CO2 Gas Absorption Research Articles

Fast modulation of a long-wave infrared laser based on the two-photon absorption of CO2

In this work, we report a long-wave infrared (LWIR) modulator based on the two-photon absorption of CO2 gas. The effect of gas pressure and laser power on the modulation under different wavelengths is discussed. A maximum modulation depth of 21.5% with a rise time (full time) less than 20 ns for a 9.36 μm laser was achieved. The gaseous modulator, which adopts a 2.75 μm laser as the pumping source, is capable of converting the pulse characteristics of the pump light into the modulation of the long-wave infrared light. It demonstrates promising potential for applications in the rapid optical modulation of LWIR lasers.

Optimization using central composite design for continuous absorption of CO2 gas with green sodium silicate in a packed bed column

If absolutely nothing is taken to reduce carbon dioxide (CO2) emissions, atmospheric concentrations of carbon dioxide will rise to 550 parts per million by 2050, which will have disastrous effects on the world's climate and food production. An apparatus has been designed and setup to convert CO2 into a useful and vital product which was silica. The effect of different experimental factors on the compositions by weight percent of SiO2 and Na2CO3 were studied including the CO2 gas flow rate (1.037, 1.648 and 2.26 L/min), initial concentration of sodium silicate (Na2SiO3) solution (5, 7.5 and 10 %wt) and the packing size (15.95, 20.175, and 24.4 mm). An optimization process was performed using the Design Expert software program to achieve the optimum experimental conditions at which the maximum weight percent of SiO2 (main product), the minimum weight percent of (Na2CO3) (side product) and the minimum reaction time were determined. From the optimization process, the maximum weight percent of SiO2 (25.63 %), the minimum weight percent of (Na2CO3) (9.62 %) and the minimum reaction time (7.59 min) were achieved at the following optimum experimental conditions of CO2 gas flow rate = 1.648 L/min, packing size = 24.4 mm and initial concentration of sodium silicate solution = 10 %wt.

Catalytic desorption of CO2‐loaded solutions of diethylethanolamine using bentonite catalyst

AbstractThe absorption of CO2 gas into aqueous alkanolamine solutions is the most advanced CO2 separation technology and a key challenge in this technique is the energy‐intensive process of solvent regeneration. The tertiary amine N,N′‐diethylethanolamine (or DEEA) is a candidate CO2‐capturing solvent with potential. To improve the energy efficiency of regeneration of DEEA, several catalysts were used for desorbing CO2 from loaded solutions of DEEA (2.5 M) at T = 363 K. Desorption trials were conducted in batch mode. The initial CO2 loading varied in the 0.3–0.35 mol CO2/mol DEEA range. The performance was analyzed by calculating the rate of CO2 desorption, cyclic capacity, and reduction in sensible energy. The amount of thermal energy needed for amine regeneration was significantly lowered by using nine transition metal oxide catalysts and the hierarchy was as follows: Al2O3 < MoO3 < V2O5 < TiO2 < MnO2 < ZnO < Cr2O3 < SiO2 < ZrO2. Among the metal oxides, Al2O3 increased desorption efficiency compared to blank runs by 89%. A clay‐based powder bentonite was also used as catalyst and its efficacy was compared with the metal oxides. This cheap and easily available bentonite catalyst was tuned through simple ion‐exchange with four acids (HCl, H3PO4, HNO3, and H2SO4). Upon treatment with H2SO4, bentonite remarkably increased desorption efficiency by 100%. Furthermore, bentonite catalyst treated with sulphuric acid (denoted here as Bt/H2SO4) was characterized by Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectrometery (FTIR), X‐ray diffraction (XRD), and ammonia temperature‐programmed desorption (NH3‐TPD). In this way, a comprehensive study on catalytic desorption of DEEA was performed.

