Bimetal Ru-Mo / gamma-Al2O3 catalyst as well as preparation method and application thereof

Abstract

The invention relates to a bimetallic Ru-Mo / gamma-Al2O3 catalyst as well as a preparation method and application thereof, and belongs to the technical field of chemical synthesis. According to the catalyst, N-gamma-Al2O3 serves as a carrier, an active component Ru and an auxiliary agent Mo are loaded on the N-gamma-Al2O3 in a dipping mode, the Ru-Mo / N-gamma-Al2O3 catalyst is prepared, the gamma-Al2O3 is treated with ammonia water, the surface of the gamma-Al2O3 is changed into Lewis alkaline sites from Lewis acid sites, a stronger anchoring effect on metal nano ions is achieved, and the metal nano ions are effectively anchored. Therefore, better dispersion of the nano ions is facilitated. The catalyst can be used for preparing the cyclohexanedicarboxylic acid dialkyl ester by catalyzing the phthalic acid dialkyl ester, after the reaction is completed, the component change of the catalyst is not large, the high activity is still kept, the catalyst can be recycled and reused, and industrial large-scale production is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of dialkyl cyclohexanedicarboxylate, and in particular to a bimetallic Ru-Mo / γ-Al2O3 catalyst and a preparation method and application thereof. Background Art

[0002] Plasticizers are the largest variety in terms of production capacity and consumption among plastic processing additives. They are widely used in a large number of durable and easy-to-shape plastic products such as toys, building materials, auto parts, electronic and medical components, and their output accounts for more than 60% of the total output of plastic additives. At present, there are more than 500 commercial plasticizers in the world, among which dialkyl phthalate plasticizers are the most widely used type of plasticizers on the market, accounting for more than 80% of the total output of plasticizers. They mainly include diisononyl phthalate, di(2-ethylhexyl) phthalate, diisooctyl phthalate and dibutyl phthalate. However, studies in recent years have shown that phthalate plasticizers (PAEs) are easy to migrate and cause pollution to food and biomedical materials, thereby causing certain harm to human health. At present, more and more countries are restricting or prohibiting their use in medical devices, children's toys, food packaging and other fields.

[0003] At present, the main methods for synthesizing dialkyl cyclohexanedicarboxylates are direct hydrogenation, direct esterification and transesterification.

[0004] The preparation of dialkyl cyclohexanedicarboxylate is usually prepared by esterification reaction of cyclohexanedicarboxylic anhydride and alkyl alcohol in the presence of an acidic catalyst. As is known to all, esterification reaction is a reversible reaction, and an excess of alcohol must be added and the water produced by the reaction must be removed in time. The esterification reaction requires a high reaction temperature (250°C to 260°C) and a long reaction time, high energy consumption, many by-products formed by the reaction, and the catalyst is also more easily deactivated.

[0005] Direct hydrogenation is a method for preparing dialkyl cyclohexanedicarboxylate by direct hydrogenation with dialkyl phthalate and hydrogen as raw materials in the presence of a catalyst. This method has the characteristics of low energy consumption, simple process, few by-products, green environmental protection and easy industrial production. Compared with direct esterification and transesterification, direct hydrogenation is the mainstream method for developing new environmentally friendly plasticizers in the future.

