Method for acylation of α,ω-alkanediol

Abstract

The present invention relates to a safe and effective method for acylation of α,ω-alkanediols, which can be used in ω-nitrooxy-C 3‑10 The method is safe for the operator and allows to obtain favorable yields on an industrial scale.

Description

[0001] The present invention relates to a method for preparing ω-nitrooxy-C 3-10 A safe and effective method for the preparation of alkan-1-ols.

[0002] Global temperatures are rising, a process known as global warming or climate change. One of the main focuses of reducing this warming effect is to reduce the amount of greenhouse gases emitted into the atmosphere. Greenhouse gases are emitted from several different natural and anthropogenic sources; however, the two sources that have the greatest impact are the agricultural industry and the fossil fuel industry. In agriculture, ruminants, especially cattle, are the main contributors to biogenic methane formation, and it has been estimated that preventing the formation of methane by ruminants would nearly stabilize the methane concentration in the atmosphere.

[0003] 3-Nitrooxypropanol (3-NOP, also known as 3-nitrooxy-propan-1-ol or 1,3-propylene glycol mononitrate) has been reported to be very effective in reducing methane formation in ruminants without affecting microbial fermentation in a manner that is harmful to the host animal (WO-2012 / 084629). In addition, WO-2012 / 084629 discloses the preparation of 3-nitrooxypropanol by reacting 3-bromopropanol with silver nitrate in acetonitrile, however, this method is not economical in industrial scale production.

[0004] For industrial-scale production of ω-nitrooxy-C 3-10 A potential route to alkan-1-ols involves direct nitrate formation of the corresponding α,ω-alkanediol. However, this reaction tends to be poorly selective and leads to the formation of large amounts of dinitrated alkanediol. Furthermore, this route requires high safety measures, since organic nitrates and even dinitrates are explosive and therefore difficult to handle even in dilute solutions.

[0005] An alternative to direct nitrate formation of α,ω-alkanediols is a three-step process involving temporary protection of one of the two alcohol groups prior to nitrate formation (e.g. by acetylation), followed by nitrate formation and continuous removal of the corresponding protecting group after the nitrate formation step. However, even though safety and selectivity are thereby improved, the additional reaction step generally results in a significant loss in overall yield and a significant increase in processing costs.

[0006] Therefore, there is a continuing need to optimize the three-step process to allow safe and economical production of large quantities of ω-nitrooxy-C 2-hydroxy-1-nitro-2-ols starting from α,ω-alkanediols. 3-10 In addition, a work-up strategy is required to allow quantitative recovery of reactants and solvents.

[0007] Surprisingly, it has now been found that ω-nitrooxy C can be obtained in high yields in a highly specialized three-step process.3-10 Alkan-1-ols, such as in particular 3-nitrooxypropanol, while maintaining reaction stability and thus ensuring process safety.

[0008] The method comprises the following consecutive steps: (a) acylation of the corresponding α,ω-alkanediol with an acylating agent; (b) acetylating the obtained α,ω-C 3-10 The nitrate ester of the alkanediol monoacylate is formed to form α,ω-C 3-10 Alkanediol mononitrate monoacylate; then (c) hydrolyze the acyl group to obtain the corresponding α,ω-C 3-10 Alkanediol mononitrate; and optionally (d) performing a solvent post-treatment.

[0009] Individual steps (a) to (d) are novel.

[0010] Therefore, in a first embodiment, the present invention relates to

[0011] (A) A method for acylation of an α,ω-alkanediol, preferably 1,3-propanediol, with an acylating agent (acylation reaction), the method comprising: 3-10 Alkanediol, α,ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 The recycled reaction components of the alkanediol diacylate are fed back to the acylation step, provided that in the acylation reaction, 0.5 to 1.5 moles of water are added per mole of recycled acylating groups and the acylating agent, α,ω-C 3-10 Alkanediol monoacylate and 2 times α,ω-C 3-10 The total molar amount of alkanediol diacylates and α,ω-C 3-10 Alkanediol, α,ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 The molar ratio of the sum of the alkanediol diacylates is selected from per mol of α, ω-C 3-10 The range of alkanediol is 0.5 mol to 1.1 mol, preferably 0.6 mol to 1 mol, most preferably 0.75 mol to 1 mol.

[0012] In another embodiment, the present invention relates to a method for preparing α,ω-C 3- A method for producing 10-10-alkanediol mononitrate, preferably propylene glycol mononitrate, comprising the following consecutive steps immediately following the above step (A):

[0013] (B) α,ω-C is carried out by the following method 3-10 Continuous nitrate ester formation of alkanediol monoacylate: a nitrating agent is reacted with a α, ω-C 3-10A solution of an alkanediol monoacylate and an inert solvent is reacted in a group of parts of an apparatus comprising at least two reactors connected in series, and the reaction is carried out by simultaneously feeding the solution into a first reactor and a second reactor to obtain the corresponding α,ω-C 3-10 Alkanediol mononitrate monoacylate;

[0014] (C) α,ω-C is carried out by the following method 3-10 Two-phase hydrolysis of alkanediol mononitrate acylates: a base and an α,ω-C 3-10 A solution of alkanediol mononitrate monoacylate and an inert solvent is continuously fed into a stirred cascade reactor to obtain a solution containing an inert solvent and α,ω-C 3-10 a solution of an alkanediol mononitrate; and optionally

[0015] (D) removing and recovering the inert solvent from the solution by distillation, the method comprising: 3-10 A fraction of the mixture of alkanediol mononitrates is partially condensed and continuously fed back into the distillation.

[0016] Definition of terms

[0017] As used herein, the term "α,ω-C 3-10 "Alkanediol" refers to a straight-chain α,ω-alkanediol having 3 to 10 carbon atoms, such as 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol and 1,10-decanediol. In all embodiments according to the present invention, the most preferred α,ω-C 3-10 The alkanediol is 1,3-propylene glycol (1,3-propanediol, also referred to herein as PD).

[0018] As used herein, the term "α,ω-C 3-10 "Alkanediol monoacylate" refers to a linear α,ω-alkanediol as defined above, in which one of the hydroxyl groups has been esterified. Preferably, the acyl moiety is a linear or branched C 1-6 Acyl, more preferably linear or branched C 1-4 Acyl, for example, most preferably acetyl (-C(=O)-CH3). In all embodiments according to the present invention, particularly preferred is 1,3-propylene glycol monoacylate. In all embodiments according to the present invention, the most preferred α,ω-C 3-10 The alkanediol monoacetate is 1,3-propanediol monoacetate (also referred to herein as PDMA).

[0019] As used herein, the term "α,ω-C 3-10"Alkanediol diacylate" refers to a straight-chain α,ω-alkanediol as defined above, in which both hydroxyl groups have been esterified. In all embodiments according to the present invention, 1,3-propanediol diacylate is particularly preferred. In all embodiments of the present invention, the most preferred α,ω-C 3-10 The alkanediol diacylate is 1,3-propanediol diacetate (also referred to herein as PDDA).

[0020] As used herein, the term "α,ω-C 3-10 "Alkanediol mononitrate" refers to a straight-chain α,ω-alkanediol as defined above, in which one of the hydroxyl groups has been nitrated, such as 3-nitrooxypropan-1-ol (also known as 3-nitrooxypropanol or 3-hydroxypropyl-1-nitrate), 4-nitrooxybutan-1-ol, 5-nitrooxypentan-1-ol, 6-nitrooxyhexan-1-ol, 7-nitrooxyheptan-1-ol, 8-nitrooxyoctan-1-ol, 9-nitrooxynonan-1-ol and 10-nitrooxydecan-1-ol. In all embodiments according to the present invention, 3-nitrooxypropan-1-ol (also known as propanediol mononitrate or PDMN in this document) is particularly preferred.

