A hydrophobic Cu / SiO2 catalyst and its preparation and application

Abstract

The present invention discloses a hydrophobic Cu / SiO2 catalyst and its preparation and application. The preparation method of the hydrophobic Cu / SiO2 catalyst includes: adding a Cu / SiO2 catalyst into a mixed solution of a hydrophobic treatment agent and an organic solvent, oscillating at 30-60 °C for 1-12 h, filtering after oscillation and washing with ethanol to remove the excess hydrophobic treatment agent, and then drying in an oven at 40-200 °C for 1-24 h to obtain the hydrophobic Cu / SiO2 catalyst; the hydrophobic treatment agent is one or more of methoxytrimethylsilane, trimethylchlorosilane, dimethyldiacetoxysilane, and triisopropyloxysilane. The present invention provides the application of the hydrophobic Cu / SiO2 catalyst in the dehydrogenation lactonization reaction of diglycol, improving the selectivity / yield of the target product.

Description

(1) Technical Field

[0001] The present invention relates to a hydrophobic Cu / SiO2 catalyst, its preparation method and its application in the dehydrogenation lactonization reaction of diglycol. (2) Background Art

[0002] 1,4-Dioxan-2-one (PDO) is an important organic chemical product with a wide range of uses. It can not only be directly used as a fragrance and food additive, but also be a monomer for the synthesis of poly(1,4-dioxan-2-one) (PPDO). Poly(1,4-dioxan-2-one) can be used to manufacture the casings of electronic components to protect circuit boards and electronic components and improve the high-temperature resistance of products. In the construction industry, it can be used to manufacture building materials such as heat insulation, sound insulation, fire resistance and waterproofing, improving the service life and quality of buildings. In the automotive industry, it can be used to manufacture automotive parts such as engine hoods and doors, improving the durability and safety performance of automobiles. In the chemical industry, it can even be used as a manufacturing material for corrosion-resistant containers, pipes and valves and other chemical equipment. In the medical industry, it can be used to manufacture surgical sutures, drug sustained-release materials, orthopedic fixation materials and tissue repair materials, etc.

[0003] There are three methods for synthesizing 1,4-dioxan-2-one: The first is the organic synthesis method, which uses ethylene glycol, sodium metal and chloroacetic acid as raw materials to synthesize 1,4-dioxan-2-one. This method has cumbersome operations and high production costs, which is not conducive to industrial production.

[0004] The second method is the catalytic carbonylation reaction method: carbon monoxide, formaldehyde and 1,2-ethylene glycol or 1,3-dioxolane are used as raw materials for carbonyl addition to synthesize 1,4-dioxan-2-one. The catalysts used mainly include carbonyl complexes of hydrogen fluoride, copper and silver, etc.

[0005] The third method is catalytic oxidative dehydrogenation cyclization. Usually, diglycol is used as the reaction raw material for synthesis, and transition metals such as copper, silver, platinum, zinc or composite oxides of the above elements supported on inert carriers such as alumina, activated carbon, and silica are used as catalysts. Diglycol is first oxidized and dehydrogenated to convert into 2-(2-hydroxyethoxy)acetaldehyde. Then, the terminal aldehyde group and the terminal hydroxyl group undergo aldol condensation cyclization to form 2-hydroxy-1,4-dioxane. 2-Hydroxy-1,4-dioxane is then dehydrogenated under the action of a catalyst to obtain p-dioxanone. For example, US Pat.2,142,033 uses a copper-chromium composite oxide catalyst (chromium content ≤ 5 wt%) to obtain the target product through gas-phase dehydrogenation lactonization of diglycol, with a selectivity of 75.0%, but the yield is only 25%. US Pat.2,807,629 increases the selectivity of p-dioxanone to 94.0% and the yield reaches 84% by changing the chromium content in the copper-chromium catalyst. US Pat.3,119,840 also uses a copper-chromium catalyst. When the molar ratio of hydrogen to the raw material is 3 to 100, the highest yield of the target product p-dioxanone can reach 96%. Japanese Patent Laid-Open No. 58-99476 uses a platinum or palladium-based metal catalyst supported on activated carbon, silica or alumina, and uses oxygen in the air as an oxidant to synthesize p-dioxanone through oxidative dehydrogenation self-condensation of diglycol, but its highest selectivity can only reach 75%. Fetizon.M. et al. (Fetizon M, et al., Tetrahedron, 1975, 31, 171-176) used silver carbonate supported on a diatomaceous earth carrier as a catalyst and refluxed diglycol in benzene for 10 hours, and the yield of p-dioxanone could reach 95%. In CN 1739852A, Wang Yuzhong et al. used a coprecipitation method to load copper, zinc and other alkali metals or alkaline earth metal compounds on an inert carrier, and the mass percentage content of the active component was 20 to 90%; the activity and selectivity of this catalyst were relatively high, but the catalyst preparation process was relatively cumbersome and not conducive to industrial scale-up production. All in all, the synthesis route for preparing p-dioxanone using diglycol as the raw material has attracted much attention. Its main advantages are: the synthesis process is relatively simple, the reaction time is short, and the reaction conversion rate is high. However, the disadvantages are also obvious: there are many side reactions (mainly two types: dehydration reaction and over-hydrogenation reaction), resulting in poor selectivity of the target product and difficulty in separation and purification.

