A study of catalyst formulations for isomerization of C7 hydrocarbons Original Research Article

Zeolite and alumina based catalysts are screened for activity and selectivity in the isomerization of n-heptane. Pt, Ni, Co, Fe, Zn, La and combinations thereof are introduced to the catalysts via inorganic (chloride, nitrate) or organometallic (carbonyl, acetylacetonate) precursors. Pt/UY and Pt/VUY catalysts show the greatest activity and selectivity to isomers, with up to 94% selectivity to isomers at 72% conversion. Their isomerization activity and selectivity increase with Pt loading up to 1.5 and 1.0%, respectively. For Pt/faujasite catalysts that show good selectivity to isomers over cracked products, isomerization of n-C7 to multibranched isomers occurs in consecutive steps. The ratio of monobranched to dibranched isomers is a unique function of conversion regardless of catalyst formulation or processing conditions. However, the selectivity to isomers over cracked products at a given conversion is a strong function of catalyst preparation and processing conditions. Less selective catalysts yield monobranched isomers, multibranched isomers, and cracked products in parallel. Pt/faujasite catalysts strongly resist inhibition by naphthenic and aromatic cyclic compounds, and are therefore suitable for the isomerization of a realistic naphtha cut. Methylcyclohexane (MCH) is isomerised without ring opening to an equilibrium mixture of C7 naphthenes while toluene is hydrogenated and partially isomerised. Conversion of n-C7 and mixed feeds yields a product stream containing branched isomers having much higher research octane rating.