Desulfurization and denitrification agent and application thereof

Abstract

A desulfurization and denitrification agent and application thereof are provided, belonging to the fields of flue gas purification and purified product recycling. In the present disclosure, an imidazoline amine oxide is used as a desulfurization and denitrification agent, which can oxidize NO.sub.x and SO.sub.x into HNO.sub.3 and H.sub.2SO.sub.4. Meanwhile, after the agent is reduced, double bonded tertiary nitrogen atoms in the agent can be used as a base for neutralizing H.sub.2SO.sub.4 and HNO.sub.3. In addition, in the present disclosure, the imidazoline amine oxide is used as the desulfurization and denitrification agent for two-stage desulfurization and denitrification of flue gas. Waste liquid produced after the reaction is injected as foaming acid liquid into carbonate and tight sandstone reservoirs, and slowly hydrolyzed into H.sub.2SO.sub.4, HNO.sub.3, and HF at the reservoir temperature, and the produced acid reacts with the reservoirs to augment production and injection of the reservoirs.

Claims

1. A desulfurization and denitrification agent, wherein the desulfurization and denitrification agent is an imidazoline amine oxide, the imidazoline amine oxide comprises two quaternary ammonium nitrogen atoms; and the imidazoline amine oxide further comprises a tetrafluoroborate.

2. The desulfurization and denitrification agent according to claim 1, wherein the imidazoline amine oxide is [MiO.sub.2][BF.sub.4].sub.2 or [MsO.sub.2][BF.sub.4].sub.2; the chemical formula of [MiO.sub.2][BF.sub.4].sub.2 is: ##STR00010## and the chemical formula of [MsO.sub.2][BF.sub.4].sub.2 is: ##STR00011##

3. A synthesis method of the desulfurization and denitrification agent according to claim 1, comprising the following steps: taking triethylenetetramine as a raw material, and dropwise adding oxalic acid or salicylic acid to react so as to obtain a gemini imidazoline intermediate; then dropwise adding 1-fluorooctane and boron trifluoride in sequence to react so as to obtain quaternized gemini imidazolinium; and finally adding hydrogen peroxide as an oxidizing agent to oxidize so as to obtain the desulfurization and denitrification agent.

4. An application of the desulfurization and denitrification agent according to claim 1, wherein the desulfurization and denitrification agent is applied to a desulfurization and denitrification of a flue gas and a recycling of a purified product, and the application comprises a flue gas desulfurization and denitrification process and a reservoir acidification process: (1) wherein the flue gas desulfurization and denitrification process comprises: spraying the desulfurization and denitrification agent into flue gas in a direction opposite to a flow direction of the flue gas at two stages to obtain waste liquid, and collecting the waste liquid produced by the desulfurization and denitrification of the flue gas in a case that a pH value of the waste liquid reaches 6 to 6.5; wherein the waste liquid produced at the first stage is named waste liquid 1, and the waste liquid produced at the second stage is named waste liquid 2; and (2) wherein the reservoir acidification process comprises: from far to near relative to an oil well, injecting a slug 1, a slug 2, a slug 3, and a slug 4 in sequence to augment production and injection, wherein the slug 1 is liquid nitrogen, the slug 2 is the waste liquid 2, the slug 3 is the waste liquid 1, and the slug 4 is liquid nitrogen.

5. An application of the desulfurization and denitrification agent according to claim 2, wherein the desulfurization and denitrification agent is applied to a desulfurization and denitrification of a flue gas and a recycling of a purified product, and the application comprises a flue gas desulfurization and denitrification process and a reservoir acidification process: (1) wherein the flue gas desulfurization and denitrification process comprises: spraying the desulfurization and denitrification agent into flue gas in a direction opposite to a flow direction of the flue gas at two stages to obtain waste liquid, and collecting the waste liquid produced by the desulfurization and denitrification of the flue gas in a case that a pH value of the waste liquid reaches 6 to 6.5; wherein the waste liquid produced at the first stage is named waste liquid 1, and the waste liquid produced at the second stage is named waste liquid 2; and (2) wherein the reservoir acidification process comprises: from far to near relative to an oil well, injecting a slug 1, a slug 2, a slug 3, and a slug 4 in sequence to augment production and injection, wherein the slug 1 is liquid nitrogen, the slug 2 is the waste liquid 2, the slug 3 is the waste liquid 1, and the slug 4 is liquid nitrogen.

