Method for producing solids

Abstract

The present invention relates to a method for producing solids from a liquid containing the solid, characterised in that the method comprises the method steps of: i) providing a liquid containing the solid; ii) dispersing a gas in the liquid under increased pressure to produce a gas–liquid two-phase mixture; iii) expanding the gas-liquid two-phase mixture produced in method step ii). The invention also relates to the use of the method according to the invention for producing crystalline or partially crystalline solid particles, and to allulose moulded bodies.

Description

[0001] Process for producing solids

[0002] The present invention relates to a process for producing solids. In particular, the present invention relates to a process by which solids, for example in crystalline or semi-crystalline form, can be produced from a liquid using simple process control.

[0003] Particulate solid products offer several advantages over liquid products such as solutions. These include better storage stability, particularly longer shelf life for food products, user-friendly dosing, and lower storage and transport costs, as no additional solvent such as water is required. However, many substances are initially in solution due to the manufacturing process. It is therefore highly relevant to establish processes for downstream solid production. Free-flowing particulate products are preferred here to ensure good dosing and user-friendly handling.

[0004] The production of such particulate products from a solution is usually achieved using spray-drying processes. The solution is first atomized, and then the droplets are dried into a powder by evaporating the solvent. However, spray-drying processes cannot be used to produce particles if the material exhibits slow crystallization kinetics and a low glass transition temperature. In such cases, the material cannot be dried even in a large spray dryer and clumps together as a supersaturated solution or softened solid above its glass transition temperature in the spray tower.

[0005] For example, the article by M. Malamatari et al., Spray Drying for the Preparation of Nanoparticle-based Drug Formulations as Dry Powders, Processes 2020, 8, 788, describes that particles can be produced using spray drying as a solidification technique.

[0006] Alternative processes for particle production include evaporation and cooling crystallization, in which crystallization takes place in a supersaturated solution with the addition of seed crystals, and the crystals must then be separated from the liquid. These processes are particularly established for substances that cannot be processed by spray drying due to their slow crystallization kinetics. However, the yield is often low and the required residence time in the crystallizer is long. For example, a required residence time of 30 to 70 hours is described in the main crystallizer alone in a multi-stage plant for the crystallization of simple sugars. Such processes are disclosed, for example, in WO 2020 / 11485.

[0007] Another method is the use of kneaders and extruders to crystallize supersaturated solutions, see EP 3 363 909 A1, WO 2022 / 049307 A1. This produces a paste of crystals and solvent. However, further processing of the paste into a free-flowing particulate product by drying and grinding is problematic. The remaining solution is trapped between the aggregated crystals in the paste and therefore cannot be completely removed. In addition, amorphization through grinding is a known phenomenon that can additionally lead to stickiness of the product and thus limits the production of a free-flowing powder. EP 1 021 241 B1 describes a method for producing a powdered product from a liquid substance or mixture of substances. For this purpose, a gas is first dissolved in the liquid substance or gas mixture in a pressure vessel and the mixture is then fed to a pressure relief device.The essential feature of the process described in this document is that an auxiliary substance is added to the liquid substance or mixture of substances to be pulverized before, in or after a relaxation device.

[0008] EP 0 744 992 B1 also describes a method for producing particles or powders. In this method, similar to the previously described document, a pressure vessel is provided in which a substance or substance mixture to be treated is provided. A fluid is dissolved in this substance or substance mixture under pressure, after which the resulting solution is expanded by means of an expansion device in such a way that the solidification temperature of the substance or substance mixture is exceeded after the expansion device, and particle formation occurs.

[0009] However, the state of the art still offers potential for improvement, particularly with regard to a simple and easily implementable solution for producing a solid from a liquid containing this solid.

[0010] The object of the present invention is to provide a measure by which at least one disadvantage of the prior art is at least partially overcome. In particular, the object of the present invention is to develop a measure by means of which a simple and easily implementable solution for producing a solid from a liquid containing this solid is possible.

[0011] The object is achieved according to the invention by a method having the features of claim 1. The object is further achieved according to the invention by a use having the features of claim 13 and by shaped bodies having the features of claim 15. Preferred embodiments of the invention are disclosed in the subclaims, in the description, and in the figure, wherein further features described or shown in the subclaims or in the description or the figure can represent an object of the invention individually or in any combination, unless the context clearly indicates the opposite.

[0012] The present invention relates to a process for producing solids from a liquid containing the solid, characterized in that the process comprises the process steps: i) providing a liquid containing the solid; ii) dispersing a gas in the liquid under increased pressure to produce a gas-liquid two-phase mixture; iii) depressurizing the gas-liquid mixture produced in process step ii).

[0013] Such a method offers significant advantages over state-of-the-art solutions.

[0014] Thus, a process is described for producing solids from a liquid containing the solid. In particular, the process serves to obtain a solid as a particulate and preferably free-flowing powder and / or the solid in crystalline or semi-crystalline form, whereby the invention also encompasses the production of amorphous solids. Processing the solid from a liquid containing the solid is challenging, particularly when producing free-flowing powders and / or crystalline or semi-crystalline powders.

[0015] To achieve this, the process comprises the following process steps. According to process step i), the process comprises providing a liquid containing the solid. Accordingly, the solid is present in a liquid at the start of the process and can, for example, be dissolved or dispersed in the liquid. However, the solid is preferably dissolved in the liquid and is particularly preferably present as a supersaturated solution. In principle, neither the solid nor the liquid are restricted; rather, the process is fundamentally suitable for any combination of solids and liquids.

