WO2016170044A1

WO2016170044A1 - Particulate poly-3-hydroxypropionate and process for the precipitation thereof

Info

Publication number: WO2016170044A1
Application number: PCT/EP2016/058879
Authority: WO
Inventors: Marek Pazicky; Rocco Paciello; Eva-Maria Hoffmann; Huanjun ZHANG; Christian Raith; Wolfgang Fischer
Original assignee: Basf Se
Priority date: 2015-04-24
Filing date: 2016-04-21
Publication date: 2016-10-27
Also published as: DE102015207553A1

Abstract

A particulate poly-3-hydroxypropionate which is obtainable by reaction of ethylene oxide with carbon monoxide in the presence of a cobalt-comprising catalyst system, wherein the particulate poly-3-hydroxypropionate has a cobalt content of less than 300 ppmw, and also a process for preparing particulate poly-3-hydroxypropionate, which comprises the following steps: a) reaction of ethylene oxide dissolved in a solvent with carbon monoxide in the presence of a catalyst system comprising at least one cobalt source to give a solution of poly-3-hydroxypropionate in the solvent; b) precipitation of poly-3-hydroxypropionate from the solution of poly-3-hydroxypropionate in the solvent by addition of an antisolvent, with the addition being carried out with mixing, to give a suspension of poly-3-hydroxypropionate in a solvent/antisolvent mixture; c) introduction of a gas comprising molecular oxygen into the solution or suspension during and/or after the precipitation b); d) isolation of poly-3-hydroxypropionate by means of solid-liquid separation; and e) washing of the poly-3-hydroxypropionate which has been separated off; wherein the particulate poly-3-hydroxypropionate has a cobalt content of less than 300 ppmw. The process allows the preparation of poly-3-hydroxypropionate in a largely cobalt-free form.

Description

Acrylic acid is an industrially significant monomer which is used as such, in the form of its alkyl esters and / or in the form of its alkali metal salts, for the preparation of polymers. The polymers are z. B. used as an adhesive or as a superabsorbent for water or aqueous solutions. For some time, the production of acrylic acid by a carbonylating reaction of ethylene oxide with carbon monoxide and thermolysis of the resulting poly-3-hydroxypropionate (poly-3HP) is known.

It is known from the dissertation "Multi-Site Catalysis - Novel Strategies to Biodegradable Polyesters from Epoxides / CO and Macrocylic Complexes as Enzyme Models" by Markus Allmendinger, University of Ulm (2003) that carbonylating reaction of ethylene oxide dissolved in an aprotic solvent with carbon monoxide at elevated pressure, elevated temperature and in the presence of a catalyst system comprising at least one cobalt source directly (ie, without the propiolactone (oxetan-2-οη) being formed as an intramolecular cyclic ester of β-hydroxypropionic acid (3-hydroxypropionic acid) as an intermediate) Upon prolonged release of the product mixture, a portion of the poly-3HP contained therein will precipitate out of the product mixture and may be separated from the product mixture by use of a mechanical separation operation (eg, filtration) Alternatively, the precipitation of Po ly-3HP be effected from the product mixture by addition of methanol to the product mixture.

J. Am. 2002, 124, pages 5646-5647, DE 10137046 A1, WO 03/01 1941 A2 and J. Org. Chem. 2001, 66, pages 5424-5426 also describe processes for the carbonylating reaction of ethylene oxide with carbon monoxide.

WO 2013/126375 A1 describes a process for the preparation of acrylic acid in which the formation and thermolysis of poly-3HP take place at separate locations.

Characteristic of the said methods for separating the precipitated poly-3HP from the cobalt catalyst system is that the isolated poly-3HP has a non-negligible content of cobalt. The remaining in the separated poly-3HP Cobalt may impair its thermolysis to acrylic acid. Methods for decoupling are known, for example, from US Pat. No. 3,330,875 A.

WO 2014/012855 A1 describes a process for the preparation of acrylic acid in which ethylene oxide is carbonylated with carbon monoxide in the presence of a cobalt-containing catalyst to form poly-3HP, the content of poly-3HP in Co with water and / or a reduced aqueous solution and the poly-3HP is further converted by thermolysis to acrylic acid. Poly-3HPs having cobalt contents of 0.05% by weight or more are disclosed.

The object of the present invention is to provide poly-3HP in a substantially cobalt-free form.

The object is achieved by a particulate poly-3-hydroxypropionate obtainable by reacting ethylene oxide with carbon monoxide in the presence of a cobalt-containing catalyst system and characterized in that the particulate poly-3-hydroxypropionate has a cobalt content of less than 300 ppmw. There is also provided a process for producing particulate poly-3-hydroxypropionate comprising the steps of: a) reacting ethylene oxide dissolved in a solvent with carbon monoxide in the presence of a catalyst system comprising at least one source of cobalt to form a solution of poly-3-hydroxypropionate in the solvent; b) Precipitation of poly-3-hydroxypropionate from the solution by addition of an antisolvent, the addition being carried out with thorough mixing to obtain a suspension of poly-3-hydroxypropionate in a solvent / antisolvent mixture; c) supplying a molecular oxygen-containing gas to the solution or

Suspension during and / or after precipitation b); d) separation of poly-3-hydroxypropionate by solid-liquid separation; and e) washing the separated poly-3-hydroxypropionate; characterized in that the particulate poly-3-hydroxypropionate has a cobalt content of less than 300 ppmw.

The weight ratio of solution to antisolvent (ΓΤΙΙ_ / ΓΤΙΑ) in step b) is preferably 0.3 to 3, in particular 0.5 to 1. At higher values for ΓΤΙΙ_ / ΓΤΙΑ, precipitation may not be achieved because the amount of antisolvent is too low to produce sufficient supersaturation of the poly-3HP solution. At lower values for ΓΤΙΙ_ / ΓΤΙΑ, larger quantities of liquid must be separated from the solid, resulting in a longer filtration time.

