CN112682131A

CN112682131A - Improved method for purifying ethanol automobile exhaust

Info

Publication number: CN112682131A
Application number: CN202011503072.XA
Authority: CN
Inventors: 刘建英; 杨皓; 杨曦怒; 徐成华; 罗兰妮; 田黎霞
Original assignee: Chengdu University of Information Technology
Current assignee: Chengdu University of Information Technology
Priority date: 2020-12-18
Filing date: 2020-12-18
Publication date: 2021-04-20

Abstract

The invention discloses an improved method for purifying ethanol automobile exhaust, relates to the field of automobile exhaust, energy conservation and environmental protection, and is a method for effectively reducing the emission of gas waste and reducing environmental pollution. The invention adopts the three-way catalyst with the adsorption bypass, the adsorption section is arranged in front of the traditional ethanol automobile three-way catalyst, the standard emission of the ethanol automobile tail gas is realized, the cost of the adsorbent used in the adsorption process of the method is only one tenth of that of the three-way catalyst, and the application of the method is much less than the economic cost invested in developing the novel low-temperature three-way catalyst.

Description

Improved method for purifying ethanol automobile exhaust

Technical Field

The invention relates to the field of automobile exhaust, energy conservation and environmental protection, and discloses a method for effectively reducing the emission of gas waste and reducing environmental pollution.

Background

At present, the urbanization level of China is continuously improved, people change the trip mode in order to improve the quality of life, and the automobile purchase quantity is rapidly improved. The problem of automobile exhaust pollution is the most important reason for threatening the air quality, and pollution generated by automobile exhaust emission in some regions accounts for more than 60% of the total amount of local air pollution indexes, so that the implementation of measures for preventing and treating the automobile exhaust pollution is urgent. Automobile exhaust directly harms human health, and can also have a profound effect on the environment of human life.

At present, more advanced ternary catalytic purification technology is mainly adopted at home and abroad to reduce the pollution of automobile exhaust. With the development of the technology, a three-way automobile exhaust purification catalyst taking cordierite honeycomb ceramic as a carrier and activated alumina as a coating and loading precious metals of platinum, rhodium and palladium is developed and matured and is widely applied.

In recent years, metal alloys, alumina, mullite, molecular sieves, glass fibers and the like have been studied as exhaust gas catalyst carriers, wherein the metal alloy carriers are most studied, and the metal alloy carriers are installed and used on automobiles with partial electric heating catalysts in the United states, Japan and the like, which is very beneficial to reducing the exhaust resistance of the automobiles, obviously improves the power performance, improves the cold start exhaust gas purification efficiency and prolongs the service life of purifiers.

The preparation process of the automobile exhaust three-way catalyst is disclosed by Liuzhou Shentong automobile science and technology Limited company CN105797744A Mitsuing and the like, and comprises the steps of mixing and ball-milling zirconium oxide and cerium oxide powder according to mass fraction, then adding aluminum oxide, iron oxide and manganese oxide powder and continuing ball-milling to obtain composite powder; preparing the composite powder into slurry by using deionized water, immersing the carrier into a palladium chloride ammonia solution after drying and roasting, taking out, drying, roasting and cooling to obtain the three-way catalyst. The invention refines the catalyst powder particles by ball milling, and the grain size reaches the nanometer level; meanwhile, the activity of the catalyst is improved by adding iron and manganese; the invention also plates palladium on the carrier, which not only has even and compact plating layer, good chemical stability, but also has high hardness and good lubricity.

Zhejiang micron energy environment science and technology Limited company CN108165327A Liu Quanzhong announced a cooling liquid additive for reducing benzene emissions, a production method and a use method, and the method comprises the following steps: SiO 2₂、Al₂O₃、Fe₂O₃、MgO、CaCO₃、TiO₂MnO and rare earth elements. Selecting natural ore containing the formula materials, screening according to the far infrared wavelength distribution of each formula material, primarily crushing the screened ore, secondarily processing to be nano-scale, adding rare earth materials for mixing, and irradiating the mixed material THz by irradiation equipment. Directly into the cooling system of the vehicle. The cooling liquid additive for reducing benzene emission can promote the gasoline to be more completely combusted after being added, and has obvious oil saving and power improving effects. So that the effect of reducing the total content of benzene substances is obvious and stable, and the effect of reducing emission is obvious. The energy-saving effect on gasoline vehicles and ethanol gasoline vehicles is obvious, and the energy-saving device has certain effect on hybrid vehicles and gas vehicles. Moreover, the additive is effective for a long time after being added at one time, and has low cost.

