This study describes the use of alkyl-aryl amine reach molecules (Ph-XX-YY) as sorbents for capturing CO2 from dilute and ultra-dilute mixtures. These amines were impregnated into solid supports of various chemical compositions such as SBA-15, and y-alumina. The organic loading of the composite Ph-XX-YY-based supports was in the 20%-60% mass range. In the case of each substrate, the high amine-loading samples (50%-60%) adsorbed the largest amount of CO2 (using 400 ppm streams, at 35° C.). For example, the CO2 adsorption capacity of 60% Ph-3-ED/SBA-15 was 1.9 mmol CO2/gSiO2, those of 50% Ph-3-PD/SBA-15 and 50% Ph-6-ED/SBA-15 were 1.23 mmol CO2/gSiO2 and 0.8 mmol CO2/gSiO2, while that of 50% Ph-6-PD/SBA-15 was 0.59 mmol CO2/gSiO2. The 50% Ph-3-PD/SBA-15 material exhibited the highest amine efficiency, 0.1 mmol CO2/mmol N. Intermediate organic loading (aka 40%) gave better performance in terms of amine efficiency: 0.13 versus 0.11 mmol CO2/mmol N for Ph-3-ED/SBA-15 (40%, 50%), 0.077 versus 0.048 mmol CO2/mmol N for Ph-6-ED/SBA-15 (40%, 50%). Interestingly, in the case of Ph-6-PD/SBA-15 the amine efficiency flattened to an average value of 0.04 mmol CO2/mmol N. Overall, the Ph-3-YY/SBA-15 composites showed a higher CO2 uptake performance than the Ph-6-YY/SBA-15 homologues. This trend was also evident from the shape of the kinetic adsorption curves. These curves consisted of two distinct regions: one abruptly linear corresponding to the initial uptake that ‘curved’ to the other almost flat, referred to as the pseudo-equilibrium region, which asymptotically approaches the true equilibrium uptake. The highly concentrated samples approached the asymptotic regime of the curve the fastest, behavior associated with their fastest CO2 uptake. The pseudo-equilibrium region was then more drawn out, approaching the true equilibrium more gradually. The exception was the 50% and 40% Ph-6-ED/SBA-15 samples that displayed slower kinetic behavior than the intermediate and low concentration ones in the initial linear regime. These data together suggest that the bulky molecular geometry of Ph-6-YY may hamper Ph-6-YY/SBA-15 composites from performing similarly to the Ph-3-YY/SBA-15 counterparts, despite their higher amine content. In addition, their packing at the pore walls and within the supports together with the confinement characteristics adds to the complex landscape of interactions that govern the properties of these materials.
In order to examine the effect of the solid substrate on CO2 adsorption performance, a 50% Ph-3-ED/γ-Al2O3 composite was prepared. After TGA and N2 physisorption measurements confirmed successful impregnation of Ph-3-ED, the measured CO2 adsorption capacity was 1.54 mmol CO2/gy-Al2O3 and the amine efficiency was 0.11 mmol CO2/mmol N. The CO2 uptake of this sample was higher than that of the similarly concentrated samples (50%) prepared using the SBA-15 support.
Because the high organic loading samples were the best performers in terms of CO2 uptake, they were further subjected to temperature-swing adsorption-desorption cycles and accelerated oxidation treatments. After 25 cycles of 1 h adsorption of 400 ppm CO2 (35° C.) followed by 10 min desorption in He (90° C.), 60% Ph-3-ED/SBA-15 retained up to 82% of its initial amine efficiency and 50% Ph-3-PD/SBA-15 retained 44.5% of the amine efficiency, with respect to the full uptake values recorded for 12 h of adsorption time in the absence of temperature-swing cycles. This value was lower for 50% Ph-6-ED/SBA-15 (40%) and 50% Ph-6-PD/SBA-15 (25%). One of the most important findings revealed by these experiments was the ability of all composites to maintain a stable working capacity, regardless of the trends in amine efficiency. The retained amine efficiency values were reduced when the best performing composite, Ph-3-YY/SBA-15, was exposed to 21% O2/He for 24 h at elevated temperatures (90° C. and 110° C.). The interactions with oxygen molecules caused diminished performance: only 39% (50% Ph-3-ED/SBA-15) and 20% (50% Ph-3-PD/SBA-15) of the original amine efficiencies were retained at 90° C. At 110° C. the values were 20% and 13%, respectively. These data confirm the idea that a bulky molecular architecture of Ph-6-YY did not favor high CO2 adsorption performance. The effect of moisture on CO2 performance was investigated by using a custom-built fixed bed setup. 60% Ph-3-ED/SBA-15 displayed double breakthrough time and three-fold increase in CO2 adsorption capacity at 30% RH (35° C., 400 ppm CO2) when compared with the dry conditions (0% RH).[KDR1] Given their demonstrated properties, Ph-3-YY/SBA-15 composites, especially Ph-3-YY/SBA-15, are promising materials that can be potentially integrated into the DAC and other CO2 adsorption technologies.
