CN118579807B - An intelligent preparation process for efficient lithium-based oxygen-generating molecular sieves - Google Patents
An intelligent preparation process for efficient lithium-based oxygen-generating molecular sieves Download PDFInfo
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Abstract
The application relates to the technical field of environment treatment and repair molecular sieves, in particular to an intelligent preparation process of a high-efficiency lithium-based oxygen-making molecular sieve, which comprises the steps of mixing bentonite, hectorite, pyrophyllite and magnesium lithium silicate, crushing, adding the mixture into sulfuric acid solution, heating, dispersing, filtering, washing and drying; mixing diabase, palygorskite and perlite, calcining, cooling, pulverizing, mixing the dried powder with the pulverized powder, adding deionized water, microwave and magnetic stirring, drying to obtain powder, preparing crystal guiding agent, mixing sodium hydroxide, sodium metaaluminate and sodium silicate nonahydrate, adding deionized water, adding the dried powder, heating, stirring, standing, adding crystal guiding agent, heating, stirring, heating again, crystallizing at constant temperature, immersing molecular sieve in lithiation solution, heating under reduced pressure, roasting, and activating to obtain lithium-based oxygen-producing molecular sieve. The application controls the crystallization time and improves the preparation quality of the lithium-based oxygen-making molecular sieve.
Description
Technical Field
The application relates to the technical field of environment treatment and repair molecular sieves, in particular to an intelligent preparation process of a high-efficiency lithium-based oxygen-making molecular sieve.
Background
The lithium-based oxygen-making molecular sieve is an artificially synthesized hydrated aluminum silicate material with a molecular screening effect, is used as an environmental treatment and repair material, has an important effect in the field of environmental repair, can supply oxygen in outdoor activities, ensures the safety of people in high altitude and deep sea environments, can adsorb nitrogen, and provides an oxygen output environment with higher purity. Because of the unique physical and chemical characteristics, the lithium-based oxygen-making molecular sieve is mainly used in the adsorption oxygen-making process in industry, namely, the selective adsorption of nitrogen and oxygen in air is carried out through the pore channel structure, so that the enrichment or separation of oxygen is realized.
In the process of preparing the lithium-based oxygen-making molecular sieve, because certain differences exist in raw material components, proportions and the like used in each preparation process, the time required for constant temperature crystallization is different in the preparation process of different batches, and the time for constant temperature crystallization needs to be strictly controlled. Too short crystallization time may result in insufficient growth of molecular sieve crystals, small and incomplete crystals, affecting the pore structure and pore distribution of the molecular sieve, and thus reducing the adsorption performance of the molecular sieve, too long crystallization time may result in excessive growth of crystals caused by impurities participating in the crystallization process, and increased crystal size, thereby resulting in change of pore channel structure of the lithium-based molecular sieve, and affecting the adsorption performance of the lithium-based molecular sieve on small molecules such as oxygen.
Disclosure of Invention
In order to solve the technical problems, the application provides an intelligent preparation process of an efficient lithium-based oxygen-making molecular sieve, which aims to solve the existing problems.
The intelligent preparation process of the high-efficiency lithium-based oxygen-making molecular sieve adopts the following technical scheme:
The embodiment of the application provides an intelligent preparation process of a high-efficiency lithium-based oxygen-making molecular sieve, which comprises the following steps of:
S1, uniformly mixing bentonite, hectorite, pyrophyllite and magnesium lithium silicate, crushing, adding into sulfuric acid solution with the molar concentration of 2mol/L, heating in water bath, performing ultrasonic dispersion, filtering, washing and drying;
S2, uniformly mixing stilbite, palygorskite and perlite, calcining, cooling to normal temperature, and crushing;
S3, mixing the powder prepared in the step S1 and the powder prepared in the step S2, adding deionized water to prepare suspension, magnetically stirring after microwave treatment, and spray drying to obtain powder;
s4, selecting raw materials for preparing the crystal guiding agent, and performing reaction treatment to obtain the crystal guiding agent;
S5, uniformly mixing sodium hydroxide, sodium metaaluminate and sodium silicate nonahydrate in the raw materials S4, adding deionized water, uniformly stirring, adding the powder prepared in the step S3, heating, stirring, standing for ageing, then adding the crystal guiding agent, heating in a water bath for stirring reaction, and heating again for constant-temperature crystallization in a glass crystallization kettle;
Determining a crystallization matching index based on precipitation characteristics in the constant temperature crystallization process, and further constructing a crystallization development index;
filtering, washing to neutrality after crystallization, drying, grinding and sieving to obtain molecular sieve;
S6, immersing the molecular sieve into lithiation solution, standing, filtering, taking out the molecular sieve, and activating to obtain the lithium-based oxygen-making molecular sieve after repeated reduced pressure heating and reduced pressure roasting.