6. The application according to claim 4, wherein the desulfurization and denitrification agent is an aqueous solution of [MiO.sub.2][BF.sub.4].sub.2 with a mass fraction of 0.010% to 0.025%, or an aqueous solution of [MsO.sub.2][BF.sub.4].sub.2 with a mass fraction of 0.010% to 0.025%.

7. The application according to claim 4, wherein in the slug 1, an injection amount of liquid nitrogen is 0.1 to 0.3 m.sup.3 per meter of oil layer; in the slug 2, an injection amount of the waste liquid 2 is 10 to 50 m.sup.3 per meter of oil layer; in the slug 3, an injection amount of the waste liquid 1 is 20 to 100 m.sup.3 per meter of oil layer; and in the slug 4, an injection amount of liquid nitrogen is 1 to 1.5 m.sup.3 per meter of oil layer.

8. The application according to claim 4, wherein the waste liquid 1 comprises a mixture of a nitrate and a tetrafluoroborate of [H.sub.2Mi].sup.4+ with a mass fraction of 0.010% to 0.025%, or a mixture of a nitrate and a tetrafluoroborate of [H.sub.2Ms].sup.4+ with a mass fraction of 0.010% to 0.025%; and the waste liquid 2 comprises a mixture of a nitrate, a sulphate, and a tetrafluoroborate of [H.sub.2Mi].sup.4+ with a mass fraction of 0.010% to 0.025%, or a mixture of a nitrate, a sulphate, and a tetrafluoroborate of [H.sub.2Ms].sup.4+ with a mass fraction of 0.010% to 0.025%.

9. The application according to claim 4, wherein an injection rate of each slug is 100 to 250 L/min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flowchart of desulfurization and denitrification;

(2) FIG. 2 is a schematic diagram of slugs for augmenting production and injection; and

(3) FIG. 3 is a diagram of changes in injection pressure and injection amount of a C-2 water injection well of Application 2 from 2019 to 2023.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) The present disclosure will be further described below with reference to specific embodiments, but is not limited to the following embodiments.

(5) It is to be noted that experimental methods in the following embodiments are conventional methods unless otherwise specified; and reagents, materials, and equipment are commercially available unless otherwise specified.

(6) A preparation of [MiO.sub.2][BF.sub.4].sub.2 includes the following steps: triethylenetetramine is added to a reactor and heated to 110 C., oxalic acid is dropwise added in a molar ratio of triethylenetetramine to oxalic acid of 1:1.2 within 0.5 h, and the reaction solution is heated to 150 C. for continuous reaction until no water is generated, and heated to 260 C. for continuous reaction for 8 h. After the reaction, the reaction solution is distilled under reduced pressure at 100 C. for 5 h to remove by-products so as to obtain a gemini imidazoline intermediate. The gemini imidazoline intermediate is placed in a three-neck flask, isopropanol is used as a solvent, and the solution is heated in a thermostatic water bath at 90 C.; 1-fluorooctane is dropwise added within 0.5 h while the solution is stirred; boron trifluoride is dropwise added within 0.5 h; a molar ratio of the gemini imidazoline intermediate to 1-fluorooctane to boron trifluoride is 1:1.1:1.05; the reaction solution reacts for 1 h after boron trifluoride is dropwise added, and a 5 wt % NaOH solution is dropwise added to regulate a pH value of the solution to 9; and the reaction solution is stirred for reaction for 4 h, and distilled under reduced pressure to obtain [Mi][BF.sub.4].sub.2. [Mi][BF.sub.4].sub.2 is uniformly mixed with a 20 wt % H.sub.2O.sub.2 solution, and the reaction solution reacts for 1 h to obtain [MiO.sub.2][BF.sub.4].sub.2. A molar ratio of [Mi][BF.sub.4].sub.2 to H.sub.2O.sub.2 is 1:3.

