CN107138044A - A kind of diesel vehicle urea liquid with cryogenic property and preparation method thereof - Google Patents

Abstract

The invention provides a urea solution for diesel vehicles with low temperature performance and a preparation method thereof, wherein the urea solution for diesel vehicles with low temperature performance comprises the following components: component A, component B, component C and Component D; the component A is high-purity water, component B is urea, component C is a small molecule liquid alcohol amine substance, and component D is a small molecule liquid alcohol substance; the parts by weight of each component are: 40-70 parts of component A, 20-35 parts of component B, 5-25 parts of component C and 5-40 parts of component D. The urea solution for diesel vehicles with low-temperature performance of the present invention has a freezing point lower than -18°C to -35°C and a surface tension lower than that of ordinary vehicle urea, and is suitable for use in all seasons in the north and south, especially in the cold seasons in the northeast region.

Description

A kind of urea solution for diesel vehicle with low temperature performance and preparation method thereof

technical field

The invention belongs to the field of diesel engine tail gas treatment, and in particular relates to a urea solution for diesel vehicles with low-temperature performance and a preparation method thereof.

Background technique

In recent years, every winter, smog occurs frequently in most parts of the central and eastern regions, and the number of smog days generally exceeds 5 days, and the national smog days generally show an increasing trend. Especially in the past two years, the smoggy weather has lasted longer. For example, in 2015, Beijing had only 186 days when the air reached the standard. In 2016, less than 50% of the days in Beijing met the air standard in November. Haze is a general expression of the excessive content of hundreds of suspended particulate matter in the atmosphere, especially PM2.5 (particulate matter with an aerodynamic equivalent diameter less than or equal to 2.5 microns) is considered to be the "culprit" of haze weather. Studies have shown that vehicle exhaust emissions account for about 30% of the total PM2.5 pollutants in the country, and are one of the "culprits" that cause my country's haze weather. Among them, the exhaust pollution from heavy-duty diesel vehicles is as high as more than two-thirds. Statistics show that the nitrogen oxides and PM pollutants emitted by diesel vehicles, which only account for 17% of my country's car ownership, account for more than 60% and 90% of total motor vehicle emissions, respectively. In order to reduce the pollution caused by automobile exhaust to the atmospheric environment, my country has fully implemented the National IV emission standards.

On May 15, 2014, the State Council issued the "2014-2015 Action Plan for Energy Conservation, Emission Reduction and Low-Carbon Development", pointing out that before the end of 2014, the national IV standard vehicle diesel will be supplied nationwide. During the "October" period of 2014, many provinces, including Jiangsu, Fujian, and Sichuan, issued their own national four oil promotion policies. The Ministry of Industry and Information Technology announced that starting from January 1, 2015, diesel vehicles nationwide will enforce the National IV emission standards. With the promotion and implementation of the National IV emission standard for vehicle diesel, the domestic vehicle urea market has ushered in a new opportunity. Although this market has just started in recent years, the domestic demand potential is huge, and the sales of urea for vehicles will grow rapidly.

The main pollutant emissions of diesel engines are NOx (nitrogen oxides) and PM (particles). Due to the influence of national conditions, oil products and other factors in my country, the SCR route is adopted for upgrading to China IV. During the combustion process of the engine adopting the SCR technology route, the diesel oil has been fully combusted through technical means to achieve the goal of effectively controlling PM emissions, while NOx needs to be reduced to nitrogen (N ₂ ) and Water (H ₂ O), the reducing agent necessary for this process is the vehicle urea solution. The exhaust gas comes out of the turbocharger and enters the exhaust pipe. A urea metering and injection device is installed on the exhaust pipe. When the temperature reaches 300°C to 500°C, the urea solution is sprayed. Under the action of the catalyst, the urea (NH ₂ CONH ₂ ) Hydrolysis produces NH ₃ and CO ₂ , NH ₃ reacts with NOx to generate nitrogen and water to be discharged, while absorbing harmful smoke particles.

