US2355219A - Hydrogenation of aryl carboxylic acids - Google Patents

Description

' basic acids.

Patent ed Aug. 8, 1944 2,355,219 HYDROGENATI'ON or AnYncARBoxyLm ACIDS Vladimir N. Ipatiefl and Vladimir Haensel, Riverside, Ill., asslgnors to Universal Oil Products Company, Chicago, Ill.

ware

, a corporation oi Dela-,

I No Drawing. Application May 31, 1943, Serial No. 489,153

Claims. (01. 260-668) This invention relates to the use of particular catalytic materials in reactions involving hydrogenation of aryl carboxylic acids.

An object of this invention is the hydrogenation of aromatic carboxylic acids so as to produce therefrom aromatic hydrocarbons or alkylated aromatic hydrocarbons having the same number of carbon atoms per molecule as present in said aromatic carboxylic acids.

Another object of .this invention is the hydrogenation of an aromatic carboxylic acid in the presence of a catalyst produced by subjecting to reduction a composite formed from copper oxide and at least another oxide selected fromthe group consisting of aluminum oxide and zinc oxide whereby to convert the carboxylic acid group into a methyl group with substantially no other influence on the aromatic carboxylic acid.

A further object of this invention is the pro--' duction of an aromatic hydrocarbon by the hydrogenation of an aromatic monocarboxylic acid 1,2,4-trimethyl-5-benzoio.

in the presenceof a catalyst comprising essentially a composite or reduced copper and at least one 01. the oxides selected from the group consisting of aluminum oxide and zinc oxide.

A still further object of this invention is the hydrogenation ofa member selected from the group consisting oi. aryl carboxylicacids and anhydrides of aryl carboxylic acids to produce alkyl aryl compounds including alkyl aromatic hydrocarbons, alkyl aryl carbinols, aromatic esters, and aromatic carbonyl compounds such as aromatic aldehydes.

In one specific embodiment the present inven-- tion comprises a process for producing alkylated aromatic hydrocarbons by reacting an aryl car- 'boxylic acid and hydrogen in the presence of a catalyst comprising essentially a composite of reduced copper and at least one of the oxides" Aryl carboxylic acids which are utilizable as starting materials in the present process maybe obtained from any source and may comprise monocyclic and polycyclic aromatic carboxylic acids including both the monobasic and also poly- Aromatic carboxylic acids which may be hydrogenated'as herein set forth also include compounds in which one or more of the hydrogen atoms of an aromatic ring may be consldered to be replaced by an organic acid group generally referred to. as a carboxyl group. Aromatic carboxylic acids also include the aryl fatty acids such as phenyl acetic acid, the different isomeric phenyl propionic acids, etc. in which one of the hydrogen atoms of the alkyl vgroup 01' an Naphthalic Some aryl carboxylic acids Melting int Aromatic acids p0 Boiling point Mono-carbozulic "'C'. Benzoic o-Toluic..-

P o-Ethylbenzoic.-. m-Ethylbenzoic .mmyir 1,2-dimethy -3- 1,3-dimethy -2-benzoic 1,4-dimethy -2- benzoic o-n-Ptopyl bcnzoi cp-n-Propyl benzo1c o-iso-Propyl benzoic.

1,3,5-mesitylene carboxylic 1,2,3.4-tetramethyl-5-benzo1c. Pentamethylbenzoic Phenyl-fatiy acids Acid: of polycyclic aromatic:

a-Naphthoic a-Naphthoic B-Naphthyl Acetic B-Anthracene carboxylio a-Anthracene carboxylio Aromatic dicarbozwliq acids Phthalic.

lsophthalicn Terephthalic The process of the present invention is also aryl carboxylic acids. The products obtainable by such :hydrogenation treatment of these acid anhydrides are essentially the same as those produced by hydrogenation of the corresponding aryl carboxylic acid.

Composites of the above-indicated materials utilizable as.catalysts in the hydrogenation of aryl carboxylic acids and their anhydrides may be made by precipitating the carbonates of zinc .nium carbonate, at ordinary or elevated temperatures. Aluminum hydroxide may be precip tated similarly either in the presence or absence of the carbonates of copperand zinc. The pre-' cipitated material so obtained is filtered, care-'- For purposes of reference some of the aromatic fully washed with water to remove water soluble and to reduce a substantial proportion of the resulting copper oxide to metallic copper in a form having relatively high hydrogenating activity. The metal carbonate may also be decomposed by heating in air prior to being heated in hydrogen to efiect reduction.

