A molecular design method and application of triazine desulfurizer

Abstract

This invention provides a molecular design method and application for triazine desulfurizers. Using Materials Studio molecular simulation software, a nucleophilic substitution reaction pathway between a triazine liquid desulfurizer and H2S is constructed. Molecular mechanics and kinetics methods are used to determine the lowest-energy configuration of the product. By comparing the energy of the reaction products of triazine molecules with different terminal functional groups and molecular chain structures and H2S, the molecular structure of the triazine liquid desulfurizer is optimized, thereby selecting triazine desulfurizers with high desulfurization capacity and stability.

Description

Technical Field

[0001] The present invention relates to the technical field of crude oil desulfurization, and in particular to a molecular design method and application of a triazine liquid desulfurizer. Background Art

[0002] H2S is a critical associated gas in oil and gas development. On the one hand, hydrogen sulfide dissolved in crude oil continuously precipitates during storage, transportation, and processing, causing wet hydrogen sulfide corrosion and poisoning catalysts in subsequent crude oil processing equipment. On the other hand, H2S is highly toxic and irritating, affecting the human respiratory system and causing serious harm to the body. Therefore, during the production, storage, and transportation of H2S-containing crude oil, every effort must be made to remove H2S to below safe concentrations. Improving technologies and developing new technologies for the treatment of hydrogen sulfide in oilfield produced fluids have become essential issues in H2S-containing oilfield production.

[0003] The main products of crude oil desulfurizers currently in common use include: alkanolamines, oxidants, aldehydes, and triazine compounds, which are reaction products of aldehydes and amines. Among them, alkanolamine desulfurizers have no selectivity for CO2 and H2S, oxidant desulfurizers can cause sulfur deposition and corrosion problems, and aldehyde desulfurizers are highly toxic and react slowly with H2S at low temperatures. Triazine compounds are macromolecular active agents with nitrogen-rich molecular chains and active hydrogen atoms that can react with S in H2S. 2- An irreversible chemical reaction occurs to generate thiadiazine, thereby achieving the purpose of removing H2S. Triazine compounds react with H2S faster than aldehydes, have better desulfurization performance, are highly safe, and do not require recovery and can be directly injected into the formation. They are currently considered the most promising crude oil desulfurizers. However, some problems have been found in the application of triazine liquid desulfurizers: (1) triazine liquid desulfurizers are easily hydrolyzed, and the desulfurization effect is easily affected by pH; (2) triazine desulfurizers are prone to precipitation during the absorption of H2S. (3) The absorption effect becomes "ineffective" over time.

[0004] However, most of the research and development in the field of traditional desulfurizers is based on inferences from existing knowledge and experience, and is achieved through repeated experiments. However, this research and development path is inefficient, has a long research cycle, a large workload, and is somewhat blind. If the production process and application evaluation of hydrogen sulfide treatment in oilfield produced fluids are considered in the later stage, the entire process is time-consuming and energy-intensive, and cannot meet the requirements of comprehensive resource utilization. With the increasing number of practical operations in industry and numerous laboratory simulation experiments, triazine desulfurizers have made great progress, but they still need to be further continuously solved and improved. The problems of easy hydrolysis, easy precipitation, and easy failure of triazine liquid crude oil desulfurizers during use need to be solved and their advantages of highly selective H2S removal are fully utilized. Therefore, it is an urgent problem to develop a molecular design method for triazine desulfurizers, and to use computer-aided molecular design to screen triazine desulfurizers with high desulfurization ability and high desulfurization stability from the source. Summary of the Invention

[0005] To address these issues, the present invention provides a molecular design method for triazine desulfurizers. Using Materials Studio molecular simulation software, the nucleophilic substitution reaction pathway between triazine liquid desulfurizers and H2S is constructed. Molecular mechanics and dynamics methods are then used to determine the lowest-energy configuration of the product. By comparing the energy of the reaction products of triazine molecules with different terminal functional groups and molecular chain structures and H2S, the molecular structure of the triazine liquid desulfurizer is optimized, thereby selecting triazine desulfurizers with high desulfurization capacity and stability.

