Electro-Fenton modified lignin, preparation method thereof and biomass synthetic resin fluid loss reducer

Abstract

The present invention belongs to the field of oil drilling fluid additives. The present invention provides an electro-Fenton modified lignin, a preparation method thereof, and a biomass synthetic resin fluid loss reducer. The preparation method of the electro-Fenton modified lignin comprises: S1, electrolyzing an electrolyte containing ferrous ions and lignin under oxygen flow conditions; the electrolysis system comprises a platinum sheet, an Hg / HgO electrode, and a gas diffusion electrode, and oxygen is passed through the gas diffusion electrode; S2, after electrolysis for a certain period of time, adjusting the electrolyte to acidic, and performing solid-liquid separation to obtain the electro-Fenton modified lignin. The modified lignin of the present invention is used to prepare a biomass synthetic resin fluid loss reducer, significantly reducing the amount of phenol used and improving biodegradability. The biomass synthetic resin fluid loss reducer has excellent performance, is temperature-resistant to 220°C, and is applicable to various water-based drilling fluids, especially high-temperature and high-density drilling fluids. The biomass synthetic resin fluid loss reducer of the present invention is simple to synthesize, requires mild conditions, and is easy to industrialize.

Description

Technical Field

[0001] The invention belongs to the technical field of oil drilling fluid additives, and in particular relates to an electro-Fenton modified lignin, a preparation method thereof and a biomass synthetic resin fluid loss reducer. Background Art

[0002] Drilling fluid, also known as drilling flushing fluid, is a water-based drilling fluid typically consisting of a colloidal suspension mixture with water as the dispersion medium and clay (bentonite), weighting agents, and various chemical treatment agents as the dispersed phase. As oil exploration and development continues to advance into deeper formations, drilling fluid systems are evolving toward high temperatures, high densities, and salt tolerance. Coupled with higher environmental protection goals, this requires core treatment agents to possess characteristics such as high-temperature resistance, resistance to saturated salts, and environmental friendliness.

[0003] Fluid loss additives (Fluid Loss Control) are chemical agents that reduce fluid loss in drilling fluids. These agents are typically water-soluble polymers. Compared to humic acid and its derivatives, resin-based Fluid Loss Controls offer superior salt tolerance, but their environmental performance and other aspects need improvement.

[0004] Lignin is one of the main supporting structures of plants, regenerating at a rate of 50 billion tons annually and accounting for approximately 30% of global organic carbon, making it a significant renewable resource. As a high-molecular compound, lignin contains highly reactive functional groups, including methoxyl groups, phenolic hydroxyl groups, and carboxyl groups, but its application efficiency is insufficient. Chinese patent application publication number CN 112210574 A discloses an enzymatic lignin hydrolysis method. The method involves mixing a lignin raw material, water, and Myrocera verrucosa and Myrocera scabra for a primary enzymatic hydrolysis to obtain an enzymatic hydrolysis product. This enzymatic hydrolysis product is then mixed with Phanerochaete chrysosporium for a secondary enzymatic hydrolysis to obtain the product, which is then used to prepare a lignin-phenolic resin fluid loss reducer. The fluid loss reducer described in this document is temperature-resistant up to 180°C, making it unsuitable for use in drilling fluid systems at higher temperatures. Summary of the Invention

[0005] In light of this, the present invention aims to provide an electro-Fenton-modified lignin, a preparation method thereof, and a biomass synthetic resin fluid loss additive for drilling fluids. The modified lignin provided by the present invention has high reactivity, and the biomass synthetic resin fluid loss additive prepared using it exhibits excellent temperature resistance, low fluid loss under high-temperature and high-pressure conditions, and is biodegradable. It is suitable for various water-based drilling fluid systems, particularly high-temperature, high-density drilling fluid systems.

[0006] The present invention provides a method for preparing electro-Fenton modified lignin, comprising the following steps:

[0007] S1, electrolyzing an electrolyte containing ferrous ions and lignin under oxygen flow conditions; the electrolysis system includes a platinum sheet, a Hg / HgO electrode and a gas diffusion electrode, and oxygen is passed through the gas diffusion electrode;

[0008] S2. After electrolysis for a certain period of time, the electrolyte is adjusted to be acidic, and solid-liquid separation is performed to obtain electro-Fenton modified lignin.

[0009] In some embodiments of the present invention, the specific operations of the preparation method may include:

[0010] (1) Platinum sheet, Hg / HgO electrode and gas diffusion electrode are placed in a beaker, and an electrolyte containing ferrous ions and lignin is added to the beaker;

[0011] (2) placing the beaker in a water bath and magnetically stirring the electrolyte at a constant temperature; introducing oxygen into the gas diffusion electrode; then connecting the external circuit of the platinum sheet, Hg / HgO electrode, and gas diffusion electrode to an electrochemical workstation, controlling the current density to be constant, and performing electrolysis;

[0012] (3) The electrolysis device is powered off and the gas supply is stopped; thereafter, the electrolyte is adjusted to be acidic, filtered, washed, dried and crushed to obtain an electro-Fenton modified lignin product.

[0013] Preferably, the gas diffusion electrode in step S1 comprises a gas chamber, a diffusion layer, a support layer, and a catalyst layer; the catalyst in the catalyst layer is carbon nanotubes. Further preferably, the catalyst is prepared by dispersing, by weight, 1 part of carbon nanotubes in 240 parts of a 2.5 mol / L nitric acid solution, ultrasonically dispersing for 1 hour, filtering, washing until neutral, drying, and then pulverizing the resultant.

