WO2006095134A1 - Production of bio-diesel - Google Patents

Production of bio-diesel Download PDF

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Publication number
WO2006095134A1
WO2006095134A1 PCT/GB2006/000682 GB2006000682W WO2006095134A1 WO 2006095134 A1 WO2006095134 A1 WO 2006095134A1 GB 2006000682 W GB2006000682 W GB 2006000682W WO 2006095134 A1 WO2006095134 A1 WO 2006095134A1
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WIPO (PCT)
Prior art keywords
bas
cation
cat
neutral
aryl
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PCT/GB2006/000682
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French (fr)
Inventor
Martin John Earle
Kenneth Richard Seddon
Natalia Vladimirovna Plechkova
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The Queen's University Of Belfast
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Application filed by The Queen's University Of Belfast filed Critical The Queen's University Of Belfast
Priority to US11/908,313 priority Critical patent/US20090235574A1/en
Priority to JP2008500252A priority patent/JP2008533232A/en
Priority to EP06709909A priority patent/EP1866086A1/en
Publication of WO2006095134A1 publication Critical patent/WO2006095134A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/0277—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature
    • B01J31/0278—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature containing nitrogen as cationic centre
    • B01J31/0279—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature containing nitrogen as cationic centre the cationic portion being acyclic or nitrogen being a substituent on a ring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/0277—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature
    • B01J31/0278—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature containing nitrogen as cationic centre
    • B01J31/0281—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature containing nitrogen as cationic centre the nitrogen being a ring member
    • B01J31/0282—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature containing nitrogen as cationic centre the nitrogen being a ring member of an aliphatic ring, e.g. morpholinium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/0277—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature
    • B01J31/0278—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature containing nitrogen as cationic centre
    • B01J31/0281—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature containing nitrogen as cationic centre the nitrogen being a ring member
    • B01J31/0284—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature containing nitrogen as cationic centre the nitrogen being a ring member of an aromatic ring, e.g. pyridinium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/0277—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature
    • B01J31/0287—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides comprising ionic liquids, as components in catalyst systems or catalysts per se, the ionic liquid compounds being used in the molten state at the respective reaction temperature containing atoms other than nitrogen as cationic centre
    • B01J31/0288—Phosphorus
    • 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
    • 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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2231/00—Catalytic reactions performed with catalysts classified in B01J31/00
    • B01J2231/40—Substitution reactions at carbon centres, e.g. C-C or C-X, i.e. carbon-hetero atom, cross-coupling, C-H activation or ring-opening reactions
    • B01J2231/49—Esterification or transesterification
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E50/00—Technologies for the production of fuel of non-fossil origin
    • Y02E50/10—Biofuels, e.g. bio-diesel
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids

Definitions

  • the present invention relates to a method of producing bio-diesel, and, more specifically, to a method of producing bio-diesel using a stable ionic liquid as both solvent and catalyst.
  • Bio-diesel is the name given to a clean burning alternative fuel produced from domestic, and renewable, resources. Bio-diesel contains no petroleum, but can be blended at any level with petroleum diesel to create a bio-diesel blend. It can be used in compression-ignition (diesel) engines with little or no modifications. Bio-diesel is considered simple to use, biodegradable, non-toxic, and essentially free of sulfur and aromatics.
  • Bio-diesel is defined as mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats. Generally, Bio-diesel is made through transesterification of animal fat, wherein the glycerin is separated from the fatty acid methyl ester. Alternatively, it can be made through the esterification of vegetable oils, wherein the water byproduct is separated from the final fatty acid methyl ester.
  • Bio-diesel must be produced to strict industry specifications (ASTM D6751) in order to ensure proper performance and is the only alternative fuel to have fully completed the health effects testing requirements of the 1990 Clean Air Act Amendments. Bio-diesel that meets ASTM D6751 is registered with the Environmental Protection Agency as a legal motor fuel for sale and distribution.
  • the term "bio-diesel” refers to the pure fuel before blending with diesel fuel. Bio- diesel blends are denoted as, "BXX” with “XX” representing the percentage of bio-diesel contained in the blend (Ze: B20 is 20% bio-diesel, 80% petroleum diesel).
  • Bio-diesel is environmentally friendly as it is made from renewable resources and has lower emissions compared to petroleum diesel. It is also less toxic than table salt and biodegrades as fast as sugar. Many syntheses of bio-diesel are known, typically using acid or base catalysis.
  • the acid catalysed esterification reaction is preferred, as water is the only by-product and this reaction occurs readily.
  • the base catalysed esterification to methyl or ethyl esters usually fails at normal temperatures and pressures, because the catalyst is inactivated by reaction with the carboxylic acid group (Scheme 1).
  • Enzymes have also been used with ionic liquids for vacuum-driven lipase-catalysed direct condensation of L-ascorbic acid and fatty acids in ionic liquids, i.e. synthesis of a natural surface active antioxidant.
  • the Br ⁇ nsted acidic ionic liquid 1-methylimidazolium tetrafluoroborate has also been used for esterification.
  • [BF 4 ] " gives HF which is ultra corrosive, highly toxic and dissolves glass.
  • chymotrypsin-catalysed transesterification in ionic liquids and ionic liquid/supercritical carbon dioxide is also known.
  • Metallic Lewis acids-catalysed acetylation of alcohols with acetic anhydride and acetic acid in ionic liquids is also known.
  • transesterification/acylation reactions mediated by N-heterocyclic carbene catalysts are also known.
  • ionic liquid refers to a liquid that is capable of being produced by melting a solid, and when so produced, consists solely of ions. Ionic liquids may be derived from organic salts.
  • An ionic liquid may be formed from a homogeneous substance comprising one species of cation and one species of anion, or can be composed of more than one species of cation and/or anion.
  • an ionic liquid may be composed of more than one species of cation and one species of anion.
  • An ionic liquid may further be composed of one species of cation, and one or more species of anion.
  • the mixed salts of the invention can comprise mixed salts containing anions and cations.
  • ionic liquid may refer to a homogeneous composition consisting of a single salt (one cationic species and one anionic species) or it may refer to a heterogeneous composition containing more than one species of cation and/or more than one species of anion.
  • a class of ionic liquids which is of special interest is that of salt compositions with melting points below 100 0 C. Such compositions are mixtures of components which are often liquid at temperatures below the individual melting points of the components.
  • base refers to Br ⁇ nsted bases having the ability to react with (neutralise) acids to form salts.
  • the pH range of bases is from 7.0 to 14.0 when dissolved or suspended in water.
  • the term "acid” refers to Br ⁇ nsted acids having the ability to react with (neutralise) bases to form salts.
  • the pH range of acids is from 1.0 to 7.0 when dissolved or suspended in water.
  • the inventors of the present invention have surprisingly found that it is possible to produce bio-diesel using an ionic liquid which is stable to reaction conditions, thereby allowing continued recycling.
  • acid or base functionality can be incorporated into the ionic liquid to allow the ionic liquid to act as a catalyst and/or a solvent.
  • a method of obtaining bio-diesel comprising the step of esterifying or trans-esterifying fatty acids derived from plant or animal in the presence of a stable ionic liquid wherein the ionic liquid acts as both a solvent and a catalyst.
  • the ionic liquid is acidic or basic.
  • the ionic liquid may comprise a basic cation and a neutral anion, or a neutral cation and a basic anion, or both a basic cation and a basic anion, or mixture thereof.
  • the ionic liquid may comprise an acidic cation and a neutral anion, or a neutral cation and an acidic anion, or both an acidic cation and an acidic anion, or mixture thereof.
  • the basic cation preferably has the formula:
  • Cat* is a cation ic species comprising or consisting of ammonium, phosphonium, pyrazolium, DBU or DBN;
  • Z is a covalent bond joining Cat * and Bas or 1 , 2 or 3 aliphatic linking groups each containing 1 to 10 carbon atoms and each optionally one, two or three oxygen atoms;
  • Bas is a basic moiety.
  • Bas preferably comprises at least one nitrogen, phosphorus, sulphur, oxygen or boron atom.
  • Bas comprises at least one primary, secondary or tertiary amino group.
  • Bas is selected from -N(RO(R 2 ), and -P(Ri)(R 2 ); and wherein Ri and R 2 can be the same or different and are each selected from hydrogen, linear or branched alkyl, cycloalkyl, aryl and substituted aryl.
  • R 1 and R 2 are preferably each selected from hydrogen, methyl, ethyl, /so-propyl, butyl, seo-butyl, /so-butyl, pentyl, hexyl, cyclohexyl, benzyl and phenyl.
  • Bas is selected from -N(CH 3 )2 and -N(CH(CH 3 )2) 2 .
  • Z may be selected from linear or branched Ci to Ci 8 alkanediyl, substituted alkanediyl, dialkanylether and dialkanylketone.
