Supplementary Materials for - Science Advances...all other metathesis catalysts adversely affect the isomerization activity of IC-1. Screening of isomerization catalysts The isomerizing

advances.sciencemag.org/cgi/content/full/3/6/e1602624/DC1

Supplementary Materials for

Biofuel by isomerizing metathesis of rapeseed oil esters with

(bio)ethylene for use in contemporary diesel engines

Kai F. Pfister, Sabrina Baader, Mathias Baader, Silvia Berndt, Lukas J. Goossen

Published 16 June 2017, Sci. Adv. 3, e1602624 (2017)

DOI: 10.1126/sciadv.1602624

The PDF file includes:

Supplementary Materials and Methods

Supplementary Text

fig. S1. Ru-based metathesis catalysts tested in the isomerizing hexenolysis,

including second-generation indenylidene-ruthenium complexes Umicore M41

(Ru-2) and M31 (Ru-3) and Hoveyda-type catalysts Umicore M51 (Ru-4), M72

SIMes (Ru-5), and M74 SIMes (Ru-6).

fig. S2. Olefin blends obtained by isomerizing hexenolysis with different Ru

catalysts.

fig. S3. State-of-the-art isomerization catalysts tested in the isomerizing

hexenolysis.

fig. S4. Mass-corrected GC with IC-1.


fig. S6. Gas chromatogram with IC-3.

fig. S7. Gas chromatogram with IC-4.





fig. S12. Mass-corrected gas chromatogram with 0 equiv 1-hexene.

fig. S13. Mass-corrected gas chromatogram with 0.3 equiv 1-hexene.



fig. S16. Calculated boiling point curves of RME product blends after isomerizing

cross-metathesis with different amounts 1-hexene, along with pure RME and

petrodiesel.

fig. S17. Boiling point curves of commercial diesel and biodiesel (RME) before

and after isomerizing hexenolysis.

fig. S18. Experimental chain length distributions; MCL: 12.9; 14.4; 17.5.

fig. S19. Simulated distributions; turnover number (TON) M = 30,000; TON I =

7500; MCL: 10.3; 13.8; 17.3.

fig. S20. Simulated distributions; TON M = 30,000; TON I = 15,000; MCL: 10.4;

13.7; 16.8.


13.5; 16.4.


13.8; 17.5.


11.7; 15.1.

fig. S24. Mass-corrected gas chromatogram of the mixture obtained by sequential

isomerizing ethenolysis.

fig. S25. Additional Ru-based metathesis catalysts tested in the isomerizing

ethenolysis.

fig. S26. Raw gas chromatograms of the product mixture obtained by single-step

isomerizing ethenolysis before and after hydrogenation.

fig. S27. Mass-corrected gas chromatogram of the product mixture obtained by

single-step isomerizing ethenolysis.

fig. S28. Boiling point curves of commercial diesel and biodiesel (RME) before

and after isomerizing ethenolysis.



12.3; 15.7.


fig. S32. Simulated distributions; TON M = 15,000; TON I = 3000; MCL: 7.6;

10.6; 13.6.

table S1. Product distributions obtained experimentally by isomerizing

hexenolysis of RME.

table S2. Equilibrium product distributions calculated for the isomerizing

hexenolysis of RME.

table S3. Comparison of product distributions obtained from isomerizing

hexenolysis of RME.

table S4. Optimization of the one-step isomerizing ethenolysis of RME.

table S5. EN ISO 3405 distillation data of isomerizing metathesis reactions with

RME.

Legend for movie S1

Legend for data file S1

References (37–49)

Other Supplementary Material for this manuscript includes the following:

(available at advances.sciencemag.org/cgi/content/full/3/6/e1602624/DC1)

movie S1 (.mp4 format). Webra “Winner” 2.5-cm3 self-igniting model diesel

engine operated with the fuel obtained via isomerizing ethenolysis of rapeseed

methyl ester.

data file S1 (.m format). MatLab simulation.

Supplementary Materials and Methods

General Methods and Chemicals

All reactions were performed in oven-dried glassware containing a Teflon-coated stirring

bar. Gas chromatography (GC) analyses were carried out using a HP 6890 with an HP-5

capillary column (Phenyl Methyl Siloxane 30 m x 320 x 0.25, 100/2.3-30-300/3) and a

time program beginning with 4 min at 60°C, followed by a 2°C/min ramp to 300°C, then

10 min at this temperature. Retention times of the substances were determined using

reference substances. The Envantage Dragon SimDist© program was used for the

simulation of boiling point curves from gas chromatograms (37). Commercial substrates

were used as received unless otherwise stated. 1-Hexene was used in 99% purity without

further purification. Ethylene was used in N4.5 (99.995%) and N3.5 (99.95%) purity. The

metathesis catalysts used herein are available commercially, for example, from Sigma-

Aldrich or Umicore. Ru-1, 1,3-bis(mesityl)-2-imidazolidinylidene]-[2-[[(2-

methylphenyl)imino]-methyl]-phenolyl]-[3-phenyl-indenyliden]-ruthenium-(II)chloride,

Umicore M42, CAS-no. 934538-12-2; Ru-2, 1,3-bis(2,4,6-trimethylphenyl)-2-

imidazolidinylidene-[2-[[(4-methylphenyl)imino]-ethyl]-4-nitrophenolyl]-[3-phenyl-1H-

inden-1-ylid-ene]ruthenium(II)chloride, Umicore M41, CAS-no. 934538-04-2; Ru-3,

1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro-(3-phenyl-1H-inden-1-

ylidene)(pyridyl)-ruthenium(II), Umicore M31, CAS-no. 1031262-76-6; Ru-4, [1,3-

Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro[[2-(1-methyl-2-

oxopropoxy)phenyl]methylene]-ruthenium(II), Umicore M51, CAS-no. 1031262-71-1,

Ru-5, [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene] dichloro[(2-isopropoxy)(5-

pentafluorobenzoylamido) benzylidene]ruthenium(II), Umicore M72 SIMes, CAS-no.

