VOCs adsorbent screening method based on molecular simulation

Abstract

The present invention belongs to the field of VOCs molecular sieve adsorbents, and specifically relates to a method for screening VOCs molecular sieve adsorbents based on molecular simulation. The method comprises: firstly, using modeling software to construct models of molecular sieves, VOCs, nitrogen and water molecules, and then using quantum chemical methods to optimize the structure and electrical properties of the constructed model; then performing Monte Carlo simulation calculations on the optimized structural model, and finally obtaining the optimal molecular sieve adsorbent structure for adsorbing specified VOC gas composition and purification conditions; the method can accurately predict the adsorption effect of different molecular sieves on different VOCs under different working conditions, which not only helps to improve the optimization efficiency of molecular sieve adsorbents, but also has practical significance for in-depth exploration of the mechanism of molecular sieve adsorption of VOCs.

Description

Technical Field

[0001] The present invention belongs to the field of VOCs molecular sieve adsorbents, and in particular relates to a VOCs molecular sieve adsorbent screening method based on molecular simulation. Background Art

[0002] There are many technologies for removing VOCs, including adsorption, membrane separation, condensation, photocatalysis, etc. Among them, adsorption has become one of the most promising purification technologies for indoor odor VOCs due to its low cost and high efficiency. Zeolite molecular sieve adsorption is widely used because of its high selectivity and strong regeneration stability.

[0003] At present, the research on methods for screening VOCs molecular sieve adsorbents is mainly focused on experiments. Chinese researchers mostly use experimental methods to test and evaluate the VOCs adsorption effect of molecular sieve adsorbents. Specifically: first, build a set of continuous and complete adsorption test benches (including VOCs generators, VOCs adsorption devices, VOCs concentration detection and data recording devices, etc.). When exploring the best adsorption conditions, it is necessary to adjust the VOCs concentration by controlling the flow rate, set the injection pump perfusion volume to adjust the humidity, and wrap the heating tape to adapt to adsorption under high humidity conditions, so as to screen out the best experimental conditions suitable for the molecular sieve to adsorb the corresponding VOC; when exploring the adsorption effect of different cation-modified molecular sieves on the same VOC, it is necessary to re-prepare the material for adsorption, so as to screen out the molecular sieve with the best adsorption effect of this VOC.

[0004] However, when using experiments to screen adsorbents, a new set of experiments must be conducted every time one of the many factors such as temperature, humidity, and concentration is changed; there are many types of VOCs and molecular sieves, and every time the type of VOCs or molecular sieves is changed, it is necessary to repurchase the preparation materials. At the same time, the better the adsorption effect of the material or condition, the longer the adsorption time, and the higher the time cost. Therefore, the method of using experiments to screen VOCs molecular sieve adsorbents is blind, cumbersome, costly, time-consuming, and labor-intensive, and the time cycle is long. At the same time, there may be experimental errors due to improper operation.

[0005] In a large number of comparisons between simulation calculations and experiments, researchers have realized that molecular simulation technology has become a powerful research tool for scientists in many fields such as chemistry, physics, and materials science. In molecular simulation, the theoretical model determines whether the simulation results are reliable, and at the same time, the accuracy of the simulation or model is determined by comparing experimental data and simulated structures. People have found that performing simulation calculations first and then conducting experimental research can often reduce blindness, increase self-awareness, save time and costs, and achieve twice the result with half the effort. However, there is currently a lack of systematic methods for screening VOCs adsorbents using molecular simulation, and related technologies are urgently needed to be developed. Summary of the invention

[0006] To solve the above problems, the present invention proposes a method for screening VOCs molecular sieve adsorbents based on molecular simulation. The method is aimed at actual high-humidity environmental conditions. The method uses molecular simulation to change the type of VOCs, the type of molecular sieve, and the experimental conditions, thereby reducing the adsorption time cost and error of the experimental screening of the best VOCs adsorbent, improving the screening efficiency and filling the gap in molecular simulation screening of VOCs molecular sieve adsorbents.

