A process for producing high-value chemicals from bamboo

Abstract

The present invention belongs to the field of biomass catalytic pyrolysis technology and provides a process for producing high-value chemicals from bamboo. Cellulose and hemicellulose in the bamboo are converted into a variety of high-value methoxyphenol products in the presence of a composite catalyst; the composite catalyst comprises at least supported iron oxide and an alkaline earth metal oxide. Using bamboo dust as the raw material, the present invention conducts a catalytic pyrolysis reaction in the presence of the composite catalyst. Through the synergistic action of the various components of the composite catalyst, the chemical bonds within the bamboo are gradually broken, reorganized, and isomerized, resulting in directional changes in the molecular structure. This ultimately increases the yield of phenolic products and efficiently produces high-value methoxyphenol chemicals, providing a novel and economical technical path for the industrial production of methoxyphenol chemicals.

Description

Technical Field

[0001] The invention belongs to the technical field of biomass catalytic pyrolysis and relates to a process for preparing high-value chemicals from bamboo. Background Art

[0002] As the fourth largest energy source after fossil fuels, biomass has become a key research and industrial focus due to its widespread availability and environmentally friendly characteristics. Biomass energy boasts numerous advantages, including zero carbon emissions, cleanliness, renewable energy, and easy accessibility, making it considered an ideal and promising alternative to fossil fuels.

[0003] Biomass pyrolysis is a technology that heats dried, shaped biomass under an inert atmosphere to produce products such as biochar, biotar, and pyrolysis gas. Compared to other processes such as biomass gasification and liquefaction, biomass pyrolysis offers advantages in terms of simplicity, relatively mild conditions, and low production costs.

[0004] Lignocellulose, the most abundant renewable biomass raw material in nature, is widely found in wood, bamboo, straw, and other materials. It is primarily composed of cellulose (40%-50%), hemicellulose (25%-30%), and lignin (20%-30%). Lignocellulosic biomass can be used to produce biochar, synthesis gas, and hydrogen, and can also be catalytically converted to produce chemicals such as aromatic hydrocarbons, levoglucose, levoglucosone, furfural, and phenols. For example, CN118993863A uses a supported Zr, Mn, or Zn-modified Cu-based metal catalyst to hydrogenolyze biomass, achieving a yield of over 65% for the target product, cyclopentanone. CN110669056A uses a metal-modified ammoniated zeolite molecular sieve as a catalyst and crop straw, wood, or wood waste as raw materials to prepare 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one (LAC). Metal modification further regulates the Lewis acid sites in the molecular sieve, thereby achieving high yield and selectivity in the preparation of LAC. CN116174025A uses bagasse as raw material and a rare earth metal-modified ZSM-5 zeolite molecular sieve as a catalyst. The catalytic pyrolysis is performed at 500°C under a nitrogen atmosphere, resulting in a liquid product containing 45.86% 2,3-dihydrobenzofuran.

[0005] CN115283006A uses an ammonium molybdate-modified HZSM-5 catalyst with pine sawdust as the raw material. At 550°C under a nitrogen atmosphere, the aromatic carbon yield is 19.5%. Patent CN114989842A uses cotton stalks, wheat straw, chestnut shells, and bamboo sawdust as biomass feedstocks. After modification with ferric nitrate and calcium nitrate, the biomass is subjected to graded pyrolysis and catalysis to produce a bio-oil rich in monocyclic aromatic hydrocarbons (benzene, toluene, and p-toluene). The content of monocyclic aromatic hydrocarbons (benzene, toluene, and p-toluene) in the product is 67.51%.

[0006] Regarding the production of phenolic substances, CN116355642A uses zeolite molecular sieves combined with seaweed charcoal for graded catalytic pyrolysis of poplar sawdust to produce light aromatic hydrocarbons and monophenols. The resulting liquid bio-oil has a monophenol content of 29.3% and an aromatic hydrocarbon content of 43.3%. CN115888849A uses pine wood as the biomass feedstock, carbonizing the sawdust and modifying it with iron and cobalt to produce a modified activated carbon catalyst. In a nitrogen atmosphere, pine sawdust is pyrolyzed at 600°C over the modified activated carbon catalyst. The pyrolysis products are all phenolic compounds, with phenol being the main product, with a selectivity of 84.01%.

