US2374095A - Process for the catalytic treatment of hydrocarbons - Google Patents

Description

April 17, .1945. c. .J. HELMi-:Rs

PROCESS FOR THE CATALYflIC TREATMENT OF HYDROCARBONS Filed July 27, 1942 BY I j/ ATTN EY acteristics.

Patented Apr. 17, 1945 PROCESS FOR THE CATALYTIC. TREATMENT F HYDROCARBQNS Carl J. Helmers, Bartlesville, Okla., assigner to Phillips Petroleum Company, a corporation of Delaware Application July 27, 1942, Serial No. 452,469

4 Claims.

This invention relates tothe catalytic conversion of hydrocarbons to produce motor fuels. More specifically the invention relates to the catalytic treatment of hydrocarbons ranging from those normally gaseous to liquids higher boiling than gasoline to produce motor fuels of improved quality and in greatly increased yields. While the process of the present invention is ap- .plicable' to a wide variety of charging stocks, it is of particular value in application to the total or the partially fractionated effluents of cracking and/or reforming operations designed to produce valuable motorl fuel components.

It is conventional refining practice to subject low-octane distillates and cracking stocks to high temperature conversion treatments in order to produce motor fuels of improved antiknock char- Thermal cracking and reforming may be thus employed, and more recently catalytic processes for producing and/or improving motor fuels have been emphasized. The products of such conversions comprise, in addition to the desired motor fuel fractions, amounts of lighter and heavier hydrocarbons which vary with the nature of the charging stock and the conditions of conversion. Thus, gasoline or naphtha reforming operations may yield largely gasoline and lighter gases, while cracking operations produce the same materi-als plus heavy recycle distillates or residual stocks.

Various methods have been proposed for increasing motor fuel yields from such processes and the use of catalysts with generally milder conditions and increased specificity of conversion, has been of great economie benefit. However, the lower-boiling fractions, comprising C5 and lighter hydrocarbons, which often are produced in large quantities by high-temperature conversions can be retained in only limited amounts in the final fuel blends, and thus must be removed by fractionation in the so-called stabilization of said fuels. In this instance, stabilization refers to the adjustment o'f thel vapor pressure and/or volatility of thev motor fuel blends. The stabilization thus requires additional fractionation equipment, reduces the volume of' product, and simultaneously removes a potential source of additional high-octane liquid products.

It has been proxposed to separate the normally gaseous products, which are often rather highly unsaturated and to partially' convert. these into liquid products of suitable boiling range by thermal and/or catalytic polymerization or alkylation. Such a procedure has ordinarily involved seeparatefacilities for obtaining and treating the feed stock and for fractionating the effluents to recover the gasoline boiling range material. This separation of the cracking and/or reforming step from the polymerization or recombining. step is ordinarily justified on the basis that optimuxm conditions for eachstep are quite different and under or over conversion have heretofore been n lacking.

It is an object of this invention to integrate y more closely the operation of a process designedV to produce maximum yields of motor fuel components from light or heavy charging stocks.

Another object of this invention is to produce high yields of motor fuel components within a single group of processing units in such a controlled volume ratio that the blends obtainable are substantially balanced with regard to volatility and distillation characteristics and have modied olefin content 'and improved susceptibility to antidetonants. Often the high octane products of conversion processes must be refractionated to remove valuable light ends or blended with heavy stocks of less desirable quality. The present invention avoids this difliculty by. providing for suitable treatment of the said conversion products to revise the distillation curve of a fuel v blend without impairing the quality thereof and with appreciable increase in overall yields.

Broadly, the invention embodies a first step wherein a hydrocarbon charge stock undergoes vhigh temperature conversion, preferably inthe presence of a catalyst, although thermally converted streams may be handled with somewhat decreased efficiency. The effluentl from the vhigh temperature conversion, comprising hydrogen and hydrocarbons ranging from methane through high-boiling liquids, are submitted to fractionation to separate and recover (l) light vapors lower boiling tha`n`about C5 hydrocarbons; (2) a light liquid condensate comprising C5 to about Cs hydrocarbons; (3) an intermediate liquid condensate comprising about C7 and higher boiling hydrocarbons up to the normal end point ofthe desired motor fuel blends; and (4) one or more heavy -distillate or residual stocks which may serve as recycle streams to thermal or catalytic cracking operations.

