US2401649A - Production of aromatics - Google Patents

Description

June 4, 1946.

F. w.` LEFFER PRODUCTION OF AROMATIGS Filed April 2e, 1945 N4 TuzA L /zEa FEEDER/CK MA EPEE/, f l

Patented June 4, 1946 UNITED STATES -PATET OFFICE PRODUCTION ofFARoMATIcs Friedrich W. Lener, naturalized as Frederick W. .Lcffer, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application April 26, 1943, Serial No. 484,549

18 Claims. (Cl.l 2611-6834) The process' comprises two initial conversion` steps in sequence for the production of the desired aromatics, accompanied by the incidental production of corresponding oleflns, as well as 1 jected in a third conversion step of the system ,to catalytic treatment under conditions regulated to effect substantial conversion of said oleflns without any substantial conversion of said aromatics, whereby a product is formed which is rich in the desired aromatics and low in or substantially devoid of olens having a. corresponding carbon atom composition andboiling range. This product is readily separated from lighter and heavier products of the olefin conversion step and recovered for use as aviation base gasoline or any of the numerous uses to which low-boiling aromatics maybe put.

When the process is operated to produce aviation base gasoline it will be rich in benzene, toluene and xylenes. lOn the ,other hand, by proper selection of the charging stock and segregation of intermediate products, any specific lower boiling aromatic may be produced rin predominance to the others. l

. process will deliver a product which, upon the addition of 4 cc. or less of leadtetraethyl and .sufiicient quantities of iso-pentane or the like,

l stage ofthe process.

increasing or assisting to increase its octane rating to the requirements for aviation gasoline. Thus, in one embodiment of the invention the to bring .its vapor pressure to the desired value, meets the rigid requirements for aviation gasoline.

The cooperative and interdependent nature of the various steps of the process 'has been previously mentioned and will now be explained.

The first conversion step of the process and its succeeding separating step serve to prepare from the initial charging stock, and froni'inter.v mediate products of the process which are recycled thereto, as will be later described, and deliver selected intermediate liquid fractions highly suitable for aromatization in the second Italso produces C4 fractions for the catalytic alkylation step and light gasoline fractions for the olefin conversion step of the system.

The aforementioned selected intermediate fractions from the first conversion step comprise heavy gasoline rich in olens and of the desired carbon atom composition which are readily converted to the desired aromatlcs in the'succeeding second step of the process. include some desirable aromatics which would be extremely diflicult to separate from the paraf- Ans, o lefins and naphthenes also present and,

in the preferred embodiment of the invention,

` the'second conversion step, Whereto these frac` Normally gaseous fractions produced in each of kylating stepI iso-butane in said C4 gases and,

when desired, additional iso-butane'from an external source, is alkylated with butylenes to produce an alkymer gasoline of high octane rating and blending value, which may be added in regulated quantities to the aviation base gasoline produced within the system for the purpose of tions are supplied, is of the type in which no sub-,- stantial detrimental conversion of the desirable aromatics supplied thereto will occur. However, it converts substantial quantities of the other components of its chargeand particularly the olens, into aromatics of the desired carbon atom composition, thereby increasing theyield of these fractions from the tlrst step and decreasing the load on the succeeding third or olen conversion step. This second step of the system also pro-V duces C4 gases for the alkylating step andrecycle stock for further advantageous conversion in said second step.

The principal or predominant product of the second step and its adjunctive separating step is a selected fraction comprising essentially the desired aromatics and' fractions `of corresponding boiling range rich in olefins. The thirdA conversion step catalytically treats this selected fraction to convert all or a major portion of the oleiins without appreciable detrimental conversion of the aromatics. it least asubstantial portion of the 'I'hese fractions also high blending value.

boil above the range of aviation base gasoline and,

therefore, can be readily separatedfrom the latter Furthermore, these higher boiling fractions are of a nature well adapted for recycling to one or both of the initial conversion steps for further conversion therein into additional yields of the desired intermediate vand final products, and the invention specifically contemplates their retreatment in .this manner.

Thus, the third or olefin conversion step ofthe system and its adjunctive separating-step not only eliminate or substantially eliminate objectionable oleilns from the nal highly aromatic product, but also produce from the latter higher boiling fractions which may be advantageously retreated within the system to produce additional yields of the 4desired products. It also produces some normally gaseous fractions which are supplied to the gas concentrating step of the system and augment the C4 fractions available for catalytic alkylation.

The alkylating ste'p of the system derives all or a major portion of its alkylation stock from the other steps, as above'described. It produces useful alkyrner gasoline of high antiknock and the alkylating step comprises alkymer bottoms tion, are segregated from the lighter products and returnedto the initial conversion step of the system for retreatment in the latter and in the subsequentsteps to produce additional yields of the desired intermediate and final products.

