A method for preparing methyl methoxyacetate by carbonylation of methylal

Abstract

The present invention provides a method for producing methyl methoxyacetate by carbonylation of methylal, comprising passing a feedstock containing methylal and carbon monoxide through a reactor loaded with a molecular sieve catalyst for reaction under desired reaction conditions to produce methyl methoxyacetate. The molecular sieve catalyst is loaded into n mutually isolated but fluidically connected reaction zones between a first end and an opposite second end of the reactor, where n is greater than or equal to 2, and the first to nth reaction zones are arranged sequentially from the first end to the second end. Methylal enters the reaction zones through different methylal feed ports on the reactor. Carbon monoxide enters the n mutually isolated reaction zones through a carbon monoxide feed port at the first end of the reactor. The reaction product exits the reactor through a product outlet at the second end. This method achieves high methylal conversion, high methyl methoxyacetate selectivity, and long catalyst life.

Description

Technical Field

[0001] The invention belongs to the field of catalytic chemistry and relates to a method for preparing methyl methoxyacetate by carbonylation of methylal. Background Art

[0002] Methyl methoxyacetate (CH3OCH2COOCH3) is an important platform chemical. It can be hydrogenated to ethylene glycol monomethyl ether, which can then be hydrolyzed to ethylene glycol. It can also be directly hydrolyzed to produce methyl glycolate and glycolic acid. Ethylene glycol is a monomer in the synthesis of polyethylene terephthalate (PET) and is in huge market demand. Methyl glycolate and glycolic acid can be directly used to synthesize the biodegradable plastic polyglycolic acid (PGA). With the promotion of the "plastic ban," market demand is expected to increase in the future. Carbonylation of inexpensive methylal is considered the most economical and green route to synthesize methyl methoxyacetate. In recent years, Professor Alexis T. Bell's research group at UC Berkeley has used acidic molecular sieves to catalyze the vapor-phase carbonylation of methylal to produce methyl methoxyacetate, but the catalyst's stability is poor. Methylal can also be converted into bulky aromatic rings on the acidic molecular sieves, making the catalyst susceptible to carbon deposition and deactivation. It is a great challenge to prepare methyl methoxyacetate with high stability and selectivity through the carbonylation reaction of methylal. Summary of the Invention

[0003] In order to overcome the above technical problems, the object of the present invention is to provide a method for preparing methyl methoxyacetate with high stability and high selectivity.

[0004] Specifically, the present application provides a method for producing methyl methoxyacetate by carbonylation of methylal, comprising: passing a raw material containing methylal and carbon monoxide through a reactor loaded with a molecular sieve catalyst to react under desired reaction conditions to produce methyl methoxyacetate;

[0005] wherein, between a first end and an opposite second end of the reactor, the molecular sieve catalyst is loaded in n reaction zones separated from each other but in fluid communication, n ≥ 2, wherein the first reaction zone to the nth reaction zone are arranged in sequence from the first end to the second end;

[0006] Methylal enters the reaction zone of the reactor through different methylal feed ports on the reactor;

[0007] Carbon monoxide is introduced into the n reaction zones separated from each other through a carbon monoxide feed port located at the first end of the reactor; and

[0008] The reaction product flows out of the reactor via a product outlet at the second end.

[0009] The main reaction equation of methylal carbonylation is as follows:

[0010] CH3OCH2OCH3+CO=CH3OCH2COOCH3

[0011] During the reaction process, there are also by-products such as dimethyl ether, methyl formate, and polymethyl acetal carbonyl.

[0012] More specifically, the first reaction zone is adjacent to the first end of the reactor and the nth reaction zone is adjacent to the second end of the reactor.

[0013] Optionally, methylal enters the n reaction zones separated from each other through different methylal feed ports on the reactor.

[0014] Optionally, the reactor is a single fixed-bed reactor comprising 2 to 10 catalyst beds forming 2 to 10 reaction zones, each of which is provided with a methylal feed port at the top of each catalyst bed to supply methylal to the respective catalyst beds. Specifically, with the exception of the methylal feed port provided at the top of the catalyst bed closest to the first end of the reactor, the remaining methylal feed ports are provided between adjacent catalyst beds.

[0015] Optionally, the reactor is a single fixed-bed reactor comprising two to four catalyst beds forming two to four reaction zones, each of which is provided with a methylal feed port at the top of each catalyst bed to supply methylal to the respective catalyst beds. Specifically, with the exception of the methylal feed port provided at the top of the catalyst bed closest to the first end of the reactor, the remaining methylal feed ports are provided between adjacent catalyst beds.

[0016] The catalyst beds are respectively referred to as the first layer, the second layer, the third layer to the nth layer according to the direction of material flow (ie, from the first end to the second end), where n is the total number of beds included.

