Methods and applications for catalytically converting glycerin into high-value-added products

Abstract

This invention provides a method for obtaining high-value-added compounds from residual glycerin derived from biodiesel synthesis. [Solution] The present invention facilitates the effective conversion of residual glycerin derived from biodiesel production to formic acid with high selectivity and stability in a heterogeneous catalytic reaction method using a synthetic silica-based catalyst in a continuous flow reaction. Even in the absence of a catalyst, it is possible to verify the production of high value-added products only in the presence of an oxidizer. In this case, the conversion of residual glycerin by a homogeneous catalytic reaction is carried out by the action of residual components derived from biodiesel synthesis, and major compounds such as formic acid, cyclic ethers, and diglycerin are formed in the continuous flow reaction and reflow reaction. In commercially available homogeneous catalytic conversion processes for glycerin, the reaction is also carried out by adding a sodium salt.

Description

Technical Field

[0001] An object of the present invention is to obtain high value-added compounds from residual glycerin derived from biodiesel synthesis.

[0002] The method of the present invention comprises conversion of glycerin through two catalytic processes: (i) a heterogeneous catalytic reaction using an acidic mesoporous silica catalyst (which does not use metals), and (ii) a homogeneous catalytic reaction where the used catalyst becomes an impurity of the residual glycerin after the addition of an oxidizing agent. The obtained product can be used, for example, for applications in the petrochemical field, based on the properties of the formed molecules.

[0003] The method applied in the present invention evaluates residual glycerin without requiring purification before conversion via the reaction used.

Background Art

[0004] Improvements to biodiesel production have attracted extensive interest worldwide, and Brazil is no exception. This is because the production still has several limitations, such as the generation of a large amount of glycerin as a by-product.

[0005] In December 2004, the Federal Government of Brazil established the National Program for the Production and Use of Biodiesel (PNPB), which aims to introduce biodiesel into Brazil's energy matrix. As of 2004, the addition of biodiesel to fossil diesel was still experimental, and 2% biodiesel was added to mineral diesel. However, in January 2008, the 2% biodiesel addition became mandatory, resulting in a fuel called B2 (ANP, 2018). This percentage has gradually increased, and the mandatory percentage reached 10% in March 2018. Due to several studies that have been conducted, this percentage may reach 15% in 2019 (ANP, 2018).

[0006] Given this situation, and because compounds obtained by converting residual glycerin, a byproduct of biodiesel, have high market value, new technologies that can significantly contribute to this important objective are constantly being sought.

[0007] The present invention aims to obtain high-value-added compounds from residual glycerin derived from biodiesel synthesis. The method of the present invention includes the conversion of glycerin by a heterogeneous catalytic reaction using a silica catalyst without the presence of metal, and the conversion by a homogeneous catalytic reaction in which the used catalyst becomes an impurity of residual glycerin when an oxidizing agent is added.

[0008] Several studies have highlighted the importance of obtaining higher value-added new products from glycerin. In "Selective oxidation of glycerol to formic acid catalyzed by iron salts," Catalysis Communications, Vol. 84, May 24, 2016, pp. 1-4, the glycerin conversion reaction is carried out by a homogeneous catalytic reaction using hydrogen peroxide as the oxidizing agent and an iron-based catalyst solubilized in acetonitrile, as used in the conversion of commercially available glycerin. In this invention, impurities present in residual glycerin from biodiesel production in the presence of hydrogen peroxide can promote the conversion of glycerin into related high-value products, thus eliminating the need to add a catalyst to the homogeneous catalytic reaction.

[0009] The paper "Oxidation of hydroxyacetone (acetol) with hydrogen peroxide in acetonitrile solution catalyzed by iron(III) chloride," Journal of Molecular Catalysis A: Chemical, Vol. 422, February 11, 2016, pp. 103-114, addresses the oxidation of acetol (1-hydroxypropanone) by a homogeneous catalytic reaction. The main objective is to produce industrially interesting compounds such as formic acid and acetic acid. To this end, the authors started with solutions of acetol, FeCl3, and H2O2 at specified concentrations and used acetonitrile as the solvent in a batch reactor to obtain satisfactory amounts of acetic acid, formic acid, and CO2. In this invention, since the substrate impurities act as a catalyst in a homogeneous process, there is no need to add a catalyst to produce industrially interesting compounds; only hydrogen peroxide is required. Also, unlike the cited paper, water is used as the solvent.

