CN110694679A

CN110694679A - EMT/FAU core-shell molecular sieve catalyst and preparation method and application thereof

Info

Publication number: CN110694679A
Application number: CN201911048174.4A
Authority: CN
Inventors: 张春秀; 余金鹏; 徐华胜; 朱琳; 王鹏飞
Original assignee: SHANGHAI LUQIANG NEW MATERIALS CO Ltd; Shanghai Research Institute of Chemical Industry SRICI
Current assignee: SHANGHAI LUQIANG NEW MATERIALS CO Ltd; Shanghai Research Institute of Chemical Industry SRICI
Priority date: 2019-10-30
Filing date: 2019-10-30
Publication date: 2020-01-17
Anticipated expiration: 2039-10-30
Also published as: CN110694679B

Abstract

The invention relates to an EMT/FAU core-shell molecular sieve catalyst, a preparation method and application thereof. Compared with the prior art, the EMT/FAU core-shell molecular sieve takes EMT as an active component, improves the conversion rate of dimethyl ether and reduces the cost on the basis of keeping higher selectivity and stability, and has obvious technical advantages.

Description

EMT/FAU core-shell molecular sieve catalyst and preparation method and application thereof

Technical Field

The invention relates to the field of catalysts, and in particular relates to an EMT/FAU core-shell molecular sieve catalyst and a preparation method and application thereof.

Background

Ethanol is used as an important clean energy source, can be directly used as liquid fuel or mixed with gasoline for use, so as to reduce the emission of carbon monoxide and hydrocarbon in automobile exhaust, and has important significance for solving the problem of atmospheric pollution in China and realizing sustainable development. Based on the energy structure of 'lean oil, less gas and relatively rich coal resources' in China and the current situation that the external dependence of petroleum is continuously rising, a new process for synthesizing ethanol by using coal or biomass-based synthesis gas is developed, the dependence of China on petroleum is expected to be remarkably reduced, and the diversified change of energy in China is promoted.

Dimethyl ether (DME) is carbonylated to synthesize methyl acetate, and the methyl acetate is further hydrogenated to obtain a target product ethanol, so that a new route for preparing ethanol in recent years is provided. The method has the advantages of high atom economy, wide source of raw material CO, mild reaction conditions and good selectivity of target products. Compared with other production processes (such as fermentation method, direct synthesis method and the like), the methyl acetate hydrogenation process avoids the generation of ethanol-water azeotrope, and greatly saves the equipment investment and energy consumption investment caused by separation. The key technical difficulty of the current process route is the development of a high-efficiency and high-stability catalyst, and related researches thereof must promote the development of the whole ethanol industry.

In recent years, various catalysts for synthesizing methyl acetate by carbonylation of dimethyl ether have been reported. The Enrique igleia research group of Berkeley in 2006 (angew.chem, int.ed.45(2006)10, 1617-containing 1620, j.catal.245(2007)110, j.am.chem.soc.129(2007)4919) found that the carbonylation of dimethyl ether can be carried out on Mordenite (Mordenite) and Ferrierite (Ferrierite) with an 8-membered ring molecular sieve system, and the selectivity of methyl acetate is very good and reaches 99%, but the carbonylation activity of dimethyl ether is very low. The difference of methyl acetate reaction activity of dimethyl ether carbonylation on MOR and ZSM-35 catalysts is compared and researched by Catal.Lett.2010, 139: 33-37, and the ZSM-35 molecular sieve is found to have better reaction stability and product selectivity, and DME/CO/N at 250 ℃ and 1MPa₂Reaction of 5/50/2.5/42.5-12.5 ml/min/He ═Under the conditions, the conversion rate of dimethyl ether reaches 11 percent, and the selectivity of methyl acetate reaches 96 percent. CN106365995B subsequently reported the carbonylation reaction over a catalyst of an acidic EMT structural molecular sieve to give methyl acetate. The method is carried out in the presence of an acidic EMT molecular sieve serving as a catalyst, so that the reaction activity is high, and the stability is obviously improved. Patent CN 106890665A reports that EMT molecular sieve is used as active component, which can greatly improve the selectivity and stability of methyl acetate, and the selectivity of methyl acetate can be maintained between 91% and 98.3% after continuous reaction on fixed bed for 100 h. But the conversion rate of the dimethyl ether is lower and is between 15 and 30 percent, and the related result can not meet the requirement of industrial production.

