Method for producing furfural by using hydrogen ions and hydroxyl ions

Abstract

The invention relates to a method for producing furfural by using hydrogen ions and hydroxyl ions. The method comprises the following steps: (1) preparing materials; and (2) mixing. And (3) hydrolysis reaction. And (4) immediately blowing out furfural generated after the hydrolysis reaction by using steam. And (5) carrying out steam treatment and condensation to obtain a dilute furfural solution. And (6) distilling. And (7) condensing. (8) neutralizing acid in the crude furfural by adding hydroxyl ions; the method comprises the following steps: feeding crude furfural into a neutralization pot with a stirrer, adding a hydroxyl ion solution, stirring, standing, and refining. And (9) refining. The purity of the refined furfural reaches 99% or above, and the acid content is 0.02% or above. According to the method, sulfuric acid is replaced with hydrogen ions, alkali is replaced with hydroxyl ions, waste residues and waste water generated during furfural production are nontoxic, harmless and free of pollution, and the yield of furfural is increased by 20%. Through detection, compared with the use of hydrogen ions and hydroxyl ions to produce furfural, the content of sulfate ions in furfural residues is 7.5 mg / l, and the content of sulfate ions in furfural hydrolysate is 15 mg / l.

Description

Technical Field

[0001] The present invention relates to a method for producing furfural by using hydrogen ions and hydroxide ions, and more particularly to a method for replacing sulfuric acid with hydrogen ions and alkali (sodium carbonate, calcium oxide, sodium hydroxide, calcium hydroxide) with hydroxide ions, and then converting the byproducts of furfural produced by preparing furfural, namely furfural residue and furfural water, into valuables, using clean water to prepare acid, reducing side reactions, hindering the generation of catalyst inhibition, and being able to increase the furfural yield by 20%. The two byproducts in the method are non-toxic, harmless, and pollution-free, and are important means of production in agricultural production. Background Art

[0002] Furfural is a chemical product, and its system name is α-furfural, which is a derivative in which the hydrogen atom at the 2nd position of furan is replaced by an aldehyde group. It is produced by hydrolyzing pentose (monosaccharide) from the plant fiber raw material under a certain temperature and catalyst, and then the pentose is dehydrated to generate furfural. This process requires the use of sulfuric acid as a catalyst, and the acid in the crude furfural must be neutralized. Neutralization generally adopts the neutralization method of adding sodium carbonate. Sulfuric acid and sodium carbonate are a source of serious environmental pollution. However, if furfural products are to be made, sulfuric acid and sodium carbonate are indispensable. If furfural products are to be made, it is necessary to increase the treatment of later pollution sources. The treatment of pollution sources requires investment and operation, which in turn increases the cost of producing furfural products, thereby reducing market competitiveness. The secondary treatment of waste residues and wastewater in the production of furfural is not only costly, but the treated products are not competitive in the market and cannot enter the market. Most furfural enterprises use recycled wastewater to make acid, but the recycled wastewater contains a large amount of sulfate, unionized sulfurous acid and other impurities, which produce catalyst inhibitors, hinder the normal catalytic hydrolysis of the catalyst, and reduce the furfural production rate, resulting in waste of materials and energy.

[0003] The furfural industry knows that the production of furfural must use sulfuric acid and sodium carbonate. It uses the hydrogen ions in sulfuric acid as a catalyst. After concentrated sulfuric acid is diluted, its molecules are ionized. In the dilute sulfuric acid liquid, there are hydrogen ions and acid radical ions. In the production of furfural, hydrogen ions play a catalytic role. Sodium carbonate is used to neutralize sulfuric acid in furfural, thus producing sulfate. If the salt content of furfural residue and furfural wastewater is high, its application in agricultural production will be limited.

[0004] Furfural wastewater contains a large amount of sulfate, unionized sulfurous acid and other impurities, which greatly reduce the activity of hydrogen ions. This phenomenon is called catalyst inhibitor. Catalytic hydrolysis reaction inhibitor, also known as retarder. It is a substance that blocks or reduces the speed of catalytic hydrolysis reaction, and its effect is the same as that of negative catalyst. Although it cannot stop the hydrolysis reaction, it only slows down the hydrolysis reaction. It is a substance that inhibits or moderates chemical reactions. Therefore, the use of acid in furfural wastewater inhibits the hydrolysis of hemicellulose catalyzed by hydrogen ions, thereby affecting the efficiency of furfural production (formaldehyde production rate).

[0005] Chemists describe and measure the contribution of protons [H + ] ability, such as sulfuric acid and hydrochloric acid in strong acids, which can be completely ionized in aqueous solution. Although the hydrogen ions they ionize are usually H + Or "hydrated hydrogen ion" H3O + The aggregate may be H5O2 + 、H7O3 + , or even H9O4 + The donation of protons is usually an intermediate step in any acidolysis reaction. Acids are often used as chemical reagents to donate protons in aqueous solution. If water can become [H + ], there will be fewer unwanted by-products from the reaction. Therefore, there will be less hazards associated with the application of these products.

[0006] In the field of chemistry, hydroxide ion, as a common anion, plays an important role. It not only exists in many compounds, but also is one of the important indicators of the acidity and alkalinity of aqueous solutions.

