Methanol gas-phase carbonylation catalyst, its preparation and application

Abstract

The application relates to a preparation method and application of a catalyst for preparing acetic acid and acetic ester through methanol gas-phase carbonylation. The catalyst is composed of a metal component gold and a carrier nitrogen-doped carbon. The application provides a catalyst for preparing acetic acid and acetic ester through methanol gas-phase carbonylation. The catalyst is used in a fixed bed reactor, and under the action of the catalyst, CH3OH and CO can be converted into acetic acid and acetic ester with high activity and high selectivity at a certain temperature and pressure.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering catalyst technology, specifically relating to the preparation of a nitrogen-doped carbon-supported gold-based catalyst and its application in the vapor-phase carbonylation of methanol to prepare acetic acid and acetate esters. Background Technology

[0002] Acetic acid is a very important organic chemical raw material with a wide range of applications. It can be used to produce a variety of downstream chemical products such as vinyl acetate monomer, acid anhydride, terephthalic acid, acetate esters, and cellulose acetate. In particular, with the rapid development of terephthalic acid and downstream products of acetic acid, acetic acid production has become an important part of the chemical industry and the national economy.

[0003] Mature acetic acid production processes include the acetylene-acetaldehyde method, the ethylene-acetaldehyde method, the ethanol-acetaldehyde method, the butane oxidation method, and the methanol carbonylation method. Among these, the methanol carbonylation process is dominant, currently accounting for 81% of the total acetic acid production capacity. Over the past 50 years, the industrialization of acetic acid production via methanol carbonylation has roughly gone through three stages of development:

[0004] The first stage: In 1960, BSAF first achieved the industrial production of acetic acid via methanol carbonylation using a cobalt catalyst at relatively high reaction temperatures and pressures (250°C, 60 MPa). The acetic acid produced by this method had low purity, and the main byproducts were higher alcohols, higher aldehydes, and higher carboxylic acids, resulting in high product separation costs. The second stage: Monsanto developed a rhodium-iodide (RhI3) catalytic system with higher activity and selectivity. The reaction temperature and pressure were also relatively low (around 175°C, 3.0 MPa), and the selectivity of acetic acid based on methanol was over 99%, while the selectivity based on CO also reached over 90%. The equipment required high corrosion resistance and needed an all-zirconium alloy reactor. The third stage: The industrialization of Ir catalysts was achieved through methanol carbonylation for acetic acid production. This process significantly improved catalyst stability, allowed the reaction to proceed under conditions of low water content, reduced the formation of liquid byproducts, and increased CO conversion. Celanese Chemicals improved the stability of Rh catalysts by adding high concentrations of inorganic iodides (mainly lithium iodide). The addition of lithium iodide and iodomethane as auxiliaries significantly reduced the water content in the reactor (by about 4% to 5%) while maintaining a high carbonylation rate, thus significantly reducing the separation cost of the new process.

[0005] Chiyoda Corporation and UOP Corporation of Japan jointly developed the Actica process, which is based on a heterogeneous Rh catalyst in which active Rh complexes are supported on polyvinylpyridine resin. Yuan Guoqing's research group at the Institute of Chemistry, Chinese Academy of Sciences, has also developed a strong-weak coordination chelating polymer catalyst system with independent intellectual property rights. This catalyst system exhibits high stability and high activity, and can improve the selectivity of CO utilization.

[0006] Although homogeneous Rh-based and Ir-based catalytic systems exhibit high catalytic activity and selectivity (with a selectivity greater than 99% for acetic acid), achieving excellent industrial applications, homogeneous catalyst systems also have many drawbacks. These include the easy loss of precious metal catalysts, difficulties in separating products from catalysts, and complex catalyst recycling and recovery processes.

