US2374933A

US2374933A - Method of forming chemical mixtures

Info

Publication number: US2374933A
Application number: US415880A
Authority: US
Inventors: Clarke T Harding
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1941-10-21
Filing date: 1941-10-21
Publication date: 1945-05-01
Anticipated expiration: 1962-05-01

Description

May 1, 1945. c. T. HARDING METHOD OF FORMING CHEMICAL MIx'ruREs Filed Oct. 21, 1941 2 Sheets-Shet 1 l 5 Azssonrr/ou /7 TOM/E2 I i I i COOLER ZTHAU GAS -7ANK May 1, 1945. c. T. HARDING METHOD OF FORMING CHEMICAL MIXTURES Filed Oct. 21, 1941 2 Sheets-Sheet 2 W NNER Patented May 1, 1945 UNITED. STATES PATENT OFFICE METHOD or FORMING cnrnncar. mx'runss Clarke T. Harding, Hillside, N. 1., allignor to pment Company, a corpo- Standard Oil Develo ration of Delaware Application October 21, 1941,8611 No. 15,880 9 Claims. (Cl. 260-6885) spontaneously explosive when the proportion,

of halogen is too high. For example, in the isomerization of low molecular weight Daraflln hydrocarbons in the presence of a catalyst, "such as aluminum chloride, free chlorine is occasionally used as a promoter of the reaction. When freechlorine is introduced directly into a portion of the hydrocarbon, such as butane, which is generally done at temperatures of about 200 F. and below, means must be provided for avoiding concentrations of chlorine which are greater than about 10% in the absence of a catalyst or 5% in the presence of a catalyst in order that the danger may be entirely eliminated. However, so long as chlorine is introduced directly into the hydrocarbon phase, it will neverbe possible, in plant scale work, to absolutely avoid the possibility of the formation, to some extent, during the operation of at least a localized composition of an explosive nature. This could occur, for example, by mechanical failure of a check valve, allowing one fluid to be sucked back into the other, or by imperfect mixing of hydrocarbon and chlorine, also by a localized condensation of chlorine in case chlorine were added as a gas.

It is an object of the invention, therefore, to provide a method of introducing a halogen, such as chlorine or bromine, into a hydrocarbon without at any .time curring the danger of even localized formati n of an explosive mixture. It is a further object of the invention to provide a means of forming mixtures of carefully controlled proportions, even when the danger of explosion is not resent.

In accordance with the present invention, the halogen is first introduced into an inert medium to form a solution or mixture with the same, whereby the halogen is considerably diluted. This mixture is then contacted with the hydrocarbon, which absorbs the chlcrlnepat least in part, from the mixture and the transfer medium is then separated from the hydrocarbon andmay be used for further absorption of halogen. By preparing mixtures of halogen and an inert medium which sufllciently dilutes the halogen, it is never possible for the halogen to become concentrated in any portion of the hydrocarbon to an extent which would become dangerous.

-The medium to be employed for the transfer of a halogento a hydrocarbn maybe either a liquid or a gas, and ,the halogen may be introduced into this medium either as a liquid or gas,

as may be found most convenient. The medium must, of course, be chemically inert to both the halogen and the hydrocarbon with which it is to come in contact, and the medium should preferably be insoluble in the hydrocarbon and easily separated therefrom by gravity; although, in some cases, it might be desirable to use a medium soluble in the hydrocarbon and to remove the same from the hydrocarbon by distillation. A

gaseous transfer medium will generally be used only when it isto come in contact with aliquid hydrocarbon, or when the medium and the hydrocarbon can be separated by condensation of one of the materials If the medium is a liquid,

it may be used for transferring halogen to either introducing chlorine into light hydrocarbons is aqueous hydrochloric acid. This material absorbs chlorinebest when in concentrated form, but an acid of anystrength may be used. For

example, a solution containing about 9.8 gram mols of hydrogen chloride per 1000 grams'of water dissolvesapproximately 0.13 gram mols of chlorine per 1000 grams of solution. Either gaseous or liquid chlorine may be contacted with the hydrochloric acid, and the mixture formed may then be contacted wtih liquid butane. mixed and separated. therefrom by gravity. This medium is of special value in isomerisation processes, since small amounts of hydrogen chloride carried along by the butane after the chlorine absorption will not only have no harmful effect upon the subsequent isomerisation reaction but will, in general, promote the reaction. In some cases, it might be desirable to use gaseous hydrogen chloride as the transfer medium in such aprocesabutinsuchacasethegasmustbe quite free from hy mcarbon when contacted with Another material which serves as a satisfactory medium in the process described is water, which readily absorbs chlorine, especially under pressure, and which separates readily from gaseous or liquid hydrocarbons. The chlorine may be introduced into contact with water either as a gas or liquid and its solution may be handled for the transfer of chlorine to hydrocarbon in the same way as aqueous hydrochloric acid. As a special case in the use of water as a transfer medium, if a very high partial pressure of chlorine is employed in contacting the same with water, chlorine hydrate (012.8310) will be formed and will separate from water as a separate phase. Thus, the chlorine may be contacted with water under superatmospheric pressure and if provision is made for settling, the chlorine hydrate may-be taken off for use as a supply of chlorine for the hydrocarbon, while the remaining water is recirculated for the absorption of more chlorine. The chlorine hydrate, on contact with the hydrocarbon, such as butane, at a higher temperature will give up its chlorine and the water released can then be removed from the hydrocarbon.

