US2375506A - Process for producing metal compositions of low apparent density - Google Patents

Description

Patented May 8, 1945 PROCESS FOR PRODUCING METAL COMPO- SITIONS OF LOW APPARENT DENSITY Joseph Abrahm Valentine 'lnrck, Jr., New mi;

vN..Y., asslg'nor to Colgate-Palmolive-Peet (lompany, Jersey City, N. J., a corporation of Delaware No Drawing. Application December 13, 1941, Serial No. 422,882

14 Claims. (Cl. IS-L5) The present invention relates to. metals and metallic alloys of low apparent density, and,

more particularly, to such metals and metallic.

alloys in a novel form suitable for various uses wherein a large surface area is desirable, such as in catalysis, and to a process for producing the same.

The value of various metals and metallic alloys in catalyzing certain chemical reactions has long been known. In general, metals are used as contact catalysts, so that it is desirable to have as large a surface available as possible. For this reason, it is common practice to employ metals in the form of metal gauzes, powders, wire, beads, grains, and. small lumps. It is also known to deposit these metals upon porous carriers, such as silica gel, thoria, diatomaceous earth, kieselguhr, etc, While these carriers provide a greatly increased surface of metal for catalytic purposes,

it is apparent that at least that surface of each metal particle which is adjacent the carrier surface at any given point is unexposed and so less efllcient as a catalyst.

It is an object of the present invention to provide a process for producing metals and metallic alloys and preparations in such form that greatly increased areas of surface are available.

It is another object of the invention to provide a process for producing rigid metallic catalysts having an apparent density as low as about 2% to about of the true density of the metals in solid form.

It is also an object of the invention to provide a novel process for producing metals and metallic alloys and preparations of low apparent density, high surface area and relatively high mechanical strength suitable for use as catalysts.

Other objects and advantages of this invention will be apparent to those skilled in' the art from the following description.

According to the present invention, reducible metallic compounds which give bulky flocculent or gelatinous precipitates are employed to produce metallic catalysts having extremely lowapparent density. The preparation of these metallic catalysts in a very porous state is preferably accomplished by precipitating the metal hydroxide, where the hydroxide of the particular metal is flocculent, in a suitable liquid protective and supporting medium. The liquid medium is then transposed to a gaseous medium. The metal hydroxide (or oxide, where the hydroxide suffers dehydration), still in its original highly expanded form, is reduced in situ to the metal, and the hydroxides can be precipitated in an aqueous medium,and,'although water can be used as a supporting medium during the entire time that a liquid medium is employed, it is ratherpreferred to replace the aqueous medium by an organlc solvent having a lower critical temperature,

such as acetone, methyl alcohol, ethyl alcohol, benzene, pentane, heptane, ether, etc.

As reducing agents, various materials may be used, depending upon the ease of reduction of the particular metallic hydroxide or oxide concerned. Thus, hydroquinone, pyrocatechimdecahydronaphthalene and other organic reductants can be used. Hydrogen, hydrazine, ammonia or ammonium chloride at high temperatures can also be used for this purpose. With certain of the metallic oxides which are relatively easily reduced, it has'been found that at high tempera- 'tures the lower aliphatic alcohols, having from 1.

to about 5 carbon atoms per molecule, are satisfactory reducing agents, and in this case said alcohols may serve both as liquidmedia and as reductants, if desired.

In going from the liquid medium to a gaseous medium, the flocculent or gelatinous precipitate of the metallic compound suspended in the liquid medium is introduced into an autoclave. The interior of the autoclave is evacuated to remove substantially all of the'air therein, and it is preferred to flush the autoclave with an inert gas to insure the removal of all oxidizing gases. A suitable pressure of the inert gas can be built up within the autoclave, and the autoclave is then slowly heated to a temperature above the critical temperature of the liquid medium employed,

the pressure within the autoclave rising during sity, the agitation normally associated with boil} ing is not produced to any undesirable extent, and the bulkiness of the solid material or residue is not substantially affected.

