A method for rapidly evaluating sulfur tolerance limit of diesel engine aftertreatment catalyst

Abstract

A kind of method for quickly evaluating sulfur tolerance limit of diesel engine aftertreatment catalyst, the intercepted catalyst sample is arranged in the tubular heating furnace of atmosphere aging platform reactor, polluted gas C3H8, C3H6, CO, NO, NH3, SO2, CO2 etc. are introduced into the heating furnace, the concentration of gas pollutant at the outlet of catalyst is recorded by analyzer, after the SO2 concentration at the outlet of the catalyst to be detected no longer changes, the polluted gas is cut off, the fast heating atmosphere in the process of simulating vehicle oil injection regeneration is introduced into the heating furnace under the condition that the space velocity of analyzer is unchanged, after the SO2 concentration at the outlet of the catalyst to be detected no longer changes, a reaction cycle is ended, the catalyst sample is taken out, the amount of sulfur compound captured by catalyst is detected, and the NOx conversion efficiency is calculated;The above steps are repeated until the NOx conversion efficiency reduces to 0, which is regarded as the sulfur tolerance limit of catalyst.The present application can be close to the actual use of vehicle, and the sulfur resistance and regeneration capacity of aftertreatment catalyst are systematically tested, the sulfur tolerance boundary of catalyst is defined, and calibration support is provided for actual vehicle application.

Description

Technical Field

[0001] The invention belongs to the technical field of diesel engine after-treatment catalyst detection methods, and in particular relates to a method for quickly evaluating the sulfur tolerance limit of a diesel engine after-treatment catalyst. Background Art

[0002] As the energy crisis intensifies, lean-burn engines are widely used in both on- and off-road applications due to their superior power and economy. Excess air not only improves fuel economy but also effectively reduces carbon monoxide (CO) and hydrocarbons (HCs). However, under oxygen-rich conditions, engine combustion can easily lead to extremely high nitrogen oxide (NOx) emissions. To effectively control NOx emissions, countries around the world have enacted strict regulations on mobile source pollution emissions. my country's currently implemented National VI emission regulations require an 80% reduction in NOx compared to National V emissions, while also improving durability by over 40%. To meet these requirements, diesel oxidation catalysts (DOCs), particulate filters (cDPFs), selective catalytic reducers (SCRs), and ammonia oxidation catalysts (ASCs) are widely used in National VI after-treatment catalytic systems. The highly efficient after-treatment catalyst combination of DOC+cDPF+SCR+ASC effectively controls emissions of pollutants such as HC, CO, NOx, PM, and NH3.

[0003] To ensure efficient catalytic performance of diesel engine aftertreatment catalysts, my country's current National VI diesel standard stipulates a fuel sulfur content limit of 10 mg / kg. However, even in low-sulfur environments, catalysts can still accumulate significant amounts of sulfur throughout their lifecycle, leading to catalyst deactivation. Sulfur poisoning is a key factor in catalyst deactivation during practical use. Furthermore, diesel and its sulfides, when burned in the engine and oxidized by the DOC, easily form a mixture of SO2, SO3, and SOx. In the hot, humid, and oxygen-rich environment of diesel engines, sulfides react with key elements such as phosphorus, iron, and alkali metals in the lubricating oil and exhaust lines to form persistent sulfate species, irreversibly deactivating the catalyst. To mitigate the risk of aftertreatment catalyst failure due to sulfur poisoning, catalyst development must consider sulfur-tolerant formulations and the catalyst's sulfur tolerance limit. A catalyst sulfur poisoning and desulfurization model was established under typical operating conditions to clarify the catalyst's performance characteristics during sulfur poisoning and after regeneration. A catalyst sulfur tolerance limit was proposed, providing a calibration basis for sulfur poisoning detoxification methods in the automotive industry.

[0004] Currently, OEMs primarily rely on downstream NOx sensors and cDPF flow resistance alarms to determine catalyst sulfur poisoning and regeneration requirements. This method closely matches actual application environments, but because NOx sensors cannot distinguish between NOx and NH3, SCR sulfur poisoning can be easily misjudged, potentially interfering with urea injection. Furthermore, DOC sulfur poisoning cannot be directly measured; the DOC's sulfur poisoning can only be indirectly assessed through the cDPF's passive regeneration. However, cDPF flow resistance does not change significantly at high temperatures, making it impossible to proactively prevent blockage caused by sulfur poisoning in vehicle aftertreatment systems, thereby increasing the safety of diesel engines operating in sulfur-poisoned conditions. This approach is not suitable for developing catalyst sulfur-resistant formulations or defining catalyst sulfur tolerance boundaries and limits during the development phase.

