Potassium Sarcosinate Research Articles

Sub-Ambient Performance of Potassium Sarcosinate for Direct Air Capture Applications: CO2 Flux and Viscosity Measurements

Absorption based direct air capture (DAC) technologies have garnered significant interest in recent years due to their scalability, competitive regeneration energy requirements, and low susceptibility to degradation. One of the key advantages of DAC lies in its flexible siting options and the potential to utilize low-value land. However, most of the research in this field has been focused on ambient climate zones (T > 20 °C), overlooking sub-ambient (−30 °C < T < 20 °C) regions, which comprise approximately 70 % of the Earth’s surface. To fully realize the potential of DAC, it is essential to understand how DAC solvents perform in these sub-ambient conditions before any large-scale deployment can be considered. Among DAC solvents of interest, potassium sarcosinate (K-SAR) has emerged as a promising candidate due to its high CO2 capacity, fast uptake kinetics, compatibility with contactor packing materials, low volatility, good thermal and oxidative stability, and competitive regeneration energy requirements compared to current industry standards. This paper characterizes the CO2 flux and viscosity of K-SAR at sub-ambient conditions and explores the potential of using ethylene glycol and triethylene glycol as additives to prevent solvent freezing in DAC applications. For 1 M K-SAR, the CO2 flux ranges between 1.3 × 10-5 and 8.0 × 10-5 mol m−2 s−1 across a temperature range of −5 °C to 45 °C. Ethylene glycol is shown to effectively suppress the freezing point of K-SAR below −30 °C with volumetric loadings of the additive as low as 0.1. A reaction model was developed to predict the CO2 flux for 1 M K-SAR at different temperatures, demonstrating good agreement between experimental and theoretical fluxes.

Direct air capture with amino acid solvent: Operational optimization using a crossflow air‐liquid contactor

AbstractDirect air capture (DAC) is a negative emission technology for removing CO2 from the atmosphere to maintain the CO2 level within a reasonable range so as to address greenhouse effects. In this study, the operational optimization of lab‐scale DAC has been investigated using a crossflow air‐liquid contactor loaded with a three dimensionally printed Gyroid packing structure and a potassium sarcosinate solvent. The effects of various parameters, including feed air flow rate, liquid solvent flow rate, contactor geometry, and ambient temperature, are examined. The results demonstrate that the Gyroid packing design achieves comparable CO2 capture performance to conventional packed beds but with a significantly lower pressure drop of up to 77.8%, suggesting its potential as an efficient and cost‐effective solution for gas–liquid contactors in DAC. Additionally, the study explores the climate impact on CO2 capture performance and finds that as the air temperature increases from 35 to 95°F at a fixed relative humidity of 80%, the CO2 capture rate increased from 23.2% to 46.8% with better stability. The research highlights the importance of optimizing contactor design and operational conditions to improve the CO2 capture rate and feasibility of DAC systems as a negative emission technology for addressing greenhouse effects.

Magnetic nanoparticle‐induced sorbent regeneration for direct air capture

AbstractDirect air capture (DAC) is a promising technology for decarbonization through the removal of CO2 from the atmosphere. In many DAC processes, the regeneration energy used to restore the capture capacity of sorbents accounts for a significant fraction of the energy required by the whole process. Here we report an effective and scalable sorbent regeneration method for liquid DAC solvents based on magnetic nanoparticles (MNPs) heating with AC magnetic fields. MNPs can be directly heated to provide uniform and rapid volumetric heating, as we demonstrate by promoting the release of captured CO2 from an aqueous solution of potassium sarcosinate. Our results showed that 90% of the solvent can be regenerated within 7.5 min of heating through proposed technique. The MNPs and solvent are found to be stable during the regeneration process and the MNPs showed long‐term stability in the CO2‐saturated solvent. Cyclic experiments showed that the nanoparticles can be reused for multiple cycles without performance deterioration. The process is operated in a noncontact mode through electromagnetic waves, making it an adoptable approach for existing carbon capture systems. The MNPs heating provides an effective regeneration strategy for liquid solvents used in carbon capture processes, in particular for DAC.

