Supported metal oxide catalyst as well as preparation method and application thereof

Abstract

The invention provides a supported metal oxide catalyst which is characterized in that an F-containing Zr-modified silicon-based molecular sieve is used as a carrier, an active metal oxide is supported on the carrier, the silicon-based molecular sieve has two independent pore structures, and the active metal oxide is one or more oxides of Ti, Ca, Sr, Rb and Cs. The invention also provides a preparation method and application of the supported metal oxide catalyst. The invention further provides a method for preparing dimethyl ketene through isobutyric acid cracking. When the supported metal oxide catalyst provided by the invention is used for catalyzing cracking reaction of isobutyric acid to prepare the dimethyl ketene, the isobutyric acid conversion rate is high, the selectivity of a target product is good, the service life of the catalyst can be greatly prolonged, and a solid foundation is provided for expanded production and application of the dimethyl ketene.

Description

Technical Field

[0001] The invention relates to the field of catalysts, and in particular to a supported metal oxide catalyst and a preparation method thereof, and use of the catalyst in catalyzing the cracking of isobutyric acid to prepare dimethyl ketone, and also to a method for preparing dimethyl ketone by cracking isobutyric acid. Background Art

[0002] Dimethyl ketone is an important chemical raw material and an important intermediate for the preparation of 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO). Dimethyl ketone can be dimerized to form 2,2,4,4-tetramethyl-1,3-cyclobutanedione, and then catalytic hydrogenation can be used to obtain the final product CBDO. CBDO is a key monomer for the production of high-performance polyester PCCT. Adding CBDO to traditional polyester can significantly improve its glass transition temperature, weather resistance, transparency, impact strength and other properties. It can be widely used in bottle flakes, high-end films, sheets, molded products, coatings and other fields.

[0003] At present, the production of dimethyl ketone in industry mainly adopts thermal cracking of isobutyric anhydride. Isobutyric anhydride is cracked at 400-500℃ and 10-20KPaA to obtain dimethyl ketone. Isobutyric anhydride is produced by dehydration of isobutyric acid in industry, so it is more economical to prepare dimethyl ketone by direct cracking of isobutyric acid. The cracking conditions of isobutyric acid are relatively more stringent, and the conversion rate is below 20% under catalyst-free conditions. The conversion rate of isobutyric acid catalyzed by catalysts such as silicon oxide reported in the literature is about 67%, and the yield is only 30%. Isobutyric acid cracking is a reversible reaction, and the occurrence of reverse reaction will seriously affect the conversion rate of isobutyric acid. The use of high-efficiency solid catalysts to improve the reaction activity while inhibiting the occurrence of reverse reaction is the key to improving the yield of dimethyl ketone.

[0004] Chinese patent CN 105732354A discloses a method for synthesizing 2,2,4,4-tetramethyl-1,3-cyclobutanedione. The patent considers using isobutyric acid as a thermal cracking raw material. The thermal cracking reaction activity of isobutyric acid is much lower than that of isobutyric anhydride. A higher thermal cracking temperature is used. 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] In Chinese patent CN 110170280A, magnesium oxide catalyst is used to crack isobutyric acid, the isobutyric acid conversion rate is about 60%, and the dimethyl ketone selectivity is 81%. Compared with thermal cracking without catalyst, the 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 summary, there is still a need to find a solid catalyst with high catalytic activity and high stability to solve the deficiencies in the prior art. Summary of the invention

[0007] In order to make up for the deficiencies in the prior art, an object of the present invention is to provide a supported metal oxide catalyst having excellent catalytic activity and good stability, and being very suitable for catalyzing the cracking of isobutyric acid to prepare dimethyl ketone.

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

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

[0010] The first aspect of the present invention provides a supported metal oxide catalyst, which uses a F-containing Zr-modified silicon-based molecular sieve as a carrier, on which an active metal oxide is loaded, wherein the silicon-based molecular sieve has two independent pore structures, and the active metal oxide is an oxide of one or more of Ti, Ca, Sr, Rb, and Cs; in terms of mass percentage of the elements, the catalyst contains 0.1-3% F, 0.005-0.1% Zr, and 2-35% active metals.

