A High-Nitrogen Material from UreaAmmoniated Peat R. 0. E. DAVIS,WALTER SCHOLL, AND R. R. ~ I I L L E R Fertilizer Investigations, Bureau of Chemistry and Soils, Washington, D. C. excess carbon dioxide. AiialyThe conditions required for the preparation HE development of an sis showed the c a r b a m a t e to organic nitrogenous fertiof ammoniated peat arid for the synthesis of urea be 97 per cent pure. The peat l i z e r m a t e r i a l by the are nery similar so that it is possible to accomplish received no special treatment. treatment of peat with liquid both processes in one operation. The particle sizes were such that ammonia h a s i n t e r e a t e d the The effects hate been defermined of ammonia 26 per cent was retained on a authors for snnie time. It has 20-mesh screen and about 23 per concentration, carbon dioxide concentration, the been shown (8) that considerable cent passed through an 80-medi nitrogen is obtained in the mapresence of j'ree water, and temperature and time screen. The apparent specific terial produced from this treatof reaction on the contersion of carbamate to urea gravity when dry ranges between ment, the aniount T-arying from in the presence of peat. 0.19 and 0.34 or it weighs from i to about 20 per cent depend12 to 21 pounds per cubic foot Products have been prepared carrying urea ing on the variation of the condi(192 to 336 kg. per cubic meter). u p to 70 per cent urea, but only those below 60 tion of temperature, pressure, All the experiments were carried time of treatnieiit, and inoidure per cent urea, when subjected to humidity tests, out in bombs made of Reeistal steel present. The nitrogen in amwere free f r o m caking and remained friable. A No. 4,having a capacity of 80 cc. moniated peat is partly waterand lined with a snugly fitting material carrying a high percentage of urea as a soluble but m o d y insoluble, the P y r e x t h i m b l e . The desired solid without the disaduantages due to hygroquantities of carbamate and peat soluble portion averaging about were loaded into the thimble and scopicity inherent in pure urea suggests a field qf 25 per cent of the total. One conmixed. When excess ammonia was stituent of the water-soluble porwider use.fulness f o r urea as fertilizer. desired. liauid ammonia was added tion has been found to be urea. and the thimble immediately enThe presence of urea is not closed in the bomb. The contents surprising, h c e the conditions employed in ammoniatiiig peat were maintained at 179" to 181' C. for 4 hours. The bomb mas then cooled in ice and the contents, after removal, exposed in are similar to those necessary for the synthesis of urea ( 7 ) ,and an open dish for the removal of free ammonia and carbon dioxide. the decomposition of peat under these conditions produces car- The material was ground and mixed to insure uniformity of bon dioxide, which in the presence of ammonia forms am- the product. For the determination of free water in the air dried product, monium carbamate, the starting material for urea synthesis. gram of material spread in low wide dishes was heated at The possibility is suggested of raising the urea content by in- one 60' C. for 5 hours. Practically no nitrogen loss occurred from creasing the carbon dioxide present. The similarity of the this procedure, but heating above 60" C. resulted in loss due to factors affecting the conversion of ammonium carbaniate t'o decomposition of urea. Nitrogen determinations were made by Ellen K. Rist of this urea and of those entering into the ammoniation of peat is using the Gunning-Arnold method ( 2 ) except that shown by t,he following established results; increasing tem- laboratory selenium was employed as catalyst in digestion instead of copper peratures