【作者】 刘晓晖；

【导师】 王艳芹；

【作者基本信息】 华东理工大学 ， 工业催化， 2011， 博士

【摘要】 “石油危机”的出现以及化石能源利用所带来的环境和气候变化问题,使得世界能源战略的重点开始转向可再生清洁能源的研究和开发,其中氢能作为一种清洁、高效、安全、可持续的新能源,被视为二十一世纪最具发展潜力的新能源。2002年,Dumesic研究小组报道了生物质衍生物—多元醇水相重整制氢的工作,将氢能与可再生的生物质资源联系起来,以实现温室气体—CO2的零排放,引起了研究人员的广泛关注。本论文选择最简单的多元醇分子—乙二醇为反应模型原料,从负载型Pt催化剂入手,研究了载体的种类及制备方法对乙二醇水相重整反应催化性能的影响,并通过设计不同的反应及各种表征手段对乙二醇水相重整反应的机理进行了初步探讨,加深了对乙二醇水相重整反应的认识。通过不同温度焙烧拟薄水铝石(AlOOH)得到y-Al2O、δ-Al2O3和α-Al03载体。将等体积浸渍法制备的Pt/γ-Al2O3、Pt/δ-Al2O3和Pt/α-Al203催化剂用于乙二醇水相重整反应,其催化活性顺序为Pt/α-Al2O3> Pt/δ-Al2O3> Pt/γ-Al2O3。在225℃,29.0KPa和乙二醇水溶液(乙二醇的体积百分比为10%)进液流速为6ml/h的条件下,负载量为1%的Pt/α-Al2O3催化乙二醇水相重整反应的产氢速率达到452μmol·min-1·gCat-1。XRD、H2-TPR、TEM-EDX、CO化学吸附和XPS等表征结果表明,与Pt/γ-Al2O3和Pt/δ-Al2O3催化剂相比,Pt/α-Al2O3催化剂表面没有含氯铂物种的存在,避免了氯的最终去除导致的Pt颗粒的烧结,提高了催化剂表面Pt的分散度；此外,Pt与羟基较少的α-Al203载体发生较强的相互作用使Pt/α-Al2O3催化剂表面形成了部分较低氧化态的氧化铂物种,这两者可能是导致Pt/α-Al2O3催化剂具有较高乙二醇水相重整反应活性的原因。采用溶剂蒸发诱导自组装法、硬模板法、固体热分解法以及沉淀法制备了比表面积和相组成各不相同的氧化铁载体。对Pt/Fe-O催化剂的乙二醇水相重整反应研究表明,Fe-O载体中Si或C的残留会影响活性组分Pt与Fe-O载体间的相互作用,抑制乙二醇水相重整反应的催化活性。大比表面积的Fe3O4载体将是Fe-O载体中的一个较好选择。对Pt/Al-O、Pt/Fe-O(?)口Pt/Ce-O催化剂分别进行了水气变换反应、甲醇和乙二醇水相重整反应研究,乙二醇水相重整反应催化活性顺序为Pt/Al-O> Pt/Fe-O> Pt/Ce-O,而水气变换反应催化活性顺序为Pt/Ce-O> Pt/Fe-O> Pt/Al-O,并且三种催化剂的乙二醇水相重整反应活性均高于其甲醇水相重整反应活性,由此推断乙二醇水相重整的催化活性与其水气变换反应的催化活性以及C-C断键的能力没有必然的关联。这一结论在对Pt/γ-Al2O3、Pt/δ-Al2O3、Pt/α-Al2O3以及掺杂Ce的Pt/Al-O催化剂的研究中得到进一步的证实。结合Pt/γ-Al2O3和Pt/α-Fe2O3催化剂的H2-TPD,乙二醇-TPD以及Pt/γ-Al2O3、Pt/δ-Al2O3和Pt/α-Al2O3催化剂上的乙二醇原位红外漫反射表征结果,发现乙二醇分子中O-H键的断键以及催化剂表面形成的碳酸氢盐或甲酸盐物种的脱除是乙二醇水相重整反应的关键。更多还原

