Field of the invention

The invention relates to the field of product production through raw materials in a reactor, where during the reaction, side products of the reaction are separated from the reaction vessel by distillation to accelerate product production.

Background of the invention

During the manufacturing of products through reactions of raw materials, only a minority of reactions is irreversible; the most reaction types undergo a chemical equilibrium.

The shift of the equilibrium to the products is made possible by removing side products during the reaction process. The fundamentals of the effect of a change in conditions on chemical equilibria were described long ago by Le Chatelier's principle. The removal of side products is therefore a key aspect for completion of all kinds of reactions.

At the end of chemical reactions, including fast and slow reactions, side product production as well as product production decreases per time unit. This decrease of side product and product production per time unit usually indicates the end of the reaction but is a product-depending variable. While in fast reactions the side product generation decreases very late in the reaction, usually somewhat close to full conversion slower reactions or those with slow side reaction pathways start much earlier to cease their side product generation. To get all - slow and fast - reactions to reaction completion and almost full conversion of raw materials the reaction is continued for some time usually tied to the remaining side product in the distillate until the reaction is finally stopped by removal of excess raw materials.

The faster the reaction kinetics, the easier it is to remove side product and the easier it is for the reaction to achieve complete conversion. Complete conversion is much more challenging in reactions that are not as fast or have many side reactions with different and much slower reaction kinetics or are slower in general. In these cases, complete conversion is difficult to achieve and can take a long time, resulting in much longer reaction times.

In addition, if removal of side product is limited, the equilibrium reaction type causes any present side product to undergo a back-reaction. In this way, any reaction progress is lost.

In some reactions, a high boiling valuable raw material is distilled off in addition to the side product.

To minimize losses of this raw material during the reaction, the side product is purified through several distillation stages until it achieves a target purity. However, in the side product purification process the column and column head contain high amounts of side product with decreasing amounts via a concentration gradient over the course of the column length towards the bottom, therefore side product is dripping back from the column into the reactor. This is of no concern as long as only little amounts of side product drips back in relation to side product being formed by the reaction, since in this case the distillation of the side product still shifts the reaction ratio to the product side of the reaction equilibrium.

However, in fast and slow reactions at the end of the reaction less side product is generated, therefore the concentration of the side product in the distillation steam coming directly from the reactor is much less rich in side product than it was at the beginning of the reaction. Since the side product purity at the column head is maintained a significant hold up of side product is present within the column and overhead system. With a lot of valuable raw material going into the column the previously side product rich concentration profile is stretched out and more side product is dripping back into the column. This leads to a shift of the equilibrium of the reaction detrimental to the production of product and in favor of the reverse reaction of the product back into raw material leading to a decelerated product production, a standstill or even a turnaround in favor of raw material production. As a result, production not only becomes uneconomical, but it also even comes to a standstill or in the worst case is reversed to some end.

Furthermore, it was surprisingly found, that the side product backflow from the column is causing significant reaction delay, especially and over proportionally more for the anyhow slow reactions. Therefore, the objective of the present invention is to provide a method that overcomes the aforementioned problems.

Summary of the invention

The invention is directed to a method for increasing a conversion rate of a reaction of a reaction mixture in a reactor system, wherein the reactor system comprises a reboiler, a reaction chamber comprising the reaction mixture, a column with a column head, a vapor transfer line, a condenser, a reflux tank, a reflux line, a distillate take off line, and a receiver vessel, and wherein the reaction mixture comprises at least one starting material which is converted by the reaction into at least one product, wherein while the reaction is running at least a portion of at least one of the products is removed by distillate take off, and wherein the conversion rate of the reaction is increased by an intermediate increase or full removal of the at least one of the products present in the column, the column head and the condenser. The present invention empties almost the entire column and overhead system once the side product has dropped below a given threshold of the side product takeoff control point to avoid slowing down of the product production or even the backshift of the reaction by side product dripping back from the column.

Thereafter, the target purity of the side product is reduced to complete the conversion of the remaining raw material into the product. The side product content in the take-off stream thus begins to decrease as more side product is removed than formed, forcing all side products in the column to distill to the head of the column since it is replaced by high boiling valuable raw material.

The result of such a column side product removal is a higher conversion and a saving in time. It was found that the time difference on a 20 hours batch can be as significant as 10%, meaning a decrease in reaction time of 2 hours, down to 18 hours.

Description of the drawings

Figure 1 illustrates a reactor system according to the invention, the reactor system comprises a reboiler (12), a reaction chamber (1), a column (2) with a column head (3), a vapor transfer line (4), a condenser (5), a reflux tank (6), a reflux line (7), a distillate take off line (8) with a mass flow meter (10), a receiver vessel (9), and a recycle line (11).

