PADDL

Context

The transition from fossil-based industries to carbon-neutral and sustainable ones is a major challenge. Aromatic chemicals play an important role in commodity, fine and specialty chemicals, but their origin is still almost exclusively petrochemical. While lignocellulosic biomass offers an important source of bioaromatics with a huge potential, its conversion to useful chemicals is still largely unaddressed. The concept of biorefineries is under extensive development, but there is still a serious gap between the biobased building blocks delivered by the biorefineries and specific end products featuring suitable properties for concrete applications in industry. New sustainable synthetic methods and routes are needed which will transform these interesting biobased building blocks into new product families. Instead of attempting to introduce biorenewable drop-ins, new biobased chemicals with at least similar performance are aimed for. Importantly, these should feature a better (eco)toxicity profile in comparison to the existing petrochemical analogues and avoid “regrettable substitutions” (solving legal bans of a product through introducing analogues with only slightly improved toxicity profile). Recent studies of the European Chemicals Agency (ECHA) on relative release potential of around 400 major polymer additives, which in combination with compound specific risks (REACH studies) will allow to obtain real risk assessments of the additives, show the big concern of society towards these compounds. This project will focus on biobased plasticizers, antioxidants, UV stabilizers and flame retardants.

Goals

The long-term overall goal is to introduce new biobased plasticizers, antioxidants, UV stabilizers and flame retardants with performance comparable to or preferably superior to the currently used petrochemical molecules. In order to ensure this goal is achieved a benchmark against existing products for every class of polymer additives is required. Major steps in the development process are: 1) development of new synthesis methods and routes to access new compound families; 2) performance assessment with feedback loop to 1; 3) (eco)toxicity assessment of the most promising candidates; 4) advanced characterization to optimize lead compounds with respect to performance. The timescale of this development clearly goes beyond 18 months, but the first two steps will be targeted within this POC SBO to identify promising lead compounds for further development. Some preliminary (eco)toxicological tests of interesting leads are already foreseen. The specific goals of this POC SBO are listed below:

1. Develop synthetic methods and routes to access new compound families

Here the preference will be given to a “template” approach starting from the available lignin oil building block monomers, which can for instance be dimerized using various methodologies to increase the number of useful functionalities for further derivatization, as well as oligomers both obtained from the “lignin-first” biorefinery. Defunctionalization methods on monomers and oligomers are required to provide intermediates allowing to install the desired functionalities on the “templates” in accordance with the specific application aimed for. When oligomers are used as substrates for functionalization, complex mixtures will be generated requiring advanced NMR techniques for characterization. Antioxidant properties will be optimized through additional oxygen and carbon substitution in the catechol and pyrogallol units of the templates. To achieve plasticizer properties, aliphatic esters will be installed. For UV stabilizers, carboxylation with CO₂ and alkylations (e.g. Friedel-Crafts type chemistry) will be explored to create renewable analogs of (poly)hydroxylated benzophenones. Finally, for flame retardants aromatic (cyclic) phosphates and/or phosphonates will be installed. In every case, we will aim to obtain molecules with the highest percentage of renewable carbon possible. Besides biorenewable carbon from lignin this also includes carbon originating from other sources such as CO₂ or sugars (e.g. alcohols or alkenes) linking with the POC SBO focusing on sugars. As a long term goal multifunctional molecules derived from the templates combining properties of more than one class of polymer additives in one molecule can even be aimed for. In order to obtain the target molecules a toolbox of synthetic methods will be used, featuring both catalytic and non-catalytic methods (e.g. homogeneous catalysis, heterogeneous catalysis, electrosynthesis) fit to the specific transformation under study. The focus in an initial phase will be on accessing the templates and producing first representatives of the new product families. To access these existing synthesis methods will have to be altered and new suitable ones will have to be developed. Though sustainability of these methods will be taken into consideration in the development phase this will not be the focus in this initial phase of development. The application (or adaptation) of these routes to allow to access new additives on a larger scale, providing sufficient quantities for further properties assessment in a variety of applications beyond the benchmark systems selected is outside the scope of this POC SBO. This will be addressed in future research once promising lead compounds are identified. 

2. Perform the “first pass” tests of new molecules/mixtures as polymer additives

Performance for the respective properties aimed for (plasticizers, antioxidants, UV stabilizers and flame retardants) will be evaluated in collaboration with expert partners of knowledge institutes or third parties. Suitable benchmarks systems will be identified based on the current industrial practice. This will involve for every type of additive the selection of a currently widely used petrochemical additive and a specific formulated polymer. In case of antioxidants, the tests will be extended to biodiesel stabilizers but this will not be the focus of the POC SBO. While the properties of plasticizers can be evaluated at KULeuven, a selection of suitable partners for performance evaluation of the other applications still needs to be made. As a next step, (eco)toxicity and biodegradability studies of the candidates which passed the first tests will be undertaken. While preliminary test on (eco)toxicity are already foreseen, biodegradability is beyond the POC SBO project objectives.