Preferably, the solid-to-liquid ratio of the crushed powder in the step S1 to the sulfuric acid solution is 1:12-16, the mixture is heated to 75-95 ℃ in a water bath, and the mixture is subjected to ultrasonic dispersion for 16-32 min.
Preferably, the calcination temperature in the step S2 is 750-850 ℃ and the calcination time is 1-2 h.
Preferably, the magnetic stirring time in the step S3 is 25-35 min, and the rotating speed is 1600-2000 r/min.
Preferably, the specific steps for preparing the crystal guiding agent in S4 are as follows:
Selecting 10-16 parts of bentonite, 4-10 parts of stilbite, 5-11 parts of hectorite, 20-29 parts of sodium metasilicate nonahydrate, 15-24 parts of sodium hydroxide and 11-15 parts of sodium metaaluminate;
Uniformly mixing bentonite, stilbite and hectorite, calcining for 1-2 hours at 650-680 ℃, naturally cooling to normal temperature, mixing with sulfuric acid solution with the molar concentration of 1.6mol/L according to the solid-to-liquid ratio of 1:15-18, heating to 72-82 ℃ in a water bath, preserving heat for 20-40 min, filtering, washing, drying, calcining for 2-3 hours at 850-900 ℃, naturally cooling to normal temperature, crushing, grinding and sieving to obtain powder A for standby;
And (3) pouring sodium hydroxide solution into deionized water which is 12-15 times of the sodium hydroxide solution, adding the powder A to be used, uniformly mixing and stirring, adding sodium metasilicate nonahydrate and sodium metaaluminate, heating for 1-2 h at 75-85 ℃, cooling to normal temperature, and standing and aging for 20-24 h to obtain the crystal directing agent.
Preferably, the heating and stirring in the step S5 are carried out for 2.5-4.5 hours under the condition of 72-81 ℃, the heating temperature in the water bath is 93-113 ℃, the stirring reaction time is 4.5-6.5 hours, and the temperature of the secondary heating is 108-119 ℃.
Preferably, the method for determining the crystallization matching index comprises the following steps:
And (3) obtaining a crystallization image of each time point, constructing a square window by taking each pixel point in the crystallization image as a center, and carrying out forward fusion on gray level differences of all any two pixel points in the window to serve as crystallization matching indexes of the pixel points in the center of the window, and correspondingly, obtaining the crystallization matching indexes of all the pixel points in the crystallization image.
Preferably, the method for constructing the crystal development index comprises the following steps:
Clustering the crystallization matching indexes of all pixel points in the crystallization image, and marking the average value of the crystallization matching indexes of each cluster as the crystallization characteristic value of each cluster;
The ratio of the crystallization characteristic value of the cluster where each pixel point is located to the sum result of the crystallization characteristic values of all clusters is recorded as the crystallization weight of each pixel point;
and taking the accumulated result of the products of the crystallization weights and the gray values of all pixel points in the crystallization image as the crystallization development index of the crystallization image.
