US2373303A - Process for modifying aromatic hydrocarbons - Google Patents

Description

April 10, 1945. F. E. FREY ETAL PROCESS FOR MODIFYING AROMATIC HYDROCARBONS Filed Aug. 22, 1936 if gig I) Y \1 [1* (I w INVENTOR. FREDERICK E. FREY BY JEAN P. JONES 1 cm on? ATTORNEYS.

yiile, Okla,

a rat read Domny, a corpretlon oi Delaware Application august 22, 1936, Serial No. 97AM i Cia.

This invention relates to-the iotion oi allsyl derivatives from aromatic hydrocarbons, and particularly to the formation from aromatic hydrocarbons of derivatives containing one or more alkyl groups more than are contained in the'original aromatic hydrocarbons, and furthermore particularly to the formation of these derivatives by the pyrolytlc treatment of a mixture comprising an aromatic hydrocarbon and an aliphatic hydrocarbon under the influence of'superatmos- .pheric pressure in-the absence'of any catalytic material other than that which incidentally may .be presented by the walls of the reaction vessel or fortuitous impurities.

It has been known for some time how to pre-' pare alkylated aromatic hydrocarbons, that is.

. attach ethyl, propyl, and other alkyl groups to the aromatic molecules by employing some catalytic means or condensing agents. These are illustrated-by the well known synthesis of Frledel and Crafts, in which an 'alkyl halide is caused to alkylate an aromatic molecule by the aid of aluminum chloride,by the reaction of an olefin and arr-aromatic hydrocarbon in the presence of some condensation agent such as phosphoric acid or aluminum chloride and-by other similar means.

' Aromatic hydrocarbons suchas benzene, naphthalene and others are produced in relative abundance in coal carbonization, in the enrichment of manufactured gas by the cracking of petroleum, and in gas reforming or pyrolysis. Relatively less amounts of alkylated derivatives such as toluene, xylene, ethyl benzene, alkylnaphthalenes are formed which differ somewhat from the purely cyclic aromatics in properties and have found a variety of: special uses.

An-oblect of our invention is to produce alkyl derivatives from aromatic hydrocarbons such as toluene, ethyl benzene and xylene from benzenethe corresponding derivatives, from naphthalene,

and to introduce alkyl groups into other aromatic hydrocarbons which may already contain one or more alkyl groups. Another object is the concomitant productionof more or less of condensa- 1 tion products of aromatic hydrocarbons formed-by union of two molecules with elision of hydrogen.

' Alkyl groups of varying molecular weight may be introduced, such as methyl, ethyl, etc.

We are aware that in the course of the ordinary uncatalyzed pyrolysis of crude non-aromatic hy-' drocarbons, materials containing more or less'of alkyl aromatics may be formed under suitable conditions, and that the thermal treatment of benzene mired with ethylene produces styrene accompanied by other products. We have discovered that a high yield 02 :1'12

companied by relatively slight amounts of contaminating by-products, can be produced by heating at an elevated pressure the aromatic hydrocarbon, into which it is desired to introduce alkyl substituents, with aliphatic hydrocarbons. The temperature required is in the neighborhood of that at which the aliphatic hydrocarbons tend to crack or polymerize, and is readily determined by experiment. The aliphatic hydrocarbons may range all the way from methane to paraffln wax or paramn oil in molecular weight, and may be of either saturated orunsaturated type. Low molecular weight hydrocarbons, normally gaseous, are usually preferable since their use minimizes the formation of by-product hydrocarbons, through splitting and polymerization, which boil in the range of the desired alkylated aromatics and may constitute undesired impurities. When simple paramns are employed, more or less decomposition takes place during reaction, but the formation of polymeric compounds is not extensive and large proportions of these hydrocarbons, admixed with the aromatic hydrocarbon may be used, since the relatively low boiling temperature makes their separation from alwlation products easily accomplished. The simple olefins may likethroughout the reaction period may be desirable to reduce the tendency to polymerize which high momentary concentrations will encourage. The quantity of aliphatic hydrocarbons then may vary from 5 per cent or less to quantities such that they predominate in the reaction mixture, and by a substantial proportion of aliphatic hydrocarbons in admixture with aromatic hydrocarbons will be understood to be as explainedand defined in the foregoing discussion. Hydrogen may be added to the reaction mixture to inhibit condensation reactions'of aromatics and this is also a part of our invention.

