Palladium-loaded magnetic silicon dioxide nanofluid, preparation method, application and oil displacement agent

Abstract

The invention discloses a palladium-loaded magnetic silicon dioxide nanofluid, a preparation method, application and an oil-displacing agent, the nanofluid is obtained by adopting a green biological base solution, and surface active substances generated by microbial metabolism have a stable dispersion effect; the magnetic core can be recycled by virtue of the action of a magnetic field, the shell layer material provides stable dispersing capacity, and the loaded palladium can inhibit the blockage damage of microorganism breeding to the stratum; the bioactive components and the nanoparticles can synergistically improve the crude oil recovery rate, the oil recovery mechanism is disclosed through microscopic oil drop stripping and imbibition experiments, and the core displacement experiment effect is remarkable.

Description

Technical Field

[0001] The invention belongs to the technical field of bionano oil displacement, and specifically relates to a palladium-loaded magnetic silica nanofluid, a preparation method, an application and an oil displacement agent. Background Art

[0002] The size of nanomaterials is very small, between atoms, molecules and macroscopic systems. Their special structure produces four effects, namely small size, quantum, surface and interface effects, and exhibits unique physical and chemical properties. Nanofluid drive, as a new type of reservoir recovery technology, has the advantages of good injectability, small reservoir damage, strong oil recovery ability, and intelligent response, and has received widespread attention. Nanomaterials used in oil fields can be roughly divided into metal and silica inorganic nanomaterials, organic carbon and cellulose nanomaterials, polymer microspheres, surfactant nanoemulsions and other materials (MD molecular membranes and 2-D smart nano black cards).

[0003] There are two main techniques for the preparation of nanomaterials: top-down and bottom-up. The top-down approach relies on the use of various distribution techniques to produce isolated atoms from bulk materials, while the bottom-up approach starts with a metal salt precursor (dissolved in a solvent), which is reduced in a chemical reaction and then forms nanoparticles through a nucleation process and then clusters. In the bottom-up approach, the use of appropriate capping agents is very important for controlling the particle size, shape and stability of the resulting nanomaterials. Traditional nanomaterial synthesis methods mainly include physical and chemical methods. Among them, physical methods such as sputtering, arc discharge and ball milling have high requirements on the instruments and equipment required for the reaction and consume a lot of energy; chemical methods such as microemulsion, coprecipitation and sol-gel methods use toxic reagents, poor degradability and are prone to environmental pollution.

[0004] Based on the above technical problems existing in the prior art, the present invention proposes a nano-palladium-loaded magnetic silica fluid, a preparation method, an application and an oil-displacing agent. Summary of the invention

[0005] The purpose of the present invention is to provide a palladium-loaded magnetic silica nanofluid, a preparation method, an application and an oil-displacing agent in view of the deficiencies in the prior art.

[0006] The present invention adopts the following technical solution:

[0007] In a first aspect, a palladium-loaded magnetic silica nanofluid is provided:

[0008] The magnetic Fe3O4 nano-precursor was prepared by double microemulsion method;

[0009] TEOS hydrolysis is used as the shell material;

[0010] Palladium was synthesized using Pseudomonas aeruginosa fermentation broth and loaded on the surface of magnetic silica nanomaterials.

[0011] In a second aspect, a method for preparing a palladium-loaded magnetic silica nanofluid is provided, comprising:

[0012] Step 1, culturing and fermenting Pseudomonas aeruginosa to purify metabolites, wherein glycolipids and amino acid active ingredients are produced in the metabolites;

[0013] Step 2, preparing magnetic Fe3O4 nano precursor by double microemulsion method;

[0014] Step 3, n-hexane, TEOS, pure water and ethanol are stirred evenly and then added to the reverse microemulsion, and heated and stirred at 50° C. for 1 hour to promote the condensation reaction of TEOS, and centrifuged at 5° C. and 8000 rpm to pour off the upper liquid, collect the precipitate, and wash it with ethanol and pure water to obtain the magnetic nanofluid;

[0015] Step 4, adding PdCl2 and Pseudomonas aeruginosa fermentation supernatant into a container, and magnetically stirring at 70° C. for 5 h to obtain a nano-palladium fluid;

[0016] Step 5, adding the nanopalladium fluid dropwise into the magnetic nanofluid, heating and stirring at 70° C. for 3 h, so that the nanopalladium modified with the microbial metabolic supernatant is fully loaded on the Fe3O4@SiO2 surface.