[0007] The present invention is achieved through the following technical solutions:

[0008] The object of the present invention is to provide a method for screening VOCs molecular sieve adsorbents based on molecular simulation, the method comprising: firstly constructing models of molecular sieves, VOCs, nitrogen and water molecules using modeling software, and then optimizing the structure and electrical properties of the constructed models using quantum chemical methods; performing Monte Carlo simulation calculations on the optimized structural model, and finally obtaining the optimal molecular sieve adsorbent structure for adsorbing specified VOC gas composition and purification conditions; the method can accurately reflect the adsorption effects of different molecular sieves on different VOCs under different working conditions, which has practical significance for basic research such as studying the adsorption of VOCs by molecular sieves, and helps to improve screening efficiency.

[0009] Furthermore, the method specifically comprises:

[0010] S1, model building: Material Studio (MS) software combined with experimental optimization was used to determine the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model for subsequent simulation;

[0011] S2, simulation experiment: using the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model to conduct simulated adsorption experiments and simulated adsorption effect experiments, and finally obtain the molecular sieve and adsorption conditions with the best adsorption effect for the specified VOC;

[0012] The simulated adsorption experiment includes: under the same conditions, two or more VOCs are subjected to simulated adsorption on the molecular sieve, and the saturated adsorption amount of multiple VOCs on the specified molecular sieve can be predicted;

[0013] The simulated adsorption effect experiment includes: changing the VOC experimental conditions to perform simulated adsorption calculation on VOC, and obtaining the difference in the adsorption effect of the specified molecular sieve on VOC under different experimental conditions;

[0014] S3, determine the silicon-aluminum ratio of the molecular sieve: simulate the effect of molecular sieves with different silicon-aluminum ratios on VOCs adsorption to determine the optimal silicon-aluminum ratio of the molecular sieve;

[0015] S4, after determining the optimal silicon-aluminum ratio, adding metal cations and optimizing the structure of the molecular sieve structure model again, after optimization, simulated adsorption calculation of VOCs is performed to obtain the saturated adsorption amount result;

[0016] S5, changing the type or amount of metal cations, repeating S4, obtaining the saturated adsorption results corresponding to the metal cations, comparing the saturated adsorption results of all molecular sieves containing metal cations, and determining the optimal metal cation for the adsorption of corresponding VOCs on the molecular sieve with the optimal silicon-aluminum ratio; finally, obtaining a VOCs molecular sieve adsorbent with the optimal silicon-aluminum ratio and the optimal metal cation for the adsorption of the specified VOC.

[0017] Furthermore, the Material Studio (MS) software includes: Forcite module, DMol3 module and silicon-aluminum ratio adjustment module.

[0018] Furthermore, the specific contents of S1 include:

[0019] S1.1, using Material Studio (MS) software to build the initial molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model;

[0020] S1.2, optimize the geometric structures of the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model;

[0021] S1.3, further optimize the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model to keep each molecule electrically neutral;

[0022] S1.4, simulate the adsorption calculation of the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model under different force fields at the specified pressure, and compare the simulated adsorption calculation results with the saturated adsorption amount obtained by the experiment to determine the force field for the simulation calculation;

[0023] S1.5, determine the charge load of the molecular sieve structure model, and finally obtain the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model for subsequent simulation.

[0024] Furthermore, the determination of the charge load of the molecular sieve structure model described in S1.5 includes two methods:

[0025] When conducting simulated adsorption under dry gas, the charge of the representative structure of the VOC molecule is continuously adjusted (±0.3) on the basis of the initially set charge (e.g., acetaldehyde is adjusted to C=O, ethanol is adjusted to -OH, and acetic acid is adjusted to -COOH) to perform simulated adsorption calculations until the result is close to the saturated adsorption amount obtained in the experiment; based on this VOC charge, the charge of the water molecule under wet gas conditions is further adjusted (±0.2) until the simulated adsorption result is close to the saturated adsorption amount result obtained in the wet gas experiment;

[0026] Under dry gas conditions: the load simulation of VOC on the molecular sieve is carried out under the fixed loading task under the sorption module in the Material Studio (MS) software to obtain the specific position of the VOC load on the molecular sieve, a fragment carrying the VOC is cut on the molecular sieve, the fragment is optimized by the DMol3 module to obtain the charge number of each atom in the fragment, the charge of each atom is attached to the molecular sieve structure model, and the VOC and the molecular sieve in the fragment are separated.

