US2416023A - Catalytic conversion of hydrocarbon oil - Google Patents

Description

Feb. 18, 1947.

. w A.-scHuLzE Erm. CATALYTIC CONVEHSILON OF HYDROCRBO OIL Filed sept. 18, 19444 n ommmmazoo BOLVNOLLOVHd aolvavd s provided.)

Other obiects and advantages will be apparent.

Patented Een. 1s, 1947 CATALYTIC CONVE CABBO RSION F HYDRO- N OIL Walter A. Schnlae'and Carl J. Helmers, Bartlesville, Okla., assigncrs to Phillips I etroleum Company, 'a corporation of Delaware Application September 18, 1944; Serial No. 554,845

' ,4 claims. (c1. zoo-ass) This invention relates to a process for converting hydrocarbon fractions into substantial yields of light unsaturated hydrocarbons with the simultaneous;l production of valuable stabilized distillate. In one of the more particular applications. the present invention relates to controlled catalytic cracking of normally liquid hydrocarbon materials such as gas oil, kerosene and naphtha to produce normally gaseous olens 'and diolefins with concurrent production of by-product distillates rich in aromatic hydrocarbons.

Generally speaking, in the refining practice of the past, catalytic cracking processes have been concerned with the manui'actureof high yields of superior motor fuels. A recognized advantage of such processes has been the production and conversion of high percentages of gaseous olens to higher boiling hydrocarbons. However. with the advent of recent developments in the design of aircraft engines, the demand for special highquality fuels shifted refining technology from motor fuel production to the manufacture of aviation gasoline. The need for the latter fuels has created a demand for light oleilns suitable for use in the production of alkylate gasoline and for aromatic hydrocarbons valuable for their favorable efiect on the rich-mixture perfomance of aviation gasoline. Existent catalytic processes have partially solved this problem in that distillates rich in aromatic hydrocarbons have been produced, but this has been accomplished at the expense of potential oleiln and diolen production. Since operating variables favorable to one reaction are unfavorable to the other, a denite lack oi exibility is evident in catalytic cracking processes described heretofore.

It is anobject of the present invention to provide a process for the catalytic conversion of hydrocarbon oils to substantial yields of light oleilns and diolefins with the simultaneous production of a high quality aviation blending stock.

Anotherobject of this invention is to provide a catalytic cracking process for hydrocarbon oils 'wherein novel means of control of temperature and contact time within the catalyst zone `is from the'followlng disclosure.

We'have now discovered that with the application of the presentinvention, normallyliquid petroleum hydrocarbons such as gas oil, kerosene and/or naphtha may vbe catalytically treated under reaction conditions leading to the production of valuable light olefins and dioleflns in'substantial yield along with concurrently valuable 2 aromatics-contalning distillates. This unusual result is realized througheilective control of temperature and contact time in dierent sections of the catalyst bed. Thus when the catalyst case f' is arranged for downward ow, a relatively long contact time at conversion temperature in the upper portion of the catalyst case favors the formation of a large proportion of-C4 and lighter hydrocarbons along with the considerable conversion of the feed to aromatic types, while at ,one or more suitable points along the length of the bed a large proportion oi' heat-carrying steam or other inert diluent is introduced. This diluent, heated to a desired temperature, furnishes additional heat necessary for dehydrogenation of butenes to butadiene and at the same time reduces the contact time, thus preventing further appreciable conversion of the olens and diolens to polymers and/or cyclic compounds. By addition of the preheated diluent at one or more selected points in the catalyst chamber. the temperature and contact time in both the upper and lower portions of the catalyst bed may be controlled to give the'unit the high degree of flexibility required to process feed stocks through the range of naphtha and gas oil fractions.

in order to permit the coexistence of aromatiz-,y

.ing-and dehydrogenating conditions in the same catalyst bed, so as to obtain both aromatic fractions and olenand dioleiin-containing fractions, it is necessary to provide relatively long contact time in the aromatizing zone and relazone. This is accomplished by introducing steam tively short contact time in the dehydrogenation or other inert-gaseous diluent, such as nitrogen,

v into that point in the catalyst bed at which the treated vapors have been subjected to the desired contact time'for the aromatizing reaction to have -taken place. At this point sufilcient diluent is introduced to provide vthe desired effective dehydrogenation contact time in the remaining portion of the bed. The contact time for the crack-V ing-aromatizing'portion of the reaction is preferably between about 0.5 and :iv seconds, while the contact time for the dehydrogenation portion of the reaction is between about 0.05 and 0.5 second.

