Process for the preparation of furfural by catalytic hydrolysis of cellulose

Abstract

The application provides a method for preparing furfural through catalytic hydrolysis of cellulose, which comprises using cellulose as raw material to efficiently prepare furfural through catalytic hydrolysis. Preparation of the hydrolysis catalyst mainly comprises the following steps: weighing a certain amount of combustible solid waste and placing it in a tube furnace, carbonizing for 2 hours in an N2 atmosphere. The black solid powder after carbonization is added into deionized water with an appropriate amount of ferric chloride and stirred to mix uniformly, then filtered, dried and calcined to complete loading. The dried solid is mixed with a certain amount of sulfuric acid in a polytetrafluoroethylene kettle and placed in an oven at 180 DEG C. After filtering and drying, the obtained hydrolysis catalyst is obtained. The cellulose hydrolysis step based on the above catalyst is as follows: the catalyst is mixed with a certain amount of cellulose according to a certain mass ratio and placed in a hydrothermal reaction kettle, an organic solvent is added, and the catalytic conversion reaction is completed under a certain reaction temperature and holding time. After cooling to room temperature, the solid-liquid mixture is taken out and filtered, and the obtained filtrate is rich in furfural.

Description

Technical Field

[0001] This application relates to a method for preparing furfural by catalytic hydrolysis of cellulose, belonging to the field of biomass hydrolysis and waste utilization technology. Background Technology

[0002] Lignocellulose is widely found in nature. If used properly, it can be used to prepare new fuels and high-value-added chemicals. In particular, the recycling of agricultural and forestry waste can not only reduce the pressure of waste disposal, but also further obtain high-value-added products. On the other hand, waste plastics, waste rubber, waste lignin and other wastes are excellent carbon-based materials. Utilizing these wastes to prepare carbon-based catalysts can turn waste into treasure and realize the resource utilization of solid waste. Therefore, combining the above two types of wastes has broad application prospects.

[0003] Lignocellulose raw materials typically consist of three main components: cellulose, hemicellulose, and lignin. The proportions of these components vary depending on the type of raw material, with cellulose being the most abundant (40%-60%) and the most abundant natural polymer in the world. Furfural (C5H4O2) is a high-value platform compound, reportedly the only biomass-derived organic compound capable of replacing crude oil-based organic compounds used in industry. Furfural can be used to directly or indirectly derive over 1600 chemical products, widely applied in pharmaceuticals, pesticides, resins, daily chemicals, textiles, and petrochemicals. Hemicellulose is mainly composed of pentose sugars, with relatively low molecular weight and degree of polymerization, making it easily hydrolyzed into furfural. Cellulose is a polysaccharide compound composed of hexose sugars linked by β-1,4 glycosidic bonds; the selectivity for furfural during cellulose hydrolysis is typically 30-40%. This invention proposes a method for converting cellulose into furfural. Summary of the Invention

[0004] Purpose of the invention

[0005] A method for preparing furfural by catalytic hydrolysis of cellulose is disclosed. The method mainly includes the preparation of a hydrolysis catalyst and the optimization of the hydrolysis method based on the catalyst. Carbon-based materials are prepared using waste plastics, waste rubber, waste lignin and other waste materials as raw materials. FeCl3 is further loaded and acidified to obtain a solid acid catalyst. Combined with an aprotic polar compound solvent, the efficient conversion of cellulose to furfural is achieved.

[0006] Traditional homogeneous catalysts have drawbacks such as difficulty in separating the subsequent products from the catalyst, inconvenience in recycling, and high pollution. The novel solid hydrolysis catalyst proposed in this invention will further overcome these disadvantages and achieve a low-pollution, high-efficiency furfural production process.

[0007] Technical solution

[0008] This application provides a method for preparing furfural by catalytic hydrolysis of cellulose. The method includes the preparation of a hydrolysis catalyst and a hydrolysis method, comprising the following steps:

[0009] Step 1: Weigh 2g-10g of carbon-based raw material and place it in a tube furnace. Remove it with N2 and set the tube furnace to 500℃. Carbide it in an N2 atmosphere. Mix the carbonized black solid powder with metal chloride and add it to deionized water and stir. Then, perform magnetic stirring in a water bath. After magnetic stirring, filter and dry to obtain carbon-based solid material loaded with metal salt.

