Process for cracking 2,2-dimethoxyalkanes with high catalyst lifetime and metal-organic framework material and method for its preparation

Abstract

The application relates to the field of cracking reactions, and discloses a method for cracking 2,2-dimethoxypropane with high catalyst service life and a metal organic framework material and a preparation method thereof. The method for cracking 2,2-dimethoxypropane comprises the following steps: contacting 2,2-dimethoxyalkane and a catalyst and performing a cracking reaction. The method for cracking 2,2-dimethoxypropane has high catalytic activity, the structure of the catalyst is stable, the catalyst can be repeatedly used, the service life is high, the production cost can be more favorably reduced, the reaction can be performed at a lower temperature in a gas phase, the post-treatment is simple, the product can be separated in a simple mode, and the synthesis efficiency is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of cracking reaction, in particular to a method for cracking 2,2-dimethoxyalkane with high catalyst life and a metal organic framework material and a preparation method thereof. BACKGROUND

[0002] 2-methoxypropene is a very important synthetic raw material, especially for the synthesis of clarithromycin, which is a key intermediate. Clarithromycin is a new type of macrolide antibiotic with broad-spectrum, high efficiency and low toxicity, and has very good clinical efficacy in the infection of accessory structural organs.

[0003] 2-methoxypropene was prepared by cracking 2,2-dimethoxypropane in liquid phase in the early stage, mostly using alkanes as solvent and sulfonic acid as catalyst. However, this method was gradually eliminated due to the relatively complicated post-treatment and the corrosion of large amount of sulfonic acid to industrial equipment. The work published by Marianne et al. in Tetrahedron Letters, 1982, 23(6):631-634 in 1982 used neodecanoic acid as catalyst, and the yield of 2-methoxypropene could reach 71.0% after 4h reaction. However, the use of organic acid cannot be used for fixed bed reaction, i.e. the separation of product and catalyst is relatively complex. The work published by Li Xiaoxi et al. in Anhui Chemical Industry, 2009, 35(6):29-30 in 2009 made improvement on the basis of the above work, using toluene instead of diethylene glycol dimethyl ether (14.6mL) as solvent, succinic anhydride (20g), pyridine (15.6mL) and benzoic acid (0.58g) as catalyst, the yield could reach 81% and the purity of product could reach 97%. The product was acidically regulated by pyridine, but it was still a homogeneous reaction, and the separation of catalyst and product was difficult. The work published by Dietrich et al. in Patent 5767325.1998-6-16 in 1998 used ZSM-5 type catalyst for gas phase catalytic cracking of 2,2-dimethoxypropane, the reaction temperature was between 280℃ and 340℃, the yield of product reached 83.3%, and the activity of catalyst before and after reaction hardly decreased. The advantage of this synthesis process is that the catalyst is easy to recover, and the disadvantage is that the preparation of catalyst is relatively complex. In the synthesis of 2-methoxypropene, the use of solid catalyst method can better meet the needs of industrialization, but the disadvantage is that the catalyst is easy to be deactivated, resulting in the increase of cost.

[0004] At present, in the synthesis of 2-methoxypropene, there are problems such as high reaction temperature, difficult separation of materials after reaction, short service life of catalyst, high cost of 2-methoxypropene synthesis, and coking in the reaction process. SUMMARY

[0005] The present application aims to overcome the above-mentioned problems existing in the prior art, and provides a method for cracking 2,2-dimethoxyalkane with high catalyst life, a metal organic framework material and a preparation method thereof. The method for cracking 2,2-dimethoxyalkane has high catalytic activity, the catalyst structure is stable, and the catalyst can be repeatedly used, has high life, is more conducive to reducing production cost, and can perform reaction at a lower temperature in a gas phase, and the post-processing is simple, the separation of products can be realized in a simple manner, and the synthesis efficiency is higher.

[0006] In order to achieve the above-mentioned purpose, the present application provides a method for cracking 2,2-dimethoxyalkane with high catalyst life, which comprises: contacting 2,2-dimethoxyalkane and a catalyst and performing a cracking reaction, wherein the catalyst is a metal organic framework material, a ligand of the metal organic framework material is provided by a substance with a structure as shown in formula (1), and a coordination metal M is selected from one of Zn, Co and Zr; in formula (1), M" includes H and an alkali metal element, and the alkali metal element is selected from one of Li, Na, K and Cs.

