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Zeolite-embedded molecular catalysts for the size-selective splitting of hydrocarbons of intermediate to high molecular weight
There is an urgent need to reprocess (waste) polymers, and in particular polyolefins, into new building blocks for the chemical industry. Such a strategy holds the potential to decouple to a large extent the production of new chemicals from further exploitation of fossil resources. Early proposals in this sense split polymers like polyethylene into mixtures of alkanes with very broad distribution of molecular weights. The current project proposes to induce an increased control on the length of the fragments produced, by embedding the splitting function inside a porous zeolite catalyst with well-defined dimensions of channels and cages. Two cases will be distinguished. First, if the feedstock contains a (limited) number of double bonds, the chains can be split by a metathetic ethenolysis. While metathesis catalysts like CH3ReO3 have previously been immobilized on amorphous supports, shape-selective zeolites have been very rarely considered as support for a metathesis catalyst. Secondly, if alternatively, fully saturated alkane feedstock is offered, it will be attempted to introduce known ‘alkane metathesis catalysts’, e.g. Ta hydrides, onto suitable zeolitic carriers. Experimentally, the work will comprise aspects of materials synthesis, e.g. of zeolite supports, their functionalisation by surface organometallic chemistry, and finally, the catalytic evaluation either with model reactants (e.g. tetradecane, tetradecene) or with ‘real’ polyolefins.
Date:1 Dec 2020 → Today
Project type:PhD project