DIRECT DME SYNTHESIS FROM SYNGAS OVER Cu/ZnO BASED CATALYSTS PREPARED FROM VARIOUS METHODS: PROMOTERS AND COPRECIPITATION

Transcription

1 23 rd World Gas Conference, Amsterdam 2006 DIRECT DME SYNTHESIS FROM SYNGAS OVER Cu/ZnO BASED CATALYSTS PREPARED FROM VARIOUS METHODS: PROMOTERS AND COPRECIPITATION Seung-Ho Lee, Yong-Gi Mo, Kyunghae Lee, Eunmee Jang, Yun Bin Yan, Wonihl Cho, Woo-Sung Ju Korea

2 ABSTRACT Natural gas conversion and utilization are important options for the new energy source. Recently, we have been made to convert methane, which is the main component of natural gas, into high valued hydrocarbon products. In addition, a recent increase in papers and patents concerning direct DME synthesis has occurred in the past decade. So, we studied the noble method and catalysis for direct DME synthesis from synthesis gas. Cu/ZnO based catalysts were prepared by various methods. By varying the conditions of coprecipitation, promoters and nanoparticles, different mixed oxides containing Cu, Zn, Ga, Mg and Al were obtained. Also, we combined various dehydration catalysts including alumina and aluminum phosphate and synthesize noble catalysts with nanoparticles by non coprecipitation method. Determination of Catalytic performance was carried out by isothermal micro reactor. Characterization was performed by BET surface area determination, thermal analysis, X-ray diffraction and Electron probe micro analysis. We were able to synthesize active and selective DME catalysts, which have over 1 kg DME /L catalyst h productivity at 50 bar and a GHSV 4000 h -1.

3 TABLE OF CONTENTS 1. Introduction 2. Body of Paper 3. References 4. List of Tables 5. List of Figures

4 1. INTRODUCTION DME (dimethyl ether) is a green energy, which discharges little greenhouse gas when it is combusted, in comparison to other fuels, and is rapidly decomposed into CO 2 and water in the atmosphere without forming ozone. DME can be prepared from various energy sources including biomass or coal, as well as natural gas. In addition to the environmental friendly property, DME has some advantages in that since it has a high cetane number and properties similar to those of LPG, it can be used for various purposes including alternative fuel for diesel automobile and LPG, fuel cells, etc., and further, when it is introduced into the market as the novel fuel, it has little obstacle to the construction of the means for transport and storage and the infrastructure [1-7]. Thus, Haldor Topsoe in Denmark, Air Products & Chemicals in USA, JFE in Japan, etc. have developed the novel direct synthetic technique which can allow the novel fuel DME to have the price competitiveness with the prior oil-based fuels, and pushed forward the commercially available DME plant utilizing the medium to small-scale natural gas beds which have a competitiveness in comparison to LNG production. Therefore, it is expected that after the year 2010 the price competitiveness of DME will be secured by mass-production. As the first market, the use of DME as the fuel for power generation where bulk consumption of the fuel is possible is promising. After the year 2010, it is expected that it will be used as the fuel in various fields including alternatives for diesel automobile and LPG, fuel cells, etc. Due to such properties of DME as the fuel, in recent Japan importing LNG is now actively carrying out the project to produce DME from natural gas under the leading by the government, and has organized DME International Company in charge of preparation, introduction and selling of DME to investigate the feasibility and commercialization of the project. Recently, China is now using DME on a scale of 10,000 tons per year, in combination with LPG for domestic use, and actively conducts the study of fuels for transport including development of engine for automobile. Thus, Korea Gas Corporation has pushed forward the preliminary feasibility study on the development and commercialization of the direct synthetic technique of DME as the new energy which is expected that in the near future it may form the new market in East-Asian territory (Japan, Korea, China, India, etc.). In the report, we describe the noble catalysts and DME development in Korea. 2. EXPERIMENTAL A solution of Cu(NO 3 )3H 2 O, Zn(NO 3 )6H 2 O and Al(NO 3 )9H 2 O and a solution of Na 2 CO 3 were added drop-wise to 300mL H 2 O under continuous stirring at 393 K while the ph was maintained at 7±0.5. After, the mixture had been aged for 1 hr without stirring at the same temperature. The precipitate was filtered and the cake was washed by distilled water until nitric acid ion was not detected. And then the cake was dried at 393 K for 15 hr. Followed by calcining at 653 K for 4 hr to