Further aspects of the present disclosure will be more readily appreciated upon review of the detailed description of its various embodiments, described below, when taken in conjunction with the accompanying drawings.
The increase of atmospheric CO2 concentration has alarming implications for global climate change. Intense efforts have been dedicated to develop effective technologies for carbon capture and sequestration (CCS), with a recently recognized new approach the facilitation of CO2 from the atmosphere.1 Direct air capture of CO2 (DAC) from the atmosphere has been recently developed as a potential negative emissions technology (NET) due to its technological, scalability and environmental advantages.2-5 One of the benchmark technologies used in CO2 capture is adsorption by amine-based aqueous solutions.6-9 While this approach has shown good performance, energy-intensive regeneration and oxidative degradation of the amine adsorbents as well rapid corrosion of the equipment are the main disadvantages.10 Another technology explored in the last years uses solid-supported amine adsorbents, especially for their CO2 adsorption performance at low temperature.11-15 Based on the sorbent processing approach, these materials have been grouped into three classes. Class 1 sorbents consists of small molecules and polymeric amines that are physically confined into porous supports.12,13,15-20 Small molecules, usually aminosilanes, covalently bound to the inner and exterior porous support surface, form the class 2 materials.11,19-21-23 While the class 1 sorbents exhibit higher CO2 adsorption capacity than the class 2 materials in many cases due to higher amine loadings, impregnated amines may be more mobile during sorbent regeneration and also may be less stable towards leaching or volatilization. Combining covalent immobilization and use of polymeric amines led to the class 3 materials.3,24 The process typically uses in-situ polymerization of amine-containing monomers inside the support pores and yields highly stable oligomeric and polymeric amine-rich species covalently bound to the solid's walls. Recently, new efforts have been focused on developing polymeric materials that exhibit combined properties of both solid supports and amine adsorbents.14 Nowadays, both high temperature aqueous solution-based DAC and low-temperature solid-supported sorbent DAC technologies are commercially available but the latter option promises potential for extensive cost reduction.25
To reduce the process costs of solid-based DAC, innovative approaches have been devoted to improve the performance and expand the library of amine sorbents. In general, simple alkyl amine molecules or macromolecules are among the most widely employed as the class 1 sorbents. For example, Zhu et al. have used tetraethylenepentamine (TEPA) impregnated into mesoporous silica and reported a high adsorptive capacity of 183 mg/g after six adsorption-desorption cycles at low CO2 concentration (5%) using an optimal 50% organic loading.26 Recently Yamada et al. has modified the amine end group of TEPA and achieved CO2 adsorption capacity values as high as 4.65 mmol/g, representing 0.42 mmol CO2/mmol N in terms of amine efficiency.27 This performance was achieved under flue gas conditions, using 14% CO2, 5% O2, 4% H2O and balance N2 at 40° C. Desorption was performed at 60° C. for one hour by sweeping argon gas (30 mL/min). Control experiments were also conducted at 100° C., the more largely used value, but differences in desorption efficiency between the two temperatures were not significant. Complex mixtures of diamines containing TEPA were also studied by Wifong et al. in post-combustion gas mixture conditions, as reported in a recent patent.28 They have disclosed that ethylenimine oligomer (EI423), TEPA, pentaethylenehexamine and hexaethyleneheptamine pelletized into silica-based supports showed a CO2 adsorption capacity higher than 1.7 mmol/g in a 10% CO2 stream. Good stability was displayed in the CO2 desorption temperature range (100-110° C.).28 A series of invention disclosures involving amine sorbents also report methods for capturing CO2 from the ambient air and adsorption performances either near or similar to the values listed above.29 30 Perhaps the most studied and widely used amine material in solid CO2 sorbents is poly(ethyleneimine) (PEI), due