[0017] Optionally, the reactor comprises 2 to 10 sub-fixed-bed reactors connected in series to form 2 to 10 reaction zones, the molecular sieve catalyst being loaded in each sub-fixed-bed reactor, and a methylal feed port being provided at the top of each sub-fixed-bed reactor to supply methylal to the respective sub-fixed-bed reactor. Specifically, a methylal feed port is provided at the top of each sub-fixed-bed reactor to supply methylal to the respective sub-fixed-bed reactor.

[0018] Optionally, the reactor comprises 2 to 4 sub-fixed-bed reactors connected in series to form 2 to 4 reaction zones, the molecular sieve catalyst is loaded in each sub-fixed-bed reactor, and a methylal feed port is provided at the top of each sub-fixed-bed reactor to supply methylal to the respective sub-fixed-bed reactor. Specifically, a methylal feed port is provided at the top of each sub-fixed-bed reactor to supply methylal to the respective sub-fixed-bed reactor.

[0019] Optionally, the sub-fixed bed reactors connected in series are respectively referred to as the first sub-fixed bed reactor, the second sub-fixed bed reactor, the third sub-fixed bed reactor, and so on to the nth sub-fixed bed reactor according to the direction of material flow (i.e., from the first end to the second end), where n is the total number of sub-fixed bed reactors connected in series.

[0020] In the present application, loading the molecular sieve catalyst into different catalyst layers of a single fixed bed reactor and loading the molecular sieve catalyst into multiple sub-fixed bed reactors connected in series are essentially loading the catalyst in stages in the fixed bed reactor.

[0021] For example, if 100 tons of catalyst are evenly loaded into a fixed-bed reactor in four sections, each section has a loading capacity of 25 tons; if 100 tons of catalyst are evenly loaded into four sub-fixed-bed reactors connected in series, each sub-fixed-bed reactor also has a loading capacity of 25 tons. In practice, the difference between these two loading methods lies in the equivalent replacement of a single large-volume fixed-bed reactor with multiple smaller fixed-bed reactors.

[0022] Optionally, a carbon monoxide feed port is provided at the top of each sub-fixed bed reactor, a carbon monoxide discharge port is provided at the bottom of each sub-fixed bed reactor, and the carbon monoxide discharge port of one sub-fixed bed reactor is connected to its adjacent carbon monoxide feed port.

[0023] Optionally, the content of methylal passed into each reaction zone per unit time is greater than 0% and less than 100% of the content passed into n reaction zones per unit time, and the molecular sieve catalyst loaded in each reaction zone accounts for greater than 0% and less than 100% of the total molecular sieve catalyst;

[0024] Optionally, the ratio of the content of methylal passed into each reaction zone per unit time to the content passed into n reaction zones per unit time is equal to the ratio of the molecular sieve catalyst loaded in the corresponding reaction zone to the total amount of molecular sieve catalyst.

[0025] Optionally, the ratio of the content of methylal fed into each reaction zone per unit time to the content fed into n reaction zones per unit time is 1 / n, and the molecular sieve catalyst loaded into each reaction zone is 1 / n of the total amount of molecular sieve catalyst.

[0026] Optionally, the reactor is a single fixed bed reactor comprising two catalyst beds, and the mass fraction of methylal entering each section is 50%.

[0027] Optionally, the reactor is a single fixed bed reactor comprising three catalyst beds, and the mass fraction of methylal entering each section is 33.3%.

[0028] Optionally, the reactor is a single fixed bed reactor comprising four catalyst beds, and the mass fraction of methylal entering each section is 25%.

[0029] Optionally, the reactor is composed of two sub-fixed bed reactors connected in series, and the mass fraction of methylal introduced into each sub-fixed bed reactor is 50%.

[0030] Optionally, the reactor is composed of three sub-fixed bed reactors connected in series, and the mass fraction of methylal introduced into each sub-fixed bed reactor is 33.3%.

[0031] Optionally, the reactor is composed of four sub-fixed bed reactors connected in series, and the mass fraction of methylal introduced into each sub-fixed bed reactor is 25%.

