Steady state and periodic operation studies of the partial oxidation of propylene. (Volumes I and II)

The double objectives of this work were to investigate the effect of periodic operation and water dosing on the partial oxidation of propylene. Experiments were performed using a differential microcatalytic reactor free of transport limitations. The majority of the experiments were performed at atmospheric pressure and 340;The effect of split and period of water cycling was studied on the Sb/Sn/V oxide catalyst. Under water cycling, small improvements in the range of 10% to 20% could be observed for the formation of acrolein and acrylic acid. High water splits (water rich) normally favours the formation of the acrylic acid. For short periods, an even split (0.5) stimulates the formation of carbon dioxide.;The effect of amplitude and period on propylene cycling was studied at a split of 0.5. Improvement as high as 90% was obtained for the formation of acrylic acid with about 75% improvement in its selectivity. Some improvement in the acrolein formation, about 50%, was obtained. Propylene cycling suppresses the formation of carbon dioxide. The optimum amplitude for propylene cycling was about 5% for both acrylic acid and acrolein. Most of the improvements obtained are located at the short period region in the vicinity of 1 to 5 minutes. The time-average rate for acrylic acid passes through a maximum at a 2 minute period, and then starts to decline sharply with the increase in the cycle period. A similar behaviour was also observed for acrolein.;Steady-state studies were performed using two catalysts, Sb/Sn/V oxide and bismuth molybdate. The former was studied more extensively. The water effect on the partial oxidation of propylene varied depending on the catalyst used. On bismuth molybdate catalyst, water was found to inhibit the formation carbon dioxide, acrolein, and acetaldehyde, whereas acetone formation increases. Its effect on this catalyst is primarily site blocking. On the other hand, the water effect on Sb/Sn/V oxide catalyst is to increase the catalyst activity towards the formation of partially oxygenated products and suppress the formation of carbon dioxide. TPD and transient isotopic experiments showed that water can adsorb on Sb/Sn/V oxide catalyst and exchange oxygen with catalyst. The role of water on the antimonate catalyst is both to protect and generate new active sites, and thus increases the activity of the catalyst. Transient and isotopic transient experiments suggest that carbon dioxide is formed from a stable surface intermediate, maybe an acrylic acid precursor.