US2202401A - Method of improving knock rating of naphthas - Google Patents

Description

May 28, 1940.l f .R.' RQsEN j METHOD Yoi'f VrraPxyING fxrlocxr RATING or; NAPHTHAS Y I Y No , kwa* ,N5

lllfl Patented May-28,

Raphael 'marina-beni, NL 1.,s'mi'mtrsur` n *'fStandard-I. 'G'.@Qpmponyg a` corporation' yof Delaware u 11 claims. (climsor The present invention toa method` for Y improving.. the octane number of naphthass: It

includes a process for so improving naphthas containing naphthenicsy andv open chain hydrocar.

bons by subjecting said naphtha successively to a.`r catalytic dehydrogenation and to arcontrolled hydrogenation. embodiment lof. ythe present invention is applicable to naphthas 'from/any source, -particularly to naphthas formedby the polymerization of` normally gaseous hydrocarbons, insofarl as -thesenaphthasfcontain -both -naphthenic and opent chain hydrocarbons.

' g The present invention also includes .the Appui cation of the controlled hydrogenatio'n {toy naphtha fromiany source having a composition analogous to that obtained by' the dehydrogenai tmn of the aforemescnbed ,naphthaa tnatis, containing aromatics and open chainoleilnesg f A number vof methods'for reforming nanh'tha.

so as to r-increase'its,octanenun'i'bei` are known inthe art. Most-of these methods consist :of high temperature treatments with or without a catalyst to` increxersethe` octane number of the. naphtha either by splitting of! hydrogen fromi naphthenlc constituents thereof or 'by increasing y l the secondstageoffthe" prvvJcess-is'l considerablythe content of light ends in the naphthav. e l VIi; has now been found that ailargei-"increase in" octane numberrthan was attainable bythe methods hitherto'practiced. can be achieved by a multi-#stage treatmentof a naphtha 'of the referred to above, in the iirst stage of ywhich the naphthenic constituents are converted intov aro-i matics and in the second v'stage' g'of` which the naphtha is treated'with" hydrogen under condi` Y tions suitable for the hydrogenation' of olefins to paraillns. -Special advantages of this ,comf bination are that the heat contained in the naphtha leaving the first stage is moreth n .sufficient to maintain` the dehydrogenated naphtha entering in thesecond stage at the.;desired. preheated condition, and that the hydrogen evolved'I in the flrstistage is usually suillcienty for the treatment in the second-stage;

Reforming catalysts/maybe divided intotwo general groups, those whichv accelerate dehydrogenation typified by oxides', l suldes, and other compounds of metals off Group VI of the periodic system, which may be employed alone'fbut are preferably associated withlv other diiicultly` re` ducible oxides, such as alumina, thorns., fc'eria, etc., and those which have ay so-called debutanizing'eifect because they accelerate the splitting off activated aluminaa stage fof the process" ofi' the A`present invention, catalysts of them-st typeareemployedparticularly a mixture offrano, lead and'chromic-oxidesH on magnesia, chromic. oxide y on v alumina,y or,y a.

`mmf-g1- '.i-.uyngstengsulf.lde."-` y V e The conditions tobeeniployed inthe vil'rst stage of the .present pr'ooessknown, andj mayA "bejmtdrin "generalffterma to jbethe. employment of a "temperaturefraging -fronif850f' F, to-

; 1100?'l F; atmosphericfor `slightly y.uperatmospheric ressureandfspace velocities ran'gingfroxnV catalyst 1 per* hour. 1 The v proper space j velocity 'forany s. given ,set yof, conditionsfis best deterfminedzbyjmeasnringthe molecularweight of the vfixed y'gases evolved-'in the treatment. value shouldjbefkeptyasflowias possible, since subl stantialfcarbon-carbonisplitting is tok be avoided.` The preferred @space-velocity iS that which4 gives the highest octane number improvementfwith' the smallestlincreaseinfthe molecular weight of thegnxed eases produced.,

The`- range of ,temperaturesfto be employed in' lower than that .employed in the first stage,.rang

n ing from aboutjzooe to about seo" F; In this stage elevated pressure is desirable.. )The y. only upper y; limit ont the pressure; be employed is that dictated f by,k economical operation.V Generally, it may be said that pressures ranging from 5o w zooiba/sg-.f'mwurbe satisfactory, anne.-

