CN101396667B - V2O5 composite catalyst loaded by Ce-V-Ti-O meso-material - Google Patents

Abstract

The invention relates to a V2O5 composite catalyst which is loaded by Ce-V-Ti-O meso-porous material. The catalyst comprises vanadium oxide and titanium sulfate which are loaded and measured by the Ce-V-Ti-O meso-porous material. The content of vanadium is counted as 10-30 percent in the weight of vanadium pentoxide, the priority range is 10-20 percent, and the loaded amount of the titanium sulfate is counted as 0.6-6 percent in the weight of sulfate. The catalyst can be used for the synthesis of methylal from the selective oxidation of methanol. The Ce-V-Ti-O meso-porous material, butyl titanate, V2O5, CeCl3 and template agent P123(PEO)20(PPO)70(PEO)20 (MW equal to 5800) are synthesized under hydrothermal condition. The prepared catalyst is applied to the synthesis of methylal from methanol in a one-step method. The conversion rate of methanol can reach 20-78 percent and the selectivity of the methylal can reach 85.0-97.9 percent.

Description

A V2O5 Composite Catalyst Supported by Ce-V-Ti-O Mesoporous Material

1. Technical field

The invention relates to a V ₂ O ₅ composite catalyst supported by a Ce-V-Ti-O mesoporous material and a preparation method thereof. The catalyst can be used for methanol oxidation to produce methylal.

2. Background technology

Since the discovery of mesoporous MCM silicon series molecular sieves by Beck et al. of Mobile Company, mesoporous materials have attracted extensive attention due to their potential applications in catalysis, adsorption separation, advanced materials and other fields. Among them, the synthesis of _TiO2 mesoporous materials with semiconductor properties is one of the hotspots in the research field, mainly because _TiO2 can be used as a catalyst carrier, photocatalyst, sensor, and energy storage. However, most of the synthesized mesoporous _TiO2 has low thermal stability, and its mesoporous structure is severely damaged above 400 °C, which limits its application as a catalyst support. At present, there are several reports on the high thermal stability of mesoporous TiO ₂ . For example, Yang Peidong synthesized mesoporous TiO ₂ with high thermal stability by using non-ionic tri-block surfactant (Nature, 1998, Vol. 396, No. 152 -155 pages), Le Yinghong reported that mesoporous TiO ₂ doped with trace amounts of Ce can improve thermal stability (Chemical Communications, 2000, pages 1755-1756). The synthesis of high specific surface area mesoporous Ce-V-Ti oxides with high thermal stability has not been reported yet.

Supported vanadium oxides, such as V ₂ O ₅ supported on TiO ₂ , are an important class of catalysts, which can be widely used in industrial reactions such as selective oxidation of hydrocarbons, selective reduction of NOx, ammonia oxidation and oxidative dehydrogenation of alkanes. It is generally believed that increasing the surface area of the support (such as TiO ₂ ) and increasing the number of reducible vanadium species under the single-layer dispersion capacity can improve the reaction performance of vanadium-based catalysts.

Methylal is chemically also known as dimethoxymethane (CH ₃ OCH ₂ OCH ₃ ). Because of its very low toxicity, it can be used as a solvent for the production of fragrances and synthetic drugs. It has low toxicity and high hydrogen content and can be used to replace highly toxic methanol for Hydrogen production by steam reforming (Journal of Catalysis, Volume 1, 2007, pages 101-110; Volume 1, 2006, pages 1-9), can also be used as an intermediate for the production of polyoxymethylene, and polyoxymethylene is a As an important engineering plastic, it is widely used in the automobile industry. In addition, due to the potential application of methylal in the field of diesel additives, methylal has attracted more and more attention.

At present, methylal is mainly formed by the dehydration condensation of methanol and formaldehyde on an acidic catalyst. Commonly used acidic catalysts include inorganic acids, acidic molecular sieves, and macroporous cationic acidic resins. Since formaldehyde can be produced by selective oxidation of methanol on silver-based or iron-molybdenum series catalysts, the direct catalytic oxidation of methanol to produce methylal under suitable acidic conditions has attracted the attention of academia and industry. As disclosed in Chinese patent 200410065321.6, a sulfate-modified vanadium-titanium oxide catalyst can obtain a methanol conversion rate of 48% and a methylal selectivity close to 90% under mild conditions (150° C.), and the catalyst surface area used is about It is 90m ² /g. Increasing the surface area of the support and increasing the number of available vanadyl species can further enhance the catalytic performance of the catalyst.

3. Contents of the invention

Mesoporous Ce-V-Ti-O has high surface area and uniform pore structure. As a carrier, it can further support V ₂ O ₅ under the single-layer dispersion capacity and improve the catalytic performance of the catalyst.