Sulfuric acid, concentrated or diluted with water, is also well suited as a carrier for introducing chlorine into saturated hydrocarbons, such as butane, and when used in concentrated form may be of value in drying the material as well as in removing traces of harmful impurities, such as oleflns, sulfur compounds and the like, which would seriously impair the activity of catalysts such as aluminum chloride in the isomerization reaction. The solubility of chlorine in 90% sulfuric acid at room temperature is 0.016 weight percent (0.029 gram/100 cc.) and increases to approximately 0.2 weight percent at approximately 33% strength and 0.3 weight percent at 16%, whereas in butane chlorine is soluble in all proportions. By using 80% acid in equal volumes with the hydrocarbon feed to insure thorough drying and saturating the acid with chlorine it is possible to introduce 0.05 gram of chlorine .per 100 cc. of bu e or 0.083 weight percent, based on the feed. s quantity is sufficient to replace normal process losses and at the same time has a good acid treating effect on the feed. If necessary to obtain larger chlorine introductions, it is permissible to either increase the rate of acid recirculation or to use, weaker acid in which the solubility of chlorine is markedly increased. In general, strengths of the acid varying from about 55% to 100% are preferred for the process, although much weaker acids may be used. Acid of 80% to 100% strength will serve for drying and for acid treating to remove sulfur compounds, as well as for chlorine introduction. Weaker acids will serve also for introducing chlorine as well as for milder treating to remove oleflns.

Among other liquid materials which may be used as transfer media in certain cases are carbon tetrachloride, hexachlorethane, chiorphenol, dichlorethyl ether, and the like.

Particular compounds for transferring the halogen will be chosen with due regard to the ease with which they may be separated from the hydrocarbon involved in a particular process. Chlorinated hydrocarbons are especially suitable in processes in which these materials are formed by reacting chlorine with hydrocarbons, the prodnet of the reaction then serving as the transfer medium. For example, when chlorine is reacted with ethane to form ethyl chloride, a portion of the liquid product may be withdrawn and used to absorb chlorine in a separate absorbing device, and the solution of chlorine thus formed is then introduced into the reaction tower where it comes into contact with the gaseous ethane. The chlorine is then removed from the solution by the hydrocarbon and the remaining ethyl chloride forms a part of the product of reaction.

When the halogen is to be introduced-into a liquid hydrocarbon, well known inert gases, such as nitrogen and carbon dioxide, may be employed as the medium. Apparatus suitable for sembbing the halogen out of the gaseous mixture by the hydrocarbon will in such case be employed.

' The process of the present invention may be applied generally to the introduction of halogens into hydrocarbons, such as the parafllns or oleflns. If unsaturated hydrocarbons are used, a reactive material such as hydrochloric acid, could not, in such case, be employed as the transfer medium.

The method of the present invention may be illustrated by a continuous process for th chlorination of ethane, illustrated by Figure 1 of the drawings. In this process, chlorine is pumped through line I, pump I and line 3 into absorption tower 4, where it meets a downflowing stream of the reaction product ethyl chloride. Recirculation of unabsorbed chlorine is provided through line 5. The solution of chlorine formed in tower 4 is transferred by means of line 6, pump I and line III to reactor l2. introduced into'line III. A portion of the solution may be recycled to tower 4 through line 0 and cooler 9 to provide a more concentrated solution. In reactor If the downflowing stream of chlorine solution meets the upflowing ethane gas introduced-into the reactor through line If and the chlorine is thus absorbed from the solution and reacted with the ethane. Heat for maintaining the proper temperature of the reaction is provided by a water coil l2a, in the bottom portion of reactor l2. Circulation of the reacting liquids is provided by line I, pump it and line It, the latter re-entering the reactor in its upper portion. Unreacted hydrocarbon and by-product gases are removed from the top of the reactor through line H. The reaction product is drawn oil at the bottom through line l8, but a portion of the same is recycled to tower l by means of line l9, pump 20, line 2| and cooler'fl, to provide a supply of the transfer medium.

The use of the present invention in an isomerization process, in which the chlorine is introduced as a promoter for the isomerization reaction, is illustrated in Figure 2 of the drawings. In this process concentrated aqueous hydrochloric acid is employed as the transfer medium. Chlorine gas is absorbed in a stream of concentrated hydrochloric acid solution in absorber I, the chlorine being introduced through line 2. The hydrochloric acid solution is introduced through line 3 and is largely recycle material Cooling means ll may be from settler 8. The mixture formed in absorber l flows out through line 4 and meets a supply of liquid n-butane introduced through line 5 and these materials aremixed in mixer 6 for extraction of the dissolved chlorine from the hydrochloric acid. All products from mixer 6 pass out through line 1 to settler 8 where the hydrochloric acid separates by gravity from the butane layer and is recycled to absorber I through line 3. By