11without?unduly.ffincreasingl coke-formation fand minimizing octane. number improvement. Y A satisfactory operationis; one Ain `which' afpressurer f or 10o; lbs/sq. 1n. is maintained in both stages;

Since the )ttemperature',employed in thev second `stage is'-uslually much" below that at which colr-Y ing of the 'hydrocarbons'can occur, f it is "possible v have greater `acifivityitiil"liydrogenation'thanr the v catalysts which must `be employedA in" vthe riirst stage-"to minimize-'cokeforxnationl Suitable 55 of butane in preference to hydrogemtypifled by'` catalystsffor the second stage are'flnelygfdivided. 55

2 v nickel or copper, alone or supported on carriers, such as pumice or diillcultly reducible oxides, such as alumina, ceria, thoria, chromic oxide, etc. The life of these catalysts, which are poisl oned by sulfur, may be increased by removing from the feed stock any sulfur which it vmay Y contain. This is suitably accomplished by passing the vaporous products from the first stage over bauxite or iron sulfide before introducing them to the second reaction zone.

The hydrogen suliide formed in the desulfurization step may be removed by contacting the products from Vthe desuli'urization zone with luxmass (hydrated iron oxide)metallic iron, or metallic copper, prior to the introduction of these products into the hydrogenation zone without the necessity of reducing the temperature. If desired, a sumcient amount of sulfur dioxide can be added to the products of the desulfurization Bone to react with the hydrogen sulde so as to yconvert it to free sulfur and water, the sulfur being condensible under the pressure necessary for the hydrogenation without a reduction o f temperature below that suitable for `the hydrogenation step. In many cases the reforming catalyst, employed in the ilrst stage, eilects suilicient desulfurization so that a separate desulfurization step may be omitted. 01' course in the event that the catalyst in the second stage is the same as the catalyst in the rst stage, and is sulfurimmune, the desulfurization step is not necessary. Such catalysts, however, require the employment of a higher temperature within the range Speied than' dov catalysts which are poisoned by sulfur.

As previously stated, the hydrogen evolved in the nrst stage is reintroduced into the naphtha in the second stage. In order to insure as complete an improvement in the octane number of the naphtha as possible, it is usually desirable to provide for the `addition oi further quantities of hydrogen prior to the second stage.

It is not clearly understood with what constituents of the naphtha the hydrogen combines. It is known, for example, that benzol maybe hydrogenated under the conditions'employed in the second stage of the present process. Nevertheless, the second stage of the present process im- '30 parts an improvement to the octane number of the naphtha, thereby strongly indicating that the aromatica are no rehydrogenated. On the other hand, itvis known that branched chain olenns have a lower octane number thanv the coril responding paraiilns, whereas the straight chain oleiins have a better octane number than the corresponding paraillns. These facts support the conclusion that in the second stage of the process of the present invention the branched chain ole- U ilns are selectively hydrogenated and this may be accounted for on the theory that the branched chain oleilns have a greater afilnity for hydrogen than do aromatica or straight chain olefins.

It follows that care has to be exercised in the .l second stage of the process of the present invention to avoid the rehydrogenation of aromatica and, if possible, straight chain oleflns. The reaction can be controlled with a. fair degree of accuracy by basing the duration of the hydrogenation treatment on bromine number reduction. In actual operation hydrogenation conditions suitable for the hydrogenation of olefnsk are selected, and any suitable hydrogenation catalyst is employed. If the hydrogenation step is a continuous operation, a rate of flow of the reactants is selected and the bromine number of the product at this rate of flow is determined and compared with the bromine number of the naphtha fed to the hydrogenation. Any rate of ow at which a substantial reduction in the bromine number is effected, is suitable. It is, of course, preferred not to reduce the bromine number to zero, since this would mean that all of the straight chain olefins would also be hydrogenated. Moreover, if the product of the hydrogenation step showed a zero bromine number, it would be impossible to conclude that the rate of flow employed to produce that product was not sufficient- .ly slow to eifect a rehydrogenation of the aromatics. Consequently, it is advisable to select such a rate of flow as will effect a substantial reduction in bromine number without reducing it to zero.

