CN102173984A - Method for preparing low-polymerization-degree polyformaldehyde dialkyl ether from petroleum fractions and application - Google Patents

Abstract

The invention belongs to the technical field of energy chemical industry and clean diesel components, and specifically relates to a main raw material such as utilizing petroleum C4 components, petroleum C5 components after removing diolefins, catalytic cracking light gasoline 30-90°C distillate low-carbon monoolefins, etc. A method for preparing polyoxymethylene dialkyl ethers with a low degree of polymerization. The general structural formula of the polyoxymethylene dialkyl ether with a low degree of polymerization is C _n H _2n+1 O(CH ₂ O) _m C _n H _2n+1 , wherein m=1-5 integers, n=2-5 an integer of . The dialkyl ether with a low degree of polymerization prepared by the present invention has a relatively high CN value, and can be widely and effectively used in diesel fuel without a high degree of polymerization, and the preparation process is relatively simple; The product petroleum C4, C5, and catalytic cracking gasoline 30-90 ℃ light distillate are used as raw materials, and the low-carbon olefins in it are used as raw materials, which not only greatly saves production costs, but also provides a better way for the comprehensive utilization of a large number of by-products in the petroleum cracking process. The technical route has obvious economic significance.

Description

Method and Application of Petroleum Distillate to Prepare Polyoxymethylene Dialkyl Ether with Low Polymerization Degree

technical field

The invention belongs to the technical field of energy chemical industry and clean diesel components, and specifically relates to a main raw material such as utilizing petroleum C4 components, petroleum C5 components after removing diolefins, catalytic cracking light gasoline 30-90°C distillate low-carbon monoolefins, etc. A method for preparing polyoxymethylene dialkyl ether with a low degree of polymerization and its application.

Background technique

In recent years, with the continuous increase of petroleum consumption and the enhancement of people's environmental awareness, the requirements for the emission of pollutants such as fuel consumption and smoke of internal combustion engines powered by petroleum have become increasingly stringent. Many countries in the world have successively formulated strict environmental protection regulations . A relatively simple, economical, effective and easy way to improve fuel quality and reduce harmful gas emissions is to add improvers to fuel.

Cetane Number (Cetane Number, hereinafter referred to as CN value) is an important index used to measure the antiknock performance of diesel. In a diesel engine, the air is first compressed, and then the diesel is injected into the combustion chamber. At this time, the diesel contacts the hot air and is vaporized. When the temperature reaches the self-ignition point, it starts to burn. Usually, the period from fuel injection to natural combustion is called "delay period". The long ignition delay period of diesel oil makes the fuel injected into the cylinder accumulate. Once the fuel is spontaneously ignited, the injected fuel will burn at the same time, resulting in a "knock" phenomenon. The ignition delay period of high CN diesel is shorter than that of low CN diesel. Increasing the CN value of diesel can reduce exhaust pollutant emissions, reduce white smoke, and make cold start faster. my country stipulates that the CN of diesel oil should not be lower than 45. The American Engine Manufacturers Association recommends that diesel engines designed to meet modern exhaust emission standards should use fuels with CN greater than 50, but should not exceed 60.

Due to the limited production of straight-run diesel components with high cetane number (about 30%) in my country, and the proportion of catalytic cracking diesel components with low cetane number is very large (about 70%), the commercially available Diesel CN generally does not meet the requirements of more than 45. Therefore, increasing the CN value of diesel oil is an urgent problem to be solved.

Polyoxymethylene dimethyl ether (general formula CH ₃ O(CH ₂ O) _m CH ₃ ) is a new type of clean oil additive, which can improve diesel combustion performance, increase CN value, reduce carbon dioxide and NOx emissions, reduce fuel consumption and An effective additive for reducing smoke emission. Because of its vapor pressure, boiling point and solubility in oil, polyoxymethylene dimethyl ether (DMM _3-8 ) with 3≤m≤8 is suitable for oil addition.

