Process for the oxidation of alkanes

{
  "publication_number": "US6492548B1",
  "country": "US",
  "kind": "B1",
  "title": "Process for the oxidation of alkanes",
  "abstract": "Processes are disclosed for the oxidation of alkanes such as, for example, propane, to form unsaturated carboxylic aldehydes and acids such as, for example, acrolein and acrylic acid. The processes utilize oxygen and recycle alkanes, e.g. propane, to the aldehyde reactor. The presence of the alkane-to-aldehyde reaction can enhance the efficiency of the processes.",
  "claims": [
    "1. A process for producing an unsaturated carboxylic acid having up to about 5 carbon atoms per molecule comprising: (i) passing a feedstream comprising an alkane having up to about 5 carbon atoms per molecule, oxygen and a recycle gas comprising the alkane, an alkene having the same number of carbon atoms as said alkane, oxygen and at least one of carbon monoxide or carbon dioxide to an alkene reaction zone wherein the feedstream is contacted with an alkene reaction catalyst at conditions effective to promote the oxidation of the alkane by oxydehydrogenation to provide a first effluent stream comprising the alkene, unreacted alkane and water wherein: (a) the conversion of the alkane to the alkene is from about 5 to 40 percent and the selectivity of the conversion of the alkane to the alkene is from about 50 to 98 percent; and (b) said alkane and oxygen being present in a molar ratio of from 5 to 40 moles of the alkane per mole of oxygen; (ii) passing the first effluent stream to an aldehyde reaction zone wherein the first effluent stream is contacted with an aldehyde reaction catalyst at conditions effective to promote the conversion of the alkene to an aldehyde having the same number of carbon atoms as said alkene to provide a second effluent stream comprising the aldehyde, the alkene and the alkane; (iii) passing the second effluent stream to a carboxylic acid reaction zone wherein the second effluent stream is contacted with a carboxylic acid reaction catalyst at conditions effective to promote the conversion the conversion of the aldehyde to an unsaturated carboxylic acid having the same number of carbon atoms as said aldehyde to provide a third effluent stream comprising the alkene, the alkane, the unsaturated carboxylic acid and at least one of carbon monoxide or carbon dioxide; (iv) separating the third effluent stream into a liquid product stream comprising the carboxylic acid and a recycle gas stream comprising said recycle stream; and (v) recycling at least a portion of the recycle gas stream to the alkene reaction zone to comprise a portion of said feedstream; characterized in that the alkene feedstream comprises an amount of alkane of from about 5 to 70 volume percent and effective to provide a alkene-to-aldehyde reaction efficiency of from about 75 to 90 mole percent.",
    "2. The process of claim 1 wherein the concentration of the alkane in the first effluent stream is from about 5 to 70 mole percent of the alkane based on the total moles in the first effluent stream.",
    "3. The process of claim 2 wherein the concentration of the alkane in the first effluent stream is from about 10 to 60 mole percent of the alkane based on the total moles in the first effluent stream.",
    "4. The process of claim 1 wherein the alkane is butane, the aldehyde is methacrolein and the carboxylic acid is methacrylic acid.",
    "5. A process for producing acrylic acid comprising: (i) passing a feedstream comprising propane, oxygen and a recycle gas comprising propane, propylene, oxygen and at least one of carbon monoxide or carbon dioxide to a propylene reaction zone wherein the feedstream is contacted with a propane reaction catalyst at conditions effective to promote the oxidation of propane by oxydehydrogenation to provide a first effluent stream comprising propylene, unreacted propane and water, wherein: (a) the conversion of propane to propylene is from about 5 to 40 percent and the selectivity of the conversion of propane to propylene from about 50 to 98 percent; and (b) said propane and oxygen being present in a molar ratio of from 5 to 40 moles of propane per mole of oxygen; (ii) passing the first effluent stream to an acrolein reaction zone wherein the first effluent stream is contacted with an acrolein reaction catalyst at conditions effective to promote the conversion of propylene to acrolein to provide a second effluent stream comprising acrolein, propylene, propane and acrylic