AU2013360529A1

AU2013360529A1 - Catalyst for manufacturing synthetic gas through steam-carbon dioxide reforming, and method for manufacturing synthetic gas by using same

Info

Publication number: AU2013360529A1
Application number: AU2013360529A
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: 2015-07-16
Anticipated expiration: 2033-12-12
Also published as: CN104955570A; MY172598A; WO2014092474A1; CN104955570B; AU2013360529B2; KR101421825B1; KR20140075996A

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 cerium by using dry mixing; 2) preparing nickel and magnesium oxide powders; and 3) mixing and firing a powder of the support in step 1) and powders of metals in step 2). 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: CATALYST FOR SYNGAS PRODUCTION BY STEAM CARBON DIOXIDE REFORMING AND METHOD FOR SYNGAS 5 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 catalyst useful for syngas production by steam-carbon dioxide reforming (SCR) and a method for preparing the catalyst. Background Art Reforming processes for producing so-called syngas, a mixture of 15 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 chemistry and is applied to the production of methanol, hydrogen, ammonia, 20 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 gases thereof, have been used for the production of syngas from hydrocarbons. 25 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 reforming, tri-reforming reactions, and other reforming reactions. 30 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) For this reaction, a nickel-based catalyst is mainly used. In the steam 1 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 atoms and the molar ratio of oxygen atoms to carbon atoms in the reaction 5 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, water gasification is relatively promoted, and as a result, syngas is obtained that 10 has 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 are carried out at a temperature of 730 to 860 OC and a pressure of 20 to 40 atm in a molar 15 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, Y.S. Baek, Catal. Today 84 (2003) 133]. Thus, there is a need to develop 20 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 as a-alumina supports, for steam reforming catalysts is very crucial. 25 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 catalyst, an auxiliary catalyst, and a general carrier wherein the auxiliary 30 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 the carrier is alumina, silica, magnesia or zirconia. Further, U.S. Patent Nos. 2 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 high space velocities when applied to steam reforming reactions. Accordingly, 5 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. In this regard, Korean Patent No. 10-0394076 (entitled "nickel-based 10 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 nickel from 5 to 20% by weight and the amount of the cerium is from 0.01 to 1.0 15 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. On the other hand, the carbon dioxide reforming reaction of methane 20 proceeds as depicted in Scheme 2:

