Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J10/00—Chemical processes in general for reacting liquid with gaseous media other than in the presence of solid particles, or apparatus specially adapted therefor
  • B01J10/002—Chemical processes in general for reacting liquid with gaseous media other than in the presence of solid particles, or apparatus specially adapted therefor carried out in foam, aerosol or bubbles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J19/24—Stationary reactors without moving elements inside
  • B01J19/2455—Stationary reactors without moving elements inside provoking a loop type movement of the reactants
  • B01J19/2465—Stationary reactors without moving elements inside provoking a loop type movement of the reactants externally, i.e. the mixture leaving the vessel and subsequently re-entering it
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J4/00—Feed or outlet devices; Feed or outlet control devices
  • B01J4/001—Feed or outlet devices as such, e.g. feeding tubes
  • B01J4/004—Sparger-type elements
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C11/00—Aliphatic unsaturated hydrocarbons
  • C07C11/02—Alkenes
  • C07C11/107—Alkenes with six carbon atoms
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
  • C07C2/02—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition between unsaturated hydrocarbons
  • C07C2/04—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition between unsaturated hydrocarbons by oligomerisation of well-defined unsaturated hydrocarbons without ring formation
  • C07C2/06—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition between unsaturated hydrocarbons by oligomerisation of well-defined unsaturated hydrocarbons without ring formation of alkenes, i.e. acyclic hydrocarbons having only one carbon-to-carbon double bond
  • C07C2/08—Catalytic processes
  • C07C2/26—Catalytic processes with hydrides or organic compounds
  • C07C2/32—Catalytic processes with hydrides or organic compounds as complexes, e.g. acetyl-acetonates

Definitions

• the present invention relates to an oligomerization process implemented in a gas / liquid reactor comprising a loop for recycling the gas overhead.
• the process relates to the oligomerization of ethylene into linear alpha-olefins such as 1-butene, 1-hexene, 1-octene or a mixture of linear alpha-olefins.
• the invention relates to the field of oligomerization processes using gas / liquid reactors also called bubble column. Due to the exothermic nature of the oligomerization reactions, the bubble columns also include a recirculation loop consisting in withdrawing a liquid fraction, cooling it and reintroducing it into the reaction chamber. Said recirculation loop makes it possible to obtain good homogeneity of the concentrations and to control the temperature throughout the reaction volume, due to the good heat transfer capacity associated with the recirculation loop.
• gas phase also called gas headspace.
• said gaseous sky comprises gaseous compounds that are not very soluble in the liquid phase, compounds that are partially soluble in the liquid but inert, as well as gaseous ethylene not dissolved in said liquid.
• the transition of gaseous ethylene from the liquid phase to the gas phase (or sky) is a phenomenon called piercing.
• the gaseous sky is purged in order to eliminate said gaseous compounds.
• the purging of the gas head causes a significant loss of ethylene, which is detrimental to the productivity and cost of the oligomerization process.
• the Applicant has described methods in applications W02019 / 011806 and W02019 / 011609 making it possible to increase the contact surface between the upper part of the liquid fraction and the gaseous sky by means of dispersion or vortex means in order to promote the passage of the ethylene contained in the gas overhead towards the liquid phase at the level of the liquid / gas interface.
• these processes are not sufficient when the quantity of ethylene in the gas overhead is large due to a high rate of piercing.
• the Applicant has observed that in a reactor operating at a constant flow rate of injected ethylene gas, the quantity of dissolved ethylene and therefore the rate of piercing depends on the dimensions of the reactors implementing the process and in particular the height of the liquid phase. In fact, the lower the height, the lower the time during which the gaseous ethylene travels through the liquid phase to dissolve and the higher the piercing rate.
• the applicant has discovered a new process implementing a step of recycling the gas overhead in the lower part of the liquid phase, making it possible to optimize the dissolution of the gaseous ethylene used in the process, and to regulate the pressure. within the reactor without causing any loss of ethylene, regardless of the dimensions of the reactor used.
• the process allows the selective production of linear alpha-olefins such as 1-butene, 1-hexene, 1-octene.
• Another advantage of the recycling step according to the invention is to make it possible to compensate in a simple and economical manner the phenomenon of piercing of gaseous ethylene in the gas overhead in an oligomerization process regardless of the dimensions of the reactor.
• the present invention relates to an oligomerization process implemented in a gas / liquid reactor at a pressure between 0.1 and 10.0 MPa, at a temperature between 30 and 200 ° C comprising the following steps: a) A step of introducing a catalytic oligomerization system comprising a metal catalyst and an activating agent, into a reaction chamber comprising a liquid phase in a lower zone and a gas phase in an upper zone,
• step d) A step of cooling the fraction withdrawn in step c) by passing said fraction through a heat exchanger
• step d) A step of introducing the fraction cooled in step d) in the upper part of the lower zone of the reaction chamber,
• the liquid phase in the lower zone of the reaction chamber has a saturation level of dissolved ethylene greater than 70.0%.
• the gas phase withdrawn in step f) is introduced as a mixture with the gaseous ethylene introduced in step b).
