Process for preparation of ome2
Patent Information
- Application Number
- EP2024718722
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-04-03
- Filing Date
- 2024-04-02
- Publication Date
- 2026-02-11
AI Technical Summary
The production of polyoxymethylene dimethyl ether (OME2) is hindered by its low boiling point, making separation from byproducts difficult in existing synthesis methods, and existing processes are inefficient, resulting in low purity and high energy consumption.
A process involving a reactant composition of methylal and polyoxymethylene dimethyl ethers, reacted in the presence of an acidic catalyst, followed by distillation to separate OME2 from other products, achieving high purity and reducing byproduct formation.
The process efficiently produces OME2 in high purity by effectively separating it from other products, reducing energy consumption and byproduct formation, and optimizing the yield through controlled distillation steps.
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Abstract
Description
[0001] FRAUNHOFER SOCIETY FOR THE ADVANCEMENT OF APPLIED RESEARCH EV
[0002] Fraunhofer Society for the Advancement of Applied Research
[0003] Hansastraße 27c, 80686 Munich, Germany
[0004] Process for the production of OME2
[0005] Polyoxymethylene dimethyl ether of the formula H3C-O-(CH2O) n -CH3, n > 3, especially those with 3-5 oxymethylene units (OME3-5), are of interest as synthetic diesel fuel or additive for diesel fuel, while OME2, i.e. a compound of the formula H3 -O-(CH2O)2-CH3 (CAS No. 628-90-0), is rather unsuitable for these applications due to its low boiling point.
[0006] However, OME2 is of interest as a solvent, e.g. for paints, varnishes, oils and rubber, as a possible additive for gasoline and as an absorbent for formaldehyde, see e.g. Z. Xue et al., “The Study on the application of Low Polymerization degree PODE2”, Al P Conference Proceedings 1839, 020017 (2017), and WO 2016 / 180085 A1.
[0007] In the synthesis of polyoxymethylene dimethyl ethers, a formaldehyde source (e.g., formaldehyde, trioxane, or paraformaldehyde) and a methyl capping compound such as methanol, methylal, or dimethyl ether are typically used as reactants. If the reactant mixture contains methanol and water, these react with formaldehyde to form polyoxymethylene glycols (MG n ; HO-(CH2O) n -H) and polyoxymethylene hemiacetals (HF n; HO-(CH2O)n-CH3) according to the following reaction equations 1-4. These reactions do not require the presence of a catalyst and reach chemical equilibrium very quickly. Furthermore, the chemical equilibrium lies predominantly on the product side, so that essentially no monomeric formaldehyde (CH2O) is present in the product mixture. For the formation of methylal (H3C-O-(CH2O)I-CH3; OME1) by the acetalization reaction between methanol and HO-CH2O-CH3 (HF1) according to the following reaction equation 5, the presence of an acidic catalyst is required. Chain growth through the incorporation of further CH2O units occurs according to the following reaction equation 7. Further acetalization reactions between methanol and the polyoxymethylene hemiacetals HF ntake place according to the following reaction equation 6. Possible side reactions with the formation of trioxane ((CH2O)s) and methyl formate (HC(O)OCH3) are shown in the following reaction equations 8 and 9.
[0008] An overview of known manufacturing processes for polyoxymethylene dimethyl ether H3C- O-(CH2O) n -CH3 with n>2 (OME>2), especially n = 3-5 (OME3-5), can be found, for example, in the publication by F. Mantei et al., Sustainable Energy & Fuels, 2022, 6, pp. 528-549. A distinction is made between anhydrous and aqueous synthesis routes. Anhydrous synthesis routes exhibit reduced by-product formation, but the preparation of the reactants is energy-intensive. The preparation of the reactants for aqueous synthesis routes is less energy-intensive, but the reaction product contains additional by-products and water.
[0009] In the anhydrous synthesis of polyoxymethylene dimethyl ethers, for example, methylal and trioxane are used as reactants. The product stream generated with this synthesis approach typically still contains significant amounts of unreacted trioxane. Since the boiling points of trioxane (115 °C) and OME2 (105 °C) are quite close, effective distillative separation of OME2 is very difficult.
