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WO1996040842A1 - Procede pour maximiser la production de xylene - Google Patents

Procede pour maximiser la production de xylene Download PDF

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Publication number
WO1996040842A1
WO1996040842A1 PCT/US1996/006828 US9606828W WO9640842A1 WO 1996040842 A1 WO1996040842 A1 WO 1996040842A1 US 9606828 W US9606828 W US 9606828W WO 9640842 A1 WO9640842 A1 WO 9640842A1
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WO
WIPO (PCT)
Prior art keywords
catalyst
temperature
xylene
aromatics
treated
Prior art date
Application number
PCT/US1996/006828
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English (en)
Inventor
Gerald J. Nacamuli
Original Assignee
Chevron Chemical Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Chevron Chemical Company filed Critical Chevron Chemical Company
Publication of WO1996040842A1 publication Critical patent/WO1996040842A1/fr

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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
    • C10G35/00—Reforming naphtha
    • C10G35/04—Catalytic reforming
    • C10G35/06—Catalytic reforming characterised by the catalyst used
    • C10G35/095—Catalytic reforming characterised by the catalyst used containing crystalline alumino-silicates, e.g. molecular sieves

Definitions

  • the present invention relates to a catalytic process for aromatizing a C 6 -C 10 heavy naphtha feed to produce benzene, toluene and C 8 and C 9 aromatics, with the amount of xylene produced being maximized as compared to prior art methods.
  • Catalytic reforming is well known in the petroleum industry and refers to the treatment of naphtha fractions to improve the octane rating by the production of aromatics.
  • One of the more important reactions occurring during reforming is the dehydrocyclization of acyclic hydrocarbons to aromatics.
  • Catalytic reforming in this regard is also an important process for the chemical industry because of the great and expanding demand for aromatic hydrocarbons for use in the manufacture of various chemical products such as synthetic fibers, insecticides, adhesives, detergents, plastics, synthetic rubbers, pharmaceutical products, perfumes, drying oils, and various other products.
  • benzene serves as a starting material for the production of other aromatics such as styrene, phenol, synthetic detergents, DDT and nylon intermediates.
  • Toluene is employed in aviation gasoline and as a high octane blending stock.
  • As a petrochemical raw material it is used in the production of solvents, gums, resins, rubber cement, vinyl organosols and other organic chemicals.
  • Mixed xylenes are primarily used in aviation gasoline and as a solvent for alkyd resins, lacquers, enamels and rubber cements, etc.
  • U.S. Patent No. 4,650,565 discloses a dehydrocyclization process which involves contacting a naphtha feed in a reaction vessel with a dehydrocyclization catalyst comprising a large-pore zeolite containing at least one Group VIII metal to produce an aromatics product and a gaseous stream.
  • the aromatics product is then separated from the gaseous stream and is passed through a molecular sieve which adsorbs paraffins present in the aromatic product, then the gaseous stream is used to strip the paraffins from the molecular sieve, and the gaseous stream and the paraffins are recycled to the reaction vessel.
  • the dehydrocyclization catalyst comprises a type L zeolite containing from 8% to 15% by weight barium and from 0.6% to 1.0% by weight platinum, wherein at least 80% of the crystals of the type L zeolite are larger than 1000 Angstroms, and an inorganic binder selected from the group consisting of silica, alumina, and aluminosilicates.
  • U.S. Patent No. 4,158,025 discloses a process for selected aromatic hydrocarbon production.
  • Selected aromatic hydrocarbon concentrates such as benzene and mixed xylenes, are produced by way of a combination process which involves catalytic reforming followed by dealkylation. While the process affords some flexibility in the concentrate produced, it is particularly directed toward the maximization of benzene.
  • dehydrocyclization or aromatization processes employed to date have generally focused on the production of benzene.
  • a process which can improve the amount of xylenes produced, and in particular para- xylenes, by successfully and efficiently using heavier naphtha feeds would help to meet some of the increasing demand for such aromatics, and specifically para- xylenes, without being cost prohibitive.
  • Another object of the present invention is to provide a process which is more selective toward the production of para-xylenes. Yet another object of the present invention is to provide such a process which can efficiently use heavy naphtha feeds.
  • a process for aromatizing a wide boiling range naphtha feed in order to produce a C 8 stream with its C 8 aromatics being rich in xylene comprises aromatizing a wide boiling range naphtha feed, e.g., a C 6 -C 10 naphtha stream, over a high temperature treated L- zeolite catalyst in the potassium form containing a Group VIII metal.
  • a high temperature treated catalyst is defined as a catalyst that has been treated in an inert gas or reducing atmosphere at a temperature greater than or equal to 1025 Q F.
  • the catalyst has been treated at a temperature in the range of from 1025°F to 1275°F while maintaining the water level of the effluent gas below 200 ppmv. Subsequent to the aromatization, a C 8 stream rich in xylene is recovered.
