AU2013360537B2

AU2013360537B2 - Catalyst containing lanthanum for manufacturing synthetic gas through steam-carbon dioxide reforming, and method for manufacturing synthetic gas by using same

Info

Publication number: AU2013360537B2
Application number: AU2013360537A
Authority: AU
Inventors: Jongtae CHUNG; Jihye Lee; Yonggi MO
Original assignee: Korea Gas Corp
Current assignee: Korea Gas Corp
Priority date: 2012-12-12
Filing date: 2013-12-12
Publication date: 2016-05-12
Anticipated expiration: 2033-12-12
Also published as: MY169114A; WO2014092482A1; KR101401170B1; AU2013360537A1; CN104955564A

Abstract

The present invention relates to a catalyst for manufacturing a synthetic gas from a natural gas by using carbon dioxide, and more specifically, to a catalyst useful for manufacturing a synthetic gas by means of steam-carbon dioxide reforming. The catalyst according to the present invention is manufactured by a method comprising the steps of: 1) manufacturing a zirconia and alumina support coated with lanthanum and cerium by wet or dry ball milling; and 2) mixing and firing a powder of the support in step 1) and a nickel powder. The ratio of hydrogen to carbon monoxide in the synthetic gas, which is manufactured by using the catalyst according to the present invention, can be controlled to 2.0±0.2, thereby easily providing the synthetic gas which is efficient for producing synthetic petrochemical products (such as wax, naphtha, and diesel).

Description

DESCRIPTION Title of the Invention: LANTHANUM-CONTAINING CATALYST FOR SYNGAS PRODUCTION BY STEAM-CARBON DIOXIDE REFORMING AND 5 METHOD FOR SYNGAS PRODUCTION USING SAME Technical Field The present invention relates to a catalyst for the production of syngas from natural gas by using carbon dioxide. More particularly, the present 10 invention relates to a lanthanum-containing catalyst useful for syngas production by steam-carbon dioxide reforming (SCR) and a method for preparing the catalyst. Background Art 15 Reforming processes for producing so-called syngas, a mixture of hydrogen and carbon monoxide, from methane, a major component of natural gas, using catalysts and oxidizing agents have already been used industrially and become important fundamental processes in the chemical industry. Syngas produced by reforming of methane constitutes the basis for C1 20 chemistry and is applied to the production of methanol, hydrogen, ammonia, etc. In recent years, the production of liquid fuels and oxygen-containing compounds based on syngas production has emerged as an important approach to utilize natural gas. Oxidizing agents, such as oxygen, steam, carbon dioxide, and mixed 25 gases thereof, have been used for the production of syngas from hydrocarbons. A great deal of research has been conducted on the development of catalysts with different characteristics depending on the kind of oxidizing agents. Reforming processes for producing syngas from methane include steam reforming, carbon dioxide reforming, partial oxidation reforming, autothermal 30 reforming, tri-reforming reactions, and other reforming reactions. The steam reforming reaction proceeds as depicted in Scheme 1:

