Kraft lignin (KL), isolated from black liquor, serves as a significant feedstock for the production of bio-aromatics by catalytic fast pyrolysis (CFP). First, the influence of pH on the chemical structure of KL isolated by the gradient acid precipitation (GAP) was investigated. Then, the dual-catalyst CFP (DC-CFP) was employed to convert KL into light aromatics by using the hierarchical NbO (Hie-NbO) and the microporous HZSM-5 as catalyst. Results showed that the decrease of pH during GAP promoted the breakage of the ether bond of KL, resulting in lower molecular weight and less content of hydroxyl group in KL. Among the four types of metal oxides (Hie-NbO, AlO, MgO, and CaO), the synergistic effect of dual-catalyst grouped by Hie-NbO and HZSM-5 was best for the production of light aromatics. In addition, the maximum production of light aromatics was reached at the pH of 2 and the mass ratio of Hie-NbO-to-HZSM-5 at 2:2.

中文翻译：

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通过梯度酸沉淀从黑液中分离硫酸盐木质素的结构解析以及通过双催化剂串联催化热解高选择性生产轻芳烃

从黑液中分离出来的硫酸盐木质素 (KL) 是通过催化快速热解 (CFP) 生产生物芳烃的重要原料。首先，研究了 pH 对梯度酸沉淀 (GAP) 分离的 KL 化学结构的影响。然后，采用多级NbO（Hie-NbO）和微孔HZSM-5作为催化剂，采用双催化剂CFP（DC-CFP）将KL转化为轻质芳烃。结果表明，GAP过程中pH值的降低促进了KL醚键的断裂，导致KL分子量降低，羟基含量减少。在四种金属氧化物（Hie-NbO、Al2O、MgO和CaO）中，Hie-NbO和HZSM-5双催化剂对轻芳烃生产的协同效果最好。此外，在pH为2、Hie-NbO-与HZSM-5的质量比为2:2时，轻芳烃产量达到最大。