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Recent advances in catalytic processes and related science in korea
Science and Technology in Catalysis 1998 Copyright © 1999 by Kodansha Ltd.
21 Recent Advances in Catalytic Processes and Related Science in Korea
Young Gul KIM, Kyung Hee LEE and Jae Sung LEE Research Center for Catalytic Technology and Department of Chemical Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang, 790-784 Korea Abstract Following a brief introduction of Korean catalyst industry and catalysis research and development status, described are catalysts and catalytic processes that have been developed and commercialized in Korea. Most of the developments have occured in the last ten years and been related to fine chemicals and environmental technologies. Many processes were developed in laboratories of universities and national institutes and transferred to industries for commercialization. 1. INTRODUCTION In the past thirty years, Korean petroleum and chemical industries have led the way in transforming the nation from an agricultural country to one which is on the verge of becoming an industrial nation. The petrochemical industry has made enormous strides and now produces 4.3 million tons of ethylene per year, which ranks Korea the fifth largest ethylene producer in the world. This rapid development, however, has been based on licensed technologies and imported catalysts. Partly due to the success of this type of development, there has been insufficient recognition of the importance of the indigenous catalytic process technology on the part of industrial management. It is only a little more than ten years ago that scientists in universities and national research laboratories began organized efforts to draw the attention of chemical industry to catalytic science and technology. The government also started to fund large research projects related to catalytic technology with an emphasis on cooperative research between industry and research institutes. As a result, substantial progress has been made and these efforts have led to a modest number of practical processes. This paper discusses processes and catalysts that were developed in Korea and achieved commercial realization. There are a number of processes that are in pilot testing stage and are expected to be commercialized in the near future. 2. KOREAN CATALYST INDUSTRY AND CATALYSIS R & D There are two major catalyst producers in Korea, Heesung-Engelhard and 0-Deg, which produce three-way catalysts for automobile. These joint venture companies are trying to diversify their business area into process catalysts. There are two small companies which produces initiators for polymerization. Recently, Ssangyong Cement Co. has started to produce catalyst supports such as alumina and active carbon by their own technology. As mentioned, however, Korean chemical industry has been developed based on licensed technologies and imported catalysts. In 1996, about 240 million US$ was spent to import catalysts [1]. Japan (35%), U.S. (30%), France (16%), and Germany (4%) are major suppliers accounting for 85% of the total. These countries are also the major suppliers of chemical process technologies with about the same shares. This strong correlation indicates that most catalyst imports are accompanied by process technology imports and thus the economic impact should be much greater than 240 million US$.
151
152 Y. G.Kim ^r«/.
Korea's R&D effort in catalytic technology started a little more than 10 years ago in earnest when the campaign by university and national laboratory people began to draw attention of industry's top management to the need of both basic and applied research in catalysis in order for Korean chemical industries to survive in global competition. It is estimated that about 500 scientists are involved in catalysis research in Korea. Because of a historical reason, most of the more experienced scientists have been working in universities and national laboratories and they have played leading roles in catalysis R&D in Korea. Hence, it is not surprising that many processes described below have been invented in universities and national laboratories and transferred to industries for implementation. Two national research institutes, Korean Institute of Science and Technology (KIST) and Korean Research Institute of Chemical Technologies (KRICT) have strong groups of catalysis R&D. The Research Center for Catalytic Technology of Pohang University of Science and Technology (POSTECH) supported by the Centers of Excellence Program of Korean government is a consortium made up of researchers drawn from the major universities and performs mission-oriented basic and applied research in catalysis with the mandate to be relevant to local industries. More recently established is the Center for Molecular Catalysis of Seoul National University which performs fundamental research with emphasis on homogeneous catalysis. The Korean Catalysis Research Consortium is an industrial organization to coordinate collaborative research among industry, university, and national laboratories. In addition to process technologies related to traditional oil refinery and petrochemical industries, recent emphasis is given to areas of olefin polymerization, fine chemicals and environmental technologies. Korea's research and development in catalytic technology is still at its beginning. There is a growing awareness that much more needs to be done in both fundamental and applied research in catalysis particularly among some of the industry's top management. 