[0005] To rapidly screen catalyst formulations for strong sulfur tolerance, define the catalyst sulfur poisoning boundary conditions, and clearly define the catalyst's sulfur tolerance limit, a simple and efficient method is needed to simulate the catalyst sulfide poisoning environment during vehicle operation, thereby rapidly evaluating the sulfur tolerance limit of diesel engine aftertreatment catalysts. This method should at least meet the following advanced requirements: First, it should be able to simulate the sulfur poisoning, detoxification, re-poisoning, and re-detoxification cycle during catalyst application, closely resembling actual reaction cycles. Second, the method should be broadly adaptable, capable of determining the catalyst tailpipe NOx emission characteristics under varying sulfur content and accumulation time, and defining the catalyst sulfur poisoning boundary. Third, in addition to conventional sulfur compounds such as SO2, SO3, and SOx, it should also be able to simulate catalyst failure caused by the coexistence of sulfur compounds with key elements such as P, Fe, and alkali metals under actual vehicle operating conditions, providing theoretical guidance for OEMs to develop OBD warning and regeneration strategies specifically for sulfur poisoning. Finally, after multiple rounds of reaction cycles, the application boundary of irreversible regeneration of the catalyst is defined, which serves as a theoretical guidance for the replacement of post-processor parts and reduces the cost of post-processing applications. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems existing in the above-mentioned prior art and provide a method for quickly evaluating the sulfur tolerance limit of a diesel engine aftertreatment catalyst.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for rapidly evaluating the sulfur tolerance limit of a diesel engine aftertreatment catalyst is performed according to the following steps:

[0009] (1) A sampler was used to intercept the catalyst sample, and after the sample was tightly wrapped with quartz wool, it was placed in the tubular heating furnace of the atmosphere aging station reactor according to the arrangement order of the post-treatment catalysts; the arrangement order of the post-treatment catalysts was DOC, cDPF, SCR, and ASC;

[0010] (2) Set the atmosphere aging station program, raise the temperature of the tubular heating furnace to 200-300℃, and stabilize it for 0.5-1.5h;

[0011] (3) Adjusting the air velocity of the atmosphere aging table, introducing pollutant gases such as C3H8, C3H6, CO, NO, NH3, SO2, CO2, O2, H2O, and N2 into the tubular heating furnace, and rapidly aging at a constant temperature for 1-50 hours; during this period, using an analyzer to record the concentration of gaseous pollutants at the catalyst outlet;

[0012] (4) After the analyzer detects that the SO2 concentration at the catalyst outlet no longer changes, the polluted gas is cut off. While maintaining the analyzer air velocity unchanged, a rapidly heated atmosphere simulating the fuel injection regeneration process of the entire vehicle is introduced into the tubular heating furnace and the temperature is raised to 500-700°C. After the analyzer detects that the SO2 concentration at the catalyst outlet no longer changes, a reaction cycle is terminated.

[0013] (5) After one cycle, the catalyst sample is taken out to detect the amount of sulfide captured by the catalyst and calculate the NOx conversion efficiency;

[0014] (6) Repeat steps (1) to (5) until the NOx conversion efficiency drops to 0, which is considered the sulfur tolerance limit of the catalyst.

[0015] Furthermore, the gas distribution conditions described in the above step (3) are: C3H8 50-500ppm, C3H6 50-500ppm, CO 50-1000ppm, NO 300-1000ppm, NH3 300-1200ppm, SO2 10-2000ppm, CO2 8-10wt.%, O2 8-15wt.%, H2O 6-15wt.%, N2 balance.

[0016] Furthermore, the analyzer space velocity in the above step (4) ranges from 20,000 to 20,0000 h-1.

[0017] Furthermore, the rapid heating atmosphere described in the above step (4) is CO2, O2, H2O and N2 balance gas, and the heating rate of the tubular heating furnace is 10-50℃ / min.

[0018] Furthermore, 0.1-15 wt.% of one of P, Fe, and alkali metal elements or a combination thereof may be added to the catalyst.

[0019] Furthermore, the catalysts used are National VI commercial DOC catalysts, cDPF catalysts, SCR catalysts, and ASC catalysts.

[0020] Furthermore, the analyzer is a Fourier infrared analyzer.

[0021] Furthermore, the polluted gases C3H8, C3H6, CO, NO, SO2, CO2 and O2 are heated and mixed and then introduced into a tubular heating furnace.

[0022] Compared with the prior art, the method of the present invention has at least the following advantages:

[0023] (1) According to the actual application situation, the required catalyst volume is intercepted to simulate the catalyst poisoning scenario caused by different types of sulfides and sulfates during the actual operation of the vehicle, which is close to the actual use of the after-treatment device.

[0024] (2) This method has broad adaptability. It generates SO2 / SO3 / SOx and their mixtures through DOC oxidation, and clarifies the relationship between catalyst sulfur poisoning content and NOx conversion efficiency at different accumulation times. It simulates the catalyst sulfur poisoning boundary under real-world application conditions, providing theoretical guidance for OEMs to develop OBD alarms and regeneration strategies specifically for sulfur poisoning.