The object of the present invention is to provide a V ₂ O ₅ composite catalyst supported by Ce-V-Ti-O mesoporous material and its preparation method, the catalyst can be used for the selective oxidation of methanol to produce methylal.

Technical scheme of the present invention is as follows:

A V ₂ O ₅ composite catalyst supported by Ce-V-Ti-O mesoporous material is composed of vanadium oxide and titanium sulfate supported by Ce-V-Ti-O mesoporous material. The content of vanadium is 10-30% by mass of vanadium pentoxide, preferably 10-20%, and the loading of titanium sulfate is 0.6-6% by mass of sulfate radical. The catalyst can be used in the selective oxidation of methanol to synthesize methylal.

A preparation method of the above Ce-V-Ti-O mesoporous material supported V ₂ O ₅ composite catalyst. It is characterized in that: mix ammonium metavanadate and oxalic acid at a mass ratio of 1:2, add water to dissolve to obtain a dark green solution, and add a metered amount of Ce-V-Ti-O mesoporous material to the solution to make Ce- The mass ratio of V-Ti-O mesoporous material to ammonium metavanadate is 1:0-1:0.55, the mixture is stirred for 10 minutes, and dried at room temperature for 20-40 hours to obtain solid A. Dissolve the measured amount of titanium sulfate in water, immerse the above solid A in the titanium sulfate solution, stir for 5-10 minutes, dry at room temperature for 20-40 hours, and bake in air at 350-450°C for 3-8 hours to obtain Ce - V ₂ O ₅ catalyst supported by V-Ti-O mesoporous material.

The above Ce-V-Ti-O mesoporous material is composed of butyl titanate, V ₂ O ₅ , CeCl ₃ and template agent P 123 with molecular formula (PEO) ₂₀ (PPO) ₇₀ (PEO) ₂₀ , MW=5800 , prepared as follows:

(1) Mix P123 and absolute ethanol at 1 g: 30-50 ml, stir for 20 minutes until P123 is completely dissolved, add measured CeCl ₃ , slowly add butyl titanate dropwise, and stir for 1-5 hours to obtain a clear solution A, Wherein the molar ratio of Ce:Ti is 0.03-0.08:1, and the molar ratio of P123 and butyl titanate is 0.02-0.05:1;

(2) Under an ice-water bath, mix 30% hydrogen peroxide and absolute ethanol at a volume ratio of 1:4-6, and add metered V ₂ O at a ratio of 1 g V ₂ O per ₁₀ ml of hydrogen peroxide with stirring. _5. Continue to stir until completely dissolved to obtain solution B;

(3) Add solution B to solution A, stir rapidly, and form a gel after about 5 minutes, then add metered water, transfer to a hydrothermal kettle, hydrothermal synthesis at 110-150°C for 12-48 hours, hydrothermal The filling degree of the kettle is 70-90%, the molar ratio of the added water to the total amount of titanium and _vanadium is 80-105:1, the V content is 0-20% based on _V2O5 mass, and the V content is not "0 ", the precipitate obtained by hydrothermal synthesis is filtered, washed with water three times, washed with absolute ethanol once, dried at room temperature for 24-48 hours, and roasted at 350-450°C for 3-8 hours to obtain Ce-V-Ti- O mesoporous materials.

The method for the V ₂ O ₅ composite catalyst supported by the Ce-V-Ti-O mesoporous material of the present invention to be used for the selective oxidation of methanol to synthesize methylal is as follows: the catalyst of the present invention is loaded in the reactor, and the temperature of the reactor is controlled at 120- 160°C, feed the mixture of methanol vapor and oxygen-containing gas preheated to 120-160°C, the molar ratio of methanol to oxygen is 5:1 to 5:15, and the volume percentage of methanol in the mixed gas is 5%. The total flow rate of the gas entering is 1.1×10 ³ ml/hour per gram of catalyst to obtain methylal. The oxygen-containing gas can be pure O ₂ , air, or nitrogen or helium containing molecular O ₂ .

The V ₂ O ₅ composite catalyst supported by the Ce-V-Ti-O mesoporous material of the present invention has a high surface area and a mesoporous structure. Using the catalyst, methanol can be selectively oxidized to produce methylal. Methanol can be produced at a temperature of 120-160°C. The conversion rate can reach 20-78%, and the methylal selectivity can reach 55.0-97.9%.

