Catalyst for catalyzing ethane to prepare ethylene or oxygen-containing compound as well as preparation method and application of catalyst

Abstract

The invention discloses a catalyst for catalyzing ethane to prepare ethylene or an oxygen-containing compound as well as a preparation method and application of the catalyst, and belongs to the field of catalysts. On the basis of ERB-1 and MCM-22, a large number of hydroxyl structures are formed through post-treatment of nitric acid or ammonium nitrate; a titanium source and molecular sieve silicon hydroxyl are subjected to a dehydrohalogenation reaction in a titanium halide gas form to form a Ti-O-Si bond, so that titanium successfully enters a molecular sieve framework and is uniformly distributed. Au or Pd is anchored by a framework Ti, Au or Pd is loaded by using a deposition-precipitation method, and the introduced Ti species can provide a better environment for further dispersing Au or Pd by changing isoelectric points on the surface of a molecular sieve carrier, so that the size of Au or Pd nanoparticles is controlled; secondly, due to the high specific surface area of the MWW molecular sieve, the gold precursor can be effectively dispersed, and agglomeration is inhibited; compared with an MWW molecular sieve of pure Si, Au or Pd nanoparticles can be dispersed and anchored by introducing a framework Ti, so that an Au and Pd-based catalyst which is about 2nm in size and good in dispersion is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a catalyst for catalytically converting ethane into ethylene or oxygenates at a reduced ethane activation temperature, and a preparation method and application thereof. Background Art

[0002] Ethylene is a basic raw material for the important chemical industry and also the basis for various consumables. It is widely used in the production of plastics, rubbers, fibers, fine chemicals, etc. The ethylene industry is the core part of the modern petrochemical industry. The annual output of ethylene is approximately 1.5×10 8 ... It is estimated that the global ethylene market size will reach 475.8 million US dollars in 2027. With the improvement of living standards, the demand for these olefins has also increased significantly, and the demand will continue to grow at a rate of 3-5% per year in the next 5 years. Thermal cracking and steam cracking are still the main ways to produce ethylene at present, and the required reaction temperature is above 800 °C. However, this is a very energy-consuming process, which makes it less attractive in terms of economy and ecological environment. The heat of the cracking furnace mainly comes from the combustion of fossil fuels. Only the pyrolysis part of the naphtha steam cracking furnace consumes about 65% of the total required process energy and generates about 75% of the total exothermic loss. Moreover, this process is accompanied by high CO2 emissions generated by fuel combustion. About 1 ton of CO2 is released for every 1 ton of ethylene produced, and the separation process of olefins also requires a large amount of energy. In addition, the transformation of the steam cracking furnace to light feedstocks makes the olefin production capacity of this process insufficient to meet the growing demand for these olefins. There are problems such as a relatively high reaction temperature and a wide distribution of product types in the preparation of light olefins by steam cracking. Considering these problems, although it is the most advanced technology, researchers have been looking for alternative processes to steam cracking in the past few years.

[0003] Acetic acid (or vinegar) is an important organic chemical product, mainly used in the synthesis of vinyl acetate (EVA), terephthalic acid (PTA), acetic anhydride, acetate esters, and chloroacetic acid, etc. In addition, it also has a wide range of uses in the fields of textiles, medicine, rubber, printing and dyeing, pesticides, electronics, and food. At present, the main production technologies of acetic acid are as follows: acetaldehyde oxidation method, methanol carbonylation method, ethylene oxidation method, and direct ethane oxidation method, etc. Among them, acetic acid produced by the methanol carbonylation method accounts for more than 90% of the total acetic acid production capacity. However, this process is cumbersome, has a high investment cost, and the catalysts used contain iodides, which are toxic and corrosive. Therefore, new process technologies need to be searched for. The Japanese company Showa Denko developed a new process for the direct oxidation of ethylene to acetic acid using supported palladium and heteropolyacid catalysts and built a production unit with a capacity of 1×10 5Industrial production unit of t / a. China's energy distribution is characterized by a lack of oil and abundance of gas. The supply of petroleum resources is insufficient, and it has long relied on imports. Light alkanes, on the other hand, are widely sourced, such as shale gas, natural gas, associated gas in oil fields, and refinery gas. Therefore, the research on activating ethane by lowering its activation temperature and converting inexpensive ethane into oxygen-containing products with high added value, such as ethylene or acetic acid, has attracted the attention of more and more researchers. Although people have been constantly striving to improve the catalytic system for ethane oxidation to acetic acid in recent decades, the single-pass yield of acetic acid is still very low so far, and industrial application has not been achieved. Union Carbide developed the ethane oxidation to acetic acid process (Ethoxene process) using ethane and ethylene as raw materials in the 1980s. Its drawback is that a large amount of ethylene exists in the products. In 2001, Sabic planned to build a 3×10 4 t / a ethane direct oxidation to acetic acid unit. According to their patent report, using Mo-V-Ln-Nb-Pd-X (X = A1, Ga, Ge or Si) as the catalyst, under the reaction conditions of 280 °C, 1.38 MPa, C2H6:O2:N2:H2O = 40:8:32:20, the ethane conversion rate is 10%, and the acetic acid selectivity can reach 85%. In addition, they also modified the catalyst by doping different elements, but the catalytic activity did not increase significantly. Although the technical route of ethane direct oxidation to acetic acid is very attractive, the currently developed catalysts have limited activation ability for ethane, and the selectivity of acetic acid does not meet the production requirements, so it has not been applied industrially.

[0004] In the research on the activation of light alkanes to synthesize acetic acid or ethylene, the research and development of catalysts is a core issue. Currently, researchers are very interested in the oxidation of ethane to oxygen-containing compounds, but the research on selective ethane oxidation using catalysts at lower ethane activation temperatures is very limited. Patent CN119056436A reported a composite catalyst material for photocatalytic oxidation of ethane to ethanol, achieving 975.77 μmol g cat -1 h -1The ethanol yield has a selectivity of 73.70%. Hutchings et al. used iron and copper as catalysts and hydrogen peroxide as an oxidant to convert ethane into acetic acid and other oxides in a batch reactor using ZSM-5 at 303 - 323 K and 0.5 - 3 MPa. The by-products were small amounts of ethylene. In addition, Kronawitter et al. used Au-Pd nanoparticles in an autoclave reactor to catalyze ethane through a peroxyl radical mechanism, and in-situ produced H2O2 with H2 and O2 to oxidize ethane to acetic acid and ethanol. However, the batch operation conditions using H2O2 are not suitable for ethane conversion in industrial processing applications. These attempts have shown that it is feasible to use gold or palladium as a catalyst and in-situ generate H2O2 with H2 and O2 to activate ethane dehydrogenation through a peroxyl radical mechanism, and by adjusting the selectivity of oxygenates and ethylene, catalytic ethane oxidation and dehydrogenation can be achieved, thereby converting it into high-value-added chemicals. In summary, catalysts with a green economy and excellent stability are needed in the field of catalytic low-carbon alkanes. Summary of the Invention

[0005] The present invention provides a catalyst for catalyzing ethane to ethylene or oxygenates by reducing the ethane activation temperature, and its preparation method and application, aiming to solve the problems existing in the above-mentioned background technology.

[0006] In order to achieve the above technical objectives, the present invention mainly adopts the following technical solutions:

[0007] In the first aspect, the present invention discloses a preparation method of a catalyst for catalyzing ethane to ethylene or oxygenates at a reduced ethane activation temperature, comprising the following steps:

[0008] (1) Obtain the silicon-boron type molecular sieve ERB-1 with the MWW structure or the silicon-aluminum type molecular sieve MCM-22, and then mix each of the prepared molecular sieves with nitric acid or ammonium nitrate solution, heat under reflux, then filter, wash, dry, and calcine to obtain the MWW molecular sieve D-ERB-1 or H-MCM-22;

[0009] (2) Load Ti on the MWW molecular sieve in step (1) by atomic in-situ transplantation method to obtain a MWW molecular sieve with a silicon-titanium framework structure;

[0010] (3) Load Au and / or Pd on the MWW molecular sieve with a silicon-titanium framework structure in step (2) to obtain the desired product.