[0010] For example, the aqueous synthesis route for producing polyoxymethylene dimethyl ethers uses an aqueous solution containing formaldehyde and methanol as reactants. The product stream obtained with this synthesis approach typically contains water and, optionally, polyoxymethylene glycols. Since their boiling points overlap with the boiling point of OME2, effective distillative separation of OME2 is very difficult, even with the aqueous synthesis route.
[0011] CN 106397142 A describes a process for the preparation of OME2, using methylal and trioxane as reactants and reacting in the presence of a zeolite as catalyst.
[0012] CN 107522602 A describes a process for the production of OME2, wherein methylal, methanol and water are reacted in a reactive distillation unit.
[0013] CN 104292085 A describes a process for the preparation of polyoxymethylene dimethyl ethers, wherein methanol or methylal is oxidized to formaldehyde, the formaldehyde is polymerized to paraformaldehyde, paraformaldehyde and methylal are converted to polyoxymethylene dimethyl ethers and these polyoxymethylene dimethyl ethers are separated into OME2 and OME3-4.
[0014] CN 105152882 A describes a process for the preparation of OME3-5, wherein methylal and OME>6 are reacted with each other as reactants.
[0015] One object of the invention is the production of OME2 by a process that can be carried out as efficiently as possible (e.g. energy-efficient) and thereby delivers OME2 in high purity.
[0016] The problem is solved by a process for preparing a compound of the formula H3C-O-(CH2O)2-CH3 (OME2), which comprises the following steps:
[0017] Introducing a reactant composition ZR containing as reactants methylal (OME1) and one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20, into a reactor R1 and reacting the reactants in the presence of an acidic catalyst to obtain a product mixture ZP containing H3C-O-(CH2O)2-CH3 (OME2), methylal (OME1) and one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, contains,
[0018] Introducing the product mixture ZP into a distillation unit D1 and separating the product mixture ZP by distillation into a first fraction containing methylal (OME1) and leaving the distillation unit D1 as the overhead stream KSDI, and a second fraction containing H3C-O-(CH2O)2-CH3 (OME2) and one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, and leaves the distillation unit D1 as bottom stream SSDI,
[0019] Introducing the bottom stream SSDI into a distillation unit D2 and distillative separation of the bottom stream SS Di into a first fraction containing H3C-O-(CH2O)2-CH3(OME2) and the distillation unit D2 as head stream KS D 2, and a second fraction containing one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20, and leaving the distillation unit D2 as bottom stream SS D2 leaves.
[0020] The use of methylal and the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, as reactants in the reactant composition Z R leads to a product composition Z P , which contains undesirable by-products such as formaldehyde, water, methanol, polyoxymethylene glycols, and polyoxymethylene hemiacetals only in very low concentrations or is even free of these undesirable by-products. In addition to OME2, the product composition ZP contains Methylal and one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20. The Methylal and the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, which in the product composition Z P may be unreacted reactants of the reactant composition ZR or may have been newly formed during the reaction in reactor R1.
[0021] Furthermore, it has proven advantageous in the context of the present invention with regard to the yield or purity of the OME2 if OME2 is first distilled in the first distillation unit D1 together with the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, is separated by distillation (as bottom stream SSDI) and a distillative separation of the OME2 from these polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, then in the distillation unit D2.
[0022] Preferably, the reactant composition ZR contains the reactants (ie methylal and the polyoxymethylene dimethyl ether(s) of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20) in a total concentration of at least 90 mass%, more preferably at least 95 mass%, even more preferably at least 98 mass%.
[0023] For example, the reactant composition ZR is formaldehyde-free, methanol-free and / or anhydrous or contains formaldehyde, methanol and water in a total concentration of less than 5% by mass, preferably less than 0.5% by mass.
[0024] In an exemplary embodiment, the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20, present in the reactant composition ZR have a weight-average molecular weight Mw in the range from 136 g / mol to 210 g / mol.