  • the present invention is based on the surprising discovery that the use of a high temperature treated L-zeolite catalyst which is in the potassium form to aromatize a heavy naphtha feed produces a product stream that is significantly richer in xylene, and more specifically produces a C 8 fraction which comprises largely xylenes, e.g., the C 8 aromatics comprises at least 80% by weight xylene.
  • the use of a heavier naphtha feed in order to obtain a C 8 stream so rich in xylenes is possible due to the particular catalyst employed in the process of the present invention.
  • the catalyst used has been demonstrated to achieve a much higher selectivity to xylenes than has heretofore been deemed possible as compared to the use of L-zeolite aro atization catalysts presently in commercial use.
  • the catalyst used contains platinum in an amount ranging from about 1.0 to about 1.5 wt %. Such higher amounts of platinum further helps the activity and stability of the catalyst when processing a wide boiling range C 6 -C l0 naphtha feed.
  • the catalyst used has been treated at a temperature in the range of from 1025°F to 1275°F while maintaining the water level of the effluent gas below 200 ppmv.
  • This pretreatment has been found to permit the catalyst to operate with a heavier naphtha feed in order to produce a C 8 stream rich in xylenes, i.e., wherein the C 8 aromatics comprises at least 75% xylene, and most preferably at least 80% xylene.
  • the catalyst of the present invention is a large-pore zeolite containing at least one Group VIII metal, and is most preferably an L-zeolite.
  • the preferred Group VIII metal is platinum, which is more selective for dehydrocyclization and which is more stable under reforming reaction conditions than other Group VIII metals.
  • the catalyst should contain between 0.1% and 5% platinum based on the weight of the catalyst, more preferably from 0.1% to 2.0%, and most preferably from about 1.0 to 1.5 wt %, e.g., about 1.2 wt %.
  • the use of at least 1.0 wt % platinum is considered preferred in accordance with the present invention as it helps the activity and stability of the catalyst in working with the heavy naphtha feedstocks.
  • L-type zeolite catalysts are known. Examples of such L- zeolites are found, for example, in U.S. Patent No. 3,216,789, which is hereby incorporated by reference.
  • Type L zeolites are synthesized largely in the potassium form. These potassium cations, however, are exchangeable, so that other type L zeolites can be obtained by ion exchanging the type L zeolite in appropriate solutions.
  • the zeolites have been exchanged in the prior art with an alkaline earth metal such as barium, strontium or calcium.
  • the potassium has also been ion exchanged in the prior art with an alkali or alkaline earth metal, such as sodium, cesium or rubidium.
  • An inorganic oxide can be used as a carrier to bind the large-pore zeolite.
  • This carrier can be natural, synthetically produced, or a combination of the two.
  • Preferred loadings of inorganic oxide are from 5% to 50% of the weight of the catalyst.
  • Useful carriers include silica, alumina, aluminosilicates, and clays.
  • the preferred carrier is silica. The preparation of bound catalysts is described, for example, in U.S. Patent No. 4,830,732, which is hereby incorporated by reference in its entirety.
  • the pretreatment process used on the catalyst occurs in the presence of a reducing gas such as hydrogen, as described in U.S. Patent No. 5,382,353, issued January 17, 1995, which is hereby expressly incorporated by reference in its entirety.
  • a reducing gas such as hydrogen
  • the contacting occurs at a pressure of from 0 to 300 psig and a temperature of from 1025°F to 1275°F for from 1 hour to 120 hours, more preferably for at least 2 hours, and most preferably at least 4-48 hours. More preferably, the temperature is from 1050°F to 1250°F.
  • the length of time for the pretreatment will be somewhat dependent upon the final treatment temperature, with the higher the final temperature the shorter the treatment time that is needed.
  • the catalyst in order to limit exposure of the catalyst to water vapor at high temperatures, it is preferred that the catalyst be reduced initially at a temperature between 300°F and 700°F. After most of the water generated during catalyst reduction has evolved from the catalyst, the temperature is raised slowly in ramping or stepwise fashion to a maximum temperature between 1025°F and 1250°F.
  • the temperature program and gas flow rates should be selected to limit water vapor levels in the reactor effluent to less than 200 ppmv and, preferably, less than 100 ppmv when the catalyst bed temperature exceeds 1025°F.
  • the rate of temperature increase to the final activation temperature will typically average between 5 and 50°F per hour.
  • the catalyst will be heated at a rate between 10 and 25°F/h.
  • the gas flow through the catalyst bed during this process exceed 500 volumes per volume of catalyst per hour, where the gas volume is measured at standard conditions of one atmosphere and 60°F. In other words, greater than 500 gas hourly space volume (GHSV) .
  • GHSV's in excess of 5000 h "1 will normally exceed the compressor capacity.
  • GHSV's between 600 and 2000 h" 1 are most preferred.
  • the pretreatment process occurs prior to contacting the reforming catalyst with a hydrocarbon feed.
  • the large- pore zeolitic catalyst is generally treated in a reducing atmosphere in the temperature range of from 1025°F to 1275°F.
  • dry hydrogen is preferred as a reducing gas.