and excess ammonia give increasing Conversion in sulfate. Soluble and insoluble nitrogen in the product were each case, a small amount of water is desirable and 4 hours determined according to the A. 0. A. C. methods for fertilizers ( 2 ) . are sufficient for maximum conversion, and superatmospheric Free ammonia nitrogen was determined in the filtrate containing soluble nitrogen by titration with standard acid. The difference pressures are required in each case (3, 5, 8). between the total soluble nitrogen and the ammonia nitrogen was I n the urea synthesis from ammonium Carbamate, a t 155' C. taken to be urea nitrogen. This is probably high because of and 100 atmospheres pressure the conversion to urea in some soluble nitrogen, of undetermined character, from the am4 hours is about 37 per cent, while Krase and Caddy (6) moniated peat portion of the product. Check analyses for urea the urease method ( 4 ) carried out by J. Y. Yee of this laborahave shown that 300 per cent excess ammonia, acting as a by tory showed that the direct determination of urea averaged dehydrating agent, gives a conversion to 85 per cent urea. slightly less than 2 per cent lower than the values obt.ained by By the simultaneous synthesis of urea and the ammoniation indicated procedure. of peat it was believed possible to obtain a material without the objectional hygroscopicity of urea, and the ammoniated EFFECT OF IMPOSED CONDITIONS peat would prevent caking. The conditions for preparing Experimental data were obtained on the effect of (1) arnsuch material and the proportions of the products obtained inonia concentration, (2) free water in the peat, (3) carbon have been 3tudied. dioxide concentration, (4) temperature, and ( 5 ) time on the conversion of carbamate to urea simultaneously with the a m EXPERIMENTAL PROCEDURE moniation of peat. The materials employed were freshly prepared ammonium The effect of varying the concentration of ammonia is carbamate, air-dried peat obtained from Capac, Mich., shown by the data in Table I and graphically in Figures 1 anhydrous ammonia, and carbon dioxide. Carbamate was and 2. Figure 1 gives the conversion of carbamate to urea prepared by partly filling a cooled bomb with liquid ammonia without and with peat. Maximum conversion to urea due and then introducing from a cylinder carbon dioxide in ex- to increasing ammonia concentration has been reached at cess of the amount necessary to react with i t The solid 275 per cent excess ammonia. The data and curves of carbamate was quickly transferred to a vacuum desiccator Figure 2 show that for a fixed ratio of carbon dioxide to peat,, and kept for 24 hours a t slightly reduced pressure to remove the amounts of total nitrogen and the yields of urea increase
T
69
I N D U S T R I A L A &' D E N G I N E E R I S G C H E M I S T R Y
70
TABLE1. DATAFROM EXPERIMENTAL PREPARATIONS
Vol. 27, No. 1
O F LTREA-AMMONl.4TED P E . i T
PRODVCT
--
CHARGI:MATERIALS--
Yield Charge (dry density weight) Grams X Grams Grams Grams I O - ~ C C . Grams 16.68 5.73 5 34 9.9 88E3 16.68 5.56 10 40 11.7 89El 11.92 12.66 15.82 51 10.6 91 EO 8.18 8.88 18.63 45 9.2 91 E 3 6.50 7.10 20.91 43 6.9 85El 8.34 11.11 0 24 6.2 86 E l 8.34 11.11 5 31 7.9 88 E l 8.34 11.12 10 37 9.9 88 E 4 8.34 11.12 20 49 10.2 85E4 6.68 17.75 0 31 7.1 17.75 86E4 6.68 4 36 9.1 85E0 5.01 19.70 0 31 7.0 8REO 5,Ol 19.70 3 35 9.5 85E3 3.34 17.75 0 26 5.7 18.05 86 E 3 3.34 2 27 7.2 87 E l 7.00 13.58 0 26 10.1 87E0 7.00 13.58 7.8 36 12.4 89E3 8.94 1 5 . 6 8 19.69 55 16.7 87E4 2.00 17.45 0 37 6.7 17.45 87E3 2.00 2.0 27 8.3 E9E3 8.94 15.68 19.69 55 16.7 E9EO 9.45 15.08 18.95 54 16.3 89E4 10.17 14.40 18.11 53 14.2 89 E l 11.92 12.66 15.8'2 51 10.6 a Average of 321 E01, 321 EO?, and 319 E01. Expi-.
