Catalysts and processes for the gas phase hydrogenation of furfural to 2-methylfuran and uses thereof

Abstract

This invention relates to the field of furfural production, and more particularly to catalysts, methods, and applications for the gas-phase hydrogenation of furfural to produce 2-methylfuran. The furfural hydrogenation dehydration catalyst is CuO / SiO2-La2O3-CeO2; the hydrogenation components are CuO, SiO2 support, and rare earth alkaline additives La2O3 and CeO2. Using chromium-free CuO / SiO2 as the base system, a one-step ammonia stripping method is employed without additional reagents, and activation is performed at a low temperature of 250℃, addressing issues of toxicity, cost, and stability. This patent introduces a composite of La2O3 and CeO2, regulating the acid strength and matching the active sites to achieve 100% furfural conversion and 98.1% selectivity for 2-methylfuran, ensuring long-term stability. Combining ammonia stripping with rare earth modification, the reaction is carried out at a low pressure of 0.05 MPa and 180~210℃, adaptable to existing equipment, improving product selectivity, and solving mass production and safety issues.

Description

Technical Field

[0001] This invention relates to the field of furfural production, and more particularly to catalysts, methods, and uses for the gas-phase hydrogenation of furfural to produce 2-methylfuran. Background Technology

[0002] 2-Methylfuran, as an important heterocyclic compound, possesses fundamental physicochemical properties that determine its broad application prospects. This substance has a molecular weight of 82.1, a melting point as low as -88.7℃, a boiling point of 63℃, and a density of 0.913 g / cm³ at room temperature, classifying it as a volatile liquid. Regarding solubility, 2-methylfuran is slightly soluble in water, forming only a small amount of miscible system with it. However, it exhibits good solubility in organic solvents such as alcohols (e.g., methanol, ethanol) and ethers (e.g., diethyl ether, propyl ether), a characteristic that allows it to be conveniently used as a reaction medium or raw material in chemical reactions. Simultaneously, 2-methylfuran exhibits certain chemical instability. Prolonged exposure to air can cause it to oxidize and turn yellow, and it decomposes upon contact with strong alkalis (e.g., sodium hydroxide, NaOH). Therefore, during storage and use, it is essential to ensure airtight sealing, protection from light, and avoid contact with alkaline substances.

[0003] In applications, 2-methylfuran is an indispensable chemical intermediate, with core applications concentrated in the pharmaceutical and pesticide industries. For example, it can be used as a key raw material in the synthesis of vitamin B1, the antimalarial drugs chloroquine phosphate and pyrethroids, as well as highly effective insecticides such as pyrethroids and various fragrances and flavorings, providing crucial support for pharmaceuticals, healthcare, and agricultural production. With the gradual advancement of global dual-carbon emission reduction strategies, the energy application value of 2-methylfuran has been further explored, and it is considered a highly promising alternative fuel additive. This substance has a high octane rating (up to 131), far exceeding that of ordinary gasoline. As a fuel additive, it can effectively improve the anti-knock performance of gasoline and reduce engine knocking. Simultaneously, its high energy density and superior combustion efficiency compared to traditional fuel ethanol demonstrate significant advantages in replacing fossil fuels and reducing carbon emissions, showing broad prospects for energy applications.

[0004] Furfural, as a core raw material for the preparation of 2-methylfuran, has inherent properties that significantly influence the reaction process. Furfural has a molecular weight of 96.09, a melting point of -38.7℃, and a boiling point of 161.7℃. At room temperature, it is a colorless, oily liquid with a density of 1.1594 g / cm³, possessing a distinctive odor similar to benzaldehyde, easily detectable by the human body. Furfural exhibits poor chemical stability, readily oxidizing in air and gradually turning dark brown. Furthermore, under light and high temperatures, furfural molecules readily polymerize, forming insoluble resinous substances, leading to a decline in its properties. Therefore, furfural storage requires strict environmental control; it must be placed in a cool, dark, and low-temperature environment to prevent deterioration and its impact on subsequent reactions.

[0005] Currently, in patent literature and related research reports, catalysts for the hydrogenation of furfural to 2-methylfuran are mainly divided into two categories: the first category is Cu-based catalysts, which are the most widely used catalyst type in industrial applications and research; the second category is transition metal catalysts such as Ni, Co, and Mo, and their compounds, which have received considerable attention in recent years for catalytic performance optimization. It is generally believed in the industry that the reaction mechanism of furfural hydrogenation to 2-methylfuran mainly involves two steps: the first step is that the aldehyde group (C=O) in the furfural molecule is located at the metal active site of the catalyst (e.g., ...). In the first step, a hydrogenation reaction occurs on a zero-valent metal, gradually reducing it to the intermediate product furfuryl alcohol. In the second step, the generated furfuryl alcohol molecules migrate to the acidic sites provided by the catalyst support or auxiliaries, undergoing a hydrogenation dehydration reaction (also known as hydrogenolysis), removing the hydroxyl (-OH) hydrogen from the side chain of furfuryl alcohol, and finally generating the target product 2-methylfuran.

[0006] This reaction process places stringent requirements on the catalyst's performance, requiring it to possess dual "metal / acid" characteristics: on the one hand, it needs a sufficient number of metal surface active sites to effectively activate hydrogen molecules, providing ample active centers for the aldehyde hydrogenation reaction; on the other hand, it needs moderate and uniformly distributed acid strength to efficiently catalyze the dehydration step of furfuryl alcohol. It is particularly important to note that the acid strength of the acidic sites cannot be too strong. Excessive acidity can lead to the destruction of the furan ring structure, generating byproducts such as γ-valerol and pentanol. Simultaneously, it can promote the polymerization reaction of furfural or furfuryl alcohol, generating oligomers such as humic substances. These byproducts not only reduce the yield and selectivity of the target product, 2-methylfuran, but also adhere to the catalyst surface, leading to decreased catalyst activity and stability, and shortening the catalyst's lifespan. The main reaction equation for the hydrogenation of furfural to 2-methylfuran and some of the main side reaction equations are as follows (Equation 1 mentioned in the text).

