Method for evaluating catalytic activity of metal oxide based on multi-field coupling effect

Abstract

The present application relates to the field of metal oxide catalytic material application evaluation, and discloses a metal oxide catalytic activity evaluation method based on multi-field coupling, comprising: realizing independent regulation and coupling loading of temperature, fluid pressure and confining pressure through a triaxial pressure reaction container, taking hydrogen peroxide as a probe reaction liquid, obtaining steady-state titration data through single-factor and orthogonal experiments, calculating catalytic conversion rate excluding non-catalytic interference to quantify catalytic activity, constructing a grey correlation model containing single-field variable and double-field interaction term, and calculating coupling contribution rate to complete quantitative evaluation; The present application solves the problem that the prior art cannot meet the precise evaluation requirement of metal oxide catalytic activity under real formation environment, can accurately simulate real multi-field working conditions of the formation, eliminate evaluation deviation, and is suitable for natural metal oxide activity screening of oil and gas formation and performance characterization of catalytic materials under multi-field coupling working conditions.

Description

Technical Field

[0001] This invention relates to the field of application evaluation of metal oxide catalytic materials, and in particular to a method for evaluating the catalytic activity of metal oxides based on multi-field coupling. Background Technology

[0002] Metal oxides are widely present natural catalysts in oil and gas formations, and their catalytic activity is jointly controlled by formation temperature, fluid pressure, and tectonic stress. The stress field can significantly regulate the electronic states, oxygen vacancy concentration, and catalytic activity of metal oxide surfaces through mechanochemical coupling effects, and is a key factor affecting the actual catalytic behavior of formations.

[0003] Current methods for evaluating catalytic activity mainly rely on thermogravimetric analysis, in-situ spectroscopic characterization, and high-pressure intermittent reaction evaluation. These methods can only couple temperature and pressure variables, failing to apply controllable mechanical stress to the samples, leaving them in a state of zero stress or freedom. This limitation leads to a fundamental difference between the experimental environment and the actual multi-field coupling conditions in oil and gas formations. The evaluation results exhibit systematic deviations from actual formation catalytic behavior, failing to capture the dynamic impact of stress redistribution on catalytic activity in deep and unconventional oil and gas development, and hindering the quantitative analysis of synergistic regulatory effects of multi-field coupling.

[0004] Therefore, existing technologies cannot meet the requirements for accurate evaluation of the catalytic activity of metal oxides in real formation environments. There is an urgent need to establish a method for evaluating the catalytic activity of metal oxides that can simultaneously achieve independent control and coupled loading of temperature, fluid pressure, and confining pressure (stress). Summary of the Invention

[0005] The present invention aims to provide a method for evaluating the catalytic activity of metal oxides based on multi-field coupling, in order to solve the problem that the existing technology cannot meet the requirements for accurate evaluation of the catalytic activity of metal oxides in real formation environments.

[0006] To achieve the above objectives, the present invention provides the following method:

[0007] This invention provides a method for evaluating the catalytic activity of metal oxides based on multi-field coupling:

[0008] S1: Sample preparation and loading: Metal oxide powder is prepared into standard samples with completely consistent geometric parameters and contact areas through constant pressure pressing process. The standard samples are loaded into a triaxial pressure reaction vessel in which temperature, fluid pressure and confining pressure can be independently and closed-loop controlled. The confining pressure is used to apply controllable mechanical stress to the standard samples.

[0009] S2: System pretreatment: Using hydrogen peroxide solution as the probe reaction solution, the probe reaction solution is continuously introduced into the triaxial pressure reaction vessel at a constant flow rate to rinse the internal pipelines of the triaxial pressure reaction vessel and the standard sample, thereby eliminating system errors caused by initial sample adsorption and dead volume of the pipeline.

[0010] S3: Multi-field coupling experiment: First, the range of variables is locked through single-factor experiments. Then, with temperature, fluid pressure and confining pressure as three experimental factors, a three-factor, five-level standard orthogonal experimental scheme is adopted to carry out continuous flow catalytic reaction experiments under various set operating conditions.

[0011] S4: Steady-state determination and sampling detection: After the catalytic reaction reaches steady state, the effluent is continuously collected at a flow rate consistent with the injection flow rate. The effluent is quantitatively detected by redox titration to obtain effective titration data for the corresponding operating conditions.

[0012] S5: Quantitative characterization of catalytic activity: Based on the titration values ​​of the blank group, the titration values ​​of the sample group and the theoretical titration value at the inlet, the catalytic conversion rate after deducting non-catalytic thermal decomposition interference is calculated, and the catalytic conversion rate is used to quantitatively characterize the catalytic activity of the metal oxide under the corresponding multi-field coupling condition.