The vapor stream from the fractionation is submitted to compression to attain the pressure required by subsequent processing steps, and hydrogen-rich vuncondensed vapors are removed carbons within the motor fuel boiling range. The

eiiiuents from the recombining catalyst are discharged into the common primary iractionating zone, and the fractionator condensate streams are continuously withdrawn from the system in the desired proportions to produce finished motor fuel blends. Stabilizer bottoms may be produced and added as required to regulate the vapor pressures of said blends. t

One specific application of the process may be further illustrated by reference to the drawing which is a'simpliiled fiow diagram showing conventional equipmentA arranged to perform the basic process steps. In the drawing a preheated hydrocarbon charge stock which may be a heavy gas oil distillate for cracking or a selected naphtha cut for reforming enters by line I and is treated over the cracking and/or reforming catalyst in vessel 2. The effluents pass through line 3, heat exchanger 4 and line 5 to fractional-,or B or products from thermal conversion may enter the system through line EA, pass through said line 3, heat exchanger 4 and line 5 into said fractionator 6. From the fractionator, C and lighter vapors are taken overhead through line 1, while a light liquid condensate is removed as a sidestream through line 8 to vessels. This light liquid fraction contains approximately Cs to Cs hy drocarbons, Vthe.(.`."1 and Cs hydrocarbons being present in relatively small amounts resulting from solution and entrapment and partial pressure relations in the fractionator as occasioned by the removal of two side streams from the fractionator and by the non-use of reflux. Refluking of fractionator 6 is not shown in the drawing nor' disclosed in the specification, and since reuxing is not used a given hydrocarbon fraction is contaminated with higher boiling hydrocarbons. It is well known in the art thatreuxing controls end points. An intermediate liquid condensate is also withdrawn through line I0 to vessel H, this condensate containing hydrocarbons from approximately Cv up to hydrocarbons of boiling points aboutequal to the end point of motor fuel, and higher boiling liquids nominally heavier or higher boiling than motor fuel are Withdrawn through line I2.A This last-named stream may be at least partially recycled to the first catalytic zone when cracking is performed therein,

` although when the originalcharge stock is a reforming naphtha, the bottoms stream comprises only a small volume of tarry residue and/or polymeric material which may be discarded.

The overhead vapors passing through line 1 are compressed in system I3, cooled in condenser 3l, and discharged into accumulator I4 for thev separation of uncondensed gases from the compression condensate. The liquid is taken from the accumulator throughline I 5, While the hydrogenrich gases pass through line I6 to be vented or recycled as described hereinafter. The liquid comasraoes pricing ordinarily Cz--Cs hydrocarbons may then pass through line Il to stabilizer i8, and/or through line i9 to line 2@ which gathers the feed to the second catalytic step. Usually, the condensate stream in line I5 is divided With a portion being fractionated in stabilizer I8L to take C4 and lighter hydrocarbons overhead through line 2l while the bottoms which are predominantly Cs boiling range hydrocarbons are removed' through line 22 as a blending stock for volatility requirements. The Cz-C4 overhead vapors from the stabilizer may be vented, or wholly or partially returned to line Athrough line 23. Usuab 1y, the operation is conducted so as to vent continuously a portion of this stream to avoid pyramiding of C2-C4 parafiins within the system.

A secondary stock comprising compression condensate from lines i9 and/or 23 and light sidestream condensate from vessel 9 through line 24 and pump 25 is taken through line 2t to heat exchanger 4 Where the necessary heat is ordinarily supplied by the high temperature stream in line 3. other methods of heating may, of course, be

employed. The heated feed then passes through line 20a to catalyst case 26 containing a recombining catalyst capable of promoting the interrelated reactions described above. 'I'he treated efiluents then .pass through line 21 to fractionator 6 for thev separation of liquid and normally gaseous products according to the previously-described scheme. As the motor fuel components are thus manufactured and separated. they may be continuously withdrawn and blended in suitable proportions through iines 22, 28 and 29-to blending line 30. Any or all of the designated product streams may also be subjected to clay-treatment or other conventional processing for the removal of color, gum, etc., and if desirable, any of the product streams may be utilized in non-related blends, such as aviation fuel blends for which the light liquid condensate of Cs-Ca hydrocarbons may be especially suitable, and for such use is withdrawn through its drawoff line 32.

Example As an example of my invention the following data are taken as illustrative of the application of my invention when treating a thermally converted, stabilized gasoline. The stabilized gasoline from. a deep thermal conversion, after removal of the recycle stock, had the following characteristics:

A.- S. T. M. octane number plus 1 cc.

TEL '17.9

When separated in a tower similar to fractionator 6, the stream obtained from line 8 had the following characteristics:

A. P. I. gravity 83.7 R. V. P 15.3 10% F 101 50% F 109 F 136 Bromine number 72 A. S. T. M. octane number 78.7

Stream 8 was then passed through the recombining catalyst chamber 2B along with the recycle gases as from line BB-IB--IQ to yield the following product: l

A. P. I. gravity 73.2 R. V, P 13.4 10% -F 102 50% F'. 120 90% F 495 Per cent evap. at 212 F '13 Brdmine number 1 17 A.`S. T. M. octane number 74.0 A. S. T. M. octane number plus 1 cc. TEL--- 83.5

The liquid volume recovery was in excess of 98 per cent.

