EXTERNAL MASS AND HEAT-TRANSFER LIMITATIONS OF THE PARTIAL OXIDATION OF METHANE OVER A PT MGO CATALYST-CONSEQUENCES FOR ADIABATIC REACTOR OPERATION/

A kinetic model for the partial oxidation of methane to syngas over a highly active Pt/MgO catalyst was developed using hyperbolic rate equa tions. The formation of syngas was derived to occur via primary methan e combustion to CO2 and H2O and secondary steam and CO2 reforming of m ethane to CO and H-2. On the basis of this kinetic model the performan ce of an adiabatic reactor was simulated. A sensitivity analysis with respect to radiation and heat conductivity of the catalyst bed on axia l temperature and concentration profiles was performed assuming T-inle t = 873 K and u(reactor,873K) = 3 m s(-1). A hot-spot temperature on t he surface of ca. 1700 K at 1 bar and 2600 K at 25 bar and large gradi ents between surface and gas-phase temperature were calculated. No sig nificant contribution of radiation to the heat transfer was predicted. The effective heat conductivity of the catalyst bed is an important f actor to decrease hot-spot temperatures. The maximum temperature amoun ts to 1380 K(1 bar) and 2100 K (25 bar), assuming a heat conductivity of the catalyst bed of 0.15 J s(-1) m(-1) K-1. Equilibrium conversion and selectivity is obtained with a bed of less than 1 mm length.