【作者】 袁晓玲；

【导师】 张文祥； 贾明君；

【作者基本信息】 吉林大学 ， 物理化学， 2012， 博士

【摘要】 多孔炭材料通常具有发达的孔隙、高的比表面积、优良的耐热、耐酸碱和独特电子传导性质，在吸附、催化、生物、电子等领域用途广泛。在炭材料中引入氮等异质元素能进一步调变材料的结构、表面化学性质及电子传导性，使其具有更加广阔的应用发展前景。在催化及吸附领域中，氮掺杂多孔炭材料作为一类新型固体碱催化剂或吸附剂已经显示出了独特的优势。目前，针对一些具有重要应用前景的碱催化反应工艺和水中重金属离子（如汞离子）吸附去除，开发性能更加优异的氮掺杂多孔炭材料，已经成为相关领域的研究热点。本论文主要采用溶胶-凝胶路线，结合高温炭化及表面后修饰等方法制备了几类氮掺杂多孔炭材料，通过不同表征手段对材料的组成、结构及表面化学性质进行了研究，并通过汞离子吸附实验及碳酸二甲酯和碳酸二乙酯酯交换反应、苯酚和草酸二甲酯酯交换反应，研究了材料的吸附性能和催化性能。论文的主要研究内容和结果概述如下：以蔗糖和柠檬酸为碳源，采用溶胶-凝胶路线，并结合高温炭化的方法制备出了一类具有介孔结构特征的多孔炭材料(NC)；采用后修饰的方法用乙二胺对NC材料进行了改性研究，得到了具有较高氮含量的氮掺杂多孔炭材料（NC-EDA）；对NC-EDA进一步加热处理（873K，惰性气氛下），得到的材料记为NC-EDA-873。上述材料均具有比表面积大、孔径分布均匀等特点，并且材料表面含有丰富的含氧官能团和含氮官能团，其中NC-EDA表面含有大量的氨基官能团，经高温处理的材料NC-EDA-873上则含有较多的吡啶氮和吡咯氮。水体系中汞离子吸附实验结果表明：NC-EDA材料对汞离子的吸附明显高于NC材料，这说明有机胺的引入能够有效提高材料对汞离子的吸附性能；经高温处理的NC-EDA-873材料依然保持了较高的汞离子吸附性能，并且吸附过程符合朗格缪尔等温吸附。结合XPS等表征结果，可以认为材料表面存在的含氮官能团（如氨基和吡啶氮）对汞离子的吸附起到了关键作用。上述含氮官能团本身所具有的弱碱性与具有弱酸性的汞离子之间能够形成较强的相互作用，从而使NC-EDA材料表现出良好的汞离子吸附性能。通过改变多孔炭材料NC的后处理温度，得到了一系列表面化学性质不同的NC材料，并考察了这些材料对碳酸二甲酯和碳酸二乙酯酯交换合成碳酸甲乙酯反应的催化性能。研究结果表明：随着热处理温度的升高，NC材料表面的含氧官能团（包括氮氧化物）逐渐减少，含氮官能团的种类和相对含量也会产生变化，继而影响了NC材料的表面化学（酸碱性）性质。不同温度处理的NC材料均对碳酸二甲酯和碳酸二乙酯酯交换合成碳酸甲乙酯反应表现出了较高的催化活性和优异的主产物选择性。其中473K处理的材料（NC-473）表现出了相对更高的催化活性，随着热处理温度的继续升高，催化剂的反应活性逐渐降低。此外，NC-473材料还表现出良好的稳定性和循环性。多次循环使用后，催化剂的活性没有明显降低，且反应过程中没有发生活性组分流失的现象，是典型的多相催化反应。XPS结果表明，NC-473材料表面存在相对较多的氨基官能团，可能是其表现出较高反应活性的主要原因。以柠檬酸和六亚甲基四胺为碳源、氮源，采用溶胶-凝胶法制备出了一系列氮掺多孔杂炭材料（NNC），使用多种表征方法对其结构和性质进行了研究。结果表明：NNC材料具有较高的比表面积和孔容，而且材料的结构和表面性质还可以通过改变六亚甲基四胺的量进行调变；NNC材料表面除了含有多种含氧官能团外，还含有大量的吡啶氮、吡咯氮、季氮等含氮官能团。将NNC作为多相催化剂，在苯酚和草酸二甲酯酯交换合成草酸二苯酯和草酸苯甲酯的反应中进行了催化性能评价。NNC催化剂在反应中表现出了非常高的催化活性和主产物选择性，催化剂通过简单的过滤、丙酮洗涤、烘干后即可重复使用，且催化性能基本保持不变，性能明显优于负载型金属氧化物催化剂、有机-无机杂化材料等多种类型的催化剂体系。结合不同的表征结果，可以认为NNC材料表面存在的含氮官能团（如吡啶氮等）是主要的活性中心，这类含氮官能团能稳定地分布在炭材料骨架中且其碱强度适合该反应的要求，应该是NNC催化剂具有高活性、高选择性及高稳定性的主要原因。更多还原

