CN-122006758-A - Preparation method of Ag/P25 composite catalyst and preparation method of catalyst in process of preparing CH4Photocatalytic conversion to CH3Use in OH

Abstract

A preparation method of Ag/P25 composite catalyst and application thereof in converting CH 4 into CH 3 OH, belonging to the technical field of CH 4 photocatalytic conversion. The preparation method comprises the steps of firstly dispersing commercial P25 in AgNO 3 aqueous solution by ultrasonic, then slowly dropwise adding NaBH 4 aqueous solution, continuing stirring reaction after the dropwise addition is completed, and finally centrifuging, washing and drying after the reaction is completed. According to the invention, the Ag/P25 composite catalyst with Ag nano particles loaded on the surface and a large amount of Ov is prepared by a simple wet impregnation method, so that the performance of CH 4 photo-catalytic conversion into CH 3 OH is greatly improved, and the yield and selectivity of CH 3 OH in 2 h respectively reach 5.5 mmol g ‑1 h ‑1 and 94% under the conditions of room temperature and 2 MPa CH 4 +O 2 (19:1) total pressure.

Inventors

• WANG MEILING
• YANG SHINENG
• TANG HAILONG

Assignees

• 安徽大学

Dates

Publication Date

20260512

Application Date

20260413

Claims (9)

1. 1. A preparation method of an Ag/P25 composite catalyst is characterized in that commercial P25 is firstly dispersed in AgNO 3 aqueous solution by ultrasonic, then NaBH 4 aqueous solution is slowly dripped, stirring reaction is continued after dripping is completed, and centrifugal separation, washing and drying are carried out after the final reaction is completed.
2. 2. The preparation method according to claim 1, wherein the addition amount of AgNO 3 is 0.3 to wt to 8.4 to wt% by mass relative to P25.
3. 3. The method of claim 1, wherein the amount of NaBH 4 added is 3 to 5 times the amount of AgNO 3 added.
4. 4. The process of claim 1, wherein the reaction temperature is room temperature and the reaction time is 1 to 10 h.
5. 5. The Ag/P25 composite catalyst according to any one of claims 1 to 4, which is composed mainly of particles having a size of 1 to 50 nm a, and has a surface Ag nanocrystalline grain size of 1 to 5a nm a, wherein the composite catalyst has a percentage of Ag of 1 to 6% and an Ov of 10 to 30%.
6. 6. The use of the Ag/P25 composite catalyst according to claim 5 for the photocatalytic conversion of CH 4 to CH 3 OH, comprising the steps of: 1) Dispersing a 5mg Ag/P25 composite catalyst in 80 mL H 2 O, placing in a high-pressure photo-catalytic reaction kettle, introducing O 2 gas before illumination to exhaust air in the kettle, introducing CH 4 +O 2 with different partial pressure ratios, and pressurizing to 2 MPa; 2) Setting working current of a xenon lamp by taking the 300W xenon lamp as a light source, maintaining a stirring state of 800 rpm by a liquid phase system, and setting the temperature of circulating water to be 30 ℃; 3) And after the photocatalytic reaction is carried out for a period of time, the light source is turned off, the temperature of the circulating water is set to be 5 ℃, and after the temperature in the reaction kettle is reduced to be below 10 ℃, the components and the content of the gas phase and the liquid phase are analyzed.
7. 7. The method according to claim 6, wherein the CH 4 、O 2 partial pressure ratio is 1.9:0.1 at a total pressure of 2 MPa.
8. 8. The use of claim 6 wherein the xenon lamp operating current is set to 16A.
9. 9. The method according to claim 6, wherein the photocatalytic reaction time is 2h.

