CS258925B1 - Light isoalkanic solvent for extraction of vegetable oils and method of its production - Google Patents

Abstract

Light isoalkane solvent for the extraction of oils from plant materials consists mainly of Cg-alkanes, in which 2-methyl- and 3-methylpentane predominate and the remainder is n-hexane, Cg-saturated hydrocarbons are also present, especially methylcyclopentane and cyclohexane, and is contaminated with a maximum of 0.1% by weight of aromatics, 0.01% by weight of olefins and a sulfur and nitrogen content of up to 1 ppm. The production method is based on a low-temperature isomerizate of light petroleum gasoline containing Cg-Cg hydrocarbons on a platinum catalyst and the solvent is isolated from the isomerization product by one or two-stage redistillation.

Description

The invention relates to a composition of a light isoalkaline solvent for the extraction of vegetable oils and a method for its production from the isomerization product of a C _g to C _g hydrocarbon fraction from petroleum gasoline.

The main method of obtaining vegetable oils, especially needed for food and cosmetic purposes, is, in addition to pressing, extraction with solvents. The requirements for the solvent are constantly increasing with regard to hygiene and safety in achieving high extraction capacity and a suitable distillation range, necessary for complete separation from the product. The solvents used so far are usually n-alkane concentrates, especially n-hexane concentrates, and their production and purification are very complex and energy-intensive. Recently, it has been found that n-hexane causes peripheral nervous system disorders and its limit concentrations for safe work have been reduced tenfold compared to isohexanes. In addition, the solvents contain higher concentrations of C _g -cyclanes, which are less volatile and remain in the extract, which increases solvent losses during extraction, the obtained oil contains measurable concentrations of hydrocarbons and has lower flash points./

The invention defines the composition of a new light isoalkane solvent and describes a method for its production from light petroleum naphtha. The solvent consists of 80 to 99 wt. % C _g -alkanes, in which 2-methyl- and 3-methylpentane predominate and the n-hexane content is 5 to 35 wt. %, further of 0.9 to 20 wt. % C g -saturated cyclic hydrocarbons, in which the ratio of methylcyclopentane and cyclohexane is 5:1 to 1:2, and further contains up to 0.1 wt. % aromatics, up to 0.01 wt. % olefins and the nitrogen and sulfur contents are below 1 ppm wt. The solvent according to the invention is produced by catalytic isomerization of catalytically refined light gasoline over a platinum catalyst and subsequent reactivation, whereby light petroleum gasoline containing _Cg and Cg-hydrocarbons is catalytically isomerized at a temperature of 125 to 190 °C under a hydrogen pressure of 3 to 10 MPa over a catalyst containing 0.2 to 0.5 wt. % platinum on a support consisting of pure gamma-alumina activated with aluminum chloride or carbon tetrachloride, and the isomerization product is separated by rectification into a run I. and a light isoalkane solvent II., which is optionally treated by redistillation to a light isoalkane solvent III. and a residue IV., whereby the run I. and the residue of redistillation IV. are combined to form high-octane motor gasoline. Light petroleum gasoline contains 35 to 70% Cj-hydrocarbons, up to 20% Cg-alkanes and up to 10% cycloalkanes including benzene.

The main advantages result from the analysis of the composition of the new solvent and the method of its production. The solvent is not primarily produced from an isolated stream in an oil refinery, but is obtained from the product of isomerization of light hydrocarbons. Isomerization is commonly carried out in a refinery to increase the octane numbers of motor gasolines and the main high-octane components are pentanes, 2,2-dimethylbutane and Cg-cyclanes. 2-methyl and 3-methylpentane together with n-hexane are the fraction that has the lowest octane number of the isomerizate. Their content can be up to 30% of the isomerizate. When they are isolated, the remaining isomerizate of higher quality by up to 3 units of octane number is obtained by the research method. Another advantage is that the isomerizate is practically completely free of aromatics, benzene and olefins. By choosing the isomerization temperature and gasoline cut, the residue can be obtained in one step, which is an excellent extraction solvent. Increased temperature causes the cleavage of some of the cyclanes, and reducing the concentration of Cg-hydrocarbons in the raw material in turn reduces the cyclanes in the isomerizate.

The example below describes the production of the solvent according to the invention and its composition.

Example

From the crude oil, gasoline boiling between 30 and 180 °C was obtained by distillation. After its hydrorefining at 290 °C on a Co-Ni-Mo catalyst under a pressure of 3.0 MPa, light gasoline was isolated from the product, the analysis of which is given in Table 1. The gasoline was fed to an isomerization unit, where it was processed at 125 and 170 °C, under a pressure of 7.0 MPa on a catalyst containing 0.37 wt. % platinum on gamma alumina with 5% aluminum chloride. The obtained products 1 and 2 are also given in Table 1. It is evident that by increasing the temperature, over 50% of the Cg-cyclanes were removed. The products were distilled into 3 and 2 fractions, respectively, and the isohexane solvents A and B according to the invention were obtained, the analyses of which are given in Table 1. 2. The run-offs from product 1 and product 2 had octane values better than the original products, as can be seen in Table 3. Such residues from the 2nd distillation of product 1 had a high octane number.

Isohexane solvents were compared for the extraction of rapeseed oil with the existing n-hexane solvent obtained by another method, the analysis of which is also in Table 2. During extractions using the standard procedure, the solvents according to the invention achieved a reduction in solvent losses of 30 to 50% and the hydrocarbon content in the extracted rapeseed oil decreased from 0.3 to a value of less than 0.1%.

The production of isohexane solvent was 20% cheaper than the production of the previous solvent.

Table 1

Feedstock and products of catalytic isomerization

Sample Raw material Product 1 (125°C) Product 2 (170°C) ^20 0.652 0.648 0.645 Cj-hydrocarbons % 59.3 59.8 60.5 Cg-alkanes % 30.4 29.5 29.4 of which 2.2 dimethylbutane 0.1 12.8 10.9 n-hexane 13.8 3.8 4.1 Cg-cyclanes % 9.1 9.0 5.2 of which methylcyclopentane 6.3 4.0 2.9 cyclohexane 2.3 5.0 2.3 benzene 0.5 0 0 Octane number VM 71 84 83.5 Table 2 Solvents for vegetable oils Sample No. A B c characteristic according to the invention according to the invention another procedure

chromatographic composition % wt.

+4-4- +++ +++

C ₆ -alkanes 94.4 ⁺⁺⁺ 78.5 ⁺⁺⁺ 50.0 ⁺⁺⁺ of which n-hexane 21.5 17.3 41.5

Cg-cyclanes 5.5 ⁺ 21.9 ⁺ 50.0 ⁺⁺

benzene under 0.01 under 0.01 below 0.01 Br-index mg/100 ml under 1 under 1 under 5 With ppm under 1 under 1 under 1 N ppm under 1 under 1 under 1

ratio of methylcyclopentane to cyclohexane 1.5:1 ratio of McC^cCg 1:1.5 practically without 2,2-dimethylbutane

Table 3

Octane characteristics of fractions from isomerizate

Characteristics Lead I prod. 1

Octane number VM 87.1 * marked according to the subject of the invention vs. 2 87.2

Remainder of II. from prod. 1 71

Overtaking I

The rest of IV.

from product 1

Claims (3)

SUBJECT OF THE INVENTION What is claimed is: 1. A light isoalkanic solvent for the extraction of vegetable oils, characterized in that it comprises from 80 to 99 wt. The C8-alkanes in which 2-methyl- and 3-methylpentane predominate and the content of n-hexane is 5-35% by weight, furthermore from 0.9-20% by weight. C8-saturated cyclic hydrocarbons in which the ratio of methylcyclopentane and cyclohexane is 5: 1 to 1: 2, and further contains up to 0.1 wt. % of aromatics, up to 0.01 wt. The olefins and the sulfur and nitrogen contents are below 1 ppm by weight. 2. A process for producing a light isoalkane solvent according to item 1 by catalytic isomerization of light petroleum on a platinum catalyst after previous hydrotreating and rectification, characterized in that the light petroleum containing C8 and C8 hydrocarbons is catalytically isomerized at 125-190 ° C under hydrogen pressure. 3 to 10 MPa on a catalyst containing 0.2 to 0.5 wt. platinum on a carrier consisting of pure gamma-alumina activated with aluminum chloride or carbon tetrachloride and the isomerization product is separated by rectification into pre-I and a light isoalkanic solvent (II), optionally further treated by redistillation to a light isoalkanic solvent (III) and residue (IV) wherein the lead I and the remainder of the redistillation (IV) combine to form high-octane gasoline. 3. A process according to claim 2 wherein the petroleum gasoline contains 35-70% C8-hydrocarbons, 55-20% C8-alkanes and up to 10% C8-cyclanes including benzene.