[0007]

[0008] The second aspect of the present application provides a metal organic framework material, which is the metal organic framework material as defined in the first aspect or the partially acidified product as described in the first aspect.

[0009] The third aspect of the present application provides a preparation method of a metal organic framework material, which is the preparation method of the partially acidified product as described in the first aspect.

[0010] The method provided by the present application for cracking 2,2-dimethoxyalkane has high catalytic activity, the catalyst structure is stable, and the catalyst can be repeatedly used, has high life, is more conducive to reducing production cost, and reduces the influence on the environment; and can perform reaction at a lower temperature in a gas phase, and the post-processing is simple, the separation of products can be realized in a simple manner, and the synthesis efficiency is higher. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 FIG. 1 is a thermogravimetric diagram of the metal organic framework material prepared in Example 1. DETAILED DESCRIPTION

[0012] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The ranges or values should be construed to be roughly about the ranges or values. The endpoints of the ranges of values, the endpoints of the ranges of values, and the individual values can be combined with one another to create new ranges or values, which are to be considered disclosed herein, unless otherwise indicated or unless it is clear from the context that the combination is not intended.

[0013] In a first aspect, the present application provides a method for cracking 2,2-dimethoxyalkane with high catalyst life, the method comprising: contacting 2,2-dimethoxyalkane and a catalyst and performing a cracking reaction, wherein the catalyst is a metal-organic framework material, the ligand of the metal-organic framework material is provided by a substance with a structure as shown in formula (1) and the coordination metal M is selected from one of Zn, Co and Zr; in formula (1), M" includes H and an alkali metal element, and the alkali metal element is selected from one of Li, Na, K and Cs;

[0014]

[0015] The inventors of the present application found in research that, when cracking 2,2-dimethoxyalkane to prepare 2-methoxyalkene by using the above method, the catalytic activity is high, which is much higher than the activity of the currently commonly used catalysts such as sulfonic acid, benzoic acid, ZSM-5 and acidic aluminum oxide, greatly improving the synthesis efficiency of 2-methoxyalkene; and the catalyst structure is stable, can be repeatedly used, has a long life, can reduce the environmental pollution caused by the preparation of the catalyst, and significantly reduces the synthesis cost of 2-methoxyalkene; the reaction can be carried out at a relatively low temperature, and can be carried out in a fixed bed, the product and yield and purity are relatively high, and the separation of the product from the catalyst after the reaction is simple. As a very important pharmaceutical intermediate, the improvement of the synthesis efficiency of 2-methoxyalkene can greatly reduce its synthesis cost, which is extremely important for the development of the pharmaceutical industry.

[0016] It can be understood that, in order to obtain 2-methoxyalkene by cracking, the number of carbon atoms of 2,2-dimethoxyalkane is greater than or equal to 3, for example, it can be 2,2-dimethoxypropane, 2,2-dimethoxybutane, etc. According to a particularly preferred embodiment of the present application, the 2,2-dimethoxyalkane is 2,2-dimethoxypropane, and the 2-methoxyalkene is 2-methoxypropene.

[0017] It can be understood that M" includes H and an alkali metal element, and the alkali metal element is selected from one of Li, Na, K and Cs, which means that the catalyst simultaneously contains a structure in which M" is H and a structure in which M" is the above-mentioned alkali metal element.

[0018] According to the present application, preferably, the molar ratio of the alkali metal element to H in M" is (0.001-1000):1, preferably (0.005-50):1, and more preferably (0.03-1):1. The catalyst is acidic, has stable sulfonic acid groups, and has a stable skeleton structure in water and organic solvents. The catalyst provided by the present application can generally exist stably. Moreover, the acidity of the catalyst can be adjusted by adjusting the molar ratio of the metal element to H, so as to further improve the efficiency of the catalyst, the selectivity and conversion rate of the product. The molar ratio of the metal element to H (i.e., the ratio of the sulfonic acid metal salt group to the sulfonic acid group) can be determined by thermogravimetric method. In the thermogravimetric curve, the weight of the metal-organic skeleton material mainly appears three times of weight loss as the temperature increases. The first time is caused by the weight loss of the sulfonic acid group, the second time is caused by the sulfonic acid metal salt group, and the last time is caused by the complete combustion of the organic skeleton.

