Mesoporous solid for controlling humidity in an enclosed space

Abstract

The present disclosure relates to the use of mesoporous solids for controlling the relative humidity in an enclosed space, while greatly reducing the energy consumption. The mesoporous solids are particularly suitable for controlling the relative humidity in a greenhouse.

Description

Technical Field

[0001] This invention relates to the use of mesoporous solids for controlling relative humidity in enclosed spaces, thereby significantly reducing energy consumption.

[0002] Mesoporous solids are particularly suitable for controlling relative humidity in greenhouses. Background Technology

[0003] Humidity control is a major challenge for all types of buildings and other enclosed spaces. The term enclosed space refers to a space that is completely or partially enclosed.

[0004] Therefore, partially enclosed spaces can contain openings to the outside, allowing occasional or limited airflow.

[0005] In agricultural greenhouses, humidity control is crucial for optimizing production. More specifically, the quantity and quality of cultivated plants depend on the climatic conditions within the greenhouse during their growth. One key parameter is relative humidity, or hygrometry, defined as the ratio of the moisture content in the air to the saturated moisture content at the greenhouse temperature. Optimal relative humidity depends on the plants being cultivated and their growth stage (cuttings, seedlings, flowering, etc.). Furthermore, excessively high relative humidity can cause water to condense on plant surfaces; this promotes disease development and must therefore be strictly avoided.

[0006] The two main methods for controlling relative humidity are heating and (natural and / or forced) ventilation. Ventilation exchanges air inside the greenhouse with outside air, which has lower humidity. The main drawback of both techniques is their high energy consumption. In fact, ventilating with cooler outside air results in significant heat loss, which must be compensated for by heating. Furthermore, ventilation is not effective at reducing humidity inside the greenhouse when the outside air has a very high moisture content, such as during rain.

[0007] Various techniques have been proposed to overcome these problems, such as those described in the article by M. Amani et al. (Comprehensive review on dehumidification strategies for agricultural greenhouse applications, Applied Thermal Engineering, Vol. 181, 2020, 115979).

[0008] The two dehumidification techniques most familiar to those skilled in the art are thermodynamic dehumidification and the use of desiccant wheels.

[0009] The principle of a thermal dehumidifier is to circulate greenhouse air through forced ventilation using cold coils to condense some of the moisture in the air. The dehumidified air is then reheated through hot coils before being reinjected into the greenhouse. Cooling and heating of the coils are provided by a heat transfer fluid that condenses at the inlet of the cold coil and evaporates at the inlet of the hot coil. This type of system effectively controls humidity, but it is costly: in addition to the initial investment, the condenser requires a significant amount of electricity to operate.

[0010] Another dehumidification technology that has been used for many years is the desiccant wheel. A solid or liquid desiccant medium is placed in a wheel that undergoes continuous rotation. A first fan allows air from the greenhouse to be injected onto the desiccant, drying the air before it is reinjected into the greenhouse. A second fan draws in outside air, circulates it through a heated system, and then through the wheel to regenerate the desiccant. Through the rotation of the wheel, the desiccant comes into contact with the greenhouse air (adsorption phase) and the hot outside air (desorption or regeneration phase). Preferred media for this type of dehumidifier are those that capture moisture at very low humidity levels, such as certain silica gels, molecular sieves (e.g., zeolites), or salt solutions. Desiccant wheels are rarely used in greenhouses because they have several major drawbacks: complex system implementation, expensive installation, and high energy consumption due to the heat-generated regeneration process.

[0011] Patent KR100890574 proposes using zeolite as an adsorbent to dehumidify greenhouse air. The zeolite is placed in a cylinder outside the greenhouse. At night, greenhouse air is injected into the cylinder, and moisture is adsorbed by the zeolite. During the day, the zeolite is regenerated using outside air. Because zeolite requires very dry air to regenerate, the patent specifies that the system can only operate in specific climatic conditions with very low relative humidity (20-40%) during the day.

[0012] Humidity control is crucial not only in greenhouses. Humidity control issues affect a variety of enclosed spaces, such as residential buildings, buildings for tertiary or industrial use, or transportation buildings. In residential, tertiary, or industrial buildings, humidity control is necessary to ensure the comfort of occupants and prevent the degradation of building and production materials. The two main technologies used here are heating and natural ventilation (air inlets) or controlled mechanical ventilation (CMV), both of which result in significant heat loss. For residential buildings, there are also mineral-based desiccants (usually calcium chloride) that absorb moisture from the air and discharge it as water into tanks that must be emptied periodically. Dehumidifiers are sometimes used in large industrial buildings, with the same drawbacks as agricultural greenhouses. When the air is too dry, air humidifiers are used.

[0013] Metal-organic framework solids (commonly referred to as MOFs) have been proposed for controlling humidity in enclosed spaces (see, for example, Menghao Qin, Pumin Hou, Zhimin Wu, Juntao Wang, Precise humidity control materials for autonomous regulation of indoor moisture, Building and Environment, Vol. 169, 2020).

[0014] MOFs are microporous solids, but they also have many drawbacks. Besides the complexity of their synthesis and shaping to form particles, their synthesis often requires the use of solvents harmful to health, such as N,N-dimethylformamide. Furthermore, their structures are generally unstable in the presence of heat and water (see Karen Leus, Thomas Bogaerts, Jeroen DeDecker, Hannes Depauw, Kevin Hendrickx, Henk Vrielinck, Veronique Van Speybroeck, Pascal Van Der Voort, Systematic study of the chemical and hydrothermalstability of selected “stable” Metal Organic Frameworks, Microporous and Mesoporous Materials, Vol. 226, 2016, pp. 110-116), which is particularly problematic for their use in potentially very humid environments.

[0015] Hall MR et al. (Acta Materialia 60 (2012) pp. 89-101) disclosed desiccant materials, particularly mesoporous silica. The total specific volume of macropores and mesopores in the proposed materials is greater than that in the materials of the present invention, and the specific volume percentage of macropores is too large relative to the specific volume of macropores and micropores.

[0016] EP 3 042 877 describes porous carbon-based adsorbent materials. However, it does not describe their ability to control humidity. Furthermore, the proposed materials have micropores (0.3 mL / g to 0.7 mL / g), while the materials of this invention are substantially free of such micropores.

