Application of experimental design in the synthesis of 1-butanol from ethanol on mixed oxide catalysts at different mg/al molar ratios

Abstract

1-Butanol, primarily sourced from petroleum, is currently being considered as a viable alternative to gasoline. Various pathways for synthesizing 1-butanol from renewable raw materials have been explored, with a particular focus on the Guerbet reactions. This study aimed to investigate the synthesis of 1-butanol from ethanol using Mg/Al mixed oxides derived from layered double hydroxides with Mg/Al molar ratios of 3:1, 5:1, 8:1, and 10:1. The catalysts were analyzed through X-ray diffraction, X-ray fluorescence, N₂ adsorption, scanning electron microscope and energy-dispersive X-ray spectroscopy. Catalytic reaction tests were performed according to a Central Composite Rotatable Design (CCRD) with three replicates at the central point (CP). Among the catalysts tested at CP, the mixed oxides with Mg/Al molar ratios of 3:1 and 5:1 exhibited the most promising results, displaying similar ethanol conversion, and 1-butanol selectivity. This similarity underscores their well-balanced combination of both acidic and basic sites. However, further assessment through a deactivation test revealed that the mixed oxides with Mg/Al molar ratio of 5:1 held the most potential for long-term 1-butanol synthesis from ethanol, thanks to its superior stability and sustained activity. Using this catalyst, other reaction tests were carried out following the CCRD, varying N₂ feed flowrate, ethanol molar content in feed flowrate, and temperature. The results indicated that an increase in ethanol conversion directly correlated with higher temperatures, while the 1-butanol selectivity depended on both the N₂ feed flowrate, ethanol molar content in feed flowrate, highlighting the importance of a well-balanced combination of both acidic and basic sites.

Keywords:

• 1-Butanol selectivity
• central composite rotatable design
• ethanol conversion
• Guerbet reactions
• heterogeneous catalysis
• layered double hydroxides

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article.

Additional information

Funding

The authors would like to thank the National Council of Technological and Scientific Development (CNPq), the Coordination for the Improvement of Higher Education Personnel (CAPES) and the Research Support Foundation of Rio Grande do Sul (FAPERGS) for the financial support for this project.