[0006] It can be seen from the publicly available literature that the main reasons for the low selectivity of dioxanone on the existing catalysts are as follows: 1) The intramolecular dehydration reaction of the raw material diglycol generates 1,4-dioxane; 2) The hydrogenolysis of the raw material diglycol produces two by-products, ethanol and ethylene glycol. In the present invention, the Cu / SiO2 catalyst is hydrophobically pretreated with a silylating agent to eliminate the acidic silanol groups on the surface of the silica support, thereby significantly reducing the formation of the dehydration by-product 1,4-dioxane of the raw material, and at the same time reducing the hydrogenolysis activity of the catalyst, and further reducing the selectivity of the by-products ethanol and ethylene glycol. (III) Summary of the Invention

[0007] The first technical problem to be solved by the present invention is to provide a preparation method of a hydrophobic Cu / SiO2 catalyst.

[0008] The second technical problem to be solved by the present invention is to provide a hydrophobic Cu / SiO2 catalyst.

[0009] The third technical problem of the present invention is to provide the application of the hydrophobic Cu / SiO2 catalyst in the dehydrogenative lactonization reaction of diglycol.

[0010] To solve the above technical problems, the present invention adopts the following technical solutions:

[0011] In the first aspect, the present invention provides a preparation method of a hydrophobic Cu / SiO2 catalyst, and the preparation method includes: adding the Cu / SiO2 catalyst into a mixed solution of a hydrophobizing agent and an organic solvent, oscillating at 30-60 °C for 1-12 h, filtering after the oscillation is completed and washing with ethanol to remove the excess hydrophobizing agent, and then drying at 40-200 °C in an oven for 1-24 h to obtain the hydrophobic Cu / SiO2 catalyst; the hydrophobizing agent is: one or more of methoxytrimethylsilane, trimethylchlorosilane, dimethyldiacetoxysilane, and triisopropyloxysilane;

[0012] The Cu / SiO2 catalyst includes the following components in weight percentage:

[0013] Silica support 62.5% - 99.5%

[0014] Copper oxide 0.5% - 37.5%.

[0015] Preferably, the organic solvent is one or more of methanol, ethanol, isopropanol, acetylacetone, chloroform, tetrahydrofuran, and N,N-dimethylformamide, etc.

[0016] Preferably, the hydrophobizing agent and the organic solvent are mixed in a volume ratio of 1-99:100, and more preferably in a volume ratio of 5-80:100.

[0017] Preferably, the specific surface area of the Cu / SiO₂ catalyst is 150-700 m 2 / g, the most probable pore diameter is 2-25 nm, the pore volume is 0.2-1.5 ml / g, the particle size is 4-40 mesh, and the particle strength: the average value is greater than 1 Kg / particle.

[0018] The Cu / SiO₂ catalyst of the present invention may contain other components that do not substantially affect its catalytic performance, such as a small amount of impurities introduced due to the use of commercial silica carriers, soluble copper salts, etc.

