Aqueous Solutions Of K2CO3 Research Articles

Martin Silicates as Partners in Photoredox/Ni Dual Catalysis for the Installation of CH3, CH2D, CD2H, CD3and13CH3Groups onto (Hetero)Arenes

Martin Silicates as Partners in Photoredox/Ni Dual Catalysis for the Installation of CH₃, CH₂D, CD₂H, CD₃and¹³CH₃Groups onto (Hetero)Arenes

Potassium carbonate decomposition modeling within rotating detonation engines for direct power extraction applications

Recently, there has been a significant interest in detonation-based combustion systems, such as rotating detonation engines (RDE), due to potential performance advantages in propulsion and energy applications. This includes improvements in thermodynamic efficiency, inherently high gas velocities, and the possibility of achieving an increase in total pressure (i.e. pressure gain) through the combustion process. Due to approximating a constant volume combustion process, these devices also tend to exhibit extremely high local gas temperatures relative to a comparable constant pressure combustor. These advantages overlap well with desirable performance characteristics of direct power extraction (DPE) technologies, such as a magnetohydrodynamic (MHD) generator. Typically, in DPE systems hot combustion products are seeded with an easily ionizable material such as potassium carbonate (K2CO3) in order to boost the electrical conductivity. However, due to the short gas residence times within an RDE, it was unclear whether forming an electrically conductive combustion plasma would be feasible for integration with a downstream MHD generator. A model is presented which describes the heating, decomposition, and ionization of solid K2CO3 particles and aqueous solutions of K2CO3 in water, for a given initial particle diameter. This model was combined with available computational fluid dynamics (CFD) data for an oxygen-methane RDE in a one-way coupled Eulerian-Lagrangian framework to predict particle trajectories and the corresponding heating, decomposition, and ionization histories. Electrical conductivities were computed using a previously developed model, and a method was proposed to determine an equivalent average electrical conductivity. Results show that particle sizes below ∼30 µm are able to fully decompose before reaching the exit of the RDE. While the one-way coupled nature of the simulations precluded rigorous evaluation of the effects of seed material on detonability, a substantial temperature reduction is expected at the detonation wave front due to heating and decomposition. A preliminary comparison is presented between the RDE and an equivalent constant pressure adiabatic combustor, showing a potential performance advantage for the RDE.

Study of CO2 absorption/desorption behaviors in aqueous (2-hydroxyethyl)-trimethyl-ammonium (S)-2-pyrrolidine-carboxylic acid salt ([Cho][Pro]) + K2CO3 solutions

In this work, an aqueous (2-hydroxyethyl)-trimethyl-ammonium (S)-2-pyrrolidinecarboxylic acid salt ([Cho][Pro]) + K2CO3 solution was studied as a novel absorbent for CO2 capture, and the kinetics and mechanism of the CO2 absorption/desorption process were systematically investigated. Adding [Cho][Pro] to the aqueous K2CO3 solution improved the absorption rate of the solution during the initial stage, and the apparent CO2 absorption rate increased as the concentration of [Cho][Pro] increased. Meanwhile, equilibrium was reached faster when [Cho][Pro] was added, and a tradeoff was noticed between the apparent absorption rate constant and equilibrium absorption amount. The desorption rates of the CO2-rich aqueous [Cho][Pro] + K2CO3 solutions were higher than that of the aqueous [Cho][Pro] solution at 363.15 K, and the highest apparent desorption rate constant was achieved for the aqueous 20 wt.% [Cho][Pro] + 10 wt.% K2CO3 solution. A further study on the aqueous 20 wt.% [Cho][Pro] + 10 wt.% K2CO3 solution indicated that the desorption amount increased with the increase in the temperature from 348.15 to 365.15 K. Moreover, with further increase in temperature, the desorption amount exhibited a lower increasing rate when temperature was higher than 361.15 K. The 20 wt.% [Cho][Pro] + 10 wt.% K2CO3 absorbent exhibited more stable regeneration performance after 7 cycles and lower desorption activation energy than the aqueous 30 wt.% monoethanolamine (MEA) and 30 wt.% [Cho][Pro] solutions as well as higher working capacity compared to the aqueous 30 wt.% [Cho][Pro] solution.

