A series of mesoporous alumina catalysts with different textural properties were prepared via the sol-gel method, and the aluminium precursor, chain length of the surfactant and calcination temperatures were varied. The influence of various preparation parameters on the resulted alumina surface area, pore size, pore volume and acidity were investigated. Mesoporous alumina with large surface area of 270-380 m(2)/g and pore size ranging from 3 to 19 nm were successfully synthesised. The activity of mesoporous alumina supported molybdenum catalysts with different properties in hydrocracking of residual oil was determined at 400 degrees C. The acidity of the catalyst enhanced the conversion and the production of light gas oil. Higher conversion and higher of liquid products yield were achieved by using catalyst with larger mesopore size as compared to catalyst with smaller pore size and similar acidity. (C) 2011 Elsevier B.V. All rights reserved.