• the flow rate for withdrawing the gaseous fraction in step f) is between 0.1 and 100% of the flow rate of gaseous ethylene introduced in step b).
• the introduction of the gas fraction withdrawn in step f) is carried out at the level of the lower lateral part of the reaction chamber.
• the flow rate for withdrawing the gaseous fraction in step f) is controlled by the pressure within the reaction chamber.
• a second purge gas stream is withdrawn from the gas phase.
• the flow rate of the second gas stream is between 0.005 and 1.00% of the ethylene flow rate introduced in step b).
• a flow of gaseous hydrogen is introduced into the reaction chamber, with a flow rate representing 0.2 to 1.0% by weight of the flow of ethylene entering.
• the concentration of catalyst in the catalytic system is between 0.1 and 50.0 ppm by mass of atomic metal relative to the reaction mass.
• the catalytic oligomerization reaction is carried out continuously.
• the linear olefins obtained comprise from 4 to 20 carbon atoms.
• the invention also relates to a device for implementing the ethylene oligomerization process described above comprising:
• reaction chamber i of elongated shape along the vertical axis comprising a liquid phase located in a lower zone comprising, and preferably consisting of, the products of the reaction, dissolved and gaseous ethylene, of a catalytic system and a possible solvent, and
• gas phase located in an upper zone above the lower zone comprising gaseous ethylene, as well as non-condensable gases (notably methane),
• a recirculation loop iv comprising a withdrawal means at the base (preferably at the bottom) of the reaction chamber for the withdrawal of a liquid fraction to a heat exchanger allowing the cooling of said liquid, and an introduction means of said cooled liquid, said introduction being carried out in the liquid phase in the upper part of the lower zone of the reaction chamber,
• a loop for recycling the gas overhead v) to the lower zone of the liquid phase comprising a means for withdrawing a gaseous fraction at the level of the gas phase of the reaction chamber and a means for introducing said fraction gas withdrawn in the liquid phase in the lower zone of the reaction chamber.
• the introduction of the withdrawn gas fraction is carried out by means of the means for introducing gaseous ethylene ii).
• the introduction of the gaseous fraction withdrawn from the recycling loop v) is carried out through a gas distributor.
• oligomerization is understood to mean any reaction of addition of a first olefin to a second olefin, identical or different from the first.
• the olefin thus obtained has the crude formula C n H 2n where n is equal to or greater than 4.
• alpha-olefin is understood to mean an olefin on which the double bond is located at the terminal position of the alkyl chain.
• catalytic system is meant the mixture of at least one metal catalyst and at least one activating agent, optionally in the presence of at least one additive and optionally in the presence of at least one solvent.
• liquid phase means the mixture of all the compounds which are in a liquid physical state under the temperature and pressure conditions of the reaction chamber.
• gas phase also called a gaseous sky, is understood to mean the mixture of all the compounds which are in the physical gas state under the temperature and pressure conditions of the reaction chamber: in the form of bubbles present in the liquid , and also in the upper part of the reactor (reactor ceiling).
• lower zone of the reaction chamber is understood to mean the part of the chamber comprising the liquid phase, gaseous ethylene, the products of the reaction such as the desired linear alpha olefin (ie butene-1, hexene-1 , octene-1), and the catalytic system.
• upper zone of the reaction chamber is meant the part of the chamber located at the top of the chamber, that is to say directly above the lower zone and consisting of the gas overhead.
• lower lateral part of the reaction chamber is meant a part of the reactor casing located in the lower part and on the side.
• non-condensable gas is understood to mean a species in the physical form of a gas which dissolves only partially in the liquid at the temperature and pressure conditions of the reaction chamber, and which can, under certain conditions, accumulate in the head of the reactor ( example here: ethane).
• t / h we mean the value of a flow expressed in tonnes per hour and per kg / s, the value of a flow in kilograms per second.
• reactor or device denote all of the means allowing the implementation of the oligomerization process according to the invention, such as in particular the reaction chamber and the recirculation loop.
• the lower part preferably designates the lower quarter of the reaction chamber.
• fresh gaseous ethylene is meant the ethylene external to the process introduced in step b) by means ii) of the process according to the invention.
• the present invention relates to an oligomerization process implemented in a gas / liquid reactor at a pressure between 0.1 and 10.0 MPa, at a temperature between 30 and 200 ° C comprising the following steps:
• step d) A step of cooling the fraction withdrawn in step c) by passing said fraction through a heat exchanger
• step d) A step of introducing the fraction cooled in step d) in the upper part of the lower zone of the reaction chamber,
• the flow of gaseous ethylene introduced in step b) is controlled by the pressure in the reaction chamber.
• the flow rate of gaseous ethylene introduced in step b) decreases which results in a decrease of the quantity of ethylene dissolved in the liquid phase, therefore of the ethylene saturation. Said decrease is detrimental to the conversion of ethylene and is accompanied by a decrease in the productivity of the reactor, and possibly in its selectivity.
