US2350834A - Conversion of hydrocarbons - Google Patents

Description

June 5, 1944 E. E. sl-:Nsl-:L ET Al.

CONVERSION OF HYDROCARBONS Filed June 18, 1941 wumdw 2 Patented June A6, 1944 CONVERSION F HYDROARBONS Eugene E. sensei and Arthur a. Goldsby, Beacon, N. Y.. assixnors. by mesne assisnments. to The Texas tion of Delaware y Company, New York, N. Y., a corpora- Appueaaon :une 1s, 1941,- smal No. a9s,5ai v 4 claims. v(ci. 26osaam This invention relates to the conversion of hydrocarbons and has to do with the isomerization oi' hydrocarbons to form branched chain hydrocarbons and particularly has to do with the isomerization of saturated gasoline hydrocarbons.

'Ihe invention broadly contemplates treating a mixture of gasoline hydrocarbons, including aliphatic and alicyclic hydrocarbons, to remove alicyclic and other objectionable constituents which tend to' cause catalyst deterioration during isomerization, and thereafter subjectingthe gasoline hydrocarbons to isomerization in the substantial absence of alicyclic and other objectionable constituents whereby the isomerization reaction is effected at relatively low temperature to obtain substantial conversion of the paramn constituents to isoparafllns.

Gasoline or naphtha usually comprises a mi-xl ture of saturated and unsaturated hydrocarbons. The saturated hydrocarbon constituents comprise paramns and saturated naphthene hydrocarbons, while the unsaturated constituents comprise oleflns including cyclo-olefins. In addition, aromatic hydrocarbons may be present, particularly if the hydrocarbon mixture is a cracked naphtha.

Aromatic and -unsaturated hydrocarbons readily react with an isomerization catalyst such as an active metallic halide catalyst to form complexes or sludge thereby causing substantial catalyst deterioration. Consequently, it has been found desirable'to remove aromatic and unsaturated hydrocarbons from thefeed to an isomerlzation reaction.

The present invention has to do with the removal of both saturated and unsaturated alicyclic hydrocarbons from the feed to the isomerization reaction and particularly where it is desired to carry out the reaction at relatively low temperatures. At relatively high temperatures the presence of saturated ialicyclic hydrocarbons, namely naphthene hydrocarbons, appears to impart a benecial action. Thus, as disclosed in copending application, Serial No. 398,530 lled June 18, 1941, for Conversion of hydrocarbons, where the isomerization reaction is carried out under temperatures, for example; in the range 160 F. and above, in order to obtain high yields of isoparamns it is desirable to effect the reaction in the presence of substantial amounts of naphthene hydrocarbons for the purpose of inhibiting cracking and side reactions which would'other- :vise occur at these relatively higher temperaures. t

However, the present invention has to do with the discovery that in the low temperature isomerization o1' gasoline or naphtha, it is advantageous to remove naphthene hydrocarbons from the feed and thus eii'ect the isomerization reaction in the substantial absence of such hydrocarbons as well as in the substantial absence of aromatic and oleiinic hydrocarbons. In other words, for a low temperature operation, it is advantageous to select a feed stock which is essentially free from naphthenes.

For, example, when isomerizing gasoline hvydrocarbons in the substantial absence of naphthene hydrocarbons so as to obtain about 30 to 40% conversion of normal parans to isoparaffins it has been found/that the reaction temperature can be maintained at least about 25 F. and in some cases as much as F.'or more, lower than the reaction temperature required where the feed contains naphthenes in substantial amount.

In practice the temperature of reaction may range from about 100 to 200 F., although the particular temperature employed will depend upon the nature of the catalyst. and the specic manner in which the reaction is carried out. It

will also depend upon the nature of the paramn feed to the reaction. 'I'hus when the feed con-- sists essentially of normal pentane vand the re` action is eli'ected with anhydrous aluminum chloride promoted with anhydrous hydrogen chloride but in the substantial absence. of extraneous agents such as isobutane, the temperature may be about 100 to 130 F. for example.

