DE102009027546A1 - Process for transesterification by means of an inductively heated heating medium - Google Patents

Abstract

The present invention relates to a process for carrying out a transesterification reaction by heating a reaction mixture containing at least one carboxylic acid ester and at least one alcohol as reactants in a reactor, the transesterification reaction being carried out in the presence of at least one metal catalyst which is essentially insoluble in the reaction mixture under the reaction conditions . In the present process, the reaction mixture is in contact with a solid heating medium which can be heated by electromagnetic induction and which is located inside the reactor and which is heated by electromagnetic induction with the aid of an inductor.

Description

The The present invention relates to a method of performing a transesterification reaction by heating a reaction mixture, containing at least one carboxylic acid ester and at least an alcohol as a reactant in a reactor, wherein the transesterification reaction performed in the presence of at least one metal catalyst is under the reaction conditions in the reaction mixture in Essentially insoluble. The reaction mixture is in the present process in contact with a by electromagnetic Induction heatable solid heating medium that is located inside of the reactor and that by electromagnetic induction is heated by means of an inductor.

The Method of inductive heating is already longer in used by the industry. The most common applications are Melting, hardening, sintering and heat treatment of alloys. But also processes like gluing, shrinking or Connecting components are known applications of this heating technology.

DE 10 2005 051637 describes a reactor system with a microstructured reactor and methods for carrying out a chemical reaction in such a reactor. In this case, the reactor is heated as such by electromagnetic induction. The heat transfer into the reaction medium takes place via the heated reactor walls. This limits on the one hand the size of the area available for heating the reaction medium. On the other hand, it is necessary to heat parts of the reactor, which are not in direct contact with the reaction medium.

The unpublished German patent application (registration no. DE2006-0131192 ) generally discloses a method for carrying out a chemical reaction by heating a reaction medium containing at least one first reactant in a reactor, thereby forming or altering a chemical bond within the first reactant or between the first and a second reactants by contacting the reaction medium with a heatable by electromagnetic induction solid heating medium, which is located within the reactor, and the heating medium is heated by electromagnetic induction by means of an inductor. As a chemical reaction, among others, ester formation reactions are disclosed.

From the Angew. Chem. 2008, 120, 9083-9086 Various chemical syntheses are known which take place under magnetically induced heating. For example, the uncatalyzed transesterification of a cinnamic acid ethyl ester to the corresponding methyl ester is described.

For a variety of industrial processes it is of great Meaning that a transesterification reaction is under reliable and controlled conditions with high reaction yields. The aim of the present invention was therefore the development of a effective transesterification process, which under a magnetically induced Warming takes place and the production of carboxylic acid esters allowed in good yields.

object The present invention is therefore a method for performing a transesterification reaction by heating a reaction mixture, containing at least one carboxylic acid ester and at least an alcohol as a reactant in a reactor, wherein the transesterification reaction performed in the presence of at least one metal catalyst is under the reaction conditions in the reaction mixture in Essentially insoluble, the reaction mixture in contact with a heatable by electromagnetic induction solid heating medium, which is located inside the reactor and that by electromagnetic induction with the help of an inductor is heated.

Under the term "substantially insoluble in the reaction mixture" within the meaning of the invention preferably to be understood that among the each selected reaction conditions less than 20 mol%, preferably less than 10 mol%, more preferably less than 5 mol% and in particular less than 1 mol% of all metal atoms of originally used metal catalyst in the reaction mixture can be detected. The proof can be, for example by atomic emission spectroscopy (AES).

at the transesterification reaction of the present invention is that is, a heterogeneously catalyzed process. Such a procedure is advantageous because the metal catalyst is easily removed from the reaction mixture can be separated and the resulting transesterification product thus no or a lower residual concentration of the catalyst used having.

The Transesterification reaction takes place by heating a reaction mixture in the presence of at least one metal catalyst, the Reaction mixture at least one carboxylic acid ester and at least contains an alcohol as a reactant. The entire reaction mixture So it can only consist of the reactants. Farther may be one or preferably both reactants in a solvent dissolved or dispersed, the solvent itself is inert or in turn represents one of the reactants, such as the alcohol involved in the reaction.

In In any case, it should be noted that the reaction mixture with the at least is in contact with a metal catalyst of the present invention, so that the transesterification reaction proceeds under high reaction yields can.

The process according to the invention has the advantage that the thermal energy for carrying out the transesterification reaction is not introduced into the reaction mixture by surfaces such as, for example, the reactor walls, heating coils, heat exchanger plates or the like, but is produced directly in the volume of the reactor. The ratio of heated surface to volume of the reaction mixture can be substantially greater than in a heating heat transfer surfaces, as for example, according to the cited above DE 10 2005 051637 the case is. In addition, the efficiency of electric power to heating efficiency is improved By switching on the inductor, the heat in the entire solid heating medium, which is in contact with the Reaktionsgemsich over a very large surface can be generated. When switching off the inductor, the further heat input is prevented very quickly. This allows a very targeted reaction and minimizes the thermal load of at least one metal catalyst involved in the reaction. In particular, thermally labile metal catalysts retain in this way over a longer period of time their catalytic activity, whereby comparatively higher reaction yields in the transesterification reaction of the present invention can be achieved.

