临氢条件下等离子体—催化甲烷偶联制C_2烃的研究
摘要
甲烷是天然气的主要成分,含量一般在95%左右。自然界存在着丰富的CH_4资源,开发应用它对保障21世纪能源供应意义非常重大。天然气的气态特性使它作为能源利用具有方便、干净、热效率高等优点,其物化特性使它在一碳化学、有机合成与烃加工和天然气伴生物(H_2、O_2、N_2、CO_2以及氦、氩等稀有气体)的利用等方面,都展现出了广阔的发展前景。
高压脉冲电晕等离子体是一种新型的非平衡等离子体技术,具有电子能量适中、有利于CH_4分子的活化、可在常温常压下操作和能量利用效率高等优点,并已在SOx、和NOx等小分子的活化研究中得到广泛应用。本论文利用脉冲电晕等离子体与催化剂结合共同作用由CH_4制备了C_2烃,为甲烷高效利用提供了一条新的技术路线。
论文取得的主要结果如下:
1.在室温常压下,高效地实现了等离子体和催化剂共同作用甲烷偶联转化,在V(CH_4)/V(H_2)=1:3条件下,得到了CH_4转化率21.8%和C_2选择性43.1%的较好结果。
2.在室温常压下,利用脉冲电晕等离子体有效地实现了在化学催化法中难以进行的临氢条件下甲烷脱氢偶联反应,在等离子体催化条件下甲烷转化率达21.8%,C_2烃选择性达到43.1%;在一定实验条件下,将等离子体与适当的催化剂结合共同作用CH_4/H_2反应,使C_2烃产物中乙烯选择性达18.4%以上,乙烯产量可达10.3%。
3.OES对等离子体作用CH_4/H_2反应的原位光谱诊断结果表明:CH_4/H_2在脉冲电晕等离子体作用下的反应是自由基反应,等离子体主要起着活化反应物和催化剂的作用,而催化剂主要是提高了产物的选择性。
4.TG、IR和XRD表征结果表明,等离子体催化CH_4/H_2转化反应中催化剂积碳的成分主要是无定型碳和碳氢聚合物。催化剂积碳主要来源于等离子体中高能电子直接作用CH_4产生的碳物种在催化剂上生成的聚合物。
The methane is principal constituent of the natural gas,the content of methane is generally about 95%.The CH_4 resource is rich in the nature.It is extremely significant to develop and apply in safeguarding the 21st century energy supplement.The natural gas gaseous state characteristic enable it to have merits such as convenient,clean,the higher thermal efficiency as the energy.Its transformation characteristic causes it all unfolded the broad prospects for development,in the utilization of a carbonization study,the organic synthesis and the hydrocarbon processing,the natural gas associated(H_2,O_2,N_2,CO_2 as well as helium,argon noble gases and so on)aspects and so on.
The pulse corona plasma is a novel technology of non-equilibrium plasma generated by highly DC voltage,in which conditions the electron temperature is very high but the ionic or molecular temperature is low.So the great advantages of pulse corona plasma is that less energy goes into activating any stability simple molecular,such as NOx and SOx.In this study, pulse corona plasma combined with catalysts,was used convert CH_4 towards C_2 hydrocarbons,and provides a new rout for activating CH_4.
The conclusions obtained from this study are summarized as follows:
1.At ambient temperature and atmosphere,effectively converted into methane under pulse corona plasma,at the conditions of the ratio of V(CH_4)/V(H_2)=1:3.The conversion of CH_4 is 21.8%and the selectivity of C_2 is 43.1%.
2.The methane coupling reaction in the hydrogen was realized under pulse corona plasma at ambient temperature and atmosphere.Under pulse corona plasma the conversion of CH_4 is 21.8%and the selectivity of C_2 is 43.1%.In the pulse corona plasma combined with catalysts was used to convert CH_4/H_2 towards C_2 hydrocarbons,the selectivity is 18.4%and the yield of C_2H_4 is 10.3%.