[0016] Examples of solids include polymers, carbohydrates, and / or bioactive substances, although the invention is not limited to these solids. Suitable solvents should, in particular, be those that do not react chemically with the solids, can form a solution or dispersion as required, and are suitable for further processing, particularly the expansion, as described below. Examples of solvents include water or other liquid inorganic or organic substances.

[0017] According to process step ii), the process comprises dispersing a gas in the liquid under elevated pressure to produce a gas-liquid two-phase mixture. It is therefore essential in this process step that a gas is dispersed into the liquid containing the solid under elevated pressure, i.e., a pressure higher than atmospheric pressure (1 bar). Dispersing occurs in such a way that the gas is not dissolved, or at least not predominantly dissolved, but rather that a gas-liquid two-phase mixture is produced. Thus, such a two-phase mixture can be described as a dispersion of the gas in the liquid. Accordingly, within the meaning of the present invention, dispersing a gas in a liquid means introducing gas bubbles into the liquid to produce a two-phase mixture with a continuous liquid phase and dispersed gas bubbles contained therein.It can be advantageous in this step that when the gas is mixed into the liquid, particularly due to the viscosity of a liquid, mechanical energy is introduced, for example in the form of shear forces, which helps to create a two-phase mixture. Thus, no single-phase solution of the gas in the liquid is created, or at least not to a significant extent. In particular, instead of a solution of the gas in the liquid, the formation of a dispersion can be made possible by the solubility of the gas in the liquid not being present under the given conditions, such as pressure, temperature and gas content. In order to achieve sufficient or complete solubility, the prior art usually involves working in the supercritical range of the gas, which is precisely what the invention aims to avoid.

[0018] Suitable pressure ranges which can be used according to the invention are in a range above atmospheric pressure, i.e. at a total pressure of > 1 bar, for example > 3 bar.

[0019] The gases used in process step ii) are not fundamentally limited and can, in particular, be those that are inert with respect to the solvent and the solid. Depending on the mixture of substances, examples include known inert gases, such as nitrogen or argon, with nitrogen being particularly preferred. Another preferably suitable gas contains or consists of, for example, carbon dioxide.

[0020] Subsequently, according to process step iii), the gas-liquid two-phase mixture produced in process step ii) is depressurized. In this step, the pressure is thus released, for example to ambient pressure, i.e., 1 bar. It is preferred that the depressurization be rapid and, in particular, that the pressure release rate be in the range of > 0.05 bar / s. In this process step, a device can preferably be used that enables sufficiently rapid depressurization of the mixture. For example, a nozzle, a diffuser, a capillary, an orifice plate, a valve, or a combination of the aforementioned depressurization devices is used as the depressurization device.

[0021] In particular, the process steps described above allow significant advantages over the state-of-the-art solutions.

[0022] The process described here enables the problem-free production of free-flowing, particularly crystalline or semi-crystalline, but also amorphous particles from a liquid or solution in a particularly advantageous manner. The liquid is first mixed with a compressed gas under increased pressure to form a two-phase mixture. Subsequently, rapid expansion of the compressed gas is initiated by pressure release, whereby the solution is atomized. The stretching of the material during atomization initiates nucleation, and particle formation occurs primarily at the numerous interfaces between the solution and the gas bubbles. This process is surprisingly particularly defined and reliable when the mixed gas is not dissolved, but rather a two-phase mixture in which the gas exists in undissolved form in the liquid.Thus, free-flowing solids can be formed even when this is not possible or only possible with great effort using state-of-the-art processes, since the interfaces between gas and liquid are completely absent when the gas is dissolved in the liquid, as is usual in the state of the art.

[0023] The process is characterized by the fact that at the gas-liquid interfaces, as described above, not only mere particle formation is possible, but in particular crystal growth can take place. Accordingly, the process according to the invention makes it possible to easily produce crystalline or semi-crystalline solids. This was sometimes very difficult to achieve with prior art processes because, in the case of a dissolved gas, there are no interfaces between gas and liquid. A suitable size for the gas bubbles for the process can, for example but not restrictively, be in a range from > 1 pm to < 1000 pm. This can be adjusted, for example, by combining the quantitative ratios of liquid to gas, the gas pressure and the mechanical energy input during dispersion, i.e. the mixing time or the intensity of the stress during dispersion.

[0024] It is advantageous if the solid is present as a solution in the liquid used, and the solution is supersaturated with respect to the solid. It has been shown that a particularly high yield can be achieved in this configuration.

[0025] The process can be carried out with minimal requirements regarding the equipment, as the selected parameters, such as pressure and temperature, can be selected much less harshly than is usual in the state of the art. Furthermore, the requirements for the components used are minimal. In principle, it may be sufficient to use three substances: the solid to be produced as the sole solid, the solvent in which it is present, and the gas to be mixed in, whereby the solvent and / or gas can also be only one component. This also makes the process highly sustainable, as no waste streams are expected.

[0026] In principle, this process can be carried out with any combination of solid, liquid, and dispersed gas, as the advantages lie particularly in the effects at the gas-liquid interface during expansion. A specific viscosity results from the solid material, the proportion of gas mixed in, and the set processing temperature. Depending on the viscosity, porous particles or foam strands, which may still contain solvent, are formed during atomization. The porous structure results in a large surface area with a small thickness of the material lamellae, so that rapid separation of residual solvent during drying can be achieved through improved mass transport. This makes solvent-free particles possible. The porous structure is also retained during drying, so that the particles can be easily further adjusted if necessary.Only a small amount of energy is required to crush the porous structures, so amorphization does not occur during the painting process. Accordingly, it is possible and may be preferable to further crush the resulting solids and thus the resulting solid particles.

[0027] However, in some cases, it may also be advantageous for the product to be produced as a foam. The production of porous solid particles or a foam can be achieved easily and simply by adjusting the predetermined parameters.

