US2810004A - Hydrogenation of catalytic naphthas - Google Patents

Description

Oct'. 15, 1957 R. c. MoRBEcK ETAL 2,810,004

HYDROGENATION y.OF CATALYTIC NAPHTHAS l i Roberv C. Morbeck Roberf J Lang Inventors nited States Patent() 2,810,004 HYDRGGENATION OF CATALYTIC NAIHTHAS Robert C. Morbeck, Fanwood, and Robert J. Lang, Cranford, N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware Application March 1, 1955, Serial No; 491,406

2 Claims. (Cl. M50-4683.6)

This invention relates to a process for improving the quality of light catalytic naphthas. The invention is directed to a specific hydrogenation treatment applicable to a particular selected fraction of a catalytically cracked naphtha. The invention. provides a means for greatly improving the Motor method octane rating of such catalytic naphtha fractions.

The invention involves fractionation of a catalytically cracked naphtha into at least two fractions, one of which constitutes the portion of the naphtha boiling in the range of about 65 to 115 F. Hydrogenation of this i lem of satisfying the octane requirements of current autofro `motive engines. VIn, the past, octane ratings of gasolines have primarily been determined by the so-called Research method, which can be' determined by ASTM- test, designated D908-47T. While this is an important and valuable anti-knock rating test, it has become appreciated that the Research octane rating of a gasoline as determined `by this method correlates poorly with actual road perform- .ance of a gasoline. search octane number is determined in a test procedure This is true in part since the Re- L; rating of a gasoline is not a complete indication of the value of a gasoline in satisfying an engine under road conditions.

As a result, other methods of determining octane ratings are commonly employed. One such method is the so-called Motor method test, designated by ASTM test particular fraction provides substantial and unexpected advantages as regards the quality of the resultant hydrogenation products. The invention is based on the discovery that the fraction of a catalytic naphtha boiling in the range of about 65 to 115 F.; that is, the pentene fraction, is particularly susceptible to improvement in' ments in the Motor method octane rating. Unexpectedly,`

however, by hydrogenating the fractionof a catalytic naphtha boiling in the range of'65" to 115"F:, it is possible to secure great improvements yin the Motor method octane rating of this particular fraction `accompanied by little, if any, loss in the Research method octane rating. lt is 'the basic concept of this invention therefore, to provide a hydrogenation treatment for upgrading the antiknock quality of this specific fraction of a catalytic naphtha which is separated from the naphtha for this treatment.

In a specific embodimentof the present invention, a catalytic naphtha is divided into the pentene fraction and a heavier naphtha fractionand both of these fractionsl are subjected to different and specific hydrogenation conditions. By this means it is possible to upgrade the total' catalytic naphtha bya' hydrogenation treatment to obtain results which cannot be achieved by hydrogenation of the total naphtha. t

The invention will be fully identified 'in the description which follows, and with reference to the accompanying drawing which diagrammatically illustrates aiflow plan of a specific Vand preferred embodiment of the invention. i One of the most important requirements of a high quality gasoline at the present time relates to the antiknock rating of the gasoline; The importance of gasolines of high anti-knock rating has been made more and critical by the trend toward engines of higher compression ratio. At thepresent time the compression ratio Method D357-47. It has been found that the Motor method octane determination correlates with the road performance of la gasoline somewhat better than the Research octane rating. e In view of these basic factors, production of present day-high quality gasolines must be carried out with reference to both the Research and Motor method octane octane rating. The over-all octane rating of the fuel is some function of both of these octane rating methods and can be approximated byl averging the Research and Motor method ratings.

` It is the principal object of this invention to provide a refining process particularly adapted for improving the Motor method octane rating of naphthas. This invention` therefore provides a valuable tool for providing higher quality gasolines in a manner heretofore unobtainable.

The nature and benefits of this invention can be apf` preciated by reference to Table I, showing data obtained by conduct of two types of hydrogenation applied Vto selected fractions of a light catalytic naphtha as com-` tions, approximately 98% of the oleins present in the feed of current automobile engines has been increased to values above 6.5, ranging upwardly toas high as,12. Engines having such high compression ratios require use of high anti-knock gasolines.- The more extended use 0f. automaiictransmssions has.. alsoiaggravatedthe probf.

were saturated. In the other hydrogenation operation employed, using the same catalyst at the same temperature and with the same amount of hydrogen, and at throughputs of about 1.5 to 2 v./v./hr., pressure was maintained at the lower figure of 50 p. s. i. g., so as to cause partial saturation of the oleins present in theV feed. Under these'V conditions, approximately 43% of the oleins were hydrogenated to saturation. Y