The Heating medium consists of an electrically conductive material, which heats up when exposed to an alternating electromagnetic field. It is preferably selected from materials used in the Compared to their volume a very large surface exhibit. For example, the heating medium can be selected be made of respectively electrically conductive chips, Wires, nets, wool, membranes, porous frits, Packings such as granules, Raschig rings and in particular from particles, which preferably have a mean diameter of not more than 1 mm. Order by electromagnetic induction to be heated, the heating medium is electrically conductive, for example, metallic (which may be diamagnetic,) or it shows a diamagnetism enhanced Interaction with a magnetic field and is particularly ferromagnetic, ferrimagnetic, paramagnetic or superparamagnetic. there it is irrelevant whether the heating medium is organic or inorganic Nature is or is it both inorganic and organic components contains.

In In a preferred embodiment, the heating medium is selected from particles electrically conductive and / or magnetizable Solid, wherein the particles have an average particle size in the range from 1 to 1000, in particular from 10 to 500 nm. The mean particle size and if necessary also the particle size distribution is for example determinable by light scattering. Preferably one chooses magnetic particles, for example ferromagnetic or superparamagnetic Particles that have the lowest possible remanence or residual magnetization exhibit. This has the advantage that the particles do not stick together be liable. The magnetic particles may be, for example in the form of so-called "ferrofluids", ie Liquids containing nano-sized ferromagnetic particles are dispersed. The liquid phase of the ferrofluid can then serve as Reaktionsgemsich.

Magnetisable particles, in particular ferromagnetic particles, which have the desired properties are known in the art and are commercially available. For example, the commercially available ferrofluids may be mentioned. Examples of the preparation of magnetic nano-particles which can be used in the context of the method according to the invention, the essay of Lu, Salabas, and Schüth: "Magnetic Nanoparticles: Synthesis, Stabilization, Functionalization, and Application," Angew. Chem. 2007, 119, pages 1242 to 1266 be removed.

Suitable magnetic nano-particles are known with different compositions and phases. Examples which may be mentioned are: pure metals such as Fe, Co and Ni, oxides such as Fe ₃ O ₄ and gamma-Fe ₂ O ₃ , spinel-like ferromagnets such as MgFe ₂ O ₄ , MnFe ₂ O ₄ and CoFe ₂ O ₄ and alloys such as CoPt ₃ and FePt. The magnetic nanoparticles can be homogeneously structured or have a core-shell structure. In the latter case, core and shell may consist of different ferromagnetic or antiferromagnetic materials. However, embodiments are also possible in which a magnetizable Core, which may be, for example, ferromagnetic, antiferromagnetic, paramagnetic or superparamagnetic, surrounded by a non-magnetic material. This material may be, for example, an organic polymer. By such a coating, a chemical interaction of the reactants with the material of the magnetic particles themselves can be prevented. Furthermore, the material of the shell can be surface-functionalized without the material of the magnetizable core interacting with the functionalizing species.

As a heating medium, for example, nanoscale particles of superparamagnetic materials can be used, which are selected from aluminum, cobalt, iron, nickel or their alloys, metal oxides of the n-maghemite type (gamma-Fe ₂ O ₃ ), n-magnetite (Fe ₃ O ₄ ) or of the MeFe ₂ O _{4 type} , where Me is a divalent metal selected from manganese, copper, zinc, cobalt, nickel, magnesium, calcium or cadmium. Preferably, these particles have an average particle size of ≦ 100 nm, preferably ≦ = 51 nm, and more preferably ≦ 30 nm.

As a heating medium nanoscale ferrites are used, as for example from the WO 03/054102 are known. These ferrites have a composition (M ^a _1-xy M ^b _x Fe ^II _y ) Fe ^III ₂ O ₄ , in which
M ^{a is} selected from Mn, Co, Ni, Mg, Ca, Cu, Zn, Y and V
M ^{b is} selected from Zn and Cd,
x is 0.05 to 0.95, preferably 0.01 to 0.8,
y stands for 0 to 0.95 and
the sum of x and y is at most 1.

The Electromagnetic induction heatable particles can represent the heating medium without further additives. However, it is also possible that by electromagnetic Induction heatable particles with other particles too mix that can not be heated by electromagnetic induction are. For example, this can be sand. The inductive Heatable particles can therefore be made non-inductive heatable particles are diluted. hereby an improved temperature control can be achieved.

Become nanoscale heatable by electromagnetic induction Particles with coarser non-inductively heatable Particles mixed, this can lead to a reduction in the packing density of the heating medium. In embodiments, in which the reaction mixture flows through a packing from the heating medium, This can be a desirable reduction in pressure loss in the flow through the reactor result.

in principle For example, the transesterification reaction of the present invention may be continuous or batchwise. Leading the reaction in batches, it is preferable that one during the reaction, the reaction mixture and the inductive heated solid heating medium moved relative to each other. At the Using a particulate heating medium can do this in particular, by mixing the reaction mixture together with the heating medium or the heating medium in the Reaktionsgemsich swirled. For example, use nets or wool from one filament-shaped heating medium, for example the reaction vessel containing the Reaktionsgemsich and the Contains heating medium, shaken.

