Supported metal oxide catalysts, processes for their preparation and use

Abstract

The application provides a supported metal oxide catalyst, which is prepared by using a Zr-modified silicon-based molecular sieve containing F as a carrier and loading active metal oxides on the carrier, wherein the silicon-based molecular sieve has two independent pore structures, and the active metal oxides are oxides of one or more of Ti, Ca, Sr, Rb and Cs. The application also provides a preparation method and application of the supported metal oxide catalyst. The application further provides a method for preparing dimethyl ethylene ketone by cracking isobutyric acid. The dimethyl ethylene ketone is prepared by using the supported metal oxide catalyst provided by the application to catalyze the cracking reaction of isobutyric acid, the conversion rate of isobutyric acid is high, the selectivity of the target product is good, and the service life of the catalyst can be greatly prolonged, thereby providing a solid foundation for the large-scale production and application of dimethyl ethylene ketone.

Description

Technical Field

[0001] This invention relates to the field of catalysts, specifically to a supported metal oxide catalyst, its preparation method, and its use in catalyzing the cracking of isobutyric acid to prepare dimethyl ketene, and also to a method for cracking isobutyric acid to prepare dimethyl ketene. Background Technology

[0002] Dimethyl ketene (DMK) is an important chemical raw material and a crucial intermediate in the preparation of 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO). DMK dimerizes to form 2,2,4,4-tetramethyl-1,3-cyclobutanediol, which is then catalytically hydrogenated to yield the final product, CBDO. CBDO is a key monomer in the production of high-performance polyester PCCT. Adding CBDO to traditional polyesters significantly improves their glass transition temperature, weather resistance, transparency, and impact strength, making it widely applicable in bottle flakes, high-grade films, sheets, molded products, and coatings.

[0003] Currently, the industrial production of dimethyl ketene mainly utilizes the thermal cracking of isobutyric anhydride. Isobutyric anhydride is cracked at 400–500℃ and 10–20 kPaA to yield dimethyl ketene. Industrially, isobutyric anhydride is obtained through the dehydration of isobutyric acid; therefore, direct cracking of isobutyric acid to produce dimethyl ketene is more economical. However, the cracking conditions for isobutyric acid are relatively harsh, with a conversion rate below 20% without a catalyst. Literature reports that isobutyric acid conversion catalyzed by catalysts such as silica reaches approximately 67%, with a yield of only 30%. Isobutyric acid cracking is a reversible reaction, and the occurrence of the reverse reaction severely affects the conversion rate. Using a highly efficient solid catalyst to improve reactivity while suppressing the reverse reaction is key to improving the yield of dimethyl ketene.

[0004] Chinese patent CN 105732354A discloses a method for synthesizing 2,2,4,4-tetramethyl-1,3-cyclobutanedione. This patent considers using isobutyric acid as a thermal cracking feedstock. The thermal cracking reactivity of isobutyric acid is much lower than that of isobutyric anhydride, and the thermal cracking temperature used is higher. The conversion rate of isobutyric anhydride is about 65%, while the conversion rate of isobutyric acid is much lower than that of isobutyric anhydride.

[0005] Chinese patent CN 110170280A uses magnesium oxide catalyst to crack isobutyric acid, with an isobutyric acid conversion rate of about 60% and a dimethyl ketene selectivity of 81%. Compared with thermal cracking without a catalyst, this catalyst can significantly improve the conversion rate of isobutyric acid, but the selectivity is still lower than that of isobutyric anhydride cracking, resulting in a low reaction yield.

[0006] In conclusion, it is still necessary to find a solid catalyst with high catalytic activity and high stability to overcome the shortcomings of existing technologies. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, one object of the present invention is to provide a supported metal oxide catalyst that has excellent catalytic activity and good stability, and is very suitable for catalytic cracking of isobutyric acid to prepare dimethyl ketone.

[0008] Another object of the present invention is to provide a method for preparing the supported metal oxide catalyst and its use.

[0009] Another object of the present invention is to provide a method for preparing dimethyl ketone by cracking isobutyric acid.

[0010] The first aspect of this invention provides a supported metal oxide catalyst, which uses an F-containing Zr-modified silica-based molecular sieve as a support, on which an active metal oxide is loaded. The silica-based molecular sieve has two independent pore structures, and the active metal oxide is one or more oxides selected from Ti, Ca, Sr, Rb, and Cs. The catalyst contains 0.1-3% F, 0.005-0.1% Zr, and 2-35% active metal by mass percentage.

