Skeletal isomerization of linear butenes on ferrierite: Effect of the presence of lower olefins in the feed and of operating conditions

The skeletal isomerization of linear butene on ferrierite, at atmospheric pressure and 0.15 atm 1-butene partial pressure, was studied by feeding 1-butene streams with different ethene and propene concentrations and exploring several operating conditions. At short time-on-stream (5 min), the strongest acid sites govern the catalytic behavior, independent of the operating conditions in the studied ranges. At longer times, the reaction temperature mainly defines the conversion level. The higher the temperature, the larger the linear butene conversion. Temperature also has a strong influence over the nature of the carbonaceous deposit formed during reaction. At 400degreesC, the deposit mainly shows an aromatic nature. The presence of lower olefins as impurities in the feed modifies both catalytic activity and by-product distribution. By decreasing the ethene concentration, the C-5(+) fraction in the product stream increases and a lower carbonaceous deposit is formed. Using a nitrogen stream saturated with water during both pretreatment and reaction, the catalytic activity increases and the coke amount slightly diminishes, but the isobutene production is unfavored.