Reducing Energy Penalty of CO2 Capture Using Fe Promoted SO42-/ZrO2/MCM-41 Catalyst.

The high energy consumption of CO2-loaded solvent regeneration is the biggest impediment for the real application of the amine-based CO2 capture process. To lower the energy requirement, three Fe promoted SO42-/ZrO2 supported on MCM-41 (SZMF) catalysts with different iron oxide content (5%, 10%, and 15%) were synthesized and applied for the rich monoethanolamine solution regeneration process at 98 °C. Results reveal that the use of SZMF hugely enhanced the CO2 desorption performances (i.e., desorption factor) by 260-388% and reduced the heat duty by about 28-40%, which is better than most of the reported catalysts for this purpose. The eminent catalytic activities of SZMF are related to their enhanced ratio of Brønsted to Lewis acid sites, weak acid sites, basic sites, and high dispersed Fe3+ species. Meanwhile, the addition of SZMF for CO2 desorption shows a promotional effect on its CO2 absorption performance, and SZMF presents an excellent cyclic stability. A possible mechanism is suggested for the SZMF catalyzed CO2 desorption process. Results of this work may provide direction for future research and rational design of more efficient catalysts for this potential catalyst-aided CO2 desorption technology.

Study of Catalytic CO2 Absorption and Desorption with Tertiary Amine DEEA and 1DMA-2P with the Aid of Solid Acid and Solid Alkaline Chemicals.

Studies of catalytic CO2 absorption and desorption were completed in two well-performed tertiary amines: diethylmonoethanolamine (DEEA) and 1-dimethylamino-2-propanol (1DMA-2P), with the aid of CaCO3 and MgCO3 in the absorption process, and with the aid of γ-Al2O3 and H-ZSM-5 in the desorption process. The batch process was used for CO2 absorption with solid alkalis, and the recirculation process was used for CO2 desorption with solid acid catalysts. The CO2 equilibrium solubility and pKa were also measured at 293 K with results comparable to the literature. The catalytic tests discovered that the heterogeneous catalysis of tertiary amines on both absorption and desorption sides were quite different from monoethanolamine (MEA) and diethanolamine (DEA). These results were illustrative as a start-up to further study of the kinetics of heterogeneous catalysis of CO2 to tertiary amines based on their special reaction schemes and base-catalyzed hydration mechanism.

Evaluating CO2 Capture Performance of Trisolvent MEA-BEA-AMP with Heterogeneous Catalysts in a Novel Bench-Scale Pilot Plant.

To reduce the huge energy cost of CO2 capture technology applicable in industry, the CO2 absorption-desorption performance was conducted in a novel bench-scale pilot plant with hot water as a heat source. The trisolvent MEA(monoethanol amine)-BEA(butylethanol amine)-AMP(2-amino-2-methyl-1-propanol) was prepared at a specific concentration to analyze the CO2 capture performance and compared with 5 M MEA as the benchmark. Meanwhile, several solid acid catalysts, blended H-ZSM-5/γ-Al2O3(1/2), or HND-8, were packed in the desorber, and the solid base catalyst, CaCO3 or CaMg(CO3)2, was packed in the absorber with random packing. The CO2 absorption efficiency (AE), cyclic capacity (CC), and heat duty (HD) were tested onto MEA-BEA-AMP and MEA under various operating conditions. Experimental results indicated that the performance of 4.3 mol/L MEA-BEA-AMP was significantly better than 5 M MEA under both catalytic and noncatalytic operation. The most energy efficient combination of this study was discovered as 0.3 + 2 + 2 mol/L MEA-BEA-AMP, with 50 g (CaCO3/CaMg(CO3)2) in the absorber and 150 g H-ZSM-5/γ-Al2O3(1/2) in the desorber. The heat duty reached as low as 2.4 GJ/tCO2 at a FG of 7.0 L/min and a FL of 70 mL/min. These results were highly applicable in an industrial amine scrubbing pilot plant for CO2 capture.

Insightful analysis of physical properties, kinetics, absorption capacity, and regeneration heat duty of monoethanolamine and N-methyl-4-piperidinol blended solvent in post-combustion carbon capture.

