Preparation method of compound solid superacid dimethyl ether catalyst

Abstract

The invention discloses a preparation method of a compound solid superacid dimethyl ether catalyst. The method comprises the following steps: 1, preparing tungsten oxide-zirconium oxide solid superacid; and 2, preparing the titanium oxide solid superacid. And 3, mixing and kneading the two solid superacid, the gamma alumina carrier and the binder according to corresponding mass, adding rare earth element dysprosium by an equivalent-volume impregnation method, drying and roasting to obtain the required compound solid superacid dimethyl ether catalyst. The dimethyl ether catalyst prepared by the invention has the characteristics of high conversion rate and good selectivity, and especially has better anti-interference capability on water, alcohol, ester, organic acid and acetone.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a dimethyl ether catalyst, in particular to a preparation method of a compounded solid superacid dimethyl ether catalyst. BACKGROUND

[0002] In 2005, the dimethyl ether industry in China realized the initial industrial breakthrough by introducing the technologies of Germany Lurgi and Japan JFE. With the development of domestic catalysts such as CNM-3 (Chinese patent CN 106984296 B) of the Southwest Chemical Research Institute and WD-1 (Chinese patent CN 101168131 B) of Wuhan Kelin Company, by 2008, the total dimethyl ether production capacity in China had broken through 2 million tons / year. At that time, dimethyl ether mainly entered the civil fuel market as a blending agent of liquefied petroleum gas (LPG), and by 2010, the blending ratio in LPG reached 15%-20%, driving the market size to break through 8 billion yuan. However, at this stage, there was also the problem of over-expansion of initial production capacity and less than 60% actual operation rate. In 2011, the General Administration of Quality Supervision of the People's Republic of China issued the "Dimethyl Ether Blended Gas Standard for Urban Gas" (GB / T 25035-2010), which clearly stipulated that the upper limit of the legal blending ratio was 20%, which led to the reduction of demand in some non-compliant markets, and a batch of small and medium-sized enterprises were eliminated under the tightening regulation, and the dimethyl ether industry entered a trough period.

[0003] Almost at the same time, with the popularization of ethanol gasoline, the ethanol industry developed vigorously. The production methods of ethanol are mainly biological fermentation method and chemical synthesis method. Although the "Standard for Ethanol Gasoline for Vehicles" (GB / T 18351-2017) stipulates that ethanol in gasoline must come from the biological fermentation method, this method has the serious problem of competing with people for food, and the purification of fermented ethanol is relatively complex. From the perspective of atomic economy and environmental protection, the chemical method has obvious advantages. The chemical method can be divided into petrochemical route and coal chemical route. The petrochemical route mainly refers to the ethylene hydration method, which is subject to the production capacity of ethylene and does not conform to the national conditions of more coal and less oil in China. The coal chemical route can be divided into acetic acid method and dimethyl ether method. Compared with the two methods, the production cost of the dimethyl ether method is much lower.

[0004] In 2013, Professor Liu Zhongmin's team of the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences invented a dimethyl ether carbonylation catalyst for methyl acetate (Chinese patent CN 106890665 B), and developed a process for synthesizing anhydrous ethanol (DMTE) from synthesis gas through dimethyl ether carbonylation with the catalyst as the core. The process can be summarized as follows: Synthesis gas -> methanol -> dimethyl ether -> methyl acetate -> ethanol + methanol In 2017, the first 100,000 tons / year industrial demonstration device in the world successfully ran in Shaanxi Yanchang Petroleum, and the technology officially entered the large-scale industrialization stage. As of early 2025, the cumulative production capacity of DMTE process ethanol has reached nearly 5 million tons. The rapid development of the technology has also doubled the demand for dimethyl ether catalysts.

[0005] In the front section of the DMTE process, in addition to fresh methanol, the methanol produced by the hydrogenation of methyl acetate is also included. This part of the methanol contains a small amount of impurities, including water, alcohol, ester, organic acid and acetone. Impurities participating in the dehydration reaction may affect the purity of dimethyl ether, which is a new challenge for dimethyl ether catalysts. Therefore, it is of positive significance to develop a dimethyl ether catalyst that can maintain high selectivity under the influence of various impurities in the DMTE process. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a catalyst for the dehydration of methanol to dimethyl ether, which has high conversion rate and is less affected by impurities such as water, alcohol, ester, organic acid and acetone.

[0007] The technical solution adopted by the present application is: Preparation of solid superacid a.

