Copper / mesoporous silica catalyst, its preparation method and application in direct synthesis of methyl ester from methanol and ethanol

Abstract

This invention discloses a copper / mesoporous silica catalyst, its preparation method, and its application in the direct synthesis of methyl ester from methanol and ethanol. The catalyst is prepared by ammonia evaporation deposition, using mesoporous silica as a support and loaded with highly dispersed copper species, including metallic copper (Cu). 0 ) and copper oxide (Cu) + and Cu 2+ ), of which Cu + Mostly Cu 0 Secondly, Cu 2+ In small quantities, metallic copper nanoparticles and oxidized copper species are spatially adjacent at the nanoscale, forming a synergistic catalytic microenvironment. The catalyst surface simultaneously possesses weak / medium-strong acidic sites and weak / medium-strong basic sites. Under mild conditions, the catalyst of this invention can achieve highly selective conversion of methanol and ethanol mixtures into methyl formate, methyl acetate, and methyl propionate. Furthermore, the process route is green, safe to operate, and highly atom-economical. The catalyst preparation method is simple and has good stability, providing a new strategy for the clean production of methyl esters.

Description

Technical Field

[0001] This invention relates to the field of heterogeneous catalysis and chemical product synthesis technology, specifically to a copper / meso-SiO2 catalyst with synergistic effects of specific active sites and its preparation method, as well as its application in the direct, one-step continuous synthesis of methyl formate, methyl acetate and methyl propionate from methanol and ethanol. Background Technology

[0002] Methanol and ethanol, as renewable resources, can be used not only as fuels but also as multifunctional platform molecules. These platform molecules have great potential in the chemical industry, enabling the production of a range of value-added chemicals, including methyl formate, methyl acetate, and methyl propionate. Methyl esters (hereinafter referred to as "methyl esters") are an important component of the chemical industry. Methyl formate continues to expand in emerging fields such as new energy, biomedicine, and environmental protection materials. Methyl acetate is a core intermediate in the synthesis of key chemical raw materials such as acetic anhydride and methyl acrylate, and is widely used in organic synthesis and battery manufacturing. Methyl propionate, as an important commercial chemical, is widely used in the synthesis of high-value-added downstream products. For example, the condensation of methyl propionate with formaldehyde can produce methyl methacrylate, which is widely used in optical instruments, electronic information materials, and aerospace.

[0003] Traditional methyl ester synthesis routes use alcohols and carboxylic acids or their derivatives as raw materials, and achieve ester synthesis through various catalytic systems and reaction mechanisms. Common synthetic methods include: Fischer esterification, acyl chloride process, acid anhydride process, Mitsunobu reaction, and transesterification. However, these traditional preparation processes typically use corrosive homogeneous catalysts, resulting in problems such as multiple steps, poor atom economy, large amounts of waste generation, and difficulties in product separation. In recent years, the development of heterogeneous catalytic direct synthesis routes based on renewable raw materials (such as methanol and ethanol) has become a research hotspot.

[0004] CN120662320A proposes a low-temperature methanol dehydrogenation method to prepare methyl formate. The catalyst needs to be pre-activated by reduction under hydrogen before catalyzing the methanol reaction, and hydrogen also needs to be introduced during the reaction. Although this method improves the selectivity of methyl formate, the raw material utilization rate is low, the experimental process is cumbersome, and the presence of hydrogen increases certain safety risks. CN119118823A proposes a method to prepare methyl acetate from methanol and formaldehyde. The catalyst needs to be activated in a 5% H2 / N2 mixed gas at 10℃·min before use. -1The temperature was increased to 300℃ for pretreatment. Furthermore, some catalysts used the precious metal Pt, resulting in high catalyst costs. The use of hydrogen also increases safety risks. CN119899107A proposed using methyl acetate, formaldehyde, and methanol to produce methyl propionate. This reaction is a hydrogenation reaction, which carries certain safety risks. The catalyst used in this invention is loaded with 0.1–20 wt% cesium and 0.1–10 wt% bismuth chloride, which increases the catalyst preparation cost to some extent.

