DAEHAN HWAHAK HWOEJEE (Journal of the Korean Chemical Society) Vol. 20, No. 5, 19花 Printed in Republic bf Korea

촉매반응에 의한 연탄 연소가스로부터 일산화탄소의 제거 (제 1보 )

鄭基鎬•李源國

한국과학원 화학 및 화학공학과

(1975. 11. 14 접수 )

Removal of Carbon Monoxide from Anthracite Flue Gas by Catalytic Oxidation (I)

Ki Ho Chung and Won Kook Lee

Korea Advanced Institute of Science, Seoul, Korea

(Received Nov. 14, 1975)

요 약. 연탄 연소가스중의 일산화탄소와 산소 사이의 반응을 몇가지 촉매에 대해 조사했다 . 이 산화망간 , 산화 동 및 그 혼합촉매를 사용하였으며 , 그 실효반응 온도 (elective reaction temper- ature) 는 각각 다음과 같다 . 즉 , MnC)2 단독촉매 및 30 % MnO2-70 % CuO 혼합촉매 는 250 °C, 60는 450 °C, 50 % MnO2-50 % CuO는 200 °C, 70 % MnO厂30 % CuO는 180 °C였다 . 실효반응 온도 이 하에서 일산화탄소의 산화율은 일산화 탄소의 농도가 증가함에 따라 감소하는 경 향을 보였 으며 , 실효반응 온도 이상에서는 변화가 없었다 . 반응기 내 체재시간은 0.9〜1.8초의 범위 내에서는 일산화탄소 산화반응에 조금도 영향을 주지 않았다 .

ABSTRACT. On the condition of adequate air supply, complete removal of carbon monoxide occurred above 650 °C. Using catalysts, the oxidation of carbon monoxide occurred at lower tempe­ ratures ；on both MnO2 and 30 % MnO2 - 70 % CuO at 250 °C, on CuO at 450 °C, on 50 % MnO 2- 50 % CuO at 200 °C, and on 70 % MnO2 - 30 % CuO at 180 °C. Manganese dioxide (/>-type) showed higher activity than cupric oxide (n-type) and a catalyst consisting of 60 % MnO2 -40 % CuO had the highest activity of all the MnO2-CuO mixture. Over the range of transitional temperature, carbon monoxide removal efficiency decreased linearly with increasing inlet carbon monoxide concentration while temperature was fixed. Residence time of gases in the catalytic reactor, in the range of 0.9 to 1. 8 seconds, gave no effect on carbon monoxide conversion.

cularly in Korea, most of the population are INTRODUCTION threatened by this gas from using anthracite Carbon monoxide seems to be the most ubi­ briquette for their heating system as the principal quitous pollutant gas in the world today. Parti­ fuel materials.

—431 一 432 鄭基鎬 •李源國

The main component of the anthracite is car­ mechanism of the catalytic oxidation of carbon bon, 1 and carbon monoxide, as well as carbon monox너 e was investigated by many workers,20^22 dioxide, is produced primarily during combustion and MnOz (/»-type) showed a high catalytic of the anthracite. 2,3 activity on carbon monoxide oxidation, however, There have been many investigations on the CuO (n-type) rather mild activity.16,17 The carbo교 monoxide pollution. Morterra and Low4 addition of foreign ions (such as Cu2+) into the investigated the chemisorption o£ carbon mono­ manganese dioxide lattice might modify the xide on reactive silica, and Hofer and his co­ concentration and distribution of holes and workers5 determined the characteristics of several electrons by suitable changes of the Fermi level catalysts f。호 the oxidation of ethylene and carbon of the semi-conductor23. monoxide. For practical purpose, the catalytic In this experiment, catalytic activities of ma­ muffler was developed to oxidize residual com­ nganese dioxide and admixtures with cupric bustible matter which was discharged from the oxide were investigated for the oxidation of automobile engine. 6 carbon monoxide contained in the anthracite flue In Korea, many workers have been investi- gas. 잉 ating on controlling carbon monoxide gas libe­ rated from anthracite briquette.7,9 An efficient EXPERIMENTAL METHOD

