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Home , Ammonium bicarbonate, Ammonium carbamate, Ammonium carbonate

A Study on Physical Chemistry of Solid A mmonium Materials for NOx Reduction of Diesel Engine Emissions

Cheon Seog (Steve) Yoon and Jong Kook Shin Hannam University, Daejeon, KOREA

Hoyeol Lee and Hongsuk Kim Korea Institute of Machinery & Materials, Daejeon, KOREA

2014 DOE CLEERS Workshop University of Michigan, Dearborn, MI, USA

1 Table of Contents

• Introduction of Solid SCR System • Salts • Chemical Reactions, Decomposition Chemistry • Chemical Kinetic Parameters by TGA, DTA and DSC • Decomposition Rate from Hot Plate Test and Chemical Kinetic Parameters • Simple Reactor with Visible Window • Equilibrium Vapor Pressure Curve for Ammonium • Acquisition of Re-solidified Materials from • Analytical Study of Re-solidified Materials from Ammonium Carbonate by XRD, FT-IR, and EA • Concluding Remarks • Acknowledgement • Reference

2 Solid SCR System

• NOx purification technology by using NH3, which is generated from solid ammonium.

• Ammonium carbonate, (NH4)2CO3 , is solid at room temperature, and it

decomposes into NH3, H2O & CO2 above temperature of 60℃.

3 Material Properties of Ammonium Salts

Solid Ammonium carbonate Ammonium cabarmate

Molecular formula (NH2)2CO (NH4)2CO3 NH2COONH4 Molecular weight 60.07 96.09 78.07 Density, g/cm3 1.33 1.5 1.6

Mols NH3 per Mol 2 2 2

Mols NH3 per kg 33.3 20.8 25.6 Decomposition temp., ℃ 140 58 60

NH2CONH2↔ NH3+HNCO Reaction mechanism (NH4)2CO3↔2NH3+CO2+H2O NH4COONH2 ↔ 2NH3 + CO2 HNCO +H2O ↔ NH3 + CO2

Cost cheap cheap moderate

* HNCO: Isocyanic

[ref] G. Fulks, G. B. Fisher, K. Rahmoeller, M. Wu, and E. D’Herde, SAE 2009-01-0907

4 Solid Based SCR

Companyny Decomposition Temperature (C ) Solid Urea Pierburg 140 FEV + Tenneco 60 Metal Amine* Amminex 32~35 (* Ammine Chloride, Strontium Ammine Chloride)

5 Advantage (Compared with Liquid Urea SCR)

• ~3 times of ammonia storage capacity

• Improvement of low temperature NOx conversion performance due to direct am monia gas injection

• Enhancement of the reactants mixing characteristics with exhaust gas

6 Chemical Reactions of Solid Urea

• Thermal decomposition(pyrolysis) of urea : 19 reactions

298K (NH2)2CO (s) → NH3 (g) + HNCO (g) for dry urea (140℃~), ΔH = 186 kJ

(NH2)2CO (s) + H2O (g) → 2NH3 (g) + CO2 (g) for the presence of

(NH2)2CO (s) + HNCO (g) → H2N-CO-NH-CO-NH2 (152 ℃ )

H2N-CO-NH-CO-NH2 (g) + HNCO (g) → (HNCO)3 (g) + NH3 (g) (175 ℃)

H2N-CO-NH-CO-NH2 (g) + HNCO (g) → C3H4N4O2(g) + H2O (g) (175 ℃)

HNCO (g) + NH3 (g) → H2O (g) + H2NCN (g) (175 ℃)

• Hydrolysis of isocyanic acid

298K HNCO (g) + H2O (g) → NH3 (g) + CO2 (g) , ΔH = -96 kJ - Isocyanic acid is very stable in the gas phase, but hydrolyzes easily on many solid oxides wit h water vapor originating from the combustion process.

[ref] P.M. Schaber, et al., Thermochimica Acta, Vo. 424, pp 131-142, 2004

7 • Slow heating for solid urea

- biuret(H2N-CO-NH-CO-NH2), triuret(H2N-CO-NH-CO-NH-CO-NH2 ), ammonium isocyanate

• Fast heating for solid urea : NH3, HNCO

Urea Sublimation (NH2) CO 2 Pyrolysis : + ν Pyrolysis : + ν Hydrolysis : + H2O

Ammonia Cyanuric Acid Isocyanic Acid NH 3 (HNCO)3 HNCO Hydrolysis : + H2O Pyrolysis : + ν

[ref] M. Kobel and E.O. Strutz, Ind. Eng. Chem, Res. Vol. 42, No. 10. pp 2093-2100, 2003

8 Decomposition Chemistry of and Ammonium Carbonate (1/2)

• Ammonium carbamate [NH4COONH2], ammonium carbonate [(NH4)2CO3 ]

