US2087691A - Process of catalytically hydeogen - Google Patents

Description

Patented July 20, 1937 UNITED STATES ATENT OFFICE PROCESS OF CATALYTICALLY HYDROGENL. ATING PHENOLS Wilbur A. Lazier, New Castle County, DeL, as. signor to E. I. du Pont de Nemours & Company, ton, Del, a corporation of Delaware No Drawing. Application May 21, 19:5 1 Serial No. 22.559

26 Claims. (01. 269-153) This invention relates to processes for the cata- 5 nols to the corresponding cyclic secondary alcohols by means 01' catalysts consisting of hydrogenating metals or their oxides admixed with or chemically combined with more acidic oxides. Specifically, this invention relates to the hydrogenation of phenols with chromite catalysts.

This application is a continuation in part of my co-pending applications Serial No. 456,298 filed May 27, 1930, and Serial No. 715,509, filed March 14, 1934.

Considerable work has been done in the field of catalysis with a view to developing emclent materials for the hydrogenation of such unsaturated compounds as the olefines. unsaturated fats and fatty acids, benzene and its derivatives,

and a large number of other compounds containing unsaturated functions; such as the nitro compounds, nitriles, and heterocyclic unsaturated ring-compounds. Most of this work has been based on the classical discovery of Sabatier that finely divided metallic nickel is capable of causing the union of hydrogen with these compounds. The method has been further expanded and supplemented by the work of Ipatief onthe application of high pressures to these reactions.

Extensiveresearch has been carried out heretofore with the result that several different modifications of the preparation of hydrogenation catalysts have been developed, the most common of which involve the precipitation and reduction of nickel or copper hydroxides or carbonates, re-v duction of nickel and copper oxides prepared by ignition of the nitrates, anodic oxidation followed by reduction, heating to their decomposition temperatures of certain organic saltsof hydrogenating metals, the 1 chemical erosion of alloys, and electrochemical deposition of hydrogenating metals.

.' Furthermore, various methods .of reductionv have been proposed, ranging from the ordinary dry reduction with hydrogen to reduction in an inert liquid vehicle or in the presence of the oil or other substance undergoing hydrogenation.

The nuclear hydrogenation ofphenols generalhas been practised for many years in themanufacture of cyclohexanol from phenol. The proc ess'may be carried out in the vapor phase as first described by Sabatier (Catalysis in Organic 55 Chemistry, Sabatier-Reid, 1923, page 166) or in decomposition temperature.

, 1y is by no means a new process. In fact, it.

the liquid phase as outlined by Brochet (U. S. 1,247,629).

In either case the catalyst consists of metallic nickel prepared by reduction of the oxide or carbonate. Phenols have also been hydrogenated 5 in the presence of the oxides and sulfides of chromium molybdenum, and tungsten for the purpose of converting them into the corresponding aromatic hydrocarbons. So far as I am aware, no one has heretofore succeeded in e1- 10 fecting the nuclear hydrogenation of a phenol in the presence of a diflicultly reducible oxide catalyst or a reducible oxide maintained in an unreduced condition. In fact, Connor and Adkins (J. A. C. S. 53, 1094 (1931)) have recently stated 15 that the copper chromite catalyst is not active towards cyanides' or towards benzene nuclei and thus ofiers a means of selective hydrogenation of compounds containing these groups which are otherwise readily reducible over nickel catalysts. They state further that toluene, phenol, aniline, and furoic acid could not be hydrogenated under the conditions described for the hydrogenation of (other) compounds".

Contrary to this statement, it has now been found according to the present invention that chromite catalysts are effective agents for use in the nuclear hydrogenation of phenols and make possible the application of the inherent advantages of these catalysts to an important class of hydrogenation reactions. According to the present invention a large number of monoe nuclear and polynuclear phenols may be hydrogenated to the corresponding secondary alcohols in th presence of copper'chromite and reduced 85 nickel chromite.

This invention, accordingly, has as an objectto carry out the catalytic hydrogenation of phenols by the use of highly eflicient hydrogenating metal or metal oxide catalysts promoted by the addition of acidic oxides such as chromium oxide. A further object is to provide a. process for the hydrogenation of phenols in either liquid or vapor phase by the use of catalysts prepared by heating a multiple chromate of a hydrogenating metal and a nitrogen base to its spontaneous It is a specific object to carry out the hydrogenation of phenols by the use of reduced chromite catalysts derived from double chromates of ammonia and a hydrogenating metal. Other objects will appear hereinafter.

