CN109054912B

CN109054912B - Composite emulsifier and application thereof in producing micro-emulsified diesel oil

Info

Publication number: CN109054912B
Application number: CN201810859901.4A
Authority: CN
Inventors: 张敏; 马锐
Original assignee: Dongying Haohan Biochemical Technology Co ltd
Current assignee: Dongying Zhuangrong Biotechnology Co.,Ltd.
Priority date: 2018-08-01
Filing date: 2018-08-01
Publication date: 2021-03-26
Anticipated expiration: 2038-08-01
Also published as: CN109054912A

Abstract

The invention discloses a composite emulsifier and application thereof in producing microemulsified diesel oil, wherein the preparation of the composite emulsifier comprises the following steps: (1) taking low-quality grease as a raw material, and carrying out pretreatment; (2) adding methanol dissolved with metal sodium into the pretreated low-quality grease, and carrying out methyl esterification modification to obtain fatty acid methyl ester; (3) adding a composite aminating agent consisting of organic amine and inorganic ammonia into fatty acid methyl ester, and carrying out amidation reaction by using metal sodium as a catalyst to prepare the composite emulsifier. The invention also discloses emulsified diesel oil prepared by using the composite emulsifier. The composite emulsifier is prepared by taking low-quality grease as a raw material through chemical modification and amidation reaction, and the production cost of the emulsifier is effectively reduced. The stability and the combustion performance of the micro-emulsified diesel oil prepared by the composite emulsifier are greatly improved.

Description

Composite emulsifier and application thereof in producing micro-emulsified diesel oil

Technical Field

The invention relates to the technical field of clean energy, in particular to a composite emulsifier and application thereof in producing micro-emulsified diesel oil.

Background

Although the combustion of emulsified diesel oil, i.e. fuel oil mixed with water, is not a new subject, new thinking and new development power are continuously provided. As early as the international combustion association's first annual meeting, it has been identified as one of three major energy saving measures. China also puts the construction plan into development projects during continuous five years, so that the research heat tide of one wave and another wave is raised.

Through continuous theoretical discussion and a large number of experiments in scientific research institutions, numerous experts and scholars have highly consistent conclusions on the energy-saving and emission-reducing characteristics of emulsified diesel oil. Although water is not fuel, a series of additional chemical reactions occur in the high-temperature and high-pressure combustion process of the engine, a large amount of O, H and OH free radicals are formed, and the active substances can greatly activate the whole combustion process, inhibit the early emission of unburned carbon, enable the unburned carbon to be more completely combusted, and reduce energy loss. The characteristic that water has the maximum specific heat in all solids and liquids can quickly absorb the heat of power parts to reduce the expansion friction between the power parts, thereby reducing the self-power consumption and saving energy. The self-oxygen-supplying effect of the water-containing fuel can reduce local overheating, oxygen deficiency, dehydrogenation and cracking coking of the hydrocarbon fuel, homogenize the temperature of each part of the wall surface of the combustion chamber and the protruding parts such as the fuel injection head and the like, ensure the normal operation of the whole machine and be favorable for saving the fuel. The boiling point of water is lower than that of diesel oil, vaporization and evaporation are early, vaporization and expansion explode a water-in-oil film, so that fuel is atomized again through a nozzle (namely, micro-explosion effect), the fuel utilization rate is further improved, and energy is saved. Countless scientific research conclusions and practical applications prove that the emission of harmful gases can be reduced by more than 30 percent by blending water with diesel oil for combustion.

However, the difficulty is self-evident in that oil and water are two incompatible liquids and they are completely miscible. Because the density of water is higher than that of diesel oil, and the coagulation effect of water, the water can spontaneously sink, aggregate and stratify in the oil under the dual actions of gravity field and coagulation until finally demulsifying and separating from the oil. Therefore, most of the developed emulsified diesel oil has the problems of long-term storage incapability and easy delamination, which greatly limits the application of the emulsified diesel oil.

At present, the research for improving the stability of the emulsified diesel oil is mainly to search for a novel emulsifier or a compound of various emulsifiers. However, the existing emulsifier product has poor emulsification stability, and the stabilization time is mostly only ten days or half a month, so that the emulsifier product is difficult to be used as a commodity for circulation; in addition, most of the existing emulsifier products take refined petroleum products and higher fatty acids as raw materials, so that the price of the emulsifier is high, and the cost for producing the emulsified diesel oil is high.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide the compound emulsifier which is prepared by taking low-quality grease as a raw material through chemical modification and amidation reaction, and effectively reduces the production cost of the emulsifier.