• the process according to the invention has a degree of saturation of ethylene dissolved in the liquid phase greater than 70.0%, preferably between 70.0 and 100%, preferably between 80.0 and 100%, preferably between between 80.0 and 99.0%, preferably between 85.0 and 99.0% and even more preferably between 90.0 and 98.0%.
• the degree of saturation in dissolved ethylene can be measured by any method known to those skilled in the art and for example by gas chromatographic analysis (commonly called GC) of a fraction of the liquid phase withdrawn from the reaction chamber. .
• GC gas chromatographic analysis
• Another advantage of the recycling step according to the invention is to make it possible to compensate in a simple and economical manner the phenomenon of piercing of gaseous ethylene in the gas overhead in an oligomerization process, whatever the dimensions of the reactor.
• the oligomerization process according to the invention allows the production of linear alpha olefins by bringing ethylene into contact with a catalytic system and optionally in the presence of a solvent.
• the catalytic systems comprise, preferably consist of:
• a metal precursor preferably based on nickel, titanium, or chromium
• the metallic precursor used in the catalytic system is chosen from compounds based on nickel, titanium or chromium.
• the metal precursor is based on nickel and preferably comprises nickel of oxidation degree (+11).
• the nickel precursor is chosen from nickel (II) carboxylates such as, for example, nickel 2-ethylhexanoate, nickel (II) phenates, nickel (II) naphthenates, nickel acetate ( ll), nickel trifluoroacetate (ll), nickel triflate (ll), nickel acetylacetonate (ll), nickel hexafluoroacetylacetonate (ll), TT-allylnickel (ll) chloride, nickel bromide TT-allylnickel (ll), methallylnickel (ll) chloride dimer, h 3 hexafluorophosphate - allylnickel (ll), the hexafluorophosphate of r
• the metal precursor is based on titanium and preferably comprises an aryloxy or alkoxy compound of titanium.
• the titanium alkoxy compound advantageously corresponds to the general formula [Ti (OR) 4 ] in which R is a linear or branched alkyl radical.
• R is a linear or branched alkyl radical.
• preferred alkoxy radicals mention may be made, by way of nonlimiting example, of: tetraethoxy, tetraisopropoxy, tetra-n-butoxy and tetra-2-ethyl-hexyloxy.
• the titanium aryloxy compound advantageously corresponds to the general formula [Ti (OR ′) 4] in which R ′ is an aryl radical which may or may not be substituted by alkyl or aryl groups.
• R ′ radical may contain substituents based on a heteroatom.
• the preferred aryloxy radicals are chosen from phenoxy, 2-methylphenoxy, 2,6-dimethylphenoxy,
• the metal precursor is based on chromium and preferably comprises a chromium (II) salt, a chromium (III) salt, or a salt of different oxidation degree which may contain one or more identical anions. or different, such as, for example, halides, carboxylates, acetylacetonates, alkoxy or aryloxy anions.
• the chromium-based precursor is chosen from CrCl 3 , CrCl 3 (tetrahydrofuran) 3 , Cr (acetylacetonate) 3 , Cr (naphthenate) 3 , Cr (2-ethylhexanoate) 3 , Cr (acetate) 3 .
• the concentration of nickel, titanium or chromium is between 0.01 and 300.0 ppm by mass of atomic metal relative to the reaction mass, preferably between 0.02 and 100.0 ppm, preferably between 0, 03 and 50.0 ppm, more preferably between 0.5 and 20.0 ppm and even more preferably between 2.0 and 50.0 ppm by weight of atomic metal relative to the reaction weight.
• the activating agent is between 0.01 and 300.0 ppm by mass of atomic metal relative to the reaction mass, preferably between 0.02 and 100.0 ppm, preferably between 0, 03 and 50.0 ppm, more preferably between 0.5 and 20.0 ppm and even more preferably between 2.0 and 50.0 ppm by weight of atomic metal relative to the reaction weight.
• the catalytic system further comprises one or more activating agents chosen from aluminum-based compounds such as methylaluminum dichloride (MeAICI 2 ), dichloroethylaluminum (EtAICI 2 ), sesquichloride of ethylaluminum (Et 3 AI 2 CI 3 ), chlorodiethylaluminum (Et 2 AICI), chlorodiisobutylaluminum (i-Bu 2 AICI), triethylaluminum (AIEt 3 ), tripropylaluminum (Al (n- Pr) 3 ), triisobutylaluminum ( Al (i-Bu) 3 ), diethyl-ethoxyaluminum (Et 2 AIOEt), methylaluminoxane (MAO), ethylaluminoxane and modified methylaluminoxanes (MMAO).
• aluminum-based compounds such as methylaluminum dichloride (MeAICI 2 ), dichloroe
• the catalytic system comprises one or more additives.