3. CATALYSTS AND PROCESSES DEVELOPED IN KOREA Table 1 summarizes catalysts and catalytic processes developed in Korea. Only the processes or catalysts that have achieved commercial realization are listed. There are a number of processes that are in pilot testing stage and are expected to be commercialized in the near future. Except for one, all development was made in the past ten years. There are also cases that the commercialization has not been realized for various reasons in spite of technical success. Because of the unusual situation in Korea as described earlier, it is not surprising that many processes are invented in universities and national laboratories and transferred to industries for implementation. Most of developments are directed to environmental technologies and fine chemicals which have become subjects of immense interest of Korean industries. In the followings, a brief description on the catalysts and processes are given. 3.1. Polyolefin synthesis catalysts Korean Petrochemical Co. (KPC) was the first producer of polypropylene (PP) in Korea from 1972 with a catalyst and process licensed from Chisso of Japan. From the knowledge learned from the operadon of the technology, they developed Ziegler-Natta type catalysts and a slurry process for high density polyethylene (HDPE) and became the first HDPE producer in 1977 based on their own technology [2]. Later, they developed a process for linear low density polyethylene (LLDPE) and an improved PP catalyst. Their catalysts are supported TiCl4-MgCl2 catalysts that could co-produce HDPE, PP, and LLDPE. 3.2. Malonic acid ester by carbonylation Malonic acid esters are important intermediates for the production of various agricultural and medical chemicals and were conventionally synthesized by stoichiometric reactions involving NaCN. A route based on carbonylafion by a homogeneous Co2(CO)8 was developed in a laboratory of KIST in 1980 [3,4]. The process was found to be more efficient and environmentally more friendly. The technology was transferred to Samsung Fine Chemicals Co. (formerly Korea Ferfilizer Co.) for commercializafion who produce CO in their ammonia plant. During three years of pilot test, operafional problems were solved. Furthermore, reaction conditions and yield were improved and a procedure for the recovery of cobalt catalyst as an organic acid salt was established. Finally, the following three step process was commercialized in 1985 and the company has become one of leading producers of malonic acid esters in the world. (1) Catalyst preparation: 2C03O4 + 8H2 + 24CO - > 3[Co(CO)4]2 + 8H2O
153
(2) Esterification: XCH2COOH + ROH --> ROCOCH2X + H2O cat. (3) Carbonylation: 2ROCOCH2X + 2 ROH + 2C0 + M2CO3 > 2ROCOCH2COOR + 2MX + H2O + CO2 where X= CI, Br or I; M= Na or K; R = Ci-Cs alkyls. 3.3. Polybutene Polybutene is produced by a cationic polymerization of isobutylene in the presence of a Lewis acid and used as a component of lubricants, jelly products, or adhesives. It is a viscous hquid with molecular weight of 300-3000 in which isobutylene is connected head-to-tail. CH3 CH3 CH3 CH3 I -10-30 oc I I I CH2 = C > CH3—C-[-CH2—C—]n—CH2—CH = CH2 I AICI3 I I CH3 CH3 CH3 Actual feed is C4 raffmate-I coming out of naphtha cracking and butadiene extraction units that contains isobutylene (40-45%) and other C4 hydrocarbons. The desired degree of polymerization of 5-50 is obtained by controlling reaction temperature, solvent, impurity level, and the concentration of the monomer in the feed. The development work was initiated in 1984 in a collaborative effort of KRICT and Daelim Industrial Co. with a partial financial support of Korean government [5]. After successful pilot test between 1988-90, the commercial operation started in 1994 in a 12000 MT/y plant. 3.4. Diesel vehicle exhaust filter Korea has heavy population of diesel fueled buses and trucks that make significant contribution to urban air pollution. Scientists in SK Corp. developed a catalyst filter that could remove and combust the hydrocarbon particulate in the exhaust of diesel vehicles [6]. The key to their technology is the preparation of noble metal catalysts by a precipitation method that gives small metal particles which are active and stable in the combustion reaction. The catalyst is known to contain PtV/Ti-Si. They also developed catalysts prepared by similar methods to remove volatile organic compounds (VOC) and applied the catalyst to remove smell from the asphalt storage tank vents. 3.5. Catalysts for acrylic acid synthesis LG Chemicals Co. is the only Korean producer of acrylic acid based on technology licensed from Nippon Shokubai of Japan. The process is composed of two step oxidation of propylene. First step: CH2=CHCH3 + O2 > CH2=CHCH0 + H2O + 81.4 kcal Second step: CH2=CHCH0 + I/2O2 --—> CH2=CHC00H + 60.7 kcal Catalysts for both oxidaUon steps are mulficomponent metal oxides, Mo-Bi-Fe-Si-0 in the first step and Mo-V-W-0 for the second step. They have developed their own catalysts which are as good as the best available in the market [7]. They constructed the catalyst manufacturing facility of their own and applied successfully their catalysts for the real plant in 1996. 