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Molasses Purification and Valorisation : Towards a sustainable production of hydroxymethylfurfural

Författare

Summary, in English

The industrial transition from petrochemical-based to a more sustainable and
circular economy requires the utilisation of renewable biobased raw materials that
do not compete with other important industries, such as the food sector, preferably
wastes or low value by-products. 5-hydroxymethylfurfural (HMF) is a versatile
platform chemical that has great potential for utilisation in various sectors in a future
bioeconomy, as it can be produced from sugars.
In this thesis, sugar beet molasses was assessed for the production of HMF. This
dark, highly viscous and impure by-product, but yet with a high content of sucrose,
could first be hydrolysed using yeast into glucose and fructose, followed by a
biphasic and acid-catalysed dehydration step to produce HMF. The challenge is to
handle the impurities of the molasses and the by-products that are formed during the
dehydration reaction. Hence, separation and purification processes are required.
Initially, membrane filtration was tested and evaluated for the purification of
molasses, and its impact on the hydrolysis and dehydration steps was determined. It
was found that ultrafiltration of the molasses has a positive impact on the
dehydration step with regards to increased conversion of fructose compared to crude
molasses. Simultaneously, it also yielded in a higher product selectivity compared
to the control sample consisting of a pure sucrose solution. This could possibly be
due to the higher salt content in molasses compared to pure sucrose, which can aid
the partitioning of HMF to the organic solvent. The reaction rate of the enzymatic
hydrolysis was unfortunately not improved by membrane filtration. However, there
is a significant difference in productivity between hydrolysis of sucrose in molasses
compared to a pure sucrose solution. Results from this study revealed that viscosity,
salt concentration and a synergistic effect of ions present in the molasses are the
main reasons.
Secondly, by-products from the dehydration step could be removed through
adsorption using granular activated carbon in order to purify the HMF product. The
HMF was thereafter recovered by an evaporation step. The organic solvent was
condensed and could successfully be reused for either extracting more HMF from
the aqueous phase to obtain more HMF and increase the overall process yield or
being recycled for another dehydration reaction.
The conclusion from this study is that it is possible to produce HMF from sugar beet
molasses, but it requires additional separation and purification steps and further
development to be efficient and economically competitive.

Publiceringsår

2023-11-21

Språk

Engelska

Dokumenttyp

Doktorsavhandling

Förlag

Chemical Engineering, Lund University

Ämne

  • Chemical Process Engineering

Nyckelord

  • sugar beet molasses
  • 5-hydroxymethylfurfural
  • membrane filtration
  • hydrolysis
  • dehydration
  • adsorption
  • purification
  • solvent regeneration

Status

Published

Projekt

  • STEPS – Sustainable Plastics and Transition Pathways, Phase 1
  • Molasses Purification and Valorisation

ISBN/ISSN/Övrigt

  • ISBN: 978-91-8096-012-0
  • ISBN: 978-91-8096-013-7

Försvarsdatum

15 december 2023

Försvarstid

09:00

Försvarsplats

Lecture Hall KC:C, Kemicentrum, Naturvetarvägen 14, Faculty of Engineering LTH, Lund University, Lund. The dissertation will be live streamed, but part of the premises is to be excluded from the live stream.

Opponent

  • Mads Koustrup Jörgensen (Assoc. Prof.)