Simultaneous transesterification and esterification of acidic oil feedstocks catalyzed by heterogeneous tungsten loaded bovine bone under mild conditions

A highly active bi-functional catalyst system for the conversion of high free fatty acid content oil feedstock, and waste cooking oil to fatty acid methyl ester (FAME), is described. Tungsten loaded CaO/hydroxyapatite materials containing both basic, and acidic sites were derived from addition of 12-phosphotungstic acid to powdered bovine bone (BV), followed by calcination at 750 °C. Addition of 10% tungsten afforded 10 W/BV, which catalyzes FAME production from high acid value oil feedstock (24.38 mg KOH/g of oil) in 7 h at 120 °C at a methanol:oil ratio of 6:1. Conversion of waste cooking oil to FAME via simultaneous transesterification/esterification can be achieved in 5 h at 100 °C and at a methanol:oil ratio of 6:1, significantly more efficient than achievable using other bi-functional catalyst systems. The 10 W/BV catalyst system, readily prepared from a cheap, biomass derived support containing basic sites, is reusable, and allows for the production of fuel quality FAME in high yields from waste cooking oil, allowing for sustainable use of an otherwise wasted resource.