[0006] Direct hydrogenation often uses precious metal catalysts (such as nickel, platinum, palladium, rhodium, ruthenium) to catalyze dialkyl phthalate for catalytic hydrogenation reaction under high temperature and high pressure to obtain dialkyl cyclohexanedicarboxylate. Although the process route is simple, it has high requirements for equipment and catalysts and is costly. In patent US6184917, BASF of Germany used Ru supported catalyst to successfully prepare dialkyl cyclohexanedicarboxylate by catalytic hydrogenation under a pressure of 20MPa, realizing industrial production. U.S. Patent US7361714 uses a catalyst for hydrogenation reaction under a pressure of 8-10MPa, and the active component of the catalyst uses at least one transition metal of Group VIII alone or at least one transition metal of Group VI or VII. Chinese patent CN107675109A discloses a method for preparing isooctyl cyclohexanedicarboxylate, which uses isooctyl phthalate and hydrogen as raw materials, Ru as catalyst, and catalytic hydrogenation reaction is performed at a temperature of 160-200°C and a pressure of 5-10MPa to prepare diisooctyl cyclohexanedicarboxylate, and the selectivity and purity of the product are all above 99%. In the above-mentioned patent, although the selectivity of the prepared dialkyl cyclohexanedicarboxylate is all above 99%, in the hydrogenation reaction process, the pressure and temperature of the reaction are all high, and the energy consumption is large, which is not conducive to industrial production. The catalyst used is generally a pure metal or a metal-supported catalyst. Its metal active components are all above 3%, and the cost is large. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a bimetallic Ru-Mo / γ-Al2O3 catalyst and a preparation method and application thereof. The catalyst has mild reaction conditions, a metal active component content of less than 2wt%, and can effectively reduce costs. The catalyst can effectively catalyze the preparation of dialkyl cyclohexanedicarboxylate. After the reaction is completed, the components of the catalyst do not change much, and still maintain a high activity. The catalyst can be recycled and reused, which is conducive to industrial large-scale production.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] In a first aspect, the present invention provides a method for preparing a bimetallic Ru-Mo / γ-Al2O3 catalyst, characterized in that it comprises the following steps:

[0010] (1) mixing γ-Al2O3 with aqueous ammonia and drying to obtain an N-γ-Al2O3 carrier;

[0011] (2) loading a ruthenium salt and a molybdenum salt on an N-γ-Al2O3 carrier, washing, calcining, and then reducing the carrier to obtain a bimetallic Ru-Mo / γ-Al2O3 catalyst; wherein the mass content of ruthenium in the catalyst is 0.1 to 2 wt%, and the mass content of molybdenum is 0.1 to 2 wt%.

[0012] The catalyst of the present invention uses N-γ-Al2O3 as a carrier, and active components Ru and Mo are loaded on N-γ-Al2O3 by impregnation to prepare a Ru-Mo / N-γ-Al2O3 catalyst. The γ-Al2O3 is treated with ammonia water to change the Lewis acid sites on its surface into Lewis basic sites, which has a stronger anchoring effect on metal nano-ions, thereby facilitating better dispersion of the nano-ions.

[0013] Specifically, the crystal form of γ-Al2O3 has a large specific surface area, high porosity, strong heat resistance, good formability, and a certain surface alkalinity. The reason for using ammonia water to alkalize γ-Al2O3 is that the γ-Al2O3 treated with ammonia water will form a pyrrole structure during the subsequent calcination process, so that the nitrogen atoms are better anchored on the carrier, thereby improving the selectivity of dialkyl cyclohexanedicarboxylate. Commonly used inorganic bases do not have this effect.

[0014] Preferably, in step (1), the concentration of the ammonia water is 5 to 15 mol / L; and the mass ratio of γ-Al2O3 to ammonia water is 1:(5 to 10).

[0015] Preferably, in step (1), the mixing temperature is 55-65°C for 5-7 hours; and the drying temperature is 110-125°C.

[0016] Preferably, the ruthenium salt solution is one of a RuCl3 solution and a Ru(NO3)3 solution; and the molybdenum salt solution is one of a Mo(NO3)2 solution and a MoCl2 solution.

[0017] Preferably, the loading treatment is to spray the ruthenium salt solution and the molybdenum salt solution on the surface of the N-γ-Al2O3 carrier, let it stand for 7 to 9 hours, and then dry it at 100 to 120°C.

[0018] Preferably, the calcination temperature is 400-600° C., and the calcination time is 2-5 h; the reduction temperature is 200-300° C., and the reduction time is 3-5 h.

[0019] Preferably, x is 0.1 to 1.5 wt %, and y is 0.1 to 1.5 wt %.

[0020] In a second aspect, the present invention provides a bimetallic Ru-Mo / γ-Al2O3 catalyst prepared by the preparation method of the bimetallic Ru-Mo / γ-Al2O3 catalyst.

[0021] In a third aspect, the present invention provides the use of a bimetallic Ru-Mo / γ-Al2O3 catalyst in the preparation of dialkyl cyclohexanedicarboxylate.

