Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
  • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
  • C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
  • C07C29/86—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by liquid-liquid treatment

Definitions

• the present invention relates to a process for purifying crude glycerol obtained from raw materials such as glycerol obtained during the manufacture of biodiesel or glycerol obtained during transformations of fats or oils.
• the invention aims in particular to dissolve glycerol in an organic solvent and form an insoluble phase comprising the salts of crude glycerol.
• Glycerol 1,2,3-propanetriol
• Glycerol is present in combination form in vegetable and animal oils and fats. It is especially present in the form of triglycerides combined with fatty acids such as stearic, oleic, palmitic and lauric acids.
• the most common industrial process for obtaining glycerol from vegetable and animal oils and fats involves saponification reactions, high pressure hydrolysis and transesterification with alcohols, such as ethanol or methanol.
• Glycerol is also a by-product of biodiesel which is generally obtained by the transesterification of glycerides with short chain alcohols, for example methanol or ethanol.
• the transesterification reaction is catalyzed by an acid or a base, depending on the characteristics of the oils and / or greases used.
• the resulting esters are separated from excess reactants, catalyst and by-products by a two-step process. First, the glycerol is separated by decantation or centrifugation, then the soaps, the catalyst and alcohol residues are removed by washing with water and bubbling or using magnesium silicate with filtration.
• the significant production of biodiesel as an alternative to fossil fuels is accompanied by a high production of by-product glycerol.
• the crude glycerol obtained comprises impurities which involve numerous and complex treatment steps.
• Such a purification process is therefore not interesting at the industrial level.
• US Patent 4,990,695 describes the purification of crude glycerol with a combination of operations such as pH adjustment in a range of 9 to 12, heating the medium to 100 ° C, microfiltration and then ultrafiltration. The glycerol obtained is then distilled, optionally after treatment with ion exchange compounds.
• the present invention thus relates to a crude glycerol purification process comprising at least the following steps:
• the insoluble phase is generally a heterogeneous dispersed phase in the majority phase and is in the form of a precipitate.
• the process of the invention can be carried out continuously or discontinuously. The steps mentioned can be performed successively and one after the other or not. Each of the steps of the process can be carried out continuously or discontinuously.
• the method according to the invention is implemented by the strict succession of steps a), b), c) and d) without performing an intermediate or additional step.
• said liquid phase comprising the dissolved glycerol formed during said step a) is not subjected, in itself, to any other treatment than the separation of said step c) during which the glycerol is separated from the solvent.
• the crude glycerol is preferably obtained from renewable raw materials, in particular the crude glycerol is obtained during the manufacture of biodiesel or obtained during the transformation of fats or oils, particularly animal or vegetable fats or oils.
• the crude glycerol is generally obtained by saponification reaction, transesterification and / or hydrolysis of animal or vegetable fats or oils.
• the crude glycerol generally comprises from 5 to 95% by weight of glycerol, in particular from 40 to 90% by weight of glycerol and more particularly from 60 to 90% of glycerol.
• Crude glycerol also includes inorganic salts, glycerides, water and other organic compounds.
• the crude glycerol may optionally be treated for the process of the invention, in particular for example by adjusting the pH, filtration or distillation. It is thus possible to filter the crude glycerol to remove insoluble organic material and / or distill it generally at temperatures between 100 and 120 ° C at atmospheric pressure to remove water and volatile compounds. Part or all of the water contained in the crude glycerol can also be evaporated before glycerol is dissolved in the solvent.
• Step a) of the process according to the invention aims at dissolving glycerol in the organic solvent and forming an insoluble phase comprising the salts of crude glycerol.
• One or more solvents can be used.
• the solvent according to the invention may in particular be a ketone, an alcohol, an aldehyde, an acetal and / or a ketal. Acetals are obtained by nucleophilic addition of an alcohol to an aldehyde in an acidic medium, followed by removal of water. The ketals are obtained by the same type of reaction performed on ketones.
• the ketones preferentially used are acetone, cyclohexanone, methyl cyclohexanone, cyclopentanone, methyl cyclopentanone and methyl isobutyl ketone (MIBK).
• the preferred aldehydes are formaldehyde, acetaldehyde and furfuraldehyde.
• the alcohols preferentially used are ethanol, methanol and isopropanol.
• the ketals and acetals are preferably dioxonals such as 2,2-dimethyl-1,3-dioxolane 4 methanol (solketal) for example.
• An organic solvent mixture such as a mixture of alcohol and ketone, particularly a mixture of acetone and ethanol, is particularly preferred.
• step a no catalyst capable of catalyzing a reaction between the glycerol and the organic solvent or solvents of the medium, especially an esterification catalyst, will be used.
• Step a) can last between 2 minutes and 1 hour. It can be carried out at a temperature of between 10 and 100 ° C., in particular between 20 and 50 ° C.
• the pH during this step can be between 6 and 12, preferably between 7 and 12.
• the mass ratio between the crude glycerol and the solvent is in particular a function of the solubility of glycerol in said solvent, and for example preferably between 1/1 and 1/50, more preferably between 1/1 and 1/25.
• Step b) aims at the separation of the precipitate obtained in step a) from the liquid phase comprising the solvent and the dissolved glycerol.
• Step c) is aimed at separating the solvent and the glycerol which is dissolved in the solvent.
• evaporation or distillation can be carried out for this purpose.
• step c) it is also possible to separate the water contained in the crude glycerol.
• the evaporation will include the passing of the organic solvent (s) in the gaseous state so as to recover the glycerol in the liquid state.
• one or more distillation columns can be used.
• the different compounds can be distilled on the same distillation column by varying the temperature, and possibly the pressure; for example proceed to the distillation of the organic solvent, then an increase in the temperature to distill the glycerol.
• Temperatures between 60 and 190 ° C are usually used and pressures between 2 and 1000 mbar are used.
• the purified glycerol is then obtained and can be used in various applications requiring a high purity level.
• the commercially available crude glycerol has the following composition: 79.3% by weight of glycerol, 15.8% by weight of water, 1.61% by weight of Na + and 2.56% by weight of Cl-. 120.2 g of crude glycerol are added at room temperature to 2464 g of acetone. The mixture is stirred for 15 minutes until dissolution of the glycerol in acetone and formation of an insoluble phase. The liquid phase is filtered using a PTFE filter with a pore diameter of 0.2 ⁇ m; then the solvent and the water are evaporated under vacuum at a temperature of 60 ° C and a pressure of 0.3 bar absolute.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 2010
  • 2010-09-15 FR FR1003665A patent/FR2964657B1/fr not_active Expired - Fee Related
• 2011
  • 2011-09-07 CN CN201180044388XA patent/CN103097327A/zh active Pending
  • 2011-09-07 WO PCT/EP2011/065437 patent/WO2012034904A1/fr active Application Filing
  • 2011-09-07 US US13/822,234 patent/US20130165699A1/en not_active Abandoned
  • 2011-09-07 BR BR112013005946A patent/BR112013005946A2/pt not_active IP Right Cessation
  • 2011-09-07 EP EP11754390.0A patent/EP2616419A1/de not_active Withdrawn

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