[0032] In the present application, when a molecular sieve catalyst is loaded in stages in each reaction zone (in the form of a catalyst layer or a sub-fixed bed reactor) and methylal is introduced into the reaction zone through a feed port corresponding to each reaction zone (i.e., methylal is shunted to be introduced into each reaction zone simultaneously), when the ratio of the total molar amount of carbon monoxide per unit time to the total molar amount of methylal per unit time remains unchanged, since carbon monoxide is introduced into the reactor only from the carbon monoxide feed port at the first end of the reactor rather than entering different reaction zones of the reactor in stages, the carbon monoxide that enters the reaction zone closest to the first end is all the carbon monoxide, and the carbon monoxide that enters the other reaction zones is the carbon monoxide that was not consumed in the previous reaction zone. As a result, the molar ratio of carbon monoxide to methylal that actually participates in the reaction in each reaction zone is increased. For example, when methylal is fed in equal amounts in four stages, the molar ratio of carbon monoxide to methylal in the reaction zone closest to the first end of the reactor is four times the total molar ratio.

[0033] Optionally, carbon monoxide is passed from the first end through the first to nth reaction zones at a predetermined total flow rate; methylal is first introduced into the nth reaction zone through the feed port corresponding to the nth reaction zone at a predetermined total flow rate; when the methylal reacts with the carbon monoxide until the methylal reaches a predetermined conversion rate, the introduction of methylal into the nth reaction zone through the feed port corresponding to the nth reaction zone is stopped, and methylal is instead introduced into the n-1th reaction zone and the nth reaction zone through the methylal feed port corresponding to the n-1th reaction zone;

[0034] When methylal reacts with carbon monoxide until the methylal conversion rate reaches the predetermined rate again, stopping the introduction of methylal into the n-1th and nth reaction zones through the methylal feed port corresponding to the n-1th reaction zone and instead introducing methylal into the n-2th to nth reaction zones through the methylal feed port corresponding to the n-2th reaction zone;

[0035] In this way, whenever methylal reacts with carbon monoxide until the methylal reaches the predetermined conversion rate, the feed port for methylal is replaced until methylal is finally fed to the first to nth reaction zones via the methylal feed port corresponding to the first reaction zone.

[0036] Optionally, 10≥n≥2.

[0037] Optionally, 4≥n≥2.

[0038] Specifically, when methylal reacts with carbon monoxide until methylal reaches the predetermined conversion rate, the feed port of methylal is replaced, and the methylal enters the reaction zone in sections from the back to the front to react, so that the highly active fresh catalyst can be fully utilized.

[0039] Optionally, the reactor is a single fixed bed reactor comprising two catalyst beds, and methylal first enters the second layer through the methylal feed port of the second layer at a predetermined total flow rate (i.e., without any diversion). When methylal reacts with carbon monoxide until methylal reaches a predetermined conversion rate, the introduction of methylal into the second catalyst bed through the methylal feed port corresponding to the second catalyst bed is stopped, and methylal is instead introduced into the first catalyst bed and the second catalyst bed through the methylal feed port corresponding to the first catalyst bed.

[0040] Optionally, the reactor is a single fixed bed reactor comprising three catalyst beds, and methylal first enters the third layer through the methylal feed port of the third layer at a predetermined total flow rate; when methylal reacts with carbon monoxide until the methylal reaches a predetermined conversion rate, the methylal is stopped from being introduced into the third catalyst bed through the methylal feed port corresponding to the third catalyst bed, and methylal is instead introduced into the second and third catalyst beds through the methylal feed port corresponding to the second catalyst bed; when methylal reacts with carbon monoxide until the methylal reaches a predetermined conversion rate again, the methylal is stopped from being introduced into the first to third catalyst beds through the methylal feed port corresponding to the first catalyst bed.

[0041] Optionally, the reactor is a single fixed bed reactor comprising four catalyst beds, wherein methylal first enters the fourth layer through the methylal feed port of the fourth layer at a predetermined total flow rate; when methylal reacts with carbon monoxide until methylal reaches a predetermined conversion rate, the introduction of methylal through the methylal feed port corresponding to the fourth catalyst bed is stopped and methylal is introduced into the third and fourth catalyst beds through the methylal feed port corresponding to the third catalyst bed; when methylal reacts with carbon monoxide until methylal reaches a predetermined conversion rate again, the reactor is stopped. When the conversion rate reaches a predetermined value, the introduction of methylal through the methylal feed port corresponding to the third catalyst bed is stopped and methylal is introduced into the second to fourth catalyst beds through the methylal feed port corresponding to the second catalyst bed; when methylal reacts with carbon monoxide until the methylal reaches a predetermined conversion rate again, the introduction of methylal through the methylal feed port corresponding to the second catalyst bed is stopped and methylal is introduced into the first to fourth catalyst beds through the methylal feed port corresponding to the first catalyst bed.

