Effect of iron, phosphorous, and Si/Al on HZSM-5 catalytic performance and stability by response surface methodology

• An optimum point for propylene yield was found by increasing Fe, P and Si/Al.
• An optimum point for catalytic stability was found by increasing P and Si/Al.
• Increasing Fe loading resulted in decreasing catalytic stability.
• The optimal set of Fe (6.34 wt.%)–P (2 wt.%)/HZSM-5(25) was achieved.

The effect of Fe and P loadings and Si/Al ratio and their interactions on ethylene and propylene production and catalytic stability of HZSM-5 were studied. For this purpose, Box–Behnken design coupled with response surface methodology was used to construct two empirical models for ethylene and propylene. It was found that there is an optimum point for initial propylene yield by increasing Fe, P and Si/Al ratio. The same trend was also observed for catalytic stability by increasing Si/Al ratio and P loading. However, increasing Fe loading resulted in decreasing catalytic stability. The optimal set, Fe (6.34 wt.%)–P (2 wt.%)/HZSM-5(25), with the goal of maximizing initial yield of propylene and minimizing reduction of propylene after 20 h was achieved.