A catalyst, a preparation method thereof, and an application thereof in the preparation of dimethyl carbonate from carbon dioxide and methanol

Abstract

The present invention discloses a catalyst, a preparation method thereof, and an application thereof in the preparation of dimethyl carbonate from carbon dioxide and methanol. The catalyst is composed of a Ce-containing oxide, an acidic molecular sieve, and a binder, wherein the mass content of the Ce-containing oxide is 20-80%, the mass content of the acidic molecular sieve is 20-50%, and the mass content of the activated clay is 20-40%. The catalyst is applied to a coupling system of an olefin hydration reaction and a carbon dioxide-methanol reaction, and can simultaneously prepare an olefin hydration product (alcohol) and dimethyl carbonate, and the process route is clean and environmentally friendly.

Description

Technical Field

[0001] The present invention relates to a catalyst, a preparation method thereof, and an application thereof in the preparation of dimethyl carbonate from carbon dioxide and methanol, belonging to the field of chemical engineering. Background Art

[0002] Dimethyl carbonate (DMC) is an important organic chemical intermediate, which can be used to produce a variety of chemical products such as polycarbonate, isocyanate, polyurethane, and polycarbonate diol. Since DMC is non-toxic, it is also an environmentally friendly solvent, gasoline additive, methylation reagent or carbonylation reagent, and can also be used to prepare the electrolyte of lithium batteries, playing an important role in the development of new energy vehicles. In addition, DMC can also be used as an additive for cleaners, surfactants and softeners. Due to its wide range of uses, DMC is known as the "new cornerstone" of modern organic synthesis.

[0003] At present, the production processes of DMC mainly include: phosgene methanol method, transesterification method (CN201410300187.7, CN201410677148.9), urea alcoholysis method (CN201410585479.X), methanol oxidative carbonylation method (CN201510257233.4), reaction method of carbon dioxide and methanol (CN201310103111.0). Since the transesterification production process has mild reaction conditions, does not corrode equipment during the production process, and has high product purity, the transesterification process has been developed on a large scale. Currently, the total production capacity accounts for more than 90% of the total, and it is also the mainstream process for DMC production in China. Nevertheless, the transesterification method still has the following disadvantages: the required raw material propylene oxide is not suitable for long-distance transportation, and the by-product 1,2-propanediol is difficult to sell due to purity problems.

[0004] Using CO2 and methanol as raw materials, through a non-reductive conversion method, the technology of synthesizing dimethyl carbonate by alcohol carboxylation reaction is a new green synthesis path that has received much attention in recent years (CN 201911150805.3). The advantages of this technology are wide raw material sources, low cost, high atomic utilization rate of the reaction up to 83% and only by-product water. Whether from the perspective of environmental protection or resource recycling, it has important theoretical and practical significance. Due to the severe thermodynamic limitations of the reaction, in order to improve the reaction conversion rate, existing methods must introduce additional chemical dehydrating agents into the reaction system, such as: dicyclohexylcarbodiimide, dimethoxypropane, trimethyl orthoformate, phenylacetonitrile, etc. However, the separation and regeneration costs of the dehydrating agent are very high. Developing low-cost and high-efficiency catalysts and dehydration methods is the key to industrializing the route of directly preparing dimethyl carbonate from carbon dioxide and methanol. Summary of the Invention

[0005] According to one aspect of the present application, a catalyst is provided for directly preparing dimethyl carbonate from carbon dioxide and methanol;

[0006] It includes a metal oxide, an acidic molecular sieve, and a binder;

[0007] The metal element in the metal oxide is selected from Ce;

[0008] The metal oxide accounts for 20 - 80 wt% of the mass of the catalyst;

[0009] The acidic molecular sieve accounts for 20 - 50 wt% of the mass of the catalyst;

[0010] The binder accounts for 20 - 40 wt% of the mass of the catalyst.

[0011] The metal element in the metal oxide includes metal element M;

[0012] The metal element M is selected from at least one of Cu, Zn, Zr, or Mn;

[0013] In the metal oxide, the atomic ratio of metal element M to Ce is 0 - 0.5.

[0014] The acidic molecular sieve is selected from at least one of hydrogen - type ZSM - 5, Beta, MOR, Y, MCM - 22, MCM - 36, MCM - 49, PSH - 3, XTQ - 2 molecular sieves;

[0015] The silica - alumina ratio of the acidic molecular sieve is 5 - 10000.

[0016] The binder is selected from at least one of silica sol, alumina sol, kaolin, attapulgite, and sepiolite.

