Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
  • C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
  • C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
  • C01B39/20—Faujasite type, e.g. type X or Y
  • C01B39/22—Type X

Definitions

• the present invention relates to an intensified process for the continuous preparation of zeolite crystals of high crystallinity, controlled size and with a low level of aggregation.
• zeolite synthesis is conventionally carried out in the industry in stirred batch reactor, of large size, generally with heating of the gel. of synthesis and / or of the reaction medium by steam injection and / or double jacket.
• the preparation of the synthesis gel consists in mixing a solution of sodium aluminate with a sodium silicate solution, this mixture can be carried out either in a plant upstream of the crystallization reactor or directly in the crystallization reactor.
• the synthesis medium is first prepared in a batch reactor in a conventional manner and then this gel reservoir continuously feeds a crystallization reactor; in this case, it is called a "semi-continuous” process since part of the process is carried out in a batch reactor (see, for example, Jingxi Ju et al., "Continuous synthesis of zeolite NaA in a microchannel reactor", Chemical Engineering Journal, 1 16, (2006), 115-121, Shumovskii et al., “Continuous process for the production of zeolite in pulsation apparatus," Chemical and Petroleum Engineering, 31 (5-6), (1995), 253-256; Zhendong Liu et al., "Ultrafast Continuous-flow synthesis of crystalline microporous AIP04-5", Chem. Mater., 2-7, (2014); US 4848509 or US 6773694);
• the synthesis medium is continuously prepared using a shear mixer and is then crystallized batch reactor in a conventional manner (see for example the documents EP0149929 and BE 869156);
• the synthesis medium is continuously prepared and feeds a reactor continuously to achieve crystallization.
• the first two categories are therefore not strictly speaking "continuous" processes since at least part of the synthesis is performed in batch.
• the literature available on the subject however relates only to batch processes and the ultrasound is applied only cold (maximum temperature at 50 ° C - 70 ° C), mainly on the mixture of reagents (synthetic gel) during the ripening phase.
• the application of higher temperature ultrasound for intensified continuous zeolite preparation processes, ie where the nucleation rate must be as high as possible, is however neither described nor suggested in the prior art.
• CN 103848436 describes a conventional synthesis of zeolite A, in batch, with a long curing time, greater than 20 hours, at 35-45 ° C and crystallization between 80 and 120 ° C and 20-50 sonication Hz for 10 to 30 minutes.
• the necessary ripening time in this synthesis makes this process incompatible with the economic requirements of an industrial process.
• the application of ultrasound is presented in a possible washing step
• the CN105271298 document describes a method of upgrading coal gangue, composed of alumina and silica, which crystallizes a zeolite type LTA.
• a first heat treatment is required to "activate" the gangue which is then mixed with water under ultrasonic irradiation.
• the reaction medium is subjected to a ripening step, and the crystallization is carried out by heating the reaction medium.
• This method does not, however, correspond to an intensified process, within the meaning of the present invention, in particular because the ultrasonic irradiation step is carried out for the preparation of the activated gangue in an aqueous medium.
• the synthesis temperature is 25 ° C, and no indication regarding the ultrasonic bath is provided (frequency / power conditions).
• the batch synthesis time is furthermore totally incompatible with economically feasible industrial synthesis.
• the objective of the increase of the crystallization temperature is to accelerate the growth kinetics of the crystals to decrease the duration of the crystallization.
• the disadvantage of such a crystallization known as "hot crystallization" is that it remains difficult to conduct, and can, when it is poorly conducted, lead to a degradation of the crystallinity of the solid formed or a co-crystallization of phases. unwanted.
• the application of ultrasound to further improve this step remains to explore.
• Some publications relate the application of ultrasound to simulate agitation of the reaction medium or to disintegrate clusters of materials, agglomerates of crystals and the like.
• the present invention relates to an intensified continuous process for the synthesis of zeolite crystals, said process comprising a continuous feed of a gel prepared continuously, said gel being then crystallized continuously, said process comprising less an application of ultrasound.
