Propene oligomerization over Ni-exchanged Na-X zeolites

The oligomerization of propene was investigated over a series of nickel ion-exchanged Na-X zeolites with varying Ni loadings. Catalyst characterization by temperature-programmed reduction, elemental analysis, and XANES indicates that all of the exchanged Ni is present as Ni2+ that charge-compensates two exchange sites. The selectivity to propene oligomers remained greater than 98% for all Ni-Na-X catalysts with dimers being the main product. In contrast, the activity of Ni-Na-X was determined to depend strongly on Ni loading. At low to intermediate Ni loadings, the catalyst activates, reaches a maximum activity, and then deactivates with further time on stream. The rates of activation and deactivation are functions of the Ni content in the zeolite and both increase with increasing Ni loading. Stable activity was achieved for low Ni loadings (