[0019] According to the present application, preferably, the average particle size of the metal-organic skeleton material is 3-20 μm, the specific surface area is 300-1800 m 2 / g, the pore volume is 1-10 ml / g, and the most probable pore size is 2-9 nm.

[0020] Preferably, the average particle size of the metal-organic skeleton material is 4-15 μm, the specific surface area is 350-1500 m 2 / g, the pore volume is 5-9 ml / g, and the most probable pore size is 2.5-8.8 nm.

[0021] Preferably, the average particle size of the metal-organic skeleton material is 5-12 (for example, can be 5, 6, 7, 8, 9, 10, 11, 12, and a range formed by any two of the above values and values within the range) μm, the specific surface area is 400-1000 (for example, can be 400, 500, 600, 700, 800, 900, 1000, and a range formed by any two of the above values and values within the range) m 2 / g, the pore volume is 5.1-8.9 (for example, can be 5.1, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 8.9, and a range formed by any two of the above values and values within the range) ml / g, and the most probable pore size is 3-8.5 (for example, can be 3, 4, 5, 6, 7, 7.5, 8, 8.5, and a range formed by any two of the above values and values within the range) nm.

[0022] According to the present application, preferably, the metal-organic skeleton material has a structure as shown in formula (2):

[0023]

[0024] As described above, it can be understood that the metal organic framework material also has a structure in which H in -SO3H in formula (2) is replaced by the above-mentioned optional metal.

[0025] According to the present application, preferably, the preparation method of the metal organic framework material comprises the following steps:

[0026] (1) allowing a compound shown in formula (3) to perform a coordination reaction with a metal source to be coordinated in the presence of a first solvent and an organic acid;

[0027] (2) allowing the product of the coordination reaction to perform partial acidification in the presence of an inorganic acid;

[0028] wherein, in formula (3), M' is selected from one of Li, Na, K and Cs; the metal M in the metal source to be coordinated is selected from one of Zn, Co and Zr;

[0029]

[0030] wherein, "partial acidification" means that the metal M' is partially replaced by H, so that the finally obtained product of partial acidification, wherein the position of M' is partially an alkali metal element and partially H.

[0031] According to the present application, preferably, in step (1), the conditions of the coordination reaction (i.e. sintering occurs) include: temperature is 85-220℃, preferably 90-130 (for example, can be 90, 100, 110, 120, 130 and any two numerical values formed range and values within the range) ℃, time is 8-30h, preferably 20-28 (for example, can be 20, 21, 22, 23, 24, 25, 26, 27, 28 and any two numerical values formed range and values within the range) h.

[0032] According to the present application, preferably, in step (1), the molar ratio of the metal source to be coordinated, the compound shown in formula (3), the first solvent and the acid is (1-4):1:(3-60):(1-10), preferably (2-3):1:(20-50):(3-8).

[0033] According to the present application, preferably, in step (1), the metal source to be coordinated is selected from one of Zn(acac)2, Cr(NO3)3 and ZrCl4. Zn(acac)2 refers to zinc acetylacetonate. The hydrates corresponding to the above-mentioned substances can also be used, for example, Cr(NO3)3·6H2O.

[0034] According to the present application, preferably, the first solvent is selected from at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide and N-methyl pyrrolidone.

[0035] According to the present application, preferably, in step (1), the organic acid is at least one selected from the group consisting of formic acid, acetic acid, benzoic acid and phenylacetic acid.

[0036] After the coordination reaction, the material can be centrifuged and suction filtered, and the obtained solid can be sequentially washed and dried. The centrifugation can be performed at 3500-6000 rpm for 10-60 min; in the washing, the solid can be first washed with DMF for 2-4 times, and then washed with methanol for 2-4 times, and the amount of the washing agent used in the washing is not particularly limited. The drying can be performed at 100-130 ℃ for 2-10 h.

[0037] According to the present application, preferably, in step (2), the inorganic acid is at least one selected from the group consisting of hydrochloric acid, sulfuric acid and nitric acid. The solid product obtained in step (1) can be mixed with an aqueous acid solution, and the concentration of the acid in the aqueous acid solution can be 0.8-8 mol / L.

