665
Ind. Eng. Chem. Prod. Res. Dev. 1886, 25, 665-670
dohexane); IR 1622,1669,1718, and 1732 cm-l; NMR 6 0.65 (s), 0.93 (s), 2.28 (s), 4.63 (m), 5.68 (s), 8.0 ( 8 ) ; yield method A 90%, method B 80%. &d.Calcd for C4&05 (MW 675): C, 78.29; H, 9.86. Found: C, 78.29; H, 9.84. Testosterone ester of 3a,l2a-bis(formyloxy)-5@cholan-24-oic acid (11) was crystallized from methanol: mp 179 "C; [ a I z 5 D +1.17" (CHC13) UV max 234 nm (e 16 537, cyclohexane); IR 1618,1665,1713, and 1725 cm-l; NMR 6 0.74 (s), 0.92 (s), 5.15 (m), 5.63 (s), 7.92 (s), 8.04 (s); yield method B 85%. Anal. Calcd for C4SH6s07 (MW 729.0): C, 75.17; H, 9.25. Found C, 75.15; H, 9.33. Testosterone ester of 3a,7a,l2a-tris(formyloxy)-5~cholan-24-oic acid (111) was crystallized from hexane: mp 112-114 "C; [(u]25D + 89.8" (CHCl,); UV max 243 nm (e 11 750, methanol); IR 1628,1673, and 1722 cm-'; NMR 6 5.18 (m), 5.6 (m) 7.90 (s), 7.98 (s), 8.06 ( 8 ) ; yield method B 85%. Anal. Calcd for CGI&09 (MW 763.03): C, 72.41; H, 8.72. Found: C, 72.33; H, 8.73. Testosterone ester of 3fl-acetoxypregn-5-ene-20acarboxylic acid (IV) was crystallized from diethyl ether: mp 253-255 "C, [a]25D + 24" (CHCl,); UV max 233 nm (e 17 516, cyclohexane);IR 1665,1725, and 2940 cm-'; NMR 6 0.7 (s), 1.0 (s), 1.2 (s), 2.0 (s), 4.5 (m), 5.3 (s), 5.65 ( 8 ) ; yield method A 85%. Anal. Calcd for CaHe205(MW 658): C, 78.38; H, 9.48. Found: C, 78.39; H, 9.62. Method A. To a solution of 1.8 mmol of testosterone in 30 mL of dry benzene is added 2.0 mmol of thallous ethoxide in 30 mL of dry benzene. The solution is refluxed under dry nitrogen gas with exclusion of moisture. The solvent is slowly distilled off and replaced by fresh anhydrous benzene. This process is repeated 3 times. A solution of 2.0 mmol of acid chloride in dry benzene is then added dropwise with stirring. Refluxing is continued until completion of the reaction, as indicated by TLC. The reaction mixture is then filtered, and the filtrate is washed with water, dried, and evaporated. Method B. A sealed flask containing 1.0 mmol of the acid, 1.1 mmol of testosterone, 1.1 mmol of DCC, and 0.1
mmol of 4-DMAP in 15 mL of anhydrous methylene chloride is agitated overnight at room temperature. The reaction mixture is diluted with 20 mL of methylene chloride and filtered. The filtrate is washed with 5% aqueous HC1, saturated NaHC03 solution, and water, dried, and evaporated in vacuo. The residue is purified by dry-column chromatography and crystallization. Acknowledgment
This work received financial support from the World Health Organization, Special Program of Research in Human Reproduction. Registry NO. I, 104323-83-3;11,104323-84-4;111,104323-85-5;