  • Z is selected from -(CH 2 -CH 2 )-, -(CH 2 -CH 2 -CH 2 )-, -(CH 2 -CH 2 -CH 2 -CH 2 )-,-(CH 2 -CH2-CH 2 -CH 2 -CH 2 )-,-(CH 2 -CH2-CH 2 -CH 2 -CH 2 -CH 2 )-, -(CH 2 -CH 2 -O-CH 2 -CH 2 )- and -(CH 2 -CH 2 -O-CH 2 -CH 2 -CH 2 )-.
  • Cat + -Z-Bas may be selected from:
  • Bas and Z are as defined above;
  • R b , R c , and R d can be the same or different, and are each independently selected from hydrogen, a C 1 to C 40 , straight chain or branched alkyl group, a C 3 to C 8 cycloalkyl group, or a C 6 to Cio aryl group, wherein said alkyl, cycloalkyl or aryl groups are either unsubstituted or may be substituted by one to three groups selected from: C 1 to Ce alkoxy, Ce to C 10 aryl, CN, OH, NO 2 , C 7 to C 30 aralkyl and C 7 to C 30 alkaryl.
  • Cat + -Z-Bas is selected from:
  • Caf-Z-Bas is selected from:
  • Cat+ may also comprise or consist of 1 , 3, 5-trialkyl pyrazolium, 1 , 2- dialkylpyrazolium, and 1, 2, 3, 5-tetraalkylpyrazolium.
  • Cat + -Z-Bas is selected from:
  • Caf-Z-Bas may be selected from:
  • Cat + -Z-Bas may also be:
  • Bas, Z and R b are as defined above.
  • the basic anion has the formula [X b ] ' , and may be selected from [F] “ , [OH] ' , [OR] “ , [R-CO 2 ] “ , [PO 4 ] 3" and [SO 4 ] 2" , wherein
  • [X 1 J is [OH] " .
  • the acidic cation preferably has the formula:
  • Cat + is a cationic species
  • Z is a covalent bond joining Cat + and Acid containing 1 to 10 carbon atoms and each optionally one, two or three oxygen atoms;
  • Acid is an acidic moiety. Acid is preferably selected from -SO 3 H, -CO 2 H, -SO 3 -Ph-R 1 -SO 3 R, RP0(0H)2 and R 2 PO(OH); wherein R is, for example, C 1 to C 6 alkyl.
  • [Cat + ] may comprise or consist of a heterocyclic ring structure selected from imidazolium, pyridini ⁇ m, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphospholium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, oxazolium, isooxazolium, isotriazolium, tetrazolium, benzofuranium, dibenzofuranium, benzothiophenium, dibenzothiophenium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholinium
  • [Caf] may comprise or consist of a heterocyclic ring structure selected from pyridinium, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphospholium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, oxazolium, isooxazolium, isotriazolium, tetrazolium, benzofuranium, dibenzofuranium, benzothiophenium, dibenzothiophenium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholinium, pyranium
  • [Caf] may comprise or consist of a heterocyclic ring structure selected from pyrazolium, isothiazolinium, tetrazolium, piperidinium, morpholinium and pyrrolidinium.
  • Cat + -Z-Acid is selected from:
  • Acid and Z are as defined above;
  • R b , R c , R d , R e , R f , R g and R h can be the same or different, and are each independently selected from hydrogen, a Ci to C 4 O 1 straight chain or branched alkyl group, a C 3 to C 8 cycloalkyl group, or a C 6 to Ci 0 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C 6 alkoxy, C 6 to C 10 aryl, CN, OH, NO 2 , C 7 to C 30 aralkyl and C 7 to C 30 alkaryl, or any two of R b , R c , R d , R e and R f attached to adjacent carbon atoms form a methylene chain -(CH2) q - wherein q is from 8 to 20.
  • Cat + -Z-Acid is selected from:-
  • Acid and Z are as defined above;
  • R b , R c , R d , R e , R f , R 3 and R h can be the same or different, and are each independently selected from hydrogen, a Ci to C 4O , straight chain or branched alkyl group, a C 3 to Cs cycloalkyl group, or a C 6 to Ci 0 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C 6 alkoxy, C 6 to C 10 aryl, CN, OH, NO 2 , C 7 to C 30 aralkyl and C 7 to C 3O alkaryl, or any two of R b , R c , R d , R e and R f attached to adjacent carbon atoms form a methylene chain -(CH2) q - wherein q is from 8 to 20.
  • Cat + -Z-Acid is:
  • [X 3 ]- is selected from [HF 2 ] “ , [HSO 4 ] “ and [H 2 PO 4 ] “ .
  • the neutral cation may comprise or consist of ammonium, phosphonium, pyrazolium, DBU or DBN.
  • the neutral cation is selected from:
  • R a , R b , R c , and R d can be the same or different, and are each independently selected from hydrogen, a C 1 to C 40 , straight chain or branched alkyl group, a C 3 to C 8 cycloalkyl group, or a C 6 to Cio aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C 6 alkoxy, C 6 to Cio aryl, CN, OH, NO 2 , C 7 to C 3 o aralkyl and C 7 to C 30 alkaryl. More preferably, the neutral cation is selected from:
  • R a is as defined above.
  • the neutral cation is selected from:
  • the neutral cation may also comprise or consist of 1, 3, 5-trialkyl pyrazolium, 1 , 2-dialkylpyrazolium, or 1, 2, 3, 5-tetraalkylpyrazolium.
  • the neutral cation is selected from:
  • neutral cation may be selected from:
  • R a , R b , R c , R d are a Ci to C 40 , straight or branched, alkyl group
  • the neutral cation may comprise or consist of a heterocyclic ring structure selected from imidazolium, pyridinium, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphospholium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, oxazolium, isooxazolium, isotriazolium, tetrazolium, benzof uranium, dibenzofurariium, benzothiophenium, dibenzothiophenium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperaz
  • the neutral cation preferably comprises or consists of a heterocyclic ring structure selected from pyridinium, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphosphoiium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, oxazolium, isooxazolium, isotriazolium, tetrazol ⁇ um, benzofuranium, dibenzofuranium, benzothiophenium, dibenzothiophenium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidin
  • the neutral cation comprises or consists of a heterocyclic ring structure selected from pyridinium, pyrazolium, thiazolium, pyrimidinium, piperazinium, piperidinium, morpholinium, quinolinium, isoquinolinium and pyrrolidinium.
  • the neutral cation is selected from:-
  • R a , R b , R G , R d , R e , R f , R g and R h can be the same or different, and are each independently selected from hydrogen, a Ci to C 40 , straight chain or branched alkyl group, a C 3 to Ce cycloalkyl group, or a Ce to C 10 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C 6 alkoxy, C 6 to C 10 aryl, CN, OH, NO 2 , C 7 to C30 aralkyl and C 7 to C 30 alkaryl, or any two of Fc b, D Rc , R d , R e and R f attached to adjacent carbon atoms form a methylene chain -(CH 2 ) q - wherein q is from 8 to 20.
  • the neutral cation is selected from:
  • R a , R b , R c , R d , R e , R f , R 9 and R h are as defined above.
  • the neutral anion may be a sulfonate, phoshinate, triflamide (amide), triflate, dicyanamide, oxide (phenoxide) or halide anionic species.
  • the neutral anion is selected from [C(CN) 3 ] “ , [NTf 2 ] “ , ⁇ OTf] * , [R-SO 3 ] “ , [R 2 PO 2 ] “ , [Cl] “ , [Br] ' and [I] “ ; wherein R is Ci to C 6 alkyl, or Ci to C 6 aryl.
  • the neutral anion may also be selected from [Me-SO 3 ] ' , [Ph-SO 3 ] “ and [Me-Ph-SO 3 ] " .
  • the plant fatty acid may be derived from vegetables or cereal, for example, rape-seed oil, canola oil or prioline.
  • the ionic liquid will dissolve in solvents (reagents) such as methanol, water or ethanol, and remain separate from the bio-diesel phase. This allows the biodiesel to be easily separated from the ionic liquid, and the ionic liquid phase can then be recycled.
  • solvents such as methanol, water or ethanol
  • Figure 2 is a picture showing a separate methyl oleate (upper layer) product layer, wherein the left tube is before reaction (methanol/glycerol/[MIBS][OTfj, and the right after reaction;
  • Figure 3 is a proton NMR of Run 12 (54% conversion to methyl oleate) showing the glycerol ester peaks at 4.25 and 4.15 and the methyl oleate peak at 3.63 ppm;
  • Figure 4 is a proton NMR of Run 1 (99% conversion to methyl oleate) showing the methyl oleate peak at 3.63 ppm and no glycerol ester peaks or ionic liquid peaks;
  • Figure 5 is a proton NMR of Run 1 showing the methanol layer.
  • the ionic liquids used in the present invention may be produced using known means, or, for example, using reactions as or similar to those described below.
  • a range of dimethylethanolamine salts and ionic liquids can be synthesised from dimethylethanolamine and alkyl halides, followed by exchange of the halide ion for other anions.
  • These ionic liquids are useful because dimethylethanolamine is cheap, stable, and the oxygen functionality lowers the melting point of these ammonium salts compared with similar tefra-alkylammonium salts.
