阅读说明：本技术 降解油气田压裂返排液中有机物的光催化剂的制备方法 (Preparation method of photocatalyst for degrading organic matters in fracturing flow-back fluid of oil and gas field ) 是由 张旭 王均 杨萍 张瀛 焦国盈 刘卫华 杨博 王�琦 丁忠佩 石书强 梁兵 王 于 2019-12-03 设计创作，主要内容包括：本发明公开了一种降解油气田压裂返排液中有机物的光催化剂的制备方法,首先是对膨润土进行无机改性,得到无机改性膨润土；然后将无机改性膨润土进行有机改性,得到复合改性膨润土；然后将含铋化合物溶于硝酸溶液中,然后加入复合改性膨润土,形成悬浮溶液A；将含钨化合物溶于去离子水中,形成透明溶液B；将溶液B滴加入溶液A中,搅拌均匀,得到混合溶液,用氨水调节混合溶液pH为1～5,然后将混合溶液在温度140～180℃,反应10～18h,最后洗涤干燥,得到改性膨润土/Bi<Sub>2</Sub>WO<Sub>6</Sub>复合光催化剂。本发明的催化剂制备方法降低了生产成本,简化了生产工艺,制备的复合催化剂能够在可见光下光催化氧化去除油田废水中的有机物。(The invention discloses a preparation method of a photocatalyst for degrading organic matters in fracturing flow-back fluid of an oil-gas field, which comprises the following steps of firstly, carrying out inorganic modification on bentonite to obtain inorganic modified bentonite; then, carrying out organic modification on the inorganic modified bentonite to obtain composite modified bentonite; then dissolving a bismuth-containing compound in a nitric acid solution, and then adding composite modified bentonite to form a suspension solution A; dissolving a tungsten-containing compound in deionized water to form a transparent solution B; dropwise adding the solution B into the solution A, uniformly stirring to obtain a mixed solution, adjusting the pH of the mixed solution to 1-5 by using ammonia water, then reacting the mixed solution at the temperature of 140-180 ℃ for 10-18 h, and finally washing and drying to obtain the modified bentoniteearth/Bi 2 WO 6 A composite photocatalyst is provided. The preparation method of the catalyst reduces the production cost, simplifies the production process, and the prepared composite catalyst can remove organic matters in the oil field wastewater by photocatalytic oxidation under visible light.)

1. A preparation method of a photocatalyst for degrading organic matters in fracturing flow-back fluid of an oil and gas field is characterized by comprising the following steps:

s1, preparing the composite modified bentonite, comprising the following steps:

s11, inorganic modification of bentonite: adding a sodium hydroxide solution into an aluminum chloride solution according to the molar ratio of 2:1 of sodium hydroxide to aluminum chloride, and stirring for 4 hours at 60 ℃ to obtain a mixed solution; adding the mixed solution into a bentonite aqueous solution, stirring for 4h, standing, removing supernatant, drying the precipitate at 80 ℃, calcining and activating at 110 ℃ for 2h to obtain inorganic modified bentonite;

s12, organically modifying bentonite: dissolving cetyl trimethyl ammonium bromide and lauryl sodium sulfate in water to prepare intercalation liquid; adding the intercalation solution into an aqueous solution containing inorganic modified bentonite, and stirring for 4 hours at 75 ℃; then standing, removing supernatant, drying the precipitate at 80 ℃, and calcining and activating at 110 ℃ for 2 hours to obtain composite modified bentonite;

s2, dissolving a bismuth-containing compound in a nitric acid solution, and then adding composite modified bentonite to form a suspension solution A;

s3, dissolving a tungsten-containing compound in deionized water to form a transparent solution B;

s4, dropwise adding the solution B into the solution A, uniformly stirring to obtain a mixed solution, adjusting the pH of the mixed solution to 1-5 by using ammonia water, then reacting the mixed solution at the temperature of 140-180 ℃ for 10-18 h, and finally washing and drying to obtain the modified bentonite/Bi₂WO₆The composite photocatalyst is a photocatalyst for degrading organic matters in the fracturing flow-back fluid of the oil and gas field.

