A catalyst, a method for preparing the same, and a method for preparing lactic acid from a saccharide using the catalyst

Abstract

The application discloses a kind of catalyst and its preparation method, method for preparing lactic acid by catalysis of saccharide, wherein the catalyst is Co-Sn catalyst supported by silicon-containing biomass, wherein the loading amount (mass fraction) of Co is 1% to 20%, and the loading amount (mass fraction) of Sn is 1% to 30%. Thus, the application takes advantage of the characteristics of natural high-activity silicon source and carbon source in silicon-containing biomass to realize mutual promotion or synergistic effect between bimetallic and metal and carbon source, thereby realizing the catalysis of catalyst in aqueous solution to generate lactic acid from saccharide, and further providing a new conversion route for the conversion of saccharide to lactic acid.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lactic acid production, and in particular to a method for catalytically preparing lactic acid from sugar. BACKGROUND

[0002] Biomass, as a sustainable green carbon source, has wide availability and huge annual production scale, has great potential to supplement fossil-derived carbon, and clean and efficient conversion of biomass into energy and chemicals has become an important direction of global development. How to use lignocellulosic biomass resources for the preparation of high-value chemicals is of great significance to reduce dependence on fossil resources and reduce CO2 emissions. Cellulose, as the most abundant component of biomass resources, can be converted into various high-value platform chemicals. Among the chemicals synthesized from biomass, lactic acid (LA) is a high-potential multifunctional platform compound, and is one of the three major organic acids recognized by the world. It is an important platform chemical for the production of lactic acid alkyl ester, propylene glycol, acrylic acid and polylactic acid.

[0003] The main methods for industrial production of lactic acid are fermentation and synthesis. Fermentation has become a relatively mature method for producing lactic acid due to its simple process, abundant raw materials and early development. However, it has a long cycle and can only be produced intermittently or semi-continuously. Moreover, the quality of domestic fermented lactic acid cannot meet international standards. Chemical method can realize large-scale continuous production of lactic acid, but the raw materials are generally toxic and do not meet the requirements of green chemistry, which is not conducive to safe production. SUMMARY

[0004] The present application aims to at least solve one of the problems in the prior art. To this end, the present application provides a method for catalytically preparing lactic acid from sugar.

[0005] According to a first aspect of some embodiments of the present application, a catalyst for catalyzing sugar to lactic acid is provided, characterized in that the catalyst is a silicon-containing biomass supported Co-Sn catalyst, and the silicon-containing biomass supported Co-Sn catalyst is formed by loading Co and Sn on a carrier in a certain proportion, wherein the loading amount (mass fraction) of Co is 1% to 20%, and the loading amount (mass fraction) of Sn is 1% to 30%.

[0006] According to some embodiments of the present application, the loading amount (mass fraction) of Co is 5%, and the loading amount (mass fraction) of Sn is 3%.

[0007] According to some embodiments of the present application, the silicon-containing biomass includes rice husk, oat hulls and reed.

[0008] According to a second aspect of some embodiments of the present application, a catalyst preparation method is provided, which includes the following steps:

[0009] The silicon-containing biomass and the Co source are mixed and subjected to a hydrothermal reaction.

[0010] After mixing the solution after the hydrothermal reaction with the Sn source, removing the solvent water, and drying, a solid powder is obtained,

[0011] After pyrolyzing the obtained solid powder under a protective gas stream, a Co-Sn catalyst loaded with silicon-containing biomass is obtained.

[0012] According to some embodiments of the present application, the Co source is CoCl2·6H2O, and the Sn source is SnCl4·5H2O.

[0013] According to a method for catalytically preparing lactic acid from a sugar according to a third aspect of the embodiments of the present application, the method comprises the following steps:

[0014] The sugar, water, and catalyst are added to a closed container, and a high-temperature reaction is performed under a protective atmosphere, and a solution containing lactic acid is obtained after the reaction, the catalyst being a Co-Sn catalyst loaded with silicon-containing biomass, wherein the loading amount (mass fraction) of Co is 1% to 20%, and the loading amount (mass fraction) of Sn is 1% to 30%.

