A catalyst for methanol-to-ethanol conversion, its preparation method and application

Abstract

This invention discloses a methanol-to-ethanol catalyst, its preparation method, and its applications, comprising: a composition satisfying the chemical formula: Cu a Zn b Rh g Co l Fe μ Ca h Al ρ O c / C 100 The atomic ratios of the elements in the formula are: a = 5.5–14, b = 0.5–1, g = (4–5) × 10. ‑5 The parameters are: l = 0.2–0.3, μ = 0.2–0.3, h = 0.002–0.003, ρ = 0.002–0.003, and c is the number of oxygen atoms required to satisfy the valence of each element. The preparation process involves mixing the prepared asphalt-based activated carbon powder and amorphous hydroxyl iron oxide powder with basic zinc carbonate powder, then impregnating them with an equal volume of a mixed solution of copper, cobalt, and rhodium salts. After drying, the mixture is kneaded and shaped with a high-alumina cement molding agent. In the continuous reaction process of methanol conversion to ethanol, this catalyst exhibits good diffusion performance, conversion activity, product selectivity, and high operational stability.

Description

Technical Field

[0001] This invention relates to the field of ethanol catalyst preparation technology, and in particular to a methanol-to-ethanol catalyst, its preparation method, and its application. Background Technology

[0002] Ethanol is an important chemical raw material and solvent, widely used in the chemical, daily chemical, dye, pharmaceutical, and food industries, and is also a potential liquid transportation fuel. Its production methods mainly include fermentation and chemical methods. The production of ethanol from methanol does not consume land resources or rely on petroleum resources, making it a promising new method for ethanol production with further development potential.

[0003] For example, in the method for converting methanol to ethanol disclosed in CN101965324A, methanol and carbon monoxide react in the presence of a catalyst, and the reaction product is then hydrogenated to prepare ethanol, which can be synthesized from biomass syngas. CN102690171A also discloses a process for producing ethanol from syngas via methanol, in which the feed gas undergoes a synthesis reaction in the presence of a catalyst to obtain methanol, which is then subjected to a carbonylation reaction to obtain acetic acid, and finally ethanol and byproducts. The process includes syngas separation and tail gas recycling, and has the advantages of high yield and energy utilization, and low cost.

[0004] CN108707060A and CN108707061A utilize in-situ hydrogen from methanol cracking, which reacts with methyl acetate via hydrogenation to produce ethanol. This eliminates the need for a hydrogen production process, improving hydrogen utilization and ethanol production efficiency, reducing costs, and overcoming the problems of low acetic acid conversion and selectivity. CN103119003A and CN103119008A disclose a methanol carbonylation process to form acetic acid, followed by hydrogenation to form ethanol. At least some of the hydrogen and carbon monoxide are derived from the separation of syngas and tail gas streams, and methanation removes residual carbon monoxide from the hydrogen stream.

[0005] CN107573214A discloses a method for preparing ethanol from methanol, which includes purification in a conversion gas purification tower and feeding crude ethanol into a distillation tower to obtain qualified ethanol product, meeting the production requirements for fuel ethanol as a gasoline additive. This method has the advantages of simple process, convenient operation, low cost, and good results. CN107011118A also discloses a process for preparing and refining ethanol from methanol. In the carbonylation synthesis step, deiodination reduces the impact on the catalyst, improves ethanol selectivity, reduces by-products, and achieves zero acetaldehyde content in the refined ethanol. Furthermore, CN120172816A discloses a one-step method for producing ethanol from methanol / dimethyl ether.

[0006] In methanol and syngas-to-ethanol processes, catalyst performance significantly impacts the conversion. Among noble metal catalysts, rhodium-based catalysts are prevalent, such as USP4096164, USP4235801, USP4351908, and CN96112685. These catalysts offer high ethanol selectivity but suffer from low carbon monoxide conversion and high cost. EP 0283586B1 also reports a method for producing ethanol from methanol and syngas using a rhodium-based catalytic system and in the presence of an organophosphine-substituted alkane ligand. Adding appropriate amounts of acetic acid and alkali metal halides or acetates further enhances the ethanol selectivity to over 90% (CN105254473A). CN116082120A discloses a continuous methanol-to-ethanol production process achieved through supported single-atom Rh or Ir catalytic carbonylation and the continuous action of a supported copper-based catalyst.

