Process for the preparation of oxalate esters using an adiabatic fixed bed reactor

Abstract

The present application relates to oxalate preparation technical field, disclose a kind of preparation of oxalate using adiabatic fixed bed reactor method, the method includes the following steps: (1) first CO and nitrite-containing material are introduced into first adiabatic fixed bed reactor and carry out first stage carbonylation reaction;(2) the first stage carbonylation reaction product is separated by gas-liquid separator to obtain first gas phase mixture, second CO and first gas phase mixture are introduced into second adiabatic fixed bed reactor and carry out second stage carbonylation reaction;Optionally, (3) the N-1 stage carbonylation reaction product is separated by gas-liquid separator to obtain N-1 gas phase mixture, N CO and N-1 gas phase mixture are introduced into N adiabatic fixed bed reactor and carry out N stage carbonylation reaction;Wherein, N=3.The method of the present application can be loaded with catalyst in the case of facilitating, reduce equipment investment, to ensure the selectivity and yield of oxalate.

Description

Technical Field

[0001] This invention relates to the field of oxalate preparation technology, and more specifically to a method for preparing oxalate using an adiabatic fixed-bed reactor. Background Technology

[0002] Ethylene glycol is an important raw material for the production of polyester fibers, polyester resins, and antifreeze. In recent years, with the rapid development of the domestic polyester industry, my country has become the world's largest consumer of ethylene glycol, accounting for more than 50% of the global market.

[0003] Significant progress has been made in the domestic syngas-to-ethylene glycol process. Currently, the industrial syngas-to-ethylene glycol process uses an indirect route with oxalate ester as an intermediate. This route has advantages such as low cost, low energy consumption, low water consumption, and low emissions. In this process, CO first reacts with nitrite ester in a gas-phase coupling reaction on a supported Pd-based catalyst to generate oxalate ester. Then, the oxalate ester is hydrogenated to obtain the product ethylene glycol (HOCH2CH2OH, EG). In addition to ethylene glycol, oxalate ester is also widely used as an intermediate in the production of oxalic acid, ammonium oxalate, and some pharmaceuticals and dyes, with broad industrial applications.

[0004] The process of preparing oxalate esters via CO gas-phase coupling was first developed by Ube Industries, Ltd. of Japan and Monte Édison of Italy in 1978. In China, institutions that have conducted extensive research on this process include the Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences; the Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences; Tianjin University; East China University of Science and Technology; and Zhejiang University. Industrially, CO gas-phase coupling devices mostly employ catalysts with α-Al₂O₃ as the support and Pd as the main active component. Related patent applications include CN1141179C, CN101138722A, and CN101851160A.

[0005] Since the CO carbonylation coupling to oxalate is an exothermic reaction, industrial CO carbonylation coupling units mostly employ tubular fixed-bed reactors, achieving heat removal through heat exchange with the coolant outside the tubes. However, tubular reactors suffer from problems such as low single-pass feed conversion, low product space-time yield, large reactor size, difficulties in catalyst loading, and high equipment investment. Therefore, it is essential to provide a low-cost, high-space-time yield CO gas-phase coupling method. Summary of the Invention

[0006] The purpose of this invention is to overcome the aforementioned problems in the prior art and to provide a method for preparing oxalate using an adiabatic fixed-bed reactor.

[0007] To achieve the above objectives, the present invention provides a method for preparing oxalate using an adiabatic fixed-bed reactor. The method involves a continuous carbonylation reaction in an apparatus comprising at least two adiabatic fixed-bed reactors connected in series, each reactor being packed with a catalyst, and a condenser and a gas-liquid separator being provided between adjacent reactors. The method includes the following steps:

[0008] (1) The first CO and the material containing nitrite esters are fed into the first adiabatic fixed bed reactor to carry out the first carbonylation reaction;

[0009] (2) The first carbonylation reaction product is separated by a gas-liquid separator to obtain a first gas phase mixture. The second CO and the first gas phase mixture are then fed into a second adiabatic fixed-bed reactor to carry out the second carbonylation reaction.

[0010] Optionally, (3) the carbonylation reaction product of the N-1th stage is separated by a gas-liquid separator to obtain the N-1th gas phase mixture, and the Nth CO and the N-1th gas phase mixture are fed into the Nth adiabatic fixed bed reactor to carry out the Nth stage carbonylation reaction; wherein, N≥3.

[0011] The method of this invention can ensure the selectivity and yield of oxalate esters while facilitating catalyst loading and reducing equipment investment. Compared with tubular reactor systems, the device of this invention has a smaller footprint, saving industrial land costs. Attached Figure Description

[0012] Figure 1 The in-situ infrared spectra of pyrrole adsorption of the catalyst AH prepared in the examples and comparative examples are shown.

[0013] Figure 2 The in-situ infrared spectrum of pyrrole adsorption of catalyst E over time is shown. In the spectrum, 0 min represents the infrared absorption curve after nitrogen purging ends; 4 min, 6 min, and 10 min are the infrared absorption curves at the 4th, 6th, and 10th min of pyrrole adsorption; and 25 min is the infrared absorption curve 15 min after nitrogen purging ends pyrrole adsorption. Detailed Implementation

[0014] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0015] This invention provides a method for preparing oxalate using an adiabatic fixed-bed reactor. The method involves a carbonylation reaction carried out in an apparatus comprising at least two adiabatic fixed-bed reactors connected in series. Each adiabatic fixed-bed reactor is packed with a catalyst, and a condenser and a gas-liquid separator are provided between adjacent adiabatic fixed-bed reactors. The method includes the following steps:

[0016] (1) The first CO and the material containing nitrite esters are fed into the first adiabatic fixed bed reactor to carry out the first carbonylation reaction;

[0017] (2) The first carbonylation reaction product is separated by a gas-liquid separator to obtain a first gas phase mixture. The second CO and the first gas phase mixture are then fed into a second adiabatic fixed-bed reactor to carry out the second carbonylation reaction.

