연료전지 자동차용 가솔린 연료 개질기의 개발

: Structured Catalyst 상에서 가솔린의 부분산화 개질반응

류종우, 문동주*, 이상득, 이병권, 안병성, 홍석인1

한국과학기술연구원 환경공정연구부, 고려대학교 화공생명공학과1

djmoon@kist.re.kr

Development of Gasoline Reformer for Fuel-Cell Powered Vehicles

: POX Reforming of Gasoline over Structured Catalyst

Jong Woo Ryu, Dong Ju Moon*, Sang Deuk Lee, Byung Gwon Lee,

Byoung Sung Ahn and Suk In Hong1

Environment & Process Technology Division, KIST

Department of Chemical & Biological Engineering, Korea University1

djmoon@kist.re.kr

Introduction

Fuel processor to produce hydrogen from conventional and alternatives fuels has been developed for fuel cell powered vehicles applications. Hydrogen is the ideal fuel for a PEM fuel cell because it simplifies the system integration [1]. However, a direct hydrogen system has many disadvantages such as the lack of widespread refueling infrastructure and high storage volume compared to the hydrocarbon based fuels [2-3]. A reformer based vehicle system has the advantage of using the existing hydrocarbon fuels that are more readily available. The successful development of a fuel cell-powered vehicle is dependent on the development of a fuel processor. In our previous works [1-3,6], we studied the characteristics of powder based catalyst in the POX reforming reaction of iso-octane over the commercial reforming catalysts (ICI-naphtha reforming and Haldor Topsoe catalysts) and our prepared KIST catalysts. In this work, we investigated the kW-class fuel processor system and structured catalysts. To develop of on-board fuel processor for automotive applications, the development of a structured catalysts is an essential technology. We designed a kW-class gasoline reformer system based on experimental data over powder catalysts. Structured commercial ICI catalysts with 400 cell density in square inch were prepared by wash coating methods using ceramic honeycomb of NGK Co. Ltd and commercial ICI catalyst. POX reforming reaction of gasoline in a kW-class gasoline reforming system were carried out in the temperature range of 500∼800℃ at the fixed reaction condition of H2O/C molar ratio=3 and O/C molar ratio=1.

Experimental

1. Chemical

The iso-octane as a fuel source was supplied from J.T. Baker. The standard iso-octane feed containing 100ppm of sulfur was prepared by mixing of the iso-octane and thiophene(99%+, Acros Organics).  Hydrogen (99.999%), air (99.999%) and nitrogen (99.999%) were used in the reaction and the pretreatment of catalysts.  Nickel nitrate, cobalt nitrate, ferric nitrate, ammonium molybdate and magnesium hydrate were provided by Aldrich Chemicals.  Also, □-alumina (2-3 microns) was obtained from High Purity Chemicals.

2. kW-class gasoline fuel processor system

The Performance of the structured catalysts was measured by a kW-class gasoline reformer system.  Gasoline fuel processor system consists of six sections: feed supply, evaporator, POX reforming reactor, HTS reactor, LTS reactor and GC. The gases were delivered by mass flow controllers, and H2O and liquid fuels were fed by a liquid flow controllers (Hi-              Tech Co., model FAC-22-E and L1-FAC-22-0).  Evaporator and POX reforming reactor made up of an Inconel 600 tube (3·1/2 inch) were used.  The HTS and LTS reactors made up of Sus 310 tube (□90.2×440□) were employed in this study.  The reaction temperature was controlled by a PID temperature controller and was monitored by a separated thermocouple placed in the catalyst bed.  This arrangement was capable of ensured an accuracy of ±1℃ of the catalyst bed temperature.  Unreacted H2O was removed by an ice trap and then gas effluent was analyzed by on-line gas chromatograph (HP-6890) equipped with TCD using a carbosphere column (10"×1/8" SS, 80/100 meshes).

3. Structured Catalysts

Structured commercial ICI catalysts with 400 cell density in square inch were prepared by wash coating methods using ceramic honeycomb of NGK Co. Ltd and commercial ICI catalyst. The catalyst formulations prepared in this work are summarized in Table 1. To develop high performance structured catalyst, the fine grinding characteristics of alumina was investigated by means of an attrition mill.  Particle size of alumina decreased with increasing time and BET surface area increased with increasing time. The higher grinding rate of alumina was proven to be obtained with the smaller ball media size, the higher impeller rotational velocity and the lower solid contents. In these conditions, the wash coating of alumina and commercial ICI catalyst on a ceramic honeycomb was performed and activity tests carried for a kw-class gasoline fuel processor.

Results and Discussion

In our previous works [1-3,6], we studied the characteristics of powder based catalyst in the POX reforming reaction of iso-octane over the commercial reforming catalysts (ICI-naphtha reforming and Haldor Topsoe catalysts) and our prepared KIST catalysts. In this work, we designed a kW-class gasoline reformer system based on experimental data over powder catalysts and we prepared structured catalysts in order to develop of on-board fuel processor for automotive applications. Structured commercial ICI catalysts with 400 cell density in square inch were prepared by wash coating methods using ceramic honeycomb of NGK Co. Ltd and commercial ICI catalyst. POX reforming reaction of gasoline in a kW-class gasoline reforming system were carried out in the temperature range of 500∼800℃ at the fixed reaction conditions as space velocity = 1000 h-1, H2O/C molar ratio=3 and O/C molar ratio=1.

