CN105152841A - Low-temperature-freezing magnetic separation method and device for long-chain alkene and long-chain alkane mixture - Google Patents

Abstract

The invention relates to a method for low-temperature freezing and magnetic separation of mixtures of long-chain olefins and alkanes that can easily realize solid-liquid separation and improve product purity. The method is to add magnetic powder to the mixture liquid containing long-chain olefins and long-chain alkanes, and then Cool the mixed liquid containing magnetic powder to a temperature range lower than the melting point of long-chain alkanes and higher than the melting point of long-chain alkenes, and the long-chain alkanes will be separated out and adsorbed on the surface of the magnetic powder to form a magnetic waxy solid. Under the action, the magnetic waxy solid is separated from the unfrozen long-chain alkene liquid, and the liquid after taking out the magnetic waxy solid and heating up to melt is the long-chain alkane. The invention can accelerate the rate of freezing and crystallization, is very easy to separate solid and liquid, and can obtain high-purity products. The method and device of the invention can be applied to the olefin separation of Fischer-Tropsch synthesis crude oil and cutting oil in coal chemical industry, as well as the separation and purification of long-chain olefin-containing mixed oil in petrochemical industry.

Description

Method and device for cryogenic freezing and magnetic separation of long-chain alkenes and alkanes

technical field

The invention relates to the separation of long-chain olefins and long-chain alkanes, in particular to a method and device for cryogenically magnetically separating long-chain olefins and alkane mixtures.

Background technique

Long-chain olefins (or high-carbon olefins) mostly refer to olefins containing more than 10 carbon atoms, and are divided into terminal olefins (α-olefins) and internal olefins according to the position of the double bond. Long-chain olefins can be used to produce olefin copolymers, lubricating oils, surfactants, oilfield chemicals and other products, which are widely used in petrochemical, light industry, textile, metallurgy, medicine, pesticide and other industries. However, the separation of long-chain olefin/alkane mixtures with the same number of carbon atoms is a major technical problem faced by petrochemical and coal chemical industries. Therefore, the separation of long-chain olefin/alkane mixtures is also a hot spot in the field of separation at home and abroad. The separation methods include rectification, complex extraction, complex adsorption and membrane separation.

US4132744 discloses a liquid-liquid extraction method for separating C6-C20 alkane and olefin mixtures, using a mixture of short-chain alcohols and aliphatic alcohol polyethers containing silver salts or cuprous salts as the extraction agent, wherein the polyether solvent is 1,2-Dimethoxyethane, diglyme, triglyme or 1,2-diethoxyethane, short-chain alcohols as methanol, ethanol or n-propanol, will extract The solvent and the mixed oil containing olefins are stirred and mixed, and most of the olefins are transferred to the extraction phase. After the extraction phase and the raffinate phase are separated, the extraction phase is distilled to obtain higher-purity olefin products.

CN103232313A discloses a method for extraction and separation of alkanes/alkenes. The extractant is N-methylpyrrolidone, N-formylmorpholine, 1-methylimidazole or γ-butyrolactone. The total volume of the extractant and the mixture to be separated The ratio is 0.25, 0.5, 1.0 or 2.0. The mixture to be separated containing alkanes and high-carbon α-olefins with the same carbon number is fully contacted and mixed with the extractant, and then allowed to stand for layering and separation, wherein the high-carbon α-olefins enter the extraction phase, and the same carbon alkanes enter the raffinate phase, to achieve the separation of alkanes with the same carbon number and higher α-olefins.

US2015/0148577 of Universal Oil Company of the United States discloses the separation of C19~C22 isomeric olefins from paraffin, using X-type zeolite with an optimal silicon-aluminum ratio of 2.4~2.6 as the adsorbent, and the adsorption temperature is 120°C~180°C. The moving bed is used to separate the mixture containing long-chain olefins, and the desorbent is C5~C10 cycloalkane, such as cyclohexane, methylcyclohexane, methylcyclopentane, etc., to obtain long-chain olefin products with high concentration.

In addition to the above literature, there are many reports on the separation of long-chain olefins and alkanes. Due to the similar boiling points of alkenes and alkanes, rectification separation requires more theoretical plates, larger reflux ratio, and higher energy consumption. Complexation extraction and complexation adsorption are relatively mature for the separation of short-chain olefins, but there are many technical obstacles in the separation of long-chain olefins. Membrane separation technology for the separation of long-chain olefins and alkanes is in the research and development stage, and there is a long distance from industrialization. Relatively speaking, the melting points of alkenes and alkanes with the same number of carbon atoms are quite different, and the difference in melting point can be used to realize the separation of alkenes and alkanes by cryogenic freezing.

