The subject of this experimental report is the application of nano particles in petroleum refinement. Sulfur removal from petroleum using mixed bed which contains nano molybdenum oxide and nano cobalt oxide, each of them in 50 volume percentage, is considered in this study. The properties related to the process characterization which is defined as X factor and pressure drop, are evaluated experimentally. The increase trend is obviously obtained however there are different curve slopes from beginning to the end. The results show the changing in diameter from 2 cm to 2.5 cm increases the value of X factor for about 0.2%, while the increase in bed diameter from 3.5 cm to 4 cm increases only 0.05%. This may relate on the poor distribution of oil in higher diameter of bed.