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  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
  • B01F23/2331—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the introduction of the gas along the axis of the stirrer or along the stirrer elements
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
  • B01F23/2335—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the direction of introduction of the gas relative to the stirrer
  • B01F23/23352—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the direction of introduction of the gas relative to the stirrer the gas moving perpendicular to the axis of rotation
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
  • B01F23/2336—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the location of the place of introduction of the gas relative to the stirrer
  • B01F23/23362—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the location of the place of introduction of the gas relative to the stirrer the gas being introduced under the stirrer
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
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  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/2366—Parts; Accessories
  • B01F23/2368—Mixing receptacles, e.g. tanks, vessels or reactors, being completely closed, e.g. hermetically closed
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  • B01J19/18—Stationary reactors having moving elements inside
  • B01J19/1868—Stationary reactors having moving elements inside resulting in a loop-type movement
  • B01J19/1881—Stationary reactors having moving elements inside resulting in a loop-type movement externally, i.e. the mixture leaving the vessel and subsequently re-entering it
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  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0201—Impregnation
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  • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
  • B01J8/005—Separating solid material from the gas/liquid stream
  • B01J8/006—Separating solid material from the gas/liquid stream by filtration
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
  • B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
  • B01J8/20—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium
  • B01J8/22—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid
  • B01J8/222—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid in the presence of a rotating device only
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
  • B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
  • B01J8/20—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium
  • B01J8/22—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid
  • B01J8/224—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid the particles being subject to a circulatory movement
  • B01J8/228—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid the particles being subject to a circulatory movement externally, i.e. the particles leaving the vessel and subsequently re-entering it
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B15/00—Peroxides; Peroxyhydrates; Peroxyacids or salts thereof; Superoxides; Ozonides
  • C01B15/01—Hydrogen peroxide
  • C01B15/029—Preparation from hydrogen and oxygen
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
  • B01F27/05—Stirrers
  • B01F27/11—Stirrers characterised by the configuration of the stirrers
  • B01F27/111—Centrifugal stirrers, i.e. stirrers with radial outlets; Stirrers of the turbine type, e.g. with means to guide the flow
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
  • B01F27/05—Stirrers
  • B01F27/11—Stirrers characterised by the configuration of the stirrers
  • B01F27/19—Stirrers with two or more mixing elements mounted in sequence on the same axis
  • B01F27/191—Stirrers with two or more mixing elements mounted in sequence on the same axis with similar elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J2208/00—Processes carried out in the presence of solid particles; Reactors therefor
  • B01J2208/00008—Controlling the process
  • B01J2208/00017—Controlling the temperature
  • B01J2208/00106—Controlling the temperature by indirect heat exchange
  • B01J2208/00168—Controlling the temperature by indirect heat exchange with heat exchange elements outside the bed of solid particles
  • B01J2208/00176—Controlling the temperature by indirect heat exchange with heat exchange elements outside the bed of solid particles outside the reactor
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J2208/00017—Controlling the temperature
  • B01J2208/00106—Controlling the temperature by indirect heat exchange
  • B01J2208/00168—Controlling the temperature by indirect heat exchange with heat exchange elements outside the bed of solid particles
  • B01J2208/00212—Plates; Jackets; Cylinders
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
  • B01J2219/18—Details relating to the spatial orientation of the reactor
  • B01J2219/185—Details relating to the spatial orientation of the reactor vertical
• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/64—Pore diameter
  • B01J35/647—2-50 nm

Definitions

• the present invention relates to a method according to which several gaseous components are reacted in the presence of a solid suspended in a liquid phase.
• the invention also relates to a device for implementing the method.
• the invention more particularly relates to a device and a method for manufacturing hydrogen peroxide directly from oxygen and hydrogen with a catalyst suspended in an aqueous phase.
• the present invention therefore aims to provide a process comprising a reaction step involving several gaseous components in the presence of a solid suspended in a liquid phase and in particular a process for the direct manufacture of hydrogen peroxide safely and with optimal productivity in hydrogen peroxide, as well as a device allowing its implementation.
• the device according to the invention comprises a vertical stirred reactor of cylindrical shape, provided with means for injecting gaseous reagents at the bottom, with outlet means at the top for discharging the gaseous reagents and with several centrifugal turbines arranged, preferably regularly, the along a single vertical stirring tree.