[0006] The technical solutions of the present invention are as follows:

[0007] The present invention provides a molecular design method for a triazine desulfurizer, which comprises the following steps:

[0008] S1: Use Materials Studio molecular simulation software to construct a molecular model of triazine desulfurizer and perform structural optimization;

[0009] S2: constructing the molecular structure of the triazine desulfurizer with different end groups and analyzing the effect of different end groups on the desulfurization ability;

[0010] S3: Screening out suitable end group types based on the analysis results in step S2, constructing molecular structures with the same end group series, and determining the effects of these molecular structures on the desulfurization reaction activity;

[0011] S4: selecting a research object based on the result in step S3, analyzing the reaction path of the research object with H2S and the minimum energy of the product, thereby determining a target triazine desulfurizer with high desulfurization ability.

[0012] Furthermore, in step S1, the Visualizer module in Materials Studio software is used to construct a single triazine desulfurizer molecular model, and the single molecule model is structurally optimized using the Geometry Optimization tool in the DMol3 module to achieve the optimal energy configuration of the molecule. Specifically, the structural optimization process is based on the B3LYP functional and DND basis set level (such as Figure 2 shown).

[0013] Furthermore, step S2 includes the following steps:

[0014] S2-1: Construction of molecular structures of triazine desulfurizers with different end groups;

[0015] S2-2: Atomic charge analysis;

[0016] S2-3: Frontier track analysis;

[0017] S2-4: Fukui function analysis.

[0018] Furthermore, in step S2-1, because the desulfurization performance of triazine desulfurizers is significantly affected by end groups, triazine molecular structures with different end groups were designed and optimized using the DMol3 module. Subsequent atomic charge analysis, frontier orbital analysis, and Fukui function analysis determined the appropriate end group type, resulting in a triazine desulfurizer with excellent performance.

[0019] Furthermore, in step S2-1, the terminal group is any one of an alkyl group, a hydroxy ether bond, an aldehyde group, a carbonyl group, a carboxyl group, an ester group, an alcohol group, or an aromatic ring. Preferably, the terminal group is an alkyl group, an alcohol group, an aromatic ring, or a carbonyl group. More preferably, the terminal group is -CH3, -(CH2)2OH, -C6H5, or -COCH3.

[0020] Furthermore, in step S2-2, the atomic charge analysis (Hirshfeld charge analysis) is performed by analyzing the atomic charges of triazine desulfurizers with different end groups. The purpose is to use the atomic charge to preliminarily determine the reaction site and the difficulty of the reaction. When the carbon atom has a higher positive charge, it can be preliminarily considered that it is more likely to undergo nucleophilic substitution, that is, more likely to react with H2S, and thus has stronger desulfurization ability.

[0021] Furthermore, in step S2-3, the frontier orbital analysis is to analyze the LUMO and HOMO orbital distributions of the triazine ring in the triazine desulfurizer with different end groups to determine the reaction of the triazine ring with H2S. 2-Which carbon cation in the triazine ring is attacked, whether the CN bond is broken, and which CN bond is prone to breakage can determine the reaction sites when the three desulfurizers react with H2S.

[0022] Furthermore, in step S2-4, the Fukui function analysis is to analyze the f(+) index and f(-) index of each atom of the triazine desulfurizer with different end groups. The atom with a larger f(+) index value represents that the atom is susceptible to attack by the nucleophile, that is, susceptible to S 2- The higher the attack, the more likely the desulfurization reaction is to occur, which in turn indicates that the corresponding desulfurizer has a high desulfurization capacity. The larger the f(-) value of an atom, the more likely the electrophilic reaction is to occur on that atom, which in turn means that the desulfurization reaction is less likely to occur near that atom. Since the reaction between the desulfurizer and H2S is a nucleophilic substitution reaction, H2S loses electrons and the desulfurizer gains electrons. Therefore, the LUMO orbital is temporarily unoccupied. Therefore, the electrons gained by the desulfurizer will occupy the lowest unoccupied molecular orbital, so the f(+) index is the main factor to determine the reaction.

[0023] Furthermore, step S3 specifically includes:

[0024] S3-1: Constructing molecular structures with the same end group series;

[0025] S3-2: Perform Fukui function analysis on each molecular structure of each identical end group series.