[0013] S6: Quantitative evaluation of multi-field coupling effect: Construct a grey relational analysis model containing single-field variables and dual-field interaction terms, calculate the grey relational degree of each variable and the contribution rate of multi-field coupling, clarify the influence weight and coupling law of each factor on catalytic activity, and complete the quantitative evaluation of the catalytic activity of metal oxides under temperature-pressure-stress multi-field coupling.

[0014] Preferably, the metal oxide is iron oxide powder; the constant pressure pressing process is dry constant pressure pressing at room temperature, with a pressing pressure of 20 MPa and a holding time of 5 min; the standard sample is a standard columnar sample with a diameter of 10 mm and a height of 20 mm, or a standard disc sample with a diameter of 20 mm and a thickness of 5 mm, obtained by the constant pressure pressing process; the probe reaction solution is a 1% hydrogen peroxide standard solution prepared with ultrapure water.

[0015] Preferably, the system pretreatment in step S2 specifically involves: continuously introducing the probe reaction solution into the triaxial pressure reaction vessel under normal temperature and pressure conditions, controlling the flow rate to be constant at 0.1 mL / min, and rinsing for at least 30 min; after rinsing, collecting the outlet liquid for titration, and determining that the system pretreatment is qualified when the relative deviation between the outlet liquid titration value and the inlet theoretical titration value is ≤0.5%.

[0016] Preferably, in step S3, the variable range is first determined through single-factor experiments, and then temperature, fluid pressure, and confining pressure are used as three experimental factors. A three-factor, five-level standard orthogonal experimental scheme is adopted to carry out continuous flow catalytic reaction experiments under various set operating conditions. Specifically, the temperature factor level is set to 30℃, 60℃, 90℃, 120℃, and 150℃ for both the single-factor experiment and the orthogonal experiment. During the temperature single-factor experiment, the confining pressure and fluid pressure are fixed at 10MPa. The confining pressure factor level is set to 10MPa for both the single-factor experiment and the orthogonal experiment. The confining pressure was set to 10 MPa, 20 MPa, 30 MPa, 40 MPa, and 50 MPa. The temperature was fixed at 90℃ and the fluid pressure at 10 MPa during the single-factor confining pressure experiment. The fluid pressure factor level was set to 5 MPa, 10 MPa, 15 MPa, 20 MPa, and 25 MPa for both the single-factor experiment and the orthogonal experiment. The temperature was fixed at 90℃ and the confining pressure at 10 MPa during the single-factor confining pressure experiment. At least three parallel repeated experiments were set for each single-factor experimental condition and each level combination of the orthogonal experiment.

[0017] Preferably, the steady-state determination and sampling detection in step S4 are specifically as follows: the potassium permanganate standard solution acidified with sulfuric acid is used as the redox titration method, and the titration endpoint determination criterion is that the test solution turns a stable slightly red color and does not fade within 30 seconds; after each set of working conditions has been continuously and stably reacted for 15 minutes, three 1 mL effluent samples are continuously collected, and the samples are detected by the redox titration method; when the difference in titration consumption of the three samples is less than 0.1 mL, the catalytic reaction is determined to have reached a steady state, and the average value of the titration values ​​of the three samples is taken as the effective titration data of the working condition.

[0018] Preferably, the formula for calculating the catalytic conversion rate in step S5 is:

[0019] ;

[0020] In the formula: the inlet theoretical titration value is the volume of titration solution consumed by the complete reaction of 1 mL of the fresh probe reaction solution; the blank titration value is the outlet liquid titration value measured under the same operating conditions, process and parameter conditions as the sample group, using an equal volume of quartz sand inert medium to replace the standard sample, to deduct the consumption of non-catalytic thermal decomposition of hydrogen peroxide; the sample group titration value is the outlet liquid titration value measured under the corresponding operating conditions after loading the standard sample.

[0021] Preferably, the method for constructing the grey relational analysis model in step S6 is as follows: The catalytic conversion rate is used as the reference sequence X0; temperature T, confining pressure Pc, and fluid pressure Pf are used as single-factor comparison sequences, corresponding to X1, X2, and X3 respectively; the interaction terms T×Pc (temperature and confining pressure), T×Pf (temperature and fluid pressure), and Pc×Pf (confining pressure and fluid pressure) are used as dual-field interaction term comparison sequences, corresponding to X4, X5, and X6 respectively; an original data matrix is ​​constructed based on the above sequences; the original data matrix is ​​subjected to dimensionless normalization; the difference sequence and the maximum and minimum differences between the two levels are calculated; then the correlation coefficient of each comparison sequence is calculated; finally, the grey relational degree ri corresponding to each sequence is obtained, where i=1,2,3,4,5,6, and ri corresponds one-to-one with sequence Xi.