  • This material is a room temperature ionic liquid.
  • the product in the first step of Scheme 2 can be alkylated with a different alkyl halide. This is shown in Scheme 3, below.
  • Ethyl DABCO methanesulfonate [C 2 DABCO][OSO 2 CH 3 ] (mp 81 °C) and hexyl DABCO methanesulfonate have also been synthesised from the reaction of DABCO and ethylmethanesulfonate or hexylmethanesulfonate.
  • Diazobicyclo-[2,2,0]-octene (1.13g, 12.5 mmol) and alkyl bromide (10 mmol) were heated under reflux (or at 150 0 C which ever is the lower) for 1 to 24 hours. On cooling a precititate formed. This was dissolved in a minimum quantity of boiling ethyl acetate/isopropanol for C 2 to Cio DABCO bromides and boiling toluene/ethyl acetate for C 12 to Ci 8 DABCO bromides. The crystals that formed on cooling were filtered off and dried by heating at 80 0 C for 4 hours under vacuum (1 mmHg). The compounds were analysed by NMR and DSC. Yields typically 60- 80%
  • Diazobicyclo-[2,2,0]-octene (1.13 g, 12.5 mmol) and alkyl methanesulfonate (10 mmol) were heated at 10O 0 C for 1 hour. On cooling a precititate formed. This was dissolved in a minimum quantity boiling ethyl acetate / isopropanol. The crystals that formed on cooling were filtered off and dried by heating at 80 0 C for 4 hours under vacuum (1 mmHg). The compounds were analysed by NMR and DSC. Yields typically 70-80%
  • Tetramethylethylenediamine (TMEDA) ionic liquids can be synthesised from TMEDA and an alkyl bromide as beiow.
  • the C 2 , C 5 , C 6 , C 8 , C 12 and Ci 8 alkyl bromides have been made and appear slightly lower melting than the DABCO ionic liquids.
  • TMEDA Tetramethylethylenediamine
  • alkyl bromide 25 mmol
  • [C 2 TMEDA]Br and [C 4 TMEDA]Br a crystalline solid formed and for [Ci ⁇ TMEDA]Br, a liquid crystalline material formed.
  • DMAP dimethylaminopyidine
  • DMAP Dimethylaminopyridine
  • ethyl or hexyl methanesulfonate 25 mmol
  • ethyl or hexyl methanesulfonate 25 mmol
  • ethyl or hexyl methanesulfonate 25 mmol
  • a precititate formed. This was dissolved in a minimum quantity boiling ethyl acetate / isopropanol for C 2 to C 6 DMAP methanesulfonates.
  • the crystals that formed on cooling were filtered off and dried by heat at 8O 0 C for 4 hours under vacuum (1 mmHg).
  • the compounds were analysed by NMR and DSC. Yields typically 80- 85%.
  • the 1-chloro-2-(diisopropylamino)ethane hydrochloride was used to alkylate dimethylaminoethanol, the resulting diamine was alkylated with propyl bromide.
  • the quaternisation reaction itself is regiospecific, the diisopropylamino group is non-nucleophilic and cannot be quaternised under the applied conditions.
  • the obtained salt shows a five atom chain between the cation and the basic diisopropylamino group.
  • the metathesis reaction with lithium bistriflimide gave a room temperature ionic liquid. Its structure is shown below.
  • the above scheme shows a synthesis of a range of basic ionic liquids, for example, bearing a 5-atom spacer between the quaternary nitrogen and the basic nitrogen.
  • the general synthetic strategy for the preparation of BIL 1-4 is simple and versatile and is shown in the Scheme above.
  • a vital part of the synthesis of the base-tethered ionic liquids involves the use of 2-diisopropylaminoethyl chloride reacting with a chosen nucleophilic reagent and is facilitated by the neighbouring group participation from the diisopropylamino moiety.
  • the synthetic strategy for the preparation of BIL 1, 2 and 4 takes into account the ability to selectively quaternise the pendant amino, imidazolyl or pyridyl groups as against the diisopropylalkylamino group which is non-nucleophilic in nature.
  • the synthetic strategy for the preparation of BIL 3 makes use of the insolubility of the mono- quatemised diamine which precipitates out of toluene (solvent) thereby preventing it from further reaction with the alkyl halide.
  • the halide anion associated with the quaternary ammonium salts was subjected to metathesis with lithium bis-triflimide to generate base tethered ionic liquids BIL 1-4.
  • the esterification reaction (Reaction 1) is an equilibrium reaction driven to completion by using an excess of methanol. As can be seen, water is the only byproduct.
  • the advantage of this method is that the ionic liquid/water methanol mixture obtained at the end of the reaction is immiscible with the FAME product and forms a separate phase (Reaction 1b).
  • the bio-diesel is isolated by phase separation.
  • Another advantage of this reaction is that the reaction occurs at room temperature and hence no energy input is required in this step.
  • Reaction 1b The phase behaviour change during Reaction 1a.
  • the catalysts (1) and (4) ⁇ 4-(3-methylimidazolium)butanesulfonic acid bistrifluoromethanesulfonylamide and 4-(3-methylimidazolium)butanesulfonic acid trifluoromethanesulfonate ⁇ catalyse the reaction well at 120 0 C (Table 3).
  • This reaction was performed in the microwave over and under pressure to stop the methanol form evaporating.
  • p-TSA conventional acid para-toluenesulfonic acid
  • the ionic liquids have the advantage that they are not volatile and remain in the methanol/glycerol layer.
  • the acid catalysts (2) and (3) are less effective and require higher reaction temperatures to catalyse the reaction. Hence this reaction provides a method for measuring the acidity of these new acidic ionic liquids.
  • Animal fat (lard - a triglyceride of mostly oleic acid) (1.Og), methanol (2.Og) and catalyst (0.25g) (unless otherwise stated) (selected from (1) to (7) above) was placed in a microwave tube with a magnetic stirrer flea and heated to the desired temperature for the desired time (See Tables 3, 4 and 5) for conditions. This was cooled to room temperature and the two layers were analysed by NMR (CDCb for fat layer and CD 3 OD for methanol layer). The yield was determined by comparing the integration of the -CH2- group in the glyceride with the OCH 3 group in the methyl ester of methyl oleate (bio-diesel) (see Figures 3 to 5).
  • Rape seed oil (1.O g), methanol (2.5, 5.0 or 1O.0 fold excess) and catalyst ([emim][HS0 4 ]) (1.0 mol %, 2.5 mol % or 5.0 mol %) was placed in a glass tube with a magnetic stirrer flea. This was stirrer at room temperature (20 0 C) and the samples were analyses by GC after 2hours, 4 hours and 144 hours (this was assumed to be long enough for equilibrium to be established) (See Tables 1 and 2; Reaction 1b; and Figure 1 for conditions). The two layers were also analysed by NMR (CDCI 3 for fat layer and (CD 3 OD for methanol layer). The yield was determined by comparing the integration of the -CH 2 - group in the glyceride with the OCH 3 group in the methyl ester of methyl oleate (bio-diesel).
  • transesterification For the acid catalysed transesterification of animal fat with methanol, higher reaction temperatures are needed (typically 90 to 160 0 C).
  • the transesterification can be carried out with an acidic or basic ionic liquid, with the acidic ionic liquids giving better results.

Abstract

Use of ionic liquids in the production of bio-diesel, wherein the ionic liquid is both a solvent and catalyst, and is stable under reaction conditions.

Description

Production of Bio-diesel
The present invention relates to a method of producing bio-diesel, and, more specifically, to a method of producing bio-diesel using a stable ionic liquid as both solvent and catalyst.
Bio-diesel is the name given to a clean burning alternative fuel produced from domestic, and renewable, resources. Bio-diesel contains no petroleum, but can be blended at any level with petroleum diesel to create a bio-diesel blend. It can be used in compression-ignition (diesel) engines with little or no modifications. Bio-diesel is considered simple to use, biodegradable, non-toxic, and essentially free of sulfur and aromatics.
Bio-diesel is defined as mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats. Generally, Bio-diesel is made through transesterification of animal fat, wherein the glycerin is separated from the fatty acid methyl ester. Alternatively, it can be made through the esterification of vegetable oils, wherein the water byproduct is separated from the final fatty acid methyl ester.
Bio-diesel must be produced to strict industry specifications (ASTM D6751) in order to ensure proper performance and is the only alternative fuel to have fully completed the health effects testing requirements of the 1990 Clean Air Act Amendments. Bio-diesel that meets ASTM D6751 is registered with the Environmental Protection Agency as a legal motor fuel for sale and distribution. The term "bio-diesel" refers to the pure fuel before blending with diesel fuel. Bio- diesel blends are denoted as, "BXX" with "XX" representing the percentage of bio-diesel contained in the blend (Ze: B20 is 20% bio-diesel, 80% petroleum diesel).
