A test method and apparatus for simulating hcs poisoning of a diesel aftertreatment catalyst

Abstract

The application discloses a test method and equipment for simulating HCs poisoning of a diesel engine aftertreatment catalyst, and the test method is a simple and efficient catalyst poisoning simulation method, which can simulate poisoning conditions of different catalytic devices / systems in different scenes through a small sample form, close to a vehicle use scene, and provide powerful theoretical support for rapid screening of anti-poisoning formula and analysis of poisoning causes. In addition, the test method can more objectively reflect catalyst poisoning conditions in actual operation of the vehicle, and reasonably evaluate the anti-poisoning capability of the catalyst. The test equipment provided by the application can be used for the test method, and the composition and dosage of toxic substances can be conveniently and quickly adjusted, so that the actual working conditions of the catalyst are more objectively and truly reflected, and a basis is provided for performance evaluation of the catalyst.

Description

Technical Field

[0001] This invention relates to the field of detection technology, and more specifically, to a test method and apparatus for simulating HCs poisoning in diesel engine aftertreatment catalysts. Background Technology

[0002] Diesel engines are widely used in various fields, including on-road, off-road, and marine applications, due to their high fuel economy, good power performance, and wide power range. The after-treatment catalysts for China VI diesel vehicles primarily employ oxidation catalysts (DOC), cDPF (cDPF), selective catalytic reduction (SCR), and ammonia oxidation catalysts (ASC). By combining different catalysts to suit the engine's emission characteristics, they achieve significant pollutant reduction.

[0003] To better evaluate catalyst performance, existing technologies typically involve collecting small samples of diesel engine aftertreatment catalysts and testing their purification capabilities for reactant gases under conditions free from poisoning or short-chain hydrocarbon (C3H6 / C3H8) poisoning. However, this testing method does not reflect the actual operating conditions of diesel engines, and the measured values ​​differ significantly from the data obtained during actual catalyst use, hindering accurate catalyst evaluation. Summary of the Invention

[0004] The purpose of this invention is to provide a test method and equipment for simulating HCs poisoning in diesel engine aftertreatment catalysts. The method and equipment are simple and convenient to operate and can quickly and accurately simulate various poisoning states of catalysts, providing strong theoretical support for the rapid screening of anti-poisoning formulations and the analysis of poisoning causes.

[0005] The embodiments of the present invention are implemented as follows:

[0006] A test method for simulating HCs poisoning in diesel engine aftertreatment catalysts, comprising:

[0007] S1. Take a small sample of the diesel engine aftertreatment catalyst and place the catalyst sample in the reactor;

[0008] S2. The mixture of toxic substances and air is mixed and pyrolyzed at 100~300℃ for 10~30min, and then the mixture is continuously injected into the reactor until toxic substances are detected at the rear end of the catalyst sample, thus completing the poisoning of the catalyst sample; wherein, the toxic substances include at least one of ordinary diesel oil, C5~C16 alkanes and biodiesel.

[0009] S3. Introduce reaction gas into the reactor, treat the reaction gas using a small sample of poisoned catalyst, and perform component analysis on the treated reaction gas.

[0010] A test device for simulating diesel engine aftertreatment catalyst poisoning, used in the above-mentioned test method for simulating diesel engine aftertreatment catalyst poisoning, includes a catalytic reaction unit, a toxic substance simulation injection unit, and an exhaust gas exhaust unit.

[0011] The catalytic reaction unit includes a reactor, inside which is a fixed bed for placing catalyst samples; the front end of the reactor is equipped with a reaction gas inlet pipe, and the rear end is connected to the tail gas exhaust unit through a tail gas outlet pipe.

[0012] The toxic substance simulation injection unit includes an external oil tank for storing toxic substances and a delivery pipeline for transporting toxic substances. One end of the delivery pipeline is connected to the external oil tank, and the other end extends into the reactor after passing through a delivery pump. A nozzle is installed at the end of the delivery pipeline inside the reactor, and the nozzle is located at the front end of the fixed bed.

[0013] The beneficial effects of the embodiments of the present invention are:

[0014] The testing method provided by this invention is a simple and efficient method for simulating catalyst poisoning. It can simulate the poisoning conditions of different catalytic devices / systems under various scenarios by using small-scale samples, closely resembling the actual vehicle usage environment. This provides strong theoretical support for rapidly screening anti-poisoning formulations and analyzing the causes of poisoning. Furthermore, this testing method can more objectively reflect the catalyst poisoning situation in actual vehicle operation and reasonably evaluate the catalyst's anti-poisoning ability. The testing equipment provided by this invention can be used in the above testing method, allowing for convenient and quick adjustment of the composition and dosage of toxic substances, more objectively and realistically reflecting the actual operating conditions of the catalyst, and providing a basis for catalyst performance evaluation. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of a test device for simulating catalyst poisoning in diesel engine aftertreatment, provided in an embodiment of the present invention.