In the conduct of these experiments, three types of naphtha feed stock were employed. v The first of these constituted the whole of a light catalytic naphtha boiling in the range of about 65 F. to 363 F. A secondfraction constituted only that portion of this naphtha boiling in the range of about to 150 F. Finally, a `third hydrogenation feed stock constituted only the pentene fraction of the light catalytic naphtha boiling.

in the range of about 65 x to 115 F. The results ofapplying these hydrogenation treatments to these feed stocks under lthe conditions specified are shownv in Table i.,

TABLE I Hydrogenaton of light catalytic naphtha `oinplet sat-matan Partial saturation Oletin Saturation, -Percent 98 43 Boiling Range, FVT o 11s/15o l C15/363 C 11s/15o (1t/'aaa'D f FEP FEP Vol. Prcent on Total Naptha 22 17 10o 22 17 `16o Octant` Change (3 cc. TEL): y

MOOI -Q. +14. O +6. 5 +4. 5 +7..0 +2.*5 +2. 5

- Net octane change +12. 5 0.5 2. 5 +8.() +1 0 +0.5

Final Motor Octane (3 coTEL) 100 9255 88.5 93 88. 5 8635 Hydrogen Consumption, S. C. F./B 650 630 520 300 300 220 Referring to Table I, lit will beobserved that hydrogenation Vof the total naphtha conducted to secure complete saturationof olefins present, resulted in a substantial drop in the Research octane rating of the gasoline. This yhydrogenation treatment resulted in a loss of 7 l'Research octane numbers.A The operation caused a small improvement in the Motor octane rating of the gasoline amounting to 4:5 octane units. However, it is apparent that the substantial loss in Research octane number would ordinarily far offset any value obtained by appreciation of the small gain in Motor octane number. When treating the total naphtha .under the milder hydrogenation conditions, causing partial saturation ofrolens present, al smaller loss in VResearch octane resulted, although in this case the Motor octane rating of the hydrogenated naphtha improved but little. Again, therefore, application of this hydrogenation treatment to the total naphtha is shown to be of little or no value so far `as improving the overall octane quality of the gasoline.

VAs opposed vto this, the data'of Table I shows the substantial and unexpected improvement Vin the anti-knock quality obtainable when applying these same hydrogenation conditions only to` the pentene fraction of the naphtha. In particular, the data show that Yin the complete saturation hydrogenationtreatment applied to the -pentene fraction of the naphtha, itwasvpossible to increase the Motorv method voctane rating 'of this fraction by l14 units. Concomitantly, there was little change'irl the Research rating of the-pentene fraction amounting only to a decrease of 1.5 units 'which was substantially less than that resulting from treating the total naphtha under the same hydrogenation conditions. The partial saturation hydrogenation'treatment, when applied to only the pentene fraction of the naphtha again showed substantial advantages over treatment of the total naphtha. Thus, th'epartial saturation treatmentof the pentene fraction resulted in'a gain of 7 octane units vby the Motor method and of. one octane unitby the Research method. The data of VTable I therefore, shows the substantial and unexpected advantages of segregating the pentene fraction lfrom a catalytic naphtha and applying a hydrogenation treatment to this specific fraction. ABy so doing, it becomes possible to greatly improve the Motor octane rating of this specific fraction while avoiding the degradatio'n inResearch octane rating otherwise resulting from hydrogenaton of the total catalytic naphtha.

With reference to the hydrogenation ofthe intermediate naphtha'fraction boiling within the range of 115 to 150 F., the data of Tablel again shows that thislfraction can not be appreciably upgraded in octane characteristics. Thus, because of loss in the Research octane rating, hydrogenation of this fraction -at either p'artial'orcompletes'aturation conditions provides substantially no 'better result than treatment of l'the total naphtha. 'This data therefore. establishes that hydrogenation vof the p'entene fraction of a catalytic naphtha byitself provides sig-y nificant and unexpectedA improvement 'in anti-knock character'istics `not obtainable by hydrogenating the total naphthajor narrow fractions kof the naphtha other than the pentene fraction.

As Aformerly *st ated, the 'overall octane 'rating of a gasolinefis bestlitrdicated "by `a consideration of yboth the Research and Motor incthod octane rating. To weigh in :this consideration net octane change 'is indicated in Table i 'which 'is simply the `sumi'of the Research and Motor method octane y'changes resulting from hydrogenation of the ditfe'reiit stocks. The` unexpected and substantial advantage of hydrogenatil'ig the pentene fraction alone'is particularly indicated 'by the net octane change data.

