【作者】 胡全红；

【导师】 黎先财；

【作者基本信息】 南昌大学 ， 工业催化， 2012， 博士

【摘要】 甲烷的二氧化碳催化重整制合成气被认为是实现甲烷、二氧化碳两大温室气体资源化利用的有效途径。Ni基催化剂对该反应具有良好的催化活性,并且价格低廉,然而Ni基催化剂在该反应中存在的一个关键问题是易于积炭失活。钛酸钡是具有钙钛矿结构的复合氧化物,结构和组成具有多样性,已被广泛应用于催化领域。制备BaTiO3基(复合)载体既可扩大BaTiO3的比表面积,又能使(复合)载体获得适合气固相催化反应特殊的宏观结构,有利于负载型催化剂性能的提高。本论文采用不同的方法制备了BaTiO3基载体,并对其宏观结构进行考察分析,以催化二氧化碳重整甲烷制合成气反应为探针,研究了不同BaTiO3基载体负载的BaTi1-xNixO3、Ni/BaTiO3-Al2O3催化剂的活性以及抗积炭、稳定性能,同时第6章还特别考察了溶胶-凝胶法和镧助剂对Ni基催化剂的宏观物性、表面性质及催化性能的影响。采用XRD、FT-IR、SEM、 TEM、EDS、N2吸附、TG、TPR、TPD、XPS、和CO2脉冲等方法对BaTiO3基载体及其负载镍催化剂进行了表征。1.以溶胶-凝胶法制备了一系列的BaT1-xNixO3(x=0.025,0.075,0.125,0.175和0.225)钙钛矿型复合氧化物。结果表明：在空气中800℃煅烧3h后,BaTi1-xNixO3试样获得了钙钛矿型复合氧化物的结构。在原位氢气还原后,BaTi1-xNixO3催化剂表面存在晶粒尺寸为10nm左右的金属单质镍。在CH4/CO2催化重整反应测试中,随催化剂中镍含量的增加,催化剂的活性增加,当x达到0.175后,催化剂的活性变化不显著。试样中BaTi1-xNixO3(x=0.175)催化剂的性能最佳。2.以溶胶-(干)凝胶法先获得BaTiO3及γ-AI2O3的(干)凝胶,然后将二者充分混合后再以热分散法合成出不同BaTiO3含量的wt.%BaTi03-Al203复合载体。结果表明：wt.%BaTiO3-Al2O3复合载体中,BaTiO3粒子以不连续间隔的方式分散在γ-A12O3的表面；同时,γ-A12O3的表面上BaAl2O4尖晶石相与BaTiO3相共存可能阻止了Ni/wt.%BaTiO3-Al2O3催化剂中NiAl2O4尖晶石的产生,改善了镍基催化剂的催化性能。在690℃温度下进行催化二氧化碳重整甲烷的测试表明,低温下Ni/BaTiO3催化剂的抗积炭和稳定性很差,论文认为这主要是源于Ni/BaTiO3催化剂过强的供电子强度以及由此在低温下导致的一氧化碳歧化反应所致。与Ni/BaTiO3催化剂相比较,添加了BaTiO3组分的Ni/wt.%BaTiO3-Al2O3催化剂,其活性组分镍的分散度较高,并且其(表面)NiOx物种的电子供给强度相对被削弱了；因此,Ni/32.4%BaTiO3-Al2O3催化剂获得较低温度下催化二氧化碳重整甲烷反应高活性、优异的稳定性和抗积炭性能。3.以CTABr为结构导向剂,采用溶胶-凝胶法制备了系列BaTiO3-BaAl2O4-Al2O3复合载体；结果表明,BaTiO3-BaAl2O4-Al2O3复合载体具有多孔织构特性和较高的比表面积,BaTiO3和BaAl2O4以晶粒状态分布在复合载体的内外表面,晶粒尺寸在20～50nm的范围,复合载体孔径为10～20nm。复合载体上BaTiO3和BaAl2O4的引入,适度削弱了Ni/BaTiO3-BaAl2O4-Al2O3催化剂中Ni物种与y-Al2O3间的强相互作用,抑止了NiAl2O4尖晶石的生成；当载体中Ba(Ti)含17.33%时,其负载的Ni催化剂上对CH4/CO2重整制合成气反应活性和稳定性最佳。4.采用溶胶-凝胶法和添加镧助剂制备了BaTiO3载体负载的不同镍基催化剂,并以甲烷的二氧化碳催化重整制合成气反应评价了催化剂的性能。结果表明,与等体积浸渍法制备的镍基催化剂相比较,溶胶-凝胶法制备的催化剂比表面积更大,催化剂活性更高,抗积炭性能更好；溶胶-凝胶制备法和添加镧助剂使得催化剂的CO2-TPD温度降低并H2-TPD温度升高,催化剂表面碱性有所减弱,镍物种晶粒和氢气易于发生还原反应；另外,还考察了镧助剂对镍基催化剂的改性作用,结果发现镍含量为5%(wt.%)、镧含量为0.75%(wt.%)的0.75NLBT催化剂性能最佳。更多还原

