Scalable synthesis of Cu-based catalysts as a tool for accelerated process development

Central elements for a climate-neutral energy system are processes that ensure the efficient use of available raw material resources and enable the cross-sectoral application of sustainable technologies. For these innovative leaps, the development of active, selective and long-lasting catalysts is a central task of research and development. A knowledge-based catalyst design requires the direct looping of determined functional properties into the material design process and the scalability of the manufacturing process.
Based on our initial work on the synthesis of Cu/ZnO/ZrO2 catalysts by continuous co-precipitation[1] we became interested on the general potential of this approach. Heterogeneous Cu-based catalysts are an important class of industrially relevant catalysts, e.g. for syngas transformation or dehydrogenation processes.[2,3] Amongst a variety of manufacturing methods, particularly precipitation in aqueous medium allows for effective combination with other metals. Industrially estab¬lished production is usually based on decades of empiri¬cally grown knowledge about the individual process steps of precipitation and ageing which is followed mostly by calcination and shaping/reduction to yield the final catalyst body (Fig. ... mehr1). The aim of our research is to realize a quality-assured production of research catalysts on a scale up to the kg range. A possible realization in the approach we use is based on two assumptions: a) The initial phase of co-precipitation is a fast process. Therefore we want to achieve a high mixing intensity in a micromixer at high flow rates. b) In comparison, ageing is a slow process that we carry out in a stirred tank reactor, so that in the result no significant temporal overlapping of precipitation and ageing shall occur.
In this contribution, we discuss the synthesis on different series of CuO/ZnO/ZrO2 catalyst precursors. Emphasis will be given on the relation of material characteristics with certain synthesis parameters, e.g. metal contents, temperature and pH. All materials are characterized by a variety of analytical and spectroscopic methods to determine important features like surface and pore characteristics, reducibility, morphology, phase composition and homogeneity (Fig. 2.). Selected materials were additionally investigated for the synthesis of methanol and in the direct synthesis of dimethyl ether from CO2/CO/H2. These experiments are summarized in comparison to other known catalyst systems.