[0007] To address the shortcomings of homogeneous catalytic systems, some researchers have turned their attention to supported heterogeneous catalytic systems. However, supported catalyst systems suffer from lower activity compared to homogeneous systems, easier removal of active components, and higher requirements for the support. Most importantly, influenced by international events, the prices of Rh and Ir metals, the active components in traditional methanol carbonylation catalysts, are volatile and trending upwards, while domestic reserves are scarce, significantly increasing catalyst investment costs and the uncontrollability of catalyst reserves. Therefore, developing a methanol carbonylation reaction system with high activity, good selectivity, excellent stability, and low catalyst investment costs is of significant industrial importance.

[0008] Au is significantly cheaper than Rh and Ir, and its reserves are abundant and readily available. Constructing optimal coordination environments for active sites can greatly improve the stability of methanol carbonylation catalysts. Here, we propose a nitrogen-doped carbon-supported, nitrogen-coordinated single-atom gold-based catalyst for the gas-phase carbonylation of methanol to prepare acetic acid and acetate esters. This catalyst exhibits high activity, selectivity, and stability. Furthermore, it reduces catalyst investment costs, is environmentally friendly, and has broad industrial application prospects. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing a nitrogen-doped carbon-supported gold-based catalyst and its application in the vapor-phase carbonylation of methanol to prepare acetic acid and acetate esters.

[0010] The technical solution of this invention is as follows:

[0011] A supported catalyst for the gas-phase carbonylation of methanol to prepare acetic acid and acetate esters. The catalyst consists of a metal component, gold, and a nitrogen-doped carbon support.

[0012] The catalyst is prepared by dissolving a gold precursor in a solvent to obtain a gold precursor solution, loading the gold precursor solution onto a nitrogen-doped carbon support by wet impregnation, and finally drying and calcining at high temperature to obtain the catalyst.

[0013] The solvent for dissolving the gold precursor is an aqueous solution of aqua regia or water, consisting of 0.5-16M nitric acid and 0.5-12M hydrochloric acid in a volume ratio of 1-3:3-1.

[0014] The catalyst contains 0.05-5% gold by mass, preferably 0.2-1.0%, with the remainder being nitrogen-doped carbon.

[0015] The gold precursor is one or more of the following: gold triphenylphosphine nitrate (Au(PPh3)(NO3)), gold hydroxide (Au(OH)3), gold oxide (Au2O3), tetrachloroauric acid trihydrate (HAuCl4·3H2O), gold bromide (AuBr3), gold iodide (AuI3), and gold acetate (Au(CH3COO)3);

[0016] Preferred ingredients include one or more of the following: triphenylphosphine gold nitrate (Au(PPh3)(NO3)), tetrachloroauric acid trihydrate (HAuCl4·3H2O), gold iodide (AuI3), and gold acetate (Au(CH3COO)3).

[0017] The solvent for dissolving the gold precursor is preferably aqua regia (V). HNO3 :V HCl =1:3, the volume ratio of concentrated nitric acid (16M) to concentrated hydrochloric acid (12M) is 1:3; aqua regia 1 (V HNO3 :V HCl =1:1, the volume ratio of concentrated nitric acid (16M) to concentrated hydrochloric acid (12M) is 1:1; aqua regia 2 (V HNO3 :V HCl =3:1, the volume ratio of concentrated nitric acid (16M) to concentrated hydrochloric acid (12M) is 3:1; aqua regia 3 (V HNO3 :V HCl =1:3, dilute nitric acid (8M) and dilute hydrochloric acid (6M) in a volume ratio of 1:3 or aqua regia 4 (V HNO3 :V HCl = 1:3, the volume ratio of dilute nitric acid (0.5M) to dilute hydrochloric acid (0.5M) is 1:3.

[0018] The nitrogen-doped carbon is obtained by pyrolysis of one or more of dicyandiamide, melamine, cyanamide, urea or polyaniline at 200-1200°C for 0.5-5 hours under a nitrogen atmosphere, preferably at a pyrolysis temperature of 600-1000°C and preferably for a pyrolysis time of 1-2 hours.

[0019] The catalyst is prepared by one or two of the following methods: equal-volume wet impregnation and over-volume wet impregnation.

