AU673440B2 - Process for the continuous preparation of relatively high-molecular-weight carboxylic acids - Google Patents

Abstract

By the oxidation of olefins having 16 to 70 C atoms by means of chromosulphuric acid in a single- or multi-stage process in at least one reactor having a narrow residence time spectrum, carboxylic acid mixtures can be produced. These can be processed with monoalcohols or polyols such as glycol, glycerol, trimethylolpropane, pentaerythritol or sorbitol to give esters and partial esters or to give mixtures of such esters. By reaction with basic oxides or metal hydroxides, the corresponding soaps of the carboxylic acids can be produced by direct reaction or by reprecipitation. By reaction with amines or aminoalcohols the amides, amido esters and amino esters are obtained. These products are distinguished by a pale colour, good heat stability and a wide application spectrum. <IMAGE>

Description

RogulaiIon 3,2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged:

S

*4 S

S

*..tSS S. *5 Invention Title: PROCESS FOR THE CONTINUOUS PREPARATION OF RELATIVELY HIGH-MOLECULAR-WEIGHT CARBOXYLIC ACIDS The following statement is a full description of this invention, including the best method of performing it known to us

I

HOECHST AKTIENGESELLSCHAFT HOE 93/F 212 Dr.DA/sch Description Process for the continuous preparation of relatively high-molecular-weight carboxylic acids The invention relates to a process for preparing relatively high-molecular-weight carboxylic acids by oxidation of ethylenically unsaturated compounds with chromic acid.

There are numerous syntheses known for preparing relat- I' 10 ively high-molecular-weight, linear aliphatic carboxylic acids. However, only a few processes are used industrially.

Thus, the demand for relatively high-molecular-weight fatty or wax acids is met almost exclusively by natural products.

The oxidation of paraffins to carboxylic acids has been implemented industrially. However, this process has the disadvantage that the attack of the oxidant cannot be controlled and a wide range of carboxylic acids and other oxygen-containing compounds is formed.

These disadvantages can be avoided if the raw materials used are long-chain olefins and the oxidant used is, for example, chromic acid in sulfuric acid solution. There are single-stage or multi-stage processes known for the oxidation of olefins (cf. DE 2 165 858, DE 2 262 130, DE 23 10 425). These processes have, besides the incomplete conversion, the high oxidant consumption and the poor separation, the further disadvantage that the olefin is only insufficiently dispersed in the oxidant. In addition, there is the formation of a viscous, chromiumcontaining organic phase which interferes with a controlled reaction course.

I I L It is known that the disadvantages of a batchwise mode of operation can be compensated for in a continuous mode of operation. Thus, for example, the oxidative bleaching of natural waxes is, for the purpose of better handling of the viscous reaction mixture, carried out with exploitation of gaseous oxidation products in a reactor having the characteristic of a narrow residence time spectrum (cf. DE 28 55 263).

It has been found that the oxidation of olefins is possible in a modified process procedure.

The invention accordingly provides a process for the continuous preparation of relatively high-molecular-weight, linear aliphatic carboxylic acids by oxidation of olefins having from 16 to 70 carbon atoms with approximately 1 molar, based on Cr0 3 chromic/sulfuric acid at a temperature of from 90 to 2000C and a pressure of from 100 mbar to 20 bar, which comprises carrying out the reaction in cocurrent mode in at least one reactor having a narrow residence time spectrum, the mixing of the reactants being carried out by the steam formed as a result of the heat of reaction and the reaction gas and also the additional blowing-in of air.

:Preferably, C 20

-C

50 -olefins having internal double bonds or having vinylidene double bonds or having vinyl double bonds or mixtures of these S 20 compounds are used.

