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(12) United States Patent (10) Patent No.: US 7,119,226 B2 Sen Et Al

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(12) United States Patent (10) Patent No.: US 7,119,226 B2 Sen Et Al US007 119226B2 (12) United States Patent (10) Patent No.: US 7,119,226 B2 Sen et al. (45) Date of Patent: Oct. 10, 2006 (54) PROCESS FOR THE CONVERSION OF B. Arndtsen, et al., Selective Intermolecular Carbon-Hydrogen METHANE Bond Activation by Synthetic Metal Complexes in Homogeneous Solution, Acc. Chem. Res., 1995, 154-162. (75) Inventors: Ayusman Sen, State College, PA (US); J. Labinger, Methane Activation in Homogeneous Systems, Fuel Minren Lin, State College, PA (US) Processing Technology, 1995, Elsevier, 325-338. T. Hall, et al., Catalytic Synthesis of Methanol and Formaldehyde (73) Assignee: The Penn State Research Foundation, by Partial Oxidation of Methane, Fuel Processing Technology, University Park, PA (US) 1995, Elsevier, 151-178. J.L.G. Fierro, Catalysis in C1 Chemistry: Future and Prospect, Catalysis Letters 22, 1993, JC Baltzer AG, Science Publishers, (*) Notice: Subject to any disclaimer, the term of this 67-91. patent is extended or adjusted under 35 S. Mukhopadhyay, et al., Catalyzed Sulfonation of Methane to U.S.C. 154(b) by 0 days. Methanesulfonic Acid, Journal of Molecular Catalysis A Chemical 211, 2004, Elvisevier, 59-65. (21) Appl. No.: 11/105.245 N. Basickes, et al., Radical-Initiated Functionalization of Methane and Ethane in Fuming Sulfuric Acid, J. Am. Chem. Soc., 1996, (22) Filed: Apr. 13, 2005 13111-13112. S. Mukhopadhyay, et al., Synthesis of Methanesulfonyl Chloride (65) Prior Publication Data (MSC) from Methane and Sulfuryl Choloride, The Royal Society of US 2006/O1 OO458 A1 May 11, 2006 Chemistry, 2004, 472-473. S. Mukhopadhyay, et al., A High-Yield Approach to the Sulfonation Related U.S. Application Data of Methane to Methanesulfonic Acid Initiated by H2O2 and a Metal Chloride, Angew. Chem. Int. Ed. 2003, 2990. (60) Provisional application No. 60/563,717, filed on Apr. S. Mukhopadhyay, et al., Direct Liquid-Phase Sulfonation of Meth 20, 2004. ane to Methanesulfonic Acid by SO3 in the Presence of a Metal Peroxide, Angew. Chem. Int. Ed., 2003, 1019-1021. (51) Int. Cl. S. Mukhopadhyay, et al., Direct Sulfonation of Methane to C07C 309/00 (2006.01) Methanesulfonic Acid with SO2 Using Ca Salts as Promoters, J. (52) U.S. Cl. ...................................... 562/123 Am. Chem. Soc., 2003, 4406-4407. M. Lin, et al., Oxidation and Oxidative Carbonylation of Methane (58) Field of Classification Search ..................... None and Ethane by Hexaoxo-u-peroxiodisulfate (2-) Ion in Aqueous See application file for complete search history. Medium, J. Chem. Soc., 1992, 892-893. (56) References Cited C. Walling, Fre Radical Reactions, Energetics of Organic Free Radicals, Blackie Academic & Professional, 1-21. U.S. PATENT DOCUMENTS G. Russell, Reactivity, Selectivity, and Polar Effects in Hydrogen tom Transfer Reactions, Free Radicals, John Wiley & Sons, 275 2.492.983 A 1/1950 Grosse et al. 331. 3,927, 189 A 12/1975 Jayawant Primary Examiner Sikarl A. Witherspoon OTHER PUBLICATIONS (74) Attorney, Agent, or Firm McQuaide, Blasko, Fleming M.G.Axelrod, et al., Natural Gas: Fuel or Feedstock, Natural Gas & Faulkner, Inc Conversion II, 1994, 93-101, Elvevier. Natural Gas Conversion VI, Table of Contents, ix-xiii, 2001, (57) ABSTRACT Elsevier. A. Sen, Catalytic Functionalization of Carbon-Hydrogen and Car bon-Carbon Bonds in Protic Media, Acc. Chem. Res. 1998, 550 A process for the facile two-step synthesis of methanol from 557. methane is disclosed. In accordance with the invention, an S. Stahl, et al., Homogeneous Oxidation of Alkanes by Electrophilic appropriate combination of initiator and reaction medium is Late Transition Metals, Angew, Chem. Int. Ed. 1998, 218 1-2192. employed to achieve methane conversion in very high R. Crabtree, Aspects of Methane Chemistry, Chem. Rev., 1995, 987-1007. selectivity and yield under near-ambient temperature. A. Shilov, et al., Activation of C-H Bonds by Metal Complexes, Chem. Rev., 1997, 2879-2932. 4 Claims, 3 Drawing Sheets U.S. Patent Oct. 10, 2006 Sheet 1 of 3 US 7,119,226 B2 2 Plot of Ln MSA vs CH4 O 200 400 600 800 1000 1200 1400 Pressure of CH4 (psi) Fig.1 U.S. Patent Oct. 10, 2006 Sheet 2 of 3 US 7,119,226 B2 1.4 Plot of LNMSA vs LN H2S208 -1.6 -1.4 -1.2 - -0.8 -0.6 -0.4 LNH2S208 (M) Fig.2 U.S. Patent Oct. 10, 2006 Sheet 3 of 3 US 7,119,226 B2 -4.1 Arrhenius Plot -4.15 = -2.192x + 2.5445 -4.2 R = 0.9642 -4.25 -4.3 -4.35 -4.4 -4.45 -4.5 3.04 3.06 3.08 3.1 3.12 3.14 3.16 3.18 3.2 1000X1/T (K-1) Fig.3 US 7,119,226 B2 1. 