[0021] As used herein, the term "α,ω-C 3-10 "Alkanediol mononitrate monoacylate" refers to the α,ω-C 3-10 Alkanediol monoacylate, wherein the remaining hydroxyl groups have been nitrated. In all embodiments according to the present invention, 1,3-propylene glycol mononitrate monoacylate is particularly preferred. In all embodiments according to the present invention, the most preferred α,ω-C 3-10 The alkanediol mononitrate monoacylate is 1,3-propanediol mononitrate monoacetate (also referred to herein as PDMNMA).

[0022] As used herein, the term "α,ω-alkanediol dinitrate" refers to a straight-chain α,ω-alkanediol as defined above, in which both hydroxyl groups have been nitrated, such as 1,3-propanediol dinitrate, 1,4-butanediol dinitrate, 1,5-pentanediol dinitrate, 1,6-hexanediol dinitrate, 1,7-heptanediol dinitrate, 1,8-octanediol dinitrate, 1,9-nonanediol dinitrate and 1,10-decanediol dinitrate. In all embodiments according to the present invention, 1,3-propanediol dinitrate (1,3-propanediol dinitrate, also referred to herein as PDDN) is particularly preferred.

[0023] The term "inert solvent" (also abbreviated as "S") as used herein is understood to mean a solvent that does not participate in the chemical reaction in the reaction medium and under the operating conditions and is inert to both the reactants and the reaction products. In a preferred embodiment, the inert solvent is a halogenated solvent. The term 'halogenated solvent' means a solvent containing one or more halogen atoms, and refers to any solvent selected from, but not limited to, dichloromethane, diiodomethane, carbon tetrachloride, dichloroethane or chloroform. Most preferably, in all embodiments of the present invention, the inert solvent is dichloromethane (also referred to herein as DCM).

[0024] The term "essentially consisting of" as used according to the present invention means that no further components are purposefully added besides the listed components / ingredients / solvents etc. However, it is not excluded that small amounts of impurities introduced by the corresponding raw materials may be present.

[0025] Acylation

[0026] The present invention relates to the acylation of α,ω-alkanediol using an acylating agent (acylation reaction), the acylation comprising a step of re-feeding recycled reaction components into the acylation reaction.

[0027] It should be understood that the acylation may further include separating and / or purifying the obtained α,ω-C 3-10 Alkanediol monoacylate step.

[0028] It should be understood that the term "reaction component" as used herein refers to the acylation reaction component involved in the acylation reaction, i.e., α,ω-alkanediol, α,ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 Alkanediol diacylate as well as acylating agent and water, however excluding any solvent or other inert ingredients or additives.

[0029] In all embodiments of the present invention, the term "recycled reaction components" (RRC) refers to unreacted α,ω-C 3-10 Alkanediol, α,ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 Alkanediol diacylate, water and an acylating agent.

[0030] Furthermore, it should be understood that the recycled reaction components may be separated individually or as any mixture thereof and may thus be re-fed individually or as any mixture thereof. Preferably, the recycled reaction components consist essentially of

[0031] (1)α,ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 Mixture of alkanediol diacylates (RCC-(I))

[0032] (2) Unreacted α,ω-C 3-10 Alkanediol (RCC-(II)) and

[0033] (3) A mixture of water and an acylating agent (RCC-(III)).

[0034] In all embodiments of the present invention, it is preferred that at least the recycled reaction components RCC-(I) and RCC-(II) are admixed before being fed back into the acylation reaction (see Figure 1 ).

[0035] The acylation according to the invention can be carried out batchwise or continuously.

[0036] Preferably, the acylation of the α,ω-alkanediol with the acylating agent according to the invention is carried out in a reactor into which the recycled reaction components are (continuously) re-fed.

[0037] Suitable reactors include any type of vessel such as, but not limited to, stirred tank reactors, cascade reactors, loop reactors, tubular reactors.

[0038] In one embodiment, the acylation according to the present invention further comprises separating the obtained α,ω-C 3-10 The step of preparing the alkanediol monoacylate preferably results in:

[0039] Based on α,ω-C 3-10 Alkanediol monoacylate, α,ω-C 3-10 α,ω-C 3-10 The amount of alkanediol is less than 0.5 wt%, preferably less than 0.1 wt%, and

[0040] Based on α,ω-C 3-10 Alkanediol monoacylate, α,ω-C 3-10 α,ω-C 3-10 The amount of alkanediol diacylate is less than 5% by weight, preferably less than 2.5% by weight.

[0041] It is further preferred that, during the separation, reaction components to be recycled are collected.

[0042] Preferably, in all embodiments of the present invention, α,ω-C 3-10The acylation and continuous separation of the alkanediol monoacylate is a (completely) continuous process carried out in a vessel cascade apparatus or a cascade reactor as outlined in Figure (1) for example.

[0043] A container cascade arrangement (also referred to as a reactor cascade arrangement) for the purposes of the present invention is an arrangement comprising at least two consecutive containers in which a reaction can be performed and in which each step can only be performed after the previous step. The containers / reactors can be of the same or different types. It will be appreciated by those skilled in the art that a container cascade arrangement can include equipment for separation and / or distillation.

[0044] The cascade reactor for the purpose of the present invention is such equipment, the equipment includes an external reactor shell having at least one inlet at one end and at least one outlet at the opposite end; an optional additional outlet for removing steam and / or by-products; and an optional port for monitoring, sampling and / or mixing. In the reactor, a series of two or more segmented reaction chambers (corresponding to at least two continuous containers) can be limited by a partition, and the reaction can be performed in the reaction chamber and each chamber / partition can only be flowed through after the previous chamber / partition. The reactor is preferably suitable for a variety of different chemical reactions and does not need to be customized for a specific reaction. The cascade reactor can be, for example, a flow reactor.

[0045] In one embodiment of the present invention, acylation (including the obtained α,ω-C 3-10 The subsequent separation of the alkanediol monoacylate) is a process comprising the following steps:

[0046] (A-1) Acylation of α,ω-C with an acylating agent in an initial container 3-10 alkanediol (acylation reaction), provided that in the acylation reaction, 0.5 to 1.5 moles of water are present per mole of recycled acylate group and the acylating agent, α,ω-C 3-10 Alkanediol monoacylate and 2 times α,ω-C 3-10 The total molar amount of alkanediol diacylates and α,ω-C 3-10 Alkanediol, α,ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 The molar ratio of the sum of the alkanediol diacylates is selected from per mol of α, ω-C 3-10 Alkanediol (also called acetylation reaction mixture or ARM) in the range of 0.5 mol to 1.1 mol,

[0047] (A-2) removing the acylating agent and water to form a 3-10Alkanediols and mono- and di-acylated α,ω-C 3-10 A mixture of alkanediols (also called AM-I),

[0048] (A-3) Separating α,ω-C from the mixture (i.e., from AM-I) by distillation 3-10 Alkanediol monoacylate, so that the α,ω-C 3-10 The alkanediol monoacylate contains less than 0.5% by weight of α,ω-C 3-10 Alkanediols and less than 5% by weight of α,ω-C 3-10 Alkanediol diacylate,

[0049] (A-4) collecting reaction components to be recycled, and

[0050] (A-5) will contain at least α,ω-C 3-10 Alkanediol, α,ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 The recycled reaction components of the alkanediol diacylate are fed back into the initial vessel.