• the additive is chosen from,
• - compounds of nitrogen type such as trimethylamine, triethylamine, pyrrole, 2,5-dimethylpyridine, pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-methoxypyridine, 3 -methoxypyridine, 4-methoxypyridine, 2-fluoropyridine, 3-fluoropyridine, 3-tri f I u ro m éthy I py ri dine, 2-phenylpyridine,
• nitrogen type such as trimethylamine, triethylamine, pyrrole, 2,5-dimethylpyridine, pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-methoxypyridine, 3 -methoxypyridine, 4-methoxypyridine, 2-fluoropyridine, 3-fluoropyridine, 3-tri f I u ro m éthy I py ri dine, 2-phenylpyridine,
• phosphine type independently chosen from tributylphosphine, triisopropylphosphine, tricyclopentylphosphine, tricyclohexylphosphine, triphenylphosphine, tris (o-tolyl) phosphine, bis (diphenylphosphino) ethane, trioctylphosphine oxide, triphenylphosphine, triphenylphosphite, or
• R 1a and R 1b groups are independently chosen from methyl, trifluoromethyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, cyclohexyl, adamantyl groups, substituted or not, containing or not containing heteroelements; phenyl, o-tolyl, m-tolyl, p-tolyl, mesityl groups,
• the R 2 group is independently selected from methyl, trifluoromethyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, pentyl, cyclohexyl, adamantyl, substituted or unsubstituted groups, containing heteroelements or not ; phenyl, o-tolyl, m-tolyl, p-tolyl, mesityl, 3,5-dimethylphenyl, 4-n-butylephenyl, 4-methoxyphenyl, 2-methoxyphenyl, 3-methoxyphenyl, 4-methoxyphenyl, 2-isopropoxyphenyl, 4-methoxy-3,5-dimethylphenyl, 3,5-ditert-butyl-4-methoxyphenyl, 4-chlorophenyl, 3,5- bis (trifluoromethyl) phenyl, benzyl, naph
• the additive is chosen from diethyl ether, diisopropyl ether, dibutyl ether, diphenyl ether, 2-methoxy-2-methylpropane, 2-methoxy-2-methylbutane, dimethoxy- 2,2 propane, di (2-ethylhexyloxy) - 2,2 propane, 2,5-dihydrofuran, tetrahydrofuran, 2-methoxytetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2,3-dihydropyran, tetrahydropyran, 1, 3-dioxolane, 1, 3-dioxane, 1, 4-dioxane, dimethoxyethane, di (2-methoxyethyl) ether, benzofuran, glyme and diglyme taken alone or as a mixture.
• the additive is chosen from diethyl ether, diisopropyl ether, dibutyl ether
• - compounds of nitrogen type such as trimethylamine, triethylamine, pyrrole, 2,5-dimethylpyrrole, pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-methoxypyridine, 3 -methoxypyridine, 4-methoxypyridine,
• M is chosen from magnesium, calcium, strontium and barium, preferably magnesium,
• R 3 is an aryl radical containing from 6 to 30 carbon atoms
• X is a halogen or an alkyl radical containing from 1 to 20 carbon atoms
• n is an integer which can take the values of 0 or 1
• y is an integer between 1 and 10, preferably y is equal to 1, 2, 3 or 4.
• the aryloxy radical R s O is chosen from 4-phenylphenoxy, 2-phenylphenoxy, 2,6-diphenylphenoxy, 2,4,6-triphenylphenoxy, 2, 3,5,6-tetraphenylphenoxy, 2-tert-butyl-6-phenylphenoxy, 2,4-ditertbutyl-6-phenylphenoxy, 2,6-diisopropylphenoxy, 2,6-dimethylphenoxy, 2,6-ditert-butylphenoxy, 4-methyl-2 , 6-ditert-butylphenoxy, 2,6-dichloro-4-tert-butylphenoxy and 2,6-dibromo-4-tert-butylphenoxy.
• the two aryloxy radicals can be carried by the same molecule, such as for example the biphenoxy radical, binaphthoxy or 1, 8-naphthalene-dioxy,
• the aryloxy radical R s O is 2,6-diphenylphenoxy, 2 -tert-butyl-6-phenylphenoxy or 2,4-ditert-butyl-6-phenylphenoxy.
• the catalytic system optionally comprises one or more solvents.
• the solvent is chosen from the group formed by aliphatic and cycloaliphatic hydrocarbons such as hexane, cyclohexane, heptane, butane or isobutane.
• the solvent used is cyclohexane.
• a solvent or a mixture of solvents can be used during the oligomerization reaction.
• Said solvent is advantageously chosen independently from the group formed by aliphatic and cycloaliphatic hydrocarbons such as hexane, cyclohexane, heptane, butane or isobutane.
• the linear alpha olefins obtained comprise from 4 to 20 carbon atoms, preferably from 4 to 18 carbon atoms, preferably from 4 to 10 carbon atoms, and preferably from 4 to 8 carbon atoms.
• the olefins are linear alpha-olefins, selected from but-1-ene, hex-1-ene or oct-1-ene.
• the oligomerization process is carried out at a pressure of between 0.1 and 10.0 MPa, preferably between 0.2 and 9.0 MPa and preferentially between 0.3 and 8.0 MPa, at a temperature between 30 and 200 ° C, preferably between 35 and 150 ° C and preferably between 45 and 140 ° C.