NH4COONH2 (s) ↔ 2NH3 (g) + CO2 (g)

(NH4)2CO3 (s) ↔ 2NH3 (g) + CO2 (g) + H2O (g)

• Ammonium carbamate [NH4COONH2] : 2 steps, (unstable in termediate, HCOONH2 )

NH4COONH2 (s) ↔ NH3 (g) + HCOONH2 (g)

HCOONH2 (g) ↔ NH3 (g) + CO2 (g)

• Ammonium carbonate [(NH4)2CO3 ] : 2 steps, ammonium (sta ble intermediate, (NH4)HCO3 )

(NH4)2CO3 (s) ↔ NH3 (g) + (NH4)HCO3 (g)

[ref] J. E. (NH House,4 )HCOJr., “A TG3 study(g) ↔of the NH kinetics3 (g) of decomposition+ CO2 (g) of + ammonium H2O (g) carbonate and , ” Thermochimica Acta, 40, 225-233, 1980

9 Decomposition Chemistry of Ammonium Carbamate and Ammonium Carbonate (2/2)

• Commercially available ammonium carbonate : ammonium carbamate + a

mmonium bicarbonate [(NH4)2CO3 ]

heating • Ammonium carbamate urea (NH2CONH2) is byproduct

NH4COONH2 (s) ↔ NH2CONH2 (g) + H2O (g)

• @ high temperature, urea isocyanic acid [HNCO], NH3

NH2CONH2 ↔ NH3 (g) + HNCO (g)

HNCO + H2O ↔ NH3 (g) + CO2 (g)

• Cycles of heating and cooling processes during the vehicle operation mixt ure of ammonium carbamate, ammonium carbonate, ammonium bicarbonat e, and urea are existed.

[ref] C. B. Sclar and L. C. Carrisonm “Phase composition of commercial ammonium carbonate,” Science, Vol. 14, pp. 1205-1207, 1963 [ref] B. R. Rahachandran, A. M. Halpern, and E. D. Glendening, “Kinetics and mechanism of the reversible dissociation of ammonium carbamate: involvement of carbamic acid,” J. Phys. Chem. A, 102, 3934-3941, 1998 10 Decomposition Characteristics of Solid Urea (1/2)

By-product substance formed from heating and cooling process of solid urea • Biuret and isocyanic acid can be formed in the process of thermal decomposition. • It decomposes to ammonia at high temperatures of 200 ∼ 300℃. • It is one of limitations for the practical use of solid urea.

[ref] H. Kim, C. S. Yoon, J. Lee, and H. Lee, SAE 2014-01-1535

11 Decomposition Characteristics of Solid Urea (2/2)

Dosing valve clogging when abnormal temperature control of the solid urea system

• Heating up the dosing module with high temperatures to prevent clogging is another difficulty for solid urea system.

[ref] H. Kim, C. S. Yoon, J. Lee, and H. Lee, SAE 2014-01-1535

12 Hot Plate Experiment (Device)

plate supporter

plate

heater

13 Chemical Kinetic Parameters and Decomposition Rate of Solid Urea

- Chemical kinetic parameters(activation energy and frequency factor) of solid urea (TGA Q500 used) 4 step reactions

Activation Energy(E) Frequency factor(A) Step kJ/mol s-1

Step 1-1 64.26 2.2.E+04

Step 1-2 40.85 2.3.E+01

Step 2 65.64 1.5.E+03 < TGA graph for solid ure > Step 3 128.14 1.3.E+08

- Decomposition rate of solid urea in hot plate experiment

Temperature Decomposition rate

℃ %/min

173 0.53

198 12.23

230 16.88

240 20.39

255 29.15 < Comparison of decomposition rate for solid urea in 273 35.06 hot plate experiment and TGA analysis >

14 Chemical Kinetic Parameters and Decomposition Rate of Ammonium Carbonate

- Chemical kinetic parameters(activation energy and frequency factor) of ammonium carbonate(TGA Q500 used)

1 STEP Range(α) 1 step reaction E(kJ/mole) A(s-1)

α = 0.04 - 0.5 62.22±5.76 4.23.E+06

α = 0.04 - 0.8 53.40±5.67 1.75.E+05

α= (mo-mt)/mo < TGA graph for ammonium carbonate > - Decomposition rate of ammonium carbonate in hot plate experiment

Temperature(℃) %/min

75 15.83

85 19.13

95 28.43

105 33.62

115 36 < Comparison of decomposition rate for ammonium carbonate > 15 Chemical Kinetic Parameters and Decomposition Rate of Ammonium Carbamate

- Chemical kinetic parameters(activation energy and frequency factor) of ammonium carbamate(TGA Q500 used)

