US2402626A - Catalyst and method of preparation - Google Patents

Description

Patented June 25,

:7 PATENT OFFICE CATALYST AND METHOD OF PREPARATION Benjamin Wilson Howk, Wilmington, DeL, as-

signor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application August 23, 1940, Serial No. 353,936

UNITED STATES lysts. More specifically, it relates to alloy-skeleton metal sulfide catalysts characterized by high activity and resistance to poisons and corrosion, and to a process for their preparation.

For many years technical progress and commercial development in the field of catalytic hydrogenation has been largely dependent on the use of the more familiar types of base metal cat- .alyst such as nickel, cobalt, iron, and copper. In general, these catalysts are employed either in the form of finely divided metals, as oxides, or

as oxidecombinations containing one or more dimcultly reducible oxides, such as chromium oxide, which serve as promoters. Catalysts of I tivity is partly or wholly destroyed by the cor-- rosive action of acids and in some cases by strong alkaiies as well. These disadvantages have accordingly operated to restrict the utility of these familiar base metal catalysts exceptin connection with hydrogenations in which the problems of poisoningfor corrosion are seldom met.

For the more diiiicuit types of hydrogenations it has been largely necessary to rely on noble metal catalysts of the platinum sub-grou in order to accomplish desired hydrogenations for which nickel, cobalt, etc., are unsuited for the reasons set forth above. Although metals of this group, particularly platinum and palladium are valuable catalysts for conducting hydrogenation reactions under adverse conditions, few if any commercial processes based on their use have been developed on account of their relative scarcity and high cost.

It is therefore an object of this invention to provide anew hydrogenation catalyst that is relatively inexpensive, highly active, poison-resistant, and non-corroding. Another object is to provide a process for the manufacture of such a catalyst. Still another object is to provide a more effective method for catalytic hydrogenation. Other objects will be apparent from the following description of the invention.

14 Claims. (Cl. 252-2284) These objects are accomplished by treating an alloy of an alkali, soluble metal and a metal se-- lected from the group consisting of the hydrogenating metals of the 1st,- 6th, and 8th groups 5 of the periodic table with an alkali metal sulfide. According to the preferred embodiments of the invention hydrogenation catalysts are prepared by treating alloys of metal selected from the group consisting of the hydrogenating metals of the 1st, 6th, and 8th groups of the periodic table and alkali-soluble metals with solutions of alkali metal sulfides and polysulfides at temperatures in excess'of 0., thereby preparing an alloyskeleton metal sulfide catalyst. I

. A hydrogenating metal of the class referred to above, such a iron, cobalt, nickel, copper, tungsten, or molybdenum is alloyed with aluminum preferably in the proportions of to parts of the former and to 50 parts of the latter, and go the alloy is ground to a fine powder by conventional methods. One hundred parts of the alloy powderis suspended in 400 parts of boiling water and a solutionof parts .of hydrated sodium sulfide (NB.2S.9H20) in approximately parts 25 of water added slowly over a period of i to 1.5

hours. The mixture is boiled with efiicient stirring for an additional 4 hours and allowed to settle. The supernatant liquid is separated and the sludge washed once or twice with water by 30 decantation to remove soluble salts. The precipitate is'then taken up in a solution of 100 parts of hydrated sodium sulfide and-50 parts of caustic soda in 400 parts of water and boiled for 3 to 4 hours to complete the digestion. The product is allowed to settle, the supernatant liquid decanted, and the sludge washed thoroughly with water until free from alkali, salts, and hydrogen sulfide. The resulting product, which comprises an alloy-skeleton metal sulfide cata- 40 lyst supported on alumina, is obtained as a thick aqueous paste ready for use. In some cases, particularly for employment in non-aqueous hydrogenation systems, it may be desirable to transfer the catalyst to alcohol or some other appropriate organic liquid.

The following examples set forth certain well defined instances of the application of this invention. They are, however, not to be considered as limitations thereof, since many modifications may be made without departing from the spirit and scope of this invention.

