Study on Reaction Mechanisms of Amine Absorbent and Aldehydes TOSHIBA Corporation, Corporate Research and Development Center Asato Kondo, Satoshi Saito, Hiroko Watando, Takashi Kuboki Regina, 8 th Sept. 2015 © 2015 Toshiba Corporation Outline • Introduction • Experimental Quantitative analysis of aldehydes Qualitative analysis of reaction products • Results and Discussions Reaction mechanism of amines and aldehydes • Primary amine • Secondary amines • Tertiary amines • Summary Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 2 Outline • Introduction • Experimental Quantitative analysis of aldehydes Qualitative analysis of reaction products • Results and Discussions Reaction mechanism of amines and aldehydes • Primary amine • Secondary amines • Tertiary amines • Summary Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 3 Background of this Study Process flow diagram for CO2 capture TREATED FLUE GAS PURIFIED CO2 CO2 absorbent: Amine aqueous solution ER BER PP Degradation RR products of amines TRIP ammonia, BSO SS organic acids, A aldehydes, etc. FLUE GAS Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 4 Background of this Study Amine degradation Less in absorbent NlNot easy to analyze Aldehyde oxidization Fig. Incr ease in concentration of or ganic Increase acid in absorbent during operation Organic Acid Ref. S. Saito, Energy Procedia, 51, 176( 2014 ) In this study, we describe specific reaction mechanisms of amines and aldehydes. Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 5 Research on the reactivity of amines and aldehydes Table Amines used in this study Amine Function Abbreviation Amine compound Primary amine MEA Monoethanol amine DEA Diethanol amine Secondary amines MAE Methy l aaoetaomino ethanol PZ Piperazine TEA Triethanol amine Tertiary amines DMAE Dimethyl amino ethanol MDEA Methyl diethanol amine acetaldehyde 0.2 g/L and 10 g/L acetaldehyde solution in amine aqueous solution was prepared. 50 g/L amine aqueous solution Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 6 Outline • Introduction • Experimental Quantitative analysis of aldehydes Qualitative analysis of reaction products • Results and Discussions Reaction mechanism of amines and aldehydes • Primary amine • Secondary amines • Tertiary amines • Summary Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 7 Quantitative analysis method for acetaldehyde derivatized by PFBOA Aldehydes were derivatized by O-(2,3,4,5,6-pentafluorobenzyl)- hydroxylamine (PFBOA), and the derivatives were extracted with n-hexane before determination byy/ GC/MS as aldoximes. Derivatization of acetaldehyde using PFBOA O O NH N 2 CH3 FF FF ＋ H3C O F F F F acetaldehyde F PFBOA F PFBOA-acetaldehyde PFBOA-acetaldehyde ＊PFBOA-acetaldehyde shows two peaks due to geometric isomer . Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 8 Recovery amount of aldehydes in MEA aqueous solution TblTable RtfldhdiMEARecovery amount of aldehyde in MEA Addition amount Reaction time *1of Derivatization Recovery of Sample of aldehyde amine and aldehyde pH acetaldehyde（％） Water 0.2 g/L - *2 100 10 min Weak-acid 106 10 min WkWeak-bibasic 60 0.2 g/L MEA 7 days Weak-acid 102 ((g/)50g/L) 7days7 days Weak-basic 68 10 min Weak-acid 95 10 g/L 3 days Weak-acid 54 *1 The time period between addition of aldehyde and analysis of recovery amount of aldehyde in amine aqueous solution. *2 WkWeak-acid-samples were Recovery amounts vary widely diluted with water and H SO , 2 4 → Analysis cannot be performed stably and weak-basic-samples →Investigation of reaction mechanisms were diluted with only water. is necessary for stable analysis Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 9 Recovery amount of aldehydes in MEA aqueous solution Fig. Recovery amount of aldehyde in MEA Addition of 0.2g/L acetaldehyde results in ・low recovery amount of aldehyde under basic condition. ・high recovery amount of aldehyde under acid condition. Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 10 Reaction mechanisms of primary amines and aldehydes Reactions of aldehydes and primary amines are reversible, and aldehydes are formed under acid condition, generally. 1 1 R R O OH -H2O N 1 NH R H2N R + R R R R R Aldehydes Hemiaminals Imines Low pH High pH (weak acid condition) (basic condition) Ref. Guangtong Wang, Langmuir., 30, 1531 (2014) ・Under acid condition → Aldehydes are separated from amines. ・Undbder basic con dition → Alde hy des an d amines form imines. All aldehydes which can be separated from amines are analyzed under acid condition. Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 11 Recovery amount of aldehydes in MEA aqueous solution Fig. RtfldhdiMEARecovery amount of aldehyde in MEA Addition of 10 g/L acetaldehyde and long reaction time results in ・low recovery amount of aldehyde even under acid condition. Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 12 Reaction mechanisms of primary amines and aldehydes 1 1 R R O OH -H2O N 1 NH R H2N R + R R R R R Aldehydes Hemiaminals Imines Low pH High pH (weak acidic condition) (basic condition) Ref. Guangtong Wang, Langmuir., 30, 1531 (2014) ・Under acidic condition ・Large amount of aldehyde Low recovery amount of aldehyde ・Long reaction time → Reaction of amine and aldehyde is different from the above scheme. → Investigation of reaction products Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 13 Outline • Introduction • Experimental Quantitative analysis of aldehydes Qualitative analysis of reaction products • Results and Discussions Reaction mechanism of amines and aldehydes • Primary amine • Secondary amines • Tertiary amines • Summary Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 14 Compounds produced from amines and aldehyde In order to iiinvestigate the prodfducts from am ines an d acetaldehyde, we added acetaldehyde to 50 g/L amine aqueous solution and 1 g/L or 10 g/L acetaldehyde solution was prepared. They were analyzed by LC/MS and GC/MS. acetaldehyde To investigate ionic compounds LC/MS analysis 10 g/L 0〜4days later 50 g/L amine aqueous solution 4days later 1 g/L GC/MS analysis To investigate volatile compounds Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 15 Outline • Introduction • Experimental Quantitative analysis of aldehydes Qualitative analysis of reaction products • Results and Discussions Reaction mechanism of amines and aldehydes • Primary amine • Secondary amines • Tertiary amines • Summary Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 16 LC/MS analysis of MEA reacted with acetaldehyde Four days a fter a ddition o f ace ta lde hy de Mass spectrum of MEA containing acetaldehyde. m/z 114 m/z 132 m/z 140 m/z 88 MS signals of m//,,,z 88, 114, 132, 140 increased after addition of aldehyde. IiImine from MEA:m/88/z 88 OH H3C N Chromatogram of LC/MS Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 17 Reaction mechanisms of MEA and acetaldehyde O CH3 OH ーH2O OH OH OH H C N H2N H3C NH 3 Mass number 87 （m/z 88） Under basic condition Imine Fig. m/z 88 Chromatogram of LC/MS Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 18 Reaction mechanisms of MEA and acetaldehyde O CH3 OH ーH2O OH OH OH H C N H2N H3C NH 3 Mass nu mbe r 87 （m/z 88） Under basic condition Imine OH H2C NH Mass number 87 （m/z 88） enamine Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 19 Reaction mechanisms of MEA and two acetaldehydes O CH3 OH ーH2O OH OH OH H C NH H2N H3C NH 2 Mass number 87 （m/88/z 88） enamine OH O CH + OH + OH 3 ＋ H2C N H2C NH ーH2O H2C NH ーH OH H2C H3C H2C Mass number 113 Mass number 114 （m/z 114） （m/z 114） Enamines can react withhh another aldehyde. The m/z 114 compound is the dienamine that MEA combined with two acetaldehydes. Fig. m/z 114 Chromatogram of LC/MS Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 20 Reaction mechanisms of MEA and three acetaldehydes If another acetaldehyde reacts with MEA combined with two acetaldehydes, the m/z 140 compound is formed. H3C OH CH2 OH O CH H2C N 3 ーH2O OH + OH + H C H2C N 2 N H2C H C Mass number 114 H2C 2 Mass number 140 （m/z 114） （m/z 140） When the addition amount of aldehyde is large, quaternary ammonium（m/z 140 ;in the case of MEA） is formed. Fig. m/z 140 Chromatogram of LC/MS Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 21 Recovery amount of aldehydes in MEA aqueous solution Fig. Recovery amount of aldehyde in MEA Addition amoun t o f Addit ion amount o f aldehyde is small aldehyde is large enamine Quaternary ammonium （Secondary or tertiary amine) RibltiReversible reaction Irr ev er sible r eaction Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 22 Outline • Introduction • Experimental Quantitative analysis of aldehydes Qualitative analysis of reaction products • Results and Discussions Reaction mechanism of amines and aldehydes • Primary amine • Secondary amines • Tertiary amines • Summary Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 23 Recovery amount of aldehyde in DEA aqueous solution Table Recovery amount of aldehyde in DEA Addition amount Reaction time Derivatization Recovery of Sample of aldehyde (amine and aldehyde) pH acetaldehyde（％） Water 0.2g/L - 100 10 min Weak-acid 100 DEA 10 min Weak-basic 50 0.2g/L (50g/L) 7 days Weak-acid 63 7 days Weak-basic 32 When the reaction time was long, the recovery amount of aldehyde was low in the case of DEA.