[0017] JP 2002 / 284520 describes a silica-alumina based mesoporous material. Aside from the diameter of the mesopores, almost no information is given about the material structure. However, it should be noted that materials with mesopores less than 10 nm in diameter can control humidity in the range of 75% to 90%, while the material of the present invention with mesopores less than 10 nm in diameter can control humidity in the range of 40% to 60%. Therefore, the material described in JP 2002 / 284520 does not possess all the characteristics of the material of the present invention.

[0018] Tomita Yumiko et al. (Journal of the Ceramic Society of Japan 112(9) pp. 491-495) disclosed a porous silica monolith with a bimodal pore distribution. The macropore specific volume of the proposed material is greater than that of the material of the present invention, or the total specific volume of macropores and mesopores is greater than that of the material of the present invention.

[0019] Furthermore, none of the four cited papers demonstrate the control capabilities of the proposed solids. More specifically, using measuring devices such as dynamic vapor adsorption (DVS) or dryers, only static adsorption and / or desorption capabilities are measured, known as water adsorption isotherms. These measuring devices are equipped with independent humidity regulators, which do not utilize the control capabilities of the solids. In the case of DVS devices, relative humidity is controlled by bubbling incoming air into liquid water at a given temperature. In the case of dryers, relative humidity is controlled by static contact between air and liquid water, which may or may not contain humidity-regulating mineral salts. Therefore, in these devices, the solids do not play a role in controlling relative humidity. Consequently, the dynamic and passive control characteristics of these solids cannot be measured and demonstrated.

[0020] Therefore, there remains a need for a technology capable of controlling relative humidity in enclosed spaces that avoids the drawbacks of the proposed solution, particularly one that requires little or no energy. It is understood that the proposed solution poses no risk to the environment or human health. Furthermore, the proposed solution will occupy a minimal volume within the enclosed space, thus not interfering with users and / or various functions associated with the enclosed space, such as plant cultivation. Summary of the Invention

[0021] This invention relates to the use of mesoporous solids for controlling relative humidity in enclosed spaces. The mesoporous solid has:

[0022] - Mesopores with an average diameter of 3 to 50 nm, measured by nitrogen adsorption combined with the BJH method according to standard ASTM D4641-17;

[0023] - Mesoporous specific volume greater than or equal to 0.2 mL / g, measured according to standard ASTM D4641-17 by nitrogen adsorption combined with the BJH method; and

[0024] - The ratio of the average mesopore diameter measured by nitrogen desorption to the average mesopore diameter measured by nitrogen adsorption ([desorption average diameter] / [adsorption average diameter]) is 0.3 to 1;

[0025] When a mesoporous solid also contains macropores, micropores, or a combination of micropores and macropores:

[0026] - The total specific volume of macropores and mesopores is 0.3 to 2 mL / g;

[0027] The ratio of (macropore specific volume) / (total specific volume of macropores and mesopores) is less than 0.6; and

[0028] - The micropore volume ratio is less than 0.2 mL / g.

[0029] The present invention also relates to a device for controlling relative humidity in an enclosed space, comprising:

[0030] - The container, preferably made of an airtight material, is provided with one or more openings for connecting to the atmosphere of the enclosed space;

[0031] - Mesoporous solids, as described herein, are placed in a container.

[0032] The present invention also relates to a method for controlling relative humidity in an enclosed space, comprising one of the following steps:

[0033] (a1) Placing the mesoporous solid as described herein in a closed space; or

[0034] (a2) Placing the mesoporous solid as described herein in one or more containers within a closed space, the containers being made of an airtight material and having openings connected to the atmosphere of the closed space; or

[0035] (a3) Placing one or more devices according to the invention within the enclosed space; or

[0036] (a4) Place a mesoporous solid, as described herein, on one or more surfaces of an enclosed space.

[0037] Other aspects of the invention are described in the following claims. Detailed Implementation

[0038] Surprisingly, it has been found that certain mesoporous solids can control relative humidity in enclosed spaces while significantly reducing energy consumption. These mesoporous solids are particularly suitable for controlling relative humidity in greenhouses.

[0039] Therefore, the present invention relates to the use of mesoporous solids for controlling relative humidity in enclosed spaces, methods of using these mesoporous solids, and apparatus for incorporating these mesoporous solids.

[0040] The term "mesoporous solid" refers to a solid having pores (called "mesoporous pores") with an average diameter of 2 to 50 nanometers within its structure.

[0041] "Control" refers to the ability of mesoporous solids to capture moisture from the air when the relative humidity exceeds a desired maximum, and to spontaneously release moisture once the relative humidity falls below a desired minimum. This control can be achieved without the addition of external energy. Therefore, in other words, the mesoporous solids of this invention can automatically control the relative humidity in enclosed spaces, i.e., control relative humidity without external intervention, such as without the addition of external energy, control devices, or commands. However, in some embodiments, the addition of external energy may be necessary. The terms "control" and "automatic control" are used herein without distinction and interchangeably. Furthermore, this ability to control relative humidity means that the mesoporous solids used in the context of this invention are stable in the presence of water; in other words, their porous properties are not altered in the presence of water. The stability of the mesoporous solids can be assessed by determining the mesopore size distribution using the BJH method (standard ASTM D4641-17) for nitrogen adsorption and desorption. Changes in the mesopore size distribution over time reflect the instability of the mesoporous solids. Therefore, stable mesoporous solids will have a constant mesopore size distribution over time (e.g., a constant mesopore size distribution over months or even years, such as one month, three months, six months, one year, or two years). For crystalline mesoporous solids, the stability of the mesoporous solid can alternatively be determined by X-ray diffraction, a technique capable of detecting any changes in the solid crystal structure.

[0042] It should be noted that the controllability of porous solids cannot be evaluated solely based on their water adsorption or desorption properties, because the solid must be able to capture water when the relative humidity is above the desired upper limit and desorb it when it is below the desired lower limit. To make the solid passive, it is necessary to consider these properties, whether adsorption or desorption, without increasing energy consumption.

[0043] Furthermore, it is well known that mesoporous solids exhibit adsorption hysteresis for water; therefore, adsorption and desorption properties depend on the initial humidity level of the solid. Thus, a mesoporous solid fully saturated with water will begin to regenerate at a different relative humidity than a solid whose pores are only partially filled with water.

