This article describes the effect of the preparation method of binary oxide supports (TiO2-Al2O3) on catalytic performance of V2O5/TiO2-Al2O3 catalysts for methanol selective oxidation to dimethoxymethane (DMM). The optimized catalyst exhibits a methanol conversion of 48.9% and a high DMM selectivity of 89.9% at 393 K, superior to V2O5/TiO2 and V2O5/Al2O3 catalysts.
Reported by Prof. Gong Jinlong of Tianjin University, the research article titled "Selective Oxidation of Methanol to Dimethoxymethane over V2O5/TiO2-Al2O3 Catalysts" was published on Science Bulletin June 2015, Volume 60, Issue 11, pp 1009-1018, as the cover story.
DMM is an important intermediate in organic synthesis and an excellent solvent in perfume and pharmaceutical industries. It can also be used as an environmentally friendly fuel and a starting monomer in the synthesis of polyoxymethylene dimethylether. The traditional DMM synthesis method suffers from high reaction temperatures, complicated processes, severe equipment corrosion, and relatively low selectivity. Here, the authors demonstrate an alternative synthetic pathway with one-step selective oxidation of methanol to DMM under mild reaction conditions, where V2O5/TiO2-Al2O3 with binary oxide supports (TiO2-Al2O3) is proposed as the catalyst.
The V2O5/TiO2-Al2O3 samples have superior catalytic properties than the V2O5/TiO2 and V2O5/Al2O3 samples. The catalyst prepared by the sol-gel method has the best catalytic performance with a maximum conversion of 48.9% and a high DMM selectivity of 89.9% at 393 K. The catalyst with the ball-milling method has also relatively high methanol conversion (43%) and DMM selectivity (90.7%), which is surpassed only by the V2O5/TiO2-Al2O3-sol sample. The excellent catalytic performance of the V2O5/TiO2-Al2O3 samples for menthol oxidation to DMM is attributed to the effectively modified interaction between the active component and the support coupled with the appropriate acidic sites provided by the mixed TiO2-Al2O3 support. Optimized preparation methods can further improve the interaction between the catalytic V component and the mixed support as well as providing weaker acidic sites. The interaction between the V component and support changes the chemical states of supported active V components, producing more V4+ species. The V4+ could provide more oxygen vacancies to facilitate the electron transfer between the support and active component, enhancing the redox capability of the V2O5/TiO2-Al2O3 catalyst for increased methanol conversion. In addition, the resulted weaker acidic sites is favorable for improving the DMM selectivity.
This study emphasizes the role of the mixed support on the chemical properties of active vanadium oxide species and the acidic properties. The coordinated environment of the V chemical state and the mixed TiO2-Al2O3 support is significant for improving the catalytic efficiency on selective methanol oxidation to DMM.
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This research was funded by the National Science Foundation of China (21006068, 21222604), the Program for New Century Excellent Talents in University (NCET-10-0611), Specialized Research Fund for the Doctoral Program of Higher Education (20120032110024), the Scientific Research Foundation for the Returned Overseas Chinese Scholars (MoE), and the Program of Introducing Talents of Discipline to Universities (B06006).
See the article:
Tuo Wang, Yali Meng, Liang Zeng, and Jinlong Gong*, "Selective Oxidation of Methanol to Dimethoxymethane over V2O5/TiO2-Al2O3 Catalysts," Sci. Bull. 2015, 60, 1009-1018. doi: 10.1007/s11434-015-0782-3
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