[0038] According to the present application, preferably, the partial acidification is performed at a temperature of 20-50 (for example, 20, 25, 30, 35, 40, 45, 50 and any two of the above values or a range formed by the above values) ℃ for 1-8 (for example, 1, 2, 3, 4, 5, 6, 7, 8 and any two of the above values or a range formed by the above values) h.

[0039] According to the present application, preferably, the amount of the inorganic acid used is 0.01-0.99 mol per mol of the compound represented by formula (3).

[0040] After the partial acidification, the material obtained by the partial acidification can be suction filtered, and the obtained solid can be washed with water for 2-4 times. The amount of the water used in the washing is not particularly limited.

[0041] In the present application, the method for obtaining the compound represented by formula (3) is not particularly limited. Preferably, the preparation of the compound represented by formula (3) comprises: performing a substitution reaction of 4,4’-diphenyldicarboxylic acid with chlorosulfonate in the presence of a second solvent and a metal halide.

[0042] According to the present application, preferably, the substitution reaction is performed at a temperature of 30-100 ℃, preferably 40-80 (for example, 40, 45, 48, 49, 50, 51, 52, 53, 55, 58, 60, 65, 70, 75, 80 and any two of the above values or a range formed by the above values) ℃ for 5-30 h, preferably 8-24 (for example, 8, 10, 12, 18, 20, 22, 23, 24 and any two of the above values or a range formed by the above values) h.

[0043] According to the present application, preferably, the molar ratio of 4,4'-biphenyldicarboxylic acid, chlorosulfonate and metal halide is 1:(0.7-1.5):(0.01-0.2).

[0044] The metal halide can be RuCl3. The second solvent can be dichloroethane. The amount of the second solvent is not particularly limited, for example, the amount of the second solvent can be 30-150 ml relative to 1 g of 4,4'-biphenyldicarboxylic acid. The metal element in the chlorosulfonate is M'.

[0045] After the substitution reaction is completed, the material after the substitution reaction can be sequentially subjected to suction filtration, washing and drying. Washing can be performed using dichloroethane first, the number of times can be 2-4 times, and then using methanol, the number of times can also be 2-4 times; the drying temperature can be 80-120°C, and the time can be 2-8 h.

[0046] According to the present application, preferably, the cracking reaction is performed by introducing a gas containing 2,2-dimethoxyalkane into a reactor loaded with a catalyst.

[0047] According to a preferred embodiment of the present application, the reactor is a fixed bed reactor. The catalyst is filled in the fixed bed reactor, and the gas is introduced to perform the reaction.

[0048] Preferably, the amount of the gas containing 2,2-dimethoxyalkane introduced is such that the space velocity of 2,2-dimethoxyalkane is 2000-20000 ml / h. The gas containing 2,2-dimethoxyalkane uses a non-reactive gas as a carrier gas, and the non-reactive gas can be selected from at least one of nitrogen, helium and argon.

[0049] According to the present application, preferably, the cracking reaction is performed at a temperature of 25-250°C, preferably 45-155 (for example, 45, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 155 and any two of the above values form a range and values within the range) °C.

[0050] Preferably, after the cracking reaction, the method further comprises: subjecting the liquid phase obtained by the cracking reaction to rectification. By using the method of the present application, the separation of the material after the reaction can be achieved in a simple manner. The reduced pressure rectification can be performed at 0.1-0.5 atm.

[0051] Preferably, the distillation is carried out in a distillation column at a distillation temperature of 30-90°C, preferably 45-65 (e.g. 45, 50, 55, 60, 65 and any range formed by any two of these values and values within the range) °C.

[0052] In a second aspect, the present application provides a metal organic framework material, which is the metal organic framework material defined in the first aspect or the partially acidified product of the first aspect.

[0053] In a third aspect, the present application provides a method for preparing a metal organic framework material, which is the method for preparing the partially acidified product of the first aspect.

[0054] The present application will be described in detail below by way of examples.