[0020] The molar concentration of gold in the gold precursor solution is 0.2–30.0 mmol / L, preferably 1.0–5.0 mmol / L; the drying temperature is 50–150 °C, preferably 60–100 °C, and the drying time is 2–20 h, preferably 5–15 h.

[0021] The catalyst is calcined at a temperature of 400–1200°C, preferably 600–1000°C, for a time of 2–10 h, preferably 3–8 h, in a nitrogen atmosphere.

[0022] The application of the nitrogen-doped carbon-supported gold-based catalyst in the gas-phase carbonylation of methanol to prepare acetic acid and acetate esters. The catalyst requires in-situ activation before the reaction. The activation atmosphere is a mixture of syngas (CO / H2 = 20 / 1 to 1 / 20, preferably CO / H2 = 15 / 1 to 1 / 1, molar ratio) and methanol and iodomethane (CH3OH / CH3I = 50 / 1 to 1 / 5, preferably CH3OH / CH3I = 30 / 1 to 1 / 1, molar ratio) (where CH3OH / CO = 5 / 1 to 1 / 5, preferably CH3OH / CO = 2 / 1 to 1 / 1, molar ratio). The activation temperature is 100–300℃, preferably 200–260℃, and the activation time is 10–100 h, preferably 50–80 h.

[0023] A fixed-bed reactor is used, with a reaction temperature of 150–300℃, preferably 200–250℃, a reaction pressure of 0.1–3.5 MPa, preferably 0.5–2.0 MPa, and a liquid hourly space velocity of 0.1–15 h⁻¹. -1 Preferably 2-12h -1 ;

[0024] The molar ratio of CO to CH3OH is 0.25–10, preferably 0.5–5, and the volume ratio of H2 to CO is 0.01–2.0, preferably 0.1–1.

[0025] The reaction requires the addition of iodomethane as a co-catalyst, with the amount added being 5-50 wt.% of the raw material methanol, preferably 10-20 wt.%.

[0026] The fixed-bed reactor is filled with catalyst and quartz sand, both of which are 40-60 mesh. There is a preheater in front of the reactor, which is filled with θ rings with a specification of φ5.0×5.0mm and made of Hastelloy or silicon dioxide.

[0027] The reaction system used is made of Hastelloy.

[0028] The main products of this reaction are acetic acid and methyl acetate, with trace amounts of dimethyl ether and methane as byproducts.

[0029] The beneficial effects of this invention are as follows:

[0030] Compared with existing metal catalytic technologies for methanol carbonylation, the catalyst of this invention has a simple preparation method and low investment cost. When applied to the methanol gas-phase carbonylation reaction, it only requires a Hastelloy reactor and has the advantages of high activity, high selectivity, and good stability.

[0031] Furthermore, the nitrogen-doped carbon-supported gold-based catalyst (Au / NC) prepared in this invention and its application in the heterogeneous carbonylation of methanol differ from the previous Co, Ir, and Rh system methanol carbonylation process, representing a novel methanol carbonylation catalytic system. Iodine promoters activate methanol, and Au adsorbs CO at the active sites in the catalyst, completing carbonyl insertion and acetyl iodide removal on the CO, thus completing the methanol carbonylation reaction. This novel Au-based methanol carbonylation reaction system, while ensuring high space-time yields of acetic acid and acetate esters, can significantly reduce catalyst investment costs and has potential for industrialization. Detailed Implementation

[0032] The following embodiments illustrate, but are not limited to, the content to be protected by this invention.

