DFT Study on Thermodynamic Parameters of CO2 Absorption into Aqueous Solution of Aliphatic Amines

Using density functional theory （DFT）, the thermodynamic parameters of the CO2 absorp-tion into the aqueous solution of the aliphatic amines including some alkylamines, alka-nolamines, diamines and a type of aminoamide were calculated. The geometry optimiza-tion and the calculation of vibrational frequencies in the gas phase were performed at the B3LYP/6-311＋ G（d,p） level of theory. Moreover, the standard solvation free energies of the studied species were computed upon the solution phase optimized geometries through the latest continuum solvation model （SMD/IEF-PCM） at the HF/6-31G（d） level of theory. With this approach, two important properties of the CO2 absorption into the aqueous so-lutions of the studied amines were evaluated： the acid dissociation constant （pKa） of the parent amines and the standard enthalpy change （ΔH^φabs） related to the CO2 absorption process. A roughly linear relationship was observed between pKa and ΔH^φabs. This finding suggests that a raise in the basicity of an amine leads to an increase in the heat released in CO2 absorption and consequently in the required energy for the regeneration of amine.

Preparation of Nanoporous Carbonaceous Promoters for Enhanced CO2 Absorption in Tertiary Amines

Aqueous solutions of tertiary amines are promising absorbents for CO2 capture,as they are typically characterized by a high absorption capacity,low heat of reaction,and low corrosivity.However,tertiary amines also exhibit very low kinetics of CO2 absorption,which has made them unattractive options for large-scale utilization.Here,a series of novel nanoporous carbonaceous promoters(NCPs)with different properties were synthesized,characterized,and used as rate promoters for CO2 absorption in aqueous N,N-diethylethanolamine(DEEA)solutions.To prepare a DEEA–NCP nanofluid,NCPs were dispersed into aqueous 3 mol∙L1 DEEA solution using ultrasonication.The results revealed that among microporous(GC)and mesoporous(GS)carbonaceous structures functionalized with ethylenediamine(EDA)and polyethyleneimine(PEI)molecules,the GC–EDA promoter exhibited the best performance.A comparison between DEEA–GC–EDA nanofluid and typical aqueous DEEA solutions highlighted that the GC-EDA promoter enhances the rate of CO2 absorption at 40C by 38.6%(36.8–50.7 kPamin1)and improves the equilibrium CO2 absorption capacity(15 kPa;40C)by 13.2%(0.69–0.78 mol of CO2 per mole of DEEA).Moreover,the recyclability of DEEA–GC–EDA nanofluid was determined and a promotion mechanism is suggested.The outcomes demonstrate that NCP–GC–EDA in tertiary amines is a promising strategy to enhance the rate of CO2 absorption and facilitate their large-scale deployment.

A robust predictive tool for estimating CO2 solubility in potassium based amino acid salt solutions

The acid gas absorption in four potassium based amino acid salt solutions was predicted using artificial neural network(ANN). Two hundred fifty-five experimental data points for CO_2 absorption in the four potassium based amino acid salt solutions containing potassium lysinate, potassium prolinate, potassium glycinate, and potassium taurate were used in this modeling. Amine salt solution's type, temperature, equilibrium partial pressure of acid gas, the molar concentration of the solution, molecular weight, and the boiling point were considered as inputs to ANN to prognosticate the capacity of amino acid salt solution to absorb acid gas. Regression analysis was employed to assess the performance of the network. Levenberg–Marquardt back-propagation algorithm was used to train the optimal ANN with 5:12:1 architecture. The model findings indicated that the proposed ANN has the capability to predict precisely the absorption of acid gases in various amino acid salt solutions with Mean Square Error(MSE) value of 0.0011, the Average Absolute Relative Deviation(AARD) percent of 5.54%,and the correlation coefficient(R^2) of 0.9828.

An Algorithm for Detecting Ice Cloud at Different Altitudes by Combining Dual CrIS Full Spectrum Resolution CO2 Channels

Using infrared sensors to detect ice clouds in different atmospheric layers is still a challenge.The different scattering and absorption properties of longwave and shortwave infrared channels can be utilized to fulfill this purpose.In this study,the release of Suomi-NPP Cross-track Infrared Sounder(Cr IS)full spectrum resolution is used to select and pair channels from longwave(~15μm)and shortwave(~4.3μm)CO2 absorption bands under stricter conditions,so as to better detect ice clouds.Besides,the differences of the weighting function peaks and cloud insensitive level altitudes of the paired channels are both within 50 h Pa so that the variances due to atmospheric conditions can be minimized.The training data of clear sky are determined by Visible Infrared Imaging Radiometer Suite(VIIRS)cloud mask product and used to find the linear relationship between the paired longwave and shortwave CO2 absorption channels.From the linear relationship,the so-called cloud emission and scattering index(CESI)is derived to detect ice clouds.CESI clearly captures the center and the ice cloud features of the Super Typhoon Hato located above 415 h Pa.Moreover,the CESI distributions agree with cloud top pressure from the VIIRS in both daytime and nighttime in different atmospheric layers.

