CN112661976B - Preparation method of low-rank coal-based high-efficiency water reducing agent - Google Patents
Preparation method of low-rank coal-based high-efficiency water reducing agent Download PDFInfo
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Abstract
The invention discloses a preparation method of a low-rank coal-based high-efficiency water reducing agent, and belongs to the technical field of low-rank coal resource utilization and fine chemical engineering. The invention takes low-rank coal such as lignite and subbituminous coal as raw materials, sulfonated coal is obtained by sulfonation of sulfite, sulfonated coal-based humic acid is obtained by liquid-phase oxidative cracking of the sulfonated coal, and finally the obtained sulfonated coal-based humic acid is condensed and polymerized into the coal-based humic acid high-efficiency water reducing agent by formaldehyde. The method for synthesizing the high-efficiency water reducing agent by using the low-rank coal such as lignite, subbituminous coal and the like as the raw materials has the characteristics of high yield of sulfonated coal-based humic acid and water reducing agent, low cost, clean process and the like, and the synthesized coal-based humic acid water reducing agent has good dispersing, water reducing and slump retaining properties and has a water reducing effect superior to that of a commercial naphthalene-based high-efficiency water reducing agent. Under the condition of 0.4 percent of mixing amount, the water reducing rate can reach 24.5 percent at most, the initial net slurry fluidity of the cement is 162mm, the mortar fluidity is 305mm, and the loss rate of the mortar fluidity in 2 hours is 6.9 percent.
Description
Technical Field
The invention relates to a preparation method of a low-rank coal sulfonation and coal-based humic acid high-efficiency water reducing agent, belonging to the technical field of low-rank coal resource utilization and fine chemical engineering.
Background
The low-rank coal in China is abundant in resource and accounts for about 47% of the reserve volume of the proven coal, wherein the reserve volume of the lignite is up to 1300 hundred million t and accounts for about 13% of the coal resource. The low-rank coal has low deterioration degree and high H/C and O percent, so that the low-rank coal has high moisture, volatile components and chemical reactivity, poor calorific value and thermal stability and easy spontaneous combustion. In addition, most brown coal ash in China is high in content. The low-rank coal mainly used for combustion power generation has low utilization efficiency and large environmental pollution. Therefore, based on the structural and property characteristics of hydrogen enrichment, high oxygen content and easiness in reaction of the low-rank coal, the coal-based fine chemicals are developed, so that the resource utilization of the low-rank coal can be realized, and the shortage of petroleum resources can be relieved. Has huge potential application prospect in the production fields of bulk fine chemicals such as concrete admixture, oil extraction auxiliary agent, coal water slurry dispersant and the like.
The production of coal-based humic acid is one of the important ways for the resource utilization of low-rank coal. However, the conventional method for extracting low-rank coal by using an alkali solution to separate out primary humic acid has the disadvantages of low yield of humic acid, high cost and serious pollution due to the limitation of the content of the primary humic acid in coal (generally, the content of the humic acid in lignite is 10-30%). Meanwhile, the lack of a high-value utilization way of the coal-based humic acid is also an important factor for limiting the production of the coal-based humic acid. However, the aromatic structure content of the lignite humic acid is high, and particularly, the content of the condensed ring structure is obviously higher than that of other natural humic acid. Therefore, the lignite humic acid has good chemical derivation activity and is suitable for preparing fine chemical products such as heavy metal adsorbents, water treatment agents, mineral sintering agents and the like. In recent years, in Ashtari et al (Energy)&Based on petroleum coke liquid phase oxidative cracking technology provided by fuels:2016,30,6,4596), the inventor carries out research on the preparation of coal-based humic acid by liquid phase oxidative cracking of low-rank coal, realizes the high-efficiency conversion of lignite under the conditions of lower temperature (80-160 ℃) and low alkali/coal ratio (0.2-0.5), the yield of humic acid can reach 80 percent at most, and CO can reach 80 percent at most2The yield was low (Solid Fuel Chemistry: 2021).