The composite catalytic material may also be prepared by coprecipitating copper carbonate, zinc carbonate, and/or aluminum hydroxide; or for the preparation of a copper oxide-zinc oxidealuminum oxide mixture, the zinc carbonate may be first precipitated on alumina followed by precipitation of the basic copper carbonate on the mixture. The proportions of the various components may be varied considerably. A good catalyst is prepared containing 25 parts by weight of zinc, 25 parts by weight of copper, and 50 parts by weight of alumina; while others: consist of approximately equal parts by weight of zinc, copper, and alumina. Similarly, composites of copper and alumina also yield highly active catalysts which after reduction with a hydrogencontaining gas comprise essentially copper and alumina, said composites containing from about 1 to about 50% by weight of alumina mixed with reduced copper.

The catalyst granules or pellets of the type hereinabove described may be used as filling materials in suitable heated reactors through which the aryl carboxylic acid and hydrogen are passed at a temperature of from about 200 to about 350 C. and under a pressure of from about 25 to about 300 atmospheres. Under some circumstances it-may be advantageous to commingle the aryl carboxylic acid with a solvent such as ethyl alcohol, dioxane, etc. before it is subjected to hydrogenation in the presence of the catalyst. However, when analcohol is present in the reaction mixture, some of the carboxylicacid may" react therewith to form an ester. As the conditions of operation are not necessarily the same for the hydrogenation of the different aryl carboxylic acids, the catalyst temperature. charging rate of said carboxylic acid, and ratio of hydrogen to carboxylic acid employed are chosen to give a high degree of conversion to alkylated aromatic hydrocarbons with a relatively small or it may be mixed with the hydrogen in a so-- called fluidized type of operation; and thereafter the hydrogen-catalyst mixture may be contacted with pre-hea'ted aryl carboxylic acid. After such a hydr igenation treatment in the presence of a powdered catalyst the reaction products are separated from the catalyst and fractionated to recover the desired products and to separate unconverted aryl carboxylic acid and used catalyst which are recycled to the reaction zone for further use. 'A powdered catalyst may thus be used in either batch or continuous hydrogenation of an aryl carboxylic acid.

The process of this invention is particularly advantageous for producing aromatic hydrocarbons from aryl carboxylic acids since the composite catalyst containing copper and at least one of the oxides selected from the group consisting of aluminum oxide and zinc oxide is able to catalyze the hydrogenation of the carboxylic acid group to a methyl group without simultaneous hydrogenation of the aromatic ring or aromatic rings to naphthenic or cyclohexane rings. A number of catalysts of the prior art have been utilized in hydrogenations of aryl carboxylic acids, but with these catalysts the aromatic rin underwent reduction to a cycloparafiin ring which is generally referred to as a naphthene ring. The catalysts of the present process, however, are sufficiently active to catalyze the conversion of the carboxyl group or carboxyl groups, in case a polycarboxylic acid is being hydrogenated, substantially without afiecting the aromatic nucleus of the aryl carboxylic acid.

' erally hard and resistant to breakage, have relaof aromatic acids.

as after a long period of service, it is usually ad- .lowed to cool and settle.

tively high activities, and do not undergo excessive carbonization during use in hydrogenation When carbonization occurs,

visable to burn the carbonaceous deposit from the catalyst by treatment with a gas of controlled oxygen concentration followed by heating in a reducing gas such as hydrogen, carbon 'monoxide, a mixture of hydrogen and carbon monoxide; Or a gas mixture containing a substantial amount of a reducing gas.

The following examples are given to indicate results obtained by the process although these data are not introduced with the intention of unduly limiting the generally broad scope of the in 12 liters of water. Another solution was prepared by dissolving 770 grams of ammonium carbonate monohydratein 5 liters of water. Then the ammonium carbonate solution was added slowlywith stirring to the solution containing copper nitrate and aluminum nitrate. Upon completion of the precipitation the entire reaction mixture containing precipitated copper carbonate and aluminum hydroxide was heated at 70 to C. during a period of between 0.5 and 1 hour. Upon reaching 80 C. the heating was discontinued and the precipitate was al- Then approximately 12 liters of solution were decanted from the precipitate which was then washed by the addition of 12 liters of distilled water. This procedure of washing by decantation was repeated four times and finally the precipitate was separated from the wash water by filtration with suction. The filter cake so obtained was washed again with 2 liters of water and separated by filtration. The washed catalyst was then dried at 240 C. during 13 hours in a self-regulating drying oven. The dried material so obtained had a dark brown color and weighed approximately 500 grams.

water.

The dried material was then reduced and of the material was placed in a glass tube heated in a horizontal furnace. A mixture of 2 volumes of nitrogen and 1 volume ofhydrogen was passed over the catalyst at a temperature of 1'70 to 180 C. during 48 hours after which the reduction was complete as evidenced by the fact that water was no longer present in the eflluent gases. The mixture of nitrogen and hydrogen was then displaced by nitrogen and thereafter a mixture of 60% nitrogen and 40% air was passed over; the reduced material at room temperature for approximately 12 hours. The resultant material which was black in color was a stabilized active catalyst.