1030618-02-0; Ru-6 [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro[5-

(2-ethoxy-2-oxoethanamido)-2-isopropoxy-benzylidene]ruthenium(II), Umicore M74

SIMes, CAS-no. 1030618-11-1; Ru-7 [1,3-Bis(2,4,6-trimethylphenyl)-2-

imidazolidinylidene]dichloro(2-iodophenylmethylene)ruthenium(II), Umicore M91,

CAS-no. 1415725-62-0; Ru-8 [1,3-Bis(2,4,6-trimethylphenyl)-2-

imidazolidinylidene]dichloro[(8-iodo-1-naphtalene)methylene]ruthenium(II), Umicore

M92, CAS-no 1415725-73-3; Ru-9 [1,3-Bis(2,4,6-trimethylphenyl)-2-

imidazolidinylidene]dichloro[(2-bromo-5-

dimethylamino)phenylmethylene]ruthenium(II), Umicore M93, CAS-no. 1415725-68-6;

Ru-10 cis-[1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(3-phenyl-1H-

inden-1-ylidene)(triisopropylphosphite)ruthenium(II), Umicore M22, CAS-no. 1255536-

61-8; Ru-11 [1,3-Bis(2,6-diisopropylphenyl)-2-imidazolidinylidene]dichloro[5-

(isobutoxycarbonylamido)-2-isopropoxybenzylidene]ruthenium(II), Umicore M73 SIPr,

CAS-No. 1212009-05-6; Ru-12 [1,3-Bis(2,4,6-trimethylphenyl)-2-

imidazolidinylidene]dichloro[5-(isobutoxycarbonylamido)-2-

isopropoxybenzylidene]ruthenium(II), Umicore M73 SIMes, CAS-no. 1025728-57-7;

Ru-13 [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro[(2-isopropoxy)(5-

trifluoroacetamido)benzylidene]ruthenium(II), Umicore M71 SIMes, CAS-no. 1025728-

56-6; Ru-14 [1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(3-phenyl-

1H-inden-1-ylidene)(4,5-dichloro-1,3-diethyl-1,3-dihydro-2H-imidazol-2-

ylidene)ruthenium(II), Umicore M81 SIMes, CAS-no. 1228169-92-3; Ru-CAAC [[1-

[2,6-bis(1-methylethyl)phenyl]-3,3,5,5-tetramethyl-2- pyrrolidinylidene]dichloro[[2-(1-

methylethoxy-κO)phenyl]methylene-κC]ruthenium(II), CAS-no. 959712-80-2 was

prepared according to (36); Hoveyda Grubbs I catalyst: Dichloro(o-

isopropoxyphenylmethylene)(tricyclohexylphosphine)ruthenium(II), CAS-no. 203714-

71-0. The isomerization catalyst IC-1 can be obtained, for example, from Sigma-Aldrich:

Bromo(tri-tert-butylphosphine)-palladium(I)dimer, CAS-no. 185812-86-6. IC-6

Acetonitrile(cyclopentadienyl)[2-(di-i-propylphosphino)-4-(t-butyl)-1-methyl-1H-

imidazole]ruthenium(II) hexafluorophosphate, CAS-no. 930601-66-4; IC-7

bis[(1,2,3,4,5-η)-2,4-cyclooctadien-1-yl]hydro-ruthenium tetrafluoroborate, CAS-no.

104390-14-9; IC-8 Chloro(1-phenylindenyl)bis(triphenylphosphine)ruthenium(II), CAS-

no. 1360949-97-8. Hoveyda Grubbs I catalyst Dichloro(o-

isopropoxyphenylmethylene)(tricyclohexylphosphine)ruthenium(II), CAS-no. 203714-

71-0.

Supplementary Text

Preparation of Rapeseed Methyl Ester (RME)

Transesterification was performed by adding commercial rapeseed oil (500 mL) to a

stirred solution of NaOH (2.00 g, 50.0 mmol) in methanol (500 mL). The solution was

vigorously stirred and heated to reflux for 3 h. After cooling to 25°C, the methanolic

glycerin phase was separated and residual methanol was removed from the crude product

by distillation. After washing with cold water (2 x 100 mL), pure RME was obtained by

distillation (1x10-3 mbar, 160°C) and stored under an argon atmosphere.

Identification of a catalyst system for the model reaction of RME and 1-hexene

Objective. In this series of experiments, we investigated catalyst systems for the

conversion of RME into a distribution of olefins, mono-, and diesters by isomerizing

metathesis. To identify a catalyst system effective for the isomerizing cross-metathesis of

RME and 1-hexene, catalysts and conditions were systematically tested. 1-Hexene was

added in order to reduce the mean chain lengths from 18 carbon atoms (excluding the

methyl ester carbon).

General procedure for the isomerizing hexenolysis of RME

In a glovebox under nitrogen atmosphere, an oven-dried 20 mL headspace vial with a

Teflon-coated stirring bar was charged with IC-cat., Ru-cat., RME and 1-hexene. The

vial was closed with a Teflon-coated crimp cap, removed from the glovebox, and the

mixture was stirred at 50°C for 20 h. The reaction mixture was cooled to 25°C, opened

and diluted with EtOAc (3 mL). GC analysis of the raw mixture gave the required

chromatogram for the SimDist boiling point curve simulation (see chapter Simulated

boiling curves of the isomerizing hexenolysis product blends).

To obtain simplified GC chromatograms, the mixture was then hydrogenated, converting

all double-bond isomers of a given olefinic product into a single saturated compound.