[0007] Among Cu-based catalysts, Cr-containing copper chromite catalysts are the most widely studied and applied type in the early stages. Chinese patent CN1047100 reports a catalyst for the gas-phase hydrogenation of furfural to 2-methylfuran. This catalyst uses copper oxide, aluminum oxide, and chromium oxide as the main active components, with the addition of alkali metals, alkaline earth metals, and other auxiliary elements. The contents of each component are as follows: copper oxide 5-15%, chromium trioxide 0.5-5%, aluminum oxide 80-90%, and approximately 2% other additives. The reaction conditions are 230-240℃, atmospheric pressure, and a liquid hourly space velocity (LHSV) of 0.25-0.4 h⁻¹. -1Under certain conditions, this catalyst exhibits good catalytic performance, with a furfural conversion rate of 99-100% and a 2-methylfuran yield of approximately 93%. Another patent, CN1089035, discloses a catalyst for the gas-phase hydrogenation of furfural to prepare 2-methylfuran, with a composition of 50-53% CuO, 46-49% Cr₂O₃, and 0.2-1.1% NiO, at 230-250℃, 0.06 MPa, and a liquid hourly space velocity of 0.4-0.5 h⁻¹. -1 Under the given reaction conditions, furfural conversion can reach approximately 100%, and the selectivity for 2-methylfuran is approximately 96%.

[0008] Furthermore, Chinese patent CN104148115 discloses a method for preparing a foamed catalyst for the hydrogenation of furfural to 2-methylfuran. This method uses copper nitrate and ammonium dichromate as raw materials, employing a co-precipitation method to prepare a catalyst precursor. The precursor is then added to an ethanol-water solution, and a dispersant or surfactant is added to improve dispersibility. Finally, this precursor is coated onto a foamed body and sintered at high temperature. Simultaneously, cellulose, citric acid, and other additives are added, and the catalyst is extruded into a fixed shape. Under reaction conditions of 180℃, 8MPa, and a Cu-Cr catalyst, the furfural conversion rate can reach 100%, and the selectivity for 2-methylfuran is approximately 90%. Although the above-mentioned Cr-containing catalyst exhibits good catalytic activity and can achieve high conversion and yield rates, it contains the highly toxic and carcinogenic element Cr. During the preparation, use, and disposal of the catalyst, it poses serious risks to human health and the ecological environment, failing to meet the requirements of green chemistry and environmental protection. Therefore, it is gradually being replaced by Cr-free catalysts.

[0009] Cr-free Cu-based catalysts have become a research hotspot in recent years, with numerous related patent reports. Chinese patent CN101143324 reports a catalyst for the gas-phase hydrogenation of furfural to 2-methylfuran and its preparation method. This catalyst uses copper as the active component, silica as the support, and alkali metals or alkaline earth metals as promoters. The content of each component is: copper oxide 18-22%, silica support approximately 73-77%, and metal oxide promoters 3-7%. The promoters can be one or more of K₂O, MgO, MnO, BaO, CaO, SrO, or ZnO. The reaction was carried out at 230℃, atmospheric pressure, and a liquid hourly space velocity (LHSV) of 0.4 h⁻¹. -1 Under the specified reaction conditions, this catalyst can achieve approximately 100% furfural conversion and a selectivity of up to 90% for 2-methylfuran. Patent CN102614883 describes another catalyst and its preparation method for the gas-phase hydrogenation of furfural to 2-methylfuran. Its composition is 15-50% CuO, 40-80% alumina, and 40-80% silicon oxide, with one or two of the following additives—Na₂O, K₂O, CaO, BaO, and ZnO—at a content of 0-15%. This catalyst can achieve a 2-methylfuran yield of approximately 92%.

[0010] Chinese patent CN104368346 discloses a catalyst for the gas-phase hydrogenation of furfural to prepare 2-methylfuran, composed of CuO, SiO2, and CeO2, with contents of 52-56%, 40-42%, and 3-6%, respectively. The synthesis steps of the catalyst are as follows: (1) Prepare soluble salt solutions of copper nitrate and cerium nitrate and silica sol respectively, and mix them evenly to obtain a mixed solution; (2) Add an alkaline precipitant to the mixed solution to carry out a precipitation reaction, and obtain a precipitate after heating treatment; (3) Dry and calcine the precipitate in sequence to obtain the target catalyst. The reaction was carried out at a reaction temperature of 228℃, atmospheric pressure, a hydrogen-aldehyde molar ratio of 25, and a liquid hourly space velocity of 0.29 h⁻¹. -1 Under these conditions, the catalyst can achieve a furfural conversion rate of approximately 100% and a selectivity of approximately 94% for 2-methylfuran.

[0011] Patent CN107970934 describes a method for preparing a catalyst for the hydrogenation of furfural to 2-methylfuran. The specific steps are as follows: (1) Tetraethyl orthosilicate is added to a uniformly mixed solution of anhydrous ethanol / polyethylene glycol / deionized water / ammonia to carry out a hydrolysis reaction. After the reaction is completed, the SiO2 support is obtained by centrifugation; (2) The SiO2 support is mixed with CuO precursor solution and alkaline solution and then added to a reaction flask. The pH value of the precipitate is controlled between 5 and 8, and the mixture is continuously stirred for 0.5-3.5 hours. The precipitate is then filtered, dried, and calcined to obtain CuO / SiO2 catalyst powder. In a fixed-bed reactor, the reaction temperature is 220℃, the pressure is atmospheric, and the liquid hourly space velocity is 0.4hr. -1 Under conditions of a hydrogen-aldehyde molar ratio of 15, this catalyst can achieve a yield of approximately 94% for 2-methylfuran.

[0012] Chinese patent CN110180553 discloses a catalyst for the gas-phase conversion of furfural to 2-methylfuran. The preparation method involves mixing a soluble Cu salt with one or two of Ni, Pd, and Au salts, and one of an alkaline earth metal or alkali metal (such as Mg, Ca, Ba, Na, K, etc.) to prepare a salt solution. Then, silica sol, orthosilicate, or silica gel powder are added to a concentrated ammonia solution, along with a certain amount of aluminum sol, and stirred for 1-5 hours to form an ammonia colloidal solution. Subsequently, the prepared salt solution is added to the ammonia colloidal solution, and the mixture is stirred further for 1-6 hours. After heating to dryness, washing, and calcination, the target catalyst is obtained. Under conditions of 180-260℃, atmospheric pressure, and the addition of a hydrogen transfer reagent (such as methanol, ethanol, propanol, isopropanol, etc.), this catalyst can achieve a 2-methylfuran yield of approximately 86%.

