Hydrogenolysis of Propane over Sol-Gel Pt-Rh/SiO2: Activity, Selectivity and Kinetics

Abstract

The catalytic properties of Pt_xRh₁ _ _x (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0)
bimetallic catalysts supported on SiO₂ and prepared by the sol-gel method
have been investigated in the hydrogenolysis of propane in the temperature
range of 150-550^oC. The measured BET surface area of these catalysts is
relatively high (ca. 580 m²/g). Their temperature of 100% conversion of
propane to ethane and methane at H₂/C₃H₈ = 3 and space velocity of 12,000
h ^-1 is relatively low (200-270°C). All Pt-Rh/SiO₂ catalysts are very active
in this respect. whereas Pt/SlO₂ is relatively inactive. Their selectivity
towards the production of ethane is ca. 50%. The kinetic parameters for
this reaction over Pt₅₀Rh₅₀/SiO₂  are  also reported, where increasing the
hydrogen pressure has an adverse effect on the rate of this conversion. The
reaction order with respect to hydrogen pressure is strongly negative (-2).
Propane pressure has a slight effect on the rate of conversion, and is with
an observed reaction order of +0.55. The apparent activation energy was
determined and found to be 123 ± 7 kJ/mot.