[0019] The Cu / SiO₂ catalyst is prepared by an impregnation method, that is, a metal copper precursor is loaded onto the surface of a silica carrier by impregnation, and then the silica carrier loaded with the metal copper precursor is calcined in an air or inert gas atmosphere to obtain the Cu / SiO₂ catalyst. The specific preparation steps of the Cu / SiO₂ catalyst of the present invention are as follows:

[0020] (1) Immerse the silica carrier in a mixed solution of a copper precursor and a complexing agent, and oscillate and impregnate for 1-48 h;

[0021] (2) Dry the mixture obtained in step (1) to uniformly load the copper precursor onto the inner and outer surfaces of the silica carrier;

[0022] (3) Put the dried catalyst precursor obtained in step (2) into a muffle furnace and perform a calcination treatment in an air or inert gas atmosphere to obtain the Cu / SiO₂ catalyst.

[0023] In the above preparation method, the copper precursor may be a soluble copper salt such as copper nitrate, copper chloride, copper acetate, copper acetylacetonate, etc., the complexing agent is ammonia water, ethylenediamine, ethylenediaminetetraacetic acid or citric acid, and the molar ratio of the complexing agent to the copper precursor is 1-150:1, preferably 5-100:1. The drying treatment is carried out in a rotary evaporator and an oven. First, dry at 10-60 °C and 0.005-0.1 MPa in the rotary evaporator for 1-24 h, and then dry at 50-150 °C in the oven for 1-48 h. The catalyst calcination is carried out in a muffle furnace, and the temperature is raised to 150-800 °C at a heating rate of 0.5-20 °C / min for calcination for 1-10 h, preferably the temperature is raised to 300-600 °C at a heating rate of 3-15 °C / min for calcination for 2-6 h.

[0024] In a second aspect, the present invention provides a hydrophobic Cu / SiO₂ catalyst prepared by the preparation method according to the first aspect.

[0025] In a third aspect, the present invention provides an application of the hydrophobic Cu / SiO2 catalyst described in the second aspect in the dehydrogenative lactonization reaction of diglycol. The hydrophobic Cu / SiO2 catalyst is reduced with hydrogen before the dehydrogenative lactonization reaction of diglycol is carried out.

[0026] Preferably, the dehydrogenative lactonization reaction of diglycol is continuously carried out in a fixed-bed reactor. The hydrophobic catalyst is reduced with a hydrogen-nitrogen mixed gas (1:1 - 9, v / v) before use. The reduction conditions are: normal pressure, temperature 200 - 350 °C, reduction time 1 - 12 h, and the space velocity of the hydrogen-nitrogen mixed gas is 200 - 1600 h -1 .

[0027] The reaction conditions for the dehydrogenative lactonization reaction of diglycol are: temperature 220 - 280 °C, reaction pressure 0.1 - 1 MPa, the liquid space velocity of the raw material is 0.2 - 1.5 h -1 , and the space velocity of the carrier gas hydrogen is 100 - 800 h -1 . Under these conditions, the selectivity and yield of the dehydrogenative lactonization product p-dioxanone of the catalyst are high, and the main by-products of the reaction, such as 1,4-dioxane, ethanol, and ethylene glycol, are significantly reduced after the Cu / SiO2 catalyst is hydrophobically treated.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] (1) The by-products of the dehydrogenative lactonization reaction of diglycol are mainly generated by the surface silanol acid sites existing on the surface of the catalyst support. The hydrophobic reagent combines with the silanols to reduce the number of surface silanol acid sites on the Cu / SiO2 catalyst, avoiding the generation of dehydration by-products; at the same time, the removal of the surface silanols on the catalyst also reduces the hydrogenation ability of the Cu / SiO2 catalyst, reducing the degree of hydrogenolysis of the raw materials, thereby further improving the selectivity / yield of the target product.

[0030] (2) The preparation method of the hydrophobic Cu / SiO2 catalyst of the present invention is simple and reliable, and the production cost is relatively low. At the same time, when it is applied to the dehydrogenative lactonization reaction of diglycol, a fixed-bed continuous reaction process is adopted, so it is suitable for industrial application. (4) Brief Description of the Drawings

[0031] Figure 1Schematic diagram of a reaction device for the continuous catalytic synthesis of p-dioxanone with diethylene glycol: 1 - hydrogen gas cylinder, 2 - nitrogen gas cylinder, 3 - raw material bottle, 4 - high-pressure constant flow pump, 5 - three-way valve, 6 - pressure reducing valve, 7 - stop valve, 8 - mass flowmeter, 9 - check valve, 10 - reaction tube, 11 - reaction furnace, 12 - condenser, 13 and 14 - condensate inlet and outlet, 15 - filter, 16 - back pressure valve, 17 - product collection tank, 18 - catalyst bed. (V) Specific implementation mode

[0032] The present invention will be further described below through specific examples, but the protection scope of the present invention is not limited thereto.

