Applied Catalysis A: General, Vol.173, No.1, 19-25, 1998
The promotions of MnO and K2O to Fe/silicalite-2 catalyst for the production of light alkenes from CO2 hydrogenation
MnO and K2O are two kinds of promoters incorporated onto a Fe/silicalite (denoted as Fe/Si-2) catalyst for light olefin formation from CO2 hydrogenation. Addition of MnO into the Fe/Si-2 catalyst increased the selectivity toward light olefins. Meanwhile, CH4 yield as well as CO formation were practically unaffected by the MnO addition. Moreover, the conversion of CO2 was also insensitive to the addition of the MnO promoter. With the addition of K2O onto the Fe-Mn/Si-2 catalyst, the selectivity for light olefins increased further, while CH4 formation was inhibited. An obvious increase in CO2 conversion was also observed. CO2-TPD, CO2/H-2-TPSR and CO/H-2-TPSR, as well as CO2 pulse reactions were employed to probe the promotional functions of MnO and K2O. The results revealed that CO adsorption capacity was enhanced by the addition of MnO, and that incorporation of K2O could further increase both the capacity and bonding strength of the Fe-Mn/Si-2 catalyst with strongly adsorbed CO2 and CO species. On the basis of a two step reaction mechanism in which a reversible water gas shift reaction and a Fischer-Tropsch reaction are involved, the promotional effects of these two kinds of promoters for the formation of C2H4 and C3H6 can be explained.