阅读说明：本技术 一种秸秆基减水剂秸秆原料预处理及磺化-羟甲基化改性的方法 (Method for pretreatment and sulfonation-hydroxymethylation modification of straw raw material of straw-based water reducing agent ) 是由 章德玉 张惠琴 张建斌 朱元成 唐慧安 王鹏 刘岿 司长代 王小芳 刘新文 雷新 于 2019-02-21 设计创作，主要内容包括：本发明公开了一种秸秆基减水剂秸秆原料预处理及磺化-羟甲基化改性的方法,制备出符合秸秆基减水剂所需的前驱体秸秆木质纤维素预处理和磺化-羟甲基化改性物料。包括如下步骤：1)初碎：粉碎成1-3cm左右的秸秆段；2)清洗：把泥砂等杂质清洗干净；3)干燥：进行烘干,使其含水率在10％以下；4)二次粉碎：粉碎成1-10mm的秸秆段；5)微碎：通过球磨机使得出料粒度400μm以下；6)水解：在挤出机中加入润滑添加剂、主催化酸和助催化酸进行水解；7)氧化：在挤出机加入氧化剂进行氧化断链反应；8)磺化：在挤出机中加入磺化剂反应；9)碱化在挤出机中加入碱液反应；10)羟甲基化。在挤出机中加入羟甲基化试剂反应。(The invention discloses a method for pretreatment and sulfonation-hydroxymethylation modification of straw raw materials of a straw-based water reducing agent, and a precursor straw lignocellulose pretreatment and sulfonation-hydroxymethylation modified material meeting the requirement of the straw-based water reducing agent is prepared. The method comprises the following steps: 1) primary crushing: crushing into straw sections of about 1-3 cm; 2) cleaning: cleaning impurities such as mud and sand; 3) and (3) drying: drying to make the water content below 10%; 4) and (3) secondary crushing: crushing into straw sections of 1-10 mm; 5) micro-crushing: the discharged material is made to have the granularity of below 400 mu m by a ball mill; 6) hydrolysis: adding a lubricating additive, a main catalytic acid and a cocatalyst acid into an extruder for hydrolysis; 7) and (3) oxidation: adding an oxidant into the extruder to perform oxidation chain scission reaction; 8) sulfonation: adding a sulfonating agent into an extruder for reaction; 9) alkalizing, adding alkali liquor into an extruder for reaction; 10) hydroxymethylation. Adding a hydroxymethylation reagent into the extruder for reaction.)

1. A method for pretreatment and sulfonation-hydroxymethylation modification of straw raw materials of a straw-based water reducing agent is characterized by comprising the following steps of: 1) primarily crushing the naturally air-dried straws, and crushing the straws into straw sections of about 1-3 cm; 2) cleaning impurities such as mud and sand in the straw sections after the primary crushing; 3) drying the dried and cleaned straw sections to enable the water content of the straw sections to be below 10%; 4) crushing the dried straw sections into 1-10mm straw sections by secondary crushing; 5) carrying out ball milling and fine crushing on the straw sections subjected to the micro-crushing and secondary crushing through a ball mill to ensure that the discharge particle size of the crushed raw materials is below 400 mu m; 6) feeding the hydrolyzed and crushed raw materials into an extruder, simultaneously adding a lubricating additive, a main catalytic acid and a cocatalyst acid, and maintaining the temperature at about 50 ℃ for hydrolysis for 20 minutes; 7) feeding the mixture after the oxidation and hydrolysis into an extruder, adding an oxidant, and keeping the temperature at about 70 ℃ to perform oxidation chain scission reaction on the straw lignocellulose for 10 minutes; 8) adding a sulfonating agent into the mixture after sulfonation and oxidation in an extruder, and keeping the temperature at about 70 ℃ for reaction for 10 minutes; 9) adding alkali liquor into the mixture after alkalization and sulfonation in an extruder, adjusting the pH value to 8-9, and keeping the temperature at about 70 ℃ for reaction for 10 minutes; 10) adding a hydroxymethylation reagent into the mixture after hydroxymethylation and alkalization in an extruder, and keeping the temperature at about 70 ℃ for reaction for 10 minutes.