Preferably, the step of obtaining the crystallization maturity index to control the constant temperature crystallization time comprises the following specific steps:
forming crystallization observation sequences of time points by using the crystallization development indexes of the crystallization images of a plurality of time points before the time points, and performing first-order difference to obtain crystallization generation sequences;
Taking each crystal development index in the crystallization generation sequence as an independent variable of a sign function to obtain a sign item of each crystal development index, and forming the sign items of all the crystal development indexes in the crystallization generation sequence into a crystallization trend sequence;
Taking the ratio of the sum of the numbers of the symbol items with the symbol items of-1 and 0 in the crystallization trend sequence to the total number of the symbol items in the crystallization trend sequence as crystallization slowing weight, and obtaining the crystallization maturity index of each time point according to the summation result after normalization of the reciprocal of all the crystallization development indexes in the crystallization generation sequence and the product of the summation result and the crystallization slowing weight;
and ending the constant-temperature crystallization when the normalized crystallization maturity index of a plurality of continuous time points is equal to or more than the crystallization maturity index threshold value.
Preferably, the lithiation solution of S6 uses ethanol as a solvent, lithium perchlorate as a lithium salt, the amount concentration is 1mol/L, the reduced pressure heating is that the reduced pressure heating is performed for 1-2 hours at 81-92 ℃, the reduced pressure roasting is that the reduced pressure roasting is performed for 2-3 hours at 168-188 ℃, and the activation is that the activation is performed for 3-4 hours at 285-325 ℃.
The application has at least the following beneficial effects:
The method comprises the steps of constructing a crystallization matching index by analyzing the precipitation characteristics of crystals in the constant temperature crystallization process, reflecting the degree that each pixel point in a crystallization image belongs to a crystallization area, analyzing the crystallization degree and constructing a crystallization development index based on the crystallization matching index, reflecting the crystallization degree in the crystallization image at the current time point, analyzing the change trend of the crystallization growth rate and constructing a crystallization maturation index based on the crystallization development index, reflecting the degree that the constant temperature crystallization process should be ended at the current time point, controlling the constant temperature crystallization time based on the crystallization maturation index, solving the problems of impurity crystallization, overgrowth of crystals and change of pore channel structures caused by overlong crystallization time, and remarkably improving the adsorption performance of the lithium-based oxygen-making molecular sieve on small molecules such as oxygen.
Drawings
In order to more clearly illustrate the embodiments of the application or the technical solutions and advantages of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are only some embodiments of the application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a step flow diagram of an intelligent preparation process of a high-efficiency lithium-based oxygen-making molecular sieve provided by the application;
FIG. 2 is a schematic diagram of crystallized image acquisition;
FIG. 3 is a graph showing analysis of crystal development index;
FIG. 4 is a schematic view of a clustering effect;
FIG. 5 is a flow chart of the constant temperature crystallization time control.
Detailed Description
In order to further illustrate the technical means and effects adopted by the application to achieve the preset aim, the following is a detailed description of specific embodiments, structures, features and effects of an intelligent preparation process of a high-efficiency lithium-based oxygen-making molecular sieve according to the application in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" means that the embodiments are not necessarily the same. Furthermore, the particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.
Unless otherwise defined, terms such as "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a circuit structure, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such article or apparatus. Without further limitation, the statement "comprises an" or "comprising" does not exclude that an additional identical element is present in an article or device comprising the element. In addition, the term "and/or" as used herein includes any and all combinations of one or more of the associated listed items. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
The following specifically describes a specific scheme of the intelligent preparation process of the high-efficiency lithium-based oxygen-making molecular sieve provided by the application with reference to the accompanying drawings.