Disclosure of Invention

The invention aims to solve the problems and provide an EMT/FAU core-shell molecular sieve catalyst and a preparation method and application thereof, the EMT/FAU core-shell molecular sieve has great advantages in improving the conversion rate of dimethyl ether, the EMT/FAU core-shell molecular sieve has the advantages of both the EMT molecular sieve and the FAU molecular sieve, the FAU molecular sieve has strong adsorption capacity on polar molecules, the EMT molecular sieve has strong acidity and more acid amount, and has excellent isomerization, alkylation and aromatization performances in petroleum processing, and the adsorption of the FAU molecular sieve on the dimethyl ether molecules and the acid catalysis of the EMT molecular sieve are utilized, so that the concentration of the dimethyl ether molecules on the surface of the catalyst is improved, the outer surface acidity of the zeolite catalyst is improved, and the conversion rate of the dimethyl ether can be improved.

The purpose of the invention is realized by the following technical scheme:

an EMT/FAU core-shell molecular sieve catalyst is of a core-shell structure, an EMT molecular sieve is used as an inner core, an FAU molecular sieve is used as a shell layer, the EMT molecular sieve is treated by a weak base solution, and a cocatalyst is added.

The EMT molecular sieve and the FAU molecular sieve are formed by connecting the same cage-shaped structural unit (double 6-membered ring and beta cage) in different modes, and the structural similarity characteristic provides good conditions for the preparation of the EMT/FAU core-shell molecular sieve. The two molecular sieves have a 3-dimensional 12-membered ring channel system, have small substance diffusion resistance and excellent channel connectivity, are more favorable for the adsorption of reactant molecules and the diffusion of product molecules, can fully exert the synergistic effect of the EMT molecular sieve and the FAU molecular sieve in the dimethyl ether carbonylation reaction, improve the stability and the conversion rate of the catalyst, and simultaneously ensure that the catalyst has good regeneration performance in the dimethyl ether carbonylation reaction.

Preferably, the promoter is introduced into the EMT molecular sieve through in-situ synthesis, metal ion exchange or impregnation loading, and is selected from one or more of copper, iron, gallium or silver, and the content of the promoter is 0.05-1.0 wt% calculated by a metal simple substance. The acid site of the EMT molecular sieve has an isomerization function, the metal auxiliary agent has a hydrogenation-dehydrogenation function, the selectivity and the stability of the catalyst can be improved by adding the cocatalyst, and the olefin is hydrogenated into the alkane with the assistance of the cocatalyst, so that the formation of oligomers and coke precursors is greatly reduced.

Preferably, SiO in the FAU molecular sieve₂With Al₂O₃The molar ratio is 2.0-6.0, and SiO in the FAU molecular sieve is preferably selected₂With Al₂O₃The molar ratio is 2.6-3.0. The smaller molar ratio of the FAU molecular sieve enables the FAU molecular sieve to have stronger polarity, and easily adsorb polar and easily polarized molecules. The proper mass ratio of the EMT molecular sieve to the synthetic gel enables the FAU molecular sieve to grow on the EMT molecular sieve better, and synthesis of the FAU molecular sieve with pure crystalline phase is avoided.

Preferably, the grain size of the EMT molecular sieve is 1-3 μm. The EMT molecular sieve with the particle size range of 1-3 mu m has higher utilization rate and is easier to synthesize.

Preferably, the FAU molecular sieve is coated on the surface of the EMT molecular sieve by a vapor phase conversion method, and the thickness of the FAU molecular sieve is 0.1-1 μm. The thinner shell layer molecular sieve can enable reactants to have a shorter diffusion path and accelerate the catalytic rate.