[0018] Optionally, (3) the carbonylation reaction product of the N-1th stage is separated by a gas-liquid separator to obtain the N-1th gas phase mixture, and the Nth CO and the N-1th gas phase mixture are fed into the Nth adiabatic fixed bed reactor to carry out the Nth stage carbonylation reaction; wherein, N≥3.

[0019] According to the present invention, preferably, the inlet temperature of each adiabatic fixed-bed reactor increases sequentially; more preferably, the difference between the inlet temperatures of two adjacent adiabatic fixed-bed reactors is 5-15°C.

[0020] According to the present invention, preferably, the inlet temperature of each adiabatic fixed-bed reactor is 65-130°C (for example, it can be 65°C, 70°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 120°C, 125°C, 130°C, or any two of the above), preferably 85-115°C. Controlling the temperature within the above range is beneficial to improving the oxalate yield.

[0021] According to the present invention, preferably, the reaction pressure (gauge pressure) of each adiabatic fixed-bed reactor is 0.1-3.5 MPa (for example, it can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 1 MPa, 1.5 MPa, 1.6 MPa, 1.7 MPa, 1.8 MPa, 1.9 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, and any two of the above points), preferably 0.1-2 MPa. Controlling the pressure within the above range is beneficial to improving the oxalate yield.

[0022] According to the present invention, preferably, the inlet gas phase volume hourly space velocity of the first adiabatic fixed-bed reactor is 5000-16000 h⁻¹. -1(For example, it can be 5000h) -1 6000h -1 7000h -1 8000h -1 9000h -1 10000h -1 11000h -1 12000h -1 13000h -1 14000h -1 15000h -1 16000h -1 The range of , and any two of the above points, is preferably 7000-13000h. -1 Controlling the gaseous volume hourly space velocity at the reactor inlet within the above-mentioned range is beneficial for improving the oxalate yield and removing the heat of reaction.

[0023] According to the present invention, preferably, in step (1), the content of nitrite in the mixture of the first CO and the nitrite-containing material is 3-15 vol%, preferably 5-13 vol%.

[0024] According to the present invention, preferably, the molar ratio of the first CO to the nitrite in the nitrite-containing material is 1-8:1 (for example, it can be 1:1, 1.5:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.5:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, and any two of the above), preferably 1.2-6:1. Controlling the molar ratio within the above range is beneficial to improving the selectivity of oxalate.

[0025] According to the present invention, preferably, in step (2), the molar ratio of the second CO stream to the nitrite in the first gas phase mixture is 1.5-15:1 (for example, it can be 1.5:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.5:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 12:1, 13:1, 14:1, 15:1, and any two of the above ranges), preferably 1.8-10:1. Supplementing the second CO stream in the second adiabatic fixed-bed reactor is beneficial to improving the conversion rate of nitrite.

[0026] According to the present invention, preferably, in step (3), the molar ratio of nitrite in the Nth CO and the (N-1)th gas phase mixture is 1-30:1, more preferably 1.2-20:1.

[0027] According to the present invention, step (3) is an optional step and may or may not be performed. "N" refers to the number of adiabatic fixed-bed reactors, that is, the product of the previous adiabatic fixed-bed reactor will be introduced into the 2nd, 3rd, ... Nth adiabatic fixed-bed reactors in sequence. The carbonylation reaction in each adiabatic fixed-bed reactor is carried out as follows: the product of the previous carbonylation reaction is separated by a gas-liquid separator to obtain the previous gas phase mixture, and CO and the previous gas phase mixture are introduced into the adiabatic fixed-bed reactor to carry out the carbonylation reaction.

[0028] According to a preferred embodiment of the present invention, along the flow direction, the C of each adiabatic fixed-bed reactor decreases sequentially, where C refers to the percentage of nitrite converted in a single adiabatic fixed-bed reactor to the percentage of nitrite entering the first adiabatic fixed-bed reactor.

[0029] In this invention, the nitrite conversion rate (C) in a single adiabatic fixed-bed reactor is calculated as follows: (molar amount of nitrite at the inlet of a certain adiabatic fixed-bed reactor - molar amount of nitrite at the outlet of a certain adiabatic fixed-bed reactor) ÷ molar amount of nitrite at the inlet of the first adiabatic fixed-bed reactor × 100%. To more clearly represent the nitrite conversion rate in a single adiabatic fixed-bed reactor, the nitrite conversion rate in the second adiabatic fixed-bed reactor is used as an example. The nitrite conversion rate (C2) in the second adiabatic fixed-bed reactor is calculated as follows: (molar amount of nitrite at the inlet of the second adiabatic fixed-bed reactor - molar amount of nitrite at the outlet of the second adiabatic fixed-bed reactor) ÷ molar amount of nitrite at the inlet of the first adiabatic fixed-bed reactor × 100%.

[0030] Similarly, it can be understood that the total nitrite conversion rate = (molar amount of nitrite at the inlet of the first adiabatic fixed-bed reactor - molar amount of nitrite at the outlet of the last adiabatic fixed-bed reactor) ÷ molar amount of nitrite at the inlet of the first adiabatic fixed-bed reactor × 100%.