[0005] Existing technologies have reported the synthesis of specific methyl esters from single alcohols (such as methanol) using heterogeneous catalysts. However, these methods often produce single products, require the use of precious metals, necessitate hydrogen during the reaction, or cannot efficiently convert mixed alcohols (such as methanol and ethanol) simultaneously into multiple high-value methyl esters. The fundamental reason is that catalysts struggle to synergistically catalyze multi-step cascade reactions such as alcohol dehydrogenation, aldehyde-aldehyde condensation, aldehyde-alcohol condensation, and hemiacetal dehydrogenation in a single system. Therefore, developing a novel non-precious metal catalyst capable of achieving efficient and highly selective one-step conversion of methanol and ethanol mixtures through precise control of active sites has significant industrial application value and green chemistry implications.

[0006] Mesoporous silica (meso-SiO2) possesses a unique structure that effectively supports metal nanoparticles and utilizes spatial confinement to restrict particle aggregation. The abundant silanol groups on its pore surface can anchor metal precursors via ammonia evaporation deposition, resulting in highly dispersed active centers after calcination. Ammonia evaporation deposition effectively controls the dispersion of metal species on the meso-SiO2 support, forming metal nanoparticles with uniform and highly stable particle size distribution. Cu-based catalysts prepared by ammonia evaporation deposition have been widely used in the development of heterogeneous catalysts for various reactions due to their excellent dispersibility, good dehydrogenation performance, and relatively low cost.

[0007] This invention is based on the high activity of Cu-based catalysts in the dehydrogenation reaction of alcohols, making them ideal materials for this reaction. We designed and prepared a supported metal-oxide catalyst and studied the catalytic activity of Cu / meso-SiO2 catalysts with different Cu contents for the direct synthesis of methyl esters in a fixed-bed reactor, achieving high yields and ensuring full utilization of methanol and ethanol. This catalyst exhibits good catalytic activity and high stability, and the reaction process does not use hazardous gases, providing a new research approach for the synthesis of methyl esters from methanol and ethanol. Summary of the Invention

[0008] To address the problems of cumbersome steps, low selectivity, and limited catalyst function in the synthesis of methyl esters in existing technologies, this invention provides a copper / mesoporous silica catalyst, its preparation method, and its application.

[0009] This invention presents a novel copper-based catalyst with clearly defined synergistic effects at its active sites, a simple preparation method, and good stability. It can efficiently catalyze the direct synthesis of various methyl esters from methanol and ethanol under mild conditions. The process route of this invention is green, safe to operate, and highly atom-economical, providing a new strategy for the clean production of methyl ester compounds.

[0010] The technical solution of the present invention is as follows: A copper / mesoporous silica catalyst was prepared by the following method: (1) Preparation of mesoporous silica support Hexadecyltrimethylammonium bromide (CTAB) was dissolved in deionized water, and ammonia and tetraethyl orthosilicate (TEOS) were added and mixed well. The mixture was aged at 90 °C for 76 h, and a white solid precipitate was collected. The precipitate was washed until neutral, dried, ground, and then placed in a muffle furnace and calcined at 450-600 °C for 3-5 h in air atmosphere to obtain a mesoporous silica support (denoted as meso-SiO2). The preferred feeding ratio of hexadecyltrimethylammonium bromide, ammonia, and tetraethyl orthosilicate is 14.55 g: 55 mL: 60 g; The specific surface area of ​​the obtained mesoporous silica support is 300~1100 m². 2 / g, average pore size 3.5~8.5 nm; (2) Preparation of copper / mesoporous silica catalyst The mesoporous silica support obtained in step (1) was dispersed in a copper salt solution, and ammonia was added dropwise to adjust the pH to 10-13 (preferably 11-12). The mixture was stirred for 8-12 h (to allow the copper amine complex to be uniformly deposited on the surface and in the pores of the support). Then, ammonia was evaporated at 90 °C until the system was neutral, and then evaporated to dryness at 90 °C. The resulting solid was dried, ground, and placed in a muffle furnace. It was then calcined in air at 350-500 °C for 3-5 h to obtain a copper / mesoporous silica catalyst (denoted as Cu / meso-SiO2). The copper salt solution is obtained by dissolving copper salt in deionized water; the preferred copper salt is Cu(NO3)2·3H2O. Based on the mass of the copper / mesoporous silica catalyst, the loading of copper element is 5~25wt%, preferably 10~20wt%; Copper / mesoporous silica catalysts contain metallic copper (Cu) 0 ) and copper oxide (Cu) + and Cu 2+ The catalyst contains both weak / medium-strong acidic sites and weak / medium-strong basic sites on its surface.