Kinetics of CO2 absorption in N-Methyldiethanolamine solution promoted by potassium sarcosine

Potassium sarcosine (KSar) shows promise as an effective co-promoter of N-methyldiethanolamine (MDEA), a tertiary amine known for its high CO2 absorption capacity but relatively slow kinetics. This study investigated the CO2 absorption kinetics in a KSar + MDEA + H2O solution using the pressure-decay technique in a stirred cell reactor. The experiments were performed at temperatures ranging from 303.15 K to 333.15 K, with varying concentrations of KSar (ranging from 3% to 15% by weight), while keeping the MDEA concentration constant at 20% by weight. Furthermore, the study involved assessing the physicochemical and mass transfer properties and comparing them to those of a solution containing MDEA (30 wt%) + H2O solution. Properties like density, viscosity, Henry's constant (HN2O), and the physical mass-transfer coefficient of the liquid phase (kl) were measured and applied to analyze CO2 absorption kinetics. The overall reaction rate constant (kOV) was assessed using both termolecular and zwitterion mechanisms within a pseudo-first-order reaction regime. Additionally, kOV was estimated via correlated Arrhenius power law expression of the individual rate contributions of CO2−MDEA, CO2–H2O, and CO2−KSar. The calculated kOV values were found to closely match the experimental data, with absolute average relative deviations (AARD) of 4.53% and 3.03% for the termolecular and zwitterion models, respectively. The experimental results clearly showed that the rate of CO2 absorption, represented by kOV, can be significantly enhanced by adding a small amount of KSar into the MDEA + H2O solution.

An effective air–liquid contactor for CO2 direct air capture using aqueous solvents

The development of a cost-effective, corrosion resistant, high-flux direct air capture (HiDAC) contactor for a solvent-based direct air capture (DAC) process is reported. Literature technoeconomic analyses suggest that the air–liquid contactor can cost over 20 % of the overall DAC plant’s annualized capital costs. To bring down the overall cost of DAC, it is imperative that an effective contactor is developed. A hybrid contactor consisting of a commercial polyvinylchloride structured packing enhanced with stainless-steel 410 random packing has been developed to provide a high surface area for air–liquid contact. The contactor geometry, wettability, corrosion resistance, pressure drop, along with its CO₂ uptake efficiency, CO₂ uptake rates, and extended loading potential using potassium sarcosinate solutions are investigated. Results show that the HiDAC contactor has a relatively high specific surface area (885 m2/m3), which allows for CO₂ uptake efficiencies of up to 75 % and capture rates of up to 550 g of CO₂ per day for a 0.3 × 0.25 × 0.3 m contactor. The contactor also exhibits high levels of wettability and corrosion resistance with amino acid-based DAC solvents. A CO₂ uptake model was developed, and modeling results are compared to experimental data to simulate and predict the performance of the contactor in a DAC process using potassium sarcosinate solvent. The system’s overall mass transfer coefficient and theoretical pressure drop were also calculated, and these results were compared to DAC data found in literature. The results presented indicate that the HiDAC contactor is well suited for DAC due to its high specific surface area, resistance to corrosion, and high degree of wettability.

Determination of the regeneration energy of direct air capture solvents/sorbents using calorimetric methods

Regeneration energy and recyclability are important parameters that dictate the viability of a CO₂ direct air capture (DAC) process. In this study, differential scanning calorimetry (DSC) is used in conjunction with thermogravimetric analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR) to evaluate the regeneration energy required for CO2-loaded 3 M aqueous potassium sarcosinate (K-SAR) solvent and crystalline methyl-glyoxal-bisiminoguanidine (MGBIG) sorbent. Based on calorimetric measurements, for aqueous K-SAR, the sensible heat amounts to 1.5 GJ/tCO2 and the enthalpy of desorption is estimated at 3.68 GJ/tCO2. The total energy of regeneration will also include the enthalpy of solvent vaporization, which will depend on the thermodynamic conditions and the level of regeneration. For MGBIG, the total regeneration energy required was measured at approximately 7.0 GJ/tCO2. FTIR measurements were used to observe CO₂ and H2O release during the thermal regeneration process. For K-SAR, CO₂ release is seen to take place at temperatures greater than 80 °C and, for MGBIG, the CO₂ release takes place at temperatures greater than 100 °C. The moderate temperatures required for K-SAR and MGBIG regenerations compared to other DAC solvents/sorbents suggest that low-cost sources of heat, such as geothermal heat, could potentially be used for regeneration to drive down the cost of direct air capture.

