Chemicals based on renewable resources are much desired in view of the dwindling supply of fossil fuels and the climatic problems caused by the accompanying rise in CO2 production. Polymers are among the highest volume chemical materials and thus their production from renewable resources would be highly rewarding. Two different strategies can be followed. On the one hand one can aim to develop new synthetic strategies towards existing monomers, such as adipic acid, caprolactam, or acrylic acid.[1] In the lecture, examples will be given how these monomers can be made from the platform chemicals 5-hydroxymethylfurfural (HMF) and levulinic acid (LA). Another and perhaps long term more rewarding strategy is based on the use of novel monomers that can be prepared in a limited number of steps from renewable resources. One compound that can be obtained in a rather straightforward manner from lignocellulose is levulinic acid (LA). LA can be easily cyclized to α-Angelica lactone (AL) in excellent yield by reactive distillation. α-AL has been used as a monomer in polymerisations, although the quality of the formed polymers is not very good. α-AL can be isomerised to β-AL by treatment with base, but this results in a mixture of the two isomers that are not easily separated. We have nevertheless shown that it is possible to distil it to obtain a pure mixture which contains 90% of the β- and 10% of the α-isomer. This mixture undergoes Diels-Alder reactions with dienes like cyclopentadiene (Cp), isoprene, myrcene and β-farnesene in good yields.[2]The remaining α-Al can easily be separated off and reused in the isomerisation. The DA adduct between Cp and β-AL was subjected to a ROMP reaction catalysed by the Grubbs II catalyst. This gave a polymer with some resemblance to poly-norbornene, which, however, has a higher (surface) hydrophilicity. This property may enhance its processability.
It is also possible to hydrogenate LA to 1,4-pentanediol. We have made polyesters based on this diol using bio-based diacids. One of these polymers showed a low-temperature memory effect.[3]
We will also discuss our efforts to enable the economic recycle of polymers. The major problem in recycling polymers is the fact that the recycled polymers or monomers cannot really compete with the virgin material, either on quality or on price or both. A good solution to deal with this is to upcycle the polymer to a higher value-added material. This we have achieved by hydrogenation of polyesters to the polyethers.[4] These polyethers can be used for application in adhesives.
[1] Catalytic Approaches to Monomers for Polymers Based on Renewables. B. M. Stadler, C. Wulf, T. Werner, S. Tin, J. G. de Vries, ACS Catal. 2019, 9, 8012−8067.
[2] Scalable synthesis and polymerisation of a β-angelica lactone derived monomer. A. Dell’Acqua, B. M. Stadler, S. Kirchhecker, S. Tin, J. G. de Vries, Green Chem. 2020, 22, 5267–5273.
[3] Properties of Novel Polyesters Made from Renewable 1,4-Pentanediol. B.M. Stadler, A. Brandt, A. Kux, H. Beck, J. G. de Vries, ChemSusChem 2020, 13, 556-563.
[4] Hydrogenation of Polyesters to Polyether Polyols. B. M. Stadler, S. Hinze, S. Tin, J. G. de Vries, ChemSusChem 2019, 12, 4082– 4087.
Prof. Johannes G. de Vries (Leibniz Institut für Katalyse e. V., Albert-Einstein-Strasse 29a, 18059, Rostock, Germany, johannes.devries@catalysis.de)
Watch a recording of the talk below:
Biography
Johannes G. de Vries received a PhD (bio-organic chemistry) from the University of Groningen in 1979. After a postdoc at Brandeis University, Waltham, USA, his first job was as a medicinal chemist with Sandoz in Vienna and in London. From 1988-2013 he worked for DSM in Geleen, The Netherlands, lastly as a Principal Scientist in the area of Homogeneous Catalysis. From 1999-2018 he was part-time professor at the University of Groningen. In 2014 he became Department Head Catalysis with Renewables at the Leibniz Institute for Catalysis in Rostock, Germany. In 2013 he received the Paul N. Rylander Award for outstanding contributions in the field of catalysis as it applies to organic synthesis.