations of iso-octanes and related branched-chain hydrocarbons of seven to twelve carbon atoms by the polymerization of olefins having three to five carbon atoms, and subsequent non-destructive hydrogenation of resulting polymers. Especially satisfactory have been various catalytic polymerization processes utilizing olefin feed stocks containing large percentages. of isobutylene to form the corresponding dimers and trimer of high octane number. copolymerization of tertiary base, olefins and straight-chain olefins, followed by non-destructive hydrogenation, the thermal or catalytic alkylation of parafilns with olefins to form paratfins and the like. Said polymerization processes difier in the source ofthe olefin feed stock and the type of catalyst used, and, further, it hasof said fuels toward tetraethyl lead or other antl detonants decrease proportionately the value of the base stocks.

An object of this invention is to provide a means of improving the lead response of the base stocks described above, and hence of the ,fuels in which said base stocks are blended.

Another object of our invention is to remove from a motor fuel stock of high octane number nonhydrocarbon impurities which adversely affeet the efficacy of, or response to, added anti-' detonants.

Other objects and advantages of our invention will become apparent to those skilled in the art from the accompanying disclosure and discus- Still other processes include the twenty per cent or more in the response to tetraethyl lead, depending upon the type of catalyst used in the polymerization step.

importance of maximum antidetonant response,

sion.

We have discovered that, although the original octane number is notgreatly affected, the lead response of hydrocarbon fuels of hi h octane number such as are produced by the po' ymerization of normally gaseous olefins and subsequent hydrogenation of resulting polymers is greatly decreased by the presence of oxygenated compounds of structure analogous to, or isomeric with, any of the possible combinations of the original olefin structure boiling within the range of the hydrocarbon fuel. Such oxygenated impurities include alcohols and impurities of the alcohol type which result from the hydration and/or oxidation of olefins or polymers of said olefins in connection with the polymerization process, and the like, and which may be altered but not entirely removed by non-destructive hydrogenation.

While the mechanism of formation of these alcohol-like bodies is not a fundamental consideration nor a limiting function of our invention, it is thought that said impurities result from a concurrent hydration of the olefinic hydrocarbons during polymerization or alkylation which results in the formation of primary, secondary or tertiary alcohols or esters of same with organic radicals present in the catalyst and/or in the ketones, acids, ethers and the corresponding perbe satisfactorily polymer stock to saturation, or nondestructive oxides from the alcohols. These impurities which are closely related to alcohols are hereinafter termed impurities of the alcohol type and are thought to be present principally in the form of alcohols, although the methods of treatment herein described are applicable to the removal of any of the possible forms of impurities which may be present in such stocks and have adverse effects on the lead response, or the like, of the final product.

The magnitude of the effect of impurities of the alcohol type in hydrogenated polymer fuels is indicated by the fact that the presence of about two per cent by volume or less of primary and secondary alcohols in a fuel of 92 octane number (both with and without said impurities) lowers the antiknock rating of said fuel containing 1 cc.

of tetraethyl lead per gallon from 102 octane number to 100 octane number, or a loss of lead susceptibility equivalent to about per cent of the lead response of the alcohol-free fuel. The effect of tertiary alcohols is-somewhat less, but increases with the length of the carbon chain of the alcohol. When such a base stock is blended with straight run naphthas and/or natural gasoline fractions to provide the requisite vapor pressure and distillation characteristics, the oc-- tane number is lowered proportionately, and the effect of decreased lead susceptibility is magnified, particularly in fuels which must rate 100 'octane number with a maximum of 3 cc. of tetraethyl lead.

We have now further discovered that fuels of high octane numbers comprising di-isobutyiene concentrates, copolymers of isobutylene with normal butenes and/or propene and the like resulttion is not thereby limited to such application, since it is of generally wide scope.

We have 'found that polymer gasoline stocks, such as di-isobutylene concentrates and the like, which are segregated by fractionation subsequent to passage of an olefin feed stock over a polymerization catalyst, may be substantially freed of impurities of the alcohol type by a catalytic treatment over suitable catalysts, said treatment being effected at temperatures and pressures chosen to avoid further polymerization and/or depolymerization or other material alteration of the hydrocarbon components of the stock undergoin treatment. Such catalytic treatment, or dehydration, may be carried out prior to the nondestructive hydrogenation of such fuel stocks, and the heat supplied therein may be utilized for said hydrogenation and/or other final processing steps. In some instances the desired result may reached by subjecting the hydrogenation, which will generally tend to remove a portion of said impurities and subsequently to treat the saturated stock as disclosed herein to remove impurities remaining in the hydrocarbon fuel stock. If the catalytic treatthe manufacturing process, although the invena ment of this invention be applied to parafilnic stocks, no deterioration of the fuel occurs, since only the impurities of the alcohol type are decomposed. However, in such instances, removal of the olefins resulting from the catalytic dehydration may be necessary if said olefins are present in quantities sufficient to alter the total unsaturation of the fuel beyond specified limits. or course, if paraflinicity is neither necessary nor desirable for the finished fuel, this consideration is of little importance.