[0022] Preferably, the formula for calculating the multi-field coupling contribution rate in step S6 is:

[0023] ;

[0024] In the formula: r1 is the grey relational degree of the single-factor comparison sequence X1 corresponding to temperature; r2 is the grey relational degree of the single-factor comparison sequence X2 corresponding to confining pressure; r3 is the grey relational degree of the single-factor comparison sequence X3 corresponding to fluid pressure; r4 is the grey relational degree of the two-field interaction term comparison sequence X4 of temperature and confining pressure; r5 is the grey relational degree of the two-field interaction term comparison sequence X5 of temperature and fluid pressure; r6 is the grey relational degree of the two-field interaction term comparison sequence X6 of confining pressure and fluid pressure; when the coupling contribution rate is >20%, it is determined that the multi-field coupling effect between temperature, confining pressure and fluid pressure has a significant impact on catalytic activity; when the coupling contribution rate is >40%, it is determined that there is a significant synergistic coupling effect among the three fields.

[0025] Preferably, the influence weights of temperature, confining pressure, and fluid pressure on the catalytic activity of metal oxides are determined based on the values ​​of the grey relational degrees r1, r2, and r3 corresponding to the single-factor comparison sequence, and the correlation degree values ​​are positively correlated with the influence weights; the order of the main control of each factor on the catalytic activity is determined according to the influence weights from high to low.

[0026] Preferably, by combining the influence weights, the main control order, and the multi-field coupling contribution rate, and matching the temperature, pressure, and stress parameter ranges of the actual working conditions of oil and gas formations, an activity classification standard and a working condition adaptation screening method for metal oxide catalysts are established.

[0027] The beneficial effects of this invention are reflected in:

[0028] Filling the gap in stress dimension and restoring the real working conditions of the formation: By using a triaxial pressure reaction vessel to achieve independent control and coupled loading of temperature, fluid pressure and confining pressure, it accurately simulates the real multi-field environment of oil and gas formations, and solves the core defects of existing technologies that cannot apply controllable mechanical stress and that experiments are disconnected from actual working conditions.

[0029] Eliminating systematic biases and accurately quantifying catalytic activity: Through standardized pretreatment, blank control, and strict steady-state judgment rules, systematic errors such as initial adsorption and non-catalytic thermal decomposition are eliminated, enabling accurate quantification of the intrinsic catalytic activity of metal oxides and avoiding systematic evaluation biases of existing technologies.

[0030] Quantitative analysis of coupling effects and identification of catalytic controlling factors: Through a grey relational analysis model containing single-field variables and dual-field interaction terms, the influence weights, controlling order and multi-field coupling contribution rates of each factor can be accurately calculated, breaking through the technical bottleneck of existing technologies that cannot quantify multi-field coupling effects.

[0031] The process is standardized and repeatable with a wide range of applications: The standardized design of the entire process ensures the high reproducibility of experimental results. It is not only applicable to the activity evaluation and screening of natural metal oxides in oil and gas formations, but can also be extended to the performance characterization of various catalytic materials under multi-field coupling conditions, and has both scientific research and engineering application value. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0033] Figure 1 A schematic diagram of a method for evaluating the catalytic activity of metal oxides based on multi-field coupling is provided in an embodiment of the present invention.

[0034] Figure 2 The catalytic conversion rate versus temperature curve is provided for embodiments of the present invention;

[0035] Figure 3 The catalytic conversion rate versus confining pressure curve is provided for embodiments of the present invention.

[0036] Figure 4 The catalytic conversion rate versus fluid pressure curve is provided for an embodiment of the present invention. Detailed Implementation

[0037] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this invention are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, apparatus, product, or end that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or ends.

[0039] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0040] Current methods for evaluating catalytic activity mainly rely on thermogravimetric analysis, in-situ spectroscopic characterization, and high-pressure intermittent reaction evaluation. These methods can only couple temperature and pressure variables, failing to apply controllable mechanical stress to the samples, leaving them in a state of zero stress or freedom. This limitation leads to a fundamental difference between the experimental environment and the actual multi-field coupling conditions in oil and gas formations. The evaluation results exhibit systematic deviations from actual formation catalytic behavior, failing to capture the dynamic impact of stress redistribution on catalytic activity in deep and unconventional oil and gas development, and hindering the quantitative analysis of synergistic regulatory effects of multi-field coupling.

[0041] Therefore, existing technologies cannot meet the requirements for accurate evaluation of the catalytic activity of metal oxides in real formation environments. There is an urgent need to establish a method for evaluating the catalytic activity of metal oxides that can simultaneously achieve independent control and coupled loading of temperature, fluid pressure, and confining pressure (stress).

[0042] The present invention aims to provide a method for evaluating the catalytic activity of metal oxides based on multi-field coupling, in order to solve the problem that the existing technology cannot meet the requirements for accurate evaluation of the catalytic activity of metal oxides in real formation environments.