IV,104323-86-6; 4-DMAP, 1122-58-3;DCC, 538-75-0;testoeterone, 58-22-0; testosterone thallium salt, 104323-87-7; 3a-(formyloxy)-5P-cholan-24-oicacid chloride, 4966-78-3; 3a,12a-(formyloxy)-5/3-cholan-24-oicacid chloride, 86678-83-3;3a,7a,12a-tris(formyloxy)-5~-cholan-24-oic acid chloride, 74670-08-9;30-acetoxy-pregn-5-ene-20a-carboxylic acid chloride, 67711-02-8; 3a(formyloxy)-5/3-cholan-24-oic acid, 5015-59-8; 3a,l2a-(formyloxy)-5P-cholan-24-oic acid, 2287-93-6; 3a,7a,12a-tris(formyloxy)-5fl-cholan-24-oicacid, 2097-89-4; 3P-acetoxy-pregn-5-ene2Oa-carboxylic acid, 1474-14-2;TlOEt, 20398-06-5. L i t e r a t u r e Cited Briggs, M.; Briggs, M. Nature (London) 1974, 252, 585. Harper, M. J. K.; Sanford, B. A. I n FerU//ty Control: 6iologica/ and 8ehavhual Aspects; Stein, R. N., Pauenstein, C. J., Eds.; Harper and Row: Hagerstown, MD, 1980; p 100. Herz, J. E.; Cruz, S.; Torres, J. V.; Murllo, A. Synrtr Commun. 1977, 7 , 383. Herz, J. E.; Sandoval, J. SteroMs 1983, 41. 327. Nelses, 8.; Steglich, W. Angew. Chem., Int. ed. Engl. 1978, 17, 522. Stelnberger, E.; Smith, K. D.; Rodriguez-Rigau, L. J. Int. J . Androl., Suppl. 1978, 2, 748. Ulsteln, M.; Netto, N.; Leonard, J.; Paulson, C. A. Contraception 1975, 72, 437. Wissner, A.; Grudzlnskas, C. J . Org. Chem. 1978, 4 3 , 3972. "World Health Organlzatlon Special Program of Research, Development and Research Training in Human Reproduction, 1lth; WHO Annual RepWr; WHO Geneva, 1982; p 79.
.
Received for review January 28, 1986 Accepted April 17, 1986
Nickel Recuperation Process from Solutions Contaminated with Foreign Cations via Thermohydrolysis Constantln I. Manolache Chemical Works of Cralova, Crakwa 1100, Romanla
Nickel is a vital metal for many applicatlons of chemical processing. Since nickel is a limited natural resource, its recuperation from spent catalysts is becoming an issue of major importance. Existing methods of separation through successhe treatments with specific reagents, electrochemical separations, and so on are inadequate for nickel recuperation because they require CompHcated phases and high costs. These difficulties have been overcome for the first time by using a new technique: thermohydrolysis. Experiments performed with nibate aqueous solutions have shown that in solutions of finite concentrations or in salt melts under conditions of thermic and chemical instability of one or more salts the introduction of water in the system causes the ions of those salts to react completely with the water. By removal of the resultant acid simultaneously and at low pressure, using water or water vapors, thermohydrolysis takes place. This method has resulted in recuperating the nickel in the form of pure nickel nitrate.
