Isomerization of n-butene over ferrierite zeolite modified by silicon tetrachloride treatment

Ferrierite zeolite modified by the deposition of SiCl4, was prepared and investigated as a catalyst for the skeletal isomerization of 1-butene. The prepared catalysts were characterized by XRD, atomic absorption spectroscopy, ammonia TPD, FT-IR, BET/pore size distribution and pyridine chemisorption. The deposition of SiCl4 preserved zeolite crystallinity although XRD and FT-IR analysis suggested a little framework de-alumination not evidenced by chemical analysis. This treatment narrowed pore size and diminished the strong/weak and Bronsted/Lewis acid sites ratio. As the SiCl4 amount increased, the conversion of 1-butene decreased and selectivity to isobutene increased. This may be attributed to the higher spatial constraints inside the pores which restrict undesired reactions, such as 1-butene dimerization followed by cracking. The effect of temperature, weight hour space velocity and partial pressure of 1-butene was studied over modified and parent catalyst, indicating that a unimolecular mechanism prevails on modified samples while bimolecular processes are present on fresh ferrierite specially at short times on stream. (C) 2000 Elsevier Science B.V. All rights reserved.