5 obtain methanol synthesis catalyst. Calcined catalyst prepared to powder and gamma alumina, AlPO4 which have a role of methanol dehydration were mixed, palletized at mm. For pre-treatment, the catalyst was reduced under H 2 atmosphere at C for 6 hours. The reaction product was analyzed by gas chromatograph. The DME synthesis systems were set up as in Fig. 1. The two type reactors were used. One is air-cooled, the other is sand-bath type isothermal reactor. The DME synthesis reaction was carried out at 260 C, 50 bar in a fixed bed flow reactor by feeding a gas mixture of H 2 and CO with a molar ratio of H 2 /CO = 1. In case of air cooled type reactor, CO 2 and N 2 was added 3% separately. Figure 1. Schematic diagram of experimental apparatus for DME synthesis 3. RESULTS AND DISCUSSION 3.1 Coprecipitation Method We tried two different coprecipitation methods. First, the precipitating solution was added on the metal solution. The ph was varied on precipitation and finally reached to 7. Second, the precipitating solution and the metal solution were simultaneously dropped to deionised water. The ph was maintained at 7 during the precipitation. Figure 2 shows EPMA (Electron Probe Micro Analyzer, JEOL, JXA-8900R) results. In figure 2 (a) show dispersion of Cu, Zn, Al in the MeOH catalyst made by first method described above. Figure 2 (b) is the picture of that by second method. From these results, we know that metal dispersion depend on precipitation method. Also,

6 reactivity results show precipitation method and degree of dispersion is very important factor for catalytic activity. Figure 2. EPMA results of the two catalyst precipitated different method. Table 1 show that the conversion, selectivity and productivity are effective in case of ph maintained at same value during precipitation. Table 1. Change of catalytic activity for DME synthesis by Precipitation method Precipitation method (a) (b) CO conversion (%) DME Selectivity (%) DME Productivity (kg/l.cat.hr) Activity Increase by Metal Oxides In this study, we tested various metal oxides as promoters. Table 2 shows the activities of a DME catalyst containing Ga 2 O 3, MgO and ZrO 2 on varying the content from 0.05 to 5 wt. %. We selected Ga 2 O 3, MgO and ZrO 2 as promoters. The addition of Ga 2 O 3 improves the dispersion of Cu particles and activity of a Cu/ZnO catalyst. But Ga 2 O 3 can not increase life time, so we used MgO as a promoter for preventing coke formation reduced by the basicity of MgO. In the other hands, ZrO 2 that has water resistance and strong basicity increases activity and durability simultaneously. Table 2. Activities of Cu/ZnO based DME catalysts containing the metal oxides

7 Catalyst Composition Productivity (kg/l.cat.hr) CuO/ZnO/Al 2 O 3 /Ga 2 O 3 /MgO 40 / 40 / / 1.0 / CuO/ZnO/Al 2 O 3 /Ga 2 O 3 /MgO 40 / 40 / 18.5 / 1.0 / CuO/ZnO/Al 2 O 3 /Ga 2 O 3 /MgO 40 / 40 / 14 / 1.0 / CuO/ZnO/Al 2 O 3 /Ga 2 O 3 /MgO 40 / 40 / 18 / 1.0 / CuO/ZnO/Al 2 O 3 /Ga 2 O 3 /MgO 40 / 40 / 17 / 1.0 / CuO/ZnO/Al 2 O 3 /ZrO 2 40 / 40 / 19.5 / CuO/ZnO/Al 2 O 3 /ZrO 2 40 / 40 / 15 / * Reaction conditions: weight ratio of the above catalyst / dehydration catalyst (gamma alumina/ AlPO4 = 1/ 1) = 70 / 30, weight of catalyst = 3 g, H 2 /CO 2 ratio in the feed = 1, GHSV = 4,000 hr-1, temperature = 260 C, pressure = 50 bar, reaction t ime = hr Development of DME Demo Plant In case of Korea where much energy is consumed in these days of high oil price, the new fuel DME provides the new energy source and forms the basis of an increase in employment and a creation of gaining through the heightening of cooperate image of Korea Gas Corporation and further, the diversification of new business when DME is utilized as the complementary fuel for the clean fuel LNG. Therefore, there is a necessity of promoting the clean energy DME project as the business required for Korea Gas Corporation. The Korea Institute of Science and Technology, the Korea Institute of Energy Research and the Korea Research Institute of Chemical Technology as well as Korea Gas Corporation conducted the study of the procedures for preparing and synthesizing methanol and DME from the raw material carbon dioxide by hydrogenation, as the program of carbon dioxide treatment, and are currently under operation of the experiment in the pilot plant scale enlarged from the laboratory scale [5, 8-10]. Particularly, in 1997 Korea Gas Corporation has conducted the project study of the preparation of liquid fuels from natural gas in the support of the Ministry of Commerce, Industry and Energy, and then has proposed that DME preparation according to GTL (Gas to Liquid) procedures for liquefying natural gas is the optimum process in connection with the program for removal of carbon dioxide. Meanwhile, from the year 2000 the study of the development of technology for preparing DME from natural gas and carbon dioxide was conducted in the self-support of Korea Gas Corporation. Further, in the year 2001 they set about making the study of development of the 50 kg/day DME process in the support of the Ministry of Science & Technology, and then established the pilot plant in the year 2002, successfully operated the plant in the year At present, this process is in the 10 ton/day demonstration stage for practical use. The construction of this demo plant will be completed in the year 2008 by the catalyst, reactor and process of KOGAS.