[0028] The mixing of the liquid containing the solid with the gas under increased pressure or with the compressed gas, and the atomization or expansion, can be carried out both discontinuously and continuously, with continuous processes enabling higher throughput. Discontinuous processes are particularly preferable for changing products or for smaller applications.

[0029] The process, or process step ii), can be carried out batchwise in a pressure vessel equipped with an agitator. This vessel can, for example, be equipped with an inlet for introducing the liquid containing the solid and another inlet for the gas through which gas can be introduced. A valve can also be provided to allow pressure to be released. For a continuous process, flow-through pipelines, for example with static mixers, or extruders can be used. The throughput fundamentally depends on the design of the mixing units, such as the extruder. When using larger plants, the process can easily be expanded to produce several tons of solid per day, making large-scale industrial application a breeze.

[0030] Preferably, after process step ii), the proportion of gas dissolved in the liquid to the total amount of gas introduced into the process can be in a range of < 10 wt. %, preferably < 5 wt. %, particularly preferably < 1 wt. In this embodiment, it is clear that the gas mixed in process step ii) is at least largely not dissolved in the liquid, but rather a two-phase mixture is generated. As described above, it has been shown that the formation of a two-phase mixture, in particular, demonstrates the advantages of the process described here particularly effectively. Thus, the process according to the invention can be particularly advantageous, particularly in this embodiment.

[0031] It may further be advantageous for process step i) to be carried out under a pressure in a range of > 3 bar, for example from > 5 bar to < 500 bar. It has been shown that such pressure ranges are particularly advantageous for dispersing the gas in the liquid, which is subsequently present in a two-phase mixture and is not, or at least not significantly, dissolved in the liquid. Particularly preferred pressure ranges can then be in a range from > 10 bar to < 100 bar. In principle, however, the pressures can be in a range that is significantly lower than in the prior art, which sometimes requires working in the supercritical range.

[0032] In principle, the selected pressure range depends on the other parameters, as described above. In order to carry out the method described above particularly safely and reliably, it can also be advantageous to use a pressure release rate in a range from > 0.1 bar / s to < 5000 bar / s in method step ii). Particularly preferred ranges for the pressure release rate are in a range from > 1 bar / s to < 1000 bar / s or from > 10 bar / s to < 500 bar / s. It has been shown that the reliability and thus the feasibility of the method described here are particularly high, especially with such pressure release rates. Accordingly, the advantages according to the invention can be particularly effective in this embodiment.

[0033] In a preferred embodiment, the process for producing solids from a liquid containing the solid can be a process for producing at least partially crystalline solids. The process according to the invention can be particularly suitable for increasing the degree of crystallinity of solids. In particular, the process according to the invention can also achieve high degrees of crystallization for solids that are difficult to crystallize. In addition to the ability to quantitatively produce a high degree of ordered crystal structures in the solids, the process according to the invention is also characterized in particular by the fact that, compared to other processes, the crystalline portion in the solid can be achieved significantly more quickly and with lower equipment and energy expenditure.

[0034] In a further preferred aspect of the process, process step i) can involve providing a mixture of an amorphous or semi-crystalline solid and a liquid in a reactor. The process according to the invention can be used to convert both completely amorphous solids into crystalline solids and semi-crystalline solids into solids with a higher degree of crystallinity. The mixture can be provided by preparing a mixture of the solid, which may be amorphous or semi-crystalline, and a liquid. The proportions between liquid and solid can vary, so that the mixture can also result in a solution of the solid in the liquid. In this case, the solid loses its amorphous, crystalline, or semi-crystalline properties.However, it is also possible that the solubility of the solid in the liquid is too low for the proportion of solid, so that the mixture consists of a mixture of partly solid and partly dissolved solid in the liquid. The proportion of the solid present as undissolved solid can then be in amorphous, semi-crystalline or crystalline form. The term mixture in this context means that the two substances, liquid and solid, are mixed together. Alternatively, it is also possible that the preparation does not occur by adding the individual components. For example, preparation can involve adding a ready-made mixture of the solid and liquid components. The proportion of solid in a highly ordered, crystalline form can be quantitatively determined in the mixture, for example using X-ray methods.Preferably, the solid can be a pure substance. However, solids containing a certain degree of impurities or intentional admixtures in the form of other components can also be used. The composition of the mixture is advantageously not changed by the process. Thus, even more complex substance compositions can be processed in a targeted manner. Preferably, however, the solid can be present in a purity of greater than or equal to 80 mol%, further preferably greater than or equal to 90 mol%, and further preferably greater than or equal to 99 mol%.

[0035] In a further preferred aspect of the process, process step ii) can comprise the mechanical circulation of the mixture provided in process step i) and the dispersing of an inert gas into the mixture, wherein the dispersion of the inert gas results in a two-phase gas-liquid dispersion in the reactor. The use of inert gases has proven particularly useful for forming a two-phase gas-liquid dispersion in the reactor. Under the selected reaction conditions, inert gases do not react with the solids, the liquid, or with the mixture of solid and liquid. In particular, the gas does not dissolve in the mixture in any significant proportions. Overall, a large portion of the inert gas remains as a gas phase within the mixture of solid and liquid. Examples of inert gases include noble gases or inert gases such as nitrogen or carbon dioxide.

