Hydrogen generation from steam reforming of ethanol in dielectric barrier discharge Hydrogen generation from steam reforming of ethanol in dielectric barrier discharge

Hydrogen generation from steam reforming of ethanol in dielectric barrier discharge

  • 期刊名字:天然气化学(英文版)
  • 文件大小:658kb
  • 论文作者:Baowei Wang,Yijun Lü
  • 作者单位:Key Laboratory for Green Chemical Technology
  • 更新时间:2020-10-22
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论文简介

Availableonlineatwww.sciencedirect.comJoumal ofScience DirectNatural GasChemistryELSEVIERJournal of Natural gas Chemistry 20(201Hydrogen generation from steam reforming of ethanol indielectric barrier dischargeBaowei Wang, Yijun Li, Xu Zhang, Shuanghui HuKey Laboratory for Green Chemical Technology, School of Chemical Engineering Technology, Tianjin University Tianjin 300072, ChinaI Manuscript received July 23, 2010: revised October 19, 2010 1AbstractDielectric barrier discharge(DBD)was used for the generation of hydrogen from ethanol reforming. Effects of reaction conditions, such asvaporization temperature, ethanol flow rate, water/ethanol ratio, and addition of oxygen, on the ethanol conversion and hydrogen yield, werestudied. The results showed that the increase of ethanol flow rate decreased ethanol conversion and hydrogen yield, and high water/ethanolratio and addition of oxygen were advantageous.nd hydro dn yield increased with the vaporization room temperature upto the maximum at first, and then decreased slightly /he maxinum hydrogen ld of 31.8% was obtained at an ethanol conversion of88.4%under the optimum operation conditions of vaporizeboC, ethanol flux of 0.18 mL/min, water/ethanol ratio of 7.7and oxygen volume concentration of 13.3%0hydrogen; ethanol; reforming; dielectric bar1. Introductionwas also reported in which plasma was employed toproduce high reactive particles with high energy consistingof electrons. ions, excited atoms and free radicals to recom-Hydrogen is considered as a clean energy source whichbine into new desirable reactants. Due to its high energy denprovides a considerable quantity of thermal energy per ui sity and high-activity, hydrogen generation using non-thermalweight three times as petrol does. Moreover, as a renewablefuel, hydrogen is an effective solution to reduce the emissionsplasma can greatly lower the reaction conditions, improve theof CO2 and to protect against the environmental polluticreaction speed, and optimize the reaction process compareature and high pressure. Several papers had reported thewhich seriously restricts its application. As a result, how to of non-thermal plasma for the hydrogen production throughobtain more hydrogen and conveniently to reduce the transportation and storage is very significant. During the recentethanol steam reforming [12-15]. The results showed that ityears, hydrogen obtained from easily transported liquid feed- gained more hydrogen-rich syngasesstocks, such as methanol and ethanol were intensively stud-The aim of this work is to study the effects of many paied. However, as a safe and renewable energy source which rameters, such as ethanol flow rate, vaporization room tempercan be conveniently obtained by fermentation of agricultural ature, and water/ethanol ratio, as well as addition of oxygen,surplus, ethanol is more suitable to produce hydrogen comon hydrogen production in the steam reforming of ethanol inpared to methanol. Ethanol reforming has more advantages a dielectric barrier discharge reactorin the future. Researches on H2 production through ethanolcatalytic reforming has been reported in many previous stud- 2. Experimentalies [4-1ll, including steam reforming and partial oxidationreforming, using inexpensive catalysts like cuprum, nickelcobalt, or iron and precious metal catalysts like platinum,Figure 1 shows the schematic diagram of reaction usingruthenium. Moreover, ethanol reforming under non-thermal dbd reactor designed and built for this research. It consistedCorresponding author. Tel: +86-22-27402944, Fax: +86-22-27890905; E-mail: wangbw(@ tju.edu中国煤化工This work was supported by the National Natural Science Foundation of China No. 20606023HCNMHGCopyright(2011, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. All rights reservedoi:10.1016S1003-9953(1060160-0152Baowei Wang et al. Journal of Natural Gas Chemistry VoL. 20 No. 2 2011of a RBD reactor, a high-voltage transformer, a gas supply where, Fout represents the outlet total gas flowrate(mL/min)d an analysis systemH, and XCn represent volume fraction rate of hydrogen, Cn(CO(= 1, 2 ), CH4, and C2 hydrocarbons)in outlet total gasflowrateH2 yield (%)= H2 selectivity x ethanol conversion ratio(4)口FigQ. Schematic diagram of reaction setup. I--Argon, 2-Additive gas3-Pump, 4-Vaporization room, 5-Outer electrode, 6-Inner electrode. Figure 2. Schematic diagram of DBD reactor. 