US2684325A

US2684325A - Production of saturated gasolines with increased antiknock properties

Info

Publication number: US2684325A
Application number: US263429A
Authority: US
Inventors: Richard M Deanesly
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1951-12-26
Filing date: 1951-12-26
Publication date: 1954-07-20
Anticipated expiration: 1971-07-20

Description

July 20, 1954 R.v M. DEANESLY PRODUCTION OF SATURATED GASOLINES WITH INCREASED ANTIKNOCK PROPERTIES Filed Dec. 26, 1951 L HYDROGEN PRIMARY FRACTIONATION FRACTION FRACTION CRACKING 5 REFORMING f"""" REACTOR REACTOR GAS FUEL GAS FUEL 8 T 16 SEPARATION SEPARATION ZONE ZQNE n 0 200 F. 200 350" F. FRACTION FRACTION T 2oo -4oo"F l9 0 200F.

R T N 9 F AC FRAOTl0N./

|| POLYMERIZATION I ALKYLATION ZONE RESIDUE GAS FUEL 22 E 24 L SEPARATION zone FRACTION c -4oo- F FINISHED FRACTION GASOLINE iNVENTORI RICHARD M. DEANESLY ATTORNEYS:

Patented July 20, 1954 PRODUCTION OF SATURATED GASOLINES WITH INCREASED ANTIKNOCK PROP- ERTIES Richard M. Deanesly, Hinsdale, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application December 26, 1951, Serial No. 263,429

1 '7 Claims.

This invention relates to a combination process designed to convert certain parailinic gasoline fractions into a fuel more desirable for use in an internal combustion engine. More specifically, the invention concerns a combination of cracking, reforming, and alkylation processes for corn a satiu'ated gasoline to an improved motor fuel product of higher octane number and lower volatility.

It is widely recognized that the motor fuels known as natural and straight-run gasolines, that the liquid hydrocarbons recovered from natural gas and distilled from petroleum crudes, respectively do not fully satisfy all of the optimum requirements of a motor fuel for use in internal combustion engines of the spark-firing type, particularly since the increase in compression ratios for internal combustion engines of recent design. This inherent deficiency in the cornbastion properties of natural and straight-run gasoline is based upon the characteristically low number of the liquid straight-chain parafiinic and naphthenic hydrocarbons present in asoline fractions. The normally liquid,

natural gases include a relatively large proportion of components boiling below about 200 F. and a considerable proportion of these hydrocarbons (relative to the higher boiling hydrocarbon components) consists of the relatively volatile buta-nes and pentanes which increase excessively the vapor pressure of gasoline fractions from other sources if blended therewith in too large a proportion. it is therefore evident that to eifect an improvement in the volatility characteristics of natural and straight-run gasolines for motor fuel use, at least the light ends of these fractions must be converted into less volatile hydrocarbons generally of greater molecular weight. Furthermore, any improvement in the anti-knock properties of these hydrocarbons must involve a furthe r basic alteration in structure of at least a portion or" the hydrocarbon components from eslly straight-chain configuration to a onc l chain or aromatic structure. The

ntion provides a process for converting separate portions of a natural. and/or straight-run gasoline feed stock whereby the combustion properties of the gasoline are improved for use in an internal combustion engine; the provision of a practical means to effect such conversion is broadly the intended object of this invention.

in one of its embodiments the present invention concerns a process for improving the volatilic hydrocarbon vapors recovered from boiling range fraction from the product of said reforming reaction, subjecting said light hydrocarbon fraction and said intermediate boiling range fraction to a combination polymerization alkylation reaction, and recovering the remaining normally liquid fractions boiling up to about 400 F. from the products of said cracking, reforming and polymerization-alkylation reactions as an improved gasoline motor fuel.

A more specific embodiment of the invention relates to a process for improving the volatility and anti-knock properties of a gasoline fraction comprising essentially saturated hydrocarbons which comprises separating a fraction having an end boiling point of from about 200 to about 300 F. from said gasoline, subjecting said fraction to thermal cracking, separating a fraction containing C3 and C4 olefinic hydrocarbons from a product of said cracking reaction, subjecting the remainder of said gasoline to a catalytic hydrocarbon reforming reaction, separating a fraction boiling from about to about 350 1 from the product of said reforming reaction, subjecting said 03 and C4 olefin-containing fraction and said 160 to 350 P. fraction to a catalytic polymerization-alkylation reaction, combining the remaining normally liquid fractions boiling up to about 400 F. from the products of said cracking, reforming and polymerization allrylation re actions to form an improved gasoline motor fuel.

