Low-Temperature Reduction
G. C. WILLIAMS AND R. A. RAGATZ University of Wisconsin, Madison, Wis.
of
For the determination of the comparative effects of compounds of various metals, a constant weight ratio of 20 to 1 was maintained between the carbonaceous reducing medium and the metal combined in the compound. In those instances where a compound contained two metals, the proportioning was based on only one of the metallic elements, and the other metallic element was ignored. For example, in working with sodium chromate in connection with the investigation of sodium compounds, the change was made up so that a 20 to 1 weight ratio existed between the carbonaceous reducing agent and the sodium, with no attention being paid to the chromium.
Magnetite Ore Effect of Catalytic
Comparative Effect of Various Catalysts The results are summarized in Table I. The average results are given for reductions of magnetite ore by a solid carbonaceous material (coke unless otherwise specified) when the ratio of ore to carbonaceous material was 2 to 1, the ratio of carbonaceous material to the specifically considered metallic element of the catalyst was 20 to 1, and the reduction was carried on a t 900" C. for a period of 3.5 hours. Results are expressed in percentage reduction. The agreement between check runs depended to some extent upon the catalyst employed. In working with potassium carbonate, the eight runs yielded values for percentage reduction ranging from 93.5 to 99.9, with an average of 95.9 and an average deviation of 1.7. When using plain coke with no added catalyst, the nine runs gave values for percentage reduction ranging from 2.96 to 5.22, with an average of 4.10 and an average deviation of 0.84. These examples serve to
'1
Compounds
I
IY A PREVIOUS paper the writers
(3) considered the effect of sodium carbonate on the low-temperature reduction of iron ores in the presence of a solid carbonaceous reducing agent, and reported a marked catalytic effect under certain conditions. While the work was confined solely to the effect of sodium carbonate additions, it was predicted that compounds other than sodium carbonate might be expected to accelerate the rate of reduction. The work carried out subsequently and reported in the present paper has been along three main lines: (1) A general survey was made to determine the effect of a wide variety of compounds on the rate of reduction of iron ore in the presence of solid carbon. (2) A more detailed survey was made of the catalytic effect of alkali and alkaline earth carbonates in which the effect of concentration was investigated. (3) A further study on sodium carbonate additions was carried out, in which the continuity of the catalytic effect was investigated. Since the publication of the first paper that was concerned with the effect of sodium carbonate additions, a number of papers have appeared in the technical literature dealing with the low-temperature reduction of iron ores. However, the only one (1) touching on the effect of catalytic agents is an English translation of the Japanese paper (9) discussed in the previous paper of the writers.
Certain sodium and potassium compounds greatly accelerate the rate of reduction of magnetite ore at 900' C. No other materials except certain barium compounds exert a catalytic effect comparable to the active sodium and potassium compounds. Hardwood charcoal is a much more active reducing agent than metallurgical coke and responds to the action of sodium carbonate as catalyst. The catalytic effect of various compounds is a function of their concentration in the reducing mixture as judged by the action of alkali and alkaline earth carbonates. The presence of silica tends to inhibit the catalytic effect of sodium carbonate. A considerable loss of sodium occurs in using a reducing mixture containing sodium carbonate.
