Intrinsic rate equations were derived for the steam reforming of methane, accompanied by water-gas shift on a Ni / MgA1204 catalyst. A large number of detailed reaction mechanisms were considered. Thermodynamic analysis helped in reducing the number of possible mechanisms. Twenty one sets of three rate equations were retained and subjected to model discrimination and parameter estimation. The parameter estimates in the best model are statistically significant and thermodynamically consistent.

Given the intrinsic kinetics, the tortuosity factor of a Ni/MgAI,O, catalyst was determined under reaction conditions by minimizing the sum of squares of residuals of the experimental and the simulated conversions. The parallel cross-linked pore model with uncorrelated pore size distribution and orientation was used in the calculation of the effective diffusivities. A modified collocation method was used to obtain the partial pressure profiles of the reacting components in the catalyst pellet. The simulation of the experimental reactor during the optimization of the tortuosity factor also yielded the effectiveness factors of the reactions. The results of the simulation of an industrial steam reformer are also discussed.

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of C02 formation and the final product distributions for both mono-and bifunctional compounds. AcknowledgmentThis work was partly supported by a Grant-in-Aid for Scientific Research (No. 61030017) from the Ministry of Education, Science and Culture, Japan.

Coke formation in the thermal cracking of hydrocarbons was studied in a pilot plant unit and in a microreactor with complete mixing of the gas phase, containing a hollow cylinder suspended at the arm of an electrobalance. The morphology of the coke was studied by SEM, while EDX was used to determine the concentration of metals in the coke layer. The influence of the metal surface composition, of its pretreatment, and of the addition of various sulfur compounds on the coking rate and CO production was investigated for conditions typical for those in the cracking coil. The CO yield is not a measure of the coking rate. Sulfur compounds are very efficient in reducing the CO yield but promote coke formation.

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