165 results about "Levulinic acid" patented technology

The invention relates to the field of genetic engineering, in particular to a genetically engineered bacterium for efficiently synthesizing 5-aminolevulinic acid. According to the invention, a synthetic biological technology and a genetic engineering means are utilized, escherichia coli E.coli BL21 (DE3) is taken as an original strain, a C5 way of the escherichia coli E.coli BL21 (DE3) is modified, and degradation of glutamic acid is reduced by knocking out a gadA gene and replacing a promoter of an argE gene; the synthesis of the 5-aminolevulinic acid is increased by enhancing the expression of gdhA, hemAS and hemL genes, replacing promoters and increasing the carbon flux flowing to the 5-aminolevulinic acid; in addition, by knocking out acetic acid synthesis genes ackA, poxB and pta, the loss of carbon flux flowing to TCA circulation is reduced, so that the purpose of increasing the yield of 5-aminolevulinic acid is achieved.

The invention belongs to the technical field of anhydrous emulsions, and discloses an anhydrous self-emulsifying drug-loaded emulsion based on a deep eutectic solvent and a preparation method thereof.The preparation method comprises the following steps that 1, betaine and a hydrogen bond donor are mixed, the deep eutectic solvent is prepared through a mixed heating method, a drug is dissolved in the deep eutectic solvent, and a drug solution is prepared; the hydrogen bond donor is levulinic acid or lactic acid; (2) mixing Tween 80 and Span 80 according to a mass ratio of (1-2): 1 to obtain a surfactant, adding absolute ethyl alcohol as a co-emulsifier, adding isopropyl myristate, and uniformly stirring and mixing to obtain a dispersion liquid; and (3) dropwise adding the drug solution in the step (1) into the dispersion liquid in the step (2), and stirring at the same time to finally form the anhydrous self-emulsifying drug-loaded emulsion. According to the invention, the loading capacity, the stability and the bioavailability of the medicine can be obviously improved; in addition, the efficiency of transdermal drug delivery of the emulsion is high, and the emulsion can be applied to skin external preparations.

The invention belongs to the field of food fresh-keeping materials, and particularly relates to a deep-eutectic propolis extract and CS / DPE composite film, a preparation method thereof and application of the deep-eutectic propolis extract and CS / DPE composite film in fresh-keeping films. The preparation method of the deep-eutectic propolis extract comprises the following steps: propolis is subjected to extraction treatment by adopting a deep-eutectic mixed solution containing a deep-eutectic solvent and water, the deep-eutectic solvent is a mixture of betaine and levulinic acid, and the extraction condition is that the polyphenol content in the obtained extracting solution is 25 mg / g or above and the flavone content is 250 mg / g or above; the obtained extracting solution is the eutectic propolis extract. The preparation method of the food preservative film comprises the following steps: mixing a chitosan solution and the eutectic propolis extract, casting to form a film, standing, and drying to obtain the food preservative film. The eutectic propolis extract obtained by the method provided by the invention is rich in polyphenols and flavones, and the mechanical property of the chitosan-based preservative film can be improved and the preservation effect on foods can be prolonged when the eutectic propolis extract is added into the chitosan-based preservative film.

The disclosure relates to systems and methods for the production of levulinic acid, furfural, and formic acid from feedstock materials containing cellulose and hemicellulose. The levulinic acid, furfural, and formic acid can each be produced in relatively high yield simultaneously and in the same reactor vessel.

The present invention discloses a method for co-producing bio-aviation fuel from corncobs, which comprises the following steps: screening and pulverizing corncobs to control the particle size to be 10-15 mm; mixing the pulverized corncobs with furfural production wastewater containing acetic acid for hydrolysis reaction to generate a dilute furfural solution at 195-205 °C and 1.25-1.3 MPa; subjecting the solid residue after hydrolysis to alkali treatment to separate and obtain crude cellulose; subjecting the crude cellulose to acidolysis reaction by microwave heating in a solid acid catalyst and formic acid solution to generate a dilute levulinic acid solution; catalytically polymerizing the dilute furfural solution and the dilute levulinic acid solution under the action of a copper-based catalyst to generate a C10-C15 hydrocarbon mixture; generating a C10-C15 saturated hydrocarbon liquid mixture through oil-water separation and deoxygenation and hydrogenation reaction of a nickel-based catalyst; and finally through fractional distillation and activated carbon filtration; this method realizes the efficient co-production of furfural, cellulose and bio-aviation fuel from corncobs, and has the advantages of high raw material utilization rate, excellent catalytic efficiency, low energy consumption and environmental friendliness.