Bio-diesel is environmentally friendly as it is made from renewable resources and has lower emissions compared to petroleum diesel. It is also less toxic than table salt and biodegrades as fast as sugar. Many syntheses of bio-diesel are known, typically using acid or base catalysis.
Figure imgf000003_0001
Add cata
Figure imgf000003_0002
Figure imgf000003_0003
\. Base catalyst
Figure imgf000003_0004
Scheme 1, The acid and base catalysed esterification of fatty acids.
For fatty acids (vegetable oil), the acid catalysed esterification reaction is preferred, as water is the only by-product and this reaction occurs readily. The base catalysed esterification to methyl or ethyl esters usually fails at normal temperatures and pressures, because the catalyst is inactivated by reaction with the carboxylic acid group (Scheme 1).
For fatty esters (animal fats - usually the glycerol ester), both the acid and base catalysed trans-esterification reaction occurs readily. The base catalysed transesterification to methyl or ethyl esters usually requires slightly higher reaction temperatures and pressures, because this is a slower reaction (Scheme
2).
Figure imgf000003_0005
Scheme 2, The acid and base catalysed transesterification of triglycerides, the major constituent of animal fat. Esterification of various organic acids with C4-Ci8 alcohols using 1 -octyl-3-methyIimidazolium tetrafluoroborate-para-toluenesulfonic acid ([OMIM][BF4J-PTSA), without organic solvent, has been carried out but required excessive heating or microwave irradiation to activate the reaction. Catalysed esterifications at room temperature, using ionic liquids are also known, but a catalyst must be present. However, this only applies to short chain acids (less than 10 carbon atoms) and in no way has been carried out with plant or animal derived fatty acids or esters. (Fraga-Dubreuil, J., Bourahala, K., Rahmouni, M., Bazureau, J. P., Hamelin, J., Catalysis Communication, 2002, 3, 185-190).
Enzymes have also been used with ionic liquids for vacuum-driven lipase-catalysed direct condensation of L-ascorbic acid and fatty acids in ionic liquids, i.e. synthesis of a natural surface active antioxidant. The Brδnsted acidic ionic liquid 1-methylimidazolium tetrafluoroborate has also been used for esterification. However, under acidic conditions, [BF4]" gives HF which is ultra corrosive, highly toxic and dissolves glass.
Also known is chymotrypsin-catalysed transesterification in ionic liquids and ionic liquid/supercritical carbon dioxide; Metallic Lewis acids-catalysed acetylation of alcohols with acetic anhydride and acetic acid in ionic liquids; transesterification/acylation reactions mediated by N-heterocyclic carbene catalysts, and, Lipase-catalysed transesterification in ionic liquids and organic solvents.
[BF4] and [PFe] ionic liquids are not stable, and imidazolium ionic liquids are not base stable.
The term "ionic liquid" as used herein refers to a liquid that is capable of being produced by melting a solid, and when so produced, consists solely of ions. Ionic liquids may be derived from organic salts.
An ionic liquid may be formed from a homogeneous substance comprising one species of cation and one species of anion, or can be composed of more than one species of cation and/or anion. Thus, an ionic liquid may be composed of more than one species of cation and one species of anion. An ionic liquid may further be composed of one species of cation, and one or more species of anion. Thus the mixed salts of the invention can comprise mixed salts containing anions and cations.
Thus, in summary, the term "ionic liquid" as used herein may refer to a homogeneous composition consisting of a single salt (one cationic species and one anionic species) or it may refer to a heterogeneous composition containing more than one species of cation and/or more than one species of anion.
A class of ionic liquids which is of special interest is that of salt compositions with melting points below 1000C. Such compositions are mixtures of components which are often liquid at temperatures below the individual melting points of the components.
The term "base" refers to Brδnsted bases having the ability to react with (neutralise) acids to form salts. The pH range of bases is from 7.0 to 14.0 when dissolved or suspended in water.
The term "acid" refers to Brδnsted acids having the ability to react with (neutralise) bases to form salts. The pH range of acids is from 1.0 to 7.0 when dissolved or suspended in water.
The inventors of the present invention have surprisingly found that it is possible to produce bio-diesel using an ionic liquid which is stable to reaction conditions, thereby allowing continued recycling.
Further, the inventors have surprisingly found that acid or base functionality can be incorporated into the ionic liquid to allow the ionic liquid to act as a catalyst and/or a solvent.
In accordance with the present invention, there is provided a method of obtaining bio-diesel comprising the step of esterifying or trans-esterifying fatty acids derived from plant or animal in the presence of a stable ionic liquid wherein the ionic liquid acts as both a solvent and a catalyst. Preferably, the ionic liquid is acidic or basic.
Where the ionic liquid is basic, it may comprise a basic cation and a neutral anion, or a neutral cation and a basic anion, or both a basic cation and a basic anion, or mixture thereof.
Where the ionic liquid is acidic, it may comprise an acidic cation and a neutral anion, or a neutral cation and an acidic anion, or both an acidic cation and an acidic anion, or mixture thereof.
The basic cation preferably has the formula:
[Cat+-Z-Bas]
wherein: Cat* is a cation ic species comprising or consisting of ammonium, phosphonium, pyrazolium, DBU or DBN;
Z is a covalent bond joining Cat* and Bas or 1 , 2 or 3 aliphatic linking groups each containing 1 to 10 carbon atoms and each optionally one, two or three oxygen atoms; and
Bas is a basic moiety.
Bas preferably comprises at least one nitrogen, phosphorus, sulphur, oxygen or boron atom.
More preferably, Bas comprises at least one primary, secondary or tertiary amino group.
Still more preferably, Bas is selected from -N(RO(R2), and -P(Ri)(R2); and wherein Ri and R2 can be the same or different and are each selected from hydrogen, linear or branched alkyl, cycloalkyl, aryl and substituted aryl. R1 and R2, are preferably each selected from hydrogen, methyl, ethyl, /so-propyl, butyl, seo-butyl, /so-butyl, pentyl, hexyl, cyclohexyl, benzyl and phenyl.
More preferably, Bas is selected from -N(CH3)2 and -N(CH(CH3)2)2.
Z may be selected from linear or branched Ci to Ci8 alkanediyl, substituted alkanediyl, dialkanylether and dialkanylketone.
Preferably, Z is selected from -(CH2-CH2)-, -(CH2-CH2-CH2)-, -(CH2-CH2-CH2-CH2)-,-(CH2-CH2-CH2-CH2-CH2)-,-(CH2-CH2-CH2-CH2-CH2-CH2)-, -(CH2-CH2-O-CH2-CH2)- and -(CH2-CH2-O-CH2-CH2-CH2)-.
In accordance with the present invention, Cat+-Z-Bas may be selected from:
[N(Z-Bas)(Rb)(Rc)(Rd)]+ and [P(Z-Bas)(Rb)(Rc)(Rd)]+
wherein: Bas and Z are as defined above; and
Rb, Rc, and Rd can be the same or different, and are each independently selected from hydrogen, a C1 to C40, straight chain or branched alkyl group, a C3 to C8 cycloalkyl group, or a C6 to Cio aryl group, wherein said alkyl, cycloalkyl or aryl groups are either unsubstituted or may be substituted by one to three groups selected from: C1 to Ce alkoxy, Ce to C10 aryl, CN, OH, NO2, C7 to C30 aralkyl and C7 to C30 alkaryl.
Preferably, Cat+-Z-Bas is selected from:
Figure imgf000008_0001
wherein: Z, Bas and R are as defined above.
More preferably, Caf-Z-Bas is selected from:
Figure imgf000008_0002
Cat+ may also comprise or consist of 1 , 3, 5-trialkyl pyrazolium, 1 , 2- dialkylpyrazolium, and 1, 2, 3, 5-tetraalkylpyrazolium. Preferably, Cat+-Z-Bas is selected from:
Figure imgf000008_0003
wherein: Z and Bas are as defined above. Still further, Caf-Z-Bas may be selected from:
Figure imgf000009_0001
Preferably, Cat+-Z-Bas may also be:
Figure imgf000009_0002
wherein: Bas, Z and Rb are as defined above.
In accordance with the present invention, the basic anion has the formula [Xb]', and may be selected from [F]", [OH]', [OR]", [R-CO2]", [PO4]3" and [SO4]2", wherein
Figure imgf000009_0003
Preferably, [X1J is [OH]".
Further in accordance with the present invention, the acidic cation preferably has the formula:
[Cat+-Z-Acid]
wherein: Cat+ is a cationic species;
Z is a covalent bond joining Cat+ and Acid containing 1 to 10 carbon atoms and each optionally one, two or three oxygen atoms; and
Acid is an acidic moiety. Acid is preferably selected from -SO3H, -CO2H, -SO3-Ph-R1 -SO3R, RP0(0H)2 and R2PO(OH); wherein R is, for example, C1 to C6 alkyl.
[Cat+] may comprise or consist of a heterocyclic ring structure selected from imidazolium, pyridiniυm, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphospholium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, oxazolium, isooxazolium, isotriazolium, tetrazolium, benzofuranium, dibenzofuranium, benzothiophenium, dibenzothiophenium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholinium, pyranium, annolinium, phthalazinium, quinazolinium, quinazalinium, quinolinium, isoquinolinium, thazinium, oxazinium, azaannulenium and pyrrolidinium.
