CuO/ZrO_2催化水煤气变换反应制氢:ZrO_2载体焙烧温度的影响

以经不同温度(120、250、350、450℃)焙烧处理的ZrO_2为载体,采用沉积-沉淀法制备了系列CuO/ZrO_2催化剂;考察了富氢气氛下催化剂的水煤气变换反应(WGS)催化性能。结果表明,CuO/ZrO_2催化剂的催化活性随ZrO_2载体焙烧温度的升高呈现先升高后降低的"火山型"变化趋势,在焙烧温度为250℃时取得最高值。采用X射线粉末衍射、N_2物理吸附-脱附、N_2O滴定、H_2程序升温还原和CO程序升温还原及质谱跟踪等技术研究了系列ZrO_2载体及CuO/ZrO_2催化剂的结构和还原性能。结果表明,随着ZrO_2焙烧温度的升高,一方面,CuO/ZrO_2催化剂的Cu分散度逐渐降低,与ZrO_2具有强相互作用的高分散活性Cu-[O]-Zr物种("[]"表示ZrO_2表面氧空位)逐渐减少;另一方面,Cu-[O]-Zr物种的还原能力逐渐增强,并诱导催化剂活性表面羟基的还原能力也相应增强(CO为还原剂),即降低了催化剂对WGS反应的起活温度。两方面的综合作用使得ZrO_2载体焙烧温度为250℃(中等温度)时,CuO/ZrO_2催化剂的WGS催化活性最高。     

碱金属助剂对 Au-Pt/CeO2 催化剂催化水煤气变换反应活性的影响

 制备了碱金属 M (M = Na, K, Rb 和 Cs) 掺杂的 Au-Pt/CeO2 催化剂, 考察了其催化水煤气变换反应的活性, 并采用 X 射线衍射、H2 程序升温还原、紫外-可见漫反射光谱和 X 射线光电子能谱技术研究了 K 助剂对 Au-Pt/CeO2 催化剂结构和表面性质的影响. 结果表明, 添加少量电负性较低的 K 虽然使 Pt 的还原变得困难, 但有利于 Au 金属态的稳定, 并使催化剂表面 Ce3+ 富集而产生氧空位, 显著提高了 Au-Pt/CeO2 催化剂活性. 当 K 负载量为 0.025%, 反应温度 250 oC 时, CO 转化率可达 95%.     

La2O3对CuO/CeO2水煤气变换反应催化剂微观结构及催化性能的影响（英文）

以La2O3为助剂,采用共沉淀法制备了具有良好催化活性和热稳定性的CuO/CeO2-La2O3水煤气变换反应催化剂,其中,当La2O3含量为2wt%时,催化剂的催化性能最为优异.同时运用X射线衍射、N2吸附-脱附、Raman光谱、程序升温还原等手段,研究了不同含量的La2O3对CuO/CeO2催化剂微观结构及催化性能的影响.结果表明,La2O3助剂进入了载体CeO2的晶格并对CuO/CeO2催化剂的微观结构和催化性能产生了直接影响,适量La2O3的添加可以抑制CuO和CeO2晶格的长大、增强CuO与CeO2间的相互作用、提高催化剂的比表面积、促进CeO2载体中生成更多的氧空位,CuO/CeO2催化剂的催化活性和热稳定性也明显改善.     

Au负载催化剂应用于水煤气变换制氢反应的研究进展

水煤气变换反应是目前广泛应用于制氢的方法 ,应用于水煤气变换反应的催化剂成为了重要的研究热点.我们在简述传统水煤气变换催化剂的基础上,重点介绍了Au负载型催化剂应用于水煤气变换反应的相关文献,针对Au负载型催化剂的载体种类、制备方法以及催化剂活性机理做出了详细分析.强调了影响水煤气变换反应催化剂的重点参数及Au负载型催化剂的发展趋势,以便为提高催化剂催化活性、设计Au负载催化剂并应用在水煤气变换反应中的研究者提供必要的参考信息.     

