Preparation method of oxidation-acid bifunctional molecular sieve catalyst

Abstract

The invention belongs to the technical field of heterogeneous catalysis, and particularly relates to a preparation method of an oxidation-acid bifunctional molecular sieve catalyst, which comprises the following steps: S1, introduction of oxidation sites: sequentially mixing a silicon source, a titanium source, a template agent, isopropanol and water to form a suspension, and hydrolyzing; loading the hydrolysate into a crystallization kettle, and crystallizing at 150-220 DEG C for 12-72 hours; and carrying out solid-liquid separation on the obtained turbid liquid, drying, and roasting at 500-900 DEG C for 2-8 hours to obtain the molecular sieve catalyst containing oxidation sites, which is marked as Ti-MFI. S2, introduction of acid sites: mixing heteroatoms, a template agent, an ammonium source and water to prepare a treatment solution, and adding Ti-MFI into the treatment solution; putting the solid-liquid mixture into a crystallization kettle, and treating at 130-230 DEG C for 12-72 hours; and carrying out solid-liquid separation on the obtained product, drying, and roasting at 500-900 DEG C for 2-8 hours to obtain the molecular sieve catalyst simultaneously containing the oxidation site and the acid site. The bifunctional catalyst prepared by the method can be used for various reactions needing oxidation and acid site concerted catalysis, such as direct preparation of diol from olefin and hydrogen peroxide and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of heterogeneous catalysis, and relates to a preparation method of an oxidation-acid bifunctional molecular sieve catalyst. Background Art

[0002] A bifunctional catalyst is a catalyst with two catalytic active centers that can catalyze two types of reactions simultaneously. By adding aluminum to titanium silicate molecular sieve TS-1, an oxidation-acid bifunctional catalyst can be formed, which can then catalyze reactions such as the epoxidation-hydration of olefins with hydrogen peroxide to produce diols. Bifunctional catalysts can make reactions more efficient and the catalytic process simpler, and have received increasing attention in recent years.

[0003] Bifunctional molecular sieve catalysts are mostly prepared by the eutectic crystallization method, that is, a titanium source and another metal source are simultaneously added to the synthesis gel. Chinese Patent CN102274749A reports a preparation method of a bifunctional titanium silicate molecular sieve. In this method, titanium and trivalent ions are simultaneously added in a hydrothermal system to synthesize M-TS-1 molecular sieves (M = Al, B, Fe), and titanium and trivalent ions provide the oxidation and acid-catalyzed reaction activities for the catalyst respectively.

[0004] In fact, as early as in the 1990s, Ovejero et al. found that in Al-TS-1, the content of titanium in the molecular sieve framework is much lower than that in TS-1, indicating that there is a competitive relationship between the entry of aluminum and titanium into the framework. The reduction in the content of framework titanium caused by this competition is not conducive to the progress of catalytic oxidation reactions, and thus the overall reaction performance deteriorates. Summary of the Invention

[0005] To solve the problem of the negative impact of the introduction of trivalent ions on the coordination state and content of titanium in the existing preparation method of bifunctional molecular sieves, the present invention provides a preparation method of Ti-M-MFI molecular sieve by sequentially introducing titanium and trivalent ion M 3+ That is, titanium is first introduced into the molecular sieve framework to obtain Ti-MFI; then trivalent ion M 3+ is introduced through post-treatment to obtain Ti-M-MFI. This method will not have an adverse effect on the state of titanium, and the relative strengths of oxidation and acid-catalyzed activities can be achieved by adjusting the introduction amount of M 3+ to be suitable for different reaction processes.

