CuO-CdO / OH-Hbeta acidic catalyst, and preparation method and application thereof

Abstract

The application discloses a CuO-CdO / OH-Hbeta acidic catalyst and a preparation method and application thereof, the catalyst comprising an OH-Hbeta molecular sieve carrier with hierarchical pores, and CuO and CdO being loaded on the OH-Hbeta molecular sieve carrier; the CuO accounts for 1-10wt% of the total mass of the catalyst, and the CdO accounts for 1-10wt% of the total mass of the catalyst. The preparation method comprises the following steps: calcining, alkali treating and ion exchanging Hbeta molecular sieves to obtain the OH-Hbeta molecular sieve carrier with hierarchical pores; then, the OH-Hbeta molecular sieve carrier is immersed in a mixed solution of copper salt and cadmium salt, and then taken out, dried, ground and calcined to obtain the CuO-CdO / OH-Hbeta acidic catalyst. The catalyst has the advantages of high stability, anti-coking performance, high conversion rate and service life, and the conversion rate of formaldehyde reaches 99.9%, and the content of imidazole in the reaction product reaches 72.1%.

Description

TECHNICAL FIELD

[0001] The application relates to an acidic catalyst and a preparation method and application thereof, in particular to a CuO-CdO / OH-Hbeta acidic catalyst and a preparation method and application thereof BACKGROUND

[0002] Imidazoles are one of the most important five-membered heterocycles with a variety of functions and applications, such as pharmaceuticals, biologically active natural products and acylating reagents. In addition, imidazolium salts are used as ionic liquids and precursors of stable carbene ligands in organometallic chemistry. Imidazoles have also been proposed as absorbents for improving current carbon dioxide capture and storage (CCS) technologies. Imidazole is an important medicine, pesticide intermediate and chemical raw material, which is widely used as a curing agent for epoxy resin, an antifungal agent for pharmaceuticals and a pesticide insecticide. Imidazole can be used as an epoxy resin curing agent, which can improve the mechanical properties such as bending, stretching and compression of products, improve the electrical properties of insulation, improve the chemical properties of chemical resistance, and is widely used in computers and electrical appliances; imidazole is a main raw material for preparing antifungal drugs such as dichlorophenyl imidazole, econazole, ketoconazole and clotrimazole, and has important significance in production and manufacturing.

[0003] The acidic medium can inhibit the rearrangement of 1-alkyl and the hydrolysis of azomethine back to the starting amine and aldehyde species. The stability of glyoxal under acidic conditions is also improved. Therefore, the addition of acidic copper nitrate and acidic cadmium nitrate is extremely important for improving the reaction yield.

[0004] Common imidazole synthesis methods include the Radziszewski method, the Phillips method, the bromoacetaldehyde method and the like. Initially, ammonia water is added into a reaction kettle, glyoxal is added dropwise, the reaction temperature is controlled at 60-70 DEG C, and a new compound imidazole is generated after two hours of reaction, but the yield is only about 12%. In 1882, Radziszewski et al. improved the method, and successfully synthesized imidazole by using ammonia water, glyoxal and formaldehyde. The Radziszewski method for synthesizing imidazole has become a commonly used method for preparing imidazole in industry because of easy availability of raw materials and simple operation.

[0005] The Hbeta molecular sieve with a large number of acid sites exhibits relatively high catalytic performance, but a large amount of by-products are generated, which leads to rapid coking and deactivation of the catalyst, thereby limiting the further application of the catalyst in industry. Therefore, it is of important industrial application value to develop micro-mesoporous molecular sieves with higher conversion rate and anti-coking ability and longer catalyst service life. SUMMARY

[0006] The application aims to provide a CuO-CdO / OH-Hbeta acidic catalyst with higher conversion rate and anti-coking ability and longer catalyst service life;

[0007] The second object of the present application is to provide a preparation method of the CuO-CdO / OH-Hβ acidic catalyst.

[0008] The third object of the present application is to provide an application of the CuO-CdO / OH-Hβ acidic catalyst.