[0031] In this invention, the molar amount of nitrite at the inlet (or outlet) = the molar flow rate at the inlet (or outlet) * the molar percentage at the inlet (or outlet).

[0032] According to the present invention, in order to improve the yield of oxalate, preferably, the difference in C between two adjacent adiabatic fixed-bed reactors is greater than 10%, more preferably 20-80%, and even more preferably 30-65%.

[0033] According to a preferred embodiment of the present invention, the apparatus comprises two adiabatic fixed-bed reactors connected in series.

[0034] According to a preferred embodiment of the present invention, the difference in C between the first adiabatic fixed-bed reactor and the second adiabatic fixed-bed reactor is 20-70%. This preferred embodiment can improve the oxalate yield while avoiding catalyst deactivation due to runaway temperatures.

[0035] According to a preferred embodiment of the present invention, the C1 of the first adiabatic fixed-bed reactor is 45-90%, preferably 50-80%. When the C value of the first adiabatic fixed-bed reactor is within the above range, the oxalate yield can be further improved, while ensuring that the temperature rise of the catalyst bed is within 60°C, thus extending the service life of the catalyst.

[0036] According to a preferred embodiment of the present invention, the C2 of the second adiabatic fixed-bed reactor is 10-55%, preferably 10-20%. When the C value of the second adiabatic fixed-bed reactor is within the above range, the yield of oxalate can be further improved, while ensuring that the temperature rise of the catalyst bed is within 40°C, thus extending the service life of the catalyst.

[0037] In this invention, the material containing nitrite may also contain at least one of N2, NO and CH3OH in addition to nitrite. Preferably, the content of N2 is 0-80 vol%, the content of NO is 0-5 vol%, and the content of CH3OH is 0-5 vol%.

[0038] According to the present invention, preferably, the nitrite has 1-3 carbon atoms; more preferably, the nitrite is methyl nitrite.

[0039] According to the present invention, preferably, the catalyst comprises a support, palladium, and optional modifying components, and the catalyst is tested at 40°C in the in-situ infrared spectrum of pyrrole adsorption, 3200-3410 cm⁻¹. -1 An absorption peak for the stretching vibration of NH bonds appears within the range;

[0040] The in-situ infrared spectrum (3160-3420 cm⁻¹) obtained after the catalyst adsorbed pyrrole at 40°C and was purged with nitrogen for 0 minutes is shown in the image. -1 The peak height of the absorption peak within the range is 3160-3420 cm⁻¹ in the in-situ infrared spectrum obtained after purging with nitrogen for 15 minutes. -1 The ratio of absorption peak height within the range is greater than 5.

[0041] The catalyst can be in the range of 3200-3410 cm⁻¹ -1 The catalyst exhibits one or more NH bond stretching vibration absorption peaks within a certain range. Preferably, in the in-situ infrared spectrum of pyrrole adsorption tested at 40°C, the peaks are at least in the 3350-3400 cm⁻¹ range. -1An NH bond stretching vibration absorption peak appears within the specified range. Weakly basic centers exhibiting this specific NH bond stretching vibration absorption peak can impart better catalytic performance to the catalyst.

[0042] The catalyst, when tested at 40°C in situ with pyrrole adsorption, showed a range of 3160-3300 cm⁻¹. -1 An absorption peak for the stretching vibration of NH bonds appears within the range.

[0043] Preferably, the in-situ infrared spectrum measured after the catalyst adsorbs pyrrole at 40°C and is then purged with nitrogen for 0 minutes (3160-3410 cm⁻¹) is obtained. -1 The peak height of the absorption peak within the range is 3160-3420 cm⁻¹ in the in-situ infrared spectrum obtained after purging with nitrogen for 15 minutes. -1 The ratio of absorption peak height within the range is greater than 10.

[0044] Specifically, the in-situ infrared spectrum of the pyrophoric adsorption of the catalyst can be obtained using the following method:

[0045] a) The powdered catalyst sample was placed in an infrared cell, and after vacuum treatment, it was heated to 350℃ at a heating rate of 20℃ / min.

[0046] b) Hold at 350°C for 2 hours in a vacuum, then cool down to 40°C at a rate of 20°C / min.

[0047] c) Maintain the temperature at 40℃ and purge with nitrogen gas for 30 minutes at a flow rate of 5 mL / min;

[0048] d) Maintain the temperature at 40℃, introduce gaseous pyrrole, allow it to adsorb for 10 minutes at a gas flow rate of 5 mL / min, and record the in-situ infrared spectrum of the sample.

[0049] e) Maintain the temperature at 40℃, then purge with nitrogen for 30 minutes at a flow rate of 5 mL / min, and record the in-situ infrared spectrum of the sample.

[0050] Before testing, the granular catalyst sample should be ground into powder, filled into the in-situ sample cell, and the surface kept flat. Steps a to c aim to remove water and impurities adsorbed on the catalyst surface.

[0051] In the pyrrole adsorption step (step d), the in-situ infrared spectrum of the sample can be recorded at different times as needed, such as 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, and 10 minutes. In the pyrrole adsorption in-situ infrared spectrum, the range is 3160-3420 cm⁻¹. -1The presence of NH bond stretching vibration absorption peaks within this range corresponds to the basicity of the basic centers on the catalyst surface; higher wavenumbers at the peak position indicate weaker basicity at that center. (3160-3420 cm⁻¹) -1 The presence of multiple NH bond stretching vibration absorption peaks within the range indicates a diverse spectrum of basic centers on the catalyst surface. The elution positions of pyrrole adsorption vary significantly among different catalysts; typically, two or more peaks overlap, and in some cases, one peak becomes a shoulder peak for another. To calculate the elution positions of each adsorption peak, commonly used data processing software can be used to analyze the 3160-3420 cm⁻¹ range. -1 Peak fitting was performed on the absorption curves of the interval.

