Integrated process for synthesizing dimethyl ether by one-step method of synthesis gas

Abstract

The present application belongs to the technical field of dimethyl ether prepared from synthetic gas, and particularly relates to an integrated process for preparing dimethyl ether from synthetic gas by one-step method. The present application adopts a hydrogen adjustment mode mainly in situ low-temperature shift and supplemented by trace hydrogen addition, so that the energy consumption is reduced, the side reactions in the reactor are reduced, the catalyst activity decay is reduced, the reaction temperature is approximately isothermal, the sintering rate of the catalyst is low, the continuous operation time is prolonged, the selectivity of dimethyl ether is high, the gradient condensation and rectification separation and purification process is adopted, the comprehensive energy consumption per unit product is low, the total recovery rate of dimethyl ether is improved, and the purity of the dimethyl ether product is stable and greater than or equal to 99.5%.

Description

Technical Field

[0001] This invention belongs to the field of syngas to dimethyl ether technology, specifically relating to an integrated process for one-step syngas to dimethyl ether production. Background Technology

[0002] Dimethyl ether is an important clean energy source and chemical raw material. The one-step synthesis of dimethyl ether from syngas couples three types of reactions—methanol synthesis, methanol dehydration, and water-gas shift—into the same reaction system. It has advantages such as a short process, low equipment investment, and low theoretical energy consumption, and is currently a key research and development direction in the field of coal chemical industry.

[0003] However, the existing one-step synthesis of dimethyl ether from syngas generally suffers from the following core defects: (1) The performance of bifunctional catalysts is mismatched. The activity temperature of the mainstream Cu-based methanol synthesis catalyst is not matched with that of γ-Al2O3 and ZSM-5 dehydration catalysts. The low-temperature dehydration activity is insufficient, and the high temperature can easily cause Cu-based catalysts to sinter and hydrothermally deactivate. The catalyst components interfere with each other, the acidic sites are covered, there are many by-products, the dimethyl ether selectivity is low, and the catalyst has a short stable operating time. (2) The heat of reaction is difficult to control. The one-step process is a strongly exothermic reaction. The traditional fixed-bed reactor has a large axial temperature rise and local hot spots are overheated, which aggravates catalyst deactivation and side reactions. The slurry-bed reactor suffers from catalyst wear, low gas-liquid-solid mass transfer efficiency, and low CO single-pass conversion rate. (3) The adaptability of raw material syngas is poor. The H2 / CO volume ratio of the mainstream coal-based syngas in China is only 0.6 to 0.8, while the optimal H2 / CO ratio of the one-step process is 1.0 to 2.0. The existing processes mostly use external hydrogen supplementation or deep water-gas shift to adjust hydrogen, which increases energy consumption. Under low hydrogen ratio conditions, the catalyst is prone to carbon deposition and deactivation. (4) High energy consumption and low recovery rate of product separation. The traditional low-temperature condensation + absorption and desorption process has high energy consumption. Dimethyl ether escapes in the gas phase and is entrained by the absorbent, resulting in low recovery rate. Methanol, water and dimethyl ether form an azeotrope, making it difficult for the product purity to meet industrial grade requirements. (5) Difficulty in controlling side reactions. Side reactions such as methanol coupling, deep dehydration of dimethyl ether, CO disproportionation and methanation are prone to occur in the reaction system. The total amount of by-products is large, which further increases the separation difficulty and reduces product quality.

[0004] Currently, this technology is still in the pilot and intermediate stages and has not yet been applied on a large scale industrial basis. Therefore, developing a one-step integrated process for producing dimethyl ether from syngas with good catalyst stability, precise temperature control, strong raw material adaptability, low separation energy consumption, and few by-products has significant industrial application value. Summary of the Invention

