| Fossil fuels are increasingly exhausted, leading to globle energy crisis.Environmental pollution has become increasingly serious. Bio-oil as a renewableclean energy, and has caught the researchers’ great attention. However, the quality ofbio-oil is still not ideal. Bio-oil contains large amounts of water andoxygen-containing compounds, resulting in low calorific value, high viscosity,immiscible, thermal stability and corrosion. Therefore, the hydrodeoxygenationupgrading is necessary for the present bio-oil to replace gasoline and diesel. Thequality of upgrading bio-oil is decided by the hydrodeoxygenation activity ofcatalysts to a large extent. At present commonly used catalysts are single-phasecatalysts, without considering the hydrophilic and hydrophobic, so it is difficult forsuch catalysts to simultaneously catalyze bio-oil oil-water two-phase system. And thesupport is mainly microporous material, active particles easily sintered, pluggingholes and coke on the microporous support. While microporous also increases themass transfer resistance of bio-oil macromolecules. According to the above mentions,and in view of the advantages of mesoporous materials, a kinds of amphiphilicmesoporous materials Pd/Carbon-Silica-Alumina was designed and prepared in thispaper and their hydrodeoxygenation activities were tested using phenol as bio-oilmodel oxygenic compound.Highly ordered mesoporous carbon-silica-alumina amphiphilic nanocompositeshave been successfully synthesized by the evaporation-induced tetraconstituentco-assembly method, wherein triblock copolymer F127is used as template, solubleresol polymer is used as carbon precursor, tetraethyl orthosilicate is used as silicaprecursor, and aluminum chloride hexahydrate is used as alumina precursor. Themass ratio of carbon and silica-alumina in the catalysts can be adjusted by changingthe input amount of resol precursors and etraethyl orthosilicate and aluminumchloride hexahydrate. Finally, amphiphilic catalyst Pd/C-SiO2-Al2O3is prepared bywet impregnation. The carbon content in material is characterized by TG-DTG.Detailed characterization by XRD, N2sorption, TEM, and NH3-TPD indicates the highly ordered2-D hexagonal mesostruture, high surface areas of275m2/g, uniformmesoporous sizes of4.9nm, pore volumes of0.34cm3/g, appropriate acid sites, and ahigh dispersion of palladium nanoparticles (about5nm) in the mesopores. At thesame time, the presence of inorganic silica-alumina in catalysts effectively inhibitsframework shrinkage during the calcinations. The hydrophilicity/hydrophobicity ofcatalysts is investigated on the basis of water adsorption behavior and oil-water twophase distribution.In the catalytic reaction, we use decalin and water to simulate oil-water systemof bio-oil. The results show that, amphiphilic catalysts Pd/C-SiO2-Al2O3show higherhydrodeoxygenation activity than hydrophilic Pd/Al-SBA-15and hydrophobic Pd/C.The hydrophilicity/hydrophobicity of amphiphilic mesoporous C-SiO2-Al2O3, whichhave a greater impact on its catalytic activity is adjusted. Under the condition of T=200°C, P=5MPa, and reaction time2h, the conversion rate of phenol is up to98%,the selectivity of deoxidizing product cyclohexane is up to87.7%. The presence ofmesoporous carbon in catalysts effectively dramatically improves the thermalstability of catalysts.The combination of hydrophobic carbon and hydrophilic silica-alumina makesthe catalyst amphiphilic and thus catalyze the hydrodeoxygenation reactions both inoil and aqueous phases. An amphiphilic mesoporous Pd/Carbon-Silica-Aluminacatalyst that simultaneously stabilizes water/oil emulsions and catalyze reactions atthe liquid/liquid interface would be highly advantageous in biomass upgradingreactions. |
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