Carbon Dioxide Absorption from Biogas by Amino Acid Salt Promoted Potassium Carbonate Solutions in a Hollow Fiber Membrane Contactor: A Numerical Study

Aqueous K2CO3 solution is a promising absorbent in removing CO2 from gas mixtures using a hollow fiber membrane contactor (HFMC). The use of amino acid salts (AASs) as a promoter in K2CO3 solutions may further improve absorption performance. In this study, a two-dimensional mathematical model was developed to simulate the CO2 absorption process in an HFMC, where potassium salts of glycinate (PG), lysine (PL), and arginine (PA) were considered as promoters in K2CO3 solution. The absorption performances of K2CO3 solutions with and without promoters were analyzed theoretically. The effects of operating parameters, such as AAS concentration, temperature, pressure, flow rate, and initial CO2 content, on the absorption process were also investigated. The results showed that the use of AASs as promoters in K2CO3 solution significantly enhances the CO2 absorption performance. PG-promoted K2CO3 solution outperformed the other two, as it showed the highest absorption flux and CO2 removal efficiency under any operat...

Reduction of Tar and Soot Formation from Entrained-Flow Gasification of Woody Biomass by Alkali Impregnation

Tar and soot in product gas have been a major technical challenge toward the large-scale industrial installation of biomass gasification. This study aims at demonstrating that the formation of tar and soot can be reduced simultaneously using the catalytic activity of alkali metal species. Pine sawdust was impregnated with aqueous K2CO3 solution by wet impregnation methods prior to the gasification experiments. Raw and alkali-impregnated sawdust were gasified in a laminar drop-tube furnace at 900–1400 °C in a N2–CO2 mixture, because that creates conditions representative for an entrained-flow gasification process. At 900–1100 °C, char, soot and tar decreased with the temperature rise for both raw and alkali-impregnated sawdust. The change in tar and soot yields indicated that potassium inhibited the growth of polycyclic aromatic hydrocarbons and promoted the decomposition of light tar (with 1–2 aromatic rings). The results also indicated that the catalytic activity of potassium on tar decomposition exists ...

Experimental investigation of explosion mitigating properties of aqueous potassium carbonate solutions

The oil industry operates installations and processes with important quantities of flammable substances within a wide range of pressures and temperatures. A particular hazard for this type of installations is an accidental release of a large quantity of flammable material resulting in the formation of a flammable cloud within the installation. Upon ignition, such a cloud can lead to a devastating explosion. Such accidents are commonly named “Vapor Cloud Explosions” (VCE).Water mist systems are known to be effective for inhibition and suppression of fires. Other systems for inhibition and suppression of fires are based on the action of dry powders as inhibitors. Alkali compounds, applied as powders, have proven to be effective not only for mitigation of fires but also for inhibition of vapor cloud explosions. The combination of the physical effects of water mist on flames combined with the inhibiting effects of alkali compounds on combustion chemistry might result in a superior Vapor Cloud Explosion mitigating agent.In this article, the results are given and discussed of an experimental study of explosion mitigation by using various concentrations of aqueous K2CO3 concentrations (varying from 10 to 70 g/l K2CO3) in lean, stoichiometric and rich propane/air mixtures in a 135 L channel. The tests with inhibitor-solutions were compared to that of pure water and dry tests (only propane/air). Four different congested configurations were applied, creating different degrees of turbulence and explosion violence.The experimental results show that by increasing the amount of potassium carbonate in water, an increase of the degree of mitigation (reduction of flame velocity and explosion overpressure) is observed up to possible full quenching. For the same mass loading density, aqueous solutions of K2CO3 in concentrations above 50–60 g/l have superior inhibition properties compared to dry K2CO3 powders with a particle distribution in the range of 20–100 μm.

CO2 capture using aqueous solutions of K2CO3+2-methylpiperazine and monoethanolamine: Specific heat capacity and heat of absorption

The specific heat capacity, heat of CCO2 absorption, and CCO2 absorption capacity of aqueous solutions of potassium carbonate (K2CO3)+2-methylpiperazine (2-MPZ) and monoethanolamine (MEA) were measured over various temperatures. An aqueous solution of K2CO3+2-MPZ is a promising absorbent for CCO2 capture because it has high CCO2 absorption capacity with improved absorption rate and degradation stability. Aqueous solution of MEA was used as a reference absorbent for comprison of the thermodynamic characteristics. Specific heat capacity was measured using a differential scanning calorimeter (DSC), and heat of CCO2 absorption and CCO2 absorption capacity were measured using a differential reaction calorimeter (DRC). The CCO2-loaded solutions had lower specific heat capacities than those of fresh solutions. Aqueous solutions of K2CO3+2-MPZ had lower specific heat capacity than those of MEA over the temperature ranges of 303-353 K. Under the typical operating conditions for the process (CCO2 loading=0.23mol-CCO2·mol−1-solute in fresh solution, T=313 K), the heat of absorption (−ΔHabs) of aqueous solutions of K2CO3+2-MPZ and MEA were approximately 49 and 75 kJ·mol-CO2, respectively. The thermodynamic data from this study can be used to design a process for CCO2 capture.