[0042] Optionally, the reactor is composed of two sub-fixed bed reactors connected in series, each sub-fixed bed reactor is loaded with a molecular sieve catalyst, and methylal is first introduced into the second sub-fixed bed reactor through the feed port corresponding to the second sub-fixed bed reactor at a predetermined total flow rate. When methylal reacts with carbon monoxide until methylal reaches a predetermined conversion rate, the introduction of methylal through the feed port corresponding to the second sub-fixed bed reactor is stopped and methylal is instead introduced into the first sub-fixed bed reactor and the second sub-fixed bed reactor through the methylal feed port corresponding to the first sub-fixed bed reactor.

[0043] Optionally, the reactor is composed of three sub-fixed bed reactors connected in series, each sub-fixed bed reactor is loaded with a molecular sieve catalyst, and methylal is first introduced into the third sub-fixed bed reactor through the feed port corresponding to the third sub-fixed bed reactor at a predetermined total flow rate; when methylal reacts with carbon monoxide until methylal reaches a predetermined conversion rate, the introduction of methylal through the feed port corresponding to the third sub-fixed bed reactor is stopped, and methylal is instead introduced into the second and third sub-fixed bed reactors through the methylal feed port corresponding to the second sub-fixed bed reactor; when methylal reacts with carbon monoxide until methylal reaches a predetermined conversion rate, the introduction of methylal through the feed port corresponding to the second sub-fixed bed reactor is stopped, and methylal is instead introduced into the first to third sub-fixed bed reactors through the methylal feed port corresponding to the first sub-fixed bed reactor.

[0044] Optionally, the reactor is composed of four sub-fixed bed reactors connected in series, each sub-fixed bed reactor is loaded with a molecular sieve catalyst, and methylal is first introduced into the fourth sub-fixed bed reactor through the feed port corresponding to the fourth sub-fixed bed reactor at a predetermined total flow rate. When methylal reacts with carbon monoxide until methylal reaches a predetermined conversion rate, the introduction of methylal through the feed port corresponding to the fourth sub-fixed bed reactor is stopped and methylal is introduced into the third and fourth sub-fixed bed reactors through the methylal feed port corresponding to the third sub-fixed bed reactor; when methylal and carbon monoxide react until methylal reaches a predetermined conversion rate, the introduction of methylal through the feed port corresponding to the fourth sub-fixed bed reactor is stopped and the methylal is introduced into the third and fourth sub-fixed bed reactors through the methylal feed port corresponding to the third sub-fixed bed reactor; When carbon monoxide reacts until methylal reaches a predetermined conversion rate, the introduction of methylal through the feed port corresponding to the third sub-fixed-bed reactor is stopped, and methylal is instead introduced into the second to fourth sub-fixed-bed reactors through the methylal feed port corresponding to the second sub-fixed-bed reactor; when methylal and carbon monoxide react until methylal reaches a predetermined conversion rate, the introduction of methylal through the feed port corresponding to the second sub-fixed-bed reactor is stopped, and methylal is instead introduced into the first to fourth sub-fixed-bed reactors through the methylal feed port corresponding to the first sub-fixed-bed reactor.

[0045] In the present application, the total flow rate refers to the total mass or total molar amount of carbon monoxide or methylal introduced into the reactor per unit time during the reaction.

[0046] Optionally, the molecular sieve catalyst is an acidic molecular sieve catalyst, which is selected from at least one of an acidic molecular sieve having an MFI structure, an acidic molecular sieve having a Y structure, and an acidic molecular sieve having a BEA structure.

[0047] Optionally, the molecular sieve catalyst is selected from any one of ZSM-5 molecular sieve, β molecular sieve or Y molecular sieve, or a mixture of any two of them.

[0048] Optionally, the molecular sieve catalyst is an acidic molecular sieve catalyst, which is selected from any one of HZSM-5 molecular sieve, H-β molecular sieve or HY molecular sieve, or a mixture of any two of them.

[0049] Optionally, the reaction conditions are a gas-liquid-solid three-phase reaction state.

[0050] Optionally, the reaction conditions are: reaction temperature of 60-140°C, reaction pressure of 2-10 MPa, and methylal mass space velocity of 0.2-10.0 h -1 The ratio of the total molar amount of carbon monoxide entering the reactor per unit time to the total molar amount of methylal entering the reactor per unit time is 2:1 to 20:1.

[0051] In the present application, when the molecular sieve catalyst is loaded in sections in each reaction zone (which is in the form of a catalyst layer or a sub-fixed bed reactor) and the total feed port of methylal is continuously changed (i.e., methylal is introduced at a total flow rate at the feed port corresponding to a specific reaction zone over time), the reaction process of the raw materials is as follows.

