Experimental and Modelling Studies of CO2/N2 Mixture Separations Using Amine Functionalised Silicas

E. Tsalaporta, N. Brady, J.M.D. MacElroy*

UCD School of Chemical and Bioprocess Engineering, and the Earth Sciences Institute, University College Dublin, Belfield, Dublin 4, Ireland.

*Corresponding Author. E-mail:

Supplementary Materials

2.2Characterization

XPS

XPS elemental data are presented in Tables S1 and S2, with the elemental curves indicating that the material has not been affected or decomposed after pelletisation and calcination. The presence of the monoamine (APTES) has further reduced the surface area of the pellet without seriously affecting the pore size. The XPS analysis (Table S3) has shown an increase in the nitrogen content, due to the presence of the monoamine. The surface area of diamine SBA-15 is smaller compared to monoamine SBA-15, due to the length of the molecule. As expected, the nitrogen content is higher compared to monoamine SBA-15 because of the presence of two amines (Table S4). The surface area of triamine SBA-15 is not significantly smaller compared to diamine SBA-15. A possible explanation is the attachment of less triamine molecules onto the silica sites because of the extended length of the triamine chain, which also explains the decrease in the nitrogen content of the pellet (see Table S5).

TableS1. XPS for SBA-15 powder

Peak / Type / Position
BE (eV) / FWHM / Raw Area
(cps eV) / RSF / Atomic
Mass / Atomic
Conc % / Mass
Conc %
O 1s / Reg / 530 / 3.077 / 223400 / 0.78 / 15.999 / 54.84 / 48.2
N 1s / Reg / 397 / 2.548 / 530 / 0.477 / 14.007 / 0.20 / 0.16
Ca 2p / Reg / 346 / 3.322 / 1555 / 1.833 / 40.078 / 0.15 / 0.34
C 1s / Reg / 282 / 3.168 / 31080 / 0.278 / 12.011 / 20.17 / 13.31
Si 2s / Reg / 101 / 3.059 / 46402 / 0.328 / 28.086 / 24.63 / 38

TableS2. XPS for SBA-15 pellet

Peak / Type / Position
BE (eV) / FWHM / Raw Area
(cps eV) / RSF / Atomic
Mass / Atomic
Conc % / Mass
Conc %
O 1s / Reg / 531 / 3.359 / 168170 / 0.78 / 15.999 / 61.47 / 52.42
N 1s / Reg / 392 / 1.024 / 500 / 0.477 / 14.007 / 0.29 / 0.21
Ca 2p / Reg / 350 / 1.980 / 2070 / 1.833 / 40.078 / 0.31 / 0.65
C 1s / Reg / 282 / 3.059 / 12195 / 0.278 / 12.011 / 11.78 / 7.54
Si 2s / Reg / 101 / 3.166 / 33122 / 0.328 / 28.086 / 26.16 / 39.17

TableS3. XPS for monoamine modified SBA-15

Peak / Type / Position
BE (eV) / FWHM / Raw Area
(cps eV) / RSF / Atomic
Mass / Atomic
Conc % / Mass
Conc %
O 1s / Reg / 533 / 3.152 / 49700 / 0.78 / 15.999 / 40.39 / 37.97
N 1s / Reg / 401 / 2.188 / 1053.3 / 0.477 / 14.007 / 1.34 / 1.1
C 1s / Reg / 284 / 4.655 / 17296.7 / 0.278 / 12.011 / 37.16 / 26.22
Si 2s / Reg / 154 / 3.958 / 10616.7 / 0.324 / 28.086 / 19.02 / 31.39
Al 2p / Reg / 75 / 3.336 / 705 / 0.193 / 26.982 / 2.09 / 3.31

TableS4. XPS for diamine modified SBA-15

Peak / Type / Position
BE (eV) / FWHM / Raw Area
(cps eV) / RSF / Atomic
Mass / Atomic
Conc % / Mass
Conc %
O 1s / Reg / 533 / 3.583 / 48135 / 0.78 / 15.999 / 36.32 / 34.62
N 1s / Reg / 401 / 3.902 / 2883.3 / 0.477 / 14.007 / 3.4 / 2.84
C 1s / Reg / 286 / 3.321 / 20001.7 / 0.278 / 12.011 / 39.93 / 28.57
Si 2s / Reg / 155 / 4.044 / 11748.3 / 0.324 / 28.086 / 19.54 / 32.69
Al 2p / Reg / 76 / 2.336 / 290 / 0.193 / 26.982 / 0.8 / 1.28

