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Ethanol Coupling Reactions over MgO-Al2O3 Mixed Oxide-Based Catalysts for Producing Biofuel Additives.
Anna Vikár1, Ferenc Lónyi1, Amosi Makoye1,2
1Institute of Materials and Environmental Chemistry, Research Centre for Natural Sciences, Magyar Tudósok Körútja 2, 1117 Budapest, Hungary.
Molecules (Basel, Switzerland)
|May 13, 2023
Summary
Optimizing MgO-Al2O3 catalysts for ethanol to 1-butanol conversion requires balancing strong-base and medium-strong Lewis acid sites. Metal promoters enhance activity but decrease selectivity at higher temperatures due to side reactions.
Area of Science:
- Heterogeneous catalysis
- Surface chemistry
- Catalyst design
Background:
- Catalytic conversion of ethanol to 1-butanol is a key process for producing biofuels and chemicals.
- Understanding the interplay between catalyst properties and reaction mechanisms is crucial for optimizing selectivity and yield.
- Mixed oxide catalysts offer tunable acid-base properties for targeted chemical transformations.
Purpose of the Study:
- To investigate the catalytic performance of MgO-Al2O3 mixed oxide catalysts for ethanol to 1-butanol conversion.
- To correlate acid-base properties and metal promoter effects with catalytic activity and selectivity.
- To elucidate the reaction pathways and surface species involved in the ethanol coupling reaction.
Main Methods:
- Characterization of acid-base properties using temperature-programmed desorption (CO2, NH3) and FT-IR spectroscopy of adsorbed pyridine.
- Determination of metal promoter dispersion (Pd, Pt, Ru, Ni) via CO pulse chemisorption.
- Evaluation of catalytic performance in a flow-through microreactor system under varying conditions (21 bar, 200-350 °C).
- In-situ analysis of surface species using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT).
Main Results:
- Optimal butanol selectivity and yield were achieved with MgO-Al2O3 catalysts possessing a high concentration of strong-base and medium-strong Lewis acid sites.
- Metal promoters (Pd, Pt, Ru, Ni) enhanced overall activity but led to decreased butanol selectivity at temperatures above 300 °C due to accelerated side reactions.
- DRIFT spectroscopy indicated that active metals promoted hydrogen transfer from H2 within a narrow temperature window (200-250 °C).
Conclusions:
- The acid-base properties of MgO-Al2O3 catalysts are critical for selective ethanol to 1-butanol conversion.
- Careful control of reaction temperature and catalyst composition, including metal promoters, is necessary to maximize butanol yield and minimize side reactions.
- Understanding the role of active metals in hydrogen transfer provides insights for designing more efficient catalysts for this transformation.
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