[0011] The copper / mesoporous silica catalyst of this invention can be used in the direct synthesis of methyl ester from methanol and ethanol. Specifically: A copper / mesoporous silica catalyst was packed into a fixed-bed reactor. The reaction conditions were: temperature 200–450 °C (preferably 250 °C), N2 as the carrier gas, carrier gas pressure 1.0–3.0 MPa (preferably 2 MPa), and mass hourly space velocity (WHSV) of 10–30 h⁻¹. -1 (Preferred 21 h) -1 The product methyl ester is obtained by reacting a mixture of methanol and ethanol. The molar ratio of methanol to ethanol is 2~15:1, preferably 9:1; The methyl esters produced include methyl formate, methyl acetate, and methyl propionate; The reaction mechanism for the direct synthesis of methyl formate, methyl acetate, and methyl propionate from a mixture of methanol and ethanol is described in [reference needed]. Figure 1 The reaction is a non-oxidative dehydrogenation coupling pathway, including: (1) methanol dehydrogenation to formaldehyde, ethanol dehydrogenation to acetaldehyde; (2) formaldehyde and acetaldehyde condense to form 3-hydroxypropanal; (3) 3-hydroxypropanal dehydrates to form acrolein; (4) acrolein is hydrogenated to form propional; (5) propional reacts with methanol to form methyl propionate; (6) at the same time, formaldehyde reacts with methanol to form methyl formate; (7) acetaldehyde reacts with methanol to form methyl acetate.

[0012] The key technical points of this invention include: This invention employs an ammonia evaporation-deposition method to prepare a Cu / meso-SiO2 catalyst. This catalyst uses mesoporous silica as a support and is loaded with highly dispersed copper species (Table 6); the copper species include metallic copper (Cu). 0 ) and copper oxide (Cu) + and Cu 2+ ), of which Cu + Mostly Cu 0 Secondly, Cu 2+ Small amounts; metallic copper nanoparticles and oxidized copper species are spatially adjacent at the nanoscale, which can form a synergistic catalytic microenvironment (Table 7); the catalyst surface has both weak / medium-strong acidic sites and weak / medium-strong basic sites (Table 8).

[0013] The catalyst does not require H2 reduction treatment during use; Cu mainly exists in the oxide state (Cu). + and Cu 2+ ) exists in species form, among which Cu + Mostly. Because methanol and ethanol reduce some of the oxidized copper to metallic copper at reaction temperatures of 200-450℃, Cu will also be present. 0 It exists. (Cu) 0 Nanoparticles and Cu +Species are spatially adjacent and synergistic on the mesoporous SiO2 support, Cu 0 The site-dominant dehydrogenation of the alcohol to aldehyde and the secondary dehydrogenation of the hemiacetal intermediate to methyl ester, while the adjacent Cu + It synergistically catalyzes the cross-condensation of formaldehyde and acetaldehyde, as well as the aldol condensation of various aldehydes and methanol, thereby efficiently connecting the entire reaction pathway.

[0014] The Cu-based catalyst of this invention exhibits high activity in the dehydrogenation reaction of alcohols, and the mesoporous silica effectively supports metal nanoparticles, limiting particle aggregation and thus obtaining highly dispersed active centers. The use of mesoporous silica also allows the formation of methyl acetate and methyl propionate, whose molecular sizes are larger than methyl formate. Under mild conditions (200–450 °C, 1.0–3.0 MPa N₂), this catalyst can achieve highly selective (total ester selectivity >90%) conversion of methanol and ethanol mixtures into methyl formate, methyl acetate, and methyl propionate.

[0015] The beneficial effects of this invention are: 1. Unique catalyst design: Cu was achieved through ammonia evaporation deposition method. 0 and Cu + The controlled construction and high dispersion of species, forming a spatially proximate synergistic system. From Figure 1 As shown in Table 9, Cu 0 Primarily responsible for the dehydrogenation of methanol and ethanol to formaldehyde and acetaldehyde, as well as the dehydrogenation of hemiacetal intermediates to methyl esters; Cu + The catalyst is responsible for the condensation of formaldehyde and acetaldehyde to ultimately form propional, as well as the condensation of formaldehyde, acetaldehyde, propional, and methanol to form a hemiacetal. This "multi-site synergistic" mechanism has not been clearly revealed or fully utilized in existing catalyst designs. Furthermore, the use of mesoporous silica allows the formation of methyl acetate and methyl propionate, whose molecular sizes are larger than methyl formate.