When recombined with stream i0 the following product was obtained and compared with the original charge:

'l'he outlined operation is obviously capable of y various modifications depending on the nature of the charge stock, the catalysts employed, and the type of product which is desired. Thus, the hydrogen-rich gas in line I6 may be recycled to the initial catalytic treatment in chamber 2 through of heavy products boiling above the motor fuel range in the second catalytic stage.

' While the present process is not limited to any particular high temperature cracking or reformlng step, it, is preferred to employ catalysts in order to have a more selective conversion and to lines 3 3 andan and, utilized to control-the olefin content of the products and to prolong the catalyst life. Such recycled hydrogen should not be allowed to pyramidv in the first catalytic zone t0 the extent that the conversion is adversely affected. Also, this hydrogen-rich gas may be added inthe second catalytic step by injection through line 35 to chamber 26. Alternately, hy-

drogen for the second step may be provided by taking a portion of the total overhead stream,

` after compression in system I3, through' lines 36,

I5, I9 and 20a to the catalyst chamber 26..

When it is desired to produce larger volumes of the light condensate indicated at vessel 9, a portion or all .of the intermediate condensate from vessel' Il may be recycled through line 3l to a reforming catalyst. This intermediate condensate fraction of rather narrow boiling range and relatively free of refractory light hydrocarbons may be an excellent recycle feed stock for continuation of the dehydrogenation, alkylation, isomerization, cyclization and other reactions' which may take place in the two successive catalytic zones.

In some types of operation involving catalytic cracking of selected fractions with hydrogen recycle and relatively long contact time, it may be found that the intermediate-.condensate from vessel 'Il is rich in aromatics such as benzene, toluene and homologues. In this case the con-l densate may be .withdrawn and processed by pre. cise fractionation, solvent extraction or other suitable means for segregation of aromatics. Or

the condensate may be employed as a high octane base stock in the production of special fuel blends. In this type'of operation the initial separation ofthe lightI and intermediate condensates is of benefit in avoiding possible excessive formation related catalytic-treatment and produce larger amounts of unsaturates in the light gas fractions for recombination in the second step. For example, the first step may employ a catalyst of known activity in cracking and/or reforming conversions such as bauxite, active natural silicates, synthetic silica-alumina combinations, or the like. 'I'hese catalysts may also be promoted with minor quantities of active metal oxides such as those of chromium, nickel, zinc, manganese, cobalt, etc. The conversion step over these catalysts will ordinarily be conducted at temperatures in the range of about 850 to about 1150 F. and at pressures ranging from about atmospheric to about 500 pounds gage or even higher. The particular combination of operlating conditions will be determined by the nature a somewhat more selective feed to the second step may be produced by arelatively complete depentanization of most o-f the compression condensate and returnof the predominantly C: and

C4 vapors to the recombining catalyst. 'I'he process steps employed .will again depend on the the products which are desired.

1 Thesecond catalytic step in which recombina..l

tion vof the .light products occurs is ordinarily operated at moderately high superatmospheric pressures in lorder to promote the reoombining and the desired products. In general, pressures lin the range of about 100 to about 1 000 Apounds gage are suitable even with catalysts of restricted activity, while temperatures range from about 200 or somewhat less to about 600 F. Higher temperates may be desirable in certain instances, but are usually not as favorable to the class of reactions which are promoted in this second catalytic treatment.

The flow rates of the feed stock to the second catalytic zoneand the time of contact of reactants with the catalyst may'be adjusted to conform. to the operating temperature and pressure and the catalyst activity. It is considered importantl in this operation to employ vcatalysts ofl relatively moderate activity and hence to provide ample reaction timefor the recombinationreactions. At the elevated pressures and moderate temperatures employed, part or all of the hydrocarbons passing through the catalyst are in liquid phase, and the contact time even at rather h igh liquid through-put is satisfactorily long. In this liquid or mixed liquid-vaPOr phase treatment, both the catalyst life and the degree of conversion are much improved over those obdesirable and the catalyst activity is an important iactor in controlling the boiling range and quality of the liquid products fromA this catalytic zone. It is preferred to employ contact catalysts which combine mild activity for promoting alkylation, polymerization and hydrogenation reactions so that ultimate process control will lie` in the proportioning of the feed streams and the zone pressure and temperature.