The purity and cleanliness of the urea solution for vehicles are relatively high. Compared with industrial urea, the content of biuret, insoluble matter, iron, sulfide, chloride, etc. has strict requirements. Since the SCR catalyst carrier is extremely prone to metal ion poisoning and thus loses its catalytic effect, the urea solution for vehicles must use first-grade ultrapure water in the electronics industry. At present, the urea solution for vehicles generally consists of 32.5% high-purity urea and 67.5% ultra-pure water. The urea solution with this concentration has the lowest crystallization point, and it will crystallize when it is lower than -11°C. In actual use, it will completely freeze at -20°C, which limits its use in cold winter weather in the north, especially in the northeast. Adding a modifier to reduce the freezing point of the urea solution for vehicles is the most convenient and low-cost method, but due to the high requirements of the SCR catalyst on the purity and cleanliness of the urea solution for vehicles, metal salts that can significantly reduce the freezing point of the aqueous solution cannot be used, making the modification The selection range of the modifier is very limited, the inorganic salt can basically only choose ammonium substances, and most of the organic modifiers choose amines or amides.

The search found that there are many existing patents that use urea as the ammonia source and add modifiers to improve the freezing point, but most of them are ammonium substances, such as ammonium formate, ammonium carbonate, ammonium bicarbonate, etc. When the content is high, the CO ₂ The detected amount is easy to exceed the standard, and the stability is poor, and it is easy to decompose. Triethanolamine is used in China's published patent 201410193227 "Automobile Exhaust Emission Purification Treatment Liquid", but the composition of the treatment liquid is very complicated, which greatly increases the cost and difficulty of the process, and according to the general standard of urea for vehicles, the detection amount of phosphate (≦0.5 ) also exceeded the standard. The complex composition is likely to easily poison the sensitive catalyst and affect its reactivity.

Many patents such as Chinese patents CN201110134706.3 "A Urea Solution Composition for Low-Temperature Vehicles", CN201110134698.2 "A Urea Solution Composition for Ultra-low Temperature Vehicles", CN201510015958 "A Low Freezing Point Nitrogen Oxide Reductant and Its Preparation Method " and CN 201510017530 "An Ultra-Low Freezing Point Nitrogen Oxide Reductant and Its Preparation Method" both use small molecular liquid alcohols as composite additives, but the composition is more complicated than this patent, which increases the difficulty of the process. In addition, all of them contain formamide, which is flammable. In the presence of a catalyst, heated to below 35°C, it can decompose highly toxic hydrogen cyanide, and can strongly corrode copper, brass, lead, and rubber, which is inconvenient. Storage and transportation. CN201510015958 and CN 201510017530 also include sulfur-containing organic compound dimethyl sulfoxide, which may produce sulfur pollutants after pyrolysis. Because the composition of the modifier is simple and no content-limited components are introduced in this formula, all quality indicators are qualified.

In summary, the small molecule liquid alcohol amine modifier used in the present invention does not involve the claims of existing patents, and has a simple formula and remarkable effect.

Contents of the invention

In view of this, the present invention aims to propose a kind of urea solution for diesel vehicles with low temperature performance, to overcome the defects of the prior art, liquid alcohol amine and liquid alcohol modifier can be miscible with water, can be mixed with common organic matter It has the advantages of simple composition and preparation method, convenient operation, no ingredients with limited content, all quality indicators are qualified, and can be used in spring, summer, autumn, early winter and cold seasons in different regions.

In order to achieve the above object, technical solution of the present invention is achieved in that way:

A urea solution for diesel vehicles with low temperature performance, comprising the following components: component A, component B, component C and component D; the component A is high-purity water, component B is urea, and the component Component C is a small molecule liquid alcohol amine substance, and component D is a small molecule liquid alcohol substance.

Preferably, the parts by weight of each component are: 40-70 parts of component A, 20-35 parts of component B, 5-25 parts of component C and 5-40 parts of component D.

Preferably, the parts by weight of each component are: 45-65 parts of component A, 23-30 parts of component B, 8-22 parts of component C, and 9-35 parts of component D.

Preferably, the parts by weight of each component are: 50-60 parts of component A, 25-28 parts of component B, 13-20 parts of component C, and 15-28 parts of component D.

Preferably, the component C is ethanolamine and/or diethanolamine; the content of the component C is 20 parts.

Preferably, the component D is one or more of methanol, ethanol and ethylene glycol.

The high-purity water is industrial-grade high-purity water.