[0025] How a mass-average molecular weight of a mixture containing several components (in this case a mixture of polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20) is known to the person skilled in the art. For each polyoxymethylene dimethyl ether of the formula H3C-O-(CH2O) present in the reactant composition n-CH3, 3 < n < 20, its relative mass fraction, based on the total mass of the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, and multiplied by its molar mass. The sum of these values gives the mass-average molecular weight Mw of the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20.
[0026] Due to the relative mass fractions of the respective polyoxymethylene dimethyl ethers, the mass-average molecular weight M w be set.
[0027] For example, at least 80% by mass or at least 90% by mass of the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, which are present in the reactant composition ZR, one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 10.
[0028] For example, at least 50 mass% (e.g. 50-90 mass%) of the
[0029] Polyoxymethylene dimethyl ether of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, which are present in the reactant composition ZR, one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 5.
[0030] In a further exemplary embodiment, the methylal and the polyoxymethylene dimethyl ether(s) of the reactant composition ZR have a weight-average molecular weight in the range from 90 g / mol to 190 g / mol, more preferably 90 g / mol to 136 g / mol or 100 g / mol to 120 g / mol. This results in a further improvement in the yield of OME2 in the reaction of the reactants in reactor R1.
[0031] As already mentioned above, the person skilled in the art knows how to determine the weight-average molecular weight of a mixture of several components (in this case, a mixture of methylal and the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20). For the methylal present in the reactant composition and for each polyoxymethylene dimethyl ether of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20, its relative mass fraction, based on the total mass of methylal and polyoxymethylene dimethyl ethers, is determined and multiplied by its molar mass. The sum of these values gives the weight-average molecular weight Mw of the mixture of methylal and the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20. The mass average molecular weight Mw can be adjusted by the relative mass fractions of the methylal and the respective polyoxymethylene dimethyl ethers.
[0032] The reactants of the reactant composition can be introduced into reactor R1 separately. Alternatively, the reactants can be mixed together outside of reactor R1, and this mixture can then be fed to reactor R1.
[0033] In an exemplary embodiment, the polyoxymethylene dimethyl ethers of the reactant composition ZR are at least partially produced in a separate production unit and subsequently fed to the reactor R1 (either without intermediate storage or alternatively after temporary intermediate storage).
[0034] Suitable conditions for the reaction of methylal and polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, to OME2 are known to the person skilled in the art or can be readily determined taking into account general specialist knowledge.
[0035] The reaction takes place in the presence of an acidic catalyst. Suitable acidic catalysts are known to those skilled in the art. Solid catalysts or liquid acids can be used. Examples of suitable catalysts include: an ion exchange resin containing acidic groups (i.e., a cation exchange resin), a zeolite, an aluminosilicate, an aluminum oxide, a transition metal oxide (optionally present on a support material), a graphene oxide, a mineral acid (e.g., sulfuric acid), an organic acid (e.g., a sulfonic acid), an acidic ionic liquid, and an oxonium salt (e.g., a trimethyloxonium salt).
[0036] Reactor R1 is operated, for example, at a pressure of 1-10 bar and a temperature of 20-120 °C. Preferably, pressure and temperature are selected such that the reactant composition ZR is present at least partially as a liquid phase during the reaction in reactor R1. Reactor R1 is, for example, a fixed-bed reactor. However, other reactor types can also be used for the reaction of the reactant composition within the scope of the present invention.
[0037] As mentioned above, the use of Methylal and the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, as reactants in the reactant composition ZR means that undesirable by-products such as formaldehyde, water, methanol, polyoxymethylene glycols and polyoxymethylene hemiacetals are not formed or are formed only in low concentrations during the reaction.
[0038] For example, the product mixture ZP OME2 contains methylal and one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, in a total concentration of at least 90 mass%, more preferably at least 95 mass%, even more preferably at least 99 mass%.
[0039] For example, the product mixture formed in reactor R1 contains ZP OME2 in a concentration of at least 5 mass%, more preferably at least 10 mass%, e.g. 5-40 mass% or 10-35 mass%.
[0040] For example, at least 80% by mass or at least 90% by mass of the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, which in the product mixture Z P one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 10.
[0041] For example, at least 45 mass% (e.g. 45-90 mass%) of the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n-CH3, 3 < n < 20, which are present in the product mixture ZP, one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 5.