[0008] Step one, dissolve ammonium metatungstate and zirconium oxychloride in deionized water respectively, slowly add the ammonium metatungstate solution to the zirconium oxychloride solution under continuous stirring, Step two, add 14% urea precipitant, control the pH value of the solution to 8-10, and generate gelatinous precipitate. The obtained precipitate is placed together with the solution at 0℃ for aging for 24 hours. Then filter and repeatedly wash the filter cake with deionized water until there is no chloride ion in the filtrate. The washed filter cake is preliminarily dried at 120℃.

[0009] Step three, grind the dried solid into fine powder, immerse it in 10% ammonium phosphate solution for 12 hours, so that phosphate ions are fully adsorbed on the surface of zirconium hydroxide. Dry the immersed solid at 120℃ and calcine it at 600℃ for 6 hours to obtain solid superacid a.

[0010] Preparation of solid superacid b.

[0011] Step one, dissolve titanium tetrachloride in deionized water, then add 14% urea precipitant, control the pH value of the solution to 8-10, and generate gelatinous precipitate. The obtained precipitate is placed together with the solution at 0℃ for aging for 24 hours. Then filter and repeatedly wash the filter cake with deionized water until there is no chloride ion. The washed filter cake is preliminarily dried at 120℃.

[0012] Step two, the dried solid is ground into fine powder, then immersed in 12% of ammonium thiosulfate solution for 12 hours, so that the thiosulfate ions are fully adsorbed on the surface of titanium hydroxide. The immersed solid is dried again, then calcined at 500-600°C for 6 hours to prepare solid super acid b.

[0013] The solid super acid a and the solid super acid b are kneaded with γ-alumina carrier and binder. An equal volume of 1% dysprosium nitrate solution is impregnated. After the catalyst is extruded into a strip, it is dried at 120°C, and calcined at 600°C for 4 hours to prepare a compounded solid super acid dimethyl ether catalyst.

[0014] The dimethyl ether catalyst prepared by the present application can still maintain a conversion rate of more than 80% when the water content of methanol is as high as 5%. In the presence of ethanol, methyl acetate, acetic acid and acetone impurities, the selectivity is not less than 99.4%. The catalyst has good anti-interference ability for impurities that may be introduced in the DMTE process. DETAILED DESCRIPTION

[0015] The following specific examples further illustrate the above content of the present application. However, it should not be understood that the scope of the invention is limited to the following embodiments. Any technology realized based on the above content of the present application falls within the scope of the present application.

[0016] Preparation of solid super acid a Ammonium metatungstate 11.78g, zirconium oxychloride 130.89g, are dissolved in deionized water respectively, and continuously stirred. The ammonium metatungstate solution is slowly added to the zirconium oxychloride solution, and then a 14% mass concentration urea precipitant is added. The pH value of the solution is controlled to be in the alkaline range of 8-10, and a gel-like precipitate is generated. The obtained precipitate is placed together with the solution at 0°C for aging for 24 hours. Then, filtration is performed, and the filter cake is repeatedly washed with deionized water until the chloride ions are washed out. The washed filter cake is preliminarily dried at 120°C. The dried solid is ground into fine powder, then immersed in 10% of ammonium phosphate solution for 12 hours, so that the phosphate ions are fully adsorbed on the surface of zirconium hydroxide. The immersed solid is dried again, then calcined at 600°C for 6 hours to prepare solid super acid a.

[0017] Preparation of solid super acid b 189.7 g of titanium tetrachloride was dissolved in deionized water, and then 14% urea precipitant was added to control the pH of the solution to an alkaline range of 8-9, thereby forming a gel-like precipitate. The precipitate and solution were allowed to stand at 0°C for 24 hours. The mixture was then filtered, and the filter cake was repeatedly washed with deionized water until chloride ions were removed. The washed filter cake was then preliminarily dried at 120°C. The dried solid was ground into a fine powder and then immersed in a sodium thiosulfate solution of a certain concentration for 12 hours to allow thiosulfate ions to be fully adsorbed onto the surface of titanium hydroxide. The impregnated solid was dried again and then calcined at 600°C for 6 hours to obtain solid superacid b. Example 1

[0018] Mix 100g of γ-alumina support and 2g of citric acid. Add 1% dysprosium nitrate solution by equal volume impregnation. After extruding the catalyst into strips, dry them and calcine them at 600℃ for 4 hours to obtain a blank sample of dimethyl ether catalyst.

[0019] Examples 2-8 0.2g, 0.5g, 1g, 2g, 3g, 4g, and 5g of solid superacid a were respectively mixed with 100g of γ-alumina and 2g of citric acid. An equal volume of 1% dysprosium nitrate solution was then added via impregnation. The mixtures were extruded, dried, and calcined at 600℃ for 4 hours to obtain the catalyst samples described in Examples 2-8.

