Biomimetic Sorbents for Selective CO2 Capture

Jen Wilcox, Zhenan Bao, Daniel T. Stack, Jiajun He, John To, Chris Lyons and Erik Rupp

GCEP Symposium, Stanford, California

October 8th, 2013

•  Scale of CO2 and Minimum Work •  Carbon-Based Sorbents •  Biomimetic Sorbents

Agenda

To Prevent 2 °C Warming …

•  Between  2000-‐2050  if  cumula3ve  emissions  are  less  than:  –  1,000  Gt  →  25%  probability  

global  warming  beyond  2  °C  –  1,440  Gt  →  50%  probability  

global  warming  beyond  2  °C  

Where  we’re  projected  to  go  (BAU):  –  Assuming  annual  increases:  

•  Coal  –  0.3%  •  Oil  –  0.9%  •  Natural  Gas  –  2.3%  

–  ≈  31  Gt  CO2  emiUed  in  2011  –  ≈  44  Gt  CO2  projected  in  2050  –  1790  cum.  Gt  CO2  in  2050!  

BAU  

2009 2050

Ref:  Allen  et  al.,  Nature,  2009  Ref:  BP  Sta3s3cal  Rev.  of  World  Energy,  2012  

Expanding the Impact of CCS

BAU  -‐  1790  Gt  CO2  

1000  Gt  CO2  →  25%  probability  of  ↑2°C  

1440  Gt  CO2  →  50%  probability  of  ↑2°C  

Scenario   Avoided  Cum.  Gt  CO2  Replace  Coal  w/  NG   1512  

90%  Capture  (Point  Source  Electric  Sector)   1288  

90%  Capture  (Point  Source  Electric  Sector)  +  50%  Transport  (on-‐board  capture;  EV;  DAC)  

1083  

1

3

5

7

9

11

13

15

17

19

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Minim

um  W

ork  (kJ/mol  CO

2  Cap

tured)  

CO2  ConcentraPon  

50%  capture;  80%  purity  75%  capture;  80%  purity  90%  capture;  80%  purity  50%  capture;  95%  purity  75%  capture;  95%  purity  90%  capture;  95%  purity  50%  capture;  99%  purity  75%  capture;  99%  purity  90%  capture;  99%  purity  

Minimum  Work  

Coal  GasificaPon  

1-‐4  kJ/mol  CO2  

Natural  Gas  CombusPon  6-‐9  kJ/mol  CO2  

Coal  CombusPon  5-‐7  kJ/mol  CO2  

Direct  Air  Capture  19  –  21  kJ/mol  CO2  

•  DAC  is  always  ≈  20  kJ/mol  CO2,  regardless  of  %  capture  and  purity  

•  Reason:  capturing  less  of  a  given  total  gas  

•  Addi3onal  work  required  due  to  density  changes  w/  mixtures  of  CO2  and  N2  

•  95%CO2  +  5%N2:  681  kg/m3  •  80%CO2  +  20%N2:  343  kg/m3  •  ≈  0.5  kJ/mol  CO2  addi3onal  

compression  energy!  

Wilcox, Carbon Capture, 2012

Low-‐Hanging  Fruit  –  Point  Sources  

•  Most  adsorp3on  and  absorp3on  separa3on  process  studies  focus  on  material  capacity  for  CO2  

 

But…      •  Single  500-‐MW  power  plant  emits  ≈  11,000  tons  CO2  per  day!    

–  In  2011  ≈  600  500-‐MW  plants    (coal  and  NG)  US-‐wide  •  If  the  kine3cs  are  too  slow  →  capital  costs  ↑  due  to  need  for  

high  #  units  to  process  the  flue  gas  •  How  can  we  speed  up  the  kine3cs  of  a  separa3on  process?    

