CN115304078B - Preparation method and application of molecular sieve - Google Patents
Preparation method and application of molecular sieve Download PDFInfo
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Abstract
The application discloses a preparation method and application of a molecular sieve, comprising the following steps: a) Dropwise adding a silicon source into a mixed solution containing an aluminum source, a doped heterologous element source and an alkaline substance, stirring, standing and aging to obtain a gel-like substance; b) Crystallizing the gel-like substance in a closed container, filtering, and drying to obtain a NaMY-M molecular sieve; the doping heterologous element source is selected from a gallium source or a boron source; wherein, the NaMY molecular sieve, M is doping hetero element source. The method adopts a template-free and guiding agent-free method, and adopts one-step hydrothermal synthesis to prepare the framework-doped Y-type molecular sieve, so that the synthesis method is simple, green and environment-friendly, shortens the synthesis time, reduces influencing factors on a synthesis route, and improves the synthesis efficiency. The molecular sieve is used as a catalyst carrier in the indirect and dimethyl carbonate formation of methanol gas phase oxidative carbonylation, so that the conversion rate of carbon monoxide and the yield of the dimethyl carbonate in the reaction are improved.
Description
Technical Field
The application relates to a preparation method and application of a molecular sieve, and belongs to the technical field of catalysis.
Background
Dimethyl carbonate (DMC) is an environment-friendly and green organic compound, has wide application and good application prospect in the chemical industry field, and has extremely active chemical properties because DMC molecules have various groups such as methoxy, carbonyl, carboxymethyl and the like. DMC has lower toxicity and can be used as carbonylation and methylation reagent to replace toxic phosgene and dimethyl sulfate. DMC also has a high oxygen content and rapid biodegradability, which makes it a very promising oil additive. Moreover, DMC can also be used as an electrolyte for lithium ion batteries, which is also a common monomer for the production of polycarbonates. It follows that DMC has very broad market prospects. Among the synthesis methods, the indirect method of methanol gas phase oxidation carbonylation is considered as one of the most promising process routes by the majority of researchers due to mild process conditions, low cost and high atomic efficiency.
The palladium-based catalyst is a catalyst commonly used in the indirect reaction of the gas-phase oxidative carbonylation of methanol, and can be divided into a chlorine system and a chlorine-free system according to whether the catalyst contains chlorine or not, and the catalyst of the chlorine system has higher activity and selectivity at the initial stage of the reaction, but the loss of chloride ions with the lapse of time causes the reduction of the reaction activity, so that the hydrogen chloride gas needs to be supplemented into the system to maintain the stability of the reaction, and the loss of the chloride ions can cause corrosiveness to reaction equipment, thereby increasing the production cost. In recent years, the chlorine-free system has better stability, and the chlorine-free system thoroughly avoids the problem of equipment corrosion, so that the research and study of vast scientific researchers on the chlorine-free system catalyst are attracted, but the reaction activity of the catalyst is far less than that of the chlorine-free system, so that the improvement of the activity and the selectivity of the chlorine-free system catalyst is very important for the reaction.
The chlorine-free system catalyst carrier mainly takes a Y molecular sieve system as a main component, the Y molecular sieve is a solid acid material with a twelve-binary-ring three-dimensional pore structure, and consists of a hexagonal prism cage, a sodalite cage and a super cage, and the unique pore structure and the ion exchange characteristic of the catalyst carrier have important applications in the fields of gas separation and catalysis, so that the Y molecular sieve is synthesized by a hydrothermal synthesis method in the industry currently. In the hydrothermal synthesis process, the silica-alumina gel is depolymerized under the action of a mineralizer at a certain temperature and pressure to generate 'nutrient substances' required by the growth of the molecular sieve. After a certain period of reaction, molecular sieve crystals are formed, and the molecular sieve is formed according to the composition of the silica-alumina gel and the reaction conditions.