The temperature during precipitation b) is preferably from 10 to 90 ° C.

Preferably, the addition of the antisolvent in step b) to the temperature of 10 to 90 ° C having solution. The term temperature is understood here as meaning the temperature of the mixture of antisolvent and solution. The mixture has a temperature of 10 to 90 ° C over the entire period of Antisolvens addition.

Preferably, the addition of the antisolvent and the supply of the molecular oxygen-containing gas take place in parallel or overlapping in time or separately.

The supply of an oxygen-containing gas to the solution or suspension causes the oxidation of the cobalt contained in the catalyst system to cobalt cations, which solubilized in Antisolvens and so separated in the solid-liquid-T separation or when washing the precipitated poly-3HP can be. Preferably, the antisolvent contains anions which, together with Co (II) ions, form soluble salts in the antisolvent. By optimizing the precipitation and decoupling conditions, very low cobalt contents can be achieved in the poly-3HP. The particulate poly-3HP has a cobalt content of less than 300 ppmw, preferably less than 250 ppmw. Most preferably, the cobalt content is in the range of 5 to less than 250 ppmw. Such cobalt contents appear to be tolerable in industrial practice with regard to the cleaning effort and trouble-free thermolysis of the poly-3HP. The term poly-3-hydroxypropionate polyester are the structure

understood, n is an integer> 2, and z. B. up to 150, or up to 200, or up to 500 and more. a, b form the polyester terminating end groups, the nature of which depends on the preparation conditions (eg of the catalyst system used).

For example, a = and

O

Alternatively, a = and

Alternatively, a = and

-CH, O H

"CH

b = his.

N

H C C H H C c

Alternatively, a = and b = -OH. The reaction of ethylene oxide dissolved in a solvent with carbon monoxide is carried out in the presence of a catalyst system comprising at least one cobalt source.

Based on the molar amount of ethylene oxide, the molar amount of cobalt present in the at least one cobalt source of the catalyst system is normally in the range from 0.005 to 20 mol%, preferably in the range from 0.05 to 10 mol%, more preferably in Range of 0.1 to 8 mol% and most preferably in the range of 0.5 to 5 mol%.

As a suitable source of cobalt, any cobalt-containing chemical compound can be used, since it is usually converted into the actual catalytically active compound of the cobalt under the carbon monoxide pressure to be used in the process.

Among others come as a suitable cobalt sources z. For example, cobalt salts such as cobalt chloride, cobalt formate, cobalt acetate, cobalt acetylacetonate, cobalt sulfate and cobalt 2-ethylhexanoate ("cobalt soap") are readily carbonylated under the applicable carbon monoxide pressures ("in situ", a presence of small amounts molecular hydrogen may be advantageous in this respect). But also finely divided cobalt metal (eg in dust form) can be used in the process as cobalt source.

As cobalt sources, preformed cobalt carbonyl compounds (including compounds which contain at least one cobalt atom and at least one carbon monoxide ligand) are preferred, of which the dicobaltoctacarbonyl (Co 2 (CO) s) is very particularly preferred (this contains [Co (CO) 4] ⁺ [Co (CO) 4] ^_ the [Co (CO) 4] ~ as it were preformed). In terms of application, it is used as sole cobalt source of the catalyst system.

The co-use of co-catalysts (at least one) in the catalyst system comprising at least one cobalt source and having at least one nucleophilic bransted-base functionality as well as at least one branst-acidic functionality is particularly advantageous.

These co-catalysts include, in particular, aromatic nitrogen heterocycles (for example, they may be 5-, 6- or 7-membered rings, have at least one nitrogen atom in the aromatic ring (cycle)), and in addition to the bransted-base Nitrogen at least one branstedsaure (free) hydroxyl group (-OH) and / or at least one branstedsaure (free) carboxyl group (-COOH) have covalently bonded. Of course, the aromatic nitrogen heterocycle may in this case again be fused with other aromatic and / or aliphatic (eg, 5-, 6- or 7-membered) ring systems. The at least one hydroxyl group and / or carboxyl group may be located both on the aromatic nitrogen-nitrogen heterocycle (preferred) and (and / or) on the fused aliphatic and / or aromatic ring system. Of course, the annealed part may also have one or more than one nitrogen atom as a heteroatom. In addition to the at least one hydroxyl group and / or carboxyl group may additionally also z. As aliphatic, aromatic and / or halogen substituents may be present.

Examples of particularly preferred co-catalysts which may be mentioned are 2-hydroxypyridine, 3-hydroxypyridine, 4-hydroxypyridine, 3,4-dihydroxypyridine, 3-hydroxyquinoline, 4-hydroxy-2-methylpyridine, 3-hydroxy-4-methylpyridine, 2 , 6-dihydroxypyridine, 2-hydroxyquinoline, 1-hydroxyisoquinoline, 3-hydroxyquinoline, 2,3-dihydroxyquinoxaline, 8-hydroxyquinoline, 2-pyridylmethanol, 3-pyridylmethanol and 2- (2-pyridyl) ethanol. Of course, as already stated, instead of and / or in addition to the hydroxyl group, a carboxyl group may be present, as is the case with nicotinic acid. Very particular preference is given to using 3-hydroxypyridine as co-catalyst in the preparation process (and this in particular in combination with diglyme as aprotic). scheme solvent and Dicobaltoctacarbonyl as cobalt source of the catalyst system).

As a rule, the co-catalyst in the production process in such total molar amounts of Mco-Kat will be used, that the ratio Mc ₀ -Kat: Mcobait, formed with the total molar amount of mcobaite on cobalt contained in the catalyst system used, is 5: 1 to 1: 5, preferably 4: 1 to 1: 4, more preferably 3: 1 to 1: 3 and most preferably 2: 1 to 1: 2 or 2: 1 to 1: 1. Carbon monoxide is preferably used in excess in all the above cases (relative to the reaction stoichiometry).

