US2767124A - Catalytic reforming process - Google Patents

Description

^ Oct.. '16, 1956 J. w. MYERS 2,757,124

cATALYTIc REFORMING PROCESS Filed April 29, 1952 JOHN W. MYERS United States Patent O CATALYTIC REFoaMING PRoCEss John W. Myers, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application April 29, 1952, Serial No. 284,929 8 Claims. (Cl. 196-50) This invention relates to the conversion of hydrocarbons. In one of its aspects it relates to a process wherein a low octane number naphtha is upgraded to produce valuable high octane motor fuels, e. g. gasoline. In another of its aspects it relates to a process wherein a low octane number naphtha is fractionated to produce a relatively heavy naphtha which is treated to produce a high octane motor fuel and a substantially saturated C3-C4 hydrocarbon fraction for still further treatment. In still another aspect the invention relates to a process wherein a low octane naphtha is fractionated to produce a relatively light naphtha and a relatively heavy naphtha which are then further treated under conditions optimum to each. In a still further aspect the invention relates to a process wherein the yield and quality of the gasoline produced from a low octane number naphtha are increased by more ethcient utilization of the C3 and C4 hydrocarbons formed during the treatment of segregated fractions of an original naphtha, i. e. admixing the C3 and C4 hydrocarbons formed during treatment of a heavy fraction of an original naphtha, with a light fraction of said original or another naphtha and charging the mixture to a conversion step to produce a high octane motor fuel and a stream of substantially olenic C3 and C4 hydrocarbons which is then further treated to produce hydrocarbons boiling within the gasoline range.

The invention has particularly satisfying application in the treatment of virgin naphthas and is for this reason so set forth and described inV this application. Although all types of virgin naphthas can be used, operation is especially satisfactory when the naphthenic content in the low boiling naphtha is not excessive, say less than about 25 percent. Consequently, virgin paranic naphthas containing not more than 30 percent naphthenes comprise a preferred feed stock for this invention. However, the high pressure step to be described, can tolerate as high as 100 percent naphthenes. Other applications can be readily devised after a perusal of this specication and claims.

Since the advent of motor fuels of increased octane number the problem of how best to handle the relatively low octane number virgin naphthas present in nearly all crude oils has been given much attention by technologists in the petroleum industry. Various processes such as thermal reforming, catalytic reforming, hydroforming, etc. have been developed and are being used today.

The proportion of C3 and C4 hydrocarbons, both saturated and unsaturated, formed in these processes varies with each process and is dependent, to some extent, on the operating conditions in each. However, the relative amounts of the unsaturated and saturated hydrocarbons for each process are more or less constant. It is Well known that the unsaturated Ca and C4 hydrocarbons are much more valuable than the corresponding saturated hydrocarbons because the unsaturated hydrocarbons can be readily converted into more valuable vhigher boiling hydrocarbons. Therefore, any reforming process frs which will give an increased ratio of unsaturated C3 and C4 hydrocarbons represents a distinct advance in the art.

I have found that when a virgin naphtha is fractionated into a relatively heavy fraction and a relatively light fraction, and each fraction catalytically reformed under optimum conditions, that the C3 and C4 hydrocarbons resulting from the relatively light naphtha fraction soconverted are substantially olenic in nature, Whereas the C3 and C4 hydrocarbons from the relatively heavy naphtha fraction, so converted, are substantially paraiinic in nature. I have further found that when these parainic C3 and C4 hydrocarbons resulting from the reforming of the relatively heavy naphtha fraction are admixed with the relatively light naphtha fraction and the mixture charged to a catalytic reforming step, operated under conditions optimum for that fraction, a substantial portion of the C3 and C4 hydrocarbons are dehydrogenated simultaneously with the upgrading of the light naphtha to give a substantial increase in the yield of olelins which, when charged to a succeeding polymerization or alkylation operation results in a substantial increase in the yield of high octane motor fuel. The dehydrogenation of the saturated C3 and C4 hydrocarbons in the presence of the naphtha being reformed appears to assist in the suppression of undesirable reactions and side reactions.

Accordingly, my invention comprises fractionating a virgin naphtha into a relatively light naphtha fraction and a relatively heavy naphtha fraction, catalytically reforming the light naphtha under low pressure conditions, catalytically reforming the heavy naphtha under high pressure conditions, and admixing the Cs and C4 hydrocarbons from the heavy naphtha reforming step with the feed to the light naphtha reforming step to effect simultaneously a dehydrogenation of the admixed C3 and C4 hydrocarbons and an upgrading of the light naphtha fraction to give an increase in the yield of olenic hydrocarbons therefrom. The olenic C3 and C4 hydrocarbons from the light naphtha reforming step are then charged successively to polymerization and hydrogenation steps to give increased yields of high octane gasoline. Or, if desired, the olenic C3 and C4 hydrocarbons may be charged to an alkylation step, such as alkylation of isobutane in the presence of anhydrous hydrofluoric acid.

