3,371,110 United States Patent Office Patented Feb. 27, 1968 1. 2 3,371,110 isions of these pores are such as to accept for adsorption (CATALYTC CONVERSION OF AROMATIC molecules of certain dimensions while rejecting those of CARBOXYLIC ACDS TO PHENOLS large dimensions, these materials have come to be known Eye A. Hamilton, Pitman, and Philip S. Landis, Wood as "molecular sieves' and are utilized in a variety of ways bEry, N.J., assignors to Mobil Oil Corporation, a cor 5 to take advantage of these properties. poration of New York The present invention, as aforesaid, involves the use No Drawing. Filed Jan. 29, 1964, Ser. No. 341,120. of such zeolitic materials (or isomorphs thereof) for the 17 Claims. (C. 260-476) purpose of catalytically converting aromatic carboxylic acids to phenols. More specifically, the present invention This invention relates to the catalytic conversion of aro O comprises the oxidation of an aromatic carboxylic acid matic carboxylic acids to phenols and, more particularly, to a corresponding ester of the carboxylic acid and the to such conversions involving the use of the novel catalytic subsequent hydrolysis of such ester to the desired phenolic materials. compound and the starting aromatic carboxylic acid, at As a result of the need for plentiful sources of phenolic least the oxidation reaction and preferably both the compounds, processes for the production of phenols uti 5 oxidation and the hydrolysis reactions taking place under lizing aromatic carboxylic acids as starting materials have reaction conditions in the presence of a solid, porous crys been developed. One such process involves the oxidation talline aluminosilicate catalyst or an isomorph thereof. of aromatic carboxylic acids to form the corresponding The starting materials of the present invention may esters of such acids and the subsequent conversion of such include any aromatic carboxylic acid. Such acid may con esters to the corresponding phenols through a hydrolysis tain either an aryl or a naphthyl nucleus (as exemplified, reaction, a by-product of the hydrolysis reaction being the for example, by benzoic acid, salicylic acid, tertiary butyl starting aromatic carboxylic acid. This process may be benzoic acids, toluic acids and naphthoic acids). Aromatic broadly represented by the following equations (wherein monocarboxylic acids containing biphenyl, bibenzyl or Ar represents an aryl radical): stilbene nuclei can also be converted to phenolic com (1) 2Ar COOH -- 1/2O2 - Air COO Air + H2O + CO2 25 pounds in accordance with the process of the present in (2) Air COO Air -- H2O - Air COOH - Aro H vention. The above process is ordinarily carried out in the pres Those acids found most useful in the carrying out of ence of a catalyst and, for practical purposes, prior art the process of the present invention are monocarboxylic investigators have restricted such catalyst to copper or to acids of the benzene series having at least one open posi a copper-containing material. 30 tion on the benzene ring adjacent to the point of attach In accordance with the present invention, it has now ment of the carboxyl group and in which any non-car been found that extremely advantageous results may be boxyl substituents are stable groups, such as phenyl, alkyl, obtained in the conversion of aromatic carboxylic acids to alkoxy, nitro, halogen, etc. Merely by way of example phenols using solid, porous crystalline aluminosilicates or of carboxylic acids which may be converted to phenols, isomorphs thereof. As will become apparent from the en 35 it is within the contemplation of the present invention suing description, while particularly advantageous results to convert benzoic acid to phenol; o-toluic acid to m are obtained with the use of copper-containing crystalline cresol; m-toluic acid to o- and p-cresol; p-toluic acid to aluminosilicate catalysts, the present invention is not so m-cresol; m-nitrobenzoic acid to p-nitrophenol; p-nitro restricted. benzoic acid to m-nitrophenol; p-chlorobenzoic acid to It is accordingly a primary object of the present inven 40 m-chlorophenol; p-methoxybenzoic acid to m-methoxy tion to provide a novel process for the conversion of aro phenol; p-phenylbenzoic acid to m-phenylphenol; 2,4-di matic carboxylic acids to phenols using solid, porous methylbenzoic acid to 3,5-dimethylphenol; etc. crystalline aluminosilicates or isomorphs thereof. Preferably, the starting aromatic carboxylic acid is it is another important object of the present invention utilized in liquid phase. Such acid may be liquefied either to provide a novel process for the conversion of aromatic 45 by melting it or by dissolving it in an inert medium such carboxylic acids to phenols involving the use of metal as water, benzene, toluene, xylene, biphenyl, phenyl ben cation-containing crystalline aluminosilicates or isomorphs