[0011] The supported metal oxide catalyst provided by the present invention uses a silicon-based molecular sieve with two independent pore structures as a base material. The two different pore structures have an efficient shape-selective adsorption effect. The molecular sieve is modified by adding Zr in situ, which can replace part of the Si position to form an oxide, thereby changing the silicon oxide coordination vacancies, enhancing the interaction with the active metal, and then improving its catalytic activity and stability. F mainly bonds with the Si-OH of the molecular sieve, and its hydrophobicity helps the water generated by the reaction to be quickly separated from the pores. Based on these characteristics, the modified catalyst has higher catalytic activity when used to catalyze the cracking of isobutyric acid to prepare dimethyl ethylene ketone, and can also shorten the contact time between dimethyl ethylene ketone and water, thereby inhibiting the occurrence of reverse reaction, improving reaction efficiency, and solving the problem of low cracking yield of isobutyric acid.

[0012] In the supported metal oxide catalyst provided by the present 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 interval. In some preferred embodiments, the mass percentage of F element can be 0.2-2%.

[0013] In the supported metal oxide catalyst provided by the present invention, the mass percentage of the Zr element 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 interval. In some preferred embodiments, the mass percentage of the Zr element can be 0.008-0.08%.

[0014] In the supported metal oxide catalyst provided by the present 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 interval. In some preferred embodiments, the mass percentage of the active metal element can be 3-25%.

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

[0016] In the supported metal oxide catalyst provided by the present invention, the two independent channel structures of the silicon-based molecular sieve can be independently six-membered ring channels, ten-membered ring channels or twelve-membered ring channels. In some preferred embodiments, the two independent channel structures of the silicon-based molecular sieve can be independently ten-membered ring channels or twelve-membered ring channels. 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 the present invention, the active metal oxide may be an oxide of one or more of Ti, Ca, Sr, Rb, and Cs. In some preferred embodiments, the active metal oxide may be an oxide of at least two of Ti, Ca, Sr, Rb, and Cs.

[0018] In the supported metal oxide catalyst provided by the present invention, the active metal oxide may be TiO2 and Rb2O, and the mass ratio of the two may 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 interval. In some preferred embodiments, the mass ratio of the active metal oxide TiO2 and Rb2O may be 2 to 5:1.

[0019] The second aspect of the present invention provides a method for preparing a supported metal oxide catalyst according to any one of the above technical solutions, comprising the following steps:

[0020] S1: mixing the template, Zr source and silicon source and performing a hydrothermal reaction;

[0021] S2: adding a F-containing additive to the hydrothermal material obtained in step S1 and aging the material, separating the obtained solid, and drying the solid to obtain a molecular sieve precursor; and

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

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

[0024] In the preparation method provided by the present invention, the Zr source may be a common organic salt or inorganic salt containing Zr, for example, it may be 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 may be a silicon source commonly used in the preparation of MCM molecular sieves, for example, it may be one or both of tetraethyl orthosilicate and pseudo-boehmite.

[0026] In the preparation method provided by the present invention, the amount of the Zr source can be adjusted by those skilled in the art according to the amount of Zr required for the catalyst, the type of the Zr source, etc. In some preferred embodiments, based on silicon oxide, the amount of Zr in the Zr source can be 0.01 to 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 interval. In some more preferred embodiments, based on silicon oxide, the amount of Zr in the Zr source can be 0.01 to 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 the present invention, the hydrothermal reaction can be carried out at a pH value not exceeding 2 (e.g., 0 to 1). Carrying out the hydrothermal reaction under acidic conditions can effectively control the hydrolysis rate of the silicon source and adjust the catalyst molding. 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 to 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 the present invention, the F-containing auxiliary agent can be a C1-C4 alkyl diester of tetrafluoroterephthalic acid. The inventors have found that the removal of F from the molecular structure of the F-containing auxiliary agent will affect the pore structure of the molecular sieve, thereby affecting the selectivity of the target product. Alkyl tetrafluoroterephthalate can achieve the best selectivity effect as the F-containing auxiliary agent. In some preferred embodiments, the F-containing auxiliary agent can be one or both of dimethyl tetrafluoroterephthalate and diethyl tetrafluoroterephthalate.