4. Specific implementation

The present invention will be further described with following examples:

Example 1:

Dissolve 6.0 g of P123 in 35 ml of absolute ethanol solution, add 0.9 g of CeCl ₃ , stir at room temperature until completely dissolved, add 17.0 g of butyl titanate dropwise, and stir for 1 hour to obtain solution A. Dissolve 4ml of 30% hydrogen peroxide in 20ml of ethanol, and then add 0.4g of V ₂ O ₅ to obtain solution B after complete dissolution. Add solution B to solution A and form a gel under stirring. The gel was transferred to an autoclave, 75ml of water was added, and hydrothermal reaction was carried out in an oven at 120°C for 24 hours. Cool to room temperature, filter, wash the filter cake three times with deionized water and once with absolute ethanol, dry at room temperature for 24 hours, and calcinate at 400°C for 8 hours to obtain a light yellow Ce-V-Ti-O mesoporous material. Its surface area was determined to be 162m ² /g, the pore diameter was 5.0nm, the pore volume was 0.27ml/g, and the vanadium content was 9.6% (calculated by the mass percentage of vanadium pentoxide).

Example 2:

Dissolve 6.0 g of P123 in 35 ml of absolute ethanol solution, add 0.9 g of CeCl ₃ , stir at room temperature until completely dissolved, add 17.0 g of butyl titanate dropwise, and stir for 1 hour to obtain solution A. Dissolve 7ml of 30% hydrogen peroxide in 20ml of ethanol, and then add 0.7g of V ₂ O ₅ to obtain solution B after complete dissolution. Add solution B to solution A and form a gel under stirring. The gel was transferred to an autoclave, 72ml of water was added, and hydrothermal reaction was carried out in an oven at 120°C for 24 hours. The obtained precipitate was filtered, washed three times with deionized water, washed once with absolute ethanol, dried at room temperature for 24 hours, and finally calcined at 400°C for 6 hours to obtain a light yellow Ce-V-Ti-O mesoporous material. Its surface area was determined to be 159m ² /g, the pore diameter was 3.6nm, the pore volume was 0.2ml/g, and the vanadium content was 19.8% (calculated by the mass percentage of vanadium pentoxide).

Example 3:

Add 1.2g of titanium sulfate into a 150ml crucible, add 15ml of distilled water to dissolve it, then add 14.2g of the Ce-V-Ti-O mesoporous material prepared in Example 1, stir to form a paste, dry at room temperature, and roast at 400°C for 3.5 Hours, the composite catalyst was obtained, and the vanadium content was 9.6% (by mass percentage of vanadium pentoxide), and the sulfur was 3.9% (by mass percentage of sulfate radical). The prepared catalyst was pressed into tablets, crushed, and sieved to be 20-40 mesh for activity determination. Using a Φ8mm U-shaped tube reactor, preheat the mixed gas of 5% methanol, 15% _O2 , and 80% _N2 by volume to 120°C and feed it into the reactor. When the reaction temperature is 150°C, the analysis The conversion rate of methanol is 25%, the selectivity of methylal is 91.6%, the selectivity of formaldehyde is 1.1%, the selectivity of dimethyl ether is 3.9%, and the selectivity of methyl formate is 3.4%.

Methanol conversion and product selectivity are calculated by the following method:

Example 4:

Add 1.7g of titanium sulfate to a 150ml crucible, add 21ml of distilled water to fully dissolve it, then add 17.2g of the Ce-V-Ti-O mesoporous material prepared in Example 2, stir to form a paste, and dry at room temperature for 30 hours. Calcined at ℃ for 4 hours to obtain a composite catalyst, in which the vanadium content was measured to be 19.6% (in terms of mass percentage of vanadium pentoxide), and the sulfur content was 2.3% (in terms of mass percentage of sulfate radical). The prepared composite catalyst was pressed into tablets, crushed, and sieved to 20-40 mesh for activity determination. Using a Φ8mm U-shaped tube reactor, preheat the mixed gas of 5% methanol, 15% _O2 , and 80% _N2 by volume to 120°C and feed it into the reactor. When the reaction temperature is 150°C, the analysis The conversion rate of methanol was 41%, the selectivity of methylal was 92.0%, the selectivity of formaldehyde was 1.0%, the selectivity of dimethyl ether was 1.0%, and the selectivity of methyl formate was 6.0%.

