A new heterogeneous ZnL2 catalyst on a structured support for biodiesel production

Although the transesterification reaction of triglycerides with alcohols (using acid or alkaline catalysts) is well known and practiced on a commercial scale, there is plenty of scope to improve this process. The turning of a batch into a continuous process, and the use of a catalyst that is more favourable to fatty acids in the feed, are challenges of particular interest. With these objectives in mind, results are presented of experiments in which a zinc amino acid complex [ZnL2], was used as a catalyst. This was fixed onto a structured monolith support (cordierite), so as to enable the catalysts to be retained in a fixed bed. To advance this work, reaction experiments were performed in a 120 ml batch reactor, using 10 mm × 10 mm × 10 mm sections of catalyst coated monolith (1.1 mm square channels, 62 cells cm−2). With a 12:1 molar ratio of methanol and rapeseed oil (triglyceride), at 195 °C and 20 bar, and using 0.3 g of zinc catalyst (coated on a monolith), it was shown that 54% of the triglyceride was converted into biodiesel. This compares very favourably with a conversion of 69% in batch experiments, when 0.3 g of the catalyst was dispersed in the solution in the form of a very fine powder. Interestingly, it was also shown, that the cordierite monolith support on its own exhibited catalytic activity (27% conversion of the triglyceride).