[0009] Technical solution: The CuO-CdO / OH-Hβ acidic catalyst comprises an OH-Hβ molecular sieve carrier with multi-level pores, and CuO and CdO are loaded on the OH-Hβ molecular sieve carrier; wherein the content of CuO is 1-10wt% of the total mass of the catalyst, and the content of CdO is 1-10wt% of the total mass of the catalyst.

[0010] The Hβ molecular sieve carrier has a silicon-aluminum ratio of 25-40.

[0011] The preparation method of the CuO-CdO / OH-Hβ acidic catalyst comprises the following steps:

[0012] (1) The Hβ molecular sieve is subjected to calcination treatment, alkali treatment and ion exchange to obtain an OH-Hβ molecular sieve carrier with multi-level pores;

[0013] (2) The OH-Hβ molecular sieve carrier is immersed in a mixed solution of copper salt and cadmium salt, then taken out, dried, ground and calcined to obtain the CuO-CdO / OH-Hβ acidic catalyst.

[0014] In step (2), preferably, the copper salt and the cadmium salt are dissolved in deionized water to form a mixed aqueous solution; and the volume ratio of the OH-Hβ molecular sieve carrier to the mixed aqueous solution is 1:1-1:10.

[0015] In step (2), the loading amount of CuO and CdO in the CuO-CdO / OH-Hβ acidic catalyst obtained after calcination is 1-10wt% and 1-10wt%, respectively.

[0016] In step (2), the mass ratio of the copper salt, the cadmium salt to the OH-Hβ molecular sieve carrier is 1:1-1:10 and 1:1-1:10, respectively.

[0017] In step (2), the immersion time is 10-24h.

[0018] In step (1) and step (2), the calcination temperature is 450-650℃, and the calcination time is 3-5h. The OH-Hβ molecular sieve carrier with multi-level pores in step (1) can be obtained by using the method of the prior art.

[0019] The application of the CuO-CdO / OH-Hβ acidic catalyst in catalytic synthesis of imidazole.

[0020] The imidazole is prepared by the reaction of mixed aldehyde and ammonia water as raw materials through aldehyde-amine condensation reaction, wherein the CuO-CdO / OH-Hβ is used as the catalyst, the volume ratio of the mixed aldehyde and ammonia water is 0.5:1-2:1, the mixed aldehyde includes formaldehyde and glyoxal, and the volume ratio of the formaldehyde and glyoxal in the mixed aldehyde is 0.4:1-0.7:1.

[0021] The reaction conditions are as follows: normal pressure, reaction temperature is 100-150℃, the mass space velocity of the reaction raw material is 0.7-1.8h -1 .

[0022] The principle of the application is as follows: in the preparation process of the catalyst, the original Hβ is modified by alkali, so that the molecular sieve has mesopores in the original microporous structure, and the specific surface area of the metal salt that can be loaded is increased. Since the reaction involves 1-alkyl rearrangement and azomethine hydrolysis, increasing the acidic medium can greatly inhibit the occurrence of the reaction, so that the generation of by-products is reduced, the reaction is promoted in the forward direction, and therefore the acidic metal salt is selected for loading. The condensation reaction of aldehyde group and amino group is more rapid under the catalysis of copper, and the reaction conditions are more mild, and the ketone or alcohol generated in the reaction is not further reduced, which is beneficial to the forward reaction. Under the catalysis of cadmium, the intermediate generated by the reaction of aldehyde has high electrophilicity, so that the molecule is easy to attack the aldehyde molecule and form an imine intermediate, which promotes the forward reaction, reduces the required temperature, and greatly accelerates the reaction rate.

[0023] The application has the following advantages compared with the prior art:

[0024] (1) The CuO-CdO / OH-Hβ acidic catalyst has high stability, anti-coking performance, high conversion rate and long service life, which is mainly because the catalyst retains the high stability of the original microporous molecular sieve. (2) The imidazole is prepared by the continuous tubular gas phase catalytic reaction, and the catalyst performance is improved due to the loading of the bimetallic catalyst. Under the catalysis of the CuO-CdO / OH-Hβ acidic catalyst, the conversion rate of formaldehyde reaches 99.9%, and the content of imidazole in the reaction product is as high as 72.1% (not including water content). BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The XRD patterns of Hβ, CuO-CdO / OH-Hβ in the present application comparative example 1 and example 1 are shown in the following figure.