A preferred embodiment of a batch carried out Transesterification reaction is that the reaction mixture together with particles of the heating medium in a reaction vessel and with the aid of a movement element located in the reaction mixture is moved, wherein the moving element is set up as an inductor is through which the particles of the heating medium by electromagnetic Induction heated. In this embodiment So is the inductor within the Reaktionsgemsichs. The moving element can, for example, as a stirrer or be formed as moving up and down stamp.

you may additionally provide that the reactor during the chemical reaction is cooled from the outside. This is especially possible in batch mode if, As indicated above, the inductor is immersed in the Reaktionsgemsich. The feeding of the alternating electromagnetic field in the reactor is then not obstructed by the cooling device.

A cooling of the reactor can be done from the inside via cooling coils or heat exchangers or preferably from the outside. For cooling, it is possible to use, for example, optionally precooled water or else a cooling mixture whose temperature is below 0 ° C. Examples of such cooling mixtures are Ice-salt mixtures, methanol / dry ice or liquid nitrogen. By cooling, a temperature gradient between the reactor wall and the inductively heated heating medium can be produced. This is particularly pronounced when using a cooling mixture with a temperature well below 0 ° C, for example, methanol / dry ice or liquid nitrogen. The Reaktionsgemsich, which is heated by the inductively heated heating medium is then cooled externally again. The transesterification reaction of the present invention thus preferably takes place only when the reactants are in contact with, or at least in close proximity to, the heating medium. The carboxylic acid ester formed in the reaction passes rapidly through the relative movement of the Reaktionsgemsichs to the heating medium in cooler areas of Reaktionsgemsichs, so that its thermal reaction is inhibited.

In an alternative embodiment leads to the the transesterification reaction of the present invention continuously in a flow-through reactor, which at least partially with the solid heating medium is filled and thereby at least a heatable by electromagnetic induction heating zone wherein the reaction mixture is the flow reactor continuously flows through and wherein the inductor outside of the reactor is located. Preferably, the flow-through reactor is as Tubular reactor executed. In this case, the inductor completely or at least partially surrounding the reactor. The alternating electromagnetic field generated by the inductor then becomes introduced into the reactor on all sides or at least from several points.

at this continuous procedure in a flow reactor it is possible that the reactor has several heating zones. For example, different heating zones can be different to be heated strongly. This can be done either by the arrangement different heating media in the flow reactor or through differently designed inductors take place along the reactor.

Farther can be provided that the reaction mixture after leaving the heating zone is brought into contact with an absorber substance, the by-products or impurities from the reaction mixture away. For example, from one over the course of Reaction obtained mixture of various carboxylic acid esters those carboxylic acid esters that are not removed have the desired chemical structure, such as mixtures from mono-, di- or tri-stems.

ever after reactivity of the metal catalyst and the used If necessary, reactants can increase the product yield, that the reaction mixture after flowing through the solid Heating medium at least partially to re-flow the solid heating medium is returned. there you can after the respective flow through the solid heating medium Provide that impurities, by-products or even the desired Main product are removed from the reaction mixture. Therefor the known different separation methods are suitable, for example, absorption on an absorber substance, precipitation by cooling or by distillation. This can ultimately achieved complete reaction of the reactants become.

The expediently to be selected entire Contact time of the reaction mixture with the inductively heated Heating medium depends on the kinetics of the transesterification reaction of the present invention. The contact time is the longer to choose, the slower the respective transesterification reaction is. This has to be adjusted empirically in individual cases. As a clue may be considered that preferably the reaction mixture is the tubular reactor perfused once or several times at such a speed, that the entire contact time of the reaction mixture with the inductive heated heating medium in the range of about 1 second to about 2 hours. Shorter contact times are possible but harder to control. Longer contact times can in particularly slow transesterification reactions of the present invention be required, but increasingly worsen the economy of the procedure.

Independently of whether the transesterification reaction of the present invention batchwise or continuously in a flow-through reactor, it can be provided that the reactor is designed as a pressure reactor and the transesterification reaction at a pressure above 1013 mbar, preferably at least 1.5 bar is performed.

In a specific embodiment of the method according to the invention, the heating medium is ferromagnetic and has a Curie temperature in the range of about 40 to about 250 ° C, which is selected so that the Curie temperature by not more than 20 ° C, preferably not more than 10 ° C from the selected reaction temperature. This leads to inherent protection against accidental overheating. The heating medium can be heated by electromagnetic induction only up to its Curie temperature, while at an overlying temperature not further by the electromagnetic alternating field is heated. Even with a malfunction of the inductor can be prevented in this way that the temperature of the reaction mixture unintentionally increases to a value well above the Curie temperature of the heating medium. If the temperature of the heating medium falls below its Curie temperature again, it can be heated again by electromagnetic induction. This leads to a self-regulation of the temperature of the heating medium in the range of the Curie temperature and also makes it possible to use thermally labile metal catalysts with a high degree of process reliability, provided that their decomposition temperature is below the Curie temperature of the heating medium.

It It goes without saying that the nature of the heating medium and the Design of the inductor must be adapted to each other so that the desired heating of the Reaktionsgemsichs can be realized. A critical size this is on the one hand the expressible in watts Power of the inductor and the frequency of the inductor generated AC field. In principle, the performance has to be higher to be chosen, the greater the mass of the is to be heated inductively heating medium. In practice is the achievable performance in particular by the possibility limited, the generator required to supply the inductor to cool.

