Combining bio- and chemo-catalysis : treatment of bio-alcohols employing ionic liquids as media

• Main Author: Liu, Xiaohan
• Published: Queen's University Belfast 2017
• Subjects: 660
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.727426

This project was based on the principle of green chemistry, aiming at developing an energy conserving process to produce chemicals from biomass. The designed route was employing ionic liquids (ILs) as intermediary to separate/link bio- and chemo-catalysis procedure, where the ILs played the role of both extractant and reaction solvent. The substrates studied were 1,3-propanediol (1,3-PDO) and 2,3-butanediol (2,3-BDO). By designing the structure and combination of the cation and anion, the functionality and the hydrophobicity could be integrated in one compound. Various bistriflimide based ILs and trihexyltetradecylphosphonium ([P66614]+) based ILs were synthesised and applied in the extraction of 1,3-PDO and 2,3-PDO. Taking the chemical and thermal stability into account, the novel IL trihexyltetradecylphosphonium 1-octanesulfonate ([P66614][C8S]) was considered the best choice exhibiting good phase behaviour and high distribution coefficient (D2.3-BDO = 0.440 and D1,3-PDO = 0.224 at 35 °C). Along with the experiments, the simulation by the COSMO-RS also supported this result. With a total amount of 200 wt% of extractant, in a three-step extraction, 66.7% of 2,3-BDO and 41.0% of 1,3-PDO could be recovered from the broth. The catalytic reaction, as the second step of the project, was conducted within the IL solution of [P66614][C8S]. The dehydration of 2,3-BDO could be catalysed by Bronsted acids, among which the cation exchange resin, Amberlyst 15, gave the highest catalytic activity. In the modified condition, the yield of methyl ethyl ketone (MEK) reached 80 %. By combining the extraction and reaction, the overall yield of MEK was 24.4 % in one cycle. For the reaction of 1,3-PDO, the best system was hydrogen transfer initiated dehydration process to produce propanal. With the iridium based compound Cp*lrCI2(BzMIM), the yield of propanal reached 65 %. In summary, the concept of combining bio- and chemo-catalysis using an ionic liquid solvent intermediary was feasible to treat bio-alcohols.