3.6. Claus plant tail gas treatment process Claus process is most widely employed to remove sulfur compounds from industrial vents. After thermal oxidation of H2S, the following condensation reaction over alumina gives elemental sulfur. 2H2S + SO2 < > S + H2S Because of the reversible nature of the reaction, the conversion is not complete and the tail gas of the Claus plant usually contains ca. 1% of sulfur compound. This much of sulfur cannot be discharged into atmosphere under current environmental regulations. Scientists at POSTECH developed a process to reduce SO2 in the tail gas to H2S and to retum whole stream to the inlet of the Claus plant, and thus achieved zero sulfur emission [8,9]. A M0-C0-S/AI2O3 catalyst completely reduced SO2 to H2S at 300 OC and GHSV of 19,000 h"!. SO2 + 3H2 > H2S + 2H2O
154 Y. G. Km
etai
The process was implemented at a coke oven gas (COG) treatment plant of Pohang Iron & Steel Co in 1995 to treat 8,000 NM^/h of tail gas. Instead of pure hydrogen, the actual process uses COG containing 50% H2. 3.7. Sulfur removal by partial oxidation and reduction (SPOR) process The same group of POSTECH who developed the tail gas treatment process extended the scope of the process to possible replacement of the conventional Claus process. The key to the success was the development of selective catalysts for oxidation of H2S (V/Si02) and reduction of SO2 (C0M0S/AI2O3) into elemental sulfur using stoichiometric amounts of oxygen or hydrogen at relatively low temperature of 200-300 ^C [10]. When CO is used for reduction, Ti02-Sn02 was found to be efficient catalyst. The oxidation catalyst performs better than commercial MODOP (Ti02based) or Superclaus (Fe/Si02 or Fe-Cr/a-Al203) catalysts because it is more water tolerable and does not need excess oxygen. SO2 + 2H2 —-> S + 2 H2O 2H2S + O2 —-> 2S + 2H2O By repeating these two reactions, the SPOR process can replace entirely Claus process or be used for treating its tail gas like MODOP and Superclaus processes are used. Two demonstration plants have been operating in Pohang Iron & Steel Co. and Daelim Industrials Co. (5 MT S/day). 3.8. CFC substitutes Ulsan Chemicals Co. has been producing some chlorofluorocarbons (CFC-11/12) and halons (1211, 1301) since 1981 by technologies developed by KIST. Because of the globally imposed mandate to replace these ozone depleting chemicals, Korean government established a research center in KIST in 1990 to develop technologies to produce substitutes such as hydrochlorofluorocarbons (HCFC) and hydrofluorocarbons (HFC). By 1996, two processes for the production of HCFC-22 (CHCIF2) and HCFC-141b (CH3CFCl2)/142b (CH3CF2CI) have been commercialized by Ulsan Chemicals Co. in capacities of 7500 MT/y and 12,000 MT/y, respectively [11]. Furthermore, basic design has been completed for processes of HCFC-123/HFC-125 (12000 MT/y), HFC-134a (10,000 MT/y), HFC-152a (5,000 MT/y) and HFC-32 (5,000 MT/y), and a process for HFC-143a is being tested in pilot plant. 3.9. Low temperature catalytic combuster Korean Institute of Energy Research (KIER) developed a catalytic combuster based on a noble metal catalyst supported on alumina fiber mat [12]. It uses natural gas as a fuel and operates at 450 ^C with combustion efficiency of 99%. It employs forced circulation type burner with a complete premixing of air and fuel. This arrangement gives improved heat load and flexibility in installation compared to more conventional diffusion combustion type burners. In a test, the new combuster reduced energy consumption by 15-35% and energy cost by 70-80% compared to electric heating. This combuster could be applied places which require large amounts of low temperature heat such as drying processes in textile and paper manufacturing plants and fine chemical processes. The technology was transferred to Samhyun Co. to manufacture commercial combusters. 3.10. Single layer Pd/Rh catalyst for CCC applications Increasingly stringent regulation for automobile exhaust gas dictates the position of three way catalyst located closer to engine. These manifold catalytic converter (MCC) or Close Coupled Catalytic Converter (CCC) applications require the improved thermal stability and increased activity at low temperatures. Instead of usual Pt, Pd is preferred metal as the component of oxidizing CO and hydrocarbons due to better thermal stability. Hyundai Automobile and Heesung-Engelhard joined forces to develop a single layer Pd/Rh catalyst for CCC applications. In order to satisfy the requirements, following considerations were given in the catalyst design: high dispersion of noble metals and ceria, employment of base metal oxides (BMO) to inhibit sintering of metals, improvement of thermal stability by using rare earth oxides, prevention of alloying between Pd and Rh and improvement of oxygen storage capacity. The developed catalyst will be loaded to Hyundai's passenger cars. 3.11. Catalytic distillation of methyl acetate
155
