Hydrogen Generation from Bioethanol Reforming: Bench-Scale Unit Performance with Cu/Nb_2O_5 Catalyst

摘要

As an alternative route for hydrogen production, ethanol reforming was studied in a bench-scale unit using a 5%Cu/Nb_2O_5 catalyst previously selected in a micro reactor. X-Ray Diffraction analysis has shown that this catalyst contains copper oxide in an amorphous form, or in particles smaller than 20 nm, while the Nb_2O_5 is highly crystalline. Analysis of the calcinated catalyst by X-Ray Photoelectron Spectroscopy revealed that 35% of total copper was on the surface as Cu~I (55%) or Cu~(II) (45%). The catalyst presented a low surface area (35 m~2/g), mainly from meso and macropores, as textural analysis revealed. Temperature Programmed Reduction showed a two-step reduction of Cu~(II) to Cu, at 245 ℃ and 306℃. It was also observed the reduction of 6% of Nb_2O_5. The reaction unit consisted of an integral reactor with 16 g of catalyst pellets, approximately 3 mm × 5 mm in size. Reaction temperature and feed rate were varied to optimize hydrogen production, with CO_2 as the main byproduct. Reagents (water and ethanol) in stoichiometric proportion were fed into an electric pre-heater and vaporized. An increase on reaction temperature from 300℃ to 400℃ has led to an increase in mean conversion from 17% to 35%. Ethene and ethyl ether were also detected as minor byproducts.