hide
Free keywords:
-
Abstract:
Bifunctional nickel tungsten carbide catalysis was used for the
conversion of aqueous sugar solutions into short-chain polyols such as
ethylene glycol. It is shown that very concentrated sugar solutions,
viz, up to 0.2 kg L-1, can be converted without toss of ethylene glycol
selectivity by gradually feeding the sugar solution. Detailed
investigation of the reaction network shows that, under the applied
reaction conditions, glucose is converted via a retro-aldol reaction
into glycol aldehyde, which is further transformed into ethylene glycol
by hydrogenation. The main byproducts are sorbitol, erythritol, glycerol
and 1,2-propanediol. They are formed through a series of unwanted side
reactions including hydrogenation, isomerisation, hydrogenolysis and
dehydration. Hydrogenolysis of sorbitol is only a minor source of
ethylene glycol. To assess the relevance of the fed-batch system in
biomass conversions, both the influence of the catalyst composition and
the reactor setup parameters like temperature, pressure and glucose
addition rate were optimized, culminating in ethylene glycol yields up
to 66% and separately, volume productivities of nearly 300 gEG L-1
h-1.
