Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
  • B01D3/009—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping in combination with chemical reactions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
  • B01D3/14—Fractional distillation or use of a fractionation or rectification column
  • B01D3/143—Fractional distillation or use of a fractionation or rectification column by two or more of a fractionation, separation or rectification step
  • B01D3/146—Multiple effect distillation
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
  • C07C41/01—Preparation of ethers
  • C07C41/05—Preparation of ethers by addition of compounds to unsaturated compounds
  • C07C41/06—Preparation of ethers by addition of compounds to unsaturated compounds by addition of organic compounds only
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C41/00—Preparation of ethers; Preparation of compounds having groups, groups or groups
  • C07C41/01—Preparation of ethers
  • C07C41/34—Separation; Purification; Stabilisation; Use of additives
  • C07C41/40—Separation; Purification; Stabilisation; Use of additives by change of physical state, e.g. by crystallisation
  • C07C41/42—Separation; Purification; Stabilisation; Use of additives by change of physical state, e.g. by crystallisation by distillation
• • 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
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/10—Process efficiency

Definitions

• the present invention concerns a process for preparing tertiary alkyl ethers in a catalytic distillation reactor system comprising a distillation column and at least one first reaction zone, which is connected to the distillation column.
• Such a process comprises the step of reacting C 5 to C 8 isoolefines of an olefmic hydrocarbon feedstock with lower alkanols in a reaction zone under conditions which promote the formation of ethers.
• the invention also relates to an apparatus for preparing tertiary alkyl ethers.
• the apparatus typically comprises a distillation column and at least one first reaction zone connected thereto and containing a catalyst which comprises cation exchange resin.
• the controllability of the reaction conditions is good. If side reactors are used, they can be operated under conditions differing from the operating conditions of the distillation column, whereby the temperature and pressure in the first reaction zone can be adjusted optimal for the reaction.
• the reactive distillation column system can further be operated so as to allow for the removal of all of the unreacted methanol or ethanol in the form of an azeotrope in the preparation of methyl and ethyl ethers, and thus, a separate washing unit for the alkanol is not needed.
• the present invention aims at eliminating the problems related to the prior art while providing an entirely novel process and apparatus for preparing tertiary alkyl ethers.
• the invention is based on the concept of increasing the conversion of of the hydrocarbon feedstock, in particular of 2-methyl-2-butene (2M2B) and corresponding isoolefins, by connecting a side rectifying unit to the above-described etherification process and apparatus.
• a side rectifying unit preferably comprises a separator into which a side stream can be conducted from the lower part of the distillation column and which can be used to divide the side stream into a light fraction and a heavy fraction, and a reactor into which the light fraction of the separator can be conducted to rereact in the presence of a catalyst.
• the process according to the invention is mainly characterized by the steps of reacting C 5 to C 8 isoolefines of an olefinic hydrocarbon feedstock with a lower alkanol to produce the corresponding ethers within said reaction zone, withdrawing a side draw from the lower part of the distillation column and conducting it to a separator where the side draw is divided into a low- boiling fraction and a high-boiling fraction, returning at least a part of the high-boiling fraction into the column, conducting at least a part of the low-boiling fraction into at least one second reaction zone, where it is subjected to an etherification reaction in the presence of a catalyst, and subsequently returned to the distillation column, and removing the ether product from the bottom of the column.
• the apparatus comprises a distillation column and at least one first reaction zone connected thereto and containing a catalyst which is comprised of cation exchange resin.
• the apparatus further comprises a side rectifying unit connected to the lower part of the distillation column and consisting of a separator and a reactor connected thereto.
