| 摘要: | 本研究主軸概分為二，其一以Sol-gel 法進行製備CeNi-γAl2O3及CoNi-γAl2O3觸媒，應用於觸媒結合電漿系統進行CO2分解，另一為使用BOLSIG+軟體進行電漿系統分解CO2之模擬。使用電漿系統結合觸媒於特定操作參數可獲得高CO2分解效率，其中操作參數將影響CO2分解效率，如CO2濃度、載氣、操作電壓及空間速度，添加Ar使放電電場具更高強度電子且能量密度更高，進而提高CO2分解效率，研究結果顯示10% CO2/Ar、11 kV及170 h-1時添加CoNi -γAl2O3獲得最高CO2的分解效率為(82.5%)，觸媒特性分析可知溶膠-凝膠法具高比表面積，有利於氣體分子於觸媒空隙間移動且提供更多的活性位點，CoNi -γAl2O3具高晶格氧比率，以上特性使其具有良好CO2分解效率。本研究亦發現觸媒經電漿系統反應後未影響兩種觸媒之熱穩定性且無產生大量碳沉積，並於347oC及437oC出現失重，推測觸媒表面具有吸附碳及不定型碳。10% CO2/Ar、7kV及170 h-1時添加CoNi-γAl2O3獲得最高CO2的分解效率最高的能源效率(263 g/kWh)，增加操作電壓可增加折合電場強度以提升CO2之分解效率，但折合電場隨之提高且操作功率也上升，導致能量效率隨操作電壓上升而逐漸下降。增加進流氣體流量會使CO2分解效率下降，但具備一定CO2分解效率，能量效率將會提升。添加Ar及觸媒結合電漿系統於50% CO2/Ar條件下進行CO2分解反應，產物為CO (9.51%)。於電漿動力學部分，模擬結果顯示提升折合電場（E/N）可有效提高反應區域內的平均電子能量，進而促進CO2的分解反應。在反應速率常數方面，隨著CO2濃度降低，CO2的dissociative attachment、excitation及ionization等反應速率常數皆呈上升趨勢。折合電場的增加使高能電子對CO¬2分子的激發反應增強，並促使Ar與CO2發生電荷轉移反應，進一步提升CO2 excitation與ionization的反應速率常數。電漿動力學模擬結果顯示CO2分解效率隨折合電場的提升而增加。進一步分析顯示CO2的主要分解途徑為CO2 excitation反應，當折合電場低於 90 Td 時，主要反應機制為能量閾值7.0 eV的CO2 excitation；當折合電場超過 90 Td，則以能量閥值約10.5 eV的高能量CO2 excitation為主。此結果證實CO2分子在電場中與電子碰撞所形成的電子能量分佈，會隨折合電場增加而偏向高能量區，進而提升整體反應速率常數，有助於提高CO2的分解效率。;This study is divided into two main parts: one involves the preparation of CeNi-γAl2O3 and CoNi-γAl2O3 catalysts using the Sol-gel method, applied in a plasma-catalyst combined system for CO2 decomposition; the other involves using BOLSIG+ software to simulate CO2 decomposition in the plasma system. Using a plasma-catalyst combined system under specific operational parameters can achieve high CO2 decomposition efficiency. Parameters such as CO2 concentration, carrier gas, operating voltage, and space velocity affect CO2 decomposition efficiency. Adding Ar increases the intensity and energy density of the discharge field, thereby enhancing CO2 decomposition efficiency. The result shows that the highest CO2 decomposition efficiency (82.5%) was achieved by adding CoNi-γAl2O3 at 10% CO2/Ar, 11 kV, and 170 h-1. The catalyst characteristics analysis reveals that the Sol-gel method produces high surface area catalysts, facilitating the movement of gas molecules within the catalyst pores and providing more active sites. CoNi-γAl2O3 has a high lattice oxygen ratio, contributing to its excellent CO2 decomposition efficiency. This study also found that the catalysts′ thermal stability was unaffected by the plasma reaction, with no significant carbon deposition. Weight loss was observed at 347°C and 437°C, suggesting the presence of adsorbed carbon and amorphous carbon on the catalyst surface. The highest energy efficiency (263 g/kWh) for CO2 decomposition was achieved by integrating with CoNi-γAl2O3 at 10% CO2/Ar, 7 kV, and 170 h-1. Increasing the operating voltage can enhance the reduced field, thereby improving CO2 decomposition efficiency, but this also increases operating power, leading to a gradual decrease in energy efficiency. Increasing the gas flow rate reduces CO2 decomposition efficiency but enhances energy efficiency if a certain CO2 decomposition efficiency is maintained. Adding Ar and a catalyst in the plasma system produces CO (9.51%). In terms of plasma kinetics, the simulation results show that increasing the reduced field (E/N) effectively enhances the average electron energy within the reaction zone, thereby promoting the dissociation of CO2. Regarding the reaction rate constants, a decrease in CO2 concentration leads to accelerated rates for CO2 dissociative attachment, excitation, and ionization. Furthermore, a higher E/N facilitates electron-induced high-energy excitation of CO2 molecules and enables charge transfer processes involving Ar and CO2, which significantly increases the rate constants for CO2 excitation and ionization. These plasma kinetic results collectively demonstrate that CO2 dissociation efficiency can be improved by increasing the reduced electric field. Detailed pathway analysis reveals that electron excitation is the dominant mechanism for CO2 dissociation: when E/N is below 90 Td, the primary pathway involves excitation with an energy threshold of approximately 7.0 eV; as E/N exceeds 90 Td, higher-energy excitation around 10.5 eV becomes predominant. This suggests that the electron energy distribution function (EEDF) shifts toward the high-energy region with increasing E/N, thereby enhancing reaction rate constants and overall CO2 dissociation performance. |