1--outer electrode(aluminum7-Quartz tube, &Cool trap, g-Gas chromatography, 10--Bubbltape): 2--inner electrode(stainless-steel rod ); 3--dielectric barrier(quartz)controller, 11--Oscilloscope, 12-High voltage transformer, 13--Gas mixerThe DBd reactor was made of the following parts as 3 Results and discussiondepicted in Figure 2. Aluminum tape(1)which covers externally the quartz tube is used as the outer electrode. Atainless- steel rod (2) is inner electrode (3 mm in outer diam-Effect of the change in vaporization room temperatureon ethanol conversion and hydrogen yield is shown in Figeter). The quartz tube(3)acts as dielectric barrier (90 mm ure 3. It is clear that ethanol conversion and hydrogen yieldlong, 9mm and 15 mm inner and outer diameters, respec- increased with increase of the vaporization room temperaturetively). Power of 40W and 18.7 kHz was used to generate from 96 Cto 120C. While the vaporization room tempera-the plasma in the study. The transformer provides a maxcilloscope with P6015A high voltage probe and A622 curviously, preheating ethanol makes contribution to ethanol decomposition and hydrogen production. But at a temperaturerent probe. Argon or oxygen as carried gas went to a mixer higher than 120 C, ethanol conversion and hydrogen yieldby controlling their flow rates precisely controlled by MFc decreased with the rise of the temperature because ethanolDO7-7A/2MM(Beijing, Jianzhong). Then the mixed gases flux increased with the higher temperature and then the resand ethanol were introduced into the quartz tube by a pump idence time of the reactants decreased. As shown in Figure 4to generate the hydrogen-rich gases. Effluents passed througha similar effect of vaporization room temperature on the sea cool trap to condense non-converted ethanol and were an- lectivities of gaseous products(H2, CO, CH4, C2H2 /4, C2H6alyzed by gas chromatography( GC9790). The main com- C3H&)was also observed as the effects on ethanol conversionponents in gas mixture were H2, CO, CH4, C2 H4, C2H6, and and hydrogen yield, indicating that the residence time wascritical parameter of affecting ethanol decomposition andh 9Ethanol conversion is defined as Equation(1)Conversion (%)=Input ethanol- Out ethanol x100here, [Input ethanol is the inlet ethanol flowrate(g) andoutput ethanol] is the outlet ethanol flowrate(g). The se-lectivities of hydrogen, carbon monoxide, carbon dioxidemethane, and C2 hydrocarbons are calculated as shown inb Ethanol conversionEquations(2)and (3), respectivelyH2 selectivity(%)=0.1869x×100(2)Cnleox, CH4, C2H4, C2H6, C3 Hs)selectivities(%)中国煤化工1401500.2803n× Fout X Xc×t10CNMH902,0conversion andT30150Vap or i zati on roomt enper atur eloJournal of Natural Gas Chemistry VoL. 20 No. 2 201I5(40-CHVC H/CH- C,H/CH30F-9CHyC,Hs0.150.200.250.300.35.400.45Vaporization room temperature(C)Ethanol flowrate(mL/min)Figure 4. Effect of vaporization room temperature on selectivities of gasFigure 6. Effect of ethanol flowrate on selectivities of gas productsductsThe effect of water/ethanol ratio on the ethanol conver-Figure 5 shows the effect of inlet ethanol flowrate on the sion and hydrogen yield as well as on the selectivities ofethanol conversion. Ethanol flowrate varied within the range gaseous products is shown in Table I and Figure 7,respecof 0. 18-0.44 mL/min, while the length of discharge zone, tively. Water/ethanol ratio varied from one to eight, whilecarried gas flux, input power, discharge frequency, and vapoother operating parameters were kept constant values as the3ion room temperature were fixed at 90 mm, 16.6 mL/min, above. As the inlet water/ethanol ratio rised, ethanol conW, 18.7kHz, and 120C, respectivelyversion and hydrogen yield increased up to the maximum ofIt is apparent that ethanol conversion and hydrogen yield 77% and 31.1%, respectively. It was reported that additiondecreased with increasing the ethanol flowrate. This can be of water is in favor of ethanol decomposition and H2 producplained that the energy used in per ethanol molecule de- tion 12]. As the water/ethanol ratio increased, oxygen radicalcomposition was reduced when input power was fixed at con- and hydroxyl radical from water molecules became more acstant value, which directly reduced the number of ethanol tive to transfer the energy and collide with ethanol moleculesolecules decomposition and leaded to a decrease on ethanol to promote its decomposition. From Figure 7, among theconversion and H2 yield. The effects of ethanol flowrate on gaseous products, hydrogen and carbon monoxide were thealso investigated. FImajor products and theof C3 hydrocarbon stillure 6, it can be seen that the selectivities of other gaseous stayed at a relatively low level. In addition, the selectivitiesducts decreased as ethanol flowrate increased, but hydro- of gaseous products increased continuously as water/ethanolgen and C2 unsaturated hydrocarbons originally decreased ratio rised from one to eight. Such an increasing trend was inand then slightly increased. This