[0055] In the following examples, the average particle size is determined by Thermo Scientific TM Apreo scanning electron microscope, the specific surface area, pore volume, most probable pore diameter are determined by physical adsorption instrument Anton Paar QuantaTec. In the catalyst, the molar ratio of alkali metal elements and H in M" is determined by the ratio of sulfonic acid metal salt root and sulfonic acid root, that is, by thermogravimetric method: the weight of the material mainly appears three times of weight loss as the temperature rises, the first time is caused by the weight loss of sulfonic acid root, and the second time is caused by the weight loss of sulfonic acid metal salt root. For example, as shown in the metal organic framework material prepared in Example 1, the weight loss near 300-400°C is caused by the sulfonic acid root, and the weight loss near 400-500°C is caused by the sulfonic acid metal salt root. Figure 1

[0056] In the following examples, the reaction tube length used in the cracking reaction (using a fixed bed reaction) is 1 meter, and the inner diameter is 1 centimeter.

[0057] In the following examples, the liquid phase obtained after the reaction is subjected to distillation (distillation under reduced pressure at 50°C, 0.2 atm), and 2-methoxypropene, methanol and 2,2-dimethoxypropane are separated, and each substance and the corresponding content are confirmed by GC.

[0058] In the following examples, the conversion rate of 2,2-dimethoxypropane is calculated as follows: 100%-the mass percentage of 2,2-dimethoxypropane in the liquid phase obtained by reaction;

[0059] The reaction selectivity is calculated as follows: the ratio of the sum of the amount of 2-methoxypropene and the amount of methanol in the liquid phase obtained by reaction to the conversion rate value of 2,2-dimethoxypropane.

[0060] Example 1

[0061] ​(1) Preparation of acidic metal organic framework material 1, which corresponds to a coordination metal M of Zn, M" of H and Na.

[0062] To the reaction bottle, 1.04 g of RuCl3, 24.20 g of 4,4'-diphenyldicarboxylic acid, 16.5 g of sodium chlorosulfonate and 1000 mL of 1,2-dichloroethane were added, and substitution reaction was performed at 50°C for 10 h, suction filtration was performed, the solid was washed with 100 mL of 1,2-dichloroethane three times, washed with 100 mL of methanol three times, and dried at 80°C for 10 h to obtain 38.9 g of a white powder (confirmed by NMR to be a compound represented by formula (3) in which M' is Na).

[0063] Subsequently, Zn(acac)2, the compound represented by formula (3) described above, DMF and benzoic acid were mixed in a molar ratio of 2.5:1:40:6, and coordination reaction (sintering crystal) was performed at 95°C for 24 h, centrifugation was performed at 4000 rpm for 60 min, and then suction filtration was performed, the solid was washed with 50 mL of DMF three times, washed with 50 mL of methanol three times, and the solid was dried at 105°C for 8 h to obtain a white solid.

[0064] To the white solid obtained in the above step, 5 mol / L of sulfuric acid was added in an amount of 0.08 mol per 1 mol of the compound represented by formula (3), and acidification was performed at 25°C for 5 h with stirring; suction filtration was performed, and the solid was washed with 50 mL of water three times to obtain an acidified metal organic framework material (it was confirmed by XRD spectrum and scanning electron microscope image that the same framework structure as in formula (2) was obtained, in which Zn is a coordination metal). The average particle diameter of the obtained metal organic framework material was 7 μm, the specific surface area was 774 m 2 / g, the pore volume was 8.3 ml / g, and the most probable pore diameter was 5.5 nm. The ratio of sodium sulfonate to sulfonic acid in the catalyst was 0.05:1.

[0065] (2) Cleavage of 2,2-dimethoxypropane: The acidic metal organic framework material prepared in step (1) was loaded into a reaction tube, and the loading length was 1 cm. The amount of 2,2-dimethoxypropane-containing gas (carrier gas: nitrogen) was adjusted so that the space velocity of 2,2-dimethoxypropane was 8000 ml / h, and the reaction temperature was 100°C. The reaction product was monitored by GC (gas chromatography), and after 2 hours of stable reaction, the mass content of 2-methoxypropene, methanol and 2,2-dimethoxypropane in the liquid phase of the reaction product was 67.2 wt%, 29.9 wt% and 2.5 wt%, respectively, i.e., the conversion rate was 97.5% and the selectivity was 99.6%. After 1500 hours of reaction, the content of 2-methoxypropene began to decrease, indicating that the reaction life of the above catalyst was 1500 hours.

[0066] Example 2

[0067] (1) Preparation of acidic metal organic framework material 2, which corresponds to a coordination metal M of Zr, M" of H and Na.

