Regeneration of waste SCR catalyst by air lift loop reactor

Abstract

A solution of 0.1 mol/L to 1.0 mol/L H₂SO₄ can dissolve alkali metals and alkaline earth metals which weaken an active site of SCR catalyst. The waste catalyst washed with 0.5 mol/L H₂SO₄ regained the best catalytic activity. When a concentration of the sulfuric acid is less than 0.5 mol/L, sufficient cleaning effects cannot be obtained. In contrast, when the concentration is greater than 1.0 mol/L, the active components, vanadium and tungsten are undesirably eluted. The total BET surface of the catalyst regenerated by air lift loop reactor showed almost the same as that of fresh catalyst due to the removal of insoluble compounds which may be penetrated into pores of catalyst. The addition of a solution of 0.075 mol/L ammonium vanadate (NH₄VO₃) and 0.075 mol/L ammonium paratungstate (5(NH₄)₂O·12WO₃·5H₂O) to 0.1 mol/L H₂SO₄ significantly increases the activity of the waste catalyst.

Keywords

nitrogen oxide / regeneration / selective catalyst reduction / air lift loop reactor catalyst

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