Promotional Effect of B2O3, WO3 and ZrO2 on the Structural, Textural and Catalytic Properties of FePO4 Catalyst Towards the Selective Dehydration of Methanol into Dimethyl Ether

摘要

In this work, catalysts of pure FePO4 and mixed with (1-20 wt%) of B2O3, WO3 and ZrO2 were synthesized and examined for the selective dehydration of methanol into dimethyl ether (DME). The synthesized catalysts were extensively characterized by different techniques such as thermal analysis (thermogravimetry and differential thermal analysis), X-ray diffraction, Fourier transform infrared, BET-surface area and Mossbauer spectroscopy. The surface acidities are also measured and discussed in details. Our results revealed that loading with 1-10 wt% of the various additives resulted in a remarkable improvement in both S-BET and total number of acid sites of the catalysts. The results of poisoning of acid sites with pyridine (PY) and dimethyl pyridine (DMPY) specified that the acidic sites are of Bronsted type, while PY-TPD indicated that almost all of acid sites over the surface of these catalysts are of weak and intermediate strength. Catalytic activity studies established that the FePO4 promoted with 10 wt% of B2O3 or WO3 or ZrO2 are the most active catalysts with complete conversions of methanol into DME at 375, 350, and 325 degrees C, respectively. The significant catalytic performance of these catalysts is correlated well with the enhancement observed in both S-BET and total acidity. Finally, these catalysts also exhibit a long-term stability towards the dehydration of methanol into DME for a duration time of 160 h.