US2400732A - Conversion of hydrocarbons - Google Patents

Description

May 21, 1946. G. B. ARNOLD CONVERSION OF HYDROCARBONS Filed Oct. 9, 1941 Patented May 21, 1946 CONVERSION F HYDROCARBON S George B. Arnold, Beacon, N. Y., assignor, by mesne assignments, to The Texas Company, New York, N. Y., a corporation of Delaware Application October 9, 1941, Serial No. 414,253

Claims.

This invention relates to the conversion of hydrocarbons and has to do with the isomerization of hydrocarbons to lform branchedchain hydrocarbons. It is applicable to the isomerization of naphtha hydrocarbons.

The invention contemplates the treatment of naphtha hydrocarbon mixtures containing aromatic and non-aromatic hydrocarbons to selectively remove aromatic hydrocarbon constituents ltherefrom and subject the hydrocarbons from which aromatic constituentshave been removed to isomerization for the production of gasoline hydrocarbons having high antlknock value and Aother desirable characteristics.4 Isomerized hydrocarbons thus produced may, if desired, be

blended all or in part with laromatic hydrocar-v `bons initially extracted from the naphtha hydrocarbon mixture.

In accordance with the invention a hydrocarbon mixture containing aromatic and non-arcmatic hydrocarbon constituents, including parafilns and naphthenes, is extracted with water or with a solvent consisting essentially of water under conditions such that 'aromatic hydrocarbons are removed. The remaining non-aromatic hydrocarbon mixture containing naphthenes is subjected to contact with a catalyst under conditions such that isomerization constitutes the principal reaction. s

The extractive treatment with Ywater or a solvent consisting essentially of Water is advantageously effected at a temperature in the range about 400 up to 600 F. or up to the critical tem- No. 382.327, filed March a, 1941, for separation ofaromatic hydrocarbons from hydrocarbon mixtures, water under the foregoing conditions exerts a preferential solvent action upon aromatic hydrocarbon constituents of naphtha so that aromatic constituents can be extracted from naphtha without eilecting substantiall removal of naphthenic and paraflnic constituents Moreover, under the foregoing conditions water exerts relatively low solvent action upon oleflnic constituents of naphtha so that the extractive treatment may be applied to naphtha containing l a metallic halide type of catalyst.

.perature of the lowest boiling constituent which it oleilns without effecting substantial removal of olenic hydrocarbons.

Accordingly, the invention has to do with the removal of aromatic hydrocarbon constituents from the'feed to an isomerizing reaction without effecting substantial removal of other hydrocarbon constituents desirable as components of the feed to the isomerizing reaction. It contemplates extraction of aromatics from straight-run naphtha following which the non-aromatic fraction or a portion thereof is isomerized by contact with It also contemplates extraction of aromatics from cracked naphtha following which the non-aromatic fraction or a portion thereof is subjected to contact with a suitable conversion catalyst to effect isomerization of oleflnic constituents.

Thus, in the lsomerization of straight run naphtha or fractions thereof by contact with a metallic halide type of isomerization catalyst, the naphtha hydrocarbons are subjected to extraction with water or a solvent consisting essentially of water to remove aromatic constituents without effecting substantial removal of naphthenic constituents, the presence of which is desirable during the isomerization reaction of paraiiin hydrocarbons with a metallic halide catalyst. It has been found that the presence of naphthenic hydrocarbons in the reaction zone substantially inhibits cracking of the hydrocarbons undergoing treatment and also substantially inhibits deterioration of the catalyst.

Aromatic hydrocarbons when present in the feed to an isomerization reaction employing a metallic halide catalyst such as aluminum'chloride and hydrogen chloride appear to inhibit the isomerization reaction. Aromatics also react Very readily with lthe metallic halide to form objectionable complex compounds with consequent deterioration of the catalyst.

Therefore, an important advantage of the invention resides in eiectlng removal of the aromatic constituents without effecting substantial removal of naphthenic constituents which are desirable in the feed to an isomerization process employing a metallic halide catalyst.

Olenic hydrocarbons are also usually undesirable in an isomerization reaction employing a me- Percent aluminum chloride catalyst in the absence,

'l space velocity through the catalyst so thatisomerization of olens action. Accordingly,

constitutes the principal rein this type of reaction oleiinic constituents are essential components of the feed.