Ultra-fast microwave regeneration of CO2 solid sorbents for energy-efficient direct air capture

Large-scale deployment of direct air capture (DAC) technologies has become critical for mitigating climate change. Towards this end, energy-efficient regeneration of the sorbents used in the process of carbon capture from air is very important to significantly reduce the high operational cost of DAC. Guanidine compounds can be used with environmentally friendly aqueous amino acids (e.g., potassium sarcosinate) for fast and effective CO2 capture from air, and have a strong potential for low-energy CO2 release and sorbent regeneration. In this process, the amino acid absorbs the CO2 from the air, and the guanidine compounds react with the CO2-rich amino acid solution and crystallize as an insoluble carbonate salt. Separation and thermal regeneration of the precipitated guanidine carbonate salt leads to an overall low-temperature and low-energy direct air capture process. Effective CO2 release from the solid guanidine compound can be achieved by mild heating at 120 °C. In this study, to overcome the relatively inefficient traditional conductive heating of the crystalline solid (i.e., Methylglyoxal-bis(iminoguanidine) carbonate, MGBIG carbonate), we evaluated the feasibility of microwave heating of MGBIG carbonate in terms of power requirement, radiation time, and solids mass for efficient CO2 desorption. The energy consumption needed by a microwave oven and a conventional oven to regenerate the same mass of the sorbent was directly measured to compare the total energy required per unit mass of regenerated sample and provide an understanding of the potential benefits of microwave regeneration. We found that microwave heating effectively regenerates MGBIG carbonate, which may be facilitated by the water molecules that are co-crystallized with carbonate in the guanidine crystals. Microwave heating at 2.54 GHz with 1250 W is up to 17 times faster than conventional conductive heating at 160 °C, resulting in 40 % electrical energy reduction. These results indicate that microwave regeneration may be an energy-efficient method for fast regeneration of solid sorbents used for direct air capture.

Sulfur recycle in biogas production: Novel Higee desulfurization process using natural amino acid salts

In this work, a desulfurization method using natural amino acid salts (AAS), which can be green prepared by biological fermentation, is proposed to remove H2S from raw biogas. Biogas purification and fertilizer production can be simultaneously achieved to close sulfur recycle. The reaction kinetic characteristics of H2S absorption with three kinds of AAS, including potassium β-alaninate (PA), potassium sarcosinate (PS) and potassium l-prolinate (PP) are first studied. Kinetic parameters including orders of reaction, rate constants, pre-exponential factors and activation energies are given. AAS absorbent exhibits good potential for biogas desulfurization. Higee (high gravity) technology is utilized to intensify H2S removal. The effects of operating conditions on H2S removal efficiency are investigated and PP shows the best desulfurization performance. The phytotoxicity of AAS and amino acid salt sulfide (AASS) is assessed by the germination index of mungbean seeds. PP and its salt sulfide (PPS) show relatively low phytotoxicity and their allowable agricultural feeding concentrations are below 0.08 M and 0.04 M, respectively. The desulfurization method demonstrates a green route for biogas purification to achieve sulfur recycle.