[0017] Further, in step 3, the reverse microemulsion is formed by stirring 28 g of n-hexanol, 20 g of n-hexane and 7 g of Triton X-100 at 40° C. for 10 min.

[0018] Furthermore, in step 4, there are a large number of reducing substances in the fermentation broth, which can reduce the palladium ions, and continuous heating is required to increase the reaction rate to obtain the palladium nanofluid.

[0019] Further, step 1 comprises:

[0020] Step 1.1, preparing a fermentation medium, wherein the medium comprises:

[0021] The carbon sources were glucose and corn syrup powder;

[0022] The nitrogen sources are NaNO3 and CaMg(NO3)4;

[0023] The phosphorus source is K2HPO4;

[0024] Corn oil;

[0025] The trace elements are a mixture of ZnSO4·7H2O, CuSO4·5H2O, Ni(NO3)2·6H2O, MnSO4·4H2O and FeSO4·7H2O;

[0026] Sterilize the culture medium in a high pressure steam cooker at 121°C for 20 minutes, and after cooling naturally, take it out and carry out inoculation operation on a clean bench;

[0027] Step 1.2, obtaining microbial fermentation supernatant;

[0028] The refrigerated Pseudomonas aeruginosa was taken out, thawed and activated at room temperature for 15 minutes, 1 ml of bacterial solution was inoculated into the culture medium, covered with a sealing film, placed in a constant temperature incubator at 37°C and 180 rpm for mixing and shaking for 72 hours, and the fermentation liquid was ultrasonically treated for 10 minutes using an ultrasonic cell disruptor, with each ultrasonication for 6 seconds and an interval of 4 seconds; the fermentation liquid was placed in a 50 ml centrifuge tube, and the centrifuge parameters were adjusted to 4°C and 8000 rpm for centrifugation for 15 minutes to remove precipitated impurities to obtain a supernatant; a distillate was obtained by heating at 260°C through a distillation device; the distillate was filtered using a vacuum pump, filter paper and suction flask combination device to obtain a purified Pseudomonas aeruginosa fermentation supernatant.

[0029] Furthermore, step 1 includes the step of detecting components of the Pseudomonas aeruginosa fermentation supernatant.

[0030] Furthermore, step 2 of preparing a magnetic Fe3O4 nano precursor by a double microemulsion method comprises:

[0031] Add n-hexanol, n-hexane and Triton X-100 to a container, stir at 40°C for 10 min to form a microemulsion, add FeSO4·7H2O and FeCl3·6H2O, stir to fully dissolve, add methylamine and keep reacting for 5 min, then add concentrated NH3·H2O dropwise until the color turns black, and keep stirring.

[0032] Furthermore, in step 3, the magnetic nanofluid is obtained and the nanoparticles are evenly dispersed using ultrasound, and the ultrasound parameters are set to 20 seconds each time, 2 seconds interval, and a total of 30 times.

[0033] Further, step 4 includes a step of detecting the surface plasmon resonance band SPR of nano-palladium by UV-Vis to confirm the synthesis of nanoparticles.

[0034] In a third aspect, a palladium-loaded magnetic silica nanofluid is provided for use in improving crude oil recovery.

[0035] In a fourth aspect, an oil displacing agent is provided, the oil displacing agent comprising the palladium-loaded magnetic silica nanofluid.

[0036] Furthermore, in the palladium-loaded magnetic silica nanofluid, the palladium loading is less than 10 wt %.

