Preparation method and application of a binder-free self-forming MOR molecular sieve

Abstract

The present invention discloses a preparation method and application of a binder-free self-forming MOR molecular sieve. The preparation steps are to mix sodium hydroxide, alkaline silica sol and aluminum source, stir and age to form a gel, transfer it to a hydrothermal kettle, seal it, and crystallize it at 170°C for 5 days. After the crystallization, a formed centimeter-level MOR molecular sieve can be obtained. When the catalyst is used for the carbonylation of dimethyl ether to prepare methyl acetate, it has a higher dimethyl ether conversion rate than commercial MOR. In the present invention, a centimeter-level formed MOR molecular sieve is directly prepared by a one-pot method, and a simple scale-up experiment is carried out. In the entire synthesis process, no expensive and toxic organic template is used, and no additional binder is needed. This is not only beneficial to environmental protection, but also can reduce production costs and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to a MOR molecular sieve catalyst, in particular to a preparation method and application of a binder-free self-forming MOR molecular sieve, belonging to the field of catalysts. Background Art

[0002] As a raw material, green solvent and fuel additive, ethanol is widely demanded in the global market. Carbonylation of dimethyl ether (DME) to prepare methyl acetate (MA) and hydrogenation of MA to synthesize ethanol is a novel, green and economical ethanol synthesis route. Due to its unique spatial structure and acidic sites, MOR molecular sieves show extremely high catalytic activity in the carbonylation process of dimethyl ether.

[0003] At present, the research on MOR molecular sieves mainly focuses on the regulation of acid sites, morphology, and pores. However, the synthesis of traditional molecular sieves only obtains powder samples. The powder is fine, difficult to recover, easy to lose, and not suitable for direct loading into large equipment. The catalyst must go through the molding process before it can be used in industrial applications. In the traditional MOR molecular sieve molding process, in order to improve the mechanical strength of the catalyst, binders such as silica sol and pseudo-boehmite are usually added. The type and content of the binder will directly affect the mechanical properties and catalytic properties of the catalyst. For example, it reduces the active components of the catalyst, covers the surface of the molecular sieve, and blocks pores and channels. If the binder is not added, the resulting molded molecular sieve often has low mechanical strength. If the binder is converted into the target molecular sieve through secondary crystallization, not only will the synthesis process be more complicated, but it will also increase the amount of organic template used. Organic templates are not only expensive, but also bring a large amount of wastewater and harmful gases produced by roasting.

[0004] Therefore, it is necessary to seek a synthesis route for MOR molecular sieves that does not use binders and organic templates and can self-form. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a binder-free self-forming MOR molecular sieve, which has a simple process, does not use a binder and an organic template, and has low cost.

[0006] Another object of the present invention is to provide the application of the MOR molecular sieve prepared by the above method.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] In one aspect, the present invention provides a method for preparing a binder-free self-forming MOR molecular sieve, comprising the following steps:

[0009] (1) Sodium hydroxide was dissolved in alkaline silica sol and stirred at room temperature for 30 min; then aluminum source was added and stirred for 1 h. The molar ratio of each component in the gel based on its oxide was SiO 2 :Al 2 O 3 :Na 2 O:H 2 O=1:0.05:0.20:7.79; after stirring, age at room temperature for 1h;

[0010] (2) transferring the gel prepared in step (1) to a hydrothermal autoclave, sealing it and crystallizing it at 170° C. for 5 days; cooling the obtained solid product after the crystallization is completed, washing and drying it to obtain a sodium-type MOR molecular sieve;

[0011] (3) placing the sodium-type MOR molecular sieve obtained in step (2) into an ammonium salt solution for ion exchange, repeating this process three times, and then washing, drying, and calcining to obtain a hydrogen-type MOR molecular sieve.

[0012] Preferably, the SiO 2 The mass fraction is 30%.

[0013] Preferably, the aluminum source in step (1) is selected from one of sodium aluminate, pseudo-boehmite, aluminum sulfate, aluminum hydroxide and aluminum chloride; more preferably, the aluminum source is sodium aluminate.

[0014] Preferably, the drying temperature in step (2) is 50° C. to 80° C., and the drying time is 12 hours.

[0015] Preferably, the ammonium salt described in step (3) is ammonium nitrate or ammonium chloride, the concentration of the ammonium salt solution is 1 mol / L, the conditions for ion exchange are: exchange temperature is 80° C., exchange time is 8 h, exchange times are 3 to 6 times, and the solid-liquid ratio of the sodium MOR molecular sieve to the ammonium salt solution is 1:100 g / mL.

[0016] Preferably, the ion exchange process in step (3) is carried out on a shaking bed.