Example I Two hundred twenty-seven parts of finely 5; ground cobalt-aluminum alloy containing ap- 'suspensibility in liquids. sulfur and alumina indicated a weight ratio of reaction accompanied by the evolution of hydrogen and traces of hydrogen sulfide ensued, and the suspended alloy was converted to a gray sludge. After boiling for an additional 4 hours the'mixture'was allowed to settle, the supernatant liquid decanted and the residue washed twice with water to remove soluble salts. The

sludge was then resuspended in a solution con-- taining 1000 parts of water, 226 parts of hydrated sodium sulfide, and 113 parts of sodium hydroxide and boiled during a further period of 4 hours, the water lost by evaporation being replaced from time to time. The catalyst sludge was then allowed to settle and was washed with water by decantatlon until essentially free from alkali, sodium sulfide, andhydrogen sulfide. The resulting aqueous paste was washed with alcohol and stored under absolute alcohol. catalyst was characterized by an extremely fine state of subdivision and a. remarkable ease of Analysis for cobalt,

1.94 parts cobalt, 1.0 part sulfur, and 1.8 parts of alumina. The molecular ration of cobalt to sulfur was 1:1 and the composition of the catalyst mixture corresponded to approximately 33 parts of cobalt sulfide supported on 67 parts of hydrated alumina.

Example II A solution of sodium polysulfide was prepared by dissolving 533.5 parts of hydrated sodium sulfide (Na2S.9Ha0) in 750 parts of water and adding 142.6 parts of sulfur with vigorous stiralloy containing about parts of cobalt and 65 parts of aluminum in 1000 parts of water. A vigorous evolution of gas occurred and the alloy was converted rapidly to a finely divided black powder. The mixture was boiled four hours.

' table.

The solid was separated from the supernatant liquid by decantation and washed several times with water to eliminate caustic soda, soluble salts, and hydrogen sulfide. The product was an aqueous paste of finely divided catalyst comprising essentially cobalt polysulfide on alumina.

Although in the foregoing examples the use of specific alloys and certain definite procedure for producing corrosion-resistant, sulfactive alloyskeleton hydrogenation catalysts have been referred to, it is to be understood that these factors are subject to wide variation within the scope of the invention without departing from the spirit thereof.

In general, the process of the invention is applicable to the preparation of a new and highly active' class of poison-resistant. non-ccrroding hydrogenation catalysts comprising alloy-skeleton sulfides and poly-sulfides of metals selected from the group comprising the hydrogenating metals of the 1st, 6th, and 8th groups of the periodic Typical metals of this class are iron, cobait, nickel, copper, silver, tungsten, and molybdenum. According to the preferred embodiments of the invention, alloys of these metals with apsilicon, which are not only readily attacked by caustic solutions but which ifail to yield sulfides and polysulfides that are stable in aqueous media.

after completing addition of the sodium polysulfide, and the precipitate was allowed to settle overnight on a steam bath. The black catalyst sludge was washed thoroughly with water until free from soluble salts and stored as a thin aqueous paste. The product was essentially free from alumina, and contained 1.34 moles of sulfur per mole of cobalt.-

Examplc III Two hundred twenty-seven parts of a finely powdered cobalt-aluminum alloy containing about 35 parts of cobalt and 65 partsof aluminum was suspended in 1000 parts of boiling water.

' The mixture was stirred mechanically while add- In general, alloys containing as much as 90% or as little as 10% of the hydrogenating metal component and corresponding amounts of the caustic soluble component are satisfactory for activation. It is particularly convenient, however, to employ alloys containing between 30 and 50% by weight of hydrogenating metal and between 70% and 50% of the soluble metal. Within these limits suitable alloys are prepared according to any of the conventional methods of the prior art, either as binary compositions containing only one of each class or component or as multiple compositions containing various combinations of metals coming within the scope of the invention.