[0051] In all embodiments of the present invention, it is preferred that in the acylation reaction, for example in particular in step (A-1)

[0052] preferably 0.75 mol to 1.25 mol, most preferably 0.85 mol to 1.1 mol, such as especially 0.95 mol to 1.05 mol, of water are present per mole of recycled acylate groups, and

[0053] ·Acylating agent, α,ω-C 3-10 Alkanediol monoacylate and 2 times α,ω-C 3-10 The total molar amount of alkanediol diacylates and α,ω-C 3-10 Alkanediol, α,ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 The molar ratio of the sum of the alkanediol diacylates is preferably selected from the range of 0.6 mol to 1 mol, most preferably from the range of 0.7 mol to 1 mol, such as in particular from the range of 0.75 mol to 1 mol.

[0054] As used herein, the term "per mole of acylate groups" refers to the mole of acyl groups from α, ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 The sum of the acyl groups of the alkanediol diacylates (i.e. for each α,ω-C 3-10 The alkanediol monoacylate is 1 mol, and for each α,ω-C 3-10 Alkanediol diacylate is 2 mol).

[0055] As already outlined above, the reaction components to be recycled in step (A-5) consist essentially of α,ω-C 3-10 Alkanediol, α,ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 However, the present invention does not exclude that the acylating agent and / or water removed in step (A-2) can also be recycled and fed again when deemed appropriate.

[0056] Furthermore, it should be understood that fresh α,ω-C is added as needed to adjust the ratios and amounts as defined herein. 3-10 Alkanediol, water and / or acylating agent.

[0057] Suitable acylating agents (also referred to herein as AA) for use in the acylation process according to the present invention are carboxylic acids and their derivatives, such as their corresponding esters and acyl halides. Preferably, the acylating agent is selected from the group consisting of: linear or branched C 1-6 Alkanoic acid, its ester or acid chloride, more preferably selected from linear C 1-4 Carboxylic acids, such as acetic acid, propionic acid, butyric acid and valeric acid. The most preferred acylating agent is acetic acid. Any acetic acid, i.e., an aqueous solution thereof, can be used in all embodiments of the acylation. However, it should be understood that the water content must be adjusted accordingly to meet the requirements of the present invention.

[0058] The reaction temperature of the acylation reaction is preferably selected from the range of 80 to 200° C., more preferably from the range of 100 to 160° C., most preferably from the range of 120 to 150° C. It will be appreciated that the pressure must ultimately be adjusted depending on the desired reaction temperature.

[0059] The reaction time of the acylation reaction (eg in particular in step (A-1)) is preferably selected from the range of 1 hour to 10 hours, preferably from the range of 2 hours to 8 hours, most preferably from the range of 3 hours to 6 hours.

[0060] The removal of the acylating agent and reaction water in step (A-2) is preferably performed by distillation under reduced pressure and heating, which can be easily adjusted by a person skilled in the art. Suitable pressures include 40 mbar to 120 mbar absolute pressure.

[0061] Separation of α,ω-C from the reaction mixture (i.e., from AM-I) 3-10 The alkanediol monoacylate is preferably prepared such that the α,ω-C 3-10 The amount of alkanediol diacylate is less than 4 wt%, more preferably less than 3 wt%, most preferably less than 2.5 wt%, for example less than 1 wt%, and wherein the corresponding α,ω-C 3-10The amount of alkanediol is less than 0.4 wt%, more preferably less than 0.25 wt%, most preferably less than 0.2 wt%, for example in particular less than 0.1 wt% (all amounts based on α,ω-C 3-10 The amount of alkylene glycol monoacylate).

[0062] In the separated (distilled) α,ω-C 3-10 The residual α,ω-C 3-10 Alkanediol diacylate and α,ω-C 3-10 The amount of alkanediol is usually determined by GC chromatography using a FID detector.

[0063] In a particularly advantageous embodiment, α,ω-C 3-10 The separation / purification of the alkanediol monoacylate (i.e., step (A-3)) is carried out in two consecutive steps, namely

[0064] Step (A-3'), which consists of distilling off most of the α,ω-C 3-10 Alkanediol diacylate, until a mixture (AM-Ia) is obtained, which is essentially composed of α, ω-C 3-10 Alkanediol and α,ω-C 3-10 Alkanediol monoacylate, followed by

[0065] Step (A-3``), which consists of distilling off α,ω-C from the mixture (AM-Ia) 3-10 Alkanediol monoacylate, so that the distilled α, ω-C 3-10 α,ω-C in alkylene glycol monoacetate 3-10 The amount of alkanediol is as defined herein, while unreacted α,ω-C 3-10 Alkanediol.

[0066] The term "substantially" in step (A-3') does not exclude small amounts of α,ω-C 3-10 The presence of alkanediol diacetate, however, the α,ω-C 3-10 The amount of alkanediol diacetate must be controlled so that the α,ω-C 3-10 α,ω-C in alkylene glycol monoacetate 3-10 The final amount of alkanediol diacetate is as defined herein. Preferably, however, the amount does not exceed 3 mol%.

[0067] Even more preferably, step (A-3') and step (A-3") are performed in two different vessels (distillation apparatuses).

[0068] In an even more preferred embodiment, step (A-3') and step (A-3") are performed using two separate distillation columns.

[0069] In a specific embodiment, the mixture (AM-I) consists essentially of 40 mol % to 60 mol % of α,ω-C 3-10 alkanediol, 30 mol% to 50 mol% of α,ω-C 3-10 Alkanediol monoacylate and 5-15 mol% α,ω-C 3-10 Alkanediol diacylate composition.

[0070] In another specific embodiment, the mixture (AM-Ia) consists essentially of 50 mol % to 70 mol % of α,ω-C 3-10 alkanediol and 30 mol% to 50 mol% of α,ω-C 3-10 Alkanediol monoacylate and up to 3 mol% of α,ω-C 3-10 Alkanediol diacylate composition.

[0071] The reaction components to be recycled, i.e., to be fed back into the acylation reaction, for example, in particular to the reaction components fed into the above step (A-1), usually consist of the distillate of step (A-3') and the bottoms of step (A-3''), wherein the distillate of step (A-3') consists essentially of α,ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 The bottom distillate is composed of unreacted α, ω-C 3-10 Alkanediol diacylate composition.

[0072] Preferably, the distillate of step (A-3') consists essentially of 10 to 40 wt% of α,ω-C 3-10 Alkanediol monoacylate and 60 to 90 wt % of α,ω-C 3-10 Alkanediol diacylate and up to 5% by weight of α,ω-C 3-10 Alkanediol composition.

[0073] Preferably, the bottom distillate of step (A-3") consists essentially of more than 95% by weight, more preferably more than 97% by weight, and most preferably more than 99% by weight of α,ω-C 3-10 Alkanediol composition.

[0074] The α,ω-C obtained in step (A-3``) 3-10 The alkanediol monoacylate preferably exhibits a purity of greater than 95% by weight, preferably greater than 97% by weight, most preferably greater than 98.5% by weight, as determined by analysis by GC using a FID detector.