• the catalyst concentration in the catalytic system is between 0.1 and 50.0 ppm by mass of atomic metal relative to the reaction mass, preferably between 0.4 and 30.0 ppm, preferably between 0 , 6 and 20.0 ppm, preferably between 0.8 and 10.0 ppm and preferably between 1.0 and 6.0 ppm by weight of atomic metal relative to the reaction weight.
• the oligomerization process is carried out batchwise.
• the catalytic system constituted as described above, is introduced into a reactor fitted with the usual stirring, heating and cooling devices, then pressurized with ethylene to the desired pressure, and the temperature is adjusted to the desired pressure. desired value.
• the oligomerization device is maintained at constant pressure by introducing gaseous ethylene until the total volume of liquid produced represents, for example, from 2 to 50 times the volume of the catalytic solution introduced beforehand.
• the catalyst is then destroyed by any usual means known to those skilled in the art, then the reaction products and the solvent are withdrawn and separated.
• the oligomerization process is carried out continuously.
• the catalytic system formed as described above, is injected at the same time as the ethylene into a reactor stirred by conventional mechanical means known to those skilled in the art or by external recirculation, and maintained at the desired temperature.
• the components of the catalytic system can also be injected separately into the reaction medium.
• the gaseous ethylene is introduced through a pressure-controlled inlet valve, which maintains the latter constant in the reactor.
• the reaction mixture is withdrawn by means of a valve controlled by the liquid level so as to keep the latter constant.
• the catalyst is destroyed continuously by any usual means known to those skilled in the art, then the products resulting from the reaction as well as the solvent are separated, for example by distillation. Ethylene which has not been converted can be recycled to the reactor.
• the catalyst residues included in a heavy fraction can be incinerated.
• the method according to the invention comprises a step a) of introducing a catalytic system comprising a metal catalyst and an activating agent, and optionally a solvent or a mixture of solvents, into a reaction chamber comprising a liquid phase in a lower zone and a gas phase in an upper zone.
• the introduction of the catalytic system is carried out in the liquid phase in the lower part of the reaction chamber and preferably in the bottom of the reaction chamber.
• the pressure of introduction into the reaction chamber is between 0.1 and 10.0 MPa, preferably between 0.2 and 9.0 MPa and preferably between 0.3 and 8.0 MPa.
• the temperature of introduction into the reaction chamber is between 30 and 200 ° C, preferably between 35 and 150 ° C and more preferably between 45 and 140 ° C.
• the method according to the invention comprises a step b) of bringing the catalytic system introduced in step a) into contact with gaseous ethylene.
• Said gaseous ethylene is introduced into the liquid phase at the lower part of the reaction chamber, preferably on the lower lateral part of the reaction chamber.
• the introduced gaseous ethylene comprises fresh gaseous ethylene, and preferably, said fresh gaseous ethylene is combined with recycled gaseous ethylene at a separation step subsequent to the oligomerization process.
• the liquid phase comprises undissolved gaseous ethylene, thus depending on the zones of the reaction chamber, the liquid phase liquid phase corresponds to a gas-liquid mixture between in particular the liquid phase and gaseous ethylene.
• the area in the bottom of the reaction chamber below the level of introduction of the gaseous ethylene comprises, preferably consists of the liquid phase without gaseous ethylene.
• the gaseous ethylene is distributed by dispersion during its introduction into the lower liquid phase of the reaction chamber by a means suitable for producing said dispersion uniformly over the entire section of the reactor.
• the dispersion means is chosen from a distribution network with a homogeneous distribution of the ethylene injection points over the entire section of the reactor.
• the speed of the gaseous ethylene leaving the orifices is between 1.0 and 30.0 m / s. Its surface speed (volume speed of gas divided by the section of the reaction chamber) is between 0.5 and 10.0 cm / s and preferably between 1.0 and 8.0 cm / s.
• the gaseous ethylene is introduced at a flow rate of between 1 and 250 t / h, preferably between 3 and 200 t / h, preferably between 5 and 150 t / h and preferably between 10 and 100 t / h .
• the flow of gaseous ethylene introduced in step b) is controlled by the pressure in the reaction chamber.
• a flow of gaseous hydrogen can also be introduced into the reaction chamber, with a flow rate representing 0.2 to 1.0% by mass of the incoming ethylene flow.
• the flow of gaseous hydrogen is introduced through the pipe used for the introduction of the gaseous ethylene.
• Step c) withdrawing a fraction of the liquid phase
• the method according to the invention comprises a step c) of withdrawing a fraction of the liquid phase, preferably in the lower part of the reaction chamber.
• the withdrawal carried out in step c) is preferably carried out in the lower part of the reaction chamber, preferably below the level of the injection of gaseous ethylene, and preferably in the bottom of the. pregnant.
• the withdrawal is carried out by any means suitable for carrying out the withdrawal and preferably by a pump.
• the withdrawal rate is between 500 and 10,000 t / h, and preferably between 800 and 7,000 t / h.
• a second stream is withdrawn from the liquid phase.
