Process for production of methanol
A catalytic process using a transition metal and Lewis base ligand with a nucleophilic promoter converts CO and H2 into methanol efficiently at lower temperatures and pressures, addressing energy intensity issues in existing methanol production methods.
Patent Information
- Application Number
- CN202411338790.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2018-12-28
- Filing Date
- 2019-12-10
- Publication Date
- 2024-12-31
AI Technical Summary
Current methanol production methods require harsh conditions (above 250 °C and high pressures over 100 bar), making them energy-intensive and economically and environmentally unsustainable.
A catalytic process using a transition metal as a central ion, Lewis base ligand, and nucleophilic promoter to convert CO and H2 into methanol under milder conditions (below 160 °C and 50 bar) without intermediate separation steps, utilizing a novel carbon monoxide hydrogenation scheme.
Reduces energy consumption and operating costs while maintaining high methanol production efficiency, allowing for the use of synthesis gas from various sources without purification, and enabling both batch and continuous processes.
Smart Images
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Abstract
Description
[0001] This application is a divisional application based on the Chinese patent application with application number 201980086710.1, application date December 10, 2019, and invention name “Method for producing methanol”.
[0002] The present invention relates to a method for catalyzing the reaction of CO and H2 to produce methanol as a product by using a catalytic complex containing a transition metal as a central ion and at least one Lewis base ligand and a nucleophilic promoter.
[0003] Methanol is a chemical with the formula CH3OH (a methyl group attached to a hydroxyl group, often abbreviated to MeOH). It is a key component of the chemical industry. It can be used not only as a fuel component but also as a basic building block of the chemical industry, with production exceeding 100 million tons in 2018.
[0004] However, a disadvantage in all known reaction mechanisms is that the reactions must be carried out under relatively harsh conditions, in particular above 250 °C and high pressures of more than 100 bar. This makes current methods very energy-intensive, which is problematic from both an economic and environmental point of view. By reducing energy consumption, operating expenditures (opex) and capital expenditures (capex) can be reduced and the sustainability of the method can be improved.
[0005] It is therefore an object of the present invention to provide a process for producing methanol whose energy requirement is significantly lower than the processes known from the prior art.
[0006] This object is achieved by a process having the features of claim 1 .
[0007] Such a process converts CO and H2 from a catalytic complex having a transition metal as a central ion and a Lewis base ligand. The reaction is also carried out in the presence of a nucleophilic promoter.
[0008] The present invention discloses a novel carbon monoxide hydrogenation scheme. The method comprises capturing CO and converting CO into formamide or methyl formate by a promoter under an atmosphere containing H2, followed by hydrogenation of the intermediate produced in one process step, i.e. hydrogenation to methanol. The fixation of CO can be achieved by various nucleophilic promoters such as amines and nitrogen heterocycles. As for the hydrogenolysis of amide or methyl formate, Mn, Fe and Ru can be used to promote it.
[0009] The potential reaction routes are described as follows:
[0010]
[0011] 1. Addition of carbon monoxide to metal ions
[0012] 2. The Lewis base assists the XH bond splitting of the promoter and adds CO, then eliminates the carbonylated HX to H-CO-X
[0013] 3. Elimination of H-CO-X
[0014] 4. Hydrogenation of H-CO-X by catalyst
[0015] 5. Elimination of formaldehyde
[0016] 6. Formaldehyde hydrogenation to methanol
[0017] In this reaction route, the active centers of catalyst M-LB and promoter XH are crucial to the reaction.
[0018] The key discovery to achieve methanol synthesis was to find a suitable catalyst and promoter combination that is compatible with CO and produces methanol in an H2-containing atmosphere. Therefore, in the initial stage of this research, various transition metal Lewis basic ligand complexes were investigated for their effectiveness in the cleavage of amides to amines and methanol, or esters to alcohols, in H2 / CO mixtures.
[0019] It is essential for the present invention that the entire reaction is carried out in one mixture without the need for temporary and / or partial separation steps.
[0020] Furthermore, the process can be carried out as a batch process or as a continuous process.
[0021] There may be additional compounds in the reaction mixture, in particular CO 2. This makes it possible to use synthesis gas from different sources such as the reverse water gas shift reaction without any clean-up steps.
[0022] The catalyst is a metal catalyst having the directing structure M-LB, where M is a metal ion and LB is at least one Lewis base center. In its simplest form, the catalyst can be described as M x N y (x=1-4, y=1-2), which is shown in Formula 2.
[0023]
[0024] In its simplest form, the catalyst is usually a solid compound without any ligands.