[0025] (3) This method combines a tubular heating furnace with a Fourier transform infrared analyzer to simulate the sulfur accumulation and regeneration patterns during actual vehicle operation, as well as the effect of sulfur content on the NOx treatment capacity of the catalyst after-treatment. Following the patterns and processes of catalyst sulfur poisoning-detoxification-repoisoning-redetoxification, the relationship between sulfur content, poisoning time, and nitrogen oxide conversion efficiency is established, and the catalyst's sulfur tolerance limit is examined, providing a theoretical basis for the screening of sulfur-resistant catalyst formulations and significantly reducing the cost of engine bench testing and vehicle testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of how to quickly evaluate the sulfur tolerance limit of a diesel engine aftertreatment catalyst using an atmosphere aging bench. DETAILED DESCRIPTION

[0027] The present invention is described clearly and completely below with reference to the embodiments. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, and not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0028] A method for rapidly evaluating the sulfur tolerance limit of diesel engine aftertreatment catalysts, using Figure 1 The atmospheric aging station shown is used in conjunction with an analyzer to quickly evaluate the sulfur tolerance limit of diesel engine aftertreatment catalysts. The atmospheric aging station is a prior art device.

[0029] The steps are as follows:

[0030] (1) A sampler is used to intercept the catalyst sample. After the sample is tightly wrapped with quartz wool, it is arranged in the tubular heating furnace 1 of the atmosphere aging station reactor according to the order of the post-treatment catalysts. The post-treatment catalysts used are the National VI commercial DOC catalyst, cDPF catalyst, SCR catalyst, and ASC catalyst. The order of the post-treatment catalysts is DOC catalyst, cDPF catalyst, SCR catalyst, and ASC catalyst.

[0031] The catalyst can be supplemented with 0.1-15 wt.% of one or a combination of P, Fe, and alkali metals. These combinations can be in the form of Fe / K, Fe / Na, Na2SO4, or potassium dihydrogen phosphate. Extensive early testing and catalyst failure reports revealed that, in addition to being affected by sulfur in substandard diesel, P, Fe, and alkali metals in engine oil or lubricating oil react with sulfides to form non-regenerable substances such as iron sulfate and potassium dihydrogen phosphate, which are trapped in the cDPF in the catalyst. Therefore, to ensure practical application, these elements can be incorporated to analyze sulfur poisoning.

[0032] (2) Set the atmosphere aging station program, raise the temperature of the tubular heating furnace to 200-300℃, and stabilize it for 0.5-1.5h.

[0033] (3) Adjust the air velocity of the atmosphere aging table and introduce pollutant gases C3H8, C3H6, CO, NO, N2, NH3, SO2, CO2, O2, and a mixture of H2O and N2 into the tubular heating furnace through different pipelines equipped with flow meters. C3H8, C3H6, CO, NO, part of N2, and CO2 are heated and mixed in the first heating mixer 3. The mixture of H2O and part of N2, SO2, and O2 are mixed and heated in the second heating mixer 4. After the mixed and heated pollutant gases and unheated NH3 enter the tubular heating furnace, they are rapidly aged at a constant temperature for 1-50 hours. During this period, the analyzer 5 connected to the catalyst outlet 2 is used to record the concentration of gaseous pollutants at the catalyst outlet. The gas distribution conditions are: C3H8 50-500ppm, C3H6 50-500ppm, CO 50-1000ppm, NO 300-1000ppm, NH3 300-1200ppm, SO2 10-2000ppm, CO2 8-10wt.%, O2 8-15wt.%, H2O 6-15wt.%, and N2 balance. The analyzer used in this embodiment is a Fourier transform infrared analyzer (FTIR).

[0034] (4) After the SO2 concentration at the outlet of the catalyst is no longer changed by the analyzer, the contaminated gas is cut off, the CO2, O2, H2O and N2 balance gas in the simulated whole vehicle oil injection regeneration process is introduced into the tubular heating furnace, the tubular heating furnace is rapidly heated to 500-700℃ at a heating rate of 10-50℃ / min, and after the SO2 concentration at the outlet of the catalyst is no longer changed by the analyzer, one reaction cycle is ended. The analyzer air speed range is 20,000-20,0000h-1.

[0035] (5) After one cycle is ended, the catalyst sample is taken out, the amount of sulfur compounds captured by the catalyst is detected, and the NOx conversion efficiency is calculated.

[0036] (6) Repeat steps (1) to (5) until the NOx conversion efficiency is reduced to 0, which is regarded as the sulfur tolerance limit of the catalyst. The tested exhaust gas enters the gas-liquid separation tank 6.

[0037] The present application tests the working condition of catalyst poisoning-catalyst regeneration-catalyst re-poisoning-catalyst re-regeneration, when the catalyst is poisoned to a certain extent, the performance will not recover, at this time it is regarded as the sulfur tolerance limit of the catalyst. Compared with adding non-compliant diesel on the whole vehicle for tens of thousands of kilometers, this method not only evaluates fast, but also can greatly reduce the evaluation cost.