In this study, the high potential tertiary N-methyl-4-piperidinol or MPDL (0.25-1.00 M) was blended with 5 M monoethanolamine (MEA) to formulate 5.25-6.00 M MEA-MPDL solvent and compare with the benchmark 5 M MEA. It was found that the density and the Henry's constant slightly decreased, while the viscosity increased as the MPDL concentration in the blend increased. Even though the equilibrium CO2-loaded viscosity considerably increased (by 34.3-40.2%) as the MPDL content increased, it was still in a great operating region of less than 10 mPa.s. Experimental overall reaction kinetics constant ( k ov ) was well corresponding with the zwitterion mechanism of MEA and the base-catalyze hydration mechanism of MPDL based absorption kinetics model, with %AAD of 0.56%. Interestingly, an addition of MPDL into 5 M MEA slightly enhanced k ov (1.2-3.3% increment) and considerably favored absorption capacity (13-31% elevation), and regeneration heat duty (28-47% reduction), respecting 5 M MEA. The proposed strategic blending can maintain the overall solvent reactivity at the same level of the benchmark, while obviously increase the absorption capacity and largely reduce the regeneration heat duty. This highly favors a solvent upgrading for the existing 5 M MEA based CO2 capture plant. According to the recent data, 5 M MEA + 1.00 M MPDL was suggested. Since the blend was formulated at high concentration, its corrosiveness should also be considered.

Comprehensive mass transfer analysis of CO2 absorption in high potential ternary AMP-PZ-MEA solvent using three-level factorial design.

Mass transfer of CO2 absorption in 2-amino-2-methyl-1-propanol (AMP) - piperazine (PZ) - monoethanolamine (MEA) was statistically investigated in terms of overall mass transfer coefficient ([Formula: see text]) and CO2 removal percentage. The parameters of interest were lean solvent flux (A), rich gas flux (B), CO2 loading in the lean solvent (C), and ratio of the sampling height to the total column height [Formula: see text] (D). From ANOVA, A was the most impactable parameter on both responses with three-quarters of the overall contribution. Regarding the three-level factorial design, a second-order polynomial increasing trend of [Formula: see text] was observed as C and/or D increased. Additionally, [Formula: see text] linearly increased as A increased but was not affected by B. On the other hand, the CO2 removal percentage linearly increased as A and/or D increased but linearly decreased as B and/or C increased. Surface analysis suggested the optimum condition for both responses at a high level of A, low level of B, low level of C, and middle level of D. In this work, D was statistically investigated and included in the predictive correlation for [Formula: see text] for the first time. The main advantage of the proposed correlation over the recently reported correlations was that it did not require a measurement of CO2 partial pressure along the column height. For each amine component in the blend, (i) AMP played a positive key role in cyclic capacity and solvent regeneration duty, (ii) PZ enhanced transfer rate, and (iii) MEA elevated total amine concentration. As a result, 1.5:1.5:3 was recommended due to (i) elevations of 68.2% [Formula: see text], 14% CO2 removal percentage, 15.1% absorption capacity, and 66.7% cyclic capacity and (ii) reduction of 50% regeneration duty compared with 5 M MEA. With respect to the other literature-reported solvents, AMP-PZ-MEA is very competitive in terms of transfer coefficient, cyclic capacity, and solvent regeneration heat duty.

Experimental investigations and the modeling approach for CO2 solubility in aqueous blended amine systems of monoethanolamine, 2-amino-2-methyl-1-propanol, and 2-(butylamino)ethanol.

In this work, new CO2 solubility data on three types of aqueous amine blends were reported to complement existing databases. The experiments were conducted at temperatures of 313 K (absorption condition) and 363 K (desorption condition). The effect of the MEA concentration on the CO2 solubility in several amine blends at low CO2 partial pressure (8 to 50.65 kPa) were studied in this work, including 0.1, 0.3, 0.5 mol/L MEA + 2 mol/L AMP; 0.1, 0.3, 0.5 mol/L MEA + 2 mol/L BEA; and 0.1, 0.3, 0.5 mol/L MEA + 1, 2 mol/L AMP + 1, 2 mol/L BEA. Besides, an additional group of equilibrium CO2 solubility data were conducted at 298 K in order to estimate the heat of CO2 absorption of the blended solvents at a temperature range from 298 to 313 K. A new simplified Kent-Eisenberg model was developed for the predictions of blended solvents, and a multilayer neural network model with Levenberg-Marquardt backpropagation algorithm was developed upon five hundred reliable published experimental data. The predictions from two methods are both in good agreement with the experimental CO2 solubility data.

The CO2 absorption and desorption analysis of tri-solvent MEA + EAE + AMP compared with MEA + BEA + AMP along with "coordination effects" evaluation.