[0017] Icons: 10-Testing equipment; 100-Reaction furnace; 110-Fixed bed; 120-Reaction gas inlet pipe; 130-Tail gas outlet pipe; 200-External oil tank; 210-Transfer pipeline; 220-Transfer pump; 230-Nozzle; 310-Pre-sampler; 320-Post-sampler; 330-Pre-sampler pipeline; 340-Post-sampler pipeline; 350-Analyzer; 360-Switcher; 400-Tail gas venting unit. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0019] The following is a detailed description of a test method and equipment for simulating catalyst poisoning in diesel engine aftertreatment according to an embodiment of the present invention.

[0020] This invention provides a test method for simulating catalyst poisoning in diesel engine aftertreatment, comprising:

[0021] S1. Take a small sample of the diesel engine aftertreatment catalyst and place the catalyst sample in the reactor;

[0022] S2. The mixture of toxic substances and air is mixed and pyrolyzed at 100~300℃ for 10~30min, and then the mixture is continuously injected into the reactor until toxic substances are detected at the rear end of the catalyst sample, thus completing the poisoning of the catalyst sample; wherein, the toxic substances include at least one of ordinary diesel, biodiesel, C5~C16 alkanes and biodiesel.

[0023] S3. Introduce reaction gas into the reactor, treat the reaction gas using a small sample of poisoned catalyst, and perform component analysis on the treated reaction gas.

[0024] Through long-term research, the inventors discovered that diesel vehicles, limited by urban operating conditions or short-distance transportation, require frequent cold starts due to low speed and low load. Frequent cold starts result in high hydrocarbon emission concentrations during cold starts; according to FTP-75 test results, hydrocarbon emissions during the cold start phase account for over 60% of the total emissions in the entire test. During the low-temperature cold start phase, the catalyst bed temperature is too low to effectively catalyze the oxidation of hydrocarbons. A large amount of unburned hydrocarbons easily coat the catalyst surface during cold starts or idling, isolating pollutants from the adsorption and catalytic reaction of active species, leading to catalyst hydrocarbon poisoning and exacerbating emissions exceeding standards.

[0025] To more effectively address catalyst poisoning caused by hydrocarbons and to meet the future requirements of China VII ultra-low emissions standards, developing catalysts with excellent low-temperature oxidation capabilities and superior resistance to poisoning has been a crucial research direction in this field. Conducting catalyst resistance testing is a vital step in developing new catalysts. Currently, to study the resistance of diesel vehicle catalysts to hydrocarbon poisoning, domestic and international scholars often use C3H6 / C3H8 short-chain hydrocarbons to simulate catalyst poisoning, introducing standard gases to examine the impact of short-chain hydrocarbons on catalyst performance. However, diesel fuel is primarily composed of a mixture of long-chain liquid alkanes with C10 to C22 carbon molecules, and the influence of long-chain and short-chain hydrocarbons on catalyst performance differs fundamentally. During cold starts, when fuel is injected into the DOC front end after in-cylinder combustion, in addition to some being broken down into short-chain hydrocarbons, alkanes, aromatics, alkylbenzenes, naphthalenes, and indene, unburned liquid hydrocarbons account for more than 35%. Existing methods do not acknowledge the impact of unburned liquid hydrocarbons on the catalyst. Literature reports that catalyst performance can be fully restored after heat treatment at 450℃ for 15-30 minutes following poisoning by C3H6 / C3H8 short-chain hydrocarbons. However, in actual vehicles, catalyst deactivation caused by large amounts of liquid hydrocarbons cannot be fully recovered. Therefore, simple poisoning by C3H6 / C3H8 short-chain hydrocarbons does not objectively reflect the true extent of catalyst poisoning.

[0026] Based on this, this application develops a testing method that can realistically reflect the actual poisoning conditions of catalysts. In this testing method, the inventors select at least one of ordinary diesel oil, biodiesel, and C5-C16 alkanes as toxic substances, which are then pyrolyzed at high temperatures to poison the catalyst. The data from the reaction of the poisoned catalyst with the reaction gas are more consistent with the actual operating conditions of the catalyst.

[0027] Furthermore, the toxic substances also include metal oxides, which include at least one of ZnO, CaO, Fe2O3, K2O, MgO, and Na2O. During their research, the inventors discovered that additives (e.g., metal oxides) and other unusual elements in engine oil can also affect catalyst activity. To consider the actual application environment of the catalyst, the influence of additives must also be taken into account. After extensive experimentation, the inventors found that a metal oxide content of 0.5wt% to 10wt% of the total toxic substances best approximates real-world operating conditions.