Methylacetate (MA) is less valuable solvent produced as a byproduct in purified terephthalic acid (PTA) and polyvinylalcohol plants. Its hydrolysis allows low reaction yields due to equilibrium limitation (K=0.14) and requires distillation of azeotropic mixtures of MA-CH3OH-H2O. CH2COOCH3 + H2O <-—> CH3COOH + CH3OH To make this reaction forward, excess feed water and a large recycle of MA are required in addition to several distillation towers. The process could be much simplified by catalytic distillation where MA hydrolysis and separation of the reaction mixture occur in the single column. It has been estimated that employment of catalytic distillation could reduce capital cost and energy consumption by 50% [13]. The effective catalyst for the hydrolysis is an acidic ion exchange resin such as a sulfonated polystyrene with divinyl benzene crosslinking. However, the catalyst used in catalyst distillation serves as packing in distillation and thus requires sufficient open area for gas and liquid flow. Usual void fraction of the resin bead is 0.3-0.4 whereas distillation packings have a void fraction near 0.7. Hence, the key to the success is the development of a catalyst packing that are not only active for the reaction but also of an open structure for a smooth countercurrent operation of gas and liquid streams. The process has been operated since June 1996 in a SK Chem's PTA plant located in Ulsan, Korea at a capacity of 10 MT MA/day. 3.12. Neopentyl glycol Neopentyl glycol (NPG) has experienced increasing demand for various applications in coatings, powder paintings, and resins, and is produced only by a handful of companies in the world. LG Chemicals developed their own technology in four years of research and built a 18,000 MT/y plant in 1997 [14]. The process utilizes isobutyraldehyde as a raw material which is produced in their 0x0 plant as a byproduct. The key step of the process is the hydrogenation of the intermediate hydroxypivaldehyde (HPA). CH3 CH3 CH3 I HCHO I H2 I HC—CHO > HOH2C—C—CHO > HOH2C—C—CH2OH I I Ni I CH3 CH3 CH3 The catalyst employed in LG Chem's NPG process is Raney nickel for slurry reactor applications. This marks the first application of a slurry Ni catalyst for a continuous process. The process employs a 6 M^ loop reactor which continuously separates catalyst and product by filtration and recycles the catalyst back to the reaction zone. 3.13. Treatment of PTA plant vent stream Carbon monoxide is a common air pollutant present in many industrial emissions involving partial oxidation reaction. These streams also contain moisture usually at its saturation levels and other contaminant such as halogens. Current industrial catalysts based on supported noble metals are poisoned by these contaminant and thus require high temperatures above 300 ^C although the oxidation of pure CO is a fairly easy reaction. Reactor vents of paraxylene oxidation to produce PTA contain 3500 ppm of CO and 35 ppm of CH3Br and other hydrocarbons saturated with water, and a commercial supported Pt-Pd catalyst for the treatment of the vent gas operates at 320 ^C to completely oxidize CO. The system need a large furnace to obtain the high reaction temperature and thus high capital and fuel costs. Furthermore, the catalyst also oxidizes CH3Br to HBr and Br2 during CO oxidation which cause corrosion problems in the downstream if their scrubbing is not complete. Samsung Petrochemicalc Co. and POSTECH have developed a new process that selectively converts CO in the presence of CH3Br and water at low temperatures (100-150 ^C) so that low quality steam could be used as a sole heat source. A heterogenized Wacker-type catalyst was employed, in which pores of carbon were filled with an aqueous solution of PdCl2-CuCl2. At 120 OC and 9.5 bar, an activity of 20,000 NM^ feed/kg-cat/h was achieved. The first application of the process was made successfully in March 1998 to handle 50,000 NM^/h of vent stream.
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4. SUMMARY A modest number of new catalysts and catalytic processes have been developed and commercialized in the past ten years in Korea. Because more experienced catalysis scientists were working in universities and national laboratories, their contribution and leadership have been instrumental in these developments. Environmental technologies and fine chemicals.synthesis processes have been the most popular targets of catalysis R&D in Korea References [I] K.W. Lee, "A Report on the Petrochemical and Environmental Catalysis Research Planning", KRICT, Taejon, 1997. [2] S.C. Kang, Catalysis (Korean), 4 (1988) 51. [3] K.J. Yoo, Catalysis (Korean), 4 (1988) 66. [4] S.J. Uhm, Korean Patent 12983 (1980). [5] H.K. Yoon, Proc. 7th Catalysis Meeting, Taejon, 1994, p. 31. [6] Y.W. Kim, Catalysis (Korean), 12 (1996) 57. [7] W.H. Lee, Proc. 7th Catalysis Meeting, Taejon, 1994, p. 3. [8] S.C. Paik, H. Kim, and J.S. Chung, Catal. Today, 38 (1997) 193. [9] S.C. Paik and J.S. Chung, Appl. Catal. B., 5 (1995) 233. [10] S.C. Paik, H.S. Kim, J.W. Song, L-S. Nam and J.S. Chung, Catal. Today, 35 (1997) 37. [II] H.G. Kim, B.S. Ahn, H.S. Kim, and W.S. Kim, Catalysis (Korean), 14 (1998) 19. [12] S.K. Kang, Catalysis (Korean), 12 (1996) 58. [13] Y. Fuchigami, J. Chem. Eng. Jpn., 23 (1990) 354. [14] J.W. Choi, Catalysis (Korean), 14 (1998) 151. [15] K.D. Kim, L-S. Nam, J.S. Chung, J.S. Lee, S.G. Ryu and Y.S. Yang, Appl. Catal. B., 5 (1994) 103. [16] J.S. Lee, S.H. Choi, K.D. Kim, and M. Nomura, Appl. Catal., B., 7 (1996) 199.
