HAP solids were prepared with different Ca/P ratios and Na+ cations before being characterized by XRD, XPS, LEIS, NMR, IR, and TGA. Their acid–base properties were then measured and discussed in relation to the characterization results.

The Guerbet reaction of ethanol to produce heavier products was performed over a series of extensively characterized carbonate-containing hydroxyapatites (HAPs) with different Ca/P ratios and thus different densities, strengths and natures of acid and basic sites. These properties were correlated with the reactivity of the solids and an optimal ratio between the amount of acid and basic sites was evidenced (ca. 5). The best performance was accordingly obtained over the Hap-CO 3 catalyst, which gave a yield of 30% of heavier alcohols at 40% ethanol conversion.Catal. Sci. Technol. This journal is † Electronic supplementary information (ESI) available: Supplementary correlations drawn between isopropanol and ethanol reactivity and supplementary correlations drawn between directly measured acid-base properties and ethanol reactivity. See