[0052] After purging with nitrogen, the intensity of the pyrrole infrared absorption peak gradually decreased. The spectrum after 15 minutes of purging is 3160-3420 cm⁻¹. -1 Absorption peaks within the range and 0-minute purge spectrum 3160-3420 cm⁻¹ -1 The peak height ratio of the absorption peaks within the range can be used to illustrate the adsorption capacity of the basic centers on the catalyst surface for pyrrole, proving the existence of the basic centers.

[0053] After the measurement is completed, nitrogen purging can be continued until the temperature drops to room temperature, with a nitrogen flow rate of 3-7 mL / min.

[0054] The catalyst of the present invention uses palladium as the catalytically active component, and its content can be selected within a wide range. Preferably, the palladium content in the catalyst, calculated as metal element, is 0.01-10 wt% of the total weight of the support, for example, it can be 0.01, 0.02, 0.05, 0.1, 0.5, 1, 5, 10 wt%, or any range between any two values, preferably 0.01-6 wt%, more preferably 0.02-2 wt%.

[0055] Palladium can exist on the catalyst surface in oxidized form, elemental form, other palladium compound forms, or a mixture of two or more of them.

[0056] The catalyst support can be a support conventionally used in the art. For example, the catalyst support can be selected from at least one of alumina, titanium dioxide, zirconium oxide, gallium oxide, silicon dioxide, magnesium oxide, molecular sieve, zeolite, activated carbon, clay, bentonite, and polymer materials (such as polyvinylpyrrolidone, polystyrene, carbon support, etc.).

[0057] The carrier's shape includes, but is not limited to, powder, granules, spheres, toothed spheres, Raschig rings, strips, cylinders, flakes, or irregular strips such as clover shapes. Preferably, the specific surface area of ​​the carrier is 0.5-800 m². 2 / g, preferably 4-200m 2 / g, more preferably 15-110m 2 / g.

[0058] The catalyst of this invention can be a single palladium supported catalyst or a composite catalyst, comprising palladium and a modifying component. The modifying component can be a conventional modifying component in the art, such as selected from Bi, Sb, Pb, Sn, Y, Zn, Co, W, Si, Group VIII elements different from palladium (e.g., Fe, Co, Ni, Ru, Rh, Os, Ir, Pt), Group IB elements (e.g., Cu, Ag, Au), Group VIIB elements (e.g., Mn), Group IIIA elements (e.g., Ga, In, Tl), rare earth elements (e.g., La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Sc), alkali metal elements (e.g., Na, K), and alkaline earth metal elements (e.g., Mg, Ca, Sr). Ba) and at least one of halogen elements (such as F, Cl, Br, I), more preferably at least one selected from Ag, Cu, Zn, Ga, In, Cs, Y, Fe, Ni and Au.

[0059] Preferably, the content of the modified component in the catalyst, calculated by metal element, is 0-20 wt% of the total weight of the support, for example, it can be 0, 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 15, 20 wt%, or any range between any two values. The modified component can be distributed at specific locations on the support as a co-activating component, or it can be uniformly distributed within the support as a modifier of the support.

[0060] The present invention also provides a method for preparing a supported palladium catalyst, the method comprising the following steps: (1) loading palladium and optional modified components onto a support, and obtaining an intermediate after drying and calcination; (2) loading an alkaline compound onto the intermediate, and then drying and optionally calcining to obtain a catalyst.

[0061] In this invention, the loading method can be a conventional method in the art, such as spraying or dipping, and the specific operation will not be described in detail.

[0062] In step (1), the palladium and the precursor of the modified component can be pre-prepared as a solution and loaded onto the support using a spraying or impregnation method. When the catalyst contains the modified component, if the modified component is used as a co-activating component, it can be loaded onto the support alone or simultaneously with palladium; if the modified component is used as a modifier for the support, it can be added during the support preparation process.

[0063] Preferably, palladium is loaded in the form of a solution containing a palladium precursor.

[0064] In step (1), the palladium precursor can be a conventional acid or base or water-soluble substance in the art, such as one or more selected from palladium chloride, palladium nitrate, palladium acetate, palladium sulfate, palladium oxide and palladium organometallic compounds (such as palladium neopentanoate, octaethylporphyrin palladium, trimethylacetate palladium, trifluoroacetate palladium, etc.).

[0065] The content of the palladium precursor in the solution containing the palladium precursor can be selected within a wide range, for example, the content of the palladium precursor in the solution containing the palladium precursor is 1-200 g / L.

[0066] Preferably, the amount of palladium used, based on metal elements, is such that the palladium content in the catalyst is 0.01-10 wt% of the total weight of the support, more preferably 0.01-6 wt%, and even more preferably 0.02-2 wt%.

[0067] Preferably, the modified component is loaded in the form of a solution containing a precursor of the modified component.

[0068] Preferably, the precursor of the modified component is selected from at least one of halides (such as chlorides, bromides, iodides), nitrates, acetates, carbonates, sulfates, hydroxides, ammonium compounds, and organometallic compounds (such as citrates, oxalates, etc.).

[0069] The content of the precursor of the modified component in the solution containing the precursor of the modified component can be selected within a wide range, for example, the content of the precursor of the modified component in the solution containing the precursor of the modified component is 0.1-400 g / L.

