Tandem catalysis process for preparing methyl acetate / ethanol from synthesis gas in one step

Abstract

The invention relates to a tandem catalytic process for preparing methyl acetate / ethanol from synthesis gas in one step. According to the process, a small amount of metal is adopted to modify an acidic molecular sieve catalyst with methanol dehydration performance, and then the acidic molecular sieve catalyst is simply and physically mixed with a catalyst for preparing methanol through synthesis gas hydrogenation, so that a water-gas shift active site is directionally constructed, and the tandem catalyst is endowed with excellent water-gas shift activity; the novel catalyst for preparing the dimethyl ether from the synthesis gas is prepared. And then the novel catalyst for preparing dimethyl ether from synthesis gas, a dimethyl ether carbonylation catalyst and a hydrogenation catalyst are sequentially connected in series and integrated in a reactor through double bed layers or three bed layers, so that efficient and stable synthesis of methyl acetate and ethanol is realized. The preparation method of the multifunctional series catalyst system provided by the invention is simple in process and easy to realize large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysis and chemical process, and particularly relates to a series catalyst system for efficiently preparing methyl acetate / ethanol by series synthesis of synthesis gas in one step and its application. Background Art

[0002] Based on the current situation of my country's coal-based energy structure and high dependence on foreign oil, the development of new catalysts can achieve efficient and directional production of C from syngas. 2+ Oxygen-containing compounds have attracted widespread attention from researchers. Among them, methyl acetate is currently a commonly used environmentally friendly solvent and chemical raw material. Its further hydrogenation product, ethanol, is an excellent solvent, green chemical raw material and disinfectant, and is also widely used in the fields of chemical industry, medicine, daily chemicals, etc. At present, the process of producing methyl acetate or ethanol from synthesis gas has the following problems: (1) The traditional process of producing methyl acetate or ethanol from synthesis gas is complicated, involving multiple reaction and separation steps, and the fixed investment is high; (2) The multifunctional catalyst series connection reported in the literature can realize the direct production of methyl acetate / ethanol from synthesis gas in one reactor, but there are problems such as high acetic acid content in dimethyl ether carbonylation product (>12%), low methyl acetate selectivity (<85%) or low CO single-pass conversion rate (<10%) and strong corrosiveness of the subsequent hydrogenation system; (3) At the same time, the combination of multifunctional series catalysts is relatively fixed, and there is no regularity in the kinetic matching between them, which requires a lot of trial and error experience.

[0003] In general, the key reaction steps in the tandem catalysis of syngas to methyl acetate / ethanol are syngas to methanol, methanol dehydration to dimethyl ether, water vapor shift reaction, dimethyl ether carbonylation to methyl acetate, and methyl acetate hydrogenation. Problem (2) is mainly caused by the fact that the intermediate water produced by methanol dehydration to dimethyl ether will lead to a decrease in the activity and selectivity of the subsequent catalyst. Problem (3) is mainly due to the difficulty in regulating the dehydration performance of molecular sieves and the performance of syngas to methanol and water vapor shift. Molecular sieves are commonly used catalysts for methanol dehydration to dimethyl ether, and their acidity is an important factor in determining the dehydration performance of methanol. However, for traditional syngas to methanol catalysts, although they have certain water vapor shift performance, their ability is difficult to fully match the dehydration ability of molecular sieves, and it is difficult to meet the requirements of in-situ complete water removal. Therefore, if a simple method can be used to regulate the acid properties of molecular sieves while constructing water vapor shift active sites, water can be converted in time, solving the problems of the existing tandem system caused by the adverse effects of intermediate water, such as high acetic acid content, low methyl acetate selectivity, and strong corrosiveness of the subsequent hydrogenation system. Summary of the Invention

[0004] In view of the limitations existing in the current technology, the present invention provides a tandem catalytic process for directly synthesizing methyl acetate / ethanol from syngas. In this process, an acidic molecular sieve catalyst with methanol dehydration performance is modified with a small amount of metal, and then it is physically mixed simply with a syngas hydrogenation catalyst to produce methanol, thereby constructing water-gas shift active sites in a targeted manner, endowing the tandem catalyst with excellent water-gas shift activity, and preparing a novel syngas-to-dimethyl ether catalyst. Subsequently, the novel syngas-to-dimethyl ether catalyst, a dimethyl ether carbonylation catalyst, and a hydrogenation catalyst are sequentially integrated in series in a reactor through a two-bed or three-bed configuration, achieving the efficient and stable synthesis of methyl acetate and ethanol. The obtained multifunctional catalyst system can freely adjust the proportion of each catalyst according to the performance of the syngas hydrogenation catalyst to methanol while maintaining the selectivity of methyl acetate (>90%), further improving the CO conversion rate and the yield of methyl acetate. At the same time, the present invention also achieves the goal of a low acetic acid selectivity, avoiding the subsequent problems of corrosion in the hydrogenation system and difficult conversion. The preparation method of the multifunctional tandem catalyst system provided by the present invention has a simple process and is easy to scale up production.