[0044] Therefore, it is impossible to assess control performance or even compare the relative performance of different solids simply by considering the different amounts of water adsorbed when relative humidity increases or the different amounts of water desorbed when relative humidity decreases.

[0045] Finally, the controllability of porous solids also depends on adsorption and desorption kinetics, which must be fast enough to capture water in the air at the same time when the relative humidity exceeds the desired level.

[0046] Therefore, the optimal properties of porous solids used for passive humidity control are very different from those used for drying or as desiccants, regardless of regeneration. Solids can adsorb large amounts of water, making them very useful for drying, but difficult to regenerate, requiring very high regeneration energy, which renders them useless for passive control processes. This is the case, for example, with microporous solids where water is absorbed very strongly, thus requiring a large amount of additional energy for regeneration.

[0047] The term "enclosed space" refers to a space that is completely or partially enclosed. A "partially enclosed" space, also known as a "semi-enclosed" space, is one that may include openings to the outside, allowing occasional or limited airflow.

[0048] In enclosed or semi-enclosed spaces, the volume occupied by porous solids must be as small as possible. Indeed, it is obvious that the solid must be able to be placed in the space without disturbing the user. In the case of agricultural greenhouses, it is desirable to retain as much usable space as possible for cultivating plants; furthermore, the solid must not hinder plant care and harvesting. In the case of residential or professional buildings, the solid must not interfere with activities, or more generally, reduce the usable space for primary activities. Furthermore, it is well known (see, for example, the work of Calas et al., Mechanical Strength Evolution from Aerogels to Silica Glass. Journal of Porous Materials 4, 211-217 (1997) or de Wagh et al., Dependence of ceramic fracture properties on porosity. J Mater Sci 28, 3589-3593 (1993)), that the mechanical strength of porous solids is inversely proportional to the total porosity specific volume.

[0049] Therefore, it is desirable to minimize any porous specific volume that is ineffective in humidity control; in other words, to minimize all pores that do not possess the characteristics claimed in this invention. In particular, the specific volume occupied by micropores and macropores must be minimized.

[0050] Unlike the solids used in dehumidifying wheels, the solids used in the context of this invention do not require startup or contact with preheated airflow for regeneration.

[0051] Unlike the zeolite described in KR100890574, the solid used in this invention does not contain zeolite or any other microporous solids, and therefore does not require very dry air for regeneration. Thus, the solid used in the context of this invention can be adapted to any type of climate.

[0052] Generally, the pore size of porous solids can range from less than one nanometer to hundreds of nanometers. According to the IUPAC definition, if the pore size is less than 2 nanometers, the solid is called micropore, mesopore is 2 to 50 nanometers, and macropore exceeds this range. One of the standardized methods for measuring the pore size distribution of mesoporous solids (standard ASTM D4641-17 (2017)) is the nitrogen adsorption combined with the Barrett-Joyner-Halenda model, which is named with the initials BJH, as described in the literature (EP Barrett, LG Joyner, PH Halenda, "The determination of pore volume and area distributions in porous substances. 1. Computations from nitrogen isotherms" Journal of the American Chemical Society, Vol. 73 (1), pp. 373-380 (1951)).

[0053] The nitrogen adsorption isotherm of mesoporous solids differs during adsorption and desorption (hysteresis). For a given solid, this results in two pore size distributions for the nitrogen adsorption and desorption branches, and consequently, two average pore diameters: one related to the adsorption branch and the other to the desorption branch. These two diameters are referred to below by the terms "adsorption average diameter" and "desorption average diameter," respectively.

[0054] Surprisingly, it has been found that certain mesoporous solids can control relative humidity in enclosed spaces either passively (without adding external energy) or with minimal energy input (e.g., when using a fan to transfer water and heat from the air to the solid as quickly as possible). To increase mass transfer kinetics or prevent the formation of solid water in the pores, another minimal energy input can be used to heat the air before it comes into contact with the solid. These mesoporous solids can trap water from the air once the relative humidity exceeds a desired maximum, but can also spontaneously release water when the relative humidity falls below a certain value, thus regenerating without the need for external energy input. It has also been found that maximum and minimum humidity levels can be controlled by manipulating the pore size distribution of the solid, above which the solid traps and releases water.

[0055] Characterization techniques

[0056] In this specification, when referring to the total specific volume of macropores and mesopores, this total specific volume of macropores and mesopores is measured by mercury intrusion porosimetry according to standard ASTM D4284-12 at a maximum pressure of 4000 bar. The surface tension is fixed at 484 dyne / cm, and the contact angle is 140°. The macropore specific volume is evaluated by subtracting the mesopore specific volume measured by mercury intrusion porosimetry from the total specific volume of macropores and mesopores measured by the same method.

[0057] In this specification, when referring to mesopore specific volume, pore size distribution, and average pore diameter, these parameters are measured by nitrogen porosity determination according to the BJH method (standard ASTM D4641-17). Mesopore specific volume is the cumulative specific volume of all mesopores with P / P0 = 0.96. The average pore diameter (average diameter in terms of specific volume) is estimated by the formula d = 4V / A, where d is the average diameter, V is the mesopore specific volume, and A is the cumulative surface area of ​​all mesopores with P / P0 = 0.96. Micropore specific volume is determined by nitrogen porosity determination using the t-plot method by applying standard ISO 15901-2:2022 and calculating the statistical thickness t using the Harkins-Jura equation.

[0058] Mesoporous solids

[0059] In the context of this invention, mesoporous solids are solids having the following characteristics:

[0060] - Mesopores with an average diameter of 3 to 50 nm, preferably 4 to 35 nm, more preferably 4 to 30 nm, measured by nitrogen adsorption combined with the BJH method according to standard ASTM D4641-17;

[0061] - A mesoporous volumetric ratio greater than or equal to 0.2 mL / g, preferably greater than or equal to 0.4 mL / g, more preferably greater than or equal to 0.5 mL / g, measured according to standard ASTM D4641-17 by nitrogen adsorption combined with the BJH method; and

[0062] - is the ratio of the average mesopore diameter measured by nitrogen desorption to the average mesopore diameter measured by nitrogen adsorption ([desorption average diameter] / [adsorption average diameter]) from 0.3 to 1;

[0063] When a mesoporous solid also includes macropores, micropores, or a combination of micropores and macropores:

[0064] - The total specific volume of macropores and mesopores is 0.3 to 2 mL / g;

[0065] The ratio of (macropore specific volume) / (total specific volume of macropores and mesopores) is less than 0.6; and

[0066] - The micropore volume ratio is less than 0.2 mL / g.