Introduction
Nickel catalysts have been used in large quantities in several fields such as hydrogenation or dehydrogenation proc-s of organic compounds (Carmichael, 1966). Finely 0196-4321/86/1225-0665$01.50/0
divided nickel, various nickel alloys, and some nickel combinations are also used as catalysts in decomposition, oxidation, condensation, and polymerization reactions and also in reactions that lead to the formation of cyclic and 0 1986 American Chemical Society
666
Ind. Eng. Chem. Prod. Res. Dev., Vol. 25, No. 4, 1986
isomeric compounds (Ripan and Ceteanu, 1969). Nickel recuperation from spent catalysts or other waste materials, so that this rare metal can be reused for the preparation of new catalysts or for other purposes, is an important economic problem. Existing purification methods to separate the foreign undesirable cations consist of successive treatments with reagents specific to the cation to be removed. These treatments include the separation of intermediate products as well (Macarovici, 1969; Popa and Croitoru, 1971). Raw metallic nickel is electrochemically purified by melting or transforming it into Ni(C0)4that decomposes thermically at 200 "C. The Ni electrolytic refining uses raw nickel anodes in diaphragm electrolyzers containing very weak acid solutions of nickel sulfate or nickel chloride (Ripan and Ceteanu, 1969). Nickel recuperation from spent catalysts cannot be done using the above-mentioned methods because the solutions resulting from metal dissolution contain large quantities of foreign cations such as Fe3+,A13+,Ca2+,Na+, and so on. Iron and aluminum cations cannot be separated through precipitation with specific reagents because, like nickel, they precipitate in the same pH 3-8 range. Thus, because of the difficulties with the separation and the high costs, nickel recuperation by the use of electrolysis is not economical. These difficulties have been overcome for the first time in chemistry by using a new technique that we have called thermohydrolysis. The nickel recuperation process discussed here uses nitrate aqueous solutions which result from the nickel recuperation of spent catalysts when an aqueous solution of 10-20% nitric acid is used. The nitrate solutions obtained are concentrated, and then thermohydrolysis is performed under vacuum at 0.5-0.6 atm. Iron nitrate is heated a t a temperature of 125-133 "C for 2 or 3 h, forming iron hydroxide, which then is separated by filtration. Aluminum nitrate, under the same conditions of pressure, is heated at a temperature of 135-140 "C for 1or 2 h, separating part of the aluminum hydroxide, while the other part of the aluminum hydroxide is formed by raising the temperature to 140-145 "C for another 1 or 2 h. The aluminum hydroxide is then separated by filtration. From the resultant solution calcium and possibly sodium are separated by using well-known methods. The nitric acid in excess is removed with water or water vapors, and the nickel nitrate is concentrated, crystallized, and finally filtered and dried. Thermohydrolysis takes place under conditions of thermic and chemical instability of aluminum and iron salts, when due to increasing ion mobility, the latter releases free ions capable of reacting with water. Thus, this paper deals with nickel recuperation as pure nickel from spent catalysts and offers an explanation of the physical and chemical phenomena of the thermohydrolysis process. Experimental Section In this paper examples are given of the nickel recuperation from four types of spent catalysts using the thermohydrolysis process (Manolache and Cotocu, 1982). A. Nickel Recuperation from the Catalyst Spent during Fats Hydrogenation. In a flask provided with stirrer, barbotage tube, distilled water recipient connected to the bubble flask, thermometer, heating source, descendent cooler, and collecting flask connected to a vacuum pump, an aqueous solution containing 108.72 g/L Ni(NO3I2, 12.95 g/L Fe(N03),, 5.05 g/L A1(N03)3,18.27 g/L NaC1, and 47.92 g/L HN03 is concentrated at a temperature of 130-135 "C under a vacuum of 0.4-0.6 atm. This aqueous solution i s the result of nickel extraction using
nitric acid of the spent catalyst residues (nickel on diatomite support) from which the organic products have been removed by calcination a t 300-400 O C . The iron and aluminum are separated by thermohydrolysis, and sodium is separated by the well-known precipitation method. In order to do this, distilled water is continuously introduced at a regulated flow through the barbotage tube a t a temperature of 135-140 "C and under a vacuum of 0.4-0.6 atm for 2 or 3 h. The total thermohydrolysis of the iron nitrate and aluminum nitrate takes place following the equations Fe(NO3I3+ 3Hz0 Al(N03), + 3H20
-
-
Fe(OH),
+ 3HN03
Al(OH),
+ 3HN0,