The present combination process is par "'cularly effective when utilizing a charging stool; comprising a natural gasoline product, since a large proportion of the latter feed stocks consists of hydrocarbons having poor detonating properties in internal combustion engines, the hydrocarbons comprising straight-chain paraiiinic components of relatively low, and at best, of only mediocre octane number ratings which tend to predetonate and produce a resulting knock when ignited under compression in a spark-fired engine. The process, however, may also be applied with substantially similar advantages to the conversion of straight-run gasoline fractions recovered from 3 petroleum crudes of any available source containing predominantly naphthenic and paraiiinic hydrocarbons, particularly the relatively volatile, initial boiling ends of these fractions. The process may also be applied to the gasoline boiling range fraction of a destructively hydrogenated hydrocarbon mixture in which straight-chain paraffinic hydrocarbons are also present as a result of hydrogenation which accompanies cracking of the higher molecular weight components of the feed stock into hydrocarbons containing fewer carbon atoms per molecule. It is noted that although the process is particularly effective and economically advantageous when applied to predominantly paraflinic feed stocks, the advantages of the present method of conversion are also obtained for feed stocks containing olefinic and/or aromatic hydrocarbons, preferably in minor proportion, which may also be present in admixture with the paraffinic and naphthenic hydrocarbons comprising the feed stock, without departing from the essential operation of the process. in characterizing the present feed stocks as essentially parafiinic gasoline boiling range fractions, it is intended to specify thereby hydrocarbon mixtures comprising aliphatic paraihns as well as cycloparaflinic or naphthenic components, which undergo cracking, i'somerization and dehydrogenation to yield the present improved gasoline fuel products.

The invention is further described with respect to various alternative flow arrangements as well as the preferred means for effecting the desired conversion in the accompanying flow diagram and in the description which follows. For the sake of simplicity, the process will be described with reference to a feed stool: comprising a natural gasoline containing C4 and higher paraffinic hydrocarbons predominantly and boiling up to about 400 F.

Referring to the accompanying diagram, a suitable saturated gasoline fraction, such as the present natural gasoline feed stock containing C4 paraifini'c' hydrocarbons and boiling up to about 400 is fractionated into low boiling and high boiling cuts in a primary fractional distillation columnl having feed stock charging line 2 through which the natural gasoline is fed into the process flow. The low boiling cut, ha *ing an end boiling point generally of from about 200 to about 300 F. and preferably a boiling range from the initial boiling point of the fraction to about 275 F., is separated from the natural gasoline and removed from fractionation unit 5 through line 3. The remaining higher boiling fraction, comprising the remainder of the natural gasoline boiling up to the end boiling point of the feed stock is separated in distillation column removed therefrom through line 5, and treated as hereinafter described.

The process of the present invention is designed to convert the low boiling components of the natural gasoline fraction, consisting largely of volatile, paramnic hydrocarbons of low or only intermediate octane number into olefins which may be subsequently converted into higher molecular weight allzylate and polymer hydrocarbons of lesser volatility and of higher anti-knock value. The conversion of the low boiling fraction into principally olefinic hydrocarbons is accomplished in the present process by subjecting the fraction to temperatures and pressures sufficient to effect a thermal cracking reaction. Thermal cracking of the low boiling fraction of the feed stock is obtained at pressures of from atmospheric to ap- 4 proximately 2,000 lbs. per square inch or higher, but preferably at pressures of from about to about 1,000 pounds per square inch at temperatures of from about 700 to about 1200 E2, the preferred range being from about 900 to about 1100 F.