8 4. CONCLUSION Due to environmental friendly property and broad applicability of DME, it has been promised that the demand of DME as the fuel will be rapidly increased in the Asian territory including China, India, Japan, Korea, etc., where show the rapid economical development and require the improvement of environmental problems. In Japan, for using DME as the fuel the development of related-utilization technology, construction of infrastructure, improvement of distribution system including improvement of the laws and regulations, etc. have been actively pushed forward. In Korea, it is expected that after 2010, DME will be used as various fuels including as alternatives for diesel fuel for transportation, and as the fuel to be mixed with LPG for home use, or for electrical generation or fuel cells. However, since the infrastructure and market for DME were not constructed as yet, DME is in the state that the risk of business is higher than that of other alternative fuels. Although the use as the alternative for LPG and the fuel for the power plant have been examined as the primary alternative market, in order to grow DME eventually as the alternatives fuel for diesel in the fuel market the government s polity will on the diversification of energy resources and the use of environmental friendly fuel, and the development of DME preparing technology by which DME having competitiveness can be produced must be preceded. We obtained high efficient catalytic performances on Cu/ZnO based catalyst compared to commercial catalyst along with stability for production of DME. The addition of Ga 2 O 3, MgO and ZrO 2 as promoters shows effectiveness of activity and life time. From these founding, this catalyst can be attributed to the efficient catalyst for DME production process (10 ton/day) that is now under designing at our company. REFERENCES 1. Adachi, Y., Komoto, M., Watanabe, I., Ohno, Y. and Fujimoto, K. (2000). Effective utilization of remote coal through dimethyl ether synthesis. Fuel, 79(3-4): Semelsberger, T. A., Borup, R. L. and Greene, H. L. (2005). Dimethyl ether (DME) as an alternative fuel. J. Power Sources, in press. 3. Saito, M., Fujitani, T., Takeuchi, M. and Watanabe T. (1996). Development of copper/zinc oxide-based multicomponent catalysts for methanol synthesis from carbon dioxide and hydrogen. Appl. Catal. A: Gen., 138: Rostrup-Nielsen, J. R., Sehested, J. and Nørskov, J. K. (2002). Hydrogen and synthesis gas by steam- and CO 2 reforming. Advan. Catal., 47:

9 5. Kim, J.-H., Park, M. J., Kim, S. J., Joo, O.-S. and Jung, K.-D. (2004). DME synthesis from synthesis gas on the admixed catalysts of Cu/ZnO/Al 2 O 3 and ZSM-5. Appl. Catal. A: Gen., 264: Fei, J.-H., Yang, M.-X. Hou, Z.-Y. and Zheng, X.-M. (2004). Effect of the Addition of Manganese and Zinc on the Properties of Copper-Based Catalyst for the Synthesis of Syngas to Dimethyl Ether. Energy & Fuels, 18: Sun, K., Lu, W., Qiu, F., Liu, S. and Xu, X. (2003). Direct synthesis of DME over bifunctional catalyst:surface properties and catalytic performance. Appl. Catal. A: Gen., 252: Lee, S.-H., Cho, W., Ju, W.-S., Cho, B.-H., Lee, Y.-C. and Baek, Y.-S. (2003). Tri-reforming of CH 4 using CO 2 for production of synthesis gas to dimethyl ether. Catalysis Today, 87: Ju, W.-S., Choi, C. W., Lee, S.-H., Cho, W., Hwang, J.-S., Park, S.-E. and Baek, Y.-S. (2004). Catalytic Reactivity for the Formation of Dimethyl Ether from Synthesis Gas over Hybrid Catalysts. Stud. Surf. Sci. Catal., 153: Roh, H.-S., Jun, K.-W., Baek, S.-C. and Park, S.-E. (2002). Highly Active and Stable All- Round Catalyst for Methane Reforming Reactions: Ni/Ce-ZrO 2 /θ-al 2 O 3. Bull. Korean Chem. Soc., 23(6):

10 List of Tables Table 1. Change of catalytic activity for DME synthesis by Precipitation method Table 2. Activities of Cu/ZnO based DME catalysts containing the metal oxides * Reaction conditions: weight ratio of the above catalyst / dehydration catalyst (gamma alumina/ AlPO4 = 1/ 1) = 70 / 30, weight of catalyst = 3 g, H 2 /CO 2 ratio in the feed = 1, GHSV = 4,000 hr-1, temperature = 260 C, pressure = 50 bar, reaction t ime = hr. List of Figures Figure 1. Schematic diagram of experimental apparatus for DME synthesis Figure 2. EPMA results of the two catalyst precipitated different method.