US2642356A - Low-temperature reduction of nickel chloride - Google Patents

Description

Patented June 16, 1953 LOW-T MPERATURE. REDUCTIQN 1 NICKEL CHLORIDE Edward A. Beidler, Columbus, 0hlo,as signor,' by mesne assignments, to Crowley-Republic *Steel Corporation, Cleveland, Ohio, a corporation of Delaware Serial No. 163,791

No Drawing. Applicationz M-ay23,1950,

1 iciaims. (c1. r s-=05) T e present invention relates to the low temperature reduction of nickel chloride and more particularly to the reduction of nickel chloride to form finely divided metallic nickel at tem.- peratures below that at which this material could be reduced in the absence of a catalyst in accordance with previously known methods.

For many purposes it is desired to prepare nickel in a very finely divided condition. Such material may, for example, find a use as a,

catalyst in numerous hydrogenation reactions, wherein the value of a material as a catalyst is to a certain extent at least enhanced by a finer state of subdivision. Finely divided nickel is also useful in powder metallurgy, particularly where the nickel is to bemixed with some other powdered metal, for example iron, in making composite articles. When the nickel used is in a very finely divided condition, the resulting articles made by powder metallurgy processes are much more homogeneous than if the nickel were used in the form of coarser particles. In

' some instances also the fineness of the nickel powder may make for greater strength in'a product made therefrom.

It is known that nickel powder formed by chemically reducing a compound of nickel is smaller in particle size'substantially in proportion as the temperature at which the reduction takes place is lower. For this reason, it has been economical practicable rate.

the minimum amount of metallic nickel nor-.

desired, when finely divided nickel is the desired 1 product, to eifect the. reductionat as low a temperature or temperature range as possible. Prior art practices and certain tests hereinafter set out in the examples given demonstrate that at temperatures below about 650 F. the reduction to nickel from one of its salts, for example, from nickel chloride, proceeds at such an extremely slow rate that it may be said for practical purposes, that it is impossible to reduce nickel chloride below this temperature in the absence of some catalyst which will enable the reaction to take place at an appreciable rate in the desired lowertemperature range. i

The present invention may be summarized therefore as one providing a process for the 'p'reparation of finely divided metallic. nickel from a salt of nickel, for example, nickel chlorideyin a temperature range of about 475 F. to about 650 F. In this range it is found that the reduction 2 process is autocatalytic, that is,'it will proceed at a practical irate once-it is initiated by the presence of at least a trace, or a so-called threshold amount of the catalyst. It is further found thatthe rate of such reduc 'tion is enhanced by greater .amounts of the catalyst and also, independently, by increased temperatures in .the range at which the reduction reaction takes place. It has been found, for example, that at temperatures above about 650 F. the reaction will goon even without a catalyst to initiate it, even though thereduced'. material at these higher temperatures is in .much larger particle size than is desired in accordance with the present invention.

While it is contemplated, and it has been proven as hereinafter set forth, that a trace, or a :so-called threshold amount only of the catalyst (i. e., finely divided metallic nickel) will be suflicient to initiate the reduction reaction, it is believed that, from a practical standpoint, at least about 0.1% of metallic nickel (calculated by weight based upon the weight of the nickel chloride to be reduced) is required in order to start the reduction reaction at anyiappreciable and For this reason many usable in initiating the reduction ofthe nickel chloride may be said for purposes of this invention to be about 0.1%, calculated as aforesaid.

In view of theiact that larger amounts of.

the catalyst will cause the reaction to occur with is useful to employ larger amounts of the catalyst: than the'minimum above referred to. This causes no substantial loss, as the. product itself is the catalyst and, therefor a p o h eof may be returned from onebatch to a succeeding batch in the practical workingof the process.

In this way the only loss in the repeated practice reaction will take place if it is catalyzed by the reaction being catalyzed, it-may be said that the illustrated by the following examples:

of the process is the heat-that is required to 1'6? heat a certain amount of the'catalyst, i. e., the product of an earlier batch. Corresponding economies maybe effected on :a continuous basis of operation. The process as a whole, which is carried on at a substantially lower temperature than was heretofore deemed possible, will save a muchlarger total amount of heat than that lost as aforesaid and hence is more economical. Theprocess of the present invention is best Example I About 10 grams of anhydrous nickel chloride was placed into each of two similar porcelain added to and thoroughly mixed with the nickel chloride prior to the placing of this mixed material in the furnace; while in the other'no metallic nickel was intentionally placed. The material was maintained in the furnace at the tempera- I ture aforesaid and exposed to a continuous flowhours. At the end of this time the contents of the two porcelain boats were cooled, removed and analyzed. The sample consisting of a nickel chlorid mixed with metallic nickel was found to have been substantially completely reduced, actual analysis of the content of this sample, showing 99.3% metallic nickel. Thecontents of the other boat, to which no metallic nickel was intentionally added, was found to be almost completely unreduced. The only metallic nickel found in this second boat was at a pinpoint location in the sample and indicated that a particle of metallic nickel was probably accidentally transferred to this point in the second sample by entrainment in the gas stream. Immediately around this pining stream of hydrogen for a period of about 35 point area there was a spot about T 6 in diameter where the nickel chloride had been reduced to metallic nickel. The remainder "of the sample was completely unreduced.