to its high content of primary and secondary amine groups. Xu et al. have developed a composite of linear PEI (50%)-mesoporous molecular sieve (MCM-41) with a CO2 adsorption capacity as high as 215 mg/g at 75° C. and 99.8% bone-dry CO2 introduced at a flow rate of 100 mL/min.31 Li et al. reported 202 mg/g adsorption capacity at 105° C. and 1 atm for 60% PEI loading under a pure CO2 stream (60 mL/min). Additionally, the authors have conducted adsorption experiments under 15% CO2 conditions and the sorption capacity was 132 mg/g.32 Branched PEI (10-70%) infused into a porous silica support was also investigated and the resulting composite material achieved high CO2 sorption capacities of 4 up to 13 mol/g at 25° C., 10% CO2 and 2% H2O).33 Regardless of the molecular architecture of linear versus branched, the adsorption capacity depended on the PEI molecular weight.32 Also, the desorption rate of CO2 was markedly slower for linear PEI than for branched PEI, as was the enthalpy of CO2 adsorption.34 According to a disclosure by Eisenberger, PEI displayed good thermal stability over consecutive adsorption-desorption cycles performed in both humid and dry atmospheric CO2 conditions, which suggested the potential for cyclic stability.35 Because PEI was affected by oxidation when exposed to conditions simulating a process upset, combining high oxygen partial pressures and elevated temperatures, more oxidatively stable sorbents have been sought. For example, Wang et al. have used composite materials made by infusing SBA-15 with polyallylamine (PAA).36 They have found that PAA displayed better resistance to thermal degradation than PEI-based homologues. The best CO2 adsorption performance was achieved at 65% PAA loading (109 mg CO2/g) at 140° C. and 10% CO2 stream. In another study, Bali et al. reported that PAA adsorbents were more stable than branched PEI counterparts at elevated temperatures (110° C.) and high O2 concentrations (21%) during humid oxidation conditions.37 PAA-containing samples retained about 88% of their CO2 capacity irrespective of the treatment conditions. Alkhabbaz et al. have functionalized PAA with guanidine and found that the modified PAA sorbents presented better working capacity at high temperature (120° C.) than the control PAA ones under dry 10% CO2 conditions.38 Recently, linear poly(propyleneimine), PPI, was prepared and determined to be a more oxidatively stable sorbent.12 The PPI compounds used, ranging from 700 Da to 36,000 Da in molecular weight, were more efficient at CO2 capture than linear PEI homologues in a 400 ppm CO2 stream, and they retained 65-83% of their CO2 capacity after harsh oxidative treatment.12,15,39 In contrast, only 20-40% retention was recorded for linear PEI under similar conditions. In addition, branched PPI prepared by ring-opening polymerization of azetidine was also found as a promising alternative to PEI-based adsorbents.13
To overcome limitations in CO2 adsorption performance due to limited thermal and oxidative stability, synthesis of new solid-supported amine-rich sorbents continues.40 It is known that thermal stability of aromatic amines and amides is higher than that of aliphatic counterparts. In line with this idea, Mane et al. synthesized a series of porous, amine-rich polymers that were thermally stable in the 300° C.-500° C. temperature range.41 The maximum CO2 capacity recorded at 25° C. was 208.3 mg/g at 0° CO2 bar and highly pure CO2 stream (99.999%). For experiments performed under the same conditions but at 25° C., the adsorption capacity was as high as 164.1 mg/g.41 Puthiaraj et al. post-synthetically functionalized aromatic polymers with diethyleneamine yielding microporous porous materials that were thermally stable and showed CO2 adsorption capacities of 216.0-231.6 mg/g at 25° C. and 1 bar CO2.42 It should be noted that many of the examples cited above that appear to have high uptake capacities were tested under conditions that are not relevant to practical carbon capture, for example using pure CO2 and/or very low temperatures. It is expected that impregnation of alkyl-aryl small molecules into various mesoporous substrates will yield composite materials that exhibit better thermal and oxidative stability than PEI, the benchmark amine polymer used in prototype DAC and post-combustion capture technologies.
