阅读说明：本技术 一种相变储能蜡及其制备方法 (Phase-change energy-storage wax and preparation method thereof ) 是由 钱震 苗恒 李俊诚 周岩 菅青娥 马国清 郑会月 郭良兰 王海国 于 2019-09-24 设计创作，主要内容包括：一种相变储能蜡及其制备方法,所述制备方法包括：(1)将费托合成产物经催化加氢得到费托精制蜡；(2)将所述费托精制蜡分离出馏程在200-550℃内的多个窄馏分；(3)将所述窄馏分经分步结晶制备相变储能蜡。本发明具有操作简单、能耗低、不需要溶剂、三废排放少等优点。(A phase change energy storage wax and a preparation method thereof, wherein the preparation method comprises the following steps: (1) carrying out catalytic hydrogenation on the Fischer-Tropsch synthesis product to obtain Fischer-Tropsch refined wax; (2) separating the Fischer-Tropsch refined wax into a plurality of narrow fractions with the distillation range within 200-550 ℃; (3) and (3) performing fractional crystallization on the narrow fraction to prepare the phase change energy storage wax. The method has the advantages of simple operation, low energy consumption, no need of solvent, less discharge of three wastes and the like.)

1. A method of preparing a phase change energy storage wax comprising:

(1) carrying out catalytic hydrogenation on the Fischer-Tropsch synthesis product to obtain Fischer-Tropsch refined wax;

(2) separating the Fischer-Tropsch refined wax into a plurality of narrow fractions with the distillation range within 200-550 ℃;

(3) and (3) performing fractional crystallization on the narrow fraction to prepare the phase change energy storage wax.

2. The method according to claim 1, wherein the separation in step (2) is selected from the group consisting of atmospheric or vacuum distillation, short path molecular distillation, thin film distillation, and any combination thereof.

3. The production process according to claim 1 or 2, wherein the separation in step (2) is carried out at an operating pressure of 0.1PaA (absolute) to atmospheric pressure.

4. The production method according to claim 1, wherein the narrow fraction has a distillation range width of 5 to 30 ℃, such as 10 ℃, 15 ℃, 20 ℃ or 25 ℃.

5. The production method according to claim 1, wherein the step of fractional crystallization comprises: crystallizing the narrow fraction at a temperature of 5-10 deg.C below the melting point of the narrow fraction, maintaining the temperature for 3-10h (e.g. 4h, 6h, 8h), and discharging mother liquor residue; then the temperature of the crystal is raised to sweat, and finally the temperature is raised to the melting point; and finally, heating, melting and discharging the crystal to obtain the phase change energy storage wax or repeatedly performing fractional crystallization to obtain the phase change energy storage wax.

6. The production method according to claim 5, wherein the temperature rise includes a plurality of temperature gradients.

7. The method of claim 1, wherein the method further comprises mixing products obtained by fractional crystallization of different narrow fractions with each other to prepare the phase change energy storage wax.

8. A phase change energy storage wax produced by the production method according to any one of claims 1 to 7.

9. The phase change energy storage wax of claim 8, wherein the phase change energy storage wax has an enthalpy greater than 200J/g and a melting point of 5-90 ℃.

10. The phase change energy storage wax of claim 8, wherein the isomeric hydrocarbon content of the phase change energy storage wax is less than 5 wt%.

Technical Field

The invention belongs to the technical field of chemical industry, and particularly relates to a phase change energy storage wax and a preparation method thereof.

Background

The phase-change energy storage wax is one of phase-change energy storage materials, can effectively avoid the supercooling phenomenon and the phase separation phenomenon of inorganic phase-change materials, and overcomes the defects that the inorganic phase-change materials cannot be repeatedly used and the like. The phase change energy storage wax can be divided into high temperature, medium temperature, low temperature and the like according to the temperature range of energy storage. The low-medium temperature phase-change wax can be widely applied to civil fields, including the fields of building energy conservation, facility agriculture, daily necessities (such as temperature-adjusting textiles, electric appliance heat-proof shells and the like) and the pharmaceutical industry, and the high-temperature phase-change wax is mainly applied to the fields of solar energy utilization, hot water systems, electronic elements, automatic control and the like. Generally, a phase change material is required to have a proper phase change temperature and a large latent heat of phase change.