[0015] According to some embodiments of the present application, when the sugar, water, and catalyst are added to a closed container and a high-temperature reaction is performed under a protective atmosphere, the pressure of the protective atmosphere ranges from 2 MPa to 8 MPa.

[0016] According to some embodiments of the present application, when the sugar, water, and catalyst are added to a closed container and a high-temperature reaction is performed under a protective atmosphere, the reaction temperature ranges from 220 to 280 °C.

[0017] According to some embodiments of the present application, the sugar includes cellulose, cellobiose, glucose, and fructose.

[0018] Advantages:

[0019] The present application takes advantage of the fact that silicon-containing biomass contains natural high-activity silicon sources and carbon sources, and realizes mutual promotion or synergy between bimetallic and metal and carbon sources, thereby realizing the catalysis of a Co-Sn catalyst loaded with silicon-containing biomass in an aqueous environment to generate lactic acid from a sugar, and further providing a new conversion route for converting a sugar into lactic acid.

[0020] The catalyst used in the present application is a biomass carrier, thereby promoting the resource utilization of waste biomass (especially silicon-containing biomass). BRIEF DESCRIPTION OF DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the following drawings, in which:

[0022] Figure 1is a transmission electron microscope image of a 3% Sn-5% Co / RHC catalyst according to an embodiment of the present application;

[0023] Figure 2 is an XRD image of a 3% Sn-5% Co / RHC catalyst according to an embodiment of the present application. DETAILED DESCRIPTION

[0024] Embodiments of the present application are described in detail below, with reference to the accompanying drawings described by way of example.

[0025] Reference is made below Figures 1-2 to a method for catalytically preparing lactic acid from a saccharide according to an embodiment of the present application.

[0026] The method for catalytically preparing lactic acid from a saccharide according to an embodiment of the present application comprises the following steps:

[0027] The saccharide, water and catalyst are added into a high-pressure reactor, and the reaction is carried out under the conditions of nitrogen as a protective atmosphere, a pressure ranging from 2 MPa to 8 MPa, and a reaction temperature ranging from 220 to 280°C. After the reaction is completed, the solution containing lactic acid is obtained after cooling. The saccharide includes cellulose, cellobiose, glucose, and fructose. The catalyst can be a Co-Sn catalyst supported by a silicon-containing biomass, which is prepared by supporting Co and Sn on a silicon-containing biomass carrier in a certain proportion. The mass ratio of Co to Sn is 1:0.2 to 1:20. The loading amount (mass fraction) of Co is 1% to 20%, and the loading amount (mass fraction) of Sn is 1% to 30%.

[0028] Specifically, the saccharide, water and catalyst in the high-pressure reactor will undergo a series of reactions. Taking the catalytic lactic acid from cellulose as an example, in the process of converting cellulose to lactic acid, the cellulose first undergoes a hydrolysis reaction to generate glucose. This reaction usually needs to be carried out under acidic conditions, but under subcritical water phase conditions, H+ produced by water ionization can also catalyze the hydrolysis of cellulose. Subsequently, the glucose undergoes an isomerization reaction under Lewis acid or alkaline conditions to generate fructose. The fructose further undergoes a Retro-aldol condensation reaction under Lewis acid or alkaline conditions to generate a C3 intermediate, which is further hydrated to generate lactic acid.

[0029] In the above reaction, the presence of Sn can combine with the SiO2 carrier, thereby significantly affecting the electronic state of Sn species, forming non-integer valence Sn δ+ and SnO x species, which can provide strong alkaline sites for the catalyst, efficiently catalyze the isomerization of glucose and the Retro-aldol condensation of fructose to generate C3 products, and further facilitate the generation of lactic acid. At the same time, the combination of Sn and Co can also significantly increase the non-integer valence SnO xThe Si species increases the basicity of the catalyst, promotes the isomerization of glucose and the Retro-aldol condensation reaction of fructose, and provides a basic site for catalyzing the conversion of glucose into C3 molecules.

