Silica-Supported Nanoscale Hydrotalcite-Derived Oxides for C4 Chemicals from Ethanol Condensation

We demonstrated that the surface nature of nanoscale hydrotalcite-derived oxide (HTO) can be simply tailored through the addition of amorphous silica during the coprecipitation process of material preparation. The change in physical/chemical properties of the modified surface has been carefully scrutinized by a series of surface characterization techniques. The results showed that the HTO nanocomposite has molecular interactions with amorphous silica to form ternary Mg, Al, and Si interfaces, in accordance with enhancing chemically accessible aluminum (Al³⁺_tetra) as acidic sites. Moreover, the silica-supported HTO (HTO/SiO₂-X) could catalyze ethanol condensation to foster C4 chemicals at 250 °C through the flow reactor. HTO with a strong basic nature promoted 1-butanol production (66% selectivity), while HTO/SiO₂-5 with more well-distributed acidic sites favored 1,3-butadiene production (43% selectivity). This difference in catalytic performance could be attributed to the redistribution of acidic and basic sites upon the newly formed ternary interfaces, which could facilitate the surface-mediated Meerwein-Ponndorf-Verley (MPV) reduction reaction due to the relatively high ethanol affinity.