(195a) Catalytic Valorization of Isosorbide As Versatile Renewable Platform Chemical

Catalytic Valorization of Isosorbide
as Versatile Renewable Platform Chemical

Marcus Rose, Rebecca Pfützenreuther, Katharina Thenert,
Regina Palkovits

RWTH Aachen University, Aachen, Germany

The substitution of fossil resources in the
production of crude oil-based products such as polymers or fuels by renewable lignocellulosic biomass is essential in the future.
Cellulosic feedstock such as straw, wood residues or other bio-waste can be
converted by efficient catalytic processes to platform chemicals of great
importance such as isosorbide.

Isosorbide poses great potential as an
intermediate in the production of biofuels, fuel additives, high boiling
solvents, surfactants and polymers. Thus, the development of catalytic
processes for a highly efficient isosorbide conversion is crucial. Main target
is the functionalization or substitution of the two hydroxyl groups maintaining
the cis-fused
ditetrahydrofurane scaffold. Numerous investigations
on feasible isosorbide transformation routes have been reported in the middle
of the 20^th century. Nowadays, two isosorbide derivatives are
already commercially available. Isosorbide nitrates are used in medicine as
vasodilating pharmaceuticals, whereas isosorbide dimethyl ether gained interest
as a versatile non-toxic pharmaceutical solvent. Several publications deal with
the isosorbide functionalization via the Williamson etherification using
alkyl halides. A disadvantage of this process is the formation of huge amounts
of halogen containing side product. Alternatively, the etherification by
telomerization with 1,3-butadiene has been shown
recently, resulting in several isomeric products.

One focus of our work is the conversion of
isosorbide to defined tert-butyl ether derivatives
heterogeneously catalyzed by acidic ion exchange resins such as Amberlyst-15.
Instead of the Williamson method, two
different approaches, the condensation reaction of isosorbide with tert-butanol avoiding side products other than water
as well as the addition of isosorbide hydroxyl groups to isobutene, have been
investigated. In the reaction with tert-butanol an isosorbide conversion of 27 % was
achieved due to the water formation shifting the equilibrium reaction to the
side of the substrates. With isobutene close to full conversion of isosorbide was observed with up to 60 % yield of the diether and two different monoethers
as by-products. In our current work we develop an energy efficient process for
the continuous etherification of the biogenic platform chemical isosorbide with isobutene.

In this contribution we want to give a critical
overview on the different aspects of isosorbide chemistry and feasible
catalytic conversions as well as present recent results on the development of
efficient processes for the etherification of isosorbide to produce novel
value-added products such as green solvents and fuel additives.