[0010] The paper "Nb and V-modified silicate for conversion of glycerol: Comparison between the waste and commercial product," Catalysis Today, Vol. 289, September 22, 2016, pp. 258-263, demonstrates that a heterogeneous catalytic reaction can be used to obtain high-value-added products using both commercially available glycerol and residual glycerol from biodiesel production as substrates. Unlike the present invention, the reaction is carried out in a batch reactor using Nb and V catalysts supported on silica, yielding allyl alcohol as the main product when commercially available glycerol is used as the substrate, and acetone as the main product when residual glycerol is used as the substrate.

[0011] The paper "Oxidation of bio-renewable glycerol to value-added chemicals through catalytic and electro-chemical processes," Applied Energy, Vol. 230, September 2, 2018, pp. 1347-1349, refers to a review of several studies that have investigated the conversion of glycerol molecules into various products. Due to the versatility of this molecule, several products can be obtained by changing the process (homogeneous, heterogeneous, electrochemical catalysts, etc.) and the type of catalyst used.

[0012] The article "Synthetic niobium oxyhydroxide as a bifunctional catalyst for production of ethers and allyl alcohol from waste glycerol," Journal of the Brazilian Chemical Society, Vol. 28, 2017, pp. 2244-2253, reports the synthesis of a novel niobium catalyst and its use in a reaction that converts waste glycerol into value-added products. The reaction used a batch reactor, the niobium catalyst, hydrogen peroxide as an oxidizing agent, and waste glycerol to preferably yield allyl alcohol and cyclic ethers. This study and the present invention differ in how the reaction is carried out by a heterogeneous catalytic reaction. In the present invention, mesoporous silica is used as the catalyst, there is no need to incorporate a metal to enhance activity, and the reaction is carried out in a reactor operating in continuous flow, simulating an industrial process.

[0013] The paper "Zirconium-modified mesoporous silica as an efficient catalyst for the production of fuel additives from glycerol," Catalys Communications, Vol. 110, February 26, 2018, pp. 1-4, describes the acetylation reaction of glycerol molecules using acetic acid. A zirconium-modified mesoporous silica catalyst was used in the reaction, and the conversion rate and selectivity of diacylglycerol and triacylglycerol to glycerol were evaluated as a function of time.

[0014] The cited studies primarily use supported catalysts to facilitate the formation of compounds such as metallate peroxides, and never alter the form of support synthesis / preparation. Furthermore, they do not mention obtaining products via the catalyst without immobilizing other elements as the active phase, for example.

[0015] Generally, the studies described in the background information only use commercially available glycerin and do not mention methods or techniques for using residual glycerin derived from biodiesel production.

[0016] Patent PI0803767-1 (Production process of glycerin mono ethers and its application as an additive for biodiesel) describes a process reporting a catalytic reaction for glycerin conversion. This study describes the selective production of glycerin mono ethers using solid acid catalysts such as zeolites. The method used involves organic solvents and harsh reaction conditions, making the industrial process very expensive.

[0017] Patent 9304714 (Degussa Corporation) (Process for the preparation of acrolein) and US20080183019 (Novel catalysts and process for dehydrating glycerol) describe the use of tungsten-based compounds, and this process is carried out at a temperature of 180 to 350°C and a pressure of 0.1 to 200 atmospheres (101.325 kPa and 20.265 MPa).

[0018] Furthermore, other patents report production processes for 1,3-propanediol, including PI9910519 (Process for bioproduction of 1,3-propanediol and transformed host cell), US5821092 (Production of 1,3-propanediol from glycerol by recombinant bacteria expressing recombinant diol dehydratase), and US5633362 (Production of 1,3-propanediol from glycerol by recombinant bacteria expressing recombinant diol dehydratase). These processes use microorganisms to convert glycerol into 1,3-propanediol.

