阅读说明：本技术 一种制备沥青基氧化球的方法 (Method for preparing asphalt-based oxidation ball ) 是由 李开喜 张果丽 管涛涛 于 2019-09-05 设计创作，主要内容包括：本发明公开了一种成球及氧化不融化同步进行制备沥青基氧化球的方法,属于活性炭的制备领域。本发明提供的制备沥青基氧化球的具体过程为：将中低温沥青、导热剂和含C、H、O、N的改性剂置于高压反应釜中加热混合均匀,得到改性沥青,经破碎筛分后,在含不同氧浓度的空气中吹扫,加热氧化；沥青颗粒在氧化过程中,依靠自身表面张力,收缩成球的同时分子氧化交联固化,维持住球形形貌。本发明直接以中低温沥青为原料,首次实现了干法成球与氧化不融化过程的同步完成,制备过程简单,耗时短,成本低；解决了原料成本高,成球与氧化不融化分阶段进行,以及加萘-除萘过程冗杂等的问题；所得产品球形度好,可进一步产业化。(The invention discloses a method for preparing asphalt-based oxidized balls synchronously through balling and oxidization without melting, and belongs to the field of preparation of activated carbon. The specific process for preparing the asphalt-based oxidation ball provided by the invention comprises the following steps: placing the medium-low temperature asphalt, the heat conducting agent and the modifier containing C, H, O, N in a high-pressure reaction kettle, heating and mixing uniformly to obtain modified asphalt, crushing and screening, blowing in air containing different oxygen concentrations, and heating and oxidizing; in the oxidation process, asphalt particles shrink into balls by virtue of surface tension of the asphalt particles, and meanwhile, molecules are oxidized, crosslinked and cured to maintain the spherical shape. The invention directly takes the medium-low temperature asphalt as the raw material, realizes the synchronous completion of the dry method balling and the oxidation non-melting process for the first time, and has simple preparation process, short time consumption and low cost; solves the problems of high cost of raw materials, staged proceeding of balling and oxidation without melting, complicated naphthalene adding-removing process and the like; the obtained product has good sphericity and can be further industrialized.)

1. A method for preparing asphalt-based oxidation balls is characterized by comprising the following steps: the balling and the oxidation non-melting process are carried out synchronously, and the method comprises the following steps:

1) modification of asphalt: placing medium-low temperature asphalt, a heat conducting agent and a modifying agent containing C, H, O, N into a high-pressure reaction kettle, and heating, melting and stirring to a modification temperature under the protection of nitrogen to modify the asphalt; naturally cooling, and discharging to obtain modified asphalt;

2) Preparing asphalt oxidation balls: crushing and screening modified asphalt to obtain modified asphalt particles, placing the modified asphalt particles in an oxidation furnace, heating the modified asphalt particles from room temperature to oxidation reaction temperature under the blowing of air with different oxygen concentrations, and keeping the temperature constant; and naturally cooling, and discharging to obtain the asphalt-based oxidation ball.

2. The method for preparing asphalt-based oxidizing balls according to claim 1, wherein: the heat conducting agent comprises one or a mixture of more of graphite powder, carbon nano tubes, carbon fibers, iron oxide, zinc oxide and nickel oxide.

3. The method for preparing asphalt-based oxidizing balls according to claim 1, wherein: the modifier C, H, O, N comprises one or more of 4-cumylphenol, p-isopropylbenzaldehyde, 4-isopropylaniline, cumyl hydroperoxide or 2-phenyl-2-propanol.

4. The method for preparing asphalt-based oxidizing balls according to claim 3, wherein: the modifier C, H, O, N is a mixture of any two of 4-cumyl phenol, p-isopropyl benzaldehyde, 4-isopropyl aniline, cumyl hydroperoxide or 2-phenyl-2-propanol in any ratio.

5. The method for preparing asphalt-based oxidizing balls according to claim 1, wherein: the softening point of the low-temperature asphalt in the step 1) is 50-130 ℃, and the low-temperature asphalt comprises one or a mixture of more of natural asphalt, coal asphalt and petroleum asphalt.

6. The method for preparing asphalt-based oxidizing balls according to claim 1, wherein: the mass ratio of the low-temperature asphalt, the heat conducting agent and the C, H, O, N-containing modifier in the step 1) is 1: (0.1-5): (1-10).