[0010] Step 2: The dried carbon-based solid loaded with metal salts is mixed with sulfuric acid in a polytetrafluoroethylene reactor. The reactor is then placed in an oven for acidification for 12 hours to obtain a black solid-liquid mixture.

[0011] Step 3: After the reaction vessel is cooled to 25°C, the black solid-liquid mixture is washed with deionized water, filtered to obtain a black solid substance, and calcined to obtain a metal halide-carbon-based solid acid hydrolysis catalyst.

[0012] Step 4: Weigh the hydrolysis catalyst metal halide-carbon-based solid acid obtained in Step 3 and the cellulose raw material, mix them and place them in a hydrothermal reactor, add solvent and mix evenly;

[0013] Step 5: After setting the reaction temperature of the hydrothermal reactor, maintain the temperature until the reaction is complete and the temperature drops to 25°C. Then, remove the solid-liquid mixture and filter it. The resulting filtrate is rich in furfural.

[0014] The present invention has the following beneficial effects:

[0015] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0016] (1) The present invention provides a method for preparing furfural by catalytic hydrolysis of cellulose. The hydrolysis catalyst (solid) has the advantages of easy separation of the subsequent products from the catalyst and convenient recycling compared with the current technology. Based on this, the reusability efficiency of the catalyst can be effectively improved and the water pollution during the hydrolysis process can be reduced.

[0017] (2) In the prior art, the yield of cellulose hydrolysis to furfural is 30-40%. However, the reaction media used in this application, γ-valerolactone, γ-butyrolactone and sulfolane, are typical aprotic polar solvents. The solvent molecules affect the reaction kinetics by changing the stability of the protonated transition state of the intermediate substances, so as to accelerate the acid-catalyzed cellulose conversion process. The aprotic polar solvent can dissolve the intermediates, by-products and polymers formed in the catalytic or non-catalytic reaction process, eliminate them to prevent them from participating in the furfural degradation reaction, reduce the deactivation of the catalyst caused by the deposition of carbon-containing compounds on the surface, thereby slowing down the furfural degradation rate, enhancing the stability of furfural in the system, and ultimately improving the yield and selectivity of furfural.

[0018] (3) In the hydrolysis catalyst prepared in this invention, Lewis acid sites required for the hydrolysis reaction are provided by metal salt loading, and Brønsted acid sites in the hydrolysis reaction are provided by acidification. Therefore, the prepared hydrolysis catalyst can have both Lewis acid and Brønsted acid sites. Lewis acid can effectively promote the isomerization of glucose into aldose-ketose, and then Brønsted acid is used to catalyze its dehydration to generate furfural. The catalytic system formed by the combination of the catalyst and the hydrolysis solvent has a synergistic effect, which greatly promotes the furfural yield when cellulose is used as a hydrolysis raw material. In addition, selecting specific metal chlorides for loading can further provide catalytic active sites on the catalyst surface by using chloride ions, thereby realizing a three-in-one (-Fe, -SO3H, -Cl three different catalytic active sites) hydrolysis catalyst, which effectively improves the utilization value of cellulose raw materials, and the furfural yield can reach 66%.

[0019] (4) This invention can use cellulose-rich agricultural waste as raw material and combustible solid waste carbonized as catalyst to prepare substrate. Through a series of optimized preparation processes, the conversion efficiency of cellulose hydrolysis to furfural can be effectively improved. Applying this technology to industrial production can effectively reduce economic costs and achieve cost reduction and efficiency improvement, and has good economic and applicable prospects. Attached Figure Description

[0020] Figure 1 Please provide a flowchart of the method for preparing furfural by catalytic hydrolysis of cellulose;

[0021] Figure 2 This application includes a diagram showing the furfural yield in the liquid product. Detailed Implementation

[0022] The preferred embodiments of the present invention will now be described in detail with reference to specific examples. It should be understood that the following examples are given for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from its spirit and essence.

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0024] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0025] One embodiment of this application provides a method for preparing furfural by catalytic hydrolysis of cellulose. The method includes the preparation of a hydrolysis catalyst and a hydrolysis method, comprising the following steps:

[0026] Step 1: Weigh 2g-10g of carbon-based raw material and place it in a tube furnace. Remove it with N2 and set the tube furnace to 500℃. Carbide it in an N2 atmosphere. Mix the carbonized black solid powder with metal chloride and add it to deionized water and stir. Then, perform magnetic stirring in a water bath. After magnetic stirring, filter and dry to obtain carbon-based solid material loaded with metal salt.

