Classifications

• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
  • C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
  • C11C3/04—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fats or fatty oils
  • C11C3/10—Ester interchange
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/03—Preparation of carboxylic acid esters by reacting an ester group with a hydroxy group
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C67/00—Preparation of carboxylic acid esters
  • C07C67/08—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11C—FATTY ACIDS FROM FATS, OILS OR WAXES; CANDLES; FATS, OILS OR FATTY ACIDS BY CHEMICAL MODIFICATION OF FATS, OILS, OR FATTY ACIDS OBTAINED THEREFROM
  • C11C3/00—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom
  • C11C3/003—Fats, oils, or fatty acids by chemical modification of fats, oils, or fatty acids obtained therefrom by esterification of fatty acids with alcohols

Definitions

• the present invention relates to a method for production of alkyl esters from mixtures of glycerides and free fatty acids, in particular mixtures of glycerides and free fatty acids from grease trap waste, tallows, animal fats, vegetable lipids and other high fatty acid content lipids.
• mixtures of glycerides and free fatty acids from grease trap waste, tallows, animal fats, vegetable lipids and other high fatty acid content lipids.
• it has been found to be very effective in efficiently producing alkyl esters from lower fatty acid, higher glyceride content lipids.
• Biodiesel Alkyl esters of fatty acids found in natural lipids, commonly known as biodiesel, are becoming increasingly recognised as viable fuel alternatives for diesel engines. They are known to reduce the output of particulate, hydrocarbon pollutants and improve the lubrication of diesel engines. Biodiesel may also be successfully used as a lubricant, a hydraulic fluid and as a multi-purpose solvent.
• biodiesel is attractive from a commercial and environmental viewpoint because the raw materials applicable to this invention may be sourced from renewable oilseed feedstocks, used vegetable oils, palm oil, coconut oil, soapstock materials as a lipid-rich byproduct of vegetable oil refining, tallows, animal fats, or from grease trap waste which would normally be disposed of in land fill and other waste disposal facilities.
• the Haas et al method for synthesis of fatty acid methyl esters from soapstock involves another two-step process wherein the soapstock is first saponified and then esterified in an acidic alcohol solution.
• Haas et al reports that a 60% recovery of fatty acid methyl ester is achieved with this method.
• the method is characterised, however, by high consumption of the reagents.
• the present invention attempts to overcome at least in part some of the aforementioned disadvantages and to provide new advantages including low or nil glycerol production and the method is amenable to low capital plant costs and plant mobility.
• a method for production of alkyl esters from a mixture of glycerides and free fatty acids comprising: a) addition of an acid to an alcoholic solution of the mixture to decrease the pH of the solution to about 1 to 2 to effect acid-catalysed alkyl esterification; b) treatment of the solution from step a) with a concentrated alkoxide solution to raise the pH of the solution to about 12 to effect base-catalysed transesterification of glycerides contained in the mixture; c) treatment of the solution from step b) with acid to decrease the pH of the solution to about 2 to effect acid-catalysed esterification of residual saponified by-products from step b); d) removal of alcohol from the solution from step c); and e) separation of resulting alkyl esters.
• the present invention describes a method for reacting a mixture of free fatty acids and glycerides, commonly found in grease trap waste, tallows, animal fats, palm oil, coconut oil, and other naturally occurring lipids, including waste or fresh unused vegetable oils and tallows with short-chain alcohols such as methanol, ethanol, propanol, or butanol to produce corresponding alkyl esters.
• grease trap waste encompasses a highly variable mixture of organic fats, greases and vegetable oils, comprising a high free fatty acid and mono-, di-, and triglyceride content, contaminated by detergents, water, soaps, inorganic and particulate matter.
• free fatty acid (FFA) and glycerides will be taken to mean the total content of free fatty acids and mono-, di-, and triglycerides comprised in grease trap waste, tallows, animal fats, and other naturally occurring lipids, and available for alkyl esterification.
• the grease trap waste is between 80 to 100% free fatty acid and glycerides.
• the alcohol includes low-boiling point alcohols, preferably methanol, ethanol, propanol, and butanol in their single-chain and isomerised forms.
• low-boiling point alcohols preferably methanol, ethanol, propanol, and butanol in their single-chain and isomerised forms.
• longer-chain alcohols can be utilised in a similar fashion in accordance with the present invention.
• a mixture of free fatty acids and glycerides, in the form of grease extracted from grease trap waste, tallows, animal fats, and other naturally occurring animal or vegetable lipids, is mixed and agitated in the alcohol to form a miscible single-phase alcoholic solution of the mixture.
• an immiscible suspension of lipids may form in the alcohol.
• the suspension is continually agitated to prevent separation of the lipid and alcohol into two distinct phases.
• the agitated suspension is to be regarded and treated as an alcoholic solution of the mixture of lipids and glycerides.
• Neither type of mixture is dependent on, or requires a co-solvent in the process.
• use of such co-solvents will not impair the reaction or its final alkyl ester product.
• Co-solvent usage may marginally increase the reaction rate but the reaction is quite rapid and goes to completion in the absence of co-solvent.
• the mixture of free fatty acids and glycerides is dissolved in a similar volume of alcohol to afford about 50% v/v alcoholic solution of the mixture. In this way, the alcohol is in molar excess of the total free fatty acid content, preferably in a range of 1:10 to 1:25.
• the reaction proceeds satisfactorily with a lesser or greater proportion of alcohol to lipids, however the reaction proceeds optimally at about 50% v/v.
• vigorous agitation of the two-phase homogeneous solution throughout the reaction procedure effects similar results with regard to alkyl ester production.
• the alcoholic solution of the mixture is first treated with an acid catalyst to effect acid-catalysed alkyl esterification, then treated with a base catalyst to effect base- catalysed transesterification of glycerides contained in the mixture.