[0019] The process developed by Shell Corporation, owner of U.S. Patent No. 6080898 (Hydrogenolysis of glycerol), uses a homogeneous catalyst based on platinum or a platinum group metal compound. EP1853541b1 (Process for dehydrating glycerol to acrolein) reports a process for producing acrolein by dehydrating glycerol in the presence of molecular oxygen.

[0020] The most commonly used routes for glycerin conversion involve homogeneous catalytic reactions using heat treatment in the presence of an inorganic acid or base, which results in low process selectivity and the production of a variety of products with low selectivity.

[0021] The method applied to this invention utilizes residual glycerin derived from biodiesel production. To obtain some of the products of this invention, silica catalysts (without immobilizing other elements as the active phase) and unprecedented experimental conditions are used. Furthermore, the reaction systems used are not reported in the background art and employ two different residual glycerin conversion reactions: semi-batch and continuous flow, using homogeneous and heterogeneous catalytic reactions.

[0022] The reaction system, catalyst, and reaction products obtained in this invention differ from those described in the background art.

[0023] The method of the present invention is innovative in that (i) it is used under mild temperature / pressure conditions and uses a pure silica heterogeneous catalyst without the need to incorporate a metal active phase, (ii) only one oxidizing agent is added and impurities present in the residual glycerin are used as a catalyst in the homogeneous catalytic reaction for the conversion of glycerin, (iii) compounds suitable for petrochemical applications, mainly formic acid and ethers, are obtained with high selectivity, and (iv) the reaction is carried out without the use of organic solvents, resulting in lower process costs and being environmentally friendly. [Overview of the project]

[0024] The present invention comprises a process for developing a pure silica catalyst and a process for converting residual glycerin and / or commercially available glycerin using an oxidizing agent via a homogeneous catalytic reaction and a heterogeneous catalytic reaction. [Brief explanation of the drawing]

[0025] The present invention will be described in more detail below with reference to the accompanying drawings, which illustrate examples of embodiments without limiting the scope of the invention.

[0026] [Figure 1] Shows the infrared absorption spectrum of the SiO₂ catalyst, wherein a) corresponds to the spectrum after pyridine adsorption, and b) corresponds to the result after addition of H₂O₂ and subsequent pyridine adsorption. Shows the Raman spectrum of the SiO₂ catalyst, wherein c) corresponds to the spectrum before treatment with H₂O₂, and d) corresponds to the result after treatment with H₂O₂. In the Raman spectrum, bands 1, 2 and 3 are attributed to different Si-O-Si vibrations, and band 4 is attributed to a new bond between silicon atoms and oxygen deposited by H₂O₂ at vacant sites of SiO₂. [Figure 2] Shows a general schematic diagram of a continuous flow reactor. The system consists of a filling container (1) to which a reaction mixture containing residual glycerin and peroxide is added, and the reaction mixture is conveyed to the reactor by a pump (2). Before the inlet of the reactor, there is a safety valve (3) that serves to control the internal pressure of the reactor. Feeding is performed at the lower part (4) of the reactor, and three thermocouples (6a, 6b, 6c) capable of controlling the temperature of different zones are arranged at the upper part (5) of the reactor. The reactor, which is placed in an oven throughout the entire reaction, is divided into three parts: Zone I, filled with an inert material (silicon carbide), is a place for preheating reagents; Zone II, where a mixture of silicon carbide and a catalyst is placed, is where the reaction proceeds; and Zone III is also filled only with silicon carbide. On one side of the reactor, at one end of Zone III, there is a gas outlet (7) connected to a condenser (8) for liquefying the reaction product, and the reaction product is recovered in a recovery flask (9) throughout the entire reaction. [Figure 3] Shows data of glycerin conversion rate and selectivity for one of the reaction products obtained from the reaction using the SiO₂ catalyst. The bars represent the glycerin conversion rate (%), and the solid line with squares represents the selectivity (%) for formic acid. [Figure 4] Shows data of glycerin conversion rate and selectivity for main reaction products. The bars represent the glycerin conversion rate (%), the solid line with squares represents the selectivity (%) for formic acid, the solid line with circles represents the selectivity (%) for diglycerin, and the solid line with triangles represents the selectivity (%) for dioxane. [Figure 5]A schematic diagram of the experimental reflow reactor used in the conversion reaction of residual glycerin is shown. The product outlet (a), H2O2 addition (b), condenser (8), magnetic plate (10), and volumetric flask (11) are identifiable. [Figure 6] The conversion data between residual glycerin (e) and commercially available glycerin (f), and the selectivity of the main reaction products in the reflow process are shown. The bars indicate the conversion rate (%) of glycerin. In (e) and (f), the square-shaped solid line indicates the selectivity (%) of formic acid, the circle-shaped solid line indicates the selectivity (%) of diglycerin, the triangle-shaped solid line indicates the selectivity (%) of dioxane, and the diamond-shaped solid line indicates the selectivity (%) of hydroxypropanone. [Modes for carrying out the invention]

