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
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C7/00—Purification; Separation; Use of additives
  • C07C7/20—Use of additives, e.g. for stabilisation
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L10/00—Use of additives to fuels or fires for particular purposes
  • C10L10/04—Use of additives to fuels or fires for particular purposes for minimising corrosion or incrustation
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S585/00—Chemistry of hydrocarbon compounds
  • Y10S585/949—Miscellaneous considerations
  • Y10S585/95—Prevention or removal of corrosion or solid deposits

Definitions

• the present invention relates to a method for controll ing fouling in equipment for processing and storing hydrocarbon compositions containing unsaturated compounds . More specif ically the processing may include , for example , preheating , hydrogenation , f ractionation , extraction and the l ike of hydrocarbon streams to remove , concentrate , or have added thereto the unsaturated hydrocarbons prior to storage or use .
• fouling can be controlled according to the present invention, by the judicious use of an appropriate stable free radical or a suitable precursor that under the process conditions yields the active stable free radical in situ.
• the fouling is controlled by the action of the stable free radicals in terminating radical polymerization chain reactions in the processing equipment.
• the present invention relates to the discovery that polymerization of unsaturated organic compounds (olefinic or acetylenic unsaturation) contained in organic feed streams can be controlled and inhibited during processing of the streams by incorporating from 20 to less than 1000 ppb (parts per billion by weight), preferably to 900 ppb, of a stable free radical into the stream, based on the total stream being processed.
• ppb parts per billion by weight
• the present invention is a method for inhibiting polymerization of unsaturated compounds in organic feed streams during processing of said feed streams comprising having present from 20 to less than 1000 ppb, preferably 50 to 900 ppb and more preferably less than 700 ppb by weight of a stable free radical, based on the total weight of said feed stream, thereby controlling fouling of processing equipment.
• the feed streams may be hydrocarbons or unsaturated compounds and may contain other substituents in addition to hydrogen and carbon. Similarly the entire feed stream may be comprised of substituted hydrocarbons.
• the unsaturated compounds may comprise from 1 to 100% of the feed stream.
• the processing may include distillation, extraction, heating, vaporizing and hydrotreating of the feed stream, wherein the unsaturated compound is removed, concentrated or reacted, as in hydrotreating, or some other component of the feed stream is removed, concentrated or reacted.
• the amount of stable free radical used in the process is quite small, hence product streams, e.g., olefins, produced according to the present method can be utilized for polymerization by the addition of conventional amounts of polymerization catalyst under polymerization conditions, which will overcome the inhibiting effect of any stable free radical remaining in the product.
• the stable free radical may be selected to be higher boiling than the overhead, hence it will remain bottoms.
• the present method excludes any process carried out for the purpose of polymerizing the unsaturated compounds, particularly in the presence of effective amounts of polymerization catalyst.
• the spontaneous and unexplained formation of "popcorn polymer" in distillation equipment in the vapor portion of the equipment used to separate and recover some olefins, e.g., butadiene and styrene overhead is inhibited according to the present invention.
• stable free radical shall mean a free radical that can be prepared by conventional chemical methods and will exist long enough to be used in a subsequent chemical reaction or examined in a static system by normal methods of spectroscopy.
• the stable free radicals of the present invention have a half life of at least one (1) year.
• half life as used herein means that period of time at the end of which one-half of the radicals, existing at the beginning of said time period are still in existence.
• stable free radical shall also be understood to include the precursor to a stable free radical from which the stable free radical may be produced in situ.
• BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a plot showing the results from a process carried out according to the present invention and from the same process carried out in accordance with prior practice. The scale of the wall resistance is increased by a factor of 10 4 for the drawing.
• stable free radical (or precursor thereof under conditions which produce the stable free radical in situ) as defined may be used in the present invention.
• the stable free radicals suitable for use in this invention may be selected from, but are not limited to, the following groups of chemicals: nitroxides (e.g., di-tert-butylnitroxide), hindered phenoxys (e.g., galvinoxyl), hydrazyls (e.g., diphenylpicrylhydrazyl), and stabilized hydrocarbon radicals (e.g., triphenylmethyl), as well as polyradicals, preferably biradicals of these types.
• nitroxides e.g., di-tert-butylnitroxide
• hindered phenoxys e.g., galvinoxyl
• hydrazyls e.g., diphenylpicrylhydrazyl
• stabilized hydrocarbon radicals e.g., triphenylmethyl
• certain precursors that produce stable free radicals in situ may be selected from the following groups: nitrones, nitrosos, thioketones, benzoquinones, and hydroxylamines.
• These stable free radicals exist over a wide range of temperatures up to 260° C.
• a limiting factor i n their use is the temperature of the processing wherein they are employed.
• the present method applies to processing carried on at temperatures at which said stable free radical exists. Generally such processing is conducted at less than 260° C eg, 0 to 260o C . Pressure has not been seen to be significant to the present method, hence, atmospheric, sub or superatmospheric conditions may be employed.
• a preferred stable free radical for use in this invention is a nitroxide having the formula:
• R 1 , R 2 , R 3 and R 4 are alkyl groups or heteroatom substituted alkyl groups and R 5 and R 6 are such that no hydrogen is bound to the remaining valences on the carbon atoms bound to the nitrogen.
• the alkyl (or heteroatom substituted) groups R 1 -R 4 may be the same or different, and preferably contain 1 to 15 carbon atoms.
• R 1 -R 4 are methyl, ethyl, or propyl groups.
• the heteroatom substituents may include halogen, oxygen, sulfur and nitrogen.
• R 5 and R 6 may be satisfied by any atom or group except hydrogen which can bond covalently to carbon, although some groups may reduce the stabilizing power of the nitroxide structure and are undesirable.
• R 5 and R 6 are halogen, cyano, -COOR wherein R is alkyl or aryl, -CONH 2 , -S-C 6 B 5 , -S-COCH 3 , -OCOC 2 H 5 , carbonyl, alkenyl where the double bond is not conjugated with the nitroxide moiety or alkyl of 1 to 15 carbon atoms, R 5 and R 6 may also form a ring of 4 or 5 carbon atoms and up to two heteroatoms, such as O, N or S by R 5 and R 6 together.
• suitable compounds having the structure above and in which R 5 and R 6 form part of the ring are those containing a carbonyl group such as the pyrrolidin-1-oxys, piper idinyl-1-oxys, or pyrrolin-1-oxys and the morpholines and piperazines. Particular examples wherein the
• R 5 and R 6 above form part of a ring are 4-hydroxy-2,2,6,6-tetramethyl-piperindino-1-oxy, 2,2,6,6-tetramethyl-piperidino-1-oxy, 4-oxo-2,2,6,6-tetramethyl-piperidino-1-oxy and
• R 5 and R 6 groups are methyl, ethyl and propyl groups.
• R 1 , R 2 , R 3 , R 4 , R 5 and R 6 may each be, for example, methyl, ethyl or propyl.
• a specific example of a suitable compound where R 1 - R 6 are alkyl groups is di-tert-butylnitr oxide.
• the preferred carbonyl containing nitroxides are those wherein the R 5 and R 6 form a ring structure with the nitrogen, preferably a six number ring, for example, 4-oxo-2,2,6,6-tetramethylpiperidino-1-oxy.
• the nitroxide is present in the feed stream at a concentration of from 20 to 100 ppb.
• the feed streams are organic, preferably hydrocarbons containing hydrocarbon olefinic and/or acetylenic compounds.
• the unsaturated compounds may be pure hydrocarbons or organic unsaturated compounds or mixtures thereof.
• the processing to which the present invention is directed includes distillation, extraction, extractive distillation, countercurrent extraction, hydrotreating, hydrofining, thermal treatments and the like, and the preheating prior to such processing.
• the olefinic compounds include hydrocarbon monomers generally having two to 20 carbon atoms such as ethylene, propylene, butene-1, isobutene, pentene, hexene, octene, dodecene, butadiene, isoprene, hexadiene and the like; vinyl monomers such as vinyl chloride, vinyl acetate, vinylidene chloride, ethyl vinyl ketone, chloroprene, styrene, divinylbenzene, vinyl pyridiene, chlorostyrenes, esters of acrylic acid and methacrylic acid, acrylamide, acrylonitrile, methacrylonitrile, acrolein, methacrolein and the like.