The Fischer-Tropsch wax is a methylene polymer, is an alkane mixture obtained by catalytic polymerization of synthesis gas at medium temperature and medium pressure, has relatively simple composition, has normal straight-chain alkane content up to over 90 percent, and basically contains branched-chain alkane and basically no cyclic hydrocarbon and aromatic hydrocarbon, has larger phase-change latent heat of normal alkane compared with isoparaffin and cycloparaffin, and has stable chemical property, no corrosiveness and no environmental pollution, which is the greatest advantage of Fischer-Tropsch wax used for producing phase-change wax. But the Fischer-Tropsch wax has wider carbon number distribution range, smaller phase change latent heat and wider phase change interval when being directly used as a phase change wax material, and simultaneously, the improvement of the phase change latent heat of a small amount of isoparaffin contained in the Fischer-Tropsch wax also influences the phase change latent heat.

After the Fischer-Tropsch wax is subjected to narrow fraction separation, the distillation range width ranges from 5 ℃ to 30 ℃, the content of isomeric hydrocarbon is a main factor influencing the enthalpy value of the fraction, and the boiling point difference of normal isoparaffin with the same carbon number is smaller, and the melting point difference is larger.

In the phase-change wax preparation method, coal-based Fischer-Tropsch synthetic wax is used as a raw material, refined wax products with different phase-change enthalpy values are obtained through molecular short-path distillation, and stable phase-change wax products are obtained by adding NNO.

In the preparation method of the phase-change wax material for energy saving, the phase-change wax product is produced by deoiling paraffin in an improved sweating deoiling mode.

The Fischer-Tropsch wax is subjected to short-range distillation to obtain a phase-change wax product, firstly, the raw materials are directly subjected to evaporation operation at high temperature without any pretreatment process, and carbon deposition and coking are easily generated in the separation process due to a small amount of olefin, oxygen-containing organic matters and polycyclic hydrocarbon in the raw materials, so that the product quality is influenced. Secondly, the separation precision of the short-distance separation process is not high, the overlap of light and heavy components is large, the carbon number distribution of each product is still wide, the purity is not high, the enthalpy value of the product is not high, the separation precision of the molecular short-distance distillation is lower than that of a rectifying device, and the carbon number distribution of the product is wide and the enthalpy value is lower; at the same time, the separated fraction needs to be added with NNO to form a stable product.

The phase-change wax production is carried out by the sweating deoiling, and for the common sweating deoiling method, the solid component (wax with higher melting point) and the liquid component (oil and wax with lower melting point) are respectively in two phase states of solid and liquid, but are difficult to be completely separated. In order to meet the oil content of the final product, methods of prolonging the sweating time and raising the sweating termination temperature are generally used, but this results in long production cycles and a decrease in product yield.

Technical terms:

Fischer-Tropsch wax: synthesis gas (CO and H)₂) The alkane mixture obtained by the F-T reaction at a certain temperature and pressure and under the action of a catalyst contains a small amount of olefin, oxygen-containing compounds and the like.

Phase change energy storage: the method refers to storing energy by utilizing latent heat absorbed or released by a phase change material in a phase change process. The phase change process is an isothermal or approximately isothermal process, and the heat absorbed or released in the phase change process is far larger than the heat absorbed in the sensible heat change process.

Disclosure of Invention

Based on the facts, the invention adopts a melting fractional crystallization process, and the main process is to utilize the melting point difference of the components, firstly, cool and crystallize the melting material, discharge the uncrystallized part as mother liquor, then heat and sweat the crystallized material, discharge the occluded impurities, and finally achieve the refining of the crystallized product.

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

a method of preparing a phase change energy storage wax comprising:

(1) carrying out catalytic hydrogenation on the Fischer-Tropsch synthesis product to obtain Fischer-Tropsch refined wax;

(2) separating the Fischer-Tropsch refined wax into a plurality of narrow fractions with the distillation range within 200-550 ℃;

(3) and (3) performing fractional crystallization on the narrow fraction to prepare the phase change energy storage wax.