[0007] CN111234848A uses biomass as raw material, and loads ammonium sulfate on the biomass by an impregnation method to obtain loaded biomass; the loaded biomass is pyrolyzed under anaerobic conditions, and the obtained pyrolysis gas is condensed to obtain phenol-rich bio-oil with a liquid yield of 43.6-46.3wt%, and the yield of phenolic substances is only 5.1-5.4wt%.

[0008] CN102199435A uses sodium carbonate as a catalyst and fir sawdust, pine sawdust, straw and pine wood as raw materials to react at 450-480° C. to prepare guaiacol. The yield of the liquid product is 40.2%-45.5%, and the guaiacol content is 40.19%-45.53%.

[0009] CN112409140A discloses a method for depolymerizing lignin to prepare lignin phenolic monomers. Willow sawdust is used as the raw material, placed in ethylene glycol with a Ru / C catalyst, and phosphoric acid is added. The reaction proceeds at 160-200°C to produce lignin phenolic monomers. The total yield of propylguaiacol, propylsyringol, propenylguaiacol, and propenylsyringol is 21.8% by weight, with a selectivity of 95.1% for propylguaiacol and propylsyringol. The composition and distribution of other products are not provided.

[0010] Bamboo, as a biomass resource, is abundant and concentrated in many parts of my country. Converting it into high-grade, clean energy and high-value chemicals is one of the effective ways to address energy shortages and environmental pollution. Pyrolysis of bamboo can produce bamboo tar, bamboo charcoal, and combustible gas. Bamboo tar, the primary product of bamboo pyrolysis, has a complex composition consisting primarily of oxygenated compounds, including phenols, ketones, aldehydes, acids, alcohols, furans, hydrocarbons, and sugars, making it a potential liquid fuel and chemical feedstock. However, its high water content, high oxygen content, and low pH value result in low calorific value, poor thermal stability, and corrosiveness, significantly limiting its application. Currently, relatively little research exists on the production of high-value-added chemicals from bamboo via pyrolysis or catalytic pyrolysis.

[0011] CN116333773A uses bamboo dust mixed with ferroferric oxide and / or calcium oxide for catalytic pyrolysis. While producing bamboo tar, it also reduces its acid, water, and oxygen contents and promotes the conversion of organic components into high-value-added ingredients such as ketones, hydrocarbons, and phenols. Compared to pyrolysis alone, the addition of a mixed catalyst of ferroferric oxide and calcium oxide to bamboo dust reduces the water content from 24.68% to 7.17%, the oxygen content from 38.48% to 30.75%, and the acid content from 6.72% to 0.98%. Furthermore, the use of the mixed catalyst significantly increases the phenolic compound content, from an initial 52.06% to 60.12%, compared to using a single catalyst. However, the composition of the phenolic compounds is not provided.

[0012] CN104341273A uses bamboo as raw material, mechanically mixes it with a palladium-based catalyst, and then rapidly pyrolyzes it in a nitrogen atmosphere at 250°C-380°C to obtain a liquid yield of 35.3%-39.6%, and the yield of 4-ethylphenol is 1.6%-2.5%. The content of 4-ethylphenol in the organic liquid product (excluding water) is 10.2%-15.2%.

[0013] CN107337587A crushes and screens bamboo to obtain a pyrolysis feedstock, then conducts a pyrolysis reaction in an atmosphere containing ammonia and an inert gas. The resulting phenol-rich liquid oil contains phenol, 2-methylphenol, p-methylphenol, 4-ethylphenol, 2-methoxyphenol, 2-methoxy-4-propenylphenol, 2,6-dimethoxyphenol, and other phenolic compounds with a selectivity of 60%-65%. However, the composition distribution of the different phenolic products is not provided.

[0014] CN117902958A discloses a method for extracting 2,6-dimethoxyphenol from bamboo using an ethylene glycol solvothermal process. Bamboo cuttings, ethylene glycol, and water are placed in a hydrothermal kettle, maintained at 200-240°C for 1-2 hours, and then cooled to room temperature to obtain an ethylene glycol extract. After ether extraction and evaporation of the ether solution, the 2,6-dimethoxyphenol peak in the remaining liquid has the largest area, accounting for 72%-80%. Because data such as product mass and the composition and distribution of other compounds are not provided, the actual yield and selectivity of the target product cannot be determined.

