CS256085B1 - A process for producing benzyl esters of aliphatic carboxylic acids having from 1 to 6 carbon atoms - Google Patents

Abstract

The solution relates to a method for producing benzyl esters of aliphatic carboxylic acids with a carbon number of 1 to 6 by esterification in the presence of a hydrocarbon solvent as a water carrier. The essence of the solution is that natural and/or synthetic zeolite in acid form is used as a catalyst in an amount of 0.1 to 5% by weight based on the weight of benzyl alcohol. The above substances are used as flavorings in the food industry or as fragrances in cosmetics.

Description

The present invention relates to a process for the preparation of benzyl esters of aliphatic carboxylic acids having carbon numbers 1-6.

For the production of benzylic esters of aliphatic carboxylic acids, acocatalysts are commonly used with strong mineral acids, in particular sulfuric acid, which, upon isolation of the esters, where they are distilled from the reaction mixture between the esterifications within one cycle after concentration, are dehydrated. and polymerizing, and particularly suitable for the benzyl esters of lower carboxylic acids having a carbon number of 1 to 3, revitalize the reaction mixture, resulting in an esterification reactor accident at elevated temperature.

This drawback is avoided by the production of benzyl esters of carboxylic acids having a carbon number of from 1 to 6 by reacting benzyl alcohol with the appropriate acids in the presence of a non-toxic hydrocarbon solvent as a water discharger. The essence of the method. the production of benzyl esters is that the esterification is carried out under the catalysis of natural and synthetic zeolites, in acid form, in an amount of 0.1-5% by weight based on the weight of the starting benzyl alcohol.

According to the proposed process, complete conversion of the benzyl alcohol or the acid or both to the ester is achieved. The zeolite can be used in powder form or molded.

In the preparation of these esters, it is necessary to work in excess of one of the components because in the case of esters of acids having carbon numbers 1 to 3 with water and the effluent, these acids also leave azeotropes in part, whereby the acids pass into the water phase, thereby losing the reaction mixture. mixtures. For this reason, for acids with carbon numbers 1 to 3, an excess of 1.05 to 2 moles of acid is employed per mole of benzyl alcohol. For acids counting carbons 4 to 6, it is necessary to work in an excess of 1.01 to 1.5 moles of benzyl alcohol / moles of acid in order to react the full acids because there is a considerable smell and even in the small amounts they can get used to be used in the food industry. An advantage of the process according to the invention is that the ester isolation from the reaction mixture does not arrive at polymerization of the reaction mixture at higher temperature and the zeolitic catalyst can be used multiple times and can be filtered from the reaction mixture after the end of the esterification cycle. Zeolite catalysts are non-toxic, non-corrosive, non-corrosive, still at higher temperatures, Tahko are regenerated and can be used again. The esterification rate is comparable to that of sulfuric acid. The ester yields are close to the theory of purity of the products produced min. 99.5 ° / o.

The process for the preparation of benzyl esters is further described in several examples of transfer, but is not limited thereto. Example 1 L) of an esterification reactor with a volume of 500 cm 3 provided with a rectification column (OTP = 5), a thermometer and a siphon transfer of the organic phase from the phase separator to the reactor was charged with 108 g (1 mol of benzyl alcohol, 92 g (2%). mole formic acid and 1.1 g (1% by weight, based on benzyl alcohol-activated zeolite H-ZSM-5. The reaction mixture was kept at reflux for 30 minutes. Then, 40 cm 3 of n-heptane was added to the doreaktor and formed The formic acid was added to the reaction mixture by adding 46 g (1 mole) and the reaction continued for a further 30 minutes when the esterification was complete, after distilling off the water formed as an azeotrope. unreacted formic acid was distilled off by the addition of n-heptane, and the benzyl formate was distilled off at a pressure of 1.99 kPa by allowing 15% by weight of the ester and catalyst to be passed on to the next esterification agent. The ester produced had a purity of 99.5% Example 2 In the same apparatus as in Example 1, the esterification of acetic acid with benzyl alcohol was carried out.

108 g (1 mol) of benzyl alcohol, 78 g (1.3 mol) of acetic acid, 50 cm3 of heptane as a discharger and 0.5 g (0.47% of hmoite) of zeolite H — ZSM — were charged into the reactor. was carried out for 60 min, at which time the resulting water was separated in a phase separation of 18 g. The heptane phase was continuously returned to the reactor by the siphon trap. After the esterification was complete, n-heptane was distilled off, the residue of unreacted formic acid and 90% by weight at a pressure of 1.99 kPa. produced ester. The ester residue and the catalyst were left and loaded for further esterification. The esterification was complete and the ester produced was 99.8% pure. With one catalyst, several esterifications are carried out while the catalyst activity decreases. In the case of non-deactivation, the zeolite is inactivated by annealing at a temperature of 500 to 600 ° C while burning the organic matter present. EXAMPLE 3 In an apparatus as in Example 1 and as in Example 2, the esters of the butyric acid with benzyl alcohol were carried out by catalysis of the activated synthetic mordenite in the H-form.

88.1 g (1 mol) of butyric acid, 113.5 g (1.05 mol) of benzyl alcohol, 35 cm 3 of n-heptane and 2.26 g (2% by weight of benzyl alcohol) of synthetic mordenite were charged into the reactor. . Esterification takes-

Claims (1)

5 la and 50 minutes. Thereafter, n-heptane was distilled off under reduced pressure from the reaction mixture under reduced pressure (1.99 kPa), and excess benzylalcohol was distilled off as the first fraction, and benzylbutyrate was further the main fraction. The distillation residue was 10% of the ester produced and the zeolite catalyst. The esterification of the butyric acid was complete (18 g of water separated). The purity of the ester produced was 99.9%. EXAMPLE 4 The procedure of Example 3 was followed by esterification of valeric acid with benzyl alcohol by catalyzing the Y-type zeolite in H-form to produce the benzyl valerate. 102.1 g (1 mol of valeric acid), 110.3 g (1.02 mol) of benzyl alcohol of 50 cm 3 of n-heptane and 3.3 g (3 wt%) of activated Y zeolite in H- were charged into the reactor. form. The esterification was carried out for 50 minutes, when 18 cm @ 3 of water formed were separated in the separator to complete the reaction. Sa95 is washed from the ester produced. i.e., 182 g distilled at 1.99 kPa and 5 wt. i.e., 10 g was left in the reactor as a distillation residue. Upon further esterification within one cycle, the amount of valeric acid and benzyl alcohol added was added to the distillation residue. The reaction was continued in the same manner. The ester produced had a purity of B9.5pere. SUBSTITUTE A method for producing benzyl esters of aliphatic carboxylic acids with carbons having from 1 to 6 by esterification in the presence of a hydrogen chloride solvent as a catalyst, characterized in that the acid catalyst is a natural and / or synthetic zeolite in acid form. in an amount of 0.1 to 5. wt. based on the weight of the starting benzyl alcohol.