【作者】 石凤娟；

【导师】 戴洪兴；

【作者基本信息】 北京工业大学 ， 应用化学， 2012， 博士

【摘要】 CH4是仅次于CO₂的重要温室气体，因其排入大气而引起的气候异常以及对臭氧层的破坏，已经成为全世界共同面临的重大问题。煤矿乏风是最大的甲烷工业排放源，但由于煤矿乏风存在流量大、瓦斯浓度低、甲烷富集困难和安全隐患等问题，使得收集和利用煤矿乏风瓦斯，减少温室气体排放，成为我国面临的紧迫任务。因此，设计对甲烷具有高选择性、高吸附容量、低解吸能耗的新型吸附分离材料以降低煤矿乏风中CH₄的含量是本课题解决的主要问题。活性炭或各种类型的分子筛等多孔材料因其特定的骨架结构、大比表面积和良好的热稳定性而成为吸附甲烷的首选对象。实践证明，大比表面积的活性炭或分子筛即使微孔、介孔甚至大孔所占的百分比再高，也不能有效地吸附甲烷分子。因为甲烷分子的动力半径只有3.82，孔径大小不适宜的单一表面并不能捕获它。这一特点也成为吸附甲烷分子的障碍。文献表明，多孔分子筛对气体吸附性能的好坏，不仅与材料的骨架结构和比表面积有关，孔道极性、孔径大小和孔容也是影响气体吸附的重要原因。围绕如何设计合成新型的多孔材料，孔径尺寸与所吸附气体分子的动力半径相匹配为目的，改善和提高多孔分子筛对CH₄和N₂的变压吸附性能，本论文通过改变表面活性剂种类和控制合成条件，采用水热法制备了具有球状、棒状和多面体状的有序或蠕虫状介孔二氧化硅SBA-15和SBA-16；采用离子交换的方法改性Beta分子筛；选用多齿配体构筑具有一维孔道的新型三维金属-有机骨架配合物；通过X-射线衍射（XRD）、扫描电子显微镜（SEM）、氮气吸附-脱附（BET）、程序升温脱附（TPD）、等离子体发射光谱（ICP-AES）、电子发射能谱（EDS）、单晶衍射、热重分析（TGA）等技术表征了这些吸附材料的物化性质，并考察对CH4和N2的变压吸附性能。研究内容主要包括：（1）采用水热合成法，改变表面活性剂种类和控制合成条件，制备得到具有球状、棒状和多面体状的有序或蠕虫状介孔二氧化硅吸附剂SBA-15和SBA-16。在室温和压力为725³630mmHg的条件下，具有有序介孔结构和较大孔容的棒状SBA-15对CH₄和N₂的变压吸附分离性能最好，其分离因子（CH₄/N₂）高达6.84。孔容、孔有序度和粒子形貌是影响此类材料变压吸附分离CH4和N2性能的主要因素。（2）采用离子交换的方法改性Beta分子筛制得M-Beta （M=H, Mg, Sr, Ba, Cu,Co, Ni, Ce）多孔分子筛。样品经过550℃的灼烧并没有改变分子筛的晶相结构。发现Sr-Beta分子筛对N2的吸附选择性最佳，Ba-Beta分子筛是对CH4和N2吸附量最大的吸附剂；碱土金属阳离子半径与N2吸附有关，离子半径越大，其对应的改性Beta分子筛对N2的吸附量也越大；确定在0¹000mmHg低压范围内，孔径和分子筛孔道酸性是影响分子筛对CH4和N2的变压吸附分离性能的主要因素，在强酸位，酸量按Ba-Beta> Sr-Beta> Co-Beta> Mg-Beta> Ce-Beta>Na-Beta> H-Beta> Ni-Beta的顺序减少，各吸附剂对CH₄吸附量也呈相同趋势递减，强酸位越多，对CH4的吸附量越大；在2000⁶000mmHg高压范围内，比表面积是影响两种气体吸附的主要原因。（3）采用层析法和水热合成法，以吡啶-3,5-二羧酸、异烟酸和吡啶-2,6-二羧酸为有机配体，分别以Co、Ni、Mn和Cu的氯化物为金属前躯体合成新型金属有机配合物。（4）采用水热合成法，以吡啶-2,6-二羧酸为配体，与稀土金属离子和碱土金属Ca或Sr的金属前躯体氢氧化物合成新型金属-有机骨架材料。通过单晶衍射结果发现，在相同的反应条件下，吡啶-2,6-二羧酸为配体，稀土金属离子和碱土金属离子Ca的摩尔比不同，所得的金属-有机骨架结构不同。其中，Ln系的金属-有机聚合物为一维链状结构，而Ln-Ca（Ln=Eu, Sm, Tb和Pr）系列金属-有机骨架材料则具有一维孔道的三维骨架结构，通过粉末XRD及热重分析（TGA）技术表征金属-有机骨架材料的晶相结构和热稳定性，确定孔道中的客体水分子具有支撑孔道的作用，客体水分子和配位水分子的脱出会引起骨架结构的坍塌。在相似的反应条件下，由于不同的碱土金属离子配位方式不同，即使与相同的配体配位，所得金属-有机骨架材料的结构也不同。与Ln-Ca系列金属-有机骨架相比，以Sr的氢氧化物为金属前躯体的金属-有机聚合物为一维带状结构。（5）采用水热合成法，以4-羟基-吡啶-2,6-二甲酸为配体，与水合Cu（NO₃）2原位合成3-硝基-4-羟基-吡啶-6-羧酸铜（[Cu（C₆H₅N₂O₆）2]·2（H₂O））配合物。（6）采用溶剂热方法，以1,4-苯二甲酸和异烟酸为有机配体，Zn（NO3）2·6H₂O为金属前躯体制得具有一维孔道的新型三维金属-有机骨架材料。通过TGA及PXRD表征技术确定金属-有机聚合物具有良好的热稳定性，150oC条件下真空干燥3h后仍能保持骨架结构的完整。由其对CH₄和N₂的吸附性能可得出，在0¹000mmHg低压范围内，金属-有机聚合物对CH₄吸附量小于Ba-Beta分子筛，随着压力增大，前者对CH₄吸附量逐渐大于后者；在整个压力范围内，金属-有机聚合物对N2吸附量均小于Ba-Beta分子筛。显然，在1000⁶000mmHg压力范围，金属-有机聚合物对CH4吸附量的吸附选择性较好。更多还原

【Abstract】 Methane is the main greenhouse gas in addition to carbon dioxide. The emissionof a large quantity of methane to the atmosphere is harmful to the climate and theozone layer. Hence, it has become the great problem to control methane emissions inthe word. Coal mine is one of the largest methane emission sources. It is very difficultto enrich methane gas due to the low concentration and involved safety problems.Therefore, it is urgent to design the novel porous materials with high selectivity andadsorption capacity and low desorption energy consumption of ventilated minemethane to reduce the content of methane in coal mine.Activated carbon or various types of molecular sieves have become the mostsuitable porous materials for methane adsorption because of their unique