CS240147B1 - A method for the partial hyrogenation of glycerides of polyunsaturated fatty acids in rapeseed oil - Google Patents

Abstract

The method belongs to the field of food industry and solves the problem of ensuring constant quality of products of partial hydrogenation of glycerides of polyunsaturated fatty acids in rapeseed oil with minimized erucic acid content. The essence of the method lies in the fact that hydrogenation, carried out at temperatures of 350 to 520 K and a pressure of 1.105 to 3.10® Pa in the presence of a selective nickel catalyst, is terminated when hydrogen consumption, determined from the flow rate or from the pressure drop, corresponds to a decrease in iodine value by 10 to 25 units relative to the iodine value of the raw material.

Description

The invention relates to a process for the partial hydrogenation of glycerides of polyunsaturated fatty acids in rapeseed oil, in which linolenic acid is converted into linoleic or into oleic and/or elaidic acid.

Currently, rapeseed oil with a minimized content of erucic acid is increasingly used for nutritional purposes. From the point of view of its stability, especially taste properties, the content of linolenic acid (-· 10 wt. %} is a disadvantage, which is easily oxidized during prolonged storage of the oil or products made from it, and the resulting compounds deteriorate the quality of the products. In technical practice, partial hydrogenation is therefore carried out with the aim of either completely removing linolenic acid or significantly reducing its content. Partial hydrogenation of rapeseed oil is usually carried out at temperatures from 350 K to 520 K and a hydrogen pressure of 1. . ΙΟ ³ 3 . io ³ Pa, using a selective nickel catalyst. The hydrogenation time depends on the selected temperature, hydrogen pressure and activity of the catalyst used. The degree of hydrogenation is assessed according to the iodine number or melting point, and the content of individual fatty acids is determined chromatographically.

For further use of partially hydrogenated rapeseed oil with minimized erucic acid content, its quality must be consistent. This depends on achieving the same composition of fatty acid glycerides forming the product for the same starting material. Existing control methods (for example, determination of iodine value) are lengthy and do not allow process control in such a way that, especially when reaction conditions (temperature, hydrogen pressure) fluctuate, it is always possible to achieve the same content of individual fatty acids and thus the same quality of hydrogenated rapeseed oil.

This deficiency is eliminated by the solution according to the invention, which is a method of partial hydrogenation of glycerides of polyunsaturated fatty acids in rapeseed oil with a minimized content of erucic acid, in which linolenic acid is converted into linoleic or oleic and/or elaidic acid at temperatures of 350 to 520 K and a pressure of 1.10 ⁵ to 3.10 ^s Pa in the presence of a selectively acting nickel catalyst containing preferably 0.05 s to 1.0 wt. % boron. The essence of the invention lies in the fact that hydrogenation is terminated when hydrogen consumption, determined from the flow rate or from the decrease in its pressure, corresponds to a decrease in the iodine number by 10 to 25 units relative to the iodine number of the raw material.

The solution according to the invention is based on the knowledge that when using a selective nickel catalyst, regardless of the temperature regime and therefore the rate of hydrogenation, the content of individual fatty acids depends only on the achieved iodine value, which makes it possible to control the hydrogenation of rapeseed oil only according to the hydrogen consumption, determined from the flow rate or from the decrease in its pressure. The advantage of the solution according to the invention is therefore to ensure a constant quality of the final product when using a simple method of controlling the hydrogenation process.

The method according to the invention and the effect achieved thereby are illustrated by the following embodiment.

5 tons of rapeseed oil with minimized erucic acid content with an iodine number (I) of 114.6 was pumped into the autoclave and a selective nickel catalyst containing 0.08 wt. % boron was added, in an amount corresponding to 0.57 wt. % Ni, based on the raw material. The contents of the autoclave were heated with stirring and the hydrogen consumption was monitored. In the first experiment, )È - 94.6 of the product was achieved in 90 minutes at a temperature of 194Ό, in the second experiment, the same I in 150 minutes at a temperature of 181 °C. In both cases, the hydrogen consumption was 88 Nm ³ . The composition of C-18 fatty acids determined by chromatography is shown in Table I.

TABLE I

C-18 fatty acid content in the raw material and in hydrogenation products

Acid (% by weight)

JC stearate oil linoleic linolenic Raw material 114.6 1.5 59.3 22.1 10.3 Attempt 1 94.6 2.0 76.0 15.1 0.8 Attempt 2 94.6 1.9 73.1 15.6 1.1

Claims (1)

SUBJECT A partial hydrogenation of glycerides of polyunsaturated fatty acids in rapeseed oil with minimized erucic 'at which the linolenic acid is converted to linoleic or oleic or elaidic acid ester, at a temperature ranging from 350 to 520 K and a pressure in the range 10.1 ^5-3 .10 Pa in the presence of a selectively acting nickel catalyst containing 0.05 to 1.0 wt. % of boron, characterized in that the hydrogenation is terminated at the consumption of hydrogen as determined by the flow or loss of its pressure, corresponding to a reduction of the iodine value by 10 to 25 units relative to the iodine value of the feedstock.