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Phase Diagrams of Na2CO3−CO(NH2)2−H2O2−H2O System at 0 °C and 25 °C and the Production of Urea Peroxide and Sodium Percarbonate Jilin Cao,* Huiyong Jing, Tianyang Lan, and Jingjie Wang Hebei Provincial Key Laboratory of Green Chemical Technology & High Efficient Energy Saving, School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin, 300130 China ABSTRACT: There is a great deal of H2O2 loss and low production benefit in the traditional technology of urea peroxide production. To develop a new method of producing urea peroxide, the mutual solubilities in the quaternary system Na2CO3−CO(NH2)2−H2O2−H2O were measured, and the corresponding diagrams were plotted at 0 °C and 25 °C. Based on the analysis about the phase diagram, this work put forward a new technology of the combination production of urea peroxide and sodium percarbonate. Urea peroxide was first produced at 0 °C; then sodium percarbonate was produced according to the reaction of Na2CO3 with the residual solution after urea peroxide production at 25 °C. After sodium percarbonate production, the residual solution was evaporated and concentrated and then used to produce urea peroxide, and thereby the stable recycle production of CO(NH2)2·H2O2 and Na2CO3·1.5H2O2 could be realized. CO(NH2)2·H2O2 reaction with Na2CO3 and increased the utilization of H2O2. To validate feasibility of the above technology, this article carried out a study on phase diagrams of the Na2CO3−CO(NH2)2−H2O2−H2O system at 0 °C and 25 °C and their application.
1. INTRODUCTION CO(NH2)2·H2O2 is a compound of H2O2 and CO(NH2)2 combination by hydrogen bonds. As a solid disinfectant and resources for oxygen, CO(NH2)2·H2O2 is widely used in organic synthesis, bleaching, textile, waste management, daily chemical products, medicine, agriculture, and aquaculture, and so forth.1−3 CO(NH2)2 and H2O2 (w = 0.30) are commonly used in the production of urea peroxide by the wet method, and the residual mother solution of this processing technique is relatively rich in CO(NH2)2 and H2O2 (w = 0.08 at 0 °C). However, there is no good method to deal with this solution so far, because H2O2 would be decomposed and led to considerable loss when this solution was evaporated and concentrated to cyclic utilization. If the mother solution is directly discharged without using CO(NH2)2 and H2O2, it will be a waste of resources.4 Therefore, to reduce the loss of H2O2 and improve the production benefit of urea peroxide, the traditional technology of urea peroxide production should be improved. Na2CO3·1.5H2O2 has the same characteristics as CO(NH2)2·H2O2 and is also widely used in medicine, electroplating, weaving, catering industry, and washing powder formulations.5,6 The main industrial method for the preparation of Na2CO3·1.5H2O2 is the wet method by Na2CO3 reaction with H2O2 in solution.7 This technology also produces the residual mother solution which contains H2O2 w = 0.01 to 0.02 at 0 °C. However, the residual solution can be used after concentration and decomposing H2O2 because a small amount of H2O2 loss almost did not affect economic benefits of Na2CO3·1.5H2O2.8 Comparing the technology of CO(NH 2 ) 2·H 2O 2 and Na2CO3·1.5H2O2, we put forward a new technology which was production Na2CO3·1.5H2O2 using the residual solution of © 2013 American Chemical Society