[0005] To address the technical shortcomings of existing one-step syngas-to-dimethyl ether processes, such as catalyst deactivation, reaction thermal runaway, poor feed gas compatibility, high separation energy consumption, and numerous byproducts, this invention provides an integrated one-step syngas-to-dimethyl ether process that achieves long-term stable operation, high conversion rate, high selectivity, low energy consumption, and high product purity, meeting the requirements of large-scale industrial production.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An integrated one-step process for producing dimethyl ether from syngas comprises five core units: a feed gas pretreatment and in-situ graded hydrogen regulation unit, a segmented temperature-controlled radial flow reaction unit, a gradient condensation and distillation separation and purification unit, a recycle gas reuse unit, and an in-situ side reaction suppression unit. The specific steps are as follows: (1) Raw material gas pretreatment and in-situ step-by-step hydrogen adjustment: Coal-based syngas first enters the low-temperature water-gas shift unit, using Cu-ZnO-Al2O3 low-temperature shift catalyst, controlling the reaction temperature at 180-200℃, and using the water vapor carried by the raw material gas to carry out in-situ water-gas shift, increasing the H2 / CO volume ratio of the syngas from 0.6-0.8 to 0.9-1.1; After the shift, the gas enters the micro-hydrogen replenishment section, where a small amount of hydrogen is precisely replenished (the amount of hydrogen replenishment accounts for <5% of the total gas volume), and finally the H2 / CO is stably controlled at 1.0-1.2; The hydrogen replenishment section has a built-in sulfur and chlorine composite adsorbent to simultaneously remove trace impurities from the raw material gas and protect the downstream catalyst.

[0007] (2) Segmented temperature-controlled radial flow reaction: The hydrogen-treated syngas is fed into a segmented temperature-controlled radial flow reactor. The reactor is divided into three sections along the axial direction: a low-temperature reaction section, a medium-temperature coupling section, and a deep conversion section. Each section is independently temperature-controlled and independently loaded with catalyst. The temperature of the low-temperature reaction section is 220-240℃, and it is loaded with a core-shell type weak acid bifunctional catalyst, which mainly carries out the main reaction of syngas to methanol. The temperature of the medium-temperature coupling section is 240-260℃, and it is loaded with a modified dehydration aid, which rapidly dehydrates the methanol intermediate to generate dimethyl ether. The temperature of the deep conversion section is 250-270℃, and it is loaded with an anti-carbon deposition composite catalyst to achieve deep conversion of unreacted syngas, while suppressing carbon deposition and methanation side reactions.

[0008] (3) Gradient condensation and distillation separation and purification: The reaction mixture at the reactor outlet enters the three-stage gradient condensation system in sequence. After condensation, the crude dimethyl ether enters the distillation column and is purified by distillation to obtain industrial-grade dimethyl ether product with a purity of ≥99.5%. (4) Recycled gas reuse: The unreacted syngas after the third-stage cryogenic treatment is pressurized and recycled back to the feed gas hydrogen regulation unit. The recycling ratio is controlled at 1.5 to 2.0 to improve the utilization rate of feed gas.

[0009] (5) In-situ suppression of side reactions: Mg and Ca composite oxide solid additives are arranged in layers in the gap between the catalyst bed and the gas phase space of the reactor to neutralize the acidic free radicals of the system, suppress methanol coupling and deep dehydration of dimethyl ether to generate olefins; adsorb carbon deposition precursors to suppress CO disproportionation carbon deposition, and realize in-situ control of side reactions.

[0010] Furthermore, the reactor adopts a radial flow structure, with each section having an independent heat exchange component to achieve near-isothermal reactions in each section, and the bed temperature rise is controlled to ≤8℃.

[0011] Furthermore, the core-shell type weakly acidic bifunctional catalyst has a three-layer core-shell structure. The core is a Cu-ZnO-Al2O3 methanol synthesis active core with a particle size of 200-400 nm; the middle is an ultrathin SiO2 isolation layer with a thickness of 20-50 nm; the outer shell is a La and Ce modified weakly acidic molecular sieve-composite alumina with a strong acidic site ratio of <5%; and the core-shell mass ratio is 7:3-8:2.

[0012] Furthermore, the first-stage condensation temperature is 40–50°C, separating most of the high-boiling-point components such as water and methanol in the system; the second-stage condensation temperature is 0–10°C, initially enriching dimethyl ether and separating heavy hydrocarbon byproducts; the third-stage cryogenic temperature is -20–-25°C, deeply condensing dimethyl ether, and the uncondensed gas phase is reused as circulating gas.

