Amine Efficiency Research Articles

Effects of Alkyl Groups on Monoethanolamine Derivatives for Biomethane from Biogas Upgrading

Amine scrubbing is one of the key technologies for biogas upgrading to biomethane, which can be used to increase the calorific value of biomethane by separating out CO2 to meet the global demand for renewable energy. In this paper, several monoethanolamine (MEA) derivatives with alkyl groups as variables are screened as sorbents for the biogas upgrading process. The effect of alkyl groups on the efficiency of biogas upgrading, the effectiveness of sorbent regeneration, and the selectivity of CO2/CH4 during biogas upgrading are investigated. The analysis of biogas upgrading experiments with different MEA derivatives shows that methyl and butyl are more favorable for improving CO2 absorption and meeting the biogas upgrading effect of methane purity for a long period of time applicable in some countries, and ethyl is more conducive to the regeneration efficiency of amines. The results of the CO2 desorption heat calculations show that the CO2 desorption heat of ethyl monoethanolamine (EMEA) (66.67 kJ/mol CO2), formed by replacing a hydrogen near the nitrogen with an ethyl group, is significantly lower than those of methyl monoethanolamine (MMEA) (73.04 kJ/mol CO2) and butyl monoethanolamine (BMEA) (73.27 kJ/mol CO2), formed by replacing a hydrogen near the nitrogen with a methyl group and a butyl group, respectively. The CO2 desorption heats were significantly lower than those of MEA (82.12 kJ/mol CO2), suggesting that ethyl can significantly reduce the CO2 desorption heat of the amine compared to other alkyl groups. In the CO2/CH4 selectivity experiments, BMEA showed the fastest initial CO2 absorption rate of 0.83%/s, while dimethyl monoethanolamine (DMMEA) showed the lowest initial CO2 absorption rate of 0.16%/s. All amine solutions showed less than 1% absorption of CH4 and had high CO2/CH4 selectivity.

Amine-incorporated adsorbents with reversible sites and high amine efficiency for CO2 capture in wet environment

CO2 adsorption in wet environments is attractive but difficult in terms of the unsatisfied adsorption capacity and low efficiency of active sites. Herein, we report the fabrication of a thermal-responsive adsorbent with reversible amine sites by copolymerizing N-acryloyl glycinamide (NAGA), N-[3-(dimethylamino)propyl]methacrylamide (DMAPM), and styrene (ST). During adsorption at 20 °C, the tertiary amines of the DMAPM units stretch out and act as the strong sites in water. The adsorption capacity can reach 98 mL g−1, corresponding to the highest amine efficiency (0.99 mol CO2 per mol amine), which is superior to most reported adsorbents. When elevating temperature for desorption, these active sites are shielded in the adsorbent particles because of the formation of intramolecular hydrogen bonds between the NAGA and DMAPM units. The exquisite utilization of thermal responsiveness endows the adsorbents with reversible amine sites and high amine efficiency, making them promising in practical CO2 capture.

Sequential polymer infusion into solid substrates (SPISS): Impact of processing on sorbent CO2 adsorption properties

Solid sorbents made of small amine molecules and polyamines infused into mesoporous substrates are promising materials for CO2 capture technologies. To date, their preparation is mainly based on wet infusion with focus on increasing amine content by varying the structure of the amine sorbent and designing solid substrates of various pore parameters. Less explored in the field are changes in processing to afford efficient CO2 sorbents. In this study, branched poly(ethylenimine) (bPEI, Mw = 800 Da) alone and blends with linear poly(propylenimine) (LPPI, Mn = 6,700 Da) are infused into solid SBA-15 substrates by a method that varies the solution processing called sequential polymer infusion into solid substrates (SPISS). The reference 40 % bPEI-SBA-15 samples are split by two methods: split batch in dry suspension (SBD) and split batch in liquid suspension (SBL). Sequentially, alcoholic 10% of bPEI (non-blends) and 10% of LPPI (blends) solutions are introduced to afford the desired products. Under dry conditions, the resulting 50% bPEI-SBA-15 SBD & SBL sorbents display high CO2 capacities up to 3.47 mmol CO2/gSiO2 for simulated flue gas (10% CO2) and 2.62 mmol CO2/gSiO2 for direct air capture (DAC, 400 ppm CO2). Under humid DAC conditions the CO2 performance is further enhanced with an uptake of 4.62 mmol CO2/gSiO2 and amine efficiency of 0.22 mmol CO2/mmol N. Subjected to extended temperature swing adsorption kinetic cycling (20 cycles), the SPISS samples display stable working capacities and retain over 70% (blends) and over 90% (non-blends) of their initial 12 h adsorption performance. LPPI is demonstrated to be an effective water sorption limiting agent using dynamic vapor sorption measurements. Solid state NMR techniques reveal important insights into the dynamics of the amine polymers confined into SBA-15 pores, as impacted by processing conditions. The results suggest that the conformation of the polymers is different depending on the processing method, displaying relatively tight (SBD) and loose (SBL) packing. The simple solution processing approaches presented here show that processing variations may guide the design of solid amine sorbents with desirable properties relevant for integration into CO2 capture technologies.