[0042] As described in more detail below, the product mixture Z P into a distillation unit D1. Optionally, the product mixture Z P before being introduced into the distillation unit D1, are passed through a unit containing a basic material and / or a filter unit. Acidic catalyst residues that may be contained in the product mixture ZP can be neutralized by the basic material, and solids that may be present in the product mixture Z can be removed by the filter unit. Pare dispersed, are removed. The product mixture ZP is introduced into a distillation unit D1 and the product mixture ZP is separated by distillation into a first fraction containing methylal and leaving the distillation unit D1 as the top stream KSDI, and a second fraction containing OME2 and one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20, and leaving the distillation unit D1 as the bottom stream SSDI.
[0043] The distillation unit D1 is therefore designed for the distillative separation of the product mixture ZP SO, that methylal in the overhead stream and OME2 and the polyoxymethylene dimethyl ether(s) of the formula H3C-O-(CH2O) n-CH3, 3 < n < 20, are withdrawn in the bottom stream from the distillation unit D1. Suitable conditions for this can be determined by the person skilled in the art taking into account general specialist knowledge. The distillation unit D1 is, for example, a distillation column. The distillation unit typically contains internals for distillative separation, in particular trays, random packings or structured packings, as are generally known to the person skilled in the art. The distillation unit D1 is preferably catalyst-free (in particular free of acidic catalysts). The distillation unit D1 is preferably not a reactive distillation unit. For example, the distillation unit D1 is operated at a pressure of 1-5 bar and a temperature of 40-200 °C.
[0044] For example, the overhead stream leaving the distillation unit D1 contains KSDI methylal in a concentration of at least 60 mass%, more preferably at least 90 mass%, even more preferably at least 99 mass%.
[0045] The overhead stream KSDI leaving the distillation unit D1 can be at least partially recycled to the reactor R1, so that the methylal contained in the overhead stream KSDI can act as a reactant in the reactor R1.
[0046] For example, the bottom stream leaving the distillation unit D1 contains SSDI OME2 and the polyoxymethylene dimethyl ether(s) of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, in a total concentration of at least 80 mass%, more preferably at least 95 mass%.
[0047] For example, the bottom stream leaving the distillation unit D1 contains SSDI OME2 in a concentration of at least 15 mass%, e.g. 15 mass% to 90 mass%.
[0048] For example, at least 80% by mass or at least 90% by mass of the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n-CH3, 3 < n < 20, which are present in the bottom stream SSDI, one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 10.
[0049] For example, at least 45 mass% (e.g. 45-90 mass%) of the
[0050] Polyoxymethylene dimethyl ether of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, which are present in the bottom stream SSDI, one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 5.
[0051] The bottom stream SSDI withdrawn from the distillation unit D1 is introduced into a distillation unit D2 and the bottom stream SSDI is separated by distillation into a first fraction containing OME2 and leaving the distillation unit D2 as the top stream KSD2, and a second fraction containing one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, and leaves the distillation unit D2 as bottom stream SSD2.
[0052] The distillation unit D2 is therefore designed for the distillative separation of the bottom stream SSDI SO that OME2 in the top stream and the polyoxymethylene dimethyl ether(s) of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, are withdrawn in the bottom stream from the distillation unit D2. Suitable conditions for this can be determined by those skilled in the art taking into account general specialist knowledge. The distillation unit D2 is, for example, a distillation column. The distillation unit typically contains internals for distillative separation, in particular trays, random packings or structured packings, as are generally known to those skilled in the art. The distillation unit D2 is preferably catalyst-free (in particular free of acidic catalysts). The distillation unit D2 is preferably not a reactive distillation unit. For example, the distillation unit D2 is operated at a pressure of 0.5-3 bar and a temperature of 50-220 °C.
[0053] As already mentioned above, it has proven advantageous in the context of the present invention with regard to the yield or purity of the OME2 if the OME2 is first distilled in the first distillation unit D1 together with the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 10, is separated by distillation (as bottom stream SSDI) and a distillative separation of the OME2 from these polyoxymethylene dimethyl ethers subsequently takes place in the distillation unit D2.