The viscous nickel nitrate solution containing iron and aluminum hydroxides is cooled, diluted with distilled water up to a content of 200-300 g/L nickel nitrate, and then filtered. The iron hydroxide,the aluminum hydroxide, and small quantities of fat substances that have not been removed by the calcination of the residues from the catalyst are separated by filtration. From the clear filtrate, which is an aqueous solution of nickel nitrate and sodium chloride, the nickel nitrate is precipitated as carbonate or nickel hydroxide by using carbonate or sodium hydroxide, respectively. The solution containing the nickel carbonate or the nickel hydroxide is filtered. The precipitate is washed with distilled water in order to remove the sodium salt and then is dissolved in a dilute nitric acid solution. The solution obtained is concentrated, and the nitric acid in excess is removed with water vapors a t a temperature of 130-135 "C and under a vacuum of 0.4-0.6 atm in an apparatus identical with the one in which thermohydrolysis is performed. After the nitric acid is removed, the solution is diluted to a concentration of 50-55% Ni(NO&, crystallized, and filtered, and the resultant crystals are dried. The noncaking crystalline product obtained contains a minimum of 99.6% Ni(N03)z.6Hz0and can be included in the pure substances class. The purification yield a t a minimum is 96%. B. Nickel Recuperation from the Catalyst Spent during Crotonaldehyde Hydrogenation. An aqueous solution containing 173.13g/L Ni(N03)2,6.8 g/L Fe(N03),, and 8.99 g/L HNO, that results from nickel extraction, using nitric acid, from the catalyst spent during hydrogenation (nickel on diatomite support) is concentrated, and the thermohydrolysis of the iron nitrate is performed as in example A. During the concentration of the aqueous nickel nitrate solution, the organic compounds dissolved during the extraction of nickel from the spent catalyst are removed as well. The thermohydrolysis takes place for 30-60 min. The nickel nitrate solution that contains the iron hydroxide is cooled, diluted with distilled water to a content of 200-300 g/L nickel nitrate, and filtered in order to separate the iron hydroxide. The filtrate, a clear solution of nickel nitrate, is concentrated to a content of 50-55% Ni(N03)2,crystallized, and filtered, and the crystals obtained are dried. The noncaking crystalline product obtained contains a minimum of 99.6% Ni(NO3)r6H20and can be included in the pure substances class. The purification yield at a minimum is 98%. C. Nickel Recuperation from the Catalyst Spent during Methane Conversion. An aqueous solution containing 117.4 g/L Ni(N03)2,16.27 g/L Fe(NO3I3,35.35 g/L A1(N03),,31.24 g/L Ca(N03)z,and 104.82 g/L HN03, obtained from nickel extraction using nitric acid from the catalyst spent during methane conversion (nickel on refractory support) is concentrated at a temperature of
Ind. Eng. Chem. Prod. Res. Dev., Vol. 25, No. 4, 1986 887
120-130 "C and under a vacuum of 0.4-0.6 atm. The thermohydrolysis of the iron nitrate takes place at a temperature of 125-133 "C and under a vacuum of 0.4-0.6 atm for 2 or 3 h. The viscous nitrate solution containing the iron hydroxide is cooled and diluted with distilled water until the content of nickel becomes 200-300 g/L, and the iron hydroxide is separated by using a centrifuge or a filter. The filtrate, an iron-free aqueous nitrate solution, is concentrated at a temperature of 130-135 "C under a vacuum of 0.4-0.6 atm. Partial thermohydrolysis of the aluminum nitrate takes place then at a temperature of 135-140 "C and under a vacuum of 0.4-0.6 atm for another 1 or 2 h. The nitrate solution containing the aluminum hydroxide is cooled and diluted with distilled water to a content of 200-300 g/L nickel nitrate, and the aluminum hydroxide is separated by using a filter or a centrifuge. The filtrate is concentrated at a temperature of 130-140 "C under a vacuum of 0.4-0.6 atm, and then the final thermohydrolysis of the aluminum nitrate takes place at a temperature of 135-140 "C under a vacuum of 0 . 4 4 6 atm for another 1or 2 h. The nitrate solution that contains the aluminum hydroxide is cooled and diluted with distilled water to a content of 200-300 g/L nickel nitrate, and the aluminum hydroxide is separated by filtration or centrifuging. From the limpid filtrate (an aqueous solution of nickel nitrate and calcium nitrate) the nickel nitrate is precipitated by using the classical precipitation method for calcium separation, and the nickel precipitate is processed in order to obtain nickel nitrate as in example A. The noncaking crystalline product obtained contains a minimum of 99.5% Ni(N03)2.6H20and can be included in the pure substances class. From the aluminum hydroxide, the nickel nitrate included is recuperated by dissolving it in water with heating and stirring. After that, the aluminum hydroxide is separated by filtration or centrifuging. The clear filtrate (an aqueous solution of nickel nitrate) is concentrated to obtain the nickel nitrate salt. The purification yield at a minimum is 90%. D. Nickel Recuperation from the Catalyst Spent during Methanation. An aqueous solution containing 204.4 g/L Ni(N03)2,111 g/L A1(N03)3,and 59.9 g/L HNO,, resulting from nickel extraction from the catalyst spent