Preparation method for catalyzing carbohydrates to prepare indole

Abstract

The invention discloses a method for preparing indole by catalyzing carbohydrates, which comprises the following steps: adding carbohydrates, water, aniline and a catalyst into a closed container, and carrying out high-temperature reaction in a hydrogen reducing atmosphere at the pressure range of 2-8MPa and the temperature range of 150-300 DEG C to obtain a mixed solution containing indole, the carbohydrate is any one or a combination of at least two of cellulose, cellobiose, glucose, fructose, starch and cane sugar. Therefore, by utilizing the characteristics that the catalyst exerts different catalytic activities in different components in the heterogeneous solvent, the heterogeneous solvent regulates and controls a reaction path, a high-activity silicon source in silicon dioxide and the like, mutual promotion or synergy between an intermediate product and the solvent, effects between double metals and effects between the metal and the silicon source are realized; therefore, the purpose that the catalyst catalyzes carbohydrates to generate indole in the solvent environment of water and aniline is achieved, and a new conversion way is provided for converting the carbohydrates into the indole.

Description

Technical Field

[0001] The present invention relates to the field of indole production, and in particular to a preparation method for preparing indole from saccharides. Background Art

[0002] The organic compound indole has important applications in the fields of medicine, spices, dyes, etc. The industrial synthesis of indole by the Fischer method involves aldehydes, ketones, and aryl hydrazines, but it has problems such as low yield and poor regioselectivity.

[0003] Biomass, as the world's largest renewable energy source, is widely present in all plants, microorganisms, animals, and their produced wastes. In the renewable energy market, biomass energy accounts for more than 50%. With the large-scale use of non-renewable energy sources such as coal, oil, and natural gas, the need for renewable energy is becoming increasingly strong.

[0004] Lignocellulose accounts for the largest proportion in biomass, and cellulose is the largest component in lignocellulose. Therefore, cellulose has a wide source and low cost. If cellulose is catalytically hydrogenated to prepare compounds, it can not only alleviate the shortage of traditional fossil energy, but also the high-value-added compounds produced can be applied to many industries. However, due to the intractability of cellulose and the complex distribution of products, the application of saccharides in the preparation of compounds such as indole is restricted. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a catalyst and a preparation method for catalytically preparing indole from saccharides.

[0006] According to a preparation method for catalytically preparing indole from saccharides according to the first aspect of the embodiments of the present invention, the preparation method includes: adding saccharides, water, aniline, and a catalyst into a closed container, and performing a high-temperature reaction under a hydrogen reduction atmosphere. At this time, the pressure range of the reduction atmosphere is 2 MPa to 8 MPa, and the temperature range is 150 °C to 300 °C, to obtain a mixed solution containing indole. Among them, the saccharides are any one or at least two combinations of cellulose, cellobiose, glucose, fructose, starch, and sucrose. Preferably, the pressure of the reduction atmosphere is 4 MPa, and the reaction temperature is 250 °C.

[0007] The catalyst includes a silica-supported bimetallic catalyst and / or a carbon-supported bimetallic catalyst. Among them, the silica-supported bimetallic catalyst includes a silica-supported Co-Sn catalyst, a silica-supported Ni-Sn catalyst, a silica-supported Co-W catalyst, and a silica-supported Ni-W catalyst; the carbon-supported bimetallic catalyst includes a carbon-supported Co-Sn catalyst.

[0008] It should be noted here that: Co is cobalt metal, Sn is tin metal, Ni is nickel metal, and W is tungsten metal.

[0009] Specifically, the silica-supported Co-Sn catalyst is formed by loading Co and Sn on a carrier in proportion. Among them, the loading amount of Co is 1% to 20% by mass fraction, and the loading amount of Sn is 1% to 40% by mass fraction.

[0010] The silica-supported Ni-Sn catalyst is formed by loading Ni and Sn on a carrier in proportion. The loading amount of Ni is 1% to 20% by mass fraction, and the loading amount of Sn is 1% to 40% by mass fraction.

[0011] The silica-supported Co-W catalyst is formed by loading Co and W on a carrier in proportion. The loading amount of Co is 1% to 20% by mass fraction, and the loading amount of W is 1% to 40% by mass fraction.