[0075] In a particularly advantageous embodiment of the present invention, the acylation (including the obtained α,ω-C 3-10 The subsequent separation of the alkanediol monoacylate is as follows Figure 1 The method comprises the following steps:

[0076] (A-0) Provide container cascade equipment,

[0077] (A-1') is acylated with an acylating agent having all the definitions and preferred embodiments as given herein. 3-10 The acylation is carried out by loading α,ω-C 3-10 The alkanediol, acylating agent and recycled reaction components are reacted to form a reaction mixture (ARM), followed by

[0078] (A-2') feeding the reaction mixture (ARM) to a first distillation column (V2) and distilling off the acylating agent and water to form a distillation column (V2) consisting essentially of unreacted α,ω-C 3-10 Alkanediols and mono- and di-acylated α,ω-C 3-10 The mixture (AM-I) is then

[0079] (A-3') The mixture (AM-I) is fed to the second distillation column (V3) and α,ω-C 3-10 A mixture of mono-acylated and di-acylated alkanediols (ie, RRC-(I)) to form a cyclic alkylene glycol having a molecular weight of 1,2-diols and a molecular weight of 1,2-diols. 3-10 Alkanediol and α,ω-C 3-10 A mixture of alkylene glycol monoacetates (AM-Ia),

[0080] (A-3") The mixture (AM-Ia) is fed to the third distillation column (V4) and α,ω-C 3-10 Alkanediol monoacylate, so that the distilled α, ω-C 3-10 α,ω-C in alkanediol monoacetate 3-10 The amount of alkanediol is less than 0.1 wt %, and α,ω-C 3-10 Alkanediol,

[0081] (A-4') collecting and optionally mixing the reaction components to be recycled, and

[0082] (A-5') re-feeding the optionally admixed recycled reaction components RRC-(I) and RRC-(II) from steps (iv) and (v) into the first reaction vessel (V1),

[0083] The prerequisite is that in the first reactor

[0084] (a) there are from 0.5 to 1.5, preferably from 0.75 to 1.25, most preferably from 0.85 to 1.1, such as especially from 0.95 to 1.05, moles of water per mole of recycled acylate groups, and

[0085] (b) acylating agent, α,ω-C 3-10 Alkanediol monoacylate and 2 times α,ω-C 3-10 The total molar amount of alkanediol diacylates and α,ω-C 3-10 Alkanediol, α,ω-C 3-10 Alkanediol monoacylate and α,ω-C 3-10 The molar ratio of the total amount of alkanediol diacylates was adjusted to be 1:1 per mol of α, ω-C 3-10 The alkanediol is in the range of 0.5 mol to 1.1 mol, preferably in the range of 0.6 mol to 1 mol, more preferably in the range of 0.7 mol to 1 mol, for example in the range of 0.75 mol to 1 mol.

[0086] It will be appreciated that the recycled reaction component (I) may contain, for example, α,ω-C 3-10 Alkanediol monoacylate as determined by analysis, for example, by GC using a FID detector.

[0087] Preferably, in all embodiments, the recycled reaction component (II) consists of more than 90% by weight of α,ω-C 3-10 Alkanediol, more preferably greater than 95% by weight, most preferably greater than 98% by weight of α,ω-C 3-10 Alkanediol composition as determined by analysis, for example, by GC using a FID detector.

[0088] Of course, it should be understood that all definitions and preferences herein for acylation (including acylation reaction and separation) also apply to the process comprising steps (A-1) to (A-5) and (A-0) to (A-5').

[0089] Nitrate formation

[0090] In a preferred embodiment, the method according to the present invention further comprises a step (B) after step (A), wherein step (B) involves preparing α,ω-C 3-10 A continuous nitrate formation process of alkanediol mononitrate monoacylate, the process comprising reacting a nitrating agent with a nitrating agent containing a corresponding α, ω-C 3-10A solution of an alkanediol monoacylate and an inert solvent (hereinafter also referred to as (BI)) is reacted, characterized in that the solution is fed simultaneously into a first reactor (hereinafter also referred to as reactor B1) and a second reactor (hereinafter also referred to as reactor B2) (see Figure 2 ).

[0091] Preferably, the nitrate ester formation is carried out continuously in a flow reactor, such as for example in Figure 2 Described in.

[0092] A flow reactor according to the invention is a device in which a chemical reaction takes place in a channel or pipe. A flow reactor is usually operated continuously (as opposed to a batch reactor) and has a channel / pipe (e.g. Figure 2 The reaction stoichiometry is defined by the concentrations of the reagents and the ratio of their flow rates. The (average) residence time is given by the ratio of the volume of the reactor to the total flow rate. The flow reactor preferably comprises a (static) mixing element, such as an SMX mixer or a Kenics mixer.

[0093] As used herein, the term "residence time" refers to the volume of the reaction zone divided by the outlet volume flow rate of the reactants at the temperature and pressure of the reaction system. In one embodiment of the present invention, the average residence time is calculated using the density of the corresponding outlet temperature of the reactor.

[0094] Preferably, the mass flow ratio of the solution (BI) entering the first reactor is selected from the range of 40% to 60% of the total mass flow of the solution (BI), and the remainder is fed to the second reactor.

[0095] The term "mass flow rate" or "mass flow rate" as used herein may include not only the actual or measured mass flow rate, but also the calculated mass flow rate. It generally refers to the mass flow rate of the reaction solution as measured in the corresponding feed line. The mass flow rate may be calculated or measured with a suitable sensor located in the corresponding feed line.

[0096] In a particularly advantageous embodiment, the continuous nitrate ester formation according to the invention comprises the following consecutive steps:

[0097] (N-1) providing a continuously operated flow reactor, the flow reactor comprising at least two reactors connected in series, reactor (1) (also referred to herein as B1) and reactor (2) (also referred to herein as B2)

[0098] (N-2) provides α,ω-C 3-10 a solution of an alkanediol monoacylate and an inert solvent (i.e., BI), and

[0099] (N-3) feeding the nitrating agent and the first part of the solution into the reactor (1), and then

[0100] (N-4) adding a second portion of the solution to the reactor (2),

[0101] The prerequisite is that the mass flow rate of the solution entering the reactor 1 is selected from the range of 40% to 60% of the total mass flow rate of the solution, while the remaining solution is fed into the reactor 2.

[0102] As used herein, the term "nitrating agent" (also referred to herein as NA) refers to a compound that, when reacted with a reactant substrate, forms a compound having a nitrate ester (-O-NO2) group. Exemplary nitrating agents include, but are not limited to, nitric acid and nitrates, such as alkali metal nitrates, such as KNO3, and nitrosulfuric acid (i.e., a mixture of nitric acid and sulfuric acid).

[0103] In all embodiments of the invention, the nitrating agent is preferably nitric acid applied as nitrosulfuric acid, ie a mixture of nitric acid and sulfuric acid.

[0104] In the continuous nitrate ester formation according to the invention, preferably 1.5 mol to 2.5 mol equivalents, more preferably 1.7 mol to 2.3 mol equivalents, most preferably 1.9 mol to 2.0 mol equivalents of H2SO4 are used, based on HNO3.

[0105] In the continuous nitrate formation according to the invention, the α,ω-C 3-10 As the alkanediol monoacylate, preferably 1 mol to 1.5 mol equivalent, more preferably 1.1 mol to 1.2 mol equivalent of HNO3 is used.

[0106] In the continuous nitrate ester formation according to the present invention, it is further preferred that the reaction volumes of reactor (1) and reactor (2) are selected from the range of 4:1 to 1:4, preferably 3:1 to 1:3, most preferably 2:1 to 1:2.

[0107] The continuous nitrate ester formation is preferably carried out in two reactors, namely reactor (1) and reactor (2) ( Figure 2 : in B1 and B2) for an average residence time ranging from about 5 seconds to about 30 seconds, preferably from about 10 seconds to about 20 seconds, most preferably from about 15 seconds to 19 seconds.

[0108] Preferably, in all embodiments of continuous nitrate formation, the solution (i.e., BI) consists essentially of α,ω-C 3-10 It is composed of alkanediol monoacylate and an inert solvent.

[0109] The term "essentially consisting of" as used according to the present invention means that apart from the listed components / ingredients / solvents no further components are purposefully added. However, it is not excluded that small amounts of impurities introduced by the corresponding raw materials may be present.

[0110] Even more preferably, the α,ω-C 3-10 The concentration of the alkanediol monoacylate is selected from the range of 10 to 60 wt %, more preferably 20 to 50 wt %, most preferably 35 to 45 wt %, with the remainder being an inert solvent.