Especially suitable for the reccmbining step are bauxite catalysts used in natural form or modined by treatment with metal salts or oxides which may affect the rate of one or more of the catalytic reactions. Thus polymerization may be promoted with iron, aluminum or zinc chlorides While chromium, nickel and iron 'salts may be employed to promote polymerization and hydrogenation. Instead of natural minerals, synthetic combinations of silica, alumina, zirconia and other metal oxides may be used to promote recombination of the low-boiling unsaturates in the secondary feed stream. Highly active and non-selective polymerization catalysts such as various phosphoric acid catalysts with or Without metal salt promoters may also be employed in certain instances, although they are not preferred in most applications o the process. Also specific catalysts for promoting isomerization of hydrocarbons, particularly the mono-oleiins, may be used in the second catalytic zone to promote re-arrangement prior to or simultaneous with the recombining reactions.

It has been noted that the unsaturation of the products of the second catalytic treatment may be altered appreciably by the inclusion of varying amounts of hydrogen in the secondary feed stream. This function of the recombining catalyst may be of great benefit in the production of high octane products of greatly reduced olefin content from treatment of both the light condensate and the normally gaseous mixtures separated from the compression and/0r the stabilisation operations of the present process. The advantages peculiar to the present invention are that over-conversion is avoided by the combination of the feed streams ahead of the catalyst, and the integration of the steps which produce and utilize both feed and product streams.

The products of the second catalyst step comprise liquid hydrocarbons resulting from the possible catalytic recombinations of (a) low-boiling olefins in the primary reaction gases and (b) lowboiling olefns in said gases with liquid components of the light condensate. A portion of unreactive components of thev gas streams must of course be continuously removed from the system by venting at the fractionator and/or the stabilizer. When only a controlled portion of the compression condensate stream is fed to the stabilizer, this removal of Cz-Cr paraihns may be accomplished by venting the overhead vapors from the stabilizer.

The volatility of the motor fuel products of the process may be further controlled Within the desired range by varying the proportions of light condensate which are withdrawn through line 28 to blending operations. Thus, treatment of a major proportion of this light condensate through envases the second catalytic zone tends to produce a heavier product of high octane number butvery low volatility. -On the other hand, withdrawal of larger amounts of the condensate for blending purposes may lower the average boiling range of I The process of the present invention is of particular value in such operations as the catalytic reforming of gasoline or naphtha stocks and the catalytic cracking of heavier distillates. The ilexibility and economy of operation and the improved yields obtained permit, for example, a reforming treatment in which the depth of conversion is much greater in the rst catalytic z'one because the normally gaseous products and the low-boiling liquid products are at least partially recombined to produce high octane liquids of suitable boiling range. The overall motor fuel yield of such a process may thus be increased by as much as about 5 to about l0 or more per cent of the charge, and with an appreciable improvement in the quality and lead susceptibility of the produ ct. The net effects therefore may include increased liquid' recovery, controlled olefin content and improved response to antidetonants.

In 'catalytic cracking, the improved yields attributable to recombination of the light products to liquid products of controlled olen content is also obtained, and the depths of per pass cracking may be economically increased.l In fact, it may be desirable to increase conversion in the rst step far beyond that producing maximum yield of gasoline boiling range material, and to employ r the exibility of this invention to recombine and/ or reconstitute both the normally gaseous and the light condensate fractions. As an example of this type of operation, it is possible to crack gas oil with controlled hydrogen recycle to produce varying amounts of unsaturates in the gaseous and light liquid fractions and substantial amounts of aromatics in the intermediate condensate fraction. From this application of the process it is possible to obtain stocks of high octane number due in'one case to aromatics and in the other case to recombined or reconstituted 'branched chain structure. These stocks are suitable with 'a minimum of treatment for use as special base stocks in aviation fuels.

In the operation of this invention. it will be understood thatvarious modiiications may be made. Fonexample, the catalyst in both catalytic zones will become spent in use, thus requiring replacement or reactivation. In such case, in order to obtain continuous operation, as many catalyst cases may be provided as are required. Also, the products of the process, whether blended or utilized separately may receive any conventional treatment which improves gum or color characteristics or minimizes deterioration in storage.

The preceding disclosure has included specific descriptions and diagrams of preferred operations cations involving the substitutionof obvious and equivalent elements 'for the specifically described means or equipment are included within the scope of the disclosure. No limitations are, therefore, implied except as defined in the appended claims.