2. The preparation method of the photocatalyst for degrading organic matters in the oil and gas field fracturing flow-back fluid according to claim 1, wherein the step S11 is as follows:

(1) stirring 250mL of 0.2mol/L aluminum chloride solution at 60 ℃ for 30min, then slowly adding 250mL of 0.4mol/L sodium hydroxide solution into the aluminum chloride solution, and stirring for 4h to obtain a mixed solution;

(2) adding 25g of bentonite into 500ml of distilled water, stirring for 30min at 75 ℃, and adjusting the pH value to 9 by using 0.1mol/L sodium hydroxide solution to obtain a bentonite aqueous solution;

(3) and (2) adding the mixed solution obtained in the step (1) into a bentonite aqueous solution, stirring for 4h, standing, removing a supernatant, washing the precipitate with deionized water, drying the precipitate at 80 ℃, and calcining and activating for 2h at 110 ℃ to obtain the inorganic modified bentonite.

3. The preparation method of the photocatalyst for degrading organic matters in the oil and gas field fracturing flow-back fluid according to claim 2, wherein the step S12 is as follows:

(1) cetyl trimethyl ammonium bromide and lauryl sodium sulfate are dissolved in water to prepare intercalation liquid, wherein, the concentration of the cetyl trimethyl ammonium bromide is 0.1mol/L, and the concentration of the lauryl sodium sulfate is 0.026 mol/L;

(2) adding 4g of inorganic modified bentonite into 200ml of distilled water, and stirring for 30min at 75 ℃ to obtain an inorganic modified bentonite aqueous solution;

(3) adding 10ml of intercalation solution into inorganic modified bentonite aqueous solution, and stirring for 4 hours at 75 ℃; and then standing, removing supernatant, washing the precipitate with deionized water, drying the precipitate at 80 ℃, and calcining and activating at 110 ℃ for 2 hours to obtain the composite modified bentonite.

4. The method for preparing the photocatalyst for degrading the organic matters in the oil and gas field fracturing flow-back fluid according to claim 1, wherein the molar ratio of bismuth element in the bismuth-containing compound to tungsten element in the tungsten-containing compound is 2: 1.

5. The method for preparing the photocatalyst for degrading the organic matters in the oil and gas field fracturing flow-back fluid according to claim 4, wherein the bismuth-containing compound is bismuth nitrate pentahydrate, and the tungsten-containing compound is sodium tungstate.

6. The method for preparing the photocatalyst for degrading the organic matters in the oil and gas field fracturing flow-back fluid as claimed in claim 5, wherein the concentration of the bismuth nitrate pentahydrate in the suspension solution A is 0.1-0.2 mol/L.

7. The method for preparing the photocatalyst for degrading the organic matters in the oil and gas field fracturing flow-back fluid as claimed in claim 6, wherein the mass percentage concentration of the composite modified bentonite in the obtained composite photocatalyst is 4-12%.

8. The method for preparing the photocatalyst for degrading the organic matters in the oil and gas field fracturing flow-back fluid as claimed in claim 6, wherein the concentration of sodium tungstate in the solution B is 0.05-0.1 mol/L.

9. The method of claim 1, wherein in step S4, the pH of the mixed solution is adjusted to 2 with ammonia water.

10. The photocatalyst prepared by the preparation method of any one of claims 1 to 9, which is used for removing acrylamide in fracturing fluid flowback fluid by photocatalytic oxidation under visible light.

Technical Field

The invention relates to the technical field of photocatalysts, in particular to modified bentonite/Bi for photocatalytic degradation of organic matters in fracturing fluid flowback fluid₂WO₆A preparation method of a composite photocatalyst.

Background

A large amount of various organic additives such as guanidine gum, organic boron, acrylamide and the like in fracturing flowback fluid in the process of exploiting an oil-gas field have the characteristics of high viscosity, large turbidity, toxicity, harm, high stability and the like, and if the fracturing flowback fluid is directly discharged without being treated, the fracturing flowback fluid can pollute the environment and cause serious pollution. The treatment method of the fracturing flow-back fluid mainly comprises natural evaporation, freeze thawing, filtration, ozone oxidation, electrocoagulation, reverse osmosis, distillation and the like. Over decades, many new technologies have been applied, such as: ozone/ultrasonic wave/electric flocculation/reverse osmosis compounding, clean wave technology, mechanical vapor recompression and other technologies. However, these techniques mainly treat inorganic substances in the fracturing flow-back fluid, and have very limited treatment of a large amount of organic additives such as guanidine gum, organic boron, acrylamide and the like in the fracturing flow-back fluid. Therefore, the method for treating the organic matters in the fracturing flow-back fluid is an important technology for guaranteeing the normal production and the sustainable development of the oil and gas field.

