【作者】 张迪；

【导师】 赵云鹏；

【作者基本信息】 中国矿业大学 ， 化学工艺， 2018， 硕士

【摘要】 随着燃料和化学品需求的日益增长,寻找可持续性替代能源已经迫在眉睫。由于生物质储量丰富且可再生,其催化转化制备高附加值化学品和液体燃料已经引起广泛关注。γ-戊内酯（GVL）可以作为绿色溶剂及食品和燃料的添加剂,被认为是最具有研究价值的平台分子化合物之一。本文采用等体积浸渍法制备了不同Ni负载量和不同硅铝比的Ni/HZSM-5催化剂,考察了其催化乙酰丙酸（LA）和纤维素制备GVL的性能,并推测了相关反应机理。采用电感耦合等离子体发射光谱（ICP-MS）、扫描电子显微镜（SEM）、场发射透射电子显微镜（TEM）、氮气吸脱附、X射线衍射（XRD）、X射线光电子能谱（XPS）、氨气程序升温脱附（NH₃-TPD）、氢气程序升温还原（H₂-TPR）和吡啶红外吸附（Py-FTIR）对催化剂的表观形貌和物理化学性质进行表征。结果表明:镍颗粒均匀分散在载体上,镍的加入增加了载体的介孔数量,促进了反应物和产物的扩散;同时活性组分与载体之间具有较强的相互作用,但不会改变载体的MFI骨架结构。LA制备GVL最优反应条件是:反应温度210 ^oC,反应时间2 h,反应初始压力3 MPa H₂,催化剂为5 wt%Ni/HZSM-5-50,GVL的产率达到100%。催化剂的强酸数量决定活性位点的数量,强酸越多催化剂活性越高;同时弱酸峰强度越大也有利于整个反应的进行。催化剂表面同时存在B酸和L酸能有效提高催化剂活性。LA加氢制备GVL的可能反应机理:氢气首先在金属表面吸附和解离,随后LA在酸性位点上吸附并加氢生成4-羟基戊酸（HPA）,然后HPA经过脱水生成GVL。纤维素在上述最优反应条件下制备GVL的转化率、产率和选择性分别为32.3%、31.9%和98.9%。纤维素在Ni/HZSM-5催化剂作用下制备GVL的可能反应机理:水分子在催化剂表面均裂形成的H⁺促进纤维素水解生成纤维二糖;催化剂表面上的B酸诱使β-1,4糖苷键变形和断裂生成葡萄糖,然后葡萄糖在L酸作用下生成5-羟甲基糠醛（HMF）;HMF经过加氢、脱水和脱羧等反应得到LA,LA在B酸作用下进一步加氢转化得到目标产物GVL。更多还原

【Abstract】 With increasing demands for chemicals and fuels,it is urgent to find sustainable alternatives energy resources.The catalytic conversion of biomass to high value-added chemicals and liquid fuels has attracted much attentions because of its abundance reserves and renewability.As an important biomass platform molecular compound,gamma-valerolactone（GVL）can be used as the green solvents or the additive of fuels and foods.A series of Ni/HZSM-5 catalysts with different Ni-loading capacities and Si/Al ratios were prepared by incipient wetness impregnation.The catalytic performances of the prepared Ni/HZSM-5 catalysts for the transformation of levulinic acid（LA）and cellulose to GVL were investigated,and the relevant reaction mechanism was also proposed.The surface morphology and physicochemical properties of the catalysts were characterized by inductively coupled plasma mass spectrometry（ICP-MS）,scanning electron microscope（SEM）,transmission electron microscopy（TEM）,nitrogen adsorption-desorption,X-ray diffraction（XRD）,X-ray photoelectron spectrometer（XPS）,temperature-programmed desorption of ammonia（NH₃-TPD）,temperature-programmed reduction of hydrogen（H₂-TPR）,and Fourier transform infrared（FTIR）spectra of pyridine adsorption.The results show that nickel particles were uniformly distributed on the surface of HZSM-5,and the addition of nickel particles increased the amount of mesoporous in the support,which facilitates the diffusion of reactants and products.Meanwhile,there exist a strong interaction between active component and the support,while the MFI structure of support has been unchanged.The maximum GVL yield was 100%over 5 wt%Ni/HZSM-5-50 under the optimized reaction conditions of 210 ^oC,2 h,and 3 MPa initial H₂ pressure.The amount of strong acid in catalysts determines the amount of active sites and the activity of catalysts.Meanwhile,high weak acid intensity of catalysts also is in favor of the conversion of LA to GVL.Moreover,the coexistence of B and L acid sites in catalysts efficiently improved the catalytic activity of the catalyst.The possible reaction mechanism for the transformation of LA to GVL is as follows.Hydrogen is firstly adsorbed and dissociated on the metal surface,afterwards LA is adsorbed on the acid sites and hydrogenated to 4-hydroxypentanoic acid（HPA）,then HPA is converted to GVL by dehydration.Under the optimized reaction conditions mentioned above,the conversion,yield and selectivity for the transformation of cellulose to GVL are 32.2%,31.9%and 98.9%,respectively.The possible reaction mechanism of cellulose to GVL is as follows.The H⁺form the split of water molecules on the surface of the catalyst promotes the hydrolysis of cellulose into cellobiose.Afterwards,the B acids on the surface of the catalyst promote the deformation and cleavage ofβ-1,4 glycosidic bond to produce glucose,then the produced glucose is converted into 5-hydroxymethylfurfural（HMF）catalyzed by the L acid sites.Subsequently,HMF is converted to LA through a series of reactions including hydrogenation,dehydration and decarboxylation,then LA is hydrogenated to GVL catalyzed by the B acid sites.更多还原