CATALYST FOR SYNTHESIZING METHANOL OR ITS PRECURSOR, METHOD FOR PREPARING THE CATALYST AND METHOD FOR PRODUCING METHANOL OR ITS PRECURSOR USING THE CATALYST

Abstract

Disclosed is a novel catalyst having amine ligands for synthesizing methanol or its precursor. When the catalyst is allowed to react with an alkane in the presence of an acid, at least one CH bond of the alkane is catalytically oxidized. Therefore, the catalyst is suitable for use in forming an alkyl ester from an alkane.

Claims

1. A catalyst for synthesizing methanol or its precursor, represented by one of Formulae 1, 2, and 3: ##STR00035## wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group, X and X are the same as or different from each other and are each independently selected from hydrogen, C.sub.1-C.sub.3 alkyl groups, halogen groups, C.sub.1-C.sub.3 alkoxy groups, a nitro group, a carboxyl group, and a sulfonic acid group (SO.sub.3H), and Y.sub.1, Y.sub.1, Y.sub.2, and Y.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group; ##STR00036## wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are as defined in Formula 1 and Z and Z are all hydrogen or together form a benzene or cyclohexyl ring with adjacent carbon atoms; and ##STR00037## wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are as defined in Formula 1 and Z and Z are as defined in Formula 2.

2. The catalyst according to claim 1, wherein the catalyst has the structure of Formula 1 wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group, X and X are the same as or different from each other and are each independently selected from hydrogen, C.sub.1-C.sub.3 alkyl groups, halogen groups, C.sub.1-C.sub.3 alkoxy groups, a nitro group, a carboxyl group, and a sulfonic acid group (SO.sub.3H), and Y.sub.1, Y.sub.1, Y.sub.2, and Y.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group.

3. The catalyst according to claim 2, wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a methyl group, X and X are the same as or different from each other and are each independently selected from hydrogen, a methyl group, halogen groups, a methoxy group, a nitro group, a carboxyl group, and a sulfonic acid group (SO.sub.3H), and Y.sub.1, Y.sub.1, Y.sub.2, and Y.sub.2 are the same as or different from each other and are each independently hydrogen or a methyl group.

4. The catalyst according to claim 2, wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are all hydrogen, X and X are the same and are selected from hydrogen, C.sub.1-C.sub.3 alkyl groups, halogen groups, C.sub.1-C.sub.3 alkoxy groups, a nitro group, a carboxyl group, and a sulfonic acid group (SO.sub.3H), and Y.sub.1, Y.sub.1, Y.sub.2, and Y.sub.2 are the same and are hydrogen or a C.sub.1-C.sub.3 alkyl group.

5. The catalyst according to claim 2, wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are all hydrogen, X and X are the same and are selected from hydrogen, a methyl group, halogen groups, a methoxy group, a nitro group, a carboxyl group, and a sulfonic acid group (SO.sub.3H), and Y.sub.1, Y.sub.1, Y.sub.2, and Y.sub.2 are the same and are hydrogen or a methyl group.

6. The catalyst according to claim 1, wherein the catalyst has the structure of Formula 2 wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group and Z and Z are all hydrogen or together form a benzene ring with adjacent carbon atoms.

7. The catalyst according to claim 6, wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a methyl group and Z and Z are all hydrogen or together form a benzene ring with adjacent carbon atoms.

8. The catalyst according to claim 6, wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same and are hydrogen or a C.sub.1-C.sub.3 alkyl group and Z and Z are all hydrogen or together form a benzene ring with adjacent carbon atoms.

9. The catalyst according to claim 6, wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same and are hydrogen or a methyl and Z and Z are all hydrogen or together form a benzene ring with adjacent carbon atoms.

10. The catalyst according to claim 1, wherein the catalyst has the structure of Formula 3 wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group and Z and Z are all hydrogen or together form a cyclohexyl ring with adjacent carbon atoms.

11. The catalyst according to claim 10, wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a methyl group and Z and Z are all hydrogen or together form a cyclohexyl ring with adjacent carbon atoms.

12. The catalyst according to claim 10, wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same and are hydrogen or a C.sub.1-C.sub.3 alkyl group and Z and Z are all hydrogen or together form a cyclohexyl ring with adjacent carbon atoms.

13. The catalyst according to claim 10, wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same and are hydrogen or a methyl and Z and Z are all hydrogen or together form a cyclohexyl ring with adjacent carbon atoms.

