1. Field of the Invention

This invention relates to an improved process for the acid-catalyzed conversion of a reactant into a reaction product. Reactants which may be converted into reaction products in the process of this invention include hydrocarbons and heteroatom-substituted hydrocarbons, wherein said heteroatoms may be selected from the group consisting of nitrogen, oxygen, sulfur, phosphorus and halogen atoms. For example, in the present inventive process, olefins may be reacted with tertiary alkanes to provide alkylated products; olefins may be reacted with carboxylic acids to obtain esters; alcohols may be dehydrated to obtain olefins or ethers or reacted with an aromatic compound or a carboxylic acid to obtain an alkylated product or an ester, respectively; anhydrides may be reacted with an aromatic or an olefinic compound to obtain acetylated derivatives thereof; epoxides may be reacted to the corresponding glycols; etc.

2. Background of the Art

Many chemical reactions are catalyzed by acidic catalysts. The acidic catalyst may be used in a homogeneous or heterogeneous mode, i.e. the catalyst can be dissolved in the reactant-containing solution or the catalyst may exist in a different phase than the reactant and/or the reaction products. Homogeneous acid catalysts may have certain advantages over heterogeneous acid

catalysts, such as increased activity or selectivity, provided separation of the reaction products from the catalyst is easily carried out. Since such separation may be difficult, many times a heterogeneous acid catalyst is preferred, even if when the activity or selectivity is less than a homogeneous catalyst in the same reaction. One widely used class of heterogeneous acid catalysts is the solid polystyrene sulfonic acids. These polymers are known to be effective as acid catalysts for many rections, but, due to the organic polymer backbone, are not always as stable as desired. Moreover, the organic nature of the polymer may hinder polar reactants from contacting the functional sulfonic acid sites. In addition, the well known high temperatures utilized to remove such organic tars from inorganic acid catalysts, such as zeolites, of course, cannot be used to reactivate polystyrene sulfonic acids because of the thermal instability of the organic polymer backbone.

SUMMARY OF THE INVENTION

The present invention provides a process for the conversion of a reactant into a reaction product in the presence of an acid catalyst which comprises contacting said reactant with an acid catalyst comprising a compound represented by the general formula

wherein X is selected from the group consisting of oxygen, sulfur or represents 2 hydrogen atoms; Z is the anion of a strong acid, 'and preferably Z is selected from the group consisting of chloride, bromide, bisulfate, nitrate or dihydrogen phosphate; R is hydrogen or a lower alkyl radical having from one to four carbon atoms; R is hydrogen or a methyl radical; m.is an integer of from 2 to 6; n is 0 or 1 and o is 0 or an integer of from 1 to 17, at reaction conditions, and recovering a reaction product.

Preferably, X is oxygen, Z is bromide, R is methyl, R ¹ is hydrogen and n is 0. More preferably, m is 4 and o is an integer of from 1 to 17, e.g. an integer of from 5 to 11. Most preferably, o is 11. Thus, the most preferred acid catalyst comprises n-dodecyl- azacycloheptan-2-one, e.g. as the HBr salt.

DESCRIPTION OF THE INVENTION

This invention provides an improved process for converting reactants, especially organic reactants, to reaction products in the presence of an acid catalyst. The improvement in said process is found in the choice of the compounds which function as the acid catalyst and are defined below. In particular, these compounds increase the rate, of reaction, as compared to other well known acid catalysts, e.g. polystyrene sulfonic acids, (which comprises sulfonic acid groups pendant from a polystyrene polymer backbone) and are more stable with time and temperature, as compared to said polystyrene sulfonic acid catalysts.

Preferably, the reactants utilized in the process of this invention are hydrocarbons or hydrocarbons substituted with heteroato s such as nitrogen, oxygen, sulfur, phosphorus and halogen atoms; and especially oxygen atoms.

In another embodiment of this invention, the olefin is contacted with the acid catalyst, described below, in the presence of another reactant to yield reaction products of said olefin and said other reactant. Thus, said second reactant may include a hydroxyl group to yield an ether or an alcohol. For example, alkanols having from one to four carbon atoms may be reacted with olefins having from two to seven carbon atoms in the presence of the acid catalysts described below to yield ethers. Particularly preferred is the reaction of methanol and isobutylene, isoa ylene or propylene to yield methyl- tertiary butyl ether, methyl-tertiary amyl ether or methyl isopropyl ether, respectively. Such reactions may take place at a temperature of from 15 to 200°C. and a pressure of from 1 to 10 atmospheres.