The stability and the combustion performance of the micro-emulsified diesel oil prepared by the composite emulsifier are greatly improved.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect of the present invention, a preparation method of a composite emulsifier is provided, which comprises the following steps:

(1) taking low-quality grease as a raw material, and carrying out pretreatment;

(2) adding methanol dissolved with metal sodium into the pretreated low-quality grease, and carrying out methyl esterification modification to obtain fatty acid methyl ester;

(3) adding a composite aminating agent consisting of organic amine and inorganic ammonia into fatty acid methyl ester, and carrying out amidation reaction by using metal sodium as a catalyst to prepare the composite emulsifier.

Preferably, in the step (1), the low-quality grease includes: illegal cooking oil, sewage oil of animal slaughterhouse, reclaimed oil of leather factory, acid oil produced by refining food oil, and inedible castor oil, Jatropha curcas oil and palm oil with high condensation point.

Preferably, in the step (1), the pretreatment method comprises the following steps: mechanically filtering low-quality grease to remove impurities; adding chemical oxidant in 3-5 wt% of low quality oil, heating to 70-80 deg.c, stirring to react for 15-20 min, and centrifuging to eliminate water and unreacted chemical oxidant.

Further preferably, the chemical oxidant is prepared from the following raw materials:

2-4 parts of hydrogen peroxide, 0.5-1.5 parts of sodium percarbonate and 0.001 part of titanium salt.

Preferably, in the step (2), the adding amount of the methanol dissolved with the metal sodium accounts for 15-25% of the weight of the pretreated low-quality grease; the dissolving amount of the metal sodium is 0.3-0.7% of the total weight of the pretreated low-quality grease and the methanol.

Preferably, in the step (2), the temperature condition for methyl esterification modification is 40-45 ℃.

Preferably, in the step (3), the composite aminating agent consists of diethanolamine and ammonium hydroxide; the addition amount of the diethanol amine is 6-10% of the weight of the fatty acid methyl ester, and the addition amount of the ammonium hydroxide is 8-12% of the weight of the fatty acid methyl ester.

Preferably, in step (3), the amount of sodium metal added is 0.1% by weight of the fatty acid methyl ester.

In a second aspect of the invention, a composite emulsifier prepared by the above method is provided. The composite emulsifier prepared by the invention comprises: fatty acid methyl ester amides and fatty acid ammonium.

In a third aspect of the present invention, there is provided a continuous flow reaction system for preparing the composite emulsifier, the continuous flow reaction system comprising: the reactor comprises an impinging stream reactor, a microwave reactor and an ultrasonic reactor which are connected in sequence.

The application of the compound emulsifier in the preparation of emulsified diesel oil is also the protection scope of the invention.

The invention provides a micro-emulsified diesel oil, which is prepared by adding the composite emulsifier, water, a water-solubilizing agent, a stabilizer and a water cracking catalyst into diesel oil and then uniformly mixing.

Preferably, the micro-emulsified diesel oil is prepared from the following raw materials in parts by weight:

72-85 parts of diesel oil, 8-15 parts of water, 5-8 parts of composite emulsifier, 1.5-3.5 parts of hydrotropic agent, 0.5-1.2 parts of stabilizer and 0.01-0.05 part of water cracking catalyst.

More preferably, the micro-emulsified diesel oil is prepared from the following raw materials in parts by weight:

78-80 parts of diesel oil, 9-12 parts of water, 6-7 parts of composite emulsifier, 2-3 parts of hydrotropic agent, 0.7-1 part of stabilizer and 0.02-0.03 part of water cracking catalyst.

In the micro-emulsified diesel oil, preferably, the cosolvent is formed by mixing n-propanol, n-butanol and n-pentanol according to a volume ratio of 0.5:1: 0.5.

The stabilizer is castor oil methyl ester amide.

The water cracking catalyst is formed by mixing one or two of titanate and permanganate in any ratio; preferably, the water cracking catalyst is formed by mixing titanate and permanganate according to the mass ratio of 1: 1.

In a fifth aspect of the present invention, a method for preparing the above microemulsified diesel oil is provided, which comprises the following steps:

mixing diesel oil, water, a composite emulsifier, a dissolving assistant agent, a stabilizer and a water cracking catalyst, reacting in an impinging stream reactor, dividing the mixed material into two equal liquid flows through a rotor flow meter, coaxially and oppositely entering a central area from two ends of the impinging stream reactor at high speed for collision, and introducing into an oil storage tank through a static mixer to obtain the micro-emulsified diesel oil.