7. The method for preparing asphalt-based oxidizing balls according to claim 1, wherein: the modification temperature in the step 1) is 70-150 ℃, and the modification time is 0.5-5 h.

8. The method for preparing asphalt-based oxidizing balls according to claim 1, wherein: in the step 2), the heating rate of heating from room temperature to the oxidation reaction temperature is 0.1-5 ℃ for min-1, the oxidation reaction temperature is 200-300 ℃, and the heating oxidation reaction time is 0-5 h.

9. The method for preparing asphalt-based oxidizing balls according to claim 1, wherein: the volume concentration of oxygen in the air with different oxygen concentrations in the step 2) is 10-80%.

10. the method for preparing asphalt-based oxidizing balls according to claim 1, wherein: the air purge rate in the step 2) is 200-800L h-1.

Technical Field

The invention relates to a method for preparing asphalt-based oxidation balls, in particular to a method for preparing asphalt-based oxidation balls synchronously by balling and oxidizing without melting, belonging to the field of preparation of activated carbon.

background

Compared with commercial powdery, granular and columnar activated carbon, the asphalt-based spherical activated carbon has the advantages of good fluidity, high mechanical strength, high loading density, high conductivity, good physiological compatibility and the like due to the special spherical shape, so that the asphalt-based spherical activated carbon has wide application potential in high-end fields such as blood purification, air purification, military protection, aerospace, national defense and military, electronics, environmental protection and the like. Generally, the process for preparing pitch-based spherical activated carbon comprises: pitch modulation, balling, extraction separation, oxidation without melting and carbon activation. Wherein, the balling and oxidation non-melting process is a key step for determining the morphology of the asphalt balls and is also a step which must be carried out in the preparation of the active carbon at present.

at present, the traditional method for balling asphalt balls is a suspension method, namely, the asphalt balls are balling under the action of surface tension by utilizing the thermoplasticity of asphalt molecules, the used raw material is the asphalt with a super-high softening point, the softening point of the asphalt is generally higher than 250 ℃, the asphalt with the high softening point is obtained by carrying out hot polycondensation on medium and low temperature asphalt in advance, the yield in the hot polycondensation process is lower than 40%, and the air pollution is serious. When the asphalt with the ultra-high softening point is pelletized, a viscosity reducer (generally naphthalene is used) is added to ensure the plasticity required by the pelletizing of the asphalt, so that the viscosity reducer must be removed before the asphalt is oxidized and does not melt, and then the asphalt can be oxidized and does not melt. That is, from the pitch to the pellet which is not melted after oxidation, at least balling, naphthalene removing and oxidation are needed to obtain the pitch oxidation pellet, for example, Chinese patent CN 109052397A uniformly mixes high temperature coal pitch with the softening point of 240 plus one of 280 ℃ and 10-35% refined naphthalene for modification to obtain the modulated pitch with low softening point, crushing and screening, balling by a suspension method, extracting for 10-20 h by organic solvents such as organic solvent petroleum ether, toluene and the like, and then performing later oxidation stabilization by air diffusion. Chinese patent CN 106348290A uniformly mixes high softening point asphalt with 20-50% naphthalene for modification, and makes the mixture into balls by a suspension method, and then makes the balls undergo the process of oxidation stabilization by using air containing SO 2.

In addition, the method for producing the asphalt beads includes an emulsification method, a melt granulation method, a spray granulation method, and the like. For example, in chinese patent CN 109399632 a, medium-low temperature asphalt and a modifier are mixed uniformly, and then added into a reaction kettle to be heated and modified for 0.5-4 h, and the obtained modified asphalt particles are pelletized by an emulsification method, and then oxidized without melting. Chinese patent CN 108395899A prepares asphalt-based spherical activated carbon by a melt granulation method, melt asphalt is sprayed into a water-cooling container in the form of liquid drops, the liquid drops of the asphalt contract and cool into spheres by the self tension in water, and then the spheres are subjected to subsequent oxidation without melting. The Chinese patent CN 109368639A takes coal asphalt with the softening point of 160-260 ℃ as a raw material, and the coal asphalt is evenly mixed with a modifier, and then the mixture is added into a spray granulator for spray granulation to obtain asphalt balls, and then the asphalt balls are oxidized without melting. Therefore, the preparation process of the asphalt oxidation ball is carried out by grading the ball forming process and the oxidation non-melting process. Wherein, the melt granulation method can cause adhesion due to mutual collision, so that the spherical shape is irregular, the surface is rough, the sphere diameter is larger and difficult to control; the spray granulation method has strict requirements on the size of liquid drops and gas phase media or liquid, and the diameter of the obtained ball is very small and cannot reach millimeter level; the emulsion method and the suspension method can control the sphere diameter by regulating and controlling the particle size of raw materials, but the sphere diameter distribution range obtained by the emulsion method is wider in comparison.