[0036] In a further preferred aspect of the process, process step iii) can comprise discharging the gas-liquid dispersion generated in process step ii) from the reactor, wherein the gas-liquid dispersion forms a foam after discharge from the reactor. To increase the proportion of crystals in the mixture, it has proven particularly advantageous for a coherent structure of the mixture to still be present after discharge. Due to the fact that an inert gas is present in the two-phase mixture, the gasified mixture is correspondingly formed in the form of a foam. This embodiment is significantly more efficient for increasing the crystalline content than, for example, atomizing the gas-liquid dispersion into individual, isolated droplets. Without being bound by theory, the crystallization rate of the solid appears to be significantly increased by discharging a coherent foam.It also appears to be very advantageous for crystallization that the foam is present as a very uniform foam with a uniform bubble size distribution. This can increase the crystallization rate and the overall achievable degree of crystallization. The foam can be discharged as a continuous entity. Alternatively, it is also possible to mechanically divide the foam into smaller foam units at regular or irregular intervals during discharge. To achieve the most homogeneous foam properties possible, the volume of the connected foam pieces can be greater than or equal to 1 cm. 3 , greater than or equal to 10 cm 3 , still preferably greater than or equal to 50 cm 3 and preferably greater than or equal to 100 cm 3 In these foam volumes, improved solidification or crystallization of the solid can be achieved compared to smaller volumes.

[0037] In a further preferred embodiment of the method, the method can comprise a further step iv), wherein step iv) comprises at least partial solidification of the foam, wherein the solidification of the foam increases the crystalline proportion of the solid in the foam. Due to the solidification kinetics and in particular the crystallization kinetics of the solid, it can be advantageous for the discharged foam to be reacted for a certain time in order to achieve the highest possible degree of crystallization. The reacting can take place with or without changing the ambient parameters, such as temperature, humidity or pressure. The reacting can also involve a reduction in the proportion of liquid in the foam, but this does not have to be the case.This step can preferably be carried out in a temperature range of greater than or equal to 15°C and less than or equal to 30°C, a pressure of greater than or equal to 950 mbar and less than or equal to 1100 mbar, and a humidity in a range of greater than or equal to 40% rh and less than or equal to 70% rh. These environmental parameters within this step allow for rapid solidification of the discharged foam and high crystalline content. This process step can advantageously be carried out under ambient conditions.

[0038] In a further preferred embodiment of the process, the process can comprise a further, optional step v), wherein in step v) the solidified foam is broken down into smaller components by the introduction of mechanical energy. To obtain pourable or flowable, crystalline products, it can be advantageous for the larger, solidified foam components to be converted into smaller components by the introduction of mechanical energy. This can be achieved, for example, by mortaring, rolling, grinding, or calendering. The solidified foam components display such mechanical stability that deagglomeration of the macroscopic foam pieces can be achieved even with relatively low forces. Advantageously, the foam does not display any adhesive properties, so that even large quantities can be converted within short periods of time.

[0039] Furthermore, the invention relates to a process for producing at least partially crystalline solids, the process comprising at least the following process steps: i) providing a mixture of an amorphous or partially crystalline solid and a liquid in a reactor; ii) mechanically circulating the mixture provided in process step i) and dispersing an inert gas into the mixture, wherein the dispersion of the inert gas results in a two-phase gas-liquid dispersion in the reactor; iii) discharging the gas-liquid dispersion produced in process step ii) from the reactor, wherein the gas-liquid dispersion forms a foam after being discharged from the reactor; and iv) at least partially solidifying the foam, wherein the solidification of the foam increases the crystalline proportion of the solid in the foam.

[0040] Surprisingly, it has been shown that the process according to the invention for producing at least partially crystalline solids can be used to convert even solids that are difficult to crystallize into crystalline solids very quickly and in high proportions with low energy consumption. This process enables the cost-effective preparation of very homogeneous solids with a high degree of order. The resulting crystalline solids are very stable in storage, have low hygroscopicity, can be easily disaggregated or compacted into smaller agglomerates, and display very rapid dissolution in liquid media.

[0041] In a further preferred characteristic of the process for producing at least partially crystalline solids, the dry matter content in the mixture present in process step ii) before dispensing in process step iii) can be greater than or equal to 90.0 wt. % and less than or equal to 99.0 wt. %. The process according to the invention can lead to faster and more complete crystallizations, particularly in cases where the dry matter content in this stage is relatively high. This results in favorable viscosities and stable two-phase gas-liquid dispersions, which enable uniform discharge of the dispersion and a stable foam after discharge. These foams can be solidified quickly and are characterized by a high crystalline content. Furthermore, the solids concentration can preferably be greater than or equal to 92.0 wt. % and less than or equal to 98 wt. % and more preferably greater than or equal to 93.0 wt.-% and less than or equal to 96 wt.%. The quantitative determination of the dry matter content can be performed using the Karl Fischer method if water is used as the liquid. If other liquids are used, the quantitative solids content can be determined by calibrating the solid. One possible method is given further down in the examples; alternatively, calibrations can also be performed using NIR.

[0042] In a further preferred characteristic of the process for producing at least partially crystalline solids, a sugar, preferably a monosaccharide, can be provided as the solid in process step i). The process according to the invention is particularly suitable for processing sugars. Compared to prior art processes, the sugars used can be solidified and converted into crystalline sugars relatively quickly, easily, and with low energy consumption using the process according to the invention.

[0043] In a further preferred feature of the process for producing at least partially crystalline solids, the solid in process step i) can be a ketohexose. The process according to the invention is particularly suitable for processing ketohexoses. The ketohexoses can be converted relatively quickly and easily into crystalline ketohexoses.

[0044] In a further preferred characteristic of the process for producing at least partially crystalline solids, the solid in process step i) can be allulose (D-psicose, (3A,4A,5A)-1,3,4,5,6-pentahydroxy-2-hexanone). The process according to the invention is particularly suitable for processing allulose. The allulose can be converted relatively quickly and easily into crystalline allulose. This process is therefore particularly suitable for processing allulose, since other processes with a similar goal are significantly more cost-intensive and time-consuming.

