【作者】 贺茂云；

【导师】 肖波；

【作者基本信息】 华中科技大学 ， 环境工程， 2009， 博士

【摘要】 化石能源的大量使用产生了严峻的环境问题，严重威胁着人类的健康和生存。能源危机与环境污染的双重压力迫使人们重新认识到需要寻找可再生能源，以逐步替代化石燃料，缓解能源短缺和环境污染。目前，城市生活垃圾排放量的快速增长带来了新的环境问题。而城市生活垃圾中的各种厨余、纸张、织物、树枝和塑料等有机组分可以实现废物—能量的转化，不仅可以减轻能源和环境的双重压力，减少化石燃料的使用，还能对城市生活垃圾进行资源化利用。城市生活垃圾裂解气化处理过程中，存在产氢率低、气化效率不高和大量焦油出现的问题，要解决这些问题，主要依靠高效催化剂进行催化裂解气化，提高反应速率，降低反应温度，以及去除焦油等。本文进行了纳米镍基催化剂的制备及其对城市生活垃圾裂解气化的催化性能研究：首先，以Ni（NO₃）₂·6H₂O和氨水为原料，采用配位均匀沉淀法制备纳米NiO前驱体，对前驱体制备过程中的反应温度、反应时间、用水量及镍氨比等影响因素进行了深入的探讨。利用XRD，FTIR和TG／DTA对前驱体进行表征。表征结果表明，前驱体为高纯度的六方体晶相的纳米β-Ni（OH）₂。和非纳米Ni（OH）₂相比，纳米Ni（OH）₂的δ（OH）峰都发生了一定的红移，而v（Ni-O）峰都发生了一定的蓝移。对制备的纳米NiO进行XRD，FTIR，SEM和TEM表征，结果表明，产物为标准面心立方相纳米NiO。随着前驱体煅烧温度的升高和煅烧时间的增加，制备的纳米NiO平均粒径明显变大，晶格畸变率变小。通过控制沉淀条件可以制备出不同形貌和粒径的纳米NiO，制备的球状纳米NiO粒径为20-25 nm；棒状纳米NiO直径约为5 nm，长度为30—50 nm，不同NiO纳米棒的晶面间距都约为0．24 nm，沿[111]方向生长。然后，以Ni（NO₃）₂·6H₂O和（NH₄）₂C₂O₄·H₂O为原料，采用超声化学沉淀法制备出氧化镍前驱体，XRD图谱表明前驱体为NiC₂O₄·2H₂O，FTIR谱图分析进一步验证得到的前驱体是NiC₂O₄·2H₂O。TEM表征结果说明Nano-NiO颗粒有轻微的团聚，平均粒径在70 nm左右。而且随着反应物（NH₄）₂C₂O₄和Ni（NO₃）₂·6H₂O物质的量的比值增至0．3后，制备的粉末产品出现了Ni单质。此外，为了比较纳米NiO和非纳米NiO的物理化学性质差异，采用直接煅烧法制备出平均粒径为0．6μm的近似立方体形的大颗粒NiO。同时，利用热重／差热分析法比较纳米NiO和大颗粒NiO的催化活性，纳米NiO较大颗粒NiO具有较好的催化活性，更能促进城市生活垃圾中树枝组分的裂解。在探讨树枝组分的催化裂解特性的基础上，提出了树枝的裂解动力学模型。同样，采用配位均匀沉淀法在氧化铝载体上负载纳米NiO，制备出负载型纳米NiO／Al₂O₃催化剂，载体上均匀负载的NiO涂层厚度约为8—500μm，由NiO纳米片组成，NiO纳米片直立向上相互交错生长，厚度40 nm-3μm。SEM表征证实涂层由不同形貌和尺寸的NiO纳米片组成，利用XRD，FTIR和SEM对纳米NiO／Al₂O₃催化剂进行全面的分析和表征，结果表明，制备过程中的反应温度、反应时间、用水量及镍氨比等影响因素对载体表面上负载的NiO纳米片的形貌和尺寸影响很大。然后，将制备的负载型纳米NiO／Al₂O₃催化剂用于城市生活垃圾裂解气化，以评估其催化活性，并和煅烧白云石催化活性进行比较，实验结果表明，两者就去除焦油和提高H₂产率而言，负载型纳米NiO／Al₂O₃催化剂的催化活性优于煅烧白云石。同时，在添加煅烧白云石和负载型纳米NiO／Al₂O₃催化剂的条件下，研究城市生活垃圾裂解和气化特性发现，温度和升温速率对垃圾催化裂解影响非常显著，高温和快速加热能降低催化裂解过程中焦油产率，提高H₂产率；在城市生活垃圾催化气化过程中，高温和高S／M值（水蒸气垃圾质量比）有利于降低催化气化过程中焦油产率，提高H₂产率。在添加煅烧白云石的条件下，对比垃圾催化气化产气各组分含量和由GasEq model软件的计算结果表明，垃圾催化气化产气达到了热力学平衡，拟合的垃圾催化气化动力学可以很好的描述碳转化率、氢气产率和水蒸气垃圾质量比之间的关系。最后，采用热重／差热分析法对垃圾焦油进行催化裂解实验，得到垃圾焦油的催化裂解动力学方程，并评价催化剂对垃圾焦油裂解的催化活性，发现添加纳米NiO和煅烧白云石都能显著降低焦油裂解活化能。根据动力学方程，分析了垃圾焦油催化裂解的反应机理。更多还原

