Speaker
Description
A potential strategy for the re-use of carbon dioxide is to convert it into a platform chemical, from which valuable products can be prepared. In particular, from all the possible products, light olefins (C$_{2}$$^{=}$, C$_{3}$$^{=}$) and higher alcohols are of great interest as important synthesis building blocks, so seeking an appropriate catalyst for this process is a key challenge. In particular, catalytic phenomena on solid materials take place on the outer layers of catalyst particles. This fact, together with the dynamic response of solid surfaces under reaction conditions, makes both catalyst design and the prediction of the active phase in solid catalysts a complex problem.$^{1}$ To tackle such complexity, we focus on developing syntheses via automated batch and hydrothermal reactors, where all parameters can be monitored and recorded to ensure reproducibility.
For the production of light olefins, the goal is to investigate the direct hydrogenation of CO$_{2}$ by using a standalone tandem catalyst. The focus of our work is on one hand a systematic comparison of the performance of several methanol synthesis catalysts, and on the other hand, the modification of the acidity of the zeolitic/acidic component. Cu/ZnO/Al$_{2}$O$_{3}$,$^{2}$ ZnGa$_{2}$O$_{4}$, ZnO/ZrO$_{2}$ and ZrO$_{2}$/In$_{2}$O$_{3}$ were prepared via precipitation. In a first kinetic study, the materials were tested in methanol synthesis from CO$_{2}$/H$_{2}$ and CO/CO$_{2}$/H$_{2}$. Cu/ZnO/Al$_{2}$O$_{3}$ exhibited comparable behaviour to the industrial standard. However, at higher temperatures (350 °C) the other materials show higher methanol space time yields. In particular, ZnO/ZrO$_{2}$ suffers no deactivation under temperature variations, and exhibits the best performance among all materials. The present results provide a good starting point for performing a study among the possible combinations of known zeotype/metal oxides, with the aim of selecting the most suitable zeotype for targeted modifications of acid site strength and density.
For the production of higher alcohols, we took the paradigmatic example of RhMnFe/SiO$_{2}$ catalysts.$^{1}$ These materials are generally synthesized by impregnation, with the subsequent lack of control over the distribution of the constituent elements in the catalyst precursor. We aim to develop synthesis approaches that lead to a more controlled atomic distribution in the catalyst precursor. The strategy consists in the preparation of mixed metal oxides with well-defined crystal structure and composition. A series of Rh-doped ZnFe$_{2}$O$_{4}$ metal oxides with a spinel structure were synthesized hydrothermally via an oxalate formation-decomposition strategy. A study on the behaviour of the pre-catalysts under reducing conditions was conducted in order to understand the active phase formation from the doped spinels. By controlling reduction temperature and time it is possible to exsolve Rh nanoparticles/clusters from the spinel structure, while retaining the original metal oxide precursor structure, which would act as a support.
References
1. X. Huang, D. Teschner, M. Dimitrakopoulou, A. Fedorov, B. Frank, R. Kraehnert, F. Rosowski, H. Kaiser, S. Schunk, C. Kuretschka, R. Schlögl, M-G. Willinger, A. Trunschke, Angewandte Chemie International Edition, 58, 8709 (2019).
2. Julia Schumann, Thomas Lunkenbein, Andrey Tarasov, Nygil Thomas, Robert Schlögl, and Malte Behrens, ChemCatChem 6, 2889 (2014).
| Abstract Number (department-wise) | AC 1.3 |
|---|---|
| Department | AC (Schlögl) |