US1313275 discloses a method for cold-temperature freezing and separation of long-chain olefins, using acetone, methyl isobutyl ketone or naphtha, etc. as solvents, the solvent is combined with a mixture containing long-chain olefins and alkanes, and the temperature is lowered to make a higher melting point The long-chain alkanes are solidified and precipitated, and then the entrapped olefin molecules are removed by washing with solvents such as acetone or methyl isobutyl ketone, the waxy solid is subjected to solid-liquid separation, and the solvent in the filtrate is evaporated by air stripping to obtain higher-purity olefins.

Relatively speaking, the separation of long-chain olefins and alkanes by cryogenic refrigeration has the advantages of simple operation, no introduction of impurities and low energy consumption. At present, falling-film crystallizers and kettle-type crystallizers are mostly used for cryogenic crystallization separation. After cooling crystallization, sweating and purification, and then heating and thawing, the falling-film crystallizer mainly forms a crystallization film on the tube wall without solid-liquid separation. , but impurities are easily contained in the film layer. Although a small amount of impurities are discharged in the form of sweat by heating up and sweating, due to the high viscosity, most of the impurities are still trapped inside the crystal layer, reducing the purity of the product. The advantage of the tank-type crystallizer is that during the cooling crystallization process, stirring makes the liquid phase temperature more uniform. The disadvantage is that it is difficult to form crystal nuclei and waxy solids are not easy to separate solid-liquid, or the temperature changes during the solid-liquid separation process, causing partial condensation The substance melts back into a liquid.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for low-temperature freezing and magnetic separation of long-chain olefin and alkane mixtures that can easily realize solid-liquid separation and can improve product purity.

In order to solve the above technical problems, the technical solution adopted in the present invention is: a method for cryogenically freezing and magnetically separating long-chain olefins and alkane mixtures, adding magnetic powder to the mixture liquid containing long-chain olefins and long-chain alkane, and then The mixed liquid containing magnetic powder is cooled to a temperature range lower than the melting point of long-chain alkanes and higher than the melting point of long-chain alkenes, and the long-chain alkanes are analyzed and adsorbed on the surface of the magnetic powder to form a magnetic waxy solid. The magnetic waxy solid is separated from the unfrozen long-chain olefin liquid. After the magnetic waxy solid is taken out, the liquid after heating up and melting is the long-chain alkane. Magnetically separated magnetic media can be reused. Long-chain alkenes and alkanes mixtures refer to alkenes and alkanes of the same carbon chain with more than 10 carbon atoms.

At the same time, the present invention also provides a device for cryogenically magnetically separating long-chain olefins and alkanes. The design principle and usage method of the device have the same idea as the aforementioned separation method.

The described device comprises three parts of stirring mixer, cooling system and magnetic separation system,

——The stirring mixer consists of a double-layer jacket and a cylindrical cylinder. The upper end of the cylinder is provided with a feeding port, and the lower end is provided with a liquid discharge port. The agitator driven by a motor is installed inside the cylinder, and a jacket is arranged around the cylinder. There is a liquid inlet at the lower end of the jacket, and a liquid outlet at the upper end of the jacket;

——The cooling system includes a high and low temperature circulating machine and a circulating pump, the circulating pump is connected to the liquid inlet at the lower end of the jacket of the stirring mixer, and the liquid outlet at the upper end of the jacket is connected to the high and low temperature circulating machine;

- The magnetic separation system includes an external magnetic field and is set at the bottom of the stirring mixer.

The way to separate long-chain olefins and long-chain alkanes with the above-mentioned device is: add the mixed liquid containing long-chain olefins and long-chain alkanes and magnetic powder into the stirring mixer, start the motor to stir, and suspend the magnetic powder In the oil phase; start the cooling system, the refrigerant enters from the liquid inlet of the stirring mixer jacket through the circulating pump and fills the jacket, and returns to the cooling system through the liquid outlet; when the liquid temperature in the stirring mixer reaches the set temperature , the cooling system maintains the heat preservation state, and the long-chain alkane components are frozen and precipitated and adsorbed on the surface of the magnetic powder to form a magnetic waxy solid, which is kept for 2-10 hours ; then the external magnetic field is moved close to the bottom of the stirring mixer, and stirred The magnetic waxy solid in the container is condensed at the bottom of the mixer. Open the discharge port of the stirring mixer to discharge the unfrozen long-chain olefin liquid. After the liquid is drained, take out the magnetic waxy solid and heat it up to melt. After melting, the liquid is long paraffin products.

