【作者】 郭海军；

【导师】 杨民；

【作者基本信息】 大连交通大学 ， 环境科学， 2010， 硕士

【摘要】 甲烷二氧化碳重整反应对于缓解能源危机、保护环境具有重要的科学意义。它不仅可以制备低H2/CO比（<1）的合成气,为费托合成及其他深度转化提供理想的原料,同时这一过程有利于控制甲烷和二氧化碳这两种温室气体的排放。常规使用的Ni基催化剂易发生积炭和活性组分的流失,导致催化剂活性快速降低,贵金属催化剂由于活性高、抗积炭能力强而成为重整反应研究的一个热点方向。本论文旨在通过载体改性、改进制备方法、添加助剂等过程来制备高分散Pt基催化剂,改善Pt粒子的稳定性,同时提高其抗积炭能力。采用环境友好的离子交换树脂法,通过单因素实验考察得出制备改性纳米MgO载体的最佳条件为:0.2 mol/L的MgCl2溶液,在400 r/min的搅拌下,与体积比为1 : 2.5的树脂在323 K下反应8 h,经抽滤洗涤得Mg（OH）2水凝胶,然后在通N2条件下于673 K焙烧6 h。所制备的MgO具有均匀的六方片状结构,平均粒径为15 nm左右,比表面积可高达105.7 m2/g,适合用作Pt基催化剂载体。采用共浸渍法制备了一系列0.8%Pt-3%CeO₂-3%ZrO₂/MgO催化剂,考察载体改性过程对催化剂性能的影响,通过活性评价,并结合XRD、SEM、BET、CO₂-TPD等手段对催化剂进行了表征。结果表明,由离子交换树脂法制备的Mg（OH）2水溶胶经抽滤、洗涤、393 K普通干燥6 h后所得Mg（OH）2粉作为载体的催化剂具有较大的比表面积,有利于Pt的分散,表现出很好的催化活性。采用分步浸渍法制备了一系列0.8%Pt-3%CeO₂-3%ZrO₂/MgO催化剂,考察活性组分与助剂的浸渍顺序对催化剂性能的影响。XRD测试和活性评价结果表明,先浸Pt有利于提高活性组分在MgO载体上的分散,CeO₂和ZrO₂的添加有助于增强金属-载体间的相互作用,从而使催化剂0.8Pt-3Ce3Zr/MO800-IE、0.8Pt-3Ce3Zr/MO800显示出很高的催化活性;先浸CeO₂和ZrO₂,载体的部分孔道有可能会被ZrO₂所堵塞,尤其是在ZrO₂的添加量较大时,从而减小了金属Pt的分散度,使催化剂活性下降。以MOH（GD）-IE作为载体制备催化剂时,CeO₂和ZrO₂助催化剂添加的最佳质量分数比为1 : 0.33。CO₂-TPD结果表明,这主要是因为CeO₂助剂的添加量越大,载体的碱性位越多,越有利于重整反应的进行。更多还原

【Abstract】 Methane reforming with carbon dioxide has important scientific significance on mitigating the energy crisis and protecting the environment not only because it yields syngas with low H2/CO（<1） desirable for Fischer-Tropsch synthesis and other depth conversion, but also because it is beneficial to control the emission of greenhouse gas CH4 and CO₂. Owing to the rapid deactivation resulted from carbon deposition and loss of active components on the conventional Ni-based catalysts, the noble catalysts with higher activity and stability have been attracting enormous interest. This paper is focused on the preparation of highly dispersed Pt-based catalysts by support modification, improvement of preparation method and addition of promoter, which can reduce the cost of Pt, improve the stability and resistence to carbon deposition of the catalysts.The optimal conditions of modified nano-MgO support which is prepared by environmental friendly ion exchange resin method are obtained from monofactor experiment study for the first time as follows: under continuous stirring of 400 r/min, 100 mL MgCl2 solution of 0.2 mol/L is added to 250 mL 201×7 strong-base anion exchange resin to react for 8 h at 323 K, the Mg（OH）2 hydrogel is obtained after vacuum filtrating and washing, and then calcined at 673 K for 6 h under nitrogen atmosphere. The obtained nano-MgO has a regular hexagonal lamellar morphology with an average diameter of 15 nm and SBET of 105.7 m2/g, which is suitable to act as Pt-based catalyst support.In order to investigate the effect of the support modification process on catalysts performance, a series of 0.8%Pt-3%CeO₂-3%ZrO₂/MgO catalysts are prepared by co-impregnation method, and their characterization and the performance of CO₂ reforming CH4 are investigated by activity measurement, XRD, SEM, BET and CO₂-TPD et.al. Experiment results reveal that the catalysts supported on Mg（OH）2 powder which is generated from Mg（OH）2 hydrosol after vacuum filtration and general drying at 393 K for 6 h have larger surface area and show higher Pt metal dispersion and catalytic activity.In order to investigate the effect of the impregnation order between the active component and promoter on catalyst performance, a series of 0.8%Pt-3%CeO₂-3%ZrO₂/MgO catalysts are prepared by seq-impregnation method. XRD and activity evaluation results indicate that, when Pt is impregnated firstly, and then promoter CeO₂ and ZrO₂ which can contribute to the improvement of metal-support interaction, the prepared catalysts 0.8Pt-3Ce3Zr/MO800-IE and 0.8Pt-3Ce3Zr/MO800 have better dispersion of Pt metal on MgO, thus show high catalytic activity. However, the catalytic activity reduces when the impregnation order is opposite, because some pore channels of MgO may be blocked, especially in the case of large amount of ZrO₂. When the catalysts are prepared using the MOH（GD）-IE as the support, the optimum mass ratio of CeO₂ to ZrO₂ promoter is 1 : 0.33. According to the CO₂-TPD result, this is mainly because the large additive amount of CeO₂ results in the increase of basic sites of support, consequently, the reforming reaction is easily performed.更多还原