Preferably, [Caf] may comprise or consist of a heterocyclic ring structure selected from pyridinium, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphospholium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, oxazolium, isooxazolium, isotriazolium, tetrazolium, benzofuranium, dibenzofuranium, benzothiophenium, dibenzothiophenium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholinium, pyranium, annolinium, phthalazinium, quinazolinium, quinazalinium, quinolinium, isoquinolinium, thazinium, oxazinium, azaannulenium and pyrrolidinium
More preferably, [Caf] may comprise or consist of a heterocyclic ring structure selected from pyrazolium, isothiazolinium, tetrazolium, piperidinium, morpholinium and pyrrolidinium. Preferably, Cat+-Z-Acid is selected from:
Figure imgf000011_0001
Figure imgf000011_0002
and
Figure imgf000012_0001
wherein: Acid and Z are as defined above; and
Rb, Rc, Rd, Re, Rf, Rg and Rh can be the same or different, and are each independently selected from hydrogen, a Ci to C4O1 straight chain or branched alkyl group, a C3 to C8 cycloalkyl group, or a C6 to Ci0 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C6 alkoxy, C6 to C10 aryl, CN, OH, NO2, C7 to C30 aralkyl and C7 to C30 alkaryl, or any two of Rb, Rc, Rd, Re and Rf attached to adjacent carbon atoms form a methylene chain -(CH2)q- wherein q is from 8 to 20.
More preferably, Cat+-Z-Acid is selected from:-
Figure imgf000012_0002
Figure imgf000013_0001
wherein: Acid and Z are as defined above; and
Rb, Rc, Rd, Re, Rf, R3 and Rh can be the same or different, and are each independently selected from hydrogen, a Ci to C4O, straight chain or branched alkyl group, a C3 to Cs cycloalkyl group, or a C6 to Ci0 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C6 alkoxy, C6 to C10 aryl, CN, OH, NO2, C7 to C30 aralkyl and C7 to C3O alkaryl, or any two of Rb, Rc, Rd, Re and Rf attached to adjacent carbon atoms form a methylene chain -(CH2)q- wherein q is from 8 to 20.
Most preferably, Cat+-Z-Acid is:
Figure imgf000014_0001
In accordance with the present invention, the acidic anion has the formula [Xa]~, and is selected from [HSO4]Y [H2PO4]", [HPO4]2", [HCI2]" and [HX2]"; wherein X = F1 Cl, Br or I.
Preferably, [X3]- is selected from [HF2]", [HSO4]" and [H2PO4]".
Where the ionic liquid comprises a basic anion, the neutral cation may comprise or consist of ammonium, phosphonium, pyrazolium, DBU or DBN.
Preferably, the neutral cation is selected from:
[N(Ra)(Rb)(Rc)(Rd)]+ and [P(Ra)(Rb)(R°)(Rd)]+
wherein: Ra, Rb, Rc, and Rd can be the same or different, and are each independently selected from hydrogen, a C1 to C40, straight chain or branched alkyl group, a C3 to C8 cycloalkyl group, or a C6 to Cio aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C6 alkoxy, C6 to Cio aryl, CN, OH, NO2, C7 to C3o aralkyl and C7 to C30 alkaryl. More preferably, the neutral cation is selected from:
Figure imgf000015_0001
wherein: Ra is as defined above.
Still more preferably, the neutral cation is selected from:
Figure imgf000015_0002
Figure imgf000015_0003
The neutral cation may also comprise or consist of 1, 3, 5-trialkyl pyrazolium, 1 , 2-dialkylpyrazolium, or 1, 2, 3, 5-tetraalkylpyrazolium. Preferably, the neutral cation is selected from:
Figure imgf000016_0001
Still further, the neutral cation may be selected from:
Figure imgf000016_0002
wherein: Ra, Rb, Rc, Rd are a Ci to C40, straight or branched, alkyl group
Where the ionic liquid comprises an acidic anion, the neutral cation may comprise or consist of a heterocyclic ring structure selected from imidazolium, pyridinium, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphospholium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, oxazolium, isooxazolium, isotriazolium, tetrazolium, benzof uranium, dibenzofurariium, benzothiophenium, dibenzothiophenium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholinium, pyranium, annolinium, phthalazinium, quinazolinium, quinazalinium, quinolinium, isoquinolinium, thazinium, oxazinium, azaannulenium and pyrrolidinium.
Preferably, where the anion is acidic, the neutral cation preferably comprises or consists of a heterocyclic ring structure selected from pyridinium, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphosphoiium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, oxazolium, isooxazolium, isotriazolium, tetrazolϊum, benzofuranium, dibenzofuranium, benzothiophenium, dibenzothiophenium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholinium, pyranium, annolinium, phthalazinium, quinazolinium, quinazalinium, quinolinium, isoquinolinium, thazinium, oxazinium, azaannulenium and pyrrolidinium.
More preferably, the neutral cation comprises or consists of a heterocyclic ring structure selected from pyridinium, pyrazolium, thiazolium, pyrimidinium, piperazinium, piperidinium, morpholinium, quinolinium, isoquinolinium and pyrrolidinium.
Preferably the neutral cation is selected from:-
Figure imgf000017_0001
Figure imgf000018_0001
Figure imgf000018_0002
and
Figure imgf000018_0003
wherein: Ra, Rb, RG, Rd, Re, Rf, Rg and Rh can be the same or different, and are each independently selected from hydrogen, a Ci to C40, straight chain or branched alkyl group, a C3 to Ce cycloalkyl group, or a Ce to C10 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C6 alkoxy, C6 to C10 aryl, CN, OH, NO2, C7 to C30 aralkyl and C7 to C30 alkaryl, or any two of Fc b, D Rc , Rd, Re and Rf attached to adjacent carbon atoms form a methylene chain -(CH2)q- wherein q is from 8 to 20.
More preferably, the neutral cation is selected from:
Figure imgf000019_0001
Figure imgf000020_0001
wherein: Ra, Rb, Rc, Rd, Re, Rf, R9 and Rh are as defined above.
Where the ionic liquid comprises a basic cation or an acidic cation, the neutral anion may be a sulfonate, phoshinate, triflamide (amide), triflate, dicyanamide, oxide (phenoxide) or halide anionic species.
Preferably, the neutral anion is selected from [C(CN)3]", [NTf2]", {OTf]*, [R-SO3]", [R2PO2]", [Cl]", [Br]' and [I]"; wherein R is Ci to C6 alkyl, or Ci to C6 aryl.
The neutral anion may also be selected from [Me-SO3]', [Ph-SO3]" and [Me-Ph-SO3]".
In accordance with any part of the present invention, the plant fatty acid may be derived from vegetables or cereal, for example, rape-seed oil, canola oil or prioline. At the end of the method of the present invention, e.g.:
Fatty acid + alcohol IL ^ Biodiesel + H2O Fatty ester + R-OH U ^, Biodiesel + glycerol
the ionic liquid will dissolve in solvents (reagents) such as methanol, water or ethanol, and remain separate from the bio-diesel phase. This allows the biodiesel to be easily separated from the ionic liquid, and the ionic liquid phase can then be recycled.
The present invention will now be further described by way of examples, and with reference to the figures in which:
Figure 1 is a graph displaying variation of conversion with time for different methanol/catalyst concentrations. (Catalyst = [emim][HS04] and determined by GC analysis);
Figure 2 is a picture showing a separate methyl oleate (upper layer) product layer, wherein the left tube is before reaction (methanol/glycerol/[MIBS][OTfj, and the right after reaction;
Figure 3 is a proton NMR of Run 12 (54% conversion to methyl oleate) showing the glycerol ester peaks at 4.25 and 4.15 and the methyl oleate peak at 3.63 ppm;
Figure 4 is a proton NMR of Run 1 (99% conversion to methyl oleate) showing the methyl oleate peak at 3.63 ppm and no glycerol ester peaks or ionic liquid peaks; and
Figure 5 is a proton NMR of Run 1 showing the methanol layer. The ionic liquids used in the present invention may be produced using known means, or, for example, using reactions as or similar to those described below.
AMMONIUM SALTS
N, N-DIMETHYLETHANOLAMINE IONIC LIQUIDS
Figure imgf000022_0001
N-alkyl-O-alkyl-N,N-dimethyl rø-dimethyl- ethanolammonium ionic liquids ethanolamine or
[N-alkyl-O-alkyl DMEA] [X]" R = H, alkyl. R' = H,alkyl5 X = anion
A range of dimethylethanolamine salts and ionic liquids can be synthesised from dimethylethanolamine and alkyl halides, followed by exchange of the halide ion for other anions. These ionic liquids are useful because dimethylethanolamine is cheap, stable, and the oxygen functionality lowers the melting point of these ammonium salts compared with similar tefra-alkylammonium salts. This material is a room temperature ionic liquid.
