【作者】 毛继平；

【导师】 路勇；

【作者基本信息】 华东师范大学 ， 物理化学， 2010， 博士

【摘要】 醇选择性氧化制备醛酮等羰基化合物的反应在化学工业中占有十分重要的地位,银基催化剂在醇的选择性氧化反应中有着非常广泛的应用和研究。本文采用固定床反应器技术,以空气中的分子氧为氧化剂,在制备的各种整体式银基催化剂上实现各类醇的气相选择性氧化,研究内容主要包括:1)通过高温烧结Ni微纤复合材料载体技术,将微米尺度的负载型银催化剂颗粒（Ag/α-Al₂O₃、Ag/γ-Al₂O₃及Ag/SiO₂）包结于Ni微纤三维网状结构中,从而制得新型整体式镍微纤结构化负载银催化剂复合材料（Ag-α-Al₂O₃/Ni-fiber、Ag-γ-Al₂O₃/Ni-fiber及Ag-SiO₂/Ni-fiber）。将该复合材料用作苯甲醇选择性氧化制苯甲醛的催化剂,考查其催化氧化活性,并与其相对的负载型银催化剂进行了对比,结果发现:复合材料的催化氧化活性均高于相应的负载银催化剂,这源于镍微纤的三维网络结构使负载银催化剂颗粒彼此分开,同时催化剂颗粒周围的Ni微纤具有良好的传热性能,增强了催化剂颗粒间的传热,同时也增强了催化剂颗粒内部的传热,热量的迅速转移使反应床层温度保持均一,从而维持了催化剂的高活性。2)采用造纸/烧结技术将微米尺度的载体颗粒（α-Al₂O₃、γ-Al₂O₃及SiO₂）包结于金属微纤（镍或不锈钢）三维网状结构中,从而制得整体式微纤结构化细粒子颗粒复合材料（α-Al₂O₃-Ni-fiber、γ-Al₂O₃-Ni-fiber、SiO₂-Ni-fiber及α-Al₂O₃-Steel-fiber、γ-Al₂O₃-Steel-fiber及SiO₂-Steel-fiber）,以该复合材料为载体,硝酸银水溶液为浸渍液,采用初湿浸润法制得整体式微纤结构化细粒子颗粒复合材料负载银催化剂（Ag/α-Al₂O₃-Ni-fiber、Ag/γ-Al₂O₃-Ni-fiber、Ag/SiO₂-Ni-fiber及Ag/α-Al₂O₃-Steel-fiber、Ag/γ-Al₂O₃-Steel-fiber、Ag/SiO₂-Steel-fiber）。考查了该整体式催化剂在苯甲醇选择性氧化制苯甲醛、正丁醇选择性氧化制正丁醛及1,2-丙二醇选择性氧化制丙酮醛反应中的催化氧化活性,Ag/α-Al₂O₃-Ni-fiber催化剂表现出了较好的催化氧化活性,在苯甲醇选择性氧化反应中,与三明治夹心型和普通填充床型催化剂相比,整体式微纤结构化复合材料催化剂Ag/α-Al₂O₃-Ni-fiber具有高的催化活性,转化率可以提高25个百分点,选择性提高了10个百分点。3)采用造纸/烧结技术制备具有三维网状结构的金属微纤载体（体积含量为3-4%直径为8μm的镍纤维或直径为12μm的SS-316L型不锈钢纤维）,其孔隙率为96-97%。然后将活性银组分采用初湿浸润法负载在金属微纤的表面,制得整体式金属微纤负载银催化剂Ag/Ni-fiber及Ag/Steel-fiber,并将其用于醇的气相选择性氧化反应中,研究发现:银的最佳负载量为10%左右,而最佳的焙烧温度为600℃。在单元醇/芳香醇/二元醇选择性氧化反应中,在相对较低的反应温度下,金属微纤负载银催化剂比电解银及Ag/α-Al₂O₃催化剂表现出了更高的活性与选择性,体现了金属微纤作为载体用于醇选择氧化等强放热反应的优越性。4)采用一系列表征手段如XPS、SEM、H₂-TPR、UV-vis DRS及化学吸附等对电解银、Ag/Ni-fiber及Ag/Steel-fiber催化剂进行了表征,以研究催化剂的活性位及活性组分与载体之间的相互作用对醇选择性氧化反应的影响。研究发现:金属微纤负载银催化剂上比电解银催化剂具有更多的Ag⁺离子和团簇的Ag_n^δ+,这是金属微纤负载银催化剂比电解银及Ag/α-Al₂O₃催化剂具有高活性/选择性的原因之一。此外,相对于电解银及Ag/α-Al₂O₃催化剂,金属微纤具有大的孔隙率、开放的孔结构、良好的传质传热性和高渗透性及热稳定性等良好的特性。特别是,Ag/Ni-fiber比Ag/Steel-fiber表现出了更佳的低温催化氧化活性,这主要源自Ag与镍微纤载体的协同效应,不仅导致高的Ag⁺离子和Ag_n^δ+团簇浓度而且吸附的氧物种具有更好的低温氧化活性。更多还原