Peat (NHs)zCOz NH3
I-ield based on total Mois- Total weight ture nitrogen CO(NHr)i of (dry on air(dry charge drying basis) basis)
~~
ISSUL. --TOTAL
NITROGEN AS:-Ammonia WaterWater.hi insol. N sol. (dry (dr,y hi basis) basis)
s
A0
( X H I I O - ExcEas CO? AM-
Cor-
YERTED
UOSIA OVER
ACTIVE T O CO- CARN ("2)s BAMATE (DRY (DRY ArR h s ~ s ) BASIS) M O N I A
%
%
%
%
%
39 37 27 26 20 34 33 34 26 31 32 30 35 28 34 50 44 38 35 39 38 38 34 27
6.2 2.1 1.6 1.6 1.5 5.9 1.9 1.2 1.1 6.1 1.4 6.1 1.4 3.3 0.9 2.2 1.6 1.6 1.3 1.5 1.6 1.5 1.5 1.8
12.5 16.8 26.6 28.8 28.5 16.0 24.4 29.6 30.5 25.0 31.3 30.7 34.6 38.6 35.5 19.8 26.9 29.7 34.4 36.9 29.7 29.0 27.8 26.6
%
70
%
%
13.2 24.8 47.4 51.7 54.1 20.2 42.5 56.5 58,s 42.4 58.8 57.3 65.5 62.9 69.6 28.0 48.0 53.1 66.8 69.9 53.1 55.3 34.9 47.3
54.1 69.6 83.7 85.0 89.0 71.9 83.7 98.3 90.2 84.4 87.8 91.5 89.3 91.9 92.3 80.0 86.3 84.2 05.8 90.2 84.2 89.4 81.3 83.7
70
3.7 0.4 0.6 0 9 0.5 13.1 2.4 0.3 0.2 5.6 0.7 4.1 0.8 1.8 0.8 15.8 4.3 0.8 6.2 3.4 0.8 0.5 0.4 0 6
45,9 30.4 16.3 15.0 11.0 28.1 16.3 11.7 9.8 15.6 12.2 8.5 10.7 8.1 7.7 20.0 13 7 15.8 4.2 9.8 18 8 10.6 15.7 16.3
45 62 79 90 96 44 55 64 76 53 85 65 93 71 85
71 68 51 67 70 14 39 63 70 22 39 26 41 26 40 27 57 74 33 43 74 78 45 51
206 413 287 482 678 0 103 206 413 0 52 0 35 0 25 0 132 289 0 26 289 280 789 287
with an increase in concentration of ammonia up t o a definite concentration. The influence of free water content in the peat also is shown by the data in Table I and Figure 2. Curves 7 and 8 with no water as compared to 2 and 6 with 40 per cent water, respectively, and the same carbon dioxide-peat ratios show : (1) when the ratio of carbon dioxide to peat is 1.01, a maximum yield of urea is obtained with a ratio of ammonia to dry peat of 3.00, while with moisture content of 40 per cent a ratio of 6.0 is required; (2) using the higher ratio of carbon dioxide to peat of 4.97, the maximum yield of urea is the same regardless of moisture a t a ratio of ammonia to dry peat of 5.0; (3) for ratios of ammonia to peat below the maximum yield of urea, the higher concentrations of water lower the yield of urea.
TEST
7 -
Total N
3
The effect of varying the concentration of free water is shown in Table I. I n the last four samples of this table the ratios of peat to carbon dioxide and of ammonia to carbon dioxide were 1.01 and 3.04, respectively. Increase in water from 1 to 40 per cent lowered the yield of urea by approximately 28 per cent. I n Figure 3 is shown the influence of carbon dioxide concentration on the yield of urea. For a fixed ratio of ammonia
1rt.
38,8
38.8 38.8 38.8 38.8 38.8 38.8 38.8 38.8 38.8 38.8 38.8 38.8 38.8 38.8 1.28 1.28 1.28 1.28 1.28 1.28 11.11 21.08 40.80
TABLE11. EFFECTOF TEMPERATURE ON NITROGEN CONTENTAND UREACONVERSION
1 2
PER CENT EXCESSAMMONIA
73 87 61 94 87 70 74 79
IN
%b
to peat the yield of urea is proportional to the concentration of carbon dioxide up to a ratio of approximately 1.25 carbon dioxide t o peat, and beyond a ratio of 3.6 the yield falls rather rapidly. Excess carbon dioxide does not act as a dehydrating agent, as an excess of ammonia, and causes the equilibrium of the reaction to shift to the carbamate side. The temperature effect on the total nitrogen and on urea conversion obtained in the product is shown in Table 11. Data are given comparing the results obtained for treatment of three charges a t 155" and 180" C. for 5 hours. A higher conversion to urea is obtained in each case a t the higher temperature.