It is, of course, not easy to determine by this method a rate of flow such that only the branched olefins are hydrogenated. `This is not a serious objection, however, because even though the hydrogenation of some of the straight chain oleflns might reduce the octane number of the product from the hydrogenation step to a value below that of the feed of the hydrogenation step, it a1- ways results in an increase in the lead susceptibility of the naphtha so that upon the addition of lead, which is customary practice. the hydrogenated fuel will have a greater octane number than the feed to the hydrogenation step. After the hydrogenation unit has been in operation for some time, the rate of flow of the reaction material thru the unit can be adjusted with a fair degree of accuracy so as to effect the hydrogenation of only the branched chain oleilns by plotting bromine number determinations against octane number determinations. In general, it may be stated that the bromine number reduction which gives the greatest increase in clear octane nurnber is that reduction which is obtained when the branched olens are hydrogenated to the exclusion ofstraight chain oleilns.

When the hydrogenation is conducted as a batch operation, whichvis rarely the case in commercial practice, the duration of treatment can be likewise determined by test runs followed by bromine number determinations. Here, as in the case of the continuous operation, the duration of treatment selected is one which substantially reduces the bromine number without reducing it to zero, and is preferably that duration of treatment which gives that reduction in bromine number which is accompanied by the greatest increase in octane number.

As is apparent from the above discussion, the present invention is based, to a large extent, upon the discovery of the fact that in a mixture of straight chain and branched chain oleiins and aromatics, branched oleiins can be hydrogenated l to the exclusion of the other unsaturated constituents, under conditions which are suitable for the hydrogenation of all the constituents but for a period shorter than that required for the hydrogenation of all of them. Consequently, there is contemplated, within the'scope of the present invention, the improvement of the octane number of any gasoline containing branched oleflns together with straight chain oleflns or aromatics by a controlled hydrogenation carried out under conventional hydrogenation conditions for a period of time determined by bromine number reduction. There is also contemplated the improvement in the lead susceptibility of any gasoline containing straight chain oleflns-and aromatics `byfa similarly controlled hydrogenation. l This embodiment of vthe present inventionh is par- '7, accadol f K Z of lth4 klira-gerrit.' invention, la. yTennis lstraight having yaAIlOende point was .fed at atmospheric pressure at a `r ateof 0.534

ticularly applicable. to aL gasoline whichy has-.been

stored for along period. Especially'one whichf i has been lstored after beingcatalytlcallyreformed The treatment; withhydrogen not'only exerts a marked influenceupon octane number and/or `lead susceptibility, .but also 'has an "extremely y and.8'.2% by weightofthe feed andthehydrogen]` ,.,producediwas between .45-and:1f.f1% ,byeweight ofthe .'feed. v The product hadan octane numbenefcial veffect upon copper 'dish gum andthe breakdown characteristics Vof f the gasoline 'Breakdown time is determined by lplacinga'test tube containing 25 ,cc.s of gasolinein a. bomb of specified size, feeding .oxygen into the 'bomb at atmospheric temperatureuntil 100 IbsoXyg'en pressure has been built up, and then heatingllthe bomb in aksteam bath.' The pressurebuilds up to a maximum and then begins to drop. The

time intervening between the point at which Vthe maximum pressure is. reached yand thelpointlat which the pressure has dropped 2 lbs. from Vthe maximum pressure is designatedas the break- 1 down time. The breakdown timeofthe gasoline is a direct measure of the stability of the gasoline in storage.

d A front' elevation "of anapparatussuitableffor carrying out the -process of the presentinvem.

tion is illustrated in diagranilmatic'form in the accompanyingdrawingin'which I` is a feed line thru which naphtha may be ,passed-after being y.put under pressureby pump 2, if desired, into 'preheater' 3, then into reaction chamber l containing a suitable catalyst of ,the hydrogen "splitting type, and rmaintained'at a.A temperature suitable.v forl catalytic reforming. Chamber l is connected to chamber 5, which contains bauxite.r 'or any other desired desulfurlzation catalyst, by 'a line 6 provided with a` valve l.` Chamber 5 is connectedto a chamber @containing lui'cmass,

metallic -iron,'or metallic copper,by line 9 pro-r ngividedwith a valve I0., Chamber 01s connected to a cooling. chamber II by afline I2 provided with a valve Il. Line 6 is` connected to line 9;' by