The slow kinetics of CO2 absorption and high energy cost of CO2 desorption were the main challenges for CO2 capture technology. To overcome these drawbacks, a novel tri-solvent MEA (monoethanolamine) + EAE (2-(ethylamino)ethanol) + AMP (2-amino-2-methyl-1-propanol) was prepared at different amine concentrations of 0.1 ~ 0.5 + 2 + 2 mol/L. The CO2 absorption and desorption experiments were conducted on MEA + EAE + AMP and their precursor MEA + EAE to evaluate the absorption-desorption parameters. Results demonstrated that the optimized concentrations of the bi-blend were 0.2 + 2 mol/L for absorption and 0.4 + 2 mol/L for desorption. For the tri-solvent, the optimized concentration was 0.2 + 2 + 2 mol/L, consistently for both abs-desorption sides. Compared with tri-solvent of MEA + BEA + AMP, MEA + EAE + AMP proved better in absorption but poorer in desorption, while its CO2 loading of operation line was 0.35 ~ 0.70 mol/mol, higher than that of 0.30-0.60 mol/mol MEA + BEA + AMP. These results led to another tri-solvent candidate of amine solvents in an industrial pilot plant.

Synthesis of Cu3P/SnO2 composites for degradation of tetracycline hydrochloride in wastewater.

Antibiotic drugs have become dominating organic pollutants in water resources, and efficient removal of antibiotic drugs is the priority task to protect the water environment. Cu3P/SnO2 photocatalysts of various Cu3P loadings (10-40 wt% Cu3P) were synthesized using a combination of hydrothermal synthesis and a partial annealing method. Their photocatalytic activity was tested for tetracycline hydrochloride (TC-HCl) degradation under visible light irradiation. Cu3P/SnO2 samples were characterized by X-ray diffraction (XRD), N2-adsorption, ultraviolet-visible diffuse reflectance spectra (UV-vis DRS), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The results showed that the p-n type heterostructure between Cu3P and SnO2 was successfully constructed, and addition of Cu3P to SnO2 could improve its photocatalytic activity at an optimized loading of 30 wt% Cu3P. In photocatalytic degradation studies, removal rates of around 80% were found in 30 minutes of dark reaction and 140 min of photodegradation. The removal rate was superior to that of Cu3P and SnO2 alone under the same experimental conditions. According to trapping experiments and electron spin resonance (ESR) measurements, photogenerated holes (h+) and superoxide radicals ˙O2 - were considered as the main oxidation species in the present system. Finally, the reuse experiments showed high stability of Cu3P/SnO2. This study reports Cu3P as a cocatalyst combined with semiconductor SnO2 to form a highly efficient heterogeneous photocatalyst for the degradation of tetracycline hydrochloride for the first time.

Applied Artificial Neural Network for Hydrogen Sulfide Solubility in Natural Gas Purification.

Solubility of hydrogen sulfide (H2S) in 46 single and blended physical absorbents, amines, ionic liquids, and hybrid absorbents of amines + ionic liquids and amines + physical absorbents was successfully predicted based on artificial neural networks (ANNs). Three neural network algorithms of Levenberg-Marquardt (LM), Bayesian regularization (BR), and scaled conjugate gradient (SCG) were applied for architecting the ANN models. The results showed that both the number of hidden neurons and the prediction algorithm affected the prediction of H2S solubility. Based on the mean square error (MSE) and determination coefficient (R 2), the most attractive model was the LM-ANN model with 17 hidden neurons. As a result, very satisfactory prediction performance (for the testing data set) with an MSE of 0.0014 and an R 2 of 0.9817 was obtained from the developed LM-ANN model. Additionally, a parity chart confirmed that the predicted solubility of H2S well aligned with the experimental data. To effectively absorb H2S and maintain high solubility of H2S, the absorbent should be well complied with the operating pressure. For a low-pressure range of less than 100 kPa, amines are very attractive. As the pressure elevated to 100-1000 kPa, amines and hybrid amine + physical absorbents are suggested. Lastly, at a high pressure over 1000 kPa, physical absorbents and ionic liquids are recommended.

Eley-Rideal model of heterogeneous catalytic carbamate formation based on CO2-MEA absorptions with CaCO3, MgCO3 and BaCO3.

The mechanism was proposed of heterogeneous catalytic CO2 absorptions with primary/secondary amines involving 'catalytic carbamate formation'. Compared with the non-catalytic 'Zwitterion mechanism', this Eley-Rideal model was proposed for CO2 + RR'NH with MCO3 (M = Ca, Mg, and Ba) with four elementary reaction steps: (B1) amine adsorption, (B2) Zwitterion formation, (B3) carbamate formation, and (B4) carbamate desorption. The rate law if determining step of each elementary step was generated based on 'steady-state approximation'. Furthermore, the solid chemicals were characterized by SEM and BET, and this rate model was verified with 39 sets of experimental datasets of catalytic CO2-MEA absorptions with the existence of 0-25 g CaCO3, MgCO3 and BaCO3. The results indicated that the rate-determining step was B1 as amine adsorption onto solid surface, which was pseudo-first-order for MEA. This was the first time that the Eley-Rideal model had been adopted onto the reactions of CO2 + primary/secondary amines over alkaline earth metal carbonate (MCO3).