[0052] 3 reaction zones that take the catalyst bed as example, it is arranged from top to bottom, the uppermost end of reactor is the first end, and the lowermost end of reactor is the second end, catalyzer is loaded on three different catalyst beds (being the 1st catalyst bed, the 2nd catalyst bed and the 3rd catalyst bed from top to bottom), each bed all has corresponding methylal feed opening (being the 1st methylal feed opening, the 2nd methylal feed opening and the 3rd methylal feed opening), carbon monoxide is fed from the carbon monoxide feed opening of reactor first end, earlier methylal is fed methylal (this moment, the 1st catalyst bed and the 2nd catalyst bed all did not have methylal) to the 3rd catalyst bed with total flow via the 3rd methylal feed opening, carbon monoxide and methylal react at the 3rd catalyst bed, when the transformation efficiency that detects methylal reaches predetermined transformation efficiency (for example adjacent to 50%), stop via the 3rd methylal feed opening feeding; and at the same time, methylal is first fed into the second catalyst bed at a total flow rate through the second methylal feed port (at this time, no methylal is fed into the first catalyst bed), carbon monoxide and methylal react in the second catalyst bed, and due to the unidirectional flow of the raw materials from top to bottom, the methylal that has not reacted in the second catalyst bed continues to react with carbon monoxide in the third catalyst bed, and when it is detected that the conversion rate of methylal reaches a predetermined conversion rate (for example, close to 50%), feeding through the second methylal feed port is stopped; and at the same time, methylal is first fed into the first catalyst bed at a total flow rate through the first methylal feed port, formaldehyde is first fed into the first catalyst bed, carbon monoxide and methylal react in the first catalyst bed, and due to the unidirectional flow of the raw materials from top to bottom, the methylal that has not reacted in the first catalyst bed continues to react with carbon monoxide in the second catalyst bed and the third catalyst bed, respectively. This method of continuously changing the methylal feed port allows the methylal feedstock to continuously react on the highly active molecular sieve catalyst, thereby maintaining a predetermined conversion rate. Experimental data also demonstrates that this method significantly extends the catalyst lifespan. This method avoids the drawback of the prior art method of directly introducing methylal and carbon monoxide from the first end of the reactor. Consequently, the reaction products in the upper catalyst bed inevitably pass through the lower catalyst bed, causing the reaction products to accumulate in the lower catalyst bed and causing the lower catalyst to deactivate more rapidly due to carbon deposition.

[0053] The present invention can produce the following beneficial effects:

[0054] (1) Without changing the total molar ratio of carbon monoxide to methylal per unit time, the molar ratio of carbon monoxide to methylal actually reacted in each reaction zone can be increased by feeding methylal in stages (i.e., feeding methylal in a split stream), thereby improving the selectivity of methyl methoxyacetate.

[0055] (2) Without changing the ratio of the total molar amount of carbon monoxide to the total molar amount of methylal per unit time, by feeding methylal from the second end to the first end (i.e., the feed port from the back to the front) in sequence into the corresponding reaction zone at a predetermined total flow rate, the high activity of the fresh catalyst can be fully utilized, the overall carbonylation reaction efficiency can be improved, and the overall catalyst life can be extended. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 Schematic diagram of a single fixed bed reactor comprising multiple spaced catalyst beds.

[0057] Figure 2 Schematic diagram of a reactor consisting of multiple sub-fixed bed reactors connected in series.

[0058] Figure 3 Schematic diagram of a conventional fixed bed reactor with a continuous catalyst bed. DETAILED DESCRIPTION

[0059] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0060] The endpoints of the ranges disclosed in this application and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include approximate ranges or values. For numerical ranges, the endpoints of each range and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0061] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0062] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0063] Unless otherwise specified, the detection and measurement methods of the embodiments of the present invention are achieved through conventional technical means.

[0064] In the examples, the conversion of methylal and the selectivity of methyl methoxyacetate are calculated based on the carbon molar number of methylal:

[0065] Methylal conversion rate = [(mole number of carbon methylal in the raw material) - (mole number of carbon methylal in the product)] ÷ (mole number of carbon methylal in the raw material) × (100%)

[0066] Methyl methoxyacetate selectivity = (the number of moles of carbon in the product after the carbonyl group is removed from methyl methoxyacetate) ÷ [(the number of moles of carbon in the raw material) - (the number of moles of carbon in the product)] × (100%)

[0067] The present invention is described in detail below by way of examples, but the present invention is not limited to these examples.