[0013] Furthermore, the Mg / Ca composite oxide solid additive in this invention is selected from MgO-CaO composite oxide particles, with a molar ratio of MgO:CaO = 1:2 to 1:4; it is formed into spherical particles with a diameter of 3 to 5 mm, a bulk density of 1.1 to 1.3 g / cm³, and a specific surface area of ​​80 to 150 m² / g; it is insoluble in the reaction gas phase, physically and chemically stable under reactor conditions of 220°C to 270°C, and exhibits no pulverization, melting, or volatilization, and does not mix with the product dimethyl ether. The reactor is divided into a low-temperature reaction section, a medium-temperature coupling section, and a deep conversion section from top to bottom. The Mg / Ca composite oxide solid additive is layered and arranged in differentiated zones, and is not mixed with the main catalyst particles.

[0014] Furthermore, the Mg and Ca composite oxide solid additives are arranged in layers within the catalyst bed. Each section of the catalyst bed is filled in layers, namely, catalyst layer—additive interlayer—catalyst layer. For each section of the bed, a layer of Mg and Ca composite oxide additives with a thickness of 8-12 cm is laid flat for every 1.0-1.2 m of main catalyst. The additive layer is supported by an inert ceramic grid with an opening rate of 40%-50% to ensure smooth radial passage of syngas without increasing bed resistance. In the low-temperature reaction section (220-240℃), methanol is generated in large quantities and trace amounts of acidic intermediates are generated earliest, resulting in the highest interlayer density. The additive loading amount is 4%-5% of the catalyst mass in this section. In the medium-temperature coupling section (240-260℃), dimethyl ether is concentratedly generated and is most prone to deep cracking to produce olefins. The additive loading amount is 5%-6% (the highest in the entire reactor). In the deep conversion section (250-270℃), carbon deposition is easy and CO disproportionation is frequent. The additive loading amount is 3%-4%.

[0015] Furthermore, the Mg and Ca composite oxide solid additive is filled in the outer ring gas distribution chamber and the central gas collection cylinder of the radial flow reactor. The gaseous material (raw material gas or reaction gas) passes through the Mg and Ca composite oxide solid additive layer. The gaseous acidic precursor is pre-neutralized before contacting the catalyst and contacts the Mg and Ca composite oxide solid additive in the central gas collection cylinder to capture the residual acidic free radicals and carbon deposit precursors after the reaction.

[0016] The microscopic mechanism of action of the Mg and Ca composite oxide solid additive is as follows: due to the occurrence of side reactions during the reaction process, there are two inducing factors for the side reactions. One is that the trace amounts of residual strongly acidic sites (Al-OH-Si) in the molecular sieve shell dissociate under the reaction conditions to produce H. + The Mg and Ca composite oxide solid additives neutralize acidic free radicals and inhibit methanol coupling and the deep cracking of dimethyl ether into olefins. The reaction involves trace amounts of water and CO2 to generate trace amounts of formic acid and acetic acid, which then volatilize into the gas phase. The acidic species are the active sites for catalyzing the reactions CH3OH→C2H5OH+H2O and CH3OCH3→C2C4 olefins+H2. 2- Hydroxyl groups (-OH, basic sites) diffuse to the surface of the additive, where gaseous acidic free radicals and organic acid molecules undergo acid-base neutralization (CaO + 2H+). + →Ca 2+ (+H2O, MgO+2HCOOH→Mg(HCOO)2+H2O), acidic active substances are fixed on the surface of the additive solid, removing the catalytic active source for olefin formation from the reaction system and blocking the conversion pathway of dimethyl ether and methanol to low-carbon olefins. The formate formed at temperatures of 220-270℃ is a solid adhering to the surface of the additive, and does not decompose or volatilize pollutants.

[0017] Regarding the suppression of CO disproportionation and carbon deposition: Since the subcarbon species and polymeric hydrocarbon intermediates generated by CO adsorption at the Cu active center are precursors for CO disproportionation and graphite formation; MgO and CaO are alkaline metal oxides, and lattice oxygen possesses oxygen storage and active adsorption sites. On one hand, it adsorbs the gaseous primary free carbon precursors and reacts with lattice oxygen (C+CaO+O2→CaCO3, C+MgO+O2→MgCO3), with solid carbonates stably remaining on the surface of the additive; on the other hand, the additive adsorbs trace amounts of free water vapor in the system, moderately increasing the local water-to-gas ratio, and thermodynamically suppressing the forward shift of the CO disproportionation reaction equilibrium; thus preventing carbon deposition from covering the active sites of the Cu catalyst and clogging the molecular sieve channels, reducing the catalyst deactivation rate from the source.