2. EXPERIMENTAL SECTION 2.1. Materials. Hydrogen peroxide (H2O2, w = 0.30, analytical reagent), sodium carbonate (Na2CO3, w = 0.30, analytical reagent), and urea (CO(NH2)2, w = 0.99, analytical reagent) were supplied by Tianjin Second Reagents Corporation. The water used to prepare solutions is twice-distilled water (conductivity < 5 μS·cm−1). 2.2. Procedure. The experimental facility was shown in ref 9. The mixture of hydrogen peroxide, sodium carbonate, urea, and water with a certain ratio was added into the equilibrium glass tube and agitated by the stirrer. When the mixture reached phase equilibrium, the stirrer was stopped. After the mixture standing and layering process, the solution was first pulled out from the equilibrium glass tube by a 5 mL pipet and analyzed. Then the residual wet solids were pulled out from the equilibrium glass tube by a small glass ladle and analyzed. The experiment showed that the phase equilibrium time was 6 h. 2.3. Analysis. The hydrogen peroxide concentration was determined by titrating the acidified solution with standard potassium permanganate. The sodium carbonate concentration was titrated with a standard solution of hydrochloric acid. The urea concentration was determined by titrating with a standard Received: September 27, 2012 Accepted: December 13, 2012 Published: January 16, 2013 377
dx.doi.org/10.1021/je301058k | J. Chem. Eng. Data 2013, 58, 377−382
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Table 1. Solubilities of the System Na2CO3−H2O2−CO(NH2)2−H2O at 25 °Ca composition of liquid phase %(wt) point
P1
Q1
F1 E1 B1 a
composition of wet solid phase %(wt)
Na2CO3
H2O2
CO(NH2)2
H2O2
Na2CO3
H2O2
CO(NH2)2
H2O
equilibrium solid phase
22.26 23.16 25.32 21.46 21.88 21.08 20.70 20.33 19.57 16.11 18.46 17.93 15.60 16.56 14.75 14.12 13.31 12.36 12.06 11.93 11.13 11.20 6.76 4.58 2.75 2.08 1.82 1.57 1.60 1.57 1.47 1.30 0.00 2.08 2.33 2.05 2.36 2.37 2.55 2.23 2.46 0.00 11.33 24.41
0.78 0.73 0.65 0.62 0.55 0.54 0.48 0.47 0.42 0.40 0.39 0.36 0.38 0.27 0.26 0.17 0.30 0.30 0.31 0.23 0.28 0.19 0.54 1.03 2.09 3.22 3.85 4.53 5.27 6.12 7.55 8.08 9.40 4.77 5.48 5.64 6.64 6.92 8.27 9.57 14.54 9.40 0.00 1.10
5.27 7.85 9.98 12.18 14.05 14.78 16.85 18.16 20.23 21.98 24.67 27.07 29.49 31.61 33.60 34.74 37.65 40.07 41.93 41.36 42.46 50.08 49.10 50.38 49.58 60.96 59.72 58.83 56.37 55.62 57.79 57.42 57.32 48.21 52.19 48.25 46.80 44.53 42.56 42.69 38.56 57.32 41.80 0.00
71.69 68.26 64.05 65.74 63.52 63.6 61.97 61.04 59.78 61.51 56.48 54.64 54.53 51.56 51.39 50.97 48.74 47.27 45.7 46.48 46.13 38.53 43.6 44.01 45.58 33.74 34.61 35.07 36.76 36.69 33.19 33.2 33.28 44.94 40 44.06 44.2 46.18 46.62 45.51 44.44 33.28 46.87 74.49
35.52 35.95 36.47 35.68 33.80 34.68 32.53 31.57 29.59 32.57 31.11 29.99 30.57 29.24 32.18 34.50 28.84 27.74 26.78 20.91 22.08 33.08 31.68 41.69 32.06 35.95 34.29 43.18 5.99 8.05 52.51 5.45 0.00 57.74 58.59 61.90 20.82 59.96 59.13 58.85 59.48
7.20 7.95 8.85 8.76 7.62 8.63 7.52 7.04 7.00 7.52 7.82 6.72 8.75 4.35 8.21 6.93 5.91 6.24 4.70 4.29 6.67 11.85 9.53 7.67 5.08 8.13 6.54 1.20 4.98 5.59 6.66 5.81 16.66 8.48 2.60 2.94 13.08 4.00 8.50 11.31 12.58
4.97 5.77 14.79 7.47 9.14 9.34 11.99 13.80 17.21 16.21 17.74 19.98 21.65 23.27 25.48 24.81 27.94 32.81 36.39 47.10 48.20 42.85 31.27 24.55 10.35 43.01 45.25 40.90 74.27 70.63 57.28 76.05 67.16 14.90 17.21 12.97 35.18 12.40 14.67 12.95 11.42
52.31 50.33 39.89 48.09 49.44 47.36 47.97 47.59 46.21 43.70 43.33 43.31 39.03 43.14 34.13 33.76 37.31 33.21 32.13 27.70 23.05 12.22 27.52 26.09 52.51 12.91 13.92 14.72 14.76 15.73 16.45 12.69 16.18 18.88 21.60 22.19 30.92 23.64 17.70 16.89 16.52
C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A C10+A+U C10+U A+U A+U A+U A+U A+U A+U A+U A+U A+U+Up U+Up U+Up U+Up U+Up A+Up A+Up A+Up A+Up A+Up A+Up A+Up A+Up U+Up C10+U C10+A
A: Na2CO3·1.5H2O2; Up: CO(NH2)2·H2O2; U: CO(NH2)2; C10: Na2CO3·10H2O.