The proportion may vary widely; as little as 5 mol per cent may be adequate at high pressures and when thermally treating non-oleflnic hydrocarbon mixtures, while when oleflns are employed as the alkylating agent hydrogen will be consumed by hydrogenation of olefins and to obtain maximum inhibitingv of aromatic to aromatic union, over 50 mol per cent of hydrogen may be required. By a substantial proportion of hydrogen will be understood its addition as the foregoing discussion directs.

An initial mixture of aromatic and aliphatic hydrocarbons-is continuously introduced into a reaction zoneunder a pressure in excess of 250 pounds per square inch, and preferably between 1,000 and 5,000 pounds per square inch, at a temperature determined by experiment and usually of 400 to 800 C., and is held in this reaction zone for a period of time readily determined by trial but brdinarily not less than 0.5 minute nor more than minutes, the resulting mixture being removed from the reaction zone and the desired derivatives separated therefrom.

We have found that extensive reaction, wherein the aromatic hydrocarbons are more or less completely converted in a single thermal treatment, may lead to excessive formation of heavy condensation products, and consequentl it is usually desirable to interrupt the reaction while 50 per cent or even more of the original aromatic hydrocarbons remain unreacted. Such unreacted hydrocarbons may be separated from the effluents to be subjected once more to thermal alkyiating conversion. In some cases polynuclear condensation compounds, which form at the expense of the alkyl derivatives, are not desired. If hydrogen is added as-previously set forth to the mixture of aromatic and aliphatic hydrocarbons to be subjected to reaction, the formation of condensation compounds is inhibited, while alkylation proceeds readily.

Unreacted components may be reintroduced into the heating and reacting zones. Undesirable polynuclear aromatic hydrocarbons formed may be reintroduced into the heating and reacting zones for dissociation, or they may be separately reacted in the presence of hydrogen and reintroduced into the system as will be described and shown. The temperature of the reaction zone will vary in an inverse relationship with the pressure to which the reactants are subjected. Actual conditions of operation will vary somewhat with variation in the initial aromatic and aliphatic materials and upon the products desired, and may be readily determined by experiment. Upper limits of temperature or pressure will be dependent also upon the materials used in the apparatus.

An example of our invention is as follows:

A mixture comprising 88.9 per cent by weight of benzene and 11.1 per cent by weight of ethane was continuously passed through a reaction zone heated to 605 C. and at a pressure of 2865 pounds per square inch. The mixture was subjected to this temperature for a period of about 2 minutes, immediately cooled and withdrawn. There was produced ethyl benzene and toluene, in the ratio of approximately 5.5:1 along with traces of unsaturated materials and some polynuclear aromatic compounds. In a similar experiment, the reaction was allowed to proceed in the presence of hydrogen, which decreased the formation of polynuclear aromatic hydrocarbons to the ultimate benefit of the formation of the alkylated products of about the same composition.

As a further example of this invention a mixture comprising 91.8 per cent by weight of naphthalene and 8.2 per cent by weight of ethane may be passed continuously through areaction zone heated to 600 C. under a pressure: of 2900 pounds per square inch, being subjected to this temperature for a period of about 2 minutes, then immediately cooled and withdrawn. The product will contain a fraction comprising a mixture of methasvasos yl naphthalene and a" considerably larger amount of ethyl naphthalene along with small amounts of unsaturated compounds and heavier polynuclear compounds.

A further and more complete operation of our process will now be presented with reference to entering the fra'ctionator 2|. stood that heat from some other, or extraneous the accompanying drawing, wherein:

The figure illustrates diagrammatically one type of apparatus for practicing the present invention.

Aromatic hydrocarbons, such as benzene, are maintained under suitable pressure and introduced through pipe i0 and mixed therein with suitable aliphatic material, which may be ethane and which is introduced through pipe II. The mixture of aromatic and aliphatic hydrocarbons is compressed by the pump l2 in pipe ill to a suitable pressure in excess-of 250 pounds per square inch, and preferably to a pressure between 1,000 and 4,000 pounds per square inch. If desired, hydrogen may be introduced by way of pipe I! and added to the mixture of hydrocarbons in pipe l0, and the induction thereof may be controlled by valves l4 and Ill, and any necessary or desired compression of the hydrogen may be effected by pump 16.