At present, the production and preparation of polyoxymethylene dimethyl ether has caused extensive research, such as US patents US 5746785, US 6392102, US 2008/0207954 A1, and Chinese patent CN101182367A, all of which disclose methods for preparing polyoxymethylene dimethyl ether . However, it can also be seen from the above that the dimer with m=2 is the main product in the mixed product obtained by this reaction, and the content of the polymer with 3≤m≤8 suitable for addition is not high, and due to the formation of dimer as the main product The dimer has a lower boiling point, so it also reduces its flash point, so the effect of the reaction mixture as an additive added to diesel fuel is still open to question; It is relatively low, which affects its vapor pressure and boiling point accordingly, so that the degree of polymerization of the added polyoxymethylene dimethyl ether must be kept in the range of 3≤m≤8, and it is known that the production conditions and production process of components with higher polymerization degrees are more difficult. Complex, which also affects the application of polyoxymethylene dimethyl ether as a diesel additive.

The CN value of diesel fuel can be increased by mixing linear ethers. The Chinese patent CN101213274A of BASF discloses a biodiesel fuel mixture comprising polyoxymethylene dialkyl ether, wherein 0.1-20% by weight of polyoxymethylene dialkyl ether of formula RO(CH ₂ O) _n R is added, wherein R is an alkyl group having 1-10 carbon atoms, and n=2-10, and preferably n=3, 4, 5 polyoxymethylene dialkyl ethers and mixtures thereof. Since the molecular weight of R as an end group is slightly larger, the CN value of polyoxymethylene dialkyl ether with a lower degree of polymerization of n=3, 4, and 5 has also reached more than 50. Moreover, since the synthesis process steps of the product with a low degree of polymerization are relatively simple, in terms of production technology, polyoxymethylene dialkyl ether has more advantages than polyoxymethylene dimethyl ether as a diesel additive.

The Chinese patent CN101198576A of BASF discloses a method for preparing polyoxymethylene dialkyl ether from trioxane and dialkyl ether. In this method, trioxane and dialkyl ether selected from dimethyl ether, methyl ethyl ether and diethyl ether are added to the reactor and reacted in the presence of an acidic catalyst to obtain a diesel fuel suitable for use as Additives for polyoxymethylene dialkyl ethers. However, this reaction requires that the amount of water introduced by the reactants and/or catalyst into the reaction mixture is less than 1% based on the reaction mixture, mainly because in the presence of water or alcohol, a large amount of polyoxymethylene glycol and hemicondensation will occur. The chemical reaction of aldehydes will form reactive azeotropes, and the process of distillation and separation is more complicated. This has also led to relatively harsh requirements for the reaction conditions and relatively strict requirements for the reaction raw materials in the reaction process; Special preparation or purchase makes the corresponding cost increase; in addition, this patent only discusses the situation that the end groups of the prepared polyoxymethylene dialkyl ether are methyl and ethyl, and the corresponding polymerization of the polyoxymethylene dialkyl ether Degree is 2-10, and this product also still exists the problem that aforementioned polyoxymethylene dimethyl ether exists.

Contents of the invention

For this reason, the technical problem to be solved by the present invention is to overcome the problem in the prior art that the polymerization degree of polyoxymethylene dimethyl ether as a diesel additive is relatively high and the effective content is low, and then provide a method for preparing polyoxymethylene dimethyl ether with a low degree of polymerization. Alkyl ether method.

Further, the present invention provides a method of using low-cost petroleum cracking by-product petroleum C4 components, petroleum C5 components after removal of diolefins, or catalytic cracking light gasoline 30-90 ° C fractions as starting materials to prepare low-polymerization degree Process for polyoxymethylene dialkyl ethers.

Furthermore, the present invention also provides the application of the polyoxymethylene dialkyl ether with a low degree of polymerization as a diesel additive.

In order to solve the problems of the technologies described above, the method for preparing polyoxymethylene dialkyl ethers with a low degree of polymerization from petroleum fractions of the present invention is characterized in that it comprises the steps:

(1) Put the reaction raw materials and acidic catalyst into the reaction kettle, pass the protective gas to replace the air in the reaction kettle, control the initial pressure of the reaction kettle to 0.1-0.8MPa, and control the reaction temperature to 50-200℃ to react until each component Equilibrium, preferably reacting for 10-12 hours; The reaction raw materials include low-carbon olefins, polyoxymethylenes and initiators, wherein:

The low-carbon olefins are one or a mixture of several of the low-carbon olefins with the general formula C _n H _2n , wherein n=2-5 integer;