Activated carbon produced from paulownia sawdust for high-performance CO_2 sorbents

In this paper, activated carbons （ACs） with high specific surface areas were successfully synthesized by simple one-step carbonization-activation from paulownia sawdust biomass, and the effects of the synthetic conditions on their CO2 capture capacity were investigated as well. The results show that, when the mass ratio between activator and biomass is 4, the activation temperature is 700℃ and the activation time is 1 h, as-made AC provides the most micropores for CO2 adsorption. As a consequence, the maximum CO2 uptake of 8.0 mmol/g is obtained at 0 ℃ and 1 bar.

Current status and future development of solvent-based carbon capture

Solvent-based carbon capture is the most commercially-ready technology for economically and sustainably reaching carbon emission reduction targets in the power sector. Globally, the technology has been deployed to deal with flue gases from large scale power plants and different carbon-intensive industries. The success of the technology is due to significant R＆D activities on the process development and decades of industrial experience on acid gas removal processes from gaseous mixtures. In this paper, current status of PCC based on chemical absorption--commercial deployment and demonstration projects, analysis of different solvents and process configurations--is reviewed. Although some successes have been recorded in developing this technology, its commercialization has been generally slow as evidenced in the cancellation of high profile projects across the world. This is partly due to the huge cost burden of the technology and unpredictable government policies. Different research directions, namely new process development involving process intensification, new solvent development and a combination of both, are discussed in this paper as possible pathways for reducing the huge cost of the technology.

CO_2 capture through halogen bonding: A theoretical perspective

Halogen bonding interactions between several halogenated ion pairs and CO2 molecules have been investigated by means of density functional theory calculations. To account for the influence of solvent environment, the implicit polarized continuum model was also employed. The bromide and iodide cations of ionic liquids (ILs) under study can interact with CO2 molecules via X O interactions, which become much stronger in strength than those in the complexes of iodo-perfluorobenzenes, very effective halogen bond donors, with CO2 molecules. Such interactions, albeit somewhat weaker in strength, are also observed between halogenated ion pairs and CO2 molecules. Thus, the solubility of CO2 may be improved when using halogenated ILs, as a result of the formation of X O halogen bonds. Under solvent effects, the strength of the interactions tends to be weakened to some degree, with a concomitant elongation of intermolecular distances. The results presented here would be very useful in the design and synthesis of novel and potent ILs for CO2 physical absorption.

Impacts of CaO Solid Particles in Carbon Dioxide Absorption Process from Ship Emission with NaOH Solution

CO_2 emitted from ship exhaust is one of the major sources of atmospheric pollution. In order to reduce ship CO_2 emissions, this paper comes up with the idea of recovering CO_2 from ship exhaust by Na OH solution and improves the absorption rate by adding Ca O solid particles. The effect mechanism of Ca O solid particles on CO_2 absorption efficiency is analyzed in detail, and the mathematical model is deduced and the Ca O enhancement factor is calculated through experiments. Experiment result demonstrates that the effect of CaO solid particles on the absorption of CO_2 in alkali solution is significant. The absorption rate of pure CO_2 gas,the simulated ship exhaust gas and 6135 AZG marine diesel engine emission can be increased by 10%, 15.85% and10.30%, respectively. So it can be seen that CaO solid particles play an important role in improving the absorption efficiency of ship CO_2 emission.

Single-frequency and free-running operation of a single-pass pulsed Ho:YLF amplifier

A single-frequency pulsed holmium-doped yttrium lithium fluoride(Ho:YLF)amplifier pumped by a Tm-doped fiber laser was demonstrated.The seed was an injection-seeded Q-switched Ho:YLF laser.The output energy from the singlefrequency pulsed amplifier was 24.2 mJ,with a pulse width of 250 ns at a pulse repetition frequency(PRF)of 100 Hz.The energy stability during 30 min was improved to 1%after the single-frequency pulsed Ho:YLF laser was amplified.The line width of the single-frequency pulsed spectrum of the Ho:YLF amplifier was 2.81 MHz.The single-frequency pulsed Ho:YLF amplifier can be applied to differential absorption lidar(DIAL),since its output spectrum is around the P12 CO2 absorption line.