Methanol

About This Product

Methanol, formula CH4O and CAS number 67-56-1, is the simplest alcohol: a clear, colourless, volatile liquid boiling at about 65 °C and fully miscible with water. In a biodiesel plant it is the reagent that supplies the methyl group of every fatty acid methyl ester. Transesterification replaces the glycerol backbone of a triglyceride with three methyl groups, giving three molecules of methyl ester and one of glycerine. The reaction is an equilibrium, so plants typically charge about twice the stoichiometric methanol, around six moles per mole of oil, to drive it to completion, then recover the excess from both the ester and glycerine phases by distillation and recycle it. Methanol also carries the catalyst, since sodium or potassium hydroxide dissolved in it forms the methoxide that does the work, and with acid catalysts it esterifies the free fatty acids in used cooking oil, acid oils and fatty acid distillates during pretreatment. Water is the specification point to watch: it hydrolyses esters to free fatty acids, which the alkaline catalyst turns into soap, lowering yield and complicating separation. Conventional methanol is made from natural gas or coal, and its carbon ends up in the ester. It is used in biodiesel transesterification, in sodium and potassium methoxide preparation, and in acid-catalysed esterification of high free fatty acid feedstocks such as used cooking oil and acid oils. Bio Green Fuels supplies methanol at 99 percent minimum in 160 kg drums or ISO tanks, with water and the full specification confirmed with the quotation. It is highly flammable and toxic if swallowed, inhaled or absorbed through the skin; handle to the safety data sheet.