14. The catalyst according to claim 1, wherein the catalyst has one of the following structures: ##STR00038## ##STR00039##

15. The catalyst according to claim 1, wherein the catalyst has the structure of Formula 2-1: ##STR00040##

16. The catalyst according to claim 1, wherein the catalyst has one of the following structures: ##STR00041##

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

[0018] FIG. 1 is a .sup.1H-NMR spectrum of methyl bisulfate (CH.sub.3OSO.sub.3H) synthesized using the catalyst of Formula 3-2 in Example 2;

[0019] FIG. 2 shows the results of HPLC analysis for methanol synthesized using the catalyst of Formula 3-2 in Example 2; and

[0020] FIGS. 3 to 15 are .sup.1H-NMR spectra of catalysts prepared in Example 1.

DETAILED DESCRIPTION OF THE INVENTION

[0021] Several aspects and various embodiments of the present invention will now be described in more detail.

[0022] One aspect of the present invention is directed to a catalyst for synthesizing methanol or its precursor, represented by one of Formulae 1, 2, and 3:

##STR00001##

[0023] wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group, X and X are the same as or different from each other and are each independently selected from hydrogen, C.sub.1-C.sub.3 alkyl groups, halogen groups, C.sub.1-C.sub.3 alkoxy groups, a nitro group, a carboxyl group, and a sulfonic acid group (SO.sub.3H), and Y.sub.1, Y.sub.1, Y.sub.2, and Y.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group;

##STR00002##

[0024] wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are as defined in Formula 1 and Z and Z are all hydrogen or together form a benzene or cyclohexyl ring with adjacent carbon atoms; and

##STR00003##

[0025] wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are as defined in Formula 1 and Z and Z are as defined in Formula 2.

[0026] According to one embodiment, the catalyst has the structure of Formula 1 wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group, X and X are the same as or different from each other and are each independently selected from hydrogen, C.sub.1-C.sub.3 alkyl groups, halogen groups, C.sub.1-C.sub.3 alkoxy groups, a nitro group, a carboxyl group, and a sulfonic acid group (SO.sub.3H), and Y.sub.1, Y.sub.1, Y.sub.2, and Y.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group.

[0027] In a preferred embodiment, in Formula 1, R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a methyl group, X and X are the same as or different from each other and are each independently selected from hydrogen, a methyl group, halogen groups, a methoxy group, a nitro group, a carboxyl group, and a sulfonic acid group (SO.sub.3H), and Y.sub.1, Y.sub.1, Y.sub.2, and Y.sub.2 are the same as or different from each other and are each independently hydrogen or a methyl group.

[0028] In a more preferred embodiment, in Formula 1, R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are all hydrogen, X and X are the same and are selected from hydrogen, C.sub.1-C.sub.3 alkyl groups, halogen groups, C.sub.1-C.sub.3 alkoxy groups, a nitro group, a carboxyl group, and a sulfonic acid group (SO.sub.3H), and Y.sub.1, Y.sub.1, Y.sub.2, and Y.sub.2 are the same and are hydrogen or a C.sub.1-C.sub.3 alkyl group.

[0029] In a most preferred embodiment, in Formula 1, R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are all hydrogen, X and X are the same and are selected from hydrogen, a methyl group, halogen groups, a methoxy group, a nitro group, a carboxyl group, and a sulfonic acid group (SO.sub.3H), and Y.sub.1, Y.sub.1, Y.sub.2, and Y.sub.2 are the same and are hydrogen or a methyl group.

[0030] According to a further embodiment, the catalyst has the structure of Formula 2 wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group and Z and Z are all hydrogen or together form a benzene ring with adjacent carbon atoms.

[0031] In a preferred embodiment, in Formula 2, R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a methyl group and Z and Z are all hydrogen or together form a benzene ring with adjacent carbon atoms.

[0032] In a more preferred embodiment, in Formula 2, R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same and are hydrogen or a C.sub.1-C.sub.3 alkyl group and Z and Z are all hydrogen or together form a benzene ring with adjacent carbon atoms.

[0033] In a most preferred embodiment, in Formula 2, R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same and are hydrogen or a methyl and Z and Z are all hydrogen or together form a benzene ring with adjacent carbon atoms.

[0034] According to another embodiment, the catalyst has the structure of Formula 3 wherein R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a C.sub.1-C.sub.3 alkyl group and Z and Z are all hydrogen or together form a cyclohexyl ring with adjacent carbon atoms.

[0035] In a preferred embodiment, in Formula 3, R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same as or different from each other and are each independently hydrogen or a methyl group and Z and Z are all hydrogen or together form a cyclohexyl ring with adjacent carbon atoms.

[0036] In a more preferred embodiment, in Formula 3, R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same and are hydrogen or a C.sub.1-C.sub.3 alkyl group and Z and Z are all hydrogen or together form a cyclohexyl ring with adjacent carbon atoms.

[0037] In a most preferred embodiment, in Formula 3, R.sub.1, R.sub.1, R.sub.2, and R.sub.2 are the same and are hydrogen or a methyl and Z and Z are all hydrogen or together form a cyclohexyl ring with adjacent carbon atoms.