[0014] Specifically, the area of the platinum sheet can be 12 cm 2 The Hg / HgO electrode is a commercially available reference electrode. The gas diffusion electrode consists of a gas chamber, a diffusion layer, a support layer, and a catalytic layer. The gas chamber volume can be 40 cm 3 , connected to the oxygen cylinder through a hose, stores and provides oxygen to the diffusion layer; the diffusion layer is preferably mixed with 0.25g carbon black and 1g binder PTFE emulsion, evenly coated on one side of the support layer, and connected to the air chamber; the support layer can be 20cm 2 catalytic layer is preferably mixed with 0.25g catalyst and 1g PTFE emulsion, and evenly coated with the other side of the support layer.

[0015] Preferably, the electrolyte in step S1 is a sodium sulfate solution containing ferrous chloride and lignin, with a pH of 12-14, wherein the concentration of ferrous chloride is 1-3 mmol / L, and the concentration of lignin is 2-4 wt.%. In addition, the concentration of sodium sulfate may be 0.1 mol / L; and the lignin is extracted from corn cobs and straw.

[0016] Preferably, in step S1, the electrolysis temperature is controlled at 20-60°C by water bath, the oxygen flow rate is 0.5-0.7 L / min, and the current density is controlled at 8-14 mA / cm 2 The electrolysis time is 30 to 120 minutes. The electrochemical workstation is an electrochemical measurement system used in the present invention to provide a constant current.

[0017] Preferably, in step S2, the pH of the electrolyte is adjusted to 3-5.

[0018] The present invention provides an electro-Fenton modified lignin, which is prepared by the above-mentioned method and has a phenolic hydroxyl content of preferably above 2.5 mmol / g.

[0019] The invention provides a biomass synthetic resin fluid loss reducer, which is prepared by sulfonation and polycondensation reaction of electro-Fenton modified lignin, phenol, formaldehyde and a sulfonating agent.

[0020] Preferably, in the preparation process of the biomass synthetic resin fluid loss reducer, the mass ratio of the electro-Fenton modified lignin, phenol, formaldehyde and sulfonating agent is (25-35): (15-25): (50-60): (30-40); the sulfonating agent is one or both of sodium metabisulfite and anhydrous sodium sulfite.

[0021] Preferably, the preparation process of the biomass synthetic resin fluid loss reducer is to mix the electro-Fenton modified lignin, phenol, and formaldehyde, stir for 5 to 10 minutes; add a sulfonating agent, heat to 65 to 75°C, and react for 20 to 30 minutes; then raise the temperature to 100 to 105°C, add water every 15 to 25 minutes, add water 5 to 7 times in total, continue to react for 0.5 to 1 hour, cool, discharge, and spray dry to obtain the product. Furthermore, the mass ratio of the electro-Fenton modified lignin, phenol, formaldehyde, sulfonating agent, and single water addition is (25 to 35): (15 to 25): (50 to 60): (30 to 40): (20 to 25).

[0022] The present invention provides a drilling fluid, which comprises the biomass synthetic resin fluid loss reducer described above.

[0023] Electro-Fenton is an electrochemical advanced oxidation technology that can control and generate in situ the highly oxidizing hydroxyl radical (·OH), and has the advantages of environmental safety, versatility, and automation.

[0024] Compared to existing technologies, the present invention provides an electro-Fenton-modified lignin and its preparation method. Lignin, an abundant biomass resource in nature, has a benzene ring structure and stable chemical properties, but its effective utilization rate has been low. This invention uses electro-Fenton technology to generate highly oxidizing ·OH, which degrades lignin macromolecules. This helps reduce lignin molecular weight, releases or generates more active groups, and particularly increases the phenolic hydroxyl content, resulting in excellent performance in synthetic drilling fluid fluid loss reducers.

[0025] The electro-Fenton modified lignin provided by the present invention is used to prepare a biomass synthetic resin fluid loss reducer. Compared with traditional sulfonated phenolic resins, the amount of phenol used is greatly reduced, and biodegradability is improved. The biomass synthetic resin fluid loss reducer provided by the present invention has excellent performance, temperature resistance of 220°C, salt resistance of 30% (saturated) in the base slurry, apparent viscosity of 22mPa·s, 220°C / 16h, high temperature and high pressure water loss of <25mL, and can be applied to various water-based drilling fluids, especially high temperature and high density drilling fluids. The synthesis process of the biomass synthetic resin fluid loss reducer provided by the present invention is simple, the conditions are mild, and it is easy to realize industrialization. DETAILED DESCRIPTION

[0026] The present invention provides an electro-Fenton modified lignin, a preparation method thereof, a biomass synthetic resin fluid loss reducer, and an application thereof. Those skilled in the art can refer to the contents of this article and appropriately improve the process parameters to achieve the desired results. It should be noted in particular that all similar substitutions and modifications are obvious to those skilled in the art and fall within the scope of protection of the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications herein without departing from the content, spirit, and scope of the present invention to implement and apply the technology of the present invention.

[0027] The present invention provides a preparation method of electro-Fenton modified lignin, comprising the following steps: S1, electrolyzing an electrolyte containing ferrous ions and lignin under oxygen flow conditions; the electrolysis system comprises a platinum sheet, a Hg / HgO electrode and a gas diffusion electrode, and oxygen is flowed through the gas diffusion electrode; S2, after electrolysis for a certain period of time, adjusting the electrolyte to be acidic, and performing solid-liquid separation to obtain the electro-Fenton modified lignin.