The process of the invention is carried out in continuously operated reactors having the characteristics of a narrow residence time spectrum, for example in tube reactors, cascades of stirred reactors or cascaded bubble column reactors having mesh trays, with preference being given to using the 25 cascaded bubble column reactors. In these reactors, the mixing of the reactants by the steam formed as a result of the exothermic reaction, by the liberation of gaseous reaction products, by the blowing-in of air/steam and by the arrangement and shape of the mesh trays is particularly effective, without the oeooe S incorporation of moving mechanical parts being required for this purpose. A further advantage of the bubble-column cascade reactors is that low-molecularweight and steam- 3 volatile oxidation products are carried out of the reactor by the steam formed. Without this stripping process, these products would either remain in the used chromic/sulfuric acid and interfere with the regeneration thereof, or they remain in the oxidate and interfere with the further use of this oxidate.

The apparatus used for the process of the invention is shown in the figures, Figure 1 showing an apparatus for a single-stage mode of operation, Figure 2 showing an apparatus for a two-stage mode of operation and Figure 3 showing an apparatus for a three-stage mode of operation.

In the figures 111 112 113 114 115 116 211 212 213 214 215 216 217 311 312 313 314 315 316 317 411 412 Reactor for the first stage Feedline for olefin Feedline for chromic/sulfuric acid Feedline for air Pipe Feedline for separating agent Reactor for the 2nd stage Feedline for olefin/carboxylic acid mixture Feedline for fresh chromic/sulfuric acid Feedline for air Pipe Separation vessel Outflow line Reactor for the 3rd stage Feedline for olefin/carboxylic acid mixture Feedline for fresh chromic/sulfuric acid Feedline for air Pipe Separation vessel Outflow line Degassing vessel Separation vessel for final product 4 413 Dechromer 414 Condensate separator 415 Pipe 416 Pipe 417 Outflow line 418 Waste gas line 419 Waste gas line 420 Waste gas line 421 Outflow line 422 Discharge line for final product 423 Condensate outflow line The reactors (111), (211) and (311) are divided into individual reaction chambers by a plurality of sieve trays. The distance of the trays from one another is from 15 1 to 5 times, preferably from 1 to 3 times, the column diameter.

In the figure, the sieve trays are only indicated.

In accordance with Figure 1, the reactor (111) is provided at the bottom with feedlines for olefin (112), 20 chromic/sulfuric acid (113) and air (114). From the top of the reactor (111), a pipe (115) leads into the top third of the degassing vessel (411). From the bottom of .the degassing vessel (411), a pipe leads into a point halfway up the separation vessel (412), the upper part of 25 which is connected by a pipe (416) to the lower part of the dechromer (413). A waste gas line (419) from the top of the degassing vessel (411) and a waste gas line (418) from the top of the separation vessel (412) lead to a condensate separator (414). Furthermore, an outflow line (417) leads from the bottom of the separation vessel (412) to a chromic acid preparation facility (not shown).

An outflow line (421) coming from the bottom of the dechromer (413) enters this outflow line (417). The dechromer (413) is here shown as an adsorption column. It is discharged from the top via the line (422). The condensate separator (414) is provided with a waste gas line (420) at the top and with an outflow line (423) at 5 the bottom.

The apparatus for the two-stage process is identical with the apparatus for the single-stage process, but with the additional apparatus components of items (211) to (216).

In Figure 2, the reactor (111) is provided at the bottom with feedlines for olefin (112), chromic/sulfuric acid (113) and air (114). From the top of the reactor (111), a pipe (115) leads into the separation vessel (216) from the upper third of which a pipe (212) leads to the bottom of the reactor (211). At the same time, a feedline (214) for air and a feedline (213) for fresh chromic/sulfuric acid are connected to the pipe (212) in the vicinity of the bottom of the reactor (211). From the top of the reactor (211), a pipe (215) leads into the top third of 15 the degassing vessel (411). From the bottom of the degassing vessel (411), a pipe leads to a point halfway up the separation vessel (412), the upper part of which is connected via a pipe (416) to the lower part of the dechromer (413). A waste gas line (419) from the '.jp of 20 the degassing vessel (411) and a waste gas line (418) from the top of the separation vessel (412) lead to a condensate separator (414). Furthermore, an outflow line (417) leads from the bottom of the separation vessel (412) to a chromic acid preparation facility (not shown).