[0012] The silica-supported Ni-W catalyst is formed by loading Ni and W on a carrier in proportion. The loading amount of Ni is 1% to 20% by mass fraction, and the loading amount of W is 1% to 40% by mass fraction.

[0013] Preferably, in the silica-supported Co-Sn catalyst, the loading amount of Co is 5% by mass fraction, and the loading amount of Sn is 10% by mass fraction; in the silica-supported Ni-Sn catalyst, the loading amount of Ni is 5% by mass fraction, and the loading amount of Sn is 10% by mass fraction; in the silica-supported Co-W catalyst, the loading amount of Co is 10% by mass fraction, and the loading amount of W is 30% by mass fraction; in the silica-supported Ni-W catalyst, the loading amount of Ni is 10% by mass fraction, and the loading amount of W is 30% by mass fraction.

[0014] In actual production, the above Co source uses Co(NO3)2·6H2O, CoCl2·6H2O, Co(CH3COO)2·4H2O, the Ni source uses Ni(NO3)2·6H2O, NiCl2·6H2O, Ni(CH3COO)2·4H2O, the Sn source uses SnCl4·5H2O, SnCl2·2H2O, and the W source uses ammonium metatungstate hydrate, ammonium tungstate, Na2WO4·2H2O.

[0015] Among them, the silica-supported Co-Sn catalyst is obtained by simultaneously mixing and impregnating silica with Co solution and Sn solution, and then removing the solvent. The solvent of the hydrophobic carrier here is absolute ethanol.

[0016] Taking the small-scale preparation in the laboratory as an example, hydrophobic silica with a specific surface area of 300 m 2 / g was selected. 0.5 g of the carrier was added to a 100 ml round-bottom flask, and 60 ml of absolute ethanol was added to the flask to dissolve and disperse the catalyst. A small beaker was used to dissolve a certain amount of Co(NO3)2·6H2O with 5 mL of absolute ethanol, and another small beaker was used to dissolve a certain amount of SnCl4·5H2O with 5 mL of absolute ethanol. The solutions of the two were slowly dropped into the round-bottom flask respectively, keeping the volume of the solvent at 70 ml, and continuously stirring and heating at 45 °C for 12 h. After completion, the absolute ethanol was removed with a rotary evaporator and dried overnight at 105 °C to obtain a Co-Sn bimetallic catalyst supported on hydrophobic silica.

[0017] Different from the above-mentioned silica-supported Co-Sn catalyst, the solvent for the hydrophilic group carrier is deionized water. The hydrophilic silica-supported Co-Sn catalyst is obtained by simultaneously mixing and impregnating silica with Co solution and Sn solution, and then removing the solvent to obtain the silica-supported Co-Sn catalyst.

[0018] 0.5 g of the carrier was added to a 100 ml round-bottom flask, and 60 ml of deionized water was added to the flask to dissolve and disperse the catalyst. A small beaker was used to dissolve a certain amount of Co(NO3)2·6H2O with 5 mL of deionized water, and another small beaker was used to dissolve a certain amount of SnCl4·5H2O with 5 mL of deionized water. The solutions of the two were slowly dropped into the round-bottom flask respectively, keeping the volume of the solvent at 70 ml, and continuously stirring and heating at 45 °C for 12 h. After completion, the deionized water was removed with a rotary evaporator and dried overnight at 105 °C to obtain a Co-Sn bimetallic catalyst supported on hydrophilic silica.

[0019] Similarly, the hydrophilic silica-supported Co-W catalyst is obtained by simultaneously mixing and impregnating silica with Co solution and W solution, and then removing the solvent to obtain the silica-supported Co-W catalyst, and the solvent is deionized water. However, since ammonium metatungstate hydrate is insoluble in absolute ethanol, and the solvent for preparing the hydrophobic silica catalyst is absolute ethanol, the hydrophobic catalyst cannot completely load metal W. Therefore, only the hydrophilic catalyst is loaded with metal W.

[0020] 0.5 g of the carrier was added to a 100 ml round-bottom flask, and 60 ml of deionized water was added to the flask to dissolve and disperse the catalyst. A small beaker was used to dissolve a certain amount of Co(NO3)2·6H2O with 5 mL of deionized water, and another small beaker was used to dissolve a certain amount of ammonium metatungstate hydrate with 5 mL of deionized water. The solutions of the two were slowly dropped into the round-bottom flask respectively, keeping the volume of the solvent at 70 ml, and continuously stirring and heating at 45 °C for 12 h. After completion, the deionized water was removed with a rotary evaporator and dried overnight at 105 °C to obtain a Co-W bimetallic catalyst supported on hydrophilic silica.