Thus, a further advantage of the invention` resides in subjecting cracked naphtha .to4 ex- -tractive treatment with water or a solvent consisting essentially of water so as to remove aro matic constituents and leave a naphtha mixture comprising olefins, parailns and naphthenes which is particularly suitable as a v'feed to the isoforming reaction. f

The data appearing below afford a comparison ofresults obtainable when isomerizing a naphtha hydrocarbon such as normal pentane by contact with an active aluminum chloride catalyst in the absence of, and in the presence of, an aromatic Vhydrocarbon such'as benzene or toluene. The data were obtained in batch liquid phase experiments carried out at a temperature of either 160 F. or 200 F. as indicated, with a reaction time of four hours. In each case powdered anhydrous aluminum chloride of .about 200 mesh was charged to the reaction vessel to the extent of about 10% by weight of the total hydrocarbon feed, the reaction being promoted by the addition of a small amount of hydrogen chloride.

drous aluminum chloride ot about '.200 mesh was charged to the reaction vessel to the extent ot 10% by weight 'of the normal pentane. charge. the reaction being promoted by the addition o! a small amount of lhydrogen chloride.

Run

F G H Per cent hydrogen chloride, by weight of total feed hydrocarbon..-. 0. 5 0. 6 0. 7 Per cent cyclohexane, by weight o! npentane l0 Composition of hydrocarbon reaction mixture by fractional distillation, per cent by weight:

Hydrocarbons of lower molecule weight than isobutane 0. 5 Isobutane.-- 51.2 1.7 1. Normal butano L 5 0. Isopontane 22. 7 05. 6 55. n-Pentane 6. l v 2 8. 7 27. Hydrocarbons of higher molecular weight than normal pentane '15.0 4. 0 14. Fontane converted to isopentane and other materials, weight per cent 94. 2 75. 0 69. 0 Weight ratio of isopentane to n-pentane converted Z3 92 77 ,Appearance of used catalyst (l) (2) l Brown liquid complex. 2 Light brown gummy solid. l Light brown sticky solid.

As indicated, substantially better conversion yields to isopentane are realized by carrying out vthe reaction in the presence of the naphthene hydrocarbon. The results also reveal that cracking is substantially eliminated by eiecting the reaction in the presence of the naphthene hydrocarbon. This is borne out by the fact that in runs G and H the yields of hydrocarbons of lowerv molecular weight than pentane are relatively small, namely, 1.7 and 2.1 respectively.

Thus the foregoing experimental data demon- -strate that while aromatic hydrocarbons are `un Run Temperature F Aromatic added aromatic by weight of n-pentana Per cent hydrogen chloride by weight of n-pentane Composition of hydrocar on reaction mixture by fractional distillation, per ce t by weight:

Hydrocarbons of lower molecular weight than isobutane- Isobutane. n-Butane l'ennnnfsmn n-Pentene. Hexanes and higher Appearance of used catalyst 17.6.l Red liquid complex.

200. Toluene. i0.

Wet gummy. solid.-

1.0 Greenish brown dry 'hick redf black liquid.

lumpy solid.

As indicated by the `foregoing data, where the aromatic hydrocarbon was present the conversion reactionY was practically stopped, as indicated by the fact that the hydrocarbon reaction mixture at the termination of the experiment still consisted almost entirely of normal pentane.

On the other hand the advantage of retain- Adesirable in the feed to the ,isomerization reaction Y stituents from the vfeed sirable naphthene constituents to remain therein.`

hydronaphthene hydrocarbons on' the other hand are desirable. For this reason of water las contemplated by the present invention is advantageous since it permits extractingthe undesired aromatic conwhile permitting the de Reference will now be made to the accompanying vdrawing comprising a diagram of ow for i 1 an operation involving isomerization of naphtha hydrocarbons by. contact with an active metallic halide catalyst.

As indicated in the drawing straight run naphtha from a source not shown is conducted through a pipe l to a heater 2 wherein itis heated lto a temperature in the range 400 to 600 F. and then the pretreatment of the feed hydrocarbons with water or a solvent' consisting -essentially .tion of extract and raffinate phases occurs.

The extraction tower 3 is advantageously pro-` vided With a suitable inert packing material such as Raschig rings.

The naphtha flows upwardly through the extraction tower and countercurrently to a body oi' water maintained at the aforesaid temperature. Water is continuously introduced to the upper portion of the tower through a pipe 4 and to which reference will be made later.

As a result of the 4contact between water and naphtha within the extraction towerv 3 forma- The extract phase accumulates in the bottom of the tower and comprises a large proportion of water containing aromatic constituents of the naphtha dissolved therein. l

'I'his extract phase is continuously drawn off through a pipe 5 and passed through a cooling depending to some extent upon the boiiin'range of the hydrocarbons undergoing conversion and also upon the form in which the catalyst is employed.