[0028] Furthermore, the toxic substances include 93wt%~98wt% ordinary diesel oil and 2wt%~7wt% metal oxides, which are a mixture of ZnO, CaO, and Fe2O3. The toxic substances obtained according to the above proportions more accurately reflect the catalyst's actual operating conditions and can more accurately evaluate the catalyst's resistance to poisoning.

[0029] Furthermore, in step S2, the concentration of toxic substances detected at the downstream end of the catalyst sample reaches 2500-5000 ppm, indicating that the catalyst sample has been poisoned. Within this range, a good poisoning effect can be achieved while maintaining a high poisoning efficiency.

[0030] In addition, in step S2, the flow rate of the toxic substance is 0.6~1.2 mL / min, and the flow rate of air is 5.8~23 L / min. Within these ranges, the pyrolysis effect between the toxic substance and air is better.

[0031] Furthermore, the testing method of this invention is applicable to commonly used catalyst combinations in diesel vehicle aftertreatment, including at least one of DOC, cDPF, SCR, ASC, CC-SCR, PNA, and SDPF. Catalyst samples are tightly wrapped in quartz wool and then placed into the reactor sequentially according to the actual vehicle placement order. The catalyst samples in the reactor can be pre-treated by heating the reactor to 400-550°C, stabilizing for 15-30 minutes, then cooling to 100-200°C and stabilizing for 15-20 minutes.

[0032] Furthermore, the reaction gases used in this invention include CO, NO, and O. 2、 H2O and NH3; optionally, the reactant gases include CO 400~600ppm, NO 400~600ppm, NH3 400~600ppm, CO2 5wt%~10wt%, O2 8wt%~13wt%, and H2O 8wt%~13wt%. In step S3, the reactor temperature is increased to 500~600℃ at a rate of 10~30℃ / min. During the reaction, the concentrations of CO, NO, and NH3 at the front and rear ends of the catalyst are collected, and the conversion efficiency is calculated.

[0033] Under normal circumstances, the percentage of NO2 in exhaust gas can be selected ( r ), and NO during the reaction process x Conversion efficiency ( φ (NO2) is used as a standard for evaluating catalyst activity. The formula for calculating the NO2 content is:

[0034] .

[0035] NO x The formula for calculating the conversion efficiency is:

[0036] .

[0037] The formula for calculating the cumulative amount of HCs is as follows:

[0038] .

[0039] Where, m HCs V represents the cumulative weight of HCs (g) and the catalyst volume (L).

[0040] The test method for simulating catalyst poisoning in diesel engine aftertreatment according to the present invention has at least the following application scenarios.

[0041] 1. By adjusting the composition and proportion of toxic substances, post-treatment catalysts with different degrees of poisoning are obtained. By comparing the catalytic performance of post-treatment catalysts with different degrees of poisoning and catalysts under actual working conditions, the composition and proportion of toxic substances that best fit the actual working conditions are determined, thereby providing a basis for analyzing the composition of toxic substances under actual working conditions and studying catalyst activation schemes.

[0042] 2. Once the composition and proportion of toxic substances best reflect actual operating conditions are determined, the post-treatment catalyst poisoned under these conditions is tested to obtain a catalytic efficiency decay curve over mileage. This curve allows for estimation of the catalyst's catalytic efficiency, given the actual mileage of the catalyst's service life, to determine whether the catalyst needs replacement.

[0043] 3. Once the composition and proportion of toxic substances best reflect actual operating conditions are determined, the post-treatment catalyst poisoned under these conditions is tested to obtain a decay curve of catalytic efficiency as a function of the accumulated amount of hydrocarbons (increase in catalyst volume per unit weight). Therefore, given the actual increase in catalyst volume per unit weight, this curve can be used to estimate the catalyst's catalytic efficiency and determine whether replacement is necessary.

[0044] 4. After determining the composition and proportion of toxic substances that best fit the actual working conditions, the post-treatment catalyst poisoned under these conditions is tested. By adjusting the type and order of the catalysts, the catalyst combination with the highest catalytic efficiency under these actual working conditions is screened, providing a theoretical basis for the development of catalysts with excellent low-temperature oxidation performance and high resistance to poisoning.

[0045] This invention also provides a test device for simulating diesel engine aftertreatment catalyst poisoning, which is used for the above-mentioned test method for simulating diesel engine aftertreatment catalyst poisoning. It includes a catalytic reaction unit, a toxic substance simulation injection unit, and an exhaust gas exhaust unit.

[0046] The catalytic reaction unit includes a reactor, inside which is a fixed bed for placing catalyst samples; the front end of the reactor is equipped with a reaction gas inlet pipe, and the rear end is connected to the tail gas exhaust unit through a tail gas outlet pipe.

[0047] The toxic substance simulation injection unit includes an external oil tank for storing toxic substances and a delivery pipeline for transporting toxic substances. One end of the delivery pipeline is connected to the external oil tank, and the other end extends into the reactor after passing through a delivery pump. A nozzle is installed at the end of the delivery pipeline inside the reactor, and the nozzle is located at the front end of the fixed bed.

