| The influences of dopants (Ce, Mn, Pr) on the surface properties and catalytic performance of Cu/ZrO2 catalysts for CO hydrogenation to methanol have been investigated to determine the key parameters in designing active methanol synthesis catalysts. Selected methanol synthesis catalysts have been also screened for their activity in steam reforming of methanol. Steady-state activity tests were supplemented with XRD, infrared (IR) and Raman spectroscopies, temperature-programmed reduction (TPR) and desorption (TPD) catalysts characterization studies. The nature and relative dynamics of formation and consumption of surface species were examined using in-situ infrared spectroscopy. The mechanism for methanol synthesis from CO on Cu/CexZr1-xO2 catalysts has been proposed based on the results of dynamics studies.; Surface properties, activity and selectivity for methanol synthesis from CO/H2 on Cu/MxZr1-xO2 (M = Ce, Mn, Pr) were found to be highly dependent on the catalyst composition. The direct correlation between H2 adsorption capacity and methanol synthesis activity has been established. The results of IR-spectroscopy studies indicated that H2 is stored in the form of hydroxyl groups formed upon reduction of the catalyst in H2. Infrared spectroscopy results indicated that CO adsorption on each material leads to the formation of bidentate formate species through interaction with a hydroxyl group on the surface of MxZr1-xO2. The formate species are hydrogenated to methoxide species by hydrogen provided by Cu via spillover. The elimination of methoxide species by reaction with acidic OH groups is the rate-limiting step for methanol synthesis on each catalyst. The relative rates of elimination of methoxide species are faster for catalysts with higher concentration of more highly acidic bridging hydroxyl groups. The methanol synthesis activity per unit of surface area was highest for 3wt% Cu/Ce0.5Zr0.5 O2 catalyst which exhibits highest H2 storage capacity and relative concentration of more highly Bronsted acidic bridging hydroxyl groups.; The steam reforming of methanol to H2 was investigated for a series of Cu/MxZr1-xO2 (M = Ce, Mn, and Pr) catalysts. The most active catalysts were Cu/Ce0.5Zr0.5 O2 and Cu/Mn0.3Zr0.7O2. At 548 K rates of H2 production approaching 400 mmol H2·g-cat -1·h-1 were achieved with 3wt% Cu/Mn0.3 Zr0.7O2 catalyst. CO was observed to form via the reverse-water-gas-shift reaction, particularly at high methanol conversions and reaction temperatures. Formation of this byproduct could be suppressed by increasing the loading of Cu and increasing the H2O:CH 3OH ratio in the feed. Catalyst deactivation appears due to deposition of carbon on the surface of the catalyst. The extent of catalyst deactivation can be decreased significantly by increasing the Cu loading of the catalyst and the H2O:CH3OH ratio in the feed. |
