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Cosmo high-activity hds catalyst: its development and performance properties
Science and Technology in Catalysis 1998 Copyright © 1999 by Kodansha Ltd.
41 Cosmo High-activity HDS Catalyst: Its Development and Performance Properties
Takashi FUJIKAWA, Osamu CHIYODA, Kazuo IDEI, Takashi YOSHIZAWA and Kazushi USUI Cosmo Research Institute, 1134-2, Gongendo, Satte, Saitama 340-0193, Japan Abstract Cosmo Oil introduced a new highly active and stable HDS (hydrodesulfurization) catalyst C-603A in 1994. The preparation of this catalyst combines the use of zeolite technology and impregnation technology to provide excellent HDS activity. C-603A possesses considerably higher activity than conventional Co-Mo/alumina catalyst. Long duration test demonstrated high activity and stability for HDS of vacuum gas oil. Several industrial demonstrations with this catalyst have successfully proven its high performance. 1. INTRODUCTION Recently, since air pollution by exhaust gas from diesel engine has become a serious problem, much attention has been paid to deep HDS of diesel fuel [1, 2]. For this purpose, it has been strongly desired to develop a catalyst which is considerably increased in HDS activity. To resolve this assignment, it is necessary to effectively remove refractory sulfur-containing compounds such as 4,6-dimethyldibenzothiophene (4,6-DMDBT) [3]. Under such circumstances, Cosmo Oil and Petroleum Energy Center (PEC) have developed an improved, highly active HDS catalyst, C-603A [4]. C-603A possesses higher activity than the best of commercial HDS catalysts. Furthermore, C-603A is now in service in three light gas oil HDS units and three vacuum gas oil HDS units of Cosmo Oil refineries. These industrial demonstrations with this catalyst have successfully proven the high HDS activity and stability of C-603A. This paper describes the performance properties and some industrial demonstrations of C-603A in the hydrotreatment of light gas oil and vacuum gas oil. Also, we will show some results regarding the characterization of this catalyst. 2. EXPERIMENTAL 2.1. Catalysts C-603A was prepared by means of the one-step incipient wetness impregnation, using aqueous solution containing the required amounts of cobalt, molybdenum and phosphorus on carrier composed of HY zeolite containing alumina. After the impregnation, this sample was air-dried and calcined at 500 °C . Prior to the activity test, a fresh catalyst was presulfided in situ with straight run gas oil under normal conditions. For comparison, alumina-supported commercial catalysts ( a , /3 , 7 ) were also presulfided and tested under the same 277
278 T. Fujikawa et al.
conditions. HY zeolite-alumina, silica-alumina, and alumina without active metals were also used for model reaction (reaction of 4,6-DMDBT in n-decane). 2.2. Feedstock properties Middle East straight run gas oils containing sulfur between 0.8 and 2.0 mass% and vacuum gas oil containing sulfur 2.65 mass% were used as feedstock for this work. 4,6-DMDBT/n-decane (0.05 mass% as sulfur) was also used as model feedstock. 4,6-DMDBT was synthesized according to the method given in the patent [5]. 2.3. Equipment HDS of light gas oil and vacuum gas oil was carried out using both bench-scale plant and commercial HDS unit. The bench-scale plant was composed of an isothermal fixed-bed reactor operating in down-flow mode. The demonstration operation with C-603A has been carried out with the light gas oil HDS units of Cosmo Oil Sakai and Sakaide refineries and in the vacuum gas oil HDS units of Cosmo Oil Chiba, Yokkaichi and Sakaide refineries. Model reaction was carried out using a continuous flow micro-reactor. 2.4. Reaction Conditions HDS of light gas oil was carried out under the following conditions: temperature, 320-370 °C ; total pressure, 3 - 5 MPa; liquid hourly space velocity (LHSV), 1.0 - 4.5 h ' . HDS of vacuum gas oil was carried out under the following conditions: temperature, 320-400 °C ; total pressure, 3 - 5 MPa; LHSV, 1.0 - 4.5 h ' . Model reaction was carried out under following conditions: temperature, 200-290 °C ; total pressure, 3.4 MPa; LHSV, 1.5 h ' . 2.5. Analytical The amount of sulfur was determined by energy-dispersive X-ray fluorescence spectroscopy (Mitsubishi Kagaku RX-500SAH). The sulfur-containing compounds was analyzed by a gas chromatograph (GC) (Hewlett Packard 5890 11 plus) equipped with a capillary column (HP-1, 25 m, 0.32 mm diameter) and an atomic emission detector (AED) (Hewlett Packard 5921 A). The product analysis of model reaction was performed by a GC (Hewlett Packard 5890 II ) equipped with a capillary column (HP-1, 25 m, 0.32 mm diameter) and a flame ionization detector. 2.6. Kinetic calculations The following equation was used to analyze the results of each experiment, since it was proven by laboratory experiment that expressing the overall HDS rate with 1.5 order reaction in terms of sulfur content was reasonable. k=(l/ / " Sp - 1/ ^
Sf) X (LHSV) X 2
k : Rate constant, h ' ' Sp : Amount of sulfur in product Sf : Amount of sulfur in feedstock
2.7. Catalyst Characterization Transmission electron spectroscopy (TEM) was carried out using a JEOL JEM-2000FX, with an accelerating voltage of 200 keV. For the determination of the chemical composition of zeolite phase and amorphous phase of C-603A, energy dispersive spectroscopy (EDS) was used in a TEM.