[0028] The specific operations for preparing the modified lignin in the embodiment of the present invention include:

[0029] (1) Place a platinum sheet, Hg / HgO electrode, and gas diffusion electrode in a beaker, and add electrolyte to the beaker;

[0030] (2) placing the beaker in a water bath and magnetically stirring the electrolyte at a constant temperature; introducing oxygen into the gas diffusion electrode; then connecting the external circuit of the platinum sheet, Hg / HgO electrode, and gas diffusion electrode to an electrochemical workstation, controlling the current density to be constant, and performing electrolysis;

[0031] (3) The electrolysis device is powered off and the gas supply is stopped; thereafter, the electrolyte is adjusted to be acidic, filtered, washed, dried and crushed to obtain electro-Fenton modified lignin.

[0032] In this embodiment of the present invention, the selected lignin is primarily derived from corn cobs and straw and is composed of phenylpropane units connected by ether and carbon-carbon bonds, with β-O-4 bonds being the predominant linker, accounting for approximately 50% of the total structure. For example, the lignin may have a phenolic hydroxyl content of 0.7 to 0.8 mmol / g and a carboxyl content of 0.9 to 1.1 mmol / g.

[0033] Electro-Fenton is an advanced oxidation technology that produces H2O2 by an indirect two-electron pathway of cathode oxygen reduction. 2+ , can quickly decompose hydrogen peroxide H2O2 to produce OH, Fe 2+ It can be reduced and regenerated on the cathode surface. The OH oxidation potential is 2.80V, indicating strong oxidizing properties and indiscriminate degradation of organic matter. Cathode oxygen reduction primarily breaks ether bonds. By controlling appropriate electrolysis temperature, electrolysis time, and current density, the present invention effectively controls the depolymerization yield and products of lignin.

[0034] Oxygen has low solubility in solution and a slow mass transfer diffusion rate. The concentration of oxygen reaching the cathode surface and participating in oxygen reduction is low, which directly leads to high oxygen consumption and low H2O2 production. In the present invention, a special three-phase porous electrode - a gas diffusion electrode is used as the cathode, which is mainly a pathway for oxygen transmission. On the one hand, it contains abundant pores, which allow oxygen to easily diffuse to various places inside the electrode; on the other hand, the surface of the catalyst layer is covered with a liquid film, which can directly flow freely with the electrolyte, providing favorable conditions for gas-liquid-solid coexistence for the oxygen reduction reaction. The addition of PTFE emulsion in the catalyst layer makes the catalyst surface hydrophobic, and the electrolyte cannot wet the catalyst layer, so a liquid film is formed between the solid and liquid phases.

[0035] In the embodiment of the present invention, the gas diffusion electrode is composed of a gas chamber, a diffusion layer, a support layer and a catalyst layer, wherein the volume of the gas chamber can be 40 cm 3, connected to the oxygen cylinder through a hose to provide the oxygen required for the oxygen reduction reaction; preferably, the diffusion layer is coated on one side of the support layer by mixing 0.25g of carbon black and 1g of binder polytetrafluoroethylene (PTFE) emulsion to provide an oxygen delivery channel; the catalytic layer is coated on the other side of the support layer by mixing 0.25g of catalyst and 1g of PTFE emulsion to catalyze the oxygen reduction reaction.

[0036] In an embodiment of the present invention, the catalyst in the catalytic layer is carbon nanotubes. A specific method for preparing the catalyst is as follows: by weight, 1 part of carbon nanotubes is dispersed in 240 parts of a 2.5 mol / L nitric acid solution, ultrasonicated for 1 hour, filtered, washed until neutral, dried, and then crushed to obtain the catalyst.

[0037] In addition, the platinum sheet area can be 12cm 2 ; Hg / HgO electrode is a commercially available reference electrode (commonly used reference electrode in alkaline solutions).

[0038] In the embodiment of the present invention, the ferrous chloride in the electrolyte provides the ferrous ions Fe required for the reaction. 2+ , due to Fe 2+ It can be recycled and regenerated at the cathode, and its concentration does not need to be too high, preferably 1-3 mmol / L, more preferably 2 mmol / L; to facilitate the dissolution of lignin, the pH of the electrolyte sodium sulfate solution is 12-14, the concentration is 0.1 mol / L, and the concentration of lignin is 2-4 wt.%.

[0039] In the embodiment of the present invention, during electrolysis, the temperature of the oxygen reduction reaction, the rate of oxygen introduction, the current density and the electrolysis time all affect the yield of H2O2. Preferably, the water bath temperature is 20-60°C, more preferably 20-40°C; the oxygen introduction rate is 0.5-0.7 L / min; the current density is controlled to be 8-14 mA / cm 2 , more preferably 12 to 14 mA / cm 2 ; The electrolysis time may be 30 to 120 min, more preferably 100 to 120 min.

[0040] In an embodiment of the present invention, after the electrolysis is completed, the pH of the electrolyte is adjusted to 3-5, and a solid is precipitated, which is then filtered, washed, dried, and crushed to obtain electro-Fenton modified lignin.

[0041] The present invention provides an electro-Fenton modified lignin obtained by the preparation method described above. The lignin of the embodiment of the present invention is electro-Fenton modified, and its phenolic hydroxyl content is above 2.5mmol / g. In the molecular structure of the electro-Fenton modified lignin, the carboxyl content can be 2.7123~3.6201mmol / g. -1 .

[0042] The molecular weight of the electro-Fenton modified lignin described in the embodiment of the present invention was tested by gel chromatography, and the result was 940-1575 g / mol; the phenolic hydroxyl and carboxyl content of the lignin was determined by aqueous phase potentiometric titration, and the phenolic hydroxyl content was specifically 2.5512-3.3723 mmol / g. -1 , carboxyl content is 2.7123~3.6201mmol / g -1 .

