Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C4/00—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms
  • C07C4/08—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by splitting-off an aliphatic or cycloaliphatic part from the molecule
  • C07C4/12—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by splitting-off an aliphatic or cycloaliphatic part from the molecule from hydrocarbons containing a six-membered aromatic ring, e.g. propyltoluene to vinyltoluene
  • C07C4/14—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by splitting-off an aliphatic or cycloaliphatic part from the molecule from hydrocarbons containing a six-membered aromatic ring, e.g. propyltoluene to vinyltoluene splitting taking place at an aromatic-aliphatic bond
  • C07C4/16—Thermal processes
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G47/00—Cracking of hydrocarbon oils, in the presence of hydrogen or hydrogen- generating compounds, to obtain lower boiling fractions
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G47/00—Cracking of hydrocarbon oils, in the presence of hydrogen or hydrogen- generating compounds, to obtain lower boiling fractions
  • C10G47/22—Non-catalytic cracking in the presence of hydrogen

Definitions

• Alkyl aromatics such as toluene
• the alkyl group is cleaved from the alkyl aromatic and combines with the hydrogen present to form a saturated aliphatic hydrocarbon.
• the desired aromatic can be separated from the saturated aliphatic hydrocarbon and unreacted alkyl aromatic, if present, in any convenient way.
• the temperature of the mixture of alkyl aromatic and hydrogen during such reaction be maintained within a range of about 1150 to about 1800 F., preferably about 1250 to about 1350 F. for about one to about 400 seconds, preferably about 10 to about 100 seconds.
• the initial step in the process therefore, involves heating the mixture of alkyl aromatic and hydrogen to the reaction temperature.
• Sufificient hydro-gen must be present to replace the alkyl chain cleaved from the aromatic ring at the elevated reaction temperatures and also to combine with the alkyl chain to form therewith a saturated aliphatic hydrocarbon.
• aromatic charge can be from about 1.5 to about 20, preferably from about three to about eight.
• Any alkyl aromatic can be so treated, for example, toluene, xylenes, tri methyl benzene isomers, alkyl nap'hthalenes and mixtures thereof, alkyl phenols, etc.
• Toluene for example, has a tendency during the initial heating period to be converted to methylcyclohexane.
• This procedure is particularly applicable during the start-up.
• initially hydrogen can be passed through the system in a closed cycle, and suitable heat can be added thereto in the preheating zone to raise the temperature of the system to a defined temperature level, for example, about 1000 to about ll00 F.
• Cold alkyl aromatic is then introduced into the preheating zone with the hot circulating hydrogen. Since the addition of cold alkyl aromatic to the pre'heater will have a tendency to lower the temperature level thus obtained in the preheating zone, additional heat is added thereto in order to quickly raise the temperature therein again to the defined level.
• This procedure will avoid excessive residence time of the reactants at the undesired low temperature level and thereby eliminate the defined hydrogenation in the preheating zone and the cracking of the saturated ring compounds in the thermal hydrodealkylation zone to form undesirable gases and coke.
• the mixture of hydrogen and alkyl aromatic when introduced into the preheating zone is at a temperature of about to about 800 F., preferably at a temperature of about 700 to about 800 F.
• the mixture of alkyl aromatic and hydrogen when it is introduced into the preheating zone, it can be heated to such temperature in any convenient manner, for example, by indirect heat exchange relationship with the heated products from the thermal hydrodealkylation reaction zone.
• the time the reaction mixture is maintained above about 75 F., but below about 850 to about 950 F., preferably below about 900 F. during the defined preheating period, whether all or only a portion of the heat acquired by said mixture was obtained in the preheating zone, must be about one to about 10 seconds, but in no event more than about 50 seconds.
• the preheating zone can be heated in any suitable manner, for example indirectly by gas-fired heaters.
• the mixture leaving the preheating zone is at a temperature of about 1150 to about 1250 F. Therefore the temperature therein can range from a low of about 70 F. to a high of about 125 0 F., but the average temperature in the preheating zone will be from about 1000 to about 1100 F., preferably about 1050 F. Under these conditions no more than about five percent, and generally less than about two percent, by Weight of the alkyl aromatic is dealkylated therein.
• the heated mixture is then introduced into the hydrodealkylation zone, at which point the desired hydrodealkylation reaction takes place. Since this reaction is exothermic it is accompanied with release of heat.
• the temperature can be maintained therein at any temperature level in any suitable manner or the heat resulting from hydrodealkylation can be permitted in large measure to remain therein, resulting in an appreciable temperature rise of the products in the hydrodealkylation reaction zone. In any event the temperature in the hydrodealkylation reaction zone will remain Within a range of about 1150 to about 1800 F., preferably about 1250 to about 1350 F.
• the residence period Will be about one to about 400 seconds, preferably about 10 to about seconds.
• the pressure drop throughout the system will not be appreciable and therefore the pressure will be substantially the same throughout.
• the pressure can be from about 100 to about 1000 pounds per square inch gauge, preferably about 400 to about 600 pounds per square inch gauge.
• the product resulting from the reaction therein will comprise principally dealkylated alkyl aromatic, unreacted charge aromatic, methane and excess or unreacted hydrogen.
