A method for basicity determination of thermally labile samples

Background Layered double hydroxides (LDH) belong to the group of catalytic materials used in basic catalysis. Their basicity is the most important property for catalytic performance. Our work presents a possible method for the determination of such thermally labile materialś basicity using liquid phase sorption of a specific probe. Results Anthranilic acid was chosen as an optimal probe, and two methods were used for measuring the basic site amount – HPLC-MS and DRUV–Vis. The chosen methods described exactly the behavior of the tested LDHs in the model reaction. The basicity of LDHs increased in the row LDH2 < LDH3 < LDH2.5 which was the same trend for the conversion of reactant achieved in a model reaction. The important parameter in the model reaction and in the basicity determination was the particle size of the materials. The amount of adsorbed anthranilic acid on LDHs was in the range 197.8–199.7 mg/g, which was ten times higher than the amount adsorbed on mixed oxides (MO, the precursor for LDH preparation, adsorbed amount of anthranilic acid 13.8–18.5 mg/g). The MO adsorption of anthranilic acid showed differences in overall basicity that were not visible under conventionally used method (TPD). Significance The developed method seems to be promising in the determination of the basicity of especially thermally labile materials for which the conventional methods cannot be used.