[0021] In the preparation process, cellulose hydrolysis reaction generates glucose. In a high-temperature aqueous phase system, H⁺ generated by the ionization of water can catalyze the hydrolysis of cellulose. Subsequently, glucose undergoes a retro-aldol condensation reaction under L-acid or alkaline conditions to generate glycolaldehyde, which is further hydrogenated to form ethylene glycol. Finally, ethylene glycol and aniline react in an acidic environment to form indole.

[0022] In the above reaction, the presence of Sn will combine with the SiO₂ support, thereby significantly affecting the electronic state of Sn species, forming non-integer valence Snδ⁺ and SnOx species. These species can provide strong basic sites for the catalyst, efficiently catalyze the retro-aldol condensation of glucose to form glycolaldehyde, and then promote the hydrogenation of glycolaldehyde to form ethylene glycol under the action of hydrogenation sites. Finally, ethylene glycol and aniline form indole. At the same time, the combination of Co and Sn can also significantly increase the non-integer valence SnOx species in the catalyst, thereby increasing the alkalinity of the catalyst, promoting the retro-aldol condensation reaction of glucose, and providing the basic sites for catalyzing the conversion of glucose to glycolaldehyde.

[0023] Furthermore, the combination of Ni and Sn follows a similar principle. For the tungsten-containing silica catalyst, due to the introduction of Co, the formation of W basic sites can be appropriately increased, thereby promoting the formation of oxygen vacancies in W. The increase in these oxygen vacancies can provide more active sites for the catalyst, which is beneficial to optimizing hydrogen adsorption and hydrolysis dissociation. The improvement of these two abilities plays an important promoting role in the process of sugar conversion.

[0024] In addition, tungsten oxides tend to be reduced to HxWO3 in a hydrogen reduction atmosphere and then re-oxidized to WO3 after being exposed to ambient air after the reaction. Both WO3 and HxWO3 are insoluble in water and act as heterogeneous catalysts in the catalytic conversion reaction of sugars.

[0025] In addition, due to its high-active silicon source, silica is more likely to have a strong interaction with metals. Compared with ordinary silicon supports, the high specific surface area and adsorption capacity of silica can improve the effect of metal impregnation and enhance the binding force between the support and the metal. From this perspective, the stability of the catalyst is improved, which plays a certain inhibitory role in the agglomeration and sintering of metals on the catalyst during the sugar conversion process.

[0026] On the other hand, since the solvent system is a heterogeneous solvent of water and aniline, in the aqueous phase, sugars are hydrolyzed, undergo retro-aldol condensation, and are hydrogenated to form C2 and C3 intermediates. Subsequently, the intermediates react with aniline to form indole. During this process, aniline will extract the oil phase, and this effect prevents the concentration of intermediates and products in water from being too high to inhibit the conversion of sugars and the formation of products.

[0027] Beneficial effects:

[0028] The present invention utilizes the characteristics that the catalyst exhibits different catalytic activities in different components of a heterogeneous solvent, the heterogeneous solvent regulates the reaction pathway, and the highly active silicon source in silica, etc., to achieve the mutual promotion or synergy between the intermediate product and the solvent, between the bimetals, and between the metal and the silicon source, thereby enabling the catalyst to catalyze sugars to produce indole in a solvent environment of water and aniline, and further providing a new conversion pathway for the conversion of sugars to indole.

[0029] In the method for preparing indole from cellulose in a liquid phase according to the present invention, water and aniline are used as heterogeneous solvents. Compared with traditional water solvents, since ethylene glycol, indole, etc. are more likely to dissolve in the aniline organic phase and undergo synthesis reactions therein, the heterogeneous solvent can inhibit the occurrence of side reactions and the separation of products is simpler. Brief Description of the Drawings

[0030] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, wherein:

[0031] Figure 1 is the transmission electron microscope image of the 5% Co - 10% Sn@SiO2 catalyst according to Example 5 of the present invention. Detailed Description of the Embodiments

[0032] The embodiments of the present invention will be described in detail below. The embodiments described with reference to the drawings are exemplary.

