CO2 Absorption Capacity Research Articles

Enhancing carbonation and thermal insulation of reactive magnesium oxide cement (RMC)-based 3D printable pastes with cenospheres

Reactive magnesium oxide cement (RMC) has been proposed as a sustainable alternative to ordinary Portland cement (OPC) due to its lower production temperature and ability to permanently sequester carbon dioxide (CO2) through carbonation. However, mixtures with only RMC can have significantly reduced CO2 absorption capacity due to limited CO2 diffusion, thereby compromising the performance of RMCs. This paper demonstrates the adoption of cenospheres, an industrial waste, as a lightweight filler in RMC-based 3D printable composites to enhance carbonation and improve thermal insulation. This work investigates the effect of incorporating different dosages of cenospheres on the rheological properties, compressive strength, thermal conductivity, and microstructural development of the RMC mixtures using X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The study reveals that substituting 30 % of RMC with cenospheres not only improves the printability and carbonation of the composite but also results in a 16 % reduction in density, achieving 1.72 g/cm³, and reduces the thermal conductivity by 59 % compared to the control without cenospheres to 0.63 W/(m·K). The findings provide valuable insights for developing lightweight 3D printable RMC-based composites.

Evaluating solvent efficiency for carbon capture: Comparative analysis of temperature, concentration and diffusivity effects

In the pursuit of efficient carbon capture technologies, the selection and design of solvents play a pivotal role, directly impacting various crucial factors such as CO2 absorption capacity, equipment size, and regeneration energy requirements. The primary focus is on optimizing solvent systems through a comprehensive analysis of intermolecular interaction intensity, diffusion coefficient, and intra-molecular interaction intensity. This study employs a molecular dynamics simulation model to identify the most suitable solvent system by assessing the effect of operating variables like temperature, concentration, interaction intensity, and diffusivity of various single and blended amine systems. The assessment utilizes the radial distribution function and mean square displacement analysis. The results indicate that intermolecular interactions with CO2 are most significant in 30 wt% 2EAE, 40 wt% 2DMAE and 10% DMCA with 20% MCA ratio concentrations. TMPAD, in particular, stands out for its high repulsive interaction and low energy requirement for breaking the carbamate/bicarbonate ion. Diffusion behavior in various observed solvent systems is as follows: EAE > MEA > DMAE > MAE-DEAB > MAE-DMA2P > EAE-TMPAD > AMP-PZ > EAE-DEAB > MAE-TMPAD > EAE-DMA2P > MAE-DMAE > EAE-DMAE > TMPAD > MEA-AMP > DMA2P > DMCA-MCA > DEAB > MEA-PZ. Moreover, elevated temperatures facilitate enhanced diffusivity, leading to accelerated mass transfer rates. This implies the possibility of reducing the size of absorber units and lowering energy consumption. Further studies on heat of absorption and kinetic characteristics of solvent blends are necessary to ensure their practical applicability in carbon capture and industrial operations.

Structure effects of imidazolium ionic liquids on integrated CO2 absorption and transformation to dimethyl carbonate

The integration of chemical absorption of CO2 and in situ transformation to highly valuable chemicals is a promising process as an alternative toward fossil fuels. Here, three imidazolium ionic liquids (ILs), 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium 1,2,4-triazole ([Bmim][Tz]), and 1-butyl-2,3-dimethylimidazolium 1,2,4-triazole were synthesized to absorb and activate CO2 by the formation of CO2-adducts, which can be in situ converted into dialkyl carbonates with alcohols (ROH, R = CH3, C2H5, and C4H9) in solvent diiodomethane under ambient temperature and pressure. The results show [Bmim][Tz] exhibits the best CO2 absorption capacity and dimethyl carbonates (DMC) yield, where CO2 capacity is up to 0.216 gCO2/gIL and DMC yield (based on methanol) is as high as 20.2 %. The structures of imidazolium ILs have significant effects on the absorption of CO2 and subsequent transformation process. Fourier transform infrared and carbon nuclear magnetic resonance spectroscopies demonstrate ILs structures influence binding sites for CO2 absorption, which can combine with CO2 to form CO2-adducts, zwitterion [Bmim-CO2], and [Tz-CO2]−. Furthermore, density functional theory calculations verify the structure effects (binding sites and steric hindrance) of ILs on the activation of CO2 and methanol, through the elongated CO bond lengths of CO2-adducts and O-H bond lengths of methanol in IL-methanol complexes, respectively, leading to different DMC yields. The integrated process is promising for the energy-efficient capture and utilization of CO2 under ambient conditions.