[0031] In the preparation method provided by the present invention, the amount of the F-containing additive can be adjusted by a person skilled in the art according to the F content required by the catalyst, the type of the F-containing additive, etc. In some preferred embodiments, the amount of the F-containing additive can be 0.1 to 1 wt.% of the silicon source in terms of silicon oxide, for example, it can be 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 interval. In some more preferred embodiments, the amount of the F-containing additive can be 0.1 to 0.5 wt.% of the silicon source in terms of silicon oxide.

[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, 3 to 4), the aging temperature can be 100 to 200° C. (for example, 120 to 180° C.), and the aging time can be 1 to 48 h (for example, 12 to 24 h).

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

[0034] In the preparation method provided by the present invention, the 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 obtaining the supported metal oxide catalyst after calcination.

[0035] In the preparation method provided by the present invention, the active metal source can be one or more of the nitrates, chlorides, carbonates, sulfates, and phosphates of the active metal, 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 may be aqueous ammonia, a sodium hydroxide solution or a potassium hydroxide solution with a mass percentage concentration of 1 to 10% (eg, 1 to 5%).

[0038] In the preparation method provided by the present invention, after the precipitant is added, the pH value of the obtained coprecipitation system is 7-8, and the 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, for example, a precipitate can be separated, and the separation equipment or method can be a common equipment or method in the art, including but not limited to natural sedimentation, (normal pressure or vacuum) filtration, centrifugation and the like and their common equipment.

[0041] In the preparation method provided by the present 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, and the number of washing times can be adjusted according to actual conditions, for example, it can be 2 to 5 times, usually 3 times.

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

[0043] A fourth aspect of the present invention provides a method for preparing dimethyl vinyl ketone by cracking isobutyric acid, the method comprising: preparing dimethyl vinyl ketone by cracking reaction using isobutyric acid as a raw material in the presence of a catalyst, wherein the catalyst is a supported metal oxide catalyst described in any one of the above technical schemes, or a supported metal oxide catalyst obtained by the preparation method described in any one of the above technical schemes.

[0044] In some preferred embodiments, the reaction temperature of the cracking reaction may be 500-700° C., and the reaction pressure may be 10-30 KPaA.

[0045] In some preferred embodiments, the cleavage reaction may be performed in a batch process or a continuous process. In some more preferred embodiments, the cleavage reaction may be performed in a continuous process, wherein isobutyric acid stays in a tubular reaction device filled with a catalyst for a certain time (e.g., 0.2 to 2 seconds) to prepare dimethyl ketene through a cleavage reaction.

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

[0047] (1) The supported metal oxide catalyst provided by the present invention adopts a silicon-based molecular sieve having two independent pore structures as a base material and is modified by two elements, Zr and F. The obtained catalyst has a unique microscopic pore structure suitable for catalyzing the cracking reaction of isobutyric acid, has high catalytic activity and can effectively inhibit the occurrence of reverse reaction. Therefore, it is very suitable for use as a catalyst for preparing dimethyl ethylene ketone by cracking isobutyric acid.

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

[0049] (3) The supported metal oxide catalyst provided by the present invention has a simple preparation process, strong operability, and is easy to control without the use of expensive reagents, and thus has good industrial applicability.

[0050] (4) The method for preparing dimethyl ketone provided by the present invention uses a highly active and highly stable supported metal oxide as a catalyst, has a high raw material conversion rate and good target product selectivity, thereby significantly improving production efficiency and greatly reducing manufacturing costs, thereby providing a solid foundation for the expanded production and application of dimethyl ketone. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments.