[0027] Furthermore, the Material Studio software includes: Forcite module, Sorption module, DMol3 module, Castep module, VASP module and silicon-aluminum ratio adjustment module.

[0028] Furthermore, the Forcite module is used for optimization in S1.2.

[0029] Furthermore, the DMol3 module is used for optimization in S1.3.

[0030] Furthermore, the force field includes: Universal, Dreiding, COMPASS and COMPASSⅡ, preferably COMPASSⅡ.

[0031] Furthermore, the experimental conditions described in S2 include: VOCs concentration (0.001 ppb to 200000 ppm), different relative humidity (0 to 100% RH) and temperature (-50 to 500° C.).

[0032] Furthermore, in S3, the number of silicon atoms required to adjust the silicon-to-aluminum ratio is achieved by increasing or decreasing the unit cell of the molecular sieve, and a silicon-to-aluminum ratio adjustment module [the molecular sieve structure satisfies the Lowenstein principle (two aluminum-oxygen tetrahedrons cannot be connected together)] is used to obtain a molecular sieve structure model with an adjusted silicon-to-aluminum ratio.

[0033] Furthermore, the specific contents of using the silicon-aluminum ratio adjustment module to adjust the silicon-aluminum ratio of the molecular sieve include:

[0034] Step 1: Understand the amount of silicon and aluminum in the molecular sieve to be adjusted, calculate according to the silicon-aluminum ratio to be set, get the new amount of silicon and aluminum, and calculate the reduction percentage of the reduced amount of silicon or aluminum;

[0035] Step 2: Enter the file name of the corresponding molecular sieve;

[0036] Step 3: Input the initial element, new element and reduction percentage; the initial element and new element are both silicon and aluminum;

[0037] Step 4: After running the silicon-aluminum ratio adjustment module, a molecular sieve structure model with an adjusted silicon-aluminum ratio is obtained.

[0038] Furthermore, the metal cations include: one or more of alkali metals, alkaline earth metals, noble metals and rare earth metals.

[0039] Furthermore, the method further comprises:

[0040] The molecular sieve structure model is replaced with an activated carbon or metal organic framework material (MOFs) molecular model, and steps S2, S4 to S5 are repeated to obtain activated carbon or metal organic framework material (MOFs) corresponding to the optimal metal cation.

[0041] Furthermore, the method further comprises: selecting another VOC, repeating steps S1 to S5, and obtaining a molecular sieve adsorbent structure of the another VOC.

[0042] Furthermore, after the VOCs model is established, the method first optimizes its geometric structure and performs a preliminary setting of the charge based on the optimization result;

[0043] The method establishes structural models of different adsorbents (molecular sieves, activated carbon, MOFs, etc.), adjusts and optimizes the models (silicon-aluminum ratio, charge, hydrogenation, etc.), and then performs subsequent simulation adsorption calculations;

[0044] The method is carried out under the combined use of multiple force fields when simulating the screening of molecular sieves. COMPASSⅡ force field and Dreiding force field are used for comparison in the simulation of adsorption calculations, and the geometric structure optimization after modeling is carried out under the Universal force field.

[0045] The method verifies the accuracy of the simulated adsorption calculation force field of the adsorbent and adsorbate by comparing with multiple experimental results of dry / wet gas, high / low temperature, and high / low concentration;

[0046] The method proposes a method for calculating, analyzing and selecting massive adsorption and desorption data using molecular simulation to obtain the optimal adsorbent for target VOCs;

[0047] The method is aimed at actual molecular sieve synthesis and modification methods, adds modified cations into the adsorbent structure model, and predicts the adsorption and desorption performance of the modified molecular sieve for VOCs.

[0048] Furthermore, the method simulates the adsorption of two or more VOCs on the molecular sieve, and can predict the saturated adsorption amount of multiple VOCs on the molecular sieve.

[0049] The VOCs molecular sieve adsorbent screening method based on molecular simulation of the present invention has at least the following beneficial technical effects:

[0050] 1) The existing experimental screening process is transformed into a simulation screening process, which greatly reduces the time cost and improves the screening efficiency.

[0051] 2) Use molecular simulation to screen VOCs molecular sieve adsorbents, filling the gap in molecular simulation screening. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 : is the structural model of acetaldehyde molecule A in the embodiment of the present invention.

