A catalyst system for synthesizing methyl acetate from synthesis gas, and a preparation method and application thereof

Abstract

The application discloses a catalyst system for synthesizing methyl acetate from synthesis gas as well as a preparation method and application thereof. The catalyst system comprises a first part located at an upstream and a second part located at a downstream. The first part comprises a methanol synthesis catalyst and a dehydrating agent, and the second part comprises a carbonylation reaction catalyst. The application realizes direct synthesis of methyl acetate from synthesis gas in one reactor by developing a series catalyst system. Further, the application adopts a post-grafting method to hydrophobically modify the hydroxyl groups on the surface of a molecular sieve by using a silylating agent, thereby improving the selectivity and yield of methyl acetate. In addition, the catalyst preparation process is simple and controllable, and is beneficial to large-scale industrial production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of methyl acetate preparation, and particularly relates to a series catalyst system for directly preparing methyl acetate from synthesis gas as well as a preparation method and application thereof. BACKGROUND

[0002] Methyl acetate is a colorless transparent liquid, which is mainly used as an organic solvent and can be used in the production of paint spraying, spices, resins, artificial leather and the like instead of acetone, and is also an important chemical intermediate, which can be used to produce acetic anhydride, methyl methacrylate, vinyl acetate and the like. In addition, methyl acetate hydrogenation can also obtain ethanol. With the popularization of ethanol fuel, the preparation of methyl acetate has also attracted widespread attention.

[0003] At present, the main preparation methods of methyl acetate include methyl acetate esterification, methanol carbonylation, methyl formate homologation and dimethyl ether carbonylation. The above-mentioned methyl acetate preparation methods are complicated, and the generation of methyl acetate is accompanied by the consumption of another high-cost raw material, such as methyl acetate, methanol and the like.

[0004] Therefore, if low-cost raw materials are selected, methyl acetate can be efficiently generated by a simple method under the condition of ensuring the selectivity and yield of methyl acetate.

[0005] In order to solve the above problems, the application is proposed. SUMMARY

[0006] The application combines a metal or metal oxide catalyst with a zeolite with hydrophobic properties to inhibit the influence of water on the molecular sieve catalyst in the carbonylation step in the reaction system for directly preparing methyl acetate from synthesis gas, so as to realize efficient catalytic synthesis of methyl acetate from synthesis gas by one-step method. Specifically, the application realizes the direct preparation of methyl acetate from synthesis gas in one reactor by developing a series catalyst system. Further, the application improves the selectivity and yield of methyl acetate by hydrophobic modification of the hydroxyl groups on the surface of the molecular sieve through a silanization reagent by using a post-grafting method. In addition, the catalyst preparation process provided by the application is simple and controllable, which is beneficial to large-scale industrial production.

[0007] The application provides a catalyst system for preparing methyl acetate from synthesis gas, which comprises a first part located in an upstream and a second part located in a downstream, wherein the first part comprises a methanol synthesis catalyst and a dehydrating agent, and the second part comprises a carbonylation reaction catalyst.

[0008] In the application, the upstream and downstream are defined according to the flow direction of the gas, that is, the gas moves from the upstream to the downstream.

[0009] Preferably, the first part and the second part are separated by a quartz cotton or silicon carbide or quartz sand bed layer.

[0010] Preferably, the methanol synthesis catalyst is selected from Cu-ZnO-MOx catalysts, wherein M is selected from Al, Ce, Zr, La, In. The methanol synthesis catalyst can be a commercially available Cu-ZnO-Al2O3 methanol synthesis catalyst, or a Cu-ZnO-MOx catalyst (M can be Al, Ce, Zr, La, In) prepared by co-precipitation or impregnation, wherein the mass fraction of Cu is preferably 30-60% based on the total mass of the Cu-ZnO-MOx catalyst.

[0011] Preferably, the dehydration agent is selected from alumina or an acidic molecular sieve, and the acidic molecular sieve is selected from ZSM-5 molecular sieves. More preferably, the acidic molecular sieve is selected from ZSM-5 molecular sieves.

[0012] Preferably, the carbonylation reaction catalyst is a hydrophobically modified carbonylation reaction molecular sieve, and the molecular sieve includes H-MOR, H-FER, and H-SSZ-13.

[0013] The second aspect of the present application provides a preparation method of the catalyst system described in the first aspect of the present application, and the preparation steps of the hydrophobically modified carbonylation reaction molecular sieve are as follows:

[0014] (1) uniformly mixing a molecular sieve powder and an organic solvent, and then heating under reflux conditions;

[0015] (2) adding an organosilane reagent, and maintaining heating under reflux conditions;

[0016] (3) separating the mixture obtained in step (2), drying the obtained catalyst, and calcining to obtain the hydrophobically modified carbonylation reaction molecular sieve;

[0017] (4) tabletting and sieving the obtained hydrophobically modified carbonylation reaction molecular sieve.

