The Hydroformylation via Autogenous Cobalt Carbonyl Species Derived from a Heterogeneous Cobalt–Zirconium Precursor
摘要
The hydroformylation of 1-olefins derived from Fischer–Tropsch synthesis (FTS) provides an alternative production of oxygen-containing chemicals such as aldehyde or alcohols. Traditionally, homogeneous catalysts have been adopted in the case. Nonetheless, heterogeneous cobalt-based catalysts exhibit facile separation from liquid reactants, offering an opportunity for the continuous improvement of process. Taking homogeneous cobalt carbonyl species (Co2(CO)8) catalyst as a reference, the influence of heterogeneous cobalt–zirconium (Co–ZrO2) catalyst preparation parameters, as well as process conditions on hydroformylation, was studied. Based on the hot filtration and recycle test, it is evident that the hydroformylation catalyzed by Co–ZrO2 essentially occurred via cobalt carbonyl intermediate species, which was further confirmed by the cobalt loss. Nonetheless, the Co–ZrO2 catalyst parameters such as the reducibility or crystalline size of Co, as well as reaction conditions like stirring speed rate and hydrogen-to-carbon monoxide (H2/CO) ratio, influence the formation rate of labile Co2(CO)8, thus modifying the hydroformylation. In addition, the Co–ZrO2 catalyst yielded a significant number of isomerized products, 2-hexene, due to abundance of cobalt ion (Co2+) or Co–ZrO2 interface. The hydroformylation and isomerization mechanism over a heterogeneous Co–ZrO2 catalyst are schemed to explain those observations.
Graphical Abstract