Salts of the anion Co (CO) 4 ^" and / or its brominated acid HCo (CO) 4 can also be used as sources of cobalt for such a process Examples of such salts are the tetramethylammonium tetracarbonyl cobalt (III) at, Et.4NCo (CO) 4, and the bis (triphenylphosphoranylidene) ammonium tetracarbonyl cobalt (-l) at. Further examples are disclosed, for example, in DE 10149269 A1.

The type and amount of the solvent are preferably chosen so that they are sufficient under the reaction conditions to be used to keep the required amount of the cobalt-containing catalyst system in solution in the reaction mixture, since the process is preferably carried out homogeneously catalyzed.

By a solvent is meant a solvent for poly-3HP. Preferably, poly-3HP is soluble in the antisolvent at 25 ° C to at least 25 g (poly-3HP) / 100 g (antisolvent), more preferably at least 40 g (poly-3HP) / 100 g (antisolvent). The solvent preferably has a boiling point of more than 20 ° C. The solubility of poly-3HP in the solvent depends on the molecular weight of the poly-3HP. The suitability of a solvent as solvent in the reaction a) depends on the solubility of the poly-3HP prepared in reaction a).

The solvent is usually an aprotic solvent. An aprotic solvent is understood as meaning organic compounds (and mixtures of two or more of these two compounds) which contain no atom other than carbon (no type of atom other than carbon) to which a hydrogen atom is covalently bonded, and neither ethylenically nor alkinically (in each case one or more times) are unsaturated. The solvent is at a pressure of 1, 0133-10 ⁵ Pa (= normal pressure) at least one of in the range of 0 ° C to 50 ° C, preferably at least one of the range of 5 ° C to 40 ° C and especially preferably at least one of the lying in the range of 10 ° C to 30 ° C temperatures liquid.

Suitable aprotic solvents are those which have at least one covalently bonded oxygen atom, preferably an ether oxygen atom, i. an oxygen atom that forms an ether bridge.

Furthermore, it is advantageous if the aprotic solvent is or comprises a substance which contains at most oxygen and / or sulfur as atomic species other than carbon and hydrogen.

Suitable aprotic solvents are those whose relative static permittivity ε (also referred to as dielectric constant, dielectric constant or permittivity number) at a temperature of 293.15 K and a pressure of 1, 0133-10 ⁵ Pa (= normal pressure) as the liquid pure substance in the Range of 2 to 50, preferably 3 to 20, more preferably 4 to 15 and most preferably 5 to 10 (the relative static permittivity of vacuum = 1).

If the aprotic substance at 293,15 K and atmospheric pressure is not liquid, but solid, the above statement refers to the temperature of its melting point at normal pressure. If the aprotic substance (aprotic (chemical) compound) at 293,15 K and atmospheric pressure is not liquid but gaseous, then the above specification refers to a temperature of 293,15 K and the corresponding saturation vapor pressure (the (self) vapor pressure at which the substance condenses at 293.15 K).

A suitable source with information on relative static permittivities of suitable relevant aprotic substances is z. See, for example, the HANDBOOK of CHEMISTRY and PHYSICS, 92th Edition (2010-2011), CRC PRESS. According to the information there, the relevant £ z. For tetrahydrofuran = 7.56, for ethylene oxide = 12.43, for 1, 4-dioxane = 2.22, for ethylene glycol dimethyl ether (1, 2-dimethoxyethane) = 7.41, for diethylene glycol dimethyl ether (diglyme) = 7.38 and for triethylene glycol dimethyl ether (triglyme) = 7.62.

Very particularly preferred aprotic solvents are therefore those whose ε is 2 to 35, advantageously 3 to 20, particularly advantageously 4 to 15, and very particularly advantageously 5 to 10, and which at the same time contain at least one covalently bonded oxygen in which it reacts with particular advantage is an ether oxygen atom. Examples of suitable aprotic solvents for the suitable process are: saturated (cyclic and noncyclic) and aromatic hydrocarbons such as n-hexane, n-heptane, petroleum ether, cyclohexane, benzene and toluene, halogenated saturated and aromatic hydrocarbons such as dichloromethane, chlorobenzene and 1 , 4-dichlorobutane, esters of organic acids (especially organic carboxylic acids) such as n-butyl propionate, phenyl acetate, glycerol triacetate, ethyl acetate and diethyl phthalate,

Ketones such as acetone, ethyl methyl ketone, methyl isobutyl ketone, benzophenone, cyclohexanone and 2,4-dimethyl-3-pentanone,

Nitriles such as acetonitrile, propionitrile, n-butyronitrile and benzonitrile,

Dialkylamides such as dimethylformamide and dimethylacetamide, carbonic acid esters such as dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, ethylenecarbonate and propylene carbonate,

Sulfoxides such as dimethyl sulfoxide, sulfones such as sulfolane,

N-alkylpyrrolidones such as N-methylpyrrolidone and cyclic and noncyclic ethers such as diethyl ether, anisole (methylphenyl ether), tetrahydrofuran, 2 methyltetrahydrofuran, 1, 4-dioxane, diphenyl ether, benzyl methyl ether, ethoxybenzene, 1, 2-dimethoxybenzene, alkylene glycol dialkyl ethers (z. B. Ethylenglykoldialkylether as the ethylene glycol dimethyl ether (= monoglyme)) and Polyalkylenglykoldialkyl ethers such as Diethylenglykoldiethylether, the Diethylenglykoldimethylether (= diglyme), the triethylene glycol dimethyl ether (= triglyme), the Tetraethylenglykoldime- (= Tetraglyme), the Dipropylenglykoldimethylether (= Proglyme) and the diethylene glycol dibutyl ether (= butyldiglyme).