Normal butane fractions, supplied to the 4alkyla-l tion step with the iso-butane and butylenes, passA through this step without substantial conversion. This unconverted normal butane is preferably segregated from the other products'in the separating step to which they are supplied and, in the preferred Vembodiment of the invention, is returned, all or in part, to one or both of the initial An additional product of 1 which, in the preferred embodiment of the inven- First converston step The 'rststage'of the process, indicated at 2 in the drawing, may comprise an operation'similar to that widely known as thermal reforming. In thermal reforming operations, light distillates, such as gasoline, naphtha and the like, of low antiknock value, are subjected to high cracking temperature at substantial superatmospheric pressure to effect their conversion into substantial yields of gasoline boiling range fractions of materially improved antiknock value. The improvement in antiknock value results to a large extent from the formation of oleiins and some aromatics. At somewhat more severe conditions (higher ternperature, higher pressure or longer conversion time or tany combination thereof) than ordinarily employed for the` same charging stock in such operations, the yield of aromatic fractions may be improved and it is this more `severe type of reforming treatment Which-I propose to employ for the first stage of the system in one embodiment of the invention. The most suitable charging stock for this type of operation is selected naphtha or heavy gasoline fractions having a boiling range of the order of. 200 to 400 F., or an even narrower boiling range within these approximate limits; Thetemperature employed is preferably of the order of 950 to 1250J F. with a. high superatmospheric pressure of the order of 500 to 1000 pounds, or more, per square irnch at the outlet of the heating coil. The oil preferably is quickly heated in theeoil to a temperature approaching 'the maximum employed and is maintained at or to a. temperature of the order of 700 F., or less.

conversion steps wherein it is usefully employed.

I do not attempt to offerl a conclusive explanation of the advantage of this feature but have found that its incorporation in the process gives im proved yields of the desired products in the initial conversion steps wherein olelns and aromatics are produced. It may be that the normal butane is cracked or dehydrogenated and resulting products condensed by polymerization, `alkylation or the like to desirable liquid fractions' or they may in the'novel and advantageous manner in which the various steps have been combined in cooperative and interdependent relation.

One of. the advantageous characteristics of the invention resides 'in the relatively wide choice which it offers with respect toV type of equipment, operating conditions, catalysts and the 'like for conducting the process'. This will enable many refiners to make judicious use of existing equipment, now employed for less profitable purposes, asv satisfactory equipment in which to conduct one When the charging stock comprises a heavier oil than that above mentioned or an oil of substantially wider boiling range, thermal cracking conditions of less severity than those above specified are preferably employed in the first step of the system in order'to avoid coking difficulties.

.Such an operation will not produce as high a yield l'as the treatment above specified of the selected fractions for treatment in the second stage of the system, in a once-through operation,

but the yield of the desired fractions may be materially increased by recycling higher boiling products from the succeeding separating step to v superatmospheric pressure at this point in the tive and protable process.

system ranging from to 800 pounds, or more, per square inch. In general, operating conditions of greater severity (higher temperature and higher pressure, or both) `are employed for the lighterand more refractory oils as compared with those employed for the heavier and less refractory oils. Y

The invention also contemplates catalytic cracking of the charging oil in the nrst step of the system, particularly when charging stocks of the nature of gas oil are employed. The preferred catalyst for this type of operation is of the silica-alumina type comprising either-a synthetic catalyst, substantially free of alkali metal ions the acid treatment.

and prepared b'y any of the several weil known methods, or a treated natural clay from which all or a major portion of the alkali metals have been removed, or a, thus treated natural clay. fortified by the subsequent addition of alumina, to at least partially compensate for that removed in This type of operation is preferably conducted at a temperature of the order of 900 to 950 F. and at substantially atmospheric or low superatmospheric pressure with a weight hourly space velocity (dened as the weight of oil supplied to the reaction zone per hour, per unit weight of catalyst present in the reaction zone) of the order of 1:1 to 10:1.

The catalytic cracking operation, when employed, may be of. the fixed bed type in which the catalyst is periodically regenerated, by burning combustible contaminants therefrom, in the same zone in which the cracking operation has been previously conducted. However, I prefer to employ a moving bed type of operation having a reaction chamber and a separate regenerating chamber, wherein catalyst is continuously transferred from the reaction zone to the regeneratingvzone and hot regenerated catalyst continuously returned from the regenerating lzone to the reaction zone.

