Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C7/00—Purification; Separation; Use of additives
  • C07C7/04—Purification; Separation; Use of additives by distillation
  • C07C7/05—Purification; Separation; Use of additives by distillation with the aid of auxiliary compounds
• • 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
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/52—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning
  • C09K8/524—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning organic depositions, e.g. paraffins or asphaltenes
• • 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
  • C10G75/00—Inhibiting corrosion or fouling in apparatus for treatment or conversion of hydrocarbon oils, in general
  • C10G75/02—Inhibiting corrosion or fouling in apparatus for treatment or conversion of hydrocarbon oils, in general by addition of corrosion inhibitors
• • 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
  • C10G75/00—Inhibiting corrosion or fouling in apparatus for treatment or conversion of hydrocarbon oils, in general
  • C10G75/04—Inhibiting corrosion or fouling in apparatus for treatment or conversion of hydrocarbon oils, in general by addition of antifouling agents
• • 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 relates to a process for preventing polymeric fouling during the transfer of a hydrocarbon stream containing olefinic compounds through apparatuses for the relevant treatment, like, e.g., tne production, the storage, the refining, the fractionation, the compression, the extraction and the heating of the olefinic compounds contained in the stream.
• olefinic compounds may form complex mixtures of ethylene, propylene, butadiene, isoprene, cyclopentadiene, styrene and of other higher olefins.
• the process s based on the use of a stabilizing mixture consisting of a nitroxide or a dinitroxide compound and an aromatic amine.
• the mixture comprising both the two types of nitroxide compound and an aromatic amine for the above mentioned use is novel to the state of the art and it has a synergistic effect experimentally verifiable with respect to the individual and separate use of the two types of compounds.
• aromatic amines ⁇ r general, ana ID particular phenylene ⁇ iammes and diphenylamines, are widely used as antioxidants and stabilizers.
• polymeric fouling deposits During the olefin production process by pyrolisis of gaseous or liquid hydrocarbon streams, the formation of polymeric fouling deposits is incurred: such deposits usually generate onto the surfaces of the apparatuses, with a formation mechanism which usually includes a polymerization following the formation of carbon or oxygen radicals, by thermal induction and catalysis of metals deriving from corrosion phenomena.
• Polymeric fouling reduces thermal exchange, may adversely affect plant performance and stall the production capacity: in some cases the deposit that may be generated is so copious to cause the clogging of the sets of heat exchangers, the transfer pipes, the distillation column plates, and it may cause the unplanned shutdown of the plant itself.
• Deposits are usually localized in the heat exchanger sets, the bottom column reboilers, on the column bottom itself, onto the plates and in the intermediate pumparounds, as well as onto the top of rectification and extraction columns, in the transfer pipes and on the bottom of containers for the temporary storage of pure monomers .
• an object of the present invention is a process for preventing polymeric fouling in petrochemical plants for the treatment of olefinic compounds, in which in the supply stream of the treatment plants an amount of a stabilizing composition effective to prevent said fouling, comprising nitroxides and aromatic amines in a mixture therebetween in a weight ratio of 2:1 to 1:20, is introduced.
• a further object of the invention is such stabilizing mixture and the use thereof to hinder fouling in plants for the treatment of olefinic compounds through petrochemical processes.
• Nitroxides compounds suitable for use in the present invention are those containing free radicals. Particularly suitable ones are those selected from the group comprising 4-hydroxy-tetramethyl-piperidino-l-oxy) , or a nitroxide having the general formula
• R" 0° R" wherein R, R' , and R' ' represent H, alkyl, cycloalkyl, aryl (Ci - C ⁇ 5 ) , substituted or unsubstituted with heteroatoms such as N, S, P, halogens and the like, or a dinitroxide, in particular of the type 1- piperidinyloxy-4, 4' - (1, 10-dioxo-l, 10-decanediyl) -bis- 2, 2, 6, 6-tetramethyl and mixtures thereof.
• Suitable aromatic amines are in particular diphenylamines (DPA) and phenylene diamines (PDA) or aromatic amines of general formula
• R wherein R, R' , R' ' have the above stated meaning, and mixtures thereof.
• the quantitative weight ratio of nitroxide and/or dinitroxide compound with respect to the aromatic amines ranges from 2:1 to 1:20, preferably from 1:7,5 to 2:5.
• the mixture is preferably a solution wherein the active substances nitroxide and aromatic amines are dissolved in an extractant.
• Suitable extractants are, by way of example, aliphatic extractants, xylene, benzene and higher homologous substances.