• the crystallization step of the gel is carried out continuously, that is to say without transient phase in batch.
• the process of the present invention makes it possible in particular to synthesize zeolite crystals of very high purity, that is to say having a purity equal to or greater than 95%, preferably equal to or greater than 98%, and of still preferably between 98% and 100%, as determined by quantitative XRD analysis.
• the process according to the present invention generally allows the synthesis of zeolite crystals of particle size (number average diameter determined by counting on SEM plates) ranging from 0.05 pm to 20 pm, preferably from 0.1 pm to 20 ⁇ m, more preferably from 0.2 ⁇ m to 10 ⁇ m, and more preferably from 0.3 ⁇ m to 8 ⁇ m, most preferably from 0.3 ⁇ m to 5 ⁇ m.
• the aggregation of the crystals is evaluated by size measurement using the laser diffraction particle size analysis technique with a device of the Malvern Mastersizer 3000 type, as explained for example by Jordens et al., Ibid.
• the subject of the present invention is a process for the preparation of zeolite crystals continuously, comprising at least the following steps:
• step b) continuously recovering the crystals formed in step b).
• composition capable of generating zeolite crystals is meant in the sense of the present invention, any type of composition well known to those skilled in the art depending on the type of zeolite to be prepared.
• a composition typically comprises at least one source of silica and at least one source of alumina and / or any other source element (s) may constitute a zeolite framework, such as for example source of phosphorus, titanium, zirconium, and other.
• the "composition capable of generating zeolite crystals" comprises a gel prepared continuously, as mentioned above.
• the composition capable of generating zeolite crystals consists of the continuously prepared gel defined above.
• the continuously prepared gel comprises at least one source of silica and a source of alumina and / or any other source of element (s) that can constitute a zeolite framework, such as for example a source of phosphorus, titanium, zirconium, and other.
• composition may be added optionally, but preferably, at least one aqueous solution of alkali metal hydroxide or alkaline earth metal, preferably alkali metal, typically sodium and / or organic structuring agents (" structure-directing agent "or" template "in English).
• alkali metal hydroxide or alkaline earth metal preferably alkali metal, typically sodium and / or organic structuring agents
• sica source any source well known to those skilled in the art and in particular a solution, preferably aqueous, silicate, in particular alkali or alkaline earth metal silicate, for example sodium or colloidal silica.
• alumina source any source of alumina well known to those skilled in the art and in particular a solution, preferably aqueous, of aluminate, in particular of alkali metal or alkali metal aluminate. earthy, for example sodium.
• concentrations of the various solutions of silica and alumina are adapted according to the nature of the silica source, the source of alumina, the respective proportions of the sources of alumina and silica to which are added the solution of alkali metal or alkaline earth metal hydroxide and / or one or more organic structuring agents, according to the knowledge of those skilled in the art.
• TMA tetramethylammonium
• TPA tetra-n-propylammonium
• MTEA methyltriethylammonium
• the intensification of the process results from the implementation of ultrasound, in other words the intensification of the process results from the application at one or more locations along the continuous process, frequency ultrasound and well-defined power, the power and frequency may vary from one ultrasound source to another, fulfilling one or more of the following objectives:
• Ultrasound is applied at at least one point of the continuous synthesis of zeolite crystals, for example in the crystallization zone (to promote the formation of crystals) and / or in the end-of-synthesis zone (to disaggregate possible aggregates of crystals), but also in the ripening zone, etc.
• Ultrasound can be applied continuously, or sequenced or alternated or a combination of these different methods.
• the application of ultrasound in a liquid medium creates an acoustic cavitation.
• This acoustic cavitation in the liquid medium depends on a large number of sonochemical parameters (such as, for example, frequency, power, reactor geometry, and the like), and operating conditions (such as, for example, pressure, temperature, dissolved gas, and others) which directly affect the sonochemical effects obtained.
• Ultrasound is generally produced by a device called transducer, in particular based on the properties of piezoelectric materials, which converts electrical energy into mechanical energy. This mechanical vibration is transmitted in the reaction medium in the form of an acoustic wave.