[0011] The supported metal oxide catalyst provided by this invention uses a silicon-based molecular sieve with two independent pore structures as the substrate material. These two different pore structures exhibit highly efficient shape-selective adsorption. The molecular sieve is modified in situ with Zr, which can replace some Si sites to form oxides, thereby altering the coordination vacancies in silicon oxide and enhancing the interaction with the active metal, thus improving its catalytic activity and stability. F mainly bonds with the Si-OH groups of the molecular sieve, and its hydrophobicity facilitates the rapid separation of water generated in the reaction from the pores. Based on these characteristics, the modified catalyst exhibits higher catalytic activity when used to catalyze the cracking of isobutyric acid to prepare dimethyl ketene. Furthermore, it can shorten the contact time between dimethyl ketene and water, thereby inhibiting the occurrence of the reverse reaction, improving reaction efficiency, and solving the problem of low yield in isobutyric acid cracking.

[0012] In the supported metal oxide catalyst provided by this invention, the mass percentage of F element can be about 0.1%, about 0.2%, about 0.5%, about 0.8%, about 1%, about 1.2%, about 1.5%, about 1.8%, about 2%, about 2.2%, about 2.5%, about 2.8%, about 3%, or any mass percentage range. In some preferred embodiments, the mass percentage of F element can be 0.2% to 2%.

[0013] In the supported metal oxide catalyst provided by this invention, the mass percentage of Zr can be about 0.005%, about 0.008%, about 0.01%, about 0.015%, about 0.02%, about 0.025%, about 0.03%, about 0.035%, about 0.04%, about 0.045%, about 0.05%, about 0.055%, about 0.06%, about 0.065%, about 0.07%, about 0.075%, about 0.08%, about 0.09%, about 0.1%, or any mass percentage range. In some preferred embodiments, the mass percentage of Zr can be from 0.008% to 0.08%.

[0014] In the supported metal oxide catalyst provided by this invention, the mass percentage of the active metal element can be about 2%, about 5%, about 8%, about 10%, about 12%, about 15%, about 18%, about 20%, about 22%, about 25%, about 28%, about 30%, about 32%, about 35%, or any mass percentage range. In some preferred embodiments, the mass percentage of the active metal element can be 3% to 25%.

[0015] The supported metal oxide catalyst provided by the present invention is composed of an active metal oxide and a modified silica-based molecular sieve. The active metal content can be 2-35% by mass percentage of the elements, and can be further 3-25%. The balance after removing the active metal oxide is a Zr-modified silica-based molecular sieve containing F.

[0016] In the supported metal oxide catalyst provided by this invention, the two independent pore structures of the silicon-based molecular sieve can each independently be a six-membered ring channel, a ten-membered ring channel, or a twelve-membered ring channel. In some preferred embodiments, the two independent pore structures of the silicon-based molecular sieve can each independently be a ten-membered ring channel or a twelve-membered ring channel. In some more preferred embodiments, the silicon-based molecular sieve can be an MCM molecular sieve, for example, an MCM-22 molecular sieve.

[0017] In the supported metal oxide catalyst provided by this invention, the active metal oxide can be one or more oxides selected from Ti, Ca, Sr, Rb, and Cs. In some preferred embodiments, the active metal oxide can be an oxide of at least two of Ti, Ca, Sr, Rb, and Cs.

[0018] In the supported metal oxide catalyst provided by this invention, the active metal oxide can be TiO2 and Rb2O, and their mass ratio can be 1 to 10:1, for example, about 1:1, about 2:1, about 3:1, about 4:1, about 5:1, about 6:1, about 7:1, about 8:1, about 9:1, about 10:1, or any mass ratio range. In some preferred embodiments, the mass ratio of the active metal oxide TiO2 to Rb2O can be 2 to 5:1.

[0019] A second aspect of the present invention provides a method for preparing the supported metal oxide catalyst as described in any of the above technical solutions, comprising the following steps:

[0020] S1: Mix the template agent, Zr source and silicon source and carry out a hydrothermal reaction;

[0021] S2: Add an additive containing F to the hydrothermal material obtained in step S1 and age it to separate the resulting solid. After drying, a molecular sieve precursor is obtained; and

[0022] S3: In the presence of a precipitant, the molecular sieve precursor and active metal source obtained in step S2 are co-precipitated in an aqueous solution, the precipitate is separated, and then calcined to obtain the final product.

[0023] In the preparation method provided by the present invention, the template agent can be a template agent commonly used in the preparation of MCM molecular sieves, such as hexamethylimine.

[0024] In the preparation method provided by the present invention, the Zr source can be a common Zr-containing organic or inorganic salt, such as one or more of zirconium chloride, zirconium nitrate, and zirconium tert-butoxide.

[0025] In the preparation method provided by the present invention, the silicon source can be a silicon source commonly used in the preparation of MCM molecular sieves, such as one or two of tetraethyl orthosilicate and boehmite.

