| Autor: |
Kalmár J; Department of Inorganic and Analytical Chemistry, University of Debrecen, H-4032 Debrecen, Egyetem tér 1, Hungary. ifabian@science.unideb.hu., Szabó M, Simic N, Fábián I |
| Jazyk: |
angličtina |
| Zdroj: |
Dalton transactions (Cambridge, England : 2003) [Dalton Trans] 2018 Mar 12; Vol. 47 (11), pp. 3831-3840. |
| DOI: |
10.1039/c8dt00120k |
| Abstrakt: |
An important reaction step in the industrial production of NaClO 3 (electrochemical chlorate process) is the thermal decomposition of HOCl/OCl - to yield ClO 3 - and Cl - . It is widely accepted that this reaction is accelerated by aqueous chromium(vi) species. A detailed kinetic study was conducted under industrially relevant conditions, i.e. at high ionic strength (6.0 M) and elevated temperature (80 °C), to investigate this phenomenon. The decomposition of hypochlorous acid was followed in the presence of Cr(vi) or phosphate (PO 4 3- ) or without any additive. In addition to the beneficial pH buffering effect of Cr(vi), the CrO 4 2- form of chromium(vi) was found to slightly catalyze the decomposition of hypochlorous acid. The overall rate of HOCl decomposition can be expressed as -dc HOCl /dt = k dec [HOCl] 2 [OCl - ] + k cat [HOCl] 2 [CrO 4 2- ]. The corresponding rate constants were determined, k dec = 9.4 ± 0.1 M -2 s -1 and k cat = 4.6 ± 0.8 M -2 s -1 , and mechanistic interpretation of the catalytic rate law is given. The contribution of the catalytic path to the overall rate of decomposition changes from ca. 30% at pH = 8 to ca. 70% at pH = 6. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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