Thermal hazards related to the use of potassium and sodium methoxides in the biodiesel industry

Abstract

The introduction of sodium and potassium methoxides in processes leading to biodiesel production has triggered several questions about their stability under actual biofuel manufacturing conditions. In most biodiesel production facilities, basic homogenous catalysis is obtained through the introduction of caustic potash (KOH) or caustic soda (NaOH) in the reactor. In this process, the hydroxides are converted into their corresponding methoxide forms (CH3OK/Na), which then become the actual catalysts in the reactor. Supplying the actual catalyst directly, instead of the low cost hydroxides, may offer several advantages, but may also introduce new hazards that deserve further characterisation work. From a review of the available literature, it was found that very little was known about the thermal decomposition properties of these methoxides. Therefore, as a starting point, l’Institut National de l’Environnement Industriel et des Risques (France) and the Canadian Explosives Research Laboratory (Canada) have recently undertaken a joint effort to better characterise their thermal behaviour. This was achieved by means of a variety of calorimetric techniques including differential scanning calorimetry, accelerating rate calorimetry and ‘large scale’ thermogravimetry–differential thermal analysis. It was found that these chemicals can become self-reactive close to room temperature under specific physical conditions.