[0052] The sources of raw materials or reagents used in the examples and comparative examples of the present invention are shown in the following table. Other raw materials or reagents are commercially available unless otherwise specified.

[0053]

[0054]

[0055] The source information of the equipment used in the embodiments and comparative examples of the present invention is shown in the following table. Other equipment are commercially available unless otherwise specified.

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

[0057] The analytical characterization methods used in the embodiments and comparative examples of the present invention are as follows, and other methods are common methods in the art unless otherwise specified.

[0058] The analysis was carried out using a gas chromatograph equipped with a FID detector and a SE-54 capillary column (25.0m×0.53mm×0.02mm). The chromatography was analyzed using a programmed temperature method, maintaining 120°C for 1 min, increasing to 200°C at 15°C / min and maintaining for 10 min, with an injection port at 240°C, a split ratio of 50:1, and a detector of FID at 240°C.

[0059] The percentages used in the embodiments and comparative examples of the present invention are all mass percentages unless otherwise specified.

[0060] Example 1

[0061] Weigh 4 g of template hexamethylimine and 0.0008 g of zirconium chloride into a 500 mL beaker, then add 160 mL of dilute hydrochloric acid (1 mol / L) to adjust the pH to 0, stir and dissolve at 10°C, add 10.4165 g of tetraethyl orthosilicate dropwise, and continue stirring to react for 8 h.

[0062] 0.1051 g of dimethyl tetrafluoroterephthalate was weighed and added to the above solution, and the pH value was adjusted to 1 by dropping a 2% sodium hydroxide aqueous solution, and stirring was continued for 4 hours, and then aged at 180°C for 48 hours, filtered, washed with deionized water, and dried at 40°C for 1 hour to obtain a zirconium-modified molecular sieve.

[0063] Weigh 0.1256 g of titanium nitrate and 0.1260 g of rubidium nitrate and dissolve them in deionized water to prepare a solution with a total salt concentration of 10%. Add the above-mentioned zirconium-modified molecular sieve carrier to the solution, add ammonia water dropwise to adjust the pH value of the solution to 7-8, react at 40°C for 1 hour, filter and wash, and calcine at 400°C for 8 hours to obtain TiRb / Zr-MCM-22 / composite solid catalyst A.

[0064] Example 2

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

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

[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 carrier was added to the solution, and a 2% sodium hydroxide aqueous solution was added dropwise to adjust the pH value of the solution to 7-8. The solution was reacted at 50°C for 2 h. After filtering and washing, it was calcined at 500°C for 4 h to obtain TiRb / Zr-MCM-22 / composite solid catalyst B.

[0068] Example 3

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

[0070] 0.0526 g of dimethyl tetrafluoroterephthalate was weighed and added to the above solution, and the pH value was adjusted to 3 by adding a 2% sodium hydroxide aqueous solution, and stirring was continued for 4 hours, and then aged at 140°C for 18 hours, filtered, washed with deionized water, and dried at 60°C for 2 hours to obtain a zirconium-modified molecular sieve.

[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 carrier was added to the solution, and ammonia water was added dropwise to adjust the pH value of the solution to 7-8. The solution was reacted at 40°C for 1 hour. After filtering and washing, it was calcined at 450°C for 7 hours to obtain TiRb / Zr-MCM-22 / composite solid catalyst C.

[0072] Example 4

[0073] Weigh 4 g of template hexamethylimine and 0.0054 g of zirconium chloride into a 500 mL beaker, then add 160 mL of dilute hydrochloric acid (1 mol / L) to adjust the pH to 0.5, stir and dissolve at 40°C, add 10.4165 g of tetraethyl orthosilicate dropwise, and continue stirring to react for 8 h.

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

[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 carrier was added to the solution, and a 2% potassium hydroxide aqueous solution was added dropwise to adjust the pH value of the solution to 7-8. The solution was reacted at 60°C for 2 h, filtered and washed, and then calcined at 480°C for 5 h to obtain TiRb / Zr-MCM-22 / composite solid catalyst D.