[0013] Patent CN111085203 describes a Cu / SiO2 catalyst for the catalytic hydrogenation of furfural to 2-methylfuran, prepared by a sol-gel method. The specific steps include: (1) adding silicon salt, anhydrous ethanol, and water to a synthesis vessel, and continuously adding copper salt solution while stirring to obtain a uniform mixed solution; (2) titrating the mixed solution with alkaline solution until the pH value reaches 7, stopping stirring, and then refluxing and aging to obtain a precipitated colloid; (3) filtering, washing, and drying the precipitated colloid, followed by calcination to obtain a catalyst precursor; (4) reducing the catalyst precursor under a hydrogen atmosphere to finally obtain the Cu / SiO2 catalyst. In an intermittent high-pressure reactor, under the conditions of controlling the mass ratio of furfural to catalyst at 1:1-10:3, the reaction temperature at 210-250℃, the reaction pressure at 2-5MPa, and the reaction time at 1-7 hours, the yield of 2-methylfuran can reach approximately 98%. Although the aforementioned Cr-free Cu-based catalysts have solved the toxicity problem of Cr, many patent-reported catalysts have the problem of complex preparation processes. In addition, some preparation processes require the addition of auxiliary substances such as alcohol solvents and hydrogen transfer alcohol reagents, which not only increases the preparation cost and operation difficulty of the catalyst, but may also introduce impurities during the reaction process, increasing the burden of subsequent separation and purification, resulting in an increase in overall operating costs.

[0014] Besides Cu-based catalysts, numerous studies and reports on second-class Ni, Co, and Mo-based catalysts have been published in literature and patents. For example, a study in the *Journal of Dalian University of Technology*, Vol. 60, No. 5, 2020 (pp. 477-485), pointed out that transition metal phosphides have unique advantages in the hydrogenation reaction of furfural. Their weakly acidic surface helps promote the hydrogenolysis of CO bonds, thereby improving the selectivity of 2-methylfuran. Furthermore, Mo has strong oxyphilicity; using MoP as a furfural hydrogenation catalyst facilitates the adsorption of furfural on the catalyst surface, thus improving the activity and selectivity of the furfural hydrogenation reaction. This study prepared unsupported transition metal phosphides (such as MoP, Ni3P, Fe2P, Co2P, etc.) using a temperature-programmed reduction method and investigated their catalytic performance in the selective hydrogenation reaction of furfural in a fixed-bed reactor using isopropanol as a solvent. The experimental conditions were as follows: a fixed-bed reactor with an inner diameter of 8 mm, a reaction feedstock of isopropanol containing 1% (mass fraction) furfural, a catalyst crushed to 20-40 mesh, a reaction temperature of 200℃, and a reaction pressure of 2 MPa; among them, MoP showed the best catalytic activity, with a furfural conversion rate of 96.9% and a selectivity of 91.5% for 2-methylfuran.

[0015] Chinese patent CN110054602 reports a method for the hydrogenation of furfural to 2-methylfuran. In a high-pressure reactor, using a cobalt phosphide catalyst, and under controlled conditions of a reaction temperature of 180–230°C, a reaction pressure of 0.5 MPa–2.5 MPa, and the introduction of hydrogen gas, the yield of 2-methylfuran is approximately 89%. Patent CN114367289 describes a copper-based bimetallic alloy catalyst for the hydrogenation of furfural to 2-methylfuran. This catalyst comprises a support and an active component. The support is silica, and the active component is a copper-based bimetallic alloy, in which, besides copper, the other metal is one of Fe, Co, Ni, Mn, or Ti. The preparation of the copper-based bimetallic alloy catalyst mainly includes three steps: (1) preparation of SiO2 electrodeposition solution; (2) preparation of copper-cobalt (or other metal) metal alloy electrodeposition solution; (3) preparation of copper-cobalt metal alloy catalyst, specifically, collecting the electrodeposition deposits scraped off multiple times, drying and grinding them, and calcining them at 300-800℃ for 2-10 hours in a hydrogen atmosphere to obtain the target copper-based bimetallic alloy catalyst.

[0016] Chinese patent CN112264032 reports that, under controlled conditions of 180℃ reaction temperature, 3MPa reaction pressure, and a NiMo / ZrO2 catalyst to furfural mass ratio of 10%, the yield of 2-methylfuran after 6 hours of furfural hydrogenation reaction is approximately 94%. However, the catalyst exhibits poor stability; after four reuses, the yield of 2-methylfuran drops to approximately 86%, which is insufficient for continuous industrial production. Meanwhile, an article in *Chemical Engineering*, Vol. 52, No. 1 (pp. 13-18), 2024, introduces different proportions of CoRu / Al2O3 bimetallic catalysts to explore their performance in catalyzing the hydrogenation and deoxygenation of furfural to prepare 2-methylfuran. The study shows that a small amount of Ru doping can significantly promote the hydrogenation conversion of furfural. When the Co / Ru molar ratio is 50:1, a relatively high yield of 2-methylfuran (68%) can be achieved under milder reaction conditions (160℃, 1MPa). Further research revealed that when the Ru doping level is low, it can be highly dispersed on the Co surface to form an alloy structure, and electron transfer between Co and Ru occurs, forming a structure containing surface oxygen vacancies. The proportion of surface oxygen vacancies is affected by the Ru doping amount, which in turn determines the distribution ratio of acidic sites on the catalyst surface, ultimately affecting the hydrodeoxygenation performance of the CoRu / Al2O3 catalyst.

[0017] In summary, the Ni, Mo, and Co catalysts for the hydrogenation of furfural to 2-methylfuran discussed above, while exhibiting certain advantages in catalytic activity and selectivity, share a common problem: the activation temperature of their active metals (Ni, Co, Mo, etc.) is relatively high. They typically require reduction activation in a tube furnace at high temperatures (450–650 °C) under a hydrogen atmosphere. This not only results in high energy consumption but also imposes stringent requirements on the high-temperature and high-pressure resistance of the reaction equipment, increasing equipment investment and safety risks during production, thus limiting their widespread application in industrial production.

[0018] In industrial production, furfural is mainly produced from agricultural and forestry waste such as corn cobs and sugarcane bagasse through hydrolysis and refining processes. As a major agricultural country, China has abundant agricultural and forestry waste resources, and its furfural production capacity accounts for over 90% of the world's total, providing ample raw material support for the industrial production of 2-methylfuran. To extend the furfural industrial chain and increase product added value, Shandong Yinuo Biomass Materials Co., Ltd. has built a 20,000-ton-per-year furfural hydrogenation plant to produce 2-methylfuran, employing Cu-based catalysts and furfural gas-phase catalytic hydrogenation fixed-bed production technology to achieve large-scale production of 2-methylfuran. This invention patent, through systematic analysis of relevant literature and patent technologies on furfural hydrogenation to produce 2-methylfuran, combined with the company's years of experience in applying Cu-based catalysts, reveals that the copper silicate catalyst currently used for ammonia stripping synthesis suffers from excessive Lewis acidity, leading to low selectivity for 2-methylfuran during the reaction and affecting product quality and yield. Therefore, this invention provides a novel catalyst for the preparation of 2-methylfuran by adding alkaline rare earth additives to comprehensively coordinate the acid strength and distribution of the active sites of the catalyst, thereby effectively promoting the improvement of catalytic performance and solving the shortcomings of existing catalysts.

