Claus Reaction 2

[imans]

I tried to calculate heat of reaction of Claus reaction. Using this reaction 2H2S + SO2 ===> 3S + 2H2O, the reaction is endothermic instead of what should be, which is exothermic. Does anyone know what's wrong with that?

 

[25362]

The Claus reaction includes partial (1/3) oxidation of H₂S to SO₂ i/o to enable the reaction you mentioned. The reaction you mentioned is exothermic [Δ]H^o₂₉₈= -147 kJ/mol.
For the chemistry and thermodynamics of the Claus process see:

http://thor.tech.chemie.tu-muenchen.de/~tc2/eng/teaching/industr_chem_process2/1.2_claus_process.pdf