本研究的目的是開發及比較多種觸媒，以提高在低溫下進行逆水氣轉移反應時二氧化碳的轉化率和一氧化碳的選擇性。該反應中通常使用的擔體是金屬氧化物，如TiO2、CeO2、Al2O3，它們可以使金屬高度分散，並且有足夠的擔體氧空位可以進行反應，而且過渡金屬氧化物的擔體的氧原子的流動性可以減少結焦以保持觸媒的穩定性。鹼金屬的添加用來提高觸媒的活性。在這項研究中，採用了兩種製備方法，初濕含浸法以及共沉澱法。觸媒都在300-450 ℃的溫度範圍內進行鍛燒。所製備的觸媒通過X射線衍射、氮氣吸附脫附曲線以及透射電子顯微鏡進行了特徵分析。反應是在一個連續的固定床反應器系統中進行的。觸媒首先在10%的H2/He氣體還原，溫度在200-500 ℃之間，流量為12,000 ml/g*h。當反應進行時，CO2/H2的進料比為1/2，反應溫度在200到500 ℃之間，在一大氣壓中，在固定床反應器中，觸媒重量為0.5克，氣體流速為30-60 cm3/min。XRD結果顯示，氧化鈰的晶粒更大，排列更有規律，並且存在氧化銅的晶粒摻雜。銅鐵比為4:1的共沉澱法製備的銅鐵氧化鋁觸媒在XRD圖譜中出現了低強度的峰，表明分散在氧化鋁擔體上的銅鐵為小晶體或是非晶體。氮氣吸附結果表明，觸媒具有較高的BET表面積和大量的微孔，利於反應的進行。HRTEM圖顯示金屬氧化物均勻地分散在擔體上，以及呈現晶格的結構。反應結果表明，負載貴重金屬的觸媒沒有高轉化率；含有50 wt.% CuFe/Al2O3的銅鐵鋁觸媒具有較高的轉化率；而銅鐵摻雜的氧化鈰觸媒在所有觸媒中顯示出最高的轉化率和選擇性。;The purpose of this study was to develop a catalyst to improve the conversion of CO2 and the selectivity of CO for a reverse water-gas shift reaction at low temperatures. The supports generally used in this reaction is metal oxide such as TiO2, CeO2, and Al2O3. They allowed high dispersion of the metal and the mobility of the oxygen atoms in the support of the transition metal oxide to reduce coking and maintain the stability of the catalyst, and there were enough oxygen vacancies for the reaction. The addition of alkali metals has been used to increase the activity of the catalyst. In this study, the incipient-wetness impregnation method and coprecipitation methods were applied. Catalysts were calcined at the temperature range of 300-450 ℃. The as-prepared catalysts were characterized by X-ray diffraction, N2 sorption, and transmission electron microscope. The reaction was carried out in a continuous fixed-bed reactor system. The catalyst was firstly reduced with 10% H2/He gas at a temperature between 200 and 500 ℃ with a flow rate of 12,000 ml/g*h. When reaction proceeded, CO2/H2 with feed ratio 1/2, reaction temperature between 200 and 500 °C and at atmosphere, in a fixed bed reactor, catalyst weight 0.5 g, gas flow rate 30-60 cm3/min. The XRD results showed that the grains of cerium oxide were larger and more regularly arranged, and there was grain doping of copper oxide. The copper-iron alumina catalysts prepared by the co-precipitation method with a copper to iron ratio of 4: 1 had low intensity peaks in XRD patterns, indicating that the copper and iron dispersed on the alumina support with small crystals or amorphous phase. The N2 sorption results showed that the catalysts had high BET surface area with a huge number of micropores. The TEM images displayed the metal oxides homogeneously dispersed on the support. Reaction results showed that the precious metal loaded on the support did not have high conversion. The Cu-Fe-Al catalysts with 50 wt.% CuFe/Al2O3 had the high conversion; and the cerium oxide-supported CuFe catalysts displayed the highest conversion and selectivity among all catalysts.