21 Recent Advances in Catalytic Processes and Related Science in Korea
Young Gul KIM, Kyung Hee LEE and Jae Sung LEE Research Center for Catalytic Technology and Department of Chemical Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang, 790-784 Korea Abstract Following a brief introduction of Korean catalyst industry and catalysis research and development status, described are catalysts and catalytic processes that have been developed and commercialized in Korea. Most of the developments have occured in the last ten years and been related to fine chemicals and environmental technologies. Many processes were developed in laboratories of universities and national institutes and transferred to industries for commercialization. 1. INTRODUCTION In the past thirty years, Korean petroleum and chemical industries have led the way in transforming the nation from an agricultural country to one which is on the verge of becoming an industrial nation. The petrochemical industry has made enormous strides and now produces 4.3 million tons of ethylene per year, which ranks Korea the fifth largest ethylene producer in the world. This rapid development, however, has been based on licensed technologies and imported catalysts. Partly due to the success of this type of development, there has been insufficient recognition of the importance of the indigenous catalytic process technology on the part of industrial management. It is only a little more than ten years ago that scientists in universities and national research laboratories began organized efforts to draw the attention of chemical industry to catalytic science and technology. The government also started to fund large research projects related to catalytic technology with an emphasis on cooperative research between industry and research institutes. As a result, substantial progress has been made and these efforts have led to a modest number of practical processes. This paper discusses processes and catalysts that were developed in Korea and achieved commercial realization. There are a number of processes that are in pilot testing stage and are expected to be commercialized in the near future. 2. KOREAN CATALYST INDUSTRY AND CATALYSIS R & D There are two major catalyst producers in Korea, Heesung-Engelhard and 0-Deg, which produce three-way catalysts for automobile. These joint venture companies are trying to diversify their business area into process catalysts. There are two small companies which produces initiators for polymerization. Recently, Ssangyong Cement Co. has started to produce catalyst supports such as alumina and active carbon by their own technology. As mentioned, however, Korean chemical industry has been developed based on licensed technologies and imported catalysts. In 1996, about 240 million US$ was spent to import catalysts [1]. Japan (35%), U.S. (30%), France (16%), and Germany (4%) are major suppliers accounting for 85% of the total. These countries are also the major suppliers of chemical process technologies with about the same shares. This strong correlation indicates that most catalyst imports are accompanied by process technology imports and thus the economic impact should be much greater than 240 million US$.
151
152 Y. G.Kim ^r«/.
Korea's R&D effort in catalytic technology started a little more than 10 years ago in earnest when the campaign by university and national laboratory people began to draw attention of industry's top management to the need of both basic and applied research in catalysis in order for Korean chemical industries to survive in global competition. It is estimated that about 500 scientists are involved in catalysis research in Korea. Because of a historical reason, most of the more experienced scientists have been working in universities and national laboratories and they have played leading roles in catalysis R&D in Korea. Hence, it is not surprising that many processes described below have been invented in universities and national laboratories and transferred to industries for implementation. Two national research institutes, Korean Institute of Science and Technology (KIST) and Korean Research Institute of Chemical Technologies (KRICT) have strong groups of catalysis R&D. The Research Center for Catalytic Technology of Pohang University of Science and Technology (POSTECH) supported by the Centers of Excellence Program of Korean government is a consortium made up of researchers drawn from the major universities and performs mission-oriented basic and applied research in catalysis with the mandate to be relevant to local industries. More recently established is the Center for Molecular Catalysis of Seoul National University which performs fundamental research with emphasis on homogeneous catalysis. The Korean Catalysis Research Consortium is an industrial organization to coordinate collaborative research among industry, university, and national laboratories. In addition to process technologies related to traditional oil refinery and petrochemical industries, recent emphasis is given to areas of olefin polymerization, fine chemicals and environmental technologies. Korea's research and development in catalytic technology is still at its beginning. There is a growing awareness that much more needs to be done in both fundamental and applied research in catalysis particularly among some of the industry's top management. 