Molecular simulation of CO2 capturing by dual functionalized phosphonium-based amino acid ionic liquids

Various solvents have been proposed considering the importance of CO2 gas removal from the environment. Over the past few decades, ionic liquids (ILs) have elicited much attention due to their unique properties. In this regard, capturing the CO2 gas by phosphonium-based amino acid ILs (AAILs) was studied by molecular dynamics (MD) simulation. The effect of cation functionalization was studied. The anion was glycinate, [GLY]-, and the cation was tetrabutylphosphonium, [P4444]+, functionalized by different functional groups including acidic (−COOH), alcoholic (−OH), amine (−ΝΗ2), and ether (−OCH3). Density, absorption energy, radial distribution function (RDF), mean square displacement (MSD), concentration profile, free volume, and fractional free volume were under investigation. According to density values calculated from MD simulation, functionalized AAIL with a carboxylic acid group ([P4444COOH][Gly]) is the most concentrated system with the maximum interaction energy between AAIL and the trapped CO2 gas equal to − 1.917 kcal.mol−1. In addition, the lowest volume variation was observed through this physical absorption. RDF analysis reveals that anion interaction with CO2 gas is the most considerable one in the case of [P4444COOH][Gly] AAIL. The CO2 uptake is 2:1 for functionalized AAILs that shows cation functionalization improves CO2 gas absorption capacity; each mole of [P4444COOH][Gly] AAIL is capable of surrounding 2.11 mol of CO2. Finally, the gas diffusion coefficient is the lowest one in [P4444COOH][Gly] AAIL as the solvent-free volume is observed as a continuous channel to trap CO2 gas with the lowest gas diffusivity parameter.

Speeds of Sound in Binary Mixtures of Water and Carbon Dioxide at Temperatures from 273 K to 313 K and at Pressures up to 50 MPa

Knowledge of thermodynamic properties of aqueous solutions of CO2 is crucial for various applications including climate science, carbon capture, utilisation and storage (CCUS), and seawater desalination. However, there is a lack of reliable experimental data, and the equation of state (EOS) predictions are not reliable, particularly for sound speeds in low CO2 concentrations typical of water resources. For this reason, we have measured speeds of sound in three different aqueous solutions containing CO2. We report speeds of sound in the single-phase liquid region for binary mixtures of water and CO2 for mole fractions of CO2 of 0.0118, 0.0066 and 0.0015 at temperatures from 273.15 K to 313.15 K and at pressures up to 50 MPa, measured using a dual-path pulse-echo apparatus. The relative standard uncertainties of the sound speeds are 0.05 %, 0.03 % and 0.01 % at 0.0118, 0.0066 and 0.0015 CO2 mole fractions, respectively. The change in sound speeds as functions of composition, pressure and temperature are analysed in this study. We find that dissolution of CO2 in water increases its sound speeds at all conditions, with the greatest increase occurring at the highest mole fractions of CO2. Our sound speed data agree well with the limited available experimental data in the literature but deviate from the EOS-CG of Gernert and Span by up to 7 % at the lowest temperatures, highest pressures, and highest CO2 mole fraction. The new low-uncertainty sound speed data presented in this work could provide a basis for development of an improved EOS and in establishing reliable predictions of the change in thermodynamic properties of seawater-like mixtures due to absorption of CO2 gas.

Optimization Study of CO2 Gas Absorption with NaOH Absorbent Continuous System in Raschig Ring Packing Column Using Box–Behnken Design

Increasing CO2 gas emissions results in climate change by increasing air temperature and worsening environmental problems. It is necessary to control CO2 gas in the air to overcome this. This research aims to optimize the absorption of CO2 gas in the air with 0.1 M NaOH absorbent in the column of the Raschig ring stuffing material using the response surface methodology (RSM). This research was conducted using a continuous system of three independent variables by varying the contact time (10–80 min), the flow rate of NaOH absorbent (2–5 L/min), and the flow rate of CO2 gas (1–5 L/min). The response variables in this study were the absorption rate (L/min) and mass transfer coefficient, while the air flow rate was constant at 20 L/min. Air and CO2 gas mix before absorption occurs and flow into the Raschig ring packing column so that contact occurs with the NaOH absorbent. Mass transfer of CO2 gas occurs into the NaOH absorbent, resulting in absorption. The results showed that the effect of contact time (min), the flow rate of NaOH absorbent (L/min), and CO2 gas flow rate individually and the interaction on CO2 absorption rate and mass transfer coefficient were very significant at a p-value of 0.05. Chemical absorption of CO2 also occurred due to the reaction between CO2 and OH- to form CO32− and HCO3−, so the pH decreased, and the reaction was a function of pH. Optimization using Design Expert 13 RSM Box–Behnken Design (BBD) yielded optimal conditions at an absorption time of 80 min, NaOH absorbent flow rate of 5 L/min, CO2 gas flow rate of 5 L/min, absorption rate of CO2 gas of 3.97 L/min, and CO2 gas mass transfer coefficient of 1.443 mol/min m2 atm, with the desirability of 0.999 (≈100%).