Hydrogenation of the diluted product mixture was carried out in the presence of Pd/C

(0.1 mmol) and hydrogen (10 bar) at 50°C for 12 h. After releasing the hydrogen

pressure, the sample was filtered over celite and MgSO4 and analyzed by gas

chromatography. The signals of the chromatograms were corrected for molecular weight

(38) and assigned by GC-MS.

Screening of Ru-based metathesis catalysts

The isomerizing hexenolysis of RME (1.65 g, 5.00 mmol, 1.88 mL) with 1-hexene (420

mg, 5.00 mmol, 558 µL) was carried out following the general procedure using IC-1

(3.89 mg, 5.00 µmol) and Ru-cat. (5.00 µmol, fig. S1). The product mixtures were

hydrogenated and analyzed by GC. For each Ru-cat., the signals of the olefin fraction

were selected from the chromatogram and corrected for molecular weight. They are

visualized in the superimposed histograms of the olefin fractions in fig. S2.

fig. S1. Ru-based metathesis catalysts tested in the isomerizing hexenolysis,

including second-generation indenylidene-ruthenium complexes Umicore M41 (Ru-

2) and M31 (Ru-3) and Hoveyda-type catalysts Umicore M51 (Ru-4), M72 SIMes

(Ru-5), and M74 SIMes (Ru-6).

fig. S2. Olefin blends obtained by isomerizing hexenolysis with different Ru

catalysts. Mono- and diester fractions displayed an analogous distribution.

In the olefin fractions shown in fig. S2, the non-isomerized metathesis products decene,

tetradecene and octadecene are overrepresented for all catalyst systems except for the IC-

1 / Ru-1 combination (black bars with superimposed black trend line). This indicates that

all other metathesis catalysts adversely affect the isomerization activity of IC-1.

Screening of isomerization catalysts

The isomerizing hexenolysis of RME (1.65 g, 5.00 mmol, 1.88 mL) with 1-hexene (434

mg, 5.00 mmol, 640 µL) was carried out following the general procedure using IC-cat.

(5.00 µmol, fig. S3) and Ru-1 (4.22 mg, 5.00 µmol). The hydrogenated product fractions

are shown in figs. S4-S11.

fig. S3. State-of-the-art isomerization catalysts tested in the isomerizing hexenolysis.

For a detailed description of the catalysts see:

IC-1: (19, 39-42).

IC-2, IC-3: [Rh]/BiPhePhos = 1:10, (43-45).

IC-4: (31, 46, 47).

IC-5: (33).

IC-6: (26, 32).

IC-7: (30).

IC-8: (48, 49).



fig. S6. Gas chromatogram with IC-3. Conditions: 2.5 mmol methyl oleate, 0.50 mol%

IC-3, 0.20 mol% Ru-1, neat, 20 h, 45°C.

fig. S7. Gas chromatogram with IC-4. Conditions: 2.5 mmol methyl oleate, 0.50 mol%

IC-4, 0.20 mol% Ru-1, neat, 20 h, 70°C.

fig. S8. Mass-corrected GC with IC-5. (Sample hydrogenated prior to GC analysis).




Figures S4 to S11 show that IC-1 was the only isomerization catalyst to be compatible

with the ruthenium metathesis catalyst.

Result. A combination of isomerization catalyst IC-1 (0.05 mol%) and metathesis

catalyst Ru-1 (0.05 mol%) effectively mediates the isomerizing cross-metathesis of RME

and 1-hexene at 50°C with a reaction time of 20 h.

Optimization of the boiling behavior with different 1-hexene/RME ratios

Objective. The effect of different 1-hexene / RME ratios on the boiling behavior of the

resulting olefin blends was investigated, with the goal of optimizing the mean boiling

temperature, initial and terminal boiling points of the curve.

Synthesis of hexenolysis products

Several olefin blends were synthesized using the optimal catalyst system IC-1 and Ru-1

following the general procedure of the isomerizing hexenolysis using different amounts

of 1-hexene (0, 0.3, 1.0, 1.5 equivalents).

The gas chromatograms obtained for the resulting product fractions after hydrogenation

show a shift of the distributions towards lower chain lengths (figs. S12 to S15).





The olefin / monoester / diester ratio increases with increasing amounts of 1-hexene,

while the carbon-chain lengths of the largest peaks and the mean chain lengths of the

distributions decrease (table S1).

table S1. Product distributions obtained experimentally by isomerizing hexenolysis

of RME.

[1-hexene] / [RME]

Mean chain lengths found Olefins Monoesters Diesters

0.0 <16.8a 17.5 18.8 0.3 <14.8a 16.1 18.3 1.0 <12.9a 14.4 17.5 1.5 <12.4a 14.0 17.6

a) Volatile olefins < C8 not integrated.

Calculated boiling curves of the isomerizing hexenolysis product blends

Boiling point curves were calculated from GC data of the raw product mixtures using the

Envantage Dragon SimDist© software (37). The software specifies a GC method for

sample analysis. It compares the GC signal areas at given retention times with the boiling

points of reference substances with known retention times and from this, calculates the

boiling point curve. This allows predicting the overall boiling behavior of the product

mixture (ca. 5 mmol/1.6 mL reaction volume) without the need to synthesize large

quantities of material.

The ability of the calculations to predict the atmospheric distillation results is limited by

the absence of reference material at high recovery, as well as the low intensity and low

response factor of GC signals at high temperatures. Values >90% recovery are

extrapolated by SimDist from the signal area of the GC sample. As a result, the intrinsic

drawback of this method are the unrealistic steps within the curves, and the steep rise at

>95% recovery.