[0011] In a preferred embodiment of the present invention, in step (1):

[0012] Synthesis of silicon-boron microporous molecular sieve ERB-1 with MWW structure: Using piperidine as a template agent, adding a silicon source, a boron source, the template agent and water in a mass ratio of 10:(5 - 30):(5 - 30):(50 - 500) into a polytetrafluoroethylene inner liner, performing dynamic crystallization at high temperature, and obtaining the silicon-boron microporous molecular sieve ERB-1 after washing, filtering, drying and calcination;

[0013] Synthesis of silicon-aluminum molecular sieve MCM-22 with MWW structure: Using hexamethyleneimine as a template agent, adding a silicon source, an aluminum source, the template agent and water in a mass ratio of 10:(5 - 30):(5 - 30):(50 - 500) into a polytetrafluoroethylene inner liner, performing dynamic crystallization at high temperature, and obtaining the silicon-aluminum microporous molecular sieve MCM-22 after washing, filtering, drying and calcination.

[0014] In a preferred embodiment of the present invention, step (2) includes the following steps:

[0015] Put D-ERB-1 or H-MCM-22 into a quartz tube reactor, first perform dehydration pretreatment, then add a titanium source in an evaporator for Ti loading, control the Ti loading amount by controlling the Ti loading time, after the reaction, place the molecular sieve in absolute ethanol for alcoholysis, and then obtain the MWW molecular sieve Ti / D-ERB-1 or Ti / H-MCM-22 with a silicon-titanium framework structure after drying and calcination.

[0016] Preferably, the dehydration pretreatment is carried out under nitrogen purge, the nitrogen flow rate is 20 - 100 ml / min, the dehydration pretreatment time is 1 - 5 h, and the temperature is 300 - 750 °C; the titanium source is a TiCl4 solution, the reaction time is 20 - 30 h; the alcoholysis time is 1 - 20 h; calcination is carried out at 300 - 700 °C for 5 - 10 h, and the heating rate is 5 - 10 °C / min.

[0017] In a preferred embodiment of the present invention, in step (3), when only Au is loaded on the MWW molecular sieve with a silicon-titanium framework structure, it includes the following steps:

[0018] (1) Perform calcination dehydration treatment on Ti / D-ERB-1 or Ti / H-MCM-22;

[0019] (2) Dissolve the Au precursor in deionized water, perform condensation reflux, slowly adjust the pH of the solution with an alkaline solution, and maintain for a period of time to obtain solution A;

[0020] (3) Disperse the molecular sieve Ti / D-ERB-1 or Ti / H-MCM-22 obtained in step (1) in solution A, stir well, slowly adjust the pH of the solution with an alkaline solution, and maintain for a period of time to obtain suspension B;

[0021] (4) After subjecting the suspension B to centrifugation, vacuum drying, and calcination, the catalysts Au-Ti / D-ERB-1 or Au-Ti / H-MCM-22 are obtained respectively;

[0022] When only Pd is loaded on the MWW zeolite with a silicon-titanium framework structure, the following steps are included:

[0023] (1) Subject Ti / H-MCM-22 to calcination dehydration treatment;

[0024] (2) Dissolve the precursor of Pd in deionized water, stir evenly, disperse the zeolite Ti / H-MCM-22 obtained in step (1) in the solution, carry out condensation reflux, slowly adjust the pH of the solution with an alkaline solution, and maintain for a period of time to obtain a suspension C;

[0025] (3) After subjecting the suspension C to centrifugation, vacuum drying, and calcination, the catalyst Pd-Ti / H-MCM-22 is obtained;

[0026] When Au and Pd are loaded on the MWW zeolite with a silicon-titanium framework structure, the following steps are included:

[0027] (1) Subject Ti / H-MCM-22 to calcination dehydration treatment;

[0028] (2) Dissolve the precursor of Au in deionized water, carry out condensation reflux, slowly adjust the pH of the solution with an alkaline solution, and maintain for a period of time to obtain a solution D;

[0029] (3) Disperse the precursor of Pd and the zeolite Ti / H-MCM-22 obtained in step 5.1) in the solution D, carry out condensation reflux, slowly adjust the pH of the solution with an alkaline solution, and maintain for a period of time to obtain a suspension E;

[0030] (4) After subjecting the suspension E to centrifugation, vacuum drying, and calcination, the catalyst Au-Pd-Ti / H-MCM-22 is obtained.

[0031] Preferably, the precursor of Au is chloroauric acid, and the precursor of Pd is tetraammine palladium nitrate;

[0032] The temperature during the calcination dehydration treatment is 300 - 650 °C, the calcination time is 3 - 5 h, and the heating rate is 5 - 10 °C / min;

[0033] The water bath temperature for condensation reflux is 40 - 120 °C;

[0034] The alkaline solution is an aqueous solution of sodium hydroxide or ammonia water, with a concentration of 0.01 - 2 mol / L; when only loading Au, the pH is adjusted to >4 for the first time, with a duration of 3 - 24 h, and the pH is adjusted to >6 for the second time, with a duration of 3 - 24 h; when only loading Pd, the pH is adjusted to >6, with a duration of 3 - 24 h; when loading Au and Pd, the pH is adjusted to >4 for the first time, with a duration of 3 - 24 h, and the pH is adjusted to >6 for the second time, with a duration of 3 - 24 h;

[0035] The centrifugation speed is 8000 - 10000 r / min, and the centrifugation time is 15 - 20 min;

[0036] The vacuum drying temperature is 50 - 80 °C;

[0037] The temperature during roasting after vacuum drying is 200 - 400 °C, the roasting time is 3 - 5 h, and the heating rate is 2 - 5 °C / min.

[0038] In a second aspect, the present invention discloses a catalyst prepared by the method described in the first aspect, including Au-Ti / D-ERB-1(x), Au-Ti / H-MCM-22(x), Pd-Ti / H-MCM-22(x), Au-Pd-Ti / H-MCM-22(x), where x represents the time of loading Ti.

[0039] In a preferred embodiment of the present invention, the catalyst is:

[0040] Au-Ti / D-ERB-1(8 h), where the loading amount of Au is 1.0 wt%, and the loading amount of Ti is 3.0 wt%; Au exists in the form of a single substance; the existing form of Ti includes framework Ti and TiO2 on the surface of the molecular sieve;

[0041] Au-Ti / H-MCM-22(2 h), where the loading amount of Au is 1.0 wt%, and the loading amount of Ti is 2.0 wt%; Au exists in the form of a single substance; the existing form of Ti includes framework Ti and TiO2 on the surface of the molecular sieve;

[0042] Pd-Ti / H-MCM-22(2 h), where the loading amount of Pd is 1.0 wt%, and the loading amount of Ti is 2.0 wt%; Pd exists in the form of a single substance; the existing form of Ti includes framework Ti and TiO2 on the surface of the molecular sieve;

[0043] Au-Pd-Ti / H-MCM-22(2 h), where the loading amount of Au is 1.0 wt%, the loading amount of Pd is 1.0 wt%, and the loading amount of Ti is 2.0 wt%; Pd exists in the form of a single substance; the existing form of Ti includes framework Ti and TiO2 on the surface of the molecular sieve.

[0044] Furthermore, Au-Ti / D-ERB-1(8h) is used for catalyzing ethane to prepare oxygenates and ethylene;

[0045] Au-Ti / H-MCM-22(2h) is used for catalyzing ethane to prepare oxygenates;

[0046] Pd-Ti / H-MCM-22(2h) is used for catalyzing ethane to prepare oxygenates;

[0047] Au-Pd-Ti / H-MCM-22(2h) is used for catalyzing ethane to prepare oxygenates;

[0048] The oxygenates are acetic acid, acetaldehyde or ethanol.

