US2285727A - Treatment of gasoline - Google Patents

Description

TREATMENT 0F GASOLINE Filed Jan. .'50, 1959 @ASE OUS PROD'UC 71s SEPARA TION Z ONEJYJ. n

estema June 9, 1942 TREATMENT F GAS OLINE .Y

Vasili I. Komarewsky,` Chicago, Ill., assignor to Universal Oil Products Company, Chlcago,'lll., a corporation of Delaware Y Application January 30, 1939, Serial No. 253,603

17 Claims.

This invention relates particularly to the treatment of gasolines of inferior knock-rating to improve them in this respect and is specially con- 1 cerned with a catalytic treating process for accomplishing this object.

While the'proces's to be disclosed is primarilyl adapted to the treatment of straight-run gasoline's produced by the simple distillation of crude oils, it may be also applied under suitably modied conditions of operation to cracked gasolines in conjunction with the cracking process to increase the overall eciency thereof. "i Apart from the small amounts of contami nating compounds containingV sulfur, nitrogen, and oxygen which are present in varying amounts in straight-run gasolines, extensive analyses for hydrocarbon groups have shown that straightrun gasolines consist essentially of mixtures of 6-carbon atom naphthene hydrocarbons and var ious parain hydrocarbons in varying proportions. 'I'he group analyses thus far madel do not gompletely distinguish between naphthenes of 5, 6, and 'l carbon atoms inthe ring orbetween paramn hydrocarbons of normal or branched chain structure, but for the purpose of the present description of a 'process applicable to improving the knock rating of these gasolines, they may be considered as consisting of varying proportions v of cyclo-hexane and its alkylated derivatives on the one hand and the various normal paraiiln hydrocarbons ranging from approximately to 12 carbon atoms to the molecule on the other hand.

It is a known fact that in general the more highly unsaturated compounds of a given molecular structure have a higher antiknockyalue than the saturated compounds. VIt is further known in general that cyclic compounds have a generally higher antiknock value than straight chain compounds of asimilar number of `carbon atoms unless the latter are of a branchedchain or isomeric structure. 'I'he process of the present invention utilizes both of these facts in converting in the most selective and generally advantageous manner substantial proportions of the naphthene content of gasolines into aromatics and substantial proportions of the paraffin content into oleflns and aromatics as will be hereinafter more fully disclosed.

In one speciiic 'embodiment the present invention comprises a process for improving the anti-knock value of gasolines which comprises first subjecting the gasoline to contact with catalysts eiective in dehydrogenating the naphthenesl step to further treatment with catalysts effective in dehydrogenating and producingfcyclic compounds from the parailln hydrocarbons.

It is within the scope of the invention to employ different catalysts in the two stages or to employ the same catalyst with the temperature and other conditions so that the dehydrogenation 'of the naphthenes is brought about in the primary stage withv substantially no eect on aliphatic hydrocarbonswhile the said aliphatic hydrocarbons are dehydrogenated and cyclicized in the second stage under moresevere conditions of operation in regard to temperature and timeof contact. This point will be developedfin later examples. f Y

The process of the present invention -is to some extent based on thefact that the conditions and catalysts best employed for dehydrogenating naphthenes are sharply differentiated from those which are best for dehydrogenating and cyclicizing straight chain hydrocarbons. Whereas catalytic reforming processes are known for improving the antiknock value of gasolines inferior in this respect, substantially all ofthese processes operate in a single stage with aselected catalyst under average conditions which are foundgby trial to produce the best overall results but usually not the 'optimum for the treatment of the vdiiferent hydrocarbon groups separately. For example, cyclo-hexane and other naphthenes are readily dehydrogenated to benzol and its alkylated derivativesy by contacting their vapors with nickel or other members of the iron group at temperatures of the order of 250-300 C. 'I'hese conditons, however, are usually without material eflect upon paraiiin hydrocarbons of gasoline boiling range and if conditions oi' increasing severity are employed'with the same catalysts, the paraiilns show a greater tendency to suier carbonto-carbon splitting and the formation of undesirablylarge amounts of gases and heavy liquid v byproducts.

