Hydroconversion of n-hexane over Pt-supported on fibrous silica mordenite catalysts: effect of transition metals on acidity and activity

The effect of incorporation of either Zr, Co, Mo or Zn on Pt/HFSM was investigated for the hydroconversion of n-hexane in a pulsed micro-reactor at a temperature range 423-623 K. The acidity of all the studied catalysts were investigated using pyridine adsorption and Fourier Transform Infrared Spectroscopy. The FTIR-pyridine study showed that the catalysts possessed different concentration and strength of both Lewis and Brønsted acid sites. It was revealed that the moderate acid sites distribution on PtZr/HFSM and PtZn/HFSM facilitated the isomerization of the intermediate hexene while the strong acid sites were selective towards cracking reaction. The trend for the bimetallic catalysts studied in n-hexane hydroisomerization is in the order: PtZr/HFSM>PtZn/HFSM>PtMo/HFSM>PtCo/HFSM. The highest activity for hydrocracking and hydrogenolysis were exhibited by PtMo/HFSM and PtCo/HFSM respectively. The PtZr/HFSM exhibited the highest hydroisomerization activity due to the moderate acidity and abundant Lewis acid sites capable of generating protonic acid sites by the hydrogen-spill over phenomena