A single centre aluminium(III) catalyst and TBAB as an ionic organo-catalyst for the homogeneous catalytic synthesis of styrene carbonate

摘要

A non-symmetrical aluminium complex containing a single metal centre has been synthesised and usedudas a catalyst in the cycloaddition reaction of carbon dioxide to styrene oxide to yield a cyclic carbonate.udThe reaction proceeds to around 70% conversion using the catalyst alone; however, it can be increasedudto 90% conversion with the addition of tetrabutylammonium bromide (TBAB) as a co-catalyst. Interestingly,udthe reaction proceeds as well with the organo-catalyst TBAB alone as it does with the aluminium catalystudalone. This offers the potential for reduced cost processing and scale-up of the reaction through eliminationudof the aluminium catalyst due to reduced catalyst costs and ease of separation of TBAB as a salt from theudreaction mixture. The rate constants for the aluminium catalysed reactions were determined as a function ofudprocess temperature in the range 80–150 °C, as well as the activation energies for the reactions determinedudfrom the Arrhenius plots. The activation energy for the aluminium catalyst alone was determined to beud34 kJ mol−1, while adding TBAB as a co-catalyst reduced the activation energy by 11 kJ mol−1.