Referring to fig. 1, the process for preparing the high-efficiency lithium-based oxygen-making molecular sieve according to the embodiment of the application comprises the following steps:
S1, uniformly mixing bentonite, hectorite, pyrophyllite and lithium magnesium silicate, crushing, sieving with a 200-mesh sieve, adding the sieved powder into sulfuric acid solution with the molar concentration of 2mol/L according to the solid-to-liquid ratio of 1:12 as a first embodiment of the application, heating to 75 ℃ in a water bath, performing ultrasonic dispersion for 16min, and filtering, washing and drying for later use;
Preferably, in the second embodiment of the application, the solid-to-liquid ratio of the sieved powder to the sulfuric acid solution is 1:14, the water bath heating temperature is 85 ℃, and the ultrasonic dispersion time is 24min;
preferably, in the third embodiment of the application, the solid-to-liquid ratio of the sieved powder to the sulfuric acid solution is 1:16, the water bath heating temperature is 95 ℃, and the ultrasonic dispersion time is 32min.
S2, uniformly mixing stilbite, palygorskite and perlite, preferably calcining for 1h at 750 ℃ as a first embodiment of the application, naturally cooling to normal temperature, crushing, and sieving with a 200-mesh sieve for later use;
Preferably, as a second embodiment of the present application, in step S2, the calcination temperature is 800 ℃ and the calcination time period is 1.5 hours;
Preferably, as a third embodiment of the present application, in step S2, the calcination temperature is 850 ℃ and the calcination time period is 2 hours.
S3, uniformly mixing the powder prepared in the step S1 and the powder prepared in the step S2, adding a proper amount of deionized water to prepare a suspension with the concentration of 60%, carrying out microwave treatment for half an hour, wherein the microwave power is 450W, then carrying out magnetic stirring for 25 minutes, and then carrying out spray drying to obtain powder for later use at the rotating speed of 1600 r/min;
preferably, as a second embodiment of the present application, in step S3, the magnetic stirring time is 30 minutes, and the rotation speed is 1800r/min;
Preferably, as a third embodiment of the present application, in step S3, the magnetic stirring is performed for 35 minutes at a rotational speed of 2000r/min.
S4, preparing a crystal guiding agent, wherein the raw materials comprise bentonite, stilbite, hectorite, sodium metasilicate nonahydrate, sodium hydroxide and sodium metaaluminate;
Preferably, in the first embodiment of the application, the weight parts of the raw materials are respectively bentonite 10, stilbite 4, hectorite 5, sodium metasilicate nonahydrate 20, sodium hydroxide 15 and sodium metaaluminate 11, and then bentonite, stilbite and hectorite are uniformly mixed and calcined to obtain a solid matter after calcination, wherein the calcination temperature is 650 ℃ and the calcination time is 1h;
Naturally cooling to normal temperature, mixing the calcined solid with sulfuric acid solution, in the first embodiment of the application, mixing the calcined solid with sulfuric acid solution with the molar concentration of 1.6mol/L according to the solid-to-liquid ratio of 1:15, heating to 72 ℃ in water bath, preserving heat for 20min, filtering, washing and drying, calcining for 2h in 850 ℃ environment, naturally cooling to normal temperature, crushing and grinding, sieving with a 200-mesh sieve, wherein a specific sieve number implementer can select according to actual conditions to obtain standby powder A;
and then, pouring sodium hydroxide solution into deionized water which is 13 times of the sodium hydroxide solution, adding the powder A to be used, uniformly mixing, adding sodium metasilicate nonahydrate and sodium metaaluminate under the condition of stirring, heating for 1h at 75 ℃, cooling to normal temperature by water, and standing and ageing for 20h to obtain the crystal guiding agent.
Preferably, in the second embodiment of the present application, in the step S4, the weight portions of the raw materials are respectively bentonite 13, stilbite 7, hectorite 8, sodium metasilicate nonahydrate 25, sodium hydroxide 20 and sodium metaaluminate 13, in the second embodiment, the calcination temperature is 665 ℃ and the calcination time period is 1.5 hours, the solid after calcination is mixed with sulfuric acid solution with the molar concentration of 1.6mol/L according to the solid-to-liquid ratio of 1:16, the mixture is heated to 77 ℃ in a water bath, the mixture is kept for 30 minutes, and is subjected to filtration, washing and drying treatment, calcination is carried out for 2.5 hours in the environment of 875 ℃, natural cooling is carried out to normal temperature, crushing and grinding treatment are carried out, and 200-mesh sieve is carried out, thus obtaining standby powder a, the sodium hydroxide solution is poured into deionized water which is 13 times of the standby powder a, the sodium metasilicate nonahydrate and the sodium metaaluminate are then added under the condition of stirring after the mixture is uniformly mixed, and the mixture is heated for 1.5 hours under the condition of 80 ℃ and the heating temperature is kept stand for aging time period of 22 hours.