The water reducing agent is a concrete admixture with the widest application and the highest use amount. The mixing amount of the water reducing agent in the concrete is about 3 percent and accounts for about 67 percent of the concrete admixture. The concrete water reducing agent mainly comprises a first generation lignosulfonate water reducing agent, a second generation naphthalene series aromatic sulfonate high-efficiency water reducing agent and a third generation polycarboxylate high-performance water reducing agent. At present, water reducing agents commonly used in the construction industry are naphthalene-based high-efficiency water reducing agents and polycarboxylic acid-based high-performance water reducing agents. The naphthalene water reducing agent is mainly synthesized by taking industrial naphthalene as a raw material through reactions such as sulfonation, hydrolysis, alkali neutralization and the like, and has the advantages of simple operation, mature process, low cost, high water reducing rate and the like, but large slump loss. Meanwhile, the industrial naphthalene has high cost and limited sources, and the concentrated sulfuric acid sulfonation process has large pollution. The polycarboxylic acid high-performance water reducing agent is mainly synthesized by copolymerizing organic acid (anhydride) such as maleic anhydride, acrylic acid and the like with formaldehyde, acetone, ethylene oxide and the like. Macromolecular water-soluble resin sulfonate and carboxylate are formed by polymerization, so that high dispersing performance is endowed, and good water reducing and slump retaining capabilities are achieved. However, the raw materials for generating the polycarboxylic acid high-performance water reducing agent mainly come from petrochemical industry, and the synthesis process is complex and has high cost. Meanwhile, the problems of cement adaptability and sensitivity of the series of water reducing agents are more prominent.
According to the leading functional group theory, the sulfonic acid group and the carboxyl group are leading functional groups which determine the performance of the water reducing agent. Wherein, the sulfonic group mainly endows the water reducing agent with high-efficiency dispersion and high water reducing effect; the complex ability of carboxyl is strong, and the product has good retardation and plasticizing effect, and has high dispersion and water reducing effect. In addition, non-leading functional groups such as hydroxyl, amino, ether bond and the like can form hydrogen bond action with water, and water retention and certain retardation are displayed. In order to improve the comprehensive performance of the water reducing agent and reduce the cost, a large amount of chemical modification and new water reducing agent development research is developed at home and abroad. For example, functional groups such as carboxyl, hydroxyl, amino and the like are introduced in a grafting and copolymerization mode to make up for the defect of excessively fast slump loss of the naphthalene water reducer; the high-efficiency water reducing agent is synthesized by replacing or partially replacing industrial naphthalene with low-cost washing oil, lignin depolymerization products, papermaking waste liquid and the like, so that the defects of the industrial naphthalene raw material are overcome, and the cost is reduced. Recently, the inventor also designs and develops a modified lignite humic acid water reducing agent (CN 2020102590047). Lignite oxidative cracking humic acid is taken as a raw material, and the lignite humic acid high-efficiency water reducing agent with good water reducing and collapse degree maintaining capabilities is successfully prepared through sulfonation and polycondensation. The low-cost oxidative cracking humic acid is used as a raw material, so that the cost is low, the humic acid is rich in oxygen-containing functional groups such as aromatic structures, carboxyl groups, phenolic hydroxyl groups and the like, and the synergistic effect of the multifunctional groups such as the carboxyl groups, the phenolic hydroxyl groups, the sulfonic acid groups and the like and the good dispersing performance of humic acid macromolecules can be exerted.
Disclosure of Invention
In order to further improve the yield of the coal-based humic acid water reducing agent and improve the sulfonation performance of the coal-based humic acid, the invention aims to solve the technical problems that: the method for preparing the coal-based superplasticizer by using the low-rank coal as the raw material is provided, so that the coal-based superplasticizer with good water reducing and collapse degree maintaining capabilities is prepared, and the utilization efficiency of lignite is obviously improved.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the method comprises the following steps of taking low-rank coal such as lignite and subbituminous coal as raw materials, sulfonating the raw materials by sulfite to obtain sulfonated coal, then carrying out liquid-phase oxidative cracking on the sulfonated coal to obtain sulfonated coal-based humic acid, and finally carrying out condensation polymerization on the obtained sulfonated coal-based humic acid by formaldehyde to obtain the coal-based humic acid high-efficiency water reducing agent, wherein the method specifically comprises the following steps:
(1) sulfonation of coal: the sulfite and water are added into a reactor and stirred to dissolve. Then adding the coal, ferrous salt and sulfuric acid, and stirring and mixing uniformly. Then slowly dropwise adding 0.5-2.5% of H2O2And (3) solution. After the feeding is finished, stirring and reacting for 1-2 h at normal temperature, heating to 60-100 ℃, and reacting for 1-2 h under heat preservation. And finally, centrifugally separating and drying the obtained product to obtain the sulfonated coal. Wherein the mass ratio of the reaction materials is as follows: coal sulfite (as SO)3 2-In proportion of H2O2Ferrous salt (in terms of Fe)2+In proportion of H2SO4∶H2O＝1∶0.5～1.5∶0.10～0.25∶0.007～0.020∶0.008～0.025∶10～20。
(2) Oxidative cracking of sulfonated coal: according to the ratio of sulfonated coal to alkali (according to OH)-The mass ratio of the sulfonated coal to the water is 1: 0.06-0.3: 5-20, the sulfonated coal and the alkali solution are sequentially added into the autoclave, and after uniform stirring and mixing, oxygen is added to the autoclave to reach 0.5-5 MPa. Then, stirring is started, the temperature is raised to 80-180 ℃, and the constant temperature oxidative cracking is carried out for 1-2 h. And finally, centrifugally separating the obtained oxidative cracking product to remove solid residual coal. And carrying out acid precipitation on the obtained water-soluble product by using 2mol/L sulfuric acid until the pH value is 1, standing for 2h, and then carrying out centrifugal separation to obtain an acid precipitation product, namely the sulfonated coal-based humic acid.