The solvent is preferably selected from alkylene glycol dialkyl ethers, 1,4-dioxane, methyl phenyl ether, cyclohexanone, 2,4-dimethyl-3-pentanone, chlorobenzene, 1,4-dichloroethane. butane, diethyl carbonate, ethyl acetate, N-methylpyrrole, ethoxybenzene, 1, 2-dimethoxybenzene, tetrahydrofuran, 2-methyltetrahydrofuran, benzyl methyl ether and diethyl phthalate. Of these, alkylene glycol dialkyl ethers and polyalkylene glycol dialkyl ethers such as ethylene glycol dimethyl ether (1,2-dimethoxyethane, monoglyme), diethylene glycol dimethyl ether (bis (2-methoxyethyl) ether, diglyme), dipropylene glycol dimethyl ether (proglyme) and diethylene glycol dibutyl ether (= butyl diglyme) are particularly preferred. Diglyme is especially preferred.

The reaction temperature to be used in the reaction of ethylene oxide with carbon monoxide or the working pressure to be used (the absolute pressure in the gas atmosphere of the reaction space) are not critical and may vary within wide limits. The reaction can be carried out at comparatively mild reaction conditions. Suitable reaction temperatures are in the range of 25 to 150 ° C, preferably in the range of 35 or 50 to 120 ° C, more preferably in the range of 60 to 100 ° C and most preferably in the range of 70 to 90 ° C. At relatively low temperatures, the reaction proceeds with a somewhat reduced reaction rate, but with a comparatively increased target product selectivity, which is close to 100 mol%. By over-atmospheric working pressures the implementation of the invention is favored. In terms of application, the working pressure in the reaction normally does not exceed 2.5-10 ⁷ Pa, since higher working pressures can cause excessive installation costs. Working pressures of 2-10 ⁵ Pa to 2-10 ⁷ Pa are advantageous according to the invention. Is preferred for the reaction, a working pressure in the range of 5-10 ⁵ Pa to 1, 5-10 ⁷ Pa, more preferably in the range of 1 -10 ⁶ Pa to 1 × 10 ⁷ Pa and very particularly preferably in the range of 2-10 ⁶ Pa to 12-10 ⁶ Pa or in the range of 4-10 ⁶ Pa to 10-10 ⁶ Pa applied. The reaction is usually carried out in an overpressure reactor such as an autoclave.

Oxidizing gases (eg O 2, N 2 O), CO 2 and water vapor normally act as catalyst poisons with respect to the reaction according to the invention or react with ethylene oxide to form byproducts and therefore become largely or preferably completely composed of the carbon monoxide to be used (or in general of those to be used Components of the reaction mixture) excluded. Their individual volume fractions of the total volume of carbon monoxide used should be <1 % By volume, better <0.1% by volume, preferably 0.01% by volume, more preferably -i 0.001% by volume, and very particularly preferably be vanishing.

Accordingly, the polyester formation of the present invention is preferably carried out under inert conditions, i. H. performed in the absence of moisture and air. Since ethylene oxide forms a highly flammable gas, the presence of molecular oxygen is also disadvantageous in this aspect of the carbonylation according to the invention. Water vapor can also open the ethylene oxide ring in an undesirable manner, which is why an absence of water vapor (apart from the already mentioned small amounts) in the pressure vessel is undesirable even from this angle.

The carbon monoxide to be used for the carbonylating reaction according to the invention can thus be supplied to the overpressure reactor both in admixture with inert gases (eg N 2, noble gases such as Ar) and essentially as pure substance. The latter is preferred, which is why the working pressures set out above for the reaction also form favorable (in the gas atmosphere of the reaction space) CO partial pressures for the carbonylation according to the invention.

The reaction of the invention is normally carried out in a gas-tight sealable pressure vessel for reactions in the overpressure range, for. B. in an autoclave. In principle, the poly-3HP formation in an overpressure reactor can be carried out both batchwise and continuously. If it is carried out batchwise, the working pressure (and with this the CO partial pressure) can be kept constant or decrease following the conversion of the carbonylation. The former can be achieved in a more simple way by continuously reusing spent CO in the reaction space of the pressure reactor.

For a carbonylation according to the invention is carbon monoxide having a purity of 99 vol .-% or higher, in particular 99.5 vol .-% or higher.

Furthermore, ethylene oxide having a purity of 99.9% by weight or higher can be used as raw material for the process according to the invention (the statements relate to the liquid phase). In this case, a residual aldehyde content of the ethylene oxide can be removed by treatment thereof in a manner known per se with aldehyde scavengers (such as, for example, aminoguanidine hydrogencarbonate) prior to its use.

Normally, in the case of a batchwise carbonylation of the ethylene oxide according to the invention, the procedure is such that the reaction chamber of the autoclave is expediently initially flushed with inert gas (eg Ar) for practical purposes. subse- ßend is under inert gas atmosphere and at a comparatively low temperature, the catalyst system, the aprotic solvent and the ethylene oxide in the reaction chamber of the autoclave and close selbigen. Preferably, the reaction space is operated stirred. Thereafter, an appropriate amount of carbon monoxide is pressed into the reaction space of the autoclave by a suitable pressure valve for the purpose of carbonylation.

Then the temperature in the reaction space is increased by external heating to the reaction temperature, and the reaction mixture is stirred in an autoclave for. B. stirred while maintaining the reaction temperature. If no carbon monoxide is pressed into the reaction space in the course of the reaction, the reaction is usually stopped when the internal pressure in the reaction space has dropped to a value that does not change over time. By appropriate cooling, the temperature is lowered in the interior of the reaction chamber, the increased internal pressure subsequently relaxed to atmospheric pressure and the autoclave opened, so that the access to the same in the reaction space of the product mixture A is given. As already mentioned, the carbon monoxide is used in particular in a batchwise embodiment of the method according to the invention normally in superstoichiometric amounts. In principle, however, it is also possible to use the amount corresponding to the stoichiometry or else a substoichiometric amount of CO in the process according to the invention.

