Electron spin resonance study of sulfur dioxide(1-) radicals on synthetic zeolites

Abstract

Publication costs assisted by the Tokyo Institute of Technology Formation of SO2-radicals over various zeolites and alumina has been confirmed using an esr technique.In the case of NH4Y, the number of radicals is maximum at the adsorption temperature of 200°, and two types of SO2-radicals are observed. One gives an esr signal with g) = 2.008 and gj_ = 2.002, is unstable over 300°, undergoes a collisional broadening in the presence of oxygen at room temperature, and reacts with oxygen at 200°. The other gives an esr signal with g|| = 2.010 and g± = 2.002, is stable up to 500°, and does not interact with oxygen. It is concluded that the adsorption sites for the former are located in the supercage and that those for the latter are located in the sodalite unit. The effect of the calcination temperature on radical formation indicates that adsorption sites for SO2-radicals are formed as a result of deamination and dehydroxylation of NH4Y. The presence of preadsorbed SO2-radicals enhances the formation of O2-radicals on decationated zeolites.

Synthesis, characterization and adsorptive performance of MgFe2O4 nanospheres for SO2 removal

“…Moreover, when a very large amount of surface sulfate species is formed, another component appears near 1400 cm −1 , attributed to chemisorbed SO 3 like species [30,34]. The main band at 1141 cm −1 with shoulders at 1039 and 973 may be attributed to the symmetric stretching sulfite vibrations [35,36]. These results imply that sulfite and sulfate species can be formed on the surface of MgFe 2 O 4 , which is in good agreement with our XPS results.…”

New Cuprous Adsorbent Prepared by a Bioreduction Method for SO2 Removal at Low Temperature

“…For Cu(I)/γ-Al 2 O 3 , another broadband appearing at 1145 cm −1 belongs to the bulk sulfate of CuSO 4 , it indicates that some cuprous ions are oxidized into cupric ions and copper sulfates are formed which is in good agreement with our experiment results. For bio-Cu, a new absorption peak at 1102 cm −1 is observed in curve d which may be attributed to symmetric stretching sulfite vibrations. , However this band is not observed in the spectra of Cu(I)/γ-Al 2 O 3 prepared by autoreduction; the reason may be that it is a new sulfite species adsorbed on bio-Cu that is influenced by carboxyl groups and amido groups chelated with Cu + . The results imply that sulfate species can be rapidly formed on γ-Al 2 O 3 , Cu(II)/γ-Al 2 O 3 , and Cu(I)/γ-Al 2 O 3 exposed to an O 2 atmosphere at 80 °C, while SO 2 cannot be easily oxidized on bio-Cu at the same condition.…”

SO2−Faujasite Interaction: A Study by in Situ FTIR and Thermogravimetry

“…The first paper on this field was written in 1971 4 and a few others in the following years. [6][7][8][9][10][11][12][13][14][15] Karge et al [16][17][18][19][20] and Lavalley et al [21][22][23][24][25][26] have studied this system in a deep and extensive way. Recently, some papers, mainly computational simulations, have been also published.…”

“…[27][28][29] The main conclusions of these studies, carried out mainly by using IR spectroscopy, are that NaY at room temperature only physisorbs SO 2 , showing a single band at 1320 cm -1 . 4,18,20 On the other hand, NaX at roomtemperature both physisorbs (band located at 1320 cm -1 ) and chemisorbs SO 2 as HSO 3 -(bands at 1240 and 1080 cm -1 ) [9][10][11][12]20 and as S 2 O 5 2-. This latter species, formed only at high coverage, has never been observed by IR but only by UV-vis.…”

“…The interest of the SO 2 −zeolite interaction can be noticed by the numerous papers devoted to its study. The first paper on this field was written in 1971 4 and a few others in the following years. − Karge et al − and Lavalley et al − have studied this system in a deep and extensive way. Recently, some papers, mainly computational simulations, have been also published. − …”