As a preferred technical solution, the magnetic powder described in the present invention has superparamagnetism and is any one of Fe ₃ O ₄ , γ-Fe ₂ O ₃ , CoFe ₂ O, NiFe ₂ O ₄ and BaFe ₂ O ₄ kind. Superparamagnetic magnetic powder is magnetic when there is an external magnetic field. When the external magnetic field is removed, the residual magnetism disappears quickly. The magnetic powder is non-magnetic and has a small particle size. It is in a dispersed state when it is slightly stirred in the liquid.

As a preferred technical solution, the applied magnetic field of the present invention adopts a permanent magnet, selected from any one of neodymium iron boron magnets, samarium cobalt magnets, alnico magnets and ferrite magnets.

In the present invention, by adding magnetic powder, in the crystallization process, the homogeneous nucleation process is converted into heterogeneous nucleation, which can greatly promote the rate of freezing crystallization, and the crystallized precipitates are attached to the surface of the magnetic medium, and in the external magnetic field environment , very easy solid-liquid separation, and high-purity products can be obtained. The method and device of the invention can be applied to the olefin separation of Fischer-Tropsch synthesis crude oil and cutting oil in coal chemical industry, as well as the separation and purification of long-chain olefin-containing mixed oil in petrochemical industry.

Description of drawings

Fig. 1 is a schematic structural view of the magnetic separation reactor of the present invention.

In the figure, 1 stirring mixer, 1-1 barrel, 1-2 motor, 1-3 feeding port, 1-4 liquid outlet, 1-5 liquid outlet, 1-6 liquid inlet, 1-7 jacket, 1-8 agitator, 2 cooling system, 2-1 high temperature and low circulation integrated machine, 2-2 circulating pump, 3 magnetic separation system, 3-1 external magnetic field, 3-2 lifter, 3-3 handle, 3-4 base.

Detailed ways

Example 1

The structure and application method of the low-temperature freezing and magnetic separation device for long-chain olefin and alkane mixture.

As shown in Fig. 1, this device comprises stirring mixer 1, cooling system 2 and magnetic separation system 3 three parts, and wherein, stirring mixer 1 comprises a double-layer jacket and cylindrical cylinder 1-1, and cylinder upper end is provided with There is a feeding port 1-3, a liquid discharge port 1-4 is provided at the lower end, an agitator 1-8 driven by a motor 1-2 is installed in the cylinder, a jacket 1-7 is arranged on the periphery of the cylinder, and the lower end of the jacket 1-7 There is a liquid inlet 1-6, and the upper end of the jacket 1-7 is provided with a liquid outlet 1-5; the cooling system 2 includes a high and low temperature circulating machine 2-1, a circulating pump 2-2, a circulating pump 2-2 and a stirring The lower end of the jacket 1-7 of the mixer 1 is connected to the liquid inlet 1-6, and the liquid outlet 1-5 at the upper end of the jacket 1-7 is connected to the high and low temperature cycle integrated machine 2-1; the magnetic separation system 3 includes an external magnetic field 3 -1, set at the bottom of stirring mixer 1. The external magnetic field 3-1 adopts permanent magnets, and any one of NdFeB magnets, SmCo magnets, AlNiCo magnets and ferrite magnets can be selected. The external magnetic field 3-1 is placed on a lifter 3-2 with a handle 3-3, the bottom of the lifter 3-2

There are bases 3-4.

When in use, add the mixed liquid and magnetic powder containing long-chain olefins and long-chain alkanes into the stirring mixer 1, start the motor 1-2 to stir, and suspend the magnetic powder in the oil phase; start the cooling system 2, resulting in The refrigerant enters from the liquid inlet 1-6 of the stirring mixer jacket 1-7 through the circulating pump 2-2 and fills the jacket 1-7, and returns to the cooling system 2 through the liquid outlet 1-5; when the stirring mixer 1 When the temperature of the internal liquid reaches the set temperature, the set temperature is within the temperature range below the melting point of long-chain alkanes and higher than the melting point of long-chain alkenes, the cooling system 2 maintains the heat preservation state, and the long-chain alkanes components are frozen and precipitated and adsorbed Form a magnetic wax-like solid on the surface of the magnetic powder, keep warm for 2-10 h ; then turn the handle 3-3 to make the lifter 3-2 rise, move the external magnetic field 3-1 close to the bottom of the stirring mixer 1, stir the mixer 1. The inner magnetic waxy solid is condensed at the bottom of the mixer. Open the liquid outlet 1-4 of the stirring mixer 1 to discharge the unfrozen long-chain olefin liquid. After the liquid is drained, take out the magnetic waxy solid and heat it up to melt. The latter liquid is a long chain alkane product.