[0026] In the preparation method provided by this invention, the amount of Zr source can be adjusted by those skilled in the art based on the required Zr content of the catalyst, the type of Zr source, etc. In some preferred embodiments, the amount of Zr in the Zr source, based on silicon oxide, can be 0.01–0.1 wt.% of the silicon source, for example, about 0.01 wt.%, about 0.02 wt.%, about 0.03 wt.%, about 0.04 wt.%, about 0.05 wt.%, about 0.06 wt.%, about 0.07 wt.%, about 0.08 wt.%, about 0.09 wt.%, about 0.1 wt.%, or any mass percentage range. In some more preferred embodiments, the amount of Zr in the Zr source, based on silicon oxide, can be 0.01–0.05 wt.% of the silicon source.

[0027] In the preparation method provided by the present invention, the hydrothermal reaction can be carried out at 10–50°C.

[0028] In the preparation method provided by this invention, the hydrothermal reaction can be carried out at a pH value not exceeding 2 (e.g., 0-1). Carrying the hydrothermal reaction under acidic conditions can effectively control the hydrolysis rate of the silicon source and adjust the catalyst formation. The pH value can be adjusted by adding an acid solution, such as adding a dilute hydrochloric acid solution with a concentration of 0.5-1.5 mol / L.

[0029] In the preparation method provided by the present invention, the reaction time of the hydrothermal reaction can be 1 to 15 hours (for example, 2 to 8 hours).

[0030] In the preparation method provided by this invention, the fluorine-containing auxiliary agent can be a C1-C4 alkyl diester of tetrafluoroterephthalic acid. The inventors have discovered that removing fluorine from the molecular structure of the fluorine-containing auxiliary agent affects the pore structure of the molecular sieve, thereby affecting the selectivity of the target product. Alkyl tetrafluoroterephthalic acid esters, as fluorine-containing auxiliary agents, achieve the best selectivity. In some preferred embodiments, the fluorine-containing auxiliary agent can be one or both of dimethyl tetrafluoroterephthalate and diethyl tetrafluoroterephthalate.

[0031] In the preparation method provided by this invention, the amount of the F-containing auxiliary agent can be adjusted by those skilled in the art based on the required F content of the catalyst, the type of F-containing auxiliary agent, etc. In some preferred embodiments, the amount of the F-containing auxiliary agent, based on silicon oxide, can be 0.1–1 wt.% of the silicon source, for example, about 0.1 wt.%, about 0.2 wt.%, about 0.3 wt.%, about 0.4 wt.%, about 0.5 wt.%, about 0.6 wt.%, about 0.7 wt.%, about 0.8 wt.%, about 0.9 wt.%, about 1 wt.%, or any mass percentage range. In some more preferred embodiments, the amount of the F-containing auxiliary agent, based on silicon oxide, can be 0.1–0.5 wt.% of the silicon source.

[0032] In the preparation method provided by the present invention, the aging is carried out at a pH value of 1 to 4 (for example, it can be 3 to 4), the aging temperature can be 100 to 200°C (for example, it can be 120 to 180°C), and the aging time can be 1 to 48 hours (for example, it can be 12 to 24 hours).

[0033] In the preparation method provided by the present invention, in step S2, the drying temperature after aging can be 40-60℃, and the drying time can be 1-3h.

[0034] In the preparation method provided by the present invention, step S3 may further include the following process: adding the molecular sieve precursor obtained in step S2 to an aqueous solution of an active metal source, then adding a precipitant for co-precipitation, separating the obtained precipitate, and calcining to obtain the supported metal oxide catalyst.

[0035] In the preparation method provided by the present invention, the active metal source can be one or more of the active metal nitrate, chloride, carbonate, sulfate, and phosphate, including but not limited to one or more of titanium nitrate, titanium chloride, and tetrabutyl titanate, and one or more of rubidium nitrate, rubidium chloride, and rubidium carbonate.

[0036] In the preparation method provided by the present invention, the mass percentage concentration of the aqueous solution of the active metal source can be 5% to 20%. In some preferred embodiments, the mass percentage concentration of the aqueous solution of the active metal source can be 8% to 15% (for example, 10%).

[0037] In the preparation method provided by the present invention, the precipitant can be ammonia, sodium hydroxide solution or potassium hydroxide solution with a mass percentage concentration of 1-10% (e.g., 1-5%).

[0038] In the preparation method provided by the present invention, after adding the precipitant, the pH value of the resulting coprecipitation system is 7-8, and coprecipitation is carried out at 30-70°C for 1-6 hours.

[0039] In the preparation method provided by the present invention, the precipitate is calcined at 400-600°C for 2-10 hours in an inert atmosphere.

[0040] In the preparation method provided by the present invention, the desired material can be obtained through a separation step, such as separating precipitates. The separation equipment or method can be common in the art, including but not limited to natural sedimentation, (atmospheric pressure or vacuum) filtration, centrifugation and other common equipment.

[0041] In the preparation method provided by this invention, the washing step refers to washing the material with distilled water or deionized water until the surface of the material is close to or neutral. The number of washing times can be adjusted according to the actual situation, for example, it can be 2 to 5 times, and usually it can be 3 times.