Experimental Procedure In general, the experimental procedure followed was the same as that described previously, except that the reduction retorts were of larger diameter (1-inch standard pipe fittings). Fixed conditions for all runs in the present investigation were as follows: (a)The ore was Lake Champlain magnetite. (b) The reducing agent was metallurgical coke except in the few instances noted. ( c ) The ratio of ore to carbonaceous material was 2 t o 1by weight. (d) The reduction temperature was 900' C. (e) The reduction time was 3.5 hours. ($) Percentage reduction was calculated as Per cent metallic iron x 100 Per cent total iron 130
INDUSTRIAL AND ENGINEERING CHEMISTRY
JANUARY, 1936
131
OF MAGNETITE OREBY SOLIDCARBONACEOUS MATERIAL TABLEI. REDUCTIONS
Compound Aluminum : AlzOa Barium: Ba CnHsOz)z.HrO
Weight Per Cent of Catalytic Compound I n reducing In total mixture mixture
Per Cent Reduction
No. of Runs Averaged
8.63
3.05
3.88
2
9.06 6.70 8.44 10.30 8.69 20.3 5.28 7.84
3.22 2.34 2.98 3.69 3.07 7.81
6 5 2 3 6 4
2.75
30.0 8.00 3.56 63.3 30.5 15.76 42.6 27.6
22.2
8.65
1.87
2
IS. 0 7.40 11.10 19.36 8.47 22.8 15.41 6.54 11.61 17.7 14.54
6.81 2.60 3.99 7.40 2.99 8.95 5.72 2.28 4.12 6.69 5.37
33.1 5.16 16.10 15.2 16.83 18.1 10.75 15.68 3.81 5.70 10.51
3 2
9.02 6.82
3.20 2.38
6.53 4.43
2 2
9.24 6.57
3.28 2.29
4.22 4.30
2
8.42
2.97
5 46
2
42.4 21.0 14.7 26.8 31.6
19.7 8.15 5.43 10.90 13,35
31.45 14.57 22.3 22.9 14.2
4 4 2 2 2
Mgf CSHSOZ)Z.~H~O 3 0 . 6
Bab03
BaCrOi Ba(O'H)z.SHzO Ba( NOdz BaCzOa.Hz0 BaO Bas04 Boron: HsBOa Calcium : Ch~HsOz)z.HzO CaCOs CaCr04.2HzO Ca(OH)z Ca(NOs)~4Hz0 CaCatOcHzO CaO Caa(P04)z Ca804.2HzO Cas04 Chromium: Cr(OH)a CrzCls Cobalt: Cocoa ConOa C o per
8Ud'
;
Lithium: LiCpHs0~.2HzO LizC'Oa LiOH Li,c:204
LitSOt HzO Magnttsium:
(Mg:cOa)r\ ,,5Hz0 Mgl'0H)s Mg('NOs)r,6H10 Mgb LM~BOIQHZO Manganese : MnlC03 MniOa Molybdenum: MoOa C Aq. (85% Moos) (NII4)aMorOzr.4HsO Nickel: NirOs
1.82
8
3 2 3 4 3 2 1 2
2
12.80
2.92
2
6.24
2.23
2
34.56 7.65 33.6
14.96 2.69 14.45
4.79 5.08 3.06
2 2 2
3.38 2.57
2.63 10.51
11.14 11.35 8 12 8.70 11.03 15 82 7 69 12 31 12.35 7.70 10 55 16.81 8.30 10 02
6 6
16.65
9.47 7.34
Compound
2 2
8.11 8.43
2.86 2.98
0.67 0.70
2 2
6.58
2.30
0.85
2
indic&e approximately the degree of agreement between duplicate experiments, The average value for reduction obtained with plain c o k e 4 . 1 0 per cent-may be kept in mind as a reference point in evaluating the catalytic effect exerted by various compounds. An examination of the data given in Table I shows that in eleven out of the fourteen potassium compounds investigated, the reduction values ranged from 94.5to 99.4per cent, a variation of only 4.9 per cent. The chloride, phosphate, and fluosilicate were much less effective; the latter was practically without any effect. For the sodium compounds a similar narrow range of reduction values was obtained, with eight out of the twelve compounds yielding results ranging from 73.3to 80.9 per cent. The materials deviating from this group were the chloride, phonphate, fluoride, and borate, and again the decrease in percentage reduction was marked. I n one run which was made with a vertical retort, a freshly cut piece of metallic sodium about the size of a pea was placed in the bottom,of the retort and the charge filled in over it. The appearance of the ore after reduction indicated a high value near the location of the piece of metal and a gradual drop to a comparatively low value near the top of the retort. The average for the wellmixed mass was 43.7 per cent reduction. The compounds of sodium that yield values between 73.3 and 80.9 per cent are of the same type as the compounds of
Weight Per Cent of Catalytic Compound In reducing I n total mixture mixture
Silver: 5 10 AgzO Sodium : Metal NaCzHsO? 3Hz0 2i:oo NazB4O r' 10Hz0 29.3 NaHC03 15.49 NazCOa 10.33 NaCl 11.30 NazCrOc4HzO 20.3 9.65 NaCN 8.37 NaF NaOH Aq. 8.42 12.71 NazCzO4 NasP04.12HzO 21.6 13.40 NazSOd Stronti urn : 10.90 Sr C Z H ~ O ~ Z . ~ / Z H Z O srboa 7.78 Sr(OH)z4Hz0 13.18 10.79 Sr NOdz 9.95 Sr&zOd.HzO 5.59 SrO 9.50 SrSO4 Titanium: 7.70 Ti02 Zirconium : 9.15 ZrSiOP
+
4.01 4.09 2.86 3.08 3.97 5.90 2.70 4.47 4.48 2.71 3.78 6.31 2.93 3.67 1.76
... 8.98
12.13 5.74 3.70 4.07 7.81 3.43 2.96 2.97 4.63 8.40 4.90
Per Reduotion Cent
No. of Runs Averaged
99.4 94.7 95.9 73.0 96.3 96.5 94.5 96.8 6.75 97.6 96.4 96.8 44.6 97.1
2 2 8 4 2 4 2 2
2.87
2
43.7 80.9 9.85 78.8 73.5 34.6 73.8 80.4 18.5 76.8 73.3 14.8 73.6
2
2 2 2 2 2
1
2 2 2
16
4 3 2 4 2 5 4 2