'a pipe I4 provided with valves. l5 and ls. Line "5 is also connected to line I2 by a branch linefII' provided with valves I8 and I9.'v

Chamber vII is provided with a ou zo 'which ,may be employed eitheras a cooling or a heating means, the latter, in4 case'l thereactionmixture,` inpassing thru chambers v5 and -I`is cooled to a temperature' below that preferred Vfor -u .Chamber II is connected to Vhydrogenation chamber 23 by line 24 in which is varranged a pump25 by which the. desired pressure. may be imposed upon thereaction material incase preceding. steps are conducted under a lower pres sure. Chamber 23 iselledmwith a catalyst, 25 of the typel heretofore described.r The products from chamber 23 pass thru line 21 intoseparator 28 provided with a cooling coil 29, a ,heatingv coil 30,'a draw-c1112 for normally gaseousvproducts anda draw-off 3| for finished naphtha.

In the event that it isdesiredto vfurther de" sulfurize the reformed naphtha, valves 1, I0`and I3 are openedvand valves I5, I6, Il!V and I9 aref closed. If it be only desired to remove Hydrogen sulfide from the product. leaving the reforming Y.

chamber, valves I5, I6 and I3 are'opened and valves "I, I0, I8 and I9 are closed. f When no gil'- fur removalis necessary,fvalves I8 and I5 lare opened and valves 1, I3 and I5 are closed.

n Example I.-In a specific application of the vthat ,oi the kreformed product, whileJth-lead cc."sr'xerhourl perv of catalyst at la "temperaturer between 1 000 and 1060 F. over acata1ystcomgasoline yield variedbetween 89.3 and 95% by volume of the feed, vthe gas loss wasbetween 5.1

ber whichvaried between 67 and,.69, -a bromlne number of 0.28 and afgumfcontentasmeasured posed of chromium, lead and zinc oxides. The

by thecopper dish.testent-.1500'rug.:per\.100;fcc;'s oy vaporous product containing free hydrogenwas fed to a bomb where it was mixedl with an additionallZ-liters of hydrogenzper liter of vaporous product and placed under `apressure of 800,2

lbs./sq. in.' The bombcontained 'a catalyst comtainedv for two "hours,y y. Thefproduct" obtained had-'a` bro'mlne number of '0.18,'ia` gum content..

was Swed fOr @bout a year, arthe endfbfewmcn tunet'lhd 'a bronilne r""iimb'fvrr of` 0.28, a? gum content measured by the coppe;-l dis'hmethod of y1261.6 mg,./100"cc.s, a'breakdownlperiod of.10.'4

hour a.ndfa.cle`ar octane #number-` oflv56. `naphtha wasagitated *with lbongblaclrf and filtered and then hydrogenated 'under the 'conditions andfor the same length of vtime a'sthe'reformed productin Example I. v'lhefflproduct of y Athis treatment had a bromine knumber` off 0;l8,'a ,gum content measured by thecopperdish method y hours and [a 1 clear CFR.- MM j octan'eilnumber` yof Example: Ille-@Av West Terras straight run naphtha ofA different origin f from that' employed :posed of copper,manganes'e oxide `vandzirle oxide, and was heated to 1751C. at which it was mainf Texas vnaphthav resulting from] thefilrst stage of the process described. in 'the preceding example vin .Example I and having a. vclearoctanefnuma clear CFR MM/octane number of 65.7and an .octane number fwith'3. cc.s` of Aleadl tetraethyl/gal. 1 .i 'L

.of.78.8. lWhenthisjK-productnvrras hydrogenated, y as describedzlnfExdamplekI; under vthe same-com i d breakdown period! of .r2.4 hours,1a-':clear CFR vMIM benoted that theclear octanenumberv of fthehydrogenatedproduct. in this run `vvasless than susceptibility of the latterwasdistinctly superiori.

to the former. d This indicates that A.the yperiod lemployed for' hydrogenatlonwas somewhattoo long 'and res-uitedfin4 'the hydrogenation of some furthe straight cnam olenrm;frhijslis borne out by tnefaet that in this thefbromine number. of the reformedv productewas" reducednby [.17 y

` whereasthe bromine numberI of the l'iydx'joformedvL productin. the-firstgexample'was reduced lby f f j.) 2l

hydrogenation onlylOn.vv v- The method of determining the bromine numbers given in the above examples was according to the Buc-Seaman'modication ofthe Francis method. From 5 to 10 grams of solid KBr is introduced into a glass stoppered fiask, thev required volume of KBrOa-KBr 0.5 or 0.7 gram of the sample diluted with chloroform, and shake vigorously for exactly two minutes. Finally add cc. of saturated KI solution `and titrate the liberated'iodine with n Nalao.

