US2169494A

US2169494A - Treatment of butane

Info

Publication number: US2169494A
Application number: US103390A
Authority: US
Inventors: Ipatieff Vladimir; Pines Herman
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1936-09-30
Filing date: 1936-09-30
Publication date: 1939-08-15
Anticipated expiration: 1956-08-15

Description

Patented Aug. 15, 1939 PATENT o Fi fcs murmur F nv'raits .Vladimir Ipatiefl and 'Herman Pines, Chicago, lll assignors to Universal Oil Products Com pany, Chicago, 111., a corporation of Delaware No Drawing.

Application- September so, 1936, Serial No. 103,390

This invention relates particularly to the treatmentof butan'eof normal or straight-chain structure.

In a more specific sense, the invention is con- ,5 cemed with a. process whereby normal butane is converted into iso-butane, the process involving the use of special catalysts and particular con-i ditionsoi operation which favor the isomerization reactions so that relatively high yields of I!) the iso-compound are produced. v

Since the invention is concerned principally withthe two i-carbon' atom paraiiln hydrocarbons and their transformation, one into the other, the foliowingtable is introduced to indicate the}.

structure and the principal physical characteristics of these'two compounds: 1

Butanes are produced in considerable quan titles in the oil refining industry. They occur in substantial amounts in natural gases-(in which the normal compound usually predominates), in refinery gases 'which are evolved from crude petroleum storage-tanks, and in the primary dis-. tillation oi, crudes, and they are also present inconsiderable percentages in the gases produced incidental .to cracking heavy petroleum fractions for the production of gasoline. In the case of cracked gas mixtures the relative proportions of iso and normal butanes vary, but the ratio of the iso to the normal compound is as a rule considerably higher than in natural gas.

Butanes may be considered as moreor' less marginal compounds in respect to their. desirability in ordinary gasoline, that is,'a certain percentage of them is essential for sufllcient vapor pressure to insure ease in starting, while an excess tends to produce vapor lock. For these reasons the total percentage of 4-carbon atom hy-,

an drocarbons is commonly adjusted in conjunction with the boilingrange and vapor pressure of the othergasoline components to produce a gasoline of desirable starting characteristics according to seasonal demands. Y r

The butanes at the present time bear a further- "tion is concerned.

important relationship to oil refining inthat their excess production is being utilized as a 'source of gasoline either by ordinary'thermalt cracking orby special catalytic dehydrogenation processes iollowed by polymerizationinwhich 5';

catalystsmay or may not be used. Investigations have shown thatiso-buta ne is considerably more amenable to cracking and dehydrogenation, I both with and without catalysts, than the normal c o m p o u n d. Considering the ;-corresponding Inmono-oleflns, the normal butenes are considerablymore dimcult to polymerize, either thermally or catalytically, than iso-butene, and it is foundalso that the 'octenes representing the dimers oi the iso-butene are of higher antiknock value than is. 7

those from n-butenes, which'holds; also for the octanes produced by hydrogenation. It is. therelore, of considerable importance at'the present time to convert as much as possible of the normal butane production, into iso-butane,.and the present invention is especially concerned with a process for accomplishing this object. r

In one specific embodiment, the present invention comprises treatment of normal butane for the isomerization'there'oi into iso-butane, with 25 a'catalyst comprising essentially anhydrous aluminum chloride supported on activated carbon.-

In 'eifecting various reactions'among organic. compounds, utilizing aluminum chloride as a catalyst, difliculty is frequently encountered in that intermediate addition compounds are formed which are more or less of a sticky and viscous character, so that the original granules of anhydrous chlorlde become coated and the effective catalytic surface is lost. This tendency may be 35 overcome to some extent by employing vigorous agitation during the course of the catalytic reactions, but it can never be entirely obviated, so that in general the full effectiveness of aluminum chloride is neverattained. These phenomena 40 are particularly noticeable in hydrocarbon reactions such as those with which the present invenr f Another property oi. anhydrous aluminum chloride which must, be taken into account is its 45 tendency to sublime at a temperature of approximately C., so that ii itis employed at temperatures above this pointit must be injectedor sublim'e'd into the reaction zone. In the process ofthe present invention, in which the aluminum 60 chloride employed is strongly absi'n'bed by activated carbons, both of the disadvantages enumer- 'ated are to a large extent overcome since the tendency of the aluminum chloride to volatilize is partially counteracted by the absorbent action of the carbons or chars employed, and these supports further act to absorb and retain some of the viscous addition compounds and .prevent the composite catalyst granules from adhering to form large agglomerates.

