Method for preparing chain-like cu(ca) / zsm-5 catalyst by synergistic compounding and application thereof

Abstract

The application relates to the technical field of ZSM-5 type molecular sieve preparation, in particular to a method for preparing a chain-shaped Cu(CA) / ZSM-5 catalyst through CA synergic compounding and application, wherein an acid mixed solution of citric acid and copper nitrate is added into ZSM-5 molecular sieve precursors; after stirring and mixing, ultrasonic treatment is carried out at normal temperature, and then the precursors are obtained through separation, washing, drying, grinding and calcination; the precursors are placed in a hydrogen atmosphere for reduction to obtain the chain-shaped Cu(CA) / ZSM-5 catalyst. Compared with the conventional method, the CA synergic compounding can effectively enhance the combination capacity of copper nanoparticles and the carrier, improve the stability and anti-sintering capacity of the catalyst, obtain the catalyst with small metal particles and high dispersity, and further improve the activity and product selectivity of the catalyst, and the Cu(CA) / ZSM-5 catalyst has obvious performance advantages compared with a Cu / ZSM-5-CA catalyst. Therefore, the Cu(CA) / ZSM-5 catalyst is a kind of efficient catalyst.

Description

Technical Field

[0001] This invention relates to the field of ZSM-5 molecular sieve preparation technology, and in particular to a method and application for preparing chain-like Cu(CA) / ZSM-5 catalysts by synergistic compounding of citric acid (CA). Background Technology

[0002] ZSM-5 molecular sieves belong to the mesoporous and microporous molecular sieve category, possessing a unique three-dimensional cross-channel system and ten-membered ring pores. They exhibit excellent thermal stability, high specific surface area, hydrothermal stability, mechanical stability, and tunable acidity, demonstrating superior performance in catalytic applications, including high selectivity, high activity, and strong resistance to coking and deactivation. They play a significant role in adsorption and catalysis. However, traditional ZSM-5 molecular sieves, with their single microporous structure and redundant strong acid sites, are prone to causing excessive reactions of reactants, converting them to CO or resulting in carbon deposition, leading to catalyst deactivation. Therefore, appropriate modification of the molecular sieve (such as preparing molecular sieves with special morphologies and performing elemental or composite modifications to the physical properties of ZSM-5 molecular sieves) can enhance their adaptability to various reactions. Compared to traditional ZSM-5 molecular sieves, self-assembled chain-like ZSM-5 molecular sieves exhibit superior pore structure, with chains reaching up to 11 μm in length. These chain-like molecular sieves maintain structural and morphological stability under high temperature, high pressure, ultrasonic, and acid treatment conditions, providing a reliable foundation for introducing metals to form high-performance catalysts. Furthermore, the uniform crystal size of the self-assembled chain-like ZSM-5 molecular sieves provides a high specific surface area and abundant surface hydroxyl groups, which is beneficial for the anchoring and dispersion of active metals, achieving effective matching between metal active sites and acidic sites. This has already been successfully applied in the preparation of some supported catalysts.

[0003] Typically, catalysts loaded with high concentrations of active components can effectively improve the reaction activity in the methanol dehydrogenation to methyl formate reaction. However, since the reaction takes place at high temperatures, the activity and lifetime of copper-based catalysts are often inversely proportional to their particle size. Increasing the copper loading easily leads to sintering / agglomeration, poisoning, and coking of metal nanoparticles. Smaller active copper particles help increase the contact area with reactants and reduce catalyst deactivation during the reaction. Therefore, preparing catalysts with small particle size and high loading is an effective strategy to improve catalytic activity. Currently, conventional impregnation, dual-solvent impregnation, and gel-sol methods are commonly used methods for preparing supported catalysts, but all have problems such as uneven metal particle distribution and difficulty in controlling the size. Furthermore, when preparing silicon-supported copper catalysts by impregnation, the weak interaction between Si and Cu leads to sintering and deactivation during the reaction. Therefore, developing an effective method to control the size of metallic copper particles is crucial. Summary of the Invention

[0004] To address the issues of large metal particle size and weak interaction in catalysts prepared by conventional impregnation methods, this invention provides a method and application for preparing chain-like Cu(CA) / ZSM-5 catalysts through CA synergistic compounding.