The following conversion yields aord a comparison of the results obtained in the low temperature isomerization of normal pentane .with aluminum chloride and hydrogen chloride; first in the absence of cyclohexane and, second, in the presence of cyclohexane, the naphthene being present in the latter case to the extent of about 25% by weight ofthe pentane feed to the reaction. The data were obtained in batch liquid phase experiments carried out at temperatures of 100, 130, and 200 F. witha reaction time in each case of 4 hours. In each experit powdered anhydrous aluminum chloride of 200 mesh was charged to a reaction vessel extent of by weight of the feed hydrocarbon, the reaction. being promoted by the addition of about 0.5 to 0.7% 'of hydrogen chloride by weight of theyfeed hydrocarbon.

temper-aimes up to 130 and somewhat above, the

conversion -of normal pentane to isopentane and other hydrocarbons is substantially greater in the absence of the naphthene hydrocarbon. In fact there is little orfno conversion in this temperature range in the presence of the naphthene. Moreover. in the lower portion ofthe reaction temperature rance. for example, in the range 100 to Labout 120 1".. the conversion product' obtained in the absence of the naphthene consists essentially of isoparaiiin. i. e., isopentane. However. at temperatures of 130 Il'. and above where thereactionia carrledoutinthe absence of the naphthene hydrocarbon. the content of isopentane in the reaction product is proportionately less. falling oi! rather markedly at temperatures in the neighborhood of 100 F. due to cracking and side reactions with. the formation of products other than isopentane.

\ As previously explained naphtha or other mixinra of gasoline hydrocarbons substantial amounts of naphthene hydrocarbons, In some instances, feed stocks may be selected from which an isomeriaation feed substantially free from naphthene constituents may be obtained by conventional methods of fractional disdistillation, extraction with solvents or by other methods.

l'br example, the hydrocarbon mixture containing naphthene constituents may be subjected to contact with a suitable dehydrogenation catalyst auch as chromium oxide or molybdenumoaideadvantageouslydisposedupon a.

mpporting material such as alumina. and the contact effected under suitable conditions of temmay becontinuously recycled through the reaction zone.

For example, the reaction may be carried out employing a space velocity of about 0.5 to 1.0 (volumesof liquid feed measured at 60 F. per volume of catalyst). 'The light gases produced in the reaction and rich in hydrogen may be recycled at the rate of about 2500 cubic feet of gas per barrel of hydrocarbon feed to the reaction where the feed is a virgin naphtha, and may be as high as 10,000 cubic feet where the feed is a cracked naphtha.

If desired the products `of reaction of the'hydroformlng reaction may be subjected to a hydroiining action in which the hydroformed products are passed to a separate reaction zone containing a hydroforming catalyst and maintained at a somewhat lower temperature so that the olefinic constituents are subjected to hydrogenation. V f

The catalytically converted naphtha resulting from the foregoing operationswill comprise paramn, aromatic and oleflnic constituents, the

naphthene constituents originally present in the a initial feed having been converted to aromatic and other constituents as a result of the reaction.

After fractionation to remove normally gaseous constituents and also heavier hydrocarbons boiling above the motor fuel range the converted gasoline is subjected to a conventional extraction with a solventsuch as liquid sulfur dioxide,

usually contain Vsventureaailpressuresoastoob'tainthe@Stilisti ,75

dichloroethyl ether, furfural, nitrobenzene, etc., to effect a separation into extract and raillnate phases. The raillnate phase comprises paraffin hydrocarbons substantially free from naphthene, aromatic and unsaturated hydrocarbons while the extract phase comprises aromatic and unsaturated hydrocarbons. 'Ihe extract phase after removal of the solvent will thus comprise gasoline hydrocarbons having a relatively high octane number, for example, about 80 to 100 and therefore, suitable as a blending stock for motor fuel. y

The rainate after removal of the solvent is then subjected to contact ,with an isomerization catalyst at a relatively low temperature in order to convert the paraffin constituents to isoparaiiln hydrocarbons, thereby producing a mixture of gasoline 'hydrocarbons of high antiknock value.

