4-substituted tetrahydroquinoline oxides, processes for their preparation and use

Abstract

The present application relates to a kind of 4-substituted tetraalkylpyridine oxide and its preparation method and purposes.Mainly solve TEMPO in the process of oxidation is unstable, itself can degrade, leading to the increase of catalyst dosage;TEMPO is relatively expensive, cost is higher;For natural cellulose oxidation effect is not good and so on Problem, by using a kind of 4-substituted-tetraalkylpiperidine oxide, with formula (I) structure shown in: wherein, R1 It is C1-C 10 Straight-chain or branched-chain alkyl group;R2 It is C1-C4 straight-chain or branched-chain alkyl group, multiple R2 Between each other different or same;R3 It is C0-C4 straight-chain or branched-chain alkyl group, when R3 It is C0, carbonyl carbon is connected with benzene ring;X is halogen or H, multiple X Between each other different or same technical scheme, preferably solve the problem, can be used in the process production of high selectivity, high stability oxidation nanocellulose.

Description

Technical Field

[0001] This invention relates to the field of oilfield production, specifically to a 4-substituted tetraalkylpyridine oxide, its preparation method, and its uses. Background Technology

[0002] Cellulose, as a natural and renewable polymer, is an inexhaustible resource in nature. Through a series of chemical reactions, altering the structure of cellulose can endow it with many new functions, resulting in functional materials for various applications. Utilizing cellulose to replace non-renewable resources such as petroleum to obtain sustainable chemical raw materials is a feasible technical route with broad application prospects, and it is of great significance in solving the energy, resource, and environmental problems facing humanity.

[0003] Oxyvitamin, as a cellulose derivative, is widely used due to its excellent biocompatibility, biodegradability, environmental friendliness, and non-toxicity. The selective oxidation products of the C2, C3, and C6 hydroxyl groups in cellulose glucose residues can be used as functional polymers for fluorescence, energy storage, chelating agents, oil extraction, and biomedical applications.

[0004] Cellulose oxidation is classified into two categories: general oxidation and selective oxidation. General oxidation involves the random oxidation of hydroxyl groups on the carbon atoms of cellulose units, typically causing both primary and secondary hydroxyl groups to react simultaneously, generating aldehydes, ketones, acids, etc. Selective oxidation occurs only at the primary or secondary hydroxyl groups, while inhibiting oxidation at other sites.

[0005] Common selective oxidation methods include sodium bromate-sodium chlorate-sodium chlorite oxidation system, hypochlorite oxidation system, TEMPO / NaClO / NaBr oxidation system, etc. Among them, the TEMPO / NaClO / NaBr oxidation system has good selectivity for primary hydroxyl groups, the reaction conditions are relatively mild, the reaction process is relatively simple, and only a small amount of TEMPO needs to be added for the reaction to be well achieved, which has become a research hotspot.

[0006] However, TEMPO has its own drawbacks and shortcomings as a catalyst for oxidation reactions. TEMPO is unstable during the oxidation process and may degrade, leading to an increase in the amount of catalyst required. TEMPO itself is relatively expensive, resulting in higher costs. It is also not very effective for the oxidation of natural cellulose. Summary of the Invention

[0007] This invention addresses the shortcomings of existing technologies by improving and modifying the parent structure of 4-hydroxy-TEMPO as a catalyst, thereby enhancing its stability and reactivity, significantly improving oxidation efficiency and yield, and realizing a new method for preparing oxidized nanocellulose with high selectivity and high stability.

[0008] One of the technical problems to be solved by this invention is the poor solubility and difficulty in injection of modified nanocellulose. A 4-substituted tetraalkylpyridine oxide is provided as an oxidation catalyst, which can significantly improve the degree of carboxylation of the primary hydroxyl groups of cellulose and improve the water solubility of nanocellulose, thereby meeting the requirements for oilfield injection.

[0009] The second technical problem to be solved by the present invention is to provide a method for preparing 4-substituted tetraalkylpyridine oxide, which corresponds to solving one of the above-mentioned technical problems.