One or more mixtures of the polyoxymethylene material formaldehyde or paraformaldehyde, paraformaldehyde with a low degree of polymerization;

The molar ratio of the low-carbon olefins and polyoxymethylenes is 2-4:1-4, and the amount of the catalyst is 0.1-5.0% of the total weight of the total reaction raw materials;

(2) After the reaction, adjust the pH of the mixture to neutral or slightly alkaline, separate and collect fractions at 150-340°C, and refine to obtain the general structural formula C _n H _2n+1 O(CH ₂ O ) _m C _n H _2n+1 polyoxymethylene dialkyl ether with a low degree of polymerization, wherein m and n are the same or different values, m is an integer of 1-5, and n is an integer of 2-5.

The initiator is water and/or lower alcohol, and the lower alcohol is preferably methanol. The molar ratio of the initiator to the polyoxymethylene is 1:1-4.

The low-carbon olefins are petroleum C4 components in petroleum fractions, petroleum C5 components from which diolefins have been removed, or fractions of catalytically cracked light gasoline at 30-90°C, and preferably catalytically cracked light gasoline at 30-70°C The lower fraction.

The molar ratio of the low-carbon olefin substances to the polyoxymethylene substances is 2-3:3-4.

The catalyst is strongly acidic cation exchange resin or protonic acid.

The protonic acid is one or a mixture of p-toluenesulfonic acid, trifluoromethanesulfonic acid, formic acid, and benzoic acid.

The protective gas is nitrogen and/or inert gas.

The reaction temperature of the step (1) is 70-120°C.

The reaction time of the step (1) is 10-12 hours.

The reactor is a batch type high pressure reactor.

A kind of diesel fuel is characterized in that comprising following component:

The polyoxymethylene dialkyl ether with low degree of polymerization prepared by the above-mentioned method, 1-20wt%

Diesel 80-99wt%.

The polyoxymethylene dialkyl ether with a low degree of polymerization prepared according to the above preparation method, the CN value of the polyoxymethylene dialkyl ether with a low degree of polymerization is greater than 55, its boiling point is 156-340°C, and its density is 0.88-0.97g/mL (20°C), the flash point is 45-75°C.

Petroleum _C5 is the by-product _C5 hydrocarbon fraction in the steam cracking of petroleum hydrocarbons to ethylene. Its composition is relatively complex, rich in diolefins and monoolefins, mainly isoprene (2-methyl-butadiene) , cyclopentadiene (usually extracted as dimer dicyclopentadiene), piperylene (cis and trans 1,3-pentadiene), isopentene (2-methyl 2- butene), and a small amount of 1-pentene. Among them, the diolefin content is 40%-55%, and the monoolefin content is 15-25%. The total yield and composition of cracked _C5 mainly depend on the properties of cracking raw materials. Generally, the _C5 yield obtained by cracking gaseous hydrocarbons ( _C2 - _C4 alkanes) is 2-6% of the ethylene yield; while liquid hydrocarbons (such as naphtha Oil and light diesel oil) as the cracking raw material, the _C5 yield can reach 14-20% of the ethylene output. With the development of the petrochemical industry, the production capacity of producing ethylene with liquid hydrocarbons as raw materials continues to increase, and the cracked C ₅ resources are becoming more and more abundant. How to use cracked C ₅ has become a key issue in rationally utilizing petroleum resources, reducing ethylene production costs, and improving benefits. important aspects, and has attracted the general attention of the ethylene industry and related researchers.

In developed countries, the research on the comprehensive utilization of petroleum C ₅ has been far ahead, and the industrial production system was gradually established and improved from the 1970s to the 1980s. However, the separation and utilization of C ₅ fractions in China is still in its infancy. So far, most of the C ₅ fractions are burned as fuel. Therefore, the development and utilization of C ₅ resources has obvious economic significance.