CH

4 + C02 -- * 2CO + 2H 2 , A H'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. Alternatively, a precious metal-based catalyst may be used. Syngas produced 25 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 catalysts that are free from the problem associated with carbon deposition were 30 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 proposes that precious metal (e.g., iridium, rhodium and ruthenium)-supported 3 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 due to their high prices. 5 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 dioxide reforming that has superior activity and stability to prevent deactivation 15 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 syngas production, which is prepared by a method including: 20 1) preparing a zirconia/alumina support modified with cerium by dry mixing; 2) preparing a nickel powder and a magnesium oxide powder; and 3) mixing the support powder prepared in step 1) with the metal powders prepared in step 2) 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 changes in the conversion of methane from natural gas according to a working example of the present invention. 10 Fig. 2 is a graph showing changes in the molar ratio between hydrogen and carbon monoxide constituting syngas according a working example of the present invention. Best Mode for Carrying out the Invention 15 The present invention is directed to a nickel-based steam reforming catalyst using magnesium and a lanthanide element 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 cerium by dry mixing; 2) preparing a nickel powder and a magnesium oxide powder; and 3) mixing the support powder prepared in step 1) with the metal powders prepared in step 2) and calcining the mixture. 25 According to a preferred embodiment of the present invention, in step 2), the nickel powder and the magnesium oxide powder are in a weight ratio of 1:1 20, more preferably 1:1-3. According to a preferred embodiment of the present invention, in step 1), the cerium, the zirconia, and the alumina are in a weight ratio of 1:5-10:20-40. 30 Outside this range, undesirable carbon deposition occurs. According to a preferred embodiment of the present invention, in step 3), the calcination is performed at a temperature of 700 to 1200 0C in air. 5 According to a preferred embodiment of the present invention, in step 3), the support powder is mixed with the metal powders by a series of dry mixing, drying, kneading, and extrusion. The present invention is distinguished from the prior art in that an impregnation or melting process conventionally used for 5 catalyst production is not carried out. Preferably, the reforming catalyst contains 5 to 20% by weight of the nickel and magnesium as active components supported on the zirconia/alumina support modified with cerium (Ce-ZrO 2 /Al 2 0 3 ). If the total amount of the nickel and magnesium supported is outside the range defined above, it may be difficult 10 to produce syngas having a hydrogen/carbon monoxide ratio of about 2. The present invention also provides a method for syngas production including supplying carbon dioxide, steam, and methane at a temperature of 700 to 1200 0C, a pressure of 15 to 20 bar, and a space velocity of 4000 to 7000 h 1 and subjecting the gases to a reforming reaction in the presence of the 15 catalyst. Syngas produced by the reforming reaction has a hydrogen/carbon monoxide 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. The present invention will now be described in more detail. 20 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/magnesium metal on a zirconia/alumina support modified with cerium, enables the production a 25 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 carbon dioxide reforming of methane, a major component of natural gas, and is preferably a reforming catalyst in which 5 to 20% by weight of nickel and 30 magnesium as active components are supported on a zirconia/alumina support modified with cerium (Ce-ZrO 2 /Al 2 0 3 ). If the total amount of the nickel/magnesium supported is less than 5% by weight, the catalyst exhibits 6 poor activity. Meanwhile, if the total amount of the nickel/magnesium supported exceeds 20% by weight, the catalyst is undesirably deactivated by coke deposition. In the zirconia/alumina support modified with cerium (Ce-ZrO 2 /Al 2 0 3 ), 5 the zirconia and the alumina are hybridized with cerium (Ce), which is present in an amount of 0.01 to 1.0 mole per mole of the zirconia/alumina. If the cerium is present in an amount exceeding 1.0 mole, the support is excessively modified with the cerium, resulting in poor activity of the catalyst. The zirconia/alumina support is modified with cerium and the 10 nickel/magnesium are supported on the support by a series of dry mixing, drying, kneading, extrusion, and calcination, instead of general processes known in the art, i.e. co-precipitation, precipitation-deposition, sol-gel, melting, and impregnation processes. Most preferably, the zirconia/alumina support modified with cerium is 15 obtained by mixing desired proportions of ceria, zirconia, and alumina. The mixing may be performed by any suitable process commonly used in the art. For example, the mixing process may be ball milling. A mixture of nickel oxide and magnesium oxide in the form of powders is mixed with the zirconia/alumina support modified with cerium, kneaded, 20 extruded, and calcined. The calcination is preferably performed at a temperature of 700 to 1200 0C in air for 5 to 8 hours. 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 25 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 700 0C for 1 hour before the 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 30 methane to steam is 1:1-3 and the molar ratio of methane to carbon dioxide is 1:0.4-1. If needed, nitrogen is added as a diluting gas. The temperature of the reactor is controlled to the range of 700 to 1200 0C using an electric heater and 7 a programmable automatic thermostat, the reaction pressure is adjusted to 15 to 20 bar, and the flow rates of the gases are controlled using mass flow controllers such that the space velocity is from 4000 to 7000 hr- 1 . The gases whose flow rates are controlled can react continuously to produce syngas. The 5 compositions of the gases before and after the reaction are analyzed using a gas chromatograph, which is directly connected to the reactor system and equipped with a Porapak column for gas separation. The high-temperature activity of the reforming catalyst is measured at 750 0C. The thermal stability of the reforming catalyst with the passage of time 10 is evaluated by measuring the initial activity of the catalyst at 750 0C and the activity after 200 minutes from the yield of hydrogen in the products and the 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 15 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 velocity, suggesting its potential applicability as an industrial catalyst. Mode for the Invention 20 The present invention will be explained in more detail with reference to the following examples but is not limited thereto. Example 1 Ceria, zirconia, and alumina were mixed in the proportions shown in 25 Table 1 in a dry state. Magnesia, nickel oxide, and alumina were mixed in the proportions shown in Table 1. The mixtures were separately calcined at 900 0C for 6 h to obtain powders. The two powders were sufficiently mixed together, heated to 750 0C at a rate of 3 OC/min, followed by calcination for 6 h to obtain a catalyst. The physical properties of the catalyst are shown in Table 2. 30 [Table 1] | Sample Raw material Content (wt%) 1 hole type CeO 2 1-3 8 MgO 1-3 NiO 3-8 ZrO 2 2-8 CeO 2 1-5 5 hole type MgO 1-5 NiO 3-8 ZrO 2 2-8 [Table 2] Specific surface Bulk density Example 1 L axis strength R axis strength area (m 2 /g) (g/L) 3240.86 190.12 3.84 1.9 Example 2 5 The catalyst (1 hole type) prepared in Example 1 was applied to steam carbon dioxide reforming (SCR), which was performed while maintaining a temperature of 900 0C and a pressure of 18 bar. Steam, carbon dioxide, and methane were introduced in the ratios shown in Table 3. The reforming of methane was performed at different space velocities of 4000 hr- 1 and 7000 hr- 1 . 10 The reaction results are shown in Table 3 and Figs. 1 and 2. [Table 3]