不同方法制备的CeO2载体对CuO/CeO2催化剂水煤气变换活性和稳定性的影响

分别采用沉淀法(A),水热法(B)和柠檬酸溶胶-凝胶法(C)制备了三种CeO2材料,并以其为载体采用沉积-沉淀法制备了CuO/CeO2催化剂.运用N2物理吸附、粉末X射线衍射(PXRD)、原位粉末X射线衍射(in situ PXRD)、氢气-程序升温还原(H2-TPR)和循环伏安法(CV)等技术对其进行了表征,考察了不同方法制备的CeO2载体对CuO/CeO2水煤气变换(WGS)催化剂的结构、氧化-还原性能、催化活性和稳定性的影响.结果表明,它们的催化活性和稳定性顺序都是CuO/CeO2-A＞CuO/CeO2-B＞CuO/CeO2-C.联系表征结果,CuO/CeO2催化剂的活性与催化剂中CuO的颗粒度、CuO的微观应力和中等大小且与二氧化铈相互作用的CuO的数量等有关,而这些因素很大程度上受CeO2载体本身的热稳定性的影响.根据CV中扫描次数的增加,Cu2+←→Cu0氧化还原峰面积减小,推断CuO/CeO2催化剂在一定条件下氧化还原是不可逆的,这可能是其在反应气氛下经受温度循环之后活性降低的原因.     

以ZrO_2-Al_2O_3为载体的Co-Mo-K耐硫水煤气变换催化剂

采用沉淀法和浸渍法分别制备了 Zr O2 - Al2 O3复合载体和 Co- Mo- K耐硫变换催化剂 .研究了 Zr O2 对 Co- Mo- K耐硫变换催化剂活性及热稳定性的影响 .利用 XRD、BET、TG、XPS等手段对催化剂及其载体的结构、吸硫吸水性能和氧化还原性能进行了表征 .结果表明以 Zr O2 - Al2 O3代替传统的 γ- Al2 O3作为 Co- Mo- K耐硫变换催化剂的载体 ,可提高催化剂的活性 ,尤其是低温活性 ,并可改善催化剂的热稳定性、氧化还原性、吸硫和吸水性能     

纳米Li_2ZrO_3吸收剂原位移除CO_2强化水煤气变换反应制氢

采用浸渍法制备了在水煤气变换(WGS)反应中具有高催化活性的Ni/γ-Al2O3催化剂,使用柠檬酸法合成出高效CO2吸收剂Li2ZrO3纳米材料.在固定床微反应器上对WGS和吸附强化水煤气变换(SE-WGS)反应制氢过程进行了比较研究.前者只使用20%Ni/γ-Al2O3催化剂,而后者将20%Ni/γ-Al2O3催化剂与纳米Li2ZrO3吸收剂混合装填.结果表明,纳米Li2ZrO3具有比已报道的CO2吸收剂更快的吸收速率及优异的吸脱附循环稳定性,可应用于吸附强化过程,通过原位吸收WGS反应产生的CO2,使得反应超越化学平衡限制,直接制得高纯度H2.在823K,0.1MPa和H2O/CO=4的条件下,在SE-WGS过程一步制得纯度高于98%的H,验证了吸附强化反应进程制高纯氢的可行性.     

La_2O_3对CuO/CeO_2水煤气变换反应催化剂微观结构及催化性能的影响(英文)

以La2O3为助剂,采用共沉淀法制备了具有良好催化活性和热稳定性的CuO/CeO2-La2O3水煤气变换反应催化剂,其中,当La2O3含量为2wt%时,催化剂的催化性能最为优异.同时运用X射线衍射、N2吸附-脱附、Raman光谱、程序升温还原等手段,研究了不同含量的La2O3对CuO/CeO2催化剂微观结构及催化性能的影响.结果表明,La2O3助剂进入了载体CeO2的晶格并对CuO/CeO2催化剂的微观结构和催化性能产生了直接影响,适量La2O3的添加可以抑制CuO和CeO2晶格的长大、增强CuO与CeO2间的相互作用、提高催化剂的比表面积、促进CeO2载体中生成更多的氧空位,CuO/CeO2催化剂的催化活性和热稳定性也明显改善.     

不同方法制备的CeO2载体对CuO/CeO2催化剂水煤气变换活性和稳定性的影响

分别采用沉淀法(A), 水热法(B)和柠檬酸溶胶-凝胶法(C)制备了三种CeO2材料, 并以其为载体采用沉积-沉淀法制备了CuO/CeO2催化剂. 运用N2物理吸附、粉末X射线衍射(PXRD)、原位粉末X射线衍射(in situ PXRD)、氢气-程序升温还原(H2-TPR)和循环伏安法(CV)等技术对其进行了表征, 考察了不同方法制备的CeO2载体对CuO/CeO2水煤气变换(WGS)催化剂的结构、氧化-还原性能、催化活性和稳定性的影响. 结果表明, 它们的催化活性和稳定性顺序都是CuO/CeO2-A>CuO/CeO2-B>CuO/CeO2-C. 联系表征结果, CuO/CeO2催化剂的活性与催化剂中CuO的颗粒度、CuO的微观应力和中等大小且与二氧化铈相互作用的CuO的数量等有关, 而这些因素很大程度上受CeO2载体本身的热稳定性的影响. 根据CV中扫描次数的增加, Cu2+←→Cu0氧化还原峰面积减小, 推断CuO/CeO2催化剂在一定条件下氧化还原是不可逆的, 这可能是其在反应气氛下经受温度循环之后活性降低的原因.     