in conclusion, the preparation of the asphalt-based oxidation ball usually adopts the extra-high temperature asphalt as the raw material, but the quantity of the extra-high softening point asphalt in the market is very small, the special reservation is needed, and the price of the extra-high softening point asphalt is far higher than that of the medium-low temperature asphalt; before the high-softening-point asphalt is balled, naphthalene must be melted into the asphalt in advance, and the obtained modified asphalt needs to be extracted and removed by using a solvent after the balling, namely, the naphthalene must be added and removed, so that the naphthalene volatilizes and escapes in the treatment process to cause serious environmental pollution, and the stability of the product is greatly influenced; in the prior art, balling and oxidation are not required to be carried out independently, and the oxidation is not slow in melting process, so that the preparation cost is high, the period is long, and the operation is complex.

Disclosure of Invention

the invention aims to provide a method for preparing asphalt-based oxidized balls synchronously by balling and oxidizing without melting, which directly takes medium-low temperature asphalt as a raw material, provides a method for preparing asphalt-based oxidized balls synchronously without a naphthalene adding-naphthalene removing process and balling and oxidizing without melting, and solves the problems that in the prior art, high-softening-point asphalt is required to be selected as a raw material, the balling and oxidizing without melting are carried out in stages, and the steps of adding naphthalene and removing naphthalene are complicated in process, high in cost and the like.

The invention utilizes the self-thermoplastic characteristic of the asphalt to directly sweep the solid particles in the hot air atmosphere with different oxygen concentrations, on one hand, the solid particles shrink into balls by virtue of the surface tension of the asphalt, and on the other hand, the solid particles are synchronously solidified by virtue of the oxidation crosslinking reaction of the molecules, so that the spherical morphology is finally maintained. Namely, the process of ' balling ' and ' oxidizing without melting ' in the invention ' preparing the asphalt-based oxidized ball by ' balling and oxidizing without melting ' can be synchronously carried out.

The invention provides a method for preparing asphalt-based oxidized balls, which is characterized in that the ball forming and the oxidation are carried out synchronously without melting, and the preparation method comprises the following steps:

1) Modification of asphalt: placing medium-low temperature asphalt, a heat conducting agent and a modifying agent containing C, H, O, N into a high-pressure reaction kettle, and heating, melting and stirring to a modification temperature under the protection of nitrogen to modify the asphalt; naturally cooling, and discharging to obtain modified asphalt;

2) Preparing asphalt oxidation balls: crushing and screening modified asphalt to obtain modified asphalt particles, placing the modified asphalt particles in an oxidation furnace, heating the modified asphalt particles from room temperature to oxidation reaction temperature under the blowing of air with different oxygen concentrations, and keeping the temperature constant for a period of time; and naturally cooling, and discharging to obtain the asphalt-based oxidation ball.

Further, the softening point of the low-temperature asphalt in the step 1) is 50-130 ℃, and the low-temperature asphalt comprises one or a mixture of more of natural asphalt, coal asphalt and petroleum asphalt. The heat conducting agent comprises one or a mixture of more of graphite powder, carbon nano tubes, carbon fibers, iron oxide, zinc oxide and nickel oxide. The modifier C, H, O, N comprises one or more of 4-cumylphenol, p-isopropylbenzaldehyde, 4-isopropylaniline, cumyl hydroperoxide or 2-phenyl-2-propanol.

Further, the modifying agent containing C, H, O, N is a mixture of any two of 4-cumyl phenol, p-isopropyl benzaldehyde, 4-isopropyl aniline, cumyl hydroperoxide or 2-phenyl-2-propanol in any ratio.

because the softening point of the selected medium-low temperature asphalt precursor is lower and has a larger difference with the oxidation temperature, in order to prevent complete melting before the oxidation reaction, two modifiers with different temperatures, which generate free radicals through chemical bond breakage, are selected to promote rapid crosslinking in the temperature range of asphalt molecules before the oxidation reaction, relay to provide active free radicals to promote the oxidation reaction, improve the softening point of the asphalt molecules, and assist the asphalt molecules to reach the oxidation temperature without complete melting.

