PRIORITY DOCUMENT

[0001 ] The present application claims priority from Australian Provisional Patent Application No.

2014902456 titled "BIODIESEL PRODUCTION" and filed on 26 June 2014, the content of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0002 ] The present disclosure relates to processes for the production of saturated or unsaturated fatty acid ester mixtures that are suitable for use as fuels, such as biodiesel, fuel additives and lubricants. The present invention also relates to fuels, such as biodiesel, produced using the processes.

BACKGROUND

[00031 The combustion of fossil fuels, such as coal, oil, and natural gas, accounts for eighty five percent of the global energy usage. However, fossil fuels are a non-renewable source of energy and our supply of these fuels is finite. Consequently, there has been a shift towards utilising renewable energy sources including solar, tidal, wind, geothermal and biofuels.

[0004 ] Biofuels are an alternative to fossil fuels that do not have the same negative environmental impacts as fossil fuels because they are derived from atmospheric carbon dioxide, and thus do not increase the net amount of carbon dioxide in the atmosphere. Furthermore, the use of biofuels may not require substantive changes to existing infrastructure and machinery as may be required from some other alternative energy sources. Biodiesel is a biodegradable transportation fuel for use in diesel engines that is produced from plant- or animal -derived oils or fats. Biodiesel is used as a component of diesel fuel or as a replacement for diesel fuel. Biodiesel can be readily used in diesel-engine vehicles, which distinguishes biodiesel from the straight vegetable oils (SVO) or waste vegetable oils (WVO) used as fuels in some modified diesel vehicles. Biodiesel is biodegradable and non-toxic, and has significantly fewer emissions than petroleum-based diesel when burned and, therefore, its use can result in substantial environmental benefits.

[0005 ] The use of biodiesel as an alternative to petroleum diesel is widely welcomed by environmental groups and the community. Biodiesel is Europe's dominant renewable fuel and, as part of a range of measures to reduce greenhouse gas emissions, the European Union is encouraging the use of biofuels. For example, the 2003 EU Biofuels Directive requires 20% of the energy for transport to come from renewable sources by the end of 2020. [0006] Biodiesel is comprised of a mix of mono-alkyl esters of long chain fatty acids, and is typically produced by transesterification of vegetabl e oil or animal fat with methanol using acid or basic catalysts. For example, International patent application WO03/022961 describes a method for producing biofuel from waste oil or oil by-products by transeterification with methanol in the presence of sulfuric acid. In another example, International patent application WO2006/128881 describes a method for producing biodiesel from rapeseed oil or sunflower oil by transesterification with methanol in the presence of sodium hydroxide. There have also been suggestions that biodiesel can be produced from vegetable oils by an enzyme (Candida cylindracea) catalysed transesterification reaction (for example see published United States patent application 2005/0084941 ).

[0007] Whilst the integration of biodiesel as a transport fuel has generally been successful, there remain some problems with its production. Current biodiesel production processes are typically based on batch processing which requires heating, the use of co-solvents such as acetone, tetrahydrofuran, dimethyl and diethyl ether, the use of large excesses of basic methanol, operating under anhydrous conditions as well as the need for complex downstream processing to remove the catalyst, glycerol and unwanted products. Furthermore, the mass and heat transfer characteristics of the transesterification reaction that is typically used to produce biodiesel are not particularly favourable. Overcoming the low mass transfer as well as providing continuous flow processing of biodiesels has been established for a dynamic thin film rotating tube processor (RTP) (Lodha, et ah, 2012; Chen, et al., 2014). However, this approach requires heating, the use of dry solvents and high ratios of methanol to oil feedstock, as well as the use of condensing units to circumvent the evaporation of methanol from the system. A laminar flow biodiesel reactor has also been developed (Boucher, et al., 2009; Unker, et al., 2010) which operates at high temperatures using relatively large quantities of solvent.

[0008 ] There is a need for processes for the production of biodiesel fuels that do not have some of the disadvantages of prior art biodiesel fuel processes.

SUMMARY

[ 0009] The present disclsoure arises from research in which we showed that a thin film vortex fluid device (VFD) is effective in the room temperature continuous flow conversion of sunflower oil to biodiesel. Optimised VFD operating parameters affords high purity biodiesel, with substantially no saponification, without the need for the otherwise conventional use of a co-solvent or the use of complex catalysts. The biodiesel, glycerol by-product and catalyst also spontaneously separate post-VFD processing, and the catalyst can then be recycled without the need for further down-streaming processing.

[0010] According to a first aspect, there is provided a process for producing CpQ, alkyl fatty acid esters, the process comprising: providing a reactant fluid comprising a fatty acid, fatty acid glyceride or mixture thereof; providing a catalyst fluid comprising a C] -C ₆ alkyl alcohol and an acid or base catalyst; contacting the reactant fluid and the catalyst fluid in a thin film tube reactor comprising a tube having a longitudinal axis, wherein the angle of the longitudinal axis relative to the horizontal is between about 0 degrees and about 90 degrees; rotating the tube about the longitudinal axis under conditions to produce Ci-C ₆ alkyl fatty acid esters; and recovering the Ci-C ₆ alkyl fatty acid esters from the reactor.

