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Oxidation of Aqueous Sulphur Dioxide Catalysed by Poly‐4‐vinylpyridine–Cu(II) Complex. Part 2: Combined Homogeneous and Heterogeneous Phase Oxidation
Author(s) -
Siva Kumar S.,
Govindarao V. M. H.,
Chanda Manas
Publication year - 1997
Publication title -
journal of chemical technology and biotechnology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.64
H-Index - 117
eISSN - 1097-4660
pISSN - 0268-2575
DOI - 10.1002/(sici)1097-4660(199706)69:2<209::aid-jctb701>3.0.co;2-b
Subject(s) - chemistry , catalysis , aqueous solution , adsorption , phase (matter) , inorganic chemistry , solubility , aqueous two phase system , sulfur dioxide , reaction rate , redox , catalytic oxidation , reaction mechanism , organic chemistry
Aqueous phase oxidation of sulphur dioxide at low concentrations catalysed by a PVP–Cu complex in the solid phase and dissolved Cu(II) in the liquid phase is studied in a rotating catalyst basket reactor (RCBR). The equilibrium adsorption of Cu(II) and S(VI) on PVP particles is found to be of the Langmuir‐type. The diffusional effects of S(IV) species in PVP–Cu resin are found to be insignificant whereas that of product S(VI) are found to be significant. The intraparticle diffusivity of S(VI) is obtained from independent tracer experiments. In the oxidation reaction HSO 3 − is the reactive species. Both the S(IV) species in the solution, namely SO 2 (aq) and HSO 3 − , get adsorbed onto the active PVP–Cu sites of the catalyst, but only HSO 3 − undergoes oxidation. A kinetic mechanism is proposed based on this feature which shows that SO 2 (aq) has a deactivating effect on the catalyst. A rate model is developed for the three‐phase reaction system incorporating these factors along with the effect of concentration of H 2 SO 4 on the solubility of SO 2 in the dilute aqueous solutions of Cu(II). Transient oxidation experiments are conducted at different conditions of concentration of SO 2 and O 2 in the gas phase and catalyst concentration, and the rate parameters are estimated from the data. The observed and calculated profiles are in very good agreement. This confirms the deactivating effect of non‐reactive SO 2 (aq) on the heterogeneous catalysis. © 1997 SCI.