II International Symposium on Carbon for Catalysis ABSTRACTS

OP-I-9
Hydrogenations were carried out in a batch stainless steel reactor equipped with a heating
jacket and a hydrogen supply system at temperatures of 293-323K and hydrogen pressures
between 0.4-1.7 MPa. The structured Pd/ACF catalyst was placed between two metal grids.
As the reaction products, 1-hexene, n-hexane, 2-trans-hexene and 2-cis-hexene were found by
GC. n-Heptane was used as a solvent.
Results and discussion
Catalysts with different Pd loading (0.4 wt.%, 0.6 wt.%, 1.2 wt.%) and the same
dispersion showed an identical initial activity of 0.140 ±0.004 kmolH 2·kgPd -1·s -1 (at 303 K,
1.3 MPa), indicating the absence of mass transfer limitations. Selectivity to 1-hexene was
97±0.4% up to 80% conversion, and 96±0.4% at 90% conversion was obtained.
The catalyst activity and selectivity were observed to be stable from the second run and
no Pd leaching occurred during repeated catalyst reuse. The catalyst does not require any
conditioning between runs. Both fresh and used Pd/ACF catalysts showed better catalytic
performance than fresh conventional Lindlar catalyst (Figs. 1 and 2).
0.5
0.5100
0.4
98
0.4
Concentration, kmol/m 3
0.3
0.2
0.1
Pd/ACF, 1-hexyne
Pd/ACF, 1-hexene
Pd/ACF, by-roducts
Lindlar, 1-hexyne
Lindlar, 1-hexene
Lindlar, by-products
Concentration, kmol/m 3
Selectivity to 1-hexene, %
96
0.3 94
92
0.2
90
88
0.1
Pd/ACF
Lindlar
Pd/ACF, 1-hexyne
Pd/ACF, 1-hexene
Pd/ACF, by-roducts
Lindlar, 1-hexyne
Lindlar, 1-hexene
Lindlar, by-products
86
0.0
0 10 20 30 40 50
Time, min
0.0
84
0
20
10
40
20 30
60
40
80
50
100
Time,
Conversion,
min
%
Figs.1 and 2: “Concentration – time” and “selectivity-conversion” profiles during 1-hexyne
hydrogenation over the used 0.4 wt.% Pd/ACF catalyst (6 th run) and fresh Lindlar catalyst
(0.5 kmol/m 3 1-hexyne in n-heptane, 303K, H 2 pressure of 1.3 MPa, 1500 rpm,
substrate/Pd=23,000 mol/mol).
Hydrogenation kinetics over Pd/ACF catalyst was studied and kinetic modelling was
performed using Langmuir-Hinshelwood mechanism assuming weak hydrogen adsorption.
The activation energy was found to be in the order of 50 kJ·mol -1 .
The improved catalytic performance of the new material in comparison with Lindlar
catalyst was also demonstrated in solvent-free reactions. Higher maximum yield of 1-hexene
was achieved (92% vs. 90% for Lindlar catalyst) for 1.2-fold lower reaction time.
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