Modified HY zeolites impregnated with an optimum amount of lanthanum was found to be an effective catalyst for the clean alkylation of a-methylnaphthalene with long-chain olefins. It was found that Bronsted acid was the main catalytically active center and that the reaction required an optimal concentration of acidic sites. The deactivated LaHY zeolite catalyst can be regenerated by temperature-programmed calcination. (c) 2006 Elsevier B.V. All rights reserved.