[0054] For example, the overhead stream KSD2 leaving the distillation unit D2 contains OME2 in a concentration of at least 75 mass%, more preferably at least 95 mass%.
[0055] The bottom stream SSD2 leaving the distillation unit D2 can, for example, be at least partially recycled to the reactor R1, so that the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n-CH3, 3 < n < 20, can act as reactants in reactor R1.
[0056] As already mentioned above, the polyoxymethylene dimethyl ethers of reactant composition ZR can, for example, be at least partially produced in a separate production unit and subsequently fed to reactor R1 (either without intermediate storage or alternatively after temporary intermediate storage). In this exemplary embodiment, it may be advantageous to at least partially feed the overhead stream KSDI leaving distillation unit D1 and / or the bottoms stream SSD2 leaving distillation unit D2 to this separate production unit. This measure can achieve improved heat integration.
[0057] An exemplary embodiment of the method according to the invention is described in more detail below with reference to Figure 1.
[0058] One or more polyoxymethylene ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, supplied via line 1, and methylal, supplied via line 2, are introduced into reactor R1 via line 3 as reactant composition. In Figure 1, "OME3-20" stands for one or more polyoxymethylene ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20, and "OME1" stands for methylal.
[0059] In this reactor R1, the reactants are reacted in the presence of an acid catalyst and a product mixture is obtained which contains H3C-O-(CH2O)2-CH3 (“OME2” in Figure 1), methylal, and one or more polyoxymethylene ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, contains.
[0060] The product mixture obtained in reactor R1 is fed to distillation unit D1 via line 4. In this distillation unit D1, a distillative separation takes place into a fraction containing methylal, which leaves distillation unit D1 as the overhead stream via line 5, and a fraction containing OME2 and one or more polyoxymethylene ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, and leaves the distillation unit D1 as a bottom stream via line 6.
[0061] The overhead stream leaving the distillation unit D1 via line 5 is recycled to reactor R1 so that the methylal contained in the overhead stream can act as a reactant in reactor R1. If the polyoxymethylene ether(s) of the formula H3C-O-(CH2O) present in the reactant composition n-CH3, 3 < n < 20, are produced in a separate production unit and subsequently fed via line 1, the overhead stream withdrawn from the distillation unit D1 via line 5 can be fed at least partially to this separate production unit (not shown in Figure 1).
[0062] The bottom stream withdrawn from distillation unit D1 via line 6 is fed to distillation unit D2. In this distillation unit D2, a distillative separation takes place into a fraction containing OME2, which leaves distillation unit D2 as the overhead stream via line 7, and a fraction containing one or more polyoxymethylene ethers of the formula H3C-O-(CH2O) n-CH3, 3 < n < 20, and leaves the distillation unit D2 as a bottom stream via line 8. The bottom stream leaving the distillation unit D2 via line 8 is recycled to the reactor R1, so that the polyoxymethylene ethers of the formula H3C-O-(CH2O) present in the bottom stream n -CH3, 3 < n < 20, can act as reactants in reactor R1. If the polyoxymethylene ethers of the reactant composition are prepared in a separate production unit and subsequently fed via line 1, the bottoms stream withdrawn from the distillation unit D2 via line 8 can be fed at least partially to this separate production unit (not shown in Figure 1).
[0063] In an alternative embodiment, the object is achieved by a process for preparing a compound of the formula H3C-O-(CH2O)2-CH3 (OME2), which comprises the following steps:
[0064] Introducing a reactant composition ZR containing as reactants methylal (OME1) and one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20, into a reactor R1 and reacting the reactants in the presence of an acidic catalyst to obtain a product mixture ZP containing H3C-O-(CH2O)2-CH3 (OME2), methylal (OME1) and one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, contains,
[0065] Introducing the product mixture ZP into a distillation unit D1 and distillatively separating the product mixture ZP into a first fraction containing methylal (OME1) and H3C-O-(CH2O)2-CH3 (OME2) and a second fraction containing one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, contains,
[0066] Separating the first fraction of the distillation unit D1 into a stream SOMEI containing at least 50 mass% methylal and a stream SOME2 containing at least 50 mass% H3C-O-(CH2O)2-CH3 (OME2).