To account for this limitation, the boiling point curves were also calculated for pure RME

and petrodiesel GC samples for comparison (fig. S16).

fig. S16. Calculated boiling point curves of RME product blends after isomerizing

cross-metathesis with different amounts 1-hexene, along with pure RME and

petrodiesel.

All curves displayed the desired evenly rising shape (fig. S16). With increasing

1-hexene / RME ratio, the mean boiling points gradually shift towards lower

temperatures and the slope becomes more even. At low 1-hexene / RME ratios, the

predicted boiling points were clearly too high at >80% recovery. However, the calculated

boiling point curve for the reaction of RME with 1.0 eq. of 1-hexene approximated that

of the diesel fuel reference even at higher recoveries. Increasing the amount of 1-hexene

further did not result in a significant shift of the boiling point curve.

Large-scale procedure for the isomerizing hexenolysis of RME

In order to measure the atmospheric boiling behavior of the product mixture, the reaction

was performed on large scale.

In a glovebox under nitrogen atmosphere, a 100 mL Büchi bmd 075 miniclave drive

autoclave was charged with RME (26.4 g, 30.1 mL, 80.0 mmol), 1-hexene (6.73 g, 9.93

mL, 80.0 mmol), IC-1 (62.2 mg, 80.0 µmol) and Ru-1 (67.5 mg, 80.0 µmol), then

removed from the glovebox. The resulting reaction mixture was stirred for 18 h at 50°C.

The reactor was cooled to ambient temperature and a 30% solution of H2O2 (16.3 mL,

160 mmol) was slowly added at 0°C under vigorous stirring to remove the catalyst (1000

rpm, overhead stirrer). The organic phase was separated, dried over 3 Å molecular sieves

and filtered over a short column of celite and MgSO4. Because RME is a mixture of

different compounds, it is only possible to give a volume-based yield. Starting from 30.1

mL RME and 9.93 mL 1-hexene, 32 mL of the isomerizing metathesis blend was isolated

(80%).

Atmospheric distillation of the product provided the boiling point curve shown in fig.

S17.

fig. S17. Boiling point curves of commercial diesel and biodiesel (RME) before and

after isomerizing hexenolysis. The hashed areas represent the limits specified in EN

590.

* = smoke formation.

Result. A 1-hexene / RME ratio of 1:1 was determined to provide the optimal boiling

behavior of the product blend. The resulting boiling point curve closely matches that of

petrodiesel in terms of initial and mean boiling point. It still has deficits in the final

recovery percentages, because it crosses the specification limits and progressively

decomposes with smoke formation above 360°C.

Simulation of the isomerizing hexenolysis reaction mixtures

Objective. A simulation program was developed with the aim of understanding the

factors related to stoichiometry and catalyst performance that affect product distributions

in reaction mixtures at any stage before reaching equilibrium.

General methods for the simulations

All simulations were generated using MathWorks MATLAB R2014b. The simulation

code is available as a separate .m file in the supplementary material or directly from the

authors. In the simulation program, a given number of randomly chosen molecules from a

mixture of methyl oleate/hexene at a given ratio undergo a single shift of their double

bond. Then, another given number of randomly chosen molecules undergo metathesis.

These two steps are iterated a given number of times, so that different overall and relative

turnover numbers for both catalyst systems can be modelled.

The simulated histograms were then compared with the experimental data, and the mean

chain lengths (MCL) of the simulated distributions were calculated by weighted

arithmetic mean.

The simulated boiling point curves (Fig. 3 in the main manuscript) were calculated from

the simulated product distributions. The boiling point curves could not be calculated with

SimDist, because this requires GC input data. Instead, the boiling points of all simulated

product molecules were either taken from the literature or extrapolated from literature

values, and were used as input to calculate the boiling point curves using a Visual Basic

macro. The macro file is available from the authors upon request.

The simulation output obtained with this macro was calibrated with experimental results

obtained in a series of model reactions and SimDist results for the respective sample.

Simulations for a 1:1 mixture of methyl oleate and 1-hexene

The experimentally observed product fractions, i.e. olefins (blue bars), mono- (red bars),

and diesters (green bars), were plotted as separate histograms. These were overlaid with

normalized integrals for the simulated product fractions (solid black lines) that were set

to 1 for each fraction (figs. S18 - S23).

Since olefins (blue) <C8 were not detected via GC, the normalized integrals were too

high compared to the simulated solid black curve, which also covered the olefins <C8.

The simulated curves were scaled to account for this issue (dotted black lines).

The simulation was run with different turnover numbers for the isomerization (TON I)

and metathesis (TON M). For the isomerizing hexenolysis, the amount of olefin

molecules was set to 2,000 per catalyst molecule. This equals the experimental catalyst

loading of 0.05 mol%.

For the isomerizing hexenolysis, the best fit was achieved for turnover numbers of 30,000

for the metathesis and 7,500 for the isomerization catalyst (fig. S19). This translates to 15

metathesis and 3.75 isomerization steps per molecule. The simulated histogram in fig.

S19 demonstrates that the reaction had not quite reached equilibrium but was close to

becoming homogeneous.


fig. S19. Simulated distributions; turnover number (TON) M = 30,000; TON I =

7500; MCL: 10.3; 13.8; 17.3.


13.7; 16.8.


13.5; 16.4.


13.8; 17.5.


11.7; 15.1.

Calculation of the carbon-chain length distribution

The carboxylate carbons do not take part in the transformation and is therefore omitted in

all calculations. For example, methyl oleate has 19 carbon atoms but is calculated as C18.

Close to equilibrium, the product distribution is determined by the relative abundance of

C–C double bonds, functionalized and unfunctionalized chain termini. Thus, for the

isomerizing hexenolysis of pure C18 monounsaturated fatty acid esters, the calculated

ratio of olefins, mono- and diesters is (¾ * ¾) : (¾ * ¼ * 2) : (¼ * ¼) = 9:6:1.

