X-ray diffraction data were obtained using a General Electric
XRD-5 unit. Copper K a radiation, filtered with nickel, was used to irradiate the samples. The relative intensities of the lines and degrees 28 were obtained from a chart readout of the instrument.
Results
Several precipitate fractions could be obtained from the electrolysis of one sample solution. The electrolysis was terminated after the precipitation process became very slow. This last precipitate fraction was extremely gelatinous and difficult to separate from the mother liquor. The solids were dried at 110°C. and analyzed. Yields were 805 or above. The calcium content was found to be less than 1% for all precipitate fractions except the last one, collected from a sample solution. The last fraction showed a considerable increase in calcium content, while the percentage of fluoride present was decreased. A qualitative test for chlorine was made by dissolving the sample in nitric acid and adding silver nitrate solution. Lack of a silver chloride precipitate indicated that the sample contained less than 0.1% chloride. When the F:A1 ratio in the electrolysis solution was 2 to 1 or less, the F:A1 mole ratio in the collected solid fractions was the same as that of the original solution. At F:A1 ratios of 4 to 1 or larger in the electrolysis solution, aluminum fluoride (A1F.j.xH,O) precipitates. Table I shows the results of some representative samples. Thermal gravimetric analysis indicated that there might be a stable intermediate a t 300’C. When samples of different F:AI ratios were heated at 300” for 24 hours, quantitative analysis showed that the products were unspecific in composition. After heating at 900”C.,
however, all of the samples showed x-ray diffraction patterns corresponding to that for a-alumina. Table I1 shows the x-ray diffraction data obtained for samples in Table I. The standard d values were taken from the American Society for Testing Materials (1963). The first two samples closely resemble those reported by Crowley and Scott (1948) for aluminum hydroxyfluorides, where the differences in intensities may be attributed to different quantities of water of hydration. Conclusions
I t is possible to obtain any desired F:A1 mole ratio in solid aluminum hydroxyfluorides by electrolysis of a solution containing the aluminum and the fluoride in the desired ratio. Literature Cited
Allen, D. R., “Aluminum Fluorides,” Division of Inorganic Chemistry, Meeting-in-Miniature, American Chemical Society, Hollywood Beach, Fla., 1961. American Society for Testing and Materials, “Wyandotte ASTM Index to X-Ray Power Data,” 1963. Crowley, J. M., Scott, T. R., J . A m . Chem. SOC.70, 105 (1948). Huckabay, W. B., Welch, E. T., Metler, A. V., Anal. Chem. i9, 154 (1947). Rowley, R. J., Churchill, H. V., Ind. Eng. Chem., Anal. Ed.9, 551 (1937). Ter Haar, K., Brazen, J., Anal Chim. Acta 9, 235 (1953). Weinrotter, F., Chem. Eng. 71, KO.9, 132 (1964). Willard, H. H., Winter, D. B., Ind. Eng. Chem., Anal. Ed.5 , 7 (1933). RECEIVED for review March 29, 1968 ACCPETED June 17, 1968
PREPARATION OF SYNTHETIC MALACHITE Reaction between Cupric Sulfate and Sodium Carbonate Solutions H .
5 .
PAREKH’
A N D
ANDREW
C .