• the vertical shaft is generally driven by a geared motor group, which most often is located either at the top or below the reactor. Depending on its length, the shaft can be supported by one or more bearings.
• the reactor can also be equipped with counter-blades and / or heat exchanger.
• the perfectly stirred reactor consists of a single capacity without a horizontal fixed partition.
• the height of the reactor is generally between 1, 5 and 10 times the diameter and preferably between
• the reactor is also provided with a bottom and a cover which can be flat or semi-spherical.
• FIG. 1 is a simplified diagram of a particular device of the invention.
• the device comprises a vertical stirred reactor (V) provided with several centrifugal turbines (a) arranged along a stirring shaft driven by a motor (M).
• the reactor is also equipped with counter-blades (c) and a heat exchanger (R).
• Injection means (1, 2) of gaseous reagents are provided at the bottom of the reactor and an outlet (3) located at the top of the reactor is used to evacuate the gaseous reagents.
• any type of centrifugal turbine capable of sucking at the level of the central axis of the reactor a mixture of liquid, gas bubbles and solid in suspension, and of projecting this mixture radially along a horizontal plane in order to ensuring a circulation of liquid mixture, gas bubbles and solid according to FIG. 1, may be suitable.
• Flanged radial turbines with one or two central openings are preferred. Flanged turbines similar to those used for centrifugal water pumps with the pumping port pointing downwards are particularly suitable.
• the turbines can be equipped with several blades arranged radially or inclined or in spirals.
• the number of blades is preferably between 3 and 24.
• the number of turbines depends on the ratio of the height of the reactor to the diameter of the reactor and is generally between 2 and 20, preferably between 3 and 8.
• the distance between two turbines is preferably between 0.5 and 1.5 times the outside diameter of the turbine; this is preferably between 0.2 and 0.5 times the diameter of the reactor.
• the thickness of the turbines is preferably between 0.07 and
• thickness is meant the distance between the two flanges of the turbine.
• the device according to the invention can also include a filter installed inside or outside the reactor.
• the lower part of the reactor In operating mode, the lower part of the reactor is occupied by a liquid phase comprising solid catalysts in suspension and a multitude of small bubbles of gaseous reactants, while the upper part is occupied by a continuous gas phase.
• the volume occupied by the continuous gas phase represents between 10 to 30% of the total volume of the reactor and preferably 20 to 25%.
• the turbines are arranged along the stirring shaft so that they are immersed, and preferably completely submerged, in the liquid phase when the stirring is stopped.
• the speed of rotation of the turbine is chosen so as to obtain both the maximum possible gas bubbles per unit volume of liquid phase and a minimum diameter of bubbles.
• the reactor is equipped with counter-blades, preferably made up of several vertical rectangular plates, arranged around the turbines.
• the counter-blades are generally located between the cylindrical wall of the reactor and the turbines.
• the height of these metal plates is generally close to that of the cylindrical part of the reactor.
• the width is generally between 0.05 and 0.2 times the diameter of the reactor.
• the number of counter-blades chosen is determined according to their width and is generally between 3 and 24 and preferably between 4 and 8.
• the counter-blades (c) are preferably placed vertically at a distance between 1 and 10 mm from the wall (p) of the reactor and oriented in the axis of the rays coming from the center of the reactor, as indicated in FIG. 2 which is a cross section of the reactor equipped with a particular turbine with (O) representing the turbine suction port, (f) the turbine flange and (u) the turbine blade.
• the counter-blades can be replaced, in whole or in part, by a heat exchanger.
• the exchanger is preferably constituted by a bundle of vertical cylindrical tubes of a height close to or equal to that of the cylindrical part of the reactor. These tubes (t) are generally arranged vertically around the turbines according to FIG. 2.
• the number and diameter of these tubes are determined in order to keep the temperature of the liquid phase within the desired limits.
• the number of tubes is often between 8 and 64.
• the device according to the invention can be used for carrying out a reaction at atmospheric pressure, it is most often preferred to operate under pressure. High pressures of the order of 10 to 80 bar are advantageously chosen to accelerate the reaction speed.
• the reactor, the stirring means and the exchangers can be made of any standard material from the chemical industry, such as, for example, stainless steel (304 L or 31 6 L).