nary system Na2CO3−CO(NH2)2−H2O2−H2O at 0 °Cand 25 °C are given in Tables 1 and 2. Figure 1 is the corresponding dry salt phase diagram which is plotted according to the each composition mass fractions per 100 g of salt. In Figure 1, the solid line and broad dotted lines represent the boundary line of crystalline region at 0 °C and 25 °C, respectively, and the thin dotted line represents the operating line of phase diagram analysis and calculation. It can be seen that, when the concentration of hydrogen peroxide employed in the experiments is below 30 mass %, there are four solids formed in the system, which correspond to Na2CO3·10H2O, CO(NH2)2, Na2CO3·1.5H2O2, and CO(NH2)2·H2O2 respectively. CEPB and CE1P1B1 corresponding
solution of sodium hydroxide. The water content was determined by subtraction. The errors of analysis were less than w = 0.015. The equilibrium phase solid was determined by the wet dregs method with the help of X-ray diffraction (XRD) analysis. XRD patterns were taken by the use of a Rigaku D/MaxII2500VB2+/PC X-ray diffractometer using Cu Kα radiation (λ = 0.15406 nm) and the scan mode with a speed of 0.25 deg·min−1.
3. RESULTS AND DISCUSSION 3.1. Solubilities and Phase Diagram of the Na2CO3− CO(NH2)2−H2O2−H2OSystem. The solubilities in the quater378
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Table 2. Solubilities of the System Na2CO3−H2O2−CO(NH2)2−H2O at 0 °Ca composition of liquid phase %(wt) Na2CO3
H2O2
CO(NH2)2
H2O
Na2CO3
H2O2
CO(NH2)2
H2O
equilibrium solid phase
B
14.62 9.30 11.41 8.38 8.62 7.62 6.67 6.17 6.36 2.44 3.59 3.38 3.34 4.53 3.74 4.01 5.46 5.26 5.01 4.19 0.00
1.32 2.37 2.84 2.11 2.21 1.62 1.83 1.86 2.71 4.65 6.15 6.92 7.40 8.03 8.89 10.40 1.58 1.27 1.60 0.00 5.25
0.00 3.36 4.76 9.39 10.75 15.87 20.25 34.69 39.45 37.56 48.05 40.67 38.22 33.40 22.14 17.27 32.25 34.67 44.56 37.31 44.23
84.06 84.97 80.99 80.12 78.42 74.89 71.25 57.28 51.48 55.35 42.21 49.03 51.04 54.04 65.23 68.32 60.71 58.8 48.83 58.5 50.52
16.49 28.78 31.04 19.11 34.12 31.45 27.52 24.97 17.48 22.09 16.59 15.43 11.64 10.58 8.01 15.01 16.511 27.77 21.94 4.94 5.12
42.10 5.90 6.67 7.00 7.58 5.12 4.94 5.36 4.69 11.23 16.10 21.72 22.47 23.22 30.55 21.10 1.47 5.35 5.11 27.52 31.45
0.00 0.62 1.22 7.90 7.52 7.89 11.10 26.94 41.48 33.85 46.23 45.32 44.14 43.85 61.44 28.46 49.69 14.97 37.94 11.10 7.89
41.41 64.7 61.07 65.99 50.78 55.54 56.44 42.73 36.35 32.83 21.08 17.53 21.75 22.35 0 35.43 32.329 51.91 35.01 56.44 55.54
C10+A C10+A C10+A C10+A C10+A C10+A C10+A U+C10+A U+A Up+U+A Up+A Up+A Up+A Up+A Up+A Up+A U+C10 U+C10 U+C10 U+C10 U+Up
P Q
E F a
composition of wet solid phase %(wt)
point
A: Na2CO3·1.5H2O2; Up: CO(NH2)2·H2O2; U: CO(NH2)2; C10: Na2CO3·10H2O.
