Experimental and Theoretical Investigation of SO₂ Adsorption over the 1,3-Phenylenediamine/SiO₂ System

Abstract

The reversible adsorption of SO 2 on 1,3-phenylenediamine was investigated using the step transient response technique coupled with operando infrared spectroscopy, mass spectrometry, UV−vis spectrometry, and density functional theory (DFT). At 50°C, the reaction of SO 2 at the amine site resulted in fixation of sulfur as hydrogen-bonded SO 3 2− (sulfite) and SO 4 2− (sulfate) species. Simulated infrared and UV−vis spectra at the DFT B3LYP/6-31G(d,p) level were compared to the experimental results to help characterize the infrared spectra, molecular interactions, and bonding of the adsorbing species. The theoretically calculated binding energies revealed the sulfite and sulfate species bind stronger at the ammonium sites as compared to the amine site, which agrees with the infrared spectroscopic observations. Temperature-programmed desorption showed a capacity of 1.39 mol SO 2 /mol sorbent for pure 1,3-phenylenediamine and 2.8 mol SO 2 /mol sorbent for the SiO 2 supported sorbent. The presence of sulfite and sulfate in the sorbent layer at 50°C resulted in the oxidative degradation of the amine site to produce −NO 2 groups and deactivation of adsorption sites in the sorbent. The infrared data indicates that the adsorbed sulfite and sulfate species remained strongly bonded at the ammonium site, whereas the SO 2 , sulfite, and sulfate species at the amine site may be thermally desorbed from the sorbent. The retained SO 3 2− and SO 4 2− species led to the rapid deactivation of the sorbent during multicycle testing. INTRODUCTIONThe separation of sulfur dioxide (SO 2 ) from the flue gas in fossil fuel combustion processes are of particular interest for two primary reasons: (i) SO 2 is harmful to human health and the environment and (ii) SO 2 has the capability of poisoning the active site of various CO 2 capture technologies. 1,2 The mechanism of active site deactivation for amine-based sorbents is generally attributed to the irreversible adsorption of SO 2 and its competitive adsorption with CO 2 . The sorbent's capability to avoid irreversible reactions with SO 2 is an important characteristic for postcombustion applications. A solid amine sorbent for SO 2 removal having high adsorption capacity, longterm regeneration capacity, and low regeneration energy requirement may also improve plant operating costs. Our focus in investigating an amine-based sorbent for SO 2 removal is to study the amine reactive site in order to gain a greater understanding of the SO 2 −amine interactions with the purpose of creating a more effective SO 2 solid sorbent for the large-scale postcombustion scrubbing application.Recently, ionic liquids (ILs) have been proposed as adsorbents for acid gases such as SO 2 , 3−9 CO 2 , 10−14 and H 2 S, 15−17 as compared to technologies developed over the last several decades for flue gas desulfurization (FGD), such as limestone scrubbing, ammonia scrubbing, and adsorption by organic solvents. 18−20 These previous technologies have inherent disadvantages such as the production of large quantities of was...

Stability of amine-based hollow fiber CO2 adsorbents in the presence of NO and SO2

“…The SO 2 reaction with amine groups occurs with the formation of electron donor-acceptor complexes between the acid and base [43]. The stability of such complexes is related to the amine basicity [44]. The stronger electron donating property of the methyl group is supposed to make MAPS a stronger base than the primary amine containing APS [45], but MAPS also has a higher steric hindrance than APS.…”

Theoretical evidence of charge transfer interaction between SO2and deep eutectic solvents formed by choline chloride and glycerol

“…8 In addition, the calculated interaction energies for SO 2 absorption range from À7.1 kcal mol À1 to À16.5 kcal mol À1 in the 1,3-phenylenediamine system. 58 It was also found that the adsorption energies range from À5.5 kcal mol À1 to À16.5 kcal mol À1 on polyphenylene based membranes. 5 These interaction energies as well as the current results imply a moderate interaction between SO 2 and the solvents.…”

“…Furthermore, chemical interactions for the mechanism of SO 2 absorption/adsorption in other systems have been also reported. 19,58 However, NMR ( 1 H and 13 C) results show that SO 2 interacts physically with glycerol and the cation of ChCl. 25 This is not obviously contradictory with the current results, because the effects on the 1 H and 13 C NMR spectra may be negligible when the O-S and Cl-S bonds are formed.…”

“…Moreover, the interaction energies between SO 2 and other solvents have been reported. 8,58 It was found that the calculated absorption enthalpies of SO 2 for [SCN] and [C(CN) 3 ] based ILs are À17.4 kcal mol À1 and À7.7 kcal mol À1 . 8 In addition, the calculated interaction energies for SO 2 absorption range from À7.1 kcal mol À1 to À16.5 kcal mol À1 in the 1,3-phenylenediamine system.…”

“…The SO 2 capture concept is built on the integration of acid-base chemistry with a novel approach for manipulating the active basic site. 58 Charge transfer interactions between the nucleophile Cl À and acidic SO 2 were proposed by experimental researchers to understand the effects of different compositions for DESs formed by ChCl and glycerol. 25 Therefore, it is desirable to perform a charge analysis for the current DES system.…”