Compared with the prior art, the above-mentioned technical scheme of the present invention has the following advantages. 1. The dialkyl ether with a low degree of polymerization prepared by the present invention has a relatively high CN value, and can be widely and effectively used without a high degree of polymerization. In diesel fuel, the preparation process is relatively simple; 2. The present invention uses low-carbon monoolefins, methanol and formaldehyde (or paraformaldehyde with a low degree of polymerization) to react, and the whole process can be completed by only one feeding; 3. The petroleum cracking ethylene process is selected The by-product distillate petroleum C4 and C5 in the petroleum cracking process are used as raw materials, and the low-carbon olefins are used, which not only greatly saves the production cost, but also provides a better technical route for the comprehensive utilization of a large number of by-products in the petroleum cracking process, which has obvious advantages Economic significance; 4. Select 30-90°C light fraction of catalytic cracking gasoline (preferably 30-70°C light fraction) to prepare polyoxymethylene dialkyl ether with low polymerization degree, increase the output ratio of diesel oil to gasoline, and reduce the yield of catalytic cracking gasoline Olefin content.

Description of drawings

In order to make the content of the present invention more easily understood, the present invention will be described in further detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

Fig. 1 is the process flow diagram of preparation method of the present invention.

Reference numerals in the figure are represented as: 1-raw material flow, 2-raw material flow, 3 high-pressure reactor, 4-primary product, 5-filter, 6-secondary product, 7-extraction tower, 8-tertiary product , 9-atmospheric pressure separation tower, 10-low boiling fraction, 11-quaternary product, 12-vacuum separation tower, 13-high polymer component, 14-target product.

Detailed ways

The chemical reaction formula of the preparation method of low polymerization degree polyoxymethylene dialkyl ether of the present invention is:

C _n H _2n + H ₂ O → C _n H _{2n + 1} OH (1)

C _n H _2n+1 OH+mCH ₂ O→C _n H _2n+1 O(CH ₂ O) _m C _n H _2n+1 +H ₂ O (2)

Therefore, this reaction can only take place under the condition of containing water, when the selected reactant is anhydrous formaldehyde, anhydrous paraformaldehyde or anhydrous low degree of polymerization paraformaldehyde, need to add a small amount of methyl alcohol as initiator, in order to React with anhydrous formaldehyde or anhydrous low-polymerization paraformaldehyde to generate water and trigger the reaction. The reaction equation at this time is:

2mCH ₃ OH + (CH ₂ O) _m → mCH ₃ OCH ₂ OCH ₃ +mH ₂ O (1)

C _n H _2n + H ₂ O → C _n H _{2n + 1} OH (2)

C _n H _2n+1 OH+mCH ₂ O→C _n H _2n+1 O(CH ₂ O) _m C _n H _2n+1 +H ₂ O (3)

The raw material flow 1 and the raw material flow 2 that respectively comprise low-carbon olefins and polyoxymethylenes are transported into the high-pressure reactor 3, and the acidic catalyst is dropped in together, and nitrogen and/or inert gas are passed into the reactor as a protective gas to replace the Air, control the initial pressure of the reactor to 0.1-0.8MPa, keep a constant temperature of 50-200°C and react for 10-12 hours until the reaction of each component is balanced. At the end of the reaction a primary product 4 comprising polyalkoxy formals with a low degree of polymerization is formed. The resulting primary product 4 passes through the filter 5 and filters the solid impurities to obtain a secondary product 6 substantially free of solid impurities, then the secondary product 6 is transported into the extraction tower 7, and its pH is adjusted to neutral. Extraction and separation after neutrality or alkalinity. The third-stage product 8 obtained after extraction enters the atmospheric separation tower 9 for separation, and the low-boiling fraction 10 with a boiling point (B.P) less than 150°C is refluxed into the high-pressure reactor 3 to continue to react again; while the fourth-stage product composed of other light components The product 11 continues to enter the decompression separation tower 12 for further separation. After separation, the high-polymerization component 13 with m>5 is refluxed into the high-pressure reactor 3 to participate in the reaction again, while the final component 14 with m=2-5 is in accordance with The desired target product is the required low degree of polymerization polyoxymethylene dialkyl ether.