[0037] The beneficial effects of the present invention are:

[0038] The palladium-loaded magnetic silica nanofluid, preparation method, application and oil-displacing agent of the present invention adopt green bio-based liquid to obtain the nanofluid, and the surfactant produced by microbial metabolism has the effect of stable dispersion; the magnetic core can be recycled and reused with the help of the magnetic field, the shell material provides stable dispersion ability, and the loaded palladium can inhibit the blockage and damage of microbial reproduction to the formation; the biologically active ingredients and nanoparticles can synergistically improve the crude oil recovery rate, and the oil recovery mechanism is revealed through microscopic oil droplet peeling and imbibition experiments, and the core displacement experiment has significant effect, which has the advantages of being bio-environmentally friendly and having huge application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the optimal concentration of the Pseudomonas aeruginosa fermentation supernatant in an embodiment of the present invention;

[0040] Figure 2 Schematic diagram of Zeta potential detection results of the particle size of the bio-nanofluid in an embodiment of the present invention;

[0041] Figure 3 A transmission electron microscope image of a bionanomaterial in an embodiment of the present invention;

[0042] Figure 4 is a Fourier infrared image of the bio-nanomaterial in the embodiment of the present invention;

[0043] Figure 5a , Figure 5b Schematic diagram of the magnetic induction detection results of bio-nanomaterials in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to more clearly understand the above-mentioned purposes, features and advantages of the present invention, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0045] Example 1

[0046] Example 1 of the present application provides a method for obtaining a Pseudomonas aeruginosa fermentation supernatant, comprising:

[0047] S1.1, prepare efficient fermentation medium, use conical flask to prepare medium, carbon source is: 10g / L glucose, 4g / L corn steep liquor powder; nitrogen source is: 1.6g / L NaNO3, 0.4g / L CaMg(NO3)4; phosphorus source is: 1.6g / L K2HPO4; 1ml / L trace elements; 5ml / L corn oil, wherein the trace elements include 0.6g / L ZnSO4·7H2O, 0.5g / L CuSO4·5H2O, 0.3g / LNi(NO3)2·6H2O, 0.5g / L MnSO4·4H2O, 0.5g / L FeSO4·7H2O, sterilize the medium in a high pressure steam cooker at 121°C for 20 minutes, take it out after natural cooling and carry out inoculation operation on the clean bench;

[0048] S1.2, obtaining the supernatant of microbial fermentation, taking out the Pseudomonas aeruginosa refrigerated in the laboratory, thawing and activating it at room temperature for 15 minutes, inoculating 1 ml of bacterial liquid in the culture medium, covering it with a sealing film, placing it in a constant temperature incubator under the experimental conditions of 37°C and 180rpm for mixing and shaking for 72 hours, using an ultrasonic cell disruptor to ultrasonicate the fermentation liquid for 10 minutes, with each ultrasonication for 6 seconds and an interval of 4 seconds, then placing the fermentation liquid in a 50 ml centrifuge tube, adjusting the centrifuge parameters to 4°C and 8000rpm for centrifugation for 15 minutes, removing the precipitated impurities to obtain the supernatant, in order to remove the inorganic salt impurities in the fermentation liquid, heating it at 260°C through a distillation device to obtain a distillate, and finally filtering the distillate with a vacuum pump, filter paper and suction flask combination device as the final purified Pseudomonas aeruginosa fermentation supernatant;

[0049] S1.3, detection of components of P. aeruginosa fermentation supernatant;

[0050] a. Acid precipitation: adjust the pH of the fermentation liquid to 2 with HCl and place it in a refrigerator at 4°C overnight. A small amount of white precipitate will be produced, indicating the presence of a small amount of lipopeptide surfactants;

[0051] b. TLC, take 0.1g sample into a test tube, add 5mL concentrated H2SO4, seal the test tube and hydrolyze at 100℃ for 4h, add sufficient BaCO3 to neutralize the hydrolyzate after cooling, add pure water and pour all into a centrifuge tube, centrifuge at 4500rpm for 10min, collect the supernatant into a sample tube, concentrate at 40℃ for 30min and set aside, spot the sample on a thin layer chromatography silica gel plate, add a developing agent for development, spray the color developer and heat to 105℃ to develop until the spots are clear, indicating the presence of a large number of glycolipids and lipopeptides;