Improved quasi-cycle capacity method based on microcalorimetry strategy for the fast screening of amino acid salt absorbents for CO2 capture

Reaction rate and energy consumption are important factors that determine whether the chemical absorbent is suitable for capturing carbon dioxide (CO2). In this work, a high-precision microcalorimetry instead of the traditional estimation method based on the Gibbs-Helmholtz equation was used to directly measure the CO2 absorption heat of six amino acid salt absorbents (potassium taurinate (PT), potassium sarcosinate (PS), potassium L-Prolinate (PL-P), potassium β-Alaninate (Pβ-A), potassium L-Threonine (PL-T), and potassium glycinate (PG)) and the sensible heat of their solutions. In addition, the absorption rate, desorption rate, absorption time, desorption time, and CO2 loading of the absorbents were studied and were integrated into a parameter called the CO2 quasi-cycle capacity to evaluate the reaction rate. Based on thermodynamic data and CO2 quasi-cycle capacity, the absorbent screening method was improved in this work, and PS was identified as a promising absorbent by this method. The CO2 quasi-cycle capacity of the PS solution was similar to that of MEA. In addition, PS solution has the lowest CO2 absorption heat (-75.79 kJ/mol CO2) and the lowest sensible heat which were 14.1% and 23.2% lower than those of MEA solution.

Evaluation of CO2 Absorption by Amino Acid Salt Aqueous Solution Using Hybrid Soft Computing Methods.

Amino acid salt (AAs) aqueous solutions have recently exhibited a great potential in CO2 absorption from various gas mixtures. In this work, four hybrid machine learning methods were developed to evaluate 626 CO2 and AAs equilibrium data for different aqueous solutions of AAs (potassium sarcosinate, potassium l-asparaginate, potassium l-glutaminate, sodium l-phenylalanine, sodium glycinate, and potassium lysinate) gathered from reliable references. The models are the hybrids of the least squares support vector machine and coupled simulated annealing optimization algorithm, radial basis function neural network (RBF-NN), particle swarm optimization–adaptive neuro-fuzzy inference system, and hybrid adaptive neuro-fuzzy inference system. The inputs of the models are the CO2 partial pressure, temperature, mass concentration in the aqueous solution, molecular weight of AAs, hydrogen bond donor count, hydrogen bond acceptor count, rotatable bond count, heavy atom count, and complexity, and the CO2 loading capacity of AAs aqueous solution is considered as the output of the models. The accuracies of the models’ results were verified through graphical and statistical analyses. RBF-NN performance is promising and surpassed that of other models in estimating the CO2 loading capacities of AAs aqueous solutions.

Insights into dual functions of amino acid salts as CO2 carriers and CaCO3 regulators for integrated CO2 absorption and mineralisation

Integrated CO2 absorption and mineralisation (IAM) is a promising technology for rapidly CO2 absorption and sequestration. However, the traditional IAM using alkanolamines as CO2 solvents and solid wastes as carbonation feedstocks still suffers from the utilization difficulty of low value products and environmental risks of amine degradation. In this study, the green solvent, amino acid salts (AAS), including potassium l-argininate (ArgK), potassium glycinate, potassium sarcosinate, potassium l-alaninate, potassium β-alaninate, were selected for IAM using rejected brine as the carbonation feedstock. Results shows that compared to amines (monoethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, piperazine, 2-amino-2-methy-1-propanol), the selected AASs in IAM were not only more effective CO2 carriers that passed CO2 to calcium ions to form CaCO3, but also better CaCO3 growth regulators to tune morphology properties of products. CO2 desorption efficiencies in CO2-loaded AASs (nearly 100 %) were much higher than those of in CO2-loaded amines especially than in MEA (38 %). ArgK stood out in regulating the morphology of crystal with smallest particle size. Then ArgK was selected for optimization experiments at various conditions (temperature, Ca2+/CO2 ratio, reactant concentration and chelating agent) to further investigate effects of operating conditions on CaCO3 properties and to provide some basic information for the polymorph and morphology regulation of CaCO3. Ethylene diamine tetraacetic acid (EDTA) as a chelating agent was found a notable influence on controlling the polymorph of CaCO3, where the amorphous CaCO3 and new structures of calcite appeared. However, the effect of EDTA on CO2 absorption step was not clear and required further investigation.