[0010] The third technical problem to be solved by the present invention is to provide a use of 4-substituted tetraalkylpyridine oxide corresponding to solving one of the above-mentioned technical problems, specifically as an oxidation catalyst for modifying nanocellulose.

[0011] The fourth technical problem to be solved by the present invention is to provide a specific application of 4-substituted tetraalkylpyridine oxide corresponding to solving one of the above-mentioned technical problems, specifically providing a method for oxidative modification of nanocellulose.

[0012] To solve one of the above-mentioned technical problems, the present invention adopts the following technical solution: a 4-substituted-tetraalkylpiperidine oxide, wherein the 4-substituted-tetraalkylpiperidine oxide has the structure shown in formula (I):

[0013]

[0014] Where R1 is C1-C 10 The carbonyl group is either straight-chain or branched; R2 is a C1-C4 straight-chain or branched carbonyl group, and R2 may be different from or the same to each other; R3 is a C0-C4 straight-chain or branched carbonyl group, and when R3 is C0, the carbonyl carbon is connected to the benzene ring, as shown in formula (I'); X is a halogen or H, and multiple X may be different from or the same to each other.

[0015]

[0016] In the above technical solution, as a preferred embodiment: R1 is C1-C 10 Straight-chain hydrocarbon group; R2 is a C1-C4 straight-chain hydrocarbon group; R3 is a C0-C4 straight-chain hydrocarbon group.

[0017] In the above technical solution, as a preferred embodiment: R1 is C1-C 10 Straight-chain alkyl; R2 is a C1-C4 straight-chain alkyl; R3 is a C0-C4 straight-chain alkyl.

[0018] In the above technical solution, as a preferred embodiment: R1 is a C1-C2 straight-chain alkyl group; R2 is a C1-C2 straight-chain alkyl group, and R2 are the same for each other; R3 is a C0-C2 straight-chain alkyl group.

[0019] To solve the second technical problem mentioned above, the technical solution adopted by the present invention is: a method for preparing 4-substituted-tetraalkylpiperidine oxide, comprising the following steps:

[0020] The compound shown in Formula 1 and the compound shown in Formula 2 were reacted in the presence of a catalyst and a selectively added solvent to obtain a reaction mixture containing the 4-substituted-tetraalkylpiperidine oxide shown in Formula 3.

[0021]

[0022] Where R1 is C1-C 10 R2 is a C1-C4 straight-chain or branched hydrocarbon group, and R2 may be different from or the same to each other; R3 is a C0-C4 straight-chain or branched hydrocarbon group, and when R3 is C0, the carbonyl carbon is connected to the benzene ring; X is a halogen or H, and multiple X may be different from or the same to each other.

[0023] In the above technical solution, as a preferred embodiment: R1 is C1-C 10 Straight-chain hydrocarbon group; R2 is a C1-C4 straight-chain hydrocarbon group; R3 is a C0-C4 straight-chain hydrocarbon group.

[0024] More preferably, R1 is C1-C 10 Straight-chain alkyl; R2 is a C1-C4 straight-chain alkyl; R3 is a C0-C4 straight-chain alkyl.

[0025] More preferably, R1 is a C1-C2 straight-chain alkyl group; R2 is a C1-C2 straight-chain alkyl group, and R2 are the same for each other; R3 is a C0-C2 straight-chain alkyl group.

[0026] In the above technical solution, as a preferred embodiment, the catalyst is a dehydrating agent; preferably, the catalyst is a carbodiimide compound, and more preferably N,N'-dicyclohexylcarbodiimide.

[0027] In the above technical solutions, as a preferred embodiment: the molar ratio of the compound shown in Formula 1, the compound shown in Formula 2, and the catalyst is 1:(1-10):(1-10); and / or,

[0028] Preferably, the reaction conditions are: under inert gas protection, the reaction temperature is 25-120°C, and the reaction time is 0.5-12h; more preferably, the inert gas is nitrogen.