[0020] The catalyst evaluation feedstock consisted of methanol mixed with 5% water, 1% ethanol, 0.5% methyl acetate, 0.1% acetic acid, and 0.1% acetone.

[0021] Evaluation method: Measure 30 ml of the original particle size catalyst sample of this invention, place it in a high-pressure reactor, heat to 260°C, and after the raw material is gasified, preheat to 240°C and introduce into the reactor. Adjust the system pressure to 0.8 MPa and the liquid hourly space velocity of the raw material to 2 h⁻¹. -1 The effluent components were analyzed using gas chromatography, and the conversion rate and selectivity for dimethyl ether were calculated. The results are shown in Table 1, which also includes the performance of the blank catalyst in Example 1 without the addition of a solid superacid.

[0022] Table 1. Catalyst performance with different amounts of solid superacid a added. Example 1 2 3 4 5 6 7 8 Amount of acid a, g / 100 g 0 0.2 0.5 1 2 3 4 5 Ethanol, % 0.90 0.61 0.57 0.50 0.43 0.36 0.29 0.21 Methyl acetate, % 0.50 0.49 0.49 0.49 0.49 0.49 0.48 0.46 Acetic acid, % 0.09 0.05 0.05 0.04 0.04 0.03 0.02 0.01 Acetone, % 0.09 0.09 0.09 0.09 0.09 0.08 0.07 0.06 Conversion, % 60.1 69.2 77.5 83.2 83.5 83.7 84.0 84.3 Selectivity, % 99.5 99.5 99.5 99.5 99.4 99.2 98.9 98.5 As shown in Table 1, with increasing addition of solid superacid a, the catalyst conversion rate increases while the selectivity decreases. The catalyst exhibits relatively weak resistance to interference from ethanol and acetic acid, but relatively strong resistance to interference from ethyl acetate and acetone. The optimal amount of solid superacid a is 1–3 g / 100 g.

[0023] Examples 9-15 0.2g, 0.5g, 1g, 2g, 3g, 4g, and 5g of solid superacid b were respectively mixed with 100g of γ-alumina and 2g of citric acid. An equal amount of 1% dysprosium nitrate solution was added via impregnation. After extrusion molding and drying, the mixture was calcined at 600℃ for 4 hours to obtain the catalyst samples described in Examples 9-15.

[0024] The raw materials and methods for evaluating the catalyst are the same as those in embodiments 2-8.

[0025] The test results are shown in Table 2, which also includes the performance of the blank catalyst in Implementation 1 without the addition of solid superacid.

[0026] Table 2. Catalyst performance with different amounts of solid superacid b added. Example 1 9 10 11 12 13 14 15 Amount of acid b, g / 100 g 0 0.2 0.5 1 2 3 4 5 Ethanol, % 0.90 0.61 0.55 0.48 0.39 0.31 0.21 0.12 Methyl acetate, % 0.50 0.49 0.49 0.49 0.49 0.49 0.48 0.46 Acetic acid, % 0.09 0.08 0.08 0.08 0.08 0.07 0.06 0.05 Acetone, % 0.09 0.05 0.05 0.04 0.04 0.03 0.02 0.01 Conversion, % 60.1 68.3 75.3 80.1 80.5 80.7 81.1 81.8 Selectivity, % 99.5 99.4 99.4 99.4 99.3 99.0 98.8 98.5 Table 2 shows that as the amount of solid superacid b added increases, the catalyst conversion rate increases, but the selectivity decreases. The catalyst has relatively weak resistance to interference from ethanol and acetone, but relatively strong resistance to interference from acetic acid and ethyl acetate. The optimal amount of solid superacid b is 1~3 g / 100 g.

[0027] Examples 16-22

[0028] Based on the orthogonal experimental results above, dimethyl ether catalysts 16-22, composed of compound solid superacids a and b, were prepared using the same method. The catalysts were evaluated using the same raw materials and methods. The results are shown in Table 3.

