3-Methylhexane aromatization under H₂ and N₂ atmospheres on Pt/ Al₂O₃ catalysts

Abstract

The aromatization reaction of 3-methylhexane on Pt/ Al₂O₃ in a pulse microcatalytic reactor has been studied under H₂ and N₂ atmospheres at temperatures ranging between 330°C and 500°C and at a total pressure of 4.0 kg/cm². Results showed that the production of only cracked products (mainly methane) from deep fragmentation of 3-methylhexane in H₂

sharply contrasts with the reaction in N₂ which appears to impart intrinsic aromaticity to the catalyst with the production of methane, benzene and toluene although with an attenuation of the overall activity. In H₂-N₂ mixtures, 50% H₂ was required to reduce the aromatization activity of the catalyst to zero. A test of the kinetic data using Sica's method [Sica <i>et al., Latin</i> <i>Am J Chem Eng Appl Chem, </i>4 (1974)108] of pulse kinetic analysis suggests a first order in 3-methylhexane with activation energy of 107 kJ/mol in N₂ and 202.03 kJ/mol in H₂. The difference in activation energies in both gases is consistent with a difference in reaction mechanisms.