Based on the molar total amount of ethylene oxide fed into the autoclave, conversions of> 90 mol%, advantageously> 95 mol% or> 98 mol, are usually obtained with comparatively short reaction times (generally 0.5 to 3.0 h). %, preferably a 99 mol%, and particularly preferably> 99.9 mol%.

In general, the product mixture obtained in the carbonylation of ethylene oxide contains at least the majority of the poly-3HP formed in a dissolved state.

Preferably, the poly-3HP concentration in the solution is in the range of 5 to 35 wt .-%, in particular 10 to 20 wt .-%. The solution may contain, in addition to the solvent and the dissolved poly-3HP further components, for. B. (co) catalysts and by-products of the previous implementation. Solvent and dissolved poly-3HP together preferably comprise at least 80% by weight of the solution. Preferably, a solution obtained in the synthesis is used as such, ie without intermediate purification, in the subsequent precipitation. The precipitation of poly-3-hydroxypropionate from the solution of poly-3-hydroxypropionate in the solvent is effected by adding an antisolvent. For the purposes of the present application, an antisolvent is understood as meaning a solvent in which the poly-3HP is soluble at 25 ° C. to at most 1 g (poly-3HP) / 100 g (antisolvent) and which has a boiling point of more than 20 ° C has. The solubility of poly-3HP in the solvent depends on the molecular weight of the poly-3HP. The suitability of a solvent as antisolvent in precipitation b) depends on the solubility of the poly-3HP prepared in reaction a). Preferably, the solvent and the antisolvent are at least partially miscible with one another and are completely miscible, in particular in the applied weight ratio of solution to antisolvent.

Alcohols are less preferred as antisolvents. If z. For example, methanol is used as Antisolvens, ester formation is carried out with terminal carboxyl groups of the poly-3HPs. This requires the formation of methyl acrylate as an undesirable by-product during later thermolysis thereof.

Preferably, the antisolvent is water or an aqueous solution. The use of aqueous antisolvents allows the recovery of poly-3HP with reduced cobalt content attributed to the catalyst system used for carbonylation.

Preferably, the aqueous solution used as Antisolvens has a pH at a temperature of 25 ° C and at atmospheric pressure of <7.5, preferably <7. The abovementioned pH of the aqueous antisolvent is preferably 6 6, more preferably ≦ 5, and most preferably ≦ 4. In general, the abovementioned pH of the aqueous antisolvent will not fall below the value 0 and in many cases> 1 or> 2 be. Advantageously, the above pH values (likewise based on 25 ° C. and normal pressure) also apply to the aqueous mixtures resulting from the addition of the aqueous antisolvent to the poly-3HP solution, which are advantageously treated advantageously with a gas containing molecular oxygen and of which the precipitated poly-3HP is separated by the application of at least one mechanical separation operation. Preferably, the pH (25 ° C, atmospheric pressure) of these aqueous mixtures is 2 to 4, z. B. 3.

In order to set the relevant pH, inorganic and / or organic acids come into consideration (in the sense of Bransted). Examples include sulfuric acid. carbonic acid, hydrochloric acid and / or phosphoric acid as possible inorganic acids. Organic carboxylic acids, in particular alkanoic acids, are preferably used as pH adjusting agents. Among these are exemplified acrylic acid, oxalic acid, formic acid, acetic acid, propionic acid, fumaric acid and / or maleic acid. It goes without saying that organic sulfonic acids, such as, for example, can be used to adjust the relevant pH value. B. methanesulfonic acid used or co-used.

As suitable aqueous Antisolventien thus come z. For example, aqueous solutions having dissolved one or more than one of the aforementioned inorganic and / or organic acids see. Such aqueous antisolvents are z. For example, aqueous sulfuric acid, aqueous carbonic acid, aqueous hydrochloric acid, aqueous phosphoric acid, aqueous acrylic acid, aqueous oxalic acid, aqueous formic acid, aqueous acetic acid, aqueous propionic acid, aqueous fumaric acid, aqueous maleic acid and / or aqueous methanesulfonic acid. Of course, the addition of water and one or more acids for the purpose of precipitation of poly-3HP also temporally and / or spatially separated from each other, so that the effectively added acidic aqueous antisolvent z. B. first formed in the poly-3HP having aqueous mixture. An advantage of the use of carboxylic acids is the increased solubility of the subsequently oxidized to cobalt cations catalyst by the formation of salts soluble in the reaction solution, consisting of cobalt cations and carboxylic acid anions. Acetic acid and propionic acid have proven to be particularly suitable here. Suitably from an application point of view, one of the abovementioned suitable aqueous antisolvents, based on the weight of the aqueous liquid, contains at least 10% by weight, better at least 20% by weight or at least 30% by weight, advantageously at least 40% by weight or at least 50% % By weight, particularly advantageously at least 60% by weight or at least 70% by weight, optionally at least 80% by weight or at least 90% by weight, often at least 95% by weight, or at least 97% by weight %, or at least 99% by weight of water.