[0030] In addition, a large amount of plant silicate (amorphous silicon dioxide) is contained in the silicon-containing biomass such as wheat husks and rice husks, and the Si species has high activity and is more likely to interact with metals. In addition, the reducing gases such as H2, CH4 and CO generated in the pyrolysis process of the organic carbon source of the silicon-containing biomass after the hydrothermal reaction can reduce metal ions in situ, and the presence of the biomass char can inhibit the agglomeration of nanosilica in the silicon-containing biomass, thereby improving the stability of the catalyst and solving the problems of poor catalyst stability and difficulty in reuse in the cellulose conversion process.

[0031] Therefore, the present application takes advantage of the natural high-activity silicon source and carbon source in the silicon-containing biomass to realize the mutual promotion or synergy between the two metals and between the metal and the carbon source, thereby realizing the catalysis of the Co-Sn catalyst supported by the silicon-containing biomass to generate lactic acid from sugars in an aqueous solution, and providing a new conversion route for the conversion of sugars to lactic acid.

[0032] The catalyst used in the method is supported by biomass, thereby promoting the resource utilization of waste biomass (especially silicon-containing biomass); at the same time, water is used as the solvent in the method, thereby avoiding the environmental pollution problem caused by the use of organic solvents.

[0033] The reducing gases such as H2, CH4 and CO generated in the pyrolysis process of the organic carbon source of the silicon-containing biomass after the hydrothermal reaction can reduce metal ions in situ, thereby inhibiting the agglomeration of nanosilica in the silicon-containing biomass, and improving the stability of the catalyst.

[0034] Further, based on the above embodiment, the loading amount (mass fraction) of Co is 5%, and the loading amount (mass fraction) of Sn is 3%. Specifically, according to the results of Example 2, the yield of lactic acid is as high as 66.5% when 3% Sn-5% Co / RHC is used to catalyze the preparation of lactic acid from cellulose, thereby greatly improving the yield of lactic acid prepared from sugars, which is conducive to industrial production.

[0035] In combination with Figure 1 , Figure 2As shown, the preparation method of the catalyst according to the embodiment of the application, wherein the catalyst refers to: the catalyst is a Co-Sn catalyst supported by a silicon-containing biomass, the silicon-containing biomass includes any one or a combination of two or more of rice husk, oat husk and reed, and the preparation method includes the following steps: mixing the silicon-containing biomass and a CoCl2·6H2O solution, and then performing a hydrothermal reaction, mixing the solution after the hydrothermal reaction with a SnCl4·5H2O solution, removing solvent water, and drying to obtain a solid powder, and then pyrolyzing the solid powder under a protective gas flow to obtain the Co-Sn catalyst supported by the silicon-containing biomass.

[0036] More specifically, 5.0 g of the carrier is added to a 100 mL hydrothermal kettle, a certain amount of CoCl2·6H2O is dissolved in 50 mL of deionized water, and then added to the above hydrothermal kettle for mixing, and heated at 200℃ for 12 h. After cooling to room temperature, it is directly transferred to a round-bottom flask, a certain amount of SnCl4·5H2O is dissolved in 10 mL of water in a small beaker, and then slowly dripped into the round-bottom flask, and 50 mL of deionized water is added, and stirred at 45℃ for 12 h, and then the solvent water is removed by rotary evaporation, and dried at 105℃ overnight, and then the solid powder is pyrolyzed at a temperature of 600℃ for 2 h in a N2 flow, and after cooling to room temperature, it is purged with 1% O2 / N2 for 30 min, to obtain the Co-Sn bimetallic catalyst supported by the silicon-containing biomass.

[0037] Therefore, the method first loads Co by hydrothermal method, and then loads Sn, in this way, Co can first combine with active Si in the silicon-containing biomass, and different from the pure SiO2 carrier, the active Si in the biomass can promote the combination of Sn and Co to form CoSn alloy (see Figure 2 ), and affect the combination of Co, Sn and C, and in this process, the organic carbon in the biomass carrier forms a carbon layer to wrap the metal, thereby significantly inhibiting the agglomeration and loss of the active metal, and promoting the conversion of cellulose and other sugars into lactic acid.