[0033] To compare the performance differences of catalysts prepared under different conditions in the methanol gas-phase carbonylation reaction and the differences in catalytic activity of the same catalyst under different reaction conditions, the following specific implementation examples are provided: Au / NC-01 catalyst: gold precursor is HAuCl6·6H2O, solvent is aqua regia (V... HNO3 :V HCl =1:3, the volume ratio of concentrated nitric acid (16M) to concentrated hydrochloric acid (12M) is 1:3; the nitrogen source is polyaniline; the impregnation method is equal volume impregnation; the catalyst calcination temperature is 800℃; Au / NC-02 catalyst: the gold precursor is Au(OH)3; the solvent is aqua regia (V... HNO3 :V HCl =1:3, concentrated nitric acid (16M) to concentrated hydrochloric acid (12M) volume ratio is 1:3, nitrogen source is polyaniline, impregnation method is equal volume impregnation, catalyst calcination temperature is 800℃; Au / NC-03 catalyst: gold precursor is HAuCl6·6H2O, solvent is deionized water, nitrogen source is polyaniline, impregnation method is equal volume impregnation, catalyst calcination temperature is 800℃; Au / NC-04 catalyst: gold precursor is HAuCl6·6H2O, solvent is aqua regia (V HNO3 :V HCl=1:3, the volume ratio of concentrated nitric acid (16M) to concentrated hydrochloric acid (12M) is 1:3; the nitrogen source is dicyandiamide; the impregnation method is equal volume impregnation; the catalyst calcination temperature is 800℃; Au / NC-05 catalyst: the gold precursor is HAuCl6·6H2O; the solvent is aqua regia (V... HNO3 :V HCl =1:3, concentrated nitric acid (16M) to concentrated hydrochloric acid (12M) volume ratio is 1:3, nitrogen source is polyaniline, impregnation method is excess impregnation, catalyst calcination temperature is 800℃; Au / NC-06 catalyst: gold precursor is HAuCl6·6H2O, solvent is aqua regia (V HNO3 :V HCl The ratio of concentrated nitric acid (16M) to concentrated hydrochloric acid (12M) is 1:3 (volume ratio 1:3), the nitrogen source is polyaniline, the impregnation method is equal volume impregnation, and the catalyst calcination temperature is 500℃. Catalyst preparation method: A gold precursor solution is prepared by dissolving the gold precursor in a solvent. This gold precursor solution is then loaded onto nitrogen-doped carbon support via wet impregnation. Finally, the catalyst is dried at low temperature and calcined at high temperature to obtain the Au / NC catalyst, wherein the Au content is 0.5 wt.%.

[0034] A fixed-bed reactor was used, filled with catalyst and quartz sand, both 40-60 mesh. A preheater was installed before the reactor, filled with θ-rings, φ5.0×5.0mm in size, made of Hastelloy alloy. Variations in reaction conditions are shown in the examples.

[0035] Example 1

[0036] Preparation of Au / NC-01 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V... HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then dried in an oven at 80℃ for 13 hours. Subsequently, it is calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-01 catalyst.

[0037] Methanol carbonylation reaction: Weigh 0.6g Au / NC-01 catalyst, activation conditions: activation temperature 240℃, activation pressure 1.0MPa, activation time 10h; CO / H2=10, CO / CH3OH=2, CH3OH / CH3I=20, (molar ratio, the same below);

[0038] Reaction conditions: reaction temperature 240℃, reaction pressure 1.0MPa; CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20 (molar ratio, the same below); LHSV = 6h -1 .

[0039] Example 2

[0040] Preparation of Au / NC-02 catalyst: Weigh 0.00579 g Au(OH)3 and dissolve it in 2 mL of aqua regia (V). HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, transferred to an oven at 80℃ for 13 hours, and then calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-02 catalyst.

[0041] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0042] Example 3

[0043] Preparation of Au / NC-03 catalyst: 0.01046 g of HAuCl6·6H2O was dissolved in 2 mL of deionized water and stirred to form a homogeneous solution A. An appropriate amount of polyaniline was placed in a tube furnace and carbonized at 800 °C for 1 h under a nitrogen atmosphere at a rate of 5 °C / min to obtain the NC support. Solution A was added dropwise to 1 g of the NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then transferred to an oven to dry at 80 °C for 13 h. Subsequently, it was calcined in a tube furnace at 800 °C under nitrogen for 5 h to obtain the Au / NC-03 catalyst.

