FCC-units are an integral part in the state-of-the-art petroleum refinery process in every modern fuel-orientated refinery. With this FCC-process high boiling, long-chained hydrocarbons are catalytically cracked in a fluidized bed to lower boiling, short-chained hydrocarbons. The FCC-process is an essential technique in order to meet the demand of motor fuels, prior-ranking gasoline. Recently the value of the petroolefines production for subsequent petrochemical conversions augments. At the Institute of Chemical Engineering of the Vienna University of Technology fully continuous FCC-pilot facilities with an internal circulating fluidized bed design are available. With these research and development in the domain of the FCC-process are promoted. Within the scope of these thesis the question was pursued, if the FCC-process is feasible with an admixture of a second individual catalysts and as a consequence of this which impact is has on the product spectrum. The applied zeolite-based catalysts were NektorTM and ProtAgonTM made by Grace-Davison. Each of these catalysts is used by default in a different refinery facility. The feed used for the experiments was non-hydrogenated vacuum gas oil from that refinery, which deploys the catalyst NektorTM by default. At first fluid dynamic examinations were made, followed by preliminary tests with feed. After this successfully proof-of-principle, the actual examinations took place. For the basis points, each catalyst was processed purely. Two cracking examinations were followed with admixtures of 15 and 30 mass fraction of ProtAgonTM respectively. All mixture ratios could be applied successfully. Their impact on the spectrum of products could be depicted. The experimental results of the pure catalysts reflect the designated specifications from the manufacturer. ProtAgonTM is optimized for the formation of gaseous olefins. NektorTM is designed for the conversion of heavy, contaminated feeds to motor fuels. With the blends of catalysts, it becomes apparent that an approximate linear correlation exists between the grade of mixture and the resulted spectrum of products. Present deviations could be exposed with accompanied alteration of fluid dynamics. One essential conclusion of this thesis is, that the admixing of the second catalyst ProtAgonTM has a direct impact on the resulted spectrum of products. The admixing of another catalyst provides an additional opportunity to optimize this industrial process.