  • the hydrogen is generally mixed with an inert gas such as nitrogen, with the amount of hydrogen in the mixture generally ranging from l%-99% by volume. More typically, however, the amount of hydrogen in the mixture ranges from about 10%-50% by volume.
  • the reducing gas entering the reactor should contain less than 100 ppmv water. It is preferred that it contain less than 10 ppmv water.
  • the reactor effluent may be passed through a drier containing a desiccant or sorbent such as 4 A molecular sieves.
  • a desiccant or sorbent such as 4 A molecular sieves.
  • the dried gas containing less than 100 ppmv water or, preferably, less than 10 ppmv water may then be recycled to the reactor.
  • the catalyst can be pretreated using an inert gaseous environment in the temperature range of from 1025-1275°F, as described in copending
  • the preferred inert gas used is nitrogen, for reasons of availability and cost.
  • Other inert gases can be used, such as helium, argon and krypton, or mixtures thereof.
  • the inert gas entering the reactor should contain less than 100 ppmv water. It is preferred that it contain less than 10 ppmv water.
  • the reactor effluent may be passed through a drier containing a desiccant or sorbent such as 4 A molecular sieves. The dried gas containing less than 100 ppmv water or, preferably, less than 10 ppmv water may then be recycled to the reactor.
  • the catalyst be reduced prior to the high temperature treatment in the inert atmosphere in the temperature range of from 1025 to 1275°F.
  • the reducing gas used is preferably hydrogen, although other reducing gases can also be used.
  • the hydrogen is generally mixed with an inert gas such as nitrogen, with the amount of hydrogen in the mixture generally ranging from 1-99% by volume. More typically, however, the amount of hydrogen (or other reducing gas) in the mixture ranges from about 10-50% by volume.
  • the zeolite catalyst is reduced by contact with a reducing gas in a temperature range of from 300 to 900°F.
  • a reducing gas in a temperature range of from 300 to 900°F.
  • the temperature can then be raised to the range of from 1025°F to 1275°F either stepwise or in a ramping fashion.
  • the gaseous atmosphere is preferably inert in the temperature range from 900°F up to 1025°F. It is also preferred that the effluent gas water level be maintained below 200 ppmv in the temperature range of from 900°F to 1025°F.
  • the catalyst can be dried in an inert atmosphere such as a nitrogen atmosphere prior to reduction.
  • the drying can take place while heating the catalyst from ambient
  • the catalyst in order to limit exposure of the catalyst to water vapor at high temperatures, it is preferred that the catalyst be reduced initially at a temperature between 300°F and 700°F. After most of the water generated during catalyst reduction has evolved from the catalyst, the temperature is raised slowly in ramping or stepwise fashion to a maximum temperature between 1025°F and 1250°F. During the treatment in the temperature range of from 1025°F to 1250°F, the atmosphere is that of an inert gas.
  • the temperature program and gas flow rates when employing the inert gas atmosphere treatment should be selected to limit water vapor levels in the reactor effluent to less than 200 ppmv and, preferably, less than 100 ppmv when the catalyst bed temperature exceeds 1025°F.
  • the rate of temperature increase to the final activation temperature can typically average between 5 and 50°F per hour.
  • the catalyst be heated at a rate between 10 and 25°F/h.
  • the gas flow through the catalyst bed (GHSV) during this process exceed 500 volumes per volume of catalyst per hour, where the gas volume is measured at standard conditions of one atmosphere and 60°F temperature.
  • the feed to the reforming process is typically a naphtha that contains at least some acyclic hydrocarbons or alkylcyclopentanes.
  • This feed should be substantially free of sulfur, nitrogen, metals and other known poisons. These poisons can be removed by first using conventional hydrofining techniques, then using sorbents to remove the remaining sulfur compounds and water.
  • An example of a suitable feed, which feed has been hydrorefined to reduce sulfur content to acceptable levels, is shown below in Table 1:
  • the catalyst of the present invention exhibits a longer run life with heavier feedstocks, e.g., containing at least 5 wt % C 9 + hydrocarbons, than similar catalysts having been subjected to a different treatment.
  • the catalyst obtained via the treatment of the present invention makes it quite practical to process feedstocks containing at least 5 wt % C 9 + hydrocarbons, and for example at least 10 wt % C 9 + hydrocarbons, with from 10-20 wt % C 9 + hydrocarbons being preferred.
  • Such larger amounts of C 9 + hydrocarbons permits one to take better advantage of the present process as such a feedstock will have more C 8 precursors to permit even greater amounts of xylene to be produced.
  • the feed can be contacted with the catalyst in either a fixed bed system, a moving bed system, a fluidized system, or a batch system. Either a fixed bed system or a moving bed system is preferred.
  • a fixed bed system the preheated feed is passed into at least one reactor that contains a fixed bed of the catalyst.
  • the flow of the feed can be either upward, downward, or radial.
  • the pressure is from about 1 atmosphere to about 500 psig, with the preferred pressure being from abut 50 psig to about 200 psig.
  • the preferred temperature is from about 800°F to about 1025°F.