[0015] At present, research on the high-value utilization of methoxyphenols based on bamboo biomass is still relatively limited. It is of great significance to develop suitable methods to achieve catalytic pyrolysis of bamboo to produce high-value chemicals. Summary of the Invention

[0016] As a key biomass resource, bamboo boasts significant advantages in abundance and rapid growth, attracting significant attention in the global exploration of renewable energy and materials. my country boasts abundant and relatively concentrated bamboo resources. Converting bamboo into high-quality, clean energy is undoubtedly a potential and effective way to replace some fossil fuels. The differences between bamboo and wood primarily lie in their chemical composition and physical properties. While bamboo's chemical composition is similar to that of wood, the main difference is that wood comprises 40%-50% cellulose, 25%-35% lignin, and 15%-30% hemicellulose. Bamboo, on the other hand, is primarily composed of cellulose and hemicellulose, with a higher cellulose content than wood. Regarding pyrolysis temperatures, wood typically decomposes between 150-270°C, while bamboo decomposes over a wider range, from 100-500°C.

[0017] The present invention proposes a process for producing high-value chemicals from bamboo. Using bamboo dust (bamboo powder) as the raw material, a composite catalyst is added during pyrolysis. The goal is to leverage the synergistic effects of the components of the specifically formulated composite catalyst to gradually break, restructure, and isomerize the chemical bonds within the bamboo, resulting in directional changes in the molecular structure. This increases the yield of phenolic products and efficiently produces high-value methoxyphenol chemicals such as guaiacol, 2,6-dimethoxyphenol, 4-methylguaiacol, and 4-ethylguaiacol. The technical solution provided by this invention can achieve directional catalytic conversion of biomass, achieving efficient, high-value, and environmentally friendly utilization of biomass while also partially replacing fossil energy.

[0018] To achieve the above object, the technical solution of the present invention is as follows:

[0019] A process for producing high-value chemicals from bamboo, wherein cellulose and hemicellulose in the bamboo are converted into a variety of methoxyphenol products in the presence of a composite catalyst; the composite catalyst comprises at least supported iron oxide and alkaline earth metal oxide.

[0020] Bamboo dust is used as raw material, nitrogen is used as carrier gas, and a catalytic pyrolysis reaction is carried out at a reaction temperature of 450-500° C. and a pressure of 0.1-0.4 MPa.

[0021] The mass ratio of the composite catalyst to the bamboo dust is 0.2-1.5:1.

[0022] The various methoxyphenols include guaiacol, 2,6-dimethoxyphenol, 4-methylguaiacol and 4-ethylguaiacol.

[0023] The iron oxide in the supported iron oxide is a mixture of ferric oxide and ferrosoferric oxide, with a content of 10-30%; the carrier is a mixed aluminum oxide and silicon oxide, with a content of 10-40%; and the content of alkaline earth metal oxide is 5-40%.

[0024] The composite catalyst also includes nanometer HZSM-5 molecular sieve with a silicon-aluminum ratio of 20-30, and the content is 1-10%.

[0025] The alkaline earth metal oxide in the composite catalyst includes calcium oxide and / or magnesium oxide.

[0026] The molar ratio of silicon oxide to aluminum oxide in the carrier is 1-15:1.

[0027] The method also includes drying and crushing the bamboo powder. The drying temperature is 80-100° C. and the drying time is 10-12 hours.

[0028] The particle size of the bamboo powder is 40-80 meshes.

[0029] The preparation method of the composite catalyst comprises the following steps:

[0030] (1) The aluminum source is prepared into an aqueous solution with a mass concentration of 10-30 wt%, the silicon source is added to the aluminum source aqueous solution at 30-60°C, and the mixture is rapidly stirred for 3-4 hours. The iron salt is added while stirring, and the mixture is stirred for 2-3 hours. The mixture is heated to 80-100°C, and the pH value is titrated to 7-8 with 10%-30% sodium carbonate solution. The mixture is reacted for 3-4 hours, cooled, filtered, and the filter cake is washed with deionized water until the conductivity of the filtrate is no more than 300 S / m;

[0031] (2) mixing the filter cake, silica sol and / or aluminum sol aqueous solution with alkaline earth metal oxide or a mixture of nano-HZSM-5 molecular sieve and alkaline earth metal oxide and beating the mixture to uniformly prepare a catalyst slurry;

[0032] (3) The catalyst slurry is sent to a spray dryer for drying and granulation, and then calcined to obtain a composite catalyst.