The invention discloses a catalyst for preparing alkyl levulinate from furfuryl alcohol as well as a preparation method and application of the catalyst. The preparation method of the catalyst comprises the following steps: (1) adding precursor salt of copper and aluminum oxide into deionized water, stirring at normal temperature, then adding 2-methylimidazole, stirring at normal temperature, and finally heating and stirring to obtain a mixed solution; (2) adding sodium carbonate into the mixed solution, heating and stirring, then filtering, washing filter residues with ionized water until the filter residues are neutral, and then drying to obtain a precursor; and (3) roasting the precursor to obtain the catalyst for preparing alkyl levulinate from furfuryl alcohol. The method for preparing the alkyl levulinate by catalyzing the hydrogenolysis of the furfuryl alcohol is mild in reaction condition, the alkyl levulinate is prepared by the hydrogenolysis of the furfuryl alcohol under the mild condition, and the yield of the alkyl levulinate is relatively high.

The invention relates to a fixed bed continuous production method for preparing levulinate from furfural, and mainly solves the problems of low selectivity and incapability of continuous production of levulinate prepared from a bifunctional catalyst in the prior art. The method mainly comprises the following steps: in a fixed bed, carrying out furfural catalytic hydrogenation on a mixture of furfural, alcohol and water on an upper-layer metal catalyst to prepare furfuryl alcohol, and then catalyzing furfuryl alcohol etherification and ring opening by a lower-layer oxide catalyst to prepare levulinate. According to the method, hydrogenation of furfural and ring opening of furfuryl alcohol are separated in time and space, a fixed bed continuous production process is further utilized, levulinate can be efficiently, continuously and stably prepared, and the method can be applied to industrial production of preparing high additional products from furfural. The conversion rate of furfural in the whole reaction can reach 100%, and the total yield of levulinate is greater than 95%.

The invention belongs to the technical field of adsorption separation, and particularly relates to application of MOF-808 and / or HKUST-1 in separation of 5-hydroxymethylfurfural and impure-phase substances. According to the application, MOF-808 and / or HKUST-1 are / is used as an adsorbent, 5-hydroxymethylfurfural can be well separated from fructose, formic acid, levulinic acid and other impurities, especially HMF and LA can be separated, the selection factor reaches up to 43.8, the defect that efficient separation of the two substances is difficult to achieve in the prior art is overcome, the purity of the separated HMF is high, energy consumption is low during HMF separation, the flow rate is large, and the method is suitable for industrial production. The separation time is short.

The objective is to provide 5-aminolevulinic acid or its salts and a method for producing the same, which have fewer impurities and residual solvents and suppressed discoloration compared to conventional methods. The objective is to provide 5-aminolevulinic acid or its salts, wherein, based on peak area obtained by HPLC analysis, the ratio of the content of individual impurities to the content of 5-aminolevulinic acid or its salt is 0.0007 or less, and the sum of the ratios of the content of individual impurities to the content of 5-aminolevulinic acid or its salt is 0.0016 or less.

The invention relates to the technical field of chemical substance preparation, and particularly discloses preparation equipment and a preparation method of 5-aminolevulinate, the preparation equipment comprises a preparation table, and further comprises a feeding unit arranged on the preparation table; the screening unit is arranged below the feeding unit; through the arrangement of the feeding bin, crushing of raw materials can be achieved, meanwhile, the raw materials can be screened during crushing, secondary screening is conducted through the screening bin below after screening, meanwhile, through the arrangement of the first driving unit and the moving unit, the screening bin can be driven to move while feeding is conducted, and in the back-and-forth moving process, the screening efficiency is improved. The feeding bin and the screening bin are impacted by the moving strips to generate vibration, so that the screening efficiency of the feeding bin and the screening bin is improved, raw materials clamped on the screening holes and the screening plate can be vibrated off through impact, the raw materials can be cleaned without shutdown, the caked raw materials can be crushed in the impact process, and the screening efficiency is improved. And therefore, subsequent screening work is facilitated.