3. CATALYSTS AND PROCESSES DEVELOPED IN KOREA Table 1 summarizes catalysts and catalytic processes developed in Korea. Only the processes or catalysts that have achieved commercial realization are listed. There are a number of processes that are in pilot testing stage and are expected to be commercialized in the near future. Except for one, all development was made in the past ten years. There are also cases that the commercialization has not been realized for various reasons in spite of technical success. Because of the unusual situation in Korea as described earlier, it is not surprising that many processes are invented in universities and national laboratories and transferred to industries for implementation. Most of developments are directed to environmental technologies and fine chemicals which have become subjects of immense interest of Korean industries. In the followings, a brief description on the catalysts and processes are given. 3.1. Polyolefin synthesis catalysts Korean Petrochemical Co. (KPC) was the first producer of polypropylene (PP) in Korea from 1972 with a catalyst and process licensed from Chisso of Japan. From the knowledge learned from the operadon of the technology, they developed Ziegler-Natta type catalysts and a slurry process for high density polyethylene (HDPE) and became the first HDPE producer in 1977 based on their own technology [2]. Later, they developed a process for linear low density polyethylene (LLDPE) and an improved PP catalyst. Their catalysts are supported TiCl4-MgCl2 catalysts that could co-produce HDPE, PP, and LLDPE. 3.2. Malonic acid ester by carbonylation Malonic acid esters are important intermediates for the production of various agricultural and medical chemicals and were conventionally synthesized by stoichiometric reactions involving NaCN. A route based on carbonylafion by a homogeneous Co2(CO)8 was developed in a laboratory of KIST in 1980 [3,4]. The process was found to be more efficient and environmentally more friendly. The technology was transferred to Samsung Fine Chemicals Co. (formerly Korea Ferfilizer Co.) for commercializafion who produce CO in their ammonia plant. During three years of pilot test, operafional problems were solved. Furthermore, reaction conditions and yield were improved and a procedure for the recovery of cobalt catalyst as an organic acid salt was established. Finally, the following three step process was commercialized in 1985 and the company has become one of leading producers of malonic acid esters in the world. (1) Catalyst preparation: 2C03O4 + 8H2 + 24CO - > 3[Co(CO)4]2 + 8H2O
153
(2) Esterification: XCH2COOH + ROH --> ROCOCH2X + H2O cat. (3) Carbonylation: 2ROCOCH2X + 2 ROH + 2C0 + M2CO3 > 2ROCOCH2COOR + 2MX + H2O + CO2 where X= CI, Br or I; M= Na or K; R = Ci-Cs alkyls. 3.3. Polybutene Polybutene is produced by a cationic polymerization of isobutylene in the presence of a Lewis acid and used as a component of lubricants, jelly products, or adhesives. It is a viscous hquid with molecular weight of 300-3000 in which isobutylene is connected head-to-tail. CH3 CH3 CH3 CH3 I -10-30 oc I I I CH2 = C > CH3—C-[-CH2—C—]n—CH2—CH = CH2 I AICI3 I I CH3 CH3 CH3 Actual feed is C4 raffmate-I coming out of naphtha cracking and butadiene extraction units that contains isobutylene (40-45%) and other C4 hydrocarbons. The desired degree of polymerization of 5-50 is obtained by controlling reaction temperature, solvent, impurity level, and the concentration of the monomer in the feed. The development work was initiated in 1984 in a collaborative effort of KRICT and Daelim Industrial Co. with a partial financial support of Korean government [5]. After successful pilot test between 1988-90, the commercial operation started in 1994 in a 12000 MT/y plant. 3.4. Diesel vehicle exhaust filter Korea has heavy population of diesel fueled buses and trucks that make significant contribution to urban air pollution. Scientists in SK Corp. developed a catalyst filter that could remove and combust the hydrocarbon particulate in the exhaust of diesel vehicles [6]. The key to their technology is the preparation of noble metal catalysts by a precipitation method that gives small metal particles which are active and stable in the combustion reaction. The catalyst is known to contain PtV/Ti-Si. They also developed catalysts prepared by similar methods to remove volatile organic compounds (VOC) and applied the catalyst to remove smell from the asphalt storage tank vents. 3.5. Catalysts for acrylic acid synthesis LG Chemicals Co. is the only Korean producer of acrylic acid based on technology licensed from Nippon Shokubai of Japan. The process is composed of two step oxidation of propylene. First step: CH2=CHCH3 + O2 > CH2=CHCH0 + H2O + 81.4 kcal Second step: CH2=CHCH0 + I/2O2 --—> CH2=CHC00H + 60.7 kcal Catalysts for both oxidaUon steps are mulficomponent metal oxides, Mo-Bi-Fe-Si-0 in the first step and Mo-V-W-0 for the second step. They have developed their own catalysts which are as good as the best available in the market [7]. They constructed the catalyst manufacturing facility of their own and applied successfully their catalysts for the real plant in 1996. 