DE2038727A1 - Improved Process for the Production of Benzoic Acid Esters - Google Patents

Description

MÖHLSTRASSE 22, NUMBER 48 39 21/22

H / Kn Oase: 14 191-F

IHE DOW OHEMICiLD COMPANY Midland, Michigan, V.St, A.

Improved Process for the Production of Benaoic Acid

ester

In the "known process for the preparation of benzoic acid esters becomes an alcohol with a benzoic acid in the presence of a hydrogen ion catalyst and with no more than about s to chi ome tri s rather amount of acid converted. This procedure delivers however, an undesirably dark colored product that with increasing temperature or when the conversion is about 50 # of ! Theory Exceeds becomes even darker. According to the state of Seelmik, glycols were also found on the way via the Sätireohlorid esterified (see e.g. U.S.P. 2,956,978).

The method of the present invention leads to considerable less colored end products, even if the process

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is carried out continuously,

The present invention provides an improved method for Veresterung'von benzoic sit 11.ICoIiOI. * The esterification er-.folgt characterized »that acid and alcohol at a temperature of 180 to 35O ⁰ C in the absence of. Air or oxygen is coutacted under conditions whereby contact of the ester with the water produced is possible; is kept low and the method is characterized in that

(1) at least 1.1 moles of acid used per hydroxyl equivalent will 'and

(2) the reaction carried out in the absence of a catalyst will. .

Benzoic acid and benzoic acids with not more than three inert subs ti. Doctors are generally suitable for the method of the present invention. The substituents on the acid are preferably in the meta or para position to the carboxyl group. Useful inert substituents include alkyl groups with up to about 10 carbon atoms, such as methyl, propyl, butyl, heptyl and nonyl, alkoxy groups with up to about 10 Carbon atoms such as ethoxy, pentoxy and octoxy and -CP, examples include o-methyltenoic acid, p-konylbenzoic acid, m-Prüpyl-p-butylbenzenic acid, _t p-trifluoromethyl-

benzoic acid, o-Metlioxybeiiaoeoäüxe and in -Metlioxy-p-butoxyben--

zoesäiire.

The alcohols j useful for this, esterification Bindj include .Alkylen- and Polyaikylenglykole and their aliphatic Monoätliex · with bie Zn atoms is about 10 in total carbon (xlykolmoiioaryläther up with at least three OH-groups with up to to about a total of 14 carbon atoms, polyol about a total of 10 carbon atoms, and alkanols,

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Aralkanols and alkenols having 4 to a total of about 20 carbon atoms.

Examples of the above alcohols include ethylene glycol, Propylene glycol, butylene glycol, dipropylene glycol, diethylene glycol, Dibutylene glycol, hexylene glycol, triethylene glycol, Dipropylene glycol monoethyl ether, triethylene glycol monobutyl ether, 2-phenoxyethanol, glycerine, sorbitol, 1,4-bis (2-hydroxylithyl) benzene, Butanol, n-nonadeeanol, n-dodecanol, oleyl alcohol and 10-Undeoen-l-ol.

If you work according to the teaching of the present invention, so one generally obtains esters which are unusually pure and which contain a minimum of dark colored product. In order to achieve this, however, it is necessary that each Hydroxyl equivalent brought into contact with at least 1.1 moles of acid, preferably with 1.1 to about 3 moles of acid will. Catalysts must be excluded from the reaction in order to prevent the formation of dark colored product.

It is also necessary that the water formed during the esterification be removed or deactivated, otherwise it will hydrolyze the ester product. Suitable measures by which this can be achieved include maintaining the reaction temperature above the boiling point of the water at the pressure used and then removing the water vapors formed by condensation or with an inert stripping gas. The reaction mixture kannn suitably between about 180 and 35O ° C, preferably between about 200 and 300 ⁰ C. If the temperature is allowed to rise too high, ie significantly above about 325 ^° C., decomposition can take place. Too low a temperature, however, leads to an undesirably slow conversion.

109808/2262

Must have oxygen and air or other oxidizing agents rigorously excluded from the reaction as oxidizing agents largely contribute to the discoloration of the products.

The reaction pressure is only to control the boiling point important in the reaction mixture. Any pressure that allows the removal of water at a temperature within the above specified range is allowed, i3t suitable, a pressure of about 0.3 to 2 atmospheres is preferred.

A reaction time of about 0.5 to 24 hours is useful, while about 1.5 to 5 hours are generally preferred. ^ Shorter contact times can be used at higher temperatures.

If desired, the reaction can be carried out in solution in an inert solvent. Preferred solvents are those which can be easily separated from H ₂ O. Examples are dimethano-naphthalene, biphenyl, acid bleached petroleum distillates, docosane and tetraethylbenzenes,

The process can, as desired, continuously or "be operated. The reactants can tk below reaction temperature in any order or fashion. Be -Seamlessly. At reaction temperature, they should" begin to all be united together at one time or the alcohol is added incrementally.

The following examples are intended to illustrate the invention without, however, restricting it.

Example 1

Benzoic acid is filled into a 500 ml three-necked glass reactor and an alcohol. The reactor content is continuously with

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Ν «rinsed and the water formed is overhead over a short distillation column removed.

The reactants are heated to the stated temperature for the stated time. The reaction mixture is analyzed and the APHA earbe determined (APIIA Color # 1). Then the excess acid is extracted with dilute sodium hydroxide solution (caustic) and the APHA-I color of the ester is determined (APiIA Color $ 2).

The results are summarized in (Table I.

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a T) θ 11 e

Ver
search MolTer-
ratio * alcohol Temp *
O ₀ Time
{StdnJ $ Yield
Best APHA
Color ff 1 APHA
Color ff 2 1 1.57 glycerin 260-270 97 ILA. *** N / A.*** O
co 2 1.25 2-phanoxy
ethanol 260 3 92 50 ' 10-20 - 6 -
808/2262 3 1.23
1.74 Benzyl
alcohol
Dipropylene
* glycol 232
230-260 4th 97
95 30th
N / A*** 10

* Molsensolic acid / -OH Iquiralent

** no ITgT rinsing, Og not excluded

*** not received

oo ■ -ο ro

Example 2

A small mini-experimental facility was built and continued operated to show that the inventive method can be carried out continuously.

0.41 to 0.73 kg / hour Benzoic acid and 0.18 to 0.27 kg / hour. Dipropylene glycol were fed into two heated, continuously stirred reactors connected in series, each Reactor a small distillation column for the planter removal of water possessed.

The excess reactants were removed by vacuum evaporation removed and a sodium hydroxide skiubber was used, to remove all traces of acid from the product remove. The product was then washed with water.

The product yield was 94 to 95 1> with an average APHA Faibe of about 40th

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Claims (3)

PATENT CLAIMS Process for the esterification of benzoic acid and alcohol by reacting the acid and the alcohol in the absence of air or oxygen, "at a temperature of 180 Ms 35O ⁰ C and under conditions under which the resulting ester and the resulting water come into contact with one another as little as possible , characterized in that at least 1.1 moles of acid are used per hydroxyl equivalent and the reaction is carried out in the absence of a catalyst. 2. The method according to claim 1, characterized in that the amount of acid is 1.1 to 3 mol per hydroxyl equivalent. 3. The method according to claim 1 or 2, characterized in that that the acid is benzoic acid or a benzoic acid having no more than three substituents and these substituents are inert. 103808/2262