The invention discloses a method for synthesizing a pyrrolidone compound by reductive amination of biomass-based levulinic acid and derivatives thereof, which comprises the following steps: taking a stainless steel high-temperature reaction kettle as a reaction container, respectively adding 0.5-20 mmol of biomass-based levulinic acid or derivatives thereof, 10-200 mg of catalyst and 0.1-1 mL of ammonia water into 5-10 mL of solvent, and sealing the reaction container, the mass concentration of the ammonia water is 28%; the method comprises the following steps: introducing hydrogen into a stainless steel high-temperature reaction kettle, pressurizing to 0.1-5 MPa, reacting at 40-120 DEG C for 0.1-8 hours, putting the reaction kettle into water, cooling to room temperature, deflating, additionally adding 0.5-5 mmol of toluene as an internal standard, and carrying out solid-liquid separation by using a needle type organic filter to obtain the target product 5-methyl-N-methyl-2-pyrrolidone. The method has the advantages of simple reaction system, mild conditions, no pollution to the environment, high efficiency, energy saving, low cost, few byproducts, high yield and high selectivity, and can realize green closed loop from raw materials to products.

The invention relates to a solvent composition comprising at least one specific levulinic acid ester as a first solvent and at least one specific amide ester as a second solvent. The invention also relates to the use of the solvent composition for producing agrochemical formulations and to the agrochemical formulations themselves.

The present invention discloses a biochar-supported aluminum-zirconium dual acid type solid acid catalyst and a preparation method and application thereof, belonging to the technical field of heterogeneous solid acid catalysts. 3 ) 3 and CO 4 Zr is used as raw material, and a full solid phase method strategy of mechanical activation treatment combined with high temperature calcination is adopted to construct a biochar-loaded aluminum-zirconium double acid type solid acid catalyst. The catalyst is a double acid type solid acid catalyst of green economy, stable performance and directional catalysis, and the acid content thereof is about 3.6 μmol / g, and the Lewis acid content is about 47.7 μmol / g. The preparation method of the catalyst of the present invention is simple to operate, the raw materials are easy to obtain, the conditions are simple and mild, and the production cost is low. The catalyst of the present invention is applied to catalyze cellulose to prepare levulinic acid, the conversion rate of cellulose can reach 97.5%, and the yield of levulinic acid can reach 67.5%, which has a good application prospect for efficiently converting cellulose to prepare levulinic acid, and has important research significance for effectively promoting the high value utilization of cellulose resources.

The invention discloses a preparation method for synthesizing 2, 5-furandimethanol (BHMF) from biomass saccharides through a one-pot method based on a water-phase catalysis system, and belongs to the technical field of chemical synthesis. According to the method, in a single water phase reaction system, efficient catalytic conversion is realized through two key steps of integrating biomass sugar dehydration to generate 5-hydroxymethylfurfural (HMF) and biologically reducing HMF to convert into BHMF. Wherein in the dehydration reaction stage, an acid catalyst is adopted, and a polyethylene glycol additive is introduced, so that the yield of HMF is remarkably increased, the generation of by-products levulinic acid and formic acid is effectively inhibited, and the toxic influence of the by-products on thalli in the subsequent reduction stage is reduced; meanwhile, due to the excellent biocompatibility, the inhibition effect on the thallus activity in the whole-cell catalytic reduction process is avoided. The innovative design ensures the continuity and system compatibility of the whole catalytic process, and realizes an efficient and stable catalytic conversion process.

The invention belongs to the technical field of biomass chemical industry, and particularly relates to a technological method for preparing levulinic acid through furfural residue hydrolysis. The process method comprises the following steps: S1, connecting three hydrolysis reaction kettles in series, and arranging a set of filtering device between every two stages of reaction kettles; s2, filling furfural residue raw materials into each stage of hydrolysis reaction kettle; s3, injecting a mixed acid solution of dilute sulfuric acid and dilute phosphoric acid into the primary hydrolysis reaction kettle, performing hydrolysis, and filtering hydrolysate after hydrolysis is completed; the hydrolysate enters a secondary hydrolysis reaction kettle, and the hydrolysis reaction of the secondary hydrolysis reaction kettle is started; the hydrolysate is filtered and then enters a third-stage hydrolysis reaction kettle, and the third-stage hydrolysis reaction kettle is started for hydrolysis reaction; s4, hydrolysate of the third-stage hydrolysis reaction kettle is filtered and then enters an extraction device, and after extraction separation, the water phase part returns to the first-stage hydrolysis reaction kettle to be used for hydrolysis of the next batch of furfural residues; the organic phase part is precisely filtered, filtrate enters a rectification device, and the levulinic acid product is obtained through separation of the rectification device.