Catalysts which have been found suitable for use in the present process for the decomposition or dehydration, and removal of impurities of the alcohol'type from synthetic hydrocarbon fuels are. amorphous clays, in various forms such as kaolin, natural aluminum silicates,-unglazed porcelain and the like. Also effective are such metal oxides as the various forms of alumina, such as the natural bauxite or synthetic aluminas, and the oxides of metals, titanium, zirconium, cerium, hafnium, and thorium of group IV (B), of the periodic table, either alone or in combination with other of the above named materials or with inert carrier materials. Further active catalysts are such metal salts as aluminum phosphate and magnesium phosphate and silicate. By solid granular dehydration catalyst, as used in the present specification and claims, is meant a solid granular material such as is discussed above which has the property of promoting the dehydration of organic compounds, such as an alcohol, by the elision of water from the molecule.

Passage of hydrocarbon fuel stocks containing impurities of the alcohol type over said catalysts at temperatures below those causing deterioration of the hydrocarbon constituents results in the conversion of oxygenated compounds to the corresponding olefins and water or other elision product. Said olefins may be converted to paraffins by subsequent hydrogenation, and final disposition will depend on their boiling range. The elision product produced may be removed from the hydrocarbon material by a suitable drying agent following the catalytic treatment or said elision product may be allowed to pass unchanged along with the hydrocarbon material through subsequent processing steps.

The temperatures preferred for the catalytic treatment of this invention are dependent on the activity of the catalyst being used in any particular instance, and in general are well below the temperatures which would induce deterioration or alteration of the hydrocarbon constituents of the fuel. The catalysts named above will 4 support the dehydration or other decomposition of impurities of the alcohol type at temperatures between about 400 and 750 F., with the greatest activity generally evident between about 550 and 650 F. However, the temperature of treatment is dependent on the flow rate of reactant vapors over the catalyst, and at temperatures in the high part of the active range, very high flow rates resulting in contact times between 0.5 and 1 second are satisfactory. Thus, if lower temperatures and longer contact times are desirable, satisfactory operation is obtained at lower flow rates. In general, within the temperature range mentioned, fiow rates of 1 tolO liquid volumesof reactants per hour per volume of catalyst are satisfactory.

The pressures used in the practice of this invention may be low superatmospheric pressures, usually between zero and 500 pounds per square inch gage, although higher pressures may be used if desired, for example, up to 1500 pounds per when said catalytic treatment is carried out prior I to hydrogenation at substantially the same or even higher temperatures and pressures. Thus, the

.eflluent olefinic polymer fuel from said catalytic treatment maybe passed without cooling or lowering of the pressure directly to a hydrogenation unit for substantially complete conversion to paraifinic form. Such an arrangement allows -most economical operation by utilizing the heat and pressure supplied to the material undergoing treatment for both dehydration and hydrogenation operations.

In the practice of one modification of thisinvention, the eflluent material from a catalytic polymerization operation is fractionated to remove fractions boiling outside the motor fuel range. Following this fractionation, the liquid fuel containing impurities of the alcohol type is heated to the desired temperature within the specified range and passed at high flow rates over a dehydration catalyst. A preferred catalyst for this operation is 8 to 16 mesh particles of unglazed orcelain mixed with alumina of somewhat similarparticle size. The dehydration catalyst may be independently heated or the temperature within the catalyst chamber may be maintained solely by the heat of the incoming raw material. After contact with the catalyst for a time of 0.5 to seconds, depending on the temperature, the treated material passes from the catalyst chamber, to the hydrogenation step for the conversion of olefini c hydrocarbons to paraffinic form. Any low-boiling parafins formed as a result of the dehydration may be removed if necessary by subsequent fractionation.

As specific examples of the practice of this invention, the following are included, although these examples are not intended to limit in any way the scope of the invention.

Egrample I A synthetic iso-octane base stock manufactured by the polymerization of isobutylene and subsequent nondestructive hydrogenation of the polymer was found to contain more than 1 per cent by volume of aliphatic alcohols and7or' alcohol-like compounds. This stock with an original, or unleaded, octane number of 91, after addition of 1 cc. per gallon of tetraethyl lead had a rating of 100 octane number, and in the preparation of a gasoline of 100 octane number with a maximum of 3 cc. of tetraethyl lead, said base stock could be blended with natural gasoline fractions to make only 1.5 gallons of finished gasoline per gallon of base stock.