An outflow line (421) coming from the bottom of the dechromer (413) and an outflow line (217) from the bottom of the separation vessel (216) enter this outflow line (417).

The apparatus for a three-stage mode of operation in accordance with Figure 3, comprises a further group of apparatus components of items (311) to (316). In Figure 3, the reactor (111) is provided at the bottom with feedlines for olefin (112), chromic/sulfuric acid (113) and air (114). From the top of the reactor (111), a pipe (115) leads into the separation vessel (216), from the upper third of which a pipe (212) leads to the bottom of the reactor (211). At the same time, a feedline (214) for 6 air and a feedline (213) for fresh chromic/sulfuric acid are connected to the pipe (212) in the proximity of the bottom of the reactor (211). From the top of the reactor (211), a pipe (215) leads into the separation vessel (316), from the upper third of which a pipe (312) leads to the bottom of the reactor (311). At the same time, a feedline (314) for air and a feedline (313) for fresh chromic/sulfuric acid are connected to the pipe (312) in the vicinity of the bottom of the reactor (311). From the top of the reactor (311), a pipe (315) leads into the upper third of the degassing vessel (411). The bottom of the separation vessel (316) is connected via an outflow line (317) with the outflow line (217). From the bottom of the degassing vessel (411), a pipe leads to a point 15 halfway up the separation vessel (412), the upper part of which is connected via a pipe (416) with the lower part of the dechromer (413). A waste gas line (419) from the top of the degassing vessel (411) and a waste gas line (418) from the top of the separation vessel (412) lead to a condensate separator (414). Furthermore, an outflow line (417) leads from the bottom of the separation vessel (412) to a chromic acid preparation facility (not shown) An outflow line (421) coming from the bottom of the dechromer (413) and an outflow line (217) coming from the 25 bottom of the separation vessel (216) enter this outflow line (417).

.All reactors, vessels and pipes are provided with temperature control facilities.

For carrying out the process of the invention, use of one, two or three stages can be chosen. For this purpose, the various reactor stages can be combined with one another. In addition, a single reactor or a plurality of reactors can be used for each stage.

In the single-stage mode of operation in accordance with Figure 1, the olefin, together with a part of the chromic/sulfuric acid (feedline (113)) and air (feedline 7 is introduced, via the feedline (112), into the first reactor (111). The mixture flows, with intensive mixing, through the reactor (111). The product is then conducted into a degassing stage comprising the degassing vessel (411) and the separation vessel (412). Here the volatile components are separated off via the top, and in a condensate separator (414) the condensable constituents are removed from the waste gas stream. The waste gas is conducted away via the outflow line (420) and the condensate is conducted away via the outflow line (423). After separation of the oxidate and oxidant in the separation vessel (412), the oxidate is further freed, in the dechromer (413), of colloidal or chemically bound chromium i: compounds. This purification can be carried out in the form of a scrubbing stage, an adsorption stage or a separation by means of a centrifuge. The oxidate is drawn off via the line (422). The used chromic/sulfuric acid is conducted via lines (417) and (421) to regeneration.

In the two-stage mode of operation in accordance with 20 Figure 2, the reaction mixture is fed from reactor (111) "-into a separation vessel (216) There the oxidate separates from the chromic/sulfuric acid which flows through the line (217) to regeneration, and is metered into the o reactor (211) with fresh chromic/sulfuric acid and air via the line (212). From this reactor, the reaction mixture again flows into the above-described work-up stages.

The three-stage mode of operation in accordance with Figure 3 proceeds in the same way, an additional reactor (311) and a separation vessel (316) being incorporated between the reactor (211) and the degassing vessel (411).

The reaction mixture is thus separated after each stage and either worked up to give the final product or metered into the next stage together with fresh chromic/sulfuric acid and air.