• Said second stream corresponds to the effluent obtained at the end of the oligomerization process and can be sent to a separation section located downstream of the device used in the process according to the invention.
• the liquid fraction withdrawn from the liquid phase is divided into two streams.
• the first so-called main stream is sent to cooling step d), and the second stream corresponds to the effluent and is sent to the downstream separation section.
• the flow rate of said second stream is regulated to maintain a constant liquid level in the reactor.
• the flow rate of said second stream is 5 to 200 times lower than the liquid flow rate sent to the cooling step.
• the flow rate of said effluent is 5 to 150 times lower, preferably 10 to 120 times lower and preferably 20 to 100 times lower.
• the method according to the invention comprises a step d) of cooling the liquid fraction withdrawn in step c).
• the cooling step is implemented by the circulation of the main liquid stream withdrawn in step c), through one or more heat exchangers located inside or outside the reaction chamber and preferably outdoors.
• the heat exchanger makes it possible to decrease the temperature of the liquid fraction from 1.0 to 30.0 ° C, preferably between 2.0 and 20 ° C, preferably between 2.0 and 15.0 ° C, preferably between 2.5 and 10.0 ° C, preferably 3.0 to 9.0 ° C, preferably 4.0 to 8.0 ° C.
• the cooling of the liquid fraction makes it possible to maintain the temperature of the reaction medium within the desired temperature ranges.
• the implementation of the liquid cooling step, via the recirculation loop also makes it possible to carry out the stirring of the reaction medium, and thus to homogenize the concentrations of the reactive species throughout the volume. liquid from the reaction chamber.
• the method according to the invention comprises a step e) of introducing the cooled liquid fraction in step d).
• step d) The introduction of the cooled liquid fraction resulting from step d) is preferably carried out in the liquid phase of the reaction chamber, preferably in the upper part of said chamber, by any means known to those skilled in the art. job.
• the rate of introduction of the cooled liquid fraction is between 500 and 10,000 t / h, and preferably between 800 and 7,000 t / h.
• Steps c) to e) constitute a recirculation loop.
• the recirculation loop allows the reaction medium to be stirred, and thus to homogenize the concentrations of the reactive species throughout the liquid volume of the reaction chamber.
• Step f) of recycling a gaseous fraction withdrawn from the gas phase comprises a step f) of recycling a gaseous fraction withdrawn from the gas phase of the reaction chamber and introduced at the level of the bottom of the reaction chamber in the liquid phase, preferably on the lower lateral part of the reaction chamber, preferably at the bottom of the reaction chamber.
• the lower part designates the lower quarter of the reaction chamber.
• Step f) of recycling the gas fraction is also called a recycling loop.
• the withdrawal of the gas fraction implemented in step f) is carried out by any means capable of carrying out the withdrawal and preferably by a compressor.
• An advantage of the recycling step according to the invention is to compensate for the phenomenon of ethylene piercing in the gas overhead.
• the piercing phenomenon corresponds to gaseous ethylene which passes through the liquid phase without dissolving and which passes into the gas sky.
• the drilling then causes an increase in pressure in the reaction chamber.
• the rate of introduction of ethylene in step b) is controlled by the pressure in the reaction chamber.
• the flow rate of gaseous ethylene introduced in step b) decreases which results in a decrease of the quantity of ethylene dissolved in the liquid phase and therefore of the saturation.
• the decrease in saturation is detrimental to the conversion of ethylene and is accompanied by a decrease in the productivity of the reactor.
• the step of recycling a gas fraction according to the invention therefore makes it possible to optimize the saturation of the dissolved ethylene and therefore to improve the volume productivity of the process.
• the gas phase withdrawn in step f) can be introduced into the reaction chamber alone or as a mixture with the gaseous ethylene introduced in step b).
• the gas phase is introduced as a mixture with the gaseous ethylene introduced in step b).
• the gaseous phase withdrawn in step f) is introduced into the reaction chamber by dispersion in the lower liquid phase of the reaction chamber by means capable of producing said dispersion uniformly over the entire surface.
• the dispersion means is chosen from a distribution network with a homogeneous distribution of the injection points of the gas phase withdrawn in step f) over the entire section of the reactor.
• the speed of the gas fraction withdrawn at the outlet of the orifices is between 1.0 and 30.0 m / s. Its surface speed (volume speed of gas divided by the cross section of the reaction chamber) is between 0.5 and 10.0 cm / s and preferably between 1.0 and 8.0 cm / s.
• the fraction withdrawal flow rate is between 0.1 and 100% of the ethylene gas flow introduced in step b), preferably 0.5 and 90.0%, preferably 1.0 and 80.0%, preferably between 2.0 and 70.0%, preferably between 4.0 and 60.0%, preferably between 5.0 and 50.0%, preferably between 10.0 and 40, 0% and preferably between 15.0 and 30.0%.
• the flow rate for withdrawing the gaseous fraction in step f) is controlled by the pressure within the reaction chamber, which makes it possible to maintain the pressure at a desired value or range and therefore to compensate for the phenomenon of piercing ethylene gas in the air.