The photocatalysis technology is a new process for treating organic pollutants difficult to degrade developed in the later stage of 20 th century, and is characterized in that free radicals with extremely strong activity are generated under the action of a semiconductor catalyst, so that the organic pollutants difficult to degrade in wastewater can be almost non-selectively oxidized and degraded into non-toxic or low-toxic micromolecule substances, and even directly mineralized into carbon dioxide, water and other micromolecule carboxylic acids, and the aim of harmlessness is fulfilled. The technology has the advantages of no selectivity, strong oxidation capability, high reaction speed, high treatment efficiency, no secondary pollution and the like. The characteristics enable the photocatalysis technology to show great application space in the field of processing shale gas flow-back liquid. In the technical field of photocatalysis, a photocatalyst plays a very important role, and the modification of the catalyst is the main direction of research, and the main methods for modification are as follows: the construction of the composite photocatalyst can simultaneously improve the photon absorption efficiency and the carrier separation efficiency of the photocatalyst, thereby greatly improving the photocatalytic activity.

Bismuth is a green metal, bismuth-based catalysts are novel catalysts developed in recent years, and are widely applied to the aspects of water pollutant degradation, antibiosis and the like due to the characteristics of no toxicity, low price, strong oxidation-reduction capability, stable chemical property, light corrosion resistance and the like. The electron-hole recombination efficiency of the monomer bismuth catalyst is high, and the photocatalytic activity is not good, so that the practical application of the monomer bismuth catalyst is severely restricted. Bismuth tungstate (Bi)₂WO₆) The bismuth tungstate composite catalyst is a narrow-bandgap semiconductor, has excellent response performance to visible light, and can be prepared by modifying and compounding bismuth tungstate in order to further improve the catalytic activity. The bentonite is a non-metal mineral product with montmorillonite as a main mineral component, and the unique layered structure of the bentonite has good ion exchange performance. Modified Bi with bentonite as carrier material₂WO₆Preparing high-activity bentonite/Bi₂WO₆The novelty of composite materials has attracted our researchers. However, since the montmorillonite structure is a 2: a type 1 crystal structure. For the intercalation modification of the phyllosilicate, the interlayer spacing needs to be enlarged firstly to facilitate the entry of other molecules, and because the inner surface of the phyllosilicate layer has exchangeable cations, the interlayer spacing needs to be enlarged by modification so as to carry out the next intercalation. The modified composite material has increased specific surface area and specific pore structure, and may be used as molecular level composite material.

Disclosure of Invention

The invention aims to provide a preparation method of a photocatalyst for degrading organic matters in fracturing flow-back fluid of an oil-gas field. Prepared modified bentonite/Bi₂WO₆The composite catalyst is used for removing organic matters in the oil field wastewater by photocatalytic oxidation under visible light, in particular to removing acrylamide in fracturing fluid flowback fluid.

The invention provides modified bentonite/Bi₂WO₆The preparation method of the composite photocatalyst comprises the following steps:

s1, preparing composite modified bentonite: firstly, carrying out inorganic modification on bentonite to obtain inorganic modified bentonite; then, carrying out organic modification on the inorganic modified bentonite to obtain composite modified bentonite; wherein the content of the first and second substances,

the inorganic modification step comprises: adding a sodium hydroxide solution into an aluminum chloride solution according to the molar ratio of 2:1 of sodium hydroxide to aluminum chloride, and stirring for 4 hours at 60 ℃ to obtain a mixed solution; adding the mixed solution into a bentonite aqueous solution, stirring for 4h, standing, removing supernatant, drying the precipitate at 80 ℃, calcining at 110 ℃ and activating for 2h to obtain inorganic modified bentonite;

the organic modification step comprises the following steps: dissolving cetyl trimethyl ammonium bromide and lauryl sodium sulfate in water to prepare intercalation liquid; adding the intercalation solution into an aqueous solution containing inorganic modified bentonite, and stirring for 4 hours at 75 ℃; then standing, removing supernatant, drying the precipitate at 80 ℃, and calcining and activating at 110 ℃ for 2h to obtain the composite modified bentonite.

S2, dissolving the bismuth-containing compound in a nitric acid solution, adding the composite modified bentonite, and stirring for 30min to form a suspension solution A. HNO in nitric acid solution₃The volume ratio to water was 1: 1.

S3, dissolving the tungsten-containing compound in deionized water, and stirring for 30min to form a transparent solution B; the molar ratio of bismuth element in the bismuth-containing compound to tungsten element in the tungsten-containing compound is 2: 1.