[0006] Specifically, the present invention provides a preparation method of an oxidation-acid bifunctional molecular sieve catalyst. This catalyst is prepared by sequentially introducing two active sites, and specifically includes the following steps: S1. Introduction of oxidation sites: Mix a silicon source, a template agent, and water to form suspension A, and hydrolyze to obtain a hydrolyzed solution of silicon; mix a titanium source, a template agent, isopropanol, and water to form suspension B, and hydrolyze to obtain a hydrolyzed solution of titanium; mix the hydrolyzed solution of silicon and the hydrolyzed solution of titanium, and remove alcohol; finally, put the clarified solution into a crystallization kettle and crystallize at 150 - 220 °C for 12 - 72 h; the obtained suspension C is subjected to solid-liquid separation, drying, and calcination at 500 - 900 °C for 2 - 8 h to obtain a molecular sieve catalyst containing oxidation sites, denoted as Ti-MFI; S2. Introduction of acid sites: Mix a heteroatom, a template agent, an ammonium source, and water to prepare a treatment solution, add the Ti-MFI obtained in step S1 to the treatment solution, stir evenly, put the solid-liquid mixture into a crystallization kettle, and treat at 130 - 230 °C for 12 - 72 h; the obtained product is subjected to solid-liquid separation, drying, and calcination at 500 - 900 °C for 2 - 8 h to obtain a molecular sieve catalyst containing both oxidation sites and acid sites, denoted as Ti-M-MFI.

[0007] Further, in step S1, the silicon source is at least one of tetraethyl orthosilicate and silica sol; the titanium source is at least one of tetraethyl titanate, tetrabutyl titanate, titanium trichloride, and titanium tetrachloride; the template agent is tetrapropylammonium hydroxide.

[0008] Further, in step S1, the molar ratio of the silicon source, titanium source, template agent, water, and isopropanol is Si : Ti : TPA + : H2O : IPA = 1 : (0.01 - 0.05) : (0.2 - 0.4) : (5 - 50) : 40.

[0009] Further, in step S2, the heteroatom is at least one of a boron source, an aluminum source, a gallium source, a zinc source, and a zirconium source; the boron source is boric acid; the aluminum source is at least one of aluminum isopropoxide, aluminum trichloride, aluminum nitrate, and aluminum sulfate; the gallium source is at least one of gallium chloride and gallium nitrate; the zinc source is at least one of zinc acetate, zinc chloride, and zinc nitrate; the zirconium source is at least one of zirconium oxychloride, zirconyl nitrate, and zirconium tetrachloride.

[0010] Further, in step S2, the molar ratio of the heteroatom to Ti-MFI is M : Si = 0.0002 - 0.02.

[0011] Further, in step S2, the template agent is tetrapropylammonium hydroxide; the concentration of tetrapropylammonium hydroxide in the treatment solution is 0.02 - 0.15 mol / L.

[0012] Further, the ammonium source in step S2 is at least one of ammonium sulfate, ammonium bisulfate, ammonium phosphate, ammonium hydrogen phosphate, diammonium hydrogen phosphate, ammonium chloride, ammonium carbonate, and ammonium bicarbonate; the concentration of the ammonium salt in the ammonium source in the treatment solution is 0.02 - 0.20 mol / L.

[0013] Further, the suspension A in step S1 is hydrolyzed at 40°C for 4 h to obtain a hydrolyzed solution of silicon; the suspension B is hydrolyzed at room temperature for 0.5 h to obtain a hydrolyzed solution of titanium.

[0014] Further, the hydrolyzed solution of silicon is mixed with the hydrolyzed solution of titanium, and the alcohol is removed at 85°C for 6 h.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) When introducing trivalent ions, this method will not have an adverse effect on the state of titanium.

[0016] (2) During the treatment process, the function of the alkali solution can convert the tetracoordinated titanium in the molecular sieve framework into hexacoordinated titanium with higher catalytic oxidation activity, promoting the oxidation reaction.

[0017] (3) By adjusting the concentration of M 3+ during the post-treatment process, the relative strength of the oxidation activity and the acid catalytic activity can be regulated to be suitable for different reaction processes. Specific Embodiments

[0018] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0019] Comparative Example 1 A molecular sieve catalyst containing oxidation sites was prepared according to the method provided in Chinese Patent CN02132325.9: 35.5 g of tetraethyl orthosilicate was added to a three-necked flask, and 32.0 g of an aqueous solution of tetrapropylammonium hydroxide and 28.4 g of water were added under stirring at 40°C to hydrolyze tetraethyl orthosilicate for 4 h; 1.4 g of tetrabutyl titanate was added to 10.6 g of isopropanol, and 12.1 g of a tetrapropylammonium hydroxide solution and 14.2 g of water were successively added under stirring and hydrolyzed at room temperature for 0.5 h to obtain a hydrolyzate of tetrabutyl titanate. The hydrolyzates of the silicon ester and the titanium ester were mixed, and the alcohol was removed at 85°C for 6 h. The obtained clear solution was filled into a crystallization kettle and crystallized at 170°C for 48 h. The crystallization product was washed and dried, and then calcined at 540°C for 5 h to obtain a molecular sieve catalyst containing oxidation sites, denoted as PTS-1.