[0007] 1. The symbol of hydroxide ion The symbol for the hydroxide ion is OH⁻. "O" represents the oxygen atom, "H" represents the hydrogen atom, and the — " means that the ion carries one unit of negative charge. This symbolic representation method is concise and clear, and is a commonly used way to represent ions in chemistry.

[0008] 2. Expression of Hydroxyl Ions In chemical equations or formulas, hydroxide ions are often represented directly by their symbol "OH⁻". For example, when representing the compound sodium hydroxide, we can write "NaOH", where "Na" represents the sodium ion and "OH⁻" represents the hydroxide ion.

[0009] 3. Application of Hydroxyl Ions in Chemical Reactions We also need to use chemical equations when describing the properties or reactions of hydroxide ions. For example, the reaction of hydroxide ions combining with hydrogen ions to form water can be expressed as: [H^+ + OH^- =H2O]. This equation shows the important role of hydroxide ions in acid-base neutralization reactions.

[0010] In practical applications, hydroxide ions exist in compounds, such as various alkalis: sodium hydroxide, calcium hydroxide, potassium hydroxide, etc. Due to the presence of metal ions, they produce unwanted salts and many environmental problems when participating in chemical reactions. Hydroxyl ion water is a solution of hydroxide ions mixed with trace metal ions and water molecules. Hydroxyl ions are usually represented by OH⁻. The aggregate may be n OH⁻, which can produce a large amount of negatively charged water. It has a large number of practical applications, which is very important. Negatively charged water has the ability to contribute hydroxide ions (OH⁻), and its industrial value is immeasurable. The contribution of hydroxide ions is usually completed by alkaline hydrolysis, and alkali is often used as a chemical reagent to contribute hydroxide ions in aqueous solutions. If water can be a source of hydrogen ions, then there will be fewer unwanted byproducts (toxins) from the reaction, so the hazards associated with the application of these products will be smaller, and the industrial value is great.

[0011] In the modern chemical theory system, hydroxide ions exist with metal ions as carriers. The hydroxide ions in the hydroxide aqueous solution exist with water as carrier. The hydroxide ions existing with water as carrier have removed the strong corrosiveness and strong oxidizing properties, do not produce any odor (non-volatile), do not produce unnecessary compounds in the catalytic process, are effective in water with a wide range of temperatures, are relatively harmless when used in excess, can be neutralized after use, are non-carcinogenic, non-mutagenic, non-toxic, almost harmless in water and the environment, are compatible with the environment, and can be stored for a long time without decomposing or turning into dangerous compounds.

[0012] At present, in the furfural production process, most manufacturers add dilute sulfuric acid with a concentration of about 5% as a catalyst to crushed corn cobs to produce furfural. Under the action of hydrogen ions, the glycosidic bonds are broken, and pentose is converted into pentose. The hydroxyl groups of pentose are protonated by hydrogen ions to remove three water molecules on the pentose to generate furfural. The crude furfural produced needs to be neutralized with alkali to remove the acid in the crude furfural. Traditionally, sodium carbonate solution is used for neutralization.

[0013] This process is a traditional production process with mature and stable technology. However, during the hydrolysis reaction of this traditional production process, there are many side reactions when furfural is generated, which affects the yield of furfural, and also produces furfural slag and furfural wastewater. Since sulfuric acid and sodium carbonate are used in the production process, the side reactions in the furfural production cause a large amount of sulfate and other impurities to remain in the furfural slag, resulting in a high salt content. The wastewater generated by the production of furfural also contains a large amount of sulfate.

[0014] Furfural is produced by using hydrogen ions and hydroxide ions. Without sulfate ions and metal ions, there are no side reactions in furfural production, and wastewater and waste residue do not need secondary environmental protection treatment. Wastewater and waste residue are important means of production in organic agricultural production. Low-salt furfural residue contains very high organic matter. It is a good product for managing agricultural planting and a high-quality soil conditioner. After furfural water is concentrated, it can produce high-grade wood vinegar. This wood vinegar can replace imported products. In addition, in order not to discharge wastewater, some furfural production evaporates the wastewater and recycles it for diluting sulfuric acid (acid preparation).

[0015] The present invention aims to solve the problem of converting furfural waste residue and furfural waste water generated in the furfural production process into treasure, solve the problem that the furfural residue and furfural water have high salt content, and their accumulation and loss will pollute the atmosphere, soil and rivers, and solve the problem that acidification of furfural waste water inhibits the hydrolysis of hemicellulose catalyzed by hydrogen ions, thereby affecting the efficiency of furfural production (formaldehyde yield).

[0016] Furfural residue, as a biomass waste, contains a large amount of organic matter and has good recycling value. Furfural wastewater contains organic matter and unionized sulfurous acid and inorganic salts (sulfates). Without sulfate ions, there will be no inorganic salts (sulfates). The organic matter in furfural wastewater is the core component of wood vinegar. After simple separation, furfural wastewater becomes high-quality wood vinegar. Reasonable resource utilization of furfural residue and aldehyde water can eliminate their pollution to the environment, while increasing the added value of furfural, achieving the goal of zero discharge of pollutants in the production process of furfural enterprises, and achieving the purpose of clean production and recycling. Summary of the invention

[0017] In order to solve the above technical problems, the present invention provides a method for producing furfural using hydrogen ions and hydroxide ions. Without affecting the hydrolysis rate of pentosans in hemicellulose, the produced furfural residues and furfural wastewater are turned into treasure, while the furfural output rate of furfural production is increased, and zero discharge of pollutants in furfural production is achieved, thereby achieving the purpose of clean production and recycling.

