The public deliverable “D2.6 – Catalytic performance of novel catalyst mixtures for the direct synthesis of DME” has been released and it is available for download in the dedicated website section.
This deliverable reports the results of obtained in our study to identify the optimum catalysts mixture for the direct synthesis of DME (dimethyl ether) from syngas. Two kind of acid catalysts for the DME production from methanol were tested, the commercial catalyst γ-Al2O3 and the supported heteropolyacid HWSi/TiO2 (HPA). For the methanol synthesis from syngas we used a Cu-based commercial KATALCOTM51-8 (referred to as CZA_com). Both catalysts were mixed in m:a (metallic:acid) ratios of 10:90, 50:50 ad 90:10. The DME production from syngas was tested in a fixed bed reactor at 270 ºC, 25-50 bar, 5000-7500 1/h for the mix with γ-Al2O3 and 7500-15000 h 1/h for the mix with HPA. The mixture containing HPA was also tested at 240 ºC. Syngas CO2/CO-ratio= 1.9 with M=2 was used.
The results obtained show that mixtures containing HPA are not selective to DME, and products such as olefins are formed. The catalysts mixtures with γ-Al2O3 are selective to DME and methanol, and the highest productivity to DME was obtained with the m:a= 50:50 at 270 ºC, 50 bar and 5000 1/h. Nevertheless, the highest DME/methanol productivity-ratio was obtained with the m:a= 10:90, at the same reaction conditions.
The catalyst mixture 50:50 was selected to study the stability with the time on stream (TOS), at the optimum reaction conditions. It was observed that after 140 h under study, CO conversion drops by 50 %, while the CO2 conversion remains constant. It was also observed that the methanol productivity decreases very significantly during the TOS, while the DME one increases slightly within the same time.