(3) Condensation polymerization of sulfonated humic acid: sequentially adding sulfonated coal-based humic acid and 2% NaOH solution according to the mass ratio of 1: 0.2-0.8: 0.2-0.5 of sulfonated coal-based humic acid, formaldehyde and NaOH, stirring and dissolving, slowly adding 37% formaldehyde solution, and reacting for 2-5 h under the condition of controlling the reaction temperature to be 80-100 ℃. And finally, dehydrating and drying to obtain the coal-based humic acid high-efficiency water reducing agent.
In step (1), the coal is low-rank coal, preferably lignite or subbituminous coal.
In the step (1), sulfite is used as a main sulfonating agent, and H is used2O2And ferrous salt is used as a co-sulfonating agent, and the sulfite is preferably sodium bisulfite. The ferrous salt is water-soluble ferrous salt, preferably ferrous sulfate.
In step (2), the base is preferably KOH.
The coal-based humic acid high-efficiency water reducing agent is obtained according to the preparation method.
The scientific principle of the invention is as follows:
(1) by utilizing the characteristic that an aromatic structure in low-rank coal is easier to sulfonate than humic acid, the problem that the humic acid is difficult to sulfonate can be effectively solved by a method of first sulfonation and then oxidative cracking, and the sulfonation degree of the prepared coal-based humic acid water reducing agent is improved. Meanwhile, the hydrophilic property of the sulfonated coal can be improved by sulfonation, the oxidative cracking of the sulfonated coal in a subsequent aqueous solution is promoted, and the yield of the oxidative cracking humic acid is improved.
(2) With FeSO4As catalyst, initiating H in aqueous solution2O2And sodium sulfite is used for carrying out free radical substitution sulfooxidation on the coal, so that the sulfonation of aromatic carbon and aliphatic carbon with lower electron cloud density is realized, and the use of excessive sulfuric acid in electrophilic substitution sulfonation of concentrated sulfuric acid and fuming sulfuric acid is avoided.
Compared with the prior art, the invention has the following technical effects:
1. provides a method for sulfonating coal, which takes sulfite as a main sulfonating agent and H2O2And ferrous salt sulfonation aid, and the sulfonation of the coal is carried out in an acidic aqueous solution. The method has the characteristics of mild reaction conditions, low cost, clean process, high product sulfonation degree and the like, and can improve the sulfur content of the Ceylor brown coal from 1.0% to 6.1%.
2. Compared with the method for preparing the coal-based humic acid high-efficiency water aqua by coal oxidative cracking, the method for preparing the coal-based humic acid high-efficiency water aqua by sulfonation, oxidative cracking and polycondensation of low-rank coal has the advantages of obviously improving the utilization efficiency of coal and the sulfonation degree of a water reducing agent, along with high yield, low cost, clean process and the like of the sulfonated coal-based humic acid and the water reducing agent, and can realize high-value utilization of the low-rank coal. The method takes the Ceylor brown coal as a raw material, and the highest mass yields of the sulfonated coal, the sulfonated humic acid and the water reducing agent under the optimized conditions respectively reach 118.5 percent, 85.5 percent and 109.1 percent.
3. Provides a coal-based high-efficiency water reducing agent, and the dispersing water reducing effect and slump retaining capability of the coal-based high-efficiency water reducing agent are superior to those of a commercial naphthalene-based high-efficiency water reducing agent. Under the condition of low doping amount of 0.4 percent, the water reducing rate can reach 24.5 percent at most, the initial net slurry fluidity of the cement is 162mm, the mortar fluidity is 305mm, and the loss rate of the mortar fluidity in 2 hours is 6.9 percent.