• the reaction mixture is cooled by any convenient means, for example, by indirect heat exchange relationship with fresh alkyl aromatic and hydrogen charge, to a temperature below about 600 F. and after further cooling through heat exchangers to ambient temperature. Hydrogen and other gases are then vented from the reaction mixture and the remainder is separated into its component parts by any suitable means, preferably by distillation at a temperature of about 175 to about 250 F. and a pressure of about one to about 10 pounds per square inch gauge.
• the invention can further be illustrated by the following. Four runs were made on a mixture of toluene and hydrogen wherein the temperature of the preheater and the hydrodealkylation reactor were varied and the residence times in the preheater were also varied. The results obtained are set forth below in the table. The mixture of toluene and hydrogen was in each run introduced into the preheater at a temperature of 75 F.
• a process for the hydrodealkylation of an alkyl aromatic which comprises heating a mixture of said alkyl aromatic and hydrogen to a temperature of about 1150 to about 1250 F., maintaining the temperature of said mixture during said heating period at a temperature below about 950 F. for a time less than about 50 seconds, and thereafter subjecting the resultant heated mixture to a temperature of about 1150 to about 1800" F. and a pressure of at least about pounds per square inch gauge for about one to about 400 seconds to effect dealkylation of said alkyl aromatic.
• a process for the hydrodealkylation of an alkyl aromatic which comprises heating a mixture of said alkyl aromatic and hydrogen to a temperature of about 1150 to about 1250 F., maintaining the temperature of said mixture during said heating period at a temperature below about 950 F. for about one to about 10 seconds, and thereafter subjecting the resultant heated mixture to a temperature of about 1150 to about 1800 F. and a pressure of at least about 100 pounds per square inch gauge for about one to about 400 seconds to effect dealkylation of said alkyl aromatic.
• a process for the hydrodealkylation of toluene which comprises heating a mixture of said toluene and hydrogen to a temperature of about 1150 to about 1250 F., maintaining the temperature of said mixture during said heating period at a temperature below about 950 F. for a time less than about 50 seconds, and thereafter subjecting the resultant heated mixture to a temperature of about 1150 to about 1800 F. and a pressure of at least about 100 pounds per square inch gauge for about one to about 400 seconds to etfect dealkylation of said toluene.
• a process for the hydrodealkylation of toluene which comprises heating a mixture of said toluene and hydrogen to a temperature of about 1150 to about 1250 F., maintaining the temperature of said mixture during said heating period at a temperature below about 950 F. for about one to about 10 seconds, and thereafter subjecting the resultant heated mixture to a temperature of about 1150 to about 1800 F. and a pressure of at least about 100 pounds per square inch gauge for about one to about 400 seconds to effect dealkylation of said toluene.
• a process for the hydrodealkylation of an alkyl aromatic which comprises heating a mixture of said alkyl aromatic and hydrogen to a temperature of about 1150" to about 1250 F., maintaining the temperature of said mixture during said heating period at a temperature below about 850 F. for a time less than about 50 seconds, and thereafter subjecting the resultant heated mixture to a temperature of about 1250 F. to about 1350 F. and a pressure of at least about 100 pounds per square inch gauge for about 10 to about 100 seconds to effect dealkylation of said alkyl aromatic.
• a process for the hydrodealkylation of an alkyl aromatic which comprises heating a mixture of said alkyl aromatic and hydrogen to a temperature of about 1150 to about 1250 F., maintaining the temperature of said mixture during said heating period at a temperature below about 850 F. for about one to about 10 seconds, and thereafter subjecting the resultant heated mixture to a temperature of about 1250 to about 1350 F. and a 10 pressure of at least about 100 pounds per square inch gauge for about 10 to about 100 seconds to effect dealkylation of said alkyl aromatic.
• a process for the hydrodealkylation of toluene which comprises heating a mixture of said toluene and hydrogen to a temperature of about ll50 to about 1250 F., maintaining the temperature of said mixture during said heating period at a temperature below about 850 F. for a time less than about 50 seconds, and thereafter subjecting the resultant heated mixture to a temperature of about 1250 F. to about 1350 F. and a pressure of at least about 100 pounds per square inch gauge for about 10 to about 100 seconds to effect dealkylation of said toluene.
• a process for the hydrodealkylation of toluene which comprises heating a mixture of said toluene and hydrogen 25 to a temperature of about 1150 to about 1250" F., maintaining the temperature of said mixture during said heating period at a temperature below about 850 F. for about one to about 10 seconds, and thereafter subjecting the resultant heated mixture to a temperature of about 1250 F. to about 1350 F. and a pressure of at least about 100 pounds per square inch gauge for about 10 to about 100 seconds to effect dealkylation of said toluene.
• a process for the hydrodealkylation of toluene which comprises heating a mixture of toluene and hydrogen to a temperature of about 1175 F. in less than about six seconds and thereafter subjecting the resultant heated mixture to a temperature of about 1280 F. and a pressure of about 460 pounds per square inch gauge for about 50 seconds to effect dealkylation of said toluene.

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• Oil, Petroleum & Natural Gas (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
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• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Cited By (15)

Citations (2)

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• 1963
  • 1963-09-04 US US306598A patent/US3284526A/en not_active Expired - Lifetime
• 1964
  • 1964-07-24 DE DEG41186A patent/DE1283212B/de active Pending
  • 1964-08-04 GB GB31068/64A patent/GB1048112A/en not_active Expired
  • 1964-09-03 NL NL6410268A patent/NL6410268A/xx unknown
  • 1964-09-03 DK DK434364AA patent/DK112938B/da unknown

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