during methanation (nickel on alumina support), is concentrated at a temperature of 135-140 "C and under a vacuum of 0.4-0.6 atm. The partial thermohydrolysis of the aluminum nitrate takes place at a temperature of 135-140 "C and under a vacuum of 0.4-0.6 atm for 1 or 2 h. The nitrate solution containing aluminum hydroxide is cooled and diluted with distilled water to a content of 200-300 g/L nickel nitrate, and the aluminum hydroxide is separated by centrifuging. The clear nitrate solution obtained by centrifuging is concentrated at a temperautre of 135-140 "C under a vacuum of 0.4-0.6 atm. The final thermohydrolysis of the aluminum nitrate takes place at a temperature of 135-140 "C and under a vacuum of 0.4-0.6 atm for another 1or 2 h. The nickel nitrate solution containing aluminum hydroxide is cooled and diluted with distilled watter to a content of 200-300 g/L nickel nitrate, and the aluminum hydroxide is separated by centrifuging. The limpid nickel nitrate solution resulting from centrifuging is concentrated to a content of -55% Ni(N03)2,crystallized, and filtered, and the resulting crystals are dried. The noncaking crystalline product obtained contains a minimum of 99.5% Ni(N03)2.6H20and can be included in the pure substances class.
From the aluminum hydroxide obtained by centrifuging, the nickel nitrate included is recuperated by dissolving it in water with heating and stirring, and the aluminum hydroxide is separated by centrifuging. The limpid nickel nitrate solution obtained by centrifuging is concentrated to obtain the nickel nitrate salt. The purification yield at a minimum is 87 % . Results and Discussions I t is difficult to obtain metallic nickel nowadays since the ores have a relatively small content of nickel and the quantities in which they are found are more and more reduced. Due to these factors, the development of a new technology for nickel recuperation from waste materials and the elaboration of a program to be put into practice represent an economic necessity of major importance. This paper presents a nickel recuperation process from spent catalysts, using a new method that we have called thermohydrolysis. The results of the experiments are presented in Table I. In the first through third columns there is shown the content of nitrates, and in the fourth column the concentration of the unreacted acid from the aqueous solutions used in experiments A-D is shown. The compositions of the solutions vary and depend on the support type, the content of nickel, the impurities from the spent catalysts, and the concentration of the aqueous solution used for extraction. The working conditions for performing the thermohydrolysis are shown in the fifth through seventh columns. The experiments have been done at temperatures generally higher than the decomposition temperature of the iron and aluminum hydroxides (Perry, 1963; Pascal and Dupont, 1955) and at a constant vacuum. The duration of thermohydrolysis depends on the necessary time to remove the acid from the system, and not on the reaction rate. Like decomposition reactions, the thermohydrolysis reactions are fast and take place only in conditions of thermic and chemical instability of the substances. In the eighth column are shown the concentrations of the nickel nitrate obtained, and in the ninth column are the purification yields. In order to give a clear picture of the process, Figures 1-4 present the diagram of the main operations for nickel recuperation from the spent catalysts used in the experiments described above. The physical and chemical phenomena that take place during thermohydrolysis can form a new chapter in chemistry, with larger applications than those shown in this paper. It is well-known that strong electrolytes are completely dissociated in aqueous solution, but the mobility of the ions decreases through electrostatic interaction with ions of opposite charge. Because of this, in solutions with certain concentrations only a fraction of the total number of ions is available for the determination of phenomena such as hydrolysis, electricity transport through electrolytes, electromotive force of electric cells, decrease of vapor pressure, decrease of osmotic pressure, and so on. The ideal state in which the ions of opposite charge do not influence one another is a limited state that can be reached only at infinite dilution. Each ion from the solution is surrounded by an atmosphere of ions of opposite charge attracted by the electrostatic forces between ions. Some ions exist as pairs of ions (C+A-) or as triplets (C+A-C+or A-C+A-) or as associations of more than one ion. When an ion migrates under the influence of the difference in potential between the electrodes, it is obstructed in its migration by the ions of opposite charge, which surround it, and thus its mobility is reduced. This
668
Ind. Eng. Chem. Prod. Res. Dev., Vol. 25, No. 4, 1986
I
I
J
CWSTAL L IZATlON
Figure 1. Diagram of the main operations of Ni recuperation from the catalyst spent in the fats hydrogenation process.
