Hydrogen Production from Water using Non-Stoichiometric Oxide

使用非化学计量氧化物从水中制氢

• 批准号: 07805071
• 负责人: OMATA Kohji
• 金额: $ 1.28万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07805071/
• 关键词: Hydrodegen Production; Non-Stoichiometric Oxide; Water Decomposition; Oxygen Desorption; Methane; Ethylene; Tin Oxide; K_2NiF_4 Type Mixed Oxide

It is well known that under low oxygen pressure and at high temperature, dioxygen is evolved from some special mixed oxide, such as perovskite type and spinel type, and from oxide of Co, Mn, Pr, Tb. On the other hand some oxide at low oxidation number (metal was excluded in this study) can reduce water to produce dihydrogen. From thermodynamical consideration, oxide of Ce, Nb, V,Ti, Fe and Sn can have such special low oxidation number. If mixed metal consisted from metals of these two groups are synthesized, it is possible that dioxygen is evolved at high temperature and water is reduced at low temperature to produce hydrogen with regenerating the original oxide. Totally water should be decomposed with thermal cycle.In this study variety of oxides were tested by periodic reaction where inert gas (Ar) and water/Ar were alternately supplied for oxygen evolution and re-oxidation, respectively. From Co_3, O_4, PrO_<22>, MnO_2 and mixed oxide containing Fe, Co, Mn, Pr or Ag, dioxygen was ev … More olved in Ar at high temperature. From oxide of Sn or Ce and mixed oxide containing Sn, Ce or Nb, hydrogen was generated in water/Ar atmosphere. The behavior of simple oxide could be predicted from thermodynamical calculation. It is revealed that such calculation is a useful guideline for a search of oxides. Because cerium oxide was assumed to be most suitable site for water reduction among the oxide mentioned above, mixed cerium oxide was mainly surveyed. When it is mixed with Ag or Rh, oxygen was evolved from cerium oxide. However, hydrogen was not produced by the successive water feed.The purpose of this study is to develop a process to produce hydrogen without waste product. If lattice oxygen of oxide is not used for combustion but is used to produce useful chemicals, usage of a reducing agent doesn't degrade the merit of this process. In this study methane was used for the reducing agent to produce ethylene by partial oxidation. From the thermodynamical calculation only oxide of Sn or Fe can produce ethylene from methane and can reduce water in normal reaction temperature range. The latter showed high activity for methane oxidation but selectivity was quite low. Tin oxide showed high selectivity when it was mixed with alkaline earth metal oxide. Especially K_2NiF_4 type oxide showed high activity for C2 hydrocarbon production. Preparation procedure and additives were investigated and the activity was successfully increased without deterioration of selectivity. Less

众所周知，在低氧压力和高温下，分子氧是由某些特殊的混合氧化物（例如钙钛矿型和尖晶石型）以及Co、Mn、Pr、Tb的氧化物产生的，而另一方面，某些氧化物是由某些氧化物产生的。低氧化数（本研究中排除金属）可以还原水产生氢气，从热力学考虑，Ce、Nb、V、Ti、Fe和Sn的氧化物可以具有如此特殊的低氧化数。如果从这两组金属开始合成混合金属，则可能在高温下放出分子氧，并且在低温下将水还原成氢气，并再生原始氧化物。在此，水应该通过热循环被完全分解。研究通过周期性反应测试各种氧化物，其中交替供应惰性气体（Ar）和水/Ar，分别从Co_3、O_4、PrO_<22>、 MnO_2和含有Fe、Co、Mn、Pr或Ag的混合氧化物在Ar中高温下析出分子氧，由Sn或Ce的氧化物和含有Sn、Ce或Nb的混合氧化物在水/Ar中生成氢气。简单氧化物的行为可以通过热力学计算来预测，这对于寻找氧化物来说是一个有用的指导，因为氧化铈被认为是最适合水还原的位置。在上述氧化物中，主要研究了当与Ag或Rh混合时，从氧化铈中释放出氧气，但是，通过连续的水供给却不会产生氢气。本研究的目的是开发一种工艺来产生氢气。如果氧化物的晶格氧不用于燃烧而是用于生产有用的化学品，则还原剂的使用不会降低该过程的优点。在本研究中，使用甲烷作为还原剂。生产乙烯从热力学计算来看，在正常反应温度范围内，只有Sn或Fe的氧化物可以还原水，后者对甲烷氧化表现出较高的活性，但氧化锡表现出较高的选择性。特别是与碱土金属氧化物混合时，K_2NiF_4型氧化物对C2烃生产表现出高活性，并对制备过程和添加剂进行了研究，成功地提高了活性。选择性恶化较少。

项目成果

K.Omata: "Methane-water redox reaction on A_2SnO_4 (A=Mg, Ca, Sr, Ba) oxide to produce C2 hydrocarbons" Catalysis Letters. 45. 245-248 (1997)

K.Omata：“A_2SnO_4（A=Mg、Ca、Sr、Ba）氧化物上的甲烷-水氧化还原反应生成 C2 碳氢化合物”催化快报。