279
3. RESULTS and DISCUSSION 3.1. Catalyst design for deep HDS To attain deep HDS, it is vital to remove refractory sulfur-containing compounds such as 4,6-DMDBT effectively. Therefore, we performed a two-step approach to increasing HDS activity as follows: (a) To increase the dispersion of active metals in order to enhance the intrinsic HDS activity. (b) To add a new catalytic function in order to convert 4,6-DMDBT to compounds that are easy to be desulfurized. It is well-known from the literature [6-8] that phosphorus generally enhances the HDS activity of Co(Ni)-Mo hydroprocessing catalysts. Many researchers suggest that the addition of phosphorus increase the dispersion of the Co(Ni) and Mo active metals [9, 10]. Therefore, in order to achieve the increase of dispersion of the Co and Mo active metals, we tried to add a small amount of phosphorus to impregnation solution containing cobalt and molybdenum. Besides, in order to alleviate the steric hindrance, that is, the retarding effect of methyl substituents on the 4- and 6-position of DBT on the HDS rates, we tried to use zeolite which has the ability to promote isomerization reaction. However, zeolite also drastically promotes the undesirable cracking activity, which accelerates the rate of coke deposition and enhances the yields of naphtha product and less diesel product. Thus, in order to overcome this drawback, we controlled the acidity of zeolite and the amount of zeolite in catalyst. After extensive studies based on the technologies of Cosmo's patents [11-13], we have successfully developed a high activity HDS catalyst containing zeolite, C-603A. Chemical and physical properties of C-603A was listed in Table 1. Table 1 Catalyst Active phase Support Surface area Extrudate shape Diameter
Catalyst description
m^/g inch
C-603A Co-Mo-P HY zeoIite-Al203 >250 cylinder 1/16
3.2. Performance advantages of C-603A Cosmo's C-603A is formulated to maximize HDS activity and stability. Its start-of-run performance is compared to three other commercial hydrotreating catalysts in Table 2. Catalyst a is a commercial HDS catalyst, C0-M0/AI2O3, for middle distillates. Catalyst jS is a commercial deep HDS catalyst for middle distillates which outperformed a group of other commercial, non-Cosmo catalysts in laboratory evaluation and is in service in many HDS units worldwide. Catalyst r is a commercial HDS catalyst for vacuum gas oil fractions. From the results shown in Table 2, we could see that our developed catalyst C-603A enables HDS of both light gas oil and vacuum gas oil to a high degree as compared with conventional HDS catalysts. A longer term stability test on a vacuum gas oil feed was also carried out to compare catalyst 7 and C-603A. Feed properties are shown in Table 2. Results of the stability test are shown in Fig. 1. Each plot shows the temperature required to maintain 0.1 mass% sulfur in the product. As can seen in Fig. 1, C-603A significantly outperformed catalyst r , and with comparable stability. Generally, coke formation is the most important cause for deactivation of zeolite [14-17]. As the reason of the high stability of C-603A containing HY zeolite, we assumed that the rate of deactivation by coking was suppressed slightly, since the higher activity of this
280 T. Fujikawa ^r«/. catalyst could lower the reaction temperature in the mode of constant sulfur operation and also the acidity were well-controlled. Table 2
+20
Performance test of C-603A
Test Feed Density g/ml Sulfur mass% Reaction Conditions Pressure MPa Temperature X2 Catalyst Relative Activity
A
Catalyst r
B
LOG 0.859 1.63
VGO 0.934 2.65