\
Figure 2. Diagram of the main operations of Ni recuperation from the catalyst spent in the crotonaldehyde hydrogenation process.
effect is diminished during dilution and disappears at infinite dilution (Nenipscu, 1963). Strong acids are practically completely ionized in aqueous solution. The proton existence is inconceivable; when it is generated, it is also hydrated and forms the hydronium ion (Nenitescu, 1963; Onciu, 1977).
From the experiments described here it can be seen that in finite concentration solutions or in electrolyte melts, in conditions of thermohydrolysis, the ion behavior is the same as in the case of infinite dilution. This is the only explanation for the fact that in these solutions or salt melts the thermohydrolysisreactions take
Ind. Eng. Chem. Prod. Res. Dev., Vol. 25,
No. 4, 1986 660
I
FILTRATION
I
Figure 3. Diagram of the main operations of Ni recuperation from the catalyst spent in the methane conversion process.
coo”
md ntric oc~d
4
c
H20 FlLTWTlON
1
I
AI (OH13
FILTRATION
I
I DRYING
‘‘lNo3’‘
sa
Figure 4. Diagram of the main operations of Ni recuperation from the catalyst spent in the methanation process.
place. Therefore, thermohydrolysis completes these theories, specifying the following. The ideal state in which the opposite-chargeions do not influence one another is reached not only a t infinite dilution but also at finite concentrations, this state being
selectively influenced by temperature and depending on the thermic and chemical stability of the substances. The ideal state for each substance is reached in finite concentration solutions or in electrolyte melts, at temperatures close to, equal to,and especially higher than the decomposition temperature of the substance. The elec-
Ind. Eng. Chem. Prod. Res. Dev., Vol. 25, No. 4, 1986
670
Table I. Working Conditions and Experimental Results composn o f aq nitrate soln, g/L expt
Ni(N03)
A B C D
108.72 176.13 117.3 204.4
Al(N03)B 5.05
Fe(N03)3
12.95 6.8 16.27
35.35 111.00
HN03 47.92 8.99 104.82 59.9
temp,
135-140 135-140 125-145 135-145
trostatic attraction between the opposite-charge ions of the substance brought to the conditions of thermic and chemical instability, as well as the attraction between the ions of this substance and the ions of other electrolytes that are present, disappears almost completely as a consequence of the increase in the mobility of the ions of the substance. Owing to this, the formation of triplets or even active macroions can be admitted. In solutions with finite concentrations or in salt melts, in conditions of thermic and chemical instability of one or more salts and by including water in the system, the triplet ions or macroions of those salts react completely with water. By removing the acid obtained together with water or water vapors simultaneously and at low pressure, thermohydrolysis takes place according to the diagram of the reaction mechanisms shown in Scheme I. In order to simplify, it was considered the general case of an electrolyte monovalent salt where reaction 7 is undesirable in the case of separations by thermohydrolysis,and it takes place only when the acid has not been completely removed from the system. Scheme I nC+ + nAnC+AC+A- C+ AnC+A- nC+ nAA- H 2 0 AH + HO-
-- ++ - +