[0042] The third aspect of the present invention provides the use of the supported metal oxide catalyst as described in any one of the above technical solutions, or the supported metal oxide catalyst prepared by any one of the above technical solutions, for catalytic cracking of isobutyric acid to prepare dimethyl ketone.

[0043] The fourth aspect of the present invention provides a method for preparing dimethyl ketene by cracking isobutyric acid. The method is as follows: in the presence of a catalyst, dimethyl ketene is prepared by cracking isobutyric acid as a raw material. The catalyst is a supported metal oxide catalyst as described in any one of the above technical solutions, or a supported metal oxide catalyst prepared by any one of the above technical solutions.

[0044] In some preferred embodiments, the reaction temperature of the pyrolysis reaction can be 500–700°C, and the reaction pressure can be 10–30 kPaA.

[0045] In some preferred embodiments, the pyrolysis reaction can be carried out using a batch process or a continuous process. In some more preferred embodiments, the pyrolysis reaction can be carried out using a continuous process, wherein isobutyric acid is held in a tubular reactor packed with a catalyst for a certain period of time (e.g., 0.2 to 2 s) to prepare dimethyl ketene via pyrolysis.

[0046] The technical solution provided by this invention has the following advantages:

[0047] (1) The supported metal oxide catalyst provided by the present invention uses a silicon-based molecular sieve with two independent pore structures as the substrate material and is modified with two elements, Zr and F. The resulting catalyst has a unique micro-pore structure suitable for catalyzing the cracking reaction of isobutyric acid. It has high catalytic activity and can effectively suppress the occurrence of reverse reaction. Therefore, it is very suitable as a catalyst for the cracking of isobutyric acid to prepare dimethyl ketone.

[0048] (2) When using the supported metal oxide catalyst provided by the present invention to prepare dimethyl ketone, the isobutyric acid conversion rate can reach up to 80%, and the selectivity of the target product dimethyl ketone can reach up to 92%. Moreover, the catalyst of the present invention also has good stability, and the catalytic activity does not decrease significantly under long-term operation, and the service life is greatly extended.

[0049] (3) The preparation process of the supported metal oxide catalyst provided by the present invention is simple, highly operable, easy to control, and does not require expensive reagents, thus having good industrial applicability.

[0050] (4) The method for preparing dimethyl ketone provided by the present invention uses a highly active and stable supported metal oxide as a catalyst, resulting in a high raw material conversion rate and good target product selectivity. Therefore, the production efficiency can be significantly improved and the manufacturing cost can be greatly reduced, providing a solid foundation for the expanded production and application of dimethyl ketone. Detailed Implementation

[0051] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0052] The source information of the raw materials or reagents used in the embodiments and comparative examples of the present invention is shown in the table below. Unless otherwise specified, other raw materials or reagents are commercially available products.

[0053]

[0054]

[0055] The equipment source information used in the embodiments and comparative examples of the present invention is shown in the table below. Unless otherwise specified, other equipment are commercially purchased products.

[0056] Equipment Name model factory muffle furnace SXL-1016 Shanghai Jinghong Equipment & Instrument Co., Ltd. Fixed bed —— Yantai Keli Chemical Equipment Co., Ltd. Gas chromatography 2010 PLUS Shimadzu

[0057] The analytical characterization methods used in the embodiments and comparative examples of the present invention are shown below. Unless otherwise specified, all other methods are common in the art.

[0058] The analysis was performed using a gas chromatograph equipped with an FID detector and an SE-54 capillary column (25.0m × 0.53mm × 0.02mm). The chromatogram was performed using a temperature-programmed method: 120℃ for 1 min, then increased to 200℃ at a rate of 15℃ / min and held for 10 min. The injection port was set at 240℃, the split ratio was 50:1, and the detector was FID at 240℃.

[0059] Unless otherwise specified, all percentages used in the embodiments and comparative examples of this invention are mass percentages.

[0060] Example 1

[0061] Weigh 4g of the template agent hexamethylimine and 0.0008g of zirconium chloride and add them to a 500mL beaker. Then add 160mL of dilute hydrochloric acid (1mol / L) to adjust the pH to 0. Stir and dissolve at 10℃. Add 10.4165g of tetraethyl orthosilicate dropwise and continue stirring for 8h.

[0062] 0.1051 g of dimethyl tetrafluoroterephthalate was weighed and added to the above solution. The pH value was adjusted to 1 by adding 2% sodium hydroxide aqueous solution. The mixture was stirred for 4 h and then aged at 180 °C for 48 h. After filtration, washing with deionized water and drying at 40 °C for 1 h, zirconium-modified molecular sieve was obtained.

[0063] 0.1256 g of titanium nitrate and 0.1260 g of rubidium nitrate were weighed and dissolved in deionized water to prepare a solution with a total salt concentration of 10%. The above-mentioned zirconium-modified molecular sieve support was added to the solution, and ammonia water was added dropwise to adjust the pH of the solution to 7-8. The reaction was carried out at 40 °C for 1 h. After filtration and washing, the solution was calcined at 400 °C for 8 h to obtain TiRb / Zr-MCM-22 / composite solid catalyst A.

