Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
  • C07C2/76—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by condensation of hydrocarbons with partial elimination of hydrogen
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2531/00—Catalysts comprising hydrides, coordination complexes or organic compounds
  • C07C2531/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides

Definitions

• the apparatus employed in such operations generally includes a hydrocarbon vaporizer together with one or more pyrolyzing tubes or passageways extending from the vaporizer to a suitable condenser or other conventional means in which the product is separated from the more volatile starting material.
• a suitable condenser or other conventional means in which the product is separated from the more volatile starting material.
• Any suitable heat source can be used to provide the requisite temperature for the vaporizer and the pyrolysis tubes.
• promoters included alcohols. aldehydes, ketones. aliphatic acids. acid esters and ethers. Particularly preferred promoters included lower aliphatic alcohols and acetone premixed at concentrations of from about 0.1 to 2.0 percent by weight of the aromatic feed.
• the conversion of aromatics to polyphenyls by pyrogenie dehydrogenation is increased by introducing into the pyrolysis zone at one or more points a reaction promoter selected from the group consisting of oxygenfree lower alkyl-substituted aromatic and aliphatic hydrocarbons and mixtures thereof.
• the promoters are preferably introduced at each point at a rate of from about 0.05 to 0.5 percent by weight of the aromatic hydrocarbon feed.
• Particularly preferred promoters include C2 to C alkyl-substituted aromatics. e.g. isopropyl benzene. and C to C alkyl-substituted aliphatics. e.g. trimethyl pentane.
• Pyrolytic conversions of aromatic hydrocarbons are normally conducted in the vapor state under a gauge pressure of between about 10 and 200 pounds per square inch and at between about 600C. and 950C.
• the rate of conversion is generally uneconomically slow at temperatures less than about 600C. whereas excessive degradation occurs at temperatures above about 950C.
• an aromatic hydrocarbon such as benzene is vaporized and the vapors heated to a temperature of about 600C. by any conventional means.
• the heated vapors are then passed into a pyrolysis zone maintained between about 600C. and 950C., and more preferably between 700and 800C.
• the vapors exiting the pyrolysis zone are condensed and the polyphenyls separated from the unconverted hydrocarbon feed.
• Preferred apparatus employed in accordance with conventional procedures includes a hydrocarbon vaporizer. a pyrolyzing element or tube and a product collecting means such as a condenser. These units are provided with suitable connecting means to permit fluid flow from the vaporizer through the pyrolyzing element into the condenser. Any conventional means may be employed to obtain proper operating temperatures throughout'the apparatus.
• One or more pyrolytic tubes can be incorporated in the apparatus. the size and number of tubes depend upon the relative size of the vaporizer and upon the rate of production desired.
• the pyrolytic conduits are preferably tubular and straight but can assume any convenient cross-sectional configuration and can also follow curved. tortuous or helical paths provided that the flow of the vapor stream is not impeded.
• the flow rate through the tubes is preferably at a sufficiently high rate to provide turbulent flow.
• a recycle circuit is normally provided to conduct the unconverted hydrocarbon feed from the condenser to the vaporizer.
• An alternative process which may be employed is the molten bath process wherein vapors of the aromatic hydrocarbon are passed directly through a heat transfer medium comprising a suitable relatively inert and nonvolatile molten material. such as molten lead or lead alloys or molten salt.
• a suitable relatively inert and nonvolatile molten material such as molten lead or lead alloys or molten salt.
• the promoters of the instant invention are introduced into the vaporized aromatic feed immediately preceding introduction of that feed into the molten bath.
• a tubular pyrogenic converter is preferred to the molten bath because it allows greater flexibility of operation and provides for multiple injections of promoter at various stages of the pyrolysis zone. Accordingly, the following detailed description of the preferred embodiments of the instant invention are directed to the use of a tubular converter.
• polyphenyf is used herein in its broadest sense to designate polymerized benzene and substituted benzenes. Thus, it encompasses biphenyl, ter- 3 phenyl, quaterphenyls. alkyl-substituted polyphenyls, naphthylenes. phenyl-substituted naphthylenes and the like.
• pyrolysis is used herein to designate high temperature reactions wherein promoters activate or accelerate the process and not in the more restrictive sense of the term sometimes found in texts which excludes the presence of catalytic bodies.
• the rate or degree of conversion of the aromatic hydrocarbon to the polyphenyl is increased by introducing one or more reaction promoters into the pyrolysis zone at one or more points within the zone.
• the promoter is preferably injected into the pyrolysis zone at points spaced to provide substantially equal incremental reaction zones between points of injection and between the final point of injection and the exit of the converter.
• promoters are advantageously injected at points located at three-sixths, four-sixths. and fivesixths of the distance from the entrance to the exit of the converter corresponding to incremental reaction zones of l second dwell time and to total dwell times within the converter of 3, 2, and 1 second respectively.
