A method for preparing low-carbon esters by one-step method of methanol and methyl acetate

Abstract

The present invention provides a method for synthesizing low-carbon esters by reacting methanol and methyl acetate in one step by a catalyst loading method. The present invention is based on the process design concept of "relay catalysis". Two catalysts with specific chemical structures and properties are designed and selected, including a copper-based catalyst and a cesium-based catalyst. The two catalysts are stacked in a fixed bed reactor in different mixed loading methods. Under the condition of a reaction temperature of 250 to 400° C., the raw materials of methanol and methyl acetate are passed into the fixed bed with nitrogen as a carrier gas to contact and react with the catalyst, and low-carbon esters are efficiently synthesized in one step. The process can greatly improve the atomic utilization rate and reduce the separation energy consumption without increasing the catalyst preparation cost and equipment cost, while improving the anti-sintering characteristics of the catalyst, and has the prospect of large-scale industrial application.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy and petrochemical catalytic materials, and specifically relates to a method for preparing low-carbon esters from methanol and methyl acetate in one step by means of catalyst loading, wherein the low-carbon esters are any one of methyl acrylate, methyl propionate and methyl methacrylate, or a mixture of any of the foregoing. Background Art

[0002] Low-carbon esters are an important class of chemical monomers, including methyl acrylate MA, methyl propionate MP, and methyl methacrylate MMA. Among them, polymers synthesized from MA are widely used in coatings, textiles, adhesives and other fields, and can also be used to produce high-temperature and oil-resistant rubber, activators and synthetic resin monomers; MP is mainly used to prepare fine chemical products such as propionic acid and its related salts, advanced esters and MMA, and as an excellent solvent and additive, it is also widely used in the fields of food and cosmetics; MMA has a wide range of uses, the most important of which is used to synthesize organic glass (PMMA).

[0003] At present, the preparation methods of MA mainly include methanol esterification, acetylene method, ethylene oxidation carbonylation method, propylene oxidation method, acrylonitrile hydrolysis method, acrylone method and propane oxidation method. Among them, the main method used in industrial production is propylene oxidation method, which can be specifically divided into one-step method and two-step method for preparing methyl acrylate. The one-step method is to directly oxidize propylene to produce acrylic acid, and then esterify with methanol to produce methyl acrylate. This method has a series of problems such as low yield, poor catalyst stability and fast deactivation rate; the two-step method is that propylene is first oxidized to acrolein, and then further oxidized to acrylic acid, and finally esterified with methanol to produce methyl acrylate. Although the process flow of this method is long, the catalytic efficiency of each step is high, so that the overall yield is high. However, this process requires the use of a large amount of concentrated sulfuric acid as a catalyst, causing serious equipment corrosion and environmental pollution. In addition, due to the increase in the production cost of propylene as a raw material, scientific researchers have also tried to use propane oxidation to replace direct oxidation of propylene, but due to the disadvantages of low product yield and high cost, this method is still in the laboratory research stage. The acrylonitrile hydrolysis method is to hydrolyze acrylonitrile under the action of sulfuric acid catalyst to generate acrylamide sulfate, and further esterify with methanol to obtain crude methyl acrylate, and then obtain methyl acrylate product after subsequent treatment by salting out, fractionation, etc. This method has the advantages of simple reaction, controllable process, and low equipment investment. However, similar to the direct oxidation of propylene, there are also serious environmental pollution problems. At the same time, the large amount of by-products such as ammonium bisulfate also increases the processing cost. In addition, the ketene method using boron trifluoride as a catalyst has a significant increase in production cost because its raw materials are mainly derived from the high-temperature pyrolysis of acetic acid or acetone, and β-propanolate as a production intermediate is also considered to be a carcinogen, so this method is no longer used by industry.

[0004] The preparation methods of MP mainly include propionic acid and methanol esterification, methanol and n-propanol oxidative esterification, propionaldehyde and methanol oxidative esterification, ethylene carbonylation and ethylene hydroesterification. At present, the industry mainly uses concentrated sulfuric acid to catalyze the esterification reaction of propionic acid and methanol to produce methyl propionate. This method can obtain methyl propionate with a purity of more than 99% through subsequent distillation and extraction, and the yield can reach 95%; but due to its complex process, high equipment investment, and concentrated sulfuric acid will cause equipment corrosion, and will also lead to the production of a large number of by-products, so this process is not green and economical. On this basis, researchers have developed new catalysts such as inorganic acids, ionic liquids, and precious metals, but there are still deficiencies in preparation methods and thermal stability. The methanol and n-propanol oxidative esterification method uses precious metals as catalysts and uses oxygen to directly oxidize propanol and methanol to produce methyl propionate. Under suitable catalysts and reaction conditions, the conversion rate of n-propanol can reach 63%, and the selectivity of methyl propionate can reach 99%. Compared with the technical route of using concentrated sulfuric acid to catalyze the reaction of propionic acid and methanol to produce methyl propionate, this method is more green and economical, and the catalyst is also easy to prepare, but the stability of the catalyst needs to be further improved. In the propionaldehyde and methanol oxidative esterification method, propionaldehyde and methanol can be directly converted into methyl propionate under an oxygen atmosphere. The catalyst is doped with precious metals such as Pb as an auxiliary agent to promote the reaction, which can effectively improve the reaction rate and selectivity. However, this method has greater environmental pollution, and the preparation process of the catalyst is relatively complicated, and the stability needs to be improved. The ethylene carbonylation method is based on Pd(OAc) 2 Or Ru / oxide as catalyst, ethylene, methanol, carbon monoxide as reactants to produce methyl propionate, borate or Bronsted acidic ionic liquid can also be added as a reaction promoter. This method can process cheap and easily available ethylene into high value-added methyl propionate and no corrosive substances are generated during the reaction, which has little harm to the equipment, but using carbon monoxide as a reactant will bring safety hazards in the production process. In addition, since methanol and methyl propionate will form azeotropes, the subsequent separation and purification requirements are high, and the equipment investment cost is increased. The ethylene hydroesterification method also uses ethylene as a raw material to produce methyl propionate. The catalyst used in this technical route is a compound of Pd, Rh and Ru. Compared with the oxidative esterification method, this technical route is more environmentally friendly, has a high atomic utilization rate, and the reactants are cheap and easy to obtain; compared with the carbonylation method, this technical route also omits the carbonylation process of carbon monoxide and methanol, avoiding safety hazards in the production process. However, the reaction conditions of this method are relatively harsh, the preparation method of the catalyst is relatively complicated, the toxicity of the catalyst is relatively large, and the stability needs to be improved.