[0019] Based on the aforementioned existing technology reports, the current technology for the hydrogenation of furfural to 2-methylfuran has the following comprehensive shortcomings: First, there are significant shortcomings in the catalysts. Although CrCu-based catalysts have good activity, the toxicity of Cr is high and it pollutes the environment, failing to meet the requirements of green chemistry. CrCu-free catalysts often involve complex preparation processes and require the addition of extra solvents or reagents, leading to increased operating costs. Ni, Co, and Mo-based catalysts require high-temperature reduction and activation, placing stringent demands on equipment and consuming high energy. Some catalysts also exhibit poor stability and reusability. Second, there is room for optimization in the reaction performance. Some catalysts suffer from insufficient "metal / acid" bifunctional matching. Either the acidity is too strong, leading to increased byproducts and catalyst deactivation, or there are insufficient active sites, resulting in low conversion or selectivity. It is difficult to simultaneously achieve high conversion, high selectivity, and long-term stability. Third, the adaptability to industrial applications is insufficient. The preparation processes of some catalysts are complex and costly, making large-scale mass production difficult. Some reaction conditions are harsh (such as high temperature and high pressure), increasing equipment investment and safety risks in industrial production. At the same time, the company's existing copper silicate catalysts have the problem of excessive Lewis acidity, which directly affects product selectivity and restricts the improvement of product quality in industrial production. Fourth, the overall process economy needs to be improved. The auxiliary reagents added during the preparation of some catalysts, the energy consumption required for high-temperature activation, and the replacement costs caused by poor catalyst stability all increase the economic burden of overall production, which is not conducive to the realization of large-scale, low-cost production. Summary of the Invention

[0020] Purpose of the invention: To provide a more effective catalyst, method and use for the gas-phase hydrogenation of furfural to produce 2-methylfuran, the specific purpose of which is described in several substantial technical effects in the detailed embodiments section.

[0021] To achieve the above objectives, the present invention adopts the following technical solution: A catalyst for the gas-phase hydrogenation of furfural to produce 2-methylfuran, characterized in that the furfural hydrogenation dehydration catalyst is CuO / SiO2-La2O3-CeO2; wherein the hydrogenation components are CuO, SiO2 support, and rare earth basic additives La2O3 and CeO2.

[0022] A further technical solution of the present invention is that, based on the total weight of the catalyst, the content of each component is as follows: CuO content is 28-35%, SiO2 content is 60-65%, La2O3 content is 1-5%, and CeO2 content is 1-3%.

[0023] A further technical solution of the present invention is that the furfural hydrogenation dehydration catalyst is 32% CuO / 64% SiO2-3% La2O3-1% CeO2. The method for preparing the catalyst for the gas-phase hydrogenation of furfural to produce 2-methylfuran is characterized by comprising the following steps: Copper nitrate, lanthanum nitrate, and cerium nitrate were weighed and dissolved in deionized water. Ammonia was added to the solution to bring the pH of the copper-ammonia complex solution to approximately 11. Silica sol was then slowly added dropwise to the copper-ammonia solution, and the solution was aged for 3 hours after the addition was complete. The water bath temperature was raised to 95°C, and ammonia evaporation was initiated. Ammonia evaporation was stopped when the pH of the solution reached approximately 7. Finally, the suspension was filtered, washed with water, dried, and calcined to obtain the hydrogenation dehydration catalyst.

[0024] A further technical solution of the present invention is that, (1) Prepare a 1 mol / L solution of copper nitrate, lanthanum nitrate and cerium nitrate, then stir to dissolve and mix evenly to obtain a uniformly mixed acidic salt solution; (2) Prepare a 15% ammonia solution as a precipitant; and a 30% silica sol solution as a silicon source; (3) Add the acid solution prepared in (1) above to the precipitation vessel, stir and add ammonia water dropwise, and control the pH value of the copper ammonia complex solution to about 11 at about 45°C; then add the silica sol to the copper ammonia solution, and age for 3 hours after the addition is complete. (4) Raise the water bath temperature to 95°C and start ammonia evaporation. Stop ammonia evaporation when the pH of the solution drops to about 7. (5) Filter and wash to remove residual nitrate ions, pH value ~7; (6) Dry at 110℃ for 12 hours; (7) The catalyst was obtained by calcining at 450°C for 5 hours.

[0025] The use of alkaline rare earth additives lanthanum oxide (La2O3) and cerium oxide (CeO2) to optimize the acid strength and distribution of active sites in Cu / SiO2 catalysts for ammonia distillation and to improve the performance of catalysts for the hydrogenation of furfural to 2-methylfuran.

[0026] A method for producing 2-methylfuran by gas-phase hydrogenation of furfural, characterized in that it utilizes the furfural hydrogenation and dehydration catalyst described in any one of the above methods; the method involves selectively hydrogenating and dehydrating furfural to generate 2-methylfuran under the action of a rare earth-modified copper silicate catalyst.

[0027] A further technical solution of the present invention involves first reducing a rare-earth modified copper silicate catalyst with a hydrogen-nitrogen mixture at 250°C for 5 hours, then using pure furfural at a reaction temperature of 180–210°C, a hydrogen pressure of 0.05 MPa, and a space velocity of 0.1 h⁻¹. -1 Under conditions of a hydrogen-aldehyde molar ratio of 8, 2-methylfuran is produced by reaction; pure furfural without added solvent is used; the method uses a continuous gas-phase fixed-bed reactor to prepare 2-methylfuran.

[0028] A further technical solution of the present invention is that the hydrogenation catalyst is dehydrated to 2-methylfuran, with γ-valerol and pentanol as byproducts; the hydrogenation reaction is carried out in a continuous gas-phase fixed-bed reactor; the fixed-bed reactor is a tubular fixed-bed reactor; the raw material furfural is of industrial grade purity.

[0029] A further technical solution of the present invention is that the hydrodehydration catalyst needs to be reduced and activated before use. The activation steps are as follows: first, 1~15 vol% hydrogen gas is introduced, and the other components are inert gases. The temperature is gradually increased from room temperature to about 150°C within 10 hours and held at that temperature for 2 hours. Then, the temperature is slowly increased to 250°C within 10 hours and held at that temperature for 5 hours. This process is carried out at atmospheric pressure. Then, the gas is gradually switched to pure hydrogen gas, and the reduction is completed.