As previously intimated, it is within the scope of the invention to use other catalysts than nickel or the other members ofV the iron group in the first stage and these catalysts may be of'a mixed character such as, for example, alumina supporting both nickel and chromium sesquioxide. In the manipulation of the process with such catalysts it is possible to regulate conditions sothat substantially only naphthenes are dehydrogenate'd in the 'primary stage, the temperatures usually employed for thsbelng of the orderoi 35o-450 C. depending upon the percentage of naphthenes wise aromatization of gasolines using first combinations ofcatalysts and conditions specific to the dehydrogenation of naphthenes and secondly those catalysts and conditions which tend to cause dehydrogenation and dehydrocyclization of parafns.

For-the dehydrogenation of naphthenes, nickel, cobalt and iron have already been mentioned,

but it is within the scope of the invention toV employ if desired more expensive materials such as the members of the platinum group, including platinum, palladium, iridium, osmiurn, etc. In the operation of the process, best results are usually obtained when these metals are used on relatively inert granular supports to present a larger `catalytic surface due to their extensive distribution. Various types of supporting materials of a siliceous or alurnrifous character may be employed as carrierssuch as, for example, s kieselguhr and other forms of silica, clays, and' other silicates, alumina, either naturalbrprepared and other inert materials. In the treatment of most gasolines with such catalysts, temperatures of approximately300 C. are employed in the first stage, thegasoline being vaporized andpas'sed over a selected and active dehydrogenating metal catalyst at a rate commensurate with obtaining best results in converting the naphthene -content into aromatics.v Obviously the exact conditions ofoperation will be determined by the amount andcharacter of the naphthenes present in whatever gas mixture is being treated.

After the aromatization of 'the naphthene content, the type of catalyst is changed and the vapors with or without separation of hydrogen and other reaction products are contacted with catalysts which have a dehydrogenating and cyclicizing activity with respect to residual parain hydrocarbons. Catalysts of this character include generally compounds and particularly oxides of the elements in the left-hand columns of groups 4, 5, and 6 of the periodic table, including titanium, zirconium, cerium, hafniurn,'tho rium, vanadium, columbium, tantalum, chromium, molybdenum, tungsten, and uranium. Such catalysts are readily prepared by depositing nitrates or other salts or hydroxides of the elements on miscellaneous supports andcalcining and reducing with hydrogen orhydrocarbons to produce the lower oxides. centages of these oxides which are suitable for effecting the desired dehydrogenation and cyclicizing-of mixtures of paraffin hydrocarbons will obviously vary with the amount and character of the paraffin hydrocarbons and the lactivity of the particular oxide promoter. However, a few trials will determine which is the most effective in a given instance. Granular activated V.aluminas prepared from precipitated aluminum hydroxide by calcination methods or by similar hydroxides or carbonates furnish suitable supports for the catalytic oxides and a catalyst which has given excellent-service consists of granular activated alumina supporting minor proportions (usually -20% by weight) of chromium sesquioxide. The temperatures employed in the second step are preferably somewhat higher thvan'those employed in' therprimary stage of the process and are usually 450 C. or higher, this combination of temperature and catalyst being substantially without effect on the aromatic hydrocarbons produced from the first stage.V

The accompanyingv drawing is a flow diagram of the process of vmy invention. The naphtha charging VVstock'isV supplied to tne vsystem by way of line l from which it is Ydirected to the first dehydrogenating zone indicated by 2 in the drawing.t In this zone the hydrocarbonsare subjected to contact with a dehydrogenating catalyst under conditions effectivefin the dehydrogenation of naphthenes to form aromatics. As hereinbefore set forth, the temperature' of the catalyst in this stage is of the order of 25o-450 C. while utilizing suchcatalysts as 'nickel on` supporting materials such as kieselguhr or other substances ofsiliceous or alumin'ous character.

The products of this `dehydrogenation'zone are The optimum perremoved byway of line 3 and, if desired, may be directed to a separation zoneY No. 1, ,indicated by 5 in the drawing.V Inthis separation zone, hydrogen together with smaller quantities' of normally gaseous hydrocarbons is removed from the 'system' by wayfofI line 6." If 1desi'red, this separation vstep may be omittedand the reaction products from the first dehydrogenation zone in .this case are directed from line 3 to'iline I which connects with line l, rsi'ipplying the second dehydrogenation zoneindicated by B in the drawing. y In'the second dehydrogenationzone the'v paraillns are Yldehydrocycliciz'ed to form aromatic hydrocarbons. The temperature in the second zone lies within the approximate rlimits of 450- l750" C. Effective catalysts in the' second zone comprise particularly group 5 and group 6 oxides 'supported on refractory materials-suchas alumina.` GroupV 4 oxides `have'also been used but in general are regarded as less electiveA than such oxides as those'of vanadium, chromium and molybdenum. The products 4from the second dehydrogenation zone"v are directed by way of line 9 to a`second separation zone indicated by l0 in the drawing. Inthis second separation zone, hydrogen and normally gaseous. hydrocarbons are separated from ,the stabilized gaso- .line which constitutes the product ofthe process.