Figure imgf000022_0002
Figure imgf000022_0003
Scheme 1. The synthesis of[NC3-0Co DMEA][NTf2J The alkylation of dimethylethanolamine occurs on the nitrogen atom. Di-alkylation . on both the nitrogen and oxygen is observed when at least two moles of alkylating agent are used. Note: a base is also required. Hence a range of mono and dialkyl dimethylethanolamine salts can be synthesised (see Scheme 2).
Figure imgf000023_0001
Scheme 2. The general synthesis of dimethylethanolamine ionic liquids.
If different /V-alkyl and O-alkyl groups are required, the product in the first step of Scheme 2 can be alkylated with a different alkyl halide. This is shown in Scheme 3, below.
Figure imgf000023_0002
Scheme 3. The synthesis of dimethylethanolamine ionic liquids with different N- and O-alkyl groups.
DABCO IONIC LIQUIDS
The reaction of an alkyl halide with excess diazabicyclo[2,2,2]octane give a base stable (and basic) series of ionic liquids.
Figure imgf000023_0003
[CnDabco] Br These mono alkyl DABCO bromides have fairly high melting points, but the hexyl, octyl and decyl DABCO bromides are ionic liquids (m.p. <100°C). The decomposition temperatures are all in the 220-2500C range by DSC. The melting point of the [C6DABCO] bromide ionic liquid (950C) falls to mp = -550C (by DSC) for [C6DABCO][N(SO2CF3^] which forms a gel at this temperature.
Ethyl DABCO methanesulfonate [C2DABCO][OSO2CH3] (mp 81 °C) and hexyl DABCO methanesulfonate have also been synthesised from the reaction of DABCO and ethylmethanesulfonate or hexylmethanesulfonate.
Typical Experimental Procedure
[CnDABCO] [Br]
Diazobicyclo-[2,2,0]-octene (1.13g, 12.5 mmol) and alkyl bromide (10 mmol) were heated under reflux (or at 1500C which ever is the lower) for 1 to 24 hours. On cooling a precititate formed. This was dissolved in a minimum quantity of boiling ethyl acetate/isopropanol for C2 to Cio DABCO bromides and boiling toluene/ethyl acetate for C12 to Ci8 DABCO bromides. The crystals that formed on cooling were filtered off and dried by heating at 800C for 4 hours under vacuum (1 mmHg). The compounds were analysed by NMR and DSC. Yields typically 60- 80%
[CnDABCO][OSO2CH3]
Diazobicyclo-[2,2,0]-octene (1.13 g, 12.5 mmol) and alkyl methanesulfonate (10 mmol) were heated at 10O0C for 1 hour. On cooling a precititate formed. This was dissolved in a minimum quantity boiling ethyl acetate / isopropanol. The crystals that formed on cooling were filtered off and dried by heating at 800C for 4 hours under vacuum (1 mmHg). The compounds were analysed by NMR and DSC. Yields typically 70-80%
[CnDABCO][N(SO2CF3)2]
[C6DABCO]Br (2.75 g, 10.0 mmol) and lithium bistrifluoromethanesulfinimide (3.15 g, 11 mmol) were each dissolved in water (10 cm3). The two solutions were mixed and a dense ionic liquid phase formed. This was extracted with dichloromethane (3 x 10 cm3), dried over Na2SO4, filtered and the solvent evaporated to give a colourless paste, which became liquid at 250C. This paste was dried by heating at 800C for 4 hours under vacuum (1 mmHg). The compounds were analysed by NMR and DSC.
TMEDA SALTS
Tetramethylethylenediamine (TMEDA) ionic liquids can be synthesised from TMEDA and an alkyl bromide as beiow. The C2, C5, C6, C8, C12 and Ci8 alkyl bromides have been made and appear slightly lower melting than the DABCO ionic liquids. [CnTMEDA]Br where N = 5, 6, 8, 10 are room temperature ionic liquids.
Figure imgf000025_0001
The synthesis of TMEDA ionic liquids.
[CnTMEDA]Br
Tetramethylethylenediamine (TMEDA) (2.32 g, 20 mmol) and alkyl bromide (25 mmol) were heated under reflux (or at 1300C which ever is the lower) for 1 hour resulting in a dense phase forming. This was cooled to room temperature. For [C2TMEDA]Br and [C4TMEDA]Br a crystalline solid formed and for [CiβTMEDA]Br, a liquid crystalline material formed. These products were washed with cyclohexane and dried under vacuum (24h at 800C, 1 mmHg). Yields typically 60-80%. PYRAZOLIUM IONIC LIQUIDS
The synthesis of pyrazolium ionic liquids from a pyrazole compound and alkyl iodides is feasible but rather expensive. The main difficulty encountered is that pyrazoles are poor nucleophiles and only react slowly with reactive alkylating agents. Maximum yields are approximately 90% with iodides, 60-80% with bromides and <5% with chlorides.
Figure imgf000026_0001
1-methylpyrazole
Scheme 4. Synthesis of 1-methylpyrazolium ionic liquids.
Figure imgf000026_0002
or thermal heating
Scheme 5. Synthesis of pyrazolium ionic liquids.
A new synthesis of pyrazolium ionic liquids was invented to eliminate decomposition. The approach used involved the reaction of alkyl methanesulfonate salts with pyrazoles, to obtain methanesulfonate ionic liquids. Using this approach, the elimination side reaction was no longer a significant problem. The redesigned synthesis is shown below in Scheme 6. O r M,o ,s Et3N /EtOAc
H3C-S-Cl + HO^ UH(2n+l) ^ CnH(2n+i)OSO2CH3 O
Figure imgf000027_0001
Scheme 6. An alternate synthesis ofpyrazolium ionic liquids.
DMAP SALTS
/V,Λ/-dimethylaminopyidine (DMAP) ionic liquids are synthesised from DMAP and an alkyl methanesulfonate as below.
Figure imgf000027_0002
[CnDMAP] [OMs]
Synthesis of new DMAP ionic liquids.
Dimethylaminopyridine (DMAP) (2.443 g, 20 mmol) and either ethyl or hexyl bromide (25 mmol) were heated under reflux (or at 13O0C which ever is the lowest temperature) for 1 hour. On cooling a precititate formed. This was dissolved in a minimum quantity boiling ethyl acetate / isopropanol for C2 to Ce DMAP bromides. The crystals that formed on cooling were filtered off and dried by heat at 8O0C for 4 hours under vacuum (1 mmHg). The compounds were analysed by NMR and DSC. Yields typically 60-80%.
Dimethylaminopyridine (DMAP) (2.443 g, 20 mmol) and either ethyl or hexyl methanesulfonate (25 mmol) were heated at 1000C for 1 hour. On cooling a precititate formed. This was dissolved in a minimum quantity boiling ethyl acetate / isopropanol for C2 to C6 DMAP methanesulfonates. The crystals that formed on cooling were filtered off and dried by heat at 8O0C for 4 hours under vacuum (1 mmHg). The compounds were analysed by NMR and DSC. Yields typically 80- 85%.
BASICITY
Increasing the distance between the cationic centre and the hindered base increases the basisity of the ionic liquid. This can be achieved by the reaction sequence described below.
Figure imgf000028_0001
Synthesis of an ionic liquid with a longer distance between cation and the basic group
The 1-chloro-2-(diisopropylamino)ethane hydrochloride was used to alkylate dimethylaminoethanol, the resulting diamine was alkylated with propyl bromide. The quaternisation reaction itself is regiospecific, the diisopropylamino group is non-nucleophilic and cannot be quaternised under the applied conditions. The obtained salt shows a five atom chain between the cation and the basic diisopropylamino group. The metathesis reaction with lithium bistriflimide gave a room temperature ionic liquid. Its structure is shown below.
Figure imgf000028_0002
Figure imgf000029_0001
1. C2H5I/ toluene
2. LiNTf,
Figure imgf000029_0002
Figure imgf000029_0003
Figure imgf000029_0004
The above scheme shows a synthesis of a range of basic ionic liquids, for example, bearing a 5-atom spacer between the quaternary nitrogen and the basic nitrogen. The general synthetic strategy for the preparation of BIL 1-4 is simple and versatile and is shown in the Scheme above. A vital part of the synthesis of the base-tethered ionic liquids involves the use of 2-diisopropylaminoethyl chloride reacting with a chosen nucleophilic reagent and is facilitated by the neighbouring group participation from the diisopropylamino moiety. The synthetic strategy for the preparation of BIL 1, 2 and 4 takes into account the ability to selectively quaternise the pendant amino, imidazolyl or pyridyl groups as against the diisopropylalkylamino group which is non-nucleophilic in nature. The synthetic strategy for the preparation of BIL 3 makes use of the insolubility of the mono- quatemised diamine which precipitates out of toluene (solvent) thereby preventing it from further reaction with the alkyl halide. In all cases the halide anion associated with the quaternary ammonium salts was subjected to metathesis with lithium bis-triflimide to generate base tethered ionic liquids BIL 1-4.