[0020] Comparative Example 2 According to Chinese Patent CN102923730A, a preparation method of a molecular sieve catalyst containing both oxidation sites and acid sites is also reported: tetrabutyl titanate, tetraethyl orthosilicate, tetrapropylammonium hydroxide, and aluminum chloride hexahydrate are successively mixed. After removing alcohol and adding water, it is crystallized at 180 °C for 120 h. It is denoted as ATS-1-A.

[0021] Example 1 S1: Add 35.5 g of tetraethyl orthosilicate to a three-necked flask. At 40 °C and with stirring, add 32.0 g of tetrapropylammonium hydroxide aqueous solution and 28.4 g of water to hydrolyze tetraethyl orthosilicate for 4 h; add 1.4 g of tetrabutyl titanate to 10.6 g of isopropanol. With stirring, successively add 12.1 g of tetrapropylammonium hydroxide solution and 14.2 g of water, and hydrolyze at room temperature for 0.5 h to obtain a tetrabutyl titanate hydrolyzate. Mix the silicon ester and the titanium ester hydrolyzate, and remove alcohol at 85 °C for 6 h. Transfer the obtained clear solution into a crystallization kettle and crystallize at 170 °C for 48 h. After washing and drying the crystallization product, calcine it at 540 °C for 5 h to obtain a molecular sieve catalyst containing oxidation sites, denoted as Ti-MFI.

[0022] S2: Add 3.3 mL of tetrapropylammonium hydroxide solution, 2.24 g of ammonium carbonate, and 0.12 g of aluminum isopropoxide to 66 mL of water successively, and stir at 40 °C for 0.5 h to obtain a treatment solution. Weigh 7.0 g of Ti-MFI synthesized in S1 and add it to the treatment solution, and stir at 40 °C for 4 h. Transfer the obtained suspension to a stainless-steel crystallization kettle with a polytetrafluoroethylene lining and treat it at 170 °C for 24 h. Centrifuge to separate the solid, dry it at 80 °C for 12 h, and calcine it at 540 °C for 6 h to obtain a molecular sieve catalyst Ti-Al-MFI containing both oxidation sites and acid sites, denoted as ATS-1-B.

[0023] Example 2 S1: Add 35.5 g of tetraethyl orthosilicate to a three-necked flask. At 40 °C and with stirring, add 39.0 g of tetrapropylammonium hydroxide aqueous solution and 26.5 g of water to hydrolyze tetraethyl orthosilicate for 4 h; add 2.7 g of tetrabutyl titanate to 10.6 g of isopropanol. With stirring, successively add 11.3 g of tetrapropylammonium hydroxide solution and 13.7 g of water, and hydrolyze at room temperature for 0.5 h to obtain a tetrabutyl titanate hydrolyzate. Mix the silicon ester and the titanium ester hydrolyzate, and remove alcohol at 85 °C for 6 h. Transfer the obtained clear solution into a crystallization kettle and crystallize at 170 °C for 48 h. After washing and drying the crystallization product, calcine it at 540 °C for 5 h to obtain a molecular sieve catalyst containing oxidation sites, denoted as Ti-MFI.

[0024] S2: Add 1.65 mL of tetrapropylammonium hydroxide solution, 1.12 g of ammonium carbonate, and 0.12 g of aluminum isopropoxide to 68 mL of water in sequence. Stir at 40 °C for 0.5 h to obtain a treatment solution. Weigh 7.0 g of Ti-MFI synthesized by S1 and add it to the treatment solution. Stir at 50 °C for 2 h. Transfer the obtained suspension to a stainless-steel crystallization kettle with a polytetrafluoroethylene lining, treat at 200 °C for 48 h, centrifuge to separate the solid, dry at 80 °C for 12 h, and calcine at 540 °C for 6 h to obtain a molecular sieve catalyst Ti-Al-MFI containing both oxidation sites and acid sites, denoted as ATS-1-C.

