The catalytically supported upgrading of green ethanol and green methanol mixtures can produce higher alcohols, such as iso-butanol, in a sustainable manner. Iso-butanol can be used as a feedstock to defossilize the chemical and transportation sectors. MgO-Al2O3 hydrotalcite-based catalysts are a promising option for this purpose. In this paper, samples were synthesized using co-precipitation and urea methods with different Mg/Al molar ratios with Ni acting as the active catalytic component. Thereby, the catalysts synthesized using the urea method exhibited the greatest activity, producing iso-butanol concentrations of up to 170 mmol L−1 at 185 °C, with selectivities towards iso-butanol of 85–89% and a maximum space–time yield of 8.2 mmol g−1 h−1. The most active catalyst among all samples from this paper was characterized by 100% proportions of strong basic and medium acidic catalyst sites and the largest specific surface area. XRD analysis revealed the presence of NiO, MgO and the spinels Al2NiO4 and Al2MgO4 in both synthesis variants as well as elemental Ni in one sample from the urea synthesis. CO2-TPD and NH3-TPD experiments showed the dominance of strong basic and medium/strong acidic catalyst sites in both synthesis pathways.
Pasel et al. (Thu,) studied this question.