[001 1 ] Advantageously, the process can be used to produce biodiesel from readily available oils and solid fats. Thus, in a second aspect, there is provided a process for producing biodiesel, the process comprising: providing a reactant fluid comprising a fatty acid, fatty acid glyceride or mixture thereof; providing a catalyst fluid comprising a Ci -C ₆ alkyl alcohol and an acid or base catalyst; contacting the reactant fluid and the catalyst fluid in a thin film tube reactor comprising a tube having a longitudinal axis, wherein the angle of the longitudinal axis relative to the horizontal is between about 0 degrees and about 90 degrees; rotating the tube about the longitudinal axis under conditions to produce biodiesel; and recovering biodiesel from the reactor.

[0012 ] In embodiments of the first and second aspects, the angle of the longitudinal axis relative to the horizontal is between about 10 degrees and about 90 degrees.

[0013 J In embodiments of the first and second aspects, the thin film tube reactor comprises an inner cylindrical surface and a hemispherical base.

[0014 ] In embodiments of the first and second aspects, the thin film tube reactor comprises a hemispherical base. [0015 J In embodiments of the first and second aspects, the process is carried out without the need for heating.

[0016] In embodiments of the first and second aspects, the reactant fluid comprises substantially no solvent.

[0017] In embodiments of the first and second aspects, the catalyst fluid comprises substantially no solvent other than the C _r C ₆ alkyl alcohol.

[0018J In embodiments of the first and second aspects, the recovered Ci-C ₆ alkyl fatty acid esters or biodiesel are substantially free of glycerol.

[0019] In embodiments of the first and second aspects, the process is a continuous process.

[0020] In embodiments of the first and second aspects, the thin film tube reactor comprises a plurality of thin film tube reactors.

[0021 ] In a third aspect there is provided a C _r C ₆ alkyl fatty acid ester produced according to the process of the first aspect.

[0022 ] In a fourth aspect there is provided biodiesel produced according to the process of the second aspect.

BRIEF DESCRIPTION OF DRAWINGS

[0023 ] Embodiments of the present invention will be discussed with reference to the accompanying drawings wherein:

[0024] Figure 1 shows a schematic of the transesterification process occurring within the vortex fluidic device (VFD). This shows the catalytic conversion of oil to biodiesel (Fatty Acid Methyl Ester (FAME)) and a photograph of a VFD;

[0025] Figure 2 is a plot of % acetone co-solvent vs % conversion to biodiesel. The figure shows the effect of a co-solvent (acetone) on the conversion of pure oil into biodiesel; for single feed experiments, 0.50 g of triolein (99.5 % purity) was used with 20 mL of 10 % KOH (in methanol) with different ratios of acetone. When two separate feeds were used, 2 mL of triolein was used with an equi- volume of 10 % KOH (in methanol) with different volumes of acetone. A rotational speed of 5250 rpm was used, at an angle of incline, 0, of 45° relative to the horizontal position. Three separate experiments were carried out per data point; [0026] Figure 3 is a plot of concentration of KOH vs % conversion into biodiesel. The plot shows a variation in concentration of KOH biodiesel production from sunflower oil; 10 mL samples were used in a 1 : 1 ratio (oil: methanol), a rotational speed of 5250 rpm, o 45° relative to the horizontal position. Three separate experiments were carried out per data point;

[0027] Figure 4 is a plot of flow rate vs % conversion into biodiesel. The plot shows the effect of change in flow rate for the generation of biodiesel from sunflower oil; a rotational speed of 5250 rpm, 0 45° relative to the horizontal position, 1.0 M KOH. Three separate experiments were carried out per data point;

[0028] Figure 5 shows: (a) a three-phase separation; (b) colour change from using pure 1 M KOH (left) and the recycled catalyst three times (right), which arises from impurities; and (c) a plot of catalyst turnover vs % conversion into biodiesel showing the effect on conversion of sunflower oil to biodiesel versus the number of times of recycling the catalyst. Three separate experiments were carried out per data point;

[0029] Figure 6 is a plot of methanol/oil ratio vs free fatty acid conversion. The plot shows the effect of volumetric ratio of methanol to oil on the conversion of FFA to the corresponding methyl ester using the VFD for different flow rates of the lipid oil. Results are in triplicate. Optimum conditions are 1 :6 volume ratio of oil feedstock to methanol and 0.2 molar equivalents of sulphuric acid catalyst loading for a combined flow rate of 3.5 ml/min in a 17. 7 ID tube rotating at 7500 rpm;

[0030] Figure 7 is a plot of rotational flow rate vs % free fatty acid showing the flow rate of oil into the VFD for both five and six volumetric ratios of methanol to oil. Results are in triplicate and the average is taken;

