US2342922A - Conversion of hydrocarbons - Google Patents

Description

4F125 29, 194.4 f J. D. DANFoRTH 2,342,922 I Y v CONVERSION OF HY-DROCARBONS Filed Feb. 27, 1942 m N EN? rs f RECEIVE/Q.

S TUP T013/ Patented Feb. 29,` 1944 Joseph D.

Universal Danforth, Chicago, Ill., assigner toV Oil Products Company, Chicago, Ill.,

a corporation ofDelaware Application February 27, 194,2, Serial No. 432,613

Claims.

This is a continuation-in-part of my co-pending application Serial No. 373,961, led January 10, 1941.

This invention relates to a process for thel somerization of essentially saturated hydrocarbons including parafllns and cycloparaiiins andl \is more speciiically concerned with processes in- `volving the use of metal halide-hydrogen halide catalysts. l

The invention is still more specifically directed to a process ilow which permits continuous oper- A ation over relatively long periods of time.

v ing range hydrocarbons of high antiknock value are readily producible by these methods. Also, when isobutane is dehydrogenated to lsobutene they-latter compound may beA catalyti'cally polymcrized and then hydrogenated to produce isooc ianes of unusually high antiknock rating which v are used as blending agents' in aviation fuels.

inthe case of normally liquid saturated hydrocarbons such as, for example, normal or mildly branched paraiiins which occur in straight run -gaso1ines, it is advantageous to isomerize these compounds 1n order to increase the ant'lknock value of the gasoline. Many methods have been tried for accomplishing this object. In the case of normal butane isomerlzation may be eiiected with metal halide-hydrogen halide catalysts without too great difllculty since normal butane has the least tendency of the normal paraiilns to undergo undesirable decomposition reactions at temperatures at which isomerization proceeds at a practical rate. In the case of normal pentane and other normally liquid parailin hydrocarbons, vhowever, decomposition reactions tends to occur so that the yields or desired isomers are reduced and catalysts are contaminated and lose their catalytic effectiveness due to accumulations of metal halide-hydrocarbon complexes which coat the active surfaces of the primary catalyst. In the present process advantage is taken of the fact that normal butane does not undergo extensive decomposition reactions during isomerization in order to more eiiectlvely isomerize higher boil- (Ci. Mil-683.5)

ing hydrocarbons and hydrocarbon fractions which have decomposition tendencies.

In one specific embodiment the present invention comprises a process for the isomerization of essentially saturated hydrocarbons by passing normal butane through a bed of granular aluminum chloride to dissolve a portion of the aluminum chloride, introducing the solution of aluminum chloride in normal butane along with higher boiling hydrocarbons and added hydrogen chloride into a reaction zone containing granular packing material. i'ractionating the products from the reaction zone to produce a light gas mixture comprising hydrogen chloride, isobutane, normal butane, and heavier hydrocarbons and recycling ther gas mixture containing hydrogen chloride back to the packed reaction zone and the normal butane back to further contact with the aluminum chloride.

The essential features of the present process will be brought out in a description of the operation given in connection with the attached diagrammatic drawing which shows by the use of conventional gures in side elevation an arrangement of apparatus in which the process may be conducted.

yReferring to the drawing normal butane is introduced to the plant arrangement by way of line I containing valve 2 to a pump or compresser 3 which discharges through line 4 containing valve 5 through a. heating element 0 arranged to receive heat from a furnace 1. It is preferable that the normal butane pass through the granular aluminum chloride in liquid phase and that ordinarily it should be at an elevated.

temperature since its solvent capacity for the aluminum chloride increases with temperature. Thus, it has been found to be good operating practice to pass the liquid butane through the granular aluminum chloride at temperatures of from about to about 200 F. under pressures of the order of 250 pounds per square inch, or higher temperatures at higher pressures as high as 500 pounds per square inch, the butane from the heating element in the drawing passing through line 8 containing valve 9 under these approximate conditions and then owing upwardly through a bed oi aluminum chloride I0' contained in a saturator I0.