[0064] Example 2

[0065] Weigh 4g of the template agent hexamethylimine and 0.0022g of zirconium nitrate into a 500mL beaker, then add 160mL of dilute hydrochloric acid (1mol / L) to adjust the pH to 1, stir and dissolve at 20℃, then add 10.4165g of tetraethyl orthosilicate dropwise and continue stirring for 4h.

[0066] 0.0232 g of diethyl tetrafluoroterephthalate was weighed and added to the above solution. The pH value was adjusted to 2 by adding 2% sodium hydroxide aqueous solution. The mixture was stirred for 4 h and then aged at 150 °C for 12 h. After filtration, washing with deionized water and drying at 50 °C for 2 h, zirconium-modified molecular sieve was obtained.

[0067] 1.1023 g of titanium chloride and 0.0859 g of rubidium chloride were weighed and dissolved in deionized water to prepare a solution with a total salt concentration of 10%. The above-mentioned zirconium-modified molecular sieve support was added to the solution, and a 2% sodium hydroxide aqueous solution was added dropwise to adjust the pH of the solution to 7-8. The reaction was carried out at 50 °C for 2 h. After filtration and washing, the solution was calcined at 500 °C for 4 h to obtain TiRb / Zr-MCM-22 / composite solid catalyst B.

[0068] Example 3

[0069] Weigh 4g of the template agent hexamethylimine and 0.0038g of zirconium tert-butoxide into a 500mL beaker, then add 160mL of dilute hydrochloric acid (1mol / L) to adjust the pH to 0.1, stir and dissolve at 30℃, then add 10.4165g of tetraethyl orthosilicate dropwise and continue stirring for 6h.

[0070] 0.0526 g of dimethyl tetrafluoroterephthalate was weighed and added to the above solution. The pH value was adjusted to 3 by adding 2% sodium hydroxide aqueous solution. The mixture was stirred for 4 h and then aged at 140 °C for 18 h. After filtration, washing with deionized water and drying at 60 °C for 2 h, zirconium-modified molecular sieve was obtained.

[0071] 2.6766 g of tetrabutyl titanate and 0.0993 g of rubidium carbonate were weighed and dissolved in deionized water to prepare a solution with a total salt concentration of 10%. The above-mentioned zirconium-modified molecular sieve support was added to the solution, and ammonia water was added dropwise to adjust the pH of the solution to 7-8. The reaction was carried out at 40 °C for 1 h. After filtration and washing, the solution was calcined at 450 °C for 7 h to obtain TiRb / Zr-MCM-22 / composite solid catalyst C.

[0072] Example 4

[0073] Weigh 4g of the template agent hexamethylimine and 0.0054g of zirconium chloride and add them to a 500mL beaker. Then add 160mL of dilute hydrochloric acid (1mol / L) to adjust the pH to 0.5. Stir and dissolve at 40℃. Add 10.4165g of tetraethyl orthosilicate dropwise and continue stirring for 8h.

[0074] 0.0814 g of diethyl tetrafluoroterephthalate was weighed and added to the above solution. The pH value was adjusted to 4 by adding 2% sodium hydroxide aqueous solution. The mixture was stirred for 4 hours and then aged at 120°C for 24 hours. After filtration, washing with deionized water, and drying at 50°C for 1 hour, zirconium-modified molecular sieve was obtained.

[0075] 2.8618 g of tetrabutyl titanate and 0.5308 g of rubidium nitrate were weighed and dissolved in deionized water to prepare a solution with a total salt concentration of 10%. The above-mentioned zirconium-modified molecular sieve support was added to the solution, and a 2% potassium hydroxide aqueous solution was added dropwise to adjust the pH of the solution to 7-8. The reaction was carried out at 60 °C for 2 h. After filtration and washing, the solution was calcined at 480 °C for 5 h to obtain TiRb / Zr-MCM-22 / composite solid catalyst D.

[0076] Example 5

[0077] Weigh 4g of the template agent hexamethylimine and 0.0112g of zirconium nitrate into a 500mL beaker, then add 160mL of dilute hydrochloric acid (1mol / L) to adjust the pH to 1, stir to dissolve at 50℃, add 10.4165g of tetraethyl orthosilicate dropwise and continue stirring for 2h.

[0078] 0.0116 g of diethyl tetrafluoroterephthalate was weighed and added to the above solution. The pH value was adjusted to 1 by adding 2% sodium hydroxide aqueous solution. The mixture was stirred for 4 hours and then aged at 100°C for 1 hour. The mixture was then filtered, washed with deionized water, and dried at 40°C for 2 hours to obtain zirconium-modified molecular sieve.

