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Direct valorisation of waste cocoa butter triglycerides via catalytic epoxidation, ring-opening and polymerisation

Published version
Peer-reviewed

Type

Article

Change log

Authors

Plaza, DD 
Strobel, V 
Heer, PKK 
Sellars, AB 
Hoong, SS 

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 (H3PO4) or boron trifluoride diethyl etherate (BF3·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.

Description

Keywords

cocoa butter, epoxidation, flow chemistry, food waste, phase-transfer catalysis, polyurethane, renewable feedstocks, ring-opening, polymerisation

Journal Title

Journal of Chemical Technology and Biotechnology

Conference Name

Journal ISSN

0268-2575
1097-4660

Volume Title

Publisher

Wiley
Sponsorship
Engineering and Physical Sciences Research Council (EP/K014889/1)
DP is grateful to the University of Warwick for funding PhD scholarship. This work was in part funded by EPSRC project ‘Terpene-based manufacturing for sustainable chemical feedstocks’ EP/K014889.