Classifications

• • 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
  • C10G9/00—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
  • C10G9/14—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils in pipes or coils with or without auxiliary means, e.g. digesters, soaking drums, expansion means
  • C10G9/16—Preventing or removing incrustation

Definitions

• the present invention comprises, in the preparation of unsaturated hydrocarbons by the pyrolysis of hydrocarbons by passing them through a heated furnace and thereafter separating out the products thus produced, the step comprising injecting an effective amount of an oxy-compound inhibitor into the process stream at a point downstream from said furnace to reduce the formation of solid deposits.
• the invention further comprises gaseous hydrocarboncontainiug compositions inhibited against varnish formation comprising 10 to about 90 mole percent acetylene and derivatives, 10 to about 90 mole percent ethylene and derivatives, and 0.0001 to 0.05 mole percent of an oxycompound inhibitor.
• Unsaturated hydrocarbons are useful as chemical intermediates and particularly as starting materials for the formation of various polymers.
• the present invention relates to the preparation of unsaturated hydrocarbons and in its preferred embodiments relates to improved processes for the preparation of acetylene and ethylene from non-gaseous hydrocarbons.
• FIGURE 1 such processes typically consist of a furnace in which the thermal cracking of hydrocarbons is accomplished generally at temperatures above about l,500 F. for carefully controlled contact periods generally less than about lO seconds. A rapid cooling of the efiluent from the furnace is usually essential to the attaining of the desired ethylene and acetylene products.
• the percentage of acetylene and ethylene can be controlled generally within the range of about 10 to 90 mole percent of each.
• the hydrocarbons fed to such processes have generally been the gaseous aliphatic hydrocarbons, i.e., methane, ethane, propane, and butane.
• the furnace produces a substantial amount of tars which are removed by a trap located in the efiluent stream. Even with an efiicient trap, some build-up of tars is encountered in the equipment downstream from the trap. Since the separation of the efiluent acetylene and ethylene requires a relatively complex selective absorption and stripping section, maintenance in removing tar deposits from this equipment can present a significant problem.
• the present invention embodies the discovery that these deposits are primarily composed of oxygenated varnishlike materials which are apparently primarily formed from diolefins, especially diacetylenes.
• these deposits are primarily composed of oxygenated varnishlike materials which are apparently primarily formed from diolefins, especially diacetylenes.
• the invention by the addition of certain inhibitors into the process stream at a point downstream from the furnace, formation of varnishes is reduced and those varnishes which form are maintained in a substantially fluid condition. By maintaining the varnishes in a fluid condition, they are prevented from depositing on equipment and are readily removed with other fluid by-products of the process.
• a conventional tar placed upstream from the point of injection of the inhibitors.
• the inhibitors are injected downstream from the tar removal apparatus at a number of points so spaced as to maintain a relatively constant concentration of the inhibitor in each of the process streams in which tar formation is likely to occur.
• inhibitors to be utilized with the present invention are not narrowly critical. In general, inhibitors which prevent the formation of oxy substances, and particularly those which prevent the formation of peroxides have been discovered to be valuable. While the present invention is not to be taken as being dependent upon any mechanism by which the formation of deposits or the inhibition occurs, it is believed that the formation of peroxides greatly accelerates the formation of deposits and the solidification of such deposits.
• tertiary butyl catechol is the most preferred inhibitor for the process of the present invention
• other oxy-compound inhibitors including other alkyl catechols, cresylic acid and its derivatives, butyl phenols, phenylene diamine, 2,4,6-trimethylphenol, 2,4-dimethyl-6-t-butylphenol, 2,4-dimethyl-6-isobutylphenol, 2,6-di-sec-butyl-4- methylphenol, 2,6-di-t-butyl-4-isopropylphenol, N,N'-di- (sec-butyl)-p-phenylene diamine, p-phenylene diamine, N,N'-di(tert-butyl)-p-phenylene diamine, and p-butylaminophenol are useful in the process. All such inhibitors are included within the term oxy-compound inhibitor as used herein.
• the inhibitors will be utilized in whatever mole percent is found to give 'best results at reasonable cost. Generally from about 0.0001 to about 0.05 mole percent inhibitor will be injected based on the moles of product.
• the molecular weights of inhibitors may be chosen so as to provide desirable boiling points and other physical properties, e.g., by varying the length of the alkyl group in alkyl catechols. A mixture of different inhibitors may be desirable under some circumstances. While heavier feeds normally produce larger amounts of viscous deposits, it should be understood that the present invention is beneficial when crude oils, light and heavy naphthas, gaseous hydrocarbons and other feed stocks are utilized in the Wulif Process and analogous processes.
• Example I A naphtha feed stock having a boiling range of from about 250 to 350 F. is fed to a modified WuliT process according to the process of US. 2,236,534.
• the maximum temperature in the furnace is approximately 2,400 F. and the residence time is approximately 0.015 second.
• the step comprising injecting an effective amount of an oXy-compound inhibitor into the process stream at a point downstream from said furnace to reduce the formation of solid deposits.
• the step comprising injecting into the process stream after said rapid cooling from 0.0001 to about 0.05 mole of an oxy-compound inhibitor per mole of product to reduce the formation of solid deposits.
• Gaseous hydrocarbon-containing compositions inhibited against varnish formation comprising 10 to about mole percent acetylene and derivatives, 10 to about 90 mole percent ethylene and derivatives, varnish-forming materials and 0.0001 to 0.05 mole percent of an oXy-cornpound inhibitor.
• compositions of claim 7 wherein the oxy-compound inhibitor is tert-butyl catechol.

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• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

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Cited By (12)

Citations (2)

• 1965
  • 1965-05-03 US US452842A patent/US3366702A/en not_active Expired - Lifetime
• 1966
  • 1966-05-03 DE DE19661593010 patent/DE1593010A1/de active Pending

Patent Citations (2)

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