Thus, in a vapor phase type of operation the vapors may be passed through a reaction zone packed with the catalyst in solid fragmentary form. For example, the catalyst may comprise a comprising for example. aluminum chloride-MFl Sdrocarbon complex. Such anoperation may be coil or heat exchanger B wherein it is cooled to about room temperature or to a temperature in the .range about 70 to 250 F., for example.

The cooled mixture is then conducted toa separating vessel I wherein separation between aro matic hydrocarbons and water occurs. The separated laromatic hydrocarbons are continuously drawn off from the top or" the separator l through a pipe 8 While the water substantially free from aromatic hydrocarbons is continuously drawn off from the bottom of the vessel 'I through a pipe 9. v L

The withdrawn water is advantageously con ducted through a pipe I0 and forced by a pump II through a heater or heat exchanger I2 communicating with the previously mentioned pipe 4.

The apparatus may be arrangedso as Ato permit recycling of the water bythermo-siphon action.

The rafilhate phase accumulating in the top of the extraction tower 3 comprises a relatively small amount of water mixed with the insoluble portion of the naphtha consistingessentially of parainie and naphthenic hydrocarbons. This ranate phase is continuously drawn oi through a pipe I3 and conducted through a cooler or heat exchange I4 wherein the temperature is reduced to about room temperature or in the range about 70 to 250 F.

The cooled mixture is passed to a separating vessel I5 wherein separation between raiilnate hydrocarbons and water occurs. The separated water is continuously drawn off from the bottom of the vessel I5 and all or in Dart returned through the heater I2 and the pipe 4 to the upper portion of the extractiontower 3.

The separated raiiinate hydrocarbons are drawn off from the top of the vessel I5 through a pipe I6 and conducted tofa vessel I 'I'wherein they are subjected to further settling at the same or a lower temperature to permit settling of the remaining water. If desired the raffinate hydrocarbons may be subjected to any, suitable treatment at this point such as drying to effect complete or substantially complete removal of water.l

- temperature of reaction may bein the range of about 160 to 300 F. or higher. The reaction `may be effected in either vapor or liquid phase carried outin a` continuous manner in a reaction zone'having provision for maintaining a substantial body of reaction mixture therein with pro vision for continuous withdrawal of a stream of l the reaction mixture and continuous recycling of at least a substantial portion of the withdrawn stream to the reaction zone so as to impart thorough agitation to the reaction mixture within the reaction zone. Such an operation permits maintaining a relatively high ratio of naphthene f hydrocarbon to entering feed hydrocarbon. This ratio at the point of introduction of the freshvfeed to the reaction zone advantageously ranges from 1 to as high as 1000 or more by volume.

That portion of the reaction mixture continuously discharged from the isomerization unit I5 is conducted through a pipe 20 to a fractionation y unit 2I wherein it is subjected to fractionation.

This fractionation may include separation of normally gaseous material including hydrogen halide promoter used in the isomerization reaction, segregation of iso'merized hydrocarbons into one or more gasoline fractions of desired boiling range,

and l,separation of heavier material as, for example, hydrocarbons boiling above the range of the desired gasoline fractin or fractions.

Provision may be made for fractionating from the reaction mixture a fraction rich in naphthenic hydrocarbons, which fraction is desired for recycling to the isomerization unit for the purpose of maintaining the desired high ratio of naphthenes to paramns entering the isomerization unit. This high boiling naphthenic fraction may comprise, for example, a fraction drawn off from the bottom of the fractlonator through a pipe 22 Hydrogen chloride fractionated out of the reaction mixture may be recycled through. a pipe 25 to the isomerization unit I9. Any hydrogen formed in the isomerization reaction can likewise be fractionated out of the reaction mixture and may also be recycled all or in part to the isomerization reaction through the pipe 25.

If it is desired to carry out the isomerization reaction in the presence of extraneous low boiling gaseous hydrocarbons such as ethane, propane/f butane or isobutane, provision can be rnade for segregating a fraction comprising these gaseous materials from the reaction mixture. For example, such fraction may be drawn off from the fractionation unit through a pipe 26 and'recycled all or in part through branched pipe 21 leading to the isomerization unit I9.