[0031 ] Figure 8 is a plot of flow rate vs free fatty acid conversion showing the residence time of methanol in the rotating tube at 6950 rpm, tilted 45 degree relative to the horizontal position. Results are in triplicate and the average taken;

[0032] Figure 9 is a plot of molar ratio of sulphuric acid to free fatty acid vs free fatty acid conversion. Results are in triplicate and the average taken; and

[0033 ] Figure 10 is a plot of rotational speed vs free fatty acid conversion. The plot shows the effect of tube rotation speed on the conversion of FFA into FAME. Results are in triplicate. DESCRIPTION OF EMBODIMENTS

[0034] Provided herein is a process for producing Ci -C ₆ alkyl fatty acid esters. The process comprises providing a reactant fluid comprising a fatty acid, fatty acid glyceride or mixture thereof and a catalyst fluid comprising a C _r C ₆ alkyl alcohol and an acid or base catalyst. The reactant fluid and the catalyst fluid are contacted in a thin film tube reactor comprising a tube. The angle of the longitudinal axis relative to the horizontal is between about 0 degrees and about 90 degrees. The tube is rotated about the longitudinal axis under conditions to produce Ci-C ₆ alkyl fatty acid esters which are then recovered from the reactor. The process is particularly useful for the production of biodiesel from readily available oils.

[0035 ] In embodiments, the tube comprises an inner cylindrical surface. In embodiments, the tube comprises a hemispherical base.

[0036] The reactor is a vortex fluidic device (VFD). The reactant fluid and catalyst fluid mix in the thin film tube, thereby triggering a reaction between them to produce the biodiesel and glycerol. The mixing is convection-enhanced by shear stress induced circulation occurring within each of the reactants with intense micro-mixing. Separation of glycerol from the biodiesel occurs simultaneously post processing using the vortex fluidic device. The reactor can be a continuous throughput reactor and a number of reactors can be connected in parallel to improve throughput.

[0037] Details of the VFD are shown in Figure 1 and described in published United States patent application US 2013/0289282, the details of which are incorporated herein by reference. Briefly, the thin film tube reactor 10 comprises a tube 12 rotatable about its longitudinal axis by a motor 14. The tube 12 is substantially cylindrical or comprises a portion that is tapered. The motor 14 can be a variable speed motor for varying the rotational speed of the tube 12 and can be operated in controlled set frequency and set change in speed. A generally cylindrical tube 12 is shown in the accompanying drawings but it is contemplated that the tube could also take other forms and could, for example, be a tapered tube, a stepped tube comprising a number of sections of different diameter, and the like. The tube 12 can be made of any suitable material including glass, metal, plastic, ceramic, and the like. In certain

embodiments, the tube 12 is made from borosilicate. Optionally, the inner surface of the tube can comprise surface structures or aberrations.

[0038] An optional jacket 16 can be used to partially or wholly surround the circumference of the tube 12 for heating and/or cooling and/or insulating the tube 12. The jacket 16 may also insulate the tube 12 from the external environment.

[0039] The tube 12 is situated on an angle of incline 18 relative to the horizontal 20 of above 0 degrees and less than 90 degrees. In certain embodiments, the tube 12 is situated on an angle of incline 1 8 relative to the horizontal 20 of between 10 degrees and 90 degrees The angl e of incline 18 can be varied. In the embodiment illustrated in Figure 1 , the angle of incline 18 is 45 degrees. However, other angles of incline 1 8 can be used including, but not limited to, 1 degree, 2 degrees, 3 degrees, 4 degrees, 5 degrees, 6 degrees, 7 degrees, 8 degrees, 9 degrees, 10 degrees, 1 1 degrees, 12 degrees, 13 degrees, 14 degrees, 15 degrees, 16 degrees, 17 degrees, 18 degrees, 19 degrees, 20 degrees, 21 degrees, 22 degrees, 23 degrees, 24 degrees, 25 degrees, 26 degrees, 27 degrees, 28 degrees, 29 degrees, 30 degrees, 31 degrees, 32 degrees, 33 degrees, 34 degrees, 35 degrees, 36 degrees, 37 degrees, 38 degrees, 39 degrees, 40 degrees, 41 degrees, 42 degrees, 43 degrees, 44 degrees, 46 degrees, 47 degrees, 48 degrees, 49 degrees, 50 degrees, 51 degrees, 52 degrees, 53 degrees, 54 degrees, 55 degrees, 56 degrees, 57 degrees, 58 degrees, 59 degrees, 60 degrees, 61 degrees, 62 degrees, 63 degrees, 64 degrees, 65 degrees, 66 degrees, 67 degrees, 68 degrees, 69 degrees, 70 degrees, 71 degrees, 72 degrees, 73 degrees, 74 degrees, 75 degrees, 76 degrees, 77 degrees, 78 degrees, 79 degrees, 80 degrees, 81 degrees, 82 degrees, 83 degrees, 84 degrees, 85 degrees, 86 degrees, 87 degrees, 88 degrees, and 89 degrees. If necessary, the angle of incline 18 can be adjusted so as to adjust the location of the vortex that forms in the rotating tube 12 relative to the closed end of the tube. Optionally, the angle of incline 18 of tube 12 can be varied in a time- dependent way during operation for dynamic adjustment of the location and shape of the vortex. This also leads to a dynamic adjustment of the mechanical induced shear within the thin liquid film.