[0025] Example 3 S1: Add 35.5 g of tetraethyl orthosilicate to a three-necked flask. Add 20.0 g of aqueous tetrapropylammonium hydroxide solution and 40.4 g of water at 40 °C with stirring to hydrolyze tetraethyl orthosilicate for 4 h; add 0.05 g of tetrabutyl titanate to 10.6 g of isopropanol, and sequentially add 6.0 g of tetrapropylammonium hydroxide solution and 20.3 g of water with stirring, and hydrolyze at room temperature for 0.5 h to obtain a hydrolyzate of tetrabutyl titanate. Mix the silicon ester and the titanium ester hydrolyzate, and remove alcohol at 85 °C for 6 h. Load the obtained clear solution into a crystallization kettle and crystallize at 170 °C for 48 h. After washing and drying the crystallization product, calcine at 540 °C for 5 h to obtain a molecular sieve catalyst containing oxidation sites, denoted as Ti-MFI.

[0026] S2: Add 5.5 mL of tetrapropylammonium hydroxide solution, 0.56 g of ammonium carbonate, and 1.2 g of aluminum isopropoxide to 64 mL of water in sequence. Stir at 40 °C for 0.5 h to obtain a treatment solution. Weigh 7.0 g of Ti-MFI synthesized by S1 and add it to the treatment solution. Stir at 30 °C for 5 h. Transfer the obtained suspension to a stainless-steel crystallization kettle with a polytetrafluoroethylene lining, treat at 170 °C for 48 h, centrifuge to separate the solid, dry at 80 °C for 12 h, and calcine at 540 °C for 6 h to obtain a molecular sieve catalyst Ti-Al-MFI containing both oxidation sites and acid sites, denoted as ATS-1-D.

[0027] Example 4 S1: Add 35.5 g of tetraethyl orthosilicate into a three-necked flask. Under stirring at 40 °C, add 32.0 g of aqueous tetrapropylammonium hydroxide solution and 28.4 g of water to hydrolyze tetraethyl orthosilicate for 4 h. Add 1.4 g of tetrabutyl titanate into 10.6 g of isopropanol. Under stirring, successively add 12.1 g of tetrapropylammonium hydroxide solution and 14.2 g of water, and hydrolyze at room temperature for 0.5 h to obtain a tetrabutyl titanate hydrolyzate. Mix the silicon ester and the titanate hydrolyzate, and remove the alcohol at 85 °C for 6 h. Transfer the obtained clear solution into a crystallization kettle and crystallize at 170 °C for 48 h. After washing and drying the crystallization product, calcine it at 540 °C for 5 h to obtain a molecular sieve catalyst containing oxidation sites, denoted as Ti-MFI.

[0028] S2: Add 6.6 mL of tetrapropylammonium hydroxide solution, 0.22 g of ammonium carbonate and 0.12 g of aluminum isopropoxide into 63 mL of water successively, and stir at 40 °C for 0.5 h to obtain a treatment solution. Weigh 7.0 g of Ti-MFI synthesized in S1 and add it into the treatment solution, and stir at 40 °C for 4 h. Transfer the obtained suspension into a stainless-steel crystallization kettle with a polytetrafluoroethylene liner, treat it at 220 °C for 48 h, centrifuge to separate the solid, dry it at 80 °C for 12 h, and calcine it at 500 °C for 8 h to obtain a molecular sieve catalyst Ti-Al-MFI containing both oxidation sites and acid sites, denoted as ATS-1-E.

[0029] Example 5 S1: Add 35.5 g of tetraethyl orthosilicate into a three-necked flask. Under stirring at 40 °C, add 32.0 g of aqueous tetrapropylammonium hydroxide solution and 28.4 g of water to hydrolyze tetraethyl orthosilicate for 4 h. Add 1.4 g of tetrabutyl titanate into 10.6 g of isopropanol. Under stirring, successively add 12.1 g of tetrapropylammonium hydroxide solution and 14.2 g of water, and hydrolyze at room temperature for 0.5 h to obtain a tetrabutyl titanate hydrolyzate. Mix the silicon ester and the titanate hydrolyzate, and remove the alcohol at 85 °C for 6 h. Transfer the obtained clear solution into a crystallization kettle and crystallize at 170 °C for 48 h. After washing and drying the crystallization product, calcine it at 540 °C for 5 h to obtain a molecular sieve catalyst containing oxidation sites, denoted as Ti-MFI.

