1 PCC3 CONFERENCE The role of bicarbonate(hco 3- ) in the VLE of DEAB and blended MEA-DEAB systems under room and regeneration temperatures, an NMR study. Huancong Shi, 1, 2 Raphael Idem, 1 * Abdulaziz Naami Paitoon Tontiwachwuthikul 1 1. Clean Energy Technology Institution, Faculty of Engineering, University of Regina, Regina SK, Canada * Corresponding Author: Raphael. Idem; Tel 1-306-585-4470 Fax: 1-306- 585-4855 E-mail address: raphael.idem@uregina.ca 2. Department of Environmental Science and Engineering, University of Shanghai for Science and Technology, Shanghai, China 200093
2 Outline of the presentation Background and introductions Research Target: Bicarbonate vs Carbamate Background: Solvent Chemistry Background: VLE models Introduction: Role of bicarbonate under different conditions Experiments and materials Results and discussions NMR spectra and calibration curves of amine-co 2 -H 2 O solutions VLE of various amine-co 2 -H 2 O solutions from 24-90 degree Role of bicarbonate under these plots, and shift trend. Summary and Conclusions Acknowledgment e
3 Background and introductions Research target: bicarbonate vs carbamate The research Target, Carbamate (RNH-COO - ) and bicarbonate (HCO 3- ) anions, are the major format of CO 2 dissolved in the solutions. 1. MEA-CO 2 -H 2 O, the majority of [CO 2 ] 0 is carbamate (RNH-COO - ). 2. DEAB-CO 2 -H 2 O, the majority is bicarbonate (HCO 3- ). 3. Blended MEA-DEAB-CO 2 -H 2 O contains both carbamate and bicarbonateb at tdifferent ratios. 4. VLE plots from 13 C NMR analysis of single and blended amine solutions, both in 24 C and 70 C to detect trend of the ratio of (HCO 3- ) vs C-mate in (MEA-DEAB solutions) 5. Experimental data indicated the carbamate exchange reaction is endothermic. With increase of temperature, ratio of bicarbonate increased accordingly and that of carbamate decrease.
4 Background and introductions 1. Solvent Chemistry: Besides CO 2 solubility, solvent chemistry analyses contain three major sections due to different aspects of the solvent behavior: 1. the equilibrium i state t (reaction equilibrium i and vapor liquid id equilibrium) (Shi et al. 2012a); 2. the CO 2 absorption aspects (reaction kinetics),(sema et al. 2012) 3. the acidity/alkalinity of amines (PKa) analysis.(rayer et al. 2012) 2. Vapor-Liquid-Equilibrium (VLE) model analysis of amine solution 1. The database from VLE models can reveal many secrets of CO 2 absorption at room and CO 2 desorption at higher temperature. 2. Most previous researches have been focused on single amine solutions. MEA, DEA, MDEA, TEA, PZ, and AMP 3. Until recently, we have managed to investigate blended amine solutions with novel 13 C NMR analysis successfully.
5 Background and introductions 2. (continue) The VLE models tests: 13 C NMR analyses of various amine-co 2 -H 2 O systems: Objective: single amine MEA-CO 2 -H 2 O, DEAB-CO 2 -H 2 O, blended amine (MEA-DEAB-CO 2 -H 2 O) Operation conditions: room temperature (absorption), regeneration temperature (regeneration) 3. The role of HCO 3- in the ion speciation plots detected under different amine solutions and different temperatures 1. The role of bicarbonate was very important for the amine regeneration and CO 2 desorption. 2. Carbamate and bicarbonate can convert to each other based on certain conditions, (acid / base, endothermic / exothermic). RNH-COO - +HO - 2 RNH 2 + HCO 3 (1) 3. For MEA-DEAB-CO 2 -H 2 O, The ratio of carbamate / bicarbonate was the research interest, which was determined by ratio of amines, CO 2 loadings, and operation temperatures, etc.