[0040 J A spinning guide 22 assists in maintaining the angle of incline 18 and a substantially consistent rotation around the longitudinal axis of the tube 12.

[0041 ] The reactant fluid and the catalyst fluid are supplied to the inner surface of the tube 12 by way of at least one feed tube 24. Any suitable pump can be used to pump the reactant fluid and the catalyst fluid from a reactant fluid source and a catalyst fluid source to the feed tube(s) 24. Separate pumps may be used for the reactant fluid and the catalyst fluid so that each component can be introduced into the feed tube(s) 24 at different flow rates, as required. When more than one feed tube 24 is used, the tubes 24 may be of different lengths to supply fluids to variable locations on the inner surface of the tube 12 with controlled flow rates.

[0042 ] Solid reactants can also be added to the tube 12 so that heterogeneous reactions can be carried out in the tube 12. Solid reactants can be added via feed tube 24 or they may be added directly to the tube 12 which may be the case when solid catalysts are used in the tube 12, for example. In this embodiment, a further gas feed tube 70 can supply gas to the tube 1 10 as is required for processes using the thin film tube reactor 100. One or more clamps 80 may be employed to hold feed tubes 60 and gas feed tubes 70 in position either externally or within tube 1 10. [0043] A collector 26 positioned substantially adjacent to the opening of the tube 12 can be used to collect product exiting the tube 12. Fluid product exiting the tube 12 may migrate under centrifugal force to the wall of the collector where it can exit through a product outlet.

[0044 ] The VFD has several features which enhance the generation of biodiesel, compared to the prior art horizontally aligned rapid thermal processing (RTP). This includes high shear rates associated with the angle of incline 18 of the tube, reduction in the relative amount of solvent required, finer control of the residence time, and reduced capital outlay.

[00451 The reactant fluid can be a liquid, solution, suspension or emulsion comprising one or more fatty acid(s) or one or more fatty acid glyceride(s), or mixtures of these. As used herein, the term "fatty acid" means a carboxylic acid with a long saturated or unsaturated aliphatic tail, or with an aromatic component. Fatty acids that are particularly suitable for the production of biodiesel include, but are not limited to palmitic acid, stearic acid, oleic acid, linoleic acid, and mixtures of these. As used herein, the term "glyceride" means a mono-, di- or triglyceride glycol ester.

[0046] Most conveniently, the source of the one or more fatty acid(s) or one or more fatty acid glyceride(s) in the reactant fluid is one or more plant oils and/or an animal fats. Glyceride containing plant oils or animal fats can be any oil or fat product of plant or animal origin that contains glycerides. Plant oils and animal fats contain mostly triglycerides, although they typically also contain some monoglycerides and diglycerides. The glyceride containing plant oil or animal fat may be selected from the group including, but not limited to, animal tallow, plant oils, used cooking oils and fats, seeds, seed residue feedstocks, and grease trap oils.

[0047] Suitable plant oils that may be used in the production of biodiesel include: rapeseed oil, soybean oil, palm oil, mustard oil, castor oil, coconut oil (copra oil), corn oil, cottonseed oil, false flax oil, hemp oil, peanut oil, radish oil, ramtil oil, rice bran oil, safflower oil, sunflower oil, tung oil, algae oil, copaiba oil, honge oil, jatropha oil, jojoba oil, milk bush oil, petroleum nut oil, walnut oil, sunflower oil, dammar oil, linseed oil, poppyseed oil, stillingia oil, vernonia oil, amur cork tree fruit oil, apple seed oil, balanos oil, bladderpod oil, bruceajavanica oil, burdock oil (bur oil), candlenut oil (kukui nut oil), carrot seed oil, chaulmoogra oil, crambe oil, cuphea oil, lemon oil, orange oil, mango oil, mowrah butter, neem oil, rosehip seed oil, sea buckthorn oil, shea butter, snowball seed oil (viburnum oil), tall oil, tamanu oil, and tonka bean oil (cumaru oil). In specific embodiments, the reactant fluid comprises sunflower oil.

[0048] Advantageously, the plant oils may be used "as is" (ie without further purification and/or treatment) in the process of the invention, but the invention is not limited to these embodiments.