[0053] Figure 2 It is the structural model of BETA25 molecular sieve B in the embodiment of the present invention.

[0054] Figure 3 It is the Mulliken atomic charges in the embodiments of the present invention.

[0055] Figure 4 Schematic diagram of a process for screening VOCs molecular sieve adsorbents based on molecular simulation in an embodiment of the present invention. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0057] On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, some specific details are described in detail in the following detailed description of the present invention. Those skilled in the art can fully understand the present invention without the description of these details.

[0058] The following examples serve to illustrate the present invention. In the examples, unless otherwise indicated, parts are by weight, percentages are by weight, and temperatures are in degrees Celsius. The relationship between parts by weight and parts by volume is the same as the relationship between grams and cubic centimeters.

[0059] An embodiment of the present invention provides a method for screening VOCs molecular sieve adsorbents based on molecular simulation, comprising: firstly, using modeling software to construct models of molecular sieves, VOCs, nitrogen and water molecules, and then using quantum chemical methods to optimize the structure and electrical properties of the constructed models; performing Monte Carlo simulation calculations on the optimized structural model, and finally obtaining the optimal molecular sieve adsorbent structure for adsorbing specified VOC gas composition and purification conditions; the method can accurately reflect the adsorption effects of different molecular sieves on different VOCs under different working conditions, which has practical significance for basic research such as studying the adsorption of VOCs by molecular sieves, and helps to improve screening efficiency.

[0060] The embodiment of the present invention provides a method for screening VOCs molecular sieve adsorbents based on molecular simulation, which simulates the adsorption of two or more VOCs on molecular sieves and can predict the saturated adsorption amount of multiple VOCs on the molecular sieve. The existing experimental screening process is converted into a simulation screening process, which greatly reduces the time cost and improves the screening efficiency. In addition, the use of molecular simulation to screen VOCs molecular sieve adsorbents fills the gap in molecular simulation screening.

[0061] In some embodiments of the present invention, Figure 1 , 2 As shown in Figure 4, a method for screening VOCs molecular sieve adsorbents based on molecular simulation specifically includes the following steps:

[0062] S1, model building: Material Studio (MS) software combined with experimental optimization was used to determine the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model for subsequent simulation;

[0063] S2, simulation experiment: using molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model to carry out simulated adsorption experiment and simulated adsorption effect experiment, and finally obtain the molecular sieve and adsorption conditions with the best adsorption effect for the specified VOC;

[0064] S3, determine the silicon-aluminum ratio of the molecular sieve: simulate the effect of molecular sieves with different silicon-aluminum ratios on VOCs adsorption to determine the optimal silicon-aluminum ratio of the molecular sieve;

[0065] S4, after determining the optimal silicon-aluminum ratio, adding metal cations and optimizing the structure of the molecular sieve structure model again, after optimization, simulated adsorption calculation of VOCs is performed to obtain the saturated adsorption amount result;

[0066] S5, changing the type or amount of metal cations, repeating S4, obtaining the saturated adsorption results corresponding to the metal cations, comparing the saturated adsorption results of all molecular sieves containing metal cations, and determining the optimal metal cation for the adsorption of corresponding VOCs on the molecular sieve with the optimal silicon-aluminum ratio; finally, obtaining a VOCs molecular sieve adsorbent with the optimal silicon-aluminum ratio and the optimal metal cation for the adsorption of the specified VOC.

[0067] In some embodiments of the present invention, a method for screening VOCs molecular sieve adsorbents based on molecular simulation is used to establish a VOCs model, first optimize its geometric structure, and perform a preliminary charge setting based on the optimization result; the method establishes structural models of different adsorbents (molecular sieves, activated carbon, MOFs, etc.), and adjusts and optimizes the models (silicon-aluminum ratio, charge, hydrogenation, etc.), and then performs subsequent simulated adsorption calculations; the method is carried out under the combined use of multiple force fields when simulating the screening of molecular sieves, and COMPASSⅡ force field and Dreidi are used in the simulated adsorption calculation. ng force field, and the geometric structure optimization after modeling is carried out under the Universal force field; the method verifies the accuracy of the simulated adsorption calculation force field of the adsorbent and adsorbate by comparing with multiple experimental results of dry / wet gas, high / low temperature, high / low concentration; the method proposes a method to use molecular simulation to calculate, analyze and select massive adsorption and desorption data to obtain the optimal adsorbent for the target VOCs; the method adds modified cations to the adsorbent structure model according to the actual molecular sieve synthesis and modification methods, and predicts the adsorption and desorption performance of the modified molecular sieve for VOCs.

