Direct esterification of butanol to butylbutanoate in the absence of butanoic acid has been investigated by a series of green solid acid catalysts, including H-14[NaP5W30O110], H-14-P-5, H-14[NaP5W29MoO110], H-14-P5Mo and silica supported H-14[NaP5W30O110], H-14-P-5/SiO2, with H2O2 as oxidizing agent at reflux and at room temperatures. The performance of these eco-friendly catalysts were compared with H2SO4. Maximum butylbutanoate yield and product selectivity (100%) was observed by using H-14-P5Mo as the catalyst. The effects of various parameters such as catalyst type, reaction times, reaction temperatures, and molar ratio of n-butanol to hydrogen peroxide have been studied. The green catalysts can be easily recovered and recycled with retention of their initial structure and activity. (C) 2007 Elsevier B.V. All rights reserved.