This moving bed type of operation has numerous well recognized advantages over the fixed bed l upwardly through the bed in the reactor at a l suilicient velocity to impart a fluid-like condition to the catalyst particles.

A similar uid-like condition is also preferably maintained in the catalyst bed in the regenerator, by passing the air Second conversion step The second conversion stage of the process, in-- dicated at I4 in the drawing, may comprise an additional thermal reforming step, similar to that employed in the initial step and operated under substantially the same conditions or at higher temperature, pressure and/or conversion time, to

produce additional yields of the desired low-boilyields of the desired lower boiling aromatics than will thermal treatment in the second step` 4 In addition to the advantages of fluid bed operation over fixed bed operation as applied to catalytic cracking, it has additional advantages asY applied to catalytic -aromatizatiomdue 'to the relatively large amounts of catalyst deposits.I formed in the aromatizing operation. Inthe uid bed type of operation, these contaminating deposits can be readily handled due to continuous regeneration of the catalyst, and the necessity for periodic and extremely frequent periods of regeneration with short intermediate processing pei riods, as encountered in fixed bed operation, is avoided without the danger of excessively fouling the catalyst bed. In uid bed operation, the

catalyst may be kept at the desired high degree of activity and the aromatizing operation is also conducted at a substantially uniformtemperature Without necessitating the use of a heat exchange type reactor and a circulating heat transor other oxidizing gas employed for regeneration and the resulting combustion gases upwardly through the catalyst bed at` a sufcient velocity to fluidize' the catalyst particles. locities are maintained at a higher value than the net upward velocity of the catalyst particles so that a two-phase condition is obtained in each of the catalyst beds, the.lower portion of each bed being relatively dense due to pronounced hin- The gas vedered settling of the catalyst particles therein, l

and the upper portion of each bed being materially less dense, due to the absence or reduction of hindered settling in this zone.

With the uid bedtype of operation, transportation of the stream of catalyst particles from the dense phase of the fluid bed in the reaction zone to the `dense phase of the uid bed in the regenerating zone and back from the dense phase of the fluid bed in the regenerating zone to the dense 4phase of the uid bed in the reaction zone is readily accomplished, without mechanical conveyers and the like, by maintaining a. higher hydrostatic pressure in the transfer lines, as compared with that in the regions of the iiuid beds into which they` discharge. Thedetails of this type lof operation, as well as the fixed bed type' of operation, are now welllknown to those conversant with the catalytic cracking art and-their specific illustration is not considered necessary to an understanding of the fundamental features of the invention. With a fluid bed type of cracking operation employed in the first step of the process, the catalyst-oil weight ratio (denedas the weight of freshly regenerated catalyst entering the reaction zone per unit weight of hydrocarbons entering the same) is preferably of the order of 0.5;1to 10:1.

fer uidto supply heat to the reaction .zone and abstract heat from the regenerating zone. 4I, therefore, prefer to conduct the catalytic aromatizing step in a uid bed type system.

Any of the numerous catalysts capable .of pro- Irnoting the aromatizing reaction may be employed within the scope of the invention. In general, any good dehydrogenating catalyst will produce suitable results, although their order of activity for promoting aromatization is not necessarily the same as for dehydrogenation. Such catalysts include those containing oxides of the metals appearing in the left-hand column of groups V andV VI of the periodic table, deposited on or incorporated with a relatively inert carrier, such as alumina, silica, kieselguhr, diatomaceous earth, clays andthe like. Alumina or clays of relatively high alumina content are the preferred carriers and chromia, molybdena and vanadia, alone or in various admixtures, are the preferred promoters.

. One specific catalyst which has been found.

particularly suitable for aromatization is a synthetic composite of alumina, chromia, and magnesia, containing approximately 12% chromia determined as the sesquioxde (CrzOsland approximately 2% magnesia, which acts as a stabilizer for the 4alumina to prevent conversion of the active gamma alumina to the relatively inactive' alpha, alumina at the-high temperatures encountered in regenerating the catalyst. The magnesia is also believed to perform .the additional and possibly more important function of preventing or reducing the formationV 'of deleterious alumina-chromia complexes. l

The catalytic aromatizing stepmay be conducted at la temperature of the order of 900 to 1200? F. with a weight' hourly space velocity (a8 defined above) er the order o: 0.10 'te 1.o and with a catalyst oil weight ratio (as dened above) of the order of 10:1 t'o 60:1. The preferred operating conditions inv most instances are: a temperature-of the order of from 950 to 11-50 F., a weight hourly space velocity of 0.25 to 0.50 and a catalyst-oil weight ratio of from 20:1 to 50:1. A- pressure ranging from sube-atmospheric up to about "iv pounds gauge may be employed in the v reaction zone, substantially vatmospheric or subatmospheric pressure being preferred. The catalyst is ordinarily regenerated at a temperature of the order of 1000 to 1200 F. andpreferably care is exercised to prevent the maximumv temperature in the regenerating zone from exceeding 1250 to 1300 F.