[0067] Regarding the properties of the reactant composition ZR, reference can be made to the above statements.
[0068] Regarding suitable conditions for the operation of reactor R1, reference can be made to the above statements.
[0069] With regard to suitable acid catalysts for the conversion of the reactants in the reactor R1, reference can be made to the above statements.
[0070] The distillation unit D1 is operated in such a way that a separation into a first fraction containing methylal (OME1) and H3C-O-(CH2O)2-CH3 (OME2) and a second fraction containing one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n-CH3, 3 < n < 20. Suitable conditions for this can be determined by the person skilled in the art on the basis of his general technical knowledge. The second fraction, which contains the polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, leaves the distillation unit D1 as the bottom stream SSDI. The separation of the first fraction from the distillation unit D1 into a stream SOMEI containing at least 50 mass% methylal and a stream SOME2 containing at least 50 mass% H3C-O-(CH2O)2-CH3 (OME2) takes place, for example, in a condenser and / or a further distillation unit D2. For example, the first fraction leaves the distillation unit D1 as the overhead stream KSDI, and the separation of the overhead stream KSDI into the streams SOMEI and SOME2 takes place in a condenser and / or a further distillation unit D2.
[0071] Example
[0072] The simulated example described below demonstrates that the compound H3C-O-(CH2O)2-CH3 (OME2) can be produced efficiently and with high purity using the process according to the invention. The simulated example was based on the plant shown in Figure 1 (containing reactor R1 and distillation units D1 and D2). The simulation of the example was carried out using the software and methodological principles specified in the following publication: F. Mantei, O. Salem, R. Ali, A. Schaadt, et al., "Techno-economic assessment and carbon footprint of processes for the large-scale production of oxymethylene dimethyl ethers from carbon dioxide and hydrogen", Sustainable Energy Fuels, 2022, 6, 528.
[0073] A current was supplied via line 1 with the following composition:
[0074] OME3: 50 mass%
[0075] OME4: 33 mass%
[0076] OME5: 17 mass%
[0077] Methylal (OME1) was added via line 2.
[0078] Methylal, which was withdrawn as overhead stream in the distillation unit D1, was recycled via line 5 and OME3-10, which was withdrawn as bottom stream in the distillation unit D2, was recycled via line 8.
[0079] These streams from lines 1, 2, 5 and 8 were mixed together; a reactant composition ZR was obtained, which was fed to reactor R1 via line 3.
[0080] The reactant composition ZR had the following composition:
[0081] OME1: 26 mass%
[0082] OME3: 20 mass%
[0083] OME4: 16 mass% OMEs: 12 mass%
[0084] OMEs: 8 mass%
[0085] OME?: 6 mass%
[0086] OMEs: 5 mass%
[0087] OME9: 4 mass%
[0088] OME10: 3 mass%
[0089] Reactor R1 is a fixed-bed reactor operated at a pressure of 1 bar and a temperature of 50°C. Amberlyst 46 (an ion exchange resin containing sulfonic acid groups) was used as the acid catalyst.
[0090] The product mixture ZP, which was withdrawn from the reactor R1 via line 4 and introduced into the distillation unit D1, had the following composition:
[0091] OME1: 18 mass%
[0092] OME2: 17 mass%
[0093] OME3: 15 mass%
[0094] OME4: 13 mass%
[0095] OME5: 11 mass%
[0096] OMEe: 8 mass%
[0097] OME?: 6 mass%
[0098] OMEs: 5 mass%
[0099] OME9: 4 mass%
[0100] OME10: 3 mass%
[0101] In the distillation unit D1, the product mixture ZP was separated by distillation into a fraction containing methylal, which left the distillation unit D1 as the top stream KSDI, and a fraction containing OME2 and OME3-10, which left the distillation unit D1 as the bottom stream SS Di left. Temperature and pressure of the overhead stream: 42 °C, 1 bar. Temperature and pressure of the bottom stream: 141 °C, 1 bar.
