EFFECT OF SODIUM-OXIDE ON THE MORPHOLOGY AND BASICITY OF ALUMINA

Various samples of alumina were compared to study the effect of crysta llinity and sodium impurity on alumina morphology and basicity. Carbon dioxide adsorption, followed by FT-IR and desorption (TPD), and COS h ydrolysis test reaction were used. The decrease of surface area observ ed on rather amorphous samples after introduction of small amounts of sodium is ascribed to a better crystallinity due to migration of a par t of Na+ into the bulk. The charge compensation phenomenon decreases t he number of defects in the anion subnetwork. It also provokes a decre ase of the number of OH groups which could explain the decrease of act ivity towards COS hydrolysis of the samples containing very small amou nts of Na2O (<1000 ppm). For larger amounts, COS conversion and carbon dioxide experiments showed an increase in basicity.