1. H S U
Department of Chemical Engineering, Auburn University, Auburn, Ala. 36830
COPPER carbonate
exists only in its basic form, since the normal salt is unstable in the presence of moisture under atmospheric conditions. A recent work (Pistorius, 1960) indicates that the normal salt could exist after a precipitated basic copper carbonate had been subjected to an atmosphere of carbon dioxide and moisture (90% CO, and 10‘; HLO) under a total pressure of 500 bars at 180’C.for 36 hours. The commonly known natural basic copper carbonates are malachite and azurite (Kirk and Othmer, 1965; Mellor, 1923). Rocchiccioli (1964) investigated the preparation and properties of deuterated basic copper carbonates thermogravimetrically and by infrared spectrography. I
Present address, Kerr-McGee Chemical Corp., Atlanta, Ga. 30332 222
I & E C PRODUCT RESEARCH A N D DEVELOPMEN1
The basic salt has been widely used as a fungicide, as an additive in fertilizers and animal feeds, and as a catalyst in a variety of applications (Johnson, 1951; Koenig, 1965; Schute, 1957). Recent studies (Land et ai., 1967; Shidlovskii et al., 1964) of the effect of copper carbonate on the combustion of ammonium perchlorate are of particular interest. Hsu (1956) studied the conditions under which basic copper carbonates of different characteristics were obtained. He was able to recommend the conditions for producing basic copper carbonate of definite composition and desirable filtering and drying properties. For relatively simple salts, such as barium sulfate, extensive investigations (Cobbett and French, 1954; Johnson and O’Rourke, 1954; Kolthoff and van’t Riet, 1959;
The preparation of malachite, CUCO~.CU( OH) 2, from copper sulfate and sodium . . carbonate solutions was investigated. Chemical analysis and x-ray powder diffraction results verified that pure malachite was obtained on aging, with the reactant molecular ratio at 1.1 or higher. Unless the proper preparation conditions were followed, tribasic copper sulfate was present in varying extents as the main impurity in the final product. The effects of temperature in the range 20' to 60'C. and mode of mixing-i.e., copper sulfate solution added to sodium carbonate solution and vice versa-on the precipitation and precipitate transformation were studied and discussed. ~~
Nielsen, 1958; Suito and Takiyama, 1955) have been made in respect to their nucleation and crystal growth in the course of precipitation and aging. For complex salts, such as basic copper carbonates, a multitude of stable forms and equilibria may be involved during precipitation and aging. So far, there is little information available in this general domain. Presented in this report are the results obtained in preparing basic copper carbonate (in the form of malachite) from copper sulfate and sodium carbonate solutions. The preparation consisted of the initial precipitation of a gelatinous mass and its subsequent transformation into desirable crystalline particles. X-ray diffraction was employed in examining the composition of the final product. Experimental Procedure and Results
Effect of Na2C03-CuS04Reactant Molecular Ratio. A series of basic copper carbonate precipitates was prepared by slowly adding 50 ml. of 1.033M copper sulfate solution to 120-ml. portions of sodium carbonate solutions, which ranged in concentration from 0.345 to 0.604M. Reagent grade cupric sulfate and sodium carbonate were used. The resulting NaZCO3-CuSO4 molecular ratio in the mixed solution varied from 0.80 to 1.40. The precipitations were carried out at 27" C. and atmospheric pressure with gentle shaking of the solutions. After the intended amount of copper sulfate had been added, the flasks containing the gelatinous precipitates were stoppered and allowed to stand. All precipitates as initially formed here blue and voluminous, and remained in suspension. On standing, some of the precipitates gradually turned green and crystalline with a drastic reduction in volume. The bulk volume of green crystalline precipitates was, in most cases, only about one tenth or less of that of the blue gelatinous Table 1. Effect of Reactant Ratio on Transformation Time and CuO-CO2 Ratio in Final Products
N a , CO i- CuSO, Transformation CuO-CO2 Ratio' in Product Molecular Ratio Time", Hours 0.80 400 2.52 0.90 250 2.35 0.95 110 2.28 1.00 28 2.16 1.05 15 2.01 1.10 7 1.99 1.20 5 2.00 1.40 4 1.99 Aging time required to effect complete blue-to-green transformation. ' CuO-CO, ratio of malachite, CUCO.~. Cu(OH),, equals 2.0.
form. Table I shows the influence of the molecular ratio of NaeC03-CuSOr on the time required for the complete blue-to-green transformation of the precipitates as determined by the marked change in color and structural appearance. When the molecular ratio was 0.80, the precipitates took about 400 hours to accomplish complete transformation; the time taken was only 7 hours when the molecular ratio was 1.10. The precipitates were subsequently filtered, and the filtrates were collected and analyzed for their copper oxide, carbon dioxide, and sulfate content (Scott, 1930). Analysis of Filtrates. The filtrates of reacting solutions having Na2C03-CuS04 molecular ratio less than 1.0 were bluish in color because of the unreacted copper sulfate. Colorless filtrates resulted when the reactant ratio exceeded 1.0. None of the precipitation runs in this series with the reactant ratio greater than 1.0, up to 1.40, yielded filtrates alkaline to phenolphthalein. This indicates that the carbon dioxide liberated in the primary reaction was sufficient to convert all the excess sodium carbonate into the corresponding bicarbonate.