[0016] 2. The reaction process is green, efficient, and safe: It achieves a one-step direct and continuous synthesis of three high-value methyl esters from two simple renewable alcohols. The reaction route has high atom economy and avoids the problems of using hazardous reagents and generating large amounts of wastewater in traditional methods. Under mild conditions (250℃, 2 MPa), an ethanol conversion rate of up to 80.5% and a total methyl ester selectivity of 90.2% can be obtained. The reaction process does not use hydrogen, ensuring high safety.

[0017] 3. Excellent and stable catalyst performance: The catalyst has high activity and good selectivity, and can maintain stable ester yield and high selectivity during continuous operation, showing good potential for industrial application.

[0018] 4. The preparation method is simple and easy to implement: the raw materials of the catalyst are inexpensive and readily available, and the ammonia evaporation deposition method is simple, reproducible, and easy to scale up for production. Attached Figure Description

[0019] Figure 1 : Reaction mechanism diagram for the synthesis of methyl ester from methanol and ethanol. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. For process parameters not specifically specified, conventional techniques can be referred to.

[0021] Example 1: Preparation of 15wt% Cu / meso-SiO2 catalyst

[0022] (1) Weigh 14.55 g of cetyltrimethylammonium bromide (CTAB), add it to a 1000 mL beaker containing 750 mL of deionized water, and stir at 35 °C for 1 h.

[0023] (2) Add 55 mL of NH3 to the above solution. H2O, continue stirring at room temperature for 30 min.

[0024] (3) Add 60 g of tetraethyl orthosilicate (TEOS) to the above solution and stir again for 2 h.

[0025] (4) The white solid precipitate obtained by aging the above mixture at 90 °C for 76 h was washed with deionized water until neutral and dried at 90 °C overnight.

[0026] (5) After drying, the solid is ground and crushed and placed in a muffle furnace and calcined at 550 °C for 5 h in air atmosphere to obtain meso-SiO2 support.

[0027] (6) Weigh 1.1406 g Cu(NO3)2·3H2O and add it to a 100 mL beaker containing 40 mL of deionized water. Stir until Cu(NO3)2·3H2O is completely dissolved.

[0028] (7) Add 2 g of meso-SiO2 to the above solution, add 40 mL of deionized water, continue stirring until the mixture is uniform, then add ammonia water dropwise until the pH of the solution in the beaker is about 11~12, and then stir overnight.

[0029] (8) Use oil bath heating, evaporate ammonia at 90 ℃ until the solution is neutral, continue to evaporate to dryness at 90 ℃, and then transfer the substance in the beaker to the oven to dry.

[0030] (9) The dried solid was ground into powder and placed in a muffle furnace. After calcination at 450 °C in air atmosphere for 4 h, it was ground into fine powder to obtain 15wt%Cu / meso-SiO2.

[0031] The preparation methods of Cu / meso-SiO2 catalysts with different Cu loadings (5wt%, 10wt%, 20wt%, 25wt%) are the same as those described above, only the amount of Cu(NO3)2·3H2O needs to be changed.

[0032] Example 2: Reaction evaluation of 15wt% Cu / meso-SiO2 catalyst

[0033] 0.2 g of 15 wt% Cu / meso-SiO2 catalyst was packed into a micro fixed-bed reactor (YZUBPR-G2-L2-B). N2 was introduced as the carrier gas, and a mixture of methanol and ethanol (molar ratio 9:1) was saturated at 2 MPa for 21 h⁻¹. -1 The feed was prepared at a mass hourly space velocity (WHSV). The performance of the catalyst in catalyzing the reaction of methanol and ethanol to produce methyl ester was evaluated using a temperature-programmed method: an initial reaction temperature of 250 °C was maintained for 78 min, followed by sampling; samples were then taken at 10 °C / min. -1 The temperature was increased to 300 °C at a controlled heating rate, held for 78 min, and a sample was taken once. This operation was repeated until 400 °C was reached. After the reaction was complete, the temperature was allowed to cool naturally to 250 °C, held for another 78 min, and a sample was taken once more. The reaction product was passed through the high-temperature holding section and sampled online by a ten-port valve sampler into the chromatogram (PoraPLOT Q-HT capillary column, FID detector). The reaction performance of the catalyst is shown in Table 1.

