Synthesis, Characterization, and Formulation of Framework Fe-Al-MFI to FCC Additive

Charles Kanyi

Johnson Matthey

Demand for propylene continues to increase with refineries using different approaches to increase propylene: increasing riser temperature, using base catalyst with lower REO, and higher usage of ZSM-5 additive. The above approaches result in, higher coke yield, lower stabilized base catalyst, and dilution of inventory, respectively. Of the three, use of ZSM-5 is most preferred as it offers flexibility; ability to use on as need basis.

To circumvent inventory dilution, more active ZSM-5 additive is required (achieve higher propylene yields at low inventory). Recently there is increased attention in using metals in ZSM-5 additives to increase activity. This talk will initially focus on synthesis and characterization of ZSM-5 containing both iron and aluminum in the framework. The latter part will focus on formulation of the zeolites to additives and testing of the additives for propylene make.

Mixing of the raw materials to make the zeolite gel has great impact on the time iron get incorporated into the framework as well as crystallization time. The zeolite morphology changes with iron and/or alumina content. Above certain aluminum and iron content, presence of iron outside the framework is evident. Formulating Fe-Al-ZSM-5 into additive requires slightly different optimization compared to standard Al-ZSM-5. Significant improvement in performance (propylene) is observed with Fe-Al-ZSM-5 additive compared to standard additive (Al-ZSM-5).