[0018] Preferably, steps (1)-(3) are repeated one or more times to improve the silanization degree of the surface of the molecular sieve.

[0019] Preferably, the molecular sieve in step (1) includes H-MOR, H-FER, and H-SSZ-13, the H-MOR has a SiO2 / Al2O3 ratio of 8-40 in its composition, the organic solvent is one or more of toluene, cyclohexane, and methanol, and the solid-liquid ratio of the molecular sieve powder to the organic solvent is 1 g: (20-50) mL.

[0020] The organosilane reagent in step (2) is one or more of tetraethyl orthosilicate, 3-aminopropyl triethoxysilane, n-propyl trimethoxysilane, and 3-aminopropyl trimethoxysilane; the addition amount of the organosilane reagent is 2-10%; the reflux time is 1-5 h; and the reflux temperature is 60-80°C.

[0021] Preferably, the drying condition in step (3) is that the drying temperature is 100-150 DEG C, and the drying time is 6-24h; the calcination condition is that the calcination temperature is 400-600 DEG C, the calcination time is 4-8h, and the heating rate is 1-5 DEG C / min.

[0022] The third aspect of the present application provides an application of the series catalyst system of the first aspect of the present application, after the catalyst system is sequentially filled on a fixed bed reactor, and is pretreated under nitrogen atmosphere with slow heating to 200-400 DEG C for 2-10h, then is switched to pure hydrogen or hydrogen-containing gas for continuous treatment for 2-5h, the pressure is 1-3MPa, then the feed is switched to synthesis gas, wherein H2:CO is 0.5-2, the space velocity is 100-2000h-1, the temperature is 200-300 DEG C, and the pressure is 1-3MPa. -1

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] 1. Based on the energy structure of poor oil, less gas and rich coal in China, the present application directly prepares methyl acetate from coal-based synthesis gas by one-step method, simplifies the process flow, and reduces fixed investment and production cost. The present application realizes the direct preparation of methyl acetate from synthesis gas in one reactor by developing a series catalyst system and adjusting the combination mode, specifically, first, the synthesis gas generates dimethyl ether through methanol synthesis and dehydration reaction in the upper layer, and then the carbonylation reaction occurs on the hydrophobic modified molecular sieve to generate methyl acetate.

[0025] 2. In order to improve the selectivity and yield of methyl acetate, the molecular sieve is hydrophobically modified, specifically, the hydroxyl groups on the surface of the molecular sieve are hydrophobically modified by silanization reagent through post-grafting method, and the surface groups of the molecular sieve are regulated through chemical modification, thereby avoiding the competitive adsorption of CO and water on the catalyst, and improving the selectivity and yield of methyl acetate. Water has a significant influence on the catalyst in the process of directly preparing methyl acetate from synthesis gas, and the hydrophobic mordenite can effectively inhibit the influence of water on the reaction system of directly preparing methyl acetate from synthesis gas, and a high yield of methyl acetate can be obtained at low temperature. The catalyst designed in the present application can realize high CO conversion rate and high selectivity of methyl acetate.

[0026] 3. The catalyst preparation process provided by the present application is simple and controllable, and is beneficial to large-scale industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Schematic diagram of the catalyst system for preparing methyl acetate from synthesis gas. DETAILED DESCRIPTION

[0028] ​The application will be described in further detail in connection with the specific embodiments. It should be noted that the following examples are illustrative, and are not meant to limit the scope of the application. The starting materials used in the following examples are commercially available.

[0029] Example 1

[0030] The commercial Cu-ZnO-Al2O3 methanol synthesis catalyst (mass fraction of Cu is 60%) and the dehydrating agent H-ZSM-5 were mixed physically in a mass ratio of 2:1, and then tabletted and sieved.

[0031] Preparation of hydrophobically modified H-MOR molecular sieve:

[0032] (1) 1 g of mordenite molecular sieve powder and 25 mL of cyclohexane were mixed uniformly, and then heated under reflux;

[0033] (2) 4% of tetraethyl orthosilicate was added, and the mixture was heated under reflux at 80°C for 1 h;

[0034] (3) The mixture obtained in step (2) was separated, and the obtained catalyst was dried;

[0035] (4) The dried catalyst was calcined at 500°C for 5 h;

[0036] (5) Tabletted and sieved.

