Deactivation Kinetics of Cu/ZnO/Al2O3 via Methanol Steam Reforming for Pure Hydrogen Generation

Comprehensive studies on reaction kinetics and mechanisms of SRM in early decades have confirmed that all three reactions (Steam reforming, Water gas shift and decomposition) involve simultaneously in the process. Because all methanol is not converted to H2 and CO2, the RWGS reaction won’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 catalysts were studied in a fixed bed reactor with 1:1 molar ratio of methanol-water mixture. The tests were carried out at different temperatures: 250, 280 , 310°C for one week. The curves of the products yield were drawn at 250, 280 and 310 °C. In this work, effective reaction rate constant was calculated by determination of feed conversion throughout time on-stream and then were fitted with hypothetical model resulting from Fuentes expression including three adjustable parameters: KS, KF and SS/S0. Because of the main difference between adjustable SS/S0 in hypothetical sinteringmodel and its real magnitude, Fuentes model is not efficient for fitting and processing of experimental data. For this reason, general deactivation model 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 this modified model is valid and useful for initial deactivation. Temperature has increasing effect on reaction rate constant, therefore, catalyst activity in the range of 250-310 °C.

Keywords:

Deactivation Kinetic , Steam reforming , Methanol , Hydrogen generation , Cu-based catalyst