WO2017084195A1 - Multifunctional cetane number improver for diesel fuel and method for preparing same - Google Patents

Abstract

A multifunctional cetane number improver for diesel fuel, comprising 1-20% of hydrocarbon and 80-99% of conventional cetane number improver. This improver has a simple and safe synthetic process, light product color, high stability, and good synergistic effect.

Description

Multifunctional diesel cetane number improver and preparation method thereof Technical field

The present invention relates to a diesel additive, and more particularly to the synthesis and compounding of a hydrocarbon used as a diesel cetane number improver and an antioxidant.

technical background

Cetane number is an important quality indicator for diesel combustion performance and antiknock performance. Its size has an important impact on engine cold start, pollutant discharge, fuel consumption and working noise. To a certain extent, the higher the cetane number of diesel, the shorter the retardation period, the lower the temperature of diesel self-ignition, and the better the combustion performance of diesel. Diesel has a long period of deflagration, and there are many diesel fuel injected into the cylinder before the deflagration. At the same time, a large amount of diesel fuel is burned at the same time, which causes the pressure inside the cylinder to increase sharply, and the phenomenon of knocking the cylinder and overheating the engine occurs, that is, knocking occurs. China's national standards stipulate that CN for vehicle diesel is not less than 49. At present, global crude oil reserve resources are becoming increasingly tense, and the trend of heavy weight is becoming more and more serious, resulting in changes in the properties of petroleum products and a decrease in the production of straight-run diesel. In this case, each refinery generally adopts a catalytic cracking secondary processing process to increase the production of light oil, but the diesel produced by this process has a low cetane number and poor stability. Therefore, increasing the cetane number of diesel fuel is one of the problems to be solved.

At present, there are three main methods for increasing the cetane number: 1) the use of diesel with low cetane number and straight-run diesel. The problem with this method is the limited production of straight-run diesel. 2) The method of solvent extraction and hydrogenation is used to increase the cetane number of the diesel. This method is costly and costly. 3) Add cetane number improver. The method has the advantages of low cost and simple process, and is the most simple and economical method for increasing the cetane number of diesel oil.

The study of cetane improvers began in the 1930s. Alkyl nitrates are currently used more frequently, such as DII22 and DII23 from Ethyl Corporation, ECA28478 from Exxon, USA, and Associated Octel in the United Kingdom. The company's CI-20801. China's development of diesel cetane number improver started late, and the products developed mainly include amyl nitrate and octyl nitrate. Due to the harsh production process conditions of alkyl nitrates, the equipment is seriously corroded, and a large amount of NOx is generated during combustion, which pollutes the environment. In recent years, the type of cetane improver containing no nitrogen has attracted more and more attention from users.

The nitrogen-free cetane number improver consists of only three elements: C, H, and O. The combustion products are only CO ₂ and H ₂ O. While increasing the cetane number, it can promote diesel combustion and reduce particulate matter emissions. The requirements and development trends of environmentally friendly products are the focus of future development of cetane improvers. Nitrogen-free cetane number improvers are most commonly used as organic peroxides and esters. The organic peroxide-based improver is t-butyl peroxide, di-tert-butyl peroxide, acetone peroxide or the like. Such compounds are less stable and tend to decompose to generate free radicals, which increases the instability of diesel fuel and is currently used less frequently.

The ester cetane number improver not only can increase the cetane number, but also maintain the low temperature fluidity of the diesel oil, and also has a certain inhibitory effect on the phase separation phenomenon existing in the diesel oil. A representative product is an oxalate ester in which the synthesis of diisobutyl oxalate and diisoamyl oxalate is now industrialized. The production process of oxalate improver is simple and safe, the source of raw materials is wide, the cost is low, and the pollution is small, but the improvement effect of cetane number is not as good as that of alkyl nitrate and peroxide improver. %), low cost performance.

