Highly Selective Synthesis of High Octane-Number Gasoline from Light Olefins on Fe-Silicates

The conversion of light olefins such as ethylene, propylene, and butenes to gasoline was investigated with various metallosilicates having a pentasil pore-opening structure. The metallosilicates were prepared using a novel rapid crystallization method by replacing the Al ingredient in the H-ZSM-5 with various metal salts at the gel formation stage. The silicates of Al(i.e., H-ZSM-5), Ga, V, Cr, and Zr were not highly effective for selective conversion to liquid products because of a significant formation of gaseous C₁-C₄ paraffins accompanied with the formation of aromatics. On the other hand, Fe-silicates were highly effective for selective formation of liquid products in the gasoline fraction. For example, 95.6% propylene fed was converted under the space velocity of 4,500 h^-1 and at 300°C to the liquid products with a space-time yield as high as 8.09 kg/l.h. The octane-number of the gasoline produced was as high as 95 because of the high percentage of branched internal-olefins found in the liquid products. The Fe-silicate exhibited high activity and selectivity under various conditions, and maintained its steady performance at least 100 h on stream. The reason for this high gasoline selectivity of Fe-silicate was discussed in relation to its properties and performance in methanol conversion to hydrocarbons.