• the resulting reaction mixture is finally treated with an acid catalyst to effect acid-catalysed alkyl esterification of residual saponified by-products resulting from the previous treatment steps.
• the acid-catalysed esterification and base-catalysed transesterification steps are performed under reflux conditions, although said steps may also be performed at ambient temperatures, albeit with longer reaction times unless high pressures are used.
• the method of the present invention is preferably performed at ambient atmospheric pressure. However, it is envisaged that said method can be successfully performed under higher pressures with use of a pressure Vessel, or under autoclave conditions.
• Acid catalysts include, but are not limited to, concentrated strong inorganic acids such as sulphuric acid, hydrochloric acid, phosphoric acid, and perchloric acid.
• the ratio of added acid-catalyst to total fatty acid content is about 1 :20 in the first acid-catalysed alkyl esterification reaction step, and about 1:5 in the second acid- catalysed esterification reaction step.
• Base catalysts include, but are not limited to, alcoholic solutions of sodium hydroxide and/or potassium hydroxide, or sodium or potassium dissolved in the short-chain alcohol of choice.
• alcoholic solutions of sodium hydroxide and/or potassium hydroxide, or sodium or potassium dissolved in the short-chain alcohol of choice Preferably, a 10% w/w alkali metal alkoxide solution is used as the base catalyst, such that the ratio of added base-catalyst to total fatty acid content is about 1:5.
• the alcohol is removed from the resulting reaction mixture by distillation or by separation with microfiltration membranes, with or without vacuum assistance, leaving a two-phase heterogeneous mixture of alkyl esters and a solid phase.
• the alkyl esters are separated from the solid phase by decantation, and further purified by filtration or separated by filtration alone.
• the alkyl ester can be treated with a weak base to effectively neutralise residual acid remaining in the alky ester phase, or alternatively by ion exchange or microfiltration. It is envisaged that the pH of the alkyl ester phase will be neutralised to about pH 6-7.
• the neutralisation step is achieved by addition of small amounts of sodium bicarbonate or calcium carbonate or magnesium carbonate to the alkyl ester phase. It is envisaged that other well known means for neutralising pH such as elution of the liquid phase through an ion exchange resin or membrane separation, can be successfully employed to effect neutralisation of residual acid within the alkyl ester phase.
• Residual water can then be removed by conventional means such as passing the alkyl ester phase over a hygrosopic dessicant or by heating the alkyl ester sufficiently to remove steam at atmospheric pressures or under vacuum or by microfiltration. Depending on the final intended use of the alkyl ester, a small amount of entrained water may be acceptable and its removal may not be necessary.
• the inventors have found that the alkyl esters produced by the method of the present invention remain uncontaminated by glycerol byproducts from the acid- catalysed esterification and base-catalysed transesterification reactions of this invention. An exception was found from the treatment of fresh unused vegetable oil whereby a small quantity of good quality glycerol was readily separated.
• the amount of glycerol byproduct was at less than 8% of the starting oil and noticeably less than the amount generated by other esterification methods. No noticeable glycerol production occurred when treating other lipids such as palm oil, coconut oil, animal tallow or grease trap waste. The residual product after alkyl ester separation showed no signs of glycerol by gas chromatography testing.
• Example A single phase 1:1 v/v methanolic solution of grease trap waste (800 ml) in methanol (800 ml) was prepared.
• a GC/MS analysis of the grease trap waste indicated that the major components of the grease trap waste were octadecanoic acid and n- hexadecanoic acid.
• the pH of the methanolic solution of grease trap waste was 4, reflecting a high fatty acid content.
• Concentrated sulphuric acid (98%) (8.5 g) was added with stirring to the methanolic solution resulting in a solution pH of between 1 and 2.
• the methanolic solution was refluxed for 30 minutes.
• a sodium methoxide solution of 10% w/w NaOH in methanol (160 ml) was then added dropwise to the stirred refluxing methanolic solution resulting in a final pH of 12.
• the residual sediment formed from the reaction mixture using ethanol and potassium hydroxide was less crustiform than the sediment described in the Example, it was readily separated from the ethyl esters by filtration.
• the crustiform residue was found to comprise mostly sodium sulphate with minor entrained methyl ester that combined with the sodium sulphate totalled 9% by weight of the starting grease trap waste.
• the conversion of grease trap waste to methyl ester therefore exceeded 91%.
• the entire processing time to final product alkyl ester is less than 1 hour. Furthermore, by increasing the amount of acid in the first step it was found that the reaction time was accelerated thereby reducing the overall reactions processing time.
• the process is not sensitive to or damaged by residual water contaminating the starting lipid. It is a rapid and efficient process and method that can be made even faster by increasing reaction kinetics by increasing the catalytic dosage amounts and/or many well known methods including increased heat, pressure and agitation.
• the final product alkyl ester does not require water washing thereby eliminating a major processing step common to other methods that is both time consuming and polluting. Glycerol byproduction is eliminated in most lipid feedstocks tested.
• the method and process permits design of commercial plants that should be low in capital cost, small in size, with high production rates and be portable as truck mounted, trailer-coupled units, or as a static plant.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Wood Science & Technology (AREA)
• Fats And Perfumes (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Liquid Carbonaceous Fuels (AREA)
• Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

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• 2002
  • 2002-11-27 EP EP02779013A patent/EP1565424A4/de not_active Withdrawn
  • 2002-11-27 JP JP2004554042A patent/JP2006508148A/ja active Pending
  • 2002-11-27 CN CN02830146.3A patent/CN1720214A/zh active Pending
  • 2002-11-27 CA CA002507329A patent/CA2507329A1/en not_active Abandoned
  • 2002-11-27 WO PCT/AU2002/001594 patent/WO2004048311A1/en not_active Application Discontinuation
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