INFLUENCE OF CARBON-DIOXIDE ADDITION UPON DECAY OF ACTIVITY OF A POTASSIUM-PROMOTED IRON-OXIDE CATALYST FOR DEHYDROGENATION OF ETHYLBENZENE

In the catalytic dehydrogenation of ethylbenzene to styrene, the detailed influence of the addition of carbon dioxide upon the decay of activity of commercial potassium-promoted iron oxide catalyst has been investigated in the presence of steam. In addition, the rates of potassium component losses from the catalyst bed were experimentally determined by measuring potassium concentration in the layer of condensed water from the effluent during the catalytic reaction. The close correlation between the rate of potassium loss and decay of catalytic activity suggested that catalyst deactivation is mainly due to a decrease in the amount of potassium ferrite (K2Fe2O4) which plays an important role, providing active sites for the catalytic reaction of ethylbenzene dehydrogenation. Furthermore, the addition of small amounts of carbon dioxide to reactant feed gas (in concentrations ranging from 0.1 to 0.5 mol-% of CO2/ total mol of feed) resulted in a slight decrease in the rate of styrene formation; however, it was found to be effective to a certain extent for depression of the decay of the catalyst's activity.