摘要
　　CO2造成之溫室效應使地球氣溫不斷提高，各地氣候異常，因此如何有效降低CO2的含量甚至進一步的將CO2分解及轉換，便成為各國重視的課題。
　　為分解CO2並進一步將之轉換成有用氣體，本研究是以水熱法製備高比表面積之ZnFe2O4觸媒粉末，並利用此觸媒粉末來進行CO2之甲烷化反應。實驗是藉由XRD、BET、TEM、TG等儀器來分析與觀察反應前後觸媒粉末的特性；利用GC來分析CO2之甲烷化反應；並檢討反應溫度、壓力及氣體流率( CO2及H2 )對CO2甲烷化反應之影響。
　　尖晶石結構之ZnFe2O4觸媒粉末以硝酸鹽類為起始原料，氨水為沉澱劑，在150℃水熱處理2 h合成而得。合成粉末之結晶子大小為7.7 nm，比表面積為147.9 m2/g。此合成粉末在300℃、50 % H2及1.8 atm壓力下，活化3 h後仍維持尖晶石結構的相；而在350℃以上的溫度活化後則有ZnO及α-Fe相之產生。隨著活化溫度之提高，ZnFe2O4觸媒粉末所產生之氧空缺及粒徑大小亦隨之增加。
　　活化後之ZnFe2O4觸媒被應用於CO2甲烷化反應之結果：在300℃及1.8 atm的反應條件下，ZnFe2O4觸媒可使CO2的轉化率及CH4的生成率比反應條件為300℃及1 atm時為高。當反應溫度逐漸增加至400℃時，CO2轉化率及CH4生成率隨之增加。當反應氣體流率增加時，並無法對CO2轉化率及CH4生成率有增加之效果。

Abstract
　　The greenhouse effect as a result of CO2 causes the raise of earth temperature and unusual weather phenomenon. Nowadays it is an important topic to find the way of CO2 reduction or conversion.
　　ZnFe2O4 powders with high specific surface area were synthesized by the hydrothermal treatment and were used as the catalysts for CO2 methanation in this study. The synthesized powders before and after reaction of CO2 methanation were characterized by XRD、BET、TEM and TG and the CO2 methanation was analyzed by GC. Effects of parameters of reaction temperature、pressure and flow rate of reactant gas ( CO2 and H2 ) on the CO2 methanation were investigated.
　　ZnFe2O4 powders with spinel structure were hydrothermally synthesized at 150℃ for 2 h using metal nitrate as the raw materials. The crystallite size and specific surface area of synthesized powders were 7.7 nm and 147.9 m2/g, respectively. After reducing by 50 % H2 + 50 % N2 at 300℃ for 3h in the reaction pressure 1.8 atm, the synthesized powders were still spinel structure ; however, ZnO and α-Fe were formed at ≥ 350℃. The amount of oxygen-deficient and particle sizes of ZnFe2O4 powders increased with the increase of reducing temperature.
　　The reduced powders of ZnFe2O4-δ were applied for CO2 methanation. The results show that the efficiency of CO2 conversion and CH4 yield at the reaction condition of 1.8 atm and 300℃was better than that in 1 atm. The efficiency of CO2 conversion and CH4 yield increased with the increasing reaction temperature. The efficiency of CO2 conversion and CH4 yield couldn’t be improved by the increasing flow rate of reactant gas.

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