Carbonic Anhydrase (CA) for CO2 Capture

Ø   Fast  reacPon  8  orders  of  magnitude  faster  than  noncatalyzed  bicarbonate  forma3on  in  water  

Ø   Low  reacPon  heat  low  energy  penalty  for  regenera3on  

Ø   High  selecPvity  over  N2  and  H2O  

 Ø   Tolerance  of  water  

 

Carbon as a Substrate

Assume:    Heat  of  regenera3on  =  CpΔT  +  ΔH    hea%ng  up  all  material  in  system  from  T1  to  T2    +    breaking  the  CO2  interac%on    

Materials  Synthesis  

The Team - Synthesis, Characterization, Testing

PI:  Zhenan  Bao  John  To,  PhD  Student  Chemical  Engineering

               

Materials  TesPng  and  CharacterizaPon    

PI:  Jen  Wilcox  Dr.  Erik  Rupp,  Research  Associate  Energy  Resources  Engineering  

Jiajun  He    PhD  Student    

Dr.  Reza  Haghpanah  Post-‐doc    

PI:  Daniel  T.  Stack  Chris  Lyons,  PhD  Student  

Chemistry  

•  Scale of CO2 and Minimum Work •  Carbon-Based Sorbents •  Biomimetic Sorbents

Agenda

Recent Studies

Sorbent CO2 Cap.* (mmol/g)

Testing Methods

Reference

N-Doped Polypyrrole 0.8 Nova Sevilla et al. Adv. Funct. Mater. 2011

Imine-Linked Polymer 0.6 Autosorb 1 Wang et al. Appl. Mater. Inter. 2013

“Click” N-doped C 0.73 Belsorp Gu et al. Carbon 2013

Carbon Nitride 0.7 Autosorb-1MP Deng et al. Chem. Eng. J. 2012

Polyindole 1.1 Belsorp Saleh et al. Environ. Sci. Techol. 2012

Poly(benzoxazine-co-resol) 0.7 Micromeritics Hao et al. J. Am. Chem. Soc. 2011

＊All values are taken at 25 °C and 0.1 bar of CO2

Effects of Carbonization Temperature

Carbonization Temperature (°C)

BET area (m2/g)

Pore Volume (cc/g)

Elemental Analysis CO2 Capacity* (mmol/g) N% C%

600 62.3 0.077 8.29 46.21 0.16

700 48.1 0.083 8.11 49.67 0.20

800 148.3 0.172 5.66 58.39 1.13

900 511.2 0.342 4.09 62.34 0.96

＊Measured  by  BT  at  25  °C  with  0.1  bar  of  CO2   Ways  to  further  improve  CO2  capacity?  

•  Highest  capacity  at  800  oC  (close  to  the  literature  max)  

•  Surface  area  significantly  increases  from  700  to  900  oC  

 

KOH Activation Before  Ac3va3on   Aver  Ac3va3on  

•  Similar  morphology  •  More  space  in  the  networks  aver  ac3va3on      

1 µm 1 µm

•  Microporous features with exceptional surface area (from 1500 to 3468 m2/g by BET) and pore volume (from 0.98 to 2.25 cc/g by QSDFT)

•  High CO2 capacity at 25 oC and 0.1 bar: 1.42 mmol/g (800_3ac)

KOH Activation

Sample

Textural properties N/C comp.

[wt%]

SBET

[m2/g]

Vt

[cm3/g] Vmicro

[cm3/g] N C

500_3ac 3410.2 1.864 0.847 - -

600_3ac 3468.0 2.248 0.723 0.92 76.87

800_3ac 2640.8 1.615 0.582 1.17 75.21

900_3ac 1499.7 0.980 0.544 2.33 80.50 !

CO2 Sorption Isotherms (25 oC)

AC sample Adsorption conditions CO2 capacity (mmol/g)

Yeast 25 °C, 1 bar 4.8 Eucalyptus sawdust 25 °C, 1 bar 4.8

This work 25 °C, 1 bar 6.1

Chen, Z. et al., Front. Environ. Sci. Eng. 2013, 7(3), 326-340.

