reaction to form nox it can be speculated that higher regenerator temperatures may also require a change in promoter formulation the nox selectivity of a given metal oxide formulation at 1350 u00b0 f may not be suitable even if such formation is suitable at 1300 u00b0 f 1000 ppm of base metal oxide added to an fcc catalyst should be expected to have an impact on coke and h 2 yields on the riser side preferred formulations will have higher co promotion activity per unit metal oxide in order that the coke and h2 yield impacts can be minimized if such higher activity mixed metal oxides are employed this should not lead to one increasing the activity per unit weight of promoter beyond the claimed limits as this will increase nox instead the benefit of the higher specific activity of the mixed base metals is to be taken as a reduced base metal oxide loading on the additive itself with the same additive dose being used in the fcc catalyst inventory finally it is worth noting that long catalyst contact time tests such as the mat or ffb exaggerate the activity of metals to produce h 2 and contaminant coke circulating pilot plant results.