[0025] However, metal organic complexes as shown in formula 3 are also possible, in which M is a metal ion and LB is the center of at least one Lewis base. R is at least one ligand containing at least one atom selected from N, P, O or S. In this variant, LB contains at least one atom selected from N, P, O, S or C, regardless of the atoms of the ligand. R and LB can be connected by a C2 (-C2H4-) or C3 (-C3H6-) chain. Chelating ligands are particularly preferred. According to this scheme (formula 3), the ligand can also be o-aminoaniline.
[0026]
[0027] Other metal organic complexes with two different ligands are shown in formula 4. According to this scheme, the ligand can also be, for example, an o-aminoaniline derivative with a third chelating group.
[0028]
[0029] Particularly preferred are systems having a metal ion selected from the group consisting of Mn, Fe, Cr, Mo, W, Re, Co, Rh, Ir, Ni and Pd, a Lewis base containing at least one nitrogen atom, and R, R1 and / or R2 each containing at least one phosphorus, nitrogen or sulfur atom.
[0030] The ligand can be a clamp type complex. It can be selected from the clamp type group of PNP, where R1 = P(iPr)2, R2 = P(iPr)2, LB = NH. Other clamp types are PNN, NNN, NNS or NNC, where P can be P = PPh2, PEt2, N can be N = NH2, NEt2, pyridine, pyrrole, indole, isoindole, imidazole, benzimidazole, aniline, and S can be S = SMe, SEt, SPh.
[0031] The transition metal is an ion selected from manganese, iron, molybdenum, chromium, cobalt, ruthenium, rhodium, nickel or palladium, wherein manganese, iron or molybdenum particularly show good capabilities. In particular, the use of manganese as the central ion shows a high turnover rate (TON).
[0032] It is also preferred that the process is carried out in the presence of a base, which can further stabilize the coordination and / or deprotonation of the central ion. In particular, it has been found that hydroxides and / or basic oxides of at least one of the elements lithium, sodium, potassium or calcium can be used.
[0033] It has been found that promoters play an important role in the hydrogenation of CO. In particular, promoters such as primary amines, secondary amines, primary anilines and nitrogen heterocycles: pyrrole, indole, imidazole, carbazole, benzimidazole have been found to be active.
[0034] Promoters showing TON values above 50 are of particular interest as they indicate that methanol is produced in excess of the nitrogen promoter. The most effective promoters are secondary anilines, pyrroles, indoles and carbazoles.
[0035] In general, the following accelerators were tested successfully:
[0036]
[0037]
[0038] It has also been shown that a ratio of promoter to base r1 of 1:1 to 3:1 and / or a ratio of base to catalyst r2 of 25:1 to 100:1 is particularly advantageous. The highest conversions are found here.
[0039] Furthermore, it has proven to be particularly advantageous to carry out the method at a temperature below 160° C. The temperature of the sample is therefore below 160° C. This allows for further energy savings.
[0040] Advantageously, the reaction is carried out in a weakly coordinating (towards the catalyst) or nonpolar solvent. Cyclohexane is particularly preferred here. This avoids interaction with the active centers of the catalyst.
[0041] Carbon monoxide and hydrogen are preferably introduced into the process at a partial pressure of 0.1 to 50 bar. In particular, CO at a pressure of 0.1 to 25 bar and hydrogen at a pressure of 30 to 50 bar are introduced into the system. Increasing the pressure of hydrogen to a pressure slightly higher than that of carbon monoxide ensures that the downstream hydrogenation process is carried out as completely as possible. For CO, it is not necessary to increase these pressures further.
[0042] Furthermore, homogeneously catalyzed reactions can be performed. The advantage of homogeneously catalyzed reactions is that there are no additional mass transfer effects such as adsorption or desorption on the surface or additional restrictions due to limited surface area.
[0043] At the same time, however, it is also conceivable according to the invention to stabilize the complex on a surface and to carry out a heterogeneous catalytic reduction. The advantages of this reaction are that, on the one hand, it corresponds to the processes used in the chemical industry, so that only the catalyst needs to be replaced and the operating conditions changed; on the other hand, hydrogen catalytic processes generally facilitate the separation of the catalyst.
[0044] Therefore, it is particularly preferred to produce methanol from CO and H2 at a pressure of 10 to 40 bar, the pressure of each component being independent of each other. The temperature is 120 to 150°C. The concentration of the catalyst is 1 to 10 mmol. A manganese-PNP complex is used as a catalyst. In addition, 0.2 to 1 mmol of aniline is used as a promoter, or 0.1 to 0.5 mmol is used as a base. The entire reaction is carried out in cyclohexane.
[0045] The following examples illustrate individual aspects of the invention.All described and / or depicted features, either alone or in any combination, form the subject matter of the present application, regardless of whether they are depicted in the claims or mentioned therein.