[0034] Table 1 Performance of 15wt% Cu / meso-SiO2 catalyst

[0035] [a] Target products methyl esters, including methyl formate, methyl acetate and methyl propionate.

[0036] [b]Total yield of methyl esters relative to ethanol conversion.

[0037] Table 1 shows that, when only the catalytic reaction temperature is changed, the conversion rates of methanol and ethanol increase from 250 °C to 400 °C; however, the overall selectivity of methyl ester decreases, and the total yield of methyl ester relative to the ethanol conversion also decreases. At a reaction temperature of 250 °C, the selectivity of methyl ester reaches its highest level of 90.2%, and the yield also reaches its highest level of 72.6%.

[0038] Example 3

[0039] The evaluation method in this embodiment is the same as that in Example 2, except that the 15wt% Cu / meso-SiO2 catalyst is replaced with a 10wt% Cu / meso-SiO2 catalyst.

[0040] Table 2 Performance of 10wt% Cu / meso-SiO2 catalyst

[0041] [a] Target products methyl esters, including methyl formate, methyl acetate and methyl propionate.

[0042] [b]Total yield of methyl esters relative to ethanol conversion.

[0043] Table 2 shows that, when only the catalytic reaction temperature is changed, the conversion rates of methanol and ethanol increase from 250 °C to 400 °C; however, the overall selectivity of methyl ester decreases, and the total yield of methyl ester relative to the ethanol conversion also decreases. At a reaction temperature of 250 °C, the selectivity of methyl ester reaches its highest level of 89.9%, and the yield also reaches its highest level of 70.5%.

[0044] Example 4

[0045] The evaluation method in this embodiment is the same as that in Example 2, except that the 15wt% Cu / meso-SiO2 catalyst is replaced with a 20wt% Cu / meso-SiO2 catalyst.

[0046] Table 3 Performance of 20wt% Cu / meso-SiO2 catalyst

[0047] [a] Target products methyl esters, including methyl formate, methyl acetate and methyl propionate.

[0048] [b]Total yield of methyl esters relative to ethanol conversion.

[0049] Table 3 shows that, when only the catalytic reaction temperature is changed, the conversion rates of methanol and ethanol increase from 250 °C to 400 °C; however, the overall selectivity of methyl ester decreases, and the total yield of methyl ester relative to the ethanol conversion also decreases. At a reaction temperature of 250 °C, the selectivity of methyl ester reaches its highest level of 89.9%, and the yield also reaches its highest level of 71.3%.

[0050] Furthermore, according to the data in Tables 1 to 3, when the reaction temperature was reduced from 400 °C to 250 °C, comparing the conversion rates of methanol and ethanol and the selectivity of methyl ester at the initial 250 °C, the catalyst did not show significant deactivation, either from the perspective of conversion rate or product selectivity. This indicates that the catalyst has good stability under high temperature conditions.

[0051] Comparative Example 1

[0052] The comparative example uses the same evaluation method as Example 2, except that the 15wt% Cu / meso-SiO2 catalyst is replaced with a 5wt% Cu / meso-SiO2 catalyst.

[0053] Table 4 Performance of 5wt% Cu / meso-SiO2 catalyst

[0054] [a] Target products methyl esters, including methyl formate, methyl acetate and methyl propionate.

[0055] [b]Total yield of methyl esters relative to ethanol conversion.

[0056] Table 4 shows that, when only the catalytic reaction temperature is changed, the conversion rates of methanol and ethanol increase from 250 °C to 400 °C; however, the overall selectivity of methyl ester decreases, and the total yield of methyl ester relative to the ethanol conversion also decreases. The methyl ester selectivity reaches its highest value of 91.0% at a reaction temperature of 250 °C, while the yield reaches its highest value of 72.1% at 300 °C.

[0057] Comparative Example 2

[0058] The evaluation method in this embodiment is the same as that in Example 2, except that the 15wt% Cu / meso-SiO2 catalyst is replaced with a 25wt% Cu / meso-SiO2 catalyst.