Generally, no solvent will be required, thereby reducing costs and safety issues associated with the use of solvents. [0049] Animal fats are fats obtained from animal sources. Suitable animal fats that may be used in the production of biodiesel include: tallow (beef fat), lard (pork fat), schmaltz (chicken fat), blubber, cod liver oil, yellow grease, and the by-products of the production of omega-3 fatty acids from fish oil. Some animal fats may be solid or gelatinous at room temperature and, in those cases, it is contemplated that the reactant fluid will contain a solvent or heated using dissipated heat from the motor used for spinning the tube, or other sources. However, the solvent is preferably a C] -C ₆ alcohol and more preferably the C C ₆ alcohol used in the catalyst fluid.

[0050] The catalyst fluid can be a liquid, solution, suspension or emulsion comprising a Ci-C ₆ alcohol and an acid or base catalyst. The Ci-C ₆ alcohol may be selected from one or more of the group consisting of: methanol, ethanol, n-propanol, i-propranol, n-butanol, s-butanol, and t-butanol. Methanol is an alcohol that is commonly used in biodiesel production and we have found it to be suitable for use in the processes described herein. However, it is contemplated that ethanol may also be particularly suitable.

[0051 ] The catalyst fluid also comprises an acid or base transesterification catalyst. The acid catalyst may be any suitable mineral acid, such as hydrochloric acid, sulphuric acid, nitric acid, etc. The base catalyst may be potassium hydroxide, sodium hydroxide, sodium methoxide, etc. Other transesterification catalysts, including metal or enzyme catalysts can also be included in the catalyst fluid.

[0052] In specific embodiments, the transesterification catalyst is potassium hydroxide (KOH). We observed a dramatic increase in conversion using KOH in methanol at a concentration of greater than 0.75 M. Specifically, high purity biodiesel was generated using 1.0 M KOH.

[0053 ] In other embodiments, the transesterification catalyst is sodium hydroxide which is less expensive than potassium hydroxide.

[0054] In other embodiments, the transesterification catalyst is sulphuric acid.

[0055] Surprisingly, we have found that there is no need to use anhydrous solvents or to eliminate water from the system in order to produce high quality biodiesel. Typically, hydroxide ions (which would be formed when water is present in the catalyst fluid) can hydrolyse the sunflower oil causing a fatty acid sodium salt (saponification). However, we found no evidence of saponification in the processes described herein when water was present in the system.

[0056] A second catalyst can be bound to an internal surface of the tube 12. In these embodiments, the catalyst may be a solid acid, base, metal or enzyme catalyst. These embodiments may be particularly effective when the VFD is operated in confined mode and the reactant fluid and catalyst fluid are in contact with the solid catalyst for a sufficient time. [0057] We have found that the flow rate of reactant fluid and catalyst fluid into the VFD affects the purity of the biodiesel product, with an almost l inear decline in biodiesel purity for increasing flow rate. Thus, in some embodiments in which the reactor tube is a 20 mm external diameter tube, the flow rate of the reactant fluid and the catalyst fluid is less than 2 mL/min, and in certain embodiments it is less than 1 mL/min.

[0058 ] The liquid produced according to the processes described herein spontaneously separates into three layers. The lower level is glycerol with the highest density, ~ 1 .26 g/mL, and can be readily removed, for use in a wide range of commercial applications. The middle layer is biodiesel. The upper layer contains methanol and the catalyst. The upper layer (ie. a used catalyst fluid comprising methanol, around 10 % FAME and catalyst) can be reused by removing the Cj -C ₆ alcohol to fonn a substantially dry- used catalyst and then re-introducing fresh Ci-C ₆ alcohol. The resultant catalyst fluid can then be introduced back into the system for further biodiesel generation without any further purification. Greater than 95 % conversion to biodiesel can be maintained for a number of cycles. However, in our system we found that the conversion decreased at the fourth cycle.

[0059 ] The reactant fluid and the catalyst fluid are supplied to the inner surface of the tube by way of feed tube which is fed through a flow control device from an injection pump. In the reactor the fatty acid and/or fatty acid glyceride and the alkoxide of the C] -C ₆ alcohol react to form a mixture of methyl ester, glycerol, and residual methanol and catalyst. During the reaction, the tube is spun at high speeds

(including, but not limited to 3500 rpm - 10,000 rpm) and under rapid rotation the fluids fonn a dynamic thin film down to about 200 μιη thick, with the thickness depending on the rotational speed, tilt angle of incline and flow rates or volume of the fluid when operating under confined mode (Gandy, et al., 2014) where Stewartson/Ekman layers arise from the liquid being driven up the rotating tube with gravity forcing the liquid back (Bennetts and Hocking, 1973).

[0060 ] The VFD can be operated in a batch mode in which the reactor is configured to retain a finite amount of liquid in the tube 12. However, the VFD is advantageously operated in continuous flow mode wherein the reactant fluid and catalyst fluid are introduced continuously into the reactor via the feed tube and the products are removed from the top of the reactor continuously. The continuous flow mode of operation imparts additional shear relative to the confined mode (angle of incline > 0°) arising from the viscous drag as the fluid whirls along the tube prior to exiting at the top. Surprisingly, we have found that glycerol has enough translational energy to overcome the viscous drag and exit the system, thus enhancing the position of equilibrium in favour of the desired products. Although the flow rates we used are lower than previous examples (Boucher, et al., 2009; Unker, et al., 2010), the size and the diameter of the tube can be increased and/or a plurality of VFD reactors can be connected in parallel in order to increase throughput, as can multiple passes of the liquid through a number of VFD reactors. [0061 ] The processes described herein have a number of desirable features such as high volume, low capital and operating costs, short residence times, compact and modular process equipment design, moderate process conditions, and low energy usage.