【Abstract】 The methane catalytic reforming with carbon dioxide to synthesis gas has been suggested as an effective route to realize the resource utilization of methane and carbon dioxide, the two main greenhouse gas. The low cost Ni-based catalyst owns the well catalytic activity for the reaction of dry reforming of methane. However, the Ni-based catalyst is prone to deactivation, which is a key problem, due to the carbon deposition during the catalytic reforming reaction.The barium titanium oxide is a kind of composite oxide with the perovskite structure.The barium titanium material has been extensively used in the field of catalysis. The preparation of BaTiO3-based (composite) support can both increase the specific surface area of BaTiO3and make the (composite) support get a special macrostructure which is suitable for the gas-solid phase catalytic reaction, and is benefit for the improvement of catalyst performance.In this dissertation, the BaTiO-based supports were prepared by various methods and the macrostructure of the BaTiO3-based supports were investigated. Moreover, the activities, the anti-coking properties and the catalytic stabilities of BaTiO3-based supports supported BaTi1-xNixO3、Ni/BaTiO3-Al2O3Ni/BaTiO3-BaAl2O4-Al2O3catalysts were studied by the probe reaction of methane catalytic reforming with carbon dioxide to synthesis gas. Meanwhile, the effects of sol-gel method and La addition on the macro-properties, the surface properties and the catalytic performance of the catalysts were studied particularly in the sixth chapter.The BaTiO3-based supports and their supported nickel catalysts were characterized by means of XRD, FT-IR, BET, SEM, N2adsorption,EDS, XPS, TPR, TG, TPD、CO2pulse etc.1. A series of Ni-doped perovskite oxides BaTii-xNiO3were prepared by sol-gel method and characterized by XRD and TPR, and their catalytic performances for CO2reforming of CH4were evaluated. The results showed that the BaTi1-xNixO3samples possessed the characteristic perovskite structure after calcined in air at800℃for3h, and as they were reduced in situ by hydrogen some nickel crystallites of about10nm in size existed on the surface of the catalysts. The catalysts activities increased with the increase of nickel contents for the reaction of CH4reforming with CO2; however, the changes of the catalysts activities are not obvious as the x value of BaTi1-xNixO3reached0.175. The BaTi1-xNixO3catalyst with the x of0.175had the best performance.2. Wt.%BaTiO3-Al2O3(wt.%BaTiO3=0～100%) composite supports were synthesized through varying the BaTiO3content by the "sol-(xero)gel" method. Ni/wt.%BaTiO3-Al2O3nickel-based catalysts prepared by incipient wetness method were evaluated for dry reforming of methane carried out between690℃and800℃. The results demonstrate that BaTiO3particles are discontinuously dispersed on the surface of γ-Al2O3in the form of individual isolated particles for the wt.%BaTiO3-Al2O3composite supports. Meanwhile, the coexistence of BaAl2O4spinel phase with the BaTiO3phase on the surface of γ-Al2O3probably inhibits the Ni/wt.%BaTiO3-Al2O3catalysts from the formation of NiAl2O4spinel phase, improving the catalytic performance of the catalysts. The Ni/BaTiO3catalyst showed poor stability and severe coke formation in the dry reforming of methane tested at690℃, which was thought to be mainly originated from the excessive strong electronic donor intensity of Ni/BaTiO3catalyst as well as the resulted CO disproportionation reaction. Compared with the Ni/BaTiO3catalyst, the Ni/wt.%BaTiO3-Al2O3catalysts with the addition of BaTiO3had a higher dispersion of active nickel and a weakened electronic donor intensity of the NiOx species. As a result, the synthesized Ni/32.4%BaTiO3-Al2O3catalyst exhibited a high catalytic activity, excellent stability as well as coking resistance for lower temperature dry reforming of methane.3. A series of BaTiO3-BaAl2O4-Al2O3composite supports were prepared by the sol-gel method using hexadecyltrimethylammonium bromide as the structure template. The BaTiO3-BaAl2O4-Al2O3composite supports were characterized by X-ray diffraction, infrared spectroscopy, N2adsorption-desorption, transmission electron microscopy, and H2temperature-programmed reduction. The catalytic performance of the Ni/BaTiO3-BaAl2O4-Al2O3catalyst was investigated by CH4reforming with CO2. The results showed that the BaTiO3-BaAl2O4-Al2O3composite supports own a porous texture and high specific surface area, the BaTiO3and BaAl2O4phases, whose crystalline size is in the range of20～50nm, exist on the inside and outside surface of the composite support in the form of crystalline particles. The size of micropores of the composite support is10～20nm, The presence of both BaTiO3and BaAl2O4phases on the surface of the composite support weakens the strong interaction between the nickel species and γ-Al2O3of the Ni/BaTiO3-BaAl2O4-Al2O3catalyst, and the possibility of the formation of NiAl2O4spinel is decreased. The Ni/BaTiO3-BaAl2O4-Al2O3catalyst with17.33%Ba (Ti) content showed the excellent activity and stability for CH4reforming with CO2to synthesis gas.4. The various BaTiO3supported nickel-based catalysts were prepared by the sol-gel method/or modified by the addition of La, and the catalytic performance of the nickel-based catalysts were evaluated by the reaction of CH4reforming with CO2to synthesis gas. Compared with the catalysts prepared by impregnation method, the results indicated that the catalysts prepared by sol-gel method had a larger specific surface areas, exhibited higher catalytic activities and perfect performance of anti-coking. The decrease of CO2-TPD temperature and the increase of H2-TPD temperature of the catalysts indicated that the surface alkalinity of the catalyst is lowered and the reduction reaction between hydrogen and nickel crystalline particles of the catalyst is easy to take place. In addition, the modification effect of rare earth La addition was investigated, and it was found that the0.75NLBT catalyst with the composition of5wt%Ni-0.75wt%La owns the optimum catalytic performance.更多还原