The foregoing fractionation and solvent extraction operations may be modified to make provision for segregating from the converted naphtha a toluene fraction or concentrate where it is desired to segregate the toluene for some particularpurpose. l

If desired, the raillnate, prior to isomerization, may be subjected to a further chemical treatment in order to remove any remaining small quantities of aromatic and olefin constituents. Por example, the raiilnate, after removal of the solvent. may be subjected to treatment with sulfuric acid followed by neutralization with caus- .The isomerization reaction may also be cartic or other suitable alkaline material.

The accompanying `drailvingcomprises a flow diagram illustratingmne method of Vcarrying-out the reaction.l Thus, referring to the drawing, a

The resulting reaction mixture is conducted through a pipe I to a fractionator l wherein fixed or normally gaseous constituents are removed as a gaseous fraction from the topof the fractionator whilel hydrocarbons boiling above the motor fuel rangeare removed as a residual fraction from' the bottom of the fractionator.

As previously mentioned, in the case of a hydroforming reaction the gaseous fraction or any portion thereof rich in hydrogen removed from the top of the i'ractionator l may be recycled to the reactor 2.

A side stream comprising hydrocarbons of motor fiel boiling range is drawn off from the 4fractionator through a pipe 5. This side stream will comprise parailin hydrocarbons together with unsaturated hydrocarbons and aromatic hydrocarbons including aromatic compounds formed as a result of the conversion of naphthenes in the reactor 2. This stream is conducted to an extractor 8 wherein it is subjected to extraction with a selective solvent such as already mentioned.

I'he resulting railinate phase is drawn off through a pipe 'Iv to a stripper 8 wherein the solvent is stripped from the ralnate hydrocarbons, the solvent being recovered for reuse.

The solvent free raiiinateV through a pipe 9 to a chemical treating plant III wherein it is subjected to conventional acid and caustic 'treatments to remove any remaining traces of aromatic and unsaturated hydrocarbons.

is conducted The treated raffinate thereafter is lconducted through a pipe Il to a reactor I2. A5 indicated in the drawing the chemical treating stepmay be bypassed in which case the ramnate is conpipe I3 ydirectly toV the reactor chloride and in which case the reaction isl carried out at a temperature in the range about 100 to notin excess of about 130 F. Temperatures as low as 50 F. maybe used, and temperatures higher than 130 F. may be used provided the reaction is carried out under conditions such that cracking and side reactions. are avoided. The temperature will depend upon the feed hydrocarbon, that is, higher temperatures maybe permissible with some stocks even though naphthene hydrocarbons are absent. Other metallic halides may be employed as, for example, aluminum bromide.- Other hydrogen halides may be employed such as hydrogen bromide.

ried out in either the gas or liquid phase, employing the catalyst in the form j of' a massof solid particles or lumps, `or in the form o f a fiu'id mixture of vpowdered catalyst dissolved or suspended in a'iiquid medium such as metallic halide-hydrocarbon complex. 'I'he reaction may be carried out with finely divided solid catalyst suspended lin vaporized hydrocarbons undergoing conversion.

In any case the iscmerized hydrocarbon mixture is" conducted through a pipe I 4 to Ya fractionator Il. In the fractionating .step gaseous hydrocarbons tending toaccumulat'e v-in the reaction are removed through a pipe I6. These gases will comprise normally gaseous hydrocarbons such as normal butane and isobutane and some hydrogen as well as hydrogen chloride. If desired, a suitable proportion of the gaseous hydrocarbons such as isobutane or the hydrogen as well as the hydrogen chloride may be continuously recycled through the isomerization reactions zone for the purpose of facilitating the reaction and inhibiting the occurrence of cracking and side reactions.