[0079] 2.3184 g of titanium nitrate and 0.1163 g of rubidium carbonate were weighed and dissolved in deionized water to prepare a solution with a total salt concentration of 10%. The above-mentioned zirconium-modified molecular sieve support was added to the solution, and ammonia water was added dropwise to adjust the pH of the solution to 7-8. The reaction was carried out at 50 °C for 2 h. After filtration and washing, the solution was calcined at 420 °C for 6 h to obtain TiRb / Zr-MCM-22 / composite solid catalyst E.

[0080] Comparative Example 1

[0081] Weigh 4g of template agent P123 and 0.0008g of zirconium chloride into a 500mL beaker, then add 160mL of dilute hydrochloric acid (1mol / L) to adjust the pH to 0, stir and dissolve at 50℃, then add 10.4165g of tetraethyl orthosilicate dropwise and continue stirring for 3h.

[0082] 0.1051 g of dimethyl tetrafluoroterephthalate was weighed and added to the above solution. The pH value was adjusted to 1 by adding 2% sodium hydroxide aqueous solution. The mixture was stirred for 4 h and then aged at 180 °C for 48 h. After filtration, washing with deionized water and drying at 40 °C for 1 h, zirconium-modified molecular sieve was obtained.

[0083] 0.1256 g of titanium nitrate and 0.1260 g of rubidium nitrate were dissolved in deionized water to prepare a solution with a total salt concentration of 10%. The zirconium-modified molecular sieve support was added to the solution, and ammonia was added dropwise to adjust the pH to 7-8. The reaction was carried out at 40 °C for 1 h. After filtration and washing, the solution was calcined at 400 °C for 8 h to obtain TiRb / Zr-SBA-15 / composite solid catalyst F. This molecular sieve is an SBA-15 molecular sieve with a two-dimensional straight pore structure and only a single pore structure.

[0084] Comparative Example 2

[0085] Except for the absence of zirconium chloride for molecular sieve modification, all other steps were the same as in Example 1, yielding the TiRb / MCM-22 / composite solid catalyst G.

[0086] Comparative Example 3

[0087] Except for the absence of dimethyl tetrafluoroterephthalate (TTPT) additive, all other steps were the same as in Example 1, yielding the TiRb / Zr-MCM-22 / composite solid catalyst H.

[0088] Comparative Example 4

[0089] Except for replacing the auxiliary agent dimethyl tetrafluoroterephthalate with 0.0395g tetrafluoroethylene, all other steps were the same as in Example 1, resulting in TiRb / Zr-MCM-22 / composite solid catalyst I.

[0090] The composition of the catalysts prepared in the above examples and comparative examples was tested by XRF and ICP, and the results are shown in Table 1:

[0091] Table 1 Catalyst composition

[0092] catalyst Fluorine content % Zirconium content % Titanium content % Rubidium content % Silicon content % A 0.9317 0.0093 1.4859 2.2658 43.9162 B 0.5808 0.0168 7.8151 1.7024 39.4410 C 1.3543 0.0234 9.9370 3.0305 36.7492 D 1.7669 0.0510 9.9487 7.5853 34.2115 E 0.2235 0.0645 19.0166 2.8998 30.2625 F 0.8493 0.0085 1.4002 2.1352 44.0882 G 0.8490 0.0000 1.2859 1.9609 44.2701 H 0.0000 0.0086 1.3999 2.1347 44.4850 I 0.8519 0.0086 1.3437 2.0489 44.1749

[0093] Application examples

[0094] The catalysts prepared in the above examples and comparative examples were used to catalyze the cracking of isobutyric acid to prepare dimethyl ketone.

[0095] Application Example 1

[0096] A continuous experiment was conducted using a fixed bed. 50g of catalyst A prepared in Example 1 was packed into the bed. Under the conditions of temperature 550℃, pressure 10KPaA, and residence time 2s, 180g of isobutyric acid was fed. After the reaction was completed, the material was quantified by gas chromatography. The conversion rate of isobutyric acid was 68%, and the product of dimethyl ketene was 78g. The selectivity of dimethyl ketene was 80%.

[0097] Application Example 2

[0098] A continuous experiment was conducted using a fixed bed reactor. 50g of catalyst B prepared in Example 2 was packed into the reactor. Under the conditions of 600℃, 15KPaA, and a residence time of 1.5s, 180g of isobutyric acid was fed. After the reaction was completed, the material was quantified by gas chromatography. The conversion rate of isobutyric acid was 69.3%, and the product of dimethyl ketene was 84.4g. The selectivity of dimethyl ketene was 85.1%.

[0099] Application Example 3

[0100] A continuous experiment was conducted using a fixed bed. 50g of catalyst C prepared in Example 3 was packed into the bed. Under the conditions of 650℃, 10KPaA, and 1s residence time, 180g of isobutyric acid was fed. After the reaction was completed, the material was quantified by gas chromatography. The conversion rate of isobutyric acid was 75.5%, the product of dimethyl ketene was 99.5g, and the selectivity of dimethyl ketene was 92%.

