Aluminum exchanged sepiolite as components of FCC catalysts

Sepiolite is a fibrous magnesium silicate, which is formed of talc-like ribbons arranged in such a way that the tetrahedral sheet is continuous but inverts apical directions in adjacent ribbons. In this way, channels of 10.8 {times} 4.0 {angstrom} in a cross-section perpendicular to the length of the fiber (C axis) are generated. The average fiber length of the mineral varies between 0.5 and 1.0 {mu}m, and reagent molecules have only access to a small portion of the interior of the channels. Natural or acid leached sepiolite have been found useful for vanadium passivation in FCC catalysts. The authors have modified the sepiolite in order to improve the textural characteristics, while removing the Mg{sup 2+} ions of the border and introducing other cations which can give acid properties to this material. Conclusions are as follows: (1) It is possible to prepare, by a conventional treatment, sepiolites in which the magnesium at the borders of the channels has been substituted by Al{sup 3+}. (2) These samples show a much higher acidity and hydrothermal stability than natural sepiolites, being most of the acidity in the range of mild strengths. (3) Aluminic sepiolites, while being good for vanadium passivation, do not present themore » inconvenience due to Mg migrations to the zeolite (if in the same particle) shown by natural sepiolite. (4) They present a good gasoil cracking activity and selectivity, specially useful for bottoms conversion. All these characteristics make aluminum sepiolites materials worth testing in a larger scale for catalytic cracking of residues.« less