• Piezoelectric transducers use the inverse piezoelectric effect of natural or synthetic monocrystals such as quartz or ceramics such as barium titanate. These materials are easily machinable in the form of disks, plates or rings on the faces of which are fixed two metal electrodes. Thus, when an electric voltage is applied to these electrodes, the material expands or compresses depending on the orientation of the voltage relative to the polarization of the material, for example ceramic.
• Ultrasonic Apparatus adapted for the purposes of the invention may for example be selected from devices transducer device, such as those marketed for example by Weber Ultrasonics Company-under Sonopush Duotransducer ® HD denominations, Multi Sonoplate , Flow-Through Cell, or those marketed by the Hielscher Company, for example the UP200S, to name a few of them, without being limiting.
• devices transducer device such as those marketed for example by Weber Ultrasonics Company-under Sonopush Duotransducer ® HD denominations, Multi Sonoplate , Flow-Through Cell, or those marketed by the Hielscher Company, for example the UP200S, to name a few of them, without being limiting.
• the frequency of ultrasound applied largely depends on the desired effect and the nature of the medium to which they are applied. This frequency is generally between 10 kHz and 5 MHz, preferably between 10 kHz and 1.5 MHz, more preferably between 15 kHz and 1 MHz, very particularly preferably between 15 kHz and 500 kHz, typically between 15 kHz and 200 kHz.
• the acoustic power of ultrasound that is dissipated in the medium largely depends on the desired effect and the nature of the medium to which the ultrasound is applied.
• This acoustic power is directly related to the electrical power supplied by the generator.
• the electric power supplied by the generator is generally between 3 W and 500 W, preferably between 5 W and 400 W, more preferably between 8 W and 300 W.
• the ultrasounds applied are with relatively low powers, typically of powers less than 100 W.
• the Crystal size (number average diameter) tends to decrease as the power of the applied ultrasound increases.
• the ultrasounds applied are with higher powers, typically powers greater than 100 W. In this case, the size of the agglomerates decreases with the power of applied ultrasound.
• the ultrasonic exposure time of the continuous synthesis medium can vary in large proportions depending on the desired effect, depending on the nature of the reaction medium and others.
• the fraction of the ultrasonic exposure time with respect to the residence time of the reaction medium in the continuous reactor is between 0.05% and 50%, preferably between 0.1% and 30%, more preferably 0.1% and 20%, more preferably between 0.1% and 10%, inclusive.
• the ultrasound can be applied continuously, sequentially or alternately, the continuous application at one or more points throughout the continuous synthesis process is however preferred. Any other combination of ultrasound applications, with variations in application time and / or frequency variations, or even variations in power are of course possible and within the abilities of those skilled in the art.
• the duration of ultrasonic exposure, as well as the power of ultrasound applied per unit volume of gel have an influence on the kinetics of crystallization and on the disintegration of the zeolite crystals. Crystals tend to form more quickly when exposure time and / or applied power increases. Likewise, the disintegration of the crystals is greater when the duration of exposure and / or the power applied increases.
• the process of the present invention may be conducted at any temperature that the skilled person will adapt according to the type of zeolite to be produced and the degree of intensification of the desired process.
• the process according to the invention is carried out at a temperature of between 70 ° C. and 180 ° C., preferably between 75 ° C. and 160 ° C., more preferably between 80 ° C. and 140 ° C. .
• the reaction temperature can be advantageously set between 75 ° C. and 180 ° C., preferably between 80 ° C. and 140 ° C., to obtain an optimal compromise between degree of intensification. of the process and purity of the crystals obtained.
• the method of the present invention may optionally comprise one or more steps of adding seed (s) to the reaction medium.
• seed in the synthesis medium makes it possible to obtain even greater crystallization kinetics to be compatible with the constraints of a continuous process.
• the addition (s) of seed (s) can or can be performed (s) by any means known to those skilled in the art and for example using a static mixer which has the advantage of promoting the homogenization of the synthesis medium / seed mixture.
• Seed also called “seeding agent”