[0005] The industrial production methods of MMA mainly include the acetone cyanohydrin (ACH) method, isobutylene oxidation method and Alpha method. Among them, the ACH process technology is mature and the process is simple, but there are still problems such as the highly toxic raw material HCN, the use of concentrated sulfuric acid in production, high requirements for equipment corrosion protection, and the by-product NH 4 HSO 4 This brings the disadvantages of increasing processing units and investment. The isobutylene oxidation method prepares methacrylic acid MAA and MMA by oxidizing isobutylene, which has the advantages of high atomic utilization and low environmental harm, but it also has problems such as insufficient raw material supply, complex process flow and low yield of methacrolein MAL to MAA. The Alpha process synthesizes methyl propionate from ethylene, MeOH and CO in the presence of a palladium-based homogeneous catalyst, and then reacts with formaldehyde to directly generate MMA. The reaction conditions of this process are simple, the catalyst activity is high, and the selectivity of MMA is high, but the conversion rate of methyl propionate is low.

[0006] CN108101767A and CN108097286 disclose methods for preparing acrylic acid and methyl acrylate using formaldehyde compounds and carbon monoxide as raw materials; CN111437879A discloses a catalyst and method for preparing methyl acrylate from methyl formate and acetylene; CN108993602A discloses a catalyst for catalyzing ethylene, CO 2 A catalytic system for preparing methyl propionate from methanol, comprising a ruthenium cluster carbonyl complex, an imidazole ionic liquid and an inorganic salt promoter; CN104383918A discloses a method for preparing methyl propionate by hydrogenating methyl acrylate, wherein Ru and Rh are added to form a binary metal active component system; CN104513163A discloses a method for producing methyl methacrylate from methyl acetate and formaldehyde as raw materials using a fluidized bed reactor and a fixed bed reactor in combination; compared with traditional processes, the novel low-carbon ester preparation method reported in the above patents can reduce the discharge of polluted waste liquid while ensuring the selectivity of the final product and the conversion rate of the reactants, but there are still problems such as low catalyst stability, complex preparation method and high cost.

[0007] my country currently has a huge overcapacity in methanol production capacity, so it is very important to develop technologies for the high-value utilization of methanol. If the one-step synthesis of low-carbon esters from methanol and methyl acetate can be achieved, it will bring huge industrial value to the rational and efficient utilization of methanol and the development of low-carbon ester downstream products. Summary of the invention

[0008] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a method for preparing low-carbon esters from methanol and methyl acetate (MeOAc) in one step by a catalyst loading method, wherein methanol reacts at a dehydrogenation active site to generate formaldehyde and hydrogen, and then formaldehyde further reacts with methyl acetate at an aldol condensation active site to generate MA, which can be converted into MP by hydrogen removed from methanol, and MP can further aldol condense with formaldehyde FA after dehydrogenation to generate MMA, thereby ultimately achieving the purpose of generating a series of low-carbon esters. The method converts the traditional industrial production mode of multiple reactors in series into a "relay catalysis" production mode in one reactor, greatly reducing the equipment investment cost, and can effectively further process methanol into high value-added products.

[0009] The technical solution adopted by the present invention is as follows:

[0010] A method for preparing low-carbon esters by one-step process of methanol and methyl acetate comprises the following steps:

[0011] (1) two different catalysts, a first catalyst A and a second catalyst B, are loaded in a tubular fixed bed reactor in different orders, methods and proportions;

[0012] The active component of the first catalyst A is Cu, and has the general formula shown in formula (I):

[0013] Cu / oxide formula (I);

[0014] The active component of the second catalyst B is Cs, which has the general formula (II):

[0015] Cs / oxide formula (II);

[0016] The first catalyst A and the second catalyst B are loaded in the tubular fixed bed reactor in the following manner: A and B are loaded after being mechanically evenly mixed; or A is loaded at the inlet or outlet of the reactor, and B is loaded at the other end; or A and B are loaded at the inlet or outlet of the reactor after being mechanically evenly mixed, and B is loaded at the other end.

[0017] (2) Continuously introducing methanol and methyl acetate as raw materials into the above-mentioned tubular fixed bed reactor loaded with the catalyst to synthesize low-carbon esters in one step.

