Steady State and Dynamic Modelling of a Packed Bed Reactor for the Partial Oxidation of Methanol to Formaldehyde Ii. Experimental Results Compared With Model Predictions

Abstract

Heterogeneous and pseudohomogeneous two-dimensional models are compared to steady state and dynamic experimental data from a packed bed reactor for the partial oxidation of methanol to formaldehyde over an iron oxide-molybdenum oxide catalyst. Highly effective parameter estimation software was used to fit selected model parameters to large sets of experimental data so as to obtain small residuals. Heat transfer parameters which were successful in matching data from experiments without reaction were not capable of fitting data from experiments with reaction, and it was necessary to increase the radial heat transfer for higher temperatures or reaction rates. Axial composition profile data was represented by estimating the preexponential factors and activation energy in a half-order redox rate expression for methanol oxidation. After some decline in catalyst activity, a time-varying axial catalyst activity profile was determined from the data. A redox-type rate expression for the oxidation of formaldehyde to carbon monoxide was proposed to fit the data. The dynamics of the reactor temperature profile were accurately represented by the model. The heterogeneous and pseudohomogeneous models gave similar results in fitting experimental data, although the parameters determined for the two models were somewhat different.

Oxidation of ethene in a wall-cooled packed-bed reactor

“…Vortmeyer (1982), Ramkrishna and Arce (1989) and Schwedock et al_ (1989)]. Chandrasekharan and Calderbank (1979), Hofmann (1979Hofmann ( ), L6we (1984 and Schwedock et al (1989) observed that heat transport parameters depend on chemical reaction and they state that models generally predict too high hot-spot temperatures for exothermic reactions if the heat transport relations used are determined under non-reaction conditions. They conclude that heat transport and its parameters, ;teff.r and o~,,, should be increased under reaction conditions, whereas this increase depends on the extent of reaction.…”

Kinetics of the partial oxidation of methanol over a Fe-Mo catalyst

“…The results of these rate equations have been presented before in the figures showing the experimental results (Figs. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. With the derived kinetic model the reaction rates could be well described within typically 5-15% accuracy (deviation).…”

“…The experimentally determined steady-state formaldehyde partial oxidation reaction rates have been compared with literature data from Edwards et al [6], Diakov et al [14], Schwedock et al [11] and Dente et al [21]. Although the formaldehyde partial oxidation is the most important consecutive reaction during the partial oxidation of methanol to formaldehyde, relatively few kinetic studies have been carried out to determine the intrinsic reaction rate for this reaction.…”

“…Most of the kinetic studies performed in the past have been carried out at relatively high oxygen concentrations, because the current industrial process is operated under oxygen rich conditions. Schwedock et al [11] found that a redox rate expression was needed for the kinetics of the carbon monoxide production. Table 6 compares our activation energy with the literature data.…”

“…Schwedock et al [11] carried out a comprehensive study of the partial oxidation of methanol in a packed bed reactor. They reported the results of a large number of high-quality steady-state and transient kinetic experiments.…”