In order to improve the activity and selectivity of chlorine-free molecular sieve system catalysts, in the last decades, researchers have made a great deal of research on chlorine-free molecular sieve system catalysts, wherein NaY molecular sieves are used as carriers for methanol gas-phase oxidative carbonylation indirect reaction for the first time in 1997 by Japanese UBE company, and the catalyst using NaY as carriers has good stability but low activity, and the DMC space-time yield is only 200 g/(L) cat-1 H). The NaY molecular sieve is doped with potassium in the form of liquid ion exchange by Tianjin university and the catalyst prepared by taking the potassium as a carrier is applied to the reaction, the synergistic effect of the potassium and the palladium is utilized to improve the catalytic performance, and the space-time yield is still lower than 696 g/(L) although the catalytic performance is improved to a certain extent cat-1 H). At present, the application of the Y molecular sieve is mostly limited to commercial molecular sieves, the process of autonomously synthesizing the framework doped molecular sieve is complicated, a template agent and a guiding agent method are often adopted, and the template agent can cause certain pollution to the environment and is contrary to the green synthesis concept; the guiding agent method has complicated synthesis steps and quite many factors influencing synthesis, and a strategy for regulating and controlling the application of carrier acidity to the indirect reaction of methanol gas-phase oxidative carbonylation by doping different elements through a framework has not been reported yet.
In conclusion, the Y-type molecular sieve with the in-situ framework doped with the different elements, the synthesis method is simple, the acidity can be regulated and controlled, and the Y-type molecular sieve is very important in meaning and value when being used as a carrier in the indirect reaction of the methanol gas-phase oxidative carbonylation.
Disclosure of Invention
In order to solve the defects and shortcomings of the existing in-situ framework doped Y-type molecular sieve synthesis route, the synthesis route provided by the application adopts a template-free and guiding agent-free method, the method is simple, green and environment-friendly, shortens the synthesis time, reduces influencing factors on the synthesis route, improves the synthesis efficiency, and uses the catalyst as a carrier to be applied to a catalyst for indirect reaction of methanol gas phase oxidation carbonylation.
According to one aspect of the present application, there is provided a method of preparing a molecular sieve comprising the steps of:
a) Dropwise adding a silicon source into a mixed solution containing an aluminum source, a doped heterologous element source and an alkaline substance, stirring, standing and aging to obtain a gel-like substance;
b) Crystallizing the gel-like substance in a closed container, filtering, and drying to obtain a NaMY molecular sieve;
the doped metal source is selected from a gallium source or a boron source;
wherein, the NaMY molecular sieve, M is the heterologous element doped with the heterologous element.
Optionally, the aluminum source is selected from at least one of sodium aluminate, aluminum nitrate, aluminum sulfate.
Optionally, the silicon source is selected from at least one of kaolin, silica sol, sodium silicate, tetraethyl orthosilicate.
Optionally, the gallium source is selected from at least one of gallium nitrate, gallium sulfate, gallium hydroxide.
Optionally, the boron source is selected from sodium metaborate.
Optionally, the alkaline substance is at least one selected from sodium hydroxide and ammonia water.
Optionally, the gel-like substance (Al 2 O 3 +Ga 2 O 3 /B 2 O 3 )：Na 2 O：SiO 2 ：H 2 The molar ratio of O is 1: (10-14): (8-16): (300-600), wherein the mole numbers of the aluminum source, the doping hetero element source, the alkaline substance, and the silicon source are respectively calculated by the mole number of the oxide of the metal element thereof, the (Al 2 O 3 +Ga 2 O 3 /B 2 O 3 ) Expressed as Al 2 O 3 With Ga 2 O 3 Or total mole number of Al 2 O 3 And B is connected with 2 O 3 Is used in the present application.
Optionally, the molar ratio of the aluminum source to the doping hetero element source is 1: (0.25-5) based on the molar amount of aluminum element and doping hetero element.
Optionally, the molar ratio of the aluminum source to the dopant heterologous element source is selected from any ratio of 1:0.25, 1:0.5, 1:1, 1:1.5, 1:2, 1:3, 1:5 or a range of values between the two ratios.
Optionally, the molar ratio of the aluminum source to the doping hetero element source is 1: (0.25-3).
Optionally, the stirring time is 30-180 min.
Optionally, the stirring time is selected from any value or range of values between 30min, 60min, 90min, 120min, 180min.
Optionally, the stirring time is 60-120 min.