2. The pretreatment and sulfonation-hydroxymethylation modification method according to claim 1, wherein in the 6) hydrolysis step, the lubricating additive is one or a combination of stearic acid and oleic acid, and the solid-to-solid ratio of the straw to the lubricating additive is 1000g to (6-10) ml; the main catalytic acid is one or more of monobasic (carboxylic) acid, dibasic (carboxylic) acid or polybasic (carboxylic) acid, wherein the monobasic (carboxylic) acid is one or more of hypophosphorous acid, formic acid, acetic acid, benzoic acid, acrylic acid, methacrylic acid, stearic acid and oleic acid, the dibasic (carboxylic) acid is one or more of phosphorous acid, oxalic acid (oxalic acid), terephthalic acid, itaconic acid, maleic acid and maleic anhydride, the polybasic (carboxylic) acid is one or two of phosphoric acid and citric acid, the solid-acid ratio of the straw to the main catalytic acid is 1000g to (20-90) ml, the cocatalyst acid is dilute sulfuric acid or dilute hydrochloric acid with the mass concentration of 30g/L, and the solid-acid ratio of the straw to the cocatalyst diluted acid is 1000g to 100 ml; in the step 7) of oxidation, the oxidant is hydrogen peroxide with the mass concentration of 30 percent or potassium permanganate or potassium ferrate solution with the molar concentration of 1.0M, and the ratio of the straw to the oxidant is 1000g to (30-45) mL; in the step 8) of sulfonation, the sulfonating agent is one or a mixture of sodium sulfite and sodium bisulfite with the mass concentration of 50%, and the ratio of the straw to the sulfonating agent is 1000g to (75-100); in the step of 9) alkalization, the alkali liquor is one of sodium hydroxide and potassium hydroxide with the mass concentration of 40%; in the step 10) of hydroxymethylation, the hydroxymethylation reagent is a formaldehyde solution with the mass concentration of 37 percent, and the ratio of the straw to the formaldehyde is 1000g to (15-20).

Technical Field

The invention relates to the technical field of pretreatment and sulfonation modification of crop straw-based biomass water reducer precursor straw raw materials, in particular to a method for pretreatment and sulfonation-hydroxymethylation modification of straw-based water reducer straw raw materials.

Background

At present, along with the increasing shortage of petrochemical raw materials required by a new generation of high-performance petroleum-based polycarboxylate water reducer for preparing a concrete admixture, the price is increased all the way, high-quality aggregate of concrete is gradually consumed, and the outstanding problem that low-quality sandstone aggregate with high mud content is forced to be used is solved, the rapid development of the new generation of high-performance polycarboxylate water reducer is restricted, the production cost is continuously increased, and the loss of high performance such as high water reduction, high fluidity, high strength, high durability and the like of the polycarboxylate water reducer in concrete is caused by the high mud content of sandstone in the concrete, the polycarboxylic acid water reducing agent brings potential safety hazards to the quality of concrete, so that the polycarboxylic acid water reducing agent with higher performance advantages than naphthalene series, aliphatic series, sulfamate series, lignin series and other water reducing agents cannot be widely popularized and applied in the building industry to improve the building quality.

With the problems of high cost, low mud resistance and the like faced by the polycarboxylic acid water reducing agent serving as a novel additive of concrete, the key bottleneck technical problems of raw material selection, synthesis method and the like in the recent years of researches on the low-cost, mud-resistant and salt-resistant polycarboxylic acid water reducing agent by domestic and foreign scholars.

The research progress of the low-cost polycarboxylic acid water reducing agent is mainly reflected in that a biomass-based renewable raw material is used as a main method for reducing the polycarboxylic acid water reducing agent, the application of the modified biomass-based renewable raw material in the water reducing agent is mainly reported at present, and the modification methods mainly comprise sulfonation, esterification, etherification, amidation and the like.