It was observed that the catalytic activity of prepared structured catalysts in POX reforming reaction of gasoline for a kW-class gasoline reforming system. The catalytic run is performed at 750oC with a space velocity of 1000 h-1 and by using the feed molar ratios as H2O/C = 3.0 and O/C = 1.0.  The result is presented in Figure 1. It was found that the Cat. 2-2 catalyst displayed better activity than the others prepared catalysts in the POX reforming reaction.

Figure 2 shows the product distribution as a function of the reaction temperature over the catalysts. The H2 concentration increased up to 750oC and remained almost unaffected with further rise in temperature. A rapid decrease in the CO concentration was observed up to 750oC, and, thereafter, only a slight increase was noticed up to 800oC. The CO2  concentrations a little increased with increasing the temperature.  Thus, for the maximum H2 selectivity, it is always desirable to operate the POX reforming system at high temperature; however, there is an adverse affect due to rapid decrease in the CO concentration. A reaction temperature of 750oC is found to be good for operating the system.

Comparison of the performances of prepared Cat. 2-2 catalyst with that of commercial ICI catalyst is shown in Table 2. It was found that the structured catalyst displayed a little lower activity than the powder catalyst in the same reaction condition. Studies on the development of a high performance structured catalyst will be needed.

References

[1] D.J. Moon, K. Sreekumar, S.D. Lee, B.G. Lee and H.S. Kim, Studies on Gasoline Fuel      Processor System for Fuel-Cell Powered Vehicles Applications, Appl. Catal. A, General 215     1-9 (2001) .

[2] D.J. Moon, J.W. Ryu, S.D. Lee, B.S. Ahn and S.I. Hong, Development of Gasoline Fuel     Processor System for PEMFC Automotive Applications, 2002 Fuel Cell Seminar # 422        (2002).

[3] D.J. Moon, J.W. Ryu, S.K. Lee, B.G. Lee and B.S. Ahn, Transition metal catalysts for       the POX reforming of gasoline for fuel-cell powered vehicles applications, Korea Patent       Application 02-21236 (2002) and in application to U.S. Patent (2002).

[4] J. Patt, D.J. Moon, C. Phillips and L. Thompson, Molybdenum carbide catalysts for water     gas shift, Catalysis Letters 65 193-195 (2000).

[5] L. Thompson, J. Patt, D.J. Moon, and C. Phillips, Metal carbides and Nitrides and Borides     useful as water gas shift catalysts, International PCT patent, 60/193 553 (2001).

[6] D.J. Moon, K. Sreekumar, S.D. Lee and H.S. Kim, Studies on Partial Oxidation             Reforming of iso-octane, Proceeding of the 8th Japan-Korea Symposium on catalysts.         263-266, May (2001).

[7] P.J. de Wild, M.J.F.M. Verhaak, Catalysis Today, 60 (2000) 3.

[8] E. Borroni-Bird, Soc. Automotive Eng. 952762 (1995) 2118.

[9] A. Docter, A. Lamm, J. Power Sources, 84 (1999) 194.

Structured Catalysts	Cat.1-1	Cat.1-2	Cat.1-3	Cat.2-1	Cat.2-2	Cat.2-3
□-Alumina coating frequency	1	1	1	2	2	2
Com. ICI Cat. coating frequency	1	2	3	1	2	3

Table 1. The design of the prepared structured catalysts.

Table 2. The effect of reaction temperature on product composition in POX reforming reaction of iso-octane over ICI and Structured catalysts (Cat. 2-2) ; Reaction Temperature=750℃, Space velocity : 1000 h-1,Feed molar ratios of H2O/C=3, O/C=1.

Temperature		550℃		600℃		650℃		700℃		750℃
Catalyst		ICI	Cat.2-2	ICI	Cat.2-2	ICI	Cat.2-2	ICI	Cat.2-2	ICI	Cat.2-2
Product composition (%)	H2	34.9	27.4	40.7	32.8	44.3	34.78	46.5	38.42	46.8	40.87
	CO	19.9	24.3	14.8	21.2	10.6	18.21	8.4	17.11	8.1	14.75
	CO2	9.8	7.8	10.4	7.8	12.4	9.86	14.8	8.92	13.0	9.83
	CH4	0.5	3.0	0.2	2.7	0.2	2.70	0.2	3.73	0.5	4.01
	Air	34.9	37.5	33.9	35.5	32.5	34.45	30.1	32.82	31.6	30.54

Fig. 2 Product distribution as a function of reaction temperature over structured catalysts (Cat. 2-2) in the POX reforming reaction of iso-octane for a kW-class gasoline reforming system. ; Space velocity =1000 h-1, Feed molar ratios of H2O/C=3 and O/C=1.

Fig. 1 POX reforming activity of iso-octane over the various structured catalysts in a kW-class gasoline reforming system.

; Reaction Temperature=750℃, Space Velocity=1000h-1, Feed molar ratios of H2O/C=3, O/C=1.