Example 2

Add 10L of dodecene and dodecane mixture with an olefin content of 10% (mass ratio) to the stirring mixer, then add 1kg of NiFe ₂ O ₄ powder with a particle size of 500nm, start the motor, and stir to make the NiFe ₂ O ₄ powder body suspended in the oil phase. Set the cooling temperature to -20°C (note: the melting point of dodecane is -9°C, and the melting point of dodecene is -33°C), start the cooling system, and cool down the mixed liquid in the stirring mixer to -20°C Keep warm for 3 hours, stir at 50 rpm, discharge and collect the liquid after magnetic separation, and obtain a carbadodecene product with a content of 90%. Take out the magnetic waxy solid, place it at room temperature to melt to obtain dodecane.

Example 3

Add 10L of tridecene and tridecane mixture with an olefin content of 50% (mass ratio) to the stirring mixer, then add 2kg of Fe ₃ O ₄ powder with a particle size of 500nm, start the motor, and stir to make the Fe ₃ O ₄ powder suspended in the oil phase. Set the cooling temperature to -15°C (note: the melting point of tridecane is -5°C, and the melting point of tridecene is -23°C), start the cooling system, and cool down the mixed liquid in the stirring mixer to -15°C Left and right, heat preservation for 5 hours, the stirring speed is 60rpm, after magnetic separation, the liquid is discharged and collected, and the carbadodecene product with a content of 93% is obtained. Take out the magnetic waxy solid, and place it at room temperature to melt to obtain tridecane.

Example 4

Add 20L olefin content of 70% (mass ratio) pentacene and pentadecane mixture to the stirring mixer, then add 1kg of Fe ₃ O ₄ powder with a particle size of 500nm, start the motor, and stir to make the Fe ₃ O ₄ powder suspended in the oil phase. Set the cooling temperature to 3°C (note: the melting point of pentadecane is 8°C, and the melting point of pentacene is -3°C), start the cooling system, and cool down the mixed liquid in the stirring mixer until it drops to about 3°C and keep warm 5h, the stirring speed was 40rpm, the liquid was discharged and collected after magnetic separation, and the carbapentacene product with a content of 92% was obtained. Take out the magnetic waxy solid, place it at room temperature to melt to obtain pentadecane.

Example 5

Add 10L olefin content of 30% (mass ratio) octadecene and octadecane mixture to the stirring mixer, then add 2kg of γ-Fe ₂ O ₃ powder with a particle size of 400nm, start the motor, and stir to make γ-Fe ₂ O ₃ powder is suspended in the oil phase. Set the cooling temperature to 20°C (note: the melting point of octadecane is 28°C, and the melting point of octadecene is 17°C), start the cooling system, and cool down the mixed liquid in the stirring mixer to about 3°C, and keep it warm for 4 hours , the stirring speed is 60rpm, the liquid is discharged and collected after magnetic separation, and the carbadecene product with a content of 90% is obtained. Take out the magnetic waxy solid, place it at room temperature to melt to obtain octadecane.

Example 6

Add 20L olefin content of 70% (mass ratio) pentacene and pentadecane mixture to the stirring mixer, then add 1kg of CoFe ₂ O4 powder with a particle size of 500nm, start the motor, and stir to suspend the CoFe ₂ O4 powder in the oily phase. Set the cooling temperature to 3°C (note: the melting point of pentadecane is 8°C, and the melting point of pentacene is -3°C), start the cooling system, and cool down the mixed liquid in the stirring mixer until it drops to about 3°C and keep warm 2h, the stirring speed was 40rpm, the liquid was discharged and collected after magnetic separation, and the carbapentacene product with a content of 92% was obtained. Take out the magnetic waxy solid, place it at room temperature to melt to obtain pentadecane.

