Development of catalysts for the production of aromatics from syngas

Different combinations of FT catalysts Fe/MnO and Cu-Fe/MnO with zeolites HZSM-5 and GaZSM-5 have been used for converting syngas directly to aromatics. The manganese rich Fe/MnO FT-catalyst was prepared from nitrates by continuous coprecipitation and the copper as modifier of Fe/MnO was introduced by impregnation. Commercially available HZSM-5 and its Ga substituted form were mechanically mixed with the FT-catalysts and was used in single-bed reaction at 543 and 573 K. Dual-bed reaction has also been tried with Cu-Fe/MnO in the first bed and GaZSM-5 in the second bed. It has been observed that mixing zeolite with FT-catalysts significantly changes the product distribution in alkene/alkane and aromatics. The selectivity to aromatic hydrocarbons over composite catalysts is higher than that in dual-bed. The highest selectivity to aromatics reached 50% over Fe/MnO-GaZSM-5 composite catalyst at 543 K after 5 h on stream, however, a serious deactivation was observed with this catalyst. The conversion of CO with this catalyst reduced from 80 to 9.37% during 22 h. Via XPS measurements, a strong enrichment of Ga was found on the surface, while Mn-content on the surface was reduced. The deactivation of this catalyst might be attributed to the migration of Ga-species.