The isomerized hydrocarbons or any desired fraction thereof drawn off from the fractionation unit through a pipe 28 may be passed all or in part through a branched pipe 29 to a tank 30 and um chloride, antimony chloride, mixed metal halides such as AlClzF, AlFzCl, etc., or mixtures of halides such as AlCla-SbCla. Metallic halide may fbe used in fragmentary form or supported upon, solid materials such as Porocel, alumina, charcoal, etc. Y

Suitable promoters may comprise besides hydrogen chloride, other hydrogen halides, carbon tetrachloride, alkyl chlorides, etc.

As already indicated, in addition to the advantage of effecting the isomerization reaction in the presence of naphthene hydrocarbons for the purthe solvent oi' the solution to a temperature in the range about v 70 t0 250 F;

pose of preventing cracking of the'parans uny dergoing treatment and deterioration of the catalyst during the conversion, other extraneous materials may be employed invaddition for still furtherA inhibiting cracking and cat'alystdeterioration. 'I 'hese other materials may comprise normally gaseous materials such as-hydrogen, hy-4 drogen-containing gases and normally gaseous hydrocarbons or mixtures thereof,

As already mentioned the solvent employed in the extraction step may consist entirely of water or essentially of water. Thus, it is contemplated that water may contain a suitable auxiliary substance for the purpose of increasing the solubility of aromatic hydrocarbons in the solvent mixture without substantially reducing the'selectivity of the mixture as between aromatic and non-'aromatic constituents of the hydrocarbon mixture undergoing extraction. Suitable auxiliary substances comprise hydroxy and polyhydroxy organic compounds which are substantially com- Y pletely soluble in water at least at temperatures of the order of 70 to 600 F. Dihydroxy saturated and unsaturated alcohols s uch as ethylene and polyethylene glycols have been found eiective for this purpose. The di, tri and hexa ethylene glycols may also be used as well as the halogenated derivatives of the dihydroxy alcohols such as tri.

methylenechlorohydrine, glycerol b-dichlorohy- Adrine and a-chloroglycerol.

Other organic compoun ds whichmay be used Thus, the proportion of above-mentioned hydroxy material contained in the water may range from a fraction of a per cent to or more'by weight of the solvent mixture and preferably will range fromabout 5 to 25% b`y weight.A

Instead of using an extraction tower as illustrated in the drawing, the extraction may beeffected in other types of apparatus including mixers and settlers arranged in stages.

The invention may be applied to the treatment of naphtha or to any desired fraction or fractions thereof. For example, straight run naphtha may be fractionatedinto light and heavy fractions; the light fraction may comprise hydrocarbons boiling up to about 200 F. and substantially free from aromatic hydrocarbons, while the heavier fraction will comprise hydrocarbons boiling above 200"l F. and which will contain substantially all of the aromatic constituents present inthe straight run naphtha. The heavy fraction may thus be subjected to the' extractive treatment to remove aromatic constituents and thereafter isomerized. The light fraction may be separately isomerized or subjected to isomerization along with the aromatic free heavier fraction.`

A substantially similar pretreatment may be applied in the case of cracked naphthas which are to be subjected to the isoforming reaction already referred to above.

Also with respect to the isoforming of cracked naphtha it is contemplated that the vsolvent exl traction step may be controlled so as to remove 'y n all of the aromatics from the feed to the isomeri- V zation reaction nevertheless it may be suilicient in some instances merely to substantially reduce the aromatic content. For example,'where the include polyoleiin glycols, polyvinyl alcohols,

- polyhydroxyl alcohols such as glycerine, mannitol and sorbitol. Phenolic compounds such as reso'rcinol, phloroglucinol and 4pyrogallol may be used. Still other compounds includev the hydroxy vacids such as salicylic' and lactic acids, and the aliphatic alcohols including amino'andvnitro derivatives thereof, such as mono, di, and tri ethanol amines and 2nitro ethanol.

' The proportion of added substance which may be employed is such that the mixture of water isomerization reaction is to be carried out under relatively high temperatures, for example, teml peratures substantially. above 200 F., the retention of a small amount of aromatic material in the feed may be tolerated.

Obviously, many modifications and variations. may be made in the invention as herein set forth'. without departing from the spirit and scope thereof, and therefore onlyl such` limitations should be'imposed as are indicated inthe apand secondary solvent will exert substantial sol- -vent action upon aromatic hydrocarbons at temperatures o 200 F. and above bt will exert substantially little solvent action-upon aromatic hydrocarbons at ordinary temperatures, for example, from about room temperature to about 250 F. In other words, the proportion of secondary solvent and water in the solvent mixture is such that when the solution of desired aromatic hydrocarbons in the solvent is separated from the extraction zone the desired aromatic hydrocarbons can be substantially entirely separated from pended claims.