, This inventionin its general aspects comprises the employment in-the liquid or gas phase 1 hydrogenation of phenols, oi catalysts prepared 55 by associating or chemically combining hydrogenating metal oxides with acidic metal oxides. Thecatalyst compositions utilized in'accordance with the present invention may consist of purely physical mixtures. They may, on the other hand, consist of complex salts containing the hydrogenating oxide and the acidic promoter oxide in chemical combination. Thus, within the scope of the invention are included such compositions as mixtures of copper oxide and chromium oxide, and compounds such as copper chromite.

The specific nature and purpose of the invention requires that the catalytic mass contain an acidic metal oxide associated with or combined with a hydrogenating metal and/or metal oxide. The preparation of catalysts suitable for use in the present invention conforms generally to the following methods which will be illustrated by nickel-chromium oxide catalysts. It will be understood that these methods may be applied in the same way to the preparation of catalysts containing hydrogenating metals other than nickel or their oxides, and containing acidic oxides other than chromium oxides. The illustrative methods of preparation of the catalysts are as follows:

(1) The hydrogenating metals or their oxides may be simply mixed with the acidic oxides in any desirable proportions, thus equal parts of nickel oxide and chromium oxide may be admixed to form a suitable catalyst.

(2) Concentrated solutions of nickel chloride and neutral ammonium chromate are permitted to react at room temperature. Upon standing, a green crystalline salt of nickel ammonium chromate is formed. The solution is filtered with suction and the precipitate dried and heated slightly to start the decomposition reaction, which thereafter proceeds spontaneously with the evolution of sufiicient heat to leave a glowing residue probably consisting of combined nickel oxide and chromium oxide. This composition may be subsequently further reduced with hydrogen to produce the desired catalyst.

(3) Two-molar solutions of nickel nitrate and ammonium chromate are mixed in equivalent amounts and heated to boiling, whereupon a brlck-recLprecipitate of basic nickel ammonium chromate is separated. Ammonia may be added to neutralize the acid solution formed by the precipitation and greatly improves the yield. As in method (2), the double ammonium compound is heated slightly to occasion spontaneous decomposition and the resulting ignited product may be further reduced with hydrogen.

(4) Nickel oxide or carbonate is digested with chromic acid until completely dissolved. On evaporating the solution to dryness, the residue is reduced with hydrogen, or is first heated to redness, representing a temperature in the vicinity of 800 C., to convert it to the chromite form, followed by hydrogen reduction.

The methods described above are equally applicable to the preparation of chromites of hydrogenating metals other than nickel, for example, copper and silver and other members of the ferrous metal group, such as iron and cobalt.

(5) A very active copper chromite preparation is formed by the interaction of equimolecular proportions of copper nitrate and neutral ammonium chromate solutions, followed by ignition. Basic copper ammonium chromate is formed by the precipitation, which yields a complex mixture of copper oxide and copper'chromite on gentle ignition. This product is active for the hydrogenation of phenols and other unsaturated compounds without further treatment, and is therefore a very convenient hydrogenation catalyst to prepare. As in the preparation of the nickel catalysts, the copper oxide-copper chromite catalyst may be further reduced with hydrogen to yield a catalyst mass containing metallic copper commingled with copper oxide and copper chromite. The copper chromite catalyst, prepared by ignition of the double chromate, without having been subjected to further reduction by hydrogen is highly emcient for the purposes of the invention.

I have disclosed above the preparation of chromite catalysts by the spontaneous decomposition of double ammonium chromates. By the term nitrogen base" I include, besides ammoniuin compounds, organic derivatives such as salts of pyridine, aniline and methylamine. When heated, these organic derivatives behave in a manner similar to the ammonium derivatives and yield chromites, which, upon reduction, possess the same catalytic properties. Various formulae have been assigned to these double salts by individual investigators. Cold concentrated solutions of nickel chloride and ammonium chromate yield a green salt to which the formula:

(NH4) zNi (CrO4) 2.61120 has been assigned, while more dilute solutions at higher temperatures give rise to-the formation of a brick-red precipitate probably having the formula:

(um) macro) 2.2m.

Both of these compounds decompose spontaneously on heating and yield a product in which chromium is present in the trivalent form.