[0017] According to another aspect of the present application, a preparation method of the above - mentioned catalyst is provided, which at least includes the following steps:

[0018] (1) Prepare a solution containing a metal element according to the ratio described in claim 1, mix it with a precipitant, co - precipitate, dry, and calcine I to obtain a Ce - containing oxide;

[0019] (2) Mix the Ce - containing oxide, the acidic molecular sieve, and the binder according to the ratio described in claim 1, then mix with water, spray - dry and form, and calcine II to obtain the catalyst.

[0020] The ratio is the proportional relationship in claim 1.

[0021] In (1), the metal element precursor is selected from at least one of nitrates, sulfates, acetates, and chlorides of the corresponding metal elements;

[0022] The precipitant is selected from at least one of Na2CO3, NaOH, and ammonia water;

[0023] The pH of the coprecipitation reaction is 8-12;

[0024] The time of the coprecipitation reaction is 6-96 h;

[0025] The temperature of the first calcination is 300-600 °C;

[0026] The time of the first calcination is 3-8 h;

[0027] The temperature of the second calcination is 300-900 °C;

[0028] The time of the second calcination is 3-8 h.

[0029] According to another aspect of the present application, there is provided a method for preparing dimethyl carbonate from carbon dioxide and methanol, which at least includes the following steps:

[0030] Contacting a raw material containing an olefin, carbon dioxide, and methanol with a catalyst, reacting, to obtain a product containing dimethyl carbonate;

[0031] That is, coupling an olefin hydration reaction and a carbon dioxide-methanol reaction to prepare dimethyl carbonate, effectively improving the methanol conversion rate and the dimethyl carbonate yield.

[0032] The catalyst is selected from the above catalysts or the catalysts prepared by the above preparation method.

[0033] The olefin is selected from ethylene, propylene, isobutene, or cyclohexene;

[0034] The temperature of the reaction is 60-200 °C;

[0035] The pressure of the reaction is 2-20 MPa.

[0036] The product containing dimethyl carbonate contains the alcohol obtained by the hydration of the corresponding olefin;

[0037] The selectivity of dimethyl carbonate is greater than 99%.

[0038] The beneficial effects that can be produced by the present application include:

[0039] 1) By coupling an olefin hydration reaction and a carbon dioxide-methanol reaction, water in the reaction system is quickly removed, the reaction efficiency is improved, and the high-efficiency preparation of dimethyl carbonate from carbon dioxide and methanol is realized.

[0040] 2) The catalyst preparation method provided by the present invention is simple, easy to operate, low in cost, reusable, and has potential economic benefits. Detailed implementation mode

[0041] The present invention will be described in detail below in conjunction with embodiments, but the present invention is not limited to these embodiments.

[0042] Unless otherwise specified, the raw materials in the embodiments of the present invention are all purchased through commercial channels.

[0043] The analysis methods, conversion rates, and selectivities in the embodiments are calculated as follows:

[0044] The qualitative and quantitative analysis of the products is carried out offline by an Agilent 7890A gas chromatograph, separated by Agilent HP-PLOT Q and CP-WAX capillary columns, and detected and analyzed by a flame ionization detector (FID).

[0045] Methanol conversion rate = (total mass of methanol - remaining mass of methanol) / total mass of methanol * 100

[0046] DMC selectivity = (number of moles of DMC * 2) / number of moles of converted methanol * 100;

[0047] Olefin conversion rate = (total amount of olefins - remaining amount of olefins) / total amount of olefins * 100;

[0048] Alcohol selectivity = number of moles of alcohol / number of moles of converted olefins * 100.

[0049] Unless otherwise specified, the ratios of ions in each embodiment are all molar ratios.

[0050] Example 1 Preparation of Ce oxide

[0051] Take 43.42 g of Ce(NO3)3·6H2O and add it to 200 mL of deionized water, dissolve it, stir at high speed at 70 °C, add a 1.0 mol / L Na2CO3 solution to adjust the pH to 8, and age at a constant temperature for 24 h. After cooling and filtering, wash it with distilled water until it is neutral and dried, and further calcine the obtained precursor at 500 °C for 4 h to obtain the catalyst.

[0052] Examples 2 - 8 Preparation of Ce oxide

[0053] The operation steps are the same as those in Example 1. The types, masses, precipitants, and precipitation conditions of the metal salts are shown in Table 1.

[0054] Table 1 Preparation conditions of Ce oxide

[0055]

[0056]

[0057] Examples 9 - 23 Preparation of catalyst

[0058] Mix Ce oxide, acidic molecular sieve, and binder evenly in proportion, add an appropriate amount of water and stir for 30 min. The content of all solid materials is 40% of the total mass. Then, perform spray drying and molding. The obtained solid is calcined at 550 °C for 4 h to prepare the catalyst. The name and preparation conditions of the catalyst are shown in Table 2.

