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In this work, various single and blended amines (namely, MEA, MEA-DEEA, MEA-MDEA, MEA-1DMA2P) with three types of catalysts (H-ZSM-5, MCM-41 and SO4²⁻/ZrO2) were studied to determine the respective roles of catalyst and solvent in heat duty for solvent regeneration and rate of CO2 desorption during the desorption of CO2 from the solvents having an...
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“In a pioneering research study, experimental data for the absorption rates of CO2, H2S and a mixture of both in hindered amine,2-amino-2-methyl-1-propanol (AMP) aqueous solutions (0.1M, 0.2 and 0.3M) are presented for the first time. Results are compared with the absorption rate in monoethanolamine (MEA) solutions of similar concentrations. The ob...
For decades, carbon dioxide emissions have been an environmental and health issue. Amines like Monoethanolamine (MEA) have long been favoured in strategies based on chemical absorption aimed at CO2 capture and thus reduction of its harmful environmental impacts. However, some drawbacks, such as toxicity, low stability and high cost limit widespread...
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... The chosen catalyst/ solvent ratio was 1:80. 28,39 The reaction was conducted for 90 min. The concentration of CO 2 was determined at regular time intervals by the titration method. ...
An aqueous mixture of the sterically hindered amine 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD) and the cyclic diamine piperazine (PZ) is a credible CO2 separation solvent. In this work, CO2 absorption kinetics in AHPD/PZ mixtures was investigated in a stirred cell reactor. The solute gas CO2 reacted in parallel with both amines AHPD and PZ. From the absorption rate measurements at 308 K, the second-order rate constant for the reaction between CO2 and PZ was found (k2,PZ = 28 685 m3 (kmol s)−1). Several properties of this blend, such as density, viscosity, and CO2 diffusivity and solubility, were measured. Besides, the dependency of the equilibrium CO2 partial pressure on the loading capacity was studied in a low-pressure vapor–liquid equilibrium setup at 308 K. The highest value of CO2 solubility in this study was 0.83 mol CO2/mol amine, and the corresponding CO2 partial pressure was 130 kPa. The performance of the blend AHPD/PZ (1/0.5 kmol m–3) was tested in a continuous, closed-loop setup comprising an absorber (313 K) and a desorber (383 K). The efficiency of CO2 separation from a CO2/air mixture (12:88 v/v) was 62%, and the regeneration energy constraint was 4.21 MJ (kg CO2)−1. Finally, alumina catalyst was employed for faster CO2 desorption at 368 K in a batch setup. This comprehensive study will promote the application of this candidate AHPD/PZ solvent.
... We further tested other well-known acid zeolites, viz., H-Y and H-Beta, and we observed a similar result with a very low k CAT ( Figure S3): the zeolite facilitates CO 2 release at low temperatures, and yet, there is no significant CO 2 release once reaching the isothermal condition. In fact, closer self-inspection of few reported data also divulges such unnoticed behavior for different acid zeolites 20,21,28,35 and some sulfuric acid-treated oxides. 24,27,28,35,36 To further investigate the role of acidic zeolite, we carried out a similar CO 2 desorption experiment with varying amounts of H-ZSM-5, viz., 1, 2, 4, and 6 wt % with respect to the aqueous MEA solution. ...
... In fact, closer self-inspection of few reported data also divulges such unnoticed behavior for different acid zeolites 20,21,28,35 and some sulfuric acid-treated oxides. 24,27,28,35,36 To further investigate the role of acidic zeolite, we carried out a similar CO 2 desorption experiment with varying amounts of H-ZSM-5, viz., 1, 2, 4, and 6 wt % with respect to the aqueous MEA solution. As shown in Figure 1c, the improvement of the CO 2 desorption amount during the temperature increase is linearly correlated to the loading of H-ZSM-5. ...
... Therefore, its performance was inferior to HZSM-5, which has both a large MSA and an even larger B/L. This trend also shows similar results to Zhang et al. [140]. ...