Post-combustion capture of CO2 using novel aqueous Triethylenetetramine and 2-Dimethylaminoethanol amine blend: Equilibrium CO2 loading-empirical model and optimization, CO2 desorption, absorption heat, and 13C NMR analysis

The equilibrium CO2 loading was estimated by absorption of CO2 gas in the bubble column reactor for novel aqueous amine blend of triethylenetetramine (TETA) and 2-dimethylaminoethanol (DMAE). The absorption study was performed at a temperature of 298.15 to 333.15 K, mole fraction of TETA from 0.05 to 0.2, solution concentration varied from 1 to 3 mol/L, and CO2 partial pressure ranging from 10.13 to 25.33 kPa. The maximum experimental equilibrium CO2 loading was 0.92 mol CO2/mol amine at 315.65 K temperature, 17.73 kPa CO2 partial pressure, 0.13 mol fraction of TETA, and 1 mol/L solution concentration. The absorption results were validated by an empirical model with an average absolute relative deviation of 5.631 %. The desorption study was performed at a constant temperature and pressure of 393.15 K and 17.73 kPa, respectively. The cyclic loading capacity of this blend at 3 mol/L concentration showed 55.03 % higher results than that of 30 wt% (5 mol/L) monoethanolamine (MEA). The Gibbs-Helmholtz equation calculated the heat of CO2 absorption, and for this amine blend, it was found to be −67.135 KJ/mol. 13C nuclear magnetic resonance (NMR) spectroscopy was adopted to identify the chemical species in CO2-loaded and unloaded amine blends. Response surface methodology software optimized the final response. It predicted optimal equilibrium CO2 loading of 0.926207 mol CO2/mol amine at 304.36 K temperature, 0.14 mol fraction of TETA, 17.24 kPa partial pressure of CO2, and 1 mol/L solution concentration.

Carbon Footprint Analysis of Household Activities and CO2 Reduction Efforts in Pondambea Village, Kadia District, Kendari City

The increase in population causes an effect on increasing CO2 production, especially from the household energy sector. The increase in the concentration of CO2 in the atmosphere is the main trigger for climate change and the effects of greenhouse gases. Indications of the occurrence of this phenomenon can be seen from the increase in air temperature and the formation of an urban heat island in Kendari City in the last 10 years. This study aims to determine the amount of CO₂ emissions from household activities and the absorption of CO2 gas from tree species in Pondambea Village, Kadia District, Kendari City. The method used is a quantitative technique to calculate primary and secondary CO2 emissions. The results show that the total CO2 emission in Pondambea Village is 424.22 tons/month. Meanwhile, the carbon absorption capacity of tree species in Pondambea Village is 421.15 tons/month, so that the remaining carbon emissions are 3.07 tons/month. Therefore, to maintain emission absorption and create zero emission in Pondambea Village, this study recommends maintaining the number of existing trees and adding at least 6 glodokan pole trees or at least 5 king palm trees

Cooperative effect of surfactant and porous media on CO2 hydrate formation and capacity of gas storage