4.9 340 a jS C-603A 100 127 140
4.9 360 r C-603A 100 130
Base S
•3
^
C-603A -20
0
20
40
60 80 100 Days on Stream
120
140
Fig. 1 Temperature required to give 0.1 mass% sulfur in product using C-603A
Also, we measured C-603A by TEM and EDS. Detailed investigation reveals that cobalt and molybdenum exist in both zeolite matrix and amorphous phase (Fig. 2, 3). As the other reason of higher stability of C-603A, it is assumed that the cobalt species in zeolite play a major role in maintaining the proper hydrogenation/cracking ratio in order to minimize the opportunities of early deactivation. Isoda et al. [18] and Mochida [19] have reported that Co-Mo/alumina + Ni-HY mixed catalyst exhibited a high and stable activity for HDS of light gas oil. They also assumed that the high hydrogenation activity due to the loaded Ni in Ni-HY zeolite appears to reduce the effect of coking deactivation.
4 5 Energy, keV
Fig. 2 TEM of C-603A
Fig. 3 EDS of C-603A
3.3. Demonstration Operation with C-603A Based on above-mentioned results, we started the practical demonstration of C-603A. Table 3 gives an indication of applications for C-603A until July, 1998. These industrial operations have actually proven the HDS activity and stability of C-603A. Fig. 4 illustrates the relationship between the amount of sulfur in the product and reaction temperature over C-603A and commercial catalyst jS with the light gas oil HDS unit of Cosmo Oil Sakai refinery. Compared
281
to catalyst i3 , C-603A exhibited higher HDS activity. Especially at the region of deep HDS, the HDS ability of C-603A is outstanding. For example, while the difference of required temperature to give 0.1 mass% sulfur between C-603A and catalyst jS is about 4 °C , that of required temperature to give 0.04 mass% sulfur between these catalysts is about 6 °C . Table 3 Applications of Cosmo C-603A Feed type Middle distillates Vacuum gas oils Total
0.15
/"
\ ****•
Total tons 151 630 781
^
Demonstration operation of C-603A with the commercial unit of Cosmo Sakai reflnery V J
n E u
'••.,^^^ Catalyst i3
i
0.05 \-
C-603A
+10
+20 WABT, X:
+30
Fig. 4 Relationship between the amount of sulfur and reaction temperature over C-603A and Catalyst jS 3.4. Model Reaction The main characteristics of C-603A is to add HY zeolite into catalyst. Hence, in order to investigate the difference between C-603A containing zeolite and Catalyst a (C0-M0/AI2O3), we performed reaction studies of the conversion of 4,6-DMDBT in n-decane (Fig. 5). The reaction products treated with Catalyst a were 3-(3'-methylcyclohexyl)toluene (3-(3'-MeCH)T) and a small amount of 3,3'-dimethylbiphenyl (3,3'-DiMeBPH). Hence, it is assumed that the HDS of 4,6-DMDBT over C0-M0/AI2O3 takes place through the hydrogenation of one of benzene rings. On the other hand, the reaction products treated with C-603A were 3,3'-DiMeBPH, 3-(3'-MeCH)T, and 3,4'-DiMeBPH. From these results, it is assumed that the addition of zeolite makes new HDS routes which pass the isomerization and hydrogenolysis of 4,6-DMDBT. Furthermore, in order to investigate the effect of zeolite on the HDS activity in more detail, the reactivity of 4,6-DMDBT in n-decane was measured over non active metal HY zeolite-alumina, silica-alumina, and alumina, respectively. As shown in Fig. 6, it can be observed that only HY zeolite-alumina promotes the conversion of 4,6-DMDBT. The reaction products were 3,6-DMDBT and a small amount of 2,8-DMDBT, 4-MDBT, and C3-DBTs. From the results, it is assumed that the cause of high performance of C-603A is that zeolite plays role in converting 4,6-DMDBT to 3,6-DMDBT which is easy to be desulfurized. Product