[0026] Figure 2 The SEM patterns of Hβ, CuO-CdO / OH-Hβ in the present application comparative example 1 and example 1 are shown in the following figure.

[0027] Figure 3N2 adsorption-desorption graph of Hβ, CuO-CdO / OH-Hβ in the present application comparative example 1 and example 1;

[0028] Figure 4 Pore size distribution graph of Hβ, CuO-CdO / OH-Hβ in the present application comparative example 1 and example 1;

[0029] Figure 5 Catalytic performance comparison graph of Hβ, CuO-CdO / OH-Hβ in the present application comparative example 1 and example 1;

[0030] Figure 6 Trend graph of CuO-CdO / OH-Hβ in the present application example 1 life investigation experiment results. DETAILED DESCRIPTION

[0031] The present application is described in further detail below.

[0032] Example 1

[0033] A preparation method of CuO-CdO / OH-Hβ acidic catalyst, the steps are as follows:

[0034] (1) Preparation of NaOH-Hβ molecular sieve carrier:

[0035] Take Hβ molecular sieve raw powder and calcine at 550℃ for 5h; the calcined Hβ molecular sieve is mixed with 0.5mol / L NaOH solution at a solid-liquid ratio (g / mL) of 1:20, and stirred in a round-bottom flask at 65℃ for 0.5h, then the round-bottom flask is cooled to room temperature in water, washed with water and filtered to pH=7, dried at 110℃ for 10h, and the obtained solid is ground into powder; the powder is added to 0.5mol / L NH4Cl solution at a solid-liquid ratio (g / mL) of 1:20, ion exchange is carried out at 60℃ for 1h and filtered, the above operation is repeated four times, then washed with deionized water until the filtrate is free of chloride ions, placed in a 110℃ oven for drying for 10h, then ground into powder and placed in a muffle furnace, calcined at 550℃ for 5h, to obtain micro-mesoporous Hβ molecular sieve, denoted as multi-level pore NaOH-Hβ molecular sieve;

[0036] (2) Preparation of CuO-CdO / OH-Hβ metal acidic catalyst

[0037] 1.215 g of copper nitrate trihydrate and 0.961 g of cadmium nitrate tetrahydrate were dissolved in 40 ml of deionized water to obtain a brine solution. 8 g of a NaOH-Hβ molecular sieve carrier and the brine solution were mixed in a round-bottom flask and stirred at 800 rpm at 65° C. for 18 h. The mixture was filtered and then dried in an oven at 105° C. for 13 h to obtain a solid, which was ground into a powder. The powder was placed in a muffle furnace and heated to 500° C. at 2° C. / min in an air atmosphere. The powder was calcined for 5 h to obtain a CuO-CdO / OH-Hβ metal acid catalyst.

[0038] Example 2

[0039] The CuO-CdO / OH-Hβ modified molecular sieve material prepared in Example 1 was used as a catalyst to synthesize imidazole. The specific steps are as follows:

[0040] 5 g of catalyst was loaded into the reaction tube, and ammonia, formaldehyde, and glyoxal were used as the reaction raw materials. Ammonia and mixed formaldehyde were fed into the tubular reactor in two streams. The reaction conditions were: normal pressure, reaction temperature of 120 ° C, and mass space velocity of 1.2 h -1 The volume ratio of formaldehyde to glyoxal is 0.61:1.0. The raw materials are cooled after the reaction, and the products are collected and detected by a thermal conductivity detector, a moisture meter and titration.

[0041] Comparative Example 1

[0042] On the basis of Example 2, the difference from Example 2 is that the Hβ molecular sieve in Example 1 is used as a catalyst to synthesize imidazole.

