Highly Selective Synthesis of Gasoline from Light Olefins

Abstract

Selective synthesis of high octane value gasoline from light olefins was investigated by developing novel shape-selective metallosilicates. The metallosilicates were synthesized by replacing the Al ingredient of ZSM-5 zeolite with various metal at the stage of gel formation in the rapid crystallization method. Among various metallosilicates, iron-group metal silicates were found to exhibit the highest selectivity to light olefins from methanol. Therefore, preparation method of the Fe-silicate was studied more extensively. It was proved that the Fe ingredient is concentrated in the core part of the crystal particles, especially in Fe-silicates having high Si/Fe atomic ratios, and the particles are covered by Fe-poor silica layer. Light olefins were exclusively converted to gasoline on these Fe-silicates ; e. g. 95.6 % propylene fed was converted to a high octane value (95) gasoline with a very high space-time yield (8.09kg/l·h) at 295°C and a space velocity of 4, 500h^-1. The catalytic activity of the Fe-silicate for propylene conversion and the selectivity to gasoline was consistently maintained at least 100h on stream under the corresponding condition of SV 1, 000h^-1.