[0067] The mesoporous volume is typically less than 1.7 mL / g, preferably less than 1.6 mL / g, and more preferably less than 1.5 mL / g.

[0068] The term "mesopore volume" refers to the cumulative volume of mesopores per unit mass of solid.

[0069] The term "macropore volume" refers to the cumulative volume of macropores per unit mass of solid.

[0070] The term "micropore volume ratio" refers to the cumulative volume of micropores per unit mass of solid.

[0071] In some embodiments, the mesoporous solids used in the context of this invention have mesopores with an average diameter of 3 to 50 nm, preferably 4 to 35 nm, more preferably 4 to 30 nm, as measured by nitrogen desorption combined with the BJH method according to standard ASTM D4641-17.

[0072] In some embodiments, the ratio of the average mesopore diameter (measured by nitrogen desorption) to the average mesopore diameter (measured by nitrogen adsorption) of the mesoporous solid used in the context of this invention ([average desorption diameter] / [average adsorption diameter]) is 0.35 to 1, more preferably 0.4 to 1, and even more preferably 0.6 to 1.

[0073] In some embodiments, the total specific volume of macropores and mesopores of the mesoporous solid used in the context of this invention is 0.4 to 1.9 mL / g, preferably 0.5 to 1.8 mL / g, as measured by mercury porosimetry according to standard ASTM D4284-12.

[0074] In order to limit the volume occupied by porous solids in an enclosed space, the ratio of solids (specific volume of macropores) / (total specific volume of macropores and mesopores) used in the context of this invention is less than 0.6, preferably less than 0.55, and more preferably less than 0.5.

[0075] Micropores are undesirable in the context of this invention because they require external energy to regenerate. Therefore, it is desirable to minimize the micropore specific volume. Consequently, the micropore specific volume of the solid according to the invention is less than 0.2 mL / g, preferably less than 0.1 mL / g, more preferably less than 0.05 mL / g, or even zero.

[0076] It has been observed that when the mesopore size distribution is less dispersed, in other words, when the standard deviation of such distribution is low, the control precision (defined as the difference between the desired relative humidity and the measured relative humidity) is higher, which is true for distributions obtained by nitrogen adsorption and desorption. Therefore, the standard deviation of the mesopore size distribution is preferably less than 150% of the average diameter, more preferably less than 130% of the average diameter, and particularly preferably less than 100% of the average diameter.

[0077] The chemical properties of mesoporous solids have little or no effect on their properties; however, the selected solids are preferably the most stable over time, meaning their porous properties do not degrade in the presence of water vapor and sudden, large temperature changes. Because metal-organic framework solids are generally unstable in the presence of water, mesoporous solids used in the context of this invention are preferably not metal-organic framework solids. Preferably, the solids used in the context of this invention are selected from the group consisting of metal oxide-based solids (e.g., oxides of silicon, aluminum, or mixtures of silicon and aluminum), carbon-based solids (e.g., activated carbon and carbon nanotubes), and mixtures thereof. In some embodiments, the solids used in the context of this invention are selected from the group consisting of silicon oxide-based solids, alumina-based solids, and carbon-based solids. Various mixtures of solids and / or crystalline phases can be used, particularly to improve the solid properties and / or the stability of those properties over time.

[0078] Over time and with use, the porosity of a solid can be altered and partially blocked by deposits (organic or mineral impurities) of various natures. The solid can then be regenerated / cleaned by injecting high-pressure air or by heating it to a high temperature (above 100°C) in the presence of air. In the latter case, a solid stable at high temperatures is preferred.

[0079] In the context of this invention, solids are typically crystalline forms with dimensions less than 100 μm (maximum size) as measured by scanning electron microscopy.

[0080] In the context of this invention, mesoporous solids can consist of a single type of crystal or a mixture of crystals of different mesoporous solids, such as crystals of different chemical compositions or sizes, to optimize the properties and / or thermal and mechanical properties of the mesoporous solid. When the mesoporous solid consists of a mixture of crystals, the solid can be manufactured from a homogeneous or heterogeneous mixture of various crystals. For example, when the solid is deposited on a porous carrier, multiple consecutive layers of different crystals can be deposited.

[0081] Mesoporous solids used in the context of this invention can be synthesized by any method known to those skilled in the art. For example, mesoporous solids can be prepared by sol-gel, precipitation, or hydrothermal methods, typically followed by heat treatment. Alumina-based solids can be prepared according to the synthesis methods described in FR2080526, FR2282863, US3322495, US 4016108, WO2001038252, US20180208478, US6511642, and US20140161716. Silica-based solids can be prepared according to the methods described in US5958577, US20100272996, US20110081416, and US5094829. Oxides containing multiple chemical elements can be prepared according to the methods described in US20140367311, US20070010395, and US5260251. Mesoporous solids, i.e., solids with mesopores having uniform morphology and size and periodically distributed among them, can be prepared according to one of the methods disclosed by Naik et al. (A Review on Chemical Methodologies for Preparation of Mesoporous Silica and Alumina Based Materials, Recent Patents on Nanotechnology, Vol. 3, No. 3, 2009, 213-224) and Wu et al. (Synthesis of mesoporous silica nanoparticles, Chem. Soc. Rev., 2013, 42, 3862-3875). Carbon-based solids can be prepared according to the method described in US20100021366.

[0082] Mesoporous solids are advantageously able to be controlled at the desired relative humidity values, ranging from 20% to 97%.

[0083] Relative humidity can be measured using capacitive, resistive, or gravimetric hygrometers.

[0084] Mesoporous solids with an average pore size of 10 to 40 nm during adsorption and an average pore size of 10 to 35 nm during desorption are preferably selected to control the relative humidity at a value of 80% to about 95%.

[0085] Mesoporous solids with an average pore size of 5 to 15 nm during adsorption and an average pore size of 5 to 13 nm during desorption are preferably selected to control the relative humidity at a value of 60% to about 80%.