[0043] Figure 1 The XRD spectra of the two catalysts Hβ and CuO-CdO / OH-Hβ are shown in Figure 2. Figure 1 Both samples exhibit characteristic Hβ diffraction peaks at angles of approximately 2θ = 7.8° and 22.4°, indicating that the Hβ zeolite's crystal structure remains intact despite vigorous stirring, heating, ion exchange, CuO and CdO loading, and alkaline treatment. The diffraction peak intensity reflects the integrity of the zeolite's crystal structure. Compared to Hβ, the diffraction peak intensity of the CuO-CdO / OH-Hβ sample decreases, indicating that the NaOH solution treatment desiliconizes and degrades the framework silicon, leading to reduced crystallinity. The absence of distinct CuO and CdO diffraction peaks in the spectra suggests a low metal loading, leading to the lack of corresponding signals during XRD measurements. Alternatively, the CuO and CdO loaded on the NaOH-Hβ sample are uniformly distributed on the catalyst surface, lacking distinct metal clusters.

[0044] Figure 2 (a) is the SEM image of Hβ catalyst. Figure 2SEM image of (b) CuO-CdO / OH-Hβ catalyst in the figure. From Figure 2 It can be seen that before the alkali treatment, the surface of Hβ molecular sieve is relatively neat and flat, and the crystal morphology is mainly cubic. After the alkali treatment, the molecular sieve changes, the crystal produces many pores, becomes rough and flat, and the corners disappear. The main reason is that the alkali solution dissolves the silicon species in the molecular sieve, produces cavities in the molecular sieve framework, and thus forms a micro-mesoporous structure. In addition, it can be seen that the particle size of the molecular sieve after the alkali treatment is relatively uniform, which is beneficial to the amine aldehyde condensation reaction.

[0045] Figure 3 and Figure 4 N2 adsorption-desorption curve and pore size distribution curve of Hβ and CuO-CdO / OH-Hβ catalysts. From Figure 3 It can be seen that the isotherm of Hβ rises rapidly in the low pressure region, and the adsorption curve occurs in the micropore, which shows a typical type I isotherm, proving the microporous structure of Hβ sample. At the same time, H4 type hysteresis loop belonging to narrow slit type pore can be observed at P / P0>0.5, which indicates that there are irregular pore gaps between Hβ particles. The CuO-CdO / OH-Hβ sample still maintains the similar characteristics as the Hβ sample, from Figure 4 The pore size distribution graph also shows that the CuO-CdO / OH-Hβ sample has more mesopores than the Hβ molecular sieve, and the mesopore size range is concentrated in 2-6 nm. However, due to the loading of CuO and CdO on the sample, the pore size and pore volume are slightly smaller than those of the Hβ sample.

[0046] The conversion rate of formaldehyde to imidazole and the content of imidazole excluding water content of Hβ molecular sieve and CuO-CdO / OH-Hβ were compared, and the results are shown in Table 1 and Figure 5

[0047] Table 1 Comparison of properties of Hβ and CuO-CdO / OH-Hβ

[0048] Catalyst Water content / wt% Conversion % / wt% Hβ 58 86.5 CuO-CdO / OH-Hβ 72.1 99.9

[0049] From Table 1 and Figure 5 It can be seen that the catalytic activity of CuO-CdO / OH-Hβ is significantly improved compared with Hβ, and the content of imidazole in organic matter is increased by 14.1% (excluding water content); the conversion rate of imidazole is increased by 13.4% (excluding water content) compared with Hβ molecular sieve. The reason is that under the catalysis of copper and cadmium, not only the condensation rate of reactants to imidazole ring is accelerated, but also the energy required for the reaction is reduced, so that the reaction proceeds more quickly and accurately to the positive direction.