[0052] c. LC-MS acquisition of chromatogram and mass spectrum, experimental conditions: mobile phase A is 0.1% formic acid aqueous solution, mobile phase B is acetonitrile solution, flow rate is 0.3 ml / min, injection volume is 5 ul, chromatographic column waters BEH C18 2.1*100mm 1.7um, mass spectrometry scanning range is primary 100-1400 m / z, sheath gas temperature is 350°C, sheath gas flow is 12 L / min, ESI+ mode voltage is 4000 V, ESI- mode voltage is 3200 V, and the presence of rhamnolipids is detected;

[0053] e. Measure CMC. Dilute the purified Pseudomonas aeruginosa fermentation supernatant by 1, 10, 100, 1000, and 10000 times respectively, measure the surface tension value, and take the inflection point 10% volume concentration as the experimental optimal concentration diagram, as shown in the figure below: Figure 1 shown.

[0054] Example 2

[0055] Embodiment 2 of the present application provides a method for synthesizing a bionanofluid, comprising:

[0056] S2.1, Fe3O4 precursor was prepared by double microemulsion method, 28g n-hexanol, 20g n-hexane and 7g Triton X-100 were added to a 300ml conical flask, stirred at 40℃ for 10min to form a microemulsion, 0.2g FeSO4·7H2O and 0.2g FeCl3·6H2O were added, stirred slowly to make them fully dissolved, 2ml methylamine was added to keep the reaction for 5min, and then concentrated NH3·H2O was added dropwise until the color turned black, and stirring was maintained continuously. During this period, vigorous stirring was avoided to introduce too much oxygen and excessive temperature to avoid enlarging the nanoparticle size;

[0057] S2.2, add 5ml n-hexane, 0.2ml TEOS, 2ml pure water and 3ml ethanol to a 50ml beaker, stir well and add to the reverse microemulsion. Since TEOS and water have poor mutual solubility, while ethanol can be well miscible with both, the phenomenon of turbidity and stratification caused by the reaction between the two is avoided. TEOS molecules diffuse from the hydrophobic phase to the hydrophilic phase, and hydrolyze and condense around the Fe3O4 precursor. On the one hand, the addition of ethanol can replace the non-bridging hydroxyl groups on the surface of Fe3O4 with organic groups, reduce the attraction of particles, and reduce the agglomeration ability of particles; on the other hand, it reduces the interfacial tension of water, so that the SiO2 coating layer is better formed and the stability of the particles is improved; continue to heat at 50℃ The mixture was heated and stirred for 1 hour to further promote the condensation reaction of TEOS; the upper liquid was discarded after centrifugation at 5°C and 8000rpm, and the precipitate was collected; the mixture was washed with ethanol and pure water five times, and the precipitate was collected by repeated centrifugation; finally, the volume of the magnetic nanofluid was fixed to 150ml, and the nanoparticles were evenly dispersed by ultrasound. The ultrasound parameters were set to 20s each time, 2s interval, and 30 times in total. The magnetic nanofluid formed had good stability because the SiO2 coating on the ferrite contained rich hydrophilic silanol groups, which could attract a large number of water molecules, thus promoting the good dissolution and monodispersion of the nanoparticles in water;

[0058] S2.3, add 0.02g of PdCl2 and 20ml of Pseudomonas aeruginosa fermentation supernatant to another conical flask, dilute to 100ml with pure water, and stir magnetically at 70℃ for 5h. During this process, the color of the liquid gradually deepens from light gray to brown, and finally turns completely black, confirming the synthesis of nanoparticles. The position, symmetry, narrowness and / or width of SPR can not only provide information about the existence of nanoparticles, but also provide information about shape, size, agglomeration or oxidation. For example, spherical particles have only one scattering peak, while rod-shaped, triangular prism and cube-shaped particles show multiple scattering peaks. The maximum absorption peak at 350-450nm is the typical SPR detection range of nanopalladium particles.