During thistemperature rise or at or above the critical temperature, the reducing agent reduces the metallic compound to the metal, and the fluid in the pores and cavities of the metal metal retains the expanded form, The metallic as is in the gaseous state. The vapors are with-- At this point, therefore, the liquid the system'being preferably evacuated, I and the autoclave is allowed to cool. state is not appreciably altered on strong oxidacoppercan be cut into blocks, and its physical In general, it is preferred not to have a metal tion. :The copper can be wet with water and catalyst exposed to an oxidizing'medium at any will retain its form, porosity, large surface, rigid- 7 time, and it is therefore desirable to run an inert jo ity, and low apparent: density even after drying.

ovum-oxidizing gas, preferably nitrogen,- into In forming thenovel metallic copper body of the autoclave before it is opened; The metal is i the present invention, ithas been discoyered that thentransferred, after cooling, to a -storage conthe copperhydroxide can be precipitated in an tair 'er having an inert atmosphere, say, of nitroimproved manner for this'purpose by first obtain- .gen. However, where such precautions are ,not 10 ving the copper-anunonia complex ion. When this required, the metal may alternatively. be cooled I complex ion is first formed, the addition of cupric to a sufliciently low. temperature so that there is nitrate to the blue solution does not immediately no danger of substantial oxidatiolrif e posed to precipitate the cupric hydroxide, as the complex air, and air can then be admitted to the auto- 1 ion must'have time for breaking down. Since the.

clave, or the autoclave canbe opened; 1 l6 precipitation is not instantaneous, this method of The metal p odu ed n t s manner is rigid d production of the hydroxide gives time for mixin e t y P o form a ay have an aping, so that an even, uniform deposition of the P density as low as ou or. less, in the cupric hydroxide can be obtained. Curds and case ofsome of the metals, of the true density of the so d o co p e- In general. it Will 20 hydroxide are thereby eliminated. Other methbe found that the apparent density of meta p cads of precipitation may also be employed.

duced in this manner will run as lowas l to15% of the apparent density of the precipitated metal H Example H 1 powders which have heretofore commonly. been About 21 grams .of cupric chloride dihydrate are used'as catalysts. The enormously increasedsurg dissolved in about 250 cc. of water, and ammonium race, area of 'metallic catalysts produced in. achydro id is adu y dd d, t pr ip tat upri cordance with the process herein disclosed is of y r i e addition of ammonium y r i e" great advantage in the catalysis of many reacis continued until the original cupric hydroxide tions. I precipitate is completely dissolved to form the The following example are merely illustrative 30 comp copper-ammonia Cuprio chloride of the present invention, and it willbe underabout solution is then slowly added to the stood that the invention is notlimited thereto. deep blue ol ion of he c mplex ion until the precipitate obtained and the supernatantliquor Example I are greenish blue. The total amount of copper lumping caused by sudden precipitation of cupric' About 25 grams of cupric nitrate trihydrate .85 present, on a cupricchloride dihydrate basis, is

[Cu(NQ3):.3H2Ol is dissolved'in about 250 cc. of about grams, and this is made up with water water,, and ammonium hydroxide is gradually to about 40000. The precipitated'slurry is peradded to "precipitate cupric hydroxide. The mitted to settle until-it'has a, volume of about 150 precipitated slurry is permitted to settle, and the cc., and the clear supernatant liquorabove it is clear supernatant liquorabove is then siphoned thendecanted. Methyl alcohol is added to bring off. Acetone is 'added to bring the volume up to the volume to about400 cc. again. The precipiabout 40000. The material is then agitated to tate is then mixed throughout the entire volume mix the precipitate throughout the entire volume, by stirring, and the slurry is again allowed to and the slurry is again allowed to settle, to about; tt e t about 150 C- s p oc dure s r peated,

100 cc This procedure is repeated until the finally using absolute me ylalcohol, until /the amount of water present in the solution is reduced m unt f w t r pre nt n t e sup r a ant liqu r to'about 1 to about 3%, and about 15 grams of is of the order ofabout 1% or less.