Preferably, in the third embodiment of the present application, in the step S4, the weight parts of the raw materials are respectively bentonite 16, stilbite 10, hectorite 11, sodium metasilicate nonahydrate 29, sodium hydroxide 24 and sodium metaaluminate 15, in the third embodiment, the calcination temperature is 680 ℃ and the calcination time period is 2 hours, the solid after calcination is mixed with sulfuric acid solution with the molar concentration of 1.6mol/L according to the solid-to-liquid ratio of 1:18, the mixture is heated to 82 ℃ in a water bath, the temperature is kept for 40 minutes, and the mixture is subjected to filtration, washing and drying treatment, calcination is carried out for 3 hours in the environment of 900 ℃, the mixture is naturally cooled to normal temperature, and is subjected to crushing and grinding treatment, and is sieved by a 200-mesh sieve, so as to obtain standby powder a, the sodium hydroxide solution is poured into deionized water which is 13 times of the sodium hydroxide solution, then the standby powder a is added, the sodium metasilicate nonahydrate and the sodium metaaluminate are stirred under the condition of stirring, and the mixture is heated for 2 hours under the temperature condition of 85 ℃ for standing and aging time period for 24 hours, so as to obtain the crystal guide agent.
And S5, uniformly mixing sodium hydroxide, sodium metaaluminate and sodium silicate nonahydrate, adding deionized water which is 20 times of the mixture, uniformly stirring, adding the powder prepared in the step S3, heating, stirring, standing for ageing, determining the standing and ageing time by an operator according to the actual application scene, in the embodiment, adding the crystal guide agent prepared in the step S4, heating in a water bath for stirring reaction, heating again, crystallizing in a glass crystallization kettle at constant temperature, filtering after the reaction is finished, washing with water until pH is neutral, drying, grinding and sieving.
Preferably, as a first embodiment of the present application, the heating and stirring in step S5 is performed at 72 ℃ for 2.5 hours, the water bath heating temperature is 93 ℃, the stirring reaction time is 4.5 hours, and the temperature of the re-heating is 108 ℃;
Preferably, as a second embodiment of the present application, the heating and stirring in step S5 is performed at 76 ℃ for 3.5 hours, the water bath heating temperature is 103 ℃, the stirring reaction time is 5.5 hours, and the temperature of the re-heating is 113 ℃;
Preferably, as a third embodiment of the present application, the heating and stirring in step S5 is performed at 81 ℃ for 4.5 hours, the water bath heating temperature is 113 ℃, the stirring reaction time is 6.5 hours, and the temperature of the reheating is 119 ℃.
Considering that when the constant temperature crystallization is carried out in the glass crystallization kettle, the influence of the constant temperature crystallization time on the crystallization state is large, the crystallization state in the glass crystallization kettle is analyzed, the constant temperature crystallization time is controlled, the constant temperature crystallization time range is 11-16 h, and the specific constant temperature crystallization time control process is as follows:
Step one, collecting a crystallization image in the constant temperature crystallization process.
The industrial high-definition camera is placed right in front of the glass crystallization kettle, and the industrial high-definition camera continuously and uninterruptedly collects crystallization images in the constant temperature crystallization process at equal time intervals, and the collection schematic diagram is shown in the following figure 2. The obtained crystallized image is an image in an RGB space, and the crystallized image in the RGB space is converted into a crystallized image in a gray scale space by a gray scale average method. Wherein the size of the time interval is 20s as an empirical value in the application.