[0059] S2.4, adding the nanopalladium fluid dropwise into the magnetic nanofluid, heating and stirring at 70°C for 3h, so that the nanopalladium modified by the microbial metabolism supernatant is fully loaded on the Fe3O4@SiO2 surface, and the volume is fixed to 200ml with pure water, and finally the Pseudomonas aeruginosa fermentation supernatant-mediated synthesis of palladium-loaded (Fe3O4@SiO2-Pd) magnetic nanofluid is obtained, and the separation ability of the magnetic nanoparticles is observed by a neodymium magnet;

[0060] S2.5, characterize the powder and use SEM-EDX and TEM to characterize the morphology and size of the nanoparticles. The SEM-EDX test steps are as follows: take a trace amount of powder sample and stick it directly on the conductive glue, and use Quorum SC7620 sputtering coater to spray gold for 45s, the gold spraying current is 10mA, and the gold spraying target is pure gold; then use SEM to photograph the sample morphology, energy spectrum EDS point scan and surface scan test, the acceleration voltage is 3kV when taking the morphology, and the acceleration voltage is 15kV when taking the energy spectrum mapping, and the detector is SE2 secondary electron detector;

[0061] TEM test steps: take the sample and disperse it in aqueous solution for 10 minutes of ultrasonic treatment, then drop the dispersed liquid onto the copper mesh, and after drying, use TEM to photograph the sample morphology, with an accelerating voltage of 200 kV and a thermal emission electron gun of W filament; use FTIR to characterize the functional groups on the surface of the nanoparticles and analyze the structure of biological organic matter. Test process: take 1-2 mg of powder sample and 200 mg of pure KBr, grind them evenly, put them in a mold, press them into a transparent sheet on a hydraulic press, and put the sample into FTIR for testing, with a wave number range of 4000-400 cm -1 , scan times 32, resolution 4cm -1 ;like Figure 5a , Figure 5b As shown, VSM was used to analyze the magnetic properties of bionanomaterials. The test conditions were: 5 cm pole diameter, room temperature measurement sensitivity of 5×10 -7 emu, moment measurement range 5×10 -7 emu~10 3 emu, maximum magnetic field 2.17T@16.2mm pole head spacing;

[0062] It should be noted that palladium can also be replaced by copper, silver, zinc, cobalt, and nickel.

[0063] It is known that bio-nanofluids have Tyndall effect, good response to magnetic field, viscosity <30cp, and good injectability, such as Figure 2-4 As shown, the Zeta potential is -48.2mV, the surface of the nanoparticles is negatively charged and can maintain long-term stable dispersion. TEM shows that the nanoparticle size is only 30-50nm, showing a wrapped core-shell structure with a shell layer of about 10nm; FTIR shows that the main functional groups C=O and CN are involved in the surface modification of the nanoparticles; VSM shows that the material has good superparamagnetism, with a high saturation magnetization intensity of 11.3emu / g, and a coercive force of only 1.8G, which has good application potential.

[0064] Example 3

[0065] Example 3 of the present application provides a method for measuring interfacial tension using a spinning drop method, comprising:

[0066] Bio-nanofluids of different concentrations were injected into the sample tube using a microinjector, and oil droplets were sent to the center of the liquid to place the droplets in a certain centrifugal field to avoid contact with the surface of the sample tube. The instrument speed was adjusted to 8000 rpm. At this time, the oil droplets were elongated under the combined action of centrifugal force and interfacial tension. The interfacial tension values ​​of nanofluids of different concentrations were obtained through video image analysis.