Conversion, % C-603A
100
Catalyst a 99.8 0
20 40 60 80 Product Distribution, %
100
180
200
220
240
260
280
Temperture, 'C
Fig. 5 HDS of 4,6-DMDBT
Fig. 6 Conversion of 4,6-DMDBT
300
282 T. Fujikawa et al.
4. CONCLUSIONS In this paper, the development and performance properties of a highly active HDS catalyst, C-603A, have been presented. The main conclusions of this work can be summarized below. 1. C-603A is a successful, HY zeolite-containing HDS catalyst for middle distillates developed by Cosmo Oil. 2. Both the bench-scale plant tests and the industrial data have proven that C-603A possesses significantly higher activity than alumina-supported commercial HDS catalysts. Especially the deep HDS performance of C-603A is outstanding. 3. A longer term stability test on a vacuum gas oil feed demonstrated the excellent stability of C-603A. 4. Based on the results of the model reactions, it is assumed that the cause of high performance of C-603A is that HY zeolite plays role in converting 4,6-DMDBT to sulfur-containing compound which is easy to be desulfurized. Acknowledgements This R&D was supported by the Petroleum Energy Center (PEC), under sponsorship of the Ministry of International Trade and Industry (MITI) of Japan. We thank Mr. Takeshi Ebihara for his contribution to the TEM study. References [1] H. Tops0e, B. S. Clausen and F. E. Massoth, in Hydrotreating Catalysis Science and Technology, Springer-Verlag Berlin Heidelberg, Berlin, 1996. [2] T. Takatsuka, S. Inoue and Y. Wada, Catal. Today 39 (1997) 69. [3] T. Kabe, A. Ishihara and H. Tajima, Ind. Eng. Chem. Res. 31 (1992) 1577. [4] T. Fujikawa, O. Chiyoda, M. Tsukagoshi, K. Idei and S. Takehara, Proc. Third Japan-EU Joint Workshop of the Frontiers of Catalytic Science & Technology, (JECAT'97), 1997, P189. [5] T. Fujikawa and K. Usui, Japan Patent, Application No. H6-67968, 1994. [6] C. W. Fitz and H. F. Rase, Ind. Eng. Chem. Prod. Res. Dev. 22 (1983) 40. [7] P. Atanasova, T. Halachev, J. Uchytil and M. Klaus, Appl. Catal. 38 (1988) 235. [8] P. D. Hopkins and B. L. Meyers, Ind. Eng. Chem. Prod. Res. Dev. 22 (1983) 421. [9] Y. Okamoto, T. Gomi, Y. Mori, T. Imanaka and S. Teranishi, React. Kinet. Catal. Lett. 22 (1983) 417. [10] A. Morales, M. M. Ramirez and M. M. de Agudelo, Appl. Catal. 23 (1986) 23. [11] K. Usui and K. Tawara, U. S. Patent, 4,585,748, 1986, to Cosmo Oil. [12] M. Tsujii, K. Usui and K. Ohki, Japan Patent, 2120579, 1996, to Cosmo Research Institute and Cosmo Oil. [13] T. Yoshinari, K. Usui, Y. Yamamoto and M. Ohi, Japan Patent, 2547115, 1996, to Cosmo Oil and Petroleum Energy Center. [14] A. Lopez Agudo, R. Cid, F. Orellana and J. L. G. Fierro, Polyhedron 5 (1986) 187. [15] A. Lopez Agudo, A. Benitez, J. L. G. Fierro, J. M. Palacios, J. Neira and R. Cid, J. Chem. Soc, Faraday Trans. 88 (1992) 385. [16] R. Cid, J. Neira, J. Godoy, J. M. Palacios, S. Mendioroz and A. Lopez Agudo, J. Catal. 141 (1993) 206. [17] W. J. J. Welters, V. H. J. de Beer and R. A. van Santen, Appl. Catal.: General 119 (1994) 253. [18] T. Isoda, S. Nagao, Y. Korai and I. Mochida, J. Japan Petrol. Inst. 41 (1998) 22. [19] I. Mochida, Japan Patent, Application No. H7-217751, 1995.