[0038] Example 1

[0039] Preparation of Sn-Co bimetallic catalyst supported by rice husk (for example, x% Sn-5% Co / RHC)

[0040] 5.0 g of rice husk sieved through 80 mesh was added to a 100 mL autoclave, 1.06 g of CoCl2-6H2O was dissolved in 50 mL of deionized water, and the solution was ultrasonically dissolved and then added to the autoclave and mixed well. The mixture was heated at 200°C for 12 h. After cooling to room temperature, it was directly transferred to a round-bottom flask. A certain amount of SnCl4 was dissolved in 10 mL of water in a small beaker, and the solution was slowly added to the round-bottom flask. Then, 50 mL of deionized water was added, and the mixture was stirred at 45°C for 12 h. The solvent water was removed by rotary evaporation, and the solid was dried at 105°C overnight. Then, the solid was pyrolyzed at 600°C for 2 h under a N2 flow. After cooling to room temperature, the solid was purged with 1% O2 / N2 for 30 min to obtain a x% Sn-5% Co / RHC catalyst.

[0041] Table 1. Preparation of Sn-Co / RHC catalysts with different Sn / Co ratios

[0042]

[0043] Example 2.

[0044] Preparation of lactic acid from cellulose catalyzed by Sn-Co / RHC with different Sn / Co ratios

[0045] In a 25 mL high-pressure reactor, 50 mg of cellulose and 50 mg of catalyst were added, and 10 mL of water was used as a solvent. The reaction was carried out at a N2 pressure of 4 MPa and a temperature of 250°C for 1 h. After the reaction, the reaction solution was filtered and used for liquid-phase detection (HPLC, Waters 1525, Shodex RI-201H detector, Bio-Rad Aminex HPX-87H column, using 0.005 M H2SO4 as the mobile phase). The results are shown in Table 2.

[0046] Table 2. Preparation of lactic acid from cellulose catalyzed by Sn-Co / RHC with different Sn / Co ratios

[0047]

[0048]

[0049] Example 3

[0050] Preparation of lactic acid from various sugars catalyzed by 3% Sn-5% Co / RHC

[0051] In a 25 mL autoclave, 50 mg of substrate, 50 mg of 3% Sn-5% Co / RHC catalyst, 10 mL of water as solvent, under N2pressure of 4 MPa, temperature of 250 °C for 1 h. After the reaction, the reaction solution was cooled, filtered and used for liquid detection (HPLC, Waters 1525, Shodex RI-201H detector, Bio-Rad Aminex HPX-87H column, using 0.005 M H2SO4as mobile phase). The results are shown in Table 3:

[0052] Table 3. Lactic acid production from various sugars catalyzed by 20% Sn-10% Co / SiO2

[0053] Substrate Lactic acid yield / % Cellulose 66.5 Cellubiose 58.8 Glucose 60.7 Fructose 69.8

[0054] Example 4

[0055] Effect of different silicon-containing biomass supports loaded with 3% Sn-5% Co catalysts on the conversion of cellulose to lactic acid

[0056] In a 25 mL autoclave, 50 mg of cellulose, 50 mg of silicon-containing biomass support loaded with 3% Sn-5% Co catalyst, 10 mL of water as solvent, under N2pressure of 4 MPa, temperature of 250 °C for 1 h. After the reaction, the reaction solution was cooled, filtered and used for liquid detection (HPLC, Waters 1525, Shodex RI-201H detector, Bio-Rad Aminex HPX-87H column, using 0.005 M H2SO4as mobile phase). The results are shown in Table 4:

[0057] Table 4. Effect of different silicon-containing biomass supports loaded with 3% Sn-5% Co catalysts on the conversion of cellulose to lactic acid

[0058] Carrier Lactic acid yield / % Rice hulls 66.5 Oat hulls 60.7 Reed canary grass 48.2

[0059] Example 5

[0060] Effect of different N2pressure on the conversion of cellulose to lactic acid