【Abstract】 Porous carbon materials with well-developed pore, high specific surface area,excellent heat resistance and/or unique electronic conduction properties are of greatinterest for their important applications in many fields such as adsorption, catalysis,biology and electronics. The introduction of nitrogen into the carbon materials canfurther tune their structure, surface chemical properties and electronic conductivity,thus giving rise to a wide spectrum of potential applications. In the fields ofheterogeneous catalysis and adsorption, porous nitrogen-doped carbon materials haveshown unique advantage as new types of solid base catalysts or adsorbents. Currently,the preparation of high active porous nitrogen-doped carbon materials for theapplications in some importent basic catalytic reactions and the removal of heavymetal ions (such as mercury ion) have attention in the related fields.In this thesis, a series of porous nitrogen-doped carbon materials were prepared bysol-gel route, combining with high temperature carbonization and post-modificationmethods. The structure and surface properties of porous nitrogen-doped carbonmaterials were studied by various characterization means. The adsorption propertiesof mercury ion, as well as the catalytic properties for the transeterification of dimethyloxalate with phenol or dimethyl carbonate with diethyl carbonate were investigatedover various porous nitrogen-doped carbon materials. The main study contents andresults are summarized as follows:A series of porous carbon (NC) materials with mesoporous characteristics wereprepared by sol-gel method via high temperature carbonization using sucrose andcitric acid as the carbon and nitrogen precursors. The nitrogen amount in theethylenediamine-modified porous carbon (NC-EDA) is higher than that of NCmaterials. The materials of NC, NC-EDA and thermal-treated NC-EDA-873(NC-EDA after thermal-treatment at873K) possess high specific surface area, similarpore size distributions and various oxygen-containing and nitrogen-containing groups.The adsorption performance of NC, NC-EDA and NC-EDA-873for mercury (Ⅱ)ions were investigated in aqueous system. The NC material exhibited relatively high adsorption capacity for mercury (Ⅱ) ions, which can be improved significantly byethylenediamine modification. The adsorption capacity of the NC-EDA-873materialstill maintained at a relatively high level. Kinetic experimental results indicated thatthe adsorption isotherms can be fitted well using Langmuir model. Based on variouscharacterization results, it can be proposed that the presence of abundant N-containingfunctional groups on the surface of NC materials is beneficial for the adsorption ofmercury ions. Basic species of the materials can interact with mercury ions directly,and thus significantly improving the adsorption capacity of carbon material.A series of porous carbon materials with different thermal-treatment temperature(NC-T) were prepared, and their catalytic properties were investigated in thetransesterificatoion of dimethyl carbonate (DMC) with diethyl carbonate (DEC). Withincrease of thermal-treatment, the amount of surface O-containing functional groups(including nitrogen oxides) decreased, and the types and contents of N-containingfunctional groups also changed somewhat. All NC materials were ateive catalysts forthe transesterification of DEC with DMC. It was found that NC-473show very highactivity, stability, and can be easily recycled without any special treatment on the usedcatalyst. On the basis of XPS results, it can be concluded that the presence ofabundant amio-functional groups on the surface of porous carbon NC-T materialshould play a critical role on the activation of the reactants in the transesterificationreaction.A series of nanoporous nitrogen-doped carbon (NNC) materials were prepared bysol-gel method, with hexamethylene tetramine (HMT) and citric acid as the carbonand nitrogen precursors. The structure and surface properties of these NNC materialswere characterized by different characterization methods. The materials of NNCmaterials possess high specific surface area, similar pore size distributions. Besidespossessing various oxygen-containing groups, these NNC materials also containdifferent types of nitrogen-containing groups, including pyridinic-N, pyrrolic-N andquaternary-N groups. The resulting NNC materials are highly active and selectiveheterogeneous catalysts for the transesterification of dimethyl oxalate (DMO) withphenol to produce methyl phenyl oxalate (MPO) and diphenyl oxalate (DPO), and canbe easily recycled after simple filtrening, washing with acetone and drying. Thepresence of suitable surface basic sites should be mainly responsible for the excellentcatalytic performance of NNC materials in the transesterification reaction.更多还原