[0030] S2: Add 3.3 mL of tetrapropylammonium hydroxide solution, 2.24 g of ammonium carbonate and 0.08 g of aluminum isopropoxide into 66 mL of water successively, and stir at 40 °C for 0.5 h to obtain a treatment solution. Weigh 7.0 g of Ti-MFI synthesized in S1 and add it into the treatment solution, and stir at 50 °C for 2 h. Transfer the obtained suspension into a stainless-steel crystallization kettle with a polytetrafluoroethylene liner, treat it at 150 °C for 48 h, centrifuge to separate the solid, dry it at 80 °C for 12 h, and calcine it at 540 °C for 6 h to obtain a molecular sieve catalyst Ti-Al-MFI containing both oxidation sites and acid sites, denoted as ATS-1-F.

[0031] Example 6 S1: Add 35.5 g of tetraethyl orthosilicate into a three-necked flask. Under stirring at 40 °C, add 32.0 g of aqueous tetrapropylammonium hydroxide solution and 28.4 g of water to hydrolyze tetraethyl orthosilicate for 4 h. Add 1.4 g of tetrabutyl titanate into 10.6 g of isopropanol. Under stirring, sequentially add 12.1 g of tetrapropylammonium hydroxide solution and 14.2 g of water, and hydrolyze at room temperature for 0.5 h to obtain a tetrabutyl titanate hydrolyzate. Mix the silicate ester with the titanate ester hydrolyzate, and remove alcohol at 85 °C for 6 h. Transfer the obtained clear solution into a crystallization kettle, and crystallize at 170 °C for 48 h. After washing and drying the crystallization product, calcine it at 540 °C for 5 h to obtain a molecular sieve catalyst containing oxidation sites, denoted as Ti-MFI.

[0032] S2: Sequentially add 1.1 mL of tetrapropylammonium hydroxide solution, 2.24 g of ammonium carbonate, and 0.08 g of aluminum isopropoxide into 68 mL of water, and stir at 40 °C for 0.5 h to obtain a treatment solution. Weigh 7.0 g of Ti-MFI synthesized in S1 and add it into the treatment solution, and stir at 40 °C for 4 h. Transfer the obtained suspension into a stainless-steel crystallization kettle with a polytetrafluoroethylene lining, treat it at 170 °C for 24 h, centrifuge to separate the solid, dry it at 80 °C for 12 h, and calcine it at 540 °C for 6 h to obtain a molecular sieve catalyst Ti-Al-MFI containing both oxidation sites and acid sites, denoted as ATS-1-G.

[0033] Example 7 S1: Add 35.5 g of tetraethyl orthosilicate into a three-necked flask. Under stirring at 40 °C, add 32.0 g of aqueous tetrapropylammonium hydroxide solution and 28.4 g of water to hydrolyze tetraethyl orthosilicate for 4 h. Add 1.4 g of tetrabutyl titanate into 10.6 g of isopropanol. Under stirring, sequentially add 12.1 g of tetrapropylammonium hydroxide solution and 14.2 g of water, and hydrolyze at room temperature for 0.5 h to obtain a tetrabutyl titanate hydrolyzate. Mix the silicate ester with the titanate ester hydrolyzate, and remove alcohol at 85 °C for 6 h. Transfer the obtained clear solution into a crystallization kettle, and crystallize at 170 °C for 48 h. After washing and drying the crystallization product, calcine it at 540 °C for 5 h to obtain a molecular sieve catalyst containing oxidation sites, denoted as Ti-MFI.

[0034] S2: Add 8.2 mL of tetrapropylammonium hydroxide solution, 2.24 g of ammonium carbonate, and 0.12 g of aluminum isopropoxide to 61 mL of water in sequence. Stir at 40 °C for 0.5 h to obtain a treatment solution. Weigh 7.0 g of Ti-MFI synthesized in S1 and add it to the treatment solution. Stir at 40 °C for 4 h. Transfer the obtained suspension to a stainless-steel crystallization kettle with a polytetrafluoroethylene lining, treat at 140 °C for 48 h, centrifuge to separate the solid, dry at 80 °C for 12 h, and calcine at 540 °C for 6 h to obtain a molecular sieve catalyst Ti-Al-MFI containing both oxidation sites and acid sites, denoted as ATS-1-H.