6 Experiments and Materials Chemicals and CO 2 loading tests Chemicals, MEA, HCl, CO 2, D 2 O are commercially available. DEAB was synthesised within our lab based on patent Determination of CO 2 loading (α) was performed based on titration with a Chittick apparatus according the Association of Official Analytical Chemists (AOAC) method. Experimental procedures: ph + NMR and NMR calibration methods The first is ph + NMR combination, which has been developed around 1998;[1] The second method was the recently developed one, which was invented and published since 2012;[2, 3] Reference 1. Holmes, P. E.; Naaz, M.; Poling, B. E. 1998, Ind. Eng. Chem. Res.,1998, 37, 3281 3287. 2. Shi, H.; Sema, T.; Naami, A.; Liang, Z.; Idem, R. O.; Tontiwachwuthikul, P.2012. Ind. Eng. Chem. Res. 2012, 51, 8608 8615. 3. Shi, H.; Naami, N.; Idem, R.; Tontiwachwuthikul, P. 2014a. Ind. Eng. Chem. Res. 2014, 53, 8577 8591
7 Template: VLE model and ion speciation plots Target: VLE models and ion speciation plots as a database. For absorption conditions 40 ºC 120 ºC For regeneration conditions These plots above were performed with software simulation with E-NRTL model. (Liu et al. Ind. Eng. Chem. Res. 1999, 2080-2090) NMR Experimental testes can validate the simulative results and generate the accurate VLE plots.
8 Results: 13 C NMR spectra of DEAB 13 C NMR spectra of DEAB-H 2 O DEAB molecular structure (8 C atoms in a molecule) DEAB s typical 13 C spectra. (6 13 C peaks as symmetry) Fig 1a. 13 C NMR spectra of DEAB-H 2 O solutions
Results: 1D NMR spectra for MEA-DEAB-CO 2 - H 2 O blended amine system Complicated NMR spectra interpretation process 9 Carbamate Peak position (assignation). Area integration Fig 1b. 13 C NMR spectra of MEA-DEAB-CO 2 -H 2 O blended amine solutions
10 Results: 1D NMR for MEA-CO 2 -H 2 O Ion speciation plots of solution systems at 24ºC, with conventional ph + NMR method. Fig 2a. Amine speciation plots against the CO 2 / MEA for 5M MEA solution (Fan et al. Ind. Eng. Chem. Res. (2009), 2717-2720 in our research group)
Results: The calibration curves NMR calibration curves and method This method is independent, the ph meter is no longer necessary. 11
12 Results: The calibration plots for MEA and DEAB MEA C2 at 40-70 C DEAB C1, C3 at 40 70 C
13 Results: 1D NMR for DEAB-CO 2 -H 2 O Ion speciation plots of solution systems at 24ºC: with both methods together NMR calibration curve smooth. Fig 2b. Ion speciation (mole fraction) plot of the DEAB CO 2 H 2 O system at 24.5 C and an initial DEAB concentration of 1.50 M
Results: 1D NMR for MEA-DEAB-CO 2 -H 2 O blended amine system at 24ºC Ion speciation plots with NMR calibration 14 Fig. 3a. Ion speciation plot of MEA-DEAB-CO 2 -H 2 O (5M MEA / 1.25M DEAB) at 24
Results: 1D NMR for MEA-DEAB-CO 2 -H 2 O blended amine system at 40ºC Ion speciation plots with NMR calibration 15 Fig. 3b. Ion speciation plot of MEA-DEAB-CO 2 -H 2 O (5M MEA / 1.25M DEAB) at 40
Results: 1D NMR for MEA-DEAB-CO 2 -H 2 O blended amine system at 60ºC Ion speciation plots with NMR calibration 16 Fig. 3c. Ion speciation plot of MEA-DEAB-CO 2 -H 2 O (5M MEA / 1.25M DEAB) at 60
Results: 1D NMR for MEA-DEAB-CO 2 -H 2 O blended amine system at 70ºC Ion speciation plots with NMR calibration 17 Fig. 3d. Ion speciation plot of MEA-DEAB-CO 2 -H 2 O (5M MEA / 1.25M DEAB) at 70 C