Olefins may also be contacted with a carboxylic acid in the process of this invention to yield esters. Thus,

straight chain olefins, having from two to ten carbon atoms, isobutylene or cyclohexene may be reacted in the presence of carboxylic acids having from one to eight carbon atoms at a temperature within the range of 0°C. to 100°C. to yield the corresponding esters as the reaction product. U.S. Patent 3,037,052 to Bortnick gives the details on this general reaction and is hereby incorporated by reference to show specific reactants and reaction conditions. Particularly preferred reactions, within this embodiment of the present process, include the reaction of monoolefins having from one to eight carbon atoms, more preferably from two to four carbon atoms, with methacrylic acid, acrylic acid, acetic acid or phthalic acid to obtain the corresponding esters. These esters of acrylic acid and methacrylic acid are useful monomers for the preparation of acrylic plastics and rubbers. The acetate esters, of course are useful as solvents. The phthalic esters are useful as plasticizers.

Other reactants useful in the process of the present invention include alcohols. Thus, in one embodiment of the invention, alcohols having from one to eight carbon atoms, more preferbly from one to four carbon atoms, are reacted, in the presence of the acid catalyst described below, to yield either ethers or olefins (by dehydration). For example, methanol or ethanol may be reacted at a temperature of from 40° to 100°C and a pressure of from 1 to 5 atmospheres to yield dimethyl ether or diethyl ether, respectively. Tertiary butanol may be dehydrated to isobutene at a temperature of from 40°to 100 ^Q C. Similarly, butanediol may be dehydrated to tetrahydrofuran.

Like the olefin, alcohols may be reacted in the presence of a second reactant to provide reaction products of said alcohol and said second reactant. In particular, said second reactant may comprise a carboxylic acid group

or an aromatic group to yield an ester or an alkylated aromatic, respectively. The reactants and the conditions for these reactions have been described above.

Another reactant that may be used in the process of the present invention is an anhydride. For example, anhydrides, such as acetic anhydride, may be reacted with a compound having an aromatic group or an olefinic group to yield acetylated aromatics or acetylated olefins, respectively. In particular, acetic anhydride may be reacted with anisole to provide p-methoxyacetophenone or with diisobutylene to provide 2,2-methyl, 6-oxo-hept-4- ene. These reactions can be carried out at a temperature of from 40° to 100°C and a pressure of from 1 to 5 atmospheres.

Aldehydes or ketones may be condensed to provide the respective condensed products by means of the process of the present invention. For example, 2-ethylhexenal may be prepared by condensing two molecules of n-butyraldehyde at a temperature of from 40° to 100°C and a pressure of from 1 to 5 atmospheres. Similarly, methylisobutyl ketone may be condensed to l-methyl-4-methyl-6-oxo-9-methylnon-4-ene. In general, aldehydes and ketones, having from one to ten carbon atoms,may be condensed to provide dimers thereof in the process of the present invention. In addition, the above aldehydes and ketones may be reacted in the presence of-an aromatic compound to obtain the resulting reaction products. In particular, acetone may be reacted with phenol to yield bisphenol A and formaldehyde may be reacted with aniline to yield diaminodiphenylmethane.

In addition, the above aldehydes and ketones may be reacted in the presence of an aromatic compound to obtain the resulting reaction products. In particular, acetone may be reacted with phenol to yield bisphenol A and formalehyde may be reacted with aniline to yield diaminodiphenylmethane.

Peroxides or hydroperoxides may be decomposed to the corresponding decomposition products by the process of this invention. For example, cumene hydroperoxide may be decomposed to acetone and phenol at low temperatures as compared to the non-acid catalyzed decomposition. Moreover, unlike the prior art polystyrene sulfonic acid catalysts, which are sensitive to heat (and thus the reacto must be designed to remove heat and avoid catalyst degradation), the acid catalysts of this invention are not heat sensitive.

Glycols may be prepared by utilizing an epoxide as the reactant in the process of the present invention. In particular, ethylene oxide and propylene oxide may be converted to ethylene glycol and propylene glycol, respectively.

Esters may be converted, efficiently, to carboxylic acid and alcohol in the present inventive process. Similarl acetals may be hydrolyzed by this process. For example, sucrose may be hydrolyzed to fructose and glucose. It is important to note that all of the above examples of reactants, reaction products and reaction conditions are known in the art. The present invention resides in the improvement to such process examples by use of the compounds described below, in detail, as the acidic catalyst to obtain increased rates of reaction, on an equivalent acid basis, as compared to other known catalysts, such as polystyrene sulfonic acid.

