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Lookup NU author(s): Abdul Rehman,
Dr Valentine Eze,
Mohamad Gunam Resul,
Professor Adam Harvey
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).
© 2018 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences Formation of styrene carbonate (SC) by the cycloaddition of CO2 to styrene oxide (SO) catalysed by pyrrolidinopyridinium iodide (PPI) in combination with zinc halides (ZnCl2, ZnBr2 and ZnI2) was investigated. Complete conversion of the SO to SC was achieved in 3 h with 100% selectivity using 1/0.5 molar (PPI/ZnI2) catalyst ratio under mild reaction conditions i.e., 100 °C and 10 bar CO2 pressure. The synergistic effect of ZnI2 and PPI resulted in more than 7-fold increase in reaction rate than using PPI alone. The cycloaddition reaction demonstrated the first-order dependence with respect to the epoxide, CO2 and catalyst concentrations. Moreover, the kinetic and thermodynamic activation parameters of SC formation were determined using the Arrhenius and Eyring equations. The positive values of ΔH‡ (42.8 kJ mol–1) and ΔG‡ (102.3 kJ mol–1) revealed endergonic and chemically controlled nature of the reaction, whereas the large negative values of ΔS‡ (–159.4 J mol–1 K–1) indicate a highly ordered activated complex at the transition state. The activation energy for SC formation catalyzed by PPI alone was found to be 73.2 kJ mol–1 over a temperature range of 100–140 °C, which was reduced to 46.1 kJ mol–1 when using PPI in combination with ZnI2 as a binary catalyst. Based on the kinetic study, a synergistic acid-based reaction mechanism was proposed.
Author(s): Rehman A, Eze VC, Gunam Resul MFM, Harvey A
Publication type: Article
Publication status: Published
Journal: Journal of Energy Chemistry
Print publication date: 01/10/2019
Online publication date: 05/12/2018
Acceptance date: 29/11/2018
Date deposited: 22/02/2019
ISSN (print): 2095-4956
Publisher: Elsevier Inc.
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