Example 5:

Mix 2.3g of ammonium metavanadate and 4.8g of oxalic acid, add 13ml of water, stir and dissolve to obtain a dark green solution, add 14.2g of the Ce-V-Ti-O mesoporous material prepared in Example 1 to the upper solution, and stir at room temperature to form In the form of a paste, it was dried at room temperature for 40 hours to obtain a solid sample. Dissolve 1.4g of titanium sulfate in 10ml of water, add the above solid sample, stir at room temperature to form a paste, dry at room temperature for 30 hours, and bake in air at 400°C for 6 hours to obtain Ce-V-Ti-O mesoporous material supported V ₂ O ₅ composite catalyst. It is measured that the vanadium content is 19.2% (in the mass percentage of vanadium pentoxide), and the sulfur is 5.0% (in the mass percentage of sulfate radical). The prepared composite catalyst was pressed into tablets, crushed, sieved, and the particle size of 20-40 mesh was taken for activity detection. Using a Φ8mm U-shaped tube reactor, preheat the mixed gas of 5% methanol, 15% O ₂ , and 80% N ₂ by volume to 120°C and feed it into the reactor. When the reaction temperature is 145°C, the measured The conversion rate of methanol was 57%, the selectivity of methylal was 92.0%, the selectivity of formaldehyde was 0, the selectivity of dimethyl ether was 0.3%, and the selectivity of methyl formate was 7.7%. When the reaction temperature was 150°C, It was measured that the conversion rate of methanol was 72%, the selectivity of methylal was 85.0%, the selectivity of formaldehyde was 0.4%, the selectivity of dimethyl ether was 0.8%, and the selectivity of methyl formate was 13.8%.

Claims (3)

1. a kind of Ce-V-Ti-O mesoporous material supported V ₂ O ₅ composite catalyst, it is made of vanadium oxide and titanium sulfate of Ce-V-Ti-O mesoporous material load metering, wherein vanadium The content is 10-30% based on the mass of vanadium pentoxide, and the loading amount of titanium sulfate is 0.6-6% based on the mass of sulfate radicals. The catalyst can be used for the selective oxidation of methanol to synthesize methylal; The Ce-V-Ti-O mesoporous material consists of butyl titanate, V ₂ O ₅ , CeCl ₃ and template agent P123 with molecular formula (PEO) ₂₀ (PPO) ₇₀ (PEO) ₂₀ , MW=5800, Prepare as follows: (1) Mix P123 and absolute ethanol at 1 g: 30-50 ml, stir for 20 minutes until P123 is completely dissolved, add measured CeCl ₃ , slowly add butyl titanate dropwise, and stir for 1-5 hours to obtain a clear solution A, Wherein the molar ratio of Ce:Ti is 0.03-0.08:1, and the molar ratio of P123 and butyl titanate is 0.02-0.05:1; (2) Under an ice-water bath, mix 30% hydrogen peroxide and absolute ethanol at a volume ratio of 1:4-6, and add metered V ₂ O at a ratio of 1 g V ₂ O per ₁₀ ml of hydrogen peroxide with stirring. _5. Continue to stir until completely dissolved to obtain solution B; (3) Add solution B to solution A, stir rapidly, and form a gel after about 5 minutes, then add metered water, transfer to a hydrothermal kettle, hydrothermal synthesis at 110-150°C for 12-48 hours, hydrothermal The filling degree of the kettle is 70-90%, the molar ratio of the added water to the total titanium vanadium is 80-105:1, the V content is 0-20% based on V ₂ O ₅ mass, and the V content is not "0" , the resulting precipitate was filtered, washed three times with water and once with absolute ethanol, dried at room temperature for 24-48 hours, and calcined at 350-450°C for 3-8 hours to obtain Ce-V-Ti-O mesoporous material. 2. a kind of V of claim 1 described in Ce-V-Ti-O mesoporous material load ₂ O The preparation method of ₅ composite catalysts, it is characterized in that: with the mass ratio of ammonium metavanadate and oxalic acid 1: 2 Proportional mixing, adding water to dissolve to obtain a dark green solution, adding a metered amount of Ce-V-Ti-O mesoporous material to the solution, so that the mass ratio of Ce-V-Ti-O mesoporous material to ammonium metavanadate is 1 : 0-1: 0.55, stir the mixture for 10 minutes, dry at room temperature for 20-40 hours to obtain solid A, dissolve the measured titanium sulfate in water, immerse the above solid A in the titanium sulfate solution, and stir for 5-10 minutes , dry at room temperature for 20-40 hours, and bake in air at 350-450° C. for 3-8 hours to obtain the V ₂ O ₅ catalyst supported by Ce-V-Ti-O mesoporous material. 3. a method for producing methylal with the V ₂ O ₅ composite catalyst supported by Ce-V-Ti-O mesoporous material claimed in claim 1, characterized in that: the catalyst is loaded in the reactor, and the reaction is controlled The temperature of the device is 120-160°C, and the mixture of methanol vapor and oxygen-containing gas preheated to 120-160°C is fed. The molar ratio of methanol to oxygen is 5:1 to 5:15, and the volume percentage of methanol in the mixed gas 5%, and the total flow rate of the gas is 1.1×10 ³ ml/hour per gram of catalyst to obtain methylal, wherein the oxygen-containing gas is pure O ₂ , air or nitrogen or helium containing molecular O ₂ .