The polymer base stock, immediately prior to hydrogenation, was heated to 550 F., and the vapors passed at atmospheric pressure and without substantial cooling at flow rates of 2 liquid volumes per hour per volume of catalyst over a catalyst consisting of dehydrated alumina supported on crushed unglazed porcelain. The vapors leaving the catalyst were then condensed and the liquid was passed to the hydrogenation unit.

The base stock produced by this means had an original, or unleaded, octane number of 91, and with the addition of -1 cc. per gallon of tetraethyl lead had a rating of 103 octane number. Said base stock when used in the preparation of 100 octane fuel by blending and leading as described above produced 1.8 gallons of fuel per gallon of base, or a volume yield increase of 20 per cent over the stock which was not treated by this inventlon.

- Example II The hydrogenated synthetic iso-octane base stock of Example I was treated at 500 F. and a pressure of 100 pounds per square inch gage over a granular catalyst consisting of dehydrated alumina promoted with thorium oxide. The flow rate is maintained at 1 liquid volume per hour per volume of catalyst. The treated fuel with 1 cc. of tetraethyl lead per gallon has an octane number of 102.6. This treated :base stock blended to make 1.7 gallons of 100 octane fuel with 3 cc. of tetraethyl lead per gallon.

Example III tylene, with a sulfur content of less than 0.001

per cent, may be passed under a pressure of about 175 pounds per square inch into intimate contact with aqueous sulfuric acid, having a strength of about 68%, at a temperature of about 185 F. for a reaction period such that substantially all the isobutylene is polymerized, together with about an equal amount of normal butenes. The resulting hydrocarbon material is freed from the bulk of the acid, is washed with alkali, and a polymer base stock in the gasoline boiling range is recovered. The resulting polymer base stock, prior to hydrogenation and consisting principally of iso-octenes, is treated by the following modification of this invention. The oleflnic material was heated to a temperature between 400 and 570 F. and passed at a fiow rate of 2 liquid volumes per hour per volume of catalyst overa catalyst consisting of mixed alumina and aluminum phosphate at a, pressure ranging from 400 to 600 pounds per square inch gage to accomplish decomposition of the impurities of the a cohol type, The eiiiuent material from this catalytic treatment was then passed directly without substantial cooling or decrease in pressure to a hydrogenation unit wherein hydrogenation of the olefinic material to substantially completely paraillnilc state was carried out in the presence of hydrogen gas and a nickel catalyst. The finished paramnic iso-octane ibase stock had an octane number of 92, and with Ice. of tetraethyl lead received a rating of 103 octane, indicating an improved response to antidetonants, which comprises passing an olefinic hydrocarbon polymer fuel stock boiling in the motor fuel range including oxygen-containing hydrocarbon derivatives over a. solid granular dehydration catalyst at temperatures between about 550 and 650 F.. to decompose said impurities without substantial alteration of the hydrocarbons, submitting the resultant substantially purified polymer fuel stock to nondestructive hydrogenation to produce a substantially completely saturated fuel and to obtain a hydrocarbon fuel stock of high antidetonating value and of increased response to additions of antidetonants.

2. The method of removing impurities including oxygen-containing hydrocarbon derivatives from polymer gasoline stocks produced by the catalytic polymerization of olefinic hydrocarbons and containing said impurities by reason of reaction of minor amounts of said olefinic hydrocarbons with components of the polymerization catalyst, which comprises passing the vapors of such a gasoline stock at suitable flow rates over a catalyst comprising alumina supported on unglazed porcelain at temperatures between about 550 and 650 F. to decompose said impurities into olefins without substantial decomposition of the hydrocarbons, and removing from the treated stock products of said decomposed impurities.

3. The method of removing impurities of the alcohol type from hydrogenated polymer gasolines containing same and produced by thecatadecompose impurities of the alcohol type without substantial alteration of the hydrocarbons and to obtain a gasoline stock with an improved response to additions of tetraethyl lead.

4. The process of producing hydrocarbon fuel stocks of high octane number and of improved response to tetraethyl lead, which comprises catalytically polymerizing normally gaseous olefinic hydrocarbons in the presence of an aqueous strong oxygen-containing mineral acid to produce an olefinic polymer fuel stock boiling within the motor fuel range, separating and passing said fuel stock including oxygen containing hydrocarbon derivatives as impurities at temperatures between about 400 and 750 F. and pressures between 400 and 600 pounds per square inch gage over an alumina catalyst to decompose said impurities without substantial alteration of the hydrocarbons, then passing the fuel at substantially the same temperature and pressure together with added free hydrogen gas over a nickel catalyst to convert the olefinic hydrocarbons substantially completely to parafflnic hydrocarbons and to obtain a paraffinic hydrocarbon fuel stock of high octane number and of improved lead response.