NO.
FIGURE1. EFFECTOF EXCESSAMMONIA ON CARBAMATE CONVERSION TO UREA
80
H?O PEAT
155' C.Conversion
-180' Total N
2 ' .Conversion
%
%
%
%
25.4 25.5 31.5
37 38 36
26.6 29.6 31.3
51 63 39
The effect of time of heating was determined on one typical mixture. The charge consisted of peat containing 38.8 per cent moisture, ammonia to peat ratio of 2.883, ammonium carbamate to peat ratio of 1.192, temperature of 180' C. Table I11 gives the results for different lengths of time at 180" C. The total heating is somewhat longer than indicated, since about 2.5 hours were required to bring the bombs t o 180" and 2 hours to cool to ice temperature. After 2 hours a t 180' C. the increase in total nitrogen is negligible, but the conversion to urea requires nearly 4 hours to reach a maximum. Carbamate conversion is 85 per cent complete by the time 180" is attained. The water-soluble nitrogen shows a slight decrease on prolonged heating, while the total nitrogen shows a slight increase. TABLE111. EFFECTOF TIMEOF HEATINGAT 180" C. --DRY TIME Hour8
0 1 2 3 5.5
PRODCCT--
Total N Urea
Watersol. N
%
%
%
24.4 27.0 27.6 26.8 27.5
44.6 51.2 50.8 49.8 52.0
87.3 89.6 87.4 89.0 90.5
-DRY TIME T o t a l N Hours % 6 27.9 7 28.5 7.5 27.4 10 28.3 24 28.5
PRODCCTWaterad. N
Urea
%
%
52.8 53.8 51.0 63.1 50.9
89.4 93.0 88.4 88.8 87.0
I N D U S T R I A L A K D E I\; G I N E E R 1 X G C H E 11 I S T R I'
Januarg, 1935
PROPERTIES OF THE PRODUCT
Table I shows t h a t several experiments resulted in products containing as high as 70 per cent of urea with total nitrogen content of 35 to 37 per cent. Because of such high urea content, tests were made on products containing from 20 to 70 per cent urea subjecting them to relative humidities of
T--
I
1
0
0'5
IC
I
I
15 20 RATIO:
L'5
30
35
l 40
NH, TO DRY P E A T
I , 45 5C (BY WT,
l 55
1
FIGURE2. EFFECTOF AMMONIAON UREA IN AMMO^-I ATED
PEAT
85 and 40 per cent at a summer temperature of auout 30' C. (86" F,), hIechanica1 mixtures of urea and ammoniated peat were subjected to the same conditions for comparison. The exposures lasted for 7 days at 85 per cent, and the gain in weight was determined. The samples were then exposed for 3 days to a relative humidity of 40 per cent to determine the segregation and caking on drying. Table 17'gives the data obtained on the ammoniated products. TABLEIV. HYQROSCOPIC~TY TESTS ORIQ. F v A T E R I N SAMPLE U R E A WATER WATER I N S.4MPLE mATEE IN ABTER EXPOSURE TO IN AFTER EXPOSURE TO I N D R Y DRY PROD- PROD- REL. HUMIDITYOF: OF: PROD- PROD- REL.HUMIDITY UCT 85% 40% 85% 40% UCT UCT UCT % % % % % % % % ._ 37.2 5.88 12.75 7.04 57.3 6.12 11.73 20.18 34.4 1.34 2.24 18.8 8.60 58.8 3.77 28.0 24.6 37.2 8.76 62.9 3.30 9.42 6.08 42.4 33.3 26.5 65.5 1.37 14.38 1.91 4.27 42.5 3 1.0 1.26 7.47 35.0 66.8 4.54 1.63 48.0 0.91 69.6 34.6 4.87 53.1" 69.9 1.15 36.4 2.94 5 6 . Sa 4 Visual observations only mere made, as dishes were broken acridentally. 0 RI Q
URD< IN
Thc humidity employed was well above the value 72.5 per cent as determined by Adams and Merz (1) for the equilibrium with the saturated urea solution, so that any free urea under
71