41 Cosmo High-activity HDS Catalyst: Its Development and Performance Properties
Takashi FUJIKAWA, Osamu CHIYODA, Kazuo IDEI, Takashi YOSHIZAWA and Kazushi USUI Cosmo Research Institute, 1134-2, Gongendo, Satte, Saitama 340-0193, Japan Abstract Cosmo Oil introduced a new highly active and stable HDS (hydrodesulfurization) catalyst C-603A in 1994. The preparation of this catalyst combines the use of zeolite technology and impregnation technology to provide excellent HDS activity. C-603A possesses considerably higher activity than conventional Co-Mo/alumina catalyst. Long duration test demonstrated high activity and stability for HDS of vacuum gas oil. Several industrial demonstrations with this catalyst have successfully proven its high performance. 1. INTRODUCTION Recently, since air pollution by exhaust gas from diesel engine has become a serious problem, much attention has been paid to deep HDS of diesel fuel [1, 2]. For this purpose, it has been strongly desired to develop a catalyst which is considerably increased in HDS activity. To resolve this assignment, it is necessary to effectively remove refractory sulfur-containing compounds such as 4,6-dimethyldibenzothiophene (4,6-DMDBT) [3]. Under such circumstances, Cosmo Oil and Petroleum Energy Center (PEC) have developed an improved, highly active HDS catalyst, C-603A [4]. C-603A possesses higher activity than the best of commercial HDS catalysts. Furthermore, C-603A is now in service in three light gas oil HDS units and three vacuum gas oil HDS units of Cosmo Oil refineries. These industrial demonstrations with this catalyst have successfully proven the high HDS activity and stability of C-603A. This paper describes the performance properties and some industrial demonstrations of C-603A in the hydrotreatment of light gas oil and vacuum gas oil. Also, we will show some results regarding the characterization of this catalyst. 2. EXPERIMENTAL 2.1. Catalysts C-603A was prepared by means of the one-step incipient wetness impregnation, using aqueous solution containing the required amounts of cobalt, molybdenum and phosphorus on carrier composed of HY zeolite containing alumina. After the impregnation, this sample was air-dried and calcined at 500 °C . Prior to the activity test, a fresh catalyst was presulfided in situ with straight run gas oil under normal conditions. For comparison, alumina-supported commercial catalysts ( a , /3 , 7 ) were also presulfided and tested under the same 277
278 T. Fujikawa et al.
conditions. HY zeolite-alumina, silica-alumina, and alumina without active metals were also used for model reaction (reaction of 4,6-DMDBT in n-decane). 2.2. Feedstock properties Middle East straight run gas oils containing sulfur between 0.8 and 2.0 mass% and vacuum gas oil containing sulfur 2.65 mass% were used as feedstock for this work. 4,6-DMDBT/n-decane (0.05 mass% as sulfur) was also used as model feedstock. 4,6-DMDBT was synthesized according to the method given in the patent [5]. 2.3. Equipment HDS of light gas oil and vacuum gas oil was carried out using both bench-scale plant and commercial HDS unit. The bench-scale plant was composed of an isothermal fixed-bed reactor operating in down-flow mode. The demonstration operation with C-603A has been carried out with the light gas oil HDS units of Cosmo Oil Sakai and Sakaide refineries and in the vacuum gas oil HDS units of Cosmo Oil Chiba, Yokkaichi and Sakaide refineries. Model reaction was carried out using a continuous flow micro-reactor. 2.4. Reaction Conditions HDS of light gas oil was carried out under the following conditions: temperature, 320-370 °C ; total pressure, 3 - 5 MPa; liquid hourly space velocity (LHSV), 1.0 - 4.5 h ' . HDS of vacuum gas oil was carried out under the following conditions: temperature, 320-400 °C ; total pressure, 3 - 5 MPa; LHSV, 1.0 - 4.5 h ' . Model reaction was carried out under following conditions: temperature, 200-290 °C ; total pressure, 3.4 MPa; LHSV, 1.5 h ' . 2.5. Analytical The amount of sulfur was determined by energy-dispersive X-ray fluorescence spectroscopy (Mitsubishi Kagaku RX-500SAH). The sulfur-containing compounds was analyzed by a gas chromatograph (GC) (Hewlett Packard 5890 11 plus) equipped with a capillary column (HP-1, 25 m, 0.32 mm diameter) and an atomic emission detector (AED) (Hewlett Packard 5921 A). The product analysis of model reaction was performed by a GC (Hewlett Packard 5890 II ) equipped with a capillary column (HP-1, 25 m, 0.32 mm diameter) and a flame ionization detector. 2.6. Kinetic calculations The following equation was used to analyze the results of each experiment, since it was proven by laboratory experiment that expressing the overall HDS rate with 1.5 order reaction in terms of sulfur content was reasonable. k=(l/ / " Sp - 1/ ^
Sf) X (LHSV) X 2
k : Rate constant, h ' ' Sp : Amount of sulfur in product Sf : Amount of sulfur in feedstock
2.7. Catalyst Characterization Transmission electron spectroscopy (TEM) was carried out using a JEOL JEM-2000FX, with an accelerating voltage of 200 keV. For the determination of the chemical composition of zeolite phase and amorphous phase of C-603A, energy dispersive spectroscopy (EDS) was used in a TEM.