(7) A synthesis method of [MsO.sub.2][BF.sub.4].sub.2 includes the following steps: triethylenetetramine is added to a reactor and heated to 115 C., salicylic acid is dropwise added in a molar ratio of triethylenetetramine to salicylic acid of 1:0.6 within 0.5 h, and the reaction solution is heated to 150 C. for continuous reaction until no water is generated, and heated to 255 C. for continuous reaction for 8 h. After the reaction, the reaction solution is distilled under reduced pressure at 100 C. for 5 h to remove by-products so as to obtain a gemini imidazoline intermediate. The gemini imidazoline intermediate is placed in a three-neck flask, isopropanol is used as a solvent, and the solution is heated in a thermostatic water bath at 90 C.: 1-fluorooctane is dropwise added within 0.5 h while the solution is stirred; boron trifluoride is dropwise added within 0.5 h: a molar ratio of the gemini imidazoline intermediate to 1-fluorooctane to boron trifluoride is 1:1.1:1.05; the reaction solution reacts for 1 h after boron trifluoride is dropwise added, and a 5 wt % NaOH solution is dropwise added to regulate a pH value of the solution to 10; and the reaction solution is stirred for reaction for 4 h, and distilled under reduced pressure to obtain quaternized gemini imidazolinium.

(8) LiOH is added to quaternized gemini imidazolinium in a molar ratio of quaternized gemini imidazolinium to LiOH of 1:3, and the solution is stirred in 60 mL of tetrahydrofuran and 10 ml of water, and heated to 70 C. for reflux for 1 h. Triglycol dichloride is added in a molar ratio of quaternized gemini imidazolinium to triglycol dichloride of 1:1, and the reaction solution reacts for 72 h. After the reaction, tetrahydrofuran is removed by rotary evaporation, residues are washed with water and extracted with chloroform, tetrahydrofuran is removed by rotary evaporation, and the residues are crystallized with heptane to obtain [Ms][BF.sub.4].sub.2. [Ms][BF.sub.4].sub.2 is uniformly mixed with a 20 wt % H.sub.2O.sub.2 solution, and the reaction solution reacts for 1 h to obtain [MsO.sub.2][BF.sub.4].sub.2. A molar ratio of [Mi][BF.sub.4].sub.2 to H.sub.2O.sub.2 is 1:3.

Example 1

(9) Application of a desulfurization and denitrification agent to desulfurization and denitrification of flue gas and recycling of a purified product included the following steps: (1) A flue gas desulfurization and denitrification process: desulfurization and denitrification was performed at two stages. At each stage, an aqueous solution of 0.020 wt % [MiO.sub.2][BF.sub.4].sub.2 was sprayed into flue gas in a direction opposite to a flow direction of the flue gas, an air heat exchange pipe was arranged at each stage, and air flowed through the second stage and first stage air heat exchange pipes in sequence, and finally entered a furnace. After a pH value of the system reached 6.5, waste liquid produced by desulfurization and denitrification was collected. The waste liquid produced at the first stage was named waste liquid 1, and the waste liquid produced at the second stage was named waste liquid 2. The waste liquid was acid liquid. (2) A reservoir acidification process: before acidification, liquid nitrogen was injected into a target layer as a slug 1 according to an injection amount of 0.2 m.sup.3 per meter of oil layer. The waste liquid 2 was injected as a front slug 2 according to an injection amount of 15 m.sup.3 per meter of oil layer. The waste liquid 1 was injected as a slug 3 according to an injection amount of 80 m.sup.3 per meter of oil layer. Finally, liquid nitrogen was injected as a slug 4 according to an injection amount of 1.2 m.sup.3 per meter of oil layer. An injection rate of each slug was 200 L/min. The waste liquid 1 mainly contained a mixture of a nitrate and a tetrafluoroborate of [H.sub.2Mi].sup.4+ or [H.sub.2Ms].sup.4+ with a mass fraction of 0.020%, and the waste liquid 2 contained a mixture of a nitrate, a sulfate, and a tetrafluoroborate of [H.sub.2Mi].sup.4+ or [H.sub.2Ms].sup.4+ with a mass fraction of 0.020%.