[0068] To a reaction bottle, 1.04 g of RuCl3, 24.20 g of 4,4'-diphenyldicarboxylic acid, 16.5 g of sodium chlorosulfonate and 1000 mL of 1,2-dichloroethane were added, and substitution reaction was performed at 50°C for 10 h. The solid was washed with 100 mL of 1,2-dichloroethane three times, washed with 100 mL of methanol three times, and dried at 80°C for 5 h to obtain 38.9 g of a white powder (confirmed by NMR to be a compound represented by formula (3) in which M' is Na).

[0069] Subsequently, ZrCl4, the compound represented by formula (3) described above, DMF and benzoic acid were subjected to coordination reaction (sintering crystal) at a molar ratio of 2.5:1:40:6 at 120°C for 24 h, centrifuged at 4000 rpm for 50 min, and then suction filtered. The solid was washed with 50 mL of DMF three times, washed with 50 mL of methanol three times, and the solid was dried at 105°C for 8 h to obtain a white solid.

[0070] To the obtained white solid, 1 mol / L of sulfuric acid was added in an amount of 0.07 mol per 1 mol of the compound represented by formula (3), and acidification was performed at 25°C for 5 h with stirring. The solid was washed with 50 mL of water three times to obtain an acidified metal organic framework material (confirmed by XRD pattern and scanning electron microscope to have the same framework structure as in formula (2) in which Zr is a coordination metal). The average particle diameter of the obtained metal organic framework material was 12 μm, the specific surface area was 828 m2 / g, the pore volume was 8 ml / g, and the most probable pore diameter was 3 nm. The ratio of sodium sulfonate to sulfonic acid in this catalyst was 0.77:1. 2

[0071] (2) Cleavage of 2,2-dimethoxypropane: The acidic metal organic framework material prepared in step (1) was loaded into a reaction tube at a length of 1 cm. A gas containing 2,2-dimethoxypropane (carrier gas: nitrogen) was introduced in an amount such that the space velocity of 2,2-dimethoxypropane was 10000 ml / h, and the reaction temperature was 120°C. The reaction product was monitored by GC, and after 2 hours of stable reaction, the mass content of 2-methoxypropene, methanol and 2,2-dimethoxypropane in the liquid phase of the reaction product was 65.9 wt%, 29.3 wt% and 3.7 wt%, respectively, i.e., the conversion rate was 96.3% and the selectivity was 98.8%. After 1600 hours of reaction, the content of 2-methoxypropene began to decrease, indicating that the reaction life of the above-described catalyst was 1600 hours.

[0072] Example 3 ​

[0073] (1) Preparation of acidic metal organic framework material 3, which corresponds to a coordination metal M of Co, M" of H and Na.

[0074] Into a reaction bottle, 1.04 g of RuCl3, 24.20 g of 4,4'-diphenyldicarboxylic acid, 16.5 g of sodium chlorosulfonate and 1000 mL of 1,2-dichloroethane were added, and substitution reaction was carried out at 50°C for 10 h. The solid was washed with 100 mL of 1,2-dichloroethane three times, 100 mL of methanol three times, and dried at 100°C for 8 h to obtain 38.9 g of white powder (confirmed by NMR to be a compound represented by formula (3) wherein M' is Na).

[0075] Subsequently, Co(NO3)2 6H2O, the compound represented by formula (3), DMF and acetic acid were mixed in a molar ratio of 2.5:1:40:6, and coordination reaction (sintering crystal) was carried out at 120°C for 24 h. After centrifugation at 4000 rpm for 50 min, the solid was washed with 50 mL of DMF three times, 50 mL of methanol three times, and the solid was dried at 105°C for 8 h to obtain a white solid.

