FR3143384A1 - Carbonaceous zeolite replica monolith and its preparation method - Google Patents

Abstract

The present invention relates to a method for preparing a carbonaceous replica monolith of zeolite comprising a step of loading a mold reactor with a zeolite in powder form, a step of filling the microporosity of the zeolite and the inter-crystalline space with the two-step injection of two different carbon sources, a step of transforming the carbon sources into carbon by temperature treatment, a step of dissolving the zeolite in order to release the microporosity of the carbonaceous replica and to obtain a monolith composed of a carbonaceous replica of zeolite having hierarchical porosity and good mechanical resistance to crushing. The invention also relates to the monolith and its use as a catalyst support, adsorbent or separation agent.

Description

Carbonaceous zeolite replica monolith and its preparation method

The present invention relates to the field of carbonaceous replicas of zeolites, their manufacture and their use, in particular the preparation of monoliths composed of a microporous material of the carbonaceous replica of zeolite type having good mechanical resistance to crushing.

Carbonaceous replicas of zeolites (or “ZTC” for “zeolite templated carbon” according to Anglo-Saxon terminology) are carbonaceous materials with organized microporosity. Their synthesis is based on the use of zeolites, which have a microporous structure ordered in three dimensions (3D), as a matrix (“template”) and a carbon source which is introduced into the porosity of the zeolite. The carbon source used is introduced in the gas phase (e.g. acetylene, ethylene) or in the liquid phase (e.g. solutions of glycerol, furfuryl alcohol, saccharides). The impregnation step is followed by a high temperature pyrolysis step (typically at a temperature above 850°C) allowing the condensation of the carbon network inside the microporosity but also in the inter-crystalline space of zeolite. The last step consists of the release of the porosity of the carbonaceous replica which is done by dissolving the zeolite matrix with an acid or basic treatment, very often using hydrofluoric acid. The carbonaceous replica of zeolite obtained has an ordered structure of pores which is an inverse replica of the structure of the starting zeolite.

We thus commonly designate by carbonaceous replicas of zeolites, or abbreviated carbonaceous replicas in the present description, such inverse replicas (also called negative) of zeolite structures.

Zeolites are crystalline microporous aluminosilicates having an ordered three-dimensional structure and which find applications in many fields. These materials are formed from a three-dimensional arrangement of interconnected SiO ₄ and AlO ₄ tetrahedra leading to well-defined structures. To date, there are more than two hundred different structures, for example listed on the website of the IZA (International Zeolite Association) synthesis commission, and characterized by their microporous structure comprising windows (pore opening, also called opening of channels) of minimum 8 oxygen atoms (8MR, MR meaning “member ring” according to Anglo-Saxon terminology) and more (10MR, 12MR). Thus an 8MR zeolite is a zeolite having channels (pores) whose opening is defined by a ring with 8 oxygen atoms, a 10MR zeolite having channels whose opening is defined by a ring with 10 oxygen atoms , etc. The micropores of 8MR zeolites have openings typically ranging from 0.3 nm to less than 0.45 nm, the micropores of 10MR zeolites have openings typically ranging from 0.45 nm to less than 0.60 nm, and the micropores of 12 MR zeolites have apertures ranging from 0.60 nm to less than 0.80 nm. More information on zeolites and their definitions can be found in the classification “Atlas of Zeolite Framework Types, 6th revised edition”, Ch. Baerlocher, LB Mc Cusker, DH Olson, 6th Edition, Elsevier, 2007. Dimensions and The arrangement of micropores are key elements that govern the transformation of a zeolite into a successful carbonaceous replica. Among the three-dimensional structures most used for the synthesis of carbonaceous replicas of zeolites we can cite the following zeolite structures: CHA, FAU, MOR, MFI and BEA.

The carbonaceous replicas obtained from zeolites have very high microporous volumes (up to 1.7 cm ³ /g) and specific surfaces beyond 1500 m ² /g and which can reach 4000 m ² /g. (F. Su, L.Lv, TM Hui, XSZhao, Carbon, 43, 2005, 1156-1164).

Carbonaceous replicas of zeolites can be used in industry for the treatment of drinking or waste water, air purification, decolorization of food liquids, as supports for the storage of hydrogen or methane, as catalysts hydrogenation, or for the liquid phase separation of phenolic molecules, monoaromatics or pharmaceutical products (L. Ji, F. Liu, Z.Xu, et al, Environ.Sci.Technol. 2010, 44, 3116-3122 ; Jun Miao et al., Adv. Sci. 2020, 7, 2001335).

To be used in industrial processes, the carbonaceous replicas of zeolites must be shaped to obtain objects of larger size (millimeters or centimeters), and thus facilitate their handling and filling in reactors, but also facilitate the passage of the load in the reactors.

Shaping these materials is difficult, especially to obtain objects without a binder and with good mechanical resistance to crushing.

Atsushi et al. (“High-density monolithic pellets of double-sided graphene fragments based on zeolite-templated carbon”, J. Mater. Chem. A, 2021, 9, 7503) obtained a material containing a carbonaceous replica of zeolite with good mechanical resistance by pelletizing at high pressure (345 MPa) and hot (300°C) a mixture of carbonaceous zeolite replica powders with a reduced carbon oxide used as a binder (5% by weight).

Norah Balahmar et al. (“Templating of carbon in zeolites under pressure: synthesis of pelletized zeolite templated carbons with improved porosity and packing density for superior gas (CO ₂ and H ₂ ) uptake properties”, J. Mater. Chem. A, 2016, 4, 14254) have described a method for preparing a carbonaceous replica of zeolite using a step of pelletizing the zeolite powder at high pressure (370 MPa or 740 MPa) before preparing the carbonaceous replica by chemical vapor deposition (CVD for chemical vapor deposition according to Anglo-Saxon terminology) of furfuryl alcohol and dissolution of the zeolite with solutions of HF and HCl. The size of the crystals used is greater than one micrometer. The carbonaceous replica is formed only inside the microporosity of the zeolite and very little outside. There are no data on the mechanical resistance of the materials obtained.

Lerato Molefe et al. (“Polymer-Based Shaping Strategy for Zeolite Templated Carbons (ZTC) and Their Metal Organic Framework (MOF) Composites for Improved Hydrogen Storage Properties”, Front. Chem. 7:864. doi: 10.3389/fchem.2019.00864, 2019) described the preparation of a monolith type composite but without a well-defined shape by mixing a carbonaceous replica of zeolite (80% by weight) with a PIM-1 type polymer (20% by weight) used as a binder.

Patent application US2020290016 presents a method for obtaining a shaped material containing a carbonaceous replica of zeolite. The method consists of mixing a carbonaceous zeolite replica powder with a binder, typically polyvinyl alcohol, and water followed by pelletizing the mixture at a pressure between 100 MPa and 350 MPa and at temperatures between 400 K and 550 K (approximately 126-277°C). The percentage of the binder is between 5 and 10% by weight. The resulting tablets have a crushing strength of less than 50 MPa, but the size of the tablets is not indicated, making comparison with other materials difficult.

The processes of the prior art show that it is difficult to shape a mixture containing a very high content of carbonaceous replicas of zeolites (e.g. more than 95% by weight) and to obtain a shaped object having good strength. mechanical.