[0022] Preferably, the method for preparing dialkyl cyclohexanedicarboxylate comprises the following steps:

[0023] Taking dialkyl phthalate and hydrogen as raw materials, a catalytic hydrogenation reaction is carried out under the action of the bimetallic Ru-Mo / γ-Al2O3 catalyst to obtain the dialkyl cyclohexanedicarboxylate.

[0024] The catalyst uses Mo to modify the Ru / N-γ-Al2O3 catalyst. In the H2 atmosphere used in the catalytic reaction, there is a hydrogen overflow effect between the Ru-Mo metal particles, making H2 more easily activated. The introduction of Mo not only greatly improves the activity of the catalyst, but also reduces the amount of the active component Ru. After the reaction is completed, the components of the catalyst do not change much, and still maintain a high activity. It can be recycled and reused, which is conducive to industrial large-scale production.

[0025] Preferably, the reaction temperature of the catalytic hydrogenation is 130-150°C, and the reaction pressure is 3.0-5.0 MPa; more preferably, the reaction temperature of the catalytic hydrogenation is 140°C, and the reaction pressure is 4 MPa. The liquid space velocity of the dialkyl phthalate is 0.1-2 h -1 .

[0026] Preferably, the dialkyl phthalate is at least one of diisononyl phthalate, di(2-ethylhexyl) phthalate, diisooctyl phthalate and dibutyl phthalate.

[0027] Preferably, the molar ratio of hydrogen to the dialkyl phthalate is (5-10): 1. More preferably, the molar ratio of hydrogen to the dialkyl phthalate is (5-8): 1.

[0028] Preferably, the addition amount of the bimetallic Ru-Mo / γ-Al2O3 catalyst is 2%-8% of the raw material mass.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The preparation method of the catalyst of the present invention is to use N-γ-Al2O3 as a carrier, load the active component Ru and the auxiliary agent Mo on N-γ-Al2O3 by impregnation, and prepare Ru-Mo / N-γ-Al2O3 catalyst, and treat the γ-Al2O3 with ammonia water to change the Lewis acid site on its surface into a Lewis basic site, which has a stronger anchoring effect on metal nano-ions, thereby facilitating better dispersion of the nano-ions. Wherein, the Ru and Mo metal loadings are both less than 3wt%, which can effectively reduce costs.

[0031] (2) The catalyst can be used to catalyze the preparation of dialkyl cyclohexanedicarboxylate from dialkyl phthalate, because Mo can modify the Ru / N-γ-Al2O3 catalyst. In the H2 atmosphere during the catalytic reaction of the product, there is a hydrogen overflow effect between the Ru-Mo metal particles, making H2 more easily activated. The introduction of Mo not only greatly improves the activity of the catalyst, but also reduces the amount of the active component Ru. After the reaction is completed, the components of the catalyst do not change much, and still maintain a high activity. It can be recycled and reused, which is conducive to industrial large-scale production. DETAILED DESCRIPTION

[0032] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0033] Example 1

[0034] The preparation method of the bimetallic Ru-Mo / γ-Al2O3 catalyst comprises the following steps:

[0035] (1) Add 5 g of γ-Al2O3 to 50 ml of an aqueous ammonia solution with a concentration of 10 mol / L, stir at 60°C for 6 h, and dry in an oven at 120°C to obtain N-γ-Al2O3.

[0036] (2) Spray a mixed solution of RuCl3 solution with a carrier mass concentration of 1% and Mo(NO3)2 with a mass concentration of 0.2% into the dried N-γ-Al2O3, stir for 5 hours, let stand for 8 hours, dry at 110°C overnight, wash with deionized water to remove chloride ions, and calcine at 500°C in a muffle furnace for 2 hours. Then, place in a tubular furnace at 200°C in a hydrogen atmosphere for reduction reaction for 3 hours to prepare 1%Ru-0.2%Mo / N-γ-Al2O3.

[0037] Example 2

[0038] The catalyst of Example 2 is different from that of Example 1 in that the sprayed carrier in Example 2 has a mass fraction of 0.5% Mo(NO3)2.

[0039] Example 3

[0040] The catalyst of Example 3 is different from that of Example 1 in that the sprayed carrier in Example 3 has a mass fraction of 1% Mo(NO3)2.