The mixture of aromatic and aliphatic hydrocarbons plus the added hydrogen then passes through pipe l0 into and through the reaction coils H, which are suitably housed in the furnace I, wherein it is heated to some temperature in excess of 400 C. and held at that temperature for a period of time in excess of 0.5 minute. The resultant products or eiliuents then pass from the reaction coils I! through the pipe i9 and the expansion valve 20 and into the fractionator )2]. If desired a part or all of the eiliuents from reaction coil I! may be passed through pipe 22 and into coil 23, located in the kettle of the fractionator 2i, in order to utilize some of the sensible heat of the eiliuents. From coil 23 the eilluents pass through pipe 2 and again re-enter pipe i! and flow into the fractionator. To provide for such a utilization of the sensible heat of the effiuents valve 25 is provided in pipe is adjacent the fractionator, and valve 26 is provided in pipe 22. By manipulation of these valves all or any part of the eiiluents flowing through pipe [8 may be caused to circulate through the coils 23 before It is to be undersource, other than the sensible heat of the eilluents may be supplied to heat the kettle contents.

contains the desired alkylated products along with other heavier material which may be formed. .These kettle products are removed from the fractionator 2| by way of pipe 21 and are passed to a system of rectifying units designated by the reference numeral 28, wherein a separation is made between the desired allrylated product or controlled by the valve 52.

i'radtionator kettle 02 if desired.

' Fractionator, or separator, 32 operates at some superatmospheric pressure, but at a pressure less than the operating pressure of fractionator 2i, and preferably in the neighborhood of 300- pounds per square inch; Within the iractionator; or separator, 82 separation is made between fixed s, which may include methane and hydrogen, and heavier material which is withdrawn by way of pipe ill} and passed baclr through pipe 39,

valve t0, and pipe 01 to be introduced into pipe i0. Or, in lieu of passing the heavier material back for introduction into pipe as described. they may be withdrawn through the pipe t2 controlled by valve 63.

A cooling coil 00 may be interposed in the top of the fractionator, or separator, 02 and additional cooling means such as that diagrammatically designated by the reference numeral 00 may also be provided if desired, so that the gases leav ing the fractionator orseparator by way of pipe 06, will if desired, be freedfrom substantially all of the hydrocarbons containing two or more carbon atoms. To aid in stripping these gases of the more volatile of the last mentioned hydrocarbons, an absorbing liquid which may be either an aliphatic or aromatic oil is introduced through line 01? and valve 08- into the fractionator, or

separator, 32, and which oil will eventually be withdrawn therefrom along with the kettle products.

Moderate cooling means may be used in fractionator, or separator; 32 so that only asmall 1 part oi the ,lightertmaterial need be treated in"- cooler d5.

Fixed gases leaving fractionator, or separator, 32 and cooler 65 may be recycled back through pipe 09 and valve 50 for further treatment in the process, and introduced into pipe it, or in lieu thereof any part or-all of these gases may be withdrawn from the process through pipe bi However it is to be understood that-the gases which pass through pipe 0! may be treated in apparatus not illustrated, and a hydrogen rich mixture resulting therefrom may be introduced into theprocess through pipe i3.

Polynuclear aromatic material, either alone at elevated temperatures or in solution with hydrocarbon material, is withdrawn from the rectitying units 28 through pipes 53 and t and valve 55, and forced by pump 06 through the remainder of pipe 50 and through valve 5? andzinto the reaction coils 58 which are'housed in the-furnace 59.

Hydrogen from any suitable source, such. as from line it may be passed'through pipe 60 and valve 8! and compressed by pump 62 and-forced through the remainder of pipe 00 and through" valve 63 and introduced intopipe 5d. The re- .sultant mixture in pipe 50, which will include polynuclear aromatic material together with hydrogen then passes at a pressure in excess of 250 iii 00, which coils are heated to some temperature in excess of 400 C. The mixture is exposed in the reaction coils for a period of time which may be greater than 0.0 minute, but less than minutes. By this thermal treatment of the mixture of polynuclear material and hydrogen dissociation into simpler aromatics is effected.

Actual pressure, temperature and exposure times will be dependent upon the nature of the polynuclear material to be treated, and may readily be experimentally determined.

The eiiiuents from the reaction coils 50 pass through pipe 0t and valve 00, and expansion valve 00 and into the pipe it. If necessary, or

desired, additionaal pressure may be applied to the eii'iuents. leaving the reaction coils by closing valve 0% in pipe t0 and by passing the eilluents' through pipe ti, valve 00, pump 00, pipe i0 and valve 'ii, and thence back into pipe 00.