[0045] In a further preferred characteristic of the process for producing at least partially crystalline solids, the liquid in process step i) can be water. The use of water as a liquid has proven particularly useful in the processing of sugars, for example in the form of allulose. For this purpose, a mixture of water and sugar can be prepared in this process step, or such a mixture can be added. High degrees of crystallinity can be achieved for the sugars and allulose, and the resulting products are particularly suitable for use in the food or medical sectors.

[0046] In a further preferred characteristic of the process for producing at least partially crystalline solids, the inert gas in process step ii) can be carbon dioxide. The use of carbon dioxide as an inert gas has proven effective for forming a stable dispersion and a stable foam. In combination with the sugars, for example allulose, high degrees of crystallization are achieved with very rapid kinetics. A further advantage can be that carbon dioxide is physiologically harmless, so that the obtainable products can also be used as food or in the food sector. In a further preferred characteristic of the process for producing at least partially crystalline solids, the concentration of gas in the mixture in process step ii) can be greater than or equal to 0.1 wt.% and less than or equal to 5 wt.%.This gas content in the two-phase dispersion or mixture can lead to particularly good foam properties. Very stable foams are formed, which can exhibit particularly rapid solidification and crystallization kinetics.

[0047] In a further preferred characteristic of the process for producing at least partially crystalline solids, in process step iii), the temperature of the foam immediately after dispensing can be greater than or equal to 25°C and less than or equal to 35°C. For efficient solidification and crystallization of the foams, it has proven advantageous to keep the temperature of the foam within a very narrow temperature window. This allows fully crystallized solids to be obtained in a short period of time.

[0048] In a further preferred characteristic of the process for producing at least partially crystalline solids, in process step ii) the mechanical circulation and dispersion of the inert gas into the mixture can take place continuously, wherein the ratio of the gas flow rate of the inert gas and the molar flow rate of the mixture, calculated from the gas flow rate in g / min divided by the molar flow rate in g / min, is greater than or equal to 0.5% and less than or equal to 3%. The formation of homogeneous gas bubbles in the mixture can be very advantageous for rapid solidification and crystallization. These can be achieved in particular when a constant and specific mixing ratio of mixture to gas is set. A smaller ratio can be disadvantageous since in these cases no coherent foam can be obtained and the gas is discharged in an uncontrolled manner.Larger ratios, however, can be disadvantageous, as in these cases, only an insufficient gas phase is formed. This can, in particular, lead to insufficient strength and crystallization. This ratio is particularly suitable for the solidification and crystallization of sugars, and in particular for the solidification of allulose.

[0049] In a further preferred characteristic of the process for producing at least partially crystalline solids, process steps i) - iii) can be carried out in an extruder, wherein in process step i) a mixture of liquid and solid is fed into the extruder; ii) the inert gas is metered into a feed point located further toward the extruder output; and iii) the gas-liquid dispersion is discharged from the extruder through a nozzle. The process according to the invention can be carried out in a highly controlled manner, particularly using an extruder. This results in very precisely controllable mechanical mixing of the mixture and a high degree of controllability of the feed quantities of mixture and gas. A very stable gas-liquid dispersion with a homogeneous gas size distribution is formed, which can particularly contribute to improved solidification and crystallization.

[0050] In a preferred aspect of the process using an extruder, additional solid can be added to the mixture in process step ii) prior to the addition of the inert gas in the extruder. Processing a highly supersaturated mixture and introducing the inert gas into such a mixture has proven particularly suitable for rapid and complete solidification of the discharged material. The additional solid can, for example, be added in amorphous or crystalline form. Preferably, a crystalline solid can be added. This step can preferably be used to solidify allulose. Preferably, the amount of solid allulose added in this step can be greater than or equal to 5% and less than or equal to 20% based on the allulose content fed into the extruder. In these cases, very stable foams with very rapid solidification kinetics and a high degree of crystallinity are obtained.

[0051] In a preferred aspect of the process using an extruder, in process step ii), the inert gas can be added to the extruder at a distance of greater than or equal to 10% and less than or equal to 70%, based on the total internal length of the extruder, from the extruder discharge nozzle. The gas addition point defined above has proven to be very suitable for obtaining a very homogeneous foam with a uniform bubble distribution of the inert gas in the foam. The inert gas is therefore preferably added to the extruder at the earliest in the second half of the extruder. After the gas is added, the resulting dispersion is homogenized to form a foam within an extruder length of 10%, based on the total internal length of the extruder. This design provides the mixture with a sufficient inlet section for mechanical processing in the extruder.Furthermore, there is sufficient clearance within the extruder to allow for the addition of additional solids. This positioning also essentially prevents short-circuited gas flows through both the component inlet and the extruder nozzle. This setup is particularly suitable for solidifying sugars, especially allulose. Highly homogeneous and stable foams with high solidification rates and a high degree of crystallinity are obtained. Furthermore, the clearance can be greater than or equal to 15% and less than or equal to 50%.

[0052] In a further preferred characteristic of the process using an extruder, the temperature in process step ii) can be greater than or equal to 20°C and less than or equal to 35°C. For the homogeneous introduction of the inert gas into the mixture, operating the extruder within the specified temperature range has proven particularly suitable. A wider range of solids contents of the mixture can be processed without the risk of an unsuitable viscosity range for the mixture. Higher temperatures in the extruder can lead to a reduction in the solids range window, since in these cases there is a risk of an unsuitably low viscosity of the mixture. This would result in no homogeneous foam leaving the extruder die. Lower temperatures can also lead to a reduction in the processing window, since the viscosities of the mixture can increase excessively.These statements apply particularly to the processing of sugars, especially to the processing of allulose.