[0038] Catalyst sample preparation

[0039] Six sets of used after-treatment catalysts for the national sixth stage are prepared and are marked as #1, #2, #3, #4, #5 and #6. Among them, the #5 catalyst adds 5wt.% phosphorus element in the preparation process, and the #6 catalyst adds 15wt.% iron element in the preparation process. The specific information of each catalyst is shown in the following table:

[0040]

[0041] Bench test sample

[0042] The #1 sample is taken out and packaged, then is loaded into a national six 4L diesel engine bench, the bench uses 1500ppm high sulfur content fuel, according to the requirements of the reference “Heavy-duty diesel vehicle pollutant emission limits and measurement methods (China sixth stage) (GB17691-2018)”, after WHTC cycle test is carried out for 4h, the ECU regeneration mode is entered. After the test is ended, the sampling machine is used to cut off the DOC, cDPF, SCR and ASC catalysts, and the four catalyst small samples have a diameter of 25.4mm and heights of 50.8mm, 76.2mm, 76.2mm and 76.2mm respectively, the small sample performance test is carried out, and the NOx conversion efficiency is tested. The sample is recorded as “bench aging”.

[0043] Vehicle test samples

[0044] Take the #2 sample, package it, and then install it in a National VI 4L diesel vehicle for whole vehicle testing. The whole vehicle is added with 1500ppm of high sulfur content fuel for road testing. The vehicle is driven according to suburban conditions (about 70km / h), and a recorder is used to record the upstream (DOC front end) and downstream (ASC rear end) NOx data during driving. During operation, when the NOx conversion efficiency decreases, the ECU automatically enters the regeneration mode. After the vehicle has traveled a total of 350km, the post-treatment catalyst is removed, and the DOC, cDPF, SCR, and ASC catalysts are intercepted respectively. The diameter of the four catalyst samples is 25.4mm, and the height is 50.8mm, 76.2mm, 76.2mm, and 76.2mm respectively. The sample performance test is carried out to test the NOx conversion efficiency. The sample is recorded as "whole vehicle aging."

[0045] Vehicle durability samples

[0046] Sample #3 was packaged and loaded onto a China VI 4L diesel vehicle for full vehicle testing. The vehicle was road tested with 10ppm of compliant fuel. A recorder was used to record upstream and downstream NOx data while the vehicle was in motion. During operation, when the NOx conversion efficiency decreased, the ECU automatically entered regeneration mode. After the vehicle had accumulated 200,000km, the post-treatment catalyst was removed and the DOC, cDPF, SCR, and ASC catalysts were intercepted. Four catalyst samples, each with a diameter of 25.4mm and heights of 50.8mm, 76.2mm, 76.2mm, and 76.2mm, were used for performance testing of the samples to test NOx conversion efficiency. The samples were labeled "durable aging."

[0047] Example 1

[0048] A sampler was used to extract the DOC, cDPF, SCR, and ASC catalysts from sample #4. Each of the four catalyst samples had a diameter of 25.4 mm and heights of 50.8 mm, 76.2 mm, 76.2 mm, and 76.2 mm, respectively. After being tightly wrapped with quartz wool, the catalysts were arranged in the tubular furnace of the atmosphere aging reactor. The atmosphere aging program was set, and the furnace temperature was raised to 200°C at a heating rate of 10°C / min. A mass flow meter was used to control the gas flow rate. The following gas flow conditions were used: C3H8 200 ppm, C3H6 100 ppm, CO 500 ppm, NO 500 ppm, SO2 130 ppm, CO2 8 wt.%, O2 10 wt.%, H2O 10 wt.%, and N2 in balance. The catalysts were then aged at a constant temperature for 4 h at a space velocity of 40,000 h⁻¹. During the aging period, an analyzer is used to record the concentration of gaseous pollutants. After the analyzer detects that the SO2 concentration at the catalyst outlet no longer changes, the gas distribution is cut off. While maintaining the space velocity unchanged, the temperature of the tubular heating furnace is raised to 600°C at a heating rate of 10°C / min. After the analyzer detects that the SO2 concentration at the catalyst outlet no longer changes, the first cycle is terminated and the NOx conversion efficiency of the post-treatment catalyst is calculated.

