Selective Direct Synthesis of Ethane from Methane with Carbon Dioxide at Low Temperatures

甲烷与二氧化碳低温选择性直接合成乙烷

• 批准号: 10555275
• 负责人: OHTSUKA Yasuo
• 金额: $ 7.81万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B).
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-10555275/
• 关键词: Carbon dioxide; Natural gas; Ethane; Ethylene; Composite oxide catalysts; ランタノイド酸化物

The present project focuses on a novel method to convert CH_4 directly to C_2H_6 including C_2H_4 as a secondary product at low temperatures by utilizing CO_2 as an oxidant. When Pr and TB oxides are used under ambient pressure with a fixed- bed quartz reactor, the presence of CO_2 remarkably enhances the selective conversion of CH_4 to C_2H_6 with a formation of almost the same amount of CO from CO_2 at 450-650℃. Yield of C_2H_6 increases with increasing W/F and reaches 8 mol% at the highest, though their catalytic activity is unstable. It is likely that oxygen vacancies in these oxides play key roles in this low -temperature reaction.In order to develop a composite oxide catalyst with high and stable performance, CeO_2, Cr_2O_3, orMnO_2 with high redox potential is modified with CaO with strong basicity by impregnating each oxide powder with Ca(NO_3) solution, followed air calcination .All of these binary catalysts show remarkable synergistic effects on C_2 formation at 850℃. C_2 selectivity and C_2 yield increase with increasing partial pressure of CO_2 , irrespective of the kind of catalyst, and the selectivity reaches 65-75% at 70 kPa. These catalysts provide stable performances with time on stream of 8 - 10 h. The TPD, XRD and XPS measurements strongly suggest that CO_2 first adsorbs on Ca^<2+> sites and the activation subsequently occurs on neighboring Ce^<3+>, Cr^<3+> or Mn^<2+> sites to yield active oxygen species, which work as the oxidant for selective formation of C_2 hydrocarbons.In may be expectable that the present achievements develop into a direct conversion process of low- grade natural gas containing a large amount of Co_2 to valuable chemical feedstock.

本课题研究了一种以CO_2为氧化剂，在低温下将CH_4直接转化为C_2H_6的新方法。在常压、石英固定床反应器中，用Pr和TB氧化物作催化剂，在450-650℃下，CO_2的存在显著提高了CH_4选择性转化为C_2H_6的反应，并使CO的生成量基本相同。C_2H_6产率随W/F的增加而增加，最高可达8mol%，但催化活性不稳定。为了开发性能稳定的高性能复合氧化物催化剂，采用Ca（NO_3）溶液浸渍高氧化还原电位的CeO_2、Cr_2O_3或MnO_2粉末，用强碱性的CaO改性，在850℃时，所有的二元催化剂对C_2的生成都表现出明显的协同效应。C_2选择性和C_2收率随CO_2分压的增加而增加，在70 kPa时，C_2选择性可达65-75%。这些催化剂在8 - 10小时的运行时间内提供稳定的性能。TPD、XRD和XPS研究结果表明，CO_2首先吸附在Ca^<2+>位上，随后在相邻的Ce^<3+>、Cr^<3+>或Mn^<2+>位上发生活化反应，生成活性氧物种。可以预见，目前的研究成果将发展成为一种低成本、低成本的C_2烃直接转化工艺。高品位含CO_2天然气转化为有价值的化工原料。

项目成果

Y.Ohtsuka: "Utilization of Carbon Dioxide for Direct, Selective Conversion of Methane to Ethane and Ethylene with Calcium Based Binary Catalysts, in CO_2 Conversion and Utilization"American Chemical Society (In press). (2001)

Y.Ohtsuka：“在 CO_2 转化和利用中，利用钙基二元催化剂直接、选择性地将甲烷转化为乙烷和乙烯”美国化学会（正在出版）。

Y.Wang, Y.Takahashi, Y.Ohtsuka: "Carbon Dioxide as Oxidant for the Conversion of Methane to Ethane and Ethylene Using Modified CeO_2 Catalysts"J.Catalysis. 186. 160-168 (1999)

Y.Wang、Y.Takahashi、Y.Ohtsuka：“使用改性 CeO_2 催化剂以二氧化碳作为氧化剂将甲烷转化为乙烷和乙烯”J.Catalysis。

Ye Wong: "CaO-ZnO Catalyst for Selective Conversion of Methane to C2 Hydrocarbons Using Carbon Dioxide as the Oxident."J.Catalyst. 192. 252-255 (2000)

Ye Wong：“使用二氧化碳作为氧化剂将甲烷选择性转化为 C2 碳氢化合物的 CaO-ZnO 催化剂。”J.Catalyst。

Ye Wang: "Effective catelybs for conversion of methane to ethane and ethylone using carbon dioxide" Chemstry Letters. 1209-1210 (1998)

王晔：“使用二氧化碳将甲烷转化为乙烷和乙酮的有效催化剂”《化学快报》。

Y.Ohtsuka: "Utilization of Carbon Dioxide for Direct, Selective Conversion of Methane to Ethane and Ethylene with Calcium Based Binary Catalysts"CO_2 Conversion and Utilization, ed. by C.SOng American Chemical Society. in oress. (2001)

Y.Ohtsuka：“利用二氧化碳通过钙基二元催化剂将甲烷直接选择性转化为乙烷和乙烯”CO_2 转化和利用，编辑。