Production and treatment of rapeseed oil methyl esters as alternative fuels for diesel engines

Rapeseed oil methyl esters are important alternative diesel fuels based on renewable sources. A discontinuous plant production of methyl esters (ME) is described using two-stage low-temperature transesterification of cold-pressed rapeseed oil with methanol at temperatures up to 70°C. The total methanol:acyls molar ratio is 4:3, with an optimum distribution of methanol between the two stages. Four percent NaOH in methanol is used as the catalyst. The final treatment of ME with phosphoric acid and ammonia provides for an exchange of ashy soap forms in ME for ashless forms, thus rendering ME non-corrosive.