WO1994012435A1

WO1994012435A1 - Process for making solutions containing basic zirconium and hafnium chlorides

Info

Publication number: WO1994012435A1
Application number: PCT/US1993/011325
Authority: WO
Inventors: James A. Sommers
Original assignee: Teledyne Industries, Inc.
Priority date: 1992-11-20
Filing date: 1993-11-22
Publication date: 1994-06-09
Also published as: AU5674494A

Abstract

A process for the production of zirconium or hafnium rich aqueous solutions containing a substantial concentration of the hydroxychloride of the metal comprising the steps of providing a zirconium or hafnium containing chloride or oxychloride produced from zirconium or hafnium tetrachloride; oxidizing the chloride or oxychloride sufficiently to evolve substantially all the excess chlorine over that which would be present as the hydroxychloride of the metal; and recovering an aqueous solution of the resultant hydroxychloride having at least 25 % by weight of the metal calculated as its oxide and a chlorine to metal ratio of from about .75 to about 1.5. The aqueous solution is prepared by dissolving zirconium or hafnium tetrachloride in water before oxidizing. The process includes the aqueous solution being extracted with an organic solvent such as methyl isobutyl ketone which is capable of removing substantially all of the iron impurity present in the aqueous solution.

Description

PROCESS FOR MAKING SOLUTIONS CONTAINING BASIC ZIRCONIUM

AND HAFNIUM CHLORIDES

BACKGROUND OF THE INVENTION

So-called zirconium-rich liquids (ZRLs) and hafnium-rich liquids (HRLs) are aqueous solutions of zirconium hydroxychloride, ZrO(OH)Cl, or hafnium hydroxychloride HfO(OH)Cl. Nominally, such solutions contain 10-40 weight percent Zrθ₂ or 15 to 70 weight percent Hf0₂. They are also characterized by a Cl/Zr or a Cl/Hf molar ratio near one, as opposed to a value of two for zirconium oxychloride, ZrOCl-.- 8H₂0 or hafnium oxychloride, HfOCl-.- 8H₂0. Thus, the hydroxychlorides are more concentrated in Zr0₂ or Hf0₂ and, therefore, less acidic than solutions of the oxychlorides. They are sometimes referred to as basic zirconyl chlorides or basic hafnyl chlorides. Since they exhibit lower acidity and contain a higher concentration of zirconium or hafnium, they are more economical to ship a d easier to use in some preparations of Zr-containing or Hf-containing industrial chemicals. Unfortunately, the methods for producing zirconium-rich or hafnium-rich liquids containing basic chlorides have involved processes which required expensive starting materials in order to meet the stringent purity requirements desired for their use in skin contacting cosmetic applications, such as in antiperspirants.

Blumenthal, "The Chemical Behavior of Zirconium", (Van Nostrand, Princeton NJ, 1958), p. 132, describes how a water soluble solid ZrO(OH)Cl* nH₂0 can be obtained by adding ether to zirconium oxychloride. Als'o, a slurry of hydrous zirconia in hydrochloric acid can be heated to achieve zirconium-rich liquid containing zirconium hydroxychloride. Farnworth, Jones and McΛlpine, in "Specialty Inorganic Chemicals", R . Thompson, ed. , Royal Society of Chemistry, London, 1981, p. 201, describes how zirconium hydroxychloride can be obtained by adding hydrochloric acid to zirconium basic carbonate.