[0037] 0.5 g of hydrophobically modified H-MOR, 1 cm of quartz wool, and 0.5 g of the physically mixed catalyst were loaded into a reaction tube in the order from bottom to top, and the catalysts were all 40-60 mesh. Under a nitrogen atmosphere, heating was performed at a temperature increasing rate of 5°C / min to 250°C, the flow rate was 25 mL / min, and after 2 h of pretreatment, switching was performed to 5% H2 / Ar for 2 h of treatment, and the pressure was 2 MPa. After the pretreatment, the temperature was adjusted to 200°C, and switching was performed to feed in synthesis gas, wherein the volume ratio of H2:CO was 1, the space velocity was 750 h-1, and the pressure was 2 MPa. The tail gas of the reaction was analyzed by gas phase online chromatography. The specific results are shown in Table 1. -1

[0038] The commercial Cu-ZnO-Al2O3 methanol synthesis catalyst used was purchased from Dalian Ruikeli Technology Co., Ltd., the dehydrating agent H-ZSM-5 and the carbonylation catalyst H-MOR (SiO2 / Al2O3 is 15) were purchased from the Catalyst Factory of Nankai University.

[0039] Examples 2-3

[0040] ​The preparation of hydrophobically modified H-MOR molecular sieve steps (1)-(4) in Example 1 were carried out twice (Example 2), thrice (Example 3) under the same conditions as in Example 1 except that the organic silane reagent was changed to 3-aminopropyltriethoxysilane. The specific results are shown in Table 1.

[0041]

Example 4

[0042] The preparation of hydrophobically modified H-MOR molecular sieve steps (1)-(4) in Example 1 were carried out twice (Example 2), thrice (Example 3) under the same conditions as in Example 1 except that the organic silane reagent was changed to 3-aminopropyltriethoxysilane. The specific results are shown in Table 1.

[0043]

Examples 5-6

[0044] The preparation of hydrophobically modified H-MOR molecular sieve steps (1)-(4) in Example 1 were carried out twice (Example 5), thrice (Example 6) under the same conditions as in Example 1 except that the organic silane reagent was changed to 3-aminopropyltriethoxysilane. The specific results are shown in Table 1.

[0045]

Example 7

[0046] The preparation of hydrophobically modified H-MOR molecular sieve steps (1)-(4) in Example 1 were carried out twice (Example 2), thrice (Example 3) under the same conditions as in Example 1 except that the organic silane reagent was changed to 3-aminopropyltriethoxysilane. The specific results are shown in Table 1.

[0047]

Example 8

[0048] The preparation of hydrophobically modified H-MOR molecular sieve steps (1)-(4) in Example 1 were carried out twice (Example 2), thrice (Example 3) under the same conditions as in Example 1 except that the organic silane reagent was changed to 3-aminopropyltriethoxysilane. The specific results are shown in Table 1.

[0049]

Examples 9-10

[0050] The preparation of hydrophobically modified H-MOR molecular sieve steps (1)-(4) in Example 1 were carried out twice (Example 2), thrice (Example 3) under the same conditions as in Example 1 except that the organic silane reagent was changed to 3-aminopropyltriethoxysilane. The specific results are shown in Table 1.

[0051]

Examples 11-12

[0052] The preparation of hydrophobically modified H-MOR molecular sieve steps (1)-(4) in Example 1 were carried out twice (Example 2), thrice (Example 3) under the same conditions as in Example 1 except that the organic silane reagent was changed to 3-aminopropyltriethoxysilane. The specific results are shown in Table 1.

[0053]

Example 13

[0054] The preparation of hydrophobically modified H-MOR molecular sieve steps (1)-(4) in Example 1 were carried out twice (Example 2), thrice (Example 3) under the same conditions as in Example 1 except that the organic silane reagent was changed to 3-aminopropyltriethoxysilane. The specific results are shown in Table 1.

[0055]

Comparative Example 1

[0056] Under the conditions identical to those of Example 1 except that only the unhydrophobically-modified commercial H-MOR was selected as the carbonylation catalyst, the specific results are shown in Table 1.

[0057] Table 1 Reaction performance of continuous catalysts consisting of Cu-ZnO-Al2O3, dehydrating agent and carbonylation catalyst in synthesis gas directly to methyl acetate

[0058]

[0059]

[0060] From the comparison of the comparative example and Examples 1-13, it can be seen that the hydroxyl groups on the surface of the molecular sieve are hydrophobically modified by the silanization reagent through the post-grafting method, and the surface groups of the molecular sieve can be regulated by chemical modification, which can effectively avoid the competitive adsorption of CO and water on the catalyst, thereby improving the selectivity of methyl acetate and the CO conversion rate.