The invention has the beneficial effects that:

(1) the invention takes a large amount of inedible animal and vegetable oil such as illegal cooking oil as raw materials, and prepares the compound emulsifier after effective chemical modification, thereby realizing reasonable utilization of resources and reducing the production cost of the emulsifier.

(2) The emulsified diesel oil prepared by the composite emulsifier has the characteristics of microemulsion, is clear and transparent, is a thermodynamically stable system, has high stability, and can be stored for more than 3 months.

(3) The micro-emulsified diesel oil provided by the invention can greatly reduce the exhaust smoke intensity, reduce the discharge amount of nitride and carbide, and has a very obvious emission reduction effect.

(4) The invention combines an impinging stream reactor, a microwave reactor and an ultrasonic reactor into a continuous flow chemical production line to implement industrial production.

The production line firstly utilizes the kinetic energy of the impinging stream reactor to push the reaction liquid to form turbulent flow, and the turbulent flow is quickly heated by the microwave reactor to generate a heating effect, so that the collision and friction among the molecules of the reaction liquid are generated, and the reaction activity and the reaction rate are greatly improved; the reaction liquid is pushed by the impinging stream and then passes through the acoustic cavitation effect of the ultrasonic wave. The reaction activation energy of the microwave reactor has certain selectivity to the polarity of the reaction liquid, the reaction activity of the ultrasonic sound field has broad spectrum, and the two have different activation energy properties, so that the two have complementarity. When used in combination, the advantages of the two components are improved in heating, energy transfer and the like, the utilization efficiency of energy is improved, the energy consumption is reduced, and the yield and the quality of products are improved. The combined technology of impinging stream mixing reaction, microwave heating reaction and ultrasonic chemical reaction is a high-efficiency green environmental protection industrial technology with important application prospect.

Drawings

FIG. 1: the continuous flow reaction system of the invention has a schematic structure; in the figure, 1-a dosing tank, 2-a centrifugal pump, 3-a rotor flow meter, 4-an impinging stream reactor, 5-a microwave reactor, 6-an ultrasonic reactor, 7-a microwave generating device, 8-an ultrasonic transmitting component and 9-a storage tank.

FIG. 2: HLB value and emulsion stabilization phase relation chart; in the figure, a is castor oil methyl ester amide and b is low quality methyl ester amide.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

As introduced in the background art, the conventional emulsifier for preparing emulsified diesel oil has poor stability and high production cost, so that the emulsified diesel oil is difficult to popularize and use in a large area. Based on the above, the invention aims to provide the composite emulsifier prepared from the low-quality oil, so that the production cost of the emulsifier is reduced, and the resource utilization and harmless treatment of a large amount of waste oil are realized.

In one embodiment of the invention, the method for preparing the composite emulsifier by using low-quality grease as a raw material comprises the following steps:

(1) pretreatment of raw materials:

mechanically filtering low-quality grease to remove impurities; adding chemical oxidant in 3-5 wt% of low quality oil, heating to 70-80 deg.c, stirring to react for 15-20 min, and centrifuging to eliminate water and unreacted chemical oxidant.

(2) Methyl esterification modification:

adding methanol dissolved with metal sodium into the pretreated low-quality grease, and carrying out methyl esterification modification to obtain fatty acid methyl ester; the adding amount of the methanol dissolved with the metal sodium accounts for 15-25% of the weight of the pretreated low-quality grease; the dissolving amount of the metal sodium is 0.3-0.7% of the total weight of the pretreated low-quality grease and the methanol.

The "low-quality grease" of the present invention includes: illegal cooking oil, sewage oil of animal slaughter house, reclaimed oil of leather factory, acid oil produced by refining food oil, and some illegal edible animal and vegetable oils such as castor oil, jatropha curcas oil, and palm oil with high solidifying point. Compared with the high-grade grease raw material used by the commercial emulsifier, if the emulsified diesel oil is produced by directly carrying out amidation reaction on the low-quality grease serving as the raw material and organic amine to prepare the fatty acid amide emulsifier, the stability of the emulsified diesel oil cannot meet the requirement, and the indexes such as the acid value, the condensation point, the viscosity and the like of the emulsified diesel oil are not suitable for being put into the diesel oil for use. The difficulty of comprehensive utilization of the low-quality grease is also solved. In order to solve the technical problem, the invention firstly pretreats low-quality grease, then carries out chemical modification to prepare fatty acid methyl ester as an intermediate, and then carries out amidation reaction on the intermediate and a composite aminating agent consisting of organic amine and high-concentration inorganic ammonia under the action of a metal sodium (dissolved in methanol) catalyst to prepare the composite emulsifier containing fatty acid methyl ester amide and fatty acid ammonium.