[0068] Example 1

[0069] Acidic H-β molecular sieve (SiO2 / Al2O3=50) catalyst is loaded into a single fixed bed reactor in stages, such as Figure 1 As shown. 300g of the above catalyst was loaded into a In the fixed bed reactor, there is The catalyst was packed in four sections, each approximately 120 mm. The top catalyst bed had carbon monoxide and methylal feed ports located at the top, while the remaining catalyst beds each had a methylal feed port located at the top. The bottom catalyst bed had a reaction product discharge port located at the bottom. The product was vaporized and analyzed online using an Agilent 7890A gas chromatograph equipped with an FFAP capillary column and an FID detector. A thermocouple was located in the middle of each catalyst layer to measure the reaction temperature. The reaction conditions were: reaction temperature = 70°C, reaction pressure = 5 MPa, and a methylal mass space velocity of 1.0 h / min. -1 The ratio of the total molar amount of carbon monoxide to the total molar amount of methylal in the reactor per unit time was 8:1. The mass fraction of methylal entering each catalyst bed was equal, at 25% of the total methylal content. After 10 days of operation, the reaction results are shown in Table 1.

[0070] Example 2

[0071] Acidic H-β molecular sieve (SiO2 / Al2O3=50) catalyst was loaded into a single fixed bed reactor in sections. 300g of the above catalyst was loaded into a fixed bed reactor with an inner diameter of In the fixed bed reactor, there is The catalyst was packed in three sections, each approximately 160 mm. The top catalyst bed had carbon monoxide and methylal feed ports located at the top, while the remaining catalyst beds each had a methylal feed port located at the top. The bottom catalyst bed had a reaction product discharge port located at the bottom. The product was vaporized and analyzed online using an Agilent 7890A gas chromatograph equipped with an FFAP capillary column and an FID detector. A thermocouple was located in the middle of each catalyst layer to measure the reaction temperature. The reaction conditions were: reaction temperature = 70°C, reaction pressure = 5 MPa, and a methylal mass space velocity of 1.0 h / min. -1The ratio of the total molar amount of carbon monoxide to the total molar amount of methylal in the reactor per unit time was 8:1. The mass fraction of methylal entering each catalyst bed was equal, at 33.3% of the total methylal content. After 10 days of operation, the reaction results are shown in Table 1.

[0072] Example 3

[0073] Acidic H-β molecular sieve (SiO2 / Al2O3=50) catalyst was loaded into a single fixed bed reactor in sections. 300g of the above catalyst was loaded into a fixed bed reactor with an inner diameter of In the fixed bed reactor, there is The catalyst was packed in two sections, each approximately 240 mm. The top catalyst bed had carbon monoxide and methylal feed ports located at the top, while the remaining catalyst beds each had a methylal feed port located at the top. The bottom catalyst bed had a reaction product discharge port located at the bottom. The product was vaporized and analyzed online using an Agilent 7890A gas chromatograph equipped with an FFAP capillary column and an FID detector. A thermocouple was located in the middle of each catalyst layer to measure the reaction temperature. The reaction conditions were: reaction temperature = 70°C, reaction pressure = 5 MPa, and a methylal mass space velocity of 1.0 h / min. -1 The ratio of the total molar amount of carbon monoxide to the total molar amount of methylal in the reactor per unit time was 8:1. The mass fraction of methylal entering each catalyst bed was equal, at 50% of the total methylal content. After 10 days of operation, the reaction results are shown in Table 1.

[0074] Example 4

[0075] Acidic H-β molecular sieve (SiO2 / Al2O3=50) catalyst was loaded into four fixed bed reactors connected in series. Figure 2 As shown. 300g of the above catalyst was loaded into a There are four fixed bed reactors in series, and there are Each fixed bed is loaded with 75g of catalyst, and each section is approximately 120mm. Each sub-fixed-bed reactor is equipped with an upper methylal feed port and a carbon monoxide feed port at the top, and a carbon monoxide discharge port at the bottom. The carbon monoxide feed port of the leftmost sub-fixed-bed reactor is the source of carbon monoxide entering the reactor, and the carbon monoxide discharge port of the previous sub-fixed-bed reactor is connected to the carbon monoxide feed port of the adjacent sub-fixed-bed reactor. After vaporization, the product was analyzed online using an Agilent 7890A gas chromatograph equipped with an FFAP capillary column and an FID detector. A thermocouple was located in the middle of each catalyst layer to measure the reaction temperature. The reaction conditions were: reaction temperature = 70°C, reaction pressure = 5 MPa, and methylal mass space velocity = 1.0 h-1. -1The ratio of the total molar amount of carbon monoxide to the total molar amount of methylal in the reactor per unit time was 8:1. The mass fraction of methylal entering each catalyst bed was equal, at 25% of the total methylal content. After 10 days of operation, the reaction results are shown in Table 1.

