Temporal and Oscillatory Behavior Observed during Methanol Synthesis on a Cu/ZnO/Al2O3 (60:30:10) Catalyst

The rate of Methanol synthesis over a Cu/ZnO/Al2O3 (60:30:10) catalyst has been measured using CO2/H2 (10:90) and CO/CO2/H2 (10:10:80) streams at 433, 443, 453, 463 and 473 K. Using the CO2/H2 stream, it requires 12 × 103 s to achieve steady-state performance; this time reduces to 5.4 × 103 s on increasing the temperature to 463 K. Using the CO/CO2/H2 stream, steady State performance is not achieved even after 14.4 × 103 s at 433 K but is achieved after 9 × 103 s at 463 K. Significant deviations from steady state behavior (~40% of steady state) are observed only at 453 K and only using the CO2/H2 feed when gas chromatography (GC) is the analysis system. When the reactor output is connected directly into a flame ionization detector (FID), oscillation is observed at all temperatures studied using a CO2/H2 stream. Injection of CO into the CO2/H2 stream, which is synthesizing methanol at 473 K, produces a sharply spiked increase in the rate of methanol synthesis followed by an oscillatory relaxation to steady state behavior. At 433 and 443 K, the injection of CO into the CO2/H2 stream again produces the sharply spiked increase in the rater of methanol synthesis, which returns to the baseline value without oscillations.