[0049] Preferably, hydrogen peroxide is in-situ synthesized on the Au and / or Pd active sites by hydrogen and oxygen, and further, ethane is activated by hydrogen peroxide to synthesize oxygenates and / or ethylene;

[0050] The reaction conditions for the oxidation of ethane to oxygenates are as follows: the reaction temperature is 200 - 400 °C, the total gas hourly space velocity of the reaction gas phase is 1400 - 8000 h -1 , and the volume ratio of ethane, hydrogen, oxygen and nitrogen in the reaction raw materials is 1 - 10:1 - 10:0.5 - 3:10 - 20;

[0051] The reaction conditions for the dehydrogenation of ethane to ethylene are as follows: the reaction temperature is 400 - 550 °C, the total volume hourly space velocity of the reaction gas phase is 1400 - 8000 h -1 , and the volume ratio of ethane, hydrogen, oxygen and nitrogen in the reaction raw materials is 1 - 10:1 - 10:0.5 - 3:10 - 20.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. The MWW molecular sieve catalyst loaded with Au-Ti provided by the present invention, based on the MWW molecular sieve of ERB-1 and MCM-22, is post-treated with nitric acid or ammonium nitrate. In the post-treatment process, the O-B and O-Na bonds in the Si-O-B and Si-O-Na bonds of the molecular sieve crystal are extremely easy to break, and boron or sodium atoms are extremely easy to be removed from the molecular sieve, forming atomic vacancies and a large number of hydroxyl structures; the titanium source reacts with the silanol groups of the molecular sieve in the form of titanium halide gas to form Ti-O-Si bonds, enabling Ti to successfully enter the molecular sieve framework and be evenly distributed. Au is anchored by framework Ti to control the size of Au nanoparticles; the deposition-precipitation method is used to load Au nanoparticles. The introduced Ti species can change the isoelectric point of the surface, providing a better environment for further Au dispersion, making it attract [Au(OH) x (Cl) 4-x- Combined tightly. Compared with pure Si MWW zeolite, the introduction of framework Ti can disperse and anchor Au nanoparticles, and prepare Au nanoparticles with uniform size and good dispersion.

[0054] 2. For the Au-Ti / H-MCM-22(2h) catalyst prepared by the present invention, the Au nanoparticles have uniform size and good dispersion. The synergistic effect of protonic acid and Au-TiO x interface active sites in the catalyst is beneficial to the stable existence of hydrogen peroxide in situ generated on the surface of Au nanoparticles by H2 and O2, and then oxidize ethane to oxygenates. The oxygen-containing products are mainly acetic acid, realizing a new way to catalytically convert ethane into high-value products at a reduced ethane activation temperature.

[0055] 3. For the Au-Ti / D-ERB-1(8h) catalyst prepared by the present invention, the Au nanoparticles have uniform size and good dispersion. Hydrogen peroxide is generated in situ on the surface of Au nanoparticles by H2 and O2, which can activate ethane to form oxygenates; in addition, the Lewis acid strength of the metal and the elevated temperature are beneficial to the decomposition of hydrogen peroxide. The decomposition of hydrogen peroxide into hydroxyl radicals activates ethane dehydrogenation to form ethylene on the catalyst surface. This catalyst realizes the activation of ethane to form oxygenates at a reduced ethane activation temperature and the activation of ethane dehydrogenation to form ethylene under certain conditions.

[0056] 4. For the Pd-Ti / H-MCM-22(2h) catalyst prepared by the present invention, the Au nanoparticles have uniform size and good dispersion. The Pd active sites in the catalyst exhibit catalytic characteristics similar to those of Au, and can efficiently catalyze the in-situ generation of H2O2 by H2 and O2, and then selectively oxidize ethane to high-value oxygenates. This discovery not only confirms that Pd can replace noble metal Au as an active component, but also provides a new strategy for realizing the efficient conversion of ethane under mild conditions.

[0057] 5. For the Au-Pd-Ti / H-MCM-22(2h) catalyst prepared by the present invention, the Au and Pd nanoparticles have uniform size and form an alloy structure, and are well dispersed. The synergistic mechanism between the protonic acid sites and the Pd-Au-TiO x interface active sites in the catalyst further promotes the in-situ generation and stabilization of H2O2 on the catalyst surface by H2 and O2. Thereby enhancing the C-H bond activation and selective oxidation of ethane. The synergistic effect of multiple active sites in the catalyst improves the catalytic efficiency, and this reaction system can efficiently selectively oxidize ethane to oxygenates mainly composed of acetic acid, providing a new catalytic route for the directional conversion of ethane to high-value chemicals under mild conditions.

[0058] ​6. The Pd-Au-Ti / MWW zeolite bifunctional catalytic system realizes the catalytic conversion of ethane to oxygenates or ethylene by the in-situ generated H2O2 from H2 and oxygen. The specific mechanism is as follows: H2 is activated on the surface of gold nanoparticles, while O2 is activated through two different mechanisms, i.e., at the Au-TiO x interface and on the surface of gold nanoparticles. First, the activated O2 molecules on the surface of gold nanoparticles combine with active H* to form HOO*, which further combines with active H* to form H2O2, or overflows to the Au-TiO x interface to form a stable Ti-OOH transition state. At the same time, the adsorbed ethane molecules on the catalyst are activated by the active species Au to form C2H5*, and then C2H5* on the catalyst surface interacts with HOO* to form CH3CH2OOH; subsequently, CH3CH2OOH is directly oxidized to CH3COOH. Second, the H2O2 generated on the surface of gold nanoparticles decomposes to form OH* when far from the Au-TiO x interface; subsequently, OH* on the surface of Au nanoparticles activates C2H5* to generate CH3CH2OH or dehydrogenates to form ethylene. CH3CH2OH can be further oxidized to CH3CHO or CH3COOH, while CH3CH2OOH is directly oxidized to CH3COOH. Similarly, for the Pd-based catalyst and the Au-based catalyst, H2 and O2 can also directly synthesize hydrogen peroxide on the Pd-based catalyst, and then activate ethane to form oxygenates. Description of the Drawings

[0059] Figure 1 XRD patterns of different Au-based catalysts, where (A) D-ERB-1 series: (a) ERB-1; (b) D-ERB-1; (c) Ti / D-ERB-1; (d) Au / D-ERB-1; (e) 0.1 wt% Au-Ti / D-ERB-1; (f) 0.5 wt% Au-Ti / D-ERB-1; (g) Au-Ti / D-ERB-1; (h) 1.5 wt% Au-Ti / D-ERB-1; (i) Au-Ti / D-ERB-1 (2 h). (B) H-MCM-22 series: (a) H-MCM-22; (b) Ti / H-MCM-22; (c) Au-Ti / H-MCM-22 (0.5 h); (d) Au-Ti / H-MCM-22 (1 h); (e) Au-Ti / H-MCM-22 (2 h); (f) Au-Ti / H-MCM-22 (4 h); (g) Au-Ti / H-MCM-22 (8 h); (h) Au-Pd-Ti / H-MCM-22 (2 h); (i) Pd-Ti / H-MCM-22 (2 h); (j) Pd-Ti / H-MCM-22;

[0060] Figure 2 In-situ Fourier transform infrared spectra of different catalysts; where (a) ERB-1; (b) D-ERB-1; (c) Ti-D-ERB-1; (d) Au / Ti-D-ERB-1 (8h);

[0061] Figure 3 TEM images of catalysts with different Au nanoparticle sizes;

[0062] Figure 4 In-situ diffuse reflectance Fourier transform infrared spectra of Au-based catalysts;

[0063] Figure 5 For the condensate after reaction of different Au-based catalysts 1 1H NMR spectra. Specific embodiments

[0064] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0065] In the present invention:

[0066] Synthesis of the silicon-boron microporous molecular sieve ERB-1 with the MWW structure:

[0067] The silicon-boron molecular sieve ERB-1 is synthesized by the dynamic hydrothermal method. Piperidine is used as the template agent, the boron source is boric acid, and the silicon source is fumed silica. The molar ratio of the raw materials is H2BO3:SiO2:PI:H2O = 2:1:1.4:19. Boric acid, piperidine, and fumed silica are slowly added in sequence to the polytetrafluoroethylene liner, the solution is stirred evenly, and then the polytetrafluoroethylene liner is placed in a stainless steel autoclave. Then, it is hydrothermally synthesized and crystallized in a homogeneous reactor at 175 °C for 7 days. After the reaction, it is filtered and washed until neutral, and then placed in a vacuum drying oven to dry to obtain the precursor ERB-1, denoted as ERB-1(P). In order to remove the template agent in the molecular sieve, ERB-1(P) is calcined at 823 K for 5 h to obtain the silicon-boron molecular sieve ERB-1.

[0068] Synthesis of the silicon-aluminum molecular sieve MCM-22 with the MWW structure:

[0069] The silicoaluminophosphate molecular sieve MCM-22 was synthesized by the dynamic hydrothermal method. Hexamethyleneimine (HMI) was used as the template agent, the silicon source was liquid silica, and the aluminum source was sodium aluminate. The molar ratio of the raw materials was Si:Al:HMI:Na:H2O = 1.0:0.072:0.5:0.1:40. Sodium aluminate, hexamethyleneimine, and liquid silica were slowly added to the polytetrafluoroethylene inner liner in sequence. After stirring evenly, they were loaded into a high-pressure reactor and then hydrothermally synthesized and crystallized in a homogeneous reactor at 150 °C for 7 days. After the reaction, it was filtered and washed to neutral, and then dried in a vacuum drying oven to obtain the precursor MCM-22, denoted as MCM-22(P). In order to remove the template agent in the molecular sieve, MCM-22(P) was calcined at 823 K for 5 h to obtain the silicoaluminophosphate molecular sieve MCM-22.