(10) The dissolution rate and corrosion rate of debris in the acid liquid were detected according to Formation Damage Evaluation by Flow Test (SY/T 5358-2002). Steps for detecting the dissolution rate and corrosion rate of debris in different acid systems were as follows:

(11) 5 g of debris was placed in a test tube containing 500 mL of acid liquid, the test tube was placed in a water bath at 90 C., the debris thoroughly reacted with the acid liquid for 120 min, and filtered, and the dissolution rate of debris was calculated. According to the coupon weight loss method, a coupon was subjected to rust removal and oil removal, dried, weighed, immersed in the acid liquid, taken out after 120 min, washed for removing remaining acid liquid, dried, and weighed, and the corrosion rate was calculated. Results are shown in Table 1.

Example 2

(12) Application of a desulfurization and denitrification agent to desulfurization and denitrification of flue gas and recycling of a purified product included the following steps: (1) A flue gas desulfurization and denitrification process: desulfurization and denitrification was performed at two stages. At each stage, a 0.020 wt % [MsO.sub.2][BF.sub.4].sub.2 solution was sprayed into flue gas in a direction opposite to a flow direction of the flue gas, an air heat exchange pipe was arranged at each stage, and air flowed through the second stage and first stage air heat exchange pipes in sequence, and finally entered a furnace. After a pH value of the system reached 6.5, waste liquid produced by desulfurization and denitrification was collected. The waste liquid produced at the first stage was named waste liquid 1, and the waste liquid produced at the second stage was named waste liquid 2. The waste liquid was acid liquid. (2) A reservoir acidification process: before acidification, liquid nitrogen was injected into a target layer as a slug 1 according to an injection amount of 0.2 m.sup.3 per meter of oil layer. The waste liquid 2 was injected as a front slug 2 according to an injection amount of 15 m.sup.3 per meter of oil layer. The waste liquid 1 was injected as a slug 3 according to an injection amount of 80 m.sup.3 per meter of oil layer. Finally, liquid nitrogen was injected as a slug 4 according to an injection amount of 1.2 m.sup.3 per meter of oil layer. An injection rate of each slug was 200 L/min. The dissolution rate and corrosion rate of debris in the acid liquid were detected by the method in Example 1. Results are shown in Table 1.
Contrast 1 (1) A flue gas desulfurization and denitrification process: 0.015% THEED was added to a 15% H.sub.2O.sub.2 solution to prepare a mixed solution, a volume ratio of THEED to H.sub.2O.sub.2 was 75:1, the mixed solution was sprayed into flue gas in a direction opposite to a flow direction of the flue gas, and after a pH value of the system reached 6.5, waste liquid produced by desulfurization and denitrification was collected. The waste liquid was acid liquid. (2) The obtained acid liquid was directly injected into the formation to augment production and injection. The acid liquid contained approximately 0.015% [H.sub.2THEED].sup.2+. The dissolution rate and corrosion rate of debris in the acid liquid were detected by the method in Example 1. Results are shown in Table 1.
Contrast 2 (1) A flue gas desulfurization and denitrification process: 0.015% bipy was added to a 15% H.sub.2O.sub.2 solution to prepare a mixed solution, a volume ratio of bipy to H.sub.2O.sub.2 was 400:3, the mixed solution was sprayed into flue gas in a direction opposite to a flow direction of the flue gas, and after a pH value of the system reached 6.5, waste liquid produced by desulfurization and denitrification was collected. The waste liquid was acid liquid. (2) The obtained acid liquid was directly injected into the formation to augment production and injection. The acid liquid contained approximately 0.015% [H.sub.2bipy].sup.2+. The dissolution rate and corrosion rate of debris in the acid liquid were detected by the method in Example 1. Results are shown in Table 1.
Contrast 3 (1) A flue gas desulfurization and denitrification process: desulfurization and denitrification was performed at two stages. At each stage, 0.015% THEED was added to a 15% H.sub.2O.sub.2 solution to prepare a mixed solution, a volume ratio of THEED to H.sub.2O.sub.2 was 75:1, the mixed solution was sprayed into flue gas in a direction opposite to a flow direction of the flue gas, an air heat exchange pipe was arranged at each stage, and air flowed through the second stage and first stage air heat exchange pipes in sequence, and finally entered a furnace. After a pH value of the system reached 6.5, waste liquid produced by desulfurization and denitrification was collected. The waste liquid produced at the first stage was named waste liquid 1, and the waste liquid produced at the second stage was named waste liquid 2. The waste liquid was acid liquid. (2) A reservoir acidification process: before acidification, liquid nitrogen was injected into a target layer as a slug 1 according to an injection amount of 0.2 m.sup.3 per meter of oil layer. The waste liquid 2 was injected as a front slug 2 according to an injection amount of 15 m.sup.3 per meter of oil layer. The waste liquid 1 was injected as a slug 3 according to an injection amount of 80 m.sup.3 per meter of oil layer. Finally, liquid nitrogen was injected as a slug 4 according to an injection amount of 1.2 m.sup.3 per meter of oil layer. An injection rate of each slug was 200 L/min. The dissolution rate and corrosion rate of debris in the acid liquid were detected by the method in Example 1. Results are shown in Table 1.

