Preparation Of CeO₂with Different Morphology And Their Application For Ethanol Steam Reforming

Hydrogen has been one of the most potential secondhand energy due to its cleaningand high efficiency, and widely used in fuel cell. Ethanol Steam Reforming（SRE） forhydrogen has attracted more attention owing to its features of lower reaction temperatureand relatively higher H2production. Cobalt-based catalysts have better ethanol conversionand H2selectivity for SRE. However, the key problem is deactivation caused by carbondeposition of catalysts and cobalt particles sintering. The morphologies of CeO₂affect theiroxygen-storage capacity, and modulate the interaction with active components, both ofwhich could enhance catalysts stability. In this paper, we focused on Co/CeO₂catalysts,and proceed with design of carriers. CeO₂with nanoparticles form, mesoporous pattern anddifferent morphologies were prepared by liquid precipitation, hard template andhydrothermal methods respectively. Then the influences of CeO₂structures andmorphologies on catalytic performance of SRE were discussed. We attempted enhancingoxygen-storage capacity of CeO₂to modulate the interaction between supports and metal.The purpose is improving anti-carbon capacity of catalysts.The nanoparticles CeO₂have been prepared by liquid precipitation, we looked into theinfluences of CTAB addition on carriers morphologies and catalytic performance of SRE.TEM, BET and TPR results showed that CeO₂with CTAB grow integrated and hasuniform size, larger specific surface area and better capacity of oxygen-storage. Theinteraction between supports and metal particles presents as Ce-O-Co, higheroxygen-storage capacity of CeO₂-A and larger specific surface area of Co/CeO₂-A increasethe catalytic performance and carbon resistance ability of SRE.Mesoporous CeO₂were synthesised by hard template method using SBA-15andCMK-3（made by ourself） as rigid structure matrices. We investigated the effects ofdifferent structure matrixs on support structures, properties and catalysts performance.Characterization results indicated that Ce-CMK-3has larger specific surface area andordered porous structure in short range. Bore diameter mainly distribute at3nm, andexpose the more active （110） planes, thus they own better oxygen storage and releasecapacities. In addition, Co entering into Ce-CMK-3lattice enhance the interaction betweenCe-CMK-3and supported metal, which make Co3O4easier to restore. Compared with traditional nanoparticles catalysts, special pore structure in short-range of CeO₂enhancethe interaction between cobalt and CeO₂, which are essential for superior activity andselectivity of the mesoporous catalysts. Moreover, Co/Ce-CMK-3also have a preferablecarbon resistance property.CeO₂with different morphologies and particle size were prepared throughhydrothermal. We studied the impacts of CeO₂morphologies （Flowerlike, Polyhedron,Prism, Fusiformis, Bouquet, Ricelike and Spindle） on SRE performance. Characterizationresults showed that flowerlike CeO₂have unique3D opened pore structures and expose themost active （100） planes and more active （110） planes, which make them own the bestoxygen storage capacity, promote reduction of catalysts active components, and improveethanol conversion as well as carbon resistance capacity. Catalysts test indicated that theH2production is higher than68%in the whole reaction, which illustrates the mainlyexposed planes （100） and （110） of supports optimize the distrubution of products.The relative results of supports morphologies, catalysts structures and catalyticperformance indicated that there are different exposed planes, oxygen storage capacitiesand ineraction between Co and CeO₂for supports with different morphologies andstructures, thus affects ethanol conversion and products distribution, which results indifferences of carbon deposition types. CeO₂（flowerlike） own the largest specific surfacearea and uniforn pore size distribution focused on3.5nm. They have more oxygenvacancies due to the most reactive （100） and （110） planes they exposed. For catalysts, thereare more Co ions entering into CeO₂lattice, which enhance the interaction between Co andceria. It is easier to reduce Co species to active components, and enhance ethanolconversion as well as carbon resistance capacity, then optimize products distribution.