THE CATALYST REVIEW - The Catalyst Group

EXPERIMENTAL
Next-Generation Catalysis for Renewables: Combining Enzymatic with
Inorganic Heterogeneous Catalysis for Bulk Chemical Production...
The conversion of biomass necessitates the development of a new generation of catalysts that enable new kinds of reactions,
processes, and conditions than those conventionally employed. Both enzymatic catalysis (biocatalysis) and heterogeneous inorganic
catalysis are likely to play a major role and, potentially, be combined. One type of combination involves one-pot cascade catalysis
with active sites from bio and inorganic catalysts as key components in the development of a biorefinery - a facility that integrates a
number of processes in biomass conversion to produce fuels, power, and chemicals.
Currently, three phases can be
distinguished in the development of
biorefineries (Figure 1, top). Limiting
the discussion to the feedstock and
available conversions, the three phases
in biorefinery development can briefly be
described as follows. A phase 1 biorefinery
holds limited and fixed processing
possibilities with feedstocks limited to
simple sugars. A phase 2 biorefinery
operates with more sophisticated process
options, focusing on different integrated
and flexible product solutions that can
be adjusted to meet market demands.
In a phase 3 biorefinery, the focus is
not fixed upon the product range but
rather on flexibility in the use of various
feedstocks for adaptability towards supply
and demand in animal feed, food, and
industrial commodities.
Figure 1. Overview of different biorefinery scenarios depending on the
overall feedstock.
Transportation, availability and demand
for the feedstock are all important factors
when it comes to what type of biorefinery
is best suited for a specific location
and whether the production should
be centralized or decentralized. In this
respect, three different approaches for
the production of chemicals and fuels are
debated (Figure 1, bottom).
The authors discuss new routes and combinations which can be envisioned when considering these combined systems that would
otherwise be difficult or impossible with conventional conversion methods. However, these new systems do have some limitations.
Combinations are only possible within a limited and defined set of reaction conditions and catalyst kinetics must be matched. For
the same reason, deactivation issues become more critical. Furthermore, regeneration and separation of used catalysts must be
developed for commercial purposes. A new generation of catalysts able to withstand aqueous conditions and match the conditions
of biocatalysis is needed in a chemicals industry that will be increasingly reliant on renewable feedstocks. The authors therefore
propose that more emphasis be placed on systems integrating enzymatic and heterogeneous catalysts in one-pot cascade reactions
because such conversions offer a new approach to a chemical industry in need of new catalyst designs. Source: ChemCatChem 2010,
2, 249 – 258; Vennestrøm et al.
The Catalyst Review March 2010
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