Optionally, the standing and ageing temperature is 20-65 ℃, and the standing and ageing time is 8-48 h.
Optionally, the temperature of the standing and aging is selected from any value or a range of values between any two values of 20 ℃, 30 ℃, 45 ℃, 50 ℃, 65 ℃.
Optionally, the time of standing and aging is selected from any value or range of values between any two values of 8h, 15h, 24h, 28h and 48h.
Optionally, the standing and ageing time is 12-28 h.
Optionally, the crystallization temperature is 80-120 ℃, and the crystallization time is 8-48 h.
Alternatively, the crystallization temperature is selected from any value or a range of values between any two values of 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃.
Optionally, the crystallization time is selected from any value or range of values between 8h, 12h, 24h, 30h, 48h.
Optionally, the crystallization time is 12-30 h.
Optionally, the temperature of the drying is 80-120 ℃, and the drying time is 6-18 h.
Optionally, the temperature of the drying is selected from any value or a range of values between any two values of 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃.
Optionally, the drying time is selected from any value or range of values between 6h, 8h, 12h, 16h and 18h.
According to a further aspect of the application, there is provided the use of a molecular sieve obtained based on the above preparation method in the indirect synthesis of dimethyl carbonate by gas phase oxidative carbonylation.
The specific application mode of the molecular sieve is as follows: as a carrier for indirectly synthesizing the dimethyl carbonate catalyst by gas phase oxidative carbonylation;
the catalyst comprises a molecular sieve, an active component and an auxiliary component, wherein the active component and the auxiliary component are loaded on the molecular sieve;
the active component is active metal element palladium, and the auxiliary component is auxiliary metal element copper.
Optionally, the active component accounts for 0.5-5 wt% of the catalyst.
Optionally, the active component accounts for any value or a range of values between any two values of 0.5wt%, 1wt%, 3wt%, 4wt% and 5wt% of the catalyst in percentage by mass.
Optionally, the active component accounts for 0.5-3% of the mass of the catalyst.
Optionally, the auxiliary component accounts for 0.5-5 wt% of the catalyst.
Optionally, the auxiliary component accounts for any value or a range of values between any two values of 0.5wt%, 1wt%, 3wt%, 4wt% and 5wt% of the catalyst in percentage by mass.
Optionally, the auxiliary component accounts for 0.5-3% of the mass of the catalyst.
As a specific implementation method, the preparation process of the catalyst for indirectly synthesizing the dimethyl carbonate by the gas-phase oxidative carbonylation of methanol comprises the following steps:
A. dissolving an aluminum source, a gallium source or a boron source in deionized water, adding an alkaline substance, slowly dropwise adding the silicon source into the solution under stirring after the alkaline substance is completely dissolved, continuously stirring for 30-180min, preferably 60-120min, standing and aging for 8-48h, preferably 12-28h, at an aging temperature of 20-65 ℃, preferably 30-40 ℃ to form gel, transferring the gel into a hydrothermal kettle, crystallizing for 8-48h, preferably 12-30h, and at a crystallization temperature of 80-120 ℃.
In the gel, na element is Na 2 Expressed in the form of O, the element Al is expressed as Al 2 O 3 Expressed in terms of (a), the element Si is represented by SiO 2 Expressed in terms of (a), the elements Ga and B are expressed in terms of Ga 2 O 3 And B 2 O 3 Expressed in terms of (a) in which (Al 2 O 3 +Ga 2 O 3 /B 2 O 3 )、Na 2 O、SiO 2 、H 2 The molar ratio of O is 1:10-14:8-16:300-600, wherein the ratio of gallium/boron source to aluminum source is 0.25-5, preferably in the range of 0.25-3.
Wherein the aluminum source can be one or more of sodium aluminate, aluminum nitrate and aluminum sulfate; the silicon source can be one or more of kaolin, silica sol, sodium silicate and tetraethyl orthosilicate; the gallium source can be one or more of gallium nitrate, gallium sulfate and gallium hydroxide; the boron source may be sodium metaborate; the alkaline substance can be one or more of sodium hydroxide and ammonia water.
B. And (3) carrying out suction filtration, washing and drying on the crystallized substance for 6-15h, preferably 8-12h, and drying to obtain the NaMY-x type molecular sieve (x is the molar ratio of doping element to aluminum; M is other doping element: B, ga).