[0043] This invention provides a method for evaluating the catalytic activity of metal oxides based on multi-field coupling, comprising the following steps:

[0044] S1: Sample preparation and loading: Metal oxide powder is prepared into standard samples with identical geometric parameters and contact areas through constant pressure pressing process. The standard samples are loaded into a triaxial pressure reaction vessel with independently closed-loop control of temperature, fluid pressure and confining pressure. The confining pressure is used to apply controllable mechanical stress to the standard samples.

[0045] In this embodiment of the invention, the metal oxide is iron oxide powder; the constant pressure pressing process is dry constant pressure pressing at room temperature, with a pressing pressure of 20 MPa and a holding time of 5 min; the standard sample is a standard columnar sample with a diameter of 10 mm and a height of 20 mm, or a standard circular sample with a diameter of 20 mm and a thickness of 5 mm, obtained by the constant pressure pressing process.

[0046] S2: System pretreatment: Using hydrogen peroxide solution as the probe reaction solution, the probe reaction solution is continuously introduced into the triaxial pressure reaction vessel at a constant flow rate to rinse the internal pipelines and standard samples of the triaxial pressure reaction vessel, eliminating system errors caused by initial sample adsorption and dead volume of pipelines.

[0047] In this embodiment of the invention, the probe reaction solution is a 1% hydrogen peroxide standard solution prepared with ultrapure water. Under normal temperature and pressure conditions, the probe reaction solution is continuously introduced into the triaxial pressure reaction vessel, and the flow rate is controlled to be constant at 0.1 mL / min. The rinsing time is not less than 30 min. After rinsing, the outlet liquid is collected for titration. When the relative deviation between the outlet liquid titration value and the inlet theoretical titration value is ≤0.5%, the system pretreatment is deemed qualified.

[0048] S3: Multi-field coupling experiment: First, the range of variables is determined through single-factor experiments. Then, temperature, fluid pressure, and confining pressure are used as three experimental factors. A standard orthogonal experimental scheme with three factors and five levels is adopted to carry out continuous flow catalytic reaction experiments under various set operating conditions.

[0049] In this embodiment of the invention, the range of variables is first determined through single-factor experiments. Then, temperature, fluid pressure, and confining pressure are used as three experimental factors. A standard orthogonal experimental scheme with three factors and five levels is adopted to conduct continuous flow catalytic reaction experiments under various set operating conditions. Specifically, the temperature factor level is set to 30℃, 60℃, 90℃, 120℃, and 150℃ for both the single-factor and orthogonal experiments. During the single-factor temperature experiment, the confining pressure and fluid pressure are fixed at 10MPa. The confining pressure factor level is set to 10MPa for both the single-factor and orthogonal experiments. All pressures were set to 10MPa, 20MPa, 30MPa, 40MPa, and 50MPa. During the single-factor confining pressure experiment, the temperature was fixed at 90℃ and the fluid pressure was fixed at 10MPa. The fluid pressure factor levels for both the single-factor and orthogonal experiments were set to 5MPa, 10MPa, 15MPa, 20MPa, and 25MPa. During the single-factor fluid pressure experiment, the temperature was fixed at 90℃ and the confining pressure was fixed at 10MPa. Each single-factor experimental condition and each level combination in the orthogonal experiment was repeated at least three times.

[0050] S4: Steady-state determination and sampling detection: After the catalytic reaction reaches steady state, the effluent is continuously collected at a flow rate consistent with the injection flow rate. The effluent is quantitatively detected by redox titration to obtain effective titration data for the corresponding operating conditions.

[0051] In this embodiment of the invention, the potassium permanganate standard solution acidified with sulfuric acid is used as the redox titration method. The endpoint of the titration is determined by the test solution turning a stable, slightly red color that does not fade within 30 seconds. After each set of conditions has been continuously and stably reacted for 15 minutes, three 1 mL eluent samples are collected consecutively and tested using the redox titration method. When the difference in titration consumption of the three samples is less than 0.1 mL, the catalytic reaction is determined to have reached a steady state, and the average value of the titration values ​​of the three samples is taken as the effective titration data for that condition.

[0052] S5: Quantitative characterization of catalytic activity: Based on the titration values ​​of the blank group, the titration values ​​of the sample group and the theoretical titration value at the inlet, the catalytic conversion rate after deducting the interference of non-catalytic thermal decomposition is calculated, and the catalytic activity of the metal oxide under the corresponding multi-field coupling condition is quantitatively characterized by the catalytic conversion rate.

[0053] In this embodiment of the invention, the formula for calculating the catalytic conversion rate is:

[0054] ;

[0055] In the formula: the theoretical inlet titration value is the volume of titration solution consumed by the complete reaction of 1 mL of fresh probe reaction solution; the blank titration value is the outlet titration value measured under the same operating conditions, process and parameter conditions as the sample group, using an equal volume of quartz sand inert medium to replace the standard sample, to deduct the consumption of non-catalytic thermal decomposition of hydrogen peroxide; the sample group titration value is the outlet titration value measured under the corresponding operating conditions after loading the standard sample.