The method of preparation of the type oi catalyst used for the isomerization of normal butane is to mix a properly activated and adsorbent carbon with anhydrous aluminum chloride and then heat the mass under elevated tempera-e tures and'pressures until the chloride has been adsorbed into the oi the carbon. The proportions of adsorbent carrier and aluminum chloride maybe varied as desired to make'catalyst composites of varying activity. It has been found possible and practical to make stable granular catalysts resistant to disintegrating influences by using approximately equal parts by weight or. absorbent carbon and anhydrous aluminum chloride. Such proportions, after thorough mechaniheated at a temperature of approximately 250% C. for several hours. After such a treatment of the original mix the product obtained is dry. and granular, the aluminum chloride apparently having disappeared, though it is actually present in the pores and on the surface of the carbon as evidenced by the violent reaction of'the granules with water and their catalytic activity in organic reactions.

Owing to the adsorptive properties of the ac-.

tivated carbon, catalysts of the above character may be employed iniso'merizing normal butane 'wlth substantially no tendency for the original particles to run together due to the formation of intermediate sludge like products, so that much larger quantities of material may be treated before the catalyst has lost its activity. Another advantage resides in the fact that the; adsorbed aluminum chloride will remain in place without yolatilization-at considerably higher tempera-- lar bed of catalyst.

The term activated carbon" as used in the present specification is intended to'include any type of prepared carbon or carbonaceous material which is more or less granular and possessed of good porosity and structural strength and which has been prepared by general steps involvably under vacuum, to expel adsorbed liquids and 60 gases. It is recognized that various forms of active granular chars will vary considerably in adsorptive capacity so that therefore the proper- "ties of catalysts prepared in accordance with the present invention will vary both in respect to the amount of aluminum chloride which they are able to absorb and in respect to the periods of service in which they are able, to maintain a practical activity in diiferent organic reactions.

We have determined that by the use of the class of catalystsmentioned, and particularly by the concurrent use of considerable superatmospheric pressure, normal butane may be converted into isobutane with ayleld of as high as 60% to 65%; Evidently the use of superatmosphericpressures of the order of 1050 atmospheres at temperatures 01150? c. and higher, besides depressing the volatilization of the aluminum chloride, tends also 'to depress numerous undesirable side reactions which would result in the formation of hydrogen and low molecular weight hydrocarbons, sothat the reaction proceeds more or less in one direction until an equilibrium is established.

The following example is introduced as characteristic of the practical operations of the present process, though it is not introduced with the intention of limiting the scope of the invention in exact correspondence with the numerical data since some latitude is possible in the proportions of activated carbon and aluminum chloride, and

temperature and pressure may also be varied within the limits already specified. These variations may be considerable in the case of gas mixtures, in which normal butane occurs as a constituent in varying percentages.

, In the manufacture oi the catalyst for the isomerization reaction, 100 parts by weight of an activated carbon and 100 parts by weight of anhydrous aluminum chloride were thoroughly mixed in a dry atmosphere and then placed in a pressure vessel lined with glass to avoid corrosion.

An amount of hydrogen chloride gas was intro-' duced equal to 5% by weight of the total mix and the pressure was then raisedto a total ofatmospheres by the introduction of substantially dry hydrogen. The vessel was heated to a temperature of 250 C. and the contents mechanically agitated for a period of three hours. The product had the general appearance of granular carbon but was somewhat more gray than black. The particles were entirely homogeneous in appearance and gave a vigorous evolution of heat when contacted with water, I

Normal butane conta ning about 2% by weight I of hydrogen chloride was passed through a granular mass of the catalyst at a temperature of about 200 0., a pressure of 650 lbs. per sq. in.

changed n-butane.- Compared-with an equivalent weight of ordinary annular anhydrous aluminum chloride, the prepared catalyst could be) used approximately four-times as long before the ma.

- ual deposition of carbonaceous :esidues and byaluminum chloride ineiiective. The herein disclosed method oi preparing the catalyst is not claimed per se in the present ap plication inasmuch as this subject matter is claimed in our companion application, Serial No'. 103,391. Theuse of metallic halides broadly, including aluminum chloride, in the isomerlzation of n-butane is claimed in our companion application, serial No. 103,383..

We claim as our invention:

1. A process for producing isobutane which products rendered the action .of the ads rbed comprises subjecting normal butane,- in the substantlal absence of polymeriza'ble oleflns, to the action' of activated carbon impregnated with anhydrous aluminum chloride under conditions I such that isomerization of normal butane constitutes the principle reaction in the process, wherethe order of about 150 to 250 C., and under pressures of the order of about 10-to 50 atmospheres,

whereby to eflect isomerization of normal butane into isobutane as the principal, reaction in the process.

3. A process for producing isobutane which comprises subjecting normal butane, in the subride under conditions such that isomerization of normal butane constitutes the principal reaction in the process, whereby to convert a major portion of the normal butane into isobutane.

4. A process for producing isobutane which comprises subjecting normal butane, in the substantial absence of polymerizable oleflns and in the presence of a relatively small amount of hydrogen chloride, to the action of activated carbon impregnated with anhydrous aluminum chloride at temperatures of the order 0! about 150 to 250 C. and under pressures of the order of about 10 to 50 atmospheres, whereby to effect isomerizationuof normal butane into isobutane as the principal reaction'in the process.

VLADIMIR IPATIEFF. HERMAN PINES.