The invention provides a wild jujube pulp polyphenol extraction process based on a deep eutectic solvent. The deep eutectic solvent (DES) technology is adopted to optimize the extraction process of the wild jujube pulp polyphenol, and the antioxidant activity of the extracted wild jujube pulp polyphenol is evaluated. According to the method, five different eutectic solvents are prepared and screened, and choline chloride / levulinic acid (ChCl / LA) is determined as the optimal solvent of wild jujube pulp polyphenol. Through single factor and orthogonal experiment optimization, the optimal extraction conditions of the wild jujube pulp polyphenol are determined as follows: the water content is 10%, the extraction time is 40 min, the extraction temperature is 60 DEG C, the material-liquid ratio is 1: 30 g / mL, and the polyphenol yield can reach 10.5 mg / g and is increased by 1.6 times compared with that before optimization. The method provides a technical path for green and efficient extraction and high-valued utilization of wild jujube pulp polyphenol, and provides reference for deep application of DES in plant resources.

The present invention relates to a method for preparing 2-methyltetrahydrofuran using a mixture of compounds derived from lignocellulosic biomass, a catalyst used therefor, and a method for preparing the catalyst. According to the present invention, 2-methyltetrahydrofuran can be prepared in high yield from a mixed lignocellulosic biomass-derived compound by performing a hydrogenation dehydration reaction using a furfural compound and a levulinic acid compound as reactants, and the effect can be maximized through optimization of the composition and reaction conditions of the reactants. In addition, the selectivity of 2-MTHF can be further improved by using a catalyst in which nickel and copper, which are non-noble metal-based materials, are supported on an acid support in the reaction.

The application discloses a polyacid zeolite imidazolate framework loaded monatomic catalyst and a preparation method and application thereof, and belongs to the technical field of catalysts. The preparation method of the catalyst is as follows: (1) preparing a zeolite imidazolate framework material; (2) mixing the dried zeolite imidazolate framework material and a metal salt in a solvent and stirring; then adding a heteropoly acid, controlling the pH in the system to be 5-7, and performing a solvothermal reaction under the condition of 80-120 DEG C; after the reaction is completed, cooling and centrifugal separation are performed to obtain a precipitate; and (3) performing calcination treatment on the precipitate to obtain the polyacid zeolite imidazolate framework loaded monatomic catalyst. The polyacid zeolite imidazolate framework loaded monatomic catalyst prepared by the method has high catalytic activity, high selectivity and good cycle stability, and has a good application prospect in acetyl propionate esterification reaction.

The invention discloses a method for electrically synthesizing 5-aminolevulinic acid by using pichia pastoris. According to the method, based on construction of pichia pastoris for reducing a glycine pathway and a 5-ALA synthesis pathway, a microbial electrochemical system is used for providing external electric energy to realize electric synthesis of 5-ALA. According to the method, pichia pastoris is selected as a research object, an efficient carbon sequestration glycine reduction pathway and a 5-ALA generation pathway are constructed in the earlier stage, the recombinant pichia pastoris is applied to a microbial electrochemical system, formic acid or CO2 is used as a carbon source, electric energy supplied by the microbial electrochemical system is used as an energy source, and the microbial electrochemical system is constructed. And the generation condition of the pichia pastoris 5-ALA under the electric energy condition is researched.

The utility model relates to the technical field of content detection, and discloses an accurate detection device for the content of 5-aminolevulinic acid, which solves the problem that a 5-aminolevulinic acid sample and a reagent are not uniformly mixed at present, and comprises a base, a detection cylinder is arranged right above the base, a stirring mechanism is arranged between the base and the detection cylinder, and the stirring mechanism is connected with the detection cylinder. The stirring mechanism comprises an L-shaped frame fixed at the top of the base; according to the device, through the cooperation between the motor and the transmission shaft as well as between the conveyor belt and the stirring shaft, the stirring rod rotates to stir a solution in the detection cylinder, through the cooperation between the bevel gear I and the bevel gear II as well as the driven shaft, the disc rotates conveniently, and through the cooperation between the driving rod and the sleeve plate as well as the cooperation between the U-shaped round rod and the U-shaped plate, the detection efficiency is improved. The detection barrel can continuously move up and down conveniently, then a solution in the detection barrel can continuously move, and meanwhile, the position of a stirring rod in the detection barrel is changed, so that a 5-aminolevulinic acid sample and a reagent can be uniformly mixed conveniently.