[0070] Preferably, the amount of the modified component, calculated by metal element, is such that the content of the modified component in the catalyst is 0-20 wt% of the total weight of the support, for example, it can be 0, 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 20 wt%, or any range between any two values.

[0071] The solvents in the solutions containing the palladium precursor and the solutions containing the modified component can each independently be water, diethyl ether, ethanol, isobutanol, etc.

[0072] The types of modified components and carriers have been described above and will not be repeated here.

[0073] In step (2), preferably, the alkaline compound is loaded in the form of a solution containing the alkaline compound.

[0074] The basic compound may be an inorganic basic compound and / or an organic basic compound. The basic compound is a weak basic compound.

[0075] Preferably, the organic basic compound is selected from at least one of dimethylamine, triethylamine, aniline, pyridine, 4-dimethylaminopyridine, triethanolamine, triethylenediamine, tetramethylethylenediamine, N,N-diisopropylethylamine, N-methylmorpholine, sodium methoxide, potassium ethoxide, potassium tert-butoxide, sodium tert-butoxide, n-butyllithium, citrate (e.g., sodium citrate or potassium citrate), oxalate (e.g., sodium oxalate, potassium oxalate), and acetate (e.g., sodium acetate, potassium acetate).

[0076] Preferably, the inorganic alkaline compound is selected from at least one of ammonia, alkali metal hydroxides (such as sodium hydroxide or potassium hydroxide), alkaline earth metal hydroxides (such as magnesium hydroxide or calcium hydroxide), halides (such as potassium fluoride or lithium chloride), and carbonates (such as sodium carbonate or potassium carbonate).

[0077] The solvent in the solution containing the alkaline compound can be any solution capable of dissolving the alkaline compound, preferably selected from at least one of water, methanol, ethanol, diethyl ether, acetone, tetrahydrofuran, and N,N-dimethylformamide.

[0078] Preferably, the content of the alkaline compound in the solution is 5-70 wt%.

[0079] Preferably, the amount of the alkaline compound used is 0.1-10 wt% relative to the total weight of the carrier.

[0080] In a preferred embodiment of the present invention, the method includes: (1) loading palladium onto a support, and obtaining an intermediate by drying and calcining; (2) loading an alkaline compound onto the intermediate, and obtaining a catalyst by drying and optionally calcining.

[0081] In another preferred embodiment of the present invention, the method includes: (1) loading palladium and a modified component onto a support, and obtaining an intermediate by drying and calcining; (2) loading an alkaline compound onto the intermediate, and obtaining a catalyst by drying and optionally calcining.

[0082] In another preferred embodiment of the present invention, the method includes: (1) loading a first modified component onto a support, and obtaining a modified support after drying and calcination; loading palladium and optionally a second modified component onto the support, and obtaining an intermediate after drying and calcination; (2) loading an alkaline compound onto the intermediate, and obtaining a catalyst after drying and optionally calcination.

[0083] In step (1), the intermediate loaded with palladium precursor and modified component precursor usually needs to be calcined and decomposed at high temperature; in step (2), the catalyst can be obtained by loading the intermediate with a solution containing alkaline compound and then drying it, or the catalyst can be obtained by loading the intermediate with a solution containing alkaline compound and then drying and calcining it at high temperature.

[0084] In steps (1) and (2), when preparing the intermediate, modified support, or catalyst, the drying temperature can be independently set to 60-180°C, for example, 60, 80, 120, 160, 180°C, or any range between any two values. The drying time can be independently set to 1-48 hours, for example, 1, 5, 10, 20, 30, 40, 48 hours, or any range between any two values. It should be understood that the drying process can be performed at least once, and the conditions for each drying can be different.

[0085] In step (1), the calcination temperature can be 300-1500℃, for example, it can be any range of 300, 400, 600, 800, 1000, 1200, 1400, 1500℃, or any two of these values. Preferably, during the preparation of the intermediate, the calcination temperature is 600-1500℃, for example, it can be any range of 600, 800, 1000, 1200, 1400, 1500℃, or any two of these values. During the preparation of the modified carrier, the calcination temperature is preferably 300-1000℃, for example, it can be any range of 300, 400, 600, 800, 1000℃, or any two of these values.

[0086] In step (2), the roasting temperature is preferably 250-500℃, for example, it can be 200, 250, 300, 350, 400, 450, 500℃ and any range between any two values.

[0087] In steps (1) and (2), the roasting time can be independently set to 2-24h, for example, it can be 2, 4, 8, 12, 16, 20, 24h and any range between any two values.

[0088] In steps (1) and (2) of the preparation method of the present invention, the drying and calcination can be carried out independently in an air atmosphere or in a vacuum, preferably in an air atmosphere.

[0089] According to a particularly preferred embodiment of the present invention, the method for preparing the catalyst includes:

[0090] (1) Preparation of Pd / Al2O3 intermediate: PdSO4 aqueous solution is sprayed onto Al2O3 support, then dried at 130-150℃ for 10-14h, and calcined at 600-640℃ for 8-12h. The amount of PdSO4 used is 2-3g per 500g of support, calculated as Pd.

[0091] (2) Spray an aqueous solution of NaHCO3 onto the Pd / Al2O3 intermediate, then dry it at 120-130℃ for 8-10h and calcine it at 420-450℃ for 15-20h. The amount of NaHCO3 used is 0.5-0.7g relative to each 500g carrier.