[0056] S6: Quantitative evaluation of multi-field coupling effect: Construct a grey relational analysis model containing single-field variables and dual-field interaction terms, calculate the grey relational degree of each variable and the contribution rate of multi-field coupling, clarify the influence weight and coupling law of each factor on catalytic activity, and complete the quantitative evaluation of the catalytic activity of metal oxides under temperature-pressure-stress multi-field coupling.

[0057] In this embodiment of the invention, the method for constructing the grey relational analysis model is as follows: The catalytic conversion rate is used as the reference sequence X0; temperature T, confining pressure Pc, and fluid pressure Pf are used as single-factor comparison sequences, corresponding to X1, X2, and X3 respectively; the interaction terms T×Pc (temperature and confining pressure), T×Pf (temperature and fluid pressure), and Pc×Pf (confining pressure and fluid pressure) are used as dual-field interaction term comparison sequences, corresponding to X4, X5, and X6 respectively; an original data matrix is ​​constructed based on the above sequences; the original data matrix is ​​subjected to dimensionless normalization; the difference sequence and the maximum and minimum differences between the two levels are calculated; then the correlation coefficient of each comparison sequence is calculated; finally, the grey relational degree ri corresponding to each sequence is obtained, where i=1,2,3,4,5,6, and ri corresponds one-to-one with the sequence Xi; the formula for calculating the multi-field coupling contribution rate is:

[0058] ;

[0059] In the formula: r1 is the grey relational degree of the single-factor comparison sequence X1 corresponding to temperature; r2 is the grey relational degree of the single-factor comparison sequence X2 corresponding to confining pressure; r3 is the grey relational degree of the single-factor comparison sequence X3 corresponding to fluid pressure; r4 is the grey relational degree of the comparison sequence X4 of the two-field interaction terms of temperature and confining pressure; r5 is the grey relational degree of the comparison sequence X5 of the two-field interaction terms of temperature and fluid pressure; r6 is the grey relational degree of the comparison sequence X6 of the two-field interaction terms of confining pressure and fluid pressure; when the coupling contribution rate is >20%, the influence of the multi-field coupling effect between temperature, confining pressure, and fluid pressure on catalytic activity is determined to be... It can be ignored; when the coupling contribution rate is >40%, it is determined that there is a significant synergistic coupling effect among the three fields; based on the magnitude of the gray correlation r1, r2, and r3 corresponding to the single-factor comparison sequence, the influence weights of temperature, confining pressure, and fluid pressure on the catalytic activity of metal oxides are determined, and the correlation value is positively correlated with the influence weight; according to the influence weight from high to low, the order of control of each factor on catalytic activity is determined; combining the influence weight, the order of control, and the multi-field coupling contribution rate, the temperature, pressure, and stress parameter ranges of the actual working conditions of oil and gas formations are matched, and the activity classification standard and working condition adaptation screening method of metal oxide catalysts are established.

[0060] Example 1

[0061] This embodiment uses iron oxide, which is widely found in oil and gas formations, as the evaluation object to conduct a catalytic activity evaluation under multi-field coupling effects. The specific steps are as follows:

[0062] Sample preparation and loading: Iron oxide powder was used to prepare standard samples using a room temperature dry constant pressure pressing process. The pressing pressure was 20 MPa and the holding time was 5 min, resulting in standard columnar samples with a diameter of 10 mm and a height of 20 mm, ensuring that the geometric parameters and contact area of ​​the samples were completely consistent. The prepared standard samples were loaded into a triaxial pressure reaction vessel with independently closed-loop control of temperature, fluid pressure, and confining pressure. Controllable mechanical stress was applied to the standard samples through the confining pressure.

[0063] The system pretreatment used a 1% hydrogen peroxide standard solution prepared with ultrapure water as the probe reaction solution. Under normal temperature and pressure conditions, the probe reaction solution was continuously introduced into the triaxial pressure reaction vessel at a constant flow rate of 0.1 mL / min for 30 min to eliminate systematic errors caused by initial sample adsorption and dead volume in the pipeline. After rinsing, the outlet liquid was collected for titration. When the relative deviation between the outlet liquid titration value and the inlet theoretical titration value was ≤0.5%, the system pretreatment was deemed qualified.

[0064] The multi-field coupling experiment first determined the variable range through single-factor experiments, and then used temperature, fluid pressure, and confining pressure as three experimental factors, employing a 3-factor, 5-level L-factor model. 25 A standard orthogonal experimental design was used to conduct continuous flow catalytic reaction experiments, with the following specific parameter settings:

[0065] Temperature single-factor experiment: The temperature gradient was set to 30℃, 60℃, 90℃, 120℃, and 150℃. During the experiment, the confining pressure was fixed at 10MPa and the fluid pressure was fixed at 10MPa.