[0005] The technical solution of the present invention is as follows:

[0006] A tandem catalytic process for directly synthesizing methyl acetate / ethanol from syngas, which is one of the following two methods:

[0007] Method 1 includes the following steps:

[0008] Feed the raw material gases H2 and CO into a fixed-bed reactor successively filled with a syngas-to-dimethyl ether catalyst and a dimethyl ether carbonylation catalyst to obtain methyl acetate;

[0009] Among them, the reaction temperature is 200 - 350 °C, the reaction pressure is 1 - 6 MPa, and the molar ratio of H2 / CO in the raw material gas is 0.2 - 4; the total reaction space velocity is 500 - 6000 mL / g cat / h; in the bed layer, the syngas-to-dimethyl ether catalyst is a mixture of a syngas hydrogenation catalyst to methanol and a methanol dehydration catalyst to dimethyl ether; the mass ratio is that the syngas hydrogenation catalyst to methanol: the methanol dehydration catalyst to dimethyl ether = (1 - 8):1; the upper-layer syngas-to-dimethyl ether catalyst: the lower-layer dimethyl ether carbonylation catalyst = 1:(0.5 - 3).

[0010] Alternatively, Method 2 includes the following steps:

[0011] Feed the raw material gases H2 and CO into a fixed-bed reactor successively filled with the syngas-to-dimethyl ether catalyst, the dimethyl ether carbonylation catalyst, and the hydrogenation catalyst to obtain ethanol;

[0012] Among them, the reaction temperature is 200 - 350 °C, the reaction pressure is 1 - 6 MPa, and the molar ratio of H2 / CO in the feed gas is 0.2 - 4; the total reaction space velocity is 500 - 6000 mL / g cat / h; in the bed layer, the catalyst for synthesizing dimethyl ether from syngas is a mixture of a catalyst for synthesizing methanol from syngas by hydrogenation and a catalyst for dehydrating methanol to dimethyl ether; the mass ratio is that the catalyst for synthesizing methanol from syngas by hydrogenation: the catalyst for dehydrating methanol to dimethyl ether = (1 - 8):1; the catalyst for synthesizing dimethyl ether from syngas in the upper layer: the catalyst for dimethyl ether carbonylation in the middle layer: the hydrogenation catalyst in the lower layer = 1:(0.5 - 3):(0.5 - 2).

[0013] The mixture in the catalyst for synthesizing dimethyl ether from syngas in Method 1 or Method 2 is obtained by granulating or mixing small particles after mixing the catalyst for synthesizing methanol from syngas by hydrogenation and the catalyst for dehydrating methanol to dimethyl ether powder; the particle size of the small particle mixture is 150 - 750 um.

[0014] The catalyst for synthesizing methanol from syngas by hydrogenation is a common low-temperature catalyst for synthesizing methanol from syngas by hydrogenation, that is, a copper-based metal oxide catalyst or a medium- and high-temperature composite oxide catalyst prepared by an impregnation method, a co-precipitation method, a sol-gel method or an ammonia evaporation method;

[0015] Preferably, it is ZnO-ZrO2, ZnO-Cr2O3 or CuZnAlO x ;

[0016] In the low-temperature methanol synthesis copper-based metal oxide catalyst, the loading of the active metal Cu is 5 - 60 wt.%, preferably 40% - 50 wt.%;

[0017] In the medium- and high-temperature methanol synthesis composite oxide catalyst, the loading of the active metal Zn is 5 - 50 wt.%, preferably 30% - 40 wt.%.

[0018] The catalyst for dimethyl ether carbonylation is a hydrogen-type molecular sieve with an eight-membered ring pore structure and a hydrogen-type molecular sieve catalyst modified with a metal promoter, preferably MOR or FER;

[0019] Preferably, the silica-alumina ratio of the hydrogen-type molecular sieve catalyst is: MOR (SiO2 / Al2O3 = 5 - 30), FER (SiO2 / Al2O3 = 5 - 30);

[0020] The promoter metal element is one or more of cerium, tin, gallium, iron, copper, nickel, silver, cobalt, zinc, and the loading is 0.5 - 10 wt.%.

[0021] The hydrogenation catalyst is a supported copper-based methyl acetate hydrogenation catalyst prepared by an impregnation method, a deposition-precipitation method or an ammonia evaporation method;

[0022] The loading of the active metal Cu is 5-40 wt.%, preferably 10%-30 wt.%;

[0023] The carrier is one or more of SiO2, CeO2, ZnO, ZrO2, and Al2O3;

[0024] The promoter element is one or more of molybdenum, cobalt, zinc, manganese, iron, and lanthanum, and the loading is 0.05-3 wt.%.

[0025] The methanol dehydration to dimethyl ether catalyst described above is prepared by one of the following methods:

[0026] (1) Liquid ion exchange method: Mix a copper salt precursor and water to form a salt solution, then stir and mix the salt solution and the molecular sieve, perform liquid ion exchange at room temperature to 95 °C for 0.5-24 hours, then filter and wash until the filtrate is neutral, and dry at 80-150 °C for 1-24 hours. Repeat the ion exchange process 1-3 times, and then calcine at 200-600 °C for 1-24 hours to obtain the required methanol dehydration to dimethyl ether catalyst.

[0027] The copper salt precursor is one or more of copper nitrate, copper sulfate, copper acetate, and copper chloride, preferably copper nitrate;

[0028] In the salt solution, the copper ion concentration is 0.1-2 mol / L, preferably 0.2-1 mol / L;

[0029] Add 5-100 mL of the salt solution to every 1 g of the molecular sieve, preferably 10-50 mL;

[0030] The copper loading in the obtained methanol dehydration to dimethyl ether catalyst is 0.1-2 wt.%, preferably 0.5-1 wt.%;

[0031] Preferably, the molecular sieve is a common hydrogen-type or ammonium-type aluminosilicate molecular sieve such as ZSM-5, β, Y, MOR, etc., or a silicoaluminophosphate molecular sieve such as SAPO-11, SAPO-34, etc.; preferably ZSM-5 molecular sieve, and the molar ratio of SiO2 / Al2O3 is 10-200.