[0018] The present invention is further configured such that the first catalyst A and the second catalyst B are loaded in the tubular fixed bed reactor in the following manner:

[0019] A and B are mixed uniformly mechanically and then filled;

[0020] A and B are respectively loaded at the inlet and outlet of the reactor;

[0021] A and B are respectively loaded at the outlet and inlet of the reactor;

[0022] A and B are mechanically mixed uniformly and then loaded with B at the inlet and outlet of the reactor respectively; or

[0023] After A and B are uniformly mixed mechanically, A and B are respectively loaded at the outlet and inlet of the reactor.

[0024] The present invention is further configured that the first catalyst A and the second catalyst B use oxides as catalyst carriers, which are selected from but not limited to one or more of titanium dioxide, cerium dioxide, and silicon dioxide, and are preferably silicon dioxide.

[0025] The present invention is further configured such that the loading mass ratio of the first catalyst A to the second catalyst B is 4:1 to 1:11, preferably 1:1 to 1:11; the total loading mass of the first catalyst A and the second catalyst B is 0.1 to 0.6 g, preferably 0.2 to 0.4 g.

[0026] The present invention is further configured such that the feeding method of methanol and methyl acetate is co-feeding, and nitrogen is used as a carrier gas to carry the reactant raw materials into the reactor by bubbling. The flow rate of the carrier gas is controlled to be 15 to 25 sccm; the molar ratio of methanol to methyl acetate in the carrier gas is controlled to be 1:4 to 4:1 (mol:mol), preferably 1:2 to 2:1 (mol:mol).

[0027] The present invention is further configured such that the reaction temperature in the tubular fixed bed reactor is controlled within a range of 250 to 400°C, preferably 300 to 400°C.

[0028] The present invention is further configured such that when the target product of the relay catalysis is MA, the first catalyst A and the second catalyst B are preferably loaded in the tubular fixed bed reactor in such a manner that A and B are loaded at the inlet and outlet of the reactor respectively.

[0029] Furthermore, the loading mass ratio of the first catalyst A and the second catalyst B is 1:1 to 1:5, preferably 1:3; the flow rate of the carrier gas is controlled to be 15 to 25 sccm, and the ratio of methanol to methyl acetate in the carrier gas is 1:2 to 2:1 (mol:mol), preferably 2:1 (mol:mol); the reaction temperature in the shell-and-tube fixed bed reactor is 300 to 400°C, preferably 300 to 375°C.

[0030] The present invention is further configured such that, when the target product of the relay catalysis is MP, the first catalyst A and the second catalyst B are preferably loaded in the tubular fixed bed reactor in such a manner that A and B are mechanically evenly mixed and then loaded.

[0031] Furthermore, the loading mass ratio of the first catalyst A and the second catalyst B is 1:1 to 1:7, preferably 1:3 to 1:5; the flow rate of the carrier gas is controlled to be 15 to 25 sccm, preferably 15 sccm, and the ratio of methanol to methyl acetate in the carrier gas is 1:2 to 2:1 (mol:mol), preferably 2:1 (mol:mol); the reaction temperature in the shell-and-tube fixed bed reactor is preferably 300 to 375°C.

[0032] The present invention is further configured such that, when the target product of the required relay catalysis is MMA, the first catalyst A and the second catalyst B are preferably loaded in the tubular fixed bed reactor in such a manner that A and B are mechanically evenly mixed and then loaded at the inlet and outlet of the reactor respectively.

[0033] Furthermore, the filling mass ratio of the first catalyst A and the second catalyst B is preferably 1:5-1:11, and the filling mass ratio of the first catalyst A and the second catalyst B in the mixed layer is 1:1-1:5, preferably 1:3, the filling mass ratio of the first catalyst A and the second catalyst B on the outlet side is 1:4-1:8, the flow rate of the carrier gas is controlled to be 15sccm, the ratio of methanol to methyl acetate in the carrier gas is 1:2-2:1 (mol:mol), preferably 2:1 (mol:mol); the reaction temperature in the shell-and-tube fixed bed reactor is preferably 325-400°C.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) Compared with the existing multi-step process for generating low-carbon esters, the present invention can significantly shorten the process flow by adjusting the two catalyst loading methods, using methanol and methyl acetate as raw materials, and catalytically synthesizing low-carbon esters in one step, without increasing the catalyst preparation cost and equipment cost. The atomic utilization rate in the reaction is greatly improved, and the production cost of low-carbon esters is greatly reduced; in addition, by coupling the methanol dehydrogenation and the aldol condensation reaction of methyl acetate, on the one hand, the intermediate product formaldehyde can react quickly with methyl acetate, thereby promoting the thermodynamic equilibrium of the methanol dehydrogenation reaction to move toward the product direction; on the other hand, by matching the dehydrogenation and aldol condensation reaction rates, the toxic side reactions of the aldol condensation reaction intermediates can be effectively suppressed, thereby suppressing the coking of the catalyst surface and improving the catalytic stability.

[0036] (2) Compared with the existing technical solutions of two-stage or multi-stage serial tube-in-tube fixed-bed reactors, the method for loading the two catalysts provided by the present invention has obvious advantages in terms of reactor manufacturing cost and safety hazard control, and is environmentally friendly, less polluting, and has abundant raw material sources and low prices. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1The present invention is a schematic diagram of a simple device for preparing low-carbon esters by one-step synthesis of methanol and methyl acetate.