• seeding agent is understood to mean a solid or a liquid which promotes the orientation of the synthesis towards the desired zeolite.
• the method of the invention comprises the addition, in one or more times, before, after or during the crystallization step, of one or more seeding agents. This addition of sowing agent (s) notably makes it possible to substantially accelerate the crystallization step.
• seeding agent or seed
• seed is meant a solution or a suspension, in liquid form or in gel form, of a solid or a liquid which promotes the orientation of the synthesis towards the zeolite desired.
• the seeding agents are well known to those skilled in the art and are for example chosen from nucleating gels, zeolite crystals, mineral particles of any kind, and the like, and mixtures thereof.
• the seeding agent is a nucleation gel and more preferably, said nucleating gel comprises a homogeneous mixture of a source of silica (for example sodium silicate), a source of alumina (for example alumina trihydrate), optionally but advantageously a strong mineral base, such as, for example, sodium hydroxide, potassium hydroxide, or calcium hydroxide, to mention only the main and most commonly used, and water .
• a source of silica for example sodium silicate
• a source of alumina for example alumina trihydrate
• a strong mineral base such as, for example, sodium hydroxide, potassium hydroxide, or calcium hydroxide, to mention only the main and most commonly used, and water .
• One or more structuring agents typically organic structuring agents, may also optionally be introduced into the nucleation gel.
• the method of the invention may comprise a step allowing the suppression or at least the reduction of the post-grinding step by ultrasonic irradiation at the end of synthesis, where the Crystals are usually milled "dry" after filtration and drying, the drying step having the effect of making more resistant aggregates, so more difficult to dislocate.
• the application of ultrasound according to the process of the present invention makes possible the disintegration in a humid environment, before separation of the mother liquors, which makes it possible to reduce the overall energy balance of the process.
• the process of the present invention makes it possible to propose an industrial process which benefits from the advantages of Continuous synthesis by minimizing or even eliminating problems related to fouling of installations.
• the method of the present invention allows the preparation of any type of zeolites known to those skilled in the art and for example, and in a non-limiting manner, any MFI-type zeolite, and in particular silicalite, any MOR-type zeolite, OFF type, MAZ type, CHA type and HEU type type, all zeolite type FAU, and especially zeolite Y, zeolite X, zeolite MSX, zeolite LSX, any zeolite EMT type or any zeolite of the LTA type, that is to say zeolite A, as well as the other zeotypes, such as, for example, titanosilicalites.
• any MFI-type zeolite and in particular silicalite
• any MOR-type zeolite OFF type
• MAZ type MAZ type
• CHA type and HEU type type all zeolite type FAU
• zeolite Y zeolite X
• zeolite MSX Medium Silica X
• zeolite LSX Low Silica X
• zeolite LSX a zeolite of FAU type having an Si / Al atomic ratio equal to about 1.
• the process according to the invention is particularly suitable for the preparation of zeolites chosen from MFI-type zeolites, and in particular silicalite, of the FAU type, and in particular zeolite Y, zeolite X, zeolite MSX, zeolite LSX, and type LTA, that is to say zeolite A, as well as type zeolites CHA and zeolites type HEU.
• zeolites chosen from MFI-type zeolites, and in particular silicalite, of the FAU type, and in particular zeolite Y, zeolite X, zeolite MSX, zeolite LSX, and type LTA, that is to say zeolite A, as well as type zeolites CHA and zeolites type HEU.
• the process according to the invention is furthermore particularly suitable for the preparation of any zeolite of the FAU type, and in particular zeolite X, zeolite MSX, zeolite LSX.
• zeolite X zeolite X
• zeolite MSX zeolite MSX
• zeolite LSX zeolite LSX.
• the MFI-type zeolites, and especially silicalite can also be very advantageously prepared according to the process of the invention.
• the continuous preparation process of the present invention is not limited to the preparation of the zeolites described above, but also includes the corresponding zeolites with hierarchical porosity.
• the zeolites with hierarchical porosity are solids, well known to those skilled in the art, comprising a microporous network linked to a mesopore network, and thus make it possible to reconcile the properties of accessibility to the active sites of the mesoporous zeolites known in the art. and those of maximum crystallinity and microporosity of so-called "conventional" zeolites (without mesoporosity).