Drawings
FIG. 1 is FTIR chart of intermediate and target products of example 1;
as can be seen from the figure: the intermediate product and the target product in example 1 both contain obvious characteristic peaks of sulfonic acid groups, which confirms that coal is sulfonated, and thus sulfonated humic acid containing sulfonic acid groups and a coal-based humic acid water reducing agent are prepared.
FIG. 2 is a SEM comparison of the cement paste after 3d of curing;
wherein: (a) blank, (b) doping 0.4% of coal-based high-efficiency water reducing agent;
as can be seen from the figure, compared with a blank sample, the rod-shaped crystals in the cement paste are obviously reduced after the water reducing agent is added, a more compact gel sheet-shaped stacked structure and calcium hydroxide plate-shaped crystals are formed, and the strength of the cement paste is improved.
Detailed Description
The present invention will be described in detail below with reference to the drawings and examples, but the present invention is not limited to the examples.
Example 1
(1) Sulfonation of coal: 120ml of H is added into a 500ml reaction kettle2O、24g NaHSO3、0.4g FeSO44ml of 1mol/L dilute sulfuric acid, stirring and dissolving, adding 20g of 100-mesh dried Ceylor brown coal, and uniformly mixing. Then, 1.5% H was added dropwise to the reaction vessel at room temperature2O2240ml of the solution was stirred while adding. After the dropwise addition, the reaction was continued for 1 hour with stirring. Then the temperature is raised to 60 ℃, the reaction is carried out for 1h, and the heating is stopped. After the reaction kettle is cooled to room temperature, centrifugally separating the obtained product, and washing the product with water until the pH value of the washing liquid is reached>And 5, drying to obtain the sulfonated coal. The mass yield of the sulfonated coal based on raw coal is 110.6 percent.
(2) Oxidative cracking of sulfonated coal: sequentially adding H into a 250ml high-pressure reaction kettle2O100 ml, KOH 5g and (1) prepared sulfonated coal 10g, after stirring and mixing evenly, the O is added2To 5.0 MPa. Then, stirring is started and the temperature is raised to 120 ℃, and the mixture is oxidized and cracked for 2 hours at constant temperature. After the reaction is finished, the product is centrifuged for 10min under the condition of 14000rpm, and the oxidative cracking residual coal is separated. And (3) carrying out acid precipitation on the obtained solution by using 2mol/L sulfuric acid until the pH value is 1, standing for 2h for precipitation, and carrying out centrifugal separation to obtain the sulfonated coal-based humic acid. The mass yield of the sulfonated humic acid based on the sulfonated coal is 85.5 percent.
(3) Condensation polymerization of sulfonated humic acid: and (3) sequentially adding 6g of the sulfonated coal-based humic acid prepared in the step (2) and 100ml of 2% NaOH solution into a 250ml flask, stirring and dissolving, slowly adding 6ml of 37% formaldehyde solution, and reacting for 2 hours at 80 ℃. And finally, dehydrating and drying to obtain the modified lignite humic acid high-efficiency water reducing agent. The mass yield of the water reducing agent based on the sulfonated humic acid is 98.9 percent
Example 2
(1) Sulfonation of coal: 120ml of H is added into a 500ml reaction kettle2O、40g Na2SO3、0.9g FeSO48ml of 1mol/L dilute sulfuric acid, stirring and dissolving, adding 20g of 100-mesh dried Ceylor brown coal, and uniformly mixing. Then, 1.5% H was added dropwise to the reaction vessel at room temperature2O2240ml of the solution was stirred while adding. After the dropwise addition, the reaction was continued for 2 hours with stirring. Then the temperature is increased to 100 ℃, the reflux reaction is carried out for 1h, and the heating is stopped. After the reaction kettle is cooled to room temperature, centrifugally separating the obtained product, and washing the product with water until the pH value of the washing liquid is reached>And 5, drying to obtain the sulfonated coal. The mass yield of the sulfonated coal based on raw coal is 112.5 percent.
(2) Oxidative cracking of sulfonated coal: sequentially adding H into a 250ml high-pressure reaction kettle2O150 ml, KOH 8g and (1) prepared sulfonated coal 10g, after stirring and mixing evenly, the mixture is washedInto O2To 3.0 MPa. Then, stirring is started, the temperature is raised to 100 ℃, and the constant temperature oxidative cracking is carried out for 2 h. After the reaction is finished, the product is centrifuged for 10min under the condition of 14000rpm, and the oxidative cracking residual coal is separated. And (3) carrying out acid precipitation on the obtained solution by using 2mol/L sulfuric acid until the pH value is 1, standing for 2h for precipitation, and carrying out centrifugal separation to obtain the sulfonated coal-based humic acid. The mass yield of the sulfonated humic acid based on the sulfonated coal is 84.3 percent.