Especially suitable inductors, which are an alternating field with a frequency in the range of about 1 to about 100 kHz, especially in the range from about 10 to about 30 kHz. Such inductors as well as the associated generators are commercially available, For example, from the IFF GmbH in Ismaning (Germany).

As a general rule But can any type of carboxylic acid ester in the present Method used, provided that under the respective reaction conditions a transesterification reaction is accessible. Preferably the carboxylic acid ester is selected from methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl and iso-butyl carboxylic acid esters selected. However, methyl and / or ethyl carboxylic esters preferred, since these in the transesterification reaction the volatile Alcohol release methanol or ethanol, which is easily separated from the reaction mixture can be, so that the reaction equilibrium on the side of desired transesterification product is postponed.

Next any mixtures of various carboxylic acid esters can in the context of the present invention also carboxylic acid esters used, which have at least one C-C double and / or Triple bond.

useful Carboxylic acid esters may be selected, for example are made from esters of acetic acid, phenylacetic acid, Triphenylacetic acid, propionic acid, acrylic acid, Methacrylic acid, β-phenylacrylic acid, n-butyric acid, Isobutyric acid, valeric acid, isovaleric acid, 5-phenyl-n-valeric acid, hexanoic acid, 2-ethylhexanoic acid, Heptanoic acid, caproic acid, octanoic acid, Pelargonic acid, lauric acid, myristic acid, Palmitic acid, stearic acid, oleic acid, Erucic acid, linoleic acid, linolenic acid, Oleostearic acid, lignoceric acid, malonic acid, Succinic acid, glutaric acid, adipic acid, Pimelic acid, azelaic acid, sebacic acid, Decane-1,10-dicarboxylic acid, pentadecane-1,15-dicarboxylic acid, Pentacosane-1,25-dicarboxylic acid, propane-1,2,3-tricarboxylic acid, Crotonic acid, maleic acid, fumaric acid, Mesaconic acid, citraconic acid, itaconic acid, Muconic acid, aconitic acid, cyclopropanecarboxylic acid, Cyclobutanecarboxylic acid, cyclohexanecarboxylic acid, Cyclopropanedicarboxylic acid, cyclohexanedicarboxylic acid, Cyclohexane-1,2,3,4,5,6-hexacarboxylic acid, cyclopentene-2-carboxylic acid, Cyclohexadiene-1,2-dicarboxylic acid, benzoic acid, Toluic acid, alpha-naphthoic acid, β-naphthoic acid, ortho-, meta- and para-ethylbenzoic acid, p-phenylbenzophthalic acid, Isophthalic acid, terephthalic acid, trimellitic acid, Pyromellitic acid, hydroxyacetic acid, chloroacetic acid, Bromoacetic acid, lactic acid, alpha or beta-hydroxypropionic acid, Citric acid, castor oil acid, alpha or β-chloroacrylic acid, 2-hydroxycyclohexanecarboxylic acid, ortho, meta or para, chloro, bromo, nitro or methoxybenzoic acid, Hydroxyphthalic acid, tall oil fatty acid, Lanolin fatty acids, coconut fatty acids, Mountain wax acids, polymeric acids and the like.

wobei R¹ ein verzweigter oder unverzweigter Alkylrest mit 1 bis 6 C-Atomen ist, wie beispielsweise Methyl, Ethyl, n-Propyl, i-Propyl, n-Butyl, sec-Butyl und t-Butyl und X ausgewählt wird aus Wasserstoff, Cyanid und Alkyl, wie beispielsweise Methyl, Ethyl, n-Propyl, i-Propyl, n-Butyl, sec-Butyl und t-Butyl, wobei R¹ besonders bevorzugt Methyl oder Ethyl ist.In particular, compounds of the general formula (II) are preferred as the carboxylic ester

wherein R ^{1 is} a branched or unbranched alkyl radical having 1 to 6 C atoms, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl and t-butyl and X is selected from hydrogen, cyanide and Al kyl, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl and t-butyl, wherein R ^{1 is} particularly preferably methyl or ethyl.

wobei R¹ wie oben definiert ist.Highly preferred carboxylic esters of the present invention are selected from compounds of general formula (IIa)

wherein R ^{1 is} as defined above.

ausgewählt werden, wobei n eine ganze Zahl von 1 bis 6 ist und R ein n-valenter Rest ist, der 1 bis 100 C-Atomen umfasst.In a specific embodiment, alcohols are used in the process according to the invention which are prepared from alcohols of the general formula (III)

wherein n is an integer from 1 to 6 and R is an n-valent radical comprising 1 to 100 carbon atoms.

Under an n-valent radical R is within the meaning of the present invention to understand an n-valent organic radical having 1 to 100 carbon atoms, that starting from the cyanoacrylic acid ester of the general formula (I) or alcohol of the general formula (III) formally by the homolytic Cleavage of n carbon-oxygen bonds is formed.

The term of the n-valent radical will be explained in more detail below using the example of the trivalent alcohol TMP (n = 3):

By the formal homolytic cleavage of the three C-OH bonds in the TMP molecule A trivalent organic residue is formed in the sense of the present invention Invention.

In a specific embodiment of the invention is the Alcohol selected from diols and triols, given to this Synthetic difficult to access di- or Tricabonsäureester can be produced.

