Experimental and theoretical investigation on the roles of heterogeneous and homogeneous phases in the oxidative dehydrogenation of light paraffins in novel short contact time reactors

Abstract

The role of a Pt/Al 2 O 3 catalyst in the oxidative dehydrogenation of light paraflins was investigated by means of a novel annular reactor which allows to realize very high space velocities and controlled temperature conditions. While a number of previous papers claimed that Pt is extremely active in the selective oxidation to olefins, the experiments in the annular reactor showed that the present noble-metal catalyst is highly active in the non selective oxidation to CO x , H 2 and H 2 0 only. Gas-phase experiments and simulations of a homogeneous reactor showed that the formation of olefins at high temperature and short contact times can be largely explained by the gas-phase oxidative pyrolysis. However, autothermal experiments demonstrated that the catalytic phase can be exploited in an adiabatic reactor for igniting and thermally supporting the pyrolytic process; the combined catalytic-homogeneous reactor performed as a homogeneous reactor, but the presence of the catalyst allowed to produce high yields to olefms at much lower reactor volume and lower pre-heat temperatures.