[0049] Example 2

[0050] On sample #4, a sampler was used to cut the DOC, cDPF, SCR, and ASC catalysts. The diameter of the four catalyst samples was 25.4 mm, and the heights were 50.8 mm, 76.2 mm, 76.2 mm, and 76.2 mm, respectively. After wrapping the four catalysts tightly with quartz wool, Figure 1 The catalysts DOC, cDPF, SCR, and ASC were arranged in the order shown in the aging test. The aging test was programmed to raise the furnace temperature to 200°C at a rate of 10°C / min. A mass flowmeter was used to control the gas flow rate, and the following gas distribution conditions were used: C3H8 200ppm, C3H6 100ppm, CO 500ppm, NO 500ppm, SO2 130ppm, CO2 8%, O2 10%, H2O 10%, and N2 in balance. The catalysts were aged at a constant temperature for 4 hours at a space velocity of 40,000 h⁻¹. During the aging process, an analyzer was used to record the concentration of gaseous pollutants. Once the analyzer detected no change in the SO2 concentration at the catalyst outlet, the gas distribution was cut off. Maintaining the space velocity, the aging test was then conducted to 600°C at a rate of 10°C / min. The analyzer detected no change in the SO2 concentration at the catalyst outlet, marking the end of the first cycle.

[0051] The atmosphere aging bench repeats the above steps for 10 cycles according to the program settings. After the 10th cycle, the NOx conversion efficiency drops to 0. Calculate the NOx conversion efficiency of the post-treatment catalyst.

[0052] Example 3

[0053] On sample #4, a sampler was used to cut the DOC, cDPF, SCR, and ASC catalysts. The diameter of the four catalyst samples was 25.4 mm, and the heights were 50.8 mm, 76.2 mm, 76.2 mm, and 76.2 mm, respectively. After wrapping the four catalysts tightly with quartz wool, Figure 1 The catalysts were arranged in the tubular furnace in the order shown. The atmosphere aging station program was set. After the furnace temperature was raised to 200°C at a heating rate of 10°C / min, a mass flowmeter was used to control the gas flow rate. A gas mixture consisting of 200ppm C3H8, 100ppm C3H6, 500ppm CO, 500ppm NO, 130ppm SO2, 8% CO2, 10% O2, 10% H2O, and a balance of N2 was introduced into the tubular furnace. The catalysts were aged at a constant temperature for 4 hours at a space velocity of 40,000 h⁻¹. During the aging period, an analyzer was used to record the concentration of gaseous pollutants. Once the analyzer detected no change in the SO2 concentration at the catalyst outlet, the gas supply was cut off. Maintaining the space velocity, the atmosphere aging station temperature was raised to 600°C at a heating rate of 10°C / min, ending the first cycle.

[0054] The atmosphere aging bench repeats the above steps for 20 cycles according to the programmed program. After the 20th cycle, the NOx conversion efficiency drops to 0. Calculate the NOx conversion efficiency of the post-treatment catalyst.

[0055] Example 4

[0056] On sample #4, a sampler was used to cut the DOC, cDPF, SCR, and ASC catalysts. The diameter of the four catalyst samples was 25.4 mm, and the heights were 50.8 mm, 76.2 mm, 76.2 mm, and 76.2 mm, respectively. After wrapping the four catalysts tightly with quartz wool, Figure 1The catalysts were arranged in the order shown in the figure and placed in a tubular furnace in an atmosphere aging station. The atmosphere aging station program was set, and the furnace temperature was raised to 200°C at a heating rate of 10°C / min. A mass flowmeter was used to control the gas flow rate, and the following gas distribution conditions were used: C3H8 200ppm, C3H6 100ppm, CO 500ppm, NO 500ppm, SO2 130ppm, CO2 8%, O2 10%, H2O 10%, and N2 were balanced. The catalysts were aged at a constant temperature for 4 hours at a space velocity of 40,000 h-1. During the aging period, the concentration of gaseous pollutants was recorded using an analyzer. Once the analyzer detected no change in the SO2 concentration at the catalyst outlet, the gas distribution was cut off. Maintaining the space velocity, the furnace temperature was raised to 600°C at a heating rate of 10°C / min, ending the first cycle.

[0057] The atmosphere aging bench repeats the above steps for 30 cycles according to the program. After the 30th cycle, the NOx conversion efficiency drops to 0. Calculate the NOx conversion efficiency of the post-treatment catalyst.

[0058] Example 5

[0059] On sample #4, a sampler was used to cut the DOC, cDPF, SCR, and ASC catalysts. The diameter of the four catalyst samples was 25.4 mm, and the heights were 50.8 mm, 76.2 mm, 76.2 mm, and 76.2 mm, respectively. After wrapping the four catalysts tightly with quartz wool, Figure 1 The catalysts were arranged in the tubular furnace in the order shown. The atmosphere aging station program was set. After the tubular furnace temperature was raised to 200°C at a heating rate of 10°C / min, a mass flowmeter was used to control the gas flow rate. The following gas distribution conditions were used: C3H8 200ppm, C3H6 100ppm, CO 500ppm, NO 500ppm, SO2 130ppm, CO2 8%, O2 10%, H2O 10%, and N2 in balance. The catalysts were aged at a constant temperature for 4 hours at a space velocity of 40,000 h⁻¹. During the aging period, the concentration of gaseous pollutants was recorded using an analyzer. Once the analyzer detected no change in the SO2 concentration at the catalyst outlet, the gas distribution was cut off. Maintaining the space velocity, the atmosphere aging station temperature was raised to 600°C at a heating rate of 10°C / min, ending the first cycle.