Chengdu information engineering university CN110465323A Liujiangying, etc. announced a molecular sieve modified Pd/Al₂O₃The three-way catalyst comprises the following components in percentage by mass: 30-70% of molecular sieve, 28-68% of alumina and 2% of active component Pd. The modified aluminum oxide material with the mass percent of the molecular sieve of 0-70% is obtained by dripping aluminum nitrate solution and ammonia water into a container containing molecular sieve mother liquor in a cocurrent flow manner, and then aging, filtering, washing, drying and roasting. The molecular sieve modified aluminum oxide material prepared by the method has larger specific surface area; when used as Pd-based catalyst carrier, the catalyst can not only improve the traditional Pd/Al₂O₃The adsorption performance of the three-way catalyst on VOCs discharged from an ethanol gasoline vehicle in cold start can also promote the low-temperature catalytic oxidation activity of the catalyst on the VOCs; and the preparation method is simple and easy to operate.

The invention can show that: the inventor focuses on an improved method of an automobile exhaust catalyst, and the aim of improving the efficiency can be achieved only by improving the performance of the catalyst and replacing the existing automobile catalyst.

During the cold start and idling of the automobile, the exhaust temperature is low, the activation difficulty of the catalyst is high, pollutants are not effectively treated in the period, and the emission amount of the pollutants accounts for more than 80% of the whole emission amount.

Disclosure of Invention

The activation temperature of the traditional ethanol automobile three-way catalyst is usually higher than 150 ℃, the lowest temperature for realizing the standard emission of automobile exhaust is usually higher than 220 ℃, and the temperature is recorded as Tmin ℃.

The traditional three-way catalyst for the ethanol automobile is not provided with an adsorption section, and when the temperature of tail gas is 20-Tmin at the initial stage of low-temperature start and during idling of the automobile, the emission of CO, NOx and VOCs in the tail gas can hardly reach the standard.

The adsorbent can effectively adsorb H at 20-250 DEG C₂O, CO, NOx and VOCs, but pollutants can not be completely catalyzed and reacted, and the pollutants can still be converted up to the standard by the catalytic action of a three-way catalyst.

The method of the invention adopts a three-way catalyst with an adsorption bypass. The temperature of the tail gas is 20-Tmin ℃, an air inlet passage is switched to enable the tail gas to pass through an adsorption bed, wherein H₂H which is difficult to adsorb and is adsorbed by the adsorbent₂、N₂、O₂Directly sent into a three-way catalyst and then discharged into the atmosphere, and the concentration of CO, NOx and VOCs at the outlet of the three-way catalyst is lower than that of the traditional method by more than 50 percent.

When the temperature of the tail gas is higher than Tmin ℃, the tail gas passes through an adsorption bed, and H in the adsorbent₂And the O, CO, NOx and VOCs are gradually desorbed along with the rise of the temperature. When the tail gas temperature reaches 480 ℃, the adsorbent working for a long time is easy to cause the collapse of a pore structure. If regeneration is complete, the intake passage may be switched in advance. When the temperature of the tail gas is between Tmin and 480 ℃, the regenerated gas and the inlet gas simultaneously enter the three-way catalyst for reaction and then are discharged into the atmosphere.

And at the end of regeneration, the temperature of the tail gas should be 350-480 ℃. After the tail gas regeneration is finished, the tail gas directly enters the three-way catalyst without passing through the adsorption bed to react and then is discharged into the atmosphere, so that the collapse of the pore structure of the adsorbent is avoided.

Drawings

FIG. 1 is a schematic diagram of the gas path structure of a three-way catalyst with an adsorption bypass at low and medium temperatures.

FIG. 2 is a schematic diagram of the gas path structure of a three-way catalyst with an adsorption bypass at high temperature.