(3) Condensation polymerization of sulfonated humic acid: and (3) sequentially adding 6g of the sulfonated coal-based humic acid prepared in the step (2) and 150ml of 2% NaOH solution into a 250ml flask, stirring to dissolve, slowly adding 10ml of 37% formaldehyde solution, and reacting for 5 hours at 80 ℃. And finally, dehydrating and drying to obtain the modified lignite humic acid high-efficiency water reducing agent. The quality yield of the water reducing agent based on the sulfonated humic acid is 103.5 percent.
Example 3
(1) Sulfonation of coal: 50ml of H is added into a 500ml reaction kettle2O、8g NaHSO3、0.6g Fe(NO3)22ml of 1mol/L dilute sulfuric acid, stirring and dissolving, adding 10g of 100-mesh dry Ceylor brown coal, and uniformly mixing. Then, 0.5% H is dripped into the reaction kettle at normal temperature2O2The solution (200 ml) was stirred with stirring. After the dropwise addition, the reaction was continued for 2 hours with stirring. Then the temperature is raised to 60 ℃, the reaction is kept for 2 hours, and the heating is stopped. After the reaction kettle is cooled to room temperature, centrifugally separating the obtained product, and washing the product with water until the pH value of the washing liquid is reached>And 5, drying to obtain the sulfonated coal. The mass yield of the sulfonated coal based on raw coal is 108.2 percent.
(2) Oxidative cracking of sulfonated coal: sequentially adding H into a 250ml high-pressure reaction kettle2O100 ml, KOH 2g and (1) prepared sulfonated coal 10g, after stirring and mixing evenly, the O is added2To 5.0 MPa. Then, stirring is started, the temperature is raised to 180 ℃, and the constant temperature oxidative cracking is carried out for 1 h. After the reaction is finished, the product is centrifuged for 10min under the condition of 14000rpm, and the oxidative cracking residual coal is separated. And (3) separating the obtained solution with 2mol/L sulfuric acid until the pH value is 1, standing for 2h for precipitation, and centrifuging to separate the sulfonated coal-based humic acid. The mass yield of the sulfonated humic acid based on the sulfonated coal is 70.1 percent.
(3) Condensation polymerization of sulfonated humic acid: and (3) sequentially adding 6g of the sulfonated coal-based humic acid prepared in the step (2) and 150ml of 2% NaOH solution into a 250ml flask, stirring and dissolving, slowly adding 15ml of 37% formaldehyde solution, and reacting for 3 hours at 80 ℃. And finally, dehydrating and drying to obtain the modified lignite humic acid high-efficiency water reducing agent. The mass yield of the water reducing agent based on the sulfonated humic acid is 109.1 percent.
Example 4
(1) Sulfonation of coal: 80ml of H is added into a 500ml reaction kettle2O、20g NH4HSO3、1.1g FeSO44ml of 1mol/L dilute sulfuric acid, stirring and dissolving, adding 20g of 100-mesh dried Ceylo brown coal, and uniformly mixing. Then, 1.0% H was added dropwise to the reaction vessel at room temperature2O2The solution (200 ml) was stirred while adding. After the dropwise addition, the reaction was continued for 1 hour with stirring. Then the temperature is increased to 80 ℃, the reaction is carried out for 2 hours, and the heating is stopped. After the reaction kettle is cooled to room temperature, centrifugally separating the obtained product, and washing the product with water until the pH value of the washing liquid is reached>And 5, drying to obtain the sulfonated coal. The mass yield of the sulfonated coal based on raw coal is 114.3 percent.
(2) Oxidative cracking of sulfonated coal: sequentially adding H into a 250ml high-pressure reaction kettle2O200 ml, KOH 10g and (1) prepared sulfonated coal 10g, after stirring and mixing evenly, the O is added2To 0.5 MPa. Then, stirring is started, the temperature is raised to 160 ℃, and the constant temperature oxidative cracking is carried out for 2 h. After the reaction is finished, the product is centrifuged for 10min under the condition of 14000rpm, and the oxidative cracking residual coal is separated. And (3) carrying out acid precipitation on the obtained solution by using 2mol/L sulfuric acid until the pH value is 1, standing for 2h for precipitation, and carrying out centrifugal separation to obtain the sulfonated coal-based humic acid. The mass yield of the sulfonated humic acid based on the sulfonated coal is 75.9 percent.
