Patented Dec. 11, 1951 2,577,788

UNITED STATES PATENT OFFICE 2,577,788 ? CONCURRENT DEALKYLATION OF ARO MATIC AND DEHY- , DROGENATION OF NAPHTHENIC HY OROCARBONS James H. McAteer, Cranford, and Charles E. Mor rell, Westfield, N.J., assignors to Standard Oil Development Company, a corporation of Dela ware No Drawing. Application July 26, 1949, Serial No. 106,978 10 Claims. (C. 260-668) 2 This invention relates to a novel process for placing split-off alkyl groups in the aromatic effecting the dealkylation of alkylated aromatic nuclei. compounds by simultaneously effecting the dehy Experimental data show that when the desired drogenation of allicyclic, and particularly naph reaction is obtained, the alicyclic or naphthenic thenic, compounds. compound is dehydrogenated at a rate closely Hydrogen transfer reactions are known which correlated to the rate at which the alkyl aromatic involve the reaction between hydrogen acceptors, cumpound is dealkylated. It is therefore neces Such as olefins or aromatics, with hydrogen do sary to avoid undesired side reactions by remov nors, such as alcohols or naphthenes, in the pres ing the products as they are formed from the ence of various catalystS active for hydrogena O reaction zone, these products being eSSentially tion and dehydrogenation. These reactions af and principally the partially dehydrogenated al fect the relative Saturation of the carbon atoms icyclic compound or result of the hydrogen donor and acceptor but do not ing therefrom, the paraffinic compound formed affect the total carbon numbers of the reacting from the split-off alkyl group, and the dealkyl compounds, i. e., they do not result in a selective 5 ated aromatic compound, with only a restricted fission of carbon to carbon linkages. amount of hydrogen. This invention is a process for dealkylating al It can be seen that the present invention pro kylated aromatic compounds by a double decom vides a useful technique for obtaining a con position with allicyclic, and particularly naph trolled dehydrogenation of alicyclic compounds thenic, compounds under conditions that prevent 20 and controlled dealkylation of alkylated aromatic hydrogenation of the aromatic nucleus. The re compounds insofar as it involves proportioning action is carried out in the vapor phase with these reactants to the exclusion of other reactive the use of a catalyst comprising, preferably, acti substances, so that a pair of hydrogen atoms is Wated carbon. given off by the alicyclic compound for each alkyl In contrast to the conventional hydrogen trans 25 group split off from the alkylated aromatic com fer reactions, in which hydrogen is transferred pound. from Saturated carbons of one reactant to un The process of this invention can therefore be saturated carbons of another reactant, the proc carried out under much milder conditions than is ess of the present invention is carried out to avoid necessitated when alkylated aromatic compounds such a transfer, because the presence of free hy :30 are dealkylated with hydrogen. The milder Con drogen and addition of hydrogen to unsaturated ditions result in much greater selectivities and a carbon atoms interferes with the desired deal great diminution in undesirable degradation re kylation. It has been shown that the dealkyla actions. tion of the mono- and polyalkylated aromatic The alicyclic compounds that may be employed compounds proceeds most advantageously when 3 5 are those in general having five or more alicyclic tle two eSSential reactants, i. e., the naphthenic carbon atons and those that are also relatively or alicyclic compound and the alkyl aromatic nore Saturated than the aromatic compound be compound, are substantially free of other reactive ing dealkylated. Typical alicyclic compounds substances, such as olefins and aromatic com usable in this invention are polycyclic naphthenes pounds, corresponding to the dealkylated, alkyl 40 such as decalin; polycyclic compounds in which aromatic compound, or free hydrogen, when reac at least one ring is non-aromatic, e. g., tetralin, tion is initiated. Thus, in the desired reaction, hydrindene; unsaturated hydrocarbons contain the efficiency is greater when the hydrogen, given ing non-aromatic rings, the unsaturation being up by the alicyclic compound, is utilized to a cither in the ring or side chain; mixtures of these greater extent in combining with the alkyl groupS 4. and mixtures rich in these with other types of split from the aromatic compounds and in rers hydrocarbons. 2,577,788 4. 