Lower-boiling paramns such as methane and ethane are also relatively inert since the reaction f may be made as This may accomplished by superheating the steam or other diluent to a point'suiiiciently above the temperature of the reactants at the point in the bed at which the diluent is introduced, to elevate the temperature in the dehydrogenation zoneto the desired point. Preferably the cracking-aromatizing reaction is carried out at a temperature between about 1100-1300 F. while the dehydrogenation reaction is also carried out at representing the optimum depth of cracking in this process. Sumcient diluent preheated to 1200-1400 F. then enters the chamber in amount sumcient to raise the vapor temperature to about 1150 F. and at the same time to reduce the 4 i ed, however, that the invention should be limited to this particular type of reactor.

Leaving the, catalyst chamber, the Lreaction mixture passcsthrough line 'I with appropriate cooling by the heat exchanger l and, where steam is used as diluent, through line ,0 into the separator I from which water is withdrawn at the bottom through line I2. The overhead vapors 'from theseparator are taken through line II into the accumulatori 22 while the normally liquid hydrocarbonmaterial'is withdrawn at the side of the separator and taken 'through line I3 through hydrocarbon partial pressure and residence time.

In the dehydrogenation section of the catalyst bed, additional diluent may be injected at points corresponding to temperature drops of about 50 F., so that the overall temperature in the after sectionoi the catalyst bed is maintained between about 110D-1150 F., and the hydrocarbon partial pressure at about 0.05 to about 0.01 atmosphere.

Thus the point in the bed at which cracking has proceeded to an optimum extent is represented by the temperature drop off about 100LF. and at and beyond that point sufficient diluent is introduced to provide the hydrocarbon partial pressure and contact time necessary to give the desired dehydrogenation conditions in the remainder oi the bed.

The accompanying diagram shows in conventional sideelevation one particular embodiment of the invention. It should be emphasized, however. that modiiications and` variations in the equipment apparent to those skilled in the art desired without departing from the broad scope of the invention.

With reference now to the drawing, the feed stock to the operation, which may comprise a gas oil such as that fraction boiling between 450 and 650 F. and which may be obtained either by the straight distillation of a crude oil or by' the mild cracking oi a reduced crude. is led through transfer line I into the iumace 2. A diluent, comprising steam or other inert gas, may be introduced by line Lheated in the furnace 2 and added to the vaporized hydrocarbon. The heated mixture of gas oil and diluent then passes by line l into the reaction chamber 6 to which an additional amount of superheated steam or other inert diluent is added through line I to serve Vas heat carrier and to reduce the contact time. Means are illustrated for introducing the diluent at one or more points in the latter portion of the bed, as desired.

I'he reaction chamber 8 may be any of various reactors known to those versed in the art.

'inasmuch as the invention. pertains to a novel and advantageous cracking procedure rather than to a particular type oi equipment, no attempt w ill be made to describe the catalyst chamber in detail. An appropriate reaction vessel for use in this process, however, may suitably be a multiple-bed type of chamber provided with suitable arrangements for the injection of heat car rier' media -at different points. It is not intenda suitable heat exchange element I4 and through line I5 into the f ractionator I8. The iractionator bottoms, comprising gas oil and higher boiling material, are removed through line I8 while the overhead from the fractionator is taken through line I1 to the stabilizer I9. The stabilizer bottoms withdrawn by line 2| comprise debutanized end-point `gasoline which, upon refractionation and further treatment, is suitable forutilization as a high-octane, aromatic aviation fuel.4 'Ihe overhead from the stabilizer, comprising C4 and lighter gases, is taken through line 20 to the accumulator 22. A portion of the liquid condensed in accumulator 22 andcomprsng essentially C: and C4 hydrocarbons is withdrawn through line 23 and pump 26 and returned to the stabilizer through lines 25 and 26 as reiiux. The remainder oi the Ca--Ci hydrocarbon is taken through line 21, the heat exchanger 36 and line 31, to the depropanizer 38, The gaseous material from the accumulator 22 is taken through line 28, the compressor 28 and the cooling coil 3i to the accumulator from whence the Cz and lower-boiling products are 4vented to an ethylene recovery system or to the reiinery gasplant through-line Il. The liquid condensate from the accumulator Il comprising predominantly propane and propylene is combined through line 34 with the excess reflux liquid in line 21. The bottoms from the depropanizer, comprising the C4 ycut is taken through line 4 0 to an appropriate system II for effecting the separation of the fraction into such components as butadiene which is of use in the manufacture of synthetic rubber and into butylenes and isobutane which may be used as feed to alkylation and polymerization processes. The amount of isobutane available for these processes may be increased by the use of isomerization reactions. The Ca overhead from the depropanizing column may be taken through line 39 for'further treatment or for use in alkvlation or polymerization processes.