[0017] Preferably, the drying temperature in step (3) is 100-120° C. and the drying time is 12 hours.

[0018] Preferably, the calcination temperature in step (3) is 550° C. and the calcination time is 12 h.

[0019] On the other hand, the present invention also provides the use of the MOR molecular sieve prepared by the above method in the carbonylation reaction of dimethyl ether to prepare methyl acetate.

[0020] The molar ratio of dimethyl ether to CO in the raw material is 1:(5-100), preferably 1:(5-50); the reaction temperature is 180-300°C, the reaction pressure is 1-3MPa; the gas hourly space velocity is 1000-5000h -1 .

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The method provided by the present invention does not use expensive and toxic organic templates in the entire preparation process, which not only reduces the production cost but also can be widely used in industrial production;

[0023] 2. The method provided by the present invention does not use a binder in the entire preparation process, which not only makes the molding of the molecular sieve easier, but also avoids the reduction of active components and the blockage of the molecular sieve pores caused by the addition of a binder;

[0024] 3. The preparation method provided by the present invention uses alkaline silica sol as a silicon source. The silica sol itself contains water, and no additional water needs to be added. In addition, the silica sol is added during the preparation process, and centimeter-scale MOR molecular sieves can be directly prepared in one pot, which is more suitable for industrial production and industrial application of molecular sieves.

[0025] 4. For the reaction of carbonylation of dimethyl ether to prepare methyl acetate, the molded MOR without adding a binder has a higher dimethyl ether conversion rate than the commercial MOR. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the XRD diagram of the shaped MOR molecular sieve prepared in Example 1, Example 2 and Example 3 of the present invention.

[0027] Figure 2 This is a scanning electron microscope image of the molded MOR molecular sieve prepared in Example 1 of the present invention.

[0028] Figure 3 This is a mechanical strength test diagram of the molded MOR molecular sieve prepared in Example 1 of the present invention.

[0029] Figure 4 This is an evaluation of the catalytic performance of the shaped MOR molecular sieve prepared in Example 1 of the present invention and the MOR molecular sieve of Comparative Example 1.

[0030] Figure 5 These are actual pictures of the shaped MOR molecular sieves prepared in Examples 1, 2, and 3 of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] 2.90 g of sodium hydroxide (96 wt%) was dissolved in 53.55 g of alkaline silica sol (SiO 2 The mass fraction of 30%) was stirred with a glass rod at the beginning of dissolution. After about 5 minutes, a homogeneous gel was formed. At this time, magnetic stirring was changed to 30 minutes. Then 2.77g sodium aluminate (Na 2 O:42.02%,Al 2 O 3 :51.24%)) and stirred for 1 hour. After the stirring, it was aged at room temperature for 1 hour, and then transferred to a hydrothermal kettle and hydrothermally crystallized at 170°C for 5 days. After the crystallization, the hydrothermal kettle was cooled with cold water, and the prepared molded catalyst was taken out. It was washed with deionized water until neutral, and dried in an oven at 50°C for 12 hours to obtain a sodium-type molded MOR molecular sieve.

[0034] Place the sodium-type formed MOR molecular sieve in a beaker, add 1.0 mol / L ammonium chloride solution to the beaker, and perform ion exchange for 8 hours at a water bath temperature of 80°C. After completion, wash with deionized water and dry in an oven at 110°C overnight. The solid-liquid ratio of the sodium-type formed MOR molecular sieve to the ammonium salt solution is 1:100 g / mL. The above ion exchange process is carried out on a shaking bed and repeated 3 times.

[0035] The prepared sample was calcined at 550°C for 12 h in air atmosphere to obtain the hydrogen-formed MOR molecular sieve.

[0036] Example 2

[0037] The masses of sodium hydroxide, alkaline silica sol and sodium metaaluminate were changed to 8.08 g, 149.46 g and 7.72 g respectively. The remaining preparation conditions were the same as those in Example 1.

[0038] Example 3

[0039] The masses of sodium hydroxide, alkaline silica sol and sodium metaaluminate were changed to 12.89 g, 238.42 g and 12.32 g respectively. The remaining preparation conditions were the same as those in Example 1.

[0040] Comparative Example 1

[0041] Commercial MOR (Si:Al ratio 20-25) was purchased from Yangzhou Zhonghe Petrochemical Co., Ltd.