[0038] According to another embodiment, the catalyst has one of the following structures:

##STR00004## ##STR00005##

[0039] According to another embodiment, the catalyst has the structure of Formula 2-1:

##STR00006##

[0040] According to another embodiment, the catalyst has one of the following structures:

##STR00007##

[0041] A further aspect of the present invention is directed to a method for methane oxidation including bringing the catalyst for synthesizing methanol or its precursor according to any one of the embodiments into contact with methane in the presence of an acid.

[0042] Another aspect of the present invention is directed to a method for methanol production including (a) bringing the catalyst for synthesizing methanol or its precursor according to any one of the embodiments into contact with methane in the presence of an acid to obtain a methanol precursor and (b) bringing the methanol precursor into contact with water to obtain methanol.

[0043] Due to its structure, the catalyst of the present invention is highly stable so as not to be easily lost, destroyed, and decomposed in a strongly acidic atmosphere or by oxidation and exhibits good catalytic activity to induce oxidation of the CH bond of methane. The high stability and good catalytic activity enable the use of the Pt coordination compound represented by Formula 1 as a catalyst in various reactions, such as the oxidation reactions. Specifically, the Pt coordination compound can be used as a catalyst for methane oxidation or a catalyst for the synthesis of methanol from methane.

[0044] Particularly, it was confirmed that the catalyst having the structure of Formula 3 does not need to be regenerated for reuse and is stable enough to maintain its activity even after repeated use.

[0045] Another aspect of the present invention is directed to a method for preparing the catalyst including reacting a substituted or unsubstituted aniline with a Pt salt, as depicted in the following reaction scheme:

##STR00008##

[0046] Another aspect of the present invention is directed to a method for methane oxidation including (a) bringing the catalyst for synthesizing methanol or its precursor according to any one of the embodiments into contact with methane in the presence of an acid.

[0047] As explained earlier, the catalyst for synthesizing methanol or its precursor according to the present invention, which is represented by one of Formulae 1 to 3, can be used to form a methyl ester through an esterification reaction for methane oxidation. The methyl ester can be used to form a functional derivative by subsequent reaction with a nucleophile.

[0048] Specifically, the methyl ether may react with water as a nucleophile to synthesize methanol as a functional derivative. The methyl ester may also react with a hydrogen halide, such as HCl, HBr or HI, as a nucleophile to synthesize a methyl halide as a functional derivative. The methyl ester may also react with NH.sub.3 as a nucleophile to synthesize methylamine. The methyl ester may also react with HCN, H.sub.2S or acetonitrile as a nucleophile to synthesize their methyl derivatives.

[0049] The catalyst represented by one of Formulae 1 to 3 for synthesizing methanol or its precursor according to the present invention can be used to oxidize methane to a methyl ester (e.g., methyl bisulfate), which reacts with water to form methanol. This series of reactions will be described in more detail below.

[0050] Any compound having an unshared pair of electrons may be used without particular limitation as the nucleophile. Examples of preferred nucleophiles include water, inorganic acids, organic acids, amines, and phenols.

[0051] The acids may be acid solutions commonly used in the art but are not particularly limited thereto. Preferably, the acids are sulfuric acid and fuming sulfuric acid.

[0052] Fuming sulfuric acid refers to a solution of sulfur trioxide (SO.sub.3) in sulfuric acid. The content of SO.sub.3 may vary in a broad range but is typically from 1 to 60% by weight, more preferably 20% by weight. For example, fuming sulfuric acid containing 20% by weight of SO.sub.3 means the presence of 20 g of SO.sub.3 in 100 g of fuming sulfuric acid.

[0053] The production of the alkyl ester may vary depending on the mixing weight ratio between the catalyst represented by one of Formulae 1 to 3 for synthesizing methanol or its precursor and the acid. Accordingly, the mixing weight ratio between the catalyst for synthesizing methanol or its precursor and the acid is considered a very important factor in determining the yield of the alkyl ester.

[0054] Preferably, the content of the catalyst represented by one of Formulae 1 to 3 for synthesizing methanol or its precursor is from 0.00001 to 1 mmol or the mixing weight ratio between the catalyst for synthesizing methanol or its precursor and the acid is from 0.000001:1 to 0.1:1. When the catalyst for synthesizing methanol or its precursor meets the preferred requirement, it has a TON of at least 1,000 and a TOF (/h) of at least 300, which are at least 10 times higher than those of existing platinum coordination compounds.

[0055] Step (a) is preferably carried out at 150 to 300 C. Out of this temperature range, the catalyst is less catalytically active for the oxidation of at least one CH bond of the C.sub.1-C.sub.8 alkane, and as a result, the corresponding alkyl ester is produced in an amount less than about half (1 g) the amount produced when step (a) is carried out at 150 to 300 C. and the TON and TOF (/h) of the catalyst are significantly reduced to 1000 and 700, respectively. Meanwhile, if step (a) is carried out at a temperature exceeding 300 C., there is a risk that the reaction may proceed too rapidly and the catalyst can decompose.