[0076] To the obtained white solid, 5 mol / L sulfuric acid was added in an amount of 0.06 mol per 1 mol of the compound represented by formula (3), and acidification was carried out at 25°C for 5 h with stirring. The solid was washed with 50 mL of water three times to obtain an acidified metal organic framework material (confirmed by XRD pattern and scanning electron microscope to have the same framework structure as in formula (2) wherein Co is a coordination metal). The average particle diameter of the obtained metal organic framework material was 7 μm, the specific surface area was 789 m2 / g, the pore volume was 8.9 ml / g, and the most probable pore diameter was 8.5 nm. The ratio of sodium sulfonate to sulfonic acid in the catalyst was 0.04:1. 2

[0077] (2) Cleavage of 2,2-dimethoxypropane: The acidic metal organic framework material prepared in step (1) was loaded into a reaction tube with a loading length of 1 cm. A gas containing 2,2-dimethoxypropane (carrier gas: nitrogen) was introduced in an amount such that the space velocity of 2,2-dimethoxypropane was 7000 ml / h, and the reaction temperature was 110°C. The reaction product was monitored by GC, and after 1 h of stable reaction, the mass content of 2-methoxypropene, methanol and 2,2-dimethoxypropane in the liquid phase of the reaction product was 66.0 wt%, 29.3 wt% and 4.4 wt%, respectively, the conversion rate was 95.6%, and the selectivity was 99.68%. After 1800 h of reaction, the content of 2-methoxypropene began to decrease, indicating that the reaction life of the above catalyst was 1800 h.

[0078] Example 4 ​

[0079] The metal-organic framework material was prepared according to the method of Example 3, except that sodium chlorosulfonate was replaced by lithium chlorosulfonate, i.e. in the obtained metal-organic framework material, M" is H and Li, and the molar ratio of lithium sulfonate to sulfonate in this catalyst is 1:4. After the reaction was stable for 1 hour, the mass content of 2-methoxypropene, methanol and 2,2-dimethoxypropane in the liquid phase obtained by the reaction was 63.0 wt%, 29.3 wt%, 6.4 wt%, i.e. the conversion rate was 93.6% and the selectivity was 98.6%.

[0080] Comparative Example 1

[0081] According to the method of step (2) in Example 1, except that the catalyst was an acidic ceramic filler (purchased from Inoceram, model number I11206). After the reaction was stable for 1 hour, it was monitored by GC, and the mass content of 2-methoxypropene, methanol and 2,2-dimethoxypropane in the liquid phase obtained by the reaction was 34.9 wt%, 14.7 wt%, 38.9 wt%, i.e. the conversion rate was 61.1% and the selectivity was 81.2%. The low selectivity and the absence of other by-products in the product indicate that organic substances in the system were carbonized on the surface of the catalyst.

[0082] Comparative Example 2

[0083] According to steps (1)-(2) of Example 3, except that when partially acidifying, an excess of sulfuric acid was added so that the corresponding position of M" in the catalyst was completely H. After the reaction was stable for 1 hour, it was monitored by GC in real time, and the mass content of 2-methoxypropene, methanol and 2,2-dimethoxypropane in the liquid phase obtained by the reaction was 44.2 wt%, 30.6 wt%, 14.2 wt%, i.e. the conversion rate was 85.8% and the selectivity was 87.2%. The low selectivity and the absence of other by-products in the product indicate that organic substances in the system were carbonized on the surface of the catalyst.

[0084] Comparative Example 3

[0085] According to steps (1)-(2) of Example 3, except that the step of partial acidification was not performed. After the reaction was balanced for 1 hour, it was monitored by GC in real time, and the mass content of 2-methoxypropene, methanol and 2,2-dimethoxypropane in the liquid phase obtained by the reaction was 8.6 wt%, 3.8 wt%, 85.8 wt%, i.e. the conversion rate was 14.2% and the selectivity was 87.3%.

[0086] It can be seen from the above examples and comparative examples that the method provided by the present application has high catalytic activity, stable catalyst structure, long service life, and can be repeatedly used, which is more conducive to reducing production cost and reducing environmental pollution; the reaction can be carried out at a lower temperature in a gas phase, the post-treatment is simple, the product can be separated in a simple way, the synthesis efficiency is high, the catalyst structure is stable, and the catalyst can be repeatedly used, which is more conducive to reducing production cost.

[0087] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and belong to the protection scope of the present application.

Claims

1. A method for cracking 2,2-dimethoxyalkanes with a high catalyst lifetime, characterized in that, The method includes: contacting 2,2-dimethoxyalkane with a catalyst and carrying out a cracking reaction, wherein the catalyst is a metal-organic framework material, the ligands of the metal-organic framework material are provided by a substance with the structure shown in formula (1) and the coordinating metal M is selected from Zn, Co and Zr; in formula (1), M" is H and an alkali metal element, the alkali metal element being selected from Li, Na, K and Cs; （1）； The metal-organic framework material has a structure as shown in formula (2): （2）。 2. The method according to claim 1, wherein, In M", the molar ratio of alkali metal element to H is (0.001-1000):

1.

