Morphology-controlled Preparation Of Hybrid Solid Acid Catalysts And Their Applications In Biomass Conversion Process

In order to alleviate the worldwide shortage of energy,the development of conversion of low-cost biomass and biomass-derived compounds to obtain fuels and organic chemicals is a focus in Green Chemistry.Additionally,the design and preparation of solid acid catalysts which is effiecient,stable,segregative and recyclable is one of the key research issues.At present,homogenous acids can catalyze the biomass conversion processes effectively,nevertheless,the implementation of these acids requires significant costs in terms of separation and reuse after the reactions.Unfortunately,traditional solid acid catalysts are improved,but there are some factors leading to it poor catalytic activity such as poor porosity parameters,terrible morphologies,hydrophilic surface and low stability.Thereore,this thesis is devoted to the preparation of solid acid nanohybrid catalysts which possess unique morphology and hydropholic suface,and successfully prepared 2D hexagonal mesostructure,nanotubular and hollow nanospherical structure solid acid nanohybrid catalysts by P123-templated sol-gel cocondensation strategies and fine-tuning of the preparation conditions.Their heterogeneous acid catalytic activity and stability towards esterification of levulinic acid with methanol or glycerol with lauric acid,and alcoholysis or hydrolysis of furfuryl alcohol were investigated.1.A series of highly orderd mesoporous Nb₂O₅-based hybrid catalysts bifunctionalized by the Keggin-type heteropoly acid and phenyl-bridged organosilica moties[PW12/Nb₂O₅-Si（Ph）Si] were succesfully prepared by carefully adjusting Si-to-Nb molar ratio in the initial gel mixture.The morphologies,porosity properties,chemical composition and structural information of the prepared catalysts were characterized by TEM,nitrogen gas porosimetry measurement,ICP-AES,pyridine-adsorbed FT-IR spectroscopy,31 P MAS NMR and ¹³C CP-MAS NMR spectroscopy.The influence of levulinic acid-to-methanol molar ratio and morphologies of the prepared nanohybrid catalysts on catalytic activity was studied by using esterification of levulinic acid with methanol as the model reaction.Additionally,their catalytic stability was evaluated by recycling tests.2.Morphology evolution of sulfonic acid functionalized organosilica nanohybrids[Si（Et）Si-Pr/ArSO₃H] with 1D tubular structure,2D hexagonal mesostructure,and 3D hollow spherical structure was successfully realized through carefully adjusting the acidity in the starting preparation system followed by aging or hydrothermal treatment.The morphologies,porosity properties,acid site density,? SO₃ H loading,thermostability,chemical composition and structural information of the prepared catalysts were characterized by TEM,nitrogen gas porosimetry measurement,ICP-OES,TGA,31 P MAS NMR and ¹³C CP-MAS NMR spectroscopy.The influence of morphologies of the prepared nanohybrid catalysts,activegroup precusors and ? ArSO₃ H loading on catalytic activity was studied by using esterification of levulinic acid with methanol and alcoholysis of furfuryl alocohol with ethanol as the model reactions.Additionally,their catalytic stability was evaluated by recycling tests and characterized by TEM and ¹³C CP-MAS NMR spectroscopy.3.A series of arenesulfonic acid-functionalized alkyl-bridged organosilica hollow nanospheres,Si（R）Si-ArSO₃H-HNS,with different bridging alkyl groups such as ethyl,phenyl,or biphenyl in the silica/carbon framework were successfully fabricated by carefully adjusted the concentration of micelle-expanding agent and the acidity in the starting preparation system.The morphologies,porosity properties,Br?nsted acid site strength and density,? SO₃ H loading,surface hydrophobicity,chemical composition and structural information of the prepared catalysts were characterized by TEM,nitrogen gas porosimetry measurement,potentiometric titration instrument,ICP-OES,water vapor adsorption measurement,XPS,31 P MAS NMR and ¹³C CP-MAS NMR spectroscopy.The prepared Si（R）Si-ArSO₃H-HNS nanohybrids were applied in the selective synthesis of glycerol monoand dilaurate from the esterification of glycerol with lauric acid,and the influence of glycerol-to-lauric acid molar ratio,structure of the bridging alkyl groups,and morphology of the nanohybrids on the catalytic activity were studied.Additionally,selective formation of glycerol mono-or dilaurate and Si（R）Si-ArSO₃H-HNS-catalyzed possible esterification mechanism were studied.Afterward,the reusability of the prepared catalysts was evaluated by recycling tests and characterized by TEM and ¹³C CP-MAS NMR spectroscopy.4.A series of arenesulfonic acid-functionalized alkyl-bridged organosilica hollow nanospheres,ArSO₃H-Et-HNS,with different shell thickness were successfully fabricated by carefully adjusted the concentration of surfactant and other component in the starting preparation system.The morphologies,porosity properties,Br?nsted acid site strength,? SO₃ H loading,thermostability,chemical composition and structural information of the prepared catalysts were characterized by TEM,nitrogen gas porosimetry measurement,potentiometric titration instrument,ICP-OES,TGA,XPS,31 P MAS NMR and ¹³C CP-MAS NMR spectroscopy.The prepared ArSO₃H-Et-HNS nanohybrids were applied in the synthesis of levulinic acid from the hydrolysis of furfuryl alcohol,and the influence of the kind of solvents,solvent-to-water volumn ratio,furfuryl alcohol-to-water volumn ratio,reaction temperature,and the shell thickness of the prepared catalysts on the catalytic activity of ArSO₃H-Et-HNS were studied.Additionally,Si（R）Si-ArSO₃H-HNS-catalyzed possible esterification mechanism were revealed.Finally,the reusability of the prepared catalysts was evaluated by recycling tests and characterized by ¹³C CP-MAS NMR spectroscopy.