In a specific embodiment of the process according to the invention, the radical R in formula (III) comprises a C ₃ to C ₁₀₀ chain, preferably a C ₅ to C ₇₀ chain and in particular a C ₁₀ to C ₅₀ chain which is protected by at least one oxygen atom is interrupted. The rest R can be linear, branched or cyclic.

Especially radicals R are preferred which contain at least one polyethylene glycol and / or have at least one polypropylene glycol unit.

In an alternative embodiment of the invention Method, the radical R in formula (III) 3 to 18, in particular 4, 8, 10 or 12 directly connected C atoms. The rest R can also be arranged linear, branched or cyclic be. The radical R can furthermore contain an aromatic group or in addition to hydrogen and carbon atoms at least a heteroatom, for example selected from halogen, Oxygen and / or nitrogen atoms.

The alcohols used in the process according to the invention are preferably primary or secondary alcohols, with primary alcohols being preferred since these have a higher reactivity in the transesterification have reaction. In general, any mixtures of different alcohols can be used.

useful Alcohols can be selected, for example from ethanol, chloroethanol, cyanoethanol, n-propanol, sec-propano-1, -n-butanol, tert-butano1, isoamyl alcohol, n-hexanol, 2-ethylhexanol, n-octanol, n-decanol, isodecanol, cyclohexanol, benzyl alcohol, ortho, meta- and para-methoxybenzyl alcohol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,4-pentanediol, 3-methyl-1,5-pentanediol, 2-, 3-dimethyl-2,3-butanediol, phenylethyl alcohol, Triphenylethyl alcohol, trimethylolpropane, mannitol, sorbitol, glycerol, Pentaerythritol, 1,4-cyclohexanedimethanol, xylenol, bisphenols, Diethylene glycol, triethylene glycol, polyoxyethylene or polyoxypropylene glycols preferably having a molecular weight of up to about 4,000, diethylene glycol monomethyl ether, Diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, Butoxyethanol, butylene glycol monobutyl ether, dipentaerythritol, tetrapentaerythritol, Diglycerin, triglycerin and the like.

The alcohol of the general formula (III) used in the process according to the invention is prepared in a preferred embodiment of the present invention from compounds of the general formula (IIIa) R ² COO (CH ₂ CH ₂ O) _m H formula (IIIa) in which R ² CO is a linear or branched acyl radical having 12 to 22 carbon atoms and m is a number from 5 to 30 and preferably 15 to 25. Typical examples are addition products of ethylene oxide with lauric acid, isotridecanoic acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, isostearic acid, oleic acid, elaidic acid, petroselinic acid, linoleic acid, linolenic acid, elaeostearic acid, arachidic acid, gadoleic acid, behenic acid and erucic acid, and their technical mixtures, which are e.g. B. in the pressure splitting of natural fats and oils or in the reduction of aldehydes from the Roelen oxo synthesis. Preferably, addition products of ethylene oxide are used to fatty acids having 16 to 18 carbon atoms.

The Molar ratios of carboxylic acid ester to alcohol can in the process according to the invention vary from 0.01 to 100. Advantageously, the carboxylic ester is in excess used. The molar ratio of carboxylic acid ester the alcohol ranges in particular from 20: 1 to 1: 1, more preferably from 10: 1 to 1.5: 1.

The Reaction time can be between 1 minute and 48 hours depending on the reactivity of the Metal catalyst for the single reaction mixture.

The Process of the present invention may be carried out at any temperature become. However, it has been found that temperatures between 50 ° C and 200 ° C give sufficient reaction rates. Temperatures between 70 ° C and 100 ° C are preferred.

und/oder ein Bis-Carbonsäureester der allgemeinen Formel (Ib),

und/oder aus Tris-Carbonsäureester der allgemeinen Formel (Ic),

wobei die Reste R und X wie oben definiert sind.The reaction product of the process according to the invention is a carboxylic acid ester, such as a mono-carboxylic acid ester of general formula (Ia),

and / or a bis-carboxylic acid ester of the general formula (Ib),

and / or from tris-carboxylic acid esters of the general formula (Ic),

wherein the radicals R and X are as defined above.

Since the process according to the invention is a transesterification reaction, the radicals R and R ¹ can not be identical. In particular, it is preferred that the radical R has at least one carbon atom, in particular at least two carbon atoms more than the radical R ¹ .

When Metal catalysts are all within the meaning of the present invention Suitable compounds which comprise at least one metal atom and a catalytic activity in the inventive Have performed process transesterification reaction.

For example For example, the metal catalyst may be a Lewis acid act, such as the Lewis acid of a main group or transition metal.

The term "transition metal" in the context of the invention denotes a metallic element selected from the groups Ib, IIb, IIIa (including the lanthanides), IVa, Va, VIa, VIIa and VIII of the Periodic Table of the Elements, published in the Supplement of Bulletin de la Société Chimique de France No. 1 (January 1966) , is selected. In other words, it is an element whose atomic number lies between and including 21 and 30, between and including 39 and 48, or between 57 and 80 inclusive.

Examples of suitable Lewis acids are, but are not limited to, Sn (OTf) ₂ , Sm (OTf) ₃ , SnCl ₄ , Bu ₂ SnO, AlCl ₃ , BF ₃ , BCl ₃ , FeCl ₃ , Fe (OTf) ₃ , ZnCl ₂ , Zn (OTf) ₂ , Sc (OTf) ₃ , Y (OTf) ₃ , Gd (OTf) ₃ .