[0062 ] Also provided herein is a Ci -C ₆ alkyl fatty acid ester or biodiesel produced according to the described processes.

EXAMPLES

[0063] Example 1 - Production of biodiesel

[0064] The VFD was equipped with a 20 mm external diameter glass tube (borosilicate glass, as a standard NMR tube). The tube was rotated at 5250 rpm at a tilt angle Θ of 45 ° relative to the horizontal position. The reactants were injected via automated pumps at a flow rate of 0.50 mL/min. A 10 mL solution of 1 M base (KOH, NaOH, or NaOMe in methanol) was injected through one jet feed whilst 10 ml of untreated oil was injected in via another parallel aligned jet feed, at the same flow rate. Products were collected in a separating funnel via an exit tube, which resulted in instantaneous separation into three layers. The lower layer (glycerol) was removed first, followed by the middle layer (biodiesel) then the top layer (catalyst, methanol , impurities and - 10 % of the synthesised FAME). The oil layer was washed with 50 °C water (3 x 25 mL), 2 M NaHC0 ₃ ( 1 x 25 mL) and 2 M HC1 ( 1 x 25 mL), to remove any possible free fatty acids (FFA), impurities and remaining catalyst. Yields were calculated based on the maximum amount of transesterification product possible when using a 10 mL sample of commercial sunflower oil sample. All biodiesel was subjected to a typical "shake" test with water and a pH test to make sure that the catalyst and any possible FFA had been removed

[0065] Both ¾ and ¹³ C NMR were obtained on a 600 MHz Bruker spectrometer. Typical quantitative conditions were used (Delayed pulse (D]) - 10.00 and Number of Scans - 64) to ascertain the purity of the biodiesel. The biodiesel gave identical spectra to that of previous published material (Basumatary, et ai, 2013). FT-IR were recorded using a Perkin Elmer FT1R monitor. GCMS were recorded on a Varian CP-3800 gas chromatography unit coupled with a 2200 Saturn MS detection unit. Injection occurred at 40 °C and increased at a rate of 20 °C /min until 300 °C was achieved. A reverse phase column (30 M X 25 μΜ X 0.25 mM) was used, and mass spectrometry data was analysed with NIST 05 molecular recognition software.

[0066] Results and Discussion

[0067] The effect of a co-solvent on the conversion to biodiesel was first investigated, as the system has high mass transfer and intense micromixing, noting that acetone is commonly used in batch processing of biodiesel to increase mass transfer (Guan, et al., 2009; Thanh, et al, 2013). Even a small amount of acetone hindered the reaction, and in the case of pre-mixing the oil and methanol, and then injecting the mixture through a single jet feed completely shut down the reaction, Figure 2. Thus, we established that the use of a co-solvent should be avoided, and this features in further optimisation of the processing.

[00681 Variation in the concentration of KOH in methanol was also studied in optimising the VFD processing. A sigmoidal relationship was observed with 0.4 M KOH giving a noticeable increase in conversion, Figure 3. A dramatic increase in conversion was observed prior to using 0.75 M KOH, and then high purity oil was generated using 1.0 M KOH. Due to the energy intensive down streaming processing required removing glycerol, mono and diglycerides, subsequent experiments focused exclusively on using 1.0 M KOH.

[0069] The flow rate of reagents into the base of the VFD was varied and the product purity monitored, Figure 4, establishing an almost linear decline in biodiesel purity for increasing flow rate. As mentioned above, the processed liquid instantaneously separates into three layers, Figure 5. The lower level is glycerol with the highest density, ~ 1.26 g/mL, and can be readily removed, for use in a wide range of commercial applications (Pagliaro, et al., 2007; Kenar, 2007). The middle layer is the biodiesel, while the upper layer was shown to contain methanol and the catalyst, and to further increase the green chemistry metrics of the system recycling of the catalyst was explored. For this, the upper layer was evaporated to dryness and the residue taken up in 10 mL of methanol for the recycling process, Figure 5. This was to ensure that the volume of methanol used in each cycle was constant, thus allowing direct comparison throughout the study.

10070] The catalyst was introduced back into the system for further biodiesel generation without any purification on the above removal of the solvent. The percent conversion remained high at 95 % until the fourth cycle, whereupon there was a dramatic reduction in conversion to ca 22 %, Figure 5. This possibly arises from a build up in contaminants, which is evident with a change in colour (which does not change colour when neutralised with 2 M HCl), disrupting the transesterification of the sunflower oil.