[0027] The present invention aims to provide a method for obtaining high-value-added compounds from residual glycerin derived from biodiesel synthesis or from commercially available glycerin. The glycerin conversion carried out in the present invention is performed by two catalytic processes: (i) a heterogeneous catalytic reaction using a synthetic silica catalyst (without metals) that exhibits mesopores in an acidic environment, and (ii) a homogeneous catalytic reaction in which only an oxidizing agent such as benzoyl peroxide or hydrogen peroxide (H2O2) is added, and the spent catalyst becomes an impurity in the residual glycerin.

[0028] The catalytic conversion reaction targeted by this invention was carried out in a continuous flow reactor (fixed bed reactor, PBR) in a semi-batch manner at a temperature of 100 to 250°C.

[0029] Residual glycerin and commercially available glycerin were tested using flow and semi-batch systems. In homogeneous catalytic reactions, the main reaction products in the semi-batch reactor using residual glycerin were formic acid and 1-hydroxypropanone. On the other hand, in the reaction using commercially available glycerin, diglycerin was obtained as the main product. In PBR, both residual glycerin and commercially available glycerin were converted to dioxane (cyclic ether).

[0030] Furthermore, it is worth emphasizing that, even in homogeneous catalytic reactions where a catalyst is absent, using the method employed in this invention, only in the presence of an oxidizing agent, can promote the conversion of residual glycerin from commercially available glycerin through the action of residual components derived from biodiesel synthesis.

[0031] To convert commercially available glycerin, the reaction is carried out by adding sodium methylate. When using commercially available glycerin, sodium methylate provides a methoxy anion (exhibiting complementary homogeneous catalytic activity).

[0032] In heterogeneous catalytic reactions, a synthetic silica-based catalyst is used to facilitate the effective conversion of residual glycerin derived from biodiesel production to formic acid with high selectivity and stability in a continuous flow reaction.

[0033] The method described in the present invention allows for the acquisition of compounds with high selectivity, and since the reaction is carried out without the use of organic solvents, either heterogeneous or homogeneous catalytic reactions, the process is low-cost and environmentally friendly.

[0034] The catalytic conversion method for glycerin developed in this invention, in the case of heterogeneous catalytic reactions, includes a step for producing a pure silica catalyst and a subsequent conversion reaction. In homogeneous catalytic reactions of residual glycerin and / or commercially available glycerin, the formed products are formic acid and green ethers (such as diglycerin, cyclic ethers, and / or 1-hydroxypropanone), named for their acquisition from residual glycerin derived from biodiesel synthesis using 35-50% peroxide as an oxidizing agent. In heterogeneous catalytic reactions, a high specific surface area (>1000 m) is required. 2 g -1 A heterogeneous catalyst formed from pure synthetic silica (SiO2) containing acidic groups is used.

[0035] The two reactions are carried out at temperatures of 100–250°C in a continuous flow reactor and / or in a semi-batch manner.