[0018] To achieve the above purpose, the present invention adopts the following technical solutions: A method for producing furfural using hydrogen ions and hydroxide ions, characterized in that it comprises the following steps: (1) Prepare the ingredients: take corn cobs, wash, dry and crush into corn cob particles.

[0019] (2) Mixing: Weigh the prepared corn cob particles and mix the corn cob particles with the hydrogen ion solution prepared with clean water in a solid-liquid ratio of 1:(0.3-0.6), such as 1:0.3, 1:0.4, 1:0.5 or 1:0.6. Adjust the mixture until the hydrogen ions in the corn cob particles reach saturation.

[0020] (3) The corn cobs that have reached a hydrogen ion saturation state are hydrolyzed in a hydrolysis pot to produce pentoses, which are then dehydrated by protonation of the hydrogen ion hydroxyl groups to produce furfural.

[0021] (4) The furfural generated after the hydrolysis reaction is immediately blown out with steam.

[0022] (5) Steam treatment and condensation: The aldehyde vapor discharged from the hydrolysis pot must be neutralized with a hydroxide ion solution before entering the distillation tower. The aldehyde vapor enters the condenser and condenses to obtain a dilute furfural solution.

[0023] (6) Distillation: The dilute furfural solution is sent to the distillation tower for distillation.

[0024] (7) The steam drawn out from the top of the distillation tower enters the condenser and then enters the crude furfural collector after condensation.

[0025] (8) The acid in the crude furfural is neutralized by adding hydroxide ions; the crude furfural is placed in a stirred neutralization pot, and a hydroxide ion solution is added in an amount of 3% of the crude furfural. After stirring and standing, the crude furfural is refined.

[0026] (9) Refining: The furfural is refined by vacuum distillation or steam distillation. The purity of the refined furfural reaches more than 99%, and the acid content is more than 0.02%.

[0027] The above scheme also includes: The pH value of the hydrogen ion solution in step (2) is 0; and the pH value of the hydroxide ion solution in step (8) is 12.

[0028] The temperature used in step (3) is 170-190°C and the steam pressure is 8-12 kg / cm 2 The reaction time for hydrolysis to produce aldehyde is 1-4 hours.

[0029] In the step (7), during operation, the top temperature of the distillation tower is maintained at 94-97°C, the bottom temperature is maintained at 98-102°C, and the distillate temperature is maintained below 55°C.

[0030] The steps of the hydrogen ion preparation method are as follows: (1) Mix dilute sulfuric acid solution and diatomaceous earth in equal proportions, stir, and allow to stand, and take the supernatant; the supernatant is tested using a sulfate ion detector.

[0031] (2) Based on the test data, an equal amount of diatomaceous earth is added to the residual sulfate in the supernatant, and then the above step (1) is repeated, and the extraction is cyclically performed until the sulfate in the supernatant is less than 1%.

[0032] (3) Diatomaceous earth purification: Use diatomaceous earth to produce hydrogen ions. Select raw ores from Linjiang and Changbai, Jilin, which contain more than 88% diatomaceous earth particles and have a whiteness of more than 85%, and purify them using the scrubbing method.

[0033] The steps of the method for preparing the hydroxide ion solution are as follows: (1) Mix inorganic strong alkali solution and diatomaceous earth in proportion, stir, let stand, and take the supernatant.

[0034] (2) Detect the metal ion content in the supernatant, then add diatomaceous earth according to the metal ion content and stir and adsorb until the supernatant meets the hydroxide ion solution index. That is, the obtained hydroxide ion solution has metal ions <5% and pH>12.

[0035] The inorganic strong base is sodium hydroxide, potassium hydroxide, calcium hydroxide or barium hydroxide.

[0036] Further, a method for producing furfural using hydrogen ions and hydroxide ions is characterized by comprising the following steps: Prepare the materials: take corn cobs, wash, dry and crush into corn cob particles. The diameter of the corn cob particles should not exceed 5mm.

[0037] Mix the materials, weigh the prepared corn cob particles, add the hydrogen ion solution prepared with clean water, the pH value of the hydrogen ion solution at this time is 0, mix the corn cob particles with the hydrogen ion solution in a solid-liquid ratio of 1:0.3, and adjust the mixture until the hydrogen ions in the corn cob particles reach saturation.

[0038] The corn cobs that have reached the hydrogen ion saturation state are hydrolyzed in the hydrolysis pot. The pentosan in the corn cobs uses hydrogen ions as a hydrolysis catalyst and is hydrolyzed into pentose. Then, the hydrogen ion hydroxyl group is protonated and dehydrated to generate furfural. Since the two reactions are not easy to proceed at room temperature, the temperature is 170-190℃ and the steam pressure is 8-12 (kg / cm 2 The reaction time for hydrolysis to produce aldehyde is 4 hours, the first 2 hours are the time for injection, and the last 2 hours are the time for extraction. If the steam pressure is always maintained at 10kg / cm 2 The reaction time can be shortened by 1 hour.