The vrel'narlcable increase in the Motor Voctane rating of the pe'ntene Cfraction obtainable by hydrogenation is primarily due to the increased lead susceptibility of the hydo'genated lpentnes. -Data 4establishing thisare shown in Tablet-l. ,A l

TABLE II Motor-octane Number Feed saturated A Product Leaded (s M1. TELL-.. 86.0 99.9 +1a9 clear 81.2. l sal +o.9

A Due to 'ran +4.21 +118 These data show that while the clear octane number of the hydrogenated pentene fraction is but little better than that of the unhydrogenated fraction, remarkably, the leaded Motor octane number attributable to the presence of'tetraethyl-lead is increased by 17.8 octane units.

An important featureqof this invention is the manner in which hydrogen is conserved while achieving improvement in anti-knock quality. VA catalytic naphtha contains a substantial amount of olefinic constituents resultinginhi'gh lhydrogen consumptions when such naphthas are hydrogenated For example, when hydrogenatng aitot'allight catalytic naphtha boiling in the range of about 65 "to 363 F., a'hydrogen'consumption of about 500 to 600 standard cubic feet per barrel is required. From, an economic' viewpoint, this substantial consumption of hydrogen'could not bejustied for attaining the relativelyinsignificant change in anti-knock characteristicsshown in TableAI. However, by hydrogenating onlythe-'pentene fraction of a catalytic naphtha, while about thesarne amount of hydrogen is required per barrel of penitene feed, over-al1 hydrogen requirements are onlyja fraction of those required for treating the total naphtha. This Ycan be appreciated by the fact that approximatelyia l2.() Motoroctan'e grain per 100 standard cubic feet *of hydrogenper barrel can be achieved by treating `tliepentene jfraction v'while the 'Motor method octane gain intreatingthe total naphtha with the lsame `amount-ofhydrogeniSonIy'abOut0.5.. Consequently, in considering thehydrogenation rof catalytic pentenes in accordance WiththisV invention, opposed to hydrogenation of other fractions of a catalytic naphtha, it is apparent that this invention provides a remarkable improve-` ment in anti-knock quality for quantity of hydrogen required. i The data of Table I, shows thatpartial saturation of the pentene fraction attainsabout, half the improvement in Motor octane number'which can be obtained by total saturation. These data are particularly significant in considering makeup of a relinery gasoline pool. Olefinic constituents have a more desirable octane blending factor thanparaflinic constituents, and for this reason by partially saturating the pentene fraction as shown'in `Table I, the over-all effect in'a gasoline pool is substantially thatl obtainable by complete saturation of the pentene fraction. Por this reason it is a particular feature of this invention to partially saturate. rather than to completely saturate the pentene fraction of alight catalytic naphtha so as to further conserve hydrogen consumption and to provide a pool gasoline product of substantially the octane characteristics obtainable by. other processes requiring greater amounts of hydrogen. In this connection it is generally preferred to saturate about 30% to 60%, for example, about 40% of the olefns present in the pentene fraction.

While the process of this invention has a desirable effect on the sulfur content of naphthas treated in accordance with the invention, the process would not normallybe used for this purpose and cannot be considered a desulfurization operation. l Catalytic naphthas by their nature are generally of low sulfur content due Yto conversion and elimination of sulfur compounds during catalytic cracking. Consequently, catalytic naphthas ordinarily have sulfur contents in the relatively low range of about 0.02 to 0.10%. Of this sulfur content, practically all of the sulfur is contained in the higher boiling fractions of the naphtha. The pentene fraction of a catalytic naphtha separated by fractionation only contains about 0.02% of sulfur constituting less than of the total sulfur in the naphtha. Hydrogenation of the pentene fraction even when conducted to secure maximum desulfurization only reduces the sulfur content to a level of about 0.0002% to 0.001%. Thus, if this desulfurized pentene fraction were to be blended back with the heavier naphtha fractions to reconstitute the total naphtha, the sulfur content of the total naphtha would only be changed by about 5%. It is apparent then that the process of this invention, while being of advantage in somewhat reducing sulfur content of a naphtha cannot be considered as constituting or replacing other desulfurization operations.