[0070] In Au-Ti / D-ERB-1(8h) or Au-Ti / H-MCM-22(2h), Ti was introduced into the MWW zeolite by in-situ atomic transplantation, and then Au was anchored by the deposition-precipitation method to prepare the Au-Ti / MWW catalyst. Au NPs with a size of about 2 nm were most suitable for in-situ H2O2 generation. At 350 °C, H2O2 generated in-situ on the surface of Au nanoparticles from H2 and O2 peroxidatively activated ethane. Au-Ti / D-ERB-1(8h) in-situ generated sufficient H2O2 by controlling the appropriate Au NPs size and Au loading amount; Au-Ti / H-MCM-22(2h) was through the protonic acid of the molecular sieve and Au-TiO x The synergistic effect of the interfacial active sites controlled the stable existence of in-situ H2O2, and finally, the in-situ generated H2O2 catalyzed ethane to produce oxygenates or ethylene. The specific mechanism is as follows: H2 was activated on the surface of Au nanoparticles, while O2 was activated through two different mechanisms, namely, at the Au-TiO x interface and on the surface of Au nanoparticles. First, the activated O2 molecules on the surface of Au nanoparticles combined with active H* to form HOO*, and further combined with active H* to form H2O2, or overflowed to the Au-TiO x interface to form a stable Ti-OOH transition state. At the same time, the adsorbed ethane molecules on the catalyst were activated by the active species Au to form C2H5*, and then C2H5* on the catalyst surface interacted with HOO* to form CH3CH2OOH; subsequently, CH3CH2OOH was directly oxidized to CH3COOH. Second, the H2O2 generated on the surface of Au nanoparticles was far from the Au-TiO xWhen at the interface, it decomposes to form OH*. Subsequently, OH* on the surface of Au nanoparticles activates C2H5* to generate CH3CH2OH or dehydrogenates to produce ethylene. CH3CH2OH can be further oxidized to CH3CHO or CH3COOH, while CH3CH2OOH is directly oxidized to CH3COOH. Similarly, for the Pd-based catalyst, H2 and O2 can also directly synthesize hydrogen peroxide on the Pd-based catalyst, and then activate ethane to generate oxygen-containing compounds.

[0071] The following is illustrated by specific examples.

[0072] Example 1 Preparation of Au-Ti / D-ERB-1(8h) catalyst

[0073] Put the MWW zeolite D-ERB-1 into a quartz tube reactor. Under a nitrogen purge of 40 mL / min, first perform a pretreatment for 5 h to remove water in the zeolite and the pipeline. Then, add TiCl4 into the evaporator and carry out Ti loading under a nitrogen purge at 550 °C for 8 h. After the reaction for 8 h, place the zeolite in absolute ethanol for alcoholysis, dry it overnight at 70 °C, and then calcine it at 550 °C for 5 h to obtain Ti / D-ERB-1(8h). Take 1.0 ml of 0.05 mol / L HAuCl4 solution and dissolve it in 50 ml of deionized water. After stirring evenly, adjust the pH>4 with 0.1 mol / L NaOH solution, and this process lasts for 3 h. Then, add 1.0 g of Ti / D-ERB-1(8h) support. After stirring evenly, adjust the pH>6 with 0.1 mol / L NaOH solution again, and this process lasts for 3 h. Centrifuge the obtained mixture, and vacuum-dry the separated solid at 70 °C for 10 h, and then calcine it at 400 °C for 2 h, denoted as Au-Ti / D-ERB-1(8h). The loading amount of Au in the catalyst is 1.0 wt%, and the loading amount of Ti is 3.0 wt%.

[0074] Example 2 Preparation of Au-Ti / H-MCM-22(2h) catalyst

[0075] The MWW zeolite H-MCM-22 was placed in a quartz tube reactor and pretreated for 5 h under a nitrogen purge of 40 mL / min to remove the water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and Ti was loaded under a nitrogen purge at 550 °C. After reacting for 2 h, the zeolite was subjected to alcoholysis in absolute ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / H-MCM-22(2 h). 1.0 mL of a 0.05 mol / L HAuCl4 solution was dissolved in 50 mL of deionized water. After stirring evenly, the pH was adjusted to be >4 with a 0.1 mol / L NaOH solution, and this process lasted for 3 h. Then, 1.0 g of the Ti / H-MCM-22(2 h) support was added. After stirring evenly, the pH was further adjusted to be >6 with a 0.1 mol / L NaOH solution, and this process lasted for 3 h. The resulting mixture was centrifuged, and the separated solid was dried in vacuo at 70 °C for 10 h and then calcined at 400 °C for 2 h, denoted as Au-Ti / H-MCM-22(2 h). The loading amount of Au in the catalyst was 1.0 wt%, and the loading amount of Ti was 2.0 wt%.

[0076] Preparation of the Pd-Ti / H-MCM-22(2 h) catalyst in Example 3

[0077] The MWW zeolite H-MCM-22 was placed in a quartz tube reactor and pretreated for 5 h under a nitrogen purge of 40 mL / min to remove the water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and Ti was loaded under a nitrogen purge at 550 °C. After reacting for 2 h, the zeolite was subjected to alcoholysis in absolute ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / H-MCM-22(2 h). 9.7 mL of a 0.01 mol / L Pd(NH4)4(NO3)2 solution was dissolved in 50 mL of deionized water. After stirring evenly, 1.0 g of the Ti / H-MCM-22(2 h) support was added, and the mixture was refluxed under condensation at 40 °C. The pH of the solution was adjusted to be >6 with 0.1 mol / L NaOH, and this process lasted for 3 h. After the reaction ended, it was filtered, washed, dried, and calcined at 400 °C for 2 h to obtain the catalyst denoted as Pd-Ti / H-MCM-22(2 h). The loading amount of Pd in the catalyst was 1.0 wt%, and the loading amount of Ti was 2.0 wt%.

[0078] Preparation of the Au-Pd-Ti / H-MCM-22(2 h) catalyst in Example 4

[0079] The MWW zeolite H-MCM-22 was placed in a quartz tube reactor. Under a nitrogen purge of 40 mL / min, it was first pretreated for 5 h to remove the water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and nitrogen purging was carried out at 550 °C for Ti loading. After reacting for 2 h, the zeolite was subjected to alcoholysis in absolute ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / H-MCM-22(2 h). 1.0 mL of 0.05 mol / L HAuCl4 solution was dissolved in 50 mL of deionized water, stirred evenly, and the pH was adjusted to >4 with 0.1 mol / L NaOH solution. This process lasted for 3 h. Then, 1.0 g of Ti / H-MCM-22(2 h) support and 9.7 mL of 0.01 mol / L Pd(NH4)4(NO3)2 solution were added, stirred evenly, and the pH was adjusted to >6 with 0.1 mol / L NaOH solution. This process lasted for 3 h. The resulting mixture was centrifuged, and the separated solid was vacuum dried at 70 °C for 10 h and then calcined at 400 °C for 2 h, denoted as Au-Pd-Ti / H-MCM-22(2 h). The Au loading in the catalyst was 1.0 wt%, the Pd loading was 1.0 wt%, and the Ti loading was 2.0 wt%.

[0080] Comparative Example 1 Preparation of 0.1 wt% Au-Ti / D-ERB-1 Catalyst

[0081] The MWW zeolite D-ERB-1 was placed in a quartz tube reactor. Under a nitrogen purge of 40 mL / min, it was first pretreated for 5 h to remove the water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and nitrogen purging was carried out at 550 °C for Ti loading. After reacting for 8 h, the zeolite was subjected to alcoholysis in absolute ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / D-ERB-1. 0.1 mL of 0.05 mol / L HAuCl4 solution was dissolved in 50 mL of deionized water, stirred evenly, and the pH was adjusted to >4 with 0.1 mol / L NaOH solution. This process lasted for 3 h. Then, 1.0 g of Ti / D-ERB-1 support was added, stirred evenly, and the pH was adjusted to >6 with 0.1 mol / L NaOH solution. This process lasted for 3 h. The resulting mixture was centrifuged, and the separated solid was vacuum dried at 70 °C for 10 h and then calcined at 400 °C for 2 h, denoted as 0.1 wt% Au-Ti / D-ERB-1. The Au loading in the catalyst was 0.1 wt%, and the Ti loading was 3.0 wt%.

