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La/ZrO2 catalysts were prepared by co-precipitation method. The physical and chemical properties of the catalysts were characterized by N2 adsorption–desorption method, X-ray diffraction and temperature programmed desorption. The selective conversions of ethanol to propylene over these synthesized La/ZrO2 catalysts were also investigated. The optimum propylene yield reached 42.3% over La(1)/ZrO2 catalyst. A coordination of redox and acid–base properties accounts for the remarkable improvement of reaction performance over La/ZrO2 catalysts. On the basis of calculation results, the introduction of oxygen vacancy or La results in significant charge transfer. The Lewis acid–base (Zr–O) pair sites become more active as a result of charge transfer over La/ZrO2 catalysts. Furthermore, the formation of O vacancies over La/ZrO2 (101) is easier than that over t-ZrO2(101). Therefore, La modification improves the performance of ZrO2 on conversion of ethanol to propylene. [ABSTRACT FROM AUTHOR]

Abstract: The selectivity of propylene was constant at 20% during continuous experiments for 8 h on HZSM-5. However, HLEV catalysts produced almost no C3H6 after 2 h. The rapid change is probably due to coke deposition. Excessive adsorption of ethanol on HLEV leads to coke deposition. Lower adsorption energy of ethylene on HLEV makes ethylene desorb quickly after formation.Graphical Abstract: [ABSTRACT FROM AUTHOR]

[Display omitted] • Propylene selectivity is enhanced over Sr/ZSM-5 for ethanol conversion. • Catalytic stability is also improved on Sr/ZSM-5 in ethanol conversion. • Sr modification changes the electronic environment of active sites on HZSM-5. • Ethanol is better to absorb and propylene are easier to desorb on Sr/ZSM-5 catalyst. • Sr modification inhibits the ethylene dimerization and coking for ethanol conversion. Protonated ZSM-5 zeolites doped with alkaline earth metals (M/ZSM-5, M: Mg, Ca, Sr and Ba) were prepared by impregnation method. The effects of reaction conditions and alkaline earth metals modifications on the conversion of ethanol to olefins were systematically investigated. The maximum yield of propylene reach 29.8 %. The physical and chemical properties of the catalysts were characterized by X-ray diffraction, N 2 adsorption-desorption measurement, and temperature programmed desorption of ammonia. The structure and electronic properties of Sr modified ZSM-5 catalysts were studied by density functional theory. The calculation results demonstrate that the adsorption of ethanol on Sr/ZSM-5 catalyst is more suitable, while ethylene and propylene are more easily desorbed on Sr/ZSM-5. Simultaneously, the activation energy of ethylene protonation reaction increases after Sr modification, which could suppress the carbon deposition. The lifetime of the catalyst is prolonged. The experimental results of enhanced selectivity and stability could be interpreted from the computational study. [ABSTRACT FROM AUTHOR]