The employment of nanoparticles in solvents is a promising method to reduce the energy consumption during solvent regeneration. Numerous experimental and theoretical studies have been conducted to investigate the remarkable enhancement of nanoparticles. Yet, there are limited reviews on the mechanistic role of nanoparticles in enhancing the solvent regeneration performance. This review addresses the recent development on the employment of various nanoparticles, which include metals oxides, zeolites and mesoporous silicas, to enhance the mass and heat transfer, which subsequently minimize the solvent regeneration energy. The enhancement mechanisms of the nanoparticles are elaborated based on their physical and chemical effects, with a comprehensive comparison on each nanoparticle along with its enhancement ratio. This review also provides the criteria for selecting or synthesizing nanoparticles that can provide a high regeneration enhancement ratio. Furthermore, the future research prospects for the employment of nanoparticles in solvent regeneration are also recommended.
... The solid acid catalysts like zeolite molecular sieve, [16][17][18] transition metal oxides, 19,20 hydroxy metal oxides, 15 sulfated metal oxides, 21,22 metal ion mediated, 23 and thermostable carbonic anhydrase 24 were usually applied for the CO 2 desorption from CO 2 -rich MEA solution. ...
High heat duty is an urgent challenge for industrial applications of amine‐based CO2 capture. The temperature (>110°C) of carbamate breakdown in amine regeneration requires large energy consumption. In this work, we report a novel, stable, efficient, and inexpensive Ni‐HZSM‐5 catalyst to improve the CO2 desorption rate and reduce the heat duty. The impregnation method was applied for varying nickel content in the catalysts from 2.16 to 9.80 wt% in HZSM‐5. The catalysts were characterized by scanning electron microscope, X‐ray powder diffraction, N2 adsorption–desorption, inductively coupled plasma‐optical emission spectrometry, ultraviolet‐visible diffuse reflectance spectroscopy, X‐ray photoelectron spectroscopy, NH3‐temperature programmed desorption (TPD), Infrared spectroscopy of pyridine adsorption, and Fourier transform infrared spectroscopy. The catalytic performance was evaluated by CO2 desorption of rich amine solvent at 90°C. It was found that the introduction of nickel increased the acid sites of catalysts compared with parent HZSM‐5. This phenomenon plays a key role on improving the CO2 desorption rate. The density functional theory (DFT) calculations successfully explain the catalytic performance. The catalytic activity associates with the combined properties of MSA × B/L × Ni²⁺. The 7.85‐Ni‐HZ catalyst presents an excellent catalytic activity for the CO2 desorption: it increases the amount of desorbed CO2 up to 36%, reduces the relative heat duty by 27.07% with the same reaction time, and possesses high stability during five cyclic tests. A possible catalytic mechanism for the Ni‐HZSM‐5 catalysts through assisting carbamate breakdown and promoting CO2 desorption is proposed based on experimental results and theoretical calculations. Therefore, the results present that the 7.85‐Ni‐HZ catalyst significantly accelerates the protons transfer in CO2 desorption and can potentially apply in industrial CO2 capture.
... 80 During the past several decades, a series of mesoporous silica nanomaterials with different properties have been developed in which MCM-41 and SBA-15 are the most common with wide-ranging applications in drug delivery and catalysis. 81 The use of MCM-41 mesoporous silica for catalyst-aided solvent regeneration in CO 2 capture was initially reported by both Idem et al. 82 and Liang et al. 83 in 2017. The recorded values by Idem et al. 82 show that MCM-41 reduces energy consumption from 20.7 to 16.9 MJ/kg of CO 2 (i.e., 81.64% relative heat duty) for thermal regeneration of 5 M MEA at 98°C. ...