Experimental and kinetics investigations of low-concentration CO2 adsorption on several amine-functionalized adsorbents

The rapid cleanup of endogenous CO2 has become a necessity in environmental control and life support systems (ECLSSs), to ensure crew safety and long-term task execution. The extensively used non-regenerable LiOH and soda lime adsorbents, although exhibit high CO2 storage capacities and fast kinetics, can hardly fulfill the demands of reduced launch weight and storage volume in the space- and load-limited ECLSSs. New CO2 adsorbents with desirable attributes including high CO2 uptakes, good selectivity, facile regeneration, fast adsorption and desorption kinetics, and good multicycle stability are urgently needed. We developed amine-functionalized adsorbents by loading tetraethylenepentamine (TEPA) on mesoporous supports of activated carbon (AC), aluminum oxide (AO) and silica gel (SG). The adsorbents were characterized by N2 adsorption-desorption, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscope (SEM) to study their microstructural properties. CO2 adsorption capacities and kinetic performance of the adsorbents with different supports and various amine loadings (10–50 wt%) were evaluated in 2%CO2 at 20 °C. The effects of support and amine loading on the structure-performance relationships of the adsorbents were demonstrated. The TEPA-SG-20 adsorbent (20 wt% TEPA loaded on silica gel support) exhibits the highest CO2 adsorption capacity of 1.90 mmol CO2/g and the maximum amine efficiency of 0.48 mmol CO2/mmol N. TEPA-SG-20 also exhibits fast CO2 adsorption kinetics, and the Avrami fractional order kinetic model provides a satisfactory correlation of the experimental CO2 uptakes. Furthermore, the TEPA-SG-20 adsorbent can be efficiently regenerated at 110 °C with a great regeneration efficacy of 97%. The desired adsorbent also exhibits good working stability with a low loss-in-capacity of 4.32% in 10 consecutive cycles. The good CO2 adsorption performance of TEPA-SG-20 is associated with the excellent microstructural properties such as high surface area, great pore volume and uniform dispersion of amine species. Overall, the desired TEPA-SG-20 adsorbent shows promise for low-concentration CO2 removal in ECLSSs.

Mixed polyamines promotes CO2 adsorption from air

The deployment of large-scale direct air capture (DAC) technology relies on the development of energy-efficient and cost-effective CO2 capture materials. The high desorption temperature of the current DAC adsorbents, especially the supported polyamines, is undesirable. In this work, the "mixed-polyamines" concept was adopted to prepare class 1 adsorbents by impregnating both tetraethylenepentamine (TEPA) and diethanolamine (DEA) into the mesoporous SBA-15. The synergy of TEPA and DEA influences the reaction mechanism between CO2 and amines sites, resulting in higher amine efficiency and lower regeneration temperature. Moreover, CO2 adsorption and desorption kinetics are enhanced by the introduction of hydroxyl groups from DEA. The desorption process of solid polyamines-loaded adsorbents fits well with the Avrami model under ultra-dilute CO2 concentrations. SBA-15 loaded mixed polyamine with a weight ratio of TEPA to DEA equaling to 4 shows a maximum CO2 adsorption amount of 1.93 mmol/g at 400 ppm CO2 and 25 °C, a fast adsorption rate of 1.82 mmol/(g·h), and a desorption rate of 0.26 mmol/(g·min) at 80 °C within the first 5 min, which is believed to be a promising DAC adsorbent for practical application.