•  Scale of CO2 and Minimum Work •  Carbon-Based Sorbents •  Biomimetic Sorbents

Agenda

•  Use commercially-available porous materials as supports •  Functionalize via a simple mechanism •  Sorbent test and study the surface functional groups on

CO2 adsorption

Proof-of-Concept Experiments

Simplified  Zinc  FuncPonal  Group  

Synthetic method and chemisorption of CO2

Sample zinc silica 1: heated up to 250 °C prior to surface modification Sample zinc silica 2: direction functionalization without preheating

Sample Zinc Loading (mmol/g)

Silica gel 0.00003

Zinc silica 1 1.63

Zinc silica 2 1.82 Digested and analyzed by ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy)

19

Breakthrough  Experiments:  Zinc  Silica  Dry Humid

0 20 40 60 80 100

0.00

0.04

0.08

0.12

CO

2  Con

centratio

n  (-‐)

T ime  (s )

 B lank  S ilica  G e l  Z inc  S ilica  1  Z inc  S ilica  2

0 20 40 60 80 100

0.00

0.04

0.08

0.12

CO

2  Con

centratio

n  (-‐)

T ime  (s )

 B lank  S ilica  G e l  Z inc  S ilica  1  Z inc  S ilica  2

Sorbent CO2 Capacity

(mmol/g) Preparation Process

Zinc Loading (mmol/g)

Surface Area (m2/g)

Avg. Pore Size (nm)

Pore Volume (cc/g) Dry Humid

Silica gel 0.10 0.04 Commercial 0.0003 511 12.6 0.75 Zinc silica 1 0.06 0.06 Preheated 1.62 378 12.6 0.55 Zinc silica 2 0.36 0.30 Direct func. 1.83 349 6.8 0.53

In  Summary  

•  This  work  aims  to  develop  affordable  and  scalable  carbon-‐based  sorbents  with  covalently  bonded  zinc  func3onali3es  for  selec3ve  CO2  capture  

•  High-‐surface  area  microporous  carbon  was  synthesized  by  a  simple  solu3on-‐based  process,  with  CO2  adsorp3on  capacity  up  to  6.1  mmol/g,  which  exceeds  materials  presented  in  the  literature  

•  Preliminary  results  indicate  equivalent  CO2  capacity  under  dry  and  humid  condi3ons,  by  simple  func3onaliza3on  of  silica  gel  with  zinc  

•  Future  work  will  include  controlled  mesoporous  carbons  to  support  Zn  func3onaliza3on  

   

Acknowledgements  

Funding  Global  Climate  Energy  Project,  Stanford  University  

 

QuesPons?    

Minimum Work for Separation combined first and second laws

€

Wmin = RT nBCO2 ln(yB

CO2 ) + nBB −CO2 ln(yB

B −CO2 )[ ] + RT nCCO2 ln(yCCO2 ) + nCC −CO2 ln(yCC −CO2 )[ ]−RT nA

CO2 ln(yACO2 ) + nA

A −CO2 ln(yAA −CO2 )[ ]

Wilcox, Carbon Capture, Springer, 2012

Chemical Activation - Mechanism •  For  alkaline  hydroxide,  K+  or  Na+  are  easily  diffuse  into  the  amorphous  region  •  For  some  materials,  K+  is  beUer;  others  Na+  is  beUer  

Viswanathan, Neel, Varadarajan, Methods of Activation and Specific Applications of Carbon Materials, 2009

Polymer Hydrogel

Sample Monomer: Crosslinker

BET Area

(m2/g)

CO2 Capacity* (mmol/g)

900_2c 1：2 511.2 0.92

＊Measured by BT at 25 °C with 0.1 bar of CO2

900_2c

500 nm

Easy synthesis of polymer hydrogel, followed by

carbonization

Pore  Analysis  by  N2  SorpPon  

BET Surface Area (m2/g)

Average Pore Diameter

(nm)

Pore Volume (cc/g)

Silica gel 510.7 12.6 0.75

Zinc silica 1 337.8 12.6 0.55

Zinc silica 2 348.8 6.8 0.53

0.0 0.2 0.4 0.6 0.8 1.00

100

200

300

400

500

600

 

 

Volum

e  at  S

TP  (cc

/g)

p/p0

 S ilica  G el  Z inc  S ilica  1  Z inc  S ilica  2

0 10 20 30 40 500.0

0.5

1.0

1.5

2.0

 

 

Pore  Volum

e  (cc/g)

P ore  D iamter  (nm)

 S ilica  G el  Z inc  S ilica  1  Z inc  S ilica  2

N2 isotherms Pore size distribution by DFT method