Example 7

Add 10L olefin content of 50% (mass ratio) tridecene and tridecane mixture to the stirring mixer, then add 2kg of BaFe ₂ O ₄ powder with a particle size of 500nm, start the motor, and stir to make the BaFe ₂ O ₄ powder suspended in the oil phase. Set the cooling temperature to -15°C (note: the melting point of tridecane is -5°C, and the melting point of tridecene is -23°C), start the cooling system, and cool down the mixed liquid in the stirring mixer to -15°C Keep warm for 10 hours, stir at 60 rpm, discharge and collect the liquid after magnetic separation, and obtain a carbatridecene product with a content of 93%. Take out the magnetic waxy solid, and place it at room temperature to melt to obtain tridecane.

Claims (6)

1. A method for low-temperature freezing and magnetic separation of long-chain olefins and alkane mixtures, characterized in that: magnetic powder is added to the mixture liquid containing long-chain olefins and long-chain alkane, and then the mixed liquid containing magnetic powder is cooled In the temperature range below the melting point of long-chain alkanes and higher than the melting point of long-chain alkenes, the long-chain alkanes group is separated out and adsorbed on the surface of the magnetic powder to form a magnetic waxy solid. Under the action of an external magnetic field, the magnetic waxy solid and unfrozen The liquid separation of long-chain olefins, take out the magnetic waxy solid, heat up and melt the liquid is the long-chain alkanes. 2. A device for low-temperature freezing and magnetic separation of long-chain olefins and alkane mixtures, characterized in that: the device includes three parts: a stirring mixer (1), a cooling system (2) and a magnetic separation system (3), ——The agitating mixer (1) includes a double-layer jacket and a cylindrical cylinder (1-1). The upper end of the cylinder is provided with a feeding port (1-3), and the lower end is provided with a liquid discharge port (1-4). The cylinder is equipped with an agitator (1-8) driven by a motor (1-2), a jacket (1-7) is arranged on the periphery of the cylinder, and a liquid inlet (1-6) is provided at the lower end of the jacket (1-7). ), the upper end of the jacket (1-7) is provided with a liquid outlet (1-5); ——Cooling system (2) includes high and low temperature circulation integrated machine (2-1) and circulation pump (2-2), the lower end of jacket (1-7) of circulation pump (2-2) and stirring mixer (1) The liquid inlet (1-6) is connected, and the liquid outlet (1-5) at the upper end of the jacket (1-7) is connected with the high and low temperature cycle integrated machine (2-1); - The magnetic separation system (3) includes an external magnetic field (3-1), which is arranged at the bottom of the stirring mixer (1). 3. Utilize the method for the low-temperature freezing and magnetic separation of long-chain olefins and alkane mixtures of the device according to claim 2, characterized in that: the mixed liquid and magnetic powder containing long-chain olefins and long-chain alkane are added to the stirring mixer (1 ), start the motor (1-2) to stir, so that the magnetic powder is suspended in the oil phase; start the cooling system (2), and the refrigerant passes through the circulating pump (2-2) from the stirring mixer jacket (1-7) The liquid inlet (1-6) enters and fills the jacket (1-7), and returns to the cooling system (2) through the liquid outlet (1-5); when the temperature of the liquid in the stirring mixer (1) reaches the set temperature, the cooling system (2) maintains the heat preservation state, and the long-chain alkane components are frozen and precipitated and adsorbed on the surface of the magnetic powder to form a magnetic waxy solid, which is kept for 2~10 hours ; then the external magnetic field (3-1) is moved closer to Stick it to the bottom of the stirring mixer (1), the magnetic waxy solid in the stirring mixer (1) condenses at the bottom of the mixer, open the drain port (1-4) of the stirring mixer (1), and discharge the unfrozen long Alkene liquid, after the liquid is drained, the magnetic waxy solid is taken out and heated up to melt, and the melted liquid is a long-chain alkane product. 4. The method according to claim 1 or 3, characterized in that: the magnetic powder has superparamagnetism and is Fe ₃ O ₄ , γ-Fe ₂ O ₃ , CoFe ₂ O, NiFe ₂ O ₄ and Any one of BaFe ₂ O ₄ . 5. The method according to claim 1 or 3, characterized in that: said external magnetic field adopts a permanent magnet. 6. The method according to claim 5, wherein the permanent magnet is selected from any one of NdFeB magnets, SmCo magnets, AlNiCo magnets and ferrite magnets.