【作者】 邓庆芳；

【导师】 袁忠勇；

【作者基本信息】 南开大学 ， 物理化学， 2013， 博士

【摘要】 化能,从而提高了催化剂的催化活性。此外,Ce的加入还增强了催化剂的稳定性,反应60h后,催化剂的活性得以良好地保持。以不同结构的碳材料为载体,制备得到了负载型Ni基催化剂,对所得的Ni/carbon催化剂进行了Mn改性处理,得到Mn-Ni/carbon催化剂。另一方面,先在不同结构载体上引入Mn,对不同结构的碳载体进行刻蚀,后制备得到了负载型Ni/Mn-carbon催化剂。不管是怎样的引入方式,Mn的加入都有效地提高了催化剂的氨分解催化性能,但是,Ni/Mn-carbon催化剂表现出更优良的氨分解催化活性,说明助剂Mn的引入方式对催化剂的催化性能产生重要影响。同时,载体的结构性质也对催化剂的催化性能有很重要的影响。具有高比表面积、大孔体积的介孔碳材料为载体的Ni基催化剂表现出明显高于以活性碳和石墨为载体的Ni基催化剂的氨分解催化性能。载体的介孔结构,Mn的引入都提高了表面Ni的金属分散度,从而进一步提高了催化剂的催化活性。另外,使用玉米棒部分活化后的碳材料为载体,并添加了A1203进行改性,制备得到负载型Ni基催化剂用于氨分解制取无COx氢。考察了A1203的引入方式和不同Ni的负载量的Ni基催化剂的催化性能。Ni/CCW-Al2O3-P催化剂表现出良好的催化性能,600℃时,氨的转化率达到了90%,且明显高寸Ni/CCW-Al2O3-M、Ni/Al2O3和Ni/CCW催化剂的催化活性。载体的孔结构、表面性质阻止Ni粒了的烧结,提高了Ni的分散度,从而提高了催化剂的催化活性。3.CO：捕获：使用介孔硅基材料SBA-15为硬模板,合成了介孔氮化碳材料。所得到的MCN以及MCN/C复合物材料具有高比表面积,大孔体积以及高的N含量(分别为20.5%及24.9%)。MCN/C复合物中碳的引入提高了微孔性,更有利于CO2吸附。高的比表面积和高的N含量均对高的CO2吸附量起到重要作用。MCN/C复合物在常压下,0℃和25℃的吸附量分别为3.05及2.35mmolg-1,同时,所合成的材料具有良好的CO2/N2选择性及循环稳定性,是一种良好的,有前景的CO2吸附材料。同时,以Y型分子筛为模板,使用硬模板法合成了微孔氮化碳,所合成的微孔氮化碳具有高比表面积、大孔体积和高的氮含量(14.4%)。微孔氮化碳表现出高的CO2吸附量,0,25,50和75℃的吸附量分别为2.7,2.2,1.6和1.2mmol g-1。微孔氮化碳进一步使用KOH活化后,所得到的微孔氮掺杂碳材料具有高的比表面积(1045-2623m2/g)和微孔孔容(0.37-0.81cm3/g)。由于大量微孔和含氮官能团的存在,所合成的活化后微孔碳材料表现出十分优异的CO2吸附性能。700℃活化的样品在0℃时CO2的吸附量可达5.9mmolg-1,25℃时达到3.9mmol g-1。在较高的温度下,活化的微孔碳材料依然保持了高的CO2吸附量,50和75℃的吸附量分别为2.7和1.9mmol g-1。而且,所合成的含氮微孔碳材料还表现出很好的选择性吸附能力和再生能力。使用可持续性材料的卷烟厂的废烟丝为原料,合成了具有高CO2吸附性能的价格低廉的活化碳材料。高CO2吸附量,良好的C02/N2选择性和循环稳定性表明所得到的烟丝活化碳材料是一种非常具有应用前景的吸附剂。对材料的小微孔孔径分布和CO2吸附量进行分析发现,孔径约为0.55nm处的微孔体积对常压下CO2吸附的影响很大。另外,孔径<0.7nm的微孔体积与CO2吸附量之间呈线性关系,表明这一范围内的微孔可以成为评估CO2吸附能力的标准,也可以为新型CO2吸附剂的设计提供一定的理论依据。更多还原

【Abstract】 Recently, the environment and energy problem have gathered much attention. Volatile organic compounds (VOCs), emitted from a variety of industrial processes and transportation activities, are considered as an important class of air pollutants. As a typical greenhouse gas, CO2has drawn considerable attention in recent years because of its rapidly increasing concentration in the atmosphere and the concern about the global warming effect. For these reasons, our mian researching content is divided into the following sections:1. VOCs total catalytic oxidation:Mesoporous manganese oxide nanoparticles with the phases of tetragonal hausmannite, mixture of hausmannite Mn3O4and monoclinic Mn5O8, and bixbyite Mn2O3have been prepared by calcination of manganese acetate hydrate precursor at200,300,400and700℃, respectively, all which were found to be active for catalytic total oxidation of toluene. Their catalytic behavior depended on the oxidation state of manganese, the oxygen mobility and the amount of surface adsorbed oxygen species. The400℃-calcined mesoporous nanoparticles exhibited the highest catalytic performance with the complete toluene conversion temperature of275℃, suggesting that incorporating Mn5O8into Mn3O4could promote oxygen mobility, increase the amount of surface adsorbed oxygen and facilitate the activation of surface oxygen for the oxidation of toluene. Mesoporous CexZr1-xO2solid solutions were prepared and used as support of CuO nanocatalysts for catalytic oxidation of CO and toluene. The prepared CuO/CexZr1-xO2catalysts have wormhole-like mesoporous structure with high surface area and uniform pore size distribution. The intermediate doping of ZrO2in CeO2promotes the dispersion of active copper species and enhances the reducibility of copper species. The effect of Ce/Zr ratio, calcination temperature and CuO loading amount on the catalytic performance of CuO/CexZr1-xO2were investigated in detail. The400℃-calcined8CuO/Ce0.8Zr0.2O2catalyst