Study on Reaction Mechanisms of Amine Absorbent and ......Reaction mechanisms of primary amines and aldehydes Reactions of aldehydes and primary amines are reversible, and aldehydes

Study on Reaction yMechanisms of Amine Absorbent and AldehydesAbsorbent and AldehydesTOSHIBA Corporation,Corporate Research and Development Center

Asato Kondo, Satoshi Saito, Hiroko Watando, Takashi Kuboki

Regina 8th Sept 2015

© 2015 Toshiba Corporation

Regina, 8 Sept. 2015

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

© 2015 Toshiba Corporation 2Study on reaction mechanisms of amine absorbent and aldehydes

Outline




• Summary


Background of this Study

Process flow diagram for CO2 capture

PURIFIED CO2TREATED FLUE GAS

CO absorbent:

RBE

R

PER

CO2 absorbent:Amine aqueous solution

BS

OR

STR

IPP

Degradation products of aminesammonia A Sammonia, organic acids, aldehydes, etc.

FLUE GAS


Background of this Study

Amine

Less in absorbentN l

degradation

Not easy to analyze

Aldehyde

IncreaseFig Inc ease in concent ation of o ganicoxidization

IncreaseFig. Increase in concentration of organic acid in absorbent during operation Ref. S. Saito, Energy Procedia, 51, 176( 2014 )

Organic Acid

In this study, we describe specific reaction mechanisms of amines and aldehydes.


Research on the reactivity of amines and aldehydes

Amine Function Abbreviation Amine compoundPrimary amine MEA Monoethanol amine

Table Amines used in this study

Primary amine MEA Monoethanol amine

Secondary amines

DEA Diethanol amineMAE Methyl amino ethanolSecondary amines et y a o et a oPZ Piperazine

TEA Triethanol amine

Tertiary amines DMAE Dimethyl amino ethanolMDEA Methyl diethanol amine

0.2 g/L and 10 g/L acetaldehyde solution in amine aqueous solution

acetaldehyde

solution in amine aqueous solution was prepared.

50 g/L amine aqueous solution


Outline




• Summary


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 by GC/MS as aldoximes.

Derivatization of acetaldehyde using PFBOA

y /

F F

ONH2

CH3 OF F

ON CH3

＋F

F

F

C3 O

FF

F

PFBOA acetaldehydePFBOA acetaldehyde

＋

PFBOA-acetaldehyde PFBOA-acetaldehyde

＊PFBOA-acetaldehyde shows two peaks due to geometric isomer

© 2015 Toshiba Corporation 8

peaks due to geometric isomer.

Study on reaction mechanisms of amine absorbent and aldehydes

Recovery amount of aldehydes in MEA aqueous solutionT bl R t f ld h d i MEA

Sample Addition amount of aldehyde

Reaction time *1ofamine and aldehyde

DerivatizationpH

Recovery of acetaldehyde（％）

Table Recovery amount of aldehyde in MEA

Water 0.2 g/L - *2 10010 min Weak-acid 10610 i W k b i 60

MEA(50g/L)

0.2 g/L10 min Weak-basic 607 days Weak-acid 1027 days Weak-basic 68( g/ ) 7 days Weak basic 68

10 g/L10 min Weak-acid 953 days Weak-acid 54

*1 The time period between addition of aldehyde and analysis of recovery amount of aldehyde in amine aqueous solution.

*2 W k id l Recovery amounts vary widely→ Analysis cannot be performed stably→ Investigation of reaction mechanisms

*2 Weak-acid-samples were diluted with water and H2SO4, and weak-basic-samples were diluted with only water


gis necessary for stable analysis were diluted with only water.

Recovery amount of aldehydes in MEA aqueous solution

Addition of 0.2g/L acetaldehyde results in

Fig. Recovery amount of aldehyde in MEA

g/ y・low recovery amount of aldehyde under basic condition.・high recovery amount of aldehyde under acid condition.