[0067] Embodiment 3 of the present application provides a microscopic oil stripping experimental method, comprising:

[0068] Static stripping of oil droplets: the quartz plate was pretreated at 90℃ for 1h, immersed in a mixed solution (concentrated H2SO4:H2O2=1:4) to remove residual organic impurities on the surface, washed with pure water for many times, dried for standby use, crude oil was dropped on the surface of the quartz plate, and it was quickly turned upside down in a square container filled with oil-displacing agent nano-palladium-loaded magnetic silica fluid to observe the changes in the oil droplets; dynamic stripping of oil film: one end of the capillary was immersed in simulated oil, and crude oil entered the tube under the action of capillary force, and it was slowly inverted 90° and repeated many times, covering the inner wall of the capillary with a layer of oil film, and a section of formation water and oil-displacing agent were sucked in the same way to observe the stripping effect on the oil film, and the difference in oil film stripping on the inner wall of different plugs was observed under a microscope;

[0069] Example 3 of the present application provides an experimental method for absorbing crude oil through an oil displacement agent, comprising:

[0070] A 0.5mD dense core was selected and dried in an oven for 8h to be thoroughly dried, and the initial mass was weighed. The core was evacuated with a vacuum pump for 24h, and the simulated formation water was used to saturate the core for 72h. The saturated core was taken out, the core surface was wiped dry and the mass was weighed, and the pore saturated water volume was calculated. The core was displaced with simulated oil at 0.5mL / min until oil was continuously seen at the outlet, and then soaked in simulated oil for 72h to establish bound water saturation. The oil on the core surface was wiped clean and the core mass was weighed. The saturated simulated oil volume was calculated by the oil-water density difference. The core was quickly transferred to an imbibition bottle, and crude oil was imbibed by an oil displacement agent. The simulated formation water was used as a control to compare the crude oil seepage capacity.

[0071] The simulated oil-water interfacial tension is 22.51mN / m. As a control, under the action of centrifugal force, the bio-nanofluid with a concentration of only 100ppm can easily elongate and disperse the oil droplets, reducing the interfacial tension to 4.2mN / m. Microscopic peeling of oil droplets shows that nanoparticles can quickly separate the oil droplets from the quartz plate, and disperse into a sheet-like oil film after rising to the upper surface. The wedge-shaped structure separation pressure "shovels" the oil droplets. The dynamic oil film peeling experiment shows that the nanoparticles have a large specific surface area and strong adsorption capacity, and can "roll up the remaining oil". The absorption experiment shows that the bio-nanofluid has increased the absorption of crude oil by 117.9% compared with the simulated formation water, and the effect is obvious. The core surface is clean and the oil droplets are efficiently separated from the core surface. The permeability cores of 8mD, 50mD and 130mD were selected for oil displacement experiments. The bio-nanofluid can play a good effect in medium and high permeability cores, and the recovery rate is increased by about 20.3%.

[0072] In summary, the palladium-loaded magnetic silica nanofluid synthesized by the Pseudomonas aeruginosa fermentation supernatant provided in the examples of the present application can be used to improve oil recovery, is environmentally friendly, and has an obvious oil displacement effect.

[0073] The present invention is not limited by the above embodiments. The above embodiments and descriptions are only for explaining the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, which are within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A palladium-loaded magnetic silica nanofluid, characterized in that: The magnetic Fe3O4 nano-precursor was prepared by double microemulsion method; TEOS hydrolysis is used as the shell material; Palladium was synthesized using Pseudomonas aeruginosa fermentation broth and loaded on the surface of magnetic silica nanomaterials.

