【作者】 张佳；

【导师】 刘艳华；

【作者基本信息】 吉林大学 ， 物理化学， 2014， 硕士

【摘要】 二氧化硅（功能二氧化硅或白炭黑）是一类重要的功能材料，应用领域广泛，市场需求巨大。但是目前存在诸多问题影响了白炭黑行业的发展。（1）白炭黑生产主要以硅砂为原料，近年来高品位矿砂越来越少，低品位硅砂杂质含量多，提纯困难，因此高档二氧化硅生产面临无米之炊；（2）生产白炭黑的水玻璃工序是硅砂与氢氧化钠在1300~1500°C高温熔融，能耗大，占总成本的70%，属于高能耗行业；（3）碳酸钠与二氧化硅在高温反应，排放大量二氧化碳，引起温室效应。因此，寻求可再生原料代替硅砂、开发绿色合成工艺已经成为这个领域的重要研究课题。我国是农业大国，年产稻壳4千多万吨，含有天然二氧化硅约720万吨。近几年稻壳热解作为能源，副产的稻壳灰没有得到充分利用，已经成为污染环境的垃圾。如果能够利用稻壳硅作为生产各种二氧化硅的原料，不仅可以解决二氧化硅生产的原料来源问题，而且充分利用了稻壳灰，变废为宝。本论文首先研究稻壳热解、热解灰制备高模数水玻璃的工艺条件，再以高模数水玻璃为原料制备高比表面积多孔二氧化硅微球和单分散纳米二氧化硅材料。1.常压碱溶制备高模数水玻璃本章以稻壳为原料通过热解、控制碱的浓度和固液比，在常压下制备出了高模数的水玻璃溶液。(1)采用低温热解稻壳，保持二氧化硅为非晶态的特点，在常压低温条件下制备出高模数水玻璃，液态水玻璃模数最高可达3.44，也可以根据需求调控水玻璃模数。(2)采用增加低温热解时间，彻底脱除热解灰中的焦油，高模数水玻璃产品无色、透明。(3)本实验制备水玻璃的方法与传统工艺比较，低温常压、能耗低、设备投资小，生产工艺流程简单，具有实际应用价值。2.微乳液法制备介孔二氧化硅微米球利用第二章热解稻壳制备出的高模数水玻璃为二氧化硅前驱体，采用微乳液法，通过W/O/W界面反应，制备出了稳定的介孔二氧化硅微米球。(1)产物球形完整，粒径均匀且尺寸可调节。转速控制在12000rpm，乳化时间为5min，微球粒径约为5μm。(2)二氧化硅微球具有孔隙丰富的三维网状结构，通过加入沉淀剂和造孔剂的作用，调节其质量比为SiO2:PEG:NH4Cl=10:1:40，所得介孔比率达到80%以上，比表面积高达970m2·g-1。经过洗涤和煅烧，有机试剂脱除完全，球体纯度高。(3)本章实验首次实现了以稻壳中的无定形二氧化硅为原料，制备出形貌规则的微米级二氧化硅球型粒子，也是将其转变成功能材料的一个重要突破。3.溶胶-凝胶法制备单分散纳米二氧化硅通过溶胶-凝胶法和水热反应相结合制备单分散多孔纳米二氧化硅粒子。干燥过程采用冷冻干燥脱水及有机溶剂脱水。(1)调节水玻璃的浓度为，用3mol/L的H3PO4溶液以0.2mL/min的速度滴定，所得胶体在120C进行水热反应，反应时间为22h，可得纳米级二氧化硅粒子可呈单分散状态，纳米粒子粒径可控制在20nm左右，克服了二氧化硅粒子易团聚、黏连的特点。(2)纳米二氧化硅粒子具有高的比表面积，孔径分布集中，加入表面活性剂可使其性能提高。(3)采用冷冻干燥技术，防止了干燥过程造成的孔道塌陷，保证了二氧化硅的孔道完整结构。本论文通过系统的实验研究，首先将稻壳中的二氧化硅制备成高模数水玻璃，再以其为原料，制备出高性能介孔二氧化硅微米球和单分散的纳米二氧化硅，充分利用了稻壳中的二氧化硅资源，为稻壳硅的利用提供了广阔的前景，更为功能性二氧化硅材料的制备提供了崭新的方案。更多还原