3.The analysis results of OES show that the conversion reactions of CH_4/H_2 are both radical mechanisms under pulse corona plasma.While the conversion CH_4 into C_2 hydrocarbons under plasma with catalyst,the plasma mostly activates the reactants and catalysts,and the catalyst affects the selectivity of products.
4.The analytic results of TG,IR,XRD show the coking of the catalyst mainly results from the deposit of amorphous carbon and hydrocarbons of highly molecular weight,formed from carbon species that dissociated CH_4 by plasma and the active species produced by CH_4 plasma.
高压脉冲电晕等离子体是一种新型的非平衡等离子体技术,具有电子能量适中、有利于CH_4分子的活化、可在常温常压下操作和能量利用效率高等优点,并已在SOx、和NOx等小分子的活化研究中得到广泛应用。本论文利用脉冲电晕等离子体与催化剂结合共同作用由CH_4制备了C_2烃,为甲烷高效利用提供了一条新的技术路线。
论文取得的主要结果如下:
1.在室温常压下,高效地实现了等离子体和催化剂共同作用甲烷偶联转化,在V(CH_4)/V(H_2)=1:3条件下,得到了CH_4转化率21.8%和C_2选择性43.1%的较好结果。
2.在室温常压下,利用脉冲电晕等离子体有效地实现了在化学催化法中难以进行的临氢条件下甲烷脱氢偶联反应,在等离子体催化条件下甲烷转化率达21.8%,C_2烃选择性达到43.1%;在一定实验条件下,将等离子体与适当的催化剂结合共同作用CH_4/H_2反应,使C_2烃产物中乙烯选择性达18.4%以上,乙烯产量可达10.3%。
3.OES对等离子体作用CH_4/H_2反应的原位光谱诊断结果表明:CH_4/H_2在脉冲电晕等离子体作用下的反应是自由基反应,等离子体主要起着活化反应物和催化剂的作用,而催化剂主要是提高了产物的选择性。
4.TG、IR和XRD表征结果表明,等离子体催化CH_4/H_2转化反应中催化剂积碳的成分主要是无定型碳和碳氢聚合物。催化剂积碳主要来源于等离子体中高能电子直接作用CH_4产生的碳物种在催化剂上生成的聚合物。
The methane is principal constituent of the natural gas,the content of methane is generally about 95%.The CH_4 resource is rich in the nature.It is extremely significant to develop and apply in safeguarding the 21st century energy supplement.The natural gas gaseous state characteristic enable it to have merits such as convenient,clean,the higher thermal efficiency as the energy.Its transformation characteristic causes it all unfolded the broad prospects for development,in the utilization of a carbonization study,the organic synthesis and the hydrocarbon processing,the natural gas associated(H_2,O_2,N_2,CO_2 as well as helium,argon noble gases and so on)aspects and so on.
The pulse corona plasma is a novel technology of non-equilibrium plasma generated by highly DC voltage,in which conditions the electron temperature is very high but the ionic or molecular temperature is low.So the great advantages of pulse corona plasma is that less energy goes into activating any stability simple molecular,such as NOx and SOx.In this study, pulse corona plasma combined with catalysts,was used convert CH_4 towards C_2 hydrocarbons,and provides a new rout for activating CH_4.
The conclusions obtained from this study are summarized as follows:
1.At ambient temperature and atmosphere,effectively converted into methane under pulse corona plasma,at the conditions of the ratio of V(CH_4)/V(H_2)=1:3.The conversion of CH_4 is 21.8%and the selectivity of C_2 is 43.1%.
2.The methane coupling reaction in the hydrogen was realized under pulse corona plasma at ambient temperature and atmosphere.Under pulse corona plasma the conversion of CH_4 is 21.8%and the selectivity of C_2 is 43.1%.In the pulse corona plasma combined with catalysts was used to convert CH_4/H_2 towards C_2 hydrocarbons,the selectivity is 18.4%and the yield of C_2H_4 is 10.3%.
3.The analysis results of OES show that the conversion reactions of CH_4/H_2 are both radical mechanisms under pulse corona plasma.While the conversion CH_4 into C_2 hydrocarbons under plasma with catalyst,the plasma mostly activates the reactants and catalysts,and the catalyst affects the selectivity of products.