[0036] The present invention can be better understood through the development process of pure silica catalysts and the glycerol conversion reactions by homogeneous and heterogeneous catalytic reactions, as highlighted below.

[0037] Step 1: Synthesize a pure silica catalyst. Add a solution of NaOH and CTAB (cetyltrimethylammonium bromide) to a beaker. Slowly add a solution of TEOS (tetraethyl orthosilicate) dropwise to the resulting mixture and leave the reaction system under magnetic stirring. When the formation of a white solid is observed, filter it under vacuum and wash it with distilled water until the pH becomes neutral. After filtering and washing, place the solid in an oven, immerse it to soften it, and heat treat it with a heating lamp.

[0038] Several analyses were performed on the catalyst obtained in Step 1 to evaluate its material properties. To measure the acidity, the surface of the compound was washed with an N2 stream at a temperature of 150°C, and then pyridine was adsorbed. The interaction between this basic molecule and the acidic site of the catalyst was evaluated by the presence of a specific absorption band in the infrared region, as shown in Figure 1a), where 1447 cm⁻¹. -1 The bands are related to the interaction between the pyridine molecule and Lewis acidic sites. These Lewis acidic sites are associated with the presence of empty oxygen sites on some silicon atoms.

[0039] The oxidizing properties of the catalyst are related to its ability to decompose H2O2 and the resulting deposition of oxygen atoms at empty sites of silicon atoms or oxygen atoms, as shown in Figure 1b). The presence of these oxygen atoms at Lewis empty sites was suggested by analysis of the infrared absorption spectrum of the sample after the addition of H2O2 and subsequent adsorption of pyridine (Figure 1b), and the Raman spectra of the catalyst before the addition of H2O2 (Figure 1c)) and after the addition of H2O2 (Figure 1d). The absence of Lewis acidic sites in the sample in contact with H2O2 suggests that these empty sites may be occupied. Furthermore, the presence of a band in the Raman spectrum was observed after the addition of H2O2 to the catalyst, which is thought to be due to new bonding between silicon atoms and oxygen atoms (active species) deposited after the decomposition of H2O2. Other bands in the Raman spectrum (1, 2, 3) are the same for this material before and after the addition of H2O2, and are thought to be due to different Si-O-Si vibrations (Figure 1c) and d).

[0040] Step 2: A catalyst test is performed using a pure silica catalyst to convert residual glycerin via a continuous flow reaction. The continuous flow reaction carried out in this invention takes place in a reactor that remains inside an oven throughout the entire process, as shown in Figure 2. A packed container (1) contains the reaction mixture, which is transported to the reactor by a pump (2). A feed is provided to the lower part (4) of the reactor, and the upper part (5) has three thermocouples (6a, 6b, 6c) which can control the temperature of different zones of the reactor. The reactor is divided into three parts: Zone I is filled with an inert substance (silicon carbide), Zone II contains a mixture of silicon carbide and a catalyst, and Zone III is also filled with silicon carbide alone. On one side and at one end of Zone III is a gas outlet (7) connected to a condenser (8) for liquefying the reaction products, which are recovered into a recovery flask (9) during the entire reaction.

[0041] In this reaction, zones I and III of the reactor are filled with silicon carbide, and zone II is filled with a solid mixture of silicon carbide and catalyst. The reaction mixture consists of residual glycerin and an aqueous hydrogen peroxide solution, and the feed flow to the reactor is 1 mL / min. -1 That is the case.

[0042] The volume and mass of the product generated were determined at one-hour intervals, and the maximum reaction time in the experiment was set to 8 hours. Samples recovered during the reaction were analyzed by GC-MS. Conversion rates and selectivity were determined from the calibration curve.

[0043] The pure silica catalyst, called SiO2, showed a constant conversion rate (approximately 90%) during a continuous 8-hour reaction, suggesting that this catalyst is highly stable in the conversion reaction of residual glycerin. Furthermore, as shown in Figure 3, the SiO2 catalyst can promote the conversion of glycerin to formic acid with high selectivity (approximately 80%) throughout the entire study period.