[0053] The invention further describes the use of a method as described above for producing, in particular, crystalline or semi-crystalline solid particles. As stated above, the method is particularly suitable for producing solid particles, which are produced from a liquid containing them. These particles are particularly preferably crystalline or semi-crystalline, although amorphous particles are also encompassed by the invention. In a preferred embodiment, the crystalline or semi-crystalline solid particles can be allulose foams or allulose particles.

[0054] In a preferred embodiment of the use, the process can be a process for the crystallization of simple sugars. The process according to the invention is particularly suitable for the reproducible and energy-efficient crystallization of simple sugars. Highly crystalline simple sugars are obtained with low energy consumption and rapid reaction times.

[0055] In a preferred embodiment of the use, the process can be a process for the crystallization of ketohexoses. The process according to the invention is particularly suitable for the reproducible and energy-efficient crystallization of ketohexoses. Highly crystalline ketohexoses are obtained with low energy input and rapid reaction times. In a preferred embodiment of the use, the process can be a process for the crystallization of allulose. The process according to the invention is particularly suitable for the reproducible and energy-efficient crystallization of allulose. Highly crystalline allulose is obtained with low energy input and rapid reaction times.

[0056] Also according to the invention are allulose foams, wherein the allulose foams were obtained by the process according to the invention.

[0057] Also according to the invention are allulose aggregates, wherein the allulose aggregates are obtained by mechanical comminution from the allulose foams obtainable by the process according to the invention. The allulose aggregates are particularly suitable as components in the production of tablets, chewing gum, or sprinkles.

[0058] Furthermore, according to the invention, allulose shaped bodies are provided, wherein the allulose shaped bodies have a surface area determined via BET of greater than or equal to 0.25 m 2 / g and less than or equal to 0.8 m 2 / g. The shaped bodies can be in the form of foams, for example, or, alternatively, in the form of particles or aggregates obtained from the foams by mechanical comminution. A number-average particle or aggregate size, obtained via laser light scattering, can preferably be greater than or equal to 1 pm and less than or equal to 250 pm. Due to the larger, accessible surface area, the aggregates or particles can exhibit improved properties with regard to wettability, dissolution, and compaction. In addition, the aggregates obtainable according to the invention exhibit a high degree of crystallinity. However, the solidification of allulose gas dispersions can, in particular, lead to the obtaining of allulose foams with a larger surface area compared to other processes known from the prior art.Due to the larger, accessible surface area, the foams can exhibit improved properties with regard to wettability, dissolution, and compaction. Furthermore, the foams according to the invention exhibit a high degree of crystallinity. The allulose moldings can preferably have a surface area, determined via BET, of greater than or equal to 0.28 m². 2 / g and less than or equal to 0.4 m 2 / g. The BET measurement can be performed according to DIN ISO 9277:2014-01.

[0059] In a preferred embodiment of the allulose moldings, the moldings can be in the form of pourable particles, wherein the particles have an angle of repose determined according to DIN ISO 4324: 1983-12 of greater than or equal to 35° and less than or equal to 50°. The particles can be converted from the allulose foams into pourable particles using the roller method described below. Due to the achievable high degree of crystallinity and based on the surface properties of the particles, these particles exhibit smaller angles of repose compared to particles obtainable by other manufacturing processes. The particles are more flowable and therefore easier to process.

[0060] In a further preferred embodiment of the allulose shaped bodies, the shaped bodies can be in the form of pourable particles, wherein the particles have a bulk density determined according to ISO 3923 (Pharmacopeia Apparatus Bulk Density Scott Volumeter) of greater than or equal to 400 kg / m 3 and less than or equal to 700 kg / m 3 Due to the (internal) structure of the particles, the bulk density can be significantly lower than that of crystals obtained from cooling crystallization.

[0061] In a further preferred embodiment of the allulose moldings, the moldings can have a fructose content of at most 5.0 wt.%, 4.5 wt.%, 4.0 wt.%, 3.5 wt.%, 3.0 wt.%, 2.5 wt.%, 2.0 wt.%, 1.5 wt.%, 1.0 wt.% or 0.5 wt.%. Thus, the process according to the invention yields very pure allulose moldings with a high allulose content and a high content of crystalline allulose. The fructose content in the moldings can preferably be greater than or equal to 0 wt.% and less than or equal to 5.0 wt.%, wherein the limits stated above up to the lower limit of 0.5 wt.% can be used for the upper limit. More preferably, the lower concentration limit of fructose may preferably be greater than 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt% or 1.0 wt%.Small amounts of fructose in the allulose can improve the physical properties of the shaped body. This is especially true compared to crystals produced by cooling crystallization and the shaped bodies obtainable therefrom, which typically have very low fructose contents. Crystallization by cooling an allulose solution generally results in a different admixture profile, since crystal formation promotes the formation of purer allulose crystals. These shaped bodies can be obtained in particular by the process according to the invention, the process according to the invention for producing crystalline solids, and the process according to the invention for producing crystalline solids using an extruder.