Advantageously, the carboxylic acid is selected from acetic acid and propionic acid, and most preferably the aqueous solution comprises 5% by weight to 30% by weight, more preferably 7% by weight to 25% by weight of carboxylic acid, most preferably 10 to 15 Wt .-% carboxylic acid. At a lower carboxylic acid concentration, the cobalt content of the poly-3HP particles is unfavorably increased; at a higher carboxylic acid concentration, the yield of poly-3HP is reduced by increased solubility of the poly-3HP in the liquid mixture. Preferably, the addition of the antisolvent is carried out at a temperature of 10 to 90 ° C having solution. The addition of the antisolvent is carried out with mixing, z. B. with stirring. Preferably, the stirrer power input is controlled. The power input from the beginning of the antisolvent addition to the separation d) is preferably 0.1 to 10 W per kg of the sum of the mass of solution and antisolvent, more preferably 0.3 to 3 W per kg of the sum of the mass of solution and antisolvent , If the amount of stirring energy input is too low, sufficient extraction of the cobalt from the poly-3HP particles may not take place.

The solution or suspension is fed during and / or after the precipitation of an oxygen-containing gas. Conveniently, the molecular oxygen-containing gas is air or contains air. The supply of the molecular oxygen-containing gas serves to oxidize the cobalt catalyst. The salts of the cobalt cations resulting from the oxidation are, depending on the counterion (s), different degrees of solubility in water. The preferred carboxylic acid anions, in particular acetate and propionate, form well-soluble salts with cobalt cations in the reaction solution. These can be separated off from the particulate poly-3HP in the filtration step and / or in a subsequent washing step.

For example, it is preferable to carry out the above-mentioned supply in the presence of air and / or in the presence of a gas containing molecular oxygen other than air. In a simple way, this can be done by flowing through the intensively mixed aqueous mixture of molecular oxygen or of the molecular oxygen-containing gas.

With the supply of the molecular oxygen-containing gas, a gas dispersion forms at sufficiently high stirring power, which permits a large contact area of the oxygen-containing gas with the solution or the suspension and thus advantageously influences the oxidation of the cobalt catalyst. The stirrer energy input is preferably at least 0.3 W per kg of the sum of the mass of solution and antisolvent. At lower power input, the gas dispersion does not sufficiently dissipate or segregate, negatively impacting decolorization. The power input is particularly preferably at least 0.5 W per kg of the sum of the mass of solution and antisolvent. Particularly preferably, the stirring power is in the range of 0.8 to 2.0 W per kg of the sum of the mass of solution and Antisolvens. In preferred embodiments, the passage of the molecular oxygen-containing gas is under conditions such that the value Q is given by the following equation

V

Q = - ^{■ ■} q ₀₂

nCo is about 0.05 to about 10, in which

V for the volume flow of the molecular oxygen-containing gas in L / h, nco for the total molar amount of cobalt in mmol,

t for the duration in h, over which the molecular oxygen-containing gas is supplied, and

qo2 represents the content of the gas of molecular oxygen in% by volume. In particular, ^ ²² - ranges from about 0.048 to about 0.150 LJ (mmol-h), t is nCo

from about 0.001 to about 3.0 hours, preferably from about 0.3 to about 1.5 hours, most preferably from 0.5 to about 1 hour, and qo2 ranges from about 1 to about 25% by volume, preferably about 20% by volume. Preferably, the supply of the molecular oxygen-containing gas to the solution or suspension during and / or after the precipitation b) takes place at a temperature of z. B. 10 to 90 ° C, or 20 to 90 ° C, or 30 to 90 ° C, preferably 40 to 90 ° C. The term temperature refers here to the temperature of the solution or suspension over the entire duration of the supply of the molecular oxygen-containing gas. When the solvent is an alkylene glycol dialkyl such as diglyme, the temperature is preferably 40 to 50 ° C; when the solvent is an ester of an organic acid such as diethyl phthalate, the temperature is preferably 65 to 90 ° C.

Subsequently, the aqueous mixture can be cooled to temperatures <25 ° C, preferably <20 ° C and more preferably <15 ° C or <10 ° C to promote the precipitation of the poly-3HPs.

Finally, the precipitated poly-3HP is separated from the liquid mixture by at least one solid-liquid separation step. Of course, the separation of precipitated poly-3HP can also be done on the warm liquid mixture. The remaining liquid phase (which comprises a further subset of the product mixture) can be further processed in a corresponding manner (for example, for the purpose of increasing the yield of separated poly-3HP) (the initial added amount of antisolvent can in principle also be so be sufficiently selected that the desired target amount of poly-3HP already fails in the first precipitation step).

The washing step is preferably carried out with deionized water, preference being given to a ratio of detergent mass (WM mass) to suspension mass (suspension mass) in the range from 0.05 to 5.0, particularly preferably 0.07 to 3.0. The washing is carried out as described in the reference example. Alternatively, a mash washing is possible, after which it is filtered again.

Poly-3HP obtained in such a way has a significantly reduced to vanishing Co content (this of course applies correspondingly to the respective total content of the various possible individual oxidation states of the Co, ie for the total content of Co ²⁺ , or to Co ⁺ , or to Co ⁰ , or to Co-). It can, for. B. dried under the action of heat and finally subjected to the desired thermolysis to acrylic acid. Due to its low cobalt content, the poly-3HP obtained according to the invention is particularly suitable for the thermolytic conversion to acrylic acid.

As described, the process according to the invention comprises the separation of the precipitated poly-3HP by means of solid-liquid separation. The economics of a manufacturing process that uses solid-liquid separation depend to a large extent on the efficiency of this process step. In the case of solid-liquid separation by filtration, the occurring filter resistance is a meaningful indicator of the quality of the filterability. The filter resistance is determined by various parameters, including the filtration time, the pressure difference between the pressure and suction sides of the filter and the filter surface.

