Synthesis and characterization of lanthanum-modified pseudoboehmite - The precursor of alumina supports and catalysts

Abstract

The present work shows that the introduction of 0.25–1.25 wt% lanthanum to the composition of aluminum hydroxide at the stage of its hydrothermal synthesis allows increasing the content of the pseudoboehmite phase in the product up to 95 wt% and, as a consequence, reduces the content of the “amorphous” component. Lanthanum uniformly distributes over the surface of aluminum hydroxide as isolated cations with a surface density of 10–15 cations per 10 nm 2 . During plasticizing of lanthanum-modified pseudoboehmite followed by granulation and heat treatment, the formation of the oxide form of La is not observed, and the cations retain their isolated state. The specific surface area of La-modified alumina increases by 18–26 m 2 /g compared to the unmodified sample, while the pore volume remains the same and the average pore diameter slightly reduces. It was found that when the content of La in pseudoboehmite was 1 wt%, the temperature of reaching a residual sulfur content of 10 ppm in the hydrotreated diesel fuel was 5 °C lower comparing to the unmodified sample. • The effect of La addition at the stage of pseudoboehmite preparation was studied. • La promotes the formation of pseudoboehmite phase. • La is present as isolated cations on the surface of pseudoboehmite and alumina. • Catalyst with 1 wt% La shows the highest HDS and HDN activity.