RO137600A0 - Integrated system for glycerine purification - Google Patents

Abstract

The invention relates to a process for purifying glycerine resulting from the transesterification of rapeseed oil to obtain biodiesel fuel. According to the invention, the process consists of the following steps: mixing the impure glycerine, while mechanically stirring, with a mixture consisting of acetone or ethyl alcohol/acetone solvent and aluminium sulphate, in a glycerine : acetone or ethyl alcohol/acetone ratio of 1:1...1:30 and a solvent: aluminium sulphate ratio of 1000:1...2000:1, stirring for 30...50 min at 30°C, separating two phases: a lower phase at the base, containing organic and inorganic impurities and at the top an organic phase containing solubilized glycerine, filtering on activated carbon and α -cellulose, followed by removing solvent traces by distillation at 50°C under vacuum, to result in glycerine with a purity of more than 99% confirmed by gas-chromatographic analysis.

Description

RO 137600 AO

STATE AUTHORITY FOR iWEK |ii AND BRANDS

Invention patent application

No. ........^.9..2R...........

Date of deposit..............D.3....0.Z7..2ÎIZ3..

INTEGRATED GLYCERIN PURIFICATION SYSTEM

Description of the invention:

The invention describes an integrated system for the purification of glycerin obtained as a by-product in the manufacture of methyl esters of fatty acids (biodiesel).

Glycerin (glycerol, propane-triol) is a compound with three hydroxyl groups that gives the compound a specific water solubility and hygroscopicity. It is the basic element in the composition of vegetable oils and fats. Carboxylic acids C4-C24 (saturated and/or unsaturated with 2-4 double bonds) form esters with glycerin known as triglycerides.

The substitution of glycerin with an aliphatic alcohol (polar or non-polar Ci - C4) leads to obtaining some aliphatic esters in a process called transesterification, when biodiesel is obtained and as a by-product glycerin with various impurities is obtained (alcohols, monoglycerides, diglycerides, triglycerides , sterols, tocopherols, diglycerols, polyglycerols, colored and/or inorganic impurities, water, etc.). The presence of these compounds is due to the chemical composition of triglycerides, as well as some preliminary stages of their treatment.

Purification of this glycerin requires large amounts of chemicals, energy and time.

The traditional purification of glycerin can be done through the following processes:

- treatment with sulfuric acid, or hydrochloric acid, phosphoric acid, acetic acid, citric acid, etc.

- treatment with alkaline bases: sodium hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide.

- ion exchange resins (zeolites or resins - Amberlite 252, Amberlite IRA-120, Amberlite IRA-420, etc.).

- ion exclusion resins.

- various chemicals: salts or flocculating agents.

- adsorption on activated carbon

- vacuum evaporators (10-15 kPa) fractional distillation with descending film - dialysis

- crystallization

These processes require a long processing time, high energy consumption due to the high viscosity of glycerin and the high pressure drop, finally obtaining a low purity of glycerin that requires redistillations and low yields. There are also a number of economic and technological disadvantages, including an exaggerated consumption of utilities, the complexity of the separation plant, environmental pollution, high investment and operating costs.

Several purification processes are known. A method of treating with activated carbon in the presence of oxygenated water is known ( US 2120227 ) which allows correcting the color and smell, but does not solve the problem of inorganic impurities. Acid treatment leads to the formation of dimer and polyglycerol as impurities.

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RO 137600 AO

Another known procedure for purifying glycerin by treating it with sulfuric acid at 100...140°C for 1...6 hours, neutralizing the solution with an ion exchange resin (anionite) or alkali metal oxides followed by a fractional distillation of glycerin (US 2977291). The process is highly energy intensive.

Another process is based on the alkalization at a temperature of 90...100°C of glycerine and oxidation with air, followed by re-distillation of the residue, rectification and re-evaporation in a falling film evaporator, followed by decolorization under the cushion of nitrogen and activated carbon (US 4655879 ). The process involves an expensive installation, successive distillations, an increased corrosion of the installation, there are also product losses due to polymerization in an alkaline environment.

Other processes are known that are based on centrifugation, ultrafiltration and microfiltration on polymeric membranes (US 5527974, RO 96185, GB 2437516), or ceramic microfilters (US 4990695). These processes are demanding and can be applied to large productions where the quality of the raw material is practically constant.

Another glycerin purification process is known, which consists in the extraction of glycerin with supercritical liquids (carbon dioxide) and the separation of the extracted glycerin ( US 4683347 ).

Another process uses electro-osmotic purification ( GB 214576 ), a very expensive process.

The technical problem that the invention solves consists in realizing a glycerin purification process, eliminating organic compounds and inorganic salts, using a reduced number of unit operations, improving the yield and purity of glycerin, greater than 99%, with reduced energy consumption and low costs for industrial viability.