2Na2C03 + 2CuS04 + H 2 0 = C U C O ~ . C U ( O H+) 2Na2S04 ~ + CO, C 0 2 + H 2 0 + Na2C03= 2NaHC03
(1)
(2)
The residual alkalinity of the filtrates was, therefore, in the form of sodium bicarbonate as titrated by hydrochloric acid with methyl orange as indicator. When the reactant ratio was 1.1 or higher, the excess alkalinity was linear with the Na2C03-CuS04ratio. This signifies that the precipitates formed were of the same chemical species and were not affected by the excess alkalinity. Chemical Analysis of Precipitates. The voluminous blue precipitates were highly adsorptive and difficult to filter and wash. The subsequent crystalline variety, however, possessed good filtering, washing, and drying properties, thus rendering meaningful analysis feasible (Table I ) . The results confirm that when the reactant ratio is 1.1 or higher, the CuO-COZmolecular ratio of the products is essentially 2.0, corresponding to that of malachite, CuCO&u(OH)z. When the reactant ratio is 1.05 or lower, the amount of sulfate in the precipitates- increases, giving rise to higher CuO-COZ ratios, with decreasing Na2C03CuSOl ratio. The sulfate present in the precipitates is probably in the form of the relatively stable tribasic copper sulfate, CuSO4-3Cu(OH)2.This is supported by the x-ray powder diffraction results discussed below. A slight excess of sodium carbonate is necessary to VOL. 7 NO. 3 SEPTEMBER 1968
223
make the transformation to pure malachite possible and complete within a reasonably short time. Although a large excess of sodium carbonate, up to 1.40 in the reactant ratio, had no further effect on composition of the final precipitates, it did favor the formation of larger malachite particles. X-Ray Powder Diffraction of Precipitates. A similar series of basic copper carbonate samples was prepared in the manner described above, with the Na,COq-CuSO, molecular ratio ranging from 0.75 to 2.40. For each sample, the particles were made into a whisker about 0.2 mm. in diameter with Duco cement as hinder and examined by x-ray powder diffraction, using a circular camera 11.46 cm. in diameter. The interplanar spacing values of the precipitate particles and their relative intensity were noted and compared with the ASTM x-ray powder data for malachite and tribasic copper sulfate. When the reactant ratio was 0.75, the resulting precipitate had tribasic copper sulfate as one of the main constituents, as indicated hy the intensity of the characteristic lines in the diffraction picture. The intensity of these lines diminishes rapidly as the reactant ratio increases. These lines are essentially absent when the reactant ratio reaches 1.10. On the other hand, the characteristic lines of malachite are present in the diffraction picture of all the samples. They are the only lines present in those samples resulting when the reactant ratio is 1.10 or higher. The x-ray powder pictures for the samples resulting from Na2COs-CuS04 ratios a t 0.75 and 1.10 are shown in Figure 1. Together with chemical analyses, the results firmly establish that the composition of the final product was dictated by the reactant ratio used in the precipitation. Effect of Temperuture
To study the effect of temperature on the transformation time and particle size of precipitates, a series of basic copper carbonate samples was prepared a t different teniperatures by adding, with agitation, 50 ml. of 1.12M copper sulfate solution to 123 ml. of 0.50M sodium carbonate solution. The NalC03-CuS04 molecular ratio was 1.10. The precipitation and aging were conducted in constant temperature bath maintained within +0.2"C. The temperature range covered was 20" to 60" C. The initial gelatinous precipitates were allowed to stand, and the time required for each to undergo complete transformation was noted. The resulting crystalline precipitates were filtered, washed, and dried, and their particle size was measured