The invention belongs to the technical field of metal surface treatment, and discloses a high-permeability and low-corrosion die-casting aluminum degreasing agent as well as a preparation method and application thereof. The die-casting aluminum degreasing agent comprises an active matter and water, the active matters comprise 6 to 10 percent of organic weak acid, 0.5 to 1.5 percent of chitosan oligosaccharide, 0.5 to 1.2 percent of tea polyphenol, 0.7 to 1.8 percent of curcumin, 4 to 6 percent of surfactant, 0.4 to 1.0 percent of cyclodextrin, 0.5 to 0.8 percent of low-foaming additive, 1.0 to 2.0 percent of buffering agent, 0.6 to 1.5 percent of corrosion inhibitor and 0.2 to 0.5 percent of lipase by taking the total mass of the die-casting aluminum degreasing agent as 100 percent; the organic weak acid comprises levulinic acid, lactic acid and acetoacetic acid; the corrosion inhibitor comprises polycarboxylate and hydroxy carboxylate. The die-casting aluminum degreasing agent has excellent removal capacity for common silicone oil / ester release agents on the surface of a die-casting aluminum alloy, is low in corrosivity and does not contain phosphorus or fluorine or other components prone to polluting water.

The invention provides a separation microneedle of a loaded lipidosome nanoreactor as well as a preparation method and application of the separation microneedle, and belongs to the technical field of biological medicines. The preparation method comprises the following steps: by taking phospholipid, cholesterol, tetramethoxysilane and 3-aminopropyltriethoxysilane as raw materials, entrapping cis-platinum, 5-aminolevulinic acid and catalase to prepare a liposome nano-reactor; polyvinylpyrrolidone, citric acid, sodium bicarbonate and regenerated silk cellulose are used as raw materials, a liposome nano reactor is dispersed in a microneedle body through a pouring method, and the microneedle capable of being rapidly separated is successfully prepared. Experimental research proves that the separation microneedle has good biocompatibility and mechanical properties, can effectively break through cuticle and realizes efficient transdermal delivery of a liposome nanoreactor. The liposome nanoreactor can be locally planted in deep tumor tissues, continuously supplies oxygen through enzymatic reaction, effectively improves the difficulty of insufficient oxygen supply in tumor photodynamic therapy, and has obvious advantages and wide prospects in the aspects of skin tumor photodynamic therapy application and the like.

The present application relates to the field of metabolic engineering and microbial fermentation, and in particular to a recombinant shewanella producing 5-amino levulinic acid and its application. The present application discloses a new 5-amino levulinic acid producing strain, which is obtained by modularly modifying shewanella by synergistically expressing 5-amino levulinic acid production module genes (hemA, hemL and gltX) derived from shewanella, antioxidant module genes (katE, sodB) derived from escherichia coli, and introducing inhibition modules (the inhibition genes are hemB2 and sucA), so that the shewanella can efficiently produce 5-amino levulinic acid, and the yield of 5-amino levulinic acid can be increased by 134.0 times compared with the original strain.

The invention belongs to the technical field of fine chemistry, and discloses a migration-resistant ABS resin lubricant and a preparation method and application thereof.The migration-resistant ABS resin lubricant is prepared by taking levulinic acid and fatty alcohol as raw materials, obtaining levulinic acid ester through esterification reaction and then conducting ketalation reaction. The migration-resistant ABS resin lubricant has better intermiscibility with ABS resin, and a corresponding ABS product has good mechanical properties, melt flowability and migration resistance; and the migration-resistant ABS resin lubricant takes the bio-based compound levulinic acid as the main raw material, so that the dependence on petrochemical raw materials is avoided, and the use of the bio-based raw materials is improved.

The utility model discloses a 5-aminolevulinic acid separation and purification device which comprises a base, a controller is installed on the front face of the base, a rotation driving assembly is installed at the top end of the base, a centrifugal separation assembly is arranged above the base and comprises a centrifugal barrel, a piston plate is movably installed in the centrifugal barrel, and the piston plate is movably installed on the base. The outer wall of the piston plate is tightly attached to the inner wall of the centrifugal barrel, a hanging plate is installed at the top end of the piston plate, two vertical plates are symmetrically installed at the bottom end of the hanging plate and symmetrically arranged on the two sides of the centrifugal barrel, and transverse plates are fixedly installed at the bottom ends of the vertical plates; according to the centrifugal separation device, in the working process, the centrifugal cylinder is filled with a set solution, after the centrifugal cylinder rotates, the solution enters the liquid storage tank through the screening holes under the action of centrifugal force, solid crystals are left in the centrifugal cylinder, separation is convenient, and meanwhile the piston plate moves upwards while centrifugation is conducted; and the solution is continuously pushed upwards to the height flush with the screening holes, so that a large amount of solution can be conveniently separated.