4 70 grams of benzoic acid, 63 grams of ethyl alcohol, and 15 grams ofthe above-described reduced and stabilized copper-alumina catalyst were placed in a rotatable steel autoclave, hydrogen was added to 100 atmospheres initial pressure, and the resultant reaction mixture was The predominant reaction was the formationof stabilized as follows. Approximately 300 grams heated and rotated at 300 C. for a period of 4 hours. After this treatment, the autoclave and contents were cooled to room temperature and the reaction product was removed and analyzed. The reaction product consisted of toluene and ethyl benzoate in the respective yields of 39% and 30% of the theoretical based upon thereduced and stabilized copper-alumina catalyst described in Example I were placed in a steel autoclave to which hydrogen was added to 100 atmospheres initial pressure, and the reaction mixture was then heated to 300 C. for four hours. The reaction product contained toluene in a yield of 41% of the theoretical together .with small amounts of benzyl benzoate, benzaldehyde, and benzyl alcohol. Since the benzyl benzoate, benzaldehyde, and benzyl alcohol are apparently intermediates in the formation of toluene from benzoic acid, it is believed that the yield of toluene would'have been increased appreciably by increasing the time of treatment with hydrogen at the reaction temperature.

The results'of this'example show that the hy drogenation is selective and does not involve 'the ployed.

4 Example III 80 grams of phthalic .anhydride and 15 grams of the reduced and stabilized copper-alumina catalyst described in Example I were placed in a steel autoclave of 850 cc. capacity under an initial hydrogen pressure of 150 atmospheres and heated to 300 C. for five hours. The 79.6 grams of recovered liquid product contained 8 ams of The liquid product was dried and was then separated by fractional distillation into the following fractions having the properties indicated. I

' Refractive Per cent by Fraction No. Boiling point, G. volume index Total 100.0

orthoxylene although some toluene was also formed. The foregoing specification and examples indicate the character and value of the present process, althoug'h it is not intended that either section should unduly limit the generally broad scope of the invention.

We claim as our invention: a

1. A process for producing alkyl aryl compounds which comprises reacting hydrogen and a member selected from the group consisting of aryl carboxylic acids and anhydrides' of aryl carboxylic acidsunderhydrogenating conditions in the presence of a catalyst produced by subjecting to reduction a composite comprising copper oxide and at least another oxide selected from the group consisting of aluminum 'oxide and zinc oxide.

2. A process for producing alkyl aryl compounds which comprises reacting hydrogen and an aryl carboxylic acid under'hydrogenating conditions in the presence of a catalyst produced by subjecting to reduction a composite comprising copper. oxide and at least another oxide selected from the group consisting of aluminum oxide and zinc oxide.

3. A process for producing alkyl aryl compounds which comprises reacting hydrogen and an anhydride of an aryl carboxylic acid under hydrogenating conditions in the presence of a catalyst produced by subjecting to reduction a composite comprising essentially copper oxide and at least another oxide selected from the group consisting of aluminum oxid and zinc oxide.

4. A process for producing an alkyl aromatic hydrocarbon which comprises hydrogenating an aryl carboxylic acid in the presence of a' catalyst produced lay-subjecting to reduction a composite comprising essentially copper oxide and at least another oxide selected from the group consisting V of aluminum oxide and zinc oxide.

hydrocarbon which comprises reacting an aryl carboxylic acid and hydrogen at a temperature of from about 200 to about 350 C. in the presenc of acatalyst produced by subjecting to reduction a composite comprising essentially copper oxide and at least another oxide selected from the group consisting of aluminum oxide and zinc oxide.

6. A process for producing an alkyl aromatic hydrocarbon which comprises reacting an aryl carboxylic acid and hydrogen at a temperature of from about 200 to about 350C. under a pressure .of from about 25 to about 300 atmospheres in the presence of a catalyst produced by subjecting to reduction a composite comprising essentially copper oxide and at'least another oxide selected from the group consisting of aluminum oxide and zinc oxide.

7. A process for producing an alkyl aromatic hydrocarbon which comprises reacting an aryl carboxylic acid and hydrogen at a temperature of from about 200 to about 350 C. under a pressure ofirom about 25 to about 300 atmospheres in the presence of a catalyst produced by subjecting to reduction a composite comprising essentially a major proportion by weight of copper oxide and a relatively minorv proportion of at of from about 200 to about 350 C. under a pres sure of from about 25 to about 300 atmospheres in the presence or a catalyst produced by subjecting -to reduction a composite comprising essentially copper oxide and aluminum oxide.

sentially copper oxide, zinc oxide, and aluminum oxide.

10. A process for producing an alkyl aromatic hydrocarbon which comprises reacting an aryl carboxylic acid and hydrogen at a temperature of from about 200 to about 350 C. under a pressure of from about 25 to about 300 atmospheres in the presence of a catalyst produced by subjecting to reduction a composite comprising esio esentially copper oxide and zinc oinde.

VLADIMIR N. IPATIEFF. VLADIMIR HAENSEL.