Sung Chan Nam

Immobilization of carbonic anhydrase on spherical SBA-15 for hydration and sequestration of CO2.

Bovine carbonic anhydrase (BCA) was immobilized on spherical SBA-15 through various approaches, including covalent attachment (BCA-CA), adsorption (BCA-ADS), and cross-linked enzyme aggregation (BCA-CLEA). The spherical SBA-15 was characterized by XRD, BET, and FE-SEM analysis. (29)Si CP-MAS NMR was used to confirm the 3-aminopropyltriethoxysilane grafting (an intermediate step in the immobilization technique), and the immobilization of BCA was confirmed by FT-IR spectrum. The catalytic activities for hydration of CO(2) were calculated for free and immobilized BCA with and without buffer. The K(cat) values for free BCA, BCA-CLEA, BCA-CA and BCA-ADS were 0.79, 0.78, 0.58 and 0.36 s(-1), respectively, indicating that BCA-CLEA showed a comparatively higher hydration of CO(2) than BCA-CA and BCA-ADS, which was nearly the same as free BCA. The amount of CaCO(3) precipitated over free BCA, BCA-CLEA, BCA-CA and BCA-ADS were 140, 138, 135 and 130 mg, respectively. Performance studies, including assays on reusability, thermal stability and storage stability, were also carried out for BCA-CLEA. The results confirmed that BCA-CLEA is reusable, thermally stable and, withstands storage, and is thus a suitable candidate for use in hydration and sequestration of CO(2).

Carbonic anhydrase immobilized on encapsulated magnetic nanoparticles for CO2 sequestration.

Bovine carbonic anhydrase (BCA) was covalently immobilized onto OAPS (octa(aminophenyl)silsesquioxane)-functionalized Fe(3)O(4)/SiO(2) nanoparticles by using glutaraldehyde as a spacer. The Fe(3)O(4) nanoparticles were coated with SiO(2), onto which was grafted OAPS, and the product was characterized using SEM, TEM, XRD, IR, X-ray photoelectron spectroscopy (XPS), and magnetometer analysis. The enzymatic activities of the free and Fe(3)O(4)/SiO(2)/OAPS-conjugated BCA (Fe-CA) were investigated by hydrolyzing p-nitrophenylacetate (p-NPA), and hydration and sequestration of CO(2) to CaCO(3). The CO(2) conversion efficiency and reusability of the Fe-CA were studied before and after washing the recovered Fe-CA by applying a magnetic field and quantifying the unreacted Ca(2+) ions by using ion chromatography. After 30 cycles, the Fe-CA displayed strong activity, and the CO(2) capture efficiency was 26-fold higher than that of the free enzyme. Storage stability studies suggested that Fe-CA retained nearly 82 % of its activity after 30 days. Nucleation of the precipitated CaCO(3) was monitored by using polarized light microscopy, which revealed the formation of two phases, calcite and valerite, at pH 10 upon addition of serine. The magnetic nanobiocatalyst was shown to be an excellent reusable catalyst for the sequestration of CO(2).

CO2 Absorption and Sequestration as Various Polymorphs of CaCO3 Using Sterically Hindered Amine

One aspect of the attempt to restrain global warming is the reduction of the levels of atmospheric CO2 produced by fossil fuel power systems. This study attempted to develop a method that reduces CO2 emissions by investigating the absorption of CO2 into sterically hindered amine 2-amino-2-methyl-1-propanol (AMP), the acceleration of the absorption rate by using the enzyme carbonic anhydrase (CA), and the conversion of the absorption product to stable carbonates. CO2 absorbed by AMP is converted via a zwitterion mechanism to bicarbonate species; the presence of these anions was confirmed with (1)H and (13)C NMR spectral analysis. The catalytic efficiency (kcat/Km), CO2 absorption capacities, and enthalpy changes (ΔHabs) of aqueous AMP in the presence or absence of CA were found to be 2.61 × 10(6) or 1.35 × 10(2) M(-1) s(-1), 0.97 or 0.96 mol/mol, and -69 or -67 kJ/mol, respectively. The carbonation of AMP-absorbed CO2 was performed by using various Ca(2+) sources, viz., CaCl2 (CAC), Ca(OOCCH3)2 (CAA), and Ca(OOCCH2CH3)2 (CAP), to obtain various polymorphs of CaCO3. The yields of CaCO3 from the Ca(2+) sources were found in the order CAP > CAA > CAC as a result of the effects of the corresponding anions. CAC produces pure rhombohedral calcite, and CAA and CAP produce the unusual phase transformation of calcite to spherical vaterite crystals. Thus, AMP in combination with CAA and CAP can be used as a CO2 absorbent and buffering agent for the sequestration of CO2 in porous CaCO3.