[0068] In some embodiments of the present invention, in the above step S1, Material Studio (MS) software includes: Forcite module, DMol3 module and silicon-aluminum ratio adjustment module.

[0069] In some embodiments of the present invention, in the above step S1, the specific content of S1 includes:

[0070] S1.1, using Material Studio (MS) software to build the initial molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model;

[0071] S1.2, optimize the geometric structures of the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model;

[0072] S1.3, further optimize the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model to keep each molecule electrically neutral;

[0073] S1.4, simulate the adsorption calculation of the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model under different force fields at the specified pressure, and compare the simulated adsorption calculation results with the saturated adsorption amount obtained by the experiment to determine the force field for the simulation calculation;

[0074] S1.5, determine the charge load of the molecular sieve structure model, and finally obtain the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model for subsequent simulation.

[0075] In some embodiments of the present invention, in the above step S1.1, the Material Studio software includes: Forcite module, Sorption module, DMol3 module, Castep module, VASP module and silicon-aluminum ratio adjustment module.

[0076] In some embodiments of the present invention, in the above step S1.2, the Forcite module is used for optimization.

[0077] In some embodiments of the present invention, in the above step S1.3, the DMol3 module is used for optimization.

[0078] In some embodiments of the present invention, in the above step S1.4, the force field includes: Universal, Dreiding, COMPASS and COMPASSⅡ, preferably COMPASSⅡ.

[0079] In some embodiments of the present invention, in the above step S1.5, determining the charge load of the molecular sieve structure model includes two methods:

[0080] When conducting simulated adsorption under dry gas, the charge of the representative structure of the VOC molecule is continuously adjusted (±0.3) on the basis of the initially set charge (e.g., acetaldehyde is adjusted to C=O, ethanol is adjusted to -OH, and acetic acid is adjusted to -COOH) to perform simulated adsorption calculations until the result is close to the saturated adsorption amount obtained in the experiment; based on this VOC charge, the charge of the water molecule under wet gas conditions is further adjusted (±0.2) until the simulated adsorption result is close to the saturated adsorption amount result obtained in the wet gas experiment;

[0081] Under dry gas conditions: the load simulation of VOC on the molecular sieve is carried out under the fixed loading task under the sorption module in Material Studio (MS) software to obtain the specific position of the VOC load on the molecular sieve, and the fragment with the VOC is cut on the molecular sieve. The fragment is optimized by the DMol3 module to obtain the charge number of each atom in the fragment, the charge of each atom is attached to the molecular sieve structure model, and the VOC and molecular sieve in the fragment are separated.

[0082] In some embodiments of the present invention, in the above step S2, the experimental conditions include: VOCs concentration (0.001 ppb to 200000 ppm), different relative humidity (0 to 100% RH) and temperature (-50 to 500° C.).

[0083] In some embodiments of the present invention, in the above step S2, the simulated adsorption experiment includes: under the same conditions, two or more VOCs are subjected to simulated adsorption with a molecular sieve, and the saturated adsorption amount of multiple VOCs on a specified molecular sieve can be predicted;

[0084] The simulated adsorption effect experiment includes: changing the VOC experimental conditions to perform simulated adsorption calculations on VOC, and obtaining the difference in the adsorption effect of a specified molecular sieve on VOC under different experimental conditions.

[0085] In some embodiments of the present invention, in the above step S3, the number of silicon atoms required for adjusting the silicon-to-aluminum ratio is achieved by increasing or decreasing the unit cell of the molecular sieve, and a silicon-to-aluminum ratio adjustment module [the molecular sieve structure satisfies the Lowenstein principle (two aluminum-oxygen tetrahedrons cannot be connected together)] is used to obtain a molecular sieve structure model with an adjusted silicon-to-aluminum ratio.