` Third conversion step The third conversion step of the process, indicated at Il in the drawing, is conducted to `convert all or substantial quantities of the light liquid olens supplied thereto into heavier olefins boiling above the range of the desired highly aromatic product and readily separable therefrom. Some conversion of these ole'flnic fractions into aromatics or other non-olenic hydrocarbons probably also occurs. In any event, oleflnic fractions boiling within the range of and corresponding in carbon atom content to the desired aromatic product are substantially eliminated in the l ol'en conversion step and higher boiling fractionssuitable for further treatment, as above described, are produced. There are several catalysts capable of promoting this type of operation and several modes of 'operation which may be employed in this step within the scope of the invention. These will now be described.

One type of catalyst particularly suitable for use in the olefin conversion step comprises that now generally known in the industry as/solid phosphoric acid. In its most commonly used `form this catalyst comprises granules or preformed shapes, consisting essentially of a relatively inert siliceous carrier, such as kieselguhr, for example, impregnated with phosphoric acid. Pyrophosphoric acid has been found the most active for producing the desired results and the catalyst is calcined prior to its use to reduce itsmoisture content to the optimum value for preventing conversion of the pyro acid to the less desirable metaphosphoric acid. After use vand regeneration of the catalyst, it is preferably steamed before being reused, to maintain the optimum degre of hydration. With this type of catalyst a temperature of the order of 450-to 600 F. and preferably from 500 to 550 F. is emsure is employed in the reaction zone. Fixed bed catalystzoil ratio (as above defined) is preferably employed, for example, of the order of 2:1, or less, to 5: 1, or thereabouts. At higher temperatures within this range (900 to 1000" FJ, a catalystwil ratio of the order of 5:1 to 30:1 may be employed. In general, the catalyst oil ratio should be varied in direct relation to the temperature. Substantially atmospheric or low superatmospheric presor uid bed type of operation maybe employed, the latter being preferred. This olefin conversion step is characterized and distinguished from catalytic cracking as applied to heavier oils by relatively high -yields of liquid products low in oleflns and boiling within the range of the stock subjected to conversion therein, and by relatively ,low yields of gas and other light fractions.

Fourth conversion step The fourth or catalyticalkylation step of the system, indicated at 3|, may be conducted embutylenes.

'ployed with4 sufficient pressure in the reaction zone to maintain theA reactants in liquid state or in a state of high density resembling that of liquid. The liquid hourly space velocity (defined as the volume of reactants supplied tothe reaction zone, per hour, per unit volume of catalyst present in the reaction zone) may be of the order of 0.5 to 5 and is preferably within the range of y 1 to 2. The fixed bed type of operation is preferably employed with the solid phosphoric acid catalyst, since relatively infrequent regeneration is ordinarily required.

Silica-alumina type cracking catalysts, such as previously mentioned, are also suitable for the olefin conversion step of the system and a wide range of temperatures may be successfully employed with this' catalyst. The wide temperature range permissible is of the order of 600 to 1100 F.

At temperatures of the lower order within the I range mentioned (600 to 900 F.) a relatively low ploying either sulfuric acid or hydrogen fluoride as the alkylating agent or catalyst. With hydrogen fluoride, a temperature of the order of 30 to 200 F. may be employed, the preferred range being fr'om 50 to 150 or thereabouts. A sumcient superatmospheric pressure is maintained in the reaction zone to keep the reactants in essentially liquid state or in a dense phase condition resembling that of a liquid. 'This operating pressure will, of course, depend upon the temperature employed and isusually of the order of 100 to 250 pounds, gauge. It is essential to obtain good mixing between the reactants and the acid in the 'reaction zone and .various forms 'of mixers or contactors are vavailable for this purpose, any of which may be employed within the`scope of the invention. To prevent or retard polymerization of the `o1eiins, the stream entering the reaction zone should contain a high excess of iso-butano to Preferably, an isobutane:butylene ratio of the order of 3:1 to 10:1 on a -mol basis, is maintained in the feed stock, includingthe isobutane recycled from the separating step. Preferably, the fresh acid chargedl to the system is a commercial grade of anhydrous acid, containing not substantially more than 1 to 2% water. A Watercontent up to 10% is permissible in the fresh acid, but does not give as good results. A space-time in the reaction zone (defined as the volume of catalyst present in the reaction zone, per unit volume of hydrocarbon reactants permit the use of a somewhat lower operating pressure.- A temperature ranging from the freezing point of the acid to as high as F. may be employed and-is preferably of the order of 30 to 50 F. The operating pressure may range, for example, from 50 to 150 pounds, gauge, depending upon the temperature employed. *Preferably',

a concentrated acid of or more should be employed and the concentration is preferably of the order of 94 to 98%. The ratio of iso-butane to butylenes'may be approximately the same as specified above for conducting the process with hydrogen fluoride as the catalyst or alkylatlng lversion step I I.