3.82 2.73 4.81 3.87 3.55 1.93
3.38
30.65 8.01 16.75 15.01 19.42 8.63 14.81
2 2 2
2.70
2.64
2
3.25
1.44
2
2
2
2
2
Miscellaneous Plain coke mixture Plain hardwood charcoal mixture Hardwood charcoal with CaCOa Hardwood charcoal with Na;COa Hardwood charcoal with BaCOi z, Natural mineral
4.10 52.9
9 8
11.10
3.99
37.6
6
10.33
3.70
99.0
2
6.70
2.34
48.3
6
potassium that yield values between 94.5 and 99.4 per cent. Furthermore, the drop in catalytic effect exhibited by the chloride and phosphate of potassium is paralleled by a similar drop shown by the corresponding sodium compounds. The lithium compounds were variabk in their effect, but with a maximum value of only 31.4 per cent reduction obtained with the acetate, it is evident that they are far less effective than the sodium and potassium compounds. Barium compounds also gave variable results. The maximum reduction was obtained wit5 the hydroxide with an average of 63.3per cent, while the oxide ran second with 42.6 per cent. Barium acetate, nitrate, and sulfate grouped around 30 per cent, whereas the oxalate produced only 15.8 per cent reduction. The carbonate and chromate were practically inert. For the strontium and calcium compounds, less than 20 per cent reduction was found for all but the acetates, whereas certain stable materials (such as calcium carbide and calcium phosphate) gave negligible results, 5.16 and 3.81 per cent, respectively. Moreover, although five magnesium compounds were tried, no reductions exceeded 6.0 per cent for this POUP. Compounds (chiefly oxides) of aluminum, boron, chromium, copper, manganese, molybdenum, nickel, silver, titanium, and zirconium were tried as addition agents. No positive effect was noted except in the case of manganese dioxide with which
132
INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 28, NO. 1
proximately 10 per cent. For sodium carbonate, there appears to be no increase beyond a concentration of approximately 16 per cent.
Further Investigation of Sodium Carbonate EFFECT OF SILICA. To determine the effect of silica, some of the ore was concentrated magnetically, thereby eliminating some of the siliceous gangue. This concentrated material was subjected to reduction tests, employing various concentrations of sodium carbonate. The magnetically treated ore yielded higher reduction values than did the untreated ore, as shown by the following results: Per Cent Sodium Carbonate in Reducing Mixture 2 4 6 8
--__ Per Cent Reduction-------, Ore as crushed and Ore magnetically sieved 8.0 16.7 33.7 56.5
concentrated 7.1 28.9 55.4 89.9
Further work on magnetically separated ore with 8 per cent sodium carbonate and various amounts of added silica in the reducing mixture showed that silica definitely decreases the catalytic effect of sodium carbonate. With the addition of progressively greater amounts of silica, the percentage reduction showed a continuous decrease. When sufficient silica was added theoretically to convert the sodium carbonate to sodium metasilicate, the percentage reduction fell to 31.2, and with 100 per cent excess of silica over this theoretical amount, the value for reduction stood a t 13.8 per cent. It is apparent that a t the temperature of reduction (900' C.) the sodium unites at least in part with the silica to form a relatively inactive compound. CONTINUITY OF CATALYTIC EFFECT. In order to determine the continuity of the catalytic effect when using sodium carbonate, magnetically separated ore and coke were run with I
'ST IN '&DUC~&'
I
I
MIXTURE
a reduction of 10,51per cent was obtained. In fact, the compounds of boron, molybdenum, nickel, and zirconium appeared to have a negative action. The last portion of Table I presents data obtained with hardwood charcoal in place of metallurgical coke. With no added material whatsoever, an average value of 52.9 per cent was obtained, a large increase over the result obtained with plain coke. Barium carbonate with a reduction value of 48.3 per cent appeared practically inert again, but calcium carbonate with a value of 37.6 per cent definitely indicated a negative effect. In contrast to the carbonates of barium and calcium, sodium carbonate greatly increased the percentage reduction and furnished almost completely reduced iron. The relatively high yield of metallic iron by a plain charcoal mix is probably due to the catalytic effect of the alkali metal compounds in the charcoal and also to the effect of the hydrocarbon gases evolved on heating the charcoal.