[0038] Figure 2 The schematic diagrams are of three loading methods of the catalyst of the present invention in the reactor. These are only preferred loading methods of the present invention, not the only three loading methods shown in the figure. DETAILED DESCRIPTION

[0039] After extensive and in-depth research, the inventors have invented a method for synthesizing low-carbon esters in one step by reacting methanol with methyl acetate through a catalyst loading method. The method is mainly based on the direct dehydrogenation of methanol to prepare anhydrous formaldehyde and the aldol condensation reaction of formaldehyde and methyl acetate to generate MA and a series of products. The method shows the feasibility of synthesizing low-carbon esters in one step. On this basis, the goal of synthesizing low-carbon esters in one step is achieved by using oxides as carriers, Cu, Cs, etc. as catalyst active components and using a specific catalyst loading method.

[0040] The reaction method of the present invention is gas-solid phase catalysis in a fixed bed reactor. Figure 1 As shown, the reaction device includes a carrier gas bottle 1, a gas flow meter 2, a wash bottle 3, a vaporization chamber 5 and a shell-and-tube fixed bed reactor 6 which are connected in sequence. The wash bottle 3 is placed in a low-temperature constant temperature bath 4. The inlet and outlet of the wash bottle 3 are respectively connected to a tee 8, and the two tees 8 are connected to form a bypass for the carrier gas to pass directly without carrying the reaction raw materials. The outlet of the shell-and-tube fixed bed reactor 6 is connected to a gas chromatograph 7 to analyze the composition of the outlet gas phase product online.

[0041] The raw materials required for the reaction are methanol and methyl acetate solution. Methanol and methyl acetate are mixed evenly in a volume ratio (ml / ml) of 1:2-10:1, and the resulting solution is loaded into a gas washing bottle 3, and the temperature of the low temperature constant temperature bath 4 is set to -10 to 10°C. The carrier gas is preferably nitrogen, which is directly introduced into the reactor 6 from a bypass and gradually heated to the reaction temperature. After the temperature of the reactor 6 and the temperature of the low temperature constant temperature bath 4 are stabilized, nitrogen flows through the gas washing bottle 3 to pass the raw materials methanol and methyl acetate into the reactor 6 along with the carrier gas, and when the mixed gas contacts the catalyst, the reaction begins to obtain a low carbon ester.

[0042] In the reaction of synthesizing low-carbon esters by reacting methanol and methyl acetate in one step, economical and green Cu-based catalysts and Cs-based catalysts are selected, and the catalysts are prepared by conventional methods in the art, wherein the Cu-based catalyst is preferably prepared by an ammonia evaporation method, and the Cs-based catalyst is preferably prepared by an equal volume impregnation method.

[0043] The prepared Cu-based catalyst and Cs-based catalyst are loaded into the reactor tubes in different mass ratios through different mixed loading methods. The mixed loading method is that the Cu-based catalyst and the Cs-based catalyst are loaded in two layers, or completely mixed after mechanical mixing, or part of the Cu-based catalyst and the Cs-based catalyst are mechanically mixed and then loaded in layers with the Cs-based catalyst. Figure 2 As shown, they are schematic diagrams of preferred loading methods when the target products of the desired relay catalysis are MA, MP and MMA. The catalyst layers of the layered loading may be physically spaced or not physically spaced. The layer spacing lines in the figure are only schematic diagrams of the layers.

[0044] The technical scheme of the present invention is described clearly and completely with specific embodiments below. It should be understood that the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Unless otherwise stated, all percentages, ratios, proportions, or parts are by weight. Unless otherwise defined, all professional and scientific terms used in the text have the same meaning as those familiar to those skilled in the art.

[0045] Example 1

[0046] In this embodiment, the Cu-based catalyst is prepared by the ammonia evaporation method: 10% of the active component Cu is loaded on the silicon oxide carrier; the Cs-based catalyst is prepared by the equal volume impregnation method: 10% of the active component Cs is loaded on the silicon oxide carrier.

[0047] In a fixed-bed continuous flow reactor, 0.05 g of each Cu-based catalyst and Cs-based catalyst were weighed and loaded into the constant temperature section of the reaction tube in a completely mechanically mixed manner, and quartz wool was placed at the upper and lower ends thereof to form a multifunctional catalyst system.

[0048] Setting N 2 The flow rate is 25 sccm, and the temperature is increased to 300°C at a heating rate of 5°C / min. At the same time, the low-temperature thermostat is turned on and the temperature is set to 0°C. After the temperature of the reactor and the thermostat is stable, nitrogen is introduced through the gas washing bottle to bring in the raw materials methanol and methyl acetate. At this time, the molar ratio of methanol and methyl acetate is 1:2. When the mixed gas contacts the catalyst and starts to react, low-carbon esters are obtained. The composition of the outlet gas phase product is analyzed online by gas chromatography, where the FID connected to the capillary column is used to detect MA, MP, MMA, etc., and the TCD connected to the filling column is used to detect CO, H 2The reaction activity of the catalyst is represented by the conversion rate of MeOAc, and the selectivity is represented by the percentage (%C) of methyl acetate converted to products such as MMA, MA, and MP.

[0049] Example 2

[0050] The preparation and loading methods of the catalyst are the same as those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.1 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 1.