The nitrogen base compounds, typified by nickel ammonium chromate, are preferably heated slowly to start the reaction after which they decompose spontaneously, leaving a residue of nickel chromite. The spontaneous decomposition temperature will vary for the different compounds, but in general, it may be said to range from 200 C. to 400C. ing composition with hydrogen may be carried out at 400 C. to 600 C., preferably at 500 C.

The simple chromates, typified by nickel chromate prepared as illustrated in method (4), may be reduced to the chromite by igniting at a temperature somewhat higher than is required for the nitrogen base multiple chromates. Ignition of chromates of this type takes place at about 600 to 800 C., although higher temperatures may be used in special cases. Where further reduction-by means of hydrogen is desired, it may be Reduction of the resulteffected at about 400 to 800 C. and preferably at about 500 C.

It is possible to carry out the reduction of chromates of either of the above types by exposing them to the action of hydrogen at elevated temperature, without having submitted the material to previous ignition. Thus, catalysts may be prepared by subjecting the chromates to hydrogen at a temperature of 400 to 600 C. for a period of time sufficient to convert the chromates into compositions containing either free hydrogenating metal or its oxide associated or combined with chromium oxide containing chromium in the trivalent form. It is generally desirable, however, to first ignite the material to reduce the chromate to chromite, since the resulting composition is more compact and convenient to handle than would otherwise be the case.

In general, any other hydrogenating metal or its oxide can be substituted for nickel, this class including zinc, copper, silver, cobalt and iron.

' my invention, the following examples which are included merely for purposes of illustration and not as a limitation, disclose specific methods used in carrying the invention into practice and the improved. results accruing from; its use.

Example I A nickel chromite hydrogenation catalyst was prepared as follows: 8'72 g. of'nickel nitrate (NiNO3.6H2O) and 300 g. of chromium trioxide (0203) were dissolved in 900 cc. of distilled water. Nickel ammonium chromate was precipitated by adding rapidly with vigorous stirring 600 cc. of 28.3 per cent aqueous ammonia. The precipitate was filtered from the'mother liquor, dried at C., and decomposed to the chromite by heating at 350 C. for four hours; The nickel chromite thus obtained was ground to 100 mesh and reduced in hydrogen for 18 hours at 350 C. and at 540 C. for 1.5 hours longer. After cooling in hydrogen and sweeping the system out with car- Hydrogenation was carried out with vigorous agitation at a hydrogen, pressure of about 1000 pounds per square inch and at a temperature of about 185 C. Hydrogen absorption was rapid under these conditions and the reaction was complete in about two hours. Distillation of the flltered product gave a yield of about 95 per cent of cyclohexanol.

In a similar manner, mixed cresols may be hydrogenated to the corresponding methyl cyclohexanols and .xylenols to the corresponding dimethyl cyclohexanols.

Example II Two hundred and twenty-eight grams of pure nickel hydroxide was suspended in water and treated with 200 g. of chromic anhydride. The resulting paste was filtered, dried, and ignited four hours at 400 C. Five grams of the residual nickel chromite composition was reduced 24 hours with hydrogen at 500 C. The resulting mass was cooled and transferred without exposure to air to a vessel containing 200 g. of 85 per cent phenol in water. The mixture was heated and agitated for two hours with pure hydrogen at 800 lbs. pressure. Hydrogenation began at C. and was quite rapid at 170 C. Pure cyclohexanol was formed under these conditions and the yield was almost quantitative.

Crude meta cresol, known commercially as.

cresylic acid, may be hydrogenated effectively at about 200 C. when similar technique is used. Likewise, betanaphthol may be readily hydrogenated to yield the correspondingtetrahydro monia.

parts of chromic acid were dissolved in 1668 parts of water and 34 parts of. anhydrous ammonia was added with agitation during a period of 15 to 30 minutes. After washing the precipitate by decantation, 161 parts of .chromic acid was added to redissolve the precipitate and the solution was made up to a volume equal to the original copper suliate-chromic acid solution. Copper ammonium chromate was reprecipitated by the addition of 32 parts 01' anhydrous amand dried, after which it was ignited ,at 400 C. The resulting chromitewas then extracted twice by stirring for 15 minutes each time in a solution of 100' parts of glacial acetic acid and 900 parts of water. After extraction, the chromite was washed free from acid, filtered and dried at C. and screened to 20 mesh size.