[0061] In a 25 mL autoclave, 50 mg of cellulose, 50 mg of 3% Sn-5% Co / RHC catalyst, 10 mL of water as solvent, under N2pressure of 0.5-8 MPa, temperature of 250 °C for 1 h. After the reaction, the reaction solution was cooled, filtered and used for liquid detection (HPLC, Waters 1525, Shodex RI-201H detector, Bio-Rad Aminex HPX-87H column, using 0.005 M H2SO4as mobile phase). The results are shown in Table 5:

[0062] Table 5. Effect of different reaction hydrogen pressure on cellulose conversion to lactic acid

[0063] [N2 pressure (MPa)] Lactic acid yield / % 0.5 32.1 1 40.4 2 50.7 3 58.2 4 66.5 5 66.8 6 60.2 7 55.4 8 51.1

[0064] Example 6.

[0065] Effect of different reaction temperature on cellulose conversion to lactic acid

[0066] In a 25 mL high pressure reactor, 50 mg of cellulose, 50 mg of 3% Sn-5% Co / RHC catalyst, 10 mL of water as solvent, under the condition of N2 pressure of 4 MPa and temperature of 150-300°C for 1 h, after the reaction was completed, the reaction solution was filtered and used for liquid phase detection (HPLC, Waters 1525, Shodex RI-201H detector, Bio-Rad Aminex HPX-87H chromatographic column, using 0.005 M H2SO4 as the mobile phase). The results are shown in Table 6:

[0067] Table 6. Effect of different reaction temperature on cellulose conversion to lactic acid

[0068] Temperature (°C) Lactic acid yield / % 150 19.9 180 25.5 200 30.2 220 42.6 240 63.3 250 66.5 260 55.7 280 48.8 300 40.2

[0069] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0070] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example.

[0071] Although embodiments of the present application have been shown and described, those skilled in the art can understand that various changes, modifications, replacements and variations can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A method for producing a catalyst, characterized by, The catalyst is used for catalyzing sugar into lactic acid, and the catalyst is a silicon-biomass supported Co-Sn catalyst, which is prepared by loading Co and Sn on a carrier in a certain proportion, wherein the mass fraction of Co loading is 1-20%, and the mass fraction of Sn loading is 1-30%, and the preparation method comprises the following steps: The silicon-biomass and a Co source are mixed and then subjected to a hydrothermal reaction, wherein the silicon-biomass comprises rice husk, oat husk and reed; The solution after the hydrothermal reaction is mixed with a Sn source, and then solvent water is removed, and the solid powder is dried to obtain a solid powder; The solid powder is subjected to pyrolysis under a protective gas flow to obtain a silicon-biomass supported Co-Sn catalyst.

2. The method of claim 1, wherein the catalyst is prepared by the steps of: The Co source is CoCl2·6H2O, and the Sn source is SnCl4·5H2O.

3. A catalyst for catalyzing a saccharide to lactic acid, characterized by, The catalyst is a silicon-biomass supported Co-Sn catalyst prepared by the preparation method of the catalyst in claim 1 or 2.

4. The catalyst of claim 3, wherein The mass fraction of Co loading is 5%, and the mass fraction of Sn loading is 3%.

5. A method for the catalytic production of lactic acid from a saccharide, characterized in that, The method comprises the following steps: The sugar, water and catalyst are added into a closed container, and high-temperature reaction is carried out under a protective atmosphere, and then a solution containing lactic acid is obtained after the reaction, wherein the catalyst is the catalyst in claim 3 or 4.

6. The method of claim 5, wherein the catalyst is a sugar. 5 When the sugar, water and catalyst are added into a closed container and high-temperature reaction is carried out under a protective atmosphere, the pressure of the protective atmosphere ranges from 2 MPa to 8 MPa.

7. The method of claim 5, wherein the catalytic preparation of lactic acid from a saccharide is characterized by, When the sugar, water and catalyst are added into a closed container and high-temperature reaction is carried out under a protective atmosphere, the reaction temperature ranges from 220 to 280℃.

8. The method for catalytic production of lactic acid from saccharides according to claim 5, characterized in that, The sugar comprises cellulose, cellobiose, glucose and fructose.

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