Preparation and structure tuning of CO2 adsorbent based on in-situ amine-functionalized hierarchical porous polymer

Amine-functionalized porous adsorbent is one kind of important materials in carbon dioxide capture due to its stability and efficiency. In this study, a copolymer (polyHIPE) with interconnected macropore networks, hierarchical porous structure and abundant branched amino groups was prepared by high internal phase emulsion (HIPE) strategy via copolymerization of styrene (St), divinylbenzene (DVB), tetraethyl orthosilicate (TEOS), and triethoxyvinylsilane (VTEO), and then a novel amine-functionalized CO 2 adsorbent was synthesized by in situ ring-opening grafting copolymerization of aziridine with the polyHIPE. The structure, morphology, and physicochemical properties of the polyHIPEs were characterized by FTIR, TEM, TGA, and SEM. The key roles of VTEO and TEOS in introducing active hydroxyl groups onto the surface of the inert polymer was evaluated, which was essential to improve the hydrophilicity of the polyHIPE and to provide reactive sites to combine with amine agents. The contact angle of the polyHIPE while copolymerized with TEOS and VTEO significantly was decreased from 144° to 72°. In order to further increase the specific surface area of the polyHIPEs, post crosslinking of polyHIPEs was implemented through a Friedel–Crafts reaction. The specific surface area of post-crosslinked polyHIPE could reach 513 m 2 /g, which was proven to be effective to enhance its CO 2 adsorption capacity. Finally, the abundant branched amino sites via aziridine grafting and high surface area greatly enhanced CO 2 adsorption capacity of the amino-modified polyHIPEs. The adsorption capacity of 2.40 and 3.25 mmol CO 2 /g could be achieved under dry and humid conditions in 0.1 atm partial pressure of CO 2 , respectively. • The hydroxyl groups modified monolithic was synthesized by one-step high inner phase emulsion copolymerization. • The post-crosslinking and in-situ grafting of amino obtained higher specific surface area and more CO 2 adsorption sites. • The polyHIPE-V 1 T 2 -HCP-NH monolithic exhibits obviously high CO 2 adsorption capacity and amino efficiency. • 3.25 mmol CO 2 /g-adsorbent and amine efficiency of 0.65 mmol CO 2 /mmol N could be achieved under humid conditions.

Insights into the Critical Role of Abundant-Porosity Supports in Polyethylenimine Functionalization as Efficient and Stable CO2 Adsorbents.

The emerging polyethylenimine (PEI)-functionalized solid adsorbents have witnessed significant development in the implementation of CO2 capture and separation because of their decent adsorption capacity, recyclability, and scalability. As an indispensable substrate, the importance of selecting porous solid supports in PEI functionalization for CO2 adsorption was commonly overlooked in many previous investigations, which instead emphasized screening amine types or developing complex porous materials. To this end, we scrutinized the critical role of different commercial porous supports (silica, alumina, activated carbon, and polymeric resins) in PEI impregnation in this study, taking into account multiple perspectives. Hereinto, the present results identified that abundant larger pore structures and surface functional groups were conducive to loading a considerable amount of PEI molecules. Various supports after PEI functionalization had great differences in adsorption capacities, amine efficiencies, and the corresponding optimal temperatures. In addition, more attention was paid to the role of porous supports in long-term stability during the consecutive adsorption-regeneration cycles, while N2 and CO2 purging as regeneration strategies, respectively. Especially, CO2-induced degradation due to urea species formation was specifically recognized in a SiO2-based adsorbent, which would induce serious concerns in CO2 cyclic capture. On the other side, we also confirmed that adopting conventional porous supports, for example, HP20, could achieve superior adsorption performance (above 4 mmol CO2/g) and cyclic stability (around 1% loss after 30 cycles) rather than the ones synthesized through complex approaches, which ensured the availability and scalability of PEI-functionalized CO2 adsorbents.

Role of brush-like additives in CO2 adsorbents for the enhancement of amine efficiency