• the stabilizing mixture may preferably be added, with respect to the fluid material to be treated, in an amount of from 0,5 to 50 ppm.
• the combined additive consisting of the two active substances, may be added in sites which correspond to the plant sites, related to the whole range of steps of production, selective extraction, rectification and storage, that can be liable to fouling due to particularly disadvantageous thermal conditions or to the presence of metal-containing oxygen or water, or in presence of particularly high concentrations of markedly reactive olefins.
• the stabilizing mixture which is a combination of the two active substances, is added to the load streams. However it may also be supplied at the column bottom reboilers.
• the term "column" is intended to mean the distillation apparatus of a hydrocarbon stream containing olefins for the separation of a mixture made of C n .
• the stabilizing mixture may be supplied at the bottom reboiler of the quench oil column (cooling of the hydrocarbon stream carried out with quench oil) in the cracking gas compression section, in particular under suction among the 3 rd , 4 th and 5 th stage, in the cuts directed to hydrogenation processes (pyrolysis or cracking gasoline) , in the mixtures directed to temporary storage and in the feed and/or in the overhead reflux of the rectification and purification processes of the olefinic compounds.
• the use of the mixture according to the invention enables the control of the undesirable polymerization reactions to be increased, as well as the nitroxide amounts required for the antifouling treatment (with the entailed cost reduction) to be decreased.
• the instrument represents one of the most technically sophisticated modules for reproducing fouling situations in any one plant: by controlling the heating of the liquid in the circuit, as well as measuring the ⁇ P both at the inlet and at the outlet of the cell provided for the purpose, full information may be obtained, for assessing the tendency of- a certain fluid to deposit organic fouling.
• the instrument was used in the ⁇ P configuration, using the cell module provided for the purpose and automatically recording over time the pressure exerted onto a filter for collecting the insoluble substances formed upon heating of the processed fluid.
• the operative temperature or skin temperature was set at 120 °C. This represents the temperature at which the filament transferring heat to the exchanger 1 is electrically heated.
• the tested fluid F is run onto the outer surface of the exchanger.
• the two lines 2, 3 at the top of the exchanger are connected to a transducer which detects the pressure difference ⁇ p between the circuit section upstream of the strain 4 and the downstream one.
• the internal pressure of the apparatus is of about 21 Atm .
• a fluid exactly corresponding to that present at the bottom of a depropanizing column (this is the column section wherein the conditions required to form insoluble polymers are most likely to occur, usually under 10-12 atm) would be, under the instrument conditions, in a near-gaseous state.
• the cut density was set at 0,65 gr/cm 3 : moreover, the mixture employed was further enriched in C4 by scrubbing gaseous butadiene (previously TBC-freed by soda washing) into the cooled liquid (-20°C).
• Aromatic amine 10 ppm PDA + hydroxyl amine: 2 ppm + 2 ppm 4H-TEMPO x 1: 200 ppb
• the second test series, (Table 4) carried out with a second sampling of the same cut confirms the preceding inclinations, with the utmost efficiency, both as the initial sinuosity and after 480 min, of the dinitroxide - PDA mixture.
• PDA + Dinitroxide (5:2): 1 ppm + 400 ppb
• the isoprene employed is the commercially available one, and, prior of being fed into the autoclave, it was washed in a separatory funnel with repeated soda and water washings, then dehydrated with anhydrous sodium sulfate .
• Table 6 reports the weight of the polymer obtained by heating at 90°C a fixed amount of pure isoprene, under the initial pressure of 2 atm obtained with a nitrogen pressure-controlling device.
• the test duration was set at 24 hours with constant stirring of 200 rpm: then the residual isoprene left over was evaporated at 100°C, under nitrogen stream.
• Table 7 reports other results, always obtained with isoprene, mixed in this case, at the beginning of the test, to an equal amount of isooctane.
• the solvent allows more isoprene to remain in a liquid state, whereby the effect of the additives, which of course remain dissolved in the liquid phase, becomes more evident. Furthermore, the test temperature was brought to 100°C.
• the mixture of isoprene-solvent-anti- polymerization agents forms a more homogeneous phase, hence the results of polymerization inhibition are markedly improved with respect to the first test series, notwithstanding a markedly lower concentration of the additive.

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

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• 1999
  • 1999-12-24 IT IT1999RM000795A patent/IT1307306B1/it active
• 2000
  • 2000-12-27 EP EP00987638A patent/EP1240123A1/en not_active Withdrawn
  • 2000-12-27 WO PCT/IT2000/000548 patent/WO2001047844A1/en not_active Application Discontinuation

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