[0018] Compared with the prior art, the beneficial effects of the present invention are: (1) The catalyst performance is greatly improved: the core-shell structure catalyst isolates the active component from the acid support and avoids mutual interference between components; the weak acid shell reduces side reactions, the catalyst activity decay is reduced, the continuous operation time is longer, and the dimethyl ether selectivity is high.

[0019] (2) Precise temperature control and high conversion efficiency: The segmented temperature-controlled radial flow reactor achieves near-isothermal reaction throughout the process, completely eliminating local hot spots and preventing catalyst sintering; the single-pass CO conversion rate increases, bed resistance decreases, and production capacity increases.

[0020] (3) Strong raw material adaptability and reduced energy consumption: The hydrogen adjustment mode adopts in-situ low temperature conversion as the main method and micro-hydrogen supplementation as the auxiliary method, which is suitable for various syngas with H2 / CO=0.6~2.0. Compared with the traditional full hydrogen supplementation process, the front-end energy consumption is reduced.

[0021] (4) The separation system has low energy consumption and high recovery rate: the gradient condensation and distillation separation and purification process has low comprehensive energy consumption per unit product, improved total recovery rate of dimethyl ether, and stable product purity ≥99.5%.

[0022] (5) Significant reduction of byproducts: The Mg and Ca composite oxide solid additive of the present invention only captures the active intermediates of the side reaction, and does not adsorb CO, H2, methanol and dimethyl ether main products, and does not reduce the conversion rate and selectivity of dimethyl ether main reaction; the in-situ side reaction inhibition system controls the total amount of byproducts to less than 4%, the product composition is simple, and the separation load is reduced.

[0023] (6) High process integration: The whole process is designed as an integrated whole, with close connection between processes and cascade utilization of waste heat. The overall process stability and economy are significantly improved, and it can be directly applied to large-scale industrial production. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall process for the one-step synthesis of dimethyl ether from syngas according to the present invention. Figure 2 This is a partial cross-sectional structural schematic diagram of the radial flow reactor of the present invention; Figure 3 This is a top view of the radial flow reactor of the present invention; Figure 4 This is a schematic diagram of the radial flow reactor structure from the left side of the present invention; Figure 5 For the present invention Figure 1 Schematic diagram of the cross-sectional structure of the radial flow reactor in the AA direction; In the diagram: 1-Raw gas pretreatment and in-situ graded hydrogen regulation unit; 2-Segmented temperature-controlled radial flow reaction unit; 3-Gradient condensation and distillation separation and purification unit; 4-Circulating gas reuse unit; 5-Situ side reaction suppression unit; 6-Mixed gas inlet; 7-Shell; 8-First compartment; 9-Second compartment; 10-Third compartment; 11-Heat exchange assembly; 12-Central gas collector; 13-Channel a; 14-Circular baffle; 15-Low-temperature heat exchange medium outlet; 16-Channel b; 17-Medium-temperature heat exchange medium outlet; 18-High-temperature heat exchange medium outlet; 19-Reactor outlet; 20-Low-temperature heat exchange medium inlet; 21-Medium-temperature heat exchange medium inlet; 22-High-temperature heat exchange medium inlet. Detailed Implementation Example 1