[0044] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0045] Example 4

[0046] Preparation of Au / NC-01 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL of aqua regia (V HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a 1:1 volume ratio and stirring. An appropriate amount of polyaniline is placed in a tube furnace and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then dried in an oven at 80℃ for 13 hours. Subsequently, it is calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-01 catalyst.

[0047] Methanol carbonylation reaction: Weigh 0.6g Au / NC-01 catalyst, activation conditions: activation temperature 240℃, activation pressure 1.0MPa, activation time 10h; CO / H2=10, CO / CH3OH=2, CH3OH / CH3I=20, (molar ratio, the same below);

[0048] Reaction conditions: reaction temperature 240℃, reaction pressure 1.0MPa; CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20 (molar ratio, the same below); LHSV = 6h -1 .

[0049] Example 5

[0050] Preparation of Au / NC-01 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL of aqua regia (V 2). HNO3 :V HClA homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 3:1 and stirring. An appropriate amount of polyaniline is placed in a tube furnace and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then dried in an oven at 80℃ for 13 hours. Subsequently, it is calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-01 catalyst.

[0051] Methanol carbonylation reaction: Weigh 0.6g Au / NC-01 catalyst, activation conditions: activation temperature 240℃, activation pressure 1.0MPa, activation time 10h; CO / H2=10, CO / CH3OH=2, CH3OH / CH3I=20, (molar ratio, the same below);

[0052] Reaction conditions: reaction temperature 240℃, reaction pressure 1.0MPa; CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20 (molar ratio, the same below); LHSV = 6h -1 .

[0053] Example 6

[0054] Preparation of Au / NC-04 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of dicyandiamide is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, transferred to an oven at 80℃ for 13 hours, and then calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-04 catalyst.

[0055] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0056] Example 7

[0057] Preparation of Au / NC-05 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 10 mL aqua regia (V... HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an excess impregnation method, stirred evenly with a glass rod, transferred to an oven at 80℃ for 13 hours, and then calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-05 catalyst.

[0058] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0059] Example 8

[0060] Preparation of Au / NC-01 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V... HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then dried in an oven at 150℃ for 13 hours. Subsequently, it is calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-01 catalyst.

[0061] Methanol carbonylation reaction: Weigh 0.6g Au / NC-01 catalyst, activation conditions: activation temperature 240℃, activation pressure 1.0MPa, activation time 10h; CO / H2=10, CO / CH3OH=2, CH3OH / CH3I=20, (molar ratio, the same below);

[0062] Reaction conditions: reaction temperature 240℃, reaction pressure 1.0MPa; CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20 (molar ratio, the same below); LHSV = 6h-1 .

[0063] Example 9

[0064] Preparation of Au / NC-01 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V... HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, transferred to an oven at 80℃ for 2 hours of drying, and then calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-01 catalyst.

[0065] Methanol carbonylation reaction: Weigh 0.6g Au / NC-01 catalyst, activation conditions: activation temperature 240℃, activation pressure 1.0MPa, activation time 10h; CO / H2=10, CO / CH3OH=2, CH3OH / CH3I=20, (molar ratio, the same below);

[0066] Reaction conditions: reaction temperature 240℃, reaction pressure 1.0MPa; CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20 (molar ratio, the same below); LHSV = 6h -1 .

[0067] Example 10

[0068] Preparation of Au / NC-06 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V... HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then dried in an oven at 80℃ for 13 hours. Subsequently, it is calcined in a tube furnace at 500℃ under nitrogen for 5 hours to obtain the Au / NC-06 catalyst.

[0069] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0070] Example 11

[0071] Preparation of Au / NC-06 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V... HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, transferred to an oven at 80℃ for drying for 13 hours, and then calcined in a tube furnace at 800℃ under nitrogen for 8 hours to obtain the Au / NC-06 catalyst.

[0072] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0073] Example 12

[0074] Preparation of Au / NC-01 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V... HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then dried in an oven at 80℃ for 13 hours. Subsequently, it is calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-01 catalyst.