isopropyl alcohol are then added as a reducing, The cupric hydroxide is's'uspended in about 250 agent, cc. of methyl alcohol, and the suspension is put The cupric hydroxide,suspended in about 115 in an autoclave, as described in Example I." The cc. of the acetone-isopropyl alcohol solution and autoclave s evacuated d swept of residual air, held in a large test tube or glass liner, is placed and a Pressure of about 300 pounds D square inside an autoclave. The autoclave is' closed and inch f ni r gen is built up Wit n t autoclave, fixed in'a. heating chamber and is then evacuated. whereafter it is sealed. The autoclave is heated A stream of nitrogen is then employed t osweep to about Which i pp o m e y 0 above all residual air out of the autoclave, and a pressure the Critical p lat e f methyl alcohol, the of nitrogen of about 300 pounds per square inch temperature being s y i c as d v a p i d is built up within the autoclave, .which is then of about two hours; The methyl alcohol vapors sealed. The autoclave is heated to a temperature together with the formaldehyde that is formed are above the critical temperature of acetone, say, to co e se and pt out of t y t m W th fresh about 250 C., the temperature being raised slowly nitrogen at a rate sufliciently slow to avoid subover a period of about one and one-half to about stantial decrease'in temperature within the autotwo hours. During this heating, the pressure rises clave. After the autoclave has cooled for some to about 1,700 pounds per square inch. a r it sopen and tired, metallic copper The acetone vapors are then bled out of the sponge similar to that described in Example I is system, at a r'ate'sufliciently slow to prevent any obtained. A yield of about 9.8 grams of copper, substantial drop in the temperature within the which is approximately 90% of the theoretical, is

- autoclave, which is keptbetween about 240 and p u ed- Y about 250 C, durin such releaseof thgvapors, It Will be understood that the exchange of liquid The system is then evacuated and permitted to media, such as from water to methyl alcohol, as

cool for some hours. Upon opening the autoclave, explained in a pr d p r r ph, can be cara sponge of red, metallic copper having an apried out between more than two solvents, where parent density of only about 0.30 gram per cubic successive solvents are at least partly miscible.

centimeter'is obtained;Inthis,form.' the metalliclys Similarly, the precipitation can be carried out with alkali, ammonium hydroxide, or basic salts hydroxide suspended therein is then mu eum dlrectlyin methyl alcohol. into the autoclave, and all air is evacuated and Example III swept therefrom. The pressure within the auto- Cupric hydroxide is precipitated by dissolving about 90 grams of cupric nitratetrihydrate in about 450 cc. of methyl alcohol, adding about 56 cc. of vabout lzlammonium hydroxide toapproximately one-third of this solution to form the deep blue copper-ammonia complex, and then adding the other two-thirds of the methyl alcohol solution with agitation. A very uniform,

Example 1V About 97 grams of nickelous nitrate hexahydrate [Ni (NO3)2.6H2O] are dissolved in about 500 cc. of water. Dilute ammonium hydroxide is gradually added until no further precipitation occurs. After the precipitated nickelous hydroxide has settled, the supernatant liquor is siphoned oil, and methyl alcohol is added to make up to approximately the original volume. The precipitate is mixed throughout the liquid body by agitation and is again allowed to settle, thesupernatant liquor again being drawn oif. Repeated additions of methyl alcohol and decantations are made until the amount of water present is reduced to about 1%. Upon drawing oil the major part of the final portion of methyl alcohol as supernatant liquor, the body is again clave is then raised toabout 300 pounds per square inch with hydrogen, and the autoclave is slowly heated to a temperature of about 350 C.,

the pressure rising during this heating. The vapors are bled from the autoclave, andthe system is evacuated. It is permitted to stand for some hours until cool, when it is opened. Jet black nickel ina form similar to that described in the preceding example is thereby produced.

Where sodium hydroxide or other alkali or an alkaline salt is employed as the precipitating medium, in place of ammonium hydroxide, it may be found necessary to carry out the precipitation in an aqueous medium and then to leach out the soluble inorganic salts with additional portions of. water before replacing-the. water with an organic solvent. In this way, the metal cata Cupric hydroxide and nickelous hydroxide are precipitated together by adding'sodium hydroxide in excess to a solution of about .15 grams of cupric nitrate trihydrate and about 18 grams of 1 original volume; the precipitate is then mixed nickelous nitrate hexahydrate inabcut 300 cc.

of water. After the precipitate has settled, the

throughout the volume and is permitted tosettle, and the supernatantliquor is again withdrawn. This procedure is repeated with addimade up to approximately the original volume by the addition of ethyl ether. The precipitated nickelous hydroxide is mixedin the ether, and, by repeated settling, decanting, and adding fresh ether, the methyl alcohol content of the solution is reduced to about,l%. About 40 grams of hydroquinone are added to the suspension, which is introduced into the autoclave and'heated there in in an atmosphere of nitrogen, as described in Example I, to a temperature of about 245, .C. The procedure followed thereafter is similar to that set forth in Example I. About 5.5 grams of jet black nickel with an apparent density of about 0.18 gram per cubic centimetenas compared with a density of 8.90 grams, per cubic centimeter for solid nickel, are obtained. While the nickel thus produced does not hold together quite so well as the copper, so that it cannot as practicably be cut into blocks, it has been found that the nickel tendsv to crumble rather than to powder. The jet black nickel formed has been found to be practically pure nickel.