A preparation method of an EMT/FAU core-shell molecular sieve catalyst comprises the following steps:

(1) performing surface treatment on the EMT molecular sieve by adopting a weak base solution, and then adding a cocatalyst;

(2) SiO with the molecular molar ratio of (3-10)₂：1Al₂O₃：(3～24)Na₂O：(200-1322)H₂Taking the mixed solution of a silicon source, an aluminum source, alkali and water of O as FAU type molecular sieve synthetic solution;

(3) adding the FAU type molecular sieve synthetic liquid into the EMT molecular sieve powder which is dried after being processed in the step (1), uniformly stirring, carrying out aging treatment, crystallizing in a reaction kettle by adopting a vapor phase synthesis method, and then washing, drying and roasting to obtain the EMT/FAU core-shell type molecular sieve.

The weak base treatment in the step (1) can increase the surface roughness, so that the FAU molecular sieve is easy to grow on the EMT molecular sieve; on the other hand, the weak base treatment can improve the reaction activity of the carbonylation of the dimethyl ether.

The traditional core-shell molecular sieve is synthesized by adding crystals into growth mother liquor and applying an in-situ hydrothermal synthesis method, and has more defects, the mother liquor is only slightly loaded on the added crystals, most of the mother liquor is crystallized to form an isolated molecular sieve, the defect can be overcome by adopting a vapor phase synthesis method in the step (3), and the vapor phase synthesis method can be used for irregular carriers and can control the thickness of a shell layer; on the other hand, only a small amount of prepared synthetic solution can be used for synthesizing the shell layer molecular sieve, so that the formation of an isolated molecular sieve is reduced, and the pollution to the environment caused by the discharge of mother solution is avoided.

Preferably, the weak base is selected from one or a mixture of sodium acetate, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, sodium fatty acid, sodium alkyl benzene sulfonate, sodium dodecyl benzene sulfonate, sodium hexadecyl benzene sulfonate or alkaline aluminum chloride, and the solubility of the weak base solution is 0.05-2 mol/L.

Preferably, the EMT molecular sieve is treated by the weak base solution in the step (1) at room temperature for 1-12h, washed by deionized water until the pH of the washing liquid is about 10, and then dried. The weak base treatment condition of 1-12h ensures that the EMT molecular sieve has certain surface roughness.

The silicon source in the step (2) is one or a mixture of methyl orthosilicate, ethyl orthosilicate, tetraethyl orthosilicate, silicic acid, sodium silicate, potassium silicate, calcium silicate, magnesium silicate, silica sol, water glass, silicon dioxide, white carbon black and fly ash; the aluminum source is one or the mixture of sodium aluminate, calcium aluminate, alumina sol and alumina; the alkali is one or mixture of lithium oxide, sodium oxide, potassium oxide, lithium hydroxide, sodium hydroxide and potassium hydroxide.

Preferably, the mass ratio of the EMT molecular sieve to the FAU type molecular sieve synthetic fluid in the step (3) is 1: 0.1-5; the aging treatment condition is that the temperature is 20-60 ℃ and the time is 2-24 h; and (3) crystallizing for 6-24h at 95-110 ℃, washing, drying, and roasting for 2h at 400-600 ℃ to finally obtain the EMT/FAU core-shell molecular sieve.

The catalyst is used for synthesizing methyl acetate by dimethyl ether carbonylation, and is treated for 6 hours in a nitrogen atmosphere at 200-400 ℃ before use.

The experimental apparatus was evaluated for one of a fixed bed reactor, a fluidized bed reactor or a moving bed reactor. The specific experimental process comprises the steps of firstly filling a catalyst into a reaction mixture, wherein the temperature is 170-240 ℃, the pressure is 1.0-15.0 MPa, and the mass airspeed of dimethyl ether feeding is 0.1-2.5 h^-1And the molar ratio of the carbon monoxide to the dimethyl ether is 15: 1-1: 1.

Compared with the prior art, the invention has the following technical characteristics:

(1) the EMT/FAU core-shell molecular sieve can improve the conversion rate of the catalyst, and the FAU type molecular sieve has an adsorption effect on polar and easily polarized molecules and can improve the concentration of reactants, so that the conversion rate of the reactants is improved.

(2) The EMT/FAU core-shell molecular sieve can improve the stability of the catalyst, and the EMT/FAU core-shell structure can prevent the inactivation speed caused by strong acidity of the outer surface of the EMT molecular sieve from being high.

