超微孔氧化铝基材料的制备及性能研究

发布时间：2018-02-16 11:16

  本文关键词： 超微孔 氧化铝 脂肪醇聚氧乙烯醚 选择性催化还原反应　出处：《太原理工大学》2015年博士论文　论文类型：学位论文

【摘要】：氧化铝作为催化剂或催化剂载体，在石油化工、有机合成、精细化工等领域具有广泛的用途。传统的γ-Al2O3比表面较低且孔径较大、孔分布较宽而不能充分满足在催化过程中对选择性、稳定性、反应接触面积等有特殊要求的反应。因此，合成具有更大比表面积、较小孔径和较窄孔分布的氧化铝分子筛具有重要意义和广阔的应用前景。 文献所报道的采用溶胶凝胶法、水热合成法、沉淀法、微乳液法、双水解法、硬模板法等得到氧化铝前驱体，然后通过煅烧或者溶剂萃取的方法除去模板剂分子后得到氧化铝孔材料，其合成路线大多比较复杂，成本较高不易工业放大或生产。目前国内外鲜有软模板合成微孔级氧化铝的报道和应用。我们通过采用溶胶凝胶溶剂挥发诱导自组装法，以廉价的表面活性剂脂肪醇聚氧乙烯醚为模板剂，制备出超微孔级（孔径1-2nm）氧化铝材料突破了传统氧化铝材料孔径尺寸的限制，通过简单改变有限的反应条件就能有效地控制前躯体的聚集形态，而产生超微孔结构，从而改变氧化铝的孔径尺寸和性能，以扩大其应用范围。 超微孔(super-microporous)氧化铝基材料的孔径介于微孔和介孔之间，其所特有分子择形性能，将会在包括重油精制处理、新特种化学品发展、分子反应有特殊要求的催化反应和制药前驱体的合成等方面发挥其特有的优越性。但目前对于此方面的研究尚处于起步阶段，如合成所用的模板剂较昂贵不易获得或环境非友好；很难合成出具有热稳定性和催化活性兼备的微孔级氧化铝基材料等。因此，，寻找价格适宜、性能优越、环境友好的模板剂，不断地优化和完善其合成工艺和合成路线已成为当前亟待解决的问题，以使其最终能达到实际生产应用的目的。 本论文以非离子表面活性剂脂肪醇聚氧乙烯醚AEO-7为模板剂，采用溶剂挥发自组装方法，成功制备出超微孔高比表面积微晶氧化铝材料。该材料比表面积超过650m2/g，孔分布相对集中，平均孔径在1.0-2.0nm之间，且具有较强的路易斯酸性，选区电子衍射显示其为晶体结构。合成所用模板剂原料廉价易得，且合成路径简便直接，环境友好。同时，较系统的考察了模板剂添加量、无机酸量、有机羧酸类型等因素对材料制备和孔结构的影响。 在成功制备出微孔级氧化铝基础上，运用一锅法将Zr组分引入Al2O3的结构中，形成复合金属氧化物微孔材料。由于Zr组分的引入，抑制了氧化铝的晶相转变和晶粒团聚，使氧化铝的晶相在1200℃才转变为γ-Al2O3，相对于普通γ-Al2O3在500℃左右晶相的生成，较大幅度的延迟了氧化铝晶相的转变温度。微孔氧化铝材料在600℃焙烧后，即转变为介孔材料，而添加适量的锆组分后，即使经过900℃焙烧，仍然能保持具有微孔结构，从而提高了其热稳定性能。 同时，本文运用P123和AEO-7复合模板剂成功制备出含有中微孔的氧化铝基材料，并详细考察了各模板剂不同含量对材料孔结构的影响变化规律。同单一模板剂相比，复合模板剂所制备材料的热稳定性大大提高，900℃焙烧后，比表面积仍然有188m2/g。并能根据实际需要通过改变不同模板剂的含量对其孔径和孔分布进行有效的调变。 采用原位合成法或浸渍法引入活性组分CuO,成功制备出超微孔基铜铝基脱硝催化剂。并系统考察了不同活性组分含量催化剂的结构和性能，及其在甲烷选择性催化还原NO反应中的活性及规律。氮吸附结果显示两种制备方法的铜铝基催化剂主体都是微孔材料，具有高的且稳定的催化活性。原位合成引入铜的摩尔分率不低于15%或浸渍法铜的摩尔分率不低于5%时，以甲烷（CH4）为还原剂，反应温度超过400°C，转化率随温度的增加而明显提高，当温度达到600°C时，NO的转化率接近100%。并且在无还原剂甲烷参与的条件下，该催化反应能将部分NO直接分解转化为N2，是目前铝基脱硝催化剂鲜有报道的。
[Abstract]:As a catalyst or a catalyst carrier , the alumina has wide application in the fields of petrochemical industry , organic synthesis , fine chemical engineering and the like . The traditional gamma - Al2O3 has low specific surface and large pore size , and has wide pore distribution , and can not fully meet the special requirements for selectivity , stability , reaction contact area and the like in the catalytic process . An alumina precursor is prepared by sol - gel method , hydrothermal synthesis method , precipitation method , microemulsion method , double hydrolysis method and hard template method . The pore size of super - microporous aluminum oxide - based material is between the micropores and the mesoporous . Its specific molecular - selective properties will exert its unique advantages in the synthesis of catalytic reactions and pharmaceutical precursors including heavy oil refining , new special chemical development , molecular reaction , special requirements for molecular reactions , etc . It is difficult to synthesize the microporous grade aluminum oxide based materials with thermal stability and catalytic activity . Therefore , it is difficult to synthesize the template agent with good thermal stability and catalytic activity . Therefore , it is difficult to synthesize the template agent with good thermal stability and catalytic activity . Therefore , it is difficult to synthesize the template agent with good thermal stability and catalytic activity . Therefore , it is difficult to synthesize the template agent with good thermal stability and catalytic activity . Therefore , it is difficult to synthesize the template agent with good thermal stability and catalytic activity . Therefore , it is difficult to synthesize the template agent with good thermal stability and catalytic activity . Therefore , it is difficult to synthesize the template agent with good thermal stability and catalytic activity . Therefore , it is difficult to synthesize the template agent with good thermal stability and catalytic activity . Therefore , it is difficult to synthesize the synthetic technology and synthetic route which is urgently needed to be solved , so that it can finally achieve the purpose of practical production application . This paper uses non - ionic surfactant fatty alcohol polyoxyethylene ether AEO - 7 as template agent , and adopts solvent volatilization self - assembly method to successfully prepare ultra - microporous high specific surface area microcrystalline alumina material . The specific surface area of this material is more than 650m2 / g , the pore distribution is relatively concentrated , the average pore diameter is between 1.0 and 2.0nm , the average pore diameter is between 1.0 and 2.0nm , and the synthetic route is simple and direct , and is environment - friendly . On the basis of the successful preparation of microporous - grade alumina , the Zr component is introduced into the structure of Al2O3 by one - pot method . As the Zr component is introduced , the phase transition and grain agglomeration of the alumina are inhibited , and the transformation temperature of the alumina crystal phase is greatly delayed by the generation of the crystal phase at 1200 DEG C . At the same time , using P123 and AEO - 7 composite template agent to successfully prepare alumina - based material containing mesoporous silica , the influence of different content of template agent on the pore structure of material is investigated in detail . Compared with single template agent , the thermal stability of the prepared material is greatly improved . After calcination at 900 鈩

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