+ AH + HzO F! H30+ AC+ + HOCOH
+ + + + + + +
COH AC+
C+A- + H,O
AH
C+
A-
[A-C+A-]-
A-
C+
[C+A-C+]+
H20 C+A- + AH + HOAH H 2 0 s H30+ + A[C+A-C+]+ + H 2 0 C+A- + COH + H+ H+ + HO- H2O COH + AH C+A- + H 2 0 [(n - l)C+.nA-](n - 1)C+ + nA[(n + l)C+.nA-]+ (n + 1)C- + nA[(n - l)C+.nA-]- + H,O (n - 1)C+A- + AH + HO(15) AH + H,O + H30+ + A(5) [(n + l)C+-nA-]++ H20 nC+A- + COH + H+ (16) H+ + HO- H20 (12) COH + AH C+A- + HzO (7) [A-C+A-]-
---
-
--
-
"C
working conditions vacuum, a t m duration,
0.4-0.6 0.4-0.6 0.4-0.6 0.4-0.6
Ni(NO&
h
2-3 0.5-1 4-7 2-4
6H20, g/100 g purifn yield, % 99.6 96 99.6 98 99.5 90 99.6 87
Conclusions The thermohydrolysis principle is based on the thermic and chemical instability of the electrolytes. Any salt that presents thermic and chemical instability can be precipitated with water or water vapors by thermohydrolysis. In order to perform the thermohydrolysis in a determined optimum time, it is necessary to work at as low as possible pressures to remove the acid quickly from the systems and also at temperatures equal to or higher than the decomposition temperature of the salt that undergoes the thermohydrolysis process. If a voluminous precipitate is obtained, the thermohydrolysis is performed in stages in order to reduce the filtration or centrifuging losses. The nickel nitrate obtained by thermohydrolysis has high purity, and this demonstrates that by using this method the impurities from the nickel nitrate used for the preparation of the primary catalyst are also separated. I t is also well-known that in catalytic processes small impurities from the undesirable metals can result in small yields. Thus, using the pure nickel nitrate for the preparation of new catalysts, we obtain catalysts with superior qualities and performances. From this paper it can be seen that by thermohydrolysis we can separate the cations that precipitate in the same range of pH. This cannot be done or it is done with difficulty by using the already known processes. This process is distinctly advantageous if we compare it with the known processes because it uses only water vapors. This method offers a wide range of applications in practice, being used for the recuperation of some expensive and rare metals from waste materials or for obtaining some salts with high purity. Registry No. Ni, 7440-02-0.
Literature Cited Carmichaei, R. L. Chem. Eng. ( N . Y . )lS66, 7 3 , 139-146. Macarovici, G. C. Chimie analifici canfitativi; Tehnic5: Bucuregti, 1959: pp 188-209. Manolache, I . C.; Cotocu, V. C. Rom. Patent 71 156, 1982. Nenifescu, D. C. Chimie generag; Tehnici: Bucuregti, 1963; pp 183-184, 240-242, 287. Onciu, L. Chimie-fizici -e/ectrochimie; DdactiG si Pedaaoaic5: Bucuresti, 1977; pp 114-118. Pascal, P.; Dupont, G. Constantes Physico-Chimiques; Paris, 1955; pp 120. - - 124 .- .. Perry, H. Y. Chemical Engineers Handbook, 4th ed.;McGraw-Hill: New York, 1963; Section 3, pp 4-15. Popa, G.; Croitoru, V. Chimie analiti& gi cantifafivEi : Didactic5 gi Pedagogic&: Bucuregti, 1971; pp 149-164, 193-198. Ripan, R.; Ceteanu, I . Chimia metalelor; Didactic5 gi Pedagogic5: Bucuregti, 1969; Voi. 2, pp 542-547.
_ _
Received for reuiew D e c e m b e r 14, 1984 Revised manuscript receiued August 30, 1985 Accepted April 28. 1986