1 STEP Range(α) 1 step reaction E(kJ/mole) A(s-1)

α = 0.04 - 0.5 57.22±4.10 1.48E+06

α = 0.04 - 0.8 49.41±3.77 7.84E+04

< TGA graph for ammonium carbamate > α= (mo-mt)/mo

- Decomposition rate of ammonium carbamate in hot plate experiment

Temperature(℃) %/min

64 5.68

74 9.01

84 15.46

90 21.8

97 27.14 < Comparison of decomposition rate for ammonium 110 47.65 carbamate >

16 Calculations of Chemical Kinetic Parameters for DSC Results of Ammonium Carbonate

• By Kissinger method

Tm Kissinger method

Activation energy(E) Frequency factor(A) Ammonia kJ/mol s-1 Ammonium carbonate 75.49 6.254 × 107

17 Calculations of Chemical Kinetic Parameters for DSC Results of Ammonium Carbamate

• By Kissinger method

T m Kissinger method

Activation energy(E) Frequency factor(A) Ammonia salt kJ/mol s-1 Ammonium carbamate 67.96 1.159 × 108

18 Comparison of Activation Energy

• Validation

Activation energy(E)(kJ/mol)

Paper DSC TGA-a TGA-b

Ammonium carbonate 86.73±6.02 1) 75.49 62.22±5.76 53.40±5.67

Ammonium carbamate 53.59 2) 69.96 57.22±4.10 49.41±3.77

* a(α = 0.04~0.5), b(α = 0.04 ~ 0.8) α= (mo-mt)/mo

Activation energy(E) : Ammonium carbonate > Ammonium carbamate

1) J. E. House, Jr., “A TG study of the kinetics of decomposition of ammonium carbonate and ammonium bicarbonate, ” Thermochimica Acta, 40, 225-233, 1980

2) B. R. Rahachandran, A. M. Halpern, and E. D. Glendening, “Kinetics and mechanism of the reversible dissociation of ammonium carbamate: involvement of carbamic acid,” J. Phys. Chem. A, 102, 3934-3941. 1998

19 Equilibrium Vapor Pressure of Ammonium Carb onate

Pressure sensor

Pressure vessel Heater controller

Heater

Minimum temperature is required for reactor and dosing device

20 Simple Reactor with Visible Window

T/C Pressure Sensor

Heater

Visible window Heater controller < Test conditions for reactor temperature and pressure with ac-1 >

ac-1

Closed vessel Visible window Resolidification materials around cooling pipe in the reactor

ac-2

< Test conditions for three cycles of heating and cooling with ac-2 > Closed vessel Inside of reactor after 12 hours

21 XRD Analysis of Re-solidified Materials from A mmonium Carbonate

• Sample (ac-1) : around the cooling pipe in the reactor • Sample (ac-2) : inside of the reactor after 3 times of heating & cooling cycles.

- XRD peak : 29.68˚, 23.9 ˚, 30.92 ˚, 24.45 ˚, 31.03 ˚, 36.43 ˚

< XRD spectra of ac-1, ac-2, ammonium carbonate, ammonium carbamate, and solid urea standards >

Re-solidified samples (ac-1 & ac-2) have similar patterns of XRD peak with pure ammonium carbonate.

22 XRD Summary Data of Re-solidified Materials f rom Ammonium Carbonate

Standard 2θ d Relative • XRD summary Data(wavelength 1.54056Å) (deg) (spacing-Å Intensity(%) ) Ammonium 29.6 3.01 100 carbonate[1] 23.4 3.74 49.7 34.4 2.6 42.8 Ammonium 29.68 3.002 100 • XRD Bragg’s Law bicarbonate 23.9 3.669 37.1 30.92 2.893 17.0 ac-1 29.76 2.995 100 23.87 3.674 69 26.22 3.365 54.1 ac-2 29.72 2.999 100 23.87 3.674 48.7 26.19 3.368 37.8 Ammonium 30.32 2.945 100 carbamate 32.37 2.777 15.82 19.53 4.447 11.41 Solid urea 22.26 3.924 100 [ref] 1. Analytical Chemistry. 2005, 77, 5947-5952 35.44 2.564 17.75 2. “Phase Composition of Commercial Ammonium Carbonate”, Science 14(1963), 1205-1207 36.96 2.474 9.43 23 FT-IR Analysis of Re-solidified Materials from Ammonium Carbonate

• Sample (ac-1) : around the cooling pipe in the reactor • Sample (ac-2) : inside of the reactor after 3 times of heating & cooling cycles.

1300 ~ 1600 cm-1 bands : CO group of carbonate

3033 cm-1 bands : group of ammonium ion

< FT-IR spectra of ac-1, ac-2, ammonium carbonate, ammonium carbamate, and solid urea standards >

Re-solidified samples (ac-1 & ac-2) have similar patterns of FT-IR spectra with pure ammonium carbonate.