Surprisingly, the inventors have demonstrated that it is possible to produce a shaped material having both hierarchical porosity and good mechanical strength from a direct preparation of a carbonaceous replica monolith.

The present invention aims to overcome, at least in part, the problems of the prior art, and generally aims to provide a simultaneous process for forming and shaping a carbonaceous replica of zeolite, in particular without having to use a binder, leading to the production of a monolith of carbonaceous zeolite replica having hierarchical porosity and good mechanical resistance to crushing.

It is thus very generally aimed at the production of a carbonaceous replica of zeolite in the form of a monolith, which is directly usable in a product or an industrial process, and which is efficient from the point of view of its mechanical resistance and its relative function. to its porous nature (e.g. its adsorption capacity, etc.).

The present invention thus proposes, according to a first aspect, a process for preparing a carbonaceous zeolite replica monolith comprising the following steps:
a) loading a zeolite powder into a reactor;
b) activation of said zeolite loaded into the reactor in step a) at a temperature between 100°C and 300°C under a flow of inert gas;
c) the transformation, in said reactor, of said zeolite activated at the end of step b) into a carbonaceous replica of zeolite comprising a first injection of a source of carbon A in gaseous form followed by the carbonization of said source of carbon A, then a second injection of a source of carbon B in liquid form followed by the carbonization of said source of carbon B, then the dissolution of said zeolite;
d) washing, preferably with water, possibly followed by drying, of said carbonaceous zeolite replica;
e) an activation of said carbonaceous replica of zeolite washed at the end of step d), at a temperature between 100°C and 140°C and under a flow of inert gas, to form said carbonaceous replica monolith.

The present invention makes it possible to obtain a carbonaceous replica of zeolite in the form of a monolith having both hierarchical porosity and high mechanical resistance, in particular thanks to the implementation of filling the porosity of the zeolite in two steps.

According to one or more embodiments, step c) of transforming said zeolite into a carbonaceous replica of zeolite comprises:
c1) the hot injection of said carbon source A into the reactor at the end of step b), at a temperature between 500°C and 700°C, in the form of a gas mixture containing a inert gas and between 7% and 10% by volume of said carbon source A, at a constant flow rate of said gas mixture, preferably 10 ml/min/g of zeolite, and preferably for a period of between 5 hours and 70 hours;
c2) the carbonization of said carbon source A contained in said reactor at the end of step c1) at a temperature between 700°C and 1100°C, under a flow of inert gas, preferably for a duration of between 30 minutes and 4 p.m.;
c3) cooling said reactor at the end of step c2) under a flow of inert gas at an ambient temperature between 18°C and 35°C.
c4) the cold injection of said carbon source B into the reactor at the end of step c3) in the form of a liquid mixture comprising said carbon source B and water at a constant flow rate, preferably 1 ml/min/g of zeolite, for a period of between 45 minutes and 14 hours;
c5) the heat treatment of the reactor at the end of step c4), at a temperature between 90°C and 120°C under a flow of inert gas, for a period of between 30 minutes and 16 hours;
c6) the carbonization of said carbon source B at the end of step c5) at a temperature between 700°C and 1100°C under a flow of inert gas, for a period of between 30 minutes and 16 hours;
c7) cooling the reactor at the end of step c6), under a flow of inert gas, at an ambient temperature between 18°C and 35°C;
c8) dissolving the zeolite contained in the reactor at the end of step c7) with an aqueous solution of hydrofluoric acid (HF) or sodium hydroxide (NaOH), preferably at 40% by weight of HF or NaOH, at a constant liquid flow rate, preferably 1 ml/min/g of zeolite, for a period of between 3 hours and 34 hours.

According to one or more embodiments, the carbon source A is chosen from alkenes comprising from 1 to 6 carbon atoms, preferably from acetylene, ethylene, propylene, taken alone or as a mixture, and the source of carbon B is chosen from monosaccharides, disaccharides, glycerol, furfuryl alcohol, taken alone or in mixture.

According to one or more embodiments, the inert gas used in the different stages is nitrogen.

According to one or more embodiments, the flow of inert gas in the different stages is at a constant flow rate of 10 ml/min/g of zeolite.

According to one or more embodiments, the reactor has a length of between 20 mm and 200 mm and an internal diameter of between 7 mm and 148 mm, and the carbonaceous zeolite replica monolith has a length and a diameter identical to the length and the internal diameter of the reactor.

According to one or more embodiments, the reactor is tubular or half-shell.

According to one or more embodiments, the drying in step d) is carried out by blowing with dry air, at an ambient temperature between 18°C and 35°C, preferably at a constant air flow. of 10 ml/min/g of zeolite, for a period of between 15 minutes and 3 hours.

According to one or more embodiments, the zeolite comprises a microporous structure comprising pores whose opening is greater than or equal to 8MR.

According to one or more embodiments, the zeolite is chosen from zeolites of structure CHA, FAU, MOR, MFI and BEA, alone or as a mixture.

According to one or more embodiments, the carbonaceous zeolite replica monolith has a hierarchical porosity comprising micropores, mesopores and macropores, and:
- a microporous volume of between 0.500 and 0.900 cm ³ .g ^-1 ;
- a mesoporous volume of between 0.500 and 0.600 cm ³ .g ^-1 ;
^- a macroporous volume of between 0.600 and 0.900 cm ³ .g ^-1 ; And
- a total pore volume of between 1,600 and 2,400 cm ³ .g ^-1 .

According to one or more embodiments, the carbonaceous zeolite replica monolith has a grain crushing strength (EGG) greater than or equal to 0.7 daN/mm, preferably greater than or equal to 1 daN/mm.

The invention also relates to a monolith of carbonaceous replica of zeolite comprising more than 95% by weight, preferably more than 98% by weight, more preferably more than 99% by weight, of carbonaceous replica of zeolite, said monolith preferably having a length between 20 mm and 200 mm and a diameter between 7 mm and 148 mm, having a grain crushing strength (EGG) greater than or equal to 0.7 daN/mm, preferably greater than or equal to 1 daN/mm, and having a hierarchical porosity including micropores, mesopores and macropores.

According to one or more embodiments, the monolith has a hierarchical porosity comprising micropores, mesopores and macropores, and:
- a microporous volume of between 0.500 and 0.900 cm ³ .g ^-1 ;
- a mesoporous volume of between 0.500 and 0.600 cm ³ .g ^-1 ;
^- a macroporous volume of between 0.600 and 0.900 cm ³ .g ^-1 ; And
- a total pore volume of between 1,600 and 2,400 cm ³ .g ^-1 .

The invention also relates, according to another aspect, to the use of such a carbonaceous zeolite replica monolith, advantageously obtained according to any of the variants of the process according to the invention, as a catalyst support, adsorbent or detoxifying agent. separation.

According to one or more embodiments, the zeolite carbon replica monolith is used for the liquid phase separation of monosaccharides, such as glucose or fructose, and 5-hydroxymethylfurfural.

Other objects and advantages of the invention will appear on reading the following description of particular embodiments of the invention, given as non-limiting examples.

According to the present invention, the expression “between… and…” means that the limit values of the interval are included in the range of values described, unless otherwise specified.