[0051] Example 3

[0052] The preparation and loading methods of the catalyst are the same as those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.15 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 1.

[0053] Example 4

[0054] The preparation and loading methods of the catalyst are the same as those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.2 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 1.

[0055] Example 5

[0056] The preparation and loading methods of the catalyst are consistent with those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.15 g. The reaction steps of methanol and methyl acetate are also consistent with those in Example 1, except that the molar ratio of the methanol and methyl acetate raw materials is 1:1.

[0057] Example 6

[0058] The preparation and loading methods of the catalyst are consistent with those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.15 g. The reaction steps of methanol and methyl acetate are also consistent with those in Example 1, except that the molar ratio of the methanol and methyl acetate raw materials is 2:1.

[0059] Example 7

[0060] In this embodiment, the Cu-based catalyst is prepared by the ammonia evaporation method: 10% of the active component Cu is loaded on the silicon oxide carrier; the Cs-based catalyst is prepared by the equal volume impregnation method: 10% of the active component Cs is loaded on the silicon oxide carrier.

[0061] In a fixed bed continuous flow reactor, 0.05 g of Cu-based catalyst was placed at the outlet of the reactor's constant temperature section, 0.15 g of Cs-based catalyst was placed at the inlet of the reactor's constant temperature section, and quartz wool was placed at both ends to form a multifunctional catalyst system.

[0062] Setting N 2 The flow rate is 25 sccm, and the temperature is increased to 300°C at a heating rate of 5°C / min. At the same time, the low-temperature thermostat is turned on and the temperature is set to 0°C. After the temperature of the reactor and the thermostat is stable, nitrogen is introduced through the gas washing bottle to bring in the raw materials methanol and methyl acetate. At this time, the molar ratio of methanol and methyl acetate is 2:1. When the mixed gas contacts the catalyst and starts to react, low-carbon esters are obtained. The composition of the outlet gas phase product is analyzed online by gas chromatography, where the FID connected to the capillary column is used to detect MA, MP, MMA, etc., and the TCD connected to the filling column is used to detect CO, H 2 The reaction activity of the catalyst is represented by the conversion rate of MeOAc, and the selectivity is represented by the percentage (%C) of methyl acetate converted to products such as MMA, MA, and MP.

[0063] Example 8

[0064] The preparation method and loading method of the catalyst are the same as those in Example 7. The reaction steps of methanol and methyl acetate are the same as those in Example 1, except that N 2 The flow rate was 15 sccm, and the temperature was increased to 350°C at a ramp rate of 5°C / min.

[0065] Example 9

[0066] In this embodiment, the Cu-based catalyst is prepared by the ammonia evaporation method: 10% of the active component Cu is loaded on the silicon oxide carrier; the Cs-based catalyst is prepared by the equal volume impregnation method: 10% of the active component Cs is loaded on the silicon oxide carrier.

[0067] In a fixed bed continuous flow reactor, 0.05 g of Cu-based catalyst was placed at the inlet of the reactor's constant temperature section, 0.15 g of Cs-based catalyst was placed at the outlet of the reactor's constant temperature section, and quartz wool was placed at both ends to form a multifunctional catalyst system.

[0068] Setting N 2 The flow rate is 25 sccm, and the temperature is increased to 300°C at a heating rate of 5°C / min. At the same time, the low-temperature thermostat is turned on and the temperature is set to 0°C. After the temperature of the reactor and the thermostat is stable, nitrogen is introduced through the gas washing bottle to bring in the raw materials methanol and methyl acetate. At this time, the molar ratio of methanol and methyl acetate is 2:1. When the mixed gas contacts the catalyst and starts to react, low-carbon esters are obtained. The composition of the outlet gas phase product is analyzed online by gas chromatography, where the FID connected to the capillary column is used to detect MA, MP, MMA, etc., and the TCD connected to the filling column is used to detect CO, H 2 The reaction activity of the catalyst is represented by the conversion rate of MeOAc, and the selectivity is represented by the percentage (%C) of methyl acetate converted to products such as MMA, MA, and MP.

[0069] Example 10

[0070] The preparation and loading method of the catalyst is the same as that in Example 9. The reaction steps of methanol and methyl acetate are also the same as those in Example 9, except that N is set 2 It is heated to 400 °C at a heating rate of 5 °C / min.

[0071] Example 11

[0072] The preparation and loading method of the catalyst is the same as that in Example 9. The reaction steps of methanol and methyl acetate are also the same as those in Example 9, except that N is set 2 It is heated to 350 °C at a heating rate of 5 °C / min.

[0073] Example 12

[0074] The preparation and loading method of the catalyst is the same as that in Example 9. The reaction steps of methanol and methyl acetate are also the same as those in Example 9, except that N is set 2 The flow rate is 20 sccm, and it is heated to 350 °C at a heating rate of 5 °C / min.

[0075] Example 13

[0076] The preparation and loading method of the catalyst is the same as that in Example 9. The reaction steps of methanol and methyl acetate are also the same as those in Example 9, except that N is set 2 The flow rate is 15 sccm, and it is heated to 325 °C at a heating rate of 5 °C / min.

[0077] Example 14

[0078] The preparation and loading method of the catalyst is the same as that in Example 9. The reaction steps of methanol and methyl acetate are also the same as those in Example 9, except that N is set 2 The flow rate is 15 sccm, and it is heated to 350 °C at a heating rate of 5 °C / min.

