Evaluation of intrinsic steam reforming kinetic parameters from rate measurements on full particle size

Abstract

Steam reforming of n-heptane has been studied in laboratory experiments on nickel catalyst particles shaped as 4.2 × 4.2 mm cylinders. Reaction rates were measured at isothermal conditions in a single pellet string reactor that gives a convenient simulation of an industrial packed bed. The pressure was varied in the range 5–30 bar and the temperature in the range 450–550° C. At these conditions the rate is strongly retarded by intraparticle diffusion. The results show that the reaction rate for the catalyst particles in a pseudo-homogeneous model can be described by the following rate expression: [Display omitted] An intrinsic rate expression based on an assumed reaction mechanism has been proposed in literature. The suitablity of this expression has been investigated by applying a heterogeneous model, which takes interfacial as well as intraparticle gradients into account. The pre-exponential factor as well as the adsorption constants were estimated by fitting calculated conversions to experimental conversions. The estimated constants showed no significant variation in the investigated operating ranges. This fact demonstrates the applicability of the proposed intrinsic rate expression in the following adjusted form: [Display omitted]