[0005] This invention is achieved through the following technical solution: a method for preparing chain-like Cu(CA) / ZSM-5 catalyst by synergistic compounding of CA, comprising the following steps:

[0006] A mixed solution of citric acid and copper nitrate was added to the ZSM-5 molecular sieve precursor. After stirring and mixing, the precursor was ultrasonically treated at room temperature, and then separated, washed, dried, ground, and calcined to obtain the precursor. The calcination temperature was 400-550℃ and the calcination time was 3-5h. Finally, it was reduced in a hydrogen atmosphere at a reduction temperature of 350℃ for 4h to obtain a chain-like Cu(CA) / ZSM-5 catalyst.

[0007] As a further improvement to the technical solution of this invention, the liquid-to-solid ratio of the acid mixture to the ZSM-5 molecular sieve precursor is 20 mL / g, and the molar ratio of citric acid to copper nitrate in the mixture is 0.6–3.0.

[0008] As a further improvement to the technical solution of the present invention, the ultrasonic treatment is performed at least once, and each treatment lasts at least 60 minutes.

[0009] As a further improvement to the technical solution of the present invention, the ZSM-5 molecular sieve precursor is a ZSM-5 molecular sieve precursor that has not undergone programmed temperature rise to burn off the template agent, wherein Si / Al = 50.

[0010] As a further improvement to the technical solution of the present invention, the copper loading in the Cu(CA) / ZSM-5 catalyst is 10-30 wt%.

[0011] This invention also provides the application of the Cu(CA) / ZSM-5 catalyst prepared by the above-mentioned method for preparing chain-like Cu(CA) / ZSM-5 catalyst in the preparation of methyl formate.

[0012] The method and application of CA synergistic compounding for preparing chain-like Cu(CA) / ZSM-5 catalysts provided by this invention have the following advantages compared with existing technologies:

[0013] The Cu(CA) / ZSM-5 catalyst prepared by CA synergistic compounding provided by this invention can control the metal particle size to below 10 nm, while the copper particle size of Cu / ZSM-5 catalysts obtained by conventional impregnation methods is typically 30 nm. Furthermore, the structural parameters of the Cu(CA) / ZSM-5 catalyst are superior to those of Cu / ZSM-5 catalysts obtained by ordinary impregnation. CA synergistic compounding effectively enhances the binding ability of copper nanoparticles to the support, improves catalyst stability and anti-sintering ability, and yields a catalyst with small metal particles and high dispersion, thereby improving catalyst activity and product selectivity. Compared with Cu / ZSM-5-CA catalysts, it also has significant performance advantages. Therefore, the Cu(CA) / ZSM-5 catalyst prepared by CA synergistic compounding is an effective catalyst. Attached Figure Description

[0014] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 TEM images (a, c, e) and particle size distribution diagrams (b, d, f) of the catalysts obtained after ordinary impregnation (Cu / ZSM-5, Comparative Example 1), acid treatment-impregnation (Cu / ZSM-5-CA, Comparative Example 2), and CA synergistic compounding (Cu(CA) / ZSM-5, Example 1). As can be seen from the figures, the Cu(CA) / ZSM-5 catalyst has the smallest copper particle size on its surface, with the copper particles mainly concentrated at 6.5 nm, which is much smaller than the copper particle size on the surfaces of the Cu / ZSM-5 and Cu / ZSM-5-CA catalysts. This indicates that the CA synergistic compounding method is more advantageous for obtaining small-particle-size supported copper catalysts.

[0017] Figure 2 A comparison of the XRD spectra of the ordinary impregnation method (Cu / ZSM-5, Comparative Example 1), acid treatment-impregnation (Cu / ZSM-5-CA, Comparative Example 2), and catalyst after CA synergistic compounding (Cu(CA) / ZSM-5, Example 1) shows that the crystal forms of the three materials all exhibit the characteristic peaks of ZSM-5 molecular sieve, proving that the addition of citric acid during the preparation process did not change the crystal structure and material composition of ZSM-5.

[0018] Figure 3The FT-IR spectrum of the CA synergistic catalyst (Cu(CA) / ZSM-5, Example 1) is shown. The dry Cu(CA) / ZSM-5 sample was analyzed at 1720 cm⁻¹. -1 A C=O bond absorption peak appeared in the region; while in the Cu(CA) / ZSM-5 catalyst, a peak was observed at 1630 cm⁻¹. -1 An absorption peak corresponding to the C=O bond vibration of the carboxyl group appeared at 1720 cm⁻¹. The C=O bond absorption peak extends from 1720 cm⁻¹. -1 Up to 1630cm -1 The red shift indicates that the Cu(CA) / ZSM-5 catalyst formed metal coordination bonds during the reduction process, confirming the complexation effect of CA.