The urea needs to meet the technical requirements for AUS32-specific urea in the standard GB29518-2013 "Aqueous Solution of Nitrogen Oxide Reductant for Diesel Engines (AUS32)".

The pure water needs to meet the technical requirements for pure water in the GB29518-2013 "Diesel Engine Nitrogen Oxide Reductant Urea Aqueous Solution (AUS32)" standard

Both the small molecule liquid alcohol amines and the small molecule liquid alcohols are products of analytical grade or above.

Ethanolamine, also known as 2-hydroxyethylamine, has a molecular formula of HO(CH ₂ ) ₂ NH ₂ . It is a colorless and transparent liquid, miscible with water, methanol, ethanol, acetone, etc., and has good stability. Experiments have shown that when a certain amount of ethanolamine is added to ordinary urea for vehicles, the freezing point of the solution is significantly lowered. In order to reduce the cost, the content of ethanolamine should not be too high, preferably 20%, and some low molecular weight liquid alcohols can be added at the same time. In addition, diethanolamine is also miscible with water, ethanol, etc., and adding one or more of them may be considered.

Small molecular liquid alcohols have a very low freezing point and low density, such as methanol (-97°C, 0.792g/cm ³ ), ethanol (-114°C, 0.798g/cm ³ ), which can make the urea solution more Low freezing point and viscosity. However, due to their strong volatility and strong flammability of volatile substances, the amount of addition should not be too much. After compounding with liquid alcohol amine, the volatility of methanol and ethanol is obviously weakened, and it is found that the freezing point of the solution does not drop significantly after being placed for three months. Although ethylene glycol is often used in the preparation of automobile antifreeze, its density is slightly higher, which will increase the viscosity of urea solution and reduce the fluidity, so it is not suitable to add too much. In consideration of cost, availability, safety and viscosity, methanol is preferred in the present invention, and various combinations of methanol, ethanol, and ethylene glycol can also be selected according to properties and effects.

When the urea solution for vehicles is atomized and sprayed into the exhaust pipe of the engine, the atomization effect is a key issue. The atomization effect is good, the sprayed urea particles are small in size, can be quickly hydrolyzed, pyrolyzed, enter the catalyst carrier section, diffuse to the catalyst surface, absorb, and react. After the reaction, NH ₃ escapes less, and the efficiency of reducing NOx is improved. The atomization effect is closely related to the surface tension of the reducing agent solution. At room temperature, the surface tension of water is 72mN/m. The traditional urea solution for vehicles is made of high-purity urea and water. /m or less, ethylene glycol is 50mN/m. It can be predicted that the surface tension of the solution will decrease after adding the above substances to the traditional urea solution, and the sprayed reducing agent droplets will be smaller, thereby improving the atomization effect of the urea solution for vehicles.

The conductivity also has a certain influence during the use of urea solution. The lower the conductivity, the slower the flow of solution charge in the reaction system, which is easy to cause charge accumulation and form a flowing potential. When the flowing potential is high to a certain extent, it is easy to generate electric sparks, which is harmful to vehicles. Potentially dangerous. Since the organic alcohol amine is basically non-ionized and has a very small electrical conductivity, adding it to the urea solution will inevitably lead to a decrease in its electrical conductivity. However, even when the addition amount is 20%, the conductivity of the urea solution is still greater than 300 μS/cm, which is higher than that of the first-grade industrial electronic water, which is less than 1 μS/cm.

Another object of the present invention is to propose a method for preparing the above-mentioned urea solution for diesel vehicles with low-temperature performance, so as to prepare the above-mentioned urea solution for diesel vehicles with low-temperature performance.

In order to achieve the above object, technical solution of the present invention is achieved in that way:

A method for preparing the urea solution for diesel vehicles with low temperature performance as described above, comprising the following steps:

(1) Add component B to component A to fully dissolve it to obtain a transparent solution;

(2) Add component C and component D sequentially to the transparent solution described in step (1), fully stir and mix, and the resulting mixed solution obtains the urea solution for diesel vehicles with low temperature performance according to the present invention.

Preferably, in the step (2), component C and component D are sequentially added to the transparent solution described in step (1), fully stirred and mixed, and the resulting mixed solution is filtered to obtain the compound having the properties of the present invention. Urea solution for diesel vehicles with low temperature performance.