[0066] Single-factor confining pressure experiment: The confining pressure gradient was set to 10MPa, 20MPa, 30MPa, 40MPa and 50MPa. The temperature was fixed at 90℃ and the fluid pressure was fixed at 10MPa during the experiment.

[0067] Single-factor fluid pressure experiment: The fluid pressure gradient was set to 5MPa, 10MPa, 15MPa, 20MPa and 25MPa. The temperature was fixed at 90℃ and the confining pressure was 10MPa during the experiment. Each single-factor experimental condition and each level combination of the orthogonal experiment was set up with 3 parallel repeated experiments.

[0068] Steady-state determination and sampling detection adopted the potassium permanganate standard solution acidified with sulfuric acid titration as the redox titration method. The titration endpoint was determined when the test solution turned a stable, slightly red color and did not fade within 30 seconds. After each set of operating conditions and the reaction was stable for 15 minutes, three 1 mL eluent samples were collected continuously and tested using the above titration method. When the difference in titration consumption of the three samples was less than 0.1 mL, the catalytic reaction was determined to have reached steady state, and the average value of the titration values ​​of the three samples was taken as the effective titration data for that operating condition.

[0069] Quantitative characterization of catalytic activity was conducted concurrently with a blank control experiment. An equal volume of inert quartz sand was used as a substitute for the iron oxide standard sample. Testing was performed under identical operating conditions, processes, and parameters as the sample group, and the blank titration value was obtained. Based on the blank titration value, the sample titration value, and the theoretical inlet titration value, the catalytic conversion rate, after deducting interference from non-catalytic thermal decomposition, was calculated using the catalytic conversion rate formula. The catalytic conversion rate was used to quantitatively characterize the catalytic activity of iron oxide under the corresponding operating conditions. The single-factor experimental results of this embodiment are as follows:

[0070] Effect of temperature on catalytic conversion rate: The catalytic conversion rate was 3.7% at 30℃, 7.8% at 60℃, 15.1% at 90℃, 23.1% at 120℃, and 27.8% at 150℃. The catalytic conversion rate increased significantly with increasing temperature, and the sensitivity was highest in the 90~120℃ range.

[0071] Effect of confining pressure on catalytic conversion rate: The catalytic conversion rate was 27.0% at 10 MPa, 26.1% at 20 MPa, 24.4% at 30 MPa, 23.1% at 40 MPa, and 21.4% at 50 MPa. The catalytic conversion rate decreased slowly with increasing confining pressure, and the sample still maintained high activity under high stress.

[0072] Effect of fluid pressure on catalytic conversion rate: The catalytic conversion rate is 27.8% at 5 MPa, 27.0% at 10 MPa, 26.4% at 15 MPa, 25.9% at 20 MPa, and 25.3% at 25 MPa. The catalytic conversion rate decreases slightly with increasing fluid pressure, and the effect of fluid pressure on catalytic activity is weak.

[0073] A grey relational analysis model was constructed to quantitatively evaluate the multi-field coupling effect: catalytic conversion rate was used as the reference sequence X0; temperature T, confining pressure Pc, and fluid pressure Pf were used as single-factor comparison sequences X1, X2, and X3; and T×Pc, T×Pf, and Pc×Pf were used as two-field interaction term comparison sequences X4, X5, and X6, thus constructing the original data matrix. The data were then subjected to dimensionless normalization, and the grey relational degrees of each sequence were calculated as follows: r1=0.892, r2=0.621, r3=0.315, r4=0.783, r5=0.526, and r6=0.217. The multi-field coupling contribution rate was calculated as follows: Coupling contribution rate = (0.783 + 0.526 + 0.217) / (0.892 + 0.621 + 0.315 + 0.783 + 0.526 + 0.217) × 100% = 48.7%, which is greater than 40%, indicating a significant synergistic coupling effect among temperature, confining pressure, and fluid pressure. Based on the single-factor correlation, the influence weights and control order were determined: temperature was the primary controlling factor, confining pressure was the secondary controlling factor, and fluid pressure was the secondary influencing factor. Combining these results, the actual operating condition parameter range of the oil and gas formation was matched to establish an activity grading standard and operating condition adaptation screening method for iron oxide catalysts.