[0101] Application Example 4

[0102] A continuous experiment was conducted using a fixed bed. 50g of catalyst D prepared in Example 4 was packed into the bed. Under the conditions of 700℃, 25KPaA, and a residence time of 0.2s, 180g of isobutyric acid was fed. After the reaction was completed, the material was quantified by gas chromatography. The conversion rate of isobutyric acid was 80.3%, and the product of dimethyl ketene was 105.2g. The selectivity of dimethyl ketene was 91.5%.

[0103] Application Example 5

[0104] A continuous experiment was conducted using a fixed bed. 50g of catalyst E prepared in Example 5 was packed into the bed. Under the conditions of 700℃, 30KPaA, and a residence time of 0.5s, 180g of isobutyric acid was fed. After the reaction was completed, the material was quantified by gas chromatography. The conversion rate of isobutyric acid was 80.5%, and the product of dimethyl ketene was 88.9g. The selectivity of dimethyl ketene was 77.1%.

[0105] Application Example 6

[0106] A continuous experiment was conducted using a fixed bed, filled with 50g of catalyst A prepared in Example 1 (which had been continuously run for 200h under the same experimental conditions). Under conditions of 550℃, 10KPaA, and 2s residence time, 180g of isobutyric acid was fed. The reaction product was quantified by gas chromatography. The conversion rate of isobutyric acid was 67.7%, the product of dimethyl ketene was 76.1g, and the selectivity of dimethyl ketene was 78.5%.

[0107] Application Example 7

[0108] A continuous experiment was conducted using a fixed bed reactor. 50 g of catalyst F prepared in Comparative Example 1 was packed into the reactor. Under the conditions of 550 °C, 10 kPaA, and a residence time of 2 s, 180 g of isobutyric acid was fed. After the reaction was completed, the material was quantified by gas chromatography. The conversion rate of isobutyric acid was 52.1%, the product of dimethyl ketene was 37.4 g, and the selectivity of dimethyl ketene was 50.2%.

[0109] Application Example 8

[0110] A continuous experiment was conducted using a fixed bed. 50g of catalyst G prepared in Comparative Example 2 was packed into the bed. Under the conditions of temperature 550℃, pressure 10KPaA, and residence time 2s, 180g of isobutyric acid was fed. After the reaction was completed, the material was quantified by gas chromatography. The conversion rate of isobutyric acid was 60%, and the product of dimethyl ketene was 58.8g. The selectivity of dimethyl ketene was 68.5%.

[0111] Application Example 9

[0112] A continuous experiment was conducted using a fixed bed. 50g of catalyst H prepared in Comparative Example 3 was packed into the bed. Under the conditions of temperature 550℃, pressure 10KPaA, and residence time 2s, 180g of isobutyric acid was fed. After the reaction was completed, the material was quantified by gas chromatography. The conversion rate of isobutyric acid was 48.5%, the product of dimethyl ketene was 45.1g, and the selectivity of dimethyl ketene was 65%.

[0113] Application Example 10

[0114] A continuous experiment was conducted using a fixed bed. 50g of catalyst I prepared in Comparative Example 4 was packed into the bed. Under the conditions of 550℃, 10KPaA, and 2s residence time, 180g of isobutyric acid was fed. After the reaction was completed, the material was quantified by gas chromatography. The conversion rate of isobutyric acid was 65%, the product of dimethyl ketene was 68.2g, and the selectivity of dimethyl ketene was 73.3%.

[0115] As can be seen from the above application examples, the supported metal oxide catalyst provided by the present invention has excellent catalytic activity (Application Examples 1-5). Compared with the catalysts of the comparative examples (Application Examples 7-10), the conversion rate of isobutyric acid and the selectivity of dimethyl ketene are significantly improved. Moreover, the catalyst of the present invention also has excellent stability, and the catalytic activity does not decrease significantly under long-term operation (Application Example 6).

[0116] Unless otherwise specified, the terms used in this invention have the meanings commonly understood by those skilled in the art.

[0117] The embodiments described in this invention are for illustrative purposes only and are not intended to limit the scope of protection of this invention. Those skilled in the art can make various other substitutions, changes and improvements within the scope of this invention. Therefore, this invention is not limited to the above embodiments, but is only defined by the claims.

Claims

1. A supported metal oxide catalyst characterized in that, The catalyst is supported on a Zr-modified silicon-based molecular sieve containing F, and an active metal oxide is loaded thereon, wherein the silicon-based molecular sieve has two independent pore structures, and the active metal oxide is Ti and Rb oxides; the catalyst contains 0.1-3% of F, 0.005-0.1% of Zr and 2-35% of active metal in terms of mass percentage of elements; the Zr-modified silicon-based molecular sieve containing F is prepared by using C1-C4 alkyl diesters of tetrachloroterephthalic acid as the F-containing additive; and the two independent pore structures of the silicon-based molecular sieve are independently six-membered ring pores, ten-membered ring pores or twelve-membered ring pores.