Example 1

The method for preparing low polymerization degree polyoxymethylene dialkyl ether C _n H _2n+1 O(CH ₂ O) _m C _n H _2n+1 by using petroleum fractions is:

Add petroleum C ₅ and industrial formaldehyde with a formaldehyde content of 37% in sequence in a molar ratio of 2:4 to the intermittent high-pressure reactor. The water contained in the industrial formaldehyde can be used as an initiator to participate in the reaction, and it is selected to account for 2% of the total weight of the reactants. P-toluenesulfonic acid was put into the reaction kettle together as a catalyst, filled with nitrogen to replace the air in the reaction kettle, and the initial pressure in the reaction kettle was controlled to 0.2Mpa, and kept at a constant temperature of 70-90°C for 10 hours to each Component balance. After the reaction is completed, go through the above-mentioned extraction and separation process steps, separate and finally collect the fraction at 150-340° C., and refine the obtained product. According to the detection by chromatography-mass spectrometry (GC-MS), the product distribution of each degree of polymerization is: m=1, 8.32%; m=2, 34.5%; m=3, 21.4%; m=4, 7.1%; m= 5, 0.9%; m>5, trace amount; ∑PODAE _2-5 =63.9%. The mixed liquid had a cetane number of 59 and a density of 0.917 g/cm ³ at 20°C.

Add about 10% polyoxymethylene dialkyl ether with a low degree of polymerization to diesel fuel, and the obtained diesel fuel has a cetane number of 47 and a flash point of 56, which can not only meet the ultra-low sulfur diesel index, but also greatly reduce NO _X and other harmful gases are discharged, and the pollution discharge is reduced by more than 30%.

Example 2:

The method for preparing low polymerization degree polyoxymethylene dialkyl ether C _n H _2n+1 O(CH ₂ O) _m C _n H _2n+1 by using petroleum fractions is:

A mixture of petroleum C ₄ , methanol, anhydrous low-polymerization paraformaldehyde and anhydrous formaldehyde is sequentially added in a molar ratio of 4:1:4 in a batch-type high-pressure reactor, wherein methanol is used as an initiator to trigger the reaction. The strongly acidic cation-exchange resin that accounts for 5% of the total weight of the reactant is put into the reactor together as a catalyst, and the air in the reactor is charged with inert gas replacement, and the initial pressure in the reactor is controlled at 0.3Mpa, and kept at 90°C under 100rpm rotating speed stirring. -120°C constant temperature reaction for 10 hours. After the reaction is completed, go through the above-mentioned extraction and separation process steps, separate and finally collect the fraction at 150-340° C., and refine the obtained product. According to the detection by chromatography-mass spectrometry, the product distribution of each degree of polymerization is: m=1, 2.7%; m=2, 39.6%; m=3, 19.5%; m=4, 11.1%; m=5, 0.75%; m>5, trace; ∑PODAE _2-5 =70.95%. The mixed liquid had a cetane number of 56 and a density of 0.932 g/cm ³ at 20°C.

Add about 5% polyoxymethylene dialkyl ether with a low degree of polymerization to diesel fuel, and the obtained diesel fuel has a cetane number of 45 and a flash point of 60, which can not only meet the ultra-low sulfur diesel index, but also greatly reduce NO _X and other harmful gases are discharged, and the pollution discharge is reduced by more than 20%.

Example 3:

The method for preparing low polymerization degree polyoxymethylene dialkyl ether C _n H _2n+1 O(CH ₂ O) _m C _n H _2n+1 by using petroleum fractions is:

In the intermittent high-pressure reactor, add catalytically cracked light gasoline 30-70°C distillate, methanol and anhydrous paraformaldehyde in a molar ratio of 3:1:2. Methanol is used as an initiator to trigger the reaction. Select the total weight of the reactants. The mixture of 0.1% trifluoromethanesulfonic acid and p-toluenesulfonic acid is put into the reactor together as a catalyst, and the air in the nitrogen replacement reactor is charged, and the initial pressure in the reactor is controlled at 0.6Mpa, and kept under stirring at 100rpm. 50-70°C constant temperature reaction for 10 hours. After the reaction is completed, go through the above-mentioned extraction and separation process steps, separate and finally collect the fraction at 150-340° C., and refine the obtained product. According to the detection by chromatography-mass spectrometry, the product distribution of each degree of polymerization is: m=1, 8.42%; m=2, 43.6%; m=3, 21.2%; m=4, 10.6%; m=5, 0.78%; m>5, trace; ∑PODAE _2-5 =76.18%. The mixed liquid had a cetane number of 56 and a density of 0.941 g/cm ³ at 20°C.