Detailed description of the invention

Unless otherwise particularly defined herein, the related terms used in the present invention have the following definitions.

As used herein, the term "reaction" refers, for example, to a (trans)esterification or (trans)esterification reaction.

As used herein, the term "reaction mixture" refers to substances that undergo a reaction. These substances can comprise or consist of the starting material, of the starting material and possible additives such as auxiliary substances, which can be, for example, catalysts or other reaction accelerators, of the starting material and products including possible side-products, of the starting material, additives and products including possible side-products, of the products including possible side-products and the additives, of the products alone and additives, of the products including possible side-products, or of the products alone.

As used herein, the term "reactor system" refers to a reactor in which a chemical reaction of a reaction mixture can take place, and wherein the contents of the reactor can be subjected to a distillation process before the course of a chemical reaction and/or during the course of a chemical reaction and/or after the course of a chemical reaction or independently of a chemical reaction. The advantage of such a reactor is that it is not necessary to provide several chambers, one for a reaction to take place and one for the substance or substances to be distilled, thus saving material, time for a transfer of the substances and costs. The reactor system comprises at least a reboiler, a reaction chamber, a column with a column head, a vapor transfer line, a condenser, a reflux tank, a reflux line, a distillate take off line (optionally with a mass flow meter), a receiver vessel, and, optionally, a recycle line.

As used herein, the term "(trans)esterification" or "(trans)esterification reaction" refers to both an esterification reaction and a transesterification reaction. Or it refers to either an esterification reaction or a transesterification reaction depending on the respective context.

As used herein, the term "(meth)acrylate" refers to both (meth)acrylic acid and (meth)acrylic acid ester. Furthermore, it refers to both methacrylate and acrylate. Or it refers to methacrylate or acrylate depending on the respective context. It also refers to methacrylic acid and methacrylic acid ester. For example, the term "a (meth)acrylate compound" refers to (meth)acrylic acid and a (meth)acrylic acid ester, e.g. an alkyl (meth)acrylate.

As used herein, the term "starting material" refers to raw material, initial material, educts, feedstock, reactants or initial reactants which can be used to undergo a chemical reaction, whereby the chemical reaction may result at least in a product or products, which can include side-products or byproducts.

As used herein, the term "reboiler" refers to an apparatus for heating a liquid and/or converting a liquid to its vapor or, in other words, gaseous state.

As used herein, the term "reaction chamber" refers to a container in which a chemical reaction is carried out. There are a wide variety of chambers being referred to as such. For example, the sizes of reaction chambers range from micro reaction chambers, which hold a few microliters, to reaction chambers for a few milliliters, to chambers with a volume of numerous cubic meters. The most important characteristic of each reaction chamber is its resistance to the reaction conditions.

As used herein, the term "column" refers to an apparatus for the thermal separation of mixtures. To avoid heat loss, the column can be an insulated, preferably cylindrical, tube, which can be made in particular of steel, high-alloy stainless steels, glass or plastic. The height of the column body can mainly be dictated by the required quality of separation; the diameter by the volume flow of the mixture to be separated. The column can be placed between the reaction chamber and the distillation head. The number of individual distillations required for the same separation performance can also be referred to as the "theoretical plate number". At the surface of the column, the equilibrium between the liquid and gaseous phases can constantly be re-established by condensation and evaporation. As a result, the proportion of the low-boiling component continues to increase towards the top, while the higher-boiling component flows back into the reaction chamber, the sump. The size of the surface area of the column can be greatly increased in various ways by the design of trays, as in the Vigreux column, or by filling with packing or structured packing.

As used herein, the term "feed line" refers to supply lines which feed substances or substance mixtures to e.g. the reaction chamber or to the column.

As used herein, the term "condenser" refers to a unit in which the vapor produced during distillation, which can be composed of the various volatile components of the solution to be separated, can liquefy by cooling.

As used herein, the term "reflux tank" refers to a container into which condensed distillate flows, which then either flows back to the column and/or into the reaction chamber or is removed from the system.

As used herein, the term "reflux line" refers to a line which can feed distillate from the reflux tank back to the column or to the reaction chamber.

As used herein, the term "distillate take off line" refers to a line which can remove at least a portion of distillate from the reflux tank, or in general from the reactor system, or the distillation system.

The problem underlying the present invention is solved by a method for increasing a conversion rate of a reaction of a reaction mixture in a reactor system, the reactor system comprises a reboiler, a reaction chamber comprising the reaction mixture, a column with a column head, a vapor transfer line, a condenser, a reflux tank, a reflux line, a distillate take off line, and a receiver vessel, the reaction mixture comprises at least one starting material which is converted by the reaction into at least one product, wherein while the reaction is running at least a portion of at least one of the products is removed by distillate take off, wherein the conversion rate of the reaction is increased by an intermediate increased or full removal of the at least one of the products present in the column, the column head and the condenser.

