Mg-A1 hydrotalcites were synthesized using different preparation methods (a co-precipitation method,a urea method,and a simple one) to analyze their effect on the catalytic activity of these solid base catalysts.The method strongly affected the structure of their layers (e.g.,the growth and stacking of the layers,and the type of intercalated anions) and,accordingly,their catalytic activity.The Mg-Al hydrotalcite prepared by co-precipitation showed the best catalytic performance in the isomerization of glucose into fructose,due to the small crystallite size and sand rose morphology enhancing the exposure of surface active sites to reactants.