Typical operating conditions which may be employed to carry out the process are approxiimately as follows: 'Ihe hydrocarbon oil change stock is vaporized in the furnace coil, being heated to temperatures markedly higher than those normally utilized for the production oi motor fuels by thermal treatment oi heavier oils, these temperatures employed being in the approximate range of 1100" to 1300* F. The hydrocarbon vapors are passed over the catalytic mass which preferably comprises a naturally-occurring material such as bauxite. Certain activated adsorbent clays may also be used as wellas synthetic materials such as alumina or alumina admixed with minor proportions of certain activating agents such as various metal oxides or salts. In some instances, Synthetic inaterlals ,comprising various combinations of silica geland metal oxidessuch as silica-alumina Vor silica-alumina-zirconia catalysts may be suitable.

with steam or other inert gases to the extent vof about 0.5 to mols of diluent per mol of feed.

`Additional diluent equivalent to from to 25 mols per mol of feed, preheated .to 12001400 F.,

is inJected into the catalyst case at suitable points spaced along the catalyst case in the direction of ilow. Since the cracking reaction is vhighly endothermic, the introduction oi.' the auxiliary heat carrier ordinarily have traversed about one-third oi the length of the catalyst bed. Additional injection points may be Aprovided along the latter two-thirds of the length of the bed. This method of operation, by virtue ofthe high temperature level maintained and low partial pressure of reactants, favors additional dehydrogenation reactions to further increase oleiln and dioleiin. production. 0n the other hand, the addition oi' auxiliary diluent greatly shortens the contact time, thereby preventing excessive polymerization and cyclization of the gaseous olens and dioleiins.

The operation may be carried out under moderately superatmospheric pressure which may range from atmospheric to about 250 pounds per square inch gage in order that the desired contact time may be achieved for a given diluent ratio. Ordinarily, in prder to produce increased yields oi diolens, relatively low near-atmospheric pressures are preferred, as for example between about zero and 50 pounds gage.

In order to indicate the novelty and utility of the process, the following example is given of a specic embodiment of the invention which employs the preferred conditionsI of temperature and pressure an'd ow rate along with a prei'erred feed stock and catalyst. This example is merely illustrative of results normally obtained and should not be construed as a limiting feature of the invention, as various changes in the cata lyst and catalyst chamber design as well as modications in the reaction conditions apparent to those versed in the art may be made.

ample A 42- degee A. P. I. gravity kerosene having an initial boiling point of 400 F. was admitted to a catalyst chamber illled with a regenerated 10- mesh bauxite catalyst, at'a charge rate of about 1 liquid volume of kerosene per volume of catalyst per hour, with steam at the inlet in the proportion of 1 mol of kerosene to 2 mols oi steam per hour. The feed was introduced into the catalyst bed at a temperature' of 1200 F. and after traversing about one-third of the bed the tem-- perature at that point was found to have dropped to about 1100 F. Additional steam was introduced at this point at a temperature of 1400 F. at the rate oi' 5 mols per mol of hydrocarbon feed per hour, .raising the temperature to 1150 F. When the hydrocarbon-steam mixture had traversed approximately another third of the bed the temperature drop was about 50 F. and at this point additionalsteam at a temperatureof about 1400 F. and a rate of about 8 mols per hour per mol of hydrocarbon feed was introduced. The eilluent product left the bed at a temperature of about 1100 F. Fractionation of the eilluent yielded a C4 fraction amounting to 11.5 per cent by volume of the charge and of this fraction 32 per cent by volume was butadiene, while -04.3 per cent of thefraction consisted of butenes. of which occurs after the charge vapors and aromatic content.