[0048] Furthermore, the testing equipment also includes a detection unit, which comprises a pre-sampler and a post-sampler. The pre-sampler is located at the front end of the fixed bed and is connected to the analyzer via a pre-sampler pipe; the post-sampler is located at the rear end of the fixed bed and is connected to the analyzer via a post-sampler pipe. Optionally, the pre-sampler and post-sampler pipes can share the same analyzer via a switch.

[0049] Furthermore, the analyzer may employ at least one of a Fourier Transmission Infrared Spectrometer (FTIR) or a Flame Ionization Detector (FID), or a combination of both.

[0050] In addition, multiple primary temperature detectors can be installed in the fixed bed to monitor the catalyst temperature in real time. A secondary temperature detector is installed inside the reactor to monitor the inlet temperature of each catalyst element.

[0051] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0052] Example 1

[0053] This embodiment provides a test method for simulating catalyst poisoning in diesel engine aftertreatment, and its operation method is as follows:

[0054] After tightly wrapping four catalysts with quartz wool, the catalysts were arranged in the order of DOC, cDPF, SCR, and ASC in the reactor. The reactor was pretreated at 550℃ for 30 minutes, then the temperature was lowered to 250℃ and maintained constant. No. 0 China VI standard diesel oil was added to the external tank, and the delivery pipeline temperature was set to 200℃ and maintained for 20 minutes. The oil was then transferred into the reactor, and the hydrocarbon concentration in the FTIR was continuously monitored until it reached 2500 ppm. The diesel oil supply was then cut off, and the reactor temperature was lowered to room temperature. The sample was then removed and weighed to obtain sample 1.

[0055] Sample 1 was arranged in the order of DOC, cDPF, SCR, and ASC in the reactor. The reactor temperature was maintained at 100℃ for 20 minutes. The gas flow rate was then controlled using a mass flow meter, and the following gas mixture was introduced into the reactor: CO 500 ppm, NO 500 ppm, NH3 500 ppm, CO2 8 wt%, O2 10 wt%, H2O 10 wt.%, and N2 in equilibrium. The reactor was then subjected to an incubation period of 80,000 h. -1 At space velocity, the furnace temperature was raised to 600℃ at a heating rate of 10℃ / min. Then, the concentrations of CO, NO, and NH3 at the back end of the ASC were detected by FTIR, and the conversion efficiency was calculated.

[0056] Example 2

[0057] This embodiment provides a test method for simulating catalyst poisoning in diesel engine aftertreatment, and its operation method is as follows:

[0058] After tightly wrapping four catalysts with quartz wool, the catalysts were arranged in the order of DOC, cDPF, SCR, and ASC in the reactor. The reactor was pretreated at 550℃ for 30 minutes, then the temperature was lowered to 250℃ and maintained constant. Dodecane was added to the external tank, and the delivery pipeline temperature was set to 120℃ and maintained for 20 minutes. The reactor was then switched in, and the HCs concentration in the FID was continuously monitored until it reached 2500 ppm. The dodecane supply was then cut off, and the reactor temperature was lowered to room temperature. The sample was then removed and weighed to obtain sample 2.

[0059] Sample 2 was arranged in the reactor in the order of DOC, cDPF, SCR, and ASC. The reactor temperature was maintained at 100℃ for 20 minutes. The gas flow rate was controlled using a mass flow meter, and the following gas mixture was introduced into the reactor at equilibrium: CO 500 ppm, NO 500 ppm, NH3 500 ppm, CO2 8 wt.%, O2 10 wt.%, H2O 10 wt.%, and N2. The reactor was then incubated for 80,000 h⁻¹. -1 At space velocity, the furnace temperature was raised to 600℃ at a heating rate of 10℃ / min. Then, the concentrations of CO, NO, and NH3 at the back end of the ASC were detected by FTIR, and the conversion efficiency was calculated.

[0060] Example 3

[0061] This embodiment provides a test method for simulating catalyst poisoning in diesel engine aftertreatment, and its operation method is as follows:

[0062] After tightly wrapping four catalysts with quartz wool, the catalysts were arranged in the order of DOC, cDPF, SCR, and ASC in the reactor. After pretreatment at 550℃ for 30 minutes, the reactor temperature was lowered to 250℃ and maintained constant. Decane was added to the external tank, and the delivery pipeline temperature was set to 200℃ and maintained for 30 minutes. Then, the mixture was switched into the reactor, and the HCs concentration in the FID was continuously monitored until it reached 2500 ppm. The decane supply was then cut off, and the reactor temperature was lowered to room temperature. The sample was then removed and weighed to obtain sample 3.