structures,large surface areas, and high thermal stability. Practically speaking, it has proved thatactivated carbon or various types of molecular sieves with large surface areas,including the high percentage of micropores, mesopores, and macropores, can noteffectively adsorb methane molecules because methane molecular radium is only3.82. The results reported in the literature have shown that the gas adsorptionperformance of porous materials is associated not only with the structures and surfaceareas but also with the channel polarity, pore sizes, and pore volumes.To improve and further enhance their pressure swing adsorption (PSA)performance of methane and nitrogen, we prepared spherical, rod-like, and polyhedralsilica SBA-15and SBA-16with ordered or wormhole-like mesopores under thehydrothermal conditions; Na-Beta adsorbents were obtained via the ion-exchangingroute with several metal cations; the porous metal-organic frameworks based onmultidentate ligands were synthesized. The physicochemical properties of theas-prepared materials were characterized by means of techniques, such as X-raydiffraction (XRD), scanning electron microscopy (SEM), N2adsorption-desorption(BET), temperature-programmed desorption (TPD), X-ray fluorescence spectroscopy(XRF), inductively coupled plasma-atomic emission spectrometry (ICP-AES), singlecrystal diffraction, and thermogravimetric analysis (TGA). The pressure swingadsorption behaviors for methane and nitrogen separation of these materials wereinvestigated. The main results obtained in the present investigations are as follows:(1) By changing the surfactant types and controlling the synthesis conditions, spherical, rod-like, and polyhedral silica SBA-15and SBA-16with ordered orwormhole-like mesopores were fabricated under the hydrothermal conditions. It isshown that the rod-like SBA-15sample with an ordered mesoporous structure andrelatively large pore volume exhibited the best PSA performance for the separation ofmethane and nitrogen, with the separation coefficient (CH4/N2) being up to6.84. ThePSA efficiency for methane and nitrogen separation of such kinds of mesoporoussilicas was associated with the pore volume, ordered porosity, and particlemorphology.(2) M-Beta porous adsorbents were obtained via the ion-exchanging route withseveral cations (H~+, Mg~2+, Sr~2+, Ba~2+, Cu~2+, Co~2+, Ni~2+, and Ce~3+) to study their effectson the adsorption behaviors of methane and nitrogen. It is shown that the Sr-Betamolecular sieve exhibited the best PSA performance for the separation of methane andnitrogen, whereas the maximal adsorption capacity for methane and nitrogen could beachieved for the Ba-Beta sample. For adsorbents containing alkaline-earth metalcations, the nitrogen adsorption capacity increased with increasing the cationic size. Itis confirmed that the pore size and channel acidity are the main factors in influencingthe PSA performance for the separation of methane and nitrogen in0~1000mmHgrange, whereas the surface area is the main factor in influencing the PSA performancefor the methane and