Example V to Nickelous chloride hexahydrate is dissolvedin I 1%. The n-hexane'isolutlon containing nickelous tional portions of acetone until the amount of water present is of the order of about 1%. A

I further portion of acetone is saturated with anhydrous gaseous ammonia, and this portion is then added to the precipitate. After the precipitate has again been mixed throughout the 'entire volume and has settled in avolume of about cc., the supernatant liquor is against withdrawn,and the precipitate, suspended in the aceinside is built up to about 300 pounds per square inch with anhydrous gaseous ammonia. After. being sealed, the autoclave is-slowly raised to a temperature of about 325 0. During this heat- A solid spongy product, reddish black in color and havingan apparent density of about 0.26 gram percubic centimeter, is obtained.

Example VII Stannic hydroxide is precipitated by dissolving fuming anhydrous stannic chloride in methyl alcohol and adding ammoniacal methyl ,alcohol in .excess ther'eto, followed by a small amount of water. A gel begins to form in a few, minutes time, and this is permitted to settle for a few hours. 'Ihe supernatant liquor is removedpand 1 portions of n-hexane are added, mixing thestam i nic hydroxide throughout the liquid body, allowi in: to settle, and removing the supernatant liq- 1 nor after each addition. The n-hexauecontaim 1 ing 'stannlc hydroxide suspended therein is put in an autoclave undera pressure of about 250 to about 350' pounds per square inch of hydrogen,

I and the set forth in the preceding ex- 1 amples is. followed. Theautoclave is heated to i monia in methyl alcohol is then quickly added to precipitate bismuth hydroxide. The white washeduwith'fresh portions of methyl alcohol.

'troducedinto an autoclave and treated as described in Example 11 supra; A flurry product having :an apparent density of about 0.12 grams bismuth with a small amount of bismuth oxide admixed therewith is obtained;

I am e s The procedure of Example VIII is similarly applied to a precipitate of silveroxide prepared by Qadding ammonium hydroxide to asolution of 3 silver nitrate to form the soluble silver-ammonia complex ion and then adding-more silver nitrate The precipitate suspended in the alcohol is in- I ilocculent precipitate thus formed is allowed to 1 settle to a voiume'of about 70 cc. and is then per cubic centimeter and'analyzing as metallic prepared in any such I desirable for use as cata- 4 mixtures are frequently lysts and as couples.

- The reference to the present novel metal products as "rigid" and as "of relatively high me-- chanical strength?" isintended to define themes of such strength as to be able to'support themselves when used as catalysts or otherwise in connection with chemical reactionsand to be able to withstand ordinary shocks met in such use... Gases can pass through even a long contact tube packed with the novel metal products described. q

The te bulky as applied toprecipitates is intended include those whichare amorphous.

floccuient or gelatinous.

By "apparent density" of the products of the process is meant ,the weight of an amount of the material which occupim a unit volume including the volume oi'interstitial'spaces, pores and cavities." I

Although the presentinventionhas been described in connection with illustrative examples thereof, it will be understood vby those skilled in the art that other variations and modifications of the invention can be made and various equivalents can be substituted-therefor without departing from the principles disclosed herein.