4.The analytic results of TG,IR,XRD show the coking of the catalyst mainly results from the deposit of amorphous carbon and hydrocarbons of highly molecular weight,formed from carbon species that dissociated CH_4 by plasma and the active species produced by CH_4 plasma.
引文
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[25]StevenL Suib,Richard P Zerger.Direct,continuous,low-power catalytic conversion of methane to higher hydrocarbon via microwave plasma,J Catal.,1993,139:389-391.
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[29]陈栋梁,李庆,于作龙等.甲烷和氮气在微波等离子体下的转化研究,天然气纪工[J],2000,25(4):28-33.
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[32]Marafee A,Liu C J,Xu G H,et al.An Experimental Study on the Oxidative Coupling of Methane in a Direct Current Corona Discharge Reactor over Sr/La_2O_3 Catalyst,Ind Eng Chem Res,1997,36(3):632-637.
[33]Cho Wonihl,Baek Youngsoon,Park Dalryung,et al.Conversion of Natural Gas to Higher Hydrocarbons Using a Microwave Plasma and Catalysts,Research on Chemical In termediates,1998,24(1):55-66.
[34]张劲松,Wan J K S,曹丽华,微波诱导甲烷在活性炭/碳化硅上直接转化制C_2烃等,[J].催化学报,1999,20(1):45-50.
[35]朱爱民,张秀玲,宫为民等,脉冲电晕等离子体下甲烷偶联反应研究(Ⅲ)一金属氧化物的多相催化作用,高等学校化学学报[J],2000,21(1):120-123.
[36]徐春蕾,董家黢,杨鸿生,孙永志,孙德坤,杨春,过渡金属与微波等离子体协同催化甲烷制乙炔,东南大学学报(自然科学版)2004.34(2):210-214.
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[2]方华灿,对我国能源可持续发展的若干思考,石油科技论坛,2005,2:27-31.
[3]陈同海,中国石油化工集团公司年鉴,中国石化出版社,2005.10-12
[4]阎子峰,宋林花,天然气有效利用回顾,石油大学学报(自然科学版)[J],1997,21(1):103-108.
[5]Keller G E,Bhasin M M,Synthesis of ethylene via oxidative coupling of methane.J.Catal,1982,73(1):190-191.
[6]化工部天然气化工信息站,国内碳一化学进展—甲烷化学及合成气化学,天然气化工[J],1995,20(3):484-491
[7]朱爱民,宫为民,张秀玲,等.脉冲电晕等离子体应用于甲烷偶联的探索研究,天然气化工[J],1997,22(2):1-5.
[8]MacTaggart F K.Plasma Chemistry in Electrical Discharges,Elsevier,1967.
[9]国家自然科学基金委员会编.自然科学学科发展战略调研报告(等离子物理学).北京:科学出版社,1994.
[10]赵化侨,等离子体化学与工艺,合肥:中国科学技术出版社:1993,11-12.
[11]Chang J S,Lawless P A,Yamamoto T.Corona Discharge Processes,IEEE Trans.Plasma Sci,1991,19(6):1152-1154.
[12]Masuda S,Hosokausa S,Tu X,et al.Novel plasma chemical technologies-PPCP and SPCP for control of gaseous pollutants and air toxics,Journal of Electrostatics,1995,34(4):415-438.
[13]朴东旭,陈雪芹,挥发性物质缓释体及制造方法,现代化工[J],1985,(3):20-24.
[14]后小维,张世民等,聚丙烯/层状硅酸盐纳米复合材料的制备、结构与性能,高分子通报[J],1988,(6):234-236.
[15]蒋利,西北纺织学院硕士论文,1997.
[16]赵于文,低温等离子体在化学合成中的应用,现代化工[J].1991,11(1):48-52.
[17]Tanabe.S,Okisu K,Matsumoto.H,Profiles of methane demyelization with a glow discharge plasma system,Nagasaki Daigaku Kogakubu Kenkyu Hokoku,1999,29,(53):329-332.