[0060] The atmosphere aging bench repeats the above steps for 50 cycles according to the programmed program. After the 50th cycle, the NOx conversion efficiency drops to 0. Calculate the NOx conversion efficiency of the post-treatment catalyst.

[0061] Example 6

[0062] On the #5 sample, a sampler was used to cut the DOC, cDPF, SCR, and ASC catalysts. The diameter of the four catalyst samples was 25.4 mm, and the heights were 50.8 mm, 76.2 mm, 76.2 mm, and 76.2 mm, respectively. After the four catalysts were tightly wrapped with quartz wool, the samples were cut into pieces according to the following formula: Figure 1 The catalysts were arranged in the order shown in the figure and placed in a tubular furnace. The atmosphere aging station program was set. After the furnace temperature was raised to 200°C at a heating rate of 10°C / min, a mass flowmeter was used to control the gas flow rate. The following gas distribution conditions were used: C3H8 200ppm, C3H6 100ppm, CO 500ppm, NO 500ppm, SO2 130ppm, CO2 8%, O2 10%, H2O 10%, and N2 in balance. The catalysts were aged at a constant temperature for 4 hours at a space velocity of 40,000 h⁻¹. During the aging period, the concentration of gaseous pollutants was recorded using an analyzer. Once the analyzer detected no change in the SO2 concentration at the catalyst outlet, the gas distribution was cut off. Maintaining the space velocity, the atmosphere aging station temperature was raised to 600°C at a heating rate of 10°C / min. The first cycle was completed, and the NOx conversion efficiency of the post-treatment catalyst was calculated.

[0063] Comparative Example 1

[0064] A sampler was used to extract the DOC, cDPF, SCR, and ASC catalysts from sample #6. Each of the four catalyst samples had a diameter of 25.4 mm and heights of 50.8 mm, 76.2 mm, 76.2 mm, and 76.2 mm, respectively. After being tightly wrapped with quartz wool, the catalysts were arranged in a tubular furnace within the atmosphere aging reactor. The atmosphere aging program was programmed to raise the furnace temperature to 250°C at a rate of 10°C / min. A mass flowmeter was used to control the gas flow rate. The following gas flow conditions were used: 100 ppm C₃H₈, 50 ppm C₃H₈, 500 ppm CO, 500 ppm NO, 130 ppm SO₂, 8% CO₂, 10% O₂, 8% H₂O, and a balance of N₂. The catalysts were then aged at a constant temperature for 4 hours at a space velocity of 80,000 h⁻¹. During the aging period, an analyzer was used to record the concentration of gaseous pollutants. Once the analyzer detected no change in the SO2 concentration at the catalyst outlet, the gas distribution was cut off. Maintaining a constant space velocity, the temperature of the atmosphere aging chamber was raised to 600°C at a rate of 10°C / min, ending the first cycle. The NOx conversion efficiency of the post-treatment catalyst was then tested.

[0065] Comparative Example 2

[0066] On sample #4, a sampler was used to cut the DOC, cDPF, SCR, and ASC catalysts. The diameter of the four catalyst samples was 25.4 mm, and the heights were 50.8 mm, 76.2 mm, 76.2 mm, and 76.2 mm, respectively. After wrapping the four catalysts tightly with quartz wool, Figure 1 The catalysts were arranged in the tubular heating furnace of the atmosphere aging reactor in the order shown. The atmosphere aging program was set, and the temperature of the tubular heating furnace was raised to 250°C at a heating rate of 10°C / min. A mass flowmeter was used to control the gas flow rate, and the following gas distribution conditions were used: C3H8 150ppm, C3H6 400ppm, CO 800ppm, NO 800ppm, SO2 1000ppm, CO2 8%, O2 10%, H2O 10%, and N2 were balanced. The catalysts were aged at a constant temperature for 0.5 hours at a space velocity of 80,000 h-1. During the aging period, the concentration of gaseous pollutants was recorded using an analyzer. Once the analyzer detected that the SO2 concentration at the catalyst outlet had stopped changing, the gas distribution was cut off. Maintaining the space velocity, the atmosphere aging furnace temperature was raised to 600°C at a heating rate of 10°C / min, ending the first cycle.

[0067] The atmosphere aging bench repeats the above steps according to the set program for 10 cycles. After the 10th cycle, the NOx conversion efficiency and sulfur accumulation of the post-treatment catalyst are tested.