[0075] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0076] Example 13

[0077] Preparation of Au / NC-01 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V... HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then dried in an oven at 80℃ for 13 hours. Subsequently, it is calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-01 catalyst.

[0078] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0079] Example 14

[0080] Preparation of Au / NC-01 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V... HNO3 :V HClA homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then dried in an oven at 80℃ for 13 hours. Subsequently, it is calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-01 catalyst.

[0081] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0082] Example 15

[0083] Preparation of Au / NC-01 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V... HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then dried in an oven at 80℃ for 13 hours. Subsequently, it is calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-01 catalyst.

[0084] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0085] Example 16

[0086] Preparation of Au / NC-01 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V...HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then dried in an oven at 80℃ for 13 hours. Subsequently, it is calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-01 catalyst.

[0087] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0088] Example 17

[0089] Preparation of Au / NC-01 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V... HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then dried in an oven at 80℃ for 13 hours. Subsequently, it is calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC-01 catalyst.

[0090] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC-01 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0091] Comparative Example 1

[0092] Preparation of Au / NC catalyst: 0.01046 g of HAuCl6·6H2O was dissolved in 2 mL of concentrated nitric acid (16 M) and stirred to form a homogeneous solution A. An appropriate amount of polyaniline was placed in a tube furnace and carbonized at 800 °C for 1 h under a nitrogen atmosphere at a rate of 5 °C / min to obtain the NC support. Solution A was added dropwise to 1 g of the NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then transferred to an oven to dry at 80 °C for 13 h. Subsequently, it was calcined in a tube furnace at 800 °C under nitrogen for 5 h to obtain the Au / NC catalyst.

[0093] Methanol carbonylation reaction: Weigh 0.6 g Au / NC catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0094] Comparative Example 2

[0095] Preparation of Au / NC catalyst: 0.01046 g of HAuCl6·6H2O was dissolved in 2 mL of dilute nitric acid (0.5 M) and stirred to form a homogeneous solution A. An appropriate amount of polyaniline was placed in a tube furnace and carbonized at 800 °C for 1 h at a rate of 5 °C / min under a nitrogen atmosphere to obtain the NC support. Solution A was added dropwise to 1 g of the NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then transferred to an oven to dry at 80 °C for 13 h. Subsequently, it was calcined in a tube furnace at 800 °C under nitrogen for 5 h to obtain the Au / NC catalyst.

[0096] Methanol carbonylation reaction: Weigh 0.6 g Au / NC catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0097] Comparative Example 3

[0098] Preparation of Au / NC catalyst: 0.01046 g of HAuCl6·6H2O was dissolved in 2 mL of tetrahydrofuran (THF) and stirred to form a homogeneous solution A. An appropriate amount of polyaniline was placed in a tube furnace and carbonized at 800 °C for 1 h at a rate of 5 °C / min under a nitrogen atmosphere to obtain the NC support. Solution A was added dropwise to 1 g of the NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then transferred to an oven to dry at 80 °C for 13 h. Subsequently, it was calcined in a tube furnace at 800 °C under nitrogen for 5 h to obtain the Au / NC catalyst.

[0099] Methanol carbonylation reaction: Weigh 0.6 g Au / NC catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0100] Comparative Example 4

[0101] Preparation of Au / NC catalyst: 0.01046 g of HAuCl6·6H2O was dissolved in 2 mL of dichloromethane (CH2Cl2) and stirred to form a homogeneous solution A. An appropriate amount of polyaniline was placed in a tube furnace and carbonized at 800 °C for 1 h at a rate of 5 °C / min under a nitrogen atmosphere to obtain the NC support. Solution A was added dropwise to 1 g of the NC support using an equal-volume impregnation method, stirred evenly with a glass rod, and then transferred to an oven to dry at 80 °C for 13 h. Subsequently, it was calcined in a tube furnace at 800 °C under nitrogen for 5 h to obtain the Au / NC catalyst.