Crop straws are inexpensive biomass raw materials which cannot be fully utilized, and comprise the rest parts of wheat, rice, corn, potatoes, oil plants, cotton, sugarcane and other crops after seeds are harvested. China is a big agricultural country, produces 7 hundred million tons of crop straws every year, and most of the crop straws are still incinerated, so that resource waste and environmental pollution are caused. The utilization of crop straws has been internationally regarded as a strategic industry for developing renewable energy resources in the 21 st century, and the resource utilization of crop straws mainly focuses on the development of chemical engineering and building materials. At present, the application research of crop straws as building materials is a hotspot, but the research of straws directly used as raw materials of water reducing agents is less. The main components of the straw are cellulose, hemicellulose, lignin and other bio-based macromolecules, the molecules contain ether groups, carbon-carbon double bonds, propenol hydroxyl groups, phenolic hydroxyl groups, carbonyl groups, methoxyl groups, carboxyl groups, benzene rings and other functional groups and chemical bonds, graft copolymerization and cross-linking copolymerization reactions such as etherification, esterification, sulfonation, esterification, etherification, amidation and the like can be carried out, and the obtained product has special performance.

At present, few research reports of directly using biomass straws as a water reducing agent exist, and most of the research reports are that cellulose and lignin are extracted and separated from the straws, or black liquor wastewater obtained by producing paper making and ethanol from the straws is used as a raw material for modification research of the water reducing agent or compounding research with a polycarboxylic acid water reducing agent. A study on lignin modified water reducing agent, CN 101337789A, "method for preparing water reducing agent by condensation modification of wheat straw alkali lignin", comprises dissolving wheat straw alkali lignin in 4.4-5.5 times of water, adding copper sulfate 0.6-0.9% of wheat straw alkali lignin, adjusting pH to 10-11 with caustic soda solution, adding anhydrous sodium sulfite 45-55% of wheat straw alkali lignin, heating to 88-92 deg.C, reacting for 4-5h to obtain sulfonated product, and performing condensation reaction with quantitative formaldehyde at pH 11.6-12.0 and 65-75 deg.C to obtain water reducing agent. The water reducing agent prepared by the method has low water reducing rate and can only be used as the most common water reducing agent. Chinese patent CN 101759856B "preparation method of sodium lignosulfonate water reducing agent", regard corn cob, acidolysis dreg of corn cob, bagasse or black liquor that corn stalk produces through the soda boil as the raw materials, through rough filtration, ultrafiltration membrane concentration, sulfonation and spray drying, prepare sodium lignosulfonate water reducing agent with low water content, this craft is pollution-free to the environment, the process is simple, with low costs, but the straw raw materials can't fully utilize, waste seriously. Chinese patent CN 106698993A, "a polycarboxylate water reducing agent", utilizes waste white mud to size, heat, mix with corn stalk evenly again, add sodium dodecyl sulfate, dry and extrude into pieces after stirring, the acid leaching obtains the hydrolyzate, utilize CaO to adjust the pH value of straw hydrolyzate to 6.0-7.0, the hydrolyzate that obtains is after drying, oxidizing, sulfonating, add into polycarboxylate water reducing agent, use ultrasonic treatment for 1-2h after stirring evenly, obtain modified polycarboxylate water reducing agent. The method has the main advantages that the papermaking waste liquid is used for preparing the polycarboxylic acid water reducing agent, waste materials can be well changed into valuable materials, and the strong base in the papermaking waste liquid is utilized to pretreat the corn straws, so that the corn straws can be better soaked in acid for hydrolysis. The essence is that lignin in the straws is sulfonated and compounded with a water reducing agent. Chinese patent CN 102936110A, "a lignin sulfonate-polycarboxylic acid copolymerization composite high-performance water reducing agent and a preparation method thereof", is obtained by directly synthesizing lignin sulfonate, methyl allyl polyoxyethylene ether and acrylic acid under the action of ammonium persulfate and neutralizing with sodium hydroxide. The essence of the water reducing agent is a lignosulfonate modified polycarboxylic acid water reducing agent.