Add about 20% polyoxymethylene dialkyl ether with a low degree of polymerization to diesel fuel, and the obtained diesel fuel has a cetane number of 49 and a flash point of 55, which can not only meet the ultra-low sulfur diesel index, but also greatly reduce NO _X and other harmful gases are discharged, and the pollution discharge is reduced by more than 40%.

Example 4:

The method for preparing low polymerization degree polyoxymethylene dialkyl ether C _n H _2n+1 O(CH ₂ O) _m C _n H _2n+1 by using petroleum fractions is:

A mixture of ethylene and butene and industrial formaldehyde with a formaldehyde content of 37% are sequentially added into the batch high-pressure reactor in a molar ratio of 2:3. The moisture contained in industrial formaldehyde can be used as an initiator to trigger the reaction. The mixture of benzoic acid and formic acid of 3% of the total weight of the product is put into the reactor together as a catalyst, and the air in the nitrogen replacement reactor is charged, and the initial pressure in the reactor is controlled at 0.8Mpa, and kept at 120-150 under stirring at 100rpm. ℃ constant temperature reaction for 10 hours. After the reaction is completed, go through the above-mentioned extraction and separation process steps, separate and finally collect the fraction at 150-340° C., and refine the obtained product. According to the detection by GC-MS method, the product distribution of each degree of polymerization is: m=1, 4.7%; m=2, 30.9%; m=3, 18.6%; m=4, 6.7%; m=5, 0.56%; m>5, trace; ∑PODAE _2-5 =56.76%. The mixed liquid had a cetane number of 61 and a density of 0.996 g/cm ³ at 20°C.

Add about 15% polyoxymethylene dialkyl ether with a low degree of polymerization to diesel fuel, and the obtained diesel fuel has a cetane number of 49 and a flash point of 60, which can not only meet the ultra-low sulfur diesel index, but also greatly reduce NO _X and other harmful gases are discharged, and the pollution discharge is reduced by more than 35%.

Example 5:

The method for preparing low polymerization degree polyoxymethylene dialkyl ether C _n H _2n+1 O(CH ₂ O) _m C _n H _2n+1 by using petroleum fractions is:

Add propylene, methanol solution and the mixture of anhydrous paraformaldehyde and anhydrous formaldehyde in the batch type autoclave according to the molar ratio of 4:1:1. The methanol solution can be used as an initiator to trigger the reaction. 4% by weight of formic acid is put into the reactor together as a catalyst, filled with inert gas and nitrogen to replace the air in the reactor, and the initial pressure in the reactor is controlled to 0.1Mpa, and the reaction temperature is kept at 150-170°C for 10 minutes while stirring at 100 rpm. Hour. After the reaction is completed, go through the above-mentioned extraction and separation process steps, separate and finally collect the fraction at 150-340° C., and refine the obtained product. According to the detection by GC-MS method, the product distribution of each degree of polymerization is: m=1, 3.7%; m=2, 32.3%; m=3, 11.3%; m=4, 5.1%; m=5, 0.66%; m>5, trace; ∑PODAE _2-5 =49.36%. The mixed liquid had a cetane number of 57 and a density of 0.97 g/cm ³ at 20°C.

Add about 10% polyoxymethylene dialkyl ether with a low degree of polymerization to diesel fuel, and the obtained diesel fuel has a cetane number of 46 and a flash point of 61, which can not only meet the ultra-low sulfur diesel index, but also greatly reduce NO _X and other harmful gases are discharged, and the pollution discharge is reduced by more than 30%.

Example 6

The method for preparing low polymerization degree polyoxymethylene dialkyl ether C _n H _2n+1 O(CH ₂ O) _m C _n H _2n+1 by using petroleum fractions is:

In the intermittent high-pressure reactor, add catalytically cracked light gasoline 30-90°C distillate, methanol and anhydrous paraformaldehyde in a molar ratio of 2:1:1. Methanol can be used as an initiator to trigger the reaction. 1% by weight of strong acidic cation exchange resin is put into the reaction kettle together as a catalyst, and the air in the reaction kettle is replaced by nitrogen gas, the initial pressure in the reaction kettle is controlled to 0.4Mpa, and the reaction temperature is maintained at 170-200°C under stirring at 100rpm. 10 hours. After the reaction is completed, go through the above-mentioned extraction and separation process steps, separate and finally collect the fraction at 150-340° C., and refine the obtained product. According to the detection by GC-MS method, the product distribution of each degree of polymerization is: m=1, 3.7%; m=2, 32.3%; m=3, 11.3%; m=4, 5.1%; m=5, 0.66%; m>5, trace; ∑PODAE _2-5 =49.36%. The mixed liquid had a cetane number of 57 and a density of 0.97 g/cm ³ at 20°C.