As shown in Figure 1, there are two invariant points P and Q at 0 °C or P1 and Q1 at 25 °C. P and P1 correspond to coexistence of solids Na2CO3·10H2O, Na2CO3·1.5H2O2, and CO(NH2)2. Q and Q1 correspond to the coexistence of solids CO(NH2)2·H2O2, CO(NH2)2, and Na2CO3·1.5H2O2. Figures 2
Figure 1. Phase diagram of the Na2CO3−CO(NH2)2−H2O2−H2O system at 0 °C and 25 °C. Figure 2. XRD patterns of the equilibrium solids corresponding invariant points P.
to the equilibrium of crystal Na2CO3·10H2O with saturated solution at 0 °C and 25 °C; EPQFU and E1P1Q1F1U corresponding to the equilibrium of crystal CO(NH2)2 with saturated solution at 0 °C and 25 °C; BPQGA and B1P1Q1G1A corresponding to the equilibrium of crystal Na2CO3·1.5H2O2 with saturated solution at 0 °C and 25 °C; FQGUP and F1Q1G1UP corresponding to the equilibrium of crystal CO(NH2)2·H2O2 with saturated solution at 0 °C and 25 °C. The crystalline region of Na2CO3·1.5H2O2 is the largest one among the four crystallization regions. The results indicate that the compound Na2CO3·1.5H2O2 can be easily prepared at this system.
and 3 are the X-ray patterns of the equilibrium solids corresponding invariant points P and Q respectively, which confirms the results of equilibrium solids determined by wet dregs method. 3.2. Production of CO(NH2)2·H2O2 and Na2CO3·1.5H2O2. According to the study on the urea peroxide production by the phase diagram of the ternary system CO(NH2)2−H2O2−H2O at 0 °C,4 the appropriate mother solution composition after urea peroxide production was H2O2 w = 0.0873 and CO(NH2)2 w = 0.1778. This composition spot drawn in salt diagram Figure 1 is spot M. When Na2CO3 was 379
dx.doi.org/10.1021/je301058k | J. Chem. Eng. Data 2013, 58, 377−382
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process. Thereby a joint production of urea peroxide and sodium percarbonate can be achieved. Based on the analysis about the phase diagram of Na2CO3− CO(NH2)2−H2O2−H2O system at 0 °C and 25 °C, the technological flowchart of Na 2 CO 3 ·1.5H 2 O 2 and CO(NH2)2·H2O2 production is given in Figure 4. From material balancing calculation, when all of solution N in the last production process was recycled to prepare Na2CO3·1.5H2O2 and CO(NH2)2·H2O2 again, it is concluded that the amount of solution N in the next production process will increase, and the whole recycle production of Na2CO3·1.5H2O2 and CO(NH2)2·H2O2 will become unstable. So, to get the steady and continuous production, solution N must be separated into two parts: one part of solution N was concentrated by evaporation and then used to produce CO(NH2)2·H2O2 again; another part of solution N was dried up and became the solid mixture which was used as reactant in the next production process of Na2CO3·1.5H2O2 . In Figure 4, the operating unit in top line was only used in the beginning of production, and the operating unit within the dotted line-finder was the steady and continuous production process. Taking 1000 g of urea as the beginning feed, the phase diagram calculations of preparing CO(NH2)2·H2O2 and Na2CO3·1.5H2O2 were carried out according to the material balance principle. The composition and amount of key mother solution spots and products are calculated and shown in