TableS5. XPS for triamine modified SBA-15

Peak / Type / Position
BE (eV) / FWHM / Raw Area
(cps eV) / RSF / Atomic
Mass / Atomic
Conc % / Mass
Conc %
O 1s / Reg / 531 / 3.209 / 61158.3 / 0.78 / 15.999 / 39.45 / 37.16
N 1s / Reg / 398 / 3.39 / 3330 / 0.477 / 14.007 / 3.36 / 2.77
C 1s / Reg / 283 / 3.218 / 21245 / 0.278 / 12.011 / 36.23 / 25.62
Si 2s / Reg / 153 / 3.623 / 12466.7 / 0.324 / 28.086 / 17.74 / 29.33
Al 2p / Reg / 73 / 3.569 / 1370 / 0.193 / 26.982 / 3.22 / 5.11

Nitrogen Isotherms – Surface Area - Porosity

Figure S1 summarizes the pore size distributions from desorption BJH N2 isotherms of selected SBA-15 materials.

Figure S1. Pore size distributions for the SBA-15 powder, pelletised SBA-15 and pelletised APTES SBA-15

2.5 Modelling details

Tables S6 and S7 summarize the boundary conditions and flux conditions that were used for modelling purposes.

Table S6. Boundary Conditions

Pressurization / Adsorption / Depressurization / Desorption
/ / / ,

Table S7. Flux Conditions

Pressurization / Adsorption / Depressurization / Desorption

3.1 Adsorption and Desorption Breakthrough Studies

Adsorption isotherms for APTES SBA-15

The results obtained for the adsorption breakthrough residence times (or first moments) corrected for inlet and outlet tubing lag times at the three temperatures296.5K, 306.5 K and 316.5 K,for different CO2 concentrations and feed flow rates, are reported in Tables S8, S9 and S10 and the isotherm data are extracted from these data using

Table S8. Results at 296.5 K (APTES SBA-15)

Run (% CO2) / PCO2 (Bara) /
1 / 0.011 / 3403 (+/- 1.48%)
2 / 0.023 / 2038 (+/- 1.48%)
10 / 0.113 / 632 (+/- 2.4%)
20 / 0.224 / 396 (+/- 3.15%)
30 / 0.333 / 314 (+/- 1.13%)

Table S9. Results at 306.3 K (APTES SBA-15)

Run (% CO2) / PCO2 (Bara) /
1 / 0.011 / 2800 (+/- 1.74%)
2 / 0.023 / 1692 (+/- 4.3%)
10 / 0.113 / 582 (+/- 1.77%)
20 / 0.222 / 375 (+/- 4.87%)
30 / 0.331 / 298 (+/- 0.75%)

Table S10. Results at 316.5 K (APTES SBA-15)

Run (% CO2) / PCO2 (Bara) /
1 / 0.011 / 2330 (+/- 2.55%)
2 / 0.022 / 1560 (+/- 2.14%)
10 / 0.105 / 567 (+/- 4.74%)
20 / 0.213 / 352 (+/- 3.69%)
30 / 0.331 / 273 (+/- 3.93%)

3.2 PSA/VPSA studies

Purity and Recovery

The average purity and recovery were defined as

Scenarios

The duration of the pressurisation and the depressurisation steps during the PSA cycles was fixed while the adsorption and desorption step were varied.The duration of the steps for the different scenarios were as follows:

30s cycle: pressurization 5s, adsorption 10s, depressurization 2s, desorption 13s

50s cycle: pressurization 5s, adsorption 20, depressurization 2s, desorption 23s

100s cycle: pressurization 5s, adsorption 45s, depressurization 2s, desorption 48s

Pressure and purge flow rate

Tables S11 and S12 summarize the data for a series of runs reported within the paper defined as scenarios 1 (purge flow rate: 500 cm3/min) and 2 (purge flow rate: 400 cm3/min).