[0025] refer to Figure 1-5The invention will be further described in detail below with reference to embodiments. The radial flow reactor of the present invention includes a reactor shell 7, axially segmented compartments, a radial airflow distribution assembly, a heat exchange assembly 11, a staged catalyst bed, a central gas collecting cylinder 12, and an outer ring gas distribution cavity. A mixed gas inlet 6 is provided at the top, and a reactor outlet 19 is provided at the bottom. The overall structure is a vertical cylindrical structure. The axially segmented compartments are, from top to bottom, a first compartment 8, a second compartment 9, and a third compartment 10, which correspond to the low-temperature reaction section, the medium-temperature coupling section, and the deep conversion section, respectively. The reactor shell 7 and the radial airflow distribution assembly form the outer ring gas distribution cavity. A central gas collecting cylinder 12 is provided at the center of the shell 7. A channel b16 is provided on the wall of the central gas collecting cylinder 12 to connect the compartments. An annular baffle in the outer ring gas distribution cavity and a circular baffle 14 in the central gas collecting cylinder 12 connect the three independent compartments in series. Each segment is a radial flow reaction structure. The outer ring gas distribution cavity... Between the central gas collecting cylinder 12 and the catalyst bed, a channel a13 is provided on the inner wall of the outer ring gas distribution cavity to connect the compartments. Multi-layer grids and metal wire mesh combined distributors are provided on the inner side of the outer ring gas distribution cavity and the outer side of the central gas collecting cylinder 12, in conjunction with radial guide plates, so that the airflow passes through the catalyst bed evenly, eliminating airflow deviation and short-circuiting phenomena, and reducing bed resistance. Each compartment is equipped with an independent heat exchange component 11, which is evenly distributed inside the catalyst bed. Each heat exchange component 11 in the compartment is equipped with an independent heat exchange medium inlet and heat exchange medium outlet, namely low temperature heat exchange medium inlet 20, low temperature heat exchange medium outlet 15, medium temperature heat exchange medium inlet 21, medium temperature heat exchange medium outlet 17, and high temperature heat exchange medium inlet 22 and high temperature heat exchange medium outlet 18, respectively. The central gas collecting cylinder 12 of each compartment is equipped with a catalyst loading and unloading port, a temperature measuring port, and a pressure measuring port.

[0026] The low-temperature reaction section (upper section) is filled with a core-shell type weakly acidic bifunctional catalyst, with an optimal temperature of 220–240℃. The main reaction is the synthesis of methanol from syngas. The medium-temperature coupling section (middle section) is filled with a modified methanol dehydration aid, with an optimal temperature of 240–260℃. The main reaction is the dehydration of methanol to produce dimethyl ether. The deep conversion section (lower section) is filled with an anti-carbon deposition composite catalyst, with an optimal temperature of 250–270℃. The main reaction is the deep conversion of unreacted syngas and the suppression of carbon deposition and methanation side reactions.

[0027] When the reactor of the present invention is working, the raw material synthesis gas enters the outer ring gas distribution chamber through the gas inlet at the top of the reactor, passes through the first catalyst bed in the radial direction from the outside to the inside, and flows into the central gas collecting cylinder 12. Then, it passes through the second catalyst bed from the inside to the outside of the central gas collecting cylinder 12 and enters the outer ring gas distribution chamber. Then, it flows through the third catalyst bed from the outside to the inside of the outer ring gas distribution chamber and enters the central gas collecting cylinder 12 before being discharged from the gas outlet at the bottom of the reactor.

[0028] The present invention discloses an integrated one-step synthesis gas-to-dimethyl ether production process, comprising five core units: a feed gas pretreatment and in-situ graded hydrogen regulation unit 1, a segmented temperature-controlled radial flow reaction unit 2, a gradient condensation and distillation separation and purification unit 3, a recycle gas reuse unit 4, and an in-situ side reaction suppression unit 5. The specific steps are as follows: (1) Raw material gas pretreatment and in-situ graded hydrogen adjustment: The initial H2 / CO ratio of coal-based syngas is 0.7. The syngas first enters the low-temperature water-gas shift unit, using Cu-ZnO-Al2O3 low-temperature shift catalyst, and controlling the reaction temperature at 190℃. The raw material gas carries its own water vapor for in-situ water-gas shift, increasing the volume ratio of syngas H2 / CO to 1.0. After the shift, the gas enters the micro-hydrogen replenishment section, with a precise replenishment amount of 3%, ultimately stabilizing the H2 / CO ratio at 1.0 to 1.2. The hydrogen replenishment section has a built-in sulfur and chlorine composite adsorbent to simultaneously remove trace impurities from the raw material gas and protect the downstream catalyst.

[0029] (2) Segmented temperature-controlled radial flow reactor: The hydrogen-treated syngas is fed into a segmented temperature-controlled radial flow reactor. The reactor is divided into three sections along the axial direction: a low-temperature reaction section, a medium-temperature coupling section, and a deep conversion section. Each section is independently temperature-controlled and independently loaded with catalyst. The low-temperature reaction section is at a temperature of 230℃ and is loaded with a core-shell type weakly acidic bifunctional catalyst with a core-shell mass ratio of 7.5:2.5 and an isolation layer thickness of 30nm. It mainly carries out the main reaction of syngas to methanol. The medium-temperature coupling section is at a temperature of 250℃ and is loaded with a modified dehydration aid. The methanol intermediate is rapidly dehydrated to generate dimethyl ether. The deep conversion section is at a temperature of 260℃ and is loaded with an anti-carbon deposition composite catalyst to achieve deep conversion of unreacted syngas and suppress carbon deposition and methanation side reactions. The temperature rise of each section bed is ≤6℃.