Table 3. At 0 °C, 1000 g of urea reacted with 1811.5 g of D to form 1086 g of CO(NH2)2·H2O2 and 1725.5 g of mother solution M. When 383.32 g of Na2CO3 and 1144.9 g of CO(NH2)2 were added into the solution M, the mixture system composition spot was located in spot M1. Because the mixture M is supersaturated, 372.26 g of Na2CO3·1.5H2O2 was crystallized from M1, and the 2881.4 g of the mother solution N was produced. To keep steady and continuous recycle production, the mother solution N was separated into two parts, N1 and N2, which have the same composition and different amounts. A sample of 560.37 g of solution N2 was concentrated to 313.74 g of mixture N3 by evaporation to remove water. When solution N1 was evaporated to remove 600.03 g of water and 1276.8 g of H2O2 w = 0.30 added, it can be form 2950.8 g of mixture system M2 which can precipitate 604.01 g of CO(NH2)2·H2O2 and separate out 2346.6 g of mother solution R. When 330.22 g of Na2CO3, 385.5 g of CO(NH2)2 and 313.74 g of mixture N3 were added into the solution R, the mixture M3 can be formed and precipitate 488.77 g of Na2CO3·1.5H2O2. After separation Na2CO3·1.5H2O2 from M3, 2881.4 g of the resudal mother
Figure 3. XRD patterns of the equilibrium solids corresponding invariant points Q.
added into solution M, the composition of mixture will be on the line of MC. With the increase of Na2CO3 addition, the mixture composition spot in dry salt phase diagram will move along MC from M to C. When mixture system was supersaturated solution and its composition spot located in the range of m1 to m2 in line MC, Na2CO3·1.5H2O2 will be crystallized from the mixture system. Spots m1 and m2 were the points of intersection of line MC with B1P1 and Q1G1, respectively. Comparing different spots in line m1m2 and applying the lever rule, it can be concluded that Na2CO3·1.5H2O2 production was maximum when the mixture composition spot was located in M1. The composition spot of corresponding residual mother solution is spot N after separating Na2CO3·1.5H2O2 from the mixture system. When solution N lost some water by evaporation and CO(NH2)2 and H2O2 were added to it, the mixture system composition spot M2 can be controlled in FQGUP region of crystal CO(NH2)2·H2O2 at 0 °C. Then CO(NH2)2·H2O2 will crystallize from the mixture M2, and the residual mother solution spot will be located in spot R. After separating CO(NH2)2·H2O2 from the mixture M2, the solution R can be cycled to produce Na2CO3·1.5H2O2. When Na2CO3 was added into solution R and the new mixture system spot was controlled in spot M3 which was the intersection of line CR with line AN, Na2CO3·1.5H2O2 will crystallize from the mixture M3, and the corresponding residual mother solution spot will be located in N. The solution N was continued to prepare CO(NH2)2·H2O2 according to the same way as the above analysis
Figure 4. Technological flowchart of Na2CO3·1.5H2O2 and CO(NH2)2·H2O2 production. 380
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Table 3. Phase Diagram Calculation Results of the Joint Production of Urea Peroxide and Sodium Percarbonatea changing process D+U→Up+M
M+C+U→M1 M1→N+A
N→N1+N2 N2−H2O→N3
N1−H2O+h→M2 M2→R+Up
E+N3+C+U→M3 M3→A +N
a
Na2CO3
H2O2
CO(NH2)2
H2O