In the practice of the invention, it is in general preferred to carry out the activation step essentially as described in the examples. However, as i speaking, the activation process comprises treating the alloy with solutions containing sufiicient alkali metal sulfide or polysulfide to react in equimolecular proportions with. the total amount of the hydrogenating metal contained in the alloy. It is preferred to employ soluble sulfides or polysulfides of metals such as the alkali metals which are characterized by a strongly alkaline reaction in solution. The alkali metal sulfides may be employed alone or in combination with caustic alkalies, or a preliminary treatment with the sulfiide may be followed by a treatment with caustic alkali solution to facilitate a more rapid and complete solution of the alkali-soluble component of the alloy. In general, the use of alkali metal sulfide solutions alone tends to cause the formation of a supported catalyst in which the carrier is produced in situ'from the soluble component of the alloy, whereas the use of caustic alkali favors the production of unsupported oats,

little or no activity.

lysts. Variations in the amount of caustic employed govern to a certain extent the relative proportions of metal sulfide and support in a finishedcatalyst. In accomplishing these results. the mode of bringing together the alloy and the sulfide solution may also be varied considerably. For example, the alkaline reagent may be added to a suspension of the alloy or the alloy may be added in successive small portions to the sulfide solution without materially affecting the' quality or properties of the catalyst produced. According to either variation it is preferable to operate with solutions at or near the boiling point.

The alloy-skeleton hydrogenating metal sulfide catalysts of the invention may be conveniently prepared in physical forms adapted for operation either in batchwise liquid phase or continuous gas phase lwdrogenation processes. In the former instance, the alloys are'preferably reduced mechanically to powders Prior to the activation process in order to produce finely subdivided materials that are easily suspensible in liquids and provide a maximum surface per unit of mass of catalyst. Catalysts suitable for operation in gas phase contact hydrogenation processes may be prepared either by briquetting powdered. catalysts or by surface activation of alloy lumps of suitable size. In general, the alloy-skeleton metalsulflde catalysts of the invention are characterized by a remarkable sturdiness, by their outstanding resistance to corrosion bystrong acids and alkalies at elevated temperatures, by their indifference to most types of catalyst poisons, and by their high activity and efiiciency in promoting lLvdrogenation reactions under conditions intolerable to the more familiar metal and metal oxide hydrogenation catalysts.

Alloy-skeleton metal sulfide catalysts are of wide-spread utility in the field of hydrogenation,

not only because they function smoothly to promote hydrogenation reactions in general, but more especially because of their superior activity under conditions generally considered unfavorable for catalytic reduction processes. This su periority is clearly evidenced by the following experiments showing various uses for alloy-skeleton cobalt sulfide catalysts, which are typica of those coming within the scope oi the invention.

A mixture comprising 60 parts of cycl'ohexanone, 30 parts of sulfur, and 7 parts of alloyskeleton cobalt sulfide catalyst was charged into a high pressure reaction vessel and treated with hydrogen under 1000 to 2000 lbs/sq, in. pressure at 150 C. Hydrogen was absorbed smoothly during 8 hours. On working up the product according to conventional methods there was obtained 61 parts of pure cyclohexanethiol, which corresponds to a molecular yield of 86% of theory.

In a similar experiment, the hydrogenation of heptaldehyde and sulfur with alloy-skeleton cobait polysulfide catalyst gave a high yield of heptanethiol. These experiments serve to illustrate the sulfactive properties of these catalysts. Under similar conditions ordinary nickel or cobalt catalysts are subject to severe poisoning and show Other types of hydrogenation reactions requiring a sulfactive catalyst and in which the catalysts of this invention are particularly useful are the reduction of aliphatic nitriles to th'iols, the cleavage of alkyl and aryl The following experiment demonstrates the resistance of alloy-skeleton metal sulfide catalysts to the corrosive action of strong acids at elevated temperatures: Fifty parts of nitrobenzene, 70.7 parts of 45% sulfuric acid and 1 part of alloyskeleton cobalt sulfide catalyst were charged into a corrosion-resisting high pressure autoclave and treated with hydrogen under 500 lbs. pressure at a temperature of 135 to 140 C. for a period of 3 hours. on working up the crude hydrogenation product there was obtained 10 parts of unreacted nitrobenzene, 19 parts of aniline and 8 parts of p-aminophenol. Conversely, alloy-skeleton cobalt sulfide catalysts promote the hydrogenation of aromatic nitro compounds such as nitrobenzene smoothly in caustic alkaline media at temperatures below about 115 C. at hydrogen pressures as low as 500 lbs/sq. in. From nitrobenzene the products are azobennene, azoxybenzene, and aniline.