'I he solution of aluminum chloride and normal butane passes through line ll containing valve l2 through a reactor I5 which contains granular packing material I5.- This material may be of varying character and may include materials of a relatively non-absorbent or dense character such as crushed silica, crushed firebrick, Porocel particles, etc. or may beof a more absorbent character such as clays either raw or acid treated, prepared aluminas. activated carbon and other similar materials. Hydrogen chloride sunlcient to make up for incidental losses is introduced through line I3 containing valve I4 and heavier essentially saturated hydrocarbon fractions such as, for example, a normal pentane fraction. a normal hexane fraction or a mixture of parailln and naphthene hydrocarbons constituting the lower boiling fractions of a straight run gasoline or naphtha is also introduced into line II. This heavier material is charged to pump I5 by way 0f line I5 containing valve I1 and discharged through line I9 containing valve 20 through a heating element 2I arranged to re ceive heat from a furnace setting 22, the heated material passing through line 23 containing valve 24 and then into reactor I5. The temperature to which the incoming heavier hydrocarbon charge is heated will depend upon its boiling range and chemical composition and in some instances it may not be introduced at a very high temperature. However, temperatures of from about 100 to about 400 F. may be employed at this point. Heavier fractions will usually require lower temperatures and lighter fractions may be subjected to higher temperatures without undue decomposition. If desired hydrogen may be introduced to the reactor I5 by way of line I3' containing valve I4' to diminish side reactions.

In reactor I5 alumium chloride carried in solution in the normal butane is deposited upon the surfaces of the granular packing material and thence serves to continually introduce fresh catalyst which is distributed on the granules so as to expose a large amount of surface and thus catalyze isomerization reactions most effectively. As the catalyst surfaces become coated with deposits of aluminum chloride-hydrocarbon complexes, they are conveniently renewed by thel aluminum chloride introduced by the normal butane so that the continuity of the process is only limited'by complete saturation of the particles at which time the reactor will require dismantling and cleaning. Although only one reactor is shown in the drawing it is comprised within the scope of the invention to employ reactors in parallel so that the charge may be diverted through a fresh reactor while the spent reactor is being cleaned and refilled.

During passage through reactor I5 both the normal butane and the heavier materials will undergo isomerization reactions to a varying extent. The temperature to be employed, the amount of hydrogen chloride and the rate of passage of the granular material will vary with diner-ent proportions of normal butane and heavier hydrocarbons so that no narrow limits can be xed for the conditions in the reactor. However, as previously stated the temperature will seldom exceed 400 F. and there is apparently little advantage to be gained by using more than 20 mole per cent of hydrogen chloride based on the average molecular weight of the hydrocarbon charge. The space velocity will again be dependent on such factors as temperatures, amount of hydrogen chloride used, the quality of the charge and the type of filling material.

The total products from reactor I5 are indicated in the drawing as passing through line 25 containing valve 26 to a primary fractionator 21 which may be employed for separating the products to obtain hydrogen chloride and normal butane for recycling, and isobutane and heavier isomerized hydrocarbons for recovery as products of the process. Any system of fractionation may be employed even though it may vary considerably from the one outlined in the drawing. As shown in the drawing the hydrocarbon fractions heavier than normal butane are recovered from fractionator 21 through a bottom line 28 containing valve 29. These bottoms may be further fractionated if desired to recover light blending material and reject heavier fractions if desired. The overhead from fractionator 21 consists of hydrogen chloride, hydrogen (if hydrogen has been introduced to the plant), light hydrocarbons in varying amounts consisting of methane, ethane and propane and both isobutane and normal butane and'pass through line SII containing valve 3| to condenser 52. During passage through condenser 32 conditions of temperature and pressure are employed so that the mixture of iso and normal butane is condensed and passes in liquid phase through line 35 containing valve 34 into receiver 35. As indicated in the drawing. the lighter gases and hydrogen chloride may be withdrawn from this receiver through either line 4I containing valve 42 or line 36 containing valve 31. However, this simple separation may be modied by the use of high pressure fractionation to effect a sharper separation although means for accomplishing this end are not shown in the drawing. A portion oi' the gases withdrawn from line 4I containing valve 42 may be further separated into hydrogen chloride, hydrogen and hydrocarbons. However, as indicated a portion or all of the gaseous phase in receiver 35 may pass through line 35 containing valve 31 to a recirculating pump or compressor 35 which discharges through line`39 containing valve 40 baci:l to line 23 leading to isomerizing reactor I5.