[0033] The silicon source is one or more of water glass, silica sol and sodium metasilicate; the aluminum source is one or more of aluminum sulfate, aluminum trichloride, sodium metaaluminate and aluminum sol; and the iron salt is one or more of ferric sulfate, ferric nitrate and ferric chloride.

[0034] The molar ratio of the silicon source to the aluminum source in step (1) is 1-15:1, wherein the silicon source is calculated as SiO2 and the aluminum source is calculated as Al2O3.

[0035] The molar ratio of the iron salt to the silicon source in step (1) is 1-10:1.

[0036] In step (2), the mass ratio of the silica sol and / or alumina sol aqueous solution to the filter cake is 1:1; the concentration of the silica sol and / or alumina sol aqueous solution is 5-10%.

[0037] In step (2), the stirring speed of the beating tank is not less than 300 rpm, and the beating time is 10-12 hours.

[0038] During the drying and granulation in step (3), the slurry temperature is 100-150°C, and the dryer inlet temperature is controlled not to exceed 300°C to obtain a powder catalyst after drying and forming. The particles are spherical, and the particle size of more than 90% of the particles is controlled to be 40-150 microns.

[0039] In step (3), the calcination temperature is controlled at 600-900° C. and the calcination time is 3-4 hours.

[0040] The beneficial effects of the present invention are as follows:

[0041] The present invention uses bamboo dust as raw material and conducts a catalytic pyrolysis process under the action of a composite catalyst. The synergistic effect of the components of the specifically formulated composite catalyst gradually breaks, restructures, and isomerizes the chemical bonds within the bamboo, resulting in a directional change in the molecular structure. This ultimately increases the yield of phenolic products and efficiently produces high-value methoxyphenol chemicals, providing a novel and economical technical path for the industrial production of high-value methoxyphenol chemicals. Furthermore, the catalyst has the advantages of low cost and ease of preparation. Specific implementation methods

[0042] Example 1

[0043] Catalyst preparation: Weigh 680 g of anhydrous aluminum chloride and dissolve it in 1000 g of water to make an aqueous solution. Weigh 1500 g of water glass and stir to dissolve. Add the water glass frit into the aluminum chloride solution at 35°C and mix. Stir rapidly for 3 hours. Beat into a paste. Add 407 g of anhydrous ferric chloride while stirring. Stir for 2 hours and heat to 90°C. Then titrate with 10% sodium carbonate solution to a pH of 7-8. React for 3 hours. Cool and filter. Wash the filter cake with deionized water until the filtrate conductivity is no more than 300 S / m.

[0044] The filter cake was mixed with a 6% silica sol aqueous solution in a ratio of 1:1, and then 100 g of nano HZSM-5 molecular sieve with a silicon-aluminum ratio of 20, 200 g of magnesium oxide and 280 g of calcium oxide were added, and the mixture was beaten evenly. The stirring speed of the beating tank was not less than 300 rpm, and the beating time was 11 hours to prepare a catalyst slurry;

[0045] The catalyst slurry was transferred to a spray slurrying tank and dried in a spray dryer. The mixing temperature was 100°C and the dryer inlet temperature was controlled at 280°C. The resulting powdered catalyst was spherical, with more than 90% of the particles having a size of 40-150 μm. The catalyst was then transferred to a high-temperature converter and calcined at 900°C for 3 hours to obtain 1400 g of the finished catalyst.

[0046] Bamboo catalytic pyrolysis process: Take 400 grams of the finished catalyst and 500 grams of bamboo powder that has been dried and dehydrated at 95°C for 12 hours and crushed and sieved to 40-80 mesh. Mix them in a 0.8:1 ratio and place them in a mixer for thorough mixing. The mixed materials are loaded into a pyrolysis reactor, heated to 450°C by electric heating and hot nitrogen purge, and kept at this temperature for 15 minutes for pyrolysis reaction. The pressure is maintained at 0.1 MPa. The liquid product is collected and cooled after the reaction for detection.