[0082] Comparative Example 2 Preparation of 0.5 wt% Au-Ti / D-ERB-1 Catalyst

[0083] The MWW zeolite D-ERB-1 was placed in a quartz tube reactor and pretreated for 5 h under a nitrogen purge of 40 mL / min to remove the water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and Ti loading was carried out under a nitrogen purge at 550 °C. After reacting for 8 h, the zeolite was subjected to alcoholysis in absolute ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / D-ERB-1. 0.5 mL of 0.05 mol / L HAuCl4 solution was dissolved in 50 mL of deionized water, stirred evenly, and the pH was adjusted to be >4 with 0.1 mol / L NaOH solution, and this process lasted for 3 h. Then, 1.0 g of Ti / D-ERB-1 support was added, stirred evenly, and the pH was further adjusted to be >6 with 0.1 mol / L NaOH solution, and this process lasted for 3 h. The resulting mixture was centrifuged, and the separated solid was vacuum dried at 70 °C for 10 h and then calcined at 400 °C for 2 h, denoted as 0.5 wt% Au-Ti / D-ERB-1. The Au loading in the catalyst was 0.5 wt%, and the Ti loading was 3.0 wt%.

[0084] Comparative Example 3 Preparation of 1.5 wt% Au-Ti / D-ERB-1 catalyst

[0085] The MWW zeolite D-ERB-1 was placed in a quartz tube reactor and pretreated for 5 h under a nitrogen purge of 40 mL / min to remove the water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and Ti loading was carried out under a nitrogen purge at 550 °C. After reacting for 8 h, the zeolite was subjected to alcoholysis in absolute ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / D-ERB-1. 1.5 mL of 0.05 mol / L HAuCl4 solution was dissolved in 50 mL of deionized water, stirred evenly, and the pH was adjusted to be >4 with 0.1 mol / L NaOH solution, and this process lasted for 3 h. Then, 1.0 g of Ti / D-ERB-1 support was added, stirred evenly, and the pH was further adjusted to be >6 with 0.1 mol / L NaOH solution, and this process lasted for 3 h. The resulting mixture was centrifuged, and the separated solid was vacuum dried at 70 °C for 10 h and then calcined at 400 °C for 2 h, denoted as 1.5 wt% Au-Ti / D-ERB-1. The Au loading in the catalyst was 1.5 wt%, and the Ti loading was 3.0 wt%.

[0086] Comparative Example 4 Preparation of Au-Ti / D-ERB-1(Na-11) catalyst

[0087] The MWW zeolite D-ERB-1 was placed in a quartz tube reactor. Under a nitrogen purge of 40 mL / min, it was first pretreated for 5 h to remove the water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and Ti was loaded under a nitrogen purge at 550 °C. After reacting for 8 h, the zeolite was alcoholyzed in absolute ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / D-ERB-1. 1.0 mL of a 0.05 mol / L HAuCl4 solution was dissolved in 50 mL of deionized water. After stirring evenly, the pH was adjusted to >4 with a 0.1 mol / L NaOH solution, and this process lasted for 3 h. Then, 1.0 g of the Ti / D-ERB-1 support was added. After stirring evenly, the pH was adjusted to 11 with a 0.1 mol / L NaOH solution, and this process lasted for 3 h. The resulting mixture was centrifuged, and the separated solid was vacuum-dried at 70 °C for 10 h and then calcined at 400 °C for 2 h, denoted as Au-Ti / D-ERB-1(Na-11). The Au loading in the catalyst was 1.0 wt%, and the Ti loading was 3.0 wt%.

[0088] Preparation of the Comparative Example 5 Au-Ti / D-ERB-1(NH3-9) Catalyst

[0089] The MWW zeolite D-ERB-1 was placed in a quartz tube reactor. Under a nitrogen purge of 40 mL / min, it was first pretreated for 5 h to remove the water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and Ti was loaded under a nitrogen purge at 550 °C. After reacting for 8 h, the zeolite was alcoholyzed in absolute ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / D-ERB-1. 1.0 mL of a 0.05 mol / L HAuCl4 solution was dissolved in 50 mL of deionized water. After stirring evenly, the pH was adjusted to >4 with a 0.1 mol / L aqueous ammonia solution, and this process lasted for 3 h. Then, 1.0 g of the Ti / D-ERB-1 support was added. After stirring evenly, the pH was adjusted to 9 with a 0.1 mol / L aqueous ammonia solution, and this process lasted for 3 h. The resulting mixture was centrifuged, and the separated solid was vacuum-dried at 70 °C for 10 h and then calcined at 400 °C for 2 h, denoted as Au-Ti / D-ERB-1(NH3-9). The Au loading in the catalyst was 1.0 wt%, and the Ti loading was 3.0 wt%.

[0090] Preparation of the Comparative Example 6 Au / D-ERB-1 Catalyst

[0091] Take 1.0 ml of 0.05 mol / L HAuCl4 solution and dissolve it in 50 ml of deionized water. After stirring evenly, adjust the pH > 4 with 0.1 mol / L NaOH solution, and the duration of this process is 3 h. Then, add 1.0 g of D-ERB-1 support, stir evenly, and then adjust the pH > 6 with 0.1 mol / L NaOH solution, and the duration of this process is 3 h. Centrifuge the obtained mixture, and the separated solid is dried in vacuo at 70 °C for 10 h, and then calcined at 400 °C for 2 h, denoted as Au / D-ERB-1. The loading amount of Au in the catalyst is 1.0 wt%.

[0092] Preparation of Comparative Example 7 Au-Ti / D-ERB-1(2 h) Catalyst

[0093] Put the MWW zeolite D-ERB-1 into a quartz tube reactor. Under a nitrogen purge of 40 mL / min, first perform a pretreatment for 5 h to remove the water in the zeolite and the pipeline. Then, add TiCl4 into the evaporator and carry out Ti loading under a nitrogen purge at 550 °C. After reacting for 2 h, place the zeolite in absolute ethanol for alcoholysis, dry it overnight at 70 °C, and then calcine it at 550 °C for 5 h to obtain Ti / D-ERB-1(2 h). Take 1.0 ml of 0.05 mol / L HAuCl4 solution and dissolve it in 50 ml of deionized water. After stirring evenly, adjust the pH > 4 with 0.1 mol / L NaOH solution, and the duration of this process is 3 h. Then, add 1.0 g of Ti / D-ERB-1(2 h) support, stir evenly, and then adjust the pH > 6 with 0.1 mol / L NaOH solution, and the duration of this process is 3 h. Centrifuge the obtained mixture, and the separated solid is dried in vacuo at 70 °C for 10 h, and then calcined at 400 °C for 2 h, denoted as Au-Ti / D-ERB-1(2 h). The loading amount of Au in the catalyst is 1.0 wt%, and the loading amount of Ti is 2.0 wt%.

[0094] Preparation of Comparative Example 8 Au-Ti / H-MCM-22(0.5 h) Catalyst

[0095] The MWW zeolite H-MCM-22 was placed in a quartz tube reactor and pretreated for 5 h under a nitrogen purge of 40 mL / min to remove water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and Ti was loaded under a nitrogen purge at 550 °C. After reacting for 0.5 h, the zeolite was subjected to alcoholysis in absolute ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / H-MCM-22(0.5 h). 1.0 mL of a 0.05 mol / L HAuCl4 solution was dissolved in 50 mL of deionized water, stirred evenly, and the pH was adjusted to >4 with a 0.1 mol / L NaOH solution. This process lasted for 3 h. Then, 1.0 g of the Ti / H-MCM-22(0.5 h) support was added, stirred evenly, and the pH was further adjusted to >6 with a 0.1 mol / L NaOH solution. This process lasted for 3 h. The resulting mixture was centrifuged, and the separated solid was vacuum dried at 70 °C for 10 h and then calcined at 400 °C for 2 h, denoted as Au-Ti / H-MCM-22(0.5 h). The Au loading in the catalyst was 1.0 wt%, and the Ti loading was 1.5 wt%.