I claim:

l. "A process for producing bulky metallic preparations containing a substantial proportion of elemental metal which heating a liquid phase medium.containing asuspension of 7 solid material comprising a bulky precipitate of a reducible metal compound. in the presence of a. reducing influence and under sufficient pressure.

to maintain a liquid phase, up to substantially 3 the critical temperature of said liquid medium until the precipitate"reappears. The porous me- .tallic silver removed from ltheautociave has a ivery low apparent density. r y 3 The invention-constitutes arapid and simple method of preparingactivated metals in estate ;of very low apparent density and very'large surffacearea) When employed "as activated catasupport 'for allowing" free passage of vapors through 'themyaltho'ugh such support or tiller imay beused to provide even greater bulk. These metal products can be wetted and dried without loss of form or original properties, and they can be easily reactivated after use as catalysts, as by treatment with a suitable organic solvent whereby themedium is vaporized without substantial agitation due to boiling and without substantially aifecting the bulkiness of the solid j material. i

2. A process for producing bulky metallic preparations containing asubstantialproportion of 1 elemental metal which comprises heating a liq- 1 uid phase medium containing a bulkyprecipitate V x of a reducible metal. compound in the presence llysts; the metal products thus formed need no j y 1 atmosphere to a temperature of at least about maintaining during heating up to about the critie,

of a reducing influence and of a non-oxidizing the critical temperature 'of' the -medium, and

I ebullition 0f the medium.

jand/orheating to about 300 C. in the presence 1 of hydrogen, methanol or other reducing atmosphere and/or other means. 'The novel metal products'iproduced in accordance with the new.

method herein described can be employed for any reactions in which advantageously used as activated my we'llas in any processes where a large surface area and/or finely comminuted form of the metal is desirable.'

Suitable uses are ascataiysts'for hydrogenation,

dehydrogenation, condensation reactions. 'etc.;' as couples, and as acceptors, as oi-oxy en and halogens. Nickel produced essentially as herein spe; cified has been used to great advantage in catalyticall hydrogenating unsaturated fatty acids, and the novelcopper catalyst described has given results asa dehydrogenation catahr'st which are considerably superiorto those obtained with copper catalysts provided in any other form. Metals inintimate'mixture witheachothercanalsobe 1 clent'to maintain a liquid phase up to the criti- 3. A process for producing metals of low apparent density which comprises slowly heating a.

liquid phase medium containing a bulkv precipitate of a reducible metal-compound in the presence of a reducing 'age nt and of a non-oxidizing atmosphere 'to a temperature above the critical temperature of the medium,subiecting said me- 7 dium during heating to a pressure at least sumcal temperature of the medium whereby said medium is vaporized at about the critical temperamaintaining the temperature above thecriticai ture. and removing the vaporized medium while 1 temperature..

4. A process'for producing metaisof low ap-f parent density which comprises slowly heating a liquid phase medium containinga bulky, pre- V cipitate of a reducible metal compound in the 1 presence of a reducing agent and of a non-oxif 1 dizing atmosphere to a temperature above the V critical'temperature of the subjecting said medium during heating wa pressure at least sumcient to maintain a liquid phase up to the critical temperature of the medium whereby said medium is vaporized at about thecritical temperature, slowly-rem'ovingthe vaporized medium while maintainingthe "temperature above the criticaltemperajture, and slowiyfcooling the residue in a non oxidizing atmosphere.

A process for producing metals of low apparent density which comprises establishing a bulky precipitate of a reducible metal compound in a first liquid medium; successively adding portions 05a second liquid medium at least partly miscible withthefir st liquid medium and having a lower critical temperature than the first liquid medium, mixing, settling, and removing supernatant liquor until the content of the first liquid medium is reduced to about 1% to about 3%; heating the second liquid medium containing the bulky precipitate in the presence oi. a reducing agent and of a non-oxidizing atmosphere to a temperature of at least about the critical temperature of the medium; and subjecting said second liquid medium during heating to a pressure at least sufllcient to maintain a liquid phase up to the critical temperature of the medium;

6. A process for producing metals of low apparent density which comprises precipitating a metal hydroxide in an aqueous medium; successively adding portions of a non-aqueous liquid medium at least partly miscible with water and having a critical temperature below that of water, mixing, settling, and removing supernatant liquor until the water content is reduced to about 1%; slowly heating said liquid medium containing the metal hydroxide in the presence of a reducing agent and of a non-oxidizing atmosphere to a temperature of at least about the critical temperature; and subjecting said liquid medium during heating to a pressure at least suillcient to maintain a liquid phase up to the critical temperature of the medium.

