2,5-Hexanedione: The Bridge for p-Xylene Production from Lignocellulosic Biomass via a Brand New Two-Step Route

Green and efficient upgrading of cellulose into p-xylene (PX) is critical to utilizing zymotic biomass wastes and complies with the "recycling economy". Despite the tremendous efforts devoted by researchers, a bio-based PX production route that is compact with both technical and economic feasibility is extremely desirable but still remains a significant challenge. Here, we put forward a brand new two-step PX production route via 2,5-hexanedione (HDO), efficiently simplifying the whole process and cutting down the cost. We thoroughly investigated the effect of reaction conditions and took insight into the corresponding reaction mechanism in each step. The highest yields of 64 and 85% were achieved for HDO/2,5-dimethylfuran (DMF) and PX during the first and second steps, respectively. Furan ring hydrogenation and condensation into an oligomer comprise the main side reactions during the first step. In comparison with the most promising production route for bio-based PX at present (cellulose → glucose → fructose → 5-hydroxymethyl furfural (HMF) → DMF → PX), the as-proposed two-step route may exhibit tremendous advantages: streamlining with much less operating units and laying solid foundation for industrialized production by dexterously avoiding production and separation of HMF.