Blu enthal, J. C em. Ed., 39, 606 (1962) describes how zirconium hydroxychlorides can be obtained from partially neutralizing a solution containing zirconium oxychloride. In each of the above cases, the starting material used is a relatively costly, upgraded product. For example, zirconium oxychloride is obtained from the caustic fusion of zircon sand or baddeleyite, after the removal of some of the many impurities which occur naturally in these two minerals. It is typically sold as crystals which have been derived from a costly recrystallization process. Zirconium basic carbonate is derived from zirconium basic sulfate, which is in turn made from zirconium oxychloride or zirconyl chloride. Therefore, these routes to the formation of a zirconium hydroxychloride are at an economic disadvantage, since in each case, they must use even more chemicals and conversion steps to arrive at a product having a metal to chlorine ratio of about one, i.e., a zirconium-rich liquid or a hafnium-rich liquid as the hydroxychlorides are defined herein. There is, therefore, a need for a process which makes use of less costly starting materials, such as the tetra- chlorides of zirconium and/or hafnium. Zirconium tetrachloride intended for use in the Kroll process is an economical starting material, which typically however, contains undesirable impurities, including iron, which render it unsuitable for use directly in the preparation of hydroxy- chlorides. Also, the ratio of chlorine to metal is 4:1, meaning that in conventional processing, such as by dissolution into water, the other three chlorine atoms are removed as a relatively low value product, HC1, in dilute acidic solution. The prior art has thus been unable to economically make use of this source of zirconium. There has therefore been a need for a process that utilizes zirconium tetrachloride as a starting material that avoids the drawbacks previously identified. The use of ZrO(OH)Cl_χ is varied and includes coating onto membranes for use in ultrafiltration or reverse osmosis, cross-linking agents for enzyme immobilization, coupling agents between dental enamel and restorative material and cross-linking agents for polymeric resin binders useful in flexible cast sheets for building materials. Other uses include its use in paper coating compositions, and water resistant adhesives.

OBJECTS OF THE INVENTION One object of the present invention is to provide an improved method of obtaining solutions containing basic zirconium and hafnium chlorides directly from feedstocks which are obtained directly from zirconium and hafnium separation processes producing zirconium or hafnium tetrachloride.

It is a further object of this invention to make use of anhydrous zirconium tetrachloride or hafnium tetrachloride such as may arise from carbon chlorination of zirconium or hafnium sand or an ore such as baddeleyite, or from chlorination of zirconium or hafnium scrap sources. Also, it is desired to have a process which can make use of impure chloride-based aqueous solutions, such as arise from ore-processing steps such as caustic fusion of zircon sand and from Zr-Hf separation processes.

It is yet a further object to avoid use of higher-value added intermediates to make zirconium or hafnium chlorides such as zirconium or hafnium sulfates, carbonates, or hydrous oxides.

It is still another object of the invention to provide a zirconium-rich liquid or hafnium-rich liquids in which the levels of organic contaminants are reduced making the zirconium- or hafnium-rich liquids suitable for use in skin-contacting preparations such as antiperspirants.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS It will be understood that in the various recitations of zirconium throughout this specification that hafnium can also be the object of the disclosure.

Zirconium tetrachloride can be added to a mixture of water or dilute hydrochloric acid and an organic solvent, such as methyl isobutyl ketone (MIBK) . The zirconium reports or is dissolved in the aqueous phase with its chloride ions, while impurities, such as iron, report to the organic phase. It may be necessary, as in the case of heavily contaminated feedstocks, to perform more than one contacting of the aqueous phase with fresh organic phase. The aqueous phase, heated by the exothermic dissolution process, is then separated from the impurity-laden organic phase. This leaves an aqueous phase that is saturated with the organic liquid. For example, MIBK is soluble to the extent of about 2% in water. This organic content must be substantially removed. Next, the aqueous phase is oxidized for example with a solution of hydrogen peroxide, H₂0₂, which can be added in sufficient amounts to the aqueous phase to oxidize the metal chloride present with the evolution of chlorine gas which can be recovered for recycle in the preparation of the metal chloride. The reaction of the peroxide in the acidic aqueous medium can be written as: H₂0₂ + 2 H⁺ + 2C1^" = Cl₂ (gas) + 2H₂0 In the foregoing reaction, the combined effects of the heat, chlorine gas evolution and the oxidizing environment provided by the peroxide are effective to lower the organic content of the aqueous phase to negligible levels. Thus, in one step, three objectives are accomplished: (1) elimination of chloride to arrive at the desired Cl/Zr ratio of nominally one, (2) making the available chloride into a relatively useful high value chlorine gas, and (3) lowering the level of residual organic compounds content of the product.

