Accelerated deactivation of industrial SO2 oxidation catalysts in sulfuric acid production

Abstract

This study investigates the forced deactivation of fresh catalyst used in sulfuric acid production through exposure to water vapor with the objective of gaining deeper insight into the mechanisms of catalytic deactivation for a short duration (up to 4 h). An experimental procedure was developed to reproduce deactivation phenomena under controlled conditions, considering key parameters such as temperature, SO 2 /N 2 ratio, and steam presence, to assess their effects on catalyst structure and catalytic performance. The commercial V 2 O 5 –M 2 SO 4 /SiO 2 catalyst widely employed in H 2 SO 4 production is known to progressively lose efficiency over time, with complete inactivation occurring after approximately 10 years of service, depending on the catalytic mass. Catalyst deactivation is typically linked to chemical, mechanical, and thermal factors. In this work, steam-induced deactivation was simulated using a dedicated test bench, with precise control of SO 2 and N 2 flow rates via needle control valves to achieve SO 2 /N 2 ratios of 0.84 and 1.65. The water bath temperature was maintained at 80 °C while the reaction temperature was controlled at 350 °C. The reaction time was also investigated as a critical factor influencing deactivation. Catalysts subjected to these conditions were analyzed using XRF, XRD, and FTIR techniques. Their performance was further validated by catalytic testing of SO 2 oxidation to SO 3 , with iodometric titration used to quantify reactivity. The results revealed significant structural modifications accompanied by a marked decrease in catalytic activity to approximately 36% from an initial conversion rate of about 63%.