Патент USA US2404902код для вставки
July 30, 1946. W. H. CLAUSSEN ETAL HYDROCARBON CONVERS ION Filed July 2l, 1942 2,404,902 Patented July 3o, 194s 2,404,902 UNITED STATES PATENT ori-‘ICE 2,404,902 ' HYDROCARBON CONVERSION William H. Claussen and Thomas M. Powell, Berkeley, Calif., assignors, by mesne assign ments, to California Research Corporation, San Francisco, Calif., a corporation of Delaware Application July 21, 1942, Serial No. 451,748 1o claims. (Cl. 26o-»6735) 1 This invention pertains to the production of aromatic rich hydrocarbon liquids from petroleum distillates and is directed more particularly to the production of substantially pure aromatics from , selected hydrocarbon distillates by means of a novel combination sequence of catalytic and dis tillation steps. Various methods have hitherto been proposed for extracting, by means of selective solvents, the 2 vide a relatively simple catalytic process by means of which it is possible to prepare low boiling aro matic compounds from highly parañinic petro leum fractions with a higher degree of purity and in substantially improved yields over hitherto known processes. It is a more specific object of the present inven tion to provide a catalytic process wherein cata lytic conversion steps are correlated with simple aromatic compounds occurring in certain natural 10 distillation operations in a manner such that petroleums. Methods have also been disclosed for converting a portion of the non-aromatic ma selected parañlnic petroleum distillates may be converted to substantially pure aromatic com pounds with relatively high yield. terials in petroleum distillates to aromatics, which It is a still more specific object of the present may then be separated by means of selective sol vents, just as in the case of the originally occur 15 invention to provide a catalyticv process for con ring aromatics. verting selected parañinic petroleum fractions While the aromatic compounds present or pro duced in petroleum fractions may be substan tially concentrated through the use of known methods of solvent extraction, it is, however, un fortunately a fact that no known solvent is sui‘ll ciently selective to recover by a simple operation all of an aromatic compound from admixture substantially to aromatic compounds wherein two coordinated stages of catalytic treatment are em ployed in series with a fractionation step inter posed between them. It is another` speciñc object of the present in with the associated paraillnic and naphthenic materials in a petroleum distillate and at the vention to provide a method for converting a se lected` fraction of paraiiinic petroleum to sub stantially pure aromatic compounds by catalyti- l cally preparing an aromatic rich distillate, sepa~ same time to recover it in a state of sufllcientlv rating it from non-aromatic compounds so far as high purity that it may be subjected directlyl to nitratìon as, for instance, in the preparation of practical by fractional distillation and subjecting explosives, or may be used directly as raw ma the so separated fraction to a second catalytic treatment for conversion of the residual non aromatic compounds. terial in other specific chemical processes. In our earlier filed copending application Serial No. 434,994 we disclosed a particular method of operating catalytic steps, which are already more or les`s well known in connection with the reform ing of gasolines and naphthas for their antiknock improvement, by means of which it is possible to produce substantially pure aromatic compounds, It is a more speciñc object of the present in vention to provide a process for preparing sub stantially pure toluene from a petroleum hydro carbon fraction boiling between about 180° and 235° F. and containing a substantial proportion such as benzene, toluene, ethyl benzene and tion will be apparent from the following descrip of parafñnic compounds. - Other and more specific objects of the inven xylene, from appropriately chosen fractions of pe tion and the appended claims. troleum. No complicated solvent extraction pro 40 While it is conventional practice in most chem cedure is employed in our process, the appropriate ical reactions, and particularly in the catalytic steps of catalytic conversion properly related to processing of hydrocarbons such as in catalytic' simple distillation processes being adequate to cracking and catalytic reforming operations, to produce aromatics of better than 99% purity. separate from the product unreacted components For instance, it has been found possible by means 45 of the charge for return to the reaction in order of the particular` combination of process steps that the highest possible yield of the desired which constitutes our invention to convert a product may be realized from each unit of charge, “toluene out,” boiling from about 180° to about the present operation differs significantly from 240° F., from a California straight-run petroleum such conventional recycle operation in that it is distillate, simply and directly into nitration grade 50 the desired product that is subjected to a second toluene with yields of the order of 40% by weight. catalytic treatment rather