[0061] From the comparison of Examples 1-3 and Examples 4-6, it can be seen that appropriately repeating the hydrophobic modification of the H-MOR molecular sieve can increase the silanization degree of the surface of the molecular sieve, thereby improving the selectivity of methyl acetate and the CO conversion rate, but too many modification times do not obviously improve the selectivity of methyl acetate and the CO conversion rate.

[0062] From the comparison of Example 1 and Example 4, it can be seen that selecting tetraethyl orthosilicate as the organosilane reagent is more conducive to improving the selectivity of methyl acetate and the CO conversion rate.

[0063] From the comparison of Example 1 and Example 7, it can be seen that for the organic solvent with weak polarity, the type of solvent has little effect on the selectivity of methyl acetate and the CO conversion rate.

[0064] From the comparison of Example 1 and Example 8, it can be seen that increasing the H2:CO volume ratio in the raw material gas is more conducive to improving the CO conversion rate, but the selectivity of methyl acetate decreases.

[0065] From the comparison of Example 1 and Examples 9-10, it can be seen that increasing the SiO2 / Al2O3 ratio in the H-MOR composition will result in a decrease in the CO conversion rate.

[0066] From the comparison of Example 1 and Examples 11-12, it can be seen that among H-MOR, H-FER and H-SSZ-13, the use of H-MOR has better selectivity of methyl acetate and CO conversion rate.

[0067] From the comparison of Example 1 and Example 13, it can be seen that selecting H-ZSM-5 as the dehydrating agent is more conducive to improving the selectivity of methyl acetate and the CO conversion rate under the conditions.

Claims

1. A method for preparing a catalyst system for the synthesis of methyl acetate from syngas, characterized in that, The catalyst system for producing methyl acetate from syngas includes a first part located upstream and a second part located downstream. The first part includes a methanol synthesis catalyst and a dehydrating agent, and the second part includes a carbonylation reaction catalyst. The carbonylation reaction catalyst is a hydrophobically modified carbonylation reaction molecular sieve; the molecular sieve in the hydrophobically modified carbonylation reaction molecular sieve includes H-MOR, H-FER, and H-SSZ-13; The preparation steps of the hydrophobically modified carbonylated reactive molecular sieve are as follows: (1) Mix molecular sieve powder and organic solvent and heat under reflux conditions; (2) Add organosilane reagent and maintain reflux heating; (3) Separate the mixture obtained in step (2), dry and calcine the obtained catalyst to obtain the hydrophobically modified carbonylation molecular sieve; (4) The obtained hydrophobically modified carbonylated molecular sieve is pressed into tablets and sieved; The first part and the second part are separated by a bed of quartz wool, silicon carbide, or quartz sand; The methanol synthesis catalyst is selected from Cu-ZnO-MOx catalysts, wherein M is selected from Al, Ce, Zr, La, and In; The dehydrating agent is selected from alumina or acidic molecular sieves, and the acidic molecular sieve is selected from ZSM-5 molecular sieve.

2. The preparation method according to claim 1, characterized in that, Repeat steps (1) to (3) once or multiple times to increase the degree of silanization on the molecular sieve surface.

3. The preparation method according to claim 1, characterized in that, The molecular sieve in step (1) includes H-MOR, H-FER, and H-SSZ-13. The SiO2 / Al2O3 ratio in the H-MOR composition is 8 to 40. The organic solvent is one or more of toluene, cyclohexane, and methanol. The molecular sieve powder and the organic solvent are mixed at a solid-liquid ratio of 1 g / : (20 to 50) mL. The organosilane reagent in step (2) is one or more of tetraethyl orthosilicate, 3-aminopropyltriethoxysilane, n-propyltrimethoxysilane, and 3-aminopropyltrimethoxysilane; the amount of organosilane reagent added is 2-10% by mass; the reflux time is 1-5 h; and the reflux temperature is 60-80 ℃.

4. The preparation method according to claim 1, characterized in that, The drying conditions in step (3) are: drying temperature of 100~160 ℃ and drying time of 6~24 h; the calcination conditions are: calcination temperature of 400~600 ℃ and calcination time of 4~8 h, and heating rate of 1~5 ℃ / min.

5. The application of a catalyst system obtained by the preparation method according to any one of claims 1 to 4, characterized in that, After the catalyst system is sequentially loaded into a fixed-bed reactor, it is pretreated at 200-400 °C for 2-10 h under a nitrogen atmosphere. Then, it is switched to pure hydrogen or a hydrogen-containing gas for further treatment for 2-5 h at a pressure of 1-3 MPa. Subsequently, the feed is switched to syngas, with an H2:CO volume ratio of 0.5-2 and a space velocity of 100-2000 h⁻¹. -1 The temperature is 200~300℃ and the pressure is 1~3 MPa.

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