[0086] Mesoporous solids with an average pore size of 3 to 10 nm during adsorption and an average pore size of 3 to 9 nm during desorption are preferably selected to control the relative humidity at a value of 40% to about 60%.

[0087] Implementation of mesoporous solids

[0088] Various implementations of mesoporous solids are possible to adapt to the external climate and the optimal humidity required within enclosed spaces. Generally, all implementations that allow the mesoporous solid to come into contact with the air in the enclosed space can be used.

[0089] Depending on the purpose of the enclosed space and the required relative humidity level, the mass of mesoporous solids to be carried out per unit volume of air can be 0.003 kg / m³. 3 Up to 0.8kg / m 3 .

[0090] One possible implementation simply involves placing the mesoporous solids within an enclosed space. To avoid humidity gradients, it is not recommended to place all the solids in one location; instead, disperse them throughout the enclosed space or ensure air circulation within the enclosed space, for example, by using a fan. The mesoporous solids can be placed in any suitable type of container (e.g., boxes, bags, mesh, etc.).

[0091] A second possible implementation involves placing the mesoporous solid in one or more containers made of an airtight material with openings connecting to the atmosphere of the enclosed space. In this case, internal air is injected into the containers (e.g., using a fan), where it comes into contact with the mesoporous solid and is exhausted from the containers at a controlled relative humidity. This implementation results in a more uniform relative humidity within the enclosed space and allows the desired relative humidity to be reached more quickly. For such an implementation, air from inside or outside the enclosed space can be used to regenerate the solid. When air comes from outside the enclosed space, it can be preheated or cooled by circulation within the enclosed space or by any other available means (e.g., an air / ground heat exchanger or solar heating).

[0092] For both of these first embodiments, mesoporous solids are preferably used in the form of millimeter-scale crystalline agglomerates, such as agglomerates with a size of 0.1 to 10 mm (this size refers to the largest size when the agglomerate is not spherical). Such agglomerates are easier to handle than crystals in powder form. The agglomerates can be shaped by extrusion, granulation, pressing, or any other method known to those skilled in the art. Binders or additives (e.g., clay or polymers) can be added to increase the cohesive forces between the crystals, thereby obtaining mechanically more stable agglomerates. Depending on the chosen shaping method, the agglomerates can be of various shapes (spherical, cylindrical, flake, etc.). The shape and size of the agglomerates are typically chosen to maximize the adsorption / desorption kinetics of water in the agglomerates. Therefore, agglomerates with a high “surface area to volume” ratio are preferred, such as spherical, cylindrical, trefoil, or tetralobed agglomerates with a size less than 5 mm. Therefore, larger objects, such as monolithic materials, are not recommended. Mesoporous solids can also be deposited on a carrier. The carrier allows control over the shape and mechanical strength of the resulting product. Therefore, large solids (greater than one centimeter) can be prepared. They are easy to transport and have a large surface area in contact with air.

[0093] For the second embodiment, the solid can also be used in the form of a membrane, made of pure solid or solid deposited on a porous support. This membrane acts as a selective barrier, capable of separating fluids in the presence of a driving force (in this case, a relative humidity gradient). For more details on membranes and membrane processes, see Abdullah et al., Chapter 2 - Membranes and Membrane Processes: Fundamentals, Editor(s): Angelo Basile, Sylwia Mozia, Raffaele Molinari, Current Trends and Future Developments on (Bio-)Membranes, Elsevier, 2018, pp. 45-70. In this configuration, internal air will contact one side of the membrane, and air for regeneration will contact the other side. The membrane can be tubular, planar, or even helical. Multiple membrane modules can be used in series or in parallel. A portion of the effluent from one or more membrane modules can be recirculated at the inlet of one or more modules, on the humid air side or the air for regeneration side. When using multiple membrane modules, it is advantageous to place them upstream or downstream of the heat exchanger module for better control of the temperature in the system. In cases where a ventilation system is already in place in the enclosed space, such as controlled mechanical ventilation (CMV) for living spaces, the membrane modules can be coupled to that system.

[0094] A third possible implementation involves placing a mesoporous solid within one or more surfaces defining an enclosed space, such as one or more walls of the enclosed space, or even all walls, the floor, and / or the ceiling. Typically, contact between the mesoporous solid and outside air is ensured. In this third implementation, most notably, when placing the mesoporous solid within the walls, the mesoporous solid is typically shaped to form a continuous, uniform layer between the interior and exterior of the enclosed space. Such a continuous, uniform layer prevents air leakage. The mesoporous solid can be shaped individually or deposited within or on the surface of a porous carrier. The resulting wall can thus consist of one or more layers to ensure mechanical strength and heat resistance. Therefore, the insulation of the wall can be enhanced by introducing a layer of stagnant air within the carrier.

[0095] When humidity control is particularly useful in specific locations within a room (e.g., near plants in the case of an agricultural greenhouse, or in particularly humid areas of residential and industrial buildings), solid materials can be advantageously placed near these locations. Therefore, in agricultural greenhouses, solid materials are preferably placed at least 10 meters from the plants, more preferably at least 5 meters, and particularly preferably at least 2 meters. In agricultural greenhouses, it is desirable to maximize the use of energy provided by solar radiation. Therefore, solid materials are preferably placed in a way that does not block solar radiation from reaching the plants. In residential buildings, solid materials are preferably placed in humid rooms, such as bathrooms and kitchens.

[0096] Therefore, the present invention also relates to a method for controlling relative humidity in an enclosed space, comprising the following steps:

[0097] (a1) Placing the mesoporous solid within a closed space, preferably at different locations within the closed space; or

[0098] (a2) Placing a mesoporous solid in one or more containers made of an airtight material and having an opening connected to the atmosphere of a closed space, the containers being placed within the closed space; or

[0099] (a3) Placing one or more of the devices described above or below within the enclosed space; or

[0100] (a4) Placing mesoporous solids in one or more surfaces (e.g., walls, floors, ceilings) of an enclosed space.

[0101] The mesoporous solid can be as described above. In steps (a1), (a2), and (a4), the mesoporous solid can be in free form (e.g., particulate form), or it can be deposited on a support. The mesoporous solid can be placed in any suitable type of container.