In the pretreatment process, the chemical oxidant for modification is prepared from the following raw materials: 2-4 parts of hydrogen peroxide, 0.5-1.5 parts of sodium percarbonate and 0.001 part of titanium salt. Wherein, the titanium salt can be selected from titanate, 1-butanol titanium salt or titanyl sulfate.

The composite emulsifier prepared by the invention can be used for producing emulsified diesel oil, and the stability and combustion performance of the emulsified diesel oil can be obviously improved.

It is known that the chemical reaction between substances must satisfy two basic conditions: i.e. the collision (contact) between the molecules of the participating reactants; the collision molecules must have sufficient energy. The invention uses methanol and low-quality oil to carry out methyl esterification reaction modification, while methanol and fatty acid (oil) are two immiscible liquids, if the methanol and fatty acid (oil) are processed in a traditional kettle type reactor or a fluidized bed reactor, the collision probability between molecules is small, especially the collided molecules lack enough energy, so the reaction power is small, the speed is slow, the time is long (generally in hours), the energy consumption is high, the labor consumption is high, the utilization rate of equipment is low, the conversion rate of products is low, and the production cost is improved as a result.

In order to improve the reaction efficiency, reduce the production cost and realize industrial mass production, the invention combines the impinging stream reactor, the microwave reactor and the ultrasonic reactor in a coupling way into a continuous flow reaction system (as shown in figure 1), and the respective advantages of each reactor are fully exerted. In the invention, methanol is used for modifying low-quality oil to obtain a fatty acid methyl ester intermediate, and the intermediate is subjected to amidation reaction in an organic and inorganic ammonia mixed amination agent to prepare the fatty acid methyl ester amide and fatty acid ammonium composite emulsifier which are all carried out in the continuous flow reaction system. In order to mix the two immiscible liquids of methanol and grease well at the beginning, the invention selects the impinging stream reactor, the working principle of the impinging stream mixing reactor is not complex, namely low-grade grease after filtration, water impurity removal, decolorization and degumming is premixed with methanol and catalyst in a proportioning tank, then is divided into two equal-quantity high-speed liquid flows which flow oppositely on the same axial line by an infusion pump, the two equal-quantity high-speed liquid flows enter into feed inlets at two ends of the impinging stream reactor simultaneously, and collide violently in the center of the reactor, so that the high-speed fluid after the impingement is converted into pulsating motion from the axial direction, a very violent impinging area is generated, in the area, the turbulent action of a flow field is obvious, the violent shearing action is generated, the liquid micro-cluster is crushed to be very micro, thus not only the contact area and the mass transfer driving force under the fixed liquid volume are increased, and the liquid mixing state is, the transmission quality effect of the process is enhanced; but also greatly improves the speed and the conversion rate of the methyl esterification reaction and the subsequent alkanol amidation reaction.

The reaction liquid forms a turbulent flow field from the impact area, and the turbulent flow is guided to the microwave reactor through the T-shaped pipe for heating reaction. Microwaves have been widely used as a heating energy source in various chemical fields ranging from inorganic reactions to organic reactions, from simple molecular reactions to complex reactions. It has been found that microwave energy can significantly accelerate organic chemical synthesis reactions. The microwave energy penetrates into the substance molecules, is absorbed by the movement of electrons and ions or the polarization of defective dipoles, and is converted into heat, so that the effect of overall heating inside and outside the material is achieved. The heat loss is reduced, the heating time is shortened, and the effects of rapid heating and energy saving can be achieved. The microwave strengthens the chemical reaction field, on one hand, the molecular motion is intensified after the reaction absorbs the microwave energy; on the other hand, the electric field force of the microwave field to the ions or polar molecules forces the ions or polar molecules to move in the mode of electromagnetic wave action, which is enough to show that the microwave heating reaction is selective, and obviously, the microwave heating mode is more suitable for a parallel or automatic continuous process mode.

The invention connects the ultrasonic reactor with broad-spectrum adaptability in series behind the microwave reactor. The ultrasonic reactor has the characteristics of good directivity and strong penetrating power, and enables the fluid from the microwave reactor with selective reaction to continue to react in the ultrasonic reactor.