[0044] Since formic acid is an oxidative cleavage product of glycerol, this catalyst can promote the dehydration and oxidation of glycerol molecules.

[0045] Step 3: Catalytic test to convert residual glycerin by homogeneous catalytic reaction. The transesterification of triglycerides for the production of biodiesel produces glycerin as a by-product, which undergoes a neutralization process, resulting in blonde or residual glycerin, which is transported by the biodiesel production unit and is the main component of the reaction of this invention. Impurities present in the residual glycerin can be converted into a product of commercial interest by a homogeneous catalytic reaction in the presence of an oxidizing agent such as H2O2. This result was observed in a continuous flow reactor using only residual glycerin and H2O2. The reaction was carried out in the continuous flow reactor described in Step 2.

[0046] Products such as formic acid, diglycerol, and dioxane were identified as products of this reaction by GC-MS, and their respective selectivity is shown in Figure 4.

[0047] Dioxane is the main product of this reaction and can be used as an additive in biodiesel formulations, improving their low-temperature properties and reducing their viscosity. Next, the formation of formic acid is observed. Formic acid is a product of the oxidation of glycerin and is prominent in a wide range of applications in the textile, agricultural, pharmaceutical, and chemical industries. Currently, formic acid is used as a hydrogen storage compound because it can decompose into hydrogen and CO2. At low concentrations, diglycerin may be observed as a product of the reaction. Diglycerin is formed by the etherification of glycerin and has many applications in the food, pharmaceutical, and cosmetic industries.

[0048] We investigated semi-batch reactions using reflow reactions. Furthermore, these reactions allow us to understand the mechanisms of major product formation. The reflow reactions were carried out according to the method shown in Figure 5.

[0049] The reaction mixture consisted of residual glycerin or commercially available glycerin and an H2O2 solution. The reaction was carried out at 150°C for 3 hours, and aliquots of the sample were taken every 30 minutes and analyzed by GC-MS. The results are shown in Figure 6.

[0050] As observed in Figure 6a), in the reflow reaction, formic acid, hydroxypropanone, and dioxane are produced as the main products by the conversion of residual glycerin. Diglycerin is produced only 160 minutes after the end of the reaction. The relative selectivity for formic acid production gradually increases up to 120 minutes, reaching 55%. The same behavior is observed for hydroxypropanone. Subsequently, the selectivity for formic acid decreases, and the selectivity for diglycerin increases, reaching 60%. Its presence can be explained by the oxidative cleavage mechanism of glycerin by the oxidizing agent (H2O2). The production of formic acid from glycerin can be explained by first the production of hydroxypropanone by dehydration of glycerin, and then the production of formic acid by oxidation of hydroxypropanone and / or direct oxidation of glycerin. Hydroxypropanone is obtained from glycerin by dehydration. This substance is an important intermediate used in the production of polyols and acrolein. It can also be used in the textile industry and cosmetics, and can be used as a fragrance.

[0051] In Figure 6b), the formation of diglycerin is observed as the major product (approximately 70%) in the reflow reaction of commercially available diglycerin. Dioxane, formic acid, and hydroxypropanone molecules were also identified as trace products in the reaction (less than 10%). The major product is likely obtained by oligomerization of glycerin in the reaction medium in the presence of an oxidizing agent such as hydrogen peroxide.

[0052] Comparing the above results, it is clear that it is preferable to use residual glycerin and commercially available glycerin, respectively, to produce formic acid and diglycerin. The difference in the obtained products is probably due to impurities present in the glycerin (such as sodium chloride and methanol), which, when reacted with hydrogen peroxide, generate species that cause dehydration and oxidation of the glycerin molecule, producing hydroxypropanone and formic acid.

[0053] As the reaction progresses, sodium chloride is consumed, the production of these products decreases, and an increase in diglycerin is observed. The production of diglycerin is, conversely, directly related to the reaction of hydrogen peroxide with glycerin, resulting in the oligomerization of glycerin. This result occurs with both residual glycerin and commercial glycerin, but is more pronounced with commercial glycerin because it is free of impurities. In both situations, it is emphasized that industrially important products can be obtained starting from glycerin as a byproduct of biodiesel production, under mild reaction conditions and in the absence of heterogeneous catalysts.