In this description, the term “comprising” is synonymous with (means the same as) “include” and “contain”, and is inclusive or open and does not exclude other elements that are not mentioned. It is understood that the term “understand” includes the exclusive and closed term “consist”.

In the present description, the different ranges of values of given parameters can be used alone or in combination. For example, a range of preferred pressure values may be combined with a more preferred range of temperature values.

Furthermore, in the following, particular and/or preferred embodiments of the invention can be described. They can be implemented separately or combined with each other, without limitation of combination when technically feasible.

According to the present invention, the hierarchical porosity is a porosity which consists of micropores, mesopores and macropores. According to the IUPAC standard (the International Union of Pure and Applied Chemistry, M. Thommes et al. IUPAC Technical Report, Pure Appl Chem. 2015, 87(9-10); 1051-1069) the pores are divided according to their size in diameter in: micropores with the diameter less than 2 nm, mesopores with the diameter between 2 and 50 nm, and macropores with the diameter greater than 50 nm.

In the present description, ambient temperature (Tamb) means a temperature between 18°C and 35°C, and atmospheric pressure means a pressure of 0.101325 MPa.

In this description, reference is made to the work “Atlas of Zeolite Framework Types, 6th revised edition”, Ch. Baerlocher, L. B. McCusker, D.H. Olson, 6th Edition, Elsevier, 2007, for the definition of zeolite structures mentioned.

Method for preparing monoliths of carbonaceous replicas of zeolites

The subject of the present invention is a process for preparing a carbonaceous zeolite replica monolith having a hierarchical porosity and good mechanical strength, preferably a mechanical resistance to crushing greater than or equal to 0.7 daN/mm, of preferably greater than or equal to 1 daN/mm.

The process comprising at least the following steps:
a) loading a zeolite powder into a reactor, preferably of length between 20 mm and 200 mm and internal diameter of between 7 mm and 148 mm;
b) activation of said zeolite loaded into the reactor in step a) at a temperature between 100°C and 300°C under a flow of inert gas;
c) the transformation, in said reactor, of said zeolite activated at the end of step b) into a carbonaceous replica of zeolite comprising a first injection of a source of carbon A in gaseous form followed by the carbonization of said source of carbon A, then a second injection of a source of carbon B in liquid form followed by the carbonization of said source of carbon B, then the dissolution of said zeolite;
d) washing, preferably with water, possibly followed by drying of said carbonaceous zeolite replica;
e) activation of said washed and dried carbonaceous zeolite replica at the end of step d), at a temperature between 100°C and 140°C and under a flow of inert gas, to form said replica monolith carbonaceous.

In the different stages of the process, and described in more detail below, the inert gas used, which by definition does not participate in any chemical reactions or in very few chemical reactions, under the given conditions of the different stages, can be nitrogen or argon, and is preferably nitrogen for its lower cost.

When a flow of inert gas or gas mixture is used in the stages of the process described below, it is preferably at a constant flow rate, advantageously identical in all the stages of the process where it is implemented, and more preferably the inert gas flow or the gas mixture flow is at a constant flow rate of 10 ml/min/g of zeolite.

All of the stages of the process are advantageously carried out at atmospheric pressure.

The different steps are detailed below.

Step a) loading the zeolite powder into the reactor

The process comprises a first step a) of loading the zeolite powder into a reactor, preferably a tubular or half-shell reactor, said reactor preferably having a length of between 20 mm and 200 mm, with an internal diameter of between 7 mm and 148 mm, and preferably with an external diameter of between 9 mm and 150 mm.

The reactor is preferably of circular section, although a section other than a square section cannot be excluded.

Tubular and half-shell reactors are well-known reactors. In particular, a tubular reactor, also called a “tube or tunnel reactor”, is a cylindrical system in which the charge passes in the axial direction. This type of reactor is often in the form of a cylinder. A half-shell reactor is a cylindrical system constructed in two parts called “half-shell” allowing the system to be opened in the axis, preferably vertical, of the reactor. These tubular and half-shell reactors are conventionally cylindrical in shape.

The reactor typically comprises an envelope delimiting an enclosure receiving the zeolite powder, said enclosure having a shape and dimensions substantially identical to those of the carbonaceous zeolite replica monolith which is formed at the end of the process.

By internal diameter of the reactor, we mean more precisely the internal diameter of the reactor envelope, which corresponds to the diameter of the enclosure. By diameter, it is also necessary to enter an equivalent diameter in the case where the reactor is not cylindrical and has for example a square section. The notion of equivalent diameter is also applicable to the carbonaceous zeolite replica monolith, if it is not cylindrical, like (the enclosure) of the reactor in which it is prepared.

Preferably, the reactor manufacturing material is an alloy chosen from monel and Hastelloy, or any other special steel resistant to an acidic environment, in particular resistant to hydrofluoric acid (HF) in the case where the step of dissolving the zeolite is done with an HF solution.

Preferably, the reactor is of the half-shell type if the carbonaceous zeolite replica monolith obtained is then used in a reactor of larger diameter.

The loading of the zeolite powder in step a) is preferably done at ambient temperature (i.e. 18-35°C), and at atmospheric pressure.

Preferably, the zeolite comprises a microporous structure comprising pores (micropores) with an opening equal to or greater than 8 MR

Such a zeolite is called 8MR zeolite, and corresponds to a zeolite comprising a microporous structure comprising windows, that is to say a pore opening (also called channel opening) of at least 8 oxygen atoms (8MR, MR meaning “in English: member ring” according to Anglo-Saxon terminology).

Typically, 8MR zeolite micropores have openings ranging from 0.3 nm (3 Å) to less than 0.45 nm (4.5 Å).

As an indication, a 10MR zeolite has channels (pores) whose opening is defined by a ring of 10 oxygen atoms, a 12MR zeolite has channels (pores) whose opening is defined by a ring of 12 atoms oxygen etc. 10MR zeolite micropores have apertures typically ranging from 0.45 nm to less than 0.60 nm, and 12 MR zeolite micropores have apertures ranging from 0.60 nm to less than 0.80 nm.

Preferably, the zeolite is chosen from zeolites of structure CHA, FAU, MOR, MFI and BEA, alone or as a mixture, for example a Y zeolite.

Step b) of activation of the zeolite

The process comprises a step of activating the zeolite loaded into the reactor at the end of step a) by a heat treatment at a temperature between 100°C and 300°C, preferably between 120 and 260°C , under a flow of inert gas, preferably a flow of nitrogen, preferably at a constant flow rate of 10 ml/min/g of zeolite, and preferably according to a temperature rise ramp of 5°C/min, for a duration preferably between 2 hours and 10 hours, preferably between 3 hours and 8 hours.

This step of activating the zeolite is a particular heat treatment, which makes it possible to prepare the zeolite for the step of transformation into a carbonaceous replica, in particular which makes it possible to release the porosity of the zeolite. CO ₂ or water, initially contained in the porosity of the zeolite, can be released in gaseous form during this step.

The duration of step b) can be adjusted depending on the quantity of zeolite used.