[0047] Example 2

[0048] Catalyst preparation: Weigh 680 g of anhydrous aluminum chloride and dissolve it in 1000 g of water, weigh 1200 g of silica sol, stir and dissolve, add water glass frit into the aluminum chloride solution at 35°C, mix rapidly for 3 hours, beat into a paste, add 500 g of ferric sulfate while stirring, then stir for 2 hours, and heat to 90°C, then titrate with 10% sodium carbonate solution to a pH of 7-8, react for 3 hours, cool and filter, and wash the filter cake with deionized water until the filtrate conductivity is no more than 300 S / m;

[0049] The filter cake was mixed with a 6% aluminum sol aqueous solution in a ratio of 1:1, and then 100 g of nano HZSM-5 molecular sieve with a silicon-aluminum ratio of 30, 200 g of magnesium oxide and 280 g of calcium oxide were added, and the mixture was beaten evenly to prepare a catalyst slurry, wherein the stirring speed of the beating tank was not less than 300 rpm, and the beating time was 11 hours;

[0050] The catalyst slurry was transferred to a spray slurrying tank and dried in a spray dryer. The mixing temperature was 120°C and the dryer inlet temperature was controlled at 285°C. The resulting powdered catalyst was spherical, with more than 90% of the particles having a size of 40-150 μm. The catalyst was then transferred to a high-temperature converter at 900°C and calcined for 3 hours to obtain 1450 g of the finished catalyst.

[0051] Bamboo catalytic pyrolysis process: Take 750 grams of the finished catalyst and 500 grams of bamboo powder that has been dried and dehydrated at 95°C for 12 hours and crushed and sieved to 40-80 mesh. Mix them in a 1.5:1 ratio and place them in a mixer for thorough mixing. The mixed materials are loaded into a pyrolysis reactor, heated to 450°C by electric heating and hot nitrogen purge, and kept at this temperature for 15 minutes for pyrolysis reaction. The pressure is maintained at 0.2 MPa. The liquid product is collected and cooled after the reaction for detection.

[0052] Example 3

[0053] Catalyst preparation: Weigh 400 g of sodium aluminate and dissolve it in 1000 g of water. Weigh 1000 g of water glass and stir to dissolve. Add the water glass frit into the sodium aluminate solution at 35°C and mix. Stir rapidly for 3 hours. Beat into a paste. Add 407 g of anhydrous ferric chloride while stirring. Stir for 2 hours and heat to 90°C. Then titrate with 10% sodium carbonate solution to a pH of 7-8. React for 3 hours. Cool and filter. Wash the filter cake with deionized water until the filtrate conductivity is no more than 300 S / m.

[0054] The filter cake was mixed with an aqueous solution of 3% silica sol and 3% alumina sol in a ratio of 1:1, and then 100 g of nano HZSM-5 molecular sieve with a silica-alumina ratio of 25, 200 g of magnesium oxide and 280 g of calcium oxide were added, and the mixture was beaten evenly to prepare a catalyst slurry, wherein the stirring speed of the beating tank was not less than 300 rpm, and the beating time was 11 hours;

[0055] The catalyst slurry was transferred to a spray slurrying tank and dried in a spray dryer. The mixing temperature was 125°C and the dryer inlet temperature was controlled at 290°C. The resulting powdered catalyst was spherical, with more than 90% of the particles having a size of 40-150 μm. The catalyst was then transferred to a high-temperature converter at 900°C and calcined for 3 hours to obtain 1400 g of the finished catalyst.

[0056] Bamboo catalytic pyrolysis process: Take 400 grams of the finished catalyst, take 500 grams of bamboo powder that has been dried and dehydrated at 95°C for 12 hours and crushed and sieved to 40-80 mesh, mix them in a 0.8:1 ratio and place them in a mixer for thorough mixing. The mixed materials are loaded into a pyrolysis reactor, heated to 500°C by electric heating and hot nitrogen purging, and kept at this temperature for 15 minutes for pyrolysis reaction. The pressure is maintained at 0.3 MPa; the liquid product cooled after the reaction is collected for detection.

[0057] Example 4

[0058] Catalyst preparation: Weigh 800 g of aluminum sulfate and dissolve it in 1000 g of water, weigh 1200 g of silica sol, stir and dissolve, add water glass frit into the aluminum sulfate solution at 35°C, mix rapidly for 3 hours, beat into a paste, add 600 g of ferric nitrate while stirring, then stir for 2 hours, and heat to 90°C, then titrate with 10% sodium carbonate solution to a pH of 7-8, react for 3 hours, cool and filter, and wash the filter cake with deionized water until the filtrate conductivity is no more than 300 S / m;