(13) It can be seen from Contrast 1 and Contrast 2 that in Example 1, the desulfurization and denitrification agent in the patent CN113137215A is replaced with [MiO.sub.2][BF.sub.4].sub.2, the dissolution rate is increased by 0.616 times compared with Contrast 1 and nearly 1.176 times compared with Contrast 2; and the corrosion rate is 91% of that of Contrast 1 and 98% of that of Contrast 2. In Example 2, the desulfurization and denitrification agent in the patent CN113137215A is replaced with [MsO.sub.2][BF.sub.4].sub.2, the dissolution rate is increased by 0.864 times compared with Contrast 1 and nearly 1.511 times compared with Contrast 2; and the corrosion rate is 86% of that of Contrast 1 and 93% of that of Contrast 2.

(14) In addition, it can be seen from Contrast 3 that THEED does contain a tetrafluoroborate, and may not be hydrolyzed into HF that may dissolve sandstone when heated. Although liquid nitrogen is used to cool a wellbore and an immediate vicinity of wellbore, the hydrolysis inhibition effect is not significant. THEED is less likely to form stable coordination compounds with Ca.sup.2+, Mg.sup.2+, Fe.sup.3+, Al.sup.3+, and the like, and thus, the corrosion inhibition and speed reduction effect is not as significant as that of [H.sub.2Ms].sup.4+ or [H.sub.2Mi].sup.4+. Moreover, [H.sub.2Ms].sup.4+ or [H.sub.2Mi].sup.4+ contains a hydrophobic functional group that can produce foam when exposed to liquid nitrogen to achieve the effect of diversion, and thus has a more significant corrosion inhibition and speed reduction effect. However, THEED, as a desulfurization and denitrification agent, produces [H.sub.2THEED].sup.2+ that does not contain an aliphatic chain, does not produce foam when exposed to liquid nitrogen, and cannot block a large pore throat through the Jamin effect, and the acidified formation has high heterogeneity. The dissolution rate of Contrast 3 is 70% of that of Example 1 and 60% of that of Example 2; and the corrosion rate is increased by 0.034 times compared with Example 1 and 0.091 times compared with Example 2. The dissolution rate of Contrast 3 is increased by 0.127 times compared with Contrast 1, and the corrosion rate is 94% of that of Contrast 1, which indicates that liquid nitrogen is used to cool the wellbore to prevent the desulfurization and denitrification product from being hydrolyzed into sulfuric acid and nitric acid, thereby achieving the effect of corrosion inhibition and speed reduction.