Evaluation of potassium glycinate, potassium lysinate, potassium sarcosinate and potassium threonate solutions in CO2 capture using membranes

The mitigation process of greenhouse gases emission such as CO2 into the atmosphere is known as a vital necessity in modern societies. Nowadays, amino acid salt solutions (AASSs) have been extensively applied as a promising alternative to alkanol amine absorbents to increase the CO2 sequestration efficiency from disparate gaseous flows. This article aims to computationally and theoretically evaluate the CO2 separation percentage using potassium glycinate (PG), potassium lysinate (PL), potassium sarcosinate (PS) and potassium threonate (PT) amino acid solutions from an inlet gaseous mixture inside a hydrophobic membrane contactor (HMC). To do this, the governing first principal equations inside the HMC are solved using the computational fluid dynamics procedure based on finite element technique. Acceptable agreement between the simulation results and experimental values with average deviation of approximately 3% implies the validation of developed two-dimensional (2D) simulation approach developed in this study. The analysis of obtained results demonstrated that PG is the most efficient amino acid solution for CO2 molecular sequestration with the ability of separating 90% of inlet CO2 in the system. The order of solutions is 90% sequestration using PG > 89.3% sequestration using PT > 77.4% sequestration using PL > 72.3% sequestration using PS.

Next generation amino acid technology for CO2 capture

A flexible strategy to prepare a scalable CO2 absorbent (LAHPs) via encapsulating amino acid salt solutions in a polymer matrix.

Water-lean blend mixtures of amino acid salts and 2-methoxyethanol for CO2 capture: Density, viscosity and solubility of CO2

Water-lean amino acid salt (AAS) solutions have attracted special attentions for energy-efficient CO2 absorbents. In this work, 2-methoxyethanol was proposed as a novel anti-solvent due to its excellent properties such as low volatility, low specific heat capacity and low viscosity. Density and viscosity were measured at atmospheric pressure for water-lean blends of potassium sarcosinate (SarK) or potassium L-prolinate (ProK)/water/2-methoxyethanol over the temperature range from (293 to 353) K and the AAS molality up to 4.914 mol·kg−1. Partially CO2 loaded solutions were also investigated. Equilibrium solubility of CO2 in AAS/water/2-methoxyethanol solutions was measured in a stirred equilibrium cell at temperatures of (313, 333 and 373) K and CO2 partial pressures up to 190 kPa. These property data were correlated using empirical correlations as a function of AAS molality, CO2 molality and/or temperature. The predicted values of density and viscosity matched well with the measured data, with AADs within 0.31% for density and 3.76% for viscosity. The solubility data of CO2 were fairly fitted with a proposed Soft model.

Amino-Acid-Salt-based Carbon Dioxide Capture: Precipitation Behavior of Potassium Sarcosine Solution

This work studied the precipitation behavior of solids in the aqueous solution of potassium sarcosine (KSar) during the CO2 capture process with the concentration of 5m’ (mol/kg solution). The effect of precipitation on the CO2 capture capabilities was also studied. The results showed that 5m’ KSar gives a comparable result to MEA. The relatively high initial CO2 absorption efficiency combined with the positive effect of precipitation on CO2 absorption rate and CO2 capacity have made the 5m’ KSar be a promising solvent for the CO2 capturing process with precipitation.

Direct Air Capture of CO2 with Aqueous Amino Acids and Solid Bis-iminoguanidines (BIGs)

We report a bench-scale direct air capture (DAC) process comprising CO2 absorption with aqueous amino acid salts (i.e., potassium glycinate, potassium sarcosinate), followed by room-temperature reg...