[0029] In the above technical solution, as a preferred embodiment, the preparation method further includes the step of separating the catalyst from the reaction mixture after the reaction is completed, and removing the solvent and impurities in an optional order to obtain the 4-substituted-tetraalkylpiperidine oxide shown in Formula 3.

[0030] To solve the third technical problem mentioned above, the present invention adopts the following technical solution: the use of a 4-substituted-tetraalkylpiperidine oxide prepared by any of the preparation methods described in the technical solution for solving one of the technical problems mentioned above, or a 4-substituted-tetraalkylpiperidine oxide prepared by any of the preparation methods described in the technical solution for solving the second technical problem mentioned above, as an oxidation catalyst.

[0031] In the above technical solutions, as a preferred embodiment: the application of the 4-substituted-tetraalkylpiperidine oxide as a catalyst in the oxidation of cellulose; preferably, the application of the 4-substituted-tetraalkylpiperidine oxide as an oxidation catalyst in the oxidation of nanocellulose.

[0032] To solve the fourth technical problem mentioned above, the present invention adopts the following technical solution: an oxidative modification method for nanocellulose, comprising step 1 of oxidizing the fiber slurry with an oxidizing catalyst, and step 2 of subjecting it to high-pressure homogenization; wherein the oxidizing catalyst is a 4-substituted-tetraalkylpiperidine oxide as described in any of the technical solutions for solving one of the technical problems mentioned above, or a 4-substituted-tetraalkylpiperidine oxide prepared by any of the preparation methods described in any of the technical solutions for solving the second technical problem mentioned above.

[0033] In the above technical solution, as a preferred embodiment: step 1 further includes sodium bromide and an oxidant, wherein the weight ratio of fiber pulp:oxidation catalyst:sodium bromide:sodium hypochlorite is 1:(0.01-0.1):(0.01-0.1):(1-10); and / or,

[0034] Preferably, the oxidation reaction temperature in step 1 is 25℃-100℃, and the pH value of the system is controlled at 10±1 during the reaction; and / or,

[0035] More preferably, the pH value of the system is controlled by an alkali during the reaction process, preferably NaOH; and / or, the oxidation reaction time is 1 to 24 hours.

[0036] In the above technical solution, as a preferred embodiment: the pressure used for the high-pressure homogenization process is 1000-10000 psi; and / or, the number of high-pressure homogenization processes is 5-15.

[0037] In the above technical solution, as a preferred solution: the fiber pulp is any one of wood pulp, cotton pulp, hemp pulp, bamboo pulp, and reed pulp; preferably wood pulp or cotton pulp.

[0038] Through the above technical solution, the present invention provides a special 4-substituted-tetraalkylpiperidine oxide (4-substituted-TEMPO). By using the special 4-substituted-TEMPO as a catalyst, the degree of carboxylation of nanocellulose is greatly improved, thereby improving its water solubility and enabling it to be successfully injected into the formation.

[0039] On the other hand, the nanocellulose solution of the present invention can be used simply by modifying the fiber pulp with 4-substituted TEMPO and high-pressure homogenization, avoiding subsequent complex chemical modification methods while achieving controllable carboxylation and water solubility, meeting the requirements for on-site use. The preparation method is simple, easy to control, and low in cost, and has high promotion and application value.

[0040] The technical solution of this invention uses a special 4-substituted TEMPO as a catalyst, which significantly improves the carboxylation degree of nanocellulose, far exceeding that of traditional TEMPO-modified samples. This greatly improves the water solubility and injectability of the samples, enabling them to be successfully injected into the formation. They can be used for oilfield production, significantly increasing the crude oil recovery rate by 10% to 15%, and achieving good technical results. Attached Figure Description

[0041] Figure 1 The procedure for displacement experiments.

[0042] Figure 2 The carboxyl content of samples at different reaction times.