[0027] Step 2: The dried carbon-based solid loaded with metal salts is mixed with sulfuric acid in a polytetrafluoroethylene reactor. The reactor is then placed in an oven for acidification for 12 hours to obtain a black solid-liquid mixture.

[0028] Step 3: After the reaction vessel is cooled to 25°C, the black solid-liquid mixture is washed with deionized water, filtered to obtain a black solid substance, and calcined to obtain a metal halide-carbon-based solid acid hydrolysis catalyst.

[0029] Step 4: Weigh the metal halide-carbon-based solid acid hydrolysis catalyst obtained in Step 3 and the cellulose raw material, mix them and place them in a hydrothermal reactor, add solvent and mix evenly;

[0030] Step 5: After setting the reaction temperature of the hydrothermal reactor, maintain the temperature until the reaction is complete and the temperature drops to 25°C. Then, remove the solid-liquid mixture and filter it. The resulting filtrate is rich in furfural.

[0031] In one embodiment, the carbon-based raw material includes combustible solid waste.

[0032] In one embodiment, the combustible solid waste includes waste plastics, waste rubber, and waste lignin.

[0033] In one embodiment, the metal chloride in step 1 is ferric chloride, wherein the amount of metal chloride used is: the molar ratio of metal element to cellulose is x:1, where 0≤x≤1.

[0034] In one embodiment, in step 1, the heating rate of the tube furnace is 15℃ / min - 25℃ / min; the carbonization time in the N2 atmosphere is 2h - 4h; and the temperature of the water bath is 25℃ - 40℃.

[0035] In one embodiment, in step 2, the reaction vessel is placed in an oven for acidification for 10-12 hours.

[0036] In one embodiment, in step 3, the black solid substance obtained by filtration is calcined by placing it at 500℃~600℃ for 3h~6h.

[0037] In one embodiment, in step 3, the black solid substance obtained by filtration is calcined by placing it at 500°C for 3 hours.

[0038] In one embodiment, in step 4, the mass ratio of catalyst to cellulose is m. 催化剂 :m 纤维素 =x:1, where 0.5≤x≤4.

[0039] In one embodiment, the solvent added in step 4 is an aprotic polar compound.

[0040] In one embodiment, the solvent added in step 4 includes γ-valerolactone, γ-butyrolactone, and sulfolane.

[0041] In one embodiment, in step 4, the solid-liquid ratio of the raw material to the solvent during the reaction is 1:10-20.

[0042] In one embodiment, in step 5, the reaction temperature of the hydrothermal reactor is set to 150℃-210℃, the heating rate is 10℃ / min-20℃ / min, and the holding time is 30min-180min.

[0043] One embodiment of this application provides a method for preparing furfural by catalytic hydrolysis of cellulose. This method includes the preparation of a hydrolysis catalyst and a hydrolysis process. Combustible solid waste is selected as the substrate, and metal chlorides are used as the supporting agent. A solid hydrolysis catalyst with excellent catalytic performance is prepared through acidification and excess impregnation. Benefiting from the excellent acidic sites of the catalyst and the further optimization and control of the acidic sites by the metal loading, by changing the loading amount of metal elements, acidification temperature, and time during the preparation process, a catalyst with an optimal balance point between the ratio of Lewis acid and Brønsted acid can be obtained, thus yielding a hydrolysis catalyst with high furfural selectivity. This catalyst has advantages such as high furfural selectivity and easy recovery. Furthermore, the hydrolysis solvent and hydrolysis conditions were optimized, and the synergistic effect of combining the catalyst with an aprotic polar compound hydrolysis solvent greatly improves the furfural yield during cellulose hydrolysis. This completes the integrated design of the catalyst from preparation to the hydrolysis preparation of furfural, and ultimately achieves a high conversion rate of furfural preparation from cellulose as a raw material.

[0044] One embodiment of this application provides a method for preparing a hydrolysis catalyst, comprising the following steps:

[0045] Step 1: Weigh a certain mass of combustible solid waste and place it in a tube furnace. After N2 is blown off for a certain time, set the tube furnace to heat up to 500°C at an appropriate heating rate and carbonize it in an N2 atmosphere. Add the carbonized black solid powder and an appropriate amount of metal chloride to deionized water and stir to mix it evenly. Then, perform magnetic stirring in a water bath at a certain temperature. After that, filter and dry to obtain carbon-based solid material loaded with metal salt.