[0050] The service life of the CuO-CdO / OH-Hβ catalyst prepared in Example 1 was investigated, and the results are shown in​Figure 6 As shown in the figure, the conversion rate of formaldehyde and the content of imidazole are stable with the increase of time, which indicates that the CuO-CdO / OH-Hβ catalyst has high catalytic activity and long service life, reaching 720h. Figure 6 As shown in the figure, the conversion rate of formaldehyde and the content of imidazole are stable with the increase of time, which indicates that the CuO-CdO / OH-Hβ catalyst has high catalytic activity and long service life, reaching 720h.

[0051] Example 3

[0052] This example investigates the influence of CuO and CdO loadings on the catalytic performance of the metal acidic catalyst CuO-CdO / OH-Hβ. The influence of different CuO and CdO loadings on the conversion rate of formaldehyde and the content of imidazole is shown in Table 2.

[0053] Table 2 Influence of different metal loadings on the conversion rate of formaldehyde and the content of imidazole excluding water content

[0054] CuO content / wt% CdO content / wt% Conversion % / wt% Content / wt% 0.0 10.0 91.0 62.3 2.5 7.5 96.0 69.5 5.0 5.0 99.9 72.1 7.5 2.5 95.0 70.2 10.0 0.0 92.0 69.1

[0055] As shown in Table 2, when the CuO content is 5wt% and the CdO content is 5wt%, the CuO-CdO / OH-Hβ catalyst can make the conversion rate of formaldehyde reach 99.9% and the content of imidazole reach 72.1% (excluding water content).

[0056] Example 4

[0057] This example investigates the influence of the solid-liquid ratio (g / ml) of the carrier and metal salt solution on the conversion rate of formaldehyde and the content of imidazole excluding water content of the metal acidic catalyst CuO-CdO / OH-Hβ, which is shown in Table 3.

[0058] Table 3 Influence of different metal loadings on the conversion rate of formaldehyde and the content of imidazole excluding water content

[0059] Solid-liquid ratio (g / ml) CuO content / wt% CdO content / wt% Conversion % / wt% Content / wt% 1:3 5.0 5.0 99.2 69.2 1:4 5.0 5.0 99.6 71.8 1:5 5.0 5.0 99.9 72.1 1；6 5.0 5.0 99.5 71.3 1；7 5.0 5.0 99.3 69.4

[0060] As shown in Table 3, when the solid-liquid ratio is 1:5, the metal salt can be most effectively loaded on the carrier. A too low solid-liquid ratio can greatly increase the concentration of the metal salt, thereby blocking the micropores on the surface of the molecular sieve, while a too high solid-liquid ratio can make the concentration of the metal salt too low, thereby insufficiently loading the metal salt on the molecular sieve.

[0061] Example 5

[0062] The basic steps are the same as those in Example 2, except that the reaction temperature is different. The reaction temperature is 100℃, 110℃, 120℃, 130℃, 140℃, respectively, and the experimental results are shown in Table 4. This example is a single-factor experiment of the reaction temperature in imidazole synthesis.

[0063] Table 4 Influence of reaction temperature on the conversion rate of formaldehyde and the content of imidazole excluding water content

[0064] Reaction temperature / °C Ammonia-aldehyde ratio (ml / ml) Feed air velocity / h -1 ]] Mixed aldehyde ratio (ml / ml) Conversion % / wt% Content / wt% 100 3：3 1.2 0.61:1 97.0 68.4 110 3：3 1.2 0.61:1 98.2 70.4 120 3：3 1.2 0.61:1 99.9 72.1 130 3：3 1.2 0.61:1 98.5 63.5 140 3：3 1.2 0.61:1 98.0 62.9

[0065] Note: The solution ratio in this table and the following tables is volume ratio, and the mixed aldehyde ratio is the ratio of formaldehyde and glyoxal.

[0066] As can be seen from Table 4, different reaction temperatures have greater influence on the catalytic activity of CuO-CdO / OH-Hβ catalyst. With the increase of reaction temperature, the conversion rate of formaldehyde and the conversion rate of imidazole first increase and then decrease, which is because too low temperature is not conducive to the conversion of formaldehyde, glyoxal and ammonia water into imidazole, resulting in the decrease of the conversion rate of imidazole; too high temperature is easy to generate high-boiling by-products to block the pores of the catalyst, resulting in the decrease of the activity of the catalyst and the content of imidazole. Therefore, the suitable reaction temperature of the reaction is 120°C in consideration of all factors.