[0043] The present invention will be further described below through specific embodiments. Detailed Implementation

[0044] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0045] Unless otherwise specified, the raw materials used in the examples and comparative examples are all publicly disclosed in the prior art, such as those that can be directly purchased or prepared according to publicly disclosed methods. Unless otherwise specified, all percentages and concentrations in the examples and comparative examples are weight percentages.

[0046]

Example 1

[0047] Under N2 protection, ethyl acetate was added to a dry three-necked flask, followed by compound 1A (100 mmol), compound 1B (100 mmol), and dehydrating agent DCC (110 mmol). The mixture was stirred, heated to 90 °C, and refluxed for 1 h until the reaction was complete. The mixture was then cooled to room temperature, filtered, washed with water, and the organic phase was extracted with petroleum ether and dried over anhydrous MgSO4 for 12 h. The solvent was then removed by vacuum distillation to obtain 4-tempo-A.

[0048] 10g of wood pulp was placed in a reaction vessel and dispersed with deionized water to a concentration of 1.0wt%. 1g of 4-tempo-A and 1g of sodium bromide were added sequentially, and after uniform dispersion, 100g of 10wt% sodium hypochlorite solution was added dropwise. The pH of the system was controlled at 10±1 using 0.1mol / L NaOH solution. After the pH stabilized, ethanol was added to stop the reaction. The mixture was filtered and washed to obtain 4-substituted TEMPO oxidized cellulose. The oxidized cellulose was dispersed in deionized water to prepare a 1% cellulose solution, which was homogenized eight times at 10000psi to obtain nanocellulose solution NC1.

[0049]

Example 2

[0050] Under N2 protection, ethyl acetate was added to a dry three-necked flask, followed by compound 2A (100 mmol), compound 1B (100 mmol), and dehydrating agent DCC (110 mmol). The mixture was stirred, heated to 80 °C, and refluxed for 2 h until the reaction was complete. The mixture was then cooled to room temperature, filtered, washed with water, and the organic phase was extracted with petroleum ether and dried over anhydrous MgSO4 for 12 h. The solvent was then removed by vacuum distillation to obtain 4-tempo-B.

[0051] 10g of cotton pulp was placed in a reaction vessel and dispersed with deionized water to a concentration of 1.0wt%. 0.5g of 4-tempo-B and 0.2g of sodium bromide were added sequentially, and after uniform dispersion, 100g of a 10wt% sodium hypochlorite solution was added dropwise. The pH of the system was controlled at 10±1 using 0.1mol / L NaOH solution. After the pH stabilized, ethanol was added to stop the reaction. The mixture was filtered and washed to obtain 4-substituted TEMPO oxidized cellulose. The oxidized cellulose was dispersed in deionized water to prepare a 1% cellulose solution, which was homogenized eight times at 10000psi to obtain a nanocellulose solution NC2.

[0052]

Example 3

[0053] Under N2 protection, ethyl acetate was added to a dry three-necked flask, followed by compound 3A (100 mmol), compound 2B (200 mmol), and dehydrating agent DCC (200 mmol). The mixture was stirred, heated to 100 °C, and refluxed for 4 h until the reaction was complete. The mixture was then cooled to room temperature, filtered, washed with water, and the organic phase was extracted with petroleum ether and dried over anhydrous MgSO4 for 12 h. The solvent was then removed by vacuum distillation to obtain 4-tempo-C.

[0054]

Example 4

[0055] Under N2 protection, ethyl acetate was added to a dry three-necked flask, followed by compound 4A (100 mmol), compound 1B (150 mmol), and dehydrating agent DCC (150 mmol). The mixture was stirred, heated to 100 °C, and refluxed for 4 h until the reaction was complete. The mixture was then cooled to room temperature, filtered, washed with water, and the organic phase was extracted with petroleum ether and dried over anhydrous MgSO4 for 12 h. The solvent was then removed by vacuum distillation to obtain 4-tempo-D.

