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Cinética da dessulfurização de carbonos modificados por SO2: polimerização dos intermediários alotrópicos do enxofre

  • Tarnowski, Marília Isabel
Publication Date
Jan 01, 2018
Repositório Institucional da UFSC
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Abstract : The desulfurization of carbons modified with SO2 was studied as a dispersion in boiling cyclohexane at 80.1 °C. The sulfur elimination of the solid matrix was detected and followed with a diode array spectrophotometer. There was a burst of sulfur species identified as S2 by the UV spectrum (?max 215 nm, plateau at 250-270 nm), that showed a second-order decay of absorbance with k2 = 1.82x102 M-1.min-1. The UV spectrum of the product showed ?min 212-215 nm and a shoulder at 227-230 nm, which was postulated to correspond to S4. No other reaction was observed within 60 min. However, a zero-order decay occurred up to 18 min with ?min 210 nm, followed by a second-order increase of absorbance with k2 = 90.2 M-1.min-1, where the product showed a double maximum at ?= 260-285 nm typical of S8. These results are consistent with a mechanism of consecutive dimerizations of S2 and S4, which are both thermodynamically favorable, and with the desulfurization mechanism that have been previously postulated. The desulfurization route presents a unique ocasion to study the elusive sulfur allotropes, diatomic and tetrasulfur, in solution and at low temperature.

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