• a protective polymer coating like PVDF like PVDF
• PTFE polytetrafluoroethylene
• PFA copolymer of C 2 F 4 and perfluorinated vinyl ether
• FEP copolymer of C 2 F 4 and C 3 F 6
• the coating can also be limited to certain elements subject to abrasion, such as for example turbines.
• the device is particularly suitable for the direct manufacture of hydrogen peroxide with hydrogen and oxygen injected in the form of small bubbles, with a diameter of less than 3 mm and preferably between 0.5 and 2 mm, in the aqueous liquid phase with, preferably, molar flow rates such that the molar flow ratio of hydrogen to that of oxygen is greater than 0.041 6, while the hydrogen content in the continuous gas phase is kept below the limit Flammable.
• the catalysts used in general are those described in US Pat. No. 4,724,458. They are solid catalysts based on palladium and / or platinum, optionally supported on silica, alumina, carbon or silicoaluminates.
• the aqueous phase made acidic by the addition of a mineral acid can comprise stabilizers of hydrogen peroxide and decomposition inhibitors such as for example halides. Bromide is particularly preferred and it is advantageously used in combination with bromine in the free state (Br 2 ).
• a second object of the invention is the process comprising a reaction step involving several gaseous components in the presence of a solid suspended in a liquid phase.
• This process consists in introducing the gaseous components (2 or more) at the bottom of the reactor either separately or in the form of a mixture.
• the introduction in the form of a mixture is preferred when the composition of the gas mixture is compatible with the requirements of safety.
• the supply of reagents can be done by a conduit formed in the stirring shaft and then, by a series of small holes drilled in the center of the turbine located at the bottom of the reactor so as to produce a large number of small bubbles in the liquid stream ejected by the turbine.
• the gaseous reagents are introduced separately into the reactor either by injection through separate nozzles situated in front of the suction orifice of the lowest turbine, either by separate sintered tubes located immediately below the lowest turbine. It is possible to operate both continuously and semi-continuously with the device of the present invention.
• the gaseous reactants are introduced continuously for a determined time into the lower part of the reactor, occupied by a liquid phase comprising the catalytic solid in suspension.
• the excess of gaseous reactants arriving in the continuous gas phase of the reactor is generally discharged continuously so as to keep the pressure prevailing inside the reactor constant. At the end of the determined time, the reactor is discharged to recover the reaction products.
• the filter or filters may be of the sintered metal or ceramic filter candle type, preferably placed vertically in the reactor next to the vertical cooling tubes or counter blades.
• the filters can also be placed outside the reactor and in this case, preferably consist of a porous hollow tube, of metal or ceramic, inside which circulates in closed circuit the liquid phase of the reactor comprising the catalyst in suspension.
• a device comprising a filter outside the reactor is illustrated in Figure No. 3.
• the hollow tube (g) is arranged vertically and is fed at its base by the liquid phase taken from the bottom of the reactor, the liquid phase collected in the top of the tube is returned to the top of the reactor.
• This continuous circulation can be done under the action of a pump or under the action of local overpressures created by the agitating turbines of the reactor.
• the clear liquid phase freed from the catalyst is collected in a double envelope (h) placed around the porous hollow tube then, evacuated by a regulating valve (6) so as to keep the level of liquid phase in the reactor constant .
• Reaction solution is pumped continuously into the reactor at a determined rate to maintain the concentration of reaction product soluble in the liquid phase, at a chosen value.
• Part of the reaction solution can advantageously be injected sequentially into the jacket (h) through line 7 to unclog the filter.
• the reaction solution can also be sprayed under high pressure to continuously clean the continuous gas phase of the reactor.
• the gaseous reagents are continuously introduced into the bottom (b) of the reactor via routes 1 and 2 and those which are unreacted can be recycled via route 4.
• a selected flow rate d Hydrogen is injected via (1) into the liquid phase and below the lower turbine (b).
• a selected flow of oxygen containing a small proportion of hydrogen is taken (4) from the continuous gas phase of the reactor and injected into the liquid phase via (2) and below the lower turbine (b).
• a new oxygen flow (5) is injected into the continuous gas phase of the reactor to compensate for the oxygen consumed and also to keep the continuous gas phase outside the flammability limits.
• a pressure regulator (spillway) allows the excess gaseous reagents (3) to be removed from the continuous gas phase of the reactor, as well as inert gases such as nitrogen which are possibly present in the fresh oxygen.