[0039] The furfural generated after the hydrolysis reaction is blown out immediately with steam to avoid side reactions. During the hydrolysis process, the furfural in the steam is uneven, so the steam should be adjusted according to the change in the aldehyde content during the hydrolysis operation. When the aldehyde output is high, the steam valve is opened wide, and when the aldehyde output is low, the steam valve is opened small.

[0040] Steam treatment and condensation: The steam (aldehyde steam) discharged from the hydrolysis pot contains a small amount of acetic acid, which needs to be neutralized before entering the distillation tower. The neutralization treatment is achieved by controlling the hydroxide ion solution through a gas phase neutralization tube with a needle valve. The neutralized liquid is sent to the acetic acid section for recovery after passing through the vapor-liquid separator, and the aldehyde steam enters the condenser for condensation.

[0041] Distillation: The purpose of distillation is to concentrate the dilute furfural solution, thereby increasing the concentration of furfural. The dilute furfural solution enters from the middle of the distillation tower, and the bottom of the tower is heated by indirect steam. Furfural and water have a low azeotropic point and are easy to evaporate. After the dilute furfural solution is evaporated, the steam emerges from the gap of the bubble cap of the distillation tower, and is divided into many water bubbles to the upper tower plate, while the excess liquid on the upper tower plate is refluxed to the next layer through the overflow pipe. This is repeated, and the concentrated fraction after multiple evaporations is drawn out from the top of the tower. The residual liquid is discharged from the bottom of the tower.

[0042] The steam drawn from the upper part of the tower enters the condenser, and after condensation, it enters the crude furfural collector. The products in the collector are divided into two layers: the lower layer is oily furfural, with a concentration of up to 90%, namely crude furfural; the upper layer is a saturated solution of furfural dissolved in water, containing 7-10% furfural. During operation, the tower top temperature should be maintained at 94-97℃, the tower bottom temperature at 98-102℃, and the distillate temperature should be lower than 55℃.

[0043] Neutralize the acid in the crude furfural by adding hydroxide ion neutralization method. Put the crude furfural into a stirred neutralization pot, add hydroxide ion solution with a pH value of 12, and the amount is 3% of the crude furfural. After adding, stir for 10 minutes, let it stand for 10 minutes, and then perform refining treatment.

[0044] Refining: Crude furfural has low purity and contains high-boiling point, low-boiling point substances and water, which easily darkens the color and is not suitable for certain uses, so it needs to be refined. Generally, it is refined by vacuum distillation or steam distillation. The purity of refined furfural should reach more than 99%, and the acid content should be more than 0.02%.

[0045] In the present invention, hydrogen ions replace sulfuric acid, sulfate radicals are absent, and hydrogen ion solution is repeatedly prepared with clean water, thereby avoiding sulfate radical ions from inhibiting catalysis and sulfate radical side reactions, and avoiding the generation of inorganic salts. The corncob is catalytically hydrolyzed thoroughly, and the furfural production rate is increased by 20%.

[0046] The use of hydroxide ions instead of alkali reduces the presence of metal ions in the hydrolyzate, specifically reduces the generation of inorganic salts, and reduces the generation of inorganic acids and inorganic salts in the hydrolyzate and furfural residues.

[0047] The preparation method of hydronium ion using diatomite, the steps are as follows: (1) Prepare 25% dilute sulfuric acid using 98% concentrated sulfuric acid The specific steps for preparing 1000 ml of 25% dilute sulfuric acid are as follows: Prepare 1000 ml of 25% dilute sulfuric acid, where the mass of pure sulfuric acid is 1000 ml × 25% = 250 grams.

[0048] Since all pure sulfuric acid comes from concentrated sulfuric acid, the mass of concentrated sulfuric acid required is 250 grams ÷ 98% = 255.1 grams.

[0049] The density of concentrated sulfuric acid is 1.84 g / cm³, so the volume of concentrated sulfuric acid is 255.1 g ÷ 1.84 g / cm³ = 138.6 ml. The mass of water is 1000 g - 255.1 g = 744.9 g, and the density of water is 1 g / ml, so the volume of water is 744.9 ml. ‌Measure concentrated sulfuric acid and water‌, use a measuring cylinder to measure 138.6 ml of concentrated sulfuric acid and 744.9 ml of water. ‌Mix and stir well‌. Pour the measured concentrated sulfuric acid and water into a beaker respectively, stir with a glass rod to ensure that the two are fully mixed and the pH value of the solution is <-0.6.

[0050] (2) Mix the prepared sulfuric acid solution and diatomaceous earth in equal proportions.

[0051] (3) The mixed liquid was placed in a blender and stirred for 30 minutes.

[0052] (4) The temperature of the liquid was controlled at 35°C during stirring.

[0053] (5) The mixed solution was allowed to settle for 12 hours, and the precipitate and supernatant were separated.