The mesoporous silica SB A-15 or mesoporous alumina supports were functionalized with Ph-XX-yy using a wet impregnation method. In a typical synthesis process, the desired amount of Ph-XX-YY was dissolved in methanol (10 mL). In a separate round bottom flask, the SBA-15 or mesoporous alumina support material (200 mg) was added to 50 mL of methanol and stirred vigorously for 1 h. Subsequently, the Ph-XX-YY solution was added to the SBA-15/methanol suspension and the final mixture was stirred overnight at room temperature. After that, the solvent was removed using rotary evaporation and dried overnight under high vacuum. The percentage loading of the organic content in the composite was varied by using equation 1.
where α represents the mass of added Ph-XX-YY (g) and β represents the mass of SBA-15 silica support or mesoporous alumina (γ-Al2O3) (g).
Thermogravimetric analysis was performed on a Netzsch STA409PG TGA to determine the weight loading of amine molecules in the composite materials. Weight loss between 120° C. and 900° C. was taken to represent the organic content of the material. Overall, the evaluated mass loss percentages attributed to organic content were close to the target values used in the composite material preparation. Elemental analysis also confirmed the loading of amine molecules in the mesoporous supports. Table A1 summarizes the amount of nitrogen (N) found in each sample. As expected, the content of N increased with the increase in organic loading. The determined weight loadings correspond to roughly 0-16 mmol N per gram SBA-15.
Nitrogen physisorption isotherms at 77 K were collected on a Micromeritics Tristar 3020 instrument after being degassed for 12 h at 110° C. The BET theory was used to determine specific surface area. Pore volume was calculated based on the amount of N2 adsorbed at p/p0 Of 0.95. Pore size distribution was evaluated by the BJH method available in the MicroActive software package by Micrometries. All these values are listed in Table A1.
CO2 adsorption capacities were determined gravimetrically by using a Q500 TGA instrument from TA Instruments. In a typical procedure, initially the materials were pretreated at 110° C. with a ramp rate of 5° C./min under inert He (90 mL/min) for 2 h. Then samples were cooled to 35° C. and equilibrated for 1 h. Subsequently, the gas flow was switched to a 400 ppm CO2/He for 12 h and the recorded mass gain was converted to the amount of CO2 adsorbed, and normalized by the dry mass of the sample. Table A1 summarizes the CO2 capacity of Ph-XX-YY/SBA-15 and 50% Ph-3-ED/γ-Al2O3.
Accelerated oxidative measurements were performed in the same Q500 TGA instrument from TA Instruments Q500 TGA. The samples were heated at 110 or 90° C. under a flow of ultrazero grade air for 24 h. The samples were then cooled to 35° C. and equilibrated for 1 h. Subsequently, the gas flow was switched to a premixed gas containing 400 ppm CO2/He for 12 h. The mass gain was recorded, converted to amount of CO2 adsorbed, and normalized by the dry mass of the sample.
The 60% Ph-3-ED/SBA-15 sorbent was investigated for the effect of relative humidity (30%) using an in-house custom-built fixed bed system at 35° C. and 400 ppm CO2 conditions. The dry and humid CO2 capacities were determined by using an in-house made glass fritted fixed bed system previously reported by Lee et al.43,44 CO2 adsorption was performed using 400 ppm CO2 balanced with He with constant flow rate of 90 mL/min at 35° C.[KDR2]
The CO2 adsorption performance of Ph-XX-YY/SBA-15 composites under dry direct air capture conditions was investigated gravimetrically by thermogravimetric analysis (TGA). After isothermal pretreatment at 110° C. to remove adsorbed water and trace CO2 adsorbed from the atmosphere, adsorption was performed at 35° C. for 12 h under dry 400 ppm CO2/helium (He) conditions. As shown in
The amine efficiency values of Ph-XX-YY/SBA-15 composites were further evaluated, as shown in
Additionally, the pore parameter analysis confirmed the influence of Ph-XX-YY molecular structure differences on CO2 capture performance and amine efficiency.
