CZ90892A3 - Process of obtaining glycerol when producing biological motor oil from rape-seed oil - Google Patents

Abstract

Following separation of an ester layer, the glycerinated layer gained from a product of the re-esterification of rape oil by methanol in the presence of potassium hydroxide is mixed with sulphuric or phosphoric acid. Two liquid layers are formed which are separated and the lower layer is processed. After removal of anions of the acids used by passing through an ion-exchange system made up of a series of anion-cation exchangers, that layer is purified. The resulting solution can be further refined using active charcoal.The final operation is dehydration, preferably by evaporation in a vacuum.

Description

The use of fatty acid esters as fuel for self-ignition (Diesel) engines is known. When these esters are obtained from natural materials such as various kinds of vegetable and animal oils and fats, the resulting product is called biodiesel.

These natural materials are usually chemically and physically treated, especially by catalytic re-esterification, in which the original mixture of triglycerides of higher fatty acids forms a reaction with lower monohydric alcohols (most often with methanol) a mixture of esters of these acids and glycerin.

One of the most commonly used natural materials in Europe is rapeseed oil, the re-esterifying agent is methanol, and potassium hydroxide is the most commonly used catalyst.

In all of these processes, two layers are formed after re-esterification: an upper layer containing a major proportion of fatty acid methyl esters, respectively. biodiesel and bottom containing glycerin as the main constituent. The upper layer, formed largely of crude biodiesel, is further processed to produce the desired properties according to known methods. However, the method of treating the glycerol layer has not been described in the literature.

SUMMARY OF THE INVENTION

The present invention solves a process for treating a glycerin layer formed after reesterification of rapeseed oil with methanol in the presence of potassium hydroxide. This material has been a waste so far, and is now a source of glycerin that can be used as such.

After separating the ester layer, the glycerin layer is separated again and forms two phases: the upper dark phase contains, in addition to glycerin, a considerable proportion of biodiesel, methanol, potassium hydroxide and other substances, in particular vegetable dyes and rapeseed products released during their pressing. The lower light phase contains a higher glycerin concentration. If these are mixed _; two phases, there will be no redistribution. In the process of the invention both layers are treated together as one material. The process of obtaining glycerol in the manufacture of biodiesel from rapeseed oil by re-esterification with methanol in the presence of potassium hydroxide after separation of the ester layer by treating the glycerol layer is carried out according to the invention as follows:

Methanol is first removed from the glycerol layer by evaporation under normal or reduced pressure. Dilute mineral acid such as h 2 SO 4 or H 2 PO 4 is then added. Two layers are formed, of which the lower glycerol layer is subjected to further processing. This is freed from the anions of the used strong acids by conversion to insoluble salts, eg calcium or barium, and purified by passing through a series of anion-cation exchange columns connected in series. Alternatively, water and concentrated acid can be used in any order instead of the dilute acid, and the lower glycerol layer can be freed directly from anions and cations with anion exchange resin and cation exchange resin after filtration.

The first methanol removal operation is generally carried out by evacuation under a water pump or by heating to 60 ° C. the subsequent operation (acidification) is carried out either with an aqueous solution or with H 3 PO 4 at a concentration of 0.5 to 3 M. The resulting pH is in the range of 2 to 7. Or water and concentrated acid are added to the glycerine layer successively.

This operation can be performed at normal or elevated temperatures up to 80 ° C. After acidification, two liquid phases are formed in the system - upper organic and lower aqueous. The upper organic layer is not treated according to the invention. Only the lower aqueous layer containing all glycerin is subjected to further processing. The anions SO4 or PO4 precipitate as insoluble salts, usually calcium or barium. After filtering off the insoluble salts, it is possible to remove excess cations, for example Ca4 ^{+ is} preferably done by the addition of K2CO3, (NH4 ^ CO4 or quenched with ammonium. The insoluble salt formed is removed by filtration. up to three anion-cation exchanger column pairs in series A further operation may be activated by mixing with activated carbon The preferred amount of activated carbon is 0.5 to 4 percent by weight. In optimum cases, when an aqueous layer is obtained which does not contain a large excess of anions and cations after acidification, it can be further processed without precipitation by direct removal of the anions and cations by anion exchange and cation exchange with optional pre-filtration. vacuum evaporator at 1-4 kPa and 40 - 60 [deg.] C. The yield of glycerine is at least 95% by weight of the content of the starting glycerine layer, and the product is clear and contains only glycerine and water having a glycerine concentration of 99% by weight. If phosphoric acid and potassium hydroxide are used to acidify the glycerol layer and regenerate the anion exchange resin, potassium phosphate can be obtained as a by-product.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

