Kinetics of hydroisomerization of C5-C7 alkanes and their mixtures over platinum containing mordenite

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Abstract

The hydroisomerization of n-pentane (n-C5), n-hexane (n-C6), n-heptane (n-C7), cyclohexane (c-C6) and their binary mixtures, n-C5/n-C6, n-C6/n-C7, n-C6/c-C6, was investigated over platinum loaded hydrogen mordenite catalyst at 180-220°C, 5-40 bar total pressure and hydrogen to hydrocarbon molar ratios 1-20. The apparent activation energies of isomerization are 147, 123, 118 and 114 kJ/mol in case of n-C5, n-C6, n-C7 and c-C6, respectively. The reaction orders in alkane up to 4bar are 0.33, 0.39, 0.15 and 0.18, as well as the reaction orders in hydrogen up to 36bar are -0.81, -0.65, -1.08 and -0.57 for n-C5, n-C6, n-C7 and c-C6, respectively. Rate equations were derived and parameters involved determined for the isomerization of pure paraffins. Kinetic results of n-C5, n-C6 and c-C6 in lower pressure range (palkane, pH2 ≤ 4bar) suggest that the isomerization reaction on acid sites is rate-determining step. But in the case of n-C7 or at higher pressures of n-C6 and c-C6 (pH2 ≥ 20bar, palkane > 5 bar approximately), the zeolite micropore is getting filled with reactants resulting in diffusional inhibition. Experimental data for binary mixtures showed that the reaction rate of both components decreased on mixing. The component having higher boiling point exerts higher inhibiting effect on the hydroisomerization of more volatile alkane than inversely. Kinetic equations for binary mixtures were also proposed.

Original languageEnglish
Pages (from-to)93-102
Number of pages10
JournalApplied Catalysis A: General
Volume229
Issue number1-2
DOIs
Publication statusPublished - Apr 10 2002

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Keywords

  • C-C alkanes
  • Hydrocarbon mixtures
  • Hydroisomerization
  • Kinetics
  • Platinum hydrogen-mordenite

ASJC Scopus subject areas

  • Catalysis
  • Process Chemistry and Technology

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