[0043] The present invention provides a biomass synthetic resin fluid loss reducer and a preparation method thereof, comprising:

[0044] The electro-Fenton modified lignin obtained by the preparation method described above, phenol, formaldehyde and a sulfonating agent are reacted to obtain a biomass synthetic resin fluid loss reducer.

[0045] The above reaction of the embodiment of the present invention is carried out in water, and water can be added to the system 5 to 7 times; the mass ratio of the electro-Fenton modified lignin, phenol, formaldehyde, sulfonating agent and single water addition is (25 to 35): (15 to 25): (50 to 60): (30 to 40): (20 to 25), more preferably (28 to 32): (18 to 22): (55 to 58): (34 to 36): (22 to 23). Wherein, the sulfonating agent is preferably one or both of sodium metabisulfite and anhydrous sodium sulfite.

[0046] In an embodiment of the present invention, the electro-Fenton modified lignin, phenol, and formaldehyde are mixed, preferably with a stirring time of 5 to 10 minutes, more preferably 6 to 8 minutes, to make them uniformly mixed. The first stage is a sulfonation reaction, in which a sulfonating agent is added, preferably at a reaction temperature of 65 to 75°C, more preferably 68 to 72°C; preferably, a reaction time of 20 to 30 minutes, more preferably 25 to 27 minutes. The second stage is a polycondensation reaction, after which the sulfonation reaction is completed, the reaction temperature is raised to 100 to 105°C, more preferably 102 to 103°C, water is added every 15 to 25 minutes, a total of 5 to 7 times, the reaction is continued for 0.5 to 1 hour, cooled, discharged, and spray-dried to obtain the biomass synthetic resin fluid loss reducer.

[0047] The present invention provides a biomass synthetic resin fluid loss additive, produced by the preparation method described above. In this invention, the electro-Fenton-modified lignin retains the rigid skeleton of benzene rings, and the modified lignin releases or forms a large number of reactive functional groups, such as phenolic hydroxyl groups and carboxyl groups. Using electro-Fenton-modified lignin to partially replace phenol in the synthesis of a biomass synthetic resin fluid loss additive improves the product's temperature resistance and fluid loss reduction performance while also enhancing its environmental friendliness.

[0048] In the embodiments of the present invention, the sulfonation reaction and the polycondensation reaction are a pair of competing reactions. In the first stage, the preferred reaction temperature is 65-75°C, where the sulfonation reaction primarily occurs, improving the product's heat resistance. In the second stage, the preferred reaction temperature is 100-105°C, where the polycondensation reaction primarily occurs. To avoid product solidification due to excessively high molecular weight, the present invention employs the practice of adding water in small amounts and multiple times. Resins with appropriate molecular weights have a network structure, which facilitates the formation of a low-permeability, dense mud cake, improving the product's high-temperature and high-pressure fluid loss performance.

[0049] The biomass synthetic resin fluid loss reducer prepared in the embodiment of the present invention has the appearance of yellow-brown free-flowing powder, with a dry basis mass fraction of ≥93.0%. The molecular weight thereof is tested by gel chromatography, and the result is 6500-8670 g / mol.

[0050] The biodegradability of the ultra-high temperature biomass synthetic resin fluid loss reducer was tested in accordance with SY / T 6787-2010 "Technical Requirements for Environmental Protection of Water-Soluble Oilfield Chemicals," and the BOD / COD result was 1.22 to 2.01. In accordance with the industry standard SY / T 5094-2017 "Sulfomethylphenolic Resin (SMP) for Drilling Fluid Fluid Loss Reducer," after aging at 220°C for 16 hours, the high-temperature and high-pressure fluid loss was 24.4 to 30.6 mL, and the apparent viscosity was 22 to 28 mPa·s.

[0051] The present invention provides a drilling fluid, which includes the biomass synthetic resin fluid loss reducer prepared by the method described above or the biomass synthetic resin fluid loss reducer described in the above technical solution.

[0052] In the present invention, the drilling fluid is preferably a water-based drilling fluid.

[0053] The drilling fluid preferably includes: bentonite, sulfonate copolymer (DSP-1), the biomass synthetic resin fluid loss reducer, sulfonated lignite (SMC), sulfonated asphalt (FT-1), NaOH, NaCl, KCl, barite and water.

[0054] Specifically, the mass content of the bentonite in the drilling fluid is preferably 1-3%; the mass content of the DSP-1 in the drilling fluid is preferably 0.4-0.6%; the mass content of the biomass synthetic resin fluid loss reducer is preferably 6-10%; the mass content of the SMC is preferably 6-10%; the mass content of the FT-1 is preferably 2-5%; the mass content of the NaOH is preferably 0.4-0.6%; the mass content of the NaCl is preferably 13-17%; the mass content of the KCl is preferably 5-9%, the amount of the barite is preferably added according to the required drilling fluid density; the amount of water is the balance.

[0055] The biomass synthetic resin fluid loss reducer provided by the present invention has good high temperature resistance and fluid loss reduction performance, is easily biodegradable, can replace sulfonated phenolic resin, and is suitable for various water-based drilling fluid systems.

[0056] To further understand the present invention, the biomass synthetic resin fluid loss reducer provided by the present invention is described below in conjunction with examples. The protection scope of the present invention is not limited by the following examples.