[0019] Figure 4 Thermogravimetric curves (TGA) of the dried Cu(CA) / ZSM-5 sample and the Cu(CA) / ZSM-5 catalyst are shown in Example 1. The dried Cu(CA) / ZSM-5 sample exhibited three weight loss peaks at 230, 250, and 390 °C. The first weight loss peak is attributed to the decomposition of CA, which begins at 170 °C and completely decomposes into CO2 at 250 °C. The weight loss peaks at 250 °C and 390 °C are attributed to the removal of bound water and the decomposition of Cu(NO3)2 into CuO, respectively. In comparison, no significant weight loss was observed in the Cu(CA) / ZSM-5 catalyst. This indicates that under the conditions of the example, CA and Cu(NO3)2 were completely decomposed, and no residues were found in the prepared Cu(CA) / ZSM-5 catalyst.

[0020] Figure 5 The UV-Vis-NIR spectra of catalysts prepared under different acid-copper ratios were obtained. The Cu(CA) / ZSM-5 catalyst was prepared in Example 1 with an acid-copper ratio of 1.8; the Cu(0.6CA) / ZSM-5 catalyst was prepared in Example 7, where 0.72 g of citric acid replaced 0.24 g of citric acid; and the Cu(3.0CA) / ZSM-5 catalyst was prepared in Example 8, where 0.72 g of citric acid replaced 1.2 g of citric acid. The UV-Vis-NIR spectra of the catalysts prepared under different acid-copper ratios were obtained at 17000 cm⁻¹. -1 A broad and asymmetrical peak centered on Cu is typically found in hydrated Cu. 2+ In zeolite, with Cu 2 + The dd transformation of twisted octahedral water complexes is involved, which is typical of Cu-containing compounds. 2+ Oligomeric copper species. At 22700 cm -1 There is a weaker peak nearby, belonging to μ-oxo, i.e., [Cu-O-Cu]. 2+ The oxygen in the bridge originates from the zeolite framework. 30,000–50,000 cm -1 The peak at the position is due to the charge transfer transition between the ligand and the metal (O). 2- Cu2+ →O - Cu + (Formation). Comparative analysis revealed that the Cu(CA) / ZSM-5 catalyst, at 20000–50000 cm⁻¹, formed... -1 The weakest spectral intensity within this range indicates that it possesses less [Cu-O-Cu]. 2+ The copper species on the surface of the bridge are more easily reduced; while Cu(3.0CA) / ZSM-5 at 17000 cm⁻¹ is more easily reduced. -1 The stronger peak at that location indicates the presence of a large amount of copper oligomers in the catalyst.

[0021] Figure 6 The catalyst (Cu / ZSM-5, Comparative Example 1) prepared by the conventional impregnation method was tested for its catalytic activity in the methanol dehydrogenation to methyl formate reaction.

[0022] Figure 7 The catalyst (Cu / ZSM-5-CA, Comparative Example 2) prepared by acid treatment-impregnation method was tested for its catalytic activity in the methanol dehydrogenation to methyl formate reaction.

[0023] Figure 8 The catalyst (Cu(CA) / ZSM-5, Example 1) prepared by CA synergistic compounding method was tested for its catalytic activity in the methanol dehydrogenation to methyl formate reaction. Figures 6 to 8 The comparison shows that the preparation method of copper-based catalyst has a significant impact on the catalytic performance of methanol dehydrogenation to methyl formate. Among them, the catalyst prepared by synergistic compounding of CA has the highest selectivity and conversion rate, with a methanol conversion rate of 35.0% and a methyl formate selectivity of 88.3%, which is significantly higher than the performance of catalysts prepared by the other two methods. Detailed Implementation

[0024] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0026] This invention provides a specific embodiment of a method for preparing chain-like Cu(CA) / ZSM-5 catalysts through synergistic compounding of CA, comprising the following steps:

[0027] A mixed solution of citric acid and copper nitrate was added to the ZSM-5 molecular sieve precursor. After stirring and mixing, the precursor was ultrasonically treated at room temperature, and then separated, washed, dried, ground, and calcined to obtain the precursor. The calcination temperature was 400-550℃ and the calcination time was 3-5h. Finally, it was reduced in a hydrogen atmosphere at a reduction temperature of 350℃ for 4h to obtain a chain-like Cu(CA) / ZSM-5 catalyst.

[0028] In one embodiment of the present invention, the liquid-solid ratio of the acid mixture solution to the ZSM-5 molecular sieve precursor is 20 mL / g, and the molar ratio of citric acid to copper nitrate in the mixture solution is 0.6 to 3.0.