Hydrate-based technology is considered to be a promising approach widely applied in the areas of industrial natural gas storage and transportation, CO2 capture and storage. The major technical issues related to this technology are enhancing the formation rate and gas storage capacity under different conditions. In this work, the formation characteristics of CO2 hydrate were investigated in porous media below the freezing point in the presence of SDS (Sodium Dodecyl Sulfate). The influence of cooperative effect of surfactant and porous media on hydrate formation was investigated at different concentration of SDS. The results indicated that surfactant could obviously promote the formation process of CO2 hydrate in porous media when the concentration of SDS was in the range of 0–1240 ppm and the temperature ranged from 268.15 K to 272.15 K. However, there was an optimal SDS concentration to promote the formation process of CO2 hydrate in porous media below the freezing point. When the SDS concentration was 240 ppm, the highest conversion rate of ice to hydrate and the largest gas storage capacity were obtained, which were 43.05% and 80.06 L/L, respectively. The results also indicated that, with or without SDS in porous media system, the higher the temperature was, the less time it brought to reach 90% of the CO2 gas absorption (t90). But the maximum gas storage capacity of CO2 hydrate was obtained at 270.15 K in porous media in the presence of SDS. In addition, the results demonstrated that the SDS concentration of 0.24 g/L could increase the gas storage capacity of hydrate and shorten the value of t90 at different temperature conditions. These results are helpful for comprehensively understanding the rapid formation of CO2 hydrate in industrial areas and providing an important theoretical guidance and reference for the CO2 capture and storage in the form of hydrate.

Synthesis of Cu-Al LDH nanofluid and effectiveness as a promoter for CO2 hydrate formation

The present study focuses on the synthesis of a hybrid nanofluid (Cu-Al LDH) and the investigation of its effectiveness as a promoter for CO2 hydrate formation. The Cu-Al LDH nanofluid has been prepared using the one-step co-precipitation technique. XRD (X-ray diffraction) and TEM (transmission electron microscopy) analyses have been carried out to evaluate the structural features and particle size measurement. The stability of nanofluid is evaluated using zeta potential measurements. The hydrate formation experiments are conducted in a pilot-scale reactor of 25 L volume with a design pressure of 180 bar. The wall temperature of the reactor is set at 2 °C. The charging of the reactor is carried out in both single and dual-stage at the maximum pressure of 30 bar. The results on the enhancement of gas absorption, total gas consumption, and water to hydrate conversion compared to pure water are reported. Parametric study on the effect of Cu-Al LDH nanofluid concentrations (0.25, 0.5, and 1.0 wt%) and molar ratios (Cu2+:Al3+: Na+ = 4:1:4 and 4:1:4.7) have been carried out. The gas absorption process is more sensitive to molar ratio than the concentration of LDH nanofluid, and about 20 times increase in absorption takes place due to LDH nanofluid in dual gas charging mode. The shuttle effect of the nanoparticle is primarily attributed to the increase in CO2 gas absorption. The strength of gas absorption influences the hydrate morphology. Accordingly, hydrate formation is initiated from the gas–liquid interface in low CO2 absorption case, and hydrate slurry formation inside the bulk fluid followed by layer-wise growth of hydrate from the interface takes place in high gas absorption case. Maximum 176.19% increase in gas consumption is observed at 0.5 wt% nanofluid concentration for (Cu2+:Al3+: Na+ = 4:1:4.7) molar ratio compared to pure water.

Non-Solvent Influence of Hydrophobic Polymeric Layer Deposition on PVDF Hollow Fiber Membrane for CO2 Gas Absorption.

The implementation of hydrophobicity on membranes is becoming crucial in current membrane technological development, especially in membrane gas absorption (MGA). In order to prevent membrane wetting, a polypropylene (PP) dense layer coating was deposited on a commercial poly(vinylidene fluoride) (PVDF) hollow fiber membrane as a method of enhancing surface hydrophobicity. The weight concentration of PP pellets was varied from 10 mg mL−1 to 40 mg mL−1 and dissolved in xylene. A two-step dip coating was implemented where the PVDF membrane was immersed in a non-solvent followed by a polymer coating solution. The effects of the modified membrane with the non-solvent methyl ethyl ketone (MEK) and without the non–solvent was investigated over all weight concentrations of the coating solution. The SEM investigation found that the modified membrane surface transfiguration formed microspherulites that intensified as PP concentration increased with and without MEK. To understand the coating formation further, the solvent–non-solvent compatibility with the polymer was also discussed in this study. The membrane characterizations on the porosity, the contact angle, and the FTIR spectra were also conducted in determining the polymer coating properties. Hydrophobic membrane was achieved up to 119.85° contact angle and peak porosity of 87.62% using MEK as the non-solvent 40 mg mL−1 PP concentration. The objective of the current manuscript was to test the hydrophobicity and wetting degree of the coating layer. Hence, physical absorption via the membrane contactor using CO2 as the feed gas was carried out. The maximum CO2 flux of 3.33 × 10−4 mol m−2 s−1 was achieved by 25 mg modified membrane at a fixed absorbent flow rate of 100 mL min−1 while 40 mg modified membrane showed better overall flux stability.