carbons which comprises vaporizing and heating 35 per cent was isobutylene. The C: fraction accounted i'or 17.5l volume per cent of the charge and was about v92 `per cent propylene. The C: Y fraction comprised 75 per cent ethylene and.

amounted to 30 volume per cent of the charge.

Butane-free gasoline was obtained in ayield of about 24.5 volume per cent of the charge. The olearlA. S. T. M. octane number `of the gasoline was 82.5 while the Research octane of the un.

leaded gasoline was 96.0. A high aromatic content or the gasoline is indicated by the refractive index of 1.4795. I

' .In the above example the operation was carried out at a pressure of 5 pounds per square inch gage and 'for a process period of six hours duration.

Another portion oi' the same-feed lstock was catalytically cracked underidentical conditions except that 9.3 mols of `steam diluent per mol ot hydrocarbon was initially introduced with the feed and no further diluent was added. On fractionation a C4 fraction amounting to 10.3 volume per cent of the charge was obtained and of this fraction 22.6 volume per cent was butadiene and 67.9 per cent was butenes. Of the butenes frac- 'tion 37 per cent was isobutylene. 'I'he C: fraction accounted for 16.5 volume per cent of the feed of which about 90 per cent was propylene. The C2 fraction amounted to about 29 per cent of the charge and contained about 72 per cent ethylene.

A butane-free gasoline amounting to 25.2 per cent of the charge by volume was obtained and the clear A. S; T. M. octane number of the gasoline was 81.6 while the Research octane of the unleaded gasoline was 95.0. The refractive lndex was 1.4780.

production is increased about 50%, andsomewhat greater overall production of olefins is also obtained. Slightly less of abutane-i'ree gasoline n is obtained, but this has a somewhat higher octane number due to the slightly greater olefin Weclaim:

l. A process for the conversion ofv a. normally liquidhydrocarbon distillate to an aromatic fraction and normally gaseous unsaturated hydrothesaid distillate to a temperature of 11001300 F. passing said vaporized distillate in contact with a solid adsorbent cracking and dehydrogenating catalystnfor a contact time of 0.5 to 3 seconds, injecting sufllcient steam preheated to 11001400 Ill'.` at a plurality of points spaced along/the length of the catalyst bed in the direc-v tion of vapor now after the initial contact period to allow the distillate a further contact time of 0.05 to 0.5 seconds with said catalyst, and separating butadiene, normally gaseous oleilns and an aromatic fraction fromv the eilluent.

2. The process of claim 1 in which the preheated steam is introduced at said points in the catalyst bed in a volume and at a temperature sumcient toraise the temperature to 110D-1150 F. in

the dehydrogenation zone and to maintain the` temperature in a range of 50? F. Y

3. The process of claim 1 in which the crack- .70 ing and-dehydrogenation catalyst is bauxite.

the said distillate to a temperature 01'1100-1300 4. A process for the conversion of a normallyI liquid hydrocarbon distillate to an aromatic fraction and normally gaseousl unsaturated hydro? carbons'"'which comprises vvaporizing and heating 1100-1400 F. at a plurality oi Pints spaced 5 alonx the length of the catalyst bed in the direction of vapor new after the initial contact period to allow the distillate afurther contact time oi 0.05 to 0.5 second with said catalyst and separatin: said normally gaseous hydrocarbons and said i0 aromatic fraction from the eilluent.

The followirrg references are of record in th me of this patent:

, UNITED BTA PA Number Name Date Schulze Feb. 25, 1941 Howard Aug. 5, 1941 Eglot May 12, 1942 Houdry Aug. 17. 1943 Ruthru Mar. 2,1944 Sheppard May 2, 1944 Schulze etal July 11. 1944

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