agent, except, for sulfuric acid .alkylation, a

higher ratio is required than for hydrogen.

fluoride alkylation when the charge contains a high proportion of iso-butylene.

The drawing l The accompanying drawing is aflow diagram illustrating the process provided by the invention.

Referring to the drawing, the, initial charging y oil is supplied through line I to 'the ilrst converof 200 to 250 F., or thereabouts, are separately removed from separating zone 4 through line 3 .and all r a, portion of this light gasoline may be directed through lines 59l and Ill to tlfe olefin con- Heavy liquid products or bottoms, boiling above the range of the desired aromatic fractions to be recovered from the process, are removed from the separating zone 4 through line I2 and may be directed to storage, further conversion treatment in the same or a separate system, or elsewhere, as desired.

In case the initial charge supplied through line I is a relatively heavy oil or oil of relatively wide boiling range, regulated quantities of all or selected fractions of the bottoms may be recycled by well known means, not illustrated, to the first conversion stage for further treatment therein.

Fractions 'of the desired carbon atom content and boiling range, comprising the desired aromatics and corresponding oleflns produced in the initial step of the process, are directed from separating zone 4 through line I3 to the second conversion or aromatizing step I4. When-the process is operated for theproduction of aviation base 1 gasoline, the fractions supplied through line I3 to conversion zone I4 will normally be heavy gasoline having an end boiling point of the order of initial conversion step 2. Aviation base gar-oline -of the desired boiling range, or other desired product rich in low :boiling aromatics and oflow olefin content or substantially devoid of olens, is withdrawn from separating zone 22 through line 25 and recovered.

In the gas concentrating system 1, substantially all of the Cz and lighter gases are segregated from substantially all of the Ca and C4 fractions and removed through line 26 to storage or elsewhere, as desired. The Ca fractions are separately removed through line 21 and may, when desired, be directed, al1 or in part, through lines 28 and I9 tothe second conversin step I4 and/or through lines 28 and 29 tothe first conversion step.

Four carbon atom fractions, including iso and normal butane and butylenes, substantially free of lighter gases; are directed from the gas concentrating system through line 30. to the catalytic alkylating step 3| wherein substantially all lighter gases are removed through line 234 and may, when desired, be directed by well known means, not illustrated, back to the gas concentrating zone 1 or removed lfrom the system to storage or elsewhere, as desired. A separation-of iso and normal butane is made in separating zone 33, the iso-butane being withdrawn therefrom through line and regulated quantities thereof e being recycled through line 33 to the alkylating is removed from separating zone 33 throughline rower boiling range fractions for the production of specific aromatics is, of course, also within the scope of the invention.

Fluid products of the second vconversion step I4 are directed through line I5 to the subsequent separating step I6 from which relatively heavy bottoms are withdrawn through line I1 to storage or elsewhere. as desired. Intermediate liquid fractions having an end boiling point corresponding to or somewhat greater than that of the fractions supplied-from zone 4 to the second conversion step are recycled to. the latter for further treatment therein through lines I8 and I9. Normally gaseous fractions produced in the second conversion step I4 are directed from separating zone I6 through lines 20 and 6 to the gas concentrating system 1.

Selected lightliqui'd' fractions, containing the desired aromatics produced in and supplied to the second conversion step, as well as olefns boiling within the same range, are directed from separating zone I6 through line I0 to the third or olefin conversion step II. Resulting fluid products are directed through line 2| to separating 31 and regulated quantities thereof maybe returned via line 38, line 28 and line I9 to the second conversion step and/or directed from line 20 through line 29 to the first conversion step.

Three' carbon atom gases and/or normal butane recycled, as above described, are preferably directed to the first conversion step 2 when the second conversion step I4 is a catalytic aromatizing operation. When the second conversion step I4, as well as the first conversion step 2, is a thermal operation, the Ca gases and/or normal butane may be recycled to the second step in addition to or instead of returning the same to the first conversion step.