[0026] Furthermore, in step S3-2, by comparing the f(+) index and f(-) index of molecules with the same end group series - alkyl or alcohol groups in different chain lengths, the variation pattern of the desulfurization capacity of triazine desulfurizers with different chain lengths is obtained; similarly, by comparing the f(+) index and f(-) index of molecules with the same end group series - alkyl or alcohol groups in straight chain or branched chain, the variation pattern of the desulfurization capacity of straight chain or branched chain triazine desulfurizers is obtained.

[0027] Furthermore, in step S4, a research object is selected according to the result in step S3, and the f(+) index and f(-) index of the monothioic product obtained by the first-order reaction in the reaction of the research object with H2S are analyzed. By comparing the f(+) index and the f(-) index of the monothioic product, the CN bond position where the second-order reaction to obtain the dithioic product occurs is determined.

[0028] In this invention, the following technical and scientific terms are used:

[0029] Atomic charge: Atomic charge, the point charge on each atom in a molecule, is one of the simplest and most intuitive ways to describe the charge distribution in a chemical system. It has many important applications, such as studying the state of atoms in various chemical environments, examining molecular properties, and predicting reaction sites.

[0030] Frontier Orbitals: In organic chemical reactions, the molecular orbitals involved in breaking and forming chemical bonds are generally the highest-energy occupied molecular orbitals (HOMOs) and the lowest-energy unoccupied molecular orbitals (LUMOs). The electrons in the HOMOs are the valence electrons of the molecule. They have the highest energy and are the least tightly bound, making them the most easily moved during reactions. The lowest-energy unoccupied molecular orbital (LUMO or LEMO) is the most receptive to electrons during chemical reactions. Frontier Orbital Theory posits that chemical reactions occur through charge transfer between the highest-filled molecular orbital (HOMO) and the lowest-unoccupied molecular orbital (LUMO), with atoms in the HOMOs tending to donate electrons, while atoms in the LUMOs tend to accept electrons.

[0031] Fukui functions are the most successful and well-known method for qualitatively analyzing the reactive regions of molecules based on Fukui frontier orbital theory. The f(-) (Fukui indices for electrophilic attack) measure the susceptibility of an atom to attack by electrophiles, while the f(+) (Fukui indices for nucleophilic attack) and f(0) (Fukui indices for radical attack) describe the susceptibility of an atom to attack by nucleophiles and free radicals, respectively.

[0032] The present invention also provides a molecular design method for the triazine liquid desulfurizer and its application in the field of crude oil desulfurization.

[0033] The beneficial effects of the present invention are as follows:

[0034] 1. Use Material Studio molecular simulation software to build the nucleophilic substitution reaction path of triazine desulfurizer and H2S, and obtain the lowest energy configuration of the product through molecular mechanics and kinetics methods.

[0035] 2. By comparing and analyzing the energy of triazine desulfurizer molecules with different terminal functional group types and different molecular chain structures and the reaction products of H2S, the molecular structure of triazine liquid desulfurizer is optimized, thereby solving the problems of easy hydrolysis, precipitation and failure of existing triazine liquid crude oil desulfurizers during use, and giving full play to the advantage of triazine liquid crude oil desulfurizers in highly selective H2S removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the initial molecular structure diagram of triazine desulfurizer;

[0037] Figure 2 Screenshot of DMol3 calculation parameters;

[0038] Figure 3 The molecular structure of triazine desulfurizers with different end groups;

[0039] Figure 4 The graph of molecular energy of triazine desulfurizers with different end groups changing with the number of optimizations;

[0040] Figure 5 The optimized molecular structure and atom numbering of triazine desulfurizers with different end groups;

[0041] Figure 6 is the LUMO molecular orbital of triazine desulfurizer molecules with different terminal groups;

[0042] Figure 7 is the HOMO molecular orbital of triazine desulfurizer molecules with different terminal groups;

[0043] Figure 8 This is the nucleophilic substitution reaction pathway of triazine desulfurizers and H2S;

[0044] Figure 9 is the f(+) function field of triazine desulfurizer molecules with different terminal groups;

[0045] Figure 10 is the f(-) function field of triazine desulfurizer molecules with different terminal groups;

[0046] Figure 11 The molecular structures of the designed different alkyl-terminated triazine desulfurizers;

[0047] Figure 12 is the f(+) function field of the designed different alkyl-terminated triazine desulfurizer molecules;

