Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
  • C07C5/22—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by isomerisation
  • C07C5/27—Rearrangement of carbon atoms in the hydrocarbon skeleton
  • C07C5/2767—Changing the number of side-chains
  • C07C5/277—Catalytic processes
  • C07C5/2775—Catalytic processes with crystalline alumino-silicates, e.g. molecular sieves
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D15/00—Separating processes involving the treatment of liquids with solid sorbents; Apparatus therefor
  • B01D15/08—Selective adsorption, e.g. chromatography
  • B01D15/10—Selective adsorption, e.g. chromatography characterised by constructional or operational features
  • B01D15/18—Selective adsorption, e.g. chromatography characterised by constructional or operational features relating to flow patterns
  • B01D15/1814—Recycling of the fraction to be distributed
  • B01D15/1821—Simulated moving beds
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C15/00—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts
  • C07C15/02—Monocyclic hydrocarbons
  • C07C15/067—C8H10 hydrocarbons
  • C07C15/08—Xylenes
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C5/00—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms
  • C07C5/22—Preparation of hydrocarbons from hydrocarbons containing the same number of carbon atoms by isomerisation
  • C07C5/27—Rearrangement of carbon atoms in the hydrocarbon skeleton
  • C07C5/2729—Changing the branching point of an open chain or the point of substitution on a ring
  • C07C5/2732—Catalytic processes
  • C07C5/2737—Catalytic processes with crystalline alumino-silicates, e.g. molecular sieves
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C7/00—Purification; Separation; Use of additives
  • C07C7/12—Purification; Separation; Use of additives by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers
  • C07C7/13—Purification; Separation; Use of additives by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers by molecular-sieve technique