Step c) of transformation of the activated zeolite) into a carbonaceous replica of zeolite

The process comprises a step c) of transformation, in the reactor, of the zeolite activated at the end of step b) into a carbonaceous replica of zeolite comprising a first injection of a source of carbon A in gaseous form followed by the carbonization of said carbon source A, then a second injection of a carbon source B in liquid form followed by the carbonization of said carbon source B, then the dissolution of said zeolite.

In accordance with the invention, the carbon source A incorporated in the structure of the zeolite is therefore in the gas phase, and the carbon source B incorporated in the structure of the zeolite is in the liquid phase.

Each of the carbon sources is preferentially adapted to fill a level of porosity of the zeolite: the carbon source A, introduced in a gaseous form, primarily fills the microporosity of the zeolite, and the carbon source B, introduced in a form liquid, fills the other porosity levels of the zeolite, the mesoporosity and the macroporosity, and possibly completes the filling of the microporosity of the zeolite.

Filling the porosity of the zeolite in two stages, by using a first carbon source, i.e. the carbon source A, adapted to preferentially filling the microporosity of the zeolite, then by using a second carbon source, i.e. the carbon source B, adapted to fill the rest of the porosity of the zeolite, in particular the largest pores, is an important aspect of the invention makes it possible to obtain a carbonaceous replica monolith of hierarchical porosity and mechanically resistant.

The carbon sources A and B are advantageously organic compounds.

The carbon source A is preferably chosen from alkenes containing 1 to 6 carbon atoms, preferably from acetylene, ethylene, propylene, taken alone or as a mixture.

The carbon source B is preferably chosen from monosaccharides, disaccharides, glycerol, furfuryl alcohol, taken alone or as a mixture.

The injection of the carbon sources A and B, which are organic substances, into the reactor containing the zeolite, in order to fill the porosity thereof, allows, after carbonization of said carbon sources, to form carbon, preferably in amorphous form, in the porosity of the zeolite. The porosity of the carbon-filled zeolite forms the structure of the carbonaceous replica of the zeolite after dissolution of the zeolite as described below.

In particular, step c) advantageously comprises the following sub-steps:

c1) hot injection of the carbon source A into the reactor at the end of step b), at a temperature between 500°C and 700°C, and preferably between 600°C and 650 °C, in the form of a gas mixture containing an inert gas, preferably nitrogen, and between 7 and 10% by volume of said carbon source A at a constant flow rate of said gas mixture, preferably 10 ml /min/g of zeolite, and preferably for a period of between 5 hours and 70 hours, more preferably between 7 hours and 50 hours;
c2) carbonization of the carbon source A contained in the reactor at the end of step c1) by heat treatment at a temperature between 700°C and 1100°C, preferably between 900°C and 1000°C , under a flow of inert gas, preferably nitrogen, and preferably at a constant flow rate of 10 ml/min/g of zeolite, for a period of between 30 minutes and 16 hours, preferably between 2 and 14 hours ;
c3) cooling the reactor at the end of step c2) to ambient temperature (ie a temperature between 18°C and 35°C) under a flow of inert gas, preferably nitrogen, preferably at a constant flow rate of 10 ml/min/g of zeolite, and advantageously according to a temperature ramp of 5°C/min;
c4) cold injection, ie at room temperature, of the carbon source B into the reactor at the end of step c3), in the form of a liquid mixture comprising said carbon source B and l water, preferably distilled or ultra pure water (for example Type 1 ultra pure water obtained via MERCK Mili-Q type system), and which may also contain an alcohol, and preferably containing between 25% and 90% by weight, more preferably between 25% and 80% by weight, for example 50% by weight of said carbon source B in water, at a constant flow rate, preferably 1 ml/min/g of zeolite, for a period between 45 minutes and 14 hours, and preferably between 2 and 10 hours;
c5) the heat treatment of the reactor at the end of step c4), at a temperature between 90°C and 120°C, preferably between 100°C and 110°C, under a flow of inert gas, preferably nitrogen, and preferably at a constant flow rate, such as a flow rate of 10 ml/min/g of zeolite, and preferably at a constant temperature ramp of 3°C/min, for a duration of between 30 minutes and 16 hours, preferably between 2 hours and 14 hours;
c6) carbonization of the carbon source B at the end of step c5) by heat treatment at a temperature between 700°C and 1100°C, preferably between 900°C and 1000°C under a flow of inert gas, preferably nitrogen, preferably at a constant flow rate such as a flow rate of 10 ml/min/g of zeolite, for a period of between 30 minutes and 16 hours, preferably between 2 hours and 14 hours ;
c7) cooling the reactor at the end of step c6) to ambient temperature (ie a temperature between 18°C and 35°C), under a flow of inert gas (eg nitrogen), preferably at a constant flow rate, such as a flow rate of 10 ml/min/g of zeolite, and preferably at a temperature ramp of 5°C/min;
c8) dissolving the zeolite contained in the reactor at the end of step c7) with an aqueous solution of hydrofluoric acid (HF), preferably 40% by weight, or with an aqueous solution of sodium hydroxide ( NaOH), preferably at 40% by weight, at a constant liquid flow rate, such as a liquid flow rate of 1 ml/min/g of zeolite, for a period of between 3 hours and 34 hours, preferably between 5 hours and 32 hours.

Step d) of washing and possible drying of the carbonaceous zeolite replica

The process comprises a step d) a washing, preferably with water, preferably followed by drying, of said carbonaceous zeolite replica obtained at the end of step c), in particular at the end of step c8). Washing is preferably carried out with distilled or ultra-pure water (for example Type 1 ultra-pure water obtained via a Mili-Q type system from MERCK), preferably at a constant liquid flow rate, for example 1 ml/min/ g of zeolite, and preferably for a period of between 45 minutes and 14 hours, more preferably between 2 hours and 12 hours.
Preferably, drying by blowing with dry air after washing is carried out at room temperature, at a constant air flow rate of 10 ml/min/g of zeolite, preferably for a period of between 15 minutes and 3 hours, and more preferably between 30 minutes and 2 hours. Another way of drying is to carry out a heat treatment in dry air, preferably at a temperature between 100°C and 140°C, preferably between 120°C and 130°C at a constant air flow of 10 ml/min/g of zeolite, preferably for a period of between 15 minutes and 3 hours, and more preferably between 30 minutes and 2 hours.

At this stage, the carbonaceous zeolite replica is in the form of a monolith, similar in shape and dimensions to those of the reactor which contains said replica.

Step e) of activation of the carbonaceous zeolite replica

The process comprises a step e) of activating the carbonaceous zeolite replica at the end of step d), by a heat treatment at a temperature between 100°C and 140°C, preferably between 120°C. C and 130°C, under a flow of inert gas (e.g. nitrogen), preferably at a constant flow rate, for example a flow rate of 10 ml/min/g of zeolite, and preferably for a period of between 45 minutes and 14 hours, more preferably between 2 hours and 12 hours, to form the final carbonaceous zeolite replica monolith.