The desired alkymer gasoline product which, as previously indicated, is rich in iso-octane, has a high antiknock value, a high blending value and is substantially free of oleflns, is removed from I source may be supplied to the alkylating step zone 22, wherefrom normally gaseous fractions are directed through line,23 to the gas concentrating system 1 and wherefrom liquid fractions boiling above the range of the desired highly aromatic product are returned through line 2 4 tothe the separating zone 33 through line 39 and recovered.v The invention specifically contemplates through line 4I, to

augment the supply from within the system.

Example As an exampleof a specic operation of the I process conducted ,in accordance with the provisions of the invention, the initial charging stock Hydrocarbon products of the at a ltemperature of approximately 1000 measured at lthe coil outletl with a pressure a't this point in the system of approximately 800 pounds, gauge. The resulting products discharged from the heating coil are quickly cooled to a temperature of approximately 660 F. and

are fractioned vto separate bottoms which are removed from the system, heavy gasoline fractions which are supplied to the second conversion step, light gasoline fractions which are suppliedto the third or olefin conversion step andngrmally gaseously fractions which are supplied to the gasconcentrating system. l

The heavy gasoline fractions supplied from the initial conversion operation to the second conversion step have a boiling range of approximately 212 to 392 F., a motor method octane number of approximately 75 and amount-,to about 55% of the oil charged to the initial step. These fractions are thermally treated in the second conversion step, together with normal butane from the alkylating step and some C3 fractions from the gas-concentrating system, and with bottoms from the succeeding separating step, vat a coil outlet temperature of approximately 1025 F.

The operating pressure at the outlet of the heating coil is approximately 100 pounds, gauge.

The products of the second conversion step are quickly cooled, followed their discharge from theheating coil, to a temperature of approximatelythe system. The recycle stock has a boilingv range of approximately 375 to 450 F. The Ca' fractions and normal butane supplied to .the second conversion step amount to approximately 12% by weight of the oil charged to this step.

The oleiin conversion step o'fthe system employsa solid phosphoric acid catalyst, such as above mentioned, containing approximately 70% by weight of phosphoric acid'. The oil supplied to this step from the second conversion step has an end boiling point of approximately 350 F., amounts to approximately 46% by weight of the initial charging `oilto the first conversionstep, .and has a bromine number of approximately 25.

In addition the highly oleiinic light gasoline fractions from the i-lrst conversion step are supplied f to the third conversion step and amountto about 28% of the initial charging oil.- The olefinic conmately 62% of the initial charge to the -rst conversion step, has a bromine number of approximately 5 and an end boiling point of approximately 350 F. This product has a high octane rating land lead susceptibility which, together with its low bromine number, make it excellent blending stock for aviation gasoline.

Four-carbon-atom gases from the gas-concentrating system are contacted in the alkylating step with hydrogenfluoride at a temperature of approximately F., at an operating, pressure l of about pounds, gauge, and with a. space time in the reactor of approximately 30 minutes.

The ratio of iso-butane to olens in the feed to the alkylating step, including recycled iso-butane, is approximately 6:1. The fresh hydrogen fluoride charged to the system is substantially'anhydrous (containing i to 2%v water) and the acid to cil ratio in the reaction z'one is approximately 1:1. A large portion of the acid is separated by settlingfrom the resulting hydrocarbon products and recycled to the alkylating zone. Iso-butane is also recycled, as previously mentioned. A vThe alkylating step will yield a highly paramnic alkymer gasoline rich'in iso-octane, amounting to approximately 95 weight per cent of the oleiins charged to the alkylating step. This product has an end boiling point of approximately 350 F.,

an octane number of approximately 92 and a" high blending value. Its brominenumber is approximately zero. Higher boiling liquid products the charging stock for the process, is not intended to preclude the use of' charging oil containing some aromatic fractions as well. as'other components, such as .paraiflna oleflns and naphthenes. With such stocks non-aromatic fractions are converted in the process to' aromatics while some, if not all, of the aromatic fractions in the stockA remain unconverted.

The term Icracking" lis used in a broad sense in the claims. Cracking,where a heavy stock is not speciiledis intended to include the particular type of cracking treatment generally known as reforming, as explained above, as well as including the cracking oi relatively heavy oils to form lower-boiling products.

The terms "aromatization treatment and reforming under aromatizing conditions, as used in the claims are intended to include either i thermal or catalytlctreatment to form aromatics by any of the methods above specified.