[0054] (6) The separated supernatant is tested using a sulfate ion detector.

[0055] (7) Based on the test data, add an equal amount of diatomaceous earth to the residual sulfate in the supernatant, and then repeat the above steps (3), (4), (5), and (6) to cyclically extract until the sulfate in the supernatant is less than 1%.

[0056] Diatomite purification: Diatomite is used to produce hydrogen ions, which requires the diatomite to contain very little A12O3 and Fe2O3. Select the raw ore from Linjiang and Changbai in Jilin with more than 88% diatom particles and more than 85% whiteness, and purify it by scrubbing. Greatly reduce the content of A12O3 and Fe2O3. The particle size distribution is 50 microns to 70 microns, and the content of diatom particles is not less than 92%. Diatomite is preferably disc algae, and the particle size is preferably >50 microns. The particle size of diatom particles is preferably large. After the selection, the large particle size absorbs water quickly, separates quickly, and has high production efficiency.

[0057] From the chemical structure of diatomite, we know that diatomite is weakly acidic and is a solid acid. The porosity and negative charge of the diatomite surface make it show obvious surface adsorption. There are also a large number of silanol groups (mixtures) on the surface of diatomite. These silanol groups exist in the numerous micropores of diatomite, which is also an important reason why diatomite has adsorption properties. The adsorption performance of diatomite is closely related to the number of hydroxyl groups carried on its surface and micropores. Some hydroxyl groups lose hydrogen ions due to hydrolysis, making the surface of diatomite show a certain negative charge. The pH value can affect the negative charge of the surface of diatomite. In most pH ranges, the surface of diatomite is negatively charged, but under strong acidic conditions (pH < 2), the hydroxyl groups on the surface of diatomite are protonated and positively charged.

[0058] Since the zero-point charge of diatomite is 2.0, in order to achieve a removal rate of sulfate ions of not less than 96% each time of adsorption and separation, the diatom particles need to have a relatively strong positive charge. A relatively strong positive charge requires a lower pH value, so the present invention uses dilute sulfuric acid with a pH value of less than 0. The purified and modified diatomite is used to adsorb and separate sulfate ions and hydrogen ions. When the pH value of the mixed solution of diatomite and dilute sulfuric acid is less than 2, the surface and pore walls of the diatomite are positively charged. As the pH value decreases, the silicon hydroxyl groups on the diatomite are severely protonated, and the hydroxyl groups receive a large number of hydrogen ions (the law of conservation of matter: the hydrogen ions in the diatomite are replaced). The strength of the positive charge of the diatomite gradually increases, and the speed and quantity of adsorption of sulfate ions are increasing. Positive and negative charge adsorption forms a relatively stable flocculant, which sinks according to the properties of the diatomite, and the flocculants are completely precipitated, and liquid-solid separation produces hydronium ions.

[0059] The equation and structural formula for the adsorption and separation of sulfate and hydrogen ions by diatomaceous earth (8) Diatomaceous earth molecular structure

[0060] (9) Sulfuric acid molecular structure Adsorption separation, ion exchange, displacement reaction SiO2+sulfuric acid=SiO2 + +SO4 -+2H + Further (SiO2:SO4)(mixture)+2H + Water is a polar molecule, which makes sulfuric acid dissolve and disperse. Then the complex H3O+ is stronger than HSO4 - Stable and easier to exist.

[0061] The sulfuric acid used is usually 98% grade. The amount of sulfuric acid substance can be in the range of 1 mol to 4 mol / L. Its application is specific. The diatomaceous earth in the mixed solution water is taken as diatomaceous earth with the mass of sulfate ion. The molar mass of sulfuric acid is about 98g / mol, so the mass of 1 mol of pure sulfuric acid is 98g, the hydrogen ion is 2 grams, and the sulfate ion is 96 grams, see Table 1.

[0062]

[0063] The method for preparing hydroxide ion solution by diatomaceous earth adsorption is as follows: First, prepare 1000 ml of 0.1 mol / L NaOH solution: Calculate the mass of sodium hydroxide required: You need to prepare 1000mL (1L) of 0.1mol / L sodium hydroxide solution. According to the formula C = n / V, where C is the concentration (mol / L), n is the amount of substance (mol), and V is the volume (L), you can calculate the amount of substance required. n = C × V = 0.1mol / L × 1L = 0.1mol. The molar mass of sodium hydroxide is 40.00 g / mol. Therefore, the mass of sodium hydroxide required is 0.1mol × 40.00 g / mol = 4.00 g.

[0064] Calculate the pH value of 0.1 mol / L NaOH solution: pH=14+lgC(OH - ) 0.1mol / L NaOH pH=14+lg0.1=13 The method for further producing hydroxide ions is: (1) Mix 0.1 mol / L NaOH solution and diatomaceous earth in proportion and stir rapidly for 10 minutes.

[0065] (2) The mixed solution is allowed to settle and the supernatant is collected.

[0066] (3) Detect the metal ion content in the supernatant, then add diatomaceous earth according to the metal ion content and stir to adsorb until the supernatant meets the hydroxide ion solution index.

[0067] (4) The inorganic strong base may be sodium hydroxide, potassium hydroxide, calcium hydroxide or barium hydroxide.