than unreacted com Our present invention comprises a specific modi ponents of the initial charge. Our present proc iication of such operation particularly adapting ess further differs from the usual recycle opera it to the treatment of highly paraillnic stocks, tion in that the 'once-through material is sep It is the object of the present invention to pro 55 arated as far as possible from components of the 1 3 2,404,902 original charge before being subjected to the sec ond stage of catalytic treatment whereas in re cycle operation -the recycled material is added to fresh feed prior to being passed over the catalyst. . Conditions maintained in the second stage of our 4 ic stage is then separated by distillation into a light gas fraction consisting largely of hydrogen and methane, which may be employed directly as the carrier gas already mentioned or further separated to give a butane fraction which may be removed from the process for other well known uses, a liquid fraction boiling above butane up to about 180° F., which may be either recycled for further processing or removed from the process present process are' also significantly different than prevail in the first stage. It is believed that these elements of novelty are highly significant and are in large part responsible for the peculiar advantages of the process of the present inven 10 for use elsewhere, as may be desired, a higher tion. boiling liquid fraction from 180° F. to about 227° Broadly considered, our process for producing F, which is recycled to the first catalyst stage for substantially pure aromatic compounds from se further processing, a liquid fraction boiling be lected parafiinic petroleum distillates may be di tween about 227° F. and 232° F. which is charged vided into four significant and critically related to the second catalyst stage, and a bottoms frac steps, namely. a first stage low-pressure catalytic tion boiling above about 232° F. which may be step, an interstage separation step, a second stage used as a source of higher boiling aromatics or higher pressure catalytic step and a final separa otherwise disposed of as desired. The narrow _tion step. ~ boiling cut from 227° F. to 232° F. is charged to In the first catalytic stage we have found the 20 the second stage catalyst system together with a oxides of metals of the left-hand columns of carrier gas containing hydrogen and under sub groups IV. V and VI of the periodic system. and stantially the same conditions as already de particularly the oxides of chromium, vanadium scribed for the first stagevoperation except that and molybdenum to be effective cyclizing agents. a higher pressure is maintained and the rate of These oxides may be impregnated in or supported 25 charge, and hence the time of reaction in the on activated alumina or the. active metallcom second stage, may be varied somewhat to accom ponents may be coprecipitated with the alumina modate the particular stock which is undergoing as when a solution containing a compound of the treatment so as to produce a final toluene rich metal together with aluminum ion is treated with product of the desired characteristics. This aqueous ammonia. 30 crude toluene can then be separated by ordinary In the second catalytic stage substantially the good fractional distillation with the production same group of catalysts may be used._‘the result obtained being, oualitatively at least,l more de pendent upon the conditions maintained than upon the specific catalyst employed. Specific combinations and sequences of catalysts may nevertheless possess certain quantitative advan tages. It has for instance been found that great er yields of aromatics with less loss to coke and of a toluene product that may directly, or after a slight acid treatment, be satisfactorily sub jected to nitration or such other chemical use as desired. While the process as described herein contem plates two separate catalyst stages arranged in series with an efficient fractional distillation stage between them, it will be apparent to those gas may be secured when a chromium compound 40 skilled in the art that by providing adequate stor catalyst. as described above. is employed in the age facilities the. same ultimate result can be first stage with a molvbdenum containing catalyst in the second stage than when any other catalyst obtained by preparing and storing the toluene catalysts has been found to give the smoothest operation and the most desirable results of any more or less similar gas derived from any other rich 227° to 232° F. cut and substantially passing sequence is used. it through the same catalyst stage in which it In a preferred embodiment of tbe process of the 45 was prepared but under the conditions for second l present invention a catalyst in which a chromium stage operation, as already described. This sec compound such as a chromate or dichromate is ond stage treatment is in no sense equivalent to coprecipitated with or supported on alumina is a recycle treatment through the first stage since employed in the first stage while a catalyst in it is critically and positively a treatment of the which a molybdenum component coprecipitated 50 desired