摘要
在常压下,研究了添加气的种类(N2,He,Ar,H2,NH3,CO和CO2)对介质阻挡放电低碳烷烃(甲烷、乙烷和丙烷)转化制低碳烯烃的影响.结果表明,以甲烷或乙烷为原料时,N2,He,Ar和CO的引入有利于提高原料的转化率和总烯烃的选择性;而CO2,H2和NH3的引入对甲烷、乙烷的转化率无明显影响,但H2和NH3的引入会使总烯烃的选择性显著降低.以丙烷为原料时,所研究的添加气均可提高丙烷的转化率,而只有CO的引入可提高总烯烃选择性.综上所述,80%(摩尔分数)CO添加量最有利于低碳烷烃转化成低碳烯烃,对应的甲烷、乙烷和丙烷的转化率分别提高了14.4%,17.6%和42.8%,总烯烃的选择性分别提高了19.9%,25.0%和11.9%.以CH4为例,通过对放电电流波形和等离子体区物种的发射光谱(OES)研究发现,引入CO能显著增加等离子体的电子密度,并且体系中出现激发态O*物种(777.5和844.7 nm),这种O*物种能够促进C—H键的断裂,有利于烯烃的生成.因此,等离子体区电子密度的增加和激发态O*物种的出现可能是CH4-CO体系中CH4有效转化的主要原因.
At atmospheric pressure, the influences of different types of additive gases （N2, He, Ar, H2, NH3, CO, CO2） on the transformation of low carbon alkanes（CH4, C2H6 and C3Hs） to light alkenes via the dielectric barrier discharge non-equilibrium plasma （DBD plasma） method were investigated. Results show that the additive gases have different effects on the reaction. For CH4 or C2H6 , the conversion and selectivity of feedstock increase with the introduction of N2, He, Ar, CO. While CO2, NH3 and H2 have no obvious effect to conversion of feedstock but NH3 and H2 inhibit the selectivity obviously. As for C3Hs feedstock, the conversion can be enhanced by all the additive gases mentioned above, while the selectivity decreased in different degrees except CO. Among these additive gases, 80% （ molar fraction） CO exhibits the best activity both for the feedstock conversion and selectivity of total alkenes. The conversion of CH4, Call6 and C3Hs increase by 14.4% , 17.6% and 42. 8% , respectively, and the corresponding selectivity of total alkenes increase by 19.9%, 25.0% and 11.9%, respectively. Studies on in situ optical emission spectroscopy （OES） and current waveform of discharge show that the introduction of CO can not only increase the electron density of plasma, but also generate the excited oxygen atoms （777.5 and 844.7 nm）, the latter can effectively facilitate the C-H cleavage of methane to the formation of ethylene. Therefore, the existence of ex- cited oxygen atoms and the increased electron density of plasma may be the main reasons to cause the effective transformation of methane to light alkenes when CO as additive gas.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第1期192-197,共6页
Chemical Journal of Chinese Universities
关键词
低碳烷烃
添加气
等离子体
低碳烯烃
发射光谱
Light alkane
Additive gas
Plasma
Light alkene
Optical emission spectroseopy
