Engineering Zeolites for Efficient Greenhouse Gas Capture CO SF - - PowerPoint PPT Presentation

Engineering Zeolites for Efficient Greenhouse Gas Capture

CO₂ SF₆

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Problem Conventional greenhouse gas capture methods are energy- intensive

Figure 1. Amine-based CO₂ removal process

What are zeolites?

▰ Microporous aluminosilicate

minerals

▰ Precisely uniform lattice ▰ Readily modifiable surface

properties

• Framework structure
• Cationic structure
• Silica-to-alumina ratio

Figure 2. Typical structures of zeolites

Main

• bjective

To enhance CO₂ and SF₆ adsorption capacity by introducing mesoporosity into zeolites

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Microporous: less than 2nm in diameter Mesoporous: 2nm~50nm in diameter

Figure 3. Representative structures of microporous and mesoporous zeolite

Materials & Methodology

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Synt nthe hesis is of

• f

zeolite te MF MFI Silica MFI (Si MF MFI) Aluminosilicate MFI (Al/Si Si MFI) Mesoporous aluminosilicate MFI (Me Meso Al/Si Si MF MFI)

Silica source: Tetraethylorth

• silicate

(TEOS) Silica source: Water glass Alumina source: Al₂(SO₄)₃ᐧ16H₂O Mesopores introduced via the soft- templating method

Materials & Methodology

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Chara aracte cterisation sation of f zeol

• lite

e MFI

• 1. Powder X-Ray Diffraction
• 2. Thermogravimetric Analysis
• 3. Nitrogen Physisorption Analysis
• 4. Scanning Electron Microscopy
• 5. CO₂ Adsorption Isotherm
• 6. SF₆ Adsorption Isotherm
• 7. N₂ Adsorption Isotherm
• 8. Isosteric Heat of Adsorption

• 1. Powder X-Ray Diffraction

▰

Confirms the successful synthesis of zeolites

Figure 4. Powder X-Ray diffraction patterns

• 2. Thermogravimetric

Analysis

▰

All zeolite MFI exhibit thermal stability up to 900°C

Figure 5. Thermogravimetric Analysis

• 3. Nitrogen Physisorption

Analysis

▰ Hysteresis loop

shows high degree of pore structure uniformity

Figure 6. Nitrogen Physisorption Analysis

• 3. Nitrogen Physisorption

Analysis

▰ Si MFI has the

highest surface area and micropore surface area

▰

Mesoporosity increases the surface area and pore volume

Table 1. Textural properties of zeolites

• 4. Scanning Electron

Microscopy

Figure 7. Scanning Electron Microscopy (SEM) images of zeolites

(c) Mesoporous Al/Si MFI (a) Si MFI (b) Al/Si MFI

Si MFI Al/Si MFI Meso Al/Si MFI Spherical, nanocrystalline structure, diameter 100 nm Cubical structure, diameter 1 µm Rough surface, diameter 2-3 µm

• 5. CO₂ Adsorption Isotherm

▰ Linear

adsorption isotherm of Si MFI

▰ Al/Si MFI and

meso Al/Si MFI show a type I adsorption isotherm

Figure 8. CO₂ Adsorption Isotherm

• 6. SF₆ Adsorption Isotherm

▰ At low pressure, Al/Si

MFI has high SF₆ uptake

▰ At higher pressures Si

MFI displays highest adsorption affinity for SF₆

▰ For SF6 adsorption,

Pore property is more significant than electric field strength in zeolite

Figure 9. SF₆ Adsorption Isotherm

• 7. N₂ Adsorption Isotherm

▰ All zeolites display

linear adsorption isotherms

▰ Confirms

interaction between quadrupole moment of CO₂ and adsorption center in zeolite

Figure 10. N₂ Adsorption Isotherm

• 8. Isosteric Heat of

Adsorption (CO₂)

▰ Indicates the

energy penalty for regeneration in CO₂

▰ Meso Al/Si MFI

has lower energy penalty than Al/Si MFI

Figure 11. Qst values for pure- component CO₂ loading

• 8. Isosteric Heat of

Adsorption (SF₆)

▰ Indicates the

energy penalty for regeneration in SF₆

▰ Si MFI has lowest

energy penalty despite having strongest affinity for SF₆

Figure 12. Qst values for pure- component SF₆ loading

Conclusion

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▰ CO₂ adsorption is enhanced by increased

polarity and basicity of zeolite

▰ SF₆ adsorption is dependent on pore property

• f zeolite

▰ Hence, introducing mesoporosity may not

necessarily increase adsorption capacity

Increase basicity of the zeolite

• Grafting of

surface of zeolite with functional groups eg. amine groups,

• rganosilanes

Cation exchange to alter window aperture of the zeolites

2

Future Work

1

Figure 13. Soft-templating method to synthesize hierarchically-structured zeolite

Brunauer-Emmett-Teller (BET) theory and Langmuir Theory

• To calculate the internal surface area of the zeolite
• linear plot of adsorption data

Barrett-Joyner-Halenda Theory

• measures pore size distribution

Capillary condensation

http://coatingsys.com/pdf/What%20is%20capillary%20condensation%20and%20its%20significance%20in%20nanocoatings.p df

Capillary condensation

http://coatingsys.com/pdf/What%20is%20capillary%20condensation%20and%20its%20significance%20in%20nanocoatings.p df

Calculation of isosteric heat of adsorption using the virial equation

Ideal Adsorbed Solution Theory (IAST)

• predict the adsorption selectivity and the adsorption

equilibrium of gas mixtures

• from the isotherms of the pure components

References

• Chuah, C. Y., Yu, S., Na, K., Bae, T.-H. (2018) Enhanced

SF6 recovery by hierarchically structured MFI zeolite. Journal of Industrial and Engineering Chemistry, 62: 64 - 71.

• Ciddor, L. A.; Bennett, J. A.; Hunns, J. A.; Wilson, K. and

Lee, A. F. (2015) Minireview Catalytic Upgrading of Bio- Oils by Esterification Journal of Chemistry Biotech.

• https://www.researchgate.net/figure/Representative-

zeolite-frameworks-with-pore-openings-a-zeolite-A-3D- 42-A-b_fig1_225186971

• http://www.separationprocesses.com/Adsorption/AD_C

hp01a3.htm

• Zhang, Z., Xian, S., Xia, Q., Wang, H., Li, Z. and Li, J.

(2013) Enhancement of CO2 adsorption and CO2/N2 selectivity on ZIF-8 via Postsynthetic modification. DOI 10.1002/aic.13970