【Abstract】 More and more energy resource especially fossil fuel consumed raising the question ofserious environmental pollution severely threatens the health and survival of human being,and people are aware of the importance of renewable energy,which can gradually replacethe existing fossil fuel in order to relieve the shortage of energy and environmentalpollution.At present,the quantity of Municipal Solid Waste（MSW）has increasedsignificantly in the industrialized and developing countries with the question of itssustainable disposal management.Lots of energy and money was used for transportation,treatment,and final disposal of MSW,thus the disposal of MSW is one of the mostimportant and urgent problems in environmental management in the world.The pyrolysisand gasification of MSW has been considered to be a promising method for future energysystems to meet environmental requirements,and provides one of the mostcost-competitive means of obtaining hydrogen-rich gas from MSW,and have promisingapplication in Waste-To-Energy（WTE）technology.The pyrolysis and gasification ofMSW can not only alleviate the dual-stress of energy and environmental,and reduce thepollution caused by MSW,but also achieve reclamation of MSW.However,during the pyrolysis and gasification process of MSW,much tar and lowgasification efficiency,low hydrogen yield exist.In general,nickel-based catalysts areused to eliminate the tar,increase the yield of hydrogen-rich gas,and to decrease thetemperature of pyrolysis and gasification.Coordination homogeneous precipitation method was used to synthesize nanosizednickel hydroxide powder products with the ammonia and nickel nitrate hexahydrate as theraw materials.Transmission Electron Microscope（TEM）,powder X-ray Diffraction（XRD）,Thermal Gravimetry and Differential Thermal Analysis（TG/DTA）,FourierTransform Infrared spectroscopy（FTIR）and Scanning Electronic Microscope（SEM）wereused to characterize the microstructure and morphology of the synthesized precursor andNano-NiO powder products,the XRD and FTIR patterns showed that the synthesizedprecursor was hexagonalβ-Ni（OH）₂ crystallites,which decompose at 300.3℃,and thenNiO nanocrystal was produced.During the course ofβ-Ni（OH）₂ crystallite preparation,thereaction temperature,reaction time,water volume and mole ratios of Ni（NO₃）₂·6H₂O to ammonia were studied.Compared with Bulk-NiO,δ（OH）peak of the Nano-NiO productsin FTIR pattern gives rise to red-shift.While,v（Ni—O）peak gives rise to blue-shift.XRD and FTIR patterns showed that the NiO powder products are nanosized FCCobtained from the synthesized precursorβ-Ni（OH）₂ crystallite calcined at 400℃.TEMimages showed that spherical Nano-NiO are 20—25 nm in mean particle diameter,NiOnanorods are 5 nm in mean particle diameter,30-50 nm in length and 0.24 nm ininterplanar crystal spacing（111）.All NiO nanorods grow in the direction of[111].FTIRpatterns showed that the smaller Nano-NiO powder is,more significant the red-shift ofcharacteristic peak is.Ultrasound chemical precipitation method was used to synthesize the precursor powderswith the ammonium oxalate and nickel nitrate hexahydrate as the raw materials.The XRDpatterns showed that the precursor powders are NiC₂O₄·2H₂O,and FTIR patternsconfirmed the result of XRD pattern.TEM image indicated that Nano-NiO powderproducts agglomerate slightly in a mean particle size of 70 nm.When the mole ratios ofammonium oxalate to nickel nitrate hexahydrate increased,Ni appeared in the powderproducts.The catalytic activity of Nano-NiO and Bulk-NiO powder products used in woodcomponent of MSW pryolysis with TG/DTA method was evaluated,Nano-NiO performedbetter than Bulk-NiO in promoting the decompostion of wood component.The catalyticpyrolysis characteristic was discussed,then dynamics model was proposed according tothe TG/DTA data.Coordination homogeneous precipitation method also was used to synthesize NiOnanosheets on the surface of the support Al₂O₃,the supported coating was 8-500μm inthickness,which consist of NiO nanosheets.XRD,FTIR and SEM were used tocharacterize the microstructure and morphology of the Nano-NiO/Al₂O₃ catalyst.The Nano-NiO/Al₂O₃ catalyst was use in the pyrolysis and gasification process of MSWto evaluate their catalytic activity,experimental results showed that Nano-NiO/Al_O3catalyst performed better than calcined dolomite in eliminating tar and increasinghydrogen yield.Meanwhile,during the MSW pyrolysis with Nano-NiO/Al₂O₃ catalyst orcalcined dolomite,the reactor temperature and heating rate have significant influences on the MSW pyrolysis,higher reactor temperature and heating rate can reduce tar yield andincrease gas yield and hydrogen yield.Furthermore,there was a good agreement between the experimental gas compositionand that corresponding to thermodynamic equilibrium data calculated using GasEq model.Consequently,a kinetic model was proposed for describing the variation of hydrogen yieldand carbon conversion efficiency with S/M（the weight ratio of Steam to MSW）during thecatalytic steam gasification of MSW.The kinetic model revealed a good performancebetween experimental results and the kinetic model.The tar pyrolysis with Nano-NiO and calcined dolomite as catalysts was investigatedusing the TG/DTA method.According to the TG/DTA data,Nano-NiO and calcineddolomite catalysts can lower the activation energy of tar pyrolysis,then a kinetic modelfor tar pyrolysis was developed,and the characteristic of tar pyrolysis with and withoutcatalysts were discussed,then the mechanism of tar pyrolysis was analyzed.更多还原