The mean carbon-chain lengths of the olefin, mono- and diester fractions at equilibrium

were calculated from the ratio of the unfunctionalized and ester termini and the ratio of

carbon atoms per double bond. The following formula was used, with a, b, c, X and Y

according to:

Ø (b+c) = (Y*15 + X*a) / (X + Y)

For example, in the isomerizing hexenolysis with 1.0 eq. 1-hexene X = Y = 1 and

a = 4. Therefore Ø (b+c) = 9.5. This still excludes the two carbons of the double bond, so

that the mean chain length of the olefin fraction is 9.5 + 2 = 11.5. For the full chain

lengths of the mono- and diester fractions, 1 and 2 carbons, respectively, need to be

added to this value to include the carboxylate termini (table S2).

table S2. Equilibrium product distributions calculated for the isomerizing

hexenolysis of RME.

[1-hexene] / [RME]

Mean chain lengths equilibrium Olefins Monoesters Diesters

0.0 17.0 18.0 19.0 0.3 14.5 15.5 16.5 1.0 11.5 12.5 13.5 1.5 10.4 11.4 12.4

Simulation of the isomerizing metathesis at high turnover numbers for both isomerization

and metathesis (150 isomerization and metathesis steps each per olefin molecule)

provided MCL values that match the ones obtained by the formula of the weighted

arithmetic mean above (table S2). This indicates that 150 isomerization and metathesis

steps each per olefin molecule are enough to ensure equilibrium distributions.

Compared with the experimentally obtained results of <12.9 carbons for the olefins

(excluding volatiles not detectable by GC analysis), 14.4 for the monoesters and 17.5 for

the diesters (see table S1), the calculated values at equilibrium are smaller for all

fractions (MCL: 11.5; 12.5; 13.5.). This shows how the experimental conditions, that are

not fully accounted for by the assumptions made in the simulation, affect the distributions

in practice:

RME contains saturated methyl palmitate (4%) and stearate (1%), which cannot

undergo isomerizing metathesis. This explains the protruding signals of C16 and

C18 esters and increases the proportion and mean chain length of the monoester

fraction.

The different stability and reaction rates of certain olefinic compounds, e.g. terminal

or conjugated systems, are not accounted for in the calculations.

The partial evaporation of short-chain olefins from the mixture leads to larger mean

chain lengths for all fractions.

The simulated curve that best fits the experimental distribution for the isomerizing

hexenolysis of methyl oleate was obtained with 15 metathesis and 3.75 isomerization

steps per molecule. These are substantially fewer steps than required to reach

equilibrium. This best-fit simulated curve translates to mean chain lengths of 10.3, 13.8

and 17.3 for olefins, mono- and diesters respectively (table S3, fig. S19).

table S3. Comparison of product distributions obtained from isomerizing

hexenolysis of RME.

[1-hexene] / [RME]

Mean chain lengths equilibrium / fitted curvea / found

Olefins Monoesters Diesters

0.0 17.0 / 18.0 / <16.8b 18.0 / 18.0 / 17.5 19.0 / 18.0 / 18.8 0.3 14.5 / 13.8 / <14.8b 15.5 / 15.7 / 16.1 16.5 / 17.7 / 18.3 1.0 11.5 / 10.3 / <12.9b 12.5 / 13.8 / 14.4 13.5 / 17.3 / 17.5 1.5 10.4 / 9.2 / <12.4b 11.4 / 13.1 / 14.0 12.4 / 17.1 / 17.6

a) Simulated values for 2,000 olefin molecules per catalyst after 30,000 metathesis and

7,500 isomerization steps. b) Excluding volatile olefins < C8.

In all cases, simulated mean chain lengths depart only slightly from the experimentally

observed values. The remaining deviation may be a result of the factors discussed above.

The simulations for higher isomerization rates show that although the mean chain length

of the diester fraction is shifted towards lower values, a broadening of the mono- and

diester fractions results in an undesirable overall increase of the fraction boiling at high

temperatures >380°C.

Result. The simulation program provides curves that are adjustable with regard to

substrate stoichiometry and turnover of both the isomerization and metathesis catalyst.

Development of the isomerizing ethenolysis of RME

Objective. To explore the possibility of employing gaseous ethylene in isomerizing

metathesis reactions with the goal of producing an EN 590-compatible fuel.

Procedure for the sequential isomerizing ethenolysis

A comparison of the isomerizing cross-metathesis using ethylene to the results previously

obtained with 1-hexene required a process in which an ethylene / RME stoichiometry of

close to 1:1 was reproducibly ensured. This also allowed calibrating the subsequent

simulations. It was achieved by non-isomerizing ethenolysis of RME. The product

mixture was then subjected to isomerizing metathesis for further reaction development.

Ethenolysis of RME. Under an atmosphere of argon, a 1 L stirred Parr autoclave was

charged with Hoveyda Grubbs I catalyst (3.60 g, 6.00 mmol) and rapeseed oil methyl

ester (178 g, 200 mL, 600 mmol). The vessel was pressurized with 10 bar ethylene and

stirred for 18 h at ambient temperature. The reactor was cooled to -20°C and the ethylene

pressure was slowly released. After warming up to ambient temperature, the reaction

mixture was filtered over silica and distilled under vacuum (1x10-3 mbar, up to 250°C),

yielding a mixture of 1-decene and methyl decenoate : methyl oleate : dimethyl octadec-

9-enedionate with the ratio 82.7 : 10.0 : 5.00, along with small amounts of additional

olefins and saturated components of RME.