carbon monoxide detector and alarm system Experiment was carried out by using a small were developed by Kim et. al.10 Lee et. al.11 catalytic reactor (2. 5cm I. D. and 30cm long) studied the several catalysts on burning of which was made of Vycor glass. A s사 lematic Korean anthracite, and effective combustion diagram of the catalytic reactor is illustrated in devices were also developed.12,13 Hwang and Fig. 1. Son14 found that the combustion rate was rapid The reactor was heated electrically, and con­ in the environment of proper moisture than dry. trolled by a variable transformer. Temperature Carbon monoxide can be removed by a selec­ in the catalytic reactor was measured by a tive oxidation to carbon dioxide, by catalytic pyrometer with alumel-chromel thermocouple. reaction with hydrogen to hydrocarbons, by absorption in cuprous salt solutions or by reaction with steam on a catah'st to carbon dioxide and hydrogen, but oxidation method will be the most convenient to the heating system used in - - this country. Carbon monoxide is oxidized con­ 트 —— tinuously to carbon dioxide over the temperature o w of 650°C.15 For pollution control, however, —— oxidation at rather lower temperature is required, and highly selective catalysts that will convert carbon monoxide to carbon dioxide are a great demand. It is obvious that 力一 type or n-type metal ox거 es play an important catalytic role on the oxidation of carbon monoxide alone. 16~19 The

Journal of the Korean Chemistry Society 433

Fire brick surrounded the reactor was used as a Japan Wago pure Chemical Industries and were insulator, and inlet gas was introduced from the reagent grade. Several powder mixtures of these top of the reactor. Vycor glass chips were filled two materials were knealed with distilled water at the lower side of the reactor to support cata­ and pelleted to 3 mm X 3 mm cylindrical shape lyst and 30cc of catalyst was followed on it. under the pressure of about 200 psi. Then these Fig. 2 shows a thematic diagram of the pellets were heated at the temperature of 500° C equipment set-up. From the anthracite furnace for 2 hours. Then these products were kept in to the suction pump, a gas line was built with the sealed bottle so as not to adsorb any un 4 mm glass tube. Gas could be passed through it wanted components from the air. with the aid of suction pump. Gas flow rate was checked with a rotameter, and a manometer was RESULTS AND DISCUSSION employed to show the pressure drop between While burning the anthracite, temperature entrance and exit of the reactor. The gas trap above burning area reached to 850〜900 °C at was made of alternate layers of silica gel, cal­ maximum. It showed no effect in carbon mono­ cium chloride, calcium oxide and sodium hy­ xide conversion by varying the gas flow rate droxide, which removed water vapor, hydrogen from 1,000 to 2,000 cc/min or the residence sulfide and sulfur dioxide, respectively. time in the reactor from 1.8 to 0.9 second. Samples of gas were collected respecting from These showed that this range of residence time the gas line at the place of inlet and outlet the would be sufficient for the oxidation of carbon reactor, and analyzed by the method of iodine monoxide in the catalyst bed, so that the effect pentoxide24 and by a gas chromatography.25 of surface area in catalysts used could be negli­ Cupric oxide and manganese dioxide used as gible for overall reaction in this experiment. In catalysts in this experiment were a brand of general, for a given catalyst, the greater the

Vol. 20, No. 5, 1976 434 鄭基鎬 •李源國

amount cf surface available to the reacting gas, °C. carbon monoxide was oxidized continuously the better conversion can be obtained. (Fig, 3). Both MnO2 and 30 % MnO2 - 70 % About 20,000 ppm of carbon monoxide was CuO oxidized carbon monoxide completely at liberated on dry basis when the burning was not 250 °C, CuO at 450 °C, 50 % MnO2-50 % CuO in good condition. Anthracite Rue gas ccntaincd at 200 CC, and 70 % MnO2-30 % CuO at 180° C. about 1 to 2 volume percent of CO, in general, MnO2 Cotype) showed better activity than 8 to 9% cf CO2, 15% O2, 75% N2 and a trace CuO (n-t^-pe), and the former had some catalytic (less than 0. 04%) cf H2 on dry basis. A trace activity even at room temperature. Inteipolation of sulfur oxides, hydregen sulfide and hydrocar­ in Fig. 9 indicated that the 60% MnO2 - 40 弓 bons were predicted, but not detectable. Instru­ CuO as the best catalyst of all the MnO2~C：j.O ment used was Varian Aerograph cf model 202 system. with TCD, and the column involved 90% of The effective reaction temperatures of the molecular sieve 5A and 10% of molecular sieve catalysts used in 나 ］ 诅 expariment were somewhat 13X. higher than the reaction of pure carbon mono­ The effect of temperalure on the percent con­ xide with oxygen. These results seemed to ba version of carbon monoxide is presented in Fig. from the difference in catalyst preparation p:x> 4 to 8 for each catalyst, and in Fig. 3 without cedure26 in each cases and/or the interaction of catalyst. When catalyst was not used, carbon the foreign gases in the inlet gas mixture during monoxide oxidation was started at about 4-50 °C reaction. Inlet gas used here might be a mixture but the reaction rate was very slow. Over 650 of 0务 N2, CO2, CO, H2O, H2 and a trace of