[0030] The present invention, employing the above technical solution, offers the following advantages over existing technologies: This patent innovatively uses chromium-free CuO / SiO2 as the base system, employing a one-step ammonia stripping method without additional reagents, and employing low-temperature activation at 250℃, thus resolving issues of toxicity, cost, and stability. This patent introduces a composite of La2O3 and CeO2, regulating the acid strength and matching the active sites to achieve 100% furfural conversion and 98.1% selectivity for 2-methylfuran, ensuring long-term stability. This patent combines ammonia stripping with rare earth modification, using a low pressure of 0.05 MPa and a reaction temperature of 180–210℃, adapting to existing equipment, improving product selectivity, and resolving mass production and safety issues. This patent integrates reagent-free preparation, low-temperature conditions, and a highly stable catalytic system, adapting to existing equipment, reducing energy consumption and costs, and enabling large-scale production. Attached Figure Description

[0031] To further illustrate the present invention, the following description is provided in conjunction with the accompanying drawings: Figure 1 The reaction equation for the invention; Figure 2 Table 1 shows the effect of different catalysts on the gas-phase hydrogenation of furfural to produce 2-methylfuran. Figure 3 Table 2 shows the effect of reaction temperature on furfural conversion and 2-methylfuran selectivity. Detailed Implementation

[0032] Based on the problems existing in the catalysts for the hydrogenation of furfural to prepare 2-methylfuran, the purpose of this invention is to provide a production method for 2-methylfuran, which reduces the preparation cost of the catalyst for the hydrogenation of furfural and optimizes the catalyst performance.

[0033] The objective of this invention is achieved through the following technical solution: This invention provides a method for producing 2-methylfuran. This method involves adding alkaline rare earth promoters lanthanum oxide (La₂O₃) and cerium oxide (CeO₂) to optimize the acid strength and distribution of active sites on the Cu / SiO₂ catalyst used in the ammonia distillation synthesis, thereby improving the performance of the catalyst for the hydrogenation of furfural to 2-methylfuran. To address the aforementioned technical problems, this invention provides a copper foliate catalyst for catalytic hydrogenation and dehydration, and its preparation method.

[0034] The furfural hydrogenation dehydration catalyst adapted to the method of this invention is CuO / SiO2-La2O3-CeO2. The hydrogenation components are CuO, SiO2 support, rare earth alkaline promoter La2O3, and CeO2. Based on the total weight of the catalyst, the content of each component is: CuO 28-35%, SiO2 60-65%, La2O3 1-5%, and CeO2 1-3%.

[0035] This invention provides a copper-based catalyst synthesized by ammonia stripping. Copper nitrate, lanthanum nitrate, and cerium nitrate are dissolved in deionized water. Ammonia is added to the solution to bring the pH of the copper-ammonia complex solution to approximately 11. Then, silica sol is slowly added dropwise to the copper-ammonia solution, and the mixture is aged for 3 hours after the addition is complete. The water bath temperature is raised to 95°C, and ammonia stripping begins. Stripping is stopped when the pH of the solution reaches approximately 7. Finally, the suspension is filtered, washed with water, dried, and calcined to obtain the hydrodehydration catalyst.

[0036] (1) Prepare a 1 mol / L solution of copper nitrate, lanthanum nitrate and cerium nitrate, then stir to dissolve and mix evenly to obtain a uniformly mixed acidic salt solution.

[0037] (2) Prepare a 15% ammonia solution as a precipitant; and a 30% silica sol solution as a silicon source.

[0038] (3) Add the acid solution prepared in (1) above to the precipitation vessel, stir and add ammonia water dropwise, and control the pH value of the copper ammonia complex solution to about 11 at about 45°C; then add the silica sol to the copper ammonia solution, and age for 3 hours after the addition is complete.

[0039] (4) Raise the water bath temperature to 95°C and start ammonia evaporation. Stop ammonia evaporation when the pH of the solution drops to around 7.

[0040] (5) Filter and wash to remove residual nitrate ions, pH value ~7.

[0041] (6) Dry at 110℃ for 12 hours.

[0042] (7) The catalyst was obtained by calcining at 450°C for 5 hours.

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the specific content of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention. Contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0044] This invention provides a method for producing 2-methylfuran, which involves selectively hydrogenating and dehydrating furfural under the action of a rare earth-modified copper silicate catalyst to generate 2-methylfuran.

[0045] In the above method, pure furfural without added solvent is used; The method uses a continuous gas-phase fixed-bed reactor to prepare 2-methylfuran.

[0046] The above method for preparing 2-methylfuran using a fixed-bed reaction involves: first, reducing a rare-earth-modified copper silicate catalyst at 250°C with a hydrogen-nitrogen mixed gas for 5 hours; then, using pure furfural, reacting at a temperature of 180–210°C, approximately 0.05 MPa, and a space velocity of 0.1 h⁻¹. -1 Under conditions where the hydrogen-aldehyde molar ratio is 8, the reaction produces 2-methylfuran. Example 1

[0047] First, a 1 mol / L copper nitrate solution was prepared and stirred until homogeneous to obtain an acidic solution of the metal salt. Then, 15% ammonia water was prepared as a precipitant, and 30% silica sol was prepared as a silicon source. Under vigorous stirring, the copper nitrate solution was added to a precipitation vessel, and 15% ammonia water was added dropwise, controlling the temperature at ~45℃. The pH of the copper-ammonia complex solution was approximately 11. Then, 30% silica sol was added to the copper-ammonia complex solution, and the mixture was aged for 3 hours after the addition was complete. The water bath temperature was raised to 95℃, and ammonia evaporation was started. Ammonia evaporation was stopped when the pH of the solution dropped to around 7. The solution was then filtered, washed, dried at 110℃ for 12 hours, and calcined at 450℃ for approximately 5 hours to obtain a CuO / SiO2 catalyst. The total amount of catalyst was 35% CuO and 65% SiO2. The catalyst was labeled Cat1. The reaction results are shown in Table 1. Figure 2 . Example 2