Specifically, in fig. 2, the apparatus numbered 1 represents a camera, the number 2 represents a coolant, and the number 3 represents a crystallization outlet.
So far, the crystallized image after each acquisition is obtained.
And secondly, analyzing the precipitation characteristics of crystals in the constant-temperature crystallization process to construct a crystallization matching index, analyzing the crystallization degree based on the crystallization matching index to construct a crystallization development index, and analyzing the growth rate of the crystals based on the crystallization development index to construct a crystallization maturity index.
1) And constructing a crystallization matching index based on the precipitation characteristics of the crystals.
In the process of constant temperature crystallization, on a microscopic level, since the framework of the lithium-based molecular sieve is generally composed of tetrahedral silica and alumina units, the tetrahedrons are connected through common oxygen atoms to form a three-dimensional structure with uniform pore diameters, so that crystals formed in the process of constant temperature crystallization should have uniform thickness on a macroscopic level.
Since the thickness of the crystals formed during the constant temperature crystallization is uniform, the gray values of the pixels belonging to the crystallization area should be relatively close in the crystallized image. Based on the analysis, the application constructs the crystallization matching index, reflects the degree of the pixel point belonging to the crystallization area, and constructs the crystallization matching index as follows:
And (3) marking a square window with the p-th pixel point in the crystallized image as a center and the side length of b as a crystallization monitoring window, wherein the value of the embodiment of b is 5. The crystallization matching index can be calculated as follows:
taking the gray level difference of any two pixel points in the crystallization monitoring window as the crystallization difference degree between the two pixel points, preferably, in the embodiment, the gray level difference is the absolute value of the difference value of the gray level values of the two pixel points, and in the specific application process, an implementer can set a gray level difference measurement method by himself;
It can be understood that the larger the difference of gray values of any two pixel points in the window is, the more impurities or other components are likely to exist in the window, so that the larger the crystallinity difference between the pixel point and the central pixel point of the window is calculated;
And taking the forward fusion result of the crystallinity difference degree between any two pixel points in the crystallization observation window as a crystallization matching index. Preferably, in this embodiment, the forward fusion is used to characterize that the variation trends between the variables are consistent and identical, and may be analyzed by a multiplication relationship, an addition relationship, a mean relationship, and other positive correlation relationships, and in this embodiment, the forward fusion is performed by using the mean, that is, the mean of the crystallinity difference degrees between any two pixel points in the crystallization observation window is used as the crystallization matching index, and the specific relationship is determined according to the actual application scenario.
It should be understood that the larger the crystallinity difference of any two pixel points in the crystallization monitoring window is, the more the corresponding region of the window is not in accordance with the precipitation characteristics of crystallization, so the smaller the calculated crystallization matching index of the center pixel point of the window is.
2) And constructing a crystallization development index based on the crystallization matching index.
Specifically, the analysis of the crystal development index is schematically shown in FIG. 3.
Through the crystallization matching index of each pixel point obtained by the steps, the degree that each pixel point belongs to a crystallization area is reflected, meanwhile, along with the continuous occurrence of the crystallization process, the crystals become thicker gradually, when light rays pass through the crystals, mie scattering phenomenon can occur, namely, the light rays pass through the crystals for multiple scattering and reflection, the interaction opportunity of the light rays and the crystals is increased, and therefore the total amount of scattered light is increased. When there is enough scattered light, the cumulative effect of the scattered light will make the crystal appear white. The color of the thicker crystals appears relatively white. Based on the analysis, the application constructs the crystallization development index based on the crystallization matching index, reflects the crystallization condition in the crystallization image at the current time point, and constructs the crystallization development index as follows:
the crystallization matching index of all pixel points in the crystallization image is used as the input of a K-means clustering algorithm, the size of the necessary parameter clustering number is set to be 2 in the embodiment, and the pixel points after clustering are output.
Specifically, a schematic view of the clustering effect is shown in fig. 4.