with a polarizing microscope with calibrated micrometer ocular at 430 magnifications. The results are given in Table 11. A t 20"C., the time required for the blue precipitate to transform into the stable green variety was 850 minutes; it took only 9 minutes for the 60°C. run. When the logarithm of reciorocal time needed for complete trzinsformation is plotted against reciproczil absolute tempe ratnre, a straight line results, indic;ating that the triinsformation is apparently controlled by' a rate process. 1. :- L.:__ -1 2 A ul_lll:._.l u~ucla~ W W ~~b u e u g p,rarurcu liu elucidate this transformation process. The final products were green in all the temperature runs, hut of different shades. The precipitates obtained a t higher temperatures were larger and assumed darker shades. Examination of the precipitates ohtained a t 20" and 50°C. by an electron microscope with magnifications a t 3000 to 20,000 revealed the fuzzy and irregular surfaces of the malachite particles. The electron photomicrographs show that the particles are single crystals with a very high degree of imperfection, as would he expected. Effect of Mixing Mode on Cc rse of Reaction
.".."..".-
t n e t n r l ~ r +ha affant m f TL- .!Ana m f *>*,,a 1.1117.a n.norla .-" mode of mixing-i.e., copper sulfate solution added to sodium carbonate solution and vice versa-on the reaction between these reacting solutions. The results are expected to throw some light on the wide range of products ohtained from these solutions by the early workers (Brauer, 1965; Hemar, 1937; Hephurn, 1927; Sneed et al., 1954). Addition of Copper Sulfate to Sodium Carbonate. One run was conducted by adding, a few millimeters a t a time with agitation, 0.972.U copper sulfate solution to 107 rnl. of 0.50M sodium carbonate solution maintained a t 27°C. The pH value and temperature of the solution were measured after each addition of the sulfate solution. When 50 ml. of the copper sulfate solution were added, the final Na,CO8-CuSO, reactant ratio was 1.10. The p H values of the solution at different NazCO1CuS04 ratios are plotted in Figure 2. A good reproducibility is shown by the duplicate runs. Starting with the 0.50M sodium carbonate solution with its p H a t 10.1, the slow addition of the copper sulfate solution caused a gradual decrease of pH as a result of consumption of sodium carbonate, both in the primary reaction and in the formation of the increasing amount of sodium hicar.I"
Upper NozCOi-CuS06reactant molecular ratio = 0.75 Lower. NozCO~-CuS04 reactant molecul~rratio = 1.10
224
l&EC PRODUCT RESEARCH A N D DEVELOPMENT
yy
I?"uu, l l . l
41
IU.0
50.0 27 54.2 16 60.0 9 'Arithmetic mean of 40 particles
10.8 10.1
44.3
Figure 1. X-ray powder diffraction picture of samples
..
.__^
-
c--
a
a
Figure 2. pH change of solution with Na 2CO:i-CuSO4 molecuIa r ratio Copper sulfate added to sodium carbonate
1
2
3
4
MOLECULAR RATIO
I
I
I
I
I
5
6
7
8
9
Na2C03
/
hSO4
bonate. Here, the carbon dioxide liberated in the primary reaction reacts with sodium carbdnate in the solution, forming the bicarbonate. The reaction becomes one between sodium carbonate-sodium bicarbonate and copper sulfate after the bicarbonate concentration builds up to a certain level, and one between sodium bicarbonate and copper sulfate when all the sodium carbonate is expended. Figure 2 shows the pH change with decreasing Na2C03CuS04 ratio. Apparently, sodium carbonate is completely eliminated at a reactant ratio in the vicinity of 1.6. After this, the carbon dioxide produced is present essentially as carbonic acid, which is able to lower the pH to less than 7.0. When the Na2C03-CuS04 ratio reaches 1.10, the pH of the mixed solution reads 6.25. The precipitates, of course, were unstable and underwent transformation on aging, similar to those reported earlier. Addition of Sodium Carbonate to Copper Sulfate. Another run was conducted in exactly the same manner as above, except that the sodium carbonate solution was added in small portions to the copper sulfate solution and the Na?COj-CuS04reactant ratio was extended to 2.0. Since the copper sulfate solution has a lower pH than carbonic acid, carbon dioxide produced readily escapes from the solution. This was evidenced by the profuse bubbles appearing in this run, in contrast with relatively few in the preceding run. The pH’s of the solution a t various Na?COj-CuS04ratios are shown in Figure 3. I n Figure 3, starting with the 0.972M copper sulfate solution, the pH rises with the addition of 0.50M sodium carbonate solution. The pH rise becomes steeper when the reactant ratio becomes greater than 0.75. This break probably signifies complete precipitation of copper sulfate as tribasic copper sulfate.
