Study on the interaction of kaolin matrices with vanadium in the cracking catalyst

The phase transformation of kaolin in the presence of 1% to 5% vanadium was investigated. The result indicated that vanadium-mullite emerged at 650 °C to 700 °C which was 400 °C lower than conventional mullite formation temperature. The reaction kinetics of vanadium-mullite could be expressed as low melting vanadium-kaolin eutetic transition. In addition, unit cell volume of the vanadium-mullite was found to be larger than the conventional mullite, which could be deduced that vanadium incorporated into mullites' framework and was therefore passivated. Furthermore, the modified PAL-kaolin reacted more fast with vanadium to form mullite than the reaction of REHY zeolite with vanadium to form rare earth vanadate, and therefore protected zeolite in cracking catalyst against the vanadium poisoning effectively.