[0067] Example 6

[0068] The basic steps are the same as those in Example 2, except that the mass space velocities are different. The mass space velocities are 0.72h -1 , 0.96h -1 , 1.2h -1 , 1.44h -1 , 1.68h -1 . This example is a single-factor experiment on the mass space velocity in the synthesis of imidazole, and the results are shown in Table 5.

[0069] Table 5 Influence of mass space velocity on the conversion rate of formaldehyde and the content of imidazole excluding water

[0070] Reaction temperature / °C Ammonia-aldehyde ratio (ml / ml) Feed air velocity / h -1 ]] Mixed aldehyde ratio (ml / ml) Conversion % / wt% Content / wt% 120 3：3 0.72 0.61:1 97.0 68.4 120 3：3 0.96 0.61:1 98.2 70.4 120 3：3 1.20 0.61:1 99.9 72.1 120 3：3 1.44 0.61:1 98.5 63.5 120 3：3 1.68 0.61:1 98.0 63.2

[0071] As can be seen from Table 5, different mass space velocities have smaller influence on the catalytic activity of CuO-CdO / OH-Hβ catalyst. When the space velocity is small, the residence time of the reactants in the system is long, and too high temperature is easy to cause the coking of the reactants and the increase of side reactions; when the space velocity is too large, the residence time of the reactants is short, and the reaction is not sufficient, so the content of imidazole and the yield are correspondingly reduced. Therefore, the suitable mass space velocity of the reaction is 1.2h -1 in consideration of all factors.

[0072] Example 7

[0073] The basic steps are the same as those in Example 2, except that the ammonia-aldehyde ratio is different. The volume ratio of ammonia water to mixed aldehyde in the raw materials is 4.2:1.8, 3.6:2.4, 3.0:3.0, 2.4:3.6 and 1.8:4.2, respectively. The two feeds of ammonia water and mixed aldehyde are 3ml / h each to achieve the best reaction conditions. This example is a single-factor experiment on the ammonia-aldehyde ratio in the synthesis of imidazole, and the results are shown in Table 6.

[0074] Table 6 Effect of ammonia-aldehyde ratio on conversion of formaldehyde and imidazole content

[0075] Reaction temperature / °C Ammonia-aldehyde ratio (ml / ml) Feed air velocity / h -1 ]] Mixed aldehyde ratio (ml / ml) Conversion % / wt% Content / wt% 120 4.2：1.8 1.2 0.61:1 96.0 67.8 120 3.6：2.4 1.2 0.61:1 98.2 68.7 120 3.0：3.0 1.2 0.61:1 99.9 72.1 120 2.4：3.6 1.2 0.61:1 98.2 71.7 120 1.8：4.2 1.2 0.61:1 98.0 70.2

[0076] As shown in Table 6, when the amount of ammonia water is insufficient, the conversion of formaldehyde is low due to insufficient reaction, and when the amount of ammonia water is large, the glyoxal is consumed excessively, thus reducing the ring formation reaction rate and resulting in incomplete reaction. Therefore, the optimal amount of ammonia water in the reaction should be controlled to V(ammonia):V(mixed aldehyde) = 3:3.

[0077] Example 8

[0078] The basic steps are the same as in Example 2, except that the ratio of formaldehyde to glyoxal is different. The volume ratio of formaldehyde to glyoxal in the raw materials is 0.67:1, 0.64:1, 0.61:1, 0.58:1, and 0.55:1, respectively. This example is a single-factor experiment on the ratio of mixed aldehyde in imidazole synthesis, and the results are shown in Table 7.