[0029] In another embodiment of the present invention, the ultrasonic treatment is performed at least once, with each treatment lasting at least 60 minutes. Preferably, the ultrasonic treatment is performed three times, with a power of 1000W and a frequency of 2000-5000Hz.

[0030] In this invention, the preferred catalyst is dried at a temperature of 80°C. Furthermore, in specific embodiments of this invention, the calcination process is carried out in a muffle furnace, and the reduction in a hydrogen atmosphere is carried out in a tube furnace. It should be noted that the calcination process in this invention is conducted in an air environment.

[0031] In one embodiment of the present invention, the ZSM-5 molecular sieve precursor is a ZSM-5 molecular sieve precursor that has not undergone programmed temperature burning to remove the template agent, wherein Si / Al = 50. In the following embodiments of the present invention, the ZSM-5 molecular sieve precursor used is self-made. The specific method for self-making the ZSM-5 molecular sieve precursor is as follows: using tetraethyl orthosilicate (TEOS), aluminum nitrate, and tetrapropylammonium hydroxide (TPAOH) as the main raw materials, ZSM-5 molecular sieve is synthesized according to the molar ratio of Si:Al:TPAOH:H2O = 1:0.02:0.4:50. The specific operation steps are as follows: First, mix TPAOH aqueous solution with a certain amount of aluminum nitrate solution and stir for 2 hours; then, slowly add TEOS dropwise to the above solution and continue stirring at room temperature for 24 hours to obtain a transparent and uniform mixed solution; after evaporating alcohol in a water bath at 58°C, transfer the synthesis solution to a stainless steel autoclave with a polytetrafluoroethylene liner (100mL), crystallize at 200°C for 5 days in a homogeneous reactor, remove and cool to room temperature, wash thoroughly with deionized water until neutral, and then dry in an oven at 100°C for 12 hours to obtain the chain-like ZSM-5 molecular sieve precursor.

[0032] In another embodiment of the present invention, the copper loading in the Cu(CA) / ZSM-5 catalyst is 10-30 wt%.

[0033] This invention also provides a method for preparing chain-like Cu(CA) / ZSM-5 catalysts through synergistic compounding of CA and the application of Cu(CA) / ZSM-5 catalysts in the direct dehydrogenation of methanol to methyl formate.

[0034] In this invention, the ZSM-5 molecular sieve precursor has a large number of hydroxyl groups on its surface. The CA complexation and auxiliary effect helps to strengthen the bonding between the support and metallic copper, forming O-Cu bonds, improving the interaction between copper nanoparticles and the support, effectively anchoring copper metal particles, effectively reducing the formation of large copper oxide species during calcination, and facilitating metal particle dispersion. The resulting catalyst size is controlled at 6.5 nm, far lower than the copper particle size of catalysts prepared by ordinary impregnation methods, which is above 30 nm. Furthermore, when applied to the methanol dehydrogenation reaction, it improves the contact degree between the active component and the reactants during the reaction, ensures effective bonding between Cu and the support, reduces loss, and fundamentally solves the problems of low activity and poor stability of catalysts in the methanol dehydrogenation to methyl formate reaction.

[0035] The specific embodiments of the present invention will be described in detail below.

[0036] Example 1

[0037] A method for preparing chain-like Cu(CA) / ZSM-5 catalyst by synergistic compounding of CA includes the following steps:

[0038] 0.72 g of citric acid and 0.4 g of copper nitrate were dissolved in 10 mL of deionized water. After complete dissolution, the solution was added dropwise to the chain-like ZSM-5 molecular sieve precursor using a peristaltic pump. The liquid-to-solid ratio of the acid mixture to the molecular sieve was 20 mL / g. After stirring and mixing, the mixture was ultrasonically treated at room temperature for 60 min, filtered, washed with deionized water until neutral, dried at 80 °C overnight, and then ground into powder. The powder was calcined in a muffle furnace at 450 °C for 4 h to obtain the precursor. Finally, the calcined powder was reduced in a tube furnace at 350 °C under a hydrogen atmosphere for 4 h to obtain the catalyst, denoted as Cu(CA) / ZSM-5.

[0039] Examples 2-8

[0040] A method for preparing chain-like Cu(CA) / ZSM-5 catalyst by CA synergistic compounding is provided. The steps are the same as in Example 1, and the specific parameter adjustments are shown in Table 1.