[0059] The filter cake was mixed with an aqueous solution of 2% silica sol and 6% alumina sol in a ratio of 1:1, and then 100 g of nano HZSM-5 molecular sieve with a silica-alumina ratio of 25, 200 g of magnesium oxide and 280 g of calcium oxide were added, and the mixture was beaten evenly to prepare a catalyst slurry, wherein the stirring speed of the beating tank was not less than 300 rpm, and the beating time was 11 hours;

[0060] The catalyst slurry was transferred to a spray slurrying tank and dried in a spray dryer. The mixing temperature was 150°C and the dryer inlet temperature was controlled at 295°C. The resulting powdered catalyst was spherical, with more than 90% of the particles having a size of 40-150 μm. The catalyst was then transferred to a high-temperature converter at 900°C and calcined for 3 hours to obtain 1500 g of the finished catalyst.

[0061] Bamboo catalytic pyrolysis process: Take 750 grams of the finished catalyst, take 500 grams of bamboo powder that has been dried and dehydrated at 95°C for 12 hours and crushed and sieved to 40-80 mesh, mix them in a 1.5:1 ratio and place them in a mixer for thorough mixing. The mixed materials are loaded into a pyrolysis reactor, heated to 500°C by electric heating and hot nitrogen purging, and kept at this temperature for 15 minutes for pyrolysis reaction. The pressure is maintained at 0.4 MPa; the liquid product cooled after the reaction is collected for detection.

[0062] Example 5

[0063] Catalyst preparation: Weigh 680 g of anhydrous aluminum chloride and dissolve it in 1000 g of water, weigh 1200 g of silica sol, stir and dissolve, add water glass frit into the aluminum chloride solution at 35°C, mix rapidly for 3 hours, beat into a paste, add 500 g of ferric sulfate while stirring, then stir for 2 hours, and heat to 90°C, then titrate with 10% sodium carbonate solution to a pH of 7-8, react for 3 hours, cool and filter, and wash the filter cake with deionized water until the filtrate conductivity is no more than 300 S / m;

[0064] The filter cake was mixed with an aqueous solution of 2% silica sol and 4% aluminum sol in a ratio of 1:1, and then 200 g of magnesium oxide and 280 g of calcium oxide were added, and the mixture was beaten evenly to prepare a catalyst slurry, wherein the stirring speed of the beating tank was not less than 300 rpm, and the beating time was 11 hours;

[0065] The catalyst slurry was transferred to a spray slurrying tank and dried in a spray dryer. The mixing temperature was 150°C and the dryer inlet temperature was controlled at 295°C. A spherical powder catalyst was obtained, with more than 90% of the particles having a size of 40-150 μm. The catalyst was then transferred to a high-temperature converter at 900°C and calcined for 3 hours to obtain 1300 g of the finished catalyst.

[0066] Bamboo catalytic pyrolysis: 400 g of the finished catalyst was taken, and 500 g of bamboo powder that had been previously dried at 95°C for 12 hours to remove water and crushed and sieved to 40-80 mesh was taken. The mixture was mixed in a mixer at a ratio of 0.8:1 and thoroughly mixed. The mixed materials were loaded into a pyrolysis reactor, heated to 500°C by electric heating and hot nitrogen purging, and kept at this temperature for 15 minutes for pyrolysis reaction. The pressure was maintained at 0.4 MPa. The liquid product that was cooled after the reaction was collected for detection.

[0067] Comparative Example 1

[0068] Bamboo pyrolysis process: Take 1000 grams of bamboo powder that has been dried and dehydrated at 95℃ for 12 hours and crushed and sieved to 40-80 mesh, put it into a pyrolysis reactor, heat it to 500℃ through electric heating and hot nitrogen purge, and keep it at this temperature for 15 minutes for pyrolysis reaction. The pressure is maintained at 0.4MPa; the liquid sample cooled after the reaction is collected for testing.

