(569do) Production of Tagatose from Galactose with CaO at Room Temperature

This study investigates the efficacy of Sn-β zeolite, triethylamine, and CaO in the isomerization of galactose to tagatose. At temperatures over 80 °C, all three reagents exhibited low tagatose yield (< 20%), with chemical/galactose molar ratios ranging from 1:20 to 1:5. Notably, CaO exhibited a galactose conversion of 70% in 10, albeit displaying decreasing tagatose selectivity over time. Whereas after 40 min of reaction at room temperature, 100% galactose conversion was reached with CaO/galactose molar ratios of 1:1 and 2:1, resulting in 56% and 73% tagatose selectivity, respectively. Interestingly, galactose conversion showed a linear relationship with the molar ratio of CaO to galactose at room temperature. This indicates that CaO functions as a stoichiometric reagent rather than a catalyst to react with galactose. A yellowish gel-like complex formed when CaO/galactose molar ratios exceeded 1:2. It is noteworthy that these phenomena were not observed with MgO, and CaO showed no analogous catalytic performance in isomerizing glucose to fructose under the same conditions.