Preferably, in the step (2), the obtained mixed solution is pressure-filtered through a filter element of 0.5-0.8 μm and 0.6 Mpa to obtain the urea solution for diesel vehicles with low-temperature performance according to the present invention.

Preferably, in the step (1), component B is added to component A, and it is fully dissolved at 35°C to 40°C to obtain a transparent solution; in the step (2), after step (1) After cooling the transparent solution in to room temperature, then add component C, after component C is completely dissolved, then add component D.

The preparation method described in the present invention is applied in the small-scale preparation of laboratory products, and its preparation process comprises the following steps:

(1) Add high-purity urea into a round-bottomed flask that has been added with high-purity water, seal it with a ground plug, heat to 35°C to 40°C, and stir until the urea is completely dissolved and the solution is transparent;

(2) Cool the solution obtained in step (1) to room temperature, add a small molecule liquid alcoholamine substance, seal it with a ground plug, and stir until the solution is completely mixed and uniform.

(3) Add small-molecule liquid alcohols to the solution obtained in step (2), seal it with a ground plug, and stir until the solution is completely mixed.

(4) The solution obtained in step (3) is pressure-filtered with a filter element having a filtration accuracy of 0.8pm and 0.6Mpa, thereby obtaining the urea solution for diesel vehicles with low-temperature performance according to the present invention.

The preparation method described in the present invention is applied to the preparation of pilot test and commercial products. The preparation method is as follows: all raw materials are scaled up in proportion, stirred vigorously until the urea is completely dissolved, then adding solid amide substances and small molecule liquid alcohols in sequence Stir vigorously until it is completely mixed evenly, and the obtained solution is pressure-filtered through a filter element of 0.5-0.8 μm and 0.6 Mpa, which is the urea solution for diesel vehicles with low-temperature performance according to the present invention.

Compared with the prior art, a kind of urea solution for diesel vehicles with low temperature performance according to the present invention has the following advantages:

A kind of urea solution for diesel vehicles with low temperature performance according to the present invention, its liquid alcohol amine and liquid alcohol modifier can be miscible with water, can be miscible with common organic matter, the composition and preparation method are simple, easy to operate, No ingredients with limited content are introduced, and all quality indicators are qualified (meeting the requirements of ISO 22241-1:2006 international standard, DIN 70070:2005 German standard and DB11/552-2008 Beijing standard), and the freezing point of the product is lower than -18°C ~-35°C, the surface tension is lower than that of ordinary urea solution for vehicles, the atomization effect is good, and it has high conductivity, which can improve the NOx reduction efficiency. It is suitable for use in all seasons in the north and south, especially in the cold season in the northeast.

A kind of urea solution for diesel vehicles with low temperature performance according to the present invention, the detection amount of carbonate and chloride all reaches the requirement in DB11/552-2008 Beijing standard (due to ISO 22241-1:2006 international standard and DIN 70070:2005 German standard does not require the detection amount of carbonate and chloride, so refer to DB11/552-2008 Beijing standard), the detection amount of the two are: carbonate (calculated as CO ₂ ) detected amount ≤ 0.2%, chloride detected amount ≤ 0.2%.

The method for preparing the above-mentioned urea solution for diesel vehicles with low-temperature performance has the same advantages as the above-mentioned urea solution for diesel vehicles with low-temperature performance over the prior art, and will not be repeated here.

detailed description

Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods, unless otherwise specified, are conventional methods.

The present invention will be described in detail below in conjunction with examples.

Example 1

(1) Add 4.9376g of high-purity urea into a round-bottomed flask to which 10.2411g of high-purity water has been added, seal it with a ground plug, heat in a water bath to 40°C, and stir magnetically until the urea is completely dissolved and the solution is transparent;

(2) Cool the solution obtained in step (1) to room temperature, add 2.5629 g of ethanolamine, seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(3) Add 1.1335 g of methanol to the solution obtained in step (2), seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(4) The solution obtained in step (3) is pressure-filtered with a filter element with a filtration accuracy of 0.8pm and 0.6MPa to obtain the urea solution for diesel vehicles with low temperature performance of the present invention.

It has been determined that the freezing point of the mixture solution is -18°C, the surface tension is 70.3mN/m, and the conductivity is 555μS/cm. The detected amount conforms to the DB11/552-2008 Beijing standard; after three months of sealed storage at room temperature, there is no detectable change in appearance and smell.

