燃料電池重組器中水與觸媒對優先氧化反應的影響

Abstract

燃料電池為使用氫氣及氧氣為燃料，反應後產生電及水，能降低空氣污染以及二氧化碳排放，改善目前全球生態環境，是故能應用在各種方面的燃料電池技術，開始被大量研究。 甲醇重組器可將甲醇水溶液轉化為氫氣、一氧化碳及二氧化碳。優先氧化法則可把產出氣體中的一氧化碳濃度降低至10ppm以下，解決PEMFC白金電極毒化的問題，以提供PEMFC使用。有鑑於實際重組器的運作中會有少許的水參與PROX反應，因此，本研究加入水參與PROX反應，探討水對於PROX反應中CO濃度的影響，以及對RROX反應中甲烷化的抑制效果，以期能完整呈現甲醇重組系統於實際運作過程中的表現。 實驗結果顯示，水對於觸媒的CO轉化率有所幫助，特別是5%Pt觸媒，可使CO轉化率提升，並減少CO的濃度。而加入水參與反應後，更可降低各種觸媒於高溫時產生的甲烷化現象，尤其以Ru系列觸媒最為明顯，可在220℃時，將甲烷產量降至1414ppm左右，相較於無水PROX反應，降低極多，因此減少氫氣損失，進而提升系統效率。

Fuel cell converts the chemical energy within the fossil fuel directly to electrical energy without combustion. Based on this theory, fuel cell has the advantage to reduce the air pollution and slow down the global warming. Therefore, fuel cell has drawn the most attention recently. Through the reforming process, methanol could be converted into hydrogen-rich gas for fuel cell. The Preferential Oxidation(PROX) can reduce CO in hydrogen-rich gas to a tolerant level. Consequently, it can stop poisoning the platinum anode electrode of fuel cell. Also, the water is added into system because in reality, water will participate in PROX reaction. So, the influence of water on the PROX reaction will need further investigation. The experimental results shown that the existence of water in reaction do help the CO conversion, especially in 5%Pt catalyst. Existence of water also reduces the methanation phenomenon of all catalysts in experiment at high temperature, especially in series of Ru catalysts. At reacting temperature 220℃ and water flow rate of 1 ml/min, 1%Ru catalyst can reduce the methane concentration to 1414ppm. Therefore, water can decrease the loss of hydrogen and improve the efficiency of whole system.