運用冰晶法探討乙醇對甲烷及二氧化碳水合物解離之效應

Abstract

本研究以冰晶法合成甲烷及二氧化碳水合物，並且探討乙醇蒸氣對甲烷及二氧化碳水合物之合成與解離過程所造成的影響。第一部分會先以拉曼光譜鑑定兩種合成方法(添加乙醇與否)所合成之水合物，經實驗結果得知兩種方法所合成之水合物為相同物質。 第二部分則探討合成前添加乙醇與否對合成過程之影響，發現乙醇可使甲烷及二氧化碳水合物在低溫時即可快速合成，在只經過一次加熱循環即可與不添加乙醇者經過兩次循環有相同之九成以上的轉化率，由上述兩部份證明乙醇所扮演之角色為催化劑。 第三部分是比較合成前添加乙醇與否對解離過程之影響，發現添加乙醇合成之甲烷及二氧化碳水合物在解離時明顯比未添加乙醇合成之甲烷及二氧化碳水合物快速許多，得知乙醇既可加速甲烷及二氧化碳水合物合成亦能加速水合物解離，並使甲烷及二氧化碳水合物之自我保存效應消失。 最後一部分為合成完後在高壓下加入5 ml乙醇，觀察只讓乙醇參與甲烷水合物之解離過程時，是否同樣也具有加速解離效果。實驗結果為其解離行為與合成前先添加乙醇之解離結果相似。此一發現可應用在開採自然界中之天然氣水合物，因為其可大大縮短開採甲烷水合物所需之時間。

In this study, we synthesized CH4 hydrate and CO2 hydrate using ice crystal method, and investigated the effect of ethanol vapor on hydrate synthesis and dissociation processes. In the first part of this research, Raman spectrum was applied to examine whether the addition of ethanol alters gas hydrates spectroscopic properties. According to the experimental spectra, the two substances are identical. In the second part of this research, we investigated the influence of adding at the bottom of the reactor before synthesizing gas hydrate on formation. It is found that CH4 and CO2 hydrate can be synthesized at lower temperature when ethanol vapor exists. When ethanol vapor is added, the conversion of gas hydrates is over 90 % through one heating cycle, which is the same as the conversion of gas hydrates through two heating cycles without adding ethanol vapor. The two research results above prove that ethanol behaves as catalyst. In the third part of this research, the influence of adding ethanol before hydrate formation on dissociation was investigated. It is shown that ethanol vapor can accelerate CH4 and CO2 hydrate synthesis and dissociation, and there is no self-preservation of CH4 and CO2 hydrate. In the last part of this research, we injected 5 ml ethanol after CH4 hydrate was synthesized. The results show that adding ethanol before or after hydrate formation does not cause significant difference in dissociation behavior. This finding can be applied to extract CH4 from hydrate in nature because ethanol significantly accelerates CH4 h hydrate dissociation.