3.6. Claus plant tail gas treatment process Claus process is most widely employed to remove sulfur compounds from industrial vents. After thermal oxidation of H2S, the following condensation reaction over alumina gives elemental sulfur. 2H2S + SO2 < > S + H2S Because of the reversible nature of the reaction, the conversion is not complete and the tail gas of the Claus plant usually contains ca. 1% of sulfur compound. This much of sulfur cannot be discharged into atmosphere under current environmental regulations. Scientists at POSTECH developed a process to reduce SO2 in the tail gas to H2S and to retum whole stream to the inlet of the Claus plant, and thus achieved zero sulfur emission [8,9]. A M0-C0-S/AI2O3 catalyst completely reduced SO2 to H2S at 300 OC and GHSV of 19,000 h"!. SO2 + 3H2 > H2S + 2H2O
154 Y. G. Km
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The process was implemented at a coke oven gas (COG) treatment plant of Pohang Iron & Steel Co in 1995 to treat 8,000 NM^/h of tail gas. Instead of pure hydrogen, the actual process uses COG containing 50% H2. 3.7. Sulfur removal by partial oxidation and reduction (SPOR) process The same group of POSTECH who developed the tail gas treatment process extended the scope of the process to possible replacement of the conventional Claus process. The key to the success was the development of selective catalysts for oxidation of H2S (V/Si02) and reduction of SO2 (C0M0S/AI2O3) into elemental sulfur using stoichiometric amounts of oxygen or hydrogen at relatively low temperature of 200-300 ^C [10]. When CO is used for reduction, Ti02-Sn02 was found to be efficient catalyst. The oxidation catalyst performs better than commercial MODOP (Ti02based) or Superclaus (Fe/Si02 or Fe-Cr/a-Al203) catalysts because it is more water tolerable and does not need excess oxygen. SO2 + 2H2 —-> S + 2 H2O 2H2S + O2 —-> 2S + 2H2O By repeating these two reactions, the SPOR process can replace entirely Claus process or be used for treating its tail gas like MODOP and Superclaus processes are used. Two demonstration plants have been operating in Pohang Iron & Steel Co. and Daelim Industrials Co. (5 MT S/day). 3.8. CFC substitutes Ulsan Chemicals Co. has been producing some chlorofluorocarbons (CFC-11/12) and halons (1211, 1301) since 1981 by technologies developed by KIST. Because of the globally imposed mandate to replace these ozone depleting chemicals, Korean government established a research center in KIST in 1990 to develop technologies to produce substitutes such as hydrochlorofluorocarbons (HCFC) and hydrofluorocarbons (HFC). By 1996, two processes for the production of HCFC-22 (CHCIF2) and HCFC-141b (CH3CFCl2)/142b (CH3CF2CI) have been commercialized by Ulsan Chemicals Co. in capacities of 7500 MT/y and 12,000 MT/y, respectively [11]. Furthermore, basic design has been completed for processes of HCFC-123/HFC-125 (12000 MT/y), HFC-134a (10,000 MT/y), HFC-152a (5,000 MT/y) and HFC-32 (5,000 MT/y), and a process for HFC-143a is being tested in pilot plant. 3.9. Low temperature catalytic combuster Korean Institute of Energy Research (KIER) developed a catalytic combuster based on a noble metal catalyst supported on alumina fiber mat [12]. It uses natural gas as a fuel and operates at 450 ^C with combustion efficiency of 99%. It employs forced circulation type burner with a complete premixing of air and fuel. This arrangement gives improved heat load and flexibility in installation compared to more conventional diffusion combustion type burners. In a test, the new combuster reduced energy consumption by 15-35% and energy cost by 70-80% compared to electric heating. This combuster could be applied places which require large amounts of low temperature heat such as drying processes in textile and paper manufacturing plants and fine chemical processes. The technology was transferred to Samhyun Co. to manufacture commercial combusters. 3.10. Single layer Pd/Rh catalyst for CCC applications Increasingly stringent regulation for automobile exhaust gas dictates the position of three way catalyst located closer to engine. These manifold catalytic converter (MCC) or Close Coupled Catalytic Converter (CCC) applications require the improved thermal stability and increased activity at low temperatures. Instead of usual Pt, Pd is preferred metal as the component of oxidizing CO and hydrocarbons due to better thermal stability. Hyundai Automobile and Heesung-Engelhard joined forces to develop a single layer Pd/Rh catalyst for CCC applications. In order to satisfy the requirements, following considerations were given in the catalyst design: high dispersion of noble metals and ceria, employment of base metal oxides (BMO) to inhibit sintering of metals, improvement of thermal stability by using rare earth oxides, prevention of alloying between Pd and Rh and improvement of oxygen storage capacity. The developed catalyst will be loaded to Hyundai's passenger cars. 3.11. Catalytic distillation of methyl acetate
155