To better understand the correlation between CO2 uptake values at pseudo-equilibrium, amine loading and time, the adsorption kinetic curves were compared, as shown in
Additional evidence that the molecular architecture is another factor that can govern kinetics was obtained from plotting the normalized dynamic CO2 uptake curves for 50% Ph-XX-YY/SBA-15 composites. The shape of the two regions comprising the kinetic curves displayed in
Overall, the shape of the kinetic curves demonstrates that the adsorption process reached pseudo-equilibrium in about 10 min. At low amine loadings, CO2 molecules diffuse and form covalent and physical bonds with the amine sites. The result of these interactions is the formation of an ammonium carbamate ion. The stabilization of the carbamate adduct can create intra and intermolecular crosslinks between two amine sites. Saturation of amine sites with CO2 at 20% and 30% organic loading most likely does not lead to strong diffusional limitations, owing to limited pore filling by the amine molecules. At high amine loadings, the packing of amine molecules at the walls, especially within the pores, and the confinement conditions within the pores, can strongly influence the rate at which CO2 establishes contact with free amine sites, thereby establishing intra/intermolecular crosslinks. The progressive crosslinking to stabilize the carbamate adduct can limit diffusion of CO2 through the developing network and slows down the kinetics, as shown in
The long-term stability of the Ph-XX-YY/SBA-15 composite materials was assessed by using some of the highest loaded samples (50%) for multicycle runs, as they displayed, in general, the highest CO2 adsorption capacities (
Another important aspect reflected by
Because the working conditions did not reveal significant sorbent degradation, the best performing Ph-3-YY/SBA-15 composites were further subjected to an accelerated oxidative treatment at relatively high temperature. These experiments mimic real-life sorbent operation conditions that involve exposure to the oxygen containing air should a process upset occur combining exposure to elevated temperatures and O2 partial pressures simultaneously. It is important to understand whether degradation under oxygen exposure occurs and also to assess the extent to which it will impact the sorbent performance.
B. Ph-3-ED/γ-Al2O3 Composites
The best performing Ph-3-ED compound was also used to make a composite with γ-Al2O3, as the solid support, at 50% loading by wet impregnation. After the presence of the Ph-3-ED in the composite was confirmed by TGA and N2 physisorption measurements, the CO2 capacity was studied by using 400 ppm CO2/He at 35° C. for 12 h conditions. The 50% Ph-3-ED/γ-Al2O3 composite showed a capacity of 1.54 mmol CO2/gγ-Al2O3 and an amine efficiency of 0.11 mmol CO2/mmol N (Table A1). The 50% Ph-3-ED/γ-Al2O3 composite showed a slightly lower CO2 adsorption capacity as compared to the 60% Ph-3-ED/SBA-15 sorbent material (
Because DAC typically consists of capturing CO2 in the presence of substantial amounts of humidity in the air, it is essential to evaluate the effect of moisture on the CO2 adsorbent performance. Previous studies showed that under dry conditions, the interaction between CO2 and amines leads to formation of carbamates with a CO2/N ratio of 0.5. On the other hand, in presence of moisture, the interaction between CO2 molecules and amine sites can also result in the formation of bicarbonates with CO2/N ratio of 1.49-51 For example, Wang el al. demonstrated that, the CO2 adsorption capacity and the stability of the PEI (Mw=600)-based adsorbent increased significantly in the presence of moisture. The adsorbent showed an increase in CO2 adsorption capacities by 21% and 15% for CO2 concentration of 5000 and 400 ppm, respectively, with 80% RH.52 In the case of 400 pm CO2 adsorption, the amine efficiency increased from 0.18 to 0.2 mmol CO2/mmol N (˜11%). Wang el al. suggested that the enhancement in CO2 capacity for the 400 ppm condition is lower compared to the 5000 ppm due to competitive adsorption between CO2 and H2O molecules.52
The CO2 capacity obtained for dry 400 ppm CO2 conditions and using the fixed bed system was 1.6 mmol/gSiO2, which is similar to the CO2 capacity obtained from TGA (1.9 mmol/gSiO2). CO2 from the dry feed mixture breaks through the bed after 10 min and approaches saturation at approximately 150 min (
AThe CO2 capacity and amine efficiency of 60% PEI (600)/mesoporous carbon are adopted from Wang et al. (adsorption conditions: 25° C., 400 ppm CO2/N2, flow rate of 50 mL/min, RH = 80%).52[KDR3]
Composite materials made of alkyl-aryl amine small molecules (Ph-XX-YY) and porous substrates (SBA-15 and γ-alumina) were examined with a handful of techniques to determine their performance as sorbents for CO2 adsorption. Given the characteristics of each substrate, the largest amount of CO2 was adsorbed by 60% Ph-3-ED/SBA-15 and 50% Ph-3-ED/γ-Al2O3. In the case of using a silica SBA-15 support, the largest amount of CO2 was captured by 60% Ph-3-ED/SBA-15, 50% Ph-3-PD/SBA-15, 50% Ph-6-ED/SBA-15 and 50% Ph-6-PD/SBA-15. The amine efficiency values did not follow the same trend, likely due to pore clogging that hindered access of the CO2 gas to all amine sites. The optimum organic loading that led to the highest amine efficiency was 40%. The 50% Ph-3-ED/γ-Al2O3 composite showed a slightly lower CO2 adsorption capacity as compared to the 60% Ph-3-ED/SBA-15 material but higher than that of 50% loaded homologues.