The bromine numbers given in the above examples were computed on the basis of grams of bromine per gram of naphtha.

The nature and objects of the present invention having been thus described and illustrated by examples, which are offered forthe `purpose of demonstrating the nature of the improvement e'ected by the present invention and not for the purpose of` defining the limits of applicability of the present invention, what is claimed as new and useful and as desired to be secured by Letters Patent is:

1. In the process of producing a highly refined motor fuel by`reforming a naphtha at temperatures between about 850 F. and about 1100 F. under superatmospheric pressures inv the presence of a dehydrogenation catalyst wherein the resultant products contain branched chain'and normal mono-oleflns followed by a catalytic hydrogenation with hydrogen of the reformed naphtha, the improvement which comprises controlling the hydrogenation process within the temperature range of about 200 to about 580 F. under a superatmospheric pressure of atleast 3 atmospheres and for a time suiilcient to reduce the bromine number to no less than about 0.14. ,f

2. Process as in claim 1 wherein said naphtha.'v

having a bromine number of 0.28, is hydrogenated only until the bromine number is reduced to 0.18.

3. Process as in claim 1 wherein the naphtha is hydrogenated only until its original bromine number has been reduced between about and about and wherein the bromine number is at least 0.14.

4. A process which comprises dehydrogenating a straight run naphtha in the presence of a dehydrogenation catalyst at the rate of .534 cc. per hour per cc. of catalyst at a temperature between about 1000 and about 1060 F., mixing the resultant vaporous product with hydrogen andv hydrogenating said product at about 800 lbs/sq. in. at a temperature of about C. for about'two hours in the presence'of a hydrogenation catalyst.

5. A process for improving the motor fuel characteristics of naphtha containing substantial amounts of unsaturated hydrocarbons which comprises contacting said unsaturated naphtha in vapor phase with hydrogen in contact with a hydrogenation catalyst under hydrogenating conditions of time, temperature and pressure, and

stopping the hydrogenation when the brominey comprises contacting said unsaturated naphtha in vapor phase with hydrogen in contact with a hydrogenation catalyst under hydrogenating conditions of time, temperature and pressure, and stopping the hydrogenation when the bromine number of the product is at least 0.14 but substantially below the bromine number of the unsaturated naphtha feed,

8. A process for improving the motor fuel characteristics of a reformed naphtha containing substantial amounts of aromatics, branched and straight chain mono-oleflns, which comprises contacting said naphtha in vapor phase with hydrogen in contact with a hydrogenation catalyst under hydrogenating conditions of time, temperature and pressure, and stopping the hydrogenation whergthe bromine number of the product is about 0.14.

9. A process foriimproving the motor fuel characteristics of a reformed naphtha containing substantial amounts of aromatics, branched and straight chain mono-olefins, which comprises contacting said naphtha in vapor phase with hydrogen in contact with a hydrogenation catalyst under-hydrogenating conditions of time, temperature and pressure, and stopping the hydrogenation when the bromine number of the product is about 0.18.

10. A process for improving the motor fuel characteristics of a reformed naphtha containing substantial amounts of aromatics, branched and straight chain mono-oleiins, which comprises contacting said naphtha in `vapor phase with hydrogen in contact with a hydrogenation catalyst under hydrogenating conditions of time, temperature and pressure, and stopping the hydrogenation when the bromine number of the product is at least 0.14 but substantially below the bromine number of the reformed naphtha feed.

11. A process which comprises hydrogenating a catalytically reformed West Texas straight run naphtha having a bromine number of about 0.31 in the vapor phase with hydrogen and hydrogenating said mixture at about 800 lbs./sq. in. at a temperature of about 175 C. for about 2 hours in the presence of a hydrogenation catalyst.

fis'

RAPHAEL ROSEN. u

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