452
Chemistry Letters Vol.35, No.4 (2006)
Steam Reforming of Acetic Acid to Hydrogen over Fe–Co Catalyst
Xun Hu and Gongxuan Luꢀ
State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics,
Chinese Academy of Sciences, Lanzhou 730000, P. R. China
(Received January 20, 2006; CL-060089; E-mail: gxlu@ns.lzb.ac.cn)
The steam reforming of acetic acid to hydrogen was inves-
Figure 1 shows the effects of reaction temperature on the
steam-reforming reaction over Fe–Co catalyst. It can be found
that reaction temperature markedly affected acetic acid conver-
sion and H2 and CO2 selectivities in the temperature range from
300 to 350 ꢁC. At 300 ꢁC, the conversion of acetic acid was just
10.3%, but the conversion reached 93.7% when the temperature
increased to 350 ꢁC. At the same time, a slightly decreased CO
selectivity was found, whereas the selectivity of H2 and CO2 in-
creased. When the temperature increased to 400 ꢁC, acetic acid
was converted completely, and the selectivities of H2 and CO2
reached maximum values 95.3 and 92.9%, respectively. When
the temperature increased continuously, the selectivity of CH4
increased, as a result, the selectivities of H2 and CO2 slightly de-
creased. There were trace amount of acetaldehyde and ethylene
detected from 300 to 450 ꢁC, but they were too few to be quan-
tified easily, so we did not express them in this figure and the
tables below.
It can be found from Table 1 that LHSV affected the conver-
sion of acetic acid significantly. When the LHSV increased from
3.3 to 9.9 hꢃ1, the conversion of acetic acid decreased from 100
to 70.9%. LHSV also affected the selectivities of the products,
especially the CO selectivity, which became higher with the in-
crease of LHSV. As a result, the selectivities of H2 and CO2 be-
came lower at higher LHSV.4,6 From the Table 1, we also knew
that it was unfavorable for CH4 generation at higher LHSV.
tigated over Fe–Co catalyst. The influence of temperature, liquid
hourly space velocity, and molar ratio of steam-to-carbon were
studied in detail. At 400 ꢁC, acetic acid was converted complete-
ly. The selectivities of H2 and CO2 reached maximum values
95.3 and 92.9%, respectively.
Hydrogen is recognized as a clean fuel and energy carrier in
the future economy. Most hydrogen now is produced from fossil
such as natural gas, naphtha, and coal.1 Growing environmental
concerns, global warming and fast depletion of fossil fuel re-
serves resulted in extensive research in renewable energy tech-
nology. Flash pyrolysis of biomass to bio-oil and its steam re-
forming is one of the choices.2 Acetic acid is one of the major
components in bio-oil.3,4 Therefore, study of steam reforming
of acetic acid can provide valuable method for hydrogen produc-
tion from biomass. Acetic acid is renewable and can be easily
obtained from biomass by fermentation. In addition, acetic acid,
unlike methanol and ethanol, is nonflammable, so it is a safe hy-
drogen carrier. Up to now, only very limited reports4–10 have
been published on hydrogen production from acetic acid. Usual-
ly, the temperature conducted in the reaction was higher than
600 ꢁC.
In this paper, a new catalyst for acetic acid reforming was
reported. The conversion and selectivity for hydrogen reached
about 100 and 90% at 400 ꢁC respectively. To our knowledge,
such low reaction temperature has not been reported.
100
80
Fe–Co catalyst was prepared by coprecipitation method.
The catalyst precursors were prepared by adding aqueous mix-
ture solution of metal salts, Fe(NO3)2, Co(NO3)2 (molar ratio
1:0.5), to a vigorously stirred solution of Na2CO3 at room tem-
perature. The resulted precipitate was filtered, washed with dis-
tilled water until pH was 7, and then dried in air at 110 ꢁC over-
night. Then, the coprecipitated catalyst precursor was calcined in
air at 500 ꢁC for 3 h and crashed to 0.20–0.56 mm.
C
60
SH
2
SCH
SCO
SCO
4
40
2
20
0
250
300
350
400
450
500
550
temperature /centigrate
Catalytic activities were tested in a fixed bed continuous
flow quartz reactor at normal pressure from 250 to 550 ꢁC. Typ-
ically, 1 mL of catalyst was used in each run and diluted with an
equal amount of quartz. The calcined catalyst was reduced in situ
by 50% H2 in N2 stream (flow rate 60 mL/min) at 400 ꢁC for 3 h
prior to use. The acetic acid solution was pumped with a syring
into the reactor. Nitrogen was used as carrier gas and internal
standard for gas analysis. The gas-phase effluents were analyzed
on two on-line chromatographs equipped with thermal-conduc-
tivity detectors (TCD). H2 selectivity was defined as (moles of
H2 production)/(moles of acetic acid consumed ꢂ 4) and others
were similar to H2. The X-ray diffraction spectra (XRD) meas-
urements were performed on a Philips X pert MPD instrument
using Cu Kꢀ radiation in the scanning angle range of 10–90ꢁ
at a scanning rate of 4ꢁ/min at 40 mA and 50 kV.
Figure 1. Effects of temperature on the conversion of acetic
acid and selectivities of gaseous products. Experimental condi-
tions: S/C mol ratio 7.5:1; LHSV 5.1 hꢃ1; P ¼ 1 atm.
Table 1. Effects of liquid hourly space velocity (LHSV) on the
conversion of acetic acid and selectivities of gaseous products
LHSV/hꢃ1 C/% SH2/% SCH4/% SCO/% SCO2/%
3.3
5.1
7.8
9.9
100
100
81.1
70.9
97.5
94.8
92.8
89.5
1.5
1.4
0.98
0.77
0
5.8
10.3
16.9
98.4
92.6
88.6
82.2
Experimental conditions: t ¼ 400 ꢁC; S/C mol ratio 7.5:1;
P ¼ 1 atm.
Copyright Ó 2006 The Chemical Society of Japan
Hu, Xun