[0092] According to a particularly preferred embodiment of the present invention, the method for preparing the catalyst includes:

[0093] (1) Preparation of Pd-Zn-Ag / Al2O3 intermediate: The support Al2O3 was impregnated in an aqueous solution of [(NH4)2Pd]Cl4, [(NH4)2Ag]Cl3 and ZnCl2, then dried at 100-120℃ for 10-15h and calcined at 600-700℃ for 10-15h. The amount of [(NH4)2Pd]Cl4 used per 500g of support was 0.2-0.4g based on Pd, 1-1.5g based on Zn, and 0.4-0.6g based on Ag.

[0094] (2) The Pd-Zn-Ag / Al2O3 intermediate is impregnated in an aqueous solution of KF, then dried at 150-180℃ for 3-5 hours and calcined at 280-320℃ for 1-5 hours. The amount of KF used is 0.8-1.2g per 500g of carrier.

[0095] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.

[0096] Unless otherwise specified, the reagents used in the examples and comparative examples are all conventionally used reagents in the art, and the methods used are all conventional methods in the art.

[0097] The Al2O3 supports used below were all purchased from Sinopec Catalysts (Beijing) Co., Ltd., with a specific surface area of ​​50-60 m². 2 / g.

[0098] Preparation Example 1

[0099] Prepare 250 mL of an aqueous solution containing 0.3 g Pd of [(NH4)2Pd]Cl4, 0.5 g Ag of [(NH4)2Ag]Cl3, and 1.1 g Zn of Zn. Impregnate 500 g of spherical Al2O3 support in the solution, dry at 105 °C for 12 h, and calcine at 650 °C for 15 h to obtain a Pd-Zn-Ag / Al2O3 intermediate.

[0100] Prepare 250 mL of an aqueous solution of KF containing 1.0 g K, impregnate the Pd-Zn-Ag / Al2O3 intermediate in the solution, dry at 160 °C for 4 h, and calcine at 300 °C for 4 h to obtain catalyst A.

[0101] Preparation Example 2

[0102] Prepare 400 mL of an ethanol solution containing 3.1 g Cu of copper acetate, immerse 500 g of toothed spherical support Al2O3 in the solution, dry at 75 °C for 40 h, and calcine at 1100 °C for 20 h to obtain Cu-modified support Al2O3.

[0103] Prepare 300 mL of Pd(NO3)2 aqueous solution containing 0.5 g Pd, impregnate Cu-modified support Al2O3 in the solution, dry at 105 °C for 6 h, and calcine at 700 °C for 4 h to obtain Pd-Cu / Al2O3 intermediate;

[0104] Prepare 250 mL of an aqueous solution containing 50 mL of tetramethylethylenediamine, impregnate the Pd-Cu / Al2O3 intermediate in the solution, and dry at 75 °C for 20 h to obtain catalyst B.

[0105] Preparation Example 3

[0106] Prepare 400 mL of ether solution containing 1.2 g Pd in ​​Pd(Ac)2 and 5.0 g Cs in Cs(Ac). Impregnate 500 g of clover-type support Al2O3 in this solution, dry at 80 °C for 48 h, and calcine at 450 °C for 8 h to obtain Pd-Cs / Al2O3 intermediate.

[0107] Prepare 400 mL of K(Ac) ethanol solution containing 2.0 g K, impregnate the Pd-Cs / Al2O3 intermediate in the solution, and dry at 80 °C for 30 h to obtain catalyst C.

[0108] Preparation Example 4

[0109] Prepare 265 mL of isobutanol solution containing 0.5 g Au and HAuCl4, immerse 500 g columnar support Al2O3 in the solution, dry at 110 °C for 2 h, and calcine at 1270 °C for 6 h to obtain Au-modified support Al2O3.

[0110] Prepare 300 mL of an aqueous solution containing 4.8 g Pd(NO3)2 and 0.8 g Ga(NO3)3. Impregnate Au-modified support Al2O3 in the solution, dry at 140 °C for 12 h, and calcine at 820 °C for 14 h to obtain Pd-Ga-Au / Al2O3 intermediate.

[0111] Prepare 300 mL of acetone solution containing 110 mL of 4-dimethylaminopyridine (DMAP), impregnate the Pd-Ga-Au / Al2O3 intermediate in the solution, and dry at 165 °C for 20 h to obtain catalyst D.

[0112] Preparation Example 5

[0113] Prepare 180 mL of PdSO4 aqueous solution containing 2.5 g Pd, spray the solution onto 500 g spherical support Al2O3, dry at 140 °C for 12 h, and calcine at 620 °C for 10 h to obtain Pd / Al2O3 intermediate;

[0114] Prepare 180 mL of NaHCO3 aqueous solution containing 0.6 g Na element, spray the solution onto Pd / Al2O3 intermediate, dry at 125 °C for 10 h, and calcine at 445 °C for 16 h to obtain catalyst E.

[0115] Preparation Example 6

[0116] Prepare 400 mL of an aqueous solution of NaHCO3 containing 0.6 g Na, immerse 500 g of spherical support Al2O3 in the solution, dry at 125 °C for 10 h, and calcine at 1050 °C for 20 h to obtain the Na / Al2O3 intermediate.

[0117] Prepare 180 mL of PdSO4 aqueous solution containing 2.5 g Pd, spray the solution onto Na / Al2O3 intermediate, dry at 140 °C for 12 h, and calcine at 620 °C for 10 h to obtain catalyst F.

[0118] Preparation Example 7

[0119] Prepare 220 mL of PdSO4 aqueous solution containing 2.5 g Pd, spray the solution onto 500 g spherical support Al2O3, dry at 140 °C for 6 h, and calcine at 620 °C for 10 h to obtain catalyst G.