Potassium Carbonate Slurry-Based CO2 Capture Technology

Carbonate slurry process is considered to be one of the potential technologies for large-scale CO2 capture from coal-based power stations, as it can reduce the participation of water in stripper. In this work, constant volume method was adopted to measure the CO2 loading in aqueous potassium carbonate solutions at the temperatures of 40, 70, and 120 °C for CO2 partial pressure from 0.4 to 240 kPa. Absorption heats of CO2 in aqueous solutions of K2CO3, MEA, and MDEA were measured and compared using true heat flow method. The cyclic CO2 equilibrium loading increases with K2CO3 concentration increase, which is a benefit for CO2 capture. However, the increased viscosity leads to a decrease of the apparent absorption rate. Absorption heat depends on temperature, K2CO3 concentration, and CO2 loading. Compared to MEA, potassium carbonate solution has a lower absorption heat. Generated potassium bicarbonate crystallization can enhance CO2 absorption but also increase absorption heat. Slurry desorption can reduce ...

Direct CO2 capture from ambient air by K2CO3/alumina composite sorbent for synthesis of renewable methane

Abstract A composite sorbent was synthesized by impregnating cylindrical granules of mesoporous γ-Al2O3 with an aqueous solution of K2CO3. Three fractions of the composite with the

Effect of Arginine on Carbon Dioxide Capture by Potassium Carbonate Solution

Preliminary screening experiments of carbon dioxide (CO2) absorption into aqueous 35 wt % equivalent potassium carbonate (K2CO3) solution with different additives were performed in a wetted-wall column at 322 K. Arginine was found as an effective promoter to enhance the absorption rate in aqueous K2CO3 solution. The effect of arginine concentration and CO2 loading on the absorption rate into carbonate solutions is discussed. The vapor–liquid equilibrium of 35 wt % equivalent K2CO3 with 0–5 wt % arginine was obtained in the temperature range from 323 to 343 K using inert-gas stripping method. Desorption curves of the unpromoted and arginine-promoted carbonate solutions are also discussed.

Solubility of Carbon Dioxide in Activated Potash Solutions in the Low and High Gas Loading Regions

In the Hot Potassium Carbonate Process, carbon dioxide (CO2) is removed from gaseous streams by chemical absorption in an aqueous solution of potassium carbonate (K2CO3). It is common to activate the solvent by adding borates and vanadates as promoters. In the present investigation, we investigate the influence of borates and vanadates on the equilibrium solubility of CO2 in aqueous solutions of K2CO3. The solubility of CO2 in four activated aqueous solutions of K2CO3 was determined experimentally at two temperatures that are typical for CO2 absorption (343 K) and solvent regeneration (383 K) in the Hot Potassium Carbonate Process. The mass fraction of K2CO3 in the solvent was 0.26 g/g, and the mass fractions of boron (vanadium) was varied between 0.006 g/g and 0.013 g/g (0.01 g/g and 0.02 g/g). Two experimental setups were used: A headspace gas chromatography technique was applied to determine the solubility of CO2 at partial pressures of CO2 between 1 kPa and 140 kPa, and the synthetic gas solubility te...

Kinetic study of carbon dioxide absorption with aqueous potassium carbonate promoted by arginine

The absorption of carbon dioxide (CO2) into aqueous 35wt.% equivalent potassium carbonate (K2CO3) solution was performed using a wetted wall column at temperatures from 313K to 343K. Effect of arginine concentrations on absorption rates of CO2 into carbonate solutions was investigated and the second-order rate constant k1 was obtained using two-film model. Preliminary screening results showed that arginine was an effective promoter in aqueous K2CO3 solution for CO2 capture. The reaction of CO2 with arginine is described using zwitterionic mechanism. The overall reaction kinetic constant kov strongly increased with the increase of arginine concentration and absorption temperature under the investigated range. Based on the pseudo-first-order regime, the reaction rate parameters were obtained from the kinetic measurements and k1 was determined as 33,641 and 85,367Lmol−1s−1 at 315K and 325K, respectively with activation energy of 71.9kJmol−1. The overall reaction rate for CO2 absorption into promoted K2CO3 were described as the following equation: -rCO2=2.58×1016exp-8645TCArg+4.32×1013exp-6666TCOH-CCO2.