[0079] Table 7 Effect of mixed aldehyde ratio on conversion of formaldehyde and imidazole content

[0080] Reaction temperature / °C Ammonia-aldehyde ratio (ml / ml) Feed air velocity / h ～1 ]] Mixed aldehyde ratio (ml / ml) Conversion % / wt% Content / wt% 120 3：3 1.2 0.67:1 97.5 67.2 120 3：3 1.2 0.64:1 99.0 68.7 120 3：3 1.2 0.61:1 99.9 72.1 120 3：3 1.2 0.58:1 98.7 66.5 120 3：3 1.2 0.55:1 98.6 66.2

[0081] As shown in Table 7, under the condition of excessive glyoxal, the content and yield of imidazole in the reaction solution gradually increase, and with the increase of the proportion of formaldehyde in the mixed aldehyde, the content and yield of imidazole show a decreasing trend, and when V(formaldehyde):V(glyoxal) = 0.61:1.00, the effect is best.

Claims

1. Use of CuO-CdO / OH-Hβ acidic catalyst in catalytic synthesis of imidazole, characterized by that, The CuO-CdO / OH-Hbeta acidic catalyst comprises an OH-Hbeta molecular sieve carrier with hierarchical pores, and CuO and CdO are loaded on the OH-Hbeta molecular sieve carrier; wherein the content of CuO is 1-10wt% of the total mass of the catalyst, and the content of CdO is 1-10wt% of the total mass of the catalyst. The OH-Hbeta molecular sieve carrier with hierarchical pores is prepared by calcination treatment, alkali treatment and ammonium ion exchange of Hbeta molecular sieve.

2. Use of CuO-CdO / OH-Hβ acidic catalyst according to claim 1 in the catalytic synthesis of imidazoles, characterized by, The OH-Hbeta molecular sieve carrier has a silicon-aluminum ratio of 25-40.

3. Use of CuO-CdO / OH-Hβ acidic catalyst according to claim 1 in the catalytic synthesis of imidazoles, characterized by, The preparation method of the CuO-CdO / OH-Hbeta acidic catalyst comprises the following steps: (1) preparing an OH-Hbeta molecular sieve carrier with hierarchical pores by calcination treatment, alkali treatment and ammonium ion exchange of Hbeta molecular sieve; (2) immersing the OH-Hbeta molecular sieve carrier in a mixed solution of copper salt and cadmium salt, then taking out, drying, grinding and calcination to prepare the CuO-CdO / OH-Hbeta acidic catalyst.

4. Use of CuO-CdO / OH-Hβ acidic catalyst according to claim 3 for catalyzing the synthesis of imidazole, characterized by, In step (2), the volume ratio of the OH-Hbeta molecular sieve carrier to the mixed solution is 1:1-1:

10.

5. Use of CuO-CdO / OH-Hβ acidic catalyst according to claim 3 for catalyzing the synthesis of imidazole, characterized by, In step (2), the mass ratio of copper salt to the OH-Hbeta molecular sieve carrier is 1:1-1:10, and the mass ratio of cadmium salt to the OH-Hbeta molecular sieve carrier is 1:1-1:

10.

6. Use of CuO-CdO / OH-Hβ acidic catalyst according to claim 3 for catalyzing the synthesis of imidazole, characterized by, In step (2), the immersion time is 12-24h.

7. Use of CuO-CdO / OH-Hβ acidic catalyst according to claim 3 in the catalytic synthesis of imidazoles, characterized by, In steps (1) and (2), the calcination temperature is 450-650℃, and the calcination time is 3-5h.

8. Use of CuO-CdO / OH-Hβ acidic catalyst according to claim 1 in the catalytic synthesis of imidazoles, characterized by, Imidazole is prepared by the reaction of mixed aldehyde and ammonia water as raw materials through aldehyde-amine condensation reaction, wherein the CuO-CdO / OH-Hβ catalyst of claim 1 is used; the volume ratio of the mixed aldehyde and ammonia water is 0.5:1-2:1; the mixed aldehyde comprises formaldehyde and glyoxal; the volume ratio of formaldehyde to glyoxal in the mixed aldehyde is 0.4:1-0.7:1; the reaction temperature is 100-150℃; the mass space velocity of the reaction raw materials is 0.7-1.8 h -1 .

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