Preparation and characterization of a novel solid base catalyst hydroxyapatite loaded with strontium

A novel solid base catalyst was first prepared through calcining a porous hydroxyapatite loaded with Sr(NO3)2 at 873 K. The catalyst was characterized by thermal gravimetric analysis, XRD, FT-IR, SEM, BET surface area analysis and the Hammett indicator method. The results indicated that the solid phase reaction of ion-exchange (Ca5(PO4)3(OH) + SrO → Ca5−x Srx(PO4)3(OH) + CaxSr1−xO) occurred at 873 K. Moreover, when new phase CaxSr1−xO was dispersed spontaneously onto the surface of the porous hydroxyapatite as a monolayer or submonolayer, it inhibited the decomposition and recrystallization of the porous hydroxyapatite and remained porous morphology of HAP at 873 K. The novel solid base catalyst catalyzed the transesterification of soybean oil to gave the highest conversions of soybean oil with 85%. The catalytic activity of the transesterification could result from the new phase CaxSr1−xO.