[0111] In a particularly advantageous embodiment, the continuous nitrate ester formation according to the invention further comprises the following steps:

[0112] (N-5a) quenching the reaction mixture (in B3) (also referred to herein as NRM) with water, optionally in the presence of a base, thereby producing a two-phase mixture consisting of an organic phase and an aqueous phase (also referred to herein as NBM),

[0113] (N-5b) subjecting the two-phase mixture (NBM) to phase separation (in B4) to obtain an organic phase (also referred to herein as NOP) and an aqueous phase (also referred to herein as NAP),

[0114] (N-5c) optionally concentrating the aqueous phase (NAP) from the phase separation to recover H2SO4, provided that no base is used for neutralization, and

[0115] (N-5d) Optionally washing the organic phase (NOP) obtained in (N-5c) with water at least once and / or drying the organic phase.

[0116] Figure 2 A particularly preferred continuous nitrate ester formation is outlined in , which consists of the consecutive steps (N-1), (N-2), (N-3), (N-4), (N-5a), (N-5b) and (N-5c).

[0117] It will be appreciated that the continuous nitrate ester formation according to the invention may also comprise separation / concentration of the α,ω-C from the organic phase (NOP), e.g. by (partial) distillation of the solvent. 3-10 Alkanediol mononitrate monoacylate step.

[0118] In all embodiments of the present invention, the nitrate ester forming reaction mixture (NRM) preferably consists essentially of residual / unreacted nitrating agent, α,ω-C 3-10 Alkanediol mononitrate, unreacted α,ω-C 3-10 It is composed of alkanediol monoacylate and an inert solvent.

[0119] Suitable alkalis include alkali metal or alkaline earth metal alkalis, such as alkali metal or alkaline earth metal alkaline hydroxides or carbonates and ammonia, amines, but are not limited thereto. The alkali is preferably selected from NaOH (caustic), KOH, Ca (OH) 2 or ammonia, and more preferably an aqueous solution thereof is used. Most preferably, in all embodiments of the present invention, the alkali is a NaOH (caustic) aqueous solution.

[0120] In the continuous nitrate ester formation according to the invention, preferably no base is used for quenching.

[0121] Thus, in another particularly advantageous embodiment, quenching of the nitrate forming reaction mixture (NRM) is performed with cold water, for example with water having a temperature selected from the range of 0°C to 20°C, more preferably from 5°C to 15°C.

[0122] In the continuous nitrate ester formation according to the present invention, advantageously, the outlet reaction temperature of the reactor (1) is equal to or lower than 40°C, preferably 30°C, more preferably 20°C, more preferably 10°C, most preferably equal to or lower than 5°C. The outlet reaction temperature of the reactor (2) may be slightly higher. However, preferably, the outlet temperature of the reactor (2) is selected to be in the range of 15°C to 25°C.

[0123] Advantageously, in all embodiments, the reaction temperature of the quenching step (N-6a) is equal to or lower than 20°C, preferably equal to or lower than 15°C, more preferably equal to or lower than 10°C.

[0124] hydrolysis

[0125] In a preferred embodiment, the method according to the present invention further comprises a step (C) after step (B), wherein the step (C) involves 3-10 Alkanediol mononitrate monoacylate (to the corresponding α,ω-C 3-10 A process for the two-phase hydrolysis of a monoacylated 1,3-propylene glycol mononitrate to 1,3-propylene glycol mononitrate, the process comprising reacting a base and an α,ω-C 3-10 A solution of alkanediol mononitrate monoacylate and an inert solvent, such as in particular dichloromethane (DCM), is continuously fed into a stirred cascade reactor.

[0126] In the following, including α,ω-C 3-10 The solution of alkylene glycol mononitrate monoacylate and an inert solvent is also referred to as HS-I (e.g. Figure 3 middle).

[0127] The hydrolysis process according to the invention can be carried out batchwise or continuously. Preferably, the hydrolysis process is a (fully) continuous process.

[0128] In a particularly advantageous embodiment, the hydrolysis process comprises the following consecutive steps:

[0129] (H-1) Provide vertical stirred cascade reactor equipment,

[0130] (H-2) will contain α,ω-C 3-10 A solution of alkanediol mononitrate monoacylate, an inert solvent and a base is continuously fed into the first (bottom) chamber ( Figure 3 In the hydrolysis reactor C1),

[0131] (H-3) will contain α,ω-C 3-10 The hydrolysis reaction mixture (also referred to herein as HRM) of the alkanediol mononitrate, inert solvent and remaining base solution is transferred to a decanter or container ( Figure 3 :C2) to separate the phase to obtain the α,ω-C 3-10 An organic solution (I) and an aqueous solution (also referred to herein as HS-III) of an alkanediol mononitrate and an inert solvent (also referred to herein as HS-II) are prepared, followed by

[0132] (H-4) collects α,ω-C 3-10 An organic solution (I) of an alkanediol mononitrate and an inert solvent (i.e. HS-II), optionally followed by

[0133] (H-5) The inert solvent is evaporated from the organic solution (I) by distillation.

[0134] Figure 3 An exemplary (and at the same time preferred) hydrolysis according to the invention is shown in FIG.

[0135] In a preferred embodiment, the hydrolysis method according to the present invention further comprises an additional step (H-6), which comprises the following steps

[0136] (H-6a) extracting the aqueous phase (HS-II) obtained in step (H-3) with an additional amount of an inert solvent to recover additional α,ω-C 3-10 alkanediol mononitrate, thereby producing an additional organic phase (II) (also referred to herein as HS-IV), and

[0137] (H-6b) The organic phase (II) is co-fed into step (H-5).

[0138] The hydrolysis process is preferably carried out in a container cascade apparatus or a cascade reactor (continuously), more preferably in a vertical stirred cascade reactor. In a preferred embodiment of the present invention, the hydrolysis process is performed in a vertical stirred cascade reactor having at least 10 chambers.

[0139] For the purpose of the hydrolysis process, a vertical stirred cascade reactor is a vertical reactor and also a stirred reactor. As used herein, the term "vertical reactor" or "horizontal reactor vessel" means a reactor vessel having a substantially vertical longitudinal axis. As used herein, the term "stirred reactor" means a reactor having means for stirring the reaction materials in addition to the agitation caused by flow (e.g., turbulent flow of the reaction materials).

[0140] In a preferred embodiment of the present invention, for α,ω-C 3-10 The base for the hydrolysis reaction of the alkanediol mononitrate monoacylate is an aqueous solution of NaOH, and the concentration of NaOH in water is preferably selected from the range between 1 wt % and 50 wt %, more preferably between 5 wt % and 30 wt %, most preferably between 7.5 wt % and 15 wt %.

[0141] Advantageously, the reaction temperature of the hydrolysis reaction is selected from the range of 20°C to 70°C, preferably 30°C to 60°C, most preferably 40°C to 60°C.

[0142] Furthermore, it is advantageous if the α,ω-C 3-10 The alkanediol mononitrate monoacylate is subjected to hydrolysis using 1 mol to 1.5 mol equivalents, more preferably 1.1 mol to 1.3 mol equivalents, most preferably 1.2 mol to 1.3 mol equivalents of a base, preferably NaOH.

[0143] The hydrolysis reaction is preferably carried out for a reaction time ranging from about 2 hours to about 6 hours, preferably from about 3 hours to about 5 hours, and most preferably about 4 hours.

[0144] Removal and recovery of inert solvents

[0145] In a further preferred embodiment, the process according to the present invention further comprises a step (D) after step (C), said step (D) involving the step of preparing a molten metal containing an inert solvent and α,ω-C 3-10 A process for removing and recovering an inert solvent from a mixture of alkanediol mononitrates, the process comprising: 3-10 The liquid fraction of the mixture of alkanediol mononitrates is partly evaporated and condensed and continuously fed back into the distillation.