[0076] Example 5

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

[0078] 0.0116 g of diethyl tetrafluoroterephthalate was weighed and added to the above solution, and the pH value was adjusted to 1 by dropping a 2% sodium hydroxide aqueous solution. Stirring was continued for 4 h, and then aged at 100° C. for 1 h. The zirconium-modified molecular sieve was obtained by filtering, washing with deionized water, and drying at 40° C. for 2 h.

[0079] Weigh 2.3184 g of titanium nitrate and 0.1163 g of rubidium carbonate and dissolve them in deionized water to prepare a solution with a total salt concentration of 10%. Add the above-mentioned zirconium-modified molecular sieve carrier to the solution, add ammonia water dropwise to adjust the pH value of the solution to 7-8, react at 50°C for 2h, filter and wash, and calcine at 420°C for 6h to obtain TiRb / Zr-MCM-22 / composite solid catalyst E.

[0080] Comparative Example 1

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

[0082] 0.1051 g of dimethyl tetrafluoroterephthalate was weighed and added to the above solution, and the pH value was adjusted to 1 by dropping a 2% sodium hydroxide aqueous solution, and stirring was continued for 4 hours, and then aged at 180°C for 48 hours, filtered, washed with deionized water, and dried at 40°C for 1 hour to obtain a zirconium-modified molecular sieve.

[0083] Weigh 0.1256g of titanium nitrate and 0.1260g of rubidium nitrate and dissolve them in deionized water to prepare a solution with a total salt concentration of 10%, add the above zirconium modified molecular sieve carrier to the solution, add ammonia water dropwise to adjust the pH value of the solution to 7-8, react at 40°C for 1h, filter and wash, and calcine at 400°C for 8h to obtain TiRb / Zr-SBA-15 / composite solid catalyst F. The 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 that zirconium chloride is not added for molecular sieve modification, other steps are the same as those in Example 1 to obtain TiRb / MCM-22 / composite solid catalyst G.

[0086] Comparative Example 3

[0087] Except that the dimethyl tetrafluoroterephthalate auxiliary agent was not added, the other steps were the same as those in Example 1 to obtain TiRb / Zr-MCM-22 / composite solid catalyst H.

[0088] Comparative Example 4

[0089] Except that the auxiliary agent dimethyl tetrafluoroterephthalate was changed to 0.0395 g tetrafluoroethylene, the other steps were the same as those in Example 1 to obtain TiRb / Zr-MCM-22 / composite solid catalyst I.

[0090] The compositions of the catalysts prepared in the above examples and comparative examples were 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 ketene.

[0095] Application Example 1

[0096] A continuous experiment was carried out using a fixed bed, filled with 50 g of the catalyst A prepared in Example 1, and fed with 180 g of isobutyric acid at a temperature of 550° C., a pressure of 10 KPaA, and a residence time of 2 s. The material after the reaction was quantified by gas chromatography, and the isobutyric acid conversion rate was 68%, the dimethyl ketone product was 78 g, and the dimethyl ketone selectivity was 80%.

[0097] Application Example 2

[0098] A continuous experiment was carried out using a fixed bed, filled with 50 g of the catalyst B prepared in Example 2, and fed with 180 g of isobutyric acid at a temperature of 600° C., a pressure of 15 KPaA, and a residence time of 1.5 s. After the reaction was completed, the material was quantified by gas chromatography, and the isobutyric acid conversion rate was 69.3%, the dimethyl ketone product was 84.4 g, and the dimethyl ketone selectivity was 85.1%.

[0099] Application Example 3

[0100] A continuous experiment was conducted using a fixed bed, filled with 50 g of the catalyst C prepared in Example 3, and fed with 180 g of isobutyric acid at a temperature of 650° C., a pressure of 10 KPaA, and a residence time of 1 s. The materials after the reaction were quantified using gas chromatography, and the isobutyric acid conversion rate was 75.5%, the dimethyl ketone product was 99.5 g, and the dimethyl ketone selectivity was 92%.

