However, we observe significant differences in the surface area as a function of HT composition. The largest surface areas were observed for the HT65, the Ni HT80 and the Cu HT65 samples, being 148, 149 and 140 m 2 g -1 respectively, Table . The Co HT65 sample exhibited the lowest specific surface area amongst the HT samples, 79 m 2 g -1 . The more pronounced influence of both composition and the aging temperature is observed in the pore size distributions, calculated using the BJH method. Results are shown in Figures . Despite having little effect on SBET, aging temperature has a profound effect on the morphology of hydrotalcites. For the standard sample "HT", aging at 65 °C results in the formation of narrowly distributed pores with the mean diameter of 3.6 nm. The increase in aging temperature for the HT sample to 80 ºC, and subsequently to 95 °C, clearly results in larger pores, Figure , with the average pore diameters of 5.8 and 7 nm respectively.