Direct Production of Formaldehyde by Partial Oxidation of Methane

甲烷部分氧化直接生产甲醛

• 批准号: 12450325
• 负责人: UENO Akifumi
• 金额: $ 9.41万
• 依托单位: Shizuoka University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12450325/
• 关键词: Methane; Partial Oxidation; Formaldehyde; Direct Production; Catalysts; Molybdic Acids; Silica Support; Excess Water Vapor; メタン部分酸化; 水蒸気雰囲気; シリカ担持

Studies on the evaluation of catalyst life and the mechanism of catalyst deactivation :At the beginning of this project research, we thought that the catalyst deactivation was likely caused by the deposition and accumulation of carbon over the catalyst surface. But now it is probed that the catalyst deactivation comes from the loss of molybdenum compounds during heating the catalysts to the reaction temperature and during the reaction at 600 ℃. A part of Mo compounds, mainly consisted of α- MoO_3, easily sublimated out of the reactor and deposited on the wall of tubes connected with the reactor. So, the key technique for a long life lies in the design of catalysts against sublimation of Mo compounds during both pretreatments and reaction at high temperature. Since Mo compounds dispersed out side of the silica support were found to remove rapidly, we believe that the most important technique is in the catalyst preparation to entrap the Mo compounds inside the micro-pores of silica supports.Study on the activation mechanisms of methane into oxygenates :In the present study, we use SMA (H_4SiMo_<12>O_<40>) dispersed on silica as catalysts for partial oxidation of methane into oxygenates. One of the features of SMA is to possess 4 protons in 1 SMA molecule. In this project research KOH treated silica supports were often used, where H^+ ions in SMA molecules were substituted with K^+ ions. It was found that the K^+-substituted SMA/silica catalysts showed a low activity, and that almost all of the methane in the feed remained at the outlet of the reactor. This means that the protons in SMA have an important role for the activation of methane into oxygenates. Now. we are thinking about the presence of CH_5^+, generated by the reaction of H^+ on SMA and CH_4, as an important reaction intermediate for partial oxidation of methane on SMA/Si0_2 catalysts.

催化剂寿命评价及催化剂失活机理研究：在本项目研究之初，我们认为催化剂失活可能是由于催化剂表面碳的沉积和积累造成的。目前研究表明，催化剂失活的原因是催化剂在加热至反应温度和600℃反应过程中钼化合物的损失。一部分Mo化合物（主要是α- MoO_3）很容易升华出反应器并沉积在与反应器相连的管壁上。因此，在预处理和高温反应过程中，设计防止Mo化合物升华的催化剂是实现超长寿命的关键技术。由于分散在二氧化硅载体外的Mo化合物被发现可以快速去除，我们认为最重要的技术是在催化剂制备中将Mo化合物捕获在二氧化硅载体的微孔内。甲烷成氧的活化机理研究：本研究以分散在二氧化硅上的SMA （H_4SiMo_<12>O_<40>）作为甲烷部分氧化成氧的催化剂。SMA的特征之一是在1个SMA分子中含有4个质子。在本项目研究中，经常使用KOH处理的二氧化硅载体，其中SMA分子中的H^+离子被K^+离子取代。结果表明，K^+取代的SMA/二氧化硅催化剂活性较低，进料中的甲烷几乎全部留在反应器出口。这意味着SMA中的质子对于甲烷活化成氧合物具有重要作用。现在。我们正在考虑由H^+在SMA和CH_4上反应产生的CH_5^+作为SMA/Si0_2催化剂上甲烷部分氧化的重要反应中间体的存在。