CO2 absorption characteristics of a piperazine derivative with primary, secondary, and tertiary amino groups

Thermodynamic and kinetic data are important for designing a CO2 absorption process using aqueous amine solutions. A piperazine derivative, 1-(2-aminoethyl)piperazine (AEP), was blended with aqueous amine solutions due to its thermal degradation stability, high CO2 loading (mole of CO2-absorbed per mole of amine) and high solubility in water. In this study, the vapor liquid equilibrium (VLE), absorption rate, and species distribution of aqueous AEP solutions were studied to develop an optimum amine solution in a post-combustion capture process. The VLE and apparent absorption rate of the aqueous 30wt% AEP solution were measured using a batch-type reactor at 313.15, 333.15, and 353.15 K. The AEP exhibited approximately twice higher CO2 loading compared with monoethanolamine (MEA) at all temperatures. The apparent AEP absorption rate (kapp=0.1 min−1) was similar to that of diethanolamine (DEA) at 333.15 K. Speciation of the CO2-absorbed AEP was analyzed using 13C NMR. Although AEP featured a primary amino group and secondary amino group, it did not form bicarbamate upon reaction with CO2 based on analysis results. AEP-1-carbamate was primarily formed by reactions between AEP and CO2 during the initial reaction. Bicarbonate species formed as the quantity of absorbed CO2 increased.

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.

CO2 absorption, density, viscosity and vapor pressure of aqueous potassium carbonate+2-methylpiperazine

The physical properties of the absorbent are important for designing a CO2 capture process. The density and viscosity are used to calculate the mass transfer coefficient that determines the height of the absorber. Furthermore, these physical data affect the selection of liquid pump and pipe lines. Vapor pressure is a factor that estimates absorbent loss and condenser size. In this study, the physical properties of the aqueous potassium carbonate (K2CO3)+2-methylpiperazine (2MPZ) solution were obtained in a temperature range from 303.15 K to 343.15 K. The physical properties of the different aqueous K2CO3+2MPZ solutions (various amine concentrations and amounts of CO2 absorbed) were measured to obtain the parameters for process design. A regression analysis was conducted for the experimental data. The densities of the aqueous K2CO3+2MPZ solutions increased when the amounts of absorbed CO2 or 2MPZ concentrations were increased. The densities and viscosities of the absorbents decreased according to the increase in temperature. The viscosities of the absorbent increased when 2MPZ concentrations were increased. The temperature dependency of vapor pressure follows the Antoine equation; the CO2 gas and aqueous solution of a base follows the vapor pressure variation of the mixed solution.

Electrocatalytic Stability of Tin Cathode for Electroreduction of CO2 to Formate in Aqueous Solution

The electrocatalytic stability of tin (Sn) nanoparticle for electrochemical reduction of CO2 to formate was measured using an H-type cell during electrolysis for 40 h. The Faradaic efficiency (FE) and partial current density (PCD) of formate formation reduced as much as 10% and 13% of the maximum values, respectively. To elucidate the decrease in FE and PCD, the changes in the morphology, chemical composition, the crystalline structure were investigated. The spherical Sn nanoparticles were pulverized after electrolysis. Furthermore, the crystal structure of the fresh Sn electrocatalyst was collapsed and changed into amorphous phase after 40 h electrolysis. The decrease in FE and PCD of formate production on the Sn/CFP electrode could be mainly originated from the reduction of the SnOx to Sn on the cathode surface during electrolysis.

Post-combustion CO 2 capture with potassium L-lysine

Carbon dioxide is one of the main causes of global warming. In order to develop a novel absorbent, the characteristics of amino acid salts solution as a solvent for capture in continuous process were investigated. The cost of capture is almost 70% of total cost of CCS (carbon dioxide capture and storage). In the carbon dioxide capture process, process maintenance costs consist of the absorbent including the absorption, regeneration, degradation, and etc. It is very important to study the characteristics of absorbent in continuous process. In this study, we have investigated the properties of potassium L-lysine (PL) for getting scale-up factors in continuous process. To obtain optimum condition for removal efficiency of in continuous process by varying liquid-gas (L/G) ratio, concentration of and absorbent (PL) were tested. The stable condition of absorber and regenerator (L/G) ratio is 3.5. In addition, PL system reveals the highest removal efficiency of with 3.5 of L/G and 10.5 vol% ().

CO 2 decomposition characteristics of Ni-ferrite powder

The objective of this study is the development of carbon-recycle technology, that converts carbon dioxide captured from flue gas to carbon monoxide or carbon for reuse in industrial fields. It is difficult to decompose because is very stable molecule. And then metal oxide was used as an activation agent or catalyst for the decomposition of at low temperature. Metal oxides, which converts to CO or C, were prepared using Ni-ferrite by solid state method and hydrothermal synthesis in this study. TPR/TPO and TGA were used as an analysis method to analyze the decomposition characteristics of . As the results, the reduction area of was high value at 15 wt% of NiO and the decomposition area of was superior capacity at 5 wt% of NiO. However, TGA data showed contrary results that reduction area of was 28.47wt% and oxidation area by was 26.95wt% at 2.5 wt% of NiO, one of the Ni-ferrite powders synthesized using solid state method. decomposition efficiency was 94.66% and it is excellent results in comparison with previous studies.