Thus by operating according to the invention the original naptha is more efficiently reformed and a more efficient utilization of the saturated C3 and C4 hydrocarbons is effected resulting in a greater yield of high octane motor fuel than is possible by methods known to the prior art.

While preferred operating conditions and hydrocarbon boiling ranges are given in the detailed description below, the invention should not be limited to those conditions because, depending upon the characteristics of the charge stock and the type of product desired, other operating conditions can be used.

For example the high pressure catalytic reforming zone can be operated at pressures ranging from 5 to 50 atmospheres, at temperatures ranging from 800 to l F., at space velocities from 0.5 to 5 liquid volumes per volume of catalyst per hour, and a hydrogen circulation of from 500 to 5000 cubic feet per barrel of liquid naphtha charge. y

The low pressure catalytic reforming zone can be operated at pressures ranging from l to 4 atmospheres, at temperatures ranging from 900 to 1150 F., and space velocities ranging from 0.5 to 5 liquid volumes per volunie of catalyst per hour. Ordinarily, higher temperatures are used in the low pressure reforming zone than in d 3 the high pressure reforming zone. The boilingranges of the naphtha fractions charged to the zones according to the invention may vary as follows:

Referring now to the attached diagrammatic drawing, which is one embodiment in which vseveral of the concepts involved in this invention are illustrated a virgin naphtha having an approximate ASTM boiling range vof l-430 F. and an approximate composition of'60 percent paraffins, 2 percent olens, 25 percent naphthenes ,andl3 percent aromatics, is heated in a heater (not shown) and charged through line to fractionatorV 11. A light naphtha fraction boiling from about 100 to 230 F. ASTM is taken overhead through line 26. A heavy naphtha fraction boiling from about 230 to 430 F. ASTM is" withdrawnV from fractionator 11 through line 12, through'avaporizing heater (not shown) to high pressure reforming zone 13. Hydrogen can be added through linesV 14 and 15. Typical or preferred Voperating conditions for reforming zone 13 arci temperature 900-1000" F., pressure l0 to y25 atmospheres,

'space velocity 0.8 to 3 liquid volumes per. volume of catalyst per hour and hydrogen, 1000 to 3000 cubic feet per barrel of liquid naphtha .charge to said zone.

The converted heavy naphtha vapors are passed through line 16 to fractionation zone 17 Vwherein the normally liquid hydrocarbons are separated from the normally gaseous hydrocarbons.V The heavy end liquid residue boiling above the gasoline range is withdrawn through lline 18, the Ygasoline fraction is passed through lines 19 Yand 20 to gasoline storage 21, residue gas,V largely C1 and C2 hydrocarbons, isv taken overhead through line 22 and the hydrogen'richgas Vis taken overhead through Vline 23 for recycle through' line 14 or transfer through Aline 24 to the hydrogenation zone to be described beloW. The C3 and C4 hydrocarbons (substantially saturated) are withdrawn through line 25 and admixed with the light naphtha fraction in line 26.

The light naphtha fraction in line 26 is that taken voverhead from fractionator 11. These light naphtha vapors, after admixture with the substantially saturated ACs and YC4 hydrocarbon vapors from the high pressure catalytic reforming zone 13, are passed to low pressure catalytic reforming zone 27 wherein the C3 and C4 hydrocarbons' are substantially dehydrogenated, forming free hydrogen in the said zone, while portions of the light naphtha hydrocarbons arebeing simultaneously upgraded. Typical or preferred operating conditions in low pressure catalytic reforming zone are: temperature 950 to 1075 P., pressure l to 3 atmospheres,fspace velocity 1 to 3 liquid volumes per'volume of catalyst per hour.