C. The active component loading is carried out on the obtained NaMY-x molecular sieve, and the catalyst applied to the methanol gas phase oxidation carbonylation reaction is prepared by adopting an ion exchange ammonia distillation method, and the specific preparation method is as follows:
c-1: placing the NaMY-x molecular sieve in sodium hydroxide solution to soak for 12-48 h, and drying for standby;
c-2: regulating the pH value of the mixed solution containing palladium salt and copper salt to 8-13 by ammonia water and dilute hydrochloric acid;
c-3: adding the molecular sieve prepared by the C-1 into the mixed solution prepared by the C-2 at the temperature of 30 ℃, magnetically stirring for 3-5 hours at the rotating speed of 200-500 r/min, so that metal cations in the mixed solution are fully exchanged with cations in the carrier;
c-4: evaporating ammonia in the solution subjected to ion exchange in the C-3 at a constant temperature of 70-90 ℃ until the pH value is neutral, carrying out suction filtration and water washing, and drying at 100-110 ℃ for 5-7 h to obtain the palladium-based catalyst. The chemical formula of the palladium-based catalyst is shown as PdCuNaMY-x (M is other doped elements: B, ga, x is the molar ratio of the doped elements to aluminum), wherein Pd is an active metal, cu is an auxiliary agent, and NaMY-x is a carrier; wherein Pd accounts for 0.5 to 5 weight percent of the catalyst, and is preferably 0.5 to 3 weight percent; cu accounts for 0.5 to 5 weight percent of the catalyst, and preferably 0.5 to 3 weight percent. The catalyst taking the catalyst as the carrier not only improves the conversion rate of carbon monoxide, but also obviously improves the space-time yield.
The application has the beneficial effects that:
1) The preparation method provided by the application adopts a template-free and guiding agent-free method to synthesize the framework-doped Y-type molecular sieve by a one-step method, is simple, green and environment-friendly, shortens the synthesis time and reduces the influencing factors on the synthesis route.
2) The Y-type molecular sieve provided by the application is applied to a catalyst for indirectly synthesizing dimethyl carbonate by methanol gas phase oxidative carbonylation, and the acidity of a carrier is regulated due to the difference between electronegativity of a doping element introduced into the Y-type molecular sieve and aluminum, so that Pd is more easily in an oxidation state, CO activation is promoted, CO conversion rate and dimethyl carbonate yield in the reaction are improved, and the activity is reduced due to the fact that the catalyst is not easily deactivated by reduction of reaction gas to form zero-valent palladium.
Drawings
FIG. 1 is an XRD spectrum of the molecular sieves of examples 1 to 4 and comparative example 1 of the present application;
FIG. 2 is an XRD spectrum of the molecular sieves of examples 5 to 8 and comparative example 1 of the present application;
FIG. 3 is an infrared spectrum of a framework doped gallium, boron molecular sieve of the application and a comparative molecular sieve.
Detailed Description
The present application is described in detail below with reference to examples, but the present application is not limited to these examples.
Unless otherwise indicated, the starting materials in the examples of the present application were purchased commercially.
The analysis method in the embodiment of the application is as follows:
obtaining an XRD spectrum of the molecular sieve by using a Rigaku MiniFlexII type X-ray powder diffractometer;
an infrared spectrum of the molecular sieve was obtained using Bruker Vertex70 FT-IR.
The CO conversion and dimethyl carbonate space time yield in the examples of the application were calculated as follows:
in the examples of the present application, the CO conversion and the space-time yield of dimethyl carbonate were calculated on a carbon mole basis.
Example 1
13.61g of sodium hydroxide, 1.40g of sodium metaaluminate and 2.18g of gallium nitrate are weighed and dissolved in 76.53g of deionized water, after the sodium metaaluminate and the gallium nitrate are completely dissolved, 55.54g of silica sol is dropwise added dropwise under stirring, after the dropwise addition is finished, the mixture is stirred for 2 hours, the mixture is kept stand and aged for 28 hours at 35 ℃, the obtained mixed gel-like liquid is transferred into a hydrothermal kettle, heated for 12 hours at 100 ℃, filtered, washed and dried for 6 hours at 120 ℃ to obtain a molecular sieve NaGaY-0.5 (the theoretical molar ratio of gallium and aluminum in the molecular sieve is 0.5).