  • the liquid hourly space velocity is from about 0.1 hr " 1 to about 10 hrs" 1 , with a preferred LHSV of from about 0.3 hr" 1 to about 5 hrs' 1 .
  • Enough hydrogen is used to insure a H 2 /HC ratio of up to about 20:1.
  • the preferred H 2 /HC ratio is from about 1:1 to about 7:1, and most preferred 2:1 to about 6:1. Reforming produces hydrogen. Thus, additional hydrogen is not needed except when the catalyst is reduced and when the feed is first introduced. Once reforming is underway, part of the hydrogen that is produced is recycled over the catalyst. Once the reforming process has been completed, the product can be separated into the desired streams or fractions.
  • a C 8 aromatics stream is recovered using conventional techniques such as distillation and/or extraction.
  • the effluent from the aromatization reactor is cooled and then sent to a separator where the liquid is recovered for further processing.
  • the gas from the separator is collected and part is recycled to the reactor inlet and part is excessed from the aromatization process.
  • the liquid which contains mostly C 8 -C 9 aromatics and some C 10 aromatics as well as non-aromatics is depentanized and then sent to a first distillation column to recover benzene and toluene as an overhead product.
  • This overhead cut which also includes non-aromatics in the benzene and toluene boiling range is further processed in an aromatics extraction plant, e.g., Udex, Sulfolane, Krupp, to separate the aromatics from the non-aromatics.
  • the aromatics stream is then sent to a second distillation column where the benzene is recovered as an overhead product and the toluene as a bottoms product.
  • the bottoms stream from the first distillation column which consists primarily of C 8 and C 9 aromatics, and some C j o aromatics is sent to a third distillation column where the C g aromatics are removed as an overhead product and the C 9+ aromatics as a bottoms product.
  • the C 8 aromatics stream from the third distillation column is processed in a plant where the PX (para-xylene fraction) is removed by adsorption, or crystallization, or a combination of adsorption-crystallization.
  • the PX lean stream from this process also known as the raffinate stream, is sent to a xylene isomerization plant where the xylenes are reacted to equilibrium thereby converting some of the meta and ortho-xylenes to para- xylenes.
  • the resulting effluent from the xylene isomerization plant is distilled to remove light (benzene and toluene) and heavy aromatics (C 9+ ) .
  • the remaining xylenes are then recycled to the third distillation column for further processing in the PX removal plant.
  • the process of the present invention results in at least about a 27% increase in xylene production. Moreover, the present process is more selective in that the ethylbenzene yield is generally reduced by about 40% which results in a C 8 aromatics distribution which contains at least 80% xylenes.
  • Silica bound zeolite extrudates were ion-exchanged with barium.
  • the barium exchanged extrudates were then dried and calcined at a temperature exceeding 1100°F.
  • the calcined extrudates were pore-fill impregnated using platinum tetra-ammonium di-chloride solution.
  • the resulting extrudate was dried and calcined at 500-550°F in a steam/air environment and then crushed and sieved to a particle size of 14-28 mesh.
  • the resulting catalyst was 0.6 wt.% Pt/K-Ba L zeolite.
  • a 1.2% Pt/K-Ba L zeolite silica-bound extrudate was prepared in a similar manner to that described in Example 1.
  • the catalyst was impregnated with platinum as described in Example 1, except that sufficient platinum tetra-ammoniu di- chloride was used to achieve a platinum content of 1.2 wt.%.
  • the catalyst of the present example was not calcined but dried in air at 185°F. Prior to use in the reactor, the catalyst was crushed and sieved to a particle size of 14-28 mesh.
  • a silica-bound K L zeolite extrudate was impregnated with platinum without a barium ion exchange step.
  • the platinum impregnation step was as described in Example 2 to obtain a 1.2% Pt/K L zeolite.
  • the resulting extrudate was then dried in air at 185°F. Prior to use in the reactor, the catalyst was crushed and sieved to a particle size of 14-28 mesh.
  • Nitrogen flow was established over the catalyst at room temperature and atmospheric pressure. The nitrogen flow was such as to obtain a GHSV of 1000.
  • the unit pressure was brought up to 50 psig and set to control at that pressure.
  • the catalyst was next heated from ambient temperature to 300°F at a rate of 50°F/hr.
  • the catalyst was then heated to 500°F at 25°F/hr.
  • the temperature of the catalyst/reactor was reduced to the desired starting temperature and the reactor pressure was adjusted to the desired operating pressure.
  • the reactor temperature was reduced to about 800°F and the pressure was established at 75 psig.
  • the naphtha feed which was the same as described in Table 1, was then introduced at 4 cc/hr.
  • reactor inline samples were taken and analyzed by a gas chro atograph to determine the aromatics concentration in the reactor effluent.
  • the reactor temperature was subsequently increased until the aromatics concentration of the reactor effluent was 70%.
  • the reactor temperature was increased in small increments as necessary to maintain the target severity of 70% aromatics in the reactor effluent.
  • the ethylbenzene and xylene concentration was determined as well as the C 8 aromatics and xylene distribution.

