One pot preparation of hybrid catalysts by spray drying : glucose oxidase protein-polyelectrolyte complex plus TS-1 zeolite for a chemoenzymatic epoxidation

Details

Supervisors

Debecker, Damien P. ; Dupont-Gillain, Christine C.

Faculty

Faculté des bioingénieurs

Degree label

Master [120] : bioingénieur en chimie et bioindustries

Abstract

The epoxidation reaction is an interesting route to produce reactive industrial intermediates. Epoxides can be turned into resins, coatings, plasticizers and many more products with a high added value. Currently, this reaction is carried out using organic peroxides as oxidants. In order to develop a eco-friendlier process, hydrogen peroxide can be used as it is considered the greenest oxidant because it only produces water as a by-product. Numerous heterogeneous catalysts were investigated for the epoxidation reaction using hydrogen peroxide route. Among them, Titanium silicalite-1 (TS-1) zeolite is the state-of-the-art catalyst, known to offer great performance in olefin epoxidation with H2O2. Even though using hydrogen peroxide is an eco-friendlier way to produce epoxides, the production of this oxidant at large scale is performed at a high energetic and environmental cost. To address these issues, the in-situ production of H2O2 can be envisaged, through a chemoenzymatic reaction in which glucose oxidase is used to produce hydrogen peroxide, which is then used by the inorganic catalyst (TS-1) to perform the epoxidation reaction. This work aims at developing a single hybrid catalyst featuring both the enzymatic and inorganic catalytic species. To do so, the enzyme must be combined with the zeolite in a single solid material that can be recovered and reused. Yet, the immobilization of an enzyme in the micropores of a zeolite is impossible, and its anchoring on the external surface yields very poor loading values. In this study, we exploit an innovative aerosol spray drying technique to prepare hollow particles formed by the aggregation of TS-1 nanocrystals. These structures serve as catalytically-active vessels for the enzyme, leading to a bi-functional or chemoenzymatic heterogeneous catalyst. Specifically, we studied the possibility to obtain such hybrid catalyst in one step, by processing both the TS-1 nanocrystals and the enzyme in the same spray drying step. Such one-pot synthesis would offer a more straightforward and efficient access to this kind of new hybrid catalysts. Yet, it represents a challenge because the biological material can normally not resist the relatively harsh conditions used in the spray drier. To increase the stability of the enzyme and to prevent its leakage from the material, we prepared “enzyme-polyelectrolyte complexes” (EPCs) and exploited them as a starting material for spray drying. We show that the one-step preparation of such hybrid catalysts by spray drying is possible, and that the enzyme maintains a significant level of activity. Importantly, the enzyme stability can be strongly improved thanks to the protecting effect of the polyelectrolyte, thereby validating our approach. Moreover, we observe that catalysts prepared with complexed enzymes are more resilient to leaching compared to the ones prepared with free enzymes. The successful chemoenzymatic epoxidation was demonstrated and the further optimization of the one-pot preparation of the hybrid catalysts leads to achieve unprecedented performances. The results obtained during this master thesis offer new perspectives in the field of hybrid catalysis.