[0033] Example 1

[0034] In this example, the effect of bimetallic catalysts with different metal ratios on the catalytic preparation of indole from cellulose was tested.

[0035] Add 50 mg of cellulose and 50 mg of catalyst into a 25 mL high-pressure reactor, use 10 mL of deionized water + 1 mL of aniline as the solvent, react at a H2 pressure of 4 MPa and a temperature of 250 °C for 1 h. After the reaction, cool it. The reaction solution is 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 specific results are shown in Table 1:

[0036] Table 1. Preparation of indole from cellulose catalyzed by bimetallic catalysts with different metal ratios

[0037]

[0038]

[0039] Example 2

[0040] In this example, the effects of different metal-supported catalysts on the catalytic preparation of indole from cellulose were tested.

[0041] 50 mg of cellulose and 50 mg of catalyst were added to a 25 mL high-pressure reactor, and 10 mL of deionized water + 1 mL of aniline were used as the solvent. The reaction was carried out at a H2 pressure of 4 MPa and a temperature of 250 °C for 1 h. After the reaction, it was cooled, and 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 2:

[0042] Table 2. Preparation of indole from cellulose catalyzed by different metal-supported catalysts

[0043] Catalyst Yield of C2-C3 small molecules / % <![CDATA[5%Co-10%Sn@SiO2]]> 55.34 5% Co-10% Sn@C 46.29

[0044] Example 3

[0045] In this example, the effects of different hydrogen pressures on the catalytic preparation of indole from cellulose by the catalyst were tested.

[0046] 50 mg of cellulose and 50 mg of 5% Co-10% Sn@SiO2 catalyst were added to a 25 mL high-pressure reactor, and 10 mL of deionized water + 1 mL of aniline were used as the solvent. The reaction was carried out at a H2 pressure of 4 MPa and a temperature of 250 °C for 1 h. After the reaction, it was cooled, and 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 3:

[0047] Table 3. Effects of different hydrogen pressures on the conversion of cellulose to indole

[0048] <![CDATA[H2 pressure (MPa)]]> Yield of indole / % 0.5 10.98 1 19.11 2 29.20 3 38.25 4 55.34 5 55.03 6 50.75 7 51.63 8 49.32

[0049] Example 4

[0050] In this example, the effects of different reaction temperatures on the catalytic preparation of indole from cellulose by the catalyst were tested.

[0051] Add 50 mg of cellulose and 50 mg of 5% Co-10% Sn@SiO2 catalyst into a 25 mL high-pressure reactor. Use 10 mL of water + 1 mL of aniline as the solvent, and react for 1 h under the conditions of H2 pressure of 4 MPa and temperature of 150 - 300 °C. After the reaction, cool it down. Filter the reaction solution 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).

[0052] The results are shown in Table 4 as follows:

[0053] Table 4. Influence of Different Reaction Temperatures on the Conversion of Cellulose to Indole

[0054] Temperature (°C) Yield of indole / % 150 9.30 180 17.05 200 20.99 220 23.41 240 31.40 250 55.34 260 49.68 280 45.19 300 31.78

[0055] Example 5

[0056] In this example, the influence of different solvent component ratios on the preparation of indole from cellulose by the catalyst was tested.

[0057] [[ID=1,8]]Add 50 mg of cellulose and 50 mg of 5% Co-10% Sn@hydrophobic SiO2 catalyst into a 25 mL high-pressure reactor. React for 1 h under the conditions of H2 pressure of 4 MPa and temperature of 250 °C. In the solvent component, the volume of water is 2 - 10 mL, and the volume of aniline is 1 - 9 mL, keeping the total volume unchanged at 11 mL. After the reaction, cool it down. Filter the reaction solution 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).

[0058] The results are shown in Table 5 as follows:

[0059] Table 5. Influence of Different Solvent Components on the Conversion of Cellulose to Indole

[0060]

[0061] Example 6

[0062] In this example, the influence of different saccharides on the preparation of indole from cellulose by the catalyst was tested.

