表面波微波電漿重組甲烷及二氧化碳之研究與反應機制分析

Reforming of Methane and Carbon Dioxide Using Surface-Wave Microwave Plasma

施伯勳(Po-Hsun Shih)

指導教授 ： 魏大欽

中原大學/工學院/化學工程研究所/碩士(2005年)

https://doi.org/10.6840/cycu200500102

摘要

本研究利用表面波微波電漿反應器針對甲烷與二氧化碳氣體進行轉化重組，以傅立葉轉換紅外線光譜儀及氣相層析儀分析產物之組成。探討甲烷/二氧化碳進料配比、微波功率、進料流量、操作壓力與添加劑 (H2、Ar、He、N2) 對甲烷與二氧化碳轉化率及其產物選擇性的影響；我們亦建立了甲烷/二氧化碳之電漿反應模型，以瞭解甲烷/二氧化碳在微波電漿之主要反應途徑。
實驗結果發現，二氧化碳加入對甲烷轉化率有所幫助；當二氧化碳進料含量改變時，對於H2/CO比值影響甚大；提高微波功率致使氫氣、一氧化碳及乙炔選擇性上升；增加進料流量雖使得轉化率下降，但總轉化量提高，能量效率亦隨流量之增加而有明顯的改善；以本系統而言，操作壓力改變時，較低壓力處 (0.5Torr) 或是較高壓力處 (3.5Torr) 均有較佳之轉化率與能量效率，C2產物則以乙炔選擇性最高；在添加劑 (H2、Ar、He、N2) 的添加方面，以氬氣及氦氣的添加對甲烷與二氧化碳轉化率的幫助最為明顯。
在甲烷/二氧化碳電漿反應模型中，在不同功率及不同流量下，模型計算出之甲烷/二氧化碳轉化率及其產物生成量與實驗值非常相近；再由敏感性分析歸納出電漿重組甲烷/二氧化碳之主要反應途徑。甲烷與二氧化碳之轉化除受電子碰撞解離外，自由基的碰撞解離反應，亦為重要之反應機制；而產物之分佈，以合成氣體而言，氫氣除了是經由氫原子與氣相物種碰撞之氫裂解反應生成之外，氫原子與吸附於管壁之氫原子結合亦是重要之氫氣生成路徑；而一氧化碳生成則來自於二氧化碳之電子解離反應；CHO+M®CO+H+M亦是重要之一氧化碳生成路徑。

關鍵字

合成氣體 ； 溫室效應氣體 ； 電漿模擬 ； 微波電漿

並列摘要

Reforming of methane and carbon dioxide via surface-wave microwave plasma was investigated. A series of experiments were conducted to determine methane with carbon dioxide conversion and product distributions over wide ranges of operation parameters. In the meanwhile, a mathematical model was also developed to characterize the chemical reactions taking place in methane/carbon dioxide plasmas. The model results were then compared with experimental measurements.
Experimental result showed that methane could be effectively converted in methane/carbon dioxide plasma. The CH4/CO2 ratio has extremely large effect on H2/CO ratio in the effluent. An increase in microwave power resulted in increases of hydrogen, carbon monoxide and acetylene selectivity. Increasing the feed flow rate made the conversion to decrease but the energy consumption was improved. The conversion of CH4 and CO2 were also improved when adding argon or helium to the plasma.
In the modeling studies, it was found that predictions of CH4/CO2 conversion and product flow rate agreed well with experimental data over a wide range of microwave power and CH4/CO2 flow rate. Sensitivity tests showed that the destruction of methane and carbon dioxide was not only caused by electron-impact but also by the radical induced reactions. Regarding to the product generation, hydrogen was not only formed by H-atom abstraction of hydrocarbons, but also by the recombination of H-atoms on the tube wall. Carbon monoxide was primarily formed by electron-impact dissociation of carbon dioxide, CHO+M®CO+H+M was also an important pathway.

並列關鍵字

modeling ； syngas ； microwave plasma ； greenhouse effect

參考文獻

黃曉鳳, "微波電漿技術應用於甲烷重組之研究" , 私立中原大學碩士論文 (2001)

Bou, P., Boettner, J. C. and Vandenbulcke, L. "Kinetic Calculations in Plasma Used for Diamond Depositions", Jpn. J. Appl. Phys. 31, 1505 (1992).

Bromberg. L. Cohn, D. R. and Rabinovich, A. "Plasma Reforming of Methane", Energy Fuels 12, 11 (1998).

Ceursters, B., Nguyen, H. M. T., Peeters, J. and Nguyen, M. T. "Experimental and theoretical study of the gas phase reaction of ethynyl radical with methane (HCºC+CH4)", Chem. Phys. Lett. 329, 412 (2000).

Chapman, B. "Glow Discharge Processes", (Wiley, New York, 1980).