[0046] Step 2: After completing Step 1, mix the dried solid with a certain amount of sulfuric acid in a polytetrafluoroethylene reactor, and place the reactor in an oven for acidification for 12 hours.

[0047] Step 3: After the reaction vessel cools to room temperature, wash the black solid-liquid mixture with deionized water until the filtrate is neutral. Filter to obtain a black solid substance, calcine it at 500℃ for 3 hours, and the resulting product is a metal halide-carbon-based solid acid catalyst.

[0048] Step 4: Weigh a certain mass of catalyst and cellulose raw material, mix them according to a certain mass ratio, and place them in a hydrothermal reactor. Add a certain amount of solvent according to a certain solid-liquid ratio and mix thoroughly.

[0049] Step 5: Set the reaction temperature of the hydrothermal reactor to a certain value and heat it at an appropriate heating rate. After reaching the set temperature, keep it at that temperature for a certain time. After the reaction is completed and the temperature drops to room temperature, take out the solid-liquid mixture and filter it. The resulting filtrate is rich in furfural.

[0050] In one embodiment of this application, the molar ratio of Fe element loading to cellulose is x:1, where 0≤x≤1. In another embodiment, the molar ratio of Fe element loading to cellulose is preferably 1:1.

[0051] In one embodiment of this application, the mass ratio of catalyst to cellulose is set to mcatalyst:mcellulose = x:1, 0.5≤x≤4. In another embodiment, the mass ratio of catalyst to cellulose is preferably set to x=0.5.

[0052] In one embodiment of this application, the specific organic solvent added is γ-valerolactone, γ-butyrolactone, or sulfolane. The reaction temperature of the hydrothermal reactor is set to 150-210°C, preferably 150°C, the heating rate is 10-20°C / min, preferably 15°C / min, and the holding time is 30-180 min, preferably 60 min.

[0053] Example 1: Carbonization of waste polyethylene plastic as a substrate for catalyst preparation; hydrolysis of cellulose to prepare furfural.

[0054] Step 1: Weigh 2g of waste polyethylene plastic and place it in a tube furnace. After N2 stripping for a certain time, set the tube furnace to rise to 500℃ at 20℃ / min and carbonize it in an N2 atmosphere. Add the carbonized black solid powder and an appropriate amount of ferric chloride (molar ratio 1:1) to 50ml of deionized water and stir to mix it evenly. Magnetically stir it in a water bath at 30℃ for 2h. Then filter to obtain carbon-based solid material loaded with metal salts and calcine it at 550℃ for 4h.

[0055] Step 2: After completing Step 1, mix 0.5g of the dried solid with 5ml of sulfuric acid in a polytetrafluoroethylene reactor, and place the reactor in an oven at 180℃ for 12h to acidify.

[0056] Step 3: After the reaction vessel cools to room temperature, wash the black solid-liquid mixture with deionized water until the filtrate is neutral. Filter to obtain a black solid substance, calcine it at 500℃ for 3 hours, and the resulting product is a metal halide-carbon-based solid acid catalyst.

[0057] Step 4: Mix the catalyst and cellulose raw material at a mass ratio of 1:2 and add a certain amount of solvent (γ-valerol) and mix evenly;

[0058] Step 5: Add the solid-liquid mixture from Step 1 to the high-pressure reactor, set the hydrolysis reaction temperature to 150℃, and the heating rate to 15℃ / min. Maintain the hydrolysis at 150℃ for 60 minutes. After the hydrolysis is completed, let the reactor cool down to room temperature, filter the solid-liquid mixture, and retain the liquid product.

[0059] Step Six: The liquid product was further filtered, and 2.0 ml of the liquid product was analyzed using gas chromatography-mass spectrometry (GC / MS). The product composition was analyzed against the NIST spectral library. Based on the analytical data, the furfural yield in the liquid product was calculated to be 66.5%. (See [link to relevant documentation]). Figure 2 .

[0060] Example 2: Preparation of furfural from waste lignin carbonization as a substrate for cellulose hydrolysis.

[0061] Step 1: Weigh 2g of waste lignin and place it in a tube furnace. After N2 stripping for a certain time, set the tube furnace to rise to 500℃ at 20℃ / min and perform carbonization in an N2 atmosphere. Add the carbonized black solid powder and an appropriate amount of ferric chloride (molar ratio 1:1) to 50ml of deionized water and stir to mix evenly. Magnetically stir in a water bath at 30℃ for 2h, then filter to obtain carbon-based solid material loaded with metal salts, and calcine at 550℃ for 4h.

