Study on Reaction Y Mechanisms of Amine Absorbent and Aldehydes

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

• 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

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

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 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

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.

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.

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.

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 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 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 H 3C N Chromatogram of LC/MS

O CH3 OH ーH2O OH OH OH H C N H 2N H3C NH 3 Mass number 87 （m/z 88） Under basic condition Imine

Fig. m/z 88 Chromatogram of LC/MS

O CH3 OH ーH2O OH OH OH H C N H 2N H3C NH 3 Mass nu mbe r 8 7 （m/z 88） Under basic condition Imine

OH H 2C NH Mass number 87 （m/z 88） enamine

O CH3 OH ーH2O OH OH OH H C NH H 2N 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

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

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 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.

Fig. Recovery amount of aldehyde in DEA

Quaternary ammonium Mass spectrum of DEA containing acetaldehyde. from DEA:m/z 158 H C 2 m/z 158 + N HO OH m/z 132

H2C

Chromatogram of LC/MS The quaternary ammonium ion (m/z 158) were detected. The tertiary amine (m/z 132) was also detected, but the amount was smaller than m/z 158.

Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 25 Recovery amount of aldehyde in DEA aqueous solution TblTable RfldhdiDEARecovery amount of aldehyde in DEA Addition amount Reaction time Derivatization Recovery of Sample of aldehyde (amine and aldehyde) pH acetaldehyde（％） DEA 7 days Weak-acid 63 0.2g/L (50g/L) 7 days Weak-basic 32

H3C OH H2C O CH3 NH ーH2O HO OH N N HO OH HO OH

O CH3 Mass number 131 （m/z 132） H C 2 H2C

+ + N N Quaternary HO OH HO OH H C OH ammonium 3 H2C Mass number 158（m/z 158） Since the quaternary ammonium was preferably formed, the recovery amountft of alde hy de was low.

amine amount 50g/L, Addition amount of aldehyde 0.2g/L Fig. Recovery amount of aldehyde in secondary amines

The recovery amount of aldehyde was low in the case of the other secondary amines.

amine amount 50g/L, Addition amount of aldehyde 0.2g/L Fig Recovery amount of aldehyde in tertiary amines

The recovery amount of aldehyde was also low in the case of tertiary amines.

Since tertiary amines reacted with aldehyde are unstable, the reverse reaction is considered superior.

2 + 3 3 R O ＋H 2 R 2 R R -H O R + + OH 2 + 1 N 3 4 N N R R R + 1 1 5 -H R R 5 R 5 R R4 R R4

m/z 164

Though Aldehyde recovery was low. → Investigation of MDEA reaction products

After addition of acetaldehyde, m/z 146 increased. m/z 146 ＝quaternary ammonium from MDEA

→ Even tertiary amines might react with acetaldehydes and quaternary ammonium mighbht be forme d.

CH3 CH3 + CH3 N -H O + HO 2 N OH HO N OH O CH3 HO OH+ H3C OH H2C m/z 146

Primary amines +aldehyde -aldehyde

secondary amines +aldehyde -aldehyde

tertiary amines

+aldehyde -aldehyde

Quaternary ammonium

Formation of quaternary ammonium is irreversible reaction.

Since amine absorbent pH is basic, aldehyde reaction with amine proceed, and form imine and enamine. O 1 H2N R + Imines, enamines・・・ R R Aldehydes

LHLow pH Hig h p H (weak acidic condition) (basic condition)

Analysis of aldehyde amount in absorbent ・Stored in acid condition ・Quick analysis(before reaction progress)

◆In this study, the uncommon reactions between acetaldehyde and amine absorbents were described.

・Amine solution containing acetaldehyde results in enamines and imines.

・All amines, which are primary, secondary, or tertiary, could form quaternary ammonium with acetaldehyde.

◆Quantitative analysis of aldehydes in amine absorbent requires care because aldehydes react with amines.

LC/MS analysis of MEA reacted with acetaldehyde (1g/L）

OH H 3C N

imine CH2

+ OH H C Quaternary 2 N

ammonium H2C

OH H2C N When addition amount of H2C Dienamine alde hy de was 1g /L, MEA (tertiary amine) formed imine and dienamine but quaternary ammonium in one day.

TOSHIBA Corporation engages in CCS/CCU technology deployment.

CCU demonstration plant in

SAGA, JAPAN（10〜20kg/d-CO2） CCS demonstration plant in

FUKUOKA, JAPAN（10 t/d-CO2） *Photo from TOSHIBA website http://www.toshiba.co.jp/thermalhydro/en/thermal/products/ccs/ccs.htm

flfor example; MEA Quaternary ammonium ion OH H N 2 CH2 To other 2-hydroxy- compounds + OH H C N ethyl + three acetaldehydes 2

H2C CH2 Double bond Substituent group H C N ・Polymerization? ・transferring 2 →foaming? H2C ・Oxidation? Reference Y. H a y a s h i , J. Jpn. Oil. Chem. Soc. ,Vol.36, No.6, 409(1987)

HO CH3 CH3 The Ethanol group is selectively eliminated + X- KOH O N N + from dihydroxyethyl ammonium salt under R OH 120℃ R OH basic condition. There is ppyqyossibility that quaternary ammonium from amines and aldehydes forms many deteriorating products.

Addition amount Reaction time Derivatization Recovery of Sample of aldehyde (amine and aldehyde) pH acetaldehyde（％） Water 0.2g/L - 100 10 min Weak-acid 95 MEA 10 min Weak-basic 98 (50g/L) 4 days Weak-acid 97 4 days Weak-basic 101 020.2g /L 10 min Weak-acid 94 DEA 10 min Weak-basic 101 (50g/L) 4 days Weak-acid 105 4 days Weak-basic 105

Recovery amount of formaldehyde is 100% in any cases

MEA and formaldehyde

Secondary amine and formaldehyde

Reversible reaction

Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 41 Aldehyde recovery in secondary amine aqueous solution Table Recovery amount of aldehyde in secondary amines 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 (50g/L) 7 days Weak-acid 63 7 daysWeak-basic32 10 min Weak-acid 104 0.2g/L PZ 10 min Weak-basic 86 (50g /L) 7 days Weak-acid 45 7 days Weak-basic 33 MAE 10 min Weak-acid 98 (50g/L) 10 min Weak-basic 47

Study on reaction mechanisms of amine absorbent and aldehydes © 2015 Toshiba Corporation 42 Aldehyde recovery in tertiary amine aqueous solution Table Recovery amount of aldehyde in tertiary amines Addition amount Reaction time Derivatization Recovery of Sample of aldehyde (amine and aldehyde) pH acetaldehyde（％） Water 0.2g/L - 100 10 min Weak-acid 101 TEA 10 min Weak-basic 52 (50g/L) 7 days Weak-acid 60 7 daysWeak-basic39 DMAE 10 min Weak-acid 95 0.2g/L (50g/L) 10 min Weak-basic 47 10 min Weak-acid 101 MDEA 10 min Weak-basic 43 (50g/L) 7days7 days Weak-acid 47 7 days Weak-basic 20