[0120] Preparation Example 8

[0121] Prepare 240 mL of an aqueous solution containing 2.5 g Pd SO4 and 0.6 g Na Na HCO3. Spray the solution onto 500 g of spherical support Al2O3, dry at 140 °C for 6 h, and calcine at 620 °C for 10 h to obtain catalyst H.

[0122] Test Example 1

[0123] This test example illustrates the in-situ adsorption infrared spectroscopy analysis of pyrrole on palladium-based catalysts.

[0124] The pyrrole adsorption of the catalysts prepared in the examples and comparative examples was tested using a pyrrole in-situ infrared analyzer (Thermo Nicolet 380). Approximately 10 mg of powder sample was pressed into a thin sheet, fixed in an infrared cell, and first purified under vacuum (400℃, 1×10⁻⁶). -3 After 3 hours of cooling to 40°C, the spectrum was scanned to obtain the background. The method for determining the in-situ infrared spectrum of the pyrrole adsorption of the catalyst is as follows:

[0125] a) The powdered catalyst sample was placed in an infrared cell, and after vacuum treatment, it was heated to 350℃ at a heating rate of 20℃ / min.

[0126] b) Hold at 350°C for 2 hours in a vacuum, then cool down to 40°C at a rate of 20°C / min.

[0127] c) Maintain the temperature at 40℃ and purge with nitrogen gas for 30 minutes at a flow rate of 5 mL / min;

[0128] d) Maintain the temperature at 40℃, introduce gaseous pyrrole, allow it to adsorb for 10 minutes at a gas flow rate of 5 mL / min, and record the sample values ​​at 1000–4000 cm⁻¹ at 2, 4, 6, 8, and 10 minutes after introducing the gaseous pyrrole. -1 In-situ infrared spectra in the wavenumber region;

[0129] e) Maintain the temperature at 40℃, then purge with nitrogen for 30 minutes at a flow rate of 5 mL / min;

[0130] f) Continue purging with nitrogen until the temperature drops to room temperature, with a nitrogen flow rate of 5 mL / min.

[0131] in, Figure 1 The in-situ infrared spectra of pyrrole adsorption of the catalyst AH prepared in the examples and comparative examples are shown.

[0132] Figure 2 The in-situ infrared spectrum of pyrrole adsorption of catalyst E over time is shown. In the spectrum, 0 min represents the infrared absorption curve after nitrogen purging ends; 4 min, 6 min, and 10 min are the infrared absorption curves at the 4th, 6th, and 10th min of pyrrole adsorption; and 25 min is the infrared absorption curve 15 min after nitrogen purging ends pyrrole adsorption.

[0133] according to Figure 1 and Figure 2 The calculations were performed, and the results are shown in Table 1.

[0134] Table 1 shows the values ​​of 3160-3420 cm at the 10th minute. -1 Within the specified range, the elution positions of the pyrrole infrared absorption peaks of the catalysts prepared in the examples and comparative examples, as well as the peak height ratio H... 10min / H 25min , where H 10min The pyrrole adsorption depth was 3160-3420 cm⁻¹ at 10 min. -1 The highest peak height within the range (when there are more than two peaks, the height of the highest peak is used for calculation), H 25min The 3160-3420 cm⁻¹ value at which nitrogen purging for 15 min was used to determine the adsorption of pyrrole. -1 The highest peak height within the range (when there are more than two peaks, the highest peak height is used for calculation).

[0135] Table 1

[0136]

[0137] As shown in Table 1, the infrared peak positions of pyrrole adsorption of catalyst AE prepared by the method of the embodiments of the present invention are in the wavelength range of 3200-3410 cm⁻¹. -1 The pyrrole adsorption infrared peak positions of the catalyst FH prepared in the comparative example were all greater than 3410 cm⁻¹. -1 After pyrrole adsorption is completed and nitrogen purging is used, the pyrrole adsorbed on the catalyst surface will be rapidly desorbed, and the peak height ratio of each catalyst will be above 10.

[0138] Example 1

[0139] All catalysts used were reduced with a mixture of H2 and N2 (H2 > 50 mol%) before use. The reduction temperature was 150℃ and the reduction time was 10 h.

[0140] The apparatus in this embodiment includes two adiabatic fixed-bed reactors connected in series, with a condenser and a gas-liquid separator between them. Each adiabatic fixed-bed reactor is filled with 200 mL of reduced catalyst. The composition of the first feed gas, consisting of CO and nitrite-containing material, is: CO 22.6 vol%, MN (methyl nitrite) 12.1 vol%, N2 63.8 vol%, NO 1.3 vol%, CH3OH 0.2 vol%. The volume hourly space velocity (VHSV) of the feed gas in the first adiabatic fixed-bed reactor is controlled at 10000 h⁻¹. -1The reaction pressure was 0.2 MPa. The inlet temperature and conversion rate of the first adiabatic fixed-bed reactor are shown in Table 2. The product was then condensed in a condenser and separated by a gas-liquid separator. The resulting liquid product (output as the final product) and the first gas mixture were then mixed with a second CO stream and fed into a second adiabatic fixed-bed reactor. After mixing, the molar ratio of CO to nitrite in the mixture was 5:1. The reaction pressure of the second adiabatic fixed-bed reactor was controlled at 0.2 MPa. The inlet temperature and conversion rate of the second adiabatic fixed-bed reactor are shown in Table 2. The test results are shown in Table 2.

[0141] Dimethyl oxalate (DMO) selectivity:

[0142]

[0143] space-time yield of dimethyl oxalate:

[0144]

[0145] Section 1 and Section 2 represent the first and second adiabatic fixed-bed reactors, respectively.