24 EA(Elemental Analyzer) Analysis of Re-solidified Materials from Ammonium Carbonate EA summary data (detection limit 0.05%)

Sample Standard Element(%)

Nitrogen 25.34

Ammonium carbonate Carbon 15.39

Hydrogen 7.54

Nitrogen 34.98 Ammonium carbamate Carbon 14.80 �=​12.01/79.06 �+X=79.06(​12.01/96.09​2�/12.01 Y −​�/14.01 ) Hydrogen 8.18

Nitrogen 17.43 Ammonium N=​14.01/79.06 �+Y​28.02=96.09(/96.09​�/14.01 Y −​�/12.01 ) Carbon 15.22 bicarbonate Hydrogen 6.88

Nitrogen 17.76 ac - 1 Carbon 15.50 • ac-1 is similar to ammonium bicarbonate. Hydrogen 6.66 • ac-2 is similar to mixture of ammonium Nitrogen 16.87

ac - 2 Carbon 13.29 carbonate and ammonium bicarbonate

Hydrogen 5.69

25 Concluding Remarks (1/2)

Basic research on reaction rate of solid urea, ammonium carbonate, and ammonium car bamate as ammonia sources for the application of solid SCR was performed

• Chemical kinetic parameters(activation energy and pre-exponential factor) are calcu lated by Arrhenius plot from TGA and DSC results using Kissinger method.

• From this study, activation energy of ammonium carbonate is larger than that of am monium carbamate.

• Decomposition rate from chemical kinetic parameters by TGA for solid urea, ammo nium carbonate, and ammonium carbamate, and that of hot plate experiment do not have discrepancies each other.

26 Concluding Remarks (2/2)

Analytical study of re-solidified materials from ammonium carbonate was carried out.

• Simple reactor which has heater control and temperature control of cooling water w ith visible window was designed and fabricated, pressures and temperatures are mea sured.

• Saturation pressure curve as function of temperature was obtained and governed for the design of reactor and dosing system.

• Re-solidified materials of ammonium carbonate from heating and cooling cycles are very similar to original materials of ammonium carbonate and ammonium bicarbon ate from analytical results by XRD, FT-IR, and EA.

27 Acknowledgments

• This research was supported by the Center for Environmentally Friendly V ehicle (CFEV) as a Global-Top Project of the Ministry of Environment, Ko rea (KMOE)

28 Reference

• G. Fulks, G. B. Fisher, K. Rahmoeller, M. Wu, and E. D’Herde, “A Review of Solid Materials as Alternative Ammonia Sources for Lean NOx Reduction with SCR,” SAE 2009-01-0907, 2 009. • C. B. Sclar and L. C. Carrison, “Phase Composition of Commercial Ammonium Carbonate,” Science, Vol. 14, pp. 1205-1207, 1963.

• H. Lee, C. S. Yoon, and H. Kim, “A Study on Reaction Rate of Solid SCR for NOx Reduction of Exhaust Emissions in Diesel Engine,” Transaction of KSAE, Vol. 21, No. 6, pp. 183-194, 2013. • J. K. Shin, H. Lee, C. S. Yoon, and H. Kim, “Analytical Study on Re-solidification Materials( Ammonium Carbonate Intermediates) for NOx Reduction of Exhaust Emissions in Diesel Eng ine with Solid SCR,” Transaction of KSAE, Vol. 22, No. 4, pp. 151-159, 2014. • H. Kim, C. S. Yoon, J. Lee, and H. Lee, “A Study on the Solid Ammonium SCR System for C ontrol of Diesel NOx Emissions,” SAE 2014-01-1535, 2014.

29 Thank you for your attention !

Cheon Seog Yoon ([email protected])

Professor, Ph.D. Department of Mechanical Engineering Hannam University Daejeon, KOREA

30 70 kW Off-Road Vehicle (Tractor)

◈ Specification of engine

Bore x Stroke(mm) 98 x 113 No. of Cylinder 4 Displacement(cc) 3,409 Comp. Ratio 18.5 Valve per cylinder 4(2 Intake, 2 Exhaust) Firing order 1-3-4-2 Combustion System Direct Injection Aspiration Turbocharged Max. Power 80PS @ 2500rpm Injection pressure 80 MPa

31 Re-solidification of Ammonium Carbonate

Visible window

Re-solidified material

Electric heater (a) Four different test conditions Pressure vessel Ammoium Carbonate A B C Schematic diagram of a simple reactor with a D visible window having a pipe (cooling water flow through the pipe)

(b) Photos of visual windows for different conditions ☞ Re-solidified materials were observed under the temperature of vapor pressure curve.

[ref] H. Kim, C. S. Yoon, J. Lee, and H. Lee, SAE 2014-01-1535

32