IOO ^.00 300. 400 5OC 600 Reaction terr^p ,CC Fig- 3. Effect of temperature on carbon r財 mow，：。 Fig. 5. Effect of temperature on carbon monoxide conversion (without catalyst). conversion (with CuO).

Fig. 4. Effect or temperature on carbon monoxide 恥思 .6. E任 ect of temperature on carbon monoxide ■ conversion (with MnO2). conversion (with 30% MnO2-70 % CuO).

Journal of the Korean Chemistry Society 촉매반응에 의한 연탄연소가스르부더 일산화단土의 제거 （ 제 1 느 ; 435

Fig. 7. E任 ect of temperature on carbon monoxide conversion (with 50 % MnO2~50 % CuO).

Fig. 8. Effect of temperature on carbon monoxide conversion (with 70 % MnC)2~30 % CuO). vacancy and Oaas~ is th은 oxygen atom dissaved in the active site. Oxygen was always adsorbed SOZ, H2S and hydrocarbons. It was shown22 as a negatively charged species, giving rise the that oxygen and moist air a任 ected the semi­ enhancement of conductivity to />-type oxide. conductivity of cuprous oxide at room temper­ As © is dissipated because of combining ature. carbon monoxide with © and COads++Oads----- > The initial step of the reaction of carbon COadJ-OadsL oxygen in the 흥 as mixture have monoxide oxidation on MnO2 may be the pro­ to bs dissolved in MnO2 lattice in order to fill duction of positive holes in MnO2 lattice by the up the Oads- consumed. From this viewpoint, excess of oxygen. The progressive mechanism production rate of COads+-Oads- is dependent upon of the carbon monoxide oxidation on the MnO2 the number of positive hole, and consequently may be represented； COads*-°ad厂—부 CO2 is depended mainly upon §。 涵 厂 +㊉. (1) 102 —> O\ds + ©, adsorption of O2 2—>0 It was already proved27 that 「+㊉ (2) CO + ㊉—> CO^ds， adsorption of CO 4O2—>Oad was the rate determining step in the catalytic oxidation of carbon monoxide, (3) CC广 ads+OLds—>CO+acl3-O~atis, reaction step and the partial pressure of the oxygen showed (4) CO^ads-O_ads-^CO2, desorption step severe effect on this reactionn and that carbon monoxide affected rather mildly than the oxygen. Where ® represents the positive hole, CO+ads The introduction of Cu2+ to MnOo lattice is the carbon monoxida molecule adsorbed in the might increase the number of positive hole and

Vol. 20, No. 5, 1976 436 鄭基鎬 ,李源國 60

1000 2000 3000 4000 5000 6000 7000 8000 9000 Inlet CO concentraiion,ppm Fig. io. Effect of CO concentration on removal e伍 ciency with CuO at temperature of 300 °C.

the reaction on the admixtures with CuO would comb or wire screens to remove carbon mono­ begin on the condition of higher concentration xide from the flue gas of the domestic anthracite of positive hole than M11O2 alone. Parravano23 briquette. The honeycomb unit has the advan­ and many other workers22 showed the influence tages of low pressure drop, good distribution of of doping the lower or higher-valence ions to gas to the entire catalyst surface, ease of handl the p-type semi-conductor. But exact mechanism ing, high volumetric e伍 ciency, and thermal of the catalytic reaction in this experiment was stability. not cleared at this stage, and the mechanism CONCLUSION 'will be reported in future study. In Fig. 10, the effect of inlet carbon monoxide On the condition of adequate air supply, com concentration on carbon monoxide conversion plete removal of carbon monoxide occurred was depicted for the reaction on CuO at 300°C. above 650 °C. Using catalysts, the oxidation of With enough oxygen, carbon monoxide conver carbon monoxide occurred at lower temperatures; sion was affected severely by the inlet carbon on both MnO2 and 30 % MT1O2 - 70 % CuO at monoxide concentration in the transitional tem­ 250 °C, on CuO at 450 °C, on 50 % M11O2-50 perature, but negligible above the effective % CuO at 200 °C, and on 70 % MnO2-30 % reaction temperature. During experiment, inlet CuO at 180 °C. carbon monoxide concentration was controlled Manganese dioxide (ZType) showed higher to minimize its effect on carbon monoxide con­ activity than cupric oxide (n-type) and a catalyst version. consisting of 60 % MnO2 - 40 % CuO had 바此 Pressure drop between reactor entrance and highest activity of all ,the MnO2-CuO system. -exit showed 3 mmHzO. In the actual application, Over the range of transitional temperature, the catalysts, M11O2 or admixtures with CuO, carbon monoxide removal efficiency decreased can be employed by making a shape of hone­ linearly with increasing inlet carbon monoxide

