Effects of flow on the activity of a WO₃-SiO₂ olefin disproportionation catalyst

Abstract

This investigation consisted of a study of the effects of the reactant flow rate on the activity of a tungsten oxide on silica catalyst during propylene disproportionation. A 10 percent tungsten oxide on silica catalyst (223 square meters per gram B.E.T. surface area) was used in a microcatalytic reactor. The catalyst activity was found to increase when the reactant flow rate was increased. The phenomenon responsible for the anomalous behavior was investigated.

The relationship between reactant flow rate and activity was found to be independent of the flow rate history when an anhydrous propylene feed was used. A hysteresis effect was observed when the feed contained traces of water. The activity decreased for a given flow rate following exposure at lower flow rates.

It has been suggested that a contaminant was being introduced in the driers and that the anomalous behavior of the catalyst to the reactant flow rate was due to this. However, the reactant flow rate through the dryer was found not to affect the activity.

This investigation also included studies on the effects of temporary poisons on a fully broken-in tungsten oxide on silica catalyst. The dosing of carbon monoxide caused a temporary decrease in the catalyst activity. The activity returned to the level prior to the dosing in approximately 110 minutes. Trace amounts of water in the feed resulted in an immediate decrease in activity. Following the initial poisoning, the rate of poisoning was slowed.