[0048] First, a 1 mol / L solution of copper nitrate and lanthanum nitrate was prepared and stirred until homogeneous, resulting in a mixed acidic solution of metal salts. Then, 15% ammonia was used as a precipitant, and 30% silica sol was used as a silicon source. Under vigorous stirring, the copper nitrate solution was added to a precipitation vessel, and 15% ammonia was added dropwise, maintaining the temperature at approximately 45°C and the pH of the copper-ammonia complex solution at approximately 11. Then, 30% silica sol was added to the copper-ammonia complex solution, and the mixture was aged for 3 hours after the addition was complete. The water bath temperature was raised to 95°C, and ammonia evaporation began. Ammonia evaporation was stopped when the pH of the solution dropped to approximately 7. The solution was then filtered, washed, dried at 110°C for 12 hours, and calcined at 450°C for approximately 5 hours to obtain a CuO / SiO2-La2O3 catalyst. The total content of the catalyst was: CuO 33.5%, SiO2 65%, and La2O3 1.5%. The catalyst was labeled Cat2. The reaction results are shown in Table 1. Figure 2 . Example 3

[0049] First, a 1 mol / L solution of copper nitrate and lanthanum nitrate was prepared and stirred until homogeneous, resulting in a mixed acidic solution of metal salts. Then, 15% ammonia was used as a precipitant, and 30% silica sol was used as a silicon source. Under vigorous stirring, the copper nitrate solution was added to a precipitation vessel, and 15% ammonia was added dropwise, maintaining a temperature of approximately 45°C and a pH of approximately 11 for the copper-ammonia complex solution. Then, 30% silica sol was added to the copper-ammonia complex solution, and the mixture was aged for 3 hours after the addition was complete. The water bath temperature was raised to 95°C, and ammonia evaporation was initiated. Ammonia evaporation was stopped when the pH of the solution dropped to approximately 7. The solution was then filtered, washed, dried at 110°C for 12 hours, and calcined at 450°C for approximately 5 hours to obtain a CuO / SiO2-La2O3 catalyst. The total catalyst content was: CuO 30.5%, SiO2 65%, and La2O3 4.5%. The catalyst was labeled Cat3. The reaction results are shown in Table 1. Figure 2 . Example 4

[0050] First, a 1 mol / L solution of copper nitrate and lanthanum nitrate was prepared and stirred until homogeneous, resulting in a mixed acidic solution of the metal salts. Then, 15% ammonia was used as a precipitant, and 30% silica sol was used as a silicon source. Under vigorous stirring, the copper nitrate solution was added to a precipitation vessel, and 15% ammonia was added dropwise, maintaining a temperature of approximately 45°C and a pH of approximately 11 for the copper-ammonia complex solution. Then, 30% silica sol was added to the copper-ammonia complex solution, and the mixture was aged for 3 hours after the addition was complete. The water bath temperature was raised to 95°C, and ammonia evaporation was initiated. Ammonia evaporation was stopped when the pH of the solution dropped to approximately 7. The solution was then filtered, washed, dried at 110°C for 12 hours, and calcined at 450°C for approximately 5 hours to obtain the CuO / SiO2-La2O3 catalyst. The total catalyst content was: CuO 32%, SiO2 65%, and La2O3 3%. The catalyst was labeled Cat4. The reaction results are shown in Table 1. Figure 2 . Example 5

[0051] First, a 1 mol / L solution of copper nitrate, lanthanum nitrate, and cerium nitrate was prepared and stirred until homogeneous, resulting in a mixed acidic solution of metal salts. Then, 15% ammonia was used as a precipitant, and 30% silica sol was used as a silicon source. Under vigorous stirring, the copper nitrate solution was added to a precipitation vessel, and 15% ammonia was added dropwise, maintaining a temperature of approximately 45°C and a pH of approximately 11 for the copper-ammonia complex solution. Then, 30% silica sol was added to the copper-ammonia complex solution, and the mixture was aged for 3 hours after the addition was complete. The water bath temperature was raised to 95°C, and ammonia evaporation was initiated. Ammonia evaporation was stopped when the pH of the solution dropped to approximately 7. The solution was then filtered, washed, dried at 110°C for 12 hours, and calcined at 450°C for approximately 5 hours to obtain a CuO / SiO2-La2O3-CeO2 catalyst. The total content of the catalyst was: CuO 32%, SiO2 64%, La2O3 3%, and CeO2 1%. The catalyst was labeled Cat5. The reaction results are shown in Table 1. Figure 2 . Example 6

[0052] First, a 1 mol / L solution of copper nitrate, lanthanum nitrate, and cerium nitrate was prepared and stirred until homogeneous, resulting in a mixed acidic solution of metal salts. Then, 15% ammonia was used as a precipitant, and 30% silica sol was used as a silicon source. Under vigorous stirring, the copper nitrate solution was added to a precipitation vessel, and 15% ammonia was added dropwise, maintaining a temperature of approximately 45°C and a pH of approximately 11 for the copper-ammonia complex solution. Then, 30% silica sol was added to the copper-ammonia complex solution, and the mixture was aged for 3 hours after the addition was complete. The water bath temperature was raised to 95°C, and ammonia evaporation was initiated. Ammonia evaporation was stopped when the pH of the solution dropped to approximately 7. The solution was then filtered, washed, dried at 110°C for 12 hours, and calcined at 450°C for approximately 5 hours to obtain a CuO / SiO2-La2O3-CeO2 catalyst. The total content of the catalyst was: CuO 32%, SiO2 63%, La2O3 3%, and CeO2 2%. The catalyst was labeled Cat6. The reaction results are shown in Table 1. Figure 2 .

[0053] Reaction conditions: 50g of catalyst was packed into a fixed-bed reactor, and the reaction was first reduced at 250℃ for 5 hours with a hydrogen-nitrogen mixture; the reaction pressure was 0.05MPa, the reaction temperature was 195℃, and the space velocity was 0.1h. -1 Under solvent-free conditions with a hydrogen / furfural molar ratio of 8, the furfural conversion rate and 2-methylfuran selectivity are shown in Table 1. Figure 2 As shown, other major byproducts include γ-valerol, pentanol, and 2-methyltetrahydrofuran.

[0054] Product distribution in Example 1: Pentanol 2.2%, γ-valerol 3.7%, 2-methyltetrahydrofuran 1.3%, 2-methylfuran 92.8%.

[0055] Product distribution in Example 5: Pentanol 0.3%, γ-valerol 1.4%, 2-methyltetrahydrofuran 0.2%, 2-methylfuran 98.1%. Example 7

[0056] From Table 1, i.e. Figure 2 Analysis of the effects of different catalysts on the gas-phase hydrogenation of furfural to 2-methylfuran showed that the catalyst in Example 5 yielded the best 2-methylfuran yield. Therefore, 50g of the catalyst from Example 5 was reloaded into a fixed-bed reactor and first reduced at 250°C with a hydrogen-nitrogen mixture for 5 hours; then, at a space velocity of 0.1 h⁻¹... -1 Under solvent-free conditions with a hydrogen / furfural molar ratio of 8, the effects of reaction temperature on furfural conversion and 2-methylfuran selectivity were investigated, as shown in Table 2. Figure 3 As shown.