[0146] Preferably, the distillation is performed in an evaporator setup, even more preferably in an evaporation setup comprising 1 to 5 evaporators, more preferably 2 to 4 evaporators. Figure 4 An exemplary and preferred evaporator device is shown in FIG.

[0147] The method preferably further comprises isolating the α,ω-C ions having a purity of at least 95 wt%, preferably at least 97 wt%, most preferably at least 98 wt%, as determined, for example, by GC chromatography using an FID detector. 3-10 Alkanediol mononitrate.

[0148] Preferably, the separated α,ω-C 3-10 The alkanediol mononitrate also contains less than 1% of an inert solvent, more preferably less than 0.5% of an inert solvent, and most preferably less than 0.1% of an inert solvent.

[0149] As used herein, the term "evaporator" refers to an evaporator used to evaporate a chemical substance or a mixture of chemical substances (e.g., an inert solvent and an α,ω-C 3-10 The invention relates to a device for converting a liquid form of a mixture (such as a solution of an alkylene glycol mononitrate) into its gaseous form / vapor. It should be understood that the liquid may also be only partially evaporated or partially vaporized into the gaseous form, while part of the liquid remains in the liquid state. The method can be used to separate mixtures, for example by partial evaporation and partial condensation as described herein.

[0150] The term condenser as used herein refers to a device or unit used to condense a gaseous substance or a gaseous mixture into a liquid state by cooling.

[0151] In a particularly advantageous embodiment, the solvent removal and recovery according to the invention comprises the following steps:

[0152] (S-1) providing an evaporator assembly comprising three evaporators,

[0153] (S-2) The α,ω-C 3-10 The solution of alkanediol mononitrate is fed to the first evaporator ( Figure 4 :E1) and applying a pressure of 400 mbar to 600 mbar, thereby producing a gas phase (I) (also referred to herein as GP-I) and a liquid phase (I) (also referred to herein as LP-I), wherein the liquid phase (I) comprises about 70 wt % to 95 wt % of α,ω-C 3-10 Alkanediol mononitrate,

[0154] (S-3) feeding the gas phase (I) to a first (partial) condenser (C1) to remove a first liquid fraction (also referred to herein as LF-I) by cooling to a temperature of 20°C to 40°C, preferably to a temperature of 20°C to 35°C, more preferably to a temperature of 25-30°C, while passing the remaining gas phase (II) (also referred to herein as GP-II) to a second condenser ( Figure 4 :C2) on,

[0155] (S-4) feeding the liquid phase (I) (LP-I) from step (S-2) to the second evaporator ( Figure 4 : E2) and applying a pressure of 50 mbar to 150 mbar, thereby producing a gas phase (III) (also referred to herein as GP-III) and a liquid phase (II) (also referred to herein as LP-II), wherein the liquid phase (II) comprises more than 95% by weight, preferably more than 97% by weight, most preferably more than 98% by weight of α,ω-C 3-10 Alkanediol mononitrate,

[0156] (S-5) Feeding the gas phase (III) to the third (partial) condenser ( Figure 4 : C3) to remove the second liquid fraction (also referred to herein as LF-II) by cooling to a temperature of 10° C. to 30° C., preferably to a temperature of 20° C. to 30° C., more preferably to a temperature of 20 to 25° C., while the remaining gas phase (IV) (also referred to herein as GP-IV) is passed to a fourth condenser ( Figure 4 : C4) to liquefy the inert solvent, and

[0157] (S-6) feeding the liquid phase (II) (LP-II) from step (S-4) to the third evaporator ( Figure 4 : E3) and applying a pressure of 5 mbar to 10 mbar,

[0158] A prerequisite is that at least one of LF-I and LF-II is fed back to the first evaporator or the second evaporator.

[0159] It should be understood that the liquid fractions (I) and (I) still contain α,ω-C 3-10 Alkanediol mononitrate, the α,ω-C 3-10 Alkanediol mononitrate is recovered via the recycle.

[0160] Figure 4 An exemplary (and preferred) removal and recovery process according to the present invention is shown in FIG.

[0161] In the partial condensation according to the invention, the vapor stream (evaporation stream) is partially condensed (liquefied) in a condenser. The remaining (uncondensed) vapor is passed to a subsequent (total) condenser operating at a lower temperature to nearly liquefy the remaining solvent.

[0162] Preferably, the α,ω-C 3-10 The amount of the alkanediol mononitrate is selected from the range of 10 wt % to 50 wt %, more preferably 20 wt % to 40 wt %, wherein the α,ω-C 3-10 Alkanediol mononitrates are obtainable, for example, from hydrolysis as described above.

[0163] BRIEF DESCRIPTION OF THE DRAWINGS

[0164] Figure 1 :exist Figure 1 In the embodiment of FIG. 1 , an exemplary but non-limiting container cascade arrangement for the acylation process according to the present invention is shown:

[0165] An acylating agent (AA), α,ω-alkanediol (AD) and water are fed to the first vessel of the vessel cascade (V1) to form a reaction mixture (ARM). The reaction mixture (ARM) is then fed to the first distillation column (V2) and the acylating agent and water are distilled off to form a mixture (AM-I). The mixture (AM-I) is subsequently fed to the second distillation column (V3) and a "recycled reaction component (I)" consisting essentially of α,ω-alkanediol monoacylate and α,ω-alkanediol diacylate (ADMA and ADDA) is distilled off to form a mixture (AM-Ia). The mixture (AM-Ia) is then fed to the third distillation column (V4) and ADMA is distilled off while recovering a 'recycled reaction component (II)' consisting essentially of AD. During this process, the recycled reaction components (I) and (II) are continuously re-fed to the first reaction vessel (V1). If necessary, a small fraction (less than 5%) of the recycled reaction components (I) and (II) can be purged / removed to avoid accumulation of possible by-products. Furthermore, the acylating agent and (part of) the water are re-fed into the first reaction vessel (V1) as deemed appropriate.

[0166] Figure 2 :exist Figure 2 In the embodiment of FIG. 1 , an exemplary but non-limiting continuously operated flow reactor setup for nitrate ester formation according to the present invention is shown:

[0167] The nitrating agent and the α,ω-C 3-10 A portion of the solution (BI) consisting of the alkanediol monoacylate and the inert solvent is fed to the first reactor (B1), after which a second portion of the solution (BI) is added to the second reactor (B2). The nitrate ester-forming reaction mixture (NRM) obtained after the reactor (B2) is quenched in the reactor B3. The thus obtained reaction two-phase mixture (NBM) is separated into two phases to obtain an organic phase (NOP) and an aqueous phase (NAP). α,ω-C 3-10 Alkanediol mononitrate monoacylate (ADMNMA) is in the organic phase and can be separated therefrom.

[0168] Figure 3 :exist Figure 3In the embodiment of FIG. 1 , an exemplary but non-limiting vertical stirred cascade reactor setup for the hydrolysis process according to the present invention is shown.

[0169] The first (bottom) chamber (C1) is continuously charged with a mixture consisting essentially of α, ω-C 3-10 Alkanediol mononitrate monoacylate and an inert solvent (HS-I) (e.g. Figure 2 The NOP obtained as outlined in the above is mixed with a solution of the composition and an aqueous base to form a reaction mixture (HRM). The reaction mixture (HRM) is transferred to a second container (C2) for phase separation to produce an organic phase (HS-II) and an aqueous phase (HS-III). The organic phase is transferred to an evaporator device (C4) for α,ω-C 3-10 Isolation of Alkanediol Mononitrate (ADMN). The aqueous phase (HS-III) is transferred to a third vessel (C3) for further extraction with an inert solvent to obtain an organic phase (HS-IV), which is also transferred (combined with HS-II) to an evaporator unit (C4) to recover additional ADMN.