And respectively calculating the average value of the crystallization matching indexes of all pixel points in each cluster, and marking the average value as the crystallization characteristic value of each cluster. The K-means clustering algorithm is a known technology, and the specific process is not repeated in the application. The crystal growth index of the crystallized image can be calculated as follows:
Taking the ratio of the crystallization characteristic value of the cluster where each pixel point is located to the sum result of the crystallization characteristic values of all the clusters as the crystallization weight of each pixel point, reflecting the degree that the pixel point belongs to a crystallization area, wherein the larger the crystallization characteristic value of the cluster where the pixel point is located is, the more likely the pixel point belongs to the crystallization area, so that the calculated crystallization weight is larger;
Taking the accumulated result of the product of the crystallization weights and the gray values of all the pixel points in the crystallization image as the crystallization development index of the crystallization image, wherein the greater the degree that all the pixel points in the crystallization image belong to a crystallization area, the closer the color of the pixel points is to white, which indicates that the thicker crystals are more likely to be, namely the higher the crystallization degree is, the greater the calculated crystallization development index is.
3) The crystal maturation index is constructed based on the crystal development index.
The crystallization development index of the crystallized image at each time point obtained through the steps reflects the crystallization degree at each time point, and the growth rate of crystals can be gradually reduced along with the continuous occurrence of chemical reaction in the constant temperature crystallization process and continuous consumption of raw materials. When the growth rate of the crystal is low, the reaction is closed, the constant temperature crystallization process should be ended, and the phenomenon that other impurities participate in the crystallization process due to overlong constant temperature crystallization time to cause the structural change of the lithium-based molecular sieve and influence the adsorption performance of small molecules such as oxygen is avoided. Based on the analysis, the application constructs the crystallization maturity index based on the crystallization development index, reflects the degree of the constant temperature crystallization process, and constructs the crystallization maturity index as follows:
marking a sequence formed by the crystal development indexes of the crystallization images at a time point before the time point t as a crystallization observation sequence, and if the number of the time points before the time point t is less than a, complementing the time points by using a regression filling method to ensure that the length of the crystallization observation sequence is a, wherein the value of the embodiment a is 15;
And (3) marking a sequence obtained by performing first-order difference on the crystallization observation sequence as a crystallization generation sequence, taking each crystallization development index in the crystallization generation sequence as an independent variable of a sign function to obtain a sign item of each crystallization development index in the crystallization generation sequence, and marking a sequence formed by the sign items of the crystallization generation sequence as a crystallization trend sequence. The regression filling method and the computation of the sign function are known techniques, and the specific process is not repeated. The crystal maturity index can be calculated as follows:
taking the ratio of the sum of the element numbers with the symbol items of-1 and 0 in the crystallization trend sequence to the total number of the symbol items in the crystallization trend sequence as crystallization slowing weight;
it can be understood that the more the proportion of the number of elements with the sign terms of-1 and 0 in the crystallization trend sequence is, the more obvious the slowing trend of the crystal generation rate in the constant temperature crystallization process is, so the greater the calculated crystallization slowing weight is;
Taking the product of the sum result of the inverse of all elements in the crystallization generation sequence after normalization and the crystallization slowing weight as a crystallization maturity index, and particularly, marking the normalization result as 0 when the elements are 0.
It should be understood that the larger the crystallization retarding weight, the more obvious the retarding trend of the crystal growth rate in the constant temperature crystallization process, and the larger the summation result of the inverse of all elements in the crystallization generation sequence after normalization, the faster the crystal growth rate decreases, i.e. the closer to the end of the reaction, the more the constant temperature crystallization process should be ended at this time, so the calculated crystal maturity index is larger.
And thirdly, controlling the constant-temperature crystallization time based on the crystallization maturity index.
