二氧化碳催化转化为甲酸的技术进展

Technology Progress in Catalytic Conversion of Carbon Dioxide to Formic Acid

甲酸的制备主要有传统工艺、生物法和二氧化碳加氢3种工艺,其中以二氧化碳为碳源,经还原反应制备甲酸(盐)或甲酸酯已成为C_1化学研究的热点,也是二氧化碳利用的重要途径之一。二氧化碳转化为甲酸既具有经济技术意义,又具有环保意义,可以将二氧化碳转化为用途广泛的甲酸及其衍生物,而且甲酸还是重要的液态储氢原料,在一定条件下又可分解释放出氢气,实现能量循环。从热力学上讲在二氧化碳加氢反应体系中直接得到甲酸是不可能的,欲想得到甲酸,除了改进反应工艺,抑制副反应的发生以外,更需要在反应体系中引入其他物种,即得到的是甲酸的衍生物,使二氧化碳间接转化为甲酸。二氧化碳加氢制甲酸反应研究较早的是均相催化体系,当前的研究绝大多数也都集中于此。关于其反应机理,目前最为大家认可的是二氧化碳与M-H相互作用机理,而对于均相催化剂已有大量文献报道,包括Rh、Ru、Ir及非贵金属催化体系等。相对于均相催化体系,多相催化反应由于在催化剂分离及寿命等方面的诸多优势,近年来受到研究者的关注。此外还有生物催化体系、光催化体系、电催化体系等。目前对于二氧化碳转化为甲酸反应的研究大多数还处于实验室研究阶段,选择性和转化率均不太理想,不能进行商业化推广。今后需要继续对其反应过程进行探究,得到活性高且能长周期使用的环境友好催化剂。

Formic acid preparation processes mainly include traditional process,biological method and carbon dioxide hydrogenation process.Among them,using carbon dioxide as the carbon source to prepare formic acid(salt) or formate via reduction reaction has become a hot spot in C1 chemical research and also one of the important ways to utilize carbon dioxide.The conversion of carbon dioxide to formic acid has great significance in economy,technology and environmental protection.It can convert carbon dioxide into formic acid and its derivatives with wide applications,and formic acid is an important liquid hydrogen storage material,which can decompose and release hydrogen under certain conditions to achieve energy cycle.Thermodynamically,it is impossible to directly obtain formic acid in carbon dioxide hydrogenation reaction system.In addition to im-proving the reaction process and suppressing the side reactions,it is necessary to introduce other species into the reaction system to obtain the derivatives of formic acid,thus indirectly converting carbon dioxide into formic acid.Early researches on the hydrogenation of carbon dioxide to formic acid concentrated on homoge-neous catalysis system,and most of the current research still focus on it.Currently the most recognized reac-tion mechanism is the interaction mechanism between carbon dioxide and M-H,and there are a lot of literatures on homogeneous catalysts including Rh,Ru,Ir and non-noble metal catalytic system.Compared with homogeneous catalytic system,heterogeneous catalytic reaction has attracted the attention of researchers in recent years due to its advantages in catalyst separation and life.In addition,there are biocatalytic system,photocatalytic system and electrocatalytic system.At present,most of the researches on the conversion of carbon dioxide to formic acid are still in laboratory research stage,and the selectivity and conversion rate are not ideal,so it is not suitable for commercialization.In the future,it is necessary to continue to explore its reaction process to obtain environmentally-friendly catalysts with high activity and long service life.