[0032] (2) Copper ammonia solution ion exchange method: Mix a copper source and water to form a salt solution, then dropwise add ammonia water under stirring until the pH is 8-12 to obtain a copper ammonia solution; stir and mix the copper ammonia solution and the molecular sieve, perform ion exchange at room temperature to 95 °C for 0.5-24 hours, then filter and wash until the filtrate is neutral, and dry at 80-150 °C for 1-24 hours. Repeat the ion exchange process 1-3 times, and finally calcine at 200-600 °C for 1-24 hours to obtain the required methanol dehydration to dimethyl ether catalyst.

[0033] The copper source described above is one or more of copper nitrate, copper sulfate, copper acetate, and copper chloride, and copper nitrate is preferred;

[0034] The copper ion concentration of the salt solution is 0.003 - 0.1 mol / L, and 0.006 - 0.04 mol / L is preferred;

[0035] 5 - 100 mL of the salt solution is added to every 1 g of molecular sieve, and 25 - 75 mL is preferred;

[0036] The copper loading in the obtained catalyst for methanol dehydration to dimethyl ether is 0.1 - 10 wt.%, and 2 - 5 wt.% is preferred;

[0037] Preferably, the molecular sieve is one of common hydrogen-type or ammonium-type aluminosilicate molecular sieves such as ZSM-5, β, Y, MOR, etc., and aluminophosphate molecular sieves such as SAPO-11, SAPO-34, etc.; ZSM-5 molecular sieve is preferred, and the molar ratio of SiO2 / Al2O3 is 10 - 200;

[0038] The concentration of the ammonia water described above is 25 - 28 wt.%.

[0039] (3) Solid ion exchange method: Take the copper source powder and the molecular sieve powder for physical mixing, and calcine at 350 - 600 °C for 2 - 24 hours under an inert gas atmosphere to obtain the required catalyst for methanol dehydration to dimethyl ether.

[0040] The copper source is purified cuprous chloride or copper chloride powder, and cuprous chloride is preferred;

[0041] The inert gas described above is nitrogen, argon, or helium;

[0042] Preferably, the molecular sieve is one of common hydrogen-type or ammonium-type aluminosilicate molecular sieves such as ZSM-5, β, Y, MOR, etc., and aluminophosphate molecular sieves such as SAPO-11, SAPO-34, etc.; ZSM-5 molecular sieve is preferred, and the molar ratio of SiO2 / Al2O3 is 10 - 200;

[0043] Preferably, the ratio of cuprous chloride to the molecular sieve is 1 g of cuprous chloride: 5 - 60 g of molecular sieve.

[0044] The substantial features of the present invention are:

[0045] The present invention designs a tandem catalyst system for the one-step synthesis of methyl acetate / ethanol from syngas, which mainly includes ① a catalyst for the hydrogenation of syngas to methanol, ② a catalyst for the dehydration of methanol to dimethyl ether, ③ a catalyst for the carbonylation of dimethyl ether, and ④ a hydrogenation catalyst. By slightly modifying an acidic molecular sieve catalyst (②) with methanol dehydration performance with a small amount of metal, and then physically mixing it with the catalyst for the hydrogenation of syngas to methanol (①), a water-gas shift active site is constructed, endowing the resulting syngas-to-dimethyl ether catalyst with excellent water-gas shift activity. This scheme greatly promotes the kinetic matching degree of the three reactions of methanol formation, methanol dehydration, and water-gas shift, alleviates the adverse effects of water on the subsequent dimethyl ether carbonylation and hydrogenation processes, and thus lays a good reaction foundation for the subsequent dimethyl ether carbonylation and further hydrogenation reactions, ultimately realizing the efficient and stable one-step synthesis of methyl acetate and ethanol from syngas. The specific process involved is as Figure 1 shown, and the reactions are as follows. Among them, reactions (1-3) occur on the syngas-to-dimethyl ether catalyst obtained by physically mixing ① and ②, reaction (4) occurs on the dimethyl ether carbonylation catalyst ③, and reaction (5) occurs on the hydrogenation catalyst ④:

[0046] (1) CO + 2H2 → CH3OH

[0047] (2) 2CH3OH → CH3OCH3 + H2O

[0048] (3) CO + H2O → CO2 + H2

[0049] (4) CH3OCH3 + CO → CH3COOCH3

[0050] (5) CH3COOCH3 + 2H2 → CH3OH + CH3CH2OH

[0051] In addition, the tandem catalyst for the one-step hydrogenation of syngas to methyl acetate / ethanol designed by the present invention has a precise and controllable water-gas change activity, so it can be freely adjusted according to the performance of the front-end catalyst for the hydrogenation of syngas to methanol. Therefore, on the premise of ensuring the selectivity of methyl acetate (>90%), a more excellent catalyst for the hydrogenation of syngas to methanol can be further selected for tandem coupling to obtain better CO conversion and methyl acetate yield.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] 1. The tandem catalyst system for the one-step synthesis of methyl acetate / ethanol from syngas in the present invention has excellent methyl acetate / ethanol activity. Under optimized conditions, the single-pass conversion rate of CO is greater than 50%, the selectivity of methyl acetate in the organic phase product exceeds 90%, and the space-time yield exceeds 0.5 g / g cat / h. After further connecting a hydrogenation catalyst in series, the ethanol selectivity obtained exceeds 60%, which is better than the performance reported in the current literature.