(3) The EMT/FAU core-shell molecular sieve can improve the selectivity of the catalyst, and the EMT/FAU core-shell structure can reduce byproducts generated by over-strong acidity of the outer surface of the EMT molecular sieve.

Drawings

FIG. 1 is a surface SEM of an EMT molecular sieve.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments.

Preparation of catalyst

Example 1

Treating the EMT molecular sieve: soaking EMT molecular sieve with particle size of about 1 μm in 0.05mol/L sodium acetate solution at room temperature for 1h, washing, drying, and placing in 0.01mol/L AgNO₃Soaking in the solution for 6h, washing and drying, wherein FIG. 1 is a surface SEM spectrogram of an EMT molecular sieve.

Preparing an EMT/FAU core-shell type molecular sieve: 9.7g of NaOH solution are dissolved in 80g of water, and 2.0g of NaAlO are added with vigorous stirring₂Mixing and stirring the mixture until the mixture is clear, and cooling the mixture for later use to obtain a solution A. 23g of sodium silicate was weighed out and dissolved in 100g of water, and stirred for 0.5h to obtain solution B. Slowly dripping the solution A into the solution B under the condition of stirring until uniform raw materials with the molar ratio of 10SiO are generated₂：Al₂O₃：24Na₂O：1322H₂Weighing 50g of synthetic solution of O, adding the weighed synthetic solution into 10g of EMT molecular sieve powder, uniformly stirring, aging in an oven at 20 ℃ for 24h, then placing the sol on the upper layer of a crystallization kettle, adding 30g of water at the bottom of the kettle, and crystallizing at 95 ℃ for 24h to obtain the EMT/FAU core-shell molecular sieve catalyst EF1 with the shell thickness of 0.9 mu m.

Comparative example 1

Treating the EMT molecular sieve: placing EMT molecular sieve with the particle size of about 1 mu m in 0.01mol/L AgNO₃Soaking in the solution for 6h, washing and drying to obtain the Ag-loaded EMT molecular sieve DB 1.

Comparative example 2

Preparation of FAU molecular sieve: 0.14g of NaOH solution in 20g of water was added with 3.7g of NaAlO under vigorous stirring₂Mixing and stirring the mixture until the mixture is clear, and cooling the mixture for later use to obtain a solution A. 12.8g of sodium silicate was weighed out and dissolved in 27g of water, and stirred for 0.5h to obtain solution B. Slowly dripping the solution A into the solution B under the condition of stirring until uniform raw material molar ratio of 3SiO is generated₂：Al₂O₃：3Na₂O：200H₂And (3) putting the synthetic liquid of O into a crystallization kettle, and crystallizing at 95 ℃ for 24 hours to obtain FAU molecular sieve DB 2.

Example 2

Treating the EMT molecular sieve: the EMT molecular sieve with the particle size of about 3 mu m is soaked in 2mol/L tetraethylammonium hydroxide solution for 12h at room temperature, washed and dried.

Preparing an EMT/FAU core-shell type molecular sieve: 0.14g of NaOH solution is dissolved in 20g of water, and 3.7g of NaAlO is added with vigorous stirring₂Mixing and stirring the mixture until the mixture is clear, and cooling the mixture for later use to obtain a solution A. 12.8g of sodium silicate was weighed out and dissolved in 27g of water, and stirred for 0.5h to obtain solution B. Slowly dripping the solution A into the solution B under the condition of stirring until uniform raw material molar ratio of 3SiO is generated₂：Al₂O₃：3Na₂O：200H₂Weighing 1g of synthetic solution of O, adding the synthetic solution into 10g of EMT molecular sieve powder, uniformly stirring, aging in an oven at 60 ℃ for 2h, then placing the sol on the upper layer of a crystallization kettle, adding 30g of water at the bottom of the kettle, and crystallizing at 110 ℃ for 6h to obtain the EMT/FAU core-shell molecular sieve catalyst EF2 with the shell thickness of 0.2 mu m.

Examples 3 to 8 were synthesized according to the similar method and procedure of example 1 with the synthesis ratios and synthesis conditions shown in table 1 to obtain EMT/FAU core-shell molecular sieve catalysts EF3 to EF 8.

