Higher alcohols synthesis from syngas over P-promoted non-noble metal Cu-based catalyst

A series of P-promoted non-noble metal Cu-based catalysts without alkalis and Fischer-Tropsch elements were prepared by a complete liquid-phase method and tested for the synthesis of higher alcohols (C2+OH) from syngas in slurry bed reactor. The catalysts were characterized by XRD, 27Al-MAS-NMR, N2 adsorption, XPS, H2-TPR and NH3-TPD techniques. Results showed that the incorporation of an appropriate amount of phosphorus into the non-noble metal Cu-based catalyst could increase the surface Cu content, the amount of weak acid and improved the Cu+ reducibility, which promoted the synergistic effect between Cu and Al, and thus enhanced both stability and selectivity towards to higher alcohols formation. Activity results showed that the production of alcohols and hydrocarbons over this kind of catalyst followed A-S-F distributions, similar with conventional CuFe and CuCo based catalysts. The catalysts with Cu:Zn:Al:P = 2:1:0.8:0.05 showed the best catalytic performance with long-term stability toward CO conversion and C2+OH selectivity (reaching 55%) during the lifetime test for 120 h. It was speculated that AlOOH favored CO dissociation, and the synergism of Cu0, Cu+ and AlOOH was beneficial to the formation of higher alcohols. This work provided a new sight that alkalis and F-T elements were not indispensable for direct synthesis of higher alcohols from syngas over non-noble metal Cu-based catalysts.