In obtaining a total catalytic naphtha of highest quality, it is desirable to particularly treat the portion of the naphtha remaining after separation of the pentene fraction. It is particularly desirable to treat the heavier fraction of the catalytic naphtha by a hydroining operation conducted at hydrogenation conditions different from those applied to the pentene fraction. This is achieved by hydroiining the heavier fraction of catalytic naphtha boiling above 250 F. under conditions to secure a bromine number reduction of no more than about 20%. This results Vin primarily improving the engine cleanliness and stability characteristics of this naphtha fraction while contributing a sulfur reduction of about one-third. Such hydrofining can be carried out using a hydrogenation catalyst such as cobalt molybdate at temperatures of about 400 to 700 F., at a pressure in the range of 50 to 250 pounds per square inch, throughputs of about l to 20 v./v./hr., and at hydrogen consumptions less than 60 standard cubic feet per barrel.

In conducting the hydrogenation of the pentene fraction in accordance with this invention, a wide variety of hydrogenation catalysts may be employed. Preferred catalysts constitute the oxides of cobalt or molybdenum alone or in admixture and including cobalt molybdate. Preferably, these catalytic agents are supportedY on an adsorbent support such as alumina. It is particularly preferred to employ cobalt molybdat as the catalyst.` The 'pressure employed is to be in the range of 25 to 500 pounds per square inch although it is preferred to use pressures below 200 p. s. i. g. for the hydrogenation of the pentene fraction and it is particularly desirable to employ a pressure of about 50 p. s. i. g. Throughputs of 1 to 20 v./v./hr., may be employed although the pre ferred range is about 5 to 10 v./v./hr. The temperature maintained during hydrogenation is about 500 to 800 F., and specifically 700 F. Contact of the pentene frac-y tion with the catalyst under these conditions should be carried out employing a rate of hydrogen supply above about 500 standard cubic feet of hydrogen per barrel, and generally about 1500 standard cubic feet per barrel.

The specific hydrogenation conditions are to be selected from the foregoing limits by regard to the resulting olefin saturation and/or hydrogen consumption. In general, for olefin saturations in the range of about 30 to 100% of the olens present in the pentene fraction, hydrogen consumptions of about 200 to 700 standard cubic feet per barrel will be employed. In treating a typical catalytic .pentene fraction for complete olefin saturation, a hydrogen consumption of about 650 S. C. F./B. is ordinarily required.

Referring now to the drawing, a specific embodiment of thisv invention is illustrated showing a preferred ow plan for the practice of this invention. l

As illustrated, a gas oil feed stock boiling in the range of about 400 to 1100 F., for example, may be brought into catalytic cracking zone 1 through line 2. Catalytic cracking of a conventional nature will be carried out in zone 1 permitting removal of cracked products through line 3 for introduction to fractionation zone 4. Light gaseous products including C4 and lighter hydrocarbons may be withdrawn from fractionation zone 4 through an overhead line 5. A fraction including the catalytic naphtha fraction boiling in the range of about 50 to 400 F., may be removed through line 6. Higher boiling cracked products will be recovered from the fractionation zone through lower withdrawal lines 7 and 8, etc.

The catalytic naphtha fraction may be passed to a secondary fractionation system 9, which may be operated to permit removal of residual amounts of C4 and lighter constituents through overhead line 10. In accordance with this invention, a sidestream is taken from fractionator 9 through line 11 constituting the pentene fraction boiling in the range of about 65 to 115 F. Preferably, a higher boiling fraction, boiling in the range of about to 250 F. is withdrawn as a sidestream through line 22. Finally, a fraction boiling in the range of about 250 to 400 F., will be removed as a bottoms product through line 12.

The pentene fraction of line 11 is then passed to hydrogenation zone 14. In zone 14 the pentene fraction is subjected to hydrogenation under the conditions identied hereinbefore to achieve an olefin saturation which is preferably about 40% or greater. The hydrogenated product may then be passed through line 15 to zone 23 for caustic or water washing although this is an optional step. Thereafter, the treated pentene fraction is passed to storage zone 17 through line 16 for blending with other gasoline blending stocks.