The product of this embodiment is tested under ETC and ESC working conditions on a diesel engine bench with a power of 233 horsepower (displacement 6.5L). Under the rated injection volume of the product, after being processed by the SCR post-treatment system, the NOx emission can reach the National IV standard.

Example 2

(1) Add 5.0335g of high-purity urea into a round-bottomed flask to which 10.4505g of high-purity water has been added, seal it with a ground plug, heat in a water bath to 40°C, and stir magnetically until the urea is completely dissolved and the solution is transparent;

(2) Cool the solution obtained in step (1) to room temperature, add 2.626 g of ethanolamine, seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(3) Add 2.6200 g of methanol to the solution obtained in step (2), seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(4) The solution obtained in step (3) is pressure-filtered with a filter element with a filtration accuracy of 0.8pm to obtain the urea solution for diesel vehicles with low-temperature performance of the present invention.

It has been determined that the freezing point of the mixture solution is -24°C, the surface tension is 65.5mN/m, and the conductivity is 449μS/cm. The detected amount conforms to the DB11/552-2008 Beijing standard; after three months of sealed storage at room temperature, there is no detectable change in appearance and smell.

The product of this embodiment is tested under ETC and ESC working conditions on a diesel engine bench with a power of 233 horsepower (displacement 6.5L). Under the rated injection volume of the product, after being processed by the SCR post-treatment system, the NOx emission can reach the National IV standard.

Example 3

(1) Add 5.0342g of high-purity urea into a round-bottomed flask to which 10.4476g of high-purity water has been added, seal it with a ground plug, heat in a water bath to 40°C, and stir magnetically until the urea is completely dissolved and the solution is transparent;

(2) Cool the solution obtained in step (1) to room temperature, add 2.6135 g of ethanolamine, seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(3) Add 4.4703 g of methanol to the solution obtained in step (2), seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(4) The solution obtained in step (3) is pressure-filtered with a filter element with a filtration accuracy of 0.8pm and 0.6MPa to obtain the urea solution for diesel vehicles with low temperature performance of the present invention.

It has been determined that the freezing point of the mixture solution is -28°C, the surface tension is 60.3mN/m, and the conductivity is 380μS/cm. The detected amount conforms to the DB11/552-2008 Beijing standard; after three months of sealed storage at room temperature, there is no detectable change in appearance and smell.

The product of this embodiment is tested under ETC and ESC working conditions on a diesel engine bench with a power of 233 horsepower (displacement 6.5L). Under the rated injection volume of the product, after being processed by the SCR post-treatment system, the NOx emission can reach the National IV standard.

Example 4

(1) Add 4.9765g of high-purity urea into a round-bottomed flask to which 10.3377g of high-purity water has been added, seal it with a ground plug, heat in a water bath to 40°C, and stir magnetically until the urea is completely dissolved and the solution is transparent;

(2) Cool the solution obtained in step (1) to room temperature, add 2.5896 g of ethanolamine, seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(3) Add 6.898 g of methanol to the solution obtained in step (2), seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(4) The solution obtained in step (3) is pressure-filtered with a filter element with a filtration accuracy of 0.8pm and 0.6MPa to obtain the urea solution for diesel vehicles with low temperature performance of the present invention.

It has been determined that the freezing point of the mixture solution is -32°C, the surface tension is 57.3mN/m, and the conductivity is 299μS/cm. The detected amount conforms to the DB11/552-2008 Beijing standard; after three months of sealed storage at room temperature, there is no detectable change in appearance and smell.

The product of this embodiment is tested under ETC and ESC working conditions on a diesel engine bench with a power of 233 horsepower (displacement 6.5L). Under the rated injection volume of the product, after being processed by the SCR post-treatment system, the NOx emission can reach the National IV standard.

Example 5

(1) Add 10.3200g of high-purity urea into a round-bottomed flask to which 21.4329g of high-purity water has been added, seal it with a ground plug, heat in a water bath to 40°C, and stir magnetically until the urea is completely dissolved and the solution is transparent;

(2) Cool the solution obtained in step (1) to room temperature, add 5.3551 g of ethanolamine, seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(3) Add 5.3610 g of ethanol to the solution obtained in step (2), seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(4) The solution obtained in step (3) is pressure-filtered with a filter element with a filtration accuracy of 0.8pm and 0.6MPa to obtain the urea solution for diesel vehicles with low temperature performance of the present invention.