nitrogen in2000~6000mmHg range. Furthermore, for the strongacid sites, the acidic amount of the adsorbent fellow a decreasing order of Ba-Beta>Sr-Beta> Co-Beta> Mg-Beta> Ce-Beta> Na-Beta> H-Beta> Ni-Beta, and themethane adsorption capacity decreased according to the same sequence. The more thestrong sites, the more is the methane adsorption capacity. Based on the results, weconclude that the adsorption capacity of methane is in concord with the sequence ofincreasing the strong acid sites.(3) Novel one-and two-dimensional metal-organic materials were synthesizedusing the solvent diffusion and hydrothermal method with pyridine-3,5-dicarboxylicacid, isonicotinic acid or pyridine-2,6-dicarboxylic acid as multidentate ligands, andCo, Ni, Mn and Cu as central metal ions,(4) Novel metal-organic materials were synthesized via the hydrothermal routeusing pyridine-2.6-dicarboxylic acid as ligand, and rare earth metal and alkaline earthmetal Ca or Sr hydroxides as precursors. X-ray single-crystallography reveals that twonovel coordination polymers were obtained when the molar ratio ofpyridine-2,6-dicarboxylate acid, Ln~3+, and Ca~2+was different. The Ln-organic polymer exhibited an one-dimensional chained structure. However, the novel Ln-Caheterometal-organic compounds displayed three-dimensional frameworks withone-dimensional channel. The XRD and TGA results indicate that the guest watermolecules played a role in supporting the pore structure, and the dehydration of thesematerials could induce serious collapses of the frameworks. Under the similar reactionconditions, the obtained metal–organic materials were different due to the differentcoordination modes of various alkaline earth metals and even to the coordination withthe same ligand. Ln-Sr-organic coordination polymers exhibited one-dimensionalribbon-like structure obtained solvethermally as compared to the Ln-Ca-organicframeworks.(5)[bis(3-nitryl-4-hydroxyl-pyridine-6-carboxylic) copper] dihydrate was insitu generated by using the hydrothermal method via the decarboxylation and nitrationof4-hydroxyl-pyridine-2,6-dicarboxylic acid ligand with copper nitratetrihydrate asthe metal source.(6) Novel metal-organic compound was synthesized via the solvethermal routewith isonicotinate and terephthalic acid as ligand and Zn~2+as center ion. X-raysingle-crystallography reveals that metal-organic compound displayed athree-dimensional framework with one-dimensional channel. The XRD and TGAresults indicate that the removal of DMF molecules in channel did not induce thecollapsing of the framework even when the sample was in vacuum dried at150oC for3h. The compound possessed good thermal stability. The Ba-Beta molecular sieveexhibited better PSA performance in methane adsorption capacity in the range of0~1000mmHg. The higher the pressure, the more is the methane adsorption capacityof the compound than that of Ba-Beta. Compared to metal-Beta zeolites, thecompound showed better PSA performance for nitrogen adsorption capacity andbetter methane adsorption selectivity in the range of1000~6000mmHg.更多还原