... The SO 4 2− /ZrO 2 catalyst was synthesized using a wet impregnation method followed by high-temperature calcination at 600°C for 3 h ( Figure 3). 82,83 The characterization results revealed that, although the synthesized SO 4 2− /ZrO 2 catalyst has strong acidic sites, its Lewis and Brønsted acid sites as well as its mesoporosity are much less than those of HZSM-5 and MCM-41, which explains the relatively poor catalytic performance of SO 4 2− /ZrO 2 . They reported 90.2% relative heat duty for SO 4 2− / ZrO 2 in 5 M MEA at 98°C, whereas HZSM-5 and MCM-41 showed a better performance at 75.2 and 81.6%, respectively. ...
... Opposingly, the high B/ L ratio and mesopore surface area in HZSM-5 catalysts result in a good CO 2 desorption performance in aqueous amine (primary or tertiary) solutions. This methodology was also followed by Liang et al., 73,83,99 and MSA × B/L was employed to justify the efficiency of different catalyst samples. They also used MSA × BAS and MSA × acid strength as the predominant factor to anticipate the CO 2 desorption rate and energy reduction of catalyst-aided solvent regeneration in their later publications. ...
The CO2-capturing performance of a sterically hindered amine, 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD), was systematically studied in this work. First, absorption kinetics was investigated using the stirred-cell technique. At T = 308 K, CO2 reacted with AHPD according to a second-order reaction (rate constant = 264 m³/kmol-s), whose activation energy was 33 kJ/mol. Second, the solubility of CO2 in AHPD at 308 K was measured up to 100 kPa CO2 partial pressure. For instance, it was shown that the loading capacity of AHPD (2.5 M) was 0.56 mol/mol, while the equilibrium CO2 partial pressure was 79 kPa. Third, a closed-loop absorber-desorber setup was used to test solvent performance for capturing CO2 from CO2/air mixture (12:88 v/v). The two columns were continuously operated at 313 (absorber) and 383 K (desorber) at 0.1 MPa pressure. Around 75% CO2 was absorbed using 12 wt. % AHPD (or 0.9 M). The value of QReg (regeneration energy) was 6.28 MJ/kg CO2. It was thus evident that AHPD is a credible hindered amine-based solvent. A comparison of its equilibrium, kinetic and regeneration features with 2-amino-2-methyl-1-propanol (AMP) was provided. Finally, three rate promoters–hexamethylene diamine (HMDA), monoethanolamine (MEA) and AMP–were added to AHPD. The performance of HMDA was most promising. In a batch desorption setup, it was shown that alumina catalyst improved desorption of CO2 from loaded AHPD/HMDA mixtures. This work will stimulate further interest in the use of AHPD solutions for CO2 removal.
Postcombustion CO2 capture will be more attractive if the regeneration energy constraint of amine-based solvents is lowered. Metal oxides catalyze CO2 desorption, thus resulting in efficient amine regeneration. The catalytic regeneration of the N-ethylethanolamine (EEA) solvent was investigated in this study using 10 commercially available metal oxide catalysts. Batch trials were performed with EEA (2.5 M) in a glass apparatus at T = 368 K. The initial CO2 loading was in the 0.32–0.35 mol CO2/mol EEA range. The impact of different catalysts on the regeneration process was evaluated. The catalysts improved the efficiency of CO2 desorption over its value in blank EEA in the following order: Al2O3 (167%) > CuO (104%) > MnO2 (101%) > V2O5 (96%) > TiO2 (65%) > ZnO (61%) > Cr2O3 (50%) > SiO2 (49%) > MgO (46%) > ZrO2 (40%). The effect of changing Al2O3 catalyst loading (between 3 and 12 g Al2O3/400 mL solution) on the desorption features of EEA (1.67 M) was insignificant. It was found that Al2O3 enabled desorption at lower temperatures (338 K) and reduced the sensible energy constraint by 38%. For the case when ZrO2 was impregnated with SO42–, the CO2 desorption efficiency increased in addition by 15% and sensible energy consumption decreased by 25%.