[0041] Comparative Example 1

[0042] A method for preparing Cu / ZSM-5 catalyst includes the following steps:

[0043] 0.4 g of copper nitrate was dissolved in 10 mL of deionized water. After thorough stirring and dissolution, the solution was added dropwise to the ZSM-5 molecular sieve precursor using a peristaltic pump. After stirring and mixing, the mixture was ultrasonically treated at room temperature for 60 min, then filtered, washed with deionized water until neutral, dried at 80 °C overnight, and ground into powder. The powder was then calcined in a muffle furnace at 450 °C for 4 h to obtain the precursor. Finally, the calcined powder was reduced in a tube furnace at 350 °C under a hydrogen atmosphere for 4 h to obtain the catalyst, denoted as Cu / ZSM-5.

[0044] Comparative Example 2

[0045] A method for preparing Cu / ZSM-5-CA catalyst includes the following steps:

[0046] 0.72 g of citric acid was dissolved in 10 mL of deionized water. After thorough stirring, the solution was added dropwise to the ZSM-5 molecular sieve precursor using a peristaltic pump. The liquid-solid ratio of the citric acid solution to the ZSM-5 molecular sieve precursor was 20 mL / g. The mixture was stirred for 24 h, then filtered, washed with deionized water until neutral, dried at 80 °C overnight, and ground into powder. The powder was then calcined in a muffle furnace at 450 °C for 3–5 h to obtain the acid-treated ZSM-5-CA sample.

[0047] 0.4 g of copper nitrate was dissolved in 10 mL of deionized water. After thorough stirring and dissolution, the solution was added dropwise to the ZSM-5-CA sample using a peristaltic pump. After mixing, the solution was ultrasonically treated at room temperature for 60 min, filtered, washed with deionized water until neutral, dried at 80 °C overnight, and then ground into powder. The powder was calcined in a muffle furnace at 450 °C for 4 h to obtain the precursor. Finally, the calcined powder was reduced in a tube furnace at 350 °C under a hydrogen atmosphere for 4 h to obtain the catalyst, denoted as Cu / ZSM-5-CA.

[0048] Comparative Example 3

[0049] A method for preparing Cu(HA) / ZSM-5 catalyst by synergistic compounding with hydrochloric acid (HA) is provided, with the same steps as in Example 1, except that 0.72 g of citric acid is replaced with 0.37 g of hydrochloric acid solution (37 wt%).

[0050] Comparative Example 4

[0051] A method for preparing Cu(OA) / ZSM-5 catalyst by synergistic compounding of oxalic acid (OA) is provided, with the same steps as in Example 1, except that 0.72 g of citric acid replaces 0.5 g of oxalic acid.

[0052] Test case

[0053] The catalysts of Examples 1-8 and Comparative Examples 1-4 were evaluated. The catalytic performance was assessed using a high-pressure microreactor fixed-bed chromatography apparatus (0.2 MPa, 300 °C) with a methanol liquid hourly space velocity (LHSV) of 7.9 h⁻¹.-1 The specific method is as follows: Mix 0.3g of catalyst and 3g of quartz sand evenly and place them in a reaction tube. Use a Series III constant flow microsyringe to inject the solution at a rate of 3mL / h. -1 Methanol is pumped in at a flow rate of [missing information], vaporized in a preheater before feeding, using N2 (30 mL / min) as the carrier gas. -1 The gaseous products are analyzed online by a chromatograph, while the liquid products are collected after condensation for analysis.

[0054] Table 1. Catalytic performance evaluation results of the catalysts described in each embodiment and comparative example.

[0055]

[0056]

[0057] Comparing Example 1 with Comparative Examples 1 and 2 in the table, it can be seen that in the Cu / ZSM-5 catalyst, the methanol conversion rate is only 2.9%, and the selectivity for methyl formate is 94.2%. Compared with the Cu / ZSM-5 catalyst, the Cu / ZSM-5-CA catalyst prepared by acid treatment-impregnation shows improved performance, with a methanol conversion rate of 13.3%. The chain-like Cu(CA) / ZSM-5 catalyst obtained through CA synergistic compounding achieves a conversion rate of 35% and a selectivity of 88.3%, indicating that the introduction of CA effectively reduces the particle size of active copper species, making them easier to reduce. Therefore, the catalyst preparation method has a significant impact on the methanol dehydrogenation activity.

[0058] Comparing Example 1 with Comparative Examples 3 and 4 in the table, it can be seen that the catalyst treated with citric acid has the highest performance compared to oxalic acid and hydrochloric acid. This indicates that the introduction of citric acid is more suitable for reducing the size of Cu metal particles, exposing more active sites, and thus promoting improved catalytic performance.