[0071 ] Sodium hydroxide is less expensive than potassium hydroxide, and is another common catalyst used in the production of biodiesel. Indeed, repl acing the KOH with NaOH in the methanol was equally effective in biodiesel production using the VFD, and heightens the cost-effectiveness of the process, with the less hygroscopic and safer nature of NaOH improving the green chemistry metrics of the process. Unlike previous studies, there is no need to use anhydrous solvents to eliminate water from the system. To further highlight this, the same experiment was undertaken with water as the solvent rather than methanol. There was no hydrolysis or modification of the sunflower oil at 1.0 M or 3.0 M KOH/NaOH in water, thus establishing that we have a rather unique system. Conversion is only observed when methoxide is present. In traditional processing, water is removed from the reaction process, in minimizing the potential for water hydrolyzing alkoxide ions and saponification. The resulting hydroxide ions can hydrolyse the sunflower oil causing a fatty acid sodium salt (saponification). Even though our system is not anhydrous, it gives high purity product with no evidence for any saponification. This was further corroborated when a 50 mL sample was synthesised using anhydrous methanol and anhydrous sodium methoxide, with the yields being the same as using laboratory grade methanol and pelleted NaOH/ OH. These results suggest novel reaction pathways whereby alkoxide ions rather than hydroxide ions control the reaction, adding a new exciting dimension to synthesis of biodiesel.

[0072] Analysis of the biodiesel produced using GC-MS showed that no sunflower oil is present when using 1 M KOH. Furthermore, after the catalyst was recycled twice, mono-glycerides (MG) were present, with a drop in yield of the biodiesel to 95 %. This is due to catalyst loss in the oil and glycerol fractions, an increase in pH of the glycerol layer was observed (pH = 12.28), as well as a build up of hydrophilic species solubilised from the sunflower oil, although the effect of this is only dramatic after recycling four times. We have al so established that the nature of the oil feedstock (saturated or non-saturated) does not affect conversion to the corresponding biodiesel methyl ester. The GC-MS results show that over twenty different forms of methyl ester can be detected, suggesting that the process herein is likely to work for a range of oils and fats to produce fatty acid methyl esters (FAMEs) in biodiesel.

[0073 1 Example 2 - Production of fatly acid esters

[0074 ] Stearic acid (Ci ₈ H3 ₆ 0 ₂ ), a free fatty acid of solid composition at room temperature can also be esterified with methanol using a sulphuric acid catalyst. This was achieved by firstly dissolving the solid acid ( 1 .00 g) in methanol (30.0 mL), and this solution was then passed through the vortex fluidic device at a speed of 0.50 mL/min at a tilt angle of 45 degrees relative to the horizontal position, as described in Example 1. The resultant solution was taken to dryness by reduced pressure removal of the residual methanol. The residue was washed with sodium carbonate and the solid filtered off. The white solid compound was spectroscopically identified as the steric acid methyl ester, with no indication of any free fatty acid present by Ή NMR or ¹³ C NMR.

10075] Example 3 - Production of fatty acid methyl esters

[0076] The VFD was set at a tilt angle, Θ, of 45 degrees relative to the horizontal position. A

commercially available, pristine boro-silicate glass NMR tube (internal diameter of 17.7 mm) was inserted. Two jet feeds were used in this procedure as this leads to an increase in mixing and chemical reactivity between oil and alcohol (Britton et ah, 2014). In the first instance the glass tube was rotated at 6950 rpm and the reagents added through jet feeds via the use of an automated syringe pump. This speed was established as maximising shear intensity in other esterification studies. For the volumetric ratios of acidic methanol to oil described herein, for example 6: 1 , one drop of oil (0.500 mL/min) was released to six drops of acidic methanol (3.00 inL/min) using pre-mixed solution of H ₂ S0 ₄ in methanol. The oil was collected through a Teflon exit and immediately quenched in an ice bath at ~ 2 °C. This quenching method was trialled and after three hours there was no significant change in yield, and thus this was deemed an effective quench. The sample was then centrifuged at 7180 g for 20 mins at 10 °C. The methanol layer was discarded and the oil washed with Milli-Q water (3 x 25 mL). The oil was again centrifuged at a reduced temperature to allow the water to separate. The oil was then removed, dried under vacuum and then weighed. A sample of 10 mL of oil was used each time, and the results were carried out in triplicate. The oil used was purchased from Sigma (~ 90 % technical grade Oleic acid) and was used as received for modelling a high FFA system.