[0048] Figure 13 is the f(-) function field of the designed different alkyl-terminated triazine desulfurizer molecules;

[0049] Figure 14 The molecular structures of the designed different alcohol-terminated triazine desulfurizers;

[0050] Figure 15 is the f(+) function field of the designed different alcohol-terminated triazine desulfurizer molecules;

[0051] Figure 16 is the f(-) function field of the designed different alcohol-terminated triazine desulfurizer molecules;

[0052] Figure 17 are the LUMO and HOMO molecular orbitals of the monothiazole product after the reaction of methyltriazine and H2S;

[0053] Figure 18 are the LUMO and HOMO molecular orbitals of the monothiazole product after the reaction of linear propanol triazine with H2S;

[0054] Figure 19 This is the general formula for the production of triazines by condensation of amine-aldehydes. DETAILED DESCRIPTION

[0055] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0056] Example

[0057] S1: Construction of molecular model

[0058] The Visualizer module in Materials Studio 2017 software package was used to construct molecular models of individual modified triazine H2S removal agents, such as Figure 1 As shown. The single molecule model was structurally optimized using the Geometry Optimization tool in the DMol3 module to achieve the optimal energy configuration. The Smart method was used in the optimization process. The parameters used for optimization are as follows Figure 2 shown.

[0059] S2: Effect of different end group molecular structures on H2S removal performance

[0060] (1) Molecular design of triazine H2S removal agents with different terminal groups

[0061] The desulfurization performance of triazine H2S removal agent is greatly affected by the modified end group. For this reason, this embodiment designs the following Figure 3 The molecular structure of the triazine H2S remover is shown.

[0062] The DMol3 module is used to optimize the structure of molecules with different end group types. The molecular energy changes with the optimization steps as shown in the following figure: Figure 4 As shown, from Figure 4 It can be seen that all four molecules have reached energy stability.

[0063] The optimized molecular structure and atom numbering are as follows Figure 5 As shown in the optimization results, the four triazine molecules ultimately have a centrosymmetric structure due to the identical end groups, meaning that carbon atoms 2, 4, and 6 are completely equivalent. However, due to the different steric hindrances caused by the different end groups, the central triazine ring undergoes different distortions. Tables 1 and 2 show the changes in the triazine ring molecular structure with different end groups.

[0064] Table 1 Effect of different end groups on the bond length parameters of triazine ring structure

[0065]

[0066]

[0067] Table 2 Effect of different end groups on the bond angle parameters of triazine ring structure

[0068]

[0069] It can be seen from Tables 1 and 2 that the different types of end groups have almost no effect on the original CN ring bond length, but will slightly affect the CN ring bond angle.

[0070] (2) Atomic charge analysis

[0071] This example uses Hirshfeld charge analysis. Table 3 shows the Hirshfeld charge numbers of each atom in different terminal triazine structures.

[0072] Table 3 Atomic charges in the structures of different terminal triazines

[0073] Atomic number SC-1 SC-2 SC-3 SC-4 N1 -0.0724 -0.0926 -0.114 -0.1184 C2 0.0513 0.0421 0.038 0.0396 N3 -0.0734 -0.0888 -0.115 -0.1149 C4 0.0511 0.046 0.038 0.0374 N5 -0.0694 -0.0939 -0.114 -0.1137 C6 0.0517 0.0457 0.039 0.0375 Average charge N -0.0717 -0.0918 -0.1143 -0.1157 C average charge 0.0514 0.0446 0.0383 0.0382

[0074] As can be seen from Table 3, the carbon atom of SC-1 has the highest positive charge, followed by SC-2. Therefore, it is preliminarily judged that the C atom on the SC-1 desulfurizer is most likely to undergo nucleophilic reaction, that is, the SC-1 desulfurizer is most likely to react with H2S, followed by the SC-2 desulfurizer.

[0075] (3) Frontier orbit analysis

[0076] Figure 6 and Figure 7 The molecular orbital compositions of LUMO and HOMO of triazine molecules with different terminal groups are shown. Figure 6 and 7 It can be seen that the end group has a great influence on the molecular orbital of triazine H2S removal agent. According to the reaction mechanism of triazine desulfurizer and H2S given in the figure, S2- attacks the carbon cation in the triazine ring, and the adjacent nitrogen atom combines with the hydrogen ion. Figure 6 and Figure 7 It can be seen that:

[0077] (1) All C atoms in the triazine ring of SC-1 are in the HOMO orbital, and the three C atoms are completely equivalent. At the same time, all N atoms in the triazine ring are in the LUMO orbital, and the three N atoms are completely equivalent, that is, the reaction can occur from any C-N bond.