[0057] The raw materials used in the following examples of the present invention are all commercially available products. Lignin is derived from corn cobs and the residue after desugaring in straw factories. Platinum sheets and Hg / HgO electrodes were purchased from Zhengzhou Shiruisi Instrument Technology Co., Ltd., carbon nanotubes (TNIM6, 20-40 nm, purity >95%) and carbon black (L6, conductive carbon black) were purchased from Zhongke Nano Times Co., Ltd., nickel was purchased from Henan Jinghong New Energy Co., Ltd., PTFE emulsion was purchased from Hangzhou Lvhe Environmental Protection Technology Co., Ltd., ferrous sulfate, concentrated nitric acid, and sodium hydroxide were purchased from Tianjin Komiou Chemical Reagent Co., Ltd., sodium sulfate was purchased from Shanghai Hesen Electric Co., Ltd., formaldehyde was purchased from Linyi Shengyang Chemical Co., Ltd., sodium metabisulfite was purchased from Shouguang Dinghao Economic and Trade Co., Ltd., and anhydrous sodium sulfite was purchased from Jining Kunfeng Chemical Co., Ltd.

[0058] The electrochemical workstation of the present invention was purchased from Shanghai Chenhua Instrument Co., Ltd., and the potentiometric titrator was purchased from Shanghai Hegong Scientific Instrument Co., Ltd.

[0059] The catalyst is prepared by dispersing 1 part of carbon nanotubes in 240 parts of 2.5 mol / L nitric acid solution by weight, ultrasonicating for 1 hour, filtering, washing to neutrality, drying and then crushing the obtained product.

[0060] The platinum sheet has an area of 12 cm 2 The gas diffusion electrode consists of a gas chamber, a diffusion layer, a support layer, and a catalyst layer. The gas chamber volume is 40 cm 3 , connected to the oxygen cylinder through a hose, storing and supplying oxygen to the diffusion layer; the diffusion layer is mixed with 0.25g carbon black and 1g binder PTFE emulsion, evenly coated on one side of the support layer, and connected to the gas chamber; the support layer is 20cm 2 The catalytic layer is mixed with 0.25g of catalyst and 1g of PTFE emulsion and evenly coated on the other side of the support layer.

[0061] Example 1

[0062] The preparation method of biomass synthetic resin fluid loss reducer includes the following process steps:

[0063] (1) Preparation of electro-Fenton modified lignin: 8 parts by weight of lignin were dissolved in 400 parts of an electrolyte with a pH of 12, wherein the concentration of ferrous chloride was 2 mmol / L and the concentration of sodium sulfate was 0.1 mol / L. The water bath temperature of the electro-Fenton reaction apparatus was controlled at 20°C, the oxygen flow rate was 0.6 L / min, and the current density was 8 mA / cm 2 After power and gas outages, the pH of the electrolyte was adjusted to 3, filtered, washed, dried, and crushed to obtain No. 1 electro-Fenton modified lignin.

[0064] (2) Preparation of biomass synthetic resin filtration loss reducer: 25 parts of the above-mentioned No. 1 electro-Fenton modified lignin, 25 parts of phenol, and 57 parts of formaldehyde were added in turn to a reactor equipped with a stirring device and a condensation reflux device, and stirred for 5 minutes; 14 parts of sodium metabisulfite and 17 parts of anhydrous sodium sulfite were added, heated to 70°C, and reacted for 30 minutes; the temperature was continued to rise to 103°C, and 20 parts of water were added every 20 minutes, for a total of 6 times, and the reaction was continued for 1 hour; the product was naturally cooled to room temperature and spray-dried to obtain the target product.

[0065] Example 2

[0066] (1) Preparation of electro-Fenton modified lignin: 12 parts by weight of lignin were dissolved in 400 parts of an electrolyte with a pH of 13, wherein the concentration of ferrous chloride was 2 mmol / L and the concentration of sodium sulfate was 0.1 mol / L. The water bath temperature of the electro-Fenton reaction apparatus was controlled at 40°C, the oxygen flow rate was 0.6 L / min, and the current density was 10 mA / cm 2 After power outage and gas cut-off, the pH of the electrolyte was adjusted to 4, filtered, washed, dried, and crushed to obtain 2# electro-Fenton modified lignin.

[0067] (2) Preparation of biomass synthetic resin filtration loss reducer: 35 parts of the above-mentioned 2# electro-Fenton modified lignin, 25 parts of phenol, and 60 parts of formaldehyde were added in turn to a reactor equipped with a stirring device and a condensing reflux device, and stirred for 10 minutes; 18 parts of sodium metabisulfite and 22 parts of anhydrous sodium sulfite were added, heated to 75°C, and reacted for 20 minutes; the temperature was continued to be raised to 102°C, and 25 parts of water were added every 15 minutes, for a total of 7 times, and the reaction was continued for 0.5 hours; the product was naturally cooled to room temperature and spray-dried to obtain the target product.

[0068] Example 3

[0069] (1) Preparation of electro-Fenton modified lignin: 16 parts by weight of lignin were dissolved in 400 parts of an electrolyte with a pH of 14, wherein the concentration of ferrous chloride was 3 mmol / L and the concentration of sodium sulfate was 0.1 mol / L. The water bath temperature of the electro-Fenton reaction apparatus was controlled at 60°C, the oxygen flow rate was 0.7 L / min, and the current density was 14 mA / cm 2 After power outage and gas cut-off, the pH of the electrolyte was adjusted to 5, filtered, washed, dried, and crushed to obtain 3# electro-Fenton modified lignin.