[0007] CN104892360A describes a catalyst consisting of a composite oxide containing two or more elements from iron, cobalt, manganese, copper, platinum, vanadium, tungsten, and chromium. In a fixed-bed reactor, methanol is converted into ethanol through a catalytic conversion reaction. The catalyst is a non-precious metal catalyst, which is inexpensive and readily available.

[0008] CN107899583A discloses a catalyst for the production of ethanol from methanol syngas and its preparation method. The catalyst includes a support, an active component Cu, and an auxiliary agent, which includes at least one of Zn, Co, Ni, Mn, and Fe. The preparation method includes the preparation of a Cu precursor, impregnation onto the support, and calcination. The catalyst exhibits high conversion rates and high selectivity for C2 oxygen-containing compounds. CN102557870A discloses a method for producing fuel ethanol from methanol and acetic acid, employing a copper-zinc-aluminum-rare earth composite catalyst for hydrogenation. Acetic acid and methanol are first subjected to a supercritical acetylene-methyl acetate reaction to obtain methyl acetate, which is then subjected to hydrogenation, thus improving conversion efficiency and ethanol yield.

[0009] CN104710282A discloses a method for producing ethanol and co-producing methanol, using syngas and acetic acid as co-feeds. The active component of the catalyst is copper and optionally zinc and / or aluminum, promoting the conversion of carbon monoxide to methanol while maintaining extremely high acetic acid hydrogenation activity. The ethanol to methanol ratio is adjustable, improving product flexibility. CN109331865A discloses a method for preparing a catalyst for one-step syngas-to-ethanol and co-producing methanol, by preparing a mixed-crystal molecular sieve support with methanol dehydration and dimethyl ether carbonylation activity, and loading it with a copper-based hydrogenation component. This method features mild reaction conditions, high selectivity for the target product ethanol, and co-production of methanol. CN108993557A also discloses an electrocatalytic methanol-to-ethanol CosZnC catalyst and its applications.

[0010] Whether ethanol is produced by hydrogenating methanol or carbon monoxide via acetic acid or acetate esters, or directly from acetic acid or acetate esters, it is still in the research and development stage and there are still problems such as equipment corrosion, high hydrogen-to-ester ratio, low feed space velocity and many by-products, poor catalyst stability, and low process economy. Summary of the Invention

[0011] This invention aims to solve the problems of equipment corrosion, high hydrogen-to-ester ratio, low feed space velocity and many by-products, poor catalyst stability and low process economy, and provides a methanol-to-ethanol catalyst, its preparation method and application.

[0012] To achieve the above-mentioned technical objectives, the technical solution provided by this invention is as follows: A catalyst for the conversion of methanol to ethanol, the catalyst composition of which satisfies the chemical formula: Cu a Zn b Rh g Co l Fe μ Ca h Al ρ O c / C 100 In the formula, the atomic ratios of each element are a = 5.5–14, b = 0.5–1, and g = 4 × 10⁻⁶. -5 ~5´10 -5 l=0.2~0.3, μ=0.2~0.3, h=0.002~0.003, ρ=0.002~0.003, and c is the number of oxygen atoms required to satisfy the valence of each element.

[0013] Furthermore, the catalyst has an average pore size ≥ 1 nm, a pore volume of 0.2–0.6 mL / g, a surface area of ​​300–900 m² / g, and a bulk density of 0.3–0.8 g / mL.

[0014] This invention also provides a method for preparing a methanol-to-ethanol catalyst, comprising the following steps: mixing asphalt-based activated carbon powder and amorphous iron hydroxide powder with basic zinc carbonate powder, then impregnating with an equal volume of a mixed solution of soluble copper salt, cobalt salt, and trace amounts of rhodium salt; drying and then kneading with a high-alumina cement molding agent to obtain a methanol-to-ethanol catalyst by ventilation drying at room temperature.

[0015] The molding process, which prepares columnar, block, sheet, and strip catalysts suitable for fixed-bed reaction processes, is carried out by hydraulic pressing or extrusion and pelletizing; spherical granular catalysts are formed by rolling in a catalyst rolling device.

[0016] Furthermore, the preparation method of asphalt-based activated carbon powder includes the following steps: after pulverizing petroleum asphalt, carbonizing it in an inert gas atmosphere at 500-750℃ for 1-3 hours, and then treating it with steam at 800-950℃ for 1-3 hours.