3 been described under conditions of temperature, The naphthenic hydrocarbons that may be en pressure, feed rates, and the like, so chosen as to ployed as hydrogen donors are preferably those produce the desired extent of conversion. The having at least five or six cyclic carbon atoms, equipment employed for this purpose may i.e of i.e., or . Naphthenic any type known to those skilled in the art for rings having four or less carbon atoms are too effecting a vapor phase catalytic reaction. Thus, unstable to work satisfactorily. Alkylated de for example, liquid feed is charged to a vaporizer rivatives of the indicated naphthenes can also be from which the resulting feed vapors pass through employed. The naphthenes are dehydrogenated a preheating zone and thence into the reaction during the course of the reaction to cycloolefinic Zone in which the vapors are contacted with the cr aromatic products. Thus, is con U catalyst. The effluent vapors from the reaction verted to and to cyclo ZOne are cooled and condensed to produce a pentenes and cyclopentadiene. Alkylated naph liquid reaction product and non-condensible thenes undergo both dehydrogenation and ap gases comprising low molecular weight paraffins preciable dealkylation. and only a small amount of hydrogen. The The alkylated aromatic compounds that are liquid reaction product is worked up in any dealkylated by the process of this invention are Suitable manner, for example, by fractionation, benzenoid hydrocarbons and also those belonging adsorption, or crystallization, to rucover the de to the polycyclic series, such as, e. g., diphenyl, sired constituents in the requisite degree of purity. , , , etc. Unchanged or incompletely converted reactants Primary normal alkyl groups containing less than 20 may be recycled together with fresh feed. If de about four carbon atoms are removed selectively sired, an inert diluent such as, for example, a as the corresponding . When higher nor portion of the non-condensible gaseous products mal alkyl groups, or branched groups are present may be employed. in the aromatic nucleus, some fragmentation of 25 It will be understood that the exact conditions the alkyl groups occurs with the production of employed in carrying out the reaction will be hydrocarbons of lower molecular weight determined by the nature of the feed constituents, than correspond to the original alkyl groups. the desired conversions per pass and the specific Polyalkylated aromatic hydrocarbons are deal catalyst employed. The reaction is carried out kylated in a stepwise manner. 30 under pressures ranging from subatmospheric to The preferred catalyst is activated carbon, Superatmospheric as long as it is conducted in Since this gives a minimum of degradative crack the vapor phase with a low partial pressure of ing reactions. The carbon may be activated by hydrogen, i. e., less than about 150 p.s. i. the use of steam, carbon dioxide or other inert In general, the range of temperatures for gases at elevated temperatures. The activated carrying out the reaction will be of the Order of carbon is derived from a variety of sources, in 250°-650° C., and principally between 500° and cluding vegetable matter decomposition products, 600° C. At temperatures below this range, the lignite, petroleum sources, bituminous coal, or rate of reaction tends to become impracticably Selected pure organic compounds. The catalyst Slow and hydrogenation of the aromatic nucleus should have a high surface area and a relatively 40 is favored, whereas, at temperatures higher than low content of volatile matter. Inorganic ma this range there is an increased tendency towards terials are normally present in activated charcoal the occurrence of Side reactions Such as thermal from a large number of Sources and include, cracking. The total feed rates enployed will for example, oxides or salts of such elements as normally lie in the range of 0.1 to 10 liquid zinc, copper, calcium, iron, chromium, aluminum, volumes per Volume of catalyst per hour. The nickel, etc. Salts of these metals may conven proportion of allicyclic compound to alkylated iently be employed as promoters in the original aromatic compound in the feed is controlled to process of activating the carbon. It is believed determine the extent of conversion of both re that these inorganic materials have no deleterious actants. Generally, about one mole of the naph effect on the reaction of this invention and in thenic reactant is mixed with about one to three certain instances are believed to have a promoting moles of the aromatic reactant. effect. The catalylst is normally regenerated by The relative concentrations of the naphthenes stripping with inert gases such as steam, nitro to the alkylated aromatic compounds in the feed gen, flue gases, etc. at elevated temperatures, i. e., varies with the results desired. Thus, high con 450°-900° C. 5 5 version per pass of alkylated aromatics results The reaction between the natohthenes and from the use of the larger amounts of naphthenes, alkylated aromatic compounds is illustrated by whereas use of larger amounts of the alkylated the reaction between cyclohexane and . aromatic compounds results in high conversion per pass of the naphthenes. The feed materials H 60 may be used in a relatively pure form or can be : I CE used if diluted with inert materials. -- 3 a-) 4 -- 3 CH The process may be executed in a batch, inter Ea mediate, or continuous manner. Higher over-all EI yields are