[0079] Example 15

[0080] The preparation and loading method of the catalyst is the same as that in Example 9. The reaction steps of methanol and methyl acetate are also the same as those in Example 9, except that N is set 2 The flow rate is 15 sccm, and it is heated to 375 °C at a heating rate of 5 °C / min.

[0081] Example 16

[0082] The preparation and loading method of the catalyst is the same as that in Example 9. The reaction steps of methanol and methyl acetate are also the same as those in Example 9, except that N is set 2 The flow rate is 15 sccm, and it is heated to 400 °C at a heating rate of 5 °C / min.

[0083] Embodiment 17

[0084] The preparation and loading methods of the catalysts are the same as those in Example 9, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.05 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 9, except that N 2 The flow rate was 15 sccm, and the temperature was increased to 350°C at a ramp rate of 5°C / min.

[0085] Embodiment 18

[0086] The preparation and loading methods of the catalysts are the same as those in Example 9, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.25 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 9, except that N 2 The flow rate was 15 sccm, and the temperature was increased to 350°C at a ramp rate of 5°C / min.

[0087] Embodiment 19

[0088] The preparation and loading methods of the catalyst are the same as those in Example 9. The reaction steps of methanol and methyl acetate are also the same as those in Example 9, except that N 2 The flow rate was 15 sccm, the temperature was raised to 350°C at a heating rate of 5°C / min, and the molar ratio of methanol to methyl acetate raw materials was 1:2.

[0089] Embodiment 20

[0090] The preparation and loading methods of the catalyst are the same as those in Example 9. The reaction steps of methanol and methyl acetate are also the same as those in Example 9, except that N 2 The flow rate was 15 sccm, the temperature was raised to 350°C at a heating rate of 5°C / min, and the molar ratio of methanol to methyl acetate raw materials was 1:1.

[0091] Embodiment 21

[0092] The preparation and loading methods of the catalyst are the same as those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.15 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 1, except that N 2 The flow rate was 15 sccm, the temperature was raised to 325°C at a heating rate of 5°C / min, and the molar ratio of methanol to methyl acetate raw materials was 2:1.

[0093] Embodiment 22

[0094] The preparation and loading methods of the catalyst are the same as those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.15 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 1, except that N 2 The flow rate was 15 sccm, the temperature was raised to 350°C at a rate of 5°C / min, and the molar ratio of methanol to methyl acetate raw materials was 2:1.

[0095] Embodiment 23

[0096] The preparation and loading methods of the catalyst are the same as those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.15 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 1, except that N 2 The flow rate was 15 sccm, the temperature was raised to 375°C at a heating rate of 5°C / min, and the molar ratio of methanol to methyl acetate raw materials was 2:1.

[0097] Embodiment 24

[0098] The preparation and loading methods of the catalyst are the same as those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.35 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 1, except that N 2 The flow rate was 15 sccm, the temperature was raised to 350°C at a rate of 5°C / min, and the molar ratio of methanol to methyl acetate raw materials was 2:1.

[0099] Embodiment 25

[0100] The preparation and loading methods of the catalyst are the same as those in Example 1. The reaction steps of methanol and methyl acetate are also the same as those in Example 1, except that N 2 The flow rate was 15 sccm, the temperature was raised to 350°C at a rate of 5°C / min, and the molar ratio of methanol to methyl acetate raw materials was 2:1.

[0101] Embodiment 26

[0102] The preparation and loading methods of the catalyst are the same as those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.25 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 1, except that N 2 The flow rate was 15 sccm, the temperature was raised to 350°C at a rate of 5°C / min, and the molar ratio of methanol to methyl acetate raw materials was 2:1.

[0103] Embodiment 27

[0104] The preparation and loading methods of the catalyst are the same as those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.15 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 1, except that N 2 The flow rate was 15 sccm, and the temperature was increased to 350°C at a ramp rate of 5°C / min.

[0105] Embodiment 28

[0106] The preparation and loading methods of the catalyst are the same as those in Example 1, except that the loading amount of the Cu-based catalyst is 0.05 g and the loading amount of the Cs-based catalyst is 0.15 g. The reaction steps of methanol and methyl acetate are also the same as those in Example 1, except that N 2 The flow rate was 15 sccm, the temperature was raised to 350°C at a heating rate of 5°C / min, and the molar ratio of methanol to methyl acetate raw materials was 1:1.

[0107] Embodiment 29

[0108] In this embodiment, the Cu-based catalyst is prepared by the ammonia evaporation method: 10% of the active component Cu is loaded on the silicon oxide carrier; the Cs-based catalyst is prepared by the equal volume impregnation method: 10% of the active component Cs is loaded on the silicon oxide carrier.

[0109] In a fixed-bed continuous flow reactor, 0.05 g of Cu-based catalyst and 0.15 g of Cs-based catalyst were loaded into the inlet of the constant temperature section of the reactor by completely mechanical mixing, 0.2 g of Cs-based catalyst was placed at the outlet of the constant temperature section of the reactor, and quartz wool was placed at the upper and lower ends thereof to form a multifunctional catalyst system.

