고체산화물 연료전지에서 수행되는 메탄에 의한 이산화탄소의 내부개질반응

유지영, 박종민, 이상득, 남석우, 문동주*

환경공정연구부

한국과학기술연구원

djmoon@kist.re.kr

Internal Reforming of Carbon dioxide by Methane in SOFC System

Jee Young Yoo, Jong Min Park, Sang Deuk Lee, Suck Woo Nam

And Dong Ju Moon *

Environment and Process Technology Division, KIST

djmoon@kist.re.kr

1. Introduction

Electrocatalytic reforming of CO2 with CH4 is an attractive option in the point of environmental and industrial because of cogeneration which can be produced syngas and electricity.  For example, in addition to the envisaged supply to the processing industry of electricity and process heat, of power generation using combined solid oxide fuel cell (SOFC)rgas turbine plants, and of supplying households with electricity. Furthermore, greenhouse gases are converted into valuable feedstock. . However this reaction is a highly energy consuming and coke forming processTo improve these problems, electrocatalytic reforming of CO2 with CH4 was studied in SOFCmembrane reactor system which generate high electrical power and synthesis gase

2. Experiments

Cathode was fixed as (La,Sr)MnO3, anode material was prepared. Raw materials for preparation of perovskite-type oxide powders were La(NO3)2·6H2O , SrNO3·6H2O , Ni(NO3)2·6H2O,  Cr(NO3)2·6H2O. Each materal dissolved in distillated water and stirresd for 3 h, then dried 100℃ for 2hr. After that, reactants calcined at 900 ℃ for 3 h and grinded.

Another anode material was prepared like below. Aqueous solutions of Ni(NO3)2·6H2O and Mg(NO3)2·6H2O were added on 100 ml in distillated water at room temperature and the light-green suspension was observed. And then continuously stirred magnetically, while pH was maintained at a value of 9 with a 55% NH4  The precipitate was aged in the mother liquor for 24 h at room temperature, and then it was separated, filtered off precipitate.  the solid was washed with distilled water until total removal of nitrate and sodium ions, and then was dried overnight at 100℃ in air. Green solids were obtained.  The solids were calcined in static air at 900.C for 3 h in a furnace. and grinded. Products were investigated by XRD. (Target = Cu, voltage = 40.0 (kV),           current = 30.0 (mA), scan speed = 5.0000 (deg/min))

SOFC test system was developed like figure 1. The apparatus consists of a custom-built furnace operated by a temperature controller up to 1000℃.  The test cell inlet is linked to a stainless-steel and tefron gas manifold which allows complete flexibility in gas handling, gas composition, the choice of fuel. Thus, evaluation is possible over a full range of operating conditions and fuel compositions. The reactor outlet is directly linked to a continuously sampling on-line gas chromatography HP5890 which permits the fuel processing reactions in the actual SOFC to be continuously monitored under operating conditions. The gas chromatograhy used carbosphere column and Ar carrier gas used to analyze H2, CH4, CO, CO2. The conversion rate of reactactants and products were calculated by total flow rate of out gas and the partial pressure of each gases measured by gas chromaography. CH4, CO2 was used as a fuel, Air was used as a substitute of  O2. A mixture of 50% CO2 and 50% CH4 was passed through the anode chamber with a flow rate of 20ml/min, while air (20ml/min) was the cathode side. Gas flow was coltroled by Mass Flow controller. The system was operated at 800℃ for 6hrs. Electrochemical properties were measured by potentio-galvanostate, Solartron 1287 Electrochemical Interface and 1260 Impedance/Gain phase analyzer. All current and voltage measured at steady state. Total system was prepared like figure 2.

Figure 1. Scheme SOFC test system	Figure 2. Schemetic diagram of total system

3. Results and discussion

3.1  Charicterization of anode

La1-xSrxNi1-yCryO3 and NixMg(1-x)O3 catalysts were synthesized. As shown  in Figure 3. La0.9Sr0.1Ni0.6Cr0.4O3 showed perovskite-type oxide which was desired structure to be obtained.

Figure 3. XRD pattern of  La0.9Sr0.1Ni0.6Cr0.4O3

3.2  Methane reforming by carbon dioxide

In order to investigate the catalytic activity of La1-xSrxNi1-yCryO3 and NixMg(1-x)O3 electrode, methane reforming by carbon dioxide to synthesis gas in SOFC reactor. Table 1. shows catalytic activity of methane and carbon dioxide. NixMg(1-x)O3 had excellant activty. La1-xSrxNi0.6Cr0.4O3 showed higher activity than other types.

Table 1. The catalytic activity of the SOFC reactor

Catalyst	CH4 conversion (%)	CO2 conversion (%)
NixMg(1-x)O3	80~85	80~90
La0.9Sr0.1Ni0.6Cr0.4O3	50.2	65.4
La0.8Sr0.2Ni0.6Cr0.4O3	45.8	55.9

3.3 Power generation performance.

Current votage performence of SOFC were measured by galvanostatic method. It was investigated that La0.9Sr0.1Ni0.6Cr0.4O3 and NixMg(1-x)O3 had  a similar properties. And short-circuit condition was more stable than open-circuit condition.

Figure 4. Current votage performence of La0.9Sr0.1Ni0.6Cr0.4O3	Figure 5. Powerdensity performence of La0.9Sr0.1Ni0.6Cr0.4O3

The results were showed that the stability of catalyst electrode depend on the reaction of oxygen ion transferred from cathodewith the surface carbon formed in internal CO2 reforming by CH4 in SOFC system.

Referrence.

1. A.J. Appleby, F.R. Foulkes, Fuel Cell Handbook, Van Nostrand Reinhold, New York, 1989.

2. A.L. Dicks, J. Power Sources 61 (1996) 113.

3. P.Vernoux et al . / Solid State Ionics 135 (2000) 425- 431