• the gas fraction withdrawn in step f) is divided into two streams, a first so-called main gas stream is recycled directly into the reaction chamber, and a second gas stream.
• said second gas stream corresponds to a purge of the gas overhead, which makes it possible to remove part of the non-condensable gases.
• the flow rate of the second gas stream is between 0.005 and 1.00% of the ethylene flow rate introduced in step b), preferably between 0.01 and 0.50%.
• reactors implementing a liquid phase and a gas phase consist of a reaction chamber comprising a liquid phase in a lower zone comprising gaseous ethylene and a gas phase in an upper zone, a recirculation loop of a liquid fraction to a heat exchanger allowing the cooling of the liquid fraction before it is reinjected into the main enclosure.
• the flow rate of the recirculation loop makes it possible to obtain good homogenization of the concentrations and to control the temperature in the liquid phase within the reaction chamber.
• the reaction device implemented by the process according to the invention belongs to the field of gas / liquid reactors such as bubble columns.
• the reaction device according to the invention comprises the following elements:
• reaction chamber i of elongated shape along the vertical axis comprising a liquid phase located in a lower zone comprising, and preferably consisting of, the products of the reaction, dissolved and gaseous ethylene, a catalytic system and an optional solvent, and a gas phase located in an upper zone above the lower zone comprising gaseous ethylene, as well as non-condensable gases (especially ethane),
• a recirculation loop iv comprising a withdrawal means at the base (preferably at the bottom) of the reaction chamber for the withdrawal of a liquid fraction to a heat exchanger allowing the cooling of said liquid, and an introduction means of said cooled liquid, said introduction being carried out in the liquid phase in the upper part of the lower zone of the reaction chamber,
• a loop for recycling the gaseous phase v) in the lower zone of the liquid phase comprising a means for withdrawing a gaseous fraction at the level of the gaseous phase of the reaction chamber and a means for introducing said gaseous fraction withdrawn in the liquid phase in the lower zone of the reaction chamber.
• the reaction chamber is cylindrical in shape and has a height to width ratio (denoted H / D) of between 1 and 17, preferably between 1 and 8, preferably between 2 and 7 and preferably between 2 and 4.
• H / D height to width ratio
• the reaction chamber comprises means for purging the non-condensable gases at the level of the gas phase.
• the reaction chamber also comprises a pressure sensor, making it possible to control the pressure within the reaction chamber, and preferably to keep the pressure constant.
• said pressure is kept constant by introducing gaseous ethylene into the reaction chamber.
• the gas overhead recycle loop advantageously makes it possible, in the event of drilling of the ethylene, to maintain at a given value the saturation of ethylene dissolved in the liquid phase of the lower zone.
• the reaction chamber also comprises a liquid level sensor, said level is kept constant by modulating the flow rate of the effluent withdrawn in step c).
• the level sensor is located at the interphase between the liquid phase and the gaseous sky. ii) a means of introducing ethylene
• the reaction chamber i) comprises a means for introducing gaseous ethylene located in the lower part of said chamber, more particularly in the lower lateral part.
• the means of introduction ii) of the ethylene is chosen from a pipe, a network of pipes, a multi-tube distributor, a perforated plate or any other means known to those skilled in the art.
• the means for introducing ethylene is located in the recirculation loop iv).
• a gas distributor which is a device making it possible to disperse the gas phase uniformly over the entire liquid section, is positioned at the end of the introduction means ii) within the reaction chamber i).
• Said device comprises a network of perforated pipes, the diameter of the orifices of which is between 1.0 and 12.0 mm, of preferably between 3.0 and 10.0 mm, to form bubbles of ethylene in the liquid of millimeter size.
• the reaction chamber i) comprises a means of introduction iii) of the catalytic system.
• the introduction means iii) is located on the lower part of the reaction chamber, and preferably at the bottom of said chamber.
• the introduction of the catalytic system is carried out in the recirculation loop.
• the means of introduction iii) of the catalytic system is chosen from any means known to those skilled in the art and preferably is a pipe.
• said solvent is introduced by an introduction means located in the lower part of the reaction chamber, preferably at the bottom of the reaction chamber or in the recirculation loop. iv) a recirculation loop
• the homogeneity of the liquid phase, as well as the regulation of the temperature within the reaction chamber, are achieved by the use of a recirculation loop comprising means on the lower part of the chamber. reaction, preferably at the bottom, to carry out the withdrawal of a liquid fraction to one or more heat exchanger (s) allowing the cooling of said liquid, and a means for introducing said cooled liquid into the liquid phase in the part upper part of the reaction chamber.
• a recirculation loop comprising means on the lower part of the chamber. reaction, preferably at the bottom, to carry out the withdrawal of a liquid fraction to one or more heat exchanger (s) allowing the cooling of said liquid, and a means for introducing said cooled liquid into the liquid phase in the part upper part of the reaction chamber.
• the recirculation loop can advantageously be implemented by any means necessary and known to those skilled in the art, such as a pump for withdrawing the liquid fraction, a means capable of regulating the flow rate of the withdrawn liquid fraction, or still a line for purging at least part of the liquid fraction.