【Abstract】 The research & development of renewable clean energy is becoming the focus in the worldwide, due to the "oil crisis" and the environmental and climate problems brought by the use of fossil fuels. Hydrogen, because of its cleanness, efficiency, safety and sustainability, is the most promising candidate in this area. In 2002, Dumesic reported aqueous-phase reforming of polyols (a kind of biomass derivatives) to produce hydrogen, which realized zero emission of CO2 and connected the hydrogen with renewable biomass resources.In this dissertation, ethylene glycol, the simplest polyol molecule, was chosen as reactant. The effect of supports and preparation methods of supported platinum catalysts on aqueous-phase reforming of ethylene glycol was investigated. And the reaction mechanism was discussed through the variation of reaction and characterization results of catalysts.The supports ofγ-Al2O3,δ-Al2O3 andα-Al2O3 were obtained through calcination of AlOOH at different temperatures. After impregnation with Pt, the catalysts were evaluated by aqueous-phase reforming of ethylene glycol. The results showed that the catalytic activities decreased in order of Pt/α-Al2O3> Pt/δ- Al2O3> Pt/γ- Al2O3. The yield of hydrogen reached 452μmol·min-1·gCat-1 at the condition of 225℃,29.0 KPa and 6 ml/h of ethylene glycol solution (volume percentage of ethylene glycol was 10%) with 1% Pt/α-Al2O3. The characterization of XRD, H2-TPR, TEM-EDX, CO chemisorption and XPS evidenced that no chlorinated platinum species was presented on Pt/α-Al2O3, which favored the improvement of the dispersion of surface species and avoided the sintering of Pt. Furthermore, the strong interaction between Pt andα-AI2O3 with less surface hydroxyl groups led to the formation of platinum species with low oxidation state. As a result, the combination of the above arguments was assumed to be the reasons for the higher catalytic activity of Pt/α-Al2O3.Iorn oxide supports with different surface area and phase composition were prepared by using evaporation-induced self-assembly method, hard template method, thermal solid decomposition method and precipitation method. The study on aqueous-phase reforming of ethylene glycol with Pt/Fe-0 catalysts indicated that the interaction between Pt and support would be influenced by Si or C reminded in iron oxide supports, which consequently inhibited the activity of catalysts. The results showed that Fe3O4 with large surface area should be a good choice of iorn oxide supports.Water-gas shift reaction, aqueous-phase reforming of methanol and ethylene glycol were carried out on Pt/Al-O, Pt/Fe-0 and Pt/Ce-O, respectively. For aqueous-phaes reforming of ethylene glycol, the catalytic activities decreased in order of Pt/Al-O> Pt/Fe-O> Pt/Ce-O. While, it changed as Pt/Ce-O> Pt/Fe-O> Pt/Al-O for water-gas shift reaction. Moreover, all the activities for aqueous-phase reforming of ethylene glycol were higher than those for aqueous-phase reforming of methanol. Therefore, the catalytic activity of aqueous-phase reforming of ethylene glycol did not involve any relationship with the activity of water-gas shift reaction or the catalyst capacity for C-C bond breakage. This conclusion was also confirmed by the study on Pt/γ-Al2O3, Pt/δ-Al2O3, Pt/α-Al2O3 and Ce-doped Pt/Al-0 catalyst. The H2-TPR and ethylene glycol-TPD of Pt/γ-Al2O3 and Pt/α-Fe2O3 and diffuse reflectance infrared Fourier transform spectroscopy of ethylene glycol on Pt/γ-Al2O3, Pt/δ-Al2O3 and Pt/α-Al2O3 revealed that the breakage of O-H bond in ethylene glycol and the removal of surface bicarbonate or formate species should be the crucial steps in aqueous-phaed reforming of ethylene glycol.更多还原