[0054] 2. The present invention modifies an acidic molecular sieve catalyst with methanol dehydration performance by a small amount of metal, and then physically mixes it with a synthesis gas hydrogenation to methanol catalyst to directionally construct a water-gas shift active site, accurately and controllably endowing the catalyst with excellent water-gas shift activity, and finally obtaining a new synthesis gas to dimethyl ether catalyst. This greatly promotes the kinetic matching degree of the three intermediate reactions of methanol formation, methanol dehydration and water-gas shift in the tandem catalyst system, and alleviates the adverse effects of the intermediate product water on the subsequent dimethyl ether carbonylation and hydrogenation processes.

[0055] 3. The tandem catalyst for one-step synthesis of methyl acetate / ethanol by hydrogenation of synthesis gas designed directionally by the present invention has accurate and controllable water-gas change activity, so it can be directionally designed according to the performance of the front-end synthesis gas hydrogenation to methanol catalyst, and can be freely adjusted according to needs.

[0056] 4. The multifunctional tandem catalyst system provided by the present invention not only has more accurate and controllable water-gas shift active sites compared with the traditional tandem system, but also has better catalytic performance and excellent industrial application prospects. At the same time, the preparation process of the catalyst is simple, the raw materials are widely sourced and relatively inexpensive, which is conducive to large-scale industrial production. Brief Description of the Drawings

[0057] Figure 1 is a schematic diagram of the process for one-step synthesis of methyl acetate / ethanol from synthesis gas proposed in this patent

[0058] Figure 2 is the X-ray diffraction pattern of the HZSM-5(21) sample.

[0059] Figure 3 is the scanning electron microscope image of the HZSM-5(21) sample. Detailed Embodiments

[0060] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments. It should be noted that the following embodiments are illustrative and not restrictive, and the protection scope of the present invention cannot be limited by the following embodiments. The raw materials required in the following examples and comparative examples are all commercially available.

[0061] In this embodiment, a Rigaku MiniFlex 600 type powder X-ray diffractometer of Rigaku Corporation, Japan, is used to analyze the crystal phase structure of the sample, and the diffraction source is The working voltage and working current are respectively selected as 40 kV and 200 mA, the scanning range is 5-80°, and the scanning speed is 8° / min.

[0062] In this embodiment, the morphological analysis of each sample was carried out using an Apreo S LoVac scanning electron microscope from Thermo Fisher Scientific.

[0063] The syngas hydrogenation to methanol catalyst described in the present invention is a well-known material, specifically a common low-temperature syngas hydrogenation to methanol catalyst, namely a copper-based metal oxide catalyst and a medium- and high-temperature composite oxide catalyst prepared by an impregnation method, a co-precipitation method, a sol-gel method or an ammonia evaporation method; for example, ZnO-ZrO2, ZnO-Cr2O3 or CuZnAlO x ; (Natural Gas Chemical Industry 2006, 31, 72-78, Acc. Chem. Res. 2024, 57, 714-725); but not limited thereto.

[0064] The dimethyl ether carbonylation catalyst described in the present invention is a well-known material, specifically a hydrogen-type molecular sieve with an eight-membered ring pore structure and a hydrogen-type molecular sieve catalyst modified with a metal promoter; for example, MOR (SiO2 / Al2O3 = 5-30), FER (SiO2 / Al2O3 = 5-30); (Journal of Chemical Industry and Engineering (China) 2016, 67(1), 240-247, J. Energy Chem. 2019, 36, 51-63, Journal of Chemical Industry and Engineering (China) 2021, 72, 3958-3967); but not limited thereto.

[0065] The hydrogenation catalyst described in the present invention is a well-known material, specifically a supported copper-based methyl acetate hydrogenation catalyst prepared by an impregnation method, a deposition-precipitation method or an ammonia evaporation method; for example, Cu / SiO2; (Journal of Chemical Industry and Engineering (China) 2016, 67(1), 240-247, Ind. Eng. Chem. Res. 2018, 57, 4526-4534, ACS Catal. 2022, 12, 1315-1325); but not limited thereto.

[0066] Example 1

[0067] 7.25 g of copper nitrate trihydrate was dissolved in 50 mL of deionized water to obtain a salt solution (concentration: 0.6 mol / L), and then 2 g of HZSM-5(21) molecular sieve was added to the salt solution; ion exchange was carried out at 80 °C for 6 hours, followed by filtration and washing until the filtrate was neutral, and then drying at 100 °C for 12 hours, and finally calcining at 350 °C for 5 hours to obtain the required methanol dehydration to dimethyl ether catalyst Cu1-HZSM-5(21); the copper loading in the obtained catalyst was 0.9 wt.%. The XRD pattern of the used HZSM-5(21) molecular sieve sample is as shown in the appendix Figure 2 ; the morphology of the sample is as shown in the appendix Figure 3 as shown.

[0068] Dissolve 7.25 g of copper nitrate trihydrate, 4.46 g of zinc nitrate hexahydrate, and 1.88 g of aluminum nitrate nonahydrate in 50 mL of deionized water to obtain a metal salt aqueous solution (total metal ion concentration is 1 mol / L); dissolve sodium carbonate solid in an appropriate amount of deionized water to prepare a 1 mol / L alkaline solution.

[0069] The above-mentioned metal salt aqueous solution and alkaline solution were added dropwise to 250 mL of deionized water at a volume ratio of 5:8 under stirring until the metal salt aqueous solution was consumed, and then stirred and aged at room temperature for 3 hours; then the suspension was filtered, washed to neutrality, dried at 100°C for 12 hours, and calcined at 350°C for 5 hours to obtain the desired synthesis gas hydrogenation to methanol catalyst CuZnAlO x .