[0078] (2) In SC-3, the C atom in the LUMO and the N atom in the HOMO are in the para position in the triazine ring, so the CN cleavage reaction is not easy to occur, that is, the effect of removing H2S is poor.

[0079] (3) The LUMO and HOMO of the triazine ring in SC-2 and SC-4 are unevenly distributed. It can be seen that the C6-N1 bond is the first to undergo CN cleavage in SC-2, while the C2-N3 bond is the first to undergo CN cleavage in SC-4.

[0080] (4) Fukui function analysis

[0081] Figure 9 and Figure 10 The field distribution diagrams of f(+) and f(-) are shown respectively, and Table 5 lists the f(+) and f(-) indices.

[0082] Table 4 f(+) index of triazine molecules with different terminal groups

[0083] Atomic number SC-1 SC-2 SC-3 SC-4 N1 0.011 0.006 0.006 0.024 C2 0.035 0.011 0.004 0.013 N3 0.011 0.004 -0.002 0.021 C4 0.036 0.011 0.005 0.012 N5 0.01 0.007 0.013 0.015 C6 0.035 0.036 0.008 0.012

[0084] Table 5 f(-) index of triazine molecules with different terminal groups

[0085]

[0086]

[0087] S3: Effect of the same end group series on reactivity

[0088] From the results of step S2, it can be seen that the aromatic ring triazine (SC-3) has the worst reaction activity, the alkyl triazine (SC-1) has better activity, and the alcohol triazine (SC-2) is second. Therefore, these two series were systematically studied.

[0089] (1) Effect of alkyl groups on triazine reactivity

[0090] Table 6 f(+) index of different designed alkyl-terminated triazine molecules

[0091] Atomic number SC-1-1 SC-1-2 SC-1-3 SC-1-4 N1 0.011 0.007 0.003 0.004 C2 0.035 0.027 0.023 0.018 N3 0.011 0.008 0.008 0.005 C4 0.036 0.027 0.025 0.016 N5 0.01 0.008 0.007 0.004 C6 0.035 0.027 0.026 0.016 Average value of C atom f(+) 0.0353 0.0270 0.0247 0.0167

[0092] Table 7 f(-) index of different designed alkyl-terminated triazine molecules

[0093] Atomic number SC-1-1 SC-1-2 SC-1-3 SC-1-4 N1 0.092 0.094 0.106 0.094 C2 0.027 0.026 0.028 0.024 N3 0.088 0.081 0.079 0.076 C4 0.025 0.024 0.022 0.023 N5 0.088 0.083 0.076 0.082 C6 0.026 0.027 0.026 0.026 Average value of N atom f(-) 0.089 0.086 0.087 0.084

[0094] Triazine molecules with different alkyl end groups are designed as shown in the figure. SC-1-1 to SC-1-3 have gradually increasing alkyl chain lengths, and SC-1-3 and SC-1-4 are straight-chain alkyl end and branched-chain alkyl end, respectively. Based on the quantum calculation results, the f(+) and f(-) indices and function field diagrams are shown in the figure. Figure 12 、 Figure 13 As shown in Tables 6 and 7.

[0095] From the calculation results, it can be seen that the influence of the alkyl end group on the triazine molecule has the following characteristics:

[0096] (1) With the increase of alkyl end groups, the f(+) of the carbon cation in the triazine ring gradually decreases; at the same time, the f(-) of the N atom basically does not change, so the CN bond and H + and S 2- The reactivity gradually weakened, that is, SC-1-1>SC-1-2>SC-1-3.

[0097] (2) Similarly, it can be concluded that the activity of branched alkyl groups is less than that of straight chains, that is, SC-1-3>SC-1-4.

[0098] In summary, for alkyl-terminated triazine molecules, the methane group has the greatest reactivity with H2S, which means that SC-1-1 has the highest potential efficiency in removing H2S.