[0068] Comparative Example 3

[0069] On sample #4, a sampler was used to cut the DOC, cDPF, SCR, and ASC catalysts. The diameter of the four catalyst samples was 25.4 mm, and the heights were 50.8 mm, 76.2 mm, 76.2 mm, and 76.2 mm, respectively. After wrapping the four catalysts tightly with quartz wool, Figure 1 The catalysts were arranged in the tubular furnace in the order shown. The atmosphere aging station program was set. After the furnace temperature was raised to 300°C at a heating rate of 10°C / min, a mass flowmeter was used to control the gas flow rate. A gas mixture of 150ppm C3H8, 350ppm C3H6, 1000ppm CO, 1000ppm NO, 500ppm SO2, 9% CO2, 12% O2, 7% H2O, and a balanced N2 atmosphere was introduced into the tubular furnace. The catalysts were aged at a constant temperature for 1 hour at a space velocity of 40,000 h⁻¹. During the aging period, an analyzer was used to record the concentration of gaseous pollutants. Once the analyzer detected no change in the SO2 concentration at the catalyst outlet, the gas supply was cut off. Maintaining the space velocity, the furnace temperature was raised to 600°C at a heating rate of 10°C / min, ending the first cycle.

[0070] The atmosphere aging table repeats the above steps according to the set program and continues to run for 20 cycles. After the end of the 20th cycle experiment, the NOx conversion efficiency and sulfur accumulation of the aftertreatment catalyst are detected.

[0071] Comparative Example 4

[0072] The DOC, cDPF, SCR, and ASC catalysts are cut on the #4 sample using a sampling machine, and the four catalyst samples have a diameter of 25.4 mm and heights of 50.8 mm, 76.2 mm, 76.2 mm, and 76.2 mm, respectively. After the four catalysts are wrapped and compacted with quartz wool, the catalysts are arranged in the tube furnace in the order shown in Figure 1 The atmosphere aging table repeats the above steps according to the set program and continues to run for 20 cycles. After the end of the 20th cycle experiment, the NOx conversion efficiency and sulfur accumulation of the aftertreatment catalyst are detected.

[0073] The atmosphere aging table repeats the above steps according to the set program and continues to run for 30 cycles. After the end of the 30th cycle experiment, the NOx conversion efficiency and sulfur accumulation of the aftertreatment catalyst are detected.

[0074] Comparative Example 5

[0075] The DOC, cDPF, SCR, and ASC catalysts are cut on the #4 sample using a sampling machine, and the four catalyst samples have a diameter of 25.4 mm and heights of 50.8 mm, 76.2 mm, 76.2 mm, and 76.2 mm, respectively. After the four catalysts are wrapped and compacted with quartz wool, the catalysts are arranged in the tube furnace in the order shown in Figure 1The catalysts were arranged in the order shown in the figure and placed in a tubular furnace. The atmosphere aging station program was set. After the atmosphere furnace temperature was raised to 230°C at a heating rate of 10°C / min, a mass flowmeter was used to control the gas flow rate. The following gas distribution conditions were used: C3H8 200ppm, C3H6 100ppm, CO 500ppm, NO 500ppm, SO2 10ppm, CO2 8%, O2 10%, H2O 10%, and N2 in balance. The catalysts were aged at a constant temperature for 10 hours at a space velocity of 40,000 h⁻¹. During the aging period, the concentration of gaseous pollutants was recorded using an analyzer. Once the analyzer detected no change in the SO2 concentration at the catalyst outlet, the gas distribution was cut off. Maintaining the space velocity, the atmosphere aging station temperature was raised to 600°C at a heating rate of 10°C / min, ending the first cycle.

[0076] The atmosphere aging station repeats the above steps according to the set program for 50 cycles. After the 50th cycle, the NOx conversion efficiency and sulfur accumulation of the post-treatment catalyst are tested.

[0077] The calculation method of catalyst NOx conversion efficiency is the existing method, according to

[0078] The sulfur accumulation of the catalyst was calculated and tested using a carbon sulfur analyzer. The test results are shown in the following table:

[0079]

[0080]

[0081] From the table, it can be seen that the results of the sulfur poisoning test of the diesel engine bench and the whole vehicle under the addition of 1500 ppm high-sulfur diesel are consistent with the NOx efficiency decrease law under the sulfur poisoning cycle in Example 1. When the whole vehicle is added with 10 ppm of compliant diesel for normal use, the catalyst performance after 200,000 km of durability is consistent with that of Comparative Example 5. The test results of Example 1 to Example 5 show that for the same catalyst, after being exposed to 130 ppm of SO2 and running under the durability condition, the NOx conversion efficiency of the catalyst decreases accordingly at 175-300 DEG C with the increase of the cycle number, and when the cycle number reaches 50, the NOx conversion efficiency of the catalyst decreases to 0, reaching the sulfur tolerance limit of the catalyst. The test results of Comparative Example 2 to Comparative Example 5 show that when the SO2 concentration is increased, the sulfur poisoning time can be shortened, and the sulfur poisoning effect is consistent with the bench and vehicle results. In addition, compared with Example 1, when Fe and P elements are added to the catalyst, the NOx conversion efficiency of Example 6 and Comparative Example 1 deteriorates more seriously, which shows that when the catalyst undergoes the combined poisoning process of alkali / alkaline earth metal, sulfur, iron and phosphorus, the influence of sulfur poisoning on the catalyst will be intensified. In summary, the NOx conversion efficiency of the catalyst after sulfur poisoning is closely related to the sulfur poisoning time, the S sulfur concentration, the cycle number, the mileage and the addition of other toxic elements.