obtained with multi-paSS processes. The hydrogen atoms are thus removed from 65 The catalyst may be employed in a fixed bed, the naphthenes and these atoms are catalytically moving bed, or in a fluidized manner, depending combined with and substituted for the alkyl on the type operation desired. groups that are split from the alkylated aromatic This invention will be better understood by compound. Cyclohexane and its higher homo reference to the following tables and examples, logues are particularly adapted for use in the 70 indicating the results obtained from the reaction process of this invention because each molecule of various naphthenes and alkylated aromatic of cyclohexane contains sufficient hydrogen to compounds, including hydrocarbons and other cause three carbon to carbon fissions. The reaction is carried out in vapor phase in types. The results were obtained after a single the presence of a catalyst of the type which has 75 pass operation. 2,577,788 5 6 TABLE Dealkylation of aromatic compounds by cycloheacane type compounds

Feed: Naphthene.------Cyclohexane Methyl Cyclohexane Cyclohexane Cyclohexane Cyclohexane Cyclohexane Cyclohexane Cyclohexane Aromatic Conpound. Toluene Ethyl Ethyl Ethyl Methyl Mixed C. Aromatic m,p-Cresols Benzene Benzene Benzene Naphthalene Xylenes fraction Naphthenefaromatic, moles per Iriole------0.40 0.80 1.0 1. ) 1.0 0.60 Liq. feed, W.I.W. cat.fhr-- 2.2 0.75 .5 9 0.65 0.63 Catalyst (2) (2) . () (8) (2) Catalyst Temp...--o C. 500 550 550 520 505 Conversions, por cent: Naphthenes------11 29 30 45 2 Alkylated aromatics--- 2 67 29 70 29 Yields,Dehydrogenated mole per cent: naph thenes.------25 24 40 21 Dealkylated aromatics ag 2 6 29 70 22

1 60-70° C. B. P. 2 Bituminous Activated Charcoal. Coconut Activated Charcoal. undesirable degradation reactions and do not TABLE result in the reaction proceeding in other direc Dealkylation of aromatic hydrocarbons by cyclopentane type compounds tions than the one indicated. It is to be understood that the invention is not Feed: . Naphthene------Cyclopentane Methyl Cyclo 25 limited to the specific examples which have been pentane offered merely as illustrations and that modi Aromatic ------Ethyl Benzene Xylences fications may be made in equipment and condi tions within the range specified without depart Naphthenefaromatic, moles per mole - ... O 1.0 ing from the spirit of this invention. Lic feed, w.fw. cat.fhr 1.2 0.75 What is claimed is: Catalyst.------(1) (1) 30 Catalyst Temp. 550 530 1. A process for simultaneously effecting the Conversions, pcr cent: catalytic dehydrogenation of allicyclic COIlpounds Naphthenes ------28 2 Alkylated aromatics------3 3 and dealkylation of alkylated aromatic hydrocar Yields, mole per cent: bon compounds which comprises reacting an ali Dehydrogenated naphthenes------28 22 Dealkylated aromatics------13 13 35 cyclic hydrocarbon with an alkylated aromatic compound in the vapor phase at a temperature 1 Bituminous activated charcoal. of 500 to 600° C. in the presence of an activated carbon catalyst with a liquid feed to catalyst TABLE III ratio of 0.1 to 10 v./v./hr. for a length of time Dealkylation of aromatic hydrocarbons by niaced naphthemes 40 to produce the desired dealkylated compounds, Said allicyclic hydrocarbon having at least 5 ali Feed: Naphthene------Straight Run Straight Run cyclic carbon atoms and being more saturated Naphthenic Naphthenic than the alkylated aromatic compound being de Naphthal Naphthal alkylated. Aromatic Eydrocarbol------Aromatic Kero-Aromatic Kero 45 2. A proceSS for simultaneously effecting the sene Extract 2 Sene Extract 2 catalytic dehydrogenation of allicyclic compounds Naphthenefaromatic, weight ratio. 0.38 0.38 and dealkylation of alkylated aromatic com O.75 0.5 Liq. feed, v.iv. Cat.fhr.------pounds which comprises reacting a naphthenic Catalyst.------(3) (4) Catalyst Temp------C. 52) 52) hydrocarbon with an alkylated aromatic com Conversions, Per cent: pound in the vapor phase at a temperature in Naphthenes.------7 2 Alkylated aroIEatics------38 the range of 500 to 600° C. in the presence of . Yields, Weight Per Cent: Dehydrogenated naphthenes-- g 4. an activated carbon catalyst with a liquid feed Idealkylated aromatics------15 to catalyst ratio of 0.1 to 10 v./v./hr., for a length of time to produce the desired dealkylated com B. P. 45-93° C. 5 5 pounds. 2 B. P. 200-350° C. 3 Activatcd coconut charcoal. 3. A process for effecting the catalytic dehy 4 Iron oxide-puLuice. drogenation of alicyclic compounds and dealkyla tion of alkylated aromatic compounds which The figures indicate that the dealkylated aro comprises reacting a naphthenic hydrocarbon matic compounds produced consisted of practi CO having at least five cyclic carbon atoms with an cally 100% aromatics indicating an absence of alkylated aromatic hydrocarbon in the vapor undesirable side reactions and fragmentations. phase at a temperature in the range of 500 to This high selectivity, nearly 100%, should be 600° C. in the presence of an activated carbon particularly noted. This is a particular advan catalyst with a liquid feed to catalyst ratio of tage of the process of this invention. 