Experimental and Theoretical Investigation of SO2 Adsorption over the 1,3-Phenylenediamine/SiO2 System
The reversible adsorption of SO2 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 SO2 at the amine site resulted in fixation of sulfur as hydrogen-bonded SO32– (sulfite) and SO42– (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 SO2/mol sorbent for pure 1,3-phenylenediamine and 2.8 mol SO2/mol sorbent for the SiO2 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 −NO2 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 SO2, sulfite, and sulfate species at the amine site may be thermally desorbed from the sorbent. The retained SO32– and SO42– species led to the rapid deactivation of the sorbent during multicycle testing.
The Journal of Physical Chemistry C
Miller, Duane D. and Chuang, Steven S.C., "Experimental and Theoretical Investigation of SO2 Adsorption over the 1,3-Phenylenediamine/SiO2 System" (2015). Polymer Science Faculty Research. 874.