ChemInform Abstract: Formation of Base Sites on Calcined Mg‐Ga Hydrotalcite‐Like (Mg1‐xGax( OH)2)(CO3)x/2×mH2O.

Abstract

Formation of Base Sites on Calcined Mg-Ga Hydrotalcite-Like (Mg1-xGax( OH)2)(CO3)x/2·mH2O.-The base properties of a series of title hydrotalcites with x ranging from 0.12 to 0.36, prepared by a coprecipitation method, are studied as a function of both the calcination temp. and the Mg/Ca molar ratio using TPD of CO2, FTIR analyses, and CDCl3 adsorption. Calcination in the temp. range 523 to 673 K causes an increase of the specific surface area from 46 to 156 m2/g due to dehydroxylation and decarbonation. The total number of base sites increases with calcination temp. and reaches a maximum at 873 K. The amount of base sites, which depends on the Mg/Ga ratio, is 2.4 times higher at a ratio of 7.7 than at 2.9. The relative base site distribution depends on both the calcination temp. and the Mg/Ga ratio. Higher temp. favor a greater population of medium and strong base sites and Mg-richer compounds exhibit stronger base sites. -(LOPEZ-SALINAS, E.; GARCIA-SANCHEZ, M.; LLANOS-SERRANO, M. E.; NAVARRETE-BOLANOZ, J.; J.