CA2050495A1

CA2050495A1 - Discontinuous process for conducting a heterogeneously catalysed reaction and installation for heterogeneously catalysed manufacture of products

Info

Publication number: CA2050495A1
Application number: CA002050495A
Authority: CA
Inventors: Bernhard Gutsche; Lutz Jeromin; Eberhard Peukert; Levent Yueksel; Kurt Adrian; Heinz Bollweg
Original assignee: Individual
Current assignee: Henkel AG and Co KGaA
Priority date: 1989-03-20
Filing date: 1990-03-12
Publication date: 1990-09-21
Also published as: DE3909128A1; TR25796A; DE59003903D1; WO1990011114A1; BR9007229A; JP3336004B2; EP0464045B1; MY107154A; JPH04503771A; EP0464045A1

Abstract

A b s t r a c t A discontinuous process for conducting a heterogeneously catalyzed reaction and a plant for the heterogeneously catalyzed production of products The invention relates firstly to a discontinuous process for conducting a heterogeneously catalyzed reaction taking place at elevated temperature, in which heat-sensi-tive products are formed, a heat transfer unit (4) dif-ferent from the reactor (1) being used for heating and a fixed-bed catalyst (3) being used as the catalyst and the reaction mixture being continuously circulated in succes-sion through the catalyst (3) and then through the heat transfer unit (4). The problem to be solved in this process is to avoid losses of catalyst and product and to shorten the batch time and, optionally, the reaction time in accordance with German patent applications P 38 13 612.0 and P 38 26 320.3.
The invention also relates to a plant for the dis-continuous heterogeneously catalyzed production of heat-sensitive products at elevated temperature comprising a reactor (1), characterized by a heat transfer unit (4) arranged outside and connected to the reactor (1), a catalyst container (3) containing a fixed-bed catalyst preceding the heat transfer unit and a pump (2) for con-tinuously circulating the reaction mixture in succession through the catalyst (3) and then through the heat transfer unit (4).

Figure 2 is for publication

Description

2 0 ~ v HENXEL KGaA
Dr. Schoenen/sl 16.03.1989 Patent Application D 8521 ~ C ~

A discontinuous process for conductinqLa hetero~eneously catalyzed reaction and a ~lant for the hetero~eneouslY
catalvzed ~roduction of product~

This invention relates to a discontinuous process for-conducting a heterogeneously catalyzed rea¢tion taking plac~ at elevated temperature, in which heat-sensitive products are formed.
In discontinuous processes for conducting heterogene-ously catalyzed reactions, solid catalysts directly intro-duced into the reactor are size-reduced by stirring ele-ments and have to be filtered after the reaction. This often gives rise to considerable losses o~ catalyst and product. Another problem arise~ where it is intended to take the measures descri~ed in German patent applications P 38 13 612.4 and P 38 26 320.3 to shorten the batch time and, optionally, the reaction ti~e. In this case, problems arise during circulation of the solids-laden reaotion mix-ture, particularly at the liquid distributor of the film evaporator.
The problem addressed by the present invention on the one hand is to avoid the losses of catalyst and produc~ in a process of the type mentioned at the beginning and, on the other hand, to shorten the batch time and, optionally, the reaction time in accordance with the earlier applica-tions cited above.
According to the inventionV this problem is solved in 2 0 ~

a process of the typ~ mentioned at the beginning by the fact that a heat transfer unit different ~rom the reactor i5 used for heating and the heterogeneous catalyst is used in a fixed bed and in that the reaction mixture is con-tinuously circulated in succession through the catalyst and then through the heat transfer unit.
In one particular embodiment of the invention, the heat transfer unit is a film evaporator, more especially a falling film evaporator or thin layer evaporator, in which the more readily volatile reaction products are separated.
In this embodiment of the process, the reaction mixture after passing through the fixed-bed catalyst flows through the evaporator in which more volatile readily components are evaporated, so that the reaction equilibrium is shifted towards the product side. Thus, in an esterification reac-tion for example, the water of reaction formed may be removed directly a~ter the catalyst, i.e. immediately after its formation~
If the reaction is an esteri~ication reaction cata-lyzed hy ion exchangers containing sulfonic acid groups, possible hydrolysis of the sulfonic acid, iOe. elimination of the catalytically active acidic groups, is reduced or prevented in this way. Basically, however, any solid catalysts are suitable for the purposes of the invention.
Thus, suitable catalysts are basic or acidic, organic or inorganic anion or cation exchangers or acidic aluminas or zeolite or specially prepared bleaching earths.
The coarse-particle catalyst material initially introduced into the fixed-bed catalyst i5 retained by suitable elements, for example by wedge-wire s~reens, and does not enter the stirred tank. The catalyst material may thus be reused for subsequent hatches~ Accordingly, there is no need to filter off a solid catalyst or to wash out a homogeneous catalyst.
To enhance the separation of the more readily volatile ;