The low boiling fraction of the natural gasoline feed stock, such as the C4-275 P. fraction is charged into cracking reactor 5 at the above hydrocarbon cracking conditions, the cracked products being removed from the reactor through line 6 and charged into a separation unit, such as distillation zone l, wherein the conversion products of the cracking reaction are separated into various component fractions based upon their boiling points. Separation zone '5 is preferably a series of absorbers, stabilizers and/or distillation columns wheren the light gases such as hydrogen, methane and C2 components of the product are separated as a gaseous fraction which is removed through line 8 for use in any manner desired, such as fuel for the refinery heaters, etc. A. resulting stabilized fraction boiling from about 100 to about 400 F., and preferably from about 200 to about 400 F. removed from zone contains hydrocarbon components particularly desirable for motor fuel use, not only because of the inclusion in this fraction of components which have greater anti-knock properties, but also because of their desirable boiling range for motor fuel use from the standpoint of vapor pressure; this fraction i removed from separation zone "i through line 9 and is sent to storage or to blending tanks for mixing with the gasoline boiling range products of other units of the present process. A fraction comprising the relatively low molecular weight olefinic hydrocarbons produced in cracking unit 5, such as propylene, n-butylene, isobutylene and the amylenes, boiling up to about 100 F., and preferably up to about 200 including hexenes and higher boiling homologs, is removed from zone l through line it and charged into polyinerization-a.ll ;ylation reactor H wherein the latter fraction is reacted with an arcmatic-containing fraction derived from the reforming stage of the present process, hereinafter described.

The production of olenns in the present process by splitting the paraiiinic components of the natural gasoline feed stock provides a source of hydrocarbon-reactive feed stock i.-. ch uion polymerization or condensation with aromatic hydrocarbons yields a polymer or alkylate product boiling in the gasoline range having superior anti-knock properties which make it particularly suitable for use as a motor fuel in internal combustion engines. The present process flow provides a unit, that is, alkylationpolymerization zone ll, wherein the olefin-containing fraction (comprising C3 olefins and higher molecular weight olefinic component boiling up to about 200 F.) is combined with the aromatic hydrocarbon fraction of the present reforming unit, hereinafter described, and reacted in unit 5! in the presence of a particular catalyst which effects substantially simultaneous olefin polymerization and alkylation of the aromatic hydrocarbons charged thereto-with said olefinic hydrocarbons. The catalyst and process conditions maintained in reactor I l are hereinafter described in greater detail.

Referring again to the higher boiling fraction separated from the natural gasoline feed stock in primary fractionating zone l, having an initial boiling point generally of from about 200 to about 300 F., and preferably a boiling range of from about 275 F. to the end boiling point of the natural gasoline feed stock is removed from zone I through line t and charged into reforming reactor I2 to convert the relatively low octane number straight-chain parafiinic components of the feed stock into isoparafiinic hydrocarbons of more branched-chain structure, and of higher octane number. In addition to such desirable conversion of the aliphatic components of this fraction, naphthenic hydrocarbons contained in the fraction are converted by means of the dehydrogenation and isomerization reactions occurring during the reforming conversion to aromatic hydrocarbons. The reforming conversion of the present process is effected in the presence of a reforming catalyst selected from certain catalytic composites having such properties for promoting the reforming conversion. The feed stock to the re-- forming reactor l 2 is desirably reacted at the reforming conditions in the presence of an atmosphere or" hydrogen which may accompany the hydrocarbon fraction into the reforming reactor I 2 or charged separately through line [3, generally in an amount of from about 2 to about 6 molar proportions, based upon the hydrocarbon feed.

The preferred reforming catalyst for effecting the conversion zone l2 comprises a composite of a platinum group metal, such as platinum itself or palladium with alumina and may optionally contain a halogen component in combination therewith. Alumina-supported platinum and halogen is a particularly preferred catalyst for the present reforming reaction, particularly since such composites effect the isomerization of the gilt-chain parafonic hydrocarbon compoof the fraction charged thereto into the able branched-chain parafiins of higher octane number, dehydroisomerization of the naphthenic hydrocarbon components to aromatic hydrocarbons of high octane number, and the hydrocraclring of the higher molecular weight homologs to hydrocarbons boiling in the gasoline range. Qther reforming catalyst composites such as alumina-molybdena, alumina-chromia, alumina-zirconia and other catalysts known for this purpose may likewise be utilized in the present reforming stage, although not necessarily with results equivalent to the use of an aluminapiatinum-halogen composite. The catalyst composition preferably includes a component which promotes the hydrocracking of the hydrocarbon components and in the preferred alumina-platinum metal composites containing halogen ions, a halogen component acts as the ingredient of 'atalyst composition which promotes the hydroc citing reaction. The halogens preferred for thi purpose are fluorine and chlorine, present in the composite in an amount of from about 0.01 to about 3% by weight of the composite. The platinum metal is desirably present in the composite in an amount of from about 0.01 to about 1% by weight of the composite. The hydrocarcharge stock to the reforming reactor, comig the Biff-400 F. fraction of the natural oline feed stock and hydrogen, if desired, is