[0099] (2) Effect of alcohol groups on triazine reactivity

[0100] Triazine molecules with different alcohol end groups are designed as shown in the figure. Among them, SC-2-1 to SC-2-3 have gradually increasing alcohol chain lengths and the distance between the hydroxyl group -OH and the N atom gradually increases. SC-2-3 and SC-2-4 are straight-chain alcohol end and branched alcohol end, respectively. According to the quantum calculation results, the f(+) and f(-) indices and function field diagrams are shown as follows Figure 15 , Table 8 and Figure 16 , as shown in Table 9.

[0101] Table 8 f(+) index of different alcohol-terminated triazine molecules designed

[0102] Atomic number SC-2-1 SC-2-2 SC-2-3 SC-2-4 N1 0.006 0.005 0.001 0.004 C2 0.011 0.008 0.014 0.021 N3 0.004 0.002 0.001 0.006 C4 0.011 0.01 0.011 0.007 N5 0.007 0.009 0.007 0.007 C6 0.036 0.015 0.023 0.009 Average value of C atom f(+) 0.0193 0.0110 0.0160 0.0123

[0103] Table 9 f(-) index of different alcohol-terminated triazine molecules designed

[0104] Atomic number SC-2-1 SC-2-2 SC-2-3 SC-2-4 N1 0.126 0.094 0.137 0.043 C2 0.032 0.017 0.017 0.015 N3 0.08 0.028 0.02 0.067 C4 0.022 0.023 0.018 0.028 N5 0.052 0.117 0.155 0.147 C6 0.027 0.031 0.027 0.023 Average value of N atom f(-) 0.086 0.080 0.104 0.086

[0105] from Figure 15 、 16 As can be seen from Tables 8 and 9, the effects of the alcohol end group on the triazine molecule have the following characteristics:

[0106] (1) With the increase of the alcohol end chain length, the f(+) of the carbon cation in the triazine ring first decreases and then increases; at the same time, the f(-) of the N atom also first decreases and then increases, so the CN bond and H + and S 2- The reactivity of the propanol group is the highest and the allanto group is the lowest, that is, SC-2-3>SC-2-1>SC-2-2.

[0107] (2) Similarly, it can be concluded that the activity of branched alcohol groups is less than that of straight-chain alcohol groups, that is, SC-2-3>SC-2-4.

[0108] In summary, for alcohol-terminated triazine molecules, the linear propanol group has the greatest reactivity with H2S, that is, SC-2-3 has the highest potential efficiency in removing H2S.

[0109] S4: Analysis of the reaction path and product minimum energy of modified triazine desulfurizers with H2S

[0110] Methyl triazine molecules (SC-1-1) and linear propanol triazine molecules (SC-2-3) were selected as research objects to investigate the ability of multi-stage reaction between H2S and triazine molecules.

[0111] (1) Methyltriazine:

[0112] Table 10 f(+) and f(-) indices of the monothioic acid product after the reaction of methyltriazine with H2S

[0113] Atomic number f(+) f(-) S1 0.387 0.397 C2 0.07 0.03 N3 0.01 0.053 C4 0.007 0.017 N5 0.011 0.052 C6 0.071 0.029

[0114] As mentioned above, the CN bonds in the methyltriazine ring are completely equivalent, so the first-order reaction can occur at any CN bond position. Figure 17 It is a thiol product after the S atom replaces the N1 atom after the primary reaction.

[0115] It can be seen that in the generated monothiamine product, the f(+) index of the C4 atom opposite to the S atom is one order of magnitude smaller than that of the C atom adjacent to the S atom, but the f(-) of the three N atoms remains basically unchanged, indicating that the subsequent secondary reaction will occur on the C atom adjacent to the S atom, and finally generate a dithiamine product.

[0116] (2) Linear propyl triazine:

[0117] As mentioned above, the CN bonds in the linear propyltriazine ring are not completely equivalent, among which the f(+) of the C6 atom is the largest, and the f(-) of the N5 atom among the N atoms adjacent to C6 is the largest, so the first-order reaction occurs at the C6-N5 bond position. Figure 18 It is a thiol product after the S atom replaces the N5 atom in the primary reaction.