Effect of Catalyst Concentration for Alkali and Alkaline Earth Carbonates Table I1 gives a correlation of average results obtained for the reduction of magnetite ore with coke, expressed in per cent reduction. The ratio of ore to coke was 2 to 1 by weight and the reduction was for 3.5 hours a t 900' C . The results are presented graphically in Figure 1. It is apparent that the only carbonates that exhibit a marked effect are those of sodium and potassium, with the latter showing the greatest effect. It appears that for potassium carbonate no appreciably greater yield of metallic iron will result by increasing the weight percentage in the reducing mixture over ap-
TABLE11. REDUCTION OF MAGNETITE ORE IN PRESENCE OF ALKALIAND ALKALINE EARTHCARBONATES Compound Barium carbonate, BaCOa
Calcium aarbonrtte, CaCOs
Lithium carbonate, LilCOa
Magnesium carbonate,
(MgCOdr >Hz0 +
MdOWn Potassium carbonate, &COS
Sodium carbonate, NazCOs
Strontium carbonate, SrCOa
Weight Per Cent of Catalytic Compound In reducing In total mixture mixture 5.00 1.72 6.70 2.34 10.00 3.57 15.00 5.55 20.00 7.69 5.00 1.72 3.57 10.00 11.10 3.99 15.00 5 55 20.00 7.69 5.00 1.72 10.00 3.67 15.00 5.55 7.69 20.00 21.00 8.15 1.72 6.00 3.57 10.00 5.55 15.00 6.24 16.65 7.69 20.00 2.00 0.67 3.00 1.02 1.37 4.00 1.72 5.00 2.0s 6.00 2.45 7.00 2.86 8.12 3.38 9.50 3.96 11.00 1.37 4.00 2.08 6.00 2.82 8.00 3.70 10.33 4.35 12.00 6.15 14.00 5.97 16.00 7.25 19.00 1.72 6.00 2.73 7.78 3.67 10.00 5.55 15.00 7.69 20.00
Per Cent Reduction 7.62 8.00 5.30 4.46 6.43 6.80 11.89 16.10 12.33 14.03 3.91 9.98 9.86 16.09 14.57 6.55 6.50 4.01 2.23 2.87 13.97 25.4 56.0 73.6
No. of Runs Averaged 2 5 2 2 2 2 2 8 2 2 2 2 2 2 4
81.0
89.1 95.9 94.5 99.8 16.68 33.7 56.5 73.5 81.9 93.6 94.0 94.7 5.42 8.01 6.62 6.93 8.65
2 2 2 16 4 2 2 2 2 2 2 2 2
JANUARY, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLE111
Fresh reducing agent: Grams Na er gram reducing mixture Per cent rezuction of ore Grams Ne, per gram nonmagnetic material after reduction Re-uee of reducing agent: Grams Na per gram reducing mixture Per cent reduction of ore Grams Na per gram nonmagnetic material after reduction
Sodium Carbonate in Original Reducine Mixture: 6 per cent 8 per cent 0,02604 55.4
0.03471 89.9
0.00464
0.00870
0.00464 10.6
0.00870 23.7
0.00088
0.00220
133
without the addition of any fresh catalyst, was mixed with a fresh lot of ore, and a second run was made. Separation and analysis of the ore and the nonmagnetic residue followed. Tests were conducted with reducing mixtures that originally contained 6 and 8 per cent sodium carbonate. The results are given in Table 111. The data show that the reducing power of a mixture used but once is much lower than for the original, owing to a large loss of catalyst.
