Olefin production by cofeeding methanol and n-butane: Kinetic modeling considering the deactivation of HZSM-5 zeolite



The joint transformation of methanol and n-butane fed into a fixed-bed reactor on a HZSM-5 zeolite catalyst has been studied under energy neutral conditions (methanol/n-butane molar ratio of 3/1). The kinetic scheme of lumps proposed integrates the reaction steps corresponding to the individual reactions (cracking of n-butane and MTO process at high-temperature) and takes into account the synergies between the steps of both reactions. The deactivation by coke deposition has been quantified by an expression dependent on the concentration of the components in the reaction medium, which is evidence that oxygenates are the main coke precursors. The concentration of the components in the reaction medium (methanol, dimethyl ether, n-butane, C2[BOND]C4 paraffins, C2[BOND]C4 olefins, C5[BOND]C10 lump, and methane) is satisfactorily calculated in a wide range of conditions (between 400 and 550°C, up to 9.5 (g of catalyst) h (mol CH2)−1 and with a time on stream of 5 h) by combining the equation of deactivation with the kinetic model of the main integrated process. © 2010 American Institute of Chemical Engineers AIChE J, 2011