K/MgFeZn-HTLcs催化CO加氢制低碳烯烃性能研究

以MgFeZn-HTLcs为前驱体,制备了不同Mg/Fe/Zn物质的量配比、K改性的K/MgFeZn-HTLcs催化剂,用于CO加氢直接制低碳烯烃反应。采用N2吸附-脱附、SEM、TG、XRD、XPS、H_2-TPR等手段对催化剂进行了表征。结果表明,MgFeZnHTLcs前驱体具有典型的层状结构,孔径分布均一;经焙烧、K改性后仍具有一定的层状结构,但比表面积显著减小,平均孔径增大;新鲜催化剂物相以金属氧化物和铁酸盐为主,反应后K/MgFeZn-HTLcs催化剂主要以Fe_5C_2、MgCO_3和ZnO相存在,K/2Fe-1Zn催化剂主要物相为ZnFe2O_4。在CO加氢反应中,K/MgFeZn-HTLcs催化剂具有较高的C=2-4烯烃选择性和较低的C+5含量,与K/2Fe-1Zn催化剂相比,产物分布明显改善;K/2Mg-2Fe-1Zn催化剂上O/P比值达5.15,C=2-4含量占总烃质量的48.56%。

Direct synthesis of light olefins from CO hydrogenation over K/MgFeZn-HTLcs catalysts

A series of K promoted K/MgFeZn-HTLcs catalysts with different Mg/Fe/Zn molar ratios were prepared by means of precipitation method and impregnation method for the direct synthesis of light olefins from CO hydrogenation. The samples were characterized by N₂ adsorption-desorption SEM, TG, XRD, XPS and H₂-TPR measurements. The results showed that the MgFeZn-HTLcs catalyst precursors have typical lamellar structure, larger specific surface area and average pore diameter compared with Fe/Zn catalyst. The BET surface area and the average pore diameter decreased after calcination and K promotion. The bulk composition of the calcined samples was mainly metal oxide and ferrite. Fe₅C₂, MgCO₃ and ZnO were formed in K/MgFeZn-HTLcs catalysts after reaction. However, the main phase in K/2Fe-1Zn catalyst was stabilized in ZnFe₂O₄. During CO hydrogenation, the prepared samples showed high C_2-4⁼ selectivity and low C₅⁺ weight fraction compared with that of K/2Fe-1Zn sample. The product distribution was greatly improved. Over the sample K/2Mg-2Fe-1Zn, an olefin to paraffin ratio of 5.15 and the C_2-4⁼ weight olefin content of 48.56% could be obtained.