[0063] 50 mg of saccharides and 50 mg of 5% Co-10% Sn@SiO2 catalyst were added into a 25 mL high-pressure reactor. Using 10 mL of water + 1 mL of aniline as the solvent, the reaction was carried out at a H2 pressure of 4 MPa and a temperature of 250 °C for 1 h. After the reaction, it was cooled. 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:

[0064] Table 6. Effects of different saccharides catalyzed by the catalyst on the preparation of indole

[0065] Substrate Yield of indole / % Cellulose 55.34 Cellobiose 53.01 Glucose 46.53 Fructose 44.97 Starch 35.62 Sucrose 38.75

[0066] In the description of this specification, the description of reference terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. 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 invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example.

[0067] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A preparation method for catalyzing the preparation of indole from sugars, characterized in that, The preparation method includes the following steps: Add sugars, water, aniline, and a catalyst into a closed container, and perform a high-temperature reaction under a reducing atmosphere to obtain a mixed solution containing indole. Among them, the catalyst includes a silica-supported bimetallic catalyst and / or a carbon-supported bimetallic catalyst. The silica-supported bimetallic catalyst includes a silica-supported Co-Sn catalyst, a silica-supported Ni-Sn catalyst, a silica-supported Co-W catalyst, and a silica-supported Ni-W catalyst. The carbon-supported bimetallic catalyst includes a carbon-supported Co-Sn catalyst.

2. The preparation method of indole by catalytic conversion of saccharides according to claim 1, characterized in that, The sugars are any one or a combination of at least two of cellulose, cellobiose, glucose, fructose, starch, and sucrose.

3. The preparation method of indole by catalytic conversion of saccharides according to claim 1, wherein, The silica-supported Co-Sn catalyst is formed by loading Co and Sn on a carrier in proportion. Among them, the loading amount of Co is 1% to 20% by mass fraction, and the loading amount of Sn is 1% to 40% by mass fraction; the silica-supported Ni-Sn catalyst is formed by loading Ni and Sn on a carrier in proportion. The loading amount of Ni is 1% to 20% by mass fraction, and the loading amount of Sn is 1% to 40% by mass fraction; the silica-supported Co-W catalyst is formed by loading Co and W on a carrier in proportion. The loading amount of Co is 1% to 20% by mass fraction, and the loading amount of W is 1% to 40% by mass fraction; the silica-supported Ni-W catalyst is formed by loading Ni and W on a carrier in proportion. The loading amount of Ni is 1% to 20% by mass fraction, and the loading amount of W is 1% to 40% by mass fraction.

4. A method for preparing indole by catalytic conversion of saccharides according to claim 3, wherein, In the silica-supported Co-Sn catalyst, the loading amount of Co is 5% by mass fraction, and the loading amount of Sn is 10% by mass fraction; in the silica-supported Ni-Sn catalyst, the loading amount of Ni is 5% by mass fraction, and the loading amount of Sn is 10% by mass fraction; in the silica-supported Co-W catalyst, the loading amount of Co is 10% by mass fraction, and the loading amount of W is 30% by mass fraction; in the silica-supported Ni-W catalyst, the loading amount of Ni is 10% by mass fraction, and the loading amount of W is 30% by mass fraction.

5. The preparation method of indole by catalytic saccharides according to claim 1, characterized in that, In the carbon-supported Co-Sn catalyst, the loading amount of Co is 5% by mass fraction, and the loading amount of Sn is 10% by mass fraction.

6. The preparation method of indole by catalytic conversion of saccharides according to claim 1, wherein, When the sugars, water, aniline, and catalyst perform a high-temperature reaction under a reducing atmosphere, the pressure range of the reducing atmosphere is 2 MPa to 8 MPa.

7. The preparation method of indole by catalyzing saccharides according to claim 6, characterized in that, When the sugars, water, aniline, and catalyst perform a high-temperature reaction under a reducing atmosphere, the pressure range of the reducing atmosphere is 4 MPa to 5 MPa.

8. A preparation method for catalytically preparing indole from saccharides according to claim 1, characterized in that, When the sugars, water, aniline, and catalyst perform a high-temperature reaction under a reducing atmosphere, the reaction temperature range of the reducing atmosphere is 200°C to 300°C.

9. The preparation method of indole by catalytic conversion of sugars according to claim 8, characterized in that, When the sugars, water, aniline, and catalyst perform a high-temperature reaction under a reducing atmosphere, the reaction temperature of the reducing atmosphere is 250°C.

10. The preparation method of indole by catalytic conversion of saccharides according to claim 1, characterized in that, The volume ratio of the water to the aniline ranges from 54:1 to 8:3.

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