Methylacetate (MA) is less valuable solvent produced as a byproduct in purified terephthalic acid (PTA) and polyvinylalcohol plants. Its hydrolysis allows low reaction yields due to equilibrium limitation (K=0.14) and requires distillation of azeotropic mixtures of MA-CH3OH-H2O. CH2COOCH3 + H2O <-—> CH3COOH + CH3OH To make this reaction forward, excess feed water and a large recycle of MA are required in addition to several distillation towers. The process could be much simplified by catalytic distillation where MA hydrolysis and separation of the reaction mixture occur in the single column. It has been estimated that employment of catalytic distillation could reduce capital cost and energy consumption by 50% [13]. The effective catalyst for the hydrolysis is an acidic ion exchange resin such as a sulfonated polystyrene with divinyl benzene crosslinking. However, the catalyst used in catalyst distillation serves as packing in distillation and thus requires sufficient open area for gas and liquid flow. Usual void fraction of the resin bead is 0.3-0.4 whereas distillation packings have a void fraction near 0.7. Hence, the key to the success is the development of a catalyst packing that are not only active for the reaction but also of an open structure for a smooth countercurrent operation of gas and liquid streams. The process has been operated since June 1996 in a SK Chem's PTA plant located in Ulsan, Korea at a capacity of 10 MT MA/day. 3.12. Neopentyl glycol Neopentyl glycol (NPG) has experienced increasing demand for various applications in coatings, powder paintings, and resins, and is produced only by a handful of companies in the world. LG Chemicals developed their own technology in four years of research and built a 18,000 MT/y plant in 1997 [14]. The process utilizes isobutyraldehyde as a raw material which is produced in their 0x0 plant as a byproduct. The key step of the process is the hydrogenation of the intermediate hydroxypivaldehyde (HPA). CH3 CH3 CH3 I HCHO I H2 I HC—CHO > HOH2C—C—CHO > HOH2C—C—CH2OH I I Ni I CH3 CH3 CH3 The catalyst employed in LG Chem's NPG process is Raney nickel for slurry reactor applications. This marks the first application of a slurry Ni catalyst for a continuous process. The process employs a 6 M^ loop reactor which continuously separates catalyst and product by filtration and recycles the catalyst back to the reaction zone. 3.13. Treatment of PTA plant vent stream Carbon monoxide is a common air pollutant present in many industrial emissions involving partial oxidation reaction. These streams also contain moisture usually at its saturation levels and other contaminant such as halogens. Current industrial catalysts based on supported noble metals are poisoned by these contaminant and thus require high temperatures above 300 ^C although the oxidation of pure CO is a fairly easy reaction. Reactor vents of paraxylene oxidation to produce PTA contain 3500 ppm of CO and 35 ppm of CH3Br and other hydrocarbons saturated with water, and a commercial supported Pt-Pd catalyst for the treatment of the vent gas operates at 320 ^C to completely oxidize CO. The system need a large furnace to obtain the high reaction temperature and thus high capital and fuel costs. Furthermore, the catalyst also oxidizes CH3Br to HBr and Br2 during CO oxidation which cause corrosion problems in the downstream if their scrubbing is not complete. Samsung Petrochemicalc Co. and POSTECH have developed a new process that selectively converts CO in the presence of CH3Br and water at low temperatures (100-150 ^C) so that low quality steam could be used as a sole heat source. A heterogenized Wacker-type catalyst was employed, in which pores of carbon were filled with an aqueous solution of PdCl2-CuCl2. At 120 OC and 9.5 bar, an activity of 20,000 NM^ feed/kg-cat/h was achieved. The first application of the process was made successfully in March 1998 to handle 50,000 NM^/h of vent stream.
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4. SUMMARY A modest number of new catalysts and catalytic processes have been developed and commercialized in the past ten years in Korea. Because more experienced catalysis scientists were working in universities and national laboratories, their contribution and leadership have been instrumental in these developments. Environmental technologies and fine chemicals.synthesis processes have been the most popular targets of catalysis R&D in Korea References [I] K.W. Lee, "A Report on the Petrochemical and Environmental Catalysis Research Planning", KRICT, Taejon, 1997. [2] S.C. Kang, Catalysis (Korean), 4 (1988) 51. [3] K.J. Yoo, Catalysis (Korean), 4 (1988) 66. [4] S.J. Uhm, Korean Patent 12983 (1980). [5] H.K. Yoon, Proc. 7th Catalysis Meeting, Taejon, 1994, p. 31. [6] Y.W. Kim, Catalysis (Korean), 12 (1996) 57. [7] W.H. Lee, Proc. 7th Catalysis Meeting, Taejon, 1994, p. 3. [8] S.C. Paik, H. Kim, and J.S. Chung, Catal. Today, 38 (1997) 193. [9] S.C. Paik and J.S. Chung, Appl. Catal. B., 5 (1995) 233. [10] S.C. Paik, H.S. Kim, J.W. Song, L-S. Nam and J.S. Chung, Catal. Today, 35 (1997) 37. [II] H.G. Kim, B.S. Ahn, H.S. Kim, and W.S. Kim, Catalysis (Korean), 14 (1998) 19. [12] S.K. Kang, Catalysis (Korean), 12 (1996) 58. [13] Y. Fuchigami, J. Chem. Eng. Jpn., 23 (1990) 354. [14] J.W. Choi, Catalysis (Korean), 14 (1998) 151. [15] K.D. Kim, L-S. Nam, J.S. Chung, J.S. Lee, S.G. Ryu and Y.S. Yang, Appl. Catal. B., 5 (1994) 103. [16] J.S. Lee, S.H. Choi, K.D. Kim, and M. Nomura, Appl. Catal., B., 7 (1996) 199.