Amine adsorbents have been widely investigated for direct CO2 capture from air. However, the low amine efficiency of the widely-studied amine sorbents is the critical factor to hinder the practical application under dry conditions. Herein, we developed the brush-like cetyltrimethylammonium chloride (CTAC) templating strategy to prepare micro-mesoporous silica nanoparticles (MMSN-X) and TEPA-functionalized adsorbents (MMSN-X/TEPA-Y). The character of samples was investigated by transmission electron microscopy, N2 adsorption-desorption, Fourier transform infrared spectroscopy, thermal gravimetric analyzer and X-ray photoelectron spectroscopy. The adsorbent (MMSN-30/TEPA-50) with appropriate amount of brush-like CTAC exhibited higher CO2 adsorption capacities (3.68 mmol/gadsorbent under simulated dry air conditions) than that of the adsorbents with none or less additives. The kinetic and thermodynamic model were applied to investigate the adsorption rate control factors and adsorption behavior of CO2 adsorbents with brush-like CTAC. Moreover, with the effect of brush-like CTAC, the significant variation of adsorption product (conversion from carbamate (CO2/N = 0.5) to carbamic acid (CO2/N = 1)) was detected by in situ Fourier transform infrared spectroscopy. These results demonstrated that the combination of CO2 and amine was altered in the presence of brush-like CTAC and thereby the amine efficiency was enhanced, which could be expected to be an efficient adsorbent for CO2 from air in practical applications.

The critical evaluation of the effects of imidazolium-based ionic liquids on the separation efficiency of selected biogenic amines and their metabolites during MEKC analysis

Ionic liquids (ILs) such as imidazole can be used to prevent the sorption of analytes onto the quartz walls of the capillary. Coating the capillary wall with a cation layer increases its surface stability, consequently improving the repeatability of separation process. Currently, examining the effects of dynamic coatings on the capillary wall is an emerging trend in capillary electrophoresis (CE) research. This study uses micellar electrokinetic chromatography (MEKC) to evaluate how ILs in the background electrolyte (BGE) affect the separation efficiency of biogenic amines (BAs). Specifically, this research focuses on 12 ILs built from cations containing an imidazole ring with different alkyl substituents and anions, as well as one IL containing a pyridinium cation with tetrafluoroborate anion. All analyzed ILs, which were added to the BGE in concentrations ranging from 1 to 20 mM, were tested for their ability to improve the electrophoretic separation of selected BAs, namely: homovanillic acid (HVA), vanililmandelic acid (VMA), dihydroxyphenylglicol (DHPG), 3-metoxy-4-hydroxyphenyl glicol (MHPG), normetanephrine (NM), metanephrine (M), and dihydroxyphenylacetic acid (DOPAC). The results showed that the most effective ILs added to the BGE were those with a chloride anion (1-hexyl-3-methylimidazolium chloride [HMIM+Cl−] and 1-ethyl-3-methylimidazolium chloride [EMIM+Cl−]) and those with a tetrafluoroborate anion (1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM + BF4−]). Improved separation efficiency was also obtained for the BGE containing 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM + PF6−]. On the other hand, ILs with trifluoromethanesulfonate [OTf−] or bis(trifluoromethylsulfonyl)imide [NTf2-] anions, even at low concentrations in the BGE, disturbed the flow of current through the capillary and worsened the separation process. Overall, this study provides a critical evaluation of the impact of different types and concentrations of ILs on the performance of the MEKC method during the analysis of selected BAs.

Amine-Infused Hydrogels with Nonaqueous Solvents: Facile Platforms to Control CO2 Capture Performance

Amine-infused hydrogels provide a facile platform for developing solid sorbents with improved CO2 capture performance relative to that of their liquid counterparts. In this study, we develop hydrogel materials that can be easily manufactured at a large scale and have high flow gas permeability characteristics, fast uptake kinetics, and minimal performance degradation after recycling, properties which are particularly important for applications in direct air capture (DAC). To overcome water loss issues associated with hydrogel materials for DAC, we have introduced high-boiling-point/nonaqueous solvent systems, which significantly lowered the solvent loss, leading to dramatically improved recyclability. Among the materials developed, cross-linked poly(N-2-hydroxyethylacrylamide) (PHEAA) infused with diethanolamine (DEA) exhibited 7.82 and 2.90 wt % CO2 uptake with pure CO2 and DAC, respectively. Interestingly, by changing the hydrogel platform between either a cross-linked superabsorbent [i.e., poly(acrylamide/sodium acrylate)], PHEAA, or poly(acrylamide) (PolyAA) and impregnating with different amines/solvents, the uptake kinetics could be controlled and significantly improved. In fact, the PolyAA system impregnated with DEA in ethylene glycol showed 90% of the total capacity (6.37%) in 350 s (vs 4300 s in the case of the PHEAA/DEA system) as well as an enhanced amine efficiency (0.76 vs 0.28 mol CO2 per amine). Thus, this study demonstrates the use of different nonaqueous solvents on readily synthesized hydrogel platforms to improve the DAC uptake efficiency and kinetics. The fast kinetics enable shorter adsorption/desorption cycles, which will be advantageous in improving the CO2 uptake selectivity and reducing the sorption of water in larger-scale implementations of this approach, in both urban and industrial applications.