2 PROCESS FOR THE CONVERSION OF tance. Basickes, et al. have described a process for convert METHANE ing methane to methanesulfonic acid (MSA) by reaction with sulfur trioxide using a radical initiator. The initiator RELATED APPLICATIONS used in the process was KSOs. This work was followed by Mukhopadhyay, et al., who used the same initiator, as well This application claims priority to Provisional Patent as a variant: HSOs. The present inventors have examined Application No. 60/563,717 filed Apr. 20, 2004. in detail the HSOs-initiated reaction between methane and sulfur trioxide to form methanesulfonic acid (MSA). Theo GOVERNMENT SPONSORSHIP retical modeling indicates that HSOs should initiate the 10 reaction under mild conditions. A significant discovery of This invention was made with support from the DOE the experimental protocol is the combination of high con (contract to GTL Technologies, Inc.) under Grant No. version and selectivity that exceeds what is currently DE-FG02-03ER86160. Accordingly, the Government has reported in the literature. Specifically: certain rights in the invention. (a) Methane conversion exceeding 35%; 15 (b) Sulfur trioxide conversion exceeding 90% when used as BACKGROUND OF THE INVENTION the limiting reagent; (c) Selectivity to methanesulfonic acid exceeding 90%; and Methane is by far the least reactive and the most abundant (d) One-pass total yield of methanesulfonic acid exceeding member of the hydrocarbon family with known reserves 35%. similar to that of petroleum. Thus, the selective oxidative These reaction features, including development of the functionalization of methane to useful chemical products in process and the high conversion and selectivity that derives high conversion and selectivity is of considerable practical from it, are described herein. importance. Most of the work in this area has involved homogeneous and heterogeneous catalysis by metal species. 1. Synthesis of the Initiator, Peroxydisulfuric Acid (HSOs) While there have been some notable successes, none of the 25 The initiator, HSOs, may be prepared by passing gas systems have demonstrated the optimal combination of eous sulfur trioxide (SO) diluted with nitrogen gas through selectivity and yield that allows commercialization. Using 70% aqueous hydrogen peroxide (HO) at -20°C. until the potassium persulfate as an initiator, the present inventors molar ratio of SOs to H2O, reaches 2:1. A product analysis, demonstrate the Sulfonation of methane in fuming Sulfuric as described in U.S. Pat. No. 3,927,189, indicates the acid. following: HSOs, 35–55%; HSOs, 8–20%; H.O., 30 0.1-0.6%; HSO 18–30%; SO 5–10%. This solution was BRIEF DESCRIPTION OF THE DRAWINGS found to be stable at ambient temperature and under nitrogen for several weeks in the presence of a small amount of FIG. 1 is a plot of the L, of the yield for methanesulfonic methanesulfonic acid. acid versus the pressure of methane in pounds per square 35 2. Reaction of Methane and Sulfur Trioxide to Methane inch (used to determine the reaction order in methane) in sulfonic Acid (MSA) accordance with the present invention. The reaction was carried out in a glass vessel contained in FIG. 2 is a plot of the L, of the yield for peroxydisulfuric a 125 ml autoclave. A solution of HSOs was added to a acid versus the pressure of methane in pounds per square mixture consisting of Sulfur trioxide dissolved in methane inch (used to determine the reaction order in H2SOs) in 40 Sulfonic acid. An additional quantity of liquid SO was then accordance with the present invention. added to the autoclave. The autoclave was pressurized with FIG. 3 is a plot of the L of the rate constant for 800–1400 psi of CH, and heated at 48–52° C. until the methanesulfonic acid production versus 1000x1/T in Kelvin pressure stopped decreasing. The liquid reaction product (used to determine the activation energy parameters for the was analyzed by H NMR spectroscopy and quantified by reaction) in accordance with the present invention. 45 integration versus an internal standard (DMSO in a capil lary). The gas mixture in the headspace was analyzed by G.C. DETAILED DESCRIPTION OF THE Typical results are summarized in Table 1. Note that the INVENTION amount of MSA formed is many times the amount of initiator used, establishing that the radical chain length is The Subject invention relates to a process for the manu 50 long with minimal termination. facture of methane. In accordance with the invention, an appropriate combination of initiator and reaction medium is TABLE 1. employed to achieve methane conversion in very high selectivity and yield under near-ambient temperature. Spe Yield of MSA, Conversion of CH and SOs cifically, the invention comprises a process for conversion of 55 Conver- Conver methane to methanesulfonic acid (CHS(O).OH) by reac MSA sion of sion of tion with sulfur trioxide ind98% selectivity at ~50° C. In the H2S2O3 CH SO. Time Yield CH SO presence of excess methane, essentially quantitative con Run (mmol) (mmol) (mmol) (h) (mmol) (%) (%) sumption of sulfur trioxide is observed with the methane 1 2.9 240 101 14 97 40.4 96.O conversion reaching>40%.
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