• the means for withdrawing the liquid fraction from the reaction chamber is a pipe.
• the heat exchanger (s) capable of cooling the liquid fraction is (are) chosen from any means known to those skilled in the art.
• the device comprises a loop for recycling the gas phase in the lower part of the liquid phase.
• Said loop comprising a means for withdrawing a gas fraction from the gas phase of the reaction chamber and a means for introducing said gas fraction withdrawn into the liquid phase in the lower part of the reaction chamber.
• the recycle loop advantageously makes it possible to compensate for the phenomenon of piercing and to avoid increasing the pressure in the reaction chamber, while maintaining the saturation of ethylene dissolved in the liquid phase at a desired value.
• the recycle loop further comprises a compressor.
• the introduction of the withdrawn gaseous fraction is carried out through the means of introducing gaseous ethylene ii).
• the introduction of the withdrawn gaseous fraction is carried out via a gas distributor which is a device for dispersing the gas phase uniformly over the entire liquid section, is positioned at the end of the means of introduction into the reaction chamber i).
• Said device comprises a network of perforated pipes, the diameter of the orifices of which is between 1.0 and 12.0 mm, preferably between 3.0 and 10.0 mm, to form bubbles of ethylene in the liquid of size millimeter.
• the means for introducing the gas fraction withdrawn is chosen from a pipe, a network of pipes, a multitubular distributor, a perforated plate or any other means known to those skilled in the art. DESCRIPTION OF FIGURES
• FIG. 1 illustrates a reaction device according to the prior art.
• This device consists of a reaction chamber (1) comprising a lower zone comprising a liquid phase A and an upper zone comprising a gas phase B, a means for introducing gaseous ethylene (2) via of a gas distributor (3) in the liquid phase A.
• the gas phase B comprises a purge means (4).
• At the bottom of the reaction chamber (1) is a pipe for withdrawing a liquid fraction (5). Said fraction (5) is divided into 2 streams, a first main stream (7) sent to a heat exchanger (8) then introduced via a pipe (9) into the liquid phase A and a second stream ( 6) corresponding to the effluent sent to a later stage.
• Line (10) in the bottom of the reaction chamber allows the introduction of the catalytic system.
• Figure 2 illustrates a device for implementing the method according to the invention. Said device differs from the device of FIG. 1 in that a gaseous fraction of the gas phase B is sent to a compressor (11) and is recycled via a pipe (12) connected to the means for introducing gaseous ethylene (2 ) in the lower part of zone A comprising the liquid phase A.
• Example 1 comparison corresponding to figure 1
• the ethylene oligomerization process is carried out in a bubble column type reactor.
• the reactor is operated at a pressure of 5.0 MPa and a temperature of 120 ° C.
• the reaction volume is composed, in accordance with the figure in 1, in two zones A and B, in a column of 2.97 m in diameter and 6.0 m in liquid height, and of a recirculation loop having a volume total of 5.0 m 3 .
• the column is fitted with an ethylene gas injection device, located 1.0 m from the bottom of the column.
• the catalytic system introduced into the reaction chamber is a chromium-based catalytic system with a chromium content of 4.37 ppm, as described in patent FR3019064, in the presence of cyclohexane as solvent.
• the purge flow is equal to 0.0045 kg / s.
• the volume productivity of this reactor is 0.134 tonnes of hexene-1 produced per hour and per m 3 of reaction volume.
• hexene-1 The production of hexene-1 is 6.25 tonnes / hour, the selectivity for hexene-1 is 81.2% by weight, and the residence time in the reactor is 76 minutes, for a solvent mass rate of 1 , 0. Said solvent level is calculated as the mass ratio of the flow rate of solvent injected over the flow rate of gaseous ethylene injected.
• the oligomerization process according to the invention is implemented in a device of identical dimensions to that implemented in Example 1, further comprising and in accordance with the invention a loop for recycling the gas overhead in the liquid phase as described in Figure 2.
• the ethylene oligomerization process is implemented in a bubble column type reactor. The reactor is operated at a pressure of 5.0 MPa and a temperature of 120 ° C.
• the catalytic system introduced into the reaction chamber is a chromium-based catalytic system with a chromium content of 4.38 ppm, as described in patent FR3019064, in the presence of cyclohexane as solvent.
• the volume productivity of this reactor is 0.194 tonnes of hexene-1 produced per hour and per m 3 of reaction volume.
• the performance of the oligomerization process according to the invention makes it possible to have a dissolved ethylene saturation of 90.0%.
• hexene-1 The production of hexene-1 is 9.06 tonnes / hour, the selectivity for hexene-1 is 83.3% by weight, and the residence time in the reactor is 52.5 minutes, for a rate mass of solvent of 1.0. Said solvent rate is calculated as the mass ratio of the flow rate of solvent injected over the flow rate of injected ethylene gas.
• the process according to the invention clearly makes it possible to increase the ethylene saturation in the liquid phase, which makes it possible to improve the productivity of the oligomerization process with a lower residence time and a better selectivity in hexene-1. .

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