Experimental study on the performance of a highly efficient NE‐1 absorbent for CO2 capture

AbstractCO2 capture by absorption and stripping with aqueous amine is a well‐understood and widely used technology. However, drawbacks still exist in the practical applications, such as high energy consumption and easy degradation of the absorbents during the desorption process. In this paper, a novel NE‐1 absorbent was developed, and its suitable operating conditions were determined: concentration (45 wt.%), absorption temperature (40 °C), and desorption temperature (100 °C). The NE‐1 absorbent exhibits a high CO2 absorption capacity of 3.73 mol/kg, 1.33 times that of 30% monoethanolamine (MEA). After optimizing with carbamide as a corrosion inhibitor, 45% NE‐1a1 may attain an effective CO2 capacity of 2.5 mol/kg and over 70% desorption rate in five cycles, demonstrating excellent cycling stability performance. The research results have significant implications for developing an efficient and stable commercial carbon capture solvent and promoting the development of carbon reduction technologies. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Precision Calcination Mechanism of CaCO3 to High‐Porosity Nanoscale CaO CO2 Sorbent Revealed by Direct In Situ Observations

AbstractDeploying energy storage and carbon capture at scale is hindered by the substantial endothermic penalty of decomposing CaCO3 to CaO and CO2, and the rapid loss of CO2 absorption capacity by CaO sorbent particles due to sintering at the high requisite decomposition temperatures. The decomposition reaction mechanism underlying sorbent deactivation remains unclear at the atomic level and nanoscale due to past reliance on postmortem characterization methods with insufficient spatial and temporal resolution. Thus, elucidating the important CaCO3 decomposition reaction pathway requires direct observation by time‐resolved (sub‐)nanoscale methods. Here, chemical and structural dynamics during the decomposition of CaCO3 nanoparticles to nanoporous CaO particles comprising high‐surface‐area CaO nanocrystallites are examined. Comparing in situ transmission electron microscopy (TEM) and synchrotron X‐ray diffraction experiments gives key insights into the dynamics of nanoparticle calcination, involving anisotropic CaCO3 thermal distortion before conversion to thermally dilated energetically stable CaO crystallites. Time‐resolved TEM uncovered a novel CaO formation mechanism involving heterogeneous nucleation at extended CaCO3 defects followed by sweeping reaction front motion across the initial CaCO3 particle. These observations clarify longstanding, yet incomplete, reaction mechanisms and kinetic models lacking accurate information about (sub‐)nanoscale dynamics, while also demonstrating calcination of CaCO3 without sintering through rapid heating and precise temperature control.

Investigations to intensified hydrogen production via sorption enhanced water gas shift reaction

Sorption enhanced water gas shift (SEWGS) reaction for the equilibrium enhanced hydrogen production is investigated using lithium orthosilicate (Li4SiO4) sorbents mixed with 1 wt% Pt/Al2O3 catalysts. The Li4SiO4 sorbents, synthesized using novel surfactant-mediated method, are characterized by ultra-fast CO2 capture rates with CO2 absorption capacity in the range of 319–333 mgCO2·g−s1. The thermogravimetric analysis results show ∼ 26 wt% of the carbonation sites are participating in the fast CO2 absorption (∼ 298 mgCO2·g−s1·min−1). The use of these sorbents with 1 wt% Pt/Al2O3 catalysts in the water gas shift reaction show a 103% increase in the hydrogen yield compared to the equilibrium concentration at 600◦C. The Li4SiO4 sorbent-catalyst combination show a shift in the equilibrium by preventing the reverse reaction in the temperature range of 600–650◦C. The SEWGS experiments show that the CO2 absorption capacities, and consequently the hydrogen yields, are affected by the diffusional resistance across Li2CO3 and Li2SiO3 product domains in the sorbent. The Li4SiO4 conversion rates during the SEWGS reaction are measured by sampling at different points in the SEWGS reaction and subsequent Rietveld analysis of the XRD patterns. The XRD results suggest the decrease in CO2 absorption rates as a result of the formation of additional Li2CO3 and Li2SiO3 fractions with decreasing Li4SiO4 phase in this nano-structured composite.