According to one or more embodiments, the process for preparing the carbonaceous zeolite replica monolith comprises, or even consists of, the following steps:
a) loading the zeolite powder into a tubular or half-shell reactor, preferably of a length of between 20 and 200 mm, of external diameter of between 9 and 150 mm, of internal diameter of between 7 and 148 mm;
b) activation of the zeolite loaded into the reactor at the end of step a) by heat treatment at a temperature between 100 and 300°C, preferably between 120 and 260°C, under a flow of nitrogen at a constant flow rate of 10 ml/min/g of zeolite and a temperature rise ramp of 5°C/min, for a period of between 2 hours and 10 hours, preferably between 3 hours and 8 hours;
c1) the hot injection of the carbon source A into the reactor at the end of step b), at a temperature between 500 and 700°C and preferably between 600 and 650°C, in the form of a gas mixture containing between 7% and 10% by volume of said carbon source A, chosen from acetylene, ethylene, propylene, alone or as a mixture, in a flow of nitrogen at a constant flow rate of 10 ml/min/g of zeolite, for a period of between 5 hours and 70 hours, preferably between 7 hours and 50 hours;
c2) the carbonization of said carbon source A contained in the reactor at the end of step c1) by heat treatment at a temperature between 700 and 1100°C, preferably between 900 and 1000°C under a flow of nitrogen at a constant flow rate of 10 ml/min/g of zeolite for a period of between 30 minutes and 16 hours, preferably between 2 hours and 14 hours;
c3) cooling the reactor at the end of step c2) under a flow of nitrogen at a constant flow rate of 10 ml/min/g of zeolite and a temperature ramp of 5°C/min, at a temperature ambient temperature between 18 and 35°C;
c4) cold injection (ie at room temperature) of the carbon source into the reactor at the end of step c3), in the form of a liquid mixture comprising said carbon source B chosen from among the monosaccharides, disaccharides, glycerol, furfuryl alcohol, alone or in mixture, and distilled or ultra pure water, preferably comprising between 25% and 90% by weight, or even between 25% and 85% by weight, for example 50% by weight of said carbon source B in distilled or ultra pure water, at a constant flow rate of 1 ml/min/g of zeolite for a period of between 45 minutes and 14 hours, and preferably between 2 hours and 10 a.m.;
c5) the heat treatment of the reactor at the end of step c4), at a temperature between 90 and 120°C, and preferably between 100 and 110°C, under a flow of nitrogen at a constant flow rate of 10 ml/min/g of zeolite and a constant temperature ramp of 3°C/min, for a period of between 30 minutes and 16 hours, preferably between 2 hours and 14 hours;
c6) the carbonization of the carbon source B at the end of step c5) by heat treatment at a temperature between 700 and 1100°C, preferably between 900 and 1000°C under a flow of nitrogen at a constant flow rate of 10 ml/min/g of zeolite, for a period of between 30 minutes and 16 hours, preferably between 2 hours and 14 hours;
c7) cooling the reactor at the end of step c6), under a flow of nitrogen at a constant flow rate of 10 ml/min/g of zeolite and a temperature ramp of 5°C/min, at a ambient temperature between 18 and 35°C;
c8) dissolving the zeolite contained in the reactor at the end of step c7), with an aqueous solution of HF (40% by weight) or with an aqueous solution of NaOH (40% by weight) at a constant flow rate of 1 ml/min/g of zeolite for a period of between 3 hours and 34 hours, preferably between 5 hours and 32 hours;
d) washing with ultra pure water (Type 1 obtained via MERCK Mili-Q type system) at the end of step c8), at a constant flow rate of 1 ml/min/g of zeolite for a duration between 45 minutes and 14 hours, and preferably between 2 hours and 12 hours, then
drying by blowing with dry air at room temperature, at a constant flow rate of 10 ml/min/g of zeolite for a period of between 15 minutes and 3 hours, and preferably between 30 minutes and 2 hours. The drying can alternatively be a heat treatment under dry air, preferably at a temperature between 100°C and 140°C, preferably between 120°C and 130°C, at a constant air flow rate of 10 ml/ min/g of zeolite, preferably for a period of between 15 minutes and 3 hours, and more preferably between 30 minutes and 2 hours;
e) the final activation of the carbonaceous zeolite replica obtained at the end of step d), by heat treatment at a temperature between 100 and 140°C, preferably between 120 and 130°C, under a nitrogen flow at a constant flow rate of 10 ml/min/g of zeolite for a period of between 45 minutes and 14 hours, and preferably between 2 hours and 12 hours, to obtain the carbonaceous replica of zeolite in the form of a monolith, preferably with a length of between 20 mm and 200 mm and a diameter of between 7 mm and 148 mm.

Advantageously, the process for preparing a carbonaceous zeolite replica monolith according to the invention does not use a binder to form said monolith.

The carbonaceous zeolite replica monolith obtained at the end of steps a) to e) of the process according to the invention preferably has a length of between 20 mm and 200 mm, and a diameter of between 7 mm and 148 mm.

The monolith preferably has a substantially cylindrical shape, which corresponds to that of the reactor used, preferably a so-called tubular or half-shell reactor, which has a cylindrical shape.

The carbonaceous zeolite replica monolith obtained (or capable of being obtained) by the process according to the invention preferably comprises more than 95% by weight, preferably more than 98% by weight, more preferably more than 99% by weight , carbonaceous replica of zeolite, that is to say carbon, preferably in amorphous form.

Said monolith preferably has a length of between 20 mm and 200 mm and a diameter of between 7 mm and 148 mm, and advantageously has a resistance to grain crushing (EGG) greater than or equal to 0.7 daN/mm, preferably greater than or equal to 1 daN/mm. It has hierarchical porosity including micropores, mesopores and macropores.

The carbonaceous zeolite replica monolith advantageously comprises hierarchical porosity comprising micropores, mesopores and macropores, and:
- a microporous volume of between 0.500 and 0.900 cm³.g^-1 ;
- a mesoporous volume of between 0.500 and 0.600 cm³.g^-1 ;
^-a macroporous volume of between 0.600 and 0.900 cm³.g^-1 ; And
- a total pore volume of between 1,600 and 2,400 cm³.g^-1.

The carbonaceous zeolite replica monolith advantageously has a grain crushing strength (EGG), as defined below, greater than or equal to 0.7 daN/mm, preferably greater than or equal to 1 daN/mm.

Such a carbonaceous zeolite replica monolith has advantages in terms of its durability, its handling for the applications for which it is intended as an adsorption or separation agent, or catalyst support for example, but also makes it possible to reduce pressure drops (also called "delta P" or "pressure drop" according to Anglo-Saxon terminology) in reactors where the monolith can be used, or even to present good performances with regard to absorption, separation linked to its specific porosity.

Characterization of the carbonaceous zeolite replica material obtained

The mechanical resistance of the materials obtained by the preparation process according to the invention, i.e. grain crushing resistance (EGG), is measured according to standard ASTM D 4179 – 01. This is a standardized test ( standard ASTM D4179-01) which consists of subjecting a material in the form of a millimeter object, such as a ball, a pellet (compressed), an extrusion or a monolith, to a compressive force generating rupture. This test is therefore a measure of the tensile strength of the material. The measured lateral rupture force constitutes the EGG which is expressed in the case of monoliths in units of force per unit of length (daN/mm or decaNewton per millimeter of length). According to the invention, the carbonaceous zeolite replica material obtained has a mechanical resistance thus measured greater than or equal to 1 daN/mm.