It has been determined that the freezing point of the mixture solution is -26°C, the surface tension is 54.0mN/m, and the conductivity is 316μS/cm. The detected amount conforms to the DB11/552-2008 Beijing standard; after three months of sealed storage at room temperature, there is no detectable change in appearance and smell.

The product of this embodiment is tested under ETC and ESC working conditions on a diesel engine bench with a power of 233 horsepower (displacement 6.5L). Under the rated injection volume of the product, after being processed by the SCR post-treatment system, the NOx emission can reach the National IV standard.

Example 6

(1) Add 9.2948g of high-purity urea into a round-bottomed flask to which 19.3036g of high-purity water has been added, seal it with a ground plug, heat in a water bath to 40°C, and stir magnetically until the urea is completely dissolved and the solution is transparent;

(2) Cool the solution obtained in step (1) to room temperature, add 4.8283 g of ethanolamine, seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(3) Add 8.2698 g of ethylene glycol to the solution obtained in step (2), seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(4) The solution obtained in step (3) is pressure-filtered with a filter element with a filtration accuracy of 0.8pm and 0.6MPa to obtain the urea solution for diesel vehicles with low temperature performance of the present invention.

It has been determined that the freezing point of the mixture solution is -32°C, the surface tension is 63.8mN/m, and the conductivity is 470.5μS/cm. The detected amount of chemical compounds complies with the DB11/552-2008 Beijing standard; after three months of sealed storage at room temperature, there is no detectable change in appearance and smell.

The product of this embodiment is tested under ETC and ESC working conditions on a diesel engine bench with a power of 233 horsepower (displacement 6.5L). Under the rated injection volume of the product, after being processed by the SCR post-treatment system, the NOx emission can reach the National IV standard.

Example 7

(1) Add 11.0341g of high-purity urea into a round-bottomed flask to which 22.9221g of high-purity water has been added, seal it with a ground plug, heat in a water bath to 40°C, and stir magnetically until the urea is completely dissolved and the solution is transparent;

(2) Cool the solution obtained in step (1) to room temperature, add 5.6311 g of diethanolamine, seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(3) Add 9.8861 g of methanol to the solution obtained in step (2), seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(4) The solution obtained in step (3) is pressure-filtered with a filter element with a filtration accuracy of 0.8pm and 0.6MPa to obtain the urea solution for diesel vehicles with low temperature performance of the present invention.

It has been determined that the freezing point of the mixture solution is -35°C, the surface tension is 55.9mN/m, and the conductivity is 183μS/cm. The detected amount conforms to the DB11/552-2008 Beijing standard; after three months of sealed storage at room temperature, there is no detectable change in appearance and smell.

The product of this embodiment is tested under ETC and ESC working conditions on a diesel engine bench with a power of 233 horsepower (displacement 6.5L). Under the rated injection volume of the product, after being processed by the SCR post-treatment system, the NOx emission can reach the National IV standard.

Example 8

(1) Add 9.9590g of high-purity urea into a round-bottomed flask to which 20.6847g of high-purity water has been added, seal it with a ground plug, heat in a water bath to 40°C, and stir magnetically until the urea is completely dissolved and the solution is transparent;

(2) Cool the solution obtained in step (1) to room temperature, add 5.1768 g of diethanolamine, seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(3) Add 5.1719 g of ethanol to the solution obtained in step (2), seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(4) The solution obtained in step (3) is pressure-filtered with a filter element with a filtration accuracy of 0.8pm and 0.6MPa to obtain the urea solution for diesel vehicles with low temperature performance of the present invention.

It has been determined that the freezing point of the mixture solution is -27°C, the surface tension is 52.7mN/m, and the conductivity is 212μS/cm. The detected amount conforms to the DB11/552-2008 Beijing standard; after three months of sealed storage at room temperature, there is no detectable change in appearance and smell.