[0102] Composition of the head stream KSDI : OMEi: 100 mass%
[0103] Composition of the sump stream SSDI
[0104] OME2: 21 mass%
[0105] OME3: 19 mass%
[0106] OME4: 16 mass%
[0107] OME5: 13 mass%
[0108] OMEe: 10 mass%
[0109] OME?: 8 mass%
[0110] OMEs: 6 mass%
[0111] OME9: 4 mass%
[0112] OME10: 3 mass%
[0113] The bottom stream SSDI was fed to distillation unit D2 via line 6. In distillation unit D2, distillation separated it into a fraction containing OME2, which left distillation unit D2 as the top stream KSD2, and a fraction containing OME3-10, which left distillation unit D2 as the bottom stream SSD2. The top stream temperature and pressure were 104 °C, 1 bar. The bottom stream temperature and pressure were 191 °C, 1 bar.
[0114] Composition of the head stream KSD2:
[0115] OME2: 100 mass%
[0116] Composition of the sump stream SSD2:
[0117] OME3: 23 mass%
[0118] OME4: 20 mass%
[0119] OMEs: 16 mass%
[0120] OMEe: 13 mass%
[0121] OME7: 10 mass%
[0122] OMEs: 8 mass% OMEg: 6 mass%
[0123] OME10: 4 mass%
[0124] The example demonstrates that the compound H3C-O-(CH2O)2-CH3 (OME2) can be produced efficiently and with high purity using the process according to the invention (see the overhead stream KSD2 withdrawn from the distillation unit D2, which essentially consists of OME2).
Claims
Claims 1 . A process for producing H3C-O-(CH2O)2-CH3, comprising the following steps: Introducing a reactant composition ZR containing as reactants methylal and one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20, into a reactor R1 and reacting the reactants in the presence of an acidic catalyst to obtain a product mixture ZP containing H3C-O-(CH2O)2-CH3, methylal and one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, contains, Introducing the product mixture ZP into a distillation unit D1 and separating the product mixture ZP by distillation into a first fraction containing methylal and leaving the distillation unit D1 as the overhead stream KSDI, and a second fraction containing H3C-O-(CH2O)2-CH3 and one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O) n-CH3, 3 < n < 20, and leaves the distillation unit D1 as bottom stream SSDI, Introducing the bottom stream SSDI into a distillation unit D2 and separating the bottom stream SSDI by distillation into a first fraction which contains H3C-O-(CH2O)2-CH3 and leaves the distillation unit D2 as the top stream KSD2, and a second fraction which contains one or more polyoxymethylene dimethyl ethers of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20, and leaves the distillation unit D2 as the bottom stream SS D 2 leaves.
2. The process according to claim 1, wherein the reactant composition ZR contains methylal and the polyoxymethylene dimethyl ether(s) of the formula H3C-O-(CH2O)n-CH3, 3 < n < 20, in a total concentration of at least 90% by mass, more preferably at least 95% by mass.
3. The process according to claim 1 or 2, wherein the reactant composition ZR is formaldehyde-free, methanol-free and / or anhydrous or contains formaldehyde, methanol and water in a total concentration of less than 5% by mass, preferably less than 0.5% by mass.
4. The process according to any one of the preceding claims, wherein the reactant composition Z R present polyoxymethylene dimethyl ether of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, have a mass average molecular weight in the range of 136 g / mol to 210 g / mol.
5. The process according to any one of the preceding claims, wherein methylal and the polyoxymethylene dimethyl ether(s) of the reactant composition ZR have a weight average molecular weight in the range from 90 g / mol to 190 g / mol.
6. The process according to any one of the preceding claims, wherein the top stream KSDI leaving the distillation unit D1 is recycled to the reactor R1 and / or the bottom stream SSD2 leaving the distillation unit D2 is recycled to the reactor R1.
7. The process according to any one of the preceding claims, wherein the Reactant composition ZR containing polyoxymethylene dimethyl ether of the formula H3C-O-(CH2O) n -CH3, 3 < n < 20, are produced at least partially in a separate production unit and subsequently fed to reactor R1.
8. The process according to claim 7, wherein the overhead stream KSDI leaving the distillation unit D1 and / or the bottoms stream SSD2 leaving the distillation unit D2 is / are recycled to the separate production unit.