One hundred and seventy-six grams of an-' hydrous phenol, 24 grams of water, and 14 grams of copper chromite, prepared as described above, were charged into an autoclave equipped for agitation under high pressure. The charge was heated to 240 to 260 C. and agitated for five hours under a hydrogen pressure of 2300 to 3500 pounds per square inch. Hydrogen was absorbed rapidly and was completed in about 2.5 hours. Distillation of the product gave an amount of pure cyclohexanol equivalent to a 97 per cent conversion of the phenol.

Under similar conditions o-cresol was converted into the corresponding 2-methyl cyclohexanol.

Example IV One of the importantadvantages of using copper chromite catalyst forthe hydrogenation of phenols is that in complex structures containing more than one kind of unsaturation. it may be possible to hydrogenate selectively the phenol nucleus without attacking the other. unsaturated parts of the molecule.

This precipitate was washed, filtered The point in quesion is,

illustrated by the hydrogenation of para phenyl phenol to phenyl 'cyclohexanol. -When-hydrogenated in the presence of a nickel catalyst, para phenyl phenol yields cyclohexyl cyclohexanol through hydrogenation of both the. phenyl and phenol rings. On the contrary, copper chromite is inert towards hydrogenation of the phenyl ring but allows attack on the phenol ring, thus forming as the product a phenyl cyclohexanol.

A catalyst consisting of copper chromite supported on kieselguhr was prepared exactly as described in Example III, except that 205 g.'of kieselguhr was added to the copper nitrate-chromic acid solution and kept in suspension by vigorous agitation during precipitation with ammonia. The catalyst thus prepared consisted oi! copper chromite supported on kieselguhr, the two components being present in about equal proportions. Fifteen grams of the catalyst thus prepared and 150 g. ofp-phenyl phenol were placed in a shaking autoclave and hydrogen was cated certain definite conditions of temperature,

pressure, gas concentration, amounts or materials,

. duration of reactions, etc., it is. to be understood that any and all of these may be varied widely within the scope of my invention, since the particular conditions of operation are governed largely by the specific reaction catalyzed, the materials treated, and the catalyst selected for a given reaction.

In carrying out the processes of the present invention the temperatures used may vary over a considerable range, depending on the exact composition of the catalyst used. In general, the hydrogenation of phenols with nickel chromite catalyst will'take place at lower temperatures than when copper chromite is used. The operation temperature for chromite catalysts generally is about 120 to 300 C. While pressure is not a critical factor, it is preferable to carry out phenol hydrogenations under superatmospheric pressure; for example, in the range of 10 to 500 atmospheres.

It will be apparent from the examples given that the catalysts of my invention have mariy valuable applications. Although I have described their use in certain selected liquid and vapor phase hydrogenations which illustrate their particularly advantageous properties, they are capable of use in the hydrogenation of many other phenolic bodies. Thus I may hydrogenate phenols such as ordinary phenol, cresols, xylenols, alphaand beta-naphthol, diphenylols, and crude tar acids containing large concentrations of phenols. The present invention also contemplates a new process for the hydrogenation of phenols directly to cyclic ketones. Since copper chromite may be used in the vapor phase at fairly high temperatures and low pressures, these conditions are ideal for converting the cyciohexanols first formed from the phenols by hydrogenation into the corresponding ketones by dehydrogenation.

As many apparently and widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the appended claims.

I claim:

1. The process of catalytically hydrogenating the nucleus of a hydroxyphenyl group which comprises reacting hydrogen and a phenol in the presence of a hydrogenating catalyst comprising as an essential ingredient a hydrogenating metal oxide associated with an acidic metal oxide. l

2. The .process of catalytically hydrogenating the nucleus of a hydroxyphenyl group which comprises reacting hydrogen and a. phenol in the presence of a hydrogenating catalyst comprising as an essential ingredient a hydrogenating metal oxide associated with an acidic metal oxide, which 5. The process of catalytically hydrogenating the nucleus of a hydroxyph nyl group which comprises reacting hydrogen and a phenol in the presence of a copper chromite catalyst at a temthe nucleus of a hydroxyphenyl group which comprises reacting hydrogen and a phenol in the presence of catalyst comprising essentially nickel oxide associated with chromium oxide.

7. The process of catalytically hydrogenating the nucleus of a hydroxyphenyl group which comprises reacting hydrogen and a phenol in the presence of a nickel chromite catalyst.