Review: A descriptive study of karst conditions and problems in Indonesia and the role of karst for flora, fauna, and humans

Abstract. Aprilia D, Arifiani KN, Sani MF, Jumari, Wijayanti F, Setyawan AD. 2021. Review: A descriptive study of karst conditions and problems in Indonesia and the role of karst for flora, fauna, and humans. Intl J Trop Drylands 5: 61-74. The karst area in Indonesia covers an area of about 15.4 million hectares and is spread almost throughout Indonesia. It is estimated the age of karst in Indonesia started from 470 million years ago to the most recent about 700,000 years. The existence of this area shows that many of the Indonesian islands were once seabed but were later uplifted and hardened. Most of the karst areas in Indonesia are composed of carbonate rocks, and almost none are composed of other rocks such as gypsum, salt rock, and evaporite rocks. Karst in Indonesia can be classified based on its development and climate. The amount of water available in the karst area plays an important role in human life and so do flora and fauna around the karst area. The karst area functions as an ecosystem for the habitat of various animals and plants. The richness of flora and fauna of this karst area is extraordinary. Karst area plays an important role in economy, science, and human culture. In addition, karst areas have an important role in the ecosystem, such as providing clean water, limestone-based natural materials, and controlling climate change. Its role in ecological function is that karst areas can also be a source of CO2 gas absorption. About 9.5% (155,000 km2) of the total karst area of Indonesia was damaged due to limestone mining activities, logging of vegetation, and land conversion. Given the importance of karst and limestone ecosystems as non-renewable natural resources, it is necessary to do conservation to maintain the ecological function. Steps that can be taken for conservation efforts in karst areas include limiting the sale of raw limestone to outside the area, clarifying protected areas and cultivation areas, socializing the importance of preserving karst areas, providing skills or developing other business opportunities, and reclaiming used land and mining according to the level and type of damage. This study aims to describe the geographical conditions and karst problems in Indonesia so that the conservation measures taken are known and identify the role of the karst area for flora, fauna, and humans.

Presentation of an experimental model of CO2 gas absorption by spraying method by NiO nanofluids and carbon nanotube in the presence magnetic field

Presentation of an experimental model of CO2 gas absorption by spraying method by NiO nanofluids and carbon nanotube in the presence magnetic field

NDIR CO2 gas sensing using CMOS compatible MEMS ScAlN-based pyroelectric detector

We demonstrate NDIR CO2 gas sensing using CMOS compatible MEMS ScAlN-based pyroelectric detectors. The ScAlN-based pyroelectric detectors are fabricated using 8-inch wafer level technology with 12 % Sc-doped AlN deposited at a temperature of ∼200 °C. Together with a blackbody thermal emitter, a 10 cm long enclosed gas channel with only inlet and outlet holes connected to tubings, and testing using 2 different reference gases (N2 and synthetic air), measurements show voltage signal drop due to CO2 gas absorption at the 4.26 μm wavelength at CO2 gas concentrations ranging from 5000 ppm down to 25 ppm. The signal change due to the CO2 gas response ranges from ∼2% at 100 ppm CO2 concentration to ∼40 % at 5000 ppm CO2 gas concentration for both CO2 gas measured in N2 and in synthetic air. CO2 gas response times are also measured for CO2 gas in N2 and in synthetic air at concentrations of 5000 ppm, 1000 ppm and 400 ppm. The gas response times measured around 2 s and lower. Introduction of humidity show some minor effect (<3%) to the CO2 gas response and seems most perturbed at 10 % relative humidity. To the best of our knowledge, this is the first demonstration using ScAlN-based pyroelectric detectors in NDIR CO2 gas sensing, towards practical sensor applications. The results obtained show promise in using CMOS-compatible MEMS ScAlN-based pyroelectric detectors for NDIR gas sensing, opening up possibilities for low cost, wafer-level, monolithic NDIR gas sensors with small footprint integrated with CMOS circuits.