ESTIMATIONS OF CARBON STORAGE AND ECONOMIC VALUE OF MANGROVE FOREST ON THE NORTH COAST OF CAWAN ISLAND, INDRAGIRI HILIR

Mangrove forests are important for human life and the surrounding environment, one of which is as a CO2 absorber and carbon storage. The North Coast of Cawan Island in Indragiri Hilir has a relatively good mangrove forest that is estimated to absorb and store more carbon. This study aims to (1) estimate the value of carbon storage in stands (stems), below-ground carbon (roots), litter, and sediment of mangrove forests, (2) estimate the CO2 absorption capacity of mangrove forests, and (3) estimate the economic value of absorption CO2 by mangrove forest on the North Coast of Cawan Island. The station determination method uses purposive sampling of five stations, each consisting of a transect with three plots measuring 10x10 m2. Measurement of stem and root biomass using the allometric method. Litter biomass measurement used the dry weight weighing method, and sediment carbon measurement used the Loss on Ignition (LOI) method. The result showed that average carbon storage in stems was 34.56 tons/ha, roots were 16.41 tons/ha, litter was 0.10 tons/ha, and sediment was 32.91 tons/ha. The estimated ability of mangrove forests to absorb CO2 is an average of 187.10 tons/ha or 636,450.59 tonnes for the entire North Coast of Cawan Island. The estimated economic value of mangrove forest carbon is an average of IDR 149,809,099 /ha or IDR 509,599,619,024 for the entire North Coast of Cawan Island.

Assessing Carbon Dioxide (CO2) Absorption Potential of Forests Around Landslides Along the Trans Palopo-Toraja Highways

Forests are crucial in absorbing carbon dioxide (CO2) from the atmosphere through photosynthesis and storing the carbon in its biomass. This research aimed to assess the potential for CO2 absorption of forests around landslides along the Trans Palopo-Toraja highways. This research employed a destructive sampling to measure understorey and litter biomass. Furthermore, it measured the biomass of understorey plants and litter with a destructive method. The 12 measurement plots were purposively placed on the landslide points to represent various vegetation conditions. The results revealed the presence of 77 plant species, totaling 554 individuals on the measurement plots. Plot 4 and Plot 1 showed the highest and lowest carbon absorption potential at 790.39 tons/ha and 199.63 tons/ha, respectively. The estimated average absorption of 12 plots was 461.75 tons/ha. Tree-level vegetation had the highest carbon absorption value due to its bigger diameter and CO2 absorption capacity than saplings and poles.

Creation of the Route of Bamboo, a Contribution to Net Zero by 2050 in Vietnam

The Phu An bamboo village, created in 1999, maintains over 200 taxa of living bamboo, collected in Viet Nam, Laos and Cambodia, and was awarded the UNDP Equatorial Prize in 2010. This ex situ conservation not only provides data for basic research and preserves biodiversity resources, but also contributes to actions on CO2 to reduce the greenhouse effect in climate change and create sustainable livelihoods for the community. From the Phu An Bamboo village, the "Bamboo Route" has been built since 2016 from the north to the south of Viet Nam, with the aim of multiplying bamboo in situ conservation sites, associated with research programs and public awareness actions on the importance and environmental benefits of bamboos. Along the bamboo route, an ex situ conservation site has been developed at Dong Thap with plants of 67 different vernacular species, another at Phan Rang, in the arid region, with 62 species, and a third at Dak Nong, where the climate is more favourable, with 12 different vernacular species from the in situ conservation site at Chieng Ban, Son La, where 19 vernacular species have been recorded. Thanks to its fast-growing characteristics and large biomass production, bamboo plays an important role in carbon sequestration. Research to mesure CO2 absorption was done in three different habitats on three different bamboo species. The CO2 absorption capacity of Bambusa blumeana Schultes in Gao Giong, Dong Thap province, indicates an important role of this thorny bamboo under climate change conditions. On the " Route of Bamboo", we studied also the surface area of bare soil from north to south, except in the Mekong Delta, we can plant more than 200,000 ha of thorny bamboo to complete the existing surface area of 1.5 million ha which could contribute 30% of Viet Nam’s CO2 absorption. This enables us to estimate how planting 50% of these areas could contribute to Viet Nam’s Net 0 2050 target.

