3,178,485 United States Patent Office Patented Apr. 13, 1965 2 3,178,485 alcohol, capryl alcohol, n-decyl alcohol, and the like; poly THERMAL, HYDROIDEALKYLATION OF ALKYL hydric aliphatic alcohols, such as ethylene glycol, propyl AROMATICS ene glycol, glycerol, trimethylene glycol, and the like; John W. Myers, Bartlesville, Okla., assig or to Philips monocarboxylic aliphatic acids, such as formic acid, acetic Petroleism Company, a corporation of Delaware acid, propionic acid, n-butyric acid, isobutyric acid, n No Drawing. Filed Dec. 6, 1961, Ser. No. 57,566 Valeric acid, caproic acid, n-heptylic acid, caprylic acid, 2 Claims. (CI. 260-672) pelargonic acid, and the like; esters of such carboxylic This invention relates to the thermal hydrodealkylation acids, such as methyl formate, ethyl formate, methyl of alkyl aromatics. More particularly, it relates to a acetate, ethyl acetate, n-propyl acetate, n-butyl acetate, process for the thermal hydrodealkylation of alkyl aro O n-amyl acetate, n-octyl acetate, ethyl propionate, isoamyl matics, such as toluene, in admixture with an oxygen-sub n-butyrate, ethyl n-heptylate, and the like; anhydrides of stituted organic compound. such carboxylic acid, such as acetic anhydride, propionic There is increasdi interest and activity today in the anhydride, n-butyric anhydride, n-valeric anhydride, and chemical and allied industries in the production of aro the like; aldehydes, such as acetaldehyde, chloral glyoxal, matics such as benzene and naphthalene. Attention has propionaldehyde, n-butyraldehyde, isobutyraldehyde, n been given in particular to the catalytic hydrodealkyla valeraldehyde, acrolein, crotonaldehyde, benzaldehyde, tion of alkyl aromatics for the production of these valu furfural, and the like; ketones, such as acetone, methyl able aromatics. But these catalytic processes entail the ethyl ketone, methyl n-propyl ketone, diethyl ketone, use of expensive catalysts and give rise to the attendant hexanone-2, hexanone-3, methyl t-butyl ketone, di-n- problems of coke laydown, "dusting,' catalyst fines sep 20 propyl ketone, diisopropyl ketone, acetylacetone, and the aration, and catalyst deactivation, and require large quan like; ethers, such as dimethyl ether, methyl ethyl ether, di tities of hydrogen for efficient operation. On the other ethyl ether, di-n-propyl ether, methyl n-butyl ether tetra hand, the thermal (or non-catalytic) hydrodealkylation hydrofuran, anisole, and the like; peroxy compounds, such of alkyl aromatics has generally required large reactors as tert-butyl peroxides, tert-butyl hydroperoxide, benzoyl and severe operating conditions. 25 peroxide, benzoyl hydroperoxide, dicumyl peroxide, Accordingly, an object of this invention is to provide an cumyl hydroperoxide, diisopropyl benzene peroxide, di improved process for the thermal hydrodealkylation of isopropyl benzene hydroperoxide, di-tert-butyl peroxide, alkyl aromatics. Another object is to provide a process and the like. Oxygen-substituted organic compounds for the hydrodealkylation of alkyl aromatics which is not having mixed oxygen-containing functional groups can subject to the disadvantages of catalytic hydrodealkyla 30 also be used, such as methyl cellosolve, dihydroxyacetone, tion. Another object is to provide an improved thermal g-hydroxypropionic acid, y-acetoxybutyraldehyde, para hydrodealkylation process characterized by high rates of formaldehyde, 3-hydroxy-n-butyraldehyde, ethyl-n-butyl reaction, thus permitting the use of smaller reactors acetoacetate, o-hydroacetophenone, and the like. and/or less severe operating conditions than that found The amount of oxygen-substituted organic compound necessary in hydrodealkylation processes used or proposed 3 5 used in the practice of this invention can vary, and, stated heretofore. Further objects and advantages of this in functionally, the amount generally used will be sufficient vention will become apparent to those skilled in the art to increase the reaction rate, i.e., conversion of alkyl aro from the following discussion and appended claims. matic to lower molecular weight aromatic. Usually this The present invention provides a process wherein an amount will be less than 15 weight percent of the alkyl alkyl aromatic such as toluene, in admixture with an 40 aromatic, preferably 0.5 to 10 weight percent of the alkyl oxygen-substituted organic compound, such as acetone, is aromatic feed. The oxygen-substituted organic compound subjected to thermal hydrodealkylation conditions. can be mixed with the alkyl aromatic and the mixed feed have found that the reaction rate of the dealkylation re then preheated and vaporized, or the oxygen-substituted action is significantly increased due to the presence of the compound and alkyi aromatic can be separately pre oxygen-substituted organic compound in the feedstock. heated and vaporized prior to admixture. The feedstock Such increased reaction rate results in a more economical of vaporized alkyl aromatic and oxygen-substituted or operation since for the same size reactor and same operat ganic compound, having temperatures generally about ing conditions, faster reaction rates (i.e., greater conver 1050-1300 F., typically about 1100 F., can then be sions of alkyl aromatics) can be obtained by this inven Supplied together with a hydrogen-containing stream, such tion as compared to thermally hydrodealkylating the alkyl 50 as reformer offgas, also preheated to about the same tem aromatic in the absence of such oxygen-substituted com peratures to a hydrodealkylation reactor. Such a reactor pounds. can be a tubular type reactor lined with Gunite and pro The term "oxygen-substituted organic compound,' as vided with ceramic pipe internals. The reactor can be used in this specification and in the appended claims is operated at about 100 to 2000 p.s.i.a., typically about