An Experimental Investigation of the Influence of Vanadium Pentoxide on the Solubility of CO2 in Aqueous Solutions of Potassium Carbonate

The “hot-potash” process is one of the most commonly used processes to remove carbon dioxide from gases in the chemical industry. The solvent of that absorption process is an aqueous solution of potassium carbonate. Dissolving carbon dioxide in an aqueous solution of K2CO3 results in the conversion of carbonate and CO2 to bicarbonate; that is, carbon dioxide is predominantly dissolved chemically. In industrial applications a single substance or a mixture of several substances are added to the solvent to improve the performance of the process. The specific role of such additives is often unknown, but it is well-established that some additives improve the performance of the “hot-potash” process. One of those additives is vanadium pentoxide. The influence of a small amount of vanadium pentoxide on the equilibrium solubility of carbon dioxide in aqueous solutions of potassium hydroxide was investigated at conditions that are typical for a “hot-ash” process. The experimental results reveal that vanadium pentox...

A Novel Approach to Prepare CaCO3/Polyvinylpyrrolidone (PVP) Composite Nanofibers

A new route to prepare CaCO3 nanoparticles/polyvinylpyrrolidone (PVP) nanofibers is reported. An aqueous solution of K2CO3 was added to a solution of CaCl2/PVP, resulting in in-situ preparation of CaCO3 nanoparticles. Then composite nanofibers containing CaCO3 nanoparticles were successfully prepared by electrospinning. The morphology of the resulting composite nanofibers was characterized by field-emission scanning electron microscopy. In addition, the products were characterized by thermogravimetry analysis and Fourier transform infrared spectra.

Preparation of Polyvinylpyrrolidone (PVP) Nanofibers Supported CaCO<sub>3</sub> Nanoparticles

In this paper, a new method for the preparation of composite nanofibers surface containing calcium carbonate nanoparticles using electrospinning technology was described. In detail, firstly, the type solution is formed by the aqueous solution of CaCl2which contains polyvinylpyrrolidone (PVP) and the other is the aqueous solution of K2CO3. Two types of solution were mixed completely, and then Ca2+and CO32−generated CaCO3nanoparticles. Secondly, composite nanofibers with CaCO3nanoparticles were successfully prepared by above solution electrospun. The resulting composite nanofibers were characterized by field-emission scanning electron microscopy (FE-SEM), it determination showed that perfect mono-dispersed spherical CaCO3nanoparticles were dispersed on polyvinylpyrrolidone (PVP) nanofibers.

Post-combustion CO2 capture in coal-fired power plants: Comparison of integrated chemical absorption processes with piperazine promoted potassium carbonate and MEA

Abstract A thermodynamic and economic comparison of post-combustion CO2 capture processes using aqueous solutions of piperazine (PZ) promoted potassium carbonate (K2CO3) and monoethanolamine (MEA) based on fair boundary conditions and constant assumptions using rigorous thermodynamic models is described. In contrast to a first preliminary comparison, it is shown that under the stated assumptions and considered boundary conditions, a 7 m MEA solution performs better in both thermodynamic and economic terms than aqueous solutions of K2CO3 and PZ.

Combined Process of CO2 Capture by Potassium Carbonate and Production of Basic Zinc(II) Carbonates: CO2 Release from Bicarbonate Solutions at Room Temperature and Pressure

The absorption of CO2 in aqueous solutions of K2CO3 has been investigated at six different temperatures in the range 10–60 °C and at atmospheric pressure. The CO2 absorption is fast and occurs with high efficiency without any added catalytic activator. The CO2 capture ranges between 83 and 99% expressed as the percentage of absorbed CO2 with respect to the neat CO2 flowing through the absorbent solution. The efficiency of CO2 removal increases with the temperature, which contrasts with the exoenthalpic nature of the reaction between CO2 and CO32− and the diminished solubility of CO2 at high temperature. Our finding indicates that the increase of the CO2/CO32− reaction rate with the temperature prevails over the opposite effect on the equilibrium due to the temperature increase. The stripping of pure CO2 from the HCO3− solutions has been achieved by adding a zinc(II) salt to the absorbed solutions which releases the captured CO2 rapidly and completely at room temperature and pressure with the simultaneous separation of solid compounds identified as mixtures of commercially valuable basic zinc carbonates. Although the exact evaluation of the overall merits of the proposed CO2 capturing technology would require a complete analysis of the energy profile of the process, it is obvious that any improvement of the CO2 capture process resulting in the associated synthesis of a valuable product without additional energy burdening reduces the cost of CO2 capture and maximizes the neat balance CO2(captured) − CO2(emitted) where CO2(emitted) represents the total energy bill (electrical, thermal, mechanical) required to sustain the entire cycle of CO2 abatement.