[0086] In some embodiments of the present invention, a silicon-aluminum ratio adjustment module (such as Figure 3 The specific contents of adjusting the silicon-aluminum ratio of the molecular sieve include:

[0087] Step 1: Understand the amount of silicon and aluminum in the molecular sieve to be adjusted, calculate according to the silicon-aluminum ratio to be set, get the new amount of silicon and aluminum, and calculate the reduction percentage of the reduced amount of silicon or aluminum;

[0088] Step 2: Enter the file name of the corresponding molecular sieve;

[0089] Step 3: Input the initial element, new element and reduction percentage; the initial element and new element are both silicon and aluminum;

[0090] Step 4: After running the silicon-aluminum ratio adjustment module, a molecular sieve structure model with an adjusted silicon-aluminum ratio is obtained.

[0091] In some embodiments of the present invention, in the above step S4, the metal cations include: one or more of alkali metals, alkaline earth metals, noble metals and rare earth metals.

[0092] In some specific embodiments of the present invention, the method further comprises:

[0093] The molecular sieve structure model is replaced with an activated carbon or metal organic framework material (MOFs) molecular model, and steps S2, S4 to S5 are repeated to obtain the activated carbon or metal organic framework material (MOFs) corresponding to the optimal metal cation.

[0094] In other specific embodiments of the present invention, the method further comprises: selecting another VOC, repeating steps S1 to S5, and obtaining a molecular sieve adsorbent structure of another VOC.

[0095] The technical solution of the present invention is described below using specific embodiments.

[0096] Example 1

[0097] (1) Based on the chemical structural formula of each molecule, the structural models of nitrogen molecule, water molecule, acetaldehyde molecule A and BETA25 (beta 25) molecular sieve B were established using MS software [the structural model of acetaldehyde molecule A is shown in Figure 1 As shown, the structural model of BETA25 (beta 25) molecular sieve B is as follows Figure 2 As shown], the Forcite module of MS software [Universal force field, van der Waals (intermolecular force) and Coulomb force for non-bonded interaction, Atom Based (atom-based) for superposition processing, and fine (high-quality) for accuracy] were used to optimize the above structural models;

[0098] (2) Continue to use the DMol3 module in the MS software (select the Geometry Optimization task, select GGA (general gradient correction) and BLYP (backward correlation function) in Functional, select Population analysis in Propertis, and use Fine for accuracy) to optimize the structural models of nitrogen molecules, water molecules, and acetaldehyde molecules optimized by Forcite; find Mullikenatomic charges (such as Figure 3(as shown), and set the charges for nitrogen molecules, water molecules, and acetaldehyde molecules according to the results displayed; (3) continue to use the Sorption module in the MS software (select Fixed Pressure task, 100,000 equilibrium steps, 1,000,000 production steps, 303K temperature, select Sorbates as acetaldehyde and nitrogen for dry gas adsorption, convert concentration to pressure, set acetaldehyde pressure to 0.003 (30ppm), nitrogen pressure to 99.997; add water and set the pressure to 0.01 (RH = 25%) for wet gas adsorption, acetaldehyde remains unchanged, nitrogen pressure is set to 99.987, maintain total pressure at 100KPa, use COMPASSⅡ force field, select metropolis (a calculation method for simple molecules) for calculation method, select Ewald&Group (based on Ewald and energy) for electrostatic charge summation, set intermolecular force to Atom Based (based on atoms), fine (high quality) is used for accuracy, the BETA25 (Beta 25) molecular sieve structure model optimized by Forcite is placed in the current one, and the adsorption calculation is started;

[0099] (4) The saturated adsorption amount of acetaldehyde obtained by simulated adsorption under dry gas was compared with the saturated adsorption amount (18.16 mg / g) obtained by the experiment under the same conditions. At the same time, the charge of acetaldehyde C=O (the initial setting value was C: 0.277, O: -0.356, adjusted within the range of ±0.3) was continuously adjusted until it was close to the experimental saturated adsorption amount, and finally adjusted to C: 0.047, O: -0.126, and the simulated saturated adsorption amount was 17.83 mg / g; based on this acetaldehyde charge, the charge of water was adjusted (the initial setting value was H: 0.236, O: -0.472, adjusted within the range of ±0.2) until it was close to the saturated adsorption amount of the wet gas experiment (7.68 mg / g), and finally adjusted to H: 0.19, O: -0.38, and the simulated saturated adsorption amount was 7.7 mg / g; thus, the structural model of acetaldehyde, water, and nitrogen for subsequent simulation calculations was finally determined.