Further, the mass ratio of the low-temperature asphalt, the heat conducting agent and the C, H, O, N-containing modifier in the step 1) is 1: (0.1-5): (1-10). Because the thermal conductivity of the asphalt is poor, the heat absorption in the temperature rising process is slow, so that the heat diffusion from the surface of asphalt particles to the interior of the asphalt particles is influenced, particularly, at higher temperature, the temperature difference between the surface of the particles and the interior of the particles is large, and internal molecules do not react yet when a large amount of oxidation reaction on the surface begins, so that the oxidation is not uniform, and the strength performance of the asphalt is poor. In addition, the low-temperature asphalt has a high content of light components, so that the asphalt is molten and deformed without reaching the oxidation reaction temperature. At this time, a modifier is introduced to assist the low-temperature asphalt to generate a crosslinking reaction before the melting deformation, so that the light component is converted into the heavy component, the softening point of the heavy component is improved, and the low-temperature asphalt is oxidized and does not melt. The main component of the asphalt is C, H, and in order to uniformly modify the asphalt, the component of the modifier is similar to that of the asphalt, and the modifier containing C, H, O, N is selected in the invention. Based on the mass ratio, if the addition amount of the heat-conducting agent is less than 10% of the mass of the asphalt, the heat-conducting effect is poor, the sphericity of the obtained asphalt oxidation ball is influenced, and even a skin-core structure is caused; if the added amount is more than 5 times of the mass of the asphalt, the improvement of the product performance such as specific surface area after the pellets are converted into the activated carbon in the future is influenced; if the addition amount of the modifier containing C, H, O, N is less than the mass of the asphalt, the modifier is melted into a whole in the oxidation process of the asphalt and small balls cannot be obtained, and if the addition amount of the modifier is more than 10 times of the mass of the asphalt, the solidification speed of the asphalt is too high, namely the asphalt is solidified or is close to be solidified before the small balls are obtained, so that the small balls with good sphericity cannot be obtained.

further, the modification temperature in the step 1) is 70-150 ℃, and the modification time is 0.5-5 h. The softening point of the pitch precursor is 50-130 ℃, the modification temperature is higher than 20 ℃ of the softening point of the pitch precursor, the pitch is completely melted and changed into a liquid state in the heating process, and the modifier can be uniformly dispersed in the liquid state so as to achieve the modification effect of more uniform mixing. If the temperature is lower than 70 ℃, the raw material asphalt, the modifier and the like are difficult to be completely melted, and the mixing effect is further influenced; if the temperature is higher than 150 ℃, unstable chemical bonds in the modifier are broken to generate active free radicals, asphalt molecule crosslinking reaction is initiated, asphalt solidification is caused in advance, and therefore balling cannot be realized; if the duration is less than 0.5 h, the asphalt is not uniformly mixed with the heat-conducting agent and the modifier; if the time is longer than 5 hours, partial curing may occur while increasing the energy consumption of the process.

Further, the oxidation reaction temperature in the step 2) is 200-. According to the condition that the temperature of asphalt molecules capable of reacting with oxygen is above 200 ℃, the smaller the particle size is, the lower the reaction temperature capable of achieving homogeneous non-melting is, otherwise, the opposite is true. If the oxidation temperature is lower than 200 ℃, the modified asphalt and oxygen do not react sufficiently, so that the curing is not thorough; if the oxidation temperature is higher than 300 ℃, the crosslinking reaction is violent, excessive micromolecules and even light components are released, the sphericity is damaged, the equipment cost is increased, and the time and the energy are consumed; if the constant temperature time is more than 5 hours, excessive oxidation of the asphalt may be caused, resulting in low strength of the activated carbon in the future. In addition, the preparation cost is increased, and the time and the energy are consumed.