The research of directly using biomass straws as a water reducing agent mainly has two reports at present: chinese patent CN 106279574A 'A polycarboxylate superplasticizer modified by straws and a preparation method thereof', the first step is straw pretreatment: crushing straws, adding dilute acid, uniformly stirring and mixing, soaking for 18-36h, filtering, and washing the straws to be neutral by using clear water; step two, preparing the straw modified polycarboxylate superplasticizer: adding methallyl polyoxyethylene-1000, methallyl polyoxyethylene-2400, maleic anhydride, acrylamide, sodium methallyl sulfonate and straws into a four-reflux device and a constant-pressure dropping funnel, adding ammonium persulfate into the constant-pressure dropping funnel, beginning to drop initiator ammonium persulfate at a dropping speed of 2-4 drops/s, and preserving heat for 4-5 hours after dropping; cooling to 35-45 ℃, and adjusting the pH value to 6.8-7.2 to obtain the straw modified polycarboxylic acid water reducing agent. Chinese patent CN 105713164B, "an aliphatic water-reducing agent prepared from straws and a preparation method thereof", is prepared by the steps of straw acid cleaning, straw modified aliphatic water-reducing agent and the like. The method specifically comprises the following steps: pretreating straws, namely crushing corn straws or wheat straws, adding dilute acid, uniformly stirring and mixing, soaking for 18-36h, filtering, and washing the straws to be neutral by using clear water; adding water into a reaction kettle, then adding sodium sulfite, and dissolving; adding acetone into the dissolved sodium sulfite solution, and sulfonating for 8-12 min; then adding the pretreated straws, and stirring for reaction for 20-40 min; adding formaldehyde into the solution, and reacting for 1-2h at 90-95 ℃ to prepare the straw modified aliphatic water reducer. The technology effectively utilizes straw waste resources, overcomes the defect of poor retarding effect of the conventional aliphatic water reducing agent, improves the application range of the aliphatic water reducing agent, and reduces the production cost. However, the two research results are only small test shaking tests in laboratories, firstly, the degree and method of fine crushing are not provided for crushing the straws, but the straw crushing is only provided, secondly, excessive chloride ions and sulfate ions are brought in by the hydrolysis of the straws by using conventional dilute hydrochloric acid or dilute sulfuric acid to influence the performance of the water reducing agent, thirdly, the conception and concept of industrial tests are not provided, and the distance from the industrial production device and the production system is large.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for preprocessing straw raw materials and carrying out sulfonation-hydroxymethylation modification on straw-based water reducing agents, which is a method for preparing precursor straw lignocellulose preprocessing and sulfonation-hydroxymethylation modification materials meeting the requirements of straw-based water reducing agents, wherein the modified materials can be directly used for water reducing agents with the water reducing rate of 10-15 percent and can also be compounded with other water reducing agents for use, and can be further continuously grafted and copolymerized with unsaturated polyether macromonomers and unsaturated micromolecule monomers to prepare water reducing agents with higher performance, so that the industrialization process of low-cost straw-based biomass concrete water reducing agents is further promoted, and therefore, a new possibility is provided for recycling of crop straws.