[0100] Example 2

[0101] (1) The optimal charge setting value of BETA25 (Beta 25) molecular sieve for simulating the adsorption of ethanol was obtained by the same steps as in Example 1: the ethanol -OH charge was adjusted to O: -0.193, H: 0.046 in dry gas; the water charge was adjusted to H: 0.226, O: -0.452 in wet gas.

[0102] (2) Use the Sorption module in the MS software (select the Fixed Pressure task, set the equilibrium step number to 100,000, the production step number to 1,000,000, the temperature to 303 K, select Sorbates as acetaldehyde, ethanol and nitrogen with adjusted charge for dry gas adsorption, convert the concentration to pressure, set the acetaldehyde pressure to 0.003 (30 ppm), the ethanol pressure to 0.001 (10 ppm), the nitrogen pressure to 99.996 KPa, and maintain the total pressure at 100 KPa; use the COMPASSⅡ force field, select metropolis (a calculation method for simple molecules) for the calculation method, select Ewald&Group (based on Ewald and energy) for the electrostatic charge summation, and set the intermolecular force to Atom Based on (atom-based), fine (high-quality) is used for accuracy. The BETA25 (Beta 25) molecular sieve structure model optimized by Forcite is placed in the current state and the adsorption calculation is started. The saturated adsorption capacities of BETA25 (Beta 25) for acetaldehyde and ethanol are 5.76 mg / g and 28.47 mg / g, respectively. The total saturated adsorption capacity is 34.23 mg / g, which is close to the experimental saturated adsorption capacity of 40 mg / g. (3) When simulating the adsorption of acetaldehyde and ethanol wet gas mixture, in order to keep the charge of water molecules consistent, BETA25 is selected to simulate the adsorption of acetaldehyde and ethanol under wet conditions. The simulated adsorption capacities of acetaldehyde and ethanol under this charge are 12.01 and 8.81 mg / g respectively (the experimental saturated adsorption capacities are 7.68 and 9.71 mg / g, respectively). Sorbates (Adsorption) is selected for wet adsorption. The water pressure was set to 0.01 (RH=25%), the nitrogen pressure was set to 99.986 KPa, the acetaldehyde and ethanol pressures remained unchanged, and the total pressure was maintained at 100 KPa; the saturated adsorption amounts of acetaldehyde and ethanol obtained by simulation were 5.39 and 18.19 mg / g, respectively, and the total saturated adsorption amount was 23.58 mg / g, which was very close to the saturated adsorption amount of 23.93 mg / g obtained in the experiment, as shown in Table 1 below, thereby verifying the accuracy of this structural model and force field.

[0103] Table 1 Saturated adsorption capacity corresponding to the optimal charge value when BETA25 simulates the adsorption of acetaldehyde and ethanol mixed gas under dry and wet conditions.

[0104]

Claims

1. A method for screening VOCs molecular sieve adsorbents based on molecular simulation, characterized in that: The method comprises: firstly constructing a model of molecular sieve, VOC, nitrogen and water molecules using modeling software, and then optimizing the structure and electrical properties of the constructed model using quantum chemical methods; performing Monte Carlo simulation calculation on the optimized structural model, and finally obtaining the optimal molecular sieve adsorbent structure for adsorbing specified VOC gas composition and purification conditions; The method specifically comprises: S1, model building: Material Studio software combined with experimental optimization was used to determine the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model for subsequent simulation; S2, simulation calculation: using the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model to perform simulated adsorption calculation and simulated adsorption effect calculation to obtain the molecular sieve and adsorption conditions with the best adsorption effect for the specified VOC; S3, determine the silicon-aluminum ratio of the molecular sieve: simulate the effect of molecular sieves with different silicon-aluminum ratios on VOCs adsorption to determine the optimal silicon-aluminum ratio of the molecular sieve; S4, after determining the optimal silicon-aluminum ratio, adding metal cations and optimizing the structure of the molecular sieve structure model again, after optimization, simulated adsorption calculation of VOCs is performed to obtain the saturated adsorption amount result; S5, changing the type or amount of metal cations, repeating S4, obtaining the saturated adsorption amount result corresponding to the metal cation, comparing all the saturated adsorption amount results, determining the molecular sieve with the optimal silicon-aluminum ratio and the optimal metal cation for the corresponding VOCs adsorption; and finally obtaining the VOCs molecular sieve adsorbent with the optimal silicon-aluminum ratio and the optimal metal cation for the specified VOC adsorption; S1 specific content includes: S1.1, using Material Studio software to build the initial molecular sieve structure model, VOC molecular model, nitrogen model and water molecule model; S1.2, optimize the geometric structures of molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model; S1.3, further optimize the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model to keep each molecule electrically neutral; S1.4, simulate the adsorption calculation of the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model under different force fields at specified pressures, and compare the simulated adsorption calculation results with the saturated adsorption amount obtained from the experiment to determine the force field for the simulation calculation; S1.5, determine the charge load of the molecular sieve structure model, and finally obtain the molecular sieve structure model, VOC molecular model, nitrogen model and water molecular model for subsequent simulation.