Preferably the methanol was removed from the glycerol layer by evacuation under a water pump at room temperature. The methanol removal was checked by gas chromatography. To 100 g of this layer containing 35 g of KOH in 1 day 2 was added with stirring 100 ml of 1.5 M H 2 SO 4. After standing for one hour at rest two layers were obtained. The top was removed in the divider. Calcium hydroxide was added to the lower aqueous layer with stirring until pH = 8.5 to 9;

The resulting calcium sulfate precipitate was filtered off.

Ammonium carbonate was added to the filtrate to turbidity. The resulting calcium carbonate was filtered again. The crude glycerin solution was further purified through two anex-cation exchange column pairs connected in series. Ostion KSPC was used as the cation exchanger and Lewatit MP 600 was used as the anion exchanger. The obtained aqueous glycerin solution was concentrated at 40 ° C under a vacuum of 3 kPa. GC analysis contained 99 wt. % glycerin and water.

Example 2

The procedure of Example 1 was followed except that barium hydroxide was used to precipitate sulfate ions and potassium carbonate was used to precipitate excess barium ions. In addition, adsorption by mixing with 2 wt.% Was included as a final purification step prior to concentration in the evaporator. activated carbon at room temperature for two hours.

Example 3

100 g of the glycerol layer of Example 1 was heated to 60 ° C and, after the methanol was evaporated, 60 cm of distilled water and 5 cm 3 of concentrated H 2 PO 4 (85%) were added with stirring for 30 minutes. After standing for one hour at room temperature, two layers were obtained. The top was removed in the divider. The lower aqueous layer was purified over two in series of an anion-cation exchange column. The procedure of Example 1 or 2 was followed.

Example 4

The procedure was as in Example 3, except that the same amount of concentrated sulfuric acid was used in place of phosphoric acid, and the lower aqueous layer was removed by filtration prior to anion-cation exchange column filtration.

The industrial applicability of biodiesel makes such glycerine prepared as glycerin more commercially efficient

The process of obtaining glycerin in the production of biodiesel production and, moreover, provides the product, the china has the same quality and the same uses available.

Claims (4)

1. A process for obtaining glycerol in the manufacture of biodiesel from rapeseed oil by esterification with methanol in the presence of KOH, after separation of the ester layer, by treating the glycerol layer, characterized in that from the separated crude glycerol layer · < removes methanol preferably by evaporation under normal or reduced pressure at a temperature of up to 70 ° C, which is then mixed with a dilute strong mineral acid such as H 2 SO 4 or H 2 PO 4 at room temperature or up to 80 ° C, The layers are separated and further processed only the lower layer of glycerol, which is freed from the anions of previously used acids by converting them into insoluble salts and subsequent filtration and purified by passing through one to three, optimally two, in series connected pairs of anex-cation exchange columns. The solution obtained is dehydrated by evaporation, preferably under vacuum. 2. The process of claim 1 wherein water and concentrated or H2SO4 are used separately to acidify the crude glycerol layer at normal or elevated temperature, in any order. • 3. A process according to claim 1 or 2, characterized in that, after acidification and separation, the aqueous glycerin layer, after optional filtration, is freed of anions and cations only in a series of connected anion-cation exchange columns. 4. The process according to claim 1 or 2 or 3, characterized in that the treated solution is refined by mixing with activated carbon after passing through the ion exchange system and subjected to vacuum concentration after the activated carbon has been separated off.