product separated as far as possible from with alumina from a solution containing soluble all other materials instead of being added to fresh compounds of the two metals is used under appro feed as in a typical recycle operation. priately different conditions. described herein The diluting or carrier gas may, as mentioned - after. in the second stage. This combination of above, be the gas produced in the process or a 55 convenient source. We have found, however, that it should contain at least 40% by volume of hydrogen and preferably above 50% in order that the most eflicient use of the catalyst may be real pure toluene for nitration or use as a raw ma 60 ized. It has also been found desirable to employ terial in other chemical processes, we prepare a this carrier gas in quantities up to about 3,000 distillate from naturally occurring, essentially cubic feet, measured under standard conditions parafiinic petroleum by close fractionation to give of temperature and pressure, per barrel of the a cut boiling from about 180° to 235° F. This liquid hydrocarbon charged. The ratio of gas to stock is charged to an appropriate first catalyst hydrocarbon charge on a molecular basis is then stage employing one of the above-mentioned from zero to about three _to one, which, when catalysts and is subjected therein to a tempera the carrier gas contains 50% or more oi’ hydro _ture between about 800° and 1050° F. in the pres gen, would thus give a molecular ratio of hydro ence of a carrier gas containing a substantial gen to hydrocarbon of up to about one and one proportion of hydrogen and at a total pressure half to one. Higher ratios may, of course, be in the neighborhood of atmospheric and prefer employed but without substantial improvement ably not over about 50 pounds per square inch for in'results. a time sufiicient to give the desired conversion to In addition to the significant ratio of diluent aromatics, as will be explained in detail in a later section. The product from said first catalyt 75 gas to naphtha just explained, we have also found combination yet tried. In carrying out the process of the present in vention, when it is applied to the production of that in the second stage the proportion of hydro 8,604,902 5 gen in the diluting gas at any given total pres proportionally by such higher conversion in the sure or, more broadly, its partial pressure in the first stage. satisfactory completion of the conversion of non aromatic components into aromatics or into com pounds that are readily separable from the aro matic compound by fractional distillation. The , over-al1 effect of a substantial partial pressure of hydrogen is to lower the loss of charge to coke and simultaneously to increase the period of oper ation between catalyst regeneration treatments for the removal of coke deposited thereon. We have found that the major part of this benefit to catalyst life is realized between about two and twenty atmospheres (30 and 300 pounds per square inch) partial pressure of hydrogen and usually between about three and ten atmospheres (45 and 150 pounds per square inch). While the total pressure on the second stage system does not appear to be particularly critical, it will be seen, from what has already been said, to be substantially fixed by the limits of dilution pre scribed and by the desirable partial pressures of hydrogemto a-range between about 50 and 500 polmds per souare inch and usually to between ~ While it is possible that this optimum conver sion in the first stage for highest plant eil‘lciency and highest ultimate yield of toluene might be slightly different for charging stocks varying Widely in the nature and relative proportions of the components in the 180° to 250° ~F. boiling range, such variations will be found to be readily reaction mixture, is extremely significant to the 10 determinable and hence are believed to be corn prehended by our invention. The conditions to be maintained in the second catalyst stage are, as already indicated, substan tially different in several respects from those em 15 ployed in the first stage. These differences may vary slightly with the sequence of catalysts used but should in general fall within the ranges speci fied. In addition `to the possible slight variation in hydrogen concentration in the carrier gas and 20 in the other conditions mentioned above, it may also be desirable to alter the feed rate to the sec ond stage slightly to produce the absolute maxi mum yields of toluene with minimum loss of charge to gas and coke. 25 Instead of making adjustments in the feed rate, while maintaining a constant average tempera ture of reaction, in order to secure the desired de With the hydrogen rich stocks consisting sub gree of conversion in either first or second cata stantially of paramnaand only minor cuantities lyst stages, it has been found more desirable under of naphthenes and low boiling aromatics which are preferred for the process -oi' the present in 80 certain circumstances to maintain a fixed feed rate and to adjust the inlet temperature to the vention. it has been found that the process gas _about 100 and 400 pounds per square inch. as produced'irr the first