铁系高温变换催化剂上水煤气变换反应本征动力学的研究

采用活塞流管式积分反应器,在1.0 MPa压力下,对环境友好铁系无铬NBC-1型高温变换催化剂上变换反应本征动力学数据进行了测试。根据测定得到的数据,对幂函数动力学模型进行了模型参数估计和模型检验,得到了高度显著的动力学回归方程。从动力学方程可以得出:该高温变换催化剂上变换反应活化能比较低,因此其低温活性较好；该催化剂上H2O组分对反应速率的影响比较大；CO2对变换反应速率的抑制作用很大,因此为提高变换反应速率,应当设法减小CO2的不利影响；H2组分对反应速率的影响很小,在实际应用过程中,可以忽略。     

Influence of iron oxide support preparation method on the properties of Ru/Fe2O3 catalysts for water-gas shift reaction

Studies were undertaken of phase transitions of iron oxide obtained from iron oxide-hydroxides of type α-, β-, γ- and δ-FeOOH, and used as a support of ruthenium catalysts Ru/Fe₂O₃, employed in the water-gas shift reaction. In asprepared pure supports and ruthenium catalysts the main phase was α-Fe₂O₃. After use in the water-gas shift reaction, the support showed the presence of different phases of iron oxide. The most active Ru/Fe₂O₃ catalysts prepared on the basis of α- and δ-FeOOH, after use in the water-gas shift reaction, revealed the presence of Fe₃O₄ or a mixture of phases Fe₃O₄ and γ-Fe₂O₃. The least active catalysts, prepared on the basis of β- and γ-FeOOH, contained a solid solution of Fe₃O₄-γ-Fe₂O₃ with traces of α-Fe₂O₃.     

Development of high performance Cu/ZnO-based catalysts for methanol synthesis and the water-gas shift reaction

Our groups studies on Cu/ZnO-based catalysts for methanol synthesis via hydrogenation of CO₂ and for the water-gas shift reaction are reviewed. Effects of ZnO contained in supported Cu-based catalysts on their activities for several reactions were investigated. The addition of ZnO to Cu-based catalyst supported on Al₂O₃, ZrO₂ or SiO₂ improved its specific activity for methanol synthesis and the reverse water-gas shift reaction, but did not improve its specific activity for methanol steam reforming and the water-gas shift reaction. Methanol synthesis from CO₂ and H₂ over Cu/ZnO-based catalysts was extensively studied under a joint research project between National Institute for Resources and Environment (NIRE; one of the former research institutes reorganized to AIST) and Research Institute of Innovative Technology for the Earth (RITE). It was suggested that methanol should be produced via the hydrogenation of CO₂, but not via the hydrogenation of CO, and that H₂O produced along with methanol should greatly suppress methanol synthesis. The Cu/ZnO-based multicomponent catalysts such as Cu/ZnO/ZrO₂/Al₂O₃ and Cu/ZnO/ZrO₂/Al₂O₃/Ga₂O₃ were highly active for methanol synthesis from CO₂ and H₂. The addition of a small amount of colloidal silica to the multicomponent catalysts greatly improved their long-term stability during methanol synthesis from CO₂ and H₂. The purity of the crude methanol produced in a bench plant was 99.9 wt% and higher than that of the crude methanol from a commercial methanol synthesis from syngas. The water-gas shift reaction over Cu/ZnO-based catalysts was also studied. The activity of Cu/ZnO/ZrO₂/Al₂O₃ catalyst for the water-gas shift reaction at 523 K was less affected by the pre-treatments such as calcination and treatment in H₂ at high temperatures than that of the Cu/ZnO/Al₂O₃ catalyst. Accordingly, the Cu/ZnO/ZrO₂/Al₂O₃ catalyst was considered to be more suitable for practical use for the water-gas shift reaction. The Cu/ZnO/ZrO₂/Al₂O₃ catalyst was also highly active for the water-gas shift reaction at 673 K. Furthermore, a two-stage reaction system composed of the first reaction zone for the water-gas shift reaction at 673 K and the second reaction zone for the reaction at 523 K was found to be more efficient than a one-stage reaction system. The addition of a small amount of colloidal silica to a Cu/ZnO-based catalyst greatly improved its long-term stability in the water-gas shift reaction in a similar manner as in methanol synthesis from CO₂ and H₂.     