279
3. RESULTS and DISCUSSION 3.1. Catalyst design for deep HDS To attain deep HDS, it is vital to remove refractory sulfur-containing compounds such as 4,6-DMDBT effectively. Therefore, we performed a two-step approach to increasing HDS activity as follows: (a) To increase the dispersion of active metals in order to enhance the intrinsic HDS activity. (b) To add a new catalytic function in order to convert 4,6-DMDBT to compounds that are easy to be desulfurized. It is well-known from the literature [6-8] that phosphorus generally enhances the HDS activity of Co(Ni)-Mo hydroprocessing catalysts. Many researchers suggest that the addition of phosphorus increase the dispersion of the Co(Ni) and Mo active metals [9, 10]. Therefore, in order to achieve the increase of dispersion of the Co and Mo active metals, we tried to add a small amount of phosphorus to impregnation solution containing cobalt and molybdenum. Besides, in order to alleviate the steric hindrance, that is, the retarding effect of methyl substituents on the 4- and 6-position of DBT on the HDS rates, we tried to use zeolite which has the ability to promote isomerization reaction. However, zeolite also drastically promotes the undesirable cracking activity, which accelerates the rate of coke deposition and enhances the yields of naphtha product and less diesel product. Thus, in order to overcome this drawback, we controlled the acidity of zeolite and the amount of zeolite in catalyst. After extensive studies based on the technologies of Cosmo's patents [11-13], we have successfully developed a high activity HDS catalyst containing zeolite, C-603A. Chemical and physical properties of C-603A was listed in Table 1. Table 1 Catalyst Active phase Support Surface area Extrudate shape Diameter
Catalyst description
m^/g inch
C-603A Co-Mo-P HY zeoIite-Al203 >250 cylinder 1/16
3.2. Performance advantages of C-603A Cosmo's C-603A is formulated to maximize HDS activity and stability. Its start-of-run performance is compared to three other commercial hydrotreating catalysts in Table 2. Catalyst a is a commercial HDS catalyst, C0-M0/AI2O3, for middle distillates. Catalyst jS is a commercial deep HDS catalyst for middle distillates which outperformed a group of other commercial, non-Cosmo catalysts in laboratory evaluation and is in service in many HDS units worldwide. Catalyst r is a commercial HDS catalyst for vacuum gas oil fractions. From the results shown in Table 2, we could see that our developed catalyst C-603A enables HDS of both light gas oil and vacuum gas oil to a high degree as compared with conventional HDS catalysts. A longer term stability test on a vacuum gas oil feed was also carried out to compare catalyst 7 and C-603A. Feed properties are shown in Table 2. Results of the stability test are shown in Fig. 1. Each plot shows the temperature required to maintain 0.1 mass% sulfur in the product. As can seen in Fig. 1, C-603A significantly outperformed catalyst r , and with comparable stability. Generally, coke formation is the most important cause for deactivation of zeolite [14-17]. As the reason of the high stability of C-603A containing HY zeolite, we assumed that the rate of deactivation by coking was suppressed slightly, since the higher activity of this
280 T. Fujikawa ^r«/. catalyst could lower the reaction temperature in the mode of constant sulfur operation and also the acidity were well-controlled. Table 2
+20
Performance test of C-603A
Test Feed Density g/ml Sulfur mass% Reaction Conditions Pressure MPa Temperature X2 Catalyst Relative Activity
A
Catalyst r
B
LOG 0.859 1.63
VGO 0.934 2.65