[0070] (2) Preparation of biomass synthetic resin filtration loss reducer: 30 parts of the above-mentioned 3# electro-Fenton modified lignin, 20 parts of phenol, and 55 parts of formaldehyde were added in turn to a reactor equipped with a stirring device and a condensing reflux device, and stirred for 7 minutes; 15 parts of sodium metabisulfite and 17 parts of anhydrous sodium sulfite were added, heated to 73°C, and reacted for 25 minutes; the temperature was continued to rise to 100°C, and 20 parts of water were added every 18 minutes, for a total of 6 times, and the reaction was continued for 1 hour; it was naturally cooled to room temperature and spray-dried to obtain the target product.

[0071] Example 4

[0072] (1) Preparation of electro-Fenton modified lignin: 16 parts by weight of lignin were dissolved in 400 parts of an electrolyte with a pH of 13, wherein the concentration of ferrous chloride was 2 mmol / L and the concentration of sodium sulfate was 0.1 mol / L. The water bath temperature of the electro-Fenton reaction apparatus was controlled at 40°C, the oxygen flow rate was 0.7 L / min, and the current density was 14 mA / cm 2 After power outage and gas cut-off, the pH of the electrolyte was adjusted to 4, filtered, washed, dried, and crushed to obtain 4# electro-Fenton modified lignin.

[0073] (2) Preparation of biomass synthetic resin filtration loss reducer: 25 parts of the above-mentioned 4# electro-Fenton modified lignin, 15 parts of phenol, and 50 parts of formaldehyde were added in turn to a reactor equipped with a stirring device and a condensing reflux device, and stirred for 5 minutes; 13 parts of sodium metabisulfite and 17 parts of anhydrous sodium sulfite were added, heated to 65°C, and reacted for 20 minutes; the temperature was continued to rise to 100°C, and 20 parts of water were added every 15 minutes, for a total of 5 times, and the reaction was continued for 1 hour; it was naturally cooled to room temperature and spray-dried to obtain the target product.

[0074] Example 5

[0075] (1) Preparation of electro-Fenton modified lignin: 8 parts by weight of lignin were dissolved in 400 parts of an electrolyte with a pH of 12, wherein the concentration of ferrous chloride was 1 mmol / L and the concentration of sodium sulfate was 0.1 mol / L. The water bath temperature of the electro-Fenton reaction apparatus was controlled at 40°C, the oxygen flow rate was 0.6 L / min, and the current density was 12 mA / cm 2 After power outage and gas cut-off, the pH of the electrolyte was adjusted to 4, filtered, washed, dried, and crushed to obtain 5# electro-Fenton modified lignin.

[0076] (2) Preparation of biomass synthetic resin filtration loss reducer: 35 parts of the above-mentioned 5# electro-Fenton modified lignin, 15 parts of phenol, and 50 parts of formaldehyde were added in turn to a reactor equipped with a stirring device and a condensation reflux device, and stirred for 7 minutes; 10 parts of sodium metabisulfite and 20 parts of anhydrous sodium sulfite were added, heated to 70°C, and reacted for 20 minutes; the temperature was continued to rise to 103°C, 23 parts of water were added every 20 minutes, and water was added 6 times in total, and the reaction was continued for 0.5 hours; it was naturally cooled to room temperature and spray-dried to obtain the target product.

[0077] Example 6

[0078] (1) Preparation of electro-Fenton modified lignin: 12 parts by weight of lignin were dissolved in 400 parts of an electrolyte with a pH of 14, wherein the concentration of ferrous chloride was 3 mmol / L and the concentration of sodium sulfate was 0.1 mol / L. The water bath temperature of the electro-Fenton reaction apparatus was controlled at 20°C, the oxygen flow rate was 0.6 L / min, and the current density was 12 mA / cm 2 After power outage and gas cut-off, the pH of the electrolyte was adjusted to 5, filtered, washed, dried, and crushed to obtain 6# electro-Fenton modified lignin.

[0079] (2) Preparation of biomass synthetic resin filtration loss reducer: 30 parts by weight of the above-mentioned 6# electro-Fenton modified lignin, 25 parts by weight of phenol, and 60 parts by weight of formaldehyde were added sequentially into a reactor equipped with a stirring device and a condensation reflux device, and stirred for 10 minutes; 16 parts by weight of sodium metabisulfite and 19 parts by weight of anhydrous sodium sulfite were added, heated to 75°C, and reacted for 30 minutes; the temperature was continued to rise to 105°C, and 25 parts by weight of water were added every 25 minutes, for a total of 5 times, and the reaction was continued for 1 hour; the product was naturally cooled to room temperature and spray-dried to obtain the target product.

[0080] Comparative Example 1

[0081] Commercially available sulfonated phenolic resin provided by Bazhou Sanyuan Co., Ltd.

[0082] Comparative Example 2

[0083] In parts by weight, 25 parts of lignin, 25 parts of phenol, and 57 parts of formaldehyde are added in sequence to a reactor equipped with a stirring device and a condensing reflux device, and stirred for 5 minutes; 13 parts of sodium metabisulfite and 17 parts of anhydrous sodium sulfite are added, and the mixture is heated to 70°C and reacted for 30 minutes; the temperature is further raised to 103°C, and 20 parts of water are added every 20 minutes, for a total of 6 times, and the reaction is continued for 1 hour; the mixture is naturally cooled to room temperature and spray-dried to obtain the target product.

[0084] Performance testing

[0085] The present invention uses aqueous phase potentiometric titration to determine the phenolic hydroxyl and carboxyl content in electro-Fenton modified lignin. The detection method and results are as follows:

[0086] (1) Accurately weigh 0.1 g of sample and 0.05 g of internal standard p-hydroxybenzoic acid into a beaker. Add 2 mL of potassium hydroxide solution (pH ≈ 14) and 25 mL of deionized water to dissolve the sample and internal standard. After thorough stirring, titrate the sample with a dilute hydrochloric acid solution of known concentration.