2. The supported metal oxide catalyst of claim 1, wherein, The two independent pore structures of the silicon-based molecular sieve are independently ten-membered ring pores or twelve-membered ring pores.

3. The supported metal oxide catalyst of claim 2, wherein the metal oxide catalyst is selected from the group consisting of: 5 The silicon-based molecular sieve is an MCM molecular sieve.

4. The supported metal oxide catalyst of claim 3, wherein the metal oxide catalyst is selected from the group consisting of: 5 The silicon-based molecular sieve is an MCM-22 molecular sieve.

5. The supported metal oxide catalyst according to any one of claims 1 to 4, characterized in that, The active metal oxide is TiO2 and Rb2O, and the mass ratio of the two is 1-10:

1.

6. The supported metal oxide catalyst of claim 5, wherein the metal oxide catalyst is selected from the group consisting of copper oxide, silver oxide, zinc oxide, and mixtures thereof. The active metal oxide is TiO2 and Rb2O, and the mass ratio of the two is 2-5:

1.

7. A process for the preparation of the supported metal oxide catalyst according to any one of claims 1 to 6, characterized in that, The method comprises the following steps: S1: mixing a template agent, a Zr source and a silicon source and performing a hydrothermal reaction at 10-50°C; S2: adding the F-containing additive to the hydrothermal material obtained in step S1 and performing aging, separating the obtained solid, and drying to obtain a molecular sieve precursor; and S3: co-precipitating the molecular sieve precursor obtained in step S2 and an active metal source from an aqueous solution in the presence of a precipitant, separating the obtained precipitate, and calcining to obtain the supported metal oxide catalyst.

8. The production method according to claim 7, characterized by, The template agent is hexamethyl imine; and / or The Zr source is one or more of zirconium chloride, zirconium nitrate and zirconium tert-butylate; and / or The silicon source is one or both of tetraethyl orthosilicate and pseudoboehmite.

9. The production method according to claim 7, characterized by, The amount of Zr in the Zr source is 0.01-0.1 wt.% of the silicon source, calculated based on silicon oxide.

10. The preparation method according to claim 7, characterized in that, The hydrothermal reaction is performed at a pH value of not more than 2.

11. The preparation method according to claim 7, characterized in that, The F-containing additive is one or both of dimethyl tetrachloroterephthalate and diethyl tetrachloroterephthalate.

12. The production method according to claim 11, characterized by, The amount of the F-containing additive is 0.1-1 wt.% of the silicon source, calculated based on silicon oxide.

13. The method of claim 7, wherein The aging is performed at a pH value of 1-4, an aging temperature of 100-200°C and an aging time of 1-48 h.

14. The production method according to any one of claims 7 to 13, characterized by, The step S3 comprises the following process: adding the molecular sieve precursor obtained in step S2 to an aqueous solution of the active metal source, adding a precipitant for co-precipitation, separating the obtained precipitate, and calcining to obtain the supported metal oxide catalyst.

15. The method of claim 14, wherein, The precipitate is calcined in an inert atmosphere at 400-600°C for 2-10 h.

16. The method of claim 14, wherein, The active metal source is one or more of a nitrate, a chloride, a carbonate, a sulfate and a phosphate of the active metal.

17. The method of claim 16, wherein, The active metal source comprises one or more of titanium nitrate, titanium chloride and tetrabutyl titanate and one or more of rubidium nitrate, rubidium chloride and rubidium carbonate.

18. The method of claim 17, wherein, The aqueous solution of the active metal source has a mass percentage concentration of 5-20%.

19. The method of claim 14, wherein, The precipitant is aqueous ammonia, a sodium hydroxide solution or a potassium hydroxide solution with a mass percentage concentration of 1-10%.

20. The method of claim 14, wherein, After the addition of the precipitant, the pH value of the obtained co-precipitation system is 7-8, and the co-precipitation is carried out at 30-70 ℃ for 1-6 h.

21. Use of the supported metal oxide catalyst of any one of claims 1-6, or the supported metal oxide catalyst prepared by the preparation method of any one of claims 7-20, for catalyzing the preparation of dimethyl ethylene ketone by cracking isobutyric acid.

22. A process for the cleavage of isobutyric acid to produce dimethyl ethylene ketone, characterized in that, In the presence of a catalyst, dimethyl ethylene ketone is prepared by a cracking reaction using isobutyric acid as a raw material, wherein the catalyst is the supported metal oxide catalyst of any one of claims 1-6, or the supported metal oxide catalyst prepared by the preparation method of any one of claims 7-20.

23. The method of claim 22, wherein, The reaction temperature of the cracking reaction is 500-700 ℃, and the reaction pressure is 10-30 KPaA.

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