(3) Condensation polymerization of sulfonated humic acid: and (3) sequentially adding 6g of the sulfonated coal-based humic acid prepared in the step (2) and 60ml of 2% NaOH solution into a 250ml flask, stirring and dissolving, slowly adding 4ml of 37% formaldehyde solution, and reacting for 4 hours at 90 ℃. And finally, dehydrating and drying to obtain the modified lignite humic acid high-efficiency water reducing agent. The mass yield of the water reducing agent based on the sulfonated humic acid is 92.8 percent.
Example 5
(1) Sulfonation of coal: 160ml of H is added into a 500ml reaction kettle2O、40g K2SO3、0.6g FeSO48ml of 1mol/L dilute sulfuric acid, stirring and dissolving, adding 20g of 100-mesh drying agent, and dryingThe silura lignite is evenly mixed. Then, 2.0% H is dripped into the reaction kettle at normal temperature2O2160ml of the solution was stirred while adding. After the dropwise addition, the reaction was continued for 1 hour with stirring. Then the temperature is increased to 80 ℃, the reaction is carried out for 2 hours, and the heating is stopped. After the reaction kettle is cooled to room temperature, centrifugally separating the obtained product, and washing the product with water until the pH value of the washing liquid is reached>And 5, drying to obtain the sulfonated coal. The mass yield of the sulfonated coal based on raw coal was 105.4%.
(2) Oxidative cracking of sulfonated coal: sequentially adding H into a 250ml high-pressure reaction kettle2O50 ml, KOH 5g and (1) prepared sulfonated coal 10g, after stirring and mixing evenly, the O is added2To 3.0 MPa. Then, stirring is started, the temperature is raised to 80 ℃, and the constant temperature oxidative cracking is carried out for 2 h. After the reaction is finished, the product is centrifuged for 10min under the condition of 14000rpm, and the oxidative cracking residual coal is separated. And (3) carrying out acid precipitation on the obtained solution by using 2mol/L sulfuric acid until the pH value is 1, standing for 2h for precipitation, and carrying out centrifugal separation to obtain the sulfonated coal-based humic acid. The mass yield of the sulfonated humic acid based on the sulfonated coal is 74.7 percent.
(3) Condensation polymerization of sulfonated humic acid: and (3) sequentially adding 6g of the sulfonated coal-based humic acid prepared in the step (2) and 80ml of 2% NaOH solution into a 250ml flask, stirring to dissolve, slowly adding 8ml of 37% formaldehyde solution, and reacting for 4 hours at 90 ℃. And finally, dehydrating and drying to obtain the modified lignite humic acid high-efficiency water reducing agent. The quality yield of the water reducing agent based on the sulfonated humic acid is 97.4 percent.
Example 6
(1) Sulfonation of coal: 120ml of H is added into a 500ml reaction kettle2O、24g NaHSO3、0.4g FeCl24ml of 1mol/L dilute sulfuric acid, stirring and dissolving, adding 20g of 100-mesh dried Ceylor brown coal, and uniformly mixing. Then, 1.5% H was added dropwise to the reaction vessel at room temperature2O2250ml of the solution was stirred while adding. After the dropwise addition, the reaction was continued for 1 hour with stirring. Then the temperature is raised to 60 ℃, the reaction is kept for 2 hours, and the heating is stopped. After the reaction kettle is cooled to room temperature, centrifugally separating the obtained product, and washing the product with water until the pH value of the washing liquid is reached>5, drying to obtain the sulfonated coal. The mass yield of the sulfonated coal based on raw coal is 113.7 percent.
(2) Oxidative cracking of sulfonated coal: sequentially adding the components into a 250ml high-pressure reaction kettleInto H2O100 ml, KOH 8g and (1) prepared sulfonated coal 10g, after stirring and mixing evenly, the O is added2To 1.0 MPa. Then, stirring is started and the temperature is raised to 140 ℃, and the oxidative cleavage is carried out for 1h at constant temperature. After the reaction is finished, centrifuging the product for 10min under the condition of 14000rpm, and separating out the oxidative cracking residual coal. And (3) carrying out acid precipitation on the obtained solution by using 2mol/L sulfuric acid until the pH value is 1, standing for 2h for precipitation, and carrying out centrifugal separation to obtain the sulfonated coal-based humic acid. The mass yield of the sulfonated humic acid based on the sulfonated coal is 80.3 percent.