[0062] In a further preferred embodiment of the allulose moldings, the moldings can have a glucose content of at most 2.0 wt.%, 1.5 wt.%, 1.0 wt.%, or 0.5 wt. Thus, the process according to the invention yields very pure allulose moldings with a high allulose content and a high crystalline allulose content. The glucose content can preferably be greater than or equal to 0 wt.% and less than or equal to 2.0 wt.%, with the limits specified above being applicable for the upper limit, down to the lower limit of 0.5 wt.%. More preferably, the lower concentration limit of glucose can preferably be greater than 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1.0 wt%. Small amounts of glucose in the allulose can improve the physical properties of the molded article.This is especially true when compared to crystals produced by cooling crystallization and the molded articles obtainable therefrom, which typically have low glucose contents. Crystallization by cooling an allulose solution generally results in a different admixture profile, since crystal formation favors the formation of purer crystals. These molded articles can be obtained in particular by the process according to the invention, the process according to the invention for producing crystalline solids, and the process according to the invention for producing crystalline solids using an extruder.

[0063] In a further preferred embodiment of the allulose shaped bodies, the shaped bodies can have a glucose content of greater than or equal to 0 wt.% and less than or equal to 2.0 wt.% and a fructose content of greater than or equal to 0 wt.% and less than or equal to 5.0 wt.%. Small amounts of glucose and / or fructose in the allulose can improve the physical properties of the shaped body. This applies in particular in comparison to crystals produced by cooling crystallization and shaped bodies obtainable therefrom, which usually have low glucose and / or fructose contents. Crystallization by cooling an allulose solution generally results in a different admixture profile, since crystal formation favors the formation of purer crystals.These shaped bodies can be obtained in particular by the process according to the invention, the process according to the invention for producing crystalline solids and the process according to the invention for producing crystalline solids using an extruder.

[0064] In a further preferred embodiment of the allulose moldings, the moldings can have a content of other sugars apart from allulose, fructose, and glucose of greater than or equal to 0 wt.% and less than or equal to 1.0 wt.%. The proportion of only small amounts of other sugars in the allulose can improve the physical properties of the molding. These moldings can be obtained in particular via the process according to the invention, the process according to the invention for producing crystalline solids, and the process according to the invention for producing crystalline solids using an extruder. The moldings preferably contain no other sugars.

[0065] In preferred embodiments, the allulose molded body has a water content of at most 10 wt.%, preferably at most 8.0 wt.%, more preferably at most 6.0 wt.%, even more preferably at most 5.0 wt.%, in each case based on the total weight of the product allulose composition. Further preferably, the molded body can have a residual water content of at least 0.1 wt.%; preferably at least 0.2 wt.%, more preferably at least 0.3 wt.%, even more preferably at least 0.4 wt.%, even more preferably at least 0.5 wt.%, even more preferably at least 0.75 wt.%, most preferably at least 1.0 wt.%, and in particular at least 1.5 wt.%, in each case based on the total weight of the molded body. The water contents can be determined, for example, using Karl Fischer.

[0066] For the advantages and technical features of the use described here, reference is made to the description of this method, to the figure and to the description of the figure.

[0067] The invention is explained below by way of example with reference to the attached drawing, wherein the features shown below can represent an aspect of the invention both individually and in combination, and wherein the invention is not limited to the following drawing, the following description and the following embodiment.

[0068] It shows:

[0069] Fig. 1 is a schematic diagram illustrating the method according to the present invention. Figure 1 shows a diagram illustrating the method according to the invention.

[0070] As shown, the process is used to produce solids from a liquid containing the solid.

[0071] Step 10 is intended to represent the provision of a liquid containing the solid. This liquid may, in particular, comprise the solid in dissolved form, with the solid preferably being present in the liquid in a supersaturated form.

[0072] Step 12 involves introducing a gas under elevated pressure. This gas is then dispersed in the liquid in step 14, creating a gas-liquid two-phase mixture. This step can be carried out discontinuously, in particular in a pressure vessel equipped with a stirrer. Alternatively, this step can be carried out continuously, in particular using static mixers or an extruder.

[0073] Subsequently, according to step 16, the gas-liquid mixture is rapidly decompressed. This results in the solid being formed, particularly as free-flowing particles or as a foam. Whether a foam is formed instead of a free-flowing solid depends, among other things, on the solvent that may still be present.

[0074] According to step 18, the solid is then further processed. If a foam is present, it can be dried, i.e., the solvent is removed, to obtain free-flowing particles. This can generally be advantageous or necessary even for directly obtained particles to remove residual solvent. The resulting free-flowing particles can be further comminuted. Since the solids are primarily porous particles, this can be achieved with low energy input, for example, by grinding, thus preventing amorphization.

[0075] In an exemplary embodiment, the process can be carried out by using an aqueous sugar solution or, in principle, an aqueous polymer solution as the starting solution, and dispersing continuously in a co-rotating twin-screw extruder. Pressure release can occur via the extruder die.

[0076] The process according to the invention is illustrated by the solidification and crystallization of allulose (D-psicose, (3A,4A,5A)-1,3,4,5,6-pentahydroxy-2-hexanone). This sugar is relatively difficult to crystallize, and high degrees of crystallization can usually only be achieved with considerable equipment and energy expenditure. Water is used as the liquid in the process according to the invention, and carbon dioxide is used as the gas.

[0077] I. Production of allulose via an enzymatic reaction

[0078] The allulose usable in the process according to the invention can be obtained, for example, from D-fructose using an enzymatic process. A possible production process for converting allulose from fructose is described, for example, in WO 2022 / 049307 A1. The process can comprise the following steps:

[0079] Synthesizing allulose in a reactor; preferably from fructose; whereby the ratio of allulose to fructose at the end of this step can preferably be from 20 / 80 to 40 / 60;

[0080] - removing the product composition containing the synthesized allulose from the reactor;

[0081] - Desalting the product composition;

[0082] - Decolorization of the product composition; purification of the synthesized allulose contained in the product composition, preferably by chromatography.

