Abstract

Deactivation kinetics of methanol steam reforming catalyst for pure hydrogen generation

Author(s): M.Dehghani Mobarakeh, J.Towfighi Darian, R.Karimzadeh, M.S.Khoshtinat Nikoo

Comprehensive studies on reaction kinetics and mechanisms of steam reforming of methanol (SRM) in early decades have confirmed that all three reactions (steamreforming, SR, water gas shift,WGS, and decomposition of methanol, D) involve simultaneously in the process. Because all methanol is not converted to H2 and CO2, the reverse water gas shift, RWGS, reaction wonÂ’t be catalyzed and CO production will be stopped. The result of previous studies has presented that Cu particles are active sites for SRM reaction and selective to hydrogen production. The main drawback of using these catalysts is sintering of active Cu particles at desirable reaction temperatures. Deactivation kinetics of commercial Cu/ ZnO/Al2O3 catalystswere studied in a fixed bed reactor with 1:1molar ratio ofmethanol-water mixture. The testswere carried out at different temperatures: 250, 280 , 3100C for one week. The curves of the products yield were drawn at 250, 280 and 3100C. In this work, effective reaction rate constant was calculated by determination of feed conversion throughout time onstreamand thenwere fitted with hypotheticalmodel resulting fromFuentes expression including three adjustable parameters: KS, KF and SS/S0. Because of the main difference between adjustable SS/S0 in hypothetical sintering model and its real magnitude, Fuentes model is not efficient for fitting and processing of experimental data. For this reason, general deactivationmodel based on aS/a0 instead of SS/S0 was used for fitting of experimental data with a hypothetical model. Determination of copper surface area by N2O adsorption on copper particles was done before and after runs. It is considered that thismodifiedmodel is valid and useful for initial deactivation. In the temperature range of 250-3100C reaction rate constant increases with increasing temperature.