I claim:

1. In .the manufacture of gasoline from a naphtha hydrocarbon mixture containing aromatic and non-aromatic hydrocarbons including naphthenes and paraflins, the method which comprises subjecting the naphtha hydrocarbon mixture to treatment with a solvent consisting essentially of water at a temperature in the range above 500 F. and below the critical temperature of the lowest boiling constituent to be extracted from the naphtha mixture and under a pressure sufcient to maintain the solventf substantially in the liquid phase, such that the solvent has substantially no solvent action upon naphthenic constituents, forming an extract phase rich in aromerely by reducingl the texnperature/l matic hydrocarbons Vland a raffinate phase comprisingv non-aromatic hydrocarbons including said naphthenic constituents, separating said phases, removing solvent from the ratlinate phase hydrocarbons, subjecting the solvent-free raiiinate phase hydrocarbon mixture to contact with a metallic halide isomerization catalyst main,- tained -under isomerizing conditions at a temperature in the range about 160 to 300 F. such that isomerization constitutes the principal reaction, eiecting isomerization of paraiiin constituents of naphthenic and parafnic hydrocarbons, thel -method which comprises subjecting the naphtha mixture to treatment with a solvent consisting essentially of water at a temperature in the range about 500 to 600 F. and under a pressure sutilcient to maintain the solvent substantially in the liquid phase such that. the solvent has substantially no solvent action upon naphthenic constituents of the mixture, forming an extract phase rich in aromatic hydrocarbons and a railinate phase comprising naphthenic and parainic hydrocarbons, separating said phases, removing solvent from the rafnate phase mixture, subjecting the solvent free rainate mixture to contact with a metallic halide isomerization catalyst in a reaction zone at an elevated temperature in the range about 160 F. up to about 300 F. such that isomerization constitutes the principal reaction, effecting isomerization of parailin constituents of the mixture in the presence of said naphthene constituents, removing hydrocarbon prod'- ucts of reaction from the reaction zone, separat,-

ing from the removed products isomerized hydro-1 carbons, also separating from said removed products a fraction rich in naphthene hydrocarbons and recycling at least a portion of said naphthene rich fractions to the isomerization'reaction zone.

4. In the manufacture of gasoline from a naphtha hydrocarbon mixture containing aromatic and non-aromatic hydrocarbons including naphthenes and parafiins, the method which comprises the rainate mixture in the presence of said subjectingthe naphtha yhydrocarbon mixture to treatment with a solvent consisting essentially of water at a temperature in the range of about 500 to 600 F. and under a pressure suflicient to maintain the solvent substantially in the liquid phase such that the solvent 4exerts relatively low solvent action upon naphthene constituents and relatively high solvent action upon aromatic constituents, forming an ex tract phase rich in aromatic hydrocarbons and a ramnate phase comprising parafn hydrocarbons and naphthene hydrocarbons, subjecting the solvent free raiiinate phase hydrocarbon mixture to contact with aluminum halide isomerization catalyst in the presence of hydrogen halide in a reaction zone at a temperature in the range about 160 to 300 F. such that isomerizationv constitutes the principal reaction, effecting isomerization of parailin constituents of the railinate mixture in the presence of said naphthene constituents and removingv isomerized hydrocarbons from the re-y sulting products of reaction.

v 5. In the manufacture of gasoline from a naphtha hydrocarbon mixture containing aromatic and non-aromatic hydrocarbons including -naphthenes and parans, the method which comprises subjecting the naphtha hydrocarbon mixture to treatment with a solvent consisting essentially of water at a temperature in the range of about 500 to 600 F. and under a pressure sufficient to maintain the solvent substantially in the liquid phase such that the'solvent exerts relatively low solvent action upon naphthene constituents and relatively high solvent action upon aromatic constituents, forming an extract phase rich in aromatic hydrocarbons and a raffinate phase comprising parailin hydrocarbons and naphthene hydrocarbons, subjecting thesolvent `free rafdnate phase hydrocarbon mixture to contact with alutemperature in the range about l160 to 300 F. such that isomerization constitutes the principal reaction, effectingisomerization of paraffin constitufents of the ramnate mixture in the presence of said naphthene constituents, removing products of 'reaction from said zone, separating from the removed products a gaseous fraction comprising hydrogen halide and a fraction comprising isomerized hydrocarbons, and recycling said gaseous friction at least in part to said reaction zone.

GEORGE B. marroni). y

Images