[0056] In step (a), the C.sub.1-C.sub.8 alkane is preferably supplied at a pressure of 10 to 50 bar. If the pressure of the C.sub.1-C.sub.8 alkane supplied to a reactor is less than 10 bar, the catalyst is less catalytically active for the oxidation of at least one CH bond of the C.sub.1-C.sub.8 alkane, and as a result, the corresponding alkyl ester is produced in an amount less than about half (1 g) the amount produced when the C.sub.1-C.sub.8 alkane is supplied at a pressure of 10 to 50 bar and the TON and TOF (/h) of the catalyst are significantly reduced although the temperature is within the preferred range defined above. Particularly, if the pressure of the C.sub.1-C.sub.8 alkane supplied to a reactor is less than 10 bar, the TOF (/h) of the catalyst is reduced to 348, which corresponds to less than about half that when the C.sub.1-C.sub.8 alkane is supplied at a pressure of 10 to 50 bar.

[0057] The most preferred reaction conditions for the production of methanol using the catalyst for synthesizing methanol or its precursor according to the present invention are a temperature of 200 to 250 C. and a pressure of 25 to 35 bar. The use of the catalyst according to the present invention under the reaction conditions defined above ensures high-yield production of methyl bisulfate with a turnover number (TON) of 3,000 to 15,000 and a turnover frequency (TOF) of 1,000 to 6,000.

[0058] Yet another aspect of the present invention is directed to a method for methanol production including (a) bringing the catalyst for synthesizing methanol or its precursor according to any one of the embodiments into contact with methane in the presence of an acid to obtain a methanol precursor and (b) bringing the methanol precursor into contact with water to obtain methanol.

[0059] According to the method of the present invention, methanol is specifically synthesized by the following reaction scheme 1:

##STR00009##

[0060] wherein cat. represents the catalyst represented by one of Formulae 1 to 3 for synthesizing methanol or its precursor.

[0061] Step (b) may be carried out in the range of room temperature to 150 C. Outside this range, further energy is consumed without a significant increase in yield.

[0062] The catalyst of the present invention can be used to synthesize a methanol precursor or methanol from methane gas with high efficiency at low temperature and exhibits better results in terms of TON and TOF values than conventional catalysts. The catalyst of the present invention is highly stable so as not to be damaged, destroyed, and decomposed during the reaction, ensuring its long-term use without loss of platinum. In addition, the catalyst of the present invention exhibits good catalytic activity even without using noble metal platinum. Due to these advantages, the use of a small amount of the catalyst leads to the production of a large amount of methanol.

[0063] The catalyst represented by one of Formulae 1 to 3 for synthesizing methanol or its precursor according to the present invention, particularly, the catalyst represented by one of Formulae 4 to 7 for synthesizing methanol or its precursor, is advantageous in terms of methyl bisulfate production, catalytic activities, such as TON and TOF values, and economic efficiency over the prior art catalyst (bpym)PtCl.sub.2, which is known to induce the synthesis of methanol at a reaction temperature of 180 to 220 C. similar to that defined in the present invention.

[0064] In addition, the catalyst for synthesizing methanol or its precursor according to the present invention is prepared in an easy and simple manner through a greatly reduced number of processing steps. Therefore, the catalyst of the present invention is advantageous over conventional coordination compounds from an economic and industrial point of view.

[0065] The present invention will be explained in more detail with reference to the following examples. However, these examples are not to be construed as limiting or restricting the scope and disclosure of the invention. It is to be understood that based on the teachings of the present invention including the following examples, those skilled in the art can readily practice other embodiments of the present invention whose experimental results are not explicitly presented. It will also be understood that such modifications and variations are intended to come within the scope of the appended claims.

EXAMPLES

[0066] The experimental results of the following examples, including comparative examples, are merely representative and the effects of the exemplary embodiments of the present invention that are not explicitly presented hereinafter can be specifically found in the corresponding sections.