Isomerizing metathesis. In a glovebox under nitrogen atmosphere, a 100 mL Büchi bmd

075 miniclave drive autoclave was charged with the previously prepared ethenolysis

mixture (54.0 g, 60 mL), IC-1 (303 mg, 390 µmol) and Ru-1 (329 mg, 390 µmol). The

resulting reaction mixture was stirred for 18 h at 50°C. The reactor was cooled to ambient

temperature and a 30% solution of H2O2 (27.6 mL, 270 mmol) was slowly added at 0°C

under vigorous stirring (1000 rpm, overhead stirrer). The organic phase was separated,

dried over 3 Å molecular sieves and filtered over a short column of celite and MgSO4.

Because RME and therefore the ethenolysis product are mixtures of different compounds,

it is only possible to give a volume-based yield. Starting from 60 mL of the ethenolysis

mixture, 50 mL of the isomerizing metathesis blend was isolated (83%). The resulting

product fraction is shown in fig. S24.

fig. S24. Mass-corrected gas chromatogram of the mixture obtained by sequential

isomerizing ethenolysis. (sample hydrogenated for GC analysis).

Optimization of the one-step isomerizing ethenolysis of RME

Table S4 shows the optimization of an isomerizing ethenolysis of RME as a one-step

procedure. Various volumes of ethylene were added by pressurizing a closed vessel, by

attaching an ethylene balloon, or by passing a stream of ethylene through a rapidly stirred

reaction mixture containing 2.50 mmol RME (based on methyl oleate) and a catalyst

system in the absence of solvent at 60°C for 16 h. The product mixtures were

hydrogenated and analyzed by GC.

table S4. Optimization of the one-step isomerizing ethenolysis of RME.

table S4 (continued).

Entry Ru-cat.

Ru-cat. (mol%)

Ru-CAAC (mol%)

IC-1 (mol%)

Av. MCLa

Homogeneous distribution

Gas Volume (mL)

1b Hexenolysis (see above) 15.0 Yes - 2b Seq. ethenolysis (see above) 13.7 Yes -

3b,c Ru-1 0.05 - 0.05 - No conversion 300 4 Ru-1 0.10 - 0.10 18.0 No 20 5 Ru-3 0.10 - 0.10 16.1 No 20 6 Ru-4 0.10 - 0.10 15.7 Almost 20 7 Ru-5 0.10 - 0.10 15.3 Almost 20 8 Ru-6 0.10 - 0.10 15.7 Almost 20 9 Ru-7 0.10 - 0.10 15.2 Yes 20

10 Ru-8 0.10 - 0.10 16.3 Almost 20 11 Ru-9 0.10 - 0.10 15.8 No 20 12 Ru-10 0.10 - 0.10 17.9 No 20 13 Ru-11 0.10 - 0.10 15.3 Almost 20 14 Ru-12 0.10 - 0.10 15.3 No 20 15 Ru-13 0.10 - 0.10 15.9 Almost 20 16 Ru-14 0.10 - 0.10 16.8 No 20 17 Ru-5 0.10 - 0.40 15.8 Almost 20 18 Ru-7 0.10 - 0.40 15.5 Yes 20 19 Ru-11 0.10 - 0.40 15.4 Yes 20 21 Ru-5 0.10 0.10 0.40 15.2 Yes 20 22 Ru-7 0.10 0.10 0.40 16.0 Yes 20 23 Ru-11 0.10 0.10 0.40 15.3 Yes 20 24 Ru-5 0.10 0.10 0.40 13.2 Yes 300 25 Ru-7 0.10 0.10 0.40 12.7 Yes 300 26 Ru-11 0.10 0.10 0.40 12.5 Yes 300 27c Ru-11 0.10 0.10 0.40 14.4 Yes 300 28d Ru-11 0.10 0.10 0.40 12.9 Yes Stream 29d Ru-11 0.10 - 0.40 15.1 Yes Stream 30 - - 0.10 0.40 14.1 No 300

a) Av. MCL = The average of the mean chain length of all three product classes (olefins,

mono-, diester) indicates how far the overall product distribution has shifted towards

lower chain lengths. The average MCL for the isomerizing self-metathesis of RME

without additional olefins is 18; b) Reaction at 50°C; c) 6 bar ethylene pressure; d) 45

mmol-scale under constant stream of ethylene at atmospheric pressure.

The average mean chain length (av. MCL) of all three product fractions is a measure of

the ethylene intake and the shift of the product distributions towards lower boiling points

(compare figs. S12-S15 for the effect with 1-hexene).

Without ethylene, the average MCL is 18 (isomerizing self-metathesis of RME). Adding

short-chain olefins, for example in the isomerizing hexenolysis and the sequential

isomerizing ethenolysis, led to lower MCL values (entries 1, 2). In addition, we

compared the shape of the product distributions obtained. The system Ru-1/IC-1 was

inactive under ethylene pressure, possibly due to decomposition of the ruthenium

complex (entry 3). Conversion was first observed after switching to atmospheric ethylene

pressure (entry 4). The catalyst loading was increased to 0.10 mol% to compensate for

lower activity and stability in the presence of ethylene.

fig. S25. Additional Ru-based metathesis catalysts tested in the isomerizing

ethenolysis.

Screening of different ruthenium-NHC complexes (entries 4-16, figs. S1 and S25)

identified three catalysts (Ru-5, Ru-7, Ru-11) that mediate the isomerizing metathesis of

RME in the presence of ethylene with homogeneous product distributions and decreased

average MCLs (entries 7, 9, 13). At an IC-1 loading increased to 0.4 mol%, the

homogeneity of the distributions increased, and protruding cross-metathesis products

were no longer observed (entries 17-19).

Addition of the specialized ethenolysis catalyst Ru-CAAC as well as increasing the

ethylene volume to 300 mL resulted in a greater ethylene incorporation into the products

and shorter av. MCL down to 12.5 (entries 21-26). An increase of the ethylene pressure

to 6 bar had an adverse effect (entry 27, 300 mL gas volume at 6 bar). The best results

were obtained when passing a constant stream of ethylene through the reaction vessel

(entry 28). Control experiments confirmed the necessity of all catalyst components

(entries 29, 30).

All reactions in table S4 were performed with N4.5 (99.995%) ethylene. When

employing N3.5 (99.95%) ethylene in the optimized reaction (entry 26), the distributions

and mean chain lengths were identical.

Screening of isomerization catalysts in the isomerizing ethenolysis

In a glovebox under nitrogen atmosphere, an oven-dried 10 mL headspace vial with a

Teflon-coated stirring bar was charged with IC-cat. (16.0 µmol, fig. S3), Ru-11. (3.31

mg, 4.0 µmol) and RME (1.19 g, 4.00 mmol, 1.35 mL). The vial was closed with a

Teflon-coated crimp cap with a gas inlet and placed in an autoclave. The autoclave was

removed from the glovebox, evacuated (10-3 mbar), pressurized with ethylene (6 bar) and

the mixture was stirred at 60°C for 16 h. The autoclave was cooled to 0°C, opened and

the reaction mixture was diluted with EtOAc (3 mL).

To obtain simplified GC chromatograms, the mixture was then hydrogenated and

analyzed by GC as described in the standard procedure.

Isomerization catalysts IC-1, IC-3, IC-4, IC-6, IC-7 and IC-8 (fig. S3) were tested under

the conditions mentioned above. IC-1 was the only isomerization catalyst to give

homogeneous product distributions. With all other catalysts, predominantly cross

metathesis products were observed.

Optimized procedure for the single-stage isomerizing ethenolysis

In a glovebox under nitrogen atmosphere, a 30 mL glass reactor was charged with Ru-

CAAC (30.3 mg, 50.0 µmol), IC-1 (155 mg, 200 µmol), Ru-11 (41.3 mg, 50.0 µmol)

and RME (16.9 mL, 50 mmol based on methyl oleate). The resulting reaction mixture

was stirred under a stream of ethylene at atmospheric pressure for 16 h at 60°C. Two

such batches were combined, cooled to ambient temperature and a 30% solution of H2O2

(5.11 mL, 50 mmol) was slowly added at 0°C under vigorous stirring. The organic phase

was separated, dried over MgSO4 and filtered over a short column of celite and MgSO4,

yielding 25 mL of a brown oil (74% based on volume). After high-temperature vacuum

distillation (10-3 mbar, >350°C), 24 mL of the product mixture were obtained as a light

yellow liquid (96% recovery after distillation).

Reaction scale-up for the single-stage isomerizing ethenolysis

In a glovebox under nitrogen atmosphere, a 1 L Parr autoclave was charged with Ru-

CAAC (243 mg, 0.40 mmol), IC-1 (1.24 g, 1.60 mmol), Ru-11 (330 mg, 0.40 mmol) and

RME (135 mL, 400 mmol based on methyl oleate). The resulting reaction mixture was

stirred under a stream of ethylene at atmospheric pressure for 16 h at 60°C. The reactor

was cooled to ambient temperature and a 30% solution of H2O2 (40.9 mL, 400 mmol)

was slowly added at 0°C under vigorous stirring. The organic phase was separated, dried

over MgSO4 and filtered over a short column of celite and MgSO4, yielding 75 mL of a

brown oil (55% based on volume). After high-temperature vacuum distillation (1x10-3

mbar, >350°C), the product mixture was obtained as a light yellow liquid (73 mL, >98

wt-% recovery after distillation). A sample was analyzed by GC following hydrogenation

(fig. S26). The peaks were assigned by GC-MS and corrected for their mass to generate

the histogram in fig. S27.

fig. S26. Raw gas chromatograms of the product mixture obtained by single-step

isomerizing ethenolysis before and after hydrogenation.

fig. S27. Mass-corrected gas chromatogram of the product mixture obtained by

single-step isomerizing ethenolysis. (Sample hydrogenated for GC analysis).

Atmospheric distillation of the product provided the boiling point curve shown in fig.

S28. All experimental recovery temperatures are given in table S5.

fig. S28. Boiling point curves of commercial diesel and biodiesel (RME) before and

after isomerizing ethenolysis. The hashed areas represent the limits specified in EN 590.

Result. An effective ternary catalyst system was found that mediates the isomerizing

ethenolysis of RME, composed of the ethenolysis catalyst Ru-CAAC (0.1 mol%), the

isomerization catalyst IC-1 (0.4 mol%) and the metathesis catalyst Ru-11 (0.1 mol%),

which operates at atmospheric ethylene pressure. The product mixture obtained fulfils the

standard EN 590.

Simulation of the isomerizing ethenolysis mixtures

Objective. The isomerizing ethenolysis was simulated in order to determine the optimum

stoichiometry and catalyst turnovers.

The general methods for simulations described above were also applicable in this section.

Simulations for a 1:0.83 mixture of methyl oleate and ethylene

This simulation models the sequential isomerizing ethenolysis. It was parameterized for

an isomerizing ethenolysis starting with methyl oleate and ethylene. The ratio of methyl

oleate to ethylene was corrected for the result obtained in the non-isomerizing ethenolysis

of RME (83% ethenolysis products), which served as the starting material in the

isomerizing metathesis experiment. The simulated distributions were then compared to

the experimental data (figs. S29 and S30).



12.3; 15.7.