The reactants generate a dynamic process of high-frequency oscillation, growth and collapse closure under the action of an ultrasonic sound field, when cavitation bubbles collapse, local high temperature and high pressure can be generated in a very small space around the cavitation bubbles within a very short time, and the activity of the reactants is increased by the high temperature, so that the formation of free radicals and the occurrence of cracking reaction are promoted; the high pressure causes the generation of shock waves and micro-jets; resulting in strong collisions between the molecules, which in turn promotes high rates of methyl esterification and subsequent (amidation) reactions. Finally, methyl esterification modification of the inferior grease is completed, and then the reaction process of the microemulsified diesel oil main emulsifier, namely 'fatty acid methyl ester amide', is completed in another group of reaction systems with the same flow and the same composition in the same operation mode under different solution formulas and control conditions, so that the preparation work of the composite emulsifier is completed.

It should be noted that, in the continuous flow reaction system of the present invention, the impinging stream reactor, the microwave reactor and the ultrasonic reactor may be selected from those existing in the prior art. The invention optimizes and combines the reactors to form a reaction system suitable for industrial production.

In another embodiment of the invention, a micro-emulsified diesel oil product is provided, which is prepared by mixing the composite emulsifier as a main agent, a medium-carbon alcohol (propanol, butanol, pentanol) compound as a cosolvent, castor oil methyl ester amide as a stabilizer prepared on a coupling production line of the invention, and trace permanganate and titanate as a water splitting catalyst.

The castor oil methyl ester amide is selected as the stabilizer in the present invention because:

(1) the viscosity coefficient of the castor oil methyl ester amide is higher than that of the common long-chain fatty acid, the viscosity coefficient of the common long-chain fatty acid is 0.68Pa.S at 20 ℃, and the viscosity coefficient is 0.99Pa.S, which shows that the castor oil methyl ester amide has much stronger anti-deformation capability than the common long-chain fatty acid when relative movement exists in liquid.

(2) The wide stability performance of the castor oil methyl ester amide is also reflected on the relationship between the HLB value and the emulsion stabilization period. (see FIG. 2)

The castor oil methyl ester amide is prepared by the following method:

(1) the castor oil is used as a raw material, and the pretreatment is firstly carried out as same as that of other low-quality grease.

(2) And (3) carrying out methyl esterification modification under the same condition as other low-quality grease to prepare the castor oil methyl ester.

(3) Adding a composite amination agent consisting of organic amine and inorganic ammonia into the castor oil methyl ester, and carrying out amidation reaction by using metal sodium as a catalyst to prepare the castor oil methyl ester amide.

For the production of the micro-emulsified diesel oil, a production line with an impinging stream reactor connected with an SK type static mixer in series can be adopted to prepare a stable micro-emulsified diesel oil product.

In order to make the technical solutions of the present application more clearly understood by those skilled in the art, the technical solutions of the present application will be described in detail below with reference to specific embodiments.

The test materials used in the examples and comparative examples of the present invention are conventional in the art and are commercially available.

Example 1: preparation of composite emulsifier

1. Pretreating the illegal cooking oil:

mechanically filtering the illegal cooking oil to remove impurities. Adding a chemical oxidant accounting for 4 percent of the weight of the illegal cooking oil, and heating to 75 ℃. The reaction is stirred for 20 minutes, and the water and a small amount of unreacted chemical oxidant are removed by centrifugal separation.

The formula of the chemical oxidant is as follows:

3 parts of hydrogen peroxide, 1 part of sodium percarbonate and 0.001 part of titanium salt.

Mixing and stirring uniformly at room temperature.

2. Methyl esterification modification of illegal cooking oil:

the methyl esterification modification was carried out in the continuous flow reaction system of the present invention (FIG. 1).