Results: 1D NMR for MEA-DEAB-CO 2 -H 2 O blended amine system at 90ºC Hard to generate VLE plots experimentally at 90ºC The NMR instruments for our tests can reach up to 70 ºC. Besides 24 and 70 ºC, we also tested 40, 50 and 60 ºC. We input all the data into some tables and extrapolate the experimental results from 24-70 ºC toward 90 ºC. Finally, the ion speciation plot was generated at 90ºC The detailed operation method were provided in the reference file. The ion concentration of carbamate and bicarbonate will shift along with the increase of T. 18 Reference Shi, H.; Naami, N.; Idem, R.; Tontiwachwuthikul, P. 2014a. Ind. Eng. Chem. Res. 2014, 53, 8577 8591
Results. 1D NMR for MEA-DEAB-CO 2 -H 2 O blended amine system at 90 ºC Ion speciation plot at 90 ºC: extrapolate aefrom data a24-70 ºC 19 Fig 4. Predicted Ion speciation plot of MEA-DEAB-CO 2 -H 2 O (5.0 M + 1.25 M ±0.025 M) under 90ºC
Results: [HCO 3- ] in under various T and CO 2 loading Minimum CO 2 loading with detectable amount of HCO 3 and maximum concentration of HCO 3 20 Fig. 5. Minimum CO 2 loading with detectable amount of HCO 3 and maximum concentration of HCO 3 in MEA DEAB CO 2 H 2 O solutions (5 M/1.25 M ± 0.025 M) under 24 90 C.
21 Summary and dconclusions - 1 The role of bicarbonate within three different amine-co 2 concentrations. 1. Bicarbonate was negligible in MEA-CO 2 -H 2 O systems. 2. It is one of the major component in DEAB-CO 2 -H 2 O systems with max ratio of HCO 3- /Amine ~ 0.80. 3. The blended MEA-DEAB-CO 2 -H 2 O systems, the HCO 3- is co-exist with carbamate as the dissolved format of [CO 2 ]. HCO 3- consists 7-30% of total [CO 2 ] 0 within the amine concentration (MEA 5M, DEAB 0.5-1.5M). Effect of temperature, heat input and CO 2 loading. 1. With increase of operation temperatures, ion concentration of bicarbonate increase, and that of carbamate decrease. 2. The carbonate exchange reaction is endothermic. 3. With increased CO 2 loading(acidity), bicarbonate increase, carbamate increase and decrease after reached apex.
22 Summary and Conclusions - 2 Role of bicarbonate with in various amine-co 2 -H 2 O: 1. The ion concentration of [HCO 3- ] is constrained by reaction equilibrium and Vapor-liquid-quilibrium, the 3 most important factors are: CO 2 loading α, operating temperature t T, and ratio of tertiary ti amine vs primary amine β. [HCO 3 ] = f(α, T, β, Ki etc.) 2. The ion speciation plots of MEA-DEAB solutions (5M/1.25M) were generated under 6 different temperatures (24-90 C), we plot several typical figures. From these plots, the trend of bicarbonates under temperature swing were clearly demonstrated. 3. From 24 to 90 C, the max concentration of bicarbonate increase from 0.653 to 1.021 mol/l, and the minimum CO 2 loading where HCO - 3 started to be detectable decrease from 0.41 to 0.25 mol/mol. 4. Both trends are beneficial for amine regeneration and CO 2 desorption process. The next step is to increase concentration of bicarbonate under equilibrium solution conditions by means of solvent improvement.
23 Acknowledgement The U of Regina for the experimental e apparatusatus The Clean Energy Technology and Research Institute (CETRI) for the research work. The NSERC research fund to support the research. I(Dr Shi) am an Assistant Professor in Department of Envrionmental I(Dr. Shi) am an Assistant Professor in Department of Envrionmental Science, University of Shanghai Science and Technology. (USST)