Additional hydrogen (not shown) can be added to the Y iinic Ca and C4 hydrocarbons are passed through line k32, together with some or all of the light gases from fractionation zone 29, to polymerization zone 33 (preferably catalytic) wherein the said olens are polymerized to higher boiling hydrocarbons. The heavier liquid from polymerization zone 33 is withdrawn through line 34, residue gas is taken overhead through line 35 and unpolymerized hydrocarbons are withdrawn through line 36 for recycle to the low pressure catalytic reforming zone. By controlling conditions in polymerization zone 33, as well as the proportion of gases introduced thereto through line 32 or some other source not shown, the character and extent of the polymerization reaction effected in polymerization zone 33 can be controlled exibly as a further feature of this invention. YThe polymerized hydrocarbons are withdrawnthrough line 37,V admixed with hydrogen from an outside source through line 38 or system hydrogen from line 24 and the resulting mixture passed to hydrogenation Vzone 39, The hydrogenatedreaction product is withdrawn through lines 40vandV 20. to gasoline storage 21. Residue gas containing hydrogen is taken overhead through line 41. The hydrogen therein can be recovered and recycled if desired.Y Y n Any effective hydrogenation catalyst and correspondingly suitable hydrogenatingV conditions known to the art may be employed in hydrogenation zone 39. Likewise, any suitable polymerization catalyst such as silica-alumina, copper pyrophosphate, phosphoric acid, sulfuric acid etc. and suitable Operating conditions known to the art may be employed in polymerization zone 33. Catalysts which can be employed in the lowrpressure and the high pressure catalytic reforming zones include the chromia-alumina type, molybdena-alumina type etc. and

also platinum-containing catalysts, all well known to those skilled in the art. Y

Thev following examples illustrate thev advantages of my invention as explained at each example. Example I shows that it is more desirable to reformV the light-naphtha at Vlow pressures than at high pressures. Example II shows that the use of high pressure is desirable when reforming a heavy naphtha. Example III shows that the .C3 and C4 hydrocarbons resulting from the reforming of light naphtha at low pressure contain a substantial amount of oleiins whereas the C3 and C4 hydrocarbons from the reforming of heavy naphtha are substantially paranic and contain only a small amount of olelins. Example IV shows Vthat substantial portions of saturated Ca and C4 hydrocarbons passed through a low pressure catalytic reforming zone will be dehydrogenated and Example V shows that this dehydrogenation will be effected simultaneously in the presence of a naphtha which is upgraded in such an operation.

Example I i CATALYTIC REFORMIN G OF LIGHT NAPHTHA BOILING RAN GE 10U-263 F. ASTM .Feed Low High Pressure Pressure Temperature, F g 998 994 Pressure, atm l 21 Hydrogen, Mol/m01 of feed 2.0 2.3 Space velocity, liq. VOL/cat. vol./hr 3.0 2. 7 Yield of Q54-, wt. percent of feed (Gaso- Y line boiling range) 92.0 78. 7 Yield of Coke, wt. percent of feed 0. 25 0. 03 Octane rating of (JH-(gasoline): Y

Motor-l-L() ml. TEL 76. 3 8l. 6 79. 6 Research-FLO ml. TEL.- 76. 4 85. 1 82. 2 Catalyst Used Y(1) (1) 1 Chromia-alumina.

A comparison of the data yat the bottom of columns 42 and 3 shows that both aY greater yield of the Cs-lfraction 1 Molybdena-alumina.

These data show that the high pressure conditions are desirable for this feed stock. It should be noted in column 3 that the octane number of the gasoline formed is 70.0 and the yield of coke is 0.8 percent for the high pressure opera-tion compared to an octane number of 52.2 and a coke yield of 2.4 percent for the low pressure operation shown in column 2. The C| fraction (gasoline) obtained under the low pressure 'conditions would of necessity require further treatment to increase the octane rating to a satisfactory value.

Example III CATALYTIC REFORMING OF LIGHT NAPHTHA AND HEAVY NAPHTHA Naphtha Fraction Light Naphtha Heavy Naphtha Boiling Range of Naphtha,

F., ASTM 942-227 Pressure, atm Temperature, F. (approx.)- Hz, Cu. ftJbbl Space Velocity, Liq. VOL/cat.

vol. hr

Products, Wt. percent: Hydrogem Nlptlmne Ethylene Ethane.

Isobutanen-butane Debutanized gasoline..

Total Catalyst Used Chromiaalumna Chromia-alumina These data show that in the low pressure catalytic reforming of the light naphtha 65.9 percent of the Cs and C4 hydrocarbons are :oleiinic whereas only 8.0 percent of the C3 and C4 hydrocarbons formed during fthe high pressure catalytic -reforming of the fheavy naphtha are oleiinic.

Example IV DEHYDROGENATION OF Cs AND C4 HYDROCARBONS Dehydrogenation of Propane Butane Space velocity, gaseous vol./cat./vol.ll1r 700 760 Temperanne, F l, 100 1,080 Pressure, atm 1. 5 1. 0 Percent converted to propylene 37 Percent converted to unsaturated C3 and C4 Hydrocarbons 43 Catalyst (l) (i) 1 Chromia-alumina.