[0033] The SiO2 support used in the example is granular, with a particle diameter of 4 - 40 mesh, a specific surface area of 310 m 2 / g, an average pore diameter of 9.8 nm, and a pore volume of 1.0 mL / g.

[0034] Normal temperature in the example refers to 25 °C.

[0035] Example 1

[0036] Weigh 0.9505 g of copper nitrate trihydrate, add it to 20 mL of ammonia water solution and wait for it to completely dissolve. Then add 2 g of silica support and shake it at normal temperature for 2 h. Under the condition of 60 °C, distill the solvent under reduced pressure until it is completely evaporated. Place the dried catalyst precursor in a blast drying oven and dry it at 110 °C for 4 h, and then calcine it in a muffle furnace at 500 °C for 4 h to obtain the Cu / SiO2 catalyst. The weight content of CuO is 15.6%, and the rest is silica gel support. Add 2 g of the above Cu / SiO2 catalyst to a mixed solution of 10 mL of ethanol and 2 mL of methoxytrimethylsilane, shake it at normal temperature for 2 h. After shaking, filter it, and repeatedly wash it with ethanol to remove the excess methoxytrimethylsilane, and then dry it in an oven at 110 °C for 4 h to obtain catalyst A.

[0037] Example 2

[0038] The preparation method of catalyst B is the same as that of Example 1, but add it to a mixed solution of 10 mL of ethanol and 2 mL of methoxytrimethylsilane and shake it at normal temperature for 6 h. After shaking, filter it, and repeatedly wash it with ethanol to remove the excess methoxytrimethylsilane, and then dry it in an oven at 110 °C for 4 h to obtain catalyst B.

[0039] Example 3

[0040] The preparation method of catalyst C is the same as that of Example 1, but add it to a mixed solution of 10 ml of ethanol and 2 ml of methoxytrimethylsilane and shake it at normal temperature for 12 h. After shaking, filter it, and repeatedly wash it with ethanol to remove the excess methoxytrimethylsilane, and then dry it in an oven at 110 °C for 4 h to obtain catalyst C.

[0041] Example 4

[0042] The preparation method of catalyst D is the same as that of Example 1, but it is oscillated in a mixed solution of 10 ml of ethanol and 2 ml of methoxytrimethylsilane at 40 °C for 6 h. After oscillation, it is filtered, and the excess methoxytrimethylsilane is removed by repeated washing with ethanol, and then dried in an oven at 110 °C for 4 h to obtain catalyst D.

[0043] Comparative Example 1

[0044] The preparation method of catalyst E is the same as that of Example 1, but the calcined catalyst is not subjected to hydrophobic treatment.

[0045] Comparative Example 2

[0046] Weigh 2 g of SiO2 support and put it into a mixed solution of 10 ml of ethanol and 2 ml of methoxytrimethylsilane, oscillate at room temperature for 6 h, filter after oscillation, and remove the excess methoxytrimethylsilane by repeated washing with ethanol, and then dry in an oven at 110 °C for 4 h to obtain a hydrophobic SiO2 support. Weigh 0.9505 g of copper nitrate trihydrate, add it to 20 mL of ammonia water and wait for it to dissolve completely, then add 2 g of hydrophobic SiO2 support and oscillate at room temperature for 2 h. Under the condition of 60 °C, the solvent is evaporated to dryness under reduced pressure. The dried catalyst precursor is placed in a blast drying oven and dried at 110 °C for 4 h, and then calcined in a muffle furnace at 500 °C for 4 h to obtain catalyst F, the weight content of CuO in which is 15.6%, and the rest is silica gel support.

[0047] Example 5

[0048] The reaction device is as Figure 1 shown. The catalysts A, B, C, D, E and F prepared in the above examples and comparative examples are respectively loaded into the reaction tubes of the fixed bed reaction device. First, the catalysts are reduced under the following conditions: 320 °C, atmospheric pressure, the space velocity of the hydrogen-nitrogen mixed gas (1:9, v / v) is 900 h -1 , the reduction time is 4 h, and then the dehydrogenation lactonization reaction of diglycol is carried out. The reaction conditions are set as: 260 °C, 0.1 MPa, LHSV = 0.5 h -1 , the space velocity of the carrier gas hydrogen is 480 h -1 ; the results are shown in Table 1.