An effective way to improve the performance of the cetane improver is to compound different types of cetane improvers. For example, according to the patent US Pat. No. 4,448,587, when 0.15 wt% of isooctyl nitrate is added to diesel, the cetane number of the additive diesel can be increased from 37.2 to 41.7. Instead, the cetane number improver compounded by 50% 2-ethoxyethyl nitrate and 50% isooctyl nitrate can be used to increase the cetane number from 37.2 by adding 0.11% by weight. To 41.5. In the case of increasing the amplitude of the same cetane number, the amount of mixed ester is reduced by 26% compared to the amount of isooctyl nitrate alone, indicating that the mixture of 2-ethoxyethyl nitrate and isooctyl nitrate is diesel. The effect of improving the alkyl value has a significant synergistic effect, greatly reducing the cetane number. Improver use cost.

Patent WO 03/104360 A2 extracted from plants β- carotene and carotenoids as cetane improvers, cetane improvers obtained by this method of combustion without generating NO _x, has environmental advantages. More importantly, it is compounded with other cetane improvers and has a good synergistic effect. However, such improvers have the following problems: 1) the cost is high regardless of whether they are extracted from plants or chemically synthesized; 2) due to the long conjugated chain structure in the molecular structure, which is easily oxidized by air, usually requires the addition of stabilizers or Inert gas protection is inconvenient to use, and the addition of too much stabilizer (antioxidant) will adversely affect the diesel combustion process; 3) the color is deep, affecting the diesel phase.

In recent years, the development of colorless carotenoids has gradually become a new hot spot in the field of industrial research, mainly because it has great application prospects as an antioxidant additive in the field of cosmetics and other products that require the maintenance of primary colors. It is worth mentioning that the general carotenoids are very sensitive to light and air, and are easy to lose, but the stability and antioxidant effect of colorless carotenoids is superior to that of common carotenoids. For the above reasons, colorless or light-colored carotenoids are promising as multifunctional additives for improving cetane number and oxidation resistance of diesel fuel.

Typical colorless or light color carotenoids are phytoene and phytoene. They exhibit a colorless or pale yellow color due to the shorter conjugated double bond system in the molecular skeleton. Like other long conjugated chain carotenoids, the structure of hexahydrogen lycopene allows them to absorb ultraviolet light and quench free radicals generated by ultraviolet light. In addition to physically quenching singlet oxygen or capturing peroxidic free radicals, they also eliminate oxidative free radicals by interacting with other forms of active oxidation.

At present, the development and production mode of six (eight) hydrogen lycopene is mainly plant extraction. This method has limited production and high cost. The advantages of the chemical synthesis method are high yield and low cost, and are highly advantageous in products such as fuels that do not require pure natural additives. J.B. Davis et al. used chemical synthesis to prepare lycopene (J. Chem. Soc. C., 1966, 2154), in which 12 steps were synthesized for the synthesis of phytoene. The yield is low, and some expensive or dangerous reagents are needed in the synthesis, so the synthesis process is not an economically feasible and effective way to prepare phytoene. However, with the continuous improvement of the synthesis and purification processes, the colorless or light-colored carotenoids produced by the chemical synthesis method are completely close to or reach the level of pure natural products and are widely used in various industries.

Summary of the invention

The object of the present invention is to overcome the deficiencies of the prior art and to provide a method for preparing a lycopene hydrocarbon having a simple process and a low cost. The obtained product has light color and high stability, and is compounded with the conventional alkyl nitrate and/or oxalate without adding a stabilizer, and the synergistic effect is obvious, and the cetane number and the antioxidant property of the diesel can be remarkably improved.

The multifunctional diesel cetane number improver provided by the invention comprises the following weight components:

Hydrocarbon 1-20%

Traditional cetane number improver 80-99%.

Preferably, the improver comprises the following weight components:

Hydrocarbon 1-5%

Traditional cetane number improver 95-99%.

The conventional cetane number improver is a mixture of one or more of an alkyl nitrate and an oxalate.

The alkyl nitrate is one or a mixture of one or more of n-butyl nitrate, isobutyl nitrate, amyl nitrate, cyclohexyl nitrate, and isooctyl nitrate.

The oxalate is one or a mixture of one or more of dibutyl oxalate, diisobutyl oxalate, and diisoamyl oxalate.