• it is generally used specific agents called structuring agents which are introduced into the synthesis medium, for example structuring agents of the organosilane type, as for example described in the document FR1357762.
• the present invention relates to the use of ultrasound, during the synthesis of zeolite crystals continuously at a reaction temperature of between 70 ° C. and 180 ° C., preferably between 75 ° C. and 160 ° C, more preferably between 80 ° C and 140 ° C, said ultrasound being used at a frequency between 10 kHz and 5 MHz, preferably between 10 kHz and 1.5 MHz, more preferably between 15 kHz and 1 MHz, most preferably between 15 kHz and 500 kHz, typically between 15 kHz and 200 kHz.
• the purity of the synthesized zeolite crystals is evaluated by X-ray diffraction analysis, known to those skilled in the art under the acronym DRX. This identification is carried out on a DRX device of the brand Bruker.
• the zeolite crystals are crushed then spread and smoothed on a sample holder by simple mechanical compression.
• the amount of crystals, by weight, is determined by XRD analysis, this method is also used to measure the amount of non-crystalline phases. This analysis is carried out on a Bruker brand apparatus, then the quantity by weight of the zeolite crystals is evaluated using the Bruker TOPAS software. The purity is expressed as mass percentage of desired crystalline phase relative to the total weight of the sample.
• Crystallinity analysis The crystallinity of the zeolite crystals is estimated by conventional methods such as measurements of Dubinin volumes (adsorption of liquid nitrogen at 77 K), or toluene adsorption indices (adsorption capacities of toluene to a relative pressure of 0.5 to 25 ° C after 2 hours exposure as described in EP11 16691 A or US6464756 B).
• Example 1 Continuous process without ultrasound at 80 ° C.
• Sodium zeolite X crystals (NaX) are prepared from sodium aluminosilicate and sodium silicate solutions, with a step of addition of seeding agent.
• 100 ml of reaction medium are prepared by mixing at 80 ° C. the sodium silicate and sodium aluminosilicate solutions in a mixer with a high shear rate.
• the crystallization is carried out at 80 ° C for 2 hours, by circulating the reaction medium with a flow rate of 60 mL.min 1 to pass into a tubular reactor of 0.5 cm in diameter and 22, 5 cm in length, said reactor being equipped with a plateau transducer located outside the tube, but which remains inactive for this example.
• Example 2 Continuous process with ultrasound at 80 ° C.
• X-shaped zeolite crystals are prepared from solutions of sodium aluminosilicate and sodium silicate, with a step of addition of seeding agent.
• 100 ml of reaction medium are prepared by mixing at 80 ° C the sodium silicate and sodium aluminosilicate solutions in a high shear mixer.
• the crystallization is carried out at 80 ° C for 2 hours, by circulating the reaction medium with a flow rate of 60 mL.min 1 to pass into a tubular reactor of 0.5 cm in diameter and 22, 5 cm long which is, for the purposes of this example, exposed to ultrasound generated using the plateau transducer whose frequency is equal to 34.5 kHz.
• the electric power of the generator is fixed at 40 W.
• the ultrasound is applied continuously only at the tubular reactor, which corresponds to a continuous circulation of the synthesis gel with ultrasonic point irradiation.
• FIGS 1 and 2 show that in the absence of ultrasound, the zeolite crystals to achieve a toluene adsorption (T50) of about 24% are obtained after 120 minutes (Example 1, Figure 1). ). With the application of ultrasound (Example 2, Figure 2), the zeolite crystals to achieve a toluene adsorption (T50) of about 24% are obtained from 80 minutes, which demonstrates the great interest of the use of ultrasound for the intensified process for preparing continuous zeolite crystals according to the present invention. It is therefore observed that the synthesis time can be greatly reduced (1/3 less time in Example 2) by applying ultrasound, without degradation of the adsorption properties of the zeolite obtained. This corresponds to an intensification of the process for the preparation of zeolites, continuously.

Landscapes

• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Materials Engineering (AREA)
• Inorganic Chemistry (AREA)
• Silicates, Zeolites, And Molecular Sieves (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=61750420

Family Applications (1)

Country Status (5)

Families Citing this family (1)

Family Cites Families (18)

• 2018
  • 2018-01-15 FR FR1850299A patent/FR3076828A1/fr active Pending
• 2019
  • 2019-01-11 WO PCT/EP2019/050682 patent/WO2019138069A1/fr unknown
  • 2019-01-11 CN CN201980019447.4A patent/CN112088143A/zh active Pending
  • 2019-01-11 US US16/961,844 patent/US11292724B2/en active Active
  • 2019-01-11 EP EP19700291.8A patent/EP3740453A1/de active Pending

Also Published As

Similar Documents

Legal Events