[0069] Comparative Example 2

[0070] Catalyst preparation: Weigh 680 g of anhydrous aluminum chloride and dissolve it in 1000 g of water, weigh 1200 g of silica sol, stir and dissolve, add water glass frit into the aluminum chloride solution at 35°C, mix rapidly for 3 hours, beat into a paste, add 407 g of anhydrous ferric chloride while stirring, then stir for 2 hours, and heat to 90°C, then titrate with 10% sodium carbonate solution to a pH of 7-8, react for 3 hours, cool and filter, and wash the filter cake with deionized water until the filtrate conductivity is no more than 300 S / m;

[0071] The filter cake was mixed with a 6% silica sol aqueous solution in a ratio of 1:1 and beaten to form a catalyst slurry, wherein the stirring speed of the beating tank was not less than 300 rpm and the beating time was 11 hours;

[0072] The catalyst slurry was transferred to a spray slurrying tank and dried in a spray dryer. The mixing temperature was 150°C and the dryer inlet temperature was controlled at 285°C. A spherical powder catalyst was obtained, with more than 90% of the particles having a size of 40-150 μm. The catalyst was then transferred to a high-temperature converter and calcined at 900°C for 3 hours to obtain approximately 1,370 g of the finished catalyst.

[0073] Bamboo catalytic pyrolysis process: Take 400 grams of catalyst, pre-dry and remove water at 95°C for 12 hours, and crush 500 grams of bamboo powder into 40-80 mesh. Place it in a mixer and mix it thoroughly. The mixed materials are loaded into a pyrolysis reactor, heated to 500°C by electric heating and hot nitrogen purge, and kept at this temperature for 15 minutes to carry out the pyrolysis reaction. The pressure is maintained at 0.4 MPa; the liquid product cooled after the reaction is collected for detection.

[0074] Table 1 shows the analysis results of the liquid-phase pyrolysis oil products obtained from bamboo dust in the control and examples described above under different conditions and catalysts. Table 2 shows the selectivity of different phenolic products in the examples and comparative examples: methoxyphenols (guaiacol, 2,6-dimethoxyphenol, 4-methylguaiacol, 4-ethylguaiacol), phenol, m-cresol, p-cresol, and 4-ethylphenol.

[0075] The results show that Comparative Example 1 is a pyrolysis process of bamboo under catalyst-free conditions, with the main products being phenols and ketones, with a phenol yield of 39.64%, a ketone yield of 36.26%, an alcohol yield of 6.76%, and other products of 7.71%. From the perspective of the phenolic product composition, its products are mainly phenol and 4-ethylphenol, with very little high-value methoxyphenol products. Comparative Example 2, which uses a supported iron-based catalyst to catalyze the pyrolysis of bamboo, significantly increases the yield of phenolic substances to 56.34% compared to Comparative Example 1, with a decrease in ketone products (24.84%) and an increase in alcohol products. This indicates that the catalytic active centers of supported iron oxide are conducive to the decomposition of cellulose and hemicellulose into phenolic products. However, from the perspective of the phenolic product composition, its products are still mainly phenol and 4-ethylphenol, with a methoxyphenol selectivity of only 5.43%. This indicates that the catalytic pyrolysis process of supported iron oxide catalyst can change the breaking and recombination mode of chemical bonds in bamboo, improving the yield of phenolic products.

[0076] Embodiment 5, adopt this technical scheme, with the composite catalyst consisting of supported iron oxide, calcium oxide and magnesium oxide, the process of catalytic pyrolysis of bamboo, compared with Comparative Examples 1,2, significantly improved the yield of phenols to 64.21%, the yield of ketone products was reduced to 9.21%, but the yields of alcohols and other products were still relatively high, 7.19% and 10.74% respectively. From the perspective of phenolic product composition, the yields of products such as phenol, methylphenol and ethylphenol were significantly reduced, and the selectivity of methoxyphenol products was significantly increased to 35.12%. It can be seen that the synergistic effect of calcium oxide and magnesium oxide in the composite catalyst causes the oxygen-containing compounds in bamboo tar to be reorganized, which helps to generate high-value methoxyphenol products while improving the yield of phenolic products.

[0077] In Examples 1-4, bamboo tar was catalytically pyrolyzed using this technical solution using a catalyst composed of supported iron oxide, nano-HZSM-5 molecular sieve, calcium oxide, and magnesium oxide. Compared to Example 5, the yield of phenols was further increased to over 69%, while the yields of alcohols and other products were significantly reduced to below 1%. Among the phenolic products, the selectivity for methoxyphenols was further enhanced. This indicates that the synergistic effect of the nano-HZSM-5 molecular sieve in the composite catalyst causes the oxygen-containing compounds in bamboo tar to recombine and isomerize, resulting in a directional change in the molecular structure and the efficient production of high-value methoxyphenols.