[0054] This invention demonstrates, but is not limited to, the importance of using hydrogen peroxide as a green oxidizing agent in glycerol conversion reactions. Hydrogen peroxide is very attractive because it is inexpensive and readily available, and therefore the glycerol conversion process is simple and inexpensive.

Claims

1. By simultaneously using heterogeneous and homogeneous catalytic reactions of glycerin, Step a) homogenizing the remaining glycerin containing salts and impurities in an aqueous peroxide solution using a static mixer, Step b) involves pumping the solution obtained in step a) into a reactor containing a silica catalyst, Step c) involves letting the mixture obtained in step b) stand in the reactor for a residence time of 2 hours, A method for catalytically converting glycerin into a high-value-added product, comprising step d) recovering the product obtained in step c) and separating it by distillation.

2. Applicable to the process of the aforementioned heterogeneous catalytic reaction, high specific surface area (>1000 m²) ２ g －１ A method for catalytically converting glycerin into a high-value-added product according to claim 1, characterized by comprising the step of synthesizing a pure silica catalyst having an acidic group.

3. In the homogeneous catalytic reaction process described above, hydrogen peroxide (H ２ O ２ A method for catalytically converting glycerin into a high-value-added product according to claim 1, characterized in that 35 to 50% of a peroxide, not limited to benzoyl peroxide, is used as an oxidizing agent.

4. The method for catalytically converting glycerin into a high-value-added product according to claim 1, characterized in that the residual glycerin is derived from the process of obtaining biodiesel.

5. A method for catalytically converting glycerin into a high-value-added product according to any one of claims 1, 2, and 4, characterized in that the conversion of residual glycerin to formic acid by a heterogeneous catalytic reaction at a temperature of 100 to 250°C is promoted.

6. A method and application for catalytically converting glycerin into a high-value-added product according to claim 5, characterized in that a continuous flow reactor is used, and a batch or semi-batch reactor is also used to promote the conversion of residual glycerin to formic acid by a heterogeneous catalytic reaction.

7. A method for catalytically converting glycerin into a high-value-added product according to any one of claims 1, 3, and 4, characterized in that the conversion of residual glycerin to formic acid and green ether by a homogeneous catalytic reaction at a temperature of 100 to 250°C is promoted.

8. A method for catalytically converting glycerin into a high-value-added product according to claim 7, characterized in that a continuous flow reactor is used and / or a semi-batch system is used to facilitate the conversion of residual glycerin to formic acid and green ether by a homogeneous catalytic reaction.

9. The method for catalytically converting glycerin into a high-value-added product according to claim 1, characterized in that the conversion of residual glycerin by a homogeneous catalytic reaction is carried out by the action of residual components derived from biodiesel synthesis, and major compounds such as formic acid, cyclic ether, and diglycerin are formed.

10. A method for catalytically converting glycerin into a high-value-added product according to claim 1, characterized in that it promotes the conversion of commercially available glycerin to formic acid and green ether by a homogeneous catalytic reaction at a temperature of 100 to 250°C.

11. A method for catalytically converting glycerin into a high-value-added product according to claim 10, characterized in that it uses a continuous flow reactor and / or a semi-batch system to facilitate the conversion of commercially available glycerin to formic acid and green ether by a homogeneous catalytic reaction.

12. A method for catalytically converting glycerin into a high-value-added product according to claim 1, characterized in that a sodium salt is added before step a) in which commercially available glycerin is homogenized with an aqueous peroxide solution.

13. A method for catalytically converting glycerin into a high-value-added product according to claim 12, characterized in that glycerin itself is dissolved in water (inorganic salt) or methanol (organic salt), and an inorganic or organic salt, not limited to sodium chloride or sodium methylate, is used.

14. Applications of the product obtained by the catalytic conversion method for glycerin described in 1 into a high value-added product, characterized in that it is generated in fields such as petrochemicals, food, pharmaceuticals, and the textile industry.

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