10.1002/cctc.201701632
ChemCatChem
FULL PAPER
njoutlet
Catalytic tests. Activation of the TiC-SiC composite was performed
under methane and ethane oxychlorination/oxybromination and HCl and
HBr oxidation conditions at ambient pressure in a continuous-flow fixed-
bed reactor setup, which is detailed elsewhere.[22,23] The gases CH4
(PanGas, purity 5.5), C2H6 (PanGas, purity 3.5), HCl (Air Liquide, purity
2.8, anhydrous), HBr (Air Liquide, purity 2.8, anhydrous), O2 (PanGas,
purity 5.0), Ar (PanGas, purity 5.0; internal standard), and He (PanGas,
purity 5.0; carrier gas), were fed by digital mass flow controllers
(Bronkhorst®) to achieve a total volumetric flow, FT, of 6 L STP h-1,
containing a stoichiometric mixture (alkane:HX:O2:Ar:He = 6:6:3:4.5:80.5;
X = Cl, Br). In the case of HCl and HBr oxidation, the feed composition
used was HX:O2:He = 6:3:91. A quartz reactor (10 mm internal diameter)
was loaded with the catalyst (catalyst weight, Wcat = 1 g, particle size,
STYj =
´MWcat, molj h-1 mol-1
Eq. 6
Ti
Wcat ´ xTi
where njoutlet is the molar flow of the product j at the reactor outlet and NC,j
is the number of carbon atoms in the compound j.
The error of the carbon mass balance, eC, determined using Eq. 7,
niinlet ´NC,i - n outlet ´NC,i
+
njoutlet ´NC, j
(
)
i
å
Eq. 7
eC
=
´100, %
niinlet ´NC,i
was less than 5% in all experiments. All the catalysts were activated in
the reaction mixture for a total time of 5 h and at a final temperature of
850 K. Additionally, the activation of the TiC-SiC composite in HBr and
HCl oxidation at 810 K was monitored with time up to 20 h. After the tests,
the reactor was quenched to room temperature in He flow and the
catalyst was retrieved for ex situ characterization.
dp = 0.4-0.6 mm), and placed in an electrical oven.
A
K-type
thermocouple fixed in a coaxial quartz thermowell with the tip positioned
in the center of the catalyst bed was used to monitor the temperature
during the reaction. Prior to testing, the catalyst bed was heated in a He
flow to the desired temperature (T = 523-850 K) and allowed to stabilize
for at least 30 min before the reaction mixture was fed. The down-stream
lining was heated at 393 K to prevent the condensation of reaction
products. The effluent gas stream was sent through impinging bottles
containing an aqueous 1 M NaOH solution for neutralization prior to
release to the ventilation system. Quantification of X2 was performed by
its absorption in an impinging bottle filled with an aqueous 0.1 M KI
solution (X2 + 3I- → I3- + 2X-) followed by iodometric titration (Mettler
Acknowledgements
This work was supported by ETH Research Grant ETH-04 16-1
and by the Swiss National Science Foundation (project
no. 200021-156107). The authors thank Prof. Ralph Spolenak
and ScopeM at ETH Zurich for using their facilities. Micha Calvo
and Dr. Réne Verel are acknowledged for Raman and NMR
analyses, respectively.
Toledo
G20
Compact
Titrator)
of
the
formed
triiodide
(I3- + 2S2O32- → 3I- + S4O62-) with an aqueous 0.01 M Na2S2O3 solution
(Aldrich, 99.99%). Carbon-containing compounds (CH4, C2H6, C2H4,
CH3X, CH2X2, C2H5X, CO, and CO2) and Ar were quantified using an on-
line gas chromatograph equipped with a GS-Carbon PLOT column
coupled to a mass spectrometer (GC-MS, Agilent GC 6890, Agilent MSD
5973N).
Keywords: alkane oxyhalogenation • natural gas upgrading •
C−H activation • titanium carbide-silicon carbide composite •
titanium oxide
The conversion of reactant i, Xi, (i: CH4, or C2H6) was calculated using
Eq. 1,
[1]
[2]
[3]
J. J. H. B. Sattler, J. Ruiz-Martinez, E. Santillian-Jimenez,
B. M. Weckhuysen, Chem. Rev. 2014, 114, 10613-10653.
H. Schwarz, Angew. Chem. 2011, 123, 10276-10297; Angew. Chem.
Int. Ed. 2011, 50, 10096-10115.
ni inlet - ni outlet
Eq. 1
Xi
=
´ 100, %
ni inlet
E. V. Kondratenko, T. Peppel, D. Seeburg, V. A. Kondratenko,
N. Kalevaru, A. Martin, S. Wohlrab, Catal. Sci. Technol. 2017, 7,
366-381.
where niinlet and nioutlet are the respective molar flows of the reactant i at
the reactor inlet and outlet.
[4]
[5]
[6]
[7]
E. McFarland, Science 2012, 338, 340-342.
The conversion of HX, XHX, was calculated according to Eq. 2,
J. A. Labinger, J. E. Bercaw, Nature 2002, 417, 507-514.
R. Khalilpour, I. A. Karimi, Energy 2012, 40, 317-328.
R. Lin, A. P. Amrute, J. Pérez-Ramírez, Chem. Rev. 2017, 117,
4182-4247.
outlet
2´nX
Eq. 2
2
XHX
=
´100, %
inlet
nHX
where nX outlet and nHXinlet denote the respective molar flows of X2 and HX
[8]
[9]
U.S. Energy Information Administration, Monthly Energy Review, June
2016, U.S. Department of Energy, Washington, U.S., 2016.
2
at reactor outlet and inlet.
The reaction rate expressed with respect to the reactant i, r, (i: CH4, C2H6,
or HX) and based on the titanium content was calculated using Eq. 3,
[10] R. Horn, R. Schlögl, Catal. Lett. 2015, 145, 23-39.
[11] D. A. Goetsch, L. D. Schmidt, Science 1996, 271, 1560-1562.
[12] A. S. Bodke, D. A. Olschki, L. D. Schmidt, E. Ranzi, Science 1999, 285,
712-715.
niinlet - nioutlet
Wcat ´ xTi
r =
´MWcat, moli h-1 mol-1
Eq. 3
Ti
[13] F. Cavani, N. Ballarini, A. Cericola, Catal. Today 2007, 127, 113-131.
[14] C. A. Gärtner, A. C. van Veen, J. A. Lercher, ChemCatChem 2013, 5,
3196-3217.
where MWcat and xTi are the catalyst molecular weight and molar titanium
content, respectively.
[15] J. Oliver-Meseguer, A. Doménech-Carbó, M. Boronat, A. Leyva-Pérez,
A. Corma, Angew. Chem. 2017, 129, 6535-6539; Angew. Chem. Int. Ed.
2017, 56, 6435-6439.
The selectivity to product j, Sj, and the yield and space-time-yield of
product j, Yj, and STYj (j: CH4, C2H4, CH3X, CH2X2, C2H5X, CO, and CO2)
were calculated using Eqs. 4, 5, and 6, respectively,
[16] M. J. Dagani, H. J. Barda, T. J. Benya, D. C. Sanders, Ullmann’s
Encyclopedia of Industrial Chemistry, Vol. 6, Wiley-VCH, Weinheim,
2012, pp. 331-358.
njoutlet ´NC, j
Eq. 4
Sj =
Yj =
´100, %
njoutlet ´NC, j
Aromatics—GT-G2ASM
.
å
[17] GTC
Technology,
2017.
Gas
to
Xi ´Sj
Eq. 5
,%
100
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