[0057] Product distribution at 180℃: furfuryl alcohol 1.9%, pentanol 0.8%, γ-valerol 1.7%, 2-methyltetrahydrofuran 0.3%, 2-methylfuran 95.3%.

[0058] The product distribution at 210℃ was as follows: pentanol 0.3%, γ-valerol 3.3%, 2-methyltetrahydrofuran 0.3%, and 2-methylfuran 96.1%.

[0059] From Table 2, i.e. Figure 3 Analysis of the effects of reaction temperature on furfural conversion and 2-methylfuran selectivity showed that the optimal reaction conditions were achieved at a reaction pressure of 0.05 MPa and a furfural space velocity of 0.1 h⁻¹. -1 Under conditions of a hydrogen / furfural molar ratio of 8 and a reaction temperature range of 180~210℃, the furfural conversion rate is close to 100% and the selectivity for 2-methylfuran is at a high level.

[0060] The data above shows that a catalyst with a composition of 32% CuO / 64% SiO2-3% La2O3-1% CeO2 on a CuO / SiO2-La2O3-CeO2 hydrogenation dehydration catalyst can achieve highly selective preparation of 2-methylfuran from furfural with a yield of approximately 98%.

[0061] In summary, this invention utilizes ammonia stripping to synthesize a copper silicate-based catalyst, achieving the directed catalytic conversion of furfural under hydrogen pressure of 0.05 MPa and reaction temperature of 180-210℃. This method can be applied to continuous gas-phase and fixed-bed reactors, achieving highly efficient catalytic conversion of furfural. The catalyst exhibits stable properties, a simple separation process, and is valuable for industrial production.

[0062] The existing technology has obvious shortcomings: "CrCu-based catalysts have good activity, but Cr is highly toxic and pollutes the environment, which does not meet the requirements of green chemical industry; CrCu-free catalysts often have complicated preparation processes and require the addition of additional solvents or reagents, which increases operating costs; Ni, Co, and Mo catalysts require high-temperature reduction and activation, which places stringent requirements on equipment and consumes a lot of energy, and some catalysts have poor stability and poor reusability." In contrast to the shortcomings of existing technologies, this patent innovatively and non-obviously utilizes a chromium-free CuO / SiO2 system as the basic catalytic system, completely eliminating the carcinogenic and highly toxic Cr element. This eliminates the harm to human health and the ecological environment caused by Cr-containing catalysts at the source, fully meeting the requirements of green chemical development. Simultaneously, it innovatively employs an ammonia stripping method to prepare the CuO / SiO2-La2O3-CeO2 catalyst in a one-step process. The preparation process uses only copper nitrate, lanthanum nitrate, and cerium nitrate as metal salt raw materials, ammonia water as a precipitant, and silica sol as a silicon source, without the need for the addition of alcohols throughout the entire process. The addition of auxiliary substances such as solvents and hydrogen transfer reagents simplifies the preparation process and significantly reduces the operating costs of catalyst preparation and subsequent production. In addition, the rare earth modified copper silicate catalyst of this invention only requires 5 hours of reduction with a hydrogen-nitrogen mixed gas at 250°C, which is far lower than the high-temperature activation requirement of 450~650°C for Ni, Co, and Mo catalysts. This significantly reduces the high-temperature resistance requirements of equipment and production energy consumption. Moreover, the catalyst is a copper-based system with a composite oxide support, which is stable and meets the stability requirements of continuous industrial production, solving the problem of poor reusability of some catalysts.

[0063] In response to the shortcomings of existing technologies, "there is room for optimization of reaction performance. Some catalysts have insufficient matching degree of "metal / acid" bifunctionality. Either the acidity is too strong, which leads to an increase in by-products and catalyst deactivation, or the active sites are insufficient, resulting in low conversion or selectivity. It is difficult to achieve high conversion, high selectivity and long-term stability at the same time." In contrast to the shortcomings of existing technologies, this patent innovatively and non-obviously introduces a composite of alkaline rare earth additives La2O3 and -CeO2 into the copper silicate catalyst system for ammonia distillation. By neutralizing the excessive Lewis acidity of the copper silicate catalyst through the alkaline sites of the alkaline rare earth additives, the acid strength and acid site distribution of the catalyst's active center are precisely controlled, achieving optimal dual-function matching of "metal hydrogenation active sites" and "acidic dehydration sites". It retains sufficient metal surface sites of CuO active components to efficiently activate hydrogen and complete the hydrogenation reaction of furfural aldehyde groups, while adjusting the acid strength to a moderate level. This allows for the catalysis of furfuryl alcohol hydrogenation and dehydration reaction, while avoiding the destruction of furan rings, the generation of byproducts (γ-valerol, pentanol, etc.) and the deposition of oligomers caused by excessive acidity. Ultimately, it achieves excellent reaction performance with 100% furfural conversion and a maximum 2-methylfuran selectivity of 98.1%, while avoiding catalyst deactivation due to carbon deposition and byproduct adhesion, ensuring the long-term stability of the catalyst.

[0064] In response to the shortcomings of existing technologies, such as "insufficient adaptability to industrial applications, complex and costly preparation processes for some catalysts, making it difficult to mass-produce them on a large scale; harsh reaction conditions (such as high temperature and high pressure) increase equipment investment and safety risks in industrial production; and the problem that the company's existing copper silicate catalysts have excessive Lewis acidity, which directly affects product selectivity and restricts the improvement of product quality in industrial production." In contrast to the shortcomings of existing technologies, this patent innovatively combines the ammonia stripping process with rare earth additive modification. The ammonia stripping method is a mature industrial preparation process with readily available raw materials, simple steps, and the ability to be produced continuously on a large scale, solving the problem of complex and difficult-to-mass-produce catalysts. The catalytic reaction conditions of this invention are low pressure of 0.05 MPa and medium-low temperature of 180~210℃, which are far superior to the high temperature and high pressure conditions of some processes, significantly reducing the equipment investment and safety risks brought about by high-pressure operation in industrial production, and are compatible with the equipment conditions of existing industrial fixed-bed reactors. At the same time, addressing the industrial pain point of excessively strong Lewis acidity of existing ammonia stripping synthesis copper silicate catalysts, the acid strength is precisely controlled through composite modification of La2O3 and -CeO2, increasing the selectivity of 2-methylfuran from 92.8% of the basic CuO / SiO2 catalyst to 98.1%, significantly improving the product quality of industrial production and solving the core problem of product quality constraints imposed by the original catalyst.