10077] To calculate the acid value the EU standard EN14104 was used as guidance, but modified as described below. A solution of approximately 0.1 M KOH in propan-2-ol was prepared. The resulting solution was standardised against benzoic acid (50.0 mg) in 50 mL propan-2-ol with phenolphthalein as an indicator, and this was carried out five times in deriving an average concentration. The solution of KOH was standardised at the start of each day, and was titrated against ~ 4.0 g of oil each time. The oil to be tested was dispersed in 50 mL of propan-2-ol and swirled for 30 seconds whereupon three drops of phenolphthalein indicator was added and the solution titrated until it held a faint pink colour for ten seconds. In accordance with EN 14104, the molari ty of the solution, the acid content, and the percentage conversion were calculated using equations 1 - 3, respectively:

1000 X M _Ba

[0078 ] Concentration of KOH:

122.1 X V ₀ (1 )

56.1 X (V _t -V _n ) X C

[0079 ] : Acid Value AV) : (2)

Moil

[0080 ] % FFA conversion : ( ^{AVi AVf} ) x 100 (3)

[0081] M _ba = mass of benzoic acid (g), V ₀ - Volume of KOH titrant used (mL) , V _t - Volume of titrant used (mL), V _n - Volume of titrant required to naturalise 50 mL propan-2-ol (mL), C - Concentration of titrant (moles L ¹ ), M _0ll - mass of oil sample (g), AVi - Initial acid value (mg KOH g ^"1 ), AV _f - Final acid value (mg KOH g ^"1 ).

[0082] The volumetric ratio of methanol to oil (feedstock) was optimised first, noting this ratio is important in traditional bath processing of lipid oil (Figure 6). Larger volumes of methanol shift the equilibrium towards the methyl ester as well as increasing the solubility of the resulting biodiesel. We have used a volumetric ratio rather than a molar ratio, being more practically convenient in dealing with volumetric flow rates through the jet feeds in delivering two liquids to the base of the rapidly rotating tube. [0083 ] Initially ratios of five and six parts of methanol to oil were established as being optimum for a number of different flow rates (Figure 6). Further optimisation followed with finer control of the lipid oil flow rate for these two ratios (Figure 7), establishing a dramatic reduction in residual FFA to 1.41 % for a six to one volumetric ratio of methanol to oil, for an oil flow rate of 0.450 raL min ^"1 . A slightly faster flow rate of 0.50 mL min ^"1 resulted in 1.82% residual FFA, and this flow rate was chosen for further optimisation. The combined methanol to oil ratio corresponds to a system with a total flow rate of 3.50 mL min ^"1 , which corresponds to a 47 second residence time for the tube rotating at 6950 rpm, as established for passing methanol through the VFD (Figure 8). As expected there is an exponential reduction in residency time for increasing flow rate, and these conditions were then further optimised. Also noteworthy is that the liquid mixture appears visually mono phasic when passing through the VFD, demonstrating high mass transfer under shear.

[0084 ] In general, the catalyst loading significantly influences biodiesel processing, and this is even more important in flow chemistry systems, as in using the VFD. The VFD operates under plug flow conditions, and thus the catalyst has limited time (47 seconds) to recycle to other parts of the tube, with the effectiveness of the VFD relating to a system not governed by diffusion control. The catalyst loading of the system is a direct molar ratio between the FFA present and the moles of sulphuric acid used.

Surprisingly the molar equivalents of sulphuric acid could be reduced to 0.2 equivalents with a consistent conversion of 98. 1 % (Figure 9). Although this seems surprising, the shape of the graph (Figure 9) has been reported before, where an increase in catalyst loading detrimentally effects conversion rates.19 The rotational speed of the tube in the VFD controls the thickness of the dynamic thin film, and the faster the rotational speed the greater is the shear stress, and the thinner the film. In this study 6950 rpm was chosen as a starting rotational speed given that it results in the greatest reactivity in chemical synthesis. However, given that rotational speed is an important processing parameter of the VFD, it was further varied at 250 rpm increments, in mapping out any rotational speed variation dependence (Figure 10). This established the most efficient rotational speed for the production of biodiesel from the high FFA content feedstock was 7500 rpm, where remarkably there was no evidence for the presence of any residual FFA, as established using colorimetric titrations, N R and GCMS.

[0085] Conclusion

[0086 ] We have developed the use of a continuous flow vortex fluidic device for generating high purity biodiesel from sunflower oil and free fatty acids at room temperature. This requires a simple set of conditions using cheap, caustic bases in methanol or cheap mineral acids in methanol. It was calculated that the running costs of the device and pumps (3 x 0.20 KwH devices) in Australia per hour is $ 0. 170 USD per hour, where as in India it would be only $ 0.048 USD per hour, adding a further benefit to this process. Importantly, this process does not result in breakdown of the triglyceride fats when hydroxide is present (saponification), only alkoxides, indicating a novel pathway(s) in generating the biodiesel. Overall the process is highly efficient, with the ability to recycle the catalysts, at least three times. Furthermore, the glycerol layer can be easily removed, based on density differentials, which also avoids the need for down streaming processing, in generating a usable by product.

[0087] It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the invention is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.

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[0099] The content of each of the preceding publications is hereby incorporated by reference in its entirety.

[00100] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge.

[00101 ] Throughout the specification and the claims that follow, unless the context requires otherwise, the words "comprise" and "include" and variations such as "comprising" and "including" will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.