[0170] Figure 4 :exist Figure 4 In the embodiment of FIG. 1 , an exemplary but non-limiting evaporator device for removal and recovery of an inert solvent according to the present invention is shown:

[0171] The α,ω-C 3-10 The solution of alkanediol mononitrate is fed to a first evaporator (E1), and a first liquid fraction (LF-I) is removed from the distillate of the evaporator (E1) by partial condensation in a first condenser (C1), while the remaining vapor is transferred to a second condenser (C2) to liquefy the remaining inert solvent (S). The liquid phase (LP-I) from the evaporator (E1) is fed to a second evaporator (E2). A second liquid fraction (LF-II) is removed from the distillate of the evaporator (E2) by partial condensation in a condenser (C3), while the remaining vapor (GP-IV) is transferred to a fourth condenser (C4) to liquefy the remaining inert solvent. The liquid phase (LP-II) from the evaporator (E2) is fed to a third evaporator (E-3) to remove the remaining inert solvent and recover pure α,ω-C 3-10 Alkanediol mononitrate. Example

[0172] A) Acylation

[0173] The acylation (equilibrium formation) is performed batchwise without recycle by feeding the starting materials into the first vessel, or in a fully continuous process in a vessel cascade setup. The resulting reaction mixture from the last vessel is fed to the first distillation column to separate (remove) HO / HAc from PDDA / PDMA / PD. This mixture of PDDA / PDMA / PD is fed to the second distillation column to remove PDDA from PD / PDMA. This mixture of PD / PDMA is fed to the third distillation column to separate PDMA from PD.

[0174] Pure PDMA is obtained by distillation. The recovered PDDA, PD and HAc are recycled and fed back to the reaction vessel cascade together with an adjusted amount of water, resulting in an overall yield of 90%.

[0175] Aa) No recycle stream is used (comparative)

[0176] 1,3-Propanediol (PD, 14.0kg, 0.18kmol, 99.7%) was mixed with acetic acid (HAc, 9.8kg, 0.16kmol, 100%). After the reactor was inertized by a nitrogen stream, stirring (500rpm) was started, and the jacket temperature was raised from 20°C to 135°C within 70 minutes and maintained at 135°C for 4 hours under reflux of the reaction mixture. After 4 hours, the jacket temperature was set to 100°C and the pressure was slowly reduced to about 100 mbar absolute pressure while taking out 1.55kg of distillate. 22.0kg of residue was obtained, which contained a mixture of acetic acid, water, unreacted PD (28 wt %), 3-acetylpropan-1-ol (PDMA, 44.1 wt %) and 1,3-propylene glycol diacetate (PDDA, 11.3 wt %). Based on PD, the yield of PDMA was 44.4%, and the yield of PDDA was 8.5%.

[0177] The removal of acetic acid / water was carried out in a distillation column DN50 equipped with a condenser, a liquid separator for reflux regulation and a falling film evaporator with 3.5 m BX packing at a top pressure of 50 mbar absolute with a feed rate of 6.7 kg / h and a reflux ratio of 0.4-0.5, resulting in a take off of 1.1 kg / h and a bottom stream of 5.6 kg / h (34 wt.-% PD, 52 wt.-% PDMA, 13 wt.-% PDDA) containing acetic acid and water.

[0178] The removal of PDDA was carried out in a distillation column DN50 equipped with a condenser, a liquid separator for reflux regulation and a falling film evaporator with 3.5 m BX packing at a top pressure of 20 mbar absolute with a feed rate of 1.6 kg / h and a reflux ratio of 7-8, resulting in a top draw of 0.4 kg / h containing 1 wt.-% PD, 40 wt.-% PDMA, and 54 wt.-% PDDA. The corresponding bottoms stream (1.2 kg / h) consisted of 44 wt.-% PD, 55 wt.-% PDMA and 0.3 wt.-% PDDA.

[0179] The separation of PDMA from PD was carried out in a distillation column DN50 equipped with a condenser, a liquid separator for reflux regulation and a falling film evaporator, with 3.5 m BX packing, at a top pressure of 20 mbar absolute with a feed rate of 1.2 kg / h and a reflux ratio of 3-4, resulting in a top draw of 0.6 kg / h containing 0.5 wt.-% PD, 97-98 wt.-% PDMA, and 1 wt.-% PDDA. The corresponding bottoms stream (0.6 kg / h) consisted of 91-92 wt.-% PD and 8-9% PDMA. During the three distillation steps, the total yield of PDMA was 71-73%.

[0180] The overall yield of PDMA (of the reaction and distillation steps) was 31-33% based on PD.

[0181] Ab) Use of recycle stream in fully continuous mode (invention)

[0182] 1,3-Propanediol (PD, 76 kg / h, 0.99 kmol / h, 99.7%) was mixed with fresh acetic acid (HAc, 57 kg / h, 100%), 89 kg / h of distillate from the first distillation column (56 wt% of acetic acid, 4 wt% of water), 90 kg / h of distillate from the second distillation column (2 wt% of PD, 36.5 wt% of PDMA, 61 wt% of PDDA) and 110 kg / h of the bottoms stream from the third distillation column (97 wt% of PD, 3% of PDMA). The reaction was carried out in a continuous stirred tank reactor at reflux temperature (atmospheric pressure) with an average residence time of 5-6 hours to deliver 400 kg / h of reaction mixture (a mixture of acetic acid, water, unreacted PD (29 wt %), 3-acetylpropan-1-ol (PDMA, 35 wt %) and 1,3-propanediol diacylate (PDDA, 14.5 wt %)).

[0183] The removal of acetic acid / water was carried out in a distillation column DN 500 equipped with a condenser, a liquid separator for reflux regulation and a falling film evaporator with 3.7 m BX packing at a top pressure of 50 mbar absolute with a feed rate of 400 kg / h and a reflux ratio of 0.5-1, resulting in a top draw of 85 kg / h and a bottom stream of 315 kg / h (36 wt.-% PD, 45 wt.-% PDMA, 19 wt.-% PDDA) containing acetic acid and water.

[0184] The removal of PDDA was carried out in a distillation column DN1000 equipped with a condenser, a liquid separator for reflux regulation and a falling film evaporator with 10.8 m BX packing at a top pressure of 20 mbar absolute with a feed rate of 315 kg / h and a reflux ratio of 10-15, resulting in a top draw of 92 kg / h containing 2 wt.-% PD, 36.5 wt.-% PDMA, and 61 wt.-% PDDA. The corresponding bottoms stream (223 kg / h) consisted of 50 wt.-% PD, 48-49 wt.-% PDMA and 1-2 wt.-% PDDA.

[0185] The separation of PDMA from PD was carried out in a distillation column DN1000 equipped with a condenser, a liquid separator for reflux regulation and a falling film evaporator, with 7.5 m BX packing, at a top pressure of 10 mbar absolute with a feed rate of 223 kg / h and a reflux ratio of 5-10, resulting in a top draw of 108 kg / h containing 0.1 wt.-% PD, 98-99 wt.-% PDMA, and 1 wt.-% PDDA. The corresponding bottoms stream (115 kg / h) consisted of 98-99 wt.-% PD and 1-2% PDMA.

[0186] The overall yield of PDMA (of the reaction and distillation steps) was 90%, based on (fresh) PD.

[0187] B) Nitrate formation

[0188] A 40% w / w solution of PDMA in dichloromethane (DCM) was reacted with nitrosulfonic acid (1.1 eq. HNO3, 2.2 eq. H2SO4, less than 3 wt% water) at 5°C in a flow reactor.