Table S11. Experimental and simulated runs for different cycle times-PSA (APTES SBA-15)

Scenario / Cycle time (s) / Feed/purge
(cm3/min) / Pressure
(bar) / Temperature
(K) / Recovery / Purity
1a / 30 / 1000/500 / 6.25/1.1 / 293 / (a)63.98%
(b)68.5% / (a) 12.47%
(b) 14.1%
1b / 50 / 1000/500 / 6.25/1.1 / 293 / (a) 70.64%
(b) 73.22% / (a) 14.96%
(b) 17.63%
1c / 100 / 1000/500 / 6.25/1.1 / 293 / (a) 68.31%
(b) 71.35% / (a) 16.72%
(b) 19.8%
1d / 30 / 1000/500 / 6.25/0.5 / 293 / (a)65.02%
(b) 66.7% / (a) 13.94%
(b) 16.8%
1e / 50 / 1000/500 / 6.25/0.5 / 293 / (a) 69.78%
(b) 72.38% / (a) 15.36%
(b) 18.4%
1f / 100 / 1000/500 / 6.25/0.5 / 293 / (a) 66.82%
(b) 70.36% / (a) 17.99%
(b) 20.98%
* (a) is the simulated value and (b) is the experimental value

Table S12. Experimental and simulated runs for different cycle times-VPSA

(APTES SBA-15)

Scenario / Cycle time (s) / Feed/purge
(cm3/min) / Pressure
(bar) / Temperature
(K) / Recovery / Purity
2a / 30 / 1000/400 / 6.25/1.1 / 293 / (a) 61.9%
(b) 62.33% / (a) 14.73%
(b) 16.34%
2b / 50 / 1000/400 / 6.25/1.1 / 293 / (a) 67.42%
(b) 68.9% / (a) 16.95%
(b) 19.6%
2c / 100 / 1000/400 / 6.25/1.1 / 293 / (a) 68.5%
(b) 70.42% / (a) 20.0%
(b) 22.15%
2d / 30 / 1000/400 / 6.25/0.5 / 293 / (a) 55.06%
(b) 58% / (a) 14.98%
(b) 17.8%
2e / 50 / 1000/400 / 6.25/0.5 / 293 / (a) 62.25%
(b) 64.12% / (a) 20.43%
(b) 21.24%
2f / 100 / 1000/400 / 6.25/0.5 / 293 / (a) 64.57%
(b) 67.2% / (a) 21.72%
(b) 24.72%
* (a) is the simulated value and (b) is the experimental value

Temperature

Table S13 summarizes the data for a series of PSA runs reported within the paper defined as scenario 3. Both ambient and feed temperatures were equalised.

Table S13. Simulated runs for different temperatures-PSA (APTES SBA-15)

Scenario / Cycle time (s) / Feed/purge
(cm3/min) / Pressure
(bar) / Temperature
(K) / Recovery / Purity
3a / 100 / 1000/400 / 6.25/1.1 / 293 / (a) 67.58%
(b) 70.42% / (a) 20.13%
(b) 22.15%
3b / 100 / 1000/400 / 6.25/1.1 / 313 / (a) 69.03% / (a) 23.84%
3c / 100 / 1000/400 / 6.25/1.1 / 333 / (a) 73% / (a) 25.04%
3d / 100 / 1000/400 / 6.25/1.1 / 353 / (a) 77.17% / (a) 29.0%
* (a) is the simulated value and (b) is the experimental value

CO2 separations from streams at low CO2 concentrations

Table S14 summarizes the data for a series of low concentration CO2 PSA runs reported within the paper defined as scenario 4. Both ambient and feed temperatures were equalised.

Table S14. Simulated runs for low CO2 concentration capture (APTES SBA-15)

Scenario / Cycle time (s) / Feed/purge
(cm3/min) / Pressure
(bar) / Temperature
(K) / Recovery / Purity
4a / 50 / 1000/400 / 6.25/1.1 / 293 / 85.23% / 43.96%
4b / 50 / 1000/400 / 6.25/1.1 / 313 / 86.10% / 50.91%
4c / 50 / 1000/400 / 6.25/1.1 / 333 / 91.48% / 54.76%
4d / 50 / 1000/400 / 6.25/1.1 / 353 / 97.65% / 61.78%
4e / 50 / 1000/400 / 6.25/0.5 / 293 / 88.39% / 55.06%
4f / 50 / 1000/400 / 6.25/0.5 / 313 / 89.53% / 66.48%
4g / 50 / 1000/400 / 6.25/0.5 / 333 / 94.36% / 69.20%
4h / 50 / 1000/400 / 6.25/0.5 / 353 / 99.87% / 78.24%

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