[0059] Table 2 List of Catalyst Preparation Conditions

[0060]

[0061]

[0062] Reaction Performance Evaluation of Catalysts in Examples 24 - 43

[0063] Use a 100 mL reaction kettle for evaluation. Accurately weigh 200 mg of the catalyst and 15 g of methanol into a tetrafluoro inner liner, place a magnetic stir bar, cover the autoclave lid and tighten symmetrically; use CO2 to displace and purge the air in the kettle, about 0.5 MPa of gas is introduced each time, and repeat 5 times; after the air in the kettle is completely displaced, charge a certain amount of olefin and high-pressure CO2 gas, seal the reaction kettle, turn on the heater control switch, and record the start reaction time when the temperature in the kettle reaches the reaction temperature; after reacting for a certain time, stop heating and stirring, take out the reaction kettle and rapidly cool it in an ice-water bath. After the kettle is completely cooled, slowly release the pressure and open the reaction kettle. The gas-phase product is collected with an air bag for separate analysis; for the liquid-phase product, use an internal standard method. Accurately measure 1 mL of n-hexanol with a pipette and add it to the mixed solution in the kettle as the internal standard for quantitative analysis. Slowly stir for 30 s to make the liquid evenly mixed. Use a disposable syringe to suck the mixed solution, filter it through a filter membrane, and transfer it to a chromatographic analysis bottle for subsequent analysis. The evaluation results are listed in Table 3.

[0064] Table 3 Reaction Results of Carbon Dioxide and Methanol over the Catalyst

[0065]

[0066] Table 4 Reaction Results of Carbon Dioxide and Methanol with Different Kinds of Olefins Added

[0067]

[0068] As can be seen from Table 3 and Table 4, the catalysts provided in each example of the present invention have excellent reaction performance in the direct preparation of dimethyl carbonate from carbon dioxide and methanol. Coupling the hydration reactions of olefins such as ethylene, propylene, isobutene, and cyclohexene has a significant effect on improving the reaction performance of carbon dioxide and methanol.

[0069] As described above, these are only several embodiments of the present application and do not impose any form of limitation on the present application. Although the present application is disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the relevant art can make some changes or modifications within the scope of the technical solution of the present application by using the disclosed technical content, which are equivalent to equivalent embodiments and all fall within the scope of the technical solution.

Claims

1. A method for preparing dimethyl carbonate from carbon dioxide and methanol, characterized in that, At least include the following steps: Contact a raw material containing olefin, carbon dioxide and methanol with a catalyst and react to obtain a product containing dimethyl carbonate; The catalyst includes a metal oxide, an acidic molecular sieve and a binder; The metal element in the metal oxide is Ce; The metal oxide accounts for 20 - 80 wt% of the mass of the catalyst; The acidic molecular sieve accounts for 20 - 50 wt% of the mass of the catalyst; The binder accounts for 20 - 40 wt% of the mass of the catalyst; The total amount of the metal oxide, acidic molecular sieve and binder in the catalyst is 100%; The acidic molecular sieve is selected from at least one of hydrogen - type ZSM - 5, Beta, MOR, Y, MCM - 22, MCM - 36, MCM - 49 molecular sieves; The olefin is selected from at least one of ethylene, propylene, isobutene or cyclohexene.

2. The method according to claim 1, wherein The metal element in the metal oxide further includes a metal element M; The metal element M is selected from at least one of Cu, Zn, Zr or Mn; In the metal oxide, the atomic ratio of the metal element M to Ce is 0 - 0.

5.

3. The method according to claim 1, wherein The binder is selected from at least one of silica sol, aluminum sol, kaolin, attapulgite, sepiolite.

4. According to the method described in claim 1, the preparation method of the catalyst at least includes the following steps: (1) Prepare a solution containing a metal element according to a ratio, mix it with a precipitant, conduct coprecipitation, dry and calcine I to obtain a metal oxide; (2) Mix the metal oxide, acidic molecular sieve, binder and water evenly according to a ratio, conduct spray drying and shaping, and calcine II to obtain the catalyst.

5. The method according to claim 4, characterized in that, The metal element precursor is selected from at least one of nitrates, sulfates, acetates, chlorides of the corresponding metal elements; The precipitant is selected from at least one of Na2CO3, NaOH, ammonia water.

6. The method according to claim 4, wherein The temperature of the coprecipitation is 40 - 80 °C; The pH of the coprecipitation is 8 - 12; The time of the coprecipitation is 6 - 96 h; The temperature of the calcination I is 300 - 600 °C; The time of the calcination I is 3 - 8 h; The temperature of the calcination II is 300 - 900 °C; The time of the calcination II is 3 - 8 h.

7. According to the method described in claim 1, characterized in that, The temperature of the reaction is 60 - 200 °C; The pressure of the reaction is 2 - 20 MPa.

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