The hydrocarbon is one or more mixtures of compounds having the following I or II structure Object:

The hydrocarbon is synthesized by the following method:

a) Hydrocarbon I

The difficulty in synthesizing phytoene is the asymmetric structure of its molecule (see formula III, the C12-C13 bond is an unsaturated bond, and the C12'-C13' bond is a saturated bond). Studies have shown that the antioxidant and cetane number improvement properties of lycopene are primarily dependent on the length of the conjugated double bond in the molecular backbone. Therefore, it can be considered to reduce a non-conjugated double bond structural unit at the right end of the formula III, so that the number of non-conjugated double bonds at both ends of the molecule is uniform and the structure is symmetrical, thereby reducing the difficulty of synthesis.

Since the modified structural formula has two non-conjugated double bonds at each end, it can be formed by condensation of a molecule of pentacarbon diphosphate and two molecules of aldehyde via Wittig-Horner. The reaction equation is as follows:

The specific synthesis steps are as follows:

Add linalool (or nerolidol), pyridine and solvent petroleum ether to the reaction flask with stirring, protect with N ₂ , add phosphorus tribromide, phosphorus tribromide and linalool at -10 ° C The molar ratio of (or nerolidol) to pyridine is 1:2:1. Stirring is continued at this temperature for 6-10h, preferably 8h, and then extracted, washed with water until neutral, dried, filtered, and finally the solvent is distilled off under reduced pressure to obtain a brominated hydrocarbon, which is set aside; potassium hydroxide is added to another reaction flask. The nitropropane and the solvent isopropanol are stirred for 10-60 min, preferably 30 min, and the brominated hydrocarbon is added dropwise. The molar ratio of the brominated hydrocarbon to the nitropropane and potassium hydroxide is 1:2:2. The reaction is further carried out at room temperature for 3-5 hours, preferably 4 hours, and then extracted, washed with water until neutral, dried, filtered, and finally the solvent is distilled off under reduced pressure to obtain an aldehyde, which is used;

Isoprene is brominated at -25 ° C to give 1,4-dibromo-2-methyl-2-butene, ready to use; add triethyl phosphite in another reaction flask, pass N ₂ and raise the temperature to 120 ° C , adding 1,4-dibromo-2-methyl-2-butene, the molar ratio of triethyl phosphite to 1,4-dibromo-2-methyl-2-butene is 3:1, The condensation reaction is carried out for 7-9h, preferably 8h, and the excess triethyl phosphite is distilled off under reduced pressure to obtain a diphosphate.

Add a spare bisphosphate, a base and a solvent tetrahydrofuran (THF) to a four-neck reaction flask, stir, and add a reserve aldehyde at -5 ° C. The molar ratio of the diphosphate, base and aldehyde is 1:2.5:2.5. Stirring at a constant temperature for 7-9 h, preferably 8 h, washing with water, drying and column chromatography to obtain hydrocarbon I. The alkali used in the above process is positive One of butyl lithium, potassium t-butoxide, and sodium methoxide.

b) Hydrocarbon II

The reaction equation is as follows:

The specific synthesis steps are as follows:

Add linalool (or nerolidol) and aluminum isopropoxide to the reaction flask with stirring, pass N ₂ , heat to 150 ° C, add methyl acetoacetate, and linalool (or neroli) The molar ratio of alcohol to methyl acetoacetate and aluminum isopropoxide was 1:1.1:0.05. The reaction was carried out at 180 ° C for 3 h, and then excess methyl acetoacetate was distilled off under reduced pressure to give a ketone, which was used.

Add triethyl phosphite to a four-necked flask, pass N ₂ , raise the temperature to 120 ° C, add 1,4-dibromo-2-butene, triethyl phosphite and 1,4-dibromo-2- The molar ratio of butene is 3:1, the condensation reaction is 6-10h, preferably 8h, and then the excess triethyl phosphite is distilled off under reduced pressure to obtain a diphosphate, which is used;

Adding the alternate diphosphate, base and solvent THF to the four-neck reaction flask, and adding the residual ketone at -5 ° C under stirring, wherein the molar ratio of the diphosphate, base and ketone is 1:2.5:2.5. The mixture is stirred at a constant temperature for 6-10 h, preferably 8 h, and further washed with water, dried, filtered, and purified by column chromatography to give a hydrocarbon. The base used in the above process is one of n-butyllithium, potassium t-butoxide and sodium methoxide.