[0056]

[0057] Structures of compounds 1A-4A, 1B, 2B, and 4-substituted TEMPO

[0058]

Example 5

[0059] The oil recovery effect of this invention was evaluated using core displacement. The core samples were selected from Indiana limestone in the United States, with dimensions of 1.5 inches in diameter and 5 inches in length. The core samples were first aged with Shengli crude oil. During displacement, 29% NaCl was first used to simulate a conventional waterflooding process until no crude oil was produced. Then, a nanocellulose solution was injected until no crude oil was produced, followed by the injection of a surfactant aqueous solution until no crude oil was produced. The displacement process is as follows: Figure 1 As shown in Table 1, the displacement conditions are shown in Table 2. Cores 1 and 2 are similar in permeability, porosity, and residual oil saturation; therefore, the oil recovery rate is only affected by the injection process. Comparing cores 1 and 2, it can be found that nanocellulose has an excellent plugging effect, significantly improving the recovery rate, increasing the total recovery rate from 46.2% to 60.6%, an increase of 14.4%.

[0060] Table 1 Conditions for Displacement Use

[0061]

[0062] Table 2 Displacement Results

[0063]

[0064] Comparative Example 1

[0065] 10g of wood pulp was placed in a reaction vessel and dispersed with deionized water to a concentration of 1.0wt%. 1g of TEMPO and 1g of sodium bromide were added sequentially, and after uniform dispersion, 100g of a 10wt% sodium hypochlorite solution was added dropwise. The pH of the system was controlled at 10±1 using 0.1mol / L NaOH solution. After the pH stabilized, ethanol was added to stop the reaction. The mixture was filtered and washed to obtain TEMPO-oxidized cellulose. The oxidized cellulose was dispersed in deionized water to prepare a 1% cellulose solution, which was homogenized eight times at 10000psi to obtain a nanocellulose solution NC3.

[0066] Test case

[0067] The carboxyl content of Comparative Example 1 and Example 1 was tested. 0.3 g of samples with different reaction times were taken and added to 55 ml of water and 5 ml of 0.01 M NaCl. The product of Comparative Example 1 was a slurry, while the product of Example 1 after 2 hours of reaction was prepared into a transparent solution. 0.1 M HCl was added to adjust the pH to 2.5-3.0. Using an automatic conductivity titrator, 0.04 M NaOH was titrated at a rate of 0.1 ml / min until pH = 11. The carboxyl content in the samples was calculated based on the amount of NaOH solution consumed. (See attached table). Figure 2 The results showed that the carboxylation rate of the sample modified with 4-substituted TEMPO was much higher than that of the sample modified with traditional TEMPO, which greatly improved the water solubility and injectability of the sample, making it possible to apply it in the field.

[0068] Comparative Example 2

[0069] Patent CN 103157515 A, "Catalyst and Method for Carboxylation of Bacterial Cellulose," provides a TEMPO / soluble chlorite / soluble hypochlorite catalytic system for carboxylation of bacterial cellulose, and uses this catalyst to carry out the carboxylation reaction of bacterial cellulose. Given that the carboxylation of oxidized bacterial cellulose is far less difficult than that of natural wood, cotton, and bamboo pulp cellulose in this invention, the degree of carboxylation after oxidation is only 1 to 2.4 times higher than that of the traditional TEMPO / NaBr / NaClO system. In contrast, the degree of carboxylation of this invention can be nearly 10 times higher than that of the traditional TEMPO / NaBr / NaClO system, demonstrating a significant difference in performance.

[0070] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. The use of a 4-substituted-tetraalkylpiperidine oxide as an oxidation catalyst, characterized in that, The 4-substituted-tetraalkylpiperidine oxide has the structure shown in formula (I): Equation (I); Where R1 is C1-C 10 Straight-chain or branched hydrocarbon group; R2 is a C1-C4 straight-chain or branched hydrocarbon group, and multiple R2s may be different from each other or the same; R3 is a C0-C4 straight-chain or branched hydrocarbon group, and when R3 is C0, the carbonyl carbon is connected to the benzene ring; X is a halogen or H, and multiple Xs may be different from each other or the same. The application is that 4-substituted-tetrahydropiperidine oxide is used for the oxidation of catalytic cellulose.