CH

4 + H 2 0 - CO + 3H 2 , A H 0 298 = +206 kJ/mol (1) 1 For this reaction, a nickel-based catalyst is mainly used. In the steam reforming process, deactivation of the reforming catalyst by carbon deposition is considered the most important problem. Carbon deposition can be thermodynamically calculated from the molar ratio of hydrogen atoms to carbon 5 atoms and the molar ratio of oxygen atoms to carbon atoms in the reaction products. Accordingly, for the purpose of preventing the catalyst from deactivation resulting from carbon deposition, excess steam is added during the steam reforming of methane to increase the molar ratio of hydrogen atoms to carbon atoms and the molar ratio of oxygen atoms to carbon atoms. Thus, 10 water gasification is relatively promoted, and as a result, syngas is obtained that has a a molar ratio of hydrogen to carbon monoxide of 3 or higher. This is suitable for ammonia production processes where a high content of hydrogen is needed and syngas processes for the production of high concentration hydrogen. Currently industrially used steam reforming processes of methane 15 are carried out at a temperature of 730 to 860 0 C and a pressure of 20 to 40 atm in a molar ratio of methane to steam of 1:4-6. Nickel-based catalysts are used in most steam reforming reactions. However, deactivation of nickel-based catalysts by carbon deposition, shortens the lifetime of the catalysts [S.H. Lee, W.C. Cho, W.S. Ju, B.H. Cho, Y.C. Lee, 20 Y.S. Baek, Catal. Today 84 (2003) 133]. Thus, there is a need to develop reforming catalysts that have superior performance to conventional steam reforming catalysts. For industrial applications, such reforming catalysts are required to have good thermal and mechanical stability as well as high coking resistance. To meet these requirements, the choice of suitable supports, such 25 as a-alumina supports, for steam reforming catalysts is very crucial. Some catalysts supported on zirconia are known as steam reforming catalysts. For example, U.S. Patent No. 4,026,823 (1975) discloses a zirconia supported nickel-cobalt catalyst as a steam reforming catalyst of hydrocarbons. Further, U.S. Patent No. 4,060,498 discloses a catalyst including a nickel 30 catalyst, an auxiliary catalyst, and a general carrier wherein the auxiliary catalyst is a mixture of a metal, such as lanthanum or cerium, and silver in a proper ratio, is added to the nickel catalyst, and is supported on the carrier, and 2 the carrier is alumina, silica, magnesia or zirconia. Further, U.S. Patent Nos. 4,297,205 (1980) and 4,240,934 (1978) disclose steam reforming catalysts of hydrocarbons in which iridium is supported on a zirconia/alumina support. However, these catalysts suffer from a reduction in activity or are deactivated at 5 high space velocities when applied to steam reforming reactions. Accordingly, for use in steam reforming reactions, zirconia needs to be modified to maintain the activities of the catalysts in the reactions, the stability of the catalysts at high temperatures, and the activities of the catalysts at high space velocities of gases. 10 In this regard, Korean Patent No. 10-0394076 (entitled "nickel-based reforming catalyst for syngas production and method for producing syngas from natural gas by steam reforming using the same") proposes a nickel-based reforming catalyst (Ni/Ce-Zr 2 ) for syngas production including a cerium-modified zirconia support and nickel supported on the support wherein the amount of the 15 nickel from 5 to 20% by weight and the amount of the cerium is from 0.01 to 1.0 mole per mole of the zirconia. The catalyst is prepared by preparing a zirconia support optionally modified with cerium using a co-precipitation or sol-gel process and supporting nickel on the support using an impregnation or melting process. 20 On the other hand, the carbon dioxide reforming reaction of methane proceeds as depicted in Scheme 2:

CH

4 + C02 -- * 2CO + 2H 2 , A H 0 298 = +247.3 kJ/mol (2) As in the steam reforming reaction of methane, a nickel-based catalyst is mainly used in the carbon dioxide reforming reaction of methane. 25 Alternatively, a precious metal-based catalyst may be used. Syngas produced by the reforming reaction of methane using carbon dioxide can be utilized for the production of dimethyl ether (DME) due to the presence of a very large amount of carbon monoxide (H 2 :CO = 1:1). However, carbon deposition causes severe deactivation of the catalyst. In view of this, precious metal-based 30 catalysts that are free from the problem associated with carbon deposition were suggested. For example, Pt/A1 2 0 3 and Pd/A1 2 0 3 catalysts are known in U.S. Patent No. 5,068,057. International Patent Publication No. WO 92/11,199 3 proposes that precious metal (e.g., iridium, rhodium and ruthenium)-supported alumina catalysts exhibit strong activity and extended lifetime. The precious metal-based catalysts are highly resistant to carbon deposition and are very active compared to nickel-based catalysts, but are unsuitable for industrial use 5 due to their high prices. Thus, continued attempts have been made to develop catalysts that minimize carbon deposition in the steam-carbon dioxide reforming reaction of methane and can be prepared at reduced costs, facilitating their industrial application. 10 Disclosure of the Invention Technical Problem The present invention is intended to provide a nickel-based reforming catalyst for the production of syngas or hydrogen in high yield by steam-carbon 15 dioxide reforming that has superior activity and stability to prevent deactivation of the catalyst resulting from coke formation while maintaining long lifetime. Solution to Problem One aspect of the present invention provides a reforming catalyst for 20 syngas production, which is prepared by a method including: 1) preparing a zirconia/alumina support modified with lanthanum and cerium by wet mixing or dry ball milling; and 2) mixing the support powder prepared in step 1) with a nickel powder and calcining the mixture. 25 Another aspect of the present invention provides a method for syngas production by steam-carbon dioxide reforming using the catalyst. Advantageous Effects of the Invention The catalyst of the present invention minimizes carbon deposition during 30 syngas production by steam-carbon dioxide reforming (SCR) of methane and enables the production of syngas having a H 2 /CO ratio of 2.0+0.2, which is efficient in the manufacture of petrochemicals (e.g., waxes, naphtha, and diesel). Therefore, the use of the catalyst contributes to a reduction in the 4 production cost of syngas and the manufacturing cost of petrochemicals. The catalyst of the present invention and the process using the catalyst can be applied to dimethyl ether (DME) floating production, storage and offloading (FPSO) systems as well as gas-to-liquid (GTL) FPSO systems. Therefore, the 5 present invention is expected to find applications in various industrial fields. Brief Description of the Drawings Fig. 1 is a graph showing the molar ratios between hydrogen and carbon monoxide constituting syngas produced under conditions specified in Examples 10 1 and 6. Fig. 2 is a graph showing the conversions of methane from natural gas during the production of syngas under conditions specified in Examples 1 and 6. Best Mode for Carrying out the Invention 15 The present invention is directed to a nickel-based steam reforming catalyst using nickel and lanthanide elements that are relatively resistant to carbon deposition. Specifically, the present invention provides a reforming catalyst for syngas production, which is prepared by a method including: 20 1) preparing a zirconia/alumina support modified with lanthanum and cerium by wet or dry ball milling; and 2) mixing the support powder prepared in step 1) with a nickel powder and calcining the mixture. According to a preferred embodiment of the present invention, the 25 reforming catalyst (NiO-La/Ce-ZrO 2 /Al20 3 ) contains 1 to 7% by weight of the lanthanum in the zirconia/alumina support modified with lanthanum and cerium. According to a preferred embodiment of the present invention, in step 2), the calcination is performed at a temperature of 700 to 1200 OC in air. According to a preferred embodiment of the present invention, in step 30 2), the two powders are mixed by a series of dry ball milling or wet mixing, drying, kneading, and extrusion. According to a preferred embodiment of the present invention, the 5 reforming catalyst (NiO-La/Ce-ZrO 2 /Al 2 0 3 ) contains 5 to 20% by weight of the nickel supported on the zirconia/alumina support modified with lanthanum and cerium. If the amount of the nickel supported is outside the range defined above, it may be difficult to produce syngas having a hydrogen/carbon 5 monoxide ratio close to 2. According to a preferred embodiment of the present invention, the reforming catalyst includes the lanthanum and the cerium in a weight ratio of 1:2-10. Outside this range, it may be difficult to produce syngas having a hydrogen/carbon monoxide ratio close to 2. 