exhibits the highest activity with the complete toluene conversion temperature of275"C. The interfacial interaction between CuO and the CexZr1-xO2support, high dispersed CuO nanoparticles may contribute to the high catalytic activity of CuO/CexZr1-xO2.2. Ammonia decomposition reaction:Three kinds of Ce0.8Zr0.2O2solid solutions synthesized via surfactant-assisted route, co-precipitation, and sol-gel method were used as supports of Ni-based catalysts by impregnation. Their catalytic activities in ammonia decomposition to hydrogen were tested, and the structural effect of support and the influence of nickel content on catalytic activity were evaluated. Mesoporous/high-surface-area Ceo.sZro.2O2support synthesized by surfactant-assisted method exhibited better promoting effect than other supports when the same content of Ni was loaded. The interactions between Ni species and Ce0.8Zr0.2O2supports were found to greatly affect the chemical properties of catalysts, including redox, H2adsorption, and catalysis. The promoting effects of Ce in catalysts, plentiful vacancies in the solid solutions due to the doping of Zr4+, and high surface areas of the supports were discussed on the ammonia decomposition activities of the resultant catalysts, as well as the influence of hydrogen spillover. The ammonia conversion of95.7%with the H2producing rate of89.3mL/min-gcat was achieved at550℃over the Ni catalysts supported on the mesoporous/high-surface-area Ce0.8Zr0.2O2.A series of nano-sized Ni/ATP and Ce-Ni/ATP-y catalysts that possess high activities for NH3decomposition have been successfully synthesized by a co-precipitation method. The catalytic performance was investigated under the atmospheric conditions and a significant enhancement in the activity after the introduction of Ce was observed. The highest conversion of ammonia could be obtained when the Ce/Ni ratio was around0.1. All of supported Ni samples exhibit a pure cubic NiO crystalline phase, after H2reduction correspond to cubic Ni, and appropriate loading of CeO2could suppress the growth of Ni0on the surface. The presence of cerium could improve the dispersion of Ni, suppress Ni sintering, decrease the apparent activation energies (Ea), and facilitate the recombinative desorption of nitrogen adatoms from the surface of catalyst, which is beneficial to enhance the catalytic performance on ammonia decomposition.The Mn-doped Ni/carbon catalysts with different structural carbon were prepared by a deposition-precipitation method using KMnO4as the precursor and investigated by N2-adsorption, XRD, TG-DTG and H2-TPD techniques. The prepared catalysts are efficient for the generation of COx-free H2through ammonia decomposition. The presence of Mn was found to significantly enhance the catalytic activity of Ni/MC catalysts. The Ni/Mn-MC catalyst exhibited higher catalytic activity than Mn-Ni/MC catalyst; such an effect is strongly dependent on how Mn is introduced into the system. Moreover, the influences of the porous structures of carbon supports on the activities of the catalysts were examined. The catalytic activity over supported Ru catalysts is ranked as Ni/Mn-MC> Ni/Mn-AC> Ni/Mn-GC. On the support side, the porous structure of the carbons is critical to the activity of the supported Ni catalyst. Moreover, the prepared Ni/CCW-Al2O3-P catalyst were employed the pine waste (i.e. product of the imperfect combustion of pine) as a precursor of carbon and formed a novel structural support consisting of carbon coated with a layer of mesoporous alumina. Subsequently, we had