[0118] Table 11 f(+) and f(-) indices of the monothioic acid products after the reaction of linear propanol triazine with H2S

[0119]

[0120]

[0121] Table 11 shows that in the monothiamine product, the f(+) index of the C2 atom opposite to the S atom is one order of magnitude smaller than that of the C atom adjacent to the S atom. However, the f(+) and f(-) of the adjacent C6-N1 and C2-N3 bonds are higher, so the secondary reaction will occur at the C6-N1 bond, ultimately generating the dithiamine product.

[0122] (2) Comparison of two H2S removal agents:

[0123] Table 12 Fukui index of two-stage reaction of two H2S removal agents

[0124]

[0125] Table 12 shows that the f(+) value of the active carbon atom in the triazine ring of methyl triazine before the primary reaction is greater than that of the linear propyl triazine. However, in the two monothiazole rings before the secondary reaction, both the f(+) value of the active carbon atom and the f(-) value of the active nitrogen atom in the latter are greater than those in the former. In summary, methyl triazine has a greater primary reaction activity than linear propyl triazine, while the monothiazole reaction product of the latter has a greater secondary reaction activity than the monothiazole reaction product of the former.

[0126] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent variation based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A molecular design method for a triazine desulfurizer, characterized in that: The molecular design method comprises the following steps: S1: Use Materials Studio molecular simulation software to construct a molecular model of triazine desulfurizer and perform structural optimization; S2: constructing the molecular structure of the triazine desulfurizer with different end groups and analyzing the effect of different end groups on the desulfurization ability; The step S2 comprises the following steps: S2-1: Construction of molecular structures of triazine desulfurizers with different end groups; S2-2: Atomic charge analysis; S2-3: Frontier track analysis; S2-4: Fukui function analysis; In step S2-1, triazine molecular structures with different end groups are designed, and the DMol3 module is used to optimize the structures of molecules with different end group types; In step S2-2, the atomic charge analysis is to analyze the atomic charges of triazine desulfurizers with different end groups, thereby making a preliminary qualitative judgment on the reaction site and the difficulty of the reaction based on the atomic charge; In step S2-3, the frontier orbital analysis is to analyze the LUMO and HOMO orbital distributions of the triazine ring in the triazine desulfurizer with different end groups to determine the reaction of the triazine ring with H2S. 2- Which carbon cation in the triazine ring is attacked, whether the CN bond is broken, and which CN bond is prone to breakage, thereby determining the reaction site when the desulfurizer reacts with H2S; In step S2-4, the Fukui function analysis is to analyze the f(+) index and f(-) index of each atom of the triazine desulfurizer with different end groups. The atom with a larger f(+) index value represents that the atom is susceptible to attack by the nucleophilic reagent, indicating that the desulfurization reaction is likely to occur; the atom with a larger f(-) index value represents that the electrophilic reaction is more likely to occur on the atom, which means that the desulfurization reaction is less likely to occur near this atom. S3: Screening out suitable end group types based on the analysis results in step S2, constructing molecular structures with the same end group series, and determining the effects of these molecular structures on the desulfurization reaction activity; Step S3 includes: S3-1: Constructing molecular structures with the same end group series; S3-2: Perform Fukui function analysis on each molecular structure of each identical end group series; In step S3-2, by comparing the f(+) index and f(-) index of molecules with the same end group series, i.e., alkyl or alcohol groups, in different chain lengths, the variation pattern of the desulfurization capacity of triazine desulfurizers with different chain lengths is obtained; similarly, by comparing the f(+) index and f(-) index of molecules with the same end group series, i.e., alkyl or alcohol groups, in straight chain or branched chain, the variation pattern of the desulfurization capacity of straight chain or branched triazine desulfurizers is obtained; S4: selecting a research object based on the result in step S3, analyzing the reaction path of the research object with H2S and the minimum energy of the product, thereby determining a target triazine desulfurizer with high desulfurization ability.

2. The molecular design method according to claim 1, characterized in that In step S1, the Visualizer module in the Materials Studio software is used to construct a single triazine desulfurizer molecular model, and the geometry optimization tool in the DMol3 module is used to optimize the structure of the single molecule model so that the molecule reaches the energy optimal configuration.

3. The molecular design method according to claim 2, characterized in that The structure optimization process was based on the B3LYP functional and DND basis set level.

4. Use of the molecular design method of the triazine desulfurizer according to any one of claims 1 to 3 in the field of crude oil desulfurization.

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