I claim as my invention:

1. A processA for converting non-aromatic hydrocarbon oil to form a product rich in lowboiling aromatics and low in oleilns which comprises, cracking said oil in an initial conversionl step to form light gasoline fractions and heavy gasoline'fractions containing'some of the desired aromatics and containing other hydrocarbons, including olens, of corresponding carbon-atom content, subjecting said heavy gasoline fractions in a second conversion vstep to. aromatization treatment to convert substantial quantities of said other hydrocarbons into additional yields of the desired aromatics, separatingfrom the re 13 sulting products a selected fraction consisting predominantly of said desired aromatics and nonaromatic hydrocarbons of corresponding carbonatom content, including olefins, subjecting said selected fraction together with said lightgasoline fractions formed in said initiall conversion step to catalytic olefin-conversion treatment in a third conversion step under conditions regulated to leave said aromatics substantially unconverted and to convert substantially all of said olefins and form therefrom fractions boiling above the range of the desired highly aromatic product,

recovering the latter and returning said higher boiling fractions to the initial conversion step.

. 2. A process such as defined in claim 1, wherein sulting products a fraction consisting predomi-l liquid products, formed in the second conversion l step, which boil above the range of the selected fraction supplied to the third conversion step and are amenable to further aromatization treatment, are returned to the second conversion step.

3. A process such as defined in claim 1, wherein normally gaseous products of the first and second conversion steps are fractionated to separate substantially all of the 4 carbon atom fractionsV from lighter gases, said i carbo'n atom fractions supplied to a fourth conversion step and therein subjected to catalytic alkylation to chemically combine iso-butane with olenic C4 fractions and form a substantially saturated alkymer gasoline rich in iso-octane, and' wherein higher boiling liquid products of said'fourth conversion step are ,i returned to the first conversion step.

.4. A process for converting non-aromatic hydrocarbon oil to form a product rich in low-bolling aromatics and lowin olefins which comprises, thermally reforming a hydrocarbon -distillate boiling 'within the approximate range of 200 to 400 F. in an initial conversion step to form aromatics and olefins boiling within-the range of gasoline, separating light and heavy gasoline fractions from the resulting products, supplying said heavy gasoline fractions to a second conversion step, therein subjecting the same to further thermal reforming treatment to form low-boiling aromatics and reduce the olefin content of saidl v. heavy gasoline fractions, separating from the resulting products a selected fraction consisting predominantly of the desired aromatics and other hydrocarbons, including olefins, of corresponding carbon-atom content, commingling said selected fraction with said light gasoline fractions formed in the initiaLconversion step and supplying the mixture to a third conversion step, subjecting the same therein to the action of a precalcined solid phosphoric acid catalyst at a temperature not substantially in excess of 600 Rand at sufcient pressure to maintain the reactants in' substantially liquid state, to produce a selected fraction rich in aromatics and of materially reduced olefin fcontent, relative to the charging stock supplied to this step, and to convert substantial quantities of the olefins in said charging stock into liquid productslboiling above the range of said selected aromatic-rich fraction, recovering the latter and returning higher v'boiling products formed in said third conversion step tothe initial conversion step.

5. A process for converting non-aromatic hydrocarbon oil to form-a product rich in low-boiling aromatics and low in olefins which comprises,v

4 14 fractions from the resulting products. supplying said heavy gasoline fractions to a second conversion step, therein subjecting the same to further Vthermal reforming treatment to form low-boiling aromatics and reduce the olefin content of said heavy gasoline fractions, separating from the renantly of the desired aromatics and' other hydrocarbons, including olefins, of corresponding carbon-atom content, commingling-the same with.

said light gasoline fractions formed in the initial conversion step and supplying the mixture to a third conversion step, therein subjecting the same to the action of a silica-alumina type cracking catalyst at atemperature within the range of 600 to 1100F. with a catalyst:oil ratio, within the range of 5:1 to 30:1, regulated to effect conversion of a substantial portion ofthe olefins supplied to this step, without substantial conversion of the aromatics, and form said product rich in low-boiling aromatics and low in olefins,

the process being further characterized. by the formation of liquid products inthe third conversion step which boil above the range of said aromatic-rich product, and lreturning .higherboiling fraction formed in the third conversion step to the initial conversion step.