[0070] CuZnAlO catalyst for hydrogenation of synthesis gas to methanol x The mixture was mixed with the above-mentioned methanol dehydration dimethyl ether catalyst Cu1-HZSM-5 (21) in a mass ratio of 4:1, and then fully ground in an agate mortar for 10 minutes to obtain the desired synthesis gas to dimethyl ether catalyst CuZnAlO x / Cu1-HZSM-5-P(21).

[0071] The HMOR molecular sieve (the molar ratio of SiO2 / Al2O3 is 24) is heat-treated at room temperature to 300°C for 1 hour under pyridine vapor to finally obtain the desired dimethyl ether carbonylation catalyst Py-HMOR.

[0072] Take 0.5g of CuZnAlO after tableting and sieving (40-60 mesh) x / Cu1-HZSM-5-P(21) catalyst sample and 0.75g of sieved (40-60 mesh) tabletted dimethyl ether carbonylation catalyst Py-HMOR sample were connected in series through a double bed (reactor inner diameter 8mm, tube length 60cm), wherein the dimethyl ether carbonylation catalyst Py-HMOR was placed in the lower layer; then the reactor was heated at 265℃, 4MPa, raw gas H2 / CO molar ratio of 0.5, total gas flow rate of 50mL / min (i.e., space velocity of 2400mL / g cat The reaction was carried out in a fixed-bed reactor at 400 nm / min. Prior to the reaction, the catalyst was reduced in a 10% H₂ / 90% N₂ (volume percentage) atmosphere at 260°C for 3 hours at 25 mL / min. The reaction exhaust was held warm and fed into the gas phase for online chromatography analysis. The data were calculated using the following formula:

[0073] (1) CO conversion rate = (inlet CO moles - outlet CO moles) / inlet CO moles × 100%;

[0074] (2) CO₂ selectivity = (moles of CO₂ at the outlet) / (moles of CO at the inlet - moles of CO at the outlet) × 100%;

[0075] (3) Selectivity of product C i (excluding CO₂) = (moles of product C i at the outlet × number of carbon atoms in the molecule of product C i ) / ∑(moles of product C i at the outlet × number of carbon atoms in the molecule of the product) × 100%; i

[0076] (4) STY of product C i = moles of CO at the inlet × CO conversion rate × (1 - CO₂ selectivity) × selectivity of product C i (excluding CO₂) × molecular weight of product C i / (number of carbon atoms in the molecule of product C i × total mass of the tandem catalyst)

[0077] Example 2

[0078] Dissolve 7.25 g of copper nitrate trihydrate in 50 mL of deionized water to obtain a salt solution (concentration: 0.6 mol / L). Then add 2 g of HZSM-5(21) zeolite to the salt solution; conduct ion exchange at 80 °C for 6 hours, then filter and wash until the filtrate is neutral, and dry at 100 °C for 12 hours; repeat the above process once, and finally calcine at 350 °C for 5 hours to obtain the required catalyst for methanol dehydration to dimethyl ether, Cu₂-HZSM-5(21); the copper loading in the obtained catalyst is 1.2 wt.%. Then mix it with the catalyst for syngas hydrogenation to methanol (the steps are the same as in Example 1) to obtain the required catalyst for syngas to dimethyl ether, CuZnAlO x / Cu₂-HZSM-5-P(21).

[0079] Other evaluation conditions for the sample are exactly the same as those in Example 1.

[0080] Example 3

[0081] Dissolve 0.24 g of copper nitrate trihydrate in 50 mL of deionized water to obtain a salt solution. Dropwise add ammonia water (concentration: 0.02 mol / L) to the solution under stirring until the pH reaches 1¬0 to obtain a copper ammonia solution. Then add 2 g of HZSM-5(21) zeolite to the obtained copper ammonia solution; conduct ion exchange at room temperature for 4 hours, then filter and wash until the filtrate is neutral, and dry at 100 °C for 12 hours. Finally, calcine at 350 °C for 5 hours to obtain the required catalyst for methanol dehydration to dimethyl ether, Cu " N -HZSM-5(21); the copper loading in the obtained catalyst is %

[0082] The methanol synthesis catalyst CuZnAlO for hydrogenating syngas x and the above-mentioned dimethyl ether synthesis catalyst Cu N -HZSM-5(21) were mixed in powder form at a mass ratio of 4:1, and then thoroughly ground in an agate mortar for 10 minutes to obtain the required dimethyl ether synthesis catalyst CuZnAlO x / Cu N -HZSM-5-P(21).

[0083] Other evaluation conditions of the sample were exactly the same as those in Example 1.

[0084] Example 4

[0085] Take 5 g of cuprous chloride in a beaker, add 10 mL of hydrochloric acid (36 - 38 wt.%) and 10 mL of water, stir to dissolve, let stand for a while, and then take the supernatant; add another 5 mL of hydrochloric acid to further dissolve the undissolved cuprous chloride, let stand for a while, and take the supernatant again. Add 350 mL of water to the above supernatant, stir to allow the cuprous chloride to crystallize fully, let stand, pour off the supernatant, filter and wash the filter cake with ethanol and acetone, and then dry it at 70 °C for 6 hours under a nitrogen atmosphere of 60 mL / min to obtain purified cuprous chloride. Take 0.025 g of the purified cuprous chloride and 0.5 g of molecular sieve, physically mix them in a certain proportion, and thoroughly grind them in an agate mortar for 10 minutes, and then calcine them at 550 °C for 6 hours under a nitrogen atmosphere of 60 mL / min to obtain the required dimethyl ether synthesis catalyst Cu S -HZSM-5(21).

