NO Reduction Studies in the FCC Process. Evaluation of NO Reduction Additives for FCCU in Bench- and Pilot Plant-Scale Reactors

During FCC catalyst regeneration, part of the nitrogen in coke forms NO x , which makes up a significant part of the total NO x refinery emissions. The addition of a small percentage (≤1 wt %) of catalytic additive(s) in the FCC inventory can reduce the NO x emissions from the flue gases of the FCC regenerator. In this paper, experimental techniques are considered for evaluating, in laboratory reactors, the performance of two commercially available NO x removal additives. It has been shown that in an FCC regenerator the gas residence time and the concentration of CO in the flue gases are key parameters in controlling NO x emissions. For example, pilot plant experiments showed that the addition of a CO oxidation promoter (CP-3) in the catalytic inventory decreases the CO emissions significantly and increases the NO x emissions about 4 times. Replacement of the active CO oxidation promoter (CP-3) with an additive (XNO x ) with moderate CO oxidation activity reduced the NO x emissions by 78%. Comparison of regeneration results performed in bench-scale reactors with those measured in our FCC pilot plant unit showed that it is possible to evaluate NO x reduction additives in bench-scale experiments. The proposed protocol for this evaluation is to mix spent FCC catalyst with the NO x reduction additive and to load this mixture in a fluidized bed reactor. The above mixture is then regenerated at 700 °C by 2% O2 diluted in N2.