Reaction mechanisms of primary amines and aldehydes

Reactions of aldehydes and primary amines are reversible, and aldehydes are formed under acid condition, generally.

O

+-H2O

NH R1 NH

OHR

1

NR

R1

R R+

IminesHemiaminals

NH2 R

RR

R

R

AldehydesLow pH

(weak acid condition)High pH

(basic condition)

Ref. Guangtong Wang, Langmuir., 30, 1531 (2014)

・Under acid condition → Aldehydes are separated from amines.d b d ld h d d f・Under basic condition → Aldehydes and amines form imines.

All aldehydes which can be separated from amines are


analyzed under acid condition.


Fig R t f ld h d i MEAFig. Recovery amount of aldehyde in MEA

Addition of 10 g/L acetaldehyde and long reaction time results inAddition of 10 g/L acetaldehyde and long reaction time results in・low recovery amount of aldehyde even under acid condition.


Reaction mechanisms of primary amines and aldehydes

O -H2OOHR

1

N

R1

R R+

H2O

IminesHemiaminals

NH2 R1 NH

RR

OH N

R

R

Aldehydes IminesHemiaminalsAldehydesLow pH

(weak acidic condition)High pH

(basic condition)Ref. Guangtong Wang, Langmuir., 30, 1531 (2014)

・Under acidic condition・Large amount of aldehyde Long eaction time

Low recovery amount of aldehyde・Long reaction time → Reaction of amine and aldehyde is different from the above scheme.→ Investigation of reaction products


Outline




• Summary


Compounds produced from amines and aldehydeI d i i h d f i dIn order to investigate the products from amines and 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 compoundsacetaldehydeLC/MS analysis

To investigate ionic compounds

10 g/L

0〜4days later

4days later50 g/L amine aqueous solution

/ GC/MS analysisTo investigate volatile compounds

1 g/L


Outline




• Summary


LC/MS analysis of MEA reacted with acetaldehydeF d ft dditi f t ld h dFour days after addition of acetaldehyde

Mass spectrum of MEA containing acetaldehyde.

m/z 88

m/z 114 m/z 132 m/z 140

MS signals of m/z 88, 114, 132, 140/ , , ,

increased after addition of aldehyde.

I i f MEA / 88OH

NCH3

Imine from MEA:m/z 88


Chromatogram of LC/MS

Reaction mechanisms of MEA and acetaldehydeO CH3 OH

OHNH2

O CH3

CH3OH

NH

OHーH2O

Mass number 87

OHNCH3

Mass number 87（m/z 88）

ImineUnder basic condition

Fig. m/z 88 Chromatogram of LC/MS


Reaction mechanisms of MEA and acetaldehydeO CH3 OH

OHNH2

O CH3

CH3OH

NH

OHーH2O OH

NCH3

Mass number 87ass u be 8（m/z 88）

ImineUnder basic condition

OHNHCH2

Mass number 87Mass number 87（m/z 88）

enamine


Reaction mechanisms of MEA and two acetaldehydesO CH3 OH

OHNH2

O CH3

CH3OH

NH

OHーH2O OH

NHCH2

Mass number 87（ / 88）

OH OHOHO CH

（m/z 88）enamine

OHNH

+CH2

CH3 OH

NCH2

CH2

OHNH

+CH2

CH2

O CH3 ーH2O ーH＋

Mass number 113 Mass number 114Mass number 113（m/z 114）

Mass number 114（m/z 114）

h hEnamines can react with another aldehyde.The m/z 114 compound is the dienamine that MEA combined with two acetaldehydes.



Reaction mechanisms of MEA and three acetaldehydes

If another acetaldehyde reacts with MEA combined with two acetaldehydes, the m/z 140 compound is formed.