4.9 340 a jS C-603A 100 127 140
4.9 360 r C-603A 100 130
Base S
•3
^
C-603A -20
0
20
40
60 80 100 Days on Stream
120
140
Fig. 1 Temperature required to give 0.1 mass% sulfur in product using C-603A
Also, we measured C-603A by TEM and EDS. Detailed investigation reveals that cobalt and molybdenum exist in both zeolite matrix and amorphous phase (Fig. 2, 3). As the other reason of higher stability of C-603A, it is assumed that the cobalt species in zeolite play a major role in maintaining the proper hydrogenation/cracking ratio in order to minimize the opportunities of early deactivation. Isoda et al. [18] and Mochida [19] have reported that Co-Mo/alumina + Ni-HY mixed catalyst exhibited a high and stable activity for HDS of light gas oil. They also assumed that the high hydrogenation activity due to the loaded Ni in Ni-HY zeolite appears to reduce the effect of coking deactivation.
4 5 Energy, keV
Fig. 2 TEM of C-603A
Fig. 3 EDS of C-603A
3.3. Demonstration Operation with C-603A Based on above-mentioned results, we started the practical demonstration of C-603A. Table 3 gives an indication of applications for C-603A until July, 1998. These industrial operations have actually proven the HDS activity and stability of C-603A. Fig. 4 illustrates the relationship between the amount of sulfur in the product and reaction temperature over C-603A and commercial catalyst jS with the light gas oil HDS unit of Cosmo Oil Sakai refinery. Compared
281
to catalyst i3 , C-603A exhibited higher HDS activity. Especially at the region of deep HDS, the HDS ability of C-603A is outstanding. For example, while the difference of required temperature to give 0.1 mass% sulfur between C-603A and catalyst jS is about 4 °C , that of required temperature to give 0.04 mass% sulfur between these catalysts is about 6 °C . Table 3 Applications of Cosmo C-603A Feed type Middle distillates Vacuum gas oils Total
0.15
/"
\ ****•
Total tons 151 630 781
^
Demonstration operation of C-603A with the commercial unit of Cosmo Sakai reflnery V J
n E u
'••.,^^^ Catalyst i3
i
0.05 \-
C-603A
+10
+20 WABT, X:
+30
Fig. 4 Relationship between the amount of sulfur and reaction temperature over C-603A and Catalyst jS 3.4. Model Reaction The main characteristics of C-603A is to add HY zeolite into catalyst. Hence, in order to investigate the difference between C-603A containing zeolite and Catalyst a (C0-M0/AI2O3), we performed reaction studies of the conversion of 4,6-DMDBT in n-decane (Fig. 5). The reaction products treated with Catalyst a were 3-(3'-methylcyclohexyl)toluene (3-(3'-MeCH)T) and a small amount of 3,3'-dimethylbiphenyl (3,3'-DiMeBPH). Hence, it is assumed that the HDS of 4,6-DMDBT over C0-M0/AI2O3 takes place through the hydrogenation of one of benzene rings. On the other hand, the reaction products treated with C-603A were 3,3'-DiMeBPH, 3-(3'-MeCH)T, and 3,4'-DiMeBPH. From these results, it is assumed that the addition of zeolite makes new HDS routes which pass the isomerization and hydrogenolysis of 4,6-DMDBT. Furthermore, in order to investigate the effect of zeolite on the HDS activity in more detail, the reactivity of 4,6-DMDBT in n-decane was measured over non active metal HY zeolite-alumina, silica-alumina, and alumina, respectively. As shown in Fig. 6, it can be observed that only HY zeolite-alumina promotes the conversion of 4,6-DMDBT. The reaction products were 3,6-DMDBT and a small amount of 2,8-DMDBT, 4-MDBT, and C3-DBTs. From the results, it is assumed that the cause of high performance of C-603A is that zeolite plays role in converting 4,6-DMDBT to 3,6-DMDBT which is easy to be desulfurized. Product