Environmentally friendly gas phase grafting of mesoporous silicas

Tumbling chemical vapour deposition (T-CVD) is presented as a novel methodology for the gas phase grafting (GPG) of a variety of alkoxy- and chloro-silanes on mesoporous silica. Compared to conventional solution grafting techniques, this method is sustainable, and cost- and time-effective. Although the method was successfully applied to a variety of silanes, application of the gas phase methodology to the preparation of propylamine-grafted CO2 adsorbents (AGA) is presented in depth, for illustration. A detailed comparative characterization of AGAs derived from GPG and solution grafting is discussed. Unprecedentedly high propylamine contents were achieved (up to 5.51 mmol/g), indicating enhanced accessibility of surface hydroxyl groups and more favorable packing of propylamine chains on the support surface, thereby enabling much higher surface density compared to traditional solution grafting procedures. The gas phase method achieves higher grafting efficiency, with less silane waste, necessitating recycling. Furthermore, not only higher CO2 uptake, but also higher amine efficiency (CO2/N) was obtained from GPG-derived adsorbents compared to those obtained by solution grafting. GPG was also found to be suitable for grafting granules and pellets with limited mechanical strength, which may otherwise be crushed while being stirred during grafting in solution.

Vapor-Phase-Infiltrated AlOx/PIM-1 “Hybrid Scaffolds” as Solution-Processable Amine Supports for CO2 Adsorption

Energy-efficient adsorptive CO2 capture requires both adsorbent materials with high CO2 capacity and structured adsorption contactors possessing fast mass transfer kinetics and low pressure drop. The state-of-the-art research primarily focuses on “hard” adsorbents such as mesoporous zeolites and metal–organic frameworks, which exhibit high CO2 capacities but are challenging to translate into structured contactors. Polymer of intrinsic microporosity 1 (PIM-1), a solution-processable microporous polymer, is a “softer” alternative that can be easily fabricated into structured adsorption contactors. In prior research, PIM-1 has been utilized as a “molecular basket” for poly(ethylene imine) (PEI). Despite nanoscale amine dispersion and excellent processability, PEI/PIM-1 composites possess an unstable micropore structure, which collapses at high PEI loadings (∼30%) and results in lower CO2 adsorption capacity than PEI-loaded hard oxides. Here, we applied a post-fabrication polymer stabilization method, vapor phase infiltration (VPI), to improve the CO2 capacity of the PEI/PIM-1 composite without sacrificing its processibility. PIM-1 is fabricated into structured adsorption contactors and then reinforced with amorphous aluminum oxyhydroxide (AlOx) nanostrands via VPI. The resulting AlOx/PIM-1 is a stable, hierarchically porous support, which can be loaded with 40% PEI without pore collapse. Owing to the combination of processibility, comparable CO2 capacity, and high amine efficiency, PEI/AlOx/PIM-1 composites are a promising alternative to PEI-loaded mesoporous oxides.

CO2 capture (including direct air capture) and natural gas desulfurization of amine-grafted hierarchical bimodal silica

Amine grafting under hydrous conditions is emerging as a promising solution to developing amine grafted adsorbents with high amine loading and superior capture performance. In this study, a hierarchical bimodal mesoporous silica (HBS) that can be easily and cost-effectively synthesized was identified. Subsequently, HBS was amine grafted in anhydrous and hydrous conditions. The resulting material and its adsorptive performance were investigated. Hierarchical bimodal silica supports allow aminosilanes to more easily access the deep channels of the pores resulting in greater amine dispersion than SBA-15 type supports. The CO2 adsorption capacity of amine grafted hierarchical bimodal silica adsorbents and SBA-15 type adsorbents were measured at 25, 75, 90, 100 °C. The CO2 adsorption capacity and amine efficiency (reached 0.41 mol CO2/mol N) were significantly higher than that of SBA-15 type adsorbents. This is because HBS possesses two series of mesopores as opposed to one which promotes the diffusion of CO2 and allows for greater amine dispersion and consequently greater amine utilization. Wet grafted HBS displayed excellent cyclic stability after approximately 10 adsorption-desorption cycles. Under dry conditions and using ambient air containing 415 ppm of CO2 at 25 °C, the fixed bed breakthrough capacity of WG-HBS-0.6 was 1.04 mmol/g. To the best of our knowledge, the CO2 adsorption capacity and the direct air capture capacity exceed reported literature values for amine-grafted silica adsorbents. At similar amine loadings the H2S adsorption capacity of wet grafted hierarchical bimodal silica was similar to SBA-15 type adsorbents suggesting thermodynamics as opposed to pore structure plays a greater role during the H2S adsorption process. From the obtained results, hierarchical bimodal silicas are promising adsorbents for the capture of CO2 from ambient air and industrial gas streams and are also suitable for the removal of H2S.

