Recycling the Spent Catalysts of Claus Unit in Natural Gas Refineries and Their Application for Synthesis of Composite Adsorbents Coated by Polypyrrole for the removal of lead ions

Catalytic processes in oil and gas industries are very important for refining, purification and production of useful compounds. Regeneration of spent catalysts is interested due to their environmental problems as solid wastes in the refineries. Activated alumina is a very useful catalyst in gas refinery for conversion of hydrogen sulfide to the elemental sulfur in Claus unit.In this paper regeneration of spent catalyst of Claus process in Sulfur Recovery Unit (SRU) and application of it for synthesis of polypyrrole/Al2O3 composite as an adsorbent of lead ion was investigated.

Catalyst regeneration was performed via washing by water or caustic washing and then thermal process. Characterization and analysis of catalysts were performed by XRF, XRD, FTIR, and BET measurements. Polypyrrole /Al2O3 composite was synthesized by in situ polymerization and used for removal of lead ions in batch experiments and different values of pH, lead concentration and temperature.

Results showed that regeneration process caused to removal of impurities and sulfur without any change in the catalyst structure. Specific area of catalyst increased from 84 m2/g in spent catalyst to 186 m2/g in regenerated sample while the sulfur content decreased from 2.53% to 0.005-0.007%.

The results indicated that the composite showed high ability for lead removal. Adsorption behavior was determined as Langmuir isotherm and pseudo-second order kinetic.