• Acetylenic compounds include, for example vinyl acetylene, methyl acetylene and the like.
• the unsaturated compounds may also include higher molecular weight compounds found in crude oil and crude oil distillates and residua which are normally identified by their solubility characteristics, such as asphaltenes and maltenes.
• the processing carried out according to the present invention results in a wide variety of liquid (under the appropriate conditions of pressure) compositions containing the stable free radical. Some of these compositions may contain olefinic materials for use in polymerizations or otherwise or for other end uses or processing. There may be present in the present method in addition to the stable free radical as described, other additives such as antioxidants, anti-foaming agents, color stabilizers and the like.
• a preferred mode of operation for the present invention is the fractionation of an organic feed stream to recover olefinic compound contained therein, e.g., low molecular weight olefinic hydrocarbons, such as ethylene, propylene, butenes, butadiene and mixtures thereof from a bottoms liquid containing other C 2 to C 7 olefinic hydrocarbons thereby inhibiting
• olefinic compound contained therein e.g., low molecular weight olefinic hydrocarbons, such as ethylene, propylene, butenes, butadiene and mixtures thereof from a bottoms liquid containing other C 2 to C 7 olefinic hydrocarbons thereby inhibiting
• the stable free radical may be for example a nitroxide having a boiling point above that of the separated olefinic compound.
• FIG. 1 is presented by way of illustration only of certain aspects of the invention, and which shows what happened where a deethanizer was operated without a stable free radical and had an increase in wall resistance to the point that it was necessary to shut down for cleaning at around 36 days (Base Run).
• Wall resistance is the resistance of a wall to the flow of thermal energy from one side to the other.
• wall resistance refers to the transfer of heat across the walls of tubes in a reboiler. In this regard it is qualitatively the inverse of the more conventionally used heat transfer coefficient.
• Wall resistance can be used as an indicator of fouling because of the fact that as fouling material is deposited on the heat transfer surface it forms an additional layer of resistance that must be overcome.
• the analysis of the effects of additives is accomplished by comparing the times required for the pressure difference across the orifice to reach a predetermined value for a fluid containing the additive and the fluid alone.
• the variation in the characteristics of the fluids and the configuration of the analyzer compared to that of a full-scale plant precludes an extrapolation of the results from laboratory to plant.
• the results are useful in identifying additives that inhibit fouling of the test fluids and in ranking the effectiveness of several additives in inhibiting fouling.
• the formation of polymer is detected by observing the change in the pressure drop across the restriction. Run length is defined as the time required for the pressure to increase by a predetermined amount.
• Table 1 shows the results of tests on a number of compounds and formulations which are active in inhibiting the formation of the polymeric fouling material. TABLE 1 ADDITIVE RUN LENGTH (MINUTES Blank Feed (50% butadiene) 5 - 6 Commercial Additives (10,000 ppb - active concentration)

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Water Supply & Treatment (AREA)
• Analytical Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Polymerisation Methods In General (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Detergent Compositions (AREA)

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• 1986
  • 1986-01-13 US US06/818,583 patent/US4670131A/en not_active Expired - Lifetime
• 1987
  • 1987-01-13 AU AU68493/87A patent/AU587524B2/en not_active Ceased
  • 1987-01-13 JP JP62500807A patent/JPS63502192A/ja active Granted
  • 1987-01-13 CA CA000527255A patent/CA1281339C/en not_active Expired - Lifetime
  • 1987-01-13 ES ES87300252T patent/ES2021353B3/es not_active Expired - Lifetime
  • 1987-01-13 EP EP87300252A patent/EP0230366B1/en not_active Expired - Lifetime
  • 1987-01-13 WO PCT/US1987/000073 patent/WO1987004179A1/en not_active Ceased
  • 1987-02-26 BR BR8700914A patent/BR8700914A/pt unknown

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