3. The method according to claim 2, wherein, In M", the molar ratio of alkali metal element to H is (0.005-50):

1.

4. The method according to claim 3, wherein, In M", the molar ratio of alkali metal element to H is (0.03-1):

1.

5. The method according to claim 1, wherein, The metal-organic framework material has an average particle size of 3-20 μm and a specific surface area of ​​300-1800 m². 2 / g, pore volume is 1-10ml / g, and most probable pore size is 2-9nm.

6. The method according to claim 5, wherein, The metal-organic framework material has an average particle size of 4-15 μm and a specific surface area of ​​350-1500 m². 2 / g, pore volume is 5-9ml / g, and most probable pore size is 2.5-8.8nm.

7. The method according to claim 6, wherein, The metal-organic framework material has an average particle size of 5-12 μm and a specific surface area of ​​400-1000 m². 2 / g, pore volume is 5.1-8.9ml / g, and most probable pore size is 3-8.5nm.

8. The method according to claim 1, wherein, The preparation method of the metal-organic framework material includes the following steps: (1) In the presence of a first solvent and an organic acid, the compound shown in formula (3) undergoes a coordination reaction with the metal source to be coordinated; (2) In the presence of inorganic acid, the product of the coordination reaction is partially acidified; In formula (3), M' is selected from one of Li, Na, K and Cs; the metal M in the metal source to be coordinated is selected from one of Zn, Co and Zr. （3）。 9. The method according to claim 8, wherein, In step (1), the conditions for the coordination reaction include: temperature of 85-220℃ and time of 8-30h; And / or, in step (1), the molar ratio of the metal source to be coordinated, the compound shown in formula (3), the first solvent and the acid is (1-4):1:(3-60):(1-10).

10. The method according to claim 9, wherein, In step (1), the conditions for the coordination reaction include: a temperature of 90-130℃ and a time of 20-28h; And / or, in step (1), the molar ratio of the metal source to be coordinated, the compound shown in formula (3), the first solvent and the acid is (2-3):1:(20-50):(3-8).

11. The method according to any one of claims 8-10, wherein, In step (1), the metal source to be coordinated is selected from one of Zn(acac)2, Cr(NO3)3 and ZrCl4; And / or, the first solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone; And / or, in step (1), the organic acid is selected from at least one of formic acid, acetic acid, benzoic acid and phenylacetic acid.

12. The method according to any one of claims 8-10, wherein, In step (2), the inorganic acid is selected from at least one of hydrochloric acid, sulfuric acid, and nitric acid; And / or, the conditions for the partial acidification include: a temperature of 20-50°C and a time of 1-8 hours; And / or, the amount of the inorganic acid used is 0.01-0.99 mol relative to each mole of the compound represented by formula (3).

13. The method according to claim 1, wherein, The pyrolysis reaction is carried out by passing a gas containing 2,2-dimethoxyalkane into a reactor loaded with a catalyst.

14. The method according to claim 13, wherein, The amount of gas containing 2,2-dimethoxyalkane introduced is such that the space velocity of 2,2-dimethoxyalkane is 2000-20000 ml / h.

15. The method according to claim 1, wherein, The conditions for the pyrolysis reaction include: a temperature of 25-250℃; And / or, after the pyrolysis reaction, the method further includes: distilling the liquid phase obtained from the pyrolysis reaction.

16. The method according to claim 15, wherein, The conditions for the pyrolysis reaction include a temperature of 45-155℃.

17. The method according to claim 15, wherein, The distillation is carried out in a distillation column at a temperature of 30-90℃.

18. The method according to claim 17, wherein, The distillation temperature is 45-65℃.

19. A metal-organic framework material, characterized in that, The metal-organic framework material is the metal-organic framework material as defined in any one of claims 1-7 or the partially acidified product as described in any one of claims 8-18.

20. A method for preparing a metal-organic framework material, characterized in that, The preparation method is the method for preparing the partially acidified product as described in any one of claims 8-18.

Images