[0082] Different formulations, under the same sulfur poisoning tube furnace test conditions, the better the NOx conversion efficiency, the better the sulfur tolerance. The present application can quickly detect and evaluate the sulfur tolerance limit of the diesel engine aftertreatment catalyst, and can quickly screen the sulfur-tolerant catalyst formulation, greatly reducing the catalyst screening cost.

[0083] The catalysts used in the present application, such as DOC, cDPF, SCR and ASC, can be obtained from public channels, and the gas used in the experiment can be purchased from the market.

[0084] The present application can be close to the actual use of the whole vehicle, and can systematically test the sulfur resistance and regeneration capacity of the aftertreatment catalyst, define the sulfur tolerance boundary of the catalyst, and provide calibration support for actual whole vehicle application.

Claims

1. A method for rapidly evaluating the sulfur tolerance limit of a diesel engine aftertreatment catalyst, characterized in that: Follow these steps: (1) A sampler was used to intercept the catalyst sample. After the sample was tightly wrapped with quartz wool, it was placed in the tubular heating furnace of the atmosphere aging station reactor according to the arrangement order of the post-treatment catalysts; the arrangement order of the post-treatment catalysts was DOC, cDPF, SCR, and ASC; (2) Set the atmosphere aging station program, raise the temperature of the tubular heating furnace to 200-300℃, and stabilize it for 0.5-1.5h; (3) Adjust the air velocity of the atmosphere aging table, introduce pollutant gases such as C3H8, C3H6, CO, NO, NH3, SO2, CO2, O2, H2O and N2 into the tubular heating furnace, and perform rapid aging at a constant temperature for 1-50 hours; during this period, use an analyzer to record the concentration of gaseous pollutants at the catalyst outlet; (4) After the analyzer detects that the SO2 concentration at the catalyst outlet no longer changes, the polluted gas is cut off. While maintaining the analyzer air velocity unchanged, a rapidly heated atmosphere simulating the fuel injection regeneration process of the entire vehicle is introduced into the tubular heating furnace and the temperature is raised to 500-700°C. After the analyzer detects that the SO2 concentration at the catalyst outlet no longer changes, a reaction cycle is terminated. (5) After one cycle, take out the catalyst sample, detect the amount of sulfide captured by the catalyst, and calculate the NOx conversion efficiency; (6) Repeat steps (1) to (5) until the NOx conversion efficiency drops to 0, which is considered the sulfur tolerance limit of the catalyst.

2. The method for rapidly evaluating the sulfur tolerance limit of a diesel engine aftertreatment catalyst according to claim 1, characterized in that: The gas distribution conditions in the above step (3) are: C3H8 50-500ppm, C3H6 50-500ppm, CO 50-1000ppm, NO 300-1000ppm, NH3 300-1200ppm, SO2 10-2000ppm, CO2 8-10wt.%, O2 8-15wt.%, H2O 6-15wt.%, and N2 balance.

3. The method for rapidly evaluating the sulfur tolerance limit of a diesel engine aftertreatment catalyst according to claim 1, characterized in that: The analyzer airspeed range described in step (4) above is 20,000~200,000h -1 .

4. The method for rapidly evaluating the sulfur tolerance limit of a diesel engine aftertreatment catalyst according to claim 1, characterized in that: The rapid heating atmosphere described in the above step (4) is CO2, O2, H2O and N2 balance gas, and the heating rate of the tubular heating furnace is 10-50℃ / min.

5. The method for rapidly evaluating the sulfur tolerance limit of a diesel engine aftertreatment catalyst according to claim 1, characterized in that: 0.1-15 wt.% of one of P, Fe, and alkali metal elements or a combination thereof is added to the catalyst.

6. A method for rapidly evaluating the sulfur tolerance limit of a diesel engine aftertreatment catalyst according to any one of claims 1 to 5, characterized in that: The catalysts used are National VI commercial DOC catalysts, cDPF catalysts, SCR catalysts, and ASC catalysts.

7. A method for rapidly evaluating the sulfur tolerance limit of a diesel engine aftertreatment catalyst according to any one of claims 1 to 5, characterized in that: The analyzer is a Fourier infrared analyzer.

8. A method for rapidly evaluating the sulfur tolerance limit of a diesel engine aftertreatment catalyst according to any one of claims 1 to 5, characterized in that: The polluted gases C3H8, C3H6, CO, NO, SO2, CO2 and O2 are heated and mixed and then introduced into a tubular heating furnace.

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