Modeling and simulation of CO2 gas desorption process in promoted MDEA solution using packed column

Carbon dioxide (CO2) gas at atmospheric pressure will tend to freeze, because of low temperature (-78°C), this results in frequent blockages in the piping section. In the process of synthesis of ammonia in the industry in the presence of a catalyst, CO2 gas will be toxic because it can cover the active-side of the catalyst. The process of CO2 gas absorption that is often used is reactive absorption using promoted solvent. The most commonly used solvent is a tertiary amine alkanol solution, one of which is a solution of Methyldiethanolamin (MDEA) using a piperazine catalyst. The output solution from the absorption of CO2 gas is processed by desorption to regenerate the solvent. CO2 gas desorption process is needed to save the use of solvents and catalysts. The purpose of this research is to do modeling and simulation on the process of desorption of CO2 gas from a promote MDEA solution using a packed column. Modeling assisted software media with a rate-based model approach using numerical equations with the completion of Ordinary Differential Equation (ODE) - 45. The data obtained was simulated and validated by comparing experimental data. The research parameters are the temperature of the input solution desorber, type and concentration of catalyst. Increasing the temperature of the solution and the concentration of the catalyst will increase the percent removal of CO2. This is caused by the effect of the temperature of the solution on the value of the reaction rate constant, and the type of catalyst influences the catalyst reactivity level of CO2 gas. The results of simulation data validation with experimental data show the average deviation of 22.05%, 14.24% and 7.85%.

Simulation and experimental study of diesel engine emission temperature based on tunable diode laser absorption spectroscopy

Based on the temperature measurement technology of tunable diode laser ab-sorption spectroscopy, the simulation and experimental research on the temperature measurement of CO2 gas emitted by D4114B Diesel engine is realized. The light source model, gas chamber model and data detection model were established by using SIMULINK, which is more general numerical simulation tool in MATLAB. Under the simulated Diesel engine emission environment, the measured CO2 gas temperature was obtained by model simulation and analyzed. The simulation relative error was 0.077%. The marine D4114B Diesel engine was used as the test object, the visual window was reconstructed on the exhaust light path, and an optical path test system was established. The tunable diode laser was used as the detection light source to carry out on-line test research on the CO2 gas temperature in the exhaust gas emission. The relative error was 4.4%. The results show that the model built by SIMULINK can reflect the actual laser modulation effect and CO2 gas absorption. The simulation results have certain reference value for the research of tunable diode laser absorption spectroscopy temperature measurement system.

Experimental studies and artificial neural network modeling of surface tension of aqueous sodium l-prolinate solutions and piperazine blends

Abstract The surface tension study is very crucial for the design of CO2 gas absorption contacting equipment. The significance of the surface tension has been increasing due to its consideration in various technological fields. This property influences the mass transfer and hydrodynamics of gas absorption systems, mainly multiphase systems, in which the interface between gas and liquid exists. Therefore, in this study, surface tension of aqueous solutions of sodium l -prolinate (SP) and piperazine (PZ) blends were measured at ten different temperatures from (298.15 to 343.15) K. The SP mass fractions were 0.10, 0.20, and 0.30; while the mass fractions of PZ were 0.02 and 0.05. The experimental results showed that the surface tension increase with increasing the mass fractions of SP and PZ in aqueous blends, and decrease linearly with rising temperature. The experimental data of surface tension were correlated by two empirical correlations as a function of temperature and mass fractions for estimating the predicted data using the optimized correlation coefficients. Moreover, the modeling of surface tension data was carried out using Artificial Neural Network (ANN) approach. The results obtianed from ANN modeling were compared with applied empirical correlation. It was found that the ANN approach outperformed the empirical correlation used in this study. Besides, a quantitative analysis of variation (ANOVA) was performed in order to determine the significance of data. The surface tension of aqueous SP and SP + PZ was also compared with various conventional solvents.

The trinuclear platinum(ii) complex in Vèzes' red salt as a building block of coordination polymers.