It is to be understood that any part or all of the efliuents flowing through pipe 0t may be diverted therefrom by manipulation of valve. 00

and caused to flow through pipe i2 and valve l3 into pipe 239. Furthermore, if desired, all or any part of the untreated polynuclear aromatic hydrocarbons flowing through pipe 00 may be di rectly introduced into pipe ii, and subsequently into pipe ill. by way of pipe it in when is interposed the valve 75, without adding hydrogen to the untreated polynuclear aromatic hydrocarhops and also without passing them through the reaction coils b8. Although preferred methods of operating the process have been given, many variations in procedure or in the material processed will be apparent which may be made without departing from the spirit of the invention. The invention is not to be construed as being'limited by such described procedure as herein taught nor by the examples given, but is to be limited only as set forth in the accompanying claims forming a part of this specification.

What we claim and desire to secure by Letters Patent is: V

l. A process for converting aromatic hydrocarbons into alkyl substituted derivatives, which comprises subjecting aromatic hydrocarbons to v which has been added a substantial proportion of at least 250 pounds per square inch to; form alkyl substituted derivatives, then separating from the thermally treated hydrocarbons the alkyl substituted derivatives so produced.

2. A process for converting benzene into alkyl substituted derivatives, which comprises subject ing benzene to which has been added a substantial proportion of aliphatic hydrocarbons and also a substantial proportion of hydrogen to a reaction temperature of 400 to 800 C. while maintaining a pressure of at least 250 pounds per square inch to'form alkyl substituted derivatives, then separating from the thermally treated hydrocarbons the alkyl substituted derivatives so produced.

3. A-process for converting naphthaleneinto alkyl substituted derivatives, which comprises subjecting naphthalene to which has been-added a substantial proportion of aliphatic hydrocarhens and also a substantial proportion of hydrogen to-areaction temperature of 400 to'800 C. while maintaining a pressure ofat least 250 pounds per square inch to form alkyl substituted derivatives, then separating fromthe thermally 4 tail:

treated hydrocarbons the alkyl substituted deri atives so produced.

4. A process for converting aromatic hydrocarbons into alkyl substituted derivatives, which comprises subjecting the said aromatic hydrocarbons to which has been added a substantial proportion of aliphatic hydrocarbons to a reaction temperature of 400 to 800 C. while maintaining a pressure oi at least 250 pounds per square inch to produce alkyl substituted derivatives, separating from the thermally treated hydrocarbon the alkyl substituted hydrocarbons so produced, separating also therefrom the unconverted aromatic hydrocarbons and subjecting the last mentioned hydrocarbon to the aforesaid reaction, and separating also therefrom the polynuclear aromatic hydrocarbons formed in the aforesaid reaction, subjecting these last mentioned p lynuclear aromatic hydrocarbons in admixture with a substantial proportion of hydrogen to a reaction temperature 01' 400 to 800 C. while maintaining a pressure of at least 250 pounds per square inch to produce simpler non-alkylated aromatic hydrocarbons. and introducing at least a portion of the eilluent oi the last said treatment into the cycle of the first mentioned reaction.

5. A pyrolytic process for converting aromatic hydrocarbons into alkyl substituted derivatives, which comprises subjecting aromatic hydrocarbons to which has been added a substantial proportion of saturated aliphatic hydrocarbons to a reaction temperature between 400 and 800 C. in the absence of a catalyst for a period of time such that at least 50 per cent of the initial aromatic material remains unreacted while maintaining a pressure in excess of 250 pounds per square inch whereby alkyl substituted derivatives of said aromatic hydrocarbons are formed and separating from the products said alkyl substituted derivatives.

. 6. A pyrolytic process for reacting paramn hydrocarbons and aromatic hydrocarbons to form alkyl substituted derivatives of said aromatic hydrocarbons, which comprises subjecting in a reaction zone an aromatic hydrocarbon material with which has been dispersed a substantial proportion of a paraflin hydrocarbon of not less than two nor more than five carbon atoms per molecule to a reaction temperature of 400 to 800 C. in the absence of a catalyst while maintaining a pressure of at least 250 pounds per square inch and for a period of time of at least 0.5 minute and such that at least about 50 per cent of said aromatic material remains unreacted and adapted to produce alkyl substituted derivatives or aromatic hydrocarbons from said aromatics and said paraifins, and separating from the reaction, effluent a hydrocarbon fraction containing alkyl substituted aromatic derivatives so produced.