[0086] The methanol synthesis catalyst CuZnAlO for hydrogenating syngas x and the above-mentioned dimethyl ether synthesis catalyst Cu S -HZSM-5(21) were mixed in powder form at a mass ratio of 4:1, and then thoroughly ground in an agate mortar for 10 minutes to obtain the required dimethyl ether synthesis catalyst CuZnAlO x / Cu S -HZSM-5-P(21).

[0087] Other evaluation conditions of the sample were exactly the same as those in Example 1.

[0088] Comparative Example 1

[0089] The methanol synthesis catalyst CuZnAlO for hydrogenating syngas x and the HZSM-5(21) molecular sieve were mixed in powder form at a mass ratio of 4:1, and then thoroughly ground in an agate mortar for 10 minutes to obtain the required comparative sample of the dimethyl ether synthesis catalyst CuZnAlO x / HZSM-5-P(21).

[0090] The other evaluation conditions of the sample are exactly the same as those in Example 1.

[0091] The performance of each catalyst sample in the one-step synthesis of methyl acetate from syngas is shown in Table 1. The data listed in the table are the average performance within 5 - 11 h of the reaction. The reaction can reach a steady state within 4 - 5 h, and the fluctuation error of CO conversion and methyl acetate selectivity within the subsequent 72 h of the reaction is within ±3%, indicating good catalyst stability during the operation time. Among them, other products include a small amount of methanol, acetic acid, acetone, and hydrogen-carbon species. The subsequent tables are the same as this one.

[0092] Table 1 Performance of the one-step synthesis of methyl acetate from syngas

[0093]

[0094] It can be seen from the activity that, compared with Comparative Example 1, all the examples of the series of novel multifunctional catalysts reported in the present invention have higher CO conversion, as well as methyl acetate selectivity and space-time yield, and the acetic acid selectivity is greatly reduced.

[0095] Examples 5 - 6

[0096] Under the condition that other conditions are exactly the same as those in Example 3, the reaction pressure during the catalyst evaluation process is changed to 2 MPa (Example 5) and 3 MPa (Example 6).

[0097] The influence of reaction pressure on the performance of the obtained multifunctional tandem catalyst in the one-step synthesis of methyl acetate from syngas is shown in Table 2.

[0098] Table 2 Influence of reaction pressure on the performance of the obtained multifunctional tandem catalyst in the one-step synthesis of methyl acetate from syngas

[0099]

[0100]

[0101] It can be seen from the activity that as the reaction pressure increases, the methyl acetate yield of this multifunctional tandem catalyst system gradually increases synchronously. At the same time, with the increase of the reaction pressure, no obvious change in the selectivity of each product is observed, which indicates that the kinetic matching of multiple reactions involved in the reaction process of this directionally designed multifunctional tandem catalyst is good, and the syngas can well pass through the new path of dimethyl ether coupling and obtain excellent methyl acetate selectivity and space-time yield through tandem relay reactions, and the operating space of the reaction pressure is relatively wide.

[0102] Examples 7 - 8

[0103] Under the condition that other conditions are exactly the same as those in Example 3, only replace the dimethyl ether carbonylation catalyst Py-HMOR with FER (Example 7) or SSZ-13 (Example 8).

[0104] The influence of the type of dimethyl ether carbonylation catalyst on the reaction performance of the obtained multifunctional catalyst for the tandem one-step synthesis of methyl acetate from syngas is shown in Table 3.

[0105] Table 3 Influence of the type of dimethyl ether carbonylation catalyst on the reaction performance of the obtained multifunctional tandem catalyst for the one-step synthesis of methyl acetate from syngas

[0106]

[0107] It can be seen from the activity that when the molecular sieve used in the dimethyl ether carbonylation catalyst is Py-HMOR, the methyl acetate yield of this multifunctional tandem catalyst system is the highest.

[0108] Example 9

[0109] The preparation method of the hydrogenation catalyst Cu / SiO2 adopts the ammonia evaporation homogeneous precipitation deposition method: Weigh 15.2 g of copper nitrate trihydrate and dissolve it in 100 mL of deionized water, then add 50 mL of ammonia water (25 wt%) to form a copper ammonia solution, and stir evenly; then drop a certain amount of silica sol (30 wt%) at a certain rate and stir and age for 24 hours; Evaporate ammonia from the blue suspension at 80 °C until the pH drops to between 6 and 7 to end ammonia evaporation; After filtration, washing, drying at 80 °C for 12 hours, and calcining at 400 °C for 4 hours, the required hydrogenation catalyst Cu / SiO2 is obtained.

[0110] Take 0.5 g of the syngas-to-dimethyl ether catalyst CuZnAlO x / HZSM-5-IM(21) sample, 0.75 g of the dimethyl ether carbonylation catalyst Py-HMOR sample after tabletting and screening (40-60 mesh), and 0.5 g of the hydrogenation catalyst Cu / SiO2 sample after screening (40-60 mesh), and load them in series through three beds (reactor inner diameter 8 mm, tube length 60 cm). Among them, the syngas-to-dimethyl ether catalyst is placed in the upper layer of the fixed-bed reactor, the dimethyl ether carbonylation catalyst is placed in the middle layer of the fixed-bed reactor, and the hydrogenation catalyst is placed in the lower layer of the fixed-bed reactor. At 260 °C, 4 MPa, the raw material gases H2 and CO (molar ratio of H2 and CO is 0.5, total flow rate is 50 mL / min, that is, the space velocity is 1714 mL / g cat / h) are introduced into the reactor and sequentially pass through the syngas-to-dimethyl ether catalyst, the dimethyl ether carbonylation catalyst, and the hydrogenation catalyst, and finally ethanol with a selectivity of 62.8% and a yield of 0.244 g / g cat / h is obtained.