[0030] (3) Gradient condensation and distillation separation and purification: The reaction mixture gas at reactor outlet 19 enters the three-stage gradient condensation system in sequence, with the first stage condensation at 45℃, the second stage condensation at 5℃, and the third stage deep cooling at -22℃; after condensation, the crude dimethyl ether enters the distillation column, and after distillation purification, an industrial-grade dimethyl ether product with a purity ≥99.5% is obtained.

[0031] (4) Recycled gas reuse: The unreacted syngas after the third-stage cryogenic treatment is pressurized and recycled back to the feed gas hydrogen regulation unit. The recycling ratio is controlled at 1.8 to improve the utilization rate of feed gas.

[0032] (5) In-situ suppression of side reactions: Mg and Ca composite oxide solid additives are arranged in layers in the gap between the catalyst bed and the gas phase space of the reactor to neutralize the acidic free radicals of the system, suppress methanol coupling and deep dehydration of dimethyl ether to generate olefins; adsorb carbon deposition precursors to suppress CO disproportionation carbon deposition, and realize in-situ control of side reactions. Example 2

[0033] The difference between Example 2 and Example 1 is that the raw material is coal-based syngas, the initial H2 / CO ratio is 0.6, and the process parameters are adjusted as follows: the low-temperature shift temperature is 185℃, the hydrogen supplementation is 4%, the temperatures of each section of the reactor are 225℃, 245℃, and 255℃ respectively, the catalyst core-shell mass ratio is 7:3, and the recycle ratio is 1.6. Example 3

[0034] The difference between Example 3 and Example 1 is that the raw material is natural gas-based syngas, the initial H2 / CO ratio is 1.8, no large-scale conversion is required, only a small amount of hydrogen is adjusted, the temperature of each section of the reactor is 235℃, 255℃, and 265℃ respectively, and the recycle ratio is 2.0.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An integrated one-step process for producing dimethyl ether from syngas, characterized in that: It comprises five core units: a feed gas pretreatment and in-situ graded hydrogen regulation unit, a segmented temperature-controlled radial flow reaction unit, a gradient condensation and distillation separation and purification unit, a recycle gas reuse unit, and an in-situ side reaction suppression unit. The specific steps are as follows: (1) Raw material gas pretreatment and in-situ graded hydrogen regulation: Coal-based syngas first enters the low-temperature water-gas shift unit, and uses the water vapor carried by the raw material gas to carry out in-situ water-gas shift, increasing the H2 / CO volume ratio of the syngas from 0.6-0.8 to 0.9-1.1; After the shift, the gas enters the hydrogen replenishment section, and hydrogen is precisely replenished; Finally, the H2 / CO ratio is stably controlled at 1.0-1.2; (2) Segmented temperature-controlled radial flow reaction: The hydrogen-treated syngas is fed into a segmented temperature-controlled radial flow reactor. The reactor is divided into three sections along the axial direction: a low-temperature reaction section, a medium-temperature coupling section, and a deep conversion section. Each section is independently temperature-controlled and independently loaded with catalyst. The temperature of the low-temperature reaction section is 220-240℃, and it is loaded with a core-shell type weak acid bifunctional catalyst to synthesize methanol from syngas. The temperature of the medium-temperature coupling section is 240-260℃, and it is loaded with a modified dehydration aid to rapidly dehydrate the methanol intermediate to generate dimethyl ether. The temperature of the deep conversion section is 250-270℃, and it is loaded with an anti-carbon deposition composite catalyst to achieve deep conversion of unreacted syngas and suppress carbon deposition and methanation side reactions. (3) Gradient condensation and distillation separation and purification: The reaction mixture at the reactor outlet enters the three-stage gradient condensation system in sequence. After condensation, the crude dimethyl ether enters the distillation column and is purified by distillation to obtain industrial-grade dimethyl ether product with a purity of ≥99.5%. (4) Recycled gas reuse: The unreacted syngas after the third-stage cryogenic treatment is pressurized and recycled back to the feed gas hydrogen regulation unit. The recycling ratio is controlled at 1.5 to 2.0 to improve the utilization rate of feed gas. (5) In-situ suppression of side reactions: Mg and Ca composite oxide solid additives are arranged in layers in the gap between the catalyst bed and the gas phase space of the reactor to neutralize the acidic free radicals in the system, suppress methanol coupling, and suppress the deep dehydration of dimethyl ether to form olefins; It adsorbs carbon precursors, inhibits CO disproportionation and carbon deposition, and achieves in-situ control of side reactions.