High boiling hydrocarbons are drawn off from the bottom of the fractionator through a pipe I1, While a side stream including isomerized hydrocarbons boiling within the desired motor fuel Vboiling range is drawn oil' through a pipe I8. y

Referring again to the extractor 6, the extract phase isidrawn off through a pipe 20 and conducted to a stripper 2| wherein the solvent is recovered for reuse. 'I'he solvent free extract comprising aromatic and unsaturated hydrocarbons is drawn oil. through pipe 22 and may be subjected to further treatment for the purpose of stabilizing color andgum. forming constituents. The extract hydrocarbons, as already indicated, comprise valuable gasoline hydrocarbons of relatively high octane number and this material is advantageously conducted all or -in part through a pipe 2 3 to a tank 24 wherein itis blended in suitable proportion with the-isomerized hydrocarbon mixturedrawnofi' through pipe I8.

The arrangement of apparatus indicated in the drawing is merely diagrammatic and it is contemplated that in`actua1 practice rthe arrangement of apparatus as well as the method of flow may be varied. For example, the dehydrogenation or hydroforming reactions and also the isomerization reaction may be carried out in a batch or continuous: type of operation employing single or multistage reactors with provision for multiple injection of the feed and/or promoter to the re. action zone or zones. j The catalytic reactions may be carried out so as to permit either continuous concurrentor countercurrent flow of hydrocarbons undergoing treatment and a stream of catalyst in a reaction zone or zones. l

An `advantageous mode of carrying out the isomerization reaction involves the employment of a fluid type of operation wherein a substantial body of fluid containing ythe catalyst dissolved or suspended therein is maintained in al reaction zone with provision for continuous withdrawal of a stream of the reaction mixture and continuous recycling of the withdrawn stream to thefreaction zone. Suillcient of the liquidmixture is recycled to impart thorough agitationto the reaction mixture within the reaction zone. If desired the paraflln feed may be introduced to the reaction zone Ain the form `of a large number of separate streamssimultaneously to the mass of reaction 4 l assente Likewise the fractionating apparatus may be 5 modified so as to effect any desired degree or type of fractionation at dierent stages in the process.

l In the above described experiments a reaction of 4 hours is used. However, it is contemplated that a reaction time of 1 hour or less may be employed. For example, in continuous operations the reaction time may be about 5 to 15 minutes and as high as 2 hours or more.

Obviously many modifications and variations While specific examples of dehydrogenatlng of the invention, as hereinbeiore set forth, may and hydroiorming catalysts have been mentioned, be made without departing from the spirit and it is intended that other catalysts maybe em- A scope thereof, and therefore only such limitations ployed for this purpose. Additional examples oi .I dehydrogenating catalysts which may be employed are metals such as silver, copper, iron, nickel, cobalt, aluminum, or alloys thereof, or

sulildes or oxides of iron, nickel, cobalt, zinc, cadmium, aluminum, lead, bismuth, tin, vanadium etc. Particularly effective catalysts consist of, or contain oxides or sulfldes of the metals of tire 6th group of the periodic system, namely, chromium, molybdenum, tungsten, uranium, selenium,

tellurium and polonium. The catalysts may be used alone or in admixture with each other for deposited on solid carriers. Suitable carriers comprise silica, silicates, carbon, charcoal, etc".

Examples of hydroforming catalysts include,-

oxides of aluminum, boron, silicon, titanium, tin,

molybdenum, selenium, tellurium, etc., also activated earths and clays, etc.

Also, if desired, the feed mixture prior to introduction to the reactor 2 may be subjected to 30 lytic conversion carried out in the reactor 2 may 3 be utilized to effect removal of sulfur and other impurities to a substantial extent. The removal of such impurities-from the feed to the isomerization reaction is desirable from the standpoint of preventing catalyst deterioration. j

thereof may be subjected to further refining or processing as desired. For example, the isomerized hydrocarbons together with promoter.r removed from the fractionator I 5 may be passed 45 directly to an alkylation unit wherein theiisoparaiiin hydrocarbons are caused to react with olefin hydrocarbons by contact with a metallic halide catalyst maintained under alkylating conditions. For example, an isopentane fraction-of the isomerized hydrocarbons together with hydrogen chloride promoter may be passed to a suitable alkylation operation for reaction with an olefin such as triisobutylene in the presence of aluminum chloride catalyst to produce safety` neous gases including hydrogen tothe feed to the isomerization reaction.

