介质阻挡放电条件下甲烷水蒸气重整和部分氧化反应制氢

Hydrogen production by the steam reforming and partial oxidation of methane under the dielectric barrier discharge

构建了CH_(4)-O_(2)-N_(2)-H_(2)O反应体系,对介质阻挡放电条件下甲烷水蒸气重整和部分氧化制氢反应过程进行了研究,考察了H_(2)O/CH_(4)物质的量比、O_(2)/N_(2)物质的量比、气体总流量、放电电压及放电频率等参数对制氢效率的影响,并基于发射光谱原位诊断法分析了反应机理。结果表明,甲烷转化率和氢气产率随着H_(2)O/CH_(4)物质的量比、O_(2)/N_(2)物质的量比和放电电压的增加而增加,而随着反应气体总流量的增加而减小,随着放电频率的增加先增大后减小,在9.8 kHz处取得最大值。在H2O/CH4物质的量比1.82、O_(2)/N_(2)物质的量比2.1、总流量136 mL/min、放电电压18.6 kV及放电频率9.8 kHz的条件下,甲烷转化率与氢气产率分别达47.45%和21.33%。甲烷和水蒸气等反应物分子通过电子解离产生CHx·、H·、OH·、O·等自由基,进而通过自由基间的碰撞反应生成H_(2);H·自由基一方面来源于CH_(4)的电子解离;另一方面来源于水蒸气一次解离以及OH·的进一步离解。部分氧化反应主要表现为O_(2)电子解离形成的O·自由基以及水蒸气一次反应产物OH·自由基进一步离解形成的O·自由基对CH_(2)·自由基的氧化。

The steam reforming and partial oxidation of methane to produce hydrogen under dielectric barrier discharge were conducted in the CH_(4)-O_(2)-N_(2)-H_(2)O reaction system;the effects of H_(2)O/CH_(4) molar ratio,O_(2)/N_(2) molar ratio,total gas flow,discharge voltage and discharge frequency on the hydrogen production were investigated and the reaction mechanism was analyzed on the basis of the in-situ diagnostic emission spectroscopy.The results indicate that the conversion of methane and the yield of hydrogen increase with the increase of H_(2)O/CH_(4) molar ratio,O_(2)/N_(2) molar ratio,and discharge voltage,but decrease with the increase of the total gas flow rate and show an volcano-shape trend with the increase of discharge frequency(peaked at 9.8 kHz).Under the conditions with an H_(2)O/CH_(4) molar ratio of 1.82,O_(2)/N_(2) molar ratio of 2.1,total flow rate of 136 mL/min,discharge voltage of 18.6 kV and discharge frequency of 9.8 kHz,in particular,the conversion of methane and the yield of hydrogen reach 47.45%and 21.33%,respectively.During the reaction,methane and water vapor may dissociate by the action of high energy electrons to generate CHx·,H·,OH·,O·and other free radicals and hydrogen is then produced through the collision between the free radicals.H·may come from the electronic dissociation of CH_(4) as well as the dissociation of OH·formed primarily from the water vapor dissociation.The partial oxidation of methane is mainly manifested by the oxidation of CH_(2)·with O·,where O·is produced by the electronic dissociation of O_(2) as well as the further dissociation of OH·.