Example 2
13.78g of sodium hydroxide, 1.05g of sodium metaaluminate and 5.48g of gallium sulfate are weighed and dissolved in 76.50g of deionized water, after the sodium metaaluminate and the gallium sulfate are completely dissolved, 51.89g of sodium silicate are added, after the sodium metaaluminate and the sodium metaaluminate are uniformly mixed, stirring is carried out for 2 hours, standing and aging are carried out for 24 hours at 36 ℃, the obtained mixed gel-like liquid is transferred into a hydrothermal kettle, heating is carried out for 12 hours at 100 ℃, suction filtration and washing are carried out, and drying is carried out for 8 hours at 100 ℃, thus obtaining the molecular sieve NaGaY-1.0 (the theoretical molar ratio of gallium and aluminum in the molecular sieve is 1.0).
Example 3
12.15g of ammonia water, 3.51g of aluminum sulfate and 3.93g of gallium nitrate are weighed and dissolved in 76.47g of deionized water, 48.85g of tetraethyl orthosilicate is dropwise added dropwise under stirring after the ammonia water is completely dissolved, the mixture is stirred for 2 hours after the dripping is finished, the mixture is kept stand and aged for 24 hours at 30 ℃, the obtained mixed gel-like liquid is transferred into a hydrothermal kettle, heated for 12 hours at 100 ℃, filtered, washed and dried for 9 hours at 80 ℃ to obtain the molecular sieve NaGaY-1.5 (the theoretical molar ratio of gallium and aluminum in the molecular sieve is 1.5).
Example 4
13.95g of sodium hydroxide, 1.82g of aluminum nitrate and 2.06g of gallium hydroxide are weighed and dissolved in 76.45g of deionized water, after the sodium hydroxide and the aluminum nitrate are completely dissolved, 55.54g of silica sol is dropwise added dropwise under stirring, after the dropwise addition is finished, the mixture is stirred for 2 hours, the mixture is kept stand and aged for 20 hours at 36 ℃, the obtained mixed gel-like liquid is transferred into a hydrothermal kettle, heated for 12 hours at 100 ℃, filtered, washed and dried for 14 hours at 120 ℃ to obtain a molecular sieve NaGaY-2.0 (the theoretical molar ratio of gallium and aluminum in the molecular sieve is 2.0).
Example 5
Weighing 11.23g of sodium hydroxide, 1.68g of sodium metaaluminate and 0.56g of sodium metaborate, dissolving into 76.23g of deionized water, dropwise adding 55.54g of silica sol while stirring after the sodium metaborate is completely dissolved, stirring for 2h after the dropwise adding is finished, standing and aging for 15h at 34 ℃, transferring the obtained mixed gel-like liquid into a hydrothermal kettle, heating for 12h at 100 ℃, carrying out suction filtration, washing and drying for 6h at 120 ℃ to obtain a molecular sieve NaBY-0.25 (the theoretical molar ratio of boron and aluminum in the molecular sieve is 0.25).
Example 6
Weighing 11.23g of sodium hydroxide, 5.84g of aluminum sulfate and 0.87g of sodium metaborate, dissolving into 76.77g of deionized water, dropwise adding 48.85g of tetraethyl orthosilicate while stirring after the sodium metaborate is completely dissolved, stirring for 2 hours after the dropwise adding is finished, standing and aging for 12 hours at 32 ℃, transferring the obtained mixed gel-like liquid into a hydrothermal kettle, heating for 12 hours at 100 ℃, carrying out suction filtration, washing and drying for 9 hours at 100 ℃ to obtain a molecular sieve NaBY-0.5 (the theoretical molar ratio of boron and aluminum in the molecular sieve is 0.5).