. bed type of reactor, at a liquid hourly space velocity of from about 0.5 to about volumes of vaporized feed stock per volume of catalyst per hour, utilizing a molar ratio of hydrogen to hydrocarbons of from about 0.5 to 1 to about to 1.

The products of the reforming stage are discharged from reactor l2 through line I4 into a 6. suitable separation zone [5, such as a fractional distillation column, for the recovery of various fractions for individual further treatment. Separation zone !5 may consist of one or more fractional distillation columns in series to accomplish the desired separation. Separation zone !5 is preferably operated under such conditions as to separate a hydrogen stream which may be removed from zone [5 through line l3 and recycled to the reforming zone to provide an atmosphere of hydrogen therein, although hydrogen for this purpose may also be introduced into reforming reactor l2 from other sources, as desired. A gaseous fraction comprising methane, C2 and C3 hydrocarbons is removed from separation zone as a light gas through line It. .A fraction containing C4 and higher hydrocarbon hcmologs boiling up to about 200 F. is separated in zone id and utilized in limited amounts as a low boiling fraction to produce the finished gasoline product of this invention, the amount thereof depending upon the desired Reid vapor pressure of the finished gasoline. This fraction which contains such high octane hydrocarbons as benzene and various isoparaifins such as isopentane and the branched-chain hexanes is re moved from zone [5 through line H and is (ii-- verted into blending or storage tanks wherein the finished gasoline is prepared. A higher boiling fraction having a boiling range, for example, from about 350 to about 400 F. or slightly higher, up to about 415 F. is also incorporated into the finished gasoline blend, the latter fraction being removed from zone l5 through line it into a storage or blending tank, or the higher boiling ends, boiling initially at about may be out into line It for utilization in alkylation-polymerization reactor 1 I.

An intermediate boiling fraction of the product formed in reforming zone 32, preferably boiling from about 200 to about 350 F., although lower and higher boiling range limits such the aforesaid 160 F. initial boiling point may be selected, is removed from zone 15 through line is and charged, together with the low boiling fraction of the cracking reaction products, which generally have an end boiling point of about 200 F., into alkylation-polymerization reactor H. The polymerization phase of the reaction occurring in reactor H effects polymerization of the olefins present in these fractions to higher mo lecular weight hydrocarbons of lower volatility and of relatively higher octane number, while the alkylation reaction effects condensation of the low molecular Weight olefins in the cracked fraction, such as propylene and butylene, with the aromatic hydrocarbons boiling up to about 350 F. present in the reformate fraction. The polymerization and alkylation reactions are eirected catalytically in reactor H substantially simultaneously in the presence of a catalyst generally characterized as an acidic material, and preferably a solid catalyst of this type. An effective solid catalyst, well known for promoting polymerization and alkylation at selected reaction conditions is the silico-phosphate composite known generally in the petroleum refining art as a solid phosphoric acid, comprising a com" posite of a suitable porous support containing silica, such as fullers earth, diatomaceous earth, various clays, etc. with phosphoric acid, prefcrably pyrophosphoric acid, generally containing about 62% of P205 equivalent of phosphoric acid. The phosphoric acid may also be placed on the surface of silica particles, for example, by periodically wetting the surface of quartz chips or sand with a liquid phosphoric acid. Solid polymerization catalysts, including certain metallic phosphate salts such as copper pyrophosphate, cadmium orthophosphate, mercury pyrophosphate and others, either individually or supported on a suitable solid support such as alumina, clay, etc. are particularly effective catalysts for fixed continuous flow catalytic reactions, and although primarily polymerization catalysts, also effect alkylation at the selective reaction conditions maintained in reactor ii. The polymerizationalkylation reaction is effected in reactor ii cor-.- taining a solid catalyst of the above type at superatrnospherlc pressures, up to about 2000 pounds per square inca, and preferably at a pressure of from about 300 to about 1000 pounds per square inch, at a temperature of from about 300 to about 750 F. and at an hourly space velocity up to about 10 to volumes of gaseous charging stock per volume of catalyst per hour.