[0146] Table 2

[0147]

[0148] In Table 2, the selectivity and space-time yield of dimethyl oxalate are the average values ​​over the reaction time.

[0149] As can be seen from the results in Table 2, the carbonylation reaction using the apparatus of the present invention, which includes at least two adiabatic fixed-bed reactors connected in series and a gas-liquid separator between two adjacent adiabatic fixed-bed reactors, can not only reduce equipment investment, but also improve the selectivity and yield of oxalate.

[0150] In a preferred embodiment, the method of loading catalyst AE into the apparatus of the present invention can achieve higher selectivity and space-time yield of dimethyl oxalate, and the catalyst can also operate stably for a longer period of time. More preferably, using the two-stage adiabatic fixed-bed reactor of the present invention for the carbonylation coupling reaction can achieve high selectivity and space-time yield of dimethyl oxalate under high space velocities.

[0151] Example 2

[0152] The method was followed as in Example 1, except that the conversion rate of the first adiabatic fixed-bed reactor was controlled at 35.3% and the conversion rate of the second adiabatic fixed-bed reactor was controlled at 43.0%. The test results are shown in Table 3.

[0153] Example 3

[0154] The procedure was performed according to Example 1, except that the molar ratio of nitrite in the second CO stream to that in the first gas phase mixture was 15:1. The test results are shown in Table 3.

[0155] Table 3

[0156]

[0157] Comparing the results in Table 3 with those in Table 2 for catalyst A, it can be seen that the preferred embodiment of Example 1 is more conducive to improving the selectivity and space-time yield of dimethyl oxalate.

[0158] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing oxalate using an adiabatic fixed-bed reactor, characterized in that, The method involves a continuous carbonylation reaction in an apparatus comprising at least two adiabatic fixed-bed reactors connected in series, each reactor being packed with a catalyst, and a condenser and a gas-liquid separator being provided between adjacent adiabatic fixed-bed reactors. The method includes the following steps: (1) The first CO and the material containing nitrite esters are fed into the first adiabatic fixed bed reactor to carry out the first carbonylation reaction; (2) The first carbonylation reaction product is separated by a gas-liquid separator to obtain a first gas phase mixture. The second CO and the first gas phase mixture are then fed into a second adiabatic fixed-bed reactor to carry out the second carbonylation reaction. Optionally, (3) the N-1th carbonylation reaction product is separated by a gas-liquid separator to obtain the N-1th gas phase mixture, and the Nth CO and the N-1th gas phase mixture are fed into the Nth adiabatic fixed bed reactor to carry out the Nth carbonylation reaction; wherein, N≥3; The reaction conditions for each adiabatic fixed-bed reactor are independent and include: inlet temperature of 65-130℃; reaction pressure of 0.1-3.5MPa; and inlet gas hourly space velocity of 5000-16000 h⁻¹ for the first adiabatic fixed-bed reactor. -1 ; Along the flow direction, the concentration (C) of each adiabatic fixed-bed reactor decreases sequentially. C refers to the percentage of nitrite converted in a single adiabatic fixed-bed reactor compared to the percentage of nitrite entering the first adiabatic fixed-bed reactor; the C of the first adiabatic fixed-bed reactor is 45-90%; the C of the second adiabatic fixed-bed reactor is 10-55%. The preparation method of the catalyst includes the following steps: (1) loading palladium and optional modified components onto a support, and then drying and calcining to obtain an intermediate; (2) loading an alkaline compound onto the intermediate, and then drying and optionally calcining to obtain the catalyst.

2. The method according to claim 1, wherein, The reaction conditions for each adiabatic fixed-bed reactor independently include: inlet temperature of 85-115℃; reaction pressure of 0.1-2MPa; And / or, the inlet gas phase volume hourly space velocity of the first adiabatic fixed-bed reactor is 7000-13000 h⁻¹. -1 .

3. The method according to claim 1, wherein, In step (1), the nitrite content in the mixture of the first CO and the nitrite-containing material is 3-15 vol.

4. The method according to claim 3, wherein, In step (1), the nitrite content in the mixture of the first CO and the nitrite-containing material is 5-13 vol.

5. The method according to claim 1, wherein, The molar ratio of CO to nitrite in the first stream of material is 1-8:

1.

6. The method according to claim 5, wherein, The molar ratio of CO to nitrite in the first stream of material is 1.2-6:

1.

7. The method according to claim 1, wherein, In step (2), after the second CO stream is mixed with the first gas phase mixture, the molar ratio of CO to nitrite in the mixture is 1.5-15:

1.

8. The method according to claim 1, wherein, In step (2), after the second CO stream is mixed with the first gas phase mixture, the molar ratio of CO to nitrite in the mixture is 1.8-10:

1.

9. The method according to claim 1, wherein, In step (3), after the Nth CO and the (N-1)th gas phase mixture are mixed, the molar ratio of CO to nitrite in the gas phase mixture is 1-30:

1.

10. The method according to claim 9, wherein, In step (3), after the Nth CO and the (N-1)th gas phase mixture are mixed, the molar ratio of CO to nitrite in the gas phase mixture is 1.2-20:

1.

11. The method according to claim 1, wherein, The difference in C between two adjacent adiabatic fixed-bed reactors is greater than 10%.

12. The method according to any one of claims 1-11, wherein, The apparatus comprises two adiabatic fixed-bed reactors connected in series.

13. The method according to claim 12, wherein, The first adiabatic fixed-bed reactor has a C ratio of 50-80%. And / or, the C of the second adiabatic fixed-bed reactor is 10-20%.

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