[0035] Example 8 S1: Add 35.5 g of tetraethyl orthosilicate to a three-necked flask. Add 32.0 g of an aqueous solution of tetrapropylammonium hydroxide and 28.4 g of water at 40 °C with stirring to hydrolyze tetraethyl orthosilicate for 4 h. Add 1.4 g of tetrabutyl titanate to 10.6 g of isopropanol, and sequentially add 12.1 g of tetrapropylammonium hydroxide solution and 14.2 g of water with stirring, and hydrolyze at room temperature for 0.5 h to obtain a hydrolyzate of tetrabutyl titanate. Mix the silicon ester and the titanium ester hydrolyzate, and remove the alcohol at 85 °C for 6 h. Load the obtained clear solution into a crystallization kettle and crystallize at 170 °C for 48 h. After washing and drying the crystallization product, calcine at 540 °C for 5 h to obtain a molecular sieve catalyst containing oxidation sites, denoted as Ti-MFI.

[0036] S2: Add 3.3 mL of tetrapropylammonium hydroxide solution, 0.67 g of ammonium carbonate, and 0.12 g of aluminum isopropoxide to 66 mL of water in sequence. Stir at 60 °C for 0.5 h to obtain a treatment solution. Weigh 7.0 g of Ti-MFI synthesized in S1 and add it to the treatment solution. Stir at 20 °C for 4 h. Transfer the obtained suspension to a stainless-steel crystallization kettle with a polytetrafluoroethylene lining, treat at 140 °C for 72 h, centrifuge to separate the solid, dry at 80 °C for 12 h, and calcine at 600 °C for 6 h to obtain a molecular sieve catalyst Ti-Al-MFI containing both oxidation sites and acid sites, denoted as ATS-1-I.

[0037] Application Example Using the reaction of ethylene / hydrogen peroxide to produce ethylene glycol as a probe, the catalytic performance of the prepared Ti-Al-MFI was evaluated. First, 0.2 g of Ti-Al-MFI powder and 20 mL of 0.6 mol / L H2O2 solution were added to a 200 mL stainless steel autoclave reactor. After the reactor was sealed, ethylene was charged into the reactor at a pressure of 1.1 MPa, and the reaction was stirred at 40 °C for 1 h. After the reaction was completed, the supernatant was separated by centrifugation, and the product composition was analyzed using an Agilent GC-7890B gas chromatograph, and the concentration of hydrogen peroxide before and after the reaction was titrated by the iodometric method. The main product of the reaction was ethylene glycol, and the by-products were ethylene oxide and diethylene glycol. The conversion of hydrogen peroxide (X(H2O2)) and the selectivity of ethylene glycol (S(EG)) were calculated by the following formulas: X(H2O2) = (n0(H2O2) - n(H2O2)) / n0(H2O2) × 100% S(EG) = n(EG) / (n(EG) + n(EO) + n(DEG)) × 100% The results of the catalytic reaction are shown in Table 1.

[0038] Table 1 Catalytic performance of various samples for the reaction of ethylene to ethylene glycol Sample Number H2O2 Conversion Rate / % Ethylene Glycol Selectivity / % PTS-1 20.2 77.3 ATS-1-A 15.3 91.5 ATS-1-B 66.7 97.6 ATS-1-C 50.3 97.1 ATS-1-D 31.7 96.4 ATS-1-E 35.6 96.9 ATS-1-F 64.6 96.7 ATS-1-G 65.2 97.4 ATS-1-H 59.7 95.1 ATS-1-I 55.4 96.3 In summary, the catalytic performance of the Ti-Al-MFI prepared in the examples of the present invention was significantly better than that of the catalysts prepared in Comparative Example 1 and Comparative Example 2, indicating that the Ti-Al-MFI prepared by the method provided by the present invention has more excellent catalytic performance for reactions that require oxidative-acid synergistic catalysis. This is mainly attributed to the sequential introduction of two active sites, without changing the coordination state of the titanium sites or converting the titanium species into a coordination state with higher activity; while the aluminum sites can be located on the outer surface of the Ti-MFI particles, and the formed ethylene glycol can quickly diffuse into the liquid phase, without reducing the catalyst stability due to enrichment in the pores.