It is usually found desirableto rerun the stabilized gasoline in order toreduce the "quantityof gum formingconstituents present therein.

Thejfollowing example is given to indicate the advantages of. thejpresent type fofprocess in .improving the antiknock value of vstraight run gasolines, although it will be'understood 'that catalysts and conditions willbe considerablyV niodied in thecase ofl other gasolineslso that the example `is not intended to4 place'undue limitations y on the scope ofthe invention. l

A Pennsylvania straight run gasoline fraction boiling between ,and 150 Cfa'ndhavingan octanenumber by the motor method of 43' .was treated by three'different procedures as follows:

(l) vVapors were passed noverjacatalyst consistingof reduced nickelon alumina'at atemperature of 3007 C. .and substantially atmospheric treatment of some'naturally occurring aluminum 75 pressure. After this treatment, it was found by analysis that the percentage of aromatic hydrocarbons was 36.5 and that the octane number has been raised to 51. The gas evolved consisted of 95% hydrogen.

After separation of hydrogen the product of the first stage was passed over an aluminachromia catalyst at va temperature of 45,09 C. and analyses indicatedrthat the percentage of aromatics had been increased to 55 and the octane number raised to '15.L The gas evolved in the second stage was 92% hydrogen.

(2) A catalyst was prepared which contained both nickel and chromium oxide on alumina and thevapors of the gasoline fraction were passed over this catalyst vat a temperaturer of 450 C. to simulate a one-stage reforming operation.- This treatment produced an aromatic vcontent of 45% and raised the octane number to 65. The gas evolved contained 85% hydrogen. rIt will be seen by this test that poorer results were obtainedbyg combining the catalyst and using a single selected temperature for the reforming operation.

(3) Using `an .alumina-chromia-nickel catalyst, the vaporized gasoline fraction was treated at 405 C. to increase the aromatic contentl to 45% and raise the octane number to 57, the gas evolved consisting of 94% hydrogen. In the second stage the products were passed over the same catalyst at 450 C., the yield of products consisting of 60% aromatics and having a 75 octane Vnumber, and the gas evolved consisting of 91% hydrogen.

It will be seen from the immediately preceding data that better results were obtained with an "alumina-chromia-nickel catalyst when the aromatization of the gasoline was conducted in two stages as in section (3) since the octane number obtained was 75 whereas that obtained in the single-stage treatment under section (2) was only 65.

I claim as my. invention:

1. A process for the treatment of gasoline containing naphthenic and aliphatic hydrocarbons to increase the antiknock value thereof which comprises subjecting vapors of said gasoline in a first stage to contact at a temperature of the order of 250-450 C. with a catalyst effective in dehydrogenating naphthenic A hydrocarbons and in a second stage to contact at a temperature within the range of 45m-750 C. with a catalyst effective in dehydrogenating and cyclicizing aliphatic hydrocarbons.

2. A process for the treatment of straight run Agasoline containing naphthenic and aliphatic hydrocarbons to increase the antiknock value thereof which comprises subjecting vapors of said gasoline in a first stage to contact at a temperature of the order of Z50-450 C. with a catalyst efectiv- Ain dehydrogenating naphthenic hydrocarbons and in a second stage to contact at a temperature within the range of 45,0-'750 C. with a catalyst effective in dehydrogenating and cyclicizing aliphatic hydrocarbons.

3. A process for vthe treatment of cracked gasoline containing naphthenic and aliphatic hydrocarbons to increase the antiknock value thereof which comprises subjecting vapors of said gasoline in a first stage to contact at a temperature of the order of 250450 C. with a catalyst effective in dehydrogenating naphthenic hydrocarbons and in a second stage to contact at a temperature within the range of 45o-'750 C. with a catalyst effective in dehydrogenating and cyclicizing aliphaticl hydrocarbons.

4. A process for the treatment of gasoline to increase the antiknock value thereof which corrprises subjecting vapors of said gasoline in a first stage to contact `with a catalyst containing a metal 'effective in dehydrogenating naphthenes, and in a second stage to contact with a catalyst containing a metal oxide effective in n tive in dehydrogenating and cyclicizing paraflins.