5. In the process of producing synthetic motor fuels of high octane number, the step of improving the response of said fuels to tetraethyl lead which comprises passing a non-hydrogenated motor fuel stock roduced by catalytic polymerization of gaseous olefin hydrocarbons including oxygen containing hydrocarbon derivatives over a granular dehydration catalyst comprising a substantial proportion of an aluminum compound at temperatures within the range of 400 to 750 F. while at superatmospheric pressures, and at a flow rate of l to 10 liquid volumes per hour per volume of granular catalyst, to decompose the impurities without substantial alteration of the hydrocarbons, and subjecting the stock so treated to non-destructive hydrogenation.

6. In a process for producing a synthetic hydrocarbon gasoline stock of high antidetonating value prepared from lower boiling hydrocarbons in the presence of a polymerization catalyst, the method of improving the response thereof to the addition of tetraethyl lead which comprises subjecting such a synthetic gasoline stock which contains nonhydrocarbon impurities including oxygen containing hydrocarbon derivatives derived from incidental olefin reaction withcomponents of said catalyst to treatment in thepresence of a solid granular dehydration catalyst under a low super-atmospheric pressure and a temperature between about 400 and 750 F. for a period of time such that the hydrocarbon constitutents thereof are substantially unaffected and such that said nonhydrocarbon impurities are substantially decomposed, and recovering from the effluent a purified synthetic gasoline stock of improved tetraethyl lead response so produced.

7. In a process of producing a synthetic aliphatic hydrocarbon motor fuel stock of high octane number by catalytic synthesis of normally liquid hydrocarbons boiling in the motor fuel range from lower boiling aliphatic hydrocarbons including olefins, in which synthesis minor amounts of hydrocarbon derivative impurities deleterious to the response of said stock to lead alkyl antidetonants are formed by reaction of olefins with components of the synthesis catalyst, the improvement which comprises passing said stock over a solid dehydration catalyst at an elevated temperature and pressure and in the absence of other reactant materials to decompose substantially all said impurities without substantial alteration of the hydrocarbon materials present, and subsequently recovering a purified aliphatic hydrocarbon motor fuel stock so produced.

8. The process of producing hydrocarbon fuels of high octane number and improved response to tetraethyl lead, which comprises catalytically treating normally gaseous hydrocarbon stocks containing substantial amounts of olefins in the presence of a strong aqueous mineral acid to 'produce a synthetic polymer fuel stock boiling produced by reaction of minor amounts of olefins with components of the synthesis catalyst, the improvementwhich comprises passing said stock over a solid granular dehydration catalyst at an elevated temperature and pressure in the absence of other reactant materials to decompose substantially all said impurities without substantial alteration of the hydrocarbons present, and subsequently subjecting the stock so treated to nondestructive hydrogenation in the presence of free hydrogen to saturate the same and form a motor fuel stock essentially paraflinio in nature.

10. The process of producing hydrocarbon fuel stocks of high anti-detonatlng value and of improved response to antidetonants, which comprises passing an olefinic hydrocarbon polymer fuel stock boiling in the motor fuel range containing impurities including oxygen containing hydrocarbon derivatives over a solid granular which contains oxygen containing hydrocarbon impurities produced by reaction of minor amounts of olefins with components of the synthesis catalyst, the improvement which comprises passing said stock over a solid granular dehydration catalyst at an elevated temperature and pressure to decompose substantially all said impurities without substantial alterationto the hydrocarbons present.

,12. In the treatment of a catalytically produced synthetic olefinic hydrocarbon motor fuel stock,

which contains oxygen containing hydrocarbon impurities produced by reaction of minor amounts of olefins with components of the synthesis catalyst, the improvement which comprises passing said stock over a solid bauxite dehydration catalyst at an elevated temperature and pressure to decompose substantially all said impurities without substantial alteration to the hydrocarbons present.

GRAHAM H. SHORT.

GEORGE G. OBERFELL.

i 1 CERTIFICATE OF CORRECTION. Patent No. 2,576,558. May 22, 191p;

GRAHAM H. SHORT, ET AL.

It is hereby certified that error appears in the printed specification of the above nurnbered patent requiring correction as follows: Page 14., sec- 0nd column, lines 5 and 6, claim 6', strike out the words "including oxygen containing hydrocarbon derivatives 3 and thatvthe said Letters Patent should. be read with this correction therein thst the same may conform to. the rec- 0rd of the case in the Patent Office Signed and sealed this 18th day of September, Ar D. 19145..

Leslie Frazer (Seal) 7 First Assistant Commissioner of Patents.