Specific tuning of acid/base sites in apatite materials to enhance their methanol thiolation catalytic performances

Calcium hydroxyapatites (Hap) solids were prepared with various Ca/P atomic ratios, leading to stoichiometric Ca10(PO4)6(OH)2, calcium-deficient (Ca/P < 1.67) and calcium-rich materials. Their acid/base properties were tailored by the introduction of sodium and/or carbonate entities. The various hydroxyapatite solids were characterized by chemical analysis, IR, XRD and TGA techniques, and tested in methanol thiolation. The acid/base properties were evaluated using the isopropanol decomposition as a test reaction. Catalytic performances were found to be related to their acid/base properties. Total methanol conversion at 400 °C with high selectivity in methanethiol (60%) was obtained for the Na-CO3 modified Hap.