[0063] Sample 3 was arranged in the order of DOC, cDPF, SCR, and ASC in the reactor. After maintaining the furnace temperature at 100℃ for 20 minutes, the gas flow rate was controlled by a mass flow meter and the gas mixture was introduced into the reactor according to the following conditions: CO 500ppm, NO 500ppm, NH3 500ppm, CO2 8wt.%, O2 10wt.%, H2O 10wt.%, and N2 in equilibrium. The reaction was carried out for 80,000 h. -1 At space velocity, the furnace temperature was raised to 600℃ at a heating rate of 10℃ / min. Then, the concentrations of CO, NO, and NH3 at the back end of the ASC were detected by FTIR, and the conversion efficiency was calculated.

[0064] Example 4

[0065] This embodiment provides a test method for simulating catalyst poisoning in diesel engine aftertreatment, and its operation method is as follows:

[0066] After tightly wrapping four catalysts with quartz wool, the catalysts were arranged in the order of DOC, cDPF, SCR, and ASC in the reactor. The reactor was pretreated at 550°C for 30 minutes, then the temperature was lowered to 250°C and maintained constant. Biodiesel was added to an external tank, and the delivery pipeline temperature was set to 250°C and maintained for 20 minutes. The mixture was then switched into the reactor, and the HCs concentration in the FTIR was continuously monitored until it reached 2500 ppm. The biodiesel supply was then cut off, and the reactor temperature was lowered to room temperature. The sample was then removed and weighed, yielding sample 4.

[0067] Sample 4 was arranged in the order of DOC, cDPF, SCR, and ASC in the reactor. The reactor temperature was maintained at 100℃ for 20 minutes. Then, the gas flow rate was controlled using a mass flow meter, and the following gas mixture was introduced into the reactor at equilibrium: CO 500 ppm, NO 500 ppm, NH3 500 ppm, CO2 8 wt.%, O2 10 wt.%, H2O 10 wt.%, and N2. The reaction was carried out for 80,000 h⁻¹. -1 At space velocity, the furnace temperature was raised to 600℃ at a heating rate of 10℃ / min. Then, the concentrations of CO, NO, and NH3 at the back end of the ASC were detected by FTIR, and the conversion efficiency was calculated.

[0068] Example 5

[0069] This embodiment provides a test method for simulating catalyst poisoning in diesel engine aftertreatment, and its operation method is as follows:

[0070] After tightly wrapping four catalysts with quartz wool, the catalysts were arranged in the order of DOC, cDPF, SCR, and ASC in the reactor. After pretreatment at 550℃ for 30 minutes, the furnace temperature was lowered to 250℃ and maintained constant. A mixture of No. 0 National VI standard diesel oil and CaO, ZnO, and Fe2O3 was added to an external tank, with the addition amounts of CaO, ZnO, and Fe2O3 being 5%, 1%, and 2%, respectively. The delivery pipeline temperature was set to 200℃ and maintained for 20 minutes before being switched into the furnace. The HCs concentration in the FTIR was continuously monitored until it reached 2500 ppm. The diesel oil supply was then cut off, and the furnace temperature was lowered to room temperature. A small sample was removed and weighed, yielding sample 5.

[0071] Sample 5 was then arranged in the reactor in the order of DOC, cDPF, SCR, and ASC. The reactor temperature was maintained at 100℃ for 20 minutes. The gas flow rate was then controlled using a mass flow meter, and the following gas mixture was introduced into the reactor at equilibrium: CO 500ppm, NO 500ppm, NH3 500ppm, CO2 8wt.%, O2 10wt.%, H2O 10wt.%, and N2. The reactor was then subjected to a reaction at 80,000 h⁻¹. -1 At space velocity, the furnace temperature was raised to 600℃ at a heating rate of 10℃ / min. Then, the concentrations of CO, NO, and NH3 at the back end of the ASC were detected by FTIR, and the conversion efficiency was calculated.

[0072] Examples 6-8

[0073] Examples 6-8 provide a test method for simulating catalyst poisoning in diesel engine aftertreatment. The operation method is similar to that of Example 5, except that different catalyst combinations are used. The specific catalyst selection is shown in Table 1.

[0074] Table 1. Catalyst Combination Methods

[0075] Catalysts (arranged in order of placement) Example 6 DOC, SDPF, SCR, ASC Example 7 DDPF, SCR, ASC Example 8 CC-SCR, DOC, cDPF, SCR, ASC

[0076] Example 9

[0077] This embodiment provides a test device 10 for simulating catalyst poisoning in diesel engine aftertreatment, referring to... Figure 1 As shown, it includes a catalytic reaction unit, a toxic substance simulation injection unit, and an exhaust gas venting unit 400.

[0078] The catalytic reaction unit includes a reactor 100, and a fixed bed 110 for placing catalyst samples is provided inside the reactor 100; a reaction gas inlet pipe 120 is provided at the front end of the reactor 100, and the rear end is connected to the tail gas exhaust unit 400 through a tail gas outlet pipe 130.

