Multiobjective Evaluation of Amine-Based Absorbents for SO₂ Capture Process Using the pK_a Mathematical Model

Abstract

The screening of high-efficiency and low-energy consumption absorbents is critical for capturing SO2. In this study, absorbents with better performance are screened based on mechanism, model, calculation, verification, and analysis methods. The acidity coefficient (pK a) values of ethylenediamine (EDA), piperazine (PZ), 1-(2-hydroxyethyl)­piperazine (HEP), 1,4-bis­(2-hydroxyethyl)­piperazine (DIHEP), and 1-(2-hydroxyethyl)-4-(2-hydroxypropyl)­piperazine (HEHPP) are calculated by quantum chemical methods. A mathematical model of the SO2 cyclic absorption capacity per amine (αc) in the amine-based SO2 capture process is built based on the electroneutrality of the solution. Another model of desorption reaction heat (Q des) is also built based on the van’t Hoff equation. Correspondingly, αc and Q des of the above five diamines are calculated and verified with the experimental data. The results show that αc of the diamine changes with the increase in the pK a value, and the increase in the pK a value directly leads to changes in Q des. The order of αc of the above five diamines is EDA > PZ > HEHPP > HEP > DIHEP, and the order of Q des is EDA > PZ > HEHPP > DIHEP > HEP. The multiobjective analysis between αc and Q des suggests that it is not advisable to simply pursue a higher αc while ignoring Q des. The compound quaternary system absorbent has a wider range of αc than the single ternary absorbent, which is the direction of absorbent development. This study is expected to strengthen absorbent screening for the amine-based SO2 capture process from flue gas.

Interfacial Concentration Gradient as a Source of Anomalous Photoeffect in Photoelectrodes

“…When dissolved in deionized water, depending upon the pH, Na 2 SO 3 forms three distinct species: , , and (Figure B,C). , The percentage of varied species produced by Na 2 SO 3 in deionized water at various pH values can be obtained by using the following equations: …”

Dissociation Constants of Amine Solvents Used in CO2 Capture: Titrimetric Estimation and Density Functional Theory Calculation

“…Recently, Wang et al estimated the pK a values of amine-based absorbents ethylenediamine, PZ, 1-(2-hydroxyethyl)piperazine, 1,4-bis(2hydroxyethyl)piperazine, and 1-(2-hydroxyethyl)-4-(2hydroxypropyl)piperazine for the SO 2 capture process using the mathematical model. 17 Schenck et al 18 estimated the pK a values of a series of amines (1-methylimidazole, morpholine, benzylamine, diethylamine, 2,4-dinitrobenzoic acid, salicylic acid, aspirin, niacin, imidazole) for drug design application. Bis(3-aminopropyl) amine (APA) and its blend can be a potential candidate for CO 2 capture as reported in the literature.…”

“…using the potentiometric titration method. , They also predicted the p K a values of various amines by the Perrin–Dempsy–Serjeant (PDS) empirical model, which determines the p K a values of unkown amines by considering the conjugation of amine moieties to the parent amine. Recently, Wang et al estimated the p K a values of amine-based absorbents ethylenediamine, PZ, 1-(2-hydroxyethyl)­piperazine, 1,4-bis­(2-hydroxyethyl)­piperazine, and 1-(2-hydroxyethyl)-4-(2-hydroxypropyl)­piperazine for the SO 2 capture process using the mathematical model . Schenck et al estimated the p K a values of a series of amines (1-methylimidazole, morpholine, benzylamine, diethylamine, 2,4-dinitrobenzoic acid, salicylic acid, aspirin, niacin, imidazole) for drug design application.…”

Nafion-Mediated Proton Transfer Facilitates the Electroreduction of SO2 to H2S

“…From a thermodynamic perspective, the reactant concentration and mass transfer facilitate the reaction. Research has demonstrated that during electrolysis, SO 2 participates in the reduction reaction in its molecular form, and a higher concentration of H + on the electrode surface promotes the presence of SO 2 in its molecular state . Consequently, a strongly acidic environment was more conducive to the kinetics of the SO 2 reduction reaction and H 2 S formation (eq ).…”

“…Research has demonstrated that during electrolysis, SO 2 participates in the reduction reaction in its molecular form, and a higher concentration of H + on the electrode surface promotes the presence of SO 2 in its molecular state. 14 Consequently, a strongly acidic environment was more conducive to the kinetics of the SO 2 reduction reaction and H 2 S formation (eq 1). However, as the target current density of H 2 S increased, the mass transfer rate of H + could not meet the demand for H + consumption, resulting in the deficiency of protons near the electrode surface (Figure S1).…”