[0062] Step 2: After completing Step 1, mix 0.5g of the dried solid with 5ml of sulfuric acid in a polytetrafluoroethylene reactor, and place the reactor in an oven at 180℃ for 12h to acidify.

[0063] Step 3: After the reaction vessel cools to room temperature, wash the black solid-liquid mixture with deionized water until the filtrate is neutral. Filter to obtain a black solid substance, calcine it at 500℃ for 3 hours, and the resulting product is a metal halide-carbon-based solid acid catalyst.

[0064] Step 4: Mix the catalyst and cellulose raw material at a mass ratio of 1:2 and add a certain amount of solvent (γ-butyrolactone) and mix evenly;

[0065] Step 5: Add the solid-liquid mixture from Step 1 to the high-pressure reactor, set the hydrolysis reaction temperature to 180℃, and the heating rate to 15℃ / min. Maintain the hydrolysis at 180℃ for 50 minutes. After the hydrolysis is completed, wait for the reactor to cool down to room temperature, filter the solid-liquid mixture, and retain the liquid product.

[0066] Step Six: Further filter the liquid product and take 2.0 ml of the liquid product for analysis using gas chromatography-mass spectrometry (GC / MS). The product composition analysis was performed against the NIST spectral library. Based on the analytical data, the furfural content in the liquid product was calculated to be 63.8%. (See [link to relevant documentation]). Figure 2 .

[0067] The above are merely preferred embodiments of the present invention. It should be noted that, for those skilled in the art, numerous improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing furfural by catalytic hydrolysis of cellulose, characterized in that, The method includes the preparation of a hydrolysis catalyst and a hydrolysis method, comprising the following steps: Step 1: Weigh 2g-10g of carbon-based raw material and place it in a tube furnace. Remove it with N2 and set the tube furnace to 500℃. Carbide it in an N2 atmosphere. Mix the carbonized black solid powder with metal chloride and add it to deionized water and stir. Then, perform magnetic stirring in a water bath. After magnetic stirring, filter and dry to obtain carbon-based solid material loaded with metal salt. Step 2: The dried carbon-based solid loaded with metal salts is mixed with sulfuric acid in a polytetrafluoroethylene reactor. The reactor is then placed in an oven for acidification for 12 hours to obtain a black solid-liquid mixture. Step 3: After the reaction vessel is cooled to 25°C, the black solid-liquid mixture is washed with deionized water, filtered to obtain a black solid substance, and calcined to obtain a metal halide-carbon-based solid acid hydrolysis catalyst. Step 4: Weigh the metal halide-carbon-based solid acid hydrolysis catalyst obtained in Step 3 and the cellulose raw material, mix them and place them in a hydrothermal reactor, add solvent and mix evenly; Step 5: After setting the reaction temperature of the hydrothermal reactor, maintain the temperature until the reaction is complete and the temperature drops to 25°C. Then, remove the solid-liquid mixture and filter it. The resulting filtrate is rich in furfural. The carbon-based raw material is waste polyethylene plastic or waste lignin; the metal chloride in step 1 is ferric chloride, and the amount of metal chloride used is such that the molar ratio of metal element to cellulose is 1:1; the heating rate of the tube furnace is 15℃ / min - 25℃ / min; the carbonization time in the N2 atmosphere is 2h-4h; the temperature of the water bath is 25℃-40℃; in step 3, the black solid substance obtained by filtration is calcined at 500℃~600℃ for 3h~6h; the solvent added in step 4 is γ-valerolactone, γ-butyrolactone, or sulfolane.

2. The method for preparing furfural by catalytic hydrolysis of cellulose according to claim 1, characterized in that, In step 2, the reaction vessel is placed in an oven for acidification for 10-12 hours.

3. The method for preparing furfural by catalytic hydrolysis of cellulose according to claim 1, characterized in that, In step 4, the mass ratio of catalyst to cellulose is m. 催化剂 :m 纤维素 =x:1, where 0.5≤x≤4.

4. The method for preparing furfural by catalytic hydrolysis of cellulose according to claim 1, characterized in that, In step 5, the reaction temperature of the hydrothermal reactor is set to 150℃-210℃, the heating rate is 10℃ / min-20℃ / min, and the holding time is 30min-180min.

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