Literature Cited two specified initial concentrations of sodium carbonate in the reducing mixture. After the first the reduced ore and the reducing mixture Were separated magnetically. The-re& ' centage reduction was obtained in the usual way, and samples of the nonmagnetic residue were analyzed for total alkali by titration of a hot water extract with standard sulfuric acid to a methyl orange end point. The once-used reducing mixture,
(1) Iwas6 K.9 and Fukusima, M., Science Repts. Tohoku I m p . Univ., 1st Sei-., 22, 301 (1933). (2) Iwas6, K., Fukusima, M . , and Saito, Y., Kinzoku no Kenkuu, 8 (June 20, 1931). (3) Williams, G. C . , and Ragatz, R . A., IND. ENQ.CHEM.,24, 1397 (1932). R~CEIVE July D 15,1935.
Lecithin and Hydroquinone as Antioxidants for Vitamin A
@S
TEENBOCK, Boutwell, and Kent (1%') showed that the vitamin A content of butter fat is destroyed by heating at 100'C. for 4 hours and therefore announced that the vitamin is heatlabile. Hopkins (4, however, showed that the vitamin is quite resistant t o heat but that it is rapidly destroyed by exposure to air a t temperatures from 15' to 120' C. This work was confirmed by Drummond and Coward (1). Powick (11) in 1925 and Mattill (7) in 1927 published work showing that rancid fats destroy vitamin A. Hydroquinone (9) has been widely studied as an antioxidant for fats and oils (8, 10, 14) and has been used to protect the vitamin A of fish liver oils. Huston (6) demonstrated by feeding experiments that hydroquinone has a definite protective value on the vitamin A content of milk fat. The effect of lecithin as an antioxidant for fats and oils has been studied to a slight extent by other workers. Trusler (18) showed that lecithin inhibits the hydrolysis of fats. Kockenderfer and Smith (6) studied the effect of lecithin on the length of the induction period of fats and found it to possess an antioxidant index of 1.7: Antioxidant index = induction period of fat with antioxidant induction period of fat alone Evans (3) recently showed that lecithin exhibits a retarding effect on the formation of peroxides in fats when the oxidation is catalyzed by cobaltic oleate. During the last few years a large number of tests have been made in this laboratory with protectors for the vitamin A content of fish liver oils. This work demonstrates that lecithin has a protective action against the oxidative destruction of the vitamin and also corroborates the above-mentioned effect of hydroquinone. I n addition, a combination of hydro-
Hydroquinone and lecithin were studied as antioxidants for vitamin A in halibut liver and i n cod liver oils at room temperatures and higher. Each affords protection for the vitamin, the degree varying with the concentration of the antioxidant. The combination of the two, however, affords a remarkable protection which is much greater than would be expected from additive effects. HARRY N. HOLMES, RUTH E. CORBET, A N D EVA R. HARTZLER Oberlin College, Oberlin, Ohio
quinone with lecithin has been found to afford a remarkably strong protection which is much greater than would be expected from additive effects.
Materials OILS. The fish liver oils werg all high grade and supplied by Parke, Davis & Company, or the Abbott Laboratories. LECITHIN. The lecithin was from soy beans, and was obtained from the American Lecithin Corporation. CHLOROFORM. The chloroform was a U. S. P. grade, purchased from the Dow Chemical Company. ANTIMONY TRICHLORIDE. Baker's c. P. anhydrous antimony trichloride was used. The reagent was made up with specially purified dry chloroform to a concentration of 21 to 23 per cent (weight/volume) of antimony trichloride in chloroform. The experiments were carried out under two conditions : (1) at a temperature of 96' C. in an atmosphere of oxygen and (2) a t room temperature in an atmosphere of air. Oxidation at 96" C. i n Oxygen APPARATUS. The assembled apparatus is shown in Figbe 1. The oxidation chambers (Figure 2) were made of heavy-walled