2. The method for screening VOCs molecular sieve adsorbents based on molecular simulation according to claim 1, characterized in that: There are two methods for determining the charge load of the molecular sieve structure model described in S1.5: When conducting simulated adsorption under dry gas, the charge of the representative structure of the VOC molecule is continuously adjusted on the basis of the initially set charge to perform simulated adsorption calculations until it is close to the saturated adsorption result obtained in the experiment; based on this VOC charge, the charge of the water molecule under wet gas conditions is adjusted until the simulated adsorption result is close to the saturated adsorption result obtained in the wet gas experiment; or, Under dry gas conditions: Use the fixed loading task under the sorption module in Material Studio software to simulate the loading of VOC on the molecular sieve to obtain the specific position of the VOC loading on the molecular sieve, cut a fragment with the VOC on the molecular sieve, optimize the fragment using the Castep, DMol3 or VASP module, obtain the charge number of each atom in the fragment, attach the charge number of each atom to the molecular sieve structure model, and separate the VOC and the molecular sieve in the fragment.

3. The VOCs molecular sieve adsorbent screening method based on molecular simulation according to claim 1, characterized in that: The experimental conditions in S2 include: VOCs concentration, different relative humidity and temperature.

4. The method for screening VOCs molecular sieve adsorbents based on molecular simulation according to claim 1, characterized in that: In S3, the number of silicon atoms required for adjusting the silicon-aluminum ratio is achieved by increasing or decreasing the unit cell of the molecular sieve, and a silicon-aluminum ratio adjustment module is used to obtain a molecular sieve structure model with an adjusted silicon-aluminum ratio.

5. The method for screening VOCs molecular sieve adsorbents based on molecular simulation according to claim 4, characterized in that: The specific contents of using the silicon-aluminum ratio adjustment module to adjust the silicon-aluminum ratio of the molecular sieve include: Step 1: Understand the amount of silicon and aluminum in the molecular sieve to be adjusted, calculate according to the silicon-aluminum ratio to be set, get the new amount of silicon and aluminum, and calculate the reduction percentage of the reduced amount of silicon or aluminum; Step 2: Enter the file name of the corresponding molecular sieve; Step 3: Input the initial element, new element and reduction percentage of Si / Al ratio; Step 4: After running the silicon-aluminum ratio adjustment module, a molecular sieve structure model with an adjusted silicon-aluminum ratio is obtained.

6. The method for screening VOCs molecular sieve adsorbents based on molecular simulation according to claim 1, characterized in that: The metal cations include: one or more of alkali metals, alkaline earth metals, transition metals, noble metals and rare earth metals.

7. The method for screening VOCs molecular sieve adsorbents based on molecular simulation according to any one of claims 1 to 6, characterized in that: The method further comprises: The molecular sieve structure model is replaced with an activated carbon or metal organic framework material molecular model, and steps S2, S4-S5 are repeated to obtain the activated carbon or metal organic framework material corresponding to the optimal metal cation.

8. The method for screening VOCs molecular sieve adsorbents based on molecular simulation according to claim 7, characterized in that: The Material Studio software includes: Forcite module, Sorption module, DMol3 module, Castep module, VASP module and silicon-aluminum ratio adjustment module.

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