ABSTRACT
Supported ionic liquid phase (SILP) catalysis enables a highly efficient, Ru-based, homogeneously catalyzed water-gas shift reaction (WGSR) between 100 °C and 150 °C. The active Ru-complexes have been found to exist in imidazolium chloride melts under operating conditions in a dynamic equilibrium, which is dominated by the [Ru(CO)3 Cl3 ]- complex. Herein we present state-of-the-art theoretical calculations to elucidate the reaction mechanism in more detail. We show that the mechanism includes the intermediate formation and degradation of hydrogen chloride, which effectively reduces the high barrier for the formation of the requisite dihydrogen complex. The hypothesis that the rate-limiting step involves water is supported by using D2 O in continuous catalytic WGSR experiments. The resulting mechanism constitutes a highly competitive alternative to earlier reported generic routes involving nucleophilic addition of hydroxide in the gas phase and in solution.
ABSTRACT
BACKGROUND: Development of circular economy requires significant advances in the technologies for valorisation of waste, as waste becomes new feedstock. Food waste is a particularly important feedstock, containing large variation of complex chemical functionality. Although most food waste sources are complex mixtures, waste from food processing, no longer suitable for the human food chain, may also represent relatively clean materials. One such material requiring valorisation is cocoa butter. RESULTS: Epoxidation of a triglyceride from a food waste source, processing waste cocoa butter, into the corresponding triglyceride epoxide was carried out using a modified Ishii-Venturello catalyst in batch and continuous flow reactors. The batch reactor achieved higher yields due to the significant decomposition of hydrogen peroxide in the laminar flow tubular reactor. Integral and differential models describing the reaction and the phase transfer kinetics were developed for the epoxidation of cocoa butter and the model parameters were estimated. Ring-opening of the epoxidised cocoa butter was undertaken to provide polyols of varying molecular weight (Mw = 2000-84 000 Da), hydroxyl value (27-60 mg KOH g-1) and acid value (1-173 mg KOH g-1), using either aqueous ortho-phosphoric acid (H 3 PO 4) or boron trifluoride diethyl etherate (BF 3·OEt2)-mediated oligomerisation in bulk, using hexane or tetrahydrofuran (THF) as solvents. The thermal and tensile properties of the polyurethanes obtained from the reaction of these polyols with 4,4'-methylene diphenyl diisocyanate (MDI) are described. CONCLUSION: The paper presents a complete valorisation scheme for a food manufacturing industry waste stream, starting from the initial chemical transformation, developing a process model for the design of a scaled-up process, and leading to synthesis of the final product, in this case a polymer. This work describes aspects of optimisation of the conversion route, focusing on clean synthesis and also demonstrates the interdisciplinary nature of the development projects, requiring input from different areas of chemistry, process modelling and process design. © 2017 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