8. The process of catalytically .hydrogenating the nucleus of a hydroxyphenyl group which comprises reacting hydrogen and a phenol in the presence of a catalyst prepared by heating a multiple chromate of a nitrogen base and a. hydrogenating metal to its spontaneous decomposition temperature and thereafter subjecting the resulting composition to partial reduction.

9. The process of catalytically hydrogenating the nucleus of a hydroxyphenyl group which comprises reacting i'rvdrogen and a phenol in the presence of a catalyst prepared by heating the compound resulting from the precipitation of nickel chromate in the presence of ammonia to its spontaneous decomposition temperature and thereafter subjecting the resulting composition to partial reduction.

10. The process of catalytically hydrogenating the nucleus of a hydroxyphenyl group which comprises reacting hydrogen and a phenol at a temperature above 120 0., and at a pressure in excess of 10 atmospheres in the presence of a cat-- resulting composition in a stream of hydrogen at about 500 C.

12. The process of catalytically hydrogenating the nucleus of a hydroxyphenyl group which comprises reacting hydrogen and a phenol in the presence of a catalyst prepared by heating a multiple chromate of a nitrogen base and nickel to its spontaneous decomposition temperature and thereafter subjecting the resulting composition to partial reduction.

13. The process of catalytically hydrogenating the nucleus of a hydroxyphenyl group which comprises reacting hydrogen and a phenol at a temperature above 120 C., and at a pressure in excess of 10 atmospheres in the presence of a catalyst prepared by heating a multiple chromate of a nitrogen base and copper to its spontaneous decomposition temperature and thereafter subjecting the resulting composition to partial reduction.

14. The processdf catalytically hydrogenating the nucleus of a hydroxyphenyl group which comprises reacting hydrogen and a phenol in the presence of a catalyst prepared by heating a multiple chromate of a nitrogen base and a hydrogenating metal to its spontaneous decomposition temperature and thereafter subjecting the resulting composition to a partial hydrogen reduction.

- the nucleus of a hydroxyphenyl group which comprises reacting phenol and hydrogen at a temperature between and 300 C. in the presence of a catalyst comprising essentially a hydrogenating metal oxide associated with an acidic metal oxide.

16. The process of catalytically hydrogenating the nucleus of a'hydroxyphenyl group which com-.

prises reacting phenol andhydrogen at a temperature of about 120 to about 200 C. in the presence of a nickel chromite catalyst.

1'7. The process of catalytically hydrogenating the nucleus of a hydroxyphenyl group which comprises reacting phenol and hydrogen at a temperature of about 240 to about 260 C. in the presence of a copper chromite catalyst.

18. The process of catalytically hydrogenating the nucleus of a hydroxyphenyl group which comprises reacting phenol in a concentrated aqueous solution with hydrogen in the presence of a copper chromite hydrogenating catalyst at a temperature of about 240 to about 260 C. and at a pressure of about 2300 to about 3500 pounds per square inch and recovering the cyclohexanol formed.

19. The process of catalytically hydrogenating the nucleus of a hydroxyphenyl group which cornprises reacting hydrogen and a polynuclear phenol in the presence of a hydrogenating catalyst comprising as an essential ingredient a hydrometal oxide.

20. The process of catalytically hydrogenating.

the nucleus of a hydroxyphenyl group which comprises reacting hydrogen and a polynuclear phenol in the presence of a catalyst comprising essentially copper oxide associated with chromium oxide.

21. The process of catalytically hydrogenating the nucleus of a hydroxyphenyl group which comprises'reacting hydrogen and a polynuclear phenol in. the presence of a copper chromite catalyst.

genating metal oxide associated with an acidic 22. The process of preparing a phenyl cyclohexanol which comprises carrying out a partial selective catalytic hydrogenation of a phenyl phenol in the presence of a hydrogenating catalyst comprising as an essential ingredienta hydrogenating metal oxide associated with an acidic I metal oxide.

23. The process of claim 22 wherein the catalyst is copper chromite.

24. The process of claim 22 wherein the catalyst has been partially reduced.

25. The process or claim 22 wherein the hydrogenating catalyst comprises as the said essential ingredient a hydrogenating metal oxide asSO- ciated with chromium oxide.

26. The process of claim 22 wherein the catalyst comprises essentially copper oxide associated with chromium oxide.

p WILBUR A LAZIER.