dispersed Ni by the deposition-precipitation method and the catalysts were characterized by XRD, N2adsorption, TG-DTA, and H2-TPD techniques. The catalytic properties of the as-prepared catalysts were evaluated by generation of hydrogen via ammonia decomposition. The Ni/CCW-Al2O3-P catalyst is low cost and exhibits high activity, achieving90%conversion of pure NH3at a temperature at873K. Notably, the conversion of Ni/CCW-Al2O3-P catalyst is significantly higher than that of the corresponding Ni/CCW, Ni/Al2O3and Ni/CCW-Al2O3-P samples. The pore structure and surface properties of the support may prevente the sintering of Ni nanoparticles, enhance Ni dispersion and consequently improve catalytic activity.3. CO2capture:Mesoporous carbon nitride (MCN) and carbon nitride-carbon (MCN/C) composites with a partly graphitized structure are synthesized by using mesoporous silica SBA-15as a hard template and ethylenediamine and carbon tetrachloride as precursors, possessing uniform mesopore size of6.3nm, high surface area of278-338m2/g, and high nitrogen content of20.5-24.9%with abundant basic sites. The synthesized MCN and MCN/C composites are used as adsorbents for CO2capture, showing high adsorption capacity and good reusability. The presence of carbon coating layer in MCN/C composites introduced more micropores, which favored the capture of CO2, exhibiting high CO2capture capacity of3.05mmol/g at0℃and760mmHg and2.35mmol/g at25℃and760mmHg, with good CO2/N2selectivity and excellent regeneration stability. The microporous N-doped carbon (MNC) is synthesized by using zeolite Y as a hard template and ethylenediamine and carbon tetrachloride as precursors, possessing high surface area of425m2/g with micropore volume of0.17cm3/g and showing high CO2adsorption capacity of2.7mmol g-1at0"C and2.2mmol g-1at25℃and1.6mmol/g at50℃and1.2mmol/g at75℃at760mmHg, respectively. The activating agent KOH is utilized to improve the surface area and micropore volume, and the surface areas and micropore volumes of activated microporous N-doped carbons (AMNC) are up to1045-2623m2/g and0.37-0.81cm3/g, respectively. The chemical activation with KOH could introduce more micropores, which favored the capture of CO2, and the AMNC-700exhibit high CO2capture capacity of5.9mmol/g at0℃and3.9mmol/g at25℃and2.7mmol/g at50℃and1.9mmol/g at75℃at760mmHg, with good CO2/N2selectivity and excellent regeneration stability. Cost-effective biomass-derived activated carbons with a high CO2adsorption capacity are attractive for carbon capture. Tobacco was found to be a suitable precursor for activated carbon preparation through KOH activation. The KOH/C mass ratio and activation temperature had a significant impact on CO2adsorption. The tobacco-derived activated carbon had a high adsorption capacity and excellent selectivity for CO2, and also the adsorption process was highly reversible. The adsorbed amount of CO2on the activated carbon was up to7.0mmol g-1at273K and1bar, which was higher than almost all carbon materials. The pore characteristics of activated carbons responsible for high CO2adsorption were fully investigated. Based on the analysis of narrow micropore size distribution of several activated carbons prepared under different conditions, a more accurate micropore range contributing to CO2adsorption was proposed. The volume of micropores<0.7nm had a good linear relationship with CO2adsorption at273K and1bar, and the narrow micropores of about0.55nm produced the major contribution, which could be used to evaluate CO2adsorption on activated carbons.更多还原