OHNCH2 OH

N+CH

CH2

OH+CH

OHCH3

O CH3 ーH2O

CH2

NCH2

CH2

NCH2

CH2 Mass number 140Mass number 114（m/z 114）（m/z 140）（m/z 114）

When the addition amount of aldehyde is large, quaternary

（ammonium（m/z 140 ;in the case of MEA） is formed.




Fig. Recovery amount of aldehyde in MEAAdditi t f Addi i f

enamine Quaternary ammonium

Addition amount of aldehyde is small

Addition amount of aldehyde is large

enamine（Secondary or tertiary amine) Quaternary ammonium

I e e sible eactionR ibl ti


Irreversible reactionReversible reaction

Outline




• Summary


Recovery amount of aldehyde in DEA aqueous solutionTable Recovery amount of aldehyde in DEA


Reaction time(amine and aldehyde)

DerivatizationpH


Table Recovery amount of aldehyde in DEA

Water 0.2g/L - 100

DEA

10 min Weak-acid 10010 min Weak-basic 50DEA

(50g/L) 0.2g/L10 min Weak-basic 507 days Weak-acid 637 days Weak-basic 32

When the reaction time wasWhen the reaction time was long, the recovery amount of aldehyde was low in the case f DEAof DEA.


Fig. Recovery amount of aldehyde in DEA

LC/MS analysis of DEA reacted with acetaldehydeTh d ft dditi f t ld h d

Quaternary ammonium f DEA / 158

Mass spectrum of DEA containing acetaldehyde.

Three days after addition of acetaldehyde

m/z 158

from DEA:m/z 158

N+

CH2

m/z 132N

OHOH

CH2

The quaternary ammoniumChromatogram of LC/MS

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


Recovery amount of aldehyde in DEA aqueous solutionT bl R f ld h d i DEA



DerivatizationpH


Table Recovery amount of aldehyde in DEA

OHCH

DEA(50g/L) 0.2g/L

7 days Weak-acid 637 days Weak-basic 32

NHOHOH N

OHOH

CH2

NOHOH

OHCH3O CH3 ーH2O

CH2CH2

O CH3 Mass number 131（m/z 132）

N+

OHOH

CH2

N+

OHOH

CH3 OH

Quaternary ammonium

2

Mass number 158（m/z 158）Since the quaternary ammonium was preferably formed, the

t f ld h d l


recovery amount of aldehyde was low.

Study on reaction mechanisms of amine absorbent and aldehydes

Aldehyde recovery in secondary amine aqueous solution

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

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


y

Outline




• Summary


Aldehyde recovery in tertiary amine aqueous solution

Fig Recovery amount of aldehyde in tertiary aminesamine 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.

Reaction mechanisms of tertiary amine and acetaldehyde

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

+N

R2 ＋H+O -H2OOH

N+

R2 R

3

N+

R2 R

3

R1 N

R3

-H+RR

4

5R4 R5

R4 R5R1

NR

1N

m/z 164

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


LC/MS analysis of MDEAChromatogram of LC/MS

After addition of acetaldehyde,

Chromatogram of LC/MS

m/z 146 increased.

m/z 146/＝quaternary ammonium from MDEA

→ Even tertiary amines might react with acetaldehydes and h b f d

+CH3 CH3

quaternary ammonium might be formed.

OHN

OH

CH3

O CH3

OHN

+

OH

CH3 OH+ OH

N+

OH

CH2

-H2O


m/z 146Study on reaction mechanisms of amine absorbent and aldehydes

Amines reacted with aldehydes

Primary amines

+aldehyde aldehyde

secondary amines

+aldehyde -aldehyde

+aldehyde -aldehyde

tertiary amines

+aldehyde aldehyde

Quaternary ammonium

+aldehyde -aldehyde

Formation of quaternary ammonium is irreversible reaction.


For stable analysis of aldehyde in amine aqueous solution

Since amine absorbent pH is basic, aldehyde reaction with amine proceed and form imine and

O

+ Imines enamines・・・NH2 R1

proceed, and form imine and enamine.