0.1 to 10 v./v./hr. for a length of time to produce In general, the relative conversion of the al the desired dealkylated compounds, whereby the kylated aromatic compound to dealkylated aro alicyclic hydrocarbon is dehydrogenated as the matic varies directly with the molecular weight alkylated aromatic compound is dealkylated. of the alkylated aromatic compound. Thus alpha 4. A process for the simultaneous production methyl naphthalene gave a conversion of 7.3 rel of benzene and ethane which comprises reacting ative to toluene and the former is therefore ideal cyclohexane and in the vapor phase ly adapted to be dealkylated by the process of at a temperature in the range of 500-600° C. in this invention. the presence of an activated carbon catalyst With Other catalysts than activated carbon may be a liquid feed to catalyst ratio of 0.1 to 10 V./v./hr. employed, provided that they do not result in 5 for a length of time to produce the benzene SO 2,577,788 7 8 that hydrogen from the cyclohexane is combined 8. A process as in claim 7 in which the alicyclic with ethyl groups split off the ethyl benzene. compound is a naphthenic hydrocarbon having 5. A process for the simultaneous production at least 5 cyclic carbon atoms. of methane and benzene which comprises react 9. A process as in claim 8 in which the alkylated ing cyclohexane and toluene in the vapor phase aromatic compound being dealkylated is a hy at a temperature in the range of 500-600° C. drocarbon. in the presence of an activated carbon catalyst 10. A process for obtaining a controlled de with a liquid feed to catalyst ratio of 0.1 to 10 hydrogenation of naphthenic hydrocarbons con v./v./hr. for a length of time to produce the taining at least five cyclic carbon atoms simuli benzene so that hydrogen from the cyclohexane 10 taneously with the dealkylation of alkylated aro is combined with methyl groups split of the matic compounds which comprises the steps of toluene. admixing a predominantly organic mixture con 6. A process for the simultaneous production taining naphthenic hydrocarbons with a pre of methane and naphthalene which comprises dominantly organic mixture containing the a reacting alpha methyl naphthalene and cyclo 5 kylated aromatic compounds in a proportion such hexane in the vapor phase at a temperature in that the naphthenes supply two hydrogen atoms the range of 500-600° C. in the presence of an for each alkyl group to be split from the alkylated activated carbon catalyst with a liquid feed to aromatic compounds; passing the resulting mix catalyst ratio of 0.1 to 10 v./v./hr. for a length ture in vapor phase into a reaction zone at a of time to produce the naphthalene, so that hy 20 temperature in the range of 500 to 600° C. in drogen from the cyclohexane is combined with the presence of an activated carbon catalyst methyl groups split off the alpha methyl naph with a liquid feed to catalyst ratio of 0.1 to 10 thalene. v./v./hr. for a length of time to produce the de 7. A process for obtaining a controlled dehy sired dealkylated compounds, at which tempera drogenation of an allicyclic hydrocarbon com ture the naphthenes undergo dehydrogenation at pound simultaneously with a realkylation of an a rate controlled by the dealkylation of the alkylated aromatic compound, which comprises alkylated aromatics, and removing from the re admixing the alicyclic compound with the al action zone the gaseous products of the reaction kylated aromatic compound in a proportion such as they are formed, comprising principally the th the alicyclic compound supplies two hydro 30 dehydrogenated naphthenes, dealkylated aro gen atoms for each alkyl group to be split from matics and paraffins formed by split-off alkyl the alkylated aromatic compound, passing the groups combined with hydrogen from the alicy resulting mixture of the alicyclic compound and clic compound. alkylated aromatic compound substantially free JAMES H. McATEER. from other reactive sbstances in vapor phase into CHARES E. MORRELL. a reaction zone maintained at a temperature of 500 to 600° C. in the presence of an activated REFERENCES CTED carbon catalyst with a liquid feed to catalyst The following references are of record in the ratio of 0.1 to 10 v./v./hr, for a length of time file of this patent: to produce the desired dealkylated compound, 0 UNITED STATES PATENTS and removing from the reaction zone the gaseous products of the reaction as they are formed, Number Name Date comprising principally the dehydrogenated ali 2,168,840 Giroll ------Aug. 8, 1939 , the dealkylated aromatic com 2,222,632 Sachanen et al. ---- Nov. 26, 1940 pound, and parafin formed by split-off alkyl 2,223,133 Sachanen et al. ---- Nov. 26, 1940 groups combined with hydrogen from the alicyclic 2,257,920 Sachanen et al. ----- Oct. 7, 1941 compound. 2,425,559 Passino et al. ------Aug. 12, 1947