Firstly, putting pretreated illegal cooking oil into a batching tank 1, then adding methanol dissolved with catalyst metal sodium accounting for 20% of the weight of the pretreated illegal cooking oil into the pretreated illegal cooking oil (the dissolved amount of the metal sodium is 0.5% of the total amount of the pretreated illegal cooking oil and the methanol), heating to 40 ℃, stirring for 5 minutes, checking and opening a full-line valve, starting a centrifugal pump 2, dividing a mixed solution of grease and the methanol into two equal liquid flows, and enabling the two liquid flows to enter an impinging stream reactor 4 from two sides in opposite directions at a high speed through a rotor flow meter 3. The impact is severe in the central region of the impinging stream reactor 4 such that the high velocity fluid changes from axial to pulsating motion after the impact, creating a very turbulent impact zone. In the area, the turbulent action of the flow field is obvious, the mixing state of the grease and the methanol is greatly improved, and the transfer quality effect of the process is enhanced. Then the reaction liquid enters the bottom of a cylindrical microwave reactor 5, a plurality of groups of microwave generating devices 7 are arranged in a reaction kettle of the microwave reactor 5, each group of devices extends into a respective ceramic isolation sleeve, the upper end of the ceramic isolation sleeve is suspended on a kettle top mounting plate, and the lower end of the ceramic isolation sleeve extends into the reaction liquid. The ceramic sleeve does not absorb blocking microwaves and only serves to isolate the microwave generator assembly from the reaction liquid. The reaction liquid is heated in a microwave kettle (the temperature is controlled at 40-45 ℃), rises in a rotating way, reacts for 10 minutes and reaches a liquid outlet pipe at the top of the kettle. Then enters from the bottom of the ultrasonic reactor 6, a plurality of groups of ultrasonic emission components 8 are arranged at the top of the reaction kettle of the ultrasonic reactor 6, and the reaction kettle of the ultrasonic reactor 6 is also cylindrical, so that the reaction liquid rotates and rises as well, and further esterification reaction is carried out under the action of the sound field cavitation effect. Discharging from the top of the ultrasonic reactor 6 after 10 minutes, feeding into a material storage tank 9, completing all methyl esterification modification within 10 minutes, finally extracting and purifying in an extraction centrifuge, and taking out a light phase which is fatty acid methyl ester and a heavy phase which is crude glycerol and water.

3. Preparing a composite emulsifier:

similarly, by using the continuous flow reaction system of the invention, firstly, the prepared fatty acid methyl ester is put into a proportioning tank 1 according to calculated amount, diethanolamine with 8 percent of fatty acid methyl ester is added, ammonium hydroxide with 10 percent of fatty acid methyl ester and 40 percent of fatty acid methyl ester is added, and finally, metal sodium with 0.1 percent of fatty acid methyl ester dissolved in methanol is added, the temperature is heated to 50 ℃, the stirring is carried out for 5 minutes, a full-line valve is opened, a centrifugal pump 2 is started, the reaction liquid is divided into two liquid flows with equal amount, the two liquid flows enter an impinging flow reactor 4 at high speed through a rotor flow meter 3, and the two liquid flows collide violently in the central area of the impinging flow reactor 4, so that the high-speed fluid after the collision is changed into pulsating motion from the axial direction, and a. In the region, the turbulent action of the flow field is obvious, the mixing state of the methyl ester, the diethanol amine and the ammonium hydroxide is greatly improved, and the transfer quality effect of the process is enhanced. And then the reaction liquid enters the bottom of the cylindrical microwave reactor 5, is heated in a microwave kettle at the temperature of 95-100 ℃, rotates and rises, reacts for 10 minutes, and reaches a liquid outlet pipe at the top of the kettle. And enters from the bottom of the ultrasonic reactor 6. The reaction kettle of the ultrasonic reactor 6 is also cylindrical, so that the reaction liquid also rotates and rises, and the amidation reaction is further carried out under the action of the acoustic cavitation effect. Discharging the product from the top of the ultrasonic reactor 6 into a storage tank 9 after 10 minutes, and completing the amidation reaction within 10 minutes, wherein the amidation reaction can be completed within two hours conventionally. (in the conventional conditions, the amidation reaction of the grease and diethanol amine is carried out at the temperature of 110 ℃ for two hours, and the grease and ammonium hydroxide are reacted at the pressure of 2Mpa and the temperature of 150 ℃ for two hours).

Example 2: preparation of micro-emulsified diesel oil

1. The raw materials comprise:

80 parts of diesel oil, 10 parts of water, 6.5 parts of composite emulsifier, 2.5 parts of hydrotropic agent, 0.8 part of stabilizer and 0.02 part of water cracking catalyst.

Wherein, the compound emulsifier is prepared from the example 1; the hydrotropy agent is formed by mixing n-propanol, n-butanol and n-pentanol according to the volume ratio of 0.5:1: 0.5; the stabilizer is castor oil methyl ester amide and is prepared from castor oil in the continuous flow reaction system; the water cracking catalyst consists of titanate and permanganate in the mass ratio of 1: 1.