The mixture of butanes in receiver 35 is withdrawn by pump 45 through line 43 containing valve 44 and discharged by way of line 45 containing valve 41 through a heater 4I wherein the mixture of butanes is brought to a temperature suitable for effecting separation of isobutane and normal butane. The heated material passes through line 45 containing valve 50 to a i fractfonator 5I. This fractionator may be operated with an inlet temperature of about 150` F. under a pressure of the order of to 110 pounds per square inch. and a top temperature of F. and a bottom temperature of 150 F. Isobutane passes then through line 52 containing valve 53, along with any hydrogen chloride or light gases which may have been dissolved in the butane mixture in receiver 35.

Normal butane passes through line 54 containing valve 55 to a recycling pump 55 which discharges through line 51 containing valve 58 back to line 4 for use rst as a carrying material for aluminum chloride and then for partial isomerization in reactor I5 as already described.

The following data are introduced/to indicate the type of results obtainable when operating in accordance with the process of the present invention although it is not intended that the proper scope of the invention should be limited in exact accordance therewith.

Runs were made in apparatus similar to that described in connection with the drawing in which normal butane was used asa catalyst carrier and a commercial hexane was used as heavier isomerization charging stock.

ExAMPLs I In the iirst continuous run the saturator containing granular aluminum chloride Was maintained at a temperature of 240 F., the packed reactor was maintained at a temperature of'212 F. and a pressure of 500 pounds per square inch was maintained on both saturator and reactor. The mixture of equal parts by volume of butanes and hexane was charged to the reactor at such a rate that 0.23 volumes oi' the total charge per volume of reactor space was introducedper hour. Hydrogen chloride was introduced at the rate of 1l to 12 moles per 100 moles of total hydrocarbon charge. The following table `shows the signilicant data obtained during the course of the run:

Table 1 (gotcha Ngol Hours on yd' "w n Period No. fraction con- *mem taining no butanes Exmru II In a second test 2 parts of commercial hexane to one part of normal butane by volume was used. giving the data shown in Table 2:

Table 2 In the above runs no' dlmeultles were encountered ln connection with the formation oi aluminum chloride complexes in the saturator whereas it was found impossible to run for any length ot time ifthe total charge was introduced into the saturator even in the absence of hydrogen chloride on account of the formation of vis' cous complexes which coated the granular aluminum chloride and soon reduced its activity to a low value.

As used in the above specification, the term saturated hydrocarbon is intended to include paraillnic and cycloparaiiinic hydrocarbons.

I claim as my invention: v

1'. lAn isomerization process which comprises contacting normal butane, in liquid phase,with

,aluminum chloride under conditions such as to dissolve aluminum chloride in the liquid butane, commingling normally liquid saturated hydrocarbons with the butane-aluminum chloride solution, passing the resultant mixture through a. reaction zone containing a solid packing material and depositing aluminum chloride from the solution onto said packing material, and subjecting the hydrocarbons to isomerizing conditions during their passage through the reaction zone.

2. The process as deiined in claim 1 further characterized in that said normally liquid hydrocarbons comprise normal paralns.

3. The process as defined in claim 1 further characterized in that said normally liquid hydrocarbons comprise a parainic gasoline fraction.

4. An isomerization` process which comprises passing liqueiied normal butane through a body of aluminum chloride runder conditions such as to dissolve a portion of said body inthe butan commlngling normally liquid isomerizable paralllns and hydrogen chloride with the' solution of aluminum chloride in butane, passing the resultant mixture through a reaction zone containing a solid packing material and depositing aluminum chloride from the solution onto said packing material, maintaining the reaction zone under paraflin isomerizing conditions and therein isomerizing substantial portions of the normal butane and the normally liquid parailins...

5. An isomerization process lwhich comprises passing liquefied normal butane through a body of aluminum chloride under conditions such as to dissolve a portion vof said body in the butane, commingling normally liquid isomerizable paraiilns and hydrogen chloride with the solution of aluminum chloride in butane, passing the resultant mixture through a reaction zone containing a solid packing vmaterial and depositing aluminum chloride from the solution onto said packing material, maintaining the reaction zone under par- 'afiln lsomerizing conditions and therein isomeriz-y ing substantial portions of the normal butane and the normally liquid parafiins, fractionating the resultant products to separate therefrom a hy' drogen chloride-containing gas and a liquid normal butane traction, returning the latter to further contact with said body of aluminum chloride, and recycling at least a portion of the hydrogen chloride-containing gas to the reaction zone.

JOSEPH D. DANFORTH.

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