Selective Sulfur Dioxide Removal Using Organic Solvents

Abstract

It has been found that sulfur dioxide solubility in organic solvents can be well-correlated by Lewis basicity numbers. Mixtures of sulfur dioxide and solvent (N-methylpyrrolidone (NMP), N,N′-(dimethylpropylene)urea (DMPU) and methyldiethanolamine (MDEA)) have been prepared in a 1:1 mole ratio at low temperatures. The melting points of the mixtures are measured, and the mixtures have been analyzed by infrared, ultraviolet-visible, and nuclear magnetic resonance spectroscopy. The solubility of sulfur dioxide has been measured in NMP and DMPU at 25 °C. At sulfur dioxide concentrations of 0.2-0.6 kPa, the solubility is determined using a continuous stirred tank reactor. The absorption of sulfur dioxide proved to be completely reversible. A model where physical and chemical interactions are incorporated showed good correlation with the experimental results.

Computational Studies on the Sulfur Dioxide Absorption by Organic Lewis Bases

“…However, in the case of the SO 2 absorption and stripping, Lewis acid-base reactions involving dative bonds as shown in Scheme 1 happen while amines react with CO 2 to produce carbamates via covalent bonds. 4,6 This difference in the reaction mechanism was experimentally verified that Lewis basicity parameterized by Gutmann donor number (D N ) was related to the reactivity of the SO 2 absorption while it did not for the CO 2 case. 4 Various sulfur dioxide complexes at molecular level have been extensively studied by Kuczkowski and coworkers.…”

“…4,6 This difference in the reaction mechanism was experimentally verified that Lewis basicity parameterized by Gutmann donor number (D N ) was related to the reactivity of the SO 2 absorption while it did not for the CO 2 case. 4 Various sulfur dioxide complexes at molecular level have been extensively studied by Kuczkowski and coworkers. [7][8][9][10] They classified sulfur dioxide complexes according to the types of interactions into charge-transfer complexes, van der Waals complexes, and hydrogen-bonded complexes.…”

“…As this process gives a large amount of solid waste cakes as by-products as well, the new absorption methods using organic solvents as SO 2 -removal agents have been explored because the absorbing agents can be regenerated repeatedly. [1][2][3][4][5] The SO 2 removal method by organic solvents is generally composed of two steps; 1) a fixation of SO 2 from the flue gas by the formation of a absorbent-SO 2 complex, and 2) thermal regeneration of absorbing agents and SO 2 stripping at the same time. The working process looks similar to that of an amine-CO 2 reaction which is an important CO 2 removal method from the flue gas.…”

“…Only chemical engineers have been interested in this issue, and studied the SO 2 removal process experimentally. [1][2][3][4][5] In this regard we have conducted quantum mechanical computations to trace the reaction between amines and SO 2 , and to calculate binding energies of the stable Lewis acid-base complexes in both a gas phase and an aqueous environment. Lewis bases dealt with in this work were trimethylamine (TMA), triethylamine (TEA), monoethanolamine (MEA), pyridine, and methylpyrolidone (NMP), where NMP did not form an SO 2 complex via an N-S bond but reacts with SO 2 by forming a O(carbonyl)-S bond (Figure 1e).…”

Simple spectrophotometry method for the determination of sulfur dioxide in an alcohol-thionyl chloride reaction

“…As a result, sulfur dioxide has to be purged to below 5mg/mL to achieve satisfactory yield in the next step. The degassing process was very challenging due to the high solubility of sulfur dioxide in the reaction stream, which is mainly composed of the solvent, N-methyl-2-pyrrolidone (NMP) [3]. A combination of heating, sweeping of headspace with nitrogen gas, and application M A N U S C R I P T…”