Journal of the Korean Chemistry Society 촉매반응에 의한 연탄연소가스로부터 일산화탄소의 제거 （ 제 1보 ） 437 concentration while temperature was fixed. mination", R-71-53, MOST (1971). Residence time of gases in the catalytic re­ 12. S. S. Oh and C. S. Choe, NIRIt 20(1970). 13. S. S. Oh and C. S. Choe, NIRI, 21 (1971). actor, in the range of 0. 9 to L 응 seconds, gave 14. J. E. Hwang and M. Y. Son, Daehan Hwahank no effect on carbon monoxide conversion. Hwoejeet 11, 1 (1967). These catalysts can be practically used to 15. R. E. Kirk and D. F. Othmer, “Encyclopedia of remove comparative amount of carbon monoxide Chemical Technology**, Vol. 4, P. 430, Interscience from the anthracite flue ga옹 with a 옹 hape of Publishers. honeycomb or wire screen catalyst bed and 16. G. M. Schwab and J. Block, Zeitschrift fur placing on the anthracite briquette. Electrochemie, 58, 756(1954). 17. R.L. Moss, Chem. Eng.t June (1966). REFERENCES 18. J. M. Thomas and W. J. Thomas, ^Introduction 1. K. S. Lee and B. S. Chung, Daehan Hwahak to the Principles of Heterogeneous Catalysis, ** Hwoejee, 9, 1 (1965). Acad. Press, (1967) 2. P. L. Walker, Jr., F. Rusinko, J. r., and L. 19. T. H. Wolkenstein, Adv. in Cat., 12, 189(1960). C. Austin, Adv. in Cat.. 11, (1959). 20. W. E. Garner, J. Chem. Sco., 1239(1947). 21. P. C. Gravelle and S. J. Tei사 mer, Adv. in Cat.t 3 J. R. Arthur, Trans. Faraday Soc., 47, 164 20, 245(1969). (1951). 22. F. S. Stone, Adv. in Cat., 13,1 (1962). 4. C. Morterra and M. J. D. Low, J. Cat., 2& 23. G. Parravano, J. Amer. Chem. Soc.t 75, 1452 265 (1973). 5. L. J. E. Hofer, P. Gussey and R. B. Anderson, (1952). 24. M. C. Teague, Ind. Eng. Chem.t 12, 10(1920). J. Cat,, 3, 451(1964). 6. C. L. Thomas, “Catalytic Processes and Proven 25. R. J. Kokes, H. Tobin, J. r. and P. H. Emmet, Catalysts", Academic Press, 1970. J. er Am. Chem. Soc., 77, P. 5860. 7. T. H. Hahn, C. S. Lee and S. S. Shin, Daehan 26. R. H. Griffith, Adv. in Cat.t 1,91 (1948). 27- Hwahak Hwoejee, 16, 271 (1972). J. S. Choi and K. H. Kim, Daehan Hwanak 8. T. H. Hahn, ibid., 11, 4(1967). Hwoejee, 13, 4(1969). 9. J. E. Hwang and M. Y. Son, ibid., 16, 27(1972). 28. H. C. Parkins, "Air Pollution**, P. 51, McGraw- 10. Y. S. Kim, et al., "Study on the Development of Hill. Detector, Detecting Device and Alarm System of 29. M. L. Smith and K. W. Stinson, "Fuels and Co- Toxic Gases Liberated from Anthracite Briquette," mbustionM, P. 129, McGraw-Hill, New York, STF 69-2, MOST (1969). 1952. 11. N. K. Lee, et al., “Study on Briquette Gas Eli-

Vol. 20, No. 5, 1976