2. A method for preparing a palladium-loaded magnetic silica nanofluid as claimed in claim 1, characterized in that: include: Step 1, culturing and fermenting Pseudomonas aeruginosa to purify metabolites, wherein glycolipids and amino acid active ingredients are produced in the metabolites; Step 2, preparing magnetic Fe3O4 nano precursor by double microemulsion method; Step 3, n-hexane, TEOS, pure water and ethanol are stirred evenly and then added to the reverse microemulsion, and heated and stirred at 50° C. for 1 hour to promote the condensation reaction of TEOS, and centrifuged at 5° C. and 8000 rpm to pour off the upper liquid, collect the precipitate, and wash it with ethanol and pure water to obtain the magnetic nanofluid; Step 4, adding PdCl2 and Pseudomonas aeruginosa fermentation supernatant into a container, and magnetically stirring at 70° C. for 5 h to obtain a nano-palladium fluid; Step 5, adding the nanopalladium fluid dropwise into the magnetic nanofluid, heating and stirring at 70° C. for 3 h, so that the nanopalladium modified with the microbial metabolic supernatant is fully loaded on the Fe3O4@SiO2 surface.

3. The preparation method of palladium-loaded magnetic silica nanofluid according to claim 2, wherein Step 1 includes: Step 1.1, preparing a fermentation medium, wherein the medium comprises: The carbon sources were glucose and corn syrup powder; The nitrogen sources are NaNO3 and CaMg(NO3)4; The phosphorus source is K2HPO4; Corn oil; The trace elements are a mixture of ZnSO4·7H2O, CuSO4·5H2O, Ni(NO3)2·6H2O, MnSO4·4H2O and FeSO4·7H2O; Sterilize the culture medium in a high pressure steam cooker at 121°C for 20 minutes, and after cooling naturally, take it out and carry out inoculation operation on a clean bench; Step 1.2, obtaining microbial fermentation supernatant; The refrigerated Pseudomonas aeruginosa was taken out, thawed and activated at room temperature for 15 minutes, 1 ml of bacterial solution was inoculated into the culture medium, covered with a sealing film, placed in a constant temperature incubator at 37°C and 180 rpm for mixing and shaking for 72 hours, and the fermentation liquid was ultrasonically treated for 10 minutes using an ultrasonic cell disruptor, with each ultrasonication for 6 seconds and an interval of 4 seconds; the fermentation liquid was placed in a 50 ml centrifuge tube, and the centrifuge parameters were adjusted to 4°C and 8000 rpm for centrifugation for 15 minutes to remove precipitated impurities to obtain a supernatant; a distillate was obtained by heating at 260°C through a distillation device; the distillate was filtered using a vacuum pump, filter paper and suction flask combination device to obtain a purified Pseudomonas aeruginosa fermentation supernatant.

4. The preparation method of palladium-loaded magnetic silica nanofluid according to claim 3, characterized in that, Step 1 includes the step of detecting the components of the Pseudomonas aeruginosa fermentation supernatant.

5. The preparation method of palladium-loaded magnetic silica nanofluid according to claim 2, characterized in that, Step 2: preparing a magnetic Fe3O4 nano precursor by a double microemulsion method comprises: Add n-hexanol, n-hexane and Triton X-100 to a container, stir at 40°C for 10 min to form a microemulsion, add FeSO4·7H2O and FeCl3·6H2O, stir to fully dissolve, add methylamine and keep reacting for 5 min, then add concentrated NH3·H2O dropwise until the color turns black, and keep stirring.

6. The preparation method of palladium-loaded magnetic silica nanofluid according to claim 2, characterized in that, In step 3, the magnetic nanofluid is obtained and the nanoparticles are evenly dispersed using ultrasound, and the ultrasound parameters are set to 20 seconds each time, 2 seconds interval, and a total of 30 times.

7. The preparation method of palladium-loaded magnetic silica nanofluid according to claim 2, characterized in that, Step 4 includes a step of detecting the surface plasmon resonance band SPR of nano-palladium by UV-Vis to confirm the synthesis of nanoparticles.

8. Application of the palladium-loaded magnetic silica nanofluid according to any one of claims 1 or 2-7 in enhancing crude oil recovery.

9. An oil displacing agent, characterized in that: The oil displacing agent comprises the palladium-loaded magnetic silica nanofluid as described in any one of claims 2-7.

10. The oil-displacing agent according to claim 9, characterized in that In the palladium-loaded magnetic silica nanofluid, the palladium loading is less than 10 wt %.

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