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

Abstract

L'invention concerne un procédé pour aromatiser une charge de kérosènes à large plage de températures d'ébullition pour produire un courant à C8 dont les aromatiques C8 sont riches en xylène, c'est-à-dire contiennent, de préférence, au moins 80 % de xylène. Le procédé consiste à aromatiser la charge de kérosène sur un catalyseur au zéolithe L sous sa forme potassique, traitée à haute température et portant un métal du groupe VIII, de préférence le platine. Le catalyseur traité à haute température a été obtenu de préférence par un traitement thermique dans la plage allant de 1025 °F à 1275 °F, le niveau d'eau du gaz sortant étant maintenu simultanément à moins de 200 ppm (en volume). Un courant à C8 dont les aromatiques C8 sont riches en xylène est ainsi extrait du courant de produit.
PCT/US1996/006828 1995-06-07 1996-05-09 Procede pour maximiser la production de xylene WO1996040842A1 (fr)

Applications Claiming Priority (2)

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US47582195A 1995-06-07 1995-06-07
US08/475,821 1995-06-07

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WO1996040842A1 true WO1996040842A1 (fr) 1996-12-19

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2520636A1 (fr) * 1982-02-01 1983-08-05 Chevron Res Composition zeolitique du type l contenant du platine et du baryum et son application au reformage d'hydrocarbures
US4614834A (en) * 1984-11-05 1986-09-30 Uop Inc. Dehydrocyclization with nonacidic L zeolite
EP0309139A2 (fr) * 1987-09-21 1989-03-29 Exxon Research And Engineering Company Procédé de production de catalyseurs zéolithiques stabilisés
WO1991006616A2 (fr) * 1989-10-30 1991-05-16 Exxon Research And Engineering Company Procede de reformage de matieres premieres d'hydrocarbures de petrole

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2520636A1 (fr) * 1982-02-01 1983-08-05 Chevron Res Composition zeolitique du type l contenant du platine et du baryum et son application au reformage d'hydrocarbures
US4614834A (en) * 1984-11-05 1986-09-30 Uop Inc. Dehydrocyclization with nonacidic L zeolite
EP0309139A2 (fr) * 1987-09-21 1989-03-29 Exxon Research And Engineering Company Procédé de production de catalyseurs zéolithiques stabilisés
WO1991006616A2 (fr) * 1989-10-30 1991-05-16 Exxon Research And Engineering Company Procede de reformage de matieres premieres d'hydrocarbures de petrole

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