Example 1 - Synthesis of Bio-diesel from Fatty Acids
The esterification reaction (Reaction 1) is an equilibrium reaction driven to completion by using an excess of methanol. As can be seen, water is the only byproduct. The advantage of this method is that the ionic liquid/water methanol mixture obtained at the end of the reaction is immiscible with the FAME product and forms a separate phase (Reaction 1b). The bio-diesel is isolated by phase separation. Another advantage of this reaction is that the reaction occurs at room temperature and hence no energy input is required in this step.
Figure imgf000030_0001
FAME + H2O
(Fatty acid methyl ester)
Reaction 1a, The esterification of vegetable oil (Priolene 6927) with [emimJlHSO4]. H2O/H3COH
Vegetable oil [emim][HS04] +
Methanol
+ [emim][HS04] FAME
Reaction 1b, The phase behaviour change during Reaction 1a.
As can be seen in Figure 1 and the table below, the reaction proceeds smoothly to give the expected products. With 1% [emim][HS04] catalyst the equilibrium yields (Table) are close to what you would expect from a statistical analysis of the reaction (60, 80 and 90% yields for 250%, 500% and 1000% CH3OH respectively). Where more catalyst is present, (2.5% and 5%) the final yields are greater than 90% (by NMR). The errors in the integration approximate to plus or minus 3%.
Table 1. Final equilibrium yields (144 hours reaction time, 200C) determined by NMR analysis (Error = ± 3%).
1% emim HSO4] 2.5% emirrfl[HSO4 5% emim HSO4
250 % CH3OH 50 57 61
500 % CH3OH 76 - 81
1000 % CH3OH 90 92 98
Table 2. Composition of the 5% [emim][HS04] catalysed methyl oleate rich phase (by 1H NMR).
Component IΛΠKI IViBS
FAME (Bio-diesel) 48 87
Fatty acid •2 3
Methanol 48 10
[emim][HS04] 0 0 Example 2 - Synthesis of Bio-diesel from Triglycerides
Figure imgf000032_0001
Reaction 2, The animal fat transesterification reaction in ionic liquids
Example 3- Acid Catalysed Transesterifications of Lard (triglycerides)
(i)
(2)
Figure imgf000032_0002
r— OH
-O2C-R (1), (2), (3), (4) or p-TSA
-O2C — R + excess CH3OH 3 H3C-O2 [CC--R + h0H Q2C-R bio-diesel "—OH glycerol
Reaction 3, catalysts used in the acid catalysed transesterification of lard. Table 3, the acid catalysed transesterification of lard after 0.5 hours in microwave . oven lard (1.Og) + 2.Og of methanol and 0.25g of catalyst.
Run Catalyst (0.25g) Temperature / 0C % Yield
1 (D 120 99
2 (2) 140 2
3 (3) 140 30
4 (4) 120 96
5 P-TSA 120 98
As can be seen, the catalysts (1) and (4) {4-(3-methylimidazolium)butanesulfonic acid bistrifluoromethanesulfonylamide and 4-(3-methylimidazolium)butanesulfonic acid trifluoromethanesulfonate} catalyse the reaction well at 1200C (Table 3). This reaction was performed in the microwave over and under pressure to stop the methanol form evaporating. These gave similar results to the conventional acid para-toluenesulfonic acid (p-TSA). The ionic liquids have the advantage that they are not volatile and remain in the methanol/glycerol layer. The acid catalysts (2) and (3) are less effective and require higher reaction temperatures to catalyse the reaction. Hence this reaction provides a method for measuring the acidity of these new acidic ionic liquids.
Table 4, the acid catalysed transesterification of lard after 0.5 hours in microwave oven (0.5 g) with methanol (1.0 g) lard and 0.25 g of catalyst.
Run Catalyst (0.25g) Temperature / 0C % Yield
6 (4) 90 26
7 (4) 100 43
8 (4) 110 61
9 (4) 120 95
10 (4) 140 99
Table 4 shows that the reaction is temperature dependent and at least 1200C is needed to give over the required 95% conversion to meet the bio-diesel specification. The product forms a separate layer on the surface of the methanol/glycerol layer/ionic liquid layer as shown in Figure 2. Example 4 - Base Catalysed Transesterifications of Lard (triglyceride)
Figure imgf000034_0001
|— OH
-O2C-R (l), (2), or(3) I— fϊH
-O2C — R + excess CH3OH 3 H3C-O2C-R + Pυ"
-Q2C-R bio-diesel 0H glycerol
Reaction 4, catalysts used in the base catalysed transesterification of lard after 0.5 hours in microwave oven 1.0 g lard + 2.Og of methanol and 0.25 g of catalyst.
Run Catalyst (0.25g) Temperature / 0C % Yield
11 (5) 100 98
12 (6) 100 54
13 (7) 140 8
14 (7) 150 18
15 (7) 160 32
Reaction conditions for Runs 1-15
Animal fat (lard - a triglyceride of mostly oleic acid) (1.Og), methanol (2.Og) and catalyst (0.25g) (unless otherwise stated) (selected from (1) to (7) above) was placed in a microwave tube with a magnetic stirrer flea and heated to the desired temperature for the desired time (See Tables 3, 4 and 5) for conditions. This was cooled to room temperature and the two layers were analysed by NMR (CDCb for fat layer and CD3OD for methanol layer). The yield was determined by comparing the integration of the -CH2- group in the glyceride with the OCH3 group in the methyl ester of methyl oleate (bio-diesel) (see Figures 3 to 5).
Product isolation: The upper methyl oleate layer was decanted and the dissolved methanol was distilled off by heating to 1200C, or heating to 6O0C at 1 mmHg pressure. The product was found to be free of ionic liquid catalyst. Catalyst recycling: Methanol and water or glycerol were separated from the . catalyst by distillation or vacuum distillation. The catalyst could be then recycled and reused.
Reaction conditions for Runs 16 to 24
Rape seed oil (1.O g), methanol (2.5, 5.0 or 1O.0 fold excess) and catalyst ([emim][HS04]) (1.0 mol %, 2.5 mol % or 5.0 mol %) was placed in a glass tube with a magnetic stirrer flea. This was stirrer at room temperature (20 0C) and the samples were analyses by GC after 2hours, 4 hours and 144 hours (this was assumed to be long enough for equilibrium to be established) (See Tables 1 and 2; Reaction 1b; and Figure 1 for conditions). The two layers were also analysed by NMR (CDCI3 for fat layer and (CD3OD for methanol layer). The yield was determined by comparing the integration of the -CH2- group in the glyceride with the OCH3 group in the methyl ester of methyl oleate (bio-diesel).
Bio-diesel in accordance with European and American regulations, must be composed of 95.6% fatty acid methyl (or ethyl) ethers. Using the ionic liquid process of the present invention, 5 mol % catalyst and 10 fold excess of methanol are required to produce a bio-diesel that meets this specification for the acid ionic liquid catalyst.
For the acid catalysed transesterification of animal fat with methanol, higher reaction temperatures are needed (typically 90 to 160 0C). The transesterification can be carried out with an acidic or basic ionic liquid, with the acidic ionic liquids giving better results.

Claims

1. A method of obtaining Bio-diesel comprising the step of esterifying fatty acids derived from plant or animal in the presence of a stable ionic liquid wherein the ionic liquid is both a solvent and a catalyst.
2. A method according to Claim 1 wherein the ionic liquid is acidic or basic.
3. A method according to Claim 1 or 2, wherein the ionic liquid comprises a basic cation and a neutral anion, or a neutral cation and a basic anion, or both a basic cation and a basic anion.
4. A method according to Claim 1 or 2, wherein the ionic liquid comprises an acidic cation and a neutral anion, or a neutral cation and an acidic anion, or both an acidic cation and an acidic anion.
5. A method according to Claim 3, wherein the basic cation has the formula:
[Cat+-Z-Bas]
wherein: Cat* is a cationic species comprising or consisting of ammonium, phosphonium, pyrazolium, DBU or DBN;
Z is a covalent bond joining Cat4 and Bas or 1 , 2 or 3 aliphatic linking groups each containing 1 to 10 carbon atoms and each optionally one, two or three oxygen atoms; and
Bas is a basic moiety.
6. A method according to Claim 5, wherein Bas comprises at least one nitrogen, phosphorus, sulphur, oxygen or boron atom. 7. A method according to Claim 6, wherein Bas comprises at least one primary, secondary or tertiary amino group.
8. A method according to Claim 5 or Claim 6, wherein Bas is selected from - N(Ri)(R2), and -P(Ri)(Ra); and wherein Ri and R2 can be the same or different and are each selected from hydrogen, linear or branched alkyl, cycloalkyl, aryl and substituted aryl.
9. A method according to Claim 8, wherein Ri and R2 are each selected from hydrogen, methyl, ethyl, /sopropyl, butyl, sec-butyl, /sobutyl, pentyl, hexyl, cyclohexyl, benzyl and phenyl.
