The Co-Al-Fe-O And Co-Ce Catalysts Applied To Hydrogen Production Via Auto-thermal Reforming Of Acetic Acid

Biomass is a carbon neutral renewable energy,can be used for hydrogen production.Bio-oil can be obtained via fast-pyrolysis of biomass,while acetic acid is the main component.Acetic acid is then selected as the feed for research hydrogen production.O₂ is introduced into the steam reforming process to carry out the auto-thermal reforming of acetic acid.The Co-based catalyst has high activity for water gas shift reaction and the ability to break C-C and C-H bonds,but it will also be deactivated due to carbon deposition and oxidation.Activity and stability of catalyst in reforming process is a major issue.In this paper,based on the acetic acid conversion pathway,the Co_xAl₃Fe_yO_m±?and Co-Ce catalysts were developed,the adsorption behavior of reactant molecules was regulated to improve the redox ability of Co active metal.In addition,the relationship between catalytic performance and structure was also explored.The Co_xAl₃Fe_yO_m±?catalysts were prepared by coprecipitation method and applied to the auto-thermal reforming of acetic acid.The activity and stability of the catalysts were investigated.Characterizations of XRD,H₂-TPR,N₂ adsorption-desorption and TG were imployed.The results showed that the Fe species have been incorporated into the hydrotalcite like skeleton during the preparation process,forming?Co/Fe?_xAl₃CO₃?OH?_y·z H₂O precursors,and the spinel mixture phases were obtained after calcination.The higher specific surface area is conducive to the dispersion of active metals.After reduction,Co metal was highly dispersed on the surface of spinel oxides and interacted with Fe species to form a stable Co Fe alloy.Therefore,Co_0.45Al₃Fe_0.4O_5.55±?catalyst obtained high catalytic activity and stability in the 10-h auto-thermal reforming of acetic acid:the conversion of HOAc was stable at 100%,and the yield of H₂ reached 2.72 mol-H₂/mol-HOAc.In addition,carbon deposition was not detected on Co_0.45Al₃Fe_0.4O_5.55±?catalyst,which can be attributed to the electron donating effect of Fe to promote the reduction of Co active metal.Co Fe alloy presented the strong ability to break the C-C bond in CH₃CO*species,which inhibited the production of carbon precursor such as acetone;the decomposition of CH_x*was promoted by the interaction between Co Fe alloy and spinel carrier,controling the transformation of acetic acid to hydrogen production.A series of Co-Ce catalysts were prepared by hydrothermal method.Their catalytic activity were evaluated by auto-thermal reforming of acetic acid,and characterized by XRD,H₂-TPR,N₂ adsorption-desorption,SEM and XPS.The results indicated that he spherical crystal produced by two-step hydrothermal method would form a compact structure to reduce the specific surface area of the catalyst,which is not ideal to molecular transfer.CC-R catalyst with rod structure presented a high specific surface area,meanwhile,Co species entered into the Ce O₂ lattice forming strong interaction between Co₃O₄/Ce O₂ interface;the adsorption ability of reactant molecules CH₃COOH,H₂O,O₂ was enhanced by a large number of oxygen vacancies and surface adsorbed oxygen which generated by the Co₃O₄/Ce O₂lattice defects.Moreover,combination of C*and O*was strengthened to inhibite the generation of methane and carbon species.The water gas shift reaction was promoted during reforming process,and the CO*derived from CH₃CO*species would react with the activated H₂O molecules to generate H₂ and CO₂,and the H₂ yield of CC-R catalyst reached 2.61 mol-H₂/mol-HOAc during auto-thermal reforming of acetic acid.