Abstract
The manufacturing of technical catalysts generally involves a sequence of different process steps, of which co-precipitation is one of the most important. In this study, we investigate how continuous co-precipitation influences the properties of Cu/ZnO/ZrO2 (CZZ) catalysts and their application in the direct synthesis of dimethyl ether (DME) from CO2/CO/H2 feeds. We compare material characteristics investigated by means of XRF, XRD, N2 physisorption, H2-TPR, N2O-RFC, TEM and EDXS as well as the catalytic properties to those of CZZ catalysts prepared by a semi-batch co-precipitation method. Ultra-fast mixing in continuous co-precipitation results in high BET and copper surface areas as well as in improved metal dispersion. DME synthesis performed in combination with a ferrierite-type co-catalyst shows correspondingly improved productivity for CZZ catalysts prepared by the continuous co-precipitation method, using CO2-rich as well as CO-rich syngas feeds. Our continuous co-precipitation approach allows for improved material homogeneity due to faster and more homogeneous solid formation. The so-called “chemical memory” stamped during initial co-precipitation is kept through all process steps and is reflected in the final catalytic properties. Furthermore, our continuous co-precipitation approach may be easily scaled-up to industrial production rates by numbering-up. Hence, we believe that our approach represents a promising contribution to improve catalysts for direct DME synthesis.
Highlights
Power-to-liquid (PtL) processes are promising routes for chemical energy storage and a sustainable mobility based on renewable energies and non-fossil carbon sources like biomass or captured CO2 [1,2,3].In the future, options for combining those processes with the chemical utilisation of CO2 could gain greater relevance, especially if CO2 conversion can be efficiently linked to H2 production from electrolysis processes operated with renewable electrical energy [4]
We found out that, following the continuous co-precipitation approach, an ageing temperature of 40 ◦ C is probably sufficient to achieve useful catalytic properties of the final catalyst
MeOH catalysts are indicated as CZZ, according to their composition of
Summary
Power-to-liquid (PtL) processes are promising routes for chemical energy storage and a sustainable mobility based on renewable energies and non-fossil carbon sources like biomass or captured CO2 [1,2,3]. Options for combining those processes with the chemical utilisation of CO2 could gain greater relevance, especially if CO2 conversion can be efficiently linked to H2 production from electrolysis processes operated with renewable electrical energy [4]. DME can be produced from syngas in a two-step (indirect) process by the separate dehydration of MeOH or in a one-step (direct) process [7]. In the conversion of CO, CO2 and H2 to DME, the chemical equilibrium reactions (1) to (4) are relevant.
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