[0079] The toxic substance simulation injection unit includes an external oil tank 200 for storing toxic substances and a delivery pipe 210 for transporting toxic substances. One end of the delivery pipe 210 is connected to the external oil tank 200, and the other end extends into the reactor 100 after passing through a delivery pump 220. A nozzle 230 is provided at one end of the delivery pipe 210 inside the reactor 100, and the nozzle 230 is located at the front end of the fixed bed 110.

[0080] Furthermore, the testing device 10 also includes a detection unit, which comprises a pre-sampler 310 and a post-sampler 320. The pre-sampler 310 is located at the front end of the fixed bed 110 and is connected to the infrared spectrometer 350 via a pre-sampler pipe 330; the post-sampler 320 is located at the rear end of the fixed bed 110 and is connected to the infrared spectrometer 350 via a post-sampler pipe 340. Optionally, the analyzer 350 is at least one of a Fourier Transmission Infrared Spectrometer (FTIR) and a Flame Ionization Detector (FID), and the pre-sampler pipe 330 and the post-sampler pipe 340 can share the same analyzer 350 device via a switch 360.

[0081] In addition, multiple first temperature detectors 370 can be installed in the fixed bed 110 to monitor the temperature of the catalyst in real time; a second temperature detector 380 is installed in the reactor 100 to detect the furnace temperature of the reactor 100.

[0082] When using the test equipment 10 to perform tests according to the methods of Examples 1 to 5, the following steps are included:

[0083] 1. First, place the catalyst in the fixed bed 110 inside the reactor 100 and pretreat the catalyst at high temperature;

[0084] 2. The toxic substance is placed in the external oil tank 200, the delivery pipeline 210 is heated and air is introduced, and after the air and toxic substance are fully pyrolyzed, it is sprayed into the reactor 100 through the nozzle 230.

[0085] 3. Use the post-sampler 320 to collect the tail gas at the back end of the catalyst. When the concentration of leaked hydrocarbons reaches the target value, stop injecting toxic substances, thus completing the poisoning of the catalyst.

[0086] 4. Reaction gas is injected through reaction gas inlet pipe 120. Gas samples before and after the catalyst are collected by front sampler 310 and rear sampler 320 respectively, and then sent to infrared spectrometer 350 for detection.

[0087] 5. Calculate the conversion efficiency based on the test results.

[0088] Comparative Example 1

[0089] This comparative example provides a test method for simulating catalyst poisoning in diesel engine aftertreatment, and its operation method is as follows:

[0090] After tightly wrapping four catalysts with quartz wool, the catalysts were arranged in the order of DOC, cDPF, SCR, and ASC in the reactor. After pretreatment at 550℃ for 30 min, the furnace temperature was lowered to 250℃ and maintained constant. A C3H8 / C3H6 mixture was introduced into the reactor, with C3H8 and C3H6 concentrations of 200 ppm and 150 ppm, respectively. The HCs concentration in the FTIR was continuously monitored until it reached 350 ppm. The C3H8 / C3H6 supply was then cut off, and the furnace temperature was lowered to room temperature. A small sample was then removed and weighed, yielding sample 6.

[0091] Sample 6 was arranged in the reactor in the order of DOC, cDPF, SCR, and ASC. The reactor temperature was maintained at 100℃ for 20 minutes. Then, the gas flow rate was controlled using a mass flow meter, and the following gas mixture was introduced into the reactor at equilibrium: CO 500 ppm, NO 500 ppm, NH3 500 ppm, CO2 8 wt.%, O2 10 wt.%, H2O 10 wt.%, and N2. The reactor was incubated for 80,000 h⁻¹. -1 At space velocity, the furnace temperature was raised to 600℃ at a heating rate of 10℃ / min. Then, the concentrations of CO, NO, and NH3 at the back end of the ASC were detected by FTIR, and the conversion efficiency was calculated.

[0092] Comparative Example 2

[0093] This comparative example provides a method for bench testing of diesel engine aftertreatment catalysts, the operation method of which is as follows:

[0094] Following the GB17691-2018 actual road driving measurement method, road profile information was collected for a 2L diesel logistics vehicle of National VI emission standard N2 category, based on short-distance, urban, and suburban road conditions (locations: Changchun, Tianjin, Jinan, etc., ambient temperature around -10℃). By adjusting engine speed and torque, the collected actual road profile was run on the 2L test bench (average DOC inlet exhaust temperature 123℃, maximum exhaust temperature 156℃). In this comprehensive road profile, engine fuel consumption was estimated at 12L / 100km. After holding at 100℃ for 30 minutes in a drying oven, the mass of the aftertreatment unit from the "bench test" was measured.

