Direct Synthesis Of Methylcyclopentadiene With 2,5-Hexanedione Over Zinc Molybdates

Methylcyclopentadiene (MCPD) is a widely utilized intermediate in the synthesis of advanced aviation fuels and valuable chemicals. However, the low yield from fossil energy and the high price of MCPD greatly limit its application on a large scale. To fulfill the increasing market demand of MCPD, it is imperative to explore efficient and integrated technologies for the production of renewable MCPD from low cost and more available biomass. In this work, Zn3Mo2O9 was obtained via a simple precipitation method and demonstrated excellent catalytic performance for the direct synthesis of MCPD with 2,5-hexanedione (HD), a platform compound that can be directly produced by the selective hydrogenolysis of cellulose. Over it, a good molar yield of MCPD (65%) was obtained by the cascade intramolecular aldol condensation/selective hydrodeoxygenation reaction at 400 degrees C under atmospheric pressure. On the basis of the characterization results, the Zn3Mo2O9 catalyst has a higher specific BET surface area than the rest of the catalysts, which are favorable for the adsorption and mass transfer of the reactant. Meanwhile, the Zn3Mo2O9 catalyst also has relatively higher reducibility that will lead to the emergence of more oxygen vacancies (or Mo5+ species) under the investigated conditions. All of these characteristics lead to higher activity, better selectivity, and good stability of the Zn3Mo2O9 catalyst in the direct conversion of HD to MCPD. Because of its excellent hydrodeoxygenation performance, the Zn3Mo2O9 catalyst can also be used as the catalyst for the direct production of renewable dienes with other biomass-derived alpha,beta-unsaturated ketones.