[0074] Comparative Example 1

[0075] This comparative example uses the conventional high-pressure reactor intermittent evaluation method to evaluate the catalytic activity of the same iron oxide sample as in Example 1. This method can only couple temperature and pressure variables, and cannot apply controllable confining pressure (mechanical stress). The experimental temperature was 90℃ and the fluid pressure was 10MPa. The other reagents and titration methods were consistent with Example 1. The test results show that the catalytic conversion rate measured in this comparative example was 18.7%, which is significantly different from the 15.1% catalytic conversion rate under the same conditions in Example 1, with a deviation rate of 23.8%. This proves that the existing technology lacks the stress dimension, and the evaluation results have a systematic deviation from the catalytic behavior under actual operating conditions. The present invention can effectively reproduce the actual formation conditions, and the evaluation results are more accurate and reliable.

[0076] The above descriptions are merely embodiments of the present invention. Commonly known technical solutions or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for evaluating the catalytic activity of metal oxides based on multi-field coupling, characterized in that, The method includes: S1: Sample preparation and loading: Metal oxide powder is prepared into standard samples with completely consistent geometric parameters and contact areas through constant pressure pressing process. The standard samples are loaded into a triaxial pressure reaction vessel in which temperature, fluid pressure and confining pressure can be independently and closed-loop controlled. The confining pressure is used to apply controllable mechanical stress to the standard samples. S2: System pretreatment: Using hydrogen peroxide solution as the probe reaction solution, the probe reaction solution is continuously introduced into the triaxial pressure reaction vessel at a constant flow rate to rinse the internal pipelines of the triaxial pressure reaction vessel and the standard sample, thereby eliminating system errors caused by initial sample adsorption and dead volume of the pipeline. S3: Multi-field coupling experiment: First, the range of variables is locked through single-factor experiments. Then, with temperature, fluid pressure and confining pressure as three experimental factors, a three-factor, five-level standard orthogonal experimental scheme is adopted to carry out continuous flow catalytic reaction experiments under various set operating conditions. S4: Steady-state determination and sampling detection: After the catalytic reaction reaches steady state, the effluent is continuously collected at a flow rate consistent with the injection flow rate. The effluent is quantitatively detected by redox titration to obtain effective titration data for the corresponding operating conditions. S5: Quantitative characterization of catalytic activity: Based on the titration values ​​of the blank group, the titration values ​​of the sample group and the theoretical titration value at the inlet, the catalytic conversion rate after deducting non-catalytic thermal decomposition interference is calculated, and the catalytic conversion rate is used to quantitatively characterize the catalytic activity of the metal oxide under the corresponding multi-field coupling condition. S6: Quantitative evaluation of multi-field coupling effect: Construct a grey relational analysis model containing single-field variables and dual-field interaction terms, calculate the grey relational degree of each variable and the contribution rate of multi-field coupling, clarify the influence weight and coupling law of each factor on catalytic activity, and complete the quantitative evaluation of the catalytic activity of metal oxides under temperature-pressure-stress multi-field coupling.

2. The method for evaluating the catalytic activity of metal oxides based on multi-field coupling as described in claim 1, characterized in that: The metal oxide is iron oxide powder; The constant pressure pressing process is a dry constant pressure pressing at room temperature, with a pressing pressure of 20 MPa and a holding time of 5 min. The standard sample is a standard cylindrical sample with a diameter of 10 mm and a height of 20 mm, or a standard circular sample with a diameter of 20 mm and a thickness of 5 mm, obtained by the constant pressure pressing process. The probe reaction solution is a 1% hydrogen peroxide standard solution prepared with ultrapure water.

3. The method for evaluating the catalytic activity of metal oxides based on multi-field coupling as described in claim 1, characterized in that: The system pretreatment described in step S2 specifically involves: continuously introducing the probe reaction solution into the triaxial pressure reaction vessel under normal temperature and pressure conditions, controlling the flow rate to be constant at 0.1 mL / min, and rinsing for at least 30 min; After rinsing, the outlet liquid is collected and titrated. When the relative deviation between the outlet liquid titration value and the inlet theoretical titration value is ≤0.5%, the system pretreatment is deemed qualified.

4. The method for evaluating the catalytic activity of metal oxides based on multi-field coupling as described in claim 1, characterized in that: In step S3, the range of variables is first determined through single-factor experiments. Then, with temperature, fluid pressure, and confining pressure as three experimental factors, a three-factor, five-level standard orthogonal experimental scheme is adopted to carry out continuous flow catalytic reaction experiments under various set operating conditions. The specific method is as follows: Temperature factor levels: The temperature levels of the single-factor experiment and the orthogonal experiment were set to 30℃, 60℃, 90℃, 120℃, and 150℃. During the single-factor temperature experiment, the confining pressure was fixed at 10MPa and the fluid pressure was fixed at 10MPa. Confining pressure factor levels: The confining pressure levels of the single-factor experiment and the orthogonal experiment were set to 10MPa, 20MPa, 30MPa, 40MPa and 50MPa respectively. The temperature was fixed at 90℃ and the fluid pressure was fixed at 10MPa during the single-factor confining pressure experiment. Fluid pressure factor levels: The fluid pressure levels of the single-factor experiment and the orthogonal experiment were set to 5MPa, 10MPa, 15MPa, 20MPa and 25MPa respectively. The temperature was fixed at 90℃ and the confining pressure was fixed at 10MPa during the single-factor fluid pressure experiment. For each single-factor experimental condition and each level combination of the orthogonal experiment, at least three parallel replicate experiments are set up.