Methods for the preparation of the azacycloalkane moiety of the above acid catalysts are found in U.S. Patents 3,989,815; 3,989,816; 3,991,203; 4,122,170; 4,316,893; 4,405,616; 4,415,563; 4,423,040; 4,424,210; and 4,444,762, and U.S. Patent Applications Serial Nos. 824,436; 824,845 and 825,041, all filed on January 31, 1986 and all entitled "Compositions Comprising 1- Substituted Azacycloalkanes", which are herein

incorporated by reference. These azacycloalkanes are converted into the corresponding quaternary amine salt by reacting with a strong acid, e.g. hydrogen bromide. In particular, such reaction may be carried out as follows:

Gaseous hydrogen bromide is bubbled through a solution of l-(n-dodecyl)-azacycloheptan-2-one in diethyl ether to provide an immediate white precipitate. Upon saturation of the organic solution with hydrogen bromide, the resultant suspension is filtered and the solid washed with diethyl ether. This is then dried under vacuum to give the hydrogen bromide salt of l-(n-dodecyl)- azacycloheptan-2-one.

The above acid catalysts are also useful as acid sources. These salts are stable, non-hygroscopic solids which are useful replacements for solid acid sources known in the prior art. Since they are of known stoichiometric composition, the exact equivalent of any desired amount of acid may be conveniently weighed and safely handled. This offers significant advantage over acid solutions, which are hazardous and must be titrated to determine exact acid content.

As acid sources, examples of the above salts' utility are removal of oxide impurities from a vapor-deposited semi-conductor coating, cleaning metals ranging from solder fluxing agents to household cleaners for plumbing fixtures by the dissolution of inorganic deposit without significantly attacking the base metal, and dissolution of various oxides present in the mill scale formed in the hot rolling process (steel pickling). Thus, these agents function as acid inhibitors. Other processes include converting lignocellulose to hexose and pentose, preparing invert sugar by reaction with a sucrose solution, hydrolyzing starch to obtain sugar syrups, cleaning chemical process equipment including austenitic stainless steel parts in, for example, supercritical steam

generators and nuclear power systems, removing from equipment coritaminanδs such as wax from crude oil, tars from coal distillation, oil and grease used for lubrication, special grease-type preservatives used as protective coatings, cleaning and lubricating drilling bits, etc.

The "parent" compounds of the above acid salts are useful as acid scavengers. Thus, for example, excess acid may be removed from acid-washed equipment, acid burns may be treated with these non-toxic agents, trace amounts of acid unacceptable to chemical processes may be precipi¬ tated from the reaction solution with these agents, etc.

The invention is further illustrated by the following examples which are illustrative of various aspects of the invention, and are not intended as limiting the scope of the invention as defined by the appended claims.

Example 1 Dehydration of Alcohols

In this reaction, the reaction rate is monitored by measuring the flow of the olefin, i.e. isobutylene, which is a reaction product arising from the dehydration of tertiary-butanol according to the reaction:

t-C ₄ H _g OH _> i-C ₄ H ₈ + H ₂ 0

in the presence of the acidic catalyst described below. A small, continuous flow of isobutylene is maintained in the reactor to provide a positive pressure, as well as to initially saturate the t-butanol. (Due to the high

solubility of isobutylene in t-butanol, pressurization is required; otherwise, the reaction products, i.e. isobutylene, would dissolve in the reactant, i.e. t-Butanol, and would not be observed. The reaction rate is monitored continuously and is the difference between the outlet isobutylene flow and the inlet isobutylene flow.)

To a 500 ml. flask, 100 g. grams of the catalyst described below is then added to initiate the dehydration reaction and the resulting two-phase mixture is agitated.

The isobutylene evolved from the t-butanol is measured as a function of time and is taken as an indication of reaction progress; with time = 0 taken as the point at which the catalyst is added to the tertiary- butanol. An induction period is observed, after which the reaction rate increases to a maximum and, over a long period of time, the catalyst activity declines as the tertiary butanol becomes rich in reaction product water. The water accumulates at the acid site, thereby "levelling" the acidity.

Example 2 In this example, the reaction between isobutylene and acetic acid to give tertiary-butyl acetate is catalyzed by the. acid catalyst of Example 1. This is accomplished either batchwise or in a continuous flow reactor. At a 2.4 to 3.3 mole ratio of acetic acid to isobutylene, 85 percent conversion to t-butyl acetate, based on isobutylene, is achieved utilizing a fixed bed reactor and 9-10 minutes contact time. Polymerization is not significant as only from a trace to 1.6 percent of CgH ₁₆ is detected. The reaction conditions for this reaction is described in U.S. Patent 3,678,099 to Kemp, which is hereby incorporated by reference.

While particular embodiments of the invention have been described it will be understood of course that the invention is not limited thereto since many obvious modifications can be made and it is intended to include within this invention any such modifications as will fall within the scope fo the appended claims.