[0076] Comparative Example 1

[0077] Acidic H-β molecular sieve (SiO2 / Al2O3=50) catalyst is loaded into a conventional single fixed bed reactor, such as Figure 3 As shown. 300g of the above catalyst was loaded into a In the fixed bed reactor, there is The catalyst bed was approximately 480 mm high. The upper portion of the catalyst bed contained carbon monoxide and methylal feed ports, while the lower portion contained a reaction product discharge port. The vaporized product was analyzed online using an Agilent 7890A gas chromatograph equipped with an FFAP capillary column and an FID detector. The reaction conditions were: reaction temperature = 70°C, reaction pressure = 5 MPa, and a methylal mass space velocity of 1.0 h / min. -1 The ratio of the total molar amount of carbon monoxide to the total molar amount of methylal in the reactor per unit time was 8:1. After 10 days of operation, the reaction results are shown in Table 1.

[0078] Table 1 Reaction results of Examples 1-4 and Comparative Example 1

[0079] Examples / Comparative Examples Methylal conversion rate (%) Methyl methoxyacetate selectivity (%) Example 1 62.3 82.9 Example 2 60.5 82.8 Example 3 58.8 81.4 Example 4 62.1 82.2 Comparative Example 1 47.7 73.1

[0080] Example 5

[0081] A single fixed bed reactor with acidic HY molecular sieve (SiO2 / Al2O3=30) catalyst loaded in stages, such as Figure 1 As shown. 300g of the above catalyst was loaded into a In the fixed bed reactor, there is The catalyst was packed in four sections, each approximately 120 mm. The top catalyst bed had carbon monoxide and methylal feed ports located at the top, while the remaining catalyst beds each had a methylal feed port located at the top. The bottom catalyst bed had a reaction product discharge port located at the bottom. The product was vaporized and analyzed online using an Agilent 7890A gas chromatograph equipped with an FFAP capillary column and an FID detector. A thermocouple was located in the middle of each catalyst layer to measure the reaction temperature. The reaction conditions were: reaction temperature = 80°C, reaction pressure = 6 MPa, and a methylal mass space velocity of 0.5 h / min. -1The ratio of the total molar amount of carbon monoxide to the total molar amount of methylal in the reactor per unit time was 6:1. In this embodiment, the feeding method was as follows: methylal was first fed into the fourth section at a predetermined total flow rate. When the methylal conversion rate dropped to approximately 50%, the methylal feed port was replaced with the feed port of the third section. When the methylal conversion rate dropped to approximately 50%, the methylal feed port was replaced with the feed port of the third section and fed into the second section. When the methylal conversion rate dropped to approximately 50%, the methylal feed port was replaced with the feed port of the first section. The reaction results are shown in Table 2.

[0082] Comparative Example 2

[0083] Acidic HY molecular sieve (SiO2 / Al2O3=30) catalyst is loaded into a conventional single fixed bed reactor, such as Figure 3 As shown. 300g of the above catalyst was loaded into a In the fixed bed reactor, there is The catalyst bed was approximately 480 mm high. The upper portion of the catalyst bed contained inlets for carbon monoxide and methylal, while the lower portion contained a discharge port for the reaction products. The vaporized products were analyzed online using an Agilent 7890A gas chromatograph equipped with an FFAP capillary column and an FID detector. The reaction conditions were: reaction temperature = 80°C, reaction pressure = 6 MPa, and a methylal mass space velocity of 0.5 h / min. -1 The ratio of the total molar amount of carbon monoxide to the total molar amount of methylal in the reactor per unit time was 6:1. The reaction results are shown in Table 2.

[0084] Table 2 Reaction results of Example 5 and Comparative Example 2

[0085]

[0086] By comparing Example 5 with Comparative Example 2, it can be seen that the method of introducing methylal into the reactor by replacing the feed port is compared with the prior art method of introducing methylal into the reactor from the top inlet. The present application can maintain a methylal conversion rate of more than 50%, and the catalyst still maintains a conversion rate of more than 50% for up to 360 days, while the solution in the prior art reaches a conversion rate of 50.4% after 180 days. As time goes by, the more carbon deposits on the catalyst, the more methylal conversion rate will be lower than 50% after more than 180 days.