The temperature-swing adsorption-desorption cycles revealed a stable working capacity for these composites demonstrating no significant deactivation. Subjected to accelerated oxidation treatment at elevated temperature (110° C.), the retained performance of the samples when compared to non-treated freshly made ones decreased to 22% (50% Ph-3-ED/SBA-15) and 10% (50% Ph-6-PD/SBA-15), respectively.
CO2 capacities obtained for 60% Ph-3-ED/SBA-15 from both TGA and fixed bed methods under dry conditions showed similar performance. CO2 adsorption under humid conditions with 30% relative humidity showed a significant, three-fold enhancement in the breakthrough CO2 capacity and a two-fold increase in the breakthrough time as compared to dry conditions in the fixed bed.[KDR4].
This study revealed that the structure of the two types of alkyl-aryl molecules was a key factor that dictated their properties towards CO2 adsorption. Conceivably, the diminished CO2 uptake performance observed for Ph-6-YY/SBA-15 samples when compared to that of Ph-3-YY/SBA-15 counterparts was due to the bulky molecular architecture of the Ph-6-YY amine sorbent. Yet, given their working capacity performance as well as their thermal stability, these Ph-XX-YY sorbents are appealing for integration into direct air capturing technology.
Alkyl-aryl amine rich molecules (Ph-XX-YY) impregnated into various porous substrates were examined for potential use as sorbents for CO2 capture from dilute and ultra-dilute gas streams such as flue gas and ambient air, respectively. Regardless of the substrate characteristics, the samples with the highest organic loadings (54%, 60%) captured the largest amount of CO2. The materials retained their good performance after temperature-swing absorption-desorption cycles and accelerated oxidation treatments.
Amine molecules or polymers supported on/in solid supports are known materials with diverse applications. Here we prepare a variety of composite materials made of alky-aryl molecules impregnated into solid supports that are thermally stable and show good CO2 adsorption performance in both dry and wet conditions. While solid-supported forms of other amine molecules and polymers are known, no materials like these have been reported for use in CO2 capture technologies.
Please provide a more detailed technical description.
Previously, and Global Thermostat have developed supported amine materials for CO2 capture from air. This is another invention developed with them, and is specifically a companion filing for the related composition of matter disclosure. This is an application disclosure. Supported amine materials are effective for extraction of CO2 from air.
These new materials offer potential advantages in that they pack in the pores of the supports different from conventional amine polymers. These materials perform close to the state of the art in CO2 capture from air, and the team has hypothesized ways to improve performance to surpass the state-of-the-art. Similar composite materials combining aryl-alkylamine molecules in porous oxide supports for CO2 capture are not known.