[0096] Preparation of the Comparative Catalyst 9 Au-Ti / H-MCM-22(1 h)

[0097] The MWW zeolite H-MCM-22 was placed in a quartz tube reactor and pretreated for 5 h under a nitrogen purge of 40 mL / min to remove water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and Ti was loaded under a nitrogen purge at 550 °C. After reacting for 1 h, the zeolite was subjected to alcoholysis in absolute ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / H-MCM-22(1 h). 1.0 mL of a 0.05 mol / L HAuCl4 solution was dissolved in 50 mL of deionized water, stirred evenly, and the pH was adjusted to >4 with a 0.1 mol / L NaOH solution. This process lasted for 3 h. Then, 1.0 g of the Ti / H-MCM-22(1 h) support was added, stirred evenly, and the pH was further adjusted to >6 with a 0.1 mol / L NaOH solution. This process lasted for 3 h. The resulting mixture was centrifuged, and the separated solid was vacuum dried at 70 °C for 10 h and then calcined at 400 °C for 2 h, denoted as Au-Ti / H-MCM-22(1 h). The Au loading in the catalyst was 1.0 wt%, and the Ti loading was 1.8 wt%.

[0098] Preparation of the Comparative Catalyst 10 Au-Ti / H-MCM-22(4 h)

[0099] The MWW zeolite H-MCM-22 was placed in a quartz tube reactor. Under a nitrogen purge of 40 mL / min, it was first pretreated for 5 h to remove the water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and Ti was loaded under a nitrogen purge at 550 °C. After reacting for 4 h, the zeolite was subjected to alcoholysis in anhydrous ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / H-MCM-22(4 h). Take 1.0 mL of 0.05 mol / L HAuCl4 solution and dissolve it in 50 mL of deionized water. After stirring evenly, adjust the pH > 4 with 0.1 mol / L NaOH solution, and this process lasts for 3 h. Then, add 1.0 g of Ti / H-MCM-22(4 h) support. After stirring evenly, adjust the pH > 6 with 0.1 mol / L NaOH solution again, and this process lasts for 3 h. The obtained mixture was centrifuged, and the separated solid was vacuum dried at 70 °C for 10 h and then calcined at 400 °C for 2 h, denoted as Au-Ti / H-MCM-22(4 h). The loading amount of Au in the catalyst is 1.0 wt%, and the loading amount of Ti is 2.3 wt%.

[0100] Preparation of Comparative Example 11 Au-Ti / H-MCM-22(8 h) Catalyst

[0101] The MWW zeolite H-MCM-22 was placed in a quartz tube reactor. Under a nitrogen purge of 40 mL / min, it was first pretreated for 5 h to remove the water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and Ti was loaded under a nitrogen purge at 550 °C. After reacting for 8 h, the zeolite was subjected to alcoholysis in anhydrous ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / H-MCM-22(8 h). Take 1.0 mL of 0.05 mol / L HAuCl4 solution and dissolve it in 50 mL of deionized water. After stirring evenly, adjust the pH > 4 with 0.1 mol / L NaOH solution, and this process lasts for 3 h. Then, add 1.0 g of Ti / H-MCM-22(8 h) support. After stirring evenly, adjust the pH > 6 with 0.1 mol / L NaOH solution again, and this process lasts for 3 h. The obtained mixture was centrifuged, and the separated solid was vacuum dried at 70 °C for 10 h and then calcined at 400 °C for 2 h, denoted as Au-Ti / H-MCM-22(8 h). The loading amount of Au in the catalyst is 1.0 wt%, and the loading amount of Ti is 3.0 wt%.

[0102] Preparation of Comparative Example 12 Pd-Ti / H-MCM-22 Catalyst

[0103] The MWW zeolite H-MCM-22 was placed in a quartz tube reactor and pretreated for 5 h under a nitrogen purge of 40 mL / min to remove water in the zeolite and the pipeline. Then, TiCl4 was added to the evaporator, and Ti loading was carried out under a nitrogen purge at 550 °C for 8 h. After the reaction, the zeolite was subjected to alcoholysis in absolute ethanol, dried overnight at 70 °C, and then calcined at 550 °C for 5 h to obtain Ti / H-MCM-22. 9.7 mL of 0.01 mol / L Pd(NH4)4(NO3)2 solution was dissolved in 25 mL of deionized water, stirred evenly, and then 1.0 g of Ti / H-MCM-22 support was added. The mixture was refluxed under condensation at 40 °C, and the pH of the solution was adjusted to be >6 using 0.1 mol / L NaOH. This process lasted for 3 h. After the reaction, it was filtered, washed, dried, and calcined at 400 °C for 2 h to obtain the catalyst denoted as Pd-Ti / H-MCM-22. The Pd loading in the catalyst was 1.0 wt%, and the Ti loading was 3.0 wt%.

[0104] Test Example 1

[0105] The catalyst prepared in the present invention was subjected to X-ray diffraction, and the results are as Figure 1 shown. It can be seen from Figure 1 that the prepared Au-based catalyst samples all have obvious MWW structure characteristic peaks, such as 7.1° (100), 7.9° (101), 10° (102), 25.1° (302), and 26.1° (310), indicating that the loading of Au, Ti, and Pd does not damage the MWW structure of the zeolite. Similarly, in Figure 1 , all Au-containing catalysts have a relatively low characteristic diffraction peak of Au (38.2°), indicating that the dispersion of Au nanoparticles on the catalyst is relatively good.

[0106] The catalyst prepared in the present invention was subjected to in-situ Fourier transform infrared spectroscopy, and the results are as Figure 2 shown. It can be seen from Figure 2 that in the Fourier transform infrared spectroscopy, when comparing the two samples of ERB-1 and D-ERB-1, it was found that D-ERB-1 has a broad peak between 3420 - 3620 cm -1 due to the dealumination of the silicoborate zeolite ERB-1 after acid treatment, forming a large number of hydroxyl nests. At the same time, between 3700 - 3740 cm -1The sharp peak at [location] is the characteristic peak of silica hydroxyl groups. Apparently, D-ERB-1 has more hydroxyl nests and silanol groups. When comparing D-ERB-1 and Ti / D-ERB-1, it was found that the two characteristic peaks of Ti / D-ERB-1 weakened after the addition of Ti. This is because TiCl4 reacted with the hydroxyl nests or silanol groups, enabling the titanium atoms occupying the positions of the hydroxyl nests and silanol groups to be successfully incorporated into the zeolite framework structure of D-ERB-1. Loading Ti on H-MCM-22 using the in-situ atomic transplantation method also involves the dehydrochlorination reaction of TiCl4 with hydroxyl groups, thereby incorporating it into the zeolite framework structure of H-MCM-22.

[0107] TEM was performed on the catalyst prepared by the present invention, and the results are as Figure 3 shown. It can be Figure 3 seen that the size of the Au nanoparticles in the catalyst is about 2 nm, which is most suitable for the in-situ generation of hydrogen peroxide on the surface of the Au nanoparticles by H2 and O2.

[0108] In-situ diffuse reflectance Fourier transform infrared spectroscopy was performed on the catalyst prepared by the present invention, and the results are as Figure 4 shown. It can be Figure 4 seen that the broad peak at 840 - 920 cm -1 belongs to the characteristic peak of hydrogen peroxide species, indicating that hydrogen peroxide species are formed on the catalyst surface and participate in the ethane peroxidation reaction. The peak at 1080 cm -1 is attributed to the CH3CH2O* characteristic peak of the product CH3CH2OH or CH3CH2OOH; the peak at 1180 cm -1 is attributed to the stretching vibration of the C - O bond of the CH3CH2OOH intermediate; the peak at 1265 cm -1 is attributed to the characteristic peak of the active species HOO*; the sharp peak at 1670 cm -1 is attributed to the stretching vibration of the C = O bond of the product CH3COOH or CH3CHO; a very large broad peak appears near 3500 cm -1 attributed to the O - H stretching vibration. The results indicate that oxides such as CH3CH2OH, CH3CHO, and CH3COOH are formed in the fixed-bed reactor, and the formation of the intermediate CH3CH2OOH is also observed. As Figure 4 shown, the characteristic peak of hydrogen peroxide species appears preferentially and does not change significantly with the reaction time, while the characteristic peaks of groups such as CH3CH2O* and C = O* in the products gradually increase with the reaction time, and these results are consistent with the experimental results.