zoate, hexachlorobutadiene, etc. Of the various organic thereof, preferred metal cations being copper, nickel and media which may be used for dissolving the acid, the pre uranium. ferred solvents are biphenyl for operations at or near at It is a further important object of the present invention mospheric pressure and toluene or benzene for operations to provide a novel method for synthesizing phenolic com at elevated pressures. pounds comprising oxidizing an aromatic carboxylic acid The aluminosilicates useable as catalysts in accordance to an ester thereof and subsequently hydrolyzing said with the present invention include a wide variety of posi ester to produce a phenolic compound and the initial aro tive ion-containing crystalline aluminosilicates, both matic carboxylic acid, at least the oxidation reaction tak 55 natural and synthetic. These aluminosilicates can be de ing place under oxidation reaction conditions in the pres scribed as a rigid three-dimensional network of SiO, ence of a solid, porous crystalline aluminosilicate or an and AlO4 tetrahedra in which the tetrahedra are cross isomorph thereof. linked by the sharing of oxygen atoms whereby the ratio These and further important objects and advantages of of the total aluminum and silicon atoms to oxygen atoms the present invention will become more apparent in con 30 is 1:2. The electrovalence of the tetrahedra containing nection with the following discussion and appended aluminum is balanced by the inclusion in the crystal of claims. a cation, for example, an alkali metal or an alkaline: Zeolitic materials, both natural and synthetic, in nat earth metl cation. This equilibrium cn be expressed by urally occurring and modified forms, have been demon formula wherein the ratio of Al to the number of the strated in the past to have catalytic capabilities for vari 85 various cations, such as Ca, Sr, Na2, K2 or Lia, is equal ous types of hydrocarbon conversion. Such zeolitic ma to unity. One cation may be exchanged either in entirety terials are ordered crystalline aluminosilicates having a or partially by another cation utilizing ion exchange definite crystalline structure within which there are a techniques as discussed hereinbelow. By means of such large number of small cavities which are interconnected 70 cation exchange, it is sometimes possible, or even de by a number of still smaller channels. These cavities and sirable, to vary the size of the pores in the given alumino channels are precisely uniform in size. Since the dimen silicate by suitable selection of the particular cation. The 3,371,110 3 4. spaces between the tetrahedra are occupied by molecules 0.9–-0.2Na2O: Al2O3 : wSiO2:yHO (VIII) of water prior to dehydration. wherein w is from 2.45 to 3.65, and y, in the hydrated A description of zeolites of the type useable in the form, is about 7. present invention is found in Patent 2,971,824, whose The formula for Zeolite S in terms of oxide mole ratios disclosure is hereby incorporated herein by reference. may be written as: These aluminosilicates have well-defined intra-crystalline dimensions such that only reactant or product molecules of suitable size and shape may be transported in either wherein w is from 4.6 to 5.9 and y, in the hydrated form, direction between the exterior phase and the interior of is about 6 to 7. the crystalline zeolite. O The formula for Zeolite T in terms of oxide mole ratios In their hydrated form, the aluminosilicates may be may be written as: represented by the formula: wherein M is a cation which balances the electrovalence wherein x is any value from about 0.1 to about 0.8 and of the tetrahedra, in represents the valence of the cation, y is any value from about 0 to about 8. w the moles of SiO2, and y the moles of HO, the removal The formula for Zeolite Z in terms of oxide mole ratios of which produces the characteristic open network system. may be written as: The cation may be any one or more of a number of posi (XI) tive ions as aforesaid, such ions being discussed in greater 20 detail hereinafter. The parent zeolite is dehydrated to wherein y is any value not exceeding 3. actuate it for use as a catalyst. Although the proportions The formula for Zeolite E in terms of oxide mole ratios of inorganic oxides in the silicates and their spatial ar may be written as: rangement may vary, effecting distinct properties in the 0.9-0.1M/nO: AlO:1.95+0.1SiO:yHaO (XII) aluminosilicates, the main characteristic of these materials is their ability to undergo dehydration without substan wherein M is a metal cation, n is the valence of the cation, tially affecting the SiO4 and AlO4 framework. In this re and y is a value of 0 to 4. spect, this characteristic is essential for obtaining catalyst The formula for Zeolite F in terms of oxide mole ratios compositions of high activity in accordance with the may be written as: invention.