[0102] Methanol carbonylation reaction: Weigh 0.6 g Au / NC catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0103] Comparative Example 5

[0104] Preparation of Au / NC catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V HNO3 :V HClA homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, transferred to an oven at 80℃ for 13 hours, and then calcined in a tube furnace at 100℃ under nitrogen for 5 hours to obtain the Au / NC catalyst.

[0105] Methanol carbonylation reaction: Weigh 0.6 g Au / NC catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0106] Comparative Example 6

[0107] Preparation of Au / NC catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V HNO3 :V HCl A homogeneous solution A is formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. An appropriate amount of polyaniline is weighed and placed in a tube furnace, and carbonized at 800℃ for 1 hour at a rate of 5℃ / min under a nitrogen atmosphere to obtain the NC support. Solution A is added dropwise to 1 g of NC support using an equal-volume impregnation method, stirred evenly with a glass rod, transferred to an oven at 80℃ for 13 hours, and then calcined in a tube furnace at 800℃ under nitrogen for 5 hours to obtain the Au / NC catalyst.

[0108] Methanol carbonylation reaction: Weigh 0.6 g of Au / NC catalyst (unactivated). Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0109] Comparative Example 7

[0110] Preparation of Au / SiO2 catalyst: Weigh 0.01046 g HAuCl6·6H2O and dissolve it in 2 mL aqua regia (V... HNO3 :V HClA homogeneous solution A was formed by mixing concentrated nitric acid (16M) and concentrated hydrochloric acid (12M) in a volume ratio of 1:3. Solution A was then added dropwise to 1 g of a commercial SiO2 support (AR, 99%) using an equal-volume impregnation method. The mixture was stirred with a glass rod until homogeneous, transferred to an oven at 80°C for 13 h, and subsequently calcined in a tube furnace at 800°C under nitrogen for 5 h to obtain the Au / SiO2 catalyst.

[0111] Methanol carbonylation reaction: Weigh 0.6 g of Au / SiO2 catalyst. Activation conditions: activation temperature 240℃, activation pressure 1.0 MPa, activation time 10 h, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20; Reaction conditions: reaction temperature 240℃, reaction pressure 1.0 MPa, CO / H2 = 10, CO / CH3OH = 2, CH3OH / CH3I = 20, LHSV = 6 h. -1 .

[0112] An application example is the use of the prepared catalyst in the reaction of preparing acetic acid and acetate esters from methanol and CO.

[0113] Au / NC catalysts prepared under different conditions were obtained using Examples 1-17 and Comparative Examples 1-7, and applied to the methanol gas-phase carbonylation reaction under different reaction conditions to prepare acetic acid and acetate esters. The methanol conversion and the selectivity of acetic acid and acetate esters are shown in Table 1. (All ratios in the reaction operating conditions are molar ratios.)

[0114] Table 1

[0115]

[0116]

[0117] The results show that Examples 1-11, which present the catalysts prepared under different conditions and applied to the same reaction conditions, involve changing the gold precursor, solvent, carbon source, impregnation method, catalyst drying temperature and time, and activation calcination temperature and time, respectively. The results indicate that the Au / NC-01 catalyst exhibits the best activity. Subsequently, Examples 12-17 present the Au / NC-01 catalyst applied to the methanol gas-phase carbonylation reaction to prepare acetic acid and acetate esters under different reaction conditions, involving changes in reaction temperature, reaction pressure, CO / H2, CO / CH3OH, CH3OH / CH3I, and LHSV, respectively. Analysis of the results shows that increasing temperature and pressure, higher CO / H2, higher CO / CH3OH, lower CH3OH / CH3I, and lower LHSV are beneficial for the methanol carbonylation reaction to prepare acetic acid and acetate esters. Comparative Examples 1-2 demonstrate that the catalyst prepared using only concentrated nitric acid as a solvent has lower reactivity; using dilute nitric acid as a solvent results in even lower activity. Comparative Examples 3-4 show that the Au / NC catalyst prepared using non-acidic solvents tetrahydrofuran and dichloromethane essentially loses its methanol carbonylation activity. Comparative Example 5 indicates that the calcination temperature of the catalyst is also crucial; when the calcination temperature is 100℃, the catalyst activity is low. In Comparative Example 6, the Au / NC catalyst was not activated before the reaction, resulting in virtually no methanol carbonylation activity, highlighting the necessity of pre-reaction activation. In Comparative Example 7, a gold-based catalyst supported on a carbon support different from nitrogen-doped SiO2 was used for the methanol carbonylation reaction, exhibiting extremely low activity.

