CZ278907B6 - 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 invention relates to a process for 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 containing a major proportion of biodiesel by treating the glycerol layer.

BACKGROUND OF THE INVENTION

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 catalytic from the original mixture of triglycerides of higher reactions with lower monohydric alcohols, a mixture of esters of these acids and glycerin.

reesterification in which fatty acids are formed (most often with methanol)

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 these processes, two layers are formed after re-esterification: the top containing the major proportion of fatty acid methyl esters and biodiesel, respectively, and the bottom containing the major component glycerin. The upper layer, consisting largely of crude biodiesel, is further processed according to known methods to produce the desired properties. However, the method of treating the glycerol layer has not been described in the literature. From the point of view of practical applicability, it is not sufficient merely to separate the glycerine layer into its individual components. It is about obtaining glycerin in a quality that would allow its further usability. According to the available information, such a process for separating the glycerol layer has not been proposed yet.

SUMMARY OF THE INVENTION

These disadvantages are overcome by 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 glycerine layer. 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 compression. The lower light phase contains a higher glycerin concentration. If these two phases are mixed, they will no longer be redistributed. In the process of the present invention, both layers are treated together as a single material. The process of the invention respects the requirement of maximum technical simplicity and operational feasibility. It uses intentionally

The principles of known operations used in the isolation of organic matter. The core of the solution of the problem is the selection of the most suitable processes, determination of the optimal sequence of operations and their specific conditions. The process according to the invention thus creates a new, coherent process leading to obtaining glycerin properties which allow its further use without any further modification.

The process of obtaining glycerol in the manufacture of biodiesel from rapeseed oil by reesterification with methanol in the presence of potassium hydroxide after separation of the ester layer by treating the glycerol layer of the present invention is to first remove the methanol from the glycerol layer by evaporation up to 70 phosphorous at a concentration of 0.5 to 3 M at room temperature or at an elevated temperature of up to 80 C. Two layers are formed, from which the lower glycerol layer is subjected to further processing. This is freed from the anions of the previously used acids and purified by passing through an ion exchange system consisting of one to three, preferably two, anion-cation exchange pairs of layers. The solution thus treated is dehydrated by evaporation, preferably under vacuum.

The initial methanol evaporation is a routine operation and is carried out under conventional, known conditions. The next step, acidifying the crude glycerol layer, can be carried out instead of adding dilute acids by separately adding water and concentrated sulfuric or phosphoric acid in appropriate amounts. The addition of water and acid can be carried out in any order. The resulting pH ranges from 2 to 7. After acidification, two liquid phases are formed in the system - upper organic and lower aqueous. The topsheet of the present invention does not process. For further processing, only the lower aqueous layer containing virtually all is subjected to glycerin.

If an aqueous anion-cation exchanger treatment before the passage of the ionic or phosphate passage results in an aqueous layer which does not contain a large excess of anions after acidification, it is possible to carry out further ion removal by ion exchange with optional pre-filtration. Otherwise -

sulphate anions SO ^ “V z *

PCHs are precipitated as insoluble salts, usually calcium or barium. After filtering off the insoluble salts, excess cations, such as calcium Ca ²⁺ , can also be removed, preferably by adding potassium or ammonium carbonate or ammonium oxalate. The insoluble salt formed was removed by filtration. Another purification operation consists in passing the reaction mixture through the ion exchange system through anion-cation exchange pairs. In practice, this is accomplished using one to three, preferably two, anex-cation exchange column pairs connected in series.

Another operation may be cleaning by mixing with activated carbon. The preferred amount of activated carbon is 0.5 to 4 wt. This operation may follow or pass upstream of the ion exchange system.

The final operation, evaporation of water, is preferably carried out in a vacuum evaporator at a pressure of 1 to 4 kPa and at a temperature of 40 to 60 C. The yield of glycerine is at least 95% by weight. When phosphoric acid is used to acidify the glycerine layer and to regenerate the anion exchange resin

-2C 278907 Β6 and for the recovery of cation exchange resin potassium hydroxide, 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 dm ³ , 100 cm ^{3 of} 1.5 M sulfuric acid H ₂ SO ₄ was added with stirring. 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 at pH 7 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 over 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 was as in Example 1 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% by weight of activated carbon at room temperature for two hours was included as the final purification step prior to concentration in the evaporator.

Example 3

100 g of the glycerol layer of Example 1 was heated to 60 ° C and, after the methanol was evaporated, 60 cm ^{3 of} distilled water and 5 cm ^{3 of} concentrated phosphoric acid H ₃ 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 anex-cation exchange column pairs connected in series. 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.

-3GB 278907 B6

Industrial applicability

The process of obtaining glycerin in biodiesel production streamlines biodiesel production and additionally provides another product. The glycerin thus prepared has the same quality and the same uses as the commercially available glycerin.

Claims (4)

Process for 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, characterized in that methanol is removed from the separated crude layer by evaporation up to 70 ° C mixed with dilute 0.5 to 3 M sulfuric or phosphoric acid at room temperature or at elevated temperature up to 80 ° C, the bottom layer of glycerol is separated from the two layers, which is purified by passing through an ion exchange system from one to three, preferably two a series of ordered pairs of anion-cation exchange layers and the resulting solution is dewatered by evaporation, preferably under vacuum. Process according to claim 1, characterized in that water and sulfuric or phosphoric acid added in any order are used separately to acidify the glycerol layer. Method according to claims 1 and 2, characterized in that the separated glycerin layer formed by acidification before passing through the ion exchange system is freed from the anions of the previously used acids by converting them into insoluble salts and filtering. Method according to one of Claims 1 to 3, characterized in that the treated solution is, after passing through or before the ion exchange system, refined by mixing with activated carbon, which is removed by filtration. _to