Having described. in detail the preferred embodiments of my invention, it is to be understood that I do not limit myself to the specific embodiments thereof except as defined in the following I claims.

I claim: I

1. A process for the manufacture of a highly active, poison-resistant, non-corroding hydrogenation catalyst which comprises treating an alloy of an alkali soluble metal and a metal selected from the group consisting of the hydrogenating metals of the 1st, 6th and 8th groups of the periodic table with an alkali metal sulfide.

2. A process for' the manufacture of a highly active, poison-resistant, non-corroding hydrogenation catalyst which comprises treating an alloy of an alkali soluble metal and a metal selected from the group consisting of the hydrogenating metals of 'the 1st, 6th and 8th groups of the periodic table in finely divided form with an aqueous solution comprising an alkali metal sul-' tide and obtaining alloy-skeleton metal sulfide hydrogenation catalysts.

' soluble metal.

4. The process in accordance with claim 3 characterized in that the alkali metal sulfide is an alkali metal polysulfide.

5. A process for the preparation of a hydrogenation catalyst which comprises treating an alloy in finely divided form and in suspension in an aqueous medium containing an alkali metal sulfide and a caustic alkali, said reaction being carried out within the temperature range of from to 100 C. and said alloy consisting of from 10 to 90% of a hydrogenating metal of the 1st, 8th and 8th groups of the periodic table and 90 to 10% of an alkali soluble metal.

6. A process for the production of a hydrogenation catalyst which comprises treating a finely disulfidea to the corresponding thiols, the reduction of sulfurized olefins, the reduction of aromatic sulfo acids to thiols and hydrocarbons, and the catalytic conversion or certain inorganic salts such as sulfites to a lower valence state.

divided alloy with an aqueous solution of an alkali metal sulfide at a temperature near the boilins point of said solution, said alloy comprising to of a hydrogenating metal of the 1st, 6th and 8th groups of the periodic table and '10 to 50% of an alkali soluble metal.

7.111eprocwinaccordancewithcmme characterized in that the hydrogenating metal in said alloy is cobalt and the alkali soluble metal is aluminum.

8. A metal sulfide hydrogenation catalyst prepared by a process consisting of treating an alloy of an alkali soluble metal and a metal selected from the group consisting of the hydrogenating metals of the 1st, 6th and 8th groups of the periodic table with an alkali metal sulfide.

9. A metal sulfide hydrogenation catalyst prein finely divided form and in suspension in an aqueous medium containing an alkali metal sulfide and a caustic alkali, said reaction being carried out within the temperature range of from pared by a process consisting of treating an alloy 8. 25 C. to 100 C'., and said alloy consisting of iron 10 to 90% of a hydrogenating metal of the 1st 6th and 8th groups of the periodic table and 91 to 10% of an alkali soluble metal.

10. The catalyst of claim 8 characterized ii that the hydrogenating metal is cobalt.

11. The catalyst of claim 8 characterized ii that the alloy is an alloy of cobalt and aluminum 12. The catalyst of claim 8 characterized ii that the hydrogenating metal is copper.

13. The catalyst of claim 8 characterized it i that the hydrogenating metal is molybdenum.

14. The catalyst of claim 9 characterized i! that the alloy is an alloy of cobalt and aluminum 7 BENJAMINW. HOWK.