In In a specific embodiment, the metal catalyst the present invention by reacting at least one hydroxyl-containing Received carrier material with at least one metal alkoxide.

The Hydroxyl-containing carrier material is subject in its Structure and its chemical composition within the meaning of the present Invention no special limitations, provided that there is a connection (Immobilization), in particular a covalent attachment at least a suitable metal compound, in particular a metal alkoxide allowed.

Usually are as hydroxyl-containing support materials such used on the surface a variety of hydroxyl groups exhibit. The hydroxyl-containing support material can thereby either natural or synthetic. examples are Carbohydrate-based polymers, cyclodextrins, alumina, silica, Fumed silica, silica gel, boron oxide, clays (such as kaolinite, montmorillonite, Vermiculite, chlorite and mica types), zeolites, zirconium oxide, Titanium oxide, thorium oxide, magnesium oxide, aluminates, carbon black, synthetic inorganic oxides of silicon, magnesium, aluminum, Zinc, and their mixtures and the like.

The Hydroxyl-containing carrier material is preferably selected from silica, alumina and mixtures from that. In addition, organic polymers are also hanging Hydroxyl groups useful. Oxides of silicon and aluminum preferred hydroxyl-containing support materials.

Suitable metal alkoxides in the context of the present invention are, for example, without being limited to those selected from metal alkoxides of the general formula (I), M (OR ³⁾ R ⁴ _{u au} formula (I) wherein a is 3, 4 or 5, u is either 0, 1 or 2, M is a metal, R ^{3 is} a linear or branched optionally substituted C 1-20 alkyl group or an optionally substituted C 6-12 aryl group and R ^{4 is} a linear or branched optionally substituted C 1-4 alkyl group.

In In a specific embodiment, the metal M in formula (I) selected from transition metals such as Titanium, zirconium, hafnium, iron, zinc or vanadium, with titanium is particularly preferred.

The abovementioned alkyl and / or aryl groups may carry one or more halogen atoms and / or heteroatoms as substituents, the heteroatoms being part of a functional group which is selected, for example, from primary and secondary amines, amides, urethanes, alcohols, ethers, esters, Thiols, Thioethers and Sulfones Particularly preferred alkoxy groups OR ² having 1 to 20 C atoms are methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, 2-ethylhexyloxy, n-decyloxy, Tridecyloxy- and phenoxy preferably, wherein as alkoxy group OR ^2, in particular alkyl groups having 1 to 4 carbon atoms, preferably with 2, 3 or 4 carbon atoms can be used.

In the case where u has the value 1, R ^{3 is} preferably selected from methyl, ethyl, propyl or isopropyl groups.

The Metal alkoxide of the present invention is in particular a titanium tetraalkoxide, such as tetra-n-butyl titanate, tetra-t-butyl titanate, tetra-n-propyl titanate, Tetraisopropyl titanate, tetraphenyl titanate, tetracyclohexyl titanate and tetrabenzyl titanate or a trialkoxy-monoalkyl titanium compound.

In an alternative embodiment, the solid heating medium is superficially covered with a catalytically active substance. For example, a suitable, catalytically active metal compound can be immobilized on the surface of the heating medium, whereby a metal catalyst in the context of the present invention is obtained. In a specific embodiment of the invention, the surface of the heating medium therefore carries a hydroxyl-containing layer which can be used for the attachment, in particular for the covalent attachment of suitable metal compounds. In particular, nanoscale particles are preferred as the heating medium, which have on the surface a hydroxyl-containing layer, preferably a SiO ₂ layer. Particularly preferred immobilized metal compounds are metal alkoxides, such as, for example, the abovementioned transition metal alkoxides of the general formula (I).

• – vor und/oder während der Umsetzung mit dem Heizmedium, insbesondere mit einem Heizmedium, das an seiner Oberfläche eine Hydroxylgruppen-haltige Schicht trägt und/oder
• – vor und/oder während der Umsetzung mit dem Hydroxylgruppen-haltigen Trägermaterial

durch Teilhydrolyse in ein Metalloligomer, insbesondere ein Übergangsmetalloligomer überführt werden kann.In general, the (transition) metal alkoxide of the general formula (I),

• - Before and / or during the reaction with the heating medium, in particular with a heating medium which carries on its surface a hydroxyl-containing layer and / or
• - Before and / or during the reaction with the hydroxyl-containing carrier material

can be converted by partial hydrolysis in a metal oligomer, in particular a transition metal oligomer.

Under a metal oligomer, especially a transition metal oligomer is for the purposes of the present invention to mean a compound the 10 to 10,000 metal atoms, in particular 10 to 10,000 transition metal atoms comprising, wherein the individual (transition) metal atoms respectively linked by bridging oxygen atoms are.