The preparation method of the multifunctional diesel cetane number improver of the invention is that the hydrocarbon synthesized by the above-mentioned synthesis and the conventional cetane number improver are mixed at a normal temperature for 0.5-1 hour at a normal temperature to obtain a finished product.

Hydrocarbon 1-20%

Traditional cetane number improver 80-99%.

The preferred ratio is:

Hydrocarbon 1-5%

Traditional cetane number improver 95-99%.

The advantages of the compositions of the invention are:

1) Simple and safe synthesis process, wide source of raw materials, low cost, stable product quality and low pollution, suitable for large-scale industrial production and application;

2) The product has light color and high stability, and no stabilizer is needed when used;

3) The compounding effect is good. The hydrocarbon of the invention is compounded with the alkyl nitrate and the oxalate, and the dosage is 50-60% of the single or binary compound of the latter two, the same cetane number can be increased, and the reduction is reduced. The use of oxalate and synthetically harsh and dangerous alkyl nitrates reduces the cost of diesel production and reduces the emission of nitrogen oxides from the tail gas, thus achieving a win-win situation for both economy and environmental protection.

4) The hydrocarbon of the present invention is an antioxidant itself. After adding diesel oil (especially domestic catalytic cracking diesel oil), the storage stability of the diesel oil can be improved, the formation of the gelatin can be suppressed, and the engine carbon can be reduced and the engine can be extended. Life expectancy, improving diesel economy, reducing fuel consumption, and improving exhaust emissions are of great significance.

The invention will be further described below in conjunction with specific embodiments. However, the technical content described in this embodiment is illustrative and not limiting, and the scope of the present invention should not be limited thereto.

detailed description:

Example 1 (Synthesis of Hydrocarbon I)

38.6g of linalool, 9.9g of pyridine and 150ml of petroleum ether were added to the four-necked flask, protected with N ₂ , stirred, cooled to -10 ° C with an ice salt bath, 33.83 g of phosphorus tribromide was added dropwise, and stirred at a constant temperature for 8 h. . After completion of the reaction, saturated brine and n-hexane were added, extracted, washed with water until neutral, then dried over anhydrous sodium sulfate, filtered, and then evaporated to remove solvent to give bromohydrobenzene. Add 16.8g of potassium hydroxide, dissolve with a small amount of water, add 100ml of isopropanol and 26.73g of nitropropane, stir for 30min, add 0.15mol of spare brominated hydrocarbon, react at room temperature for 4h, after the reaction is over, add Saturated brine and n-hexane, extracted, washed with water until neutral, then dried over anhydrous sodium sulfate, filtered, and then evaporated in vacuo to remove the solvent to give aldehyde.

Isoprene is brominated at -25 ° C to give 1,4-dibromo-2-methyl-2-butene, and ready to use; add 50 g of triethyl phosphite in a four-necked flask, pass N ₂ , stir, and warm to 21.4 g of the standby 1,4-dibromo-2-methyl-2-butene was added dropwise at 120 ° C, and the mixture was condensed for 8 hours. After the reaction was completed, the excess triethyl phosphite was distilled off under reduced pressure to obtain a diphosphate. spare.

9.95 g of the standby diphosphate and 150 ml of THF were added to the four-necked flask, and 8.4 g of potassium t-butoxide was added in portions at 0 ° C, stirred, and cooled to -5 ° C, 0.075 mol of the reserve aldehyde was added dropwise, and the mixture was stirred at a constant temperature for 8 hours. Thereafter, it was washed with water, dried, and purified through silica gel column to give pale yellow hydrocarbons Ia.

According to the above process route, different alcohols and bases are used as reaction reagents, and the product yields are as follows:

Table 1 Comparison of yields of hydrocarbons Ia and Ib under different synthesis conditions

From the data in the table, regardless of linalool or nerolidol, the effect of n-butyllithium is poor, while the yield of potassium t-butoxide and sodium methoxide is comparable. Considering the cost, sodium methoxide is the best reagent.

