Studies On The Selective Hydrogenation Reactions Over Hydroxyapatite Supported Metal Catalysts

Apatites and relative calcium orthophosphates has draw widely attention in many fields,such as biology,mineralogy,orthopedics,inorganic chemistry and chemical engineering.Hydroxyapatites,as the main component of bones and teeth,has the most biocompatibility.It is hydrophilic but insoluble in water,and has excellent hydrothermal stability.People can synthesize various nano hydroxyapatite particles with or without porous structure depending on different demands.Hydroxyapatite has both acid and basic sites on its surface.It can disperse,support and anchor various metal,metal oxides or complex moleculars via ion-exchange,during which,the activity and selectivity of metal catalytic center can be improved by the coordination of phosphate groups.With these properties,hydroxyapatite has been studied in catalytic reactions in recent century.As the rapid expending of non-renewable fossil resources and the increasing problem of environment,it is urgent to develop renewable and clean energies.Biomass,as an abundant,carbon neutral,clean and renewable resource,has been widely studied as the potential alternative of fissil resources.The most promising biomass resource are lignocellulose and oil.The former contains cellulose,hemicellulose and lignin,the latter contains fatty acids and triglycerides.They can be further valorized to chemicals and fuels.Biomass feedstocks always have complex structure with abundant oxygen containing groups.So we can divide the biomass conversion to two categories:hydrodeoxygenation to fuel,and selectively converted to chemicals.The catalytic conversion of biomass derived compounds to fuels and value-added chemicals can not only enrich the biomass-based chemical library,but also follow the trend of green chemistry to broaden the utilization methods for the conversion of renewable resources.Based on the structure of biomass and the properties of hydroxyapatites,it is a good choice to use hydroxyapatite as catalyst in the selective hydrogenation of biomass.Pointing to this condition,we researched the selective hydrogenation of biomass derived chemicals over metal catalysts supported on hydroxyapatite.The main study focused on the selective hydrogenation of phenols to cyclohexanone and the hydrogenation of fatty acids and oils to long-chain alkanes.We studied the structure-function relationship of hydroxyapatite based catalysts,broaden the application of hydroxyapatite supported catalysts in selective hydrogenation reactions,and developed a hydroxyapatite derived catalytic system for the selective hydrogenation of biomass derived chemicals.In chapter one,we first introduced the structure and properties of hydroxyapatite,then reviewed the application of hydroxyapatite in catalytic researches,as well as themost recent catalytic hydrogenation of biomass.In chapter two,we introduced a study on the synthesis of hydroxyapatite,including solvothermal and hydrothermal methods,as well as the characterization of hydroxyapatites.In this study,we can make hydroxyapatite with various morphologies by control the solvent,and we find out the hydrothermal conditions have a complex impact on the growth of hydroxyapatite.In chapter three,we loaded palladium on hydroxyapatite for the selective hydrogenation of phenols to cyclohexanone.In this reaction system,phenol can be quantitatively converted to cyclohexanone in ambient temperature and hydrogen pressure without any further convertion even in extending reaction time.This catalyst can work well under low hydrogen pressure as low as 0.1 bar,or in acid-base conditions with pH=5?9.The synergistic cooperation of palladium center and hydroxyapatite lead to high efficient and selectivity.In chapter four,we use ruthenium on hydroxyapatite to convert fatty acids and oils to long-chain alkane fuel moleculars.Hydroxyapatite can adsorb and activate carboxyl groups to improve the hydrogenation over ruthenium.This catalytic system is tolerant to most of impurities in waste oil.The catalyst has a great thermal stability profit from that the ruthenium nanoclusters and hydroxyapatite can protect each other.In this paper,we studied on the selective hydrogenation of biomass derived chemicals over hydroxyapatite supported metal catalysts.We illuminated the structure-function relationship of catalysts,and broaden the hydroxyapatite catalytic system as well as the catalytic conversion and utilization of biomass.