Cu-ZnO-ZrO2 solid solution catalysts have shown very high activity for methanol synthesis in industrial reactors.cuznal methanol catalyst These catalysts have a very low activation energy, which allows the conversion of a significant proportion of CO2 to CH3OH. Unfortunately, their long-term stability is poor and performance degrades rapidly under typical methanol production conditions. An improved understanding of the structure and reactivity of these catalysts is critical for their further development to provide more sustainable solutions.
A new catalyst has been developed by co-precipitating ternary ions of Cu(NO3)2 x 3H2O, Zn(NO3)2 x 6H2O, and Al(NO3)3 x 9H2O from aqueous solutions of these reagents in an excess of sodium carbonate (JSC Lenreaktiv, Russia).cuznal methanol catalyst The methanol synthesis reaction was conducted on this solid solution catalyst under commercially relevant conditions (260 degC, 40 bar) with a composition of synthesis gas comprised of 23% CO, 7% CO2, 40% H2, and 10% O2. The methanol yield reached 2.7 kg kgcat-1 h-1 with an excellent productivity of CH3OH of 7.6%. The performance was stabilized in batch-wise recycling over 6 runs achieving a turnover number (TTON) of >12 000 corresponding to an enhancement of more than five times compared to single batch operation under identical conditions. Minimal leaching of the components was observed during distillative product separation and catalyst activity was readily restored by re-addition of the base NaOMe.
The structural characterization was performed using X-ray diffraction and (scanning) transmission electron microscopy, with a Panalytical X-Pert Pro X-ray diffractometer operating at Cu Ka radiation.cuznal methanol catalyst The specific surface area of the catalysts was determined by a Beckman Coulter SA 3100 type specific surface area instrument at -196 degC and the domain size was determined by X-ray diffraction. TG and DTG curves of the precursor catalysts were recorded by an STA 449 TG-DSC synchronous thermal analyzer. Raman spectra were obtained on the same samples.
Detailed investigation of the deactivation mechanisms was undertaken with the use of an in-house purpose-built accelerated aging reactor, where the performance of a large set of catalysts over a range of conventional methanol synthesis conditions and run lengths was evaluated after a fixed period of time at elevated temperature and pressure.cuznal methanol catalyst The characterization of this library of aged catalysts, together with model binary systems with and without Si addition, has allowed a full picture of the most important deactivation pathways to be developed.
The results show that the structure of the copper surface plays an important role in determining the catalytic behaviour.cuznal methanol catalyst The activity is significantly lower for the smaller sized particles (
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