In some embodiments, the separation means in step (2) is selected from atmospheric or vacuum distillation, short path molecular distillation, membrane distillation, or any combination thereof.

In some embodiments, the operating pressure for the separation in step (2) is from 0.1PaA (absolute) to atmospheric.

In some embodiments, the narrow fraction has a distillation range width of 5-30 ℃, e.g., 10 ℃, 15 ℃, 20 ℃, or 25 ℃.

In some embodiments, the step of fractional crystallization comprises: crystallizing the narrow fraction at a temperature of 5-10 deg.C below the melting point of the narrow fraction, maintaining the temperature for 3-10h (e.g. 4h, 6h, 8h), and discharging mother liquor residue; then the temperature of the crystal is raised to sweat, and finally the temperature is raised to the melting point; and finally, heating, melting and discharging the crystal to obtain the phase change energy storage wax or repeatedly performing fractional crystallization to obtain the phase change energy storage wax.

In some embodiments, the temperature ramp includes a plurality of temperature gradients.

In some embodiments, the method further comprises mixing products obtained by fractional crystallization of different narrow fractions with each other to prepare the phase change energy storage wax.

The phase change energy storage wax prepared by the preparation method.

In some embodiments, the phase change energy storage wax has an enthalpy greater than 200J/g.

In some embodiments, the phase change energy storage wax has a melting point of 5-90 ℃.

In some embodiments, the isomerized hydrocarbon content in the phase change energy storage wax is less than 5 wt.%.

Compared with the prior art, the invention has the following beneficial effects:

(1) the coal-based Fischer-Tropsch refined wax adopted by the invention has the characteristics of single group composition, normal alkane content of more than 90%, no impurity, no aromatic hydrocarbon and the like, and can be used as an excellent raw material for producing the phase-change wax.

(2) The invention carries out full pretreatment and hydrofining on the Fischer-Tropsch synthetic wax, and can improve the quality of target products.

(3) The fractional crystallization process can reduce the fractional width of carbon number (reduce the content of light components), has the advantage of reducing the content of isomeric hydrocarbon, and has the advantages of simple operation, low energy consumption, no need of solvent, less discharge of three wastes and the like.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments.

The invention takes Fischer-Tropsch wax as a raw material, and hydrofining is carried out in the presence of a catalyst to remove oxygen-containing compounds, olefin, other impurities such as sulfur, nitrogen and the like which affect the color and the taste of the product. The hydrogenation product is subjected to precise separation to obtain narrow fraction with the distillation range width of 5-30 ℃, and then fractional crystallization treatment is carried out to reduce the content of isomeric hydrocarbon in the distillation section to below 5 wt%, so as to obtain the final fraction with low content of isomeric hydrocarbon or a blending product between the distillation sections as a final phase change energy storage wax product. The precise separation mode can be one or a combination of several modes of normal/reduced pressure rectification, short-range molecular distillation or thin film distillation, and the like, and the melting point of the obtained phase change energy storage wax is 5-90 ℃, and the enthalpy value is more than 200J/g.

In some embodiments of the invention, coal-based Fischer-Tropsch wax is used as a raw material, the Fischer-Tropsch wax can be synthesized by a cobalt-based catalyst or an iron-based catalyst, the Fischer-Tropsch wax obtained after hydrofining is subjected to a thin film evaporator and molecular short-path distillation to separate out wide fractions, the distillation range is further shortened through reduced pressure distillation, the separation precision is improved to 10-30 ℃, and the narrow fractions are subjected to fractional crystallization.

The fractional crystallization process is completed in four different process stages, the first of which is cooling/crystallization, forming nucleation of crystals on the surface of the crystallizer. The second stage is thermostatted at the temperature of the first stage for a period of time to allow crystals to grow together and form a solid on the cooled surface. At the bottom of the crystallizer, the residual liquid portion of the feed is discharged by opening the bottom valve. In the third stage, the temperature is slowly raised, sweating occurs on the surface of the solid wax, and the isomeric components and light components are discharged. And finally, waxing the cooling plate, heating to melt and discharging. The fractional crystallization process may be repeated multiple times depending on the properties of the target product. The phase change energy storage wax product from the crystallizer has a lower carbon number distribution breadth and iso-hydrocarbon content than the feedstock.