• Figure 1 depicts the process scheme of a first preferred embodiment of the invention
• Figure 2 depicts the process scheme of a second preferred embodiment of the invention
• Figure 3 depicts the process scheme of a third preferred embodiment of the invention.
• catalytic distillation reactor system confers to process configurations comprising
• reaction bed can also be arranged on the inside of the distillation column so that it can be operated in a similar way as a separate external side reactor.
• first reaction zone the above-mentioned reaction bed (irrespective of its location) is called the "first reaction zone”.
• the side stream which is conducted to the side rectifying system is taken from the "lower part" of the column. This term is used to denote the point between the bottom of the column and the lowermost first reaction zone.
• a suitable feedstock for the above-mentioned processes for preparing tertiary alkyl ethers is Fluidized Catalytic Cracking (FCC) Gasoline containing C 4 _ 7 hydrocarbons, a substantial portion, generally at least 5 %, typically about 7 to 30 wt-%, of which comprises reactive C 4 . 7 isoolefins.
• FCC Fluidized Catalytic Cracking
• isoolefins include the following compounds: 1- isobutene, 2-methyl-l-butene, 2-methyl-2-butene, 2-methyl-l-pentene, 2-methyl-2- pentene, 2,3-dimethyl-l-butene, 2,3-dimethyl-2-butene, 2-ethyl-l-butene, 2-methyl-2- hexene, 2,3-dimethyl-l-pentene, 2,3-dimethyl-2-pentene, 2,4-dimethyl-l-pentene, 2- ethyl-1-pentene and 2-ethyl-2-pentene.
• Suitable hydrocarbon feedstocks for etherification processes are formed by pyrolysis C 5+ gasoline, Thermofor Catalytic Cracking (TCC) Gasoline, Residual Catalytic Cracking (RCC) Gasoline and Coker Gasoline.
• a side stream is taken from the main fractionator (column) used in the etherification process, said side draw being circulated into a separator, wherein it is divided into a low-boiling fraction (light fraction) and a high- boiling fraction (heavy fraction). At least a part of the high-boiling fraction is returned to the column, and at least a part of the low-boiling fraction is circulated to at least one second reaction zone where it is subjected to an etherification reaction in the presence of a catalyst and subsequently returned to the distillation column.
• said division of the side draw into two fractions is performed by distillation, whereby the fraction being conducted into the second reaction zone comprises the distillate.
• the distillate is cooled and alkanol used in the etherification reaction is mixed into it to form a reaction mixture and, subsequently, the mixture is conducted into the second reaction zone.
• a part of the product from the reaction zone is returned to distillation, and a part of the condensated effluent is returned to distillation before adding alkanol.
• the catalysts in the first and second reaction zones are preferably essentially comprised of cation exchange resins which are commonly used in etherification reactions.
• the catalysts used in the reaction zones can be alike or different, whereby in the latter case, the catalyst type can be accurately selected to suit the hydrocarbon feed of the reaction zone in question.
• the present side rectifying arrangement is combined with a reactive distillation column system comprising at least one side reactor connected to a main column intended for separating the products.
• a reactive distillation column system comprising at least one side reactor connected to a main column intended for separating the products.
• both feedstock and product streams flow in the column between the side reactor product return and the bottom part of the main column.
• the feedstock stream contains very little 2M1B and slightly more 2M2B plus some alkanol, e.g., methanol, and product stream contains the tertiary ether, such as TAME.
• at least one reactor is needed through which the unreacted components can be circulated.
• the bottoms product of the main column cannot be circulated straight through the reactor, because 1) the reaction requires more alkanol (e.g., methanol), which will remain in the product due to the equilibrium reaction, and 2) there is a large amount of tertiary alkyl ether (e.g. TAME) and it reacts back to its reactants, whereby the total conversion rate is lowered.
• alkanol such as methanol
• TAME tertiary alkyl ether
• a separator such as a distillation column, is used to separate the product, e.g., TAME and other heavier hydrocarbons, from the side stream taken from the distillation column before conducting the side stream into a new reactor, in the following termed the side rectifying reactor.
