Study the hydro-isomerization of light paraffin over bifunctional catalysts at elevated pressures

Abstract

Noble metal based catalysts being 0.8 wt.%Pd and 0.35 wt.%Pt supported on HZSM-5 zeolite were subjected to the investigation. Physico-chemical characteristics of catalysts were determined by the methods of nitrogen physi-sorption, SEM, XRD, TEM, NH₃-TPD, TPR, and Hydrogen Pulse Chemi-sorption (HPC). Activity of catalysts in the isomerization of n-C₆ and n-C₅ + n-C₆ mixture was studied in a micro-flow reactor in the temperature range of 225 − 325 ^oC at pressure of 0.1 MPa and 0.7 MPa; the molar ratio H₂/ hydrocarbon: 5.92, concentration of n-C₅ or n-C₆: 4.6 mol.%, GHSV 2698 h^-1. The stability of catalysts was also determined. The obtained catalysts expressed high acid density, good reducing property, and high metal dispersion with the cluster size in the range of nanometer. They were an excellent contact for isomerization of n-hexane or n-C₅ + n-C₆ mixture with high conversion, selectivity, and yield. At optimal temperature, n-paraffin conversions were as high as 57 – 63 % and selectivity was 90 %. Pressure had the positive effect to the catalyst conversion, selectivity, and stability. At 0.7 MPa, both catalysts produced 66-69 RON liquid product containing friendly environmental iso-paraffins which is superior blending stock for green gasoline.