Oxidation of high sulphur coal.9 3. Desulphurisation of organic sulphur by peroxyacetic acid (produced in situ) in presence of metal ions

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A chemical oxidative desulphurisation method for coal organic sulphur has been presented using peroxyacetic acid produced in situ as an oxidant. Sulphur is removed to the extent 6.92–10.02 wt.% at 1–4 h while at 24 h, it increases to 13.41 wt.%. To understand the influence of metal ions on desulphurisation, each of six metal ions of variable valence states (Cu +, Ni 2+, Co 2+, Sn 2+, Pd 2+ and Sb 3+) was externally added. Lowest sulphur loss with Ni 2+ ion (2.26–9.46 wt.% at 1–4 h and 11.01 wt.% at 24 h) while highest desulphurisation with Pd 2+ ion (23.15–32.32 wt.% at 1–4 h and 32.75 wt.% at 24 h) are observed. Application of the pseudo-first order kinetics shows rate constants for all the systems in the range (0.70–6.78)×10 −5 s −1. The activation energy and frequency factor for these systems fall in the range (8.46–12.66) kJ/mol and (1.15–2.64)×10 −3 s −1, respectively. Low frequency factor represents an associated type of desulphurisation reaction involving intermediate activated complexes. The sulphur loss reaction is non-spontaneous in nature and proceeds with the absorption of heat. Occurrence of the reaction is due to the increase in randomness which is governed by the decomposition of activated complex to products and is influenced by the characteristic property of a metal ion. Study of model sulphur compounds (methionine and dibenzothiophene) reveals that the desulphurisation reaction under the experimental conditions is primarily due to aliphatic sulphur compounds. The method described here is simple with low-cost and easily available chemical, and therefore, has considerable technological interest.