[0101] Application Example 4

[0102] A continuous experiment was conducted using a fixed bed, filled with 50 g of the catalyst D prepared in Example 4, and fed with 180 g of isobutyric acid at a temperature of 700° C., a pressure of 25 KPaA, and a residence time of 0.2 s. After the reaction was completed, the material was quantified using gas chromatography, and the isobutyric acid conversion rate was 80.3%, the dimethyl ketone product was 105.2 g, and the dimethyl ketone selectivity was 91.5%.

[0103] Application Example 5

[0104] A continuous experiment was conducted using a fixed bed, filled with 50 g of the catalyst E prepared in Example 5, and fed with 180 g of isobutyric acid at a temperature of 700° C., a pressure of 30 KPaA, and a residence time of 0.5 s. After the reaction was completed, the material was quantified by gas chromatography, and the isobutyric acid conversion rate was 80.5%, the dimethyl ketone product was 88.9 g, and the dimethyl ketone selectivity was 77.1%.

[0105] Application Example 6

[0106] A continuous experiment was carried out using a fixed bed, filled with 50 g of catalyst A prepared in Example 1 (the catalyst had been continuously operated for 200 h under the same experimental conditions), and fed with 180 g of isobutyric acid at a temperature of 550° C., a pressure of 10 KPaA, and a residence time of 2 s. After the reaction was completed, the material was quantified by gas chromatography, and the isobutyric acid conversion rate was 67.7%, the dimethyl ketone product was 76.1 g, and the dimethyl ketone selectivity was 78.5%.

[0107] Application Example 7

[0108] A continuous experiment was carried out using a fixed bed, filled with 50 g of the catalyst F prepared in Comparative Example 1, and fed with 180 g of isobutyric acid at a temperature of 550° C., a pressure of 10 KPaA, and a residence time of 2 s. The material after the reaction was quantified by gas chromatography, and the isobutyric acid conversion rate was 52.1%, the dimethyl ketone product was 37.4 g, and the dimethyl ketone selectivity was 50.2%.

[0109] Application Example 8

[0110] A continuous experiment was carried out using a fixed bed, filled with 50 g of the catalyst G prepared in Comparative Example 2, and fed with 180 g of isobutyric acid at a temperature of 550° C., a pressure of 10 KPaA, and a residence time of 2 s. The material after the reaction was quantified by gas chromatography, and the isobutyric acid conversion rate was 60%, the dimethyl ketone product was 58.8 g, and the dimethyl ketone selectivity was 68.5%.

[0111] Application Example 9

[0112] A continuous experiment was carried out using a fixed bed, filled with 50 g of the catalyst H prepared in Comparative Example 3, and fed with 180 g of isobutyric acid at a temperature of 550° C., a pressure of 10 KPaA, and a residence time of 2 s. The materials after the reaction were quantified using gas chromatography, and the isobutyric acid conversion rate was 48.5%, the dimethyl ketone product was 45.1 g, and the dimethyl ketone selectivity was 65%.

[0113] Application Example 10

[0114] A continuous experiment was carried out using a fixed bed, filled with 50 g of the catalyst I prepared in Comparative Example 4, and fed with 180 g of isobutyric acid at a temperature of 550° C., a pressure of 10 KPaA, and a residence time of 2 s. The materials after the reaction were quantified using gas chromatography, and the isobutyric acid conversion rate was 65%, the dimethyl ketone product was 68.2 g, and the dimethyl ketone selectivity was 73.3%.

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

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

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

Claims

1. A supported metal oxide catalyst, characterized in that: The catalyst uses a Zr-modified silicon-based molecular sieve containing F as a carrier, and loads active metal oxides thereon, 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; in terms of mass percentage of elements, the catalyst contains 0.1-3% of F, 0.005-0.1% of Zr, and 2-35% of active metals.