• Heavy hydrocarbons are returned into the distillation column as separator bottoms product. Because the etherification reaction is a equilibrium reaction, unreacted methanol remains in the product of the side rectifying reactor. The reactor product is therefore recycled into the main column where the methanol is removed from the bottoms product by distillation.
• All of the stream which has flown through the side rectifying reactor can be returned to the column, but the stream can also be divided into side streams, some of which are returned to the separator, some combined with the bottoms product of the separator, some combined with the bottoms product of the distillation column and/or some mixed into the product from the reaction zone in the reactive distillation column system.
• alkanol e.g., methanol
• methanol e.g., methanol
• the required additional methanol may be fed at the other feed points of the distillation reactor system (e.g., the side reactor), because, due to the C 5 methanol azeotrope, methanol constitutes one of the lightest components of the side rectifying column. In the preparation of TAME, this part of the process contains no C 4 , or very little thereof.
• the separator in the side rectifying unit consists of a conventional distillation column (e.g., a valve, bubble-cap or sieve-tray column or a packed column) and the side rectifying reactor consists of a flow-through reactor.
• the circulation between the column and the reactor can be achieved either as a forced circulation by means of a pump or according to the thermosiphon principle, whereby the thermo- siphon phenomenon is caused by the reaction heat boiling the reaction liquid.
• the reactor can be a fixed bed reactor, a tubular reactor or a fluidized bed reactor or any combination of these reactor types, or several reactors arranged in series. In a system operating according to the thermosiphon principle, only a fixed bed or tubular reactor can be used.
• Ion exchange resins in particular acid cation exchange resins, can be used as catalysts.
• the resin comprises a sulfonated polystyrene/divinyl benzene based cation exchange resin (sulfonated polystyrene cross-linked with divinylbenzene).
• zeolites can also be used as etherification catalysts.
• the resin may contain sulfonic acid groups and it can be obtained by polymerization or copoly- merization of aromatic vinyl compounds followed by sulfonation.
• aromatic ' vinyl compounds suitable for preparing polymers of copolymers are: styrene, vinyl toluene, vinyl naphthalene, vinyl ethyl-benzene, methyl styrene, vinyl chlorobenzene and vinyl xylene.
• the acid cation exchange resin typically contain some 1.3 to 1.9 sulfonic acid groups per aromatic nucleus.
• Preferred resins are based on copolymers of aromatic monovinyl compounds with aromatic poly vinyl compounds, particularly, divinyl compounds, in which the poly vinyl benzene content is from about 1 to 20 wt-% of the copolymer.
• the ion exchange resin preferably has a granular size of about 0.1 to 1 mm.
• perfluorosulfonic acid resins which are copolymers of sulfonyl fluorovinyl ethyl and fluorocarbon can be used.
• TAME and heavier ether products such as tert-amyl ethyl ether (TAEE) and tert-hexyl methyl ether
• TAME methyl ether
• the invention provides the advantage that the conversion of TAME and heavier ethers is increased to a significant degree.
• the conversion of TAME reaches at least 91.0 % (4.1 % increase) and that of THME 49.2 % (3.1 % increase). Even higher levels of conversion can be achieved by further optimizing the process.
• the prereactor consists of a reactor filled with an ion exchange resin bed.
• the reactor may be of the fixed bed, fluidized bed or tubular reactor type. Instead of one reactor, two or more reactors can be used arranged in series or in parallel. If there are more than two prereactors, these may also be arranged in series/parallel.
• the reaction causes a temperature rise in the prereactor of about 5 to 15 °C.
• distillation column 1 From the prereactor the mixture is conducted to distillation column 1.
• a steam reboiler 10 is fitted at the bottom of the distillation column.
• the distillation column may be a packed column or have valve, sieve or bubble-cap trays.
• the overhead of the column is removed via a condenser 3 to a reflux drum 4, from which a part of the overhead is forwarded to further processing, for instance to an MTBE process, and a part thereof is returned to the column.
• the reflux ratio of the column is preferably about 1/2 to 1000. In industrial-scale columns, a reflux ratio of about 50 to 700 is typically used. In pilot plant equipments, even greater ratios can be used.