Corrosion Behavior of Carbon Steel in Diethylenetriamine Solution for Post-combustion CO2 Capture.

In the realm of postcombustion carbon capture, diethylenetriamine (DETA), recognized for its substantial CO2 absorption capacity, presents a formidable challenge due to its corrosive impact on equipment. This study delves into the corrosion behavior of 20# carbon steel immersed in DETA solutions under varying conditions, employing weight loss and electrochemical methods. The investigation incorporates scanning electron microscopy/energy-dispersive spectroscopy and X-ray diffraction analyses for characterization. Corrosion experiments were also conducted in monoethanolamine (MEA) solutions for a comparative analysis. Results from the corrosion tests in DETA solutions mirror the temperature-dependent corrosion rate (CR) observed in MEA. However, a distinctive trend emerges as the CO2 loading of DETA increases from 0.2 mol CO2/mol amine to 1.2 mol CO2/mol amine, leading to a continuous decrease in the CR of carbon steel-contrary to MEA solutions. This anomaly is attributed to DETA's robust complexing ability with metal ions and its elevated solubility of Fe2+ in solution. Additionally, an examination of the corrosion mechanism in the presence of oxygen was conducted through characterizing the specimen surface and solution precipitates postexperiment. The absence of a protective FeCO3 layer can be attributed to insufficient concentrations of free Fe2+ and CO32- in the solution, failing to achieve the minimum saturation required for protective film formation. The insights gained from studying the corrosion behavior of carbon steel in DETA solutions lay the groundwork for subsequent developments in corrosion inhibitors.

Carbon stock estimation in post-mining reclamation area of open coal mining in PT Berau Coal, Berau, East Kalimantan

Postmining land reclamation and revegetation activities play an important role in restoring vegetation, degraded land and controlling climate change because CO2 is sinking from the atmosphere due to the impact of mining activities. This study aims to estimate the potential for above-ground and below-ground carbon and CO2 absorption capacity at the Binungan Mine Operations Site (BMO), PT Berau Coal, Berau, East Kalimantan. Vegetation analysis was used to estimate the potential carbon stock and CO2 absorption capacity at plant ages 1-10 years using the purposive sampling method of 5 plots (20 x 20 m) each in the post-mining area studied. Biomass and carbon stocks were estimated using existing allometric models. The results showed 14 tree species from 10 families dominated by Fabaceae. Biomass was estimated at 1.13 - 128.31 Mg ha-1, carbon stocks were 0.53-60.3 Mg ha-1, and CO2 absorption was 1.95 - 221.32 Mg ha-1. Reclamation and revegetation in 10 year-old plants on reclamaied land can restore biomass, carbon stock, and CO2 absorption capacity of 70% from the initial baseline.

Unleashing the potential of Boratrane and Silatrane: A game-changing approach for enhanced boron- and silicon- incorporation in phenol-formaldehyde resins and their thermal stability

In this study, we present an innovative and cost-effective method for the preparation of phenolic resin (PR) containing boron and silicon (BPR and BSiPR) using boratrane and silatrane. Through a one-pot synthesis via a sol-gel process, 3BPR and 3B5SiPR are successfully synthesized, utilizing boratrane and silatrane as the sources of boron and silicon. Our results demonstrate the effective introduction of boron and silicon elements into the PR matrix through the formation of BO4 (borate) and SiO4 (silicate) structures, as evidenced by Cph-O-B and B-O-Si linkages. Notably, the utilization of boratrane in the synthesis of 3BPR leads to the formation of a uniform structure of BO4, as confirmed by 11B-NMR analysis. Furthermore, the resulting resins exhibit an improved char yield of 72 % at 900 °C. The formation of borate and silicate species effectively reduces the content of phenolic hydroxyl groups, thus contributing to a decrease in weight loss during the carbonization process. Additionally, the migration of boron and silicon into the carbon structure promotes the formation of B4C and B8C crystal structures, resulting in the carbonization of resins and the formation of a graphene-like structure, as confirmed by Raman spectroscopy, which exhibits a broad 2D-band. The obtained carbon materials possess both Lewis acid and basic sites. The presence of Lewis acid sites was characterized through pyridine-adsorbed FTIR, while the Lewis basic sites and CO2 absorption were examined via TPD-CO2 analysis. The CO2 absorption capacities of 3BPR and 3B5SiPR were found to be 0.475 and 0.518 mmol/g, respectively.