catalyst stage usually catalyst chamber to give the desired conversion, the temperature being readjusted as may be nec essary to compensate for fluctuations or changes in catalyst activity in order to maintain the ex gas. when, however, it is desirable to recover 85 tent of conversion constant throughout the oper from the first stage gas butanes, and possibly also ation. Ordinarily it will be found most conven propane for use in other processes. the concen ient to fix the point of operating temperature contains sumcient hydrogen'that it may be em ployed without further adjustment as the diluent tration-of hydrogen in the remaining gas is, of control at the inlet to the catalyst chamber, the course. increased and the gas istherefore ren 40 temperature there being adjusted to that which dered even more suitable for use as the diluent is found, with a given apparatus and stock, to or carrier agent in our process. With the tem give the desired degree of conversion. This point perature, total pressure, partial pressure 'of hy of temperature control is chosen since the tem drogen and degree of dilution of hydrocarbon perature at any point within the catalyst charge by inert gas regulated substantially within 45 chamber is a much less definite quantity due to the ranges lust specified, the extent of conver the rather large temperature drop through the sion in the catalyst stages may be varied as de catalyst due to endothermic heat of reaction. sired by adjusting the time of the reaction or. One preferred embodiment of theprocess of the more directly, the rate at which the hydrocarbon ‘ present invention will now be explained with ref charge is fed to the process. 50 erence to the figure of the attached drawing. It We have found that in producing toluene from will be appreciated that this figure is a schematic a paraillnic straight-run gasoline, the toluene representation or flow diagram of the process and cut should be charged to the first catalyst stage has no reference whatever to the specific appara at such a rate as will give a debutanized product tus in which the process may be effected. All containing approximately 40% of aromatic com 55 valves, condensers, heaters and like conventional pounds in order that the highest over-'all yield items of equipment have been accordingly omit of toluene from a given amount of charge may ted. be produced with best eillciency and the least For the production of toluene the liquid hydro operating diiliculty. With the more active phys carbon charge to the first stage of the process is ical modiñcations of the above-mentioned cata 60 preferably a closely fractionated cut from 9, par lysts and the conditions of operation as already afilnlc petroleum having a boiling range from given, this degree of conversion is realized by about 180° to 235° F. This charge may be passed charging from about 0.7 to 3.0 volumes of hydro through line i to the iirst stage heating zone 5 > carbon (measured as liquid) per volume of cata' to which are also passed recycle gas from line 3, lyst (including voids) per hour. While it is true 65 light recycle liquid from line I3, heavy recycle liq that with a lower conversion in the first stage uid from line 3| and extraneous hydrogen from . a slight increase'in the over-al1 yield of toluene line 2 when necessary. The preferred ratio of re may be realized, this is possible only with a sub cycle gas to total liquid feed to the catalyst cham stantial reduction in’the capacity of any given ber is of the order of 1500 cubic feet per barrel. plant. With a conversion in the first catalyst 70 At this ratio it is desirable that the recycle gas stage to give more than about 40% of aromatics should contain at least 40%, and preferably above A in the debutanized product, the ratio of toluene 50%, of hydrogen and that the molecular ratio of to gas and light liquid, boiling below about 180° hydrogen to liquid hydrocarbon charge be 0f the F., is found to decrease rapidly and hence the order of 0.75z1. The extraneous hydrogen added yield of toluene per unit of charge is reduced through line 2, as already mentioned, is thus em 2,404,902 10 ` passes through the process of the present inven tion may be better visualized, the approximate percentage of toluene contained in the liquid passing through lines I0, I4, 23 and 21 has been product falling substantially in the same range as the original charge and containing a significantly higher concentration of aromatic compounds - indicated on the drawing. product to produce a cut boiling substantially Within the range of the original charge, subject than the charge, fractionally distilling this liquid While these values may vary somewhat with different charging stocks, they may be substantially regulated by ing said cut to a second .treatment with a metal controlling. the conversion effected in the first oxide dehydrogenation catalyst containing as the stage so that the liquid passing through line ID active component an oxide of a metal selected will containabout 40% aromatics. With the 10 from the group consisting of the metal of the left average parañinic stock used as a basis for the hand columns of groups IV, V, and VI