It has been found that the filterability of particulate poly-3HP depends primarily on the particle size distribution, which is highly dependent on the parameters chosen in the process. In particular, a) influence the weight ratio of solution to antisolvent, and b) the energy introduced into the suspension influences the particle size distribution. It has been found that the process according to the invention, in addition to the extensive cobalt removal, provides poly-3HP in a form which is readily filterable. Thus, it has been found that a weight ratio of solution to antisolvent ΓΤΙΙ_ / ΓΤΙΑ below the preferred limit values results in increasingly smaller particles being formed. This causes a worse filterability. At higher values for Precipitation may not be achieved under certain circumstances, since the amount of antisolvent is too small to produce sufficient supersaturation of the poly-3HP solution.

The shear energy acting on the precipitated poly-3HP particles is dependent on the shear energy input. Too high a stirring power leads to a shift to smaller particle sizes. With increased shear, larger particles are likely to be split into smaller particles. If the energy input in the form of the stirring power is too low, the gas containing molecular oxygen will not be sufficiently dispersed and the decoupling will be adversely affected.

The present invention is further illustrated by the following examples.

Comparative example: Preparation of a solution of poly-3-hydroxypropionate (poly-3HP) by cobalt-catalyzed carbonylation of ethylene oxide

The reaction was carried out in an autoclave which could be stirred with a paddle stirrer (the blade stirrer was moved by way of a magnetic coupling), the reaction space of which could optionally be heated or cooled from the outside. All surfaces contacting the reaction space were made of Hastelloy HC4. The reaction space of the autoclave had a circular cylindrical geometry. The height of the circular cylinder was 335 mm. The inner diameter of the circular cylinder was 107 mm. The envelope of the reaction space had a wall thickness of 19 mm (Hastelloy HC4). The head of the autoclave was equipped with a gas inlet / gas outlet valve which opened into the reaction space. The temperature in the reaction space was determined by means of a thermocouple. The control of the reaction temperature was controlled electronically. The internal pressure in the reaction space was monitored continuously with a corresponding sensor.

The reaction space of the autoclave was first rendered inert with argon (contents of the Ar:> 99.999% by volume of Ar, <2 ppm by volume 0 ₂ , 3 ppm by volume of H ₂ O and <0.5 ppm by volume of hydrocarbons).

The autoclave, then heated to 10 ° C. under argon, was treated with 8.2 g of dicobaltoctacarbonyl (Co ₂ (CO) ₈ ; Sigma-Aldrich; specification: 1 -10% hexane,> 90% Co, order number: 6081 1 ), 4.4 g of 3-hydroxypyridine (Sigma-Aldrich, specification: 99% content, order number: H57009) and 802.4 g of diglyme (Sigma-Aldrich, specification: 99% content, order number: M1402) or diethyl phthalate (DEP , Delivery company: Alfa Aesar, specification: 99% content, order number: A17529) and the autoclave is then closed. The temperature of the two solids was 25 ° C and the temperature temperature of the diglyme or DEP was 10 ° C. Then, while maintaining the internal temperature of 10 ° C through the valve, carbon monoxide was forced into the autoclave until the pressure in the reaction chamber 1, 5-10 ⁶ Pa was (BASF SE monoxide, specification: 99.2% CO). Subsequently, the temperature in the reaction space was raised to 35 ° C to verify the tightness of the autoclave (over a period of 90 minutes). Then, the atmosphere in the reaction space was depressurized by opening the valve to an internal pressure of 10 ⁶ Pa. The temperature in the interior was then 30 ° C. Subsequently, 0 g of ethylene oxide (1.5 g / min) were pumped into the reaction space through the valve 51 (supplier: BASF SE, specification: 99.9% purity). The temperature in the reaction space was reduced to 25 ° C. Thereafter, carbon monoxide was again pressed into the autoclave until the pressure in the reaction space reached 6-10 ⁶ Pa (while maintaining the internal temperature of 25 ° C).

The temperature in the reaction chamber of the autoclave was then increased substantially linearly to 75 ° C. within 45 minutes with stirring (700 rpm). This temperature was maintained with stirring for 8 h. The pressure in the reaction space dropped to 5-10 ⁶ Pa during this period. Then the heating of the autoclave was switched off. Within 5 h and 50 min, the temperature in the stirred reaction chamber cooled essentially exponentially to 25 ° C. (after 50 min, the internal temperature was 60 ° C., 150 ° C. after 40 min and 30 ° C. after 235 min energized). The associated pressure in the reaction space was 4.3-10 ⁶ Pa. The autoclave was then depressurized to normal pressure and the reaction space was flushed three times in succession with argon (10 ⁶ Pa).

The reaction chamber contained 860.2 g of a dark red-brown solution. It was removed from the autoclave.

Examples 1 to 16

300 g of the solution obtained in the reference example (about 12% by weight poly-3-Lösung solution with 78% by weight of diglyme or DEP as solvent, see Table) were mixed in a 1 l glass reactor with a 2- submitted stage stepped blade. The reactor was heated to the precipitation temperature indicated in Table 1 below by a double jacket heat exchanger and maintained at this temperature. To the poly-3HP solution was added the respective antisolvent having a temperature of 20 ° C in the ratio shown in Table 1. The addition was carried out with stirring at about 605 rpm (corresponding to a power input of 1 W per kg after complete constant dosage of the antisolvent). After the end of the addition, the reactor contents were stirred for a further 10 minutes at 605 rpm.

Thereafter, the reactor contents were purged with air (12 L / h) for the time indicated in Table 1 with the draft tube positioned below the surface near the stirrer circumference; at the same time the headspace of the reactor was purged with nitrogen (20 ° C, 700 L / min). The respective temperature is given in Table 1. The resulting suspension was stirred for a further 10 min at the same stirrer rotation speed. The reaction mixture was then allowed to cool without stirring and allowed to stand for up to approx. 18 h.