(15) The acid liquid of the present disclosure can be used to dissolve a large amount of sandstone, and has better production and injection augmentation and corrosion inhibition performance than that of the desulfurization and denitrification agent of the patent CN113137215A. In addition, [H.sub.2Ms].sup.4+ is used to acidify a reservoir. [H.sub.2Ms].sup.4+ contains a phenoxy group that easily coordinates with Fe.sup.3+ and Al.sup.3+ than [H.sub.2Mi].sup.4+, and thus [H.sub.2Ms].sup.4+ can be adsorbed onto a pipe surface to better dissolve aluminosilicate minerals, and exhibits better production and injection augmentation and corrosion inhibition performance.

(16) TABLE-US-00001 TABLE 1 Dissolution rate and corrosion rate of debris in different acid systems Desulfurization and Dissolution Corrosion denitrification agent rate/% rate/% Contrast 1 40.50 0.64 Contrast 2 30.07 0.59 Contrast 3 45.66 0.60 Example 1 65.44 0.58 Example 2 75.50 0.55
Application 1

(17) In 2022, an aqueous solution of 0.020 wt % [MiO.sub.2][BF.sub.4].sub.2 was successfully applied to desulfurization and denitrification of flue gas of P thermal power plant in T oil field. The plant adopted the desulfurization and denitrification agent of Contrast 2 before. During application, the aqueous solution of 0.020 wt % [MiO.sub.2][BF.sub.4].sub.2 was sprayed into flue gas, concentrations of NO.sub.x and SO.sub.x in the flue gas were detected by gas chromatography before and after the flue gas flows through a curing agent, and the desulfurization and denitrification rate was calculated, as shown in Table 2. Mass fractions of a sulfate and a nitrate in waste liquid produced by desulfurization and denitrification were measured by liquid chromatography. It can be seen that the desulfurization and denitrification efficiency of [MiO.sub.2][BF.sub.4].sub.2 is higher than that of bipy. Moreover, water eutrophication is treated. At the first stage, the desulfurization and denitrification agent reacts with SO.sub.x first, and the desulfurization efficiency is higher that of the second stage. Flue gas entering the second stage mainly contains NO, and thus, the denitrification efficiency of the second stage is higher than that of the first stage.

(18) TABLE-US-00002 TABLE 2 Desulfurization and denitrification efficiency of curing agents prepared from H.sub.2O.sub.2 and bipy in different volume ratios Desulfurization and Desulfurization Denitrification denitrification agent efficiency/% efficiency/% Bipy + H.sub.2O.sub.2 97.50 96.04 [MiO.sub.2][BF.sub.4].sub.2 First 98.03 90.34 stage Second 94.56 99.48 stage
Application 2

(19) In February 2019, the solution of Contrast 1 was used to acidify and augment injection of a C-2 water injection well of S oil field, the acid injection rate was 5 m.sup.3/h, and after acidification, the injection pressure was 18 MPa, and a daily injection amount was 124 m.sup.3/d. In June 2022, the injection pressure before acidification was 18 MPa, and a daily injection amount was 124 m.sup.3/d. The waste liquid produced by desulfurization and denitrification in Example 2 was used for acidification and injection augmentation, an acid injection rate was 200 L/min, and after acidification, the injection pressure was 15 MPa, and a daily injection amount was 224 m.sup.3/d, as shown in FIG. 3. The acidification and injection augmentation effect is available until now.