The kinetics of the methanol synthesis on a copper catalyst: An experimental study

The kinetics of the low pressure of methanol from feed gases containing solely CO and H2 were studied in an internally recycled gradientless reactor. As experimental accuracy impeded the application of high CO contents, the experimental range of mole fraction of CO was limited to 0.04 to 0.22. The total pressure was varied from 3 to 7 MPa and the temperature from 503 to 553 K. Residence time distribution experiments confirmed the assumption of perfect mixing on a macroscale. A maximum likelihood approach was used to fit possible kinetic equations. Although more accurate results and better fits—compared to previous experiments in a simple integral reactor—were obtained, no single rate expression could be selected as the most appropriate one. This was mainly attributed to the effects of small amounts of CO2 and H2O formed in the reactor. Three different reaction rate equations fit the experiments equally well. Arguments are given that we never can expect to elucidate the reaction mechanisms on the basis of kinetic experiments.