• Incremental dwell times are preferably from about 0.5 to 1.5 seconds, but may range from about 0.1 to 3 seconds or longer depending upon the size of the converter. the total dwell time, and the like.
• the amount of promoter injected at each point of introduction into the pyrolysis zone is preferably from about 0.05 to 0.5 percent by weight of the aromatic feed, and more preferably from 0.1 to 0.2 percent, the exact and optimum amount depending upon such conditions as operating temperature and pressure, operating rate and dwell time within the pyrolysis zone, the incremental dwell times between points of promoter introduction. and the composition of the aromatic hydrocarbon feed. Amounts of promoter in excess of 0.5 percent can. of course. be introduced at any point, but there is generally little or no process advantage to be gained thereby. When injecting the promoter at multiple points it is generally satisfactory to inject equal amounts at each point although variations in rate of injection are permissible if desired or required to optimize the effect of the promoter.
• reaction promoters of the present invention are broadly defined as oxygen-free C to C alkylsubstituted aromatic hydrocarbons such as ethyl benzene, propyl benzene, butyl benzene, methylethyl benzene, dimethylethyl benzene, and ethyl naphthylene; and C, to C alkyl-substituted aliphatic hydrocarbons such as trimethyl pentane. trimethyl hexane, dimethyl octane, methylethyl pentane, methylethyl hexane, and dimethylethyl hexane.
• Particularly preferred promoters are isopropyl benzene and trimethyl pentane.
• aromatic hydrocarbon feeds suitable for use in accordance with this invention include benzene and the lower alkyl-substituted benzenes, such as toluene and xylene, and also naphthylene and lower alkylsubstituted naphthylenes. Also the simpler nuclearsubstituted derivatives of benzene, toluene, xylene and naphthylene such as monoand dichloro and bromosubstituted compounds may be employed in conducting the reaction.
• the feed may also include minor amounts, and generally less than about 25 percent by weight, of biphenyl or terphenyl where the preparation of higher polyphenyls is desired.
• benzene was vaporized and heated to a temperature of about 500C. at a rate of about 26 grams per minute, and the vapors passed into a pyrolytic converter maintained at 750C. and comprised of a single coiled /8 inch tube having a length of 50 feet.
• the retention time of the benzene in the pyrolytic converter section was approximately 6 seconds.
• Individually controlled promoter injection ports were installed at one-half, twothirds, and five-sixths of the distance from the entrance to the exit of the converter tube.
• Selected promoters were metered into the pyrolysis zone at one, two or all three points as desired and at predetermined rates.
• the material exiting the pyrolysis zone was collected to separate and recover the polyphenyl products, and unreacted benzene was recycled to the vaporizer.
• the effect of various promoters and promoter injection rates was determined by ascertaining the degree of conversion of benzene to polyphenyl with and without promoter injection.
• Example I The method of Example I was repeated by injecting various promoters into the entrance of the pyrolysis zone only.
• the following data show the effect of these promoters on conversion and illustrate that trimethyl pentane is substantially equivalent to isopropyl benzene while ethyl benzene, although somewhat less active than the others, is still an effective promoter.
• mixtures of promoters and mixtures of aromatic hydrocarbon feeds may be employed where desired.
• Variations in pyrolysis conditions including rates. temperatures and pressures are contemplated and will be apparent to those skilled in the art. Thus. the scope of the invention is not to be limited by the details of the preceding examples.
• a method of converting benzene to polyphenyls which comprises passing benzene through a pyrolysis zone maintained at a temperature of from about 700C to about 800C, and introducing into said pyrolysis zone at one or more points a compound selected from the group consisting of isopropylbenzene, trimethylpentane and ethylbenzene. wherein the amount of compound introduced at each point is from about 0.05% to about 0.5% by weight of the hydrocarbon feed.
• a method of claim 5 wherein from 0. l 7( to 2.0 percent acetone by weight of benzene is premixed with the benzene prior to the pyrolysis zone.
• a method of converting aromatic hydrocarbons to polyphenyls which comprises passing an aromatic hydrocarbon through a pyrolysis zone maintained at pyrolyzing temperatures, the improvement comprising introducing into said pyrolysis zone at one or more points a catalytic amount of a compound selected from the group consisting of oxygen-free C to C alkylsubstituted aliphatic hydrocarbons, C to C 4 alkylsubstituted aromatic hydrocarbons, and mixtures thereof.
• incrimental reaction zones existing between the points of introduction and between the final point of introduction and the exit of the pyrolysis zone are substantially equal and include incrimental reaction dwell times of from about 0.1 to about 3.0 seconds.
• Point 1 should be 0.1% at Point 1 0.1 19.4 6.6 20.4 2.0

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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Citations (2)

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• 0
  • BE BE786919D patent/BE786919A/xx not_active IP Right Cessation
• 1971
  • 1971-07-29 US US167491A patent/US3876719A/en not_active Expired - Lifetime
• 1972
  • 1972-07-28 DE DE2237172A patent/DE2237172C3/de not_active Expired
  • 1972-07-28 GB GB3529272A patent/GB1366775A/en not_active Expired
  • 1972-07-28 FR FR727227409A patent/FR2147314B1/fr not_active Expired
  • 1972-07-28 CA CA148,243A patent/CA988247A/en not_active Expired
  • 1972-07-28 JP JP47075181A patent/JPS5246221B2/ja not_active Expired

Patent Citations (2)

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