[0087] (2) Accurately weigh 0.05 g of the internal standard p-hydroxybenzoic acid into a beaker, add 2 mL of potassium hydroxide solution with a pH of ≈ 14 and 25 mL of deionized water to dissolve the internal standard, stir thoroughly, and then perform a blank titration with a dilute hydrochloric acid solution of known concentration.

[0088] Table 1 Phenolic hydroxyl and carboxyl content of lignin and electro-Fenton modified lignin according to the present invention

[0089]

[0090]

[0091] Among them, V1, V2 and V3 represent the volumes represented by the three peaks appearing in sequence in the first derivative curve of the sample potentiometric titration curve, V 1内标 、V 2内标 and V 3内标 They represent the volumes represented by the three peaks that appear in sequence in the first derivative curve of the internal standard potentiometric titration curve, c HCl is the concentration of dilute hydrochloric acid titrant, and m is the mass of the sample.

[0092] As can be seen from Table 1, the contents of phenolic hydroxyl and carboxyl in lignin are 0.7748 mmol / g -1 and 1.0421mmol / g -1 After electro-Fenton modification, the phenolic hydroxyl content increased to 2.5512~3.3723mmol / g -1 , which is 3.29 to 4.35 times of the original; the carboxyl content increased to 2.7123 to 3.6201 mmol / g -1, which is 2.60 to 4.67 times the original.

[0093] In the embodiment of the present invention, the depolymerization efficiency of lignin is mainly related to the accumulation concentration of H2O2. With the increase of oxygen flow rate and current density, the depolymerization efficiency of lignin first increases and then decreases. The reason is that the increase of oxygen flow rate can promote the mass transfer rate of oxygen, thereby increasing the accumulation concentration of H2O2. However, too much oxygen flow rate will form bubbles on the electrode surface, hindering the synthesis of H2O2. The higher the current density, the higher the accumulation concentration of H2O2. However, if the current density is too high, hydrogen evolution, water electrolysis and other reactions are likely to occur, which is not conducive to the production of H2O2. When the electrolysis temperature and electrolysis time are within the range of 20-60°C and 30-120min, the depolymerization efficiency of lignin increases with the increase of electrolysis temperature and electrolysis time. The embodiment of the present invention adopts the electro-Fenton method to modify lignin. By controlling different electrolysis process conditions, the active functional groups of the electro-Fenton modified lignin, especially the content of phenolic hydroxyl groups, can be increased, providing conditions for subsequent sulfonation and polycondensation reactions.

[0094] Preparation of base slurry: Add 1.05g of anhydrous sodium carbonate, 14.0g of bentonite for drilling fluid experiment and 14.0g of evaluation soil for drilling fluid into a high-speed stirring cup containing 350mL of distilled water, stir at high speed for 20min, and maintain in a sealed state at 25℃ for 24h.

[0095] Preparation of saturated salt water slurry: 28 g of the product prepared in the examples or comparative examples was added to the base slurry and stirred at high speed for 15 minutes. 28 g of sulfonated lignite was added, stopping at least twice to scrape off any sample adhering to the container wall. 105 g of sodium chloride was added and stirred at high speed for 10 minutes. 8.75 g of anhydrous sodium carbonate solution was then added. The prepared drilling fluid was transferred to an aging tank and heated at 220°C for 16 hours. The aging tank was removed, opened after cooling, and stirred evenly. The water loss at 180°C was measured using a high-temperature and high-pressure filter loss instrument.

[0096] Biodegradability test: Determined in accordance with SY / T 6788-2010 "Technical Evaluation Method for Environmental Protection of Water-Soluble Oilfield Chemicals". BOD / COD ≥ 0.05 indicates easy biodegradation, BOD / COD ≤ 0.01 indicates difficult biodegradation, and 0.01 < BOD / COD < 0.05 indicates relatively difficult biodegradation.

[0097] The test results are as follows:

[0098] Table 2 Performance of biomass synthetic resin fluid loss reducers prepared in Examples of the present invention and Comparative Examples

[0099]

[0100] As shown in Table 2, the biomass synthetic resin fluid loss additive prepared by the present invention appears as a yellow-brown, free-flowing powder; its dry basis mass fraction is ≥93.0%; its BOD / COD ratio is ≥0.05, indicating that it is readily biodegradable. After aging in a saturated brine slurry at 220°C for 16 hours, its apparent viscosity is 22-28 mPa·s, and its high-temperature and high-pressure fluid loss is 24.4-30.6 mL. Furthermore, its molecular weight, as measured by gel permeation chromatography, is 6500-8670 g / mol.

[0101] In Comparative Example 1, the commercially available sulfonated phenolic resin had a BOD / COD ratio of 0.01, indicating that it is difficult to biodegrade. After aging at 220°C for 16 hours in a saturated brine slurry, the apparent viscosity was 37 mPa·s, and the high-temperature and high-pressure fluid loss was 56.8 mL, indicating that its temperature resistance does not reach 220°C. Under high temperature and high pressure, the commercially available sulfonated phenolic resin is excessively cross-linked and cannot reduce fluid loss. In Comparative Example 2, a fluid loss reducer was synthesized using lignin that had not undergone electro-Fenton modification. The BOD / COD ratio was 1.04, indicating that it is readily biodegradable. After aging at 220°C for 16 hours in a saturated brine slurry, the apparent viscosity and high-temperature and high-pressure fluid loss increased, indicating that the lignin that had not undergone electro-Fenton modification had a large molecular weight, few active groups, and poor high-temperature and high-pressure fluid loss reduction performance.

