The efficiency of the catalytic alkylation, the first step of the olefins alkylation thiophenic sulfur (OATS) process was investigated in three typical gasoline samples with different olefins contents over a fluorinated H beta zeolite catalyst. Under the reaction conditions of 120 degrees C, 1.5 MPa and WHSV 0.5 h(-1), over 95% light sulfur compounds in the feeds could be transformed to be heavier than the heptyl-thiophenes within a period of time-on-stream, The lifetime of the catalyst could prolong from 10 h to 26 h when the olefins content in the gasoline feed decreased from 40.87 wt.% to 9.20 wt% It was also found that the olefins content decrease was favorable for keeping and promoting the octane number by redistributing the components of the treated gasoline. In addition, the influence of the reaction conditions such as the temperature and WHSV on the efficiency of the catalytic alkylation was investigated. (C) 2008 Elsevier B.V. All rights reserved.