[0017] The softening point of petroleum asphalt is 170–340℃.

[0018] Furthermore, amorphous ferric hydroxide powder is obtained by mixing and reacting a soluble ferrous salt solution with a solid hydroxide at a temperature below 100°C, oxidizing with air until the ferrous iron content is less than 1 wt%, and then washing the resulting filter cake.

[0019] Furthermore, the soluble salts of copper, cobalt, rhodium, and iron are selected from any one of the sulfates, nitrates, chlorates, oxalates, and acetates of copper, cobalt, rhodium, and iron.

[0020] Furthermore, solid hydroxides include any one of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0021] It should be noted that in the preparation method of the catalyst for methanol-to-ethanol conversion provided by the present invention, the amount of deionized water and dissolved salt involved in the preparation process is mainly to meet the operational requirements and convenience, and has no impact on the performance of the final catalyst. When it does not affect the convenience of operation, the minimum amount of water should be used for dilution and dissolution to reduce consumption.

[0022] The present invention also provides a method for converting methanol to ethanol, comprising feeding a reaction feedstock consisting of methanol containing trace amounts of iodomethane and syngas into a fixed-bed reactor, reacting it with a methanol-to-ethanol catalyst, and obtaining the product ethanol after separation; the unconverted feedstock can be recycled back to the reactor after separation.

[0023] Furthermore, the liquid hourly space velocity (LHSV) of the reactants during the reaction process is 0.2–12 h⁻¹. -1 The reaction temperature is 120–290°C. o C. The reaction pressure is 1-10 MPa.

[0024] Furthermore, the content of iodomethane in methanol is 0.1% to 10%; the molar ratio of carbon monoxide to hydrogen in the synthesis gas is 1:1 to 20, and the molar ratio of carbon monoxide to methanol is 1:1 to 3.

[0025] It should be noted that the chemicals involved in this invention are commonly used industrial chemical products and laboratory reagents, which can be easily obtained through commercial purchase; the chemical unit operations involved in this invention are conventional operating techniques in the field, well known to those skilled in the art, and routinely used in chemical experiments and industrial production processes.

[0026] The present invention has the following beneficial effects: This invention provides an improved catalyst and preparation technology for methanol-to-ethanol production. By improving the performance of the catalyst's multi-component active components and support at the microscale, as well as their combination and distribution, the catalyst's diffusion performance and corrosion resistance under reaction conditions are improved, reducing side reactions and carbon deposition. This results in a catalyst with higher conversion activity, product selectivity, and activity stability, making it suitable for industrial production processes. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Methanol conversion rate = (molar amount of methanol in feedstock - molar amount of methanol in product) / molar amount of methanol in feedstock Ethanol selectivity = Molar amount of ethanol in the product / Methanol conversion rate In the embodiments, atomic emission spectroscopy and X-ray fluorescence were used to determine the element content, low-temperature nitrogen adsorption method was used to determine the specific surface area and pore volume, and gas chromatography was used to analyze the composition of raw materials and reaction products.

[0030] For other analytical tests, please refer to the relevant analytical methods in (National Standard for Testing Methods of Petroleum and Petroleum Products, published by China Standards Press, 1989) and (Analytical Methods for Petrochemical Products (RIPP Test Methods), published by Science Press, 1990).

[0031] Example 1 The industrial asphalt (softening point 265℃) obtained after distillation of residual oil is crushed to a particle diameter of less than 0.6 mm, treated at 700℃ under nitrogen protection for 2 hours, and then heated to 900℃ and treated with steam for 1 hour to obtain the asphalt-based activated carbon powder required by this invention.

[0032] Industrial grade ferrous sulfate heptahydrate was prepared into a solution, and industrial grade calcium hydroxide powder was slowly added to carry out a neutralization reaction. The temperature rise during the reaction was controlled by controlling the feeding rate to ensure that it did not exceed 95°C. After the reaction was completed, air was introduced to oxidize the iron until the divalent iron in the iron element was less than 1 wt%. The resulting filter cake was filtered, washed, and dried to obtain the amorphous iron hydroxide powder required by this invention.