Claims

1. A method for preparing a methanol gas-phase carbonylation catalyst, characterized in that: The catalyst consists of an active component and a support, wherein the active component is gold and the support is nitrogen-doped carbon. The catalyst is prepared by dissolving a gold precursor in a solvent to obtain a gold precursor solution, loading the gold precursor solution onto a nitrogen-doped carbon support by wet impregnation, and finally drying and calcining at high temperature to obtain the catalyst. The solvent for dissolving the gold precursor is an aqueous solution of 0.5-16 M nitric acid and 0.5-12 M hydrochloric acid in a volume ratio of 1-3:3-1. The catalyst has a gold content of 0.2-1.0% by mass, with the remainder being nitrogen-doped carbon. The high-temperature calcination temperature is 600-1000℃, the calcination time is 3-8 h, and the atmosphere is a nitrogen atmosphere. The catalyst needs to be activated in situ before the methanol gas-phase carbonylation reaction. The activation atmosphere is a mixture of syngas, methanol, and iodomethane, wherein the molar ratio of CO / H2 in the syngas is 15 / 1-1 / 1, the molar ratio of methanol to iodomethane is 30 / 1-1 / 1, the molar ratio of methanol to CO is 5 / 1-1 / 5, the activation temperature is 200-260℃, and the activation time is 50-80 h.

2. The method for preparing the catalyst according to claim 1, characterized in that: The precursor of gold is HAuCl6·6H2O.

3. The method for preparing the catalyst according to claim 1, characterized in that: The nitrogen-doped carbon is obtained by pyrolysis of one or more of dicyandiamide, melamine, urea or polyaniline at 600-1000 °C for 1-2 h in a nitrogen atmosphere.

4. The method for preparing the catalyst according to claim 1, characterized in that: The catalyst is prepared by one of equal-volume wet impregnation or over-volume wet impregnation. The molar concentration of gold in the gold precursor solution ranged from 1.0 to 5.0 mmol / L. The drying temperature is 60~100℃, and the drying time is 5~15 h.

5. A catalyst prepared by any one of the preparation methods described in claims 1-4.

6. The use of the catalyst according to claim 5 in the catalytic gas-phase carbonylation of methanol to prepare acetic acid, or the reaction of acetic acid and acetate esters.

7. The application according to claim 6, characterized in that: The catalyst needs to be activated in situ before the methanol gas-phase carbonylation reaction. The activation atmosphere is a mixture of syngas, methanol and iodomethane, wherein the molar ratio of CO / H2 in the syngas is 15 / 1 to 1 / 1, the molar ratio of methanol to iodomethane is 30 / 1 to 1 / 1, the molar ratio of methanol to CO is 5 / 1 to 1 / 5, the activation temperature is 200 to 260℃, and the activation time is 50 to 80 h.

8. The application according to claim 6, characterized in that: A fixed-bed reactor was used, with a reaction temperature of 200–250 °C, a reaction pressure of 0.5–2.0 MPa, and a liquid hourly space velocity of 2–12 h⁻¹. -1 ; The molar ratio of CO to CH3OH is 0.5~5, and the volume ratio of H2 to CO is 0.1~1; The reaction requires the addition of iodomethane as a co-catalyst, with the amount added being 10-20 wt.% of the raw material methanol.

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