[0095] After installing the "bench test" aftertreatment unit on the engine bench, a comprehensive data acquisition process was conducted. When the hydrocarbon leakage concentration in the tailpipe reached 2500 ppm, the aftertreatment unit was removed and weighed. Then, the engine speed and torque were adjusted, and at an air speed of 80,000 rpm, with a heating rate of 30°C / min, the exhaust pipe emissions of NO, NO2, NH3, and CO were tested within the range of 100-500°C to assess DOC and SCR performance. Thermocouples were placed at different locations inside the DOC and cDPF catalysts to collect catalyst bed temperature data.

[0096] Comparative Example 3

[0097] This comparative example provides a method for whole-vehicle testing of diesel engine aftertreatment catalysts, and the operation method is as follows:

[0098] Following the GB17691-2018 Actual Road Driving Measurement Method, and based on short-distance, urban, and suburban road conditions (locations: Changchun, Tianjin, Jinan, etc., ambient temperature around -10℃), a whole-machine PEMS test was conducted with OBD regeneration alarms disabled. PEMS equipment was used to monitor upstream and downstream NO. x Concentration. After every 5000km of driving, the aftertreatment unit is removed and weighed.

[0099] Experimental Example 1

[0100] Using the methods of Examples 1-9 and Comparative Example 1, NO was tested at 0km, 5000km, 10000km, 15000km, and 200000km (the mileage was calculated by recording the amount of liquid HCs injected and then extrapolating it based on the engine's fuel consumption per 100km). x Average conversion efficiency, hydrocarbon accumulation (i.e., the increase in catalyst volume per unit volume), and NO2 / NO in the exhaust gas x The proportions and test results are shown in Tables 1 and 2.

[0101] Table 1. NO x Average conversion efficiency test results

[0102]

[0103] As shown in Table 1, the test method of this invention can simulate HCs poisoning tests on engine benches and in vehicles. Within the same mileage (time), NO x Average conversion efficiency is correlated with HCs accumulation; as HCs accumulation increases, NO... x The conversion efficiency subsequently decreases. In Comparative Example 1, we poisoned the catalyst with a C3H8 / C3H6 mixture. The results showed that this test method resulted in significantly lower HCs accumulation and NO concentration at the same mileage. xThe degradation amount was small, far lower than the results of bench performance and whole vehicle performance tests, indicating that this method cannot truly reflect the actual operating conditions of the catalyst. In contrast, the test methods of Examples 1-5 of this application, which poison the catalyst with 0# diesel oil, n-dodecane, and n-decane, yielded conclusions that are significantly more consistent with actual operating conditions. Specifically, Examples 2-4 used n-dodecane and n-decane as toxic reagents, respectively, and compared to the whole vehicle test, the HCs accumulation was slightly lower, and the NO... x The average conversion rate is slightly higher than expected, but it accurately reflects the true data. When diesel fuel is used as the toxic reagent (Examples 1, 4, and 5), the data is closer to that of the whole vehicle test, especially when using #0 diesel fuel, where the effect is best. This may be related to the fact that diesel engines actually use #0 diesel fuel as a raw material. However, when using #0 diesel fuel (Example 1), the inventors also found some problems: using only #0 diesel fuel resulted in lower HCs accumulation and lower NO... x The phenomenon of a higher average conversion rate still exists, although it is somewhat improved compared to n-dodecane and n-decane. The inventors conducted an in-depth analysis of the actual operating conditions of diesel engines and, after numerous trials, discovered that additives in the engine oil were the main cause of this difference. Therefore, in Example 5, the inventors tried adding metal oxides, which resulted in data that highly matched the vehicle test data.

[0104] Furthermore, after identifying the type of toxic reagent, the inventors further experimented with SDPF, DDPF, CC-SCR, and other catalysts that might be used in future China VII emission standards using this toxic reagent (0# diesel fuel + metal oxides). As can be seen from Examples 6 and 7, after replacing cDPF with SDPF or DDPF, the accumulation of HCs decreased, and NO... x The average conversion rate is superior. However, when using CC-SCR, the pre-treatment of CC-SCR leads to stronger HCs adsorption, resulting in more severe degradation. Compared to conclusions from other methods used in the industry, this method more clearly reflects the impact of HCs on the pre-catalyst. The above fully demonstrates that the testing method of this invention is applicable to different catalyst systems and more accurately reflects catalyst performance, which is of great significance for screening catalysts with greater resistance to toxicity.

[0105] Table 2. NO2 / NO x Test Results

[0106]

[0107] Table 2 shows the NO2 / NO2 ratio in exhaust gas under different testing methods. xOverall, the proportion of NO2 in the exhaust gas gradually decreases with increasing mileage. The catalyst poisoned using the method in Comparative Example 1 shows a significantly slower decrease in the proportion of NO2 in the exhaust gas, which differs considerably from the bench test results, indicating that the method in Comparative Example 1 does not reflect the true poisoning situation of the catalyst. However, using the test methods of Examples 1-8 of this invention, the proportion of NO2 in the exhaust gas decreases much faster with increasing mileage, and the rate of decrease is highly similar to the bench test results. Especially when diesel fuel (Examples 1, 4, and 5) is used as the toxic agent, the decreasing trend of the proportion of NO2 in the exhaust gas is basically the same as the bench test, better reflecting the actual situation of the catalyst.