Reaction oftrans-Pd(styryl)Br(PMePh2)2with Styryl Bromide Affording 1,4-Diphenylbutadiene. An Unexpected Homocoupling Process Induced by P−C Reductive Elimination

Reaction of (Z)-styryl bromide (1) with PhB(OH)2 in toluene at 80 °C for 1 h in the presence of Pd(PPh3)4 (1.5 mol %) and an aqueous solution of K2CO3 (3 equiv) affords (Z)-stilbene as the cross-coupling product in 99% yield. On the other hand, the same reaction of the (E)-isomer of 1 forms considerable amounts of homocoupling products (1,4-diphenylbutadiene (2, 22%) and biphenyl (27%)) in addition to the cross-coupling product ((E)-stilbene, 73%). The formation of 2 was examined by kinetic experiments using trans-Pd(CH═CHPh)Br(PMePh2)2 (3) as a model of the presumed intermediate. Complex 3 reacts with 1 at 50 °C for 5 h, giving 2 (91%) and trans-PdBr2(PMePh2)2 (4, 92%), together with a small amount of Pd(η2-PhCH═CHPMePh2)Br(PMePh2) (5, 8%). The reaction rate shows first-order dependence on the concentration of 3 and 5, respectively, but is independent of the concentration of 1. A novel homocoupling process induced by P−C reductive elimination from 3 giving 5 is proposed.

Gas permeability of combined membrane systems with mobile liquid carrier

Gas transfer in a membrane system called a selective membrane valve (SMV) is studied. The SMV is a system consisting of two mobile gas phases, one mobile liquid phase, and two membranes acting as interfaces between gas and liquid. Such a membrane system has supplementary variable parameters and is designated for the separation of multicomponent gas mixtures. System permeability for individual gases (CO2, O2, and H2) and its dependence on a flow rate of a liquid phase are studied. Time dependences of the non-steady state transfer of CO2 through the immobile layer of chemisorbent (aqueous K2CO3 solution) at its different concentrations are studied for the first time. Two theoretical models are developed: the model of gas transfer through a selective membrane valve system with a mobile liquid absorbent (in the absence of chemical interaction) and the model of a non-steady-state transfer of CO2 through the immobile layer of aqueous potassium carbonate solution. The first model makes it possible to determine gas-to-liquid diffusion coefficients; the second model permits us to plot kinetic permeability curves and to calculate system permeability with allowance for the CO2 transfer accompanied by reversible chemical reaction with the carrier. The model dependences agree well with the experimental data.

XPS and in situ IR spectroscopic studies of CO/Rh/Al2O3 and CO/Rh/K–Al2O3 at high temperatures: probing the impact of the potassium functionalization of the support

Potassium-functionalised alumina (6 wt.% K–Al2O3) was obtained by calcination at 973 K of pure alumina particles (Al2O3) impregnated with an aqueous solution of K2CO3. Both Al2O3 and K–Al2O3 were, then, impregnated with aqueous RhCl3·3H2O, dried at 393 K, and in situ reduced in H2 atmosphere to obtain 1 wt.% Rh/Al2O3 and Rh/K–Al2O3 catalysts, respectively. Impacts of the potassium-functionalization on high-temperature behaviour of the Rh catalyst towards CO atmosphere were examined by (i) X-ray photoelectron spectroscopic analysis of the surface chemical composition, (ii) particle sizing of the Rh content by means of transmission electron microscopy, and (iii) in situ infrared spectroscopy of adsorbed CO. Results obtained showed the potassium-functionalization to suppress the CO-induced oxidative degradation of Rh0 metal particles into RhI, enrich the electronic density at Rh0 metal sites, and stabilize the Rh content against CO-assisted elimination at high temperatures. On the other hand, the presence of potassium was found not to affect the initially high dispersity of Rh0 metal particles on alumina despite the promoting effect on CO decomposition.