STM/CH

4 C0 2

/CH

4 4000 h-C 7000 h- 1 4

H

2 /CO OH 4 cony. H 2 /CO OH 4 cony. 1.707 1.0 - - 2.22 98.98 1.195 1.0

-

- 2.14 96.08 1.1 - - 2.03 95.88 1.0 2.27 91.77 2.00 94.84 1.024 1.1 2.17 91.81

-

1.15 2.14 91.95 - 1.2 2.11 92.02 - 0.853 1.2 2.03 89.69 - From the results in Table 3, it can be seen that the hydrogen/carbon 15 monoxide ratios of syngas produced by reforming were 2.0±0.2 and the methane conversions were maintained at a very high level. Comparative Example 1 Reforming reactions of CH 4

/STM/CO

2 mixtures were carried out at a 20 temperature of 900 0C and a pressure of 18 bar using the catalyst disclosed in 9 Korean Patent Application No. 2008-0075787, which was prepared by supporting Ni as an active component on Ce-Zr/MgAlOx as a support using an impregnation process. The results are shown in Table 4. 5 [Table 4] 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 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 10 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 economic efficiency of the inventive catalyst. In addition, the content of C02 in the reactant gases was increased by 15 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 SCR process to dispose of C02 than other processes. 20 Industrial Applicability The catalyst of the present invention minimizes carbon deposition during 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 25 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 applied to dimethyl ether (DME) floating production, storage and offloading 30 (FPSO) systems as well as gas-to-liquid (GTL) FPSO systems. Therefore, the 10 present invention is expected to find applications in various industrial fields. 11

Claims

10. [Claim 4] The reforming catalyst according to claim 1, wherein, in step 1), the cerium, the zirconia, and the alumina are in a weight ratio of 1:5-10:20-40. 20 [Claim 5] The reforming catalyst according to claim 1, wherein, in step 3), the calcination is performed at a temperature of 700 to 1200 OC in air. [Claim 6] The reforming catalyst according to claim 1, wherein, in step 3), 25 the mixing comprises dry mixing, drying, kneading, and extrusion. [Claim 7] The reforming catalyst according to claim 1, wherein the reforming catalyst contains 5 to 20% by weight of the nickel and magnesium as active components supported on the zirconia/alumina support modified with 30 cerium (Ce-ZrO 2 /Al 2 0 3 ). [Claim 8] A method for syngas production, comprising supplying carbon 12 dioxide, steam, and methane at a temperature of 700 to 1200 0C, a pressure of 15 to 20 bar, and a space velocity of 4000 to 7000 h- 1 and subjecting the gases to a reforming reaction in the presence of the reforming catalyst according to any one of claims 1 to 7. [Claim 9] The method according to claim 8, wherein syngas produced by the reforming reaction has a hydrogen/carbon monoxide ratio of 2.0±0.2. 13