The porosity of the materials obtained by the preparation process according to the invention is measured by the nitrogen adsorption isotherm at 77K. Prior to measurement, the sample is pretreated at 250°C under vacuum for 5 hours. The value of 250° is the maximum pretreatment value for hierarchical carbonaceous materials (which contain micropores, mesopores and macropores). The range of temperatures used for thermal pretreatment (before measuring the nitrogen adsorption-desorption isotherm) is 110-250°C, with preferably 150°C for this type of materials (M. Thommes, Carbon 173 ( 2021) 842-848). The measurement is then carried out on an ASAP2420 type device from Micromeritics. The isotherm is drawn between 0.01 and 1 p/p0. The micro-meso volume is calculated from a relative pressure value close to 0.99 using the nitrogen gas to liquid density conversion factor (0.0015468) and the microporous volume is calculated according to the method t-plot. The mesoporous volume is calculated by the difference between the micro-meso volume and the microporous volume.

The ranges of volume values obtained via nitrogen adsorption and desorption isotherm analysis:
- microporous volume: 0.500 – 0.900 cm ³ .g ^-1
- mesoporous volume: 0.500 – 0.600 cm ³ .g ^-1

The macroporous volume of a monolith obtained by the preparation process according to the invention is determined by mercury intrusion analysis. The analysis is carried out on an Autopore 9500 type device from Micromeritics. This experimental method, described in the operating manual of the device referring to the ASTM D4284-83 standard, makes it possible to characterize the macroporous and mesoporous volume for pores larger than 3.5 nm. The sample as is is placed in a measuring cell and then mercury at a given pressure (0.0036 MPa) is introduced by applying increasing pressure through the steps up to 400 MPa. The relationship between the applied pressure and the characteristic dimension of the inlet threshold is established using the Laplace-Young equation and assuming a cylindrical pore opening, a contact angle between mercury and the pore wall of 140° and a mercury surface tension of 485 dynes/cm. The volume increments ΔVi of mercury introduced at each pressure level Pi are recorded, which then makes it possible to plot the cumulative volume of mercury introduced as a function of the applied pressure V(Pi), or as a function of the apparent diameter of the pores V( Di).

We set the value at 0.2 MPa from which the mercury fills all the intergranular voids, and we consider that beyond that the mercury penetrates into the pores (macropores and mesopores) of the material. The grain volume Vg is then calculated by subtracting the cumulative volume of mercury at this pressure (0.2 MPa) from the volume of the porosimeter cell, and dividing this difference by the mass of materials.

The macroporous volume (VM) of the monolith is defined as the cumulative volume of mercury introduced at a pressure between 0.2 MPa and 30 MPa, corresponding to the volume contained in the pores with an apparent diameter greater than 50 nm. The mesoporous volume (Vmes) of material is defined as the cumulative volume of mercury introduced at a pressure between 30 MPa and 400 MPa. The method of measuring the pore volume by mercury intrusion does not allow access to the microporous volume, the total pore volume (Vtot) as measured by mercury intrusion, corresponds to the sum of the macroporous (VM) and mesoporous (Vmes) volumes. ).

The ranges of volume values obtained by mercury intrusion:
- macroporous volume: 0.600 – 0.900 cm ³ .g ^-1
- total volume (microporous, mesoporous and macroporous): 1,600 – 2,400 cm ³ .g ^-1

Use of monoliths of carbonaceous replicas of zeolites

The carbonaceous zeolite replica monolith as obtained by the process according to the present invention, and having high mechanical strength, can then advantageously be used as an adsorbent, catalyst support or separation agent.

The invention thus also relates to the use of carbonaceous zeolite replica monoliths such as obtained by means of the preparation process according to the invention, in particular as a catalyst support, adsorbent or even separation agent.

The carbonaceous zeolite replica monolith according to the invention can in fact be used as a catalyst support, and be associated with one or more metals giving it catalytic activity, for example for catalytic reactions in the gas phase.

The carbonaceous zeolite replica monolith according to the invention can also be advantageously used as an adsorbent in many other applications, and can for example be used for the adsorption of gaseous compounds, for example for the storage of H ₂ , CO ₂ , natural gas, the adsorption of molecules in the liquid phase, such as the adsorption of phenolic molecules in the aqueous phase, of mono-aromatic compounds, of molecules of pharmaceutical products such as antibiotics, for water purification containing pollutants, e.g. adsorption removal of phenols in wastewater, for energy storage in batteries, etc.

The carbonaceous zeolite replica monolith according to the invention can also be used as a separation agent, to separate various molecules in a given medium, for example in a liquid medium such as in an aqueous medium.

Preferably, the monolith/reactor assembly can be used directly in an application without extracting the monolith from the reactor.

The monoliths obtained by the preparation process according to the invention can thus be used for the liquid phase separation of monosaccharides, such as glucose or fructose, and furan compounds such as 5-hydroxymethylfurfural (5-HMF).

By monosaccharide we mean a sugar, in particular a C6 sugar (i.e. having 6 carbon atoms, i.e. a hexose), which is in a monomeric form (monosaccharide), for example fructose or glucose.

Thus, the invention also relates to a process for liquid phase separation of monosaccharides such as glucose or fructose and furan compounds such as 5-hydroxymethylfurfural, in which a monolith of carbonaceous replica of zeolite obtained by the preparation process according to the invention, preferably within the reactor used to prepare said monolith, and a solution comprising at least one monosaccharide and one furan compound, preferably fructose and/or glucose and 5-hydroxymethylfurfural, to produce a first stream enriched in monosaccharides, e.g. fructose and/or glucose, and a second stream enriched in furan compounds, e.g. 5-HMF.

Such separation of monosaccharides and furan compounds can be useful in the context of the production of 5-HMF from a feed comprising a sugar, more particularly a hexose, by catalytic dehydration in an organic solvent. 5-HMF is a compound of interest derived from biomass which can be used in many fields, particularly in pharmacy, agrochemistry or specialty chemistry. In the context of processes for producing 5-HMF from a sugar feedstock, such as for example described in patents EP3371157, US10526302, or US11261168, it may be required to separate the 5-HMF from unconverted sugars during the synthesis of 5HMF, and thus purify the synthesis effluent comprising 5-HMF, or even to purify an effluent of sugars with a view to subsequent transformations of said sugars.

In another context, the zeolite carbon replica monolith can be used to separate sugars from furan compounds in sugar fermentation processes to produce ethanol.

A separation test, as exemplified below, can consist of passing an aqueous solution containing the monosaccharide and 5-HMF into the reactor containing the monolith, at room temperature, and at atmospheric pressure. The solution can be introduced with the help of a pump. The effluents are analyzed by high performance liquid chromatography or “HPLC” for High pressure (or performance) liquid chromatography according to Anglo-Saxon terminology. The average exit time from the reactor containing the monolith is the time necessary for 50% of the quantity of sugar or 5-HMF to exit the reactor.

Examples

The invention is illustrated by the following examples which are in no way limiting.