[0078] The process of producing high-value chemicals from bamboo proposed in the present invention can not only increase the content of phenolic substances, but also improve the selectivity of high-value products such as methoxyphenol, phenol, m-cresol, p-cresol, and 4-ethylphenol, creating good conditions for subsequent utilization.

[0079] The above description is only an excellent embodiment of the present invention and does not limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall fall within the scope of protection of the present invention.

[0080] Table 1 Analysis results of liquid phase pyrolysis oil products obtained from bamboo dust under different conditions and catalysts in control examples and examples

[0081]

[0082] Table 2 Selectivity of phenolic substances in Examples and Comparative Examples

[0083]

Claims

1. A process for producing high-value chemicals from bamboo, characterized by: Cellulose and hemicellulose in bamboo are converted into a variety of methoxyphenol products in the presence of a composite catalyst; the composite catalyst comprises at least supported iron oxide and alkaline earth metal oxide; the method comprises using bamboo dust as raw material, carrying out a catalytic pyrolysis reaction at 400-500°C and 0.1-0.4 MPa in a nitrogen atmosphere; the mass ratio of the composite catalyst to the bamboo dust is 0.2-1.5:1; the various methoxyphenols include guaiacol, 2,6-dimethoxyphenol, 4-methylguaiacol and 4-ethylguaiacol.

2. The process for producing high-value chemicals from bamboo according to claim 1, characterized in that: The iron oxide in the supported iron oxide is a mixture of ferric oxide and ferrosoferric oxide, with a content of 10-30%; the carrier is a mixed aluminum oxide and silicon oxide, with a content of 10-40%; and the content of alkaline earth metal oxide is 5-40%.

3. A process for producing high-value chemicals from bamboo according to claim 1 or 2, characterized in that: The composite catalyst also includes nano HZSM-5 molecular sieve with a silicon-aluminum ratio of 20-30, with a content of 1-10%.

4. A process for producing high-value chemicals from bamboo according to claim 1 or 2, characterized in that: The alkaline earth metal oxide in the composite catalyst includes calcium oxide and / or magnesium oxide; and / or, The molar ratio of silicon oxide to aluminum oxide in the carrier is 1-15:

1.

5. The process for producing high-value chemicals from bamboo according to claim 1, characterized in that: The bamboo powder is dried and crushed to a size of 40-80 meshes.

6. The process for producing high-value chemicals from bamboo according to claim 1, characterized in that: The preparation process of the composite catalyst specifically comprises the following steps: (1) Prepare an aluminum source into an aqueous solution with a mass concentration of 10-30 wt%, add a silicon source to the aluminum source aqueous solution at 30-60 ° C, stir rapidly for 3-4 hours, add iron salt while stirring, stir for 2-3 hours, heat to 80-100 ° C, titrate with 10%-30% sodium carbonate solution to a pH value of 7-8, react for 3-4 hours, cool and filter, and wash the filter cake with deionized water until the filtrate conductivity is no more than 300 S / m; (2) mixing the filter cake, silica sol and / or aluminum sol aqueous solution with alkaline earth metal oxide or a mixture of nano-HZSM-5 molecular sieve and alkaline earth metal oxide and beating them uniformly to prepare a catalyst slurry; (3) The catalyst slurry is sent to a spray dryer for drying and granulation, and high-temperature calcination to obtain a composite catalyst.

7. The process for producing high-value chemicals from bamboo according to claim 6, characterized in that: In step (1), the silicon source is one or more of water glass, silica sol and sodium metasilicate; the aluminum source is one or more of aluminum sulfate, aluminum trichloride, sodium metaaluminate and aluminum sol; the iron salt is one or more of ferric sulfate, ferric nitrate and ferric chloride; and / or, The molar ratio of the iron salt to the silicon source is 1-10:

1.

8. The process for producing high-value chemicals from bamboo according to claim 6, characterized in that: In step (2), the mass ratio of the silica sol and / or aluminum sol aqueous solution to the filter cake is 1:1; the concentration of the silica sol and / or aluminum sol aqueous solution is 5-10%.

9. The process for producing high-value chemicals from bamboo according to claim 6, characterized in that: During the drying and granulation in step (3), the slurry temperature is 100-150°C, and the dryer inlet air temperature is controlled not to exceed 300°C; the pellet size is controlled to be 40-150 microns; the roasting temperature is controlled to be 600-900°C, and the roasting time is 3-4 hours.

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