The crystallization maturity index of each time point obtained through the steps reflects the degree that the constant temperature crystallization process of each time point should be ended, and the crystallization maturity index of each time point is normalized by using a Z-score normalization method to obtain a normalized crystallization maturity index. If the normalized crystallization maturity index at the time point t is greater than or equal to the crystallization maturity index threshold, the raw materials are consumed more, the crystallization rate is lower, the reaction is completed, and the constant temperature crystallization process should be ended. Meanwhile, in order to avoid misjudgment caused by special conditions of individual time points, in this embodiment, the normalized crystallization maturity index threshold value of the continuous L time points is used as a judging condition for ending the constant temperature crystallization process, i.e. when the crystallization maturity index of the continuous L time points is greater than or equal to the crystallization maturity index threshold value, it is judged that the constant temperature crystallization process should be ended at this time. Wherein the threshold of the crystal maturity index is 0.75 in this example and 7 in l in this example.
Specifically, the control flow of the constant temperature crystallization duration is schematically shown in fig. 5.
S6, taking ethanol as a solvent and LiClO 4 (lithium perchlorate) as lithium salt to prepare a lithiation solution with the concentration of 1mol/L, immersing the molecular sieve prepared in the step S5 into the lithiation solution with the concentration of 4 times that of the molecular sieve, and enabling an operator to set the proportion of the lithiation solution to the molecular sieve according to practical conditions, standing for two days, filtering, taking out the molecular sieve, and carrying out reduced pressure heating, wherein the reduced pressure heating temperature is 81 ℃, the reduced pressure heating time period is 1h, then carrying out reduced pressure roasting, the reduced pressure roasting temperature is 178 ℃, the reduced pressure roasting time period is 2h, repeating for 3 times, enabling the operator to set the repetition times according to practical conditions, and activating to obtain the high-efficiency lithium-based oxygen-producing molecular sieve with the activation temperature of 285 ℃ and the activation time period of 3 h;
Preferably, as a second embodiment of the present application, in step S6, the reduced pressure heating temperature is 86 ℃, the reduced pressure heating period is 1.5 hours, then the reduced pressure roasting is performed, the reduced pressure roasting temperature is 168 ℃, the reduced pressure roasting period is 3 hours, the activation temperature is 305 ℃, and the activation period is 3.5 hours;
Preferably, as a third embodiment of the present application, the reduced pressure heating temperature is 92 ℃ and the reduced pressure heating period is 2 hours, then the reduced pressure roasting is performed, the reduced pressure roasting temperature is 188 ℃, the reduced pressure roasting period is 2.5 hours, the activation temperature is 325 ℃, and the activation period is 4 hours.
The results of the performance tests of the high efficiency lithium-based oxygen-generating molecular sieves prepared according to the above steps and examples of the present application are shown in table 1 below:
According to the crushing resistance test method of the HG/T2783-1996 molecular sieve, the crushing resistance of the high-efficiency lithium-based oxygen-making molecular sieve product is detected;
According to the GB 6287-86 molecular sieve static water adsorption determination method, detecting the static water adsorption rate (1) of the high-efficiency lithium-based oxygen-making molecular sieve product at the temperature of 25 ℃ under the humidity of 10%;
According to the GB 6287-86 molecular sieve static water adsorption determination method, the static water adsorption rate (2) of the high-efficiency lithium-based oxygen-making molecular sieve product is detected under the conditions of 75% humidity and 35 ℃.
TABLE 1
It is appreciated that references to "one embodiment" or "some embodiments" or the like described in this specification mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in this specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise.
It should be noted that the sequence of the embodiments of the present application is only for description, and does not represent the advantages and disadvantages of the embodiments. And the foregoing description has been directed to specific embodiments of this specification. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous. Meanwhile, the sequence number of each step in the embodiment does not mean that the execution sequence is sequential, and the execution sequence of each process should be determined by the function and the internal logic, and should not be construed as limiting the implementation process of the embodiment in the present specification.
Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the foregoing embodiments may be modified or equivalents may be substituted for some of the features thereof, and that the modification or substitution does not depart from the scope of the embodiments of the present application.
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