further, the heating rate of heating from room temperature to the oxidation reaction temperature in the step 2) is 0.1-5 ℃ for min-1. The oxidation heating rate of 0.1-5 ℃ min < -1 > enables asphalt molecules to generate proper cross-linking speed, so that the asphalt particles shrink into balls by the surface tension of the asphalt particles and can be cured at the same time, namely, the thermoplastic property and the thermosetting property reach a balanced state, and the balls and the oxidation are synchronously carried out without melting to prepare the asphalt-based oxidized balls. If the oxidation heating rate is lower than 0.1 ℃ for min < -1 >, and the oxidation curing rate is too slow, the volatilization escape amount of the components in the asphalt is large, and the balling and oxidation non-melting time is too long; if the oxidation heating rate is higher than 5 ℃ min < -1 >, the oxidation curing rate is too high, the modified asphalt particles are cured into small balls before shrinkage, and only the granular oxidized asphalt can be obtained.

further, the volume concentration of oxygen in the air with different oxygen concentrations in the step 2) is 10-80%. Air with an oxygen concentration of 10-80% achieves a complete oxidative crosslinking reaction of the bitumen molecules, to the same extent that the balance between the thermoplastic and thermosetting properties of the bitumen is maintained, otherwise no balling occurs. If the occupied volume of oxygen is less than 10 percent, the oxygen content is too little, molecular crosslinking can not be well promoted, and the asphalt spheres are difficult to oxidize and not melt; if the oxygen occupied volume is more than 80%, the oxidation crosslinking is excessive, and pellets may not be obtained yet, and the asphalt is solidified, so that the pellets have poor sphericity or even do not form spheres.

Further, the air purge rate in the step 2) is 200-800L h-1. The air blowing rate of 200-800L h-1 is used to cause the asphalt molecules and oxygen to generate proper cross linking, so that the asphalt particles shrink into balls by the surface tension of the asphalt particles and can be cured at the same time, namely, the thermoplastic property and the thermosetting property reach a balanced state, and the asphalt-based oxidized balls can be prepared synchronously without melting the asphalt particles and the oxidation. If the air purging rate is lower than 200L h-1, the input amount of oxygen is low, so that asphalt molecules are not completely crosslinked and are not completely cured, and the spherical morphology is influenced; if the air purge rate is higher than 800L h-1, the asphalt molecules react with oxygen to reach a saturated state at the same temperature, so that the asphalt solidification speed exceeds the balling speed, and the balls cannot be obtained or even if the balls are obtained, the sphericity is poor.

the invention has the beneficial effects that:

1) The characteristics of the thermoplasticity of the asphalt are utilized, solid particles of the asphalt are directly swept in hot air atmosphere with different oxygen concentrations, molecules are synchronously solidified due to oxidation crosslinking reaction while shrinking into balls by virtue of the surface tension of the asphalt, the conversion of the asphalt from the thermoplasticity to the thermosetting property is realized, and corresponding asphalt oxidized balls are obtained;

2) The used raw material is asphalt with medium and low softening points, and the asphalt can be directly used without being thermally condensed into the asphalt with high softening point, so that the cost is obviously reduced;

3) The naphthalene adding-naphthalene removing process required in the traditional method is omitted, and naphthalene is not used as a viscosity reducer or a pore-forming agent in the whole reaction process;

4) the oxidation does not melt for a short time while balling, and the heat transfer property of the asphalt and the reactivity of asphalt molecules and oxygen are improved and the oxidation period is shortened due to the addition of the heat-conducting agent and the modifier containing C, H, O, N;

5) The method is extremely simple and has few steps.

Drawings

FIG. 1 is an SEM image of pitch-based oxidized spheres prepared in example 1 of the present invention;

FIG. 2 is an SEM image of asphalt-based oxidized spheres prepared in example 2 of the present invention;

FIG. 3 is an SEM image of pitch-based oxidized spheres prepared in example 3 of the present invention;

FIG. 4 is an SEM image of asphalt-based oxidized spheres prepared in example 4 of the present invention;

FIG. 5 is an SEM image of pitch-based oxidized spheres prepared in comparative example 1;

FIG. 6 is an SEM image of pitch-based oxidized spheres prepared in comparative example 2;

FIG. 7 is an SEM image of pitch-based oxidized spheres prepared in comparative example 3;

Fig. 8 is an SEM image of the pitch-based oxidized spheres prepared in comparative example 4.

Detailed Description

the present invention is further illustrated by, but is not limited to, the following examples.