of the foregoing description, the crude toluene charge periodic system at a pressure higher than em (line I4) to the second stage will then contain ployed in the ñrst stage, collecting the liquid approximately 90%- total aromatics, the second product and sharply fractionating it to separate stage product (line 23) passing to the toluene 15 the desired aromatic in a substantially pure state. still will contain about 96% toluene and the ñnal ' 2. Process for the production of toluene which product discharged through line 21 willbe sub comprises subjecting a fraction from a para?clnic stantially pure (99%-H toluene. For conven petroleum boiling in the range from about 180° to ience in visualizing the process, these iigui‘es have about 240° F. to the action of a catalyst compris been indicated enclosed in circles at the appro 20 ing chromic oxideand alumina at a temperature prlate points on the drawing. The over-al1 yields between about 900° and 1025° F. under a pressure of toluene that have thus been obtained vary of about atmospheric and in the presence of a from about 32 to 42% by volume of the liquid _ carrier gas containing at least 40% hydrogen, charge. said carrier gas being in the ratio of about 1500 The process of our present invention may be 25 cubic feet per barrel of liquid charge for a. time further illustrated by reference to the following suirlcient to produce a debutanized liquid product speciñc example: containing aboutl 40% of total aromatics, frac tionally distilling said liquid product to produce Example a sharp cut boiling between about 227° and 232° F., 30 subjecting said cut to a second catalytic treat A fraction from a parafllnic straight-run gaso line boiling between 180° and 240° F. (true boiling ment over a coprecipitated molybdena-alumina points) was subjected to the two-stage process catalyst in the presence of a carrier gas contain just described wherein a chromic oxide-alumina ing free hydrogen at a temperature between about composition was used as the catalyst in the ñrst 900 and 1025° F. and under a pressure of about stage and a molybdenum-alumina coprecipitate 35 200 p. s. i. for a time suflicient to produce a de was employed in the second. The operating con butanized product containing at least 90% ditions and results obtained were as follows: aromatics and subjecting said product to an eiîi cient fractional distillation to produce a fraction 1st stage 2d stage containing at least 99% toluene. 40 3. Process as in claim 2 wherein the catalyst in Temperature av., °F _____ ._ 950 960 the second stage is a coprecipitated vanadium Pressure p. s. i. abs-._. . 15 215 oxide-aluiminum oxide composition. Feed rate (liq.) v./v./hr _ 0. 25 1.0 _ 60 60 Gas recycle, cu. it /bbl leed _ l, 500 6, 000 Yield, vol. pei-cen Coke loss, wt. percent- On stream periods, min „ _ 80 1.0 96 l. l 15.0 20.0 3. 0 99.0 Gas loss, wt. percent„_-__ Toluene vol. percent oi pr Toluene yield vol. percent chg ______________________ ._ _ 4. Process for the production of an aromatic rich stock which comprises subjecting a `selective 45 narrow boiling parañlnic distillate to the action of >a cyclization catalyst containing as the active 35 component an oxide of a metal selected from the group consisting of the metals of the left-hand While the foregoing discussion and examples columns of groups IV, V and VI of the periodic have been directed particularly to the production 50 system at substantially atmospheric pressure and> of toluene from a typical paraiilnic stock, it is a temperature between about 900 and l025° F. in equally possible to produce the other low boiling the presence of a. carrier gas containing a sub aromatics, such as benzene, ethyl benzene and stantial proportion of free hydrogen, collecting xylene, from the appropriate fractions of a similar the liquid product, fractionally distilling said co1 stock. 55 lected liquid product for the removal of com Having now described and illustrated our “two ponents boiling both above and below the original stage catalyst” process comprising a particular charge and subjecting the so segregated liquid combination of catalytic and distillation steps boiling within the range of the original charge for the production of substantially pure aromatic to a second catalytic treatment with a catalyst liquids from selected parafflnic petroleum- frac 60 containing as the active component an oxide of a tions, we claim: ' , metal selected from the group consisting of the 1. Process for the production of a substantially metals of the left hand columns of groups IV, V, pure liquid aromatic which comprises subjecting and VI of the periodic system in the presence of a selected narrow boiling fraction from a paraf a carrier gas containing free hydrogen and at a -ñnic base petroleum to reforming, dehydrogena 65 pressure substantially higher than that employed tion and cyclization over a metal oxide catalyst in the first stage for the conversion of non containing as the active component an oxide of a aromatic compounds to render the aromatic com metal selected from the group consisting of the pound separable by fractional distillation. metals in the left-hand columns of groups IV, V 