钙钛矿催化木质素水热液化

Hydrothermal liquefaction of lignin to aromatics over the perovskite catalysts

以碱木质素为原料,采用GC-MS、FT-IR、元素分析等实验表征手段并结合DFT计算,对LaBO_(3)钙钛矿(LaCoO_(3)、LaFeO_(3)和LaNiO_(3))催化液化木质素的性能进行了研究,考察了反应时间、温度、催化剂用量和B位阳离子对木质素转化率、生物油收率及生物油化合物分布的影响。结果表明,三种钙钛矿都能促进木质素的裂解生成芳香族化合物,但LaCoO_(3)木质素液化催化性最好,其次为LaNiO_(3)和LaFeO_(3)。LaCoO_(3)添加量为5%、180℃下反应60 min时,生物油产率最高达67.20%,单芳香族化合物的相对含量最高达89.59%。LaBO_(3)晶体表面的氧原子通过吸附木质素中的氧原子降低了木质素分子内键的解离能(LaCoO_(3)的吸附能最大),同时其疏松多孔的形貌和适中的氧化还原能力,能够有效促进木质素分子内的C−C和C_(Ar)−OCH_(3)的断裂,实现大分子解聚和脱甲氧基反应,生成苯酚等高附加值化合物。

The catalytic performance of three LaBO_(3) perovskites including LaCoO_(3),LaFeO_(3) and LaNiO_(3) in the liquefaction of lignin was investigate through a series of experimental characterization methods such as GC-MS,FT-IR and elemental analysis as well as DFT calculation.The effects of reaction time,temperature,catalyst amount and B cation on the lignin conversion,bio-oil yield and products distribution were considered.The results indicate that all three perovskite catalysts can promote the liquefaction of lignin to produce aromatic compounds;among them,LaCoO_(3) shows the highest catalytic performance,following by LaNiO_(3) and LaFeO_(3).In particular,by using 5%LaCoO_(3),the bio-oil yield achieves 67.20%after reaction at 180°C for 60 min,whilst the relative content of mono-aromatic compounds reaches 89.59%.The adsorption of oxygen atoms on the LaBO_(3) crystal surface conduces to the decrease of bond dissociation energy for lignin(LaCoO_(3) shows the moderate redox capacity and greatest adsorption energy),whilst the loose and porous morphology can effectively promote the fracture of C−C and C_(Ar)−OCH_(3) of lignin.All these contribute to the macromolecular depolymerization and demethoxylation reaction,producing high value-added compounds such as phenol.