Direct valorisation of food waste: continuous metathesis of cocoa butter triglyceride. Supporting Information

Transcription

1 Direct valorisation of food waste: continuous metathesis of cocoa butter triglyceride Christiane Schotten, 1,5 Dorota Plaza, 2 Simone Manzini, 3 Stephen P. Nolan, 3 Steven V. Ley, 4 Duncan L. Browne, 4,* Alexei Lapkin 5,* Supporting Information No of pages: 11 No of Tales: 0 No of Figures: No of Schemes: 1 General Experimental page S2 Procedure for batch setup S3 Flow Setup S4 Method for Determining Conversion S5 1 H NMR of 1-decene S9 1 H NMR of cocoa butter S10 1 H NMR spectrum following metathesis S11 S1

2 General Experimental Considerations The waste cocoa butter was provided by Cadbury s (now Kraft). Ethylene was purchased from BC Ltd. Solvents and reagents were obtained from Sigma Aldrich. Catalysts were prepared following known procedures. 1 H-NMR spectra were recorded on either a Bruker Avance DPX-400 or DRX-600 (in the case of raw cocoa butter) spectrometer with the residual solvent peak as the internal reference, resonances are reported to the nearest 0.1 ppm. NMR spectra were acquired using 30 flip angle and a 3.55 second recycle delay and the data was processed using the standard software baseline and phase correction algorithms. Flow experiments were conducted using a Uniqsis Flowsyn reactor system. S2

3 Procedure for batch setup For the results described in Table 2 at one bar of ethylene pressure the following protocol was used: The catalyst (1 mol %; mmol) and a stirrer bar were added to a 5 ml vial in an argon-filled glove box. The vial was closed using a plastic septa cap. Next, this vial was removed from the glove box. Then, mg cocoa butter (0.25 mmol, average M w of cocoa butter) was added into a second 5 ml vial and closed using the septa cap (outside of the glove box). The cocoa butter vial was purged with argon from a Schlenk line before addition of 1 ml of dry and oxygen-free solvent was introduced via syringe into the cocoa butter vial. The cocoa butter was dissolved and then added via syringe into the catalyst vial. The vial was then stirred with an ethylene purge from a balloon. After the allotted time the reaction was quenched with ethyl vinyl ether, before drying under reduced pressure and analysing by 1 H NMR (as described in Method for Determining Conversion ). For greater than 1 bar pressure of ethylene: The charged reaction vial was then loaded into the autoclave. The autoclave was connected to an ethylene cylinder. After the allotted time the reaction was quenched with ethyl vinyl ether, before drying under reduced pressure and analysing by 1 H NMR (as described in Method for Determining Conversion ). *It should be noted that by conducting the same reaction using non-dried glassware, without a glovebox and with THF from a standard column type solvent purification system, conversions within 5-10% of those reported were routinely achieved.* S3

4 Flow procedure Experimental set up is illustrated in Figure S1. The mixture of cocoa butter, catalyst and THF was injected into the sample loop and the valve position switched to place the sample inline. The sample was then carried into the lumen side of the Teflon AF-2400 membrane. The tube-in-tube reactor was constructed from an inner Teflon AF-2400 tube (o.d. 1.0 mm and i.d. 0.8 mm) and an outer PTFE tube (o.d mm and i.d mm). The sample then flowed into a 20 ml or 10 ml residence coil and then through a back-pressure-regulator (BPR) rated to 6.9 bar (100 psi). The collected sample was flushed with argon to remove dissolved ethylene and to stop the reaction before drying under reduced pressure and analysing by 1 H NMR (as described in Method for Determining Conversion ). Figure S1. Experimental flow set up. S4