Take the processing mode of the thin film evaporator and the short-range evaporator as an example: controlling the membrane distillation pressure below 100Pa and the molecular short path distillation pressure within 10Pa, and separating the fractions shown in the table 1:

TABLE 1

Fraction (. degree.C.)	≤400	400-430	430-460	460-490	490-520	520-550	≥550
								Film temperature (. degree. C.)	180-190
Short range temperature (. degree. C.)		160-170	180-190	216-225	235-245	255-265

Example 1:

the fractions at 460-475 ℃ and 475-490 ℃ are separated by decompressing and rectifying the fractions at 460-490 ℃ and 1000Kpa of the decompressing tower. Melting the 460-475 ℃ fraction at the melting point of 69.5 ℃, then performing fractional crystallization, performing cooling/crystallization at the temperature of 5-10 ℃ lower than the melting point, keeping the temperature for more than 4 hours at the temperature, and discharging mother liquor residues, wherein the residue accounts for 20-80% of the raw materials; and then the crystal is heated to sweat, in order to effectively improve the product quality, the sweating process can be divided into a plurality of temperature gradients, and the temperature gradient is finally raised to be near the melting point, so that the sweating product accounts for 20-50% of the crystal, and finally the crystal is heated, melted and discharged to be used as a phase-change energy storage wax product. In order to improve the product yield, the recovered mother liquor residue can be mixed with the raw materials and then subjected to secondary crystallization treatment.

The carbon number analysis of the product after fractional crystallization treatment is as follows:

the enthalpy value of the product can be improved to more than 210J/g from 190J/g.

Example 2:

carrying out reduced pressure distillation on the fraction below 400 ℃, separating a narrow fraction with the distillation range width of 15 ℃, melting 345-360 fractions at the melting point of 34.5 ℃, then carrying out fractional crystallization, carrying out cooling/crystallization at the temperature lower than the melting point of 10 ℃, keeping the temperature at the temperature for more than 4 hours, and discharging mother liquor residues, wherein the residue accounts for 50% of the raw materials; and then the crystal is heated to sweat, in order to effectively improve the product quality, the sweating process can be divided into a plurality of temperature gradients, and the temperature gradient is finally raised to be close to the melting point, so that the sweating product accounts for 30% of the crystal, and finally the crystal is heated to melt and discharged to be used as a phase-change energy storage wax product. In order to improve the product yield, the recovered mother liquor residue can be mixed with the raw materials and then subjected to secondary crystallization treatment.

The carbon number of the treated product was analyzed as follows:

the enthalpy value of the product can be improved to more than 200J/g from 180J/g.

Example 3

Melting the 520-plus-550-DEG C fraction at the melting point of 80.5 ℃, then performing fractional crystallization, performing cooling/crystallization at the temperature of 5 ℃ lower than the melting point, keeping the temperature at the temperature for more than 4 hours, and discharging mother liquor residues, wherein the residue accounts for 30% of the raw materials; and then the crystal is heated to sweat, in order to effectively improve the product quality, the sweating process can be divided into a plurality of temperature gradients, and the temperature gradient is finally raised to be near the melting point, so that the sweating product accounts for 20-50% of the crystal, and finally the crystal is heated, melted and discharged to be used as a phase-change energy storage wax product. In order to improve the product yield, the recovered mother liquor residue can be mixed with the raw materials and then subjected to secondary crystallization treatment.

The carbon number analysis of the product after fractional crystallization treatment is as follows:

comparative example 1

The fraction with the melting point of 490-510 ℃ and the melting point of 69 ℃ are respectively subjected to sweating treatment and fractional crystallization treatment. The yield of the target product is controlled by 40-70%, the total running time of the two processes is 48-72h, the contents of the two isomeric hydrocarbons are respectively reduced to 6.8% and 3.64%, and the enthalpy values are respectively more than 200J/g and 210J/g. Therefore, compared with the common sweating deoiling method, the method adopts fractional crystallization treatment to obviously reduce the content of the isomeric hydrocarbon and improve the enthalpy value of the product.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.