[0109] 1H NMR spectroscopy was performed on the condensate after the reaction of the catalyst prepared by the present invention, and the results are as 1 shown. It can be Figure 5 seen. Figure 5It can be seen that 1 The products detected by \(^1H\) NMR are CH3CH2OH (1.10 ppm), CH3CHO (1.20 ppm), CH3COOH (1.98 ppm), CH3OH (3.23 ppm), and the product distribution will change with the change of the Ti loading time.

[0110] Test Example 2 examines the catalytic performance of the catalyst of the present invention

[0111] Evaluation conditions: The reaction of ethane oxidation to oxidation products is carried out in a fixed-bed reactor under atmospheric pressure and continuous flow; the catalysts prepared in Examples 1-4 and Comparative Examples 1-12 of the present invention are respectively loaded into the fixed-bed reactor, and then the raw material gas composed of C2H6, H2, O2 and N2 is introduced into the fixed-bed reactor for reaction. For the selection of reaction conditions, too low temperature will lead to failure to reach the activation temperature, and too high temperature will lead to direct decomposition of the in-situ generated hydrogen peroxide; too low ratio of hydrogen to oxygen will lead to insufficient in-situ generated hydrogen peroxide to oxidize ethane; therefore, the reaction temperature is preferably selected as 200 - 400 °C, 500 mg of catalyst, the raw material gas composition is C2H6:H2:O2:N2 = 5:5:5:6 (volume ratio), the total flow rate of the reaction gas is 84 mL / min, and the reaction gas phase space velocity is 7200 h -1 , and the products are analyzed online by gas chromatography.

[0112] Evaluation conditions: The reaction of ethane dehydrogenation to ethylene is carried out in a fixed-bed quartz reactor under atmospheric pressure and continuous flow; the catalysts prepared in Example 1 and Comparative Examples 11 and 12 of the present invention are respectively loaded into the fixed-bed reactor, and then the raw material gas composed of C2H6, H2, O2 and N2 is introduced into the fixed-bed reactor for reaction. The reaction conditions are: the reaction temperature for ethane dehydrogenation is 400 - 550 °C, 500 mg of catalyst, the raw material gas composition is C2H6:H2:O2:N2 = 5:5:5:6 (volume ratio), the total flow rate of the reaction gas is 84 mL / min, and the total reaction gas phase space velocity is 7200 h -1 , and sampling and analysis are started after 15 min of reaction.

[0113] The results are shown in Table 1 and Table 2 respectively.

[0114]

[0115]

[0116] Among them, Table 1 lists the activity test results of ethane oxidation over different catalysts. The catalytic activities of Au / D-ERB-1, Au-Ti / D-ERB-1(2h), and Au-Ti / D-ERB-1(8h) increase with the increase in Ti loading, and both the ethane conversion and acetic acid selectivity are improved. For the deposition-precipitation method of Au loading, according to the isoelectric point of the molecular sieve surface, the hydrated ions of gold [Au(OH) x Cl 4-x - are attracted to the molecular sieve. The IEP value of TiO2(7) is higher than that of SiO2(3) as an anchor for capturing Au NPs. Therefore, increasing Ti loading can effectively distribute Au NPs, thereby promoting ethane conversion. However, with the increase in Ti loading time, the catalytic performance of ethane oxidation over Au-Ti / H-MCM-22 and Au-Ti / D-ERB-1 is different. On the H-MCM-22 support, with the increase in Ti loading time, the ethane conversion and acetic acid selectivity show a trend of first increasing and then decreasing. Au-Ti / H-MCM-22 with 2 h of Ti loading exhibits the highest ethane conversion and acetic acid selectivity. At this time, the TOF of the Au-Ti / H-MCM-22(2h) catalyst is 4474.22 mmol g Au -1 h -1 , the ethane conversion is 16.35%, and the acetic acid selectivity is 87.08%. This may be because the proton acid in the catalyst is beneficial to the stable existence of H2O2 and the activation of the H–H bond in the proton transfer reaction, because the activation of H2 requires the help of a nearby proton acceptor; while the inhibitory effect of the proton acid site on the O–O bond dissociation is weak. When Ti is loaded on H-MCM-22 by the atomic in-situ transplantation method, Ti preferentially occupies the proton acid sites, resulting in a decrease in the proton acid content in the catalyst with the increase in Ti loading time. On the other hand, TiO x in the zeolite framework promotes the formation of the Au-TiO x interface, thereby forming a stable Ti-OOH transition state, which is beneficial to the activation of ethane. Au-Ti / H-MCM-22(2h) exhibits better ethane oxidation activity than Au-Ti / H-MCM-22(8h). This is because when the Ti loading time is 2 h, the proton acid sites retained by the molecular sieve not only stabilize the in-situ generated H2O2 but also stabilize the Ti-OOH transition state formed at the Au-TiO x interface, and this synergistic effect reaches the optimal conditions for ethane oxidation. In addition, with the increase in Ti loading time, the Lewis acid of the catalyst increases, which promotes the decomposition of H2O2 into OH*, and then the dehydrogenation of ethane molecules from the hydroxyl radicals on the Au surface to form ethylene, which leads to a slow increase in the selectivity of ethylene.

[0117] ​The Pd active sites in the Pd-Ti / H-MCM-22(2h) catalyst exhibit catalytic characteristics similar to those of Au, capable of effectively catalyzing the in-situ generation of H2O2 from H2 and O2, and then selectively oxidizing ethane to oxygenates with high added value. This discovery confirms that Pd can replace the noble metal Au as the active component. However, further preparation of the Au-Pd-Ti / H-MCM-22(2h) catalyst, the synergistic mechanism between the protonic acid sites and the Au-TiO x interface active sites in the catalyst promotes the in-situ generation and stabilization of H2O2 on the catalyst surface from H2 and O2. Meanwhile, the Pd sites further regulate the activation of H2 and the utilization of H2O2, thereby enhancing the C-H bond activation and selective oxidation of ethane. The synergistic effect of these multiple active sites not only improves the catalytic efficiency, with the ethane conversion reaching 17.52% and the acetic acid selectivity reaching 89.10%. This reaction system can efficiently selectively oxidize ethane to oxygenates mainly composed of acetic acid, providing a new catalytic route for the directional conversion of ethane to high-value-added chemicals under mild conditions.

[0118] Table 2 lists the activity test results of the catalyst for ethane dehydrogenation at different temperatures. Above 450 °C, basically no oxygenates are produced, and the main product is ethylene. The main reason is that the in-situ generated hydrogen peroxide from H2 and O2 is unstable at high temperatures and will be decomposed into OH* on the surface of Au nanoparticles; in addition, the stronger the Lewis acid strength of the supported metal, the more conducive it is to the decomposition of hydrogen peroxide, resulting in the ethane molecules adsorbed on the catalyst surface being activated by hydroxyl radicals to dehydrogenate and form ethylene. Compared with H-MCM-22, the D-ERB-1 molecular sieve has no protonic acid and will not further polymerize the generated ethylene, reducing side reactions. Therefore, An-Ti / D-ERB-1(8h) has good dehydrogenation performance at 550 °C, with the ethane conversion reaching 17.5% and the ethylene selectivity reaching 93.6%.

[0119] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for catalytic ethane to ethylene or oxygenates at a reduced ethane activation temperature, characterized in that, It includes the following steps: (1) Obtain the silicon-boron type molecular sieve ERB-1 or silicon-aluminum type molecular sieve MCM-22 with the MWW structure, then mix each prepared molecular sieve with nitric acid or ammonium nitrate solution respectively, heat under reflux, then filter, wash, dry, and calcine to obtain the MWW molecular sieve D-ERB-1 or H-MCM-22; (2) Load Ti on the MWW molecular sieve in step (1) by the atomic in-situ grafting method to obtain the MWW molecular sieve with a silicon-titanium framework structure; (3) Load Au and / or Pd on the MWW molecular sieve with a silicon-titanium framework structure in step (2) to obtain the product.

2. The preparation method of the catalyst for catalytic ethane to ethylene or oxygenates at a reduced ethane activation temperature according to claim 1, characterized in that, In step (1): Synthesis of the silicon-boron type microporous molecular sieve ERB-1 with the MWW structure: Using piperidine as a template agent, add the silicon source, boron source, template agent, and water in a mass ratio of 10:(5 - 30):(5 - 30):(50 - 500) into a polytetrafluoroethylene inner liner, perform dynamic crystallization at high temperature, and obtain the silicon-boron type microporous molecular sieve ERB-1 after washing, filtering, drying, and calcining; Synthesis of the silicon-aluminum type molecular sieve MCM-22 with the MWW structure: Using hexamethyleneimine as a template agent, add the silicon source, aluminum source, template agent, and water in a mass ratio of 10:(5 - 30):(5 - 30):(50 - 500) into a polytetrafluoroethylene inner liner, perform dynamic crystallization at high temperature, and obtain the silicon-aluminum type microporous molecular sieve MCM-22 after washing, filtering, drying, and calcining.