[0108] In summary, the testing method provided by this invention is a simple and efficient method for simulating catalyst poisoning. It can simulate the poisoning conditions of different catalytic devices / systems under various scenarios by using small-scale samples, closely resembling the actual vehicle usage environment. This provides strong theoretical support for rapidly screening anti-poisoning formulations and analyzing the causes of poisoning. Furthermore, this testing method can more objectively reflect the catalyst poisoning situation in actual vehicle operation and reasonably evaluate the catalyst's anti-poisoning ability. The testing equipment provided by this invention can be used in the above testing method, allowing for convenient and quick adjustment of the composition and dosage of toxic substances, more objectively and realistically reflecting the actual operating conditions of the catalyst, and providing a basis for catalyst performance evaluation.

[0109] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A test method for simulating HCs poisoning in diesel engine aftertreatment catalysts, characterized in that, include: S1. Take a small sample of the diesel engine aftertreatment catalyst and place the catalyst sample in the reactor; S2. The mixture of toxic substances and air is mixed and pyrolyzed at 100~300℃ for 10~30min, and then the pyrolyzed mixture is continuously injected into the reactor until the pyrolysis products of the mixture are detected at the rear end of the catalyst sample, thus completing the poisoning of the catalyst sample. S3. Introduce reaction gas into the reactor, treat the reaction gas using the poisoned catalyst sample, and perform component analysis on the treated reaction gas; The toxic substances include 93wt% to 98wt% ordinary diesel oil and 2wt% to 7wt% metal oxides, wherein the metal oxides are a mixture of ZnO, CaO and Fe2O3, and the amount of the metal oxides is 0.5wt% to 10wt% of the total amount of the toxic substances.

2. The test method for simulating HCs poisoning of diesel engine aftertreatment catalysts according to claim 1, characterized in that, In step S2, the concentration of the pyrolysis products of the mixture detected at the back end of the catalyst sample reaches 2500~5000ppm, which means that the poisoning of the catalyst sample is completed.

3. The test method for simulating HCs poisoning of diesel engine aftertreatment catalysts according to claim 2, characterized in that, In step S2, the flow rate of the toxic substance is 0.6~1.2 mL / min; the flow rate of the air is 5.8~23 L / min.

4. The test method for simulating HCs poisoning of diesel engine aftertreatment catalyst according to claim 1, characterized in that, The catalyst includes at least one of DOC, cDPF, SCR, ASC, CC-SCR, PNA, DDPF, and SDPF.

5. The test method for simulating HCs poisoning of a diesel engine aftertreatment catalyst according to claim 1, characterized in that, The reacting gases include CO, NO, and O. 2、 H2O and NH3; in step S3, the temperature of the reactor is increased to 500-600℃ at a rate of 10-30℃ / min.

6. The test method for simulating HCs poisoning in diesel engine aftertreatment catalysts according to claim 1, characterized in that, In step S1, the catalyst sample in the reactor is pretreated by heating the reactor to 400-550°C, stabilizing it for 15-30 minutes, and then cooling it to 100-200°C and stabilizing it for 15-20 minutes.

7. A test apparatus for simulating HCs poisoning in diesel engine aftertreatment catalysts, characterized in that, The test method for simulating HCs poisoning of a diesel engine aftertreatment catalyst as described in any one of claims 1 to 6 includes a catalytic reaction unit, a toxic substance simulation injection unit, and an exhaust gas exhaust unit. The catalytic reaction unit includes the reactor, and the reactor has a fixed bed for placing the catalyst sample inside; the front end of the reactor is provided with a reaction gas inlet pipe, and the rear end is connected to the tail gas exhaust unit through a tail gas outlet pipe. The toxic substance simulation injection unit includes an external oil tank for storing the toxic substance and a delivery pipeline for transporting the toxic substance. One end of the delivery pipeline is connected to the external oil tank, and the other end extends into the reactor after passing through a delivery pump. A nozzle is provided at one end of the delivery pipeline inside the reactor, and the nozzle is located at the front end of the fixed bed.

8. The test apparatus for simulating HCs poisoning of diesel engine aftertreatment catalysts according to claim 7, characterized in that, It also includes a detection unit, which includes a pre-sampler and a post-sampler. The pre-sampler is located at the front end of the fixed bed and is connected to the infrared spectrometer through a pre-sampler pipe. The post-sampler is located at the rear end of the fixed bed and is connected to the infrared spectrometer through a post-sampler pipe.

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