6. A process for converting non-aromatic hy- -drocarbon oil to form a product rich in lowboiling aromatics and low in olefins whichcom- Y prises, thermally reforming a hydrocarbon distillate boiling within the approximate range of 200 to 400` F. in an initial conversion step to form aromatics and olens boiling within the range of gasoline, separating light and heavy gasoline fractions from the resulting products, supplying said heavy gasoline fractions to a second conversion step, therein subjecting the same to the action of anaromatizing catalyst under conditions regulated to convert substantial quantities of the olefins in said heavy gasoline'v fractions into low-boiling aromatics, separating from the resulting products a selected fraction consisting predominantly of the desired aromatics and other hydrocarbons, including olefins, of corresponding carbon-atom content, commingling the same with thermally reforming a hydrocarbon distillate boiling within the approximate range of 200 to 400 F. in an initial conversion step to form i aromatics, and olefins boiling within the range of gasoline, separating light and heavy gasoline said light gasoline fractions formed in the initial lconversion step and supplying4 the mixture to a third conversion step, `subjectingthe same therein to the action of a precalcined solid phosphoric acid catalyst at a temperature not substantially 'in excess o f 600 F. to produce a selected fraction rich in aromatics and of materially reduced olefin content, relative to the charging stock supplied to this step, and to convert substantial quantities of the olefins in said charging stock into liquid 'products boiling` above the range of said selected aromatic-rich fraction, recovering the latter and returning higher boiling products formed in said third conversion step to the initial conversion step. '7. A process for converting non-aromatic hydrocarbon oil to form a product rich in low-boil- 15 aromatics and other hydrocarbons, including ole fins, of corresponding carbon-atom content, subjecting said selected fraction together with said light gasoline fractions formed in said initial conversion step to the action of a-silica-alumina type cracking catalyst in a third conversion -step ata temperature within the range of 600 to 1l00 F. with a catalystzoil ratio, within the range of 5:1 to 30:1, regulated to Aeifect conversion of 'a substantial portion of the olefins supplied to this step into liquid products boiling above thev range of the desired aromatics without substantial conversion of the latter, recovering from the resulting-products saidaromatic-rich fraction of low olefin content, and returning higher boiling fractions formed in the third conversion step to the initial conversion step.

8. A process for converting non-aromatic hy-v drocarbon oil to form a product rich in'loW--boiling aromatics and low -in oleflns which comprises, cracking said oil in an'initial conversion step to form aromatics and olefins boiling within the range of gasoline, separating light and heavy gasoline fractions' from the resulting products, supplying said heavy gasoline fractions to a second conversion step, therein reformingv the same under aromatizing conditions to form additional quantities of aromatics and materially reduce the olefin content of said gasoline fractions, separating from the resulting products a selected fraction consisting predominantly of the desired 16 products of said conversion steps, subjecting-said C4 fractions to catalytic alkylation to chemically combine iso-butano with butylenes and form a substantially saturated alkymer gasoline rich in iso-octane, and returning the higher boiling products of the alkylating step to the initial conversion step.

14. A process such as dened in claim 4, which includes the additional steps of separating 4 carbon atom fractions from lighter normally gaseous l combine iso-butane with butylenes and form a aromatics andother hydrocarbons, including olecess of 600 F. to convert substantial quantities of the olens in said selected fraction into liquid substantially saturated alkymer gasoline rich in iso-octane, returning the higher boiling products of the alkylating step to the initial conversion step, and returning unconverted normal butane from the alkylating step to the ilrst conversion step. A e

15. A process such as dened in claim 4, which includes the additional steps of separating 4 carbon atom fractions from lighter normally gaseous products of said conversion steps, subjecting said C4 fractions to catalytic alkylation to chemically combine iso-butan'e with butylenes and form a substantially saturated alkymer gasolinerich in iso-octane, returning the higher boiling products of the alkylating step to the initial'conversionv step, and returning unconverted normal butane from the alkylatingstep to the'second conversion step.

16. A process such as dei-ined in claim 4, which includes the additional steps of separating 4 carbon atom fractions from lighter normally gaseous products of said conversion steps, subjecting said C4 fractions to catalytic alkylation to chemically combine iso-'butanewith butylenes and form a products boiling above the range of the desired product rich in aromatics and low in oleiins, recovering the latter from the resulting products in said initial conversion step comprises a catalytic cracking operation employing a silicaalumina type cracking catalyst.

11. A process such as dened in claim 7, wherein said second conversion step employs an aromatizng catalyst' and is-conducted in a system of the fluid lbed type.

12. A process such as defined in claim. 8, wherein said second conversion step employs an of the fluid bed type.

13. A process such asdefined in claim 4, which includes the additional steps of separating 4 carbon atom'fractions from lighter normally gaseous list .aromatizing catalyst and is conducted in a system substantially saturated alkymer gasoline rich in isb-octane, returningthe higher boiling products of the alkylating step to the initial conversion step, and returning unconverted normal butane fromthe alkylating step to the rst and second' vbon atom fractions from lighternormally gaseous products of said conversion steps, subjecting said C4 fractions to catalytic alkylation'to chemically combine iso-butane with butylenes and form a substantially saturated alkymer gasoline rich in. iso-octane, and returning the higher boiling products of the alkylating step to the initialconversion step.

FRIEDRICH W. LEFFER.

Images