Conversion, % C-603A
100
Catalyst a 99.8 0
20 40 60 80 Product Distribution, %
100
180
200
220
240
260
280
Temperture, 'C
Fig. 5 HDS of 4,6-DMDBT
Fig. 6 Conversion of 4,6-DMDBT
300
282 T. Fujikawa et al.
4. CONCLUSIONS In this paper, the development and performance properties of a highly active HDS catalyst, C-603A, have been presented. The main conclusions of this work can be summarized below. 1. C-603A is a successful, HY zeolite-containing HDS catalyst for middle distillates developed by Cosmo Oil. 2. Both the bench-scale plant tests and the industrial data have proven that C-603A possesses significantly higher activity than alumina-supported commercial HDS catalysts. Especially the deep HDS performance of C-603A is outstanding. 3. A longer term stability test on a vacuum gas oil feed demonstrated the excellent stability of C-603A. 4. Based on the results of the model reactions, it is assumed that the cause of high performance of C-603A is that HY zeolite plays role in converting 4,6-DMDBT to sulfur-containing compound which is easy to be desulfurized. Acknowledgements This R&D was supported by the Petroleum Energy Center (PEC), under sponsorship of the Ministry of International Trade and Industry (MITI) of Japan. We thank Mr. Takeshi Ebihara for his contribution to the TEM study. References [1] H. Tops0e, B. S. Clausen and F. E. Massoth, in Hydrotreating Catalysis Science and Technology, Springer-Verlag Berlin Heidelberg, Berlin, 1996. [2] T. Takatsuka, S. Inoue and Y. Wada, Catal. Today 39 (1997) 69. [3] T. Kabe, A. Ishihara and H. Tajima, Ind. Eng. Chem. Res. 31 (1992) 1577. [4] T. Fujikawa, O. Chiyoda, M. Tsukagoshi, K. Idei and S. Takehara, Proc. Third Japan-EU Joint Workshop of the Frontiers of Catalytic Science & Technology, (JECAT'97), 1997, P189. [5] T. Fujikawa and K. Usui, Japan Patent, Application No. H6-67968, 1994. [6] C. W. Fitz and H. F. Rase, Ind. Eng. Chem. Prod. Res. Dev. 22 (1983) 40. [7] P. Atanasova, T. Halachev, J. Uchytil and M. Klaus, Appl. Catal. 38 (1988) 235. [8] P. D. Hopkins and B. L. Meyers, Ind. Eng. Chem. Prod. Res. Dev. 22 (1983) 421. [9] Y. Okamoto, T. Gomi, Y. Mori, T. Imanaka and S. Teranishi, React. Kinet. Catal. Lett. 22 (1983) 417. [10] A. Morales, M. M. Ramirez and M. M. de Agudelo, Appl. Catal. 23 (1986) 23. [11] K. Usui and K. Tawara, U. S. Patent, 4,585,748, 1986, to Cosmo Oil. [12] M. Tsujii, K. Usui and K. Ohki, Japan Patent, 2120579, 1996, to Cosmo Research Institute and Cosmo Oil. [13] T. Yoshinari, K. Usui, Y. Yamamoto and M. Ohi, Japan Patent, 2547115, 1996, to Cosmo Oil and Petroleum Energy Center. [14] A. Lopez Agudo, R. Cid, F. Orellana and J. L. G. Fierro, Polyhedron 5 (1986) 187. [15] A. Lopez Agudo, A. Benitez, J. L. G. Fierro, J. M. Palacios, J. Neira and R. Cid, J. Chem. Soc, Faraday Trans. 88 (1992) 385. [16] R. Cid, J. Neira, J. Godoy, J. M. Palacios, S. Mendioroz and A. Lopez Agudo, J. Catal. 141 (1993) 206. [17] W. J. J. Welters, V. H. J. de Beer and R. A. van Santen, Appl. Catal.: General 119 (1994) 253. [18] T. Isoda, S. Nagao, Y. Korai and I. Mochida, J. Japan Petrol. Inst. 41 (1998) 22. [19] I. Mochida, Japan Patent, Application No. H7-217751, 1995.