[0068] (5) The particle size distribution of diatomaceous earth after purification is 50 microns to 70 microns, and the diatom particle content is not less than 92%.

[0069] (6) In the obtained hydroxide ion solution, metal ions are less than 5% (mass ratio) and pH is greater than 12.

[0070] From the chemical structure of diatomite, we know that diatomite is weakly acidic and is a solid acid. The porosity and negative charge of the diatomite surface make it show obvious surface adsorption. There are also a large number of silanol groups (mixtures) on the surface of diatomite. These silanol groups exist in the numerous micropores of diatomite, which is also an important reason why diatomite has adsorption properties. The adsorption performance of diatomite is closely related to the number of hydroxyl groups carried on its surface and micropores. Some hydroxyl groups lose hydrogen ions due to hydrolysis, making the surface of diatomite show a certain negative charge. The pH value can affect the negative charge of the surface of diatomite. In most pH ranges, the surface of diatomite is negatively charged, but under strong acidic conditions (pH < 2), the hydroxyl groups on the surface of diatomite are protonated and positively charged.

[0071] Since the zero-point charge of diatomite is 2.0, in order to achieve a removal rate of no less than 95% for each adsorption and separation of metal ions, the diatom particles need to have a relatively strong negative charge. A relatively strong negative charge requires a higher pH value, so a sodium hydroxide solution with a pH value of >12 is used to produce hydroxide ions. The purified and modified diatomite is used to adsorb and separate hydroxide ions and metal ions. When the pH value of the mixed solution of diatomite and sodium hydroxide is >12, the surface and pore walls of the diatomite are negatively charged. As the pH value increases, the silicon hydroxyl groups on the diatomite lose a large number of hydrogen ions, and the strength of the negative charge of the diatomite gradually increases, and the speed and quantity of the adsorption of metal ions are increasing. Positive and negative charge adsorption forms relatively stable flocs, which sink due to the nature of the diatomite, and the flocs are all precipitated, and liquid-solid separation produces hydroxide ions.

[0072] Using diatomite to adsorb and remove metal ions in inorganic strong bases and retain hydroxide ions is environmentally friendly, low in energy consumption and simple in process, and suitable for industrial production. This reaction is not intense and does not release excessive heat. The hydroxide ions formed are ions that exist with water as a carrier, removing the strong corrosiveness and strong oxidizing properties of inorganic strong bases, and do not produce any odor (non-volatile). During the chemical reaction, no unnecessary compounds are produced. It is effective in water over a wide range of temperatures, relatively harmless when used in excess, and can be neutralized after use. It is almost harmless in water and the environment, is environmentally compatible, and can be stored for a long time without decomposing or turning into dangerous compounds.

[0073] The beneficial effects of the present invention are as follows: 1. The present invention replaces sulfuric acid with hydrogen ions and replaces alkali with hydroxide ions. The process remains unchanged, but only the materials are replaced, so that the waste residue and wastewater of furfural production are non-toxic, harmless and pollution-free. Clean water is used to prepare acid, and furfural wastewater is no longer used to prepare acid, because there is no inhibitor to inhibit hydrogen ion catalytic hydrolysis, so that the yield of furfural is increased by 20%. 2. Hydrogen ions are used to replace sulfuric acid and hydroxide ions to replace alkali. After testing, the sulfate ion content in the furfural residue without hydrogen ions and hydroxide ions is 987mg / l, and the sulfate ion content in the furfural hydrolyzate is 1320mg / l. In contrast, hydrogen ions and hydroxide ions are used to produce furfural, and the sulfuric acid content in the furfural residue is 7.5mg / l, and the sulfate ion content in the furfural hydrolyzate is 15mg / l.

[0074] The hydrolyzate produced by using hydrogen ions and hydroxide ions to produce furfural has a variety of organic substances such as alcohols, aldehydes, ketones, esters, organic acids, etc. It basically meets the standards of wood vinegar, and can be continuously discharged in the process of furfural production, turning waste into treasure, and promoted and applied as wood vinegar.

[0075] The furfural residue produced by using hydrogen ions and hydroxide ions to produce furfural husks mainly contains 90% organic matter, 11.5% humic acid, 0.36% phosphorus (P2O5), 1.18% potassium, 0.61% ammonia, 3.34% acetic acid, etc. Its composition determines the core position of furfural residue in organic fertilizer. Turn waste into treasure and promote its application as the main material of organic fertilizer. The furfural residue and hydrolyzate produced by the production of furfural by sulfuric acid-catalyzed hydrolysis contain a large amount of inorganic acids and inorganic salts, which become waste residues and wastewater. Secondary environmental protection treatment of them increases the production cost of furfural.

[0076] Furfural is produced using hydrogen ions and hydroxide ions, and furfural wastewater is no longer used to prepare acid. Because there is no inhibitor to inhibit hydrogen ion catalytic hydrolysis, the furfural yield is increased by 20%, and waste residues and wastewater are turned into treasures.

