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tion conditions. The reactor had to be filled with 200 mL H2O to in-
vestigate phase separation. Comparable proportions of catalyst,
feed, and water were used as during a regular hydrothermal deox-
ygenation as described above. More information can be found in
the Supporting Information.
The aqueous-phase reforming reactions of glycerol were per-
formed in a multiple reactor system (Parr MRS5000) containing
75 mL vessels with magnetic stirring. Pressure and temperature
were monitored continuously during catalytic tests using this
setup. After the desired time, the reactor was cooled to room tem-
perature by forced air cooling and the reactor was subsequently
rinsed with chloroform. Further work-up procedures were identical
to those mentioned above for reactions in the batch reactor
system with PTFE lining.
chemicals. Additionally, XRD and TEM showed that the palladi-
um particle size was retained when the catalyst was exposed
to a 2nd and 3rd catalytic run.
The DO activities obtained in this work are competitive with
the H2-free DO of fatty acids and triglycerides in organic sol-
vents, with activities reported between 0.3–30ꢂ10À4 molHCsꢂ
molmetalÀ1 ꢂsÀ1 using mainly saturated fatty acids and operat-
ing at reaction temperatures between 300–3608C.[16,17,23–25]
However, the obtained activities are not yet competing with
the hydrodeoxygenation process, reporting activities up to
200ꢂ10À4 molHCsꢂmolmetalÀ1 ꢂsÀ1.[14,16,17,23–29] Further devel-
opment and optimization of the current process is required for
industrial application. This process, however, shows potential
to deoxygenate a wide range of nonedible and waste fats and
oils without the necessity to remove impurities such as water
and FFAs, and without the use of additional (nonrenewable)
H2. For that reason, this proof-of-principle could be the first
step towards a one-pot hydrolysis–deoxygenation reaction
aided by in situ H2 production from glycerol reforming towards
high-performance fuels or value-added chemicals.
See the Supporting Information for more detailed experimental
procedures.
Acknowledgements
The authors would like to thank D.R. Stellwagen for the XRD
measurements, R.P. Purushothaman for the HPLC-(MS) analysis,
K. Fukuhara for his help with the Parr 2430 autoclave and C. van
de Spek for the TEM measurements. This research has been per-
formed within the framework of the CatchBio program. The au-
thors gratefully acknowledge support of the Smart Mix Program
of the Netherlands Ministry of Economic Affairs and the Nether-
lands Ministry of Education, Culture and Science.
Experimental Section
All hydrothermal deoxygenation reactions were performed in
a non-stirred batch reactor system with PTFE lining (Parr 4744;
volume 45 mL; height 89 mm; radius 11 mm). A cross-section of
the reactor can be found in the Supporting Information (Figure S3).
The PTFE cup was charged with 1.2 mmol triglyceride feed,
1.2 mmol tetradecane internal standard (Sigma–Aldrich, olefin free,
ꢀ99.0%), 0.250 g Pd/C (Strem Chemicals, Inc., 5 wt% on activated
carbon, reduced, dry powder), and 25 mL demineralized water. The
batch reactor was placed in a preheated oven at 2508C for 20 h.
After the desired time, the reactor was taken out of the oven and
cooled to room temperature by forced air cooling. The advantages
of this experimental set-up are the absence of large temperature
gradients over the reactor and the absence of dead volume in re-
actor conduits. Note that the absence of external mass transfer lim-
itations has to be shown to justify the use of this nonstirred reac-
tion setup. To investigate the occurrence of external mass transfer
limitation, we designed a reactor setup in which we could simulta-
neously heat and magnetically stir the reaction mixture (using the
Parr 4744 reactor). The reaction mixture was stirred at 600 rpm
which resulted in the most optimal mixing. Via this reaction set-up
it was found that the results obtained with a stirred autoclave
were within the experimental error of those obtained with the
nonstirred autoclave (see Supporting Information, text and
Table S1). Evaluation of potential internal mass transfer limitations
by means of the Weisz–Prater criterion further showed that internal
H2 diffusion limitation was negligible (Supporting information,
Table S3).
Keywords: biomass
·
deoxygenation
·
glycerol
·
heterogeneous catalysis · triglycerides
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ChemSusChem 2014, 7, 1057 – 1060 1061