Chemical Engineering December 2022 - 37

Feature Report
Scaling Up Hydrogenation Processes for
Biomass Conversion
When scaling up new processes involving complex feedstocks, such as biomass,
well-defined mixing is key. Guidelines presented here will help to efficiently move
biomass hydrogenation reactions from the laboratory to commercial-scale operations
O
ne of the most promising pathways
to biomass-based, sustainable
chemicals is the sugar
platform that includes conversions
of monosaccharides, disaccharides
and polysaccharides, and their derivates,
via biochemical and thermochemical processes.
Hydrogenation and hydrogenolysis
reactions are of particular significance
amongst those thermochemical pathways.
Nature produces many different unsaturated
products, including C=C double
bonds, in carbonyl groups in the structural
aldoses and ketoses of cellulose and hemicellulose.
Hydrogenation is the key reaction
to saturate those C=C and C=O bonds
through the addition of molecular hydrogen,
whereas hydrogenolysis describes a chemical
conversion in which a carbon-carbon or
carbon-heteroatom bond is broken by the
insertion of hydrogen atoms. Both are similar
in nature, as they are three-phase reactions
with a liquid phase composed of the
starting material (often solute in a solvent),
hydrogen gas and a solid catalyst. These
types of processes are best conducted in
Ekato
stirred reactors, where the liquid substrate
is homogenized, the catalyst is suspended
and the hydrogen is dispersed using a selfaspirating
agitator in a compact and wellcontained
reactor system.
However, the commercialization of such
hydrogenation processes from the laboratory
to production scale is traditionally complex
and time-consuming. This is because
the interaction between mass transfer, heat
load, catalyst concentration and catalyst
activity is intricate and requires an elaborate
alignment between the reactor system and
plant concept with the specific process requirements.
Additionally, the substrates are
refined from biomass and typically display
varying compositions, even after refining, depending
on the climate, harvest season and
area of cultivation. This variation in chemical
composition will impact selectivity and yield
- unless the reactor system allows for sufficient
process flexibility to adapt to changing
substrate qualities.
This
article
describes a practical approach
to respond to these challenges by
applying an integrated development and
optimization strategy beginning at laboratory
scale, through piloting and demonstration
scale, before building a commercial
plant. Guidelines on how to approach
specific hydrogenation problems, concepts
and tools for the design, development and
scaleup of catalytic hydrogenation processes
are discussed.
FIGURE 1. A 5-L pilot plant can be used to determine potential
process limitations that are related to hydrogen-uptake
rate measurement
Challenges at laboratory scale
The development of new chemical-production
processes usually begins with conducting
a basic experimental study of the chemical
reaction, also called a feasibility study. If
the process is a batch-wise, stirred process,
then initial laboratory tests are often carried
out in a reaction volume range between a
few milliliters and a few hundred milliliters.
At the laboratory scale, magnetic stirrers or
very simple impellers are frequently used -
however, these are often not appropriately
dimensioned. This means that they are not
representative of the process and therefore
cannot be designed to be geometrically
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
DECEMBER 2022
37
Konstantin Epp,
Wolfgang Keller,
Marc Labusch
and Peter Rojan
Ekato RMT
IN BRIEF
CHALLENGES AT
LABORATORY SCALE
PILOT TESTING
CATALYST REUSABILITY
STUDY
HYDROGENATION
REACTOR SCALEUP
PROCESS PLANT
ENGINEERING
http://WWW.CHEMENGONLINE.COM
Chemical Engineering December 2022

Table of Contents for the Digital Edition of Chemical Engineering December 2022
