A Pathway Towards Carbon Neutral Fuels: Synthesis of I-Butanol with Renewable Methanol

The Institute of Electrochemical Process Engineering (IEK-14) of the Jülich Research Center is taking part in the project C³-Mobility, exploring different pathways for the synthesis of carbon neutral fuels from green methanol. Unlike methanol and ethanol, pure C4 alcohols comply with fuel regulations.

A lot of research nowadays deals with the upgrading of ethanol into 1-butanol, because it is more favourable as fuel than ethanol¹. A disadvantage of the used Guerbert Reaction is the low selectivity and that methanol will react only as electrophile².

We therefore decided to build upon the C-methylation protocol of Siddiki et al for the synthesis of iso-butanol⁴. In a typical experiment, 10% ethanol is reacted in a methanolic NaOH solution (N₂-Atmosphere, 423K, autogenous pressure, 4h). Samples are taken every 60 minutes and measured by GC-MS . Triple determination was applied to verify the quality of the measurements. We tested different commercially available catalysts from Alfa Aesar (5% Rh, 5% Pd, 5% Ru 5% Pt, 1% Ir support: carbon), that have been examined by XRD and BET. The preliminary results show that iso-butanol is the only detectable liquid final product in differing amounts for different catalysts.

Wu et al. correlated the ethanol upgrading experiments of Riittonen et al with the d-Band center and found that the conversion decreased with a downshift of the d-Band center³. Our findings differ from those in a way, that the highest rate of formation for iso-butanol could be achieved with 1% Ir/C instead of the expected 5% Pt/C or 5% Ru/C. More detailed characterization of the catalysts is underway and includes the characterization of surface functionalities like base and acid centers, as well as the structural analysis of metal particles. Further insight into possible reasons for this difference in results will be the subject of the presentation.