Se estudio la interaccion entre acido citrico y alumina recubierta de silice mediante espectroscopia de FTIR. Los resultados indican que el acido citrico se coordina con los sitios Lewis de Al3+ y forma enlaces por puente de hidrogeno especialmente con los grupos OH tipo II y tipo III de la alumina eliminandolos casi por completo al incorporar 15% de AC, disminuyendo asi la acidez total del soporte y la posibilidad de interacciones fuertes metal – soporte entre la alumina y las fases de Mo en el catalizador final de HDS. El efecto del acido citrico es mayor en el catalizador preparado por el metodo de postratamiento donde la disminucion de la acidez da lugar a catalizadores con cristalitos de MoS2 mas pequenos y con mayor numero de sitios activos, provocando un aumento del 22% de la actividad de hidrodesulfuracion de 4,6-dimetildibenzotiofeno. NiMo/SiO2/Al2O3 hydrodesulfurization catalysts. An FTIR study of the interaction citric acid-support ABSTRACT The interaction of citric acid with alumina grafted with silica was studied by infrared spectroscopy. The results indicate that citric acid coordinates to the Al3+ Lewis centers and interacts by hydrogen bonding with the type II and III hydroxyl groups in the alumina support, which after the addition of 15 wt % citric acid to the alumina support are almost completely eliminated, decreasing the acidity and the possibility of strong metal-support interactions between the alumina support and the Mo phases in the final HDS catalyst. The effect of citric acid is greater in the catalyst prepared by post-treatment in which the decrease in acidity results in catalysts with smaller MoS2 crystallites and higher number of active sites, resulting in an increase of 22 % in the HDS of 4,6-dimethyldibenzothiophene.