In the preferred conduct of this invention, the naptha fraction of line 22 is passed directly to storage zone 17. This fraction requires no treatment except optional treatment for sulfur removal. If desired, however, the naphtha of line 22 may be combined with the naphtha of line 12 for treatment in hydroining zone 18. In all cases, the heavy naphtha fraction of line 12 is subjected to the hydroning conditions identified hereinbefore. The hydrogenated product from zone 18 is then passed into the storage zone 17 through line 20. The resultant blend of the products of lines 16, 22, and 20 constitutes a desirable high quality gasoline. It is apparent of course that other gasoline blending stocks may also be mixed with rthese `'consftitueitfs a's desirable 'in 'conventional renery practice. t Y

s described, therefore, 'the present Vinvention relates to 'the upgrading of. naphth'as derived froin a catalytic cracking process. The invention particularly concerns the treatment of Vspeciiic, selected fractions of a catalytic naphtha under specific hydrogenation conditions, The basic feature of the invention is ythe treatment of the pentene fraction of a catalytic naphtha boiling in the range of '65 F. Yto 115 F. 'Such afraction typically cons'titutes about 60% of unsaturated, olenic compouds and 40% of saturated 4parains. More particularly, a typical pent'ene 'fraction of catalytic naphtha will constitute the following general composition:

The specific proportions of these 'constituents will of course vary somewhat in accordance with variationsin the conditions of catalytic cracking and the feed stock ern'- ploy'ed. Pentene 'fractions vadaptable to treatment by the present invention may, however, be characterized as constituting at least about 50% unsaturated hydrocarbons.

What is claimed is:

. '1. A process for upgrading a catalytic naphtha which comprises the steps of fractionating the naphtha to segregate a iirst fraction boiling below about 65 F.; a second fraction comprising pen'tenes free of `Ce hydrocarbons and boiling 1in the` 'iaige "of about `65 F. t0 115 F.; a third ',lt'ra'ctioil boiling inthe range of about '115 F. to 250 F.`; a 1fourth fraction boiling 'above vabout 250 F.; hydrogenating the second fraction to secure an ol'eiin saturation in th range 'of 30% to V100% by contact with hydrogen in the fpe'snce of a hydrogenation catalyst selected kfro/rn the Ygroup consisting of cobalt oxide, inolyb denuin oxide and v'cobalt molybdate supported on an adsorbent carrier at a 'temperature in the range of about 500 to '800 F., a pressure in the range of about 25 to 500 p. s. i., at a throughput in the range of about 1 'to 20 v./v.7 hr., with 'a minimum of "500 S. C. F. of hydrogen/bbl.; `hydrgenating 'the fourth 'fraction to secure a ixirnum bromin reduction of 20% by contacting it with hydrogen inthe presence of a cobalt molybdate catalyst at a temperature in Ythe range of 400 to 700 F., 'a pressure lin 'the range of '50 to 250 lp. s. i., at a throughput in the range fof 41 to 20 v./v./hr. with amaximunrhydrogen consumption of less than about S, C. F-.7bbl. and* blending the third fraction with the treated second Vand fourth'ractions to'provide a naphtha product.

2. The process of claim l in which an oleiin saturation of 'abouty30% to "60% is obtained.

A' References "Cited in 'the tile of this patent UNiTED .STATES PATENTS l2,348,557 SMattox May 9, 1944 2,860,253 Marschner Oct. 10, 1944 l2,'420g030 Brandon May 6, 1947 2,426,903 'Sweeney -...2-a sept. 2, 1947

Claims (1)

1. A PROCESS FOR UPGRADING A CATALYTIC NAPHTHA WHICH COMPRISES THE STERPS OF FRACTIONATING THE NAPHTHA TO SEGREGATE A FIRST FRACTION BOILING BELOW ABOUT 65*F.; A SECOND FRACTION COMPRISING PENTENES FREE OF C6 HYDROCARBONS AND BOILING IN THE RANGE OF ABOUT 65*F. TO 115*F.; A THIRD FRACTION BOILING IN THE RANGE OF ABOUT 115*F. TO 250*F., A FOURTH FRACTION BOILING ABOVE ABOUT 250*F.; HYDROGENATING THE SECOND FRACTION TO SECURE AN OLEFIN SATURATION IN THE RANGE OF 30% TO 100% BY CONTACT WITH HYDROGEN IN THE PRESENCE OF A HYDROGENATION CATALYST SELECTED FROM THE GROUP CONSISTING OF COBALT OXIDE, MOLYBDENUM OXIDE AND COBALT MOLYBDATE SUPPORTED ON AN ADSORBENT CARRIER AT A TEMPERATURE IN THE RANGE OF ABOUT 500* TO 800*F., A PRESSURE IN THE RANGE OF ABOUT 25 TO 500 P.S.I., AT A THROUGHPUT IN THE RANGE OF ABOUT 1 TO 20 V./V./HR., WITH A MINIMUM OF 500 S, C. F. OF HYDROGEN/BBL.; HYDROGENATING THE FOURTH FRACTION TO SECURE A

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