3. The preparation method of the catalyst for catalytic ethane to ethylene or oxygenates under reduced ethane activation temperature according to claim 1, characterized in that, Step (2) includes the following steps: Put D-ERB-1 or H-MCM-22 into a quartz tube reactor, first perform dehydration pretreatment, then add a titanium source in an evaporator to load Ti, control the loading amount of Ti by controlling the loading time of Ti, after the reaction, place the molecular sieve in absolute ethanol for alcoholysis, and then obtain the MWW molecular sieve Ti / D-ERB-1 or Ti / H-MCM-22 with a silicon-titanium framework structure after drying and calcining.

4. The preparation method of a catalyst for catalytically converting ethane into ethylene or oxygenates at a reduced ethane activation temperature according to claim 3, characterized in that, Perform dehydration pretreatment under nitrogen purge, the nitrogen flow rate is 20 - 100 ml / min, the dehydration pretreatment time is 1 - 5 h, and the temperature is 300 - 750 °C; the titanium source is a TiCl4 solution, the reaction time is 20 - 30 h; the alcoholysis time is 1 - 20 h; calcine at 300 - 700 °C for 5 - 10 h, and the heating rate is 5 - 10 °C / min.

5. The preparation method of a catalyst for catalytic ethane conversion to ethylene or oxygenates at a reduced ethane activation temperature according to claim 1, characterized in that, In step (3), when only Au is loaded on the MWW molecular sieve with a silicon-titanium framework structure, it includes the following steps: (1) Perform calcination dehydration treatment on Ti / D-ERB-1 or Ti / H-MCM-22; (2) Dissolve the Au precursor in deionized water, perform condensation reflux, slowly adjust the pH of the solution with an alkaline solution, and maintain for a period of time to obtain solution A; (3) Disperse the molecular sieve Ti / D-ERB-1 or Ti / H-MCM-22 obtained in step (1) in solution A, stir well, slowly adjust the pH of the solution with an alkaline solution, and maintain for a period of time to obtain suspension B; (4) After subjecting the suspension B to centrifugation, vacuum drying, and calcination, the catalysts Au-Ti / D-ERB-1 or Au-Ti / H-MCM-22 are obtained respectively; When only Pd is loaded on the MWW molecular sieve with a silicon-titanium framework structure, the following steps are included: (1) Subject Ti / H-MCM-22 to calcination dehydration treatment; (2) Dissolve the precursor of Pd in deionized water, stir evenly, disperse the molecular sieve Ti / H-MCM-22 obtained in step (1) in the solution, carry out condensation reflux, slowly adjust the pH of the solution with an alkaline solution, and maintain for a period of time to obtain suspension C; (3) After subjecting the suspension C to centrifugation, vacuum drying, and calcination, the catalyst Pd-Ti / H-MCM-22 is obtained; When Au and Pd are loaded on the MWW molecular sieve with a silicon-titanium framework structure, the following steps are included: (1) Subject Ti / H-MCM-22 to calcination dehydration treatment; (2) Dissolve the precursor of Au in deionized water, carry out condensation reflux, slowly adjust the pH of the solution with an alkaline solution, and maintain for a period of time to obtain solution D; (3) Disperse the precursor of Pd and the molecular sieve Ti / H-MCM-22 obtained in step 5.1) in solution D, carry out condensation reflux, slowly adjust the pH of the solution with an alkaline solution, and maintain for a period of time to obtain suspension E; (4) After subjecting the suspension E to centrifugation, vacuum drying, and calcination, the catalyst Au-Pd-Ti / H-MCM-22 is obtained.

6. The preparation method of a catalyst for catalytically converting ethane to ethylene or oxygen-containing compounds at a reduced ethane activation temperature according to claim 5, characterized in that, The precursor of Au is chloroauric acid, and the precursor of Pd is tetraammine palladium nitrate; The temperature during the calcination dehydration treatment is 300 - 650 °C, the calcination time is 3 - 5 h, and the heating rate is 5 - 10 °C / min; The water bath temperature for condensation reflux is 40 - 120 °C; The alkaline solution is an aqueous solution of sodium hydroxide or ammonia water, with a concentration of 0.01 - 2 mol / L; when only Au is loaded, the pH is adjusted for the first time to be > 4, and the duration is 3 - 24 h, and for the second time to be > 6, and the duration is 3 - 24 h; when only Pd is loaded, the pH is adjusted to be > 6, and the duration is 3 - 24 h; when Au and Pd are loaded, the pH is adjusted for the first time to be > 4, and the duration is 3 - 24 h, and for the second time to be > 6, and the duration is 3 - 24 h; The centrifugation speed is 8000 - 10000 r / min, and the centrifugation time is 15 - 20 min; The vacuum drying temperature is 50 - 80 °C; The temperature during the calcination after vacuum drying is 200 - 400 °C, the calcination time is 3 - 5 h, and the heating rate is 2 - 5 °C / min.

7. The catalyst prepared by the method according to any one of claims 1-6, characterized in that: It includes Au-Ti / D-ERB-1(x), Au-Ti / H-MCM-22(x), Pd-Ti / H-MCM-22(x), Au-Pd-Ti / H-MCM-22(x), where x represents the time for loading Ti.

8. The catalyst according to claim 7, characterized in that, The catalysts are: Au-Ti / D-ERB-1(8 h), where the loading amount of Au is 1.0 wt%, and the loading amount of Ti is 3.0 wt%; Au exists in the form of a single substance; the existence form of Ti includes framework Ti and TiO2 on the surface of the molecular sieve; Au-Ti / H-MCM-22(2h), where the loading amount of Au is 1.0 wt%, and the loading amount of Ti is 2.0 wt%; Au exists in the form of elemental substance; the existing forms of Ti include framework Ti and TiO2 on the surface of the molecular sieve; Pd-Ti / H-MCM-22(2h), where the loading amount of Pd is 1.0 wt%, and the loading amount of Ti is 2.0 wt%; Pd exists in the form of elemental substance; the existing forms of Ti include framework Ti and TiO2 on the surface of the molecular sieve; Au-Pd-Ti / H-MCM-22(2h), where the loading amount of Au is 1.0 wt%, the loading amount of Pd is 1.0 wt%, and the loading amount of Ti is 2.0 wt%; Pd exists in the form of elemental substance; the existing forms of Ti include framework Ti and TiO2 on the surface of the molecular sieve.

9. Use of the catalyst according to claim 8 in the catalytic conversion of ethane to ethylene or oxygenates, characterized in that, Au-Ti / D-ERB-1(8h) is used for catalyzing ethane to prepare oxygenates and ethylene; Au-Ti / H-MCM-22(2h) is used for catalyzing ethane to prepare oxygenates; Pd-Ti / H-MCM-22(2h) is used for catalyzing ethane to prepare oxygenates; Au-Pd-Ti / H-MCM-22(2h) is used for catalyzing ethane to prepare oxygenates; The oxygenates are acetic acid, acetaldehyde or ethanol.

10. The application according to claim 9, characterized in that, Hydrogen peroxide is in-situ synthesized through hydrogen and oxygen on the Au and / or Pd active sites, and further oxygenates and / or ethylene are synthesized by activating ethane with hydrogen peroxide; The reaction conditions for the oxidation of ethane to oxygenates are as follows: the reaction temperature is 200 - 400 °C, and the total gas hourly space velocity of the reaction is 1400 - 8000 h -1 , and the volume ratio of ethane, hydrogen, oxygen and nitrogen in the reaction raw materials is 1 - 10:1 - 10:0.5 - 3:10 - 20; The reaction conditions for the dehydrogenation of ethane to ethylene are as follows: the reaction temperature is 400 - 550 °C, and the total volumetric space velocity of the reaction gas phase is 1400 - 8000 h -1 , and the volume ratio of ethane, hydrogen, oxygen, and nitrogen in the reaction raw materials is 1 - 10:1 - 10:0.5 - 3:10 - 20.

Images