The aqueous solution is then concentrated by evaporation to meet the desired concentration calculated as Zr0₂ content. Upon cooling, a clear, water-white solution, with 10-40 weight percent Zr0₂, preferably 20-40%, having a Cl/Zr ratio near one, is obtained.

The wet chlorine gas evolved from the oxidation is led to a drying tower, compressed and stored for use in chlorination operations. Finally, the impurity-bearing organic phase is stripped of its impurity content by contact with water, after which the organic phase is then available for re-use in further extractions.

An additional feature of this invention is that it can also be applied to a feedstock consisting of impure crystals of zirconium oxychloride, or to an impure solution of zirconium oxychloride. In such a case, the starting material is made into an aqueous solution, contacted with the organic extractant, the aqueous and organic phases separated and the aqueous phase then subjected to peroxide treatment as before. The sufficient amount of peroxide necessary should be enough to lower the Cl/Zr from an initial value of nominally two, to one. The following examples describe the practice of the reactions described: EXAMPLE 1

A mixture was made of 100 mL H-.0 containing 45 gm of dissolved zirconium tetrachloride which solution was contacted with lOO L of MIBK. To this mixture, 0.5 mL of 30% H₂0₂ was added. The final temperature of the two-phase system was 85*C. The system was stirred briskly for 5 minutes and placed into a separatory funnel and the lower aqueous phase withdrawn. Fresh MIBK (100 mL) was added with stirring and heating which was continued for 5 minutes, after which the aqueous layer was again withdrawn. A final 100 L increment of fresh MIBK was added and the mixture heated, stirred and separated as before. To the still-hot aqueous phase was added dropwise 36 g of 30% hydrogen peroxide, such that the mixture effervesced vigorously but did not boil over. The mixture turned pale yellow green as chlorine gas evolved. After evolution of chlorine ceased, the mixture was evaporated over about l*s hours, its volume going from 125 mL to about 50 mL. Upon cooling, the mixture was found to be an odorless, water-white solution. Its density was found to be 1.6 g/mL, its Zr0₂ content to be 34.7 weight percent. Its chloride content was 150 g/L, giving a Cl/Zr ratio of 0.95. The organic content was found to be 30 mg/L MIBK. A sample of the original ZrCl₄ was dissolved in water and this

<- solution analyzed alongside the liquid product of this example. The results obtained were as follows:

100.00 g, were dissolved in 99.96 g H₂0. To this solution 16.28 g of 30% H₂0₂ was incrementaly added to this solution (at ambient temperature) . The temperature of the solution was slowly raised to 92*C over the course of about 4 hours, during which time the yellow-green fumes of evolving chlorine gas were observed. After the evolution of chlorine ceased, the volume of the solution was then reduced by evaporation from an initial 175 mL to about 90 L. The solution was allowed to cool. It had a measured density of 1.48 g/mL, a Zrθ₂ content of 27.9% and a chlorine level of 160 g/L. This gives a Cl/Zr value of 1.36. EXAMPLE 3

ZrOCl₂* 8H₂0 crystals, 160.13 g, were placed into a 400 mL beaker and H₂0₂, 30%, 34.07 g, was poured directly onto the crystals. Chlorine gas began to be evolved immediately and the temperature rose from 18*C to 28*C in about 5 minutes. Within 10 minutes, the crystal bed had slumped and substantially liquified and it would have been possible to stir the mixture, but instead, it was allowed to evolve chlorine gas passively for 2 hr 25 min. At three hours from the addition, the beaker had lost 17 g, during which time the temperature slowly fell to 18^*C. The mixture was stirred slowly at ambient temperature overnight. In the morning, it was gently heated to 45*C throughout the day, until the odor of chlorine was gone. It lost a further 7 g. The final solution had a density of 1.6 g/mL, a Zr0₂ level of 550 g/L, a chloride level of 160 g/L, a Zr/Cl level of 1.019 and a Zr0₂ content of 34%. EXAMPLE 4 A series of runs were made in which all variables were held constant except the amount of hydrogen peroxide used and the final volume of the sample. In each case 115 g of ZrCl₄ (sublimed crude chloride) was added to a mixture of 250 mL of water, 125 L MIBK and 1 mL of 30% H₂0₂ added to insure that all the iron impurity present is oxidized to the +3 oxidation state which is necessary for substantially complete extraction into the MIBK. After stirring for 10 minutes, the aqueous phase was removed from the organic phase and a fresh 125 mL increment of MIBK was added. After a further 10 minutes of stirring, the phases were again separated. To the aqueous phase was slowly added a volume of 30% H₂0₂, the amounts varying in each run. During this time, the temperature would rise to about 80*C, with brisk effervescence of evolved chlorine gas. The mixture was then evaporated at temperatures of 70-75*C, with vigorous stirring, until the volume of the solution was reduced to a predetermined degree, depending upon several criteria. These criteria were as follows: appearance of crystals of ZrOCl₂' 8H₂0 evidence of high viscosity, sufficient to slow the magnetic stir bar and thus risk localized hot spots and irreversible dehydration; reaching a volume of about 110 mL. The solutions were then cooled and analyzed for several attributes as tabulated in Table 2.