[0042] The carbonylation performance of the MOR molecular sieves of Example 1 and Comparative Example 1 was tested. The molecular sieve was pressed into tablets, and the 40-60 mesh MOR molecular sieve was screened out and loaded into a stainless steel tube with an inner diameter of 8 mm. Quartz wool was filled at both ends of the catalyst bed. Before the test, Ar was introduced at a flow rate of 30 mL / min. Treated at 400°C for 2 h. After the heating was completed, the temperature was reduced to 200°C, and a mixed gas of dimethyl ether and carbon monoxide was introduced. The raw gas ratio was DME / Ar / CO=1 / 1.5 / 47.5, and the gas hourly space velocity was 3000 h -1 , the pressure is 1.5MPa.

[0043] Figure 1 The XRD spectra of the MOR molecular sieves of Example 1, Example 2, Example 3 and Comparative Example 1 are compared with the PDF card (PDF#43-0171) in the standard spectrum library, confirming that the obtained product is a MOR molecular sieve with high crystallinity.

[0044] Figure 2 This is a scanning electron microscope image of the MOR molecular sieve obtained in Example 1. The molded MOR is assembled from sheets of about 10 mm in size.

[0045] Figure 3 This is a mechanical strength test diagram of the binder-free molded MOR prepared in Example 1. The maximum crushing pressure of the molded catalyst is around 7000N, which meets the mechanical strength requirements of the molded catalyst in the industry.

[0046] Figure 4 The catalytic performance of the binder-free shaped MOR molecular sieve prepared in Example 1 and the commercial MOR molecular sieve was evaluated. Figure 3 As shown, the dimethyl ether conversion rate of the prepared binder-free shaped MOR molecular sieve is much higher than that of the commercial MOR molecular sieve.

[0047] Figure 5 The shaped MOR molecular sieves were prepared using hydrothermal reactors of different sizes. 100mL (Example 1), 250mL (Example 2), and 400mL (Example 3) hydrothermal reactors can successfully prepare shaped molecular sieves. This shows that this preparation method has high repeatability and can be expanded for production.

[0048] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a binder-free self-forming MOR molecular sieve, characterized in that: The following steps are involved: (1) dissolving sodium hydroxide in alkaline silica sol, wherein the mass fraction of SiO2 in the alkaline silica sol is 30%, stirring at room temperature for 30 minutes; then adding aluminum source, stirring for 1 hour, the molar ratio of each component in the gel in terms of its oxide is SiO2:Al2O3:Na2O:H2O = 1:0.05:0.20:7.79; aging at room temperature for 1 hour after stirring; (2) Transfer the gel prepared in step (1) to a hydrothermal reactor, seal it and heat it at 170 o C crystallize for 5 days; after the crystallization is completed, the temperature is cooled, and the obtained solid product is washed and dried to obtain the sodium-type MOR molecular sieve; (3) The sodium-type MOR molecular sieve obtained in step (2) is placed in an ammonium salt solution for ion exchange, and the process is repeated three times, followed by washing, drying, and calcining to obtain a hydrogen-type MOR molecular sieve.

2. The method for preparing a binder-free self-forming MOR molecular sieve according to claim 1, characterized in that: The aluminum source in step (1) is selected from one of sodium aluminate, pseudo-boehmite, aluminum sulfate, aluminum hydroxide and aluminum chloride.

3. The method for preparing a binder-free self-forming MOR molecular sieve according to claim 1, characterized in that: The drying temperature in step (2) is 50 o C~80 o C, time is 12h.

4. The method for preparing a binder-free self-forming MOR molecular sieve according to claim 1, characterized in that: The ammonium salt in step (3) is ammonium nitrate or ammonium chloride, the concentration of the ammonium salt solution is 1 mol / L, and the ion exchange conditions are: the exchange temperature is 80 o C, the exchange time is 8 h, the number of exchanges is 3 to 6 times, and the solid-liquid ratio of the sodium MOR molecular sieve to the ammonium salt solution is 1:100 g / mL.

5. The method for preparing a binder-free self-forming MOR molecular sieve according to claim 1, characterized in that: The ion exchange process described in step (3) is carried out on a shaking bed.

6. The method for preparing a binder-free self-forming MOR molecular sieve according to claim 1, characterized in that: The drying temperature in step (3) is 100-120 o C, time is 12h.

7. The method for preparing a binder-free self-forming MOR molecular sieve according to claim 1, characterized in that: The calcination temperature in step (3) is 550 o C, time is 12h.

8. Use of the MOR molecular sieve prepared by the method according to any one of claims 1 to 7 in the carbonylation reaction of dimethyl ether to prepare methyl acetate.

9. The use according to claim 8, characterized in that: The molar ratio of dimethyl ether to CO in the raw material is 1:5~50; the reaction temperature is 180~300 o C; reaction pressure is 1~3MPa; gas hourly space velocity is 1000~5000h -1 .

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