[0102] In summary, the biomass synthetic resin fluid loss reducer provided in the embodiment of the present invention has good temperature resistance (mainly reflected in the higher aging temperature), salt resistance, fluid loss reduction, environmental protection and other characteristics in the base slurry, and is suitable for various water-based drilling fluids.

[0103] In order to further verify the effect of the biomass synthetic resin fluid loss reducer prepared by the present invention in the drilling fluid system, water-based drilling fluid systems with different densities were prepared, and the performance of the drilling fluids prepared in Comparative Example 1 and Comparative Example 2 was compared.

[0104] The drilling fluid formula is: 1% bentonite + 0.5% DSP-1 (sulfonate copolymer) + 7% ultra-high temperature biomass synthetic resin fluid loss additive + 7% SMC (sulfonated lignite) + 3% FT-1A (sulfonated asphalt) + 15% NaCl + 7% KCl + barite + water. Aging conditions: 220°C / 16h; high temperature and high pressure fluid loss test temperature is 180°C.

[0105] Table 3 Performance of drilling fluid systems with different densities prepared from biomass synthetic resin fluid loss reducers prepared in the examples of the present invention and the comparative examples

[0106]

[0107] Wherein, AV is the apparent viscosity, PV is the plastic viscosity, YP is the dynamic shear force, Gel is the initial and final shear force, FL is the API fluid loss, and HTHP is the high temperature and high pressure fluid loss.

[0108] As shown in Table 3, the water-based drilling fluid prepared with the biomass synthetic resin fluid loss reducer provided in Examples 1 to 6 of the present invention is aged at 220°C for 16 hours and has a density of 1.4 to 2.4 g.cm -3 It has the characteristics of low viscosity, good flow pattern and low filtration loss, which can meet the field performance requirements of deep well and ultra-deep well water-based drilling fluid. After aging at 220℃ for 16h, the density is 2.4g.cm -3 Under the conditions, compared with Example 6, the flow patterns of Comparative Examples 1 and 2 are poor, the viscosity and filtration loss are high, and they cannot meet the on-site drilling fluid requirements.

[0109] As shown in the above examples, the present invention utilizes the electro-Fenton method to modify lignin, reducing its molecular weight and increasing the content of reactive functional groups, particularly phenolic hydroxyl groups. This provides favorable conditions for synthesizing a high-temperature-resistant biomass-based fluid loss additive. The biomass-based synthetic resin fluid loss additive synthesized in this invention exhibits excellent heat and salt resistance, and is environmentally friendly, making it a "green" functional product with promising application prospects.

[0110] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing electro-Fenton modified lignin, characterized in that: The following steps are involved: S1, an electrolyte containing ferrous ions and lignin is electrolyzed under oxygen flow conditions; the electrolysis system includes a platinum sheet, an Hg / HgO electrode and a gas diffusion electrode, and oxygen is passed through the gas diffusion electrode; the electrolyte is a sodium sulfate solution containing ferrous chloride and lignin, with a pH of 12-14; the concentration of ferrous chloride in the electrolyte is 1-3 mmol / L, and the concentration of lignin is 2-4 wt.%; in step S1, the electrolysis temperature is controlled at 20-60°C by a water bath, the oxygen introduction rate is 0.5-0.7 L / min; the current density is controlled at 8-14 mA / cm 2 ;Electrolysis time is 30~120min; S2. After electrolysis for a certain period of time, the electrolyte is adjusted to be acidic, and solid-liquid separation is performed to obtain electro-Fenton modified lignin.

2. The preparation method according to claim 1, characterized in that In step S1, the gas diffusion electrode is composed of a gas chamber, a diffusion layer, a support layer and a catalyst layer; the catalyst in the catalyst layer is carbon nanotubes.

3. The preparation method according to claim 1 or 2, characterized in that In step S2, the pH of the electrolyte is adjusted to 3-5.

4. An electro-Fenton modified lignin, characterized in that, The product is prepared by the method according to any one of claims 1 to 3, and has a phenolic hydroxyl content of more than 2.5 mmol / g.

5. A biomass synthetic resin fluid loss additive, prepared by sulfonation and polycondensation of the electro-Fenton modified lignin according to claim 4, phenol, formaldehyde, and a sulfonating agent; in the preparation process of the biomass synthetic resin fluid loss additive, the mass ratio of the electro-Fenton modified lignin, phenol, formaldehyde, and sulfonating agent is (25-35): (15-25): (50-60): (30-40); The sulfonating agent is one or both of sodium metabisulfite and anhydrous sodium sulfite.

6. The biomass synthetic resin fluid loss reducer according to claim 5, characterized in that: The preparation process of the biomass synthetic resin fluid loss reducer comprises the following steps: mixing the electro-Fenton modified lignin, phenol, and formaldehyde, stirring for 5 to 10 minutes; adding a sulfonating agent, heating to 65 to 75° C., and reacting for 20 to 30 minutes; then heating to 100 to 105° C., adding water every 15 to 25 minutes, adding water 5 to 7 times in total, continuing the reaction for 0.5 to 1 hour, cooling, discharging, and spray drying to obtain the product.

7. A drilling fluid, characterized in that: The biomass synthetic resin fluid loss reducer comprising the biomass synthetic resin fluid loss reducer according to any one of claims 5 to 6.

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