[0033] According to Cu a Zn b Rh g Co l Fe μ Ca h Al ρ O c / C 100 a=11, b=0.8, g=4.5×10 -5 The molar ratio of the catalyst, constrained by l=0.25, μ=0.25, h=0.003, and ρ=0.0021, is used to uniformly mix the calculated amounts of the above-prepared asphalt-based activated carbon powder and amorphous ferric hydroxide powder with industrial-grade basic zinc carbonate powder. A mixed solution is prepared using chemically pure reagents copper nitrate trihydrate, cobalt nitrate hexahydrate, ferric nitrate nonahydrate, and rhodium chloride trihydrate. This solution is then used to impregnate the mixture at room temperature with equal volumes of the above materials, followed by uniform mixing with the molding agent high-alumina cement powder (industrial grade, alumina ≥48wt%, calcium oxide ≥50wt%).

[0034] After kneading in a small laboratory kneader for more than 1 hour, the catalyst is extruded into strips with a diameter of 2 mm and a length of 1 to 1.5 cm on a small laboratory extruder; and left to dry and harden under ventilation for 2 to 3 days to obtain the catalyst of Example 1 of the present invention.

[0035] The catalyst has an average pore size of 3.5 nm, a pore volume of 0.39 ml / g, and a surface area of ​​620 m². 2 / g, bulk density is 0.52g / ml.

[0036] Example 2 The preparation process and steps of the asphalt-based activated carbon powder are the same as in Example 1, but industrial asphalt with a softening point of 332℃ is used; industrial potassium hydroxide is used in the preparation of amorphous hydroxyl iron oxide powder, and the filter cake after the neutralization reaction is completed is washed with deionized water to remove potassium ions.

[0037] The catalyst preparation process and steps are the same as in Example 1, but the molar ratio of the catalyst feed is adjusted to: Cu a Zn b Rh g Co l Fe μ Ca h Al ρ O c / C 100 a=9, b=0.7, g=4.1×10 -5 , l=0.22, μ=0.28, h=0.002, ρ=0.0028.

[0038] The catalyst was pressurized into columnar shapes with a diameter and height of 3 mm using a small laboratory tablet press; the average pore size, pore volume, surface area and bulk density of the catalyst were similar to those of the catalyst in Example 1.

[0039] Example 3 The preparation process and steps of the asphalt-based activated carbon powder are the same as in Example 1, but industrial asphalt with a softening point of 184°C is used; industrial solid caustic soda (sodium hydroxide) is used in the preparation of amorphous iron hydroxide powder, and the filter cake after the neutralization reaction is completed is washed with deionized water to remove sodium ions.

[0040] The catalyst preparation process and steps are the same as in Example 1, but the molar ratio of the catalyst feed is adjusted to: Cu a Zn b Rh g Co l Fe μ Ca h Al ρ O c / C 100 , a=12, b=0.9, g=4.6´10-5, l=0.27, μ=0.21, h=0.0022, ρ=0.0027.

[0041] The catalyst was rolled into small spherical shapes with a diameter of 3 mm using a small laboratory ball rolling machine; the average pore size, pore volume, surface area and bulk density of the catalyst were similar to those of the catalyst in Example 1.

[0042] Comparative Example 1 Referring to the preparation content and steps of the preferred embodiment in the existing technical literature, copper-zinc alumina catalyst was prepared by loading copper and zinc active components (26 wt% copper and 1.7 wt% zinc) onto a commercial alumina support (industrial grade, alumina ≥ 99.5 wt%, pore volume ≥ 0.35 mL / g).

[0043] Comparative Example 2 Referring to the preparation content and steps of the best embodiment in the existing technical literature, a copper-zinc activated carbon supported catalyst was prepared using commercial activated carbon (carbon ≥ 80 wt%, oxygen 2 wt% ~ 5 wt%, specific surface area ≥ 600 m² / g) as a support. The loading of metal active components was the same as that of Comparative Example 1.

[0044] Comparative Example 3 In the prior art, there is no preparation example with a composition similar to that of the present invention. However, in order to facilitate a further comparison with the present invention, this comparative example selects a ratio of copper, zinc, cobalt, iron, rhodium, calcium and aluminum components similar to those of the present invention and the components of Example 1 to be loaded on an activated carbon support to prepare a comparative catalyst. The preparation process and steps are the same as those in Example 2, and the copper-zinc catalyst containing multi-component metal active additives in Comparative Example 3 is obtained.

[0045] Test case This experimental example aims to investigate the performance and reaction conversion process of the catalyst provided by the present invention and the comparative methanol-to-ethanol catalyst.

