| Autor: |
Kalmár, József, Szabó, Mária, Simic, Nina, Fábián, István |
| Předmět: |
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| Zdroj: |
Dalton Transactions: An International Journal of Inorganic Chemistry; 3/21/2018, Vol. 47 Issue 11, p3831-3840, 10p |
| Abstrakt: |
An important reaction step in the industrial production of NaClO3 (electrochemical chlorate process) is the thermal decomposition of HOCl/OCl− to yield ClO3− 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 (PO43−) or without any additive. In addition to the beneficial pH buffering effect of Cr(vi), the CrO42− form of chromium(vi) was found to slightly catalyze the decomposition of hypochlorous acid. The overall rate of HOCl decomposition can be expressed as −dcHOCl/dt = kdec[HOCl]2[OCl−] + kcat[HOCl]2[CrO42−]. The corresponding rate constants were determined, kdec = 9.4 ± 0.1 M−2 s−1 and kcat = 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. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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