The product of this embodiment is tested under ETC and ESC working conditions on a diesel engine bench with a power of 233 horsepower (displacement 6.5L). Under the rated injection volume of the product, after being processed by the SCR post-treatment system, the NOx emission can reach the National IV standard.

Example 9

(1) Add 11.6944g of high-purity urea into a round-bottomed flask to which 24.2808g of high-purity water has been added, seal it with a ground plug, heat in a water bath to 40°C, and stir magnetically until the urea is completely dissolved and the solution is transparent;

(2) Cool the solution obtained in step (1) to room temperature, add 6.0732 g of diethanolamine, seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(3) Add 10.4111 g of ethylene glycol to the solution obtained in step (2), seal it with a ground plug, and stir magnetically until the solution is completely mixed and uniform.

(4) The solution obtained in step (3) is pressure-filtered with a filter element with a filtration accuracy of 0.8pm and 0.6MPa to obtain the urea solution for diesel vehicles with low temperature performance of the present invention.

It has been determined that the freezing point of the mixture solution is -31°C, the surface tension is 62.3mN/m, and the conductivity is 210μS/cm. The detected amount conforms to the DB11/552-2008 Beijing standard; after three months of sealed storage at room temperature, there is no detectable change in appearance and smell.

The product of this embodiment is tested under ETC and ESC working conditions on a diesel engine bench with a power of 233 horsepower (displacement 6.5L). Under the rated injection volume of the product, after being processed by the SCR post-treatment system, the NOx emission can reach the National IV standard.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of the present invention. within the scope of protection.

Claims (10)

1. a kind of diesel vehicle urea liquid with cryogenic property, it is characterised in that：Including following each component：Component A, group Divide B, component C and component D；The component A is high purity water, and component B is urea, and component C is small molecule liquid alcohol amine substance, group It is small molecule liquid alcohols material to divide D.

2. the diesel vehicle urea liquid according to claim 1 with cryogenic property, it is characterised in that：The weight of each component Measuring number is：5~40 parts of 40~70 parts of component A, 20~35 parts of component B, component C5~25 part and component D.

3. the diesel vehicle urea liquid according to claim 1 with cryogenic property, it is characterised in that：The weight of each component Measuring number is：45~65 parts of component A, 23~30 parts of component B, component C8~22 part, 9~35 parts of component D.

4. the diesel vehicle urea liquid according to claim 1 with cryogenic property, it is characterised in that：The weight of each component Measuring number is：50~60 parts of component A, 25~28 parts of component B, component C13~20 part, 15~28 parts of component D.

5. the diesel vehicle urea liquid with cryogenic property according to Claims 1-4 any one, its feature exists In：The component C is monoethanolamine and/or diethanol amine；The content of the component C is 20 parts.

6. the diesel vehicle urea liquid with cryogenic property according to Claims 1-4 any one, its feature exists In：The component D is more than one or both of methanol, ethanol and ethylene glycol.

7. a kind of side of the diesel vehicle urea liquid with cryogenic property prepared as described in claim 1 to 6 any one Method, it is characterised in that：Comprise the following steps：

(1) component B is added in component A, it is fully dissolved, obtain clear solution；

(2) component C and component D are sequentially added in the clear solution described in step (1), is sufficiently stirred for mixing, gained mixing is molten Liquid produces the diesel vehicle urea liquid of the present invention with cryogenic property.

8. the preparation method of the diesel vehicle urea liquid with cryogenic property described in claim 7, it is characterised in that：It is described In step (2), component C and component D are sequentially added in the clear solution described in step (1), is sufficiently stirred for mixing, gained mixing Solution is filtered, and produces the diesel vehicle urea liquid of the present invention with cryogenic property.

9. the preparation method of the diesel vehicle urea liquid according to claim 8 with cryogenic property, it is characterised in that： In the step (2), gained mixed solution produces of the present invention after the cartridge pressure filtering through 0.5-0.8 μm, 0.6Mpa Diesel vehicle urea liquid with cryogenic property.

10. the preparation method of the diesel vehicle urea liquid according to claim 7 with cryogenic property, its feature exists In：In the step (1), component B is added in component A, in making it fully dissolve at 35 DEG C~40 DEG C, clear solution is obtained； In the step (2), after the clear solution in step (1) is cooled to room temperature, component C is added, treats that component C is completely dissolved Afterwards, component D is added.