Enhancing Natural Rubber Composites with Spent Coffee Ground: Physical Properties, Odor Absorption, and Processing

AbstractThis research aims to enhance natural rubber (NR) properties by incorporating spent coffee grounds (SCGs). Scanning electron microscope (SEM) reveals well‐dispersed SCG particles in the NR matrix without interaction. Shore A hardness notably increases by up to 49.90 (19% higher than unmodified), but tensile and tear strength decline with higher SCG levels. Optimal tear strength occurs at 10 phr of SCG due to uniform dispersion. The 300% modulus remains unchanged. The odor of composites (CO2 absorption) sees a 69.2% increase at 25 phr, while odor absorption efficiency peaks at 2%. Additionally, unmodified SCG affects scorch time (2.12%–23.40% increase from 1 to 20 phr) and cure time (3.12% to 76.82% improvement from 1 to 20 phr). These findings showcase improved hardness, enhanced CO2 absorption capacity, and effective odor control. Additionally, this study sheds light on the influence of SCG on processing times, contributing valuable insights for eco‐friendly applications.

Assessing economic trade-off for advances in amine-based post-combustion capture technology

The study aims to evaluate the trade-off relationship between reducing energy consumption through technological improvements, including process modifications and the use of CO2-absorbing solvents, and the increased costs associated with their implementation in power and industrial sectors. Additionally, the economic potentials of heat-integrated CO2 capture and amine solvent degradation are explored. Four representative cases are considered, involving changes to lean vapor compression (LVC) and a blended amine solvent from a monoethanolamine (MEA) benchmark process. The findings indicate that the characteristics of combustion processes have a minor impact on the energy intensity of amine-based CO2 capture, but they significantly affect its cost. This is primarily due to substantial variations in fuel costs and equipment size. Technological advancements, such as process modifications and the use of amine solvents with high CO2 absorption capacity, play a crucial role in reducing both the energy consumption and costs associated with CO2 capture. However, the study suggests that careful consideration is needed when utilizing expensive amine solvents with high CO2 absorption capacity, particularly in situations prone to solvent degradation, as solvent loss can significantly impact the economic viability of CO2 capture.

Synergistic promotions between high purity H2 production and CO2 capture via sorption enhanced chemical looping reforming

Hydrogen energy, a promising clean source, holds potential to combat global warming. To achieve efficient and low-carbon H2 production, we proposed an isothermal sorption-enhanced chemical looping reforming (SE-CLR) process to realize the high-purity hydrogen production and in-situ CO2 capture at mild temperatures (550–650 °C). For practical application, the process is characterized to use Fe-Ni double metal oxide particles as steam methane reforming oxygen carriers, and K2CO3-promoted Li4SiO4 particles as CO2 sorbent. The oxygen transfer capacity of metal oxide matintained high at 57.4%, and the K-Li4SiO4 absorbents remained at 22.5% CO2 absorption capacity over 200 isothermal absorption-regeneration cycles. Conducting a synergistic conversion mechanism within double metal oxides and absorbents, and adjusting the absorbent-to-metal oxide mass ratio to 7:4, enhanced hydrogen purity to 92% and CO2 uptake to 95%. Furthermore, in-situ CO2 removal in CLR processes achieved methane conversion and H2 production rates equivalent to conventional CLR processes under the same reaction conditions, but at temperatures ∼60 °C lower. The effects of the reaction temperature, pressure, steam-to-methane and methane-to-solid ratios on SE-CLR performance were studied systematically. Finally, stable hydrogen production with a purity of 91%–89% and CO2 uptake of 94%–91% were obtained over 25 CLR cycles, with minimal changes in mechanical strength of particles.

Design of a Portable Analyzer to Determine the Net Exchange of CO2 in Rice Field Ecosystems.