[0189] The nitrate formation reaction was performed in a continuously operated flow reactor by mixing a DCM solution of PDMA (60 wt % DCM / 40 wt % PDMA) with nitrosulfuric acid at a constant ratio and a stable flow of the components. In order to control the reaction temperature below 40° C., the reaction was distributed by mass flow between two flow reactors in series by feeding PDMA in 2 portions (reactor 1 / reactor 2=40%:60%). The total residence time in the two reactors was maintained at 15-19 seconds.

[0190] Immediately after 2 consecutive reactors the reaction was diluted / quenched with water at 10°C, followed by phase separation. The organic phase containing the intermediate 3-acyl-propane-1-nitrate (MAMN) was washed once with water, stabilizing the mixture for intermediate storage in a buffer tank. The organic phase containing MAMN could be taken to the next step as is, or optionally washed with water before the next step, with an overall yield of 99%

[0191] The aqueous phase, consisting mainly of dilute H2SO4, is concentrated to 65% or 96% H2SO4 for use in other applications.

[0192] C) Hydrolysis

[0193] PDMNMA (about 50% in DCM) was reacted with 1,3 equivalents of NaOH (10-11% in water) at 40-56 °C.

[0194] The hydrolysis of PDMNMA was performed in a vertical stirred cascade reactor by continuously feeding PDMNMA (about 50% solution in DCM) together with 10-11% NaOH solution (in a ratio of 1 / 1.3 equiv.) from the bottom. The residence time was 4 h at a reaction temperature of 40-56°C. After complete conversion (>99.9%), the phases were cooled to about 20°C, separated, and the aqueous phase was washed / extracted with DCM in continuous mode at room temperature (strip extraction of PDMN). The combined organic phases were subjected to solvent removal (see D) workup).

[0195] After removal of DCM from the combined organic phases, the desired product was obtained in 97% yield.

[0196] D) Solvent removal and recovery (partial condensation)

[0197] After hydrolysis, the combined organic phases PDMN / DCM (77% of DCM) were subjected to solvent removal in a 3-stage evaporator setup by feeding the organic phase into a first evaporator where a PDMN solution (containing 7-8% of DCM) was produced at 500 mbar. The distillate (vapor stream) was directed to a partial condenser where the liquid fraction (PDMN / DCM, about 55-60% of PDMN) was recovered at 30° C. and fed back to the first evaporator. The remaining vapor was passed to a (total) condenser operated at 0° C. to recover high-purity DCM (<0.03% of PDMN).

[0198] The PDMN solution (containing 7-8% of DCM) from the first evaporator is fed to a second evaporator operated at 100 mbar to produce a liquid solution containing about 1% by weight of DCM. The distillate (vapor stream) is directed to a partial condenser, where the liquid fraction (PDMN / DCM, about 70-75% of PDMN) is recovered at 15° C. and fed back to the first evaporator. The remaining vapor is passed to a (total) condenser operated at 0° C. to recover DCM (about 0.1% of PDMN).

[0199] The PDMN solution (containing about 1% of DCM) from the second evaporator is fed to a third evaporator operated at 10 mbar to produce a liquid solution containing less than 0.1% by weight of DCM. The distillate (vapor stream) is directed to a partial condenser, where the liquid fraction (PDMN / DCM, about 90% of PDMN) is recovered at 0° C. and fed back to the first evaporator. The remaining vapor is discarded.

Claims

1. A method for preparing 1,3-propylene glycol mononitrate, the method comprising the following steps: (A) acylation of 1,3-propylene glycol using an acylating agent, i.e., an acylation reaction, comprising the steps of: re-feeding recycled reaction components comprising 1,3-propylene glycol, 1,3-propylene glycol monoacylate and 1,3-propylene glycol diacylate back to the acylation reaction, provided that in the acylation reaction, 0.5 mol to 1.5 mol of water is added per mol of the recycled acylating group, and the molar ratio of the total molar amount of the acylating agent, 1,3-propylene glycol monoacylate and 2 times of 1,3-propylene glycol diacylate to the total molar amount of 1,3-propylene glycol, 1,3-propylene glycol monoacylate and 1,3-propylene glycol diacylate is selected from the range of 0.5 mol to 1.1 mol per mol of 1,3-propylene glycol, wherein the acylating agent is acetic acid; (B) conducting continuous nitrate formation of the 1,3-propylene glycol monoacylate by reacting a nitrating agent with a solution comprising the 1,3-propylene glycol monoacylate and an inert solvent in a set of parts of an apparatus comprising at least two reactors connected in series, the reaction being conducted by simultaneously feeding the solution into a first reactor and a second reactor to obtain the corresponding 1,3-propylene glycol mononitrate monoacylate; (C) performing a two-phase hydrolysis of 1,3-propylene glycol mononitrate monoacylate by continuously feeding a base and a solution comprising the 1,3-propylene glycol mononitrate monoacylate and an inert solvent into a stirred cascade reactor to obtain a solution comprising the inert solvent and 1,3-propylene glycol mononitrate; and optionally (D) removing and recovering the inert solvent from the solution by distillation, comprising partially condensing and continuously feeding back into the distillation a fraction comprising a mixture of the inert solvent and 1,3-propylene glycol mononitrate.

2. The process according to claim 1, wherein the acylation process is a continuous process carried out in a vessel cascade arrangement.

3. The method according to claim 1 or 2, wherein the acylation method comprises the following steps: The 1,3-propanediol monoacylate is separated so that a) the amount of 1,3-propylene glycol in the 1,3-propylene glycol monoacylate is less than 0.5% by weight, and / or b) The amount of 1,3-propanediol diacylate in 1,3-propanediol monoacylate is less than 5% by weight.

4. The process according to claim 1, wherein in the continuous nitrate ester formation of step (B), the mass flow rate of the solution entering the first reactor is selected from the range of 40% to 60% of the total mass flow rate of the solution, while the remaining solution is fed into the second reactor.

5. The method according to claim 1 or 4, wherein in the continuous nitrate ester formation of step (B), the concentration of the 1,3-propanediol monoacylate in the inert solvent is selected between 10 wt% and 60 wt%.

6. The method according to claim 1 or 4, wherein in the continuous nitrate ester formation in step (B), the nitrating agent is a mixture of H2SO4 and HNO3, wherein a) the molar ratio of the HNO3 to the 1,3-propylene glycol monoacylate is selected from 1 to 1.5, and b) The molar ratio of the H2SO4 to the HNO3 is selected from 1.5 to 2.

5.

7. The method according to claim 1 or 4, wherein in the continuous nitrate ester formation in step (B), the reaction volumes of the first reactor and the second reactor are selected in the range of 4:1 to 1:

4.

8. The process according to claim 1 or 4, wherein in the continuous nitrate ester formation of step (B), the nitrate ester formation is carried out for an average residence time of about 5 seconds to about 30 seconds for two reactors.

9. The method according to claim 1 or 4, wherein in the continuous nitrate formation of step (B) a) the outlet reaction temperature of reactor 1 is equal to or lower than 40°C, and b) The outlet reaction temperature of the reactor 2 is equal to or lower than 25°C.

10. The process according to claim 1 or 4, wherein in the two-phase hydrolysis step (C), a base and a solution comprising 1,3-propylene glycol mononitrate monoacylate and an inert solvent are continuously fed into a stirred cascade reactor.

11. The process according to claim 1 or 4, wherein in the two-phase hydrolysis step (C), the base is selected from NaOH, KOH, Ca(OH)2 or ammonia or an aqueous solution thereof.

12. The process according to claim 1 or 4, wherein in the two-phase hydrolysis step (C), the base is an aqueous solution with a concentration between 1 wt% and 50 wt%.

13. The method according to claim 1 or 4, wherein in the two-phase hydrolysis step (C), the reaction temperature is selected in the range of 20°C to 70°C.

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