The samples containing less than 43 per cent urea subjected to 85 per cent humidity remained dry in appearance and on dehydration showed no segregation of crystals or caking. Materials with 43 to 60 per cent of urea became slightly moist but did not show free water. Those approaching 60 per cent urea were not free-flowing at high humidity. On dehydration, small crystals of urea were discernible throughout the mass and increasingly greater crystals were observed a t the higher percentages of urea, but they were uniformly distributed with no evidence of caking. With a urea content between 60 and 66 per cent some free water was discernible around the edges of the sample, a t 85 per cent humidity. On dehydration, urea crystals were numerous and a crust formed over the surface. Materials with urea content between 67 and 70 per cent showed considerable free water on exposure to the high humidity, and on dehydration cemented together into a hard mass which would require crushing and grinding to restore even distribution of the constituents. The mechanical mixtures of urea with ammoniated peat and with raw peat, subjected to similar tests, showed more crystallization of urea a t the same percentage composition of urea than the mixtures in which ammoniation and urea formation were carried out simultaneously. Mechanical mixtures with 50 per cent urea showed approximately the same properties as the processed urea-ammoniated peat with 60 per cent urea. Microscopic examination of the processed products showed that those containing below 30 per cent urea consisted of very fine urea particles intimately mixed with fine particles of ammoniated peat of about the same size. The size of the urea crystals were larger with increasing percentage u p to 60 per cent but were still uniformly distributed, and above 60 per cent small bunches of urea crystals began to appear. This accounts for the caking above 60 per cent urea. The general properties of the material are such as to make it suitable for fertilizer use. If the urea content is below 60 per cent, it retains its friability under extremely humid conditions. The major portion of the nitrogen is soluble, and under proper conditions of preparation the insoluble nitrogen is highly active. The results reported have been obtained from the small-scale laboratory experiments, so that a number of problems involved in preparation of the material remain to be investigated. The advantages of obtaining a carrier for urea as a solid offers promise of increasing its usefulness as a fert>ilizer.
LITERATURE CITED (1) Adams, J. R., and LMerz, A. R., IND.ENQ.CHEX.,21, 305 ( 1 9 2 9 ) . (2) Assoc. Official Agr. Chem., Official Methods of Analysis, 3rd ed., I
(3)
pp. 21-5 (1930).
Clark, K. G., Gaddy. V. L., and Rist, C. E., IND.E m . CHEII.. 25, 1092 (1933).
E. J., and Geldard, W. J., Ibid., 15, 743 (1923). ( 5 ) Krase, N. W., and Gaddy, V. L., Ibid., 14, 611 (1922). (6) Ibid., 22, 3088 (1930). (7) Krase, H. J., Gaddy, V. L., and Clark, K. G., Ibid., 22, 289 (1930). (8) Scholl, W., and Davis, R. 0. E. Ibid., 25, 1074 (1933). (4) Fox,
RECEIVED October 15, 1934. Presented before the Division of Fertilizer Chemistry at the 88th Meeting of the American Chemical Society, Cleveland, Ohio, September 10 to 14; 1934.
FIGURE3. EFFECTOF CARBONDIOXIDIC ON
UREA CONVERSION
these conditions would absorb water rapidly and become liquid. While these samples absorbed considerable moisture at 85 per cent humidity (the absorption ranging from 13 to 37 per cent), a t the lower humidity of 40 per cent they lost i t down to an average of 7.32 per cent.
RUHR NITROGENDEVELOPMENTS. The Department of Commerce reports that the Ruhr Chemie A. G., the 9,000,000mark synthetic nitrogen subsidiary established by Ruhr cokeoven operators, increased its sales volume in 1933-34 to 23,000 tons nitrogen from 21,862 tons in the previous year. Hydrogen for the ammonia synthesis was obtained from 108.7 million cubic meters of coke-oven gas. The company has been actively developing a plan of largescale production of motor fuel by hydrogenation of coal. A pilot plant, with an annual capacity of 1000 tons. will start production soon.