[0041] Comparative Example 1

[0042] The catalyst of Comparative Example 1 is different from that of Example 1 in that in step (2) of Comparative Example 1, the carrier N-γ-Al2O3 is not sprayed with RuCl3 and Mo(NO3)2.

[0043] Comparative Example 2

[0044] The catalyst of Comparative Example 2 is different from that of Example 1 in that in step (2) of Comparative Example 2, only 1% RuCl 3 is sprayed on the carrier N-γ-Al 2 O 3 .

[0045] Comparative Example 3

[0046] The catalyst of Comparative Example 3 is different from that of Example 1 in that the γ-Al2O3 used in step (1) is replaced by SiO2 in Comparative Example 3.

[0047] Comparative Example 4

[0048] The catalyst of Comparative Example 4 is different from that of Example 1 in that in step (2) of Comparative Example 4, Cr(NO3)2 is used instead of Mo(NO3)2.

[0049] Comparative Example 5

[0050] The catalyst of Comparative Example 5 is different from that of Example 1 in that in step (2) of Comparative Example 5, Fe(NO3)2 is used instead of Mo(NO3)2.

[0051] Application Examples 1 to 3 and Comparative Application Examples 1 to 5

[0052] The use of the catalysts of Examples 1 to 5 to prepare diisononyl cyclohexanedicarboxylate is recorded as Application Examples 1 to 3, respectively; the use of the catalysts of Comparative Examples 1 to 5 to prepare diisononyl cyclohexanedicarboxylate is recorded as Comparative Application Examples 1 to 3, respectively.

[0053] The specific steps of preparing diisononyl cyclohexanedicarboxylate in application examples 1 to 3 and comparative examples 1 to 5 are as follows: the catalytic hydrogenation reaction is carried out in a fixed bed continuous hydrogenation reactor, and the tubular fixed bed reactor has a length of 1200 mm and an inner diameter of 32 mm. The upper and lower parts of the reactor are filled with quartz sand, and the catalyst is loaded in the middle. The prepared metal-loaded catalyst is loaded in an amount of 150 mL. The diisononyl phthalate raw material liquid is pumped into the reactor by a metering pump to contact with hydrogen for hydrogenation reaction. The reaction temperature is 140°C, the reaction pressure is 4.0 MPa, and the liquid space velocity is 0.36 h -1 , the hydrogen to ester ratio is 5:1, after the hydrogenation mixture is cooled, hydrogen is separated in a gas-liquid separation tank to obtain the hydrogenation product diisononyl cyclohexanedicarboxylate. The diisononyl cyclohexanedicarboxylate obtained in each group is extracted for gas chromatography analysis, and the data results are recorded in Table 1.

[0054] Table 1 Performance of each group of catalysts in preparing diisononyl cyclohexanedicarboxylate

[0055]

[0056] As shown in Table 1, the bimetallic supported catalysts prepared in Examples 1 to 3 can be used for hydrogenation reaction to prepare diisononyl cyclohexanedicarboxylate, and the selectivity of the target acid product is higher, reaching more than 99.5%. However, the catalyst used in Comparative Example 2 does not add Mo(NO3)2, resulting in a decrease in the conversion rate of hexahydrophthalic anhydride, and the selectivity of diisononyl cyclohexanedicarboxylate is reduced to 92.3%.

[0057] The catalyst carrier used in Comparative Example 3 is SiO2, which leads to a decrease in the conversion rate of hexahydrophthalic anhydride and a decrease in the selectivity of diisononyl cyclohexyldicarboxylate to 83.4%, indicating that the N-γ-Al2O3 carrier is an important parameter for the selectivity of the catalyst hydrogenation reaction.

[0058] By using the Cr and Fe metals selected in Comparative Examples 4 to 5 to replace Mo, the selectivity of diisononyl cyclohexyl dicarboxylate was reduced to 62.8% and 65.3%. This shows that the catalyst of the technical solution is a combination of Mo and Ru to improve the selectivity of diisononyl cyclohexyl dicarboxylate. Moreover, the catalyst of the present invention is easy to separate and recover from the product after the reaction is completed, which simplifies the process operation flow and also has industrial application value.