Formulation, adsorption performance, and mechanical integrity of triamine grafted binder-based mesoporous silica pellets for CO2 capture

This work explored the formation of mesoporous silicas pellets using a range of bentonite and colloidal silica (LUDOX) fractions, aiming to optimise the binder composition that minimises any deteriorating effects on adsorption performance, while providing adequate mechanical integrity. Thermogravimetric analysis, scanning electron microscopy, and dynamic mechanical analysis were used to structurally characterise the pellets. Further, CO2 adsorption isotherms of synthesised pellets, pre and post triamine grafting, were measured. Bentonite was found to be an effective single binder that forms mechanically strong pellets and retains up to 85% of CO2 capacity of the base adsorbent. In the presence of LUDOX, pellet hardness was lower, and led to the largest decrease in CO2 capacity. Formulation with 25% bentonite was found to provide pellets with post triamine functionalisation CO2 capacity equivalent to powder SBA-15, at an amine efficiency of 0.41 mol CO2/mol, while minimising pore blockage and maintaining a compressive strength of 1.5 MPa.

Diazoamination: A simple way to enhance detonation performance of aminoaromatic and aminoheterocyclic energetic materials

In this paper, we report a theoretical study of the change in detonation efficiency of energetic amines undergone diazoamination reaction. For this purpose, we selected 17 aminoaromatic and aminoheterocyclic energetic materials, both widely known and newly synthesized, and ranked all possible triazenes derived from them according to our recently developed compositional criterion evaluation algorithm. Then, top ten structures were calculated using quantum-chemical methods to obtain more accurate estimates of their detonation properties, which were calculated using the Kamlet-Jacobs equations. To ensure that input parameters, namely, crystal density (dc) and enthalpy of formation (ΔHf) are correct, we have benchmarked a number of experimentally known triazenes as well as other structurally similar compounds. As a result, we have obtain good regression coefficients, R2 = 0.91 (for dc) and R2 = 0.96 (for ΔHf). Applying the same quantum-chemical methods for structural building blocks (constituents of triazenes) we have found that diazoamination always increases detonation performance (2-15% for detonation velocity and 0-32% for pressure). Thus, transformation of aminoaromatic and aminoheterocyclic energetic materials into triazenes is a convenient method for enhancement of their detonation properties.

New reagent regimes for potash flotation

The article presents the results of the VNII Galurgii’s studies into development of reagent regimes for flotation of potash ores of the Upper Kama deposit in fat solutions of potassium and sodium chlorides. The influence of the temperature of the saline solution and the content of magnesium chloride in it on the efficiency of aliphatic amines—collector of sylvin—was investigated. An alternative ethoxylated sludge collector for flotation de-sludging of potash ores is tested. The effect of a modified sludge depressant obtained by the synthesis of urea and formaldehyde is studied. The developed reagents are tested in full-scale processing of potash ore with variable composition and an increased content of sludge-forming silicate-carbonate and anhydrite water-insoluble impurities have been carried out. It is shown that the process stability and the production performance improve. Application of the sludge depressant in flotation of potash ore of variable composition allows stabilization of sylvin flotation and reduction in potassium chloride loss owing to stimulation of potassium chloride flotation from coarse tailings, which enables the decrease in the sylvin collector consumption and favors improvement of the process performance.