2. The integrated one-step synthesis process for dimethyl ether from syngas according to claim 1, characterized in that: A Cu-ZnO-Al2O3 low-temperature shift catalyst was used to control the reaction temperature at 180–200 °C.

3. The integrated one-step synthesis process for dimethyl ether from syngas according to claim 1, characterized in that: A sulfur and chlorine composite adsorbent is installed in the hydrogen replenishment section to further remove impurities from the feed gas and protect the downstream catalyst.

4. The integrated one-step synthesis process for dimethyl ether from syngas according to claim 1, characterized in that: The radial flow reactor adopts a radial flow structure, with each section having an independent heat exchange component, and the bed temperature rise is controlled to be ≤8℃.

5. The integrated process for one-step production of dimethyl ether from syngas according to claim 1, characterized in that: The core-shell type weakly acidic bifunctional catalyst has a three-layer core-shell structure. The core is a Cu-ZnO-Al2O3 active core for methanol synthesis with a particle size of 200-400 nm. The middle layer is an ultrathin SiO2 isolation layer with a thickness of 20-50 nm. The outer shell is a La and Ce modified weakly acidic molecular sieve-composite alumina with a strong acidic site ratio of <5%. The core-shell mass ratio is 7:3-8:

2.

6. The integrated one-step synthesis process for dimethyl ether from syngas according to claim 1, characterized in that: The first-stage condensation temperature is 40–50℃, separating high-boiling-point components in the system; the second-stage condensation temperature is 0–10℃, initially enriching dimethyl ether and separating heavy hydrocarbon by-products; the third-stage cryogenic temperature is -20–-25℃, deeply condensing dimethyl ether, and the uncondensed gas phase is reused as circulating gas.

7. The integrated one-step process for producing dimethyl ether from syngas according to any one of claims 1-7, characterized in that: The radial flow reactor comprises a reactor shell, axially segmented compartments, a radial airflow distribution assembly, a heat exchange assembly, a staged catalyst bed, a central gas collecting cylinder, and an outer annular gas distribution chamber. A mixed gas inlet is located at the top, and a reactor outlet at the bottom. The overall structure is a vertical cylindrical shape. The axially segmented compartments, from top to bottom, are designated as the first, second, and third compartments, corresponding to the low-temperature reaction section, the intermediate-temperature coupling section, and the deep conversion section, respectively. The reactor shell and the radial airflow distribution assembly form the outer annular gas distribution chamber. A central gas collecting cylinder is located at the center of the shell, with a channel b on its wall connecting the compartments. An annular baffle in the outer annular gas distribution chamber and a circular baffle in the central gas collecting cylinder connect the three independent compartments in series. Each segment is a radial flow reaction structure. The outer annular gas distribution chamber and... The catalyst bed is located between the central gas collecting cylinders. Channel A is set on the inner wall of the outer ring gas distribution chamber to connect the compartments. Multi-layer grids and metal wire mesh distributors are set on the inner side of the outer ring gas distribution chamber and the outer side of the central gas collecting cylinder, in conjunction with radial guide plates, to ensure that the airflow passes evenly through the catalyst bed, eliminate airflow deviation and short-circuiting, and reduce bed resistance. Each compartment is equipped with an independent heat exchange component, which is evenly distributed inside the catalyst bed. Each heat exchange component in the compartment has an independent heat exchange medium inlet and outlet, namely low temperature heat exchange medium inlet, low temperature heat exchange medium outlet, medium temperature heat exchange medium inlet, medium temperature heat exchange medium outlet, high temperature heat exchange medium inlet, and high temperature heat exchange medium outlet. The central gas collecting cylinder wall of each compartment is equipped with a catalyst loading and unloading port, a temperature measuring port, and a pressure measuring port.

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