properly adjusting the proportions. of chlorine, hydrochloric acid and n-butane feed, the proper concentration can be obtained in the latter for optimum isomerization. The n-lbutane-chlorine solution is withdrawn through line 9 to drier In for removal of dissolved water, the drying being effected by contacting with a drying agent, such as concentrated sulfuric acid, or a solid dehydrating agent. Chlorine is only slightly soluble in sulfuric acid, so that the latter is quickly saturated, and as the acid is only infrequently removed from the system, losses of chlorine are negligible. The n-butane from drier I0, containing the correct amount of chlorine, is then sent through line H to isomerization reactor H, where, in contact with anhydrous aluminum chlorine at elevated temperature and pressure, the isomerization reaction is carried out. The isomerized product is removed through line Hi to stripper M, where the hydrogen chloride formed in reactor l2 by reaction of the introduced chlorine with hydrocarbon is stripped out and returned through line l5 to mixer B for the purpose of maintaining the aqueous hydrochloric acid concentration at that point. A portion of the hydrogen chloride may be passed through line I6 to line H to maintain thefproper concentration in the feed for the isomerization reactor. Any deficiency in water in the aqueous hydrochloric acid circulation system is made up by introducing the same through line 3a. Nearly 100% of the chlorine added is converted into hydrogen chloride in the isomerization process through reaction with the hydrocarbon. The isomerized hydrocarbon product containing a small amount of dissolved hydrogen chloride isremoved from the bottom of stripper l4 and transferred to product finishing apparatus.

An alternative process may be carried out by using liquid chlorine and mixing the same with' hydrochloric acid under pressure in mixer l8.

(Figure 2), the resulting mixture being passed* through line I9 to drum 20, Where the unabsorbed liquid chlorine settles out and is returned to mixer l8 through line 2|, while the hydrochloric acid containing dissolved chlorine is transferred to mixer B for mixing with incoming n-butane,

as described above. The process is otherwise carried out as previously described, the recycle hydrochloric acid being brought back to mixer [8 through line 23.

Sulfuric acid may also be used as the transfer medium in place of hydrochloric acid in the above described example illustrated by Figure 2, by properly adjusting the rates of flow.

The following are typical requirements for a duction (case B) These requirements are as f OllOWSZ Case A' Case B Absorption sta e:

Conoentrat on of recirculated HG] solution, wt. percent HO] .L. 24. 7 24. 7 Pressure (atmospheres). l 8. 75 Temperature of acid feed, 85 85 Temperature rise, F 2 12 Concentration oi saturated chlorine-HCl solution:

Pounds chlorine/cu. it. solutlon 0. 023- 3. 27 Grams chlorine/liter solution. 10 52. 6

Extraction stage:

Direction 01 flow Concurrent Concurrent Rate of flow, gallons/minute: X

N-butane., 73 73 E01 solution 2. 5 0. 5 Concentrations:

- Separated n-Butane, weight percent chlorine 0. 06 0. 06 Spent HCl solution:

Pounds chlorine/cu. it. solution 0.006 0. 00642 Grams chlorine/liter solution. 0. 080 0. 087

The operating conditions in the above-described rine eventually leaves the system as hydrogen chloride.

This invention also applies to the vapor phase type of isomerization process employing a fixed bed reactor with throughputs of 0.3-1.2 volume/ volume/hour at. about, 150-300 lbs. pressure and at temperatures of 200-375" F.

This invention is not to be limited in scope by any-of thedescribed'examples which are given by way ofillustration only, but is to be limited solely by the terms 'of the appended claims.

I claim: I 1. In acatalytic hydrocarbon conversion process in which a halogen is used as a promoter of the reaction, the step which comprises mixing the halogen with a liquid inert material immiscible with the'hydrocarbon feed for said conversion process, contacting the mixture so formed with the said hydrocarbon feed, separating the said inert material from the hydrocarbon and converting the hydrocarbon in the presence of a catalyst.

2. Process according to claim 1, in which the said inert material is an aqueous hydrochloric acid solution.

chlorine as a promoter, the step which comprises mixingvthe chlorine with a concentrated aqueous solution of hydrochloric acid, contacting the mixture so formed with the butane feed for the isomerlzation process, separating the hydrochloric acid solution from the butane and subjecting the butane to isomerization conditions in the presence of aluminum chloride.

8. In a catalytic hydrocarbon conversion proces in which a halogen is used as a promoter of the reaction, the step which comprises mixing the halogen with aqueous sulfuric acid of 55 m 100% strength, contacting the mixture so formed with the said hydrocarbon teed, separating the said acid from the hydrocarbon and converting the hydrocarbon in the presence of a catalyst.

7. In a catalytic hydrocarbon conversion process in which a halogen is used as a promoter of the reaction, the step which comprises mixing the halogen with a fluid material chemically inert to halogen and the hydrocarbon feed for said conversion process and immiscible with said hydrocarbon feed, contacting the mixture so formed with the said hydrocarbon feed, separating the said inert material from the hydrocarbon and converting the hydrocarbon in the presence 01 a catalyst.