Computational simulation and theoretical modeling of CO2 separation using EDA, PZEA and PS absorbents inside the hollow fiber membrane contactor

This paper deals with developing a theoretical modeling and a two dimensional (2D) computational simulation to evaluate the CO2 separation percentage from CO2/CH4 gaseous mixture under non-wetting mode of operation inside the membrane pores and counter-current adjustment of liquid and gas flows. As the novelty, the effect of ethylenediamine (EDA), 2-(1-piperazinyl)-ethylamine (PZEA) and potassium sarcosinate (PS) liquid absorbents on the CO2 separation performance is studied and the most efficient absorbent is introduced. The results show that PZEA can sequester 88.75% of inlet CO2 while the separation percentage of CO2 using PS and EDA is 82.2 and 81%, respectively. In addition, the mathematical model outcomes corroborate that increase in some operational factors and hollow fiber module specifications such as liquid flow rate, fiber packing density, module length and number of fibers encourages the separation efficiency of CO2 due to enhancing the residence time, contact area and consequently mass transfer rates inside the HFMC while increment of tortuosity factor and gas flow rate negatively deteriorates the separation percentage of CO2 which is able to be justified due to enhancement of mass transfer resistance through the pores of microporous membrane.

Low-Concentration CO2 Capture from Natural Gas Power Plants Using a Rotating Packed Bed Reactor

A rotating packed bed (RPB) was employed as a highly effective reactor to intensify CO2 capture in a green and natural amino acid salt absorbent, potassium sarcosine (KSAR), from the flue gas containing a low CO2 concentration. Experimental results show that a good CO2 capture performance, presented in terms of CO2 capture efficiency and overall volumetric mass transfer coefficient (KGa), can be obtained at a low CO2 concentration of 2–6%. CO2 capture efficiency could reach higher than 80% at a relatively high gas–liquid ratio, with CO2 loading up to 0.17 mol of CO2/mol of KSAR. Comparison results with a packed column show that a RPB can obtain higher CO2 capture performance with a smaller device size. Moreover, a mathematical model was developed to describe the mass transfer process in a RPB. Calculated values of KGa agreed well with experimental data, with a deviation within ±25%, and the tendency of the CO2 concentration at the outlet of the RPB can be well-predicted under a high liquid flow rate and h...

Simultaneous Separation of H2S and CO2 from Biogas by Gas–Liquid Membrane Contactor Using Single and Mixed Absorbents

The present work studied the simultaneous separation of H2S and CO2 from biogas by gas–liquid membrane contactor (GLMC) using single and mixed absorbents. The synthetic biogas contained 300 to 900 ppm of H2S, 30% to 50% CO2 and CH4. To better understand the effects of different absorbents on simultaneous separation of H2S and CO2 from biogas, water, monoethanolamine (MEA, primary amine), potassium carbonate (K2CO3, inorganic salt), potassium hydroxide (KOH, inorganic salt), and potassium sarcosine (PS, organic salt) were applied as absorbent solutions. Poly(vinylidene fluoride) (PVDF) hollow fiber membrane was used in the membrane contactor modules. The simultaneous absorption performance of CO2 and H2S into single and mixed absorbents was investigated. In addition, the effects of liquid and gas velocities, absorbent concentration, acid gas content of the feed gas, and gas pressure on the absorption performance and the analysis of mass transfer coefficients were investigated. The results indicated that th...

Recent Progress on the Performance of Different Rate Promoters in Potassium Carbonate Solvents for CO2 Capture

Over recent years our research group has examined the performance of a range of rate promoters in potassium carbonate solvent for carbon dioxide absorption. Promoters including boric acid, potassium glycinate, potassium prolinate, potassium sarcosinate and a thermally stable carbonic anhydrase enzyme have been studied either with the stopped flow technique, a wetted wall column or in the pilot plant located at The University of Melbourne in Australia. The carbonic anhydrase enzyme was shown to have the best promotion performance. However, improvements are required in further improving thermal stability and recycling options in order for the enzyme to be applied in industrial solvent absorption processes. Amino acid salts including potassium sarcosinate, prolinate and glycinate were proven to have high promotion performance at bench scale. Pilot plant results showed that the promotion performance of boric acid was poor, while potassium glycinate was a good rate promoter with an increase in absorption rate of up to 5–6 times when adding 10 wt. % glycinate into 40–45 wt. % potassium carbonate solvent.