Example 1 (comparative): preparation of a carbonaceous replica of zeolite

A half-shell Hastelloy tubular reactor with a length of 50 mm, an external diameter of 12 mm and an internal diameter of 10 mm, equipped with a sintered glass at one of its goals is loaded through the other goal with 5.1 g of zeolite Y (structural type FAU, CBV720, Zeolyst). Then the reactor is introduced in a vertical position with the frit in the lower part into an oven and the temperature is raised to 200°C (ramp of 5°C/min) under a flow of air (10 ml/min/g zeolite) for 5 hours. Then the temperature is raised to 650°C (ramp of 5°C/min) under a flow of nitrogen (10 ml/min/g zeolite) and then at the same temperature (650°C) a gas mixture (10 ml/min/g zeolite) containing 8% by volume of ethylene diluted in N2 for 13.5 hours. Then the reactor temperature rose to 900°C (5°C/min) under a flow of nitrogen (10 ml/min/g zeolite) and maintained for 3 hours. At the end of the heat treatment, the reactor is cooled (ramp of 5°C/min) under a flow of nitrogen (10 ml/min/g zeolite) to room temperature (25°C) and an aqueous solution of HF (40% weight) is passed for 7 hours with a flow rate of 1 ml/min/g zeolite to dissolve the zeolite. Then ultra pure water (Type 1 obtained via MERCK Mili-Q type system) is passed through the reactor for 2 hours with a flow rate of 1 ml/min/g zeolite. Cold activation with the passage of dry air (10 ml/min/g zeolite) for 30 minutes and then a temperature rise to 120°C for hot activation for 2 hours under the same dry flow of nitrogen (10 ml/min/g zeolite). The reactor is opened and the carbonaceous zeolite replica is recovered in the form of friable agglomerates of 3 - 4 mm in diameter and without mechanical resistance to crushing. The material obtained is not a monolith. The microporous volume measured by nitrogen adsorption isotherm and calculated using the t-plot method is equal to 0.450 cm ³ .g ^-1 . The micro-meso volume is equal to 0.650 cm ³ .g ^-1 and the mesoporous volume calculated by the difference between the micro-meso volume and the microporous volume is 0.200 cm ³ .g ^-1 . The volume of the macropores determined by mercury porosimetry is 0.500 cm ³ .g ^-1 . The volume of the mesopores determined by mercury porosimetry (diameter between 3.5 and 50 nm) is equal to 0.150 cm ³ .g ^-1 . The total volume is 1,100 cm ³ .g ^-1 .

Example 2 (according to the invention): preparation of a monolith of a carbonaceous replica of zeolite

A half-shell Hastelloy tubular reactor with a length of 50 mm, an external diameter of 12 mm and an internal diameter of 10 mm, equipped with a sintered glass at one of its goals is loaded through the other goal with 5.1 g of zeolite Y (structural type FAU, CBV720, Zeolyst). Then the reactor is introduced in a vertical position with the frit in the lower part into an oven and the temperature is raised to 200°C (ramp of 5°C/min) under a flow of air (10 ml/min/g zeolite) for 5 hours. Then the temperature is raised to 650°C (ramp of 5°C/min) under a flow of nitrogen (10 ml/min/g zeolite) and then at the same temperature (650°C) a gas mixture (10 ml/min/g zeolite) containing 8% by volume of ethylene diluted in N2 for 13.5 hours. Then the reactor temperature rose to 900°C (5°C/min) under a flow of nitrogen (10 ml/min/g zeolite) and maintained for 3 hours. At the end of the heat treatment, the reactor is cooled (5°C/min) under a flow of nitrogen (10 ml/min/g zeolite) to room temperature (25°C) and a solution of glucose (50% by weight) in water is injected (1 ml/min/g zeolite) for 2 hours. Then the temperature of the reactor rose to 110°C (ramp of 3°C/min) under a flow of nitrogen (10 ml/min/g zeolite) for 3 hours. Then the reactor temperature rose to 900°C (ramp of 5°C/min) under a flow of nitrogen (10 ml/min/g zeolite) and maintained for 3 hours. At the end of the heat treatment, the reactor is cooled under a flow of nitrogen (10 ml/min/g zeolite) to room temperature (20°C) and an aqueous solution of HF (40% by weight) is passed for 7 hours with a flow rate of 1 ml/min/g zeolite to dissolve the zeolite. Then ultra pure water (Type 1 obtained via MERCK Mili-Q type system) is passed through the reactor for 2 hours with a flow rate of 1 ml/min/g zeolite. Cold activation with the passage of dry air (10 ml/min/g zeolite) for 1 hour and then a rise in temperature to 120°C for hot activation for 2 hours under the same dry flow of nitrogen (10 ml/min/g zeolite). The reactor is opened and the carbonaceous zeolite replica is recovered in the form of a monolith 50 mm long and 10 mm in diameter and weighing approximately 3.4 g. Its mechanical resistance to crushing is 1.5 daN/mm.

The microporous volume measured by nitrogen adsorption isotherm and calculated using the t-plot method is equal to 0.750 cm ³ .g ^-1 . The micro-meso volume is equal to 1.150 cm ³ .g ^-1 and the mesoporous volume calculated by the difference between the micro-meso volume and the microporous volume is 0.400 cm ³ .g ^-1 . The volume of the macropores determined by mercury porosimetry is 0.700 cm ³ .g ^-1 . The volume of the mesopores determined by mercury porosimetry (diameter between 3.5 and 50 nm) is equal to 0.200 cm ³ .g ^-1 . The total volume is 1,850 cm ³ .g ^-1 .

Example 3 ( according to the invention ): preparation of a monolith of a carbonaceous replica of zeolite

A half-shell Hastelloy tubular reactor with a length of 120 mm, an external diameter of 122 mm and an internal diameter of 120 mm, equipped with a sintered glass at one of its goals is loaded through the other goal with 1764 g of zeolite Y (structural type FAU, CBV720, Zeolyst). Zeolite crystals have an average size of 450 nm. Then the reactor is introduced in a vertical position with the frit in the lower part into an oven and the temperature is raised to 200°C (ramp 5°C/min) under a flow of air (10 ml/min/g zeolite) for 5 hours. Then the temperature is raised to 650°C (ramp of 5°C/min) under a flow of nitrogen (10 ml/min/g zeolite) and then at the same temperature (650°C) a gas mixture (10 ml/min/g zeolite) containing 8% by volume of ethylene diluted in N2 for 60 hours. Then the reactor temperature rose to 900°C (5°C/min) under a flow of nitrogen (10 ml/min/g zeolite) and maintained for 3 hours. At the end of the heat treatment, the reactor is cooled (ramp of 5°C/min) under a flow of nitrogen (10 ml/min/g zeolite) to room temperature (20°C) and a glucose solution (50% by weight ) in water is injected (1 ml/min/g zeolite) for 8.5 hours. Then the reactor temperature rose to 150°C (2°C/min ramp) under a flow of nitrogen (10 ml/min/g zeolite) for 2 hours. Then the reactor temperature rose to 900°C (ramp of 5°C/min) under a flow of nitrogen (10 ml/min/g zeolite) and maintained for 3 hours. At the end of the heat treatment, the reactor is cooled under a flow of nitrogen (10 ml/min/g zeolite) to room temperature (25°C) and an aqueous solution of HF (40% by weight) is passed for 28 hours with a flow rate of 1 ml/min/g of zeolite to dissolve the zeolite. Then ultra pure water (Type 1 obtained via MERCK Mili-Q type system) is passed through the reactor for 6 hours with a flow rate of 1 ml/min/g of zeolite. Cold activation with the passage of dry air (10 ml/min/g zeolite) for 30 minutes and then a temperature rise to 120°C for hot activation for 2 hours under the same dry flow of nitrogen (10 ml/min/g zeolite). The reactor is opened and the carbonaceous zeolite replica is recovered in the form of a monolith 120 mm long and 120 mm in diameter and weighing approximately 1200 g. Its mechanical resistance to crushing is 3 daN/mm.