10. A method according to Claim 8 or Claim 9, wherein Bas is selected from - N(CHa)2 and -N(CH(CH3)2)2.
11. A method according to any one of Claims 5 to 10, wherein Z is selected from linear or branched C1 to Ci8 alkanediyl, substituted alkanediyl, dialkanylether and dialkanylketone.
12. A method according to Claim 11, wherein Z is selected from -(CH2-CH2)-, -(CH2-CH2-CH2)-, -(CH2-CH2-CH2-CH2)-, -(CH2-CH2-CH2-CH2-CH2)-, -(CH2-CH2-CH2-CH2-CH2-CH2)-, -(CH2-CH2-O-CH2-CH2)- and -(CH2-CH2-O-CH2-CH2-CH2)-.
13. A method according to Claim 5, wherein Cat+-Z-Bas is selected from:
[N(Z-Bas)(Rb)(R°)(Rd)]+ and [P(Z-Bas)(Rb)(Rc)(Rd)]+
wherein: Bas and Z are as defined above; and
Rb, Rc, and Rd can be the same or different, and are each independently selected from hydrogen, a Ci to C4o, straight chain or branched alkyl group, a C3 to C8 cycloalkyl group, or a C6 to Cio aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C6 alkoxy, Ce to C10 aryl, CN, OH, NO2, C7 to C30 aralkyl and C7 to C30 alkaryl.
14. A method according to Claim 5, wherein Cat+-Z-Bas is selected from:
Figure imgf000038_0001
wherein: Z, Bas and R is as defined above.
15. A method according to Claim 14, wherein Cat+-Z-Bas is selected from:
Figure imgf000038_0002
16. A method according to Claim 5, wherein Cat+ comprises or consists of 1,3,5-trialkylpyrazolium, 1,2-dialkylpyrazolium, and 1,2,3,5- tetraalkylpyrazolium. 17. A method according to Claim 16, wherein Cat+-Z-Bas is selected from: '.
Figure imgf000039_0001
18. A method according to Claim 5, wherein Gat+-Z-Bas is selected from:
Figure imgf000039_0002
19. A method according to Claim 5, wherein Cat+-Z-Bas is:
Figure imgf000039_0003
wherein: Bas, Z and R are as defined above.
20. A method according to Claim 3, wherein the basic anion has the formula [Xb]", and may be selected from [F]-, [OH]-, [OR]", [R-CO2]", [PO4]3" and [SO4]2", wherein R is Ci to C6 alkyl.
21. A method according to Claim 20, wherein [Xb]" is [OH]". 2. A method according to Claim 4, wherein the acidic cation has the formula:
[Cat+-Z-Acid]
wherein: Cat* is a cationic species;
Z is a covalent bond joining Cat* and Acid containing 1 to 10 carbon atoms and each optionally one, two or three oxygen atoms; and
Acid is an acidic moiety.
23.A method according to Claim 22, wherein acid is selected from -SO3H, -CO2H, -SO3-PH-R, -SO3R, RPO(OH)2 and R2PO(OH), where R is Ci to Cβ alkyl or Ci to C6 aryl
24. A method according to Claim 22, wherein [Cat+] comprises or consists of a heterocyclic ring structure selected from imidazolium, pyridinium, pyrazolium, thiazoiium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphospholium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, oxazolium, isooxazolium, isotriazblium, tetrazolium, benzofuranium, dibenzofuranium, benzothiophenium, dibenzothiophenium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholinium, pyranium, annolinium, phthalazinium, quinazolinium, quinazalinium, quinolinium, isoquinolinium, thazinium, oxazinium, azaannulenium and pyrrolidinium.
25. A method according to Claim 24, wherein [Cat+] comprises or consists of a heterocyclic ring structure selected from pyrazolium, isothiazolinium, tetrazolium, piperidinium, morpholinium and pyrrolidinium. 6. A method according to Claim 25, wherein Caf-Z-Acid is selected from:-
Figure imgf000041_0001
Figure imgf000041_0002
and
Figure imgf000042_0001
wherein: Acid and Z are as defined above; and
Rb, Rc, Rd, Re, Rf, Rg and Rh can be the same or different, and are each independently selected from hydrogen, a Ci to C40, straight chain or branched alkyl group, a C3 to C8 cycloalkyl group, or a Cβ to C10 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: C1 to Ce alkoxy, C6 to C10 aryl, CN, OH, NO2, C7 to C30 aralkyl and C7 to C30 alkaryl, or any two of Rb, Rc, Rd, Re and Rf attached to adjacent carbon atoms form a methylene chain -(CH2)q- wherein q is from 8 to 20.
27. A method according to Claim 26, wherein Cat+-Z-Acid is:
Figure imgf000042_0002
28. A method according to Claim 4, wherein the acidic anion has the formula [Xa]", and is selected from [HSO4]", [H2PO4]-, [HPO4]2', [HCI2]" and [HX2]', wherein X = F, Cl, Br or I.
29.A method according to Claim 28, wherein [X3]" is selected from [HF2]" [HSO4]" and [H2PO4]-. 30. A method according to Claim 3, wherein the neutral cation comprises or consists of ammonium, phosphonium, pyrazolium, DBU or DBN.
31. A method according to Claim 30, wherein the neutral cation is selected from:
[N(Ra)(Rb)(Rc)(Rd)]+ and
Figure imgf000043_0001
wherein: Ra, Rb, Rc, and Rd can be the same or different, and are each independently selected from hydrogen, a Ci to C40, straight chain or branched alkyl group, a C3 to C8 cycloalkyl group, or a Cβ to C10 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C6 alkoxy, CQ to Ci0 aryl, CN, OH, NO2, C7 to C30 aralkyl and C7 to C30 alkaryl.
32. A method according to Claim 31 , wherein the neutral cation is selected from:
Figure imgf000043_0002
wherein: Ra is as defined above.
3.A method according to Claim 31, wherein the neutral cation is selected from:
Figure imgf000044_0001
34. A method according to Claim 31, wherein the neutral cation comprises or consists of 1, 3, 5-trialkyl pyrazolium, 1, 2-dialkylpyrazolium, or 1, 2, 3, 5 - tetraalkylpyrazolium.
35.A method according to Claim 34, wherein the neutral cation is selected from:
Figure imgf000044_0002
36. A method according to Claim 31, wherein the neutral cation is selected from:
Figure imgf000045_0001
37.A method according to Claim 4, wherein the neutral cation comprises or consists of a heterocyclic ring structure selected from imidazolium, pyridinium, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphospholium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, oxazolium, isooxazolium, isotriazolium, tetrazolium, benzofuranium, dibenzofuranium, benzothiophenium, dibenzothiophenium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholinium, pyranium, annolinium, phthalazinium, quinazolinium, quinazalinium, quinolinium, isoquinolinium, thazinium, oxazinium, azaannulenium and pyrrolidinium.
38. A method according to Claim 36, wherein the neutral cation comprises or consists of a heterocyclic ring structure selected from pyridinium, pyrazolium, thiazolium, pyrimidinium, piperazinium, piperidinium, morpholinium, quinolinium, isoquinolinium and pyrrolidinium.
9.A method according to Claim 38, wherein the neutral cation is selected from:-
Figure imgf000046_0001
Figure imgf000046_0002
Figure imgf000047_0001
and
Figure imgf000047_0002
wherein: Ra, Rb, Rc, Rd, Re, Rf, R9 and Rh can be the same or different, and are each independently selected from hydrogen, a Ci to C40, straight chain or branched alkyl group, a C3 to C8 cycloalkyl group, or a Ce to Ci0 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: C1 to C6 alkoxy, C6 to C10 aryl, CN1 OH, NO2, C7 to C30 aralkyl and C7 to C30 alkaryl, or any two of Rb, Rc, Rd, Re and Rf attached to adjacent carbon atoms form a methylene chain -(CH2)q- wherein q is from 8 to 20.
40. A method according to Claim 3 or Claim 4, wherein the neutral anion is a sulfonate, phoshinate, triflamide (amide), triflate, dicyanamide, oxide (phenoxide) or halide anionic species.
41. A method according to Claim 40, wherein the neutral anion is selected from [NTf2]", [OTf]", [R-SO3]', [R2PO2]", [Cl]", [Br]" and [I]"; wherein R is Ci to C6 alkyl, or Ci to C6 aryl. 42.A method according to Claim 41 , wherein the neutral anion is selected from [Me-SO3]", [Ph-SO3]" and [Me-Ph-SO3]".
43. A method according to any one of the preceding Claims, wherein the piant fatty acid is derived from rape seed oil or prioline.
45.A method according to any one of the preceding claims, wherein the bio-diesel product and the ionic liquid are immiscible.
46.A method according to any one of the preceding claims, wherein the bio-diesel product is obtained from the reactants by phase separation.
47.A method according to any one of the preceding claims, wherein the ionic liquid is recycled.
48.Use of bio-diesel obtained by the method of any one of Claims 1 to 47 in blending with a petroleum compound.
49. Use according to Claim 48, wherein the petroleum compound is diesel.
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