The technical scheme adopted by the invention is as follows: a method for pretreatment and sulfonation-hydroxymethylation modification of straw raw materials of a straw-based water reducing agent is realized by the following steps: 1) primarily crushing the naturally air-dried straws, and crushing the straws into straw sections of about 1-3 cm; 2) cleaning impurities such as mud and sand in the straw sections after the primary crushing; 3) drying the dried and cleaned straw sections to enable the water content of the straw sections to be below 10%; 4) crushing the dried straw sections into 1-10mm straw sections by secondary crushing; 5) carrying out ball milling and fine crushing on the straw sections subjected to the micro-crushing and secondary crushing through a ball mill to ensure that the discharge particle size of the crushed raw materials is below 400 mu m; 6) feeding the hydrolyzed and crushed raw materials into an extruder, simultaneously adding a lubricating additive, a main catalytic acid and a cocatalyst, and maintaining the temperature at about 50 ℃ for hydrolysis for 20 minutes; 7) feeding the mixture after the oxidation and hydrolysis into an extruder, adding an oxidant, and keeping the temperature at about 70 ℃ to perform oxidation chain scission reaction on the straw lignocellulose for 10 minutes; 8) adding a sulfonating agent into the mixture after sulfonation and oxidation in an extruder, and reacting for 10 minutes at the temperature of about 70 ℃; 9) adding alkali liquor into the mixture after alkalization and sulfonation in an extruder, adjusting the pH value to 8-9, and keeping the temperature at about 70 ℃ for reaction for 10 minutes; 10) adding a hydroxymethylation reagent into the mixture after hydroxymethylation and alkalization in an extruder, and keeping the temperature at about 70 ℃ for reaction for 10 minutes.

Preferably, in the 6) hydrolysis step, the lubricating additive is one or a combination of stearic acid and oleic acid, and the solid-to-solid ratio of the straw to the lubricating additive is 1000g to (6-10) ml; the main catalytic acid is one or more of monobasic (carboxylic) acid, dibasic (carboxylic) acid or polybasic (carboxylic) acid, wherein the monobasic (carboxylic) acid is one or more of hypophosphorous acid, formic acid, acetic acid, benzoic acid, acrylic acid, methacrylic acid, stearic acid and oleic acid, the dibasic (carboxylic) acid is one or more of phosphorous acid, oxalic acid (oxalic acid), terephthalic acid, itaconic acid, maleic acid and maleic anhydride, the polybasic (carboxylic) acid is one or two of phosphoric acid and citric acid, the solid-acid ratio of the straw to the main catalytic acid is 1000g to (20-90) ml, the cocatalyst acid is dilute sulfuric acid or dilute hydrochloric acid with the mass concentration of 30g/L, and the solid-acid ratio of the straw to the cocatalyst diluted acid is 1000g to 100 ml; in the step 7) of oxidation, the oxidant is hydrogen peroxide with the mass concentration of 30 percent or potassium permanganate or potassium ferrate solution with the molar concentration of 1.0M, and the ratio of the straw to the oxidant is 1000g to (30-45) mL; in the step 8) of sulfonation, the sulfonating agent is one or a mixture of sodium sulfite or sodium bisulfite with the mass concentration of 50%, and the ratio of the straw to the sulfonating agent is 1000g to (75-100 g); in the step of 9) alkalization, the alkali liquor is one of sodium hydroxide and potassium hydroxide with the mass concentration of 40%; in the step 10) of hydroxymethylation, the hydroxymethylation reagent is a formaldehyde solution with the mass concentration of 37 percent, and the ratio of the straw to the formaldehyde is 1000g to (15-20).

