Process features for an efficient ethanol conversion to n-butanol

Production of chemicals from ethanol and sugars is foreseen as an alternative to improve the sustainability of the chemical industry. Replacement of fossil resources by renewable materials is required for the chemical sector to achieve reduced environmental impacts and to guarantee its continuity in face of possible diminished oil reserves. One product that can be obtained from the catalysis of ethanol is n-butanol, which presents advantages in terms of fuel properties in comparison to ethanol and is also a feedstock in the chemical industry.

Different catalysts have been investigated for the production of n-butanol from ethanol, e.g. hydroxyapatites, mixed oxides and ruthenium based. The combination of ethanol conversion, n-butanol selectivity and reaction time is crucial for the performance of the process; results available in the literature provide conflicting parameters for ethanol conversion and n-butanol selectivity, which should be maximum, and reaction time, which must be long (several hours) in order to achieve high ethanol conversion. However, long reaction times require high equipment investment and also lead to production of other chemicals, decreasing n-butanol selectivity.

In this study the use of some catalysts was evaluated in a sugarcane biorefinery for the conversion of ethanol to n-butanol and other chemicals through process simulation. Catalysts features required for achieving the best economic performance were assessed, and the relative importance of each parameter was determined. It is shown that reaction time plays a major role, and can even surpass the importance of n-butanol selectivity, if co-products are to be sold in the chemical market.