It can be seen from the foregoing description of the present invention that zirconium hydroxy chloride can be produced economically from aqueous solutions of zirconium tetrachloride, zirconium oxychloride crystals derived from such solutions either directly or after preparing an aqueous solution by dissolving the crystals. Likewise, the use of an aqueous solution of zirconium tetrachloride can be treated with any suitable oxidizer such as hydrogen peroxide or a hypochlorite, to facilitate the subsequent separation of iron impurity with an organic solvent such as MIBK, and the aqueous solution separated from the organic phase and oxidized to evolve reusable chlorine gas and produce a concentrated aqueous phase which is rich in zirconium or hafnium by virtue of the production of substantial quantities of the hydroxychloride so that the halide to metal ratio is closer to unity. The oxidation fo the Fe*² to Fe*³ while essential for separation with an organic solvent is also essential where hydrogen peroxide is to be employed subsequently as the presence of iron will catalytically decompose the peroxide.

The invention as described is capable of being practiced in a different manner than specifically shown and is therefore as broad as indicated by the following claims and limited only by the applicable prior art.

Claims

CLAIMS 1. A process for the production of zirconium or hafnium rich aqueous solutions containing a substantial concentration of the hydroxychloride of the metal comprising the steps of: providing a zirconium or hafnium containing chloride or oxychloride produced from zirconium or hafnium tetrachloride; oxidizing the chloride or oxychloride sufficiently to evolve substantially all the excess chlorine over that which would be present as the hydroxychloride of the metal and; recovering an aqueous solution of the resultant hydroxychloride having at least 25% by weight of the metal calculated as its oxide and a chlorine to metal ratio of from about .75 to about 1.5.

2. The process of claim 1, wherein the chloride or oxychloride is oxidized with an aqueous solution of hydrogen peroxide.

3. The process of claim 1, wherein an aqueous solution is prepared by dissolving zirconium or hafnium tetrachloride in water before the oxidation step.

SUBSTITUTE SHEET

4. The process of claim 3, wherein the aqueous solution is contacted with sufficient compatible oxidizing agent to oxidize all iron present to its highest valence state.

5. The process of claim 4, wherein the aqueous solution is extracted with an organic solvent capable of removing substantially all of the iron impurity present in the aqueous solution.

6. The process of claim 5, wherein the aqueous solution is separated from the organic solvent and sufficient hydrogen peroxide added to remove the chlorine as evolved chlorine gas.

7. The process of claim 6, wherein the chlorine gas is recovered for reuse and the organic solvent is distilled for reuse.

8. The process of claim 6, wherein the aqueous solution containing metal hydroxychloride is concentrated by evaporation.

9. The process of claim 5, wherein the organic solvent is methyl isobutyl ketone.

10. The process of claim 9, wherein the recovered metal hydroxychloride solution contains less than 25 ppm of iron.

SUBSTITUTE SHEET

11. The process of claim 10, wherein the hydroxychloride solution contains less than 10 mg/1 of organic compound contamination.

SUBSTITUTE SHEET