[0102] Mesoporous solids or devices are typically left in place for at least 10 days. Therefore, methods for controlling relative humidity in enclosed spaces include the following steps:

[0103] (a)(a1) Placing the mesoporous solid within a closed space, preferably at different locations within the closed space; or

[0104] (a2) Placing a mesoporous solid in one or more containers made of an airtight material and having an opening connected to the atmosphere of a closed space, the containers being placed within the closed space; or

[0105] (a3) Placing one or more of the devices described above or below within the enclosed space; or

[0106] (a4) Place mesoporous solids on one or more enclosed surfaces (e.g., walls, floors, ceilings).

[0107] in; and

[0108] (b) The solid or device shall be placed in place for at least 10 days.

[0109] In step (b), the solid or device may remain in place for 10 days to several months or even years, such as one month, three months, six months, one year, or two years.

[0110] Device

[0111] The present invention also relates to a device for controlling the relative humidity in an enclosed space. The device includes:

[0112] -container;

[0113] - Mesoporous solid, placed in a container.

[0114] Mesoporous solids are as described above.

[0115] In a further embodiment, the container is made of an airtight material and has one or more openings for connecting to the atmosphere of the enclosed space. Due to the choice of material, the container is airtight. However, the container includes one or more openings that allow control of the relative humidity of the air in the enclosed space. In some embodiments, the container includes one or more openings as the only openings designed to connect the interior of the container to the atmosphere of the enclosed space in which the device is installed / to be installed. In other embodiments, the container may also include an opening that allows it to connect to the outside of the enclosed space, enabling the circulation of air from outside the enclosed space to regenerate the solids.

[0116] Use

[0117] The aforementioned mesoporous solids can be used to control the relative humidity of any type of enclosed space, such as any type of building (cultivation greenhouses, agricultural buildings specifically for storing or drying food and plants, buildings for residential or professional use, production workshops, indoor swimming pools, saunas, bathrooms, museums, etc.) or other enclosed spaces, such as transportation buildings.

[0118] Depending on the enclosed space, control requirements, particularly the required minimum and maximum humidity values, can vary. To accommodate these constraints, the properties, shape, and implementation of the mesoporous solids can be modified. The aforementioned mesoporous solids advantageously enable control of desired relative humidity values ​​from 20% to 97%.

[0119] This ability to control humidity within different relative humidity ranges will be illustrated through the following examples.

[0120] The following examples are given by way of illustration. These examples are in no way limiting of the invention.

[0121] Example

[0122] Solid

[0123] The properties of the various solids used in the following examples are detailed in Table 1.

[0124] Mesoporous solids have been synthesized using the methods described above.

[0125]

[0126] Table 1: Properties of various solids

[0127] The nitrogen adsorption-desorption isotherm was measured at -196°C using a commercial instrument (Auto Sorb 1, Quantachrome Corporation). Prior to measurement, the sample was regenerated under a secondary vacuum at 350°C.

[0128] The total specific volume of macropores and mesopores was measured using a Micromeritics Autopore IV 9500 mercury porosimeter via mercury porosimetry.

[0129] Solids AE and HJ are mesoporous solids as used in the context of this invention. Solids F and G are not according to this invention. Solid F is a zeolite (primarily microporous) with a mesoporous specific volume of less than 0.2 mL / g. Solid G has an average mesopore diameter of less than 3 nm.

[0130] Solids K, L, and M have mesoporous specific volumes and equal average diameters during adsorption, but have different average diameters during desorption.

[0131] Solid K is not specified according to the present invention because the ratio of its "average mesopore diameter as measured by nitrogen desorption" to "average mesopore diameter as measured by nitrogen adsorption" is less than 0.3.

[0132] Example 1

[0133] The objective is to control the relative humidity in tomato production greenhouses in southern France. The greenhouse floor area is 960 m². 2 The total volume is 6048m³. 3 Greenhouse per m 2 It contains three tomato plants. It is equipped with openings to allow air to enter from the outside, and heating pipes supplying hot water from a gas boiler. To avoid condensation on the leaves, the relative humidity in the greenhouse is ideally always below 90%.

[0134] The relative humidity in greenhouses with and without the following solids was compared from 06:00 on day D to 12:00 on day D+2.

[0135] -Solid C;

[0136] -Solid D;

[0137] - Solid F;

[0138] -Solid G;

[0139] - A mixture of solid C and D (50% by mass of solid C, 50% by mass of solid D);

[0140] - A mixture of solid C and E (50% by mass of solid C, 50% by mass of solid E);

[0141] - A mixture of solids C, D and E: (33.3% by mass of solid C, 33.3% by mass of solid D, and 33.3% by mass of solid E);

[0142] The solid is in the form of cylindrical particles with a diameter of 1 mm and a length of approximately 5 mm.

[0143] Figure 1 The diagram shows the change of relative humidity over time with and without solids, and with 200 kg of solids C and D.

[0144] Figure 2 The diagram shows the change of relative humidity over time in the absence of solids and in the presence of 200 kg of solids F and G (not according to the invention).

[0145] Figure 3 The changes in relative humidity over time are shown in the absence of solids and in the presence of 200 kg of a mixture of solids (C+D, C+E, C+D+E).

[0146] It was observed that, in the absence of a solid, the relative humidity repeatedly exceeded 90% during the studied time period. Adding the solid or solid mixture according to the invention makes it possible to never exceed the 90% threshold, while adding a solid not according to the invention does not alter the evolution of relative humidity over time.

[0147] Example 2:

[0148] In the same greenhouse as described in Example 1, the aim was to avoid excessively high relative humidity while reducing energy consumption from heating. Therefore, the maximum relative humidity was fixed at 94%, and the possibility of limiting the maximum temperature of the heating element to 30°C from 00:00 on day D to 00:00 on day D+2 was investigated.

[0149] In the conventional configuration, in other words, with unrestricted heating power, the total energy used during this period is 5519 kWh. By limiting heating, a consumption of 4373 kWh was observed, representing a 21% reduction in energy consumption.

[0150] Figure 4 The relative humidity during this period was compared under normal conditions (normal heating), with temperature restrictions (low heating) but without solids, and finally with temperature restrictions and the presence of 200 kg of solids A and C. The shape and implementation of the solids were the same as in Example 1. It can be noted that in the absence of solids, the reduction in heating power caused a significant increase in relative humidity in the greenhouse at certain times of the day, even at 08:00 AM on days D and D+1. Figure 4 During the 8-hour and 32-hour periods, some steam condenses. Conversely, in the presence of solids A and C, heating power can be reduced while avoiding condensation problems.