(3) Condensation polymerization of sulfonated humic acid: and (3) sequentially adding 6g of the sulfonated coal-based humic acid prepared in the step (2) and 120ml of 2% NaOH solution into a 250ml flask, stirring and dissolving, slowly adding 12ml of 37% formaldehyde solution, and reacting for 3 hours at 80 ℃. And finally, dehydrating and drying to obtain the modified lignite humic acid high-efficiency water reducing agent. The mass yield of the water reducing agent based on the sulfonated humic acid is 105.5 percent
Example 7
(1) Sulfonation of coal: 120ml of H is added into a 500ml reaction kettle2O、40g NaHSO3、0.4g FeSO44ml of 1mol/L dilute sulfuric acid, stirring and dissolving, adding 20g of 100-mesh dry Shenfu subbituminous coal, and uniformly mixing. Then, 2.0% H is dripped into the reaction kettle at normal temperature2O2250ml of the solution was stirred while adding. After the dropwise addition, the reaction was continued for 1 hour with stirring. Then the temperature is increased to 80 ℃, the reaction is carried out for 2 hours, and the heating is stopped. After the reaction kettle is cooled to room temperature, centrifugally separating the obtained product, and washing the product with water until the pH value of the washing liquid is reached>And 5, drying to obtain the sulfonated coal. The mass yield of the sulfonated coal based on raw coal is 118.5 percent.
(2) Oxidative cracking of sulfonated coal: sequentially adding H into a 250ml high-pressure reaction kettle2O100 ml, KOH 5g and (1) prepared sulfonated coal 10g, after stirring and mixing evenly, the O is added2To 3.0 MPa. Then, stirring is started and the temperature is raised to 140 ℃, and the constant temperature oxidative cracking is carried out for 2 h. After the reaction is finished, centrifuging the product for 10min under the condition of 14000rpm, and separating out the oxidative cracking residual coal. And (3) separating the obtained solution with 2mol/L sulfuric acid until the pH value is 1, standing for 2h for precipitation, and centrifuging to separate the sulfonated coal-based humic acid. The mass yield of the sulfonated humic acid based on the sulfonated coal is 82.1 percent.
(3) Condensation polymerization of sulfonated humic acid: and (3) sequentially adding 6g of the sulfonated coal-based humic acid prepared in the step (2) and 120ml of 2% NaOH solution into a 250ml flask, stirring and dissolving, slowly adding 10ml of 37% formaldehyde solution, and reacting for 2 hours at the temperature of 100 ℃. And finally, dehydrating and drying to obtain the modified lignite humic acid high-efficiency water reducing agent. The mass yield of the water reducing agent based on the sulfonated humic acid is 104.2 percent
Example 8
(1) Sulfonation of coal: 140ml of H is added into a 500ml reaction kettle2O、35g Na2SO3、0.6g Fe(NO3)28ml of 1mol/L dilute sulfuric acid, stirring and dissolving, adding 20g of 100-mesh dry Shenfu subbituminous coal, and uniformly mixing. Then, 2.5% H is dripped into the reaction kettle at normal temperature2O2The solution (200 ml) was stirred while adding. After the dropwise addition, the reaction was continued for 1 hour with stirring. Then the temperature is raised to 100 ℃, the reaction is carried out for 1h, and the heating is stopped. After the reaction kettle is cooled to room temperature, centrifugally separating the obtained product, and washing the product with water until the pH value of the washing liquid is reached>And 5, drying to obtain the sulfonated coal. The mass yield of the sulfonated coal based on raw coal is 109.8 percent.
(2) Oxidative cracking of sulfonated coal: sequentially adding H into a 250ml high-pressure reaction kettle2O150 ml, KOH 8g and (1) prepared sulfonated coal 10g, after stirring and mixing evenly, the O is added2To 5.0 MPa. Then, stirring is started, the temperature is raised to 180 ℃, and the constant temperature oxidative cracking is carried out for 1 h. After the reaction is finished, the product is centrifuged for 10min under the condition of 14000rpm, and the oxidative cracking residual coal is separated. And (3) separating the obtained solution with 2mol/L sulfuric acid until the pH value is 1, standing for 2h for precipitation, and centrifuging to separate the sulfonated coal-based humic acid. The mass yield of the sulfonated humic acid based on the sulfonated coal is 80.7 percent.
(3) Condensation polymerization of sulfonated humic acid: and (3) sequentially adding 6g of the sulfonated coal-based humic acid prepared in the step (2) and 100ml of 2% NaOH solution into a 250ml flask, stirring to dissolve, slowly adding 8ml of 37% formaldehyde solution, and reacting for 3 hours at 80 ℃. And finally, dehydrating and drying to obtain the modified lignite humic acid high-efficiency water reducing agent. The mass yield of the water reducing agent based on the sulfonated humic acid is 98.3 percent.