5. Process for the production of substantially and VI of the periodic system at a temperature 70 pure toluene from a parañlnic petroleum distillate between 800° and 1050° F., a pressure of about which comprises subjecting a fraction from said 15 p. s. i. absolute and in the presence of a hydro distillate boiling within the range from about 180° gen containing carrier gas in the ratio of about to about 240° F. to the action of a catalyst com two molecules of gas per molecule of hydrocarbon charge for a time suñlcient to produce a liquid 7 prising chromium oxide and alumina in a first stage at a temperature between about 900° and 11 223„ 404,902 1050° F. and a pressure of substantially atmos pheric in the presence o1' a recycle gas containing between about 45 and 90% free hydrogen, said gas being present in quantity less than about 3000 cubic feet per barrel of liquid charge, collecting the liquid product formed, separating from said liquid product by extreme fractionation a toluene rich fraction containing substantially only hydro carbon impurities that are inseparable from toluene by said fractionation, subjecting said crude toluene fraction to the action of a copre cipitated catalyst comprising molybdenum oxide and alumina at a temperature between about 900° and 1050° F. and a pressure between about 50 and 300 p. s. i. in the presence of a carrier gas con- , 'taining free hydrogen in the ratio of between 2000 and 12,000 cubic feet of gas per barrel oi’ liquid charge whereby the hydrocarbon materials associated with the toluene are converted to sub stances that are separable from the toluene L', hand columns oi' groups IV, V and VI of the periodic system in the presence of a carrier gas containing at least 20% by volume of hydrogen, at a total pressure higher than that maintained in said aromatizing zone and being of the order of from 50 to 500 pounds per square inch' and at a partial pressure of hydrogen :from about 30 to 300 pounds per square inch to transform said cut and render said aromatic compound separable therefrom by fractional distillationD fractionally distilling the resulting product to separate there from substantially pure aromatic compound. i?. Process as deíined in claim d, in which said ñrst mentioned metal oxide is a chromium oxide and said second mentioned metal oxide is a molyb denum oxide. 0. ‘Process as defined in claim o”, in which said first mentioned metal oxide is a 'vanadium oxide. 0. 'Process as defined in claim in which said ?lrst mentioned metal oxide is a molybdenum fractional distillation and eiîecting said separa oxide. tion to produce toluene of nitration grade. 10. Process for the production of hydrocarbon o. Process for producing a substantially pure distillate fractions rich in aromatic compounds relatively low boiling aromatic compound from a which comprises subjecting a selected parailinic para?linic hydrocarbon fraction containing con 25 petroleum fraction to the action of a metal oxide stituents boiling Within the gasoline boiling range, aromatizing catalyst containing as the active which comprises aromatizing said parafl‘lnic frac component an oxide of a metal selected from the tion by subjection to the action of a dehydrogena group consisting of the metals in the left-hand tion catalyst comprising coprecipitated alumina columns oi groups IV, V and Vl oi’ the periodic and an oxide of a metal selected from the group 30 system ata temperature of 800° to 1050° F. in the consisting of the metals in the left-hand columns presence of added hydrogen and at a pressure oi’ of groups IV, V and VI of the periodic system at about atmospheric to about 50 pounds per square a temperature from about 800° to 1050° F. in the inch, fractionally distilling the product to sepa presence of a carrier gas containing at least 40% rate a cut boiling in approximately the same by volume of hydrogen, at a total pressure from 35 range as the orginal charge and containing the about atmospheric to about 50 pounds per square desired aromatic, subjecting the so separated cut inch, with a molecular ratio of hydrogen to hy drocarbon up to one and one-half to one, and at a .to a second catalytic treatment with a catalyst containing as the active component an oxide oí’ a space velocity of about 0.2 to about 3.0 volums of liquid hydrocarbons charged per volume of 40 metal selected from the groups consisting of the metals of the left hand columns of groups IV, V, catalyst space per hour, separating from the re and VI of the periodic system at a higher pressure sulting product by fractional distillation a. rela ' than employed in the first stage to render the tively narrow cut containing essentially only the aromatic compound in said cut separable there desired aromatic compound and other con from by fractional distillation and iractionating stituents inseparable therefrom by fractional the resulting product to separate in substantially distillation, subjecting said narrow cut to the pure form the aromatic rich liquid produced. action of a catalyst comprising coprecipitated alumina and an oxide of a metal selected from the group consisting of the metals in the left H. CLAUSSEN. THÜMAEJ M., PÜVJEMJ.