Preferably, the reaction mixture comprises two or more starting materials and two or more products. Further preferably, the two or more starting materials are a first educt, a second educt, and, optionally, one or more further compounds, and wherein the two or more products are a first product, a second product, and, optionally, one or more further products. Even more preferably, the one or more further compounds are selected from further educts, solvents, catalysts, and/or additives. The "reaction" in context of the method of the invention is preferably a (trans)esterification reaction for preparing an (meth)acrylate product.

If the reaction is a transesterification reaction, the reaction mixture may comprise a (meth)acrylate as first starting material and a first alcohol as second starting material which are converted by the transesterification reaction into a second (meth)acrylate as a first product and a second alcohol as a second product. If the reaction is an esterification reaction the reaction mixture may comprises (meth)acrylic acid as first starting material and a first alcohol as second starting material which are converted by the esterification reaction into a (meth)acrylate as a first product and water as a second product.

The above mentioned at least one starting material is preferably selected from the group consisting of alkyl (meth)acrylates, hydroxyalkyl (meth)acrylates, alkyl (meth)acrylate derivatives, and (meth)acrylic acid, and/or the at least one product is selected from the group consisting of alkyl (meth)acrylates, and alkyl (meth)acrylate derivatives.

Examples for starting materials in context of the invention are methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA).

Examples for products in context of the invention are ethylene glycol dimethylacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA), N-(2-methacryloyl oxyethyl) ethylene urea (MEEU), triethylene glycol dimethacrylate (TRGDMA), glycerol formal methacrylate (CAS-Nr. 1620329-57-8).

In the method according to the invention the alkyl (meth)acrylate starting material may comprise methyl (meth)acrylate, and the product may comprise methanol, or the alkyl (meth)acrylate starting material may comprise ethyl (meth)acrylate, and the product may comprise ethanol, or the alkyl (meth)acrylate starting material may comprise n-butyl (meth)acrylate and the product may comprise butanol, or the alkyl (meth)acrylate starting material may comprise (meth)acrylic acid, and the product may comprise water, preferably the alkyl (meth)acrylate starting material comprises methyl (meth)acrylate, and the side product comprises methanol.

The reaction in the method of the invention preferably takes place in the presence of a catalyst.

In the method according to the invention the catalyst can be selected from titanium(IV) alcoholates, for example titanium(IV) tetraisopropanolate, titanium(IV) tetrabutanolate, titanium(IV) tetrakis(2- ethylhexanolate), or mixtures thereof; from zirconium acetylacetonate; or from strong basic compounds, for example alkali oxides, earth alkali oxides, alkali hydroxides, earth alkali hydroxides, alkali alkoxides, earth alkali alkoxides, alkali amides, and earth alkali amides, preferably wherein the strong basic catalyst comprises one or more compounds selected from the group consisting of calcium oxide (CaO), calcium hydroxide (Ca(OH)2), lithium hydroxide (LiOH), sodium methanolate (NaOMe), lithium methanolate (LiOMe), lithium tert-butoxide (LiOt-Bu), lithium /so-propoxide (LiOiPr), lithium amide (UNH2), or mixtures thereof.

In the method according to the invention the at least one starting material may comprise an alcohol R1-OH, and a compound of the formula R2-C(CH2)-COOR3, wherein the at least one product comprises an alkyl (meth)acrylate of the formula R2-C(CH2)-COORI and a compound of formula HO- R3, wherein R1 is alkyl or aryl, R2 is methyl or hydrogen, and R3 is alkyl or hydrogen.

In the method according to the invention it is preferred that the at least one starting material is an alcohol R1-OH as first starting material and methyl (meth)acrylate or (meth)acrylic acid as second starting material, wherein R1 is a C2-20 alkyl. Most preferably the alcohol R1-OH as first starting material is selected from the group consisting of ethylene glycol, ethyl-2-hydroxymethyl-1 ,3- propanediol, triethylene glycol, and a mixture of 5-hydroxy-1 ,3-dioxane with hydroxymethyl- 1 ,3- dioxolane.

When performing the method according to the invention the intermediate increased or full removal of the at least one of the products present in the column, the column head and the condenser while the reaction is running is preferably performed by maximizing distillate take off.

Preferably, during the intermediate increased or full removal of the at least one of the products present in the column, the column head and the condenser, the filling level for the reflux tank (5) is minimized and the concentration of the removed products in the distillate is below a concentration of 50 wt%, preferably below a concentration of 30 wt%, more preferably below a concentration of 20 wt%, and most preferably below a concentration of 15 wt%.