R RImines, enamines2

Aldehydes

L H Hi h HLow pH(weak acidic condition)

High pH(basic condition)

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


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


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

OHNCH3

OHN

+CH2

CH2imine

Quaternary CH2

ammonium

OHNCH2

CHWhen addition amount of ld h d 1 /L MEACH2

Dienamine(tertiary amine)

aldehyde was 1g/L, MEA formed imine and dienaminebut quaternary ammonium in one day.


TOSHIBA Carbon Capture plant

TOSHIBA Corporation engages in CCS/CCU technology deployment.

CCU demonstration plant inSAGA, JAPAN（10〜20kg/d-CO2）, g 2

CCS demonstration plant in FUKUOKA, JAPAN（10 t/d-CO2）


*Photo from TOSHIBA websitehttp://www.toshiba.co.jp/thermalhydro/en/thermal/products/ccs/ccs.htm

What will be formed from quaternary ammonium ion?f l MEA

CH2

Quaternary ammonium ion

2 hydroxyTo other compounds

OHNH2

for example; MEA

OHN

+CH2

CH

2-hydroxy-ethyl

compounds

+ three acetaldehydesCH2

Double bond・Polymerization? NCH2

CH2

Substituent group・transferring

Reference

Polymerization?→foaming?

・Oxidation?CH2

・transferring

+CH3OH

Y. Hayashi, J. Jpn. Oil. Chem. Soc. ,Vol.36, No.6, 409(1987)

X- KOHCH3 The Ethanol group is selectively eliminated

ON

+

R OH 120℃N

R OHfrom dihydroxyethyl ammonium salt under basic condition.

O+

There is possibility that quaternary ammonium from amines and


p y q yaldehydes forms many deteriorating products.

Formaldehyde reaction with amine



DerivatizationpH


Water 0.2g/L - 100

MEA

10 min Weak-acid 9510 min Weak basic 98MEA

(50g/L)

0 2 /L

10 min Weak-basic 984 days Weak-acid 974 days Weak-basic 101

0.2g/Ly

DEA

10 min Weak-acid 9410 min Weak-basic 101

(50g/L) 4 days Weak-acid 1054 days Weak-basic 105

Recovery amount of formaldehyde is 100% in any cases


Reaction mechanisms of amine and formaldehyde

MEA and formaldehyde

Secondary amine and formaldehyde

Reversible reaction


Amine reactAmine CO2

degradation

Amine-CO2CO2

Aldehyde SOxNOx

degradationNOxmetal

Organic acid ・・・


Aldehyde recovery in secondary amine aqueous solutionTable Recovery amount of aldehyde in secondary amines



DerivatizationpH


Table Recovery amount of aldehyde in secondary amines

Water 0.2g/L - 100

DEA

10 min Weak-acid 10010 min Weak-basic 50DEA

(50g/L)10 min Weak-basic 507 days Weak-acid 637 days Weak-basic 32

0.2g/L

y

PZ(50 /L)


(50g/L) 7 days Weak-acid 457 days Weak-basic 33

MAE 10 min Weak acid 98MAE(50g/L)



Aldehyde recovery in tertiary amine aqueous solutionTable Recovery amount of aldehyde in tertiary amines



DerivatizationpH


Table Recovery amount of aldehyde in tertiary amines

Water 0.2g/L - 100

TEA

10 min Weak-acid 10110 min Weak basic 52TEA

(50g/L)10 min Weak-basic 527 days Weak-acid 607 days Weak-basic 39

0.2g/L

y

DMAE(50g/L)


MDEA(50g/L)

10 min Weak-acid 10110 min Weak-basic 437 days Weak acid 47(50g/L) 7 days Weak-acid 477 days Weak-basic 20


Documents

Study on Reaction Mechanisms of Amine Absorbent and ......Reaction mechanisms of primary amines and aldehydes Reactions of aldehydes and primary amines are reversible, and aldehydes