[0110] Setting N 2 The flow rate is 15 sccm, and the temperature is increased to 325°C at a heating rate of 5°C / min. At the same time, the low-temperature thermostat is turned on and the temperature is set to 0°C. After the temperature of the reactor and the thermostat is stable, nitrogen is introduced through the gas washing bottle to bring in the raw materials methanol and methyl acetate. At this time, the molar ratio of methanol and methyl acetate is 2:1. When the mixed gas contacts the catalyst and starts to react, low-carbon esters are obtained. The composition of the outlet gas phase product is analyzed online by gas chromatography, where the FID connected to the capillary column is used to detect MA, MP, MMA, etc., and the TCD connected to the filling column is used to detect CO, H 2 The reaction activity of the catalyst is represented by the conversion rate of MeOAc, and the selectivity is represented by the percentage (%C) of methyl acetate converted to products such as MMA, MA, and MP.

[0111] Embodiment 30

[0112] The preparation and loading methods of the catalyst are the same as those in Example 29. The reaction steps of methanol and methyl acetate are also the same as those in Example 29, except that N2 The temperature was raised to 350°C at a heating rate of 5°C / min.

[0113] Embodiment 31

[0114] The preparation and loading methods of the catalyst are the same as those in Example 29. The reaction steps of methanol and methyl acetate are also the same as those in Example 29, except that N 2 The temperature was raised to 375°C at a heating rate of 5°C / min.

[0115] Embodiment 32

[0116] The preparation and loading methods of the catalyst are the same as those in Example 29. The reaction steps of methanol and methyl acetate are also the same as those in Example 29, except that N 2 The temperature was raised to 400°C at a heating rate of 5°C / min.

[0117] Embodiment 33

[0118] The preparation and loading methods of the catalyst are the same as those in Example 29, except that 0.05 g of Cu-based catalyst and 0.15 g of Cs-based catalyst are loaded into the inlet of the constant temperature section of the reactor by completely mechanical mixing, and 0.3 g of Cs-based catalyst is placed at the outlet of the constant temperature section of the reactor.

[0119] The reaction steps of methanol and methyl acetate are also the same as those in Example 29, except that N 2 The temperature was raised to 350°C at a heating rate of 5°C / min.

[0120] Embodiment 34

[0121] The preparation and loading methods of the catalyst are the same as those in Example 29, except that 0.05 g of Cu-based catalyst and 0.15 g of Cs-based catalyst are loaded into the inlet of the constant temperature section of the reactor by completely mechanical mixing, and 0.4 g of Cs-based catalyst is placed at the outlet of the constant temperature section of the reactor.

[0122] The reaction steps of methanol and methyl acetate are also the same as those in Example 29, except that N 2 The temperature was raised to 350°C at a heating rate of 5°C / min.

[0123] Embodiment 35

[0124] The preparation and loading methods of the catalyst are the same as those in Example 29, except that 0.05 g of Cu-based catalyst and 0.05 g of Cs-based catalyst are loaded into the inlet of the constant temperature section of the reactor by completely mechanical mixing, and 0.2 g of Cs-based catalyst is placed at the outlet of the constant temperature section of the reactor.

[0125] The reaction steps of methanol and methyl acetate are also the same as those in Example 29, except that N2 The temperature was raised to 350°C at a heating rate of 5°C / min.

[0126] Embodiment 36

[0127] The preparation and loading methods of the catalyst are the same as those in Example 29, except that 0.05 g of Cu-based catalyst and 0.25 g of Cs-based catalyst are loaded into the inlet of the constant temperature section of the reactor by completely mechanical mixing, and 0.2 g of Cs-based catalyst is placed at the outlet of the constant temperature section of the reactor.

[0128] The reaction steps of methanol and methyl acetate are also the same as those in Example 29, except that N 2 The temperature was raised to 350°C at a heating rate of 5°C / min.

[0129] Embodiment 37

[0130] The preparation and loading methods of the catalyst are the same as those in Example 29. The reaction steps of methanol and methyl acetate are also the same as those in Example 29, except that N 2 The temperature was raised to 350°C at a rate of 5°C / min, and the molar ratio of methanol to methyl acetate was 1:2.

[0131] Embodiment 38

[0132] The preparation and loading methods of the catalyst are the same as those in Example 29. The reaction steps of methanol and methyl acetate are also the same as those in Example 29, except that N 2 The temperature was raised to 350°C at a rate of 5°C / min, and the molar ratio of methanol to methyl acetate was 1:1.

[0133] Embodiment 39

[0134] The preparation of the catalyst was consistent with Example 29. The filling method was as follows: in a fixed bed continuous flow reactor, 0.05 g of Cu-based catalyst and 0.15 g of Cs-based catalyst were loaded into the outlet of the constant temperature section of the reactor by completely mechanical mixing, 0.2 g of Cs-based catalyst was placed at the inlet of the constant temperature section of the reactor, and quartz wool was placed at the upper and lower ends thereof to form a multifunctional catalyst system.

[0135] The reaction steps of methanol and methyl acetate are also the same as those in Example 29, except that N 2 The temperature was raised to 350°C at a heating rate of 5°C / min.

[0136] The low carbon esters obtained in Examples 1 to 39 were analyzed by gas-mass spectrometry and gas chromatography, and the results were compared to obtain Table 1. When the target product of the desired relay catalysis is MA, the preferred loading method is that the Cu-based catalyst and the Cs-based catalyst are loaded at the inlet and outlet of the reactor respectively; when the target product of the desired relay catalysis is MP, the preferred loading method is that the Cu-based catalyst and the Cs-based catalyst are mechanically uniformly mixed and then loaded; when the target product of the desired relay catalysis is MMA, the preferred loading method is that the Cu-based catalyst and the Cs-based catalyst are mechanically uniformly mixed and then loaded with the Cs-based catalyst at the inlet and outlet of the reactor respectively.