For solid-liquid separation, a laboratory pressure filter was used. The filter medium 42-1 100-SK012, Sefar (PTFE, air permeability: 7 L / (dm ² -min)) with a filter area of 20 cm ² was placed on a perforated support plate (lower part of the filter chute). The lower part and the cylindrical housing of the filter chute (V is 0.32 L / 0.52 L) were connected. A filtrate container was placed under the filtrate outlet on a balance. The suction filter was filled with the suspension (msus is about 250 to 450 g). The experiment was carried out at room temperature (about 20 ° C), the exact temperature was recorded during the filtration. The suction filter was not tempered. The suction filter was closed by connecting the header (which included the gas inlet port, a pressure gauge and a pressure relief valve) to the Nutsche main body. The filtration was carried out by the application of nitrogen gas pressure (Δρ is 2 bar). The filtration was stopped as soon as nitrogen passed through the filter medium.

Deionized water was added to the filter cake as washing liquid. The suction filter was closed again and the washing liquid was forced through the filter cake by application of nitrogen gas pressure (Δρ is 2 bar). The pH of the wash filtrate was noted during the wash process. After washing, nitrogen gas (100 L / h) was passed through the suction filter for 120 seconds to mechanically dehumidify the filter cake.

The filter cake was dried in a vacuum drying oven at 10 mbar and 60 ° C for three days. Before and after drying, the filter cake was weighed to calculate dry matter content and yield. The yield was defined as the mass ratio between the collected dried filter cake and the expected amount of poly-3HP, based on 100% theoretical conversion of the carbonylation reaction. The cobalt content in the dried product was determined by atomic emission spectroscopy (Varian 720-ES ICP-OES spectrometer, Co-line 237.86 nm). The molecular weights of the poly-3HP products were analyzed by gel permeation chromatography (GPC, also known as size exclusion chromatography, SEC) using polymethyl methacrylate as standard for the average chain length and molecular weight dispersity of the poly-3HP To characterize molecules. For the examples listed, a weight average M _w in the range of 6160 to 9240 g / mol with a molecular weight dispersity of 1.5 to 2.8 was found.

The test parameters and results are given in the following table.

DEP = diethyl phthalate, AcOH = acetic acid, PrOH = propionic acid, TF = temperature on precipitation, TEC = temperature on decoupling

^* Comparative Example Bzgl. the total mass of the mixture after complete dosing

² Decoction ³ The precipitation was carried out at 1.0 W / kg and the decobalting at 0.4 W / kg

^4, according to the specifications of the dicobaltoctacarbonyl used (90 to 99% Co), an average value was given

It can be seen from Examples 1 to 3 that as the value Q increases, the cobalt content in the precipitate decreases.

From Examples 4 and 5 it can be seen that a higher temperature during the precipitation or decoupling favors the cobalt extraction.

From Examples 6 to 9 it can be seen that a higher carboxylic acid concentration in the antisolvent promotes the cobalt extraction. However, if the acid concentration is too high, precipitation is prevented, presumably because the acid then acts as a solvent.

Claims

claims

1 . Particulate poly-3-hydroxypropionate obtainable by reacting ethylene oxide with carbon monoxide in the presence of a cobalt-containing catalyst system, characterized in that the particulate poly-3-hydroxypropionate has a cobalt content of less than 300 ppmw.

2. A process for producing particulate poly-3-hydroxypropionate comprising the steps of: a) reacting ethylene oxide dissolved in a solvent with carbon monoxide in the presence of a catalyst system comprising at least one source of cobalt to form a solution of poly-3-ol hydroxypropionate in the solvent; b) Precipitation of poly-3-hydroxypropionate from the solution of poly-3-hydroxypropionate in the solvent by addition of an antisolvent, the addition being carried out with thorough mixing, whereby a suspension of poly-3-hydroxypropionate in a solvent / antisolvent Receives mixture; c) supplying a molecular oxygen-containing gas to the solution or

3. The method of claim 2 wherein the weight ratio of solution to antisolvent is 0.3 to 3.

4. A method according to claim 2 or 3, wherein the stirring energy input is 0.1 to 10 W per kg of the sum of the mass of solution and antisolvent.

5. The method according to any one of claims 2 to 4, wherein the molecular oxygen-containing gas is air or contains air.

6. The method according to any one of claims 2 to 5, wherein the value Q according to the following equation

about 0.05 to about 10, wherein

V is the volume flow of the molecular oxygen-containing gas in L / h, qo2 is the content of the gas of molecular oxygen in% by volume,

nco for the amount of cobalt in mmol, and

t for the duration in h, over which the molecular oxygen-containing gas is supplied stands.

The method of claim 6, wherein -qo2 is in the range of 0.048 to

0.150 LJ (mmol-h).

8. The method of claim 6 or 7, wherein t is 0.001 to 3.0 h.

9. The method according to any one of claims 6 to 8, wherein qo2 in the range of 1 to

25% by volume.

10. The method of claim 2 to 9, wherein the solvent under alkylenglykoldial- kylethern, 1, 4-dioxane, methyl phenyl ether, cyclohexanone, 2,4-dimethyl-3-pentanone, chlorobenzene, 1, 4-dichlorobutane, diethyl carbonate, ethyl acetate, N Methylpyrrole, ethoxybenzene, 1, 2-dimethoxybenzene, tetrahydrofuran, 2-methyltetrahydrofuran, benzyl methyl ether and diethyl phthalate is selected.

1 1. The method of any one of claims 2 to 10, wherein the antisolvent is water or an aqueous solution.

12. The method of claim 2, wherein the antisolvent is an aqueous solution of a

Carboxylic acid is.

13. The method of claim 12, wherein the aqueous solution is 5 wt .-% to

30 wt .-% carboxylic acid.

14. The method according to any one of claims 2 to 13, wherein the temperature during the precipitation b) is 10 to 90 ° C.

15. The method according to any one of claims 2 to 14, wherein the temperature during the supply c) of a molecular oxygen-containing gas is 10 to 90 ° C.