Example 7
Weighing 11.23g of sodium hydroxide, 3.12g of aluminum nitrate and 1.20g of sodium metaborate, dissolving into 76.68g of deionized water, dropwise adding 55.54g of silica sol while stirring after the sodium metaborate is completely dissolved, stirring for 2h after the dropwise adding is finished, standing and aging for 24h at 30 ℃, transferring the obtained mixed gel-like liquid into a hydrothermal kettle, heating for 12h at 100 ℃, carrying out suction filtration, washing and drying for 6h at 120 ℃ to obtain a molecular sieve NaBY-0.75 (the theoretical molar ratio of boron and aluminum in the molecular sieve is 0.75).
Example 8
Weighing 11.23g of sodium hydroxide, 1.04g of sodium metaaluminate and 1.30g of sodium metaborate, dissolving into 76.63g of deionized water, dropwise adding 55.54g of silica sol while stirring after the sodium metaborate is completely dissolved, stirring for 2h after the dropwise adding is finished, standing and aging for 24h at 30 ℃, transferring the obtained mixed gel-like liquid into a hydrothermal kettle, heating for 12h at 100 ℃, carrying out suction filtration, washing and drying for 10h at 80 ℃ to obtain a molecular sieve NaBY-1.0 (the theoretical molar ratio of boron and aluminum in the molecular sieve is 1.0).
Comparative example 1
11.60g of ammonia water and 2.09g of sodium metaaluminate are weighed and dissolved in 76.52g of deionized water, 55.54g of silica sol is dropwise added while stirring after the solution is completely dissolved, the solution is stirred for 2 hours after the dripping is finished, the solution is kept stand and aged for 24 hours at 30 ℃, the obtained mixed gel-like liquid is transferred into a hydrothermal kettle, heated for 12 hours at 100 ℃, filtered, washed and dried for 7 hours at 100 ℃ to obtain the molecular sieve NaY.
Comparative example 2
13.61g of sodium hydroxide, 2.18g of sodium metaaluminate, 3.98g of gallium nitrate and 55.54g of silica sol are weighed and dissolved in 76.53g of deionized water, stirred for 2 hours, kept stand and aged for 28 hours at 35 ℃, the obtained mixed sol-like liquid is transferred into a hydrothermal kettle, heated for 12 hours at 100 ℃, filtered and washed by suction, and dried for 6 hours at 120 ℃ to obtain the molecular sieve NaGaY-0.5.
Application example
Ten samples of examples 1 to 8 and comparative examples 1 and 2 were used as carriers and the active metal Pd was supported by ion exchange 2+ Auxiliary Cu 2+ The catalyst for the indirect reaction of methanol gas phase oxidative carbonylation is prepared by dissolving 0.0385g of copper nitrate in 10ml of deionized water, dropwise adding 102 microlitres of palladium nitrate solution after the copper nitrate is dissolved, dropwise adding 1ml of 28% concentrated ammonia water after the palladium nitrate solution is uniformly mixed,continuously stirring for 0.5h to obtain a palladium copper ammonia mixed solution; 1g of the carrier is weighed and placed in a palladium-copper-ammonia mixed solution, stirred for 6 hours at room temperature, filtered by suction, and dried overnight in a 100 ℃ oven to obtain a catalyst precursor.
And (3) placing the catalyst precursor in a muffle furnace at 200 ℃ for calcination for 4 hours to obtain the corresponding catalyst. The content of active palladium and auxiliary copper in the catalyst was tested by ICP, and the results are shown in Table 1.
The calcined catalyst was crushed and sieved to obtain 20 mesh catalyst particles for the following activity characterization experiments.
Catalyst activity test experiment: in a gas-solid phase fixed bed reactor, 200mg of the catalyst particles are filled in the middle part of a reaction tube, the reaction temperature is 120 ℃, and the airspeed is 3600h -1 Reacting at normal pressure; the raw materials respectively comprise CO 1.5ml/min; CH (CH) 3 ONO is 5.0ml/min; n (N) 2 5.5ml/min; the reactants reacted on the catalyst surface to form a dimethyl carbonate-containing reactant, and the evaluation results are shown in table 1.
TABLE 1
As can be seen from Table 1, the conversion of CO was 57% to 70%, and the space-time yield of dimethyl carbonate was 1065 to 1500 g.kg -1 cat h -1 . Meanwhile, the molecular sieve doped with the dissimilar metal element can be used for effectively improving the conversion rate of CO and the space-time yield of the dimethyl carbonate.