The products of the polymerization-alkylation conversion in reactor ii are removed therefrom through line and discharged into a suitable separation zone 2i, such as a distillation column, for the recovery of certain desired fractions from th product. Unconverted gases, such as proetc, are removed from zone 2! through line 22 and may be utilized as a gaseous fuel, or recycled to charging line 50 as a diluent of the olefinic feed stock to reactor l l. A gasoline boiling range fraction having an end boiling point from about 400 to about 415 and including C4 hydrocarbon components is separated and removed from zone 25 through line 23 which connects with line the latter conduit conveying the gasoline fraction to storage or a blending tank for production of the finished gasoline product. The fraction boiling above the end point of the gasoline product coin ising the residue in separation charged intocracking reactor 5 wherehigh boiling hydrocarbons contained in the fraction are split into lower molecular roducts which enter the stream of hydro processed in the pre ent flow. T he e boiling range fractions from the various separation zones of the present process which segregate these fractions from the products of the cracking reaction, the products of the reforming reaction and the products of the polyznerization-alkylation reaction and which all enter line in the above flow when combined blended in the proportions produced in each of the above reaction stages produce a highly desirable gasoline blend containing a variable ratio of volatile and higher boiling fractions, the finished gasoline product having a vapor pressure suitable for use as a gasoline motor fuel. The particular combination or reaction stages also produces a product of considerably higher octane number than the natural gasoline feed stool; utilized in the process flow.

The present invention is further illustrated with respect to specific embodiments thereof in e following example, which, however, is not inresidue of the gasoline feed stock. The lower boiling fraction (3. P.:C4-275 F), representing about 55% of the feed stock, is charged into a thermal cracking reactor at a temperature of 1050* F. and at a pressure of 900 pounds per square inch. The products of the reaction are cooled and fractionated to separate gaseous fraction containing hydrogen, methane, and C2 hydrocarbons which is vented to a gas storage chamber. A fraction containing C3 and higher homologs boiling up to about 200 F. is separately collected and reserved for a subsequent polymeriration-alkylation conversion, hereinafter described. A third fraction boiling from 200-400 F. and representing approximately 35% by weight of the initial low boiling fraction separated from the natural gasoline feed stock is separated and reserved for subsequent gasoline blending operations. fraction individually has a leaded (contai ing 3 cc. of tetraethyl lead per research octane number of -3 compared to a leaded research octane number of for the (34-275)" F. natural gasoline fraction utilized feed stock to the cracking reactor.

The higher boiling fraction of the initial gasoline feed stock, representing approximately 45% by Weight of the latter, is charged at a temperature of 94A) F., at a pressure of 000 pounds per square inch gauge, together with hydrogen in a molar ratio of hydrogen to hydrocarbons of a to 5 and at a liquid hourly space velocity of approx imately 2 volumes of feed per volur e of cat. vst

per hour into a tubular reactor containing a pilled catalyst consisting of platinum supported on alumina and containing combined fluoride and chlo- The products of the reaction are passed ride.

F. fraction of the cracking reaction product (con taining a large proportion of oleflnic hydrocarbons) and the 1704350 F. fraction of the reforming reaction product are charged into cat packed tube containing solid phosphoric acid catalyst at a temperature of eso F., at a prey sure of 450 pounds per square inch and at a l quid hourly space velocity of 2.5 for the combine-:1 polymerization-alkylation reaction. The effluent products of the alkylation-polymerization reactor are separated by distillation into a gasoline boiling range fraction boiling up to about 400 E. which is utilized for preparing the final gasoline blend. A fraction comprising unconverted C3 hydrocarbons, such as propane, is removed to storage. The distillation residue comprising components boiling above about 400 F. and representing about 10% by volume of the procuct is recycled to the cracking reactor.