[0083] This process sequence can provide an allulose mixture with a D-fructose content of at most 5.0 wt.%, preferably at most 4.0 wt.%, preferably at most 3.0 wt.%, preferably at most 2.0 wt.%, preferably at most 1.0 wt.%, based in each case on the total weight of the liquid allulose composition. This composition can preferably contain very low or no amounts of glucose or other sugars.

[0084] II. Preparation of solids or crystalline solids

[0085] An aqueous allulose premix is ​​prepared from the allulose mixture obtained in step I. The dry matter content of the mixture is approximately 85% by weight. The dry matter content can be measured, for example, using the Brix value, using the following calibration curve at a measurement temperature of 20 °C:

[0086] TS = 1.1219 • Brix - 4.8017

[0087] This aqueous allulose premix is ​​concentrated in a batch cooker under heat to a dry matter content of greater than 90%. With these allulose contents, a supersaturated mixture is obtained.

[0088] This mixture is metered into an extruder, where it is further supersaturated by the addition of crystalline allulose in the extruder. The addition of additional allulose is optional. The dry matter content of the mixture before the addition of the gas is approximately 93 wt.% due to the further addition. The level of the dry matter content and overall also the residence time under shear in the extruder can have a beneficial effect on the solidification kinetics. For example, shear rates in the range of greater than or equal to 100 1 / s and less than or equal to 3000 1 / s have proven particularly advantageous. Higher dry matter contents and longer residence times generally lead to a reduction in the solidification times after exiting the extruder. Carbon dioxide is added to the thus supersaturated mixture at a weight proportion of 1 wt.% based on the total mixture.The inert gas is metered in at a distance from the discharge nozzle of approximately 1 / 3 of the total extruder length. The extruder mechanically circulates the mixture, creating a homogeneous two-phase liquid-gas dispersion upstream of the extruder nozzle. The liquid-gas dispersion is extruded from the extruder in the form of a coherent foam. The foam is stable, and after a solidification time of 0.5 to 48 hours under ambient conditions, a dry-feeling, solid, crystalline, and porous foam is obtained. The degree of crystallinity of the solid, determined by PXRD, is 100%. The foam can be easily broken down into smaller agglomerates by mechanical means, is non-hygroscopic, and can be easily compacted. The foam and aggregates exhibit a larger BET surface area compared to molds produced using state-of-the-art technology.

[0089] Aggregates can be obtained from the foams, for example, using a roller mill (prototype roller cooler, BBA INNOVA AG, Strengelbach, Switzerland) with a large (diameter 500 mm) and a small (80 mm) roller, gap distance 2 mm and a speed of the large roller of 3 revolutions per minute.

Claims

Patent claims 1. A process for producing solids from a liquid containing the solid, characterized in that the process comprises the process steps: i) providing a liquid containing the solid; ii) dispersing a gas in the liquid under increased pressure to produce a gas-liquid two-phase mixture; iii) depressurizing the gas-liquid two-phase mixture produced in process step ii).

2. The process according to claim 1, characterized in that after process step ii), the proportion of gas dissolved in the liquid to the total amount of gas introduced into the process is in a range of < 10 wt. %.

3. The process according to claim 1 or 2, characterized in that process step i) is carried out under a pressure in a range from > 3 bar to < 500 bar.

4. The process according to any one of claims 1 to 3, characterized in that in process step ii), a pressure release rate in a range from > 0.1 bar / s to < 5000 bar / s is used.

5. Process according to one of claims 1 to 4, characterized in that the liquid provided in process step i) is supersaturated with regard to the content of the solid.

6. Process according to one of claims 1 to 5, characterized in that a crystalline or semi-crystalline solid is formed during the relaxation.

7. Process according to one of claims 1 to 6, characterized in that the solids obtained are further comminuted.

8. Process according to one of claims 1 to 7, characterized in that the process is carried out discontinuously, in particular wherein process step ii) is carried out in a pressure vessel equipped with an agitator.

9. Process according to one of claims 1 to 7, characterized in that the process is carried out continuously, in particular wherein process step ii) is carried out using static mixers or an extruder.

10. The process according to any one of claims 1 to 9, characterized in that i) a mixture of an amorphous or semi-crystalline solid and a liquid is provided in a reactor; ii) a mechanical circulation of the mixture provided in process step i) and dispersing an inert gas into the mixture takes place, wherein the dispersion of the inert gas results in a two-phase gas-liquid dispersion in the reactor; iii) the gas-liquid dispersion produced in process step ii) is discharged from the reactor, wherein the gas-liquid dispersion forms a foam after being discharged from the reactor.

11. The method according to claim 10, characterized in that the method comprises a further step iv), wherein in step iv) an at least partial solidification of the foam takes place, wherein the solidification of the foam increases the crystalline proportion of the solid in the foam.

12. Process according to one of the preceding claims, characterized in that in process step ii) the concentration of gas in the mixture is greater than or equal to 0.1 wt.% and less than or equal to 5 wt.%.

13. Use of a method according to one of claims 1 to 12 for producing, in particular, crystalline or semi-crystalline solid particles. 14 Use according to claim 13, characterized in that the crystalline or semi-crystalline solid particles are allulose foams or allulose particles.

15. Allulose molded body, characterized in that the allulose molded body has a surface area, determined by BET, of greater than or equal to 0.25 m 2 / g and less than or equal to 0.8 m 2 / g.

16. Allulose molded body according to claim 15, characterized in that the allulose molded body has a fructose content of greater than or equal to 0 wt.% and less than or equal to 5.0 wt.%.

17. Allulose molded body according to claim 15 or 16, characterized in that the allulose molded body has a glucose content of greater than or equal to 0 wt.% and less than or equal to 2.0 wt.%.

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