【Abstract】 The selective oxidation of alcohols to the corresponding carbonyl compounds is one of the most important chemical transformations in organic chemistry. Silver-based catalysts are widely used in the selective oxidation of alcohols.In this paper,a series of novel monolithic catalysts of Ag-based catalysts were used in the gas-phase selective oxidation of alcohols on a fixed-bed reactor under atmospheric pressure with molecular oxygen as the oxidant.The research included the following aspects:Firstly,by using papermaking/sintering process,sinter-locked three-dimensional microfibrous networks consisting of～3vo%8μm（dia.） nickel microfibers were utilized to entrap～25vol%100-200μm dia.supported silver catalysts（Ag/α-Al₂O₃, Ag/γ-Al₂O₃ and Ag/SiO₂） particulates.The reaction of gas-phase selective oxidation for benzyl alcohol was carried out over the monolithic catalysts.It was found that the nickel microfibrous structure with supported silver catalysts exhibited much higher activity and selectivity than the corresponding supported silver catalysts.The excellent catalytic activity of the monolithic catalysts had connection with the novel structure of the metal microfibers.This nickel microfibrous media provides unique three dimensional web structures,large void volume,entirely open structure,large surface-to-volume ratio,high permeability,and high thermal conductivity.Due to these advantages,it can intensify interlayer heat/mass transfer between the supported silver catalysts particulates and then make the reaction bed temperature isothermal to maintain the high activity of the monolithic catalysts in the gas-phase selective oxidation of benzyl alcohol.Secondly,by using the regular papermaking/sintering processes,metal micro fibers entrapped support particulates（α-Al₂O₃,γ-Al₂O₃ and SiO₂） were prepared. Active Ag component was then deposited onto the surface of the microfibrous structure withα-Al₂O₃,γ-Al₂O₃ and SiO₂ support particulates by incipient wetness impregnation method,in order to obtain the new-type monolithic catalysts of Ag/α-Al₂O₃-Ni-fiber,Ag/γ-Al₂O₃-Ni-fiber,Ag/SiO₂-Ni-fiber,Ag/α-Al₂O₃-Steel-fiber, Ag/γ-Al₂O₃-Steel-fiber and Ag/SiO₂-Steel-fiber.The reactions of gas-phase selective oxidation for butanol,benzyl alcohol and 1,2-propylene glycol were carried out over these catalysts.It was found that Ag/α-Al₂O₃-Ni-fiber and Ag/α-Al₂O₃-Steel-fiber exhibited much higher activity than the other catalysts.In the process of gas-phase selective oxidation for benzyl alcohol,the Ag/α-Al₂O₃-Ni-fiber catalyst exhibited higher activity/selectivity compared to sandwiched bed and the packed bed with Ag/α-Al₂O₃ particulates.We obtained 25%increase in conversion and 10%increase in selectivity to benzaldehyde.Thirdly,a new-type microfibrous-structure-supported silver catalysts was developed and demonstrated for high efficiency gas-phase oxidation of various alcohols to their corresponding carbonyl products.Sinter-locked three-dimensional microfibrous networks consisting of 3-4 vol%8μm（dia.） Ni fibers or 12μm（dia.） SS-316L fibers and 96-97 vol%void volume were built up by the regular papermaking/sintering processes.Active Ag component was then deposited onto the surface of the sinter-locked fibers by incipient wetness impregnation method to obtain the monolithic catalysts of Ag/Ni-fiber and Ag/Steel-fiber.The gas-phase selective oxidation of alcohols to their corresponding carbonyl products were carried out over the monolithic catalysts.It was found that the optimal Ag loading was 10%and the optimal calcination temperature was 600℃in air.At relatively low reaction temperatures（e.g.,380℃）,as-made microfibrous structured silver catalysts provided quite higher activity/selectivity for the oxidation of mono-/aromatic-/di-alcohols compared to the traditional electrolytic silver and Ag/α-Al₂O₃ catalysts.Finally,catalytically relevant physiochemical properties of the electrolytic silver, Ag/Ni-fiber,and Ag/Steel-fiber catalysts were explored by XRD,XPS,SEM,H₂-TPR, O₂-TPO,UV-visible diffuse reflectance spectroscopy,and chemisorption techniques. The remarkably high activity and selectivity of the monolithic catalysts were partially attributed to certain amount of Ag⁺ ions and Agn^δ+ clusters.In addition,the microfibrous structure provided a unique combination of large void volume,entirely open structure,excellent heat/mass transfer and high permeability good thermal stability,and therefore led to a significant increase in the steady-state volumetric reaction rate,compared to electrolytic silver and Ag/α-Al₂O₃ catalysts.Especially,the Ag/Ni-fiber catalysts offered much better low-temperature activity than the Ag/steel-fiber catalysts,mostly due to the synergistic effect between Ag particles and Ni-fiber.The interaction at Ag particles and Ni-fiber interface not only visibly increased the amount of active/selective sites of Ag⁺ ions and Agn^δ+ clusters but also significantly promoted their activity as evidenced by the low-temperature reduction feature.更多还原