8 In the process of the invention, olefins having an internal double bond and a total of from 16 to preferably from 20 to 50, carbon atoms are used. Examples of such olefins are those of the formula R'-CH=CH-R 2 in which R 1 and R 2 are a hydrogen atom or a Cl-Cg,-, preferably Cl-C 48 -alkyl group and R 1 and R 2 together have from 14 to 68, preferably from 18 to 48, carbon atoms, or of the formula R 3

-C(R

4 in which R 3 and R 4 are a preferably Ci-C4,-alkyl group and R 3 and R 4 together have from 14 to 68, preferably from 18 to 48, carbon atoms.

Examples of such olefins are hexadec-1-ene, octadec- 1-ene, Eicos-l-ene, docos-l-ene, tetracos-1-ene, triacont-1-ene, 2-ethyltriacont-l-ene and also 1-olefin mixtures which predominantly comprise C 22 to C 50 -olefins.

The oxidant used is a solution of Cr0 3 and Cr 2

(SO

4 3 if desired even of alkali metal dichromate, in aqueous sulfuric acid. Approximately 1-molar solutions, based on the Cr0 3 content, are used. In general, the chromic/ sulfuric acid used comprises from 500 to 600 g of H 2

SO

4 20 and from 95 to 110 g of Cr0 3 per dm 3 The amount of chromic/sulfuric acid required for the oxidation of the olefin to the desired degree of conversion can, in the multistage process, be fed together with the olefin melt into the reactor of the first reaction 25 stage. However, the process procedure of metering in the chromic/sulfuric acid in portions has proven more suitable. In this method, the used oxidant is separated off in a separation vessel and transferred out prior to the addition of the fresh chromic/sulfuric acid.

The ratio of amounts of olefin to oxidant here depends on the molecular weight of the olefinic components and their reactivity. In the oxidation of an olefin mixture comprising vinylolefin, vinylideneolefin and olefin having internal double bonds and the iodine number (IN) of such as is, for example, commercially available as ®Chevron C 30 +-olefin, a total amount of from 120 to 150 9 by weight, corresponding to from 165 to 200 mol%, of Cr0 3 based on the olefin used, is required to obtain a mixture of long-chain aliphatic carboxylic acids having an acid number (AN) of from 105 to 125. In a two-stage reaction, about 90% of the olefin used can here be converted. A carboxylic acid mixture having an AN of 105 is obtained.

About 60% by weight of the oxidant is here added in the first stage and in the second stage.

A three-stage reaction using 60% by weight of oxidant in the first stage, 50% by weight in the second stage and in the third stage leads, at an olefin conversion of 95%, to a carboxylic acid mixture having an acid number AN of from 120 to 125.

The mixing required for the process to be successful o 15 automatically results from the type of reactor and from the acti~n of the steam formed and the volatile reaction gases. In addition, air is blown into the first reactor of each stage.

The reaction is carried out at a temperature of from 20 about 90°C to 200°C, preferably in the range from 110 0

C

to 125 0 C, and at a pressure of from 100 mbar to 20 bar, preferably from 1 bar to 5 bar. The residence times in the individual reactor stages are from 60 minutes to 180 minutes. The residence time depends on the phase 25 ratio and on the desired conversion of olefin or oxidant.

Carboxylic acid mixtures prepared by the process of the invention can be further processed with monoalcohols or polyols such as glycol, glycerol, trimethylolpropane, pentaerythritol or sorbitol to give esters and partial esters or mixtures of such esters. Reaction with basic oxides or metal hydroxides can be used to prepare the corresponding soaps of the carboxylic acids by direct reaction or by trans-precipitation. Reaction with amines or aminoalcohols gives the amides, amidoesters and aminoesters.

I 10 These products have a pale colour, good thermal stability and a wide range of applications.

The esters and/or soaps can thus be used as paste waxes, emulsion waxes, release agents or as lubricants.

The following examples illustrate the invention.