2. The use according to claim 1, characterized in that, R1 is C1-C 10 Straight-chain hydrocarbon group; R2 is a C1-C4 straight-chain hydrocarbon group; R3 is a C0-C4 straight-chain hydrocarbon group.

3. The use according to claim 1, characterized in that, R1 is C1-C 10 Straight-chain alkyl; R2 is a C1-C4 straight-chain alkyl; R3 is a C0-C4 straight-chain alkyl.

4. The use according to claim 1, characterized in that, R1 is a C1-C2 straight-chain alkyl group; R2 is a C1-C2 straight-chain alkyl group, and R2 are the same for all of them; R3 is a C0-C2 straight-chain alkyl group.

5. The use according to claim 1, characterized in that, The preparation method of 4-substituted-tetraalkylpiperidine oxide includes the following steps: The compound shown in Formula 1 and the compound shown in Formula 2 were reacted in the presence of a catalyst and a selectively added solvent to obtain a reaction mixture containing the 4-substituted-tetraalkylpiperidine oxide shown in Formula (I). ， Where R1 is C1-C 10 Straight-chain or branched hydrocarbon group; R2 is a C1-C4 straight-chain or branched hydrocarbon group, and multiple R2s may be different from each other or the same; R3 is a C0-C4 straight-chain or branched hydrocarbon group, and when R3 is C0, the carbonyl carbon is connected to the benzene ring; X is a halogen or H, and multiple Xs may be different from each other or the same. The catalyst is a dehydrating agent.

6. The use according to claim 5, characterized in that, The catalyst is a carbodiimide compound.

7. The use according to claim 5, characterized in that, The catalyst is N,N'-bicyclohexylcarbodiimide.

8. The use according to any one of claims 5 to 7, characterized in that, The molar ratio of the compound shown in Formula 1, the compound shown in Formula 2, and the catalyst is 1:(1-10):(1-10); and / or, The reaction conditions are as follows: under inert gas protection, the reaction temperature is 25-120℃, and the reaction time is 0.5-12h.

9. The use according to any one of claims 5 to 7, characterized in that, The preparation method further includes the step of separating the catalyst from the reaction mixture after the reaction is completed, and removing the solvent and impurities in an optional order to obtain the 4-substituted-tetraalkylpiperidine oxide shown in formula (I).

10. The use according to claim 1, characterized in that, The application is that 4-substituted-tetrahydropiperidine oxide is used for the oxidation catalysis of nanocellulose.

11. The use according to claim 10, characterized in that, The method for oxidative modification of nanocellulose includes step 1 of oxidizing the fiber slurry with an oxidizing catalyst, and step 2 of homogenizing it under high pressure; wherein the oxidizing catalyst is the 4-substituted-tetraalkylpiperidine oxide.

12. The use according to claim 11, characterized in that, Step 1 also includes the addition of sodium bromide and an oxidizing agent, wherein the oxidizing agent is one or both of sodium hypochlorite and sodium chlorite; and / or, The oxidation reaction temperature in step 1 is 25℃-100℃, and the pH value of the system is controlled at 10±1 during the reaction.

13. The use according to claim 12, characterized in that, In step 1, the weight ratio of fiber pulp: oxidation catalyst: sodium bromide: sodium hypochlorite is 1:(0.01-0.1):(0.01-0.1):(1-10).

14. The use according to claim 12, characterized in that, In step 1, the pH value of the system is controlled by an alkali, namely NaOH, during the reaction process; and / or, the oxidation reaction time is 1 to 24 hours.

15. The use according to claim 11, characterized in that, The high-pressure homogenization process is performed at a pressure of 1000-10000 psi; and / or, the high-pressure homogenization process is performed 5-15 times.

16. The use according to claim 11, characterized in that, The fiber pulp is any one of wood pulp, cotton pulp, hemp pulp, bamboo pulp, and reed pulp.

17. The use according to claim 11, characterized in that, The fiber pulp is wood pulp or cotton pulp.

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