The Relationship between Hexane-Steam Reaction and Coke Formation on Silica-Supported Nickel Catalysts at High Temperatures

Abstract

In order to obtain additional information regarding the relationship between hexanesteam reaction and coke formation on silica-supported nickel catalysts at high temperatures, studies have been made using a flow system under atmospheric pressure.The effects of the catalyst preparation methods on the catalyst activity. for the hexane-steam reaction and on the coke yield were examined. The activity sequence is as follows: PI>PII>>W. M. On the other hand, the coke yield on W. M catalyst is found to be much higher than on PI catalyst or PII catalyst.The hexane-steam reaction is approximately first order with respect to steam and zero order with respect to hexane. The coke formation is approximately first order with respect to hexane. The rate of coke-steam reaction is approximately proportional to the amount of coke and to the pressure of steam. The rate of formation of CO plus that of CO2 is over ten times the rate of coke formation or the rate of coke-steam reaction.From these results, it may be supposed that the surface sites on which the hexane-steam reaction occurs are not identical with those on which the coke formation occurs, and the macro reaction scheme may be suggested as: