EP0673281A1

EP0673281A1 - Process for regenerating used oil-containing clays

Info

Publication number: EP0673281A1
Application number: EP94927570A
Authority: EP
Inventors: Reinhard HÄHN; Max Eisgruber; Hubert Simmler-Hübenthal
Original assignee: Sued Chemie AG
Current assignee: Sued Chemie AG
Priority date: 1993-09-07
Filing date: 1994-09-06
Publication date: 1995-09-27
Also published as: WO1995007137A1; DE4330274A1

Abstract

A process for regenerating used oil-containing clays is characterised by a combination of the following steps; (a) de-oiling the used clay by extraction with an oil solvent down to a maximum 25% by weight (of C) residual content of carbonated substances; (b) thermal treatment of the de-oiled clay in an oxidising atmosphere at a temperature from 500 to 650°C until the clay is practically free from organic carbonated substances, whereas the structure of the clay remains largely intact and the montmorillonite content of the clay is practically not reduced; (c) admixture to the thus obtained product of an aqueous acid in an amount, concentration and temperature selected so that practically no inorganic components are dissolved out of the product and the water content of the product lies between 2 and 10, preferably between 5 and 8% by weight.

Description

Process for the regeneration of used oil-containing

Bleaching earth

DESCRIPTION

The invention relates to a process for the regeneration of used oil-containing bleaching earth. The term “oil-containing bleaching earth” is to be understood as bleaching earth which is used in the refining of edible oils, and also in the broader sense in the refining of edible fats, liquid and solid hydrocarbon products, solvents and other solid or liquid organic substances which are immiscible with water punch.

The regeneration of such used bleaching earth has hitherto generally been carried out in such a way that the excess oil has been largely extracted and recovered with the aid of a solvent. The non-recoverable portion of the organic substances adsorbed on the bleaching earth (e.g. resins and other polymers, organic compounds such as dyes and proteins and phospholipids) had to be removed by thermal treatment.

So O. Eckart already points out in Seifensieder-Zeitung No. 13/1931, pages 200 to 201, that the bleaching earth residues are first degreased with a solvent. The solvent removes the oil or fat adhering to the bleaching earth. The impurities in the oil absorbed by the bleaching earth during the bleaching process, such as protein substances, cell debris, dyes and resins, cannot be removed by a solvent, which is why they are burnt off. This process, which is generally equivalent to a roasting process, must be carried out to such an extent that no tarry constituents remain, i.e. the roasting process should be carried out at least at temperatures of 400 to 500 ° C. At these temperatures, however, the bleaching power should decrease considerably.

From Ullmann's Encyclopedia of Technical Chemistry, 3rd edition, volume 4, page 544, it is known that the temperatures during the regeneration of used bleaching earth must not exceed 600 ° C, since otherwise the effectiveness of the regenerates decreases sharply.

In contrast to this, DD-B-109 605 proposes a process for the regeneration of used bleaching earth which, with short dwell times in the firing zone, a corresponding air supply and temperatures above 700 ° C., provides regenerates which are highly effective Bleaching of mineral oil components and solid hydrocarbons should be suitable. The treatment is to be carried out in particular in a rotary kiln at temperatures of 750 to 1000 ° C., in particular 800 to 900 ° C. and a residence time in the firing zone of 15 to 30 minutes.

It is also known from US-A-1 810 155 which is used in the roasting of used oil-containing bleaching earth with air coming in, subsequently heating the products with 1 - 4% sulfuric acid. As a result of the heating, inorganic constituents, such as alkali or alkaline earth ions, are dissolved out of the bleaching earth.

The object of the invention was to find a process for the regeneration of used oil-containing bleaching earth, in which the process product (regrind) largely regains its original bleaching activity, does not release any disruptive substances to the medium to be bleached, and is capable of To bind phospholipids and heavy metals and to destroy peroxides that cause the oils to become rancid.

This object is achieved with the aid of a method which is characterized by the combination of the following method steps:

(a) de-oiling the used bleaching earth by extraction with a solvent for the oil except for a residual content of carbon-containing substances of at most 25% by weight (determined as C);

(b) thermal treatment of the de-oiled bleaching earth in an oxidizing atmosphere at a temperature of 500 to 650 ° C. until the bleaching earth is practically free from organic carbon-containing substances, but the structure of the bleaching earth is still largely preserved and the montmorillonite content of the bleaching earth is unchanged has practically not diminished;

(c) coating the product thus obtained with an aqueous acid, the amount, concentration and temperature of which are selected such that practically no inorganic components are dissolved out of the product and that the water content of the product is between about 2 and 10, preferably between 5 and 8% by weight. Also in step (c) it is essential that the montmorillonite content of the bleaching earth practically does not decrease, which would be the case with a more intensive acid treatment (increase in the acid concentration, the temperature and / or the time) at which the inorganic components, in particular the alkali and alkaline earth metal cations, would be removed from the montmorillonite lattice. By "coating with an aqueous acid" is meant only the absorption of the aqueous acid in the pores of the bleaching earth, without a reaction taking place.

The term "carbon-containing substances" includes the remaining parts from oils, fats and hydrocarbons, polymers, dyes, proteins, phospholipids and activated carbon. The total carbon content is determined by combustion analysis.

The deoiling (stage a) is usually carried out with an organic solvent such as gasoline, toluene, ethanol, acetone, chlorinated hydrocarbons or mixtures thereof. The deoiling can also be carried out with supercritical carbon dioxide, which has the advantage that the solvent can be removed at lower temperatures and no solvent residues remain.

It is also important that a practically alkali-free solvent is used for deoiling, since an alkali-containing solvent reacts with the bleaching earth or saponifies the oil. The presence of alkali is disadvantageous in the subsequent thermal treatment (step b) because the alkali reacts with the bleaching earth, which reduces the active surface.

The thermal treatment of the de-oiled bleaching earth is usually carried out in air or an oxygen atmosphere, it being possible to shorten the treatment time by increasing the oxygen content of the oxidizing atmosphere; on the other hand there is an increased oxygen concentration the risk that the specified temperature range of 500 - 650 ° C will be exceeded. The thermal treatment of the de-oiled bleaching earth is usually carried out over a period of from 0.5 to 5, preferably from 0.5 to 2, hours, the treatment time not only depending on the oxygen content of the oxidizing atmosphere, but also on the temperature and removing amount of carbonaceous substances depends.

The montmorillonite content of the oil-containing bleaching earth is generally 25 to 50% and should practically not be reduced by the thermal treatment. The montmorillonite content is determined indirectly via the ion exchange capacity (IUF = mVal / 100 g bleaching earth) as follows:

The bleaching earth is treated with a large excess of ammonium chloride solution, the alkali and alkaline earth metal ions being replaced by ammonium ions. After filtering off the ammonium chloride solution and washing and drying, the nitrogen content in the bleaching earth is determined according to the Kjeldahl method. Montmorillonite has an IUF of 100mVal / 100g in the pure state,

The amount of acid used when the product is coated with the dilute aqueous acid (stage c) is preferably about 0.2 to 2% by weight, in particular 0.25 to 1% by weight (calculated as "anhydrous acid") of the total product Acid in a concentration of about 15 to 50 parts by weight, in particular of about 15 to 25 parts by weight.

The invention furthermore relates to the use of the bleaching earth regenerated by the above process in the refining of edible oils, fats, liquid and solid hydrocarbon products. In particular, the regenerated bleaching earth is suitable for removing phospholipids in oil refining. The phospholipids are fixed in the weakly acidic, liquid phase, which is in the pores of the regenerated bleaching earth. The regenerated bleaching earth is also suitable for the catalytic decomposition of the peroxides present in various oils.

The invention is illustrated by the examples below.

example 1

A bleaching earth resulting from the bleaching of rapeseed oil (1 part by weight of bleaching earth to 100 parts by weight of oil, bleaching for 30 minutes at 95 ° C.), the oil content of which was determined to be 41.8% by solvent extraction, was extracted with hexane at 70 ° C., with the weight ratio between bleaching earth and extractant was 0.4: 1. The oil was recovered by evaporating the extractant under reduced pressure.

The residual total carbon content in the bleaching earth was determined on a sample by combustion analysis to be 16.7% by weight.

The bleaching earth, which had been deoiled in this way, was heated under air at 600 ° C. for a period of 0.5 hours and then allowed to cool to room temperature in a stream of air. A sample of the regenerated bleaching earth was examined by X-ray, and it was found that the intensities of the X-ray diffraction reflections of the montmorillonite had not changed. The specific surface of the bleaching earth obtained (BET single-point method with nitrogen according to DIN 66 132) was 215 m ² / g. This value roughly corresponded to the value of the active bleaching earth which was originally used to refine the rapeseed oil (see Table 1).

The thermally treated bleaching earth regenerate was treated with a 2.5% strength sulfuric acid, with 0.6 part by weight of sulfuric acid (as anhydrous acid) being used per 100 parts by weight of bleaching earth. The regenerate was still pourable. 1 part by weight of the bleaching earth coated with the dilute sulfuric acid was used to bleach 40 parts by weight of linseed oil. The bleaching was carried out at 95 ° C. for 30 minutes. The sample obtained was examined spectrophotometrically compared to the untreated sample. The transmission at the 460 nm wavelength increased from 0.5 to 24%. The original bleaching earth showed an increase in transmission from 0.5 to 28% under the same conditions. A regenerate was obtained by thermal treatment without subsequent acid treatment, which showed an increase in transmission from 0.5 to 21% (see Table 1).

Example 2

The regenerated bleaching earth of Example 1 was used in the Old * oil bleaching, in which 1 part by weight of bleaching earth used oil has been used to 25 parts by weight ^'. It was acidified waste oil, which was bleached for 30 minutes at 160 ° C and 76 hP vacuum. The ASTM color number of the raffinate was 3.6 (see Table 2).

Table 1

Regeneration of a bleaching earth coated with rapeseed oil

Original regenerated bleaching earth after thermal treatment and acid treatment.

spec. Oberf1. (m ² / g) 232 215 212 IUF (mVal / lOOg) 27.2 27.3 27.0

Bleaching effect on linseed oil (% transm. On 28 21 24 undiluted oil)

Table 2

Bleaching of 100 g waste oil with 4 g regenerated bleaching earth

Mineral oil bleaching activity 3.0 4.0 3.6 (ASTM color number) Example 3

The oil-containing bleaching earth from Example 1 was extracted with supercritical carbon dioxide at 60 ° C. and 350 bar pressure. The bleaching earth which had been deoiled in this way was thermally treated as in Example 1 and coated with dilute sulfuric acid.

The bleaching effect was determined as in Example 1. The transmission was 27%. The bleaching action on acidified waste oil according to Example 2 corresponded to an ASTM color number of 4.0.

Example 4

A bleaching earth originating from the bleaching of linseed oil was extracted with petrol except for a residual content of 6.8% of carbonaceous substances. The bleaching earth, which had been deoiled in this way, was heated for 50 minutes at 550 ° C. with access to air and then allowed to cool. The thermally treated bleaching earth was coated with H2SO4, 0.75 part by weight of H2SO4 in the form of a 48% strength acid being used per 100 parts by weight of bleaching earth. The bleaching results are given in Table 3.

Table 3

Bleaching of 80 g linseed oil with 2.0 g regenerated bleaching earth, with

Sulfuric acid occupied.

Bleaching activity (transmission at 460 nm)

Regenerated bleaching earth 32

Original bleaching earth 34

Example 5

A bleaching earth, which was coated with a mixture of different hard fats for margarine production, was regenerated analogously to Example 1 (C content after deoiling 19.8%). The regenerate was used for the bleaching of linseed oil. For this, 80 g linseed oil was mixed with 2 g regenerate. A transmission value of 29% was achieved.

Example 6

A bleaching earth regenerated according to Example 1 was used for the bleaching of soybean oil containing phospholipid. The phosphorus content of the untreated oil was 25 ppm (determined according to the AOCS method Yes 5-55).

80g of the degummed soybean oil was bleached with 0.8g of the regenerate. The phosphorus content of the oil bleached with the regenerate was 7 ppm.

Claims

claims

1. Process for the regeneration of used, oil-containing bleaching earth, characterized by the combination of the following process steps:

(a) de-oiling the used bleaching earth by extraction with a solvent for the oil to a residual content of carbon-containing substances of at most 25% by weight (determined as C);

(b) thermal treatment of the de-oiled bleaching earth in an oxidizing atmosphere at a temperature of 500 to 650 ° C. until the bleaching earth is practically free of organic carbon-containing substances, but the structure of the bleaching earth is still largely preserved and the montmorillonite content of the bleaching earth is practically has not diminished;

(c) coating the product thus obtained with an aqueous acid, the amount, concentration and temperature of which are selected such that practically no inorganic components are dissolved out of the product and that the water content of the product is between about 2 and 10, preferably between 5 and 8 % By weight. lies.

2. The method according to claim 1, characterized in that one carries out the deoiling with an organic solvent or with supercritical carbon dioxide.

3. The method according to claim 1 or 2, characterized in that a virtually alkali-free solvent is used for de-oiling.

4. The method according to any one of claims 1 to 3, characterized ge indicates that one carries out the thermal treatment of the de-oiled bleaching earth in air or an oxygenate atmosphere.

5. The method according to any one of claims 1 to 4, characterized ge indicates that one carries out the thermal treatment of the de-oiled bleaching earth over a period of 0.5 to 5, preferably from 0.5 to 2 hours.

6. The method according to any one of claims 1 to 5, characterized ge indicates that the amount of acid used in the coating of the product with the dilute aqueous acid (stage c), about 0.2 to 2, preferably from 0.25 to 1 wt .-. (calculated as anhydrous acid) of the total product.

7. The method according to any one of claims 1 to 6, characterized ge indicates that the dilute aqueous acid in a concentration of about 15 to 50 wt .- *., Preferably from about 15 to 25 wt .-%.

8. Use of the bleaching earth regenerated by the process according to one of claims 1 to 7 in the refining of edible oils, fats, liquid and solid hydrocarbon products.

9. Use of the bleaching earth regenerated by the process according to one of claims 1 to 8 for removing phospholipids and / or for decomposing peroxides in the

Oil refining.