2 al ~ 3 reaction product formed, the film evaporator is if neces-sary operated under reduced pressure.
In addition, the pressure in the fil~ evaporator may advantageously be lowered during the production process, more especially beginning at normal pressure. Thus, the reaction equilibrium may be kept in a desired position in accordance with the proqress of the reaction~
To obtain a better separating e~ect than that ob-tained with a film evaporator alone~ educts and secondary products are not separated simply by distillation, instead a rectification column connected to the reactor, in which the more readily volatile reaction products are separated, is additionally used. In many case~, not only is the reaction product removed, at least one component of the starting product is also separated, so that the starting product has to be replenished accordingly. To avoid exces-sive replenishment, the more readily volatile components of the reaction mixture are rectified before their separation.
This process is used, for example, in esterification reac-tions where an educt, for example a short-chain alcohol, is separated from a secondary product, for examplP water, by rectification to avoid the need to replenish the low-boiling educt, namely alcohol.
To prevent the reaction equilibrium from shifting, the starting products removed during separation of the more readily volatile reaction products are r~plenished.
It is particularly avantageous to use ~he process according to the invention for esterification and/or trans-esterification reactions. It is also particularly advan-tageous to use ~he process according to the invention for transacetalization and/or acetal-forming reactions, above all in the production of fo~maldehyde ethyl cyclododecyl acetal. This compound i5 known und~r the name of Bois-ambrene Forte which is a reyistered trade mark. Where the proces~ according to the invention is used for esterifica-'3 tion or transesterification reactions, the production o~
wax esters or fragrances is particularly advantageous.
In reactions involving a pressure-dPpendent azeotrope between an educt and a reaction product, it i5 of advanta~e to carry out th~ reaction under the pressure at which maxi-mum recycling of the educt can be guaranteed. In addition, it is proposed, particularly ~or the production oP Bois-ambrene Forte, tha~ the reaction be carried out under a~
elevated pressure o~ up to 6 bar absolute and more especi~
ally up to 4 bar absolute. This is because the increase in pressure results in a reduction in the quantity of ethylal to be replenished in view of the dependence on pressure of the ethylal/ethanol azeotrope.
The invention also relates to a plant for the clis-continuous heterogeneously catalyzed production of heat-sensitive products at elevated temperature comprising a reactor. To shorten the batch time and, optionally, the reaction time without creating additional problems during circulation of the reaction mixture, it is propos~d that this plant be provided with a heat transfer unit arranged outside and connected to the reactor, a fixed-beA catalyst preceding the heat trans~er unit and a pump for continu-ously circulating the reaction mixture in succession through the catalyst and then through the heat transfer unit.
The heat trans~er unit is advantageously a ilm evaporator, more especially a falling film avaporator, which is designed to separate the more readily volatile reaction products ~ vacuo In addition, it is proposed that the catalyst con-tainer comprise elements for retainin~ catalyst material.
Further advantages mentioned above are obtalned when the plant is designed to carry out the reaction under elevated pressure.

3~ Examples o~ embodiment of the invention are described 2 ~

in detail in the following with reference to the accompany-ing drawings, wherein:
Figure 1 shows a firs~ embodiment comprising a thin layer evaporator and an external fixed catalyst bed.
Figure 2 shows a second e~bodiment of the plant according to the invention comprising an external fixed catalyst bed, a falling film evaporator and a rectification column, the latter being mounted on th~ reactor.

Examples xample 1 Production of a wax ester from hexadecanoic acid and hexa-decyl alcohol in the plant shown in Figure 1.
739.5 g hexadecanoic acid ~2.88 mol) and 706.4 g fatty alcohol 12.91 mol) are introduced intG a heated stirred tank (1). A laborato~y piston pump (~) transpor~s the mixture through a heated glass vessel (3), the external fixed bed, into which 157 g of the strongly acidic ion exchanger resin Amberlite XE 365 ~a product of Rohm and Haas~ were introduced for catalysis at 130C, to the thin layer evaporator (4) in which the water o~ reaction is removed by distillationO During the test, the pressure is reduced in step~ from normal pressure to 20 mbar. The pro-gress of the reaction is monitored through the acid content (AV) in the reaction mixture. After 5 hours, a conversion of 98.3%, based on the acid, is reached. 43 g distillate (H20) are collected in the disti}late container (8), the remaining water being in the cold trap ~7) preceding the vacuum pump.

Ex mple 2 Production of formaldehyde ethyl cyclododecyl acetal (Bois~
ambrene Forte~R)) (Figure 2) Formaldehyde ethyl cyclododecyl acetal is a fragrance 2 ~