As can be seen from fig. 1 and fig. 2, the molecular sieve synthesized by the present application is compared with the peak of the standard card in the spectrum, and the framework structure of the NaY molecular sieve is not destroyed after gallium and boron are introduced to replace the framework aluminum, so that the crystal form of the NaY molecular sieve is maintained. And it can be found from FIG. 1 that the order of addition of the silica gel plays a very important role in the synthesis of the molecular sieve.
As can be seen from the infrared spectrum of fig. 3, the shift of the infrared vibration peak proves that gallium and boron are introduced into the molecular sieve framework.
While the application has been described in terms of preferred embodiments, it will be understood by those skilled in the art that various changes and modifications can be made without departing from the scope of the application, and it is intended that the application is not limited to the specific embodiments disclosed.
Claims (14)
1. A method for indirectly synthesizing dimethyl carbonate by methanol gas-phase oxidative carbonylation is characterized in that a molecular sieve is used as a catalyst carrier to be applied to indirectly synthesizing dimethyl carbonate by methanol gas-phase oxidative carbonylation;
the preparation method of the molecular sieve comprises the following steps:
a) Dropwise adding a silicon source into a mixed solution containing an aluminum source, a doped heterologous element source and an alkaline substance, stirring, standing and aging to obtain a gel-like substance;
b) Crystallizing the gel-like substance obtained in the step a) in a closed container, filtering and drying to obtain a NaMY molecular sieve;
the doping heterologous element source is selected from a gallium source or a boron source;
in the NaMY molecular sieve, M is an hetero element doped with a hetero element source;
the catalyst comprises a molecular sieve, an active component and an auxiliary component, wherein the active component and the auxiliary component are loaded on the molecular sieve;
the active component is active metal element palladium, and the auxiliary component is auxiliary metal element copper;
the active component accounts for 0.5-5wt% of the catalyst;
the auxiliary agent component accounts for 0.5-5wt% of the catalyst;
in the gel-like substance (Al 2 O 3 + Ga 2 O 3 / B 2 O 3 ）：Na 2 O：SiO 2 ：H 2 The molar ratio of O is 1: (10-14): (8-16): (300-600), wherein the mole numbers of the aluminum source, the doping hetero element source, the alkaline substance and the silicon source are calculated by the mole number of the oxide of the metal element,
said (Al) 2 O 3 +Ga 2 O 3 /B 2 O 3 ) Expressed as Al 2 O 3 With Ga 2 O 3 Or total mole number of Al 2 O 3 And B is connected with 2 O 3 Is the total number of moles of (a);
the molar ratio of the aluminum source to the doping hetero element source is 1: (0.25-5) based on the molar amount of aluminum element and doping different elements.
2. The method of claim 1, wherein the aluminum source is selected from at least one of sodium aluminate, aluminum nitrate, aluminum sulfate.
3. The method of claim 1, wherein the silicon source is selected from at least one of kaolin, silica sol, sodium silicate, tetraethyl orthosilicate.
4. The method of claim 1, wherein the gallium source is selected from at least one of gallium nitrate, gallium sulfate, gallium hydroxide.
5. The method of claim 1, wherein the boron source is selected from sodium metaborate.
6. The method according to claim 1, wherein the alkaline substance is at least one selected from sodium hydroxide and ammonia water.
7. The method of claim 1, wherein the molar ratio of aluminum element to dopant source of the hetero-element is 1: (0.25-3).
8. The method of claim 1, wherein the stirring time is 30-180 min.
9. The method of claim 1, wherein the stirring time is 60-120 min.
10. The method according to claim 1, wherein the standing and aging temperature is 20-65 ℃ and the standing and aging time is 8-48 h.
11. The method of claim 10, wherein the standing and aging time is 12-28 hours.
12. The method according to claim 1, wherein the crystallization temperature is 80-120 ℃, and the crystallization time is 8-48 hours.
13. The method of claim 12, wherein the crystallization time is 12-30 hours.
14. The method according to claim 1, wherein the drying temperature is 80-120 ℃ and the drying time is 6-18 h.
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