7. A process according to claim 5 in which the aromatic hydrocarbon comprise benzene and in which the saturated aliphatic hydrocarbons contain not less than two nor more than five carbon atoms per molecule.

8. A pyrolytic process for converting aromatic hydrocarbons into alkyl substituted derivatives,

which comprises heating under a pressure in excess of 250 pound per square inch a stream of aromatic hydrocarbons in which a substantial proportion of aliphatic hydrocarbons and a substantial proportion of hydrogen are dispersed to a reaction temperature between 400 and 800 C. for a period of time such that at least 50 per cent of said aromatic hydrocarbons rema n unreacted whereby alkyl substituted derivatives of said aromatic hydrocarbons are formed and subsequently removing from the stream a fraction containing said derivatives.

9. A continuous pyrolytic process tor iormins alkyl derivatives of aromatic hydrocarbons. which comprises subjecting aromatic hydrocarbons, with which have been dispersed substantial proportion of saturated aliphatic hydrocarbon and also a substantial proportion of hydrogen, to a reaction temperature between 400 and 800 C. while maintaining a pressure on the reaction mixture 01' at least about 250 pounds per square inch forming alkyl substituted derivatives or said aromatic hydrocarbons and polynuclear aromatic hydrocarbons. separating from the reaction mixture a fraction containing alkyl substituted hydrocarbons so produced, separating also a traction containing unreacied aromatic hydrocarbons and said polynuclear aromatic hydrocarbons and returnins said fraction to be mixed with aromatic hydrocarbons charged to the process.

10. A multistep process for converting aromatic hydrocarbons into aikyl substituted derivatives, which comprises dispersing in a stream of aromatic hydrocarbons a substantial proportion of saturated aliphatic hydrocarbons and submitting the mixture in a first step to a reaction temperature between about 400 and 800 C. in the absence of a catalyst while maintaining a pressure of at least 250 pounds per square inch formins alkyl substituted derivatives of aromatic hydrocarbons and polynuclear aromatic hydrocarbons. separating from the eiliuent 01' said step a fraction containing alkyl substituted aromatic hydrocarbons so produced, separating also therefrom unreacted aromatic hydrocarbons and introducing said hydrocarbons to the first said step, and separating also polynuclear aromatic hydrocarbons formed in said first step, subjecting said polynuclear aromatic hydrocarbons in admixture with a substantial proportion oi. hydrogen in a second step to a reaction temperature between 400 to 800 C. while maintaining a pressure of at least 250 pounds per square inch whereby simpler aromatic hydrocarbons are produced, and passing the effluent of said second step into the cycle of the first mentioned step.

11. A process for converting aromatic hydrocarbons into alkyl substituted derivatives, which comprises subjecting an aromatic hydrocarbon material with which has been dispersed a substantial proportion of aliphatic hydrocarbons and also a substantial proportion of hydrogen to a reaction temperature between 400 and 800 C. for a period between 0.5 and 15 minutes in the absence of a catalyst and under a pressure between 250 and 5000 lb./sq. in. to form alkyl substituted derivatives of said aromatic hydrocarbon material, and separating from the eflluent alkyl substituted derivatives so formed. 1

12. The process of claim 11 wherein the said aliphatic hydrocarbons comprise substantially a paramn hydrocarbon of not les than two and not mor than five carbon atoms per molecule.

13. The process of claim 11 wherein the said aliphatic hydrocarbons comprise an olefin hydrocarbon of not more than five carbon atoms per molecule.

14. A process for converting aromatic hydrocomprises subjecting in a first reaction zone an aromatic hydrocarbon material with which hasbeen dispersed a substantial proportion oi al phatic hydrocarbons to a reaction temperature of 400 to 800 C. in the absence of a catalyst while maintaining a pressure of at least 250 pounds per square inch to produce alkyl substituted derivatives, passing the efliuent of said first reaction zone to separating means, separating from the thermally treated hydrocarbons the alkyl substituted hydrocarbons so produced, separating also therefrom aromatic hydrocarbons corresponding to said aromatic hydrocarbon material and returning the same to said first reaction zone, and separating also polynuclear aromatic hydrocarbons formed in the aforesaid reaction, subjecting these last mentioned polynuclear aromatic hydrocarbons in admixture with a substantial propor-

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