Production of jet fuel is not only promising but challenging in the field of biomass utilization. Here we proposed a novel route to produce highly branched alkanes with ultra-low freezing point using n-butyraldehyde as feedstock by self-aldol condensation and subsequent hydrodeoxygenation (HDO). The catalyst characterization revealed that the MgO-SiO2 catalyst played an acid-base synergetic effect role in the self-aldol condensation of n-butyraldehyde using n-butanol as solvent, which obtained C8 oxygenate and C12 oxygenate with yield of 69.3 % and 26.8 % respectively. The medium Brønsted base site of the catalyst captured α-H to promote the formation of enolate from n-butyraldehyde, and the Lewis acid sites promoted the dehydration of intermediate products. DFT simulation showed that n-butanol activated α-C in enolate in aldol condensation, and deactivated the oxygen atoms in enolate by hydrogen bonds to inhibit side reactions. Finally, the obtained condensation products were subjected to HDO reaction over the 5 wt% Pd/C and HZSM-5 catalysts, obtaining the highly branched alkanes with an ultra-low freezing point of -120.7 °C for C8 alkane and -78.7 °C for C12 alkane suitable for bio-jet fuels.

中文翻译：

---

MgO-SiO2催化剂上正丁醛自醛醇缩合Pd/C和HZSM-5催化剂加氢脱氧合成超低凝固点烷烃


在生物质利用领域，喷气燃料的生产不仅前景广阔，而且充满挑战。在这里，我们提出了一种以正丁醛为原料，通过自醇醛缩合和随后的加氢脱氧（HDO）生产具有超低凝固点的高度支化烷烃的新路线。催化剂表征表明，MgO-SiO2催化剂在正丁醛以正丁醇为溶剂的自醛醇缩合反应中发挥酸碱协同作用，得到C8含氧化合物和C12含氧化合物，收率分别为69.3 %和26.8 %分别。催化剂的中等布朗斯台德碱位捕获α-H促进正丁醛形成烯醇化物，路易斯酸位促进中间产物脱水。 DFT模拟表明，醇醛缩合过程中，正丁醇会活化烯醇化物中的α-C，并通过氢键使烯醇化物中的氧原子失活，从而抑制副反应。最后，将所得缩合产物在5 wt% Pd/C和HZSM-5催化剂上进行HDO反应，得到C8烷烃和-78.7 ℃超低凝固点的高度支化烷烃。适用于生物喷气燃料的 C12 烷烃。