The blend of gasoline boiling range fractions recovered from the cracking, eforming and alkylation-polymerization stages above has a Reid vapor pressure of 5 pounds per square inch, a clear octane number of 90, and a Research Motor Method octane number (containing 3 cc. of tetraethyl lead per gallon. added thereto) of 95, compared to the Research Motor Method octane number of the natural gasoline feed stock (containing 3 cc. of T. E. L. per gallon) of 85.

I claim as my invention:

1. A process for improving the volatility and anti-knock properties of an essentially paraffinic gasoline boiling range fraction for use in an internal combustion engine which comprises separating said gasoline into a relatively volatile fraction and a relatively higher boiling fraction, subjecting said volatile fraction to thermal cracking reaction conditions, separating from the product of said cracking reaction a light hydrocarbon fraction having an end boiling point of at least 100 F. and containing normally gaseous and normally liquid olefins, subjecting said higher boiling fraction to a hydrocarbon reforming reaction in the presence of a reforming catalyst, separating an intermediate boiling range fraction from the product of said reforming reaction, combining said light hydrocarbon fraction containing aromatic hydrocarbon and said intermediate fraction and subjecting the resulting mixture to a combination polymerizationalkylation reaction, and blending the remaining normally liquid fractions boiling up to about 400 F. from the products of said cracking, reforming and polymerization reactions to form an improved gasoline motor fuel blend.

2. The process of claim 1 further characterized in that said volatile fraction has an end boiling point of from about 200 to about 300 F.

3. The process of claim 1 further characterized in that said high boiling fraction has an initial boiling point of from about 200 to about 300 F. and an end boiling point corresponding to the end boiling point of said gasoline boiling range fraction.

4. The process of claim 1 further characterized in that said light hydrocarbon fraction is a hydrocarbon mixture comprising propylene, and having an end boiling point of about 200 F.

5. The process of claim 1 further characterized in that said intermediate boiling range fraction separated from the product of said reforming reaction has a boiling range of from about to about 350 F.

6. The process of claim 1 further characterized in that a fraction boiling above about 400 F. is separated from the product of said polymerization-alkylation reaction and recycled to said cracking reaction.

'7. The process of claim 1 further characterized in that said light hydrocarbon fraction includes Ca hydrocarbons and has an end boiling point of about 200F.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,983,693 Eglofi Dec. 11, 1934 2,213,114 Atwell Aug. 27, 1940 2,276,171 Ewell Mar. 10, 1942

Claims

1. A PROCESS FOR IMPROVING THE VOLATILITY AND ANTI-KNOCK PROPERTIES OF AN ESSENTIALLY PARAFFINIC GASOLINE BOILING RANGE FRACTION FOR USE IN AN INTERNAL COMBUSTION ENGINE WHICH COMPRISES SEPARATING SAID GASOLINE INTO A RELATIVELY VOLATILE FRACTION AND A RELATIVELY HIGHER BOILING FRACTION, SUBJECTING SAID COLATILE FRACTION TO THERMAL CRACKING REACTION CONDITIONS, SEPARATING FROM THE PRODUCT OF SAID CRACKING REACTION A LIGHT HYDROCARBON FRACTION HAVING AN END BOILING POINT OF AT LEAST 100* F. AND CONTAINING NORMALLY GASEOUS AND NORMNALLY LIQUID OLEFINS, SUBJECTING SAID HIGHER BOILING FRACTION TO A HYDROCARBON REFORMING REACTION IN THE PRESENCE OF A REFORMING CATALYST, SEPARATING AN INTERMEDIATE BOILING RANGE FRACTION FROM THE PRODUCT OF SAID REFORMING REACTION, COMBINING SAID LIGHT HYDROCARBON FRACTION CONTAINING AROMATIC HYDROCARBON AND SAID INTERMEDIATE FRACTION AND SUBJECTING THE RESULTING MIXTURE TO A COMBINATION POLYMERIZATIONALKYLATION REACTION, AND BLENDING THE REMAINING NORMALLY LIQUID FRACTIONS BOILING UP TO ABOUT 400* F. FROM THE PRODUCTS OF SAID CRACKING, REFORMING AND POLYMERIZATION REACTIONS TO FORM AN IMPROVED GASOLINE MOTOR FUEL BLEND.