Global warming is influenced by an increase in greenhouse gas (GHG) concentration in the atmosphere. Consequently, Net Ecosystem Exchange (NEE) is the main factor that influences the exchange of carbon (C) between the atmosphere and the soil. As a result, agricultural ecosystems are a potential carbon dioxide (CO2) sink, particularly rice paddies (Oryza sativa). Therefore, a static chamber with a portable CO2 analyzer was designed and implemented for three rice plots to monitor CO2 emissions. Furthermore, a weather station was installed to record meteorological variables. The vegetative, reproductive, and maturation phases of the crop lasted 95, 35, and 42 days post-sowing (DPS), respectively. In total, the crop lasted 172 DPS. Diurnal NEE had the highest CO2 absorption capacity at 10:00 a.m. for the tillering stage (82 and 89 DPS), floral primordium (102 DPS), panicle initiation (111 DPS), and flowering (126 DPS). On the other hand, the maximum CO2 emission at 82, 111, and 126 DPS occurred at 6:00 p.m. At 89 and 102 DPS, it occurred at 4:00 and 6:00 a.m., respectively. NEE in the vegetative stage was -25 μmolCO2 m2 s-1, and in the reproductive stage, it was -35 μmolCO2 m2 s-1, indicating the highest absorption capacity of the plots. The seasonal dynamics of NEE were mainly controlled by the air temperature inside the chamber (Tc) (R = -0.69), the relative humidity inside the chamber (RHc) (R = -0.66), and net radiation (Rn) (R = -0.75). These results are similar to previous studies obtained via chromatographic analysis and eddy covariance (EC), which suggests that the portable analyzer could be an alternative for CO2 monitoring.

Assessment of CO2 Capture in FA/GGBS-Blended Cement Systems: From Cement Paste to Commercial Products

The cement industry’s intricate production process, including kiln heating and fossil fuel use, contributes 5–8% of global CO2 emissions, marking it as a significant carbon emitter in construction. This study focuses on quantifying CO2 capture potential in blended cement systems through the utilisation of phenolphthalein and thermalgravimetric methodologies. Its primary objective is to assess the CO2 absorption capacity of these blended systems’ pastes. Initial evaluation involves calculating the carbon capture capacity within the paste, subsequently extended to estimate CO2 content in the resultant concrete products. The findings indicate that incorporating ground granulated blast-furnace slag (GGBS) or an ettringite-based expansive agent did not notably elevate carbonation depth, irrespective of their fineness. Conversely, the introduction of fly ash (FA) notably augmented the carbonation depth, leading to a substantial 36.4% rise in captured CO2 content. The observed distinctions in carbonation behaviour primarily stem from variances in pore structure, attributable to distinct hydration characteristics between GGBS and FA. Thermal analysis confirms the increased stabilisation of CO2 in FA blends, highlighting the crucial influence of material composition on carbonation and emission reduction. Incorporating both GGBS and FA notably diminishes binder emissions, constituting almost half of PC-concrete emissions. Initially, 60% GGBS shows lower emissions than 50% FA, but when considering CO2 capture, this emission dynamic significantly changes, emphasising the intricate influence of additives on emission patterns. This underscores the complexity of evaluating carbonation-induced emissions in cementitious systems.

Analysis and insights of the second-generation ternary AMP-PZ-MEA solvents for post-combustion carbon capture: Absorption-regeneration performance