S4, dropwise adding the solution B into the solution A, uniformly stirring to obtain a mixed solution, adjusting the pH of the mixed solution to 1-5, preferably 2, stirring for 30min, then placing the mixed solution into a high-temperature high-pressure reaction kettle, reacting for 10-18 h at the temperature of 140-180 ℃, finally washing and drying, and drying for 8-16h at the temperature of 70-90 ℃ to obtain the modified bentonite/Bi₂WO₆A composite photocatalyst is provided.

Preferably, the inorganic modification comprises the following specific steps:

(1) stirring 250mL of 0.2mol/L aluminum chloride solution at 60 ℃ for 30min, then slowly adding 250mL of 0.4mol/L sodium hydroxide solution into the aluminum chloride solution, and stirring for 4h to obtain a mixed solution;

(2) adding 25g of bentonite into 500ml of distilled water, stirring for 30min at 75 ℃, and adjusting the pH value to 9 by using 0.1mol/L sodium hydroxide solution to obtain a bentonite aqueous solution;

(3) and (2) adding the mixed solution obtained in the step (1) into a bentonite aqueous solution, stirring for 4h, standing, removing a supernatant, washing the precipitate with deionized water, drying the precipitate at 80 ℃, and calcining and activating for 2h at 110 ℃ to obtain the inorganic modified bentonite.

The organic modification comprises the following specific steps:

(1) dissolving cetyl trimethyl ammonium bromide and lauryl sodium sulfate in water to prepare intercalation solution, wherein the concentration of the cetyl trimethyl ammonium bromide is 0.1mol/L, and the concentration of the lauryl sodium sulfate is 0.026 mol/L;

(2) adding 4g of inorganic modified bentonite into 200ml of distilled water, and stirring for 30min at 75 ℃ to obtain an inorganic modified bentonite aqueous solution;

(3) adding 10ml of intercalation solution into inorganic modified bentonite aqueous solution, and stirring for 4 hours at 75 ℃; and then standing, removing supernatant liquid, washing the precipitate with deionized water, drying the precipitate at 80 ℃, and calcining and activating at 110 ℃ for 2 hours to obtain the composite modified bentonite.

Preferably, the bismuth-containing compound is bismuth nitrate pentahydrate. The concentration of the bismuth nitrate pentahydrate in the suspension solution A is 0.1-0.2 mol/L. In the obtained composite photocatalyst, the mass percentage concentration of the composite modified bentonite is 4-12%, and the further optimization is 8%. The tungsten-containing compound is sodium tungstate, and the concentration of the sodium tungstate in the solution B is 0.05-0.1 mol/L.

Compared with the prior art, the invention has the advantages that:

(1) the invention is realized by adding Bi₂WO₆In the preparation process, bentonite subjected to inorganic and organic composite modification is added to obtain modified bentonite/Bi₂WO₆A composite photocatalyst is provided. The inorganic modification has smaller particle size and larger specific surface area, and the pore diameter and pore structure of the inorganic modification are adjustable, so the inorganic modification is an ideal catalyst material; and a special structure of an inorganic interlayer compound capable of accommodating the converted metal ions and changing the oxygen thereof in a catalytic process with oxide reductionAnd is used as a catalyst carrier in a molten state. The organic modification obviously increases the space between bentonite layers. The specific surface area is increased after composite modification, and the composite material has an interlayer porous structure with a specific size and is a molecular-grade composite material.

(2) Prepared modified bentonite/Bi₂WO₆The catalytic activity of the composite photocatalyst is superior to that of Bi₂WO₆A photocatalyst. The composite photocatalyst has a layered structure and ultrathin property, and improves the photocatalytic activity. The composite photocatalyst can excite more photoproduction electrons under visible light, the electron-hole recombination rate is reduced, the photocatalytic activity is obviously improved, the preparation method is simple, the condition is mild, the purposes of reducing the cost and simplifying the production flow are achieved, and the composite photocatalyst is mainly applied to organic matters in the oxidation fracturing flow-back fluid. For example, the rate of acrylamide degradation is significantly increased. Under the irradiation of visible light, the removal rate of the acrylamide solution with the original COD of 200mg/L in 4h is 86.9%, and the photocatalytic performance is improved.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

FIG. 1, composite photocatalyst obtained in example 1 and Bi obtained in comparative example 2₂WO₆XRD pattern of photocatalyst.

FIG. 2, composite photocatalyst of example 1 and Bi obtained in comparative example 2₂WO₆DRS plot of photocatalyst.

Figure 3 is a graph comparing the effect of the composite photocatalyst of example 1 and the catalysts of comparative examples 1 and 2 in degrading acrylamide.

Detailed Description

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.