[0151] Example 3:

[0152] Different implementations of the solid were tested in the same greenhouse and at the same time period as in Example 2. The solid was placed in two cylindrical containers. Flexible conduits were connected to both ends of the containers, allowing air to circulate between the solid particles. Air circulation was generated using a fan. Two three-way valves at the container's inlet and outlet allowed for alternating operation in two modes. In adsorption mode, the container's inlet and outlet were connected to the inside of the greenhouse. In regeneration mode, the container's inlet and outlet were connected to the outside of the greenhouse through an opening in the wall 50 cm above ground level. The container had a diameter of 1 m and a length of 2 m.

[0153] The process operates in adsorption mode from 06:00 to 09:00 on day D and from 05:00 to 08:00 on day D+1, and in regeneration mode from 12:00 to 17:00 on days D and D+1. During the remaining time, the fan is off and the valves are closed.

[0154] Depending on the solid, the fan flow rate is fixed at different values: solids A and D are 4000m³ / h. 3 / h, solid C, F and G are 5000m 3 / h, solid E is 6000m 3 / h.

[0155] Figure 5 The relative humidity over time was compared under normal conditions (normal heating), under temperature limitations (low heating) but without solids, and finally under temperature limitations and with various solids A, C, E, and D, as described above.

[0156] Figure 6 and Figure 5 The same, except that the solids implemented are solids G and F (not according to the invention).

[0157] It was observed that in this implementation, solids A, C, E, and D enabled humidity control to prevent condensation in the greenhouse, while solids G and F had little effect on the relative humidity in the greenhouse.

[0158] Example 4:

[0159] The goal is to control the relative humidity in the office located in Paris, France. To ensure the comfort of the occupants, the relative humidity must be between 40% and 70%.

[0160] The office has a floor area of ​​12m². 2 The office has a ceiling height of 2.5m and is equipped with controlled mechanical ventilation, which can completely refresh the indoor air within 1.4 hours. The office is occupied from 8:00 AM to 6:00 PM.

[0161] The solid structure is implemented in the form of a square plate with a thickness of 2.5cm and a side length of 100cm, and is fixed to the office ceiling.

[0162] Figure 7 The relative humidity of the office (without solids and with solids B, H, I, and J) can be compared from 00:00 on day D to 00:00 on day D+4.

[0163] For solids G and F (not according to the invention), Figure 8 and Figure 7 same.

[0164] In the absence of solids or in the presence of solids G and F, relative humidity often exceeds the range recommended for ensuring good occupant comfort. In contrast, in the presence of solids B, H, I, and J, relative humidity is controlled between 40% and 70%.

[0165] Example 5:

[0166] In Paris, during the same period as in Example 4, relative humidity was controlled in an apartment that included living space with a living room and kitchen, as well as three bedrooms.

[0167] The apartment has a floor area of ​​105 square meters. 2 The ceiling is 2.4m high and equipped with controlled mechanical ventilation, which can completely refresh the indoor air within 1.4 hours. The apartment is occupied daily from 6:00 PM to 8:00 AM.

[0168] The solid structure is implemented in the form of five square panels, each 2.5 cm thick and 110 cm on each side. One panel is fixed to the ceiling of each bedroom, and two panels are fixed to the ceiling of the living room.

[0169] Figure 9 The relative humidity of the apartment (without solids and with solids B, H, I, and J) can be compared from 00:00 on day D to 00:00 on day D+4.

[0170] For solids G and F (not according to the invention), Figure 10 and Figure 9 same.

[0171] Figure 9 and Figure 10 The results show that solids B, H, I, and J can control the relative humidity in an apartment between 40% and 70%, while solids G and f cannot.

[0172] Example 6:

[0173] In the same greenhouse as described in Example 1, the goal is to control the relative humidity therein to keep it below 90% at all times.

[0174] The relative humidity in greenhouses with and without the following solids was compared from midnight on day D to 16:00 on day D+4.

[0175] - Solid K;

[0176] -Solid L;

[0177] -Solid M.

[0178] The solid is in the form of cylindrical particles with a diameter of 1 mm and a length of approximately 5 mm.

[0179] Figure 11 The diagram shows the change of relative humidity over time with and without solids, and with 500 kg of solids K, L, and M.

[0180] It was observed that, in the absence of solids, the relative humidity repeatedly exceeded 90% during the studied time period. The addition of solids L and M, used in the context of this invention, ensures that the 90% threshold is never exceeded, unlike the case with solid K which is not based on this invention.

[0181] Example 7:

[0182] In the same greenhouse as described in Example 1, the goal is to control the relative humidity therein to keep it below 90% at all times.

[0183] The relative humidity in the greenhouse was compared between midnight on day D and 16:00 on day D+4 with and without the following solids.

[0184] -Solid D;

[0185] -Solid H;

[0186] -Solid L.

[0187] The solid is in the form of cylindrical particles with a diameter of 1 mm and a length of approximately 5 mm.

[0188] All solids are according to the present invention, but it is not recommended to control them within the same range of relative humidity:

[0189] - The average diameter of solid I during adsorption is 4.1 nm, which is less than 5 nm. Therefore, it is recommended for use when the relative humidity is controlled between 40% and 60%.

[0190] The average diameter of solid H adsorption is 5.2 nm, therefore it is recommended for use when the relative humidity is controlled between 40% and 80%.

[0191] - The average diameter of solid D during adsorption is 14 nm, therefore it is recommended for use when the relative humidity is controlled at approximately 75% to 95%.

[0192] During this period, the average relative humidity inside the greenhouse was 79%, the minimum was 57%, and the maximum was 95%.

[0193] Figure 12 The diagram shows the change of relative humidity over time with and without solids, and with 200 kg of solids D, H, and I.

[0194] Table 2 shows the average, minimum, and maximum relative humidity values ​​inside the greenhouse during this period.

[0195] No solid D H I Average value 79％ 79％ 79％ 79％ Maximum value 95％ 88％ 95％ 95％ Minimum value 57％ 61％ 57％ 57％

[0196] Table 2: Average, minimum, and maximum relative humidity values ​​in the greenhouse (with or without solids) during this period

[0197] It can be seen that the two solids H and I with diameters less than 6 nm during adsorption are not suitable for controlling the relative humidity in the greenhouse to the required level.