The hydrogen from the dehydrogenation reaction may advantageously be used in the isomerization reaction to decrease' catalysi-consumption and enable higher conversions to bel obtained without substantial cracking.

should be imposed as are indicated in the appended claims.

We claim:

1. The method of isomerizing gasoline hydrocarbons present in mixtures of straight chain and cycloparamn hydrocarbons by the action of an isomerization catalyst selected from the group consisting of aluminum chloride and aluminum lbromide in the presence of hydrogen halide promoter at relatively low temperatures, which comprises removing from the feed mixture at least a substantial portion of the cycloparaiiin constituents present therein, and then subjecting residual straight chain parailin constituents to contact with the catalyst under isomerizing conditions in the substantial absence of said cycloparaflln constituents and at a temperature in the range F. to substantially below 160 F. such that the weight ratio of isoparafiin produced to normal paramn converted is not substantially less than .77 and such that conversion of normal paramn constituents to isoparamns is substantially greater than that obtained under substantially similar conditions of reaction in the presence of said removed cycloparailln hydrocarbons.

2. The method of isomerizing gasoline hydrocarbons present in mixtures of straight chain and cycloparamn hydrocarbons by the action of an isomerization catalyst selected from the group 40 consisting of aluminum chloride and aluminum The isomerized hydrocarbons or any portion bromide in the presence of hydrogen halide p romoter at relatively low temperatures, which comprises removing from the feed mixture at least a substantial portion of the cycloparaiin constituents present therein, and then subjecting residual straight chain paraflin constituents to contact with the catalyst under isomerizing conditions in the substantial absence of said cycloparaflln constituents and at a temperature in the range about 100 to 130 F. suchthat the conversion of normal parailin constituents to isoparaillns is substantially greater than that obtained under substantially similar conditions of reaction in the `presence of said removed cycloparailln hydrocarbons. l e

3. The method of isomerizing gasoline hydrocarbons present in mixtures of straight chain and cycloparailln hydrocarbons by the action of an isomerization catalyst selected from the group consisting of aluminum chloride and aluminum bromide in the presence of hydrogen halide promoter at relatively low temperatures, which comprises obtaining a saturated gasoline fraction comprising straight chain and cycloparaiilnshy- 5 drocarbons having from 5 to 7 carbon atoms per molecule, removing from said fraction substantially all of the cycloparamn constituents present therein, and then subjecting residual straight chain paraflln constituents to contact with the catalyst under isomerizing conditions in the substantial absence of said cycloparaiiin constituents and at a temperature in the` range about 100 to F. such that the conversion of normal parafiin constituents to isoparafllns is substantially greater than obtained under substantially similar conditions of reaction in the presence of said removed cycloparamn hydrocarbons.

4. The method of isomerizig gasoline hydrocarbons present in mixtures of straight chain and cycloparamn hydrocarbons by the action of an isomerization catalyst selected from the group consisting of aluminum chloride and aluminum bromide in the presence of hydrogen halide promoter at relatively low temperatures, which comprises removing trom the feed mixture at least a substantial portion oi' the cycloparamn constituents present therein. and then subjecting residual straight chain paramn constituents to contact with the catalyst under isomerizing conditions in the substantial absence of said cycloparailln constituents at a temperature in the range not substantially above 130 F. such that conversion oi normal parafiln constituents to isoparamns is substantially greater than that obtained under substantially similar conditions of reaction in the presence of said removed cyclo- 10 paramn hydrocarbons.

EGENE E. SENSEL. ARTHUR GOLDSBY.

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