The study describes the use of alkyl-aryl amine reach molecules (Ph-XX-YY) as sorbents for capturing CO2 from dilute and ultra-dilute mixtures. These amines were impregnated into solid supports of various chemical compositions such as SBA-15, and γ-alumina. The organic loading of the composite Ph-XX-YY-based supports was in the 20%-60% mass range. In the case of each substrate, the high amine-loading samples (50%-60%) absorbed the largest amount of CO2 (using 400 ppm streams, at 35° C.). For example, the CO2 absorption capacity of 60% Ph-3-ED/SBA-15 was 1.9 mmol CO2/gSiO2, those of 50% Ph-3-PD/SBA-15 and 50% Ph-6-ED/SBA-15 were 1.23 mmol CO2/gSiO2 and 0.08 mmol PD/SBA-15 material exhibited the highest amine efficiency, 0.1 mmol CO2/mmol N. Intermediate organic loading (aka 40%) gave better performance in terms of amine efficiency: 0.13 versus 0.11 mmol CO2/mmol N for Ph-3-ED/SBA-15 (40%, 50%). Interestingly, in the case of Ph-6-PD/SBA-15 the amine efficiency flattened to an average value of 0.04 mmol CO2/mmol N. Overall, the PH 3-YY/SBA-15 composites showed a higher CO2 uptake performance than the PH-6-YY/SBA-15 homologues. This trend was also evident from the shape of the kinetic adsorption curves. These curves consisted of two distinct regions: one abruptly linear corresponding to the initial uptake that ‘curved’ to the other almost flat, referred to as the pseudo-equilibrium region, which asymptotically approaches the true equilibrium uptake. The highly concentrated samples approached the asymptotic regime of the curve the fastest, behavior associated with their fastest CO2 uptake. The pseudo-equilibrium region was then more drawn out, approaching the true equilibrium more gradually. The exception was the 50% and 40% Ph-6-ED/SBA-15 samples that displayed slower kinetic behavior than the intermediate and low concentration ones in the initial linear regime. These data together suggest that the bulky molecular geometry of Ph-6-YY may hamper Ph-6-YY/SBA-15 composites from performing similarly to the Ph-3-YY/SBA-15 counterparts, despite their higher amine content. In addition, their packing at the pore walls and within the supports together with the confinement characteristics adds to the complex landscape of interactions that govern the properties of these materials.
In order to examine the effect of the solid substrate on CO2 adsorption performance, a 50% Ph-3-ED/γ-Al2O3 composite was prepared. After TGA and N2 physisorption measurements confirmed successful impregnation of Ph-3-ED, the measured CO2 adsorption capacity was 1.54 mmol CO2/g γ-Al2O3 and the amine efficiency was 0.11 mmol CO2/mmol N. The CO2 uptake of this sample was higher than that of the similarly concentrated samples (50%) prepared using the SBA-15 support.
Because the high organic loading samples were the best performers in terms of CO2 uptake, they were further subjected to temperature-swing adsorption-desorption cycles and accelerated oxidation treatments. After 25 cycles of 1 h adsorption of 400 ppm CO2 (35° C.) followed by 10 min desorption in He (90° C.), 60% Ph-3-ED/SBA-15 retained up to 82% of its initial amine efficiency and 50% Ph-3-PD/SBA-14 retained 44.5% of the amine efficiency, with respect to the full uptake values recorded for 12 h of adsorption time in the absence of temperature-swing cycles. This value was lower for 50% Ph-6-ED/SBA-15 (40%) and 50% Ph-6-PD/SBA-15 (25%). One of the most important findings revealed by these experiments was the ability of all composites to maintain a stable working capacity, regardless of the trends in amine efficiency. The retained amine efficiency values were reduced when the best performing composite, Ph-3-YY/SBA-15, was exposed to 21% 02/He for 24 h at elevated temperatures (90° C. and 110° C.). The interactions with oxygen molecules caused diminished performance: only 39% (50% Ph-3-ED/SBA-15) and 20% (50% Ph-3-PD/SBA-15) of the original amine efficiencies were retained at 90° C. At 110° C. the values were 20% and 13%, respectively. These data confirm the idea that a bulky molecular architecture of Ph-6-YY did not favor high CO2 adsorption performance. Given their demonstrated properties, Ph-3-YY/SBA-15 composites, especially Ph-3-YY/SBA-15, are promising materials that can be potentially integrated into the DAC and other CO2 adsorption technologies.
What are the commercial applications for the invention?
The capture of acid gases from gas mixtures, including (CO2, S)2, NO, NO2, H2S, etc.).
Global Thermostat has an interest in CO2 and they have developed these materials with us for this purpose.
What are the advantages of the invention mover present technologies?
The composite materials with a high content of amine disclosed here have good thermal stability in the temperature interval with CO2 capture technologies operate. These materials display good adsorption performance in direct air CO2 capture both in dry and wet conditions.
Number | Date | Country | |
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63034243 | Jun 2020 | US |