• a side reactor system represented in this case by one reactor 5 for the sake of simplicity, is arranged next to the distillation column 3.
• the reactor can be a fixed bed or fluidized bed reactor or a tubular reactor, as stated above in the general part of the description.
• the side reactor is fed with a liquid stream taken from the column, and the pressure of the liquid stream is increased before the reactor.
• additional methanol is fed into the side reactor feed and if needed, the feed is then cooled to the reaction temperature.
• the temperature in the side reactor only rises by a few degrees.
• From the side reactor system 5 the flow is routed back to column 2.
• the reactor effluent is fed into the column at a level below the feed from the prereactor 1 in order to allow the ether products to be removed by distillation from the the side reactor system 5 feed.
• a side rectifying column 6 is connected to the lower part of column 2 and fed by a drawoff from the main column 2 below the side reactor 5 reactor effluent return point.
• the feed may consist of gas or liquid. If it consists of gas, the side rectifying column 6 does not necessarily require a reboiler of its own, as the gas flow required by the distillation process already reaches the side rectifying column 6 along with the feed. If the feed consists of liquid, the side rectifying column 6 requires a reboiler of its own. If a reboiler is provided in the side rectifying column 6, the feed can be introduced at a point other than the bottom of the column.
• the side rectifying column 6 contains a sufficient number of trays (or other such separating steps) allowing for the division of the side stream into two fractions, the lighter fraction containing a significantly reduced amount of ethers in comparison with the side rectifying column 6 feed.
• the overhead vapor of the side rectifying column 6 are condensed in the condensor 7 and gathered into the reflux drum 8. A part of the liquid obtained is pumped back to the column 6 and a part to the reactor 9. If needed, methanol can be added to the stream routed into the reactor 9. 96/01244 PC ⁇ YFI95/00380
• the reactor 9 can also be located after the reflux drum 8 before the separation of the distillate of the column 6 and the reflux flow, as shown in Fig. 2.
• the side rectifying column 6 is operated as described in our application FI-921174. Then, a distillate mainly containing a mixture of C 4 hydrocarbons and methanol in the form of an azeotrope is drawn from the column 6.
• the reactor 9 feed is in this case not taken from the top of the column 6, i.e., from the distillate, but rather from a suitable point between the column 6 feed and the top of the column, as no signifact amounts of C 5 hydrocarbons are desirable at the top of the column 6.
• methanol is added into the reactor 9 feed which is then fed through reactor 9.
• the reactor product obtained from reactor 9 is returned to the main column 2 in a manner similar to the arrangement in Figs. 1 and 2.
• the distillate of the main column 2 contains unreacted methanol, and if a part of the distillate of the main column 2 is routed to the top of column 6, it will not be necessary ' to add methanol into reactor 9.
• the equipment comprised a main column (2) with 30 theoretical trays; 3 prereactors (1); and 2 side reactors (5).
• the feed consisted of FCC light gasoline containing
• the main column (2) contained 30 theoretical trays.
• the operational parametres were: Reflux ratio 97
• the equipment further included 3 prereactors (1), which were operated at the following temperatures:
• the side rectifying column (6) comprised 10 theoretical trays, and the operational parametres were:
• the reactor (9) of the side rectification system was operated at 60 to 62 °C
• the feed consisted of FCC light gasoline having the following composition: Hydrocarbons/ % by weight
• the main column (2) comprised 30 theoretical trays, and the operational parametres thereof were:
• the 2 side reactors (5) were operated at the following temperatures:
• the temperature range in the reactor (9) of the side rectifying unit was 60 to 61 °C
• the feed consisted of FCC light gasoline containing:

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Crystallography & Structural Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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Cited By (2)

Citations (4)

• 1994
  • 1994-07-01 FI FI943187A patent/FI95024C/fi active
• 1995
  • 1995-06-30 AU AU27947/95A patent/AU2794795A/en not_active Abandoned
  • 1995-06-30 WO PCT/FI1995/000380 patent/WO1996001244A1/en active Application Filing

Patent Citations (4)

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