2. The preparation process comprises the following steps:

putting diesel oil, water, a composite emulsifier, a dissolving assistant agent, a stabilizer and a water cracking catalyst into a batching tank, stirring for 3-5 minutes at room temperature, uniformly mixing, starting a centrifugal pump, dividing the mixed material into two equal-quantity liquid flows through a rotor flow meter, coaxially and oppositely entering a central area from two ends of an impinging stream reactor at a high speed for collision, and then introducing into an oil storage tank through an SK type static mixer to obtain the finished product of the micro-emulsified diesel oil.

Example 3: preparing the micro-emulsified diesel oil:

1. the raw materials comprise:

72 parts of diesel oil, 12 parts of water, 7 parts of composite emulsifier, 3.5 parts of hydrotropy agent, 0.5 part of stabilizer and 0.05 part of water cracking catalyst.

Wherein, the compound emulsifier is prepared from the example 1; the hydrotropy agent is formed by mixing n-propanol, n-butanol and n-pentanol according to the volume ratio of 0.5:1: 0.5; the stabilizer is castor oil methyl ester amide and is prepared from castor oil in the continuous flow reaction system; the water cracking catalyst consists of titanate and permanganate, and the mass ratio of the titanate to the permanganate is 1: 1.

2. The preparation process is the same as that of example 2, and the micro-emulsified diesel oil is prepared.

Example 4: preparing the micro-emulsified diesel oil:

1. the raw materials comprise:

85 parts of diesel oil, 8 parts of water, 5 parts of composite emulsifier, 1.5 parts of hydrotropy agent, 1.2 parts of stabilizer and 0.01 part of water cracking catalyst.

Wherein, the compound emulsifier is prepared from the example 1; the cosolvent is prepared by mixing n-propanol, n-butanol and n-pentanol according to the volume ratio of 0.5:1: 0.5.

The stabilizer is castor oil methyl ester amide, castor oil is used as a raw material, the preparation is carried out in the continuous flow reaction system of the invention, and the preparation method is the same as the preparation of the composite emulsifier in the embodiment 1.

The water cracking catalyst consists of titanate and permanganate, and the mass ratio of the titanate to the permanganate is 1: 1.

Comparative example 1: preparation of emulsifiers

1. Pretreating the illegal cooking oil:

mechanically filtering the illegal cooking oil to remove impurities.

2. And carrying out amidation reaction on the pretreated illegal cooking oil and diethanol amine at the reaction temperature of 110 ℃ for two hours to prepare the emulsifier.

Comparative example 2: preparation of micro-emulsified diesel oil

The composite emulsifier in the example 2 is replaced by the emulsifier prepared in the comparative example 1, and the rest of the method is the same as the example 2 to prepare the micro-emulsified diesel oil.

Comparative example 3: preparation of micro-emulsified diesel oil

The "composite emulsifier" in the example 2 is replaced by a commercially available diesel oil emulsifier, and the rest is the same as the example 2 to prepare the micro-emulsified diesel oil.

Comparative example 4: preparation of micro-emulsified diesel oil

The 'stabilizer' in the embodiment 2 is omitted, and the microemulsion diesel oil is prepared by the same method as the embodiment 2.

Comparative example 5: preparation of micro-emulsified diesel oil

The microemulsion diesel oil is prepared by the same method as the embodiment 2 except that the 'water cracking catalyst' in the embodiment 2 is omitted.

Test example 1: stability testing

The microemulsified diesel prepared in example 2, comparative example 2-comparative example 5 is allowed to stand at room temperature, and the stability is observed. The result shows that the micro-emulsified diesel oil prepared in the example 2 does not generate the phenomenon of layering and deterioration after being placed for more than 3 months; the micro-emulsified diesel oil prepared in the comparative example 2 begins to generate the phenomenon of layering and deterioration after being placed for 20 days; the micro-emulsified diesel oil prepared in the comparative example 3 begins to generate the phenomenon of layering and deterioration after being placed for 30 days; the micro-emulsified diesel oil prepared in the comparative example 4 begins to generate the phenomenon of layering and deterioration after being placed for 32 days; the micro-emulsified diesel oil prepared in the comparative example 5 has the phenomenon of layering and deterioration after being placed for 35 days.

The results show that the stability of the micro-emulsified diesel oil prepared by the invention is obviously improved.

Test example 2: test of Combustion Performance

The compression ratio of the diesel engine is tested to be 21.6, and the rated power/rotating speed is 3.8kw/2400 r.min^-1The results are shown in Table 1.