7. A process for producing metals of low apparent density which comprises establishing a bulky precipitate of a reducible metal compound in a liquid phase medium having reducing properties at high temperature, heating said medium containing the bulky precipitate in the presence of a non-oxidizing atmosphere to a temperature at which the medium exhibits reducing properties and at least about the critical temperature of the medium, subjecting the medium during heating to a pressure at least suflicient to maintain a liquid phase up to the critical temperature of the medium whereby said medium is vaporized at about its critical temperature, and removing the vaporized medium while maintaining the temperature above the critical temperature of said medium.

8. A process for producing copper of low apparent density which comprises heating a liquid phase medium containing a bulky precipitate of a copper compound in the presence of a reducing agent and under suilicient pressure to maintain a liquid phase up to substantially the critical temperature of said liquid medium whereby the medium is vaporized without substantial agitation due to boiling and without substantially affecting the bulkiness of the solid material.

9. A rocess for producing nickel of low apparent density which comprises heating a liquid phase medium containing a bulky precipitate of a nickel compound in the presence 0! a reducing agent and under sufllcient pressure to maintain a liquid phase up to substantially the critical temperature of said liquid mediumwhereby the medium is vaporized without substantial agitation the bulkiness of the solid material.

10. A process for producing copper of low ap parent density which comprises slowly heating a liquid phase medium containing a bulky precipitate of a copper compound in the presence of a reducing agent and o! a non-oxidizing atmosphere to a temperature of at least about the critical temperature of the medium, subjecting said liquid medium during heating to a pressure at least sufficient t maintain a liquid phase up to the critical temperature orthe medium whereby the liquid medium is vaporized at about its critical temperature, and removing said vaporized medium while maintaining the temperature above the critical temperature of the medium.

11. A process for producing nickel or low apparent density which comprises slowly heating a liquid phase medium containing a bulky precipitate of a nickel compound in the presence of a reducing agent and or a non-oxidizing atmosphere to a temperature of at least about the critical temperature of the medium, subjecting said liquid medium during heating to a pressure at least sufllcient to maintain a liquid phase up to the critical temperature of the medium whereby the liquid medium is vaporized at about its critical temperature, and removing said vaporized medium while maintaining the temperature above the critical temperature of the medium. I

12. A process for producing copper of low apparent density which comprises establishing a precipitate oi cupric hydroxide in an aqueous medium; successively adding portions of a non-aqueous liquid phase medium having a critical temperature below that of water, mixing, settling, and removing supernatant liquor until the water content is reduced to about 1%; slowly heating said liquid medium containing cupric hydroxide in the presence oil a reducing agent and of a non-oxidizing atmosphere to a temperature above the critical temperature of the liquid medium; subjecting said liquid medium during heating to a pressure at least suflicient to maintain a liquid phase up to the critical temperature of the medium whereby the liquid medium is vaporized at about its critical temperature; removing the vaporized medium while maintaining the temperature above the critical temperature of said medium: and slowly cooling the residue in a non-oxidizing atmosphere.

13. A process for producing nickel of low apparent density which comprises establishing a precipitate of nickelous hydroxide in an aqueous medium; successively adding portions of a nonaqueous liquid phase medium having a critical temperature below that of water, mixing, settling, and removing supernatant liquor until the water content is reduced to about 1%; slowly heating said liquid medium containingnickelous hydroxide in the presence of a reducing agent and of a non-oxidizing atmosphere to a temperature above the critical temperature of the liquid medium; subjecting said liquid medium during heating to a pressure at least sufiicient to maintain a liquid phase up to the critical temperature of the medium whereby the liquid medium is vaporized at about its critical temperature; removing the vaporized medium while maintaining the temperature above the critical temperature of said medium; and slowly cooling the residue in a nonoxidizing atmosphere.

14. A process for producing copper of low apparent density which comprises adding ammonium hydroxide to on equeoue solution oi 11 copper salt to produce cupric hydroxide; adding a. further amount of ammonium hydroxide to dieeolvethe cuprlc hydroxide and to form the cop- ;per-ammonla complex im; adding 'a further 1 amount or an aq eous solution of a copper alt fto reprecipitate eupric hydroxide; successively";

1 adding portions or a non-aqueous liquid phase non-oxidizing atmosphere.

taining cuprlc hm t obovethecritieel temperature the medium whereby the liquid mediumh va porinedpt about. its critical temperature; removi the vaporized while maintaining the temperature above i of said medium: endelcwlvcooling thereeidueina aosnrn manna VALENTINE m Jr.