Example V A mixture comprising 8.1 Weight percent of normal butane and 91.9 weight percent of normal hexane concentrate was charged over a chromia-alumina catalyst at atmospheric pressure, 979 F., and 1a space velocity of 1.8 liquid Volumes per volume of `catalyst per hour. The butane was dehydro-genated to the extent that the butane, butene, and hydrogen in the product were substantially 'at equilibrium concentrations.

Various other naphthas ysuch Ias naplrthas from naphthenic or aromatic type crudes, naphthas resulting from the cracking of topped crude, etc., may also be treated laccording to the invention. Also, in some cases, it may be desirable to charge propane and butane from an external source to the low pressure reforming step in addition to, or instead of, the C3 and C4 'hydrocarbons from the high pressure reforming step. Such operation is within the scope of the invention.

While the invention has been described las a process wherein a naphtha is fractionated into =a light naphtha fraction and a heavy naphtha fraction, with the fractions being .catalytically reformed under conditions optimum to each and the substantially `saturated Cs and C4 hydrocarbons formed in the heavy naphtha reforming step -being passed to the light naphtha reforming step itis obvious that other embodiments are within the scope :of the Iinvention.

For example, an original naphtha can be fractionated into a plurality of fractions, :the individual fractions catalytically reformed under conditions optimum to each and the substantially saturated C3 :and C4 hydrocarbons formed in lone or more .of )the heavy naphtha reforming steps being passed to yone or more of the light naphtha reforming steps. ln Isuch a process operating conditions for .the individual catalytic reforming steps will vary with the boiling range of the naphtha fraction 'and in accordance with the above-detailed ydescription of the inventi-on, i. e., the heaviest naphtha will be reformed at thehighest pressure andthe lightest naphtha at the lowest pressure. Obviously the number of light fractions and the v number tof heavy fractions into which fan original naph-tha is fraction-ated will depend upon the properties yof the original naphtha and the type lof products desired therefrom. ln some instances Fit may be desirable to segregate only one light naphtha fraction and two or more heavy fractions or, in other instances, one .heavy fraction and two or more light fractions, from an `original naphtlra for treatment in accordance with the invention.

Variations and modifications are possible within the scope of the foregoing disclosure, drawing, and appended claims to the invention, the yessence of which is a catalytic reforming process compri'sing, fractionan'ng a lfow octane number naphtha into a light naphtha and a heavy naphtha, catalytically reforming each fraction under conditions optimum lto each, .and admixing the C3 and C4 hydrocarbons from the heavy naphtha reforming step with the feed to the light naphtha reforming step to increase the yield of olenic hydrocarbons therefrom; and further, passing the loleiinic C3 and C4 hydrocarbons formed in said light naphtha reforming step to -a further treating step to convert the said olefns into more valuable hydrocarbons. In (this manner the yield of high octane gasoline from a given naphtha is increased.

I claim:

1. A process for treating =a relatively low octane number naphtha which comprises, fractionating said naphtha into ra plurality `of fractions ranging from light naphtha to heavy fnaphtha, catalytically reforming each said fraction under conditions optimum to each, and :admixing C3 and C4 hydrocarbons formed in at least one yof the said heavy naphtha fraction reforming steps with .the feed to at least :one tof the said light naphtha fraction reforming steps to form a mixture consisting essentially of said light naphtha fraction and said C3 and C4 hydrocarbons, passing said mixture to za light naphtha caltalytic reforming ze .e and therein simultaneously upgrading said light naphtha and dehydrogenating said C3 amd C4 hydrocarbons to form corresponding -olens 2. A process for treating Ia relatively low octane numinto la light :naphtha and ya heavy naphtha, passing said heavy naphtha to a catalytic reforming zone wherein the said heavy naphtha is vaporized and contacted with a reforming catalyst in the presence of hydrogen under high pressure conditions, fractionating the products from said heavy naphtha reforming step into a plurality 'of fractions including a fraction boiling within the gasoline range and a fraction comprising substantially saturated C73 and C4 hydrocarbons, :admixing said C3 and C4 hydrocarbons with the said light naphtha fraction to form :an admixture consisting essentially of said light naphtha fraction `and said C3 land' C4 hydrocarbons, contacting rthe said admixture with a reforming catalyst in a light naphtha catalytic reforming zone operated under low pressure conditions, and therein simultaneously upgrading portions of the light naphtha and dehydrogenating portions of the C3 and C4 hydrocarbons contained in said `admixture in the said -l'ow pressure catalytic reforming zone.