I claim:

l. A process for the production of high quality motor fuel which comprises catalytially cracking fraction boiling higher than the normal end point of motor fuel; stabilizing said vaporous fraction to remove C4 and lighter hydrocarbons and' hydrogen from the 'C5 hydrocarbons; withdrawing as motor fuel blending stocks said C5 hydrocarbons, a portion -of'the intermediate liquid fraction and a portion of the said light liquid. fraction; passing the stabilizer vapors containing the C4 and lighter hydrocarbons and hydrogen in admixture with another portion of the said light liquid fraction througha catalytic recombining zone at a temperature of approximately 200 to 600 F. and at such a pressure that said mixture is maintained at least in part in the liquid phase in said recombining zone, passing the eilluent of said recombining zone into said fractionating zone in admixture withythe'irst-named eiliuent,

i and recycling anotherportion lofthe said intrmediate liquid fraction into the original lcharge stock previous to the catalytic cracking step.

2. A process for the production of high quality motor fuel which comprises thermally cracking a hydrocarbon oil charge stock, passing the efliuent of the cracking step into a fractionating zone and therein separating a vaporous fraction containing predominantly hydrocarbons, and hydrogen, said hydrocarbons being of C5 and lighter; a light liquid fraction containing approximately Cs to Cs hydrocarbons; an intermediate liquid fraction containing hydrocarbons from approximately C1 up to hydrocarbons of boiling pointsapproximately equivalent to the normal endpoint of motor fuel; and a bottoms fraction boiling higher than thenormal end point of motor fuel;

stabilizing said vaporous fraction to remove C4.

and lighter hydrocarbons and hydrogen from the Cs hydrocarbons; withdrawing as motor fuel temperature of approximately 200 to 600 F.

cycling another portion of the said intermediate liquid fraction into the original charge stock previous to the cracking step. A

3. A process for the production oi' high quality motor fuel which .comprises cracking a hydrocarbon oil chargestock. passing the eiiiuent of the cracking step -into a fractionatingnone and therein separating a vaporous fraction containing ing predominantly hydrocarbons. said hydrocarbons being of Cs and lighter; a light liquid fraction containing approximately C5 to Ca hydrocarbons; an intermediate liquid fraction containing hydrocarbons from approximately C'z up to hydrocarbons of boiling points approximately equivalent to the normal end point of motor fuel; and

, a bottoms fraction boiling higher than the normal end point of motor fuelpstabilizing said vaporous fraction to remove C4 and lighter hydrocarbons and hydrogen from the Cs hydrocarbons; withdrawing as motor fuel blending stocks paid Cs hydrocarbons, a portion of the intermediate liquid fraction and a portion of the said light liquid fraction; passing the stabilizer vapors containing the- C4 and lighter hydrocarbons in'admixture with another portion of the said light liquid fraction4 through a' catalytic recombining zone at a and at such a. pressure that said mixture is maintained at least in part in the liquid phase in said recombining zone, passing the eiiiuent of said recombining zone intc said fractionating zone in admixture with the rst-named eluent. and rey cycling another portion of the said intermediate liquid fraction into the original charge stock previous to the cracking step.

4. A process for the production of high quality motor fuel which comprises cracking a hydrocarbon oil charge stock, passing the efiiuent of the cracking step into a fractionating zone and therein separating a vaporous fraction containing predominantly hydrocarbons, and hydrogen, said hydrocarbons being of Cs and lighter; a light liquid fraction containing approximately Cs to Ca hydrocarbons; an intermediate liquid fraction containing hydrocarbons from approximately C1 up to hydrocarbons ofv boiling points' approximately equivalent to the normal end point of motor fuel; and a bottoms fraction boiling higher than the normal end point of motor fuel; stabilizingsaid vaporous fraction toremove C4 and lighter hydrocarbons and hydrogen from the Cs hydrocarbons withdrawing as motor fuel blend- 'ing stocks said Ca hydrocarbons, a portion of the blending stocks said Cc hydrocarbons, a portion through a. catalytic recombining zone at a temperature of approximately 200`to 600 F. and at such a pressure that said mixture is maintained at least in part in the liquid phase in said recombining zone, passing .the eiiiuent of said recombining zone into said fractionating zone in admixture with the mst-named emuent, and reintermediate liquid fraction and a portion of the said light liquid fraction; passing the stabilizer vapors containing the C4 and lighter hydrocarbons in admixture with another portion of the said light liquid fractionthrough a catalyticrecombining zone at a temperature of approximately 200 to 600 F. and at such a. pressure that said mixture is maintained at least in part in the liquid phase in said recombining zone, passing the eiiluent of said recombining zone into said fractionating zone in admixture .with the firstlnamed eilluent. and recycling another portionot the said intermediate liquid fraction and hydroy gen into the original charge stock previous to the cracking step. l CARL J. HELMERS.

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