10 The present invention also provides a method for syngas production including supplying carbon dioxide, steam, and methane at a temperature of 700 to 950 OC, a pressure of 10 to 20 bar, and a space velocity of 300 to 4000 h- and subjecting the gases to a reforming reaction in the presence of the catalyst. The carbon dioxide and the steam are preferably supplied in amounts 15 of 0.4 to 1 mole and 1 to 3 moles, respectively, per mole of the methane. Syngas produced by the reforming reaction has a hydrogen/carbon monoxide molar ratio of 2.0±0.2. Therefore, the method of the present invention can provide syngas efficient for the manufacture of petrochemicals (e.g., waxes, naphtha, and diesel) in an easy manner. 20 The present invention will now be described in more detail. A conventional catalyst for a steam-carbon dioxide reforming reaction has the problem of deactivation or reduced activity at a high space velocity. In contrast, the reforming nickel catalyst of the present invention, which is prepared by supporting a predetermined amount of nickel metal on a 25 zirconia/alumina support modified with lanthanum and cerium, enables the production a mixture of carbon monoxide and hydrogen, so-called syngas, in high yield by steam-carbon dioxide reforming of methane, a major component of natural gas. The reforming nickel catalyst of the present invention is used for steam 30 carbon dioxide reforming of methane, a major component of natural gas, and is preferably represented by NiO-La/Ce-ZrO 2 /Al 2 0 3 in which 5 to 20% by weight of nickel as an active component is supported on a zirconia/alumina support 6 modified with lanthanum and cerium. If the amount of the nickel supported is less than 5% by weight, the catalyst exhibits poor activity. Meanwhile, if the amount of the nickel supported exceeds 20% by weight, the catalyst is undesirably deactivated by coke deposition. 5 In the zirconia/alumina support modified with lanthanum (La) and cerium (Ce), the zirconia and the alumina are hybridized with lanthanum and cerium, which are present in a weight ratio of 1:2-10. Excessive modification of the support with lanthanum and cerium leads to poor activity of the catalyst. The zirconia/alumina support is modified with lanthanum and cerium and 10 the nickel is supported on the support by a series of dry or wet mixing, drying, kneading, extrusion, and calcination. Distilled water is preferably used as a solvent. Most preferably, the zirconia/alumina support modified with lanthanum and cerium is obtained by mixing desired proportions of lanthanum oxide 15 (La 2 0 3 ), ceria, zirconia, nickel oxide, and alumina. Nickel oxide in the form of a powder is mixed with the zirconia/alumina support modified with lanthanum and cerium, kneaded, extruded, and calcined. The calcination is preferably performed at a temperature of 700 to 1200 OC in air for 5 to 8 hours. 20 The reforming activity of the catalyst is measured in a typical laboratory-made fixed-bed catalytic reactor system. The catalyst may be pretreated before the reaction. Specifically, the catalyst is shaped and pulverized so as to have a particle size of 1 to 2 mm, the required amount of the catalyst is filled in the reactor, and the catalyst is reduced by 5% hydrogen at 25 700 0 C for 1 hour before reaction. Then, methane, steam, and carbon dioxide as reactants are fed into the reactor. The reactants are used in such amounts that the molar ratio of the methane to the steam is 1:1-3 and the molar ratio of the methane to the carbon dioxide is 1:0.4-1. If needed, nitrogen is added as a diluting gas. The 30 temperature of the reactor is controlled to the range of 700 to 950 OC using an electric heater and a programmable automatic thermostat, the reaction pressure is adjusted to 10 to 20 atm, and the flow rates of the gases are controlled using 7 mass flow controllers such that the space velocity is from 3000 to 4000 hr- 1 . The gases whose flow rates are controlled can react continuously to produce syngas. The compositions of the gases before and after the reaction are analyzed using a gas chromatograph, which is directly connected to the reactor 5 system and equipped with a Porapak column for gas separation. The high-temperature activity of the reforming catalyst is measured at 750 OC. The thermal stability of the reforming catalyst with the passage of time is evaluated by measuring the initial activity of the catalyst at 750 OC and the activity after 200 minutes from the yield of hydrogen in the products and the 10 conversion of methane. The reforming catalyst of the present invention used for the production of syngas from natural gas exhibits better activity than conventional reforming nickel catalysts supported on zirconia. Due to its improved activity, the catalyst of the present invention can maintain good activity even at a high gas space 15 velocity, suggesting its potential applicability as an industrial catalyst. Mode for the Invention The present invention will be explained in more detail with reference to the following examples but is not limited thereto. 20 Preparative Example 1 Alumina, ceria, zirconia, nickel oxide, and lanthanum oxide in the form of powders were mixed in the proportions shown in Table 1. Distilled water was added to the mixture, sufficiently mixed with stirring, and dried. After sufficient 25 mixing, the resulting mixture was heated to 700-950 OC at a rate of 3 0 C/min, followed by calcination for 6 h to obtain a catalyst. Preparative Example 2 Ceria and zirconia in the form of dry powders were added to alumina 30 and mixed by ball milling. Nickel oxide, lanthanum oxide, and alumina were mixed in the same manner as above. The two powders were mixed together and calcined at 700-950 OC for 6 h to obtain NiO-La/Ce-ZrO 2 /Al20 3 . 8 [Table 1] Raw material Preparative Example 1 (wt%) Preparative Example 2 (wt%) La 2