3Na2COI+ 4CuS0,
+ 3 H 2 0=
CuSO,.3Cu(OH)L + 3 N a S 0 ,
Figures 2 and 3 clearly show that mixing of copper sulfate and sodium carbonate solutions could lead to completely diverse courses of reaction and products, depending on whether the former solution is added to the latter, or vice versa. Summary and Conclusions
I n the preparation of basic copper carbonate by adding a copper sulfate solution to a sodium carbonate solution, when the Na2C03-CuS04reactant molecular ratio was 1.10 or higher, pure malachite resulted on aging the initial precipitate. When the reactant ratio was below 1.10, the precipitates formed became increasingly contaminated, with decreasing Na2C03-CuS04ratio, by tribasic copper sulfate. With the reactant ratio a t 1.10, the time needed for complete transformation of the initial gelatinous precipi-
8
6 5
+ 3C0,
(3) I
The excess sodium carbonate, exceeding the amount required in accordance with Reaction 3, apparently has no effect on the stable tribasic copper sulfate. The precipitate formed here was greenish blue and did not undergo any appreciable transformation on aging. I t was difficultto filter, wash, and dry.
0
I
0.8 MOLECULAR R A T I O
0.4
I
J
I
1.2 1.6 Na2C03 / C u S O 4
2.0
Figure 3. pH change of solution with NaJCOICuS04 molecular ratio Sodium carbonate added to copper sulfate
VOL, 7 NO. 3 SEPTEMBER 1968
225
tates into the crystalline variety on aging decreased rapidly with temperature between 20” and 60” C., the temperature range covered in this work. The linear relation between the logarithm of reciprocal transformation time and reciprocal absolute temperature indicates that a rate process controls the over-all rate of transformation. Higher temperatures favored the formation of larger malachite particles. The course of reaction between copper sulfate and sodium carbonate solutions, hence the final product, was determined by whether the former was added to the latter, or vice versa. For the preparation of malachite, copper sulfate solution must be added to sodium carbonate solution. Acknowledgment
The authors thank P. P. Budenstein of the Physics Department for his help in the x-ray diffraction work. literature Cited
Brauer, G., “Handbook of Preparative Inorganic Chemistry,” Vol. 2, 2nd ed., p. 1024, Academic Press, New York, 1965. Cobbett, W. G., French, C. M., Discussions Faraday SOC. 18, 113 (1954). Hemar, S., Compt. Rend. 204, 1739 (1937). Hepburn, J. R. I., J . Chem. SOC.130, 2882 (1927). Hsu, C. T., J . Appl. Chem. London 6, 84 (1956). Johnson, Robert, U. S.Patent 2,568,639 (Sept. 18, 1951). Johnson, R. A., O’Rourke, J. D., J . Am. Chem. SOC. 76, 2124 (1954).