meant to cover those organic compounds wherein one or 200-600 p.s.i.g. The hydrogen-to-alkyl aromatic mol more oxygen atoms are bonded by a single or double ratio can vary between 0.5/1 to 20/1, preferably about bond to a carbon atom of the hydrocarbon residue. The 3/1 to 8/1. The hydrodealkylation reaction is exother oxygen atom can be substituted in the form of a hydroxyl, mic and non-catalytic, the reaction temperatures generally oxy, carbonyl, or peroxy radical. These oxygen-sub being about 1100-1500 F., typically about 1100-1300 stituted organic compounds are normally liquid and gen 60 F. The reactor effluent can be cooled, for example by ad erally have from 1 to 10 carbon atoms per molecule. mixture with cooled recycle aromatic product, to about One or more of these oxygen-substituted organic com 800–1100 F., and then further cooled by using suitable pounds can be admixed with the alkyl aromatic feed, the coolers such as air fin-coolers. The reaction mixture, preferred oxygen-substituted organic compounds being comprising the aromatic product in admixture with meth those which are acyclic and do not violently decompose 65 ane, hydrogen, and other reaction products, such as bi under the reaction conditions. phenyl, can then be subjected to conventional separation Representative oxygen-substituted organic compounds to recover the aromatic product. which can be used in the practice of this invention include Due to the presence of the oxygen-substituted organic monohydric aliphatic alcohols, such as methyl alcohol, compound in the alkyl aromatic feedstock, the reaction ethyl alcohol, n-propyl alcohol isopropyl alcohol, allyl 70 rates of conversion will be significantly increased, so that alcohol, n-butyl alcohol, isobutyl alcohol, n-amyl alcohol, smaller reactors and/or less severe operating conditions isoamyl alcohol, n-hexyl alcohol, cyclohexanol, n-octyl can be employed than that encountered heretofore. 3,178,485 S 4. My invention is applicable in dealkylating alkyl aro Comparison of the runs in Table I show that a signifi matics in general, in particular alkyl benzenes, the latter cant increase in reaction rate can be obtained by incor term being used herein in its generic sense to cover mono porating in the alkyl aromatic feeds an oxygen-substituted alkyl benzenes and poly-alkyl benzenes. Representative organic compound of this invention. alkylbenzenes which can be used as feeds include toluene, Various modifications and alterations of this invention Xylene, ethylbenzene, diethylbenzene, cumene, propylben will become apparent to those skilled in the art, without Zene, isopropylbenzene, diisopropylbenzene, butylbenzene, departing from the scope and spirit of this invention, amylbenzene, mesitylene, methyl-ethylbenzene, pseudo and it should be understood that this invention is not to cumene, hemimellitene, prehnitene, durene, and the like, be limited unduly to that set forth herein for illustrative including mixtures of hydrocarbons containing one or O purposes. more of these compounds. The mono-nuclear alkyl aro I claim: matics, especially toluene and xylene, are preferred. 1. In a non-catalytic hydrodealkylation process where Mono- and polyalkylated naphthalenes, such as methyl in hydrogen and a vaporized alkyl aromatic hydrocarbon naphthalene, can also be dealkylated to the corresponding feed stream are passed to a reaction zone, said hydro aromatic by the practice of this invention. carbon is dealkylated in said zone at 1100 to 1500 F., The objects and advantages of this invention are fur and the resulting dealkylated aromatic product is recov ther illustrated in the following examples, but it should ered from the reaction mixture withdrawn from said zone, be understood that the various reactants, conditions, etc., the improvement comprising admixing with said feed recited in these examples should not be construed to limit stream 0.5 to 15 weight percent thereof of an acyclic unduly this invention. A number of runs were made in which feedstocks con alcohol and passing it in vaporized form with said hydro taining toluene and an oxygen-substituted organic com carbon to said zone, said alcohol being normally liquid pound of this invention were subjected to hydrodealkyla and having 1 to 10 carbon atoms per molecule. tion conditions. For purposes of comparison, toluene 2. The process according to claim 1 wherein said was hydrodealkylated in another run in the absence of alkyl aromatic hydrocarbon is toluene, and said oxygen any oxygen-substituted oragnic compound. Data for these Substituted organic compound is isopropanol. runs, together with the percent toluene conversion and percent dealkylation efficiency, are set forth and com References Cited by the Examiner pared in Table I. These runs were carried out in a stain UNITED STATES PATENTS less steel reaction tube heated in an electric furnace. The 30 2,739,991 3/56 Hervert ------260-672 products were analyzed by chromatography. 2,768,219 10/56 Hoffmann et al. ------260-672 Table I 2,786,873 3/57 Ohsol et al. ------260-672 2,801,271 7/57 Schlatter ------260-672 3,110,745 11/63 Peck et al. ------260-672 Oxygen compound used.--- isopro- di-t-butyl OTHER REFERENCES panol peroxide Amt. of oxygen compound, Brooks et al.: The Chemistry of Petroleum Hydrocar Wit. percent ------6.3 6.4 6.4 Reaction temp., F. 1,143 1,146 1,140 1,14. bons,' vol. 2, pp. 140, 155 and 251 (1955), Reinhold Reaction pres., p.s. 300 300 300 300 Publ. Co. H/HC b, mol ratio - 4. 40 3.9 4.2 40 Contact time, Sec.------31 31 31 3. Gilman: "Organic Chemistry," vol. I, pages 538-9, Toluene conversion, (1938), John Wiley and Sons, Inc. (N.Y.). percent------12.9 29.2 21.8 34.4 Dealkylation efficiency, 98.8 98.8 93.5 96.4 ALPHONSO D. SULLIVAN, Primary Examiner. a Based on toluene. 45 b HC includes oxygen compound where used. PAUL M. COUGHLAN, JR. Examiner.