Synthesis of lower olefins from syngas over Zn/Al2O3–SAPO-34 hybrid catalysts: role of doped Zr and influence of the Zn/Al2O3ratio
- 14 June 2018
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Catalysis Science & Technology
- Vol. 8 (14), 3527-3538
- https://doi.org/10.1039/c8cy00574e
Abstract
Hybrid catalysts composed of different loadings of Zr-promoted Zn/Al2O3 with SAPO-34 zeolite were investigated for the direct synthesis of lower olefins from syngas in a fixed-bed reactor. Zn/Al2O3 catalysts and Zr-promoted Zn/Al2O3 catalysts with different weight ratios were prepared by a co-precipitation method, respectively. Nano-sized SAPO-34 zeolite was synthesized by a hydrothermal method. The crystallinity, morphology, textural properties and acidic properties of the catalysts were characterized well by XRD, ICP-OES, TEM, H2-TPR, N2 adsorption–desorption isotherm analysis, XPS, and NH3-TPD, respectively. The H2-TPR results suggested that the presence of Zr on the surface of the support favors the reducibility of zinc oxide with a shift to a lower reduction temperature. The Zr promoter improved the Zn dispersion and enhanced the surface area of Zn/Al2O3 catalysts. Various factors that influenced the catalytic activity, including the reaction temperature, the different weight ratios of the methanol synthesis catalyst to SAPO-34 zeolite, the gas flow rate and stability, were investigated in detail. The hybrid catalysts composed of Zr·Zn/Al2O3 and SAPO-34 showed excellent catalytic performance in terms of activity, selectivity and stability for the conversion of syngas into lower olefins. When Zr-free Zn/Al2O3 was used for the hybrid catalyst instead of Zr·Zn/Al2O3, the conversion and stability were low. The results show that a synergistic effect existed between the Zr·Zn/Al2O3 component and SAPO-34 zeolite and it was directly related to the resulting catalytic performance. This study will contribute to the development of efficient catalysts for the production of lower olefins from syngas.Keywords
Funding Information
- National Natural Science Foundation of China (U1510203, 21676176)
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