One-dimensional (1D) and three-dimensional (3D) coordination polymers comprising triangular [Pt3(NO2)6(μ3-O)]2- ([Pt3]2-) units were prepared from K2[Pt3]·3H2O (1), also known as Vèzes' red salt. The reaction between 1 and excess 18-crown-6 ether afforded the 1D coordination polymer [K(18-crown-6)]2[Pt3] (2), whereas the reaction between 1, excess 18-crown-6 ether, and AgPF6 afforded the 1D coordination polymer [Ag(18-crown-6)]2[Pt3]·(CH3)2CO (3). However, the reaction between 1 and equimolar amounts of 18-crown-6 and AgPF6 afforded the 3D coordination polymer [Ag2(18-crown-6)][Pt3]·(CH3)2CO (4). Furthermore, the 3D coordination polymer [Ag2Pt3(μ3-O)(NO2)6((CH3)2CO)2]·(CH3)2CO (5) containing three Pt2+ → Ag+ dative bonds was obtained by the reaction of 1, Bu4NPF6, and AgPF6. The N2, O2, and CO2 gas absorption isotherms of 1-5 were obtained, revealing that the dry crystals of 4 exhibit a selective CO2 absorption ability.

Swelling reduction of polyvinylidenefluoride hollow fiber membrane incorporated with silicoaluminophosphate-34 zeotype filler for membrane gas absorption

CO2 gas absorption is important in fuel purification and carbon capture. By incorporating a porous membrane with a large surface area in membrane gas absorption (MGA) system, the CO2 transfer between feed gas and liquid absorbent can be greatly improved. However, the absorption flux usually drops in the long-term operation due to membrane wetting by the common liquid absorbent, amine. Membrane wetting can lead to membrane swelling which induce the growth of mass transfer resistance. In this work, silicoaluminophosphate-34 (SAPO-34) zeolite was incorporated into polyvinylidene fluoride (PVDF) hollow fiber membrane to reduce flux decline caused by membrane swelling. The membrane porosity and pore size increased with increasing SAPO-34 loading. Nevertheless, significant changes in water contact angle or liquid entry pressure were not shown. PVDF hollow fiber membrane incorporated with 3 wt% of SAPO-34 showed slightly higher CO2 absorption flux to PVDF hollow fiber membrane in MGA with distilled water as the absorbent. However, the CO2 absorption flux of this PVDF/SAPO-34 membrane was greatly improved of about 140 % higher than the CO2 absorption flux of the neat membrane when diethanolamine was used as the absorption. The CO2 absorption flux of PVDF hollow fiber membrane dropped about 60 % after 96 hours. Although these membranes showed a similar water contact angle after being wetted by water or amine, they swelled differently. PVDF hollow fiber membrane swelled nearly 71.0 % after being wetted by amine, but only swelled about 2 % after being wetted by water. The incorporation of SAPO-34 into PVDF hollow fiber membrane reduced swelling by amine, down to 47.7 %. The swelling reduction could be a major cause of absorption improvement shown by PVDF/SAPO-34 hollow fiber membrane in MGA using diethanolamine.

The simultaneous effect of graphene oxide and sodium dodecyl sulphate nanoparticles on the kinetics of CO2 absorption in amine

Amine solvents are extensively used on an industrial scale for removing carbon dioxide (CO2). The presence of some additives in amine solvents has a desirable effect on CO2 absorption kinetics and also improves the absorption process. In this study, graphene oxide (GO) nanoparticles and the anionic surfactant sodium dodecyl sulphate (SDS) were used as additives to the amine solvent. The number of CO2 moles that were used (ng), the values of the diffusion coefficient (DAB), and the mass transfer coefficients of CO2 gas absorption in the amine solvent (Kc) were determined. Furthermore, the effect of the additives on the kinetics of CO2 gas absorption in the amine solvent was investigated. The results showed that mass transfer coefficients increased with a decrease in pressure and an increase in temperature as well as in the SDS and GO concentrations. The values of the mass transfer coefficient under different conditions varied between 0.0311 and 0.0587 cm/s. The molecular diffusion coefficient of CO2 in the amine solvent increased from 0.000025 to 0.000287 cm2/s with decreases in the pressure and with increases in the temperature and increases in concentrations of additives. The laboratory data were statistically analyzed via Design-Expert software using response surface experiment design and a historical method. A mathematical relation was proposed to estimate the mass transfer coefficients. Moreover, a mathematical relation was introduced to predict the molecular diffusion coefficient of CO2 in the amine solvent.