[0046] Further identified catalysts
[0047] Based on the determined reaction route, other catalysts can be identified by quantum mechanical virtual high-throughput screening. The most important steps of this reaction are the free energy of the promoter addition to the carbonyl complex (Scheme step 2) and the free energy transition barrier (TS) for the elimination of formamide (Scheme step 3).
[0048]
[0049]
[0050] General Procedure for Hydrogenation of Amides with Manganese Complexes Using CO / H2
[0051] 5 μ mmol of Mn-1, 0.25 mmol of amide and 2 mL of dry solvent were loaded into a flame-dried 8 mL vial with a magnetic stirring bar. The vial was covered with a septum and the mixture was stirred for 10 seconds. The reaction mixture was then purged with Ar for 30 seconds and 0.125 mmol of alkali (t-BuOK) was added. The septum was pierced with a needle and the vial was placed in a 300 mL autoclave. The autoclave was purged with carbon monoxide 5 times (5 to 7 atm) and then pressurized to 5 to 20 atm. The autoclave was connected to a hydrogen pipeline and filled to a total pressure of 50 atm. The autoclave was placed in a preheated aluminum block and stirred at 700 rpm for 20 hours at 150 ° C. The reaction was then placed in ice, cooled and decompressed. The reaction bottle was analyzed by GC and NMR analysis, and the amount of methanol and the corresponding amine was determined by GC using n-hexadecane as a standard.
[0052] General Procedure for CO / H2 Conversion to Methanol
[0053] 5 μ mmol of Mn-1, 0.25 to 6.0 mmol of promoter and 2 mL of dry solvent were loaded into a flame-dried 8 mL vial with a magnetic stirring bar. The vial was covered with a septum and the mixture was stirred for 10 seconds. The reaction mixture was then purged with Ar for 30 seconds and 0.125 mmol of base (t-BuOK) was added. The septum was pierced with a needle and the vial was placed in a 300 mL autoclave. The autoclave was purged with carbon monoxide 5 times (5 to 7 atm) and then pressurized to 20 atm. The autoclave was connected to a hydrogen pipeline and filled to a total pressure of 50 atm. The autoclave was placed in a preheated aluminum block and stirred at 700 rpm for 20 hours at 150 ° C. The reaction was then placed in ice, cooled and decompressed. The reaction bottle was analyzed by GC and NMR analysis, and the amount of methanol was determined by GC using n-hexadecane as a standard.
Claims
1. A method for catalyzing the reaction of CO and H2 to produce methanol as a product using a catalyst comprising a transition metal and at least one Lewis base ligand and at least one nucleophilic promoter.
2. The method according to claim 1, characterized in that The catalyst is a metal organic complex having at least one ligand, at least one atom of which is selected from N, P, O and S.
3. The method according to claim 2, characterized in that The ligand is a clamp-type complex.
4. A method according to any one of the preceding claims, characterised in that The central ion is an ion selected from Mn, Fe or Mo as the central ion.
5. A method according to any one of the preceding claims, characterised in that The catalyst is selected from the following complexes:
6. A method according to any one of the preceding claims, characterised in that This method is carried out in the presence of a base.
7. A method according to any one of the preceding claims, characterised in that The base is a hydroxide and / or alkoxide of at least one of lithium, sodium, potassium or calcium.
8. A method according to any one of the preceding claims, characterised in that The accelerator contains nitrogen.
9. A method according to any one of the preceding claims, characterised in that The accelerator contains at least one NH group and is in particular selected from primary amines, secondary amines, primary anilines and nitrogen heterocycles, in particular pyrrole, indole, imidazole, carbazole and benzimidazole.
10. The method according to any one of the preceding claims, characterized in that The accelerator is selected from the following compounds:
11. The method according to any one of the preceding claims, characterized in that The ratio r1 of promoter to base is from 1:1 to 3:1, and / or the ratio r2 of base to catalyst is from 25:1 to 100:
1.
12. A method according to any one of the preceding claims, characterised in that The process is carried out at a temperature below 200°C.
13. A method according to any one of the preceding claims, characterised in that The process is carried out in a nonpolar solvent, in particular using cyclohexane as solvent.
14. A method according to any one of the preceding claims, characterised in that All compounds were introduced at a partial pressure of 0.1 to 40 bar.
15. A method according to any one of the preceding claims, characterised in that Methanol is produced from CO and H2 in the presence of 1 to 10 μmol of the Mn-PNP complex, 0.2 to 1 mmol of aniline and 0.1 to 0.5 tBuOK in cyclohexane at a pressure of 0.1 to 40 bar and a temperature of 120 to 150°C, independently of each other.