[0198] Solid D with a diameter greater than 10 nm during adsorption can be used to control relative humidity between 61% and 88%.

[0199] Example 8:

[0200] The regeneration capacity of various porous solids was evaluated in the range of 90% to 75% relative humidity without the addition of external energy.

[0201] The "DVS Advantage" apparatus from Micromeritics was used, which allows for the weighing of solids under controlled relative humidity and temperature. Measurements were performed at 25°C. The solid was first dried in dry air (relative humidity less than 1%) for 3 hours. The relative humidity of the air was then increased to 90%, and the mass of the solid was recorded when the change in mass over time was less than 1%. The same measurement was then performed at a relative humidity of 75%. The percentage of adsorbed water was then calculated as a function of the dry mass of the solid, according to the following calculation:

[0202] The amount of adsorbed water (mass%) = (mass of solid at relative humidity of 90% (or 75%) - mass of dry solid) / mass of dry solid.

[0203] The regeneration capacity of a solid is equal to the amount of water adsorbed at a relative humidity of 90% minus the amount of water adsorbed at a relative humidity of 75%.

[0204] The results are recorded in Table 3.

[0205]

[0206] Table 3: Regeneration capacity of various solids at 25°C and 90% and 75% relative humidity

[0207] Solids 1 and 2 are the solids described in JP2002284520A.

[0208] It was observed that solids characterized by an average mesopore diameter greater than 10 nm during adsorption exhibited the best regeneration capability when the relative humidity decreased from 90% to 75%.

[0209] Example 9:

[0210] The same experiment as in Example 8 was performed, but with relative humidity of 60% and 40%. The results are recorded in Table 4.

[0211]

[0212]

[0213] Table 4: Regeneration capacity of various solids at 25°C and 60% and 40% relative humidity

[0214] It has been observed that solids characterized by an average mesopore diameter of less than 10 nm during adsorption have the best regeneration capacity when the relative humidity decreases from 60% to 40%.

Claims

1. The use of mesoporous solids for controlling relative humidity in enclosed spaces, said mesoporous solids having: - Mesopores with an average diameter of 3 to 50 nm, measured by nitrogen adsorption combined with the BJH method according to standard ASTM D4641-17; - Mesoporous specific volume greater than or equal to 0.2 mL / g, measured according to standard ASTM D4641-17 by nitrogen adsorption combined with the BJH method; and - The ratio of the average mesopore diameter measured by nitrogen desorption to the average mesopore diameter measured by nitrogen adsorption is 0.3 to 1; When a mesoporous solid also contains macropores, micropores, or a combination of micropores and macropores: - The total specific volume of macropores and mesopores is 0.3 to 2 mL / g; - The ratio of (macropore specific volume) / (total specific volume of macropores and mesopores) is less than 0.6; and - Micropore volume ratio is less than 0.2 mL / g.

2. The use according to claim 1, wherein the mesoporous solid has mesopores, and the average diameter of the mesopores is 3 to 50 nm, as measured by nitrogen desorption combined with the BJH method according to standard ASTM D4641-17.

3. The use according to claim 2, wherein the ratio of the "average diameter of mesopores as measured by nitrogen desorption" to the "average diameter of mesopores as measured by nitrogen adsorption" of the mesoporous solid is 0.4 to 1.

4. The use according to any one of the preceding claims, wherein the mesoporous solid is selected from the group consisting of metal oxide-based solids, carbon-based solids, and mixtures thereof.

5. The use according to claim 4, wherein the mesoporous solid is selected from the group consisting of oxides of silicon, oxides of aluminum, activated carbon, carbon nanotubes, and mixtures thereof.

6. The use according to claim 1, wherein the enclosed space is a building for residential use or a building for professional use.

7. The use according to claim 6, wherein the building for the specialized purpose is a cultivation greenhouse, an agricultural building specifically for storing or drying food and plants, a production workshop, an indoor swimming pool, a sauna, a bathroom, a museum, or a transportation building.

8. The use according to claim 1, wherein the average pore size of the mesoporous solid during adsorption is 10 to 40 nm and the average pore size during desorption is 10 to 35 nm, such that the relative humidity can be controlled at a value of 80% to 95%.

9. The use according to claim 1, wherein the average pore size of the mesoporous solid during adsorption is 5 to 15 nm and the average pore size during desorption is 5 to 13 nm, such that the relative humidity can be controlled at a value of 60% to 80%.

10. The use according to claim 1, wherein the average pore size of the mesoporous solid during adsorption is 3 to 10 nm and the average pore size during desorption is 3 to 9 nm, such that the relative humidity can be controlled at a value of 40% to 60%.

11. The use according to claim 1, wherein the mesoporous solid has a zero micropore specific volume.

12. The use according to claim 1, wherein the mesoporous solid is in the form of an agglomerate.

13. The use according to claim 1, wherein the mesoporous solid is a crystalline form with a size less than 100 μm as measured by scanning electron microscopy.

14. A device for controlling relative humidity in an enclosed space, comprising: - A container having one or more openings for connection to the atmosphere of an enclosed space; - A mesoporous solid placed in a container, the mesoporous solid being as defined in claim 1.

15. The apparatus of claim 14, wherein the container is made of an airtight material.

16. A method for controlling relative humidity in an enclosed space, comprising one of the following steps: (a1) Placing a mesoporous solid as defined in claim 1 within an enclosed space; or (a2) Placing the mesoporous solid as defined in claim 1 in one or more containers within a closed space, said containers being made of an airtight material and having openings connected to the atmosphere of the closed space; or (a3) Placing one or more of the devices according to claim 14 or 15 within the enclosed space; or (a4) Placing a mesoporous solid as defined in claim 1 on one or more surfaces of an enclosed space.

17. The method of claim 16, wherein the mesoporous solid or device is placed in place for at least 10 days.

18. The method of claim 16 or 17, wherein the enclosed space is a building for residential use or a building for professional use.

19. The method of claim 18, wherein the building for specialized use is a cultivation greenhouse, an agricultural building specifically for storing or drying food and plants, a production workshop, an indoor swimming pool, a sauna, a bathroom, a museum, or a transport building.

Images