Changes in the activity of Ru/Fe2O3 catalysts modified with alkali metal salts in the water-gas shift reaction

A study was undertaken to determine the activity of ruthenium catalysts, obtained by deposition of Ru₃(CO)₁₂ on products of iron oxide-hydroxide calcination modified with alkali metals, in the water-gas shift reaction. The activity depends on the kind of starting iron support, the ruthenium precursor and the amount of alkali metal salts. The most active were the catalysts obtained by deposition of Ru₃(CO)₁₂ on calcination products of σ-FeOOH, both modified and unmodified with alkali metal salts, and of α-FeOOH modified with alkali metal salts.     

ZrO2修饰Cu催化剂还原以及反应过程中表面组成的变化

通过热分解法制备Cu模型催化剂,然后经浸渍制备ZrO₂/Cu催化剂,采用SEM、XPS考察了催化剂表面形态和组成,并采用in-situ Raman考察了催化剂在还原和吸附CO和水的过程中随时间的变化。结果表明,还原前Cu催化剂表面主要存在CuO物种,而在ZrO₂/Cu表面,除了CuO物种,还存在着大量的表面羟基物种。ZrO₂/Cu相对Cu更加容易还原为Cu⁰,同时,ZrO₂在催化剂表面聚集形成絮状态,而Cu催化剂还原后主要形成Cu₂O物种。Cu催化剂表面吸附CO后,除了形成Cu-CO外,Cu₂O物种均会迅速消失形成CO₂。Cu催化剂对水的作用比较弱,但是ZrO₂/Cu催化剂和水作用较强,并且通过Cu-OH中间物形成Cu₂O物种。     

CO2加氢合成甲醇Cu/ZrO2催化剂的失活因素

采用低温氮气吸脱附、X射线衍射(XRD)、电镜(TEM)以及热重差热(TG-DSC)等手段,对不同反应时间下Cu/ZrO₂催化剂的物理结构、微观形貌以及积炭情况进行了表征,分析了催化剂的失活原因。结果表明,造成催化剂失活的主要因素是活性组分烧结;其次,表面积炭覆盖其活性中心也造成催化剂活性在一定程度上的降低;而催化剂比表面积对其活性的影响较小。     

Fe3O4(001)-B表面水煤气变换反应机理第一性原理研究

采用自旋极化的密度泛函理论方法系统地研究了Fe_3O_4(001)-B表面水煤气变换的反应机理,计算了整个反应历程。结果表明,对于Fe_3O_4(001)-B表面上的水煤气变换反应,氧化还原、联合和再生三种反应路径共存,但氧化还原和联合机理的有效能垒较低,因而更占优势。对于生成H_2的基元反应,其活性受表面H浓度和催化剂表面O缺陷浓度影响;较高的表面H浓度和O缺陷浓度均有利于H_2生成。这些结果有助于进一步认识铁氧催化剂上的水煤气变换反应机理。     

Catalytic activity of Ru/Fe2O3, obtained by adsorption of ruthenium on iron oxide supports

The effect of the method of a support preparation on its adsorption properties for ruthenium from solution and on the catalytic properties of Ru/Fe₂O₃ catalysts obtained by adsorption, has been studied. Moreover, the influence of the solvent in which a given ruthenium compound was dissolved on the properties of Ru/Fe₂O₃ catalysts was observed.     

Cu/Mn/ZrO2 catalyst for alcohol synthesis by Fischer-Tropsch modified elements

A Cu/Mn/ZrO₂ methanol synthesis catalyst modified by Fischer-Tropsch (F-T) element (Ni,Co,Fe) was prepared by an coprecipatation method. The addition of F-T elements had a great effect on the catalyst performance. The higher alcohol selectivity increased greatly compared with that of the Cu/Mn/ZrO₂ catalyst when nickel and cobalt were added, while the addition of iron improved the selectivity tohydrocarbon due to the interaction of the F-T element and the Cu/Mn/ZrO₂ catalyst.