Kirk, R. E., Othmer, D. F., “Encylopedia of Chemical Technology,” 2nd ed., Vol. 6, pp. 269-70, 278, Wiley, New York, 1965. Koenig, E., Sticlidorn, K. , Konetzke, G., German (East) Patent 35,860 (Jan. 25, 1965). Kolthoff, I. M., van’t Riet, B., J . Phys. Chem. 63, 817 (1959). Land, J. E., Hammett, R. E., Wingard, R. E., “Study of Decomposition Mechanism of Ammonium Perchlorate,” Final Report, Contract DA-01-021-AMC 12346(z), Part I, U.S. Army Missile Command, Redstone Arsenal, Ala. (June 30, 1967). Mellor, J. W., “Comprehensive Treatise on Inorganic and Theoretical Chemistry,” Vol. 3, Wiley, New York, 1923. Nielsen, A. E., Acta Chem. Scand. 11, 1512 (1957); 12, 951 (1958). Pistorius, C. W. F. T., Experientia 16, 447 (1960). Rocchiccioli, C., Compt. Rend. 259, (25), 4581 (1964). Schute, Max, German Patent 965,634 (June 13, 1957). Scott, W. W., “Standard Methods of Chemical Analysis,” Van Nostrand, New York, 1930. Shidlovskii, A. A., Shmagin, L. F., Bulanova, V. V., Izu. Vyssikh. Uchebn. Zauedenii, Khim. i Khim. Tekhnol. 7 ( 5 ) , 862 (1964). Sneed, M. C., Maynard, J. L., Brasted, R. C., “Comprehensive Inorganic Chemistry,” Vol. 2, Van Nostrand, Kew York, 1954. Suito, E., Takiyama, K., Bull. Chem. SOC.Japan 28, 305 (1955). RECEIVED for review January 22, 1968 ACCEPTED May 20, 1968 Work supported in part by the Engineering Experiment Station, Auburn University.
CORRESPONDENCE HYDROFORMYLATION OF 1 -OLEFINS IN TERTIARY ORGANOPHOSPHINE-COBALT HYDROCARBONYL CATALYST SYSTEMS and that the P to Co molar ratio of 2 is within the SIR: In a recent paper Tucci (1968) recognizes that Tucci range for high selectivity to normal products. Both the decrease in branched isomer formation obtained with hexene-1 and hexene-2 give similar product distributions the Col(CO)s-n-BuiP hydroformylation catalyst system at essentially the same reaction rate (slight catalyst decomcould arise either from a decrease in 1-olefin isomerization position may have occurred a t 195°C.). This result could prior to hydroformylation or from stereoselective attack only occur if double bond isomerization is rapid compared of the 1-olefin so as to produce a predominantly straight to the rate of hydroformylation. Furthermore, equilibrium chain product. However, he fails to distinguish between data (Schultz et al., 1966) show that the concentration these two possibilities. Further he states that isomerization of hexene-1 ( < 10%) is much lower than that of the is inhibited when the P to Co molar ratio is greater than 0.5, due to the predominance of the H C O ( C O ) ~ P B U ~ internal olefins so that the Col(CO)s-n-BulP catalyst syster- must have a tremendous selectivity with respect to catalytic species. All the data reported were for propene reaction of terminal rather than internal olefin as well or hexene-1 as feedstocks. as being highly stereoselective in the mode of its attack Patent literature (Slaugh and Mullineaux, 1966) and on the terminal double bond. results from our laboratory comparing hydroformylation One additional piece of evidence for considerable double of internal and alpha-olefins have established that stereobond isomerization is the presence of ethyl-branched selectivity of the C O ? ( C O ) ~ - ~ - Bcatalyst U ~ P system in its alcohols from the hexene-1 feed in runs 1 and 3 (about interaction with terminal olefin, and not the inhibition of the branched alcohols are ethyl-branched-Le., of double bond isomerization, produces the very high per2-ethylpentanol). The ethyl-branched product can only centage of normal products-Le., n-ROH and/or n-RCHO. occur from internal olefins. In Table I the product analyses are shown for the hydroHigher quantities of paraffin were produced in runs formylation of both hexene-1 and hexene-2 at identical 1 to 4 than reported by Tucci (1968) but this is due operating conditions. I t should be noted that our operating to operating a t a 2 to 1 Hr/CO molar ratio. I n run conditions are within the range studied by Tucci (1968) 226
I & E C PRODUCT RESEARCH A N D DEVELOPMENT
