Process for alkylating aromatic hydrocarbons with synthetic hectorite-type clay catalyst

#This invention relates to a process for the liquid phase alkylation of aromatic hydrocarbons in which the catalyst comprises certain cation-exchanged synthetic hectorite-type clays. More particularly, the present invention is concerned with a method wherein an aromatic hydrocarbon, e.g. benzene, and an alkylating agent, e.g. an olefin, are reacted in the liquid phase in the presence of a catalyst which comprises a synthetic hectorite-type mineral which has a metal cation having a Pauling electronegativity greater than 1.0 in ion-exchange positions on the surface of the clay particles, and in which the central octahedral layer contains one or more divalent metals having an ionic radius not greater than 0.75 A as more particularly described hereinafter. Alkylated aromatic hydrocarbons have many uses depending on their molecular weight and structure. Thus low molecular weight alkylbenzenes are useful in high octane gasolines and high molecular weight alkylbenzenes are useful as intermediates in the production of alkylbenzene sulfonate detergents.

#It has been reported that various materials containing acidic catalytic sites are useful in catalyzing the reaction between aromatic hydrocarbons and various alkylating agents such as olefins and alkyl halides. See for example: The Kirk-Othmer Encyclopedia of Chemical Technology, 2nd Edition, Vol. 1, pp. 882-901 (1963); "Alkylation of Benzene with Dodcene-1 Catalyzed by Supported Silicotungstic Acid," R. T. Sebulsky and A. M. Henke, Ind. Eng. Chem. Process Res. Develop., Vol. 10, No. 2, 1971, pp. 272-279; "Organic Molecule and Zeolite Crystal: At the Interface," P. B. Venuto, Chem. Tech., April, 1971, pp. 215-224; "Catalysis by Metal Halides, IV. Relative Efficiencies of Friedel-Crafts Catalysts in Cyclohexane-Methylcyclopentane Isomerization, Alkylation of Benzene and Polymerization of Styrene", G. A. Russell, J. Am. Chem. Soc., Vol. 81, 1959, pp. 4834-4838.

#It has also been proposed to use various modified clays as catalysts in various acid catalyzed reactions such as alkylation, and the like. See for example the following U.S. Pat. Nos.: 3,665,778; 3,665,780; 3,365,347; 2,392,945; 2,555,370; 2,582,956; 2,930,820; 3,360,573; 2,945,072; 3,074,983. The latter patent is the only patent known to me which discloses the use of hectorite clay as a catalyst. Other references which disclose the use of clays as catalysts are as follows: "Acid Activation of Some Bentonite Clays", G. A. Mills, J. Holmes and E. B. Cornelius, J. Phy. & Coll. Chem., Vol. 54, pp. 1170-1185 (1950); "H-Ion Catalysis by Clays", N. T. Coleman and C. McAuliffe, Clays and Clay Minerals, Vol. 4, pp. 282-14 289 (1955); "Clay Minerals as Catalysts:", R. H. S. Robertson, Clay Minerals Bull. Vol. 1, No. 2, pp. 47-54 (1948); "Catalytic Decomposition of Glycerol by Layer Silicates", G. F. Walker, Clay Minerals, Vol. 7, pp. 111-112 (1967); "Styrene Polymerization with Cation-Exchanged Alumino-silicates", T. A. Kusnitsyna and V. M. Bromolko, Vysokomol. Soedin., Ser. B1968, Vol. 10, No. 10, pp. 776-9 -- see Chem Abstracts 70:20373x (1969); "Reactions Catalyzed by Minerals. Part I. Polymerization of Styrene:, D. H. Solomon and M. J. Rosser, J. Applied Polymer Science, Vol. 9, 1261-1271 (1965).

#Various cation exchanged forms of the natural mineral hectorite were prepared as follows: The exchange cation salt was dissolved in 500 to 750 ml. of methanol. Hectorite clay which had been previously dispersed in water, centrifuged, and spray dried in order to obtain the purified clay, was mixed in this salt solution at a concentration of 300 milliequivalents of cation per 100 grams of clay. This mixture was allowed to stand for approximately 20 hours before it was filtered. The filter cake was re-dispersed in 500 - 750 ml. of methanol followed by filtration for a total of 3 successive washings. The cation exchanged hectorite was then air dried for 20 hours at room temperature followed by oven drying at 105.degree. C. for 2 hours. The clay obtained by this process was very fine and needed no grinding. In the case of Ag.sup.+ -hectorite, 10 ml. of concentrated nitric acid was added to the methanol solution before adding the clay to the solution, in order to prevent oxide formation or hydrolysis of the Ag+.

#These cation exchanged hectorite clays were evaluated as catalysts for the alkylation of benzene using the following procedure: 10 grams of the cation exchanged hectorite and 200 - 250 ml. of benzene are refluxed in a round bottom flask equipped with a Dean-Stark tube attached to remove, azeotropically, sorbed water from the clay. After 2 - 4 hours the tube was removed and the reflux condenser rinsed with methanol and air dried to remove any residual moisture trapped in the condenser. 10 grams of the alkylating agent was added to the flask and the mixture refluxed with stirring for 24 hours. The clay was removed by filtration and washed with 100 ml. of benzene. The benzene was removed from the filtrate by vacuum evaporation leaving a product of unreacted alkylating agent and/or alkylbenzene. This product was then weighed and analyzed by either infrared spectrophotometry, refractometry, or gas chromatography to determine the amount of alkyl-benzene formed. The cation exchanged hectorites evaluated and the data obtained are given in Table 1.

#The data indicate that the natural hectorite clay containing exchanged metallic cations having a Pauling electronegativity less than or equal to 1.0 were ineffective as catalysts for the alkylation of benzene. Metallic cations having a Pauling electronegativity greater than 1.0 were effective catalysts when exchanged onto hectorite. These include Be.sup.2+ and Mg.sup.2+ (Group IIA), Al.sup.3+ and In.sup.3+ (Group IIIA), La.sup.3+ (Group IIIB), Cr.sup.3+ (Group VIA), Mn.sup.2+ (Group VIIB), Fe.sup.3+, Co.sup.2+, Ni.sup.2+ and Pd.sup.2+ (Group VIII), Cu.sup.2+ and Ag.sup.+ (Group IB), and Ce.sup.3+ (rare earths). The effect of moisture within the reaction zone on the activity of certain of the catalysts can be ascertained by reference to the data for Examples 1, 4 and 6. The small amount of water which remained in the reflux condenser (Examples 1,6) or in the atmosphere (Example 4) was sufficient to decrease the activity of Al.sup.3+ -exchanged hectorite approximately 50%, whereas In.sup.3+ -exchanged hectorite was very active in the presence of such small quantities of water.