Example 1: Synthesis of Catalyst Compounds

(1) Synthesis of Compound 1-1

Bis(benzenamine)dichloroplatinum

[0067] ##STR00010##

[0068] K.sub.2PtCl.sub.4 (415 mg, 1.0 mmol) was added to an aqueous solution of aniline (502 mg, 5.4 mmol). After sufficient stirring at room temperature for 18 h, the precipitate was collected by filtration and washed with water and diethyl ether. The resulting solid was dissolved in dimethylformamide (DMF). The solution was stirred at 80 C. for 3 h. The reaction solution was concentrated under reduced pressure and precipitated with diethyl ether. The precipitate was collected by filtration to give the desired product (105 mg, 4.0 mmol) in a yield of 23%. .sup.1H NMR (400 MHz, DMSO-d.sub.6) 7.24-7.20 (m, 8H), 7.12-7.08 (m, 2H), 6.96 (s, 4H) (see FIG. 3)

(2) Synthesis of Compound 1-2

Dichlorobis(4-methylbenzenamine)platinum

[0069] ##STR00011##

[0070] The desired product was obtained in a yield of 37% in the same manner as in the synthesis of Compound 1-1, except that 4-methylaniline was used instead of aniline. .sup.1H NMR (400 MHz, DMSO-d.sub.6) 7.12 (d, J=8.4 Hz, 2H), 8.03 (d, J=8.0 Hz, 2H), 6.70 (s, 4H), 2.22 (s, 6H) (see FIG. 4)

(3) Synthesis of Compound 1-3

Dichlorobis(4-chlorobenzenamine)platinum

[0071] ##STR00012##

[0072] The desired product was obtained in a yield of 63% in the same manner as in the synthesis of Compound 1-1, except that 4-chloroaniline was used instead of aniline. .sup.1H NMR (400 MHz, DMSO-d.sub.6) 7.40 (s, 4H), 7.29 (dd, J=10.4, 9.2 Hz, 8H) (see FIG. 5)

(4) Synthesis of Compound 1-4

Dichlorobis(4-methoxybenzenamine)platinum

[0073] ##STR00013##

[0074] The desired product was obtained in a yield of 43% in the same manner as in the synthesis of Compound 1-1, except that 4-methoxyaniline was used instead of aniline. .sup.1H NMR (400 MHz, DMSO-d.sub.6) 7.17 (dd, J=2.0, 6.8 Hz, 4H), 7.10 (s, 4H), 6.75 (dd, J=2.0, 6.8 Hz, 4H), 3.69 (s, 6H) (see FIG. 6)

(5) Synthesis of Compound 1-5

Dichlorobis(4-nitrobenzenamine)platinum

[0075] ##STR00014##

[0076] The desired product was obtained in a yield of 43% in the same manner as in the synthesis of Compound 1-1, except that 4-nitroaniline was used instead of aniline. .sup.1H NMR (400 MHz, DMSO-d.sub.6) 12.80 (s, 2H), 7.82 (dd, J=6.8, 1.6 Hz, 4H), 7.32 (s, 4H), 7.27 (d, J=8.8, 4H) (see FIG. 7)

(6) Synthesis of Compound 1-6

Dichlorobis(4-hydroxycarbonylbenzenamine)platinum

[0077] ##STR00015##

[0078] The desired product was obtained in a yield of 43% in the same manner as in the synthesis of Compound 1-1, except that 4-aminobenzoic acid was used instead of aniline. .sup.1H NMR (400 MHz, DMSO-d.sub.6) 12.80 (s, 2H), 7.82 (dd, J=6.8, 1.6 Hz, 4H), 7.32 (s, 4H), 7.27 (d, J=8.8, 4H) (see FIG. 8)

(7) Synthesis of Compound 1-7

Dichlorobis(4-hydroxysulfonylbenzenamine)platinum

[0079] ##STR00016##

[0080] The desired product was obtained in a yield of 59% in the same manner as in the synthesis of Compound 1-1, except that 4-aminobenzenesulfonic acid was used instead of aniline. .sup.1H NMR (400 MHz, DMSO-d.sub.6) 7.45 (dd, J=2.8, 6.6 Hz, 4H), 7.00 (s, 4H) (see FIG. 9)

(8) Synthesis of Compound 1-8

Dichlorobis(2,4,6-trimethylbenzenamine)platinum

[0081] ##STR00017##

[0082] The desired product was obtained in a yield of 30% in the same manner as in the synthesis of Compound 1-1, except that 2,4,6-trimethylaniline was used instead of aniline. .sup.1H NMR (400 MHz, DMSO-d.sub.6) 6.72 (s, 4H), 6.13 (s, 4H), 2.44 (s, 12H), 2.18 (s, 6H) (see FIG. 10)

(9) Synthesis of Compound 2-1

Dichloro-(1,2-benzenediamine)platinum

[0083] ##STR00018##

[0084] The desired product was obtained in a yield of 73% in the same manner as in the synthesis of Compound 3-3, except that 1,2-diaminobenzene (1 eq.) was added to an aqueous solution of K.sub.2PtCl.sub.4 (1 eq.). .sup.1H NMR (400 MHz, DMSO-d.sub.6) 7.62 (s, 4H), 7.16 (s, 4H) (see FIG. 11)

