Development of an Analytical Method for Distinguishing Ammonium Bicarbonate from the Products of an Aqueous Ammonia CO 2 Scrubber Lingyu Meng, † Stuart Burris,* ,† Holt Bui, ‡ and Wei-Ping Pan* ,† Department of Chemistry, Western Kentucky University, 1 Big Red Way, Bowling Green, Kentucky 42101, and Brimrose Corp. of America, 19 Loveton Circle, Hunt Valley Loveton Center, Baltimore, Maryland 21152-9201 The link between anthropogenic emissions of carbon dioxide, increasing atmospheric CO 2 levels, and concomi- tantly increasing global temperatures is established and accepted. The use of aqueous ammonia, to capture CO 2 and produce an inexpensive nitrogen fertilizer, ammo- nium bicarbonate (ABC), is believed to be a feasible approach to CO 2 sequestration. Due to the varying con- centrations of reactants and varying reaction conditions, different ammonia-carbon compounds may be produced. ABC is the ideal product for maximizing NH 3 utilization in CO 2 capture; therefore, identification and quantification of ABC in the reaction products is mandatory. Various analytical techniques were used to distinguish and quan- tify the ABC. Fourier transform infrared spectroscopy can only be used to distinguish ammonium carbamate, and. X-ray diffraction can be used to qualitatively distinguish ABC from the other possible products of the CO 2 capture reaction. Carbon-hydrogen-nitrogen elemental analysis and near-infrared (NIR) spectroscopy were used to quan- tify ABC, with both techniques giving (5% agreement for ABC concentrations for 8 of 13 samples from a bench- scale aqueous ammonia CO 2 scrubbing system. An ad- ditional 3 of the 13 samples were within (12%. Results indicate that NIR will be an ideal tool for real-time, on- line measurements of ABC in a full-scale aqueous am- monia CO 2 scrubber. The ABC in 11 samples from the bench-scale scrubber at Western Kentucky University was determined by these techniques and assessed to have very good quality as a fertilizer in accordance with GB-3559- 92, the Agricultural Ammonium Bicarbonate National Standard of China. It has been known for more than 100 years that carbon dioxide is a greenhouse gas and that the release of CO 2 from fossil fuels may affect the climate of the earth. 1 The growing awareness of the risks of climate change has generated public concern, and since 1989, researchers have become more interested in seques- tering CO 2 . As the world population increases and energy demand rises, increased burning of fossil fuels will continue to drive atmospheric CO 2 levels upward. Herzog and co-workers noted that power production contributes one-third of the CO 2 released from fossil fuel combustion worldwide. 2 Generation of CO 2 through fossil fuel combustion will remain a substantial contributor to the total amount of atmospheric green house gases. Capturing and securely storing carbon emitted from the global energy system is an important and attainable goal. Several researchers have proposed and developed possible solutions such as chemical solvents, physical absorption, cryogenic methods, membrane systems, and biological fixation. 3-5 Of these, the chemical solvent methods are currently recognized as the most effective technolo- gies. The cost of capturing CO 2 can be reduced by finding a low- cost solvent that can minimize energy requirements, equipment size, and corrosion. An approach that may provide an inexpensive and effective route to reduce CO 2 emissions from power plants is extracting CO 2 with aqueous ammonia in a wet scrubber. 6 This technique presents many advantages for CO 2 capture over the monoethanolamine process due to its lower cost, higher CO 2 absorption efficiency and capacity, lower decomposition temper- atures of ammonium bicarbonate (ABC), and less corrosive environment for the absorber material. Bai and Yeh 7 used breakthrough curves to determine that the NH 3 scrubbing capacity was 0.35 mol of CO 2 /mol of NH 3 , or 0.9-1.2 kg of CO 2 /kg of NH 3 , with a removal efficiency of ∼99%. Smouse and co-workers 8 proposed and developed a multipollution control concept using aqueous ammonia sprayed into actual flue gas to capture CO 2 , SO 2 , and NO x emissions with a CO 2 capture efficiency in the range from 76.4 to 91.7% at 35 °C. Carbon dioxide can be removed from flue gases by ammonia scrubbing at various temperatures and operating conditions. Equation 1 illustrates ammonium carbamate (ACM; NH 2 COONH 4 ) * To whom correspondence should be addressed. E-mail: stuart.burris@ wku.edu; wei-ping.pan@wku.edu. † Western Kentucky University. ‡ Brimrose Corp. of America. (1) Arrhenius, S. London, Edinburgh, Dublin Philos. Mag. J. Sci., 5th Ser. 1896, 41, 237-277. (2) Herzog, H.; Eliasson, B.; Kaarstad, O. Sci. Am. 2000, 282(2), 72-79. (3) Wolsky, A. M.; Daniels, E. J.; Jody, B. J. Environ. Prog. 1994, 13, 214. (4) Nishikawa, N.; Hiroano, A.; Ikuta, Y.; Fukuda, Y.; Kaneko, M.; Kinoshita, T.; Ogushi, Y. Energy Convers. Manage 1995, 36, 681. (5) Kimura, N.; Omata, K.; Kiga, T.; Takano, S.; Shikisima, S. Energy Convers. Manage. 1995, 36, 805. (6) Yeh, J. T., Pennline, H. W.; Resnik, K. P. In Proceedings of the 19th Annual International Pittsburgh Coal Conference, Pittsburgh, PA, 2002. (7) Bai, H.; Yeh, A. C. Ind. Eng. Chem. Res. 1997, 36 (6), 2490-2493. (8) Smouse, S. M.; Ekmann, J. M.; Zhang, Y.; Li, Z.; Li, X.; Dong, J.; Wang, Y. In Proceedings of the Second Annual Conference on Carbon Sequestration, Alexandria, VA, 2003. Anal. Chem. 2005, 77, 5947-5952 10.1021/ac050422x CCC: $30.25 © 2005 American Chemical Society Analytical Chemistry, Vol. 77, No. 18, September 15, 2005 5947 Published on Web 08/20/2005