Process optimization studies of structured Cu–ZSM-5 zeolite catalyst for the removal of NO using design of experiments (DOE)

Abstract

There has been growing interest in structured catalytic reactors because of their several advantages over conventional fixed-bed catalytic reactor. The structured bed having open macrostructure allows high flow rates with a low-pressure drop. In the present study, the structured catalyst made of ZSM-5 zeolite coatings on stainless steel wire mesh with copper being incorporated in the ZSM-5 was used. The catalytic activity of Cu–ZSM-5 structured catalyst for the selective catalytic reduction (SCR) of NO with iso-butane as reducing agent was studied using design of experiments (DOE). The response surface methodology (RSM) coupled with center composite design (CCD) was used to obtain the optimum process conditions. The optimum conditions were 1730 ppm of NO, 1280 ppm of iso-butane and 375 °C reaction temperature with 94% reduction of NO and 4.6% SCR-HC selectivity. The NO reduction was also studied in the presence of 5–20 vol% of water vapor and 50–200 ppm of sulfur dioxide (SO 2). Water vapor caused reversible deactivation, whereas SO 2 resulted in permanent deactivation of the catalyst. The catalyst was also tested for its stability subject to time on stream study. No structural changes were found in the catalyst after 48 h of continuous operation.