[0137] More preferably, a mixed solution of methanol and methyl acetate is used as a raw material, a Cu-based catalyst and a Cs-based catalyst are mechanically mixed in a certain proportion and then loaded into the inlet end of the constant temperature section of the reactor, and then a certain amount of Cs-based catalyst is loaded into the outlet end of the constant temperature section of the reactor. Under appropriate reaction conditions, a series of low-carbon esters can be synthesized by one-step reaction, which provides a new idea for the industrial production of low-carbon esters.

[0138] Table 1 Experimental results of preparing low carbon esters by coupling methanol and methyl acetate under different reaction conditions

[0139]

[0140]

[0141] This application is described in detail for the purpose of enabling those skilled in the art to understand the contents of this application and implement them. This is not intended to limit the scope of protection of this application. Any equivalent changes or modifications made according to the spirit of this application should be included in the scope of protection of this application.

Claims

1. A method for preparing low-carbon esters by one-step process of methanol and methyl acetate, It is characterized in that The steps include: (1) A first catalyst A and a second catalyst B are loaded in a tubular fixed bed reactor, wherein the active component of the first catalyst A is Cu, and the active component of the second catalyst B is Cs, and the loading method is: A and B are loaded after being mechanically uniformly mixed; or A is loaded at the inlet or outlet of the reactor, and B is loaded at the other end; or A and B are loaded at the inlet or outlet of the reactor after being mechanically uniformly mixed, and B is loaded at the other end; The loading mass ratio of the first catalyst A to the second catalyst B is 4:1 to 1:11; (2) continuously introducing methanol and methyl acetate as raw materials into a tubular fixed bed reactor loaded with a catalyst to synthesize low-carbon esters in one step, wherein the low-carbon esters are methyl acrylate, methyl propionate and methyl methacrylate; Among them, the feeding method of methanol and methyl acetate is co-feeding, and nitrogen is used as a carrier gas to carry the reactant raw materials into the reactor by bubbling, and the flow rate of the carrier gas is controlled to be 15~25 sccm; the molar ratio of methanol to methyl acetate in the carrier gas is controlled to be 1:4~4:1, and the reaction temperature in the shell-and-tube fixed bed reactor is controlled to be 250~400 ℃.

2. The method for preparing low-carbon esters by one-step method according to claim 1, It is characterized in that The first catalyst A and the second catalyst B use oxides as catalyst carriers, which are selected from one or more of titanium dioxide, cerium dioxide, and silicon dioxide.

3. The method for preparing low-carbon esters by one step according to claim 1, It is characterized in that The loading mass ratio of the first catalyst A to the second catalyst B is 1:1-1:

11.

4. The method for preparing low-carbon esters by one step according to claim 1, It is characterized in that The molar ratio of methanol to methyl acetate in the carrier gas is controlled to be 1:2~2:1; the reaction temperature in the shell-and-tube fixed bed reactor is controlled to be 300~400 ℃.

5. The method for preparing low-carbon esters in one step according to claim 1, It is characterized in that When the target product of the relay catalysis is MA, the first catalyst A and the second catalyst B are loaded in the tubular fixed bed reactor in the following manner: A and B are loaded at the inlet and outlet of the reactor respectively.

6. The method for preparing low-carbon esters in one step according to claim 5, It is characterized in that The loading mass ratio of the first catalyst A and the second catalyst B is 1:1-1:5; the flow rate of the carrier gas is controlled to be 15-25 sccm, and the molar ratio of methanol to methyl acetate in the carrier gas is 1:2-2:1; the reaction temperature in the shell-and-tube fixed bed reactor is 300-400°C.

7. The method for preparing low-carbon esters by one step according to claim 1, It is characterized in that When the target product of the relay catalysis is MP, the first catalyst A and the second catalyst B are loaded into the tubular fixed bed reactor in the following manner: A and B are mechanically evenly mixed and then loaded.

8. The method for preparing low-carbon esters by one step according to claim 7, It is characterized in that The loading mass ratio of the first catalyst A and the second catalyst B is 1:1 to 1:7; the flow rate of the carrier gas is controlled to be 15 to 25 sccm, and the molar ratio of methanol to methyl acetate in the carrier gas is 1:2 to 2:1; the reaction temperature in the tubular fixed-bed reactor is 300 to 375 °C.

9. The one-step method for preparing lower-carbon esters according to claim 1, characterized in that when the target product requiring relay catalysis is MMA, the loading method of the first catalyst A and the second catalyst B in the tubular fixed-bed reactor is: after A and B are mechanically and uniformly mixed, A and B are respectively loaded at the inlet end and the outlet end of the reactor.

10. The one-step method for preparing lower-carbon esters according to claim 9, characterized in that the loading mass ratio of the first catalyst A and the second catalyst B is 1:5 to 1:11, and the loading mass ratio of the two in the mixed layer of the first catalyst A and the second catalyst B is 1:1 to 1:5; the flow rate of the carrier gas is controlled to be 15 sccm, and the molar ratio of methanol to methyl acetate in the carrier gas is 1:2 to 2:1; the reaction temperature in the tubular fixed-bed reactor is 325 to 400 °C.

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