Kojčinović Aleksa, Likozar Blaž, Grilc Miha
Department of Catalysis and Chemical Reaction Engineering, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.
Graduate School, University of Nova Gorica, Vipavska Cesta 13, 5000 Nova Gorica, Slovenia.
Int J Mol Sci. 2024 Dec 1;25(23):12923. doi: 10.3390/ijms252312923.
Combining carboxylation reactions using carbon dioxide (CO) as a reactant with phenol results in creation of new C-C bonds, and represents one of the most promising routes in sustainable utilization of ubiquitous and readily available resources for production of highly valuable products. This study provides a detailed and well-structured investigation of the effect of various reaction conditions (reactant loading, reaction duration, temperature, CO pressure) on the carboxylation of phenol. Sodium phenoxide carboxylation showed well-resolved trends with variation of temperature and time, and resulted in production of salicylic acid (SA) in the range of 11.4 to 47.8%, 4-hydoxybenzoic acid (4HBA) in the range of 2.0 to 8.2%, while the dicarboxylated 4-hydroxyisophthalic acid (4HiPh) was only detected in trace amounts. The effect of the variation of reactant content was shown to be significantly influenced by the reactor size, solid/vessel and gas/solid contact area, as well as the efficiency of the stirring. CO pressure was shown to be a crucial element, where reactions carried out below 2 MPa CO did not show any activity. While investigating the reaction mechanism, it was shown that the salt analogues of potential products could be acidified in situ by the moisture present, and immediately degraded back to phenol, thus lowering yields of potentially obtained products. The experimental results were successfully used to compose a kinetic model, which very well describes the experimentally obtained results. As such, this study provides a valuable dataset for valorization of lignocellulosic aromatic compounds as well as highly abundant and environmentally detrimental carbon dioxide into industrially valuable mono- and dicarboxylic acids.
将以二氧化碳（CO）为反应物的羧化反应与苯酚相结合可形成新的碳-碳键，这是可持续利用无处不在且易于获取的资源来生产高价值产品最具前景的途径之一。本研究详细且有条理地考察了各种反应条件（反应物负载量、反应持续时间、温度、CO压力）对苯酚羧化反应的影响。苯氧酸钠羧化反应随温度和时间变化呈现出明显的趋势，生成水杨酸（SA）的产率在11.4%至47.8%之间，生成4-羟基苯甲酸（4HBA）的产率在2.0%至8.2%之间，而二羧化的4-羟基间苯二甲酸（4HiPh）仅检测到痕量。结果表明，反应物含量的变化受反应器尺寸、固/器和气/固接触面积以及搅拌效率的显著影响。CO压力被证明是一个关键因素，在2 MPa CO以下进行的反应没有任何活性。在研究反应机理时发现，潜在产物的盐类似物会被存在的水分原位酸化，并立即降解回苯酚，从而降低潜在产物的产率。实验结果成功用于构建动力学模型，该模型很好地描述了实验得到的结果。因此，本研究为将木质纤维素芳香族化合物以及含量丰富且对环境有害的二氧化碳转化为具有工业价值的一元和二元羧酸提供了有价值的数据集。