6. A process for the treatment of cracked gas- 'oline to increase the antiknock value thereof which comprises subjecting the vapors of said gasoline in a first stage to contact with a catalyst containing a metal effective in dehydrogenating naphthenes, and in a second stage to contact with a catalyst containing a metal oxide effective in dehydrogenating and cyclicizing paraflns.

7. A process for'the treatment of gasoline to increase the antiknocky value thereof which comprises subjecting vapors of said gasoline in a first stage to contact at a temperature of the order of Z50-350 C. with a catalyst containing a metal eiective'in dehydrogenating naphthenes, and in a second stageto contact at a temperature of the order of 45o-750 C. with a catalyst containing a metal oxide effective-in dehydrogenating and cyclicizing paramns.l

8. A process for the treatment of straight run gasoline t increase the antiknock value thereof which comprises subjecting vapors of .said gasoline vin a first stage to contactA at a temperature of the order of 25o-350 C. with a catalyst containing a metal effective in dehydrogenating naphthenes, and in a second stage to contact at a temperature ofthe order of 45o-750 C. with a catalyst containing a metal oxide eective in dehydrogenating and cyclicizing parafllns.

9. A process for the treatment of cracked gasoline to increase the antiknock value thereof which comprises subjecting the vapors 4of said cracked gasoline in a first stage to contact at a temperature of the order of 25o-350 C. with a catalyst containing a metal effective in dehydrogenating naphthenes, and in a second stage to contact at a temperature of the order of 450-750" C.' with a catalyst containing a metal oxide effective in dehydrogenating and cyclicizing parafllns.

10. A process for the treatment of gasoline to increase the antiknock value thereof which comprises subjecting the vapors of said gasoline in a first stage to contact at-a temperature of the order of Z50-350 C. with a reduced nickel catalyst eective in dehydrogenating naphthenes,v

and ln a second stage to contact at a temperature of the order of 450-7507C. with a catalyst consisting essentially of granular activated alu- 12. A process for the treatment of gasoline `to n increase the antiknock value thereof which comprises subjecting the vapors of said gasoline in a rst stage to contact at a'tcmperature of the order of 250-350 C. with a reduced nickel catalyst eiective in dehvdrogenatingl naphthenes, and in a second stage to contact at a temperature of the order of 450750 C. with a catalyst consisting essentially of granular activated alumina' supporting vanadium sesquioxide effective in dehydrogenating and cyclicizing paramns.

13. A process for .the treatment of gasoline to increase the antiknock value thereof which comprises subjecting the vapors of saidgasoline in a rst stage to contact at a temperature of the order of 25o-350 C. with a reduced nickel cata-V lyst effective in dehydrogenating naphthenes, andA in a second stage to contact at a temperature of the order of 450-'150 C. with a catalyst consisting essentially of granular activated alumina supporting molybdenum sesquioxide effective in dehydrogenating and cyclicizing paraiiins. 14. A process for thertreatment of gasoline to increase the antiknock value thereof which comprises subjecting the vapors of said gasoline in a first stage to contact at a temperaturel of the order of 35o-450 C. with a composite catalyst comprising essentially arelatively inert matev rial supporting chromium sesquioxide and reduced nickel to dehydrogenate naphthenes and. in a second stage to contact with a separate portion of the same catalyst at a temperature of 15. A process for increasing the anti-knockl value of gasoline distillate: containing naphthenic and aliphatic hydrocarbons which com-i prises contacting the distillate with a dehydro. genating catalyst under dehydrogenating oonditions'selective for the conversion'of naphthenes` to aromatics, and thereafter subjecting the thus partially aromaticized distillate to catalytic dehydrocyclization to produce further quantities of aroinatics from the aliphatic hydrocarbons.

16. A process for increasing the anti-knock value of gasoline distillates containing naphthenic and aliphatic hydrocarbons which comprises contacting the distillate with a dehydrogenating `cataLvst under dehydrogenating conditions .selective for the conversion of naphthenes to aromatica, and thereafter subjecting the thus partially aromaticized distillate to further contact with dehydrogenatingcatalyst under condltions selective for the dehydrocyclization of aliphatics into aromatica.

the order of o-'7509 C. t0 dehydrogente and 35 cyclicize aliphatic hydrocarbons,

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