[0059] Application of the catalyst recycling method of Example 2

[0060] The catalyst of Example 2 was recycled 1 time, 5 times, 10 times and 20 times respectively according to the method of Application Example 2, and the conversion rate of diisononyl phthalate and the selectivity of diisononyl cyclohexyl dicarboxylate were tested respectively. See Table 2 for details. The recycling method is: the catalyst after the reaction was cleaned 3 times with cyclopentyl methyl ether ultrasonic vibration.

[0061] Table 2 Performance parameters of the catalyst of Example 2 after recycling

[0062]

[0063] As can be seen from Table 2, after the reaction is completed, the components of the catalyst do not change much. Even after being recycled 20 times, the catalyst still maintains a high activity and can be recycled and reused, which is conducive to industrial large-scale production.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a bimetallic Ru-Mo / γ-Al2O3 catalyst, characterized in that: The following steps are involved: (1) mixing γ-Al2O3 with aqueous ammonia and drying to obtain an N-γ-Al2O3 carrier; (2) loading a ruthenium salt and a molybdenum salt on an N-γ-Al2O3 carrier, washing, first calcining, and then performing a reduction reaction to obtain the bimetallic Ru-Mo / γ-Al2O3 catalyst; wherein the mass content of ruthenium in the catalyst is 0.1 to 2 wt%, and the mass content of molybdenum is 0.1 to 2 wt%.

2. The method for preparing the bimetallic Ru-Mo / γ-Al2O3 catalyst according to claim 1, characterized in that: In the step (1), the concentration of the ammonia water is 5 to 15 mol / L; the mass ratio of γ-Al2O3 to ammonia water is 1:(5 to 10).

3. The method for preparing the bimetallic Ru-Mo / γ-Al2O3 catalyst according to claim 1, characterized in that: In the step (1), the mixing temperature is 55-65°C for 5-7 hours; the drying temperature is 110-125°C.

4. The method for preparing the bimetallic Ru-Mo / γ-Al2O3 catalyst according to claim 1, characterized in that: The ruthenium salt solution is one of a RuCl3 solution and a Ru(NO3)3 solution; the molybdenum salt solution is one of a Mo(NO3)2 solution and a MoCl2 solution.

5. The method for preparing the bimetallic Ru-Mo / γ-Al2O3 catalyst according to claim 1, characterized in that: The calcination temperature is 400-600° C., and the calcination time is 2-5 hours; the reduction temperature is 200-300° C., and the reduction time is 3-5 hours.

6. A bimetallic Ru-Mo / γ-Al2O3 catalyst, characterized in that: The catalyst is prepared by the preparation method of the bimetallic Ru-Mo / γ-Al2O3 catalyst according to any one of claims 1 to 5.

7. Use of the bimetallic Ru-Mo / γ-Al2O3 catalyst according to claim 6 in the preparation of dialkyl cyclohexanedicarboxylate.

8. Use of the bimetallic Ru-Mo / γ-Al2O3 catalyst according to claim 7, characterized in that: The process for preparing dialkyl cyclohexanedicarboxylate comprises the following steps: Taking dialkyl phthalate and hydrogen as raw materials, a catalytic hydrogenation reaction is carried out under the action of the bimetallic Ru-Mo / γ-Al2O3 catalyst to obtain the dialkyl cyclohexanedicarboxylate.

9. Use of the bimetallic Ru-Mo / γ-Al2O3 catalyst as claimed in claim 8, characterized in that: The reaction temperature of the catalytic hydrogenation is 130-150°C, the reaction pressure is 3.0-5.0 MPa; the liquid space velocity of the dialkyl phthalate is 0.1-2 h -1 .

10. Use of the bimetallic Ru-Mo / γ-Al2O3 catalyst according to claim 8 or 9, characterized in that: At least one of the following (I) to (III): (I) the dialkyl phthalate is at least one of diisononyl phthalate, di(2-ethylhexyl) phthalate, diisooctyl phthalate and dibutyl phthalate; (II) the molar ratio of hydrogen to the dialkyl phthalate is (5-10):1; (III) The addition amount of the bimetallic Ru-Mo / γ-Al2O3 catalyst is 2%-8% of the mass of the raw material.

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