TABLE 1 examples 3-8 Synthesis ratios and Synthesis conditions

Second, catalyst Performance test example

Example 9

Tabletting 2g of EF1 molecular sieve catalyst, and sieving to obtain particles with the particle size of 20-40 meshes. Loading into a fixed bed reactor with a tubular inner diameter of 10 mm, temperature of 180 deg.C, pressure of 1.5MPa, molar ratio of carbon monoxide to dimethyl ether of 5: 1, and dimethyl ether feeding mass space velocity of 0.1h^-1After the device runs for 100 hours, the conversion rate of methyl acetate is 35.6 percent, and the selectivity is 98 percent.

Example 10

2g of DB1 molecular sieve catalyst is tableted and sieved to obtain particles with the particle size of 20-40 meshes. Loading into a fixed bed reactor with a tubular inner diameter of 10 mm, temperature of 180 deg.C, pressure of 1.5MPa, molar ratio of carbon monoxide to dimethyl ether of 5: 1, and dimethyl ether feeding mass space velocity of 0.1h^-1After the device runs for 100 hours, methyl acetateThe ester conversion rate is 26.2%, the selectivity is 83%, and since the DB1 molecular sieve catalyst has weaker polarity than the EF1 molecular sieve catalyst in example 1, and the surface of the DB1 molecular sieve catalyst has no shape-selective catalytic effect, the conversion rate and the selectivity of methyl acetate are both lower than those of example 1.

Example 11

2g of DB2 molecular sieve catalyst is tableted and sieved to obtain particles with the particle size of 20-40 meshes. Loading into a fixed bed reactor with a tubular inner diameter of 10 mm, temperature of 180 deg.C, pressure of 1.5MPa, molar ratio of carbon monoxide to dimethyl ether of 5: 1, and dimethyl ether feeding mass space velocity of 0.1h^-1After the device runs for 100 hours, the conversion rate of the methyl acetate is 0%, the selectivity is 0%, and the conversion rate and the selectivity of the methyl acetate are both 0 because the DB2 molecular sieve catalyst does not have the performance of catalyzing the dimethyl ether carbonylation reaction.

Example 12

Tabletting 2g of EF2 molecular sieve catalyst, and sieving to obtain particles with the particle size of 20-40 meshes. Loading into a fixed bed reactor with a tubular inner diameter of 10 mm, temperature of 180 deg.C, pressure of 1.5MPa, molar ratio of carbon monoxide to dimethyl ether of 5: 1, and dimethyl ether feeding mass space velocity of 0.1h^-1After the device runs for 100 hours, the conversion rate of methyl acetate is 37 percent, and the selectivity is 98 percent.

Example 13

Tabletting 2g of EF3 molecular sieve catalyst, and sieving to obtain particles with the particle size of 20-40 meshes. Loading into a fixed bed reactor with a tubular inner diameter of 10 mm, temperature of 180 deg.C, pressure of 1.5MPa, molar ratio of carbon monoxide to dimethyl ether of 5: 1, and dimethyl ether feeding mass space velocity of 0.1h^-1After the device runs for 100 hours, the conversion rate of methyl acetate is 41 percent, and the selectivity is 99 percent.

Example 14

Tabletting 2g of EF4 molecular sieve catalyst, and sieving to obtain particles with the particle size of 20-40 meshes. Loading into a fixed bed reactor with a tubular inner diameter of 10 mm, temperature of 180 deg.C, pressure of 1.5MPa, molar ratio of carbon monoxide to dimethyl ether of 5: 1, and dimethyl ether feeding mass space velocity of 0.1h^-1After the device runs for 100 hours, the conversion rate of the methyl acetate is 31 percent, and the selectivity is 97 percent.

Example 15

Tabletting 2g of EF5 molecular sieve catalyst, and sieving to obtain particles with the particle size of 20-40 meshes. Loading into a fixed bed reactor with a tubular inner diameter of 10 mm, temperature of 180 deg.C, pressure of 1.5MPa, molar ratio of carbon monoxide to dimethyl ether of 5: 1, and dimethyl ether feeding mass space velocity of 0.1h^-1After the device runs for 100 hours, the conversion rate of methyl acetate is 36 percent, and the selectivity is 99 percent.