5. The method for evaluating the catalytic activity of metal oxides based on multi-field coupling as described in claim 4, characterized in that: The steady-state determination and sampling detection in step S4 are specifically as follows: the potassium permanganate standard solution acidified with sulfuric acid is used as the redox titration method, and the titration endpoint determination criterion is that the test solution is stable and slightly red and does not fade within 30 seconds; After each set of operating conditions has been continuously and stably reacted for 15 minutes, three 1 mL effluent samples are collected consecutively and tested using the redox titration method described above. When the difference in titration consumption of the three samples is less than 0.1 mL, the catalytic reaction is determined to have reached a steady state, and the average value of the titration of the three samples is taken as the effective titration data for that operating condition.

6. The method for evaluating the catalytic activity of metal oxides based on multi-field coupling as described in claim 1, characterized in that: The formula for calculating the catalytic conversion rate in step S5 is as follows: ； In the formula: the theoretical inlet titration value is the volume of titration solution consumed by the complete reaction of 1 mL of the fresh probe reaction solution; the blank titration value is the outlet titration value measured under the same operating conditions, process and parameter conditions as the sample group, using an equal volume of quartz sand inert medium to replace the standard sample, and is used to deduct the consumption of non-catalytic thermal decomposition of hydrogen peroxide. The sample group titration value is the outlet liquid titration value measured under the corresponding operating conditions after the standard sample is loaded.

7. The method for evaluating the catalytic activity of metal oxides based on multi-field coupling as described in claim 1, characterized in that: The method for constructing the grey relational analysis model described in step S6 is as follows: The catalytic conversion rate is used as the reference sequence X0; temperature T, confining pressure Pc, and fluid pressure Pf are used as single-factor comparison sequences, corresponding to X1, X2, and X3 respectively; temperature and confining pressure interaction term T×Pc, temperature and fluid pressure interaction term T×Pf, and confining pressure and fluid pressure interaction term Pc×Pf are used as two-field interaction term comparison sequences, corresponding to X4, X5, and X6 respectively. Based on the above sequences, an original data matrix is ​​constructed. The original data matrix is ​​then subjected to dimensionless normalization. The difference sequence and the maximum and minimum differences between the two levels are calculated. Then, the correlation coefficient of each comparison sequence is calculated, and finally, the gray correlation degree ri corresponding to each sequence is obtained, where i=1,2,3,4,5,6, and ri corresponds one-to-one with the sequence Xi.

8. The method for evaluating the catalytic activity of metal oxides based on multi-field coupling as described in claim 7, characterized in that: The formula for calculating the multi-field coupling contribution rate in step S6 is as follows: ； In the formula: r1 is the grey relational degree of the single-factor comparison sequence X1 corresponding to temperature; r2 is the grey relational degree of the single-factor comparison sequence X2 corresponding to confining pressure; r3 is the grey relational degree of the single-factor comparison sequence X3 corresponding to fluid pressure; r4 is the grey relational degree of the two-field interaction term comparison sequence X4 of temperature and confining pressure; r5 is the grey relational degree of the two-field interaction term comparison sequence X5 of temperature and fluid pressure; r6 is the grey relational degree of the two-field interaction term comparison sequence X6 of confining pressure and fluid pressure; when the coupling contribution rate is >20%, it is determined that the multi-field coupling effect between temperature, confining pressure and fluid pressure has a significant impact on catalytic activity; when the coupling contribution rate is >40%, it is determined that there is a significant synergistic coupling effect among the three fields.

9. The method for evaluating the catalytic activity of metal oxides based on multi-field coupling as described in claim 8, characterized in that: Based on the values ​​of the grey relational degrees r1, r2, and r3 corresponding to the single-factor comparison sequence, the influence weights of temperature, confining pressure, and fluid pressure on the catalytic activity of metal oxides are determined. The correlation degree values ​​are positively correlated with the influence weights. According to the influence weights from high to low, the order of the main control of each factor on catalytic activity is determined.

10. The method for evaluating the catalytic activity of metal oxides based on multi-field coupling as described in claim 9, characterized in that: Based on the aforementioned influence weights, master control order, and multi-field coupling contribution rates, and matching the temperature, pressure, and stress parameter ranges of actual oil and gas formation conditions, an activity grading standard and a condition-adaptive screening method for metal oxide catalysts are established.

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