Example II Hydrated nickel chloride (NiC12.2H2O') was first dehydrated in a stream of nitrogen at about 700 then cooled to about 600 F. and thenitrogen atmosphere exchanged for a' hydrogen atmosphere which was caused to ilow continuously past Example III The same test as in Example II was made with the exception that the hydrated nickel chloride was not first dehydrated prior to being exposed at the reducing conditions stated in Example II in the hydrogen atmosphere. The results were identical with those given in Example II.

Example I V y A sample of anhydrous nickel chloride to which about 16% of its weight offinely divided metallic nickel was added and thoroughly admixed was exposed as" in Examples II and IE to a ficw of hydrogen, first at about 450 F. At this temperature, there was no discernible reduction taking place as evidenced by the fact that no HCl was found in the exit gas. Upon the temperature being raised to about 475 F. the exit gases began to show some l-ICl content. As the temperature was progressively raised in about 10" steps, the HCl content in the gases was progressively greater, indicating a progressively increased rate of reduction as the temperature was raised.

'ducing nickel chloride to metallic nickel.

Example V The same test as in Example IV was made, using nickel chloride dihydrate in lieu of anhydrous nickel chloride. The results were ex- 1 actly the same as in Example IV above.

It has been found that in order to reduce nickel chloride to metallic nickel, the gaseous reducing agent must contain hydrogen, as hydrogen is the only gas which has been found, in accordance with the present invention, to be efiective in re- It seems immaterial what the proportion of the hydrogen is in the gases or what other gases may be present, assuming, that is, that the other gases are not positively oxidizing or chloridizing in character. These other gases are preferably substantially neutral in character, such as nitrogen, for example. For this reason hydrogen is considered, in accordance with the present invention, to be the essential active reducing ingredient of the gas to which the nickel chloride is exposed in order to effect the reduction thereof.

From the above it will be noted that one way of practicing the process of the present invention is to mix with nickel chloride, with or without water of crystallization, a desired amount of finely divided metallic nickel as a catalyst to initiate the reducing reaction in the low temperature range. Another way of attaining the same results is, of course, in any way to provide in the mass of nickel chloride to be reduced, the desired catalyst. As it has been found, as above set forth, that the reduction will take place in the absence of a catalyst at higher temperatures, this high temperature reduction may sometimes be resorted to to form or to establish in the mass, the desired amount of metallic nickel to act as the catalyst. Following the establishment of the initial desired amount, the temperature may be lowered to a point or range within the desired range in accordance with the present invention, i. e., from about 475 F. to about 650 F., and then the process of the present invention carried on. The present process is to be considered to include such practice.

While there is herein described but one principal process and certain variants thereof, the present invention is intended to include all reasonable equivalents of the steps specifically set out herein, as will occur to those skilled in the art from the foregoing disclosure.

What is claimed is:

l. The process of initiating the reduction of solid nickel chloride (NiClz) with hydrogen by a dry gas-to-solid reaction to form metallic nickel in a temperature range in which hydrogen and NiClz will not commence to react together to any substantial extent in the absence of a reactioninitiating catalyst, comprising the steps of contacting dry solid NiClz, which is substantially free of metallic nickel, with a gas containing hydrogen as itsessential active reducing ingredient, while maintaining said NiClz in the temperature range of about 475 F. to about 650 F., and causing the reaction to startby providing in contact with the NlClz at least about 0.1% (by weight based upon the N1012) of metallic nickel as a reaction-initiating catalyst.

5 said metallic nickel for use as a reaction-unflating catalyst is provided by forming such metallic nickel in situ by reducing some NiCh at a. temperature above 650 F.

EDWARD A. BEIDLER.

References Cited in the file of this patent 7 UNITED STATES PATENTS Number Name Date 7 1,373,654 Danckwardt Apt. 5, 1921 1,783,662 Marx et a1. Dec. 2, 1930 OTHER REFERENCES Societe Chemique de France, Bulletin, vol. 35,

1924, pages 550-584, inclusive, and pages 729-741, inclusive. Article by M. G. Crut.

Comprehensive Treatise on Inorganic and TheoreticalChemistry, by Mellor, vol. 15, 1936,

page 411. Published by Longmans, Green and 00., New York.

Claims (1)

1. THE PROCESS OF INITIATING THE REDUCTION OF SOLID NICKEL CHLORIDE (NICL2) WITH HYDROGEN BY A DRY GAS-TO-SOLID REACTION TO FORM METALLIC NICKEL IN A TEMPERATURE RANGE IN WHICH HYDROGEN AND NICL2 WILL NOT COMMENCE TO REACT TOGETHER TO ANY SUBSTANTIAL EXTENT IN THE ABSENCE OF A REACTIONINTIATING CATALYST, COMPRISING THE STEPS OF CONTACTING DRY SOLID NICL2, WHICH IS SUBSTANTIALLY FREE OF METALLIC NICKEL, WITH A GAS CONTAINING HYDROGEN AS ITS ESSENTIAL ACTIVE REDUCING INGREDIENT, WHILE MAINTAINING SAID NICL2 IN THE TEMPERATURE RANGE OF ABOUT 475* F. TO ABOUT 650* F. AND CAUSING THE REACTION TO START BY PROVIDING IN CONTACT WITH THE NICL2 AT LEAST ABOUT 0.1% (BY WEIGHT BASED UPON THE NICL2) OF METALLIC NICKEL AS A REACTION-INITIATING CATALYST.