[0065] The shortcomings of the existing technology are that "the overall economic efficiency of the process needs to be improved. The auxiliary reagents added during the preparation of some catalysts, the energy consumption required for high-temperature activation, and the replacement costs caused by poor catalyst stability all increase the economic burden of the overall production, which is not conducive to the realization of large-scale, low-cost production." In contrast to the shortcomings of existing technologies, this patent innovatively integrates ammonia preparation process without auxiliary reagents, low-temperature activation conditions, and a highly stable and selective catalytic system. The preparation process requires no additional auxiliary reagents, eliminating the costs of reagent procurement and subsequent separation and purification. Catalyst activation and reaction occur under low-temperature and low-pressure conditions, significantly reducing energy consumption and equipment operating costs during production. Simultaneously, the catalyst exhibits stable properties, excellent activity and selectivity, reducing the frequency and cost of replacement due to catalyst deactivation and performance degradation. Furthermore, this invention uses pure furfural as raw material and a solvent-free continuous gas-phase fixed-bed reaction process, further simplifying the industrial production process and reducing raw material and separation costs. Moreover, the catalyst of this invention is optimized based on the company's existing Cu-based catalyst application system and can be directly adapted to Shandong Yinuo Biomass Materials Co., Ltd.'s 20,000-ton-per-year furfural hydrogenation production unit, eliminating the need for large-scale modifications to existing equipment, significantly reducing industrial upgrade costs, achieving large-scale, low-cost industrial production, and significantly improving the overall economic efficiency of the process.

[0066] The airspeed mentioned in the text is 0.1 h. -1 "Liquid air velocity / mass air velocity"

[0067] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0068] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims.

Claims

1. A catalyst for the gas-phase hydrogenation of furfural to produce 2-methylfuran, characterized in that, The furfural hydrogenation dehydration catalyst is CuO / SiO2-La2O3-CeO2; the hydrogenation components are CuO, SiO2 support, rare earth alkaline additives La2O3 and CeO2.

2. The catalyst for the gas-phase hydrogenation of furfural to produce 2-methylfuran as described in claim 1, characterized in that, Based on the total weight of the catalyst, the contents of each component are as follows: CuO content is 28-35%, SiO2 content is 60-65%, La2O3 content is 1-5%, and CeO2 content is 1-3%.

3. The catalyst for the gas-phase hydrogenation of furfural to produce 2-methylfuran as described in claim 1, characterized in that, The catalyst for furfural hydrogenation dehydration is 32% CuO / 64% SiO2-3% La2O3-1% CeO2.

4. A method for preparing a catalyst for the gas-phase hydrogenation of furfural to produce 2-methylfuran, characterized in that, It includes the following steps: Copper nitrate, lanthanum nitrate, and cerium nitrate were weighed and dissolved in deionized water. Ammonia was added to the solution to bring the pH of the copper-ammonia complex solution to approximately 11. Silica sol was then slowly added dropwise to the copper-ammonia solution, and the solution was aged for 3 hours after the addition was complete. The water bath temperature was raised to 95°C, and ammonia evaporation was initiated. Ammonia evaporation was stopped when the pH of the solution reached approximately 7. Finally, the suspension was filtered, washed with water, dried, and calcined to obtain the hydrogenation dehydration catalyst.

5. The method for preparing the catalyst for the gas-phase hydrogenation of furfural to produce 2-methylfuran as described in claim 4, characterized in that, (1) Prepare a 1 mol / L solution of copper nitrate, lanthanum nitrate and cerium nitrate, then stir to dissolve and mix evenly to obtain a uniformly mixed acidic salt solution; (2) Prepare a 15% ammonia solution as a precipitant; and a 30% silica sol solution as a silicon source; (3) Add the acid solution prepared in (1) above to the precipitation vessel, stir and add ammonia water dropwise, and control the pH value of the copper ammonia complex solution to about 11 at about 45°C; then add the silica sol to the copper ammonia solution, and age for 3 hours after the addition is complete. (4) Raise the water bath temperature to 95°C and start ammonia evaporation. Stop ammonia evaporation when the pH of the solution drops to about 7. (5) Filter and wash to remove residual nitrate ions, pH value ~7; (6) Dry at 110℃ for 12 hours; (7) The catalyst was obtained by calcining at 450°C for 5 hours.

6. Application of alkaline rare earth additives lanthanum oxide (La2O3) and cerium oxide (CeO2) in optimizing the acid strength and distribution of active sites in Cu / SiO2 catalysts for ammonia distillation and improving the performance of catalysts for the hydrogenation of furfural to 2-methylfuran.

7. A method for producing 2-methylfuran by gas-phase hydrogenation of furfural, characterized in that, Using the furfural hydrogenation dehydration catalyst according to any one of claims 1-3, the method involves selectively hydrogenating and dehydrating furfural to generate 2-methylfuran under the action of a rare earth modified copper silicate catalyst.

8. The method for producing 2-methylfuran by gas-phase hydrogenation of furfural as described in claim 7, characterized in that, First, a rare-earth-modified copper silicate catalyst was reduced for 5 hours at 250°C with a hydrogen-nitrogen mixture. Then, pure furfural was used, and the reaction was carried out at a temperature of 180–210°C, a hydrogen pressure of 0.05 MPa, and a space velocity of 0.1 h⁻¹. -1 Under conditions of a hydrogen-aldehyde molar ratio of 8, 2-methylfuran is produced by reaction; pure furfural without added solvent is used; the method uses a continuous gas-phase fixed-bed reactor to prepare 2-methylfuran.

9. The method for producing 2-methylfuran by gas-phase hydrogenation of furfural as described in claim 7, characterized in that, The product is converted to 2-methylfuran via dehydration over a hydrogenation catalyst, with γ-valerol and pentanol as byproducts. The hydrogenation reaction is carried out in a continuous gas-phase fixed-bed reactor, which is a tubular fixed-bed reactor. The raw material furfural is of industrial grade purity.

10. The method for producing 2-methylfuran by gas-phase hydrogenation of furfural as described in claim 7, characterized in that, Before use, the hydrodehydration catalyst needs to be reduced and activated. The activation steps are as follows: First, 1~15 vol% hydrogen gas is introduced, and the other components are inert gases. The temperature is gradually increased from room temperature to about 150°C over 10 hours and held at that temperature for 2 hours. Then, the temperature is slowly increased to 250°C over 10 hours and held at that temperature for 5 hours. This process is carried out at atmospheric pressure. Then, the gas is gradually switched to pure hydrogen gas, and the reduction is completed.

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