(10) Synthesis of Compound 3-1

Dichloro(ethylenediamine)platinum

[0085] ##STR00019##

[0086] The desired product was obtained in a yield of 60% in the same manner as in the synthesis of Compound 3-3, except that ethylene diamine (1 eq.) was added to an aqueous solution of K.sub.2PtCl.sub.4 (1 eq.). .sup.1H NMR (400 MHz, MeOD) 2.79 (s, 6H), 2.74 (s, 4H) (see FIG. 12)

(11) Synthesis of Compound 3-2

Dichloro-(N,N,N,N-tetramethylethylenediamine)platinum

[0087] ##STR00020##

[0088] The desired product was obtained in a yield of 87% in the same manner as in the synthesis of Compound 3-3, except that N,N,NN-tetramethylethylenediamine (1 eq.) was added to an aqueous solution of K.sub.2PtCl.sub.4 (1 eq.). .sup.1H NMR (400 MHz, D.sub.2SO.sub.4) 2.81 (s, 12H), 2.75 (s, 4H) (see FIG. 13)

(12) Synthesis of Compound 3-3

Dichloro-cis-1,2-cyclohexanediamine platinum

[0089] ##STR00021##

[0090] Cis-1,2-cyclohexanediamine (1 eq.) was added to an aqueous solution of K.sub.2PtCl.sub.4 (1 eq.). The mixture was stirred at room temperature for 30 min. The resulting precipitate was collected by filtration and washed with water and diethyl ether, giving the desired product in a yield of 83%. .sup.1H NMR (400 MHz, DMSO-d.sub.6) 5.52 (d, J=6.8 Hz, 2H), 4.94 (t, J=4.6 Hz, 2H), 2.59 (m, 2H) 1.64 (m, 6H) 1.14 (d, J=4.8 Hz, 2H) (see FIG. 14)

(13) Synthesis of Compound 3-4

Dichloro-(1R,2R)-1,2-cyclohexanediamine platinum

[0091] ##STR00022##

[0092] The desired product was obtained in a yield of 85% in the same manner as in the synthesis of Compound 3-3, except that trans-1,2-cyclohexanediamine (1 eq.) was added to an aqueous solution of K.sub.2PtCl.sub.4 (1 eq.). .sup.1H NMR (400 MHz, DMSO-d.sub.6) 5.57 (d, J=8.4 Hz, 2H), 5.04 (s, 2H), 2.10 (d, J=4.8 Hz, 2H), 1.85 (d, J=12.4 Hz, 2H) 1.44 (d, J=8.4 Hz, 2H) 1.22 (d, J=9.6 Hz, 2H) 0.97 (t, J=9.6, 2H) (see FIG. 15)

Example 2: Synthesis of Methanol Precursor and Methanol

[0093] (1) Synthesis of Methyl Bisulfate

[0094] 1 mg (2.610.sup.3 mmol) of the catalyst (dichloro-(N,N,N,N-tetramethylethylenediamine)platinum) represented by Formula 3-2 was mixed with 30 g of fuming sulfuric acid containing 20 wt % of SO.sub.3 in a 100 ml Inconel autoclave with a glass liner. Methane gas was filled in the reactor to a pressure of 20 bar. The methane-filled reactor was heated to 180 C. and the reaction was allowed to proceed for 3 h. The pressure of the methane at 180 C. was 35 bar at the initial stage of the reaction and decreased to 30 bar after the reaction for 3 h. After completion of the reaction, the structure of the product was identified by .sup.1H-NMR spectroscopy using D.sub.2SO.sub.4 containing methanesulfonic acid (CH.sub.3SO.sub.3H) as the internal standard (see FIG. 1).

[0095] FIG. 1 confirms the production of 1.89 g (16.9 mmol) of methyl bisulfate. The turnover number (TON) and turnover frequency (TOF) of the catalyst for the production of methyl bisulfate were calculated to be 6,484 and 2,161/h, respectively.

[0096] (2) Methanol Synthesis

[0097] 200 g of distilled water was added to the methyl bisulfate obtained above and ethanol as the internal standard was added thereto. The reaction was allowed to proceed at 90 C. for 4 h. After completion of the reaction, the reaction product was analyzed by HPLC. The results are shown in FIG. 2, confirming the production of 0.51 g of methanol.