O

3 1-8 1-13 CeO 2 1-13 1-10 NiO 3-12 5-14 ZrO 2 2-10 2-11 A1 2 0 3 70-90 70-90 [Table 2] Physical properties Strength Bulk density L axis (N) R axis (N) Bl est Preparative Example 1 6125.0 114.7 1.531 Preparative Example 2 6066.2 419.0 1.707 5 Examples 1-5 7 g of the catalyst prepared in Preparative Example 1 was applied to steam carbon dioxide reforming (SCR), which was performed while maintaining a temperature of 700-950 'C and a pressure 18 bar. Steam, carbon dioxide, 10 and methane were introduced in the ratios shown in Table 3. The reforming of methane was performed at a space velocity of 3000-4000 hr- 1 . The reaction results are shown in Table 3 and Figs. 1 and 2. [Table 3] Example No. Methane:carbon dioxide:steam CH 4 conversion (%) H 2 /CO Example 1 1:1:1-3 95.93 2.32 Example 2 1:1:1-2.5 94.69 2.11 Example 3 1:1:1-2 93.41 1.92 Example 4 1:0.5-1:1-2 93.31 2.08 Example 5 1:0.4-1:1-2 93.70 2.05 15 From the results in Table 3, it can be seen that when the ratios of the gases were in the range of 1:0.4-1:1-3, the methane conversions were maintained at 90% or higher and syngas having a H 2 /CO ratio of 1.9-2.4 was produced. 20 Examples 6-10 Reforming reactions were carried out using the catalyst prepared in Preparative Example 2 under the same conditions as described in Example 1. 9 The results are shown in Table 4. [Table 4] Example No. Methane:carbon dioxide:steam CH 4 conversion (%) H 2 /CO Example 6 1:1:1-3 97.07 2.11 Example 7 1:1:1-2.5 95.66 1.95 Example 8 1:1:1-2 95.50 1.91 Example 9 1:0.5-1:1-2 95.32 1.96 Example 10 1:0.4-1:1-2 95.57 2.02 5 Similar results were obtained even when the catalyst of Preparative Example 2 was used. Specifically, when the ratios of the gases were in the range of 1:0.4-1:1-3, the methane conversion was maintained at 95% and syngas having a H 2 /CO ratio of 1.9-2.2 was produced. 10 Comparative Example 1 Reforming reactions of CH 4

/STM/CO

2 mixtures were carried out at a temperature of 700-950 'C and a pressure of 18 bar using the catalyst disclosed in Korean Patent Application No. 2008-0075787, which was prepared by supporting Ni as an active component on Ce-Zr/MgAlOx as a support using 15 an impregnation process. The results are shown in Table 5. [Table 5] Molar ratio (CH 4

/STM/CO

2 ) Space velocity (hr-') CH 4 conv. 1/1.5/0.4 1300 95 1/1.5/0.39 1700 93 1/1.5/0.34 1700 97 As can be seen from the above results, the inventive catalyst showed 20 the same level of methane conversion as the comparative catalyst at a higher space velocity. This indicates that the use of the inventive catalyst can minimize the size of a reactor. Specifically, when the inventive catalyst is used, the same

CH

4 conversion can be obtained in a reactor having a capacity corresponding to 1/3-1/5 of the design capacity of a commercial reactor, demonstrating high 25 economic efficiency of the inventive catalyst. In addition, the content of C02 in the reactant gases was increased by 10 two times or more when the inventive catalyst was used compared to when the comparative catalyst was used. The use of a large amount of C02 as a reactant gas is advantageous from an economic viewpoint and the recovery of a large amount of C02 remaining after the reaction demonstrates a better ability of the 5 SCR process to dispose of C02 than other processes. Industrial Applicability The catalyst of the present invention minimizes carbon deposition during syngas production by steam-carbon dioxide reforming (SCR) of methane and 10 enables the production of syngas having a H 2 /CO ratio of 2.0+0.2, which is efficient in the manufacture of petrochemicals (e.g., waxes, naphtha, and diesel). Therefore, the use of the catalyst contributes to a reduction in the production cost of syngas and the manufacturing cost of petrochemicals. The catalyst of the present invention and the process using the catalyst can be 15 applied to dimethyl ether (DME) floating production, storage and offloading (FPSO) systems as well as gas-to-liquid (GTL) FPSO systems. Therefore, the present invention is expected to find applications in various industrial fields. 11