Table 1: results of Combustion Performance test

Item	NO_x(g/kw.h)	CO(g/kw.h)	Smoke intensity
				Example 2	0.8	0.3	1.0
Comparative example 2	1.9	1.4	3.1
				Comparative example 3	1.7	1.3	2.8
Comparative example 4	2.1	1.5	3.4
				Comparative example 5	2.0	1.4	3.2

As can be seen from Table 1, compared with the emulsified diesel oil prepared by the comparative example, the combustion performance of the microemulsified diesel oil prepared by the invention is greatly improved, the discharge amount of nitrogen oxides and CO is obviously reduced, and the emission reduction effect is very obvious.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. The preparation method of the compound emulsifier is characterized by comprising the following steps:

(1) taking low-quality grease as a raw material, and carrying out pretreatment;

(3) adding a composite amination agent consisting of organic amine and inorganic ammonia into fatty acid methyl ester, and carrying out amidation reaction by taking metal sodium as a catalyst to prepare a composite emulsifier;

in the step (1), the pretreatment method comprises the following steps: mechanically filtering low-quality grease to remove impurities; adding a chemical oxidant accounting for 3-5% of the weight of the low-quality grease, heating to 70-80 ℃, stirring for reaction for 15-20 minutes, and centrifugally separating to remove water and unreacted chemical oxidant;

the chemical oxidant is prepared from the following raw materials:

2-4 parts of hydrogen peroxide, 0.5-1.5 parts of sodium percarbonate and 0.001 part of titanium salt;

in the step (2), the adding amount of the methanol dissolved with the metal sodium accounts for 15-25% of the weight of the pretreated low-quality grease; the dissolving amount of the metal sodium is 0.3-0.7% of the total weight of the pretreated low-quality grease and the methanol;

in the step (3), the composite aminating agent consists of diethanolamine and ammonium hydroxide; the addition amount of the diethanol amine is 6-10% of the weight of the fatty acid methyl ester, and the addition amount of the ammonium hydroxide is 8-12% of the weight of the fatty acid methyl ester;

said steps (2) and (3) are carried out in a continuous flow reaction system comprising: the impinging stream reactor, the microwave reactor and the ultrasonic reactor are sequentially connected, a plurality of groups of microwave generating devices are installed in a reaction kettle of the microwave reactor, each group of devices extends into a respective ceramic isolation sleeve, the upper end of the ceramic isolation sleeve is suspended on a kettle top mounting plate, the lower end of the ceramic isolation sleeve extends into reaction liquid, the reaction liquid is heated in the reaction kettle of the reactor, rotationally rises and reacts, reaches a kettle top liquid outlet pipe and then enters from the bottom of the ultrasonic reactor, a plurality of groups of ultrasonic transmitting assemblies are installed at the top of the reaction kettle of the ultrasonic reactor, the reaction kettle of the ultrasonic reactor is cylindrical, the reaction liquid also rotationally rises, and further reacts under the action of a sound field cavitation effect.

2. The production method according to claim 1, wherein in the step (1), the low-quality oil comprises: illegal cooking oil, sewage oil of animal slaughterhouse, reclaimed oil of leather factory, acid oil produced by refining food oil, and inedible castor oil, Jatropha curcas oil and palm oil with high condensation point.

3. A complex emulsifier prepared by the method of claim 1 or 2.

4. The use of the compound emulsifier of claim 3 in the preparation of emulsified diesel oil.

5. A micro-emulsified diesel oil, which is characterized in that the micro-emulsified diesel oil is prepared by adding the compound emulsifier, water, a water-solubilizing agent, a stabilizer and a water cracking catalyst in the diesel oil, and then uniformly mixing;

the hydrotropy agent is formed by mixing n-propanol, n-butanol and n-pentanol according to the volume ratio of 0.5:1: 0.5;

the stabilizer is castor oil methyl ester amide;

the water cracking catalyst is formed by mixing one or two of titanate and permanganate in any ratio.

6. A microemulsified diesel according to claim 5, characterized in that the microemulsified diesel is prepared from the following raw materials in parts by weight:

7. A microemulsified diesel according to claim 6, characterized in that the microemulsified diesel is prepared from the following raw materials in parts by weight:

8. A method for preparing a microemulsified diesel as claimed in claim 6 or 7, characterized by comprising the following steps:

mixing diesel oil, water, a composite emulsifier, a dissolving assistant agent, a stabilizer and a water cracking catalyst, reacting in an impinging stream reactor, dividing the mixed material into two streams through a rotor flow meter, coaxially and oppositely entering a central area from two ends of the impinging stream reactor at a high speed for collision, and introducing into an oil storage tank through a static mixer to obtain the micro-emulsified diesel oil.