[0098] (3) Comparison of the Amounts of Methyl Bisulfate Produced when the Catalyst was Used in Different Amounts

[0099] An investigation was made as to the effect of the consumption of the catalyst represented by Formula 3-2 on the synthesis of methyl bisulfate as a methanol precursor. To this end, methyl bisulfate as a methanol precursor was produced in the same manner as in Example 2, except that the catalyst was used in the amounts shown in Table 1. After completion of the reaction, the methyl bisulfate was quantitatively analyzed by .sup.1H-NMR spectroscopy. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Amount of Compound Amount of CH.sub.3OSO.sub.3H TOF Catalyst structure No. catalyst used produced TON (/h) [00023] 3-2 10 mg, 2.6 10.sup.2 mmol 3.28 g, 29.3 mmol 1,126 376 Ditto Ditto 5 mg, 1.3 10.sup.2 mmol 2.88 g, 25.7 mmol 1,978 659 Ditto Ditto 2 mg, 5.2 10.sup.3 mmol 2.32 g, 20.7 mmol 3,980 1,327 Ditto Ditto 0.5 mg, 1.3 10.sup.3 mmol 1.38 g, 12.3 mmol 9,461 3,153 Ditto Ditto 0.25 mg, 6.5 10.sup.4 mmol 1.0 g, 8.9 mmol 13,692 4,564

[0100] As can be seen from the results in Table 1, the TON and TOF of the catalyst of Formula 3-2 for the production of methyl bisulfate increased with decreasing amount of the catalyst. That is, the mixing weight ratio of the catalyst of Formula 3-2 to fuming sulfuric acid has an important influence on the production of methyl bisulfate. It was also confirmed that the production of methyl bisulfate is proportional to the consumption of the catalyst.

[0101] These results reveal the effective content range of the catalyst. When the concentration of the catalyst was 0.0001-1 mM, the TON (2,000) and TOF (700/h) of the catalyst were significantly high. The TON and TOF values are at least 5 times higher than those of the conventional catalyst (bpym)PtCl.sub.2. Specifically, when the catalyst of Formula 3-2 was used in the same amount (0.0005-0.0007 mmol) as the conventional catalyst, the TON and TOF (/h) of the catalyst of Formula 3-2 were improved by at least 40 times compared to those of the conventional catalyst (bpym)PtCl.sub.2.

[0102] The mixing weight ratio of the catalyst of Formula 5 to fuming sulfuric acid may be from 0.000001:1 to 0.1:1. More preferably, the mixing weight ratio of the catalyst of Formula 5 to fuming sulfuric acid is in the range of 0.000008:1 to 0.0001:1. Within this range, a large amount of methyl bisulfate (1 g (8 mmol)) can be formed in the course of the synthesis of methanol and high TON (2000) and TOF (700/h) values can be achieved. That is, the catalyst of the present invention enables the production of a sufficiently large amount of methyl bisulfate even when used in a small amount. The above results demonstrate that when the catalyst of the present invention (particularly, the catalyst of Formula 5) is used in an amount of 510.sup.4 to 110.sup.3 mmol, the largest amount of methyl bisulfate or methanol can be produced from methane supplied. In conclusion, even a very small amount of the catalyst of the present invention is sufficient to convert a large amount of methane to methanol.

[0103] In contrast, the Periana catalyst used in the following comparative example 1 was confirmed to show poor catalytic activity compared to the catalyst for synthesizing methanol or its precursor according to the present invention when used in similar amounts.

[0104] (4) Comparison of the Amounts of Methyl Bisulfate Produced Depending on the Catalyst Structures

[0105] The reactivity of the catalyst depending on its structure was investigated. To this end, methyl bisulfate was produced in the same manner as described above, except that the structure of the catalyst was changed as shown in Table 2. After completion of each reaction, the product was analyzed by .sup.1H-NMR spectroscopy. The results are shown in Table 2. The amount of each catalyst used was 1 mg.

TABLE-US-00002 TABLE 2 Amount of Amount of Compound catalyst used CH.sub.3OSO.sub.3H TOF Catalyst structure No (mmol) produced TON (/h) [00024] 1-1 2.21 10.sup.3 1.46 g 13.05 mmol 6526 2175 [00025] 1-2 2.08 10.sup.3 1.28 g 11.46 mmol 5714 1904 [00026] 1-3 1.92 10.sup.3 1.40 g 12.46 mmol 6578 2192 [00027] 1-4 1.95 10.sup.3 1.33 g 11.91 mmol 6250 2083 [00028] 1-5 1.85 10.sup.3 1.34 g 11.92 mmol 6440 2146 [00029] 1-6 1.86 10.sup.3 1.35 g 12.09 mmol 6501 2167 [00030] 1-7 1.64 10.sup.3 1.15 g 10.27 mmol 6272 2090 [00031] 3-1 3.07 10.sup.3 2.13 g 19.04 mmol 6210 2070 [00032] 3-3 2.60 10.sup.3 0.45 g 4.02 mmol 1546 515 [00033] 3-4 2.60 10.sup.3 0.49 g 4.37 mmol 1680 560

[0106] (5) Comparison of the Amounts of Methyl Bisulfate Produced Depending on Reaction Conditions

[0107] An investigation was made as to the effect of reaction conditions for methanol synthesis on the synthesis of methyl bisulfate as a methanol precursor. To this end, methyl bisulfate as a methanol precursor was produced in the same manner as described above, except that the reaction conditions for methanol synthesis were changed as shown in Table 3. After completion of the reaction, the product was analyzed by .sup.1H-NMR spectroscopy. The results are shown in Table 3. The amount of the catalyst used was 1 mg (0.0026 mmol).