amount
T
composition and weight
% wt
% wt
% wt
% wt
kg
°C
CO(NH2)2 H2O2 CO(NH2)2·H2O2 mother liquid M Na2CO3 added to M CO(NH2)2 added to M mixture solution M1 precipitated Na2CO3·1.5H2O2 mother solution N separate N into N1 and N2 mother solution N1 mother solution N2 N3 removed all of H2O from N2 mother solution N1 H2O evaporated from N1 H2O2 added to N1 mixture system M2 precipitated CO(NH2)2·H2O2 mother solution R N3 added to to R Na2CO3 added to R CO(NH2)2 added to R precipitated Na2CO3·1.5H2O2 mother solution N
0 0 0 0.00 100 0 11.78 67.52 4.58
0 30 36.17 8.73 0 0 4.630 32.48 1.03
100 0 63.83 17.78 0 100 44.62 0 50.38
0 70 0 73.49 0 0 38.97 0 44.01
1000 1811.5 1086.0 1725.5 383.32 1144.9 3253.6 372.26 2881.4
0
4.58 4.58 1.094 4.58 0 0 3.602 0 4.53 1.094 100 0 67.52 4.58
1.03 1.03 0.246 1.03 0 30 13.79 36.17 8.03 0.246 0 0 32.48 1.03
50.38 50.38 12.03 50.38 0 0 39.63 63.83 33.40 12.03 0 100 0 50.38
44.01 44.01 0 44.01 100 70 42.98 0 54.04 0 0 0 0 44.01
2321.0 560.37 313.74 2321.0 600.03 1276.8 2950.8 604.01 2346.6 313.74 330.22 385.59 488.77 2881. 4
25
0
25
A: Na2CO3·1.5H2O2; Up: CO(NH2)2·H2O2; U: CO(NH2)2; C10: Na2CO3·10H2O; D: H2O2 w = 0.30; C: Na2CO3.
solution N was formed and recycled to used again. Thereby, the next stable recycle production of CO(NH2)2·H2O2 and Na2CO3·1.5H2O2 can continue carrying out. The calculated output for the above process was shown in Table 3. According to the traditional method using urea and H2O2 (w = 0.30) as reactants, the composition of the mother solution M after urea peroxide production was H2O2 ω = 0.0873, CO(NH2)2 w = 0.1778. Because there is no a good method to deal with this solution so far, the utilization of hydrogen peroxide (H2O2, w = 0.30) was only w = 0.7228. However, the new manufacturing technique can significantly reduce the H2O2 content of the residual mother solution N. Even all H2O2 w = 0.0103 was decomposed in evaporation process of solution N; the utilization of hydrogen peroxide (H2O2, w = 0.30) was up to w = 0.9225.
■
The utilization of hydrogen peroxide (H2O2, w = 0.30) was up to w = 0.9225.
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Phone: +86 22 26564731. Funding
The financial support received from the National Natural Science Foundation of China (no. 20676025) and the National Natural Science Foundation of Hebei Province (no. B2008000033) is gratefully acknowledged. Notes
The authors declare no competing financial interest.
■
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4. CONCLUSION (1) The solubilities of the quaternary system Na2CO3− CO(NH2)2−H2O2−H2O at 0 °C and 25 °C were measured, and the corresponding dry salt phase diagrams were constructed. There are four solid phases crystalline zones of Na2CO3·10H2O, Na2CO3·1.5H2O2, CO(NH2)2, and CO(NH2)2·H2O2 and two invariant points in the phase diagram. (2) Based on the analysis and calculation of the phase diagram of the system Na2CO3−CO(NH2)2−H2O2− H2O at 0 °C and 25 °C, a new technology of joint production of CO(NH2)2·H2O2 and Na2CO3·1.5H2O2 was put forward, which can decrease the loss of H2O2 decomposition and raise the economic benefits of CO(NH2)2·H2O2 and Na2CO3·1.5H2O2 production. 381
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