The microporous volume measured by nitrogen adsorption isotherm and calculated using the t-plot method is equal to 0.740 cm ³ .g ^-1 . The micro-meso volume is equal to 1.130 cm ³ .g ^-1 and the mesoporous volume calculated by the difference between the micro-meso volume and the microporous volume is 0.390 cm ³ .g ^-1 . The volume of the macropores determined by mercury porosimetry is 0.800 cm ³ .g ^-1 . The volume of the mesopores determined by mercury porosimetry (diameter between 3.5 and 50 nm) is equal to 0.250 cm ³ .g ^-1 . The total volume is 1,930 cm ³ .g ^-1 .

Example 4: separation of an aqueous mixture of 5-HMF and glucose

The reactor containing the monolith obtained according to Example 2 is connected to the liquid phase separation unit. The reactor is supplied with an aqueous solution containing 10% glucose and 5% 5-HMF with a flow rate of 0.5 ml/min at room temperature. The effluents are analyzed by HPLC. From the concentration curves at the outlet of the monolith the retention times of the compounds are deduced. The average release time for glucose is 12 minutes, and that for 5-HMF is 20 minutes.

Claims (15)

Process for preparing a carbonaceous zeolite replica monolith, comprising the following steps:
a) loading a zeolite powder into a reactor of length between 20 mm and 200 mm and internal diameter of between 7 mm and 148 mm;
b) activation of said zeolite loaded into the reactor in step a) at a temperature between 100°C and 300°C under a flow of inert gas;
c) the transformation, in said reactor, of said zeolite activated at the end of step b) into a carbonaceous replica of zeolite comprising a first injection of a source of carbon A in gaseous form followed by the carbonization of said source of carbon A, then a second injection of a source of carbon B in liquid form followed by the carbonization of said source of carbon B, then the dissolution of said zeolite;
d) washing, preferably with water, possibly followed by drying, of said carbonaceous zeolite replica;
e) an activation of said carbonaceous replica of zeolite washed at the end of step d), at a temperature between 100°C and 140°C and under a flow of inert gas, to form said carbonaceous replica monolith of zeolite. Method according to claim 1, in which step c) of transforming said zeolite into a carbonaceous replica of zeolite comprises:
c1) the hot injection of said carbon source A into the reactor at the end of step b), at a temperature between 500°C and 700°C, in the form of a gas mixture containing a inert gas and between 7% and 10% by volume of said carbon source A, at a constant flow rate of said gas mixture, preferably 10 ml/min/g of zeolite, and preferably for a period of between 5 hours and 70 hours;
c2) the carbonization of said carbon source A contained in said reactor at the end of step c1) at a temperature between 700°C and 1100°C, under a flow of inert gas, preferably for a duration comprised between 30 minutes and 4 p.m.;
c3) cooling said reactor at the end of step c2) under a flow of inert gas at an ambient temperature between 18°C and 35°C.
c4) cold injection of said carbon source B into the reactor at the end of step c3) in the form of a liquid mixture comprising said carbon source B and water, preferably comprising between 25% and 90% by weight of said carbon source B in water, at a constant flow rate, preferably 1 ml/min/g of zeolite, for a period of between 45 minutes and 14 hours;
c5) the heat treatment of the reactor at the end of step c4), at a temperature between 90°C and 120°C under a flow of inert gas, for a period of between 30 minutes and 16 hours;
c6) the carbonization of said carbon source B at the end of step c5) at a temperature between 700°C and 1100°C under a flow of inert gas, for a period of between 30 minutes and 16 hours;
c7) cooling the reactor at the end of step c6), under a flow of inert gas, at an ambient temperature between 18°C and 35°C;
c8) dissolving the zeolite contained in the reactor at the end of step c7) with an aqueous solution of hydrofluoric acid (HF) or sodium hydroxide (NaOH), preferably at 40% by weight of HF or NaOH, at a constant liquid flow rate, preferably 1 ml/min/g of zeolite, for a period of between 3 hours and 34 hours. Process according to any one of the preceding claims, in which said source of carbon A is chosen from alkenes containing 1 to 6 carbon atoms, preferably from acetylene, ethylene, propylene, taken alone or as a mixture. , and said carbon source B is chosen from monosaccharides, disaccharides, glycerol, furfuryl alcohol, taken alone or as a mixture. Process according to any one of the preceding claims, in which the inert gas used in the different stages is nitrogen. Process according to any one of the preceding claims, in which the flow of inert gas in the different stages is at a constant flow rate of 10 ml/min/g of zeolite. Method according to one of the preceding claims, in which the reactor has a length of between 20 mm and 200 mm and an internal diameter of between 7 mm and 148 mm, and the carbonaceous zeolite replica monolith has an identical length and diameter to the length and internal diameter of the reactor. Method according to one of the preceding claims, in which the reactor is tubular or half-shell. Method according to one of the preceding claims, in which the drying in step d) is carried out by blowing with dry air, at an ambient temperature between 18°C and 35°C, preferably at a flow rate d constant air of 10 ml/min/g of zeolite, for a period of between 15 minutes and 3 hours. Method according to one of the preceding claims, in which the zeolite comprises a microporous structure comprising pores whose opening is greater than or equal to 8MR. Process according to one of the preceding claims, in which the zeolite is chosen from zeolites of structure CHA, FAU, MOR, MFI and BEA, alone or as a mixture. Method according to one of the preceding claims, in which the carbonaceous zeolite replica monolith has a hierarchical porosity comprising micropores, mesopores and macropores, and:
- a microporous volume of between 0.500 and 0.900 cm³.g^-1 ;
- a mesoporous volume of between 0.500 and 0.600 cm³.g^-1 ;
^-a macroporous volume of between 0.600 and 0.900 cm³.g^-1 ; And
- a total pore volume of between 1,600 and 2,400 cm³.g^-1. Method according to one of the preceding claims, in which the carbonaceous zeolite replica monolith has a grain crushing strength (EGG) greater than or equal to 0.7 daN/mm, preferably greater than or equal to 1 daN/ mm. Carbonaceous zeolite replica monolith comprising more than 95% by weight, preferably more than 98% by weight, of carbonaceous zeolite replica, said monolith preferably having a length of between 20 mm and 200 mm and a diameter of between 7 mm and 148 mm, having a grain crushing strength (EGG) greater than or equal to 0.7 daN/mm, preferably greater than or equal to 1 daN/mm, and comprising hierarchical porosity comprising micropores, mesopores and macropores. Use of a carbonaceous zeolite replica monolith according to claim 13, or obtained by the process according to one of claims 1 to 12, as a catalyst support, adsorbent or separation agent. Use according to claim 14, wherein the monolith is used for the liquid phase separation of monosaccharides, such as glucose or fructose, and 5-hydroxymethylfurfural.