2. The supported metal oxide catalyst according to claim 1, characterized in that 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, preferably ten-membered ring pores or twelve-membered ring pores; Preferably, the silicon-based molecular sieve is an MCM molecular sieve; More preferably, the silicon-based molecular sieve is MCM-22 molecular sieve.

3. The supported metal oxide catalyst according to claim 1 or 2, characterized in that: The active metal oxides are TiO2 and Rb2O, and the mass ratio of the two is 1 to 10:1, preferably 2 to 5:

1.

4. The method for preparing a supported metal oxide catalyst according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1: mixing the template, Zr source and silicon source and performing a hydrothermal reaction; S2: adding a F-containing additive to the hydrothermal material obtained in step S1 and aging the material, separating the obtained solid, and drying the solid to obtain a molecular sieve precursor; and S3: In the presence of a precipitant, the molecular sieve precursor obtained in step S2 and the active metal source are co-precipitated in an aqueous solution, and the obtained precipitate is separated and calcined to obtain the product.

5. The preparation method according to claim 4, characterized in that: The template agent is hexamethylimine; and / or The Zr source is one or more of zirconium chloride, zirconium nitrate, and zirconium tert-butoxide; and / or The silicon source is one or two of tetraethyl orthosilicate and pseudo-boehmite; Preferably, the amount of Zr in the Zr source is 0.01 to 0.1 wt.% of the silicon source, calculated as silicon oxide; Preferably, the hydrothermal reaction is carried out at 10 to 50°C; Preferably, the hydrothermal reaction is carried out at a pH value not exceeding 2.

6. The preparation method according to claim 4 or 5, characterized in that: The F-containing auxiliary agent is a C1-C4 alkyl diester of tetrafluoroterephthalic acid, preferably one or both of dimethyl tetrafluoroterephthalate and diethyl tetrafluoroterephthalate; Preferably, the amount of the F-containing additive is 0.1 to 1 wt.% of the silicon source, calculated as silicon oxide; Preferably, the aging is carried out at a pH value of 1 to 4, an aging temperature of 100 to 200° C., and an aging time of 1 to 48 hours.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The step S3 comprises the following process: adding the molecular sieve precursor obtained in step S2 to an aqueous solution of an active metal source, adding a precipitant for co-precipitation, separating the obtained precipitate, and calcining to obtain the supported metal oxide catalyst; Preferably, the precipitate is calcined at 400-600° C. for 2-10 h in an inert atmosphere.

8. The preparation method according to claim 7, characterized in that: The active metal source is one or more of nitrates, chlorides, carbonates, sulfates and phosphates of active metals; Preferably, the active metal source includes one or more of titanium nitrate, titanium chloride, tetrabutyl titanate and one or more of rubidium nitrate, rubidium chloride, and rubidium carbonate; more preferably, the mass percentage concentration of the aqueous solution of the active metal source is 5 to 20%; Preferably, the precipitant is aqueous ammonia, a sodium hydroxide solution or a potassium hydroxide solution with a mass percentage concentration of 1 to 10%; More preferably, after adding the precipitant, the pH value of the obtained coprecipitation system is 7-8, and the coprecipitation is carried out at 30-70° C. for 1-6 hours.

9. Use of the supported metal oxide catalyst according to any one of claims 1 to 3 or the supported metal oxide catalyst prepared by the preparation method according to any one of claims 4 to 8 for catalyzing the cracking of isobutyric acid to prepare dimethyl ketone.

10. A method for preparing dimethyl ketene by cracking isobutyric acid, characterized in that: In the presence of a catalyst, dimethyl ketene is prepared by a cracking reaction using isobutyric acid as a raw material, wherein the catalyst is a supported metal oxide catalyst according to any one of claims 1 to 3, or a supported metal oxide catalyst prepared by the preparation method according to any one of claims 4 to 8; Preferably, the reaction temperature of the cracking reaction is 500-700° C., and the reaction pressure is 10-30 KPaA.

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