The Preparation Of Modified Cobalt/Sepiolite Catalysts For Hydrogen Production Over Bio-oil Models Steam Reforming

Hydrogen production by bio-oil steam reforming can effectively improve the utilization efficiency of biomass,and realize the synergetic development of renewable hydrogen energy and environmental protection.It is an important research topic to achieve carbon peak and neutrality in the field of environmental engineering.In the study of bio-oil and its models of steam reforming,Co-based catalysts have attracted the attention of researchers due to their cheapness,high C-C and C-H bonds cleavage ability and high water-gas shift reaction activity.However,due to high temperature,high steam partial pressure,complex oxidation/reduction reaction atmosphere and bio-oil composition with poor thermal sensitivity,Co-based catalysts still face deactivation issues resulting from active metal sintering and coke deposition.To develop high-performance,anti-inactivation and eco-friendly Co based catalysts,natural clay sepiolite（SEP）was selected as support with high thermal stability,high adsorption ability and flexible structural constituent.A series of modified Co/SEP catalysts were prepared by the chemical precipitation method and urea thermal method.Based on this point,this paper takes the Ce promoter and the preparation method improvement as the synthetic variables to optimize the catalyst microstructure,component and morphology.Meanwhile,combined with N₂-adsorption/desorption,In-situ XRD,SEM,TEM,H₂-TPR,and TPD-MS characterization technologies,the analysis of catalyst structure evolution,crystal composition,metal-support interaction,surface acid and morphology would reveal the catalyst construction mechanism,the anti-deactivation mechanism and the catalyst structure-performance relationship.The main research contents and conclusions are as follows:（1）For improving the hydrogen production efficiency of steam reforming,Ce modified Co/SEP catalyst was prepared by the surfactant-assisted chemical co-precipitation method to improve the surface oxygen mobility and metal dispersion of the catalyst.Hydrogen production law and the mechanism of resistance to coke deposition were explored and dominated by catalyst Co-Ce interface interaction during ethanol steam reforming.The results showed that the Co-0.3Ce/SEP-C0.4 catalyst has the strongest Co-Ce interface interaction,reaching the highest ethanol conversion rate（96.2%）and hydrogen yield（77.9%）in the reaction conditions of T=600oC,S/C=3 and WHSV=21.5 h^-1.（2）For the catalyst metal sintering issue,a series of xCo/SEP-derived Co-Al spinel catalysts by urea thermal method could realize the growth regulation of spinel phase and metal Co exsolution.In15Co/SEP catalyst,the strong interaction of fine Co⁰ nanoparticles（<10 nm）and residual Co-rich defective Co_1-xAl₂O_4-x phase effectively suppress metal sintering and promotes coke deposition removal.Under the reaction conditions of T=700oC,S/C=3 and WHSV=10.6 h^-1,15Co/SEP catalyst achieved the highest simulated bio-oil conversion（95.7%）and hydrogen yield（68.8%）with stability above 50 h.（3）The regenerability of 15Co/SEP and 15Co/Al₂O₃ derived Co-Al spinel catalysts were compared for catalyst inactivation during simulated bio-oil steam reforming.In the five reaction-regeneration cycle tests,the initial activity of the deactivated 15 Co/SEP catalyst could be recovered by regeneration treatment due to the redispersion of partially sintering Co particles.The Co⁰ particle size only increased from 17.4 nm to 25.4 nm,avoiding the formation of encapsulated graphite carbon and linear inactivation trend.It reduces the adverse effect of metal sintering on catalyst stability.（4）For the catalyst coke deposition issue,Co/SEP-Na OH derived Co-phyllosilicate catalyst was made by urea hydrothermal method and amorphous SEP silicon source.Exposure of amorphous SEP skeleton Si atoms promotes the formation of Co-phyllosilicate phase and enhances metal-support interaction.Co/SEP-Na OH phyllosilicate catalyst with a high surface area（270 m²/g）,strong metal-support interaction and strong basicity could avoid the formation of amorphous coke,and achieve the highest glycerol conversion（95%）and H₂ yield（70%）under the reaction conditions of T=600oC,S/C=3 and WHSV=10.6 h^-1.Density functional theory（DFT）simulated the glycerol molecular adsorption/activation process and found that the Co-Co O interface prompted the adsorption and dehydrogenation of glycerol molecules,followed by dehydration and decarbonylation into C1 species.（5）For the easy-coking issue of phenol and ethanol in bio-oil,nanoflower-like xCo/SEP-PS Co-phyllosilicate catalyst was prepared by template-free urea hydrothermal method and amorphous SEP silicon source to study the effect of the catalyst on the adsorption activation of coke precursor（phenol+ethanol）,hydrogen production efficiency and stability performance.Catalyst characterization results found that the synergy of highly dispersed Co nanoparticles（<20 nm）and L acid site in the Co-phyllosilicate catalyst effectively enhances the C-C and C-H bonds cleavage,improving reforming activity and inhibiting coke deposition.10Co/SEP-PS catalysts have the lowest apparent activation energy（35.5 k J/mol）of the phenol+ethanol steam reforming and a higher frequency of H₂ Turnover frequency(TOF=0.67 s^-1).Meanwhile,the developed pore structure and surface confinement effect were conductive to the minimum coke content（3.9 wt.%）of 10Co/SEP-PS catalyst.Figure[96]Table[19]Reference[199]...