can be ascribed to the de- contrast with the effect of ethanol flowrate on gaseous prodcrease of free radicals concentrations which leads to difficult ucts without addition of waterconversion of C2 unsaturated hydrocarbons into saturated hyTable 1. Effect of HO/C2 Hs OH ratio on ethanoldrocarbons by combining with hydrogen radical. The reactionconversion and H2 yieldducing C2 unsaturated hydrocarbons have competitive reH2O/C2 HS OH(mol: mol) Conversion of ethanol (% Yield of H2(%)lations with that producing saturated hydrocarbons72.722.0Ethanol conversionH, yieTable 2 shows the effect of addition of water and oxygenon ethanol conversion and H2 yield. Water/ethanol ratio wasfixed at 7.7 and volume concentration of oxygen was changedrange othat as volume fraction of oxygen increased, ethanol conversion first increased up to the maximum of 88. 4% whenume concentration of oxygen was 13.3%0, and then slightlydecreased Because oxygen radical easily combined with freeradicals produced from ethanol decomposition and was con-0.150.200.250.300.350.400.45verted into hydroc中国煤化工 o an increase inEthanol flowrate(mL/min)ethanol conversioCNMH ConcentrationQEffect of ethanoldooothanol conyversion 1.0 yieldof2 8n. Moreofu, p3Uuuigy was cug 40 to decom- 150pose added water and oxygen when the input power was fixedVap o i zati on rooteper at urelo 0154Baowei Wang et al. Journal of Natural Gas Chemistry VoL. 20 No. 2 2011at 40 W, resulting in the slight decrease of ethanol conversion tively. As ethanol flowrate increased, ethanol conversion, hylater. Hydrogen yield kept increasing up to a maximum of drogen yield and selectivities of gaseous products decreased31.8% when volume concentration of oxygen was 34.3%. As but the selectivities of C2 unsaturated hydrocarbon increased40effect of water/ethanol ratio on ethanol conversion and hy- slightly. Addition of water promoted ethanol conversion,indrogen yield, addition of oxygen also further contributed to this work the ethanol conversion increased up to 77.6% at aethanol decomposition and hydrogen generationwater/ethanol ratio of 7.7. Ethanol conversion and hydrogenyield were improved due to addition of oxygen in ethanol so-lution. Ethanol conversion and hydrogen yield increased up to88.4% and 3 1. 8% when volume concentration of oxygen was13.3%and34.3%,reely. Also, it's deduced from thestudy that the residence time and input power are critical parameters affecting ethanol conversion and H2 yield. The optimum conditions for hydrogen generation were achieved at-CHvaporization room temperature of 120C, ethanol flowrate ofPCHYCH0 18 mL/min, water/ethanol ratio of 7. 7 and oxygen volumeHconcentration of 13. 3 %o under which the maximum ethanolconversion was obtained. And hydrogen yield reached themaximum at oxygen volume concentration of 34.3%ReferencesH,O C,H,OH ratioFigure 7. Effect of H2 O/C2 Hs OH ratio on selectivities of gas products[1 Bromberg L, Cohn D R, Rabinovich A, Surma J E, virden J. IntJ Hydrogen Energy, 1999, 24(4): 341[2] Futamura S, kabashima H, IEEE, Kabashima H. IEEE T INDTable 2. Effect of volume concentration of oxygen on ethanol conversionAPPL,2004,40(6):1459and Hz yield3] Segal S R, Carrado K A, Marshall C L, Anderson K B ApplOxygen content(%) Conversion of ethanolYield of H2(%)Catal a,2003,248(1-2):33[4 Nishiguchi T, Matsumoto T, Kanai h, Utani K, Matsumura Y,2088.4Shen WJ, Imamura S Appl Catal A, 2005, 279(1-2): 27385.631.3Marino F, Boveri M, Baronetti G, Laborde M. Int HydrogerEnergy,2001,26(7):665[6 Barroso MN, Gomez M f, Arrua L A, Abello M C, Appl catalA,2006,304:116[7] Sun J, Qiu X P, Wu F, Zhu W T Int J Hydrogen Energy, 200530(4):437[8] Fajardo H V, Probst L F D. Appl Catal A, 2006, 306: 134The non-thermal plasma is a promising technique for 9] Mattos L V, Noronha FB. J Power Sources, 2005, 145(1):10hydrogen production from ethanol reforming in a dielec- [10] Klouz V, Fierro V, Denton P, Katz H, Lisse JP. Bouvot-Mauduitic barrier discharge reactor. The effects of various factorsS. Mirodatos C.aporization room temperature, ethanol flow rate. [11] Jimenez M, Yubero C, Calzada M D J Phys DPhys. 2008water/ethanol ratio and addition of oxygen in ethanol so[12] Aubry O, Met C, Khacef A, Cormier J M. Chem Eng J, 2005lution were examined. When vaporization room tempera106(3):241ture was 120C, ethanol conversion and hydrogen yield as[13] Yanguas-Gil A, Hueso J L, Cotrino J, Caballero A, gonzalezwell as the selectivities of gaseous products increased up toElipe A R Appl Phys Lett, 2004, 85(18): 4004he maximum, and then decreased at a higher vaporization [14] Sarmiento B, Javier B J, Viera I G, Agustin GE, Cotrino J. Ricoroom temperature. Ethanol conversion and hydrogen proVictor JJ Power Sources, 2007, 169(1): 140duction reached the maximum of 34.3% and 13.3%, respec- [15] Protasevich E T Technical Physics, 2003, 48(6): 795中国煤化工CNMHG4HO/Q2HCHratio

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