[0077] The embodiments of the present invention will be described in further detail below with reference to examples. DETAILED DESCRIPTION Example

[0078] Traditional method of producing furfural. Take 1000g of crushed corn cob particles (particles <0.15mm), put the corn cob particles into a hydrolysis kettle, and add 5% sulfuric acid diluted with ordinary water as a catalyst. The solid-liquid ratio of the two is 1:0.5, and then heat, the temperature is usually 180~190℃, and keep it for 4 hours, so that the hemicellulose in the raw material undergoes hydrolysis reaction under acid catalysis. After the hydrolysis reaction is completed, the steam in the reaction liquid is condensed and refluxed through a condenser to collect furfural. At this time, furfural will be collected in the condensate together with water and other impurities. Pour the condensate into a separatory funnel and let it stand to separate. Due to the limited solubility of furfural in water, it usually separates from water. The upper layer containing furfural is separated by a separatory funnel. What is separated is crude furfural. Crude furfural contains 0.4% acetic acid, which is neutralized with 10% sodium carbonate solution. Then, the furfural is distilled under reduced pressure using a rotary evaporator to further purify the furfural. During the distillation process, pure furfural can be collected according to the boiling point of furfural (about 161.7℃). According to the test, 1000g corn cobs are hydrolyzed by 5% sulfuric acid to produce 100g furfural, 1200g furfural residue, and 2400g furfural wastewater. According to the test, the sulfate ion content in the furfural residue is 987mg / l, and the sulfate ion content in the furfural hydrolyzate is 1320mg / l. Example

[0079] Another traditional method for producing furfural. Take 1000 grams of crushed corn cob particles (particles <0.15mm), put the corn cob particles into a hydrolysis kettle, and add 4% sulfuric acid diluted with the wastewater of Example 1 as a catalyst. The solid-liquid ratio of the two is 1:0.4, and then heat, the temperature is usually 180~190℃, and keep it for 4 hours, so that the hemicellulose in the raw material undergoes hydrolysis reaction under acid catalysis. After the hydrolysis reaction is completed, the steam in the reaction liquid is condensed and refluxed through a condenser to collect furfural. At this time, furfural will be collected in the condensate together with water and other impurities. Pour the condensate into a separatory funnel and let it stand for stratification. Due to the limited solubility of furfural in water, it usually separates from the water layer. The upper layer containing furfural is separated by a separatory funnel. What is separated is crude furfural. The crude furfural contains 0.4% acetic acid, which is neutralized with 10% sodium carbonate solution. Then, the furfural is subjected to reduced pressure distillation using a rotary evaporator to further purify the furfural. During the distillation process, pure furfural can be collected according to the boiling point of furfural (about 161.7℃). According to the test, 1000g corn cobs were catalytically hydrolyzed with 5% sulfuric acid diluted with furfural wastewater to produce 98g furfural, 1300g furfural residue, and 2400g furfural wastewater. According to the test, the sulfate ion content in the furfural residue was 997mg / l, and the sulfate ion content in the furfural hydrolyzate was 1380mg / l. Example

[0080] A method for producing furfural using hydrogen ions and hydroxide ions, taking 1000 grams of crushed corn cob particles (particles <0.15mm), putting the corn cob particles into a hydrolysis kettle, adding 3% hydrogen ions (hydrogen ions diluted with ordinary water) as a catalyst, and the pH value of the hydrogen ion solution at this time is 0. The solid-liquid ratio of the two is 1:0.3, and then heating, the temperature is 170~190℃, the steam pressure is 8-12kg / cm 2 , keep it for 2 hours, so that the hemicellulose in the raw material undergoes a hydrolysis reaction under the catalysis of hydrogen ions. After the hydrolysis reaction is completed, the steam in the reaction liquid is condensed and refluxed through a condenser to collect furfural. At this time, furfural will be collected in the condensate together with water and other impurities. Pour the condensate into a separatory funnel and let it stand to separate. Due to the limited solubility of furfural in water, it usually separates from the water layer. The upper layer containing furfural is separated by a separatory funnel. The crude furfural separated contains 0.4% acetic acid and 0.8% sulfite, which is neutralized with 30 ml of a hydroxide ion solution with a pH value of 12. Then, the furfural is distilled under reduced pressure using a rotary evaporator to further purify the furfural. During the distillation process, pure furfural can be collected according to the boiling point of furfural (about 161.7°C).

[0081] According to the test, 1000g corn cob produced 124g furfural, 1000g furfural residue and 2000g furfural wastewater after catalytic hydrolysis with 3% hydrogen ion liquid. According to the test, the sulfate ion content in furfural residue was 16mg / l (sulfate remained in hydrogen ion liquid), and the sulfate ion content in furfural hydrolyzate was 38mg / l (sulfate remained in hydrogen ion liquid).

