Methanol production through combined carbon capture and hydrogenation: unravelling the benefits of two-step hydrogenation
article
The combined carbon capture and hydrogenation towards methanol was demonstrated using dipropylamine as carbon capture agent. Previous works highlighted the reaction to follow a complex mechanism, in which the carbamate species formed during carbon capture is hydrogenated into N-formamide species, which are subse quently hydrogenated into methanol. The rate limiting step was observed to be the second step. Therefore, this work aimed to improve the conversion of N-formamide species into methanol. Comparing Au/ZnO, Au/MgO, Au/CeO2, Au/ZrO2 and Au/TiO2 catalysts using N,N-dipropylformamide as starting material, it was concluded that the methanol productivity strongly correlates with the surface basicity of the catalyst support. This was rationalized in relation to the reaction mechanism, in which the first hydroge nation step of the formamide species is proposed to occur via a hemiaminal intermediate. While basic catalysts are required for the hydrogenation of N-formamides into methanol, the formation of N-formamides from N carbamates requires acidic sites. Therefore, we proposed a two-step strategy within this work, using first an acidic catalyst bed (Pd/Al2O3), followed by a basic catalyst bed (Au/ZnO). The novel process configuration was compared to the state-of-the-art single step process showing the complete reaction from CO2 captured in dipropylamine in the form of carbamate to methanol. Here, the methanol productivity was observed to increase by ~100X
compared to the previously proposed single step configuration.
compared to the previously proposed single step configuration.
TNO Identifier
1017888
Source
Chemiocal Engineering Journal(522), pp. 1-10.
Pages
1-10