[18]Pietro Canepa,Gianrico Castello,Stelio Munari,Low pressure RF plasma reactions in light hydrocarbons:methane,Radiant Phys.Chem.,1979,15:485-495.
[19]Shuiliang Yao,Akira Nakayama,Eiji Suzuki,Catalysis Today[J],2001,71:219-223
[20]Jen-Shih Chang,Phil A.Lawless,Toshiaki Yamnamoto,Corona discharge processes,IEEE Transaction non Plasma Science,1991,19(6):1152-1166
[21]Gordon Christopher L,Howard Philip J,Lobban Lance L,et al.,Novel technique for the production of hydrogen using plasma reactors,Fuel Chem.,1999,44(4):874-878.
[22]朱爱民,宫为民,张秀玲,脉冲电晕等离子体作用下甲烷偶联反应的研究(Ⅱ)-反应添加气的影响,应用化学[J],1999,16(4):70-73.
[23]徐学基,诸定昌,气体放电物理,上海:复旦大学出版社,1996,243-245,221-222.
[24]Thanyachotpaiboon K,Chavadej S,Caldwell T A,et al.Conversion of Methane to Higher Hydrocarbons in AC Non-equilibrium Plasmas,AIChE Journal[J],1998,44(10):2252-2257.
[25]StevenL Suib,Richard P Zerger.Direct,continuous,low-power catalytic conversion of methane to higher hydrocarbon via microwave plasma,J Catal.,1993,139:389-391.
[26]Kopytko N,Baronnet F,Valorisation Chimique du Methane par Plasmas Micro-ondes,Can J Chem,1998,76(12):1875-1885.
[27]朱爱民,宫为民,张秀玲等.脉冲电晕等离子体作用下甲烷偶联-Ⅰ无氧气氛下,中国科学(B)[J],2000,30(2):208-214.
[28]陈栋梁,白玉新,王真等.甲烷在氢气助解下的脱氢偶联研究,天然气化工[J],2001,26(2):18-22.
[29]陈栋梁,李庆,于作龙等.甲烷和氮气在微波等离子体下的转化研究,天然气纪工[J],2000,25(4):28-33.
[30]Wan J K S,Tse M,Husby H,et al.High-power pulsed microwave catalytic processes-Decomposition of methane,J.Microwave Power Electromagnetic Energy 1990,25(i):32-38.
[31]Ioffe M S,Pollington S D,Wan J K S.High-Power Pulsed Radio-Frequency and Microwave Catalytic Processes:Selective Production of Acetylene from the Reaction of Methane over Carbon,J Catal,1995,151(2):349-355.
[32]Marafee A,Liu C J,Xu G H,et al.An Experimental Study on the Oxidative Coupling of Methane in a Direct Current Corona Discharge Reactor over Sr/La_2O_3 Catalyst,Ind Eng Chem Res,1997,36(3):632-637.
[33]Cho Wonihl,Baek Youngsoon,Park Dalryung,et al.Conversion of Natural Gas to Higher Hydrocarbons Using a Microwave Plasma and Catalysts,Research on Chemical In termediates,1998,24(1):55-66.
[34]张劲松,Wan J K S,曹丽华,微波诱导甲烷在活性炭/碳化硅上直接转化制C_2烃等,[J].催化学报,1999,20(1):45-50.
[35]朱爱民,张秀玲,宫为民等,脉冲电晕等离子体下甲烷偶联反应研究(Ⅲ)一金属氧化物的多相催化作用,高等学校化学学报[J],2000,21(1):120-123.
[36]徐春蕾,董家黢,杨鸿生,孙永志,孙德坤,杨春,过渡金属与微波等离子体协同催化甲烷制乙炔,东南大学学报(自然科学版)2004.34(2):210-214.
[37]Hiraoka K,AoyamaK,Morise K.On the distribution of ion/neutral molecule clusters in electrospray and laser spray,Can.J.Chem,1985,63(11):2899-2950.
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