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Stability of a Benzyl Amine Based CO 2 CaptureAdsorbent in View of Regeneration Strategies

View Article: PubMed Central - PubMed

ABSTRACT

Inthis work, the chemical and thermal stability of a primary amine-functionalizedion-exchange resin (Lewatit VP OC 1065) is studied in view of thepotential options of regenerating this sorbent in a CO2 removal application. The adsorbent was treated continuously in thepresence of air, different O2/CO2/N2 mixtures, concentrated CO2, and steam, and then the remainingCO2 adsorption capacity was measured. Elemental analysis,BET/BJH analysis, Fourier transform infrared spectroscopy, and thermogravimetricanalysis were applied to characterize adsorbent properties. This materialwas found to be thermally and hydrothermally stable at high temperatures.However, significant oxidative degradation occurred already at moderatetemperatures (above 70 °C). Temperatures above 120 °C leadto degradation in concentrated dry CO2. Adding moistureto the concentrated CO2 stream improves the CO2-induced stability. Adsorbent regeneration with nitrogen strippingis studied with various parameters, focusing on minimizing the molesof purge gas required per mole of CO2 desorbed.

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Effect of temperature in dry air exposure on the CO2 adsorption capacity (evaluated at 15 vol % CO2, 40 °C)as a function of treatment time.
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fig3: Effect of temperature in dry air exposure on the CO2 adsorption capacity (evaluated at 15 vol % CO2, 40 °C)as a function of treatment time.

Mentions: To evaluate the impact of oxygenduring adsorption or regeneration,experiments were done in the setup described in the section 2.2. The experiments were carriedout using a continuous flow of dry air in the temperature range of50 to 120 °C, which was deemed as practical thermal swing operatingwindow. Figure 3 showsthe CO2 adsorption capacity of the adsorbent after treatment,normalized by their adsorption capacity before treatment, and plottedas a function of the treatment duration. According to the results,the CO2 capacity of the IER is affected by the oxygen whenthe temperature is high. The IER displays a dramatic decrease in CO2 uptake capacity when the temperature is above 80 °C,whereas it seems stable (for the time span evaluated) at 50 °C.The CO2 uptake reduces by as much as 30.2%, 46.7%, and80.5% of its original capacity, when treated at temperatures of 80,100 and 120 °C, respectively, for 72 h. On the other hand, theadsorbent material does not seem to be progressively degraded by theoxygen-containing gas by the continuous exposure at the lower temperatureconditions (50–70 °C). The CO2 adsorption capacitydecreases less than 10% at 70 °C after 72 h air exposure. Itis noteworthy that the rate of losing capacity from 80 to 120 °Cis faster at the beginning and decreases with progressing time. Thedegradation rate increases with temperature; it seems that a kineticeffect is a dominant factor in the degradation mechanism. To examinethe effect of air in a prolonged condition (more than 72 h), a longermeasurement was done at 80 °C for 432 h, resulting in an additional31% of CO2 capacity losses (hence, to a total capacityloss of 61% in 432 h). To study the thermal effect separately fromthat of oxygen, the IER was also treated at elevated temperature inthe presence of pure N2. A minor 5% decrease in CO2 adsorption capacity was found in the IER after being treatedin pure N2 for 72 h at 150 °C, ruling out the thermaleffect as main contributor to capacity loss. It was therefore concludedthat the main reason for the capacity decrease observed was oxidativedegradation. Earlier studies demonstrated that primary amines are,among the amines, the most stable ones to oxidative degradation.29,30 The amine sorbents in both cited studies are supported with silica-typematerial. Our results are in line with an earlier publication of Hallenbecket al., who found 79% CO2 capacity loss after continuousexposure in air at 120 °C for 7 days using the same material.43


Stability of a Benzyl Amine Based CO 2 CaptureAdsorbent in View of Regeneration Strategies
Effect of temperature in dry air exposure on the CO2 adsorption capacity (evaluated at 15 vol % CO2, 40 °C)as a function of treatment time.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384483&req=5

fig3: Effect of temperature in dry air exposure on the CO2 adsorption capacity (evaluated at 15 vol % CO2, 40 °C)as a function of treatment time.
Mentions: To evaluate the impact of oxygenduring adsorption or regeneration,experiments were done in the setup described in the section 2.2. The experiments were carriedout using a continuous flow of dry air in the temperature range of50 to 120 °C, which was deemed as practical thermal swing operatingwindow. Figure 3 showsthe CO2 adsorption capacity of the adsorbent after treatment,normalized by their adsorption capacity before treatment, and plottedas a function of the treatment duration. According to the results,the CO2 capacity of the IER is affected by the oxygen whenthe temperature is high. The IER displays a dramatic decrease in CO2 uptake capacity when the temperature is above 80 °C,whereas it seems stable (for the time span evaluated) at 50 °C.The CO2 uptake reduces by as much as 30.2%, 46.7%, and80.5% of its original capacity, when treated at temperatures of 80,100 and 120 °C, respectively, for 72 h. On the other hand, theadsorbent material does not seem to be progressively degraded by theoxygen-containing gas by the continuous exposure at the lower temperatureconditions (50–70 °C). The CO2 adsorption capacitydecreases less than 10% at 70 °C after 72 h air exposure. Itis noteworthy that the rate of losing capacity from 80 to 120 °Cis faster at the beginning and decreases with progressing time. Thedegradation rate increases with temperature; it seems that a kineticeffect is a dominant factor in the degradation mechanism. To examinethe effect of air in a prolonged condition (more than 72 h), a longermeasurement was done at 80 °C for 432 h, resulting in an additional31% of CO2 capacity losses (hence, to a total capacityloss of 61% in 432 h). To study the thermal effect separately fromthat of oxygen, the IER was also treated at elevated temperature inthe presence of pure N2. A minor 5% decrease in CO2 adsorption capacity was found in the IER after being treatedin pure N2 for 72 h at 150 °C, ruling out the thermaleffect as main contributor to capacity loss. It was therefore concludedthat the main reason for the capacity decrease observed was oxidativedegradation. Earlier studies demonstrated that primary amines are,among the amines, the most stable ones to oxidative degradation.29,30 The amine sorbents in both cited studies are supported with silica-typematerial. Our results are in line with an earlier publication of Hallenbecket al., who found 79% CO2 capacity loss after continuousexposure in air at 120 °C for 7 days using the same material.43

View Article: PubMed Central - PubMed

ABSTRACT

Inthis work, the chemical and thermal stability of a primary amine-functionalizedion-exchange resin (Lewatit VP OC 1065) is studied in view of thepotential options of regenerating this sorbent in a CO2 removal application. The adsorbent was treated continuously in thepresence of air, different O2/CO2/N2 mixtures, concentrated CO2, and steam, and then the remainingCO2 adsorption capacity was measured. Elemental analysis,BET/BJH analysis, Fourier transform infrared spectroscopy, and thermogravimetricanalysis were applied to characterize adsorbent properties. This materialwas found to be thermally and hydrothermally stable at high temperatures.However, significant oxidative degradation occurred already at moderatetemperatures (above 70 °C). Temperatures above 120 °C leadto degradation in concentrated dry CO2. Adding moistureto the concentrated CO2 stream improves the CO2-induced stability. Adsorbent regeneration with nitrogen strippingis studied with various parameters, focusing on minimizing the molesof purge gas required per mole of CO2 desorbed.

No MeSH data available.


Related in: MedlinePlus