TABLE-US-00003 TABLE 3 Conditions for CH.sub.3OSO.sub.3H synthesis Amount of Compound Temperature Methane CH.sub.3OSO.sub.3H TOF Catalyst structure No. ( C.) pressure (bar) produced TON (/h) [00034] 3-2 120 35 0.088 g, 0.786 mmol 303 101 Ditto Ditto 150 35 0.33 g, 2.95 mmol 1,135 378 Ditto Ditto 180 25 1.29 g, 11.5 mmol 4,423 1,474 Ditto Ditto 180 10 0.70 g, 6.25 mmol 2,403 801 Ditto Ditto 220 35 3.16 g, 28.3 mmol 10,884 3,628

[0108] As shown in Table 3, when the reaction temperature for methanol synthesis was lower than 150 C., the amount of methyl bisulfate produced was considerably reduced to less than about half (0.5 g) the amount produced when the reaction temperature was not lower than 150 C. and the TON and TOF (/h) values were considerably reduced to 200 and 90, respectively. When the pressure of methane in the reactor was lower than 10 bar and the other reaction conditions, including temperature, were the same, the amount of methyl bisulfate produced was considerably reduced to less than about half (1 g) the amount produced when the pressure of methane was not lower than 10 bar and the TON and TOF (/h) values were considerably reduced to 1,000 and 300, respectively. From the above results, it can be seen that preferred reaction conditions for the production of methanol using the Pt coordination compound are a temperature of 150 to 300 C. and a pressure of 10 to 50 bar. If the reaction temperature is lower than 150 C. or higher than 300 C., the amount of methyl bisulfate produced was considerably reduced to less than about half (1 g) the amount produced when the reaction temperature was 150-300 C. and the TON and TOF (/h) values were considerably reduced to 1,000 and 700, respectively.

[0109] When the pressure of methane in the reactor was higher than 50 bar or lower than 10 bar and the other reaction conditions, including temperature, were the same, the amount of methyl bisulfate produced was considerably reduced to less than about half (1 g) the amount produced when the pressure of methane was 10-50 bar and the TON and TOF (/h) values were also reduced considerably. Particularly, the TOF (/h) was reduced to less than about half (348).

[0110] These results can lead to the conclusion that the most preferred reaction conditions for the production of methanol using the catalyst of the present invention are a temperature of 200 to 250 C. and a pressure of 25 to 35 bar. When the catalyst of the present invention is used under the conditions defined above, methyl bisulfate can be obtained in high yield with a turnover number (TON) of 3,000-15,000 and a turnover frequency (TOF) of 1,000-6,000.

Comparative Example 1

[0111] The activity of the Periana catalyst ((bpym)PtCl.sub.2) as a conventional platinum catalyst for methanol synthesis was compared with that of the platinum catalyst of the present invention. To this end, methanol was produced in the same manner as in Example 2, except that the amount of the Periana catalyst ((bpym)PtCl.sub.2) was adjusted as shown in Table 4. The Periana catalyst was prepared in accordance with the method described in Solid Catalysts for the Selective Low-Temperature Oxidation of Methane to Methanol, Author: Regina Palkovits Dr., Markus Antonietti Prof. Dr., Pierre Kuhn Dr., Arne Thomas Dr., Ferdi Schrth Prof. Dr., Volume 48, Issue 37 Sep. 1, 2009 Pages 6909-6912. After completion of the reaction, the methyl bisulfate was analyzed by .sup.1H-NMR spectroscopy. The results are shown in Table 4.

TABLE-US-00004 TABLE 4 Conditions for methanol synthesis Amount of Temper- Methane methane Amount of ature pressure sulfate TOF catalyst used ( C.) (bar) produced TON (/h) 20 mg, 4.7 150 35 0.58 g, 110 36 10.sup.2 mmol 5.17 mmol 5 mg, 1.1 180 35 0.49 g, 366 122 10.sup.2 mmol 4.3 mmol 1 mg, 2.35 180 35 10.sup.3 mmol

[0112] As can be seen from the results in Table 4, the production of methyl bisulfate was not affected by the content of the conventional catalyst (bpym)PtCl.sub.2 and the conditions for methanol synthesis. In addition, when the conventional catalyst was used, a significantly small amount (0.5 g, 0.3 mmol) of methyl bisulfate was produced and low TON (110 and 432) and TOF (36 and 144/h) were obtained. The TON and TOF values were at least 10-fold lower than those obtained when the catalyst of the present invention was used.