[0087] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing methyl methoxyacetate by carbonylation of methylal, characterized in that: Passing a raw material containing methylal and carbon monoxide through a reactor loaded with a molecular sieve catalyst to react under desired reaction conditions to produce methyl methoxyacetate; wherein, between a first end and an opposite second end of the reactor, the molecular sieve catalyst is loaded in n reaction zones separated from each other but in fluid communication, n ≥ 2, wherein the first reaction zone to the nth reaction zone are arranged in sequence from the first end to the second end; Methylal enters the reaction zone of the reactor through different methylal feed ports on the reactor; Carbon monoxide is introduced into n reaction zones separated from each other through a carbon monoxide feed port located at a first end of the reactor; and The reaction product flows out of the reactor via a product outlet at the second end; Carbon monoxide is passed from the first end through the first to nth reaction zones at a predetermined total flow rate; Methylal is first introduced into the nth reaction zone through a feed port corresponding to the nth reaction zone at a predetermined total flow rate; when the methylal reacts with carbon monoxide until the methylal reaches a predetermined conversion rate, the introduction of methylal into the nth reaction zone through the feed port corresponding to the nth reaction zone is stopped, and methylal is instead introduced into the n-1th reaction zone and the nth reaction zone through a methylal feed port corresponding to the n-1th reaction zone; When methylal reacts with carbon monoxide until the methylal conversion rate reaches the predetermined rate again, stopping the introduction of methylal into the n-1th and nth reaction zones through the methylal feed port corresponding to the n-1th reaction zone and instead introducing methylal into the n-2th to nth reaction zones through the methylal feed port corresponding to the n-2th reaction zone; In this way, whenever methylal reacts with carbon monoxide until the methylal reaches the predetermined conversion rate, the feed port for methylal is replaced until methylal is finally fed to the first to nth reaction zones via the methylal feed port corresponding to the first reaction zone.

2. The method according to claim 1, characterized in that Methylal is fed into the n reaction zones separated from each other through different methylal feed ports on the reactor.

3. The method according to claim 2, characterized in that The reactor is a single fixed bed reactor, comprising 2 to 10 catalyst beds constituting 2 to 10 reaction zones. The upper portion of each catalyst bed is provided with a methylal feed port to supply methylal to each catalyst bed.

4. The method according to claim 2, characterized in that The reactor is a single fixed bed reactor, comprising 2 to 4 catalyst beds constituting 2 to 4 reaction zones. The upper portion of each catalyst bed is provided with a methylal feed port to supply methylal to each catalyst bed.

5. The method according to claim 2, characterized in that The reactor comprises 2 to 10 sub-fixed bed reactors connected in series to form 2 to 10 reaction zones, the molecular sieve catalyst is filled in each sub-fixed bed reactor, and a methylal feed port is provided on the top of each sub-fixed bed reactor to provide methylal to each sub-fixed bed reactor.

6. The method according to claim 2, characterized in that The reactor comprises 2 to 4 sub-fixed bed reactors connected in series to form 2 to 4 reaction zones, the molecular sieve catalyst is filled in each sub-fixed bed reactor, and a methylal feed port is provided on the top of each sub-fixed bed reactor to provide methylal to each sub-fixed bed reactor.

7. The method according to claim 2, characterized in that The content of methylal introduced into each reaction zone per unit time is greater than 0% and less than 100% of the content introduced into n reaction zones per unit time, and the molecular sieve catalyst loaded into each reaction zone accounts for greater than 0% and less than 100% of the total molecular sieve catalyst.

8. The method according to claim 7, characterized in that The ratio of the content of methylal fed into each reaction zone per unit time to the content fed into n reaction zones per unit time is equal to the ratio of the molecular sieve catalyst loaded in the corresponding reaction zone to the total amount of molecular sieve catalyst.

9. The method according to claim 8, characterized in that The ratio of the methylal content fed into each reaction zone per unit time to the content fed into n reaction zones per unit time is 1 / n, and the ratio of the molecular sieve catalyst loaded into each reaction zone to the total amount of the molecular sieve catalyst is 1 / n.

10. The method according to claim 1, characterized in that 10≥n≥2。 11. The method according to claim 1, wherein 4≥n≥2。 12. The method according to claim 1, characterized in that The molecular sieve catalyst is an acidic molecular sieve catalyst, which is selected from at least one of an acidic molecular sieve with an MFI structure, an acidic molecular sieve with a Y structure, and an acidic molecular sieve with a BEA structure.

13. The method according to claim 12, characterized in that The molecular sieve catalyst is selected from any one of ZSM-5 molecular sieve, β molecular sieve or Y molecular sieve, or a mixture of any two of them.

14. The method according to claim 12, characterized in that The molecular sieve catalyst is an acidic molecular sieve catalyst, which is selected from any one of HZSM-5 molecular sieve, H-β molecular sieve or HY molecular sieve, or a mixture of any two of them.

15. The method according to claim 1, wherein The reaction conditions are a gas-liquid-solid three-phase reaction state.

16. The method according to claim 15, characterized in that The reaction conditions are as follows: reaction temperature of 60-140° C., reaction pressure of 2-10 MPa, and methylal mass space velocity of 0.2-10.0 h -1 The ratio of the total molar amount of carbon monoxide entering the reactor per unit time to the total molar amount of methylal entering the reactor per unit time is 2:1 to 20:1.

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