This work comprehensively investigates absorption and regeneration performance of the second-generation AMP-PZ-MEA in comparison with the first-generation AMP-PZ-MEA, the benchmark 5 M MEA, and the conventional MEA at the same amine concentration. The performance indicators include CO2 absorption capacity, mass transfer coefficient, CO2 removal percentage, amount of desorbed CO2, initial CO2 desorption rate, and regeneration heat duty. Both 6 M (i.e., 2:2.5:1.5, 1.3:3.2:1.5, and 0.95:3.55:1.5) and 7 M (i.e., 2:2.5:2.5, 1.3:3.2:2.5, and 0.95:3.55:2.5) second-generation blends show more promising overall absorption and regeneration performance than 5 M, 6 M, and 7 M MEA. In comparison with the first-generation blend, 6 M and 7 M second-generation blends deliver more favorable mass transfer rate. Interestingly, an increase of PZ:AMP molar ratio accelerates mass transfer and absorption capacity but unfavorably affects solvent regeneration. Also, high viscosity of the second-generation 7 M blend (especially, at its equilibrium CO2 loading) retards the solvent regeneration. The key success for a formulation of AMP-PZ-MEA is appropriate PZ:AMP molar ratio and total amine concentration. Too high and too low PZ:AMP molar ratio lead to (i) solvent precipitation and (ii) imbalance of absorption and regeneration performance. Three standouts are recommended. 2.5:0.5:3 is attractive due to its low regeneration heat duty (42.1% lower than that of 5 M MEA). In terms of mass transfer coefficient, 0.95:3.55:1.5 shows 148.6% higher than 5 M MEA. 2:2.5:1.5 is also favorable according its high mass transfer coefficient (91.3% greater respecting 5 M MEA) and low regeneration heat duty (16.3% less than 5 M MEA).

Inhibiting effect of 2-amino-2-methyl-1-propanol on gelatinous product formation in non-aqueous CO2 absorbents: Experimental study and molecular understanding

Diamines or polyamines with two or more amino groups are suitable for formulating non-aqueous absorbents (NAAs) with high CO2 loading capacity and low regeneration energy consumption. However, these two types of amines in NAAs are prone to produce insoluble gelatinous products after absorbing CO2, resulting in difficult operation of the CO2 capture system. In this study, by using 2-amino-2-methyl-1-propanol (AMP) as an inhibitor, the insoluble gelatinous products of the aminoethylethanolamine (AEEA)-N-methyl-2-pyrrolidone (NMP) (A-A-N) and 3-(methylamino)propylamine (MAPA)-NMP (M-A-N) NAAs were successfully eliminated. The experimental results showed that the AMP-regulated NAAs possessed a high absorption rate, high CO2 loading capacity, excellent desorption efficiency, and stable recyclability. The reaction mechanism of CO2 absorption and the inhibitory mechanism of AMP on the formation of gelatinous products were comprehensively elucidated. Taking the A-A-N system as a representative, AEEA reacted with CO2 to form zwitterionic protonated carbamate species (AEEACO2−(P)H+(S)), which tended to self-aggregate via hydrogen-bond interaction, resulting in the formation of insoluble gelatinous products. With the introduction of AMP, the AMP-derived products could combine easily with AEEACO2−(P)H+(S) via strong electrostatic attraction to form ion pairs, preventing the AEEACO2−(P)H+(S) molecules from self-aggregating to form insoluble gelatinous products. The regeneration heat duty of the A-A-N system was 1.89 GJ∙ton−1 CO2, which was 49.9 % lower than that of the benchmark 30 wt% MEA. Overall, introducing AMP as a gelatinous product inhibitor was beneficial for the development of NNAs with high CO2 absorption capacity and low-energy consumption.

Experimental study on CO2 capture by MEA/n-butanol/H2O phase change absorbent.

Monoethanolamines (MEAs) are widely used for CO2 capture, but their regeneration energy consumption is very high. CO2 Phase change absorbents (CPCAs) can be converted into CO2-rich and CO2-lean phases after absorbing CO2, and the regeneration energy consumption can be reduced because only the CO2-rich phase is thermally desorbed. In this paper, a novel CPCA with the composition "MEA/n-butanol/H2O (MNBH)" is proposed. Compared with the reported MEA phase change absorbent, the MNBH absorbent has higher CO2 absorption capacity, smaller absorbent viscosity and CO2-rich phase volume. The MNBH absorbent has the highest CO2 absorption capacity of 2.5227 mol CO2 per mol amine at a mass ratio of 3 : 4 : 3. The CO2 desorption efficiency reaches 89.96% at 120 °C, and the CO2 regeneration energy consumption is 2.6 GJ tCO2-1, which is about 35% lower than that of the 30 wt% MEA absorbent. When the mass ratio of MNBH absorbent was 3 : 6 : 1, the CO2 recycling capacity was 4.1918 mol CO2 L-1, which is 76% higher than that of the conventional 30 wt% MEA absorbent. The phase change absorbent developed in this paper can reduce the desorbent volume by about 50% and has good absorption performance for CO2 in flue gas.