[0046] The experimental reaction process used a laboratory micro fixed-bed reactor with a catalyst loading volume of 15 mL. The catalysts provided in Examples 1-3 and Comparative Examples 1-3 of this invention were loaded into the reactor. The reactor was reduced with hydrogen at 320 °C for 4 hours. Methanol containing 0.01 wt% iodomethane was used as the feed rate at 30 mL / h. The molar ratio of hydrogen to carbon monoxide was 4. The reaction temperature was 250 °C, the reaction pressure was 5 MPa, and the reaction time was 20 hours. After that, the samples were taken and the component content in the reaction products was analyzed by gas chromatography. The evaluation results are shown in Table 1.

[0047] Table 1. Evaluation results of catalysts in Examples 1-3 and Comparative Examples 1-3: The data in Table 1 show that the catalyst prepared by this invention can exhibit better catalytic performance in the conversion of methanol to ethanol, with better methanol conversion rate, product ethanol selectivity, and activity stability; it also has good resistance to impact etching, which can extend the service life of the catalyst, which is of positive significance for improving the prospects of industrial application.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0049] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A catalyst for methanol-to-ethanol conversion, characterized in that, The catalyst composition satisfies the chemical formula: Cu a Zn b Rh g Co l Fe μ Ca h Al ρ O c / C 100 In the formula, the atomic ratios of each element are a = 5.5–14, b = 0.5–1, and g = 4 × 10⁻⁶. -5 ~5´10 -5 l=0.2~0.3, μ=0.2~0.3, h=0.002~0.003, ρ=0.002~0.003, and c is the number of oxygen atoms required to satisfy the valence of each element.

2. The methanol-to-ethanol catalyst according to claim 1, characterized in that, The catalyst has an average pore size ≥ 1 nm, a pore volume of 0.2–0.6 mL / g, a surface area of ​​300–900 m² / g, and a bulk density of 0.3–0.8 g / mL.

3. A method for preparing a methanol-to-ethanol catalyst as described in any one of claims 1-2, characterized in that, The process includes the following steps: mixing asphalt-based activated carbon powder and amorphous iron hydroxide powder with basic zinc carbonate powder, then impregnating with an equal volume of a mixed solution of soluble copper salt, cobalt salt, and trace amounts of rhodium salt; drying and then kneading with a high-alumina cement molding agent to obtain a methanol-to-ethanol catalyst by ventilation drying at room temperature.

4. The method for preparing a methanol-to-ethanol catalyst according to claim 3, characterized in that, The preparation method of asphalt-based activated carbon powder includes the following steps: after crushing petroleum asphalt, carbonizing it in an inert gas atmosphere at 500-750 ℃ ​​for 1-3 hours, and then treating it with water vapor at 800-950 ℃ for 1-3 hours.

5. The method for preparing a methanol-to-ethanol catalyst according to claim 3, characterized in that, Amorphous ferric hydroxide powder is produced by mixing and reacting a soluble ferrous salt solution with a solid hydroxide at a temperature below 100°C, followed by oxidation with air until the ferrous iron content is less than 1 wt%, and then washing to obtain the filter cake.

6. The method for preparing a methanol-to-ethanol catalyst according to claim 3, characterized in that, The soluble salts of copper, cobalt, rhodium, and iron are selected from any one of the sulfates, nitrates, chlorates, oxalates, and acetates of copper, cobalt, and rhodium.

7. The method for preparing a methanol-to-ethanol catalyst according to claim 5, characterized in that, Solid hydroxides include any one of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

8. A method for converting methanol to ethanol, characterized in that, The reaction involves introducing a reaction feedstock consisting of methanol containing trace amounts of iodomethane and syngas into a fixed-bed reactor, where it reacts with a catalyst as described in any one of claims 1-2 or a catalyst prepared by any one of claims 3-7, and the product ethanol is obtained after separation.

9. The method for converting methanol to ethanol according to claim 8, characterized in that, The liquid hourly space velocity (LHSV) of the reactants during the reaction process is 0.2–12 h⁻¹. -1 The reaction temperature is 120–290°C. o C. The reaction pressure is 1-10 MPa.

10. The method for converting methanol to ethanol according to claim 8, characterized in that, The content of iodomethane in methanol is 0.1% to 10%; the molar ratio of carbon monoxide to hydrogen in the synthesis gas is 1:1 to 20, and the molar ratio of carbon monoxide to methanol is 1:1 to 3.

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