Corn Straw Pretreatment And Hydrodeoxygenation Of Lignin-Derived Compounds In Ionic Liquids System

Biomass is the most abundand renewable resource in earth.The efficient utilization of biomass resources could alleviate our heavy dependence on fossil energy during our daily life.However,there is very little biomass resource that has been efficiently utilized up to now.It is well known that efficient fractionation of biomass into cellulose,hemicelluloses and lignin is the key scientific technology for complete utilization of biomass resources.Therefore,developing more efficient and green technologies for separation of biomass compositions is still one of important topics to the current research.At present,the utilization of biomass resources is mainly focused on the development and application of cellulose and hemicelluloses.Lignin,as the only renewable aromatic polymer in biomass,has not received widespread attention for its utilization.Due to the complex chemical structure and stable characteristics,most of lignin is still disposed as industrial waste or burning directly.Devloping more efficient conversion strategies for lignin to value added chemicals is highly desirable for fully utilization of lignin resource.Ionic liquids(ILs),as one kind of novel green solvent,have shown great potential application in biomass fractionation and lignin conversion fields owing to their specific characteristics,such as strong hydrogen bonding,near-zero vapor pressure and high hydrogen solubility,etc.The mainly work and results are summarized as follows:(1)Developing the pretreatment of corn straw with low-cost protic ILs.A series of low-cost proton ILs(about 1 $/kg)are synthesized by one-step protonation reaction.Meanwhile,the systematic study about corn straw pretreatment by using these ILs are conducted under mild conditions.The research confirms that all the ILs based on the anion of methane sulfonic shows good separation ability for corn straw.Among them,2-hydroxy-N-(2-hydroxyethyl)-Nmethylethanaminium ethanesulfonate([BHEM]mesy)exhibits the highest efficiency for separation of cellulose I materials from corn straw.More than 90 wt%of lignin and hemicelluloses in co4n straw could be efficiently dissolved and further separated with cellulose.XRD characterization analysis certifies that the obtained materials are cellulose I crystal structure with an increasing crystallinity index from 37%of corn straw to 59%.The mechanism of cellulose separation could be verified by GC-MS analysis,it confirms that[BHEM]mesy degrades the lignin and hemicelluloses in corn straw selectively,and then dissolving the degradation products to achieve the separation of cellulose.(2)Developing the hydrodeoxygenation(HDO)of lignin-derived phenols and dimeric ethers based on ILs catalytic system.The catalytic systems that used in this work are developed by using selected ILs combining with the prepared metal catalysts.Meanwhile,the characterization of metal catalysts confirms that all nano metal particles are well-disperesed on the carriers.The catalytic experiments proves that the smaller nano metal paricles,the higher catalytic activity for HDO of lignin-derived compounds.Among them,the[Bmim]PF6-Ru/SBA-15 catalytic system shows the most excellent catalytic activity for HDO of lignin-derived compounds.The conversion of lignin-derived compounds are up to>99.0%,and the yields of corresponding alkane are>90.0%at 130? for 6 h with the H2 pressure 2 MPa.The research confirms that the metal catalyst promotes the hydrogenation reaction,while the IL catalyzes the deoxygenation processes for the whole reaction,the anion of IL is the key factor for this reaction process.(3)Study on the HDO of lignin-derived compounds based on low-cost protic ILs catalytic system.The catalytic system that using in this work are prepared with the synthesized low-cost protic ILs combining with carbon based metal catalysts.The research confirms that Rh/C-[BHEM]TfO catalytic system has the best catalytic activity for HDO of lignin-derived compounds.The conversion of phenol is up to 100%at 120 °C for 6 h with the H2 pressure 4 MPa,the yields of cyclohexane and bicyclohexyl are 93.3%and 2.1%,respectively.Meanwhile,the catalytic system also shows high efficiency for HDO of all selected lignin-derived compounds with the conversion>99.0%,and>90.0%yield of corresponding alkane.