[0039] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, should be covered within the protection scope of the present invention.

Claims

1. A method for preparing an oxidation-acid bifunctional molecular sieve catalyst, characterized in that, Specifically, it includes the following steps: S1. Introduction of oxidation sites: Mix a silicon source, a template agent, and water to form suspension A, and hydrolyze to obtain a hydrolyzed solution of silicon; mix a titanium source, a template agent, isopropanol, and water to form suspension B, and hydrolyze to obtain a hydrolyzed solution of titanium. Mix the hydrolyzed solution of silicon with the hydrolyzed solution of titanium, and remove alcohol; finally, put the clarified solution into a crystallization kettle and crystallize at 150 - 220 °C for 12 - 72 h; the obtained suspension C is subjected to solid-liquid separation, drying, and calcination at 500 - 900 °C for 2 - 8 h to obtain a molecular sieve catalyst containing oxidation sites, denoted as Ti-MFI. S2. Introduction of acid sites: Mix a heteroatom, a template agent, an ammonium source, and water to prepare a treatment solution, add the Ti-MFI obtained in step S1 to the treatment solution, stir evenly, put the solid-liquid mixture into a crystallization kettle, and treat at 130 - 230 °C for 12 - 72 h; the obtained product is subjected to solid-liquid separation, drying, and calcination at 500 - 900 °C for 2 - 8 h to obtain a molecular sieve catalyst containing both oxidation sites and acid sites, denoted as Ti-M-MFI.

2. The preparation method according to claim 1, characterized in that, In step S1, the silicon source is at least one of tetraethyl orthosilicate and silica sol; the titanium source is at least one of tetraethyl titanate, tetrabutyl titanate, titanium trichloride, and titanium tetrachloride; the template agent is tetrapropylammonium hydroxide.

3. The preparation method according to claim 1, wherein The molar ratio of the silicon source, titanium source, template agent, water, and isopropanol described in step S1 is Si : Ti : TPA + : H2O : IPA = 1 : (0.01~0.05) : (0.2~0.4) : (5~50) :

40.

4. The preparation method according to claim 1, characterized in that, In step S2, the heteroatom is at least one of a boron source, an aluminum source, a gallium source, a zinc source, and a zirconium source; the boron source is boric acid; the aluminum source is at least one of aluminum isopropoxide, aluminum trichloride, aluminum nitrate, and aluminum sulfate; the gallium source is at least one of gallium chloride and gallium nitrate; the zinc source is at least one of zinc acetate, zinc chloride, and zinc nitrate; the zirconium source is at least one of zirconium oxychloride, zirconyl nitrate, and zirconium tetrachloride.

5. The preparation method according to claim 1, characterized in that, In step S2, the molar ratio of the heteroatom to Ti-MFI is M : Si = 0.0002 - 0.

02.

6. The preparation method according to claim 1, wherein, In step S2, the template agent is tetrapropylammonium hydroxide; the concentration of tetrapropylammonium hydroxide in the treatment solution is 0.02 - 0.15 mol / L.

7. The preparation method according to claim 1, characterized in that In step S2, the ammonium source is at least one of ammonium sulfate, ammonium bisulfate, ammonium phosphate, ammonium hydrogen phosphate, diammonium hydrogen phosphate, ammonium chloride, ammonium carbonate, and ammonium bicarbonate; the concentration of the ammonium salt in the ammonium source in the treatment solution is 0.02 - 0.20 mol / L.

8. The preparation method according to claim 1, characterized in that, In step S1, suspension A is hydrolyzed at 40 °C for 4 h to obtain a hydrolyzed solution of silicon; suspension B is hydrolyzed at room temperature for 0.5 h to obtain a hydrolyzed solution of titanium.

9. The preparation method according to claim 1, characterized in that, Mix the hydrolyzed solution of silicon with the hydrolyzed solution of titanium, and remove alcohol at 85 °C for 6 h.