Definitions

• Patents FR 2 782 714, FR 2 808 270, FR 2 822 820, FR 2 829 758 and FR 2 833 592 of the applicant also illustrate separations using a simulated moving bed column from which two raffinates are drawn off separate in addition extract. They all target the co-production of paraxylene of commercial purity, metaxylene and / orthoxylene.
• the solvent for washing the paraxylene crystals is for example chosen from the following solvents: n-pentane, water, purified paraxylene or toluene, and the washing liquor resulting from the washing step can be recycled to the column feed adsorption in simulated moving bed.
• the process for producing paraxylene according to the invention from a feed containing xylenes, ethylbenzene and C9 + hydrocarbons includes at least the following steps (Figure 1):
• a separation of the head mixture (3) is carried out in a simulated moving bed in at least one separation column (LM6) containing a plurality of interconnected beds and working in a closed loop, said column comprising at least five zones delimited by the injections of the flow (3) constituting the charge of the column (LM6) and of the desorbent (5) and the withdrawals of an extract (7) containing paraxylene, of an intermediate raffinate (8) containing ethylbenzene, and a raffinate-2 (9) containing orthoxylene and metaxylene, the zone 1 for desorption of paraxylene being between the injection of the desorbent (5) and the withdrawal of the extract (7), the zone 2 for desorption ethylbenzene, orthoxylene and metaxylene being between the extraction of the extract (7) and the injection of the adsorption charge (3), the adsorption zone 3A of paraxylene being between 1 of the charge (3) and the withdrawal of the intermediate raffinate re (8), the zone 3B
• the raffinate-2 is distilled in a CD12 column to remove substantially all of the desorbent and a second distilled fraction (15) is drawn off,
• At least part of said second distilled fraction (15) is sent to a second xylenes isomerization zone (IS20) to obtain a second isomerate (21) -
• the first isomerate (22) is sent after elimination of its light fractions in a separation train (29) to the distillation column (CD2).
• the second isomerate (21) is recycled either (flow 40) to the separation column in simulated moving bed (LM6), mixed with the overhead flow (3) from the distillation column (CD2), or (flow 41) to the distillation column (CD2), mixed with the feed (1).
• the first isomerization zone (IS19) working in the gas phase is generally operated under the following conditions:
• VVH Hourly space velocity
• the content of naphthenic or paraffinic impurities is advantageously less than 1% by weight. Preferably, this content is less than 0.3% by weight and more preferably this content is less than 0.1% by weight.
• the charge can originate either from an aromizing unit, or from a disproportionation unit for toluene, or from a transalkylation unit for toluene and aromatic C9s.
• An isomerate carried by a line (22) and optionally a mother liquor carried by the lines (25) or (28) is added to the fresh charge, the paraxylene content of which is advantageously between 25 and 40%. All of the flows (1), (22) and (28) or (25) feed a distillation column (CD2).
• the effluents from the unit (LM6) are an extract (7), an intermediate raffinate (8) and a raffinate-2 (9), said separation unit comprising at least five zones delimited by the injections of charge and desorbent, and the rackings of intermediate raffinate, raffinate-2 and extract,
• the charge (1) which feeds the aromatic loop comes from reforming and has a flow rate of 460 kt / year.
• Added to the load (1) 1540 kt / year of isomerate (22) recycled from the isomerization unit (IS19) converting ethylbenzene.
• the resulting stream is distilled in the xylene column (CD2).
• the operating conditions of this column are as follows: Column: 120 trays Head temperature: 255 ° C Head pressure: 0.95 MPa Bottom temperature: 305 ° C Bottom pressure: 1.05 MPa
• This section is sent to a simulated moving bed adsorption unit with four zones (LM6) and four main flows: the feed (flow 3), the desorbent (flow 5), the extract (flow 7) and the raffinate ( flow 8).
• This unit is made up of 24 beds containing an X zeolite exchanged with barium. The temperature is 175 ° C. The configuration is: 5 beds in zone 1, 9 beds in zone 2, 7 beds in zone 3 and 3 beds in zone 4.
• the desorbent is 99% paradiethylbenzene, the flow rate of desorbent (5) is 3000 kt / year.
• the extract flow (7) at the outlet of the adsorption unit (LM6) is 1200 kt / year, it is sent to a distillation column (CD10) from which 790 kt / year of desorbent is drawn at the bottom. (16) recycled to the adsorption unit (LM6), and at the top 410 kt / year of a mixture (13) essentially consisting of toluene and paraxylene.
• This mixture (13) is sent to a distillation column (CD35) making it possible to withdraw 10 kt / year of toluene at the head (flow 39) and 400 kt / year of paraxylene at the bottom (flow
• the extract flow (flow 7) at the outlet of the adsorption unit (LM6) is 1580 kt / year. It is sent to the extract (CD10) and purification (CD35) columns.
• the extract flow rate sent to the column (CD10) is 1200 kt / year.
• the extract flow rate sent to the column (CD35) is 380 kt / year.
• a separation train (29) makes it possible to produce 25 kt / year of a gas containing mainly hydrogen, 30 kt / year of toluene and 160 kt / year of the paraffinic and naphthenic cut cited above (flow 31).
• the heaviest part of the isomerate (stream 22), or 1,540 t / year, is recycled to the inlet of the xylene column (CD2).
• the flow rate of raffinate-2 (flow 9) is 1,720 kt / year.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Analytical Chemistry (AREA)
• Crystallography & Structural Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Water Supply & Treatment (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (2)

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Cited By (3)

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• 2003
  • 2003-11-26 FR FR0313964A patent/FR2862638B1/fr not_active Expired - Lifetime
• 2004
  • 2004-11-23 EP EP04805513A patent/EP1689695B1/fr not_active Expired - Lifetime
  • 2004-11-23 ES ES04805513T patent/ES2321198T3/es not_active Expired - Lifetime
  • 2004-11-23 US US10/580,345 patent/US7915471B2/en active Active
  • 2004-11-23 AT AT04805513T patent/ATE422195T1/de not_active IP Right Cessation
  • 2004-11-23 KR KR1020067012754A patent/KR101157278B1/ko not_active Expired - Fee Related
  • 2004-11-23 JP JP2006540524A patent/JP4966664B2/ja not_active Expired - Fee Related
  • 2004-11-23 WO PCT/FR2004/002984 patent/WO2005054161A2/fr not_active Ceased
  • 2004-11-23 DE DE602004019343T patent/DE602004019343D1/de not_active Expired - Lifetime
  • 2004-11-23 CN CN200480035152XA patent/CN1886357B/zh not_active Expired - Lifetime

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