[0111] The performance of the obtained multifunctional catalyst in the tandem one-step synthesis of ethanol from syngas is shown in Table 4.

[0112] Table 4 Performance of the obtained multifunctional catalyst in the tandem one-step synthesis of ethanol from syngas

[0113]

[0114] It can be seen from the activity that this multifunctional catalyst has excellent performance in the tandem one-step synthesis of ethanol from syngas.

[0115] As can be seen from the above examples, in the technical solution of the present invention, 1) the syngas hydrogenation to methanol catalyst, the methanol dehydration to dimethyl ether catalyst, the dimethyl ether carbonylation catalyst and the hydrogenation catalyst are sequentially integrated in series in a reactor through a double-bed or triple-bed layer, realizing the direct, efficient and stable synthesis of methyl acetate and ethanol from syngas in series. 2) By using a small amount of metal to modify the acidic molecular sieve catalyst with methanol dehydration performance, and then simply physically mixing it with the syngas hydrogenation to methanol catalyst, water-gas shift active sites are directionally constructed, endowing the tandem catalyst with excellent water-gas shift activity, and a new syngas-to-dimethyl ether catalyst is prepared. The success of this attempt largely balances the kinetic matching degree of the three reactions of methanol formation, methanol dehydration and water-gas shift. Avoiding the generation of excess water and having an adverse impact on the subsequent dimethyl ether carbonylation and hydrogenation processes, and thus laying a good reaction foundation for the subsequent dimethyl ether carbonylation and further hydrogenation reactions, ultimately realizing the efficient and stable direct synthesis of methyl acetate and ethanol from syngas. And the goal of low acetic acid selectivity is achieved, which also avoids the problems of corrosion of the subsequent hydrogenation system and difficult conversion. 3) The obtained multifunctional catalyst system can freely adjust the proportion of each catalyst according to the performance of the syngas hydrogenation to methanol catalyst under the condition of basically maintaining the selectivity of methyl acetate (>90%), realizing a further increase in the CO conversion rate and the methyl acetate yield.

[0116] Matters not covered by the present invention are well-known technologies.

Claims

1. A tandem catalytic process for the one-step synthesis of methyl acetate / ethanol from syngas, characterized in that it is one of the following two methods: Method 1 includes the following steps: The raw material gases H2 and CO are introduced into a fixed-bed reactor successively equipped with a syngas-to-dimethyl ether catalyst and a dimethyl ether carbonylation catalyst to obtain methyl acetate; Among them, The reaction temperature is 200 - 350 °C, the reaction pressure is 1 - 6 MPa, the molar ratio of H2 / CO in the feed gas is 0.2 - 4; the total reaction space velocity is 500 - 6000 mL / g cat / h; in the bed layer, the catalyst for synthesizing dimethyl ether from syngas is a mixture of a catalyst for synthesizing methanol by hydrogenation of syngas and a catalyst for dehydrating methanol to dimethyl ether; the mass ratio is that the catalyst for synthesizing methanol by hydrogenation of syngas: the catalyst for dehydrating methanol to dimethyl ether = (1 - 8):1; the catalyst for synthesizing dimethyl ether from syngas in the upper layer: the catalyst for carbonylation of dimethyl ether in the lower layer = 1:(0.5 - 3); Alternatively, Method 2 includes the following steps: The raw material gases H2 and CO are introduced into a fixed-bed reactor successively equipped with the syngas-to-dimethyl ether catalyst, the dimethyl ether carbonylation catalyst, and a hydrogenation catalyst to obtain ethanol; Among them, the reaction temperature is 200 to 350 °C, the reaction pressure is 1 to 6 MPa, the molar ratio of H2 / CO in the raw material gas is 0.2 to 4; the total reaction space velocity is 500 to 6000 mL / g cat / h; in the bed layer, the catalyst for synthesizing dimethyl ether from syngas is a mixture of a catalyst for hydrogenating syngas to methanol and a catalyst for dehydrating methanol to dimethyl ether; the mass ratio is that the catalyst for hydrogenating syngas to methanol: the catalyst for dehydrating methanol to dimethyl ether = (1 to 8):1; the catalyst for synthesizing dimethyl ether from syngas in the upper layer: the catalyst for carbonylating dimethyl ether in the middle layer: the hydrogenation catalyst in the lower layer = 1:(0.5 to 3):(0.5 to 2).

2. The tandem catalytic process for directly synthesizing methyl acetate / ethanol from syngas according to claim 1, wherein, The mixture in the syngas-to-dimethyl ether catalyst in Method 1 or Method 2 is obtained by granulating or mixing small particles after mixing the powder of a syngas hydrogenation-to-methanol catalyst and a methanol dehydration-to-dimethyl ether catalyst; the particle size of the small particle mixture is 150 - 750 um.

