Metal modification effects on ethanol conversion to propylene by H-ZSM-5 with Si/Al2 ratio of 150

Abstract

Metal modification effects on ethanol conversion to propylene were examined by use of H-ZSM-5 with Si/Al2 ratio of 150. In La- and Mg-co-modified H-ZSM-5 (La/Al2 ratio: 1.0, Mg/Al2 ratio: 0.10), 32% propylene selectivity was obtained at 0.1 MPa, 550 °C. This value was higher than those of unmodified and La-modified (La/Al2 ratio: 1.0) H-ZSM-5. The number of acid sites and the acid strength (surface acidity) decreased in the order of unmodified, La-modified, and La- and Mg-co-modified H-ZSM-5. In the initial stage of ethanol introduction, ethylene production by dehydration of ethanol increased in La- and Mg-co-modified H-ZSM-5 with lower surface acidity, whereas the formation of aromatics by oligomerization-cracking increased in unmodified H-ZSM-5 with higher surface acidity. The propylene selectivity was 25% after 36.2 h in the La- and Mg-co-modified H-ZSM-5. The selectivity ratio of propylene to ethylene was 0.47 after 36.2 h; a rapid increase in ethylene formation was also depressed. Therefore, La- and Mg-co-modified H-ZSM-5 with Si/Al2 ratio of 150 was highly effective for the conversion of ethanol to propylene.