The Amount of water may vary depending on the extent of desired degree of oligomerization in a wide range vary. One mole of water is for each mole of oxygen bridge, which is formed required. It will be part of the partial hydrolysis formed both straight-chain and branched oligomers. The partial hydrolysis can be carried out in any organic solvent in which the (transition) metal alkoxide is soluble and stable. However, it is typically carried out in the alcohol, which corresponds to that of the (transition) metal alkoxide. equally the water can be pure or diluted. Often it gets along diluted in the solvent that is used to dissolve the (transition) metal alkoxide. The Water or the water solution usually becomes added dropwise, with the temperature, pressure and rate of addition the respective reactivity of the (transition) metal alkoxide are to be adapted. After the reaction, the solvent needs not necessarily to be removed. For the implementation with the heating medium, in particular with the heating medium, on its surface having a hydroxyl group-containing layer, it may be appropriate be that solvent to remove and by another To replace solvent.

In an alternative embodiment, the reaction of the (transition) metal alkoxide, for example of the (transition) metal alkoxide of the general formula (I) with the heating medium, in particular with a heating medium which carries on its surface a hydroxyl-containing layer and / or the Hy hydroxyl-containing support material under anhydrous conditions. In this way, the tendency to oligomerization is minimized, thereby obtaining other metal catalysts with different reactivities.

Under A (transition) metal alkoxide are within the scope of the present invention Invention both metal alkoxides and transition metal alkoxides to understand.

In In a specific embodiment, the metal catalyst of the present invention before use in the invention Process calcined, d. H. over a period of time in the presence of elevated temperature oxygen exposed.

useful Metal catalysts can therefore also by reaction at least a hydroxyl-containing carrier material with at least a (transition) metal alkoxide, wherein the Reaction product subsequently in the presence of oxygen Temperatures of 150 ° C to 800 ° C is exposed. Preferred temperatures are between 300 ° C and 700 ° C, in particular between 400 ° C and 600 ° C.

suitable Oxygen sources are in particular mixtures of different gases, wherein the oxygen content should be at least 10 wt .-%. In particular, the calcination can be carried out in the presence of air become.

By The calcination becomes the chemical structure of the metal catalyst significantly changed, which in many cases the catalytic activity is increased or an adaptation the catalytic activity to the special requirements a certain transesterification reaction succeeds.

Of course may in the context of the present invention, any mixtures various metal catalysts can be used.

Suitable methods for preparing the metal catalysts of the present invention may be, for example X. Ma, S. Wang, J. Gong, X. Yang and G. Xu (Journal of Molecular Catalysis A: Chemical 222 (2004) 183-187) and D. Srinivas, R. Srivastava and P. Ratnasamy (Catalysis Today 96 (2004) 127-133) be removed.

The Ratio of metal catalyst to reactant can be considerable vary, from 0.001 to 20 parts by weight of metal catalyst (Total amount of all in the process according to the invention used metal catalysts) to 100 parts by weight of reactants (Total amount of all in the process according to the invention used alcohols and carboxylic acid esters). 0.1 to 5 parts by weight However, catalyst to 100 parts by weight of reactants are preferred.

The present invention is, but is not limited to, explained in more detail by the following examples

embodiments

Used substances

Tetraisopropyl titanate, methyllithium, methyl methacrylate were purchased from Sigma Aldrich and used without further purification. 1-Decanol was purchased from Merck and used without further purification. Titanium tetrachloride was distilled over copper prior to use. Silica gel (silica 60, 0.04-0.063 mm, 230-400 mesh, specific surface area 500 m ² / g) was purchased from Macherey-Nagel.

1. Preparation of methyl triisopropyl titanate

In a 100 mL Schlenk flask, Ti (Oi-Pr) ₄ (8.98 mL, 30.0 mmol) in dry diethyl ether (5 mL) was added to TiCl ₄ (1.10 mL, 10.0 mmol) slowly at 0 ° C added and the resulting mixture stirred at 0 ° C for 10 min. After stirring for 30 minutes at 22 ° C, dry diethyl ether (15 mL) was added and the mixture was cooled to -40 ° C. Subsequently, a solution of MeLi (1.6 M in Et ₂ O, 25.0 mL, 40.0 mmol) was added dropwise. The resulting yellow mixture was stirred for 10 min at -40 ° C and then heated to 0 ° C within 45 min. Distillation under reduced pressure allowed the isolation of methyl triisopropyl titanate (MeTi (Oi-Pr) ₃ ).

2. Preparation of the metal catalyst 1

A suspension of silica gel (6.00 g, predrying in vacuo at 150 ° C for 20 h) in anhydrous toluene (30 mL) was treated with a suspension of MeTi (Oi-Pr) ₃ (1.44 g, 6.00 mmol) in anhydrous toluene (80 mL). The resulting reaction mixture was shaken for 16 h at 22 ° C. The resulting metal catalyst 1 was then separated by filtration, washed with toluene and dried for 24 h in vacuo.

3. transesterification reaction

An exemplary reaction setup can be found in the following publication:
Angew. Chem. 2008, 120, 9083-9086 ,

General experiment

One Glass reactor (14 cm length × 9 mm internal diameter) was made with a copper net or steel balls and the metal catalyst 1 (2.2 g in the copper network and 1.8 in steel balls) filled. After rinsing the reactor with anhydrous toluene (10 mL, Flow rate: 0.5 mL / min), a solution of methyl methacrylate (MMA) was added. (1.5-10 eq.), 1-decanol (1 eq.) And hydroquinone (0.005 eq./MMA) in anhydrous toluene (2-10 mL / mmol alcohol) pumped through the reactor (flow rate 0.1-1.0 mL / min), wherein the reactor by means of an inductive heating device (field frequency 20 kHz, energy 150 parts per thousand (copper net) or 280 parts per thousand (steel balls)) is heated to about 70-90 ° C. Subsequently The reactor is washed with anhydrous toluene (5 mL at 0.2 mL / min, then 10 mL at 0.4 mL / min) and the resulting solution concentrated in a vacuum. The reactor output was determined by NMR spectroscopic Methods determined.