SBA-15 Functionalized with Amines in the Presence of Water: Applications to CO2 Capture and Natural Gas Desulfurization

Conventional and pore expanded SBA-15 were amine-grafted under dry and wet conditions using N1-(3-trimethoxysilylpropyl)diethylenetriamine. The effects of pore properties and gas hourly space velocity (GHSV) as well as the CO2 and H2S capture performance were investigated, and the results indicated that pore expanded SBA-15 displayed the best performance. Clumping and agglomeration of SBA-15 were observed for conventional SBA-15 under wet grafting conditions due to interparticle polymerization of amines after pores are completely filled. This phenomenon was not observed for pore expanded SBA-15, resulting in viable adsorbents with greater amounts of grafted amines. Pore expanded SBA-15 exhibited the highest CO2 capacity (3.27 mmol/g), which to the best of our knowledge is the largest for amine-grafted adsorbents. It also exhibited high amine efficiency (0.39 mol CO2/mol N) and faster uptake rates compared to conventional SBA-15 due to enhanced amine accessibility. For direct air capture, higher GHSV values result in lower breakthrough CO2 capacities and the breakthrough CO2 capacity of wet grafted pore expanded SBA-15 is more dependent on GHSV than that of dry grafted pore expanded SBA-15 due to diffusion resistance. Last, conventional SBA-15 displayed a marginally lower H2S adsorption capacity compared to pore expanded SBA-15, suggesting that diffusion resistance does not play a significance role during H2S adsorption. These results suggest the consideration of wet grafted pore expanded mesoporous siliceous supports for the design of promising adsorbents for the capture of CO2 and the removal of H2S from natural gas.

Low to high-pressure CO2 separation using amine-functionalized Mobile Composite Matter, isotherm modelling and heat of adsorption study

ABSTRACT Adsorptive CO2 separation is an effective process in carbon capture and sequestration. In this work, Benzylamine, Monoethanolamine, and Aminoethylethanolamine impregnated MCM-48 are used to enhance CO2 adsorption capacity. The materials are characterized using BET, XRD, TGA, FT-IR, FESEM and elemental analysis techniques. The CO2 uptakes are measured using high pressure sorption equipment in the temperature and pressure ranges of 25–80°C and 0–30 bar. The effect of amine loadings is pronounced in the chemisorption of CO2. The Sips isotherm model is better to correlate the experimental data than that of in Freundlich, Langmuir and Toth models. The isosteric heat of adsorption is calculated using Van’t Hoff plot in the temperature range of 25–60°C to understand the degree of heterogeneity and the surface energy distribution of the adsorbents. The CO2 adsorption capacity (3.33 mmol CO2/g) and amine efficiency (14.1 mmol CO2/g amine) of 30% AEEA impregnated MCM-48 is highest among the amine-functionalized MCM-48 adsorbents reported till date in the open literature. The MCM-48-30%AEEA shows 5.2 times higher CO2 adsorption capacity than that of in MCM-48 (0.637 mmol/g) at 25°C and 1 bar pressure. The MCM-48-30%AEEA is proposed as a promising adsorbent in low- to high-pressure post-combustion flue gas and natural gas purification.

Direct CO2 air capture with aqueous 2-(ethylamino)ethanol and 2-(2-aminoethoxy)ethanol: 13C NMR speciation of the absorbed solutions and study of the sorbent regeneration improved by a transition metal oxide catalyst

The removal of CO2 from the atmosphere (DAC technology) has been accomplished at room temperature and pressure with aqueous solutions of 2-(ethylamino)ethanol (EMEA) and 2-(2-aminoethoxy)ethanol (DGA). The absorption efficiency of the sorbents has been investigated in five cycling steps of absorption-desorption, and the speciation of the solutions has been studied by 13C NMR analysis. The CO2 capture efficiency of both fresh amines is about 88%, and that of the regenerated EMEA solutions decreases to about 79% once the equilibrium between amine regeneration (at 110 °C) and CO2-loaded amine has been reached. Instead, the efficiency of regenerated DGA progressively decreases to 69% at the end of the fifth cycle. 13C NMR analysis of the absorbed solutions of EMEA indicates that CO2 is captured as amine carbamate and bicarbonate (nearly 1:1 proportion), whereas DGA carbamate is the sole species of captured CO2. To improve the efficiency of regenerated DGA solutions, solid WO3 has been employed as desorption catalyst in five subsequent cycles of absorption and desorption. At equilibrium, the efficiency of CO2 capture increased to 85%, substantially greater than that of regenerated EMEA. The catalyst has been recovered unchanged at the end of each desorption step.

Drastic enhancement of carbon dioxide adsorption in fluoroalkyl-modified poly(allylamine)

Aminopolymer functionalization with fluoroalkyl chains and resulting void volume afford 4.1-fold increase in amine efficiency and 2.8-fold increase in CO2 capture capacity in the fluorinated material.