[0059] Comparing Examples 1 and 2 and 3 in the table, it can be seen that the methanol dehydrogenation performance first increases and then decreases with increasing Cu loading. Increasing Cu loading provides more active sites; however, excessive Cu loading leads to Cu particle agglomeration, decreased metal dispersion, and consequently affects activity.

[0060] Comparing Examples 1 with Examples 4, 5, and 6 in the table, it can be seen that with increasing calcination temperature, the methanol conversion rate and methyl formate selectivity first increase and then decrease. This may be because the texture properties of the catalyst are affected by the calcination temperature. At a calcination temperature of 450℃, the catalyst exhibits the optimal methanol conversion rate (35.0%) and methyl formate selectivity (88.3%). This is because, at a suitable calcination temperature, all citric acid and nitrates added during the preparation process can be completely decomposed. Figure 4 Furthermore, it is not easily damaged by excessively high temperatures.

[0061] Comparing Examples 1 and 7 / 8 in the table, it can be seen that the acid-copper ratio in the catalyst preparation has a significant impact on catalytic performance. The Cu(CA) / ZSM-5 catalyst is superior to the Cu / ZSM-5 catalyst in both methanol conversion and methyl formate yield, indicating that the introduction of CA is beneficial to improving catalytic reaction performance. Furthermore, the activity of Cu(CA) / ZSM-5 first increases and then decreases with increasing acid-copper ratio, achieving optimal performance when the CA / Cu ratio reaches 1.8. This may be because adding more CA promotes the formation of complexes from most Cu species, resulting in smaller copper particles and thus yielding more Cu. 0 Species; however, when the CA / Cu ratio reaches 3.0, a large amount of CA complexes with Cu to form more difficult-to-reduce surface Cu polymer species, making them difficult to reduce. Figure 5 ).

[0062] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A method for preparing a chain-like Cu(CA) / ZSM-5 catalyst for the preparation of methyl formate, characterized in that, Includes the following steps: A mixed solution of citric acid and copper nitrate was added to the ZSM-5 molecular sieve precursor. After stirring and mixing, the precursor was subjected to ultrasonic treatment at room temperature, followed by separation, washing, drying, grinding, and calcination to obtain the precursor. The calcination temperature was 400~550 ℃ and the calcination time was 3~5 h. Finally, it was placed in a hydrogen atmosphere for reduction at a reduction temperature of 350 ℃ and a reduction time of 4 h to obtain the chain-like Cu(CA) / ZSM-5 catalyst. The liquid-to-solid ratio of the acid mixture solution to the ZSM-5 molecular sieve precursor was 20 mL / g, and the molar ratio of citric acid to copper nitrate in the mixture solution was 0.6~3.

0. The preparation method of the ZSM-5 molecular sieve precursor is as follows: First, a tetrapropylammonium hydroxide aqueous solution is mixed with a certain amount of aluminum nitrate solution and stirred for 2 h; then, tetraethyl orthosilicate is slowly added dropwise to the above solution and stirred at room temperature for 24 h to obtain a transparent and uniform mixed solution; after evaporating alcohol in a water bath at 58 ℃, the synthesis solution is transferred to a 100 mL stainless steel autoclave with a polytetrafluoroethylene liner, crystallized at 200 ℃ for 5 days in a homogeneous reactor, removed and cooled to room temperature, washed thoroughly with deionized water until neutral, and then dried in an oven at 100 ℃ for 12 h to obtain the ZSM-5 molecular sieve precursor.

2. The method for preparing a chain-like Cu(CA) / ZSM-5 catalyst for preparing methyl formate according to claim 1, characterized in that, The ultrasonic treatment is performed at least once, with each treatment lasting at least 60 minutes.

3. The method for preparing a chain-like Cu(CA) / ZSM-5 catalyst for preparing methyl formate according to claim 1, characterized in that, The ZSM-5 molecular sieve precursor is a ZSM-5 molecular sieve precursor that has not undergone programmed temperature burning to remove the template agent, wherein Si / Al=50.

4. The method for preparing a chain-like Cu(CA) / ZSM-5 catalyst for preparing methyl formate according to claim 1, characterized in that, The copper loading in the Cu(CA) / ZSM-5 catalyst is 10~30wt%.

5. The application of the Cu(CA) / ZSM-5 catalyst obtained by the preparation method of the chain Cu(CA) / ZSM-5 catalyst for the preparation of methyl formate according to any one of claims 1 to 4 in the preparation of methyl formate.

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