US2371163A - Manufacture of aromatic compounds - Google Patents

Description

eillcient manner.

Patented 13, 1945 UN IED s rAre-s', PATENT OFFICE r Vii-11.1.5

iranuracrunc or momma comroumis t't'itllt.ilftitaZii'idiffitfElliiiiitin'i Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York Nonrawing.

1 Claim.

The invention is directed particularly to the preparation of alkyl aromatics from petroleum distillates, p

The large demand for benzene and low boiling alkyl aromatics such as toluene,. ethyl benzene,

. cumene, cymene, diethyl benzene; etc'.,-is well known. These aromatics are useful principally as solvents and as raw materials for the synthesis of other organic compounds. Benzene and tol-- none are derived usually from coal tar or, as

known, may be separated from petroleum by expensive isolation metho ds when a sufiiciently debenzene, cumene, cymene and diethyl benzene do not-occur'in either coal tar orpetroleum in substantial quantities and hencemust be synthesized from the benzene or toluene.

It is an object of our invention to provide a. method of recovering aromatic hydrocarbons from petroleum. Still another specific object is to manufacture and recover valuable alkyl aromatic Application September 13,1940, Serial No. 356,848

the resultant product is distilled to substantially the same end point as used to prepare the fraction, whereby all non-aromatic material is eliminated and substantially 100% pure alkyl aromatics remain as the desired product. The alkyl aromatic product can be fractionated, if desired, into mono-, di-', etc., alkylated products and, of course,- can be used or treated in any manner that similar compounds obtained from other sources may be employed.

While, as stated, our invention may be applied to any appropriate hydrocarbon mixture, the invention is concerned principally with treating petroleum distillates, and, as known, many petroleum distillates are available which contain suitable aromatics. The aromatic content of the remanding market exists. Compounds such as ethyl hydrocarbons from petroleum in a simple and According to our invention the desired alkyl aromatics are prepared and separated. from a mixture of hydrocarbons bya process of selective alkylation and distillation. Thus a hydro carbon mixture containing say benzene and/or toluene and saturated hydrocarbons, i. e., paraffins and naphthenes; of similar boiling point, as well as, hydrocarbons of higher boiling point, may be fractionally distilled to an end point slightly above the boiling point of the aromatic desired as a reagent for producing the desired end products, for instance, about 90 C. for benzene and about 120 C. tor toluene. In this manner any higher boiling hydrocarbons, if present, are eliminated.

- We thensubject ourdesiredfraction to aselective alkylation process with gaseous olefins toe alkylate the benzene or toluene therein thereby producing the desired alkyl aromatics of higher boiling point but without alkylating any paraflins or naphthenes that may be present. Since, as is well known, aromatics are more easily alkylated than paraflins or naphthenes, the selective alkylation is quite feasible. After the alkylation step,

agent may be quite low, for instance, a product containing as little 8.84% toluene has given a useful alkylation./ But for economical, opera tions it is better to select a material with as high a content of aromatics as possible, say'50 or 60% however, a much lower content, as, for example,

"20% in a 10 0--120 C. fraction, would be excellent for use in the process.

' The olefin reagent may be pure or may be a mixture of olefins or may contain large amounts of parafllns which are inert under the conditions of reaction. Cracking still gas is a suitable olefin reagent if a pure alkyl benzene is not desired as the final product.

' The amount of gaseous olefin added in the al-' kylation process will depend upon the amount of.

aromatic present, and upon the alkylation product desired. Thus the gaseous olefin reagent does not polymerize as long as any appreciable amount of incompletelyalkylated aromatic is present. However, if more than three moles of" olefin is added for each mole of aromatic present, the excess olefin continues to be absorbed, but some of it may result in high boiling unsaturated polymers. Therefore, the concentration of olefins to aromatics should be kept-below 3 moles to 1 mole.. Liquid olefins cause undesirable side reactions, so that if present, in any or the reagents, they should be eliminated first by mild acid treatment. As noted, the degree of alkylation may be regulated by. controlling the olefin concentration. Accordingly if a mono-alleviatedproduct, such as cumene orje' thylene benzene. is desired, or even ethyl toluene or cymene, the

am u'nt of olefin added must be limited to not over a half a mole for one of aromatic, since monoalkylated aromatics are alkylated further much more readily than are the original aromatics, In such a process the mpno-alkylate may be separated from the unreacted material and the latter recycled for further treating.

Processes for alkylating aromatics with olefins are well known and understood in the art The only requirement of the present operation is that conditions are used which will not result in alkylation of the less reactive parafllns and naphthenes that may be present. Because of the difference in reactivity the conditions may be regulated quite feasibly so that this latter type alkylation does not occur at all or occurs so slowly that it can be neglected.

In our operations we prefer to alkylate the aromatics in the presence of an aluminum chloride catalyst. Using such a catalyst, room tem- ,perature (my-30 c.) is a suitable reaction temperature for propylene and higher oleflns, al-

though higher temperatures are permissible, and a reaction temperature of at least 40 C. should be used for alkylating with ethylene.

In order to illustrate the invention further the iollowing specific examples are given.

Example 1 A mixture of 90% normal heptane and 10% toluene by volume was alkylated in the presence of 1% aluminum c oride with 17.2 moles of pro,- pylene for one mole of toluene. The product obtained distilling up to 120 0. contained about 5% toluene and was saturated or rather nonoleflnicr The product boiling above 120 C. had a specific gravity of 0.8650 indicating practically 100% aromatic content and also was non-oleflnic. This latter product consisted mostly of diand tri-isopropyl toluene.

Example"? A mixture of 96% normal heptane and 4% toluene was alkylated inthe presence or 1% aluminum chloride using 2.4 moles of propylene for one mole of toluene. Again the fraction boiling below 120 C. and the fraction boiling above 120 C. were non-olefinic and the aromatic conientrof the former was about 1.4% and that of the latter practically 100%.

Example 3 A toluene rich fraction (boiling point 102-112 C.) was obtained by fractionation of a run gasoline.- Portions of-this fraction were allzylated with propylenei n the presence of 1% aluminum chloride in four different operations giving the following results:

A toluene rich cut identical with that used in runs 1 and 2 of Example 3 was alkylated in the presence of aluminum chloride with 0.45 mole of ethylene for one mole of toluene. The reaction temperature was allowed to rise (byheat of reaction) to 45 0. instead of cooling the reaction mixture as when propylating. ,The higher boiling product obtained from this operation had a density of 0.8669 and boiled mostly at 1co.-1'1o 0., indicating that it was primarily ethyl toluene;

'Example 5 An alkylation was conducted similar to that.

oi Example 4 except that the reaction mixture was warmed to C. before reaction. As a result ethylene was absorbed much more rapidly .but the results were practicallyidentical.

We claim: The process of obtaining allwl toluenes from a. petroleum oil comprising a substantial amount of toluene and a substantial amount ot'saturated hydrocarbons wherein the boiling points of the. toluene and the saturated hydrocarbons are so I close together that they cannot be separated tea-' sibly by conventional fractional distillation which comprises distilling the oil to prepare a fraction boiling substantially between about 102' O. and

112? 0., subjecting the iraction to selective alkyb" ation with gaseous oleflns in'the presence of aluminum chloride, so as to alkylate only the toluene. and then distilling the alkylated fraction to produce an alkyl toluene boiling above O. and an aliphatic traction boiling below 1 20' ('1'.

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