Example 2 (Synthesis of Hydrocarbon II)

38.6 g of linalool and 2.55 g of aluminum isopropoxide were added to a three-necked flask, and the mixture was stirred under nitrogen, and the temperature was raised to 150 ° C. 31.93 g of methyl acetoacetate was added dropwise, and the mixture was reacted at 180 ° C for 3 hours. After the reaction was completed, distillation was carried out under reduced pressure. Except for the excess methyl acetoacetate, the ketone is obtained and used.

Add 50g of triethyl phosphite to a four-necked flask, pass nitrogen, stir, heat to 120 ° C, add dropwise 21.4 g of 1,4-dibromo-2-butene was condensed for 8 hours. After the reaction was completed, excess triethyl phosphite was distilled off under reduced pressure to obtain a diphosphate, which was used.

9.95 g of the spare diphosphate and 150 ml of THF were added to the four-necked flask, and 8.4 g of potassium t-butoxide was added in portions at 0 ° C, stirred, and the ice salt bath was cooled to -5 ° C, and 0.075 mol of the remaining ketone was added dropwise. After stirring at a constant temperature for 8 hours, it was washed with water, dried and purified by silica gel column to afford colorless hydrocarbons IIa.

According to the above process route, different alcohols and bases are used as reaction reagents, and the product yields are as follows:

Table 2 Comparison of yields of hydrocarbons IIa and IIb under different synthesis conditions

From the data in the table, regardless of linalool or nerolidol, the effect of sodium methoxide is poor, while the yield of n-butyllithium and potassium t-butoxide is equivalent. The combination of cost and safety is the most potassium t-butoxide. Good reagents.

Example 3 (composition and evaluation)

The hydrocarbons Ia, Ib, IIa, IIb prepared by the above examples are mixed with the conventional cetane number improver alkyl nitrate and oxalate in proportion, and then added to a refinery in North China. In diesel fuel, the CN of the additive diesel oil was measured according to the ASTM D6890 method, and the improvement effect of the diesel cetane number was compared.

Table 3 Effect of composition hydrocarbon content on increasing cetane number

sample CN 0.1% cyclohexyl nitrate 45.0 0.099% cyclohexyl nitrate + 0.001% Ia 46.7 0.098% cyclohexyl nitrate + 0.002% Ia 47.8 0.095% cyclohexyl nitrate + 0.005% Ia 48.1 0.09% cyclohexyl nitrate + 0.01% Ia 48.5

0.08% cyclohexyl nitrate + 0.02% Ia 48.8

From the data in the table, 1) the synergy between hydrocarbon and cyclohexyl nitrate; 2) the synergistic effect with the increase of hydrocarbon content in the composition; 3) the cetane number in the composition of hydrocarbon content When the temperature is low, the lifting is faster. When the temperature is higher than 5%, the lifting is slower. Considering the cost factor, the optimum content of hydrocarbon in the composition is 5% (the following sample hydrocarbons are added according to this content).

Table 4 Effect of different hydrocarbons on increasing cetane number

sample CN Blank diesel 42.1 0.1% isooctyl nitrate 46.3 0.095% isooctyl nitrate + 0.005% Ia 48.6 0.095% isooctyl nitrate + 0.005% Ib 49.0 0.095% isooctyl nitrate + 0.005% IIa 48.0 0.095% isooctyl nitrate + 0.005% IIb 48.2

It can be seen from the data in the table that the compounding effect of Ib and alkyl nitrate is the best (Ib of the sample component hydrocarbons are selected below).

Table 4 Pairing of hydrocarbons with different traditional cetane number improvers to increase the effect of cetane number

- Dibutyl oxalate Diisobutyl oxalate Diisoamyl oxalate - - 47.9 48.0 48.5 N-butyl nitrate 48.7 49.3 49.0 49.6 Isobutyl nitrate 48.1 49.0 48.4 49.7 Amyl nitrate 48.2 49.3 49.2 49.5 Cyclohexyl nitrate 48.5 49.5 49.6 49.3 Isooctyl nitrate 49.0 49.3 49.9 50.1

Note: When the hydrocarbon Ib is compounded with the alkyl nitrate, the dosage of Ib is 0.005%, and the dosage of alkyl nitrate is 0.095%. When the hydrocarbon Ib is compounded with oxalate, the dosage of Ib is added. 0.05% oxalate The dosage is 0.95%; when Ib is compounded with alkyl nitrate and oxalate, the dosage of Ib is 0.0275%, the amount of alkyl nitrate added is 0.0475%, and the dosage of oxalate is 0.475%. .