The experiments were carried out using a laboratory apparatus having a reactor capacity of about 6 dm 3 per reaction stage.

Example 1 1. 0 Single-stage oxidation using a variable proportion of oxidant.

An olefin mixture comprising vinylolefin, vinylidene olefin and olefin having internal double bonds and an iodine number (IN) of 45 (Chevron C 30 +-olefin) waa melted and placed in a heated reservoir. The temperature of the melt was adjusted to from 95 to 100 0 C by steam heating.

The olefin was conveyed into the first reactor via a steam-heated line and a heated pump.

The chromic acid was conveyed from a temperature- 20 controlled reservoir into the reactor via an acid-resistant pump. 100 dm 3 /h of air at a pressure of 0.5 bar were introduced into the reactor. The three components were mixed in a multi-fluid nozzle at the bottom of the reactor and injected into the first reactor chamber. The reaction mixture was conveyed through the reactor chambers and after passing through the individual reactor stages was conveyed via the degassing step into the separation vessel. There the used oxidant was separated off. At this point, the separation could be improved by addition of a separating agent (amount from 0.1 to by weight, based on olefin used) Suc 5 cs. su-ce 0 Q C e (-r v it 11 Conversion of olefin and oxidant are here dependent on the amount conveyed through and thus on the residence time in the reactor.

The oxidate thus obtained was further freed of residual chromium compounds by centrifugation.

Table 1: Continuous oxidation of a-olefin Experiments using constant metering of olefin/chromic acid o e* *o o *oo* *o Experiment Wax Chromic Cr0 3 AN CrO 3 cm 3 /h Acid Feed Consumption cm 3 /h 1 400 3000 75 62 2 600 3000 50 56 48 3 600 3600 60 61 4 400 3600 90 74 72 650 3600 55 58 52 o 650 3600 7 550 3000 55 58 48 Feed Consumption Amount fed in, by weight based Consumption in by weight, olefin on olefin based on Example 2 Single-stage process with variable metered amounts at constant proportion of oxidant The olefin was melted and placed in a heated reservoir, The temperature of the melt was adjusted to from 95 to 100 0 C by steam heating. The olefin was conveyed into the 12 first reactor via a steam-heated line and a heated pump.

The chromic acid was conveyed from a temperature-controlled reservoir into the reactor via an acid-resistant pump. 100 dm 3 /h of air at a pressure of 0.5 bar were introduced into the reactor.

The three components were mixed in a multi-fluid nozzle at the bottom of the reactor and injected into the first reactor chamber. While filling the reactors, an increased conveying rate could be used. The amount of olefin and chromic acid conveyed was then reduced to set an optimum use of oxidant.

The reaction mixture was conveyed through the reactor chambers and after passing through the individual reactor Sstages was conducted via the degassing step into the S 15 separation vessel. There the used oxidant was separated off. At this point the separation could be improved by addition of a separating agent (amount from 0.1 to 0.5 by weight, based on olefin used) tcV\ oa s wr4-ce O.c~je co.pto<L<.r\c*.

The oxidate thus obtained was further freed of residual chromium by centrifugation.

Table 2: Continuous oxidation of a-olefin Experiments using variable metering of olefin/ chromic acid 9 Experiment Wax Chromic Acid Cr0 3 AN CrO 3 100 Feed Consumption cm'/h cm 3 /h 11 65-50- 39-30-24 60 57 56 13 65 40 39 24 60 65 59 60 40 36 24 60 57 17 60 40 36 24 60 58 58 Feed Amount fed in, by weight based on olefin 13 Consumption Consumption in by weight, based on olefin Example 3 Two-stage process with constant proportion of oxidant and variable metering The olefin was melted and placed in a heated reservoir, The temperature of the melt was adjusted to from 95 to 1000C by steam heating. The olefin was conveyed into the first reactor via a steam-heated line and a heated pump.