5 Method for Determining Conversion Following the reaction and solvent removal, CDCl 3 was used to dissolve samples for NMR analysis, typically 100 µl of crude solution in 0.5 ml of CDCl 3. The development of a method for the determination of conversion for this reaction was not a trivial matter. The logic used for determining the conversion by 1 H NMR spectroscopy is described in Scheme 1. GPC analysis of the starting materials showed that the oleic acid to linoleic acid ratio is 17:3. We started with the assumption that the alkene containing triglycerides underwent full ethenolysis to terminal alkene products resulting in the breaking of all double bonds (rather than partial conversion which would lead to internal alkenes from the linoleic acid). After total ethenolysis of this mixture, five products containing terminal alkene functionality would be present. Following the removal of solvent and 1,4-pentadiene on a rotary evaporator the resulting mixture would contain four products featuring terminal alkenes in a 17:17:3:3 ratio, clearly the ratio of triglyceride terminal alkenes to lower molecular weight terminal alkenes must be 1:1. S5

6 17 : 3 assume total ethanolysis 17:17:3:3:3 B.Pt. = 170 o C B.Pt. = 94 o C B.Pt. = 26 o C solvent removal rotary evaporation THF + 17:17:3:3 or greater B.Pt. = 170 o C B.Pt. = 94 o C 1 H NMR analysis Scheme S1 The linear chain hydrocarbon, terminal alkene protons all overlap in the 1 H NMR spectrum and appear in the region between ppm. The four equivalent protons of the glycerol backbone, of both the starting material and the derived triglyceride products appear in the region between 4.00 and 4.25 ppm. Figure S2 shows the region of interest from a representative reaction. The following analysis is performed to determine conversion to terminal alkenes (not to 1-decene specifically). Steps one to three refer to processing the integrals in the spectrum of a sample of pure S6

7 cocoa butter (Figure S4) whereas steps four and five refer to the processing of integrals in a given reaction sample (Figures S1 and 5): 1) The integral of the internal alkene region ( ppm) in the pure cocoa butter sample corresponds to the double bonds accessible for ethenolysis (I internal alkene=2.23; with 4.03 H total of glycerol backbone). Each double bond has two protons so that this value corresponds to 2H. 2) At a 100 % conversion, these two internal alkene protons would be converted to four terminal alkene protons per starting material (I terminal alkene, 100 % = 2 x I internal alkene=4.46). 3) This value has been normalized to the glycerol backbone of 1H (I 100 %, normalized = I terminal alkene, 100 % /4.03=1.11) 4) The integral of the terminal alkene region in the sample is taken (I internal alkene, sample=0.44) normalized to the glycerol backbone of 1H. 5) The percentage conversion to terminal alkenes (X alkene ) is then equal to I 100 %, normalized divided by I internal alkene, sample multiplied by 100. (X alkene =[0.44/1.11] x 100 % = 39.6 %) 6) As a post-calculation multiplier the value should be multiplied by This is due to the value of I internal alkene incorporating the internal alkenes corresponding to a 1,4-pentadiene product, by the time the terminal alkene product integral is measured these alkene protons are no longer present. The value of 1.15 is derived from the ratio of terminal protons 17*2:17*2:3*2:3*2:3*4 = 34:34:6:6:12 = 92 in total, to those that are actually present by the time the product NMR spectrum is recorded, (which has now lost the 1,4-pentadiene protons) 34:34:6:6 = /80 = We thank the referee for bringing our attention to this. For 1-decene specifically (assuming there is no enrichment from the starting ratio of oleic acid and linoleic acid cleavage products of 17:17:3:3 due to loss of the lighter 1-heptene on the rotary evaporator) multiply this value (X alkene ) by the ratio of oleic acid cleavage products to the remaining linoeic acid cleavage products of 0.85 ([17+17]/[ ]=0.85). This gives the conversion of oleic acid residue which equals the conversion to 1-decene (X 1-decene =X alkene x 0.85=39.6 % x 0.85 = 33.7 %). S7

8 Figure S2 S8

9 Figure S3 1 H NMR spectrum of 1-decene S9

10 Figure S4 1 H NMR spectrum of cocoa butter S10

11 Figure S5 1 H NMR spectrum following metathesis This information is available free of charge via the Internet at S11