[0059] Table 5 Performance of 25wt% Cu / meso-SiO2 catalyst

[0060] [a] Target products methyl esters, including methyl formate, methyl acetate and methyl propionate.

[0061] [b]Total yield of methyl esters relative to ethanol conversion.

[0062] Table 5 shows that, when only the catalytic reaction temperature is changed, the conversion rates of methanol and ethanol increase from 250 °C to 400 °C; however, the overall selectivity of methyl ester decreases, and the total yield of methyl ester relative to the ethanol conversion also decreases. At a reaction temperature of 250 °C, the selectivity of methyl ester reaches its highest level of 89.0%, and the yield also reaches its highest level of 68.6%.

[0063] Data from the examples and comparative studies show that, generally, the methyl ester yield is best at 250 °C. At 250 °C, changing only the Cu loading results in a volcano-shaped yield curve for the methyl ester. This may be because excessively high Cu loading leads to Cu particle agglomeration on the catalyst, thus affecting the Cu content. 0 / Cu + The formation of the interface (Table 7).

[0064] Table 6 Apparent structural properties of Cu / meso-SiO2 catalysts

[0065] [a]BET surface area.

[0066] [b]The volume of a single-point orifice when P / P0=0.99.

[0067] [c] Average aperture calculated by the BET method.

[0068] Table 7 Structural properties of Cu in Cu / meso-SiO2 catalyst

[0069] S Cu 0 : Surface area of ​​metallic Cu; D Cu : Dispersion of Cu; d eff : Effective diameter of Cu; L int Cu 0 -Cu + The perimeter of the interface.

[0070] Table 8 Acid-base properties of Cu / meso-SiO2 catalysts

[0071] Table 9. Dehydrogenation activity of alcohols and hemiacetals on Cu / meso-SiO2 catalysts.

[0072] [a] Alcohol dehydrogenation activity relative to acetaldehyde yield.

[0073] [b] Hemiacetal dehydrogenation activity relative to methyl ester yield.

[0074] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A copper / mesoporous silica catalyst, characterized in that, It is prepared according to the following method: (1) Preparation of mesoporous silica support Hexadecyltrimethylammonium bromide was dissolved in deionized water, and ammonia and tetraethyl orthosilicate were added and mixed. The mixture was aged at 90 °C for 76 h, and the white solid precipitate was collected. The precipitate was washed until neutral, dried, ground, and placed in a muffle furnace. It was then calcined in air at 450-600 °C for 3-5 h to obtain a mesoporous silica support. (2) Preparation of copper / mesoporous silica catalyst The mesoporous silica support obtained in step (1) was dispersed in a copper salt solution, and ammonia was added dropwise to adjust the pH to 10-13. The mixture was stirred for 8-12 h, and then ammonia was evaporated at 90 ℃ until the system was neutral. The mixture was then evaporated to dryness at 90 ℃. The resulting solid material was dried, ground, and placed in a muffle furnace. It was then calcined in air at 350-500 ℃ for 3-5 h to obtain a copper / mesoporous silica catalyst.

2. The copper / mesoporous silica catalyst as described in claim 1, characterized in that, In step (1), the feeding ratio of hexadecyltrimethylammonium bromide, ammonia, and tetraethyl orthosilicate is 14.55 g: 55 mL: 60 g.

3. The copper / mesoporous silica catalyst as described in claim 1, characterized in that, In step (2), the copper salt is Cu(NO3)2·3H2O.

4. The copper / mesoporous silica catalyst as described in claim 1, characterized in that, The loading of copper element is 5~25wt%, depending on the mass of the copper / mesoporous silica catalyst.

5. The application of the copper / mesoporous silica catalyst as described in claim 1 in the direct synthesis of methyl ester from methanol and ethanol.

6. The application as described in claim 5, characterized in that, The method is as follows: A copper / mesoporous silica catalyst was packed into a fixed-bed reactor. The reaction conditions were: temperature 200–450 °C, N2 as carrier gas, carrier gas pressure 1.0–3.0 MPa, and mass hourly space velocity (HHSV) 10–30 h⁻¹. -1 A mixture of methanol and ethanol is reacted to produce methyl ester. The methyl esters produced include methyl formate, methyl acetate, and methyl propionate.

7. The application as described in claim 6, characterized in that, The molar ratio of methanol to ethanol is 2~15:1.

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