It can be seen from the data that the hydrocarbon of the present invention has a good synergistic effect with various alkyl nitrates and oxalates, and the ternary compounding effect is the best.

table 5

It can be seen from the data that when the isooctyl nitrate and diisoamyl oxalate are compounded, the synergistic effect is general; while the hydrocarbon Ib is compounded with isooctyl nitrate and diisoamyl oxalate, only 50-60% dosage can achieve the effect of single or two-way compounding of the latter two, and has a high cost performance.

In addition, the oxidation stability of the above-mentioned additive diesel has been improved to a certain extent, indicating that the compounding additive has the effect of improving the antioxidant capacity of the diesel.

Claims (10)

A multifunctional diesel cetane number improver, characterized in that the improver comprises the following weight components: Hydrocarbon 1-20% Traditional cetane number improver 80-99%. A multifunctional diesel cetane number improver, characterized in that the improver comprises the following weight components: Hydrocarbon 1-5% Traditional cetane number improver 95-99%. A multifunctional diesel cetane number improver according to claim 1 or 2, wherein said component conventional cetane number improver is one of alkyl nitrate and oxalate or A mixture of two or more. The multifunctional diesel cetane number improver according to claim 3, wherein the alkyl nitrate is n-butyl nitrate, isobutyl nitrate, amyl nitrate, cyclohexyl nitrate, One or more mixtures of isooctyl nitrate. A multifunctional diesel cetane number improver according to claim 3, wherein the oxalate is one of dibutyl oxalate, diisobutyl oxalate, diisoamyl oxalate or A mixture of two or more. A multifunctional diesel cetane number improver according to claim 1 or 2, wherein the hydrocarbon is one or more mixtures of compounds having the following structure I or II:

A multifunctional diesel cetane number improver according to claim 6, wherein the synthesis of hydrocarbon I comprises the following steps: a) adding alcohol, pyridine and solvent petroleum ether to the reaction flask, adding phosphorus tribromide under nitrogen protection and -10 ° C, the molar ratio of phosphorus tribromide to alcohol and pyridine is 1:2: 1, stirring at a constant temperature for 6-10 hours, extracting, washing with water, drying, filtering, finally depressing the solvent under reduced pressure to obtain a brominated hydrocarbon; adding potassium hydroxide, nitropropane and solvent isopropanol to another reaction flask, Stir for 10 to 60 minutes, add brominated hydrocarbons, the molar ratio of the brominated hydrocarbon to nitropropane and potassium hydroxide is 1:2:2, stir at room temperature for 3-5 hours, then extract, Washed, dried, filtered, and finally distilled under reduced pressure to remove the solvent to obtain an aldehyde; b) isoprene is brominated at -25 ° C to obtain 1,4-dibromo-2-methyl-2-butene; triethyl phosphite is added to the reaction flask, and the temperature is raised to 120 ° C under the protection of nitrogen. Adding 1,4-dibromo-2-methyl-2-butene, wherein the molar ratio of triethyl phosphite to 1,4-dibromo-2-methyl-2-butene is 3:1, condensation The reaction is carried out for 7-9 hours, and then the excess triethyl phosphite is distilled off under reduced pressure to obtain a diphosphate; c) adding bisphosphate, base and solvent tetrahydrofuran to the reaction flask, adding aldehyde under nitrogen protection and -5 °C, wherein the molar ratio of diphosphate, alkali and aldehyde is 1:2.5:2.5, constant temperature stirring 7 After -9 hours, it was washed with water, dried and purified by column chromatography to give Hydrocarbon I. A multifunctional diesel cetane number improver according to claim 6, wherein the alcohol in the step a is one of linalool or nerolidol. A multifunctional diesel cetane number improver according to claim 6, wherein the step The base described in the step c is one of n-butyllithium, potassium t-butoxide and sodium methoxide. A preparation method of a multifunctional diesel cetane number improver, characterized in that a hydrocarbon is mixed with a conventional cetane number improver at room temperature for 0.5 to 1 hour to obtain a finished product.