Jet Mixer Precipitation vs. Conventional Precipitation for a Cu/ZnO/MgO MeOH Catalysts

The synthesis of precursors for MeOH catalysts usually takes place via coprecipitation, where a metal solution is precipitated with a precipitant and aged in a temperature-controlled reactor. Due to the limited addition rate of the solutions, in many cases precipitation overlaps with aging and particles are still being precipitated while the first particles are already aging. In order to better separate precipitation and aging, a jet mixer apparatus enabling this task was developed at the Institute of Thermal Process Engineering (TVT) of KIT. In this work, a Cu/ZnO/MgO catalyst system was produced using both conventional coprecipitation and jet mixer precipitation. Both systems were then exposed to gaseous difluorine to improve the catalyst properties by oxidative fluorination. A comparison of both catalyst classes produced this way showed that the properties of the systems precipitated conventionally or with the jet mixer to be comparable (metal content, surface area, infrared spectra, powder diffractograms). However, two significant differences were observed: the additional presence of an aurichalcite phase in the conventionally produced system and a significantly higher particle size of secondary particles in the jet mixer system. In terms of catalytic performance, the differences are small and the system prepared by jet mixer showed slight superiority with a by 7% higher MeOH synthesis rate under standard measurement conditions for the nonfluorinated system as well as 1–7 kJ mol^–1 lower apparent activation energies for MeOH formation.