• the device according to the invention has the advantage, in the event of accidental stopping of the agitation, to allow all the bubbles of the gaseous reactants to rise and reach the continuous gaseous phase directly under the sole action of the forces of gravity.
• the reactor with a capacity of 1,500 cm 3 consists of a cylindrical tank 200 mm high and 98 mm in diameter. The bottom and the cover are flat. A removable 1.5 mm thick PTFE sleeve is placed in the reactor bowl
• the agitation is ensured by a vertical axis in stainless steel 1 80 mm long and 8 mm in diameter driven by a magnetic coupling placed on the cover of the reactor.
• One, two or three flanged turbines with an outside diameter of 45 mm, a thickness of 9 mm (between the two flanges) fitted with a suction port of 1 2.7 mm in diameter, facing downwards, and 8 flat radial blades 9 mm wide, 1.5 mm long and 1.5 mm thick, can be fixed to the stirring shaft at different heights chosen so as to divide the liquid phase into substantially equal volumes .
• the lower turbine is placed 32 mm from the bottom, the second turbine 78 mm from the bottom and the third turbine 125 mm from the bottom.
• Cooling or heating is provided by eight vertical tubes of 6.35 mm in diameter and 1 50 mm in length arranged in a crown 35 mm from the axis of the tank.
• This stream is traversed by a stream of water at constant temperature.
• the injection of hydrogen and oxygen into the liquid phase is done by means of two separate 1.58 mm diameter stainless steel pipes leading the gases to the center of the lower turbine.
• the injection of gaseous reactants into the aqueous medium as well as that of oxygen into the continuous gas phase are regulated using mass flowmeters. Certain tests are carried out by replacing the oxygen with an oxygen-nitrogen mixture in different proportions.
• the pressure inside the reactor is kept constant thanks to an overflow valve.
• the hydrogen, oxygen and optionally nitrogen constituting the gas flow leaving the reactor are dosed online by gas phase chromatography.
• the catalyst used contains 0.7% by weight of metallic palladium and 0.03% by weight of platinum supported on a microporous silica.
• An aqueous solution is prepared by adding 1 2 g of H 3 PO 4 , 58 mg of NaBr and 5 mg of Br 2 in 1000 cm 3 of demineralized water.
• the selected volume of aqueous reaction medium is introduced into the autoclave and then the determined quantity of catalyst is added.
• the autoclave is pressurized by injecting a selected flow of oxygen into the continuous gas phase.
• the pressure remains constant thanks to the pressure regulator.
• the liquid medium is brought to the chosen temperature by circulation of water thermostatically controlled in the bundle of cooling tubes.
• Stirring is set at 1,900 rpm and the selected flow rates of oxygen and hydrogen are injected into the center of the lower turbine.
• the flow rate and the hydrogen content of the gas mixture leaving the pressure regulator are measured.
• the aqueous hydrogen peroxide solution recovered is then weighed, then separated from the catalyst by filtration on a Millipore filter.
• the resulting solution is then dosed by iodometry thus making it possible to determine the concentration of hydrogen peroxide.
• the selectivity of the synthesis is defined as being the percentage of the number of moles of hydrogen peroxide formed on the number of moles of hydrogen consumed.
• the conversion rate is defined as the percentage of the volume of hydrogen consumed over the volume of hydrogen introduced.
• Examples 1, 2, 3 and 4 show that for identical temperature, pressure and H 2 / O 2 conditions , increasing the number of radial turbines makes it possible to increase the conversion rate with the same efficiency as by the combination of several cascade reactors.
• Examples 7, 8 and 9 show that, for a reactor and identical reaction conditions, the conversion rate and the content of
• Examples 5 and 6 show that it is possible to obtain, with the reactor according to the invention, a conversion rate of 80% with only
• Examples 1 0 and 1 1 show that the reactor according to the invention makes it possible to obtain high conversion rates and H 2 O 2 concentrations when using an oxygen-nitrogen mixture (10% to 20%) instead pure oxygen.
• Examples 14 and 1 5 also show with another H 2 / O 2 ratio that the passage from 2 turbines to 3 turbines makes it possible to increase the hydrogen conversion rate and to decrease the H 2 concentration in the continuous gas phase of the reactor.

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