Optimization of basic catalyst with ammoniated polyethylene glycol for the removal of naphthenic acid from petroleum crude oil by Box-Behnken design - Shukri, Nurasmat Mohd; Jaafar, Jafariah; Abu Bakar, Wan Azelee W, Shukri, Nurasmat Mohd; Jaafar, Jafariah; Abu Bakar, Wan Azelee W (2015)