The invention has the technical effects that the straws are firstly crushed into straw sections of 1-3cm by the primary crushing device, and then impurities such as mud and sand in the straw sections are cleaned by the cleaning device, so that the raw materials can be cleaned conveniently, and the problems of large loss of organic components in straw powder and subsequent difficulty in liquid-solid separation caused by too fine crushed straws in the cleaning process are also prevented. By utilizing the characteristics of a ball mill, straw segments of about 1-3cm are easily crushed into straw powder of 75-400 mu m, so that subsequent hydrolysis and water reducing agent preparation are facilitated, lignin components in the straws are basically destroyed after ball milling treatment, cellulose is more easily hydrolyzed due to degradation of lignin, the crystallinity of the straws is reduced after long-time ball milling, the ratio and the reaction active area of amorphous cellulose are increased, and the cellulose of the straws is more easily permeated by weak acid and hydrolyzed. The straw raw material is degraded by a combined organic/inorganic acid mixed acid pretreatment method by spirally extruding by a semi-dry method (the water content in the straw reaches about 10 percent, and liquid-phase hydrolysis catalytic acid is added), and the straw raw material has the advantages of small corrosion to equipment, high degradation rate, simple reaction process, mild reaction conditions, low cost and easy industrial application; and the adverse effects of excessive chloride ions or sulfate ions on the corrosion of the subsequent water reducing agent on concrete and the like caused by only using inorganic acid, hydrochloric acid or sulfuric acid to degrade the straws are avoided or reduced. The organic acid main catalyst used for pretreating the straw raw material by combining the semidry method screw extrusion with the organic/inorganic acid mixed acid can be used as an unsaturated micromolecule monomer required for the subsequent preparation of the water reducing agent, particularly the unsaturated carboxylic acid micromolecule monomer can actively participate in the subsequent synthesis of the polycarboxylic acid water reducing agent, and the product performance is not influenced by slight excess. During the process of pretreating the straw lignocellulose raw material by combining semi-dry method screw extrusion with organic/inorganic acid mixed acid, not only are the straw lignin, hemicellulose and cellulose further separated, but also the main products of straw hydrolysis are mannose, glucose, galactose, xylose and arabinose, and various complex reactions also occur, and some small molecular compounds are generated along with the hydrolysis, such as hydrolyzed sugar, organic acid, furfural, 5-hydroxymethylfurfural, phenolic compounds and the like in the feed liquid phase of the pretreated material; hemicellulose can concomitantly produce compounds such as acetic acid, arabinose, xylose, mannose, galactose and glucose; cellulose can produce glucose; lignin can produce phenolic compounds; the extracted matter and ash can produce wood resin and the like; meanwhile, part of arabinose and xylose are further hydrolyzed and converted into furfural, mannose and galactose, glucose is further hydrolyzed and converted into hydroxymethyl furfural, furfural is further hydrolyzed and converted into formic acid, and hydroxymethyl furfural is further hydrolyzed and converted into formic acid and levulinic acid; the generated small molecular compounds can be used as small molecular monomers required for synthesizing the water reducing agent, have respective characteristics, such as the retarding and water reducing effects of monosaccharide, polysaccharide and carboxylic acid, the slump retaining effect of furfural and phenolic compounds and the like, and the generated organic weak acids such as formic acid, acetic acid, levulinic acid and the like provide H < + > which has the promotion effect on hydrolysis, accelerate the hydrolysis process, remarkably promote the degradation of cellulose and lignin in straws, have higher saccharification rate, mild reaction conditions and simple reaction process, basically have no pollution and are easy for industrial production. The screw extruder has the characteristics of functions of horizontal plug flow, high-speed extrusion and strong shearing, and the functions of long-time high-speed extrusion and strong shearing further reduce the crystallinity of the straw, and further increase the ratio of amorphous cellulose and the reaction active area, so that the cellulose of the straw is easier to be permeated by weak acid and hydrolyzed more easily, and the straw hydrolysis becomes more efficient and is easy to control.

Detailed Description

In order to make the technical means, characteristics, objectives and functions of the present invention easy to understand, the present invention will be further described with reference to the following embodiments, and the following detailed descriptions will be made.

Firstly, the characteristics of the straw raw material required by the embodiment are explained for illustration.

The straw raw materials used in the following examples are wheat straw and corn straw harvested in the Tianshui area of Gansu province in 2017, the harvested straws are air-dried, the dried straws (including roots, stems and leaves) are pulverized and ground to obtain fine powder, and the fine powder is subjected to composition content analysis and detection of lignin, hemicellulose, cellulose and the like, and the analysis results are shown in the following table 1 (mass fraction% in terms of dry substances).

Raw material components%	Cellulose, process for producing the same, and process for producing the same	Hemicellulose	Lignin	Water content ratio	Ash content
						Wheat straw	36.7	27	15.4	5.46	13.1
Corn stalk	38.1	21.1	18.0	6.77	11.5

TABLE 1 analysis and detection data of straw composition content