Examples Manufacturing of ethylene glycol dimethacrylate

9400 lbs of HEMA, 9336 lbs of methyl methacrylate (MMA), with 0.183 kg HQME as inhibitor and 18 lbs lithium amide as catalyst are combined in a stirred tank reactor provided with agitator, steam heater, distillation column and condenser and stirred while passing in air. To stabilize the column, a total of 50 Ibs/h kg of MMA containing 0.1 wt% of hydroquinone monomethyl ether and 0.01 wt% of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl in dissolved form are introduced into the column runback. The reactor is heated until distillate flow is obtained, with the column initially being operated with total reflux at 90 Ibs/min distillate flow. As soon as the Methanol concentration at the top of the column increases to 75%., the methanol/MMA mixture is taken off to that extend that the concentration is maintained at 75%, or at least 3.6 Ibs/min are taken off (whatever is required). The MMA stock in the reactor is supplemented by metered addition of equal parts of MMA per part of methanol/MMA mixture taken off. A total of 6700 lbs of MMA are thus introduced over the reaction period and no more replacement is done once the total is obtained. A further catalyst dosage than the initial is not done. The reaction is complete when the residual HEMA has an amount of less than 0.8 wt% (without MMA as part of integration) with a good constant total time of 20h. Once completed the excess MMA is taken off under reduced pressure, with the pressure gradually being reduced to 0,6 PSIA. When no more MMA distills off or the EGDMA concentration in the distillate exceeds a threshold of 35%, the vacuum is broken. The contents of the tank, comprising the catalyst-containing ethylene glycol dimethacrylate, are freed of catalyst with the aid of a sparkler filter.

This gives 14300 lbs of EGDMA crude: containing 92.4 wt% EGDMA, 0.8 wt% HEMA, 0.8 wt% MMA, 0.4 wt%, 0.24 wt% MeOH, 1.8 wt% resulting after distillation in 98.2 wt% EGDMA, 0.8 wt% HEMA, 0.7 wt% MMA, 0.2 wt%.

Example 1 :

9400 lbs of HEMA, 9336 lbs of methyl methacrylate (MMA), with 0.183 kg HOME as inhibitor and 18 lbs lithium amide as catalyst are combined in a stirred tank reactor provided with agitator, steam heater, distillation column and condenser and stirred while passing in air. To stabilize the column, a total of 50 Ibs/h kg of MMA containing 0.1 wt% of hydroquinone monomethyl ether and 0.01 wt% of 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl in dissolved form are introduced into the column runback. The reactor is heated until distillate flow is obtained, with the column initially being operated with total reflux at 90lbs/min distillate flow. As soon as the Methanol concentration at the top of the column increases to 75 %, the methanol/MMA mixture is taken off to that extend that the concentration is maintained at 75 %, or at least 3.6 Ibs/min are taken off (whatever is required). The MMA stock in the reactor is supplemented by metered addition of equal parts of MMA per part of methanol/MMA mixture taken off. A total of 6700 lbs of MMA are thus introduced over the reaction period and no more replacement is done once the total is obtained. A further catalyst dosage than the initial is not done.

A certain time within the reaction, the MeOH takeoff is getting less to maintain a stable MeOH concentration of 75 %. However, after a while the take off is that little that the initially mentioned 3.6 Ibs/min take off define the rate of distillate take off. Once this effect is getting active, the MeOH-% in the overhead starts to fall below 75 % since more MeOH is taken off that generated from the reactor. As soon as the MeOH-% in the distillate has fallen below 60 %, the take off is maximized and basically all distillate generated removed to a take off tank. At the same time the setpoint of the distillate hold up tank is continuously reduced to the minimum level for stable operation. Once the concentration of MeOH in the distillate has fallen below 20 %, the take off is reduced to minimum again and the level in the hold up tank restored to a level for regular operation. The reaction was stopped at total time of 20 hours. Once completed the excess MMA is taken off under reduced pressure, with the pressure gradually being reduced to 0.6 PSIA. When no more MMA distills off or the EGDMA concentration in the distillate exceeds a threshold of 35 %, the vacuum is broken. The contents of the tank, comprising the catalyst-containing ethyleneglycol dimethacrylate, are freed of catalyst with the aid of a sparkler filter.

The residual HEMA of this batch was surprisingly low with 0.4 wt% after analysis, indicating that the reaction was much faster than the comparative example. Examples 2-9:

The procedure of example 1 was repeated but the reaction time was shortened after each batch, if the residual HEMA was still below 0.8 wt%.