Based on the production practice and previous researchs

this article investigates the poisoning process of fluorine compounds (HF and SiF4) on vanadium catalyst (carrier contains SiO2) in the manufacture of sulfuric acid. It offers that the poisoning process of vanadium catalyst by fluoride is chiefly due to the reversible transformation in the form of fluorine

i. e. 4HF + SiO2 SiF4 + 2H2O Using thermodynamic method to investigate the poisoning process of vanadium catalyst in sulfur dioxide converter

and to make a chemical equilibrium calculation about its reaction

the result from calculation reveals that in practical production it is generally poisoned by SiF4. Equilibrium conversion chart for HF→SiF4 and empirical formulas for calculating same conversion shown in this article can be used for quantitatively estimating the possibility of fluoride poisoning both in design work and in plant operation.