Table 1 shows the specific reactor effluents in the preparation of the 1-decyl ester of methyl methacrylate (DMMA) described above No. metal catalyst Reactor input MMA / 1-decanol [molar ratio] Reactor effluent 1-Decanol / DMMA [molar ratio] heating medium 1 1 1.5 / 1 73/27 copper network 2 1 1.10 10/90 steel balls

By the inventive method was the 1-decyl ester be isolated from methyl methacrylate in very good yields.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 102005051637 [0003, 0012]
• - DE 2006-0131192 [0004]
• WO 03/054102 [0018]

Cited non-patent literature

• - Angew. Chem. 2008, 120, 9083-9086 [0005]
• - Lu, Salabas, and Schüth: "Magnetic Nanoparticles: Synthesis, Stabilization, Functionalization, and Application," Angew. Chem. 2007, 119, pages 1242 to 1266 [0015]
• - Bulletin de la Societe Chimique de France No 1 (January 1966) [0057]
• X. Ma, S. Wang, J. Gong, X. Yang and G. Xu (Journal of Molecular Catalysis A: Chemical 222 (2004) 183-187) [0079]
• D. Srinivas, R. Srivastava and P. Ratnasamy (Catalysis Today 96 (2004) 127-133) [0079]
• - Angew. Chem. 2008, 120, 9083-9086 [0085]

Claims (15)

A process for carrying out a transesterification reaction by heating a reaction mixture comprising at least one carboxylic acid ester and at least one alcohol as reactants in a reactor, characterized in that the transesterification reaction is carried out in the presence of at least one metal catalyst which is substantially insoluble in the reaction mixture under the reaction conditions the reaction mixture is in contact with a heatable by electromagnetic induction solid heating medium, which is located within the reactor and which is heated by electromagnetic induction by means of an inductor. Method according to claim 1, characterized in that that the heating medium is selected from chips, Wires, nets, wool, membranes, frits, packing and particles, preferably of particles more electrically conductive and / or magnetizable solid, wherein the particles an average particle size in the range of 1 to 1000 nm. Method according to claim 2, characterized in that that the heating medium is selected from particles magnetisierbarer Solid, wherein each particle has a core of a magnetizable Contains material made of a non-magnetic material is wrapped. Method according to one or more of the claims 1 to 3, characterized in that the chemical reaction carried out batchwise, during the Reaction the Reaktionsgemsich and the solid heating medium relative to each other emotional. Method according to one or more of the claims 1 to 4, characterized in that the transesterification reaction carried out continuously in a flow reactor, the at least partially filled with the solid heating medium and thereby at least one by electromagnetic induction heatable heating zone, wherein the reaction mixture flows through the flow reactor continuously and wherein the inductor is located outside the reactor. Method according to one or more of the claims 1 to 5, characterized in that the inductor is an alternating field generated at a frequency in the range of 1 to 100 kHz. Method according to one or more of the claims 1 to 6, characterized in that the carboxylic acid ester from methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl and Iso-butyl carboxylic acid esters is selected. Method according to one or more of the claims 1 to 7, characterized in that the carboxylic acid ester an alkyl 2-cyanoacrylic acid ester. Method according to one or more of the claims 1 to 8, characterized in that the alcohol is selected becomes diols and triplets. Method according to one or more of the claims 1 to 9, characterized in that the metal catalyst by Reaction of at least one hydroxyl-containing carrier material is obtained with at least one metal alkoxide. Method according to claim 10, characterized in that that the hydroxyl-containing carrier material is selected is made of alumina, silica, fumed silica, silica gel, boron oxide, Clay, zeolites zirconium oxide, titanium oxide, thorium oxide or magnesium oxide. Method according to one or more of claims 10 and 11, characterized in that the metal alkoxide is selected from metal alkoxides of the general formula (I), M (OR ³⁾ R ⁴ _{u au} formula (I) where a is 3, 4 or 5, u is either 0, 1 or 2, M is a metal, preferably selected from boron, aluminum, titanium, zirconium, hafnium, iron, zinc or vanadium, R ^{3 is} a linear or branched one is optionally substituted C1-20 alkyl group or an optionally substituted C6-12 aryl group and R ⁴ represents a linear or branched optionally substituted C1-4 alkyl group. Method according to one or more of the claims 10 to 12, characterized in that the metal catalyst is obtained is prepared by reacting at least one hydroxyl-containing carrier material with at least one metal alkoxide, wherein the reaction product then in the presence of oxygen temperatures of 150 ° C to 800 ° C is exposed. Method according to one or more of the claims 1 to 13, characterized in that the metal catalyst at least includes a transition metal. Method according to one or more of the claims 1 to 14, characterized in that the metal catalyst in a concentration of 0.001 to 20 parts by weight of transition metal catalyst to 100 parts by weight of reactants is present.