Simulations for a 1:1.33 mixture of methyl oleate and ethylene

This simulation models the one-step isomerizing ethenolysis. The starting parameters

were set to a 1:1.33 mixture of methyl oleate and ethylene. Since the exact amount of

ethylene in the reaction mixture and the ethylene uptake could not be determined

experimentally under flow conditions, it was assumed that each double bond in the

starting material reacts with one molecule of ethylene. Based on the FAME composition

of RME (65% methyl oleate [18:1], 22% methyl linoleate [18:2], 8% methyl linolenate

[18:3], 1% methyl stearate [18:0], and 4% methyl palmitate [16:0]) it was calculated that

100 molecules of RME contain an average of 133 olefinic double bonds and react with

133 molecules of ethylene. Therefore, a ratio of 1:1.33 was used.

The simulation was set to 1000 olefinic molecules per catalyst molecule, which equals

the experimental catalyst loading of the metathesis catalyst (0.1 mol%). The best fit was

achieved with turnover numbers of 15,000 for the metathesis and 12,000 for the

isomerization catalyst (figs. S31 and S32).

It should be noted that the simulated turnover number for the isomerization cannot be

directly compared with the values calculated for the sequential isomerizing ethenolysis or

the isomerizing hexenolysis. The loading of the isomerization catalyst had to be increased

to 0.4 mol% in the experiment to compensate for lower catalyst activity in the presence of

ethylene. Different loadings of isomerization and metathesis catalysts cannot separately

be parameterized in the simulation algorithm. Therefore, the simulations were conducted

a catalyst loading of 0.1 mol% as described above. Therefore, TON I from the simulation

(12,000) was corrected for the experimental catalyst loading to 3,000.


fig. S32. Simulated distributions; TON M = 15,000; TON I = 3000; MCL: 7.6; 10.6;

13.6.

For the overlays in Figs. 2 and 4 in the main manuscript, the simulated data from figs.

S19 and S32 were used. Both curves were smoothed by a Savitzky-Golay filter for clarity

and to suppress statistical fluctuation. All simulated curves in the supplementary

materials are unaltered and contain minimal statistical fluctuations.

Result. By fitting the simulated curves to the experimentally obtained product

distributions of the product that fulfils EN 590, the individual TON for the isomerization

and metathesis catalyst were determined to be TON M = 15,000 and TON I = 3,000.

Analysis of the physical properties of the product blends.

Atmospheric distillation (EN ISO 3405)

The isomerizing hexenolysis, the sequential and the one-step isomerizing ethenolysis of

RME were conducted on large scale as described above. 100 mL of each sample were

analyzed by atmospheric distillation in an Anton Paar ADU 4 ISO 3405 distillation

apparatus to determine the boiling point curve according to the standard DIN EN 590 for

petrodiesel (table S5). The standard defines three thresholds:

At 250°C less than 65% of the sample is collected.

At 350°C at least 85% of the sample is collected.

At least 95% of the sample is collected at a maximum of 360°C

table S5. EN ISO 3405 distillation data of isomerizing metathesis reactions with

RME.

Recovery (%)

Recorded temperature (°C)a Diesel ICM with

1-hexene Seq. ICM with

Ethylene One step ICM with ethylene

IBP 177.8 121.0 73.7 111.6 5 197.2 171.6 125.4 155.6

10 205.7 190.7 157.1 168.2 15 213.0 209.8 184.3 182.0 20 221.2 225.9 202.8 195.5 25 229.6 239.1 217.3 207.9 30 237.3 250.2 228.9 219.8 35 245.0 259.7 240.0 231.4 40 252.3 268.8 250.5 242.1 45 261.1 277.3 261.5 252.2 50 269.6 285.7 271.3 263.7 55 277.4 294.5 280.6 274.4 60 286.1 302.8 289.6 283.6 65 294.5 310.6 299.9 293.8 70 303.6 319.2 309.4 302.8 75 311.6 327.5 318.1 311.3 80 320.8 336.3 326.9 319.3 85 329.5 346.3 336.0 327.8 90 339.6 354.1 346.5 338.0 93 346.9 359.5 355.3 346.4 95 353.4 decomposition 362.4 354.1

FBP 364.3 - 366.2 357.8 IBP = Initial boiling point, FBP = final boiling point, ICM = isomerizing cross-

metathesis, seq. = sequential. a) Recorded temperature corrected for atmospheric

pressure.

The hexenolysis product showed a recovery of only 93% at 360°C, which narrowly

misses the specified value of 95%. Towards the end of the distillation, it partially

decomposed with smoke formation. This is a common problem for biodiesel, caused by

oxidation of sensitive polyunsaturated fatty acid derivatives, and is usually addressed by

partial hydrogenation of the product fractions.

In contrast, the boiling point curve for the one-step isomerizing ethenolysis product had a

lower mean boiling temperature, resulting in the specified recovery of 95% at a

maximum of 360°C, thus meeting the boiling specifications.

movie S1. Webra “Winner” 2.5-cm3 self-igniting model diesel engine operated with

the fuel obtained via isomerizing ethenolysis of rapeseed methyl ester. The small two-

stroke diesel engine has ca. 10 bar compression pressure (c.f. ca. 25 bar for full-size

diesel engines), so that self-ignition requires additives. The standard fuel recipe involves

ca. 30% petrodiesel, 30% diethyl ether and 2% amyl nitrite as ignition booster, and 30%

two-stroke oil as lubricant. Instead, we used 60% isomerizing ethenolysis product, 30%

diethyl ether, and 10% rapeseed oil to run the engine. As can be seen in the video, the

engine ran steadily even at the difficult minimal throttle. At higher throttle, the engine

produced sufficient thrust to move the model car.

data file S1. MatLab simulation. This contains the MatLab code for the mathematical

modeling of the product distributions. This .m file can be opened by MatLab R2014b or

visualized with any plain-text editor.

Supplementary Materials for - Science Advances...all other metathesis catalysts adversely affect the isomerization activity of IC-1. Screening of isomerization catalysts The isomerizing

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