Detailed Description

Example 1:

ethanol automobile exhaust I adopts a certain three-way catalyst with an adsorption bypass, the temperature of the exhaust is 20-220 ℃ at the initial starting stage and during the idling period of an automobile, the exhaust passes through an adsorption bed, and H in the exhaust₂O, CO, NOx and VOCs are adsorbed by the adsorbent, and H difficult to be adsorbed₂、N₂、O₂Directly sending the mixture into a three-way catalyst and then discharging the mixture into the atmosphere, wherein the concentration of CO, NOx and VOCs at three-way outlets is 60 percent lower than that of the CO, NOx and VOCs at the traditional method; the temperature of tail gas is 220-460 ℃, and H in the adsorbent₂The O, CO, NOx and VOCs are gradually desorbed along with the rise of the temperature, enter a three-way catalyst for reaction and then are discharged into the atmosphere; the temperature for completing the regeneration of the adsorbent is 375 ℃, and the tail gas after the regeneration of the adsorbent is not passed through the adsorption bed but directly enters the three-way catalyst for reaction and then is discharged into the atmosphere.

Example 2:

ethanol automobile exhaust II adopts a certain ternary catalyst with an adsorption bypass, the temperature of the exhaust is 30-240 ℃ at the initial starting stage and during the idling period of the automobile, the exhaust passes through an adsorption bed, and H in the exhaust₂O, CO, NOx and VOCs are adsorbed by the adsorbent, and H difficult to be adsorbed₂、N₂、O₂Directly sending the mixture into a three-way catalyst and then discharging the mixture into the atmosphere, wherein the concentration of CO, NOx and VOCs at the outlet of the three-way catalyst is 62 percent lower than that of the CO, NOx and VOCs at the outlet of the three-way catalyst in the traditional method; the temperature of tail gas is 240-465 ℃, and H in the adsorbent₂The O, CO, NOx and VOCs are gradually desorbed along with the rise of the temperature, enter a three-way catalyst for reaction and then are discharged into the atmosphere; the temperature for completing the regeneration of the adsorbent is 400 ℃, and after the regeneration of the adsorbent is completed, tail gas directly enters the three-way catalyst for reaction without passing through an adsorption bed and then is discharged into the atmosphere.

Example 3:

ethanol automobile exhaust III adopts a certain ternary catalyst with an adsorption bypass, the temperature of the exhaust is 40-260 ℃ at the initial starting stage and during the idling period of the automobile, the exhaust passes through an adsorption bed, and H in the exhaust₂O, CO, NOx and VOCs are adsorbed by the adsorbent, and H difficult to be adsorbed₂、N₂、O₂Directly sending the mixture into a three-way catalyst and then discharging the mixture into the atmosphere, wherein the concentration of CO, NOx and VOCs at three-way outlets is 70% lower than that of the CO, NOx and VOCs at the traditional method; temperature of tail gasThe temperature is 260-470 ℃, and the content of H in the adsorbent is H₂The O, CO, NOx and VOCs are gradually desorbed along with the rise of the temperature, enter a three-way catalyst for reaction and then are discharged into the atmosphere; the regeneration finishing temperature of the adsorbent is 425 ℃, and after the regeneration finishing of the adsorbent, tail gas directly enters the three-way catalyst without passing through the adsorption bed to react and then is discharged into the atmosphere.

The cost of the adsorbent used in adsorption is only one tenth of that of the three-way catalyst, and the application of the method is much less than the economic cost for developing the novel low-temperature three-way catalyst.

Claims

1. An improved method for purifying ethanol automobile exhaust is characterized in that a three-way catalyst used for purification is provided with an adsorption bypass, when an automobile is in an initial starting stage and the temperature of the exhaust is 20 ℃ to the lowest emission temperature of the three-way catalyst reaching the standard, the exhaust passes through an adsorption bed, and H in the exhaust passes through the adsorption bed₂O, CO, NOx and VOCs are adsorbed by the adsorbent, and H difficult to be adsorbed₂、N₂、O₂Directly sending the mixture into a three-way catalyst and then discharging the mixture into the atmosphere, wherein the concentrations of CO, NOx and VOCs at the outlet of the three-way catalyst are lower than those of the CO, NOx and VOCs by more than 50 percent compared with the traditional method; h in the adsorbent when the tail gas temperature is the lowest standard emission temperature of the three-way catalyst to 480 DEG C₂The O, CO, NOx and VOCs are gradually desorbed along with the rise of the temperature, enter a three-way catalyst for reaction and then are discharged into the atmosphere; when the temperature is 350-480 ℃, the adsorbent is regenerated, and the tail gas after the regeneration of the adsorbent directly enters the three-way catalyst for reaction without passing through an adsorption bed and then is discharged into the atmosphere.