3. The tandem catalytic process for the one-step synthesis of methyl acetate / ethanol from syngas according to claim 1, characterized in that, The syngas hydrogenation-to-methanol catalyst is a common low-temperature syngas hydrogenation-to-methanol catalyst, that is, a copper-based metal oxide catalyst or a medium-high temperature composite oxide catalyst prepared by the impregnation method, the co-precipitation method, the sol-gel method, or the ammonia evaporation method; The dimethyl ether carbonylation catalyst is a hydrogen-type molecular sieve with an eight-membered ring pore structure and a hydrogen-type molecular sieve catalyst modified with a metal promoter; The hydrogenation catalyst is a supported copper-based methyl acetate hydrogenation catalyst prepared by the impregnation method, the deposition-precipitation method, or the ammonia evaporation method.

4. The tandem catalytic process for the one-step synthesis of methyl acetate / ethanol from syngas according to claim 3, characterized in that In the syngas hydrogenation-to-methanol catalyst, in the low-temperature methanol synthesis copper-based metal oxide catalyst, the active metal Cu loading is 5 - 60 wt.%; In the medium-high temperature methanol synthesis composite oxide catalyst, the active metal Zn loading is 5 - 50 wt.%.

5. The tandem catalytic process for the one-step synthesis of methyl acetate / ethanol from syngas according to claim 3, characterized in that In the dimethyl ether carbonylation catalyst, the hydrogen-type molecular sieve catalyst is MOR or FER; the silica-alumina ratio is: MOR (SiO2 / Al2O3 = 5 - 30), FER (SiO2 / Al2O3 = 5 - 30); In the hydrogen-type molecular sieve catalyst modified with a metal promoter, the promoter metal element is one or more of cerium, tin, gallium, iron, copper, nickel, silver, cobalt, zinc, and the loading is 0.5 - 10 wt.%.

6. The tandem catalytic process for the one-step synthesis of methyl acetate / ethanol from syngas according to claim 3, characterized in that In the hydrogenation catalyst, the active metal Cu loading is 5 - 40 wt.%; The carrier is one or more of SiO2, CeO2, ZnO, ZrO2, Al2O3; The promoter element is one or more of molybdenum, cobalt, zinc, manganese, iron, lanthanum, and the loading is 0.05 - 3 wt.%.

7. The tandem catalytic process for the one-step synthesis of methyl acetate / ethanol from syngas according to claim 1, characterized in that, The syngas hydrogenation to methanol catalyst described above is ZnO-ZrO2, ZnO-Cr2O3 or CuZnAlO x .

8. The tandem catalytic process for directly synthesizing methyl acetate / ethanol from syngas according to claim 1, wherein, The methanol dehydration-to-dimethyl ether catalyst adopts one of the following methods: Method 1, liquid ion exchange method: Mix a copper salt precursor and water to form a salt solution. Then, stir and mix the salt solution and the molecular sieve, and conduct liquid ion exchange at room temperature to 95 °C for 0.5 to 24 hours. After that, filter and wash until the filtrate is neutral, and dry at 80 to 150 °C for 1 to 24 hours. Repeat the ion exchange process 1 to 3 times, and then calcine at 200 to 600 °C for 1 to 24 hours to obtain the required catalyst for methanol dehydration to dimethyl ether; The copper salt precursor is one or more of copper nitrate, copper sulfate, copper acetate, and copper chloride; In the salt solution, the copper ion concentration is 0.1 to 2 mol / L; Add 5 to 100 mL of the salt solution per 1 g of the molecular sieve; The copper loading in the obtained catalyst for methanol dehydration to dimethyl ether is 0.1 to 2 wt.%; Or, Method 2, copper ammonia solution ion exchange method: Mix a copper source and water to form a salt solution, and then dropwise add ammonia water under stirring until the pH is 8 to 12 to obtain a copper ammonia solution; Stir and mix the copper ammonia solution and the molecular sieve, and conduct ion exchange at room temperature to 95 °C for 0.5 to 24 hours. After that, filter and wash until the filtrate is neutral, and dry at 80 to 150 °C for 1 to 24 hours. Repeat the ion exchange process 1 to 3 times, and finally calcine at 200 to 600 °C for 1 to 24 hours to obtain the required catalyst for methanol dehydration to dimethyl ether; The copper source is one or more of copper nitrate, copper sulfate, copper acetate, and copper chloride; The copper ion concentration of the salt solution is 0.003 to 0.1 mol / L; Add 5 to 100 mL of the salt solution per 1 g of the molecular sieve; The copper loading in the obtained catalyst for methanol dehydration to dimethyl ether is 0.1 to 10 wt.%; Or, Method 3, solid ion exchange method: Physically mix copper source powder and molecular sieve powder, and calcine at 350 to 600 °C in an inert gas atmosphere for 2 to 24 hours to obtain the required catalyst for methanol dehydration to dimethyl ether; The copper source is cuprous chloride or copper chloride; The ratio of the copper source to the molecular sieve is 1 g of copper source: 5 to 60 g of molecular sieve.

9. The methanol dehydration to dimethyl ether catalyst according to claim 8, characterized in that, The molecular sieve is one of common hydrogen-type or ammonium-type aluminosilicate molecular sieves such as ZSM-5, β, Y, or MOR, and phosphosilicate molecular sieves such as SAPO-11, SAPO-34, etc.

10. The dimethyl ether catalyst for methanol dehydration as described in claim 8, when prepared by the method of ion exchange with a copper ammonia solution, is characterized in that, The concentration of the ammonia water is 25 to 28 wt.%; If the solid ion exchange method is used for preparation, the inert gas is nitrogen, argon, or helium.

Images