[0082] Comparison of the effects of the embodiments Example 1: After testing, 1000 grams of corn cobs were catalytically hydrolyzed with sulfuric acid diluted with ordinary water to produce furfural, producing 100 grams of furfural, 1200 grams of furfural residue, and 2400 grams of furfural wastewater. After testing, the sulfate ion content in the furfural residue was 987 mg / l, and the sulfate ion content in the furfural hydrolyzate was 997 mg / l. Example 2: After testing, 1000 grams of corn cobs were catalytically hydrolyzed with sulfuric acid diluted with furfural wastewater to produce furfural, producing 98 grams of furfural, 1300 grams of furfural residue, and 2400 grams of furfural wastewater. After testing, the sulfate ion content in the furfural residue was 997 mg / l, and the sulfate ion content in the furfural hydrolyzate was 1380 mg / l. Example 3: After testing, 1000 grams of corn cobs were hydrolyzed by 3% hydrogen ion liquid to produce 124 grams of furfural, 1000 grams of furfural residue, and 2000 grams of furfural wastewater. After testing, the sulfate ion content in the furfural residue was 16 mg / l (sulfate remained in the hydrogen ion liquid), and the sulfate ion content in the furfural hydrolyzate was 38 mg / l (sulfate remained in the hydrogen ion liquid).

[0083] See Table 2 for comparison.

[0084]

[0085] Conclusion: Example 3 of the present invention uses hydrogen ions instead of sulfuric acid and hydroxide ions instead of alkali. The process is similar, but the materials are replaced, so that the yield of furfural is increased by more than 20%. The waste residue from producing furfural contains lower sulfate ions, the wastewater contains lower sulfate ions, and it is non-toxic, harmless and pollution-free.

[0086] The above description is only a specific implementation mode of the present invention, and various examples do not constitute a limitation on the essential content of the present invention.

Claims

1. A method for producing furfural using hydrogen ions and hydroxide ions, characterized in that The following steps are involved: (1) Prepare the materials: take corn cobs, wash, dry and crush into corn cob particles; (2) Mixing: Weigh the prepared corn cob particles, mix the corn cob particles with the hydrogen ion solution prepared with clean water in a solid-liquid ratio of 1:0.3-0.6, and adjust the mixing until the hydrogen ions in the corn cob particles reach a saturated state; (3) The corn cobs that have reached a hydrogen ion saturation state are subjected to a hydrolysis reaction in a hydrolysis pot to be hydrolyzed into pentose, and then the hydrogen ion hydroxyl groups are protonated and dehydrated to produce furfural; (4) The furfural generated after the hydrolysis reaction is immediately blown out with steam; (5) Steam treatment and condensation: The aldehyde vapor discharged from the hydrolysis pot enters the distillation tower for distillation, and the aldehyde vapor enters the condenser for condensation to obtain a dilute furfural solution; (6) Distillation: The dilute furfural solution is sent to a distillation tower for distillation; (7) The steam drawn out from the top of the distillation tower enters the condenser and enters the crude furfural collector after condensation; (8) neutralizing the acid in the crude furfural by adding hydroxide ions; placing the crude furfural into a stirred neutralization pot, adding a hydroxide ion solution in an amount of 3% of the crude furfural, stirring, standing, and then refining; (9) Refining: The furfural is refined by vacuum distillation or steam distillation. The purity of the refined furfural is above 99%, and the acid content is above 0.01%.

2. A method for producing furfural using hydrogen ions and hydroxide ions according to claim 1, characterized in that The pH value of the hydrogen ion solution in step (2) is 0; and the pH value of the hydroxide ion solution in step (8) is 12.

3. A method for producing furfural using hydrogen ions and hydroxide ions according to claim 1 or 2, characterized in that The temperature used in step (3) is 170-190°C and the steam pressure is 8-12 kg / cm 2 The hydrolysis reaction time to produce aldehyde is 1-4 hours.

4. A method for producing furfural using hydrogen ions and hydroxide ions according to claim 3, characterized in that In the step (7), during operation, the top temperature of the distillation tower is maintained at 94-97°C, the bottom temperature is maintained at 98-102°C, and the distillate temperature is maintained below 55°C.

5. A method for producing furfural using hydrogen ions and hydroxide ions according to claim 1, characterized in that The steps of the preparation method of the hydrogen ion are as follows: (1) Mixing a dilute sulfuric acid solution and diatomaceous earth in equal proportions, stirring, and standing, taking a supernatant; and detecting the supernatant with a sulfate ion detector; (2) Based on the test data, an equal amount of diatomaceous earth is added to the residual sulfate in the supernatant, and then the above step (1) is repeated, and the extraction is cyclically performed until the sulfate in the supernatant is less than 1%; (3) Diatomaceous earth purification: Use diatomaceous earth to produce hydrogen ions. Select raw ores from Linjiang and Changbai, Jilin, which contain more than 88% diatomaceous earth particles and have a whiteness of more than 85%, and purify them using the scrubbing method.

6. A method for producing furfural using hydrogen ions and hydroxide ions according to claim 1, characterized in that The steps of the method for preparing the hydroxide ion solution are as follows: (1) Mix an inorganic strong alkali solution and diatomaceous earth in proportion, stir, let stand, and take the supernatant; (2) Detect the metal ion content in the supernatant, then add diatomaceous earth according to the metal ion content and stir to adsorb until the supernatant meets the hydroxide ion solution index; that is, the obtained hydroxide ion solution has a metal ion content of <5% and a pH value of >12.

7. A method for producing furfural using hydrogen ions and hydroxide ions according to claim 6, characterized in that The inorganic strong base is sodium hydroxide, potassium hydroxide, calcium hydroxide or barium hydroxide.

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