acid; (iii) passing the second effluent stream to an acrylic acid reaction zone wherein the second effluent stream is contacted with an acrylic acid reaction catalyst at conditions effective to promote the conversion of acrolein to acrylic acid to provide a third effluent stream comprising propylene, propane, acrylic acid and at least one of carbon monoxide or carbon dioxide; (iv) separating the third effluent stream into a liquid product stream comprising acrylic acid and a recycle gas stream comprising said recycle gas; and (v) recycling at least a portion of the recycle gas stream to the propylene reaction zone to comprise a portion of said feedstream; characterized in that the propylene feedstream comprises an amount of propane of from about 5 to 70 volume percent and effective to provide a propylene-to-acrolein reaction efficiency of from about 75 to 90 mole percent.",
    "6. The process of claim 5 wherein the concentration of propane in the first effluent stream is from about 5 to 70 mole percent of propane based on the total moles in the first effluent stream.",
    "7. The process of claim 6 wherein the concentration of propane in the first effluent stream is from about 10 to 60 mole percent of propane based on the total moles in the first effluent stream.",
    "8. The process of claim 5 wherein the propylene reaction zone and the acrolein reaction zone are combined in a single reactor.",
    "9. The process of claim 8 wherein the propylene reaction catalyst and the acrolein reaction catalyst are commingled.",
    "10. The process of claim 8 wherein the propylene reaction catalyst and the acrolein reaction catalyst are contained within separate zones within said reactor.",
    "11. The process of claim 5 wherein the feedstream comprises at least 30 mole percent propane.",
    "12. The process of claim 5 wherein the feedstream comprises at least 80 mole percent propane.",
    "13. The process of claim 5 wherein the conversion of propylene is not less than 70 mole percent."
  ],
  "description_excerpt": "This application is a continuation of U.S. Ser. No. 09/155,808, now abandoned filed Oct. 1, 1998 based on international application number PCT/US/97/05054, filed Mar. 27, 1997, which claims benefit of Provisional Application No. 60/014,679, filed Apr. 1, 1996.\n\nThis invention relates to the oxidation of alkanes such as, for example, propane, to form unsaturated, carboxylic aldehydes and acids such as, for example, acrolein and acrylic acid.\n\nProcesses for producing acrylic acid by vapor phase catalytic oxidation of propylene using molecular oxygen are known and used on an industrial scale.\n\nOne of the typical processes for industrial production of acrylic acid is as follows. Propylene is converted mainly into acrolein and a small amount of acrylic acid in a first reaction step by supplying a mixture of propylene, air and steam to produce the acrolein. The acrolein product is supplied to a second reactor without separation of products for the subsequent reaction of acrolein to form acrylic acid. Additional air and steam for the second step are supplied as required.\n\nIn another typical process, the product gas containing acrylic acid obtained from the second reactor is introduced into a collecting apparatus to obtain acrylic acid as an aqueous solution and a part of remaining waste gas containing unreacted propylene from the collecting apparatus is recycled to the first reactor inlet together with the starting gas mixture of propylene, air and steam.\n\nVarious improvements to the above-mentioned processes have been proposed to produce acrylic acid efficiently by vapor phase catalytic oxidation of propylene.",
  "cpc": [
    "C07C 51/215"
  ],
  "ipc": [
    "C07C 51/215"
  ],
  "assignees": [
    "Union Carbide Chemicals and Plastics Technology LLC"
  ],
  "inventors": [
    "Jonathan L Brockwell",
    "Mark A Young",
    "William G Etzkorn",
    "Barbara K Warren",
    "John M Maher"
  ],
  "filing_date": "2000-09-20",
  "publication_date": "2002-12-10",
  "grant_date": "2002-12-10",
  "priority_date": "1996-04-01",
  "application_number": "US-66509800-A",
  "family_id": "26686364",
  "cited_by_count": 24,
  "citations": [
    "US3293290A",
    "US4260822A",
    "US4413147A",
    "GB2118939A",
    "US4532365A",
    "EP0117146A1",
    "US5198578A",
    "US5183936A",
    "US5077434A",
    "US5218146A",
    "US5155262A",
    "US4999452A",
    "US5243082A",
    "US5354915A",
    "US5321180A",
    "US5705684A",
    "US5696282A"
  ]
}