3. The process -of claim 2 wherein the said high pressure conditions comprise a temperature Within the range of 900 to 1000 F., a pressure Within the range of 10 to atmospheres, a space velocity within rthe-range fof 0.8 to 3 liquid volumes per volume of catalyst per hour cubic feet per barrel tof naphtha; and the said low pressureconditions comprise a temperature within the range of 950 to V1075 F., a pressure within the range of 1 to 3 atmospheres and a space velocity within the range of 1 to 3 liquid volumes per volume of catalyst per hour.

4. A process for treating a low :oct-ane number naphtha which comprises: lfractionating -said naphtha into -a relatively light naphtha and a relatively heavy naphtha; catalytically reforming rthe heavy naphtha fraction under conditions to obtain `substantially saturated C3 and C4 hydrocarbons in the effluentV from the heavy naphtha reforming zone; fractionating said efduent to separate said C3 and C4 hydrocarbons Vtherefrom; admiring saidl C3 and C4 hydrocarbons formed in said heavy naphtha reforming zone with said light naphtha to form 'a mixture consisting essentially of said light naphtha yand said C3 land C4 hydrocarbons; passing said mixture to a light naphtha catalytic reforming zone and therein simultaneously upgrading said light naphtha and dehydrogenating said C3 and C4 hydrocarbons to form corresponding oleins.

Vand hydrogen volume within the range of 1000 to 3000 Y 5. A process for treating ya low octane number naphtha which comprises: fractionating said naphtha into a rela- (tively light naphtha fractionV and relatively heavy naphtha fraction; catalyticallyreforming said heavy naphtha Afraction under high pressure conditions in a catalytic Vre.-

forming zone to obtain `substantially saturated C3 and C4 hydrocarbons in the efuent from said heavy naphtha reforming zone; fractionating said eiuent to separate said C3 and'C4 hydrocarbons therefrom; 'admixing said separaited C3 fand C4 hydrocarbons formed in said heavy naphtha reforming 'zone with said light naphtha frac,- tion to form la mixture consisting essentially of said light naphtha land lsaid separated C3 and C4 hydrocarbons;` passing said mixture toV a lightnaphtha catalytic reform- Y ing zoneoperated at a temperature Within the range of 950 to 1075 F., and a pressure within the range of 1 to 3 atmospheres, land therein simultaneously upgrading sai-d light naphtha and dehydrogena-ting said C3 and'V hydrocarbons to form corresponding olefins.

6. A process yaccording to claim 5 wherei-n said high pressure conditions in said heavy naphtha reforming zone comprise a temperature within the range of 900 to 1000 F., and a pressure vwithin the range of 4`10V to 25 atmosx References Cited in the le of.v this patent,VV

UNITEDV STATES PATENTS i 2,257,723 Arveson. f ocf.7, `1941 2,288,336 Welty, Jr. et al June 20, 19,42 2,296,601 Dorsett Sept. 22, 1942 2,322,863 Marschner et al June 29, 1943 2,416,023 Schulze et tal. Feb. 18, 1947 2,504,415 Hepp Apr. 18, 1950 2,653,175 Davis Sept. 22, 1953

Claims (1)

1. A PROCESS FOR TREATING A RELATIVELY LOW OCTANE NUMBER NAPHTHA WHICH COMPRISES FRACTIONATING SAID NAPHTHA INTO A PLURALITY OF FRACTIONS RANGING FROM LIGHT NAPHTHA TO HEAVY NAPHTHA, CATALYTICALLY REFORMING EACH SAID FRACTION UNDER CONDITIONS OPTIMUM TO EACH, AND ADMIXING C3 AND C4 HYDROCARBONS FORMED IN AT LEAST ONE OF THE SAID HEAVY NAPHTHA FRACTION REFORMING STEPS WITH THE FEED TO AT LEAST ONE OF SAID LIGHT NAPHTHA FRACTION REFORMING STEPS TO FORM A MIXTURE CONSISTING ESSENTIALLY OF SAID LIGHT NAPHTHA FRACTION AND SAID C3 AND C4 HYDROCARBONS, PASSING SAID MIXTURE TO A LIGHT NAPTHA CATALYTIC REFORMING ZONE AND THEREIN SIMULTANEOUSLY UPGRADING SAID LIGHT NAPHTHA AND DEHYDROGENATING SAID C3 AND C4 HYDROCARBONS TO FORM CORRESPONDING OLEFINS.

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