1 0 The chromic acid was conveyed from a temperature-controlled reservoir into the reactor via an acid-resistant pump. 100 dm 3 /h of air at a pressure of 0.5 bar were introduced into the reactor.

The three components were mixed in a multi-fluid nozzle at the bottom of the reactor and injected into the first reactor chamber. The reaction mixture was conveyed oo through the reaction chambers and, after flowing through the first reaction stage, was passed into the separation vessel, the used oxidant was separated off and the pre- 20 oxidized olefin was conveyed together with fresh chromic oooo acid and air into the second reaction stage. After passing through all reaction chambers, the product was degassed, the used oxidant was separated off and residual chromium compounds were separated off from the oxidate in a centrifuge.

14 Table 3: Continuous oxidation of a-olefin Experiments using variable metering of olefin/ chromic acid, 2nd stage Experiment Wax Chromic CrO 3 AN Cr0 3 cm 3 /h Acid Feed Consumption 100 cm 3 /h (1 5) 60 50 36 30 60 109 54 8 65 45 36 25 55 101 9 60 40 36 24 60 108 12 (11) 65 40 39 24 60 108 59 14 (13) 65 40 39 24 60 110 58 18 (17) 60 40 36 24 60 109 58 s r r r Feed Consumption The values in first stage Amount fed in, by weight based on olefin Consumption in by weight, based on olefin indicate the experiment number of the e Example 4 Three-stage process with constant proportion of oxidant and variable amounts metered in The procedure was as in Example 3. After the second reaction stage, the oxidate and fresh chromic acid were introduced into the third reaction stage and worked up as described above. Use of 50% by weight of Cr0 3 gave an oxidate having an AN of 125.

Claims (4)

1. A process for the continuous preparation of relatively high-molecular- weight, linear aliphatic carboxylic acids by oxidation of olefins having from 16 to carbon atoms with approximately 1 molar, based on Cr0 3 chromic/sulfuric acid at a temperature of from 90 to 200 0 C and a pressure of from 100 mbar to bar, which comprises carrying out the reaction in cocurrent mode in at least one reactor having a narrow residence time spectrum of 60 to 180 minutes, the mixing of the reactants being carried out by the steam formed as a result of the heat of reaction and the reaction gas and also the additional blowing-in of air, and separating the organic and the inorganic phase after the reaction in a separation vessel.

2. The process as claimed in claim 1, wherein the reaction is carried out in a cascaded bubble column reactor.

3. The process as claimed in claim 1, wherein the reaction is carried out in a plurality of stages, used chromic/sulfuric acid being separated off after each stage and the amount of chromic/sulfuric acid required for the oxidation being S..continuously metered in portions at the beginning of each stage.

4. The process as claimed in claim 1, wherein C 20 -C 50 -olefins having internal double bonds or having vinylidene double bonds or having vinyl double bonds or mixtures of these compounds are used. The process as claimed in claim 1, wherein separation of the organic phase and the inorganic phase in the separation vessel is accelerated by the addition of surface-active compounds. DATED this 13th day of September, 1996. HOECHST AKTIENGESELLSCHAFT WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA (DOC 08 AU6860394.WPC KJS:KP) Y\ L- 8U 1 HOE 93/F 212 Abstract Process for the continuous preparation of relatively high-molecular-weight carboxylic acids The oxidation of olefins having from 16 to 70 carbon atoms by means of chromic/sulfuric acid in a single-stage or multistage process in at least one reactor having a narrow, residence time spectrum enables the preparation of carboxylic acid mixtures. These can be processed with monoalcohols or polyols such as glycol, glycerol, ii': trimethylolpropane, pentaerythritol or sorbitol to give esters and partial esters or mixtures of such esters. Reaction with basic oxides or metal hydroxides can be used to prepare the corresponding soaps of the carboxylic acids by direct reaction or by trans-precipitation. Reaction with amines or aminoalcohols gives the amides, amidoesters and aminoesters. These products have a pale colour, good thermal stability and a wide range of applications. o*