Example 16

Tabletting 2g of EF6 molecular sieve catalyst, and sieving to obtain particles with the particle size of 20-40 meshes. Loading into a fixed bed reactor with a tubular inner diameter of 10 mm, temperature of 180 deg.C, pressure of 1.5MPa, molar ratio of carbon monoxide to dimethyl ether of 5: 1, and dimethyl ether feeding mass space velocity of 0.1h^-1After the device runs for 100 hours, the conversion rate of the methyl acetate is 42 percent, and the selectivity is 98 percent.

Example 17

Tabletting 2g of EF7 molecular sieve catalyst, and sieving to obtain particles with the particle size of 20-40 meshes. Loading into a fixed bed reactor with a tubular inner diameter of 10 mm, temperature of 180 deg.C, pressure of 1.5MPa, molar ratio of carbon monoxide to dimethyl ether of 5: 1, and dimethyl ether feeding mass space velocity of 0.1h^-1After the device runs for 100 hours, the conversion rate of methyl acetate is 36 percent, and the selectivity is 96 percent.

Example 18

Tabletting 2g of EF8 molecular sieve catalyst, and sieving to obtain particles with the particle size of 20-40 meshes. Loading into a fixed bed reactor with a tubular inner diameter of 10 mm, temperature of 180 deg.C, pressure of 1.5MPa, molar ratio of carbon monoxide to dimethyl ether of 5: 1, and dimethyl ether feeding mass space velocity of 0.1h^-1After the device runs for 100 hours, the conversion rate of methyl acetate is 30 percent, and the selectivity is 96 percent.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. The EMT/FAU core-shell molecular sieve catalyst is characterized in that the catalyst is of a core-shell structure, an EMT molecular sieve is used as an inner core, an FAU molecular sieve is used as a shell layer, the EMT molecular sieve is treated by a weak base solution, and a cocatalyst is added.

2. The EMT/FAU core-shell molecular sieve catalyst as recited in claim 1, wherein the promoter is introduced into the EMT molecular sieve by in-situ synthesis, metal ion exchange or impregnation loading, the promoter is selected from one or more of copper, iron, gallium or silver, and the content of the promoter is 0.05-1.0 wt% calculated by metal elementary substance.

3. The EMT/FAU core-shell molecular sieve catalyst of claim 1, wherein SiO in the FAU molecular sieve₂With Al₂O₃The molar ratio is 2.0-6.0.

4. The EMT/FAU core-shell molecular sieve catalyst as claimed in claim 1, wherein the EMT molecular sieve has a grain size of 1-3 μm.

5. The EMT/FAU core-shell molecular sieve catalyst of claim 4, wherein the FAU molecular sieve is coated on the surface of the EMT molecular sieve by a vapor phase conversion method, and the thickness of the EMT/FAU core-shell molecular sieve catalyst is 0.1-1 μm.

6. The preparation method of the EMT/FAU core-shell molecular sieve catalyst according to claim 1, which comprises the following steps:

7. The method for preparing EMT/FAU core-shell molecular sieve catalyst according to claim 6, wherein the weak base is selected from one or a mixture of sodium acetate, tetraethyl ammonium hydroxide, tetrapropyl ammonium hydroxide, sodium fatty acid, sodium alkyl benzene sulfonate, sodium dodecyl benzene sulfonate, sodium hexadecyl benzene sulfonate or basic aluminum chloride, and the concentration of the weak base solution is 0.05-2 mol/L.

8. The preparation method of the EMT/FAU core-shell molecular sieve catalyst according to claim 7, wherein the EMT molecular sieve is treated by the weak base solution at room temperature for 1-12 h.

9. The preparation method of the EMT/FAU core-shell molecular sieve catalyst according to claim 6, wherein the mass ratio of the EMT molecular sieve to the FAU type molecular sieve synthetic fluid in the step (3) is 1: 0.1-5;

the aging treatment condition is that the temperature is 20-60 ℃ and the time is 2-24 h; the vapor phase crystallization condition is crystallization for 6-24h at 95-110 ℃.

10. The use of an EMT/FAU core-shell molecular sieve catalyst according to claim 1, wherein the catalyst is used for the carbonylation of dimethyl ether to produce methyl acetate.