[0049] Table 1 Catalytic performance of different catalysts in the continuous catalytic synthesis of p-dioxanone from diglycol in a fixed bed

[0050]

[0051] [a] DEG - diglycol; [b]PDO - p - dioxanone; [c] Diox - 1,4 - dioxane; [d] ET - ethanol; [e] EG - ethylene glycol; [f] 2-(2 - hydroxyethoxy)acetaldehyde.

Claims

1. Application of a hydrophobic Cu / SiO2 catalyst in the dehydrogenation of diethylene glycol, characterized in that: The hydrophobic Cu / SiO2 catalyst is reduced with hydrogen before the dehydrogenation of diethylene glycol. The preparation method of the hydrophobic Cu / SiO2 catalyst comprises: adding the Cu / SiO2 catalyst to a mixed solution of a hydrophobic treatment agent and an organic solvent, oscillating at 30-60°C for 1-12 h, filtering after the oscillation and washing with ethanol to remove excess hydrophobic treatment agent, and then drying in an oven at 40-200°C for 1-24 h to obtain the hydrophobic Cu / SiO2 catalyst; the hydrophobic treatment agent is one or more of methoxytrimethylsilane, trimethylchlorosilane, dimethyldiacetoxysilane, and triisopropyloxysilane; The Cu / SiO2 catalyst comprises the following components in weight percentage: Silica carrier 62.5%~99.5% Copper oxide 15.6%~37.5%; The preparation steps of the Cu / SiO2 catalyst are as follows: (1) Immersing the silica carrier in a mixed solution of a copper precursor and a ligand, and oscillating and immersing for 1 to 48 hours; the ligand is ammonia water, and the molar ratio of the ligand to the copper precursor is 5 to 100:1; the copper precursor is a soluble copper salt; (2) drying the mixture obtained in step (1), wherein the drying is carried out in a rotary evaporator and an oven, first drying the mixture in a rotary evaporator at 10-60° C. and 0.005-0.1 MPa for 1-24 h, and then drying the mixture in an oven at 50-150° C. for 1-48 h, so that the copper precursor is evenly loaded on the inner and outer surfaces of the silica carrier; (3) The dried catalyst precursor obtained in step (2) is placed in a muffle furnace and calcined in air or inert gas atmosphere, and the temperature is increased to 300-600°C at a heating rate of 3-15°C / min and calcined for 2-6 h to obtain the Cu / SiO2 catalyst.

2. The use according to claim 1, characterized in that: The organic solvent is one or more of methanol, ethanol, isopropanol, acetylacetone, chloroform, tetrahydrofuran and N,N-dimethylformamide.

3. The use according to claim 1, characterized in that: The hydrophobic treatment agent and the organic solvent are mixed in a volume ratio of 1 to 99:

100.

4. The use according to claim 3, characterized in that: The hydrophobic treatment agent and the organic solvent are mixed in a volume ratio of 5-80:

100.

5. The use according to claim 1, characterized in that: The specific surface area of ​​the Cu / SiO2 catalyst is 150-700 m 2 / g, the most probable pore size is 2~25 nm, the pore volume is 0.2~1.5 ml / g, the particle size is 4~40 mesh, and the particle strength: the average value is greater than 1 Kg / particle.

6. The use according to claim 1, characterized in that: The diethylene glycol dehydrogenation lactonization reaction is continuously carried out in a fixed bed reactor.

7. The use according to claim 6, characterized in that: The hydrophobic Cu / SiO2 catalyst is reduced by hydrogen-nitrogen mixed gas before use. The reduction conditions are: normal pressure, temperature 200-350°C, reduction time 1-12 h, and space velocity of hydrogen-nitrogen mixed gas 200-1600 h -1 ; The reaction conditions of the dehydrogenation lactonization reaction of diethylene glycol are as follows: temperature of 220-280°C, reaction pressure of 0.1-1 MPa, liquid space velocity of the raw material of 0.2-1.5 h -1 , the carrier gas hydrogen space velocity is 100~800 h -1 .

Images