【Abstract】 Silica is an important functional material, which has broad application fields andgreat market demand. Many problems impeded the growth of the silica industry.(1)The quartz sand was used as the raw material to produce silica. In recent years, highgrade quartz is running short, and low grade quartz which is hard to purify is growing.High grade silica is facing to make bricks without straw.(2) Sodium silicate isprepared via reaction of quartz sand and sodium hydroxide at1300~1500°C. Hightemperature required high consumption of energy, which accounted more than70%ofthe total cost, belongs to the high energy consumption industry.(3) High temperaturereaction of quartz and sodium hydroxide is accompanied by massive carbon dioxidewhich resulted the greenhouse effect. Looking for renewable raw materials anddeveloping green synthesis process have been a crucial research topic recently.China is a large agricultural country, which produce40million tons of rice huskannually. The yield of silica from rice husk is7.2million tons. Rice husk waspyrolyzed as a source of energy, and the by-product rice husk ash which turned intothe waste of the environment was not fully leveraged. The biosilica of the rice husk asthe raw material to produce various silicas not only solved the resource of rawmaterials, but also made full use of rice husk, which shifted the waste material ofvalue.Firstly, this thesis researches the technological conditions of sodium silicate withhigh modulus which was produced by pyrolyzed rice husk. Then sodium silicate wasused to produce porous silica microspheres with high specific surface area andmonodisperse nanoporous silica.1. Preparation of sodium silicate with high modulus using alkali-solution underatmospheric conditions In this chapter, the sodium silica with high modulus was produced, which used ricehusk as raw materials via pyrolysis and the control of the concentration of alkalinesolution and the impregnation ratio.(1) The characteristics of amorphous silica was kept under the low-temperaturepyrolysis of rice husk. The sodium silicate was produced under atmospheric pressureand low temperature conditions, and the highest modulus was3.44, which could becontrolled on demand.(2) The sodium silicate was colourless and transparent by increasing the pyrolysistime at low temperature and removing the tar of the pyrolysis ash completely.(3) The advantage of this study is under atmospheric pressure and low temperaturecondition, low energy consumption, small investment, simple production process,wide application and high efficiency compared with the traditional process.2. Preparation of mesoporous SiO2microspheres using microemulsion methodThe sodium silicate derived by pyrolysis process of rice husk was used as theprecursor to prepare silica. The stable mesoporous silica microspheres were preparedusing microemulsion method by interfacial reaction.(1) The morphology of the particle is entirely spherical, and the size of the particlewas uniform and controllable. The particle size is about5μm at12000rpm rotationnumber for5min emulsification.(2) The silica spheres have three-dimensional network structure with rich pores.The mass ratio of SiO2:PEG:NH4Cl was10:1:40. The proportion of mesopore wasmore than80%and the specific surface area reached979m2·g-1by adding precipitantand pore-making agent. After washing and calcining, the purity of the particle washigh with organic reagent removed completely.(3) In this chapter, the regular morphology silica spheres were firstly prepared fromamorphous biosilica in the rice husk turned into functional material, which was asignificant breakthrough.3. The sol-gel process of preparing monodisperse nano-silicaMonodisperse nano-silica was produced by combining sol-gel method withhydrothermal reaction. The drying methods as freeze drying and the dehydration of organic solvents were used.(1) Sodium silicate solution was diluted and precipitated by3mol/L H3PO4at thespeed of0.2mL/min. The gel reacted in hydrothermal condition at120C for22h.The size of the nano-silica was about20nm and monodispersed mostly, whichovercame the character of agglomeration.(2) The specific surface area of the nano-silica is high and the pores distributedconcentrated. These characters increased with the surface-active agent added.(3) The freeze drying was used to ensure the integrity of the pore structure andprevent collapse of the pore during drying process.A variety of high value-added materials included sodium silicate with high modulus,mesoporous silica microsphere and monodispersed nano-silica were obtained byseries of experimental researches. This study provides a new solution which exploitedthe most value of renewable resources for the comprehensive utilization of silica inrice husk.更多还原