Levulinic acid and formic acid are valuable chemical intermediaries present in byproducts of some biomass conversion processes. Described herein are commercially viable processes for extracting levulinic acid and formic acid at high recovery. Under the present approach, levulinic acid and formic acid may be extracted from an aqueous reactor product, such as an acidic brine (e.g., calcium chloride brine) feed from a biomass hydrolysis reaction. If present, mineral acid catalysts may be recovered. Embodiments use solvents such as, e.g., 2-methyl tetrahydrofuran, for extracting levulinic acid and formic acid from the aqueous solution.

The invention belongs to the technical field of carbon nanosphere preparation, and particularly relates to a monodisperse core-shell structure adjustable carbon nanosphere and a preparation method thereof. According to the preparation method, a reaction kettle and a high-pressure feeding pump are combined, glucose hydrothermal carbonization (HTC) is utilized, the hydrothermal carbon nanospheres with excellent dispersity are obtained, accurate control over the form and structural characteristics of the carbon nanospheres can be achieved by adjusting feeding kinetics, reaction time and the concentration of formic acid (FA) and levulinic acid (LA), and the preparation method is suitable for industrial production. This is because FA can promote core formation by accelerating dehydration and condensation reactions, and LA can promote shell growth by aldol condensation and crosslinking. Compared with the traditional HTC method, the preparation method disclosed by the invention does not use any catalyst and template, fully utilizes the inherent advantages of HTC, such as low energy consumption requirement and biomass compatibility, and can be used for preparing the monodisperse CNS with the core-shell structure and the polydispersity index of 0.008.

The invention provides a cleaning solution for a semiconductor chip after chemical mechanical polishing, and a preparation method and application thereof, the cleaning solution for the semiconductor chip after chemical mechanical polishing comprises the following components by mass: 5-20 parts of a strong base; 5-30 parts of a weak base; 0.5-3 parts of a cellulose derivative; 0.5 to 2 parts of a chitin derivative; and 70-95 parts of ultrapure water. The cellulose derivative is one or more of 2, 5-furandicarboxylic acid, levulinic acid and 5-aminolevulinic acid. The chitin derivative is one or more of chitosan oligosaccharide, carboxymethyl chitosan, N-acetyl glucose, glucosamine and carboxymethyl glucosamine. According to the cleaning solution for the semiconductor chip after chemical mechanical polishing, CuO generated on the surface of copper after CMP can be effectively removed, a monomolecular adsorption layer is generated on the surface of Cu, and reoxidation of the surface of Cu is effectively inhibited within waiting time, so that Vbd is prevented from being reduced, and the reliability of a gate oxide layer of an MOS (Metal Oxide Semiconductor) device is improved.

The invention discloses a herbicidal composition for improving the safety of mesosulfuron, the herbicidal composition comprises an active ingredient mesosulfuron and a safener 5-aminolevulinic acid, wherein the weight ratio of the mesosulfuron to the 5-aminolevulinic acid is 1:1 to 1:100. 5-aminolevulinic acid is added to the herbicidal composition of the invention, thereby improving the safety of mesosulfuron to crops and reducing the occurrence of phytotoxicity.

The present invention discloses a method and application for reducing the content of levulinic acid in caramel. The method for reducing the content of levulinic acid in caramel provided by the present invention comprises the following steps: S1, making a syrup having a pH of 7 to 8 undergo a caramelization reaction in a reducing atmosphere, reacting to a chroma of 12000-17000EBC, and obtaining a preliminary caramel; S2, adjusting the pH of the preliminary caramel to 8 to 9, performing a secondary caramelization reaction in a reducing atmosphere, reacting to a pH of 5 to 7, and obtaining a caramel. The present invention is carried out by two caramelization reactions under alkaline conditions, so that levulinic acid is produced later and in less amount; meanwhile, the reaction is carried out in a reducing atmosphere, and levulinic acid can be deacetylated to generate ethanol and sodium propionate, thereby further reducing the content of levulinic acid in caramel, and ensuring that the caramel has good product quality, such as good red index and salt tolerance.