[0029] Table 3. Catalyst performance when the amounts of solid superacid a and solid superacid b added are different. Example 16 17 18 19 20 21 22 23 24 Amount of acid a, g / 100 g 1 2 3 1 2 3 1 2 3 Amount of acid b, g / 100 g 1 1 1 2 2 2 3 3 3 Ethanol, % 0.49 0.46 0.42 0.44 0.42 0.38 0.40 0.37 0.34 Methyl acetate, % 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 0.49 Acetic acid, % 0.08 0.08 0.07 0.08 0.08 0.06 0.08 0.06 0.05 Acetone, % 0.09 0.09 0.08 0.09 0.08 0.06 0.07 0.06 0.05 Conversion, % 81.3 83.7 83.9 83.6 83.9 84.1 83.5 83.9 84.5 Selectivity, % 99.5 99.4 99.4 99.5 99.5 99.1 99.4 99.0 98.8 As can be seen from Table 3, when the total amount of solid superacid a and solid superacid b is 3~4g / 100g, the conversion rate of the catalyst exceeds 83.5% under the synergistic effect of solid superacid a and solid superacid b, and the conversion rate exceeds 99.4%. In addition, the anti-interference ability of methyl acetate, acetic acid and acetone is significantly improved.

[0030] Comparative Examples 1-3

[0031] Take 1g of solid superacid a and 1g of solid superacid b; 2g of solid superacid a and 2g of solid superacid b; 3g of solid superacid a and 3g of solid superacid b, and mix them evenly with 100g of γ-alumina and 2g of citric acid, without impregnating with dysprosium nitrate solution. After extrusion and drying, calcine at 600℃ for 4 hours to obtain catalyst samples of comparative examples 1, 2, and 3.

[0032] The same raw materials and methods were used for evaluation, and the results were compared with those of Examples 16, 20, and 24, which were impregnated with dysprosium nitrate. The results are shown in Table 4.

[0033] Table 4. The effect of dysprosium on catalyst performance Example 16 Comparative Example 1 Example 20 Comparative Example 2 Example 24 Comparative Example 3 Ethanol, % 0.49 0.34 0.42 0.25 0.34 0.14 Methyl acetate, % 0.49 0.49 0.49 0.48 0.49 0.48 Acetic acid, % 0.08 0.08 0.08 0.08 0.05 0.05 Acetone, % 0.09 0.09 0.08 0.08 0.05 0.05 Conversion, % 81.3 81.3 83.9 83.9 84.5 84.5 Selectivity, % 99.5 99.4 99.5 99.3 98.8 98.5 As can be seen from Table 4, the addition of the rare earth element dysprosium inhibited the effect of ethanol on the synthesis reaction of dimethyl ether.

Claims

1. A method for preparing a composite solid superacid dimethyl ether catalyst, characterized in that, The catalyst is prepared by: Step 1: Based on the carrier mass, take 1%~3% solid superacid a; Step 2: Based on the carrier mass, take 1%~3% solid superacid b; Step 3: Mix with γ-alumina support and 2% binder, then extrude the catalyst into strips and dry them; Step 4: Impregnate an equal volume of the sample with a 1% dysprosium nitrate solution and calcine at 600°C for 4 hours.

2. The method for preparing a compound solid superacid dimethyl ether catalyst according to claim 1, characterized in that, The preparation method of the solid superacid a is as follows: Step 1: Dissolve ammonium metatungstate and zirconium oxychloride separately in deionized water, and slowly add the ammonium metatungstate solution dropwise to the zirconium oxychloride solution while stirring continuously. Step 2: Add urea precipitant and control the pH of the solution to 8-10 to generate a gel-like precipitate. Let the precipitate and solution stand at 0°C for 24 hours, then filter and wash the filter cake with deionized water until there are no chloride ions in the filtrate. Dry the washed filter cake at 120°C. Step 3: After the dried solid is ground into a fine powder, it is impregnated with ammonium phosphate solution for 12 hours, the impregnated solid is dried at 120°C, and then calcined at 600°C for 6 hours to obtain solid superacid a.

3. The method for preparing a compound solid superacid dimethyl ether catalyst according to claim 1, characterized in that, The preparation method of the solid superacid b is as follows: Step 1: Dissolve titanium tetrachloride in deionized water, add urea precipitant, and control the pH of the solution to 8-10 to generate a gel-like precipitate. Let the precipitate and solution stand at 0°C for 24 hours, then filter and wash the filter cake repeatedly with deionized water until there are no chloride ions in the filtrate. Dry the washed filter cake at 120°C. Step 2: After the dried solid is ground into a fine powder, it is impregnated with ammonium thiosulfate solution for 12 hours, the impregnated solid is dried at 120°C, and then calcined at 500-600°C for 6 hours to obtain solid superacid b.

4. The method for preparing a compound solid superacid dimethyl ether catalyst according to claim 1, characterized in that, The support used to prepare the catalyst was γ-alumina.

5. The method for preparing a compound solid superacid dimethyl ether catalyst according to claim 1, characterized in that, The rare earth element used in the catalyst support modification is dysprosium.