The process according to the invention removes the previously mentioned disadvantages, in that the impure glycerin solution is mixed by mechanical stirring with a mixture consisting of a hydroxyl compound and/or carbonyl compound (glycerin/hydroxy compound and/or carbonyl compound ratio 1:1. ....1:30 ) and a flocculating agent (aluminum sulfate type polyelectrolyte, sodium aluminate, sodium silicate but not exclusively) in a gravimetric ratio organic solvent: flocculating agent 1000:1.....2000 :1 at a temperature between 2O...5O°C, for 10...60 minutes. Through this process, the initial glycerin is separated in the upper part from the inorganic part that is not soluble in the organic phase. Then the glycerin solubilized in the organic phase is removed from the rest of the impurities by filtration on activated carbon and α-cellulose. Impurities (organic and/or inorganic) are retained in the polyelectrolyte-type solid phase that separates at the lower base during agitation.

Hydroxyl compound means an organic compound (Ci - C15) that has in its molecule the hydroxyl group (- OH ) linked to an sp ³ hybridized carbon atom (saturated carbon atom). Examples of alcohols: methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butyl alcohol, etc.

By carbonyl compound is meant an organic compound (Ci - Cio) that contains in the molecule the functional group >C=O (carbonyl group). Examples of carbonyl compounds: methanal, ethanal, propanal, butanal, propanone (acetone), butanone, cyclohexanone, methylcyclohexanone, cyclopentanone, methyl-isobutyl-ketone, etc.

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RO 137600 AO

Glycerin thus purified can be decolorized with activated carbon and α-cellulose and traces of solvent are removed by distillation at 50°C under vacuum, finally obtaining a purity of the product of 99.9%, confirmed by gas-chromatographic analysis.

The method according to the invention results in the following advantages:

a high purification of glycerin of over 99% is achieved, achieving energy savings; high vacuum distillation is avoided

- the stages of the process are carried out easily, the consumption of raw materials and energy are minimal

2 (two) examples of the process according to the invention are given below.

Example 1.

To 2,000 kg of crude glycerin resulting from the transesterification reaction of rapeseed oil to obtain biodiesel, a mixture of 25, 3 kg of ethyl alcohol / acetone (1.7 kg / 23.5 kg) and 0.235 kg of aluminum sulfate. The mixture is stirred for 30 minutes. After that, two phases will be separated: the upper organic phase containing the acetone and the lower phase containing the inorganic and organic impurities. The upper phase is separated by decantation and subjected to filtration on activated carbon and α-cellulose and traces of solvent are removed by distillation at 50°C under vacuum, finally obtaining a product purity of 99.9%, confirmed by gas analysis chromatographic.

Example 2.

To 3,500 kg of crude glycerin resulting from the transesterification reaction of rapeseed oil to obtain biodiesel, a mixture of 7, 5 acetone and 0.175 kg aluminum sulfate. The mixture is stirred for 50 minutes. After that, two phases will be separated: the upper organic phase containing the acetone and the lower phase containing the inorganic and organic impurities. The upper phase is separated by decantation and subjected to filtration on activated carbon and α-cellulose and traces of solvent are removed by distillation at 50°C under vacuum, finally obtaining a product purity of 99.95%, confirmed by gas chromatography analysis.

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Claims (5)

RO 137600 AO The claims of the invention: 1. Purification of glycerin resulting as a by-product in the manufacture of methyl esters of fatty acids (biodiesel), characterized in that the impure glycerin solution is mixed by mechanical agitation with a mixture consisting of a hydroxyl compound and/or carbonyl compound (ratio glycerin/hydroxyl compound and/or carbonyl compound 1:1.....1:30) and a flocculating agent (aluminum sulfate type polyelectrolyte, sodium aluminate, sodium silicate but not exclusively) in organic solvent ratio: flocculating agent 1000:1.....2000:1 at a temperature between 2O...5O°C, for 10.....60 minutes. Through this process, the initial glycerin is separated in the upper part from the inorganic part that is not soluble in the organic phase. Then the glycerin solubilized in the organic phase is removed from the rest of the impurities by filtration on activated carbon and α-cellulose. Impurities (organic and/or inorganic) are retained in the polyelectrolyte-type solid phase that separates at the lower base during agitation. 2. Process according to claim 1, characterized in that the hydroxyl compound is chosen from an organic compound (Ci-C15) that has in its molecule the hydroxyl group (-OH) such as methyl alcohol, ethyl alcohol, 1-propanol, 2-propanol , 1-butanol, 2-butanol, tert-butyl alcohol, etc. 3. Process according to claim 1, characterized in that the carbonyl compound is chosen from an organic compound (Ci - C10) that has the functional group >C=O (carbonyl group) in the molecule such as methanal, ethanal, propanal, butanal, propanone (acetone), butanone, cyclohexanone, methyl-cyclohexanone, cyclopentanone, methyl-isobutyl-ketone, etc. 4. Process according to claim 1, characterized in that the flocculating agent (aluminum sulfate type polyelectrolyte, sodium aluminate, sodium silicate but not exclusively) is in a gravimetric ratio of organic solvent: flocculating agent 1000:1... ..2000:1 5. Process according to claim 1, characterized in that the integrated glycerin purification process takes place at a temperature between 2O...5O°C, for 10...60 minutes. Page 4 of 5