Description

Preparation method of Ag/P25 composite catalyst and application of Ag/P25 composite catalyst in photocatalytic conversion of CH 4 into CH 3 OH Technical Field The invention belongs to the technical field of CH 4 photocatalytic conversion, and particularly relates to a preparation method of an Ag/P25 composite catalyst and application of the Ag/P25 composite catalyst in converting CH 4 into CH 3 OH. Background Methane (CH 4) is a high-quality clean energy source and is widely used in the fields of power generation, heating and the like. In recent years, with the exploration and development of CH 4 hydrate, shale gas and coalbed methane, the global CH 4 reserves have proliferated. However, the high difficulty of storage and transportation demands results in the expensive cost of CH 4 energy utilization due to the flammability and explosiveness of CH 4 and remote location of origin. In addition, since CH 4 is a powerful greenhouse gas (the greenhouse effect is 25 times that of CO 2), leakage and combustion of the place of production retentate both create huge environmental pressure and energy waste. Therefore, the efficient utilization method of the deep excavation CH 4 and the realization of the resource utilization thereof are win-win strategies for realizing economic, environmental and energy benefits, and are urgent. The CH 4 is converted into liquid fuel such as methanol (CH 3 OH) which is convenient to transport and store and is directly used for industrial manufacture, so that not only can the embarrassment of increasingly shortage of petroleum resources be relieved, but also the green development of the chemical industry can be promoted. However, the activation of CH 4 molecules is very challenging, once a worldwide challenge, due to their stable regular tetrahedral structure, extremely low polarizability and extremely high C-H bond energy (439 KJ/mol). Efficient activation of CH 4 is usually achieved under severe reaction conditions such as high temperature (> 600 ℃), strong oxidants (e.g. fuming sulfuric acid) or external fields (e.g. plasma), for example, conventional CH 4 industrial conversion requires first performing CH 4 steam reforming under high temperature and high pressure conditions (800-1000 ℃, 2-7 MPa) and then performing chemical synthesis. The harsh CH 4 steam reforming conditions not only lead to energy waste and product peroxidation, but also greatly shorten catalyst life due to carbon deposition reactions. In addition, the preparation of CH 3 OH by selective photocatalysis of CH 4 is considered to be "holy cup" in the catalysis field, because the target product CH 3 OH is extremely susceptible to secondary oxidation to form byproducts such as HCHO and CO x. The high energy consumption step of synthesis gas generation is skipped, and the green sustainable light energy is utilized to directly drive CH 4 to be upgraded and converted into CH 3 OH under the mild condition (a non-strong acid medium system with the temperature of less than 150 ℃), so that the method is certainly an ideal way for realizing high-efficiency utilization of CH 4. The photocatalysis technology is an effective way to realize CH 4→CH3 OH by using light energy, and uses a photogenerated carrier to preactivate a stable C-H bond, and realizes CH 4 conversion under mild conditions by reducing an activation energy barrier. Among them, the photooxidation of CH 4 with green, low-cost O 2 as an oxidizing agent is a current research focus. Under illumination, when photon energy (hν) is greater than forbidden bandwidth E g, the semiconductor material is excited to generate electrons (E -) and holes (H +) after absorbing incident photons, wherein E - can reduce O 2 molecules to OOH, and H + can oxidize CH 4 and H 2 O molecules to form CH 3 and OH, respectively. These OH groups are further used as important active oxygen species for activating CH 4 to form CH 3, and the formed CH 3 is combined with OOH/. OH and the like to obtain the target product CH 3 OH. At present, under the condition of room temperature (25-30 ℃), representative research progress of CH 4 photocatalytic CH 3 OH production is as follows, in 2021, a group of professor topics of leaf golden flowers of Tianjin university utilizes Ag to modify TiO 2 nanosheets of a main exposure (001) crystal face, utilizes oxygen vacancies (Ov) generated by the crystal face under illumination to regulate a CH 4 conversion route (Ov- > Ti-O 2·→Ti-OO-Ti→Ti-OCH3HOTi→Ti-O-Ti+CH3 OH), and under the total pressure of 2.1 MPa CH 4+O2 (20:1), the yield and the selectivity of CH 3 OH respectively reach 4.8 3 and 80 percent In 2 3; in 2022, 3 professor group of China university of science and technology uses two oxides of Fe 3 and ZnO to polarize CH 3 molecules and enhance the O-H bond strength of CH 3 OH product to prevent peroxidation, under 1 3 pressure, the yield and selectivity of CH 3 OH reach 178.3 mu mol g 3 and 100%, in 2023, the 3 research staff group of national center