for which the first production process was described in G~rman patent 24 27 500; improved production processes were subsequently disclosed in patent applications DE-OS 30 30 543 and ~E-OS 30 30 590.
In the original process, concentratecl liquid acids are added or solid catalysts are stirred in for catalysis.
In the process according to the invention, the reac-tants cyclododecanol and ethylal are introduced in a molar ratio of 1:3 into a heatable stirred tank (1~. A circula-tion pump (2) transports the reaction mixture through an external catalyst container (3), which is concurrently heated and contains the solid catalyst material. As in the known processes, the catalyst material used i5 either an acidified clay mineral ~for example KSF, a product of Sudchemie) or an acidic organic or inorganic cation ex-changer. In contrast to the cited patents, however, the material used is in the form of coarse particles having a particle diameter of greater than 0.1 mm.
Th~ reaction mixtur~ then flows through a falling ilm evaporator ~4~ in which the more volatile components (ethanol, ethylal) are partly evaporat~dO The vapors axe concentrated to the azeotrope (approx. 40% by weight ethanol) in the rectification column (5) fitted to the reactor, condensed in the reflux condenser ~6) and partly removed as distillate. The quantity o~ ethylal (chemic~l name: diethoxymethane or formaldehyde diethyl acetal) removed at the same time is rQplsnished.
The reaction is carried out at boiling temperature, i.e. initially under normal pressure at approx. 90-C and, towards the end of the reaction, at approx. llO'C.
After a reaction time of about 10 to 14 hours, a conversion of approximately 99%, based on cyclododecanol, is obtained for a yield of 80 to 85% ethyl cyclododecyl formal.
More particularly, Boisambrene Forte~R~ is produced in 2 ~

accordance with the invention as follows:
140 g cyclododecanol and 238.4 g ethylal (diethoxy-methane) are introduced into a heated laboratory stirred tank (1~ (cf. Figure 2). The catalyst container (3~ con-tains 7 g of a montmGrillonite catalyst (KSF/0 5ranulat, a product of Sudchemie).
The reaction mix~ure is heated to 75C and then circulated through the catalyst container ~3) by the laboratory pump (2~. The temperature of the heating system for the stirred tank and falling film evaporator i8 slowly increased and, at a temperature of the reaction mixture of approximately 90CC, the first distillate accumulates at the head of the column (5). The reflux ratio a~ the head of the column is adjusted ~o 2 (1 s removal: 2 5 reflux). For every 15 ml distillate, 10 ml pure ethylal are replenished.
In just under 12 hours, a total of 90 ml distillate (ethanol/ethylal mixture) is thus removed from th~ reaction system and replaced by 50 ml pure ethylal. According to analysis by gas chromatography, the distillate accumulating contains approximately 37% ethanol.
The crude product formed is freed from residual ethylal/ethanol by distillation and, according to analysis ~y gas chromatography, contains 83.8% Boisambrene Forte and l.l~ unreacted cyclododecanol. The remaining 15.1% consist essentially of dicyclododecyl formal and traces of secon-dary produc~s.

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List of reference numerals l reactor 2 circulation pump 3 catalyst container 4 heat transfer unit/falling film evaporator (Fig. 2) or ~:
thin layer evaporator (Fig. 1 rectification column 6 reflux condenser 7 condenser (cold trap) 8 distillate container - . .

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Claims

1. A discontinuous process for conducting a heterogene-ously catalyzed reaction taking place at elevated tempera-ture, in which heat-sensitive products are formed, charac-terized in that a heat transfer unit (4) different from the reactor (1) is used for heating and a fixed bed catalyst (3) is used as the catalyst and in that the reaction mixture is continuously circulated in succession through the catalyst (3) and then through the heat transfer unit (4).

2. A process as claimed in claim 1, characterized in that the heat transfer unit (4) is a film evaporator, more especially a falling film or thin layer evaporator, in which the more readily volatile reaction products are separated.

3. A process as claimed in claim 1, characterized in that a rectification column (5) connected to the reactor (1) in which the more readily volatile reaction products are removed, is additionally used where educts and secondary products cannot be separated simply by distillation.

4. A process as claimed in any of claims 1 to 3, charac-terized in that the starting products separated with the more volatile reaction products are replenished.

5. A process as claimed in any of claims 1 to 4, charac-terized in that it is used for esterification and/or trans-esterification reactions.

6. A process as claimed in claim 1 or any of claims 3 to 5, characterized in that it is used for transacetalization and/or acetal-forming reactions, more especially for the production of formaldehyde ethyl cyclododecyl acetal.

7. A process as claimed in any of claims 1 to 6 where a pressure-dependent azeotrope occurs between an educt and a reaction product, characterized in that the process is carried out under a pressure at which maximum recycling of the educt is guaranteed.

8. A process as claimed in any of claims 1 to 7 for the production of formaldehyde ethyl cyclododecyl acetal, characterized in that the reaction is carried out under an elevated pressure of up to 6 bar absolute and more especi-ally up to 4 bar absolute.

9. A plant for the discontinuous heterogeneously cata-lyzed production of heat-sensitive products at elevated temperature comprising a reactor (1), characterized by a heat transfer unit (4) arranged outside and connected to the reactor (1), a catalyst container (3) containing a fixed-bed catalyst preceding the heat transfer unit and a pump (2) for continuously circulating the reaction mixture in succession through the catalyst (3) and then through the heat transfer unit (4).

10. A plant as claimed in claim 9; characterized in that the heat transfer unit (4) is a film evaporator, more especially a falling film evaporator or thin layer evapor-ator, which is designed to separate the more readily volatile reaction products in vacuo.

11. A process as claimed in claim 9 or 10, characterized in that the catalyst container (3) comprises elements for retaining catalyst material.

12. A plant as claimed in any of claims 9 to 11, charac-terized in that it is designed to carry out the reaction under elevated pressure.