Add about 10% polyoxymethylene dialkyl ether with a low degree of polymerization to diesel fuel, and the obtained diesel fuel has a cetane number of 46 and a flash point of 59, which can not only meet the ultra-low sulfur diesel index, but also greatly reduce NO _X and other harmful gases are discharged, and the pollution discharge is reduced by more than 25%.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (10)

1. petroleum fractions prepares the method for low polymerization degree polyoxymethylene dialkyl ether, it is characterized in that, comprises the steps:

(1) reaction raw materials and an acidic catalyst are dropped in the reactor, feed the air in the shielding gas replacement reaction kettle, the original pressure of control reactor is 0.1-0.8MPa, and control reaction temperature 50-200 ℃ reaction is component balanced to each; Described reaction raw materials comprises low-carbon alkene class material, polyoxymethylene class material and initiator, wherein:

Described low-carbon alkene class material is that general formula is C _nH _2nLow-carbon alkene in a kind of or wherein several mixture, the integer of n=2-5 wherein;

Described polyoxymethylene class material is one or more the mixture in formaldehyde or trioxymethylene, the low polymerization degree Paraformaldehyde 96;

The molar ratio of described low-carbon alkene class material and polyoxymethylene class material is 2-4:1-4, and described catalyst consumption is the 0.1-5.0% of reaction raw materials gross weight;

(2) after reaction finished, the pH value of transferring mixture was to neutrality or weakly alkaline, through separating and collect 150-340 ℃ of cut down, and made with extra care that to obtain general structure be C _nH _2n+1O (CH ₂O) _mC _nH _2n+1The low polymerization degree polyoxymethylene dialkyl ether, wherein m is a numerical value identical or inequality with n, m is the integer of 1-5, n is the integer of 2-5.

2. petroleum fractions according to claim 1 prepares the method for low polymerization degree polyoxymethylene dialkyl ether, it is characterized in that: described initiator is water and/or methyl alcohol, and the molar ratio of described initiator and described polyoxymethylene class material is 1:1-4.

3. petroleum fractions according to claim 1 and 2 prepares the method for low polymerization degree polyoxymethylene dialkyl ether, it is characterized in that: described low-carbon alkene class material is oil C4 component, remove the cut under 30-90 ℃ of the oil C5 component of diolefine or the catalytic cracking petroleum naphtha.

4. prepare the method for low polymerization degree polyoxymethylene dialkyl ether according to each described petroleum fractions of claim 1-3, it is characterized in that: the molar ratio of described low-carbon alkene class material and polyoxymethylene class material is 2-3:3-4.

5. prepare the method for low polymerization degree polyoxymethylene dialkyl ether according to each described petroleum fractions of claim 1-4, it is characterized in that: described catalyzer is storng-acid cation exchange resin or protonic acid.

6. petroleum fractions according to claim 5 prepares the method for low polymerization degree polyoxymethylene dialkyl ether, it is characterized in that: described protonic acid is a kind of or wherein several mixture in tosic acid, trifluoromethanesulfonic acid, formic acid, the phenylformic acid.

7. prepare the method for low polymerization degree polyoxymethylene dialkyl ether according to claim 1 or 2 or 3 described petroleum fractionss, it is characterized in that: described shielding gas is nitrogen and/or rare gas element.

8. prepare the method for low polymerization degree polyoxymethylene dialkyl ether according to each described petroleum fractions of claim 1-7, it is characterized in that: the temperature of reaction of described step (1) is 70-120 ℃.

9. prepare the method for low polymerization degree polyoxymethylene dialkyl ether according to each described petroleum fractions of claim 1-7, it is characterized in that: the reaction times of described step (1) is 10-12 hour.

10. diesel oil fuel is characterized in that comprising following component:

The low polymerization degree polyoxymethylene dialkyl ether that each described method of claim 1-9 prepares, 1-20wt%

Diesel oil 80-99wt%.