Comparative example
A commercial naphthalene water reducer.
Application example
The initial net slurry fluidity, mortar fluidity and mortar water reduction rate of cement are measured by using the coal-based humic acid high-efficiency water reducing agent of the embodiments 1-8 and the commercial naphthalene water reducing agent of the comparative example, according to the national standard GB 8076-2008 specification of concrete admixture by adopting standard cement. Wherein the mixing amount of the water reducing agent is 0.4 percent.
TABLE 1 elemental analysis results in wt%, daf, for the raw materials and intermediates in example 1 at each stage
| Sample (I) | N | C | S | H | O* | H/C | S/C | O/C |
| Cenlin Guo le lignite | 1.5 | 68.8 | 1.0 | 4.8 | 23.9 | 0.84 | 0.005 | 0.26 |
| Sulfonated coal | 1.1 | 59.6 | 6.1 | 4.1 | 29.1 | 0.83 | 0.038 | 0.37 |
| Sulfonated coal-based humic acid | 1.1 | 55.7 | 7.2 | 3.6 | 32.4 | 0.78 | 0.048 | 0.44 |
| Oxidative cracking residual coal | 1.2 | 62.7 | 2.6 | 2.9 | 30.6 | 0.56 | 0.016 | 0.37 |
Table 2 examples 1-8 elemental analysis results/wt% of coal-based humic acid water reducing agent
*: dry ashless base
Table 3 shows performance evaluation results of lignite humic acid water reducing agent prepared by reference, comparative example and examples 1-8
Claims (5)
1. The preparation method of the low-rank coal-based high-efficiency water reducing agent is characterized by comprising the following steps of:
(1) sulfonation of coal: adding sulfite and water into a reactor, and stirring for dissolving; then adding the low-rank coal, ferrous salt and sulfuric acid, and stirring and mixing uniformly; then slowly dripping 0.5-2.5% hydrogen peroxide solution; after the feeding is finished, stirring and reacting for 1-2 h at normal temperature, heating to 60-100 ℃, and reacting for 1-2 h in a heat preservation manner; finally, centrifugally separating the obtained product, and drying to prepare the sulfonated coal;
wherein: the mass ratio of the coal, the sulfite, the hydrogen peroxide, the ferrous salt, the sulfuric acid and the water is 1: 0.5-1.5: 0.10-0.25: 0.007-0.020: 0.008-0.025: 10-20;
said sulfite being SO3 2-Measuring the mass; the ferrite is Fe2+Measuring the mass;
(2) oxidative cracking of sulfonated coal: sequentially adding the sulfonated coal prepared in the step (1) and an alkali solution into an autoclave, stirring and mixing uniformly, and then flushing oxygen to 0.5-5 MPa; then, starting stirring and heating to 80-180 ℃, and carrying out constant-temperature oxidative cracking for 1-2 h; finally, centrifugally separating the obtained oxidation cracking product to remove solid residual coal; carrying out acid precipitation on the obtained water-soluble product by using 2mol/L sulfuric acid until the pH value is 1, standing for 2 hours, and then carrying out centrifugal separation to obtain an acid precipitation product, namely sulfonated coal-based humic acid;
wherein: the mass ratio of the sulfonated coal to the alkali to the water is 1: 0.06-0.3: 5-20;
the base is OH-Measuring the mass;
(3) condensation polymerization of sulfonated humic acid: sequentially adding the sulfonated coal-based humic acid prepared in the step (2) and a 2% sodium hydroxide solution, stirring and dissolving, slowly adding a 37% formaldehyde solution, and reacting for 2-5 h under the condition of controlling the reaction temperature to be 80-100 ℃; finally, dehydrating and drying to obtain the coal-based humic acid high-efficiency water reducing agent;
wherein: the mass ratio of the sulfonated coal-based humic acid to the formaldehyde to the sodium hydroxide is 1: 0.2-0.8: 0.2-0.5.
2. The preparation method of the low-rank coal-based superplasticizer according to claim 1, wherein in the step (1): the low-rank coal is lignite or subbituminous coal, and the particle size of the low-rank coal is not larger than 100 meshes.
3. The preparation method of the low-rank coal-based superplasticizer according to claim 1, wherein in the step (1): the sulfite is sodium bisulfite.
4. The preparation method of the low-rank coal-based superplasticizer according to claim 1, wherein in the step (1): the ferrous salt is ferrous sulfate.
5. The preparation method of the low-rank coal-based superplasticizer according to claim 1, wherein in the step (2): the base is KOH.
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